| AVS 56th International Symposium & Exhibition | |
| Surface Science | Tuesday Sessions |
| Session SS2-TuA |
| Session: | Wide Band Gap Semiconductors |
| Presenter: | M. Valtiner, Max-Planck-Institute für Eisenforschung GmbH, Germany |
| Authors: | M. Valtiner, Max-Planck-Institute für Eisenforschung GmbH, Germany M. Todorova, Max-Planck-Institute für Eisenforschung GmbH, Germany J. Neugebauer, Max-Planck-Institute für Eisenforschung GmbH, Germany G. Grundmeier, University of Paderborn, Germany |
| Correspondent: | Click to Email |
The surface chemistry of oxides in humid atmospheres and in water based electrolytes (as e.g. oxide dissolution promoting effects of H+ and OH-) is an important aspect of molecular adhesion and related phenomena. Preparation and characterization of atomically well-defined oxide/electrolyte model interfaces, which allow well-defined molecular adhesion studies, are the most challenging issue in this context. Therefore, this contribution will focus of experimental results of the preparation of single crystalline ZnO(0001)-Zn model surfaces in humid atmospheres and complementary DFT-based ab-initio thermodynamics studies.
The main focus is the preparation and characterisation of surfaces, which are well defined on an atomic scale. The atomic structure of the polar ZnO(0001) surfaces in dry and humid oxygen environment was studied by diffraction experiments and density-functional theory in combination with atomistic thermodynamics. Our results indicate that for similar stoichiometries a large number of very different, but energetically almost degenerate reconstructions exist. Thus vibrational entropy, which could be safely neglected for most semi-conductor surfaces, becomes dominant giving rise to a hitherto not reported strong dependence of surface phase diagrams on temperature. Based on this insight we are able to consistently describe and explain the experimentally observed surface structures on polar ZnO(0001) surfaces [1,2].
Moreover, it will be shown that ZnO(0001)-Zn surfaces are stable and single crystalline within a wide pH range. An in-situ AFM study of the acidic dissolution allowed an nanoscale imaging of the dissolution process and hence a mechanistic understanding of the dissolution process of ZnO can be supported on a nanoscopic level [3]. Finally, first results of combining single molecule adhesion measurements with these single crystalline substrates will be highlighted.
[1] M. Valtiner, S. Borodin, G. Grundmeier; Physical Chemistry Chemical Physics, 9(19), (2007) 2406-2412.
[2] M.Valtiner, M. Todorova, G.Grundmeier, and J. Neugebauer; submitted to Physical Review Letters.
[3] M. Valtiner, S. Borodin, G. Grundmeier; Langmuir, 24(10),(2008) 5350-5358.