Single photon detection at visible and x-ray wavelengths with Nb–Al superconducting tunnel junctions

Verhoeve, P.; Rando, N.; Peacock, A.; Dordrecht, A. van; Poelaert, A.; Goldie, D. J.; Venn, R.

doi:10.1063/1.367481

Cited by 21 publications

(25 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[254][255][256] In Sec. III C we consider photon-number resolving detectors such as the transition-edge sensor (TES), 257 superconducting-tunnel-junction (STJ) detector, [258][259][260][261] parallel superconducting nanowire single-photon detector (P-SNSPD), 262 charge-integration photon detector (CIPD), 263 visible-light photon counter (VLPC), 113,264 quantum-dot optically gated field-effect transistor (QDOGFET), 265 timemultiplexed SPAD, 266 SPAD array, and the recently reported number-resolving capability of a detector based on a single SPAD. 267 The characteristics of examples of many of these detectors are compiled in Table II for ease of comparison.…”

Section: A Characteristics Of An Ideal Single-photon Detectormentioning

confidence: 99%

Invited Review Article: Single-photon sources and detectors

Eisaman

Fan²,

Migdall³

et al. 2011

Review of Scientific Instruments

1,330

1,317

View full text Add to dashboard Cite

show abstract

Section: A Characteristics Of An Ideal Single-photon Detectormentioning

confidence: 99%

Invited Review Article: Single-photon sources and detectors

Eisaman

Fan²,

Migdall³

et al. 2011

Review of Scientific Instruments

1,330

1,317

View full text Add to dashboard Cite

show abstract

“…Especially, the performance of existing devices is still difficult to predict when the proximity effect plays a significant role. In particular, a significant difference in junction behaviour has been observed when irradiated by x-rays, as opposed to optical photons ( [20]). Note while the trend in X-ray responsivity reflects the generally increasing role of quasiparticle self-recombination with increasing photon energies, the details of this response have been difficult to model using existing theories.…”

Section: Applicationmentioning

confidence: 99%

“…Such devices used as photon detectors have produced good results in terms of energy resolution, charge output and quantum efficiency, for photon energies from the near infrared to X-rays [15]- [20]. The most important results currently achieved can be summarised as follows: Ta/Al junctions provide a typical response of up to 10 5 electrons per eV of the detected photon, at a temperature of 300 to 400 mK; the associated measured energy resolution is within a few percents of the predicted theoretical limit; the quantum efficiency at UV wavelengths is about 60%; the longest wavelength detected is currently 2µm, with the possibility to extend this limit to 10µm; the same junctions operate also at x-ray energies as high as 6 keV, with a quantum efficiency of about 10% and an energy resolution of about 40 eV FWHM.…”

Section: Applicationmentioning

confidence: 99%

Generalized proximity effect model in superconducting bi- and trilayer films

Brammertz

Poelaert

Golubov

et al. 2001

Journal of Applied Physics

Self Cite

View full text Add to dashboard Cite

This paper presents a general model for calculating the density of states and the Cooper pair potential in proximised superconducting bi-and trilayer films. It is valid for any kind of bilayer S 1 -S 2 , whatever the quality of the materials S 1 and S 2 , the quality of the S 1 -S 2 interface and the layer thicknesses. The trilayer model is valid for a thin S 3 layer, whereas the other two layers have arbitrary thicknesses. Although the equations of the dirty limit are used, it is argued that the model stays valid in clean bi-and trilayer films. The typical example of superconducting tunnel junctions is used to show that existing models, applying to very thin or very thick layers, or to perfectly transparent S 1 -S 2 interfaces, are too restrictive to apply to any bilayer. The new model is applied to existing junctions, with layer thicknesses intermediate between the 'thick' and the 'thin' approximation. 1 I INTRODUCTIONUnderstanding the proximity effect in superconducting films is important for the development of practical devices such as superconducting tunnel junctions (STJ's). Depositing a superconductor S 1 onto another S 2 modifies the properties of both S 1 and S 2 materials. If both superconductors are thick enough (typically thicker than 10 ξ S 1 (S 2 ) , with ξ S 1 (S 2 ) the coherence length of S 1 (S 2 )), the extremities of the bilayer behave as bulk materials obeying the BCS theory, though not necessarily like bulk S 1 and bulk S 2 . The intermediate region around the S 1 -S 2 interface is characterised by a relatively sharp transition between the two bulk-like regions, and can be pretty far from a BCS-like description. If the layers are relatively thin, any BCS-like behaviour can be absent from the structure. Finally, in the case where the layers are extremely thin, as described by McMillan [1], each layer behaves again like a BCS superconductor.The physical quantities affected in a proximised bulk superconductor, are the Cooper pair potential ∆, the density of states for the Cooper pairs, P , and the density of states for the quasiparticles, N. As the density of states in both superconductors is modified due to the proximity effect, the resultant bandgap ∆ g lies at an intermediate value between the bulk values for S 1 and S 2 , ∆ g,S 1 and ∆ g,S 2 respectively. This feature has been fully described in the specific case, of a thin, low bandgap material S 2 next to a thick, high bandgap material S 1 , with both superconductors in the dirty limit [2,3].The goal of the present paper is to present the need for, and develop a model of, the proximity effect, which is not restricted to this very specific case.In particular section V shows that there are many situations where this special case does not apply, and for which the simple BCS approach does not provide a satisfactory description.Specifically, in the case of STJ's used as photon detectors, a more general description of the proximity effect is required to adequately address such issues as device performance.The general conditions for an ...

show abstract

“…Another interesting feature observed is that the charge output ratio between the peaks of the K β and K α lines Q Kβ /Q Kα is equal to 1.12, instead of the energy ratio of the two lines E Kβ /E Kα , which is 1.10. In Nb and Ta based STJs this charge output ratio is usually lower or equal to 1.10 [3][4][5] because of non-linear QP self-recombination effects, which enhance losses at higher QP densities [6]. Our V/Al junctions are thus not limited by QP self-recombination despite the high densities we are dealing with.…”

mentioning

confidence: 93%

“…One can see that the base material was not completely etched through everywhere and that 8 junctions in the lower half of the array are still interconnected via this residual base material. The devices were operated at 300 mK in a 3 He cryostat, where IV curves and spectra can be acquired. The junctions presented here are low leakage junctions, although a small residual leakage is still present.…”

mentioning

confidence: 99%

Strong quasiparticle trapping In A 6×6 array of vanadium-aluminum superconducting tunnel junctions

Brammertz

Peacock

Verhoeve

et al. 2002

AIP Conference Proceedings

Self Cite

View full text Add to dashboard Cite

Abstract.A 6x6 array of symmetrical V/Al/AlOx/Al/V Superconducting Tunnel Junctions (STJs) was fabricated. The base electrode is a high quality epitaxial film with a residual resistance ratio (RRR) of ~30. The top film is polycrystalline with an RRR of ~10. The leakage currents of the 25x25 µm 2 junctions are of the order of 0.5 pA/µm 2 at a bias voltage of 100 µV, which corresponds to a dynamical resistance of ~ 3 10 5 Ω. When the array was illuminated by 6 keV X-ray photons from a 55 Fe radioactive source the single photon charge output was found to be low and strongly dependent on the temperature of the devices. This temperature dependence at X-ray energies can be explained by the existence of a very large number of quasiparticle (QP) traps in the Vanadium. QPs are confined in these traps, having a lower energy gap than the surrounding material, and are therefore not available for tunneling. The number of traps can be derived from the energy dependence of the responsivity of the devices (charge output per electron volt of photon input energy).As a process-route precursor to the fabrication of low T c STJs based on Mo and Al for use as optical to X-ray detectors in Astronomy, V-Al-AlOx-Al-V STJs were produced. Their characteristics from a film quality, leakage and spectral performance point of view are presented in this paper.The multilayer is deposited on a sapphire substrate without breaking vacuum. First a 100 nm thick epitaxial V film is sputtered at 550 o C in an UHV chamber. After cooling the sample a 30 nm thick Al film is deposited on top of the base V. 10 Å of Al are then oxidized to form the AlOx barrier of the junction. On top of this barrier another 30 nm of Al and 100 nm of V is deposited. The trilayer wafer then is removed from the UHV chamber and a ~7 nm thick VOx film naturally forms on top of the multilayer. Figure 1a shows a TEM image of the multilayer.Despite considerable lattice mismatch between the substrate and the V film, TEM has shown the base electrode to comprise an epitaxial film with a residual resistance ratio ρ 293K /ρ 10K (RRR) of ~30, as opposed to the top film which is polycrystalline with an RRR of ~10. This corresponds to a mean free path λ 10K in the base V of ~120 nm and a normal state diffusion constant D 10K of ~60 cm 2 /sec. The polycrystalline top film has a 3 times lower mean free path and diffusion constant. The junction's geometry is defined by using a photolithographical etching mask. Two different mask layouts are

show abstract

Single photon detection at visible and x-ray wavelengths with Nb–Al superconducting tunnel junctions

Cited by 21 publications

References 22 publications

Invited Review Article: Single-photon sources and detectors

Invited Review Article: Single-photon sources and detectors

Generalized proximity effect model in superconducting bi- and trilayer films

Strong quasiparticle trapping In A 6×6 array of vanadium-aluminum superconducting tunnel junctions

Contact Info

Product

Resources

About