Effects of annealing on copper substrate surface morphology and graphene growth by chemical vapor deposition

Understanding the mechanism of graphene synthesis by chemical vapor deposition and the effect of process parameters is critical for production of high-quality graphene. In the present work, we investigated the effect of H₂ concentration during annealing on evolution of Cu surface morphology, and on deposited graphene characteristics. Our results revealed that H₂ had a smoothening effect on Cu surface as its surface roughness was reduced significantly at high H₂ concentration along with the formation of surface facets, dents and nanometer-sized particles. Furthermore, H₂ content influenced the graphene morphology and its quality. A low H₂ concentration (0% and 2.5%) during annealing promoted uniform and good quality bilayer graphene. In contrast, a high concentration of H₂ (20% and 50%) resulted in multilayer, non-uniform and defective graphene. Interestingly, the annealed Cu surface morphology differed considerably from that obtained after deposition of graphene, indicating that graphene deposition has its own impact on Cu surface.