Nanofabrication of high transition temperature superconductive electronics with focused helium ion irradiation

Superconductive electronics from Josephson junctions are governed by quantum mechanical tunneling through sub-10 nm scale insulating tunnel barriers. The electrical properties are exponentially sensitive to this dimension, which necessitates fabrication with nanoscale precision and uniformity. For circuits in high-transition temperature YBa $2$Cu $3$O $7 − δ$ (YBCO) thin films, direct writing of the material with a focused helium ion beam has shown promise in the creation of uniform nanoscale insulators for YBCO Josephson junctions and other circuit regions. In this paper, we report on the procedures and variables associated with this process and discuss the potential for scaling up the number of junctions for quantum sensing and complex energy efficient digital circuits.