Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 42: Poster Session II (Nanostructures at surfaces: arrays; Nanostructures at surfaces: Dots, particles, clusters; Nanostructures at surfaces: Other; Nanostructures at surfaces: Wires, tubes; Metal substrates: Adsorption of O and/or H; Metal substrates: Clean surfaces; Metal substrates: Adsorption of organic/bio moledules; Metal substrates: Solid-liquid interfaces; Metal substrates: Adsorption of inorganic molecules; Metal substrates: Epitaxy and growth; Heterogeneous catalysis; Surface chemical reactions; Ab-initio approaches to excitations in condensed matter; Organic, polymeric, biomolecular films– also with adsorbates; Particles and clusters)

O 42.50: Poster

Mittwoch, 25. März 2009, 17:45–20:30, P2

Comparison of Different Porphyrin Derivatives in Scanning Tunneling Microscopy — •Florian Vollnhals, Florian Buchner, Ina Kellner, Yun Bai, Martin Schmid, J. Michael Gottfried, Hans-Peter Steinrück, and Hubertus Marbach — Lehrstuhl für Physikalische Chemie II, Interdisciplinary Center of Molecular Materials (ICMM), Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen

Porphyrin derivatives are considered as ideal building blocks for the self-assembly of molecular devices due to their rigid structure triggering long range order and versatile functionalities. Here we explore the appearance of different porphyrin derivatives, namely octaethylporphyrins (OEP) and tetraphenylporphyrins (TTP), on Ag(111) in scanning tunneling microscopy (STM). Additional information concerning the electronic structure, in particular the density of states close to the Fermi level, was acquired by means of ultraviolet photoelectron spectroscopy (UPS) and scanning tunneling spectroscopy (STS). It will be shown that the contrast in a layer of intermixed CoTPP and 2HTPP [1] and the appearance of individual CoTPP molecules in STM depends on the applied bias voltage. The comparison in particular of CoTPP and CoOEP reveals similar signatures in UPS but different bias dependent appearance in STM. These findings will be discussed in terms of intramolecular conformation, molecule substrate interaction and the corresponding electronic structure. Supported by the DFG through SFB 583. [1] K. Comanici et al., Langmuir, 24(2008), 1897.