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Fabrication and Optical Response Characterization of High-Tc Superconductor Josephson Junction

Esmaeili, Mohaddeseh | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48075 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Fardmanesh, Mehdi
  7. Abstract:
  8. Design of superconducting material based wide band radiation detectors has recently been attractive. Interesting features of detectors, which are based on Josephson Junctions such as high sensitivity in a wide range of frequencies and low power consumption, potentially have many advantages over other semiconductor-based photo-detectors. According to variety of applications of high-Tc superconductors, particularly YBCO, and significant progress in manufacturing of thin films and Josephson junctions, this thesis mainly focuses on investigation of radiation effects on I-V characteristics of high-Tc step-edge Josephson junctions experimentally. The current-voltage characteristics of fabricated step-edge Josephson junction are investigated. The junctions were made of the YBCO superconductor deposited on crystalline LaAlO3 substrate having a step of about 180nm on the middle. The thin film deposition was carried out to the thickness of about 150nm using in-situ RF Magnetron Sputtering technique. The thin film was patterned using the standard photo-lithography to obtain the step-edge Josephson junctions. The current-voltage characteristics of 3 junctions with different widths at several temperatures under the critical temperature had the Josephson junction's behavior. Moreover the behavior of the junctions under the irradiation of a laser beam with 635nm wavelength was measured. The radiation caused a clear shift in the critical current value of the junctions which is dependent on the bias temperature and the junction width. According to the obtained results under the modulated irradiation with frequencies up to 2 KHz, it is interpreted that the thermal component of the response is the dominant factor in the response characteristics. In this report, first, the process of device preparation and the measurement system are presented. Then the measurement results are discussed
  9. Keywords:
  10. Photoresponse ; Josephson Junction ; High Temperature Superconductor ; Step-edge Junction

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