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O: Fachverband Oberflächenphysik

O 40: Organic Molecules on Inorganic Substrates III: Electronic, Optical and other Properties

O 40.9: Vortrag

Dienstag, 17. März 2020, 12:30–12:45, REC C 213

Molecular Topology and Surface Chemical Bond of Aromatic Ring Systems — •Lukas Ruppenthal, Benedikt P. Klein, Jan Herritsch, Stefan R. Kachel, and J. Michael Gottfried — Fachbereich Chemie, Philipps-Universität Marburg, Germany

Metal/organic interfaces formed at the contacts between metal electrodes and organic semiconductors have a large impact on the performance of organic-electronic devices. The detailed understanding of their chemical, electronic and geometric structure is therefore important for the further technological development. Many common organic semiconductors contain π-electron systems with alternant topologies, whereas non-alternant alternatives have only recently found increasing attention due to their unusual electronic properties. Here, we compare naphthalene as an alternant aromatic molecule with azulene as its non-alternant isomer, both on Cu(111), using PES, NEXAFS, TPD, STM, and LEED. With the same approach, we compare the larger aromatic compounds pyrene and its isomer dicyclopenta[ef,kl]heptalene (azupyrene), which is also important as a model for the Stone-Wales defects in graphene. In both cases, we find that the non-alternant isomer forms a stronger bond to the metal surface than its alternant counterpart.The increased interaction of the non-alternant isomers is related to their reduced HOMO-LUMO gap, which brings the LUMO energetically close to the Fermi energy of the metal, causing stronger hybridization with electronic states of the metal surfaces. The resulting effects on the electronic and geometric structure will be discussed on the basis of DFT calculations.