Nonisothermal Synthesis of AB-Stacked Bilayer Graphene on Cu Foils by Atmospheric Pressure Chemical Vapor Deposition

Abstract

Since the discovery of Cu-catalyzed chemical vapor deposition (CVD), the preparation of large-area graphene films has been performed by the carbon precursor exposure under isothermal conditions. In this work, we report on a nonisothermal method to quickly synthesize the largearea AB-stacked bilayer graphene films (BGF) by atmospheric pressure CVD on the copper foils. The growth feature of the BGF is carefully studied by scanning electron microscopy, Raman spectroscopy, and transmission electron microscopy. The results show that both cooling rate and CH 4 flow rate play crucial roles on the BGF growth in the nonisothermal process. A phase diagram for the preparation of BGF is thereby derived from plenty of experiments. In addition, we find that bilayer graphene seeds grow into graphene islands at the initial growth stage and extend gradually to a continuous film. Accordingly, a possible growth mechanism combining with surface-catalyzed process and seed growth is proposed.

A simple method to tune graphene growth between monolayer and bilayer

“…Since the I 2D /I G value is ∼1, most area should be AB stacked, not twisted. 6,13,14 Results of scanning tunneling microscopy (STM) measurements are consistent with the Raman results. Most area is AB stacked as shown in the typical STM image and its Fast Fourier Transform (FFT) result in Figure 2(c).…”

“…This verifies that S25 are indeed bilayer graphene samples. 14,17,26,31 Raman mapping was used to check the uniformity of the above monolayer and bilayer samples and the I 2D /I G results are shown in Figure 2(a) and 2(b). Figure 2(a) corresponds to monolayer samples S1050.…”

“…In contrast, graphene grown on copper is typically monolayer due to the "self-limiting" effect 30 Cu-Ni alloy has been used to grow bilayer graphene [6][7][8] by carefully adjusting the atomic percentage. Recently, researchers have also grown bilayer graphene on copper by regulating various conditions including the carbon source, 9,10 copper purity, 11,12 pressure, 13 growth temperature 14 and gas flow rate. 15 However, these methods either require much prolonged growth processes or produce bilayer films which are not continuous because the second layer is much smaller than the first.…”

Equilibrium Chemical Vapor Deposition Growth of Bernal-Stacked Bilayer Graphene

“…15 AB-(Bernal-) stacked bilayer graphene (BLG) can develop a bandgap of up to 250 meV by applying a vertical electric field across the two layers, 17,18 but facile, high-yield synthesis of AB-stacked BLG remains a significant challenge. [19][20][21][22][23][24][25][26][27][28] The key point for BLG growth by CVD was to overcome the self-limiting nature of SLG on Cu, in which it is critical to maintain or recover the Cu surface for the effective catalysis. Hence, compared with the simple self-limiting process of SLG on Cu surface, the growth of BLG has 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 4 mainly been achieved by complicated pre-treatments or designed CVD process, such as spatially arranged Cu substrates, 20,23 percentage-engineered Cu-Ni alloy as catalytic substrates, 21,25 carefully adjusted nucleation pressure of methane, 22,24 a high hydrogen ratio to expose the covered Cu surface, 23 or nonisothermal growth environment with variable temperatures.…”

Manufacturing Graphene‐Encapsulated Copper Particles by Chemical Vapor Deposition in a Cold Wall Reactor

“…In most studies, graphene was typically synthesized in tube furnace, [18][19][20][21][22][23] which is also known as the hot wall reactor because the heating source (usually a resistor or inductive foil) surrounds the outside of the quartz tube. However, temperature ramp-up and cool-down procedures are time consuming for graphene synthesis in hot wall reactor, due to its large heat capacity, which reduced the efficiency of fabrication.…”