Investigation on the properties and the applications of vertically stacked Josephson tunnel junctions

Abstract

High quality vertically stacked Josephson tunnel junctions have been experimentally studied in the light of their potential applications. They have been realized using a simple fabrication process based on Nb technology. A number of aspects of such new devices were investigated. Among other things, we report on the dc characteristics (and their temperature and magnetic field dependence) of vertical stacks with particular attention to the case in which the intermediate layers are very thin. Furthermore, the Swihart velocities of the electromagnetic waves propagating in double-barrier junctions were measured from the voltages of zero field steps, Fiske steps, and flux flow steps in the current-voltage curve of electrically long devices. Each section is discussed in the light of the potential applications of vertically stacked junctions. We interpret the main features of the phenomena observed experimentally in terms of basic mechanisms. Strong evidence has been found of the proximity effect in thin intermediate layers. Vertically stacked Josephson tunnel junctions seem to be good candidates for applications as particle and photon detectors and high frequency oscillators.