New results on losses correlation with structure

Transcription

1 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

2 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

3 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.) , Frequency (GHz) 2

4 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.) Non annealed thin film Fused non-densified silica 0, Frequency (GHz) 3

5 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) 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, Density T. Deschamps, Scientific report (2014) Structure of the Ion Beam Sputtered layers closer to densified silica 4

6 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, Annealing time (h) Link with the structure? 5

7 I - Silica coatings : effect of annealing Annealing at T = 500 C << T g h 5 h 10 h 30 h 70 h 184 h 300 h

8 I - Silica coatings : effect of annealing Annealing at T = 500 C << T g 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

9 I - Silica coatings : effect of annealing Annealing at T = 500 C << T g 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

10 I - Silica coatings : effect of annealing Annealing at T = 500 C << T g 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) Calibration curve of densified bulk SiO 2 Not annealed layers Annealed layers 2, ,47 2,2 2,3 2,4 2,5 2,6 2,7 Density T. Deschamps, Scientific report (2014) 6

11 I - Silica coatings : effect of annealing Annealing at T = 500 C << T g 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) Calibration curve of densified bulk SiO 2 Not annealed layers Annealed layers 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

12 I - Silica coatings : effect of annealing Evolution of the Raman signatures 14 D 2 band relative area (%) Smaller 3-membered rings population D 2 position (cm -1 ) Stress relaxation 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 )

13 I - Silica coatings : effect of annealing Evolution of the Raman signatures Main band position (cm -1 ) Larger Si-O-Si angle HWHM Main Band (cm -1 ) Larger angle distribution Annealing time (h) 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

14 I - Silica coatings : effect of annealing Link between coating loss and structure Non-annealed thin film (d = 2,5 g.cm -3 ) Main band position (cm -1 ) HWHM Main Band (cm -1 ) ,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 D 2 Non-annealed thin film (d = 2,5 g.cm -3 ) Relative D 2 band area (%) 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

15 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

16 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, 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

17 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

18 III - Ta 2 O 5 coatings : Evolution with annealing Ta vibrations (+ Boson Peak?) as deposited t 1 = 10h t 2 = 20h t 3 = 50h Average coordination number in Ta 2 O 5 : Raman Mainly O-2Ta Rocking Mainly O-2Ta and O-3Ta stretching 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

19 III - Ta 2 O 5 coatings : Evolution with annealing T = 500 C Raman 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, Annealing time (h) 1,2x10-3 1,0x10-3 8,0x10-4 6,0x10-4 4,0x10-4 Coating loss (rad) 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

20 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, Cristalline phase associated with a-tio 2 : anatase 14

21 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

22 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

23 Vibrational spectroscopies Raman spectroscopy Optical Modes Frequency shift ν > 10 cm -1 Structural information at short and medium range order (1-20 Å) 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 cm GHz Brillouin intensity (a.u.) υ B Brillouin shift (GHz) Both give information on the structural evolution f(temperature, Pressure) 4

24 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

25 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 O-3Ta O-2Ta Glass unknown in the fused state T. Damart et al., JAP 119 (2016) 13

26 Tantalum oxide layers

27 Cristallisation TiO Cristallisé LMA Anatase RRUFF Rutile RRUFF Amorphe LMA Cristalline layers TiO 2 => Anatase Coordination Anatase : Ti 6 (octahedra) O 3 (trigonal planar)