Large-area homogeneous quasifree standing epitaxial graphene on SiC(0001): Electronic and structural characterization

The growth of epitaxial graphene on SiC has been identified as one of the most promising techniques to produce graphene for electronic applications. In this paper, we present a systematic study of the electronic and structural properties of large-area quasifree standing epitaxial monolayer graphene grown on top of the SiC(0001) surface. For this purpose, we combine the thermal treatment of SiC in Ar atmosphere to achieve a homogeneous coverage of the surface with the hydrogen intercalation process, which leads to the removal of the interaction between the substrate and the carbon layer. The band structure in the vicinity of the (K) over bar point is measured using high-resolution angle-resolved photoelectron spectroscopy. A detailed analysis of the quasiparticle dynamics reveals a renormalization of the band velocity estimated to about 3% at energies around 200 meV below the Fermi level, which mainly originates from electron-phonon interaction. Further analysis of the momentum distribution curves leads to the formulation of a model for the doping reduction in such a system in the course of sample annealing above 650 degrees C. The uniformity and homogeneity of the graphene is demonstrated by means of low-energy electron microscopy (LEEM). Microphotoelectron spectroscopy data confirm the high structural quality and homogeneity of the quasifree standing graphene. Using LEEM and scanning tunneling microscopy, we demonstrate that the hydrogen desorption at elevated temperatures of approximately 750 degrees C sets in on the graphene terraces rather than via the step edges.