In-situ annealing of In–Se amorphous precursors sputtered at low temperature

•Counterparts of the amorphous In2Se3 films vary with the increase of substrate temperature.•There is a “threshold” deposition temperature of 220 °C.•High-quality γ-In2Se3 structures were synthesized via in-situ annealing at low temperature.•Na atoms diffuse into the films in the annealing process.

Stoichiometric amorphous In2Se3 films were deposited on the soda lime glass substrates at temperatures ranging from 160 to 250 °C. Counterparts of amorphous In2Se3 films vary with the increase of substrate temperature. The resulting structure of the annealed films is influenced by the deposition condition. It is observed that there is a “threshold” deposition temperature of 220 °C and Na doping stabilizes a metastable phase (κ-In2Se3) at room temperature. Furthermore, the optical property of these films was analyzed. The results allow us to optimize the preparation method of γ-In2Se3 thin films.