Fabrication and characterization of NbN/(TaN/NbN)N stacked Josephson junctions. (1st December 2022)

• Record Type: Journal Article
• Authors: Zhang, Lu; Tao, Yuanhe; Zhong, Yulong; Yan, Kaixin; Zeng, Junwen; Shi, Weifeng; Wu, Ling; Wang, Huiwu; Chen, Lei; Peng, Wei; Wang, Zhen
• Is Part Of: Superconductor science & technology. Volume 35:Number 12(2022)
• Publication Date: 2022-12-01
• Subjects: Josephson junction -- stacked junction -- SNS junction -- NbN film -- SFQ circuit -- non-hysteretic IV curve -- Fraunhofer pattern; Superconductivity -- Periodicals; Superconductors -- Periodicals; 537.623
• DOI: 10.1088/1361-6668/ac9f83
• Languages: English
• ISSNs: 0953-2048

Abstract

Abstract: In this work, we present a detailed study of the electrical properties of stacked NbN/(TaN/NbN) N Josephson junctions. Cross-sectional scanning transmission electron microscopy analysis of the 5-stacked junction shows that the multilayer interface is very flat, each barrier has the same thickness, and the sidewalls of the junctions are nearly perpendicular to the substrate. Stacked junctions of different sizes and stacking numbers all have only one transition in their current–voltage curves. This indicates that the critical currents of the junctions in the stacked junctions are almost the same, showing the stability and repeatability of the multilayer fabrication and etching process. At 4.2 K, the 4-stacked junction shows excellent Josephson properties with characteristic voltage V c of 3.54 mV, which is about four times the 0.88 mV of the single junction. The temperature dependence of critical current density J c and V c of the stacked junction with N = 1, 2, 4 were measured, all of which can be fitted with dirty-limit theory. Stacked junctions with larger V c or more stacked layers can be achieved by optimizing electrode and barrier thickness, barrier resistivity, and thermal relaxation rate, etc.