Thermal desorption and UPS study of CO adsorbed on Cu‐covered Ru (0001)

Abstract

We have studied the electronic structure and chemisorption properties of (0–4) monolayers of Cu evaporated on a Ru (0001) single crystal substrate. HeI UPS shows that the Cu d band initially (0–1.5 monolayers) forms as an asymmetric resonance of 0.75 eV half width, 2.75 eV below EF. When the Cu coverage is increased, the resonance broadens and shifts nearer EF until a bulk (111) Cu spectrum is attained at 4.0 monolayers [Cu(111) forms on Ru(0001)]. Thermal desorption of CO from the Cu overlayers shows that CO is more strongly bound to the first layer of Cu(?15 kcal/mol) than to the second and succeeding layers of Cu [?12 kcal/mol typical of bulk (111) Cu]. There is also evidence that more CO adsorbs on the first layer of Cu than adsorbs on bulk (111) Cu.