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COATING RESEARCH & DEVELOPMENT @ LMA

COATING RESEARCH & DEVELOPMENT @ LMA. G. Cagnoli , A. Cajfinger , V. Dolique, G. Cochez, R. Flaminio , D. Forest, J. Franc, M . Granata , C. Michel, N. Morgado , L. Pinard, E. Saracco Laboratoire des Matériaux Avancés (LMA) - Lyon . in collaboration with :

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COATING RESEARCH & DEVELOPMENT @ LMA

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  1. COATING RESEARCH &DEVELOPMENT @LMA G. Cagnoli, A. Cajfinger, V. Dolique, G. Cochez, R. Flaminio, D. Forest, J. Franc, M. Granata, C. Michel, N. Morgado, L. Pinard, E. Saracco Laboratoire des Matériaux Avancés (LMA) - Lyon in collaboration with: T. Epicier & B. Van de MoortèleCentre Lyonnais de Microscopie (CLYM) E. Härkönen, M. Ritala & M. LeskeläUniversity of Helsinki GWADW – Waikoloa, May 14th 2012

  2. Outline Investigation of Multilayer-CoatingLoss Updates on Atomic Layer Deposition 2 GWADW – Waikoloa, May 14th 2012

  3. Investigation of Multilayer-CoatingLoss in collaboration with T. Epicier & B. Van de Moortèle, CLYM 3 GWADW – Waikoloa, May 14th 2012

  4. Thermal Noise of Coatings Virgotechnical note VIR–0128A–12 the sensitivitygravitational-waveinterferometers of 2nd and 3rd generationwillbelimited by coating thermal noisearound 102 Hz Advanced Virgo coatings are multilayerstacksrealizedthrough Ion BeamSputtering (IBS) lastSiO2 layer Ti:TaO2O5: HIGH (H) refractive index Ti:Ta2O5 layer ✕N SiO2: LOW (L) refractive index SiO2 layer 1st Ti:Ta2O5 layer SiO2 substrate 4 GWADW – Waikoloa, May 14th 2012

  5. The Story So Far multilayercoatings show more lossthanexpected • 1st clue [J. Franc @ GWADW10]: « mechanical losses of different multilayer coatings • (…) have been measured and confirm larger losses than expected. » • new measures [A. Villar@ LVC – Krakow[*] / E. Saracco@ GWADW11]:  the trend isconfirmed thickness of Ti:Ta2O5is NOT relevant… credits: E. Saracco …as the NUMBER OF INTERFACES matters. • characterization [R. Flaminio@Amaldi 9]: • lineardependence of losswrtnumber of interfaces credits: R. Flaminio [*] LIGO technical note G1000937 5 GWADW – Waikoloa, May 14th 2012

  6. LaterDevelopments • physico-chemical characterization of SiO2/Ti:Ta2O5 interfaces: • sample: ITM-HR coating, 1.031H(1.3927L 0.5854H)8 1.199L [18 layers] • Scanning/Transmission Electron Microscopy (SEM/TEM) @ CLYM: study at atomic scale Focused Ion Beam Microscope Transmission Electron Microscope • imagery • density profiles • energy-dispersive X-ray analysis (EDX)  atomic contentration hypothesis: interdiffusion of materials? 6 GWADW – Waikoloa, May 14th 2012

  7. Preparation of the Sample 50 nm-thickblade 7 GWADW – Waikoloa, May 14th 2012

  8. Tomography & Density Profiles [SEM] yz [SEM] density profiles SiO2 [SEM] Ti:Ta2O5 Ti:Ta2O5 depth • measuresgiveexpectedcoatingthickness and show no defects depth 3D tomography [TEM] • smooth transition betweenlayers • gradient of concentration atinterface • materials do mix xy 8 GWADW – Waikoloa, May 14th 2012

  9. The Picture • no cristalline phase observed in layers • analyses reveal a mixing interface of 20 to 35 nm • simulatedopticalspectra of multilayercoatingswith mixed materialsat • interfaces are compatible withmeasures on 1" substrate • optical simulations also show that gradients shouldbesymmetric: • Ti:Ta2O5 and SiO2 diffuse intoeachother circles = DATA • analyses of atomic concentrations are not conclusive new measures in progress line = SIMULATION 9 GWADW – Waikoloa, May 14th 2012

  10. Mixed Materials [TEM] • could mixed interfaces explainexceedingloss? • simple model of the interface: discrete gradient • mixed material 1 = 65% SiO2 + 35% Ti:Ta2O5 • mixed material 2 = 65% Ti:Ta2O5 + 35% SiO2 50 nm 100% Ti:Ta2O5 • coating of a SiO2bladewith mixed material 1 • measure of loss of mix1: mix 2 Φmix1 = (2.7 +/- 0.2) × 10-4 100% SiO2 mix 1 losssimilar to Ti:Ta2O5 • to bedone: deposit • and measure mix 2 setup for ringdown technique 10 GWADW – Waikoloa, May 14th 2012

  11. Interfaces – Results mix1 = 65% SiO2 + 35% Ti:Ta2O5 mix2 = 65% Ti:Ta2O5 + 35% SiO2 ΦTi:Ta2O5 = (2.4 +/- 0.4) × 10-4 ΦSiO2 = (4.6 +/- 0.1) × 10-5 Φmix1 = (2.7 +/- 0.2) × 10-4 Φmix1 = Φmix2 [assumption] YTi:Ta2O5 = 140 Gpa YSiO2 = 73 Gpa Ymix1 = 65% YSiO2+ 35% YTi:Ta2O5 Ymix2 = 65% YTi:Ta2O5+ 35% YSiO2 • theory: Φk: loss angle of the material tk : total thickness of the material Yk : Young’smodulus interfaces onlypartlyfill the gap 11 GWADW – Waikoloa, May 14th 2012

  12. Interfaces – Conclusions • excess of mechanicallossisobserved in multilayercoatings, depending on the number of interfaces betweenlayers • interfaces have been characterized •  analyses revealed a mixing zone with gradients of atomic concentration • loss of a mixed material (65% SiO2 + 35% Ti:Ta2O5) has been measured • lossissimilar to that of Ti:Ta2O5 … • … but the presence of mixing interfaces onlypartiallyexplains the exceedingloss [mixed material 2 has to bemeasured] do weneed a more complex model of the gradient? 12 GWADW – Waikoloa, May 14th 2012

  13. Updates on Atomic Layer Deposition in collaboration with E. Härkönen, M. Ritala & M. LeskeläUniversity of Helsinki 13 GWADW – Waikoloa, May 14th 2012

  14. Atomic Layer Deposition (ALD) the idea: investigation of new techniques to improvequality of coatings wewantlowermechanicallosses test of ALD realized@University of Helsinki • coatings of good qualityfactors[*]and opticalproperties advantages: • self-limitingmechanism of film growth • excellent coatinguniformity - even on large areas • homogeneousstoichiometry • highreproducibility • lowdeposition rate major concern: [*] O Hahtela & al., J. Micromech. Microeng. 17, 2007 14 GWADW – Waikoloa, May 14th 2012

  15. Reminder methodbased on alternatesaturative surface reactions purge [N2 – 5 s pulse] precursor 1 [Ta(OCH2CH3)5 – 0.3 s pulse] purge [N2 – 5 s pulse] precursor 2 [H2O – 0.3 s pulse] purge[N2 – 5 s pulse] back to step 2 substrate @ T = 250 °C credits: J. Franc 15 GWADW – Waikoloa, May 14th 2012

  16. ALD – Results monolayercoatings of undoped Ta2O5 onSiO2 cantilever blades • previousmeasurements: J. Franc @ GWADW11 / R. Flaminio@Amaldi 9 (ΦTa2O5)ALD > (ΦTa2O5)IBS 16 GWADW – Waikoloa, May 14th 2012

  17. ALD – Results monolayercoatings of undoped Ta2O5 on 6 SiO2substrates of 1" • previousmeasurements: J. Franc @ GWADW11 / R. Flaminio@Amaldi 9 absorption ishighlydependent on annealingtemperature  do the material structure change? lowest absorption of ALD @ 600 °C: 0.26 ppm – IBS: 1.2 ppm IBS: n = 2.035 17 GWADW – Waikoloa, May 14th 2012

  18. ALD – Conclusions • ALD is a well-estabilished technique to realizehigh-qualitycoatings • deposition rate islow • mechanicallosses of ALD coatings are larger •  no specificadvantage in using ALD instead of IBS • ALD coatings show good optical absorption • unusualbehaviorwrtannealingmightbeworthfurther investigation 18 GWADW – Waikoloa, May 14th 2012

  19. Summary • the structure of multilayercoatings has been characterized • analyses revealed interfaces of mixed materials • mixed interfaces canonlypartlyexplain the gap betweenpredicted and measuredlosses • ALD coating technique has been investigated • losses are largercompared to IBS coatings • optical absorption seemslower for Tannealing > 600 °C • nextstep: furthercharacterization of optical absorption wrtTannealing 19 GWADW – Waikoloa, May 14th 2012

  20. Thankyou for your attention. 20 GWADW – Waikoloa, May 14th 2012

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