Berlin 2024 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 90: 2D Materials VI: Growth, Structure and Substrate Interaction
O 90.8: Vortrag
Donnerstag, 21. März 2024, 16:45–17:00, MA 005
Operando Characterization and Molecular Simulations Reveal the Growth Kinetics of Graphene on Liquid Copper — Valentina Rein2, •Hao Gao1, Hendrik H. Heenen1, Oleg V. Konovalov2, Karsten Reuter1, and Maciej Jankowski2 — 1Fritz-Haber-Institut der MPG, Berlin — 2ESRF, Grenoble, France
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 and its governing factors. In a combined experimental and computational study, we investigate 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 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 potential trained to density-functional theory data provide quantitative barriers for key atomic-scale growth processes. The experimental and theoretical data can be consistently combined into a microkinetic model that reveals a mixed growth kinetics that is controlled by both precursor availability and attachment. Key mechanistic aspects that explain improved graphene quality are a largely suppressed carbon dimer attachment and a self-healing mechanism.
Keywords: graphene; catalysis; machine learning potentials; enhanced sampling; free energy calculations