Effect of vacuum and sulphur annealing on the structural properties of spray deposited Cu2SnS3 thin films

Cu2SnS3 thin films have been deposited by using non-vacuum spray pyrolysis technique on soda lime glass substrates from single aqueous solution containing all the constituents. The effect of post deposition annealing of the Cu2SnS3 thin films on the composition, structural, optical and electrical properties has been studied. The XRD study reveals that vacuum annealing of the thin film gives rise to the evolution of CuxSy secondary phases by the loss of elemental tin, while the annealing held at sulphur atmosphere increases the crystallinity of the film without giving rise to any secondary phases. The Cu2SnS3 phase with preferred orientation along the (112) crystal direction grew to greater extent upon sulphur annealing associated with an improvement in the optical band gap. From the Raman analysis it was observed that as-deposited films are dominated by the presence of tetragonal crystal symmetry of the Cu2SnS3 phase. Upon vacuum annealing the peak appearing at 474 cm(-1) grows to greater extent which corresponds to CuS phase, and is in good agreement with the XRD spectra. Eventually its sulphur annealing gives the pure phase of Cu2SnS3 with dominating tetragonal crystal structure.