Influence of deposition temperature on the properties of sputtered films grown from a Cu2OCdOTeO2 composite target: Electronic properties of CdTe2O5

Thin films were grown by sputtering targets made by compressing a mixture of the binary oxides Cu2O, CdO and TeO2. Their properties were studied as a function of the substrate temperature, which was varied from room temperature up to 450 °C. All the analyses were carried out on as-grown films. The elemental composition was analyzed by energy dispersive spectroscopy. A structural analysis was carried from grazing-angle X-ray diffraction patterns, which showed the formation of Cu2O (at 350 °C and above) and CdTe2O5 (at 400 °C and above) clusters immersed in an amorphous background. Raman scattering (room temperature) and photoluminescence (room temperature and 80 K) spectra were dominated by the signals originating from the Cu2O clusters. The optical transmittance spectra presented characteristics in agreement with the phases present in the films, as determined by X-ray diffraction. Due to the lack of information on CdTe2O5 in the literature, density functional theory calculations were carried out to analyze the optical properties of the films containing this compound in terms of the calculated electronic band structure. It was determined that CdTe2O5 is an indirect gap material. The theoretical band gap was 3.06 eV, which compares well with the experimental one ∼3.16 eV.