  Large scale synthesis of single layer graphene (SLG) by chemical vapor
deposition (CVD) has received a lot of attention recently. However, CVD
synthesis of AB stacked bi-layer graphene (BLG) is still a challenging work.
Here we report synthesis of BLG homogeneously in large area by thermal CVD. The
2D Raman band of CVD BLG splits into four components, suggesting splitting of
electronic bands due to strong interlayer coupling. The splitting of electronic
bands in CVD BLG is further evidenced by the study of near infrared (NIR)
absorption and carrier dynamics probed by transient absorption spectroscopy.
Ultraviolet photoelectron spectroscopy invesigation also indiates CVD BLG
possesses different electronic structures from those of CVD SLG. The growth
mechanism of BLG is found to be related to catalystic activity of copper
(Cu)surface, which is determined by purity of Cu foils employed in CVD process.
Our work showsthat strongly coupled or even AB stacked BLG can be grown on Cu
foils in large scale, which isof particular importance for device applications
based on their split electronic bands
