Abstract
Bi0.5Sb1.5Te3 thin films are deposited on silicon dioxide substrates by RF sputtering. By changing the substrate temperature, we acquire Bi0.5Sb1.5Te3 thin films with different grain size. The thermal conductivity of Bi0.5Sb1.5Te3 thin films is measured using the 3ω method, and the lattice thermal conductivity and the electrical thermal conductivity are separated using the Wiedemann-Franz law. The lattice thermal conductivity dominates because of the high resistivity of the Bi0.5Sb1.5Te3 thin films, and it increases with greater grain size. After annealing, the electrical thermal conductivity substantially increases because of the decreasing of the resistivity, and we conjecture that the increasing of the lattice thermal conductivity results from the decreasing of the defects number in grains due to the same grain size before and after annealing.