Study on the barrier formation of vertically-stacked interface-treated junctions

Abstract

We studied the barrier formation process in YBa2Cu3Ox (YBCO) vertically-stacked interface-treated Josephson junctions using some variations of the fabrication process, focusing on two points, i.e., the amorphous state before annealing and the effective structure as barrier at the interface after annealing. First, we simulated a surface amorphous layer in the interface treatment technique by depositing an amorphous Y–Ba–Cu–O layer with deviated composition artificially on the base YBCO electrode and succeeding annealing. However, we could not obtain Josephson junctions by this method. It was suggested that the amorphous state is not sufficient condition for the ion-bombarded layer in the interface-treated junctions. Next, we prepared interface-treated junctions using different electrode materials, i.e., YBCO as a base electrode and YbBa2Cu3Ox (YbBCO) which has the same structure as YBCO and has lattice constants a little smaller than YBCO, as a counter electrode. The yield of the junction increased by using YbBCO counter electrode. Some kind of disorder between the base and counter electrodes may contribute to the barrier.