Effect of laser irradiation on the structure and valence states of copper in Cu-phosphate glass by XPS studies

The effect of laser irradiation using three different wavelengths (IR, visible and UV) generated from Nd:YAG laser on the local glass structure as well as on the valence state of the copper ions in copper phosphate glass containing CuO with the nominal composition 0.30(CuO)–(0.70)(P2O5), has been investigated by X-ray photoelectron spectroscopy (XPS). The presence of asymmetry and satellite peaks in the Cu 2p spectrum for the unirradiated sample is an indication of the presence of two different valence states, Cu2+ and Cu+. Hence, the Cu 2p3/2 spectrum was fitted to two Gaussian–Lorentzian peaks and the corresponding ratio, Cu2+/Cutotal, determined from these relative areas clearly shows that copper ions exist predominately (>86%) in the Cu2+ state for the unirradiated glass sample under investigation. For the irradiated samples the symmetry and the absence of satellite peaks in the Cu 2p spectra indicate the existence of the copper ions mostly in Cu+ state. The O 1s spectra show slight asymmetry for the irradiated as well as unirradiated glass samples which result from two contributions, one from the presence of oxygen atoms in the P–O–P environment (bridging oxygen BO) and the other from oxygen in an P–O–Cu and Pdouble bond; length as m-dashO environment (non-bridging oxygen NBO). The ratio of NBO to total oxygen was found to increase with laser power.