Structural, Morphological and Optical Properties of Thermally Evaporated ZnS Thin Films

The present study reports the effect of the substrate temperature on the structural, morphological, and optical properties of ZnS semiconducting thin films grown via thermal evaporation technique. These properties have been thoroughly investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), and UV-visible spectroscopy. The deposition was performed on a glass substrate at room temperature (RT), 100, 150, and 250°C. Energy dispersive spectrometry (EDS) analysis revealed a high purity of the ZnS films and non-stoichiometry atomic ration of Zn:S. The synthesized films exhibited cubic structure and developed on the (111) preferential orientation plane. Furthermore, increasing the substrate temperature improved the crystallinity and surface morphology of the thin films. Compared to others deposited films, the film grown at 250°C exhibited relatively high transparency in visible light (~87%), high absorption of the ultra violet (UV) light (~94 %.), and wide band gap (3.80 eV). Moreover, the refractive index was evaluated using Herve–Vandamme, Reddy, and Kumar and Singh models, and then compared. In general, these findings revealed that ZnS thin films can be used as the buffer layer in copper indium gallium selenide (CIGS) based solar cells.