Interaction of Ultrathin Films of Cu with Rh ( 100 ) and Ru ( 0001 ) : An XPS Study
نویسندگان
چکیده
The interaction of ultrathin fdms of Cu with Rh(100) and Ru(0001) has been examined by using X-ray photoelectron spectrapcopy (XPS). The effects of surface annealing temperature, adsorbate coverage (film thickness), and CO chemisorption were investigated. The XPS data show that the atoms in a monolayer of Cu supported on Rh( 100) or Ru(0001) are electronically perturbed with respect to the surface atoms of Cu( 100). The magnitude of the electronic perturbations is larger for Cu/Rh( 100). Measurements of the C U ( ~ P , , ~ ) XPS peak position of Cu/Rh(100) and Cu/Ru(0001) as a function of film thickness show that the Cu-Rh and Cu-Ru interactions affect the electronic properties of two or three layers of Cu atoms. The present results show a correlation between the shifts in the XPS surface core-level binding energies and the variations in the desorption temperature of CO from Cu adlayers. The shifts in XPS binding energies and CO desorption temperatures can be explained in terms of (1) variations that occur in the Cu-Cu interaction when Cu adopts the lattice parameters of Rh( 100) or Ru(0001) in a pseudomorphic adlayer and (2) modifications in the electronic properties of the Cu adatoms, caused by the Cu-Rh and Cu-Ru interactions. Chemisorption of CO induces a large decrease in the electron density of the Cu adlayers.
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