Quantum effect makes fast connections

By Eric Smalley, Technology Research News

As electronic components continue to shrink, quantum mechanics come into play, and that opens up possibilities for making very short wires that are proportionally faster than their macro scale counterparts.

At the molecular scale, electrons can tunnel through barriers following a law of quantum physics that says some of the elusive particles can literally disappear and reappear on the other side.

Researchers at Stanford University and Brookhaven National Laboratory have found that electrons can tunnel through a particular molecule as far as the relatively long distance of 2.8 nanometers, or the length of 28 carbon atoms. At that length, the molecules could be used as bridges to interconnect molecular electronic components.

These oligophenylenevinylene bridges, which can operate at room temperature, could be used in organic light-emitting diodes, biosensors and future molecular computers, said John F. Smalley, a chemist at the Brookhaven National Laboratory.

"Any molecular electronic device is going to have a circuit [and] you're going to have to connect the various components of the circuit," he said.

The electrical properties of carbon-based molecules are key to molecular electronics, and researchers have used them to make tiny electronic components. Molecular electronics could take over as the basic building blocks of computers at scales too small for components made from semiconductors and metals.

The researchers used oligophenylenevinylene bridges to connect gold electrodes to other molecules that readily shed and gain electrons. They used high-speed lasers to measure how quickly the electrons crossed the bridges.

The researchers made molecular chains and tested bridges of one to five links, which measure .7 to 3.5 nanometers, and found that the electrons tunnel through four links without a significant decrease in speed and and only slowed a little bit through five links, said Smalley.

The bridges could be used in early molecular electronic computers; it will probably be five to ten years before even a rudimentary prototype molecular electronic computer is built, said Smalley. "There has to be a lot more basic research," he said.

Smalley's research colleagues were Hadley D. Sikes, Steven P. Dudek and Christopher E. D. Chidsey of Stanford University and Andrew R. Cook, Marshall D. Newton and Stephen W. Feldberg of Brookhaven National Laboratory. They published the research in the February 23, 2001 issue of Science. The research was funded by the Department of Energy.

Editor's note: The reporter and John F. Smalley are not related.

Timeline:   5-10 years
Funding:   Government
TRN Categories:   Semiconductors and Materials
Story Type:   News
Related Elements:  Technical paper, "Rapid Electron Tunneling Through Oligophenylenevinylene Bridges," Science, February 23, 2001


March 7, 2001

Page One

Neuron-chip link advances

Electricity moves fluids

Quantum effect makes fast connections

Chain reaction yields microscopic wires

Noise can bring quiet surprise


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