Chemical Vapor Deposition Growth of Bernal-Stacked Bilayer Graphene by Edge-Selective Etching with H2O

Bernal-stacked bilayer graphene is uniquely suited for application in electronic and photonic devices because of its tunable band structure. Even though chemical vapor deposition (CVD) is considered to be the method of choice to grow bilayer graphene, the direct synthesis of high quality, large-area Bernal-stacked bilayer graphene on Cu foils is complicated by overcoming the self-limiting nature of graphene growth on Cu. Here, we report a facile H2O-assisted CVD process to grow bilayer graphene on Cu foils, where graphene growth is controlled by injecting intermittent pulses of H2O vapor using a pulse valve. By optimizing CVD process parameters fully covered large area graphene with bilayer coverage of 77 3.6% and high AB stacking ratio of 93 3% can be directly obtained on Cu foils, which presents a hole concentration and mobility of 4.5 X 10(12) cm(-2)and 1100 cm(2) V-1 s(-1), respectively, at room temperature. The H2O selectively etches graphene edges without damaging graphene facets, which slows down the growth of the top layer and improves the nucleation and growth of a second graphene layer. Results from our work are important both for the industrial applications of bilayer graphene and to elucidate the growth mechanism of CVD-graphene.