|Ravi Pandya software | nanotechnology | economics||
Sat 18 Jan 2003
I went to see a great lecture this week at UW Nano by Duncan Stewart from the molecular electronics group at HP Labs. They have a great multi-disciplinary group there, with computer architecture, physical chemistry, organic synthesis, polymers, electrochemistry, materials science, and experimental & theoretical physics. They're using a cross bar architecture with Langmuir-Blodget molecular monolayer between a grid of contacts in a crossbar architecture. Not only have they built a 256-bit memory (to store "HPinvent" :-) but they have also configured it as an FPGA cell with 2-bit multiplexers on the input and output, and a lookup table in between. All this in a square micron!
One of the interesting tidbits was from Stewart's own work in trying to characterize and understand the actual operation of the device. They first tried a monolayer of Jim Heath's fancy rotaxane molecules with a movable ring system acting as a switch. The I-V curves show a nice negative differential resistance that can be used for switching and diode behavior. OK, great, it's the little ring moving along the backbone of the rotaxane. But then they tried a control substance - eicosanoic acid, "basically floor wax". The numbers were a little different, but qualitatively the behavior was the same.
So it's not the material, but probably some interface effect. But what is it? This is a real puzzle, and it's not solved yet. The best hypothesis so far is temperature dependent tunneling effects at the metal-organic interface, pretty much independent of the particular organic species. It'll be interesting to see further developments...
© 2002-2004 Ravi Pandya | All Rights Reserved