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Article Dans Une Revue Scientific Reports Année : 2018

Role of Precursor Carbides for Graphene Growth on Ni(111)

Résumé

Surface X-ray Diffraction was used to study the transformation of a carbon-supersaturated carbidic precursor toward a complete single layer of graphene in the temperature region below 703 K without carbon supply from the gas phase. The excess carbon beyond the 0.45 monolayers of C atoms within a single Ni2C layer is accompanied by sharpened reflections of the vertical bar 4772 vertical bar superstructure, along with ring-like diffraction features resulting from non-coincidence rotated Ni2C-type domains. A dynamic Ni2C reordering process, accompanied by slow carbon loss to subsurface regions, is proposed to increase the Ni2C 2D carbide long-range order via ripening toward coherent domains, and to increase the local supersaturation of near-surface dissolved carbon required for spontaneous graphene nucleation and growth. Upon transformation, the intensities of the surface carbide reflections and of specific powder-like diffraction rings vanish. The associated change of the specular X-ray reflectivity allows to quantify a single, fully surface-covering layer of graphene (2 ML C) without diffraction contributions of rotated domains. The simultaneous presence of top-fcc and bridge-top configurations of graphene explains the crystal truncation rod data of the graphene-covered surface. Structure determination of the vertical bar 4772 vertical bar precursor surface-carbide using density functional theory is in perfect agreement with the experimentally derived X-ray structure factors.
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hal-02976204 , version 1 (23-10-2020)

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Raffael Rameshan, Vedran Vonk, Dirk Franz, Jakub Drnec, Simon Penner, et al.. Role of Precursor Carbides for Graphene Growth on Ni(111). Scientific Reports, 2018, 8, pp.2662-1-2662-13. ⟨10.1038/s41598-018-20777-4⟩. ⟨hal-02976204⟩
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