| Josephson junctions are the fundamental building blocks for a variety of superconducting electronics applications, including high-speed, low-power digital logic, and sensitive magnetic field and high frequency electromagnetic detectors. Although there have been extensive efforts to develop a fabrication method for high temperature superconductor (HTSC) junctions, the reliable methods for creating HTSC Josephson junctions are still not fully developed to compare to low temperature superconductor Josephson junctions. The fabrication of HTSC Josephson junctions faces by many different aspects of difficulty such as chemical stability of HTSC materials, nano scale device engineering, chemistry compatibility of HTSC with insulator or normal metals, and interface properties such as contact resistance, and lattice mismatch. Most problematic here is the rapid atmosphere degradation of HTSC materials which occurs upon exposure to the ambient.; In this dissertation, a surface cleaning method, an annealing method, and thin film optimization methods were developed to fabricate the HTSC nano devices. In order to create functional HTSC nano devices, the parameters for three HTSC cuprate materials YBa2Cu3O7, NdBa 2Cu3O7 and Y0.6Ca0.4Ba 1.6La0.4Cu3O7 thin film deposition method were optimized successfully. Further, a surface cleaning method was developed for the thin films of HTSC surface based on self-assembled-mono layers (SAM) to control the surface chemistry of HTSC thin film devices. Also, an annealing method was developed to improve the electric contact of HTSC and normal metals in the HTSC superconductor/normal metal/superconductor (SNS) junction devices. The optimized Pulsed Laser Deposition (PLD) parameters, the surface cleaning method, the micro and nano lithography method, and the annealing methods were used to fabricate the HTSC SNS nano devices. The fact the all the evidences are in good agreement strongly proved the developed fabrication methods are reliable and reproducible methods. In addition, the exponential patterns of the critical current dependence on noble metal thickness were reported for the first time that exhibited the reproducibility and reliability of the HTSC SNS nano device fabrication methods. |
