Pyridine adsorption on the polar ZnO(0001) surface: Zn termination versus O termination

The interaction of pyridine (C5H5N) with the two differently terminated ZnO (0001) surfaces has been investigated using thermal desorption spectroscopy (TDS), x-ray photoelectron spectroscopy (XPS), and x-ray absorption spectr oscopy (NEXAFS). The binding energy of pyridine on the O-terminated ZnO(000 -1) surface amounts to 57 kJ/mol and the spectroscopic data reveal only sma ll modifications of the pyridine electronic structure, indicating the prese nce of a physisorbed species. On the Zn-terminated ZnO(0001) surface, the b inding energy is substantially higher, 112 kJ/mol, and the N1s NEXAFS data for the pyridine pi* resonance shows a shift of 0.6 eV toward higher bindin g energies. This observation indicates a substantial interaction between th e nitrogen lone pair and Zn, as is confirmed by precise ab initio calculati ons of the core-level excitation. (C) 2000 American Institute of Physics. [ S0021-9606(00)71106-8].