Understanding the Conductance Dispersion of Single-Molecule Junctions

Abstract

Molecular junctions have emerged as a powerful tool to investigate chemistry and physics at the single-molecule limit. However, their utility as a platform to develop spectroscopies and construct molecular devices is limited by the broad conductance dispersion typically encountered in experiments. The current view is that such broad dispersion arises because the detailed junction configuration is uncontrollable and varies in and between experiments. Contrary to conventional wisdom, through atomistic simulations and experiments, we show that even in ideal conditions, where the electrodes and electrode-molecule binding configurations are perfectly well-defined, measurements will still exhibit a broad conductance histogram. Such dispersion arises because of conductance changes as the junction is mechanically manipulated and the unavoidable stochastic nature of junction rupture. The results offer detailed atomistic insights into the factors that contribute to the broad conductance histograms and identify the key physical aspects that need to be controlled to narrow its width.