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O: Fachverband Oberflächenphysik

O 35: Poster Session I (Metal, semiconductor and oxide substrates: structure and adsorbates; Graphene)

O 35.55: Poster

Dienstag, 12. März 2013, 18:15–21:45, Poster B1

Self-assembly of cobalt phthalocyanine molecules on ultrathin CoO(111) films on Ir(100) — •Tobias Schmitt, Pascal Ferstl, Lutz Hammer, and M. Alexander Schneider — LS f. Festkörperphysik, Uni. Erlangen, Germany

We investigated the adsorption of cobalt phthalocyanine (CoPc) molecules on a bilayer of CoO(111) on Ir(100)[1] by low-temperature scanning tunneling microscopy in UHV. CoPc molecules prefer to lie flat on that surface with the Co-Ion centered above oxygen atoms. The rotational orientation of the molecules is determined by the interaction of N-atoms of the macrocycle with the underlying Co-atoms and between π-electrons and the oxygen atoms of the substrate. This leads to adsorption geometries which are dominated by molecule-substrate interaction similar to those found on TiO₂[2]. At higher coverage (0,7 ML) one-dimensional chains with a core-core distance of 1.3 nm are formed while the molecular adsorption site and orientation stay the same. This points to a short-ranged intermolecular interaction, that governs the self-assembly. Only at a coverage of ≃1 ML the CoPcs rotate to decrease the C-N..H hydrogen bond length. We discuss these findings also in the light of the dense structures formed on metal surfaces [3].

[1] C. Tröppner, et al., Phys. Rev. B, in press

[2] Y. Wang, et al., J. Phys. Chem. B 2006, 110, 17960

[3] Y. Wang, et al., J. Am. Chem. Soc. 2009, 131, 10400