Direct growth of an ultrathin gate dielectric layer with high uniformity and high quality on graphene remains a challenge for developing graphene-based transistors due to the chemically inert surface properties of graphene. Here, we develop a method to realize atomic-layer-deposition (ALD) growth of an ultrathin high-κ dielectric layer on graphene through premodifying the graphene surface using electron beam irradiation. An amorphous carbon layer induced by electron beam scanning is formed on graphene and then acts as seeds for ALD growth of high-κ dielectrics. A uniform HfO2 layer with an equivalent oxide thickness of 1.3 nm was grown as a gate dielectric for top-gate graphene field-effect transistors (FETs). The achieved gate capacitance is up to 2.63 μF/cm2, which is the highest gate capacitance on a graphene solid-state device to date. In addition, the fabricated top-gate graphene FETs present a high carrier mobility of up to 2500 cm2/(V·s) and a negligible gate leakage current of down to 0.1 mA/cm2, showing that the ALD-grown HfO2 dielectric layer is highly uniform and of very high quality.
Keywords: HfO2; atomic layer deposition; gate insulator; graphene; high κ.