Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 27: Organische Dünnschichten I

O 27.7: Vortrag

Donnerstag, 27. März 2003, 12:45–13:00, HSZ/02

Differential Reflection Spectroscopy of ordered organic thin films: II. PTCDA on Au(111) — •Robert Nitsche, Holger Proehl, Thomas Dienel, and Torsten Fritz — Institut für Angewandte Photophysik, Technische Universität Dresden, 01062 Dresden

Based on the findings of part I. PTCDA on Mica, this second contribution discusses the influence of the substrate on the optical properties of PTCDA films.

Highly ordered organic thin films of PTCDA on a gold single crystal have been prepared by means of OMBE 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. Differential Reflection Spectroscopy has been applied to measure the optical characteristics of those films. The results clearly show that ultrathin layers have different optical properties as compared to thicker films, which in turn match the results known for long from polycrystalline samples. Further comparison with the experimental findings of part I. PTCDA on Mica reveals that significant differences concerning the optical properties of both systems, PTCDA on Au(111) and PTCDA on Mica, exist. This behavior can be explained by assuming layer-by-layer growth for PTCDA films on Mica versus Stranski-Krastanow growth for PTCDA films grown on Au(111).