Regensburg 2002 – wissenschaftliches Programm

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SYOH: Organische Halbleiter

SYOH 7: Poster

SYOH 7.8: Poster

Montag, 11. März 2002, 18:00–21:00, C

Optical Properties of Highly Ordered Ultrathin Epitaxial Films of PTCDA on Au(111) — •Robert Nitsche, Stefan Mannsfeld, Holger Proehl, and Torsten Fritz — TU Dresden, Institut fuer Angewandte Photophysik, D-01062 Dresden, Germany

Highly ordered organic thin films on a gold single crystal have been prepared by means of organic molecular beam epitaxy and investigated by optical absorption spectroscopy. The organic dye molecule perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride (PTCDA) has been deposited on Au(111) with submonolayer to multilayer coverage. All films were structurally characterized by combining Scanning Tunneling Microscopy (STM) with Low Energy Electron Diffraction (LEED), clearly indicating epitaxial growth in the point-on-line mode. In order to determine the optical constants of those films, Differential Reflection Spectroscopy (DRS) has been applied. Subsequently, the optical constants have been calculated based on a model dispersion formula, thereby deconvoluting the absorption index k into several molecular transitions. The thickness dependence of the parameters (position, width, strength) of those transitions is discussed. The results are compared to polycrystalline PTCDA layers of comparable thickness on polycrystalline gold films, exhibiting a larger inhomogeneous broadening.