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CPP: Chemische Physik und Polymerphysik

CPP 23: POSTER Functional Organic Thin Films

CPP 23.2: Poster

Donnerstag, 30. März 2006, 17:00–19:00, P2

Growth of Pentacene on clean and modified Gold Surfaces — •Daniel Kaefer, Lars Ruppel, Gregor Witte, and Christof Woell — Physikalische Chemie I, Ruhr Universitaet Bochum, 44780 Bochum

Because of its high charge carrier mobility and the ability to form (poly-)crystalline films pentacene is still one of the most promising organic semiconductor for the fabrication of organic thin film transistors. Of particular interest is the interaction and growth at the gold interface which is commonly used as electrode material. In view of partly controversial results which have been reported so far for growth of pentacene on gold we have carried out a comprehensive study including temperature and rate dependency as well as the influence of substrate roughness. By combining various microscopy techniques (SEM, STM, AFM) with NEXAFS and UPS the growth scenario of pentacene on clean single crystals and polycrystalline gold surfaces has been compared.

On clean gold surfaces the first monolayer forms a chemisorbed seed-layer with planar adsorption geometry while subsequent growth is characterized by a pronounced dewetting and formation of needle-like islands where molecules adopt a bulk-like upright orientation. At very large deposition rates rather disordered films are formed where this molecular reorientation is quenched. A distinctly different growth scenario was observed for gold surfaces which had been modified before by a SAM. In that case no planar oriented seed-layer is formed and pentacene molecules grow immediately in an upright orientation without any dewetting.