Versatile sputtering technology for Al₂O₃ gate insulators on graphene

We report a novel, sputtering-based fabrication method of Al₂O₃ gate insulators on graphene. Electrical performance of dual-gated mono- and bilayer exfoliated graphene devices is presented. Sputtered Al₂O₃ layers possess comparable quality to oxides obtained by atomic layer deposition with respect to a high relative dielectric constant of about 8, as well as low-hysteresis performance and high breakdown voltage. We observe a moderate carrier mobility of about 1000 cm² V^-1 s^-1 in monolayer graphene and 350 cm² V^-1 s^-1 in bilayer graphene, respectively. The mobility decrease can be attributed to the resonant scattering on atomic-scale defects, likely originating from the Al precursor layer evaporated prior to sputtering.