Influence of Counter-Layer Deposition Condition on Critical Current Spread in Interface-Modified Ramp-Edge Junction Arrays

Abstract

We have fabricated interface-modified ramp-edge junctions and junction arrays with sputtered La-doped YBa2Cu3Oy (La-YBCO) and La-doped YbBa2Cu3Oy (La-YbBCO) by pulsed laser deposition (PLD) as base and counter layers, respectively. The influences of deposition conditions for the La-YbBCO counter layers, in particular the target–substrate distance (Ht–s), on the junction properties and the Ic spread in the junction arrays is investigated. For a relatively short Ht–s of 60 mm, junctions with different edge directions exhibit substantially different Ic values, suggesting that the barrier recrystallization is significantly influenced by the incident angle of ablated atoms on the ramp surface. By employing a longer Ht–s of 80 mm, this influence can be lessened, and 1 σ spreads in Ic at 4.2 K of 7.9 and 9.5% can be obtained for 100- and 1000-junction series arrays, respectively.