The interaction of ultrathin nickel films with yttria-stabilized zirconia (1 0 0)

Increasing amounts of nickel, from 0.2 up to 5 equivalent monolayers, were vapour-deposited on a clean YSZ (1 0 0) surface at room temperature and then annealed at 600 K for up to 19 h. The nickel deposit was gradually oxidized at a rate depending on the deposited amount. For submonolayer coverages, it was completely converted into NiO within a few hours, whereas for multilayer quantities only a small fraction was oxidized. Carbon monoxide TPD experiments showed an intensity attenuation of the CO desorption peak, down to extinction for complete oxidation of the nickel surface, accompanied by a decrease in the TPD peak maximum temperature. This unexpected nickel oxidation upon prolonged heating was attributed to an interfacial interaction of the deposited Ni with mobile oxygen species present on YSZ at elevated temperature, due to its ionic conductor character.