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Carbon nanotubes in a race against time to replace silicon

Lamont Wood | Nov. 11, 2015
Nascent carbon nanotube chip technology may save the computer industry from silicon’s presumed looming demise. Or it may not.

Consequently, "we need to demonstrate the practicality of CNT technology in the next two to three years, or the window of opportunity will close and the technology will not be there when needed," says Guha.

If the problems can be solved, "We could see commercial products in six or seven years, at the earliest," Guha says. "Or development could drag on for a decade, or the technology may never become economical."

"At this point it looks like standard [silicon] transistors are solid enough to last to at least 7nm and perhaps 5nm," agrees Gwennap. "CNTs could come into production in six to eight years, maybe, which is pretty far out, but it's on a list of things people are looking at to replace standard transistors."

Not everyone believes it's possible to get there in time. "I don't see CNTs in under seven years, and even 10 years is farfetched," says David Kanter, senior editor at The Linley Group's Microprocessor Report. "What will be in production two to four years from now has already been selected, and anyone who claims to see further than 10 years ahead is not credible, to use the G-rated way of saying it," he adds.

IBM scientists have measured the distribution of electrical charges in tubes of carbon that measure less than 2 nanometers in diameter, 50,000 times thinner than a strand of human hair. This technique, which relies on the interactions between electrons and phonons, provides a detailed understanding of the electrical behavior of carbon nanotubes. Credit: IBM

Alternatives are finite and few

For all its problems, the compass continues pointing toward CNT technology as a possible way to keep up with Moore's Law -- assuming no way is found to make ever-smaller silicon components.

"To make transistors you need a material with three things," says Shulaker at Stanford. The material needs a band gap -- an energy range within which electricity can't be conducted -- so that the circuit can be turned on and off. The band gap needs to be just the right size; too large and the material is an insulator, too small and it's a metal.

"CNTs have one just the right size," Shulaker says. Finally, the material needs to be thin since you want to make the circuits small. And it needs to be a very good conductor.

"There are not many materials with all three properties," he notes.

Another factor is that "any new technology needs to be mindful that silicon has dominated the industry for decades, and billions have been invested in the infrastructure. But CNTs are 100% compatible with silicon, as you can build them on a silicon substrate," Shulaker says.


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