Spectroscopic ellipsometry study of CuCdTeO thin films grown by reactive co-sputtering

Abstract

The complex dielectric function of CdTeOx and CuCdTeO thin films was determined by spectroscopic ellipsometry in the photon energy range of 1.5 to 5eV. The films were grown onto glass slides substrates by reactive rf co-sputtering using CdTe and Cu targets in an Ar+O2 atmosphere. Films with different Cu concentrations were obtained by varying the power on the Cu target. The dielectric function of the films is represented by a generalized Lorentz harmonic oscillator expression. Three-dimensional type line-shapes for the critical points E1 and E1+Δ1 of CdTe were identified in CdTeOx and CuCdTeO films even for Cu and O concentrations above 20at.%. This latter result can be indicative of CdTe alloying with those elements widening the possibilities for new photovoltaic materials.