Compositional evolution and surface-related phenomena effects in ZnS–SiO2 nanocomposite films

ZnS–Silica nanocomposite thin films were prepared by the sol–gel method. The effect of ZnS:SiO2 molar ratio on structural, morphological and optical properties of thin films was characterized by XRD, FTIR, SEM, AFM, UV–Vis and PL spectroscopy. XRD patterns indicate the phase structure of ZnS particles embedded in SiO2 composite thin films is hexagonal while hexagonal–cubic mixed phase with dominant hexagonal structure is observable beyond 40:60 ZnS:SiO2 molar ratio. SEM and AFM images revealed that the morphology of the samples was strongly affected by variation in composite ratio. According to fractal and power spectral density analyses, at lower silica mixing compositions in 50:50 molar ratio, the composite films represented superior fractal dimension and roughness parameter. The optical transmittance of the films in visible region decreases with ZnS concentration. The pertinent optical constants and single-oscillator parameters along with Urbach tail were determined and discussed. The optical band gap descended gradually (from 3.98 to 3.94 eV) with increasing ZnS content. PL study showed that with increasing ZnS molar ratio, the emission intensity enhances generally.