Structural, optical and Raman scattering studies on polycrystalline Cd0.8Zn0.2Te thin films prepared by vacuum evaporation

Cd0.8Zn0.2Te polycrystalline thin films were grown onto well-cleaned corning glass substrates at room temperature by vacuum evaporation. The optical response of vacuum-evaporated Cd0.8Zn0.2Te 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 critical point energies E-1, E-1 +Delta(1) and E-2 corresponding to the interband transitions. 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. Due to the film's sensitivity to the local atomic order, the samples were studied by Raman spectroscopy. The transverse, and longitudinal optic modes regularly found in CdTe were also observed in Cd0.8Zn0.2Te thin films. It was observed that the incorporation of Zn could not avoid the formation of Te precipitates, which are commonly detected in CdTe thin films and bulk samples. From the optical transmittance and absorption coefficient, the band gap of the films is found to be direct allowed and the energy is estimated as 1.6 eV. (C) 2002 Elsevier Science B.V. All rights reserved.