The Mechanism of Graphene Vapor–Solid Growth on Insulating Substrates

Abstract

Wafer-scale single-crystal graphene film directly grown on insulating substrates via the chemical vapor deposition (CVD) method is desired for building high-performance graphenebased devices. In comparison with the well-studied mechanism of graphene growth on transition metal substrates, the lack of understanding on the mechanism of graphene growth on insulating surfaces greatly hinders the progress. Here, by using firstprinciples calculation, we systematically explored the absorption of various carbon species CH x (x = 0, 1, 2, 3, 4) on three typical insulating substrates [h-BN, sapphire, and quartz] and reveal that graphene growth on an insulating surface is dominated by the reaction of active carbon species with the hydrogen-passivated graphene edges and thus is less sensitive to the type of the substrate. The dominating gas phase precursor, CH 3 , plays two key roles in graphene CVD growth on an insulating substrate: (i) to feed the graphene growth and (ii) to remove excessive hydrogen atoms from the edge of graphene. The threshold reaction barriers for the growth of graphene armchair (AC) and zigzag (ZZ) edges were calculated as 3.00 and 1.94 eV, respectively; thus the ZZ edge grows faster than the AC one. Our theory successfully explained why the circumference of a graphene island grown on insulating substrates is generally dominated by AC edges, which is a long-standing puzzle of graphene growth. In addition, the very slow graphene growth rate on an insulating substrate is calculated and agrees well with existing experimental observations. The comprehensive insights on the graphene growth on insulating surfaces at the atomic scale provide guidance on the experimental design for high-quality graphene growth on insulating substrates.

Recent Progress on Two-Dimensional Materials

“…Fig. 73e plots the calculated graphene growth rates at different experimental conditions and a perfect agreement is clearly seen when comparing with the experimental results 1686 .…”

“…73a, the graphene growth rate on typical insulating substrates are about 3-5 orders of magnitude slower than that of on metal substrates. Besides, the type of insulating substrates has little impact on the growth behaviors of graphene, such as the growth rate and the shape 1686 . Recently, through extensive DFT calculations and modeling, Cheng et al have successfully explained the slow growth rate and morphology of graphene grown on various insulating substrates 1686 .…”

“…Besides, the type of insulating substrates has little impact on the growth behaviors of graphene, such as the growth rate and the shape 1686 . Recently, through extensive DFT calculations and modeling, Cheng et al have successfully explained the slow growth rate and morphology of graphene grown on various insulating substrates 1686 . They unveiled that the CH3 molecules in the gas phase are the key carbon precursors, and there are three typical main reactions during the addition of new hexagons onto a graphene edge: (i) feed the graphene growth by attaching a CH3 radicles; (ii) remove the excessive H atoms of CH3 via reaction of CH3 + H → CH4, and (iii) form a new hexagonal carbon ring, as illustrated in Fig.…”

Chloroform‐Assisted Rapid Growth of Vertical Graphene Array and Its Application in Thermal Interface Materials

“…For the VG growth, all the reactions occur on the top edges of the graphene layers and thus the gas‐phase reaction is vital, which is similar with that of the vapor‐solid growth mechanism of graphene growth on the insulating substrates. [ 40 ] As suggested in previous study, [ 40 ] the threshold step of the VG is removing excessive hydrogen atoms from the graphene edge. To understand how the growth rate of VG was influenced by introducing suitable CHCl 3 , a zigzag graphene nanoribbon with hydrogen termination was constructed to present the growth front of graphene island for exploring the role of active radical *OH, *CH 3 , *Cl, and *CCl 3 during the process of removing edge hydrogen atom.…”

Complementary Chemical Vapor Deposition Fabrication for Large‐Area Uniform Graphene Glass Fiber Fabric

“…When methane precursor was introduced into the CVD system, its decomposition would result in the formation of CH 3 as the main active carbon species, which subsequently fuel the nucleation and graphene growth. [35] It should be noticed that methane possesses a relatively high energy barrier with the C-H bond energy of ≈440 kJ mol −1 to decompose into the active CH 3 species. [33] Such a high bond energy would therefore limit the amount of formed CH 3 species in the upstream of the gas flow.…”