Kinetics of Graphene Growth on Liquid Copper by Chemical Vapor Deposition: Insights from Experiments and Molecular Simulations

We report a combined experimental and computational study of the kinetics of graphene growth during chemical vapor deposition on a liquid copper catalyst. The use of liquid metal catalysts offers bright perspectives for controllable large-scale, high-quality synthesis technologies of two-dimensional materials. We carried out a series of growth experiments varying CH4-to-H2 pressure ratios and deposition temperature. By monitoring the graphene flake morphology in real time during growth using in situ optical microscopy in radiation mode, we explored the morphology and kinetics of the growth within a wide range of experimental conditions. Following an analysis of the flakes' growth rates, we consider that growth mode to be a function of methane flux/flake radius, although for a wide range of the growth parameters it can be characterized as attachment-limited. The attachment and detachment activation energies of carbon species are derived as 1.9 +- 0.3 eV and 2.0 +- 0.1 eV, respectively. We also conducted free-energy calculations of assumed key reaction steps by means of a moment tensor potential trained to density functional theory data uncovering interesting mechanistic insight. Using a microkinetic model we further explore the growth mechanism which yields apparent activation energies in excellent agreement with our experimental findings and confirms an attachment-limiting process.