Trimming, stability and passivation of YBCO step-edge junctions

We have applied the techniques of ion beam etching and heat annealing in air to trim the critical current, I-c, and the normal resistance, R-n, of YBCO step-edge Josephson junctions. This paper studies and compares the trimming effects by these two different techniques and looks at the long-term stability of the trimmed junctions. Slow drifts in I-c and R-n values have been observed in both trimmed and untrimmed junctions, the degree of which depends on the junction and film properties. The increased structure disorder and oxygen diffusion at step-edge grain boundaries are believed to be mainly responsible for the changes of junction properties due to trimming and during storage. Passivation of these stepedge junctions by depositing a thin layer of amorphous YBCO was found to improve their long-term stability. (C) 2003 Elsevier Science B.V. All rights reserved.