High-quality planar high-T_c Josephson junctions

摘要

Reproducible high-T_C Josephson junctions have been made in a rather simple two-step process using ion irradiation. A microbridge (1 to 5 μm wide) is firstly designed by ion irradiating a c-axis-oriented YBa_2Cu_3O_(7-δ) film through a gold mask such as the nonprotected part becomes insulating. A lower T_c part is then defined within the bridge by irradiating with a much lower fluence through a narrow slit (20 nm) opened in a standard electronic photoresist. These planar junctions, whose settings can be finely tuned, exhibit reproducible and nearly ideal Josephson characteristics. This process can be used to produce complex Josephson circuits.