Electric Field Breakdown in Single Molecule Junctions

Abstract

Here we study the stability and rupture of molecular junctions under high voltage bias at the single molecule/single bond level using the scanning tunneling microscope-based break-junction technique. We synthesize carbon-, silicon-, and germanium-based molecular wires terminated by aurophilic linker groups and study how the molecular backbone and linker group affect the probability of voltage-induced junction rupture. First, we find that junctions formed with covalent S-Au bonds are robust under high voltage and their rupture does not demonstrate bias dependence within our bias range. In contrast, junctions formed through donor-acceptor bonds rupture more frequently, and their rupture probability demonstrates a strong bias dependence. Moreover, we find that the junction rupture probability increases significantly above ∼1 V in junctions formed from methylthiol-terminated disilanes and digermanes, indicating a voltage-induced rupture of individual Si-Si and Ge-Ge bonds. Finally, we compare the rupture probabilities of the thiol-terminated silane derivatives containing Si-Si, Si-C, and Si-O bonds and find that Si-C backbones have higher probabilities of sustaining the highest voltage. These results establish a new method for studying electric field breakdown phenomena at the single molecule level.

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“…The only requirement for the package under consideration is the availability of a feature to take electrostatic interactions with background charges into account. The popular quantum chemistry codes GAUSSIAN09, TURBOMOLE, CHARMM,and ChemShell all contain such features and can thus be linked directly to TITAN …”

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Charge Transport through Ferrocene 1,1′‐Diamine Single‐Molecule Junctions

“…If the conductance remained constant below 1 G 0 for a few picometer of electrode displacements at room and at l N 2 temperatures, we stopped the motor at such a position and observed the conductance value over time. If the conductance turned out to be stable over several minutes, IV measurements were performed by ramping the voltage from +0.5 to −0.5 V. This range is limited by electrical breakdown of the covalently bonded Au–FDA–Au molecular junctions, which leads to instabilities and irreversible changes of the molecular contact at higher electric fields. The conductance value G at zero bias is taken as reference for each IV curve.…”

Formulation of charge transport in molecular junctions with time‐dependent molecule‐leads coupling operators

“…Ideas for single molecule switches, pumps and rectifiers, are often based on interactions of the molecule with periodic or pulsed time‐dependent (semi‐classical) electromagnetic fields . However, external driving of these kinds may lead to mechanical instability or breakdown of the molecule‐leads contacts or of intra‐molecular bonds , as demonstrated recently . In order to understand these processes, the dynamics of the junction following a time‐dependent perturbation must be considered.…”