Numerical simulations of electron tunneling currents in water

TL;DR

This study uses advanced numerical simulations to analyze electron tunneling currents in water, incorporating a tip-substrate setup, external bias, and image potential effects, to better understand water's influence on tunneling phenomena.

Contribution

It introduces a comprehensive simulation approach including all-to-all transmission calculations and water effects, extending previous models to more realistic STM-like conditions.

Findings

Computed currents match experimental STM water measurements

Water configuration influences tunneling flux distribution

Water can cause significant resolution loss in certain energy regimes

Abstract

This paper presents results of numerical simulations of electron tunneling through water that extend our previous calculations on such systems in several ways. First, a tip-substrate configuration is used; second, calculations are carried in the presence of an external potential bias; third, the image potential that reflects the interaction of the electron with the mobile metal electrons is taken into account in the static image approximation. Finally, all-to-all transmission probability calculations are performed in order to get an order-of-magnitude estimate of the current-voltage characteristics of this junction model. The computed currents are within the range of the few available experimental observations on scanning tunneling microscope (STM) currents in water, indicating that our calculation may have taken into account all the important physical attributes of such systems. In addition we examine the effect of the water medium on the spatial distribution of the tunneling flux. We find that while different water configurations scatter the tunneling electron in different ways, on the average the water affected loss of resolution is rather small in the deep tunneling regime but can be substantial in energy regimes where the tunneling is strongly affected by water-supported resonance structures.