Effect of substrate topography for YBa ₂Cu ₃O _7-x coated conductors on the nucleation mechanism of buffer layer

The surface condition of substrate tape is an important factor to obtain epitaxial buffer layer on biaxially textured Ni tape for YBa ₂Cu ₃O _7-x coated conductors. We prepare ceria films on Ni single crystal, biaxially textured Ni tape and sulfured Ni substrates by direct current magnetron sputtering. The results show that the ceria films prepared on Ni single crystal and sulfured Ni substrates each have a poor-textured grain structure. However, the ceria film fabricated on rolling assisted biaxially textured substrate (RABiTS) exhibits a good c-axis texture and desirable surface morphology. Reflection high-energy electron diffraction analysis indicates that the c(2×2) superstructure on the RABiTS Ni surface has a dramatic effect on the heteroepitaxial growth of oxide buffer layer.