AVS 49th International Symposium
    Organic Films and Devices Tuesday Sessions
       Session OF+SS+EL+SC-TuA

Paper OF+SS+EL+SC-TuA10
Optical Properties of Ordered Ultrathin Films of PTCDA

Tuesday, November 5, 2002, 5:00 pm, Room C-102

Session: Organic Molecular Films
Presenter: R. Nitsche, TU Dresden, Germany
Authors: R. Nitsche, TU Dresden, Germany
H. Proehl, TU Dresden, Germany
S. Mannsfeld, TU Dresden, Germany
T. Dienel, TU Dresden, Germany
T. Fritz, TU Dresden, Germany
Correspondent: Click to Email
Research activity on molecular solids has gathered pace in recent years as these materials have a wide range of interesting properties, emerging industrial interest with real applications at the horizon, and possible future applications that will enable electronics to move into the nanoscale. High quality samples, precise structural data, and a detailed understanding of the physical properties is essential, with special emphasis on thin films and interfaces. In this respect, the use of highly controlled growth techniques like Organic Molecular Beam Epitaxy (OMBE) is becoming more and more important, aiming at high quality thin films with controlled crystal structure and morphology, therefore displaying well defined physical properties. In our contribution we will discuss the special optical properties of ultrathin films of an archetypal organic material, namely PTCDA (perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride). Highly ordered organic thin films 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 (DRS, a variant of reflection absorption spectroscopy) both ex situ and in situ 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. The results are further compared to thin films grown on mica to discuss the influence of different substrates.