Enhancement of the Quality of Stacked-type High-Tc Josephson Junctions by Doping and Development of the Integration Technology for These Junctions

通过掺杂提高堆叠型高温约瑟夫森结的质量及其集成技术的发展

基本信息

批准号：
14350185
负责人：
HAYAKAWA Hisao
金额：
$ 9.47万
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：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14350185/
关键词：
high-Tc superconductor YBCO doping interface treatment stacked-type junction scattering TEM YbBCO 積層型接合高温超伝電導体 Pr Ga

项目摘要

The purpose of this research is to establish the fabrication technique of stacked-type high-Tc Josephson junctions by the new doping method and to enhance the technique for application to circuits. Following results were obtained.1.Investigation of the factors to worsen the junction properties : In addition to the suppression of pinholes by doping of Pr and Ga, we investigate the factors influencing scattering and deterioration of junction properties. It was found that the change in the surface morphology by the etching for forming the barrier was related to the junction properties, and we obtained junctions with overdamped characteristics and high critical current density at 30K. These junctions showed small scattering, and were of highest quality we ever obtained.2.Planarization of YBCO films by La doping : We confirmed that holes in YBCO films decreased by substituting part of Y or Ba in YBCO for La.3.Investigation of the barrier structure by TEM : Microstructure around the barrier layer which affects junction properties by transmission electron microscopy (TEM). Y_2O_3 phases were clearly observed around the barrier layer when the barrier was formed using high Ar ion acceleration voltage. Taking the relationship between the acceleration voltage and the junction critical current density, etc. into account, higher critical current density would correspond to thinner and more uniform barrier.4.Investigation of the material for the top electrode : In order to suppress the pinholes in the barrier layer, we tried YbBa_2Cu_3O_<7-x> (YbBCO) of which film can be obtained at lower temperature than YBCO as the top electrode. Junctions with YbBCO top electrode showed scattering smaller than those with YBCO top electrode. YbBCO may be effective to obtain good junction properties.

本研究的目的是通过新的掺杂方法建立堆叠型高温约瑟夫森结的制造技术，并增强该技术在电路中的应用。得到以下结果： 1.结性能恶化因素的研究：除了通过掺杂Pr和Ga抑制针孔外，我们还研究了影响散射和结性能恶化的因素。研究发现，势垒刻蚀引起的表面形貌变化与结特性有关，获得了具有过阻尼特性和30K时高临界电流密度的结。这些结显示出很小的散射，并且是我们获得的最高质量。2.通过 La 掺杂实现 YBCO 薄膜的平坦化：我们证实，通过用 YBCO 中的部分 Y 或 Ba 代替 La，YBCO 薄膜中的空穴减少。3.研究TEM 的势垒结构：通过透射电子显微镜 (TEM) 观察势垒层周围的微观结构，该微观结构影响结特性。当使用高Ar离子加速电压形成势垒时，在势垒层周围清楚地观察到Y_2O_3相。考虑到加速电压与结临界电流密度等关系，临界电流密度越高，势垒越薄、越均匀。4.顶部电极材料的研究：为了抑制结面的针孔。对于阻挡层，我们尝试了YbBa_2Cu_3O_<7-x>（YbBCO），其薄膜可以在比YBCO更低的温度下获得作为顶部电极。具有 YbBCO 顶部电极的结显示出比具有 YBCO 顶部电极的结更小的散射。 YbBCO 可有效获得良好的结特性。