Epitaxial Cuprate Superconductor/Ferroelectric Heterostructures

Abstract

Thin-film heterostructures of Bi₄Ti₃O₁₂Bi₂Sr₂CuO_6+x, have been grown on single crystals of SrTiO₃, LaAlO₃, and MgAl₂O₄ by pulsed laser deposition. X-ray diffraction studies show the presence of c-axis orientation only; Rutherford backscattering experiments show the composition to be close to the nominal stoichiometry. The films are ferroelectric and exhibit a symmetric hysteresis loop. The remanent polarization was 1.0 microcoulomb per square centimeter, and the coercive field was 2.0 x 10⁵ volts per centimeter. Similar results were obtained with YBa₂Cu₃O_7–x and Bi₂Sr₂CaCu₂O_8+x, and single-crystal Bi₂Sr₂CuO_6+xas the bottom electrodes. These films look promising for use as novel, lattice-matched, epitaxial ferroelectric film/electrode heterostructures in nonvolatile memory applications.