Scanning Tunneling Microscopy investigation of the graphene/6H-SiC(0001̄) (3×3 ) interface

The early stages of the graphitization of the 6H-SiC(0001̄) (3×3) surface in an Ultra-High Vacuum (UHV) are investigated by means of scanning tunneling microscopy (STM). Different kinds of graphitic islands are found on the surface. One kind (called G_ 3×3) consists of a single graphene-like carbon plane covering the initial (3×3) reconstructed substrate surface. We observe a broad distribution of rotation angles between the substrate and the carbon plane revealed by superstructures of different directions and periods. Low bias images show that the graphene structure is preserved close to the Fermi level. The data indicate a weak substrate-graphene coupling for the G_ 3×3 islands.