Field-induced Conductance Switching by Charge-state Alternation in Organometallic Single-Molecule Junctions

TL;DR

This study demonstrates electric field-induced conductance switching in organometallic single-molecule junctions, with the Mo compound showing a significant, reversible high-to-low current transition driven by charge-state changes.

Contribution

It reveals a novel electric field-triggered charge-state switching mechanism in organometallic molecules within two-terminal junctions, especially highlighting the unique behavior of Mo centers.

Findings

Mo compound exhibits voltage-induced conductance switching with high current ratios.

Hysteresis and conductance switching are bias-dependent and molecule-specific.

DFT calculations identify a localized orbital responsible for the switching behavior.

Abstract

Charge transport through single molecules can be influenced by the charge and spin states of redox-active metal centres placed in the transport pathway. These molecular intrinsic properties are usually addressed by varying the molecules electrochemical and magnetic environment, a procedure that requires complex setups with multiple terminals. Here we show that oxidation and reduction of organometallic compounds containing either Fe, Ru or Mo centres can solely be triggered by the electric field applied to a two-terminal molecular junction. Whereas all compounds exhibit bias-dependent hysteresis, the Mo-containing compound additionally shows an abrupt voltage-induced conductance switching, yielding high to low current ratios exceeding 1000 at voltage stimuli of less than 1.0 V. DFT calculations identify a localized, redox active molecular orbital that is weakly coupled to the electrodes and closely aligned with the Fermi energy of the leads because of the spin-polarised ground state unique to the Mo centre. This situation opens an additional slow and incoherent hopping channel for transport, triggering a transient charging effect of the entire molecule and a strong hysteresis with unprecedented high low-to-high current ratios.