CONDITIONS FOR ORIENTED GROWTH OF Y-BA-CU-O AND BI-SR-CA-CU-O FILMS BY PULSED LASER ABLATION

Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O films have been grown in situ on amorphous SiO2 by excimer laser ablation in order to study the growth and orientation of the perovskite structures and to compare it with the epitaxial growth on single-crystalline SrTiO3. Under fixed experimental conditions optimum combinations of the oxygen partial pressure and substrate temperature for the deposition of c-axis oriented films were determined. The results on the morphology and orientation of the grains, which influence the superconducting properties, are discussed with respect to thermodynamic data available for the 123 phase and kinetic constraints. While superconducting transitions T(c) of 90 K and critical current densities of about 3 X 10(6) A/cm2 at 77 K are obtained on SrTiO3, the values are reduced to about 84 K and 10(4) A/cm2 on SiO2, respectively, due to the diffusion of Si into the film and the different microstructure.