Controlling Nucleation Density While Simultaneously Promoting Edge Growth Using Oxygen-Assisted Fast Synthesis of Isolated Large-Domain Graphene

We report a two-step chemical vapor deposition growth method for rapid synthesis of isolated large-domain graphene. The key feature of the two-step growth method is to separate nucleation from growth, performing the nucleation in step one with a low carbon feedstock (methane) gas flow rate, and rapid growth in step two with a high flow rate. We find empirically that, even under the high flow rate conditions of step two, the nucleation density on the inside of the copper pocket used for growth is suppressed (preventing merging of domains into full films) until the graphene growing on the outside of the pocket merges into a full film, fully covering the outside. The mechanism for this suppression is believed to be related to oxygen-assisted passivation of nucleation sites, a decreased energetic barrier for edge-attachment growth, and diffusion of carbon through the copper bulk. These conditions enable us to finely tune the local carbon concentration on the inside surface for fast growth and minimum nucleati...