Valence band structure of the ZnOð10 10Þ surface studied by angle-resolved photoemission spectroscopy

The electronic band structure of the ZnOð10 10Þ surface has been studied by angle-resolved photoemission spectroscopy utilizing synchrotron radiation. Photon-energy-dependent measurements and K- and O2-adsorption studies revealed that the O 2p dangling-bond state exists at 3.7 eV below the Fermi level at the G point. Polarization-dependent measurements show that the state has dominant contribution of the O 2px orbital (x is parallel to the ð12 10Þ direction) at the G point. It is found that the O 2p dangling-bond band lies within the projected bulk bands along the GX and GX0 axes in the surface Brillouin zone. This result settles a controversial issue on the energetic position of the O 2p dangling-bond band, which has been in dispute among theoretical studies. The dispersion widths are found to be 0.8 and 0.5 eV along the GX and GX0 directions, respectively.