Evaporation of Ni and carbon containing species onto NiO/Ni as case study for metal support catalysts investigated by Metastable Induced Electron Spectroscopy (MIES)

The surface of NiO layers on Ni(1 0 0) has been exposed to Ni vapor in order to evaluate electronically different surface regions on a metal/metal oxide system as model for metal supported catalysts. The adsorption of Ni atoms or else small clusters of Ni atoms has been observed by Metastable Induced Electron Spectroscopy (MIES) as well as XPS and UPS. The spectrum for this situation extracted from a series of MIE spectra excludes the possibility that the adsorbed nickel takes on a metallic character up to one monolayer equivalent of adsorbed nickel. Further, the unexpected presence of a carbon containing compound emanating from the nickel oven leads to the site-specific coverage of the adsorbed nickel by hydrocarbons. Whether we observe the adsorption of hydrocarbons or the formation of hydrocarbons on site cannot be decided on the basis of the present experiment. In any case the ability of MIES to detect site-specific processes without possessing lateral resolution remains noteworthy.