Surface oxidation and thermoelectric properties of indium-doped tin telluride nanowires

摘要

The recent discovery of excellent thermoelectric properties and topologicalsurface states in SnTe-based compounds has attracted extensive attention invarious research areas. Indium doped SnTe is of particular interest because,depending on the doping level, it can either generate resonant states in thebulk valence band leading to enhanced thermoelectric properties, or inducesuperconductivity that coexists with topological states. Here we report on thevapor deposition of In-doped SnTe nanowires and the study of their surfaceoxidation and thermoelectric properties. The nanowire growth is assisted by Aucatalysts, and their morphologies vary as a function of substrate position andtemperature. Transmission electron microscopy characterization reveals theformation of amorphous surface in single crystalline nanowires. X-rayphotoelectron spectroscopy studies suggest that the nanowire surface iscomposed of In2O3, SnO2, Te and TeO2 which can be readily removed by argon ionsputtering. Exposure of the cleaned nanowires to atmosphere yields rapidoxidation of the surface within only one minute. Characterizations ofelectrical conductivity {\sigma}, thermopower S, and thermal conductivity\k{appa} were performed on the same In-doped nanowire which shows suppressed{\sigma} and \k{appa} but enhanced S yielding an improved thermoelectric figureof merit ZT than the undoped SnTe.