7/27/2019 Fabrication Methods

1/14

TOP-DOWN & BOTTOM UP

Presented by: Shardul Agarwal (CH-9265)

7/27/2019 Fabrication Methods

2/14

TOP-

DOWN

building somethingby starting with a larger componentand carving away material.

BOTTOM UP buildingsomething by assembling smallercomponents.

These phrases were coined by the

Foresight Institute in 1989.

7/27/2019 Fabrication Methods

3/14

Conventional manufacturing processes are "topdown," in which material is produced in bulk butnot atomically precise.

The top-down approach often uses the traditional

workshop or microfabrication methods whereexternally controlled tools are used to cut, mill, andshape materials into the desired shape andorder. Micropatterning techniques, suchas photolithography and inkjet printing belong tothis category.

7/27/2019 Fabrication Methods

4/14

e.g. Photolithography, to make copper circuit on aflame retardant wafer

7/27/2019 Fabrication Methods

5/14

e.g. Nanosphere lithography - SEM images of a latexnanosphere mask and triangular gold nanoprisms

obtained by evaporating gold over colloidal mask.

7/27/2019 Fabrication Methods

6/14

Effect of increasing the electrolyte concentrationin formation of ordered array.

General principle of colloid lithography

7/27/2019 Fabrication Methods

7/14

It is a molecular manufacturing process to massproduce large atomically precise objects.

Bottom-up use the chemical properties of singlemolecules to cause single-molecule components to

self-organize or self-assemble into some usefulconformation,

rely on positional assembly.

These approaches utilize the concepts of molecularself-assembly and/or molecular recognition.

e.g. sol-gel synthesis, chemical vapor deposition,chemical precipitation.

7/27/2019 Fabrication Methods

8/14

Self-assembly of organic monolayers

Electric field aligning of nanowires

Nanoparticles by flame pyrolysis

7/27/2019 Fabrication Methods

9/14

e.g. Chemical Synthesis

Figure shows a highlysimplified scheme of theprincipal steps of nanosizedparticle formation in

solution

7/27/2019 Fabrication Methods

10/14

Top-down

Once Research and

Development ofmanufacturing line is

complete costs drop

Bulk production

Self-Assembly processes

Less product defectsand more homogeneous

chemical composition

Bottom-up

7/27/2019 Fabrication Methods

11/14

Contamination

Machine Cost

Complexity

Physical limits(diffraction)

Internal stresses

Surface imperfections Heat dissipation

Material wastage (etching)

Not very robust products

Lengthy process to

obtain nanoparticles

Forming complex

patterns and structures

Top-Down Bottom Up

7/27/2019 Fabrication Methods

12/14

Crystal imperfections

of top-down approach-cavities, irregularedges, wrinkly surface

7/27/2019 Fabrication Methods

13/14

7/27/2019 Fabrication Methods

14/14

NanotechResources at Stanford- Stanford NanofabricationFacility- snf.stanford.edu/research/nanotech.htm

Nanotechnology - Wikipedia, the free encyclopedia

Some Notes on Top Down vs. Bottom Up.-David R. Forrest, 5

September 2008 people.bath.ac.uk/acb40/Dreamweaver%20Website/nanomet

rologyandnanomanufacturing.html

www.gitam.edu/eresource/nano/nanotechnology/nanotechnology%20web%201.htm

NanoYou- fundamental concepts in nanoscience andnanotechnologies

Nanoscale materials in chemistry- Kenneth J Klabunde