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The valence band structure of the (10 10) surface of wurtzite ZnO has been investigated by angle-resolved photoelectron spectroscopy utilizing polarized synchrotron radiation. The energetic position and the dispersion width of the O 2p dangling-bond (DB) state are determined along the high symmetry axes of the surface Brillouin zone (SBZ). The O 2p DB is 3.7 eV below the point and disperses to higher binding energies with a total dispersion width of ∼1.2 eV. Comparison with the projected bulk bands from the earlier theoretical studies reveals that the DB state is a surface resonance in the whole SBZ. Polarizationdependent measurements have also been carried out along the X axis suggest that the DB band with odd symmetry with respect to the mirror plane of the crystal surface has a larger dispersion than the band with even symmetry.

Angle-resolved photoemission measurements are carried out to investigate the valence electronic structure of Cu on ZnO(101̄0). The coverage-dependent measurements of the Cu 3d and 4sp bands reveal that the growth of the Cu overlayer is characterized by a cluster formation. These Cu clusters are semiconductors with an energy gap around the Fermi level at the initial stages of adsorption, while the metallic nature is developed with increasing coverage. The Cu 3d state forms a band with a bulklike energy dispersion at high Cu coverages, whereas the two-dimensional (2D) band is formed in the low-coverage region, where the clusters are semiconducting in nature. From the dispersion relation of the 2D Cu 3d band, the arrangement of the Cu adatoms within the clusters is found to be strongly influenced by the surface structure of ZnO(101̄0), i.e., the Cu adatoms are linearly arranged along the Zn−O dimer rows of the substrate surface.