Pulling and Stretching a Molecular Wire to Tune its Conductance

TL;DR

This study uses a scanning tunnelling microscope to mechanically manipulate a molecular wire, revealing that conductance can increase unexpectedly due to stress release, which could enable new mechanically controlled electronic devices.

Contribution

It demonstrates how mechanical stress release affects conductance in molecular wires, combining experimental pulling with ab initio simulations to uncover new electronic control mechanisms.

Findings

Abrupt conductance increases linked to molecular sub-unit detachment

Stress release causes conductance enhancement contrary to exponential decay

Potential for mechanically gated single-molecule electronic devices

Abstract

A scanning tunnelling microscope is used to pull a polythiophene wire from a Au(111) surface while measuring the current traversing the junction. Abrupt current increases measured during the lifting procedure are associated to the detachment of molecular sub-units, in apparent contradiction with the expected exponential decrease of the conductance with wire length. \textit{Ab initio} simulations reproduce the experimental data and demonstrate that this unexpected behavior is due to release of mechanical stress in the wire, paving the way to mechanically gated single-molecule electronic devices.