Formation of SnSSe thin films by heat treatment of SnS thin films in S/Se atmosphere

In the present work we have deposited ternary SnS-Se thin films by thermal treatment of SnS in S/Se atmosphere. The effect of annealing conditions on the formation of ternary phase was studied and the optimum condition was identified. The structural, morphological and optoelectronic studies were analyzed by techniques such as X-ray diffraction (XRD), Raman spectroscopy, AFM and photo-response. The best results were found for samples treated under S/Se atmosphere at a temperature of 500 °C during 15 min. The XRD results showed good crystallinity. The formation of SnS-Se compound is confirmed by Raman measurements which illustrated the contribution of three peaks reported at 137, 200 and 299.5 cm−1. The morphology of the film was analyzed by the AFM technique and the results were compared with SnS thin films obtaining a slight increase in the roughness of the ternary films and a similar grain size. XPS analyses confirmed the presence of Sn, S and Se elements on the surface of the film. The bandgap of the films was calculated from the optical transmittance in the visible spectrum, showing direct transitions for SnS and SnSSe at 1.3 eV and 1.12 eV respectively. As a fundamental part of this work, SnSSe thin films showed response to light with higher photosensitivity values, in comparison to SnS films without treatment.