Stacked series arrays of high-Tc trilayer Josephson junctions

摘要

We report on the properties of stacked series arrays of trilayer Josephson junctions grown by atomic layer-by-layer molecular beam epitaxy. Trilayer Josephson junctions oriented so that the current travels in the c-axis direction have been described previously. Series arrays are made by placing more than one barrier layer in the Ba2Sr2CaCu2O8-based, (2212), epitaxial structure. Single molecular layers of 2212 doped with Dy to reduce the local carrier concentration are used as barriers, and are placed very close to each other, e.g., separated by only a few molecular layers of the superconducting phase. Phase locking of a.c. Josephson currents has been observed. The critical current density of such junctions has been observed to be very uniform on wafers that are free of second phase defects, and operation up to 60 K has been obtained.