Boffins devise organic molecular microchips

Researchers at the National Institute of Standards and Technology (Nist) have identified an "evolutionary link" between today's microelectronics built from semiconductor compounds, and future generations of devices made largely from complex organic molecules.

A forthcoming paper in the Journal of the American Chemical Society will demonstrate that a single layer of organic molecules can be assembled on the same sort of substrate used in conventional microchips.

The ability to use a silicon crystal substrate that is compatible with the industry-standard CMOS (complementary metal oxide semiconductor) manufacturing technology paves the way for hybrid CMOS-molecular device circuitry.

This is the necessary precursor to a "beyond CMOS", totally molecular technology, according to the Nist researchers.

The team first demonstrated that a good quality monolayer of organic molecules could be assembled on the silicon orientation common to industrial CMOS fabrication.

They then built a simple but working molecular electronic device - a resistor - using the same techniques.

A single layer of simple chains of carbon atoms tethered on the ends with sulphur atoms were deposited in tiny 100nm-deep wells on the silicon substrate and capped with a layer of silver to form the top electrical contact.

"The Nist team fabricated two molecular electronic devices, each with a different length of carbon chain populating the monolayer," the scientists reported.

"Both devices successfully resisted electrical flow with the one possessing longer chains having the greater resistance as expected.

"A control device lacking the monolayer showed less resistance, proving that the other two units functioned as nonlinear resistors."