Probing Metal-Molecule Contact at the Atomic Scale via Conductance Jump

TL;DR

This study investigates how different bipyridine isomers form metal-molecule contacts at the atomic scale, revealing the influence of molecular structure and breaking process on contact formation using conductance measurements and simulations.

Contribution

It demonstrates the role of molecular structure and breaking dynamics in metal-molecule contact formation, combining experimental conductance data with molecular dynamics and first-principles calculations.

Findings

Conductance jump observed for 4,4'-bipyridine but not for 2,2'-bipyridine.

Contact formation depends on molecular structure and breaking process.

Statistical and computational analysis elucidates contact formation mechanisms.

Abstract

Understanding the formation of metal-molecule contact at the microscopic level is the key towards controlling and manipulating atomic scale devices. Employing two isomers of bipyridine, $4, 4^\prime$ bipyridine and $2, 2^\prime$ bipyridine between gold electrodes, here, we investigate the formation of metal-molecule bond by studying charge transport through single molecular junctions using a mechanically controlled break junction technique at room temperature. While both molecules form molecular junctions during the breaking process, closing traces show the formation of molecular junctions unambiguously for $4, 4^\prime$ bipyridine via a conductance jump from the tunneling regime, referred as `jump to molecular contact', being absent for $2, 2^\prime$ bipyridine. Through statistical analysis of the data, along with, molecular dynamics and first-principles calculations, we establish that contact formation is strongly connected with the molecular structure of the electrodes as well as how the junction is broken during breaking process, providing important insights for using a single-molecule in an electronic device.