Self-breaking in planar few-atom Au constrictions for nm-spaced electrodes

We present results on electromigrated Au nanojunctions broken near the conductance quantum $77.5 \mu$S. At room temperature we find that wires, initially narrowed by an actively-controlled electromigration technique down to a few conductance quanta, continue to narrow after removing the applied voltage. Separate electrodes form as mobile gold atoms continuously reconfigure the constriction. We find, from results obtained on over 300 samples, no evidence for gold cluster formation in junctions broken without an applied voltage, implying that gold clusters may be avoided by using this self-breaking technique.