INFLUENCE OF ATOMIC CU-LAYER EPITAXY ON CO2 AND CO PHOTOINDUCED DESORPTION FROM ZNO(0001)

CO adsorption is performed on an atomically clean ZnO(0001) surface, o n a ZnO(0001) surface covered by 1/3 Cu monolayer and on a ZnO(0001) s urface 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 spectroscop y data give evidence for CO2- chemisorption-complex formation on the Z nO surface, and for Cu oxidation during CO exposure. CO2 molecules pre dominate in the photoinduced (Xe-lamp illumination) desorption flow fr om the clean ZnO(0001) surface, and it is possible to distinguish phot odesorption and thermodesorption components. The covering of the ZnO s urface with 1/3 layer of Cu induces an increase in CO2 desorption whic h indicates an increase of adsorption capacity and of oxidation activi ty due to Cu-particle action. At the 6 Cu-layer, (111)-oriented-patch- covered surface, catalytic CO oxidation is eliminated, however; a phot odesorption mechanism is not valid here, but a predominant CO desorpti on according to a thermo-mechanism is observed.