Effect of Growth Pressure on Graphene Direct Growth on an A-Plane Sapphire Substrate: Implications for Graphene-Based Electronic Devices

Graphene direct growth was performed on an a-plane (1-120) sapphire substrate using low-pressure chemical vapor deposition (LPCVD) without a metal catalyst. The direct graphene growth on a-plane sapphire is very attractive not only for the preparation of a template substrate of remote epitaxy but also for the fabrication of low-cost graphene-based electronic devices. The growth pressure dependence was systematically studied to reveal the growth mechanism of graphene. It was found that the graphene island density decreased with growth pressure, while the growth rate increased. In addition, single-layer graphene with high uniformity was successfully obtained because the graphene growth was driven by the catalytic effect of the a-plane sapphire surface. Finally, high-quality and highly uniform single-layer graphene with a Raman D/G ratio of 0.2 was demonstrated on the whole surface of a 2 in. a-plane sapphire substrate at a growth pressure of 5 kPa.