CERN Accelerating science

Article
Title	HiPIMS deposition of superconducting Nb thin films onto Cu substrates
Author(s)	Leith, S (Siegen U. ; CERN) ; Qiao, J (Siegen U.) ; Vogel, M (Siegen U.) ; Seiler, E (Kosice, IEF) ; Ries, R (Kosice, IEF) ; Li, Y (Siegen U.) ; Wiktor, C (Siegen U.) ; Mueller, J (Siegen U.) ; Sakalli, Y (Siegen U.) ; Butz, B (Siegen U.) ; Jiang, X (Siegen U.) Show all 11 authors
Publication	2023
Number of pages	14
In:	Vacuum 212 (2023) 112041
DOI	10.1016/j.vacuum.2023.112041 (publication)
Subject category	Accelerators and Storage Rings
Abstract	The use of energetic condensation techniques, such as HiPIMS, has the potential to significantly improve the superconducting performance of coated Cu cavities by producing bulk-like Nb thin films. However, in order to benefit from these techniques, a deeper understanding of the effects of, and the relationship between, the different deposition parameters, the physical properties of the deposited films and the superconducting performance of the films, is still required. This contribution details the effects of different HiPIMS deposition parameters on the morphological, crystallographic and superconducting properties of Nb thin films deposited onto electropolished Cu substrates. Higher duty cycles (8 – 20 %) than previous HiPIMS investigations were used in the majority of the coatings. The films displayed more bulk-like crystallographic properties, indicated here by the lattice parameter, with a “transition zone” apparent in the early stages of film growth. A reduction in the surface roughness as well as interfacial voids, compared to typical DC MS Nb films, was also observed. The superconducting performance of the films, specifically the first magnetic flux entry field, showed a marked reliance on the substrate bias and the film thickness. Conversely, the HiPIMS duty cycle appears to have a comparatively insignificant effect. •Investigation of multiple HiPIMS coating parameters for the deposition of Nb thin films onto Cu substrates.•Predicted improved interface and surface roughness observed across all HiPIMS samples.•A morphological/crystallographic “transition zone” is observed between 1 and 2 μm film thickness.•Superconducting performance of Nb films directly linked to their crystallographic properties, i.e. lattice parameter and crystallite size.•HiPIMS duty cycle does not appear to influence the superconducting performance of Nb thin films.
Copyright/License	publication: © 2023-2025 The Authors (License: CC BY 4.0)

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