Fabrication of free-standing Al2O3 nanosheets for high mobility flexible graphene field effect transistors

We propose a facile methodology for large-scale fabrication of graphene-based field effect transistors (GFETs) with two types of devices, top- and bottom-gated configurations. The top-gated GFETs containing a monolayer graphene channel, a free-standing Al2O3 nanosheet as the gate dielectrics and a top-gate electrode were assembled by a poly(methyl methacrylate)-assisted wet-transfer technique. As a result, the hole mobility of the top-gated GFETs was 2306.28 ± 295.53 cm2 V−1 s−1, which is much higher than that of top-gated GFETs with Al2O3 dielectrics prepared by atomic layer deposition (15.28 cm2 V−1 s−1). We also simultaneously synthesized graphene–graphite integrated electronic devices, in which we utilized graphene and graphite layers as an active channel layer and source/drain electrodes for bottom-gated all-graphene-based FETs, respectively. In addition, a layer-by-layer stacked multilayer graphene sheet and free-standing Al2O3 dielectrics were employed as a gate electrode and a dielectric layer, respectively. Significantly, all component layers were assembled by a poly(methyl methacrylate)-assisted wet-transfer technique, which is a progression towards high-performance, transparent, and flexible GFETs.