Electron beam co-deposition of thermoelectric BiSb thin films from two separate targets

Abstract

We present the deposition of thin Bi1−xSbx-films, by electron-beam co-evaporation as an advantageous alternative method to thermal evaporation. Similar thermoelectric properties of the layers could be achieved while taking advantage of the higher speed, cleanliness, reproducibility and low operating costs of electron-beam co-evaporation.A variation of the stoichiometry of the Bi1−xSbx thin films was performed in the range of x = 0.04 – 0.23 to compare the resulting layer properties. The films were deposited via electron-beam co-evaporation and compared to samples prepared by thermal evaporation, a common production method for this material. Additionally, two annealing steps were applied to analyse their impact on said properties. For all samples Seebeck coefficient and electrical conductivity have been measured, and thermoelectric power factor has been derived before and after annealing. For the electron-beam co-evaporated Bi1−xSbx thin films a maximum Seebeck coefficient of α=-104μVK−1 was measured, together with an electrical conductivity of 203×103Ω−1m−1 for x=0.13. This results in a thermoelectric power factor of PF=2.2mW/m/K2. Furthermore, the crystallographic properties were determined to evaluate differences in the thermoelectric properties of the thin films.