Direct precipitation of multilayer graphene on c-plane sapphire using a crystallized Ni catalyst

Abstract

Graphene was precipitated using crystallized Ni catalyst, which was crystallized using a MBE-grown Ni layer as a seed. In the thermal crystallization process, the additional deposition of amorphous Ni layer was effective to suppress the dewetting of the Ni catalyst. The resulted graphene was flat and free from folds, which are the large wrinkles folded on the substrate and the graphene islands were found smoothly stitched together. It is because the islands were precisely aligned by the crystal information inherited from the Ni layer. The insitu observation of the precipitation was also performed using high intensity X-ray beam from a synchrotron apparatus. Precipitation process was clearly revealed, and the crystallized Ni catalyst was found effectively reduced the formation of defective graphene, which was conventionally produced by the carbons diffused though grain boundaries at low temperature.