Dresden 2026 – scientific programme

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O: Fachverband Oberflächenphysik

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

O 11.1: Talk

Monday, March 9, 2026, 15:00–15:15, HSZ/0401

Ethylene on Si(001) revisited: New insights from XPS, STM, and Monte Carlo Simulations — •Jannick A. Peters, Sophie Göbel, and Michael Dürr — Institut für Angewandte Physik and Zentrum für Materialforschung, Justus-Liebig-Universität Giessen, Germany

The adsorption of ethylene - the smallest organic molecule with a C=C double bond - on Si(001) seems straightforward and is widely used as reference, e.g., for the determination of absolute surface coverage. On the other hand, there is ongoing discussion about adsorption configurations, coverage dependence, and in particular the site-selective adsorption based on strongly reduced reactivity on the partially covered surface, leading to two-step adsorption kinetics. In this study, the adsorption of ethylene on Si(001) was investigated at 300 K by means of XPS and STM with special focus on the coverage dependence, and was further modelled by means of Monte Carlo simulations. We can show that the first step of the two-step adsorption kinetics results in a saturation coverage of 0.7 ML, which is significantly higher than the commonly referenced coverage of 0.5 ML. STM measurements show that this behaviour is caused by a combination of adsorption statistics, nearest-neighbour interactions, and site-selective hindrance. Higher coverage up to 1 ML is then reached with a significantly higher dose due to the reduced reactivity of the remaining surface sites. Monte Carlo simulations taking into account a limited set of reaction channels accurately describe the complete coverage dependence as well as the local order of the adsorbates on the surface.

Keywords: silicon surface; organic molecules; adsorption; STM; XPS