Study of electrical and optical properties of Cd1 ? x Zn x S thin films

Thin films of Cd_0.9Zn_0.1S and CdS were prepared by thermal evaporation under vacuum of 10^–6 Torr and with deposition rate of 60 nm/min. X ray diffraction studies confirm the hexagonal structure of both CdS and Cd_0.9Zn_0.1S films. The effect of heat treatments with or without CdCl₂ enhances the grain size growth and improves the crystalline of the films. Moreover, the activation energy is decreased by heat treatment with or without CdCl₂ for all thin films. The optical absorption coefficient of Cd_0.9Zn_0.1S thin films were determined from measured transmittance and reflectance in the wavelength range of 300 to 2500 nm. The optical absorption spectra reveal the existence of direct energy gap for these films. It was found that the optical energy gap decreases upon annealing or CdCl₂ treatments.