11-02/03 :: February / March 2011

nanotimes News in Brief

55

Image of a bismuth telluride nanorib- bon: Low-magnification transmission electron microscopy (TEM) image of a bismuth telluride nanoribbon on a holey carbon grid. © UCLA

transistor structures. These rely on an electric field to control the Fermi level and hence the conductivity of a channel. The researchers were able to demonstrate for the first time the possibility of controlling surface states in topological insulator nanostructures.

“We have demonstrated a clear surface conduction by partially removing the bulk conduction using an external electric field,” said Faxian Xiu, a UCLA staff research associate and lead author of the study. “By properly tuning the gate voltage, very high surface conduction was achieved, up to 51 percent, which represents the highest values in topological insula- tors.”

“This research is very exciting because of the possibi- lity to build nanodevices with a novel operating prin-

ciple,” said Wang, who is also associate director of the California NanoSystems Institute (CNSI) at UCLA. “Very similar to the development of graphene, the topological insulators could be made into high-speed transistors and ultra–high-sensitivity sensors.”

The new findings shed light on the controllability of the surface spin states in topological insulator nano- ribbons and demonstrate significant progress toward high surface electric conditions for practical device applications. The next step for Wang‘s team is to pro- duce high-speed devices based on their discovery.

“The ideal scenario is to achieve 100 percent surface conduction with a complete insulating state in the bulk,” Xiu said. “Based on the current work, we are targeting high-performance transistors with power