Berlin 2008 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 63: Symposium: Frontiers of Surface Sensitive Electron Microscopy II (Invited Speakers: Jürgen Kirschner, Liviu Chelaru, Michael Bauer, Claus Schneider)
O 63.3: Vortrag
Donnerstag, 28. Februar 2008, 10:30–10:45, MA 043
A PEEM Study of the Substrate Dependence of Pentacene Thin Film Growth on Silicon — •Simone Möllenbeck1, Dagmar Thien1, Peter Kury1, Kelly R. Roos1,2, Dirk Wall1, Michael Horn-von Hoegen1, and Frank-J. Meyer zu Heringdorf1 — 1Department of Physics and Center for Nanointegration Duisburg-Essen (CeNIDE) Universität Duisburg-Essen, D-47057 Duisburg, Germany — 2Department of Physics, Bradley University, Peoria, IL 61625, USA
We used Photoemission Electron Microscopy (PEEM) to compare the well known behavior of Pentacene on Si(001) with the growth of Pentacene on different silicon surfaces with orientations between Si(111) and Si(001). The growth mode and morphology of Pentacene films are neither changed by an increase of the surface step density nor by the transition from a threefold to a twofold symmetry of the surface. An explanation for the observed behavior is the covalently bonded, disordered wetting layer, that acts as an interfactant layer and isolates the film from substrate defects and the substrate’s structure. Furthermore, we have studied the electronic properties of thin Pentacene films on Si(001) with time-resolved PEEM. As result we get spatially resolved pump-probe traces whereby a "lifetime map" can be generated. The observed lifetime τ=200fs for electronic excitation in the Pentacene wetting layer is by a factor two smaller than the lifetime for the first layer. We attribute this to the difference in electronic coupling of the monolayers to the substrate, that is also apparent in the different work-function of these layers.