AVS 46th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS-WeP

Paper SS-WeP11
Structural and Chemical Investigations on Different Polar ZnO Surfaces

Wednesday, October 27, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: St. Hoevel, Ruhr-Universität Bochum, Germany
Authors: St. Hoevel, Ruhr-Universität Bochum, Germany
Th. Beker, Ruhr-Universität Bochum, Germany
Ch. Boas, Ruhr-Universität Bochum, Germany
U. Burghaus, Ruhr-Universität Bochum, Germany
K. Weiss, Ruhr-Universität Bochum, Germany
M. Wuehn, Ruhr-Universität Bochum, Germany
C. Kolczewski, Ruhr-Universität Bochum, Germany
V. Staemmler, Ruhr-Universität Bochum, Germany
Ch. Woell, Ruhr-Universität Bochum, Germany
Correspondent: Click to Email
We report on investigations of the structural and chemical properties of the two differently terminated Zn(0001) surfaces. The clean, oxygen terminated surface was studied with helium atom scattering (HAS) and LEED. The peak-shapes of the He-atom diffraction peaks and the variation of the He-atom reflectivity as a function of He-atom wavelength provide detailed information on the surface morphology (step height distribution, average terrace width, type of defects). As regards the chemical properties of the surface (e.g. presence of acidic sites), we studied the adsorption behaviour of pyridine on the two differently terminated ZnO(0001) surfaces with thermal desorption spectroscopy (TDS), x-ray photoelectron spectroscopy (XPS), and x-ray absorption spectroscopy (NEXAFS). The interpretation of the latter results is based on precise ab-initio electronic structure calculations for a model compound. The binding energy of pyridine on the O-terminated (000-1)-surface amounts to 57 kJ/mol and the spectroscopic data reveal only small modifications of the pyridine electronic structure, indicating the presence of a physisorbed species. On the Zn-terminated ZnO(0001)-surface the binding is substantially stronger, 112 kJ/mol, and the N1s NEXAFS-data for the pyridine @pi@*-resonance shows a shift of 0.6 eV towards higher binding energies. This observation indicates a substantial interaction between the nitrogen lone pair and the Zn d electrons, as confirmed by the ab-initio calculations.