High Tc superconductor, ferroelectric thin films and microwave devices

Abstract

This work examined the fabrication and application of superconducting and ferroelectric thin films for miniaturized and tunable microwave devices.Doubled-sided superconducting YBCO thin films for microstrip microwave devices were fabricated using pulsed laser deposition. The YBCO thin films were used to fabricate miniaturized dual-spiral resonators and filter. The very compact dual-spiral resonators were found to have high Q-factor and versatile inter-resonator couplings which allow the implementation of cross-coupled filters. As an example, a compact four-stage cross-coupled dual-spiral filter with enhanced selectivity was designed and fabricated.Tunable superconducting resonators were fabricated using superconducting YBCO and ferroelectric Ba0.1Sr0.9TiO3 multilayer thin films. It was found that such multilayer structure had large microwave dissipation due to the high loss tangent of Ba0.1Sr0.9TiO3. To minimize loss from ferroelectric material, a method for the fabrication of selectively patterned ferroelectric thin was developed. Tunable resonators and filter fabricated using patterned Ba0.1Sr0.9TiO3 exhibited significantly reduced microwave dissipation.