Thickness Determination of Graphene Layers Formed on SiC Using Low-Energy Electron Microscopy

Abstract

Low-energy electron microscopy (LEEM) has been used to measure reflectivity of low-energy electrons for graphene layers grown on Si-terminated 6H-SiC(0001) and 4H-SiC(0001) substrates and C-terminated 4H-SiC(000-1) substrates. We observe quantized oscillations in the reflectivity on all the substrates. The number of graphene layers grown on both the Si-terminated and C-terminated substrates can be determined microscopically as the number of dips in the reflectivity between 0 and 7 eV. We also find that the dips appear closer to the vacuum level on the C-terminated substrates than on the Si-terminated substrates. This could be explained by the differences in the work function and Fermi level position between the graphene layers grown on the Si-terminated and C-terminated substrates. [DOI: 10.1380/ejssnt.2008.107]