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Stanford Engineers Build Computer with Carbon Nanotubes

Engineers at Stanford University have created a small computer using transistors built with carbon nanotubes (CNTs) rather than silicone.

The device uses 178 transistors made of the "semiconductor material that may replace silicon in computer chips. This change could launch a new generation of electronic devices that are smaller, cheaper, faster and more energy-efficient than those of today," according to a news release from the National Science Foundation (NSF), which helped fund the research.

"People have been talking about a new era of carbon nanotube electronics moving beyond silicon," said Subhasish Mitra, an electrical engineer and computer scientist at Stanford, in a prepared statement. "But there have been few demonstrations of complete digital systems using this exciting technology. Here is the proof."

Though CNTs have shown promise "to take electronics to a magnitude in performance beyond silicon, inherent imperfections have stood in the way of putting this promising material to practical use," according to the news release. "CNTs do not necessarily grow in neat parallel lines, as chip-makers would like."

Approximately half of one percent of CNTs —dubbed "metallic" tubes — also conduct electricity at all times, without any ability to turn their conductivity off as with a semiconductor.

To deal with misaligned CNTs, the team created an algorithm "that maps out a circuit layout that is guaranteed to work no matter whether or where CNTs might be askew," according to information released by the university. Metallic tubes were dealt with by turning off the conductivity of the semiconducting CNTs, then pumping the circuit full of electricity, which concentrated in the metallic tubes and created so much heat that they vaporized.

"Nanotubes are like spaghetti," said NSF Computer Information Science and Engineering Program Manager Sankar Basu, in a prepared statement. "They are like a mound of entangled strings of materials with different conductivity. This new, 'imperfections immune design' makes this discovery truly exemplary and the most likely avenue for implementation."

"We have entered the third generation of nanotechnology," said Mihail Roco, senior advisor for Nanotechnology at NSF, in a prepared statement. "Building this prototype computer was only part of the achievement. Determining how to use it, precisely identifying which tiny devices will be tested and found to run more efficiently with this incarnation — these remain to be seen. It will be exciting to watch for the next steps in the years ahead."

Subscribers to the journal Nature can read more about the research at nature.com. Non-subscribers gain 48-hour access to the article for $3.99.

About the Author

Joshua Bolkan is the multimedia editor for Campus Technology and THE Journal. He can be reached at jbolkan@1105media.com.

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