Atomistic Simulations of Highly Conductive Molecular Transport Junctions Under Realistic Conditions

TL;DR

This study uses atomistic simulations to explore how monatomic gold chains form in molecular junctions and cause conductance increases, explaining recent experimental anomalies and aiding molecular electronics development.

Contribution

It demonstrates the link between monatomic gold chain formation and conductance enhancement in molecular junctions through detailed simulations.

Findings

Large conductance increases linked to monatomic gold chains

Enhanced s-like electronic states in gold chains cause conductance rise

Monatomic chains are more stable and detectable than other transient structures

Abstract

We report state-of-the-art atomistic simulations combined with high-fidelity conductance calculations to probe structure-conductance relationships in Au-benzenedithiolate(BDT)-Au junctions under elongation. Our results demonstrate that large increases in conductance are associated with the formation of monatomic chains (MACs) of Au atoms directly connected to BDT. An analysis of the electronic structure of the simulated junctions reveals that enhancement in the s-like states in Au MACs causes the increases in conductance. Other structures also result in increased conductance but are too short-lived to be detected in experiment, while MACs remain stable for long simulation times. Examinations of thermally evolved junctions with and without MACs show negligible overlap between conductance histograms, indicating that the increase in conductance is related to this unique structural change and not thermal fluctuation. These results, which provide an excellent explanation for a recently observed anomalous experimental result [Bruot et al., Nature Nanotech., 2012, 7, 35-40], should aid in the development of mechanically responsive molecular electronic devices.