Yüksek Tc'ye sahip Josephson eklemleri için düşük gürültülü otomatik kriyojenik karakterizasyon sistemlerinin tasarımı ve uygulaması

ABSTRACTDESIGN AND IMPLEMENTATION OF AN AUTOMATEDLOW NOISE CRYOGENIC CHARACTERIZATIONSYSTEM FOR HIGH Tc JOSEPHSON JUNCTIONSAbdulvahit YilmazM.S. in Electrical and Electronics EngineeringSupervisor: Assist. Prof. Dr. Mehdi FardmaneshSeptember 2004Since the discovery of high temperature superconductors, superconductivitybecame one of the fast emerging technologies being used in numerousapplications where in many of these applications Josephson junctions form thebasis for superconducting electronic devices and circuits. In order to use theJosephson junctions effectively and fabricate them reproducibly with the sameproperties, their characterization should be done where their main characterizationis the current vs. voltage measurement. This study concentrates on the design andimplementation of two automated low noise cryogenic characterization systemsthat let current vs. voltage, dynamic resistance vs. current, and resistance vs.temperature characterizations be done at temperatures ranging from 63.15K to120K for the Josephson junctions. In this study, also the fabrication andpreparation steps of different types of high-T c Josephson junctions, such as stepedge and bicrystal junctions of junction arrays, gradiometers?, and dc-SQUIDs?for characterization, are explained. By using the established characterizationsystems, the current vs. voltage behaviors for different types of junctions could bemeasured and classified.Keywords: Superconductor, Josephson junction, I-V characterization, cryogenicsystem.iii