Effect of film thickness on structural and optical properties of ZnS:Cu films prepared by vulcanization

Abstract ZnS:Cu thin films were prepared by vulcanizing the sputtered Zn:Cu thin films at 500°С in sulfur vapor. The crystal structure, surface morphology, optical properties and microscopic defects of the films were characterized by XRD, SEM, UV–visible spectrophotometer, Raman spectroscopy and slow positron beam Doppler broadening spectroscopy, respectively. The XRD results showed that the ZnS:Cu thin films without any detectable impurities were a cubic structure, further confirmed by Raman spectra. The grain size of ZnS:Cu films was observed to increase from ∼150 nm to ∼300 nm with film thickness. Besides, apparent changes in the compactness and stoichiometry of the ZnS:Cu films were found with increasing the film thickness. These ZnS:Cu films exhibited a low transmittance in the visible range, with the band-gap energies of 3.52–3.62eV. Also, the effect of film thickness on microscopic defects of ZnS:Cu films were discussed in detail.