Nature 462, 1039–1043 (2009)

In a conventional field-effect transistor, a voltage is applied to a gate electrode to control the flow of charge from a source electrode to a drain electrode through a semiconducting channel. One goal in nanoelectronics is to make a field-effect-transistor-like device in which a single molecule acts as the channel. Single-molecule transistors have been made before, but the flow of charge in these devices has been controlled by non-molecular mechanisms — the Coulomb blockade and Kondo effects — rather than by changing the properties of the molecule. Now Takhee Lee and co-workers at Gwangju Institute of Science and Technology, Hanyang University and Yale University have demonstrated molecular-orbital gating in a single-molecule transistor.

Lee and colleagues patterned gold nanowires on an aluminium surface, coated them with the molecules and then broke the nanowires. Sometimes a single molecule bridged the gap between the two ends of the nanowire, which acted as the source and drain electrodes. By measuring the current through the device as a function of the voltage across it for different values of the gate voltage, Lee and colleagues were able to observe transistor characteristics in 35 of the 418 devices that they fabricated. Moreover, electron tunnelling spectroscopy confirmed that the electronic structure of the molecules was being changed by the electric field from the gate, and that the coupling between the gate voltage and the molecular orbitals was surprisingly strong.