nni definition of nanotechnology - ubc ecepulfrey/nano_beyond_si_uni.pdf · lecture 1 5 9...
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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
Lecture 1
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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
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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
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• 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
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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
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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
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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