IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Organic Films and Devices Thursday Sessions
       Session OF+TF-ThM

Paper OF+TF-ThM9
Optical Properties of Highly Ordered Ultrathin Epitaxial Films of PTCDA on Au(111)

Thursday, November 1, 2001, 11:00 am, Room 131

Session: Characterization of Organic Thin Films
Presenter: T. Fritz, TU Dresden, Institut fuer Angewandte Photophysik, Germany
Authors: R. Nitsche, TU Dresden, Institut fuer Angewandte Photophysik, Germany
S. Mannsfeld, TU Dresden, Institut fuer Angewandte Photophysik, Germany
H. Proehl, TU Dresden, Institut fuer Angewandte Photophysik, Germany
T. Fritz, TU Dresden, Institut fuer Angewandte Photophysik, Germany
Correspondent: Click to Email
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. Contrary to a simple discussion of the peak position of the entire spectrum, which would indicate an energetic shift, our thorough analysis reveals that the dominant effect consists of a change in the relative contributions of the several transitions rather than an energetic shift. The results are compared to polycrystalline PTCDA layers of comparable thickness on polycrystalline gold films, exhibiting a larger inhomogeneous broadening.