Hamburg 2001 – scientific programme

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SYOF: Organische Festkörper

SYOF 2: Surfaces and Interfaces

SYOF 2.4: Talk

Tuesday, March 27, 2001, 12:20–12:35, S6

Self-assembly of PTCDA molecules on strained Ag(111) surfaces: molecular strings and tuning forks — •F.S. Tautz, M. Eremtchenko, and J.A. Schaefer — Institut für Physik, TU Ilmenau, PF 100565, 98684 Ilmenau

On Ag(111), PTCDA grows epitaxially, if the substrate is held at slightly elevated temperature. The site-specific interaction of the molecule with the substrate leads to the commensurability of the overlayer, while the herringbone pattern in which the molecules are arranged is induced (or at least favoured) by the electrostatic interaction between the molecules. If PTCDA is evaporated onto a strained Ag(111) surface, a completely different behaviour is observed. The molecules form highly complex oriented network structures consisting of monomolecular chains and threefold vertices. These structures are unfavourable with respect to the intermolecular electrostatic interaction, since the molecules align with their negatively charges ends pointing towards each other. Nevertheless, single chains can, reminiscent of molecular strings and tuning forks, move as rigid units relative to the silver surface, pointing towards an intermolecular interaction as the driving force for the surprising self-assembly in molecular wires. Possible origins for these observations are discussed.