From Event: SPIE Commercial + Scientific Sensing and Imaging, 2018
Superconducting nanowire single photon detectors (SNSPD) offer excellent performance for infrared single photon detection, combining high efficiency, low timing jitter, low dark count rates and high photon counting rates. Promising application areas for SNSPDs include quantum key distribution, space-to-ground communications and single photon remote sensing . SNSPDs are typically made with ultrathin niobium nitride (NbN) films with thickness 4 nm and a superconducting transition temperature above 9 K. NbN offers high performance in the near infrared but their sensitivity drops at wavelengths beyond 2 um. There is growing interest in potential photon counting applications in the mid infrared domain (for example remote sensing of greenhouse gases in the atmosphere ). One way to overcome the wavelength limit in NbN SNSPDs is to use films with a lower superconducting energy gap . Here we report on the study of SNSPDs fabricated with thin films of titanium nitride (TiN). We compare TiN films deposited by atomic layer deposition (ALD) and by magnetron sputtering. The TiN films range in thickness from 5 to 60 nm, with superconducting transition temperatures from ~1 K to 3.5 K. We have analyzed the films via transmission electron microscopy and variable angle spectroscopic ellipsometry. We characterize TiN SNSPDs performance from near to mid-infrared at wavelengths (1-4 um) with fast optical parametric oscillator (OPO) source. We compare the performance of TiN SNSPDs to devices based on other lower gap materials: MoSi, NbTiN, WSi.
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Dmitry Morozov, Archan Banerjee, Kleanthis Erotokritou, Gregor Taylor, Nathan R. Gemmell, Dilini Hemakumara, Iain Thayne, and Robert H. Hadfield, "Superconducting nanowire materials for mid infrared single photon detection (Conference Presentation)," Proc. SPIE 10659, Advanced Photon Counting Techniques XII, 106590G (Presented at SPIE Commercial + Scientific Sensing and Imaging: April 19, 2018; Published: 14 May 2018); https://doi.org/10.1117/12.2306980.5783313377001.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon