Two sets of superconducting thin films were deposited on SrTiO3 by laser ablation, the first using a nanocrystalline target (n-films) and the second using a commercial microcrystalline target (μ-films). The effect of film thickness on the structure of the films was investigated by using detailed X-ray diffraction analysis. It was found that for both types of film growth was a three-phase process, where at the beginning some grains with their a-axis perpendicular to the substrate surface were formed. In the second phase a purely c-axis oriented film was formed and in the last phase some a-axis oriented grains were again observed. The last phase was observed only for the μ-films. Both types of film were found to have equal numbers of c-axis oriented grains oriented with their a-axis to the 0 and 90° directions. It was also found that the twin structure observed in both types of film develops much faster in the n-films, which might be the reason for the observed high critical current densities in n-films.

Crystalline Orientation and Twin Formation in YBCO Thin Films Laser Ablated from a Nanocrystalline Target. P.Paturi, M.Peurla, K.Nilsson, J.Raittila: Superconductor Science and Technology, 2004, 17, 564-70