Improvement of the microwave properties of Y-Ba-Cu-O films with artificialdefects

In this paper, the potential of defects for optimizing the microwave proper ties of YBa2Cu3O7 (YBCO) thin films is demonstrated. On one hand, microscop ic Y2O3 precipitates, which can he created in YBCO thin Films by modificati on of the deposition process, serve as ideal scattering centres for quasipa rticles and, thus, lead to a considerable reduction of the microwave surfac e resistance R,. The modification R,(T) can be explained in terms of the tw o-fluid model. Data for the quasiparticle scattering rate can be obtained f rom the measurements. On the other hand, the impart of artificial defects, so called antidots, upon the microwave properties is analyzed. R-s measurem ents demonstrate that the ion beam etching creates a similar to 20nm broad damaged area at the edge of the antidots. First measurements of the power h andling capability of YBCO thin film resonators indicate that the magnetic contribution to the nonlinear behavior can be reduced by antidots. The impl ementation of antidots, which have been proven to be an ideal and easy tool to improve active YBCO thin film devices, might be of use for microwave ap plications as well.