Synthesis process and thermoelectric properties of n-type tin selenide thin films

Abstract

Tin selenide (SnSe) is a very promising thermoelectric material, but there are few reports related to the thermoelectric properties of its thin films, especially for n-type SnSe. In this work, n-type SnSe thin films were synthesized via thermal evaporation using powdered SnSe that was prepared directly by mechanical alloying. It was found that the crystallinity of the films gradually improved and the closer the elemental ratio of Sn and Se was to a ratio of 1:1 with increasing the current through the tungsten boat during the thermal evaporation of the SnSe precursor from 100 to 130 A. Further, the thin films obtained at 120 A show the highest power factor (0.13 μW/mK2) of all the samples fabricated in this study. The samples were then annealed, and the thermoelectric properties of the films were enhanced as this step improved their crystallinities. A Seebeck coefficient of over 100 μV/K could be achieved with an annealing time of 4 h. Combined with a recorded electrical conductivity of 47 S/cm, a maximum power factor of 120 μW/mK2 at 473 K has been obtained for the annealed film with n-type conductive characteristics; this is nearly six times higher than that reported for polycrystalline n-type bulk SnSe at the same temperature.