Operando Characterization and Molecular Simulations Reveal the Growth Kinetics of Graphene on Liquid Copper during Chemical Vapor Deposition
arXiv:2305.18331 · doi:10.1021/acsnano.4c02070
Abstract
In recent years, liquid metal catalysts have emerged as a compelling choice for the controllable, large-scale, and high-quality synthesis of two-dimensional materials. At present, there is little mechanistic understanding of the intricate catalytic process, though, of its governing factors or what renders it superior to growth at the corresponding solid catalysts. Here, we report on a combined experimental and computational study of the kinetics of graphene growth during chemical vapor deposition on a liquid copper catalyst. By monitoring the growing graphene flakes in real time using in situ radiation-mode optical microscopy, we explore the growth morphology and kinetics over a wide range of CH4-to-H2 pressure ratios and deposition temperatures. Constant growth rates of the flakes' radius indicate a growth mode limited by precursor attachment, whereas methane-flux-dependent flake shapes point to limited precursor availability. Large-scale free energy simulations enabled by an efficient machine-learning moment tensor potential trained to density-functional theory data provide quantitative barriers for key atomic-scale growth processes. The wealth of experimental and theoretical data can be consistently combined into a microkinetic model that reveals mixed growth kinetics that, in contrast to the situation at solid Cu, is partly controlled by precursor attachment alongside precursor availability. Key mechanistic aspects that directly point toward the improved graphene quality are a largely suppressed carbon dimer attachment due to the facile incorporation of this precursor species into the liquid surface and a low-barrier ring-opening process that self-heals 5-membered rings resulting from remaining dimer attachments.
References in corpus (17)
- Electric Field Effect in Atomically Thin Carbon Films
- Large-Area Synthesis of High-Quality and Uniform Graphene Films on Copper Foils
- Evolution of graphene growth on Cu and Ni studied by carbon isotope labeling
- Moment Tensor Potentials: a class of systematically improvable interatomic potentials
- Control and Characterization of Individual Grains and Grain Boundaries in Graphene Grown by Chemical Vapor Deposition
- Growth of Epitaxial Graphene: Theory and Experiment
- Factors influencing graphene growth on metal surfaces
- Contrasting Behavior of Carbon Nucleation in the Initial Stages of Graphene Epitaxial Growth on Stepped Metal Surfaces
- Effect of Metal Element in Catalytic Growth of Carbon Nanotubes
- Density-functional model for van der Waals interactions: Unifying many-body atomic approaches with nonlocal functionals
- Fast and Accurate Uncertainty Estimation in Chemical Machine Learning
- First-principles study of graphene edge properties and flake shapes
- Direct Imaging of Graphene Edges: Atomic Structure and Electronic Scattering
- Dominant Kinetic Pathways of Graphene Growth in Chemical Vapor Deposition: The Role of Hydrogen
- In Situ Characterisation of Graphene Growth on Liquid Copper-Gallium Alloys: Paving the Path for Cost-Effective Synthesis
- On the definition of the domain growth rate constant on a two dimensional substrate
- Scaling theory for two-dimensional single domain growth driven by attachment of diffusing adsorbates