Transformation of the buffer layer grown on 4H-SiC to single-layer graphene by ex situ hydrogen intercalation

The buffer layer samples grown on the Si-face of the 4H- and 6H-SiC substrates were heated in a hydrogen flow at different temperatures (600–900 °C) and heating times (40–60 min) in order to obtain quasi-freestanding monolayer graphene. Their structural properties were characterized before and after heating by using the methods of Raman spectroscopy, atomic force microscopy, Kelvin probe force microscopy, and low-energy electron diffraction. The dependence of the degree of coverage of the sample with quasi-freestanding graphene and the number of defects in the resulting films on the heating temperature was studied. As a result of optimization of the technological parameters, it is shown that the highest quality of the resulting quasi-freestanding graphene can be achieved by using the following parameters: heating time of 40 minutes and temperature of 800 °C.