Fig 1

The roles of typical metal substrates in CVD growth of graphene and the elementary steps of graphene growth on metal surfaces."

Fig 2

The behaviors of decomposition, absorption, and diffusion of active carbon species on various metal surface 53, 54. (a) Energy profiles and the corresponding structures of the initial and final states during the full decomposition of CH4 on Cu (111) surfaces; (b) Comparison of the activities of various metal surfaces based on the overall reaction energy of CH4 decomposition; (c) Surface and subsurface absorption sites including the top (T), hcp hollow (H), fcc hollow (F), bridge (B) sites, and one octahedral (O), two tetrahedral sites (TE1 and TE2). (d, e) Binding energies (d) and diffusion barriers (e) of various CHi species on four representative metal surfaces (Cu, Ni, Ir and Rh). C-I and C-II represent the carbon atom on the metal surface and subsurface, respectively. (a, b) Adapted with permission from Ref. 53. Copyright 2017, the Royal Society of Chemistry. (c–e) Adapted with permission from Ref. 54. Copyright 2017, the Royal Society of Chemistry."

Fig 3

The effects of alloy composition on the nucleation density and domain size of graphene 59. (a) Graphene nucleation density and grain size as a function of Ni content in the CuNi alloy; (b) The formation energies of C24 cluster on CuNi alloy surfaces without/with dissolved C atoms. (c–d) C diffusion on the CuNi alloy surface and through bulk with Ni composition of (c) 12.5% and (d) 25%. Adapted with permission from Ref. 59. Copyright 2018, Wiley-VCH."

Fig 4

The role of the metal surface in controlling the crystallographic orientation of graphene 60, 61. (a–c) Illustration of single-crystalline graphene growth on a polycrystalline catalyst surface via the edge epitaxy mechanism; (d) Illustration of the three modes of graphene growth: the step-attached (SA) mode, the on-terrace (OT) mode and the sunk (S) mode; (e) Illustration of the two potential combinations of graphene growth modes on different catalyst surface and the consequent large area graphene: SA + OT growth on rigid catalyst surface and SA + S growth on soft catalyst surface; (f) Relationship between formation energy of metal step (EMS) and △E. For metals with small EMS (soft metals such as Au, Pd, and Cu), the S growth mode is prederred, whereas for metals with large EMS (hard metals such as Ni, Rh, Ru, and Ir) the OT growth mode dominates. (a–c) Adapted with permission from Ref. 60. Copyright 2012, American Chemical Society. (d–f) Adapted with permission from Ref. 61. Copyright 2014, American Chemical Society."

Fig 5

The incorporation of carbon atom of graphene edge assisted by metal atoms 66. (a) Pristine AC graphene edge and AC edge terminated by isolated Cu atoms (labeled by AC-Cu-I). The relative formation energy of each structure relative to pristine AC edge are shown; (b) Formation energies of metal-terminated graphene edges on Au(111), Cu(111), Ni(111) and Rh(111) surfaces as a function of relative binding energy interaction EC/EM.EC and EM are the absorption energy of a carbon atom on metal surfaces and the cohesive energy of bulk metals, respectively; (c) Repeatable cycles of incorporating two C atoms onto Cu-terminated AC graphene edges on the Cu(111) surface. The circled regions represent the growth site. Small black and large orange balls represent C and Cu atoms, respectively. The Cu atoms that terminate the graphene edges are highlighted by green. Adapted with permission from Ref. 66. Copyright 2012, American Chemistry Society."

Fig 6

The healing of point defect of graphene assisted by metal atoms 69, 70. (a) Healing barriers of an SW defect without/with the absorption of a Ni atom; (b) Optimized structures of a SV (3DB) and a DV (4DB@M) in graphene on the Cu surface. Carbon atoms around defect and the extra metal adatom in 4DB@M are highlighted by green and blue, respectively; (c) Defect healing process in graphene on Cu(111) and Ni(111) surfaces with two additional carbon atoms.(a) Adapted with permission from Ref. 70. Copyright 2013, American Chemistry Society. (b, c) Adapted with permission from Ref. 69. Copyright 2013, American Chemistry Society."

Fig 7

The effect of symmetry of substrate surface on the graphene morphology 74. (a) Alignment of single crystalline graphene islands with various symmetries on low-index fcc surfaces. The < 110 > orientations of substrates are denoted by green lines and islands are represented by purple polygons. The symmetry groups and the number of symmetry operations are provided. (b) Scanning electron microscopy image of graphene grains on a polycrystalline Cu foil with two largest grains highlighted in color; (c–i) Monte Carlo modeling of growth: (c) isotropic kinetics, Cu(111); (d, e) Ni(111): (d) with a 103 difference between growth probabilities for ▽ and △ directions, and (e) a 101 ∆ : ▽ probability ratio; (f) two slow directions representing Cu(100); (g) two slow directions but with two degenerate orientations, Cu(110); (h) same as (g) but with two fast directions; (i) calculations with diffusion. Brightness represents time, lighter cells are more recently added. (b–i) Adapted with permission from Ref. 74. Copyright 2015, American Physics Society."

Fig 8

Corrugation of graphene grown on Cu substrates during the cooling process 79. (a) Schematic of ultraflat graphene on Cu with a premelting layer and the corrugation process during cooling. (b) SEM images of graphene grown on polycrystalline Cu foil. The red, yellow, and white arrows showed Cu step bunches, graphene wrinkles, and graphene adlayers, respectively. (c) SEM image of a graphene wrinkle. Adapted with permission from Ref. 79. Copyright 2018, Wiley-VCH."

Fig 9

Friction and adhesion effect on the wrinkle formation 83. (a) Correlation between the frequencies of the G and 2D bands acquired from wrinkles, epitaxial, and nonepitaxial graphene regions. The fitted line shows epitaxial graphene that is biaxially strained with ΔωG/Δε= −0.56 cm−1, and Δω2D/Δε= −1.55 cm−1. Structures of (b) epitaxial and (c) nonepitaxial graphene on the Cu(111) surface. (d) The variation of energy of graphene wrinkles of different shapes compared to unstrained flat graphene (ΔE), where the strain energy of a compressed flat graphene is shown for comparison. Representative structures of graphene during wrinkle formation are also shown in the bottom of panel. (e) Epitaxial and (f) nonepitaxial graphene sliding in the x (horizontal) and y (vertical) directions of the Cu(111) surface. Adapted with permission from Ref. 83. Copyright 2018, Wiley-VCH."

Fig 10

The step-bunching (SB) formation for graphene covered Cu during the cooling process 85. (a) The process of the Cu(111) surface SB beneath a graphene layer. A series of images from top to bottom showing the increase in height of the highest step in each configuration, marked by black arrows with H = 1, 2, 4, 8, 16. (b) The relative energy variation of bare Cu (black line) and SLG-covered Cu (red line) during the SB process. (c) Schematic illustrations showing the different ways of bending of the graphene overlayer during the SB process. (d) Formation energies of bare Cu (black line) and Cu covered by SLG (red line), BLG (blue line), and TLG (green line), as a function of the step height. Adapted with permission from Ref. 85. Copyright 2018, American Physics Society."