Characteristics of high-transmission-probability tunnel junctions for use as particle detectors

Interest in the problem of the galactic dark matter has stimulated development of particle detectors sensitive to very low energies. The authors describe superconducting tunnel junctions with thin barriers which may be suitable for this purpose. They present I-V (current-voltage) characteristics and data on the temperature dependence of the subgap tunneling current. They examine the barrier transmission probability and the resistance of the null junction. They also present some scanning-electron-microscope observations of the thin films of the tunnel junctions, which show that faster deposition produces smaller grains and increasing film thickness results in larger grains from an apparent fusing of smaller grains