High Resolution X-Ray Characterization of Tl-2212 Superconducting Thin Films

Abstract

AbstractThallium based high temperature superconducting films were formed on LaAlO3 (LAO) substrates by thalliation of sputtered amorphous precursor films by reaction with Tl2O. High resolution strain measurements and diffraction topographic imaging studies were performed using the synchrotron at Stanford Synchrotron Radiation Laboratory (SSRL). From these results, we have reached preliminary conclusions regarding the effect of film strain and substrate twinning on the superconducting properties of Tl-2212 films on LAO substrates. High- resolution strain measurements showed a correlation between film strain and microwave properties. The relative strain in samples in which Q>105 at 5.55 GHz (at 50 K) was approximately 30% lower than that in samples in which Q<104 when tested under the same conditions. Examination of samples where Q<104 at 5.55 GHz (at 50 K) by SEM also indicated microstructure defects that are typical in films with a high level of residual stress. White beam x-ray diffraction topographic analysis was used to quantitatively measure the degree of twinning in the substrate. The results will discuss the relationship between the measured Q values of the microwave cavity and the strain state, microstructure and defect morphology in the superconducting film/substrate couple.