EPITAXIAL BILAYER AND TRILAYER HETEROSTRUCTURES GROWN ON LAALO3 AND SRTIO3(001) SINGLE-CRYSTALS BY LASER-ABLATION

High-quality S/I and S/I/S epitaxial heterostructures (S = YBa2Cu3Ox, I = SrTiO3) have been grown in situ on LaAlO3 and SrTiO3(001) single c rystals, by the single-chamber pulsed laser deposition technique. YBa2 Cu3Ox and SrTiO3 layers were deposited sequentially, at a substrate te mperature T(h) = 760-degrees-C, and an oxygen pressure p(o2) = 300 mTo rr. Structural data showed that the SrTiO3 layer, grown either on a YB CO film or sandwiched by two YBaCuO films, was strained in the (001) p lane and exhibited an elongation of the lattice parameter in the [001] direction. This behaviour was consistent with the epitaxial growth of the S/I and S/I/S structures as revealed by the RHEED and ECP pattern s. Ion milling in conjunction with AES analysis showed that the thickn esses of the interfacial regions were less-than-or-equal-to 35 angstro m, and resulted from residual roughness of the substrates. The critica l temperature (T(c)) and resulted current density (j(c)) of the multil ayers at 77 K, as determined by an inductive AC method, were found to be T(c) = 89.5 and 90.5 K, and j(c) = 3 and 5 x 10(6) A cm-2, for tril ayers and bilayers, respectively.