Controlling ion transport through nanopores: modeling transistor behavior

TL;DR

This study models a nanopore transistor using continuum and particle simulation methods, revealing how ionic correlations and surface charges control ionic current, with implications for nanoscale device design.

Contribution

It introduces a hybrid modeling approach combining PNP and LEMC to account for ionic correlations and finite ion size in nanopore transistors.

Findings

Scaling behavior observed with pore radius to Debye length ratio.

Qualitative agreement between PNP and LEMC models.

Surface charges create depletion zones controlling current.

Abstract

We present a modeling study of a nanopore-based transistor computed by a mean-field continuum theory (Poisson-Nernst-Planck, PNP) and a hybrid method including particle simulation (Local Equilibrium Monte Carlo, LEMC) that is able to take ionic correlations into account including finite size of ions. The model is composed of three regions along the pore axis with the left and right regions determining the ionic species that is the main charge carrier, and the central region tuning the concentration of that species and, thus, the current flowing through the nanopore. We consider a model of small dimensions with the pore radius comparable to the Debye-screening length ($R_{\mathrm{pore}}/\lambda_{\mathrm{D}}\approx 1$), which, together with large surface charges provides a mechanism for creating depletion zones and, thus, controlling ionic current through the device. We report scaling behavior of the device as a function the $R_{\mathrm{pore}}/\lambda_{\mathrm{D}}$ parameter. Qualitative agreement between PNP and LEMC results indicates that mean-field electrostatic effects determine device behavior to the first order.