Raman scattering, photoluminescence and spectroscopic ellipsometry studies on polycrystalline Cd0.96Zn0.04Te thin films

Abstract

Cd0.96Zn0.04Te thin films are deposited onto well-cleaned glass substrates (Coming 7059) kept at room temperature by vacuum evaporation. Rutherford backscattering spectrometry and X-ray diffraction techniques are used to determine the thickness, composition and crystalline structure and grain size of the films, respectively. The films exhibited zinc blende structure with predominant (111) orientation. The surface morphology of the films is studied by scanning electron microscopy and atomic force rnicroscopy. The rms roughness of the as-deposited films is 3.7 nm. The Raman spectra of the films show longitudinal- and transverse-optical (LO, TO) modes, which arise from CdTe- and ZnTe-like vibrations. The photoluminescence, spectrum of the films shows intense emission due to free and bound exciton recombination and no emission associated with crystal imperfection and deeper impurity levels. The pseudodielectric-function spectra, epsilon(E) = epsilon(1) (E) + iepsilon(2)(E), of the films are measured by spectroscopic ellipsometry at room temperature. The measured dielectric function spectra reveal distinct structures at energies of the E-1, E-1 + Delta(1) and E-2 critical points. (C) 2002 Elsevier Science B.V. All rights reserved.