Topological insulators acting as insulators as well as conductors apparently restrict the flow of electrical currents and allow the movement of a charge. The surfaces of topological insulators supposedly enable the transport of spin-polarized electrons while preventing the ‘scattering’ typically linked with power consumption. In a major breakthrough, scientists found a possibility to govern over the surface states of topological insulator nanoribbons made from bismuth telluride.
The surface states of the topological insulator nanoribbons appear ‘tunable,’ so they can be turned on and off depending on the position of the Fermi level. Employment of these topological insulators may aid in crafting new-generation, low-dissipation nanoelectronic and spintronic devices, from magnetic sensing to storage. Bismuth telluride commonly referred to as a thermoelectric material is presumed to be a three-dimensional topological insulator with robust and unique surface states.
“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 insulators.”
Tests conducted with bismuth telluride bulk materials assert that two-dimensional conduction channels originate from the surface states. However, altering surface conduction is apparently not easy because of impurities and thermal excitations in such small–band-gap semiconductors. The large surface-to-volume ratios of these topological insulator nanoribbons possibly improve surface conditions and allow surface manipulation by external means.
“This research is very exciting because of the possibility to build nanodevices with a novel operating principle,” added Kang L. Wang, the Raytheon Professor of Electrical Engineering at UCLA Engineering, whose team carried out the research. “Very similar to the development of graphene, the topological insulators could be made into high-speed transistors and ultra–high-sensitivity sensors.”
During the research, scientists used thin bismuth telluride nanoribbons as conducting channels in field-effect transistor structures. These probably depend on an electric field to regulate both the Fermi level and the conductivity of a channel. On completion of the research, experts claimed to have successfully controlled the surface states in topological insulator nanostructures. The findings may result in a dramatic progress toward high surface electric conditions for practical device applications.
The research was published in Nature Nanotechnology.