The interaction of oxygen with ultrathin Ni deposits on yttria-stabilized ZrO2(1 0 0)

The interaction of oxygen with vapor-deposited Ni on yttria-stabilized ZrO2(1 0 0) and the thermal stability of the oxygenated deposit were studied by XPS, UPS and CO TPD experiments, for two different Ni deposits. For 0.4 ML of Ni deposited at 300 K, the Ni 2p core level spectra show complete oxidation above 110 L of O2 at 300 K, whereas for 5 ML of Ni deposited at 570 K, the Ni 2p and the UP spectra show that oxidation slowly approaches completion above 4500 L of O2 at 420 K. Oxidation extends up to the Ni2+ state and is accompanied by a drastic decrease of CO desorption temperature and desorbed amount. Upon annealing at increasing temperature, oxide decomposition is in both cases already complete at 870 K. At 700 K, the low-coverage Ni deposit has been reduced by more than 70%, whereas the high-coverage deposit by less than 40%. The results are discussed in comparison with the well studied interaction of O2 with Ni monocrystals and a few available reports on the oxidation of Ni clusters on other substrates.