Role of oxidation on surface conductance of the topological insulator Bi2Te2Se

Abstract

We investigated the effect of surface oxides on charge transport properties in a topological insulator (Bi2Te2Se)using conductive probe atomic force microscopy in an ultrahigh vacuum environment. Uniform distribution of themeasured friction and current were observed over a single quintuple layer terrace after exposure to the ambient environment,which is an indication of uniformsurface oxide coverage. An oxide-free topological insulator surface was exposed using tip-induced etching. By comparing surface conduction on a fresh surface versus a surface exposed to air,we observed a minor change in resistancewhen surface oxidewas present. The current density varied with applied load on the oxidized surface, which implies that the topological surface states respond to tip-induced pressure even though surface oxide is present. From these results, we conclude that surface oxidation in air has a negligible effect on surface conductance in topological insulators.