The electronic and transport properties of a molecular junction studied by an integrated piecewise thermal equilibrium approach

TL;DR

This paper introduces an integrated piecewise thermal equilibrium method based on first-principles calculations to analyze the electronic and transport properties of a gold-benzene-1,4-dithiol-gold molecular junction, matching experimental data.

Contribution

It develops a novel first-principles approach for bias-dependent electronic structure and transport calculations in molecular junctions.

Findings

Calculated currents match experimental magnitudes.

Electron transfer occurs between electrodes under bias.

Treating Au 5d electrons as core overestimates current.

Abstract

An integrated piecewise thermal equilibrium approach based on the first-principles calculation method has been developed to calculate bias dependent electronic structures and current- and differential conductance-voltage characteristics of the gold-benzene-1,4-dithiol-gold molecular junction. The calculated currents and differential conductance have the same order of magnitude as experimental ones. An electron transfer was found between the two electrodes when a bias is applied, which renders the two electrodes to have different local electronic structures. It was also found that when Au 5d electrons were treated as core electrons the calculated currents were overestimated, which can be understood as an underestimate of the Au-S covalent bonding and consequently the contact potential barrier and the replacement of delocalized Au 5d carriers by more itinerant delocalized Au 6sp carriers in the electrodes.