Preparation and characterization of electrochemically deposited nanostructured Ti-doped ZnS thin films

Abstract

In this study, nanostructured undoped and Ti-doped ZnS thin films were produced using an electrochemical deposition method. The indium doped tin oxide (ITO) glass substrate was used to deposit nanostructured ZnS samples. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), room temperature photoluminescence (PL), and UV–Vis spectroscopy were applied to analyze the deposited samples. Cyclic voltammetry (CV) demonstrates that the optimum deposition potential for reducing ZnS was -1.2 to −1.3 V. The crystallite size (D) of undoped ZnS sample was estimated 64 nm, which initially increase to 69 nm and then decreased to 61 nm, after Ti-doping. Compared to other deposited samples, the Ti 3 sample showed a higher D and the lower lattice strain, crystalline defects, and dislocation density. All samples present particle-like morphology with the size of 70–90 nm. UV–Vis spectra demonstrate that the absorbance and the reflectance percentage of ZnS samples will be respectively increased and decreased after Ti-doping. The undoped ZnS sample showed the band gap energy (Eg) of 3.82 eV, which decreased to 3.46 eV for Ti 3 sample. The PL spectra revealed five emission peaks for all samples attributed to the near band edge (NBE) of ZnS and different crystalline defects such as interstitials and vacancies. In addition, the Ti 3 sample revealed a smaller dielectric constant compared with other samples, which can be showed this sample was more suitable for applying as fast photodetectors. Consequently, the results showed that titanium is an effective dopant into ZnS lattice, which clearly affects the structural, morphological, elemental, optical and dielectric properties of ZnS thin films.