FLASH-induced damage
to various optical materials
Ryszard Sobierajski
Institute of Physics
Polish Academy of Science
J. Krzywinski, L. Juha, H. Chapman, K. Sokolowski-Tinten, N. Stojanovic,
U.Zastrau, R. Bionta, J. Chalupský, J. Cihelka, J. Hajdu, S. Hau-Riege,
U.Jastrov, M. Jurek, K. Caleman, R. London, A. Krenz-Tronnier, J. Kuba,
J. Meyer-ter-Vehn, R. Nietubyc, J.B. Pelka, K.Tiedtke, S. Toleikis,
T. Tschentscher
Layout
• Damage experiment @ FLASH
– experimental setup
– irradiation conditions
• Damage (post-mortem analysis)
–
–
–
–
–
Si bulk
a-C thin layer
SiC and B4C bulk
SiC multilayer
ScSi mulitlayer
• Damage (pump-probe microscopy)
• Transmission/Reflectivity
– during the pulse
– 1 color pump-probe
• Conclusions
Damage experiment @ FLASH
Experimental setup
P&P microscope
with relay optics
UHV exp. chamber
Sample
holder
Attenuator
GMD
VUV T
Ellip. mirror
VUV R /
mirror
VUV CCD
movement relative to the focus
Damage experiment @ FLASH
Experimental setup
Damage experiment @ FLASH
Irradiation conditions
Wavelength [nm]
13.4 – 32.5
89 – 98
Pulse duration [fs]
10 – 50
30 – 100
Pulse energy [μJ]
0.1 - 20
Spot diameter [μm]
20 – 30
15 – 100
Fluence [mJ/cm2]
1 - 5000
Pulse number
1
10-100
Damage
„Post-mortem” analysis
Optical microscopy
3000
AFM
F0 < F1 < F2 < F3
recrystalisation
2000 amrophisation
1000
0
200
400
600
800
1000
-1
Raman shift (cm )
Raman spectroscopy
X-Ray Diffraction
Si – bulk
(11 pulses@89 nm)
F<4 mJ/cm2
F~40 mJ/cm2
0
200
400
600
800
1000
0
2
4
6
8
-1
Raman shift (cm )
Położenie [µm]
2.0µm
10
0
0
50
100 150 200 250 300 350
Głębokość [nm]
5
4
1
1000
3
2000 amrophisation
2
F0 < F1 < F2 < F3
recrystalisation
Głębokość [nm]
3000
6
7
F~70 mJ/cm2
0
2
4
6
Położenie [µm]
8
10
Si – bulk
([email protected] nm)
F~325 mJ/cm2
F~640 mJ/cm2
80
600
70
500
60
400
Z[nm]
50
Z[nm]
F~1.1 J/cm2
40
300
30
200
20
100
10
0
0
0
0
2
4
6
8
10 12
5
10
15
14 16
X[µm]
X[µm]
F~2 J/cm2
3.0µm
3.6µm
a-C – thin layer on Si
@89 nm
•
Amorphous-carbon samples
(a-C) consisted of 46 nm-thick
a-C layers magnetron-sputterdeposited on a silicon wafer.
The surface roughness of the
a-C layers were less than 3 Å.
virgin area
p.12 (white strip)
p.1 (???)
p.1 (midle of white dot)
p.10 (crater)
p.15 (crater)
240
220
200
180
Intensity (a.u.)
160
140
120
100
80
60
40
20
F<10 mJ/cm2
1200
1300
1400
1500
1600
-1
Raman shift [cm ]
1700
a-C – thin layer on Si
@32.5 nm
F~100-1000 mJ/cm2
6000
2-2_032 in
2-2_04 inner border
2-2_05 "bay"
2-2_07 outer border
2-2_08 pale contour
2-2_09 virgin
5000
F~10-100 mJ/cm2
4000
3000
2000
1000
0
800
1000
1200
1400
1600
1800
2000
SiC & B4C
•
SiC slabs were fabricated using
chemical-vapor deposition and
had an average grain size of 7.5
mm. After polishing and prior to
exposure, the surface roughness
of the samples was analyzed
using atomic-force microscopy
(AFM). The root-means-square
(RMS) roughness of the sample
surface was 1.8 Å.
B4C slabs were fabricated by hotpressing of B4C powder and had
an average grain size of 5 mm.
The polishing of the hot-pressed
B4C produced numerous rip outs
of B4C grains. A smooth surface
was achieved in between the rip
outs, with an RMS surface
roughness of 5 Å.
SiC
-10
(a)
0
10
Depth (nm)
•
~0.5 J/cm2
<0.3 J/cm2
<0.3 J/cm2
(b)
20
30
40
(c)
50
60
0
10
20
30
x (μm)
40
50
60
SiC multilayer
The whole spot corrected for the angle
Linear fit
1800
1600
1400
1200
2
The multilayer films consisted
of ten Si/C bilayers, sputterdeposited on a Si (100) wafer.
In order to detect radiationinduced changes of the
multilayer, we chose multilayer
design that provided a narrow
angular reflectivity peak at a
reflection angle of 45º and a
wavelength of 32 nm. This
narrow bandwidth makes the
multilayer very sensitive to any
changes in the multilayer
structure or the optical
constants of its constituents
Area [um ]
•
1000
Spot diameter
19.9 μm +- 5.7%
Fthreshold
160.0 [mJ/cm^2] +- 40.1%
800
600
400
200
0
-0,5
0,0
0,5
1,0
1,5
Ln(energy)
2,0
2,5
3,0
3,5
Damage thresholds [mJ/cm2]
λ = 89 nm
λ = 32.5 nm
Si
<4
Si
87 ± 45
a-C
<10
a-C
65 ± 30
SiC
141 ± 70
B4C
197 ± 100
CVD
diamond
156 ± 75
Dynamic of damage processes
2 color pump & probe
Transmission/Reflectivity
during the pulse
• 50 nm Si film
• 300 nm Al film
• SiO2 monocrystal
VUVR [V]
0.08
0.06
Δa/a~2%
0.04
Calculated
0.02
0
0.02
0.04 0.06
GMD [V]
0.08
Transmission/Reflectivity
during the pulse
30 fs pulse reflectivity at 32nm
Reflectance (%)
4
increasing
fluence
3
2
During the pulse
1013 W/cm2
Si/C multilayer
1014 W/cm2
1
0
35
40
45
Angle of incidence (degrees)
50
Reflectivity, optical constants unchanged
Multilayer d spacing not changed by more
than 0.3 nm
Plasma forms, layers ablate
After pulse
Transmission/Reflectivity
pump-probe
~10 fs
only first shot at given position
2
60
1.8
50
40
~2 ps
L/R
1.6
30
1.4
20
1.2
1
10
0.5
1
1.5
delay [ps]
2
2.5
Conclusions
•
The optical response at 32.5 nm wavelength of the investigated materials
(Si, SiO2 – bulk and Si, Al – thin foils) appears to be linear up to the
maximum attainable intensities (≈ 1014 W/cm2) and deposited energy
densities in excess of 100 eV per atom [publication in preparation].
•
The multilayer performance does not degrade during the damaging pulse
Initial results from one-colour pump-probe experiments in 2006 suggest
that the optical properties of the multilayer do not change significantly
from 10 fs up to 2 ps after excitation.
•
First time-resolved reflectivity measurements in the visible range of solid
surfaces (Si, GaAs) irradiated with FLASH have been investigated using
picosecond optical imaging. Distinct differences in the material response
are found in comparison to fs optical excitation. These differences are
attributed to the increased penetration depth of the XUV-radiation and the
absence of any absorption nonlinearities.
•
Damage thresholds were obtained for a variety of inorganic materials in
the wavelength range 13.5 nm - 100 nm The threshold fluence for
surface-damage is comparable to the fluence required for thermal
melting. For larger fluences, the crater depths and morphology suggest
that the craters are formed by ejection of (2-phase) molten material. For
optical lasers such behavior is only known in the case of cw- and longpulse irradiation.
Literature
1)
2)
3)
4)
5)
6)
7)
S.P. Hau-Riege et al.: Sub-nanometer scale measurements of the
interaction of ultrafast soft x-ray free-electron-laser pulses with matter
(submitted 2006).
N. Stojanovic et al.: Ablation of solids using a femtosecond XUV free
electron laser (accepted for publication Appl. Phys. Lett., 2006).
S.P. Hau-Riege et al., “Damage threshold of solids under free-electronlaser irradiation at 32nm wavelength” (submitted 2006).
J. Krzywinski et al.: Conductors, semiconductors and insulators irradiated
with a short-wavelength free-electron laser (accepted for publication in J.
App. Phys., 2006).
FLASH beamtime report - 2005
16) L. Juha et al.: Radiation damage to amorphous-carbon optical
coatings, Proc. SPIE 5917, 91 (2005).
17) J. Chalupský et al.: Ablation of organic molecular solids by focused
soft X-ray free-electron laser radiation presented at the 10th International
Conference on X-ray Lasers – ICXRL 2006, Berlin, August 21-26 2006;
submitted to the Proceedings.