Isothermal growth and stacking evolution in highly uniform AB-stacked bilayer graphene

Controlling the stacking order in bilayer graphene (BLG) allows realising unique physical properties. In particular, the possibility of tuning the band gap in AB-stacked BLG (AB-BLG) has a great technological importance for electronic and optoelectronics applications. Most of current methods to produce AB-BLG suffer from inhomogeneous layer thickness and/or coexistence with twisted BLG. Here, we demonstrate a method to synthesise highly pure large-area AB-BLG by chemical vapour deposition (CVD) using Cu-Ni films. Increasing the reaction time resulted in a gradual increase of the AB stacking, with the BLG eventually free from twist regions for the longer times (99.4 % of BLG has AB stacking), due to catalyst-assisted continuous BLG reconstruction driven by carbon dissolution-segregation processes. The band gap opening was confirmed by the electrical measurements. The concept of the continuous reconstruction to achieve highly pure AB-BLG offers a new strategy to control the stacking order of catalytically grown two-dimensional materials.