THE GROWTH, STRUCTURE AND STABILITY OF CERIA OVERLAYERS ON PD(111)

The properties of cerium oxide overlayers grown on a Pd(lll) substrate have been investigated by XPS, AES, ISS and LEED. The initial low pressure oxidation of the deposited cerium at ambient temperatures yields a Ce2O3 oxide film with a thin capping layer of CeO2. Repeated annealing and re-exposure to O-2 gives an oxide film of CeO2-x, stoichiometry. Annealing also results in the formation of a more ordered oxide film with structural characteristics closely allied to those of the CeO2(111) or Ce2O3(001) surfaces. The thermal stability of the oxide film is principally dependent on the film thickness and oxidation state, but all films exhibit a tendency to decompose by diffusion of cerium and oxygen into the substrate upon annealing to temperatures of around 600 degrees C.