Focused helium-ion-beam technology——A promising pathway for the fabrication of high-temperature superconducting Josephson junctions

As an observable macroscopic quantum phenomenon, superconducting Josephson junctions drive the development of quantum metrology, weak-magnetic field sensing, terahertz mixing, and other weak-signal applications. Compared with low-temperature superconducting Josephson junctions, high-temperature superconducting(HTS) Josephson junctions can lower refrigeration costs and raise device operating frequencies. However, their controllable and reproducible fabrication has remained a challenge. With sub-nanometre precision and mask-free direct writing, focused helium-ion-beam technology is now being applied to the fabrication and research of HTS Josephson junctions. This technology will be reviewed from four perspectives: its evolution, its advantages in HTS device fabrication, frontier applications, and future prospects.