Berlin 2024 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 25: Organic Molecules on Inorganic Substrates III: Adsorption & Growth
O 25.1: Vortrag
Dienstag, 19. März 2024, 10:30–10:45, MA 043
(Meta)stable monolayers on metals: Kinetic trapping of the flat-lying phase — •Anna Werkovits1, Simon B. Hollweger1, Max Niederreiter2, Thomas Risse3, Johannes J. Cartus1, Martin Sterrer2, Sebastian Matera4, and Oliver T. Hofmann1 — 1Institute of Solid State Physics, TU Graz — 2Institute of Physics, KFU Graz — 3Institut für Chemie und Biochemie, Freie Universität Berlin — 4Theory Department, Fritz Haber Institute of the MPG
While conventional wisdom dictates that conjugated organic molecules on metals adopt a flat-lying configuration, recent studies indicate coverage-dependent shifts to upright-standing phases, which exhibit distinctly different physical characteristics. Our investigation challenges the prevailing notion by arguing that, from an energetic standpoint, thermodynamically stable upright-standing phases may be more widespread than previously believed. However, these phases are often not found experimentally due to kinetically trapping under typical experimental conditions. Using a combination of first principles kinetic Monte Carlo simulations and experiment, we show that during the growth process of organic molecules, phases with a lower molecular density (i.e., flat-lying molecules) are formed before the thermodynamically more stable upright standing phase. Notably, the transition to the upright-standing phases is frequently hindered kinetically in standard surface science conditions. Our exploration of growth conditions and interface energetics reveals that the phase transition time is primarily dictated by the deposition rate, and largely independent of the nature of the organic molecule.