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Study towards nanoelectronics of small-sized Josephson superlattice using high T_c superconductors

高T_c超导小尺寸约瑟夫森超晶格纳米电子学研究

基本信息

批准号：
14550316
负责人：
IRIE Akinobu
金额：
$ 2.18万
依托单位：
Utsunomiya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
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

项目摘要

The inherent characteristic of small-sized intrinsic Josephson junctions in Bi_2Sr_2CaCu_2O_y single crystals and their nanoelectronics applications have been investigated. In this study, we obtained the following results.(1)Submicron device fabrication process using electron beam lithography and Ar ion milling was established. Such technology realizes the controllable and reproducible device fabrication. (2)We fabricated mesa structure with different sizes involving intrinsic Josephson junctions and studied the size dependence of their characteristics. As a result, it was found that the gap voltage of about 60mV is independent of junction area. In addition, we found that the critical current density rapidly decreases as the junction area becomes the submicron region because of the contribution of the Coulomb blockade effect. (3)The distribution of switching current into normal state in stacked intrinsic Josephson junctions increases with increasing the junction area. The obtained results were analyzed by using the thermal activated model and we found that the increase in the distribution of the switching current is due to flux fluctuation rather than thermal noise. Additionally, we found that the temperature dependence of critical current is systematically changed as the junction area reduces and it is consistent with the RSJ model including thermal noise. (4)For example of nanoelectronics application of intrinsic Josephson junction, we fabricated the single Cooper pair tunneling device, the voltage standard device and dc SQUID using them.

研究了Bi_2Sr_2CaCu_2O_y单晶中小尺寸本征约瑟夫森结的特性及其在纳米电子学中的应用。在这项研究中，我们得到了以下结果。（1）建立了电子束光刻和氩离子刻蚀相结合的亚微米器件制备工艺。这种技术实现了可控和可再现的器件制造。(2)We制作了不同尺寸的包含本征约瑟夫森结的梅萨结构，并研究了其特性的尺寸依赖性。结果发现，约60 mV的差距电压与结面积无关。此外，我们发现，临界电流密度迅速下降，结面积成为亚微米区域，因为库仑阻塞效应的贡献。（3）叠层本征约瑟夫森结中的开关电流分布随结面积的增大而增大。利用热激活模型对实验结果进行了分析，发现开关电流分布的增加是由于磁通波动引起的，而不是热噪声引起的。此外，我们还发现临界电流的温度依赖性随着结面积的减小而系统地改变，这与包含热噪声的RSJ模型是一致的。（4）以本征Josephson结在纳米电子学中的应用为例，利用它们制作了单库珀对隧穿器件、电压标准器件和直流SQUID。