Fig. 6

Lattice polarity modulation mechanism in nitrides quasi vdW epitaxy. a Schematic diagram of the nucleation growth of GaN on N-doped graphene covered sapphire substrate. b annular bright-field (ABF)-scanning transmission electron microscopy (STEM) image of GaN/graphene/sapphire interface. c integrated differential phase contrast (iDPC)-STEM image of GaN grown on N-doped graphene-covered sapphire substrate labeled by the frame in (c). In situ reflection high energy electron diffraction (RHEED) images of GaN films grown on N doped graphene covered sapphire substrate after (d) high-temperature GaN nucleation at 780 °C and (e) 800 nm-thick GaN epilayer cooling to 550 °C [106]. f Schematic diagram of the nucleation growth of GaN on O-doped graphene. g high-angle annular dark-field (HAADF)-STEM and iDPC -STEM images of the interface atomic structure of the N-polarity film. h HAADF-STEM and iDPC -STEM images of the interface atomic structure of the Ga-polarity film [107]. Copyright from Wiley–VCH GmbH