The effect of ultraviolet light on structural properties of exfoliated and CVD graphene

摘要

We investigate the effect of UV processing of graphene with different structural properties prepared by mechanical exfoliation and CVD growth. Depending on UV exposure time, we observe different effects like oxidation, doping, and etching. For bi-layered and few-layered graphene flakes, we do not observe significant etching even after 3 h exposure which indicates the high resistance of graphene to reactive oxygen species intercalation between graphene layers. Single-layer CVD-grown graphene is fully etched after 2 h of UV treatment. The crystalline size of exfoliated single layer graphene after UV exposure drops from 45 to 5 nm while for CVD graphene from just 10 to 2nm. We investigate the effect of UV irradiation on field effect transistors, demonstrating sequential cleaning from polymer residuals, oxidation (doping), and final etching of graphene. After 30 minutes of UV irradiation, we observe the hole mobility of a CVD single layer graphene transistor increasing up to 400 cm~2/V•s.