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Rare Earth Cuprate Analysis for High Tc Superconducting Devices

  • Author(s): McCoy, Stephen
  • Advisor(s): Cybart, Shane
  • et al.

This dissertation reports on experimental results on growth fabrication and electrical transport

analysis of thin film rare earth cuprate oxide (ReBCO's) superconductors with high transition temperatures. Motivation for these studies exist based on current advancements within the superconducting community with superconducting digital logic circuits. Our studies of novel films such as HoBCO exhibit high critical current densities of 3MA/cm2 and EuBCO with the highest reported transition temperature of 94K. These film properties rival the best YBCO thin films that are commercially available based upon electrical transport data and surface morphology characterization. We hope to develop improved superconducting devices based on these optimal properties. I show based on Josephson junction tunneling effect both the critical current values as well as energy gap properties within the varied ReBCO materials. Furthermore I investigate the effect of substrate matching with the new ReBCO series to show twinning boundary alignment. For film growth I show a novel method involving an oxygen plasma source used during in-situ oxide sputtering of ReBCOs which as yet has not been reported. With this technique I am able to decrease the time required at elevated grow temperatures which allows for less boundary migration between the substrate and the thin film. Also by controlling the oxygen plasma, elemental oxygen is more easily absorbed into the lattice during growth which allows us to quench our crystals to room temperature avoiding the need for a high pressure oxygen anneal.

Also mentioned is are experimental results of creating superconducting vias for multilayer device applications. Superconducting ramps that allow a-b plane electrical transport were developed to better enhance devices such as superconducting quantum interference device (SQUID) magnetometers. Through this experiment I combine previous oxygen plasma growth techniques to mitigate ground plane electrical transport degradation brought on by the elevated temperatures required for thin film cuprate growth.

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