Optical and structural investigation of ZnS:Cu thin films synthesized by spray pyrolysis

We have investigated the effect of Cu dopant and substrate temperature on the structural and optical properties of ZnS thin films deposited on glass substrate by spray pyrolysis technique. The glass substrate temperature varied from 300 to 450 degrees C. Different characterization methods such as X-ray diffractometry, EDS, SEM, and Raman scattering analyses for studying the structural, morphological and optical properties of the prepared ZnS and ZnS:Cu samples were carried out. Improvement in crystallization, increase in crystallite size and also better growth orientation along the (111) direction are clearly evident due to the increase in the substrate temperature. Cu doping effects on the displacement of diffraction peaks towards larger angles and decrease in crystallite size which caused by this impurity are the main results of this studies. The absence of any other impurity in samples, smooth surface, homogenous structure and spherical shape of crystals have approved by EDS analysis and SEM imagining, respectively. Raman scattering spectra of ZnS and ZnS:Cu in ambient condition not only indicate E and A Raman first order scattering of ZnS, but also indicate an intense peak about 334 cm(-1) related to surface optical phonon mode in this nanostructure. Optical properties of thin films determined by UV-Vis spectroscopy and the energy band gap was calculated with ZnS doping rates. Photoluminescence analysis and origin of green emission peak at 533 nm and red peak at 745 nm were discussed.