New results on losses correlation with structure

New results on losses correlation with structure E. Coillet, V. Martinez, C. Martinet, A. Mermet Institut Lumière Matière Lyon, France M. Granata, V. Dolique, C. Michel, B. Sassolas, G. Cagnoli, Laboratoire des Matériaux Avancés CNRS Lyon, France GWADW 2016 Elba

Outline New results on the structure : I. Silica coatings : Impact of the annealing II. Silica coatings : Effect of the deposition parameters on the structure III. Ta 2 O 5 : effect of annealing IV. Comparison between TiO 2 and Ta 2 O 5 structures 1

I - Fused silica 1,4 Fused non-densified silica (d = 2,2 g.cm -3 ) 1,2 150 Fused non-densified silica 1,0 0,8 0,6 0,4 0,2 Main band D 1 D 2 θ O Si Brillouin intensity (a.u.) 125 100 75 50 25 0,0 200 400 600 0 20 25 30 35 40 45 50 Frequency (GHz) 2

I - IBS silica coatings vs fused 1,4 Non-annealed thin film (d = 2,5 g.cm -3 ) Fused non-densified silica (d = 2,2 g.cm -3 ) 1,2 1,0 0,8 0,6 0,4 0,2 Main band D 1 D 2 Brillouin intensity (a.u.) 150 125 100 75 50 25 Non annealed thin film Fused non-densified silica 0,0 200 400 600 0 20 25 30 35 40 45 50 Frequency (GHz) 3

I - IBS silica coatings vs fused 1,4 1,2 Non-annealed thin film (d = 2,5 g.cm -3 ) Fused non-densified silica (d = 2,2 g.cm -3 ) Fused densified silica (d = 2,46 g.cm -3 ) 42 1,0 0,8 0,6 0,4 Brillouin shift (GHz) 40 38 36 34 Thin film Calibration curve of densified fused SiO 2 2,5 0,2 32 Fused 2,2 2,2 2,3 2,4 2,5 2,6 2,7 0,0 200 400 600 Density T. Deschamps, Scientific report (2014) Structure of the Ion Beam Sputtered layers closer to densified silica 4

I - Silica coatings : effect of annealing 5,0x10-4 4,0x10-4 Coating loss (rad) 3,0x10-4 2,0x10-4 1,0x10-4 0,0 0 50 100 150 200 250 300 Annealing time (h) Link with the structure? 5

I - Silica coatings : effect of annealing Annealing at T = 500 C << T g 2000 1500 0 h 5 h 10 h 30 h 70 h 184 h 300 h 1000 500 0 300 400 500 600 700 6

I - Silica coatings : effect of annealing Annealing at T = 500 C << T g 2000 1500 0 h 5 h 10 h 30 h 70 h 184 h 300 h Shift of the main band position towards lower frequencies Larger inter-tetrahedral angles 1000 500 0 300 400 500 600 700 6

I - Silica coatings : effect of annealing Annealing at T = 500 C << T g 2000 1500 1000 0 h 5 h 10 h 30 h 70 h 184 h 300 h Shift of the main band position towards lower frequencies Larger inter-tetrahedral angles Decrease of the D 2 intensity Less 3-membered rings 500 0 300 400 500 600 700 6

I - Silica coatings : effect of annealing Annealing at T = 500 C << T g 2000 1500 1000 500 0 h 5 h 10 h 30 h 70 h 184 h 300 h Shift of the main band position towards lower frequencies Larger inter-tetrahedral angles Decrease of the D 2 intensity Less 3-membered rings Brillouin shift (GHz) 42 40 38 36 34 Calibration curve of densified bulk SiO 2 Not annealed layers Annealed layers 2,5 0 300 400 500 600 700 32 2,47 2,2 2,3 2,4 2,5 2,6 2,7 Density T. Deschamps, Scientific report (2014) 6

I - Silica coatings : effect of annealing Annealing at T = 500 C << T g 2000 1500 1000 500 0 h 5 h 10 h 30 h 70 h 184 h 300 h Shift of the main band position towards lower frequencies Larger inter-tetrahedral angles Decrease of the D 2 intensity Less 3-membered rings Brillouin shift (GHz) 42 40 38 36 34 Calibration curve of densified bulk SiO 2 Not annealed layers Annealed layers 2,5 0 300 400 500 600 700 32 2,47 2,2 2,3 2,4 2,5 2,6 2,7 Density T. Deschamps, Scientific report (2014) Relaxation of the structure with annealing toward a less dense thin film 6

I - Silica coatings : effect of annealing Evolution of the Raman signatures 14 D 2 band relative area (%) 13 12 11 10 9 8 7 Smaller 3-membered rings population D 2 position (cm -1 ) 611 610 609 608 607 606 Stress relaxation 6 0 50 100 150 200 250 300 605 0 50 100 150 200 250 300 Annealing time (h) Annealing time (h) D 2 Fused SiO 2 : D2 band area = 3% D2 band position = 606 cm -1 Main band position = 435 cm -1 Main band HWHM = 110 cm -1 Non-annealed thin film (d = 2,5 g.cm -3 ) 200 300 400 500 600 700 7

I - Silica coatings : effect of annealing Evolution of the Raman signatures 480 478 90 Main band position (cm -1 ) 476 474 472 470 468 466 Larger Si-O-Si angle HWHM Main Band (cm -1 ) 80 70 Larger angle distribution 464 0 50 100 150 200 250 300 Annealing time (h) 60 0 50 100 150 200 250 300 Annealing time (h) Non-annealed thin film (d = 2,5 g.cm -3 ) Main band Fused SiO 2 : D2 band area = 3% D2 band position = 606 cm -1 Main band position = 435 cm -1 Main band HWHM = 110 cm -1 200 300 400 500 600 700 8

I - Silica coatings : effect of annealing Link between coating loss and structure 480 90 478 Non-annealed thin film (d = 2,5 g.cm -3 ) 200 300 400 500 600 700 Main band position (cm -1 ) 476 474 472 470 468 466 464 HWHM Main Band (cm -1 ) 85 80 75 70 65 0,0 1,0x10-4 2,0x10-4 3,0x10-4 4,0x10-4 5,0x10-4 0,0 1,0x10-4 2,0x10-4 3,0x10-4 4,0x10-4 5,0x10-4 Coating loss (rad) Losses 14 13 D 2 Non-annealed thin film (d = 2,5 g.cm -3 ) 200 300 400 500 600 700 Relative D 2 band area (%) 12 11 10 9 8 7 Clear correlation between the 3-membered rings population and the coating loss 6 0,0 1,0x10-4 2,0x10-4 3,0x10-4 4,0x10-4 5,0x10-4 Mechanical loss (rad) 9

I - Silica layers : Annealing Link between coating loss and structure Denser structure of the layers compare to fused silica Annealing leading to a more relaxed structure and loss decrease Origin of the loss by modelisation Anderson et al : lateral motion of O perpendicularly to Si-O bonds Hamdan et al (2014) : tetrahedral chain rearrangement via rotation and stretching of Si-O bonds (10 to 100 atoms) Structural modifications needing low activation energy : available at T << T g Info given by Raman spectroscopy D 2 band : 3-membered rings breathing mode Area decrease : smaller 3-fold population-> stress relaxation Relation between 3-fold rings and two level systems (TLS) energy landscape? 10

II - Effect of the deposition parameters on the structure 2,5 2,0 1,5 1,0 Bulk non-densified silica Spector Grand Coater Grand coater compared to Spector : MB position Grand Coater > Spector Smaller inter tetrahedral angles D2 band area Grand Coater < Spector Smaller 3-membered ring population 0,5 0,0 200 300 400 500 600 Mechanical loss of Grand Coaster sample lower than Spector : linked with a more relaxed structure Correlation between 3-membered rings population and mechanical losses as seen with annealing. 11

II Silica coatings Structural relaxation of the amorphous silica coating with annealing towards less dense glass Correlation between the mechanical losses and the 3- membered rings population Important impact of deposition parameters on the amorphous silica layers What about Ta 2 O 5 layers? 12

III - Ta 2 O 5 coatings : Evolution with annealing 4500 4000 3500 Ta vibrations (+ Boson Peak?) as deposited t 1 = 10h t 2 = 20h t 3 = 50h Average coordination number in Ta 2 O 5 : Raman 3000 2500 2000 1500 1000 Mainly O-2Ta Rocking Mainly O-2Ta and O-3Ta stretching 500 0 0 200 400 600 800 1000 1200 1400 Wavenumber (cm -1 ) Coordination and band attribution done by the simulation group at the ILM. Glass unknown in the fused state T. Damart et al., JAP 119 (2016) 13

III - Ta 2 O 5 coatings : Evolution with annealing T = 500 C Raman 4500 4000 3500 3000 2500 2000 1500 1000 500 as deposited t 1 = 10h t 2 = 20h t 3 = 50h Normalized stretching band area (%) 14,8 14,6 14,4 14,2 14,0 13,8 13,6 13,4 13,2 13,0 0 10 20 30 40 50 Annealing time (h) 1,2x10-3 1,0x10-3 8,0x10-4 6,0x10-4 4,0x10-4 Coating loss (rad) 0 0 200 400 600 800 1000 1200 1400 Wavenumber (cm -1 ) Similar evolution with coating loss Less structural evolution visible on the Raman spectrum than in silica glass Need to better understand the structure and its possible evolutions 13

IV - Comparison between TiO 2 and Ta 2 O 5 structures AmorphousTiO 2 structure close to that of Ta 2 O 5 1,0 Ta/Ti vibrations (+ Boson Peak?) amorphous Ta 2 O 5 Damart et al., JAP (2016) Ta 2 O 5 0,8 amorphous TiO 2 Pham et Wang, PCCP (2015) TiO 2 0,6 0,4 Mainly O-2Ta and O-3Ta stretching 0,2 0,0 0 200 400 600 800 1000 1200 Cristalline phase associated with a-tio 2 : anatase 14

Conclusion Understand the link between the mechanical losses and the structure Vibrational spectroscopies : useful tool to probe the structural evolution of thin films Correlation between mechanical losses and the 3-membered rings population Importance of the deposition parameters on the structure and on the mechanical losses Perspectives : Effect of different doping on the structure Effect of the deposition temperature 15

Vibrational spectroscopies RAMAN BRILLOUIN Based on inelastic scattering of a monochromatic incident radiation Virtual States Vibrations and rotations ground state Rayleigh scattering Stokes process Anti-Stokes Process Raman scattering arises from fluctuations of polarizability Brillouin scattering arises from fluctuations of dielectric susceptibility 3

Vibrational spectroscopies Raman spectroscopy Optical Modes Frequency shift ν > 10 cm -1 Structural information at short and medium range order (1-20 Å) 3000 2500 400 Brillouin spectroscopy Acoustic Modes Frequency shift ν 1 cm -1 Continuous media Macroscopic properties : Sound velocity V L Elastic moduli Density d Optical index n V L = λ 0 υb 2n 2000 1500 1000 500 1 cm -1 33 GHz Brillouin intensity (a.u.) 300 200 100 υ B 0 200 300 400 500 600 700 0-40 -30-20 -10 0 10 20 30 40 Brillouin shift (GHz) Both give information on the structural evolution f(temperature, Pressure) 4

Experimental Monolayers of SiO 2 or Ta 2 O 5 around 1 and 3 µm thick Deposited by Ion Beam Sputtering at the LMA in Lyon Mechanical losses and vibrational spectra measured on the same layers Coatings Metallic tantalum Spector Fused Silica 5

Tantalum oxide layers Average coordination number in Ta2O5 1,0 Ta vibrations (+ Boson Peak?) Raman spectrum cristalline Ta 2 O 5 Raman spectrum amorphous Ta 2 O 5 0,8 0,6 0,4 Mainly O-2Ta and O-3Ta stretching 0,2 0,0 Mainly O-2Ta Rocking 0 200 400 600 800 1000 1200 O-3Ta O-2Ta Glass unknown in the fused state T. Damart et al., JAP 119 (2016) 13

Tantalum oxide layers

Cristallisation TiO 2 30000 20000 10000 Cristallisé LMA Anatase RRUFF Rutile RRUFF Amorphe LMA 0 0 200 400 600 800 1000 1200 Cristalline layers TiO 2 => Anatase Coordination Anatase : Ti 6 (octahedra) O 3 (trigonal planar)