Memristive Switches in Rigid Conjugated Single-Molecule Junctions

TL;DR

This study investigates the microscopic origins of memristive switching in rigid conjugated molecular junctions using cryogenic break junctions, revealing contact rearrangements and stacking as key factors.

Contribution

It introduces a quantitative analysis workflow for classifying and analyzing memristive IV characteristics in molecular junctions, highlighting the role of contact and connectivity.

Findings

All molecules exhibit memristive behavior with stability dependent on anchoring.

Reproducibility varies with anchoring type, with thiolate showing more consistent hysteresis.

Contact rearrangements and stacking are identified as extrinsic, mechanically mediated switching mechanisms.

Abstract

Voltage-driven memristive switching has been reported in molecular junctions, yet its microscopic origin often remains elusive. Here, we study three rigid OPE-like derivatives that lack an obvious internal switching pathway using mechanically controlled break junctions (MCBJs) and observe non-volatile, bistable hysteretic IV characteristics at cryogenic temperature. We introduce a quantitative analysis workflow that classifies memristive IVs, clusters the two conductance states, and extracts switching features and stability metrics from repeated measurements at fixed displacement. While all molecules exhibit memristive behavior, stability and hysteresis reproducibility depend strongly on anchoring and connectivity: the linear biphenyl backbone with thiolate (SAc) anchoring shows the most reproducible, predominantly field-driven hysteresis, whereas the meta-phenyl variant with thioether (SMe) anchoring is dominated by stochastic, current-driven events. The resulting conductance statistics point to an extrinsic, mechanically mediated origin involving contact rearrangements, multi-molecule transport, blinking (open-closed) contacts, injection-point shifts, and $\pi$-$\pi$-stacking dimerization.