Fabrication and characterization of sub-micron high current density NbN Josephson junctions for large-scale digital circuits

IF 1.3 3区物理与天体物理 Q4 PHYSICS, APPLIED

Physica C-superconductivity and Its Applications Pub Date : 2023-12-27 DOI:10.1016/j.physc.2023.1354434

Yingyi Shao , Huiwu Wang , Wei Peng , Jie Ren , Zhen Wang

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引用次数: 0

Abstract

We have developed a fabrication process based on Chemical Mechanical Polishing (CMP) for the sub-micron NbN Josephson junctions on single-crystal MgO substrates. The NbN junctions were fabricated with epitaxial NbN/AlN/NbN trilayers deposited by reactive DC magnetron sputtering. The top electrode of the junction was exposed using CMP to contact the NbN wire without opening the submicron via through the dielectric. It has produced submicron NbN junctions with areas as small as 0.09 μm². We have fabricated NbN tunnel junctions with a wide range of critical current density J_c. The NbN junctions show excellent Josephson tunneling characteristics, the gap voltage V_g is 5.8 mV and the quality factor R_sg/R_n is 12 for the junctions with a J_c of 10.7 kA/cm², and V_g is 5.3 mV and R_sg/R_n is 4 for the junctions with a J_c of 150.5 kA/cm². The 1000-junction arrays were fabricated and their I-V characteristics were measured, critical current uniformity was obtained and the standard deviation is about 5%. The high J_c sub-micron NbN junctions will be helpful in developing large-scale NbN SFQ circuits with high operating frequency.

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用于大规模数字电路的亚微米级高电流密度氮化铌约瑟夫森结的制作与特性分析

我们开发了一种基于化学机械抛光 (CMP) 的制造工艺，用于在单晶氧化镁基底上制造亚微米级氮化铌约瑟夫森结。氮化铌结是用反应直流磁控溅射沉积的氮化铌/氮化铝/氮化铌三层外延层制作的。使用 CMP 暴露结的顶电极，使铌镍线接触，而不打开穿过介质的亚微米孔。这种方法制造出了面积小至 0.09 μm2 的亚微米级氮化铌结。我们制造出了临界电流密度 Jc 范围很宽的氮化铌隧道结。氮化铌结显示出卓越的约瑟夫森隧道特性：Jc 为 10.7 kA/cm2 的结的间隙电压 Vg 为 5.8 mV，品质因数 Rsg/Rn 为 12；Jc 为 150.5 kA/cm2 的结的间隙电压 Vg 为 5 .3 mV，品质因数 Rsg/Rn 为 4。制作了 1000 个结阵列并测量了它们的 I-V 特性，获得了临界电流均匀性，标准偏差约为 5%。高 Jc 亚微米氮化铌结将有助于开发高工作频率的大规模氮化铌 SFQ 电路。

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来源期刊

Physica C-superconductivity and Its Applications 物理-物理：应用

CiteScore

2.70

自引率

11.80%

发文量

102

审稿时长

66 days

期刊介绍： Physica C (Superconductivity and its Applications) publishes peer-reviewed papers on novel developments in the field of superconductivity. Topics include discovery of new superconducting materials and elucidation of their mechanisms, physics of vortex matter, enhancement of critical properties of superconductors, identification of novel properties and processing methods that improve their performance and promote new routes to applications of superconductivity. The main goal of the journal is to publish: 1. Papers that substantially increase the understanding of the fundamental aspects and mechanisms of superconductivity and vortex matter through theoretical and experimental methods. 2. Papers that report on novel physical properties and processing of materials that substantially enhance their critical performance. 3. Papers that promote new or improved routes to applications of superconductivity and/or superconducting materials, and proof-of-concept novel proto-type superconducting devices. The editors of the journal will select papers that are well written and based on thorough research that provide truly novel insights.