Influence of atomic Cu-layer epitaxy on Co 2 and CO phtoinduced desorption from ZnO(0001)

Abstract

CO adsorption is performed on an atomically clean ZnO(0001) surface, on a ZnO(0001) surface covered by 1/3 Cu monolayer and on a ZnO(0001) surface approximately fully covered by an average of 6 atomic Cu layers. Geometric and electronic properties of the initial and CO-saturated surfaces are characterized by LEED, EELS and TCS. Electron spectroscopy data give evidence for CO 2 - chemisorption-complex formation on the ZnO surface, and for Cu oxidation during CO exposure. CO 2 molecules predominate in the photoinduced (Xe-lamp illumination) desorption flow from the clean ZnO(0001) surface, and it is possible to distinguish photodesorption and thermodesorption components. The covering of the ZnO surface with 1/3 layer of Cu induces an increase in CO 2 desorption which indicates an increase of adsorption capacity and of oxidation activity due to Cu-particle action. At the 6 Cu-layer, (111)-oriented-patch-covered surface, catalytic CO oxidation is eliminated, however; a photodesorption mechanism is not valid here, but a predominant CO desorption according to a thermo-mechanism is observed.