ON THE OFF STOICHIOMETRY OF CERIUM OXIDE THIN-FILMS DEPOSITED BY RF-SPUTTERING

We have studied the stoichiometry of cerium oxide films deposited by R F sputtering as a function of deposition conditions using the resonant Rutherford backscattering method. We found that some films have an of f-stoichiometry of CeOy with y greater than 2.0. Such an off-stoichiom etry cannot be due to a mixture of the known phases of bulk cerium oxi de samples. Those thin samples may have either cerium vacancies or int erstitial oxygen atomic impurities. We have tried to determine the val ence of the cerium ions by measuring the X-ray photoemission.