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 nonredox 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 behavior 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.
- Electrochemical gating
- Density functional theory
- Metal-molecule interface
Brooke, R. J., Jin, C., Szumski, D. S., Nichols, R. J., Mao, B-W., Thygesen, K. S., & Schwarzacher, W. (2015). Single-Molecule Electrochemical Transistor Utilizing a Nickel-Pyridyl Spinterface. Nano letters, 15(1), 275-280. https://doi.org/10.1021/nl503518q