Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 36: Poster Session II (Metals; Nanostructures at surfaces; Surface or interface magnetism; Spin-Orbit Interaction at Surfaces; Electron and spin dynamics; Surface dynamics; Methods; Theory and computation of electronic structure)
O 36.28: Poster
Dienstag, 15. März 2011, 18:30–22:00, P4
Site-specific polarization screening in organic thin films: Tetracene on Ag(111) — Tomoki Sueyoshi1,2, Christian Weiss1, Axel Delhey1, Markus Eschbach1, •Sergey Subach1, and Stefan Tautz1 — 1Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany and JARA-Fundamentals of Future Information Technology — 2Graduate School of Advanced Integration Science, Chiba University Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
Organic semiconductors attract considerable attention due to their relevance for electronic devices. The electronic properties of molecules on metals have been studied in particular. For example, it has been shown that the chemical bonding to a metal surface may change both the electronic levels and geometric structure of organic molecules profoundly. Upon charge transport, the electronic states of a molecular material may also be influenced by polarization screening, i.e., the stabilization of a locally injected charge through the polarization of the surrounding molecular environment. Another aspect we report on, namely, the site specificity of the polarization energy in complex unit cells and at surfaces of organic materials can thus have a significant influence on transport properties. Scanning tunneling spectroscopy and ultraviolet photoelectron spectroscopy of tetracene films reveal strong energy level shifts by up to 1 eV from molecule to molecule. This effect can be traced back to the site specificity of polarization energy caused by a combination of different molecular environments, the intrinsic anisotropy of molecular polarizability, and the influence of the substrate.