Modification of graphene/SiO2 interface by UV-irradiation: effect on electrical characteristics

Graphene is a promising material for next-generation electronic devices. The effect of UV-irradiation on the graphene devices, however, has not been fully explored yet. Here we investigate the UV-induced change of the field effect transistor (FET) characteristics of graphene/SiO2. UV-irradiation in a vacuum gives rise to the decrease in carrier mobility and a hysteresis in the transfer characteristics. Annealing at 160 °C in a vacuum eliminates the hysteresis, recovers the mobility partially, and moves the charge neutrality point to the negative direction. Corresponding Raman spectra indicated that UV-irradiation induced D band relating with defects and the annealing at 160 °C in a vacuum removed the D band. We propose a phenomenological model for the UV-irradiated graphene, in which photochemical reaction produces dangling bonds and the weak sp(3)-like bonds at the graphene/SiO2 interface, and the annealing restores the intrinsic graphene/SiO2 interface by removal of such bonds. Our results shed light to the nature of defect formation by UV-light, which is important for the practical performance of graphene based electronics.