Electron-diffraction study of the structure of epitaxial graphene grown by the method of thermal destruction of 6$H$- and 4$H$-SiC (0001) in vacuum

The method of reflection high-energy electron diffraction (RHEED) is used for studying the structure of graphene layers formed on the surface of the Si-face of conductive and semi-insulating 6$H$- and 4$H$-SiC(0001) substrates by thermal desorption of Si atoms in high vacuum, depending on the temperature and time of sublimating Si atoms as well as depending on the method of preprocessing the substrate surface. Diffraction patterns are recorded in the [$\bar1$2$\bar1$0] and [1$\bar1$00] crystallographic directions of the substrates. It is found that in all experiments the formation of graphene layers occurs with a rotation of the graphene crystal lattice by 30$^{\circ}$ relative to the SiC lattice.