The Effect of the Precursor Molarities on the Composition, Microstructure and Optical Properties of Tin Sulphide Films Obtained from S-SILAR Technique

The tin sulphide films obtained from chemical routes normally have two or more mixed phases (SnS, SnS2 and Sn2S3). The present paper reports a holistic approach to synthesize nearly stoichiometric, single phase tin sulphide (SnS) thin films by simplified SILAR (S-SILAR) technique without using any complexing agents. The material wastage due to precipitation was also reduced significantly. The cationic and anionic solutions were taken in 2:1 ratio. The solution molarity was found to have a strong bearing on the chemical composition, structural and optical properties of the films. The terminal thickness of the films was about 800 nm. The XRD patterns of the films confirmed that the films obtained from high molarity solutions were almost completely orthorhombic with preferred orientation along (040) plane without any mixed phases. The post-deposition heat treatment was found to be beneficial for the fine tuning of stoichiometry. The S/Sn ratio obtained for annealed films with 0.01 M, 200 cycles combination was 1.07. The optical absorption was substantial in visible and NIR regime with excellent photo-absorption coefficient. The films obtained from solutions with higher molarity were found to have a direct optical bandgap of 1.5 eV, which is highly desirable for NIR photodetectors and photovoltaic applications.