Dresden 2011 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 42: Poster I: Progress in Micro- and Nanopatterning: Techniques and Applications (jointly with O); Spins in Organic Materials; Ion Interactions with Nano Scale Materials; Organic Electronics and Photovoltaics; Plasmonics and Nanophotonics (jointly with HL and O); High-k and Low-k Dielectrics (jointly with DF); Organic Thin Films; Nanoengineered Thin Films; Layer Deposition Processes; Layer Properties: Electrical, Optical, and Mechanical Properties; Thin Film Characterisation: Structure Analysis and Composition; Application of Thin Films

DS 42.37: Poster

Mittwoch, 16. März 2011, 15:00–17:30, P1

Determination of molecular electronic excitations using epitaxial thin film growth: Perfluoropentacene on alkali halides — •Tobias Breuer and Gregor Witte — Molekulare Festkörperphysik, Philipps-Universität Marburg, D-35032 Marburg

The study of optical excitations is an important part of understanding electronic properties in organic semiconductors. As it is in many cases hardly possible to prepare sufficiently sized crystals, optical spectroscopy of organic single crystals is a challenging topic. Here we present an alternative approach: to study optical excitations in Perfluoropentacene (C₂₂F₁₄) we prepared epitaxial thin films on the (100)-surfaces of alkali halides. The epitaxial growth of PFP films was proved and studied by AFM and XRD measurements. While exhibiting the same crystalline phase a rather different molecular orientation is adopted on both substrates showing an upright orientation on NaF and a recumbent orientation on KCl which in both cases are stabilized by an electrostatic point-in-line relationship between the outermost fluorine atoms and the alkali cations of the substrate surfaces. While previous studies of optical excitations in PFP were hampered by the laterally isotropic (100)-growth of PFP on amorphous SiO₂[1] the different epitaxial growth modes on the alkali halides enabled access to all molecular axes. A combination of UV/Vis measurements and spectrally and polarization resolved microscopy enabled the determination of the polarization dependence of the observed optical excitations. Evidence of intermolecular coupling was found and will be discussed.

[1] A. Hinderhofer et al., J. Chem. Phys. 127, 194705 (2007).