Spectroscopic evidence for the partial dissociation of H2O on ZnO(1010)

The interaction of water with the non-polar ZnO(10 (1) over bar0) surface has been studied by high resolution electron energy loss spectroscopy (HREELS) and thermal desorption spectroscopy (TDS). Adsorption of water at room temperature leads to the partial dissociation of water molecules giving rise to a well defined (2 x 1) superstructure. This observation was conformed by the HREELS data which show the water-induced O-H stretching modes at 396 and 460 meV ( 3193 and 3709 cm(-1)) as well as the peak at 456 meV (3677 cm(-1)) arising from the OH species. The large red shift of the loss at 396 meV indicates unusually strong hydrogen bonding interactions of water to both neighbouring adsorbate molecules and the surface O atoms which are responsible for the partial dissociation of water molecules on the perfect ZnO(10 (1) over bar0) surface.