Annealing effect on the physical properties of evaporated In2S3 films

In2S3 films of different thicknesses were deposited onto Corning 7059 glass substrates using close spaced evaporation method, at a constant substrate temperature and growth rate of 300 °C and 30 Å/s, respectively. The deposited layers were then annealed in vacuum at temperatures (Ta) in the range 100–500 °C for 1 h and changes in the chemical and physical properties of the layers were investigated. The films annealed at Ta<300 °C resulted in films that consisted of both cubic and tetragonal phases, while for films annealed at Ta ≥300 °C only the tetragonal β-In2S3 phase was found to be present. A considerable change in morphology was observed for the film thickness of >300 nm and annealing temperature of 300 °C. A highest optical transmittance was found to be 92% in the annealing temperature range, 300 °C<Ta<400 °C with a nominal reduction in the energy band gap. The electrical resistivity of the layers was found to decrease with increase of annealing temperature up to 400 °C. The observed changes in the physical properties in relation to the annealing temperature for the films of different thicknesses were reported and discussed.