Initial growth of graphene on copper foil in non-equilibrium atmospheric pressure remote plasma CVD

Graphene has attracted much attention due to its excellent properties.

Initial growth of graphene on copper foil in microwave-excited non-equilibrium atmospheric pressure remote plasma (MN-APP) using a CH₄/H₂/He gas mixture has been investigated in this study.

Since the growth of graphene in the plasma enhanced chemical vapor deposition (PEVD) is driven by surface reactions of radicals generated by the plasma, it is important to identify the radicals in order to elucidate its growth process. Therefore, measurement of C₂ radicals generated in the MN-APP was also carried out using absorption spectroscopy.

At low CH₄ flow rate, the variation in graphene size at each process time was very small, although the variation increased with the increase in the process time at the high CH₄ flow rate. Therefore, at low CH₄ flow rate, the flux of precursors supplied from the MN-APP are relatively low and mainly consumed for the planar growth of graphene without inducing subsequent nucleation after the initial nucleation. However, the excess supply of precursors would induce subsequent nucleation after the initial nucleation.

In these conditions, the C₂ radical density was estimated to be less than the order of 10¹² cm^-3 by absorption spectroscopy.