Square-Shaped, Single-Crystal, Monolayer Graphene Domains by Low-Pressure Chemical Vapor Deposition

Square-shaped, single-crystal, monolayer graphene domains are grown on Cu foils by low-pressure chemical vapor deposition. The domains are remarkably well-aligned along the direction of flow of the gases. Scanning electron microscopy shows that these 'square' domains have clean, smooth edges which permit seamless, defect-free merging of the domains. Raman spectra and transmission electron microscopy together demonstrate that individual domains are single layer, and electron diffraction reveals that these domains are single crystals. The expansion mechanism of 'square' graphene domains is discussed in the context of our aligned, tailored domain shapes. This work represents an important step toward realization of fabrication of larger area, single-crystal monolayer graphene sheets with controllable shape and alignment.