Silicon chip speed record shattered on electron ``racetrack``

A "racetrack" that can shuttle electrons around at high speeds has set a new record for silicon chips.

Last Updated: Jul 17, 2010, 14:21 PM IST

London: A "racetrack" that can shuttle electrons around at high speeds has set a new record for silicon chips.

Electrons travelling through silicon have a strict speed limit due to electrical resistance. In a bid to shatter this limit, computer scientists are considering replacing silicon with carbon, as atom-thick sheets of carbon, or graphene, can conduct electricity better than any other substance at room temperature.

Graphene owes this property to an unusual interaction between its hexagonal lattice structure and the electronic structure of its atoms. This effectively brings the mass of its free electrons down to zero. And this apparent weightlessness allows them to zip across graphene like photons, reaching speeds of up to 0.003 of the speed of light in a vacuum.

Graphene, however, is difficult to make in bulk. But Han Woong Yeom and his colleagues at the Pohang University of Science and Technology in South Korea believe they can mimic its conductivity in silicon. They have clocked electrons travelling 20 times faster than usual in their silicon chips.

Yeom`s team added an atom-thick layer of lead to the surface of a silicon block. Since the lead layer is so thin, the arrangement of its atoms is influenced by the silicon atoms underneath. The team suspected that the lead`s electrons would, in turn, influence the electronic structure of the silicon at the interface.

To find out, they fired high-energy photons at the material to knock electrons out of it, and measured their momentum and energy. By subtracting the energy the photons contributed to the displaced electrons, they calculated that some of the electrons at the silicon-lead interface had an apparent mass 1/20th of that of the electrons in typical silicon chips.

"This indicates the possibility of 20-times-faster electrons," The New Scientist quoted Yeom, as saying.

That``s still just one-third of the speed of electrons in graphene, but in principle the electron mass can be further reduced - and their speed increased - if different metals are used to coat the silicon, he added.

Zahid Hasan of Princeton University said: "It`s fantastic progress."

He believes speedy silicon could easily outrace graphene to the shelves as the manufacturing infrastructure is already in place.

Yeom`s research appears in the journal Physical Review Letters.