Controlling the optical characteristics of CdS<inf>x</inf> thin film by changing the stoichiometric ratio (x)

Abstract

CdSx thin films (x = 1.0, 0.8, 0.6, 0.4, 0.2) were prepared by the sol–gel spin coating method. The grazing incidence diffraction and Raman spectroscopy techniques were applied to explore the phases formed and microstructure of the produced thin films. The chemical composition of the formed thin films was investigated using X-ray photoelectron spectroscopy (XPS) measurements. Raman spectra revealed the presence of minor CdO phase in films with x = 0.4 and 0.2. Optical parameters could be modified by changing the ratio (x). The influence of sulfur deficiency on the optical properties was explored using photoluminescence and UV–Vis–NIR spectrophotometer techniques. Relative to CdS film, the reflectivity and the refractive index of S-deficient films, except for x = 0.8, decreased in the range 300–400 nm, after that increased a little in 400–530 nm, then increased in 530–1400 nm. The optical bandgap changed from 2.49 eV for CdS to 2.47, 2.58, 2.56, and 2.46 eV for x = 0.8, 0.6, 0.4, and 0.2, respectively. The optical parameters of the films were obtained using Wemple and DiDomenico model. In the whole wavelength range, CdS0.8 attained the highest optical conductivity values. All films emitted green and blue colors but with different intensity dependent on the parameter (x).