Reactivity of oxide surfaces modified by palladium atoms

We report CO adsorption studies on modified surfaces of Al2O3 and MgO. The oxides were bulk crystals a-Al2O3 and MgO.or thin films g-Al2O3.; they were sown by palladium atoms. By using static secondary ion mass spectroscopy SSIMS., the surfaces were in situ characterized with respect to metal coverage. We found that upon deposition at room temperature, 3D palladium clusters or chains are formed on alumina depending on the oxide stoichiometry. On MgO cleavage, 2D islands grow. We show that the work function of metal deposit varies in the 8–6 eV range during the early stages of deposition. The adsorption of CO probe molecules on ultrathin Pd deposits was studied, results on their chemical reactivity are discussed with respect to the morphology of the metal clusters. q1999 Elsevier Science B.V. All rights reserved.