Surface oxidation on U2N3+xOy films in oxygen atmosphere by XPS

U2N3+xOy films were deposited on Si substrate by magnetic sputtering deposition method, and the oxidation behavior of U2N3+xOy films in air and oxygen atmosphere were investigated by X-ray photoelectron spectroscopy (XPS) at room temperature. During oxidation, U4f peaks gradually shift to higher binding energy accompanied with variations of satellites at 386.6 eV and 397.7 eV in U4f region. And similar satellites variations are observed on U2N3+xOy surface during oxidation and depth profile, which is attributed to the N-enriched intermediate product. The final product of U2N3+xOy is UO3, and oxidized nitrogen is also observed after a several-week exposure in air. A cascade mechanism is discussed and applied to explain the oxidation process, in which more than three series reactions are included.