Investigation the effect of annealing parameters on the physical properties of electrodeposited ZnS thin films

Several thin films of zinc sulfide (ZnS) were deposited on indium tin oxide (ITO) substrates through an electrochemical route. The as-prepared ZnS thin films were annealed to study the effect of annealing on the properties of ZnS films. The obtained X-ray diffraction (XRD) patterns showed that annealing improves the crystalline quality of ZnS thin films and changes the structure of the ZnS crystallites from cubic to hexagonal. The field emission scanning electron microscopy (FESEM) images exhibited a grain-like morphology for all un-annealed and annealed thin films and declared grain growth as an outcome of annealing. The photoluminescence (PL) spectra of all samples showed five emission peaks corresponding to their band gap energy (E-g) and crystalline defects, such as interstitials and vacancies. The UV-Vis spectra indicated that the reflectance and transmittance of the ZnS samples increases after annealing due to the enhancement of their crystalline quality. Furthermore, the band gap energy of the un-annealed ZnS sample was estimated as 3.71 eV. In general, all outlined results revealed that annealing has a noticeable effect on enhancing the physical properties of ZnS thin films.