Controlled reduction of critical current densities in YBCO thin films

The reduction of critical currents in HTS films has proven to be of primary importance for the fabrication of devices sensitive to small applied magnetic fields (<100 Gauss). In this work, we report on a process we have developed for the controlled reduction of critical current densities (J/sub c/'s) on thin films of YBCO. By diffusing SiO in photolithographically defined microbridges of YBCO, we have been able to obtain a reduction of up to three orders of magnitude of the J/sub c/'s of our samples in a reproducible way, without significantly lowering their transition temperatures. The microbridges treated in this way show an increased sensitivity to externally applied magnetic fields. This indicates that our method for reducing the J/sub c/'s of HTS films is a good candidate for the fabrication of flux flow devices. Preliminary experimental results on flux flow devices are discussed.<>