Nature Nanotech. http://doi.org/wdq (2014)

Continued device miniaturization means understanding the properties of molecular junctions is becoming ever more important. But thermoelectric effects are difficult to probe in these junctions, as thermal gradients cannot easily be created on such small scales, despite intense research efforts on charge transport. Youngsang Kim and colleagues have now built a device capable of generating large temperature gradients — with an electronic structure that can be actively tuned.

The quintessential set-up for probing effects related to charge is a three-terminal geometry, in which a gate electrode can regulate the current flowing between the source and drain electrodes. Guided by modelling, Kim et al. designed a three-terminal structure, based on a gold nanogap junction, in which sufficient thermal resistance between the source and the drain allows sizeable temperature gradients to form. Using an aluminium gate, the authors revealed the relationship between the electronic structure and the thermoelectric properties for two prototypical molecular junctions.