Hydrogen Kinetics on Scalable Graphene Growth by Atmospheric Pressure Chemical Vapor Deposition with Acetylene

Acetylene (C2H2) and copper foil have been chosen as carbon precursor and catalyst, respectively, for the synthesis of graphene by atmospheric pressure chemical vapor deposition. The effects of hydrogen (H-2) concentration on graphene growth have been studied by Raman spectroscopy and transmission electron microscopy. Different to methane as a carbon precursor, high-quality bilayer graphene films can be grown rapidly with the ratio of H-2 and argon (Ar) flow rates (H-2/Ar) range from 0.010 to 0.111. However, with the further increase of H-2 concentration (H-2/Ar = 0.250 and H-2/Ar = 0.429), multilayer graphene domains are dominant on top of the bilayer graphene films. These observations demonstrate that H-2 serves as an activator of the surface bound carbon for the bilayer graphene growth, while showing an etching effect that controls the morphology, nucleation density, and nucleation size of the multilayer graphene domains. The results offer useful insights into the understanding of the kinetic effect of H-2 on scalable synthesis of graphene with C2H2.