Coa Ch Coa Ch the status of art

Coa. Ch: Coa. Ch the status of art in Coating Characterization Elisabetta Cesarini Università di Urbino - INFN Firenze on behalf of Coa. Ch collaboration

Outline q The coating thermal noise in 2 nd generation of GW interferometers q A “global” approach to investigate dissipation mechanism in coating q The facilities involved in the characterization program: what and where? q Preliminary results on substrates and spare coated samples q New samples…on the way q Future work… GWADW May 2009 Meeting 2

Coating thermal noise Adv. Virgo GWADW May 2009 Meeting 3

Coating thermal noise FLUCTUATION – DISSIPATION THEOREM (Callen-Welton, 1951) Mechanical impedance (Dissipation) Fluctuation Ta 2 O 5 ≈3. 2∙ 10 -4 Si. O 2 ≈ 0. 5 ∙ 10 -4 The dominant source of mechanical loss is associated with Tantala layer S. Penn et al, Class. Q. Gravity, 20, 2917 (2003) § coating annealing § Titanium-doped coating § optimization of coating layers thickness § laser beam shaping § new material investigation GWADW May 2009 Meeting 4

The strategy Single layer sample set Characterization Modification/ alteration New samples Suprasil substrate with a single layer of Ta 2 O 5 , crafted to enhance the layer characteristics and to be easily handled Hints for Mechanical, bulk, optical, Production/ Modeling surface and interface Post-production properties Global alterations : Thermal processing/annealing in vacuum or controlled atmosphere EM radiation exposure (X-rays, UV) Local alterations : Laser heating/damaging Ion implantation GWADW May 2009 Meeting 5

Characterization Properties Description Facility Stoichiometry Chemical content of coating as function of depth RBS Firenze/INFN Legnaro/(MO) Organic contaminants Absorption signature of molecular compounds FTIR in Pisa Bonding state To evaluate the presence of dangling bonds or the oxidation state XPS-ESCA n Genova Structural Short range ordering To quantify the degree of amorphousness Tribological Roughness Nano and micro scale Index of refraction 245 -1700 nm Spectroscopic Ellipsometer in Genova Absorption At 1064 nm Photo-elastic effect facility in Firenze Scattering At 1064 nm Photo-elastic effect facility in Firenze Chemical SEM/FIB (Modena) XRD in Pisa AFM in Genova Optical AFM in Pisa/Modena(n. indent) Conductivity Photo-elastic effect facility in Firenze Expansion Photo-elastic effect facility in Firenze Thermal Mechanical Young’s modulus and density Mechanical loss Measured through the effects on mode frequencies GWADW May 2009 Meeting Q measurement setup in Perugia(LT)/Firenze(RT) Q measurement setup in FI PG & PD (Low & Cryo T) 6

Q measurements facilities Mechanical Q measurements: - Ge. NS (INFN FI) Q measurements at room temperature with a nodal suspension controlled in temperature EQUILIBRIUM Diameter >Thickness The reproducibility between two different suspensions is within 20% Q value is not depending on suspension point E. Cesarini et al. REVIEW OF SCIENTIFIC INSTRUMENTS 80, 053904 (2009) - Independent “similar” measurements in Legnaro (PD) and Perugia GWADW May 2009 Meeting 7

Q measurements facilities Auxiliary laser comb exciter Ge. NS photodiode Vacuum chamber 8 GWADW May 2009 Meeting 8

AFM study of the Annealing effect temperature Preliminary studies on Si. O 2 substrates 00 2 =1 TA °C 25 °C 10 = Ts Roughness distribution analysis central region counts time Before annealing Rmean ≈ 17 nm Roughness [nm] 30 mm Roughness distribution analysis central region counts After annealing Rmean ≈ 5 nm Roughness [nm] 30 mm GWADW May 2009 Meeting analysis performed at Università di Genova 9

Preliminary studies on Si. O 2 substrates Correlation between surface and mechanical properties measurements done at INFN Labs in Firenze After the annealing treatment the mechanical Q is increased by a factor 1. 5 and the values measured for the 2 peaks of the same resonance frequency are closer. The surface roughness in the central region decreased from 17 nm to 5 nm. GWADW May 2009 Meeting 10

Preliminary studies on Si. O 2 substrates Correlation between optical and mechanical properties ( SE analysis ) Ellipsometric ratio: Fresnel reflection coefficients 50° incidence Optical model used to fit data: Bulk 1 mm, n(λ) + roughness Bulk n(l) Surface roughness: Before annealing (0. 54± 0. 02) nm After annealing (0. 00± 0. 02) nm namb< nsub ideal interface below Brewster angle D = 180° GWADW May 2009 Meeting SE analysis performed at Università di Genova 11

Preliminary studies on Si. O 2 substrates XPS study of the Annealing effect Spectrum before any treatment High-resolution image of Silicon peak Oxygen image of Silicon silicon double large dioxide spectrum silicone. V dioxide Silicon pre-treatment peak @103. 4 before any double peak sputtering post-treatment @103. 3 e. V large spectrum after a 3 ke. V sputtering to Other gaussian peak are Carbon silicon carbide double shifted silicon dioxide remove air peaks. peak @101. 4 e. V This phenomenon is due to contaminants charge neutralization the furnace and on the sample has The carbon present by inside large Si. O 2 surface structure been bonded to silicon due to high temperature reached (observed with AFM) during the annealing, even if it was done in vacuum (rough vacuum level ≈10 -2 mbar) Binding Energy [e. V] 12 analysis done at INFN labs in Genova GWADW May 2009 Meeting 12

Preliminary measurements on spare coated samples 60 substrates Corning 7980 50 mm ø x 0. 5 mm tk Mechanical properties used to simulate resonance frequency with FEA : E=72 GPa s=0. 179 r=2201 Kg/m 3 Ion sputtered by ATFilms 20 Tantala 500 nm 20 Tantala 200 nm Q vs f measured with Ge. NS coated and uncoated samples AFM ANALYSIS substrates uncoated analysis by Università di Genova ROUGHNESS DISTRIBUTION coated 500 nm Rmean= 5 nm measurements done at INFN Labs in Firenze GWADW May 2009 Meeting 13

Preliminary analysis on spare coated samples Amorphous Ion sputtered Ta 2 O 5 films: SE analysis (raw data) Different optical models to fit SE data: 200 nm trasparent 60° incidence region d = 197. 7± 0. 2 nm 1) single material layer d = layer thickness substrate r = 0. 5 ± 0. 1 nm d = 197. 4± 0. 1 nm 2) single material layer + roughness r = roughness substrate SE analysis performed at University of Genova r = 0. 7 ± 0. 1 nm d = 193. 8± 0. 2 nm i = 9. 6± 0. 5 nm substrate GWADW May 2009 Meeting 3) single material layer + roughness + mixing interface i = interface thickness 14

Preliminary analysis on spare coated samples Amorphous Ion sputtered Ta 2 O 5 films: SE analysis (raw data) Ta 2 O 5 200 nm film: Energy gap and comparison with literature refractive index extiction coefficient Energy Gap H. Demiryont, James R. Sites, and Kent Geib APPLIED OPTICS / Vol. 24, No. 4 / 15 February 1985 oxygen imbalances (probably lack of oxygen) due to ion sputtering process SE analysis performed at Università di Genova GWADW May 2009 Meeting Impurity same analysis with 500 nm Ta 2 O 5 layer film gives very similar results 15

Preliminary analysis on spare coated samples Amorphous Ion sputtered Ta 2 O 5 films: XPS analysis (raw data) Ta 2 O 5 Metallic Ta GWADW May 2009 Meeting 16

Status of the art New optimized samples for characterization 1. n° 50 Hereaus Suprasil 311 substrates 50 mm ø x 3 mm tk (already purchased) 2. Optical processing surface polishing : • roughness <1 A RMS • flatness l/10 • final thickness 0. 5 mm 3. Tantala deposition by LMA Lyon (single layer of 131 nm) on n° 40 samples (full available next summer) READY FOR THE FIRST CHARACTERIZATION PIPELINE GWADW May 2009 Meeting 17

Future work Q measurements facilities updates: q Nodal suspension Ge. NS-like in a clean chamber to minimized the surface dust deposition trying to increase the level of reproducibility q A different nodal suspension is beeing arranged in Legnaro INFN laboratories (PD) for cryogenic Q measurements (Q vs T) …waiting for first coated samples (next months)… q A calibration pipeline will be performed with some spares samples q First characterization run with polished and blank Suprasil samples …at the end of the summer… q damages/modifications pipeline with the substrates samples q first characterization run with 20 coated samples …next Fall term… q second characterization run with other 20 coated samples with some different modifications suggested by first characterization run q purchase other 50 samples GWADW May 2009 Meeting 18

Coa. Ch Collaboration involves the following groups: Firenze/Urbino Genova Modena/Pisa Perugia Padova/Trento Led by F. Vetrano (Urbino University and INFN Florence) Funded by INFN (Virgo R&D Program) and Italian Ministry of Research and Education (PRINContract 2007 T 7 AC 3 L) GWADW May 2009 Meeting 19

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