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1995 Fiscal Year Final Research Report Summary

Research on High Tc superconducting three terminal devices utilizing the function of grain boundary

Research Project

Project/Area Number 06650349
Research Category

Grant-in-Aid for General Scientific Research (C)

Allocation TypeSingle-year Grants
Research Field Electronic materials/Electric materials
Research InstitutionTohoku University

Principal Investigator

NAKAJIMA Kensuke  Research Institute of Electrical Communication, Tohoku University Associate Professor, 電気通信研究所, 助教授 (70198084)

Co-Investigator(Kenkyū-buntansha) CHEN Jian  Research Institute of Electrical Communication, Tohoku University Research Assoc, 電気通信研究所, 助手 (90241588)
MYOREN Hiroaki  Research Institute of Electrical Communication, Tohoku University Research Assoc, 電気通信研究所, 助手 (20219827)
Project Period (FY) 1994 – 1995
KeywordsHigh Tc Superconductivity / Three terminal device / Josephson junction / Grain boundary
Research Abstract

Field effects of High-T_c Oxide Superconductors expected from their characterisctics of low carrier densities and short coherent lengths are hopefully applicable to superconducting three terminal devices. To achieve actual devices, however, a lot of difficulties, i. e fabrication of high quality ultra thin ETSC films with the thickness of several nm and development of insulating layr with a large dielectric constant still remains. From the another point of view, tilt grain boundaries not only behave as Josephson junctions but also have a large field sensitiviy because of local deficiency of charge carriers due to oxygen deficiency in the boundaries.
In this research, we have investigated the electric field effects on artificial grain boundaries of YBCO films and obtained following results.
・The carrier density of the grain boundary was evaluated to be 2-5*10^<20>cm^<-3> from the measurement of the electric field effect on a normal conducting artificial grain boundary adjoining two superc … More onducting YBCO grains. The carrier density was one drder lower than that in inner grains so that large electric field effects were expected. This is the first result indicating the usefulness of grain boudaries as field effect channels.
・As electric field effects with respect to AC and DC Josephson effects on the grain boundaries behaving as Josephson junctions, electric field modulations of both critical current, I_c and self resonance frequency were observed. For former effect, it was shown that the field effect in I_c was qualititavely explained by a charge carrier modulation in grain boundary junctions on the basis of the SNS model. For later one, the variations of the resonance frequencies were attributed to changes in the effective dielectric constants, epsilon^GB_/d reflecting the field strength dependence ofthe dielectric constant of STO used as substrates. The electric field modulation of epsilon^GB_/d is possibly applicable to the phase velocity control of electromagnetic waves transmitting in the grain boundaries in the case of Flux Flow Oscilator (FFO). Less

  • Research Products

    (6 results)

All Other

All Publications (6 results)

  • [Publications] S.J.Kim,H.Myoren,J.Chen,K.Nakajima,T.Yamashita: "Succesful fabrication of bicrystal Si Substrates for YBa_2Cu_3O_1-y Josephson junctions" Cryogenics. 35. 901-903 (1995)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] K.Nakajima,K.Yokota et al: "Field Effects on Dielectric Property of YBCO Bicrystal Groin Boundary Junctions" IEEE Trans Appl.Supercond.5. 2861-2864 (1995)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] G.Oya,C.C.Diao,K.Nakajima et al: "Atomic oxygen effect on the in situ grouth of Stoichio-metric YBCO epitaxial films by facing target sputter." J.Appl.Phys.77. 5809-5818 (1995)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] S.J.Kim, H.Myoren, J.Chen, K.Nakajima and T.Yamashita: "Successful fabrication of bicrystal Si substrates for YBa2Cu307-y Josephson junctions" Cryogenics. 35. 901-903 (1995)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] K.Nakajima, Y.Yokota, H.Myoren, J.Chen and T.Yamashita: "Field Effects on the Dielectric Property of YBCO Bicrystal Grain Boundary Junctions" IEEE Trans. Appl. Supercond.5. 2861-2864 (1995)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] G.Oya, C.C.Diao, S.Imai, T.Uzawa, Y.Sawada, T.Sugai, K.Nakajima and T.Yamashita: "Atomic oxygen effect on the in situ growth of stoichioemetric YBa2Cu307-d epitaxial films by facing targets 90゚ off-axis radiofrequency magnetron sputtering" Journal of Applied Physics. 77. 5809-5818 (1995)

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1997-03-04  

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