Resonant rutherford backscattering studies of cerium oxide thin films deposited by RF sputtering

We have studied the stoichiometry of cerium oxide films deposited by RF sputtering on sapphire and MgO as a function of deposition conditions using the resonant Rutherford backscattering method. We found that some films have the off-stoichiometry of CeOy with y greater than 2.0. Such an off-stoichiometry cannot be due to a mixture of the known phases of bulk cerium oxide samples. This may be due to either cerium vacancies or interstitial oxygen atomic impurities. The cerium ion x-ray photoemission spectra of those films cannot determine the vacancy of the cerium ions. The c-axis YBaCuo thin flims deposited by sputtering on the CeO3.3 buffer layer on saphhire was found to be epitaxial. The T-c was 86 K with Delta T-c less than 1 K.