ALD-deposited Multilayer to improve the superconducting performances of RF cavities

| PAGE 1 RSH003 | 23/11/2018 ALD-deposited Multilayer to improve the superconducting performances of RF cavities Yasmine Kalboussi1, Aurélien four1, Baptiste Delatte 1,Claire Antoine1, David Longuevergne2,Oleksandr Hryhoenko, Diana Dragoe3, Jocelyne Leroy4, Sandrine Tusseau-Nenez5,Yunlin Zheng6,David Hrabovsky6, Aurélie Gentils2, Stéphanie Jublot Leclerc2, Fréderic Miserque7, Mohamed Belhaj6, Thomas Proslier1. 1IRFU, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France ; 2Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France ; 3Plateforme ICMMO, Rue du doyen Georges Poitou, Bât 410 ,91400 Orsay France ; 4Laboratoire d’Innovation en Chimie des Surfaces et Nanosciences, 91191 Gif sur Yvette, Cedex, France ; 5Plateforme de Diffraction des Rayons X, Ecole Polytechnique, Route de Saclay, 91128 Palaiseau. 6Physics instrumentation environnement space department, coupling of spacecraft and environnement unit, ONERA. 7DEN, Service de la Corrosion et du Comportement des Matériaux dans leur Environnement (SCCME), CEA Saclay, 91191 Gif-sur-Yvette Cedex, France. Conventional Niobium Cavity Optimized Structure By ALD Future layered Cavities ➢An original approach proposed by A. Gurevich [1] to improve RF cavities through depositing a superconducting multilayer capable of screening efficiently the magnetic field. ➢To optimize this concept, we need as well a thermally stable diffusion barrier as a base and a low SEY material on the outer layer in order to limit multipacting inside the cavities. INTRODUCTION | PAGE 1 Yasmine KALBOUSSI-DACM Atomic layer depostion for RF cavities ? | PAGE 2 ALD is a chemical gas phase deposition method based on sequential, self-saturating gas-solid surface reactions. Advantages : ▪Precise Thickness control up to sub-nanometer scale . ▪Excellent conformality. ▪Large choice of possible materials ( oxides, nitrides and some metals …) ALD PROTECTIVE LAYER | PAGE 2 ➢ALD Protective layer can be: MgO, Y2O3,Al2O3,TiO2,ZrO2 Yasmine KALBOUSSI-DACM MULTIPACTING SUPPRESSION LAYER | PAGE 3 Yasmine KALBOUSSI-DACM IRFU/Service Page 6 0200 400 600 800 1000 1200 1400 1600 1800 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 SEY Primary energy [eV] 0 cycles 4 cycles 10 cyles 20 cycles 30 cycles 50 cycles 230 cycles 500 cycles After 400mC ➢Control thickness and chemical composition – uniformity ➢Tune SEY and electrical conductivity ➢Wide variety of substrates (Nb, Cu…) 050 100 150 200 250 300 350 400 450 500 550 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 As deposited 400mC R (W) # ALD cycles 100 1000 10000 100000 1000000 1E7 1E8 TiN on Al2O3 (10 nm) λ= 12 cy = 0.45 nm Other dep. ~ 10 nm CEA-ONERA SEY MAX R [Ω] MULTIPACTING SUPPRESSION LAYER MULTIPACTING SUPPRESSION LAYER | PAGE 3 Yasmine KALBOUSSI-DACM NbOx Al2O3 ALD Anneal ALD TiN Anneal ➢Replacing NbOx by Al2O3 increase the Q MULTIPACTING SUPPRESSION LAYER Al2O3 ➢TiN successfully mitigated the multipacting in RF cavity NbTiN Chemical composition : Nb1-xTixN ➢Motivation: NbTiN has good superconducting performance (Tc= 17 K) ➢AlN as an insulating layer. ➢Chemistry: Combination of TiN and NbN cycles: n (TiCl4+ NH3) + m (NbCl5 +NH3) = Nb1-xTixN Critical temperature 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0 2 4 6 8 10 Tc @450°C Tc @500°C Tc [K] X ( from XPS analysis ) Resistivity NBTiNALN bilayer 0,0 0,2 0,4 0,6 0,8 1,0 0,0 0,1 0,2 0,3 0,4 0,5 0,6 @ 450°C @ 500°C x ( from XPS analysis) Ti/(Ti+Nb) ALD 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0 100 200 300 400 500 600 700 @450°C @500°C Resistivity (µohm.cm) x ( from XPS analysis ) Diffraction on NBTiN films ➢Lattice parameter is lower than expected. ▪High vacuum oven: -650°C –10-6 mbar / 900°C 1bar N2 - Volume retort: Φ= 49 cm, L= 110 cm (1.3, 0.7 GHz cavities) ▪ALD system: -9 precursor lines (2 gases, 2 liquids, 4 solids, 1 Ultra high temp.). - RGA synthesis monitoring. 49 cm ▪Interface and control: - Labview program of ALD system and Oven. - Automatic synthesis parameter control (overnight dep.) and monitoring. ▪Status: - Deposition tests on samples - Future: Deposition on cavities Next Step : Test on Niobium cavities Yasmine KALBOUSSI - 04/05/2022 | PAGE 8 NbOx NbTiN AlN ➢First attempt: Lower Q and Emax ➢Unexpected behavior during annealing on SRF cavity. ➢Work in progress. ALD FROM COUPONS TO CAVITIES NbTiN AlN Anneal ✓We manage to deposit uniformly a thin film of Alumina and reduce drastically niobium native oxides. ✓RF test shows a slight improvement of the Q0under low and medium Fields. ✓TiN film is promising to reduce multipacting inside RF cavities. ✓Growth of superconducting NbTiN by ALD with homogeneous composition and thickness control over large surface areas. Future Goals will be: ❖Test the Al2O3-TiN structure on Niobium RF cavities. ❖Test the NbTiN-AlN structure on Niobium RF cavities. Thank you for your attention Conclusion Yasmine KALBOUSSI - 04/05/2022 | PAGE 13