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

Abstract

Overdamped Josephson junctions based on a Nb/Al-AlO <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> /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 nm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and electrically measured at 4.2 K. The simple fabrication process, leading to high current density, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> , and characteristic voltage, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> , values and good uniformity, makes these junctions promising as elementary cell in complex circuits for rapid single flux quantum and ac voltage standard applications.