Direct CVD growth of graphene on three-dimensionally-shaped dielectric substrates

Large area growth of single- and few-layer graphene has been established, yet its prerequisite of metallic catalysts has impeded direct graphene growth on three-dimensional (3D) dielectric substrates. Here, we report a new strategy for direct chemical-vapor-deposition (CVD) growth of graphene films on 3D patterned sapphire substrates by placing the target surfaces in contact with or close to a Cu catalyst. This approach can yield uniform coatings of few-layer graphene films on complex structures on the centimeter scale, as confirmed by detailed scanning electron microscopy and Raman spectroscopy studies. In addition, we showed that 3D graphene can possess ambipolar field-effect transistor (FET) characteristics by applying the gate voltage through an ion-gel dielectric sheet. The 3D graphene FET device was further employed as a pressure and touch sensing device, where the sensitivity was effectively enhanced by the 3D topology.