Berlin 2005 – scientific programme

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O: Oberflächenphysik

O 54: Adsorption an Oberfl
ächen VI

O 54.6: Talk

Wednesday, March 9, 2005, 12:00–12:15, TU EB202

Self-assembled two-dimensional supramolecular structures: Rubrene on Au(111) — •Marie-Christine Blüm, Elizabeta Ćavar, Marina Pivetta, François Patthey, and Wolf-Dieter Schneider — Institut de Physique des Nanostructures, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

We report on the study of the polycyclic aromatic hydrocarbon rubrene (5,6,11,12-Tetraphenylnaphthacene) deposited on a reconstructed Au(111) surface by means of low-temperature STM and STS under UHV conditions. The topographic images measured at 5K reveal a surprising variety of 2D self-assembled structures with different geometries and sizes ranging from dimers up to large ordered islands. A striking feature of this formation is the coexistence of 5- and 6-fold symmetries, i.e. the bonding of the molecules into pentagons, hexagons, honeycomb patterns and hexagonal close packed islands. Furthermore, the molecular pentagons act as new building blocks and line up into chains with lengths of up to 100 nm. The differential conductance spectra acquired on top of a molecule exhibit characteristic peaks which reflect the occupied and unoccupied molecular orbitals and show the presence of an energy bandgap between the HOMO and the LUMO of rubrene adsorbed on Au(111).