Electron-diffraction study of graphene-film growth stages during the thermal destruction of 6$H$-SiC (000$\bar1$) in vacuum

The structure of graphene layers grown by sublimation on a 6$H$-SiC (000$\bar1$) substrate surface is studied by electron diffraction depending on the sublimation temperature and substrate-surface pretreatment method. It is shown that the use of polishing sublimation etching of the substrate before thermal destruction at a temperature of 1350$^\circ$C on the substrate surface results in the formation of single-crystal graphene domains with graphene-lattice rotation by 30$^\circ$ with respect to the SiC lattice and a small fraction of amorphous domains. An increase in the temperature to 1500$^\circ$C leads to the partial formation of a polycrystalline graphene phase with turbostratic structure while retaining the preferred orientation of graphene crystallites as at 1350$^\circ$C. The use of pregrowth annealing before thermal destruction makes it possible to grow a graphene film with a more ordered and homogeneous structure without inclusions of amorphous and polycrystalline components. The preferred orientation of graphene domains in the film remains unchanged.