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

Abstract

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.