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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 Ernst^1,2 — 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.