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

Bi_2Sr_2Ca_<n-1>Cu_nO_x超导体中，n=3相（2223相）是一种氧化物超导体，其临界温度超过100K。该材料有可能实现比Y系更稳定、性能更好的器件本研究在2223相薄膜技术的基础上，尝试制作了以下约瑟夫森结。边缘型结：我们使用2223相作为超导电极，2201相作为中间层制造了边缘型结，它们的性质类似于RSJ，表明晶界位于上层台阶的底部。 2.晶界结：（1）双晶结：我们尝试使用2223制造晶界约瑟夫森结。其特性与 Y 系超导体相似，但高结电阻和低临界电流被证实是 2223 相晶界结的特征。分析结的特性，发现结内绝缘层附近存在正相层，并以此为基础讨论了SQUID的导电机理。双晶结的临界电流受到外部磁场的周期性调制，尽管调制较小，但观察到相对较大的输出电压，反映出其高动态电阻，尽管我们尚未评估其噪声特性。(2) 阶跃边沿结：我们通过在 MgO 阶梯基板上沉积 2223 薄膜来制造阶梯边缘型晶界结，电流-电压特性类似于 RSJ，表明晶界是。使用短时间退火的薄膜在台阶的顶部和底部形成的结揭示了结的临界温度、临界电流和I_cR_n乘积的改善，在绝缘附近存在正相层的可能性。 3.本征结：我们尝试在SrTiO_3台阶基底上使用2223相薄膜制造本征结，其间隙结构对应于SrTiO_3台阶基底。层数，即，观察到的串联约瑟夫森结。