High-temperature superconducting edge-type Josephson junctions with modified interface barriers

This paper describes recent results on the fabrication, electrical characteristics, and microstructure of high-temperature superconducting edge-type Josephson junctions with modified interface barriers. The barriers are formed by surface modification of the YBa₂Cu₃O_7-δ base layer. This process involves structural and chemical modification by ion irradiation and crystallization by annealing. The junctions showed resistively and capacitively shunted junction-like current-voltage characteristics and excellent uniformity. The spread in the critical current for one hundred junctions was smaller than 1σ=10% at 4.2 K. The uniformity is now approaching 1σ=5%. The junction characteristics have remained the same after two-year room-temperature storage. They also showed no change after high-temperature processing at about 700°C. High-resolution transmission electron microscopy revealed that both the crystal structure and chemical composition in relatively thick barriers are different from those of YBa₂Cu₃O_7-δ