Composition-dependent layered structure and transport properties in BiTe thin films

We have studied the compositional dependence of the layered structure of Bi1+xTe1-x thin films and its relation with the transport properties. We have observed that the Bi1+xTe1-x films have a stable structure near the Bi1Te1 composition and that their crystallinity depends strongly upon the compositional deviation from stoichiometric Bi1Te1. We have determined possible layered structures, configured with two sequences of Bi-Bi and Te-Bi-Te-Bi-Te, corresponding to Bi and Te binary compositions using x-ray diffraction analysis. Their c-axis lattice constants were in the range of 36 Angstrom and 136 Angstrom. Temperature-dependent thermopowers of the films reveal that as the composition changes from Te rich to Bi rich, the polarity varies from n type to p type.