| Project/Area Number |
15560040
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied physics, general
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| Research Institution | Nagaoka University of Technology |
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Principal Investigator |
HAMASAKI Katsuyoshi Nagaoka University of Technology, Department of Electrical Engineering, Professor, 工学部, 教授 (40143820)
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| Co-Investigator(Kenkyū-buntansha) |
ISHIGURO Takashi Nagaoka University of Technology, Department of Electrical Engineering, Associate Professor, 工学部, 助教授 (10183162)
WANG Zhen NICT (National Institute of Information and Communication technology), G.M., 情報通信技術研究所(超伝導エレクトロニクス・グループ), グループリーダー (70359090)
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| Project Period (FY) |
2003 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2005: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2004: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2003: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Keywords | Bi-2212 single crystal / self-flux method / Self-planarizing process / Intrinsic Josephson characteristics / high-frequency mixer / 固有ジョセフソン接合 |
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| Research Abstract |
High-quality Bi_2Sr_2CaCu_2O_<8+δ>(Bi-2212) single crystals were grown by a self-flux method without mixing and grinding of reagent starting powders. During the crystal growth process, a pressure (<0.4 N/cm^2) was applied using a brick placed on the cap on an alumina crucible. We obtained high-quality single crystals with zero-resistance transition temperature, T_<c,zero>【approximately equal】89K, with this techniques. We also developed new fabrication process of stacked intrinsic Josephson junctions using Bi-2212 crystals. For the planarization of the stacks, the crystal around the junction window was modified to insulating layer by dipping into the solution of hydrochloric acid. For the concentration is lower than 0.1%, the planarization of the stack was fully achieved. For the concentration is higher than 0.5%, however, the planarization was spoiled. The number of intrinsic junctions in the stack linearly increased with increasing the concentration in the range from 0.05 to 0.2%. The
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thickness of the acid-treated layer can be evaluated by the number of the branches in I-V curve. This well controlabillity of the number of the junctions in the planarized stacks is useful for the electronics applications, such as high-frequency mixer. The current-voltage (I-V) characteristics of the stacks were uniform and observed distinct resistive branches with large hysteresis even at 77K, which can be explained by a series connection of highly capacitive Josephson junctions. At higher temperatures than 40K, we found that the return current Ir of the intrinsic junction depended strongly on the temperature, T. We analyzed the Ir-T characteristics using simple resistively and capacitively shunted junction (RCSJ) model in view of the temperature dependence of the c-axis resistance of the stack. The Ir-T characteristics were found to be well explained by the Zappe theory based on the RCSJ model. The present results may be useful information for a better understanding of the Bi-2212 intrinsic Josephson characteristics. Less
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