Chips Could Crunch at Light Speed

Researchers at IBM have used carbon molecules to emit light, a breakthrough that could replace silicon as the foundation of chips and lead to faster computers and telecommunication equipment.

The focus of the research team was ultratiny, tube-shaped carbon molecules, or nanotubes, that are more than 50,000 times thinner than an average human hair, according to a statement from IBM released this week.

The scientists were able to engineer the carbon nanotubes not only to conduct current, but also to emit light.

Silicon Substitute

This is the first time light has ever been generated from a molecule by applying electricity, said Phaedron Avouris, manager of nanometer-scale science at IBM Research's Watson Labs.

Light, already the foundation of today's high-speed communication networks, could someday be used to process data in computers and other electronic devices, as engineers run out of ways to cram more performance into silicon chips. Carbon nanotubes with semiconductor properties can be made into transistors much smaller than current silicon transistors, increasing the number of transistors that can be placed on a single chip.

Silicon, the main material used in semiconductors, does not emit light, and therefore can't be used in optoelectronic products, Avouris said. The capability of these nanotubes to generate light means the same type of material is suitable for both electronic and optoelectronic uses, he said. Optoelectronic components include solar cells, light-emitting diodes (LED), and optical-fiber communications products.

Current optical-fiber communications devices are much larger than those that could be constructed from carbon nanotubes, said David Tomanek, professor of physics at Michigan State University. Carbon nanotubes could allow the manufacture of extremely small optical fibers, allowing a greater number of fibers to be placed in a smaller device, he said.

The more fibers in a communications device, the larger the pipe for information to flow through, Tomanek said.

Tiny Emitter

The IBM lab's solid-state light emitter, which the company says is the world's smallest, is a single nanotube. It measures just 1.4 nanometers in diameter and is configured into a three-terminal transistor.

The research team detected light with a wavelength of 1.5 micrometers, a wavelength that is already widely used in optical communications, IBM representatives said. Nanotubes with different diameters could generate light with different wavelengths used in other applications.

Thursday's announcement won't translate into products for quite some time, Avouris said.

"I am cautious about extrapolating into the future. We're demonstrating the potential (of light-emitting carbon nanotubes), but a lot more work needs to be done, and we are very hopeful," he said.

IBM is publishing a report on its research work on carbon nanotube light emission in the May 2 issue of Science magazine, the company said.