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Croissance et caractérisation de cristaux de saphir dopés Ti pour
lasers de puissanceThierry Duffar
Gourav Sen, Carmen Stelian
José Baruchel, Thu Nhi Tran Caliste
Nicolas Barthalay
RSA Le Rubis SARSA, a French company, is one of the world largest producer of synthetic sapphire, ruby and spinels.
TITANSAPHIR Project Growth of Titanium‐doped Sapphire single crystals for power laser applications.
Find growth process improvementsCharacterization of the defects inside the crystals
TITANSAPHIR Project
Industrial partners Research Labs
Crystal Growth
Growth Furnace Laser
Optics
Defect Characterisation
& Growth process
OpticalCharacterisation
2
3
Melting point: 2050 ºCMohs hardness: 9
Natural sapphire
Artificial grown sapphire
Sapphire:Al2O3
Industrial furnace
Fig. 3 Schematic representation of the Kyropoulos method
Pull Seed
Crucible
Crystal
Melt
Bottom
heater
Thermal
insulation
Side heater
Weight
Kyropoulos growth technique advantages
• Possibility to grow crystals with large diameter ( 30 cm).
• Growth inside melt and without contact with crucible.
• Low dislocation density.
Sapphire disks High power Lasers
Kyropoulos Crystal Growth
4
Crystal Morphology
20 cm5
Global modeling of thermal and velocity field(COMSOL)
Crucible diameter 30 cm
Plate formation at crystal head
h15.0t it
6
Temporal concave shape of the crystal
Marangoni No Marangoni
Effect of the Marangoni convection
Plate formation at crystal head
7
Fig. 3 Schematic representation of the Kyropoulos method
Pull Seed
Crucible
Crystal
Melt
Bottom
heater
Thermal
insulation
Side heater
Weight
Growth control system
0 10000 20000 30000Gro
wth
:Pu
llin
g(g
m/m
m)
Gro
wth
rat
e(g
m/h
r)
Mass of ingot(gm)
Ideal Growth Parameter
Growthrate(Ideal)growth:pulling(ideal)
Control Program
Feedback
Input Power control
8
0.00100.00200.00300.00400.00500.00600.00700.00800.00900.00
0.00
50.00
100.00
150.00
200.00
250.00
300.00
350.00
0 5000 10000 15000 20000 25000
Gro
wth
:Pu
llin
g(gm
/mm
)
Gro
wth
rat
e(g
m/h
r)
Mass of ingot(gm)
Growthrate(Ideal)
rate
growth:pulling(ideal)
0.00100.00200.00300.00400.00500.00600.00700.00800.00
0.00
50.00
100.00
150.00
200.00
250.00
0 1000 2000 3000 4000
Gro
wth
:Pu
llin
g(gm
/mm
)
Gro
wth
Rat
e(g
m/h
r)
Mass of Ingot(gm)
Non-uniform shape of crystal
9
10/20
0.00
200.00
400.00
600.00
800.00
1000.00
1200.00
1400.00
1600.00
0.00
50.00
100.00
150.00
200.00
250.00
300.00
0 5000 10000 15000 20000 25000
Gro
wth
:Pu
llin
g(gm
/mm
)
Gro
wth
Rat
e(g
m/h
r)
Mass of ingot(gm)
Growth rate(Ideal)
rate
growth:pulling(ideal)
growth:pulling
0.00
500.00
1000.00
1500.00
2000.00
0.00
50.00
100.00
150.00
200.00
250.00
300.00
0 1000 2000 3000 4000
Gro
wth
:Pu
llin
g(gm
/mm
)
Gro
wth
Rat
e(g
m/h
r)
Mass of ingot(gm)
(initial)
Plate formation in crystal
10
11/20
0.00
100.00
200.00
300.00
400.00
500.00
600.00
700.00
800.00
0.00
20.00
40.00
60.00
80.00
100.00
120.00
140.00
0 5000 1000015000200002500030000
Gro
wth
:Pu
llin
g(gm
/mm
)
Gro
wth
rat
e(g
m/h
r)
Mass of ingot(gm)
Growth rate(Ideal)
Growth rate
growth:pulling(ideal)
growth:pulling
0.00
200.00
400.00
600.00
800.00
0.00
20.00
40.00
60.00
80.00
0 1000 2000 3000 4000
Gro
wth
:Pu
llin
g(gm
/mm
)
Gro
wth
rat
e(g
m/h
r)
Mass of ingot(gm)
(initial)
Good crystal morphology
11
Fig. 3 Schematic representation of the Kyropoulos method
Pull Seed
Crucible
Crystal
Melt
Bottom
heater
Thermal
insulation
Side heater
Weight
Automatic crystal radius control
Growth control
hmelt
Levelsensor
Feedback
12
53.1cm8.2/cm28.4 55.1cm9.2/cm5.4
Numerical modeling Experimental visualization
of the growth interface
Numerical Modelling
13
Numerical modellingTi distribution
14
Flow
100 mm
Radial distribution of titanium
Large curvatures of the crystal-melt
interface
Radial compositionalnon-homogeneity
Variations in the intensity of the emitted
laser beam
15
Crucible diameter 15 cmSlices of 10 cm in diameter Measurements of the absorption coefficient
C. Stelian, G. Alombert-Goget, G. Sen, N. Barthalay, K. Lebbou, T. Duffar, Analysis of titanium distribution in sapphire crystalsgrown by the Kyropoulos method, article in preparation
Radial distribution of titanium
16
23⁰
26⁰
≈ 25⁰
25⁰
65⁰
Seed axis
A-axisA-axis
Solid-liquid crystal interface realised fromprevious pulling. (Interface angle: approx 25⁰)
Prepare seeds from existing crystals with an axis offset of 65⁰ with A-axis
New approach to preparation of seeds
17
A-axisA-axis
A-axis
A-axis
A-axis
Seed axis
A-axis
Crystal grown with the offset seed axis will lead to crystals having the A-plane parallel to the solid-liquid growthinterface. Thus A-Plane alligned discs can be cut out of various sizes parallel to the interface shape.
New approach to cutting Discs
18
Sapphire crystal & sample
• 6 kg in weight• Diameter – 10 cm• Height – 16 cm• Duration of growth – 6 days
A-a
xis
C-a
xis
19
X-ray diffraction imaging (x-ray topography)
• Bragg diffraction
• Image defects in the crystal lattice via the deformation around them diffracted intensity/direction altered contrast• White beam (polychromatic)• Section topography
Polychromatic (“white”) X-ray beam
SampleBeamstop
Detector
Diffraction images
(Beam sizes not to scale)
Beamline: BM – 05
20
Projection & Section topography
V
2D detector
(Photographic plate)
Crystal2D detector
(Photographic plate)
Crystal
Projection Section (slit configuration)
Reveals the features within the depth of the sampleGood lateral spatial resolution, but poor depth resolution
Polychromatic
parallel beam
Polychromatic parallel
beam passing through
thin slits
21
Diffraction spots
C-axis
Rectangular sample
A-axis
22
Dislocation density(Quantitative estimation)
a1 and a2 – dislocations,
b – scratch marks,
c – precipitate
a1
a2
c
b1mm 0
5000
10000
15000
20000
25000
30000
35000
40000
0 20 40
Dis
loca
tio
n d
ensi
tyD
islo
cati
on
s/cm
^2
Distance from centre (mm)
Total no.ofdislocations
completedislocations
15
16
17
18
23
Numerical modeling (COMSOL)
0
500
1000
1500
2000
2500
0 1 2 3Te
mp
erat
ure
gra
die
nt
(K.c
m-1
)Radial Distance From Centre (cm
Temperature gradient vs Radial location
24
Conclusions
• Growth of 20cm diameter Al2O3:Ti crystals by
Kyropoulos technique
• Top plate problem solved
• Full shape control under progress
• Radial Ti segregation solution
• Dislocations are the main type of defects,. 103-104 cm-2
• good quality which is suitable for optical applications
25
Current Segregation profileWe have a concentric profile of segregation owing to the conical interface shape. The concentric profile isvery detrimental for the optical properties.
Improved Segregation profileThough we will still have segregation the gradient will bemuch reduced. Also we get rid of the concentric gradient profile and hence the centre is not distorted.
Change in Ti segregation pattern
27
Diffraction spots(Circular Sample)
C-axis
A-axis
Circular sample
28