Thin film preparation, transport properties and superconductivity of YBa₂Cu₃O₇

The authors report the preparation of high-T_c YBa₂Cu₃O₇ films on single crystalline SrTiO₃, LaGaO₃, NdAlCaO₄, MgO, ZrO₂, and Al₂O₃ substrates by sputtering and laser ablation. In all cases c-axis oriented films with T_c's near 90 K and narrow transitions were obtained. The films grow epitaxially on SrTiO₃ and LaGaO₃, highly oriented on MgO, ZrO₂ and NdAlCaO₄ and less oriented on Al₂O₃. On patterned films the authors obtained j_c(77K)=4.10⁶ A/cm² for films on SrTiO₃, 4.10⁴ A/cm² on NdAlCaO₄ and 4.10³ A/cm² on Al₂O₃ revealing the importance of epitaxial growth. In magnetic fields of 12 Tesla with B//c-axis they find j_c(12 T, 20 K)=2.10⁶ A/cm².