Bismuth antimony tellurium is one of the most important tellurium-based materials for high-efficient thermo-electric application. In this paper, ion beam sputtering was used to deposit Bi2Te3 and Sb2Te3 bilayer thin films on borosilicate substrates at room-temperature. Then the bismuth antimony tellurium thin films were synthesized via post thermal treatment of the Bi2Te3 and Sb2Te3 bilayer thin films. The effect of annealing temperature and compositions on the thermoelectric properties of the thin films was investigated. After the thin films were annealed from 150 degrees C to 350 degrees C for 1 h in the high vacuum condition, the Seebeck coefficient changed from a negative sign to a positive sign. The X-ray diffraction results showed that the synthesized tellurium-based thermoelectric thin film exhibited various alloys phases, which contributed different thermoelectricity conductivity to the synthesized thin film. The overall Seebeck coefficient of the synthesized thin film changed from negative sign to positive sign, which was due to the change of the primary phase of the tellurium-based materials at different annealing conditions. Similarly, the thermoelectric properties of the films were also associated with the grown phase. High-quality thin film with the Seebeck coefficient of 240 mu V K-1 and the power factor of 2.67 x 10(-3) Wm(-1) K-2 showed a single Bi0.5Sb1.5Te3 phase when the Sb/Te thin film sputtering time was 40 min. (C) 2014 Elsevier B.V. All rights reserved.