Abstract: We present the results of development and research of superconducting vanadium nitride VN films ~10 nm thick having different level of disorder. It is showed that both silicon substrate temperature T sub in process of magnetron sputtering and total gas pressure P affect superconducting transition temperature of sputtered films and R 300 /R 20 ratio defining their level of disorder. VN films suitable for development of superconducting single-photon detectors on their basis are obtained.

Abstract: We report our study of detection efficiency (DE) saturation in wavelength range 400 – 1550 nm for the NbN Superconducting Microstrip Single-Photon Detectors (SMSPD) featuring the strip width up to 3 μm. We observe an expected decrease of the $DE$ saturation plateau with the increase of photon wavelength and decrease of film sheet resistance. At 1.7 K temperature DE saturation can be clearly observed at 1550 nm wavelength in strip with the width up to 2 μm when sheet resistance of the film is above 630Ω/sq. In such strips the length of the saturation plateau almost does not depend on the strip width. We used these films to make meander-shaped detectors with the light sensitive area from 20×20μm2 to a circle 50 μm in diameter. In the latter case, the detector with the strip width of 0.49 μm demonstrates saturation of DE up to 1064 nm wavelength. Although DE at 1310 and 1550 nm is not saturated, it is as high as 60%. The response time is limited by the kinetic inductance and equals to 20 ns(by 1/e decay), timing jitter is 44 ps. When coupled to multi-mode fibre large-area meanders demonstrate significantly higher dark count rate which we attribute to thermal background photons, thus advanced filtering technique would be required for practical applications.