Regulating Top-surface Graphene Growth by “Gettering” Carbon Diffusion at Backside of the Copper Foil

We reported a simple and practical strategy that enables us to control the nucleation density and growth kinetics for graphene grown on the top-surface of metal substrate through gettering the carbon source on the backside of the flat Cu foil, during chemical vapor deposition (CVD). Hitherto, for CVD graphene grown on a flat Cu foil, merely topsurface-based growth mechanism has been emphasized, while the effects from diffused carbon and graphene layer formed on the backside of the Cu foil is normally overlooked. Our systematic experimental findings indicated that graphene grown on the backside, governs the carbon diffusion through the bulk Cu, thus strongly dominate nucleation process on the top surface. This understanding steers us to devise a strategy of regulating carbon diffusion to the top surface by using a “getter” substrate such as nickel for carbon at backside of the Cu foil. Depth profiling of the nickel substrate, along with Density Functional Theory (DFT) calculation, verifies the gettering role of nickel support. Implementing, backside carbon gettering (BCG) approach to single-crystal graphene growth resulted in lowering of the nucleation density by two orders of magnitude, enabling growth of single-crystal domains of ⁓ 6 mm lateral size on untreated Cu foil. Finally, we demonstrate the growth of large area polycrystalline SLG, free of unwanted MLG domains, with significantly improved the field-effect mobility of ~ 6800 cmVs and 97.7% optical transmittance. Our approach provides an unusual methodology for control in chemical vapor deposition of 2D materials.