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Regina Soufli
Corrosion-resistant Mg-based multilayer coatings for sources > 25 nm
Regina SoufliLawrence Livermore National Laboratory
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
EUVL Workshop, LBNL, June 13-14, 2018
LLNL-PROC-754006
Regina Soufli
Technical contributors
• Jeff C. Robinson, Monica Fernández-Perea, Christopher C. Walton,
Sherry L. Baker, Jennifer Alameda (LLNL)
• Eric M. Gullikson, Julia Meyer-Ilse (CXRO/LBNL)
• Luis Rodríguez-De Marcos, Jose A. Méndez, Manuela Vidal-Dasilva,
Juan I. Larruquert (Instituto de Óptica, Consejo Superior de
Investigaciones Científicas (CSIC), Madrid, Spain)
Regina Soufli
Overview
➢ Motivation: applications at = 25 – 80 nm that benefit from Mg/SiC
multilayers
➢ Design and experimental performance of Mg/SiC multilayers
➢ Origins, propagation mechanisms and impact of Mg/SiC corrosion
➢ Al-Mg corrosion barriers for Mg/SiC
• Al-Mg spontaneous intermixing and amorphization
• Lifetime properties and performance optimization of Mg/SiC with
Al-Mg corrosion barriers
Multilayer coatings with stability > 10 years are needed for space-borne EUV solar physics telescopes
6 EUV wavelengths (94 - 304 Å) on a single telescope.
4 telescopes 2 wavelengths per telescope7 EUV wavelengths, 94 - 335 Å. 1 arcsec resolution41x41 arcmin FOV12 sec cadence 2 Tbytes / day
Soufli, Proc. SPIE 59010M (2005)
Soufli, Appl. Opt. 46, 3156-3163 (2007)
Boerner, Solar Physics 275, 41-66 (2012)
Lemen, Solar Physics 275, 17-40 (2012)
Soufli, Proc. SPIE 8443R (2012)
Martinez-Galarce, Opt. Eng. 52, 095102 (2013).
94 131
171
195284
304
NASA/NOAA’s GOES-R,-S,-T,-U space weather satellites. Launch: 2016 - 2020
Multilayer-coated SDO telescope mirror pair
193Å
193
211Å
211
NASA’s Solar Dynamics Observatory (SDO). Launched: February 11, 2010.
GOES-R secondary mirror
131 Å 93.9 Å 335.4 Å 211.3 Å
1600 Å 303.8 Å171.1 Å193.5 Å
Laser Pumped SXRL λ= 8.8– 32.6 nm
Discharge Pumped SXRL λ=46.9 nm
100 nm lines
82 nm holes
Chemical spectroscopies
Microscopy
Nanomachining
Interferometry
Compact plasma-based EUV laser sources and applications need efficient multilayer coatings
Plasma diagnostics
58 nm pillars
Nanopatterning
• High pulse energy (µJ-mJ)
• High monochromaticity (λ/Δλ < 10-4)
• High peak spectral brightness
Courtesy: Profs. Jorge Rocca and Carmen Menoni,
Colorado State University
Regina Soufli
EUV Lithography: ETS1, ETS2, MET2, MET5 EUV solar missions and laser sources
Hard x-ray /gamma-ray astrophysics, radiation detection, target diagnostics
Our group at LLNL has participated in the development of short-wavelength optics for various applications
X-ray optics for the LCLS free-electron laser
NASA’s NuSTAR
Regina Soufli
LLNL facilities for thin film deposition and characterization
DC- and RF-magnetron sputtering deposition
systems ZYGO AFM SEM
Precision surface metrology
Also (not pictured):
o Contact profilometers
o Thin film stress measurement apparatus
o Full-aperture interferometers
Custom cleaning facility for optical
substrates
X-Ray Diffractometer
Regina Soufli
Calibration and standards ALS beamline 6.3.2 λ = 1-90 nm
Light sources employed for at-wavelength testing of multilayer optics in this presentation
GOLD facility, λ = 50-200 nm
Regina Soufli
10-3
10-2
10-1
100
10 20 30 40 50 60 70 80 90 100
SiSc
Al
Mg
wavelength (nm)
exti
nct
ion
coef
fici
ent,
kMg exhibits low absorption in an extended wavelength range for > 25 nm (Mg L2,3 edge)
Refractive index = n + i*k
Extinction coefficient k values
obtained from:
1. Mg: M. Vidal-Dasilva, et al, J. Appl.
Phys. 108, 063517 (2010).
2. Al: E. Shiles, et al, Phys. Rev. B
22, 1612-1628 (1980), as compiled by
E. D. Palik, Handbook of optical
constants of solids (Academic Press,
1985).
3. Si: R. Soufli and E. M. Gullikson,
Appl. Opt. 36, 5499-5507 (1997).
H. R. Philipp, J. Appl. Phys. 43, 2835-
2839 (1972), compiled by E. D. Palik,
Handbook of optical constants of
solids (Academic Press, 1985).
4. Sc: M. Fernández-Perea, et al, J.
Opt. Soc. Am. A 23, 2880-2887
(2006).
Regina Soufli
0
0.1
0.2
0.3
0.4
20 50 100 200
measured
model
= 85a
wavelength (nm)
Ref
lect
an
ce
10-6
10-5
10-4
10-3
10-2
10-1
10 20 50 100 200
measured
model
= 85
b
wavelength (nm)
Ref
lect
an
ce
Mg/SiC achieves the highest narrowband peak reflectance at = 76.9 nm: R = 40.6% at near-normal incidence
d=52.4 nm
Mg=0.77
N=10
❑ Mesurements performed at:
• Beamline 6.3.2., Advanced Light Source, LBNL, for < 50 nm
• GOLD facility, Instituto de Óptica, Madrid, Spain, for = 50-200 nm
❑ Model = IMD software by D. L. Windt, Computers in Physics 12, 360–370 (1998)
Standard Mg/SiC (no corrosion barriers)
1st
2nd
3rd
4th
1st2nd
3rd
4th
M. Fernández-Perea, R. Soufli, J. C. Robinson, L. Rodríguez-de Marcos, J. A. Mendez, J. I. Larruquert and E.
M. Gullikson, “Triple-wavelength, narrowband Mg/SiC multilayers with corrosion barriers and high peak
reflectance in the 25-80 nm wavelength region”, Optics Express 20, 24018-24029 (2012).
Regina Soufli
Mg/SiC is the best multilayer for the 25-80 nm wavelength region, except ….
H. Takenaka et al., J.of El. Spectr. and Rel.
Phen. 144-147, 1047 (2005).
Calculated ideal reflectivity (roughness=0)
for different multilayers Mg/SiC deposited at LLNL, measured at
ALS beamline 6.3.2
Mg/SiC exhibits a unique combination of high reflectivity, near-zero stress,
thermal stability to ~350 C and good spectral selectivity compared to other
candidate multilayer pairs in the 25-80 nm region
0
0.1
0.2
0.3
0.4
0.5
25 30 35 40 45 50
Measured
Fit
Wavelength (nm)
Ref
lect
ivit
y
measured
model
LLNL-PROC-754006
Regina Soufli
(a) (b)
(c) (d)
50 m
50 m
25 m
25 m
b2b1
d1
d3
d2
R. Soufli, M. Fernández-Perea, S. L. Baker, J. C. Robinson, J. Alameda, C.
C. Walton, App. Phys. Lett. 101, 043111 (2012).
M. G. Pelizzo, A. J. Corso, P. Zuppella, P.
Nicolosi, S. Fineschi, J. Seely, B.
Kjornrattanawanich, and D. L. Windt, Opt.
Eng. 51, 023801 (2012).
Top-surface SEM of Mg/SiC with advanced corrosion
aged for 2.7 years
Mg/SiC with advanced corrosion
aged for 4 years
…atmospheric corrosion prevents Mg/SiC from being used in applications requiring long lifetime stability
Corrosion has prevented Mg/SiC use in
EUV solar telescopes, free-electron
lasers, and HHG sources
Regina Soufli
Mg/SiC with advanced, eruptive stages of corrosion aged for 3 years.
4 top bilayers (out of 20) have been consumed and are missing
Advanced corrosion exhibits eruptive effects due to formation and volume expansion of corrosion products
0.4 m
(a)
(c)
(b)
100 m
(d)
10 m 0.1 m
Mg corrosion products
Mg SiC
Binding energy (eV) Orbital Species
50.8 Mg 2p MgO, Mg(OH)2, Mg(CO)3
532.8 O 1s OH-, Mg(OH)2
Mg /SiC multilayer
TEM and XPS analysis performed at EAG Labs, Sunnyvale, California
SEM image, top surface SEM image, top surface
TEM image, cross-section
LLNL-PROC-754006
Regina Soufli
We have elucidated the origins and propagation mechanisms of corrosion in Mg/SiC multilayers
(a) (b)
(c)
0.2 m
200 m 1 m 20 nm
(d) (e)
10 nm
Mg
SiC
Mg corrosion products
Mg /SiC multilayer
Mg
SiC
Mg corrosion products
Mg/SiC aged for 3 years, with early, pre-eruptive stages of corrosion
Atmospheric corrosion attacks Mg/SiC from the top surface via localized
entry points such as pinholes and defects, inherent in sputtered thin films
SEM image, top surface SEM image
top surface
TEM image, cross-section
LLNL-PROC-754006
Regina Soufli
Al-Mg corrosion barrier structures for Mg/SiCmultilayers
0
1000
2000
3000
4000
30 35 40 45
2 days
68 days
Mg(002)
Al(111)
Al-Mg layer
2 (deg)
Inte
nsi
ty (
a.u
.)
Days after deposition
Bragg peak, 2(deg)
Lattice spacing(nm)
Crystallite size(nm)
Al(111) 2 38.44 0.23 15.13
” 68 38.41 0.23 4.57
Mg(002) 2 34.41 0.26 16.7
” 68 35.14 0.25 9.15
(b)
Mg SiC Al-MgSiC
SiCAlMg
200 m
(a)
Mg crystallites
(c)
Al-Mg
SiC
SiC
Mg
SiC
Mg
Sparse Al, Mg crystallites
(d)
(e)
Polycrystalline Al (20 nm) and Mg (19 nm) layers spontaneously intermix to produce partially
amorphous Al-Mg layer.
Sample aged for 2.5 years
R. Soufli, M. Fernández-Perea, S. L. Baker, J. C. Robinson, J. Alameda, C. C. Walton, App. Phys. Lett. 101, 043111 (2012).
LLNL-PROC-754006
LLNL-PROC-754006
Regina Soufli
We are investigating in detail the physics of the Al-Mg intermixing and amorphization process
SiC
Al-Mg
20 nm
TEM image, cross-section
d(Al)= 20 nm, d(Mg)= 19 nm
SiC
Nano-Beam Diffraction
▪ Intermixed region of Mg layer
(bottom) exhibits higher degree of
“crystallinity” than Al layer (top)
LLNL-PROC-754006
Regina Soufli
Triple-wavelength Mg/SiC multilayers with corrosion barriers can be employed in EUV imaging or spectrometer instruments
0
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
20 50 100 200
= 85 deg
a)measured
model
wavelength (nm)
Ref
lect
an
ce
O IV / Ne VIII
(78 nm)Ne VII
(46.5 nm)
1st2nd
3rd
4th
Fe XVI
(33.5 nm) d=52.2 nm
Mg=0.78
N=9
Al-Mg=15.3% wt. Al
Refractive index values
obtained from:
1. Mg: M. Vidal-Dasilva, et al, J.
Appl. Phys. 108, 063517 (2010).
2. SiC: J. B. Kortright and D. L.
Windt, Appl. Opt. 27, 2841-2846
(1988).
3. Al: E. Shiles, et al, Phys. Rev.
B 22, 1612-1628 (1980), as
compiled by E. D. Palik,
Handbook of optical constants of
solids (Academic Press, 1985).
LLNL-PROC-754006
Regina Soufli
Reflectance loss after 3 years of aging appears to increase with Al thickness
-0.05
0
0.05
0.10
0.15
0 10 20 30 40d
Al(nm)
R
(R
fres
h-R
ag
ed/R
fres
h)
Mg/SiC samples reflecting at 28 and 46 nm, with and without Al-Mg corrosion barrier layers
LLNL-PROC-754006
Regina Soufli
• Insertion of 6 barrier layers in a Mg/SiC stack of 35 layers has minimal impact in reflectance
• Significant reflectance can be achieved even with corrosion barriers in all 35 layers
• In addition to corrosion protection, AlMg barriers improve out-of-band suppression
Performance optimization of Mg/SiC coatings with and without AlMg corrosion barriers
Measured at ALS beamline 6.3.2
0
0.1
0.2
0.3
0.4
0.5
25 26 27 28 29 30 31 32 33
Mg/SiC, N=35
= 85 deg
AlMg barriers in all 35 layers
AlMg barriers in 6 layers
No corrosion barriers
Wavelength, (nm)
Ref
lecta
nce
LLNL-PROC-754006
Regina Soufli
Summary
➢ Atmospheric corrosion has prevented the use of Mg/SiC multilayers in
applications requiring good lifetime stability, such as EUV laser sources
and solar physics
➢ We have developed Al-based barrier layers that dramatically reduce
corrosion in Mg/SiC multilayers, while preserving high reflectance
➢ Corrosion barrier layers can be customized specifically for each
multilayer design and environmental conditions
➢ Mg/SiC with Al-based corrosion barriers has been implemented in
upcoming EUV solar physics missions
➢ Investigation of the physics of spontaneous intermixing and
amorphization of sputtered Al and Mg layers is ongoing
Regina Soufli
Funding acknowledgements
• Funding for the Mg/SiC corrosion barrier work was provided by the
LLNL Laboratory Directed Research and Development program
• GOLD acknowledges financial support from the National Program
for Space Research, Subdirección General de Proyectos de
Investigación, Ministerio de Ciencia y Tecnología, project number
AYA2010-22032
• Additional funding was provided by Lockheed Martin Corporation
Internal Research and Development
LLNL-PROC-754006
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