High critical currents and flux creep effects in superconducting YBa2Cu3O7 − gd films e-gun deposited using a BaF2 source

Abstract

Resistance measurements are reported, carried out on highly textured thin films of YBa2Cu3O7 − gd prepared by co-evaporation of BaF2, copper and yttrium on (100) SrTiO3 in a triple e-gun UHV system, adding oxygen during deposition. The polycrystalline films, with average grain size of the order of 10 μm, show a strong preferential orientation, with the c axis perpendicular to the substrate. The resistance measurements in a field parallel to the c axis have been interpreted in terms of a model combining thermally activated flux flow and flux pinning by twin boundaries. The agreement is satisfactory. The field and temperature dependence of the activation energy differs essentially from expressions proposed recently.