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A Study on Josephson Junctions with Controlled Barrier Layrs Operating at 10 K for Integrated Circuit Application

Research Project

Project/Area Number 09305026
Research Category

Grant-in-Aid for Scientific Research (A)

Allocation TypeSingle-year Grants
Section一般
Research Field 電子デバイス・機器工学
Research InstitutionNagoya University

Principal Investigator

HAYAKAWA Hisao  Nagoya Univ., Grad.School of Eng., Professor, 工学研究科, 教授 (60189636)

Co-Investigator(Kenkyū-buntansha) AKAIKE Hiroyuki  Nagoya Univ., Center for Cooperative Research in Advance Science and Technology., 先端技術共同研究センター, 助手 (20273287)
INOUE Masumi  Nagoya Univ., Grad.School of Eng., Assist.Professor, 工学研究科, 講師 (00203258)
FUJIMAKI Akira  Nagoya Univ., Grad.School of Eng., Assoc.Professor, 工学研究科, 助教授 (20183931)
Project Period (FY) 1997 – 1998
Project Status Completed (Fiscal Year 1998)
Budget Amount *help
¥36,400,000 (Direct Cost: ¥36,400,000)
Fiscal Year 1998: ¥4,500,000 (Direct Cost: ¥4,500,000)
Fiscal Year 1997: ¥31,900,000 (Direct Cost: ¥31,900,000)
KeywordsSuperconductor / Josephson Junctions / 10 K Operation / Niobium-nitride / Plasma-nitrided Barriers / Overdamped Junctions / High IcRn Product / オーバーダンプ型接合 / 均一性 / 臨界電流密度 / 局在準位 / 高臨界電流密度
Research Abstract

The purpose of this work is to develop Josephson junctions as basic elements in single flux quantum superconducting integrated circuits operating at 10 K.The junctions are required to have overdamped characteristics and the high IcRn products at 10 K.Here, the Ic and Rn are a critical current and a junction resistance, respectively. In order to attain the purpose, we have proposed NbN Josephson junctions with plasma-nitrided NbNx barriers and investigated the electrical characteristics of the junctions. The results we have obtained are listed as follows.
1. We have obtained overdamped NbN junctions with the IcRn product as large as 0.6 mV at 10K.
2. The Ic uniformity was within the standard deviation, 1-sigma, of 2.9% for a series of 64 junctions in a chip and the run-to-run variation in the critical current density, Jc, was within 1-sigma of 14%. This means that the junctions can be applied to Josephson ICs.
3. The Jc was obtained in the range of a few tens A/cm^2 to a few ten kA/cm^2.
4. The conduction mechanism of the junctions was investigated. It was found that the plasma-nitrided NbNx barrier has localized states in it and that quasi-particles tunnel via localized states between both of the NbN electrodes. It was also found that the junctions behave as a Superconductor-Normal layer-Insulator-Normal layer-Superconductor (SNINS) junction.
5. The junction characteristics depend strongly on the crystallinity of the base NbN layers and the NbNx barrier formation conditions.
6. The control of the localized state density in the NbNx barriers is essential for controlling the junction characteristics.

Report

(3 results)
  • 1998 Annual Research Report   Final Research Report Summary
  • 1997 Annual Research Report
  • Research Products

    (6 results)

All Other

All Publications (6 results)

  • [Publications] H.Akaike: "Overdamped NbN junctions with NbNx barriers formed by plasma nitridation." Applied Superconductivity. 5. 319-325 (1998)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] H.Akaike: "Overdamped Niobium-nitride Junctions for 10K Operation" IEEE Trans.Appl.Supercond.印刷中.

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] H.Akaike, K.Yoshizawa, R.Oke, A.Fujimaki and H.Hayakawa.: "Overdamped NbN junctions with NbNx barriers formed by plasma nitridation" Applied Superconductivity. vol.5. 319-326 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] H.Akaike, R.Oke, T.Aoyama, A.Fujimaki and H.Hayakawa.: "Overdamped Niobium-nitride Junctions for 10 K Operation" IEEE Trans.Appl.Supercond.(in press). (1999)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] H.Akaike: "Overdamped Niobium-nitride Junctions for 10K Operation" IEEE Transactions on Applied Super conductivity. (印刷中). (1999)

    • Related Report
      1998 Annual Research Report
  • [Publications] H.Akaike: "Overdamped NbN junctions with NbNx barriers formed by plasma nitridation." Applied Superconductivity. (印刷中). (1998)

    • Related Report
      1997 Annual Research Report

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Published: 1997-04-01   Modified: 2016-04-21  

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