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Low temperature dissipation in coating materials

S. Reid1, I. Martin1, H. Armandula3, R. Bassiri1, E. Chalkley1 C. Comtet4, M.M.

Feer !, A. "retarsson#, ". Harry$, %. Hou&h1, '. (u!, I. M)(aren1, %*M.M.

Ma)ko+ski4, . Mor&ado4, R. a+rodt-, S. 'enn, A. Remillieu/4, S. Ro+an1, R.

Route!, A. S)hroeter -, C. S)h+ar0-, '. Seidel-, . 2iayra&haan!, . 2odel-, A.

ood)ra5t1 1SUPA, University of Glasgow, Scotland. 2Friedrich-Schiller University, Jena, Germany. 3LIGO

Laboratory, California Institte of !echnolo"y, US#. $L%#, Lyon, France. 5Stanford University, USA.&'mbry-(iddle #eronatical University, US#.  ) LIGO Laboratory, %assachsetts Institte of

!echnolo"y, US#. *+obart and illiam Smith Colle"es, US#.

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verview

!ntroduction and e"perimental details #easurements of t$e low temperature dissipation pea%

in &a25 coatings

Possi'le dissipation mec$anism in ion 'eam sputtered

&a2(5 )ffect of &i2 doping on t$e loss in &a25 coatings

)ffect of annealing on t$e loss in &a25 coatings

*omparison of dissipation in &a25 and Si2 films as a

function of temperature #agnetron sputtered Si2 results from +ena University

slides courtesy of -onny awrodt/

Preliminary results of 0afnia.

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!ntroduction

#ec$anical dissipation from dielectric mirrorcoatings is predicted to 'e a significant source oft$ermal noise for advanced detectors.

)"periments suggest &a25 is t$e dominant source of dissipation in

current Si2&a25 coatings oping t$e &a25 wit$ &i2 can reduce t$e

mec$anical dissipation

#ec$anism responsi'le for t$e o'servedmec$anical loss in &a

2

5 as yet not clearly

identified

G)3(( mirror suspension,

wit$ 0- coating on front

face. Studying dissipation as a function of temperature of interest to4

etermine dissipation mec$anisms in t$e coatings, possi'ly allowingdissipation to 'e reduced

)valuate coating for possi'le use in proposed cryogenic gravitational

wave detectors 

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Single layer coating samples for low

temperature studies

&$in silicon su'strates used for coating Loss of silicon decreases at low temperature *oating will dominate t$e loss

Samples etc$ed from silicon wafers, wit$ t$ic%er clamping 'loc% toisolate cantilever from clamp

(.5 µm t$ic% films deposited 'y ion 'eam sputtering, including a/&a25 doped wit$ 1.5 6 1/7 &i2 '/ un8doped &a25 c/ Si2 and

d/ $afnia

34mm

500 

m48 m Coating appliedhere

Titania doped tantala coatedsilicon cantilever in clamp

uncoated silicon cantilever in clamp

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#easuring coating loss

0 200 400 600 800

-0.04

-0.02

0.00

0.02

0.04

   C  a  n   t   i   l  e  v  e  r   d   i  s  p   l  a  c  e  m  e  n   t  a  n  g   l  e   (  r  a

   d  s   )

Time (s)

 cantilever displacement angle

 exponential fit

9ending modes of cantilevere"cited electrostatically, loss

φ  ω  o'tained from

e"ponential amplitude

ringdown

Loss of coating material

calculated from losses of

coated and un8coated

cantilevers

Loss of coating material is

given 'y4

ratio of energy stored in

cantilever to energy storedin coating

difference in loss between

coated and un-coatedcantilevers

Typical amplitude of ring-down

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#ec$anical loss measurements

*omparison of t$e mec$anical loss of t$e t$ird 'ending mode :1((( 0;/

for a cantilever coated wit$ &a25 wit$ 1.5 7 &i2, and an identical un8coated cantilever in colla'oration wit$ +ena University/

6 !6 166 1!6 -66 -!6 366

6.6

!.6/16*#

1.6/16*!

1.!/16*!

-.6/16*!

-.!/16*!

3.6/16*!

3.!/16*!

 

3rd mode un)oated

 3rd )oated

   M  e  )   h  a  n   i  )  a   l    l  o  s  s       φ

7em8erature 9:

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Low temperature coating loss pea%

A dissipation pea% at :1

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#ost internal friction mec$anisms may 'e t$oug$t of as rela"ation processes

associated wit$ transitions 'etween e>uili'rium states, and typically4

w$ere τ  is t$e rela"ation time

∆ is a constant related to $eig$t of pea%

&$ermally activated processes follow Arr$enius e>uation4

w$ere τ (81 is t$e rate factor and ' a is t$e activation energy for t$e process

At t$e dissipation pea%, ωτ ?1 and

$ence

!nterpretation and analysis

( ) 21)(

ωτ 

ωτ ω φ 

+∆=

T  K 

 E 

 B

a

e−

−−

=11

0

τ τ 

 peak  B

a

T  K  E 

e−

−

=

1

0τ ω 

 peak  B

a

T  K 

 E −=

  −10lnln τ ω 

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Fittin& to Arrhenius e=uation 

&$is gives an activation energy associated wit$ t$e dissipation pea%

in doped tantala of 2 6 2/ me@, and a rate factor of .×1014 Hz.

6.64# 6.64 6.6!6 6.6!- 6.6!4 6.6!# 6.6!

!

#

$

;

16

11

 (inear 5it y  > 4;- x  ? 33.4

   l  n   9     ω

   6   :

1@78eak

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*oating Structure

*onvergent 'eam electron diffraction measurements a/ of a pureion8'eam sputtered &a25 layer see &)# image, '// s$own only

diffuse rings of intensity, confirming t$at t$e layer is amorp$ous.

&a25 layer

Si2 layer

a/ '/

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!nterpretation B dou'le well potential

Low temperature dissipation pea% in fused silica $as similar

activation energy me@/ "ygen atoms can undergo t$ermally activated

transitions 'etween two possi'le energy states in a dou'le

well potential

Cidt$ of t$e dissipation pea% t$oug$t to 'e related to t$e

distri'ution of Si8 'ond angles in t$e sample

&$e dissipation mec$anism in doped &a25 may 'e similar,

'ut re>uires furt$er study

stable Si-

bond angle

potential

barrier

stable Si-

bond angle    P  o   t  e  n   t   i  a   l  e  n  e  r  g  y

)a

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)ffect of doping &a25 wit$ 1.5 7 &i2 

*omparison of dissipation pea% in doped and un8doped &a25 for t$

 left/ and 5t$

 'ending modes rig$t/.

! 16 1! -6 -! 36 3! 46 4!

4.6/16*4

#.6/16*4

.6/16*4

1.6/16*3

1.-/16*3

Ando8ed tantala B 3366 H0 mode

Co8ed tantala B 3366 H0 mode

   M  e  )   h  a  n   i  )  a   l   l  o  s  s

7em8erature 9:

! 16 1! -6 -! 36 3! 46 4!

4.6/16*4

#.6/16*4

.6/16*4

1.6/16*3

1.-/16*3

ndo8ed tantala 1;66 H0 mode

o8ed tantala 1;66 H0 mod

   M  e  )   h  a  n   i  )  a   l   l  o  s  s

7em8erature 9:

  oping appears to reduce t$e $eig$t of t$e pea% and slig$tly reduce

t$e widt$ of t$e pea%

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6 !6 166 1!6 -66 -!6 366

-.6/16*4

4.6/16*4

#.6/16*4

.6/16*4

1.6/16*3

1.-/16*3

1.4/16*3

 

Ando8ed tantala B1666 H0 mode Co8ed tantala B 1666 H0

   M  e  )   h  a  n   i  )  a   l    l  o  s  s

7em8erature 9:

)ffect of doping &a25 wit$ 1.5 7 &i2

*omparison of t$e dissipation of &i28doped and un8doped &a25

oping reduces loss of &a25 t$roug$out temperature range

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)ffect of annealing

0eat treatment can reduce t$e dissipation in Si2 possi'ly 'y c$anging distri'ution of 'ond angles

!f dissipation mec$anism in &a25 is indeed similar to Si2 

it may 'e possi'le to modify c$aracteristics of t$edissipation pea% 'y $eat treatment

&a25 %nown to crystallise a'ove : 35( °*

)"periment currently underway to measure un8doped

&a25 coatings annealed at ((, ((, 3(( and

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6 !6 166 1!6 -66 -!6 366

-.6/16*!

4.6/16*!

#.6/16*!

.6/16*!

1.6/16*4

 66 de&ree C anneal #66 de&ree C anneal

   (  o  s  s  o   5  )  o  a   t  e   d  )  a  n   t   i   l  e  3  e  r

7em8erature 9:

)ffect of annealing temperature

Loss at 1D(( 0; of &a25 annealed at

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*omparison of Si2 and &a25

6 !6 166 1!6 -66 -!6 366

-.6/16*4

4.6/16*4

#.6/16*4

.6/16*4

1.6/16*3

 

7antala )oatin& 3!6 H0

 Sili)a )oatin& 3!6 H0

   M  e  )   h  a  n   i  )  a   l    d   i  s  s   i  8  a   t   i  o  n

7em8erature 9:

Loss of ion 'eam sputtered Si2 is significantly lower t$an loss

of &a25 'etween 1( and (( =.

scatter athigher

temperaturespossibly due to

loss into clamp#

$ecent datasuggests Si% 

loss of &4×10-5 

at room

temperature#

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*onclusions B &a25

issipation pea% o'served at : 2( = in 'ot$ pure &a25 and in &a25 doped wit$ 1.5 7 &i2 

Activation energy of dissipation process calculated to 'e 2 6 2 me@ 

for doped coating/. Possi'le dissipation mec$anism is t$ermally

activated transitions of t$e o"ygen atoms, similar to t$at in fused silica

Some evidence t$at &i2 doping reduces t$e $eig$t of t$e dissipation

pea% in &a25,in addition to reducing t$e loss at room temperature.

&a25 coatings annealed at

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#agnetron Sputtered Silica (( nm/ 8 +ena

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fre>uency4 2.< %0;

geometry4 5( mm F < mm F ( Hm

#agnetron Sputtered Silica (( nm/ 8 +ena

)oated )antileer )oatin& loss

un)oated )antileer 

thermoelasti) ? residual &as loss

 *ompara'le level of o'served loss associated wit$ t$e magnetron

sputtered silica coating at :1(( = to ion8'eam sputtered silica.

 0owever, 'elow 1(( = no dissipation pea% o'served in magnetron  sputtered silica

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 3 0; mode B resonance wit$ clamping structure

 Loss increases for all modes at low temperatures

#agnetron Sputtered Silica (( nm/ 8 +ena

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Preliminary studies on 0f2

ew cryogenic setup in Glasgow4500nm 'f% 

coating on asilicon cantilever

uncoated silicon

cantilever

thermal stresses

in coating clearlyobserved in the

bending of the

silicon substrate

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Preliminary 0f2 compared to &a25

At 1(( =, t$e level of mec$anical loss associated wit$ 'ot$ doped

tantala and $afnia appear at a level φ(ω)coating : F1(8.

9elow 1(( =, t$e loss of tantala is o'served to rise to a dissipation pea%,

w$ereas t$e loss of $afnia appears to decrease to 'elow F1(8 at :15 =.

6 !6 166 1!6 -66 -!6 366

-.6/16*4

4.6/16*4

#.6/16*4

.6/16*4

1.6/16*3

1.-/16*3

1.4/16*3

 

Ando8ed tantala B1666 H0 mode

 Co8ed tantala B 1666 H0

   M  e  )   h  a  n   i  )  a   l   l  o  s

  s

7em8erature 9:

0f0f22 at D3( 0;at D3( 0;

&a&a2255 at D3( 0;at D3( 0;

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Preliminary 0f2 compared to &a25

Preliminary results of t$e mec$anical loss of 0afnia does not s$ow a largedissipation pea% at low &.

ote4 t$e $ig$er IoungJs modulus of 0afnia s$ould lead to lower t$ermal

noise for t$e same φ.d loss8t$ic%ness product/ B in t$e case of silicon

optics not true for ot$er materials e.". fused silica/.

!nitial room temperature studies on a multi8layer silica8$afnia coating ona fused silica su'strate were found to 'e φ$afnia?5.6(./F1(8.

0owever material properties for t$in8film 0afnia are not well studied and

any c$anges over 'ul% properties will c$ange t$e results presented $ere.

&$e optical properties also re>uire furt$er investigation, w$ere initial

recent a'sorption studies of a multilayer silica8$afnia coating 'y

#ar%osyan et al. Stanford University/ lie in t$e range 3(8