Fabrication of the cube textured NiO buffer layer by line-focused infrared heating for coated conductor application

Abstract

Epitaxial growth of NiO on the bi-axially textured Ni–3at.%W (Ni–3W) substrate as seed layer for coated conductor were studied. The bi-axially textured NiO was formed on the Ni–3W tapes using a line-focused infrared heater by oxidizing the surface of the substrate at 800–950°C for 15–120s in oxygen atmosphere. The thickness of the NiO layer could be controlled by changing heat-treatment, which was estimated as approximately 200–500nm in the cross-sectional SEM micrographs of the NiO/Ni template. This thickness is enough to block the diffusion of the Ni in the substrate to the superconducting layer. The samples showed strong texture development of NiO layer. The sample oxidized at 900°C with the tape transferring speed of 30mm/h exhibited ω-scan full width at half maximum (FWHM) values for Ni–3W(200) and NiO(200) were 3.97°, and 3.67°, and φ-scan FWHM values for Ni–3W(111) and NiO(111) were 9.58°, and 8.79°, respectively. Also, the (111) pole-figure of the NiO buffer layer showed the good symmetry of the four peaks, securing the epitaxial growth of the buffer layers on the NiO layer. Also NiO layer exhibited root-mean-square roughness value of 39nm by AFM (10×10μm) investigation.