Annealing Time Effects on the Physical Properties of Spin‐Coated SnS Thin Films

In this work, SnS thin films were synthesized using spin coating on glass substrates from a solution containing SnCl 2 and SC(NH 2 ) 2 as precursors. All samples were annealed at a fixed temperature of 500°C for different times. It has been found that annealing time significantly influences the phase composition, crystallinity, morphology, element distribution (Sn and S), and optical and electrical properties of SnS thin films. X‐ray diffraction analysis revealed the presence of both orthorhombic SnS and hexagonal SnS 2 phases in the annealed samples. An annealing duration of 2 h promoted partial desulfurization, resulting in the dominance of the orthorhombic SnS phase, with the largest crystallite size and a significant improvement in crystalline quality. Under these conditions, the films exhibited a compact and homogeneous morphology, together with a near‐stoichiometric Sn/S atomic ratio, as confirmed by energy‐dispersive X‐ray spectroscopy elemental mapping. The optical study showed that the film annealed for 2 h exhibited an optical band gap of approximately 1.75 eV, in good agreement with reported values for pure phase SnS. In contrast, the other samples showed mixed‐phase SnS/SnS 2 with higher transmittance and larger gaps ranging from 2.02 to 2.40 eV. Hall effect measurements further demonstrated that the electrical conduction type and carrier density are strongly correlated with film stoichiometry. Sn‐deficient films exhibited p‐type conductivity, whereas Sn‐rich films showed n‐type behavior. These results demonstrate that annealing at 500°C for 2 h produces high‐quality, nearly single‐phase SnS layers with optimal structural, optical, and electrical properties, emphasizing the critical role of annealing time in tailoring the properties of spin‐coated SnS films.