High density synthesis of topological point defects in graphene on 6H-SiC(0001)

The control of the physical properties of graphene is a forefront challenge for the development of applications based on this material. Defect engineering is a promising strategy to attain new properties by the insertion of well-defined defects in the carbon lattice. Among the many topological defects of graphene, the one that has the lowest energy per dislocation is a quasi-point-like defect, the so-called Flower Defect (FD). It is generally produced randomly during the graphene synthesis. The deliberate insertion of this defect is promising for the tuning of graphene electronic properties but necessitate to establish a synthesis route allowing to control the formation of flower defects. Here we report a controlled synthesis of graphene with FD using gold as an activator during the graphene synthesis from a 6H-SiC(0001) silicon carbide wafer. The synthesis consists of a two-step procedure. Creation of a proto-graphene template where one monolayer of gold is evaporated followed by synthesis close to 1200 degrees C. This leads to a high density of FD, around 10(12) cm(-2). These results are supported by first-principles calculations showing that gold decreases the flower formation energy by a factor of 2. Scanning tunneling spectroscopy measurements reveal unexpected resonances close to the Fermi energy. (C) 2020 Elsevier Ltd. All rights reserved.