M. MeyyappanDi t C t f N t h lDirector, Center for Nanotechnology

NASA Ames Research CenterMoffett Field, CA 94035Moffett Field, CA 94035meyya@orbit.arc.nasa.gov

web: http://www.ipt.arc.nasa.gov

N t h l i th ti f USEFUL/FUNCTIONALNanotechnology is the creation of USEFUL/FUNCTIONALmaterials, devices and systems through control of matter on the nanometer length scale and exploitation of novelon the nanometer length scale and exploitation of novel phenomena and properties (physical, chemical, biological) at that length scale

Source: K.J. Klabunde, 200

• Nanoelectronics (CNTs, molecular electronics)d h bl• Non-CMOS circuits and architectures, reconfigurable sy

• Spintronics, quantum computing, nanomagnetics• Nanophotonics nano-optics nanoscale lasers…• Nanophotonics, nano optics, nanoscale lasers….• Chemical and biological sensors• Novel materials for all applications (CNTs, quantum do

inorganic nanowires…• Integration of nano-micro-macro

Bi f i• Bio-nano fusion•••

CNT is a tubular form of carbon with diameter as small as 1 nm. Length: few nm to microns.

CNT is configurationally equivalent to a two dimensional graphene sheet rolled into a tube.

CNT exhibits extraordinary mechanical properties: Young’s modulus over 1 Tera Pascal, as stiff as diamond, and tensile strength ~ 200 GPa.

CNT b lli i d iCNT can be metallic or semiconducting, depending on chirality.

• The strongest and most flexible molecular material because of C-C covalent bonding and seamless hexagonal network architecture

• Strength to weight ratio 500 time > for Al, steel, titanium; one

d f it d i t hit /order of magnitude improvement over graphite/epoxy

• Maximum strain ~10% much higher than any material

• Thermal conductivity ~ 3000 W/mK in the axial direction with small values in the radial direction

• Very high current carrying capacity

• Excellent field emitter; high aspect ratio and• Excellent field emitter; high aspect ratio and small tip radius of curvature are ideal for field i i

• CNT quantum wire interconnectsq

• Diodes and transistors for computing

• Capacitors

• Data Storage

• Field emitters for instrumentation

• Flat panel displays

• THz oscillators

ChallengesChallenges

• Control of diameter, chirality• Doping contactsDoping, contacts• Novel architectures (not CMOS based!)• Development of inexpensive manufacturing processes

Ch ll• CNT based microscopy: AFM, STM…

• Nanotube sensors: force, pressure, chemical…

Challenges

• Controlled growth

• Biosensors

• Molecular gears, motors, actuators

g• Functionalization withprobe molecules, robustnes

• Integration, signal proces

• Batteries, Fuel Cells: H2, Li storage

• Nanoscale reactors ion channels

• Fabrication techniques

• Nanoscale reactors, ion channels

• Biomedical- in vivo real time crew health monitoring- Lab on a chip - Drug delivery- DNA sequencingA tifi i l l b l t- Artificial muscles, bone replacement,bionic eye, ear...

• CNT has been grown by laser ablation (pioneering at Rice) and carbon arc process (NEC, Japan) - early 90s.

SWNT hi h it ifi ti th d- SWNT, high purity, purification methods

• CVD is ideal for patterned growth (electronics, sensor applications)

- Well known technique from microelectronics

- Hydrocarbon feedstock- Growth needs catalyst

(transition metal)l ll b- Multiwall tubes at

500-800° deg. C.- Numerous parameters

i fl CNT thinfluence CNT growth

- Surface masked by a 400 mesh TEM grid

- Methane, 900° C, 10 nm Al/1.0 nm Fe

- Surface masked by a 400 mesh TEM grid; 20 nm Al/ 10 nm Fe; nanotubes grown for 10 minutes

Grown using ethylene at 750o C

• Inductively coupled plasma reactor, with an rf-d b ttpowered bottom

electrode, separate heating stage to heat the wafer (in addition

to plasma heating)to plasma heating)

• DC plasma reactor with similar capabilities, but generally lowergenerally lower

plasma efficiency and more power consumption

ICP O ti diti

Cassell et al., Nanotechnology, 15 (1), 200

• ICP Operating conditionsCH4/H2 : 5 - 20%Total flow : 100 sccmPressure : 1 20 Torr Ir_ FeCr Ni Si NiPressure : 1 - 20 TorrInductive power : 100-200 WBottom electrode power : 0 - 100 W

__ S _

Ta_Ni/Co Ti_ Ni W_ Ni

*First single nanotube logic device Inverter demonstration (Appl Phys Lett Nov 2001)*First single nanotube logic device – Inverter demonstration (Appl. Phys. Lett., Nov. 2001)by Chongwu Zhou (USC) and Jie Han (NASA Ames)

Vout

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A d i f i iAs device feature size continues to shrink (180 nm 130 nm 100 nm) and chip density continuesand chip density continuesto increase, heatdissipation from thedissipation from thechip is becoming a h h llhuge challenge.

(Beyond the SIA Roadmap for Silicon)

• Must be easier and cheaper to manufacture than CMOS

• Need high current drive; should be able to drive capacitances ofNeed high current drive; should be able to drive capacitances of interconnects

of any length

• High level of integration (>1010 transistors/circuit)

• High reproducibility (better than ± 5%)

• Reliability (operating time > 10 years)

• Very low cost ( < 1 µcent/transistor)

• Better heat dissipation characteristics and amenable solutions

• Everything about the new technology must be compelling and• Everything about the new technology must be compelling and simultaneously

further CMOS scaling must become difficult and not cost-effective. Until these two happen together the enormous

• Neural tree with 14 symmetric Y-junctionsB hi d it hi f i l t h j ti i il t h t• Branching and switching of signals at each junction similar to what

happens in biological neural network• Neural tree can be trained to perform complex switching and computing functionsfunctions• Not restricted to only electronic signals; possible to use acoustic, chemical or thermal signals

Atomic Force Microscopy is a powerful technique for imagingAtomic Force Microscopy is a powerful technique for imaging, nanomanipulation, as platform for sensor work, nanolithography...

Conventional silicon or tungsten tips wear out quickly. CNT tip is robust, offers amazing resolution.

Simulated Mars dust 2 nm thick Au on Mica

193 nm IBM Version 2 Resist

Nguyen et al., App. Phys. Lett., 81 (5), 901

DUV Photoresist Patterns Generated byGenerated by Interferometric Lithography

DNA PROTEIN

CNT d tCNT advantages:(1) Small diameter(2) High aspect ratio(3) Highly conductive along the axis(4) High mechanical strength

Question: How to do this ?

M l

SiO2/Si

Metal DepositionTi, Mo, Cr, Pt

CatalystPatterning

Top Metal Layer DepositionNi

Plasma CVDAt ~ 400 to

TEOSCVD

CVD CMPAt 400 to 800° C

J. Li, Q. Ye, A. Cassell, H. T. Ng, R. Stevens, J. Han, M. M A l Ph L tt 82(15) 2491 (2003)Meyyappan, Appl. Phys. Lett., 82(15), 2491 (2003)

O i i d l f bi l d i i• Our interest is to develop sensors for astrobiology to study origins of life. CNT, though inert, can be functionalized at the tip with a probe molecule. • The technology is also being used to develop sensors for cancer• The technology is also being used to develop sensors for cancer diagnostics

- Identified probe molecule that will serve as signature of leukemia cells to be attached to CNTcells, to be attached to CNT

- Current flow due to hybridization will be through CNT electrode to an IC chip.

- Prototype biosensors catheter development

• High specificity• Direct fast response

Prototype biosensors catheter development

• The technology can be adapted for pathogen detection

• Direct, fast response• High sensitivity• Single molecule and

cell signal captureand detection

CNT DNA SensorUsing Electrochemical Detection

2+

3+

2+

3+

e

MWNT array electrode functionalized with DNA/PNA probe as an ultrasensitive

sensor for detecting the hybridization of target DNA/RNA from the sample.

• Signal from redox bases in the excess DNA single strands

The signal can be amplified with metal ion mediator oxidation Ru bPy( )2 +[ ]The signal can be amplified with metal ion mediator oxidation

catalyzed by Guanine.

Ru bPy( )3[ ]

Fabrication of Genechip

300 μm

30 dies on a 4” Si wafer200 μm

Simple Devices for Quick Molecular AnalysisAnalysis

HandheldHandheld Diagnostic Device Signal

Control

Potential applications:

Workstation

Potential applications:(1) Health monitoring and

astrobiology study in outer spaceWorkstation

DNA/RNA Sensor

p(2) Early cancer detection(3) Infectious disease detection(4) Environmental monitoring(5) Pathogen detection

Single Wall Carbon Nanotube

• Every atom in a single-walled nanotube (SWNT) is on the surface and exposed to environment Ch f ll h i h h• Charge transfer or small changes in the charge-environment of a nanotube can cause drastic changes to its electrical propertiesto its electrical properties

Sensor fabrication:1. SWCNT dispersions--Nice dispersion of CNT in DMF2. Device fabrication--(see the interdigitated electrodes below)3. SWCNT deposition—Casting, or in-situ growth

Jing Li et al., Nano Lett., 3, 929 (2003)

SWNT Sensor Response to NO2 with UV Light Aiding RecoveryAiding Recovery

Detection limit for NO2 is 44 ppb.

• When subjected to high E field, electrons near the Fermi level can overcome the energy barrier to escape to the vacuum level

• Common tips: Mo Si diamondCommon tips: Mo, Si, diamond

• Applications:- Cathode ray lighting elements- Flat panel displays- Gas discharge tubes in telecom networks- Electron guns in electron microscopyg py- Microwave amplifiers

• Fowler - Nordheim equation: φ is work function β is field enhancement factor

I = aV 2 exp(−bφ1.5 /βV )φ is work function, β is field enhancement factor

• Plot of ln (I/V2) vs. (1/V) should be linear• At low emission levels, linearity seen; in the high

i ld ifield region, current saturates• Critical: low threshold E field, high current density, high emission site density (for high resolution displays)

• N d• Needs- For displays, 1-10 mA/cm2

- For microwave amplifiers, > 500 mA/cm2For microwave amplifiers, > 500 mA/cm

• To obtain low threshold field- Low work function (φ)Low work function (φ)- Large field enhancement factor (β) ⇒ depends on geof the emitter; β ~ 1/5rβ

• Threshold field values (in V/µm) for 10 mA/cm2

- Mo - 50-100

_

Mo 50 100- Si - 50-100- P-type diamond - 130- Graphite Powder - 17- Carbon nanotubes - 1-3 (stable at 1 A/cm2)

• Working full color flat panel displays and CRT-lighting elements have been

demonstrated in Japan and KoreaJ p

• Display- Working anode, a glass substrate with phosphor coated ITOWorking anode, a glass substrate with phosphor coated ITO

stripes- Anode and cathode perpendicular to each other to form

pixels at thepixels at theintersection

- Phosphors such as Y2O2S: Eu (red), Zns: Cu, Al (green), Z S A Cl (bl )ZnS: Ag, Cl (blue)

- 38” prototype display showing a uniform and stable image

• Lighting Element- Phosphor screen printed on the inner surface of the glass

and backed by

CheMin XRD/XRF instrument, intended for quantitative mineralogy of Venus surface (1 liter 2Venus surface (1 liter, 2 kg, 5 watts).

• Surface analysis on planetary surfaces

Miniature carbon nanotube field emission X-ray tube

IMPACT: 10 X Reduction in Science Instrument Mass

• More & more components are packaged in smaller spaces whereMore & more components are packaged in smaller spaces where electromagnetic

interference can become a problemEx: Digital electronics coupled with high power- Ex: Digital electronics coupled with high power

transmitters as in manymicrowave systems or even cellular phone systems

• Growing need for thin coatings which can help isolate critical components from

other components of the system and external world

• Carbon nanofibers have been tested for EMI shielding; nanotubes have potential

as well- Act as absorber/scatterer of radar and microwaveAct as absorber/scatterer of radar and microwave

radiation- High aspect ratio is advantageous- Efficiency is boosted by small diameter Large d will

• Hi h p t r ti ll p r l ti n t l r mp iti n th n ph• High aspect ratio allows percolation at lower compositions than sph(less than 1% by weight)

l i h l i il d i l• Neat polymer properties such as elongation to failure and optical tare not decreased.

• ESD Materials: Surface resistivity should be 1012 - 105 Ω/sq- Carpeting, floor mats, wrist straps, electronics packaging

• EMI Applications: Resistivity should be < 105 Ω/sq- Cellular phone parts- Frequency shielding coatings for electronicsFrequency shielding coatings for electronics

• High Conducting Materials: Weight saving replacement for metalsAutomotive industry: body panels bumpers (ease of painting w- Automotive industry: body panels, bumpers (ease of painting wconducting primer)

- Interconnects in various systems where weight saving is crit

• Carbon nanotubes can be embedded in high performance composites as reinforcing agents and strain

ll i f d t ti it isensors allowing for nondestructive monitoring and distributed sensing of large structures

• SWNT/PVOH fibers with 60% wt SWNT ⇒ tensile strength similar to spider silk-These fibers can be woven into textiles to create

garments with sensing and EMI shielding capabilitiesshielding capabilities.

• Thermally conductive coatings (with nanotubesThermally conductive coatings (with nanotubes incorporated into polymers)

-Deicing aircrafts in cold weather by applying

V.S. Vavilov (1994)

• High single crystallinity ⇒ Low defect density grain boundary• High single crystallinity ⇒ Low defect density, grain boundary free

• Well-defined surface structuralWell defined surface structuralproperties ⇒ Enhanced interfacial engineering

• Predictable electron transportPredictable electron transportproperties ⇒ Predictable device performance

• Unique physical properties dueq p y p pto quantum confinement effects ⇒ Enhancement in device

characteristics

• Tunable electronic properties ⇒ Enhancement in device characteristics

by doping

• Truly bottom-up integration ⇒ Innovative fabrication schemesapproach

R d l li d

SiC

• Randomly aligned• Non-uniform length• Non-uniform diameter

Mostly on non conducting GaN

SiC • Mostly on non-conducting substrates

• Direct device integration almost impossible

Si

almost impossible

Si

• Planar configurationPlanar configuration• Lack of direct device integration• Lack of processing compatibility• Lack of high density alignment g y g• Poor reproducibility• Successful cases limited

(0001)

- Grown by Vapor-Liquid-Solid (VLS) Approach

C b th l d ti f i l hit- Carbothermal reduction of germanium plus graphite (1:1)

Nanowire-based Vertical Surround Gate FETNanowire based Vertical Surround Gate FET

Nanowire-based Vertical Surround Gate FET

n-NWVFET p-NWVFET

Nanowire based Vertical Surround Gate FET

The ConceptThe Concept

• Nanopore in membrane (~2nm diameter)opo e e e ( d a ete )

• DNA in buffer

• Voltage clampVoltage clamp

• Measure current

G. Church, D. Branton, J. Golovchenko, HarvardD. Deamer, UC Santa Cruz

GGA A A A

G

C CTT

GG G

Present Future

• Tree-like polymers, branching out from a central core and subdividing into hierarchical branching units

- Not more that 15 nm in size, Mol. Wt very high- Very dense surface surrounding a relatively

hollow core (vs. the linear structure in traditionalo ow co e (vs. t e ea st uctu e t ad t o a polymers)

• Dendrimers consist of series of chemical shells built on a

Courtesy of: http://www.uea.ac.uk/cap/wmcc/anc.htm

Dendrimers consist of series of chemical shells built on a small core molecule

- Surface may consist of acids or aminos ⇒ means to attach funct⇒ control/modify properties⇒ control/modify properties

- Each shell is called a generation (G0, G1, G2….)- Branch density increases with each generation

C i i i d h l b d l- Contains cavities and channels ⇒ can be used to trap guest molvarious applications.

1. Biomedical/Pharmaceutical• Drug delivery _ number of different drugs can be encapsulated in dendri

injected into the body for delivery- Incorporating sensors would allow release of drugs where needed

• Gene Therapy- Issue is getting enough genes into enough cells to make a differencIssue is getting enough genes into enough cells to make a differencviruses for this triggers immune reactions. Dendrimers provide an alternative without triggering immune response

C Th• Cancer Therapy

• Antimicrobial and Antiviral Agents

2 Ch mi l Indu tr2. Chemical Industry• Catalysis

- Encapsulating metal catalyst particles and preventing agglomorationsurface area highsurface area high

• Purification/chemical reaction scavenging

N t h l i bli t h l th t ill i t• Nanotechnology is an enabling technology that will impact electronics and computing, materials and manufacturing, energy, transportation….gy, p

• The field is interdisciplinary but everything starts with material science Challenges include:material science. Challenges include:

- Novel synthesis techniques- Characterization of nanoscale properties- Large scale production of materials- Application development

• Opportunities and rewards are great and hence, tremendous worldwide interest

• Integration of this emerging field into engineering and science curriculum is important to prepare the future