Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States.
ACS Nano. 2011 Jun 28;5(6):4698-703. doi: 10.1021/nn200556h. Epub 2011 May 23.
Bismuth selenide (Bi(2)Se(3)) is a topological insulator with metallic surface states (SS) residing in a large bulk bandgap. In experiments, synthesized Bi(2)Se(3) is often heavily n-type doped due to selenium vacancies. Furthermore, it is discovered from experiments on bulk single crystals that Bi(2)Se(3) gets additional n-type doping after exposure to the atmosphere, thereby reducing the relative contribution of SS in total conductivity. In this article, transport measurements on Bi(2)Se(3) nanoribbons provide additional evidence of such environmental doping process. Systematic surface composition analyses by X-ray photoelectron spectroscopy reveal fast formation and continuous growth of native oxide on Bi(2)Se(3) under ambient conditions. In addition to n-type doping at the surface, such surface oxidation is likely the material origin of the degradation of topological SS. Appropriate surface passivation or encapsulation may be required to probe topological SS of Bi(2)Se(3) by transport measurements.
硒化铋（Bi(2)Se(3)）是一种拓扑绝缘体，具有位于大带隙中的金属表面态（SS）。在实验中，由于硒空位，合成的 Bi(2)Se(3)通常是严重的 n 型掺杂。此外，从大块单晶的实验中发现，Bi(2)Se(3)在暴露于大气后会获得额外的 n 型掺杂，从而降低 SS 在总电导率中的相对贡献。本文通过对 Bi(2)Se(3)纳米带的输运测量，提供了这种环境掺杂过程的额外证据。通过 X 射线光电子能谱进行的系统表面成分分析表明，在环境条件下，Bi(2)Se(3)上的本征氧化物快速形成并不断生长。除了表面的 n 型掺杂外，这种表面氧化可能是拓扑 SS 退化的材料起源。通过输运测量来探测 Bi(2)Se(3)的拓扑 SS，可能需要适当的表面钝化或封装。
