Superconducting Molybdenum Silicide nanostrips for single photon detectors

When superconducting materials work as Single Photon Detectors (SPD) they are patterned in nanostrips about 100 nm wide with a typical meander structure to increase the photosensitive area. Moreover, they are biased by a DC current close to the critical current to have higher efficiency. The critical current could be non uniform mainly in proximity of the turn bends producing an increase of the dark count events. In this work MoSi nano-strips covered with a very thin (2 nm) layer of Al, have been realized and characterized in a wide interval of temperatures from 6 K down to 7 mK to investigate the critical current as a function of the temperature and then its uniformity in the presence of sharp corners and/or turn-arounds. Finally, the counts rates were recorded by a nano-meander under irradiation at two different wavelengths λ = 650 nm and 1550 nm, respectively, and compared with the events in the dark regime.