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固有特性及其纳米电子学应用。本研究取得了以下成果：(1)建立了电子束光刻和氩离子铣削的亚微米器件制造工艺。该技术实现了器件制造的可控性和可重复性。 (2)我们制作了不同尺寸的涉及本征约瑟夫森结的台面结构，并研究了其特性的尺寸依赖性。结果发现，约60mV的间隙电压与结面积无关。此外，我们发现，由于库仑阻塞效应的贡献，随着结面积变成亚微米区域，临界电流密度迅速减小。 (3)堆叠本征约瑟夫森结中进入正常状态的开关电流分布随着结面积的增加而增加。使用热激活模型对所得结果进行分析，我们发现开关电流分布的增加是由于磁通波动而不是热噪声造成的。此外，我们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，并且与包括热噪声在内的 RSJ 模型一致。 (4)以本征约瑟夫森结在纳米电子学中的应用为例，我们利用它们制作了单库珀对隧道器件、电压标准器件和直流SQUID。