Lecture 1

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NANOELECTRONICSNANOELECTRONICSbeyond beyond CMOSCMOS

David Pulfrey

2 Bourianoff04

NNI definition of NanotechnologyNNI definition of Nanotechnology

1 - 10 nm is betterBut Intel prefer ...

Lecture 1

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3 Bourianoff04

4 Moravec04

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functionaldensity

1960 2010 year

functional design

3- D

structural dimensions

nano

electr

onics

Goser04

Increasing the Integration LevelIncreasing the Integration Level

CMOS

6

NanotransistorsNanotransistors: the Candidates: the Candidates

• Molecular switches

• Spin FETs

• Single electron transistors

• Nanotube FETs

• Nanowire transistors

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Molecular ElectronicsMolecular Electronics

• Use few molecules instead of multi- material transistors• *Gates scaleable to densities of greater than 1012 gates per cm2.

Compare: 1fF at 1V ≈ 104 electrons

Approx 100 molecules

Human brain 1013 bytes

• Billions of identical molecules are easily formed• “Natural” self- assembly• Compositional flexibility of organic molecules• Tailor properties to achieve device functionality• *Memory density of 1015 bits per cm3.

*DARPA04

• Few electrons/bit - low power

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SelfSelf--assembled Molecular Switchassembled Molecular Switch

Self-assembly of moleculecontaining nitroamine redox centre

in nitride nanoporeNeutral Conductive anion Insulating

dianionChen99 2’-amino-4-ethynylphenyl-4’-ethynylphenyl-5’-nitro-1-benzenethiol

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SelfSelf--assembled reversible switchassembled reversible switch

MEC01

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Molecular electronics: prognosisMolecular electronics: prognosis

• "It's simply too early to commercialize molecular memory

technology at this point," he said.

• "The problem has turned out to be much more difficult that

we anticipated.

• I think it is very unlikely that we are going to see hybrid

molecular electronic and silicon systems anytime soon.

• It turns out that the processes are extremely difficult."

Chris Gintz, President, MECMarch 7, 2003

Gintz03

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SPINTRONICSSPINTRONICS

Morkoc04

Generic &inflated term -implies use or spin for information storage and manipulation

An extra degree of freedom

Nonvolatile and increased data storage

Faster data processing (10x) and low power (10-50x)

Addressing CMOS deficiencyPerhaps not relying on transport

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Giant Giant MagnetoresistiveMagnetoresistive EffectEffect

• R depends on: spin, and magnetization of medium (controllable by B).• Effect is much larger in artificial thin films than in metals• Used in hard disk read heads

• Scattering is energy and spin dependent

Stoner04

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What is a Spin Valve?What is a Spin Valve?

Polar

izer

Analyz

er

Transmission

No transmission

Unpolarizedlight

Polarizedlight

Magnetic analog of an optical polarizer/analyzer

Morkoc04

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Spin valveSpin valve

“Free” FM can be changed by external fieldWolf01

Modest R change

AFM/FM combination givesimmunity to external fields

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Magnetic Tunnel junctionMagnetic Tunnel junction

Replace non- magnetic metal

with

thin insulating layer

5- 10X higher R change

Zorpette01

Lower I

16

• Electrons move from S to D at high (relativistic) velocities• Stationary Egate appears to have a B component• B causes spin-dependent band splitting and precession (Rashba Effect)• Spin under gate is modulated by Egate, e.g., a normally-on FET• “Flipping” is a fast process requiring little energy.

Spin FETSpin FET

Substrate

Source

non-conducting

Dielectric Drain

Gate

This device has not yet left the drawing board!

FM thin film

“fixed”

“fixed”

“modulated”

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SingleSingle--electron Transistorelectron Transistor

Principal motivation: greatly reduced power dissipation.

Also: increased speed (tunneling)

Geppert00

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Coulomb BlockadeCoulomb Blockade

Devoret98

CnqV

qVCnqE

CqnE

CnqEn

G

G

n

n

)12(21 if allowedonly Transfer

iselectron theof changeEnergy

)12(21∆ :changeEnergy

))1((21 :electron another Add

)(21 :capacitoron electrons ofEnergy

2

2

1

2

+=∴

+=

+=

=

+

Use 2 tunnel junctions and make a FET aF..2

:Need2

≈

>>

Cei

kTC

q

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Room temperature SETRoom temperature SET

Matsumoto04

Anodization usingwater-coated tipas cathode

20

ETH, TI, UCSB

CMOS (high- speed drive, voltage gain)+ SET (ultra- low power consumption)= SETMOS (dense, low- power, analog circuits, e.g., NDR, NN, ADC)Coulomb blockade oscillations and operation at - 100C

Mahapatra03

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21 David04

NanotubesNanotubes and and NanowiresNanowires

22

2p orbital, 1e-

(π-bonds)

Hybridized carbon atom graphene monolayer carbon nanotube

SingleSingle--Walled Carbon Walled Carbon NanotubeNanotube

UBCnano (Castro)

• Metallic or semiconducting• Bandgap depends on d

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• NANOSCALE -- no photolithography

•BANDGAP TUNABILITY -- 0.5-1.5eV

• METALS AND SEMICONDUCTORS -- all-carbon ICs

• BALLISTIC TRANSPORT -- 20-300nm

• STRONG COVALENT BONDING-- strength and stability of graphite

-- no surface states (less scattering, compatibility with many insulators)

• HIGH THERMAL CONDUCTIVITY-- almost as high as diamond (dense circuits)

• SELF- ASSEMBLY -- biological, recognition-based assembly

Compelling Properties of Carbon Compelling Properties of Carbon NanotubesNanotubes

UBCnano

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CNT formation by catalytic CVDCNT formation by catalytic CVD

5µm islands in PMMApatterned by EBL

LPD of Fe/Mo/Al catalyst

Lift-off PMMA

CVD from methane at 1000C

2000nm

No field

Growth in field (1V/micron)Kong98, Ural02

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Few prototypes• [Tans98]: 1st published device• [Wind02]: Top-gated CNFET• [Rosenblatt02]: Electrolyte-gated

Nanotube

Fabricated Carbon Fabricated Carbon NanotubeNanotube FETsFETs

UBCnano (Castro)

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chirality: (16,0)

radius: 0.62 nm

bandgap: 0.63 eV

length: 15 - 100 nm

oxide thickness: (RG-RT): 2 - 6 nmq

VLV

qV

qVzRV

DDS

S

GGSG

Φ−=

Φ−=

Φ−=

),(

)0,(

),(

:ConditionsBoundary

ρ

ρ

The Ultimate “MultiThe Ultimate “Multi--gate” FETgate” FET

UBCnano

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kx

kx

kz

E

METAL (many modes)

CNT (few modes)

Doubly degenerate lowest mode

MODE CONSTRICTIONMODE CONSTRICTIONandand

TRANSMISSIONTRANSMISSION

T

Interfacial G: even when transport is ballistic in CNT

155 µS for M=2

UBCnano

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II--V dependence on S,D V dependence on S,D workfunctionworkfunction

Negative barrier(p-type) device

Positive barrier (p-type) device

VGS = - 0.4 V

nm/A5, µ≈satDI

nm/A4.015nm Intelµ≈

nm/S05 µ≈mg

nm/S115nm Intel

µ≈

John04

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SelfSelf--assemblyassemblyof of

DNADNA--templatedtemplated CNFETsCNFETs

Keren03

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• CNs have excellent thermal and mechanical properties.

• High DC currents and transconductances are feasible.

• CNFETs can be self-assembled via biological recognition.

• CNFETs are promising molecular transistors.

• But:

• Presently, cannot pre-determine conductivity type.

• Presently, coaxial FETs have not been made.

Carbon Carbon NanotubeNanotube SummarySummary

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Coaxial Coaxial NanowiresNanowires

Lauhon03

Axial growthfrom Auby CVD

Au nanocluster catalyst

Radial growthon nanowiresurface bychanging T and C

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MultiMulti--shell Crystalline shell Crystalline HeteronanowiresHeteronanowires

e.g., p- Sion i- Si

50 nm 5 nm

Lauhon03

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GeGe NanowireNanowire coaxial FETcoaxial FET

Lauhon03

gm ≈ 0.15µS/nm

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ConclusionsConclusions

• Molecular electronics, spintronics: far future.

• SETs: simulations of dense, low power circuitry,fabrication of single FETs: future.

• Carbon nanotubes: fabrication of devices and circuits,integration with Si: near future.

• Nanowires: fabrication of devices: near future.

• Complementing CMOS will be the key.

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Carbon Carbon nanotubenanotube on on SiSi ICIC

Proof- of- concept : decoder Possibilities: massive memory,dense sensors.

Tseng04

36

Complementing CMOS

CMOS

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ReferencesReferences

Bourianoff04 - ftp://download.intel.com/research/silicon/Bourianoff_Nanotrends_052604.pdfCalmec04 - http://www.calmec.com/molecula1.htmChen99 - J. Chen et al., Science, 286, 1550, 1999DARPA04 - http://www.darpa.mil/MTO/mole/David04 - ftp://download.intel.com/research/silicon/Ken_David_GSF_030604.pdfDevoret98 - http://physicsweb.org/article/world/11/9/7#world-11-9-7-3Geppert00 - L. Geppert, Spectrum, 46, 2000Gintz03 - http://www.nanoelectronicsplanet.com/nanochannels/circuit/article/0,4028,10501_2106751,00.htmlGoser04 - K. Goser et al., Nanoelectronics and Nanosystems, Springer, 2004John04 - D.L. John et al., Nanotech04, March 2004Keren03 - K. Keren et al., Science, 302, 1380, 2003Kong98 - J.Kong et al., Nature, 395, 878, 1998Lauhon03 - L.J. Lauhon et al., Nature, 420, 57, 2003Mahapatra03 - S. Mahapatra et al., IEDM, 706, 2003Matsumoto04 - http://luciano.stanford.edu/~shimbo/set.htmlMEC01 - http://www.molecularelectronics.com/logicswitch.htmlMoravec04 - http://www.frc.ri.cmu.edu/~hpm/talks/revo.slides/power.aug.curve/power.aug.htmlMorkoc04 - Morkoc H., WOCSDICE, Slovakia, 2004Stoner04 - http://www.stoner.leeds.ac.uk/research/gmr.htmTseng04 - Y-C. Tseng, Nano Letters, 4(1), 123, 2004UBCnano - http://nano.ece.ubc.caUral02 - A. Ural et al., Appl. Phys. Lett., 81, 3464, 2002Wolf01 - S.A. Wolf et al., Science, 294, 1488, 2001Zorpette01 - G. Zorpette, Spectrum, 33, Dec. 2001