Equilibrium shape of graphene domains on Ni(111)

We have determined the equilibrium shape of graphene domains grown on Ni(111) via carbon segregation at 925â̂̃C. In situ, spatially resolved electron diffraction measurements were used to determine the crystallographic orientation of the edges of the graphene domains. In contrast to recent theoretical predictions of a nearly circular shape, we show that graphene domains, which nucleate with random shapes, all evolve toward a triangular equilibrium shape with "zigzag" edges. Only one of the two possible zigzag edge orientations is observed. © 2013 American Physical Society.