Author: Blick, R.H.
Paper Title Page
MOPMB016 Successful Al₂O₃ Coating of Superconducting Niobium Cavities by Thermal ALD 104
 
  • G.K. Deyu, W. Hillert, M. Wenskat
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • R.H. Blick, I. González Díaz-Palacio, R. Zierold
    University of Hamburg, Hamburg, Germany
  
  Funding: This work is supported by the BMBF under the research Grant 05K19GUB.
Al₂O₃ is one of the po­ten­tial in­su­la­tor ma­te­ri­als in the su­per­con­duc­tor-in­su­la­tor-su­per­con­duc­tor (SIS) mul­ti­layer coat­ings of su­per­con­duct­ing ra­dio-fre­quency (SRF) cav­i­ties for push­ing their per­for­mance lim­its. We re­port on the suc­cess­ful coat­ing of two 1.3 GHz Tesla-shaped SRF cav­i­ties with 18 nm and 36 nm lay­ers of Al₂O₃ de­posited by ther­mal atomic layer de­po­si­tion (ALD). The coat­ing recipe was de­vel­oped by ther­mal atomic layer de­po­si­tion (ALD). The coat­ing recipe was op­ti­mized with re­spect to dif­fer­ent the ap­plied process pa­ra­me­ters such as ex­po­sure and purge times, sub­strate tem­per­a­ture and flow rates. After a proof-of-prin­ci­ple Al₂O₃ coat­ing of a cav­ity, sec­ond the cav­ity main­tained its max­i­mum achiev­able ac­cel­er­at­ing field of more than 40 MV/m and no de­te­ri­o­ra­tion was ob­served [1]. On the con­trary, an im­prove­ment of the sur­face re­sis­tance above 10 MV/m has been ob­served, which is now fur­ther under in­ves­ti­ga­tion.
[1].Wenskat, Marc, et al. "Successful Al₂O₃ coating of superconducting niobium cavities with thermal ALD." Superconductor Science and Technology 36.1 (2022): 015010. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB016  
About • Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 28 June 2023
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WECBA01
 Successful SIS Multilayer Activities on Cavities and Samples Using ALD  
 
  • I. González Díaz-Palacio, R.H. Blick, C. Saribal, R. Zierold
    University of Hamburg, Hamburg, Germany
  • G.K. Deyu, W. Hillert, M. Wenskat
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  
  The­o­ret­i­cally SIS mul­ti­lay­ers pre­dict to delay vor­tex pen­e­tra­tion al­low­ing for op­er­a­tion gra­di­ents more than the dou­ble of bulk Nb cav­i­ties and Q-val­ues two or­ders of mag­ni­tude above. The Uni­ver­sity of Ham­burg fo­cuses on Atomic Layer De­po­si­tion (ALD) as most promis­ing coat­ing tech­nique. In a proof-of prin­ci­ple ex­per­i­ment ther­mal ALD of Al₂O₃ was suc­cess­fully ap­plied to two 1.3GHz sin­gle-cell cav­i­ties achiev­ing gra­di­ents above 40MV/m with­out any de­te­ri­o­ra­tion in Q-value [1]. Stud­ies using plasma-en­hanced ALD (PEALD) on pla­nar sam­ples focus on AlN and NbTiN as di­elec­tric and su­per­con­duc­tor ma­te­r­ial, re­spec­tively. The de­po­si­tion process and post-de­po­si­tion treat­ments have been op­ti­mized by study­ing the su­per­con­duct­ing prop­er­ties in mag­neto-trans­port and in vi­brat­ing sam­ple mag­ne­tom­e­try of the films. Dif­fer­ent com­po­si­tions, thick­nesses, and ther­mal an­neal­ing treat­ments have been in­ves­ti­gated with re­spect to their re­sis­tance, mag­ne­ti­za­tion, flux trap­ping ef­fi­ciency, ther­mal con­duc­tance, el­e­men­tal com­po­si­tion, and crys­tallinity. Within this pre­sen­ta­tion, the ag­gre­gated re­sults of all those mea­sure­ments will be pre­sented and dis­cussed in de­tail.
[1] Marc Wenskat et al 2023 Supercond. Sci. Technol. 36 015010 		 
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