Fig 1

Schematic of the elementary steps in the CVD growth of graphene."

Fig 2

Mass transport in the gas phase during the CVD growth of graphene. (a) Schematic of the three flow regimes; (b) Molecular flow in the confined space based on the special stack configuration of growth substrates; (c) Schematic of laminar flow (top) and turbulent flow (bottom); (d) Schematic of the formation of boundary layer during the CVD growth of graphene."

Fig 3

Gas-phase reactions during the high-temperature CVD growth of graphene 62-64. (a) High-temperature reaction path of methane in the gas phase of CVD system, where the thickness of the arrow indicates the reaction probability; Adapted from Springer Nature publisher. (b) The concentrations of 15 species in the gas phase as a function of temperature; Adapted with permission from Ref. 63. Copyright 2012, American Chemical Society. (c) Illustration of the impact of pressure and temperature on the quality of graphene films deposited on the substrate; (d–e) Temperature-dependent composition variation of gas mixture under pressures of 100 mbar (d) and 1 mbar (e), respectively. Adapted with permission from Ref. 64. Copyright 2013, American Chemical Society."

Fig 4

Influence of gas-phase reactions on crystallinity of graphene 31, 78, 79. (a) Typical Raman spectra of graphene directly grown on quartz glass (red), borosilicate glass (blue) and sapphire glass (green) substrates; Adapted with permission from Ref. 78. Copyright 2015, American Chemical Society. (b) Schematic of graphene grown onto SiO2/Si substrates with the assistance of Cu vapor by placing the Cu foil in the upstream of the SiO2/Si substrates; (c) The Raman G peak intensity versus the distance between Cu foil and SiO2 substrates; Adapted with permission from Ref. 31. Copyright 2015, American Chemical Society. (d) Illustration of the graphene grown on solid glass with Cu foil placed on the top of the substrate; (e) Representative Raman spectrum of graphene grown on solid glass with the assistance of Cu vapor in the gas phase. Inset: the photograph of Cu foil-solid glass stacked structure for the growth of high-quality graphene. Adapted with permission from Ref. 79. Copyright 2019, Wiley-VCH."

Fig 5

Influence of gas-phase reactions on intrinsic cleanness of graphene 32, 55, 83. (a) Illustration of the superclean growth of graphene with the assistance of Cu foam; (b, c) Typical TEM image of unclean (b) and superclean (c) graphene. Inset: HRTEM image of the unclean (b) and superclean (c) graphene with atomic resolution; Adapted with permission from Ref. 32. Copyright 2019, Springer Nature. (d) Energy barriers of the decomposition of CH4 in the gas phase without (blue) and with (red) the participation of Cu vapor; (e) Schematic diagram of the growth of graphene with CH4 (left) and Cu(OAc)2 (right) as carbon source; (f) Representative Raman spectra of the carbon species formed during the growth of graphene using Cu(OAc)2 (red) and CH4 (blue). Adapted with permission from Ref. 55. Copyright 2019, American Chemical Society. (g) The simulated temperature distribution in cold-wall CVD (CW-CVD) system. (h, i) Schematic of reaction in the boundary layer in the hot-wall CVD (h) and CW-CVD (i) system. Adapted with permission from Ref. 83. Copyright 2020, Wiley-VCH."

Fig 6

Influence of gas-phase reactions on graphene layer 63, 89, 91. (a) Schematic diagram of the concentration distribution of the active carbon species when seven different positions independently (top) and seven separated Cu foils simultaneously (bottom) were placed along the tube; (b–c) UV-vis spectra of the graphene films grown on seven different positions independently (b) and seven separated Cu foils simultaneously (c). Note that samples 1 to 7 are placed along the direction of the gas flow. Adapted with permission from Ref. 63. Copyright 2012, American Chemical Society. (d) Distribution of the gas flow velocity in the CVD system with a single gas nozzle (left) and multiple gas nozzles (right) across the chamber; Adapted from Elsevier publisher. (e) Simulation of the gas density distribution in LPCVD with various intervals of quartz wafers; (f) Photograph of 30 pieces of graphene/quartz wafers grown in one batch.; (g) Average transmittance of 30 pieces of graphene/quartz wafers shown in (f). Inset: Transmittance mapping results. Adapted from Springer Nature publisher."

Fig 7

Influence of gas-phase reactions on domain size of graphene 34, 72, 96. (a) Schematic of single-crystal graphene growth on Cu85Ni15 alloy substrate by using the quartz with a tiny nozzle (top) and the typical photograph of graphene single crystal (bottom); (b) Schematic of graphene growth on Cu85Ni15 alloy substrate by introducing the carbon precursors homogeneously into the CVD system (top) and the corresponding photograph of graphene domains (bottom); Adapted from Springer Nature publisher. (c) Illustration of graphene growth on travelling (top, left) and stationary (top, right) substrate and the corresponding photograph of single-crystal graphene grown by evolutionary selection growth; Adapted from Springer Nature publisher. (d) Illustration of graphene growth on h-BN/Cu foils using nickelocene as the precursor; (e) Relationship between the domain size of graphene and growth time using nickelocene (red), benzoic acid (blue), and methane (black) as precursors, respectively. Adapted with permission from Ref. 72. Copyright 2017, Wiley-VCH."

Fig 8

Influence of gas-phase reactions on growth rate of graphene 35, 86, 97, 98. (a) Schematic of the fast growth of single-crystal graphene on roll of Cu foils under free molecular flow; (b) Photograph of the as-produced graphene domains grown on the inner surface of the Cu foils; Adapted with permission from Ref. 97. Copyright 2016, Wiley-VCH. (c) Growth rate of single-crystal graphene using ethane comparing with other previously reported works; Adapted with permission from Ref. 98. Copyright 2018, Wiley-VCH. (d) Coverage of graphene grown on glass as a function of the growth time using ethanol (red) and methane (blue) as carbon sources; Adapted with permission from Ref. 86. Copyright 2017, Wiley-VCH. (e) Illustration of the growth of graphene on h-BN with the gaseous catalyst-assisted method; (f) The growth duration versus the growth time of graphene with silane (black), germane (red), and no catalyst (green). Adapted with permission from Ref. 35. Copyright 2015, Springer Nature."