Mechanically-Controlled Binary Conductance Switching of a Single-Molecule Junction

TL;DR

This study demonstrates reversible binary conductance switching in a single-molecule junction by mechanically altering the contact geometry, revealing a new mechanism for molecular-scale electronic switches based on contact configuration.

Contribution

It introduces a novel mechanically-controlled switching mechanism in single-molecule junctions, supported by first-principles calculations linking conductance states to contact geometries.

Findings

Reversible conductance switching achieved through junction elongation and compression.

Distinct conductance states correspond to different N-Au contact geometries.

Switching mechanism is based on the orientation of the N-Au bond relative to the pi-system.

Abstract

Molecular-scale components are expected to be central to nanoscale electronic devices. While molecular-scale switching has been reported in atomic quantum point contacts, single-molecule junctions provide the additional flexibility of tuning the on/off conductance states through molecular design. Thus far, switching in single-molecule junctions has been attributed to changes in the conformation or charge state of the molecule. Here, we demonstrate reversible binary switching in a single-molecule junction by mechanical control of the metal-molecule contact geometry. We show that 4,4'-bipyridine-gold single-molecule junctions can be reversibly switched between two conductance states through repeated junction elongation and compression. Using first-principles calculations, we attribute the different measured conductance states to distinct contact geometries at the flexible but stable N-Au bond: conductance is low when the N-Au bond is perpendicular to the conducting pi-system, and high otherwise. This switching mechanism, inherent to the pyridine-gold link, could form the basis of a new class of mechanically-activated single-molecule switches.