Dramatic effects of chlorine doping on J sub(c) and microstructure of fluorine-free MOD Y123 thin films

Chlorine doped Y123 thin films have been successfully prepared by the fluorine-free metal organic decomposition (FF-MOD) method on SrTiO sub(3)(100) single crystal substrates. The rectangular Ba sub(2)Cu sub(3)O sub(4) Cl sub(2) (Ba2342) columns were epitaxially grown in the film without degrading crystallinity and transition temperature (T sub(c)) of Y123. Cl-doped Y123 films maintained high T sub(c) of 90.5-91.5 K and they showed higher critical current density (J sub(c)) than the Cl-free films particularly in magnetic fields. The high J sub(c) feature was observed in thick films up to ~0.93 mu m in thickness. In addition, Cl and Hf co-doped Y123 films maintained high crystallinity and showed further improved J sub(c) of 1.1 MA cm super(-2) at 40 K under 5 T. These suggested that Ba2342 precipitates have two effects on FF-MOD processed Y123 films. One is an increase in pinning force and the other is improvement of crystallinity of Y123 because of the good lattice matching between Y123 and Ba2342.