Improved Fabrication Process for Monolithic Integrated High-$T_{\text{c}}$ dc Superconducting Quantum Interference Devices

概要

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We have developed a new fabrication process for monolithic integrated high-$T_{\text{c}}$ dc superconducting quantum interference devices (SQUIDs) that enables us to prevent a degradation of the junction $T_{\text{c}}$. In the new process, bicrystal junctions are fabricated simultaneously with a flux transformer by using the top superconducting layer. The junctions in YBa2Cu3O7-x-based SQUIDs fabricated by this process exhibited a $T_{\text{c}}$ of approximately 85 K, indicating no significant degradation. In contrast, conventional monolithic SQUIDs where junctions are fabricated by using the base superconducting layer showed a junction $T_{\text{c}}$ typically below 65 K. A fabricated monolithic dc SQUID magnetometer with a 500 μm square washer, a 23-turn 5-μm-wide input coil, and a pickup loop $6\times 7$ mm2 in outer dimension showed an effective area of 1.2 mm2 and an $I_{\text{c}}R_{\text{n}}$ of 180 μV at 77 K.
2007-07-25