We have developed a fast, yet highly reproducible method to fabricate metallic electrodes with nanometer separation using electromigration (EM). We employ four-terminal instead of two-terminal devices in combination with an analog feedback to maintain the voltage U over the junction constant. After the initialization phase (U<0.2V),duringwhichthetemperatureTincreasesby80−150degsC,EMsetsinshrinkingthewirelocally.Thisquicklyleadstoatransitionfromthediffusivetoaquasi−ballisticregime(0.2V < U < 0.6V). At the end of this second regime, a gap forms (U > 0.6V). Remarkably, controlled electromigration is still possible in the quasi-ballistic regime.
@article{arxiv.cond-mat/0703649,
title = {Feedback controlled electromigration in four-terminal nano-junctions},
author = {Zheng-Ming Wu and Michael Steinacher and Roman Huber and Michel Calame and Sense Jan van der Molen and Christian Schonenberger},
journal= {arXiv preprint arXiv:cond-mat/0703649},
year = {2009}
}