Pattern evolution characterizes the mechanism and efficiency of CVD graphene growth

Abstract

Growing large-area, high-quality 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, edgereaction kinetics and the surface diffusion of active carbon sources in modulating the pattern evolution and rate of growth. We find that the contrast between the edgekinetics-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. However, common features exist in these two regimes, showing that the growth rate scales with time as t 2 in the early stage of growth and is regimeindependent, 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.

The Adatom Concentration Profile: A Paradigm for Understanding Two-Dimensional MoS2 Morphological Evolution in Chemical Vapor Deposition Growth

“…We employ a phase-field simulation , to understand the morphological evolution of MoS 2 crystals. The phase-field model accounts for the adatom diffusion and the evolution of the order parameter ψ (1 for MoS 2 and −1 for bare substrate).…”

“…In 2D material CVD growth, adatom diffusion on the substrate, edge kinetics, and precursor flux are three major physical parameters that govern growth dynamics. Phase-field models provide a means to understand the effects of these parameters on the morphology evolution of 2D materials. − Meca et al . investigated the effect of substrate anisotropy and precursor flux on graphene morphology.…”

In situgrowth of large-area and self-aligned graphene nanoribbon arrays on liquid metal

“…In experiments, the hydrogen flow rate directly controls the generation rate of free carbon atoms ( F ) from deposition, adsorption and decomposition processes on the exposed copper surface ( φ < 0), as well as the etching rate ( r e ) from the as-grown graphene domain. It has been reported that the etching effect increases with hydrogen flow rate, while growth is promoted as hydrogen increases at low flow rates but decreases at high hydrogen flow rates [ 34 , 49 ]. Specifically, we assume an initial gap distance of 16 Å and 2 L = 20 Å and choose the parameters F , r e accordingly in our model (see details in Supplementary Note 1).…”

Chemical vapor deposition growth behavior of graphene

“…Previous studies reported that graphene exhibits a variety of shapes, including triangle [14], rectangle [15][16][17][18], hexagon [19][20], U shape [21], circular [22], and dendrites [11,[23][24]. Although graphene with different morphologies could be customized by adjusting the ratio of the hydrogen and argon carrier gas mixture [23,25], the influence of the ratio of methane to hydrogen (CH 4 /H 2 ) on the formation of graphene with different morphologies was not reported systematically.…”

“…Although graphene with different morphologies could be customized by adjusting the ratio of the hydrogen and argon carrier gas mixture [23,25], the influence of the ratio of methane to hydrogen (CH 4 /H 2 ) on the formation of graphene with different morphologies was not reported systematically. The growth of fractal graphene along a preexisting scratch has been reported [24,26], while the phenomena of stitching together and stacking fractal graphene with different angles are still unrevealed. Here, two main morphologies of graphene (i.e., dendrites and hexagon) were obtained by adjusting the volume ratio of CH 4 /H 2 from 1:50 to 1:100.…”