Raman study of annealed two-dimensional heterostructure of graphene on hexagonal boron nitride

In this paper, we investigate stacked 2D graphene layers on hexagonal boron nitride (hBN). The graphene is obtained by high-quality chemical vapor deposition (CVD) and transferred to the h-BN substrate. We focus our attention on annealing effect at 1040 degrees C on single graphene layer (SGL) and bilayer graphene (BLG) on h-BN substrate using Raman spectroscopy. Our results show, before annealing, a twist angle theta = 0.63 degrees between the SGL and the h-BN substrate and a twist angle 3 degrees < theta(G1G2) < 8 degrees between the two graphene layers of the BLG. After annealing, the analysis of the graphene G and 2D bands show a rotational reorientation of the graphene layer with respect to the h-BN substrate. Raman mapping also shows that the rotational reorientation is spatially dependent. (C) 2017 Elsevier Ltd. All rights reserved.