STRUCTURAL AND SUPERCONDUCTING PROPERTIES OF HIGH-QUALITY YBCO FILMS WITH DIFFERENT ORIENTATIONS

High-quality YBCO thin films with different orientations have been grown by inverted Cylindrical Magnetron Sputtering (ICMS) deposition on LaAlO3 (100), SrTiO3 (100), SrTiO3 (110), and MgO (100) substrates. Best samples show transition temperatures T(c0) = 92 K and transition width AND T(c) = 0.5 K. Critical current density measurements have been performed yielding values as high as 5 . 10(6) A/cm2 at 77 K. Surface resistance of a typical sample is 500 muOMEGA at 4.5 GHz and 4.2 K. Films with highly preferred a-axis orientation and critical temperatures of about 70 K have been obtained on LaAlO3 (100) and SrTiO3 (100) substrates. The dependence of orientation on deposition temperature has been carefully studied on different substrates. A possible explanation of experimental data regarding film orientation in terms of surface energies and growth dynamics is examined.