The International Conference on
Physics of X-Ray and Neutron Multilayer Structures(PXRNMS) 2023
11-13 October 2023, Himeji Convention Center, Himeji,
Hyogo, Japan

Supported by
Bruker Japan K.K.
NTT Advanced Technology Corporation
TOYAMA
JTEC CORPORATIONKYOCERA SOC Corporation
Natsume Optical Corporation

Welcome address
On behalf of the Center for EUVL, Laboratory of Advanced Science and Technology for Industry,
University of Hyogo, and Optical Design Laboratory, Tokyo Polytechnic University, we invite you to attend
the International Conference on Physics of X-Ray and Neutron Multilayer Structures (PXRNMS) 2023. Thisconference follows the fruitful PXRNMS 2018 organized by the colleagues of the Laboratoire Charles Fabry,
Institut d'Optique Graduate School and the Laboratoire de Chimie Physique - Matiere et Rayonnement,
Sorbonne Universite and CNRS, as well as the former PXRMS conferences that were successfully organized
for many years.
This is an international conference, with approximately 80 participants each year, with approximately halfof the participants coming from Europe and America. It is held every two years mostly in the United States,
Europe, and Japan. The conference will then focus on the physics of nanometer-scale multilayer films
optimized for various applications such as extreme ultraviolet (EUV) and X-ray regions, as well as neutrons
and ion beams, and the main topics discussed are listed as follows. This time, 26 oral and 16 poster
presentations will be presented. and it will be expected approximately 90 attendees.
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Multilayer Design and Modeling
Film Growth and Microstructure
Roughness and Interface Formation
Surface and Thin-Film Modifications using Ion Beams
Film Removal Techniques
Growth Models and Computer Simulations
X-Ray and Neutron Scattering
Surface and Interface Topography
Layer and Interface Composition
Wavefront Characterization and Correction
Mechanical Properties and Stability
Optical Properties
Novel Characterization Techniques
Polarization Control
Metrology

The technological development of optical elements such as multilayer mirrors, which are necessary for theapplication of quantum beams to measurement technology, is essential for the future development of scienceand technology. In fact, Mo/Si multilayer film technology is an essential technology for EUV lithography,
and due to the success of this technology, it has been applied to the manufacturing technology ofsemiconductor logic devices of 7 nm and above since 2019. I sincerely hope that technologies from thisconference will be realized in the near future. The academic research that contributes to basic science andindustrially applied technology will be born through this conference, ranging from basic research to applied
technology and practical application.
All the program committee members and organizers and are very happy to hold this conference face-toface under the COVID-19 control, and we look forward to many useful discussions at this conference.
Yours sincerely,
Takeo Watanabe

Chief organizer of PXRNMS2023 in Japan
Professor,
Center for EUVL, Director,
Laboratory of Advanced Science and Technology for Industry, Special Assistant to the Director,
Special Assistant to the President,
University of Hyogo, Japan1

Organizers
Prof. Takeo Watanabe, Center for EUVL, University of Hyogo, Japan
Prof. Mitsunori Toyoda, Tokyo Polytechnic University, Kanagawa, Japan
Dr. Tetsuo Harada, Center for EUVL, University of Hyogo, Japan
Dr. Shinji Yamakawa, Center for EUVL, University of Hyogo, Japan
Program committee

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Dr. Sasa Bajt, DESY, Hamburg, Germany
Dr. Thierry Bigault, Institut Laue-Langevin, Grenoble, France
Prof. Fred Bijkerk, MESA+, University of Twente, Enschede, The
Netherlands
Dr. Nikolai Chkhalo, Institute for Physics of Microsctructures RAS,
Nizhny Novgorod, Russia
Prof. Franck Delmotte, Laboratoire Charles Fabry, Palaiseau, France
Dr. Hartmut Enkisch, Carl Zeiss SMT GmbH, Oberkochen, Germany
Dr. Eric Gullikson, CXRO, Lawrence Berkeley National Laboratory,
Berkeley, USA
Dr. Qiushi Huang, Tongji University, Shanghai, China
Dr. Philippe Jonnard, Sorbonne University, CNRS, Paris, France
Dr. Maria G. Pelizzo, University of Padua, Department of Information
Engineering, Italy
Dr. Regina Soufli, Lawrence Livermore National Laboratory, Livermore,USA
Dr. Eric Louis, MESA+, University of Twente, Enschede, The
Netherlands
Dr. Igor Makhotkin, MESA+, University of Twente, Enschede, The
Netherlands
Prof. Mitsunori Toyoda, Tokyo Polytechnic University
Prof. Takeo Watanabe, Center for EUVL, University of Hyogo, Japan2

PXRNMS2023 Program
Oral Presentation
Wednesday, 11th Oct.

Page No.

Conference Place: Medium Hall of Acrea Himeji
https://www.himeji-ccc.jp/img/pdf/pamphlet_A4-en-202304.pdf

9:00

Coffee & Sandwitch

9:55

Opening Remarks
Takeo Watanabe (Univ. of Hyogo)

10:05(Keynote)
Development and Application of Multilayer Mirror
13
Hisataka Takenaka (TOYAMA)

10:45(Invited)
Tailoring the nanoscale multilayer optics with high efficiency and precision for EUV,
X-ray and Neutron applications

14

Qiushi Huang, Runze Qi, Zhe Zhang, Zhong Zhang ,Wenbin Li, Shengzhen Yi, Zhanshan Wang (Tongji University)
Igor V. Kozhevnikov (Shubnikov Institute of Crystallography))

11:10― Coffee Break (30 min)―

11:40(Invited)
Interface characterization of neutron and X-ray multilayer using Grazing Incidence X-ray
Absorption & Fluorescence spectroscopy experiments at Indus-2 SRS

15Arup Biswas (Bhabha Atomic Research Centre)

12:05(Invited)
Current Status and Prospcet for EUV Lithograpy Which Is a Significant Application
Using Multilayers

16

Takeo Watanabe, Tetsuo Harada, and SHinji Yamakawa (Univ. of Hyogo)

12:30
14:00

― Lunch (90 min) with Lunch box @ 409 meeting room ―(Invited)
Resolving and improving the interfaces of Soft X-ray Multilayers

17
Marcelo Ackermann (Univ. of Twente)

14:25

High Reflective C/B Multilayer for Beyond EUV Lithography
Tetsuo Harada, Umi Fujimoto, Shinji Yamakawa, Takeo Watanabe (Univ. of Hyogo)

14:45― Coffee Break (30 min)―

15:15

Poster Presentations (120 min) @ Foyer of Medium Hall

17:15

Communication Party @ Foyer of Medium Hall

318

Oral Presentation
Thurthday, 12th Oct.
8:30

Coffee & Sandwitch

9:00(Invited)
Multilayer reflective optics for intense high-energy X-rays at SPring-8

19

Takahisa Koyama (Japan Synchrotron Radiation Research Institute (JASRI))

9:25

Highly efficient ultra-low blaze angle multilayer grating

20

Dmitriy Voronov, Sooyeon Park, Eric Gullikson, Farhad Salmassi and Howard Padmore(Lawrence Berkeley National Laboratory)

9:45

Multilayer-coated blazed grating for high transmission tender X-ray energy range
monochromator

21

Andrey Sokolov, Stephanie Lemke, Svyatoslav Alimov, Jeniffa Knedel, Oliver Kutz, Tino
Seliger, Grzegorz Gwalt, Franz Schfers, Friedmar Senf, Frank Siewert, Jens Viefhaus(Helmholtz-Zentrum Berlin fr Materialien und Energie, BESSY-II, Berlin, Germany)
Qiushi Huang, Yeqi Zhuang, Runze Qi, Zhong Zhang, Wenbin Li, Zhanshan Wang
(Key Laboratory of Advanced Micro-Structured Materials MOE, Institute of Precision
Optical Engineering, School of Physics Science and Engineering, Tongji University,
Shanghai, China)

10:05
10:35

― Coffee Break (30 min)―
Optimisation of Cr/Sc-based multilayer coatings for water window applications

22

Evgueni Meltchakov, Sbastien de Rossi, Eirini Papagiannouli, Franck Delmotte(Universit Paris-Saclay, Institut d'Optique Graduate School)
Blandine Capitanio, Pascal Mercere (Synchrotron Soleil)

10:55

Synthesis and characterization of short- and ultrashort W-based multilayers for soft
x-rays23

Dennis IJpes, Andrey E. Yakshin, Jacobus M. Sturm, Marcelo D. Ackermann(University of Twente)

11:15

NiV-based Multilayer for Soft and Hard X-ray Mirrors
Zhe Zhang, Qiushi Huang, Runze Qi, Zhong Zhang, Zhanshan Wang
(Key Laboratory of Advanced Micro-Structured Materials MOE, Institute of Precision
Optical Engineering, School of Physics Science and Engineering, Tongji University,
Shanghai, P. R. China)

11:35― Lunch with Lunch box @ 409 meeting room ―13:00

Bus DEPARTURE time @ Acrea Himeji
To Excursion of SPring-8, SACLA, NewSUBARU synchrotron facility

17:00

Bus Arrival time @ Himeji Station
Himeji Station South Charter Bus Boarding Area
https://goo.gl/maps/PYdjtS6vETic68cQ6

18:00

Bus DEPARTURE time @ Himeji Station
To Banquet at NADA-GIKU Japanese Sake Traditional Restaurant

19:00

Banquet 120 min

21:30

Bus Arrival time @ Himeji Station

424

Oral Presentation
Friday, 13th Oct.
8:30

Coffee & Sandwitch

9:00(Invited)
Wide Bandwidth Neutron-Spin Polarizer Due to Ferromagnetic Interlayer Exchange
Coupling

25

Ryuji Maruyama (Japan Atomic Energy Agency (JAEA))

9:25(Invited)
11B4C-containing Ni/Ti multilayer neutron optics

26

Fredrik Eriksson, Sjoerd Stendahl, Naureen Ghafoor, Anton Zubayer, and Jens Birch(Linkping University, Sweden)
Mattias Schwartzkopf (DESY, Hamburg, Germany)

9:50

Material design optimization for large-m 11B4C-based Ni/Ti supermirror neutron optics

27

Naureen Ghafoor, Sjoerd Stendahl, Anton Zubayer, Marcus Lorentzon, *Alexei Vorobiev,
Jens Birch, Fredrik Eriksson(Department of Physics, Chemistry, and Biology, IFM, Linkping University, Sweden,*Department of Physics and Astronomy, Material Physics, Uppsala University, Sweden,and Institut Max von LauePaul Langevin (ILL), Grenoble, France)

10:10

10B/11B-modulated chemically homogeneous boron carbide neutron interference
mirrors

28

Jens Birch, Sjoerd Stendahl, Samira Dorri, Anton Zubayer, Naureen Ghafoor, Fredrik
Eriksson (Linkping University)

10:30
11:00

― Coffee Break (30 min)―(Invited)
All-dielectric multilayer mirrors tuned at vacuum ultraviolet wavelengths

29

Paloma López-Reyes, Nuria Gutirrez-Luna, Carlos Honrado-Bentez, and Juan Ignacio
Larruquert (GOLD-IO-CSIC Instituto de ptica Consejo Superior de Investigaciones
Cientficas, Serrano 144, 28006 Madrid, Spain)

11:25

Design Study of Soft X-Ray Aplanat with Four Multilayer Mirrors in Grazing Incidence
Configuration

30

S. Yamashita, M. Toyoda (Tokyo Polytechnic University)

11:45

Thermally stable MoNx/Si1-xNx multilayer as a substrate for XSW study of SMSI

31

Atul Tiwari, Matteo Monai, Ksenia Matveevskii, Sergey N. Yakunin, Marcelo D. Ackermann,
Laurens D. B. Mandemaker, Florian Meirer and Igor A. Makhotkin(Industrial Focus Group XUV Optics, MESA+ Institute for Nanotechnology, University ofTwente, Enschede, Netherlands)

12:05

Surface roughening by ion beams: Is ballistics “be-all and end-all”?

32

Parikshit Phadke, Jacobus M. Sturm, Fred Bijkerk, Marcelo D. Ackermann(University of Twente)

12:25

13:55

― Lunch (90 min) with Lunch box @ 409 meeting room ―(Invited)
More accurate prediction of optical constants: A prerequisite for the development of
next-generation metrology instruments based on soft X-rays
Victor Soltwisch (PTB)

533

14:20

Bayesian Inferences and Time-Frequency Analysis Assisted Determination of Optical
Constants in the EUV

34

Qais Saadeh, Victor Soltwisch, Christian Laubis, Michael Kolbe, and Frank Scholze (PTB)

14:40

Refractive index measurements with improved accuracy for EUV/x-ray multilayer optics
Franck Delmotte, Eirini Papagiannouli (Universit Paris-Saclay)
Regina Soufli, Catherine Burcklen (Lawrence Livermore National Laboratory)
Farhad Salmassi, Eric Gullikson (Lawrence Berkeley National Laboratory)

15:00

Closeing Remarks

635

Poster Program
Wednesday, 11th Oct. 15:15 - 17:15

Page No.

The poster board will be availavle from the morning of 11th
to the end of th conference.
The board size is W1200 mm x H1800 mm.
(Recommended poster format: A0 Portrait)

1Enhancement of Diffraction Efficiency and Spectral Flux with Quasi-Graded Index
Coating (QGIC) on Soft X-Ray Laminar-Type Diffraction Gratings Optimized for B-K
and Li-K Emissions

39

Masato Koike1-3, Tadashi Hatano2, Alexander S. Pirozhkov1, Masami Terauchi2(1 Kansai Photon Science Institute, Fundamental Quantum Sciences Directorate,
National Institutes for Quantum Science and Technology
2 Institute of Multidisciplinary Research for Advanced Materials, Tohoku University
3 Laboratory of Advanced Science and Technology for Industry, University of Hyogo)2

Development of Narrowband Multilayer Mirrors for Extracting a Single Harmonic froman EUV HHG Source

40

Suet Yi Liu, Yuya Iwamoto, Hisataka Takenaka (TOYAMA Co. Ltd, Japan)
Hiroki Mashiko, Satoshi Ichimaru, Masatoshi Hatayama (NTT Advanced Technology
Corporation, Japan)
Eric Gullikson (Center for X-ray Optics, Lawrence Berkeley National Laboratory, USA)
Tomoya Mizuno, Takayuki Kurihara, Jiro Itatani ( Institute for Solid State Physics, theUniversity of Tokyo, Japan)

3

Resolving buried interfaces by Low-Energy Ion Scattering

41

Adele Valpreda, Jacobus M. Sturm, Andrey E. Yakshin, Marcelo Ackermann(University of Twente)

4

Fabrication and characterization of EUV multilayer gratings

42

A.H.K. Mahmoud, S. de Rossi, Anne-Lise Coutrot, A. Jrome,
E. Meltchakov, E. Papagianouli, F. Delmotte (Universit Paris-Saclay)
B. Capitanio, M. Thomasset (Synchrotron SOLEIL)

5

EMIL@BESSY-II: In-situ investigations of material combinations at a synchrotron lightsource43

Stefan Hendel, Regan G. Wilks, Mihaela Gorgoi, Anna Efimenko, Marcus Br(Helmholtz-Zentrum Berlin)

6

Upgrades of PTB’s EUV Reflectometry Instrumentation

44

Andreas Fischer, Christian Laubis, Michael Kolbe, Frank Scholze ((PTB)
Physikalisch-Technische Bundesanstalt)

7

Optical Constants of Carbon and Boron material for Beyond EUV Lithography
Umi Fujimoto, Tetsuo Harada, Shinji Yamakawa, Takeo Watanabe (Univ. of hyogo)

7

45

8

Improved performance of polarizing Fe/Si multilayer neutron optics by 11B4C
incorporation

46

A. Zubayer1, N. Ghafoor1, K. rarinsdttir2, S. Stendahl1, A. Glavic3, J. Stahn3, G. Nagy4, G.
Greczynski1, M. Schwarzkopf5, A. Le Febvrier1,
P. Eklund1, J. Birch1, F. Magnus2, F. Eriksson1( 1. Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM),
Linkping University, SE-581 83 Linkping, Sweden
2. Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik, Iceland
3. Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
4. Department of Physics and Astronomy, Uppsala University,
SE-75120, Uppsala, Sweden
5. Photon Science, DESY, Notkestrae 85, 22607, Hamburg, Germany)

9

CeMOX, a Collaborative facility for Development of High-Performance Multilayer
Optics (Withdraw)
Capitanio Blandine (Synchrotron-soleil, Gif-sur-Yvette)

10

Removal of Mo/Si Multilayer Coatings on Fused Silica Substrates by Wet Chemical
Etching

47

Mitsunori TOYODA, Ryo YOKOYAMA, Shuntaro WAKI, Jun CHEN
(Tokyo Polytechnic University)
Toshiyuki KAKUDATE(Tohoku University)

11

Picometer Sensitivity on Laboratory-based XRR Instrument Equipped with Fast andAccurate Sample Alignment System

48

Hitoshi Morioka (Bruker Japan K.K.)
Fernando Rinaldi, Martin Zimmermann (Bruker AXS GmbH)12

At-Wavelength Metrology for diffractive and reflective optics in the EUV, XUV andtender X-ray energy range

49

Andrey Sokolov, Frank Eggenstein, Peter Bischoff, Peter Baumgrtel, Matthias Mast, Marcel
Mertin, Ingo Packe, Franz Schfers, Frank Siewert, Jens Viefhaus (Helmholtz-Zentrum
Berlin fr Materialien und Energie (BESSY-II), Berlin)

13

Ultra-low thickness thin film multilayer devices for application in Water Window regimeof Soft X-ray (Withdraw)
Piyali Sarkar Roy, Arup Biswas, Dibyendu Bhattacharyya(Atomic and Molecular Physics Division, Bhabha Atomic Research Centre,
Mumbai-400085, INDIA)

14

Structural, electrical and magnetic properties of reactively DC sputtered Cu and Ti thinfilms. Application to CuTi neutron supermirrors for low spin-flip applications (Withdraw)
Jose Manuel Gómez-Guzmán, Peter Link (Heinz Maier-Leibnitz Zentrum,
Technische Universität München, Germany)
Matthias Opel (Walther-Meißner-Institut, Bayerische Akademie
der Wissenschaften, Germany)
Tamás Veres (Budapest Neutron Center, Centre for Energy Research , Hungary)
László Bottyán (Wigner Research Centre for Physics, Hungary)

15

Low-Cost Cleaning Method of Mo/Si Multilayer Soft X-ray Mirrors Using a Wet Process
Toshiyuki Kakudate (National Institute of Technology (KOSEN), Hachinohe College)
Mitsunori Toyoda (Tokyo Polytechnic University)

8

50

16

High Irradiance Illuminator for Transmission Extreme Ultraviolet Microscopy

51

Shuntaro Waki, Yusuke Tsukui, Jun Chen, Mitsunori Toyoda (Tokyo Polytechnic University)

17

Multilayer structures in coherent x-ray diagnostics in BISER and Relativistic Flying
Mirror experiments

52

A. S. Pirozhkov1, A. N. Shatokhin2, E. A. Vishnyakov3, A. Sagisaka1, K. Ogura1,
M. Koike1,4,5, T. Hatano4, H. Ohiro6, S. Namba6, J. K. Koga1, A. O. Kolesnikov2,
H. Kiriyama1, T. Zh. Esirkepov1, T. A. Pikuz7, E. N. Ragozin2, S. V. Bulanov3, M. Kando1(1. Kansai Institute for Photon Science (KPSI), QST,
2. P. N. Lebedev Physical Institute, RAS,
3. ELI-Beamlines, ELI-ERIC,
4. Institute of Multidisciplinary Research for Advanced Materials, Tohoku University
5. Laboratory of Advanced Science and Technology for Industry, University of Hyogo,
6. Department of Advanced Science and Engineering, Hiroshima University
7. Open and Transdisciplinary Research Initiatives, Osaka University)

17

A new variant of high-performance neutron supermirror polarizer
Thierry Bigault, Alexander K. Petoukhov, Guillaume Delphin,Sébastien Batisse, Amandine Vittoz, Pierre Courtois,
Valery V. Nesvizhevsky, Torsten Soldner, David Jullien, Anton Devishvili, Thomas Saerbeck(Institut Max von Laue - Paul Langevin, (ILL), Grenoble, France)

9

53

10

Oral Session

11

12

Development and Application of Multilayer Mirror
Hisataka Takenaka
TOYAMA Co. Ltd, Japan
E-mail: takenaka@toyama-jp.com
In the 1971, the development of multilayer mirrors started to progress after E. Spiller demonstrated
through calculations that soft X-ray practical normal incidence reflectivity could be achieved withmultilayer mirrors. In the late 1970s, United States researchers, T. W. Barbee, Jr., and J. H. Underwood,began fabricating multilayer mirrors, such as W/C and V/C, using Magnetron sputtering. At the sametime, Europe, and Russia also developed multilayers. In 1981, A. E. Rosenbulth showed throughcalculations that Mo/Si multilayer mirrors exhibited high reflectivity near a wavelength of 13 nm. This
led to the advancement of Mo/Si multilayer mirror fabrication, the development of X-ray telescopes,
and X-ray microscopes using Mo/Si multilayer coatings. In 1985, T.W. Barbee and Jr. achieved a 60%
reflectivity at a wavelength of 17nm and an incident angle of 20 degrees with Mo/Si films. Additionally,in 1987, A.B.C. Walker and Barbee's group created an X-ray telescope utilizing Mo/Si multilayer
mirrors for observing the solar corona. These developments marked an active period of multilayer
mirror advancement from the late 1970s to the 1980s.
In Japan, multilayer mirror development has been underway since the early 1980s at institutes suchas Tohoku University, NTT, Canon, Nikon. Initially, W/C multilayer mirrors were fabricated using Ion
beam sputtering at Tohoku University and NTT. In NTT, Magnetron sputtering was also used tofabricate W/C multilayer mirrors and developed a spectrometer by combining a diffraction grating andthese W/C mirrors. During that time, H. Kinoshita applied multilayer mirrors for what is now known
as EUVL (Extreme Ultraviolet Lithography, formerly called Soft-Xray Projection Lithography) anddeveloped an early-stage optical system for EUVL, initially using W/C multilayer mirrors. Later on,
Mo/Si multilayer mirrors with high reflectivity near a wavelength of 13 nm were employed as the
EUVL multilayer mirrors. Since then, Mo/Si multilayer mirrors have remained effective in EUV
applications, leading to various applications. In this presentation, the development of Mo/Si multilayer
mirrors and their applications mainly in Japan will be introduced.

13

Tailoring the nanoscale multilayer optics with high efficiency
and precision for EUV, X-ray and Neutron applications
Qiushi Huang1*, Runze Qi1, Zhe Zhang1, Zhong Zhang1, I. V. Kozhevnikov2, Wenbin Li1,
Shengzhen Yi1, Zhanshan Wang1**
1. Key Laboratory of Advanced Micro-Structured Materials MOE, Institute of Precision OpticalEngineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
2. Shubnikov Institute of Crystallography of Federal Scientific Research Centre “Crystallography andPhotonics” of the Russian Academy of Sciences, Leninskii pr. 59, Moscow 119333, Russia

E-mail: huangqs@tongji.edu.cn, wangzs@tongji.edu.cn
Multilayer (ML) optics is one of the enabling technology in EUV, X-ray and Neutron applications,based on its advantage of high efficiency beyond the total external reflection regime. Institute ofPrecision Optical Engineering (IPOE) in China started working in this field from 2001, and graduallybuilding up the capacity to develop ML coatings, ML nanostructures, and ML-based optical systems.
Our recent work in these areas will be presented. Hard X-ray multilayer monochromators can bring
one to two orders magnitude higher flux than crystal monochromators and are widely needed insynchrotron radiation facility. Pd/B4C multilayer with d-spacing of 2.5nm was developed using
magnetron sputtering with both Ar and Kr gas and the former one shows slightly better layer structure.
Its stability was further tested under liquid nitrogen cooling and different humidity environment.
Combined with the deterministic surface figuring technique and metrology, high precision multilayer
mirrors with maximum 350mm length were manufactured with 30pm d-spacing error (PV), and 1.5
nm (RMS) figure error. These mirrors have been installed in the double ML monochromator in
Shanghai synchrotron radiation facility. Sc/Si multilayer is an optimum structure for working around46.5nm. The microstructure and mechanical stability of the thick Sc/Si multilayer were studied andimproved via doping sublayers during deposition. Ni/Ti ML supermirrors with M=3 has also beendeveloped for neutron beamline application. The multilayer was further combined with nanostructures
forming high efficiency X-ray diffraction optics, like the ML gratings. In collaboration with the
BESSY-II optics group, a first Cr/C multilayer blazed grating has been installed in the monochromatorof TXM beamline in BESSY-II, providing two orders of magnitude enhancement of photon flux at
2keV. To achieve both high efficiency and high resolution, multilayer gratings using higher line density
and higher diffraction orders are being studied. Based on the above-mentioned ML technology, EUV
and X-ray optical systems are being developed. A lab-based EUV radiation damage system working
at 13.5nm has been built using laser plasma source and Mo/Si coated Schwarzschild system. Last year,
the Solar Upper Transition Region Imager (SUTRI) using Sc/Si ML based imaging system was
successfully launched and has obtained the first 46.5nm image of the sun in China.

14

Interface characterization of neutron and X-ray multilayerusing Grazing Incidence X-ray Absorption & Fluorescence
spectroscopy experiments at Indus-2 SRS
Arup Biswas
Atomic & Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai-400085, INDIA
Email: arupb@barc.gov.in
X-rays reflecting from each interface of a multilayer interfere with the incident wave and a standing
wave is created inside the multilayer structure. Using synchrotron X-ray local structures at theinterfaces and depth resolved element specific interface diffusion can be studied by Grazing Incidence
Extended X-ray Absorption Fine structure (GIEXAFS) and Grazing Incidence X-ray Fluorescence(GIXRF) measurements respectively. Along with interface roughness these interfaces properties ofmultilayer thin film are very critical in application of neutron and X-ray optics. In our laboratory using
magnetron and ion beam sputtering techniques it has been demonstrated [1-6] that the reflectivity ofneutron supermirror and soft x-ray multilayer mirror can be improved either by introducing Air or N2
gas along with Ar gas into the plasma or by introducing a very thin barrier layer of C or B4C at theinterface of the two materials. Various structural and spectroscopic investigation of the interface ofmultilayer have been done. In this presentation results of GI-EXAFS and GIXRF measurements donewith Indus-2 SRS on Ni/Ti [1-3], Mo/Si [4], Cr/Ti [5] & Cr/Sc [6] will be presented along with specularand non-specular GIXR results. Recrystallization of NiTi at the interfaces has been observed at higher
temperature annealed sample and it has been found that the amorphous Ni/Ti multilayer is more
preferable for recrystallization. This finding has been supported by molecular dynamics (MD)simulation of Ni/Ti multilayer. Along with this the effect of C and B4C diffusion barrier on the interfaceof Mo/Si EUV multilayer and Cr/Ti & Cr/Sc water-window soft x-ray multilayer will be discussed.
References
1. A. Biswas, Abharana N, S. N. Jha and D. Bhattacharyya, Applied Surface Science 542 (2021)
148733.
2. A. Biswas, Abharana N, S. Rai, and D. Bhattacharyya, J. Appl. Phys. 127 (2020) 165304.
3. Abharana. N, A. Biswas, P. Sarkar, S. Rai, S. Singh, S. Kumar, S.N. Jha, D. Bhattacharyya, Vacuum
169 (2019) 108864.
4. N.Abharana, A. Biswas, P.Sarkar, P.Rajput, De Rajnarayan, K.D.Rao, M.H.Modi, D.Bhattacharyya,
S.N.Jha, N.K.Sahoo, Thin Solid Film, 673 (2019)126-135.
5. P. Sarkar, A. Biswas, N. Abharana, S. Rai, M. H. Modi and D. Bhattacharyya, J. Synchrotron Rad.
28 (2021) 224-230.
6. Piyali Sarkar, Arup Biswas, Ravi Kumar, Sanjay Rai, S Jha, Dibyendu Bhattacharyya, Physical
Chemistry Chemical Physics 25 (2023) 3072

15

Current status and prospect for EUV lithography whichis the significant application using multilayers
Takeo Watanabe1, Tetsuo Harada1, and Shinji Yamakawa1
1Center for EUVL, Laboratory of Advanced Science and Technology for Industry,

University of Hyogo, 1-1-2, Kouto, Kamigori, Akou-gun, Hyogo 678-1205, Japan,
E-mail: takeo@lasti.u-hyogo.ac.jp

EUV (extreme ultraviolet) lithography started to use in high volume manufacturing (HVM) of 7-nm+
node logic devices from 2019. According to the International Roadmap for Devices and Systems [1],EUV lithography will be used for the HVM of 0.5-nm node logic devices.
Currently, the multilayers and exposure wavelength on EUV lithography is molybdenum/silicon(Mo/Si) and 13.5 nm, respectively. Mo/Si multilayer mirrors for EUV at the wavelength of 17 nm waspresented by the research group of Stanford University and University of California in 1985 [2]. The
contribution of R&D of Mo/Si was done by the research group at NTT in Japan [3]. The research groupof NTT Atsugi R&D Center demonstrated the X-ray projection lithography and they presented at the
47th Japan Society of Applied Physics Autumn Meeting in 1986 [4]. They used W/C multilayers on
Schwarzschild optics for the imaging optics. The stencil mask was used to replicate 0.2 mm width resist
pattern by Polymethyl methacrylate (PMMA) employed as a resist material. And the research group of
NT&T and AT&T demonstrated the X-ray projection lithography using Mo/Si Schwarzschild optics in1989 [5] and in 1990 [6], respectively. However, since the exposed area size was too small to fabricate
the semiconductor LSI devices, the Offner-type of ring-field optics was introduced to enlarge theexposure area for the practical use [7]. Using this optics, NTT research group demonstrate 150 nm resist
pattern by two aspherical imaging optics in 1991 [8]. Three aspherical imaging optics was design
independently by the research group at University of Hyogo [9] and EUV LLC [10], USA. To increase
the exposure area size on a wafer, the mask and wafer synchronized stage control system was employed.
The research group at University of Hyogo demonstrated 60 nm L/S resist pattern on a wafer with anlarge exposure area size of 10 ൈ 10 mm2 [11]. And furthermore, many research groups has been
contributed on EUV lithographic technology to pull up to the fabrication level of the semiconductor
devices. Currently, ASML products the exposure tool which employes the six aspherical imaging optics
which has the numerical aperture of 0.33 and synchronized control of mask and wafer stages toexposure ULSI pattern.
The technical issues on EUV lithography are 1) EUV resists development of the simultaneousachievement of high resolution, high sensitivity, and low line with roughness (LWR), 2) defect freemask and its metrology and repair, and EUV pellicle which has high transmittance and long lifetime on
EUV exposure, and 3) high power and high stability of EUV light source. In the presentation the current
status will be introduced. And the future prospect for EUV high and hyper NA, and the shortening the
wavelength of EUV will also be introduced and discussed [12].
References[1] URL https://irds.ieee.org/editions/2022[2] T. W. Barbee, S. Mrowka, and M. C. Hettrick, Applied Optics, 24 (1985) 883-886.
[3] H. Takenaka, Y. Ishii, H. Kinoshita, and K. Kurihara, Proc. SPIE, 1345 (1990) 213-222.
[4] H. Kinoshita, T. Kaneko, H. Takei, N. Takeuchi, and S. Ishihara, Abstract of the 47th Autumn
Meeting of the Japan Society of Applied Physics, Paper No. 28-ZF-15 (1986) 322.
[5] H. Kinoshita, K. Kurihara, Y. Ishii, and Y. Torii, J. Vac. Sci. Technol., B7 (1989) 1648.
[6] J. E. Bjorkholm, J. Boker, L. Eichner, R.R. Freeman, J. Gregus, T. E. Jewell, W. M. Mansfield, A.
A. MacDowell, E. L. Raab, W. T. Silfvast, J. H. Szeto, D. M. Tennant, W. K. Waskiewicz, D. L. White,
D. L. Windt, O. R. Wood II, and J. H. Bruning, J. Vac. Sci. Technol., B8 (1990) 1509-1513.
[7] A. MacDowell, J. E. Bjorkholm, J. Boker, L. Eichner, R. R. Freeman, W. M. Mansfield, J. Pastalan,
L. H. Szeto, D. M. Tennant, O. R. Wood II, T. E, Jewell, W. K. Waskiewicz, D. L. White, D. L. Windt,
W. T. Silfvast, and F. Zernike, J. Vac. Sci. Technol., B9 (1991) 3193-3197.
[8] (1) K. Kurihara, H. Kinoshita, T. Mizota, T. Haga, and Y. Torii, J. Vac. Sci. Technol., B9 (1991)
3189. (2) T. Haga, M. C. K. Tinone, H. Takenaka, and H. Kinoshita, Microelectronic Engineering, 30(1996) 179-182.
[9] T. Watanabe, K. Mashima, M. Niibe, and H. Kinoshita, Jpn. J. Appl. Phys., 36 (1997) 7597-7600.
[10] D. A. Tichenor, A. K. Ray-Chaudhuri, W. C. Replogle, R. H. Stulen, G. D. Kubiak, P. D. Rockett,
L. E. Klebanoff, K. J. Jefferson, A. H. Leung; J. B. Wronosky, L. C. Hale; H. N. Chapman, J. S.
Taylor, J. A. Folta, C. Montcalm, Regina Soufli, E. A. Spiller, K. L. Blaedel, G. E. Sommargren, D.
W. Sweeney, P. P. Naulleau, K. A. Goldberg, E. M. Gullikson, J. Bokor, P. J. Batson, D. T.
Attwood, K. H. Jackson, S. D. Hector, C. W. Gwyn, and P-Y. Yan, Proc. SPIE, 4343 (2001) pp. 826.
[11] (1) T. Watanabe, H. Kinoshita, H. Nii, Y. Li, K. Hamamoto, T. Oshinio, K. Sugisaki, K. Murakami,
S. Irie, S. Shirayone, Y. Gomei, and S. Okazaki, J. Vac. Sci. Technol., B18 (2000) 2905-2910. (2)K. Hamamoto, T. Watanabe, H. Tsubakino, H. Kinoshita, T. Shoki, and M. Hosoya, J. Photopolym.
Sci. Technol., 14 (2001) pp.567-572.
[12] (1) T. Watanabe, T. Harada, S. Yamakawa, Proc. SPIE, 11908, (2021) 1190807. (2) T. Watanabe,
T. Harada, and S. Yamakawa, J. Photopolym. Sci. Technol., 34 (2021) 49-53.

16

Resolving and improving the interfaces of Soft X-ray Multilayers
Nanometer-level d-spacing multilayers are key optical elements with applications from advanced
lithography to X-ray optical elements for X-ray fluorescence and astronomical instruments. In allthese applications, the quality of the thin films, but most importantly the sharpness of the interface
between the layers is key to achieving high reflectivity. Roughness, intermixing and compound
formation at these interfaces result in reflectivity losses.
In order to improve these interfaces, metrology is needed to resolve on the atomic level, what thedriving mechanisms are that lead to reflectivity loss. At the sub-nm scale, a single technique is often
insufficient to fully understand the physics of intermixing: Whereas TEM and XRR can resolve thelocal atomic or electronic density, XPS is optimal to highlight compound formation. We demonstratethat only a combination these techniques can truly resolve the interface. In addition, we havedeveloped a novel capability to resolve buried interfaces with LEIS – using a full modelling of the LEIS
signal outside the surface peaks – offering atomic density resolution rather than electronic.
For 2.5nm and 1 nm W/Si multilayers, this combination of techniques shows that the interaction
between W and Si results in WSix formation, leading to poor optical performance. The introductionof ultrathin 0.1 nm B4C diffusion barriers shows clear improvement in reflectivity, and through the
combination of these multiple surface-sensitive techniques we can directly explain how the barriers
contribute to a higher reflectivity.
Bio
Marcelo Ackermann is chair of the Industry Focus Group – X-ray and EUV (XUV) optics at the MESA+
institute of the University of Twente. He obtained his PhD in physics (cum laude) in 2007 on a sharedresearch project between Leiden University and the ESRF in Grenoble, under the guidance of Prof
Frenken and Prof. Ferrer. After that he held different leading positions in industrial research for thedevelopment of X-ray, visible and IR optics at cosine Research, Helbling Technik, SCHOTT Advanced
Optics and ASML. In 2020 he re-joined academia as full professor in the XUV group, focussing on thedevelopment of next generation reflective, refractive and transparent X-ray and EUV optics incollaboration with industrial partners like Zeiss, ASML and Malvern Panalytical.

17

High Reflective C/B Multilayer for Beyond EUV Lithography
Tetsuo Harada, Umi Fujimoto, Shinji Yamakawa, Takeo Watanabe
Center for EUV Lithography, LASTI, University of Hyogo
E-mail: harada@lasti.u-hyogo.ac.jp
Beyond EUV (BEUV) lithography technology with exposure wavelength around 6.7 nm is expected
as next generation lithography. The development of multilayer with high reflectivity is a critical issue
for BEUV lithography.
Many La/B-based multilayers were reported as a high theoretical reflective multilayer.[1] However,
the temporal stability of La/B-based multilayers is low because of the high reactivity of La. Thus, we
propose carbon/boron (C/B) multilayer as a new BEUV multilayer. The C/B multilayer has hightheoretical reflectance of about 80%, which is comparable to La/B multilayer shown in Fig. 1(Left).
The optical constant of the C film depends on its density, and high density is required to obtain highreflectance and wide reflection bandwidth. The calculated reflectance of the multilayer with varied
carbon densities is shown Fig. 1(Right). The higher density carbon is needed for the high reflectanceand wide bandwidth. In the Fig. 1(Left), high density carbon with 3.1 g/cm3 is used for the calculation,
which is highest value for the diamond like carbon (DLC) film. We will discuss the performance of
the C/B multilayer.

Figure 1. Calculated reflectance of C/B multilayers. (Left) Comparison of La, Mo, and C materials.
(Right) Carbon density dependence of the multilayer reflectance.
References[1] P. C. Uzoma, S. Shabbir, P. C. Okonkwo, and O. V. Penkov, “Multilayer Reflective Coatings for
BEUV Lithography: A Review,” Nanomaterials 2021 (2021) 2782.

18

Multilayer reflective optics
for intense high-energy X-rays at SPring-8
Takahisa Koyama1,2
Japan Synchrotron Radiation Research Institute, 1-1-1, Kouto, Sayo, Hyogo 679-5198 Japan,
2
RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148 Japan
E-mail: koyama@spring8.or.jp

1

A high-energy X-ray beam is a powerful probe for non-destructive analysis of large sized objects,
thick heavy metals, devices enclosed with exterior cases, and materials in a high-pressure cell. One of
the key characteristics of SPring-8 is to provide highly brilliant X-rays in high-energy region. Usually,
high-energy X-rays are generated by a double crystal monochromator (DCM) with an energy
bandwidth of less than 0.01%, which is too narrow for applications such as transmission X-ray imaging,orientation imaging, and total-scattering measurement. By using a double multilayer monochromator(DMM) consisting of two multilayer mirrors with an energy bandwidth of 1-5%, the photon flux canbe dramatically increased compared with that of DCM. Recently, we designed and installed DMMs at
SPring-8 in two beamlines, BL20B2 and BL05XU, for applications using intense high-energy X-rays.
At SPring-8 BL20B2 (bending magnet beamline for large field of view imaging), we designed andinstalled two pairs of W/B4C multilayer mirrors as DMMs to enhance flux density of 40 keV and 110
keV [1]. At an experimental hutch located 210 m away from the source, a large and uniform beam ofsize 14 mm (V) × 300 mm (H) was generated with a high flux density at 110 keV, which marked a 300
times increase in the photon flux when compared with a DCM with Si 511 diffraction.
At SPring-8 BL05XU (undulator beamline for test bench of developing next generation beamline
optics) [2], we designed and installed a DMM, multilayer focusing mirrors (MFMs), and a multilayer
reflective beam expander (MRBE). In this beamline, these multilayers were deposited at the SPring-8
in-house laboratory. 100 keV X-rays with 1% bandwidth were generated by using the DMM consistingof a pair of Cr/C multilayer mirrors. By combining the DMM with the MFMs that consist of W/Claterally graded multilayer mirrors in a Kirkpatrick-Baez geometry, the focusing beam size of 0.3 μm
with a high flux of 6 × 1010 ph/s at 100 keV was achieved. Additionally, by combining the DMM with
the MRBE that consists of a W/C laterally graded multilayer on a hyperbolic shape mirror, a field ofview of 5 mm square can be available for high-speed imaging of metallic bulky samples.

In this presentation, I will describe these results of the developments.
References[1] T. Koyama et al., J. Synchrotron Rad. 29 (2022) 1265.
[2] H. Yumoto et al., Proc. SPIE 11492 (2020) 114920I.

19

Highly efficient ultra-low blaze angle multilayer grating
Dmitriy Voronov, Sooyeon Park, Eric Gullikson, Farhad Salmassi and Howard Padmore
Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
E-mail: dlvoronov@lbl.gov
A multilayer blazed grating can be used as a highly efficient spectral purity filter for EUV lithography.
Angular separation of the light of wavelength of 13.5 nm from infrared and out-of-band deep
ultraviolet radiation is provided by diffraction into 1st diffraction order. To avoid excessive dispersion
of EUV radiation over the exit aperture the grating should have a large period of 5 - 10 µm. At thesame time the grating groove depth should be very small to match the multilayer d-spacing, leading to
extremely low blaze angles of 0.1 or so. Fabrication of such low aspect ratio structures is hardly
possible with existing grating fabrication techniques. We developed a process of reduction of a groove
depth of a coarse blazed grating with a blaze angle of few degrees down to a nanometer scale,achieving the ultra-low blaze angles. The coarse Si grating is planarized by a polymer material andthen etched with a plasma which provides etching of planarization layer and underlying Si gratingwith slightly different etch rates. The approach provides a way to adjust the blaze angle to any lower
value with high accuracy. We demonstrate the reduction of the blaze angle to an extremely low valueof 0.04±0.004. For a 100 lines/mm grating with a Mo/Si multilayer coating, the grating exhibits
diffraction efficiency of 58% in the 1st diffraction order at a wavelength of 13.3 nm.
1st order

0.6

Efficiency

0.5
0.4

l = 13.3 nm
a = 5o0.3
0.2

2nd order

zero order
Height, nm

0.1
10

0.0

5

4.50

0
0

5

10

15

Length, mm

20

25

30

4.75

5.00

5.25

5.50

diffraction angle, deg.

Figure 1. AFM image, groove profile and efficiency measurements of 100 lines/mm blazed gratingcoated with a Mo/Si multilayer.

20

Multilayer-coated blazed grating for high transmission tender
X-ray energy range monochromator
Andrey Sokolov(1), Qiushi Huang(2), Yeqi Zhuang(1,2), Stephanie Lemke(1), Svyatoslav Alimov(1),Jeniffa Knedel(1), Oliver Kutz(1), Tino Seliger(1), Grzegorz Gwalt(1), Franz Schäfers(1), Friedmar
Senf(1), Frank Siewert(1), Runze Qi(2), Zhong Zhang(2), Wenbin Li(2), Zhanshan Wang(2), Jens
Viefhaus(1)(1)

Helmholtz-Zentrum Berlin für Materialien und Energie, BESSY-II, Albert-Einstein-Str. 15, 12489
Berlin, Germany(2)
Key Laboratory of Advanced Micro-Structured Materials MOE, Institute of Precision OpticalEngineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092,
China
E-mail: andrey.sokolov@helmholtz-berlin.deMultilayer coating on top of high line density blazed gratings can increase its diffraction efficiency

up to one order of magnitude for a selected diffraction order. In combination with multilayer coatedpre-mirror in plane grating monochromator (PGM) the total instrument transmission can be increasedin hundreds of times. In our developments on multilayer-coated blazed gratings (MLBG) we havereached experimentally efficiency up to 60% [1,2] in tender energy range where single coated grating
would demonstrate only few percent. The key factor of high performance MLBG is in correct
optimization of both multilayer and grating profile parameters to each other [3]. After several
successful prototypes the real MLBG were designed and installed in c-PGM at u41-TXM-beamline at
BESSY-II [4].
In our contribution we present recent research on MLBGs with extended energy region up to 8.5keV.
Experimentally measured efficiency on our first prototype high line density Ni/B4C ML coated grating
demonstrated extraordinarily high value of 60% at 7keV. One of the main challenges for application
MLBGs in PGM together with ML coated pre-mirror is caused by asymmetric beam propagation in
multilayer on grating with slightly different path relative to plane mirror case. Thus, to fulfill PGM
geometry the optimal ML period thicknesses for mirror and grating should be slightly desynchronized.
This effect becomes stronger with higher energy. Several possible solutions for ML coated optics PGM
are suitable as for undulator as well for dipole based beamlines will be presented and compared.
References[1] A. Sokolov et al., Opt. Express 27(12), 16833 (2019)[2] F. Senf et al., Optics Express 24(12), 13220 (2016)[3] Q. Huang et al., Opt. Express 28, 821 (2020)[4] S. Werner et al., Small Methods 7(1), 2201382 (2023)

21

Optimisation of Cr/Sc-based multilayer coatings for water
window applications
Meltchakov E.1, Capitanio B.2, de Rossi S.1, Papagiannouli E.1, Mercere P. 2, and Delmotte F.1
1 Université Paris-Saclay, Institut d’Optique Graduate School, CNRS, Laboratoire Charles Fabry,

91127 Palaiseau, France

2 Synchrotron Soleil, L’orme des merisiers, Saint-Aubin, 91192 Gif-sur-Yvette, France

Development of efficient normal incidence optics for the soft x-ray range and, in particular
for the water window (a region between absorption edges of carbon and oxygen, from 282 to
533 eV) remains quite a challenge. Proposed more than 20 years ago, a most promisingsystem, the Cr/Sc multilayer, provides theoretical reflectivity about 60% at near-normal
incidence around the Sc L2,3 edge at 397 eV. However, the measured peak reflectance of Cr/Sc
multilayers achieved so far is much lower (around 20% in the previous publications) becauseof a number of reasons. Apart of the problem of stability while depositing several hundreds of
sub-nanometer layers, the most significant reflectivity loss is caused by formation of a roughinterfaces as a result of the material interdiffusion and/or thin film growth process.

At the last PXRNMS conference in 2018 we reported on our approach to design highreflectance Cr/Sc-based multilayer mirrors using a process of nitridation of chromium during
deposition and adding boron carbide (B4C) as a third material in the periodic structure. We
have already demonstrated that with this type of coating a peak reflectance exceeds 20% in
the vicinity of the Sc L-edge at near-normal incidence [1].
Since that time we have elaborated our method and produced several series of CrN/B4C/Sc
multilayer mirrors deposited by magnetron sputtering. The multilayers have been characterized
by grazing incidence x-ray reflectometry and at-wavelength measurements. The normal
incidence reflectivity with a peak reflectance higher than 30% was measured at the Metrology
beamline of Soleil synchrotron. We will present and discuss the main results of the study andproblems that we have encountered. In fact, an accurate calculation of the CrN/B4C/Sc
multilayer reflectivity is hardly possible due to a lack of reliable optical constants of CrN ingeneral and in this spectral range in particular. So we had to use an experimental approach inorder to find an optimal thickness ratio of materials in the multilayer structure which provides a
maximum reflectance gain. It was determined with a series of multilayers of relatively small
period number (N=50). Based on this finding, we have proceeded with 500-periods samples, thenumber closed to that corresponding to saturated values of the peak reflectance for this system.
This study was able to confirm our strategy of optimisation for this new multilayer system
which proved to be potentially interesting for various water window applications such as, forinstance, x-ray microscopy.
References[1] C. Burcklen et al., Optics Letters, 42 (2017), 1927

Physics of X-Ray and Neutron Multilayer Structures, Himeji, Japan, October 11 – 13, 2023

22

Synthesis and characterization of short- and ultrashort Wbased multilayers for soft X-rays
Dennis IJpes, Andrey E. Yakshin, Jacobus M. Sturm, Marcelo D. Ackermann

Industrial Focus Group XUV Optics, MESA+ Institute for Nanotechnology, University ofTwente, Netherlands
E-mail: d.ijpes@utwente.nl

Short- and ultra-short period multilayer (ML) structures play a crucial role in applications such assynchrotron-based research, X-ray microscopy in the water window region, soft and hard X-ray
astronomy and in wavelength dispersive X-ray fluorescence (WD-XRF). In WD-XRF a ML serves as
an analyzing crystal to resolve emission lines of light elements in the O-Kα – Al-Kα range (λ=2.36 –0.834 nm). The key requirement for the ML is to be highly reflective in the entire emission range,
while also providing sufficient angular dispersion to resolve specific XRF lines. For these reasons,MLs with periods ranging from 1.0 to 2.5 nm are of great interest in this field. Due to the short period,
the reflectance of such MLs is extremely sensitive to interface imperfections such as roughness andinterdiffusion. Furthermore, the individual layers are only several angstroms thick, approaching thelimit of materials to grow a continuous and closed film.
Our research focuses on synthesis and characterization of MLs with 2.5 nm and 1.0 nm periods,
combining tungsten (W) absorber with B4C, Si and Al spacers. These combinations show hightheoretical reflectance in the O-Kα – Al-Kα range. However, formation of optically unfavourable
compounds, high intermixing and interface roughness results in limited reflectance. In our work weused a variety of techniques including diffusion barriers, seed layers and ion polishing in sputterdeposited MLs in order to address these issues. Using the approaches described in our work, we
successfully reduced compound formation, intermixing and interface roughness – resulting in a
substantial increase in soft X-ray reflectance for W/Si, W/B4C and W/Al MLs.

(a) Delta proﬁles of 2.5 nm and 1.0 nm W/Si and Si/B4C/W/B4C reconstructed using Grazing-incidence X-ray
reﬂec�vity. (b) reﬂectance at λ=0.834 nm of 1.0 nm MLs with 100 bi-layers.

23

NiV-based Multilayer for Soft and Hard X-ray Mirrors
Zhe Zhang, Qiushi Huang, Runze Qi, Zhong Zhang, Zhanshan Wang
Key Laboratory of Advanced Micro-Structured Materials MOE, Institute of Precision OpticalEngineering, School of Physics Science and Engineering, Tongji University, Shanghai, P. R. China
E-mail: zzgight@tongji.edu.cn

Nickel is one of the ideal absorption materials in hard X-ray region, therefore, Ni-based
multilayer combination is the good choice for monochromator. But nickel is a magnetic material,
which is not compatible in magnetron sputtering for small d-spacing multilayers. Except in hard
X-ray region, small d-spacing Ni-based multilayer is also used in water window as reflector. For
solving this problem, a nonmagnetic alloy was made up of 93% nickel and 7% vanadium has been
proposed. As the substitute for Ni-based multilayer, the research of NiV-based ML is limited. In
this paper, we report the results of NiV/B4C and NiV/Ti multilayers.
To investigate the influence of background pressure during fabrication, NiV/B4C multilayers
were fabricated by magnetron sputtering with different background pressures. The electron
dispersive X-ray spectroscopy (EDX) of NiV/B4C multilayer deposited with a high backgroundpressure suggests a gradient distribution of oxygen (shown in Fig.1(a)) which corresponding to
the gradient thickness change. The detailed X-ray absorption near edge spectroscopy (XANES)
comparison of NiV/B4C multilayers, NiV coating and B4C coating shown the chemical statechange induced by background pressure (shown in Fig.1(b)). We found vanadium oxide promoted
the oxidation of boron, which induced the thickness change in NiV/B4C multilayer. To compare
the optical performance of NiV/Ti and Ni/Ti multilayers at the energy with 420eV, two samples
with similar d-spacing were fabricated by magnetron sputtering. As shown in Fig.1(c), the GIXR
results show the NiV/Ti multilayer has better interface quality.

Figure 1. (a) EDX line-scan (from surface to substrate) measurement of chemical elements in NiV/B4C
multilayer; (b) B K-edge XANES spectra of NiV/B4C multilayer deposited with different backgroundpressures; (c) GIXR results of NiV/Ti and Ni/Ti multilayers.

24Wide Bandwidth Neutron-Spin Polarizer Due toFerromagnetic Interlayer Exchange Coupling
Ryuji Maruyama
J-PARC Center, Japan Atomic Energy Agency
E-mail: ryuji.maruyama@j-parc.jp
A neutron-spin polarizing supermirror is one of the most important optical devices to polarize aneutron beam. It is a stack of alternating layers of ferromagnetic (FM) and non-magnetic materials
with a variation in bilayer thickness to extend the bandwidth of the neutron polarization. We havedeveloped Fe/Ge polarizing supermirror by using ion-beam sputtering technique. A wide bandwidth
is important especially for time-of-flight instruments installed at spallation neutron sources such as
the J-PARC MLF since it determines the available wavelength-range of polarized neutrons. The
bandwidth can be evaluated by the ratio m of the critical momentum transfer of the supermirror to thatof nickel to extend the bandwidth. The spontaneous magnetization of the ion-beam sputtered Fe/Ge
multilayer, however, disappears when the Fe layer thickness is reduced to 2-3 nm because the Curie
temperature becomes to be less than room temperature. This limits the m-value of the polarizing
supermirror because the multilayer fails to form a high and low contrast in the scattering length density
profile for spin-up and -down neutrons. The polarized neutron off-specular scattering measurement of
Fe/Ge periodic multilayers revealed that the FM interlayer exchange coupling between neighboring
Fe layers grew with decreasing Ge thickness less than 2 nm [1]. The FM interlayer exchange coupling
observed here contributed to the presence of the saturation magnetization comparable to the bulk andto smaller coercivity and larger initial permeability than the multilayer without the FM interlayer
exchange coupling. This offers a possibility to keep the spontaneous magnetization for the multilayer
with a thin bilayer thickness and hence to increase the m-value of the polarizing supermirror. We
proposed a modified layer sequence of the neutron polarizing supermirror, where the minimum Fe
thickness was set to 3.5 nm, whereas the Ge thickness was reduced. A performance test of the neutron
polarizing supermirror showed that the FM interlayer exchange coupling contributed to the presenceof the magnetization comparable to the bulk and resulted in a marked enhancement in the m-value
larger than 6. In this presentation, the discussion on the FM interlayer exchange coupling of the Fe/Ge
multilayer and its performance as a neutron-spin polarizer will be followed by the one on a recently
tested possibility to use an Fe/Cr multilayer for the neutron-spin polarization.
References[1] R. Maruyama et al., J. Appl. Phys., 130 (2021) 083904.

25

11

B4C-containing Ni/Ti multilayer neutron optics

Fredrik Eriksson,1 Sjoerd Stendahl,1 Naureen Ghafoor,1 Mattias Schwartzkopf,2 Anton Zubayer,1
and Jens Birch1
1

Department of Physics, Chemistry, and Biology, IFM, Linköping University, Linköping, Sweden
2
Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany

Reflective optical elements for both X-rays and neutrons are often made of metallic multilayers. The
performance of these mirrors in terms of reflected intensity and accessible operatingenergy/wavelength range is limited by the finite interface width between the layers. This interface
width is primarily caused by a combination of nanocrystallites, formation of intermetallics,
intermixing and interdiffusion between neighboring layers, limiting both the optical contrast and theminimum layer thickness that can be achieved in a mirror.
In this work we investigate the effects of different growth conditions on the interface
morphology of Ni/Ti based multilayers, with a focus on incorporating low-neutron-absorbing 11B4C
and using different ion assistance schemes. We demonstrate how boron-carbon incorporation, in
combination with a modulation of the ion-assistance during 11B4C magnetron sputter co-deposition of
Ni/Ti multilayers can be used to eliminate nanocrystallites and minimize kinetic roughening.
Grazing incidence small angle X-ray scattering was used to probe the structural andmorphological details of buried interfaces, revealing that the layers become more strongly correlated
and the interfaces form mounds with increasing amounts of 11B4C. Applying high flux ion assistanceduring growth can reduce mound formation but lead to interface mixing, while a high flux modulated
ion assistance scheme with an initial buffer layer grown at low ion energy and the top layer at higher
ion energy prevents intermixing. The optimal condition was found to be adding 26.0 at.% 11B4C
combined with high flux modulated ion assistance. A multilayer with a period of 48.2 Å and 100
periods was grown under these conditions, and coupled fitting to neutron and X-ray reflectivity data
revealed an average interface width of only 2.7 Å, a significant improvement over the current stateof-the-art commercial Ni/Ti multilayers. Overall, our study demonstrates that the addition of 11B4C
and the use of high flux modulated ion assistance during growth can significantly improve the interface
morphology of Ni/Ti multilayers, leading to improved neutron optics performance.

Figure 1. (a) GISAXS intensity map of a 11B4C-containing Ni/Ti multilayer. (b) Out-of-plane line scansat the first Bragg sheet of 11B4C-containing Ni/Ti multilayers with various amounts of 11B+C.

26

Material design optimization for large-m 11B4C-based Ni/Ti
supermirror neutron optics
Naureen Ghafoor, Sjoerd Stendahl, Anton Zubayer, Marcus Lorentzon, *Alexei
Vorobiev, Jens Birch, Fredrik Eriksson
Department of Physics, Chemistry, and Biology, IFM, Linköping University, Sweden*

Department of Physics and Astronomy, Material Physics, Uppsala University, Sweden, andInstitut Max von Laue—Paul Langevin (ILL), Grenoble, France
Email: naureen.ghafoor@liu.se

State-of-the-art non-polarizing Ni/Ti supermirror neutron optics suffer from a limited reflected

intensity and restricted neutron energy range due to the interface width, which reduces both theoptical contrast and the achievable minimum layer thickness in the multilayer stack. This study
presents various approaches to optimize the material design of 11B4C-containing Ni/Ti
supermirrors. Incorporating low-neutron-absorbing 11B4C, in combination with high-flux
modulated ion assistance, enhances reflectivity and allows for thinner layers to be deposited,leading to the potential for more efficient supermirrors with higher m-values. However, theincorporation of 11B4C reduces the optical contrast, which limits the attainable reflectivity at low
scattering vectors where optical contrast plays a crucial role, making this approach unfeasible forsupermirrors.
The scattering length density contrast versus interface width for multilayer reflectivity has been
investigated, for multilayer periods of 30 Å, 48 Å, and 84 Å, for designs involving pure Ni/Ti
multilayers, multilayers with 11B4C co-deposited in both Ni and Ti layers, multilayers with 11B4C
co-deposited only in Ni layers, and multilayers with 11B4C deposited as thin interlayers between
Ni and Ti layers. Our results suggest that a higher reflectivity than that of state-of-the-art Ni/Ti
multilayers can be achieved over the entire scattering vector range by applying a depth-gradedhybrid material design. Specifically, this can be accomplished by incorporating 11B4C in thethinner Ni and Ti layers, below approximately 26 Å, and introducing 1.5 Å interlayers of 11B4C
between the Ni and Ti layers in the thicker layers.

Figure. The calculated performance of a hybrid supermirror
design (red) compared to that of a conventional Ni/Ti
supermirror(blue).

27

10

B/11B-modulated chemically homogeneous boron carbide
neutron interference mirrors
Jens Birch, Sjoerd Stendahl, Samira Dorri, Anton Zubayer, Naureen Ghafoor,
and Fredrik Eriksson

Thin Film Physics division Department of Physics, Chemistry and Biology, IFM, Linköping
University, SE-581 83 Linköping, Sweden
E-mail: jens.birch@liu.se
Interface roughness, interlayer chemical reactions, and interdiffusion are the main limiting factors
for reaching high reflectivity values from element-modulated neutron multilayer mirrors.
We demonstrate the feasibility of high reflectivity neutron interference mirrors, based on 10B/11B
modulation as the sole scattering mechanism in chemically homogenous BxC layers, consequently
eliminating any chemical driving force for formation of interphase interlayers and nanocrystallites at
the interfaces. Simulations show that the large difference in scattering length density between thetwo isotopes of B gives the potential for high neutron reflectivities using fewer and thinner layers
compared to conventional chemically modulated neutron multilayer mirrors and that absorption
effects make them suitable as band-pass mirrors high q-values.
Mirrors with internal 10B/11B modulation periods, Λ, ranging from 16 Å to 128 Å with 10B-to-Λ
relative thickness ratios, Γ, from 1/8 to 7/8, have been synthesized by alternating magnetron sputter
deposition of 10BxC and 11BxC layers producing 128 nm-thick BxC coatings. Interdiffusion andkinetically limited roughness accumulation was minimized by employing low-energy-modulated (0eV/~20 eV) high flux ion assisted deposition at room temperature.1
Neutron reflectivity (NR) data exhibit clear interference (‘Bragg’) peaks corresponding to all
intended 10B/11B modulation periods Λ=16 Å – 128 Å. NR simulations reveal interface widths of~4.1 Å. The average atomic B/C ratio in the mirrors was determined to x=5.7 with < 1 at% residual
elements (O, N, and H) by ToF-ERDA. No traces of elemental modulation or crystallinity weredetected by ERDA, X-ray reflectivity, X-ray diffraction, or Transmission Electron Microscopy.
In summary, we have shown that 10B/11B modulated chemically homogenous BxC reflectors can givehigh reflectivity with relatively few periods which make them suited for high Q bandpass mirrors.
References
F. Eriksson, N. Ghafoor, F. Schäfers, E. M. Gullikson, and J. Birch, Thin Solid Films, 500, 84 (2006).

28

All-dielectric multilayer mirrors tuned at vacuum ultraviolet
wavelengths
Paloma López-Reyes, Nuria Gutiérrez-Luna, Carlos Honrado-Benítez, and Juan Ignacio
Larruquert
GOLD-IO-CSIC Instituto de Óptica –Consejo Superior de Investigaciones Científicas, Serrano 144,
28006 Madrid, Spain.
E-mail: paloma.lopez@csic.es
Optics for the FUV (100-200 nm) are challenging in general due to material absorption and thelimited knowledge of optical constants. However, this range has gained a renewed interest in spaceobservations and future space observatories like the "Habitable Worlds Observatory, NASA”. FUV
space instruments require efficient coatings for high-throughput image bandpasses, and, traditionally,
MgF2/LaF3 multilayers (MLs) have been used, but their optimization is yet to be deeply studied.
Our group, GOLD-IO-CSIC, has developed high-performance all-dielectric FUV coatings with afocus on the short FUV, down to 120 nm, a region with comparatively lower performance due to theincreased absorption of fluorides. We present combinations of MgF2/LaF3 and AlF3/LaF3 that can betuned for any FUV wavelength >120 nm, with remarkable performance above 85% at H Ly-α (121.6nm) for AlF3/LaF3 MLs (Figure 1 a). We also compare the nanostructural morphologies of the two setsof MLs (Figures 1 b, c) [1].
Below ~120 nm, there is no suitable combination of fluorides since all fluorides but LiF turnabsorbing. Therefore, we present narrowband coatings based on Al, LiF, and SiC films, tuned at ~100
nm, with strong rejection at the close H Ly-α line (Figure 1 a) [2].
c)a)Figure 1 a) Near normal reflectance in the FUV of MLs based on AlF3/LaF3, MgF2/LaF3, or Al/LiF/SiC/LiF
b) Cross-sectional back-scattered electrons SEM images of AlF3/LaF3 and MgF2/LaF3 MLs, and theretrieved RMS roughness of each interface, from the substrate (#0) to the outermost layer.

References[1] López-Reyes, P., Gutiérrez-Luna, N., Honrado-Benítez, C., Ríos-Fernández, Á., Enríquez-Pérez, E.,
Chavero-Royán, J., ... & Larruquert, J. I. (2023). Far UV narrowband mirrors tuned at H Lyman α. Optics
Express, 31(10), 15392-15408.

[2] De Marcos, L. V. R., Larruquert, J. I., Méndez, J. A., Vidal-Dasilva, M., García-Cortés, S., GutiérrezLuna, N., ... & Chavero-Royán, J. (2018). Lyman-β narrowband coatings with strong Lyman-α
rejection. Optics Express, 26(19), 25166-25177.

29

Design Study of Soft X-Ray Aplanat with Four Multilayer Mirrors
in Grazing Incidence Configuration
S. Yamashita, and ○M. Toyoda
Optical Design Lab, Fecality of Engineering, Tokyo Polytechnic Univ.
E-mail: m.toyoda@eng.t-kougei.ac.jp

Enhanced intensity of novel light sources with photon energy between 200 to 700 eV, i.e., higher
harmonics and a third-generation synchrotron facility, there is a growing demand for imaging optics
that can realize diffraction-limited imaging in these higher energy region. It is known that two
spherical mirrors in a grazing incidence layout can provide coma-free focusing in a one-dimensional(meridional) plane. This system convoys the advantages of easy substrate polishing and highreflectivity of a multilayer coating thanks to the grazing incidence layout. If we can extend the system
to 2-d imaging, a novel optical design with both high throughput and low aberration in the higher
energy region should be expected. This presentation describes the results of a global search for the
optical design of a two-dimensional imaging system with four multilayer mirrors in grazing incidence
layout.
Figure 1 shows the design
example of the four mirror
system. The mirror substrates
are almost spherical, and small
aspherical terms were applied.
Novel aspheric terms based ontheZernikepolynomials,

which are defined by theelliptic area, were introduced.
This procedure corresponds tothe circular shape of the pupil
being stretched into an ellipse
on the mirror substrates. It was
found that aberrations can be

Fig. 1. Design example of four-mirror imaging system withgrazing incidence configuration.

further reduced by using the slight deformations with low-order terms including spherical aberration,coma, and trefoil expressed with the elliptic Zernike polynomials, At the same time, practical highreflectivity of the multilayer coatings should be expected since angle of incidences were assumed to be
60 deg. on each mirrors. In the optimization of the design parameters, first, several two-mirror
solutions for 1-d imaging were employed, and we preliminary obtained the initial design of the 2-D
imaging system by combining two pairs of the 1-d solutions. Finally, numerical optimization yielded
practical solutions that minimize aberration at both the on-axis and off-axis object. As shown in Fig. 1,
it was found that the wavefront aberration can be minimized within 100 pm, in the case for numericalaperture of 0.05 and an angle of view of 0.5 degree. In the presentation, we will also report on otherinteresting design examples found in the design space of the four-mirror system.

30

Thermally stable MoNx/Si1-xNx multilayer as a substrate for XSWstudy of SMSI
Atul Tiwari(1), Matteo Monai(2), Ksenia Matveevskii(1), Sergey N. Yakunin(3), Marcelo D.
Ackermann(1), Laurens D. B. Mandemaker(2), Florian Meirer(2) and Igor A. Makhotkin(1)(1) Industrial Focus Group XUV Optics, MESA+ Institute for Nanotechnology, University of Twente,
Drienerlolaan 5, 7522 NB Enschede, The Netherlands(2) Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Institute for Sustainable
and Circular Chemistry, Utrecht University, Utrecht, The Netherlands(3) NRC Kurchatov Institute, Moscow, Russia
E-mail: a.tiwari-1@utwente.nl
The Strong Metal Support Interaction (SMSI) is a phenomenon observed in supported metal catalyst systems,
in which reducible metal-oxide supports can form overlayers over the active metal nanoparticle (NPs) surface
during reduction at elevated temperature in H2/N2 environment. X-ray standing wave (XSW) generated using
periodic multilayer (ML) can be utilized to study surfaces and buried interface profiles with elemental
selectivity at sub-nm scale. Under Bragg condition, standing wave field is formed inside and above the ML
giving rise to nodes and anti-nodes. The strength of field intensity is suppressed and enhanced at nodes andanti-nodes respectively. By varying the angle of incidence, position of nodes and anti-nodes can be modulated
allowing us to probe surfaces layers andinterfaces locally. The stability of ML
during the experiment is essential as any
expansion or contraction of the bilayers
period modifies the XSW andcomplicates
that
data
analysis,specifically when the comparison ofvariously prepared samples is required.
For example to study the SMSI effect it isnecessary to compare metal-oxide-NPs
layer before and after reduction, that
requires high-temperature treatment.
In this work, thermally stable ML of
MoNx/Si1-xNx of 20 periods was preparedto generate XSW and assess the
Figure 1. Element distribution and  profile of the sample
applicability of XSW to study SMSI in
Co/TiOx/ML in pristine state and after reduction.
Co/TiOx model catalyst system. The
model catalyst system was synthesized on top of ML. By optimizing the ML structure and the TiOx layer
thickness, we achieved maximum sensitivity for the changes in the Ti atomic distribution profile. The samples
were reduced under H2/N2 environment at 600℃ for 1 hour and characterized by a combination of X-ray
reflectivity and GIXRF. Partial or full encapsulation of Co NPs by a thin TiOx layer was identified bymonitoring the changes in the phase of the Ti fluorescence signal before and after reduction. The changes in
Ti distribution profile upon reduction are shown in figure 1.
Author contribution and acknowledgements:
The work was performed in the frame of NEXT3D project funded by TKI Connecting Industry call with thesupport of Malvern Panalytical.
AT, KM, MA and IM were involved in design and deposition of periodic multilayer, measurements and analysisof X-ray data (2020-2023); MM, LM and FM were involved in the deposition of NPs on ML surface, reduction of
the samples and AFM characterisation (2020-2023); SN prepared XSW data analysis algorithm (2020-2021).

31Surface roughening by ion beams: Is ballistics “be-all and end-all”?
Parikshit Phadke, Jacobus M. Sturm, Fred Bijkerk, Marcelo D. Ackermann
Industrial Focus Group XUV Optics, MESA+ Institute, University of Twente
Email: p.phadke@utwente.nl

Ion beams are commonly used for industrial processing of thin films, ion beam deposition, ionassisted smoothing or forming layers of compounds. The thin film morphology such as roughness
and intermixing with underlying layers are determined by tuning the ion beam energy, flux orangle of incidence. The resulting films may be smooth, rough or may have rippled patterns on thesurface. Theoretical formulations have shown ion-surface interactions can be modelled byconsidering ballistic impacts and energy deposition in the film resulting in the above outcomes.
We show that for reactive ion beams of nitrogen and oxygen having similar ballistic impact, thefinal surface morphology is diametrically opposed. This is hypothesized to be the result of changes
in surface diffusivities and cohesive energies between atoms when compounds are formed underreactive ion bombardment. The results could have wider implications in materials processing suchas reactive sputter deposition, where tuning surface/interface roughness of compound films may
be desirable.

32More accurate prediction of optical constants: A prerequisite for thedevelopment of next-generation metrology instruments based on soft X-rays
Victor Soltwisch1
1

Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587 Berlin, Germany

PTB, Germany’s national metrology institute, has been involved in soft X-ray and EUV
metrology with synchrotron radiation since 1983 with the start of BESSY. Four decades later,
PTB operates several dedicated beamlines at BESSY II and extends the spectral capabilities
with its own metrology light source (MLS) into the infrared range. The continuous growthand expansion of these capabilities is closely linked to the increasing relevance anddevelopment of EUV lithography by the semiconductor industry. Today, PTB operates
several clean rooms, large lubricant-free reflectometers and scatterometers capable ofhandling large EUV optics. In addition to providing measurement services to customers
worldwide, PTB is also developing new solutions for dimensional and analytical metrology inthe nanometer regime using soft X-rays and EUV radiation. Bringing metrology solutions
based on light-matter interactions into the sub-nm precision range requires well-controlled
experiments and extensive modelling of the entire experimental chain. Precise knowledge ofthe material parameters is a key factor in creating an accurate virtual optical response thatcan describe and simulate the measurements. In addition to the shrinking size of the latest
2D and 3D nanostructures, the increasing number of material mixtures undergoing complex
manufacturing processes poses new challenges. Oxidation, contamination, impurities, ordensity variations can have a huge impact on the optical constants. In addition, material
properties of compound materials and alloys need to be measured since for many cases
their refractive index cannot be predicted using data of the individual components. The
Optical Constants Database (OCDB) project at PTB tries to bridge the gap between existingdata sets, including reliable uncertainties. New developments in X-ray metrology are being
driven by the need to further reduce uncertainties in dimensional metrology in the lower
sub-nm range. We review recent advances in X-ray scattering (GISAXS, EUV-SAS) and the
hybrid use of X-ray fluorescence techniques (GIXRF, GEXRF) to further increase the required
sensitivities and discuss how these techniques can be transferred from large-scale researchfacilities to the laboratory.

Fig 1: Combined X-ray scattering and GEXRF from a lamellar TiO2 grating structure

33

Bayesian Inferences and Time-Frequency Analysis Assisted
Determination of Optical Constants in the EUV
Qais Saadeh, Victor Soltwisch, Christian Laubis, Michael Kolbe, and Frank Scholze
Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany
E-mail: qais.saadeh@ptb.de
Next-generation EUV Lithography (EUVL) scanners with a Numerical Aperture (NA) of 0.55 are
now in production, realizing an 8 nm half-pitch with one exposure is now possible [1]. Technologies
like EUV ptychography and scatterometry are spreading. These developments necessitate accurate
optical constants and relevant metrological capabilities. Optical constants are indispensable in thedesign of optical elements and metrology is required for their characterization and defect-inspection.
The method of choice in PTB to determine optical constants is reflectometry. It allows simultaneous
determination of both parts of the complex refractive index from multilayers, thin films and substrates,
at any wavelength. Reflectometry supports an “at-wavelength metrology” approach since most opticalelements used for EUV applications are rather reflective. These benefits cannot be realized using otherknown methods like Transmission Mode Measurements (TMM) and Electron Energy Loss
Spectroscopy (EELS). However, determining optical constants from reflectivity data requires theconvergence of a model-based inverse-problem. The method is susceptible to contamination, oxidationand imperfections of the sample such as surface roughness. To mitigate these limitations, the relevant
inverse-problem targeting optical constants in the EUV range is complemented with X-ray Reflectivity(XRR) data. XRR is known for the high sensitivity to the geometrical characteristics providing subnanometre resolution. Time-Frequency Analysis (TFA) of XRR data is one option for directly inferringgeometrical information about the sample circumventing classical trial-and-error approaches.
Initializing the inverse-problem for determining optical constants in the EUV using a model based on
XRR data supports obtaining highly accurate results.
Recently, Markov Chain Monte Carlo (MCMC) based Bayesian inferences of EUV data were
coupled TFA of XRR to determine highly accurate optical constants – with uncertainties – of many
materials, including ruthenium and cobalt [2, 3].
Our contribution shows additional details of PTB metrology and modelling latest capabilities fordetermining optical constants, with emphasizing the impact on future development of optical elements
dedicated for the soft X-ray and EUV spectral ranges [4].
References[1] B. Bilski et al., Proc. SPIE 12292, 1229204 (2022).
[2] Q. Saadeh et al., Opt. Express 29(25), 40993-41013 (2021).
[3] Q. Saadeh et al., Optik 273, 170455 (2023).
[4] Q. Saadeh et al., Opt. Mater. Express 13(1), 78-91 (2023).

34

Refractive index measurements with improved accuracy for
EUV/x-ray multilayer optics
Franck Delmotte1, Regina Soufli2, Catherine Burcklen2, Eirini Papagiannouli1,
Farhad Salmassi3, and Eric Gullikson3
1

Université Paris-Saclay, Institut d'Optique Graduate School, CNRS, Laboratoire Charles Fabry,
91127, Palaiseau, France2
Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, US
3
Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, California 94720, US
EUV/x-ray multilayer optics with complex structures and functionalities have become key
components for various applications including photolithography, plasma physics, synchrotron, laser
and ultrafast science, solar physics and astrophysics. Yet, the available refractive index values required
to design and fabricate these optics, are often unreliable [1]. This is due to challenges inherent to theEUV/x-ray spectral region, such as the extreme sensitivity of materials to contamination and oxidation,
the difficulty in fabricating appropriate thin film samples, the presence of near-edge absorption finestructure, and the presence of multiple reflections at the longer EUV wavelengths, which arecomplicating the measurements.
We are presenting a new methodology to measure the EUV refractive index and new sets ofmeasurements for several important EUV/x-ray materials including Al, Cr, W, Pt [2-4].
We use combinations of transmittance and reflectance data in the spectral range 1.5 nm to 82.5 nm
and demonstrate for the first time highly resolved fine structure in the regions of L, M, N and O
absorption edges, in both the absorptive and dispersive portions of the refractive index, resulting in
improvements of up to a factor of 3 compared to earlier values. The improved refractive index
accuracy is validated by fitting experimental reflectance and transmittance data of multilayer coatings
containing these materials. The development of new and improved measurement methodologies andthe resulting new refractive index datasets will enable the accurate design, implementation andmodeling of the in-band and out-of-band performance of the next generation of EUV/x-ray optics.
References[1] J. Rebellato et al., “Analyses of tabulated optical constants for thin films in the EUV range andapplication to solar physics multilayer coatings”, Proc. SPIE 10691, 106911U (2018).
[2] F. Delmotte et al., "Soft x-ray optical constants of sputtered chromium thin films with improved
accuracy in the L and M absorption edge regions.", Journal of Applied Physics 124, 035107 (2018).
[3] R. Soufli et al., "Optical constants of magnetron sputtered Pt thin films with improved accuracy in
the N-and O-electronic shell absorption regions.", Journal of Applied Physics 125, 085106 (2019).
[4] F. Delmotte et al., “New method for the determination of photoabsorption from transmittancemeasurements in the extreme ultraviolet”, Opt. Express 30, 23771-23782 (2022).

35

36

Poster Session

37

38

Enhancement of Diffraction Efficiency and Spectral Flux
with Quasi-Graded Index Coating (QGIC) on
Soft X-Ray Laminar-Type Diffraction Gratings
Optimized for B-K and Li-K Emissions
Masato Koike,1-3 Tadashi Hatano,2 Alexander S. Pirozhkov,1 Masami Terauchi2
Kansai Photon Science Institute, Fundamental Quantum Sciences Directorate,
National Institutes for Quantum Science and Technology
2 Institute of Multidisciplinary Research for Advanced Materials, Tohoku University
3 Laboratory of Advanced Science and Technology for Industry, University of Hyogo
E-mail: koike.masato@qst.go.jp
1

A quasi-graded index coating (QGIC) to enhance the diffraction efficiency and spectral flux [1]of soft x-ray gratings used at grazing incidence satisfying total reflection was investigated. The
QGIC grating consists of a laminar-type grating, metal coating on the grating grooves, andadditional overcoating(s) having intermediate refractive indices between vacuum and the metal
coating. (Table 1) The QGIC gratings optimized for B-K (183.3 eV) and Li-K (54.3 eV) emissions
were designed and fabricated. For the experimental evaluation of the performance of the QGIC theuse was made of a soft x-ray flat-field VLS spherical grating spectrograph installed to an electron
microscope. The intensity observed with a CCD detector was normalized by the acquisition time andthe beam current. Figure 1 (a) shows B-K spectra of β-rhombohedral B observed with an angle ofincidence fixed to 84.8°. Ratio of the integrated spectral intensities were 1.0 : 2.0 : 2.5 for Ni,
Ni/LaF3, and Ni/La/C coatings [1]. Figure 1 (b) shows the Mg-L (39.3 and 49.3 eV) spectra ofmetal Mg observed with Au and Au/B4C coated gratings at the angles of incidence of 86.0° and
84.0°, respectively.
Table 1. Complement
refractive indices (δ =1.0−n) at 183.3 and 54.3
eV.
183.3 eV (B-K)
Vaccum0.00000C
0.00892
LaF3
0.01597La
0.01669
Ni
0.0252254.3 eV ( Li-K)
Vaccum0.00000SiC
0.08121B4C
0.10302Au
0.14974

Figure 1. Normalized intensities of (a) B-K emission spectra of βrhombohedral B observed using Ni-, Ni/LaF3-, and Ni/La/C-coateddiffraction gratings,[1] and (b) Mg-L emission spectra of metal Mg
observed using Au-, and Au/B4C-coated diffraction gratings.

Reference[1] T. Hatano, et al., Appl. Opt., 60 (16), 4993‒4999 (2021).

39

Development of Narrowband Multilayer Mirrors for
Extracting a Single Harmonic from an EUV HHG Source
Suet Yi Liu,1 Yuya Iwamoto,1 Hiroki Mashiko,2 Satoshi Ichimaru,2 Masatoshi Hatayama,2Eric Gullikson,4 Tomoya Mizuno,3 Takayuki Kurihara,3 Jiro Itatani,3 Hisataka Takenaka1
1 TOYAMA Co. Ltd, Japan
2

NTT Advanced Technology Corporation, Japan
Institute for Solid State Physics, the University of Tokyo, Japan
4
Center for X-ray Optics, Lawrence Berkeley National Laboratory, USA
E-mail: shirley@toyama-jp.com
3

We developed a Y/AlSi multilayer with narrowband performance in order to extract a pure single
harmonic from HHG (High Harmonic Generation). The multilayer was optimized for 63.8 eV (53rdorder), enabling the probing of the M2,3 absorption edges of the 3d transition metals such as Mn, Fe,
and Co. Its performance and thermal stability were compared with another EUV mirror, Zr/AlSi
multilayer, which has shown good performance in the EUV region (50-73 eV). Y/AlSi multilayerswith different structure parameters were also examined. All multilayers were evaluated by measuring
incident EUV reflectance at ALS beamline 6.3.2 and X-ray reflection (XRR).
Figure 1 shows the measured reflectance of Y/AlSi and Zr/AlSi multilayer mirrors at an incidence
angle of 3°. The measured peak reflectance of Y/AlSi and Zr/AlSi multilayers are 43% at 64 eV and
52% at 63.8 eV, and the energy bandwidth (FWHM) of the reflectance curve were 1.7 eV and 2.5 eV,
respectively. Our results show that the Y/AlSi multilayer mirror can better suppress adjacent harmoniclines while still having sufficient reflectivity for the selected single harmonic. There is no significant
drop in reflectance of both multilayers after heating up to 200 °C and no deterioration of multilayer
structure were observed after storage in air for 5 months.

Figure 1. Comparison of the calculated HHG spectra (grey filled areas) and the measured EUV
reflectivity for Zr/AlSi (blue points) and Y/AlSi (red points) multilayers.

40Resolving buried interfaces by Low-Energy Ion Scattering
Adele Valpreda, Jacobus M. Sturm, Andrey E. Yakshin, Marcelo Ackermann
Industrial Focus Group XUV Optics, MESA+ Institute for Nanotechnology, University of Twente, Enschede, the Netherlands
E-mail: a.valpreda@utwente.nl

X-ray optics is based on reflective multilayers with layer thicknesses of a few nanometers at most. Theinterface quality plays a central role in determining the final properties of these structures. However, theaccurate characterization of such interfaces with the necessary quasi-atomic resolution is a challenge. In
this context, Low Energy Ion Scattering (LEIS) plays a crucial role because it provides a unique way tomeasure both the elemental composition of the outer atomic layer and the subsurface elemental
distribution.
In LEIS, ions scattered by subsurface atoms undergo charge transfer processes in addition to scattering.
They have a high probability of being neutralized while penetrating the solid and a low probability of being
re-ionized upon leaving the surface. The low reionization probability creates a clear contrast between thesurface peak and subsurface tail. While the scattering processes are well known, the charge transfer
processes that influence the tail shape are still not fully comprehended. Consequently, the correlation
between tail shape and in-depth composition is still unresolved.
In this work, we study one of the charge transfer phenomena, reionization, by comparing experiments
and Monte Carlo simulations. The study is performed on bulk Si and Si thin films deposited on W or Mo.
We show how the energy-dependent reionization probability of Si can be used to simulate LEIS spectra ofstructures with Si as the top material. With this approach, we manage to resolve the buried interface
between the thin films with a sensitivity of a fraction of a nanometer.

41

Fabrication and characterization of EUV multilayer gratings
A.H.K. Mahmoud1, S. de Rossi1, Anne-Lise Coutrot1, A. Jérome1, E. Meltchakov1,
E. Papagianouli1, B. Capitanio2, M. Thomasset2, F. Delmotte1
1

Université Paris-Saclay, Institut d'Optique Graduate School, CNRS, Laboratoire Charles Fabry,
91127, Palaiseau, France
2
Synchrotron SOLEIL, L’Orme des Merisiers, Saint Aubin, BP 48F-91192 Gif sur Yvette Cedex,
FranceBy matching multilayer Bragg interference and grating diffraction conditions, EUV
multilayer gratings provide high spectral resolution (λ/∆λ > 1000) with efficiencies
similar to the reflectance of the multilayer coating. Such components are of particularinterest for EUV spectro-imaging application. In this work, we optimized and studied
periodic multilayer on gratings with trapezoidal shape in order to reach a maximum 1storder efficiency at wavelengths ranging from 25 nm to 29 nm, a region of particularinterest for solar corona spectro-imaging [1]. We have recently reported on Al/Mo/SiC
multilayer diffraction gratings with broadband efficiency in the extreme ultraviolet [2].
We report here on the fabrication and characterization of the groove profile evolution after
deposition using TEM and AFM analyses. Different kind of multilayers have been
deposited by magnetron sputtering [3] and ion beam sputtering [4] on grating substrates
with high groove density (> 3600l/mm). We used both fused silica grating substrates
provided by Zeiss (holographic process) and silicon grating substrates processed in ourlab via e-beam lithography. The results obtained with different material combination forthe multilayer, different grating substrates and different deposition technics will be
discussed and compared.
References[1] A. Mahmoud et al., Development of multilayer gratings for Solar-C EUV spectro-imager, Proc.
SPIE 12576, EUV and X-ray Optics: Synergy between Laboratory and Space VIII, 1257608 (2023).
[2] A. Mahmoud et al., Al/Mo/SiC multilayer diffraction gratings with broadband efficiency in theextreme ultraviolet, Opt. Express 30, 38319-38338 (2022).
[3] E. Meltchakov et al., Development of Al-based multilayer optics for EUV, Appl. Phys. A98, 111(2010).
[4] A. Ziani et al., Ion beam sputtered aluminum based multilayer mirrors for extreme ultraviolet solar
imaging, Thin Solid Films 552, 62-67 (2014).

42

EMIL@BESSY-II: In-situ investigations of material combinations at asynchrotron light source
Stefan Hendel1, Regan G. Wilks2, Mihaela Gorgoi2, Anna Efimenko2, Marcus Bär2
Department Optics and Beamlines (WI-AOS), Helmholtz-Zentrum Berlin für Materialien und Energie,
Albert-Einstein-Str. 15, 12489 Berlin, Germany
2
Department Interface Design (SE-AID), Helmholtz-Zentrum Berlin für Materialien und Energie,
Albert-Einstein-Str. 15, 12489 Berlin, Germany

1

Email: stefan.hendel@helmholtz-berlin.de

The Energy Materials In-Situ Laboratory Berlin (EMIL) at BESSY-II combines modern techniques ofthin film/layer deposition with the possibility of in-situ characterization tools like (Hard X-ray)
Photoelectron Spectroscopy, X-Ray Absorption and Emission Spectroscopy and X-Ray Fluorescence
Spectroscopy. The experimental endstation, lab-based x-ray spectroscopy, and layer deposition
facilities are connected via an UHV-transfer backbone: samples can be transferred under vacuum
conditions to the endstation, characterized, and taken back to a deposition tool for further
processing. This infrastructure allows for a step by step production and analysis of different material
combinations. Magnetron sputtering, e-beam evaporation, atomic layer deposition and chemical
vapor deposition tools are available within the interconnected UHV system for different applications.
In combination with the wide energy range of 80eV – 10keV of the EMIL beamline, which is fed by acanted double undulator system and equipped with three monochromators, depth information fromthe surface down into the bulk up to 5µm are accessible.
We will show the current setup and performance, possible material combinations and some resultsof recent measurements. EMIL has been in user operation since 2020 and welcomes interested users.

Figure 1: EMIL endstation, the UHV-transfer backbone and deposition facilities

43

Upgrades of PTB’s EUV Reflectometry Instrumentation
Andreas Fischer, Christian Laubis, Michael Kolbe, and Frank Scholze
Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587 Berlin, Germany,*e-mail: christian.laubis@ptb.de

With increasing demand for EUV Lithography, optical elements and sensors for EUV radiation areneeded for a multitude of instruments and machines in its supporting ecosystem. Most of these systems
require at-wavelength characterization supporting development, manufacturing, utilization andmaintenance.
PTB provides at-wavelength characterization metrology services in the EUV spectral region for 40
years now. The requirements of the partners from research and industry increased ever since and PTB
is continuously upgrading its instrumentation. PTB now put into operation a lubricant freereflectometer, designed to handle sample sizes of “collector” type mirrors up to 670 mm in diameterand 250 mm in height and “long mirror” type samples of 1000 mm x 150 mm x 250 mm with up to
150 kg in weight combined for sample and mounting to support the characterization of production
grade optical elements in the 6 nm to 40 nm wavelength range.
We present our large lubricant free reflectometer at PTB’s MLS (Metrology Light Source) synchrotron
laboratory, as well as its supporting infrastructure and peripherals.
Preferred presentation: Poster

44

Optical Constants of Carbon and Boron material for
Beyond EUV Lithography
Umi Fujimoto, Tetsuo Harada, Shinji Yamakawa, Takeo Watanabe
University of Hyogo, LASTI, Center for EUV Lithography (Japan)
1-1-2 NewSUBARU, Kouto, Kamigori, Ako-gun, Hyogo 678-1205, Japan
TEL: +81-791-58-2546 E-mail: umi1210@lasti.u-hyogo.ac.jp
In 2019, EUV lithography technology with a wavelength of 13.5 nm was first applied to mass
production of 7 nm+ node logic devices. In the future, since semiconductor devices with higherdensity electronic circuits are required, beyond EUV (BEUV) lithography technology with an
exposure wavelength around 6.7 nm is expected as the next generation lithography. The developmentof multilayer with high reflectivity is a critical issue for BEUV lithography.
The calculated reflectance spectra of the multilayers for BEUV are shown in Fig. 1. La/B-based
multilayers, which have been developed, have a high theoretical reflectivity of about 80%. The highest
reflectance of 64.1% was reported for LaN/La/B multilayer at the angle of incidence (AOI) of 1.5° [1].
However, it is difficult to achieve high temporal stability in La/B-based multilayers because of thehigh chemical activity of La. Thus, we propose Carbon/Boron (C/B) multilayer as a new BEUV
multilayer. The performance of the C/B multilayer is comparable to that of the La/B multilayer. The
optical constant of the carbon film depends on its density, and high-density C has good optical constantfor BEUV multilayer. In the calculation of Fig. 1, the density of 3.1 g/cm3 was used, which is thehighest density of diamond-like carbon film. For the C/B multilayer fabrication, we have deposited C
and B layers, and measured actual optical constants at BEUV using a reflectometer in NewSUBARU
synchrotron light facility. The measurement results of optical constants are shown in Fig. 2. We will
discuss the performance of the C/B multilayer based on the results of theoretical calculations andmeasured optical constants.

Figure 1. Calculated reflectance spectraof BEUV multilayers.

Figure 2. Measurement results and calculated
value of optical index at 6.7-nm wavelength.

References[1] D. S. Kuznetsov, Opt. Lett., 40, (2015) 3778.

45

Improved performance of polarizing Fe/Si multilayer neutron
optics by 11B4C incorporation
A. Zubayer,1 N. Ghafoor,1 K. Þórarinsdóttir,2 S. Stendahl,1 A. Glavic,3 J. Stahn,3 G. Nagy,4 G.
Greczynski,1 M. Schwarzkopf,5 A. Le Febvrier,1 P. Eklund,1 J. Birch,1 F. Magnus,2 F. Eriksson1
1. Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping
University, SE-581 83 Linköping, Sweden
2. Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik, Iceland
3. Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
4. Department of Physics and Astronomy, Uppsala University, SE-75120, Uppsala, Sweden
5. Photon Science, DESY, Notkestraße 85, 22607, Hamburg, Germany
E-mail: anton.zubayer@liu.se
Polarized neutrons provide valuable insights in magnetism, materials science, and biology. However,polarizing multilayer neutron optics have limitations such as low reflectivity and polarization,
especially at higher scattering vectors/angles, and dependence on high external magnetic fields formagnetization. We addressed these issues by co-depositing 11B4C to Fe/Si multilayers during ionassisted magnetron sputter deposition. Our research shows that integrating 11B4C into Fe/Si multilayers
leads to amorphous multilayers with smoother interfaces, improving neutron reflectivity andpolarization. Furthermore, the 11B4C allows for scattering length density tuning for optimal
polarization. This improvement was demonstrated using X-ray and reflectivity (XRR) and polarized
neutron reflectivity (PNR). The incorporation of 11B4C reduced diffuse scattering, evidenced bygrazing incidence small-angle X-ray scattering (GISAXS), and eliminated the magnetic coercivity,
observed through vibrating sample magnetometry (VSM) and magneto-optical Kerr effect (MOKE)
measurements, rendering the multilayers magnetically soft, enabling magnetic saturation at low
external fields. By successfully addressing the limitations of polarizing multilayer neutron optics, theintegration of 11B4C into Fe/Si multilayers offers a promising approach for improving the performanceand functionality of neutron scattering facilities.

Figure 1. Fe/Si and Fe/Si + 11B4C comparison. (a) VSM. (b) TEM. (c) GISAXS raw data. (d) Out-of-plane line cuts.

46

Removal of Mo/Si Multilayer Coatings on Fused Silica Substrates
by Wet Chemical Etching
Mitsunori TOYODA1, Ryo YOKOYAMA1, Shuntaro WAKI1,
Toshiyuki KAKUDATE2, and Jun CHEN1.
1. Department of Media and Image Technology, Faculty of Engineering,Tokyo Polytechnic University, 1158 Iiyama, Atsugi, Kanagawa 243-0297, Japan
2. Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira,Aoba, Sendai, Miyagi 980-8577
E-mail: m.toyoda@eng.t-kougei.ac.jp
Mo/Si multilayer mirrors operating in the 13-nm wavelength region can provide a high reflectivity of over
60% and have been applied in numerous imaging systems, such as extreme ultraviolet (EUV) microscopy
instruments. These mirrors have a multilayer structure comprising Mo and Si bilayers on a super-polishedsubstrate that is typically made of fused silica or ultra-low-expansion glass. An iterative andtime-consuming polishing process is employed to fabricate such substrates, since the figure error must be
controlled with a spatial period between several hundred millimeters and several micrometers. The surface
figures in the low- and high-frequency regions are commonly controlled by either bowl-feed polishing13) orstate-of-the-art numerical control techniques, such as magneto-rheological finishing, combined withinterferometric surface figure measurements. However, these processes are both labor-intensive andexpensive. One promising approach to reducing costs and labor requirements is to reuse mirror substrates,by completely removing the original multilayer coatings and depositing new ones. The reuse of suchmirrors could be considered when the mirror itself shows damage, such as oxidation of the top surface layer
by contact with ambient air, carbon contamination resulting from intense EUV irradiation or thermal
diffusion in the periodic structure. These types of damage will eventually degrade the reflectivity of thedevice. During reuse processing, the multilayer coating must be completely removed while keeping theshape of the mirror substrate unchanged, and several studies have examined techniques for removing Mo/Si
multilayer structures with surface oxide layers or carbon contamination. However, to the best of ourknowledge, there have been no reports concerning techniques for removing the entire multilayer structurefrom the substrate. In the present work,1) we demonstrate a novel method for completely removing Mo/Si
multilayer coatings, based on wet chemical etching. This research examines an etchant capable ofdissolving both Mo and Si at a sufficiently high etching rate with little effect on fused silica (SiO2)
substrates. Specifically, a Mo/Si multilayer mirror was immersed in an alkaline solution containing
potassium ferricyanide (K3Fe(CN)6) and sodium hydroxide (NaOH), which was found to remove the entire
coating. The surface shape of the substrate was then evaluated using an optical profiler to confirm that theetching process did not increase the surface roughness.
Reference:
1. Mitsunori Toyoda et al., Appl. Phys. Express 14 052003 (2021).

47

Picometer Sensitivity on Laboratory-based XRR Instrument
Equipped with Fast and Accurate Sample Alignment System
Hitoshi Morioka1, Fernando Rinaldi2, Martin Zimmermann2
1 X-ray Division, Bruker Japan K.K., Yokohama, Japan
2

Bruker AXS GmbH, Karlsruhe, Germany
E-mail: hitoshi.morioka@bruker.com

X-ray reflectometry (XRR) is a powerful non-destructive evaluation method for density profile ofmultilayer structure, e.g., EUV and X-ray optics which have artificial superlattice structures to selectthe specific wavelength. XRR measurements are performed with grazing incidence and exiting
geometry, thus it requires precise sample position and incidence angle alignment before measurements,
but it is a time-consuming process due to iterate some scans although obtaining better reproducible
and repeatable measurement results. In this study, we demonstrated that the capabilities ofcommercially available X-ray diffraction platform for such XRR applications with superb picometer
sensitivity with fast and accurate sample alignment system for EUV optics samples.
XRR measurements were performed on Bruker D8 DISCOVER materials research X-ray
diffraction platform which can supply tailored solutions for multiple samples from R&D leveled small
pieces to industrial scale wafer samples. X-ray is generated in the industrial-grade sealed tube with Cu
target, and convergent into highly paralleled beam by using Göbel multilayer mirror to select CuK
wavelength with less than 0.028o divergence. The primary beam size was precisely controlled by
motorized cross-slits with 0.001 mm resolution. Samples were horizontally mounted on vacuum chuckstage which is made of porous ceramics material to avoid sample bending. Beam knife-edge was also
equipped on the sample surface which has height sensor to control sample surface position and knifeedge gap space automatically. In secondary, inverted Göbel multilayer mirror was mounted andreflected X-rays were collected by semiconductor-based X-ray detector without any attenuator. The
configuration with two symmetrically placed Göbel mirrors guarantees the highest insensitivity to
beam profile changes and to small sample misalignments. This is ideal for high reproducibility of themeasurements and allows the possibility of changing the beam shape during different part of the same
curve. The measured sample size was 25×25 mm and axial slit size was kept as 16 mm. Equatorial
slit and knife-edge gap sizes were precisely controlled depending on the scan 2 angles in 3 steps, 0.2
and 0.025 mm in 0-2.2o/2, 0.2 and 0.1 mm in 1.8-7.2o/2, and 1.2 and 0.6 mm in 6.8-17o/2,
respectively. Scan integration time and increment were kept as 0.1 s/step and 0.01o/step.
Sample shows clearly sharp superlattice satellite peaks up to 12 orders in 17o/2. The typical
reproducibility result was < 0.001o in standard deviation at 7.5o/2. This deviation is corresponding to
1 pm for the superlattice periodic thickness. We will show more detail information in the session.
Samples were courtesy supplied from optiX fab GmbH.

48

At-Wavelength Metrology for diffractive and reflective optics
in the EUV, XUV and tender X-ray energy range
Andrey Sokolov, Frank Eggenstein, Peter Bischoff, Peter Baumgärtel, Matthias Mast, Marcel
Mertin, Ingo Packe, Franz Schäfers, Frank Siewert, Jens Viefhaus
Helmholtz-Zentrum Berlin für Materialien und Energie (BESSY-II), Berlin
E-mail: andrey.sokolov@helmholtz-berlin.de
An accurate characterization of the real performance of sophisticated reflective or diffractive optics
is extremely demanding to experimental conditions task. An At-Wavelength Metrology facility for
EUV and XUV optics is under operation since many years at the BESSY-II storage ring. As the main
instrument a versatile 11-axis UHV-reflectometer is permanently connected to a dedicated Optics
beamline. The setup is suitable for measurements as well as on small test samples but also for real size
optics in limits up to 360 x 60 x 60 mm3. Moreover, a flexible sample stage support system based onan UHV-tripod gives 6 degrees of freedom for a precise alignment and mapping of optical elements
under test. 360 degrees freedom goniometers enable to bring the beam on the sample in incident angle
from 0 to 88.9 degree and scan outgoing radiation in almost complete in-plane circle as well tocontinuously rotate whole system from s to p polarization geometry. High spectral purity of theincident beam is achieved by a set of 12 absorption filters and a High-Order Suppressor System. It
was experimentally tested that it gives a nearly high-order free beam between 13.5 eV and 1800 eV.
In additional to that a small Reflectometer as a portable end-station is used to get access to UV-EUV
or X-ray energy ranges by setting it up at U125-2_NIM (4eV – 30eV) and KMC-1 (2keV – 10keV)
beamlines at BESSY-II. The present status of the metrology facility, their latest upgrade projects andmost challenging results will be presented in our contribution.

Figure 1. Optics beamline hutch, 11-axis UHV-reflectometer outside and inside view.
References[1] F. Schäfers et al., J. of Synch. Rad., Proc. PhotonDiag workshop Trieste 23(1), 67-77 (2016)[2] A. Sokolov et al., Rev. Sci. Instrum. 87, 052005-1-7 (2016)[3] Peter Baumgärtel, Ingo Packe, Journal of large-scale research facilities, 2, A53 (2016)[4] A. Sokolov et al., Opt. Express 27(12), 16833-16846 (2019)[5] Franz Schäfers, Journal of large-scale research facilities, 2, A96 (2016)49

Low-Cost Cleaning Method of Mo/Si Multilayer Soft X-ray
Mirrors Using a Wet Process
Toshiyuki Kakudate1, 2, Mitsunori Toyoda3
1

Department of Industrial Systems Engineering, National Institute of Technology (KOSEN),
Hachinohe College, 16-1 Uwanotai, Tamonoki, Hachinohe 039-1192, Japan
2
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira,Aoba, Sendai, Miyagi 980-8577, Japan3
Department of Media and Image Technology, Faculty of Engineering, Tokyo Polytechnic
University, 1158 Iiyama, Atsugi, Kanagawa 243-0297, Japan
E-mail: kakudate-e@hachinohe.kosen-ac.jp
A low cost cleaning method of Mo/Si multilayer soft X-ray mirrors using a wet process with NaOH
solutions were investigated for the realization of reusing and prolonging the lifespan of soft X-ray
mirrors. The effectiveness of the cleaning method is examined by reflectivity and X-ray photoelectron
spectroscopy (XPS) measurements of Mo/Si multilayers on SiO2 substrates. The Mo/Si multilayers
surfaces were intentionally oxidized and carbon contaminated by the storage in the atmosphere andcarbon deposition for the usage of these mirrors as models of the oxidized and carbon contaminatedmirrors. The wet process cleaning was carried out by immersing the oxidized and carbon contaminatedmirrors into NaOH solutions. The mirrors were rinsed by ultrasonication with isopropyl alcohol andacetone after the immersing. In this presentaion, we report results of the changing of the reflectivity
and the surface chemical composition of the mirrors.
Figure 1 shows the XPS spectra taken from the carbon contaminated mirror, oxidized mirror andmirror after the cleaning. On the mirror surface after the oxidation or carbon contamination, peaks
derived from the molybdenum oxides or carbon appear dominantly. In contrast, on the mirror surface
after the cleaning, peaks derived from the metal molybdenum appear, which imply that mirrors after
the cleaning process have less contaminations and a possibility to exhibit higher reflectivity than thosestoraged in the atmosphere. In the poster presentation, we explain the relation between XPS andreflectivity measurements results in detail.

Figure 1. XPS spectra taken from the carbon contaminated mirror, oxidized mirror and mirror after
the cleaning (from bottom to top).

50

High Irradiance Illuminator forTransmission Extreme Ultraviolet Microscopy
Shuntaro Waki, Yusuke Tsukui, Jun Chen, Mitsunori Toyoda
Tokyo Polytechnic University
E-mail: d2286001@st.t-kougei.ac.jp
We are developing a lab-scale transmission extreme ultraviolet (EUV) microscope using a laserproduced plasma (LPP) light source operating at a wavelength of 13.6 nm. The microscope is madeof an illuminator and a two-stage magnifying objective, that are all consisting of five Mo/Si
multilayer mirrors. We have reported good elemental contrast between oxygen and carbon on
polymer samples; a transmission image observation allows visualization of the phase-separated
structure of PS/PMMA polymer blends without staining [1]. High intensity illumination should be
one of the keys to achieve diffraction-limited imaging on the lab-scale microscope. A limited
brilliance of the light source tends to increase a photon noise on images and spoils the spatial
resolution. Therefore, we developed a novel two-aspherical-mirror system providing high intensity
illumination, as shown in Figure 1. The system can provide lager solid angles by correcting a
spherical aberration, which is inherent in the previous system with spherical mirrors. In thispresentation, first, we provide results of numerical calculations to estimate the enhanced intensity,where, as well as geometric optics, we treat two practical contributions given from experiments,
i.e., the luminance distribution of the LPP light source and reflectance of the Mo/Si multilayer
coating. The luminance distribution was obtained by imaging the light source with an EUV
microscope, and the reflectance of the multilayer mirror was measured with an EUV reflectometer[2] in our laboratory. We will also report the comparison of experimental results for intensities on
sample plane, that are given with the aspherical and spherical illumination systems as shown in
Figure 2.

0.16

Illuminance (arb.)

0.14

X direction
Y direction
Solid line: Aspherical
Dashed line: spherical

0.12
0.10
0.08

4.3x

0.06
0.04
0.02
0.00

0.05

0.10

0.15

0.20

0.25

Object height (mm)Figure 1. Schematic diagram of a two-plane
aspheric illumination optical system.

Figure 2. Calculation results consideringreflectance of multilayer mirror andluminance distribution of LPP light source.

References[1] M. Toyoda et.al, Appl. Phys. Express. 13(8), 082011 (2020).
[2] S. Nakayama et.al, Phys. Scr. 41 (6), 754 (1990).

51

Multilayer structures in coherent x-ray diagnostics in BISER
and Relativistic Flying Mirror experiments
A. S. Pirozhkov1, A. N. Shatokhin2, E. A. Vishnyakov3, A. Sagisaka1, K. Ogura1, M. Koike1,4,5,
T. Hatano4, H. Ohiro6, S. Namba6, J. K. Koga1, A. O. Kolesnikov2, H. Kiriyama1,
T. Zh. Esirkepov1, T. A. Pikuz7, E. N. Ragozin2, S. V. Bulanov3, M. Kando1
Kansai Institute for Photon Science (KPSI), QST
2
P. N. Lebedev Physical Institute, RAS
3
ELI-Beamlines, ELI-ERIC
4
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University
5 Laboratory of Advanced Science and Technology for Industry, University of Hyogo
6 Department of Advanced Science and Engineering, Hiroshima University
7 Open and Transdisciplinary Research Initiatives, Osaka University
E-mail: pirozhkov.alexander @ qst.go.jp
1

We are developing bright compact temporally and spatially coherent x-ray sources based on Burst
Intensification by Singularity Emitting Radiation (BISER) and Relativistic Flying Mirror (RFM)
concepts. BISER [1-2] is the emission of bright coherent x-rays by multi-stream flow singularities
produced in a relativistic plasma by high-power lasers. The RFM [3-5] is a mirror moving nearly at
speed of light formed by an intense laser in underdense plasma. A counter-propagating laser pulse
partially reflects from the RFM, with its wavelength and pulse duration compressed by a large factor
up to ~4γ2 resulting in bright coherent x-rays.
We present x-ray diagnostics used in our BISER and RFM experiments based on multilayer
structures: spectrographs with aperiodic broadband multilayer mirrors [6] (12.4-25 nm) and a 3channel spectrograph with a multilayer-coated laminar VLS grating [7] (1-2 keV).
Acknowledgments
We acknowledge support from the J-KAREN-P Laser Team. Financial support: JSPS Kakenhi JP
19KK0355, 19H00669 and 23H01151, RSF 20-62-46050, ELI-Beamlines, MŠMT project "Advanced
Research Using High Intensity Laser Produced Photons and Particles" (CZ.02.1.01/0.0/0.0/16_019/0000789),
High Field Initiative (CZ.02.1.01/0.0/0.0/15_003/0000449) from the European Regional Development Fund,and the Strategic Grants by the QST President: IRI and 創成的研究 #20.

References
1. A. Pirozhkov et al. "Soft-X-Ray Harmonic Comb from Relativistic Electron Spikes" PRL 108, 135004 (2012).
2. A. S. Pirozhkov, T. Zh. Esirkepov, et al., "Burst intensification by singularity emitting radiation in multistream flows," Sci. Reports 7, 17968 (2017).
3. S. Bulanov, T. Esirkepov, T. Tajima, "Light Intensification towards the Schwinger Limit," PRL 91, 085001 (2003).
4. M. Kando et al., "Demonstration of Laser-Frequency Upshift by Electron-Density Modulations in a Plasma
Wakefield," PRL 99, 135001 (2007).
5. M.Kando et al "Enhancement of Photon Number Reflected by the Relativistic Flying Mirror" PRL 103 235003 (2009)
6. A.S.Pirozhkov, E.N.Ragozin, "Aperiodic multilayer structures in soft X-ray optics," Phys.-Usp. 58, 1095 (2015).
7. M. Koike et al., "Design of soft x-ray laminar-type gratings coated with supermirror-type multilayer toenhance diffraction efficiency in a region of 2-4 keV," RSI 94, 045109 (2023).

52

A new variant of high-performance neutron supermirror polarizer
Thierry Bigault, Alexander K. Petoukhov†,Guillaume Delphin, Sébastien Batisse, Amandine Vittoz, Pierre Courtois,
Valery V. Nesvizhevsky, Torsten Soldner, David Jullien, Anton Devishvili, Thomas Saerbeck
Institut Max von Laue - Paul Langevin, (ILL), Grenoble, France
E-mail: bigault@ill.fr
Being the world’s leading facility in neutron science and technology, the ILL makes its facilities and expertiseavailable to about 1400 researchers per year, performing 1000 experiments in a wide range of scientific fields. Inan ever-growing part of these experiments, the possibility to produce spin-polarized neutron beams is exploited to
pinpoint magnetic information much more precisely. In this context, designing and producing high-performanceneutron polarizers and analyzers if essential. One of the widespread neutron polarizing technologies consists inusing broadband interferential multilayer mirrors called ”supermirrors”. Driven by the need of a “near-perfect fullbeam” polarization for neutron experiments in fundamental physics [1], we have been developing a new variant ofsupermirror-based polarizer, that pushes the limit of performance further and offers practical advantages. It is basedof Fe/Si supermirrors coated on sapphire single crystal substrates, thus getting around the coating activation andsubstrate degradation issues, while improving the accepted neutron bandwidth [2]. By taking special care to thegeometrical design, the magnetic circuit, the coating process and the mounting procedure [3], a record-breaking
full-beam polarization of 99.7% with a 31% transmission was measured for the wavelength range 0.3 – 20 nm[Figure 1]. The final device is now available for users on the PF1B instrument. While the same polarizer design
could be used for other types of instruments by tuning the geometry, in the case of a largely different instrumental
configuration most of the concepts can be kept. Indeed, we are installing a new analyzer on the polarized neutronreflectometer D17, which only differs from the PF1B device by its geometrical design. It will allow broadband highefficiency polarization analysis both in the case of specular and off-specular measurements.

Figure 1. Photograph (a) and schematic view (b) of the polarizer for PF1B. Measured performance of the polarizer(c) in terms of full beam polarization efficiency and output flux density for two values of angle  between successive
cassettes.
References[1] B. Märkisch et al., Phys. Rev. Lett. 122, 242501 (2019)[2] A. K. Petukhov, V. V. Nesvizhevsky, T. Bigault, P. Courtois, D. Jullien, and T. Soldner, Nucl. Instr. Meth. A
838, 33 (2016); Rev. Sci. Instrum. 90, 085112 (2019)[3] A. K. Petoukhov, V. V. Nesvizhevsky, T. Bigault, P. Courtois, A. Devishvili, D. Jullien, and T. Soldner, Rev.
Sci. Instr. 94, 023304 (2023)

53

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Oral Session:
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