Stacked 2D Materials For Temporal Gating of Ion Transport Through Nanopores

We present here a system consisting of a single nanopore through stacked 2D materials which allows ion transport of an electrolyte solution through the pore to be controlled by the electrical potential of a 2D gate within the stack. Previous nanopore systems operate with the classical Debye layer with changes slow enough for a electrical double-layer (EDL) to form at the liquid-solid interface. The gating here will allow temporal control faster than the formation of this EDL, up to GHz frequencies. We drill single sub-10nm nanopores by TEM in stacked 2D materials (hBN and graphene) placed over a 5um diameter micropore in a SiNx membrane on a silicon chip. Specifically we create hBN-graphene-hBN stacks, with a ~1nm conducting layer of graphene between two insulating hBN flakes. To apply gate voltages, we also develop: a thin printed circuit board (PCB), on-chip metal electrodes with fine metal contacts to the graphene, and an insulating SiO2 layer over the chip with an exposed region over the 2D materials. We measure ionic current through the pores with varying KCl concentrations, which exhibits a pH-dependent low concentration conductance saturation from the surface charges on the pore walls, and compare this pH dependence to the effect of voltage gating on pore conductivity. Our preliminary results show the possibility of gating transmembrane currents with gate voltages of a few hundreds of mV which can provide precise temporal control of ion transport in future ionic circuits and molecular sensing.