Epitaxial Cuprate Superconductor/Ferroelectric Heterostructures

Science  17 May 1991:
Vol. 252, Issue 5008, pp. 944-946
DOI: 10.1126/science.252.5008.944


Thin-film heterostructures of Bi4Ti3O12Bi2Sr2CuO6+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 YBa2Cu3O7–x and Bi2Sr2CaCu2O8+x, and single-crystal Bi2Sr2CuO6+xas the bottom electrodes. These films look promising for use as novel, lattice-matched, epitaxial ferroelectric film/electrode heterostructures in nonvolatile memory applications.