Reproducible synthesis of ultrahigh-quality graphene by oxygen-free chemical vapor deposition*

Progress in translating advances in growth of graphene films by chemical vapor deposition (CVD) to applications has been hindered by challenges in quality and reproducibility, as well as the lack of a simple model of growth kinetics. Here we show that eliminating trace oxygen leads to fast and highly reproducible CVD graphene growth. We confirm that ppm-level oxygen disrupts growth by etching the graphene edges, and map the boundary between growth and etching in the presence of hydrogen. We demonstrate that trace oxygen causes two major sources of disorder in CVD-grown graphene: pinholes and amorphous carbon deposition. The dependence of growth rate on growth time, temperature, and methane pressure follow straightforward trends, while previously unobserved behavior is seen for hydrogen pressure. Finally, we grow epitaxial graphene on sapphire-supported Cu(111) films. The graphene shows few wrinkles, no evidence of amorphous carbon, and an ultra-low defect density. After dry transfer and device assembly, this graphene shows electrical transport behavior virtually indistinguishable from that of exfoliated graphene, both at room temperature and at low temperature.