  We have fabricated pairs of platinum electrodes with separation between 20
and 3.5 nm. Our technique combines electron beam lithography and chemical
electrodeposition. We show that the measurement of the conductance between the
two electrodes through the electrolyte provides an accurate and reproducible
way to control their separation. We have tested the robustness of the
electrodes by applying large voltages across them and by using them to measure
the transport properties of Au nano-clusters. Our results show that the
technique reliably produces metallic electrodes with a separation that bridges
the minimum scale accessible by electron beam lithography with the atomic
scale.
