Thermally Induced Graphene Rotation on Hexagonal Boron Nitride.

In this Letter, we report the observation of thermally induced rotation of graphene on hexagonal boron nitride (h-BN). After the rotation, two thermally stable configurations of graphene on h-BN with a relative lattice twisting angle of 0° (most stable) and 30° (metastable), respectively, were found. Graphene on h-BN with a twisting angle below (above) a critical angle of ∼12±2° tends to rotate towards 0° (30°) at a temperature of >100 °C, which is in line with our theoretical simulations. In addition, by manipulating the annealing temperature and the flake sizes of graphene, moiré superlattices with large spatial periods of graphene on h-BN are achieved. Our studies provide a detailed understanding of the thermodynamic properties of graphene on h-BN and a feasible approach to obtaining van der Waals heterostructures with aligned lattices.