Dielectric response of epitaxial (100)SrTiO3 films between electrodes of SrRuO3 or high-T-c superconducting YBa2Cu3O7-delta

Epitaxial heterostructures (001)YBa2Cu3O7-delta parallel to(100)SrTiO(3)par allel to (001)YBa2Cu3O7-delta, (100)YBa2Cu3O7-delta parallel to(100)SrTiO(3 )parallel to (100)SrRuO3 and (100)SrRuO3 parallel to(100)SrTiO(3)parallel t o (100)SrRuO3 were grown by laser ablation on polished substrates of (100) oriented (LaAlO3)(0.3) + (Sr2AlTaO6)(0.7). Replacing YBa2Cu3O7-delta electr odes by SrRuO3 ones was accompanied by a 60% decrease in width of the rocki ng curve for the (200)SrTiO3 X-ray reflection and pronounced, up to three t imes, increase of the permittivity of the ferroelectric layer at T < 100 K and a decrease in high frequency losses. The temperature dependence of the permittivity for the SrTiO3 layer in the (100)SrRuO3 parallel to(100)SrTiO( 3)parallel to (100)SrRuO3 heterostructure was well represented by a Curie-W eiss relation (T = 80-300 K, f = 1-100 kWz). The smallest loss factor, 0.00 2-0.02, in the temperature range 10-300 K was measured for the (100)SrRuO3 parallel to(100)SrTiO3 (100)SrRuO3 capacitance heterostructure (f = 1-100 k Hz). At T > 200 K, the conductance G of the SrTiO3 layer sandwiched between YBa2Cu3O7-delta electrodes followed well the dependence logG similar to (- phi(L)/kT), where phi(L) approximate to 0.08 eV. (C) 2000 Elsevier Science B.V. All rights reserved.