Dc Magnetron Reactive Sputtering The Yyc Buffer Layer

Due to its higher critical current density and better in-field performance, YBa2Cu3O7-δ(YBCO) coated conductor becomes the most promising superconductor tape. The main problems in growth of YBCO film on NiW substrate are lattice mismatch and the diffusion of metal atoms and oxygen. Deposition of high-quality buffer layers is one of the key points of YBCO tape development. In this thesis, DC magnetron reactive sputtering was used to grow Y₂O₃/YSZ/CeO₂(YYC)buffer layers because of its simple process, easy control, and good repeatability.1. Y₂O₃ seed layer was deposited on the Rolling Assisted Biaxially Textured Substrate (RABiTS) Ni-5at%W alloy. The parameters such as substrate temperature, H2O pressure, total gas pressure, and reel speed were adjusted to optimize the growth condition. Under the optimum condition, Y₂O₃ films with single c-axis orientation were obtained. The full width at half maximum (FWHM) of in-plane and out-of-plane scan were 5.4°and 4.4°. The typical root mean square of surface roughness (RMS) was 4.3nm.2. YSZ (Yttrium Stabilized Zirconia) barrier layer and CeO₂ cap layer were deposited consecutively on Y₂O₃/NiW. YYC buffer stack was single c-axis orientation. The FWHM of in-plane and out-of-plane were 5.8°and 3.9°, respectively. RMS was 6.2nm. Electron backscatter diffraction (EBSD) observation showed that CeO₂ cap layer was dense and homogeneous. Small angle grain boundary was distributed in the range of less than 10 degrees.3. Double-sided uniformity of YYC buffer layer was characterized. Differences of in-plane FWHM and out-plane FWHM of double sides were all less than 0.3°. Difference of surface roughness RMS was less than 0.5nm. Uniformity was characterized along 50cm long tape as following: Layers of YYC,△φranged between 5°and 6°, out-plane FWHM ranged between 4°and 6°. As for Layer of CeO₂, differences of△φand△ωwere 0.5°and 1°, respectively. RMS ranged from 6 to 7nm.4. YBCO film was deposited on Y₂O₃/YSZ/CeO₂. Its△φand△ωwere 5.3°and 3.2°. The supreme Jc value of single-sided YBCO film deposited on YYC/NiW was 1.3MA/cm². The supreme Jc value of double-sided YBCO films deposited on YYC/NiW/YYC was 1.0 MA/cm² for each side.