YBa₂Cu₃O_7−x films on off-axis Y-ZrO₂ substrates using Y-ZrO₂ or Y₂O₃ barrier layers

Abstract

YBa₂Cu₃O_7−x (YBCO) and barrier layer films were deposited on single-crystal (Y₂O₃)_0.09(ZrO₂)_0.91 substrates cut between 3.6 and 35.7°off-axis from the (001) planes. The barrier layers were (Y₂O₃)_0.065(Y-ZrO₂)_0.935(Y-ZrO₂), Y₂O₃, or multilayered structures of Y-ZrO₂ and Y₂O₃. X-ray diffraction showed that the Y-ZrO₂ and Y₂O₃ barrier layers generally grew epitaxially on the off-axis substrates, with the (001) barrier layer film planes being parallel to those of the substrate, and the (100) directions being parallel. YBCO films deposited on Y₂O₃ barrier layers also showed epitaxy with the YBCO (001) planes being nearly parallel to the substrate (001) planes, even for miscuts up to 35.7°. In contrast, the (001) planes of YBCO films deposited on Y-ZrO₂ barrier layers were almost parallel to the substrate surface, not the (001) substrate planes. However, YBCO films on Y-ZrO₂ films maintained particular in-plane epitaxial orientations with respect to the substrate. The YBCO full-width at half-maximum (FWHM) x-ray peaks were slightly narrower (0.8°) on Y₂O₃ barrier layers than on Y-ZrO₂ layers (1.3°). The electrical resistivity versus temperature behavior of the YBCO/Y₂O₃ films was consistent with increased grain boundary scattering as the degree of substrate miscut increased, whereas YBCO/Y-ZrO₂ films’ resistivities showed less sensitivity to substrate miscut, consistent with the loss of epitaxy.