Revisiting the interfacial structure of graphene quasicrystal growth on SiC

We revisit the interfacial structure underlying the growth of graphene quasicrystals on SiC, previously realized by a twisted bilayer graphene with a twist angle of 30°. While the formation of graphene quasicrystals via an h-BN-mediated growth process has been established, the microscopic nature of the interface between the overlayer and the SiC substrate has remained unclear. Using a combination of low-energy electron diffraction, angle-resolved photoemission spectroscopy, and core-level X-ray photoelectron spectroscopy, we show that an amorphous boron–nitrogen buffer layer exists between h-BN with R0° orientation and the SiC substrate. Importantly, this boron–nitrogen buffer layer persists even after the conversion of h-BN into graphene with R0° orientation, contrary to the conventional assumption that R0 graphene resides on a crystalline carbon-buffer layer. Our results clarify the interfacial structure in SiC-based graphene quasicrystal growth and provide a refined framework for understanding boron-nitrogen-assisted epitaxial graphene systems.