H吸附诱发ZnO(10■0)表面的金属化

Adsorbed-H Induced Metallization of ZnO(10■0) Surface

采用基于广义梯度近似的投影缀加平面波赝势和周期性边界条件的超晶胞模型,用第一原理方法计算并分析了H在ZnO(10■0)面上的吸附能、态密度和能带结构.结果表明:1)H单原子吸附时,H在ZnO(10■0)面上的吸附(用ZnO(10■0)-H表示)只形成OH原子团,没有ZnH出现;面上剩余的Zn悬挂键导致此面显示出很强的金属性.DOS和能带分析显示导带(CB)底的Zn4s态得到电子,向下移动导致价带导带在禁带中出现交叠,呈现明显金属化.2)双H在ZnO(10■0)面上的吸附用ZnO(10■0)-2H表示,在ZnO(10■0)-2H吸附面上,2H分别吸附在O、Zn上,饱和了面上的两个悬挂键,DOS和能带分析显示ZnO(10■0)-2H吸附面与清洁ZnO(10■0)面大致相同,均为绝缘面.

The adsorption energy, density of states （DOS） and band structure of H on a ZnO（101^-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（101^-0） （denoted ZnO（101^-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 （101^-0） is denoteds ZnO（101^-0）-2H. On the surface of ZnO（101^-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（101^-0）-2H surface shows that it is the same as a clean ZuO（101^-0） surface and that both are insulating surfaces.