IBM researchers build single-molecule computer circuit

AUGUST 28--IBM (Yorktown Heights, NY;www.ibm.com) researchers have created and demonstrated reportedly the world's first logic-performing circuit within a single molecule, which may someday lead to a new class of smaller and faster computers that consume less power than today's machines.

Aug 28th, 2001

AUGUST 28--IBM (Yorktown Heights, NY;www.ibm.com) researchers have created and demonstrated reportedly the world's first logic-performing circuit within a single molecule, which may someday lead to a new class of smaller and faster computers that consume less power than today's machines. The IBM team made a "voltage inverter"--one of the three fundamental logic circuits that are the basis for all of today's computers--from a carbon nanotube--a tube-shaped molecule of carbon atoms that is 100,000 times thinner than a human hair. IBM scientists presented the achievement at the 222nd National Meeting of the American Chemical Society in Chicago, IL.

In April, the same IBM team developed a ground-breaking technique to produce arrays of carbon nanotube transistors, bypassing the need to meticulously separate metallic and semiconducting nanotubes (Science 292, 5517, April 27, 2001). The team used these nanotube transistors to make the circuit revealed today.

"Carbon nanotubes are now the top candidate to replace silicon when current chip features just can't be made any smaller, a physical barrier expected to occur in about 10 to 15 years," said Phaedon Avouris, lead scientist on the project and manager of nanoscale science, IBM Research. "Such 'beyond-silicon' nanotube electronics may then lead to unimagined progress in computing miniaturization and power."

The IBM scientists used nanotubes to make a "voltage inverter" circuit, also known as a "not" gate. They encoded the entire inverter logic function along the length of a single carbon nanotube, forming an intramolecular--or single-molecule--logic circuit. A voltage inverter changes a '1' into a '0', and a '0' into a '1' inside computer chips. The processors at the heart of today's computers are basically vast and intricate combinations of the NOT gate, with two other basic functions, "AND" and "OR" gates, which perform other computations.

Avouris is hopeful that even more-complex circuits could be made along single nanotubes. The IBM team is now working to create these more-complex circuits, which is the next step toward molecular computers. In addition, the team is working to further improve the performance of individual nanotube transistors and further integrate them into more complex circuits.

The report on this work--"Carbon nanotube inter- and intra-molecular logic gates"--by Vincent Derycke, Richard Martel, Joerg Appenzeller, and Phaeon Avouris of the IBM T. J. Watson Research Center, will be published in the August 26 Web edition of Nano Letters, a peer reviewed journal of the American Chemical Society. The online version is available at pubs.acs.org/nano.

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