Physics of Preparation of Josephson Barriers

Abstract

Josephson barriers of the tunneling type are usually prepared by oxidation in room environment, but they degrade after storage at room temperature for a few days. This paper describes a preparation technique based on an oxygen glow discharge which renders stable, reproducible superconductive tunneling devices (STDs). The barrier may also consist of organic molecules (KPR, monocarbonic acids); lead serves as the superconducting metal. Simplified models are used to discuss the main features and advantages of the glow-discharge technique. Extensive investigation has shown that arrays of STDs can be fabricated using the photoresist technique developed by Pritchard et al. The current-voltage and magnetic-field characteristics of these arrays are examined; it was found that they did not change during array storage at room temperature for more than 240 days and repeated temperature cycling from room temperature to 4.2°K.