▎ 摘　　要

We used low-energy electron microscopy to observe, in situ, the growth of graphene sheets on a polycrystalline Ni substrate through surface segregation phenomena. On a flat Ni surface with roughness of less than 5 nm, macroscopic single-domain graphene grew from an extremely small number of nucleation sites. The single-domain graphene, free of rotational disorder, expanded continuously in a carpet like manner, not only over steps on the substrate surface, but also over its domain boundaries, independent of the Miller index plane. These findings might provide a breakthrough in fabricating expansive single-domain graphene sheets on polycrystalline metal surfaces. (C) 2012 The Japan Society of Applied Physics