Expectations from the New World

NanoScience & NanoTechnologyNanoScience & NanoTechnology

Expectations from the New World

• Health

• Wealth

• Peace

As per the

Nanotechnology Initiative (NNI) of the National Science Foundation (NSF)

major implications are expected for

Affected Areas Impact Economical impact per year (in 10 to 15 years)

Manufacturing - Nanostructuring - Materials properties

$ 340 billion per year

Electronics - Materials - Structure


Pharmaceuticals $ 180 billion per year Chemical Plants - Nanostructured catalyst $ 100 billion per year Transportation - Safer and lighter vehicles

(based on materials and electronics)


Energy (Sustainability) - Reduction in energy use $ 100 billion per year (on savings)

M. C. Roco et al., Societal Implications of Nanoscience and Nanotechnology (Kluwer Acad. Publ., Dordrecht, 2001).

• Molecule:


Bottom-up ApproachTo synthesize material from atoms or molecules by means of “self-assembly”.

Si13

Spectroscopic Regions:

Ultra-small clusters: 10 – 100 atoms show strongly deviating molecular structures from the bulk.

E.g.: Si13 (metallic-like close packing)

Si45 (distorted diamond lattice)

Si45

U. Rothlisberger, et al., Phys. Rev. Lett. 72, 665 (1994).

Small clusters: ~103 - 106 atoms (bulk-like structure) but possess discrete excited electronic states if cluster diameter less than the bulk Bohr radius, ao, (typically < 10 nm)

2

2

2

e

om

h

a

• Quantum Dot:

Cont. Spectroscopic Regions:


• Polariton: Large “clusters”: > 106 atoms. In this regime the particle acts as an optical cavity (micro-cavity) due to light matter coupling

-> Polariton Laser

Kinetic Regions:Consideration of the transport properties in the media.

In semiconductors one experiences in nanocrystals:

< 106 atoms: Molecular decay kinetics

> 106 atoms: Many body kinetics (Auger recombinations etc. )

-> important in Si nanocrystal luminescence


Quantum Confinement

Quantum Devices and Quantum Effects

200 200 nm2 SFM image of InAs dots on GaAs

R. Notzel, Semicond. Sci. Techn. 11, 1365 (1996).

White and blue emitting solid-state devices based on quantum dots developed in Sandia National Laboratories.

Sandia National Laboratories, (2003).



Molecular Devices / Gates

Use of nanotubes in Field-Effect Transistors (FET)

IBM: Applied Physics Letters, vol 73, p. 2447 (1998)

Current-Voltage Characteristicsat room temperature (290 K) acts like a FET

at 77K: acts like a single electron transistor

(SET)

100 nm MOSFET (gm=570 mS/mm, fT=110 GHz).

In gates with 2 nm width it has been shown that the channel conductance is quantized in steps of 2e2/h.

D. M. Tennant, in Nanotechnology, edited by G. Timp (AIP Press, Springer Verlag, New York, 1999), p. 161.

Top-down ApproachNanoScience & NanoTechnologyNanoScience & NanoTechnology

To create and investigate the Nanoscale by means, for instance, of lithographical methods and high sensitive measurements.

Nanofabrication and Lithography


Emission of atomic hydrogen (Lyman- line)

Nearfield Exposure (not wavelength limited)

Photolithographic contact printing with phase shifting mask.

V. Liberman, M. Rothschild, P. G. Murphy, et al., J. Vac. Sci. Techn. B 20, 2567 (2002).

Lithographical Techniques


• Photo emission

• X-rays

• Electrons

• Ions

• SPM (not sketched, see below)

Submicrometerarrays of biomolecules as screening tools in proteomics and genomics.

Dip-Pen NanolithographyNanoScience & NanoTechnologyNanoScience & NanoTechnology

Ki-Bum Lee, JACS 2003, 125, 5588

Lithographical TechniquesNanoScience & NanoTechnologyNanoScience & NanoTechnology

for 50 % coverage (e.g., equal lines and spaces)

Optical step and repeat reduction printing

Challenges be met by current laboratory methods before they can be seriously considered

D. M. Tennant, in Nanotechnology, edited by G. Timp (AIP Press, Springer Verlag, New York, 1999), p. 161.

SPM


Nanoscale Imaging

Lipid Bilayer (LB Technique) on silicon oxide surface

Self-assembly of C18ISA on HOPG surface

SFM Study STM Study

S. De Feyter et al. in Organic Mesoscopic Chemistry, Ed. H. Masuhara et al., Blackwell Science 1999

R.M. Overney, Phys. Rev. Lett. 72, 3546-3549 (1994)

e.g. Film Thickness Limitation for the Photoresist in Photo-Lithography

The absorption coefficient imposes a max. thickness on the photoresist

T. M. Bloomstein, M. Rothschild, R. R. Kunz, et al., J. Vac. Sci. Techn. B 16, 3154 (1998).


Constraints in the New WorldThe Nanoscale is not only about small particles or small patterns but also about material limitation.

Other constraints for the PhotoresistIdeally:

A photoresist consists of a Polymer Matrix (e.g., PMMA) consisting of acid-labile groups and “homogeneously” distributed photoacid generators (PAG).

Photoresist with “Homogeneous” PAG distribution

SUBSTRATE


However, the reality of photolithographical imperfections (see below) suggests PAG distribution inhomogeneities.

T - tops Fat Bottoms


Spincoated Ultrathin FilmsIn polymeric systems, the molecular mobility is of particular concern if length scales below ~ 100 nm are involved

Illustrated with a study on:

tPEP 400 nm

Scan Size

10 10 m2

Scan Size

50 50 m2

tPEP 4 nm


Spin Coating Effect on Polymer Mobility below the 100 nm Film Thickness Regime

R.M. Overney et al., J. Vac. Sci. Techn. B 14(2), 1276-1279 (1996).

Dewetting and Spincoated Ultrathin Films

Dewetting Velocity

0 100 200 300 400

1.0

0.8

0.6

0.4

0.2

0.0

Nor

mal

ized

Lat

eral

Fo

rce

LateralForce

Dewetting hole velocities as function of the PEP film thickness

(▲ Poly(vinyl pyridine (PVP) screener to silicon substrate)

Lateral Force and dewettingkinetics suggest the formation of arheologically modified boundary layer of PEP towards the siliconsubstrate → “glassification” of PEP

PEPSi


R.M. Overney et al., J. Vac. Sci. Techn. B 14(2), 1276-1279 (1996).

Confined Boundary Layer of Spincoated Ultrathin Films

BU

LK

SIC

ZS

RZ

BU

LK

SIC

Z

Mean field theories consider the effect of pinning at interfaces only within a pinning regime (0.6 – 1 nm « Rg)

~ 100 nm

~ 1 nm

Lateral Force and Dewetting Studies suggest that the PEP phase is rheological modified within a 100 nm boundary region that exceeds by two orders of magnitude the theoretically predicted pinning regime of annealed elastomers at interfaces with negative spreading coefficient.


Entanglement Strength and Spincoated Ultrathin Films

• No transition, only 2D chain sliding is observed on films < ~ 20 nm thick (ICZ).

• Transition load increases with thickness up to ~230nm (SRZ).

• Transition load is constant for films thicker than ~230 nm (BULK).

Entanglement strength studies on poly (ethylene-propylene) (PEP) films revealed interfacial confinement effects on the transition load from 3D viscous shear to 2D chain sliding.

(a) low load sliding regime(b) high friction coefficient 1 = 2.1 3D flow(c) low friction coefficient 2 = 0.3 2D sliding

Transition Point Pt Entanglement Strength

t = 520 nm


C. K. Buenviaje, S. Ge, M. Rafailovich, J. Sokolov, J. M. Drake, R. M. Overney,

Confined Flow in Polymer Films at Interfaces, Langmuir, 19, 6446-6450, (1999).

Structural Model• At a thickness of 20 nm the polymer films are in a gel-like

state (“porous structure”). [ X-ray reflection data of L.W. Wu]

Chains are fully disentangled due to high shear stresses.• The polymers adjacent to the sublayer diffuse into the porous

structure of the sublayer. [Neutron Reflectivity studies on polystyrene, X. Zheng et al. Phys. Rev. Lett. 74, 407 (1995)]

two-fluid system• The anisotropy generated in normal direction recovers slowly

over a distance of about 7-10 Rg.

• Temperature annealing causes the gel to shrink and to “freeze” the anisotropic boundary structure. [Neutron Reflectivity studies on polystyrene, X. Zheng et al. Phys. Rev. Lett. 74, 407 (1995)]

Interfacially Confined Spincoated Ultrathin Films


85

90

95

100

105

0 50 100 150 200 250 300FILM THICKNESS, d ( nm )

Tg (

oC

)

12.0 kDa PS

FOX-FLORY (BULK)

BULKS ICZ SRZ

85

90

95

100

105

0 50 100 150 200 250 300

FILM THICKNESS, d ( nm )

Tg (

oC

)

12.0 kDa PS17.5 kDa PS-BCB21.0 kDa PS-BCB

30

80

130

180

10 14 18 22MW (kDa)

dM

AX (

nm

)

85

90

95

100

105

110

115

0 50 100 150 200 250 300

FILM THICKNESS d (nm)

Tg (

oC

)

CROSSLINKED Tg

INITIAL Tg

Engineering with Molecular Weight

Engineering with Crosslinking

Material Property EngineeringNanoScience & NanoTechnologyNanoScience & NanoTechnology

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Expectations from the New World