Fabrication of high-quality Josephson junctions for applications as particle detectors

The use of Josephson junctions as particle detectors requires, besides high quality of the tunnel characteristics, special geometrical configurations, and fabrication processes. A new fabrication process for Josephson junctions is presented. 'Island' geometry junctions with rhomboid shape (in order to minimize the magnetic field necessary to suppress the critical current) have been fabricated with a special Si O 'bridge' that minimized the overlap area between the insulating layer and the junction. The measured junctions exhibit high levels of tunneling quality (Vm = 91 mV at T = 4.2 K)