Epitaxial combination of NdBa2Cu3O7-delta/SrTiO3: growth characteristics, structure, and parameters

We have studied the growth characteristics, structure, and parameters of th e epitaxial heterostructures (001) NdBa2Cu3O7-delta /(100)SrTiO3/(001)NdBa2 Cu3O7-delta grown by laser ablation on a (100) LaAlO3 substrate with a thin (similar to 2 nm) YBa2Cu3O7-delta intermediate layer. The use of an YBa2Cu 3O7-delta intermediate layer promotes layered growth of the (200 nm) NdBa2C u3O7-delta layer, whose free- surface roughness is 4 - 5 nm. The resistance of the NdBa2Cu3O7-delta layers began to fall off abruptly at T592 K, and a t T approximate to 87 K it vanished completely. The critical current densit y in the NdBa2Cu3O7-delta layers at T=76 K exceeded 10(6) cm(2) A/cm(2). Th e dielectric constant of the (400 nm) SrTiO3 layer sandwiched between the N dBa2Cu3O7-delta epitaxial layers grew by roughly threefold as the temperatu re was lowered in the interval 300-4.2 K. When a bias voltage of +/-2.5 V w as applied to the NdBa2Cu3O7-delta electrodes, the relative dielectric cons tant of the (400 nm) SrTiO3 intermediate layer fell from 1150 to 400 (T=32 K, f=100 kHz). The conductivity of the SrTiO3 intermediate layer in the dir ection perpendicular to the substrate plane increased with temperature and the electric field strength. (C) 1999 American Institute of Physics. [S1063 -7834(99)00703-0].