Influence of annealing on characteristics of tin disulfide thin films by vacuum thermal evaporation

Abstract In this paper, we reported on an approach to prepare tin disulfide (SnS 2 ) thin films on soda-lime glass substrates by vacuum thermal evaporation using SnS 2 powders as a source. The influence of annealing on the chemical composition, crystal structure, surface morphology, and optical band gap of the SnS 2 thin films was systemically investigated. The as-grown SnS 2 thin film was amorphous, homogeneous, smooth, nearly stoichiometric, with no pinhole and crack free, and with an optical band gap of 2.41 eV. After the SnS 2 thin film was annealed at 300 °C, the crystallization of SnS 2 was demonstrated by X-ray diffraction and scanning electron microscope with a characteristic of a preferred orientation along (001) plane with hexagonal phase and the sheet appearance of the SnS 2 crystals. At the annealing temperature of 350 °C, some SnS 2 crystallites and a few pinholes appeared on the surface of the SnS 2 thin films, though the SnS 2 thin film was not oxidized. When the annealing temperature was increased to 400 °C, SnS 2 was gradually oxidized into an approximate spherical shape of SnO 2 from the top to the bottom of the SnS 2 thin film by trace O 2 in the furnace. Therefore, our experiment suggested that the annealing temperature of the SnS 2 thin film using the vacuum thermal evaporation should not be over 300 °C as a window layer in compound thin film solar cells.