▎ 摘　　要

We present characteristics of dual-gated graphene devices with an Al2O3 gate dielectric formed by an O-3-based atomic-layer-deposition process. Raman spectra reveal that a O-3 process at 25 degrees C on single-layered graphene introduces the least amount defects, while a substantial number of defects appear at 200 degrees C. This graphene device with O-3-based Al2O3 dielectric demonstrates a heterojunction within the graphene sheet when applying V-TG and V-BG and possesses good dielectric properties with minimal chemical doping, including a high dielectric constant similar to 8, low hysteresis width similar to 0.2 V, and low leakage current and a carrier mobility of 5000 cm(2)/V s 25 degrees C in ambient. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3467454]