Investigation of ramp-type Josephson junctions with surface-modified barriers

Abstract

Absfrucf-We have investigated the properties of YBa2Cu307-I ramp-edge Josephson junctions with surface-modified barriers produced by Ar-ion irradiation followed by oxygen annealing. The fabricated junctions displayed RSJ-like I-V characteristics and excellent uniformity. The stray capacitance of the junctions was estimated from the ramp-edge structure. The junction capacitance was obtained by subtracting the stray capacitance from the shunting capacitance. W e estimated the barrier thickness from the junction capacitance, and found that the critical current density of the junction increased exponentially with decreasing barrier thickness. The relative dielectric constant of the barriers ranged from 13 to 18.

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

“…The critical current ( ) of junction at 4.2 K is 1.1 mA and the normal state resistance ( ) is 2. 4 . The product of the junction is 2.6 mV.…”

“…Ramp-edge junctions with interface-engineered or interface-modified barriers [1]- [4] have attracted much more attention as reliable HTS junctions, because of their higher products and smaller spreads in a chip than those for the junctions with an artificial barrier. The interface-modified barrier is formed by ion irradiation to the YBa Cu O (YBCO) ramp surface and following annealing in vacuum or reduced oxygen atmosphere.…”

High-speed operation of quasi-one junction superconducting quantum interference device based on high-Tc multilayer technology

“…[6][7][8] For most SFQ circuits, a superconducting ground plane integrated into thin film multilayer structures is indispensable to reduce wire inductance. Very recently IEJs with large I c R n products and small I c spreads have also been successfully fabricated on ground planes based on NdBa 2 Cu 3 O y and La 0.2 Y 0.9 Ba 1.9 Cu 3 O y ͑La-YBCO͒ thin films with very smooth surfaces, 9,10 as well as YBCO.…”

A novel multilayer process for HTS SFQ circuit

“…After Moeckly and Char demonstrated the possibility of high-uniformity Josephson characteristics with an interface-engineering technique [2], the spread in critical current ( ) of junctions of this type has been rapidly improved [3]. However, the electric properties of IEJ's are extremely sensitive to the annealing temperature during the counter-electrode deposition process.…”