Nonisothermal Synthesis of AB-Stacked Bilayer Graphene on Cu Foils by Atmospheric Pressure Chemical Vapor Deposition

Since the discovery of Cu-catalyzed chemical vapor deposition (CVD), the preparation of large-area graphene films has been performed by the carbon precursor exposure under isothermal conditions. In this work, we report on a nonisothermal method to quickly synthesize the large-area AB-stacked bilayer graphene films (BGF) by atmospheric pressure CVD on the copper foils. The growth feature of the BGF is carefully studied by scanning electron microscopy, Raman spectroscopy, and transmission electron microscopy. The results show that both cooling rate and CH₄ flow rate play crucial roles on the BGF growth in the nonisothermal process. A phase diagram for the preparation of BGF is thereby derived from plenty of experiments. In addition, we find that bilayer graphene seeds grow into graphene islands at the initial growth stage and extend gradually to a continuous film. Accordingly, a possible growth mechanism combining with surface-catalyzed process and seed growth is proposed.