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O: Fachverband Oberflächenphysik

O 10: Organic Molecules on Inorganic Substrates II: Electronic, Optical and Other Properties II

O 10.2: Talk

Monday, March 27, 2023, 15:30–15:45, CHE 89

Structural Reorientation of Organic Molecules on Surfaces by Alkali Metal Doping — •Ralf Hemm¹, Ka-Man Yu¹, Steffen-Rambert Rothenberg¹, Sergey Soubatch², Christian Kumpf², Martin Aeschlimann¹, and Benjamin Stadtmüller^1,3 — ¹RPTU Kaiserslautern-Landau, Erwin-Schrödinger-Str. 46, 67663 Kaiserslautern, Germany — ²Peter Grünberg Institut, Forschungszentrum Jülich, 52425 Jülich, Germany — ³Johannes-Gutenberg-Universität Mainz, Staudingerweg 7, 55128 Mainz, Germany

Organic semiconductors are promising materials for the fabrication of next-generation organic-based electronic devices. The electron properties of the organic thin film can be tuned by alkali metal doping and the consequent charge transfer. Here, we study the influence of Cs doping on the structural and electronic properties of the model system PTCDA/Ag(111). Using momentum microscopy, we can simultaneously access changes in occupation of the molecular orbitals and determine modifications of the azimuthal orientation of the PTCDA molecules upon Cs doping. We can identify two structural Cs-PTCDA phases depending on the Cs concentration with either one or two Cs atoms per PTCDA. With increasing Cs concentration, we observe a gradual structural reorientation of the molecules that is accompanied by a modification of the population of the molecular states. Both cases are different from the pristine case. The structural reorientation of the PTCDA molecules can be attributed to the electrostatic interactions between the partially ionized Cs atoms and the negatively polarized oxygen end groups of PTCDA.