Temperature-dependent optical properties of epitaxial CdO thin films determined by spectroscopic ellipsometry and Raman scattering

Abstract

We report temperature-dependent optical properties of epitaxial CdO thin films grown by metal-organic vapor phase epitaxy on sapphire substrates. Dielectric function 1 i2 spectra for CdO were extracted from the multilayer modeling of ellipsometric data, using a set of Tauc-Lorentz oscillators from 0.74 to 6.43 eV in the temperature range between 24 and 650 K. Temperature dependence of the energy for the major optical structures in the spectra was analyzed by using Varshnis approximation. Raman scattering (RS) spectroscopy was used to characterize the vibrational properties of CdO from 77 to 500 K. Several RS peaks were observed in the wavenumber range from 100 to 1000 cm-1. Peak positions, accurately determined by a series of Gaussian-Lorentzian mixed line profiles, exhibit a weak linear dependence on temperature. © 2013 AIP Publishing LLC.