Regensburg 2007 – scientific programme

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DS: Fachverband Dünne Schichten

DS 18: Symposium: In situ Optics I

DS 18.3: Invited Talk

Wednesday, March 28, 2007, 16:00–16:30, H34

Surface enhanced Raman spectroscopy as a probe for studying metal/organic interfaces — •Georgeta Salvan and Dietrich Zahn — Chemnitz University of Technology, D-09107 Chemnitz, Germany

The physical and chemical properties of the interfaces between metallic contacts and organic semiconductor films in hybrid devices such as organic light emitting diodes, organic solar cells or organic field effect transistors influence significantly the device performance. In this work the metal film growth is assessed by in situ monitoring of the Raman scattering by the internal and collective vibrational modes in crystalline organic semiconductor layers. As model systems molecular layers of two perylene derivatives, viz. 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) and dimethyl 3,4,9,10-perylene-tetracarboxylic diimide (DiMe-PTCDI) grown on sulfur passivated GaAs(100) substrates were investigated. Silver, known to form rather inert contacts, magnesium, known as a very reactive metal, and indium, a metal with intermediate reactivity, were deposited each by thermal evaporation under ultra-high vacuum conditions. The experiments benefit from a strong enhancement of the scattering intensity of internal molecular modes induced by the metals layers, known as Surface Enhanced Raman Scattering (SERS). The analysis of the spectral evolution with the metal thickness allows to extract information on the chemical aspects of the interface formation, on the diffusion length of the metal atoms into the organic layers as well as on the morphology of the growing metallic layers.