High-Yield Chemical Vapor Deposition Growth of High-Quality Large-Area AB-Stacked Bilayer Graphene

Abstract

Bernal stacked (AB stacked) bilayer graphene is of significant interest for functional electronic and photonic devices due to the feasibility to continuously tune its band gap with a vertical electrical field. Mechanical exfoliation can be used to produce AB stacked bilayer graphene flakes but typically with the sizes limited to a few micrometers. Chemical vapor deposition (CVD) has been recently explored for the synthesis of bilayer graphene but usually with limited coverage and a mixture of AB and randomly stacked structures. Herein we report a rational approach to produce large-area high quality AB stacked bilayer graphene. We show that the self-limiting effect of graphene growth on Cu foil can be broken by using a high H2/CH4 ratio in a low pressure CVD process to enable the continued growth of bilayer graphene. A high temperature and low pressure nucleation step is found to be critical for the formation of bilayer graphene nuclei with high AB stacking ratio. A rational design of a two-step CVD process is developed for the growth of bilayer graphene with high AB stacking ratio (up to 90 %) and high coverage (up to 99 %). The electrical transport studies demonstrated that devices made of the as-grown bilayer graphene exhibit typical characteristics of AB stacked bilayer graphene with the highest carrier mobility exceeding 4,000 cm2/V·s at room temperature, comparable to that of the exfoliated bilayer graphene.

Chemical vapour deposition growth of large single crystals of monolayer and bilayer graphene

“…S13). To the best of our knowledge, this is the largest AB-stacked bilayer domain ever reported to date [33][34][35] . A 200-mm bilayer graphene is evaluated by both the colour contrast under the optical microscope and more clearly the contrast shown in the SEM image (Fig.…”

Control of layer stacking in CVD graphene under quasi-static condition

“…It is reasonable to accept this growth mechanism as it is consistent with the earlier reports, where they adopted a similar kind of approach to grow the second layer epitaxially from the top on already grown monolayer graphene with the aid of an additional fresh Cu foil as a catalyst to create an extra carbon flux for the growth of the second layer. 23,24 The contrast nature of layer stacking for samples with different geometries of the reaction site suggests its different underlying growth mechanisms, originating from the process which supplies the extra carbon flux, needed for the growth of second layer i.e. by diffusion through Cu foil or from the top in the presence of Cu vapor flux.…”

“…[15][16][17][18][19][20][21][22] The self-limiting effect of low pressure CVD growth of single layer graphene on copper vanishes when the set growth conditions are outside the optimized window and the percentage growth of SLG, BLG or FLG can vary with growth conditions. 23,24 Usually such a CVD process results in a mixture of AB stacked and twisted BLG and/or FLG. However, it remained a significant challenge to experimentally control the growth process, which yields BLG predominantly having one or other type of stacking, especially the twisted one.…”

The nonlinear optical properties of coupling and decoupling graphene layers

“…All of the characteristic features suggest the BLG is the coupling bi-layer graphene. 11 According to the Raman spectra of DBLG and DTLG, it is clear that they still behave like the SLG, with the G band is lower than the 2D band though there are two or three graphene layers superimposed together. In other words, the graphene layers are decoupling because of the disoriented stacking arrangements.…”