Control of nanogap separation by surface-catalyzed chemical deposition

The nanogap devices, which comprise multiple electrodes separated by a few to a few tens of nanometers, have opened up new possibilities in biomolecular sensing as well as various frontier electronics. One of the key aspects of the nanogap device research is how to control the gap distance following each specific needs of the gap structure. Here, we report the extensive study on the fine control of the gap distance between electrodes within the range of 1-80 nm via surface-catalyzed chemical deposition. The initial gap electrodes were prepared via conventional e-beam lithography, and the gap distance was narrowed to a designed value through the surface-catalyzed reduction of gold ion on the predefined electrode surfaces, by simple dipping of the electrodes into the aqueous solution of gold chloride and hydroxylamine. The final gap distance was controlled by adjusting the repetition number, reductant concentration, reaction time, and reaction temperature. The dependence of the gap-narrowing reaction on these parameters was systematically examined based on the results of field emission scanning electron microscopy and atomic-force microscopy.