Abstract
The interaction of gallium and palladium with 2 nm CeO(2)(111) layers grown on Cu(111) was studied by core level photoelectron spectroscopy and resonant valence band spectroscopy. Palladium alone interacted weakly with ceria layers.
Gallium deposited on cerium dioxide formed a mixed Ga(2)O(3)-Ce(2)O(3) oxide of 1:1 stoichiometry (cerium gallate CeGaO(3)), with both metals in the M(3+) oxidation state. Increasing Ga coverages led to the formation of lower oxidation states, i.e., Ga(1+) in Ga(2)O oxide and metallic Ga(0).
Palladium deposited onto this complex system interacted with gallium leading to a breakage of Ga-ceria bonds, a decrease of the oxidation state of gallium, and formation of a Ga-Pd intermetallic alloy in which all components (CeO(2), CeGaO(3), Ga(2)O, Ga-Pd, and Pd) are in equilibrium. (C) 2011 American Institute of Physics. [doi:10.1063/1.3627432]