Fabricate And Study Of High Temperature Planar Josephson Device

Superconducting mechanism and application of high-temperature superconducting (HTS) materials have been widely studied since its discovery. Because of Tc is higher than the temperature of liquid nitrogen temperature, HTS materials with enticing prospect, in the active devices field, study of Josephson device is one of the most active issue. The SQUID can be used as the earth's magnetic, heart magnetic, brain magnetic measurement, Nondestructive testing and digital circuits. To achieve superconductivity active devices, integrated circuits and external match, there should be excellent, reproducible superconducting guitar, and requires high-quality superconducting films.Chapter 1 is an overview of Josephson junctions and SQUIDs, as well its recent progress in high-Tc superconductivity including the references on recent developments of the superconducting device. This constitutes the theoretical basis of this dissertation.Chapter 2 discussed the fabrication and characterization of high–Tc superconductive thin films. The optimum conditions for YBCO thin film deposition by PLD(Pulsed Laser Deposition).The structures, microstructures and surface morphologies of the YBCO thin films was studied with XRD and AFM. High quality superconducting YBCO thin films were fabricated with Tc to 92.5 K, as long as the width of 0.5 K changes.Chapter 3 introduced the commonly used micro-fabrication means, and tried to use the method of micro-fabrication of nano-bridge Josephson junctions. Explored the way of nano-metal mask to high-temperature superconducting Josephson junction preparation. And optimize the process, overcome the the crack phenomenon appear in experiment. We irradiated the whole YBCO film before make junctions, and done a preliminary study on the impact of superconductivity by irradiation YBCO films. we present the investigation about the effect induced by implantation with 120 keV H2+ ions at various doses (1.0×10¹² -1.0×10¹⁷ ion/cm²) in YBCO thin films. The implanted films exhibit a gradual increase in their resistance as a function of dose. Increasing the implantation doses caused Tc to shift to lower temperature. and the normal state resistance became larger. At higher doses (≥8.0×10¹⁵ ions/cm²), the samples became semiconducting. The observations of XRD spectra of YBCO films after implantation with different fluences, with the increase of fluence, the intensity of peaks is decreased, but only (00/) peaks can be observed, which suggests that during implantation no new orientation formed. The other obvious effect introduced by ion bombardment inner strain caused by implantation and oxygen defects in chains and BaO planes should decrease the carrier concentration in planes, n, while the main effect of defects in CuO2 planes should be on carrier scattering, so the normal state resistance became larger. Finally, We found the right radiation dose to make junctions, and we succeed to make junctions by ion irradiation.