Influence of preparation conditions on superconducting properties of Bi-2223 thin films

We report electrical transport properties of Bi₂Sr₂Ca₂Cu₃O_10+x (Bi-2223) superconducting thin films fabricated by pulsed-laser deposition on SrTiO₃ substrate. The aim of the study was to investigate the influence of preparation conditions such as deposition temperature (T _S), annealing time (t _A) and deposition rate (r). A critical temperature (T _c) as high as 110 K and critical current density (J _c) of 6·2 × 10⁶ A/cm² at 20 K were obtained for T _S = 760°C, t _A = 4 h and r = 1·5 Å/s. We also investigated the effect of Li doping on Bi-2223 thin films. Li intercalation results in high resistive onset transition temperature and the resistivity shows broadening in magnetic field that increases with field. The large broadening of resistivity curve in magnetic field suggests that this phenomenon is directly related to the intrinsic superconducting properties of the copper oxide superconductors. The sudden drop in J _c at relatively low magnetic field (H < 0·5 tesla) is due to the effect of Josephson weak-links at the grain boundaries.