Solid source growth of graphene with Ni–Cu catalysts: towards high qualityin situgraphene on silicon

Abstract

We obtain a monolayer graphene on epitaxial silicon carbide on silicon substrates via solid source growth mediated by a thin Ni-Cu alloy. Raman spectroscopy consistently shows an I D /I G band ratio as low as ~0.2, indicating that the graphene obtained through this method is to-date the best quality monolayer grown on epitaxial silicon carbide films on silicon. We describe the key steps behind the graphene synthesis on the basis of extensive physical, chemical and morphological analyses. We conclude that (1) the oxidation, amorphisation and silicidation of the silicon carbide surface mediated by the Ni, (2) the liquid-phase epitaxial growth of graphene as well as (3) the self-limiting graphitization provided the molten Cu catalyst, are key characteristics of this novel synthesis method.

Growth of graphitic carbon layers around silicon carbide nanowires

“…The synthesis mechanism of the multilayer GC sheets around the 3C-SiC nanowires can be inferred on the basis of the presented data and our previously reported alloy-mediated graphitization process on flat 3C-SiC surfaces 23 . The Freckle solution wet etch is the final step needed for removing the silicides, excess carbon and unreacted metal catalysts, and expose the graphene.…”

“…We have modified a Ni/Cu alloy-mediated catalytic approach to attempt the graphitization of the SiC NWs. We had previously developed this synthesis method to grow large -scale graphene on hetero-epitaxial 3C-SiC films grown on silicon substrates [21][22][23] . The epitaxial graphene obtained through this method resulted in the best quality graphene grown to-date on 3C-SiC on silicon, thanks to its liquid phase epitaxial growth nature.…”

“…This wet etching process assists with the removal of the intermixed layer of unreacted metal, metal silicides as well as of the excess carbon produced during the graphitization process. [21][22][23]26 The morphology of the NWs was characterized using a Zeiss Supra 55VP high-resolution fieldemission scanning electron microscope (FESEM) operating between 1-5 kV. An Oxford INCAx-sight energy-dispersive X-ray (EDX) spectroscopy attached to the FESEM was used to investigate the elemental composition of the NWs at 20 kV.…”

“…A somewhat larger interlayer spacing was observed already for graphene grown on 3C-SiC hetero-epitaxial layers via the alloy-mediated graphitization process. 22,23 The significantly larger interlayer spacing of the GC grown on SiC nanowires is attributed to the combined effect of turbostratic stacking as well as the presence of epoxy groups in the graphenic layers, although such spacing is still smaller than that of GO layers. 37 Eight to ten graphitic layers can be observed on the NWs surface.…”

“…Therefore, a direct method to grow graphitic layers on the SiC NWs would be highly desirable. In this manuscript, we demonstrate a method for direct growth of graphitic carbon (GC) sheets on cubic silicon carbide (3C-SiC) NWs, which is based on the learnings from our alloy-mediated catalytic approach to grow graphene on 3C-SiC epitaxial films on silicon substrates [21][22][23] .…”