Graphene on SiC(0001) and SiC(000(1)over-bar) surfaces grown via Ni-silicidation reactions

This paper presents the structure and electronic properties of graphene grown on 6H-SiC(0001) and SiC (000 (1) over bar) surfaces via Ni-silicidation reactions at temperatures around 800 degrees C. Silicidation reactions take place at temperature higher than 400 degrees C for Ni(10 ML)/SiC and a single-phase theta-Ni2Si(0001)-layer grows epitaxially on SiC(000 (1) over bar) at 500 degrees C, whereas a mixed phase suicide-layer is formed on the SiC(0001) substrate. Annealing at 800 degrees C leads to growth of ordered graphite layers on both SiC(000 (1) over bar) and SiC(0001) surfaces with an areal occupation ratio of similar to 65%, which surround the Ni-silicide islands. High-resolution ion scattering analysis reveals that single- and double-layer of graphite grow on the SiC(000 (1) over bar) and SiC(0001), respectively. The dispersion curve of the pi 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 Gamma-point. The work functions of the SG/SiC(000 (1) over bar) 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. (C) 2010 Elsevier B.V All rights reserved.