Current Flowing Mechanism Through Interlayers in YBa2Cu3Ox–SrTiO3Multilayer Structures on Textured Tapes

Abstract

We formed multilayer epitaxial structures YBa 2 Cu 3 Ox-SrTiO 3 by pulsed laser deposition on textured Ni-W tapes in order to overcome such fundamental problem as degradation of critical current density along with YBCO layer thickness. Critical current in a four-layer structure (4 * 250 nm, 1μm thick in total) of 22.0 A/mm indicates multiplying critical current with the number of YBCO layers. High critical current values in multilayer films demonstrate free current flowing through 10- to 50-nm-thick dielectric interlayers. Using transmission electron microscopy method, we investigated a multilayer film structure to understand and reason about such effect. It could be explained by grain misorientation to high angles in textured substrate; hence, interlayers are noncontinuous near grain boundaries. Discontinuities in interlayers serve as channels for necessary oxygen diffusion into the lower YBCO layers so that critical characteristics of each YBCO layer remain high and comparable with those of monolayer YBCO films.