Large-area ferroelectricity of epitaxial Pb(Zr_0.53Ti_0.47)O₃/YBa₂Cu₃O_7-δ heterostructures

Very smooth epitaxial Pb(Zr_0.53Ti_0.47)O₃/YBa₂Cu₃O_7-δ heterostructures have been fabricated on (100) SrTiO₃ substrates by magnetron sputtering. The smooth YBCO (yttrium-barium-copper oxide) bottom layer is a-axis oriented, with low roughness of ~1.7 nm in a randomly selected 10 µm×10 µm area. Highly c-axis-oriented PZT (Pb(Zr, Ti)O₃) films were grown on the YBCO layer, with average roughness of ~1.6 nm. However, when the deposition temperature is increased, the grain size of the PZT films increases from ~0.1 µm to ~0.3 µm, and the roughness increases too. Large-area ferroelectricity was investigated for such heterostructures, and it is found that as the deposition temperature was increased, both the saturation polarization and the depolarization were enhanced, while the remanent polarization and coercive field were decreased. Further study on the depolarization induced by interfacial effects was carried out as well.