Dresden 2003 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
O: Oberflächenphysik
O 24: Postersitzung (Epitaxie und Wachstum, Oxide und Isolatoren, Elektronische Struktur, Oberfl
ächenreaktionen, Adsorption an Oberfl
ächen, Organische Dünnschichten)
O 24.80: Poster
Mittwoch, 26. März 2003, 14:30–17:30, P1
Growth dynamics of ultra thin organic films monitored by the SMART spectromicroscope — •U. Groh1, Th. Schmidt1, H. Marchetto2, R. Fink3, and E. Umbach1 — 1Exp. Physik II, Univ. Würzburg, 97074 Würzburg — 2Fritz-Haber-Institut, 14195 Berlin — 3Phys. Chemie II, Univ. Erlangen, 91058 Erlangen
Thin PTCDA films on silver surfaces represent ideal model systems for the study of medium sized organic molecules on metallic surfaces. Special interest is addressed to the growth of the organic film because this determines substantially the structure as well as the morphology and hence also all other film properties. We report on first dynamic growth studies using the spectromicroscope SMART, which is presently installed as an energyfiltered photoemission electron microscope (XPEEM) at the UE52 undulator beamline at BESSY II. The PTCDA growth on Ag(111) was studied in real time using either UV-light of a Hg short arc lamp or polarized monoenergetic synchrotron light. At elevated temperatures between 350 and 450 K we observed 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 light polarization one can clearly derive the molecular orientation as flat lying in both, the islands and the bilayer. Due to fast detection the growth is studied dynamically by x-ray photoemission, allowing to follow the chemical shifts in dependence on the film thickness.