Effect of annealing on structural and optical properties of SnS thin films prepared using physical evaporation technique

Tin sulphide (SnS) is a promising material for use as an absorber layer in low cost solar cells particularly because of its nontoxic nature and abundance in earth. In this work, SnS films with various thicknesses have been deposited on glass substrates by thermal evaporation. The studies of effect of annealing on structural and optical properties were investigated using XRD, SEM, UV- Visible spectrophotometer. The deposited SnS films are pinhole free, smooth, continuous and uniform. The atomic ratio of Sn to S indicates that S is slightly more in the deposited films. Pre- annealed and after- annealed SnS films exhibited a strong peak that belongs to [111] orientation of the orthorhombic structured SnS crystal. After annealing, crystallite size increased whereas, micro strain and dislocation density found to be decreased. Reduction in micro strain and dislocation density indicates the formation of good quality films. Optical band gap of SnS films varied from 1.96 - 2.44 eV. It has been observed that extinction coefficients are higher for lower film thickness.