Crystal structure, microstructure, surface morphology, and transport properties of Er5Ba7Cu12Oy high-temperature-superconductor thin films

Abstract

Er5Ba7Cu12Oy is a thin-film high-temperature superconductor (critical transition temperature, Tc=93 K). The crystal structure, microstructure, surface morphology, and transport properties of Er5Ba7Cu12Oy thin films were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), and four-point dc-resistivity measurements under magnetic fields. Oriented Er5Ba7Cu12Oy thin films on cubic ZrO2(100), MgO(100), LaAlO3(100), and SrTiO3(100) substrates were prepared by molecular-beam deposition and post annealing in wet and dry O2 (BaF2 technique; annealing temperature =850–890 °C). The 0.4-μm Er5Ba7Cu12Oy thin films on cubic ZrO2(100) and MgO(100) substrates grew with mixed b and c orientations. The 0.4-μm Er5Ba7Cu12Oy thin films on LaAlO3(100) and SrTiO3(100) substrates annealed at 850 °C had c- and a-oriented grains, whereas the films annealed in the temperature range 870–890 °C displayed (001) epitaxy. By XRD, the lattice constants of Er5Ba7Cu12Oy were derived as a0=10.38 Å, b0=10.52 Å, c0=11.65 Å, and α=β=γ=90°. In the SEM studies, the 0.4-μm Er5Ba7Cu12Oy thin films were found to have a smooth-surface morphology. The shape of a-oriented grains in the Er5Ba7Cu12Oy thin films was found to be thick-rod-like. The transport data of superconducting resistive transitions under magnetic fields (0–5 T) were analyzed with the models of thermally activated giant flux creep. The activation energy for flux creep was determined to be U (K) =[3×104(1-T/Tc)1.8]/H0.7 (H⊥ ab plane), where H=magnetic field (T) and T=temperature (K).

Source-reported materials — not catalogue approval

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