J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 1

NANOTECHNOLOGYPart 2. Electronics

• The Semiconductor Roadmap

• Energy Quantization and Quantum Dots

• Conductance Quantization

• Molecular Electronics

• Scanning Tunneling Microscopy

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 2

The Semiconductor Roadmap

www.iso.gmu.edu

The SIA (Semiconductor Industry Association) roadmap projects a continuing miniaturization of silicon semiconductor devices for the next 15

years. International Technology Roadmap for Semiconductors (ITRS):

public.itrs.net

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 3

Moore's Law

www.physics.udel.edu

Gordon Moore, co-founder of Intel, 1965

dot.che.gatech.edu

Hg arc lamp 0=436, 365, 248 nm, KrF laser 0=248 nm, ArF laser 0=193 nm, F2 laser 0=157 nm

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 4

Future Lithography Systems

Synchrotron radiation based lithography Lawrence Berkeley National Laboratory (2002)

Prcatically all materials absorb strongly between =157 and 14 nm

Extreme UV laser based plasma sources =10-14 nm, mirrors, reflection masks

X-ray X-ray tube, synchrotron ~1 nm, Fresnel lenses

Ion projection, (Focused Ion Beam)

EUV lithography unit

oemagazine.com

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 5

Electronic Elements: Challenges

• scaling rules

• gate dielectric silicon-dioxide ~ 1.5 nm=> high-k materials as Al2O3, TiO2,...

• dopant fluctuations, noise

• thermodynamics

• quantum effects: discretization and tunneling

• logic circuit architecturewww-hpc.jpl.nasa.gov

www.unine.ch

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 6

Possible Future Directions

Advanced MOSFET concepts

3D architecture

Superconducting electronics

Single electron devices

Spintronics

Quantum computing: qubits

DNA computing

from [3]

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 7

Energy Quantization

from [2]

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 8

Quantum Dots (1)

quantum dot size = the energy determining parameter

)(

225.11

22 0 eVEmEmm

h

mE

h

mm

e ===

Bawendi Group, MIT

II-VI as CdSe, III-V as GaAs, Si, Ge,...

22

222 1,

22ee

Em

h

m

kE

∝Δ==

h

Al e=0.36 nm

GaAs e=21.2 nm

2D GaAs e=47.3 nm

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 9

Quantum Dots (2)

Coloumb blockade

Single electron devices, single electron transistor (SET)

'Artificial atoms' with tuneable electronic properties

(simulate atom shell structure, quantum decoherence, break radial

symmetry => quantum chaos, combine QD's to make artifical bulk

materials,... )

Canditates for quantum computing

2

2

2,

e

hRTk

C

eW tunnelBC >>>>=

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 10

Quantum Dots (3)

Sketch of vertical QD

L.Kouwenhoven, C.Marcus, Physics World June 1998, p.35

(a) Current flow through a quantum dot structure, (b) analogon in terms of 2D circular orbits, (c) periodic table for artifical 2D atoms

Eadd=e2/C+ΔE

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 11

Quantum Dots (4)

www.nanoscience.unibas.ch

Lateral QD on AlxGa1-xAs / GaAs

L.Kouwenhoven, C.Marcus, Physics World June 1998, p.35

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 12

Conductance Quantization 1

Vh

eJ

eVh

edE

h

edJ

EvELDOS

dEELDOSdn

EvdnedJ

V

V

D

D

2

1

1

2

)(22

)(

1)(

)(

)(

2

1

=

−−=−=

=

=↔↔−=

hπ

Ω= ke

h9.12

2 2Unil. Leiden, NL

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 13

Conductance Quantization 2

meso.deas.harvard.edu/spm.html

Thermal conductance quantization

M.Worloch et al., Appl.Phys.Lett. 70, 2687 (1997)

h

TkG Btherm 3

22π=

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 14

Molecular Electronics (1)

Towards the ultimate (?) miniaturization by using single organic molecules as electronic switches and storage elements

electronic properties can be adjusted via the chemical structure

size, speed, power consumption, cost

individuals absolutely identical

Hybrid molecular electronics

Mono-molecular electronics

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 15

Molecular Electronics (2)

Electrodes: covalent vs. van der Waalsstability vs. self-organization

Wires: delocalized π-systems, e.g., polyene

Diodes: molecules with donor-acceptor substructure

www.ifm.liu.se

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 16

Molecular Electronics (3)

from [6]

Switches and storage elements: metalstable molecules

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 17

Scanning Tunneling Microscopy (STM) 1

stm1.phys.cmu.edu

Example:Si(111)7x76x6 nm2

SEM imageof W tip

www.nottingham.ac.uk/

nprl.bham.ac.uk

)exp( sAs

VJ φρ −=

ρLDOSwork function

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 18

STM (2)

from [3]

STM on InP Quantum corrals

M.F.Crommie et al., Science 262, 218 (1993)

M.F. Crommie, Surf. Rev. Lett. 2, 127 (1995)

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 19

Scanning Tunneling Spectroscopy

Vd

JdV

V

J

dV

dJ

ds

Jd

JJAs

J

ds

dJ

ln

ln)(

ln2

∪?=

√↵

∪?

∪−−=

ρ

φ

φφ

)exp( sAs

VJ φρ −=

cond

-mat

.phy

s.hu

ji.ac

.il

5 nm InAs nanoparticles

J.R.Krenn – Nanotechnology – CERN 2003 – Part 2 page 20

Conclusion

Conventional electronics meets its limits within 15 yrs

Novel electronic device types are to be expected

Molecular electronics has yet to prove its feasibility