AVS 47th International Symposium
    Surface Science Thursday Sessions
       Session SS1+MC-ThA

Paper SS1+MC-ThA10
Adsorption of Atomic Hydrogen on Both Polar Surfaces of ZnO

Thursday, October 5, 2000, 5:00 pm, Room 208

Session: Oxidation and Molecule-Oxide Interactions
Presenter: U. Burghaus, Ruhr-University Bochum, Germany
Authors: Th. Becker, Ruhr-University Bochum, Germany
M. Kunat, Ruhr-University Bochum, Germany
Ch. Boas, Ruhr-University Bochum, Germany
U. Burghaus, Ruhr-University Bochum, Germany
C. Wöll, Ruhr-University Bochum, Germany
Correspondent: Click to Email
The interaction of atomic hydrogen with Zn-ZnO and O-ZnO surfaces has been investigated by LEED, He atom scattering, He atom reflectivity measurements (as a function of H exposure and surface temperature, T@sub s@), and XPS. Furthermore, measurements of adsorption probabilities of CO on the two polar surfaces of ZnO are presented (see [1] for CO/O-ZnO) as well as the effect of pre-exposed atomic hydrogen on the adsorption dynamics of CO. He atom diffraction measurements indicate the formation of a well ordered H overlayer structure. The strong attenuation of the specular He atom reflectivity by hydrogen exposure indicates, however, a second competing reaction pathway; since extensive exposure to atomic hydrogen leads to a high degree of disorder on the surface. Values for the heat of adsorption for H were estimated from He-atom reflectivity curves, measured as a function of T@sub s@. The shape of the coverage dependent adsorption probability curves, S(@theta@@sub CO@), of CO are for both surfaces consistent with a precursor mediated adsorption; adsorbate assisted adsorption dominates the adsorption. The He atom reflectivity measurements point to the influence of an intrinsic precursor state. A comparison of He atom reflectivity with S(@theta@@sub CO@) curves, respectively, showed that CO initially populates defect sites. The coadsorption of H and CO can be explained by a site blocking mechanism; leading to an estimate of @theta@@sub H@. [1] Th. Becker, Ch. Boas, U. Burghaus, Ch. Wöll, Phys. Rev. B 61(7) (2000) 4538.