Hydrogen atom adsorption on graphene buffer layer grown on SiC(0001) surface: first-principles study

Thermal decomposition of SiC substrate is known as high-quality graphene fabrication method, and then has been intensively studied. The C-atom layer grown on SiC substrate is not graphene but so-called buffer layer (BL), which has similar honeycomb structure to graphene but does not have the graphene’s characteristic electronic properties due to the lack of the Dirac cone. To utilize BL grown on SiC substrate as graphene, it is necessary to anneal it under hydrogen (H) ambient to intercalate H atoms between BL and SiC substrate to break the covalent bond between BL and SiC surface. However, the lack of knowledge on the intercalation mechanism make it difficult to control this process to obtain high quality graphene. In this study, we investigated the interaction between BL grown on SiC substrate and H atoms by using ab initio density functional calculations. We found that H atoms adsorbed on BL prefer to desorb from BL than penetrate thru BL, because the activation energy of the former process is much lower than that of the latter. It is considered that H atoms enter between BL and SiC substrate from surface steps or some large cracks of BL rather than the honeycomb structures of BL. We used the Earth Simulator of JAMSTEC and the NIMS Numerical Materials Simulator for this study.