Regensburg 2007 – scientific programme

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DS: Fachverband Dünne Schichten

DS 25: Symposium: Real Time Growth Studies III

DS 25.4: Invited Talk

Thursday, March 29, 2007, 16:15–17:00, H32

Growth, Interface Formation and Electron Dynamics of Pentacene Thin Films — •Frank Meyer zu Heringdorf — Universität Duisburg-Essen, Lotharstrasse 1, 47048 Duisburg

Pentacene has attracted significant attention lately, as it is an extremely promising candidate for organic field effect transistors in organic displays and radio frequency identification (RFID) tags. We studied the growth and interface formation of Pentacene on various Si surfaces. The initial interaction between the molecule and the substrate is covalent and the molecules are forced to "lie down" on the substrate. Subsequent layers stand upright on top of this flat lying layer and exhibit a fractal shape. As the flat layer remains between the interface and the standing-up molecules, it shields the film from the surface. Consequently, the growth behaviour is independent of the orientation, reconstruction or symmetry of the initial Si surface. The combination of PEEM with pulsed fs-laser sources allows the observation of the decay of electronic excitations in the films with spatial resolution via two photon photoemission. Here, a first photon is used to generate an excitation in the film, while a second photon initiates photoemission. The time-delay between the two (pump- and probe-) photons then allows observation of the decay of the excited intermediate state. The change in the molecular orientation between the initial layer and the fractal islands is also reflected in the decay of electronic excitations in the thin films.