Yttrium Barium Copper Oxide Thin Film for Microwave Communications

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This Small Business Innovation Research Phase I project outlines a program to determine the physical origins of the degradation in performance of thin-film high-temperature superconductor (HTS) rnicrowave devices with increasing power. The most promising application for thin-film HTS is high-frequency signal processing. Passive microwave devices such as resonators, filters, and delay lines fabricated from YBa2Cu3O7-x (YBCO) thin films and operated at 77K have shown dramatically improved performance over conventional materials. However, signal power levels transmitted through these devices are on the order of only 10 milliwatts. Most commercial applications, in particular cellular communications, require signal processing with power levels exceeding 10 watts. The performance of even the very highest quality thin-film superconductors degrades dramatically at only 5 watts of input power! High quality, epitaxial YBCO films will be grown by laser ablation with deliberately altered microstructural characteristics, such as improved epitaxy, chemical dopants and enhanced grain boundaries; then the resulting films will be characterized by patterning into microstrip resonators to evaluate their microwave performance at 77K. These results will allow the Phase II effort to focus on the most promising methods for scale-up and circuit fabrication.