Diagnostics with series-connected Josephson tunnel junctions

Abstract

The prospect of incorporating Josephson tunnel junctions into future device technologies requires that fabrication procedures be developed which assure high junction yield, uniform quality, and reproducibility. Critical‐current distributions which are extracted from the I‐V characteristics of series‐connected lead and lead‐alloy junction arrays provide a quantitative measure of the yield, as revealed by a direct count of the 2Δ increments, and the quality or uniformity, as revealed by the width of the distribution. Examples of the effects of oxidation parameters, junction area, electrode thickness, magnetic fields, and thermal cycling on the critical‐current distributions demonstrate the ease in which significant statistical information on simultaneously prepared junctions is obtained. As a further illustration of the use of this diagnostic method, we present results on flux‐trapping experiments together with a preliminary survey of the effectiveness of a simple technique in which lead alloys are evaporated from a single source to completion and then oxidized in an acidic‐oxygen environment.