Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 27: Poster Session I (Methods: Scanning probe techniques; Methods: Atomic and electronic structure; Methods: Molecular simulations and statistical mechanics; Oxides and Insulators: Clean surfaces; Oxides and Insulators: Adsorption; Oxides and Insulators: Epitaxy and growth; Semiconductor substrates: Clean surfaces; Semiconductor substrates: Epitaxy and growth; Semiconductor substrates: Adsorption; Nano- optics of metallic and semiconducting nanostructures; Electronic structure; Methods: Electronic structure theory; Methods: other (experimental); Methods: other (theory); Solutions on surfaces; Epitaxial Graphene; Surface oder interface magnetism; Phase transitions; Time-resolved spectroscopies)

O 27.38: Poster

Dienstag, 24. März 2009, 18:30–21:00, P2

Correlation between structural and optical properties of PTCDA monolayers on NaCl/Ag(100) — •Mathias Müller, Eric Le Moal, Oliver Bauer, and Moritz Sokolowski — Institut für Physikalische u. Theoretische Chemie, Universität Bonn, Wegelerstraße 12, 53115 Bonn

We have investigated the structural and optical properties of PTCDA-(sub)monolayers adsorbed on NaCl. Using thin epitaxial NaCl films grown on Ag(100) it was possible to characterize the PTCDA layers by spot profile analysis-LEED and in parallel with in-situ photoluminescence spectroscopy. Under optimized evaporation conditions we succeeded to obtain ordered PTCDA films, which can be described as a 3×3 superstructure. This superstructure is similar to the one of PTCDA observed on Ag(100), but the lattice constant and azimuthal broadening prove that PTCDA is absorbed on NaCl. Presumably due to the commensurability and the high order of the structure we observed sharp peaks in the photoluminescence spectra (similar to [1]) which also show interesting finestructure at low temperature. Furthermore, by cooling the sample at 20 K during evaporation, we prepared a disordered PTCDA phase. By annealing the sample, we could observe a phase transition to the ordered structure by SPA-LEED. This phase transition can also be seen as a redshift in the photoluminescence which we explain by the dipole-dipole-coupling in the PTCDA monolayer. Funding by DFG research unit 557 is gratefully acknowledged. [1] T.Dienel et al., Adv. Mater. 20 (5), 959-963 (2008).