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arXiv:2605.25597

Nitrogen-doped W0.75Re0.25 Superconducting Nanowire Single Photon Detectors

Francesco Colangelo, Abhishek Kumar, H. Wang, Francesco Avitabile, C. Attanasio, Iman Esmaeil Zadeh, C. Cirillo

Published May 25, 2026• 0 citations
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Abstract

Nitrogen-doped Tungsten-Rhenium superconducting alloys were recently proposed as a promising material platform for superconducting nanowire single-photon detectors (SNSPDs), offering a favorable balance between high normal state resistivity and tunable superconducting properties. In this work, we report on the fabrication and characterization of SNSPDs based on thin W0.75Re0.25 films deposited by reactive DC magnetron sputtering in a mixed Ar/N2 atmosphere. Meander detectors with 70 nm linewidth exhibit saturated internal detection efficiency (IDE) up to 1310 nm and 85.3% IDE at 1550 nm at 2.5 K, with sub-nanosecond rise times, decay times of the order of a few nanoseconds, and timing jitter of 73.2 ps measured with room temperature amplifiers.

DOI
10.48550/arxiv.2605.25597

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Nitrogen-doped Tungsten-Rhenium superconducting alloys were recently proposed as a promising material platform for superconducting nanowire single-photon detectors (SNSPDs), offering a favorable balance between high normal state resistivity and tunable superconducting properties. In this work, we report on the fabrication and characterization of SNSPDs based on thin W0.75Re0.25 films deposited by reactive DC magnetron sputtering in a mixed Ar/N2 atmosphere. Meander detectors with 70 nm linewidth exhibit saturated internal detection efficiency (IDE) up to 1310 nm and 85.3% IDE at 1550 nm at 2.5 K, with sub-nanosecond rise times, decay times of the order of a few nanoseconds, and timing jitter of 73.2 ps measured with room temperature amplifiers.
In this Letter, we characterized superconducting nanowire single-photon detectors (SNSPDs) based on amorphous tungsten germanide (W0.8Ge0.2) superconducting films, which exhibit superconducting properties comparable to those of amorphous WSi. The nanowire width ranges from 60 to 90 nm, with a fixed filling factor of 30%. All fabricated devices exhibit saturated intrinsic detection efficiency for infrared photons with wavelengths up to 2 μm, indicating that WGe is a promising candidate for SNSPDs designed for mid- and far-infrared photon detection. The timing jitter of these detectors, measured with a room-temperature amplifier, ranges from 127 to 234.5 ps. Further improvements can be achieved through device geometry optimization or the implementation of cryogenic amplifiers.
We report the fabrication of superconducting nanowire single-photon detector (SNSPD, SSPD) based on molybdenum nitride (MoN) film with and without a cavity structure. Ultrathin polycrystalline γ-Mo2N films with aTcabout 6 K were obtained by reactive DC magnetron sputtering. The absorption efficiency of the device was calculated by the finite-difference time-domain (FDTD) method using the optical constants of MoN determined by ellipsometry measurements. The SNSPD with a meander of 150-nm-width and 7-nm-thick nanowire showed a long saturation plateau in the bias current dependence of the system detection efficiency (SDE) at visible wavelength. The SNSPD with a cavity structure showed an SDE of 37% and a timing jitter of 79 ps at a wavelength of 1560 nm. The results show that MoN is a promising alternative to amorphous superconductors for high-performance SNSPD.
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Superconducting Nanowire Single Photon Detectors (SNSPDs) based on Nb0.15Re0.85 disordered nanowires are developed. The devices have a meander structure of wires 50–100 nm wide and cover a circular detection area with a diameter of about 10–16 μm. The main figures of merit of the detectors are extracted from a flood illumination process at 2.8 K, featuring a saturated internal efficiency up to λ= 1301 nm, recovery times between about 8 and 19 ns, and a jitter of about 35 ps. These results confirm that Nb0.15Re0.85 is a promising candidate for the realization of fast SNSPDs, as recently suggested.
The intrinsic detection performance of superconducting nanowire single photon detectors (SNSPDs) is highly dependent on the superconducting properties of underlying thin films. This report outlines the enhancement of detection performance for single telecom wavelength photons in disordered NbTiN SNSPD at 4.2 K. By increasing the nitrogen content and deposition pressure, the NbTiN films show suppression in critical temperature and an increase in sheet resistance. Notably, the resulting SNSPDs display a broader saturation plateau at 2.2 K, leading to superior detection performance at 4.2 K. With the disordered 7-nm-thick NbTiN films, we fabricated SNSPDs with system detection efficiency up to 83% for 1550 nm photons at 4.2 K. Moreover, these devices also show saturated intrinsic detection efficiency for 2000 nm photons. With the features outlined, the devices can be integrated into the idle 4.2 K stage of the dilution refrigerator for applications in optical quantum information processing or utilize for detecting laser radar signals in airborne platforms.
Superconducting nanowire single-photon detectors (SNSPDs) are among the most sensitive single-photon detectors available and have the potential to transform fields ranging from infrared astrophysics to molecular spectroscopy. However, extending their performance into the mid-infrared spectral region - crucial for applications such as exoplanet transit spectroscopy and vibrational fingerprinting of molecules - has remained a major challenge, primarily due to material limitations and scalability constraints. Here, we report on the development of SNSPDs based on tungsten germanide, a novel material system that combines high mid-infrared sensitivity with compatibility for large-scale fabrication. Our detectors exhibit saturated internal detection efficiency at wavelengths up to 29 μm, while using 2.7x thicker films (8 nm vs 3 nm) and up to 4.5x wider nanowires (360 nm vs 80 nm) compared to mid-infrared-optimized SNSPDs fabricated from tungsten silicide. This advance will enable scalable, high-performance single-photon detection in a spectral region that was previously inaccessible, opening new frontiers in remote sensing, thermal imaging, environmental monitoring, molecular physics, and astronomy.