YBa2Cu3O7-delta/SrTiO3 epitaxial heterostructures on sapphire substrates

Double layers of YBa2Cu3O7-delta/SrTiO3 with thicknesses (250/300 nm) were grown by laser ablation on SrBi2Nb2O9/CeO2 buffer layers on sapphire substrates. Dielectric parameters of SrTiO3 (permittivity epsilon and tan delta) were determined in the temperature range 15-300 K. Strong dependence of epsilon on bias voltage was measured at 77 K. Dielectric losses slightly decreased with temperature decrease and tan delta was 10(-2) at 77 K (f = 100 kHz).