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@ARTICLE{Zaidman:632415,
      author       = {Zaidman, Artem and Vonk, Vedran and Deyu, Getnet Kacha and
                      Zierold, Robert and Blick, Robert and Wenskat, Marc and
                      Hillert, Wolfgang and Stierle, Andreas},
      title        = {{I}nfluence of an {A}l$_2${O}$_3$ {C}apping {L}ayer on the
                      {T}hermal {R}eduction of the {N}ative{N}iobium {O}xide: {A}n
                      {I}n situ {X}-ray {R}eflectivity {S}tudy},
      journal      = {Physical review materials},
      volume       = {9},
      number       = {9},
      issn         = {2475-9953},
      address      = {College Park, MD},
      publisher    = {APS},
      reportid     = {PUBDB-2025-02182},
      pages        = {094806},
      year         = {2025},
      abstract     = {Superconducting radio-frequency cavities, critical
                      components of modern particle accelerators andquantum
                      computing hardware, rely fundamentally on the surface
                      properties of niobium. However,native oxide formation and
                      impurity uptake in the near-surface region can degrade
                      superconductingperformance and increase RF losses during
                      operation. In this study, we present a systematic in
                      situX-ray reflectivity investigation of (110) niobium single
                      crystal surfaces with and without an atomiclayer deposited
                      Al$_2$O$_3$ capping layer under ultra-high vacuum conditions
                      up to 650 °C. Our resultsreveal a temperature-dependent
                      reduction of the native niobium oxide layers in both capped
                      anduncapped samples, with similarities in the overall
                      behavior but clear differences in the reductionpathways. The
                      Al$_2$O$_3$ capping layer modifies the reduction process,
                      prevents oxide regrowth uponair exposure, and protects the
                      niobium surface against impurity uptake during thermal
                      treatment.These findings demonstrate that Al$_2$O$_3$
                      capping is an effective strategy to suppress native
                      oxideformation during thermal cycling, offering clear
                      benefits for the performance and operational lifetimeof
                      superconducting radio-frequency cavities and related quantum
                      computing technologies.},
      cin          = {FS-NL / UNI/EXP / MSL / UNI-INF},
      ddc          = {530},
      cid          = {I:(DE-H253)FS-NL-20120731 / $I:(DE-H253)UNI_EXP-20120731$ /
                      I:(DE-H253)MSL-20170609 / I:(DE-H253)UNI-INF-20151110},
      pnm          = {632 - Materials – Quantum, Complex and Functional
                      Materials (POF4-632) / 05H21GURB2 - Verbundprojekt 05H2021 -
                      $R\&D$ BESCHLEUNIGER (TOSCA): Neue Ansätze zur Messung und
                      Modellierung der Oberflächeneigenschaften supraleitender
                      Resonatoren (BMBF-05H21GURB2) / 05K22GUD - Verbundprojekt
                      05K2022 - NOVALIS: Innovative Beschleunigertechnologien für
                      effiziente Strahlungsquellen. Teilprojekt 1.
                      (BMBF-05K22GUD)},
      pid          = {G:(DE-HGF)POF4-632 / G:(DE-Ds200)BMBF-05H21GURB2 /
                      G:(DE-Ds200)BMBF-05K22GUD},
      experiment   = {EXP:(DE-H253)Nanolab-03-20150101 /
                      EXP:(DE-H253)Nanolab-04-20150101 /
                      EXP:(DE-H253)Nanolab-01-20150101},
      typ          = {PUB:(DE-HGF)16},
      doi          = {10.1103/48mp-wypj},
      url          = {https://bib-pubdb1.desy.de/record/632415},
}