The polycrystalline nature of conventional chemical vapor deposition-derived graphene, consisting of many defective grain boundaries, strongly degrades its electrical and mechanical properties. While for AB-stacked bilayer graphene whose bandgap can be tuned by a transverse electric field, single-crystallinity in both layers is crucial for its electrical applications. In this sense, epitaxial growth of multiple graphene nucleation seeds, to the extent of coalescence into a uniform single crystal for both layers on a monocrystalline substrate appears favorable with easy scalability and larger growth rate. However, such routes usually need extremely expensive substrate and time-consuming processing step.

In this work, we successfully structured a Cu(111) substrate through a facile...[ Read more ]

The polycrystalline nature of conventional chemical vapor deposition-derived graphene, consisting of many defective grain boundaries, strongly degrades its electrical and mechanical properties. While for AB-stacked bilayer graphene whose bandgap can be tuned by a transverse electric field, single-crystallinity in both layers is crucial for its electrical applications. In this sense, epitaxial growth of multiple graphene nucleation seeds, to the extent of coalescence into a uniform single crystal for both layers on a monocrystalline substrate appears favorable with easy scalability and larger growth rate. However, such routes usually need extremely expensive substrate and time-consuming processing step.

In this work, we successfully structured a Cu(111) substrate through a facile monocrystallization strategy, referring to a gradient-cooling resolidification treatment. One identical set of equilateral triangle diffraction patterns by low energy electron microscopy(LEED), monochromatic blue color in electron backscattering diffraction (EBSD) mappings and a sharp Cu(111) peak in XRD with the full width at half maximum (FWHM) of 0.08° all indicate the uniform and single Cu(111) texture.

The graphene grains grown on Cu substrate exhibited highly uni-directional crystallographic orientation and formed a continuous single-crystalline graphene film through the seamless stitching. Single crystallinity of graphene film and its lattice matching with Cu are both proved by LEED. And no detectable defect in the stitching region of graphene inter-domains by Raman mapping and the unidirectional aligned hexagonal holes by hydrogen etching, both present good agreement with its commensurate stitching.

And well aligned AB-stacked bilayer domains with more than 80% coverage to the toplayer present great potential for its large-area film production. Easy accessibility and scalability of this approach would remarkably open the venue for the industrial manufacture and application of high-quality graphene.