Regensburg 2022 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 30: Semiconductor Surfaces

O 30.8: Vortrag

Dienstag, 6. September 2022, 12:30–12:45, S053

Starting from a Fixed Geometry: Real-Time XPS Investigation of a Surface Reaction with Controlled Molecular Configurations — •Timo Glaser¹, Christian Länger¹, Julian Heep¹, Jannick Meinecke², Mathieu Silly³, Ulrich Koert², and Michael Dürr¹ — ¹Institut für Angewandte Physik und Zentrum für Materialforschung, Justus-Liebig-Universität Giessen, Germany — ²Fachbereich Chemie, Philipps-Universität Marburg, Germany — ³Synchrotron SOLEIL, 91192 Gif sur Yvette, France

The relative orientation between two reactants can have a major influence on the reactivity and on the products of a chemical reaction. In gas-surface chemistry with well-defined single-crystal surfaces, the orientation and configuration of one reactant is fixed by the surface, but still the reacting gas molecules can impact on the surface in all possible orientations. Here we show how to constrain the relative orientation of both reactants by attaching a reactive group (ether) via a linker (cyclooctyne) on a single crystal surface. This keeps the reacting group in a highly-constrained configuration close to the surface. We demonstrate this concept for ether cleavage on silicon (001), the surface analogue of an S_N2 reaction. The kinetics of the further reaction of the ether group with the silicon surface is studied by means of real-time XPS using synchrotron radiation. We find both a low-energy barrier and a low prefactor, which we discuss in terms of the constrained starting configuration of the ether group. As this configuration represents the starting point of a low-energy pathway, it gives direct experimental access to the underlying reaction mechanism.