Spectroscopic properties of close-to-perfect-monolayer quasi-free-standing epitaxial graphene on 6H SiC(0001)

In this report, we present transfer-free p-type hydrogen-intercalated quasi-free-standing epitaxial Chemical Vapor Deposition graphene on 15-mm × 15-mm semi-insulating vanadium-compensated on-axis 6H-SiC(0001), characterized in that its room-temperature direct-current Hall-effect-derived hole mobility μp = 5019 cm2/Vs, and its statistical number of layers (N), as indicated by the relative intensity of the SiC-related Raman-active longitudinal optical A1 mode at 964 cm-1, equals N = 1.05. The distribution of the ellipsometric angle Ψ measured at an angle of incidence of 50° and λ = 490 nm points out to N = 0.97. The close-to-unity value of N implies that the material under study is a close-to-perfect quasi-free-standing monolayer, which is further confirmed by High-Resolution Transmission Electron Microscopy. Therefore, its spectroscopic properties, which include the Si-H peak at 2131 cm-1, the histograms of Ψ and Δ, and the Raman G and 2D band positions, widths, and the 2D-to-G band intensity ratios, constitute a valuable reference for this class of materials.