Atom-size gaps and contacts between electrodes fabricated with a self-terminated electrochemical method

We describe a method to fabricate atomic-scale gaps and contacts between two metal electrodes. The method uses a directional electrodeposition process and has a built-in self-termination mechanism. The final gap width and contact size are preset by an external resistor (R_ext) that is connected in series to one of the electrodes. If 1/R_ext is chosen to be much smaller than the conductance quantum (G₀=2e²/h), a small gap with conductance determined by electron tunneling is formed. If 1/R _ext is comparable or greater than G₀, a contact with conductance near a multiple of G₀ is fabricated.