Correlation between chemical properties and electronic structure of pseudomorphic Cu monolayers on Ni(111) and Ru(0001)

The adsorption of CO and benzene on pseudomorphic Cu monolayers on Ni(111) and Ru(0001) shows pronounced differences: For Cu/Ni(111) a behavior very similar to that of Cu(111) is observed, for Cu/Ru(0001) the adsorbate substrate bond is significantly strengthened for both molecules, as is deduced from a shift of the desorption temperature to higher values. Based on angle resolved UV photoelectron spectroscopy using synchrotron radiation at BESSY and density functional calculations we have determined the two-dimensional band structure of the pseudomorphic Cu monolayers on Ni(111) and Ru(0001). Our results show that for Cu/Ni(111) only weak coupling of the Cu 3d states to the Ni substrate states occurs. On the other hand, strong coupling is observed for Cu/Ru(0001). This difference is made responsible for the strongly modified chemical properties of Cu/Ru(0001) as compared to Cu/Ni(111). (C) 2001 Published by Elsevier Science B.V.