Low-temperature growth of γ phase in thermally deposited In2Se3 thin films

In the present report, we have studied the structural and optical change in the In2Se3 thin films prepared by the thermal evaporation method, deposited on a glass substrate and annealed at 250 degrees C. Both the structural and optical studies revealed the formation of gamma-In2Se3 phase on annealing at such low temperature as 250 degrees C which is not observed before. Raman analysis indicates that the as-prepared film consists of both a and gamma-In2Se3 phases and the annealed film contains only gamma-In2Se3 phase. The absorption mechanism in the studied film follows the direct allowed transition. The optical band gap is found to be decreased with annealing due to the increase in the width of localized states near to the band edges. Transmittance is found to be decreased and the absorption is increased with annealing due to the change in the film density which enhances its suitability for solar cell applications.