Regensburg 2010 – scientific programme
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O: Fachverband Oberflächenphysik
O 41: Poster Session I (Semiconductor Substrates: Epitaxy and growth; Semiconductor Substrates: Adsorbtion; Semiconductor Substrates: Solid-liquid interfaces; Semiconductor Substrates: Clean surfaces; Oxides and insulators: Epitaxy and growth; Oxides and insulators: Adsorption; Oxides and insulators: Clean surfaces; Organic, polymeric and biomolecular films - also with adsorbates; Organic electronics and photovoltaics, Surface chemical reactions; Heterogeneous catalysis; Phase transitions; Particles and clusters; Surface dynamics; Surface or interface magnetism; Electron and spin dynamics; Spin-Orbit Interaction at Surfaces; Electronic structure; Nanotribology; Solid/liquid interfaces; Graphene; Others)
O 41.38: Poster
Tuesday, March 23, 2010, 18:30–21:00, Poster B1
Tuning surface properties via distributing dipoles in self-assembled monolayers on Au(111) — •David A. Egger1, Ferdinand Rissner1, Gerold M. Rangger1, Oliver T. Hofmann1, Lukas Wittwer1, Georg Heimel2, and Egbert Zojer1 — 1Institute of Solid State Physics, Graz University of Technology, Austria — 2Institut für Physik, Humboldt-Universität zu Berlin, Germany
Quantum-mechanical calculations are performed to study the interface between the Au(111) surface and self-assembled monolayers (SAMs) of π-conjugated molecules. Dipolar pyrimidine rings act as building units to tune the dipole moments of the SAMs in a systematic way via the number of rings in the molecular backbone. The resulting work-function modifications and the energetic alignment of the electronic states in the SAM with respect to the Fermi level are analyzed. Compared to SAMs, where strong dipole moments are introduced by end-group substitutions on otherwise non-polar molecules, an entirely different evolution of those two quantities with the backbone length is found for the present systems, where dipoles are built directly into the backbone. The distributed-dipole approach provides an additional handle for tuning surface properties and the achievable work-function modifcations can be huge. In fact, they are limited only by pinning of the metal Fermi-level at the frontier molecular states.