The critical current, I_c, of both YBCO Josephson junctions andmicrobridges is observed to decrease by more than 50% after annealing treatments at temperatures as low as 150 °C in air. This has both positive and negative implications for devices; while it is possible to trim the lead to increased 1/f noise. Observed large changes in film I_c at temperatures normally too low to affect the physico-chemical properties of the bulk YBCO, may be associated with surface chemical effects such as accelerated atmospheric degradation and oxygen migration. This paper studies the effect of annealing on junctions and microbridges in air and suggests a new chemical model which explains this process. Implications for SQUID low frequency noise are considered.
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