Graphene on SiC(0001) and SiC(0001Ì ) surfaces grown via Ni-silicidation reactions

This paper presents the structure and electronic properties of graphene grown on 6H-SiC(0001) and SiC(0001̅) surfaces via Ni-silicidation reactions at temperatures around 800 °C. Silicidation reactions take place at temperature higher than 400 °C for Ni(10 ML)/SiC and a single-phase θ-Ni2Si(0001)-layer grows epitaxially on SiC(0001̅) at 500 °C, whereas a mixed phase silicide-layer is formed on the SiC(0001) substrate. Annealing at 800 °C leads to growth of ordered graphite layers on both SiC(0001̅) and SiC(0001) surfaces with an areal occupation ratio of ∼ 65%, which surround the Ni-silicide islands. High-resolution ion scattering analysis reveals that single- and double-layer of graphite grow on the SiC(0001̅) and SiC(0001), respectively. The dispersion curve of the π band for the double-layer graphite (DG) on the Si-face lies about 1 eV above that of the single-layer graphite (SG) on the C-face around the Γ-point. The work functions of the SG/SiC(0001̅) and DG/SiC(0001) are derived to be 5.15 ± 0.05 and 4.25 ± 0.05 eV, respectively, which coincide well with the theoretical prediction based on the ab initio calculations. The present results indicate that the electronic states of graphene are influenced by the interaction with supports.