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Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 86: Nanostructure at Surfaces: Molecular Assembly

O 86.6: Talk

Thursday, March 19, 2015, 16:30–16:45, HE 101

Ethene to graphene: surface catalyzed chemical pathways, intermediates, precursors, and assemblyBo Wang1, Michael König1, Catherine J. Bromley2, Bokwon Yoon3, •Friedrich Esch1, Ulrich Heiz1, Uzi Landman3, and Renald Schaub21Chemistry Dept., Technische Universität München, Catalysis Research Center, 85748 Garching, Germany — 2EaStCHEM and School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, United Kingdom — 3School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA

Diverse technologies, from catalyst coking to graphene synthesis, entail hydrocarbon dehydrogenation and condensation reactions on transition metal surfaces and assembly into carbon overlayers. Scanning-tunneling microscopy (STM), thermal-desorption spectroscopy (TDS), and density-functional theory (DFT) simulations were used to uncover the hierarchy of atomic-scale pathways and reaction intermediates underlying the catalyzed thermal evolution of ethene adsorbed on Rh(111) to form 2D graphene overlayers:

Upon heating, adsorbed ethene molecules evolve at first via coupling reactions to form segmented 1D polyaromatic hydrocarbon chains. Further heating leads to dimensionality-crossover (1D to 2D) and dynamical restructuring processes at the PAH chain-ends, with subsequent activated detachment of 24-carbon-atom dehydrogenated-coronene-like clusters. Rate-limiting diffusional coalescence of these dynamically self-evolved precursors culminates at even higher temperatures (1000 K) in condensation into a graphene adlayer of high structural perfection.

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