Structural and optical characteristics of nano-sized structure of Zn 0.5Cd 0.5S thin films prepared by dip-coating method

Abstract

In this work, a stoichiometry Zn 0.5Cd 0.5S nano-structured powder was synthesized. Thin films of different thicknesses of Zn 0.5Cd 0.5S were prepared by dip-coating method onto glass substrates. The X-ray diffraction analysis of the prepared powder and films were performed to investigate the crystalline structure. Some structural parameters such as the mean crystallite size and the internal lattice strain were calculated. The composition analysis was made by the energy dispersive X-ray technique, EDX. Scanning electron micrographs, SEM showed that the prepared films are nearly homogeneous and consists of nearly parallel surfaces and the thickness was determined by the cross section imaging. The transmission spectra, T( λ), of the films at normal incidence of light were obtained in the spectral region 190–1100 nm. The optical constants of Zn 0.5Cd 0.5S films were determined using the interference maxima and minima of the transmission spectrum. The dispersion of refractive index was discussed in terms of the single-oscillator model and the important oscillating parameters were determined. The dependence of absorption coefficient on the photon energy was determined and the analysis of the result showed that the optical transition in Zn 0.5Cd 0.5S is allowed and indirect. The thickness dependence of the obtained optical parameters was also considered.