  Graphene, as a promising material of post-silicon electronics, opens a new
paradigm for the novel electronic properties and device applications. On the
other hand, the 2D feature of graphene makes it technically challenging to be
integrated into 3D transistors with a sufficient processor capacity. Although
there are many attempts to assemble 2D graphene into 3D structures, the
characteristics of massless Dirac fermions cannot be well preserved in these
materials for transistor applications. Here we report a high-performance
graphene transistor by utilizing 3D nanoporous graphene which is comprised of
an interconnected single graphene sheet and a commodious open porosity to
infuse an ionic liquid for a tunable electronic state by applying electric
fields. The 3D nanoporous graphene transistor, with high carrier mobility of
5000-7500 cm$^2$V$^{-1}$s$^{-1}$, exhibits two to three orders of magnitude
higher electric conductance and capacitance than those of 2D graphene devices,
along with preserved ambipolor electronic nature of Dirac cones. Moreover, the
3D graphene networks with Dirac fermions turn out to exhibit a unique nonlinear
Hall resistance in a wide range of the gate voltages. The high quality 3D
nanoporous graphene EDLT may open a new field for utilizing Dirac fermions in
3D network structures for various fundamental and practical applications.

Materials Science;Mesoscale and Nanoscale Physics