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CO-Induced Smoluchowski Ripening of Pt Cluster Arrays on the Graphene/Ir(111) Moiré

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journal contribution
posted on 19.02.2016, 16:08 by Timm Gerber, Jan Knudsen, Peter J. Feibelman, Elin Grånäs, Patrick Stratmann, Karina Schulte, Jesper N. Andersen, Thomas Michely
Regular Pt cluster arrays grown on the moiré template formed by graphene on Ir(111) were tested for their stability with respect to CO gas exposure. Cluster stability and adsorption-induced processes were analyzed as a function of cluster size, with in situ scanning tunneling microscopy and X-ray photoelectron spectroscopy. Small clusters containing fewer than 10 atoms were unstable upon CO adsorption. They sintered through Smoluchowski ripeningcluster diffusion and coalescencerather than the frequently reported Ostwald ripening mediated by metal–adsorbate complexes. Larger clusters remained immobile upon CO adsorption but became more three-dimensional. Careful analysis of the experimental data complemented by ab initio density functional theory calculations provides insight into the origin of the CO-induced Pt cluster ripening and shape transformations.