toward carbon based electronics beyond cmos devices

15
Philip Kim Department of Physics Columbia University Toward Carbon Based Electronics Beyond CMOS Devices

Upload: zoe-stark

Post on 03-Jan-2016

36 views

Category:

Documents


1 download

DESCRIPTION

Toward Carbon Based Electronics Beyond CMOS Devices. Philip Kim Department of Physics Columbia University. End of the Road map: Quest for Beyond Si CMOS Era. Atomic orbital sp 2. Graphene. 0D. 1D. 2D. 3D. Carbon Nanotubes. Fullerenes (C 60 ). Graphite. p. s. - PowerPoint PPT Presentation

TRANSCRIPT

Page 1: Toward Carbon Based Electronics Beyond CMOS Devices

Philip Kim

Department of PhysicsColumbia University

Toward Carbon Based ElectronicsBeyond CMOS Devices

Page 2: Toward Carbon Based Electronics Beyond CMOS Devices

End of the Road map:Quest for Beyond Si CMOS Era

Page 3: Toward Carbon Based Electronics Beyond CMOS Devices

SP2 Carbon: 0-Dimension to 3-Dimension

Fullerenes (C60) Carbon Nanotubes

Atomic orbital sp2

GraphiteGraphene

0D 1D 2D 3D

Page 4: Toward Carbon Based Electronics Beyond CMOS Devices

Outline: Carbon Based Electronics

Material Platform: Low dimensional graphitic systems

• 1-D: Carbon Nanotubes (since 1991)• 2-D: Graphene (since 2004)

Device Concepts

Conventional: (extended or ultimate) CMOS, SET

Non-Conventional: Quantum Interference, Spintronics, valleytronics

Page 5: Toward Carbon Based Electronics Beyond CMOS Devices

Graphene : Dirac Particles in 2-dimension

Band structure of graphene (Wallace 1947)

kx

ky

Ene

rgy

kx' ky'

E

kvE F

Zero effective mass particles moving with a constant speed vF

hole

electron

Page 6: Toward Carbon Based Electronics Beyond CMOS Devices

Single Wall Carbon Nanotube

ky

kxkx

ky

Allowed statesMetallic nanotube

E

k1D

E

k1D

Semiconducting nanotube

Eg ~ 0.8 ev / d (nm)

Page 7: Toward Carbon Based Electronics Beyond CMOS Devices

400

200

0

6040200

Length (m)

Res

ista

nce

(k

)

T = 250 K

= 8 k/m

Extremely Long Mean Free Path in Nanotubes

Multi-terminal Device with Pd contact

* Scaling behavior of resistance:R(L)

5

678

10

2

3

4

5

678

100

2

3

4

5

67

0.12 4 6 8

12 4 6 8

102 4 6 8

L (m)

R (

k)

T = 250 K400

200

0

6040200

R (

k)

L (m)

R ~ RQ

R ~ L

el

L

Ne

h

Ne

hLR

22)(

le ~ 1 m

M. Purewall, B. Hong, A. Ravi, B. Chnadra, J. Hone and P. Kim, PRL (2007)Room temperature mean free path > 0.5 m

Page 8: Toward Carbon Based Electronics Beyond CMOS Devices

Nanotube FET

Band gap: 0.5 – 1 eVOn-off ratio: ~ 106

Mobility: ~ 100,000 cm2/Vsec @RTBallistic @RT ~ 300-500 nmFermi velocity: 106 m/secMax current density > 109 A/cm2

Vsd (V)0-0.4-0.8-1.2

I sd (

A)

Ph. Avouris et al, Nature Nanotechnology 2, 605 (2007)

Schottky barrier switching

Page 9: Toward Carbon Based Electronics Beyond CMOS Devices

Advantages of CNTFET

• Novel architecture ->Band-to-band tunneling FET:

subthreshold slop ~ 40 meV/dB @RT

• No-dangling bond at surface -> high k-dielectric compatible

Cg ~ CQ can be attainable; small RC, low energy

• Thin body (1-2 nm) -> suppressed short channel effectchannel length ~ 10 nm has been demonstrated

Javey et al. PRL (2004).

Appenzeller et al., PRL (2002)

Page 10: Toward Carbon Based Electronics Beyond CMOS Devices

Rodgers, UIUC

Aligned growth of Nanotubes

Nanotube Electronics: ChallengesPros:High mobility High on-off ratioHigh critical current densitySmall channel lengthSmall gate capacitanceLarge Fermi velocity

Con:Controlled growth

Artistic dream (DELFT)

IBM, Avouris group

Nanotube Ring Oscillators

graphene

Page 11: Toward Carbon Based Electronics Beyond CMOS Devices

Discovery of Graphene

Large scale growth efforts:CVD, MBE, chemical synthesis

Page 12: Toward Carbon Based Electronics Beyond CMOS Devices

Num

ber o

f Gra

phen

e Pu

blic

ation

s on

arX

iv /

mon

th

Oct 05

Jun 05

Feb 05

Oct 04

Feb 07

Oct 06

Jun 06

Feb 06

Feb 08

Oct 07

Jun 07

Dec 05

Aug 05

Apr 05

Dec 04

Apr 07

Dec 06

Aug 06

Apr 06

Apr 08

Dec 07

Aug 07

Growth of Graphene Research

Jun 08

60

50

40

30

20

10

01

2

4

6

810

2

4

6

8100

factor 4 / year

Page 13: Toward Carbon Based Electronics Beyond CMOS Devices

Graphene Mobility

103

104

105

-4 -2 0 2 4

n (1012 cm-2)

Mobility (cm

2/V sec)

TC17

TC12

TC145

TC130

Mechanically exfoliated graphene

Tan et al. PLR (2007)

Scattering Mechanism?

•Ripples•Substrate (charge trap)•Absorption•Structural defects

Modulate Doped GaAs: Pfeiffer et al.

GaAs HEMT

Page 14: Toward Carbon Based Electronics Beyond CMOS Devices

High mobility materials have been under intensive research as an alternative to Silicon for higher performance

mobility: Si (1,400 cm2/Vsec), InSb (77,000 cm2/Vsec)

Graphene mobility: > 100,000 cm2/Vsec @ room temperature

104

105

106

-0.2 0.0 0.2

unsuspended best

before annealing

after annealing

Density ( 1012 cm-2)

Mob

ilit

y (c

m2 /

V s

ec)

Enhanced Room Temperature Mobility of Graphene

SEM image of suspended graphene

graphene

Page 15: Toward Carbon Based Electronics Beyond CMOS Devices

Low temperature direct atomic layer deposition (ALD) of HfO2 as high-κ gate dielectric

Top-gate electrode is defined with a final lithography step.

I-V measurements at two different back gate voltages show a distinct “kink” for different top-gate voltages

Transconductance can be as high as gm = 328μS (150μS/μm)

Poor on-off ratio: ~ 5-10due to zero gap in

bulk

Graphene FET characteristics

Meric, Han, Young, Kim, and Shepard, Nature Nanotech (2008)