Dresden 2009 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 23: Organic Thin Films III
DS 23.1: Vortrag
Mittwoch, 25. März 2009, 14:45–15:00, GER 38
Adsorption of bay-substituted perylene bisimide dyes on Ag(111) investigated by PES and NEXAFS — •Markus Scholz1, Stefan Krause1, Rüdiger Schmidt2, Marc Häming1, Achim Schöll1, Frank Würthner2, and Friedrich Reinert1,3 — 1Universität Würzburg, Experimentelle Physik II, 97074 Würzburg — 2Universität Würzburg, Institut für Organische Chemie, 97074 Würzburg — 3Gemeinschaftslabor für Nanoanalytik, Forschungszentrum Karlsruhe, 76021 Karlsruhe
Perylene tetracarboxylic acid bisimides (PBI) are among the best available n-conducting organic materials. Halogen substituents attached to the perylene bay positions change the molecular structure by introducing a twist angle into the usually planar perylene backbone. This influences the optical properties, the stacking of the molecules, as well as the electronic properties. Moreover, the molecular conformation is also expected to effect the interaction with metal contacts, an aspect of crucial importance for electronic devices. We report on a high resolution photoemission (PES) and x-ray absorption (NEXAFS) study of the electronic structure and the molecular orientation of ultra-thin films of the planer PBI-H4, and the core twisted PBI-Cl4 on Ag(111) substrates. In the monolayer regime, substantial changes in the UPS and XPS data with respect to the bulk samples clearly indicate a covalent interaction at the interface. In the valence regime charge transfer induced occupied states are observed at the Fermi-level. This is corroborated by the NEXAFS results, which allow probing a possible change of the molecular conformation due to the interfacial interaction.