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Tham khảo tài liệu 'handbook of high temperature superconductor electronics part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 3 High-Temperature Superconducting Multilayer Ramp-Edge Junctions Q. X. Jia Los Alamos National Laboratory Los Alamos New Mexico U.S.A. 3.1 INTRODUCTION There has recently been tremendous progress in the development of high-temperature superconducting Josephson junctions and superconducting quantum interference devices SQUIDs fabricated from YBa2Cu3O7 YBCO thin films. Josephson junctions have potential applications to high-speed low-power digital logic whereas SQUIDs are the most sensitive sensors to the magnetic field. A Josephson junction is composed of two superconductors separated by a barrier. Cooper pairs can tunnel or diffuse through the barrier and current flows through it with no voltage appearing across the junction 1 2 . Josephson junctions and their related devices have been fabricated using conventional low-temperature superconductors where the main building block of the device is based on a configuration of superconductor insulator superconduc-tor SIS . In contrast to low-temperature superconducting junctions many junction structures have been investigated for high-temperature superconductors in order to fabricate reproducible and controllable junctions. Since the first report on the fabrication of a natural grain-boundary Josephson junction using YBCO 3 there have been many efforts in the fabrication of Josephson junctions and Copyright 2003 by Marcel Dekker Inc. All Rights Reserved. Figure 3.1 Cross-sectional diagram of a ramp-edge superconductor normal-metal superconductor SNS junction. The active area of the device is located on the ramp where the normal metal is sandwiched between the top and bottom superconductor electrodes. SQUIDs based on different device constructions. Bicrystal grain boundary 4 biepitaxial grain boundary 5 step-edge grain boundary 6 step-edge supercon-ductor normal-metal superconductor SNS 7 ramp-edge SNS 8 locally damaged superconducting line by ion beams 9 and interface-engineered junctions 10 are the most commonly .
