Self-assembly of gold nanoparticles on gallium droplets: controlling charge transport through microscopic devices

We describe the spontaneous assembly of ligand-stabilized gold nanoparticles on the surfaces of gallium droplets in suspension. By subsequent deposition of these coated droplets onto substrates with patterned electrodes, we form devices that have controlled architecture on the nanometer scale, which allows control of electron transport. In particular, we show that microscopic droplets can be brought into contact with one another with a monolayer of nanoparticles between them, resulting in a junction where electron transport is limited by the Coulomb blockade effect. We characterize the gallium surfaces by optical and electron microscopy and measurement of the interfacial tension. We measure the current-voltage characteristics of devices consisting of one or more Ga droplets and nanoparticle layers in series. The results agree well with the conventional theory of the Coulomb blockade and show how this approach could be used to form hierarchically structured electronic devices.