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Superconducting properties of Nb$_{0.85}$Sc$_{0.15}$ film deposited by magnetron co-sputtering

T0 review · 1 major / 2 minor · reviewed 2026-06-28 · grok-4.3

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Pith's one-line read Nb0.85Sc0.15 films made by magnetron co-sputtering reach a superconducting transition temperature of 6.35 K.

desk verdict This is a straightforward experimental report on Nb-Sc thin films with concrete numbers, but the 15% Sc claim rests on Auger data that may not reflect bulk composition in 30 nm films. read the letter →

arxiv 2606.04956 v1 pith:LWQ7WZG6 submitted 2026-06-03 cond-mat.supr-con

Paul Berezhnoy , Anna Elistratova , Zakhar Enbaev , Mikhail Dryazgov , Alexander Mumlyakov , Oleg Solovyev , Mikael Geodakyan , Igor Trofimov
show 3 more authors
Vasily Stolyarov Alexander Korneev Michael Tarkhov
This is my paper · ORCID
classification cond-mat.supr-con
keywords NbScsuperconductorthinfilmmagnetronsputteringcriticaltemperaturecurrentdensityupperfieldcoherencelength
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

A co-sputtering process from separate niobium and scandium targets was used to deposit Nb1-xScx thin films with controlled composition. X-ray methods established film thickness, phase, and crystal structure, while Auger spectroscopy fixed the scandium fraction. Critical temperature measurements across samples identified a peak Tc of 6.35 K near 15 percent scandium. Microbridge transport data gave a critical current density of 2.5 MA per square centimeter, and perpendicular-field magnetometry supplied the upper critical field, diffusion coefficient, and coherence length. The alloy is presented as a candidate material for cryogenic electronics components.

What carries the argument

Magnetron co-sputtering from separate Nb and Sc targets that controls scandium fraction in the deposited Nb1-xScx film.

What would settle it

An independent bulk composition measurement on the same 6.35 K sample that finds a scandium fraction significantly different from 15 percent would falsify the reported composition optimum.

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Extended reading notes

Core claim

The Nb0.85Sc0.15 film achieves a maximum critical temperature Tc of 6.35 K; microbridge measurements yield a critical current density of 2.5 MA/cm² while magnetic measurements give Hc2(0) = 3.2 T, D = 1.1 cm²/s, and ξGL = 10.1 nm.

Load-bearing premise

The scandium concentration measured by Auger spectroscopy accurately reflects the bulk film composition that determines the superconducting transition temperature.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

1 major / 2 minor

Summary. The manuscript reports the synthesis of Nb_{1-x}Sc_x thin films by magnetron co-sputtering from separate Nb and Sc targets, followed by structural characterization (XRD, XRR) and superconducting transport/magnetic measurements on 30 nm microbridges. The central experimental result is a maximum Tc of 6.35 K at ~15 at.% Sc (determined by Auger spectroscopy), together with Jc up to 2.5 MA/cm², Hc2(0) = 3.2 T, D = 1.1 cm²/s and ξ_GL = 10.1 nm; the material is presented as promising for cryogenic electronics.

Significance. If the composition-Tc correlation is reliable, the work adds an experimental data point on Nb-based alloy films with moderately enhanced Tc and usable critical current density. The measurements employ standard techniques (four-probe transport, magnetoresistance, perpendicular-field magnetization) and report concrete numbers that could be useful for device design, but the absence of bulk-composition verification limits the strength of the composition-dependent claim.

major comments (1)
  1. [Abstract] Abstract: The headline claim that Tc reaches its maximum (6.35 K) specifically at ~15 % Sc rests entirely on Auger spectroscopy. Auger is surface-sensitive (typical probe depth 1–5 nm) while the microbridge films are 30 nm thick; the text provides no Ar-ion depth profiling, calibration against bulk standards (RBS/EDS), or cross-check with XRD lattice parameters. If surface segregation or oxidation is present, the reported concentration does not correspond to the volume-averaged composition that sets Tc, rendering the Tc-vs-x curve and the “optimal 15 %” statement unsupported.
minor comments (2)
  1. [Abstract] Abstract: Typo “concentarions” should read “concentrations”.
  2. [Abstract] Abstract: The statement that “the technology has been developed” is vague; a brief description of the co-sputtering power ratios or deposition rates used to achieve the different Sc contents would improve reproducibility.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful review and constructive feedback on our manuscript. We address the single major comment below.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The headline claim that Tc reaches its maximum (6.35 K) specifically at ~15 % Sc rests entirely on Auger spectroscopy. Auger is surface-sensitive (typical probe depth 1–5 nm) while the microbridge films are 30 nm thick; the text provides no Ar-ion depth profiling, calibration against bulk standards (RBS/EDS), or cross-check with XRD lattice parameters. If surface segregation or oxidation is present, the reported concentration does not correspond to the volume-averaged composition that sets Tc, rendering the Tc-vs-x curve and the “optimal 15 %” statement unsupported.

    Authors: We agree that Auger spectroscopy is surface-sensitive (probe depth typically 1-5 nm) and that the manuscript does not report Ar-ion depth profiling, RBS/EDS calibration, or explicit cross-checks with XRD lattice parameters. The reported ~15 at.% Sc value is therefore based on surface measurements, and the possibility of segregation or oxidation affecting the volume-averaged composition cannot be ruled out from the presented data. In the revised version we will (i) qualify the abstract statement to read that the maximum Tc of 6.35 K was observed for the sample whose surface composition (by AES) was approximately 15 at.% Sc, (ii) add a brief methods paragraph noting the surface sensitivity of AES and the assumption of uniform composition supported by XRR/XRD, and (iii) explicitly state that bulk-sensitive verification would strengthen the composition-Tc correlation. These changes make the limitation transparent without altering the experimental results. revision: yes

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity: purely experimental report

full rationale

The manuscript is a standard experimental materials report describing film deposition by co-sputtering, structural characterization by XRD/XRR, composition via Auger spectroscopy, and direct transport/magnetic measurements of Tc, Jc, Hc2, D, and ξGL. No equations, models, or derivations are presented; reported quantities are measured values or standard conversions from raw data, with no fitted parameters renamed as predictions and no self-citation chains invoked to justify results. The composition-Tc link rests on experimental measurement rather than any definitional or self-referential reduction.

Assumptions & free parameters 0 free parameters · 0 assumptions · 0 invented entities

No theoretical model or derivation is present; all results are direct experimental measurements.

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Cite this review

Pith. "Pith review of Superconducting properties of Nb$_{0.85}$Sc$_{0.15}$ film deposited by magnetron co-sputtering." pith.science (2026). https://pith.science/paper/LWQ7WZG6

@misc{pith2026260604956,
  author       = {Pith},
  title        = {Pith review of: Superconducting properties of Nb$_0.85$Sc$_0.15$ film deposited by magnetron co-sputtering},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/LWQ7WZG6}},
  note         = {Machine review of arXiv:2606.04956}
}
abstract

The technology has been developed for synthesizing Nb$_{1-x}$Sc$_x$ films using magnetron co-sputtering from Nb and Sc targets. The material synthesis was accompanied by structural characterization using X-ray diffraction and X-ray reflectometry methods, which enabled the determination of thickness, phase composition and crystal structure. We also analyzed the superconducting properties. The critical temperature $T_c$ was measured for samples with different concentarions of Sc and Nb. The maximum value of $T_c$ equal to 6.35 K was observed for sample with a scandium content of approximately 15 %, which was determined by Auger spectroscopy. Transport and magnetoresistive measurements were performed in microbridges with length of 50 $\mu$m, width of 2 $\mu$m, and thickness of 30 nm. The critical current density was as high as 2.5 $\text{ MA/cm}^{2}$. Magnetic measurements were performed with the field oriented perpendicular to the sample. The upper critical field $H_{c2}(0) = 3.2$ T, electron diffusion coefficient $D = 1.1$ $\text{cm}^{2}/s$, and coherence length $\xi_{GL} = 10.1$ nm. The synthesized Nb$_{1-x}$Sc$_x$ intermetallic compound shows promise for various functional cryogenic electronics devices. \keywords{NbSc; superconductor; microbridge}

Figures

Figures reproduced from arXiv: 2606.04956 by the authors.

Figure 1
Figure 1. (a) Optical photography of plasma during co-sputtering of Nb and Sc targets. (b) Schematic illustration of [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. The fabrication process flow of microbridge structures based on NbSc. [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. XRR curves registered from the edge (blue curve) and center of the wafer using 10 mm (green curve) and 2 mm [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figures from the paper (5 more)
Figure 4
Figure 4. Figure 4: (a) Diffractograms of the Nb0.85Sc0.15 film at ω = 0.4 ◦ /0.6 ◦ /0.8 ◦ /1.0 ◦ /1.2 ◦ with the inset demonstrating the shift in (110) reflection position. (b) Diffractogram of the scandium film at ω = 1◦ . Vertical blue lines mark the positions of α-Sc phase reflections…
Figure 5
Figure 5. Figure 5: (a) Distribution of sheet resistance across the wafer.(b) Optical photography of the wafer with microbridge [PITH_FULL_IMAGE:figures/full_fig_p006_5.png]
Figure 6
Figure 6. Figure 6: (a) Temperature dependence of the sample resistance in the range of 300 K to 2.7 K. (b) Temperature dependence [PITH_FULL_IMAGE:figures/full_fig_p006_6.png]
Figure 7
Figure 7. Figure 7: (a) Current-voltage characteristic of the Nb [PITH_FULL_IMAGE:figures/full_fig_p007_7.png]
Figure 8
Figure 8. Figure 8: (a) Temperature dependences of the resistance of the Nb [PITH_FULL_IMAGE:figures/full_fig_p007_8.png]

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