THE GROWTH OF CROSSOVER STRUCTURES OF LASER-ABLATED YBCO OR BSCCO THIN-FILMS WITH DIFFERENT INSULATING MATERIALS

Trilayers of YBCO or BSCCO (2212) on SrTiO3 substrates were fabricated by laser ablation with different insulating materials like SrTiO3, CeO2 and MgO as intermediate layers. The growth of trilayer systems was investigated by SEM, RBS, XPD and electrical measurements for both in situ and ex situ ablation processes. For trilayers YBCo-SrTiO3-YBCO we found, at optimal conditions for the SrTiO3, growth chi(min) of 5% for in situ and 9% for ex situ fabricated samples. The T(CO) of both YBCO layers was higher than 89 K. The trilayers based on BSCCO showed a chi(min) of 45% and a T(CO) almost-equal-to 35 K. For crossover structures all three layers were patterned by ion beam etching. To solve the problem of growth of a top YBCO layer on a patterned bottom bilayer of YBCO and SrTiO3, the etching angles of the bottom system were modified by special choice of the parameters of the ion beam etching process. So we found T(CO) values of more than 89 K and a critical current density of j(C) (77 K) > 10(5) A cm-2 for the top YSCO layer. The resistances of the SrTiO3 and CeO2 insulating films showed semiconducting behaviour and reached 10(7) OMEGA cm and 10(6) OMEGA cm, respectively. With the described technology the first YBCO thin film coils were fabricated.