Regensburg 2007 – wissenschaftliches Programm
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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices
SYOE 8: Poster Session SYOE
SYOE 8.42: Poster
Dienstag, 27. März 2007, 18:00–20:00, Poster B
Skew crystal optics: Optical properties of pentacene probed by generalized spectroscopic ellipsometry — •Daniel Faltermeier1, Bruno Gompf1, Martin Dressel1, Mathias Schubert2, Ashutosh Tripathi1, and Jens Pflaum1 — 1Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart — 2Department of Electrical Engineering, University of Nebraska-Lincoln, P.O. Box 880511, Lincoln, U.S.A.
There exist an increasing number of band structure calculations for organic semiconductors. For verification of these theories reliable optical data from single crystals are required. In principle, with traditional spectroscopic tools the anisotropic complex dielectric properties of a crystal can be determined. Problems arise for absorbing crystals, and in general for those with symmetries lower than orthorhombic. We demonstrate that generalized spectroscopic ellipsometry measures the complex dielectric polarization response functions along major polarization axes in triclinic systems. For the example of the organic semiconductor pentacene we demonstrate, that this can be achieved on a single crystal plane, when measuring under multiple azimuth angles, distinct angles of incidence and different incoming polarization states. We obtain, in addition to the major dielectric polarization response functions, that the optically determined major polarization axes directions are almost in perfect agreement with the crystallographic x-ray data, showing that these directions are in fact equivalent, for which so far no proof or indication existed. The results are compared with band structure calculations along the main symmetry directions.