Carbon-Rich Domain in Hexagonal Boron Nitride: Carrier Mobility Degradation and Anomalous Bending of the Landau Fan Diagram in Adjacent Graphene

Hexagonal boron nitride (h-BN) crystals grown under ultrahigh pressures and ultrahigh temperatures exhibit a high crystallinity and are used throughout the world as ideal substrates and insulating layers in van der Waals heterostructures. However, in their central region, these crystals have domains which contain a significant density of carbon impurities. In this study, we utilized cathodoluminescence and far-ultraviolet photoluminescence to reveal that the carbon (C)-rich domain can exist even after exfoliation. Then, we studied the carrier transport of graphene in h-BN/graphene/h-BN van der Waals heterostructures, precisely arranging the graphene to straddle the border of the C-rich domain in h-BN. We found that the carrier mobility of graphene on the C-rich h-BN domain was significantly suppressed. In addition, characteristic bending of the Landau fan diagram was observed on the electron-doped side. These results suggest that the C-rich domain in h-BN forms an impurity level and induces extrinsic carrier scattering into adjacent graphene.