Berlin 2018 – scientific programme

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O: Fachverband Oberflächenphysik

O 14: Organic-inorganic hybrid systems and organic films II

O 14.9: Talk

Monday, March 12, 2018, 17:45–18:00, MA 042

Adsorption of squaraine molecules to Au(111) and Ag(001): Role of the substrate symmetry — •Maike Luft, Boris Gross, Manuela Schiek, and Niklas Nilius — Institute of Physics, Carl von Ossietzky University, 26111 Oldenburg, Germany

The adsorption of squaraines, an important chromophore for the use in organic solar cells, to Ag(001) and Au(111) is studied with STM. Self-assembly into square building blocks is revealed on Ag(001), while no long-range order is observed on Au(111). Squaraine binding to Ag is mediated by carbonyl-oxygen and hydroxyl groups located in the molecular center, while hydrogen bonding between the terminal isobutyl groups and the oxygen species governs the intermolecular coupling. The latter is maximized by rotating the molecules by a few degrees against a perfect square orientation. On Au(111), no squared molecular network forms due to symmetry reasons. Moreover, the high electronegativity of gold reduces the directing effect of oxygen-metal bonds that control the ordering process on Ag. As a result, only frustrated three-fold symmetric molecular units but no extended network develops on Au(111).