Nano SNIS Junctions Fabricated by 3D FIB Sculpting for Application to Digital Electronics

Overdamped Josephson junctions based on a Nb/Al-AlOx/Nb superconductor-normal metal-insulator-superconductor structure were realized at the submicrometer scale by using focused ion beam nano-sculpting technique. This approach represents an alternative solution to the classical electron beam lithography and allows for an accurate control of the junction dimensions. Superconductor-normal metal-insulator-superconductor structured junctions were downscaled to about 300 × 300 nm² and electrically measured at 4.2 K. The simple fabrication process, leading to high current density, J_c, and characteristic voltage, V_c, values and good uniformity, makes these junctions promising as elementary cell in complex circuits for rapid single flux quantum and ac voltage standard applications.