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O: Fachverband Oberflächenphysik

O 11: Metal & Semiconductor substrates: Adsorption and reaction of small molecules II

O 11.4: Vortrag

Montag, 9. März 2026, 15:45–16:00, HSZ/0401

Through Stronger Hinderance to Higher Reactivity: Influence of the Alkyl Chains on the Activation Energy of Ether Cleavage on Silicon — Timo Glaser¹, Gustav F. Nolte¹, Tamam Bohamud¹, Philip Keller¹, Mathieu G. Silly², Hendrik Weiske³, Ralf Tonner-Zech³, and •Michael Dürr¹ — ¹Institut für Angewandte Physik and Zentrum für Materialforschung, Justus-Liebig-Universität Giessen, Germany — ²Synchrotron SOLEIL, Gif sur Yvette, France — ³Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Germany

Reactivity in surface chemistry is often discussed in terms of the interaction between surface states and the functional groups of the reacting molecule. Herein we demonstrate that for finite submonolayer coverage, i.e., surface coverage at which the molecular adsorbates cannot be treated as isolated molecules anymore, the seemingly innocent side chains of the adsorbate can also play a decisive role. For the example of ether cleavage on Si(001), which represents the surface analogue of an S_N2-type reaction, we show both experimentally by means of real-time XPS as well as based on ab-initio calculations that steric hindrance by the side chains determines the activation energy for C-O dissociation into the final state. In contrast to a simple expectation, the stronger steric hindrance of the butyl group in butyl methyl ether leads to a lower activation energy for ether cleavage on Si(001) when compared to diethyl ether. This effect was traced back to different degrees of destabilization of the precursor and the transition state [1].

[1] T. Glaser, et al., Angew. Chem. Int. Ed. e19990 (2025).

Keywords: silicon surface; reaction dynamics; real-time XPS; organic molecules; ether cleavage