SurfaceScience21 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 7: Poster Session I: Heterogeneous catalysis I

O 7.1: Poster

Montag, 1. März 2021, 10:30–12:30, P

Diffusion of oxygen atoms on a highly CO-covered Ru(0001) surface — •Hannah Illner, Ann-Kathrin Henß, and Joost Wintterlin — Chemie Department, Ludwig-Maximilians-Universität München, Deutschland

It was recently shown that oxygen atoms on a Ru(0001) surface covered with 0.33 monolayers (ML) of coadsorbed CO could travel through the CO layer by means of a new diffusion mechanism (Henß et al., Science 2019). The term "door-opening mechanism" indicated that the diffusion of the O atoms was facilitated by fluctuations in the CO layer that frequently opened low-energy paths for the oxygen. Here we report about investigations at higher CO coverages (0.50 ML). The experiments were performed between 239 and 280 K by means of a variable-temperature, high-speed STM that achieves imaging rates of up to 60 frames per second. In the investigated temperature range an ordered (2√3 x 2√3)R30^∘ CO structure, which was observed at 70 K, had undergone on order-disorder transition. The trajectories of the O atoms through the disordered CO layer were analyzed, and hopping frequencies and an activation energy were extracted. It turned out that the surface diffusion of the O atoms was even faster than at the lower CO coverage and also faster than on the bare surface. We explain this finding by the weakened binding strength of the O atoms to the surface caused by CO.