Influence of initial counter-layer deposition condition using double-plume PLD method on characteristics of interface-modified Josephson junctions

Abstract In order to control critical current ( I c ) values of interface-modified Josephson junctions (JJ) for high-temperature superconductor single flux quantum (HTS-SFQ) logic circuits, we tried to make a high-quality homogeneous interface for a barrier layer by using a double-plume PLD method in the present study. We employed a two-step deposition method for the counter layer and examined the deposition conditions for the initial layer. We grew initial layers of La 0.2 -Yb 0.9 Ba 1.9 Cu 3 O x (La-YbBCO) counter electrodes on La 0.2 -Y 0.9 Ba 1.9 Cu 3 O x (La-YBCO) ramp surfaces with various distances ( L p–p ) between two laser-beam spots on the La-YbBCO target without laser-beam scanning. When the distance is relatively short, L p–p  = 1.5 mm, the junctions exhibited RSCJ-like I – V characteristics with low excess current and a clear dependence of I c on the junction width.