Ce-catalyzed oxidation of Ta(110)

Photoemission spectroscopy was used to investigate the initial oxidation of the Ce/Ta(110) interface at room temperature. The oxidation of Ta(110) is dramatically enhanced by a thin Ce overlayer. A Ta suboxide ${\mathrm{TaO}}_{\mathrm{\chi }}$ (0.5≤χ≤1) is formed first in the interface, followed by the rapid formation of ${\mathrm{Ta}}_2$ ${\mathrm{O}}_5$ upon further oxygen exposure. A weak interface reaction exists in Ce/Ta(110), but is excluded as the main cause of the catalytic oxidation. An earlier suggestion is reconfirmed that the Ce layer converts ${\mathrm{O}}_2$ to oxygen ions and thus promotes the oxidation of the substrate.