Photoelectron Spectroscopy (XPS) and Cyclic Voltammetry (CV) Investigation of UxTh1-xO2 Thin Films

Thin film samples of UO2 and U0.55Th0.45O2 have been prepared by sputter co-deposition under argon atmosphere in presence of oxygen (reactive sputtering) onto gold foil. Films were characterized by X-Ray Photoelectron Spectroscopy (XPS). Cyclic Voltammetry (CV) studies have been made by using the thin films as electrodes in 0.01 M NaCl pH neutral non-purged electrolyte. The effect of thorium in the UO2 lattice is observed by comparing the U0.55Th0.45O2 electrode to the UO2 electrode. The results indicate that uranium develops enhanced resistance to the oxidation when thorium is added to the lattice. After the CV measurements, the films were again characterized by XPS. The surface is enriched in thorium by 11%. Uranium is in a higher oxidation state; however, uranium is less oxidized in U0.55Th0.45O2 than in UO2.