Spectral Monitoring CH/C₂ Ratio of Methane Plasma for Growing Single-Layer Graphene on Cu

Single-layer graphene was grown on copper at a low temperature of 600°C by plasma-assisted thermal chemical vapor deposition. Its growth mechanism was discussed with reference to the emission spectra of the plasma. The methane plasma produces the active species (H_x, CH_x, and C_x) without the addition of flowing hydrogen, and the amounts of hydrogen-containing species can be controlled by varying the plasma power. The effective distance was found between the plasma initial stage and the deposition stage for the single-layer graphene synthesis. The results reveal that high-quality graphene can be synthesized using methane plasma at a suitable plasma power.