Magnetoconductance and photoresponse properties of disordered NbTiN films

Sidorova, Mariia; Semenov, A. D.; Hübers, Heinz‐Wilhelm; Gyger, Samuel; Steinhauer, Stephan; Zhang, Xiaofu; Schilling, Andreas

doi:10.1103/physrevb.104.184514

Cited by 15 publications

(32 citation statements)

References 54 publications

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“…These values correspond to the estimated parameters ξ ≈ 5.7 nm and λ ≈ 600 nm for T ≈ 2 K. Extrapolation to T = 0 using BCS theory gives ξ(0) ≈ 5.1 nm and λ(0) ≈ 550 nm [17]. These are consistent with previously reported values for NbTiN films [27,28]. The assumed magnetic offset B off moves the simulation data peak curve slightly closer to zero magnetic field and is needed for a good fit.…”

Section: A Critical Current Dependency On Applied Magnetic Fieldsupporting

confidence: 90%

Current crowding in nanoscale superconductors within the Ginzburg-Landau model

Jönsson¹,

Vedin²,

Gyger³

et al. 2021

Preprint

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The current density in a superconductor with turnarounds or constrictions is non-uniform due to a geometrical current crowding effect. This effect reduces the critical current in the superconducting structure compared to a straight segment and is of importance when designing superconducting devices. We investigate the current crowding effect in numerical simulations within the generalized time-dependent Ginzburg-Landau (GTDGL) model. The results are validated experimentally by measuring the magnetic field dependence of the critical current in superconducting nanowire structures, similar to those employed in single-photon detector devices. Comparing the results with London theory, we conclude that the reduction in critical current is significantly smaller in the GTDGL model. This difference is attributed to the current redistribution effect, which reduces the current density in weak points of the superconductor and counteracts the current crowding effect. We numerically investigate the effect of fill factor on the critical current in a meander and conclude that the reduction of critical current is low enough to justify fill factors higher than 33 % for applications where detection efficiency is critical. Finally, we propose a novel meander design which can combine high fill factor and low current crowding.

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Section: A Critical Current Dependency On Applied Magnetic Fieldsupporting

confidence: 90%

Current crowding in nanoscale superconductors within the Ginzburg-Landau model

Jönsson¹,

Vedin²,

Gyger³

et al. 2021

Preprint

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show abstract

“…The strips were fabricated from two NbTiN films with thicknesses 6 and 9 nm, which were studied earlier in [13]. The films were deposited on Si substrates on top of a 270 nm-thick thermally-grown SiO 2 layer.…”

Section: Experiments and Resultsmentioning

confidence: 99%

“…The value of T C was used as a fitting parameter in order to account for an expected reduction of the transition temperature in nanostructures as compared to non-structured films [26]. The best-fit values of T C listed in Table I are indeed slightly smaller than those of non-structured films (8.41 and 9.51 K for films with thicknesses 6 and 9 nm, respectively [13]). At the bath temperature of 3 K, the ratios I C /I dep for our strips are 0.56 (d = 6 nm) and 0.63 (d = 9 nm).…”

Section: Experiments and Resultsmentioning

confidence: 99%

“…TABLE I. Parameters of the NbTiN strips studied here. Electron and phonon heat capacities and the electron-phonon energy relaxation times at the transition temperatures (TC ) of the strips were obtained via extrapolation of corresponding values of non-structured films [13] according to ce ∝ T (Drude model), c ph ∝ T 3 (Debye model) and τEP ∝ T −n , respectively. The values of the exponent n were reported in [13].…”

Section: Experiments and Resultsmentioning

confidence: 99%

“…We have recently reported [12,13] a reduction of phonon heat capacities in thin polycrystalline granular films at low temperatures that was attributed to the effect of the mean grain size. This result was derived from extensive studies of the magnetoconductance and photoresponse of thin NbTiN, NbN, and WSi films.…”

Section: Introductionmentioning

confidence: 97%

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Phonon heat capacity and self-heating normal domains in NbTiN nanostrips

Sidorova,

Semenov,

Huebers

et al. 2022

Preprint

Self Cite

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Self-heating normal domains in thin superconducting NbTiN nanostrips were characterized via steady-state hysteretic current-voltage characteristics measured at different substrate temperatures. The temperature dependence and the magnitude of the current, which sustains a domain in equilibrium at different voltages, can only be explained with a phonon heat capacity noticeably less than expected for 3-d Debye phonons. This reduced heat capacity coincides with the value obtained earlier from magnetoconductance and photoresponse studies of the same films. The rate of heat flow from electrons at a temperature Te to phonons in the substrate at a temperature TB is proportional to (T p e − T p B ) with the exponent p ≈ 3, which differs from the exponents for heat flows mediated by the electron-phonon interaction or by escaping of 3-d Debye phonons via the film/substrate interface. We attribute both findings to the effect of the mean grain size on the phonon spectrum of thin granular NbTiN films. Our findings are significant for understanding the thermal transport in superconducting devices exploiting thin granular films.

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Site‐Selective Enhancement of Superconducting Nanowire Single‐Photon Detectors via Local Helium Ion Irradiation

Strohauer,

Wietschorke,

Zugliani

et al. 2023

Adv Quantum Tech

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Achieving homogeneous performance metrics between nominally identical pixels is challenging for the operation of arrays of superconducting nanowire single‐photon detectors (SNSPDs). Here, local helium ion irradiation is utilized to post‐process and tune single‐photon detection efficiency, switching current, and critical temperature of individual devices on the same chip. For 12 nm thick highly absorptive SNSPDs, which are barely sensitive to single photons with a wavelength of 780 nm prior to He ion irradiation, an increase of the system detection efficiency from <0.05% to (55.3 1.1)% is observed following irradiation. Moreover, the internal detection efficiency saturates at a temperature of 4.5 K after irradiation with 1800 ions nm−2. Compared to 8 nm SNSPDs of similar detection efficiency, a doubling of the switching current (to 20 µA) is observed for irradiated 10 nm thick detectors, increasing the amplitude of detection voltage pulses. Investigations of the scaling of superconducting thin film properties with irradiation up to a fluence of 2600 ions nm−2 revealed an increase of sheet resistance and a decrease of critical temperature towards high fluences. A physical model accounting for defect generation and sputtering during helium ion irradiation is presented and shows good qualitative agreement with experiments.

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Magnetoconductance and photoresponse properties of disordered NbTiN films

Cited by 15 publications

References 54 publications

Current crowding in nanoscale superconductors within the Ginzburg-Landau model

Current crowding in nanoscale superconductors within the Ginzburg-Landau model

Phonon heat capacity and self-heating normal domains in NbTiN nanostrips

Site‐Selective Enhancement of Superconducting Nanowire Single‐Photon Detectors via Local Helium Ion Irradiation

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