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 deg 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 alpha and beta 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 beta 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.