Fabrication of HTS Low-noise Nanobridge Josephson Junction by Gallium FIB
Fabrication of HTS Low-noise Nanobridge Josephson Junction by Gallium FIB
复制标题
镓 FIB 制造高温超导低噪声纳米桥约瑟夫森结
DOI：
10.1109/tasc.2021.3072009
复制
发表时间：
2021
影响因子：
1.8
通讯作者：
and Saburo Tanaka
中科院分区：
文献类型：
--
作者：
Kanji Hayashi;Teppei Ueda;Ryo Ohtani;Seiichiro Ariyoshi;and Saburo Tanaka
高温超导体约瑟夫森结(JJ)主要基于人工晶界。双晶JJ通常用于高温超导量子干涉器件(SQUID)。然而，双晶JJ的性能在很大程度上取决于结合处的界面质量。在这项研究中，我们研究了一种通过镓聚焦离子束(FIB)照射来形成纳米桥JJ的方法。采用脉冲激光沉积技术在氧化镁(100)衬底上沉积了厚度为100 nm的YBa2Cu3O7-δ薄膜。在原位沉积了另外一层20 nm厚的Au层，作为保护层以防止在取向过程中的离子损伤。通过光刻和Ar离子研磨确定了宽度为4μm的高温超导微通道。高温超导微通道宽度通过FIB线扫描来创建纳米桥而减小。JJ是由两种类型的高温超导薄膜制成的，其中一种的临界电流密度(JC)高于另一种。对GaFIB的制备工艺进行了优化，制备了结宽为80 nm的纳米桥。结果是，具有更高JC(5 mA/cm2)的HTS薄膜可以在77K下形成高达5个夏皮罗台阶的结。
High-temperature superconductor (HTS) Josephson junctions (JJs) are primarily based on artificial grain boundaries. Bi-crystal JJs are typically utilized in HTS superconducting quantum interference devices (SQUIDs). However, the performances of bi-crystal JJs depend significantly on the quality of the interface at the junction. In this study, we investigate a method for forming nanobridge JJs via gallium focused ion beam (FIB) irradiation. A 100-nm-thick YBa2Cu3O7-δwas deposited on an MgO (100) substrate via pulsed laser deposition. An additional 20-nm-thick Au layer, which serves as a protection layer preventing ion damage during alignment, was deposited in situ. HTS microchannels with a width of 4 μm were defined via photolithography and argon ion milling. The HTS microchannel widths are decreased via FIB line scans to create nanobridges. The JJs are fabricated using two types of HTS thin films, in which one has a higher critical current density (JC) that the other. The fabrication process using the gallium FIB was optimized and nanobridges with a junction width of 80 nm were prepared. As a result, a better with higherJC(5 MA/cm2) HTS films allowed for making junctions exhibiting up to five Shapiro steps at 77 K.