Transcript Molecular Electronic Resonant Tunneling Diode

Future of Computation with
Electronic Nanotechnogy
Presented By
Shubhra Karmakar
Outline
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Technology shifts in computation
 What is electronic nanotechnology?
 Approaches to nanoelectronic devices
 Nanoelectronic devices in future computers
 Solid-state nanoelectronic devices
 Molecular electronic devices
 Conclusions
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Technology Shifts in Computation

Rapid increase in transistor density i.e.,
number of transistors/chip
 This Increase being dictated primarily by
- Need for greater computational speed
- Need for greater computational memory

Increase in transistor density  Scaling down
device sizes
- Size shift: Inches to Microns to Nanometers
- Technology shift: Micron technology to
Nanotechnology
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What is Electronic Nanotechnology ?

Electronic Nanotechnology  Nanoelectronics

Nanoelectronics: Development of electronic devices
having smallest feature size between 1 to 10 nm

Possible electronic devices in computers that can be
scaled down to nano levels
- CMOS
- Memory
- Switches
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Place of Nanoelectronics in Moore’s Space
Nanometer
1.E+11
doubles every
few months?
1.E+10
1.E+09
1.E+06
CMOS
1.E+03
Doubles every 1.0 year
1.E+00
1.E-03
Mechanical Relays
Transistors
Doubled every 7.5 years
Doubled every 2.3 year
1.E-06
1880
1900
1920
1940
1960
1980
2000
2010
2020
2030
From Gray Turing Award Lecture
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Approaches To Nanoelectronic Devices

Two approaches:
- Develop “nano” descendants of present solid-state
microelectronics
- Fabricate nano devices from molecules  Molecular
electronics approach
Path I
Scaling down current S-State devices
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Path II
Molecular Electronics
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Promising Nanoelectronic Devices in Future
Computers

Path I: Nanoelectronic Solid-State Devices
- Nano CMOS
- Resonant Tunneling Diode (RTD)
- Single Electron Transistor (SET)

Quantum-Effect Devices
Path II: Molecular Electronic Devices
- Molecular Electronic RTD
- Spintronics
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The Future of CMOS

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Current VLSI systems rely heavily on CMOS technology
With nano miniaturization:
- A CMOS is predicted to have 1010 transistors by 2012
- Operating speeds will be 10 – 15 GHz (compare to current 1 GHz !)

Example: Today’s CMOS gate length = 120 nm  22 nm (2014)
100 nm
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Scaling Limits of CMOS
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As we scale down, devices
will become
- More variable
- More faulty

As we scale down, fabrication
will become
- More expensive
- More constrained
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As we scale down, design will
become
- More complicated
- More expensive
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From Shibayama et al, 1997
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Resonant Tunneling Diode (RTD)
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Made by placing insulating barriers on a
semiconductor => creates island or
potential well between them
Only finite number of discrete energy
levels are permitted in the island
Electrons can pass through the island by
quantum tunneling
- If incoming electron energy matches (or
resonates) with an energy state inside the
island, then current flows through: “ON”
state
- If energy states inside and outside do not
match: “OFF” state

Multiple logic states are possible
- As voltage bias is increased and
resonant states are established, switches
“ON. Then switches “OFF” and then
switches “ON” as soon as next level
energy states match
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Single Electron Transistor (SET)

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Bell Lab researchers fabricated the first SET in 1987
Similar tunneling concept as RTDs
- One electron tunnels from source to drain, through the barriers
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Summary of Quantum-State Nanoelectronic Devices
Device
Advantages
RTD
-
SET
-
Disadvantages
Status
Multiple logic states - Same scaling
- Semiconductor
limitations as
based
CMOS
- Capable of large
scale fabrication
-
In production
High Gain
- Similar operation to
FET
-
Experimental
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Very low
temperature
- Control
challenges
-
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Molecular Electronic Devices for Future Computers

Molecular Electronics – Uses covalently bonded molecules to
act as wires and switching devices
- Molecules are natural nanometer-scale structures
E.g., A molecular switching device is only 1.5 nm wide!

Molecular electronics will bring the ultimate revolution in
computing power
- 1 trillion switching devices on a single CPU chip!
- Terabyte level memory capacities!

Primary advantage – can be synthesized in large numbers; in
the order of Avagadro’s number (1023)

Present day challenge is to develop methods to incorporate
these devices in circuits
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Molecular Electronic Devices
(…continued)

Molecular Electronic Resonant Tunneling Diode
- Concept is similar to solid-state RTD

Chains of Benzene ring act like conductive wires
- “CH2” (Methylene group) act as electron barriers
- Island or potential well formed between them

Potential well in molecular RTDs is 10 to 100 times less than
solid-state RTDs
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Molecular Electronic Devices
(…continued)

Spintronics
- Spintronics  Spin electronics  Magneto-electronics
- Discovered in 1988 by German and French physicists; IBM
commercialized the concept in 1997
- Exploits the “spin” of electrons, rather than “charge” in information
circuits
- Information is stored into spins as a particular spin orientation (up
or down)
- Spins, being attached to mobile electrons, carry the information
along a wire

Spin orientation of electrons survive for a relatively longer time,
which makes Spintronic devices attractive for memory storage
devices in computers
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Spintronics
(…continued)
Computers
Hard Drive
RAM & CPU
- Uses magnetic spin to store longterm information
- Information is retained on power
loss
- Uses charge to store information
- Information is lost on power loss
Magnetic disk drives--like
this 1 GB IBM Microdrive,
are the most common
devices that takes
advantage of Spintronics
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Spintronics
(…continued)

Advantages of Spintronics-based computers
- Non-volatile: no loss of data during a power loss
- Compact: because of increased miniaturization
- Energy efficient
- Highly customizable: Reprogrammable CPU

Magnetic RAM is a more imminent development than
a magnetic CPU (CPU involves more complex h/w)
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Spintronics
(…continued)
Potential Market for Nanoelectronic Memory and Logic Products, 2003-2013
Adapted from: BCC Research Report
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Snapshot of Active Research in Nano Devices
Nano
CMOS
RTDs
SETs
Molecular MRAM
Devices
Hard Drive
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Conclusions
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The strides being made in nanoelectronics promise an exciting
future for computation
Despite enormous progress in demonstration of nanoelectronic
devices, many challenges remain
- Solid-state nanoelectronic devices: Important challenges are that
of fabrication, reliability and design
- Molecular electronic devices: Challenge is to incorporate these
devices in circuits

Spintronics device development and commercialization of this
technology in memory devices of computers seems to hold
tremendous potential
"Don't worry about what anybody else is going to do… The best way to predict the
future is to invent it. Really smart people with reasonable funding can do just about
anything that doesn't violate too many of Newton's Laws!"
— Alan Kay in 1971
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References
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http://www.cellmatrix.com/entryway/products/pub/Beckett2002.pdf
http://nanotech-now.com/spintronics.htm
http://policy.iop.org/v_production/v5.html
http://www.mitre.org/tech/nanotech/
http://www-2.cs.cmu.edu/~phoenix/
http://www.anl.gov/OPA/factsheets01/H-04.pdf
http://www.bccresearch.com/editors/RGB-286.html
http://physicsweb.org/article/world/11/9/7/1
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Questions?
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