Electric transport measurements of thin film high-Tc superconductor bicrystal grain boundary Josephson junctions

Josephson junctions are an integral component of superconducting electronics because of their non-linear response and have not only been incorporated into a number of devices including superconducting quantum interference devices (SQUIDs) to create highly sensitive magnetometers and Josephson flux vortex transistors (JVFTs) to make fast-switching, high gain transistors but also into experiments to resolve the unexplained pairing mechanisms in high-Tc superconductors. As such, chapter 2 describes the results of an investigation into the pairing mechanism of the infinite layer superconductor Sr1-xLaxCuO2 using a single Josephson junction. The main result of this was that observations of zero bias conductance peaks (ZBCP) strongly suggest that SLCO superconductors are d-wave superconductors. This also contradicts many previous reports which concluded that SLCO superconductors are s-wave superconductors. Chapter 3 describes the results of measurements of YBa2Cu3O7-δ Josephson junction arrays. The results of this showed that the device had periodical behaviour at temperatures close to Tc with a periodicity of 1.8 mA or 12 μT. Moreover, it was found that this device could also operate as a Josephson vortex flow transistor (JVFT) which produced gains as high as 19.28 ± 0.03 at 77 K. In addition, switching behaviour was also found. Therefore, the record high current gains found at 77 K and above, as well as the switching behaviour make this device highly suitable for applications as a superconducting transistor