X-ray photoelectron spectroscopy study of copper tellurite glasses

Tellurite glasses containing CuO with the nominal composition (CuO) _x(TeO₂)_1-x, where x = 0.1,0.2,0.3,0.4 and 0.5, have been prepared and investigated by X-ray photoelectron spectroscopy (XPS). The core level binding energies of Cu 2p, Te 3d, and O Is in these glasses have been measured. The appearance of a satellite peak in the Cu 2p spectra provides definitive evidence for the presence of Cu²⁺ ions in these glass samples where the asymmetry and broadening of the peaks are indicative of the presence of both Cu²⁺ and Cu⁺ ions. The broadened Cu 2p_3/2 peaks were decomposed into two distinct peaks separated by approximately 2.0eV, with the lower energy peak being associated with Cu ⁺ and the higher energy peak with Cu²⁺. The relative Cu²⁺ content determined from the relative areas under these peaks and the satellite peak is found to be 44% for x = 0.5 glass sample while it is more than 70% for the remaining samples. The O Is spectra for all glasses show slight asymmetry and were, therefore, fitted with two contributions, one from bridging oxygen (BO) and the other from non-bridging oxygen (NBO). The BO signal is due to the presence of oxygen atoms in the environment Te-O-Te while the NBO is due to oxygen atom in the environment Te-O-Cu. The ratio BO/Total oxygen was evaluated for each glass sample and was found to be in good agreement with the theoretical values. The Te 3d core level spectra show symmetry for all glass samples indicating that the chemical environment of Te atoms does not vary much with the concentration of copper.