Optimization and passivation of HTS step-edge Josephson junction rf SQUIDs

In this work, various methods of improving the performance and yield of our step-edge junction rf SQUIDs are described. These methods include adjusting the YBCO thin film thickness and trimming of the device parameters by ion beam etching and heat annealing. Significant improvement in SQUID performance and yield was demonstrated by employing these techniques. The effects of passivation of the rf SQUIDs by ex-situ deposition of an amorphous-YBCO thin film were also studied. No adverse effects were observed for the noise performance of the devices due to passivation and long-term stability was obtained.