Ramp-edge junctions with interface-modified barriers fabricated on YBCO thick films

We fabricated ramp-edge junctions with an interface-modified barrier on YBa₂Cu₃O_y (YBCO) liquid phase epitaxy (LPE) thick films. The LPE thick films were used as ground-planes. For the insulating layer between the ground plane and base electrode, a SrTiO₃ (STO)/(LaAlO₃)_0.3-(SrAl_0.5Ta_0.5O₃)_0.7 (LSAT)/STO multilayer with the dielectric constant of approximately 32 was employed. We fabricated ramp-edge junctions with La-doped YBa₂Cu₃O_y (La-YBCO) and La-doped YbBa₂Cu₃O_y (La-YbBCO) as base and counter electrodes, respectively. The fabricated junctions exhibited resistively and capacitively shunted junction (RCSJ)-like characteristics and typical I_cR_n products of 2.6 and 1.1 mV at 4.2 and 40 K, respectively. The 1 σ-spread in I_c as small as 8.1% was obtained for 100-junction series-arrays. The use of ground plane reduced the sheet inductance of electrodes to a value of 0.76-0.94 pH/square at 4.2 K.