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IBM enters realm of molecule in hunt for smaller circuits

In an advance suggesting that a new kind of ultrasmall computing circuit may one day be produced using conventional chipmaking equipment, IBM researchers have succeeded in fashioning an electronic circuit around a single carbon nanotube molecule, the company reported on Thursday in the journal Science.

The researchers wrote that their approach could be used to simplify the manufacturing of molecular electronic circuits.

Molecular electronics is an effort to build a Lilliputian world of logic and memory circuits that are less than one-tenth the size of today's most advanced microelectronic components.

Researchers think it possible to continue to scale down component size after the middle of the next decade, when today's technologies are expected to reach fundamental limits.

The IBM researchers said they were pursuing a hybrid approach that might one day blend some aspects of today's microelectronics, which has been optimized by printing circuits on silicon wafers, with new materials that make far smaller transistors possible.

Carbon nanotubes are cylindrical molecules with a diameter of approximately a single nanometer, or one-billionth of a meter, and a length that may be thousands of times that.

The molecules have a range of properties, many of them promising for electronics applications.

"This is the first time that a single carbon nanotube has been used to make an integrated electronic circuit," said Dimitri Antoniadis, a professor of electrical engineering at the Massachusetts Institute of Technology. "It is a demonstration of what can be done, but it is still a long way from being competitive with silicon."

The IBM researchers said one significant advance of their work was that they had been able to generate circuit speeds in the megahertz range for the first time in molecular computing.

Until now, researchers have reported molecular electronics switching speeds no higher than the kilohertz range, or thousand of times per second. In contrast, today's microprocessors routinely have switching speeds of billions of times per second.

The researchers report obtaining switching frequencies of 52 megahertz, which is roughly the equivalent of an Intel 486 microprocessor chip commercially available 15 years ago.

An author of the IBM paper, Zhihong Chen, said she believed that it would ultimately be possible to build molecular devices that reach switching speeds of trillions of operations a second.
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