Angle-resolved photoelectron spectroscopy study of the anion-derived dangling-bond band on ZnO(10(1)over-bar0)

The band structure of surface electronic states on the ZnO(10 (1) over bar0) surface has been investigated by angle-resolved photoelectron spectroscopy utilizing synchrotron radiation. Photon-energy dependent measurement and the K and O-2 adsorption studies have been carried out to identify the surface-localized O 2p dangling-bond state. It is found that the state exits at 3.7 eV below the Fermi level at the (Gamma) over bar point in the surface Brillouin zone and shifts to the higher binding-energy side by 0.8 and 0.5 eV along the (Gamma X) over bar and (Gamma X) over bar axes, respectively. The O 2p dangling-bond band is found to locate below the upper edge of the projected bulk bands along these two high-symmetry axes. The present study settles a controversial issue on the energetic position of the O 2p dangling-bond band, which has been in dispute among theoretical studies.