An investigation of the thermal cycling of Pb-alloy Josephson tunneling gates

Abstract

Thermal cycling stability between room temperature and 4.2°K of in-line Josephson tunneling gates employing Pb-alloy films was investigated. Pb films containing In and/or Au additions were used for the junction electrodes. Samples containing 19 gates typically had one failure after about 50 cycles, and some of those gates withstood as many as 200 cycles without any measurable change. It was found that the failure rates can be adequately described by a log-normal distribution above the 5% level. It is believed that the stability of the gates resulted from the mechanical strengthening of the Pb films by the alloying additions.