1992 Fiscal Year Final Research Report Summary
Realization of Josephson junctions with electrically controlled critical current and its application to dc-SQUIDs.
Project/Area Number |
03650261
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Research Category |
Grant-in-Aid for General Scientific Research (C)
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Allocation Type | Single-year Grants |
Research Field |
電子材料工学
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Research Institution | Nippon Institute of Technology |
Principal Investigator |
SUZUKI Toshimasa Nippon Institute of Technology, Faculty of Engineering, Professor, 工学部, 助教授 (30129142)
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Project Period (FY) |
1991 – 1992
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Keywords | Oxide High-Temperature Superconductor / Thin Film / Critical Current / Josephson Junction / DC-SQUID / Scanning Tunneling Microscope(STM) / Growth Mechanism |
Research Abstract |
The purpose of this study is to realize high sensitivity magnetic sensor SQUIDs (Superconducting QUantum Interference Devices) using Y-Ba-Cu-O(YBCO) thin films which are promissing high quality device material. Here a new conception "Josephson junctions with electrically controlled critical current" is proposed. This study was done during 1991 and 1992 academic years and the obtained results are as follows : 1.YBCO thin films were successfully grown "in situ" by single target magnetron sputtering. 2. when films were grown on (100)MgO substrates, the higher the growth temperature was, the higher the transition temperature(Tc) became. And cristallinity changed from a-axis orientation to c-axis one. YBCO thin films of Tc=77.5K was obtained when substrate temperature was 700゚C.XRD pattern of this film showed only sharp (00l) peaks indicating very high c-axis orientation. 3.Obtained thin films were observed by scanning tunneling microscope(STM). And it was found that the surface changed from textured structures to spiral ones as the growth temperature increased. These spiral structures became fairly large when YBCO films were grown on annealled substrates. This may because the density of nucleation centers of screw dislocations at substrate surface was reduced by annealing. Then, YBCO thin films were grown on (100)SrTiO_3 substrates. When substrate temperature was 700゚C, YBCO thin films of Tc=82k were obtained. XRD pattern of these films showed both a-axis orientation and c-axis one. 4.YBCO thin films were patterned by photolithography process into microbridges, which are the key structures of SQUD.Tc did not changed by chemical etching. Further study will be done to realize new conception dc-SQUID utilizing "Josephson junctions with electrically controlled critical current". The effort to obtain fundamental results for making clear the mechanism of crystal growth and superconductivity of YBCO.
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Research Products
(6 results)