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Studies on the Bi System Josephson Junctions with High Criteical Temperature

高临界温度Bi系约瑟夫森结的研究

基本信息

批准号：
07455138
负责人：
HAYAKAWA Hisao
金额：
$ 4.48万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

Among Bi_2Sr_2Ca_<n-1>Cu_nO_x superconductors, n=3 phase (2223 phase) is an oxide superconductor which has a critical temperature more than 100K.This material has the possibility to realize devices more stable and of better performance than those of Y system superconductor. In this research, on the basis of the thin film technology of 2223 phase, we tried to fabricate the following Josephson junctions.1. Edge-type Junctions :We fabricated edge type junctions using the 2223 phase as the superconducting electrodes and the 2201 phase as the middle layr. Their properties were RSJ-like. It was suggested that the grain boundary at the bottom of the step of the upper electrode also worked as a junction.2. Grain-boundary Junctions :(1) Bicrystal Junctions :We tried to fabricate grain-boundary Josephson junctions using 2223 phase films deposited on bicrystal substrates. Their properties are similar to those of Y system superconductor. On the other hand, the high junction resistances and the low … More critical current were confirmed as characteristic features of the grain-boundary junctions of the 2223 phase. By analyzing the junction characteristics, it was found that there are normal phase layrs near the insulating layr in the junction. The conduction mechanism of the junction was discussed. SQUID's were also fabricated using this bicrystal junction. The critical current was modulated periodicaly by the external magnetic field, and in spite of the small modulation, relative large output valtage was observed reflecting its high dynamic resistance, though we have not evaluated their noise properties.(2) Step-Edge Junctions :We fabricated step-edge type grain-boundary junctions by depositing the 2223 thin film on the MgO step substrate. The current-voltage characteristics was RSJ-like and it was suggested that the grain boundaries were formed at the top and the bottom of the step. Junctions using the films annealed for a short time revealed the improvement of the critical temperature, the critical current and the I_cR_n product of the junction. The possibility that there are normal phase layrs near the insulating layr in the junction was also suggested.3. Intrinsic Junctions :We tried to fabricate the intrinsic junctions using the 2223 phase thin films on the SrTiO_3 step substrates. The gap structure corresponding to the number of the layrs, i. e., the series Josephson junctions was observed. Less

在Bi2Sr2Calt；n-1&gt；CuNOx超导体中，n=3相(2223相)是一种临界温度在100K以上的氧化物超导体。这种材料有可能实现比Y系超导体更稳定、性能更好的器件。在本研究中，我们在2223相薄膜技术的基础上，尝试制作了如下约瑟夫森结。边型结：我们用2223相作为超导电极，2201相作为中间层制作了边型结。它们的性质类似于RSJ。这表明，上电极台阶底部的晶界也起到了结点的作用。晶界结：(1)双晶结：我们尝试用沉积在双晶衬底上的2223相薄膜制备晶界约瑟夫森结。它们的性质与Y系超导体的性质相似。另一方面，高结电阻和低…更多的临界电流被确认为2223相晶界结的特征。通过对结区特性的分析，发现在结区绝缘层附近存在正常相层。讨论了该结的导电机理。鱿鱼也是用这种双晶结制造出来的。临界电流受到外加磁场的周期性调制，尽管调制幅度很小，但输出电压较大，反映了其较高的动态电阻，尽管我们还没有对其噪声特性进行评估。(2)台阶-边缘结：我们在氧化镁台阶衬底上沉积了2223薄膜，制备了台阶边型晶界结。其伏安特性类似于RSJ，表明晶界形成于台阶的顶部和底部。采用短时间退火的薄膜结的临界温度、临界电流和Icr_n乘积都有所提高。还提出了在结区绝缘层附近存在正常相层的可能性。本征结：我们尝试用2223相薄膜在SrTiO3台阶衬底上制备本征结。观察到了与层数对应的带隙结构，即串联约瑟夫森结。较少