Superconducting YBa2Cu3O7−δ thin films with three different orientations

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Abstract
Epitaxial thin films of YBaCuO have been prepared with (1) the a axis perpendicular to (100) SrTiO3 ; (2) the c axis perpendicular to (100) SrTiO3 ; and (3) the [110] axis perpendicular to (110) SrTiO3. Films were fabricated using a multilayer deposition technique involving three electron guns containing Y, BaF2, and Cu under a pressure of 5×10−5 Torr of O2. As deposited films, which contained polycrystalline and amorphous regions, were later annealed in a furnace under a flowing O2‐H2 O atmosphere. X‐ray diffraction patterns as well as scanning electron microscopy and high‐resolution electron microscopy images confirm that the films are highly oriented, essentially epitaxial. The a‐axis oriented film exhibits zero resistance at 90 K and a critical current density of 2.9×106 A/cm2 at 4.2 K while the c‐axis oriented film exhibits a Tc of 88 K and a Jc of 0.9×107 A/cm2 at 4.2K; the Jc values were determined magnetically. The [110]‐orientation film shows the sharpest transition with a transition width of 1 K and zero resistance at 85 K.