Effect of ultraviolet light irradiation and ion collision on the quality of multilayer graphene prepared by microwave surface-wave plasma chemical vapor deposition

• The effect of UV light and ion collision from the plasma exposure during graphene synthesis has been reported.
• There were more defects in the graphene prepared with irradiation of UV light than with blocking of UV light. No ion collisions were observed.
• The carrier mobility was lower and the sheet resistance was larger in the graphene prepared when UV light was present than when it was blocked.

We successfully synthesized graphene by microwave surface-wave plasma chemical vapor deposition (CVD) and investigated the effect of UV light and ion collision from the plasma exposure during graphene synthesis. The graphene obtained here was multilayer graphene consisting of approximately 5 layers according to cross-sectional transmission electron microscopy results. The quality of the graphene was compared between the case where UV light was irradiated from the plasma and the case where the UV light was blocked by a grid-inserted CVD configuration. Quality was evaluated by Raman scattering spectroscopy. There were more defects in the graphene prepared with irradiation of UV light than with blocking of UV light. Furthermore, we investigated the effects of ion collisions that occurred in the plasma, but they had no effect on graphene quality. These results suggest that during graphene synthesis, UV light from the plasma affects its crystallinity. The electrical conductivity, optical transmittance and mobility of the transferred graphene films were measured to clarify the effects of UV light irradiation.

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