Fig. 4

The Scheme depicts the proposed mechanism for graphene domain growth. a The smooth Cu foil was obtained by cleaning with dilute hydrochloric acid and acetone under ultrasonic. b Formation of large oxide nanoparticles resulting from the mild oxidation by trace amounts of oxygen in Ar gas on the CVD chamber. c, d The large single-crystal monolayer graphene resulting from nucleation on the oxide nanoparticle with the growth speed on bottom layer graphene is high while on the top layer, graphene is suppressed in the high hydrogen concentration condition. e, f The multilayer graphene resulting from nucleation on the oxide nanoparticle with the growth speed between the bottom layer and top layer graphene is relatively equal in the low hydrogen concentration condition