Regensburg 2022 – scientific programme

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O: Fachverband Oberflächenphysik

O 6: Nanostructures at Surfaces 1

O 6.10: Talk

Monday, September 5, 2022, 12:45–13:00, S052

Substrate-mediated polymorphism in monolayer self-assembly at liquid-solid interfaces — •Arash Badami Behjat¹, Wolfgang Heckl^1,2, Michael Schmittel³, and Markus Lackinger^1,2 — ¹Technical University of Munich, James-Franck-Str. 1, 85748 Garching, Germany — ²Deutsches Museum, Museumsinsel 1, 80538 Munich, Germany — ³Universität Siegen, Adolf-Reichwein-Str. 2, 57068 Siegen, Germany

Scanning-Tunneling Microscopy (STM) studies of molecular self-assembly at liquid-solid interfaces require atomically flat, chemically inert, and electrically conductive substrates, hence are almost exclusively carried out on graphite. Here, we demonstrate that Au (111) passivated with a monolayer of chemisorbed iodine (I-Au(111)) constitutes a viable alternative for fundamental studies. By using aromatic homologues of tricarboxylic acids as a versatile model system, and by a direct comparison between graphite and I-Au (111), we experimentally study and demonstrate the decisive influence of molecule-surface interactions. We present three cases of a novel substrate-mediated polymorphism. On I-Au(111), we consistently find polymorphs with lower packing density and optimized intermolecular binding-a clear indication for diminished molecule-surface interactions. This hypothesis was corroborated by probing the monolayer's thermodynamic stability in variable temperature STM experiments.