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O: Oberflächenphysik
O 25: Organic films II
O 25.5: Vortrag
Dienstag, 28. März 2006, 16:45–17:00, PHY C213
Metal Electrodes to the Molecular World: Evidence for Size-dependent Interactions — •H.-G. Boyen1, P. Ziemann1, U. Wiedwald1, V. Ivanova2, M. Manolova2, D.M. Kolb2, S. Sakong3, A. Gross3, A. Romanyuk4, M. Büttner4, and P. Oelhafen4 — 1Abteilung Festkörperphysik, Universität Ulm, D-89069 Ulm — 2Abteilung Elektrochemie, Universität Ulm, D-89069 Ulm — 3Abteilung Theoretische Chemie, Universität Ulm, D-89069 Ulm — 4Institut für Physik, Universität Basel, Klingelbergstr. 82, CH-4056 Basel
Organic molecules generally need to be attached to metal electrodes via chemical bonds in order to take advantage of their electrical properties for molecular electronics applications. These chemical bonds, on the other hand, might have strong impact on the electronic properties of the metal leads themselves at the metal/molecule interface.
Here we report experiments aiming to unravel the electronic structure of the metal at the metal/molecule interface representing the early stage of electrode formation. For this purpose, strictly 2-dimensional Pd islands of different size are prepared on top of 4-mercaptopyridine (4MP) Self-Assembled Monolayers (SAMs) by means of a novel electro-chemical approach. Electron spectroscopy together with density functional theory reveal strong interactions between the organic molecules and the metal atoms forming the electrical contact resulting in a drastically reduced density of states at the Fermi level for a nearly closed Pd monolayer and even non-metallic properties in case of nanometer-sized islands.