The interaction of tungsten with CeO2(111) layers grown on Cu(111) was studied between 300 and 870K via photo-electron spectroscopy of the core levels and resonant valence band spectroscopy. The interaction was found to be very strong, even at 300K, leading to the formation of cerium tungstate Ce6WO12 in which the metal atoms were in Ce3 + and W6 + chemical states. The growth was limited by the diffusion of W atoms into the ceria layer, so subsequent tungsten deposition led to formation of W suboxides with consecutively lower chemical oxidation states, i.e. W4 + , W2 + and metallic W0 with an almost negligible contribution of W5+. Step-wise annealing of the layer showed that due to stimulated diffusion of tungsten into ceria at higher temperature, Ce6WO12 was formed more easily. Larger W overlayer thicknesses needed higher annealing temperature to promote diffusion. The thickest sample studied, 1.4nm W/CeO2, was transformed by annealing to 870K to the Ce6WO12/W system with a WO interface, whereas the rest of the W was converted to the W6 + oxidation state.

Interaction of Tungsten with CeO2(111) Layers as a Function of Temperature - a Photoelectron Spectroscopy Study. T.Skála, N.Tsud, K.C.Prince, V.Matolín: Journal of Physics - Condensed Matter, 2011, 23[21], 215001