▎ 摘　　要

In situ low-energy electron microscopy (LEEM) studies in the epitaxial growth of graphene on Ru(0001) show that the graphene growth can be tailored via surface treatments of the substrate. Downhill growth of graphene was observed over the clean Ru(0001) surface with well-defined steps, forming sector-shaped graphene sheets. When the substrate surface was treated by Ar+ sputtering to produce subsurface Ar gas bubbles, round-shape graphene sheets were obtained by growing in both uphill and downhill directions. Correspondingly, anisotropic intercalation of oxygen occurs at the graphene/normal Ru(0001) interface, whereas isotropic intercalation of oxygen occurs at the graphene/Ar-sputtered Ru(0001) interface. The subsurface gas bubbles affect C-Ru interaction, which is attributed to the observed different behaviors of the graphene growth and oxygen intercalation.