Structural Origins of Conductance Fluctuations in Gold-Thiolate Molecular Transport Junctions

TL;DR

This study uses atomistic simulations and conductance calculations to understand how structural variations in gold-molecule junctions influence conductance fluctuations, highlighting the impact of electrode deformation and mobility.

Contribution

It reveals the structural origins of conductance fluctuations in realistic gold-molecule junctions, emphasizing the role of electrode deformation and atom mobility in fluctuation behavior.

Findings

Fluctuations are 2-3 times larger in realistic junctions.

Conductance fluctuations mainly stem from gold geometry changes in deformed electrodes.

In non-deformed electrodes, molecule geometry dominates conductance fluctuations.

Abstract

We report detailed atomistic simulations combined with high-fidelity conductance calculations to probe the structural origins of conductance fluctuations in thermally evolving Au-benzene-1,4-dithiolate-Au junctions. We compare the behavior of structurally ideal junctions (electrodes with flat surfaces) to structurally realistic, experimentally representative junctions resulting from break junction simulations. The enhanced mobility of metal atoms in structurally realistic junctions results in significant changes to the magnitude and origin of the conductance fluctuations. Fluctuations are larger by a factor of 2-3 in realistic junctions compared to ideal junctions. Moreover, in junctions with highly deformed electrodes, the conductance fluctuations arise primarily from changes in the Au geometry, in contrast to results for junctions with non-deformed electrodes, where the conductance fluctuations are dominated by changes in the molecule geometry. These results provide important guidance to experimentalists developing strategies to control molecular conductance for device applications, and also to theoreticians invoking simplified structural models of junctions to predict their behavior.