Catalyst-free growth mechanism and structure of graphene-like nanosheets formed by hot-filament CVD

We report on a simple and effective method of synthesizing graphene-like nanosheets on silicon substrates pre-deposited with a carbon film or carbon nanodots in hot-filament(HF)CVD from a methane precursor. The results of field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and micro-Raman spectroscopy (RS) indicate that the structure of graphene-like nanosheets is changed with the flow rate change of methane and the pretreatment of the substrate surface. The catalyst-free growth of graphene-like nanosheets is related to the diffusion and assembly of carbon atoms on the substrate surface and the separation of graphene-like nanosheets from the substrate surface.