Molecular Computing

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Molecular Computing

• by Jason Bryant
• and
• Richard Overstreet

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Why do we need smaller computers?

• Increased ComplexityIncreased Computing Power
• To achieve this complexity, the components of a
  computer must be made smaller.
• There are both practical and scientific
  limitations on current silicon-based technology
  (Moores Law)
• One solution lies in molecular switches

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What is a molecular switch?

• The use of molecules to construct electronic
  components that perform the same function as a
  macroscopic counterpart.
• Wires, logic gates, memory circuits, etc.

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What kind of molecule do we need?

• What do we need it to do?
• Ideally, transmit or store electrons
• Need an empty low energy orbital
• Can create a "pi-conjugated system"

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Pi Conjugated system

• These pi bonds act as wires by allowing the
  passage of electrons

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Benefits of the Molecular Switch

• Obvious size advantage
• High current flow generates little heat
• Self-AssemblyCheap, identical production in mass
  quantities
• High potential circuit density
• Non-volatile RAM

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Need more than just wires

• Need Transistors
• Exploiting the pi orbital overlap
• Now we have the concepts, how do we use it?

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Mark Reed and James Tour

• Base molecule was the Benzine Ring

http//www.sciam.com/2000/0600issue/0600reed.html
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Properties of Benzine Dithol

• Allowed for trapping of electrons
• Varying voltage controlled conductive and
  nonconductive state

http//www.sciam.com/2000/0600issue/0600reed.html
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How could they turn it on and off?

• Addition of NO2 and NH2 to the center ring
  created asymmetry that allows for twisting with
  applied voltage.

http//www.sciam.com/2000/0600issue/0600reed.html
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So how did they build it?

• Self assembly
• Need to be able to attach to metal surfaces
• Addition of thiols.

http//www.sciam.com/2000/0600issue/0600reed.html
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Self Assembly Process
http//www.sciam.com/2000/0600issue/0600reed.html
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Help from Photolithography

• For now, help from current semiconductor
  technology
• Creates selected regions for self assembly
• Now we have something resembling current computer
  architecture

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Hurdles

• The Molecular Transistor- under development
• Connecting molecular switches
• Logic Gates

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Notes

• Mark A. Reed and James M. Tour Computing with
  Molecules Scientific American June 2000
  http//www.sciam.com/2000/0600issue/0600reed.html
• Ben Feringa, editor. Molecular Switches
  (Wiley-VCH New York) 2001
• David Rotman Molecular Computing Technology
  Review May/June 2000
• University of Minnesota Inorganic Chemistry
  Website www.d.umn.edu/pkiprof/chemweb/
  Overlap/overlap2.html 2001