Angle-resolved photoelectron spectroscopy study of hydrogen adsorption on ZnO($10overline {1} 0$)

The valence electronic structure of the hydrogen adsorbed ZnO($10\overline {\rm 1} 0$) surface has been investigated by angle‐resolved photoelectron spectroscopy utilizing synchrotron radiation. Adsorption of H on ZnO($10\overline {\rm 1} 0$) at room temperature induces a state with a faint photoemission intensity at around the Fermi level. The H‐induced state forms a band with a parabolic dispersion at around the center of the surface Brillouin zone (SBZ). The band has the same energy dispersion relation along two high symmetry axes of the SBZ ($\overline {\Gamma {\rm X'}}$ and $\overline {\Gamma {\rm X}}$), i.e. the isotropic two‐dimensional electronic structure is realized. We propose the mechanism of H‐adsorption‐induced metallization of the ZnO($10\overline {\rm 1} 0$) to be a partial filling of the Zn 4s conduction band as a result of H‐induced downward band bending.