Fabrication and characterization of YBa2Cu3O7 step‐edge junction arrays

We investigated one‐dimensional arrays with up to 600 step‐edge Josephson junctions (SEJ) fabricated by pulsed laser deposition of YBa2Cu3O7 (YBCO) films on steep steps in epitaxial LaAlO3 substrates. The steps were prepared by Ar‐ion milling and the YBCO thin films were patterned either by Ar‐ion milling or by an inhibit process. The current‐voltage (I‐V) characteristics and the Josephson emission of a single SEJ show that it consists of two resistively shunted‐junction‐type (RSJ) weak links in series which have different critical currents, IC1 and IC2. The I‐V characteristics of our arrays were also close to the RSJ‐model. The number of series‐connected weak links deduced from the I‐V curves was usually higher than the number of steps. Histograms of the individual weak link ICs showed two peaks at IC1 and IC2. The IC spread was about ±20% to ±40% of these two values. Radiation from arrays was detected and an evidence of phase locking in Josephson junction clusters obtained.