Hamburg 2001 – wissenschaftliches Programm
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SYOF: Organische Festkörper
SYOF 5: Poster Session
SYOF 5.31: Poster
Dienstag, 27. März 2001, 17:00–19:00, Aula S3
Optical properties of single crystalline PTCDA studied by spectroscopic ellipsometry — •M. Garriga1, M.I. Alonso1, N. Karl2, J.O. Ossó1,3, F. Schreiber3,4, and H. Dosch3,4 — 1Institut de Ciència de Materials de Barcelona, CSIC, E-08193 Bellaterra — 2Univ. of Stuttgart, 3. Phys. Inst., D-70550 Stuttgart — 3MPI für Metallforschung, Heisenbergstr. 1, D-70569 Stuttgart — 4Univ. of Stuttgart, Institut für Theoretische und Angewandte Physik, D-70550 Stuttgart
We study the anisotropic optical behavior of PTCDA by spectroscopic ellipsometry. This compound is an archetypal model system both for organic epitaxy and for achievement of optoelectronic devices based on organic semiconductors. Thus, knowledge of the optical properties of the bulk material is most desirable, not only as reference for characterization of PTCDA-containing heterostructures, but also for the study of basic questions connected with the tensorial character of the dielectric function.
Crystals of dimensions sufficient for our measurements were obtained by temperature gradient sublimation under vacuum or under a weak nitrogen gas stream at ∼1 mbar. Ellipsometric spectra were taken on different crystallographic faces of a single crystal. The spectra contain well-resolved features previously assigned in absorption to an excitonic peak at 2.2 eV, four S1[0−νn] peaks between 2.4 and 3.0 eV, and two peaks at 3.3 and 3.45 eV. An additional strong structure is observed at ∼5 eV. These observed features of the complex dielectric tensor exhibit characteristic anisotropic behaviors.
The relationship between optical anisotropy and crystalline structure will be discussed.