▎ 摘　　要

We investigated the effects of hydrogen gas flow rate in the cooling step of CVD on graphene film. We discovered that hydrogen gas in the cooling step influences the quality of graphene. The D peak (defects of graphene) intensity of the Raman spectrum tends to increase with an increasing hydrogen flow rate. Whether methane gas as a hydrocarbon source is maintained during the cooling step or not, the hydrogen flow rate during the cooling step strongly affects the quality of CVD-grown graphene.