Orientation optimization for high performance Mg 3 Sb 2 thermoelectric films via thermal evaporation.

Low-cost, highly efficient thermoelectric thin-film materials are becoming increasingly popular as miniaturization progresses. Mg3Sb2 has great potential due to its low cost and high performance. However, the fabrication of Mg3Sb2 thin films with high power factors poses a certain challenge. In this work, we propose a general approach to prepare Mg3Sb2 thin films with excellent thermoelectric properties. Using a two-step thermal evaporation and rapid annealing process, (001)-oriented Mg3Sb2 thin films are fabricated on c-plane-oriented Al2O3 substrates. The structure of the film orientation is optimized by controlling the film thickness, which modulates the thermoelectric performance. The power factor of the Mg3Sb2 at 500 nm (14 μW·m-1·K-2) would increase to 169 μW·m-1·K-2 with Ag doping (Mg3Ag0.02Sb2) at room temperature. This work provides a new strategy for developing high-performance thermoelectric thin films at room temperature.