Spectroscopic study and thermoelectric properties of copper sulfide thin films prepared by the flash evaporation method

Different phases of copper sulfide were synthesized by the Flash Evaporation method, followed by annealing at various temperatures. Pure and mixed crystal structures of the covellite, digenite and djurleite phases were identified by the X-ray diffraction patterns and Raman spectroscopy. Scanning Electron Microscopy revealed the effect of annealing on the surface morphology. The carrier concentration was found to decrease with increasing the annealing temperature due to the disappearance of copper vacancies. This results in an increase in the Seebeck coefficient and a decrease in the electrical conductivity. The thermoelectric power factor is better when the digenite phase dominates and doping may be a possible solution towards the integration of this material in the thermoelectric technology. Finally, annealing provided access to the Density Of States engineering, which is useful for future investigations. (c) 2022 Published by Elsevier B.V.