Quantized tunneling current in the metallic nanogaps formed by electrodeposition and etching

We have studied electron tunneling across the gap between two electrodes as the gap is varied by electrodeposition and etching. The tunneling current tends to change in a stepwise fashion, corresponding to a discrete change of the gap width. The stepwise change is due to the discrete nature of atoms and a series of structural relaxations of the atoms at the electrodes between stable configurations upon deposition and etching. By stabilizing the tunneling current on various steps using a feedback loop, we have demonstrated that stable molecular-scale gaps can be fabricated with subangstrom precision.