Pattern Evolution Characterizes the Mechanism and Efficiency of CVD Graphene Growth

TL;DR

This study combines modeling and experiments to understand how pattern evolution influences the growth rate and quality of large-area single-crystal graphene, highlighting key kinetic factors and growth regimes.

Contribution

It introduces a comprehensive analysis of pattern evolution during CVD graphene growth, revealing the roles of flux, edge kinetics, and surface diffusion in growth efficiency.

Findings

Growth rate scales as t^2 in early stages across regimes.

Edge-kinetics and surface diffusion regimes exhibit distinct pattern evolutions.

Final growth stage is limited by competition for surface-diffusing carbon sources.

Abstract

Growing large-area single-crystal monolayers is the holy grail of graphene synthesis. In this work, the efficiency of graphene growth and the quality of their continuous films are explored through the time evolution of individual domains and their surface coverage on the substrate. Our phase-field modeling results and experimental characterization clearly demonstrate the critical roles of the deposition flux, edge-reaction kinetics and the surface diffusion of active carbon sources in modulating the pattern evolution and rate of growth. The contrast in edge-kinetics-limited and surface-diffusion-limited regimes is remarkable, which can be characterized by the evolution of domain patterns and considered as an indicator of the growth regime. Common features exist in these two regimes, showing that the growth rate scales with time as t2 in the early stage of growth and is regime-independent, which is explained by the coarsen profiles of carbon concentration for both the compact and dendritic domains. The rate decays rapidly in the final stage of growth due to the competition between neighboring domains on the limited carbon sources diffusing on the substrate, which is highly regime-sensitive and extremely low in the surface-diffusion-limited regime with narrow gaps between the domains to be filled. Based on these findings, synthesis strategies to improve the growth efficiency and film quality are discussed.