A resonant photoemission study of the Ce and Ce-oxide/Pd(111) interfaces

作者：Skoda M^*; Libra J; Sutara F; Tsud N; Skala Y; Sedlacek L; Chab V; Prince K C; Matolin V

来源：Surface Science, 2007, 601(21): 4958-4965.

DOI：10.1016/j.susc.2007.08.01

• resonant photoemission
• XPS
• cerium
• cerium oxide
• palladium
• valence band

We have investigated the Ce 4f electronic states in the Ce/Pd(111) and Ce-oxide/Pd(111) systems, using resonant photoemission (Ce 4d -> 4f transitions), and XPS to understand Pd-Ce interactions in ultra thin layers of cerium and ceria deposited on Pd(111). Cerium deposited on Pd(111) at room temperature forms surface Ce-Pd alloys with Ce rich character, while a Pd rich Ce-Pd alloy is formed by heating to 700 degrees C. A modification of the chemical state of Ce can also be seen after oxygen exposure. RPES provides evidence that Ce-oxide layers deposited on Pd(111) have a CeO2, (Ce4+) character, however a net contribution of the Ce3+ states is also revealed. The Ce3+ states have surface character and are accompanied by oxygen vacancies. Heating to 600 degrees C causes Ce-oxide reduction. A significant shift of Pd 4d-derived states, induced by Pd 4d and Ce 4f hybridization, was observed. The resonant features in the valence band corresponding to Ce4+, Ce3+ and Ce-0 states have been investigated for various Pd-Ce(CeOx) coverages.

• 出版日期2007-11-1