Catalyst-free approach for growth of graphene sheets on high-density silica nanowires by CVD

• Graphene sheets were synthesized on silica nanowires in absence of metal catalysts.
• The graphene sheets grew along the silica nanowires.
• The quality and domain size of graphene were determined by the annealing process.
• The silicon substrate for fabricating graphene can be reused limitlessly.

A novel “two-step annealing” method is proposed for the direct synthesis of graphene sheets on high-density dielectric silica nanowires without using metal catalysts. During the first annealing at 1000 °C, the extremely thin SiO2 layer on Si substrate shrinks and forms dense nanoparticles. Using these silica nanoparticles as templates, graphene sheets and silica nanowires are synthesized simultaneously after the second annealing process at 800–850 °C. The experiment results suggest that the graphene sheets grow along the nanowires and its crystalline quality and domain size are determined by the temperature and duration of the second annealing process.