Research objective and content
Passive microwave components, such as resonators and filters, are promising applications of high-Tc superconductors (HTS) because of their low surface resistance compared to normal metals. However, most HTS microwave devices show undesirable power dependencies, such as an increase in the insertion loss caused by non-linearity of the surface resistance at moderate power levels. Since this represents a limiting factor for many system applications, a detailed investigation of this effect is needed. In this project single- and double-sided YBa2Cu307-8 (YBCO) films will be grown on different substrates up to 0=50mm diameter and him thickness by the high-oxygen pressure planar sputtering technique. The films will be characterized concerning the uniformity of the structural and transport properties. The microwave properties of the films will be measured using dielectric resonators at frequencies of 8.5 GHz and 19 GHz. The microwave power dependence of the films will be studied at temperatures between 4 and 150 K and surface fields up to 50mT. Moreover, Rs(T, H) at 2GHz on large superconducting films (0=50mm) will be investigated by local perturbation and detection methods. A systematic data analysis and identification of correlations between the measured transport properties and field limitations of superconducting films will be performed.
Training content (objectives benefit and expected impact)
One of the aims of this proposal is to increase the acknowledgments of sputtering and advanced microwave testing techniques and to acquire a good understanding of the physical limitations of YBCO films.
Links with industry / industrial relevance (22)
This research represents an important step for the application of microwave devices in mobile and satellite communication systems, since the host institution has strong links to European industries. (Cryoelectra, BOSCH, GEC, Thomson CSF).