Growth and characterization of GeSnO thin films for thermoelectric power generation applications

Abstract

In this paper, we have demonstrated the thermoelectric properties of GeSnO thin films grown by physical vapor deposition technique. The GeSn pellets were prepared by mixing of germanium (Ge) and tin (Sn) powders with 1:1 ratio using a hydraulic press. Hard pellet was evaporated in a vacuum tube furnace on glass substrate. The grown sample was cut into pieces and subjected to the annealing process at different temperatures ranging from 350 to 500 0C in an oxygen environment. XRD data confirmed the formation of GeSnO crystal structure and it was found to be improved up to annealing temperature 350 °C due to the compensation of oxygen vacancy type defects. But further annealing temperature degrades the crystal quality because oxygen atoms get additional thermal energy and it may generate interstitial defects. Raman and SEM data further supported our argument. Seebeck data confirmed the enhancement in the values of Seebeck coefficient, power factor and electrical conductivity with annealing temperature. The enhancement of thermo power with annealing temperature is due the fact that it degrades the crystal quality which resulted in the generation of secondary phases. These secondary phases are the major contributors of Seebeck coefficient and electrical conductivity.