Nanocrystalline cubic ruthenium carbide formation in the synthesis of graphene on ruthenium ultrathin filmsElectronic supplementary information (ESI) available: Details of the X-ray absorption, X-ray diffraction and electron backscattered diffraction data and analysis are presented: XANES spectra of reference samples, fitting parameters and obtained FT curves from simulations; XRD and EBSD indexing and RuC cubic phase identification. See DOI: 10.1039/c7tc02855e

• Main Authors: Jiménez-Villacorta, Félix, Álvarez-Fraga, Leo, Bartolomé, Javier, Climent-Pascual, Esteban, Salas-Colera, Eduardo, Aguilar-Pujol, Montserrat X, Ramírez-Jiménez, Rafael, Cremades, Ana, Prieto, Carlos, de Andrés, Alicia
• Format: Article
• Language: English
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c7tc02855e

Graphene is grown by chemical vapour deposition on ruthenium ultrathin films down to a nominal thickness of 5 nm. While at 910 °C multilayer graphitic films are obtained, single layer defective graphene is formed at 1000 °C. The extremely thin Ru films allow the formation of a novel nano-crystalline ruthenium carbide phase to be discerned by combining synchrotron X-ray diffraction, synchrotron X-ray absorption spectroscopy and electron diffraction. The ruthenium carbide (Ru-C) phase formed at or above 1000 °C presents cubic symmetry (cP) with a lattice parameter of 2.927 Å and a Ru-C distance of around 2.31 Å. The increase of C solubility in ruthenium seems to be sufficient to trigger the stabilization of the Ru-C phase during graphene growth preferentially in grains with orientation different to (0001). The structural transition from hcp Ru to cP Ru-C is not limited to a shell; it occurs for the whole grain. The formation of the carbide seems to favour the synthesis of single layer graphene by hindering the segregation of carbon to the surface during cooling. This simple method allows nano-crystalline ruthenium-carbide films to be obtained as well as graphene covered Ru nanograins, both with size control. These new materials are foreseen to present interesting mechanical, catalytic and sensing properties. Novel nanocrystalline cP-RuC films and graphene covered hcp-Ru nanograins are obtained with size control by CVD.