XPS studies of nitrogen doping niobium used for accelerator applications

Yang, Ziqin; Lu, Xiangyang; Tan, Weiwei; Zhao, Jun; Yang, Deyu; Yang, Yujia; He, Yuan; Zhou, Kui

doi:10.1016/j.apsusc.2017.12.214

Cited by 37 publications

(26 citation statements)

References 20 publications

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“…The sample irradiated in nitrogen atmosphere exhibits a very weak signal in the N 1s spectrum with a BE of approximately 400.0 eV (see Figure 5 ), thus discarding the presence of niobium nitrides, NbN x , which are expected to appear at lower binding energies (396.5 eV [ 39 ], 397.5 eV [ 40 ]). This is very similar to the results reported for nitrogen doped niobium [ 37 ], where the peak at 399.84 eV in the N 1s spectrum was attributed to the formation of CH 3 CN.…”

Section: Resultssupporting

confidence: 91%

“…The high resolution XPS spectra of niobium Nb 3d, plotted in Figure 4 , show very similar behavior for all samples, with the presence of the Nb 3d doublet at binding energies (BEs) of 209.80 and 207.05 eV, corresponding to Nb 2 O 5 , as the main chemical compound at the surface [ 35 , 36 , 37 ]. The peaks corresponding to metallic Nb, Nb 0 , are also observed in all samples except in the one processed in air, FS_air2.…”

Section: Resultsmentioning

confidence: 98%

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Surface Superconductivity Changes of Niobium Sheets by Femtosecond Laser-Induced Periodic Nanostructures

et al. 2020

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Irradiation with ultra-short (femtosecond) laser beams enables the generation of sub-wavelength laser-induced periodic surface structures (LIPSS) over large areas with controlled spatial periodicity, orientation, and depths affecting only a material layer on the sub-micrometer scale. This study reports on how fs-laser irradiation of commercially available Nb foil samples affects their superconducting behavior. DC magnetization and AC susceptibility measurements at cryogenic temperatures and with magnetic fields of different amplitude and orientation are thus analyzed and reported. This study pays special attention to the surface superconducting layer that persists above the upper critical magnetic field strength Hc2, and disappears at a higher nucleation field strength Hc3. Characteristic changes were distinguished between the surface properties of the laser-irradiated samples, as compared to the corresponding reference samples (non-irradiated). Clear correlations have been observed between the surface nanostructures and the nucleation field Hc3, which depends on the relative orientation of the magnetic field and the surface patterns developed by the laser irradiation.

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Section: Resultssupporting

confidence: 91%

Section: Resultsmentioning

confidence: 98%

Surface Superconductivity Changes of Niobium Sheets by Femtosecond Laser-Induced Periodic Nanostructures

et al. 2020

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“…2C, D. Nb 3d deconvolution shows doublets for Nb 3d 5/2 and Nb 3d 3/2 , at 206.4 eV and 209.1 eV, respectively. In agreement with FTIR and Raman results, it indicates that Nb is present in an oxidation state assigned to Nb 2 O 5 [15,16]. Also, O 1s deconvolution presents a major contribution (83 at.%) of the peak at 529.5 eV, assigned to Nb 2 O 5 [16].…”

Section: Resultssupporting

confidence: 86%

New insights of Nb2O5-based coatings on the 316L SS surfaces: enhanced biological responses

Moreto

Gelamo

Silva

et al. 2021

J Mater Sci: Mater Med

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This communication aims to propose new insights of Nb2O5-based coatings on the 316L SS surface with great prospects to be used in the dentistry field as brackets. The Nb2O5 thin film was incorporated into the 316L SS by using PVD method. For this purpose, the studied system was characterized structurally and morphologically by using AFM, FTIR-IRRAS, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Biological assays were performed using human gingival fibroblast cell-line HGF-1. In agreement with FTIR and Raman results, the XPS technique indicates that Nb is present in an oxidation state assigned to Nb2O5. Furthermore, the coatings produced by PVD technique are less toxic and induces less inflammation in gingival cells (cell-line HGF-1), suggesting the strategy of use Nb2O5 thin film to cover the 316L SS promoted since its protection of the physiological environment to its biocompatibility improvement.

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“…Such a nitrogen doping has been proven to be profitable for the superconducting properties of Nb in accelerating structures (see, for example, Grassellino et al, 2013;Gonnella & Liepe, 2014;Gonnella et al, 2015). Recent experiments have shown that extreme care has to be used for such a high-temperature processing of Nb cavity materials, and that, for example, traces of oxygen, carbon contaminations or remaining hydrogen from outgassing of the vacuum system may substantially alter the near-surface structure and thereby also the superconducting properties of heat-treated Nb materials (Yang et al, 2018(Yang et al, , 2019Dhakal et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…In particular for studies of processes employed for thermal treatments of superconducting RF cavities, contaminations such as oxide layers on the surfaces are not tolerable at all, as they substantially degrade the superconducting performance of the devices (see, for example, Malev & Weisser, 1995;Yang et al, 2018;Dhakal et al, 2018;Yang et al, 2019). All preparation steps and protocols have to be highly reliable, and any oxidation has to be avoided in the processing of cavity materials.…”

Section: Introductionmentioning

confidence: 99%

High-temperature treatments of niobium under high vacuum, dilute air- and nitrogen-atmospheres as investigated by in situ X-ray absorption spectroscopy

Klaes

Rothweiler

Bornmann

et al. 2021

J Synchrotron Radiat

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Niobium metal foils were heat-treated at 900°C under different conditions and in situ investigated with time-resolved X-ray absorption fine-structure (EXAFS and XANES) measurements. The present study aims to mimic the conditions usually applied for heat treatments of Nb materials used for superconducting radiofrequency cavities, in order to better understand the evolving processes during vacuum annealing as well as for heat treatments in controlled dilute gases. Annealing in vacuum in a commercially available cell showed a substantial amount of oxidation, so that a designated new cell was designed and realized, allowing treatments under clean high-vacuum conditions as well as under well controllable gas atmospheres. The experiments performed under vacuum demonstrated that the original structure of the Nb foils is preserved, while a detailed evaluation of the X-ray absorption fine-structure data acquired during treatments in dilute air atmospheres (10−5 mbar to 10−3 mbar) revealed a linear oxidation with the time of the treatment, and an oxidation rate proportional to the oxygen (air) pressure. The structure of the oxide appears to be very similar to that of polycrystalline NbO. The cell also permits controlled exposures to other reactive gases at elevated temperatures; here the Nb foils were exposed to dilute nitrogen atmospheres after a pre-conditioning of the studied Nb material for one hour under high-vacuum conditions, in order to imitate typical conditions used for nitrogen doping of cavity materials. Clear structural changes induced by the N2 exposure were found; however, no evidence for the formation of niobium nitride could be derived from the EXAFS and XANES experiments. The presented results establish the feasibility to study the structural changes of the Nb materials in situ during heat treatments in reactive gases with temporal resolution, which are important to better understand the underlaying mechanisms and the dynamics of phase formation during those heat treatments in more detail.

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XPS studies of nitrogen doping niobium used for accelerator applications

Cited by 37 publications

References 20 publications

Surface Superconductivity Changes of Niobium Sheets by Femtosecond Laser-Induced Periodic Nanostructures

Surface Superconductivity Changes of Niobium Sheets by Femtosecond Laser-Induced Periodic Nanostructures

New insights of Nb2O5-based coatings on the 316L SS surfaces: enhanced biological responses

High-temperature treatments of niobium under high vacuum, dilute air- and nitrogen-atmospheres as investigated by in situ X-ray absorption spectroscopy

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