CeO2 as insulation layer in high T c superconducting multilayer and crossover structures

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Abstract
We present a study of the electrical properties of insulating CeO2 layers in combination with superconducting (Y/Dy) Ba2Cu3O7-delta (RBCO) films over ramps and in crossover structures. CeO2 is frequently used as a buffer layer, or template layer for biepitaxial grain boundary junctions, but can also be used as an insulating layer in ramp-type junctions and other multilayer structures. Epitaxial thin films of CeO2 were deposited by pulsed laser ablation using SrTiO3 substrates. We characterized the insulating performance of CeO2 thin films in terms of breakdown field Ebd and the relative dielectric constant epsilon r. For 80 nm thick CeO2 at 77 K we found Ebd=1 × 10-6 V/cm, using a 1 nA/100 µm2 breakdown criterion, which gives us a specific resistivity of rho => 10-9 Omega cm up to breakdown. From capacitance measurements on planar RBCO/CeO2/RBCO structures we obtained for the dielectric constant: epsilon r [approximately-equal-to] 15. The texture of CeO2 in combination with RBCO on ramped surfaces, simulated by SrTiO3 (STO) (103) substrates having their normal tilted by 18° away from the STO[001] direction, has been studied by x-ray diffraction

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