Regensburg 2004 – wissenschaftliches Programm
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SYOH: Organic and Hybrid Systems for Future Electronics
SYOH 1: Geometric Organic Structures on Surfaces
SYOH 1.3: Vortrag
Donnerstag, 11. März 2004, 14:30–14:45, H37
Spectro-microscopic study of organic film growth: PTCDA/ Ag(111) — •Th. Schmidt1, U. Groh1, H. Marchetto2, R. Fink3, and E. Umbach1 — 1Exp. Physik II, Universität Würzburg, 97074 Würzburg — 2Fritz-Haber-Institut, 14195 Berlin — 3Phys. Chemie II, Univ. Erlangen, 91058 Erlangen
We report on first dynamic growth studies of PTCDA on Ag(111) using a PEEM with photon excitation by either UV-light or polarized mono-energetic synchrotron radiation. The PEEM instrument is the SMART spectro-microscope in the actual version, an energy-filtered, but not yet aberration-corrected microscope. At elevated temperatures between 350 and 450 K we observe the layer-by-layer growth of two to three layers, followed by the growth of three-dimensional islands (Stranski-Krastanov). At room temperature a transition from Stranski-Krastanov to layer-by-layer growth (Franck-van der Merwe) occurs. By laterally resolved NEXAFS spectroscopy and by switching the linear polarization of the light one can clearly derive the molecular orientation as flat-lying in both, the islands and the bilayer. Additionally, the circular polarization reveals a natural circular dichroism for the PTCDA crystallites, which is unique and unexpectedly large for these planar and non-chiral molecules. Funded by BMBF under contract no. 05-KS1WW2-0.