Berlin 2018 – scientific programme

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O: Fachverband Oberflächenphysik

O 42: Poster: Organic-Inorganic Hybrid Systems and Organic Films

O 42.1: Poster

Tuesday, March 13, 2018, 18:15–20:30, Poster A

Intermolecular Repulsion at Metal/Organic Interfaces: A Quantitative TPD Study — •Stefan Renato Kachel, Benedikt P. Klein, Maik Schöniger, Mark Hutter, Martin Schmid, and J. Michael Gottfried — Fachbereich Chemie, Philipps-Universität Marburg, Germany

Understanding the interaction of π-conjugated organic molecules with metal surfaces is crucial for the development of modern organic electronic devices. Recently we showed how the topology of the π-system influences the surface chemical bond using the example of the structural isomers azulene and naphthalene on Ag(111) and Cu(111) investigated by TPD and DFT calculations. On Cu(111), azulene has a much higher desorption temperature (520 K) than naphthalene (340 K) in the limit of low coverage, while the difference is smaller on Ag(111). With increasing submonolayer coverage, all systems show substantial peak broadening towards lower temperatures. This effect is most pronounced for azulene on Cu(111), where the monolayer signals spread over almost 300 K, adn reveals strong intermolecular repulsion. Two different approaches towards obtaining information about the desorption energy spreading over a monolayer and the strength of the repulsion are presented. Both the Persson model and the inverted Polanyi-Wigner equation are in good agreement with constant-coverage methods like heating-rate variations in the low-coverage range. These studies provide zero-coverage desorption energies of 170 kJ/mol for azulene and 100 kJ/mol for naphthalene, both on Cu(111). Nearest-neighbor repulsion energies for the four systems will be reported.