Synthesis of graphene on a polycrystalline Co film by radio-frequency plasma-enhanced chemical vapour deposition

Graphene of 1-5 layers was synthesized on a polycrystalline Co film by radio-frequency plasma-enhanced chemical vapour deposition at a relatively low temperature of 800 degrees C for only 40 s in a mixture of gases of CH4/H-2/Ar (1/5/20, with a total gas flow rate of 78 sccm). The obtained graphene is of high quality as revealed by Raman spectroscopy and x-ray photoelectron spectroscopy. It exhibits a high optical transmittance of more than 70% in the wavelength range 500-1200 nm, and a sheet resistivity of 2661 Omega/sq. A possible formation mechanism is proposed. The significant influence of octahedral and tetrahedral lattice interstitial sites in the Co crystallites on the formation of graphene is discussed.