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Realization of Josephson junctions with electrically controlled critical current and its application to dc-SQUIDs.

具有电控临界电流的约瑟夫森结的实现及其在dc-SQUID 中的应用。

基本信息

批准号：
03650261
负责人：
SUZUKI Toshimasa
金额：
$ 1.22万
依托单位：
Nippon Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

项目摘要

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.

本研究的目的是利用 Y-Ba-Cu-O(YBCO) 薄膜实现高灵敏度磁传感器 SQUID（超导量子干涉器件），Y-Ba-Cu-O(YBCO) 薄膜是有前途的高质量器件材料。这里提出了“电控临界电流约瑟夫森结”的新概念。这项研究是在1991和1992学年进行的，取得的成果如下： 1．单靶磁控溅射“原位”成功生长YBCO薄膜。2．当薄膜在(100)MgO衬底上生长时，生长温度越高，转变温度(Tc)越高。并且结晶度从a轴取向变为c轴取向。当衬底温度为700℃时，得到了Tc=77.5K的YBCO薄膜。该薄膜的XRD图谱仅显示出尖锐的(00l)峰，表明c轴取向非常高。3.通过扫描隧道显微镜(STM)对所得薄膜进行观察。研究发现，随着生长温度的升高，表面由纹理结构转变为螺旋结构。当 YBCO 薄膜在退火基板上生长时，这些螺旋结构变得相当大。这可能是因为通过退火降低了衬底表面处螺旋位错的成核中心的密度。然后，在(100)SrTiO_3衬底上生长YBCO薄膜。当衬底温度为700℃时，得到了Tc=82k的YBCO薄膜。这些薄膜的XRD图谱同时显示a轴取向和c轴取向。4.YBCO薄膜通过光刻工艺形成微桥，这是SQUD的关键结构。化学蚀刻不会改变Tc。将进一步研究利用“电控临界电流约瑟夫森结”实现新概念dc-SQUID。努力取得阐明YBCO晶体生长和超导机理的基础性成果。