Faster nanotube transistors can speed computers

TRANSISTORS MADE FROM SINGLE-walled carbon nanotubes can operate at extremely fast microwave frequencies, which opens the potential for better cell phones and computers that may be 1,000 times faster, researchers said.

"Since the invention of nanotube transistors, there have been theoretical predictions that they can operate veiy fast," said Peter Burke, Ph.D., a professor of electrical engineering and computer science at the University of California, Irvine, and lead author of a paper on the subject." Our work is the first to show that single-walled nanotube transistor devices can indeed function at very high speeds."

Burke and his team built an electrical circuit with a carbon nanotube between two gold electrodes. When they varied the voltage, the circuit operated at a frequency of 2.6 gigahertz (GHz), which means electrical current could switch on and off in about one-billionth of a second. This is the first demonstration of a nanotube operating in the frequency range of microwaves-electromagnetic waves with faster frequencies than radio waves.

Although Burke's group demonstrated that nanotube transistors could work in the GHz range, he believes that much faster speeds are possible. "I estimate that the theoretical speed limit for these nanotube transistors should be terahertz [1 THz = 1,000 GHz], which is about 1,000 times faster than computer speeds." His team is researching the theoretical cutoff frequency for these transistors.

Every transistor has a cutoff frequency, which is the maximum speed at which it can operate. For silicon, the cutoff is about 100 GHz, but current circuits typically operate at much slower speeds, Burke said. For example, some of today's newest processor chips operate below 5 GHz.

Nanotechnology is the science of the very small: a nanometer is one-billionth of a meter, or about 1,000 times smaller than the width of a human hair. A nanotube is another form of carbon, like graphite or diamond, with the atoms arranged like a rolled-up tube of chicken wire.

Electrons move without losing energy inside nanotubes, which makes them perfect candidates for connections in electrical devices.