Numerical study of surface chemical reactions in 2D-FET based pH sensors

Abstract

This work numerically evaluates the impact of surface chemical reactions on the performance of 2D-FET based pH sensors. More precisely, we focus on the adsorption of chlorine ions and the expulsion of protons at the sensing interface of FET sensors. This analysis is performed through numerical simulations encompassing the modelling of both the semiconductor device and the liquid solution to be analysed. In the semiconductor region the 2D Poisson - 1D Continuity equations are self-consistently solved, while in the electrolyte region we deal with the modified Poisson - Boltzmann system [1]. The simulator also includes the interactions taking place at the electrolyte-sensing layer interface through: i) the non-constant profile of water permittivity, and ii) the steric effects in the surface ions concentration by means of the Potentials of Mean Force (PMFs) [2], [3]. This comprehensive description of the electrolyte-device interface provides a suitable framework to unveil the relevance of multiple chemical reactions, such as the adsorption of chlorine ions, on the behaviour of 2D-FET based pH sensors.