Investigation of Cu-doped ZnS thin film: Optical, structural, and surface properties for potential thin film applications

Cu-doped ZnS thin films were synthesized on non-oriented glass substrate by metalorganic chemical vapor deposition and characterized using SEM, AFM, XRD, UV–Vis spectrophotometry, photoluminescence, Raman spectroscopy, and four-point probe measurements. Optimized deposition conditions produced uniform, crack-free films with granular morphology, and an average grain size of ∼8 nm, and surface roughness of 2.74 nm. Optical studies revealed enhanced absorption with a red-shifted edge as Cu concentration increased, accompanied by a band gap variation between 3.7 and 3.9 eV. Photoluminescence spectra showed rising emission intensity with higher Cu content, with a pronounced enhancement in the red shift region (580–650 nm). XRD confirmed a cubic ZnS phase with strong (111) preferential orientation, a lattice constant of 0.59 nm, and crystallite sizes ranging from 38.90 to 43.98 nm. Raman analysis demonstrated that Cu incorporation introduces local structural disorder and defect-activated modes while preserving the fundamental ZnS lattice framework, consistent with the polycrystalline nature observed in XRD. The ohmic behavior of the grown film shows the electrical compatibility of the device in electronic device applications. Collectively, these structural and optoelectronic properties highlight Cu:ZnS films as promising candidates for window layer, buffer layer, LEDs, and thin-film transistors.