Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 32: Oxides and Insulators: Clean Surfaces

O 32.15: Vortrag

Dienstag, 26. Februar 2008, 16:30–16:45, MA 042

The quest for ZnO(1120) surface states – an ARPES study — •Christian Pettenkofer and Stefan Andres — Hahn-Meitner-Institut, Glienicker Str. 100, D-14109 Berlin

We present angle resolved photoemission data from differently prepared ZnO(1120) single crystals and epitaxially grown thin films. ZnO(1120) single crystal surfaces were prepared by both cleaving in vacuum and sputtering-annealing cycles of pre-polished crystals. ZnO(1120) thin films were grown heteroepitaxially on the r-face of sapphire by MOMBE using diethylzinc and water as precursor molecules. The ARUPS-spectra were recorded at the TGM7 beamline at BESSY-II synchrotron light facility in Berlin.

The band dispersion along k_∥ and k_⊥ is discussed in accordance with theoretical band structure calculations of the bulk electronic states within the GGA-DFT framework. An excellent agreement between the theoretically and experimentally determined band structure is achieved for the upper valence bands. Furthermore the surface electronic structure of both the epitaxially grown thin films and the single crystals coincide very well with each other.

It is shown, that despite the very different nature of the surface preparation methods no surface states could be observed. Therefore different effects such as hydrogen adsorption, surface defects and lattice relaxation will be discussed with regard to the specific surface preparation method.