Enhanced thermoelectric properties of SnSe thin films grown by single-target magnetron sputtering

Using single-target magnetron sputtering, SnSe thin films were grown on fused silica substrates at room temperature and directly crystallized into the Pnma phase without annealing. The film texture can be manipulated using the post-deposition annealing temperature. The SnSe thin film annealed at 700 K shows superior thermoelectric performance compared with the polycrystalline SnSe bulk material as well as previously reported SnSe films. When the annealing temperature is lower than 700 K (i.e. 600 K), the SnSe thin film shows much higher electrical resistivity which leads to an obvious reduction in the power factor. At higher annealing temperatures (800 K & 1000 K), the SnSe thin films exhibit higher electrical resistivity, comparable Seebeck coefficient, and thus lower power factor. In situ X-ray diffraction reveals that annealing at temperatures above 850 K leads to a reversible phase transition from the Pnma structure to the Cmcm structure.