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.