Nano Materials Chapter 3: Fabrication

Nanomaterials1

Nano Materials

Chapter 3: Fabrication

Nanomaterials2

Contents

q Introduction

q Basics

q Synthesis of Nano Materials

q Fabrication of Nano Structure

q Nano Characterization

q Properties and Applications

Nanomaterials3

Fabrication of Nano Structure

q Lithographic techniques

q Nanomanipulation and nanolithography

q Soft lithography

q Self-assembly of nanoparticles or nanowires

q Other methods

q Quantum dots

Nanomaterials4

Fabrication of Nano Structure-lithography

Lithography:

- Photolithography

- Phase shift optical lithography

- Electron beam lithography

- X-ray lithography

- Focused ion beam lithography

- Neutral atomic beam lithography

Feynman:

How do we write small?The next question is: How do we write it? We have no standard technique to do this now. But let me argue that it is not as difficult as it first appears to be. We can reverse the lenses of the electron microscope in order to demagnify as well as magnify. A source of ions, sent through the microscope lenses in reverse, could be focused to a very small spot. We could write with that spot like we write in a TV cathode ray oscilloscope, by going across in lines, and having an adjustment which determines the amount of material which is going to be deposited as we scan in lines. This method might be very slow because of space charge limitations. There will be more rapid methods. We could first make, perhaps by some photo process, a screen which has holes in it in the form of the letters. Then we would strike an arc behind the holes and draw metallic ions through the holes; then we could again use our system of lenses and make a small image in the form of ions, which would deposit the metal on the pin. A simpler way might be this (though I am not sure it would work): We take light and, through an optical microscope running backwards, we focus it onto a very small photoelectric screen. Then electrons come away from the screen where the light is shining. These electrons are focused down in size by the electron microscope lenses to impinge directly upon the surface of the metal. Will such a beam etch away the metal if it is run long enough? I don't know. If it doesn't work for a metal surface, it must be possible to find some surface with which to coat the original pin so that, where the electrons bombard, a change is made which we could recognize later.

Feynman:

There is no intensity problem in these devices---not what you are used to in magnification, where you have to take a few electrons and spread them over a bigger and bigger screen; it is just the opposite. The light which we get from a page is concentrated onto a very small area so it is very intense. The few electrons which come from the photoelectric screen are demagnified down to a very tiny area so that, again, they are very intense. I don't know why this hasn't been done yet! That's the Encyclopaedia Brittanica on the head of a pin, but let's consider all the books in the world. The Library of Congress has approximately 9 million volumes; the British Museum Library has 5 million volumes; there are also 5 million volumes in the National Library in France. Undoubtedly there are duplications, so let us say that there are some 24 million volumes of interest in the world. What would happen if I print all this down at the scale we have been discussing? How much space would it take? It would take, of course, the area of about a million pinheads because, instead of there being just the 24 volumes of the Encyclopaedia, there are 24 million volumes. The million pinheads can be put in a square of a thousand pins on a side, or an area of about 3 square yards. That is to say, the silica replica with the paper-thin backing of plastic, with which we have made the copies, with all this information, is on an area of approximately the size of 35 pages of the Encyclopaedia. That is about half as many pages as there are in this magazine. All of the information which all of mankind has every recorded in books can be carried around in a pamphlet in your hand---and not written in code, but a simple reproduction of the original pictures, engravings, and everything else on a small scale without loss of resolution.

Nanomaterials7

Feynman:

What would our librarian at Caltech say, as she runs all over from one building to another, if I tell her that, ten years from now, all of the information that she is struggling to keep track of--- 120,000 volumes, stacked from the floor to the ceiling, drawers full of cards, storage rooms full of the older books---can be kept on just one library card! When the University of Brazil, for example, finds that their library is burned, we can send them a copy of every book in our library by striking off a copy from the master plate in a few hours and mailing it in an envelope no bigger or heavier than any other ordinary air mail letter. Now, the name of this talk is ``There is Plenty of Room at the Bottom''---not just ``There is Room at the Bottom.'' What I have demonstrated is that there is room---that you can decrease the size of things in a practical way. I now want to show that there is plenty of room. I will not now discuss how we are going to do it, but only what is possible in principle---in other words, what is possible according to the laws of physics. I am not inventing anti-gravity, which is possible someday only if the laws are not what we think. I am telling you what could be done if the laws are what we think; we are not doing it simply because we haven't yet gotten around to it.

Fabrication of Nano Structure-lithographyq Lithography- photoengraving- process of transferring a pattern into a reactive polymer film, termed at resist,

which will subsequently be used to replicate that pattern into underlyingthin film or substrate

Lithography stone and mirror-image print of a map of Munich.

http://upload.wikimedia.org/wikipedia/commons/5/59/Litography_negative_stone_and_positive_paper.jpg

http://upload.wikimedia.org/wikipedia/commons/5/59/Litography_negative_stone_and_positive_paper.jpg


q Photo-lithography- basic steps

- shadow printing- contact printingproximity printing

projection printing


q Photo-lithography- diffraction limits maximum resolution and minimum size

min2b 3 ( )2

ds

2b: grating periods: gap width: wavelengthd: photoresist thickness

- for hard contact printing, s=0, =400 nm, d=1 mm, 2bmin ~ 1mmmaximum resolution- seldom achieved because of dust on the substrate andnon-uniformity of resist thickness

Proximity printing- resolution decreases with increasing gapdifficulty in the control of constant gap space


Nanomaterials12


q Photo-lithography- projection printing- lens- lens imperfection and diffraction

- resolution- Rayleigh criterion~ /2 (200 nm)- for higher resolution, short wavelength and larger NA- for high NA, small depth of focus- sensitive to slight

variations in the thickness and absolute position ofthe resist layer

1 2

2, , sin

k kR DOF NA n

NA NA

k1: 0.61 (0.6~0.8)

k2: 0.5

: wavelength

NA: numerical aperture (~0.5)

n: refractive index(=1)


q Photo-lithography- deep ultra-violet lithography (DUV)

248 nm193 nm

157 nm

436 nm

Nanomaterials14


q Photo-lithography- extreme ultra-violet lithography (EUV)

(problems) strong absorption (all reflective optic system instead of refractivelens)

mirror- multilayer structureextremely high precision metrology is required.EUV source


q Photo-lithography- resist- three components- inactive resin (base)

photoactive compound (PAC)solvent

- ex) positive- diazonaphthoquinone (DNQ)

base: novolac

PAC: diazoquinone

decomposition upon exposure

soluble in developer

insoluble


q Phase-shifting photo-lithography- phase shifter or phase mask with thickness

phase shift by 180o- destructive interference between wave diffracted fromadjacent apertures- higher resolutiondifficult to apply to random pattern

2( 1)t

n


q Phase-shifting photo-lithography- elastomeric phase mask PDMS


q Resolution enhancement technique

T. Ito, Nature 406 (2000) 1027.

Nanomaterials19


q Electron beam lithography- focused beam of electrons- fabrication of features as small as 3-5 nm- limited by forward scattering of the electrons in the resist and back scattering

from the underlying substrate- scanning or projecting- very small throughput

Substrate

Resist

Focused

e-beam

PSF (point spread function)


q Electron beam lithography- SCALPEL (scattering angular-limited projection electron-beam lithography)

Si3N4

Cr or W back focal plane


q Electron beam lithography- PREVAIL (projection reduction exposure with variable-axis immersion lenses)

H.C. Pfeiffer et al.


q X-ray lithography- X-ray: l= 0.04~0.5 nm- difficult to focus X-ray proximity printing- mask: Si, Si3N4, SiC (transmitting)+ Au, W, Ta (absorbing)- source: electron impact, synchrotron- mirror: multilayer

Synchrotron radiation (0.65~1.2 nm, 0.7 nm)2-mm thick SiN membrane, 0.65 mm thick Ta absorber

Nanomaterials23


q X-ray lithography- ex) synchrotron radiation 1.1 nm

electroplated Au/SiC absorber and sputtered W/SiC absorberPMAA, PMAA/MAA resist on Si or Cr/Au coated Si

G. Simon, J. Vac. Sci. Tech. B15 (1997) 2489.

Nanomaterials24


q Focused ion beam (FIB) lithography- scattering of ions in MeV range- several order of magnitude less than electrons

- Ga, Au-Si-Be alloys- long lifetime and high stability- high resist exposure sensitivity, negligible ion scattering in the resist,

low back scattering from the substrate- magnetic nanostructure- less influenced by magnetic properties of material- direct etching and deposition capability

Nanomaterials25


q Focused ion beam (FIB) lithography- deposition - etching

physical sputter chemical assisted

Nanomaterials26


q Focused ion beam (FIB) lithography- nanomagnetic probe

etching depositionNi45Fe55 W


q Neutral atomic beam lithography- neutral atom- no space charge, divergent- neutral atom + laser light focusing- direct patterning- neutral chromium atoms

J.J. McClelland, Science, 262 (1993) 877.

Nanomaterials28


q Neutral atomic beam lithography- patterning of a special resist- argon atom

dodecanethiolate

ferricyanide etch

K.K. Berggren, Science, 269 (1995) 1255.

29


q Neutral atomic beam lithography- neutral chromium atoms

B. Brezger, J. Vac. Sci. Tech. B15 (1997) 2905.


q Neutral atomic beam lithography- neutral chromium atoms

B. Brezger, J. Vac. Sci. Tech. B15 (1997) 2905.


q Technological trends in lithography

T. Ito, Nature, 406 (2000) 1027.

Nanomaterials32

Fabrication of Nano Structure-Nanomanipulation

q STM- xenon atoms on an single crystal nickel surface- parallel processes- field assisted diffusion

sliding- perpendicular process- transfer near or on contact

- field evaporation-electromigration

D.E. Eigler, Nature, 344 (1990) 524.


q STM- chemical reaction


q AFM- mechanical pushing

C. Baur, nanotechnology, 9 (1998) 360.

35

Fabrication of Nano Structure-Nanolithography

□ STM- field evaporation by bias pulse on Si(111)

Nanomaterials36

Fabrication of Nano Structure-nanolithography

□ AFM- scratching

A. Notargiacomo, Nanotechnology, 10 (1999) 458.

Al

Ti

37


q AFM- scratching the native oxide covered Si by AFM (diamond-coated tip) and

electrodeposition of Cu

Nanomaterials38


q AFM- nanoshaving by AFM+ surface initiated polymerization

M. Kaholek, Nanoletter, 4(2004)373.

thiol initiatorpoly(N-isopropylacrylamide)

Nanomaterials39

Fabrication of Nano Structure-soft lithography

q Soft lithography- a set of non-photolithographic techniques for microfabrication that are based on

printing of SAMs and molding of liquid precursors- reviews

Y. Xia, Chem. Review, 99, 1823 (1999).Y. Xia, Angew. Chem. Int. Ed. 37, 550 (1998).Y. Xia, Annu. Rev. Mater. Sci. 28, 153 (1998).M. Geissler, Adv. Mater. 16, 1249 (2004).


q Microcontact printing- use an elastomeric stamp with relief on its surface to generate SAMs on the surface of

planar and curved substrate- SAM- highly ordered molecular assemblies that form spontaneously by chemisorption of

functionalized long chain molecules on the surface of appropriate substrateex) alkaneithiolates on Au, Ag, Cu


q Microcontact printing- procedures


q Microcontact printing- examples

43


q Molding- micromolding in capillary

44


q Molding- microtransfer molding

PU on silver Epoxy on glass

Glassy carbon

Epoxy on glass Epoxy on glass

Glass

45


q Molding- replica molding

46


q Nanoimprint

I. Maximov, 13 (2002) 666.

above Tg

Cr stamp PMMA

S. Zankovych, Nanotechnology, 12 (2001) 91.

ZEP520A7 resistCr mask

Nanomaterials47


q Dip-pen lithography- direct writing based on AFM and works under ambient conditions- chemisorption acts as a driving force for moving the molecules from AFM tip to the

substrate via water filled capillary when the tip is scanned across a substrate

ODT on Au(111)/mica

R.D. Piner, Science 283 (1999) 661.

48


q Dip-pen lithography

D.S. Ginger, Angew. Chem. Int. Ed. 43(2004) 30.

Nanomaterials49

q Ink Jet Printing- an attractive technique for depositing materials on surfaces with a good

spatial control

A) Droplet during inkjet printing

B) Patterning on a substrate

C) Pillar formation of lead zirconium titanate

B-J de Gans, Adv. Mater. 16 (2004) 203.

A

BC


50

q Ink Jet Printing


AB

A) Dependence on the viscosity of solution

B) Patterning on a substrate

C) transistor fabrication (gate)using ink jet printing

B-J de Gans, Adv. Mater. 16 (2004) 203.

C

Nanomaterials51

Fabrication of Nano Structure-assembly

q capillary force- lateral capillary force deformation of liquid surface

6

1

2

1

for floating force

( )

for immersion force

( )

RF K R

F R K R

1

: interfacial tension between air and liquid

R: radius of particle

L: interparticle distance

K (R): modified Bessel function

two similar particles

light and heavy hydrophilic and hydrophobic

P.A. Kralchevsky, Curr. Opin. Colloid Interf. Sci. 6(2001) 383.

52


q capillary force- colloidal crystal multilayer, SiO2 alcosol

P. Jiang, Chem. Mater. 11 (1999) 2132.

53


q capillary force- patterned colloid deposition by electrostatic and capillary force

P. Jiang, Chem. Mater. 11 (1999) 2132.

54


q Dispersion interaction- gold nanocrystals (1.5~6 nm) capped with covalently bound linear alkylthiols

size dependence of van der Waals dispersional attraction between nanoparticles

P.C. Ohara, Phys. Rev. Lett. 75 (1995) 3466.

6

1

dispersion interaction

at larger D

at small D

V D

V D

P.C. Ohara, Angew. Chem. Inter. Ed. Engl. 36 (1997) 1078.

Nanomaterials55


q Dispersion interaction- self-organization of CdSe nanocrystallites into 3-D semiconductor quantum dot

superlattice (colloidal crystals)

C.B. Murray, Science 270 (1995) 1335.

56


q Shear force assisted assembly- GaP, InP, Si NWs in ethanol solution

- passing suspension through fluidic channelsformed between PDMA and a flat surface

Y. Huang, Science 291 (2001) 630.

57


q Electric field assisted assembly- Au nanowires

- electrically isolated electrodes- 1.0x104~1.4x105 V/m

P.A. Smith, Appl. Phys. Lett. 77 (2000) 1399.

Nanomaterials58


q Electric field assisted assembly- InP

D. Huang, Nature, 409 (2001) 66.58

Nanomaterials59


q Covalently linked assembly- Au and Ag

R. Griffith, Science 267 (1995) 1629. T. Vossmeyer, Angew. Chem. Int. Ed. Engl. 36 (1997) 1080.

Nanomaterials60


q Covalently linked assembly- microcontact printing of Pd

- selective electroless deposition of Cu

P.C. Hidber, Langmuir, 12 (1996) 1375.

61


q Template assisted assembly- PS beads assembled in etched Si (100)

Y. Yin, J. Am. Chem. Soc. 123 (2001) 8718.

62 10nm

q 3-D Patterning Techniques

A) two photon polymerization in a polymer resist

B) holographic lithography in a polymer resist

C) photolithography with a gray-scale mask

D) woodpile lattice fabricated in a layer-by-layer fashion.

E) Opaline lattice of polystyrene beads self-assembled between two flat substrates

F) Silica inverse opal that was fabricated by templating a sol-gel precursor against an polymer opaline lattice, followed by selective removal of the beads.

Fabrication of Nanostructure – 3D Patterning

Adv. Mater. 2000, 16, 1250

63 10nm

q Writing with a focused laser or electron beam- carving of a surface by ablating the material with a focused beam in a serial manner- laser-induced deposition of precursor compound- photoinduced polymerization of a liquid prepolymer


64 10nm

q Holographic patterning


- 2-beam interference patterns

D. Kim, Appl. Phys. Lett. 66 91995) 1166.

- 4-beam interference patterns

M. Campbell, Nature, 404 (2000) 53.

65 10nm

q Holographic patterning


M. Campbell, Nature, 404 (2000) 53.

S. Yang, Chem Mater. 14 (2002) 2831.

Nanomaterials66 10nm

q Layer by layer fashion


J.A. Lewis, Materials Today, 7 (2004) 32.

Nanomaterials67 10nm



G. M. Gratson, Nature, 428 (2004) 386.

68 10nm



D. Therriault, Nature Mater. 2 (2003) 265.

69 10nm



S.Y. Lin, Nature, 394 (1998) 254.J.G. Fleming, Nature, 417 (2002) 52.

Nanomaterials70

q Colloidal Photonic Crystals- Opal


O.D.Velev, Curr. Opin. Colloid Interface Sci. 5 (2000) 56.

71



10nm

Experimental procedure to fabricate colloidal photonic crystals:

aqueous dispersions of colloidsinjected into the cell drying the cell peeling off the top substrate

S.H. Park, Adv. Mater. 10 (1998) 1028.

72



W.T.S. Huck, J. AM. Chem. Soc. 120 (1998) 8267.

73

q Inverse Opals


O.D. Velve, Nature, 389 (1997) 447.

Nanomaterials74

q Inverse Opals


Y.A. Vlasov, Adv. Mater. 11 (1999) 165.

Nanomaterials75

q Inverse Opals


P.V. Braun, Nature, 402 (1999) 603.

76

q Inverse Opals


A. Blanco, Nature, 405 (2000) 437.

Nanomaterials77

q Consolidation of nanomaterialsuppress the grain boundary migrationenhance grain boundary diffusion

q Two step sintering

I. W. Chen, Nature, 404 (2000) 168-171

Fabrication of Nanostructure – 3D Bulk

78

(a) (b)

500nm 500nm

Temperature(oC)

500600700800900100011001200

Relative density(%)70

75

80

85

90

95

100

SPS for 5 min.

SPS for 1h

Normal sinteringfor 1 h

q SPS (spark plasma sintering)fast heating rate

q Nonocrysatlline TiO2

Y. I. Lee, Mater Res Bull., 38 (2003)925

Fabrication of Nanostructure – 3D Bulk

79

Fabrication of Nano Structure

q Lithographic techniques

q Nanomanipulation and nanolithography

q Soft lithography

q Self-assembly of nanoparticles or nanowires

q Other methods

The End of Nanofabrication!!!!!!!

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Nano Materials Chapter 3: Fabrication