Single-Molecule Electrochemical Transistor Utilizing a Nickel-Pyridyl Spinterface

Abstract

Using a scanning tunnelling microscope break-junction technique, we produce 4,4'-bipyridine (44BP) single-molecule junctions with Ni and Au contacts. Electrochemical control is used to prevent Ni oxidation, and to modulate the conductance of the devices via non-redox gating -the first time this has been shown using non-Au contacts. Remarkably the conductance and gain of the resulting Ni-44BP-Ni electrochemical transistors is significantly higher than analogous Au-based devices. Ab-initio calculations reveal that this behaviour arises because charge transport is mediated by spin-polarized Ni d -electrons, which hybridize strongly with molecular orbitals to form a 'spinterface'.Our results highlight the important role of the contact material for single-molecule devices, and show that it can be varied to provide control of charge and spin transport. KeywordsSingle-molecule, Break-junction, Electrochemical gating, Spintronics, Density functional theory, Metal-molecule interface Main TextSingle-molecule transistor behaviour can be achieved using a gate electrode to control the energy levels of a molecule bridging two metallic electrodes. 1 This gate can be provided electrochemically using the double layer potential existing at the metal-electrolyte interface (Fig. 1a). An electrochemical gate avoids the complex fabrication of solid-state threeterminal molecular devices, can operate in room temperature liquid environments, and can produce high gate efficiencies thanks to the large electric fields which are achievable. There has been significant interest in redox active molecules such as viologens as candidates for electrochemical transistors, 2-4 however the gating of non-redox molecules has only recently been demonstrated using Au electrodes by Li et al. 5 with 4,4'-bipyridine (44BP) molecules,

In situ formation of H-bonding imidazole chains in break-junction experiments

“…Additional details on the instrument used in this study and the data acquisition/analysis process can be found in our previous publications. 43,44…”

Anti-resonance features of destructive quantum interference in single-molecule thiophene junctions achieved by electrochemical gating

“…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 DQI 18,23 .…”

Reducing Gap Distance of Ag Electrodes by Oxygen Atomic Junction Formation

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