High-yield chemical vapor deposition growth of high-quality large-area AB-stacked bilayer graphene.
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 electric 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 H(2)/CH(4) 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 demonstrate that devices made of the as-grown bilayer graphene exhibit typical characteristics of AB-stacked bilayer graphene with the highest carrier mobility exceeding 4000 cm(2)/V · s at room temperature, comparable to that of the exfoliated bilayer graphene.
Department of Materials Science and Engineering, University of California, Los Angeles, California 90095, United States.
Lixin
L
Liu
Hailong
H
Zhou
Rui
R
Cheng
Woo Jong
WJ
Yu
Yuan
Y
Liu
Yu
Y
Chen
Jonathan
J
Shaw
Xing
X
Zhong
Yu
Y
Huang
Xiangfeng
X
Duan
D000327:Adsorption; D003460:Crystallization / Q000379:methods*; D004553:Electric Conductivity; D005740:Gases / Q000737:chemistry*; D006108:Graphite / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D013499:Surface Properties
D005740:Gases; D046911:Macromolecular Substances; D006108:Graphite