Authors: M. Pröpper, D. Hanisch, C. Schmid, P. J. Ritter, M. Neumann, E. Goldobin, D. Koelle, R. Kleiner,M. Schilling, and B. Hampel
IEEE Transactions on Applied Superconductivity Volume: 34, Issue: 3, May 2024
Abstract: Josephson junctions with customizable parameters, including critical current I c and normal state resistance R n , hold great promise across a wide range of applications. Notably, high-temperature superconductors like YBa 2 Cu 3 O 7-x have been interesting since their discovery due to their simplified cooling requirements. YBa 2 Cu 3 O 7-x Josephson junctions can operate within the terahertz (THz) frequency range, rendering them highly suitable for various applications. To maximize their suitability at these high frequencies, it is imperative to precisely determine their THz parameters. Helium focused ion beam (He-FIB) technology is a very promising fabrication method for customizable Josephson junctions. It allows precise control of the He-FIB dose during the fabrication of Josephson junctions and facilitates the fine-tuning of I c and R n . This study presents the fabrication process of YBa 2 Cu 3 O 7-x Josephson junctions using He-FIB irradiation and explores the variations of parameters with dose, evaluating their suitability within the THz range. Also, the scattering of parameters of He-FIB Josephson junctions fabricated with the same He-FIB dose is investigated. Additionally, we examine the high-frequency properties of such junctions and scrutinize the associated Shapiro steps within the THz frequency spectrum. We observe an exponential relationship between I c and the He-FIB dose. Moreover, Shapiro steps emerge under the influence of radiation spanning from 40 GHz to as high as 1.4 THz.
