Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 55: Poster Session III - MA 141/144 (Methods: Atomic and Electronic Structure; Particles and Clusters; Heterogeneous Catalysis; Semiconductor Substrates: Epitaxy and Growth+Adsorption+Clean Surfaces+Solid-Liquid Interfaces; Oxides and Insulators: Solid-Liquid Interfaces+Epitaxy and Growth; Phase Transitions; Metal Substrates: Adsorption of Inorganic Molecules+Epitaxy and Growth; Surface Chemical Reactions; Bimetallic Nanosystems: Tuning Physical and Chemical Properties; Oxides and insulators: Adsorption; Organic, polymeric, biomolecular films; etc.)

O 55.41: Poster

Wednesday, February 27, 2008, 18:30–19:30, Poster F

The interface between diamond and aqueous electrolyte — •Markus Dankerl, Moritz Hauf, Ulrich Stützel, Andreas Reitinger, Jose Garrido, and Martin Stutzmann — Walter Schottky Institut, Technische Universität Müunchen, Am Coulombwall 3, 85748 Garching

Diamond, which is terminated with hydrogen at the surface, shows the intriguing property of being p-type surface conductive with a two-dimensional hole gas forming beneath the surface. If brought into electrolyte solutions, this surface conductivity shows a dependence on the diamond electrode potential. This allows for the fabrication of in-plane FETs with the electrolyte functioning as gate, therefore called EGFETs. We report on the characterization of the surface conductivity of single crystalline hydrogen terminated diamond in contact with electrolyte. The focus is put on the effect coulombic screening of charge at the interface by salts with different valency has on the surface conductivity. Experimental results are compared to simulations based on the screening effect. In this context the mechanism of the pH sensitivity is discussed, where the effect of ionic strength on pH sensitivity suggests, that pH-dependent surface charges have an equivalent effect on the surface conductivity as a change of the electrode potential.