Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 14: Metal substrates: Adsorption of organic / bio molecules II
O 14.10: Vortrag
Montag, 22. März 2010, 17:15–17:30, H36
Building 2D crystals from fivefold-symmetric molecules — •Tobias Bauert1, Leo Merz1, Manfred Parschau1, Jay S. Siegel2, Georg Koller3, and Karl-Heinz Ernst1,2 — 1Empa, Nanoscale Material Science, Dübendorf, Switzerland — 2Organisch-chemisches Institut, Universität Zürich, Switzerland — 3Institut für Physik, Karl-Franzens-Universität, Graz, Austria
Curved surface fragments of the fullerene molecule, so-called buckybowls, are promising candidates for surface modifications because of their unique electronic and chemical properties. Corannulene (C20H10) is the simplest curved fullerene fragment with a central C5 ring, surrounded by five aromatic C6 rings. Due to this fivefold symmetry, it is also a fascinating molecule for studies of fundamental phenomena in adsorbed monolayers, like molecular and chiral recognition or spontaneous symmetry breaking. Fivefold symmetry is incompatible with the translational order of a classical crystal lattice, which applies to plane group symmetries of 2D crystals grown at surfaces as well. Corannulene forms a quasi-hexagonal lattice by tilting away from the C5 symmetry. Bulky substituents, however, do not allow a tilt and enforce C5 as tiling motif. The observed molecular structures in STM are compatible with mechanical modeling experiments and Monte-Carlo simulations of hard pentagons. Apart from the self-assembly results, adsorbed corannulene shows interesting electronic properties, like induction of a large interface dipole moment (9 D), as determined with workfunction change measurements via UPS.