Silicate bonding on silicon and silica
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Transcript of Silicate bonding on silicon and silica
Silicate bonding on silicon and silica
S. Reid, J. Hough, I. Martin, P. Murray, S. Rowan,J. Scott, M.v. Veggel
University of Glasgow
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Introduction: Current applications
Originally developed for NASA’s Gravity Probe B mission, launched April 2004. (Gwo et al., patent)
GEO600 currently operates with quasi-monolithic fused silica suspensions and mirrors. This technology allows improved thermal noise in the suspension systems.
Construction of the ultra-rigid, ultra-stable optical benches for the LISA Pathfinder mission.
Picture of a GEO600 sized silica test mass in Glasgow with silica
ears jointed using hydroxy-catalysis bonding
Silica fibres are welded to the ears in the completion of the lower-
stage of the GEO600 mirror suspension.
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Introduction: Planned applications
The upgrades for Advanced LIGO plan to incorporate the GEO600 technology for significantly improved thermal noise performance – and under consideration for Advanced VIRGO (in addition to other improvements, e.g higher power lasers).
Construction of the ultra-rigid, ultra-stable optical benches for LISA.
Design sensitivity curves for the LIGO and AdvLIGO detectors.
10-21
10-22
10-23
10-24
h
Wire looparm length: 4 km
Quadruple stagesilica ribbons/fibres
eg. LIGO AdvLIGO
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Introduction: Future applications (silicon)
The construction of a 3rd generation gravitational wave observatory within Europe E.T. (Einstein Telescope) and under consideration for the construction of the DUAL resonant mass detector.
Credit: M.Punturo
LIGO 2005 Bars 2005
Advanced LIGO/Virgo (2014)
Virgo Design
GEO-HF
2009
Virgo+ 2008
Einstein GW Telescope
DUAL Mo(Quantum Limit)
M. Punturo et al.
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Studies on silicate bonding of silica in relationto the Advanced generation of GW detectors
Settling time investigate details of the underlying chemistry e.g. Through the Arrenhius
equation time available for bond adjustment and alignment
Bond structural properties Close inspection of bonds through electron microsopy can reveal properties
such as: bond thickness, molecular structures in addition to imperfections/inhomogeneities at the microscopy-scale.
Bond mechanical properties Mechanical strength (studying the factors responsible for strength and
reliability)
Mechanical loss in addition to bond thickness will allow the level of mechanical dissipation associated with the bond layer to be calculated – thus allowing precise modelling of the level of thermal noise expected from silicate bonds in future gravitational wave detectors.
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Studies on silicate bonding of silica in relationto the Advanced generation of GW detectors
Bond mechanicalproperties
Bond structuralproperties
Settling time
experiments
S. Reid et al.,PLA 363 341-345 (2006)
Activation energy:Ea = 0.545 eV permolecule of OH−
Above plot showing settling time as a function of
temperature for silica-silica bonds
Above plot showing two bonded silica cylinders, studied before and after
silicate bonding.
Experiments suggest that the level of loss associated with
silicate bonding may lie:bond ~ (0.3→1.2)×10-1
(across the differentmeasured modes).
SEM SEM
TEM
TEM
AFM
(81±4) nm
7.9 GPa
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Required studies on silicate bondingof silicon in relation to future detectors
Settling time
Bond structural properties
Bond mechanical properties
Surface preparation (oxidisation techniques)
Thermomechanical properties
Temperature cycling effects/failures
In addition to characterising these properties in relation to silicon-silicon bonds,
it is also necessary to understand the required surface preparation and the cooling performance available for bonded silicon components.
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Wealth of literature on oxidation techniques
For example: Deal, B.E., Grove, A.S. General relationship for the thermal oxidation of silicon. Journal of Applied Physics, vol. 36, no. 12, pp. 3770 – 3778, 1965 Found quantitative relations of the rate of growth of thermal
oxide
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Relevant literature knowledge
Qualitative statements B.E. Deal, A.S. Grove Wet oxidised surfaces give a less dense silicon oxide then dry
oxidised surfaces – possibility of having an effect on bond strength and thermal noise.
Carrier gas for wet oxidation doesn’t make a difference in oxidation speed (nitrogen or oxygen). Thus undissociated H2O is the oxidising agent.
In dry oxidation molecular oxygen is oxidising agent. Flow speed in wet oxidation doesn’t influence speed of
oxidation. Higher oxidation temperature gives higher density.
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Visable appearance of thermal oxides on silicon
Color of oxide as a function of thickness Note, this is also dependent on viewing angle.
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Oxidation results (oxide colors) in Glasgow
Shown layer thicknesses are expected layer thicknesses
Colours don’t match with corresponding layer thicknesses on graph in previous slide
Colours don’t match between wet and dry oxidation of the same prospected thickness
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PV flatness change as a function of oxidation regime
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0
50
100
150
200
250
300
350
oxidation regime
PV
fla
tnes
s ch
ang
e [n
m]
Delta PV flatnessgood side
Delta PV flatnessbad side
Oxidation results (change in flatness)
50 nmwet1000C
100 nmwet1000C
200 nmwet1000C
100 nmdry920C
50 nmdry1000C
100 nmdry1000C
200 nmdry1000C
Localised dip in surface
Spikes on edge of surface
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Oxidation results (change in flatness)
0
50
100
150
200
250
300
Batch no. 1
PV fl
atne
ss [
nm]
Before oxidisationAfter oxidisation
Batch no. 2
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Bond thickness
Comparison of silica-silicon SEM images
40 nm
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Thermal conductivity of silicate bondsin collaboration with Firenze
The first set of silicate bonded silicon-silicon have been fabricated with varying volumes of 1:6 sodium silicate solution at Glasgow.
Samples sent to Florence for thermal conductivity measurements.
Volumes of bonding solution: 0.4 ml cm-2, 0.2 ml cm-2 and0.1 ml cm-2. (Advanced LIGO specification)
See following talk by Enrico Campagna.
diameter = 25.4 mm 12.7 mm
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Mechanical strength of bonds
Initial tests showed that a pair of silicate bonded 1” silicon disks supported 40Kg for 2 week (~1 MPa).
40Kg load suspended Si-Si sample under load
40Kg
clamped sample wire loop
rubber ring
lightlyclamped
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Test setups for mechanical strengthtesting of silicon-silicon
New strength testing setups have been designed and ready for use.(M. v. Veggel)
pure shearstrength test
Four-point bending test (peeling test)
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The ability of silicate bonds to withstand repeated temperature cycles must be verified, in addition to withstanding the thermal stresses that may be induced during cooling.
Repeated cycles from room temperature to 77K were performed on bonded samples of silicon with no bond failures (in addition to this various samples of different materials including SiO2-ZnSe, SiO2-Ge, SiO2-ULE, SiO2
‐Al2O3, all of whom have different coeff. of thermal expansion)
Temperature cycling
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Conclusion
Silicate bonding appears to be a highly promising technique for the construction of cryogenic and ultra-low loss monolithic suspensions
Current estimates suggest that the thermal noise associated with silicate bonding will have a negligible contribution to the overall thermal noise in Advanced LIGO and likewise Advanced VIRGO.
Future work: extend the studies of bond thermal noise