Journal Article

PUBDB-2025-02182

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Influence of an Al$_2$O$_3$ Capping Layer on the Thermal Reduction of the NativeNiobium Oxide: An In situ X-ray Reflectivity Study

Zaidman, A. (Corresponding author)Extern* ; Vonk, V.XFEL.EU*DESY* ; Deyu, G. K.Extern* ; Zierold, R.Extern* ; Blick, R.Extern* ; Wenskat, M.DESY* ; Hillert, W.CFEL*Extern* ; Stierle, A.XFEL.EU*DESY*

2025
APS College Park, MD

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Please use a persistent id in citations: doi:10.1103/48mp-wypj  doi:10.3204/PUBDB-2025-02182

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.

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Contributing Institute(s):

1. Nanolab (FS-NL)
2. Uni Hamburg / Experimentalphysik (UNI/EXP)
3. Supraleitende Beschleuniger Technologie (MSL)
4. Institute of Nanostructure and Solid State Physics (UNI-INF)

Research Program(s):

1. 632 - Materials – Quantum, Complex and Functional Materials (POF4-632) (POF4-632)
2. 05H21GURB2 - Verbundprojekt 05H2021 - R&D BESCHLEUNIGER (TOSCA): Neue Ansätze zur Messung und Modellierung der Oberflächeneigenschaften supraleitender Resonatoren (BMBF-05H21GURB2) (BMBF-05H21GURB2)
3. 05K22GUD - Verbundprojekt 05K2022 - NOVALIS: Innovative Beschleunigertechnologien für effiziente Strahlungsquellen. Teilprojekt 1. (BMBF-05K22GUD) (BMBF-05K22GUD)

Experiment(s):

1. DESY NanoLab: X-Ray Diffraction
2. DESY NanoLab: Microscopy
3. DESY NanoLab: Sample Preparation

Appears in the scientific report 2025

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Database coverage:
; ; ; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; Essential Science Indicators ; IF < 5 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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