Permittivity of BaTiO3 epitaxial films grown on the YBa2Cu3O7-delta(001) surface

The epitaxial heterostructures YBa2Cu3O7 - delta/BaTiO3/YBa2Cu3O7-delta and YBa2Cu3O7-delta/(5 nm)SrTiO3/BaTiO3/(5 nm)SrTiO3/YBa2Cu3O7-delta are grown by the laser evaporation method on an LaAlO3(100) substrate. The permittiv ity of a BaTiO3 layer is approximately doubled (T = 300 K) when a SrTiO3 th in layer is inserted between a ferroelectric layer and superconducting cupr ate electrodes. A maximum in the temperature dependence of the permittivity for a barium titanate layer in the YBa2Cu3O7-delta/(5 nm)SrTiO3/BaTiO3/(5 nm)SrTiO3/YBa2Cu3O7-delta heterostructure is shifted by 70-80 K toward the low-temperature range with respect to its location in the corresponding dep endence for the BaTiO3 bulk single crystal. The bias voltage dependence of the permittivity for the BaTiO3 grown layers exhibits a clearly pronounced hysteresis (T = 300 K). The superconducting transition temperature for the lower YBa2Cu3O7-delta electrode in a superconductor/ferroelectric/supercond uctor heterostructure considerably depends on the rate of its cooling after the completion of the formation process. (C) 2001 MAIK "Nauka/Interperiodi ca".