Adsorbed-H Induced Metallization of ZnO(10-10) Surface

Abstract

The adsorption energy, density of states (DOS) and band structure of H on a ZnO(10■0) surface were studied using the first-principles projector-augmented-wave (PAW) method based on density functional theory (DFT) within the generalized gradient approximation (GGA) and the supercell model. It was found that: 1) For H adsorbed on ZnO(10■0) (denoted ZnO(10■0)-H) only the OH group was formed and the ZnH species was not detected. The unoccupied Zn 4s electronic state receives an electron and renders the surface metallic. DOS and the band structure show that the Zn 4s electronic state in the conduction band (CB) receives electrons and migrates toward the forbidden band so that overlapping of the CB and valence band (VB) below the Fermi level is observed. 2) When 2H are adsorbed, the ZnO (10■0) is denoteds ZnO(10■0)-2H. On the surface of ZnO(10■0)-2H two Hs are adsorbed separately on Zn and O and the two dangling bonds on the surface are saturated. The analysis of DOS and band structure of the ZnO(10■0)-2H surface shows that it is the same as a clean ZnO(10■0) surface and that both are insulating surfaces.