Here, we report a controllable direct graphene growth process on an insulating substrate (SiO2/Si and sapphire) by the solid phase reaction of a polymer layer. Water soluble polyvinyl alcohol (PVA) was spin coated on the SiO2/Si substrate and graphitized in presence of a Ni catalyst cap layer. Graphene growth occurs with decomposition and dehydrogenation of the polymer layer with metal catalyzation. The role of gas atmosphere, temperature, thickness of polymer and catalyst layers are investigated in the solid phase reaction process for graphene nucleation and growth. Formation of graphene flakes directly on the substrate surface is confirmed by Raman spectroscopy, optical and atomic force microscopy analysis. The as-synthesized graphene flakes interconnect with each other to create a network like structure. In the growth process, decomposing the polymeric film at an elevated temperature, atomic carbon can diffuse and segregate at the Ni/substrate interface to create the graphene structure. The developed direct growth process of the graphene structure using a simple polymer by a solid phase reaction can be significant for device integration.
