Fig. 2

Penetration distance of the potential fluctuations from the Si, GaAs, GaN, and LiF substrates. a Atomic structures of Si, GaAs, GaN, and LiF on mono-, bi-, or tri-layer graphene-coated Si, GaAs, GaN, and LiF, respectively. The corresponding (b) maps of potential fluctuation on the same scale (0–25 meV) for cross-comparison and (c) EBSD of the released surfaces of each configuration. d Schematic and EBSD of the GaN epilayer grown on mono-, bi-, and tri-layer h-BN covered GaN substrate [55]. Copyright from Springer Nature. e Cross-sectional images of charge density distribution induced by GaN substrates with BN. f Schematic, cross-sectional false-colour SEM image, EBSD, and the exfoliated image of three stacks of GaN/BN grown on a GaN substrate [56]. Copyright from Springer Nature