XPS studies of nanometer CeO2 thin films deposited by pulse ultrasonic spray pyrolysis

Cerium(IV) oxide nanometer (4.2-20 nm) thin films are deposited on Si(100) substrates by nebulization of a 0.01 M solution of cerium acetylacetonate in a 50% ethanol/water mixture followed by pyrolysis in flowing air. Influence of X-ray irradiation (Co-60) and the proportion of pulse and interval time between pulses on the microstructure of CeO2 films are determined by XPS. The results reveal that the film can be reduced from Ce4+ to Ce3+ by X-ray irradiation for about 10 h. Ce3+ content increases with the increase of irradiation dose and there is loss of lattice oxygen greatly. Peak of lattice oxygen of O-1s increases with the decrease of the proportion, but decreases obviously with the increase of irradiation dose. Appropriate proportion is necessary for obtain pure CeO2 nanometer thin films. (C) 2000 Elsevier Science S.A. All rights reserved.