Structural and optical studies on thermal-annealed In2S3 films prepared by the chemical bath deposition technique

Polycrystalline In₂S₃ films were grown on glass substrates by means of the chemical bath method and subsequently thermal-annealed in an Ar atmosphere at temperatures from 200 to 450°C. The optical and structural properties of the films were studied as a function of the annealing temperature. The experimental results show that the as-deposited films are composed by a mixture of both cubic α and β crystalline phases, with some fraction of tetragonal phase. The thermal annealing on the films produces the conversion of the cubic crystalline phases to the tetragonal β one and a crystalline reorientation of the latter phase. Two energy band gaps were determined for all the films: one indirect and other direct at higher energy. The structural modifications of the films are accompanied by changes in the two energy band gaps of the films.