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NanoScience & NanoTechnology. Expectations from the New World. As per the Nanotechnology Initiative (NNI) of the National Science Foundation (NSF) major implications are expected for. Health Wealth Peace.

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expectations from the new world
NanoScience & NanoTechnologyExpectations from the New World

As per the

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

major implications are expected for

  • Health
  • Wealth
  • Peace

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

slide2
NanoScience & NanoTechnology
  • Quantum Dot:

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)

Bottom-up Approach

To synthesize material from atoms or molecules by means of “self-assembly”.

Spectroscopic Regions:

  • Molecule:

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)

Si13

Si45

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

slide3
NanoScience & NanoTechnology

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 devices and quantum effects
NanoScience & NanoTechnologyQuantum 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 dotsdeveloped in Sandia National Laboratories.

Sandia National Laboratories, (2003).

slide6
NanoScience & NanoTechnology

Molecular Devices / Gates

Current-Voltage Characteristics

Use of nanotubes in Field-Effect Transistors (FET)

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

at room temperature (290 K) acts like a FET

at 77K: acts like a single electron transistor

(SET)

slide7
NanoScience & NanoTechnology

Top-down Approach

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

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

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

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

nanofabrication and lithography
NanoScience & NanoTechnologyNanofabrication and Lithography

Emission of atomic hydrogen (Lyman-a 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).

slide9
NanoScience & NanoTechnology

Lithographical Techniques

  • Photo emission
  • X-rays
  • Electrons
  • Ions
  • SPM (not sketched, see below)
slide10
NanoScience & NanoTechnology

Dip-Pen Nanolithography

Submicrometerarrays of biomolecules as screening tools in proteomics and genomics.

Ki-Bum Lee, JACS 2003, 125, 5588

slide11
NanoScience & NanoTechnology

Lithographical Techniques

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

Optical step and repeat reduction printing

SPM

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

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

slide12
NanoScience & NanoTechnology

Nanoscale Imaging

SFM Study

STM Study

Self-assembly of C18ISA on HOPG surface

Lipid Bilayer (LB Technique) on silicon oxide surface

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

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

slide13
NanoScience & NanoTechnology

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 World

The Nanoscale is not only about small particles or small patterns but also about material limitation.

slide14
NanoScience & NanoTechnology

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

SUBSTRATE

Fat Bottoms

T - tops

Other constraints for the Photoresist

Ideally:

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

slide15
NanoScience & NanoTechnology

Spincoated Ultrathin Films

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

Illustrated with a study on:

slide16
NanoScience & NanoTechnology

Scan Size

50  50 mm2

tPEP 400 nm

Scan Size

10  10 mm2

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).

slide17
Dewetting and Spincoated Ultrathin Films

NanoScience & NanoTechnology

1.0

0.8

0.6

0.4

0.2

0.0

Normalized Lateral Force

0 100 200 300 400

Dewetting hole velocities as function of the PEP film thickness

Dewetting Velocity

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

Lateral

Force

PEP

Si

Lateral Force and dewetting

kinetics suggest the formation of a

rheologically modified boundary

layer of PEP towards the silicon

substrate → “glassification” of PEP

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

slide18
Confined Boundary Layer of Spincoated Ultrathin Films

NanoScience & NanoTechnology

BULK

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

~ 100 nm

SRZ

BULK

ICZ

~ 1 nm

ICZ

S

S

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.

slide19
Entanglement Strength and Spincoated Ultrathin Films

NanoScience & NanoTechnology

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.

t = 520 nm

Transition Point Pt

  • Entanglement

Strength

(a) low load sliding regime

(b) high friction coefficient

1 = 2.1 3D flow

(c) low friction coefficient

2 = 0.3 2D sliding

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).

  • 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).
structural model
Interfacially Confined Spincoated Ultrathin Films

NanoScience & NanoTechnology

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)]
material property engineering
NanoScience & NanoTechnologyMaterial Property Engineering

Engineering with Molecular Weight

Engineering with Crosslinking

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