The requirement for long-range structure coherence and property uniformity for graphene-based electronics are crucial for their applications in nanoelectronics. One of our research project is to synthesize large-size single crystal graphene by Chemical Vapor Deposition (CVD) method and graphene based FET device fabrication. 

In 2013, we found that trace amount of oxygen in Ar gas during the heating process helped to reduce the graphene nucleation density significantly and the following morphology characterization correlated graphene nucleation with nanoparticles larger than 20 nm. By applying this seeded growth method, we consequently achieved large single crystal graphene with grain size of sub-centimeter. We further demonstrated that we can amplify the existing graphene grain size by limiting the second seeded growth only from the graphene seed edges initiated by a mild oxidation process. In addition, we also demonstrate that similar method can be used for the preparation of large grain size bilayer graphene flakes.