Formation mechanism of graphene buffer layer on SiC(0Â 0Â 0Â 1)

The initial stage of the growth of graphene on SiC with the underlying mechanism of carbon layer early stage formation on the single crystal silicon carbide surface was studied using silicon sublimation technique. The obtained buffer layer is organized in a form of carbon regions with 10% of sp3 defects separated 10-15 Å. Raman spectroscopy was used to assess the degree of the buffer layer's disorder. The intensity of I(D) and I(GB) buffer peaks was found to be proportional to the number of defects. Although the layer is not fully saturated with carbon atoms, it remains impenetrable. However, sublimation from the steps side walls which are not covered by the buffer layer is possible. It was observed that in the vicinity of the macro-step edges the sublimation is more effective, which leads to the production of additional free C atoms, filling the buffer layer structure, subsequently decreasing sp3 hybridization, to about 1-2%. This healing process which also continues during the graphene layer growth is reflected in a decrease in D line intensity and finally in formation of the well-organized buffer layer.