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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 15: Poster Session I

CPP 15.9: Poster

Montag, 17. März 2025, 19:00–21:00, P4

Effect of fluorinated tail groups on the properties of aromatic self-assembled monolayers — Yangbiao Liu¹, Sonja Katzbach², Andreas Terfort², and •Michael Zharnikov¹ — ¹Angewandte Physikalische Chemie, Universität Heidelberg, 69120 Heidelberg, Germany. — ²Institut für Anorganische und Analytische Chemie, Johann Wolfgang Goethe Universität Frankfurt, 60438 Frankfurt am Main, Germany

Electric transport properties of functional self-assembled monolayers (SAMs) are important for interface engineering in organic electronics and molecular electronics. As was shown recently, substituting only one terminal hydrogen atom in SAMs with a halogen atom changes their electric conductance noticeably. In this context, we studied the respective effects in a series of non-substituted and methyl-substituted biphenylthiolate (BPT) SAMs on Au(111), exchanging the terminal hydrogen atom/atoms for fluorine/fluorines and testing not only single-component but binary SAMs as well. The gradual variation of the work function with the SAM composition was accompanied by a gradual variation of electrical conductance, decreasing, in particular, by two orders of magnitude at going from CH3-BPT to CF3-BPT SAMs. The observed behavior was tentatively explained by the higher projected density-of-states at the position of the terminal tail groups in the CH3-BPT (H-BPT) case compared to CF3-BPT (F-BPT) and by the appearance of an internal electrostatic field in the SAMs, leading to a change and renormalization of the energy level alignments within the junction upon contact of the SAMs to the top EGaIn electrode.

Keywords: self-assembled monolayers; Molecular Electronics; Charge transport at nanoscale; work function