N-type thermoelectric bismuth telluride (Bi2Te3) films were grown on SiO2/Si substrates by RF magnetron co-sputtering without intentional substrate heating. The effects of annealing temperature (150-350 degrees C) on surface morphology, crystal structure and thermoelectric properties of the Bi2Te3 films were investigated. Its crystallization was significantly improved by increasing the annealing temperature, giving rise to the enhanced charge carrier mobility. It is found that the optimum of Seebeck coefficient and power factor was about -242 mu V/K and 21 mu W/K(2)cm, respectively, obtained at the annealing temperature of 300 degrees C. (C) 2013 Elsevier B.V. All rights reserved.