Broadening of hot-spot response spectrum of superconducting NbN nanowire single-photon detector with reduced nitrogen content

Henrich, D.; Dörner, Simon; Hofherr, M.; Ilin, K.; Semenov, A. D.; Heintze, Eric; Scheffler, Marc; Dressel, Martin; Siegel, M.

doi:10.1063/1.4757625

Cited by 51 publications

(52 citation statements)

References 43 publications

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“…The limit for I b is an experimentally measured I c which in turn cannot exceed the depairing critical current I c,dep . It has been shown experimentally that E min decreases with an increase of the ratio of I c /I c,dep , which has been adjusted by a variation of the stoichiometry of thin NbN films [25]. Therefore, the knowledge of the nature of the experimentally measured critical current is essential for device optimization.…”

Section: Stationary State Of Snspdmentioning

confidence: 99%

Detection mechanism of superconducting nanowire single-photon detectors

Engel¹,

Renema²,

Ilin³

et al. 2015

Supercond. Sci. Technol.

143

111

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Abstract. In this paper we intend to give a comprehensive description of the current understanding of the detection mechanism in superconducting nanowire singlephoton detectors. We will review key experimental results related to the detection mechanism, e.g. the variations of the detection probability as a function of bias current, temperature or magnetic field. Commonly used detection models will be introduced and we will analyze their predictions in view of the experimental observations. Although none of the proposed detection models is able to describe all experimental data, it is becoming increasingly clear that vortices are essential for the formation of the initial normal-conducting domain that triggers a detection event.

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Section: Stationary State Of Snspdmentioning

confidence: 99%

Detection mechanism of superconducting nanowire single-photon detectors

Engel¹,

Renema²,

Ilin³

et al. 2015

Supercond. Sci. Technol.

143

111

View full text Add to dashboard Cite

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“…A detailed description of the deposition process of NbN thin films can be found elsewhere [14]. We have chosen two designs of spirals for our experiment: normal spiral or Archimedean spiral (Fig.…”

Section: Technology and Experimental Detailsmentioning

confidence: 99%

“…where K(t) = 0.66×(3-t 5 ) 0.5 is the analytical presentation of the correction [17], R S = 300 Ω is the square resistance of our films at 20 K, D = 5·10 -5 m 2 s -1 is the typical diffusivity of normal electrons in our films [14,18], β 0 = 2.05 is the ratio of the energy gap at zero temperature to k B T C [19], w is the width of strip in the spiral structure. For the square spiral with w = 110 nm and T C = 11.8 K, we obtained a depairing critical current of 129 µA at T = 4.2 K.…”

Section: A Critical Current In Magnetic Fieldmentioning

confidence: 99%

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Asymmetry in the effect of magnetic field on photon detection and dark counts in bended nanostrips

et al. 2015

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Keywords: bended superconducting nanostrips, current crowding, photon detection, dark counts, magnetic field asymmetry PACS number(s): 74.25. Ha, 85.25.Oj, 78.67.Uh Current crowding in the bends of superconducting nano-structures not only restricts measurable critical current in such structures but also redistributes local probabilities for dark and light counts to appear. Using structures from strips in the form of a square spiral which contain bends with the very same curvature with respect to the directions of bias current and external magnetic field, we have shown that dark counts as well as light counts at small photon energies originate from areas around the bends. The minimum in the rate of dark counts reproduces the asymmetry of the maximum critical current density as function of the magnetic field. Contrary, the minimum in the rate of light counts demonstrate opposite asymmetry. The rate of light counts become symmetric at large currents and fields. Comparing locally computed absorption probabilities for photons and the simulated threshold detection current we found the approximate locations of areas near bends which deliver asymmetric light counts. Any asymmetry is absent in Archimedean spiral structures without bends.2

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“…NbN films were deposited onto different substrates under varying conditions in order to find the most suitable NbN film parameters [6][7][8]. For detectors with optimized stoichiometry [9], the superconducting transition temperature T c varies from 10 to 11 K. Other Nb-based materials have also been considered [10]. NbTiN has a slightly smaller T c as compared to NbN (T c of NbTiN is 1 K lower than T c of NbN) at film thickness d < 20 nm, but it does not require such high substrate temperatures to grow epitaxial films.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of superconducting tungsten silicide WxSi1−x for single photon detection

et al. 2016

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Superconducting properties of three series of amorphous W x Si 1x films with different thickness and stoichiometry were investigated by dc transport measurements in a magnetic field up to 9 T. These amorphous W x Si 1x films were deposited by magnetron cosputtering of the elemental source targets onto silicon substrates at room temperature and patterned in the form of bridges by optical lithography and reactive ion etching. Analysis of the data on magnetoconductivity allowed us to extract the critical temperatures, superconducting coherence lengths, magnetic penetration depths, and diffusion constants of electrons in the normal state as functions of film thickness for each stoichiometry. Two basic time constants were derived from transport and time-resolving measurements. A dynamic process of the formation of a hotspot was analyzed in the framework of a diffusion-based vortex-entry model. We used a two-stage diffusion approach and defined a hotspot size by assuming that the quasiparticles and normal-state electrons have the same diffusion constant. With this definition and these measured material parameters, the hotspot in the 5-nm-thick W 0.85 Si 0.15 film had a diameter of 107 nm at the peak of the number of nonequilibrium quasiparticles. Superconducting properties of three series of amorphous W x Si 1−x films with different thickness and stoichiometry were investigated by dc transport measurements in a magnetic field up to 9 T. These amorphous W x Si 1−x films were deposited by magnetron cosputtering of the elemental source targets onto silicon substrates at room temperature and patterned in the form of bridges by optical lithography and reactive ion etching. Analysis of the data on magnetoconductivity allowed us to extract the critical temperatures, superconducting coherence lengths, magnetic penetration depths, and diffusion constants of electrons in the normal state as functions of film thickness for each stoichiometry. Two basic time constants were derived from transport and time-resolving measurements. A dynamic process of the formation of a hotspot was analyzed in the framework of a diffusion-based vortex-entry model. We used a two-stage diffusion approach and defined a hotspot size by assuming that the quasiparticles and normal-state electrons have the same diffusion constant. With this definition and these measured material parameters, the hotspot in the 5-nm-thick W 0.85 Si 0.15 film had a diameter of 107 nm at the peak of the number of nonequilibrium quasiparticles.

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Broadening of hot-spot response spectrum of superconducting NbN nanowire single-photon detector with reduced nitrogen content

Cited by 51 publications

References 43 publications

Detection mechanism of superconducting nanowire single-photon detectors

Detection mechanism of superconducting nanowire single-photon detectors

Asymmetry in the effect of magnetic field on photon detection and dark counts in bended nanostrips

Characteristics of superconducting tungsten silicide WxSi1−x for single photon detection

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