Abstract
Controlling the electrical conductance and in particular the occurrence of quantum interference in single-molecule junctions through gating effects has potential for the realization of high-performance functional molecular devices. In this work we used an electrochemically gated, mechanically controllable break junction technique to tune the electronic behaviour of thiophene-based molecular junctions that show destructive quantum interference features. By varying the voltage applied to the electrochemical gate at room temperature, we reached a conductance minimum that provides direct evidence of charge transport controlled by an anti-resonance arising from destructive quantum interference. Our molecular system enables conductance tuning close to two orders of magnitude within the non-faradaic potential region, which is significantly higher than that achieved with molecules not showing destructive quantum interference. Our experimental results, interpreted using quantum transport theory, demonstrate that electrochemical gating is a promising strategy for obtaining improved in situ control over the electrical performance of interference-based molecular devices.
Highlights
Electrostatic gating offers an integrative approach for the tuning of the relative positions of molecule orbitals at different temperatures[12,13], electrochemical gating provides a complementary and effective approach to manipulate charge transport in the electrochemically active or inert molecular junctions at room temperature[14,15,16,17]
Since the quantum interference in the charge transport through single-molecule junctions is energy dependent, the continuous tuning of the electrode potential offers an ideal strategy for realizing interference-based single-molecule electrochemical transistors (ECTs)[16,17,18,19,20,21,22], and the high gating efficiency and relatively large gate voltage windows provide opportunities for gating single-molecule junctions between resonances associated with molecular energy levels and anti-resonances associated with DQI18,23
We develop a mechanically controllable break junction technique (MCBJ) chip integrated with the electrochemical gate for the fabrication of single-molecule ECTs in ionic liquid, and investigate the charge transport through single-molecule thiophene junctions with destructive quantum interference (DQI) controlled by electrochemical gating
Summary
Electrostatic gating offers an integrative approach for the tuning of the relative positions of molecule orbitals at different temperatures[12,13], electrochemical gating provides a complementary and effective approach to manipulate charge transport in the electrochemically active or inert molecular junctions at room temperature[14,15,16,17].
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