Prominent local transport in silicon carbide composites containing in-situ synthesized three-dimensional graphene networks

In-situ grown graphene/SiC composites developed by spark plasma sintering have emerged as a very interesting family of materials with expected high performance for advanced applications. In this work, the local functional properties of graphene/SiC ceramics are elucidated for distinct α- and β- SiC polytypes combining scanning probe microscopies. We unambiguously identify all composite constituents and demonstrate the formation of a three-dimensional graphene conductive network inside the composite. The investigated composites exhibit grains with different doping level depending on growth rate during sintering so that conduction paths associated to graphene and matrix networks may compete. The relevance of nanoscale characterization on functional graphene/semiconductor materials is proved as it evidences the type of doping and carrier concentration of the semiconductor and the critical role played by the graphene constituent in the formation of ohmic contacts. Both issues are of crucial importance for understanding the macroscale behavior of these materials and determine their applications.