UNUSUAL PEAK SHIFTS IN THE CORE LEVELS OF CEO2 FILMS DEPOSITED ON SI(100)

X-ray photoelectron spectroscopy has been used to study 20, 100 and 10 00 nm evaporated cerium oxide films on Si(100) single-crystal wafers. Upon exposure to the a-ray source there was loss of oxygen and generat ion of Ce3+ Furthermore, for the 20 nm coating, there was evidence of a shift to higher binding energies of the C Is peak and a high binding energy O Is component relative to the oxygen anion peak at 529.7+/-0. 1 eV with increased exposure time to the x-ray source. No similar shif t was observed in the O KLL Anger lines, suggesting that the effect wa s not due to differential charging of the surface with respect to the bulk of the coating. Hence the relative shift is explained in terms of electronic effects resulting from :he formation of anion vacancies in the surface. These include a shift of the Fermi level due to defect s tates in the bandgap as well as band bending due to the positive charg e set up from the anion vacancies.