MICROSTRUCTURAL EVOLUTION OF LASER DEPOSITED SUPERCONDUCTING Y-BA-CU-O FILMS - EFFECT OF DEPOSITION RATE

The microstructure of laser deposited, superconducting Y-Ba-Cu-O thin films grown on [001] SrTiO3 substrates has been characterized as a function of laser pulse rate. Over a range of deposition rates from 1-150 angstrom/s, the films consist mainly of the c-axis oriented epitaxial, YBa2Cu3O7-x phase with a high density of polytypoidic stacking defects. High transport critical current densities, J(c), are attributed to the retention of the primarily c-axis oriented microstructure along with the distribution of stacking defects that provide good flux pinning. At higher deposition rates we observe new growth directions, specifically the a,b-axis and the [103] growth directions are favored. We conclude that within the deposition rate range of 1-150 angstrom/s, there is no significant fundamental change in microstructure except for outgrowth formation. Therefore, we are optimistic that much higher rates can be attained in the near future, although controlling the outgrowth formation may be difficult.