Regensburg 2022 – scientific programme
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O: Fachverband Oberflächenphysik
O 12: Organic Molecules at Surfaces 2: Characterization of Organic Monolayers
O 12.1: Talk
Monday, September 5, 2022, 15:00–15:15, S051
Quantifying Interactions in Organic Monolayers — •Pierre-Martin Dombrowski, Stefan Renato Kachel, Leonard Neuhaus, Tobias Breuer, J. Michael Gottfried, and Gregor Witte — Philipps-Universität Marburg, Germany
The formation of molecular nanostructures is determined by the interplay of intermolecular and molecule-substrate interactions, whose experimental determination is challenging. Temperature-programmed desorption (TPD) is a well-established technique capable of quantifying these interactions, but its analysis is by no means trivial and therefore rarely done quantitatively for large adsorbates. In the present study, we analyse the desorption kinetics of the two organic semiconductors pentacene and perfluoropentacene from Au(111) and MoS2 surfaces to show the potential of TPD and highlight challenges for larger adsorbates. [1,2] Combining TPD with scanning tunnelling microscopy, work function measurements and theoretical modelling, we show that intermolecular interactions are dominated by the intramolecular charge distribution. We are further able to determine the coverage-dependent prefactor of desorption with unprecedented precision, which enables a correlation of the desorption signal with the activation of specific degrees of freedom of motion of adsorbed molecules. Lastly, we compare the differences in molecule-substrate interactions for the two substrates at hand, which reveals that entropy can stabilize organic monolayer films on MoS2 despite a weak molecule-substrate bond.
[1] S. R. Kachel et al., Chem. Sci. (2021), 12, 2575-2585.
[2] P.-M. Dombrowski et al., Nanoscale (2021), 13, 13816-13826.