Rectification of Ion Current Determined by the Nanopore Geometry: Experiments and Modelling

We provide a way to precisely control the geometry of a SiN_x nanopore by adjusting the applied electric pulse. The pore is generated by applying the current pulse across a SiN_x membrane, which is immersed in potassium chloride solution. We can generate single conical and cylindrical pores with different electric pulses. A theoretical model based on the Poisson and Nernst–Planck equations is employed to simulate the ion transport properties in the channel. In turn, we can analyze pore geometries by fitting the experimental current-voltage (I–V) curves. For the conical pores with a pore size of 0.5–2 nm in diameter, the slope angles are around -2.5^\circ to -10^\circ. Moreover, the pore orifice can be enlarged slightly by additional repeating pulses. The conic pore lumen becomes close to a cylindrical channel, resulting in a symmetry I–V transport under positive and negative biases. A qualitative understanding of these effects will help us to prepare useful solid-nanopores as demanded.