Formation and Evolution of Single Molecule Junctions

TL;DR

This study investigates how single molecule junctions form and evolve under stress, revealing that molecular length influences elongation and formation probability, with atomic-scale changes explaining conductance behavior.

Contribution

It provides new insights into the atomic-scale mechanisms and statistical properties of single molecule junction formation and evolution, supported by experimental and theoretical analysis.

Findings

Longer molecules have higher elongation and formation probability.

Atomic-scale structural changes explain conductance plateau lengths.

Multiple processes beyond bond breakage influence junction evolution.

Abstract

We analyze the formation and evolution statistics of single molecule junctions bonded to gold electrodes using amine, methyl sulfide and dimethyl phosphine link groups by measuring conductance as a function of junction elongation. For each link, maximum elongation and formation probability increase with molecular length, strongly suggesting that processes other than just metal-molecule bond breakage play a key role in junction evolution under stress. Density functional theory calculations of adiabatic trajectories show sequences of atomic-scale changes in junction structure, including shifts in attachment point, that account for the long conductance plateau lengths observed.