Sputtered Bi2Te3 and PbTe thin films

Abstract

Thin films of Bi2Te3 and PbTe were produced by sputtering using targets of stoichiometric compounds. The compositions of these sputtered thin films were analyzed by the electron microprobe; the Bi2Te3 film showed nonstoichiometric compositions of Bi=44.5 at.%, Te=55.5 at.%, whereas the compositions of PbTe films were stoichiometric. The morphology of these sputtered films was established to be polycrystalline by x-ray diffraction (XRD). XRD peaks of Bi2Te3 films revealed the existence of nonstoichiometric crystalline phases; PbTe films have a single cubic phase with (200) preferred orientation. X-ray photoelectron spectroscopy chemical state analysis on both Bi2Te3 and PbTe films showed that Bi, Pb, and Te have one chemical state consistent with the valence state in the compounds. Room temperature carrier concentration and Hall mobility of BiTe3 film were measured to be 7.2×1020 cm−3 and 15 cm2/V-s respectively; the corresponding values of PbTe films are 5.6×1019 cm−3 and 38 cm2/V-s, respectively. Doping experiments on Bi2Te3 and PbTe films using a single target sputtering system are reported. Sputtered PbTe films doped with Sn have shown promising thermoelectric properties.