LAUSR

Large-area monolayer (1LG) and multilayer graphene (MLG) grown by chemical vapor deposition (CVD) have been of great technological importance for the graphene electronics and photonics. Such CVD-grown MLG (CVD-MLG) flakes consist of multiple single crystal domains, whose stacking orders can be diverse due to the various choices of layer number, stacking sequence, and twist angle. Here, we demonstrated a way to identify the stacking order of CVD-MLG via Raman spectroscopy. The CVD-grown 1LG can be identified by comparing its optical contrast or G mode intensity with those of the corresponding mechanically exfoliated 1LG on the same substrate. Once the CVD-grown 1LG is distinguished, all the layer numbers of CVD-MLG flakes can be ascertained by the peak positions of their layer-breathing modes. The stacking sequence of a CVD-MLG flake can be determined by the shear modes, and the twist angles of twisted interfaces in the CVD-MLG flake are accessible by the so-called R modes. In this way, one can determine whether an MLG sample exhibit a fully nonstacked arrangement or if 2 or 3 of these layers are stacked in the AB stacking, including the order where the stacked layers would appear with respect to the nonstacked layers. This reliable way to identify the stacking orders advances an important step for the characterization of CVD-MLGs, shedding light on tailoring the properties of CVD-MLGs with specific stacking order on demand. Copyright © 2017 John Wiley & Sons, Ltd.