Microstructure, Raman and optical studies on Cd0.6Zn0.4Te thin films

We report the structural, Raman and optical properties of Cd0.6Zn0.4Te polycrystalline thin films deposited onto well cleaned corning glass substrates by vacuum evaporation. X-ray diffraction pattern showed that the incorporation of zinc favours the growth of films preferentially oriented parallel to the (1 1 1) planes of cubic CdTe. The optical response of vacuum evaporated Cd0.6Zn0.4Te films in the 1.5–5.5 eV photon energy range at room temperature has been studied by spectroscopic ellipsometry. The measured dielectric-function spectra reveal distinct structures at energies of the E1 (3.53 eV), E1+Δ1 (3.9 eV) and E2 (5 eV) critical points corresponding to the interband transitions. In order to check the film local atomic order, the samples were studied by Raman spectroscopy. The transverse and longitudinal optic modes regularly found in CdTe and ZnTe were also observed in Cd0.6Zn0.4Te thin films. From the optical transmittance and absorption coefficient, the band gaps of the films are found to be direct allowed.