Controlling the Interface Properties of Submicrometric Nb/A– $\hbox{AlO}_{\rm x}$–Nb Josephson Junctions

Submicron Josephson devices are of a particular interest to the emerging field of quantum information, nanosized superconducting quantum interference devices (nano-SQUID) fabrication, AC voltage synthesis circuits for quantum metrology, etc. In this paper, we report on the development of our technology for producing non-hysteretic Nb/A-AlO
_x
-Nb four-layered junctions with a diverse range of submicron dimensions, based on the focused ion beam (FIB) sculpting technique. We observed essential modifications of the main electrical characteristics as a result of the shrinking of the junction area, and relate them to the changes of the buried Nb/Al interface. We show that the electrical parameters-versus-temperature dependence can provide information on the quality of the junction interfaces. This aspect could be useful to better control of the entire fabrication process, allowing a further large-scale integration of Josephson nanodevices with improved transport characteristics.