IBM researchers create circuit with a single carbon nanotube
- IBM researchers create circuit with a single carbon nanotube By JULIE MORAN ALTERIO
THE JOURNAL NEWS
(Original publication: March 24, 2006)
A state-of-the-art PC has a 3 gigahertz microprocessor. A breakthrough by scientists at IBM Research in Yorktown Heights is a step toward a future when computers will be 300 times faster.
The IBM researchers have created the first complete electronic integrated circuit using a single "carbon nanotube."
Carbon nanotubes are hollow cylinders 50,000 times thinner than a human hair.
Despite their diminutive size, carbon nanotubes are stronger than steel. They are also excellent conductors of electricity, which is why computer companies such as IBM and Intel, as well as university researchers, are exploring their potential for replacing silicon in chips when the limits of miniaturization are reached in 10 to 15 years.
IBM researcher Joerg Appenzeller, a Valhalla resident, said the creation of the circuit is exciting because it proves the potential of carbon nanotubes, which had been in some doubt.
"We made a giant step forward," he said. "We are not at the end, but we are going in the right direction."
IBM's work is a milestone because the type of circuit the researchers built ï¿½ called a ring oscillator ï¿½ acts like a speedometer to evaluate the electrical current flowing through the nanotube.
"We can directly measure the nanotube's performance," said IBM researcher Zhihong Chen, a resident of Elmsford.
The IBM researchers clocked circuit speeds of 53 megahertz ï¿½ a million times faster than earlier efforts, which used multiple nanotubes.
Though still far slower than today's PC chips, the speed was encouraging because it was the first measurement of alternating current on a carbon nanotube. AC is the type of electricity used in PCs and in the home in general.
Eventually, researchers expect circuits built with carbon nanotubes to be as fast as 1,000 gigahertz ï¿½ also known as terahertz.
"We hope we can eventually reach this terahertz performance," Chen said. "We are working on carbon nanotubes now because we are trying to prepare for the end of silicon in 10 to 15 years."
What's particularly encouraging is the fact that the researchers created the circuit using standard semiconductor manufacturing processes.
"Compatibility of nanotubes with lithographic technology and silicon technology is very good news for us because, in the future, it can be a low-cost technology. We don't need to replace everything to use carbon nanotubes," Chen said.
Mark Lundstrom, a professor in the electrical and computer engineering department at Purdue University, said building a circuit that helps analyze the potential of carbon nanotubes is a significant leap.
Lundstrom's team has looked closely at IBM's experiments in nanotechnology and tried to simulate them using computers.
"The challenge is understanding these new kinds of materials. There's a lot of physics to figure out," he said.
The circuit IBM created had just 10 transistors, Lundstrom noted, compared to a billion in a state-of-the art silicon chip. That means there's a lot of work to be done before PC shoppers can opt for a terahertz chip upgrade.
"If you're aiming to replace the conventional technology used in silicon chips, that's far enough off that I don't even want to make a prediction. If you're looking at using the technology in a few specific high-performance applications like radio frequency chips, it might only be a few years off," Lundstrom said.
Building the nanotube circuit, which will be discussed in a paper appearing in today's issue of the journal Science, took about six months of effort, according to Chen.
There are about eight researchers in the nanotube group at IBM. The University of Florida and Columbia University collaborated with the team by providing raw materials, including the carbon nanotubes.
Richard F. Doherty, research director at the Envisioneering Group in Seaford, N.Y., said IBM has bragging rights among its competitors.
"There's a long way to go before these nanotubes replace the average integrated circuit," he said, "but they have been able to move years of progress in months of research."
Dr. Debajyoti Sarangi,
Micro and Nanosystems, ETH Zentrum CLA H 1
Tannenstrasse 3, 8092 Zurich, Switzerland.
Ph: +41 1 632 27 82 (Office) Fax: +41 1 632 14 62
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