Regensburg 2002 – wissenschaftliches Programm
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SYOH: Organische Halbleiter
SYOH 7: Poster
SYOH 7.13: Poster
Montag, 11. März 2002, 18:00–21:00, C
Anisotropic optical properties of ordered F16CuPc thin films — •M. I. Alonso1, M. Garriga1, F. Cerdeira1,2, J. O. Ossó3,1, F. Schreiber3,4, and H. Dosch3,4 — 1Institut de Ciència de Materials de Barcelona, CSIC, 08193 Bellaterra, Spain — 2Instituto de Física “Gleb Wataghin”, UNICAMP, Campinas-SP, Brazil — 3Max-Planck-Institut für Metallforschung, 70569 Stuttgart, Germany — 4Institut für Theoretische und Angewandte Physik, Universität Stuttgart, 70550 Stuttgart, Germany
We report on Raman and ellipsometric spectra of F16CuPc (copper-hexadecafluoro-phthalocyanine) thin films grown by organic molecular beam deposition on stepped sapphire surfaces. The step edges induce a molecular alignment that results in strongly anisotropic optical behavior. By combining the results of these two spectroscopic techniques, information about the arrangement of the molecules in the films is obtained.
Quantitative analysis of the Raman spectra allows to evaluate the orientation of the molecular planes relative to the substrate surface. Ellipsometric results show that the films behave as optically biaxial media with two principal axes of the dielectric tensor on the film surface, coinciding almost with the substrate c-axis direction and its perpendicular. The main spectral features, corresponding to the strong Q-band absorption of phthalocyanines, are polarized in the latter direction, in agreement with standing-up molecules following the substrate step edges. The spectral shape of the Q-band reflects the interactions between π-systems of neighboring molecules. Its dependence on the growth parameters will be discussed.