Berlin 2008 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 5: Organic Thin Films
DS 5.3: Vortrag
Montag, 25. Februar 2008, 18:15–18:30, H 2013
Anisotropic optical function of diindenoperylene thin films determined by ellipsometry — •Ute Heinemeyer1, Reinhard Scholz2, Linus Gisslen2, M. Isabel Alonso3, J. Oriol Ossó3, Miquel Garriga3, Alexander Gerlach1, and Frank Schreiber1 — 1Institut für Angewandte Physik, Auf der Morgenstelle 10, 72076 Tübingen — 2Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, 85748 Garching — 3Institut de Ciència de Materials de Barcelona, CSIC Esfera UAB, 08193 Bellaterra, Spain
Diindenoperylene (DIP) has received increased attention due to its well defined ordering and promising electronic transport properties. Furthermore DIP exhibits a well-defined vibronic progression of the HOMO-LUMO transition providing direct access to the exciton-phonon coupling. We investigate the optical properties of DIP thin films on Si-substrates by variable angle spectroscopic ellipsometry and compare the results with the absorption spectrum of monomers in solution. Since the molecules in the thin film phase are stacked in a highly ordered way the DIP films (≈ 40 nm) exhibit strongly anisotropic optical properties with uniaxial symmetry. Due to this anisotropy, it is necessary to perform a multisample analysis in order to obtain the optical function reliably. This data analysis is discussed for the energy range from 1.25 to 3 eV. A part of the vibronic progression resembles the vibronic subbands of dissolved monomers, but the quantitative interpretation of additional features requires an analysis with a model allowing for the interference between neutral molecular excitations and intermolecular charge transfer transitions.