Micro to Nano Technologies

Doccedil Dr Eylem Guumlven

Micro to Nano Technologies

Micro - Prefix meaning one millionth 11000000

Nano ndash Prefix meaning one billionth 11000000000

The Powers of 10

10+0 1 Meter

10-1 10 Centimeters

10-2 1 Centimeters

10-3 1 Millimeter

10-4 100 Microns

10-5 10 Microns

10-6 1 Micron

10-7 1000 Angstroms

10-8 100 Angstroms

10-9 1 Nanometer

10-10 1 Angstrom

10-11 10 Pico meters

10-12 1 Pico meter

10-13 100 Fermis

10-14 10 Fermis

10-15 1 Fermi

10-16 01 Fermis

10-17 001 Fermis

10-18 0001 Fermis

Perspective of Length Scale

Size of an atom (01 nm)

1 m

1 mm

1 m

1 nm

Humans

Car

Butterfly

Gnat

1 km

Boeing 747

Laptop

Wavelength of Visible Light

Micromachines

Width of DNA (2 nm)

Smallest feature in microelectronic chips

Proteins (5-50 nm)

Biological cellNucleus of a cell

Aircraft Carrier

Size of a Microprocessor

Nanostructures amp Quantum Devices

Top DownTop Down

Bottom UpBottom Up

Resolving power of the eye ~ 02 mm

Perspective of Size

Water molecules ndash 3 atoms

Protein molecules ndash thousands of atoms

DNA molecules ndash millions of atoms

Nanowires carbon nanotubes ndash millions of atoms

Carbon nanotube

water molecule

Protein molecule

Molecule of DNA

wwwiacrbbsrcacuknotebook coursesguidednasthtmwwwphyspsuedu~crespiresearch_carbon1dpublic studentbiologyarizonaedu group2crystallographyhtm

How Small is a nm

1 microm = one millionth of a meter

1 nm = one billionth of a meter

asymp 150000 thickness of a hair

asymp a string of 3 atoms

If we shrunk all distances by 110000000000 X

The sun and earth would be separated by 1 m

A football field would be 1 nm

Human hair thickness ~ 50 microm

110000000 km

110 m

More than just sizehellip

Chemical ndash take advantage of large surface to volume ratio interfacial and surface chemistry important systems too small for statistical analysis

Electronic ndash quantum confinement bandgap engineering change in density of states electron tunneling

Magnetic ndash giant magnetoresistance by nanoscale multilayers change in magnetic susceptibility

Interesting phenomena

STM of dangling bonds on a SiH surface

httppubwebacnsnwuedu~mhe663

Electron tunneling

b

More than just size hellip

Interesting phenomena

Fluorescence of quantum dots of various sizes

Phonon tunneling

Mechanical ndash improved strength hardness in light-weight nanocomposites and nanomaterials altered bending compression properties nanomechanics of molecular structures

Optical ndash absorption and fluorescence of nanocrystals single photon phenomena photonic bandgap engineering

Fluidic ndash enhanced flow properties with nanoparticles nanoscale adsorbed films important

Thermal ndash increased thermoelectric performance of nanoscale materials interfacial thermal resistance important

Micro- and NanoManufacturing ndash from TechnologyMaterials to Application

Micro- and NanoManufacturing

Electronics amp Dispays

Pharmaceutical

AutomotiveTextiles amp Clothes

Materials Process-Technology

Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik

Aerospace

Energy

industry

Microfabrication

Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition

CVD PVD Photolithography

Optical exposure PR Etching

Aqueous plasma

Many of these techniques are useful directly or indirectly in nanofabrication

Nanofabrication

Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)

ldquoTop-Downrdquo Fabrication of device structures via monolithic

processing on the nanoscale

ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of

atoms molecules or other basic units of matter

Current Micro Technologies

Photonics - Optical Apertures and Flow Orifices

Electronics ndash Semiconductor chips anodic bonding

MEMS ndash Micro Electro Mechanical Systems

Communication ndash Fiber optics switching interconnects

Biotechnology - cell filtration drug discovery

Current Nano Technologies

Molecular manufacturing ndash Precision down to the atomic level

Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies

Medicine ndash Devices that will flow through the circulatory system

Nanocomposites ndash Assisting in vast improvements in material compositions

Electronics ndash Advanced CMOS and silicon transistor integration with lithography

mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf

Micro scaling to Nano

MicroNanoFabrication Techniques

Generalized Microfabrication

Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Micro to Nano Technologies

Micro - Prefix meaning one millionth 11000000

Nano ndash Prefix meaning one billionth 11000000000

The Powers of 10

10+0 1 Meter

10-1 10 Centimeters

10-2 1 Centimeters

10-3 1 Millimeter

10-4 100 Microns

10-5 10 Microns

10-6 1 Micron

10-7 1000 Angstroms

10-8 100 Angstroms

10-9 1 Nanometer

10-10 1 Angstrom

10-11 10 Pico meters

10-12 1 Pico meter

10-13 100 Fermis

10-14 10 Fermis

10-15 1 Fermi

10-16 01 Fermis

10-17 001 Fermis

10-18 0001 Fermis

Perspective of Length Scale

Size of an atom (01 nm)

1 m

1 mm

1 m

1 nm

Humans

Car

Butterfly

Gnat

1 km

Boeing 747

Laptop

Wavelength of Visible Light

Micromachines

Width of DNA (2 nm)

Smallest feature in microelectronic chips

Proteins (5-50 nm)

Biological cellNucleus of a cell

Aircraft Carrier

Size of a Microprocessor

Nanostructures amp Quantum Devices

Top DownTop Down

Bottom UpBottom Up

Resolving power of the eye ~ 02 mm

Perspective of Size

Water molecules ndash 3 atoms

Protein molecules ndash thousands of atoms

DNA molecules ndash millions of atoms

Nanowires carbon nanotubes ndash millions of atoms

Carbon nanotube

water molecule

Protein molecule

Molecule of DNA

wwwiacrbbsrcacuknotebook coursesguidednasthtmwwwphyspsuedu~crespiresearch_carbon1dpublic studentbiologyarizonaedu group2crystallographyhtm

How Small is a nm

1 microm = one millionth of a meter

1 nm = one billionth of a meter

asymp 150000 thickness of a hair

asymp a string of 3 atoms

If we shrunk all distances by 110000000000 X

The sun and earth would be separated by 1 m

A football field would be 1 nm

Human hair thickness ~ 50 microm

110000000 km

110 m

More than just sizehellip

Chemical ndash take advantage of large surface to volume ratio interfacial and surface chemistry important systems too small for statistical analysis

Electronic ndash quantum confinement bandgap engineering change in density of states electron tunneling

Magnetic ndash giant magnetoresistance by nanoscale multilayers change in magnetic susceptibility

Interesting phenomena

STM of dangling bonds on a SiH surface

httppubwebacnsnwuedu~mhe663

Electron tunneling

b

More than just size hellip

Interesting phenomena

Fluorescence of quantum dots of various sizes

Phonon tunneling

Mechanical ndash improved strength hardness in light-weight nanocomposites and nanomaterials altered bending compression properties nanomechanics of molecular structures

Optical ndash absorption and fluorescence of nanocrystals single photon phenomena photonic bandgap engineering

Fluidic ndash enhanced flow properties with nanoparticles nanoscale adsorbed films important

Thermal ndash increased thermoelectric performance of nanoscale materials interfacial thermal resistance important

Micro- and NanoManufacturing ndash from TechnologyMaterials to Application

Micro- and NanoManufacturing

Electronics amp Dispays

Pharmaceutical

AutomotiveTextiles amp Clothes

Materials Process-Technology

Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik

Aerospace

Energy

industry

Microfabrication

Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition

CVD PVD Photolithography

Optical exposure PR Etching

Aqueous plasma

Many of these techniques are useful directly or indirectly in nanofabrication

Nanofabrication

Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)

ldquoTop-Downrdquo Fabrication of device structures via monolithic

processing on the nanoscale

ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of

atoms molecules or other basic units of matter

Current Micro Technologies

Photonics - Optical Apertures and Flow Orifices

Electronics ndash Semiconductor chips anodic bonding

MEMS ndash Micro Electro Mechanical Systems

Communication ndash Fiber optics switching interconnects

Biotechnology - cell filtration drug discovery

Current Nano Technologies

Molecular manufacturing ndash Precision down to the atomic level

Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies

Medicine ndash Devices that will flow through the circulatory system

Nanocomposites ndash Assisting in vast improvements in material compositions

Electronics ndash Advanced CMOS and silicon transistor integration with lithography

mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf

Micro scaling to Nano

MicroNanoFabrication Techniques

Generalized Microfabrication

Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

The Powers of 10

10+0 1 Meter

10-1 10 Centimeters

10-2 1 Centimeters

10-3 1 Millimeter

10-4 100 Microns

10-5 10 Microns

10-6 1 Micron

10-7 1000 Angstroms

10-8 100 Angstroms

10-9 1 Nanometer

10-10 1 Angstrom

10-11 10 Pico meters

10-12 1 Pico meter

10-13 100 Fermis

10-14 10 Fermis

10-15 1 Fermi

10-16 01 Fermis

10-17 001 Fermis

10-18 0001 Fermis

Perspective of Length Scale

Size of an atom (01 nm)

1 m

1 mm

1 m

1 nm

Humans

Car

Butterfly

Gnat

1 km

Boeing 747

Laptop

Wavelength of Visible Light

Micromachines

Width of DNA (2 nm)

Smallest feature in microelectronic chips

Proteins (5-50 nm)

Biological cellNucleus of a cell

Aircraft Carrier

Size of a Microprocessor

Nanostructures amp Quantum Devices

Top DownTop Down

Bottom UpBottom Up

Resolving power of the eye ~ 02 mm

Perspective of Size

Water molecules ndash 3 atoms

Protein molecules ndash thousands of atoms

DNA molecules ndash millions of atoms

Nanowires carbon nanotubes ndash millions of atoms

Carbon nanotube

water molecule

Protein molecule

Molecule of DNA

wwwiacrbbsrcacuknotebook coursesguidednasthtmwwwphyspsuedu~crespiresearch_carbon1dpublic studentbiologyarizonaedu group2crystallographyhtm

How Small is a nm

1 microm = one millionth of a meter

1 nm = one billionth of a meter

asymp 150000 thickness of a hair

asymp a string of 3 atoms

If we shrunk all distances by 110000000000 X

The sun and earth would be separated by 1 m

A football field would be 1 nm

Human hair thickness ~ 50 microm

110000000 km

110 m

More than just sizehellip

Chemical ndash take advantage of large surface to volume ratio interfacial and surface chemistry important systems too small for statistical analysis

Electronic ndash quantum confinement bandgap engineering change in density of states electron tunneling

Magnetic ndash giant magnetoresistance by nanoscale multilayers change in magnetic susceptibility

Interesting phenomena

STM of dangling bonds on a SiH surface

httppubwebacnsnwuedu~mhe663

Electron tunneling

b

More than just size hellip

Interesting phenomena

Fluorescence of quantum dots of various sizes

Phonon tunneling

Mechanical ndash improved strength hardness in light-weight nanocomposites and nanomaterials altered bending compression properties nanomechanics of molecular structures

Optical ndash absorption and fluorescence of nanocrystals single photon phenomena photonic bandgap engineering

Fluidic ndash enhanced flow properties with nanoparticles nanoscale adsorbed films important

Thermal ndash increased thermoelectric performance of nanoscale materials interfacial thermal resistance important

Micro- and NanoManufacturing ndash from TechnologyMaterials to Application

Micro- and NanoManufacturing

Electronics amp Dispays

Pharmaceutical

AutomotiveTextiles amp Clothes

Materials Process-Technology

Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik

Aerospace

Energy

industry

Microfabrication

Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition

CVD PVD Photolithography

Optical exposure PR Etching

Aqueous plasma

Many of these techniques are useful directly or indirectly in nanofabrication

Nanofabrication

Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)

ldquoTop-Downrdquo Fabrication of device structures via monolithic

processing on the nanoscale

ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of

atoms molecules or other basic units of matter

Current Micro Technologies

Photonics - Optical Apertures and Flow Orifices

Electronics ndash Semiconductor chips anodic bonding

MEMS ndash Micro Electro Mechanical Systems

Communication ndash Fiber optics switching interconnects

Biotechnology - cell filtration drug discovery

Current Nano Technologies

Molecular manufacturing ndash Precision down to the atomic level

Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies

Medicine ndash Devices that will flow through the circulatory system

Nanocomposites ndash Assisting in vast improvements in material compositions

Electronics ndash Advanced CMOS and silicon transistor integration with lithography

mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf

Micro scaling to Nano

MicroNanoFabrication Techniques

Generalized Microfabrication

Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Perspective of Length Scale

Size of an atom (01 nm)

1 m

1 mm

1 m

1 nm

Humans

Car

Butterfly

Gnat

1 km

Boeing 747

Laptop

Wavelength of Visible Light

Micromachines

Width of DNA (2 nm)

Smallest feature in microelectronic chips

Proteins (5-50 nm)

Biological cellNucleus of a cell

Aircraft Carrier

Size of a Microprocessor

Nanostructures amp Quantum Devices

Top DownTop Down

Bottom UpBottom Up

Resolving power of the eye ~ 02 mm

Perspective of Size

Water molecules ndash 3 atoms

Protein molecules ndash thousands of atoms

DNA molecules ndash millions of atoms

Nanowires carbon nanotubes ndash millions of atoms

Carbon nanotube

water molecule

Protein molecule

Molecule of DNA

wwwiacrbbsrcacuknotebook coursesguidednasthtmwwwphyspsuedu~crespiresearch_carbon1dpublic studentbiologyarizonaedu group2crystallographyhtm

How Small is a nm

1 microm = one millionth of a meter

1 nm = one billionth of a meter

asymp 150000 thickness of a hair

asymp a string of 3 atoms

If we shrunk all distances by 110000000000 X

The sun and earth would be separated by 1 m

A football field would be 1 nm

Human hair thickness ~ 50 microm

110000000 km

110 m

More than just sizehellip

Chemical ndash take advantage of large surface to volume ratio interfacial and surface chemistry important systems too small for statistical analysis

Electronic ndash quantum confinement bandgap engineering change in density of states electron tunneling

Magnetic ndash giant magnetoresistance by nanoscale multilayers change in magnetic susceptibility

Interesting phenomena

STM of dangling bonds on a SiH surface

httppubwebacnsnwuedu~mhe663

Electron tunneling

b

More than just size hellip

Interesting phenomena

Fluorescence of quantum dots of various sizes

Phonon tunneling

Mechanical ndash improved strength hardness in light-weight nanocomposites and nanomaterials altered bending compression properties nanomechanics of molecular structures

Optical ndash absorption and fluorescence of nanocrystals single photon phenomena photonic bandgap engineering

Fluidic ndash enhanced flow properties with nanoparticles nanoscale adsorbed films important

Thermal ndash increased thermoelectric performance of nanoscale materials interfacial thermal resistance important

Micro- and NanoManufacturing ndash from TechnologyMaterials to Application

Micro- and NanoManufacturing

Electronics amp Dispays

Pharmaceutical

AutomotiveTextiles amp Clothes

Materials Process-Technology

Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik

Aerospace

Energy

industry

Microfabrication

Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition

CVD PVD Photolithography

Optical exposure PR Etching

Aqueous plasma

Many of these techniques are useful directly or indirectly in nanofabrication

Nanofabrication

Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)

ldquoTop-Downrdquo Fabrication of device structures via monolithic

processing on the nanoscale

ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of

atoms molecules or other basic units of matter

Current Micro Technologies

Photonics - Optical Apertures and Flow Orifices

Electronics ndash Semiconductor chips anodic bonding

MEMS ndash Micro Electro Mechanical Systems

Communication ndash Fiber optics switching interconnects

Biotechnology - cell filtration drug discovery

Current Nano Technologies

Molecular manufacturing ndash Precision down to the atomic level

Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies

Medicine ndash Devices that will flow through the circulatory system

Nanocomposites ndash Assisting in vast improvements in material compositions

Electronics ndash Advanced CMOS and silicon transistor integration with lithography

mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf

Micro scaling to Nano

MicroNanoFabrication Techniques

Generalized Microfabrication

Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Perspective of Size

Water molecules ndash 3 atoms

Protein molecules ndash thousands of atoms

DNA molecules ndash millions of atoms

Nanowires carbon nanotubes ndash millions of atoms

Carbon nanotube

water molecule

Protein molecule

Molecule of DNA

wwwiacrbbsrcacuknotebook coursesguidednasthtmwwwphyspsuedu~crespiresearch_carbon1dpublic studentbiologyarizonaedu group2crystallographyhtm

How Small is a nm

1 microm = one millionth of a meter

1 nm = one billionth of a meter

asymp 150000 thickness of a hair

asymp a string of 3 atoms

If we shrunk all distances by 110000000000 X

The sun and earth would be separated by 1 m

A football field would be 1 nm

Human hair thickness ~ 50 microm

110000000 km

110 m

More than just sizehellip

Chemical ndash take advantage of large surface to volume ratio interfacial and surface chemistry important systems too small for statistical analysis

Electronic ndash quantum confinement bandgap engineering change in density of states electron tunneling

Magnetic ndash giant magnetoresistance by nanoscale multilayers change in magnetic susceptibility

Interesting phenomena

STM of dangling bonds on a SiH surface

httppubwebacnsnwuedu~mhe663

Electron tunneling

b

More than just size hellip

Interesting phenomena

Fluorescence of quantum dots of various sizes

Phonon tunneling

Mechanical ndash improved strength hardness in light-weight nanocomposites and nanomaterials altered bending compression properties nanomechanics of molecular structures

Optical ndash absorption and fluorescence of nanocrystals single photon phenomena photonic bandgap engineering

Fluidic ndash enhanced flow properties with nanoparticles nanoscale adsorbed films important

Thermal ndash increased thermoelectric performance of nanoscale materials interfacial thermal resistance important

Micro- and NanoManufacturing ndash from TechnologyMaterials to Application

Micro- and NanoManufacturing

Electronics amp Dispays

Pharmaceutical

AutomotiveTextiles amp Clothes

Materials Process-Technology

Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik

Aerospace

Energy

industry

Microfabrication

Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition

CVD PVD Photolithography

Optical exposure PR Etching

Aqueous plasma

Many of these techniques are useful directly or indirectly in nanofabrication

Nanofabrication

Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)

ldquoTop-Downrdquo Fabrication of device structures via monolithic

processing on the nanoscale

ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of

atoms molecules or other basic units of matter

Current Micro Technologies

Photonics - Optical Apertures and Flow Orifices

Electronics ndash Semiconductor chips anodic bonding

MEMS ndash Micro Electro Mechanical Systems

Communication ndash Fiber optics switching interconnects

Biotechnology - cell filtration drug discovery

Current Nano Technologies

Molecular manufacturing ndash Precision down to the atomic level

Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies

Medicine ndash Devices that will flow through the circulatory system

Nanocomposites ndash Assisting in vast improvements in material compositions

Electronics ndash Advanced CMOS and silicon transistor integration with lithography

mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf

Micro scaling to Nano

MicroNanoFabrication Techniques

Generalized Microfabrication

Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

How Small is a nm

1 microm = one millionth of a meter

1 nm = one billionth of a meter

asymp 150000 thickness of a hair

asymp a string of 3 atoms

If we shrunk all distances by 110000000000 X

The sun and earth would be separated by 1 m

A football field would be 1 nm

Human hair thickness ~ 50 microm

110000000 km

110 m

More than just sizehellip

Chemical ndash take advantage of large surface to volume ratio interfacial and surface chemistry important systems too small for statistical analysis

Electronic ndash quantum confinement bandgap engineering change in density of states electron tunneling

Magnetic ndash giant magnetoresistance by nanoscale multilayers change in magnetic susceptibility

Interesting phenomena

STM of dangling bonds on a SiH surface

httppubwebacnsnwuedu~mhe663

Electron tunneling

b

More than just size hellip

Interesting phenomena

Fluorescence of quantum dots of various sizes

Phonon tunneling

Mechanical ndash improved strength hardness in light-weight nanocomposites and nanomaterials altered bending compression properties nanomechanics of molecular structures

Optical ndash absorption and fluorescence of nanocrystals single photon phenomena photonic bandgap engineering

Fluidic ndash enhanced flow properties with nanoparticles nanoscale adsorbed films important

Thermal ndash increased thermoelectric performance of nanoscale materials interfacial thermal resistance important

Micro- and NanoManufacturing ndash from TechnologyMaterials to Application

Micro- and NanoManufacturing

Electronics amp Dispays

Pharmaceutical

AutomotiveTextiles amp Clothes

Materials Process-Technology

Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik

Aerospace

Energy

industry

Microfabrication

Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition

CVD PVD Photolithography

Optical exposure PR Etching

Aqueous plasma

Many of these techniques are useful directly or indirectly in nanofabrication

Nanofabrication

Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)

ldquoTop-Downrdquo Fabrication of device structures via monolithic

processing on the nanoscale

ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of

atoms molecules or other basic units of matter

Current Micro Technologies

Photonics - Optical Apertures and Flow Orifices

Electronics ndash Semiconductor chips anodic bonding

MEMS ndash Micro Electro Mechanical Systems

Communication ndash Fiber optics switching interconnects

Biotechnology - cell filtration drug discovery

Current Nano Technologies

Molecular manufacturing ndash Precision down to the atomic level

Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies

Medicine ndash Devices that will flow through the circulatory system

Nanocomposites ndash Assisting in vast improvements in material compositions

Electronics ndash Advanced CMOS and silicon transistor integration with lithography

mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf

Micro scaling to Nano

MicroNanoFabrication Techniques

Generalized Microfabrication

Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

More than just sizehellip

Chemical ndash take advantage of large surface to volume ratio interfacial and surface chemistry important systems too small for statistical analysis

Electronic ndash quantum confinement bandgap engineering change in density of states electron tunneling

Magnetic ndash giant magnetoresistance by nanoscale multilayers change in magnetic susceptibility

Interesting phenomena

STM of dangling bonds on a SiH surface

httppubwebacnsnwuedu~mhe663

Electron tunneling

b

More than just size hellip

Interesting phenomena

Fluorescence of quantum dots of various sizes

Phonon tunneling

Mechanical ndash improved strength hardness in light-weight nanocomposites and nanomaterials altered bending compression properties nanomechanics of molecular structures

Optical ndash absorption and fluorescence of nanocrystals single photon phenomena photonic bandgap engineering

Fluidic ndash enhanced flow properties with nanoparticles nanoscale adsorbed films important

Thermal ndash increased thermoelectric performance of nanoscale materials interfacial thermal resistance important

Micro- and NanoManufacturing ndash from TechnologyMaterials to Application

Micro- and NanoManufacturing

Electronics amp Dispays

Pharmaceutical

AutomotiveTextiles amp Clothes

Materials Process-Technology

Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik

Aerospace

Energy

industry

Microfabrication

Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition

CVD PVD Photolithography

Optical exposure PR Etching

Aqueous plasma

Many of these techniques are useful directly or indirectly in nanofabrication

Nanofabrication

Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)

ldquoTop-Downrdquo Fabrication of device structures via monolithic

processing on the nanoscale

ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of

atoms molecules or other basic units of matter

Current Micro Technologies

Photonics - Optical Apertures and Flow Orifices

Electronics ndash Semiconductor chips anodic bonding

MEMS ndash Micro Electro Mechanical Systems

Communication ndash Fiber optics switching interconnects

Biotechnology - cell filtration drug discovery

Current Nano Technologies

Molecular manufacturing ndash Precision down to the atomic level

Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies

Medicine ndash Devices that will flow through the circulatory system

Nanocomposites ndash Assisting in vast improvements in material compositions

Electronics ndash Advanced CMOS and silicon transistor integration with lithography

mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf

Micro scaling to Nano

MicroNanoFabrication Techniques

Generalized Microfabrication

Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

More than just size hellip

Interesting phenomena

Fluorescence of quantum dots of various sizes

Phonon tunneling

Mechanical ndash improved strength hardness in light-weight nanocomposites and nanomaterials altered bending compression properties nanomechanics of molecular structures

Optical ndash absorption and fluorescence of nanocrystals single photon phenomena photonic bandgap engineering

Fluidic ndash enhanced flow properties with nanoparticles nanoscale adsorbed films important

Thermal ndash increased thermoelectric performance of nanoscale materials interfacial thermal resistance important

Micro- and NanoManufacturing ndash from TechnologyMaterials to Application

Micro- and NanoManufacturing

Electronics amp Dispays

Pharmaceutical

AutomotiveTextiles amp Clothes

Materials Process-Technology

Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik

Aerospace

Energy

industry

Microfabrication

Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition

CVD PVD Photolithography

Optical exposure PR Etching

Aqueous plasma

Many of these techniques are useful directly or indirectly in nanofabrication

Nanofabrication

Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)

ldquoTop-Downrdquo Fabrication of device structures via monolithic

processing on the nanoscale

ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of

atoms molecules or other basic units of matter

Current Micro Technologies

Photonics - Optical Apertures and Flow Orifices

Electronics ndash Semiconductor chips anodic bonding

MEMS ndash Micro Electro Mechanical Systems

Communication ndash Fiber optics switching interconnects

Biotechnology - cell filtration drug discovery

Current Nano Technologies

Molecular manufacturing ndash Precision down to the atomic level

Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies

Medicine ndash Devices that will flow through the circulatory system

Nanocomposites ndash Assisting in vast improvements in material compositions

Electronics ndash Advanced CMOS and silicon transistor integration with lithography

mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf

Micro scaling to Nano

MicroNanoFabrication Techniques

Generalized Microfabrication

Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Micro- and NanoManufacturing ndash from TechnologyMaterials to Application

Micro- and NanoManufacturing

Electronics amp Dispays

Pharmaceutical

AutomotiveTextiles amp Clothes

Materials Process-Technology

Source Suumlss MicroTec Jenoptik Kugler Praumlzisionsschleifen Trumpf Lasertechnik

Aerospace

Energy

industry

Microfabrication

Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition

CVD PVD Photolithography

Optical exposure PR Etching

Aqueous plasma

Many of these techniques are useful directly or indirectly in nanofabrication

Nanofabrication

Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)

ldquoTop-Downrdquo Fabrication of device structures via monolithic

processing on the nanoscale

ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of

atoms molecules or other basic units of matter

Current Micro Technologies

Photonics - Optical Apertures and Flow Orifices

Electronics ndash Semiconductor chips anodic bonding

MEMS ndash Micro Electro Mechanical Systems

Communication ndash Fiber optics switching interconnects

Biotechnology - cell filtration drug discovery

Current Nano Technologies

Molecular manufacturing ndash Precision down to the atomic level

Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies

Medicine ndash Devices that will flow through the circulatory system

Nanocomposites ndash Assisting in vast improvements in material compositions

Electronics ndash Advanced CMOS and silicon transistor integration with lithography

mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf

Micro scaling to Nano

MicroNanoFabrication Techniques

Generalized Microfabrication

Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Microfabrication

Microfabrication is a top-down technique utilizing the following processes in sequential fashion (micrometer to milimeter range) Film Deposition

CVD PVD Photolithography

Optical exposure PR Etching

Aqueous plasma

Many of these techniques are useful directly or indirectly in nanofabrication

Nanofabrication

Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)

ldquoTop-Downrdquo Fabrication of device structures via monolithic

processing on the nanoscale

ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of

atoms molecules or other basic units of matter

Current Micro Technologies

Photonics - Optical Apertures and Flow Orifices

Electronics ndash Semiconductor chips anodic bonding

MEMS ndash Micro Electro Mechanical Systems

Communication ndash Fiber optics switching interconnects

Biotechnology - cell filtration drug discovery

Current Nano Technologies

Molecular manufacturing ndash Precision down to the atomic level

Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies

Medicine ndash Devices that will flow through the circulatory system

Nanocomposites ndash Assisting in vast improvements in material compositions

Electronics ndash Advanced CMOS and silicon transistor integration with lithography

mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf

Micro scaling to Nano

MicroNanoFabrication Techniques

Generalized Microfabrication

Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Nanofabrication

Nanofabrication can generally be divided into two categories based on the approach (1-100 nm)

ldquoTop-Downrdquo Fabrication of device structures via monolithic

processing on the nanoscale

ldquoBottom-Uprdquo Fabrication of device structures via systematic assembly of

atoms molecules or other basic units of matter

Current Micro Technologies

Photonics - Optical Apertures and Flow Orifices

Electronics ndash Semiconductor chips anodic bonding

MEMS ndash Micro Electro Mechanical Systems

Communication ndash Fiber optics switching interconnects

Biotechnology - cell filtration drug discovery

Current Nano Technologies

Molecular manufacturing ndash Precision down to the atomic level

Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies

Medicine ndash Devices that will flow through the circulatory system

Nanocomposites ndash Assisting in vast improvements in material compositions

Electronics ndash Advanced CMOS and silicon transistor integration with lithography

mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf

Micro scaling to Nano

MicroNanoFabrication Techniques

Generalized Microfabrication

Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Current Micro Technologies

Photonics - Optical Apertures and Flow Orifices

Electronics ndash Semiconductor chips anodic bonding

MEMS ndash Micro Electro Mechanical Systems

Communication ndash Fiber optics switching interconnects

Biotechnology - cell filtration drug discovery

Current Nano Technologies

Molecular manufacturing ndash Precision down to the atomic level

Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies

Medicine ndash Devices that will flow through the circulatory system

Nanocomposites ndash Assisting in vast improvements in material compositions

Electronics ndash Advanced CMOS and silicon transistor integration with lithography

mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf

Micro scaling to Nano

MicroNanoFabrication Techniques

Generalized Microfabrication

Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Current Nano Technologies

Molecular manufacturing ndash Precision down to the atomic level

Nanotubes ndashBuilding advanced lightweight materials as well as advancements in LCD technologies

Medicine ndash Devices that will flow through the circulatory system

Nanocomposites ndash Assisting in vast improvements in material compositions

Electronics ndash Advanced CMOS and silicon transistor integration with lithography

mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf

Micro scaling to Nano

MicroNanoFabrication Techniques

Generalized Microfabrication

Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

mmsstreamtechtvcomwindowsbigthinkers2002bt020225b_165_0asf

Micro scaling to Nano

MicroNanoFabrication Techniques

Generalized Microfabrication

Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

MicroNanoFabrication Techniques

Generalized Microfabrication

Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Generalized Microfabrication

Taken from httpmemscoloradoeduc1respptpptgtutorialppthtm

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Photolithography

Clean wafer to remove particles on the surface as well as any traces of organic ionic and metallic impurities

Dehydration bake to drive off the absorbed water on the surface to promote the adhesion of PR (photoresist)

Coating a) Coat wafer with adhesion promoting film (eg HMDS) (optional)b) Coat with photoresist

Soft bake to drive off excess solvent and to promote adhesion

Exposure

Post exposure bake (optional) to suppress standing wave-effect

Develop

Clean Dry

Hard bake to harden the PR and improve adhesion to the substrate

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Photolithography

Taken from httpwww2ecejhuedufacultyandreou4952003LectureNotesHandout3a_PhotolithographyIpdf

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Additive Processes

Oxidation

Thermal Oxidation of Silicon is done in a furnace in wet or dry conditions

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Additive ProcessesDoping

Purpose of Doping in MEMS- Creation of etch stop layers- Change restivity of the film (eg make piezoresistor connecting wire)

Dopants to form N type region (Phosphorous Arsenic) P type region (Boron) in silicon

Doping Methods1 Diffusion

Dopants are diffused thermally into the substrate in furnace at 950 ndash 1280 0C

It is governed by Fickrsquos Laws of Diffusion

Dopant ions bombarded into targeting substrate by high energy

Ion implantation are able to place any ion at any depth in sample

2 Ion Implantation

The introduction of certain impurities in a semiconductor can change its electrical chemical and even mechanical properties (microelectric industry-fabrication of diodes and transistors)

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Additive Processes

Physical Vapor Deposition (PVD)

1 Evaporation

Thermal Evaporator

Deposition is achieved by evaporation or sublimation of heated metal onto substrate

This can be done either by resistance heating or by e-beam bombardment

The material to be deposited is transported from a source to the wafers both being in the same chamber

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Additive Processes

Physical Vapor Deposition (PVD)

2 Sputtering

Sputtering is achieved by accelerated-high energy inert ion (Ar+) by DC or RF drive in plasma through potential gradient to bombard metallic target

Then the individual atoms of targeting material are removed from the surface and ejected toward the wafer(deposited onto substrate placed on anode)

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Additive Processes

Physical Vapor Deposition (PVD)

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Additive Processes

Chemical Vapor Deposition (CVD)

All the deposition techniques using the reaction of chemicals in a gas phase to form the deposited thin film

Materials depositedPolysilicon silicon nitride (Si3N4) silicon oxide (SiOx) silicon carbide (SiC) etc

How does CVD Work1048708 Gaseous reactants are introduced into chamber at elevated temperatures1048708 Reactant reacts and deposits onto substrate

Types of CVDLPCVD (Low Pressure CVD) PECVD (Plasma Enhanced CVD)

Salient Features1048708 CVD results depend on pressure gas and temperature1048708 Can be diffusion or reaction limited1048708 Varies from film composition crystallization deposition rate and electrical and mechanical properties

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Subtractive Processes

Dry Etching

1 Dry Chemical Etching

HF Etching

HF is a powerful etchant and hence highly dangerous

XeF2 Etching

2XeF2+Sirarr2Xe+SiF41048708 Isotropic etching (typically 1-3micrommin)1048708 Does not attack aluminum silicon dioxide and silicon nitride

Thin film and bulk substrate etching is another fabrication step that is of fundamental importance to microfbrication

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Subtractive Processes

Reaction MechanismProduce reactive species in gas-phase Reactive species diffuse to the solidAdsorption and diffuse over the surface Reaction Desorption Diffusion

Dry Etching

Plasma Etching

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Subtractive Processes

Dry Etching

3 Deep Reactive Ion Etching (DRIE)

A very high-aspect-ratio silicon etch method (usually gt 301)

BOSCH Process 1048708 Etch rate is 15 ndash 4 micrommin1048708 SF6 to etch silicon1048708 Approx 10nm flourcarbon polymer (similar is plasma deposited using C4H8

1048708 Energetic ions (SF6+) remove protective

polymer at the bottom trench

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Subtractive Processes

DRIE Etched Pillars

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Subtractive Processes

Wet Etching

Isotropic etchants etch in all directions at nearly the same rate

Commonly use chemical for Silicon is HNA (HFHNO3Acetic Acid)

This results in a finite amount of undercutting

Isotropic Wet Etching

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Subtractive Processes

Wet Etching

Anisotropic etchants etch much faster in one direction than in another

Etchants are generally Alkali Hydroxides (KOH NaOH CeOH )

KOH on silicon1048708 Slower etch rate on (111) planes1048708 Higher etch rate on (100) and (110) planes (400 times more faster than the (111) plane)1048708 Typical concentration of KOHis around 40 wt

Reaction Silicon (s) + Water + Hydroxide Ions rarr Silicates + Hydrogen

Anisotropic Wet Etching

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Surface Micromachining

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Example

An insulin pump fabricated by classic MEMS technology

(Surface Micromachining)

1 Pumping membrane 2 Pumping chamber

3 Inlet 4 Outlet

5 Large mesa 6 Upper glass plate

7 Bottom glass plate 8 patterned thin layer (for improved fluidics)

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

What are NanostructuresAt least one dimension is between 1 - 100 nm2-D structures (1-D confinement) Thin films Planar quantum wells Superlattices1-D structures (2-D confinement) Nanowires Quantum wires Nanorods Nanotubes0-D structures (3-D confinement) Nanoparticles Quantum dotsDimensionality confinement depends on structure Bulk nanocrystalline films Nanocomposites

Si076Ge024 Si084Ge016 superlattice

2 m

Si Nanowire Array

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Thin FilmsNanoscale Thin Film Single ldquotwo dimensionalrdquo film thickness lt ~100 nm Electrons can be confined in one dimension affects

wavefunction density of states Phonons can confined in one dimension affects thermal transport Boundaries interfaces affect transport

Bulk crystal

a

Free standing thin film

d

Thin film

Substrate

httpscsx01scehueswaporcojcharlascursodoctorado12

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Thin Film Applications

100 nm sputtered YSZ film for solid oxide fuel

cells

Amorphous Si TFT on a SiNx passivated polyimide foil

Solid Fuel Cells (nanostructured) thin film solid electrolytes and electrodes with high conductance

Thin Film Transistors for liquid crystal displays requires high mobility and flexible substrates

Gas sensing applications

Thin layers in electronic devices

httpwwwbuedumfgpdfTullerpdf

Wagner et al Thin Solid Films Vol 490 pp 12 ndash 19 (2003)

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Nanowires Solid ldquoone dimensionalrdquo Can be conducting semiconducting insulating Can be crystalline low defects Can exhibit quantum confinement effects (electron phonon) Narrowing wire diameter results in increase in band gap Narrowing wire diameter can result in decrease in thermal conductivity New forms include core-shell and superlattice nanowires

2 m

Si Nanowire Array

Nanotube defined ndash a long cylinder with inner and outer nm-sized diameters Nanowire defined ndash a long solid wire with nm diameter

SiSiGe NanowiresAbramson et al JMEMS (2003)

Wu et al Nanoletters Vol 2 83 ndash 86 (2002)

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Nanowires ApplicationsField effect transistorsThermoelectric materialsLight emitting diodesDetectorsSensorsNanolasersSuperlattice nanowires in applications requiring superlattices

5 nm Si nanowire FET

Cui et al Nanoletters Vol 3 149 ndash 152 (2003)

Nanolaser from 100 nm CdSe nanowire

httpwwwphotonicscomspectratechXQASPtechid1525QXreadhtm

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Carbon NanotubesCarbon nanotube properties One dimensional sheets of hexagonal network of carbon rolled to form tubes Approximately 1 nm in diameter Can be microns long Essentially free of defects Ends can be ldquocappedrdquo with half a buckyball Varieties include single-wall and multi- wall

nanotubesropes bundles arrays Structure (chirality diameter) influences properties

Semiconducting vs metallic Thermal electrical conductance Mechanical strength elasticity

Multi-wall carbon nanotube

httpwwwaiporgmgrpng2003186htm

Armchair

Zigzag

Chiralhttpphysicsweborgarticleworld11191

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Other NanotubeshellipBoron nitride nanotubes Resistance to oxidation suited

for high temperatures Youngrsquos modulus of 122 TPa Semiconducting Predictable electronic properties

independent of diameter and of layers

SiC nanotubes Resistance to oxidation Suitable for harsh environments Can functionalize surface Si

atoms

Boron nitride nanotubes

adopt various shapes

(red=boron blue=nitrogen)

httppubsacsorgcentopstory79127912notw1html

SiC nanotubes grown at NASA

Glenn

httpwwwgrcnasagovWWWRT200250005510lienhardhtml

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

NanoparticlesQuantum Dots

ldquoZero-dimensionalrdquo particle Surface effectschemistry important Radius lt 100 nm lt 106 atoms per nanoparticle Size smaller than critical length scales (eg mean free path wavelength) Nanoquantum physical phenomena present ldquoLargerdquo nanoparticles have same structure

as bulk ldquosmallrdquo may be different Synthesis RF plasma chemical thermolysis pulsed laser ldquoOldrdquo examples

Stained glass ndash small metal oxide clusters comparable in size to the wavelength of light

Photography ndash small colloidal silver particles for image formation

1 A

1 nm

10 nm

102 nm

103 nm

104 nm

105 nm

molecules

nanoparticles

Radius of particle or cluster

bulk

quantum dots

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

NanoparticlesQuantum Dots

Metalic nanoparticles

wwwavekacom

Si nanoparticle single-crystal hexagonal shape

Bapat et al J Appl Phys Vol 94 1969 ndash 1974 (2003)

Gradient of gold nanoparticles on a silica surface

httpwwwbnlgovbnlwebpubafpr2002bnlpr071802htm

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Nanoparticle Probes Objective To detect and ldquokillrdquo individual cancer cells before they

manifest as tumors using functionalized nanoparticles 5 to 10 nm particles (small enough to interact with intracellular

markers) nanoparticles are coated and functionalized with antibodies

oligonucleotides peptide ligands and drugs Introduced to body via bloodstream ldquoLookrdquo for markers inside cell by MRI or deliver agent or irradiate

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Nanocomposites Nanocomposite ndash consists of two or more synthesized materials of which at least one has nanoscale dimensions Can exhibit enhanced chemical optical physical mechanical properties as compared with constituent bulk Multiple material possibilities

Organic + organic Organic + inorganic Inorganic + inorganic

Nanoparticle or nanowire or nanotube + matrix material

Why nano and not microMicro also gives increase elastic modulus but microparticles act as stress concentrators decrease in strain to failure decrease in strength and toughness

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Nanocomposite ApplicationsLuminescent nanocomposites for opto-electronicsElectronics (eg dielectric layers)Intracellular manipulationThermoelectric materialsHigh-strength toughness structural materialsElectrolytes in batteriesInsulationCoatingsGas separationFire barriers

Polymer containing 40 wt silica particles for use as a gas

separation membrane

TiO2-oligonucleotide nanocomposites hybridized with

DNA for cellular manipulation

Paunesku et al Nature Mats Vol 2 343 ndash 346 (2003)

Merkel et al Science Vol 296 519 ndash 522 (2002)

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

What can we measure

structure

properties

composition

crystallinitystrain defects

mechanicalelectricalopticalmagnetic

thermal

atomic speciesconcentration

diffusionsegregation

tensile strength

hardness

yield

modulus of elasticity

failure

stiffness

conductivity

electron states

carrier densityband gap

conductivity

Seebeck coefficient

specific heat

susceptibilitymagneto-resistance

dielectric constant

surface roughness

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Atomic Force MicroscopyThe optical microscope ndash cannot see features smaller than ~half the wavelength of light

Can we use something other than light and lenses

AFM basic components Tip (lt~10 nm diameter) on a

cantilever Detector (generally position) Raster-scan (to drag tip) Forceheight control Image processing software

Lateral resolution 01 nm Vertical resolution 002 nm

Image of graphite using an AFM

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

AFM modes

Tip angstroms from surface (repelled)

Constant force

Highest resolution

May damage surface

contact modecontact mode non-contact modenon-contact mode

Tip hundreds of angstroms from surface (attracted)

Variable force measured

Lowest resolution

Non-destructive

tapping modetapping mode Intermittent tip contact

Variable force measured

Improved resolution

Non-destructive

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

AFM images

Cu Nanowires

R Adelung et alR Adelung et al

Ge islands on Si

K Brunner et alK Brunner et alCourtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

Scanning Electron MicroscopyInstead of light the SEM uses electrons to see 3-D imagesSEM operation Air pumped out (vacuum) e- gun emits beam of high energy electrons e- beam focused via lenses Scanning coils move beam across sample Secondary electrons are ldquoknocked offrdquo surface Detector counts electrons Image given by e-

Resolution ~5 nm

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

SEM and AFM images

SEM Cu Nanowires

AFM Cu Nanowires

R Adelung et alR Adelung et al Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

sample

Transmission Electron Microscopy

A TEM works like a slide projector but with e- instead of light

TEM operationAir pumped out (vacuum)e- gun emits beam of high energy e-

e- beam focused via lensesBeam strikes sample and some e- are

transmittedTransmitted e- are focused amplified Image contrast enhanced by blocking

out high-angle diffracted e- Image passed through lenses and

enlargedWhen image hits phosphor screen light

is generated Resolution ~lt1 nm Courtesy of F ErnstCourtesy of F Ernst

lens

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

TEM of Ge on SiTEM of Ge on Si

HRTEM Cross-Sectional View

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst

TEM comparison

Standard TEM High resolution TEM

Courtesy of F ErnstCourtesy of F Ernst