Figure 1. Design of free-standing carbon films.

Schematic illustration of the fabrication process of HCF and PACF, (a) decomposition of methane, carbon atom adsorption, diffusion and dissolution at growth temperature, (b) graphene growing and a large number of carbon atoms dissolving in Ni foil, (c) part of the carbon atoms segregating/precipitating on Ni surface to form MGF, and another part of the carbon atoms trapped in Ni foil, (d) MGFs detaching from both sides of the Ni foil in ferric chloride solution, (e) free-standing HCF after Ni foil completely etched, (f) etching Ni foil in ferric chloride solution after the removal of MGFs, (g) and (h) etching Ni foil and formation of the PACF, (i) free-standing PACF after Ni foil completely etched.