Probing the dynamics and configurations of single molecule junctions via Seebeck coefficient spectroscopy

TL;DR

This study uses simultaneous conductance and Seebeck coefficient measurements to monitor real-time structural changes in single molecule junctions, revealing how configuration dynamics affect thermoelectric properties.

Contribution

It introduces a novel AC-based measurement technique combining G and S to probe the real-time evolution of molecular junction configurations.

Findings

Most junctions show configuration changes affecting S while G remains stable.

Simultaneous G and S measurements reveal dynamic reconfiguration of single molecule junctions.

Density functional theory links observed changes to contact geometry and charge transfer.

Abstract

Single molecule junctions exhibit dynamic structural configurations that strongly influence their electronic and thermoelectric properties. Here, we combine conductance (G) and Seebeck coefficient (S) measurements using the novel AC based scanning tunnelling microscope break junction technique to probe the real-time evolution of oligo(phenylene ethynylene) molecular junctions. We show that most junctions undergo configuration changes that lead to notable changes in S while G remains nearly constant. Density functional theory and quantum transport simulations link these observations to variations in contact geometry and charge transfer at the molecule electrode interface. Our results demonstrate that simultaneous G and S measurements enable direct access to the dynamic reconfiguration of single molecule junctions and offer design insights for thermoelectric molecular devices and new routes for increasing single molecule junction stability.