Synthesis and study of the structural and optical properties of SnS and SnO2/SnS thin films prepared by spray pyrolysis

This study aims to synthesize and characterize the structural and optical properties of tin sulphide (SnS) and tin oxide/tin sulphide (SnO2/SnS) bilayer thin films by spray pyrolysis technique from aqueous solutions. X-ray diffraction revealed polycrystalline structure of the SnS films of mixed orthorhombic and zincblende phases, while the deposition of the upper SnO2 layer introduced additional crystalline SnO2 phases. Field emission scanning electron microscopy (FE-SEM) indicates a uniform porous structure of SnS, as well as significant variations in surface morphology after the deposition of the upper layer. Photoluminescence spectroscopy (PL) revealed band-to-band transitions and defect-related emissions; an additional emission peak at 420 nm, attributed to SnO₂ band-to-band transitions, appeared and intensified with increasing SnO2 thickness. UV-visible absorbance spectroscopy indicated an overall increase in absorbance spectra and slight variations in the optical bandgap induced by the incorporation of oxide states in the SnS matrix. These findings highlight the ability to modify the structural and optical properties of SnO2/SnS heterostructures, indicating their potential use in photocatalytic applications.