Dresden 2006 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 23: POSTER Functional Organic Thin Films
CPP 23.3: Poster
Donnerstag, 30. März 2006, 17:00–19:00, P2
Quantitative investigation of the dielectric properties in the ab-plane of pentacene single crystals — •Mandy Grobosch1, Thomas Pichler1, Helmuth Berger2, Martin Knupfer1, and Wieland Zahn3 — 1IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany — 2Institute of Physics of Complex Matter, EPFL, CH-1015 Lausanne, Switzerland — 3Westsaechsische Hochschule Zwickau (FH), Dr.-Friedrichs-Ring 2a, D-08056 Zwickau, Germany
Polarization dependence of the optical reflectivity spectra of pentacene single crystals grown by sublimation have been investigated over a wide range of frequencies from the middle infrared to the visible range (5meV to 3 eV) at room temperature. Furthermore measurements with electron energy-loss spectroscopy (EELS) in transmission have been performed on pentacene thin films. A series of optical phonon modes and electronic transitions have been observed. The determination of the electronic properties have been carried out in the energy rang from 1.7 eV to 2.3 eV within a Lorentz-model. In addition to previous studies we observed the onset of the optical absorption at 1.87 eV followed by a series of four excitations at 1.97 eV, 2.11 eV, 2.14 eV, and 2.28 eV. The results revealed that the dielectric function of pentacene single crystals shows a strongly anisotropic dependence in the ab-plane on the polarization of the incident light.