XPS and AES Studies on Nb Oxide Films

X-ray photoelectron spectroscopy and Auger electron spectroscopy have been used to study the oxygen depth profile of niobium surfaces which were treated by typical procedures used in the preparation of superconducting rf cavities. The outermost layer of the niobium surface consisted of Nb2O5 and NbO2. However, it was found that the homogeneous oxide layers of Nb2O5 formed on the niobium surface by anodic oxidation were decomposed into NbO 60%, NbO2 30% and Nb2O5 10% due to the preferential sputtering of oxygen from Nb2O5.