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[Author] Kouichi USAMI(3hit)

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  • Bi(Pb)-Sr-Ca-Cu-O Films Prepared by dc Sputtering with Mosaic Target

    Tadayuki KOBAYASHI  Masataka MORIYA  Kouichi USAMI  Toshinari GOTO  Xing Bao YING  Makoto HATANAKA  

     
    LETTER-Superconductivity Electronics

      Vol:
    E72-E No:10
      Page(s):
    1072-1074

    B(P)SCCO films were prepared on MgO substrate by a double cathode dc sputtering with a mosaic BiχSrCaCuyOz and (Bi0.7Pb0.3)χ SrCaCuyOz target. The films were deposited at 200 and 550, and then annealed. We have obtained the B(P)SCCO films with Tc of 90-100 K under the condition of the deposition at 550 and the in-situ annealing in 200 Torr O2 and the post-deposition annealing at 860.

  • Preparation and Properties of Y-Ba-Cu-O Thin Films by RF Magnetron Sputtering with a DC Biased Substrate Holder

    Satoshi ETO  Tadayuki KOBAYASHI  Kouichi USAMI  Toshinari GOTO  

     
    PAPER

      Vol:
    E74-C No:7
      Page(s):
    1949-1954

    In situ grown Y-Ba-Cu-O films were prepared on MgO substrate by rf magnetron sputtering with dc-biased substrate holder using a stoichiometric YBa2Cu3Oz target. The films were deposited at substrate temperature Ts about 660 and various substrate holder bias voltages VH. Influence of a dc bias voltage of substrate holder on the superconducting characteristics of Y-Ba-Cu-O thin films are investigated. Films with critical temperature higher than 80 K can be obtained at bias voltages from 20 V to 80 V for 500 mTorr. The optimum bias voltage to obtain the high Tc films depends on the sputtering gas pressure. The optimum bias voltages in 500 mTorr and 300 mTorr are 20 V and 150 V, respectively. The film morphology depends on the bias voltage rather than the sputtering gas pressure in this experiment and the smooth film surface is obtained at low voltages from 20 V to 40 V. For the films deposited at 80 V in 500 mTorr, the film of 200 nm thick is smoother than films of 400 nm and 700 nm thick. The deviation of the film composition is varied by the negative holder bias voltage. The critical temperature depends on the c-lattice parameter rather than the film composition. The films with short c-lattice parameter have the high Tc. The negative holder bias is effective for obtaining the high Tc films in the low pressure. However, in the high pressure, the films at the high bias voltages have slightly low Tc as compared with films at low bias voltage.

  • Fabrication of YBa2Cu3O7x-PrBa2Cu3O7y Hetero-Structure by Using a Hollow Cathode Discharge Sputtering System

    Akio KAWABATA  Tadayuki KOBAYASHI  Kouichi USAMI  Toshinari GOTO  

     
    PAPER

      Vol:
    E76-C No:8
      Page(s):
    1236-1240

    A sputtering system using dc hollow cathode discharge was developed for the propose of high Tc superconducting devices. Using this system, as-grown superconducting thin films of YBCO have been formed on MgO and SrTiO3 substrates. Influence of the sputtering conditions such as the substrate temperature and discharge gas pressure on the Tc and lattice parameter was investigated. It was found that superconducting films on MgO with Tczero higher than 87 K ere routinely obtained at the pressure of 820 mTorr (5%O2) and substrate temperature of 700 during deposition. The a/b-axis and c-axis oriented YBCO-PBCO hetero-structures were also successfully formed on MgO and SrTiO3 substrates.