Electrical conductance of atomic contacts in liquid environments

TL;DR

This study investigates how different liquid environments influence the electrical conductance of gold atomic contacts, revealing environment effects mainly in the tunneling regime and highlighting solvent layering at small gaps.

Contribution

It provides the first systematic comparison of conductance in various solvents for mechanically controllable break junctions, emphasizing environment effects in low conductance regimes.

Findings

High conductance regime is environment-independent

Solvents lower tunneling barrier height systematically

Evidence of solvent molecule layering at small electrode separations

Abstract

We present measurements of the electrical conductance $G$ at room temperature of mechanically controllable break junctions (MCBJ) fabricated from Au in different solvents (octane, DCM, DMSO, and toluene) and compare with measurements in air and vacuum. In the high conductance regime $G \agt G_0=2e^2/h$, the environment plays a minor role, as proven by the measured conductance histograms, which do not depend on the environment. In contrast, the environment significantly affects the electrical properties in the low conductance (tunneling) regime {$G << G_0$}. Here, we observe a systematic and reproducible lowering of the tunneling barrier height $\phi$. At shorter distances, a transition to a strongly suppressed apparent barrier height is observed in octane, providing evidence for the layering of solvent molecules at small inter-electrodes separations. The presented experimental configuration offers interesting perspectives for the electrical characterization of single molecules in a controlled environment.