Study on thermoelectric properties of co-evaporated Sn-Se films with different phase formations

Abstract

In this study, polycrystalline thin films of 330 nm in thickness with different SnSe and SnSe2 contents were prepared by co-evaporation of Sn and Se through adjusting source temperatures and substrate temperature. The result illustrates that the film with pure SnSe phase is p-type and consists by bulk-like nanoparticles, its resistivity is high up to 139 mΩ·m, which results in a low thermoelectric performance. The films with the coexistence of SnSe and SnSe2 phases are comprised of nanosheets. The existence of SnSe2 phase changes the conductivity type of the films to n-type and reduces resistivity. At the same time, the nanosheets perpendicular to the substrate can improve the Seebeck coefficient by filtering the low energy carrier. When the SnSe2 phase content is 34%, the Seebeck coefficient and the power factor of the film can reach the maximum, 255 μV/K and 155 μW/(m·K2) at 250 °C, respectively.