Adsorption of H on the ZnO(0001) Surface and d<sup>0</sup> Magnetism:\nAn Ab Initio Study

Ab\ninitio total energy calculations were performed to study the\nadsorption of atomic hydrogen on the polar surface of Zn–ZnO(0001)\nfor different degrees of surface coverage. The most stable configuration\nwas calculated as a function of the distance between H and the surface.\nThe present results show that the manifest ferromagnetism depends\non purely surface interactions. It involves charge transfer from the\nH-1s level to the Zn-4s level, leading to a magnetic moment of 1.0\nμ<sub><i>B</i></sub> for full H surface coverage in\nthe supercell. The magnetic interaction between H atoms is ferromagnetic.\nIn addition, for a fully hydrogenated ZnO monolayer with zinc vacancies\n(V<sub>Zn</sub>) or hydrogen-passivated zinc vacancies (V<sub>Zn</sub>–H), a transition from a nonmagnetic semiconductor to a magnetic\nhalf-metal semiconductor has been achieved. Both configurations exhibit\na surface magnetic moment of 2.0 μ<sub>B</sub>, which is twice\nthat obtained for the case without the vacancy. These theoretical\ncalculations agree with our previously published experimental results,\nwhere it was observed that hydrogen is incorporated into the ZnO structure\nand acts as a surface donor.