Molecular Computing by Jason Bryant and Richard Overstreet
Why do we need smaller computers? • Increased Complexity=Increased 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 (Moore’s Law) • One solution lies in molecular switches
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.
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"
www.d.umn.edu/~pkiprof/chemweb/ Overlap/overlap2.html Pi Conjugated system • These pi bonds act as wires by allowing the passage of electrons
Benefits of the Molecular Switch • Obvious size advantage • High current flow generates little heat • Self-Assembly=Cheap, identical production in mass quantities • High potential circuit density • Non-volatile RAM
Need more than just wires • Need Transistors • Exploiting the pi orbital overlap • Now we have the concepts, how do we use it?
Mark Reed and James Tour • Base molecule was the Benzine Ring http://www.sciam.com/2000/0600issue/0600reed.html
Properties of Benzine Dithol • Allowed for trapping of electrons • Varying voltage controlled conductive and nonconductive state http://www.sciam.com/2000/0600issue/0600reed.html
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
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
Self Assembly Process http://www.sciam.com/2000/0600issue/0600reed.html
Help from Photolithography • For now, help from current semiconductor technology • Creates selected regions for self assembly • Now we have something resembling current computer architecture
Hurdles • The Molecular Transistor- under development • Connecting molecular switches • Logic Gates
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