Authors: Max Pröpper, Dominik Hanisch, Christoph Schmid, Marius Neumann, Paul Julius Ritter,
Marc-André Tucholke, Edward Goldobin, Dieter Koelle, Reinhold Kleiner, Meinhard Schilling,
and Benedikt Hampel
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 35, NO. 5, AUGUST 2025
Abstract: The development of a fabrication process for Josephson junctions (JJs) using a direct-write helium-focused ion beam (He-FIB) technique provides the opportunity to control parameters such as the critical current Ic and normal-state resistance Rn of individual JJs in YBa2Cu3O7−x JJ arrays. Such arrays could be used as a voltage calibration standard that is operated at higher temperatures and higher driving frequencies than the currently used niobium JJ arrays. This study presents the fabrication process
of 79 YBa2Cu3O7−x JJs in a meander array design using a direct writing He-FIB process with the same irradiation dose for all JJs. In this design, each of the JJs can be measured individually, and adjacent JJs that exhibit similar and suitable parameters for a voltage standard array can be measured in series. The scattering of the JJ parameters was investigated at 5 K and resulted in a spread in Ic of about 60% and in Rn of 25%. However, a couple of subarrays with a spread lower than 10% could be found. In addition, these JJ subarrays were irradiated with high-frequency radiation in the GHz and THz range at a temperature of 20 K and synchronization of up to three JJs was observed in both frequency ranges.
