Abstract
Growth on a quasi 1-dimensional substrate is of fundamental interest for what it can reveal about dendrite formation and morphological instabilities. It also provides a means to fabricate nano-gaps for molecular electronics and sensor applications. Here we present a novel experimental configuration consisting of a metal-insulator-metal sandwich structure, of which the sides are exposed to electrolyte. When an appropriate potential is applied to the top and bottom metal layers, electrodeposition can take place at their edges, which form quasi 1-dimensional electrodes separated by the thickness of the insulator layer (typically 50 nm). As electrodeposition proceeds, metal grows across the gap between the edges of the top and bottom electrodes, and this process may be studied by monitoring the current between them resulting from a known applied bias potential. If the gap between the two electrodes closes smoothly, this current increases exponentially due to tunnelling between them. If, on the other hand, the gap is closed by rough or dendritic growth, the conductance is observed to increase in larger steps corresponding to conductance quantization and smaller steps that we attribute to surface relaxation. Interestingly, we can control how the gap closes, either by employing an additive (benzotriazole for Cu electrodeposition) or by varying the bias applied between the electrodes: increasing the bias appears to favour rough growth due to electric field effects.