Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 65: Oxides and Insulators
O 65.2: Poster
Mittwoch, 18. März 2015, 18:15–21:00, Poster A
The Role of H-Termination on the ZnO (10 10) Surface — •Maria E. Stournara1, Oliver T. Hoffman1,2, Patrick Rinke1,3, and Matthias Scheffler1 — 1Fritz-Haber-Institut der MPG, Berlin, Germany — 2Institut für Festkörperphysik, Technische Universität Graz, Graz, Austria — 3COMP/Department of Applied Physics, Aalto University School of Science, Aalto, Finland
The optical and electronic properties of H-terminated ZnO surfaces play a significant role for the electronic and excitonic states in hybrid inorganic/organic semiconductor technologies. As the intrinsic presence of H affects the properties of the ZnO surface even at infinitesimally low concentrations, a careful evaluation of the stable H-surface configurations is necessary to understand the effect of H adsorption on the surface electronic structure. To elucidate the role of the latter we perform density-functional theory PBE-vdWMBD calculations for various H-concentrations. We find that H adsorption results in a complex behavior with a competition between hydrogen adsorption on surface O and surface Zn atoms, even at low H concentrations. This is responsible for a diverse surface electronic structure, where OH-bonding leads to a metallic behavior, whereas a semiconducting state is restored for adsorption on Zn-sites. Our results indicate that the former is favored at infinitesimally low coverage, whereas the latter is displayed for half-monolayer concentrations where H is adsorbed on neighboring Zn- and O- sites, forming ZnO-"stripes". In light of this, we evaluate intermixed site-motifs via a lattice gas hamiltonian (LGH) to describe H adsorption for a wide range of concentrations.