Self-organized metal-semiconductor epitaxial graphene layer on off-axis 4H-SiC(0001)

The remarkable properties of graphene have shown promise for new perspectives in future electronics, notably for nanometer scale devices. Here we grow graphene epitaxially on an off-axis 4H-SiC(0001) substrate and demonstrate the formation of periodic arrangement of monolayer graphene on planar (0001) terraces and Bernal bilayer graphene on (1120) nanofacets of SiC. We investigate these lateral superlattices using Raman spectroscopy, atomic force microscopy/electrostatic force microscopy (AFM/EFM) and X-ray and angle resolved photoemission spectroscopy (XPS/ARPES). The correlation of EFM and ARPES reveals the appearance of permanent electronic band gaps in AB-stacked bilayer graphene on (1120) SiC nanofacets of 150 meV. This feature is confirmed by density functional theory (DFT) calculations. The charge transfer between the substrate and graphene bilayer results in an asymmetric charge distribution between the top and the bottom graphene layers opening an energy gap. This surface organization can be thus defined as self-organized metal-semiconductor graphene.