PREFACE
This annual report reviews the research activities of the Laboratory of Advanced
Science and Technology for Industry (LASTI) in the academic year of 2021 which is from
April 2021 to March 2022 including research activities using NewSUBARU light sourceat the SPring-8 site and other research activities carried out at the Center for Advanced
Science and Technology (CAST) II. NewSUBARU facility has a 1.0-1.5 GeV electron
storage ring, which provides light beams from infrared (IR) to hard X-ray regions, and is
the largest university-operated synchrotron light facility in Japan.
At NewSUBARU, researches are mainly focusing on the academic fields of 1)
development of new synchrotron light source technology, 2) the next generation
lithography using extreme ultraviolet (EUV) conducted at beamlines BL3, BL9B, BL9C,
and BL10, 3) applications of lithographie galvanoformung abformung (LIGA) process
technology at BL2 and BL11, 4) materials analysis by X-ray absorption spectroscopy at
BL5, BL7 and BL9A, X-ray emission spectroscopy at BL9A, and photoemission
spectroscopy at BL7. Other than the synchrotron radiation researches, various researches,such as material syntheses, device fabrication, and microfluid mechanics, are also being
conducted at CAST II. Most of our research activities are being conducted incollaboration research works with industries, research institutes, and other universities,
inside and outside Japan. We would like to take this opportunity to thank all thecollaborators.
Previously, the SPring-8 linear accelerator had also been used to injection of theelectron beam to the NewSUBARU electron storage ring in cooperation of the Spring-8
accelerator team. However, the new linear accelerator dedicated to NewSUBARU was
installed at the beam transportation tunnel in 2020 and it started operation in April 2021.
The construction of the new injector has been completed in great cooperation of theSPring-8 accelerator team. We would like to appreciate the SPring-8 accelerator team fortheir huge contributions.
Satoru Suzuki

Director of Laboratory of Advanced Scienceand Technology for Industry, University of Hyogoⅰ

ⅱ

The Organization of Laboratory of Advanced Scienceand Technology for Industry (LASTI) at University of Hyogo
Steering
Committee

Director

Department ofLight and Particle Science andTechnology

Department ofLight Application for Advanced Technology⋄Nano-Science and Technology utilizing
Synchrotron Radiation⋄Nano-Micro System⋄Bio-Medical Technology (to be established)⋄Guest Chair⋄Functional Material Property⋄Beam Physics⋄Nanostructure Science and Technology⋄Guest Chair

Staff (FY 2021
1)
Research and faculty staff

Administrative staff

WATANABE Takeo, Professor, Director
KANDA Kazuhiro, Professor
SUZUKI Satoru, Professor
UTSUMI Yuichi, Professor
HARADA Tetsuo, Associate Professor
HARUYAMA Yuichi, Associate Professor
HASHIMOTO Satoshi, Associate Professor
NAKANISHI Koji, Associate Professor
SHOJI Yoshihiko, Associate Professor
YAMAGUCHI Akinobu, Associate Professor
AMANO Sho, Research Associate
FUJII Satoshi, Research Associate
YAMAKAWA Shinji, Research Associate

HAYASHI Masahiko, General Manager
HIROKAGA Yasuhiro, Manager
KAYAHASHI Hidetoshi, Chief
AKAMATSU Sumiyo, CAST
FUJIWARA Riho, CAST
KONO Kimi, CASTYOSHIDA Mizuho, CAST
MAEDA Yasuhide, CASTSENBA Ayako, CAST
KUSUMOTO Kumi, CASTKUWATA Ayami, NewSUBARU
Guest staff
MIYAMOTO Shuji, Professor
HARADA Yoshihisa, Professor
HORIBE Hideo, Professor
KOIKE Masato, Professor
KUDO Hiroto, Professor
SASAKI Shigemi, Professor
SUGIYAMA Munehiro, Professor
NIIBE Masahito, Associate Professor
FUKUOKA Takao, Researcher
KAGEYAMA Hiroyuki, Researcher
MAEKAWA Satoshi, Researcher
OKADA Ikuo, Researcher
OKUI Masato, Researcher
SAIKI Tsunemasa, Researcher
SAKURAI Yuuya, Researcher
TOKUSHIMA Kou, Researcher
YAMADA Motoyuki, Researcher
YAMASHITA Kenji, Researcher

Specially appointed staff
TERANISHI Nobukazu, Professor

Contact address
Advanced Research Building of LASTI
3-1-2 Kouto, Kamigori-cho, Ako-gun, Hyogo, 678-1205 JAPAN.
Phone: +81-791-58-0249 Fax: +81-791-58-0242
NewSUBARU Synchrotron Radiation Facility
1-1-2 Kouto, Kamigori-cho, Ako-gun, Hyogo, 678-1205 JAPAN.
Phone: +81-791-58-2503 Fax: +81-791-58-2504
Web URL https://www.lasti.u-hyogo.ac.jp/english/index.html
https://www.lasti.u-hyogo.ac.jp/NS/
E-mmail
ns-clerk@lasti.u-hyogo.ac.jp
Accesshttps://www.lasti.u-hyogo.ac.jp/NS-en/access/ⅲ

CONTENTS
PREFACE………………………………………………………………………………………

ⅰ

ORGANIZATION of LASTI…………………………………….………………………………….

ⅲ

Part 1. Current Status of NewSUBARU and Other Light Source
Electron accelerators at NewSUBARU………………………………..………………………………
Satoshi Hashimoto (LASTI/University of Hyogo)

1

NewSUBARU Beamlines……………………………………………….……………………………….
Koji Nakanishi (LASTI/University of Hyogo)

6Part 2. Research Activities
Anomaly Detection of Electron Beam by Machine Learning……….……………………………….
H. Fujii1, S. Matsuo2, and S. Hashimoto1(1LASTI, 2University of Hyogo)

17

Fundamental Evaluation of Resist on EUV Lithography at NewSUBARU SynchrotronLight Facility………………………………………………………………………………..…………..
Takeo Watanabe, Tetsuo Harada, Shinji Yamakawa(Center for EUVL, LASTI, University of Hyogo)

19

Synthesis and Characterization of the Polymer Having Photoacid Generator
for EUV Resist………………………………………………………………………………..………….
Shinji Yamakawa, Tetsuo Harada, Takeo Watanabe(Center for EUVL, LAST, University of Hyogo)

24

Relocation and Upgrade of Tender X-ray XAFS Beamline for High-Accuracy and Advanced
Measurements……………………………………………………………………………………………
Koji Nakanishi (LASTI, University of Hyogo)

27

The Effect on Exit Beam Height by Change of Incident Beam Height in Symmetrical Layout TypeDouble Crystal Monochromator……………………………………………………………………….. 31
Masato Okui1, 2, Naoki Yato1, Atsushi Shimoguchi1 Norio Murayama1, Ichiro Tsuboki1, andKazuhiro Kanda2 (1Kohzu Precision Co., Ltd., 2LASTI, University of Hyogo)
Structural Changes of Highly Hydrogenated Diamondlike Carbon Films
by Soft X-ray Irradiation…………………………………………………………………………………. 34
Daisuke Niwa1, Tomohiro Mishima1, Hibiki Terai1, Koji Nakanishi1, Masahito Niibe1,

ⅳ

Kazuhiro Kanda1, Fuminobu Hori2, Atsushi Yabuuchi3, Atsushi Kinomura3(1LASTI, Univ. Hyogo, 2Eng., Osaka Pref., Univ., 3RNS, Kyoto Univ.)
Development of an Improved Multi-Layer Mirror for the New γ-Beam Source
via X-Ray Compton Scattering……………………………………………………………………………
Norihito Muramatsu1, Tetsuo Harada2, Schin Daté3, Kazuhiro Kanda2, Manabu Miyabe1,
Shuji Miyamoto2, Haruo Ohkuma3,4, Masahiro Okabe1, Hajime Shimizu1, Shinsuke Suzuki3,
Atsushi Tokiyasu1, Takeo Watanabe2(1ELPH, Tohoku University, 2LASTI, University of Hyogo, 3RCNP, Osaka University,
4
Aichi Synchrotron Radiation Center)
Reduction of Graphene Oxide by Combination of Atomic Hydrogen Annealing and Soft X-Ray
Irradiation…………………………………………………………………………………………………
Akira Heya1, Akinori Fujibuchi1, Masahiro Hirata1, Kazuhiro Kanda2, and Koji Sumitomo1(1University of Hyogo, 2LASTI, University of Hyogo)
PES and XAS Study of the Effect of Atomic Hydrogen Annealing Treatment for Conductive Thin
Film Sb-SnO2………………………………………………………………………………………………
Takeshi Fukuda1, Akira Heya1, Takanori Yamamoto1, Ryuki Tsuji1, Yuichi Haruyama2,Masahito Niibe2, Satoru Suzuki2, and Seigo Ito1
(1Department of Materials and Synchrotron Radiation Engineering, Graduate School ofEngineering, University of Hyogo, 2LASTI, University of Hyogo)

37

39

41

Resonant Photoemission Spectroscopy Study on the 5d Level of Ir Nanoparticles……………………. 43
Takahiro Maruyama1,2 and Yuichi Haruyama3,4(1Department of Applied Chemistry, Faculty of Science and Technology, Meijo University,
2
Nanomaterial Research Center, Meijo University, 3Department of Materials and Synchrotron
Radiation Engineering, Graduate School of Engineering, University of Hyogo, 4Laboratory of
Advanced Science and Technology for Industry, University of Hyogo)
Effect of Atomic Hydrogen Exposure on Hydrogenated Amorphous Carbon Thin Films…………… 45
Y. Haruyama1, D. Morimoto1, A. Heya2, K. Sumitomo2, S. Ito2, K. Yokota3,
and M. Tagawa3(1Laboratory of Advanced Science and Technology for Industry, University of Hyogo,
2
Graduate School of Engineering, University of Hyogo, 3Graduate School of Engineering,
Kobe University)
Fundamental Study of EUV Mask on EUV Lithography at NewSUBARU Synchrotron Light
Facility……………………………………………………………………………….……………………..
Takeo Watanabe, Tetsuo Harada, Shinji Yamakawa(Center for EUVL, LASTI, University of Hyogo)

48

Hydrogen Cleaning Evaluation of Mo/Si Multilayer Using an EUV Irradiation Tool
at NewSUBARU………………………..…………………………………………….……………………
Tetsuo Harada, Shinji Yamakawa, Takeo Watanabe(Center for EUVL, LASTI, Univ. of Hyogo)

54ⅴ

X-ray Absorption Spectroscopy of Liquids and Gases using a Simple Liquid Cell…………………
Tomoki Eguchi, Koji Takahara, Satoru Suzuki (LASTI, University of Hyogo)

55

In-situ XANES Measurements of the Heated Sugar for Clarifying the Melting Point
Fluctuation……….……………………..…………………………………………….……………………
Kae Hiramatsu and Yasuji Muramatsu(Graduate School of Engineering, University of Hyogo)

58

In-situ XANES Measurements of Eggs during Heating………………………………………………… 61
Ikuya Shimogaki and Yasuji Muramatsu(Graduate School of Engineering, University of Hyogo)
C K-XANES of Long-Chain Aliphatic Carbons Analyzed
by the First Principles Calculations………………………………………………………………………. 63
Toshiyuki Tanaka and Yasuji Muramatsu(Graduate School of Engineering, University of Hyogo)
Fabrication of Ni-W Microgears Using LIGA Process………………………………………………….
Kohzo Tamada1, Sho Amano1, Kana Okamoto2, Masaya Takeuchi1,3, Akinobu Yamaguchi1,
Yuichi Utsumi1, and Tohru Yamasaki2(1Laboratory of Advanced Science and Technology for Industry, University of Hyogo,
2
Research Center for Advanced Metallic Materials, University of Hyogo,3Graduate School ofEngineering, University of Hyogo)
Fabrication of Free-Form Shape Using LIGA Process with Independently Moving X-ray
Mask…………………………………………………………………………………………….………...
Taki Watanabe, Sho Amano, Akinobu Yamaguchi, and Yuichi Utsumi(LAST, University of Hyogo)

65

69

Deviation of Photoelectron Intensity from the Lambert-Beer’s Law in Near-Ambient Pressure
Hard X-Ray Photoelectron Spectroscopy……………………………………………………………… 73
Kento Takenaka1, Nanami Hosoe1, Koji Takahara2, Tomoaki Eguchi2, Hirosuke Sumida3,
Satoru Suzuki2(1Graduate School of Science, University of Hyogo, 2LASTI, University of Hyogo, 3Mazda Motor
Corp.)
Shape Observation of Micro- and Nanobubbles Formed In-situ
in a Scanning Electron Microscope……………………………………………………………..……….
Koji Takahara, Satoru Suzuki (LASTI, University of Hyogo)

List of Publications(1) Papers(2) International meetings(3) Academic degreesⅵ

77Part 1. Current Status of NewSUBARU
and Other Light Source

NewSUBARU Synchrotron Radiation Facility

Electron accelerators at NewSUBARU
Satoshi Hashimoto
LASTI, University of Hyogo

1. Introduction
NewSUBARU synchrotron light facility
has a 1.5 GeV electron storage ring, whichis the largest accelerator among
universities in Japan. For more than 20
years, not only basic research but also
student education and industrial use havebeen carried out using high quality soft
X-rays. Synchrotron radiation science andaccelerator science are one of the major
features of our university.
The new 1.0 GeV linac dedicated to the
NewSUBARU ring was constructed in 2020
with the help of SPring-8 accelerator staff.
FY2021 was the first year of operation of thestorage ring with the new injector, and the two
accelerators have been operating without serious
failure.

for generating ultra-short radiation pulse(SC3 project). The main parameters of thering are listed in Table I. The mainfeature of this ring is that the stored beamenergy is variable in the range of 0.5 to 1.5
GeV.
Table I Main parameters of the NewSUBARU
storage tingCircumference
118.73 m
Lattice
DBA + inv. Bends
Injection beam energy 0.5 – 1.0 GeV
Stored beam energy
0.5 – 1.5 GeV
Mac. Stored current
500 mA
Number of bends
12
Radius of curvature
3.217 mRF frequency
499.955 MHz
Harmonic number
198
Betatron tunes
6.29(H), 2.22 (V)Number of IDs
3
Radiation loss per turn 33.4 keV (@1.0GeV)
Energy acceptance±0.85%
Injection repetition rate 1 Hz

2. Overview of electron accelerators
The general layout of the ring is shownin Figure 1. The ring is consisted with 6
DBA cells with inverse bending magnets. There
are 6 straight sections between each cell, andthey are used for an injection septum, an
accelerating RF cavity and three undulators.
Of the two 15m long straight sections,
one is equipped with the 10.8m Long
Undulator (LU) and the other is used forbothgenerating
Laser
Compton
Scattering (LCS) gamma-rays and FEL

The general layout of the injector linac isshown in Figure 2. The peformace of the linac
is shown in Table II. The main characteristicsof the injector linac are as follows [1].
50 kV gun using gridded thermionic cathode
A composite RF gun with a gridted thermionicFig.1. General layout of the NewSUBARU storage ring. Electron beams are injected from the
newly-constructed 1.0 GeV linac dedicated to the ring.

1

Ⅰ

Ⅰ

Fig.2. General layout of the 1.0 GeV linac dedicated to the NewSUBARU ring.
cathode is used for generating stable and low
emittance beam [2]. Stable emission of a shortpulse beam is achieved without any special
adjustment.
238 MHz cavity
The electron gun and focusing magnetic lens
are mounted in a 238MHz cavity. The 50 keVbeam emitted by the electron gun is accelerated
by the cavity up to 500 keV to suppress
emittance growth due to space charge. The
cavity is driven by 42 kW solid state amplifier.
476 MHz cavity
The following 476 MHz cavity provides
velocity bunch compression. It decelerates
beams from 500 KeV to 270~360 keV providing
the energy chirp. Velocity bunch compression
reduces the bunch length from 200 ps (FWHM)
to several ps at S-band first cavity.

Fig.3. C-band accelerating structure of the 1.0
GeV linac.
3. Operation Status in FY2021
Our facility has two operation modes foruser-time; 1.0 GeV top-up mode and 1.5 GeV
current decay mode. The basic operation time is
9:00 - 21:00 of weekdays. Monday is used formachine R&D, Tuesday is for 1.5 GeV user
time, Wednesday and Thursday are for 1.0 GeV
top-up user time, Friday is for 1.0 GeV or 1.5
GeV user time.
Until FY2020, weekday night and weekend
could be used for additional machine study oruser time with the special mode, such as a single
bunch operation or an operation with arbitraryelectron energy. From 2021, the operation of theaccelerators has been limited to weekday
9:00-21:00, because the accelerator operation
business was outsourced to a private company.
Figure 4 shows the breakdown of machine
uptime in FY2021. The total machine timewas 1,919 hours, 188% of that of FY2020,
excluding the beam down time. The beam downtime includes not only the down due to machine
trouble, but also the off-beam period after the
beam is aborted due to beam instability orerroneous operation. The total down time in
FY2021 was about 57 hours, 3 % of the total
operation time. The tuning time and study time
have increased by about 200 hours in totalcompared to before the new injector.

S-band accelerating structure
One S-band accelerating structure is used toaccelerate the electron beam up to 50 MeV.
C-band accelerating structure
C-band accelerating structure shown in
Figure 3 is the same type as SACLA. It is wellproven and has a high acceleration gradient of
about 31MV/m [3]. The length of one
acceleration tube is 2m. One unit (8.6m,
250MeV) consists of four acceleration tubes andis driven by a C-band klystron. Four units areused for 1.0 GeV acceleration.
Table II Performance of the new injector linac.
Beam Energy
Bunch charge
Normalized emittance
Energy spread
Energy stability
Bunch length
Injection efficiency

Require1.0 GeV
100 pC<10 mm-mrad<±0.5%
5ps (FWHM)>90%

Measurement
1.0 GeV
100 pC<10 mm-mrad
0.1% (FWHM)
0.4% (STD)<1ps (FWHM)>90%

2

injector linac, but the main theme of ring R&D
was the SC3 project aimed at generating
ultrashort pulsed light. And another topic was
the preparation for resuming gamma-ray use at
beamline BL01.
5-1. Tuning of the injector linac
With one year of operation experience, wehave become proficient in operating the linac
and have endeavored to improve the beam andoperation performance. For example,n Stable operation of the injector for along period of time.
n Increased beam intensity from linac(0.9nC) and maintenance of highinjection efficiency to the ring (~90%).
n Increased stored current in the ting.
From 300 to 350 mA at 1.0 GeV top-up.
From 350 to 400 mA at 1.5 GeV decay.
n Low energy top-up operation at 0.75
GeV. This is useful for gamma-ray
generation and FEL.

Fig. 4. Operation time of NewSUBARU in
FY2021.
4. Machine Trouble
The beam down time in FY2021 was 57
hours. Typical troubles for both hardware andsoftware are as follows.

5-2. SC3 project (mono-cycle FEL)
Under the collaboration with RIKEN
SPring-8 center, University of Hyogo Graduate
School of Material Science and LASTI, we are
running the SC3 (Slippage-Controlled Coherent
radiation by Chirped micro-bunching) project,
where the generation of the extremely shortradiation pulse corresponding to only a few
wavelengths will be experimentally proved at
NewSUBARU
using
arbitrary
taperedundulators [4], a magnetic chicane and a chirped
seed laser. Main parameters of modulator,
radiator and chicane are shown in Table III.
In FY2021, we succeeded in forming
micro-bunch in a single electron bunch andobserving coherent light. Details will bereported in the near future.

4-1. Corrosion of high voltage electrodes of
sputter ion pump
The high voltage electrode of a sputter ion
pump was corroded. The cause is suspected to
be radiation and water adhering to the electrode.
All pumps will be visually checked this summer.
4-2. Failure of the real-time betatron tune
correction system
In normal operation, horizontal and verticalbetatron tunes are constantly measured andcorrected in real-time if they deviate from
optimal values. When evaluating the tune values
in real-time from a noisy waveform, ameasurement error caused the tune value to shift
and the beam to be lost. To solve this problem,
we are developing a waveform analysis
technique that applies machine learning.
4-3. Vacuum deterioration and RF reflection of
C-band klystrons
Among the four klystrons, in order to avoid
stop due to RF reflection, CB1 and CB3 areoperating at lower power than others.
4-4. Failure of the pulsed power supply for theelectron gun
The 50kV power supply failed several times
due to insufficient insulation on one of the six
high voltage boards. Repairs by the
manufacturer solved the problem.

Fig. 5. Insertion device for generating
mono-cycle FEL light pulse. Modulator andradiator with high K parameter and a magnetic
chicane between them.

5. Machine StudyIn FY2021, we spent a lot of time tuning the

3

Ⅰ

Ⅰ

Table III Main parameters of SC3 insertion
device.
[Modulator/Radiator]
magnetpermanent
wavelength
15 cm
Number of periods
24
Total length
7.2 m
Max. field
0.7 T
Max. K parameter
10Gap
280~50 mm(Gap can be longitudinally tapered)[Chicane]
MagnetElectromagnet
Number of coils
Main x1, Sub x2
Total length
600 mmMax. field
0.7 T

Fig. 8. Typical gamma-ray spectrum measured
at BL01.
5-4. Another studies
We conducted several other studies.
Examples include developing a beam instability
monitor in collaboration with KEK, operating
the ring at the new operating point, measuring
lattice functions and circulating beam
parameters, optimizing pulsed magnets forinjection, and readjusting the beam monitor.

5-3. LCS gamma-ray
BL01, a beamline for light source R&D, hasbeen built and upgraded by Prof. Miyamoto andhas been used in various studies using LCS
gamma rays [5-10]. As shown in fig. 6 and 7,
visible or infrared incident laser photons arescattered by high-energy electrons and bounce
off as high-energy photons in the γ-ray region.
The beamline was suspended in FY2020. In
FY2021, successors learned beamline operationand gamma-ray measurement techniques and thebeamline resumed use by outside users in
February 2022. Figure 8 shows a typical
spectrum of LCS gamma photons using a laser
with a wavelength of 1064 nm and an electron
beam of 1.0 GeV. We will continue to promote
the sophistication and use of gamma-ray lightsources.

SummaryIn FY2021 the operation of the 1.0 GeV
injector linac and the storage ring of
NewSUBARU was generally smooth. We
have gained a lot of experience in operating
new injectors. The stable supply ofhigh-quality electron beams from theinjector has improved the performance ofthe storage ring.
Currently, it is difficult to securesufficient operating days in FY2022 due tosoaring electricity prices. However, we willcontinue to advance the sophistication ofaccelerators, develop new light sources andprovide industrial support by providing a stablesupply of high-quality synchrotron radiation.
Acknowledgements
We would like to express our sincere gratitude to
the accelerator staff at RIKEN SPring-8 center,
JASRI and SES for their great cooperation in theoperation of the injector linac. We would also liketo thank to Dr. Y. Minagawa, Mr. K. Kajimoto, Mr. H.
Hirayama, Mr. S. Nakata of SES for their machine
operation. And we greatly thanks to Mr. T. Ushizawa
and Dr. T. Sakurai of JASRI for their efforts for stable
operation of accelerators.

Fig. 6. General scheme of Laser Compton
Scattering (LCS) gamma-ray generation at
BL01.

References[1]"Construction of a Compact Electron Injector
Using A Gridded Rf Thermionic Gun And A
C-Band Accelerator", T. Inagaki†, T. Fukui, T.
Hara, T. Hiraiwa, H. Maesaka, H. Tanaka, T.
Asaka, H. Dewa, N. Hosoda, E. Iwai, C. Kondo,

Fig. 7. Typical general scheme of LCS
gamma-ray generation at BL01.

4

Ⅰ

T. Magome, T. Ohshima, T. Sakurai, K.
Yanagida, S. Inoue, K. Kajimoto, Y. Minagawa,S. Nakata, T. Seno, H. Sumitomo, R. Takesako,
S. Tanaka, R. Yamamoto, M. Yoshioka, S.
Hashimoto, IPAC2021, WEPAB039 (2021)[2] T. Asaka, et. al., Phys. Rev. Accel. Beams 23,
063401 (2020)[3] T. Inagaki, et. al., PRST-AB 17, 080702(2014)[4]“Development of an undulator with a variablemagnetic field profile”, T. Tanaka, Y. Kida, R.
Kinjo, T. Togashi, H. Tomizawa, S. Hashimoto,
S. Miyamoto, S. Okabe, Y. Tanaka, Journal ofsynchrotron radiation 28, ｐ.404-409（2020）[5]“High-energy photon beam production withlaser-Compton backscattering”, K. Aoki et al.,Nuclear Instruments and Methods in Physics
Research A 516 (2004) 228–236[6] “Laser Compton back-scattering gamma-ray
beamline on NewSUBARU”, Shuji Miyamoto
et al., Radiation Measurements 41 (2007) S179–
S185[7] “Measurements for the energy and flux oflaser Compton scattering g-ray photons
generated in an electron storage ring:
NewSUBARU”, Ken Horikawa et al., Nuclear
Instruments and Methods in Physics Research A
618 (2010) 209–215[8] “Half-life of 184Re populated by the (γ, n)reaction from laser Compton scattering γ rays at
the electron storage ring NewSUBARU”, T.
Hayakawa et al., PHYSICAL REVIEW C 74,
065802 (2006)[9]“Experimental Study of Photonuclear
Reactions of Light Nuclei with NewSUBARU
γ-ray Beam”, Tatsushi Shima et al., Proc of
Science-NIC X. 148 (2008)[10] “New Results on Photodisintegration of 4He”,
Tatsushi Shima et al., Proc of Science-CD09, 107(2009)5

Ⅰ
NewSUBARU Beamlines
Koji Nakanishi
LASTI, University of Hyogo
The arrangement of the beamlines in the
NewSUBARU synchrotron radiation (SR) facility isshown in Fig.1. Total nine beamlines are operating in
the NewSUBARU SR facility.
Four beamlines of BL01, 03, 06 and 11 wereconstructed until 1999. Three beamlines of BL07, 09
and 10 were started the operation from 2000.
BL02 beamline was constructed for the usage of
LIGA in 2003.
BL03B beamline branched from the BL03
beamline propose for the usage of the EUVL (extreme
ultraviolet lithography) microscope for the EUVL
finished mask inspection.

BL05 was built to perform industrial analysis bysoft X-ray XAFS and PES. A major upgrade wasstarted in 2020 for more effective use. A part of BL05
was relocated to BL06, and its performance was
upgraded.
A new photoemission electron microscope (PEEM)
has been installed on BL09A.
BL09B beamline branched from BL09 beamline
for the usage of the EUV interference lithography toevaluate. And BL09C beamline branched from
BL09B beamline for the usage of the thickness
measurement of the carbon contamination originatedto the resist outgassing during the EUV exposure.

Fig. 1 Beamline arrangement in NewSUBARU.

6Ⅰ
I. BL01
BL01 is a beamline for research and developing
new light sources. This beamline is one of two longstraight section on NewSUBARU. Optical klystron
was installed at this straight section. Upstream side ofthis beamline (BL01B) is intended to be used forvisible and infrared light generated from free electron
laser (FEL) or synchrotron radiation (SR).
Downstream side of this beamline (BL01A) is used

for laser Compton scattering gamma-rays source.
Gamma-ray beamline hutch just outside of the storage
ring tunnel was constructed in 2004 for gamma-ray
irradiation experiments. Specification of this gammaray sources are listed in Table 1. New gamma-ray
irradiation hutch "GACKO" was installed at BL01A.
Table 2 shows the specification of “GACKO”.

Table 1. Specification of BL01 gamma beam
CO2 laser
10.52 µm
5W

Gamma energy : 1.7 - 4 MeV
Gamma flux*: 9 ×106 γ/s: 6×105 γ/s (1.5-1.7 MeV)
(with 3mmφ collimator)

Nd laser1.064 µm / 0.532 µm
5WGamma energy : 17 - 40 MeV
Gamma flux*: 7.5 ×106 γ/s: 3 ×105 γ/s (15-17 MeV)
(with 3 mmφ collimator)*Electron beam energy : 1-1.5 GeV*Electron beam current : 250 mA*Gamma-ray beam divergence : 0.5 mrad

Table 2. Specification of “GACKO”
Maximum gamma-ray power
0.33 mW
Maximum gamma-ray energy
1.7 MeV - 73 MeV
CO2 laser, wavelength/power
10.59 µm / 10W
1-1.7 MeV gamma-ray flux
2×107 γ/sec@10W/300mA
1.064 µm/ 30W,
Nd:YVO4 laser, wavelength/power
0.532 µm/ 20W
10-17 MeV gamma-ray flux
5×107 γ/sec@30W/300mA

II. BL02
The LIGA (abbreviated name of Lithogaphic,
Galvanoformung and Abformung) process which
consists from deep X-ray lithography, electroforming,and molding process is one of the promising
candidates for such 3D micofabrication. More thanhundreds aspect ratio for microstructure can beattained by the usage of the higher energy X-rays (415 keV) from synchrotron radiation (SR) with deeper
penetration depth to the photosensitive resist. In thissystem we have succeeded to enlarge the exposurearea up to A4 size and the fabrication dimension from
submicron to millimeter by varying the energy of the

X-ray source in accordance with the size of desired
microparts. Microstructure with high aspect ratio over
several hundred will be achieved using the X-rays
over 10 keV since high energy X-ray has deep
penetration depth to the photo-sensitive resist
materials. Whereas, in the case of lithography for low
energy X-rays from 1 keV to 2 keV, submicron
structures with high aspect ratio will be achieved
using the X-rays mask with precise line-width andthinner absorber, since low energy X-rays has low
penetration depth. Based on this principle, thebeamline for x-ray exposure have constructed with7

Ⅰ
microfabrication process using multi step exposure atvarious configuration between X-ray mask andsubstrates. The relative positions between X-ray mask
and substrates, tilt and rotation angle to the SR
incident direction can be moved simultaneously
during SR exposure using 5 axis stages. The
movement of each axis is controlled by the PC in
terms of the scanning speeds, scanning length, andrepetition number. In order to decrease the heat loadof sample substrate suffered during SR irradiation
helium introduction and substrate cooling mechanism
were also equipped. Specification of spectrometer islisted in Table 3.

continuous selectivity of X-rays from 100 eV to 15
keV by using the X-ray mirrors (plane and cylindricalmirror) and Be film filters. The horizontal angle of theoutgoing SR could be obtained up to 12.5 mrad, whichcorresponds to the horizontal size of 220 mm (A4horizontal size) at the exposure position. The second
characteristic performance of the beamline is the highefficiency differential pumping system. This wasnecessary for maintain the vacuum difference
between the storage ring (<10-9 Pa) and the endstation (<10-9 Pa) at which gasses for substratecooling will be introduced in the exposure apparatus.
The flexibility for the shapes and functions of
microstructure will be enlarged by achieving 3D

Table 3. Specification of the LIGA exposure system
OpticsPlane and cylindrical mirror, Be filters
Exposure energy
0.1 - 2 keV, and 4 – 15 keV
Exposure method
Proximity and multi-step exposure
Wafer size
A4 or 8 inch
Exposure area
230 mm(H) ×300 mm(V)
Exposure environment< 1 atm (He-gas)

III. BL03
reflectometer was UV – VUV reflectometer. At EUV
lithography, out-of-band radiation (100 – 300 nm) of
EUV source degrades image quality. Thus, optics andresist property of out-of-band region was essential toevaluate, for example EUV mask reflectivity, andEUV resist sensitivity. The monochromator
specification was shown in Table 4. The EUV
microscope (3) has Schwarzschild optics, which were
fabricated with collaboration of Dr. Toyoda (Tohoku
Univ.). The spatial resolution was quite high of lessthan 28 nm, which was equal to 7 nm at wafer printing
size.

BL03 is a beamline for the developing the next
generation lithographic technology so called extreme
ultraviolet (EUV) lithography. The extreme
ultraviolet lithography (EUVL) is a promise
technology for fabricating a fine pattern less than 7nm node. There are (1) a EUV resist-sensitivity
evaluation tools, (2) a VUV reflectometer, and (3) an
EUV microscope with Schwarzschild optics. At (1)tool, EUV resist is exposed with SR light of EUV
monochromatized by 7 Mo/Si multilayer mirrors. The
exposure spectrum of this tool was same as the ASML
exposure tools. The monochromator of (2)Table 4. VUV monochromator specification
Mount type
Collimate plane grating monochromator
Grating
Plane Grating (1,000 lines/mm)
Energy range
4 - 120 eV (UV ～ VUV)Resolving power (E/ΔE)
～1000

8

Ⅰ
IV. BL05
BL05 was constructed in response to a demand in
the industry, which is enhancement of the analysis
ability in the soft x-ray region with the developmentof nanotechnology. BL05 consists of two branch lines
for use in the wide range from 50 eV to 4000 eV.
BL05A and BL05B are designed to cover the energy
range of 1000-4000 eV and 50-1000 eV, respectively.
The incident beam from the bending magnet isprovided for two branch lines through different
windows of a mask. Therefore, these two branch lines
can be employed simultaneously.
However, both beamlines had many problems anddid not perform well enough for industrial andadvanced analysis. In order to solve these problems, adrastic upgrade was started in 2020.

New BL05A
The constant-deviation monochromator consistingof a demagnifying spherical mirror and a varied-linespacing plane grating (VLSPG), which can provide
high resolution, simple wavelength scanning with
fixed slits, was mounted on BL05A. The opticalsystem consists of a first mirror (M0), a second mirror(M1), an entrance slit (S1), a pre-mirror (M2), andthree kinds of plane grating (G), an exit slit (S2) anda focusing mirror (M3). The including angle of themonochromator is 175°. Two measurement chambers
for XAFS and PES are prepared at the end station of
Monochromator
Grating
Energy range
Resolution

BL05A. XAFS spectra in the total electron yield modeand partial fluorescence yield using a silicon drift
detector can be measured in a high vacuum chamber.
In addition, photoelectron spectra can be measured
using spherical electron analyzer (VG Sienta, R3000)
in an ultrahigh-vacuum chamber. The chambers canbe replaced by each other. Table 6 shows the
specification of the monochromator.
BL05B changed its name to BL05A due to therelocation to BL06, which will be described later.

Table 5. Monochromator specification
Varied-line-spacing plane grating monochromator
100 lines/mm, 300 lines /mm, 800 lines /mm
50 - 1000 eV
E/⊿E=3000

V. BL06
BL06 had been constructed for irradiation
experiments such as photochemical reaction, SRCVD, photo-etching, surface modification. BL06 forirradiation experiments was closed due to plans tobuild a new beamline for XAFS measurement. An Xray mirror, Golovchenko-type double crystal
monochromator, measurement systems and manyother beamline components were relocated from old
BL05A. New BL06 plans to have two XAFS
beamlines, tender X-rays and hard X-rays, in the

future. First, the hard X-ray beamline was prepared. A
Rh-coated collimating mirror with incident/reflected
angle of 0.3 degrees was selected for this beamline,
which allows the photon energy of not only 5-12 keV
but 1-3 keV. Since the use of hard X-rays required thedevelopment of a new dedicated measurement hatch,
we first installed the tender X-ray XAFS
measurement system developed for the former
BL05A. Table 6 shows the specification of
monochromator.

Table 5. Monochromator specification
Monochromator
Double crystal monochromator
Beryl(10-10), KTP(011), quartz(10-10), InSb(111),
Monochromator crystals
Ge(111), Si(111), Si(220), Ge(220), Si(331), Ge(331)Energy range
1 - 3 keV, and 5-12 keV(in future)9Ⅰ
VI. BL07
use only first mirror (switching mirror), M0, forfocusing. The MLM monochromator is designed tocover an energy range of up to about 800 eV by
combination of three kinds of mirror pairs with 4
kinds of filter. The flux deliver by this design isestimated to be between a maximum of 1017 photons/s
at 95 eV and a minimum 2×1014 photons/s at 300 eV
for a 500 mA ring current. Table 7 shows the summaryof BL07A. In addition, X-ray fluorescence (XRF)
apparatus using spherical varied line spacing grating
was mounted at the downstream of irradiationchamber. The poly capillary was used to enhancebeam-condensing efficiency. Measurement energy
range was from 30 eV to 450 eV. This XRF apparatus
was expected to utilize the chemical analysis on thelight metals, Li and Be, and light elements, B, C andN.
Two novel vacuum chambers were installed in2019 for the measurement of inverse Compton
scattering of soft X-rays. One large chamber with asize of W1120×D820×H610 mm3 was set up 16.7 m
downstream of the undulator center. A multi-layer
mirror was placed on high precision auto-stages inside
this chamber with cooling water circulation. The otherchamber was installed 2.6 m upstream of the large
mirror chamber, in order to monitor radiated andreflected X-rays.

This beamline was designed for the developmentof new materials by SR technology. This beamline
consists of two branch lines, which are provided withan incident beam from a 3-m-long undulator byswitching the first mirror. One of them is a highphoton-flux beamline with a multilayered-mirror
monochromator for the study of SR-process (BL07A)
and another is a high-resolution beamline with avaried line spacing grating monochromator for theevaluation of nano-structure characteristics by SRspectroscopy (BL07B). The useful range of emitted
photons from 50 to 800 eV is covered at bothbeamlines. The light source of BL07 is a 3-m lengthplanar undulator, which consists of 29 sets ofpermanent magnets, a period length of which is 76
mm. The incident beam from the undulator isprovided for two branch lines by translationalswitching of first mirror.
1) BL07A
The multilayered-mirror (MLM) monochromator,
which has high reflectivity in the soft X-ray region,
was installed at the BL07A. It consists of a switching
mirror chamber, a slit chamber, a MLM
monochromator, a filter chamber and a reaction
chamber. To obtain a large photon flux, we decided toEnergy range
(eV)
50-60
60-95
90-140140-194
190-400
400-560
550-800

Material

Table 7. Summary of BL07A.
Multilayer mirror
Thickness
NumberSpacing∆E/E
Ratio
of layers

Mo/Si

20 nm

0.8

20

6.2 %

Mo/B4C

11 nm

0.5

25

3.3 %

Ni/C

5 nm

0.5

60

2.5 %

10

FilterMaterial

Thickness

Al

100 nm

None

-

Ag

100 nmCr
Ni

500 nm
500 nmⅠ2) BL07B

mirrors (M2 and M3). The monochromator isdesigned to cover the energy range 50-800 eV withthree gratings, of which including angle are 168°. The
VLSPG has been well known to obtain highresolution in extreme ultraviolet region bydiminishing various kinds of aberration. The total
resolving power about 3000 can be realized in thewhole energy region. Table 8 shows the specificationof the monochromator.

The
constant-deviation
monochromatorconsisting of a demagnifying spherical mirror andvaried line spacing plane grating (VLSPG), which canprovide to high resolution, simple wavelength
scanning with fixed slits, was mounted on BL07B.
The optical system consists of a first mirror (M0), an
entrance slit (S1), a pre-mirror (M1), and three kindsof plane grating (G), an exit slit (S2) and two focusing

Table 8. Monochromator specification
Mount type
Hettrick-Underwood type
Grating G1, G2, G3
Plane VLS (600, 1200, 2400 l/mm)
Energy range
50-150 eV, 150 – 300 eV, 300-800 eVResolving power (E/ΔE)～3000

VII. BL09
A purpose of this beamline is studies on a soft x-ray
interferometry or a holographic exposure
experiment with making use of highly brilliant andcoherent photon beams radiated from 11 m longundulator in NewSUBARU.
BL09 consists of M0 mirror, M1 mirror, G gratingand M2 mirror. M0 mirror is used for horizontal
deflection and beam convergence, M1 is used forvertical beam convergence at the exit slit, and M2 isused for vertical deflection and beam convergence. A
monochromator is constructed by M1 and a planegrating. The maximum acceptance of the undulator
beam is 0.64 mrad in horizontal and 0.27 mrad invertical. The acceptance can be restricted by 4-jaw
slits equipped at upstream of the M0 mirror.

emission spectrometer (XES) was introduced at theend-station of the BL-09A. The energy range andresolving power of the XES system was designed to
be about 50-600 eV and 1500, respectively. In 2021,
a photoemission electron microscope system has been
installed on BL09A.
2) BL09B
BL09B beamline branched from BL09 beamline
for the usage of the EUV interference lithography forthe evaluation of the exposure characteristics of EUV
resist. Coherence length of 1 mm at the resist exposure
position was achieved using BL09B beamline. And
BL09C beamline branched from BL09B beamline forthe usage of the thickness measurement of the carbon
contamination originated to the resist outgassing
during the EUV exposure. Table 9 shows the
specification of the monochromator.

1) BL09A
BL09A beamline is used for material analysis: Xray absorption spectroscopy (XAS) and X-ray
photoelectron spectroscopy (XPS). In 2013, X-ray

Table 9. Monochromator specification
Mount typeMonk-Gillieson type
Grating
Plane VLS (300, 900, 1200 l/mm)
Energy range
50 – 750 eVResolving power (E/ΔE)
～3000

11

Ⅰ
VIII. BL10In addition, there are linear motions to translate thesample in two orthogonal directions (x, y). All motors
are controlled by computer. The reflectivity result
obtained at BL10 has a good agreement with that at
LBNL. Table 10 shows the specification the
monochromator.
The micro-CSM tool was adapted at the mostdownstream of the BL10 beamline for the EUV mask
defect inspection with coherent-diffraction-imaging
method. This too is very effective for the inspection of
the actinic patterned mask with phase imaging.
A large reflectometer was installed in a branch line
for large EUV optical component including EUV
collector mirrors. The reflectometer has a sample stage
with y, z, θ, φ, and Tilt axis, which can hold large
optical elements with a maximum weight of 50 kg, a
diameter of up to 800 mm, and a thickness of 250 mm.
The entire sample surface is able to be measured.

BL10 is for EUV reflectometry and soft X-ray
analysis. M0 mirror is used for horizontal deflection
and beam convergence, M1 is used for vertical beam
convergence at the exit slit, and M2 is used for verticaldeflection and beam convergence. A monochromatoris constructed by M1 and a plane grating. At the
beginning, the multilayer reflectivity measurement
was carried out at this beamline. The characteristics ofthis beamline and the result of the Mo/Si multilayer
measurement are carried out for the development of
the EUV- mask technology.
BL10 utilizes a monochromator of the varied-linespacing plane grating (VLS-PGM). The line density ofthe monochromator in central region of the gratings
were 600, 1800 and 2,400 lines/mm. The reflectometerhas a two-axis vacuum goniometer. One axis carries
the sample, which may be a mirror surface at the centerof the reflectometer vacuum chamber (θ-motion). The
other (φ-motion) carries the detector on a rotating arm.

Table 10. Monochromator specification
Mount typeMonk-Gillieson type
Grating
Plane VLS (600, 1800, 2400 l/mm)
Energy range
50 – 1,000 eVResolving power (E/ΔE)～1000

IX. BL11
submicron-scale structure and microstructure withhigh aspect ratio by selectivity of X-rays using
movable mirror system. That is, LIGA process in
NewSUBARU can provide the best 3D
microfabrication because the BL11 and BL2 arecomplementary. The beamline BL11 is consisting ofan absorber chamber, a first-mirror chamber (M1), a
4-way slit chamber, a Be and polyimide windowchamber, and an exposure chamber. The horizontal
angle of the outgoing SR could be obtained up to 17.8
mrad, providing a beam spot size on the exposure
stage ≥ 80 × 10 mm2. The micron-scale structure withhigh aspect ratio will be achieved using the toroidal
typed mirror M1 which can produce a parallel
collimated beam of X-rays. In addition, thehomogeneity of the beam is excellently controlled bya novel adding system.
Using the precision stage in the exposure
chamber, the flexibility for the shaped and functionsof microstructure will be enlarged by achieving 3D
microfabrication process using multi step exposure at

A beam line BL11 is constructed for exposure
Hard X-ray Lithography (DXL) in the LIGA
(Germanacronymfor
Lithographite
Galvanoformung and Abformung) process. LIGA
process, that utilizes a useful industrial application of
SR, is one of the promising technologies forfabrication of extremely tall three-dimensional (3D)
microstructures with a large aspect ratio. This
process was invented at the Institut Fur
Mikrostrukturtechnik (IMT) of the Karlstuhe
Nuclear Center (KfK) in 1980. Microstructures withheight of over a few hundred µm have been widely
applied to various fields such as micro-mechanics,
micro-optics, sensor and actuator technology,
chemical, medical and biological engineering, and soon. This beam line was designed by the criteria;
photon energy ranges from 2 keV to 8 keV, and adensity of total irradiated photons ≥ 1011 photons/cm2.
The BL11 can provide the most suitable photon
energy for microfabrication in X-ray lithography,
while the BL2 is equipped for fabricating fine pattern

12

Ⅰ
various configuration between x-ray mask andsubstrates. The exposure area of 200 mm × 200 mm
is brought to fruition. In order to decrease the heatload of sample substrate suffered during SR

irradiation, helium introduction and substrate coolingsystem were also equipped. The specification of the
LIGA exposure system is listed in Table 11.

Table 11. Specification of the LIGA exposure system
Exposure method
Proximity exposure
Wafer size
8 inchExposure area
200 mm(H)×200 mm(V)
Exposure environment< 1atm (He-gas)

Establishment of Research Center for Advanced Synchrotron Radiation Analysis
In order to respond to diverse analysis needs fromindustries, it is necessary to advance technologicaldevelopment for analyzing beamlines (BLs) of
NewSUBARU SR facility to advance integrated andstrategic development of analyzing technology. For
this reason, the Research Center for Advanced SR
Analysis was launched in August 2016. As anorganization crossing in university courses, this centeris consulted and administered by all members of the
LASTI related to analysis, and in collaboration with
the SR Nanotechnology Center of Hyogo Prefecture,a wide range of energy from hard X-rays to soft Xrays. We aim to respond to various analysis needs ofthe area on a one-stop basis.

Acknowledgement
We would like to thank all the staff who work at
NewSUBARU synchrotron radiation research facility
for their help to describe the update details of thebeamlines.

13

Part 2. Research Activities

EUVL R&D Beamlines

Anomaly Detection of Electron Beam by Machine Learning
H. Fujii1, S. Matsuo2, and S. Hashimoto1
1
LASTI, 2University of Hyogo
Abstract

In NewSUBARU synchrotron light facility, various researches and developments have been
carried out to realize an automatic anomaly detection system. With this system, it is possible todetect anomalies about synchrotron radiation monitor images, beam current values, and beam
lifetimes. However, this anomaly detection system has a problem that correct judgment is difficult
for undefined anomalies because this system is based on thresholds that are predefined by humans.
Therefore, we are currently conducting research to construct a more accurate and flexible anomaly
detection system by using machine learning techniques.

1. Introduction
When electron beam is injected and stored in thestorage ring, some anomalies such as a decrease in
injection efficiency, stored beam current, andlifetime, and fluctuations in the size of thesynchrotron light source may occur. Figure 1 shows
the anomalies in the beam current. In top-up
operation mode, since the beam current is added atintervals of a second, it is normal that a constantvalue is maintained as shown in Fig. 1 (a). However,in an anomaly situation like (b), it can be seen thatthe current value is greatly reduced. On the other
hand, in decay operation mode, it is normal that thecurrent value is gradually decay as shown in Fig. 1(c). If there is an anomaly, the slope of the current
value is steep as shown in Fig. 1 (d). Such anomalies
may be caused by a misconfiguration andperformance deterioration of component equipment
and changes in temperature of air and cooling water.
At present, in order to deal with these anomalies,
operators manually access a database which store thesetting parameters and measurement values of eachdevices, extract relevant data, identify the cause, andtake a corrective action. However, this process istime-consuming and needs resident operatorsfamiliar with beam physics. Therefore, wedeveloped an automatic anomaly detection system.
However, this system is based on manually defined
thresholds given by past trouble reports. Therefore,
this system cannot make a correct judgment when an
undefined anomaly occurs, and it is necessary to add
a new threshold in order to deal with it.
In order to solve these problems, we aredeveloping a more accurate and flexible anomaly
detection system by using machine learningtechniques.
Fig. 1. Examples of stored electron beam current
in storage ring. (a) and (b) are normal andanomaly current data, respectively, for topup operation mode. (c) and (d) are fordecay operation mode.

2. Experiment
In this research, autoencoder, which is a kind ofneural network, is used as an anomaly detection
system. Autoencoder consists of at least three layers:

17Ⅱinput layer, intermediate (hidden) layer, and output

Ⅱ

Fig. 3. Results of autoencoders. (a) is for top-up
mode and (b) is for decay mode. Blue andgreen lines are input and output,
respectively. Red line means meansquared error.
Fig. 2. Schematic illustration of Autoencoder.
This network is supposed to havelearned the shape of the fig. 3.
3. Results and Discussions
The learning of the autoencoder was performed
separately for top-up and decay operations. For
training, normal current data divided into a minute(60 points) were used. Figure 3 shows the input andoutput results of the autoencoder. It can be seen thatthe learning of the normal data is not sufficient andthe input cannot be completely reproduced. To
further improve the accuracy, it is necessary toincrease the number of hidden layers and optimize
the hyperparameters of the autoencoder. However,since the reconstruction error for normal data issmaller enough than that for anomaly data, it ispossible to sufficiently detect anomaly.
In this study, the stored electron beam current
value was analyzed separately for two operation
modes. However, if the expression capability of theautoencoder is increased, it will be possible to detect
anomalies in both top-up and decay modes
simultaneously with a single autoencoder. In the
future, we also plan to build a highly accurate
anomaly detection system for other data such as
beam lifetime, degree of vacuum, electromagnet
excitation current.

layer. The network is trained to output the data as it
is input. Here, it is important to reduce (compress)
the number of features (nodes) in the intermediate
layer. This forces the network to acquire acompressed representation of the input data as
shown in the figure 2. In the figure, if we give theimage of figure of three to the autoencoder that haslearned various images of three, it should output inits original form if the learning is sufficient. Now, if
we give this autoencoder an image of two, it will failto reconstruct the image of two because the network
has not learned any compressed representation for
the image of two. That is, autoencoder has theproperty that it can successfully reconstruct expected(normal) input data, but cannot reconstructunexpected (anomaly) input data. Therefore, it
become possible to judge whether an input is normal
or anomaly just by evaluating the difference between
the input and output data without defining what is
anomaly. The difference between is evaluatedquantitatively by mean squared error (MSE),
𝑁𝑁𝑁𝑁

1
𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 = �(𝑦𝑦𝑦𝑦𝑖𝑖𝑖𝑖 − 𝑡𝑡𝑡𝑡𝑖𝑖𝑖𝑖 )2 ,𝑁𝑁𝑁𝑁𝑖𝑖𝑖𝑖=1

where, 𝑦𝑦𝑦𝑦𝑖𝑖𝑖𝑖 and 𝑡𝑡𝑡𝑡𝑖𝑖𝑖𝑖 are output and input data,
respectively. 𝑁𝑁𝑁𝑁 means the number of sample data.
This MSE value is the only threshold for the
automatic anomaly detection system.

18

Fundamental Evaluation of Resist on EUV
Lithography at NewSUBARU SynchrotronLight Facility
Takeo Watanabe*, Tetsuo Harada, and Shinji Yamakawa
Center for EUVL, Laboratory of Advanced Science and Technology for Industry,
University of Hyogo, 3-1-2 Kouto, Kamigori-cho, Akou-gun, Hyogo 678-1205,
Japan*takeo@lasti.u-hyogo.ac.jp
Extreme ultraviolet lithography was started to use for the production of 7-nm nodelogic-semiconductor devices in 2019. And it was adapted to use for high volume
manufacturing (HVM) of 5-nm logic devices in 2020. EUVL is required to beextended to use in 1.5-nm-node-device fabrications. However, it still has manytechnical issues. Especially, for EUV resists, simultaneous achievement of highsensitivity and low line edge width are required. To solve the EUV resist issue, thefundamental work using synchrotron in soft X-ray region is necessary. The
fundamental evaluation study of EUV resist at NewSUBARU synchrotron lightfacility is described in this paper.
Keywords: EUVL, resist, sensitivity, line edge roughness, EUV, soft X-ray,resonant scattering, reflectivity measurement, out of band patterning, photoelectron emission microscopy

1. Introduction
Extreme ultraviolet lithography (EUVL) wasstarted to use for the production of 7-nm-nodelogic-semiconductor devices. In addition, EUVL
technology has finally begun to be used as highvolume-mass-production technology since 2020.
EUV technology is going to extend to use in the
fabrication of 1.5-nm node devices. EUVL still
has technical issues such as EUV resist
development, defect free mask fabrication
including metrology and pellicle, and EUV highpower and stable light source. Especially, it isrequired that EUV resist which has highresolution and sensitivity, low line widthroughness (LWR), and low outgassing [1]. In the
EUV resist technical issues, the simultaneousachievement of high resolution and sensitivity,and low LWR is very significant and not so easy.
Thus, more fundamental studies are still needed.
Even if the resist material itself has highresolution, as trying to replicate a resist patternwhich has narrower width, the pattern collapse
interferes the fine-pattern replication. In order toincrease the resolution, preventing from thepattern collapse is necessary. Thus, thefundamental study of the structure analysis ofresist films using synchrotron is necessary.

In order to increase the sensitivity, studying
the whole chemical reactions which occur by the
EUV irradiation is necessary. And thedevelopment of EUV resist material with highsensitivity based on this study is significant.
Since, the wavelength of EUV light and EUV
photon energy is 13.5 nm and 91.8 eV,
respectively, secondary electron ionization
reaction occurs by the high energy electron
region. To clarify the reaction by low energy
region, it is necessary to use the fundamental
evaluation using synchrotron radiation in soft Xray region.
In addition, to achieve the low LWR resist, thefundamental study of the origin of LWR isnecessary. In this study, it is also necessary to use
the fundamental evaluation using synchrotron
radiation in soft X-ray region as describe later.
As above reasons, the fundamental evaluation
studies of EUV resist at NewSUBARU
synchrotron light facility [2], University of
Hyogo, are described in this paper. Total nine
beamlines are operating, and three beamlines
which are BL03, BL09, and BL10 of
NewSUBARU. We have the EUV flood
exposure tool for the resist sensitivity evaluationby the actual EUV light spectrum, interference

19

Ⅱ

Ⅱ

lithographic exposure tool for the patterning 10
nm and below, outgassing and contamination
growth evaluation tools by ellipsometry, andchemical reaction analysis by the soft X-ray
spectroscopy (XAS). In addition, recently it isprepared additional tools for the fundamental
studies of EUV resists. This paper focuses that 1)
resist-film layer analysis by the resonant soft Xray reflectivity method in soft-X-ray energy
region, 2) stochastic origin analysis in EUV
resist by resonant soft X-ray scattering toachieve low LWR, 3) out of band systematic
analysis, and 4) preparation of the photo-electron
emission microscopy for the chemical content
spatial distribution analysis.

Table 1. Result of fitting
Layer
name
s

Thickness
(nm)

n

k

Roughness
(nm)

Top

7.4

0.99960.0004

0.22

Main
body

14.1

0.99960.0003

3.51

Botto
m

4.5

0.99990.0007

4.83

SiO2

0.8

0.99460.0018

0.1

Si
wafer

--

0.99510.0028--

3. Stochastic Origin Analysis in EUV Resist
by Resonant Soft X-ray Scattering
The low LWR is necessary to maintain theelectronic characteristics of semiconductor
device, such as logic and memory devices.
The origin of the LWR might be 1) spatial
distribution of functional material in resist
functional groups, photosensitizers (acidgenerators), additives such as amines, and so on,2) spatial distribution of free volume caused by
the solvent distribution in prebake process, 3)
EUV photon shot noise, 4) secondary electron
blur, 5) solvent effect in PEB process aciddiffusion, 6) spatial distribution of developer
penetration and development process yieldcaused by developer and rinse effects, and 7) out
of band (OoB) light effect.
In order to reduce LWR of the resist pattern,
the controls of the above stochastics are
significant. In the above list, in order to control
the chemical reaction fluctuation within thenanometer dimensions, the special distribution
control of the chemical contents is verysignificant. However, up to now themeasurementofthechemical-contents
distribution has not been carried out. Thus, themethod of resonant soft X-ray scattering(RSoXS) is used for the measurement. Thismethod is the hybrid method using soft X-ray
absorption spectroscopy [6, 7] and soft X-ray
scattering as shown in Fig. 1. The scatteringvector is defined by the following equation.

2. Layer Analysis by the Resonant Soft X-ray
Reflectivity Method in soft-X-ray Energy
RegionFor the layer analysis [3, 4] of the single layer
resist material which has a thickness of 20 – 50
nm, the resonant soft X-ray reflectivity (RSoXR)
method in soft-X-ray energy region is a powerful
method for the chemical layer analysis of theresist film [5]. This method is the hybrid method
using soft X-ray absorption spectroscopy [6, 7]
and soft X-ray reflectance measurement. By thesoft X-ray absorption spectroscopy, the incident
energy of the photon is selected for the soft Xray reflectance measurement to evaluate
refractive index of n and k values, and thicknessof a resist film coated on a wafer. The reflectivity
fringe spectrum can be fit by n and k values, andthickness of the layers.
The commercial chemical amplified (CA)resist was employed for the layer analysis. The
resist was spin-coated on a 4 inches silicon wafer
to have 26-nm thick. Then the layer analysis was
carried out. As a result, the fitting result is shownin Table.1. Even if the CA resist for a single layer
process, the thin resist film consists of threelayers. The bottom, main body, and top layers
have the thickness of 4.5 nm, 14.1 nm, and 7.4
nm, respectively. And these layers have thecomplex refractive index of k value of 0.0007,
0.0003, and 0.0004, respectively. The bottom
layer between the main body layer might be apattern collapse region.

𝑞𝑞𝑞𝑞 = |𝑞𝑞𝑞𝑞⃑| =

20

4𝜋𝜋𝜋𝜋
𝜃𝜃𝜃𝜃
sin
𝜆𝜆𝜆𝜆
2

(1)

By the soft X-ray absorption spectroscopy, theincident energy of the photon is selected for thesoft X-ray scattering to obtain the selectedchemical-bonding diffraction image. The

The scattering vector profiles of PMMA andCA resist are shown in Fig.s 2(a) and 2(b). The
𝜋𝜋𝜋𝜋* correspond to
Scattering vectors of 0.05 and 0.1
the structure size of 120 nm and 60 nm,
respectively. As the results, the spatial
distributions between the 𝜋𝜋𝜋𝜋 * bonding andacrylate group are very similar in PMMA.
However, these are quite different in CA resist.
Generally, since the LWR of PMMA is smaller
than that of CA resist, the results of the scatteringvector profiles are consistent to the LWR
tendency [11].
4. Out of Band Systematic Analysis
If the resist exposed by the light which
includes the out of band (OoB) light containing
the deep UV wavelength region, the OoB lights
affects to the LWR of the resist pattern. Thus,
reflectance measurement of the mask materials
such as Mo/Si multilayer, absorber, and blackborder (mask substrate surface). Figure 3 shows
the beamline setup of the exposure tool andreflectometer by the EUV and OoB lights at
BL03A beamline of NewSUBARU. The
monochromator setups to enable the EUV at the
wavelength of 10 - 80 nm and OoB light at the
wavelength of 100 – 200 nm are shown in Fig.s

Structure size(a)Fig. 1 Scattering vector 𝑞𝑞𝑞𝑞.

(b)Fig. 3 Beamline setup of the EUV and OoB light
exposure tool and reflectometer.

4(a). and 4(b), respectively. And LiF filter with athickness of 1 mm were used to cut the highorder lights which is shorter than the wavelengthof 100 nm. The reflectance measurement resultsof the mask materials such as Mo/Si multilayer,
absorber, and black border (mask substrate(a)Fig. 2 Scattering vector profiles of (a) PMMA and(b) CAR.

RSoXS system at BL-10 beamline of
NewSUBARU was used for this experiment [8,9]. This beamline provides monochromatizedenergy of the soft X-ray region from 80 to 1000eV [10].

(b)

Fig. 4 The monochromator optics for (a) EUV and (b)OoB wavelength regions.

21

Ⅱ

Ⅱ

surface) are shown in Fig. 5. The reflectancespectrum of the Mo/Si multilayer was measured
completely in the EUV region including highorder lights. In the OoB region, the reflectanceof Mo/Si multilayer, TaN absorber, and mask
substrate as a black border has approximately
30% in maximum. Even if the black border, it
has the reflectance of 30%, and the reflectance
reduction method should be required.

for the chemical analysis of the light atomic
elements such as carbon, nitrogen, oxygen, andfluorine etc. Thus, the PEEM in soft X-ray
region can observe the chemical imaging ofthese atomic elements. Since the penetration
depth of the soft X-ray is small enough toobserve the surface chemical imaging of theresist film, the cluster ion beam tool is employed
for the no damage-surface etching of the resist
film and enable the chemical imaging in 3D ofthe resist film.
ObservationchamberPEEM

EUV higher
order light

Loadlockchamber

Clusterion
beam
Samplepreparationchamber

Seismic
isolation
bench

Fig. 5 Reflectance spectra of Mo/Si multilayer,
TaN absorber on Mo/Si multilayer, and blackborder.

5. Preparation of Photo-Electron Emission
Microscopy for the Chemical Content Spatial
Distribution Analysis
As described in section 3 of RSoXS is one of
the methods to observe the chemical-content
distribution. However, since the scattering
method is used, the averaged distribution is
obtained. Instead of this method, we introduce
the photo-electron emission microscopy(PEEM) to observe the real chemical content
distribution not an averaged one of resist film.
The PEEM system is going to installed at theBL09A beamline of NewSUBARU. The 3D
design is shown in Fig. 6. The PEEM system
consists of load lock chamber to exchange asample, sample processing chamber adapted theion beam cluster and sample heating device, andthe sample observation chamber adapted the
PEEM device. In order to prevent from thevibration and to achieve high spatial resolution
in PEEM, the special mechanism is employed.
NewSUBARU is a middle size synchrotron
light facility and soft X-ray synchrotron
radiation is generated from the 1.0 GeV electron
beam storage ring. The soft X-ray absorption
spectroscopy in the soft X-ray region is suitable

Fig. 6 3D design of the PEEM system.

6．
．New Injector for NewSUBARU
Photograph NewSUBARU Synchrotron lightfacility which consists of new linear accelerator
for the injection and electron beam storage ringis shown in Fig. 7.
The SPring-8 linear accelerator which had
been used as an injection of the electron beam
both to SPring-8 and NewSUBARU electron
beam storage rings in cooperation of the SPring8 accelerator team, previously. This linear
accelerator was shut down on July 29, 2020.
From April to December, the new linear
accelerator for NewSUBARU was installed at
the beam transportation tunnel. This length of the
new linear accelerator has a length ofapproximately 50-m-long and it is a half-lengthof the previous one. The new one employed themicrowave frequency of approximately 6 GHz(C-band microwave) and it is double frequencyof the previous one (S-band microwave) toshortening the length.
The commissioning of NewSUBARU phase II
will start from April 20, 2021. After the beamline

22

tuning, user time will be operated at electron
beam current of 350 mA in electron energy of 1.0
GeV top-up mode. In addition, 1.5 GeV
operation will be started at the same time.

analyze the chemical content spatial distribution
analysis is in progress.
Constructionofnewinjector
for
NewSUBARU is in progress toward the
NewSUBARU phase II operation to start from
April 20, 2021.
References
1. International Symposium on Extreme
Ultraviolet Lithography, (2021) Closing
remarks.
2. Web site of NewSUBARU Synchrotoron
facility, http://www.lasti.u-hyogo.ac.jp/NS/
3. M. Nakagawa, Jpn. J. Polym.Sci. Tech. 68(2019) 24 (in Japanese)
4. M. Nakagawa, T. Uehara, Y. Ozaki, T.
Nakamura, and S. Ito, J. Vac. Sci. Technol. B
36 (2018) 06JF02.
5. T. Ishiguro, J. Tanaka, T. Harada, and T.
Watanabe, J. Photopolym. Sci. Technol. 32(2019) 333.
6. K. Tsuji and Y. Muramatsu Ed., “X-ray
Spectroscopy,” Spectroscopy Series, The
Spectroscopical Society of Japan (inJapanese), Kodansya, 2018, ISBN 978-4-06513038-4.
7. T. Ohta, “X-ray Absorption Spectrocopy,”
IPC,
in
Japanese,
2017,
ISBN
9784901493215.
8. J. Tanaka, T. Ishiguro, T. Harada, and T.
Watanabe, J. Photopolym. Sci. Technol. 32(2019) 327.
9. J. Tanaka, T. Ishiguro, T. Harada, and T.
Watanabe, J. Photopolym. Sci. Technol. 33(2020) 491.
10. M. Kuki, T. Uemura, M. Yamaguchi, T.
Harada, T. Watanabe, Y. Muramatsu, and H.
Kinoshita, J. Photopolym. Sci. Technol., 28(2015) 531.
11. B. Cardineau, P. Garczynski, W. Earley, and
R. L. Brainard, J. Photopolym. Sci. Technol.
26 (2013) 665.

New SUBARU

New linear accelerator
Fig. 7 Photograph of NewSUBARU Synchrotron
light facility.

7. Conclusions
The RSoXR method is introduced to evaluate
the chemical-layer separation of the CAR, and it
is sensitive enough to it. In the single layer resist,the preventing from the pattern collapse at theboundary between the bottom and main bodylayer might be significant for the fine patterning.
The RSoXS method is introduced to evaluate
uniformity of resist material distribution, which
can modulate absorption contrast of functionalgroup by changing the incident photon energy
around carbon absorption edge. The RSoXS
results are clarified the uniformity of resist
material structure, which can highlight the issues
to design the low LWR performance.
The out of band systematic analysis tool was
prepared at BL03 beamline. In the OoB region,
the reflectance of Mo/Si multilayer, TaN
absorber, and mask substrate as a black border
has approximately 30% in maximum. Even if theblack border, it has the reflectance of 30%. And
the reflectance reduction method of the OoB
lights should be required for the low LWR
achievement of the resist patterning.
In order to achieve low LWR, construction of
the photo-electron emission microscopy to23ⅡSynthesis and Characterizationof the Polymer Having Photoacid Generator for EUV Resist

Ⅱ

Shinji Yamakawa, Tetsuo Harada, Takeo Watanabe
Center for EUVL, Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo

Abstract

In extreme ultraviolet (EUV) lithography, the development of new resist materials is a one of thesignificant issues. It is known that there are two types of the chemical amplification resists (CARs),such as photoacid generator (PAG) blend resist (a mixture of PAG and polymer) and PAG boundresist (polymers having PAG unit in sidechain). However, there are few research targeting the PAG
bound resists. In this paper, we report the synthesis and characterization of new PAG bound resist.

Table 1. Summary of PAG structures.
Structure
PAG
CationAnion

1. Introduction
The next generation EUV photoresist is needed
to satisfy with half pitch of smaller than 10 nm,
sensitivity of higher than 15 mJ/cm2, and low line
width roughness (LWR) of lower than 1 nm. It is
known that there are two types of the CARs, suchas PAG blend resists and PAG bound resists. The
PAG blend resist is a mixture of the polymer, PAG,
and amine additive in the solvent. On the other
hand, the bound resist is the polymer having PAG
unit in side chain. The difference of the blend andbound resists has been reported. For example,
Watanabe et al. have reported that the bound resist
is more less line edge roughness (LER) than blend
resist [1]. The reason of low LER for bound resist
is expected that the uniformity of bound resist is
better than blend one, however, the chemicalcomposition distribution analysis has not been
evaluated.
In this study, we synthesized a new PAG boundresist and evaluated the dose estimation by EUV
irradiation and the chemical composition
distribution by contact angle measurement.

PAG-1

CF3SO3-

PAG-2

CF3SO3-2.2. Measurements
NMR (1H and 19F{1H }) spectra were recorded
on JEOL JNM-ECZ600R (600 MHz) spectrometer.
The peaks were referenced to DMSO (δ 2.50) in
the DMSO-d6 solvent for 1H NMR.
Gel
permeation chromatography (GPC) was performed
at 60 °C on Waters Alliance e2695 HPLC systemequipped with a differential refractometer detector
e2998 and a variable-wavelength UV-vis detector
e2410, using DMF (10 mmol/L phosphoric acidand KBr) as eluent at a flow rate of 0.6 mL min-1
with Shodex AsahiPak GF-7HMQ columns. The
molecular weights were calibrated based onpolystyrene standards. The image of the droplet
profile and calculate contact angle were recordedon Excimer SImage Entry 6. Dose estimation was
examined at NewSUBARU BL03 [2].

2. Experimental
2.1. Materials
Dimethylsulofoxide-d6 (DMSO-d6), diethyl
ether (Et2O), tetrahydrofuran (THF), γ-butyl
lactone, propylene glycol monomethyl ether
acetate (PGMEA), dimethyl amino pyridine(DMAP),
1-(3-dimethylaminopropyl)-3-ethylcarbodiimidehydrochloride (EDC·HCl), and dehydrated
dimethyl formamide (DMF) were used aspurchased.
hexamethyldisilazane(HMDS),
poly(hydroxystyrene-co-tert-butylacrylate)(PHS-TBA), were purchased from Tokyo Ohka
Kogyo Ltd.
PAG-1, 2 were provided by
San-Apro Ltd. Table 1 shows the structure of PAGs
which were employed in this study.

2.3. PAG-2 introducing to the side chain ofbase polymer
It can be introduced into phenolic acid group
under mild conditions due to PAG-2 has carboxylic
group. Thus, the condensation reaction of PAG-2
and PHS-TBA was examined (Scheme 1).

24spin-coated films were prebaked at 110 oC for 60 s.
The resist thickness was measured by the
optical-interference-type
film
thicknessmeasurement tool (NanoSpec6100, NANO metricsInc.).
The average film thickness and the degree of
introduction (DI) of PAG (mol%) in each of the
prepared samples show in Table 2.
Table 2. Summary of prepared resist samples.
Scheme 1. The condensation reaction of PHS-TBA
with PAG-2.
PHS-TBA (1239 mg, 5.0 mmol), EDC･HCl (105mg, 0.55mmol), DMAP(10 mg, 0.082 mmol) andPAG-2 (311 mg, 0.50 mmol) were charged to 50
ml two-necked flask and purged N2 gas.
Dehydrated DMF (10 ml) was added to mixture
then stirred at r.t. for 22 h. After the reaction, thereaction mixture was poured into water (150 ml).
The resulted solid was obtained by suction
filtration and dried under vacuum for 6 h at 60 oC.
The obtained crude product was dissolved a small
amount of THF, and the mixture solution waspoured into a large amount of Et2O. The resulted
solid (79% yield) was obtained by suction filtrationand dried under vacuum for 6 h at 60 oC.
The ration of the microstructure of the PHS unit
and the degree of introduction of PAG group in thepolymer was calculated from the 1H NMR peakarea ratio using the following eq (1), and (2).
[PHS unit] / ([PHS unit] + [TBA unit]) =(phenyl / 4) / [(phenyl / 4) + {alkyl – (phenyl / 4)× 3} / 12](1)[PAG unit] = PAG / 18 ×[PHS unit](2)
The signals and their positions are as follows: 1H
NMR: δ 8.19-7.39 (PAG), 7.20-6.06 (phenyl) and2.05-0.0 (alkyl); 19F{1H} NMR: δ -77.7 (CF3).

SampleThickness(nm)

PAG
structure

1
2

43
22

PAG-1
PAG-2

3

41

-

DI of
PAG
(mol%)

2.2
5.2
0

Resist
type

Blend
Bound
Base
Polymer

2.5. Contact angle measurement on the resist
thin layer surface
The contact angle was measured by the sessile
drop method. The measurement points on a 4 inch
silicon wafer show in Fig. 1 (blue dot). Ultrapure
water was used as a measurement solvent, and theliquid volume was 2.0 µl (the liquid diameter was
calculated 1.6 mm when contact angle = 90 o). The
θ/2 method was used to calculate the contact angle.
The droplet images were captured 10 s after
dripping. The average value and standard deviationof the measured values at each distance (0, 20, 40mm) from a wafer center were calculated andplotted.

2.4. Resist thin film coating on the silicon wafer
The resist solutions were filtered through a 0.22
μm PTFE syringe filter prior to spin-coating on
silicon wafers which were treated by the addhesion
process by HMDS. Spin-coating was performed at
3000 rpm for 30 s to form HMDS thin films on
silicon wafers. Then these spin-coated films were
prebaked at 130 oC for 90 s. Then, the solutions ofsample #1 and 3 in PGMEA and sample #2 in
γ-butyl lactone were spin-coated on the siliconwafer to prepare corresponding thin films.
Spin-coating was performed at 2500 rpm for 45 s
to form thin films on silicon wafers. Then theseFig. 1. Measurement points (blue dots) of thecontact angle on a silicon wafer.
3. Results and discussion
3.1. Introduction of PAG-2 into base polymer
The reaction of PHS-TBA with PAG-2 wascarried out using EDC･HCl as a condensation
reagent under DMAP as a base catalyst at r.t. for 22h, obtaining the polymer with Mn = 4,500 (Mw/Mn= 1.88) at 79% yield. The DI of PAG-2 ascalculated by 1H NMR spectroscopy was found to
be 5.2 mol%. Obtained polymer having PAG was25Ⅱhydroxy groups.

dissolved in γ-butyllactone, THF, and DMSO. Thus,
γ-butyllactone was chosen as solvent for the
preparation of resist thin film.

Ⅱ

3.2. Dose estimation
Dose estimation of EUV resists were evaluatedby sensitivity curves. Sample resists on Si wafer
were exposed to EUV while changing exposure
dose. After developing and rinse technique andmeasuring the thickness of the residual resist thinfilm, the sensitivity curve can be obtained. As aresult, E0 of PAG blend resist and bound one issmaller than 10 mJ/cm2. This result means these
resists are highly sensitive resist for EUV. However,E0 of bound resist is bigger than blend one. Thus,
we evaluated that the contact angle for resist thinfilm surface. The base polymer used in CARs
mainly has hydrophilic unit such as hydroxygroups and hydrophobic unit such as protecting
group and PAG. Therefore, it was expected that thechemical composition distribution could be
evaluated from the difference affinity (betweenhydrophobicity and hydrophilicity) by measuring
the water-contact angle on the resist thin film
surface.

Fig. 3. Contact angle results of sample #1-3, blend
resist (●), bound resist(●), and Polymer (▲).
Kawai et al. measured the refractive index andcontact angle of resist thin films composed ofnovolak resin and naphthoquinone diazide after the
spin coating, and it is reported that the refractive
index and contact angle increase from the center tothe outside of the silicon wafer [3]. The contact
angle of the PAG blend resist increased from thecenter of the wafer to the outside in our results too.
However, the result of PAG bound resist andpolymer without PAG showed opposite behavior as
shown Figure 3. This result means the type of
resists affect the chemical composition distributionof the resist thin film surface. We consider that thisdifference affects EUV sensitivity.
4. Conclusion
We synthesized and characterized a new PAG
bound resist. The obtained PAG bound resist
showed good sensitivity for EUV. It is clarified thatthe resist thin film has different chemicalcomposition distributions from the center to theoutside of wafer depend of the type of resists.
References[1] T. Watanabe, Y. Fukushima, H. Shiotani, M.
Hayakawa, S. Ogi, Y. Endo, T. Yamanaka, S.
Yusa, and H. Kinoshita, J. Photopolym. Sci.
Technol., 19, (2006), 521.
[2] T. Watanabe, H. Kinoshita, N. Sakaya, T. Shoki,
and S. Y. Lee, Jpn. J. Appl. Phys. 44, (2005),
5556.
[3]. K. Nagata, and A. Kawai, J. Adhesion Soc. of
Jpn (in Japanese), 31, (1995), 187.

Fig. 2. Sensitivity curve of sample resists.
3.3. Contact angle measurement of sample resists

Figure 3 summarizes the results of contact angle
measurement of samples #1-3. The horizontal andvertical axes show the distance from the center ofsilicon wafer and the contact angle of droplet,
respectively. The contact angle of resist samples #1(purple circle), and 2 (green circle) wasapproximately 82 o in the vicinity of the wafer
center. However, the contact angle of polymer
sample #3 (black triangle) was approximately 80 o.
These results mean that resists are morehydrophobic than base polymer without PAG unit.
It is considered that the reason of the increasing ofhydrophobicity on the blend resist thin film isderived from PAG because PAG is without

26

Relocation and Upgrade of Tender X-ray XAFS Beamlinefor High-Accuracy and Advanced Measurements
Koji NakanishiLaboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo

Abstract

In order to promote the use of industrial analysis, double crystal monochromator beamline BL05C
is relocated and reconstructed. BL05C can use X-rays in the energy range of 1-3 keV and 5-12 keV.
As an evaluation of 1-3 keV XAFS, the S K-edge XAFS measurements of FeS2 were performed. As
a result, the highly-accurate XAFS spectra can be obtained in a short time. In addition, operando
XAFS experiments of amorphous Si thin film electrodes were performed as an advanced analysis
technology. BL05C promotes the use of industrial analysis with highly accurate XAFS and original
analysis technology.

“BL05C” because of the role it has played and therecognition of the beamline name.

1. Introduction
BL05, NewSUBARU was built in 2008 to
promote industrial analysis, and has been used forthis purpose. BL05 is consisted of two beamlines,
BL05A and BL05B. BL05A is a beamline for soft
X-ray XAFS, and the photon energy of 1-4 keV (socalled “tender X-rays”) are available. On the otherhands, BL05B is a beamline for soft X-ray XAFS
and PES measurements, and the photon energy of
0.05-1 keV are available. However, both beamlines
had many problems and needed a major upgrade inorder to further expand the industry analysis. One of
the serious problems was the organic contaminationof M0 mirrors installed upstream of the beamline. A
common mirror chamber was used for the M0
mirrors of BL05A and BL05B. Because the mirror
chamber was large and the performance of thevacuum pump was low, an ultra-high vacuum could
not be maintained, resulting in severe organic
contamination of both mirrors. Especially for
BL05B, which measures carbon and oxygen, it wasa fatal problem. In order to overcome these
problems, we installed additional vacuum pumps asa partial solution. However, it was not possible toinstall a sufficient number of high-performance
vacuum pumps due to the availability of empty
ports, and a satisfactory degree of vacuum could not
be obtained. There was also another problem withempty space around the mirror chamber. Therefore,
as a drastic solution, we planned to separate BL05A
and BL05B completely and prepare appropriate
mirror chambers for each. The concrete method is
to relocate BL05A beamline to BL06. The
relocation of BL05A to BL06 was carried out from
August 2020.
The results of the evaluation and measurementof the new beamline that was relocated and rebuilt
while being upgraded are reported in this paper.
Here, the location of it is BL06, but it will be called

2. Experimental details
All experiments were performed at the newbeamline, BL05C. BL05C mainly consists of acollimating mirror, a Golovchenko-type double
crystal monochromator (DCM), an X-ray intensity
monitor (I0 monitor), a measurement chamber, aload-lock chamber and various optical apertures andslits. A pair of InSb(111) monochromatizing
crystals (2d = 7.481 Å) was used for Si K-edge andS K-edge XAFS measurements.
All samples were placed in a vacuum
measurement chamber kept below 10-4 Pa. For
anaerobic samples, a transfer vessel was used,which allows sample transport and introduction
without exposure to the air.
The total electron yield (TEY) with a sample
drain current and partial fluorescence yield (PFY)with a silicon drift detector (SDD) and digital pulse
processor were used for soft X-ray XAFS as
standard detection methods. In the PFY mode, thetypical peaking time of the SDD was 0.1 μs, and thedead time was kept below 2 %.
3. Results and discussion
3.1. Beamline configuration
The beamline configuration of BL05C is shownin Fig. 1. When BL05C was relocated, its beamline
concept was changed. The beamline before
relocation could use tender X-rays of 1-4 keV. In
order to widely industrial demands, BL05C ischanged the specifications of the X-ray mirrors. The
former BL05A was used a nickel-coated toroidal
mirror with an incident/reflection angle of 1.0
degrees, while the new BL05C is used a rhodiumcoated parabolic mirror with an incident/reflection
angle of 0.3 degrees. The comparison of the

27

Ⅱ

Ⅱ

Fig. 1. Planned BL05C configuration (a), the present configuration (b) and the photograph (c).

demand in XAFS, making it possible to respond toa wide range of industrial analyses. As of 2021, only
1-3 keV is available because a focusing mirror anda measurement hatch for hard X-rays are not ready.
Preparations for the use of hard X-rays areprogressing steadily.

reflectivity of each mirror is shown in fig. 2. Here,the RMS roughness value was poorly estimated andset to 3 nm. As a result, available photon energies in
BL05C have been changed to 1-3 keV and 5-12 keV.
This makes it possible to measure the K absorption
edges of 3d transition metals and the L absorption
edges of lanthanides, tungsten, gold, and platinum,
which were previously impossible to measure with
New Subaru. The above elements are the most in28

3.2. Evaluation of typical soft X-ray XAFS
measurement (ex situ measurements)
FeS2 is called “pyrite” in natural minerals and iswell known for its similar appearance to gold.
Although its industrial value has declined as it is nolonger used as a raw material for sulfuric acid, it isconsidered promising as a next-generation highcapacity positive electrode active material for
lithium-ion secondary batteries (LIBs) and as amaterial for thin-film solar cells, and its value has
been reassessed in recent years.
FeS2 powder was fixed on a carbon tape, and S
K-edge XAFS measurements with simultaneous
detection of the TEY and PFY were performed at
BL05C (shown in Fig. 3). The dwell time was 2
seconds per point and the total acquisition time of
the XAFS spectra in fig. 3 was approximately 25
minutes. Observed XAFS spectra have a very highS/N ratio. EXAFS oscillations over k~11 Å havebeen obtained, and the peak derived from the second
nearest neighbor is observed in the radial distance.
These results indicate that the beamline
performance is high enough for general industrial
analysis.
Furthermore, a difference in XAFS spectra wasobserved between the TEY, which is surfacesensitive, and PFY, which is bulk-sensitive, due tothe presence of sulfates on the FeS2 powder surface.

Ⅱ

Fig. 2. Simulated reflectivity of former BL05A
and new BL05C [1].

It was shown that this information on the difference
in detection depth is also effective for industry
analysis and can be fully utilized.
3.3. Operando soft X-ray XAFS measurement asadvanced analysis

Fig. 3. XAFS spectra of FeS2. (a) Photo of pyrite (Chemical formula: FeS2). (b) Crystal structure of FeS2.
Observed XAFS spectra (c), EXAFS Oscillation χ(k) (d), and radial distance (e) with the TEY andPFY detection.

29

Ⅱ

Silicon and silicon compounds are promisingmaterials for high-capacity negative electrodes ofnext-generation LIBs. Si particles cannot withstandexcessive expansion and contraction due to repeatedcharging and discharging, and physical destruction
such as cracks and pulverization occurs in the active
material [3], so the possibility of practical use is low.
On the other hand, Si nanoparticles and thin films
are less likely to cause this problem [4], so they havebeen used in many basic studies for the purpose ofinvestigating the charge-discharge reaction ofsilicon. Silicon electrodes are expected to undergo
alloying and dealloying reactions with lithium ions
during charging and discharging. In this chemical
reaction, the crystallinity of silicon is broken and it
becomes amorphous, so it is difficult to analyze by
XRD, which has been used several times in existing
LIB electrode analysis. XPS is also difficult toanalyze because an organic passivation layer called
solid electrolyte interphase (SEI), which is a resultof reductive decomposition of the electrolyte
solution, deposits thickly on the silicon negativeelectrode. XAFS is very effective for the analysis ofsilicon and silicon compound negative electrodes,
regardless of the crystallinity of the object to beanalyzed and the ability to analyze deep areas of thesample. In addition, our group owns an originallydeveloped spectro-electrochemical cell for soft Xray XAFS [2]. Therefore, it is possible to measuresilicon and silicon compound negative electrodes
during charge/discharge operation, which isdifficult to perform at other facilities.
50 nm thick amorphous Si (a-Si) film electrodewas prepared using DC magnetron sputter without
air exposure, and the operando XAFS
measurements were performed in BL05C. Observed
XAFS spectra during first charge process are shownin Fig. 4. The initial XAFS spectrum is that oftypical a-Si. As the charging progressed, the energyof the absorption edge shifted to the low energy side.
This is attributed to the decrease in the oxidation
number of Si due to the formation of the LixSi alloy.
In addition, as the charge progressed, the small peakat 1841 eV in the initial spectrum disappeared andchanged to a spectrum shape typical of metals.
In this way, BL05C enables us to observe nonequilibrium reactions of battery electrodes during
device operation, which is useful for understandingtrue phenomena occurring in device samples.

Fig. 4. operando Si K-edge XAFS spectra of aSi thin film electrodes.
performance for XAFS. In addition, it became clearthat the soft X-ray XAFS measurement during theoperation of the independently developed storage
battery is possible.
In the future, in addition to promoting the use ofthis beamline for industrial analysis, we willproceed with preparations for the setup of hard Xrays and proceed with the development of abeamline that is even more useful for industrial
analysis.
References[1] B. L. Henke, E. M. Gullikson, J. C. Davis, At.
Data Nucl. Data Tables 54, (1993), 181.
[2] K. Nakanishi, D. Kato, H. Arai, H. Tanida, T.
Mori, Y. Orikasa, Y. Uchimoto, T. Ohta, Z.
Ogumi, Rev. Sci. Instrum. 85, (2014) 084103.
[3] H. Wu, Y. Cui, Nano Today 7, (2012), 414.
[4] T. Jaumann, J. Balach, M. Klose, S. Oswald, U.
Langklotz, A. Michaelis, J. Eckertab, L.
Giebeler, Phys. Chem. Chem. Phys. 17, (2015),
24956.

4. Conclusion
In order to overcome the problems of the former
BL05 and promote the use of industrial analysis,
double crystal monochromator beamline BL05C isrelocated and reconstructed. BL05C can use X-raysin the energy range of 1-3 keV and 5-12 keV. Soft
X-ray XAFS of 1-3 keV was evaluated in this report.
As a result, it became clear that it has high30

The Effect on Exit Beam Height by Change of Incident Beam
Height in Symmetrical Layout Type Double Crystal
Monochromator
Masato Okui1, 2, Naoki Yato1, Atsushi Shimoguchi1, Norio Murayama1,
Ichiro Tsuboki 1, Kazuhiro Kanda2
1Kohzu Precision Co., Ltd., 2LASTI, University of Hyogo
Abstract

A symmetrical layout type monochromator controlled by electronic cam was developed and its
demonstration test was performed on BL06 in NewSUBARU. As the result of the demonstration
test, the monochromator shows enough performance to new generation synchrotron facilities. In thisreport, when the height of incident beam is shifted from ideal height, suitable alignment method of
this type of double crystal monochromator was examined by ray tracing and control algorithm. As
the result, It is thought better by beam offset value of symmetrical layout type double crystal
monochromator shall be changed is better than solution by the single axis alignment when theheight of incident beam is changed.

1. Introduction
The authors have reported the result ofexperiment demonstrating of symmetrical layout
type double crystal monochromator set temporally
on the beamline BL06 in New SUBARU in 2020
[1, 2]. This monochromator KOHZU NGM-RD1
is controlled by new developed control board withelectronic cam technology [1, 2]. The
monochromator has some features than previous
monochromator [3] with mechanical cam. Firstly,
the gravity center of the monochromator shall be
kept on rotation axis on theta angle through allangles. Since 1st crystal and 2nd crystal is not
combined mechanically by physical cam, it is easy
to change beam offset between 1st crystal and 2nd
crystal. I
In this report, the authors shall examine aboutalignment method of the symmetrical layout
monochromator controlled by electronic cam in
the case that height of actual incident beam isshifted from ideal beam position.

Fig. 1. Photograph of the inside vacuum
chamber of NGM-RD1 type double
crystal monochromator.

2. Experiments
2-1. Monochromator
The following Fig. 1 shows photograph ofinside vacuum chamber of the NGM-RD1 type
monochromator [1] and Fig.2 shows theschematic design drawing of the monochromator[1].
The Z1 and Z2 positions in each 1st crystal
unit and 2nd crystal unit are controlled by theelectronic cam board in real time corresponding
with rotating Bragg angle value [1]. These
positions are calculated by following equation (1)and (2) [1, 2]ℎ

1

𝑍𝑍𝑍𝑍1 (𝜃𝜃𝜃𝜃) = (− 1)
4 cos 𝜃𝜃𝜃𝜃𝑍𝑍𝑍𝑍2 (𝜃𝜃𝜃𝜃) = −𝑍𝑍𝑍𝑍2 (𝜃𝜃𝜃𝜃)

Fig. 2. Schematic design drawing of NGMRD1
typedoublecrystalmonochromator.

(1)
(2)

31

Ⅱ

30.0mm10.0mm
20.0mmFig. 4. Ray tracing drawing of NGM-RD1
type monochromator in the case ofheigh t of the incident beam down 5mm from the ideal height where thebeam offset is 30 mm and Bragg
angle is 30 degrees.

If the height of incident beam would be downfrom the above ideal height, The exit height from2nd crystal would be value add beam offset to theactual beam height and the height of exit in thiscase shall do down by same amount incident beam
go down.
Fig 4 shows ray tracing drawing when theincident beam goes down 5 mm from ideal height,
where the beam offset is 30 mm and Bragg angle
is 30 degrees. The exit beam height goes down 5mm from Fig. 3 that is the case of ideal incident
beam.

2-2. Ray tracing
Ray tracing drawing in the case of ideal height ofincident beam is shown as Fig. 3, when beam
offset shall be 30 mm and Bragg angle shall be 30
degrees. The exit height from 2nd crystal is kept
value add beam offset h to the height of ideal
incident beam if satisfied with Equation (1) and(2) corresponding to any Bragg angle.

15.0mm
30.0mm

3. Results and Discussions
As describing the above section, the actual exit
beam height would be synchronized change withthe actual incident beam height in thissymmetricallayoutdoublecrystalmonochromator controlled by electronic cam.
This situation is leads by that only beam offset
between 1st and 2nd crystal of the layout isconsidered in Equation (1) used in this electronic
cam control system. Firstly, beam stability should
be kept in the upstream like front end, but it shallbe difficult that perfectly fixed incident beam
could not be supplied from the upstream of double
crystal monochromator.
Thereat, the authors would like to propose
solution by additional control as to cancel theincident beam vibration to electronic cam control
algorithm in this report. We can suggest thechange of exit beam height from themonochromator shall be able to cancel by that

15.0mmⅡ

In the Equation (1) and (2), θ shows Bragg angle,ℎ shows the offset between the height of incident
beam to the monochromator and the height of exit
beam from it.
Okui et al. [1, 2] have already reported that theexit height from the monochromator have beenable to keep constant by satisfied with Equations(1) and (2). In the above case, the exit height fromthe monochromator is kept the added beam offset
on the incident beam height.
In NGM-RD1 type monochromator, the center
point of footprint on 2nd crystal is moving to the
upstream as Bragg angle is higher. In previous
KOHZU KHL type monochromator in KEK-PF[3], long Y axis could be removed by moving
footprint of only 2nd crystal, but the length of 2nd
crystal is longer than the monochromators [4, 5]
before KHL type.
In the present study, NGM-RD1 type
monochromator, the center of footprint on 1st
crystal is also moving to downstream as Bragg
angle is higher [2] as well as 2nd crystal. Thisgeometry causes the length of both 1st and 2nd
crystals is shorter than the case of the previous
geometry [3] since moving amount of footprint isdivided to 1st and 2nd crystal.

Fig. 3. Ray tracing drawing of NGM-RD1
type monochromator in the case ofideal heigh t of the incident beam
where the beam offset is 30 mm andBragg angle is 30 degrees.

3215.0mm35.0mmincident beam. Thus, it is necessary that theenough length of 1st and 2nd crystal should beallowed for not cutting footprint.

20.0mm

4. Conclusion
From result of ray tracing and easiness ofcontrolled electronic cam, adjustment by beam
offset value of symmetrical layout type double
crystal monochromator shall be changed is better
than solution by the single axis alignment when
the height of incident beam is changed.
Acknowledgement
The authors thank deeply for significant advice
by Miss. Naoko Sawada, Technical division,
Kohzu Precision Co., Ltd.

Fig. 5. Ray tracing drawing of NZD-RD1
type monochromator after beam offset
adjusted to fix exit position when theincident beam goes down 5 mm from
ideal height, where Bragg angle is 30
degrees and beam offset is 35 mm.

References[1] Okui et al., LASTI Annual Report 21, (2019)33.
[2] Okui et al., J. Phys.: Conf. Series (accepted).
[3] Kawata et al., AIP Conf. Proc., 705, (2004)
663.
[4] Matsushita et al., Nucl. Instrum. Methods,
A246, (1986) 377.
[5] Yabashi et al., Proc. SPIE, 3773, (1999), 2.

beam offset would be adjust, since the change ofthe exit beam height is caused by actual change ofincident beam height. Fig. 5 shows our concept ofmethod adjusting fixed beam position, where
Bragg angle is 30 degrees.
In Fig. 5, Z1 and Z2 are moved far as to keep its
beam offset is 35 mm from 30 mm respectively.
As the result, the beam offset between 1st crystal
and 2nd crystal shall be wide than the case of ideal
incident beam height but the actual exit beam
position from the ground shall be kept with theexit ideal beam position from the ground.
At this this time, In Equation (1), only beam
offset between 1st crystal and 2nd crystal should
be changed so that Z1 and Z2 are symmetricalmovement for keeping gravity point of themonochromator. When amount of changing
incident beam height is Δh, Z1 position adjusted
considering incident beam vibration is expressed
the following Equation (3)𝑍𝑍𝑍𝑍1 (𝜃𝜃𝜃𝜃) =

ℎ+∆ℎ
4

(

1

cos 𝜃𝜃𝜃𝜃

− 1)

(3)

If the adjustment of the monochromator was bedone by only either Z1 or Z2 to keep exit beam
position from ground, functions of Z1 and Z2,
especially concerned with velocities, are different
each other and complex. The difference willcause the real-time control on electronic cam
board would be difficult. By the above the authors
recommend adjusted control according toEquation (3). After this adjustment positional
moving range of footprint of beam shall change
from the range of the case of ideal height of33

ⅡStructural Changes of Highly Hydrogenated DiamondLike Carbon Films by Soft X-Ray Irradiation

Ⅱ

Daisuke Niwa1, Tomohiro Mishima1, Hibiki Terai1, Koji Nakanishi1, Masahito Niibe1,
Kazuhiro Kanda1, Fuminobu Hori2, Atsushi Yabuuchi3, Atsushi Kinomura3
1
LASTI, Univ. Hyogo, 2Eng., Osaka Pref., Univ., 3RNS, Kyoto Univ.

Abstract

Highly hydrogenated diamond-like carbon (DLC) films have characteristics of low friction
coefficient in a vacuum and they are expected to be applied as solid lubricants for devices used inspace. However, it is known that hydrogen desorbs from highly hydrogenated DLC films by soft Xray irradiation. In this report, the hydrogen desorption process and structural change of highlyhydrogenated DLC films by soft X-ray irradiation was discussed by observing free volume in the
DLC films by the measurement of positron annihilation spectroscopy (PAS) using slow positron
beams.

CVD method. Film thickness was 400 nm, and thehydrogen content in the films was about 50 %. Soft
X-ray white light was irradiated to the highlyhydrogenated DLC films at BL-6 of the
NewSUBARU [4]. The white radiation beam froma bending magnet was introduced to the sample
stage using a pair of mirrors, whose incident angle
was 3°. The electron energy of the NewSUBARU
ring was 1.0 GeV and the SR at the BL-6 sample
stage had a continuous spectrum from IR to soft Xray, which was lower than 1 keV. The typical ring
current was 300 mA during the exposure. The SR
dose [mA·h] was represented by the product of thering current [mA] with the exposure time [h]. The
irradiation doses of the sample prepared in thisexperiment are 0 mA·h, 500 mA·h, 1000 mA·h, and4000 mA·h.
The
measurementof
positronannihilation spectroscopy (PAS) was carriedout using slow positron beam equipment
installed in the B-1 experimental hole of the
Kyoto University Research Reactor (KUR).
In the B-1 experimental hole, positrons are
extracted from the reactor at 10 eV andaccelerated up to 30 keV just before injection
into the material. PAS is a method to obtain
information on the free volume by observing
γ-rays generated from the annihilation of apositron injected from the reactor and anelectron in the material. In the present work,
two types of measurements; the positronannihilation lifetime spectroscopy and the
Doppler broadening were carried out. The
process of annihilation i3n the material isillustrated in Fig. 1. The positron injected
into the material loses energy as a result of
Coulomb repulsion from the positive chargeof the ion core in the atom, and is trapped in
the free volume. The trapped positron in the

1. Introduction
Diamond-like carbon (DLC) films areamorphous carbon films composed of hydrogen, sp2
hybridized carbon (graphite structure), sp3
hybridized carbon (diamond structure), and freevolume [1]. DLC films have various excellent
properties such as high hardness, low friction, gasbarrier, abrasion resistance, chemical stability,
surface smoothness, and high X-ray resistance.
Therefore, DLC films are applied in a wide range ofindustrial fields such as coating materials andlubricants.
DLC films with high hydrogen content
are called highly hydrogenated DLC films.
Highly hydrogenated DLC films havecharacteristics
ofultra-low
frictioncoefficient in a vacuum. Therefore, they are
expected to be applied as solid lubricants fordevices used in space such as artificial
satellites and probes. It is very important tounderstand the effect of soft X-rays on highlyhydrogenated DLC films to apply highlyhydrogenated DLC films to the spaceindustry. Previous studies in our laboratory
have shown that soft X-ray irradiation
against the highly hydrogenated DLC films
causeshydrogendesorption,
carbonrecombination, and an increase in density [3].
In this work, change of free volume in thehighly hydrogenated DLC films wasobserved through positron annihilation
spectroscopy (PAS) using slow positron
beams, and the hydrogen desorption processfrom highly hydrogenated DLC films by soft
X-ray irradiation was discussed.
2. Experimental
The highly hydrogenated DLC films aredeposited on a Si substrate by plasma enhanced34

Fig. 1.

than 10 keV, the S parameters are mostly constantand show almost the same values as those of the Si
substrate. As a result, the S parameter in this energy
range is considered to obtain from the Si substrate.
The S parameter in the energy range of about 1 keV
to 2.5 keV can be obtained from the DLC films. The
S parameters of the DLC films are in the range of
0.47 to 0.49. The S parameter decrease withincreasing of a soft X-ray dose.
Figure 3 shows the soft X-ray irradiation dose
dependence of PALT and the S parameter of thehighly hydrogenated DLC films. The X-axis shows
the soft X-ray irradiation dose. The left-side Y-axis
shows the PALT represented by a black dot, and theright-side Y-axis shows the S parameter represented
by a red dot. In general crystals, the PALT increases
with the size of the free volume because thepositrons and surrounding electrons are less likely
to annihilate each other. Similarly, the S parameterincreases with the size of free volume, because thefraction of valence electrons in the free volume
increase [5]. However, in the present work, asshown in Fig. 3, the PALT increases but the S
parameter decreases with increasing the irradiation
dose.

Positron annihilation and γ-ray
generation process

free volume annihilates with an electron, in the freevolume and two γ-rays of 511 keV are emitted. In
the positron annihilation lifetime spectroscopy, apulsed positron beam was used to measure thepositron annihilation lifetime (PALT) from thedecay profile of γ-rays generated by annihilation.
When the size of the free volume is small, theelectron density is large. Therefore, positrons easilycollide with electrons, and PALT is shortened. On
the contrary, when the size of the free volume islarge, the electron density in the free volume issmall. As a result, PALT becomes longer.
n the Doppler broadening method, the energy
broadening of γ-rays generated in annihilation ismeasured. The energy of γ- rays generated inannihilation is the sum of the mass-energy of 511
keV. Positrons trapped in free volume due to
Coulomb repulsion have thermal energy. Therefore,
momentum to cause the Doppler broadening of γrays comes from electrons. Because valence
electrons have low momentum, the Doppler
broadening effect is small, as a result, the emitted γrays are observed in the energy range around 511
keV. On the other hand, because core electrons havehigh momentum, the energy dispersion due to the
Doppler effect is large, as a result, γ - ray is observedin a wide range from 511 keV. The S parameter isdefined as a ratio of counts in the central channels
to the total peak amplitude. The increase or decreaseof the S parameter corresponds to the increase or
decrease of the ratio of valence electrons in the freevolume.

Fig. 2. Incident positron energy dependenceof the S parameter.

It was reported that hydrogen is desorbed
and carbon is recombined by the irradiationof soft X-rays to the highly hydrogenated
DLC films [3]. The free volume in the films is
considered to increase because the PALT
increased. On the other hand, the decrease in
the S parameter is attributable to decreasein the density of valence electron in the freevolume. Carbon has core and valence
electron, while hydrogen has no core electron
but only valence electron. It is considered

3. Results
Figure 2 shows the incident positron energy
dependence of the S parameter of highlyhydrogenated DLC films and a Si substrate. The
detection depth changes depending on the energy of
the incident positron. In the energy range higher

35

Ⅱ

Ⅱ

Fig. 3. Soft X-ray dose dependence of positronannihilation
lifetimeandSparameterthat the S parameter is decreased because
the fraction of valence electron in the freevolume is decreased due to desorption ofhydrogen.
As described above, this study shows that soft Xray irradiation on highly hydrogenated DLC films
decreases the S parameter and increases PALT. Thiscan be interpreted as follows: soft X-ray irradiation
causes desorption of hydrogen from the highlyhydrogenated DLC film, resulting in therecombination of carbon, which increases thedensity. But in the free volume increases, and theatoms surrounding the free volume change fromhydrogen to carbon.
References[1] A. C. Ferrari, J. Robertson, Phys. Rev. B 63,(1993) 1771.
[2] D. C. Lugo, P. C. Silva, M. A. Ramirez, E. J. D.
M. Pillaca, C. L. Rodrigues, N. K. Fukumasu, E.
J. Corat, M.H. Tabacniks, V. J. Trava-Airoldia,
Surf. Coat. Tech., 332, (2017) 135.
[3] R. Imai, A. Fujimoto, M. Okada, S. Matsui, T.
Yokogawa, E. Miura, T. Yamasaki, T. Suzuki, K.
Kanda, Diam. Relat. Mater., 44, (2014) 8.
[4] K. Kanda, T. Ideta, Y. Haruyama, H. Ishigaki, S.
Matsui, Jpn. J. Appl. Phys. 42, (2003) 3983.
[5] A. Uedono, R. Suzuki, S. Tanigawa,Radioisotopes 41, (1992) 611.

36

Development of an Improved Multi-Layer Mirror for the New γBeam Source via X-Ray Compton Scattering
Norihito Muramatsu1, Tetsuo Harada2, Schin Daté3, Kazuhiro Kanda2, Manabu Miyabe1, Shuji Miyamoto2,
Haruo Ohkuma3,4, Masahiro Okabe1, Hajime Shimizu1, Shinsuke Suzuki3, Atsushi Tokiyasu1, Takeo Watanabe2
1
ELPH, Tohoku University, 2LASTI, University of Hyogo, 3RCNP, Osaka University,
4
Aichi Synchrotron Radiation Center

Abstract

We are developing new techniques to produce a high energy γ-beam via Compton scattering of soft
X-rays from 1 or 1.5 GeV electrons at NewSUBARU. The X-rays of 92 eV are obtained from theshort undulator at BL07A and reflected backwardly into the storage ring by using a Mo/Si multilayer mirror. We developed an improved multi-layer mirror for better surface condition and heatload. The new mirror shows a reflectance of 65.8% in a test at BL10.

1. Introduction
We are developing a new method to produce
a GeV γ-beam by the Compton scattering of Xrays at an electron storage ring. In our project [1],soft X-rays of 92 eV are obtained from a short
undulator (total length = 2.28 m and period length= 7.6 cm) which is located at BL07 of
NewSUBARU. These X-rays are reflected to thebackward direction at a Mo/Si multi- layer mirror
and injected into the storage ring. In such a
procedure, the maximum energy of a γ-beamproduced via Compton scattering reaches 0.58
and 1.02 GeV for the electron beam energy of 1
and 1.5 GeV, respectively. The achievableenergies are much higher than that of laser
Compton scattering.
We have installed a large vacuum chamber at
BL07A [2] to set up the Mo/Si multi-layer mirror
with a water-cooled copper holder and steppingmotor stages. An X-ray wire scanner (a profile
and intensity monitor) and gamma detectors (aPWO electromagnetic calorimeter, a beamprofile monitor, and a rate monitor) have also
been installed into BL07A, and theirperformance has been tested as described in Ref.
[3]. Currently, an improvement of the Mo/Si
multi-layer mirror is being made based on the
feedback from several tests using a prototype [4].
This report shows results of property tests for a
newly produced multi-layer mirror.

then polishing a surface flatly, and finallyreleasing the stress [3]. However, the curvatureradius of the obtained cylindrical surface wasmeasured to be 14.4 m by an ultrahigh accurate
3D profilometer [4]. There was room to improvea surface accuracy. In addition, the RMS value of
surface roughness was measured to be 0.99 nm in
2×2 µm2 by using an atomic force microscope(AFM) [4]. It was not very good compared withthe reflecting wavelength of 13.5 nm.
In Ref. [4], we also tested temperature rise on
the multi-layer mirror surface by irradiating
undulator X-rays at BL07A. The maximum
temperature reached 190°C in the measurement
using a radiation thermometer. It turned out thatheat conductance from the mirror to the watercooled holder was bad in a vacuum. This may
possibly cause a distortion of the mirror surface
and lower the ability of reflected X-ray focusing.
Thus, we have newly produced a new mirror
with a Silicon substrate, which has an area of
50×50 mm2 and a thickness of 16 mm. The
reflective surface was polished in the cylindricalshape with a curvature radius of 16.7 m byapplying magneto- rheological finishing. Heat
conductance to the mirror holder must be
improved by removing a spacer plate and puttinga thin Indium sheet to the gap.
The surface condition of this new mirror was
examined in a way similar to the case of the oldmirror. The RMS value of surface roughness was
improved to 0.2 nm in an area of 80×80 µm2. The
surface accuracy was also excellent, showing thatthe deviation from the designed cylindrical shape
was within 134 nm in an effective area of 45×45mm2. Fifty periodic layers of Mo and Si were
finally made on the reflective surface.
The performance of the produced mirror wastested at BL10. Figure 1 shows the reflectance of
X-rays around the energy of 92 eV. Different

2. Development of an improved mirror
A prototype of the Mo/Si multi-layer mirror
was made by using a substrate of a low thermal
expansion glass ceramic (Zerodur) and coating
Mo and Si layers with 50 periodic repetitions. Its
reflective surface is cylindrically polished tomake a focus on the electron beam at the 16.7 m
upstream straight section of the storage ring. Thiscylindrical surface was made by bending thesubstrate with application of stress at two edges,

37

Ⅱ

Ⅱ

Fig. 1.

Reflectance of a developed Mo/Si multilayer mirror with a Silicon substrate.

colored lines indicate the reflectance values atseven incident points on the mirror. The
maximum reflectance was 65.8% in the case of
injection at the center. This value was close to thedesign, and higher than the reflectance of the oldmirror (54.2%). A diffusion component of thereflected X-rays was also confirmed to be smallenough in the case of the new mirror.
3. Prospect of our project
We will install the developed new mirror into
the vacuum chamber at BL07A in FY2022. Afterseveral tests of heat conductance and X-ray
reflection, we are going to demonstrate theproduction of a high energy γ-beam via Compton
scattering of soft X-rays from electrons in thestorage ring. Our development of a new γ-beamsource will be helpful for next-generation
researchesofhadronphotoproduction
experiments.
Acknowledgments
This research is supported in part by Grantin-Aid for Challenging Research (Pioneering)No. 18H05325 / 20K20344, Scientific Research(B) No. 22H01225, and Challenging Research(Exploratory) No. 22K18707.
References[1] http://www.rcnp.osaka-u.ac.jp/~mura/kaitaku/[2] S. Tanaka, S. Suzuki, T. Mishima, K. Kanda,
J. Synchrotron Rad. 28, (2021) 618.
[3] N. Muramatsu et al., J. Particle Accelerator
Society of Japan Vol.16 No.3, (2019) 154.
[4] N. Muramatsu et al., LASTI Annual Report 22(2020), 29.

38

Reduction of Graphene Oxide by Combination of Atomic
Hydrogen Annealing and Soft X-Ray Irradiation
Akira Heya1, Akinori Fujibuchi1, Masahiro Hirata1, Kazuhiro Kanda2, and Koji Sumitomo1
1

University of Hyogo, 2LASTI, University of Hyogo

Abstract

The reduction of graphene oxide (GO) by atomic hydrogen annealing (AHA) and soft X-ray
irradiation was investigated using microwell substrates with µm-sized holes with and without Ni
underlayers. The GO film was reduced by AHA at 170 °C. In addition, the GO was also reduced bysoft X-ray irradiation at 150 °C. The effect of Ni underlayer on GO reduction differed between AHA
and soft X-ray irradiation. Furthermore, combinations of soft X-ray irradiation and AHA were also
investigated. The order of treatment was found to affect the properties of the reduced GO films.

MW substrate by vacuum evaporation. The GO
dispersed in 0.1 ml of solvent (0.175 mg/ml) was
dropped onto cleaned MW and Ni/NW substrates ona hot plate at 150 °C.
The AHA apparatus is shown in elsewhere [2].
A 55×55 mm2 W mesh with a wire diameter of 0.03
mm and having 50 holes/inch was used as a catalyst
for H2 decomposition. The flow rate of H2 and gas
pressure were 150 sccm and 30 Pa, respectively. The
W mesh temperature and treatment time were 1700
°C and 3600 s, respectively. The distance between
the W mesh and the sample was 80 mm. In AHA,
the sample temperature was automatically increasedby thermal radiation from the heated W mesh. The
sample temperature was measured by a K-type
thermocouple in contact with the Si substrate andwas 170 °C.
The irradiation of soft X-rays was carried out at
BL07A of NewSUBARU. Schematic diagram ofsoft X-ray irradiation apparatus is shown elsewhere[2]. The light source of BL07A was a 2.28 m
undulator. The storage-ring energy was 1 GeV
during this experiment. The undulator gap was 55.5
mm. The main photon energy was 300 eV. A
monochromator was not used to select the main
photon energy. Hence, the irradiated light also
contains other higher-order X-rays. The irradiation
time was 1 hour. The storage-ring current and dosewere 350 mA and 350 mA·h, respectively. The
saturated sample temperature during irradiation was
150 °C.
The property of GO film was evaluated by Xray photoelectron spectroscopy (XPS). Al
monochromatized X-ray source (1486.60 eV) wasused. The diameter of X-ray beam was 100 μmϕ. A
neutralizer gun was used to suppress the charge.
Unfortunately, the XPS probing size is larger than
the well diameter, so it was not possible to measure
the suspended and supported regions separately.

1. Introduction
Graphene and graphene oxide (GO) have been
widely investigated for transparent conductive films,
sensors, and other applications. The GO is acommon precursor material for graphene because
individual GO sheets are easily obtained byoxidizing graphite, permitting GO films to then beformed by solution processing. To obtain graphene(reduced GO (r-GO)) from GO, the GO film is
reduced by various post-treatment methods such as
thermal treatment above 1000 °C, hydrazine
treatment, and ultra-violet irradiation.
To improve the sensitivity of sensors using r-GO
films, the initial properties of these films are finely
controlled by the reduction process. The sensors
using suspended graphene such as pressure sensors,
microphones,
ultrasounddetectors,
andaccelerometers have been developed. A highlycontrolled reduction of the suspended GO is
expected to enhance the electrical characteristics ofgraphene sensors.
We have investigated a novel surface treatment,
named atomic hydrogen annealing (AHA) for GO
reduction [1]. Graphene on Ni thin films was alsosynthesized from pentacene molecules (C22H14)
using a high-density soft X-ray undulator source ata synchrotron facility [2]. In this study, effect of soft
X-ray irradiation on reduction of GO by AHA wasinvestigated using microwell substrate with µm
sized holes and with and without Ni underlayer.
2. Experimental
Individual GO sheets were prepared fromsynthetic graphite flakes (flake size ～ 100 µm)
based on Brodie’s method. Details are indicated inRef. 1. A 5×5 mm2 array of circular wells withdiameters of 1, 2, 4, and 8 µm, named MW substrate,
was fabricated on a SiO2(120 nm)/c-Si substrate byphotolithography and reactive ion etching. The Nifilm with 50 nm in thickness was deposited on some

39

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3. Results and discussion
The C 1s and O 1s XPS spectra of the GO/MWand GO/Ni/MW substrates before and after various
treatments are shown in Fig. 1. The C 1s spectrumof GO consists of 5 peaks, C-C (284.6 eV), C-OH
(285.5 eV), C-O-C (286.6 eV), C=O (287.5 eV) and
O=C-OH (288.9 eV) [3]. The O 1s spectrum of GO
consists of 3 peaks, C=O (531.1 eV), C-O (532.0eV), and C-OH (533.4 eV) [4]. Although the peaks
corresponding to chemical bonds between C and O
were observed before post-treatment, these peaks
were reduced by AHA and soft X-ray irradiation.
For GO/SiO2/Si substrates, C-O related peaks
remained after soft X-ray irradiation compared to
AHA irradiation. The O 1s spectra indicated thatsoft X-ray irradiation reduced the GO film but also
destroyed the six-membered ring structures. When
AHA was followed by soft X-ray irradiation, the CO related peaks increased after soft X-ray
irradiation. This may be due to the formation of
defects in the r-GO after AHA by soft X-ray
irradiation, which reacted with oxygen after air
exposure, resulting in an increase in C-O related
peaks. The condition of soft X-ray irradiation
followed by AHA was expected to promote the most
reduction of GO, but the reduction is less than thatof AHA, indicating that the six-membered ringbreakdown caused by soft X-ray irradiation is not
fully repaired by AHA. However, the combinationof soft X-ray irradiation and AHA is expected as afine turning for surface state of r-GO.
For GO/Ni/SiO2/Si substrate, no degradation
due to soft X-ray irradiation was observed in both C
1s and O 1s spectra with AHA and soft X-ray
irradiation. It is considered that the Ni underlayer
suppressed the destruction of six-membered ring
structure and/or had effect of repair. The peak due
to O=C-OH increased under condition of AHA
followed by soft X-ray irradiation. The peak of Na
KLL was observed in O 1s spectrum. The origin of
Na is considered to be residues from the GO
formation process. The peak due to O=C-OH
increased under condition of AHA followed by soft
X-ray irradiation.
The influence of Ni underlayer on GO reduction
by AHA and soft X-ray irradiation is discussed. The
results showed that the activity of reduction on theNi surface was weaker than that on the SiO2 surface.
The reduction was suppressed by the Ni underlayer
because of a decrease in the effective atomic
hydrogen density on the surface of the GO film dueto the incorporation of atomic hydrogen in the Ni
underlayer. On the other hand, it was consideredthat the effect of Ni underlayer on GO reduction
during soft X-ray irradiation was enhanced byelectrons generated by soft X-ray excitation.
Conclusion
AHA and soft X-ray irradiation reduced GO
film at low temperatures. For the GO/SiO2/Si
substrate, reduction activity of AHA was higher
than soft X-ray irradiation. In AHA, the Ni
underlayer suppressed GO reduction due todecrease in the effective atomic hydrogen density
on the GO film. In contrast, with soft X-ray
irradiation, the Ni underlayer suppressed thedestruction of six-membered ring structure. The
order of treatment affected the property of r-GO
films.
References[1] A. Heya, N. Matsuo, Jpn. J. Appl. Phys. 57,(2018), 04FL03.
[2] A. Heya, T. Oonuki, R. Utimi, K. Kanda, R.
Yamasaki, K. Sumitomo, Thin Solid Films 713,
(2020), 138365.
[3] O.-K. Park, M. G. Hahm, S. Lee, H.-I. Joh, S.-I.
Na, R. Vajtai, J. H. Lee, B.-C. Ku, and P. M.
Ajayan, Nano Lett. 12, (2012), 1789.
[4] A. Ganguly, S. Sharma, P. Papakonstantinou, J.
Hamilton, J. Phys. Chem. C 115, (2011), 17009.

Fig. 1. C 1s and O 1s XPS spectra of the GO/MW andGO/Ni/MW substrates with various treatments. (a) C
1s and (b) O 1s of the GO/SiO2/Si substrate. (c) C 1sand (d) O 1s of the GO/Ni/SiO2/Si substrate.

40

PES and XAS Study of the Effect of Atomic Hydrogen Annealing
Treatment for Conductive Thin Film Sb-SnO2
Takeshi Fukuda1, Akira Heya1, Takanori Yamamoto1, Ryuki Tsuji1, Yuichi Haruyama2,Masahito Niibe2, Satoru Suzuki2, Seigo Ito1
1
Department of Materials and Synchrotron Radiation Engineering, Graduate School of Engineering, Universityof Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan.
2
Laboratory of Advanced Science and Technology for Industry, University of Hyogo, 3-1-2 Kouto, Ako, Hyogo
678-1205, Japan.

Abstract

Antimony-doped tin oxide (Sb-SnO2) was synthesized via ozone and autoclave procedures.
Hydrogen treatment on the spin-coated Sb-SnO2 thin film significantly improved the electricalconductivity. Photoemission electron spectroscopy (PES) and X-ray absorption spectroscopy (XAS)
measurements for valence band and conduction band analysis were performed with/without atomic
hydrogen annealing (AHA) treatment on the thin films, in order to clarify the reason for thisimprovement. The results showed that the oxygen in SnO2 was reduced by the hydrogen treatment.

1. Introduction
Conductive metal oxide nanoparticles havebeen applied in various fields such as fuel cell
catalysts, solar cells, and displays as materials
showing high electrical conductivity. Tin-doped
indium oxide (ITO), which is currently themainstream material, is expected to be developed
as an alternative due to the high cost of indium.
Since SnO2 is a metal oxide with large reserves
and is thermally and chemically stable, there has
been much research on improving its electricalconductivity. In this study, antimony-doped tinoxide (Sb-SnO2) was synthesized by an ozonebased method [1] with autoclave treatment.
Hydrogen-treatment effect on spin-coated SbSnO2 thin films was investigated to further
improve conductivity.

dissolved in 95 mL of distilled water at a mol
ratio of 95:5. The doping materials used was
SbCl5. Next, 5 mL of tetramethylammoniumhydroxide (TMAH) was added. The solution was
stirred at 850 rpm with a magnetic stirrer whileozone was generated by an ozone generator andbubbled for 6 h at a flow rate of 0.3 L/min.
Afterwards, the precipitates were washed bycentrifugation using 2-propanol (IPA) anddistilled water. Finally, the precipitate wasdispersed in 5 mL of distilled water.
2.2. Fabrication method of Sb-SnO2 thin film
Figure 1b shows how the thin films were
fabricated. First, glass plates cut to 25 × 25 mm
were placed in a container containing liquid
detergent and distilled water and sonicated for 15
min. Next, the glass plates were rinsed with
distilled water and ethanol, and then placed in acontainer containing ethanol and sonicated for 15
min. After washing, the glass plates were allowed
to dry naturally, and UV-O3 cleaner was used toremove organic matter from the surface. The

2. Experiments
2.1. Fabrication method of Sb-SnO2
nanoparticle
The fabrication method of Sb-SnO2 is shownin Figure 1a. First, only 0.005 mol of tin
bifluoride (SnF2) or doping materials were

(a)

(b)

Fig. 1. Schematic images of production method,(a) Sb-SnO2 nanoparticle colloid, (b) Sb-SnO2 thin film coated glass substrate.

41

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Ⅱ

films were then spin-coated on glass plates. The
amount of solution to be dropped was 120 μL,
and the substrates were spin-coated and dried at
120 °C for 20 min. The substrates were thentransferred to an electric furnace and annealed at
450 °C for 2 h.

at the upper end of the valence band in SnO2 by
AHA treatment, resulting in a decrease in thedensity of states. The PES measurement resultsin Figure 3c show that the structure at the upper
end of the valence band was greatly changed andbroadened by AHA treatment. This is because
Sb-SnO2 reacts with hydrogen atoms more easily
than SnO2, and the reduction of oxygen by AHA
may have dramatically changed the state of SbSnO2.
Further researches are on going for the fully
understanding of the phenomenon of
conductivity improvement of Sb-SnO2 by AHA
treatments.

3. Results and discussions
Figure 2 shows the resistivity measurement
results of Sb-SnO2. It is known that the resistivityof Sb-SnO2 depends on the sintering temperature,and it is considered that the sintering treatment
significantly improves the crystallinity and theresistivity [2]. Oxygen defects appear in Sb-SnO2
after hydrogen annealing. Oxygen defects are
considered to act as donors and supply electrons
to the conductor, which further improves theresistivity [3].

Fig. 2. Comparison of resistivity of Sb-SnO2
before, after and after hydrogen annealing.
Photoemission electron spectroscopy (PES) andX-ray
absorption
spectroscopy(XAS)

measurements were performed on the samples
before and after atomic hydrogen annealing (AHA)
treatment to verify the reason of resistivity
improvement by hydrogen treatment. Figure 3a is
a schematic diagram of the AHA treatment.
Atomic hydrogen can be generated by passing H2molecules through a high-temperature tungsten
mesh in a vacuum [4]. In this study, tungsten
mesh was used as the catalyst for AHA treatment.
The XAS results show that the π* bond peak ofoxygen slightly shifts to the lower energy side
after AHA treatment. Although the shift isobscure, this may be due to the reaction ofhydrogen atoms with oxygen, which reduces theO 2p-Sn 5s and O 2p-Sn 5p bonds in SnO2,
resulting in the formation of O 2p-Sn 5p in SnO[5].
In the PES measurement result in Figure 3b,
there was a slight decrease in the peak intensity
at the upper end of the valence band and a change
in the peak position after AHA treatment. Thismay be due to the reduction of the oxygen orbital

Fig. 3. PES and XAS spectra of SnO2 and SbSnO2 thin films before and after AHA
treatment, (a) schematic diagram of
AHA treatment, (b) SnO2, (c) Sb-SnO2.
References[1] K. Iimura, et al., J. Soc. Powder Technol.,Japan, 54, (2017), 609.
[2] Cheng He, et al., ACS Appl. Energy Mater. 3,(2020), 5774.
[3] H. Kim, et al., Appl. Phys. Lett. 84, (2004),
218.
[4] A. Heya, et al., Thin Solid Films, 625 (2017).
[5] M. Minohara, et al., J. Mater. Chem. C, 21(2019).

42

Resonant Photoemission Spectroscopy Studyon the 5d Level of Ir Nanoparticles
Takahiro Maruyama1,2, Yuichi Haruyama3,4
1

Department of Applied Chemistry, Faculty of Science and Technology, Meijo University, 1-501 Shiogamaguchi,
Tempaku, Nagoya 468-8502, Japan.
2
Nanomaterial Research Center, Meijo University, 1-501 Shiogamaguchi, Tempaku, Nagoya 468-8502, Japan.
3
Department of Materials and Synchrotron Radiation Engineering, Graduate School of Engineering, Universityof Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan.
4
Laboratory of Advanced Science and Technology for Industry, University of Hyogo, 3-1-2 Kouto, Ako, Hyogo
678-1205, Japan.

Abstract

The 5d energy level of Ir nanoparticles deposited on SiO2/Si substrates was studied by resonant
photoemission spectroscopy (RPS). When the excitation energy was 68-70 eV, the intensity of asmall peak at around -3 eV was strongly enhanced. This resonance behavior is considered to be dueto the transition of photoelectron from the Ir 4f to 5d energy level, indicating that the peakcomposition was derived from the Ir 5d level. We demonstrated that the RPS is useful to determine
the 5d energy level of Ir nanoparticles, which affects the catalyst activity.

1. Introduction
Single-walled carbon nanotubes (SWCNTs)[1] are a group of widely used carbon-based
nanomaterials since they show various andtremendous electrical, thermal and mechanicalproperties. Their electronic properties are closely
related to their structure, such as diameter andchirality, therefore, selective growth of SWCNTs
with desired structures has been one of thesignificant issues in the nanocarbon field.
Recently, our group succeeded in growth ofsmall-diameter SWCNTs by alcohol catalytic
chemical vapor deposition (ACCVD) using Ir as
catalysts [2]. By using Ir catalysts, high-density
SWCNTs having diameters less than 1 nm weregrown. However, the growth mechanism of
SWCNTs from Ir catalysts has not been
investigated yet. Especially, the effect ofelectronic states of Ir nanoparticles on thereaction process with feedstock gas has been little
understood.
To determine the electronic state of a bulk
material, photoelectron spectroscopy is a
powerful tool. However, the sizes of catalyst
particles for SWCNT growth are a few nm, andthey are generally deposited on substratematerials. Therefore, it is difficult to distinguishphotoelectrons emitted from nanoparticles fromthat of substrates in the spectra measured for asample where nanoparticles are deposited on
substrates.
In this study, we attempted to investigate theIr 5d level of Ir nanoparticles by ultra-violet
photoelectron
spectroscopy(UPS).
By
performing resonant photoemission spectroscopy(RPS), we determined the 5d level of Ir

nanoparticles.
2. Experiments
Ir particles were deposited on SiO2(~100nm)/Si substrates by using pulsed arc plasma
deposition method in a high vacuum.
Transmission electron microscopy (TEM)
observation showed that the Ir particle sizes were
distributed between 1 and 3 nm. The samples
were mounted in the sample preparation chamberof the end station of BL7B. After preheating in
the preparation chamber, the samples weretransferred into the analysis chamber. Then, UPS
measurement was performed at room
temperature. To investigate the effect of
excitation energy on the spectra, RPS was
performed by varying the excitation energy
between 58 and 72 eV. For comparison, we
performed RPS for SiO2/Si substrates without Irnanoparticles under the same excitation energies.
Results
Figure 1 (a) shows UPS spectrum of thesamples which were only SiO2/Si substrates and
Ir deposited on them. The excitation energy was
58 eV. Referring to previous report, the binding
energy is calibrated to the main peak derived
from SiO2[3] and the spectral intensities arenormalized with the maximum intensity ofvalence band. In both spectra, the SiO2 valencebands were observed and the spectral shapes
were quite similar. This would be due to quite
small amount of deposited Ir nanoparticles, andthe spectral shape of valence band was little
affected by Ir.

43

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Figure 1(b) shows UPS spectra for the two
samples, where the excitation energy was 68 eV.
Although the main spectral shapes were still
similar between the two samples, a small
structure is seen at around -3 eV for the Ir
deposited on SiO2/Si sample. Considering that
this peak did not appear for the SiO2/Si sample,
it should be derived from the energy level of Ir
nanoparticles.
To investigate the origin of the Ir derived peakat around -3 eV, we performed RPS, where UPS
spectra were measured by various excitationenergy from 58 to 72 eV. Figure 2 shows thedependence of the relative intensity of small peakat around -3 eV on the excitation energy. It should
be noted that the relative intensity of the small
peak increased above 66 eV. Considering that thisenergy is close to the absorption threshold fromthe 4f to 5d level of Ir, this enhancement should
be induced by the resonance effect, and we
concluded that the peak at around -3 eV wasderived from Ir 5d level.

Fig. 2. Dependence of the relative intensity ofthe small peak at around -3 eV on the
excitation energy.

Summary
We performed RPS measurements for Ir
nanoparticles deposited on SiO2/Si substrates. A
peak derived from Ir nanoparticles was observed ataround -3 eV and its intensity was enhanced by the
excitation energy corresponding to the 4f-5dtransition, indicating that this peak was derived fromthe Ir 5d level. By utilizing RPS, we could determine
the 5d energy level of Ir nanoparticles deposited on
SiO2/Si.
Acknowlegements
This work was partially supported by JSPS
KAKENHI Grant Number 19H02563.
References[1] S. Iijima and T. Ichihashi, Nature 363, (1993),
603.
[2] T. Maruyama et al., Appl. Surf. Sci. 509,
(2020), 145340.
[3] E. Bersch, et al., Phys. Rev. B 78, (2008),
085114.

Fig. 1. UPS spectra of Ir deposited SiO2/Si
substrate and SiO2/Si substrates
measured with the excitationenergy of (a) 58 eV and (b) 68 eV.

44

Effect of Atomic Hydrogen Exposure on HydrogenatedAmorphous Carbon Thin Films
Y. Haruyama1, D. Morimoto1, A. Heya2, K. Sumitomo2, S. Ito2, K. Yokota3, and M. Tagawa3
1
Laboratory of Advanced Science and Technology for Industry, University of Hyogo
2
Graduate School of Engineering, University of Hyogo
3
Graduate School of Engineering, Kobe University

Abstract

The effect of atomic hydrogen exposure on hydrogenated amorphous carbon (a-C:H) films wasinvestigated by an X-ray photoelectron spectroscopy (XPS). From the dependence of the wide-scan
XPS spectra of an a-C:H film on atomic hydrogen exposure, it was shown that the film was etchedwith an etching rate of 0.2 nm/min. In addition, the coordination of C atoms in the a-C:H film wasinvestigated as a function of the atomic hydrogen exposure and photoelectron emission angle. This
indicated that the coordination of C atoms at the surface of the a-C:H film was not influenced byatomic hydrogen exposure.

1. Introduction
Since amorphous carbon films haveinteresting properties such as high hardness, a
low friction coefficient, and chemical inertness,they have attracted a great deal of attention for awide range of applications [1, 2]. Owing to theirproperties, amorphous carbon films are mainly
used as coatings on industrial products such themagnetic heads and media of hard disk drives,
machine parts for molds, and cutting tools. In
addition, the effect of X-ray irradiation on
amorphous carbon films was studied as they are
expected to be used as lubricating coatings inspace [3]. It was reported that amorphous carbon
films are not etched by X-ray irradiation, whilehydrogenated amorphous carbon (a-C:H) films
are etched by X-rays [4, 5]. However, materials
in space applications are subjected not only to Xrays but also bombardment by hydrogen atoms.
Therefore, it is important to investigate the effectof atomic hydrogen exposure on amorphous
carbon films. Recently, it was reported thathydrogenated amorphous carbon films are etchedon exposure to atomic hydrogen at etching rates
dependent on the hydrogen contents of the a-C:H
films [6]. However, it is not clear whether thesurface electronic structure of amorphous carbon
films is influenced by atomic hydrogen exposure.
In this study, the effect of atomic hydrogen
exposure on a-C:H films was investigated by Xray photoelectron spectroscopy (XPS). emission
angle. The surface electronic structure of a-C:H
films after exposure to atomic hydrogen is
discussed based on analysis of the XPS spectra.

at% using the elastic recoil detection analysis
method.
Atomic hydrogen was generated using acatalytic chemical vapor deposition method [7].
A schematic diagram of the atomic hydrogengeneration apparatus is shown in Fig. 1. W meshcomposed of 0.03 mmφ wire at a density of 30
wires per inch was used as the catalyst and heatedat a temperature of about 1700 °C. An Ar (95%)
and H2 (5%) gas mixture at a pressure of 10 Pa
and flow rate of 100 sccm was used to produce
the atomic hydrogen. During atomic hydrogen
exposure, the sample temperature measured by a
type-K thermocouple was kept below 110 °C by
use of a water-cooled sample holder. The distance
between the sample and W mesh was 150 mm.
Since the atomic hydrogen generation apparatus
was connected to the photoelectron analysis
chamber through a gate valve, XPS spectra of thea-C:H films after atomic hydrogen exposure were
measured without exposing them to air.
All XPS measurements were performed on
the BL7B end station at the NewSUBARU
facility, University of Hyogo. The wide-scanand C 1s XPS spectra were measured as afunction of atomic hydrogen exposure with ahemispherical spectrometer (VG Scienta R3000).

2. Experiments
a-C:H films were formed on Si wafers by the
RF plasma method. The thickness of the a-C:H
films was about 300 nm. The hydrogenconcentration of the films was estimated to be 40

Fig. 1. Schematic diagram of the AHA apparatus.

45

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Fig. 3. Relative intensity ratio of O 1s peak to C
1s peak as a function of atomic hydrogen
exposure time.
Fig. 2. Wide-scan XPS spectra of hydrogenatedamorphous carbon film as a function of atomic
hydrogen exposure time.

increase of the atomic hydrogen exposure to 1740
minutes, the intensity of the peaks at ~750 and~530 eV increased and the peaks at ~1000 and~280 eV disappeared. This means that the a-C:H
film was etched by atomic hydrogen exposure.
From the change in the wide-scan XPS spectra,
the etching rate was estimated to be 0.2 nm/min.
The evolution of the wide-scan XPS spectrum in
Fig. 2 as a function of atomic hydrogen exposureshows the distribution of the chemicalcomposition with depth in the a-C:H film. In
other words, the depth profile of the a-C:H film
could be revealed by atomic hydrogen etching. In
Fig. 3, the relative intensity ratio of the O 1s peakto the C 1s peak (O 1s/C 1s) in the XPS spectrum
is plotted as a function of atomic hydrogen
exposure time. The O 1s/C 1s relative intensity
ratio was 0.7 before atomic hydrogen exposure,and decreased remarkably with increasing
exposure up to 60 minutes. Then, it decreased
slowly and was saturated at a value of 0.25 withincreasing exposure. These results indicate that
the O content was greater at the surface anddecreased remarkably with depth in the a-C:H
film. However, some O content remained in thefilm. There are two possibilities as to the originof the O content in the a-C:H film. One is O atom
diffusion from the surface into the a-C:H film.
The other is introduction of O atoms during theformation of the film. At present, we cannot
determine the origin of the O content in the a-C:H
film with certainty.
Figure 4(a) shows the XPS spectra of the C 1s
level in the a-C:H film as a function of the atomic
hydrogen exposure time. Before atomic
hydrogen exposure, a peak at 285 eV with a tailon the higher binding energy side was observed.
With increasing exposure, the tail was observed
to become smaller while the spectral features ofMg Kα line (hν = 1253.6 eV) was used as theexcitation source. The base pressure in thephotoelectron analysis chamber was 2×10-8 Pa.
3. Results and discussion
Figure 2 shows the wide-scan XPS spectra of
an a-C:H film as a function of atomic hydrogen
exposure time. The atomic hydrogen exposure
time is indicated beside each spectrum. XPS
spectra were normalized by the maximum peakintensity. Before atomic hydrogen exposure, fourpeaks originating from the C, and O atoms wereobserved in the XPS spectrum. The four peaks at~1000, ~750, ~530, and ~280 eV were assigned
to Auger levels for the C KVV and O KLL decay
processes and the O 1s and C 1s levels,
respectively [8]. The observation of peaks at~750 and ~530 eV suggests that O atoms arepresent on the surface of the a-C:H film. This isdue to the exposure of the sample to air after theformation of the a-C:H film. As the atomic
hydrogen exposure increased from 10 to 60
minutes, the intensity of the peaks at ~750 and~530 eV decreased gradually. On further
increasing the atomic hydrogen exposure up to1260 minutes, no clear change was observed in
the XPS spectrum. At 1500 minutes of exposure,the intensity of the peaks at ~750 and ~530 eV
increased suddenly while that of the peaks at~1000 and ~280 eV decreased. In addition, twopeaks at ~150 and ~100 eV appeared. The two
peaks at ~150 and ~100 eV were assigned to Si
2s and 2p levels, respectively [8]. This indicatesthat the two peaks at ~150 and ~100 eV
originated from the Si substrate. With further

46

electrons originating from sp2 hybridized, sp3
hybridized, C-H bonded, O=C-O bonded, C=O
bonded, and O-C-O bonded C atoms,
respectively. In Fig. 4(b), the best fitting results(lines) for the a-C:H film before and after atomic
hydrogen exposure for 1500 minutes are shown.
The five components in the a-C:H film, whichwere evaluated from the integrated area of eachcomponent, are summarized in Table I. With
increasing atomic hydrogen exposure, the C
contents with the O=C-O, the C=O, and the O-CO bonded C atoms decreased while the ratio of
the intensity of the sp3 hybridized and C-H
bonded C atoms to the sp2 hybridized C atoms
was unchanged. This indicates that thecoordination of the C atoms in the a-C:H film was
unchanged independent of the atomic hydrogen
exposure or O contents.
The effect of atomic hydrogen exposure on aC:H films was investigated by XPS. Exposure of
the a-C:H film to atomic hydrogen induced
etching of the a-C:H film. The etching rate wasestimated to be 0.2 nm/min. In addition, thecoordination of C atoms in a-C:H films wasfound to be unaffected by atomic hydrogen
exposure. This indicates that the surface of the aC:H film is not subject to damage by atomic
hydrogen exposure. Therefore, we propose thatthe depth profile of a-C:H films can be measured
with no damage by atomic hydrogen etching.

Fig. 4. (a) C 1s XPS spectra for the hydrogenatedamorphous carbon film as a function of atomic
hydrogen exposure time. (b) Fitting results (lines)
for the hydrogenated amorphous carbon film before
atomic hydrogen exposure and after atomic
hydrogen exposure of 1500 minutes.

the peak at 285 eV were unchanged. In a previous
photoelectron study, the C 1s spectrum at 285 eV
was decomposed into two components at 284.4
and 285.2 eV [9]. The component at 284.4 eV
was assigned to C 1s electrons originating fromthe sp2 hybridized C atoms, while the component
at 285.2 eV was assigned to C 1s electrons
originating from sp3 hybridized and C-H bonded
C atoms [9, 10]. Thus, the coordination of C
atoms was evaluated from the spectral features ofthe peak at 285 eV. The lack of change in the
spectral features of the peak indicates that thecoordination of C atoms in the a-C:H film was
not influenced by atomic hydrogen exposure. On
the other hand, the tail at the higher binding
energy side was assigned to C 1s electrons
originating from the C atoms bonded with O
atoms [11]. Therefore, the decrease in theintensity of the tail indicates that the O content in
the a-C:H film decreased with increasing atomic
hydrogen exposure. This is consistent with theresults obtained from the wide-scan XPS spectraof the film.
In order to clarify the coordination of C atoms,
curve-fitting analysis was performed on the C 1s
XPS spectra using a Mahan line shape functions.
Before the fitting procedure, the Shirley
background was subtracted from the C 1s XPS
spectra. The XPS spectra of the C 1s level in the
a-C:H film were reproduced by five components
positioned at 284.4, 285.2, 286.8, 287.5, and288.9 eV, which were assigned to the C 1s

References[1] J. Ullmann, Nucl. Instrum. Methods Phys.
Res., Sect. B 127, (1997), 910.
[2] H. Tsai and D. B. Bogy, J. Vac. Sci. Technol.
A 5, (1987), 3287.
[3] C. Donnet et. al., Surf. Coat. Technol. 68–69,(1994), 626.
[4] H. Kyuragi and T. Urisu, Appl. Phys. Lett. 50,(1987), 1254.
[5] K. Kanda et. al., Jpn. J. Appl. Phys. 50, (2011),
055801.
[6] A. Heya et. al., J. Photopolymer Sci. and Tech.
33, (2020), 419.
[7] A. Heya, A. Masuda, and H. Matsumura, Appl.
Phys. Lett. 74, (1999), 2143.
[8] C. D. Wagner et. al., Handbook of X-ray
photoelectron spectroscopy, ed. G. E.
Muilenberg (Perkin-Elmer, Eden Prairie,
Minnesota, 1978).
[9] Y. Haruyama et. al., Jpn. J. Appl. Phys. 47,(2008), 3380.
[10] Y. Haruyama et. al., Jpn. J. Appl. Phys. 48,(2009), 055505-3.
[11] A. Heya et. al., J. Photopolymer Sci. andTech. 33, (2020), 419.

47

Ⅱ

Fundamental Study of EUV Mask on EUV Lithography
at NewSUBARU Synchrotron Light Facility

Ⅱ

Takeo Watanabe, Tetsuo Harada, Shinji Yamakawa
Center for EUVL, Laboratory of Advanced Science and Technology for Industry, University of Hyogo, 3-1-2
Kouto, Kamigori, Akou-gun, Hyogo 678-1205, Japan
Abstract
Since 2019, EUV lithography has started to be used for the mass production of 7-nm-node-logic
devices. However, many significant issues on EUV lithography still remain in the fabrication of
future devices. The technical issues are the development technologies of resist, mask, and EUV lightsource. Therefore, many significant fundamental research has been carried out at our facility. Herethe EUV mask technologies is highlighted. It is described the fundamental research activities on
EUV lithography at NewSUBARU synchrotron light facility, which is related with EUV mask
technologies.
1. Introduction
Since 1996, the program of the research anddevelopment (R&D) on EUV lithography had been
started at the Laboratory of Advanced Science andTechnology for Industry, Himeji Institute Technology(HIT) (present University of Hyogo: UoH) using the
NewSUBARU synchrotron light source1,2. The
collaboration work was started between HIT, Nikon,
and Hitachi Central Research Laboratory in 1996. We
designed three aspherical imaging optics3 anddemonstrated the patterning of 42-nm-isolated line,
and 56-nm line and space using the ETS-1 exposure
tool which consisted of three-aspherical-imaging
optics1. And in ASET program, we demonstrated 60
nm L/S pattering in a full-field exposure area of 10
mm×10 mm using the 2nd version of ETS-1 withsynchronized mask and wafer stage system.4,5 Afterthat we involved in the three more consortiums suchas Selete, EUVA, and EIDEC, and we collaborated
with many domestics and overseas private companies,
institutes, and university in the fields of optics, resist,and mask technologies. The R&D of EUV resist
evaluation is listed on the papers.6-14 The Center for
EUVL was established in the Laboratory of Advanced
Science and Technology for Industry, UoH in October2010. The mission of this center is to accelerate and to
update the EUV technology toward the phase of highvolume manufacturing (HVM). We have total nine
beamlines at the NewSUBARU synchrotron lightfacility, and three beamlines are performed to use only
for the R&D on EUVL.

2. Evaluation Tools
For a EUV mask, it was prepared that 1) the in-bandreflectometer, 2) the bright field EUV microscope forthe defect inspection of EUV masks, and 3) the EUV
coherent scatterometry microscope (CSM) for thedefect characterization of EUV masks. In addition, thelarge reflectometer for the measurement of a large
collector mirror for the EUV-laser-produced-plasma
light source was installed at the BL10B beamline. The
EUV-CSM method has a capability for the various
application including resist defect inspection.
Recently, it is prepared that 1) the high-power
exposure tools in hydrogen atmosphere in the samepressure condition of ASML EUV exposure tool toevaluate the radiation hardness of the materials which
is used for the EUV masks, and 2) the out of band
reflectometer for the EUV mask evaluation.
1.1 NewSUBARU synchrotron light facility
NewSUBARU synchrotron light facility wasestablished at the Laboratory of Advanced Scienceand Technology for Industry, University of Hyogo,
Japan in 1994. This synchrotron facility is the largest
facility which is operated by university in Japan. The
main mission of this facility is the usage of theindustrial application to support the development of
the advanced technology. The NewSUBARU storage
ring is middle-size electron-beam storage ring and thecircumstance is approximately 120 m. In this facilitynine beamlines have been operated. The Center for
EUVL was established in 2010 at this laboratory tosupport the EUV lithographic technology for the
productions of advanced semiconductor devices. Thiscenter has three beamlines for the fundamental
research on EUV lithography as shown in Fig.1.

From 2019, EUV lithography was started to use forthe mass production of 7-nm-node-logic devices.
However, many significant issues on EUV
lithography still remain for the fabrication of future
devices. Therefore, many significant fundamental
research concerning EUV masks including pellicles,
resists, and EUV optical element have been carried out
in our facility. This paper focuses about the various
evaluation system which are installed at
NewSUBARU beamlines.

NewSUBARU has restarted after an innovative
renewal from April 20th, 2021. As the light intensityof the synchrotron radiation has improved up to48

approximately 20%, the research and development offurther advanced lithographic technologies including
EUVL can accelerate. NewSUBARU is adjacent toSPring-8, electron beam has been supplied to generate
synchrotron radiation from SPring-8. From recent
years, aiming for more advanced operation, we havepromoted the construction of a new injection system(c-band linear acceleration (linac) system) which canself-sufficient electrons to the NewSUBARU storage
ring. In 2020, a new injector and an electron gun thatgenerates electrons were installed, and after a trial run
and adjustment of the new system in 2021, the user
operation of NewSUBARU has started.

this huge reflectometer. The configuration of thisreflectometer is shown in Fig. 3. The height and widthof the reflectometer are approximately 2.9 m and 2.6m, respectively. The reflectivity spectra which were
measured at NewSUBARU and PTB are shown in Fig.
4 for the round robin mirror sample. The reflectivity
spectra of those are consistent between each other. So
our huge reflectometer is assigned to be the world
standard one.

(a)

(b)

(a)
(b)

BL03
zzzzzz(b)

Figure 2. (a) Beamline setup of BL10A beamline for the
EUV reflectometer, and (b) photograph of BL10A.

BL09
BL10

Til
Y

φ800 mmθ2

Figure 1. Three beamlines for the fundamental
research on EUV lithography, (a) BL03, and (b) BL09d BL10Z

1.2 In-band reflectometer for EUV masks andoptical elements

EUV

In EUV lithography, Mo/Si multilayer (ML) is used
for the reflect the EUV light. The optics for EUV
lithography and EUV mask is reflective -type and they
are employing Mo/Si multilayer. To maintain the highthroughput of the circuit patterning on a wafer the highreflectivity of Mo/Si multilayer is significant. At
BL10A beamline, the multilayer reflectometer had
been installed. The beamline setup and its photographare shown in Fig. 2(a) and (b), respectively. The
wavelength resolution is approximately λ/3000.

Figure 3. System configuration of large reflectometer.

Peak reflectance (%)

65

In order to increase the power of the laser produced
plasma (LPP) EUV light source, the huge collector
mirror is necessary. Thus, the huge reflectometer forthe reflectivity measurement for the huge collector
mirror of the LPP EUV light source had been installedat the BL10B beamline.15 The Mo/Si ML mirror
which has a size up to 800-mm-diameter and 50-mmthick, and a weight up to 50 kg can be measured using

60
55

NewSUBARU
Left
Right
PTB
Left
Right

50
45
20

40

60

80 100 120 140 160 180 200
Radial position (mm)Figure 4. The round robin reflectance measurement
results between NewSUBARU and PTB.

49

Ⅱ

1.3 Bright field EUV microscope16, 17 for the EUV
mask defect inspection

image of 88 nm line and space (L/S) pattern with a 30
nm line defect can be reconstructed by the iteration
calculation method from the diffraction image. And
the mask defect signals can be observed by thediffraction images as a horizontal line signal.

The bright filed mask inspection tool was installed at
the BL03B beamline.18,19 This tool consists of theloadlock chamber to exchange a EUV mask, main
observation chamber to observe the absorber patternimage of EUV mask, and the zooming tube forforming the image of the mask pattern, theSchwarzschild-type imaging optics was employed as
a 30X magnification optics to observe the mask
pattern image combined with the 200X zooming tube.
The zooming tube consists of CsI and electromagnetic lens, and micro-channel plate (MCP), andCCD camera. Thus, total magnification of the mask
pattern can achieve 6,000X. The system configurationis shown in Fig. 5. Using this system, the criteria
between printable and non-printable regions byparameters of defect width and depth was clarified asshown in Fig. 6.20 The horizontal and vertical axes
indicate the width and height of the programmed
defects of EUV mask.

Ⅱ

Figure 7. System configuration of the standalone CSM
system with the high harmonic gas laser system.

As shown in Fig. 8, using Fresnel zone plate, thecoherent EUV light can focus on a mask within 140
nm in diameter. This system so-called micro-CSM.
Using this micro-CSM, the natural defect observation
was succeed as shown in Fig,s 9 and 10. Figures 9 and
10 are shown the intensity and phase reconstructed
images using micro-CSM, respectively. The microCSM observation results is consistent those of atomic
micro force (AFM). The smallest with of the mask
bump defect of 33 nm×28 nm in size and 1.7 nm inheight can be observed.23, 24z
Figure 5. System configuration of brightfield EUV
microscope.
54Line-pit defects
Resolved
Not resolved

3Hole-pit defects
Resolved
Not resolved

Depth (nm)Printable area

2

1

Figure 8. System configuration of micro-CSM.

Non-printable area

0
0

10 20

30

40

50 60

70

80

90 100 110 120 130 140 150

Width (nm)Figure 6. Defect threshold between printable and nonprintable.

1.4 EUV coherent scatterometry microscope for
the EUV mask defect inspection
The system configuration of EUV coherent
scatterometry microscope (CSM) and is shown in Fig.
7.21, 22 The high harmonic laser was employed as alight source of the EUV CSM. The coherent light canbe produced by the pin hole and the diffraction image
by the EUV coherent light can be observed by the
charged couple device (CCD) camera. The EUV mask

Figure 9. Intensity distribution result of mask dump
natural defect of 33 nm×28 nm in size and 1.7 nm inheight.

50

contamination removal modes depend on thehydrogen pressure. In the high and low hydrogenpressure regions, the carbon removal and the carbon
contamination occur dominantly, respectively. And
the Mo/Si multilayer damages might occur by theexistence of the particle additive during the multilayer
sputtering process.

Figure 10. Phase distribution result of mask dump
natural defect of 33 nm×28 nm in size and 1.7 nm inheight.

1.5 High power EUV exposure tool in hydrogen
atmosphere
Figure 12. The study results of the reflectivity changes
during high power EUV exposure as the parameter ofthe hydrogen pressures.

The hydrogen environment in the exposure tool25
which is employed in high volume manufacturing toprotect from the carbon contamination during the
EUV exposure. However, since hydrogen is thesmallest atom and it is easy to diffuse into thematerials, the hydrogen embrittlement is more likely
to occur to not only the mask materials such as
absorber, Mo/Si multilayer, and pellicle but also theresist materials, and the patterning characteristics
becomes worse. Thus, the high power EUV exposure
tool in hydrogen atmosphere is prepared at the BL09A
beamline to study the hydrogen embrittlement of EUV
masks and resists. The photograph of this system isshown in Fig. 11. The hydrogen can be introduced up
to 70 Pa. And the EUV power up to 30 W/cm2 on asample can be supplied.

2. CONCLUSIONS
From 2019, EUV lithography was started to use forthe mass production of 7-nm-node-logic devices.
However, many significant issues on EUV
lithography still remain for the fabrication of future
devices such as 5-nm-node and beyond. The technicalissues are the development technologies of resist,mask, and EUV light source. Therefore, many
significant fundamental researches have been carriedout at our facility. It is focused on the fundamental
research activities on EUV lithography at
NewSUBARU synchrotron light facility, which isrelated with EUV mask technologies such as 1) the inband reflectometer for EUV masks and opticalelements, 2) bright field EUV microscope for the EUV
mask defect inspection, 3) EUV coherent
scatterometry microscope for the EUV mask defectinspection, 4) high power EUV exposure tool inhydrogen atmosphere, 5) out of band (OoB)
reflectometer. Using these tools, EUV lithography
R&D will continue for the next generation lithography
to use the EUV lithography to guarantee the future
mass production of EUVL.

Figure 12 shows the results of the reflectivity changes
during high power EUV exposure as the parameter ofthe EUV exposure dose and the hydrogen pressure. it
is found out that the contamination mode and

REFERENCES[1] Ando, A., Amano, A., Hashimoto, S., Kinoshita,H., Miyamoto, S. Mochizuki, T., Niibe, M., Shoji, Y.,
Terasawa, M., and Watanabe, T., “VUV and Soft Xray Light Source “NewSUBARU,” Proc. of the 1997
Particle Accelerator Conference, 757-759 (1998).
[2] Hashimoto, S., Ando, A., Amano, S., Haruyama,Y., Hattori, H., Kanda, K., Kinoshita, H., Matsui, S.,

Figure 11. the hydrogen embrittlement evaluation toolof EUV masks and resist.

51

Ⅱ

Ⅱ

Mekaru, H., Miyamoto, S. Mochizuki, T., Niibe, M.,
Shoji, Y., Utsumi, Y., Watanabe, T., and Tsubakino,
H., “Present Status of Synchrotron Radiation Facility“NewSUBARU”,” Trans. Materials Research Soc.
Japan, 26, 783-786 (2001).
[3] Watanabe, T., Mashima, K., Niibe, N., andKinoshita, H., “A Novel Design of Three-AsphericalMirror Imaging Optics for Extreme Ultra-Violet
Lithography,” Jpn. J. Appl. Phys., 36, 7597-7600(1997).
[4] Watanabe, T., Kinoshita, H., Nii, H., Li, Y.,
Hamamoto, K., Oshinio, T., Sugisaki, K., Murakami,
K., Irie, S., Shirayone, S., Gomei, Y., and Okazaki, S.,“Development of the Large Field Extreme Ultraviolet
Lithography Camera,” J. Vac. Sci. Technol., B18,
2905-2910 (2000).
[5] Watanabe, T., Kinoshita, H., Hamamoto, K.,
Hosoya, M., Shoki, T., Hada, H., Komano, H., andOkazaki, S., “Fine Pattern Replication Using ETS-1
Three-Aspherical Mirror Imaging System,” Jpn, J.
Appl. Phys., 41, 4105-4110 (2002).
[6] Watanabe, T., Kinoshita, H., Sakaya, N., Shoki,T., and Lee, S. Y. “Novel Evaluation System for
Extreme Ultraviolet Resist in NewSUBARU,” Jpn. J.
Appl. Phys., 44, 5556-5559 (2005).
[7] Watanabe, T., Kinoshita, H., Nii, H., Hamamoto,K., Tsunakino, H., Hada, H., Komano, H., and Irie, S.,“Photoinduced Outgassing from the Resist for Extreme
Ultraviolet Lithography by the Analysis of Mass
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[8] Watanabe, T., Kikuchi, Y., Takahashi, T.,
Katayama, K., Takagi, I., Sugie, N., Tanaka, H.,
Shiobara, E., Inoue, S., Harada, T., and Kinoshita, H.,“Development of Tool for Contamination Layer
Thickness Measurement Using High Power Extreme
Ultraviolet Light and in Situ Ellipsometer,” Jpn. J.
Appl. Phys. 52 (2013) pp.056701-1, 056701-5.
[9] Ohnishi, R., Watanabe, T., Fukushima, Y., Osugi,M., and Kinoshita, H., “Transmission Measurement
Using Extreme Ultraviolet Light for the Developmentof Extreme Ultraviolet Resist,” Jpn. J. Appl. Phys., 48,
06FA08 (2009), 06FA08.
[10] Niihara, S., Mamezaki, D., Watanabe, M.,
Harada, T., and Watanabe, T., “Absorption Coefficient
Measurement Advanced Method of EUV Resist byDirect-Resist Coating on a Photodiode,” J.
Photopolym. Sci. Technol., 30, 87-92 (2017).
[11] Urayama, T., Watanabe, T., Yamaguchi, Y.,
Matsuda, N., Fukushima, Y., Iguchi, T., Harada, T.,
and Kinoshita, H., “EUV Interference Lithography for
1X nm,” J. Photopolymer Sci. Technol., 24, 153-157(2011).
[12] Yoshifuji, M., Niihara, S., Harada, T., Watanabe,T., “Fabrication of High-Aspect-Ratio Transmission
Grating Using DDR Process for 10-nm EUV Resist
Evaluation by EUV Interference Lithography,” J.
Photopolym. Sci. Technol., 31, 215-220 (2018).
[13] Watanabe, T., Haruyama, Y., Shiono, D.,
Emura, K., Urayama, T., Harada, T., and Kinoshita, H.,“Chemical Reaction Analysis of EUV CA Resist using
SR Absorption Spectroscopy,” J. Photopolymer Sci.
Technol., 25, 569-574 (2012).
[14] Kuki, M., Uemura, T., Yamaguchi, M., Harada,
T., Watanabe, T., Muramatsu, Y., and Kinoshita, H.,“Development of High=Reflective W/Si-multilayer
Diffraction Grating for the Analysis of Fluorine
Materials,” J. Photopolym. Sci. Technol., 28, 531- 536(2015).
[15] Iguchi, H., Hashimoto, H., Kuki, M., Harada, T.,
Watanabe, T., and Kinoshita, H., “Development of areflectometer for a large EUV mirror in
NewSUBARU,” Proc. SPIE, 9658, 965819 (2015).
[16] Haga, T., Kinoshita, H., Hamamoto, K., Takada,S., Kazui, N., Kakunai, S., Tsubakino, H. and
Watanabe, T., “Evaluation of finished extreme
ultraviolet lithography (EUVL) masks using a EUV
microscope,“ Jpn. J. Appl. Phys., 42(Part 1, No. 6B),
3771–3775 (2003).
[17] Watanabe, T., Haga, T., Shoki, T., Hamamoto, K.,
Takada, S., Kazui, N., Kakunai, S., Tsubkino, H., andKinoshita, H., “Pattern inspection of EUV mask using
a EUV microscope,” Proc. SPIE, 5130, 1005-1013(2003).
[18] Hamamoto, K., Tanaka, Y., Lee, S. Y.,
Hosokawa, N., Sakaya, N., Hosoya, M., Shoki, T.,
Watanabe, T. and Kinoshita, H., “Mask defectinspection using an extreme ultraviolet microscope,” J.
Vac. Sci. Technol., B23, 2852-2855 (2005).
[19] Mizuta, Y., Osugi, M., Kishimoto, J., Sakaya, N.,
Hamamoto, K., Watanabe, T., and Kinoshita, H.,“Development of Optical Component for EUV PhaseShift Microscopes,” Proc. SPIE, 6517, 651733 (2007).
[20] Takase, K., Kamaji, Y., Sakagami, N., Iguchi, T.,
Tada, M., Yamaguchi, Y., Fukushima, Y.,Harada, T.,
Watanabe, T. and Kinoshita, H., “Imaging
Performance Improvement of an Extreme Ultraviolet
Microscope,” Jpn. J. Appl. Phys., 49, 06GD07 (2010).
[21] Harada, T., Nakasuji, M., Kimura, T., Watanabe,
and T., Kinoshita, H., “Imagingof extreme-ultraviolet
mask patterns using coherent extreme-ultraviolet
scatterometry microscope based on coherent
diffraction imaging,” J. Vac. Sci. Technol., B29,
06F503 (2011).
[22] Nakasuji, M., Tokimasa, A., Harada, T., Nagata,Y., Watanabe, T., Midorikawa, K., and Kinoshita, H.,“Development of coherent extreme-ultraviolet
scatterometry microscope with high-Order harmonic
generation source for extreme-ultraviolet mask
inspection and metrology,” Jpn. J. Appl. Phys., 51,
06FB09 (2012).
[23] Harada, T., Hashimoto, H., Amano, T., Kinoshita,
H. and Watanabe, T., “Actual defect observation
results of an extreme-ultraviolet blank mask bycoherent diffraction imaging,” Appl. Phys. Express, 9,035202 (2016).
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[26] Tsuda, K., Harada, T., Watanabe, T.,“Development of an EUV and OoB Reflectometer at
NewSUBARU Synchrotron Light Facility,” Proc.
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micro coherent EUV scatterometry microscope,” Proc.
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[25] Ohgata, A., Harada, T., and Watanabe, T.,“Development of High-Power EUV Irradiation Tool in
Hydrogen Atmosphere,” MNC2019, Hiroshima, Japan,[27] 481N (2019).

53

ⅡHydrogen Cleaning Evaluation of Mo/Si Multilayer
Using an EUV Irradiation Tool at NewSUBARU

Ⅱ

Tetsuo Harada, Shinji Yamakawa, Takeo Watanabe
Center for EUVL, LASTI, Univ. of Hyogo

Abstract

Beamline optics of BL-09C for the EUV irradiation tool was upgrade. The irradiation intensity was
improved from 6 W/cm2 to 30 W/cm2, which is enough high to evaluate mask and pellicle material
for next generation EUV exposure tool. The preliminary irradiation result of Mo/Si multilayer
sample was reported. Carbon contamination was removed by the EUV irradiation with hydrogengas (70 Pa).

1. Introduction
In EUV lithography, the carbon contamination
causes the reflectance decrease of a Mo/Si multilayerand deterioration of resolution performance. The originof the contamination is residual carbon gas in thevacuum chamber, which is contaminated on the mirror
under the high-power EUV irradiation. In order toreduce the contamination, hydrogen gas is introduced in
the EUV lithography scanner. However, there is few
reports for contamination cleaning performance of thehydrogen gas. On the other hand, Mo/Si multilayer
could be damaged by the EUV-induced hydrogenplasma which would diffuse into the interface between
Mo and Si layers. In order to evaluate this damage andcleaning effect, the EUV irradiation tool (Fig. 1) inhydrogen gas atmosphere has been developed at theBL-09-long-undulator beamline of the NewSUBARU
synchrotron light facility [1, 2]. We upgraded thebeamline to increase the irradiation intensity.
As the result the EUV irradiation intensity was up to
30 W/cm2, which are equivalent to the EUV source
power of 900 W for the mask evaluation and 600 W forthe pellicle evaluation, respectively. The EUV dose wasFig. 2. Photograph of a Mo/Si multilayer before
and after EUV irradiation withhydrogen gas.
108 kJ/cm2 per hour. The hydrogen gas pressure was up
to 70 Pa.
2. Experiments and Results
The irradiation sample was a Mo/Si multilayer on
glass substrate. The surface of the sample was carbon
contaminated shown in Fig. 1. The EUV power was 30
W/cm2, and the hydrogen pressure was 70 Pa. The beam
size on the sample was 0.5 mm (V) × 1.2 mm (H). The
irradiation time was 9.5 hours, which was corresponded
to 960 kJ/cm2. The carbon contamination on theirradiated position was cleaned shown by an arrow in
Fig. 1. This result significantly shows the EUV induced
plasma can clean carbon contamination. In addition,
there was no damage (no blister) on the irradiation
position.
References[1] T. Harada, et al., Jpn. J. Appl. Phys. 60, (2021),
087005.
[2] T. Harada, et al., Proc. SPIE 11908, (2021) 119080U.

Fig. 1. Photograph of EUV Irradiation Tool at
NewSUBARU BL-9C.

54

X-ray Absorption Spectroscopy of Liquids and Gases
using a Simple Liquid Cell
Tomoki Eguchi, Koji Takahara, Satoru Suzuki
LASTI, University of Hyogo

Abstract

Our laboratory has been developing a simple liquid cell for scanning electron microscopy observation. Here,we applied the liquid cell to X-ray absorption spectroscopy of liquid and gas samples at NewSUBARU BL9A. Xray absorption spectra were obtained for water, ammonia borane solution, Γ-butyrolactone, and atmosphericnitrogen.

films (NTT-AT Co., Tokyo) as electrontransmission windows, the thicknesses of the SiN
and SiC films were 100 nm and 200 nm,
respectively, and the dimensions were 1.5 mm × 1.5
mm , 1.44 mm × 0.43 mm. XAS measurements were
performed at the synchrotron radiation facility
NewSUBARU BL09A using a high-brightness lightsource and a high-resolution spectrometer on a longundulator, and were performed at room temperature
in vacuum using the fluorescence yield method.

1. Introduction
Unlike solid sates, the analysis of liquid samples
is generally considered very difficult in soft X-ray
absorption spectroscopy (XAS), which requires
measurement under vacuum, because the shape is
not fixed and evaporation occurs. There have beenvarious approaches to synchrotron radiation
analysis of liquids [1-2]. As an example, in soft Xray emission using synchrotron radiation, themeasurement of liquid water using a liquid pumping
cell with a silicon nitride (SiN) thin film as awindow material has been reported [3-4]. We
developed a simple liquid cell to seal the liquid andgas [2], which enables a simple XAS measurement
without the need for additional special equipment.
In this experiment, we used encapsulated simple
liquid cells. We performed a certain number of XAS
measurements using the simple liquid cells, but thetransmission window was not broken after themeasurements. At the NewSUBARU BL9A, theprepared samples can be used not only for XAS but
also for X-ray emission spectroscopy (XES) andphotoelectron emission microscopy (PEEM), whichenables many synchrotron radiation analyses in a
microscopic region.

3. Results and discussion
Figure 2 shows the X-ray absorption spectrumof H2O (liquid) measured. Three peaks are observed
around O K region of water. the pre-peak observed
at 535 eV is mainly associated with broken or
weakened hydrogen bonds, indicating a transition
from the 1s orbital of oxygen to 4a1 of oxygen. The
main-peak observed at 537.7 eV is associated withthe presence of interstitial water molecules,
indicating a transition from the 1s orbital of oxygento 2b2 of oxygen. These two peaks can beunderstood in terms of hydrogen bonding effects,
since the excited states of both 4a1 and 2b2 of gas

2. Experiments
Figure 1 shows a schematic diagram of thesimple liquid or gas cell for XAS created in thisexperiment. Liquid cells were fabricated using Si
chips with SiN films (Silson Ltd., England) or SiC

Fig. 1. Schematic diagram of the simple liquid
or gas cell.

Fig. 2. The X-ray absorption spectrum of H2O(liquid) around O K region.

55

Ⅱ

In Figure 4(a), the absorption edge of boron wasobserved at 194 eV, and in Figure 4(b), theabsorption edge of nitrogen was observed at 400.7
eV. However, due to insufficient concentration, thedetected light intensity is low and strongly affectedby the background shape.
We report the X-ray absorption spectrum of Γbutyrolactone (GBL), for which there are currently
no reported cases. Figures 5 show the X-ray
absorption spectra of Γ-butyrolactone, respectively,
divided by the spectrum of washed gold withhypochlorous acid. In general, gold mesh is often
used as a light intensity monitor in soft X-ray
absorption measurements at the C-K absorption
edge using synchrotron radiation. However, inbeamlines not equipped with a vacuum deposition
system, it is very difficult to measure accurate
spectra because carbon absorption structures appear
in the background. In soft X-ray absorption
measurements at the C-K absorption edge, washinggold with hypochlorous acid is effective inremoving contamination due to carbon adsorption.

Ⅱ

Fig. 3. The X-ray absorption spectrum ofnitrogen in air around N K region.

phase water are polarized toward hydrogen atoms
and are thus sensitive to hydrogen bond donation.
Then, the post-peak originating from hydrogenbonding were observed at 541-543 eV [5-7]. These
values are generally consistent with the reported
XAS values for H2O (liquid), and it can be said thatthe simple liquid cell is applicable to XAS
measurements for liquid samples.
Figure 3 shows the X-ray absorption spectrumof nitrogen in air measured in this experiment. Fourpeaks were observed in the absorption spectrum of
atmospheric nitrogen. The peak at 400.7 eV
indicates a transition from the 1s orbital to the 1π
orbital of nitrogen, and the peak at 406.7 eV
indicates a transition from the 1s orbital of oxygento the electronically. It indicates a transition fromthe 1s orbital of oxygen to the Rydberg state, which
is an excited state with an energy following the
Rydberg formula. The broad bulge around 410 eVis due to the ionization energy threshold. The
ionization energy threshold is the energy required tocompletely liberate an electron from the ionic coreof an atom or molecule. The energies of the
Rydberg series converge to ionization states withionization energies: the peak observed between 414
eV and 415 eV indicates a transition to a doubly
excited state, and the peak near 419 eV indicatesshape resonance [8].These values are generally
consistent with those reported for nitrogen gas [8],indicating that the simple liquid cell is applicable to
XAS measurements of gaseous samples.
We report the X-ray absorption spectra ofaqueous ammonia borane solutions. Figures 4 show
the X-ray absorption spectra of aqueous ammonia
borane solutions, respectively. In this experiment, 1
mol/L aqueous ammonia borane solution was
prepared and XAS measurements were performed.

Fig. 4. the X-ray absorption spectra of aqueous
ammonia borane around (a) B K and (b)N K region.

56

4. Conclusion
In this experiment, the following results wereobtained by performing XAS measurements with
the NewSUBARU BL9A using a modified simple
liquid cell for SEM. First, the simple liquid cell is
now applicable to XAS measurements of liquid andgaseous samples, which are considered difficult tomeasure with the NewSUBARU BL9A. Then, Xray absorption spectra of aqueous ammonia boron
solution and Γ-butyrolactone, which is not reported
at present, were reported and their peaks wereanalyzed. In the future, we will expand theapplication of the simple liquid cell to X-ray
emission spectroscopy (XES) and photoelectron
emission microscopy (PEEM) in order to improve
the accuracy of synchrotron radiation analysis at
NewSUBARU BL9A.

effective in removing contaminants [14]. We
analyzed each peak with reference to the peaks [1013] identified in compounds such as PBT and PET,
which have similar structures and, like GBL, ester
groups.
From Figure 5(a), a peak indicating the transition of
C=O to the π* orbital at 532.5 eV, a peak indicating
the transition of C-O to the π* orbital at 535 eV, apeak indicating the transition of C-O-C to the σ*
orbital, which is not observed in the carboxyl groupand is unique to ester groups, at 538~539 eV, and at
542 eV a peak indicating the transition of C-O to thepeak indicating the transition to the C-O σ* orbital
was observed at 542 eV. From Fig. 5(b), peaks
indicating transitions to the π* orbital of aromaticrings at 285 eV and 287.2 eV, and a peak indicatinga transition to the π* orbital of C=O at 288.3 eV
were observed. At 289~291 eV, broad peaks
indicating transitions of C=C (aromatic ring), C-C,
C=O, and C-O to the σ* orbital were observed.

References[1] S. Adachi et al., The Japanese XAFS Society(2017).
[2] K. Takahara et al., J. Appl. Phys. 130, (2021),
025302.
[3] T. Tokushima, Mol. Sci. 9, (2015), A0077.
[4] T. Tokushima et al., BUNSEKI KAGAKU 64,(2015), 237.
[5] G. Pan et al., Langmuir 32, (2016), 11133.
[6] T. Fransson, Y. Harada et al., ACS. Chem. Rev.
116, (2016), 7551.
[7] J. A. Sellberg et al., J. Chem. Phys. 141,（2014）, 034507.
[8] C. T. Chen et al., Phys. Rev. A 40, (1989), 6737.
[9] M. Morishita et al., RCS Adv. 11, (2021), 14063.
[10] T. Okajima, K. Teramoto et al., J. Phys. Chem.
A 102, (1998), 7093.
[11] Y. Zubavichus, A. Shaporenko et al., J. Phys.
Chem. A 109, (2005), 6998.
[12] F. Frati, M. O. J. Y. Hunault, et al., Chem. Rev.
120, (2020), 4056.
[13] T. Okajima J. Surf. Sci. Soc. Jpn. 23, (2002),
359.
[14] Yasuji Muramatsu, Adv. X-Ray. Chem. Anal.
Jpn. 41, (2010), 127.

Fig. 5. X-ray absorption spectra of Γbutyrolactone around (a) O K and (b)C K regions.

57

ⅡIn-situ XANES Measurements of the Heated Sugar
for Clarifying the Melting Point FluctuationⅡ

Kae Hiramatsu, Yasuji Muramatsu
Graduate School of Engineering, University of Hyogo
Abstract

To clarify the fluctuation of melting point (mp) in sugars, C K and O K-XANES measurements were
performed while the sugar samples were heated from room temperature (RT) to 180°C. The in-situ
XANES spectra of heated sugar exhibited profile change dependent on heating temperature, whichsuggests thermal transformation of sugars. From theoretical XANES analysis using molecular
dynamics (MD) and density functional theory (DFT) calculations, it is suggested that the thermaltransformation of sucrose molecules depends on hydrogen bonds.

1. Introduction
Sugar consists of sucrose (C12H22O11) molecule.
Although commercially-available sugar is generally
highly purified material, it usually takes a wide
melting point (mp) range of 140-190 oC, dependingon the sugar manufacturing process, purification
methods, particle shape, and particle size. To clarify
the mp fluctuation, we have measured X-ray
absorption near-edge structure (XANES) in the C K
and O K regions of various sugar samples [1]. It canbe found that the 534.5 eV peak intensity in O KXANES depends on mp. The 534.5 eV peak can be
assigned to hydrogen bonds in water molecules [2].
Hence, it is suggested that hydrogen bonds formedin sucrose molecules affect the mp. To
experimentally clarify the fluctuations of sugars, wehave developed a sample heating system in the Xray absorption analysis station in BL10 [3, 4].
In the present study, in-situ XANES
measurements of sugars under heating were
performed by using the heating system. In addition,
theoretical XANES analysis was performed by using
molecular dynamics (MD) and density functional
theory (DFT) calculations to clarify the effect ofhydrogen bonds in sugars.

calculations by using the MD code of Forcite on the
Materials Studio platform (Dassault Systems). Initialconditions in the MD calculations were set to 30
molecules of sucrose with a temperature of 273 K
and a density of 0.92 g/cm3. In the MD calculations,hydrogen bonds can be formed among the sucrose
molecules. To simulate XANES of sucrose
molecules, two-sucrose-molecules model formingintermolecular hydrogen bonds were extracted fromthe stable states in MD calculations. XANES
simulations of the two-sucrose-molecules model
were performed by using the DFT calculation codeof CASTEP [5] on the Materials Studio platform. In
a super cell, distance between cell walls andcalculation model edge was set longer than 5 Åwhich is sufficiently longer than chemical bonds.
After the calculations in the ground state and theexcited state with a core hole in the C 1s or O 1s
orbitals of each atom, calculated XANES spectra
were obtained from transition probabilities.
3. Results and Discussion
3.1. In-situ XANES of Heated Sugars
Figure 1 shows the in-situ C K-XANES of sugars
heated between RT-180 ℃ and references of sucrose,
glucose, and fructose, which are normalized by theσ* peak intensity at 293.7 eV. In heated sugars,
spectral differences dependent on heating
temperature were clearly observed around 285 eV,287.5 eV, and 289.2 eV. The peak at 285 eV can be
assigned to π* peak of sp2 carbons. Although sucrose
molecules do not have sp2 carbon, commerciallyavailable sugars generally contain minor amounts ofreducing sugars, which includes sp2 carbons.
Therefore, the π* peak observed at RT was
considered as the initial reducing sugar. Although
there is little change in the π* peak intensity at RT
and 120 ℃, the peak intensity increased between
150–180 ℃. This means that sucrose molecules are
reduced by heating above mp.
The shoulder intensity at 287.5 eV (denoted bya) clearly decreased as the heating temperature

2. Experiments and Calculations
2.1. X-ray Absorption Measurements
Granulated sugar with a melting point of 153 °C
was used for X-ray absorption measurements.
XANES spectra in the C K and O K regions were
measured with a total electron yield (TEY) method
while heating from room temperature to 180 °C. Thebase vacuum of the measurement chamber was 10-6
Pa. During heating up to 180 °C, the vacuum
remained in the 10-5 Pa range. Hence in-situ XANES
measurements of melted sugars under heating can be
successfully performed.
2.2. MD and DFT Calculations
Calculation models of sucrose molecules wereobtained with the molecular dynamics (MD)58

peak intensity slightly increased between 150–
180 ℃. Such a π* peak evolution, which depends on
temperature in O K-XANES, corresponds to that in
C K-XANES. It is therefore confirmed that sucrose
molecules in sugars are partially reduced by heating
above mp.
Spectral intensities near 545 eV decreased as theheating temperature increased from RT to 180 ℃.
Compared to the reference compounds, referencecompounds exhibit shoulders near 533 eV,corresponding to the π* peak. This suggests that thereference compounds partially contain reducing
forms with carbonyl (>C=O) O atoms. Although σ*
peak can be observed near 538 eV in the referencecompounds and sugars, sugars exhibit wider σ* peak
profile than reference compounds; Full width at half
maximum (FWHM) of sugars is approximately 11
eV and that of the reference compounds is 8 eV.
Especially, sugars exhibit the longer tailing to 545 eV.
Such the broadening of XANES profile suggests
intermolecular interactions of O atoms in sugars.
Referring to the O K-XANES of water (H2O) in gas,liquid, and solid phases [2], the observed σ* peakbroadening in 538 - 545 eV region of sugars can be
explained by the formation of hydrogen bonds.
Decrease of spectral intensities near 545 eV byheating can also be explained by decrease ofhydrogen bonds in melted sugars than in solid sugars.
This suggests that in-situ O K-XANES

Fig. 1. In-situ C K-XANES of sugars heatedbetween RT (27 ℃)-180 ℃ andreferences.
increased between 150–180 ℃. Additionally, thepeak intensity at 289.2 eV (denoted by b) slightly
increased as the heating temperature increased. It is
well known that sucrose can be decomposed into
glucose and fructose [6]. Compared to the referencecompounds, reference compounds exhibit theshoulder at 287.5 eV, which corresponds to theshoulder a of heated sugars. The 287.5 eV shoulder
intensity of sucrose is higher than that of fructose
and glucose. Therefore, the decreased shoulder aintensity of heated sugars can be explained by thethermal decomposition of sugars (sucrose) intofragment molecules like glucose and fructose. The
reference compounds also exhibit sharp peaks at
289.2 eV, corresponding to the peak b of heatedsugars. The 289.2 eV peak intensity of sucrose islower than that of glucose and fructose. Therefore,
the increased peak b intensity of heated sugars canalso be explained by the thermal decomposition ofsugars into the molecules like glucose and fructose.
It is therefore confirmed that the in-situ C K-XANES
measurements can directly observe thermaltransformations (decompositions) of sugars.
Figure 2 shows the in-situ O K-XANES of sugars
heated at RT-180 ℃ and references of sucrose,
glucose, and fructose, which are normalized by theσ* peak intensity at 539.2 eV. The spectral
differences depend on heating temperature wereslightly observed around 533 eV and 545 eV. The
peak at 533 eV was assigned to π* peak of sp2
oxygens. The π* peak can be explained by carbonyl(>C=O) O atoms in partially contained reducing
sugars, as mentioned above for the π* peak in the C
K-XANES. Although the change in the π* peakintensity was negligible between RT–120 ℃, theFig. 2. In-situ O K-XANES of sugars heatedbetween RT (27 ℃)-180 ℃ andreferences.

59

Ⅱ

Ⅱ

Fig. 4. Calculated O K-XANES spectra of the t
wo-sucrose-molecules model, whichwere obtained from CASTEP.

Fig. 3. Calculation model composed of two
sucrose molecules, which was
obtained from MD calculations.

around mp. From the O K-XANES, thermaltransformations of sucrose molecules in sugars wereobserved, reflecting hydrogen bond transformations.
XANES simulations by DFT calculations indicatethat the O atoms forming hydrogen bonds between
sucrose molecules exhibit a higher-energy shiftedpeaks. Such the calculations can well explain the
spectral profiles of the O K-XANES of the heatedsugars. It suggests that mp fluctuation of sugars
depend on hydrogen bonds formed among sucrose
molecules.

measurements can observe thermal transformationsof sugars, reflecting hydrogen bonds in sucrose
molecules.
3.2. MD/DFT Calculations
Figure 3 shows the calculation model composedof two sucrose molecules, which was obtained from
the MD calculations. In the model, O atoms
numbered with 5 (denoted by 5O) and 8 (8O) in theupper sucrose molecule are donor atoms, and O atm
numbered with 9 (9O) in the lower sucrose molecule
is an accepter atom forming hydrogen bonds. Figure
4 shows the calculated O K-XANES obtained fromthe CASTEP. Comparing the O atoms (5O, 8O, and9O) forming hydrogen bonds to the other O atoms
not forming hydrogen bonds, calculated XANES
spectra of the upper 5O, 8O, and lower 9O exhibit
the higher-energy shifts. Such the higher-energy
shifts in O K-XANES correspond to the change inthe σ* peak width. This suggests that in-situ O KXANES measurements can observe thermaltransformations of sugars, reflecting hydrogen bonds
in sucrose molecules.

References[1] K. Maee and Y. Muramatsu, LASTI Annual
Report, 21, (2019) 57.
[2] S. Myneni, Y. Luo, L. A. Näslund, M. Cavalleri,
L. Ojamäe, H. Ogasawara, A. Pelmenschikov, P.
Wernet, P. Väterlein, C. Heske, Z. Hussain, L. G.
M. Pettersson, and A. Nilsson, J. Phys.
Condensed Matter., 14, (2002) L213.
[3] K. Hiramatsu, K. Maee, T. Tanaka, R. Maruyama,
T. Motokawa, and Y. Muramatsu, LASTI Annual
Report 22, (2020) 38.
[4] Y. Muramatsu, K. Hiramatsu, K. Maee, and K.
Sakamoto, Anal. Sci.,38, (2022) 717.
[5] S. J. Clark, M. D. Segall, C. J. Pickard, P. J.
Hasnip, M. I. J. Probert, K. Refson and M. C.
Payne, Krystallogr., 220, (2015) 567.
[6] M. Kamoda, Proceedings of the Research Societyof Japan Sugar Refineries' Technologists, 9,(1960) 158.

4. Conclusions
The C K- and O K-XANES of sugars weresuccessfully measured while heating between RT
and 180 ℃. From the C K-XANES, it can besuggested that reducing sugars are formed andsucrose molecules in sugars are decomposed intomolecules like glucose and fructose by heating60

In-situ XANES Measurements of Eggs during Heating
Ikuya Shimogaki, Yasuji Muramatsu
Graduate School of Engineering, University of Hyogo
Abstract

To clarify the thermal denaturation of proteins, from the view point of chemical states, in-situ
XANES in the C K, N K, and O K regions of heated egg yolk and egg white were measured in BL10.
The egg samples were heated from room temperature to 180 °C under the vacuum of 10-5 Pa in ameasurement chamber. Significant thermal changes were successfully observed in C K- and N KXANES, but in O K-XANES. These results suggest the thermal transformation of carbon andnitrogen atoms in protein and lipid of egg yolk and white.

.
1. Introduction
Recently, a sample heating system was installedin the X-ray absorption spectroscopy (XAS) station
at BL10, which enables to measure in-situ XAS
spectra during sample heating up to 200 °C [1]. By
using the heating system, we have observed thermaltransformation of sugars around melting point [2].
To explore further target materials for chemical
analysis dependent on heating temperature, we havefocused on thermal denaturation of proteins.
Proteins are macromolecular compounds
consisting of a large number of amino acids linked
by peptide bonds. Proteins generally take complex
conformations due to hydrogen bonds, disulfide
bonds, and hydrophobic interactions. In addition,
nonpolar side chains of amino acids aggregate inside
the protein structure due to hydrophobic interactions,and hydrophilic side chains of amino acids hydratewith the solvent outside the structure. By heating,molecular structures of proteins drastically change.
Intramolecular bonds such as hydrogen bonds arebroken and the steric structure disintegrates. This isthermal denaturation of proteins. Such the structures
result in thermal denaturation are unique andinteresting. Although molecular structures inthermal denaturation of proteins have beencommonly and widely analyzed by using X-ray
diffraction method, the detailed structures andchemical transformations have not been wellelucidated.
Hence, we have focused on thermal denaturationof proteins in egg yolk and white. In the present
study, in-situ X-ray absorption near-edge spectra(XANES) in C K, N K, and O K regions of them were
measured by using the heating system.

XANES measurements were performed at the
XAS chamber installed in BL10 with a totalelectron-yield (TEY) method. In the sample heating
system, samples are sandwiched between gold (Au)
substrate and Au mesh (#100 mesh) cover, which are
put on copper (Cu) sample plate. Liquid Egg yolk
and white samples were hold between the Au-mesh
and Au-plate substrate. Sample current of the egg
samples can be detected through the Au-mesh/Auplate and the Cu substrate. XANES spectra in the C
K, N K, and O K regions were in-situ measured byheating from room temperature (RT) to 180°C.
During heating, vacuum pressure of the XAS
chamber was kept on 10-5 Pa.
3. Results and Discussion
Figure 1 shows C K -XANES of egg yolk andwhite, which were heated from RT to 180°C, with areference ovalbumin. Egg yolk exhibits peaks at

2. Experiments
Samples are commercially available egg yolk
and white. Table 1 lists the general component ofthem. Main component of egg yolk are moisture,
lipid, and protein, and of egg white is moisture andprotein. Commercially available ovalbumin which is
the main protein of egg white was also prepared fora reference sample.

Fig. 1. C K-XANES of egg yolk and egg whiteheated from RT to 180 °C, compared to
the reference ovalbumin.

61

ⅡTable 1 Component of eggs.

Ⅱ285.2 eV and 288.3 eV. Compared to ovalbumin,these peaks may be attributed similar structure of it.
The shoulder intensity at 287.7 eV decreased as theheating temperature increased. As shown in Table 1,egg yolk contains lipid. Thus, the shoulder can be
attributed unsaturated fatty acids, and thermal
decomposition of lipid can be suggested in egg yolk.
Spectral profile of egg white is as same as that ofovalbumin with the peaks at 285.2 eV and 288.2 eV.
The 288.2-eV peak intensity of egg white slightly
decreased as the heating temperature increased. Thissuggests the change in bonding states of peptide
carbons by heating.
Figure 2 shows the N K-XANES of egg yolk, egg
white, and ovalbumin. Egg yolk and white exhibit
peaks at 401.6 eV and 406.4 eV, which correspondto the reference ovalbumin. Hence, nitrogen atoms
in egg yolk and white take similar forms in
ovalbumin. However, broad peak intensity near412.0 eV in egg yolk and white increased as theheating temperature increased. Considering the

Fig. 3. O K-XANES of egg yolk and egg whiteheated from RT to 180 °C, compared to
the reference ovalbumin.
lower 412.0-eV peak intensity in ovalbumin than in
the egg yolk and white, the enhanced 412.0-eV peak
may show the thermal transformation of peptide
bonds in egg yolk and white.
Figure 3 shows the O K-XANES. Egg yolk andwhite exhibit two peaks at 533.1 eV and 541.0 eV,
which can be attributed to π* and σ* peaks,
respectively. This profile indicates the sp2-oxygen
such as carbonyl oxygen (C=O), and is almost sameas the reference ovalbumin. Hence oxygen atoms in
egg yolk and white may arise from ovalbumin
structure. Chemical states of oxygen may not change
in thermal denaturation, because there is no
significant profile change in egg yolk and white.
4. Conclusion
XANES spectra in the C K, N K, and O K regionsof heated egg yolk and white were successfully
observed by using the sample heating system in XAS
chamber at BL10. These in-situ XANES observed
thermal denaturation process of protein in eggs.
Especially, thermal change in chemical states ofcarbon and nitrogen atoms in eggs are clearlyobserved. Such the in-situ XANES measurements
will be a powerful tool to elucidate the thermal
denaturation in proteins from the view point ofchemical states.
References[1] Y. Muramatsu, K. Hiramatsu, K. Maee, and K.
Sakamoto, Anal. Sci.,38, (2022).
[2] K. Maee and Y. Muramatsu, LASTI Annual
Report 21, (2019) 57.

Fig. 2. N K-XANES of egg yolk and egg whiteheated from RT to 180 °C, compared to
the reference ovalbumin.

62

C K-XANES of Long-Chain Aliphatic Carbons Analyzed
by the First Principles Calculations
Toshiyuki Tanaka, Yasuji Muramatsu
Graduate School of Engineering, University of Hyogo
Abstract

To clarify the σ* peak structures in C K-XANES of carbon materials, C K-XANES spectra of various
n-alkanes were measured in BL10/NewSUBARU, and the XANES profiles were theoreticallysimulated by the first principles calculations. Measured C K-XANES spectra exhibited two
characteristic peaks near 288 eV. Incident-angle-dependent C K-XANES was also measured toconfirm the molecular orientation. Considering the calculated XANES dependent on electric field
vector directions, the measured n-alkanes are oriented perpendicular to the substrate plane.

1. Introduction
X-ray absorption near-edge structure(XANES) using synchrotron radiation (SR) has
been utilized for electronic/chemical-state
analysis of carbon materials. Additionally,
theoretical XANES analysis has recently been
performed using the first principles calculations.
Hence, a combination of XANES measurements
and theoretical analysis provides an advanced
characterization method for carbon materials.
Graphitic carbons composed mainly of sp2carbon (C) atoms generally exhibit characteristic
π* and σ* peaks in C K-XANES. On the other
hand, sp3-C atoms exhibit only σ* peaks whichtake broader profiles composed of various
chemical states of sp3-C structures. Althoughsome characteristic σ* peaks are attributed totypical functional groups, there is little
theoretical analysis for the structures.
The present study aims to identify the broad
σ* peaks from the view point of local structures.
The C K-XANES measurements of various nalkanes and the theoretical XANES analysis byusing the first principles calculations will bedemonstrated.

for XANES measurements. C K-XANES spectraof these samples were measured in BL10 at
NewSUBARU by using a total-electron-yield(TEY) method.
XANES simulations were performed byusing the DFT calculation package of CASTEP
on the Materials Studio platform (Dassault
Systems). Calculation models were constructedby using the coordinate data on the Cambridge
Structural
Database(CSD).
Transition
probabilities of individual C atoms in each model
were obtained from CASTEP calculations in the
ground-states and in the excited-states with C1s
vacancies. After applying the transition energy
correction, calculated XANES spectra wereobtained by plotting the transition probabilities as
the function of transition energies. To calculate
the incident-angle-dependent XANES, electricfield directions (Ea, Eb, Ec) for the a, b, and c axeson the molecular structure were specified in
CASTEP calculations.
3. Results and Discussion
C K-XANES spectra of n-alkanes measured
at a grazing angle (θ) of 90° (normal incidence)are shown in Figure 1. All molecules exhibited
double peaks (denoted by a and b) around 288 eV
and broad peaks around 293 eV. Relative
intensities between peaks a and b are different
among compounds, which may reflect theanisotropic structures. Figure 2 shows theincident-angle-dependent C K-XANES of nalkanes. Intensities of the double peaks a and b
around 288 eV decreased as the grazing angle
become lower. This clearly shows the molecularorientation of the n-alkane samples pressed on
the In substrates.
Figure 3 shows the calculated C K-XANESof the n-C20H42 crystal model varied by the
specified electric field directions of Ea, Eb, and Ec,
compared to the measured C K-XANES (normal
incidence). The peaks a and b of the measured C
K-XANES correspond to the calculated C K-

2. XANES Measurements and Calculations
Table 1 shows the measured n-alkanes(CnH2n+2). These samples are commerciallyavailable powder compounds. Powder samples
were pressed and held on an indium (In) substrate
Table 1 Measured compounds of n-alkanes.

63

Ⅱ

Ⅱ

XANES peaks indicated by dotted lines in the
figure. Additionally, the calculated peak intensity
is clearly dependent on the electric field direction.
Intensity of peak b is enhanced in Ea direction,that of peak a is in Eb direction. However, thesepeaks are not observed in Ec direction. In Ec

direction, electric field vector is parallel tothe backbone chain of n-alkane molecule. Hence,
the measured incident-angle-dependent C KXANES suggests that the measured n-alkane
samples are partially oriented perpendicular tothe substrate plane.
4. Conclusion
To clarify the fine structures of the broad σ*peak in C K-XANES of sp3-C materials, C KXANES of various n-alkanes were measured andtheoretically analyzed by CASTEP. The
measured XANES spectra were reproduced by
the band calculations of n-alkanes crystals,
considering with the electric field direction. It
can also be confirmed that the measured nalkanes are partially oriented perpendicular to thesubstrate plane.

Fig. 1. Measured C K-XANES of n-alkanes.

Fig. 3. Upper panel (a) shows the C20H42 crystal
model. Lower (b) shows the calculated C
K-XANES of the C20H42 crystal model,
compared to the measured C K-XANES.
Calculated XANES spectra are polarized
in the electric field vectors of Ea, Eb, andEc.
Fig. 2. Incident-angle-dependent C K-XANES
of n-alkanes.

64

Fabrication of Ni-W Microgears Using LIGA Process
Kohzo Tamada1, Sho Amano1, Kana Okamoto2, Masaya Takeuchi1,3,
Akinobu Yamaguchi1, Yuichi Utsumi1, Tohru Yamasaki2
1

Laboratory of Advanced Science and Technology for Industry, University of Hyogo,
3-1-2 Kouto, Kamigori, Ako-gun, Hyogo 678-1205, Japan
2
Research Center for Advanced Metallic Materials, University of Hyogo,
2167 Shosha, Himeji, Hyogo 671-2280, Japan
3
Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan
Abstract
Microgears made of Ni-W alloy that are expected to have high strength and ductility, i.e., highdurability, were successfully fabricated by using the LIGA process with synchrotron radiation. NiW electrodeposited alloys have a Vickers hardness of about HV 600 and a tensile strength of about
2000 MPa or above for a sample thickness of up to about 20 μm. However, they lose their excellent
mechanical properties with increasing sample thickness. For this reason, Ni-W electrodepositedalloys have not yet been used in the LIGA process for the fabrication of microcomponents. We
consider that the decrease in strength is due to the increased electric resistance of the Ni-W film
during the electrodeposition. To solve this problem, we developed a new process in which copper
reversing mold are fabricated in the first step, then Ni-W alloy is electrodeposited on the copper
reversing mold to prevent the electric resistance from increasing in the second step as the moldforming process. Using this process, microgears with reference diameters from 1000 to 80 µm were
fabricated with high dimensional accuracy.

1. Introduction
Microturbines are an important component of
microfluidic systems. Microgears have similar
shapes to microturbines and are required to meet theincreasing demand for ultrasmall motors in various
fields, especially the medical field. Bothmicroturbines and microgears are required to havehigh dimensional accuracy and high durability, but it
is difficult for high dimensional accuracy on theorder of microns to be achieved for metals in
conventional machining. For example, the minimum
reference diameter of gears in practical use is about
300 μm, and it is difficult to fabricate high-precision
gears with a reference diameter of less than 300 μm[1].
On the other hand, the LIGA (an acronym for
Lithographie, Galvanoformung und Abformung inGerman) process [2, Note1] using synchrotron
radiation can be used to fabricate metallic
components with a high aspect ratio and submicronlevel dimensional accuracy. However, in theelectroplating step of the LIGA process, only soft
metals such as Ni and Cu can be deposited, andtherefore it has been difficult to fabricate metallic
micro-parts with high hardness and high durability.
For example, Ni-Co electrodeposited alloy is a hardmaterial with a Vickers hardness of HV 400, but along time is generally required to deposit a thicklayer of hard alloy plating owing to the low
electrodeposition speed, and the layer may peel off
from the substrate due to residual stress.
In this study, a Ni-W electrodeposited alloy [314] developed by Yamasaki and others, whichshowed high strength and high ductility, has been
applied to the LIGA process using synchrotron
radiation to fabricate high-precision microgears withhigh durability. Ni-W electrodeposited alloys havenanocrystalline/amorphous composite structureswith high plastic deformability despite their highstrength. However, electrodeposited films of thesealloys exhibit severe brittleness with increasing
thickness. To solve this problem, we have developed
a new process of double plating using a copper
reversing mold. As a result, we succeeded infabricating
microgears
made
of
Ni-W
electrodeposited alloy with high plastic durability,
and we evaluated their shape accuracy.
2. Materials and Methods
2.1. Double electroplating in LIGA process
In this study, a Ni-W alloy having about 17 at.%
W with a Vickers hardness of about HV 600 and atensile strength of about 2500 MPa was used as theelectrodeposited alloy in the LIGA process. When
the Ni-W alloy was directly deposited on anelectricallyinsulating
resistmicrostructure
fabricated by lithography, the deposited alloy
retained its high strength and ductility up to a
thickness of about 20 µm. However, when the
thickness exceeded 20 µm, the strength decreased
due to embrittlement. This may be due to theincrease in the electric resistance during theelectrodeposition, i.e., the electric current flowed
only from the Cu substrate (resistance of Cu ～1.68×10-8 Ω・m) and the electric resistance increased

65

Ⅱ

Ⅱ

with increasing thickness of the electrodeposited NiW (resistance of Ni-W～7×10-7 Ω・m).
Thus, we developed a new process. As shown in
Fig. 1, a metal reversing mold was made byelectroforming copper sulfate in the firstelectroforming
process,
and
then
Ni-W
electroforming was performed as the second
electroforming in the mold forming process. In thisprocess, because the current can flow not only
through the substrate but also through the copper
reversing mold, the increase in resistance can beprevented. We expected that high-strength Ni-W
layers would be formed on the substrate and sidewall
surfaces of a structure in the initial stage ofelectrodeposition, enabling the fabrication of highstrength microgears.
Figure 2 shows the results of tensile tests of
micro-tensile specimens with a thickness of 60 µm
produced by the double electroforming process,compared with those of specimens obtained by theconventional direct electroforming. As shown in Fig.
2, the nominal tensile strength of the directly
deposited Ni-19 at.% W alloy is about 1600 MPa,
while that of the alloy fabricated by the new process
shown in Fig. 1 is about 2200 MPa. The ductility of
the alloy fabricated by the double electroforming
process was higher than that of the alloy fabricatedby the conventional direct electroforming, and its
strain was about twice as high. From these results, it
was confirmed that the deposition of Ni-W on acopper reversing mold is effective for obtaining afilm with about 20 µm thickness without any
deterioration of its strength and ductility [8].

Fig. 2. Stress–strain curves obtained by tensile
testing of micro-tensile specimens fabricated bydirect resist electroforming
anddoubleelectroforming.

Fig. 2. Stress–strain curves obtained by tensile
testing of micro-tensile specimens
fabricated by direct resist electroforming
and double electroforming.

2.2. Deep X-ray lithography
X-ray exposure for resist processing was
performed at the LIGA beamline (BL11) of the New
SUBARU synchrotron radiation facility of the
University of Hyogo. The electron storage energy of
New SUBARU is 1 GeV, the storage current is 300
mA, and X-rays of 2 to 6 keV are supplied [15]. The
X-ray mask was a self-made membrane mask with
Au as a light-shielding material. Resist processing
was attempted with various gear patterns. Microgear
inversion patterns were fabricated with four different
numbers of gear teeth (12, 14, 17, and 24), twelve
different reference diameters (80 to 1000 μm), andtwo pressure angles (20 and 25°). The addendum
modification coefficient was 0, 0.05, 0.1, or 0.35.
SU-8 2100 (Nippon Kayaku Co., Ltd.) was used as
the resist, and it was applied on a brass substrate(YAMAMOTO-MS Co., Ltd.) with a thickness ofabout 100 μm using a spin coater. After the coating,the resist was preheated using a hot plate at 60 °C for
5 min, then at 75 °C for 2 h. A Kapton film (Du PontToray Co., Ltd.) was sandwiched between the X-ray
mask and the resist, and contact lithography was
carried out. The resist sample was scanned at a speedof v = 5 mm/s during X-ray exposure to standardize
the exposure intensity. The X-ray dose was set to 15
J/cm². After the exposure, the resist was postheatedat 60 °C for 5 min and at 75 °C for 2 h. Next, theresist was immersed in SU-8 developer (Nippon
Kayaku) to induce its reaction and produce thestructure. Since SU-8 is a negative photoresist, theexposed area does not react and remains unchanged.

Fig. 1. Flowchart of production process of
microgears.

66

Ⅱ
(a)

(b)

(c)

(d)

(e)

Fig. 3. SEM images of Ni-W microgears: (a) φ1000 μm, (b) φ500 μm, (c) φ300 μm, (d) φ80 μm, (e)enlargement of part of (b).

2.3. First electroforming
Copper sulfate was electrodeposited on the resist
microgear structure formed by X-ray lithography asa primary electroforming. A copper reversing moldwith a thickness of about 60 μm was fabricated inthis electrodeposition. To prevent surface oxidationof the copper reversing mold, it was immersed in a
discoloration inhibitor (Top Rinse CU-5, Okuno
Chemical Industries Co., Ltd.) for 2 min, washedwith water, and then quickly dried with a dryer. After
that, the resist remaining on the mold was dissolved
and removed using a remover. First, the substrate
was immersed in Remover PG (Nippon Kayaku) at
70 °C for 2 h to swell the resist, and then it waswashed with water. Next, the resist was stripped in a
1:1 mixture of Remover K (Parts A and B) (Nippon
Kayaku) at 70 °C for 1 h and rinsed twice. Finally, it
was neutralized with Neutralizer K (Nippon
Kayaku) and rinsed with water and dried withethanol.

a mixture of nickel sulfate and sodium tungstate,with citric acid and ammonium sulfate added ascomplexing agents. An Ir-Ta mesh was used as an
anode plate on the resist-removed brass substrate.(4,7)
In addition, the brushing technique proposed by
Nakayama et al. was applied, which can suppress thegeneration of voids and pits due to hydrogen
bubbles.(4,8) The plating time was adjusted so that thefilm thickness was approximately 100 µm. The
electrodeposited Ni-W microgears were immersed in
HNO3 solution to separate from the brass substrate
and the copper reversing mold [4].
3. Reproducibility
Scanning electron microscopy (SEM; VE-7800,
Keyence Corporation) was used to observe thefabricated Ni-W alloy microgears. The acceleration
voltage was 10 kV. Figure 3 shows SEM images of
microgears having diameters of 1000, 500, 300, and80 μm. These images show that microgears with afine metallic luster could be fabricated in accordancewith the designed mask pattern. Their thicknesses
were measured to be about 60 μm.
From the SEM images of Figs. 3(a)–3(d), thetooth tip diameter, reference circle diameter, and2.4. Second electroforming (replication)
Microgears
were
fabricatedbyNi-Welectrodeposition on a copper reversing mold as asecondary electroforming. The plating solution was

Table 1. Shape evaluation of Ni-W microgears: (a) φ1000 μm, (b) φ500 μm, (c) φ300 μm, (d) φ80 μm.
(a)

(b)

(c)

(d)

CAD
Average
CAD
Average
CAD
AverageCAD
dimensions value dimensions value dimensions value dimensions
(μm)
(μm)
(μm)
(μm)
(μm)
(μm)
(μm)

Averagevalue (μm)

Tip diameter

1075

1041

583

556

350

340

94

87

Reference
diameter

1000

966

500

479

300

291

80

75

Insidediameter

333

322

167

164

100

98

26

24

Shape error

3.3%

3.5%

67

2.6%

7.1%

Ⅱ

inner circle diameter were measured at threedifferent locations, and their average values were
calculated and compared with the CAD dimensions
to obtain the shape error. The results are shown in
Table 1. From the results, we conclude thatmicrogears can be fabricated with accuracies ofseveral percent by this process.

References[1] Y. Kitakoga: Int. J. Jpn. Soc. Precis. Eng. 58(1992) 1284 (in Japanese).
[2] N. Nakajima and A. Umeda: Advanced
Machining Technology & Development
Association: LIGA Process - Advancing ThreeDimensional Ultrafine Machining Technology(Nikkan Kogyo Shimbun, 1998) pp. 89-97 (inJapanese).
[3] T. Yamasaki, M. Yamada, H. Adachi, T.
Nabeshima, and Y. Yokoyama: Microsyst.
Technol. 20 (2014) 1941.
[4] S. Nakayama1, H. Adachi, T. Nabeshima, T.
Miyazawa, and T. Yamasaki: Sci. Adv. Mater. 8(2016) 2082.
[5] T. Yamasaki, M. Sonobe, and H. Yokoyama:
Mater. Sci. Forum 561-565 (2008) 1295.
[6] H. Hosokawa, T. Yamasaki, N. Sugamoto, M.
Tomizawa, K. Shimojima1, and M. Mabuchi:
Mater. Trans. 48-5 (2004) 1807.
[7] T. Yamasaki: Scr. Mater. 44 (2001) 1497.
[8] S. Nakayama, H. Adachi, and T. Yamasaki: J.
Alloys Compd. 643 (2015) S22.
[9] K. Fujita, K. Nagaoka, T. Suidu, T. Nabeshima,
and T. Yamasaki: J. Jpn. Inst. Met. Mater. 77(2013) 192 (in Japanese).
[10] K. Fujita, T. Suidu, and T. Yamasaki: J. Japan
Inst. Metals 75 (2011) 348 (in Japanese).
[11] H. Yokoyama, T. Yamasaki, T. Kikuchi, and T.
Fukami: Mater. Sci. Forum 561-565 (2007)1295.
[12] N. Oda, H. Matsuoka, T. Yamasaki, and T.
Fukamis: J. Metastable Nanocryst. Mater. 2425 (2005) 411.
[13] T. Nasu, M. Sakurai, T. Kamiyama, T. Usuki, O.
Uemura, K. Tokumitsu, and T. Yamasaki: Mater.
Sci. Eng., A 375-377 (2004) 163.
[14] A. S. M. A. Haseeb: Microsyst. Technol. 14(2008) 379.
[15] M. Takeuchi, A. Yamaguchi, and Y. Utsumi: J.
Synchrotron Radiat. 26 (2019) 528.

4. Summary
We succeeded in fabricating microgears madeof Ni-W electrodeposited alloy using the LIGA
process. We developed a new double plating
method that involved the production of a copper
reversing mold. The Ni-W electrodeposited alloy
is expected to enable the production of highly
durable precision microgears with a Vickers
hardness of about HV 600 and a tensile breaking
strength of about 2200 MPa because of its highstrength and high ductility. The results of thisstudy are summarized below.
(1) Microgears with a maximum reference diameterof 1000 µm and a minimum diameter of 80 µm were
fabricated.
(2) As in table 1, the shape size error between thedesign and the fabricated microgears was evaluatedto be several percent.
We are planning to clarify the material properties(composition, crystallite size, and hardness) of thegears and conduct dynamic property tests (wear andendurance tests) on interlocked gears to demonstrate
their use as highly durable microgears. Using thesame technology, a highly durable microturbine canbe realized, and it will contribute to further researchon microfluidics.
Note 1: The LIGA process was developed at
Karlsruhe Nuclear Research Center (now Karlsruhe
Institute of Technology) in Germany in the 1970s to
fabricate micro-metallic mechanical parts, which are
the components of micro-mechanisms. The LIGA
process consists of three step: lithography(Lithographie), electroplating (Galvanoformung),
and molding (Abformung). After the fabrication of apolymer (resist) microstructure by lithography, amold is fabricated by electroplating. In the molding
process, various materials such as resins, metals, andceramics are processed to replicate themicrostructures of the mold. This technology
attracted worldwide attention in the 1990s as acompletely new microfabrication technique.
However, this technique is not yet in widespread use
due to the lack of electrodeposited alloys with
sufficient strength to be used as metal micro-parts.

68

Fabrication of Free-form Shape Using LIGA Process with
Independently Moving X-Ray Mask
Taki Watanabe, Sho Amano, Akinobu Yamaguchi, Yuichi Utsumi
Laboratory of Advanced Science and Technology for Industry, University of Hyogo,
3-1-2 Kouto, Kamigori, Ako-gun, Hyogo 678-1205, Japan
Abstract
Due to its characteristics, the LIGA process is good at machining high aspect ratio structures on
surfaces with good verticality and low surface roughness. However, processing of shapes that
depend on the two-dimensional pattern of the X-ray mask used has been mainly performed. In thisstudy, we attempted to process a microstructure of a micron-order three-dimensional Free-Form
shape on the PMMA surface by using a high-precision moving mask using a piezo actuator. We arealso aiming to establish a LIGA process for making micro molds by electroforming on the PMMA
surface and manufacturing resin parts by injection molding. In the experiment with NewSUBARU
BL11, we succeeded in processing a conical shape with a lower end diameter of 63 μm, an upperend diameter of 2 μm, and a height of about 70 μm by exposing the sample while moving the sample
by controlling the piezo actuator.

1.

Introduction
The LIGA process is a processing technique thatcombines fine pattern formation by deep X-ray
lithography using synchrotron radiation, moldfabrication by electroforming, and precisionmolding by mold. The LIGA process features aminimum dimension of sub μm (currently 0.2 μm)
and a maximum height of 1 mm or more by deep Xray lithography that utilizes the characteristics ofsoft X-ray transmission of 4.0 KeV or more andhighly directional x-ray. It is possible to fabricate astructure having a high aspect ratio of (currently 3mm), and the surface roughness of the side wall of
the structure is on the order of several tens of nm,
which is a mirror surface state. Taking advantage ofthese characteristics, deep X-ray lithography of a
resist has been conventionally performed along afine pattern of an absorber that shields soft X-rays.
Therefore, in this study, we have developed amethod for processing a Free-Form threedimensional structure on the sample surface using amoving mask using a piezo actuator, which does notdepend on the pattern of the soft X-ray mask.

Piezo actuator
Substrate holder

X-ray mask

Resist material

Fig. 1. Outline of moving mask.
time, the operation of the piezo actuator creates andose amount distribution only in the pattern portion,and processes a Free-Form shape. Piezo actuator touse Since the actuator has an operating range of 200
μm up, down, left and right, and the operation
reproducibility is 10 nm, it is possible to control themoving mask with extremely accurate operation.
Fig. 1 shows the outline of the moving mask device.
The X-ray mask and the exposed sample weremechanically fixed to realize a moving mask. Soft
X-rays are incident from the left hand of Fig. 1 andare patterned by an X-ray mask. Then, the surfaceof the exposed sample fixed to the piezo actuator isirradiated, and deep X-ray lithography is performed.
By sandwiching the spacer, a gap of 500 to 1000 μm
can be created between the portion that holds the Xray mask and the portion that holds the exposed
sample. As a result, it is possible to expose an
exposed sample having a thickness in the range of 0
to 1000 μm with a moving mask.

2. Experiments
2.1. Mechanism of the Moving Mask
In order to process a shape that does not dependon the pattern of the X-ray mask, it is necessary tomove the X-ray mask relative to the exposed sample
to continuously change the exposed portion. To that
end, we have developed our own moving mask
device. The moving mask device developed in the
exposure chamber was installed at the beamline
dedicated to the LIGA process, New SUBARU
BL11, University of Hyogo. By moving theexposure stage up and down, the dose amount of theentire sample surface is made uniform. During that69

Ⅱ

depending

on

the

dose amount,

this

was

Table 1. Ingredient of G-G developer.

Ⅱ
Fig. 2. Exposure rate:
Development time = 360 min.

Fig. 3. Development rate:(dose = 37800[A*min], 37.8℃).

Vol%

2-(2-n-butoxy-ethoxy)ethanol

60

Tetrahydro-1, 4-oxazine

202-amino-ethanol-1

5

D. I. Water

15

Fig. 4. Calculation results: rM, Radius of circularmotion.

2.2. Resist Materials
Synchrotron radiation is characterized by highintensity and small divergence angle. Therefore,
PMMA is generally used as a resist material becauseof its good resolution. In this study as well,experiments were conducted using PMMA as theresist material. After irradiating PMMA with soft Xrays, development is performed using a developer.
At that time, since the processing depth changes
e developer, the presence or absence of stirring,and the like. It is necessary to continue to develop adevelopment method according to the pattern.

investigated. In addition, since the processing depthchanges depending on the length of the developing
time, the same investigation as in s was conducted.
The exposure characteristics and development
characteristics are shown in Fig. 2 and Fig. 3.
We used, G-G developer for development. Table
1 shows the ingredients. The development result ofPMMA varies greatly depending on the exposure
condition of the sample, the temperature of this circularly moved using a moving mask is
calculated. The X-ray mask used is a gold shieldwith a diameter of 30 μm arranged at () μ intervals.
The amount of exposure when the circular motion
was performed while changing the radius wascalculated. Fig.4 shows the calculation results. The
calculation formula is as follows.

2.3. Dose distribution Calculation
Machining simulation is indispensable formachining fine 3D structures in this research. Here,the exposure amount distribution when the sample

Fig. 5. Output shape:
rm=17 μm, rM=16.2μm

Parameter

Fig. 6. Output shape:
rm=15 μm, rM=16.2

70

Fig. 7. Output shape:
rm=10 μm, rM=16.2 μm.

Table 2. Experimental conditions.
Resist material

PMMA

thickness [µｍ]200dose [A*min]37800

Developing time [min]360

Developing degrees [℃]37.8

developer

G-G developer

Ⅱ

Fig. 8. Developed PMMA: rm=17 μm,
rM=16.2 μm.
1𝑎𝑎𝑎𝑎 2 + 𝑎𝑎𝑎𝑎𝑀𝑀𝑀𝑀 2 − 𝑎𝑎𝑎𝑎𝑚𝑚𝑚𝑚 2
𝐸𝐸𝐸𝐸 = 1 − 𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 ��
2𝑎𝑎𝑎𝑎𝑀𝑀𝑀𝑀 ∙ 𝑎𝑎𝑎𝑎
𝜋𝜋𝜋𝜋Here, E is the X-ray exposure energy at the distancer from the drive center, rm is the radius of the X-ray
mask absorber, and r is the distance from the drive
center. From this calculation result, the processedshape of PMMA based only on the exposure amount
was output. The results are shown in Fig. 5, Fig. 6,
and Fig. 7.
2.4. Exposure experiments
An exposure experiment using the developed
moving mask device was conducted at New
SUBARU BL11, University of Hyogo. Table 2
shows the experimental conditions.
After the exposure experiment with synchrotron
radiation X-rays, the development work was
performed using a G-G developer. At the time ofdevelopment, stirring was performed using a rotary
blade to circulate the developer in detail. The
rotation speed is 120 rpm.
Fig.8, Fig.9, and Fig.10 show the experimental
results for each operating parameter. The pattern in
Fig.8 was very different from the simulation, andthe result was that a large hole was formed in thecenter. The pattern in Fig.9 was almost the same as
the simulation, and the shape was as designed. The
pattern in Fig.10 has a shape close to that of thesimulation, although the angle of the wall surface isslightly different.
The reason why the shape differs from thesimulation is that there is a gradient of thedevelopment speed depending on the dose amount.
This is remarkable in the pattern of Fig.8. The holein the central part was in a state where synchrotron
radiation X-rays overlapped and was constantly
irradiated, and a part that was developed early and apart that was developed late at the time ofdevelopment were adjacent to each other. Therefore,
it is considered that the depressed portion in theFig. 9. Developed PMMA: rm=15 μm,
rM=16.2 μm.

Fig. 10. Output shape: rm=10 μm, rM=16.2 μm.
center was developed quickly, and the development
proceeded in the lateral direction from that portion.
Therefore, it can be inferred that the shape did notmatch the simulation.
3. Summary and conclusion
In the LIGA process, deep X-ray lithography of
resists that depend on the pattern of the X-ray mask
has been conventionally performed. Therefore, in71Ⅱthis study, we aimed to manufacture a threedimensional microstructure by moving the X-ray
mask and the resist material relatively, and moving
the resist while irradiating the resist surface with Xrays patterned by the X-ray mask. An exposure
experiment was conducted using PMMA as a resist
material using the moving mask device we invented
and the New SUBARU BL11 of the University of
Hyogo. As a result, depending on the pattern to be
manufactured, it was possible to process it into ashape very close to the simulation, but some results
were significantly different. This is because thedevelopment speed differs depending on the doseamount and the development is not uniform. A
future task is to reflect the development
characteristics in the simulation and complete amore advanced machining simulation. In addition,
we aim to develop a nebulizer filter that applies the
LIGA process using the moving mask device
developed this time.
References[1] T. Chuang, T. Fang, M. Jiang, W. Lei, B. Shew,
and C. Fu, J. Micromech. Microeng. 22 (2012)085027.
[2] K. W.-C. Lee, S. S. Lee, Sens. Actuator A Phys.
108 (2003) 121-127.
[3] O. tabata, H. You, N. Matsuzuka, T. Yamaji, S.
Uemura, I. Dama, Microsyst. Technol. 8 (2002)
93.
[4] C.-M. Cheng, R.-H. Chen: J. Micromech.
Microeng., 11 (2001) 692.
[5] M. Takeuchi, A. Yamaguchi, Y. Utsumi, J.
Synchrotron Rad. 26 (2019) 528.

72

Deviation of Photoelectron Intensity fromthe Lambert-Beer’s Law in Near-Ambient Pressure
Hard X-Ray Photoelectron Spectroscopy
Kento Takenaka1, Nanami Hosoe1, Koji Takahara2, Tomoaki Eguchi2, Hirosuke Sumida3, Satoru Suzuki2
1
Graduate School of Science, University of Hyogo, 2 LASTI, University of Hyogo, 3Mazda Motor Corp.

Abstract

In attempts to eliminate charging by introducing gas at near-ambient pressure hard X-ray
photoemission spectroscopy (NAP-HAXPES), it was found that the effect was greater when the
distance d between the sample surface and the aperture cone was longer. In this study we measured
NAP-HAXPES spectra at various distance d gas (N2 or Ar) pressures using an Au plate as a sample
to investigate the pressure dependence of the photoelectron intensity. The spectral intensity was
found to decrease exponentially with pressure. The measurement results follow I/I0 = exp {σP(d+d0)/kBT}. It is thought that d0 is necessary because gas remains inside the cone of the electronenergy analyzer and photoelectron attenuation is occurring not only outside the cone but also inside.

1. Introduction
Recently, near-ambient pressure (NAP)
photoelectron spectroscopy equipped withdifferential pumping system has become popular. It
enables us to study chemical reactions in a gas
atmosphere. It is also useful for removing or
reducing the charging effect of insulating samples
owing to the environmental charge compensation[1-3]. In a NAP photoelectron spectroscopy
apparatus, the aperture cone of an electron energy
analyzer also acts as a nozzle of a differential
pumping system in addition to collecting
photoelectrons. Under a gas pressure, attenuation ofphotoelectron intensity due to scattering by gas
molecules becomes severe. Therefore, the aperturecone is normally placed as close as possible to thesample within the range that does not cause apressure drop on the sample surface. Very recently
however, we showed that the larger the distance d
between the sample surface and the aperture cone,
the more pronounced the environmental charge
compensation effect in NAP hard X-ray
photoelectron spectroscopy (HAXPES) [4]. Here,
we systematically studied the pressure dependenceof photoelectron intensity at various d value. Formal
deviation of photoelectron intensity from theLambert-Beer’s law was observed.

Fig 1. Schematic diagram of HiPP-2 [5].

sample.
3. Results and discussion
The attenuation of electrons passing through agaseous atmosphere is considered to follow
Lambert-Beer’s law as shown below [6, 7].
I/I0 = exp (-σPd/kBT)

2. Experiments
Measurements were performed at the beamline
BL24XU, SPring-8, using a HAXPES apparatus
equipped with the HiPP-2 electron energy analyzer(Scienta Omicron) shown in Fig 1. at hν = 8 keV.
The diameter Φ of the aperture cone was 0.3 mm.
The HAXPES apparatus was mounted on a stepping
motor-controlled mobile stage. The d value waschanged by moving the stage, as schematicallyshown in Fig 2. The Au 3d and 4f photoelectron
intensities were measured at various d values andgas (N2 or Ar) pressures, using an Au plate as a(1)

where I and I0 are photoelectron intensity at a
certain pressure and a vacuum, σ is electron
scattering cross section, kB, the Boltzmann constant,and T, temperature. Fig 3 shows the decrease inphotoelectron intensity due to gas for each distanced. The larger the distance d, the greater the decreasein photoelectron intensity due to the gas. Also,ln(I/I0) decreases linearly with gas pressure P ateach distance d. The slope of the plot gives σd.

73

Ⅱ

Ⅱ

Fig 2. (a) Schematic of the beamline and analysis chamber (top view) in the initial state. (b) The analysis
chamber with the slit and ion chambers was moved to the right by a distance a. (c) Measurement
arrangement after the movement. The slit and sample surface are on the beam axis again, by moving
them to the left by a distance a.

(a)

(b)

0

(c)

(d)
0.3mm
0.6mm
0.9mm
1.2mm
1.5mm
1.8mm
2.1mm
2.4mm
2.7mm
4.0mm
5.0mm

ln(I/I0)

-5

-10

-15

0

1000

2000
3000
Pressure (Pa)4000

Fig 3. (a) N2 gas pressure dependence of the relative intensity of the Au 4f peak for each distance d. (b)N2 gas pressure dependence of the relative intensity of the Au 3d peak for each distance d. (c) Ar
gas pressure dependence of the relative intensity of the Au 4f peak for each distance d. (d) Ar gas
pressure dependence of the relative intensity of the Au 3d peak for each distance d.

74

8 x 10

(b)

(a)

-24

15 x 10

-24

σd

σd

6
4

5

2

0

0
0.0

14 x 10

-24

12

0.5

1.0

1.5
d (m)

2.0 2.5 x 10

0

-3

(c)

1

2

1

2

d (m)

3

4

5 x 103

4

5 x 10-3(d)
15 x 10

10
8

σd

σd

Ⅱ

10

6
4

-24

10

5

2
0

0
0

1

2

d (m)

3

4

5 x 10

0

-3

d (m)

-3

0

Fig 4. (a) σd vs d obtained from Au 4f photoelectron intensity in N2 gas. (b) σd vs d obtained from Au 3d
photoelectron intensity in N2 gas. (a) σd vs d obtained from Au 4f photoelectron intensity in Ar gas.
(d) σd vs d obtained from Au 3d photoelectron intensity in Ar gas.
we focus on the value of d0 obtained from themeasurement, d0 >> 0.03d, which is an inadequate
explanation for d0.
The second is that photoelectron attenuation by
the gas also occurs inside the cone. Lambert-Beer’s
law assumes that photoelectron attenuation occurs
only from the sample surface to the cone tip.
However, the inside of the cone is connected by anorifice to the outside of the cone where gas is
introduced, and it is possible that gas flows into theinside of the cone and remains. In this case,attenuation of photoelectrons by the gas also occurs
inside the cone, and the longer path ofphotoelectrons in the gas is related to d0. However,this is just one possibility, and further research isneeded to clarify the reason.

Fig. 4 shows the obtained σd plotted against d.
Unexpectedly however, the σd-d line does not passthrough the origin. This means that, to reproduce theexperimental result, d in eq. (1) needs to be formallyreplaced by d+d0 (d0 is a constant).
I/I0 = exp {-σP(d+d0)/kBT}(2)

Deriving σ and d0 from eq.(2), σ = 2.0 × 10-21 m2，
d0 = 1.7 × 10-3 m for Au 4f (7.91 keV) and σ = 3.1 ×
10-21 m2, d0 = 1.1 × 10-3 m for Au 3d (5.91 keV) forN2 gas and σ = 2.4 × 10-21 m2, d0 = 8.8 × 10-4 m forAu 4f and σ = 3.4 × 10-21 m2, d0 = 7.2 × 10-4 m forAu 3d for Ar gas. These values of σ are close to theliterature value for electron scattering cross sections(~ 2.0 × 10-21 m2) [8].
There are two possible reasons for theappearance of d0. The first is that the path ofphotoelectrons is not the shortest distance d. Fig 5shows the relationship between angular acceptanceof the electron energy analyzer θand thephotoelectron pathway. The longest distance d' thatcan be taken as the path of a photoelectron isexpressed by d' = d/cosθ. The angular acceptance of
HiPP-2 is 26° (θ = ±13°) [5], which gives d' =d/cos13° ≃ 1.03d. Assuming that the path of thephotoelectron is d', d0 = d' - d = 0.03d. However, if

Fig 5. Schematic diagram of angular
acceptance and the photoelectron75

Ⅱ

4. Conclusion
We investigated the gas pressure dependence ofthe spectral intensity at various distances d in NAPHAXPES. Photoelectron intensity was found to
decrease exponentially with pressure. In order toreproduce the measurement results, it is necessary
to replace d in Lambert-Beer’s law with d+ d0,
where d0 is considered to be the distance at whichphotoelectron decay occurs inside the cone.
Acknowledgment
HAXPES measurements were performed at thebeamline BL24XU at SPring-8 (proposal no.
2020A3231 and 2020B3231).
References[1] EnviroTM, https://www.specs-group.com/nc/envir
o/products/detail/enviroesca/[2] X. R. Yu, H. Hantsche, J. Electron Spectrosc. Relat.
Phenom. 50, (1990), 19.
[3] S. Matsumoto, T. Nanba, Y. Miura, Surf. Sci. 18,(1997), 466.
[4] S. Suzuki et al., J. Electron Spectrosc. Relat.
Phenom. 257, (2022), 147192.
[5] Scienta Omicron, https://premium.ipros.jp/omi
cron/catalog/detail/557590/.
[6] Y. Takagi, T. Uruga, M. Tada, Y. Iwasawa, T.
Yokoyama, Acc. Chem. Res. 51, (2018), 719.
[7] J. Kahk et al., J. Electron Spectrosc. Relat. Phenom.
205, (2015), 57.
[8] H. Tawara, T. Kato, At. Data Nucl. Data Tables 36,(1987), 167.

76

Shape Observation of Micro- and Nanobubbles Formed In-situ
in a Scanning Electron Microscope
Koji Takahara, Satoru Suzuki
LASTI, University of Hyogo

Abstract

Surface microbubbles and nanobubbles were generated in situ by radiolysis of water in a liquid cell.
The shape and contact angles were directly observed by scanning electron microscopy from the
bubbles generated in the corners of the window. The observed contact angles were all close to 90°
regardless of bubble size, indicating that the bubbles were shaped to maximize Laplace pressure.
This result is the opposite of the surface bubble shape observed by AFM and is close to that reported
by TEM. Bubble formation at a distance from the electron irradiation position was also analyzed byMonte Carlo simulation.

disadvantageous for survival because it increases
the Laplace pressure of the bubbles [7].
In this study, we report the cross-sectional SEM
observation of microbubbles formed at the corner ofthe electron-transparent window. We also analyzed
bubble formation at a location away from theirradiation site based on a Monte Carlo simulationof electron scattering in water. This report is basedon our recently published paper [8].

1. Introduction
In recent years, microbubbles and nanobubbles
have been utilized in a variety of fields ranging fromindustrial fields such as agriculture and fisheries todaily necessities such as washing machines. In thisstudy, among microbubbles and nanobubbles,
surface microbubbles and surface nanobubbles,
which are tiny bubbles in contact with the solidliquid interface, are the subject of research. [1-3].
A surface bubble possesses the Laplace pressure
a curvature radius-dependent additional pressurecaused by surface tension [2]. The Laplace pressure
increases the gas concentration gradient at the
bubble-liquid interface. Simple diffusion theory
predicts
thatananobubble
disappears
instantaneously (~100 μs for a 100 nm radius)
because of the diffusion of gas molecules into theliquid, driven by the large concentration gradient.
However, recent studies have revealed that the
lifetime of a nanobubble reaches several months,
although a detailed mechanism of the long lifetime
remains unclear.
There have been several studies of surface
nanobubble and microbubble shape measurements
using AFM, where flattened shapes have beenreported. [4-6]. However, in our previous study
using SEM, hemispherical bubbles were observedat the edges of the electron-transparent window,
which is contrary to previous AFM studies.
Generally, a large contact angle is considered to be

2. Experiments
Liquid cells using Si chips with SiN or Si
membranes (EM Japan Co., Ltd., Tokyo) as
electron-transparent windows were constructed.
The thickness and dimensions of the membrane
were typically 15 nm and 100 μm × 100 μm,
respectively. The contact angles of the water
droplets on SiN and Si membranes stored in theatmosphere were approximately 92° and 88°,
respectively. As far as this study is concerned, there
was no clear difference in the experimental results
obtained using SiN and Si membranes. Electron
irradiation of the water and in situ observation were
performed at room temperature in a vacuum using a
conventional scanning electron microscope (JEOL,
JSM-6700F). Without otherwise mentioning, theacceleration voltage was 5 kV, and the irradiationdose rate was ~1×1012 /cm2s. Monte Carlosimulations were performed using the Single
Scattering Monte Carlo Simulation software.

Fig. 1. (a)-(e) SEM images of bubbles with various sizes formed at the window.

77

Ⅱ

110

Si or SiN wndow
θ’ⅡContact angle θ' (°)

y

100

x

L’/2
Si wall

Si wall

90
80
70
60
50

z

0

Fig. 2. Schematic of a bubble formed at a cornerand definition of the observed bubble
size L’/2 and contact angle θ’.

2

(1)

2𝜎𝜎𝜎𝜎

𝑃𝑃𝑃𝑃 = 𝑃𝑃𝑃𝑃o + 𝑅𝑅𝑅𝑅′

−1

= 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 +(2)= √𝑅𝑅𝑅𝑅 2 − 2𝑎𝑎𝑎𝑎2 – 𝑎𝑎𝑎𝑎
𝐿𝐿𝐿𝐿′
+ 𝑎𝑎𝑎𝑎2𝜃𝜃𝜃𝜃 = tan (
)
𝑎𝑎𝑎𝑎

(3)

𝑎𝑎𝑎𝑎 = 𝐿𝐿𝐿𝐿′ /2(tan𝜃𝜃𝜃𝜃 ′ − 1)

(4)

𝐿𝐿𝐿𝐿′
2

2

3

�1 + 𝑡𝑡𝑡𝑡𝑎𝑎𝑎𝑎𝑡𝑡𝑡𝑡𝜃𝜃𝜃𝜃′ − 1 + (𝑡𝑡𝑡𝑡𝑎𝑎𝑎𝑎𝑡𝑡𝑡𝑡𝜃𝜃𝜃𝜃′ − 1)2

4𝜎𝜎𝜎𝜎

2
3
𝐿𝐿𝐿𝐿𝐿�1++tan 𝜃𝜃𝜃𝜃′ −1 (tan 𝜃𝜃𝜃𝜃′ −1)2(6)

where Po is the pressure of the surrounding liquid,and σ is the surface tension of water (7.3×10-2 N/m)[9]. The second term 2σ/R is the Laplace pressure,which is approximately 1.4 atm for R = 1 μm. For agiven L’, θ’ of 45 and 90° provides the minimum
and maximum Laplace pressures, respectively.
Therefore, our results show that the bubbles have ashape that nearly maximize the Laplace pressure.
This is relatively consistent with our previous
observation of edge bubbles (with an averagecontact angle of 69°, where 0°≤θ’≤ 90°). However,this result is contradictory to previous AFM studies.
The reason behind this discrepancy is not known,
and therefore, further studies are necessary.

From eqs. (2) and (3), a and R are given by:

𝑅𝑅𝑅𝑅 =

20

value. From eq. (3), the minimum θ’ is 45° for a >>L’/2. Consequently, a pancake-shaped bubble witha smaller contact angle cannot exist at the corner ofthe window. Therefore, if only pancake-shaped
bubbles could stably exist, no bubbles would beobserved at the corners. However, many
microbubbles are observed at the corners.
Regardless of their size, the shapes of the bubbles
were very similar. The observed contact angles θ’vs. bubble sizes L’/2 of 17 bubbles observed at thecorners are summarized in Fig. 3. All the contact
angles are distributed in a narrow range close to 90°,
regardless of the size observed in the SEM images.
Notably, the smallest contact angle was 87°. Thisvalue gives only slight corrections: a = 0.055L’/2
and R = 1.06L’/2 from eqs. (4) and (5), respectively.
The pressure inside a bubble P is given by:

From geometrical considerations, the observed
bubble size L’/2 and contact angle θ’ are given by:
𝐿𝐿𝐿𝐿′

10
15
Bubble size L'/2 (μm)

Fig. 3. Contact angles vs bubble sizes of 17 corner
bubbles.

3. Results and discussion
3-1. Observation of bubbles formed at the cornerFig. 1 shows a cross-sectional SEM image ofelectron irradiated microbubbles formed at thecorners of an electron transmission window. A
diagram of air bubbles formed at the corners isshown in Fig. 2. These bubbles attach to the window
and two Si walls orthogonal to each other. Because
the cross-section of the corner bubbles is observed
via SEM, the observed size L'/2 does not correspondto the actual radius of curvature R. The physicalproperties of bubbles, such as pressure, are thought
to be directly related to R, not L'/2. Here w
e assume that the wettability of the window and thewall is the same. Therefore, the shape of the bubble
is expressed by a sphere with (-a, -a, -a), (a≥0) as
the center of the sphere as:(𝑥𝑥𝑥𝑥 + 𝑎𝑎𝑎𝑎)2 + (𝑦𝑦𝑦𝑦 + 𝑎𝑎𝑎𝑎)2 + (𝑧𝑧𝑧𝑧 + 𝑎𝑎𝑎𝑎)2 = 𝑅𝑅𝑅𝑅 2

5(5)

As expected, θ’ = 90° results in a = 0 and r = L’/2,
that is, the observed length exactly matches the real

78

(a)

(b)

Ⅱ
500 nm

5 kV

5 µm

20 kV

Fig. 4. Monte Carlo simulation results of electron scattering in water injected through a 15 nm thick Si
window. Electron kinetic energy is (a) 5 and (b) 20 keV.

3-2. Monte Carlo simulation of electron
scattering in water
Bubble formation was also observed at ~25 μm
away from the irradiation site, when local
irradiation (~7×1016 /cm2s for 60 s) was performed
at a relatively high kinetic energy of 20 keV, as
shown in Fig. 4. To understand this mechanism, we
performed Monte Carlo simulations of electron
scattering in water. Figs. 4(a) and (b) show thesimulation results obtained for electron kinetic
energies of 5 and 20 keV, respectively. The incident
electrons are injected into the water through a 15 nm
thick Si window, demonstrating a minor effect. The
increased kinetic energy significantly increases thepenetration depth. The maximum penetration
depths in water were estimated to be 0.70 and 8.4
μm for 5 and 20 keV, respectively. These values are
consistent with those obtained from the semiempirically derived formula (0.83 and 8.4 μm,
respectively) [10]. Similarly, the lateral spreads
extend to ~0.5 μm and 5 μm from the irradiation site,
respectively. Therefore, the radiolysis of water andformation of bubbles are considered to occur withinthese ranges. Once a bubble is formed, the range isfurther expanded as electron scattering issignificantly suppressed in a gas. Because of therelatively long travelling length at 20 keV,nanobubble formation at locations away from a
local irradiation site is possible when a microbubble
is formed at the irradiation site. We believe thatmultiple nanobubbles merge at the corners andedges to grow into microbubbles.

shapes maximize Laplace pressure. This result is
contrary to the AFM study but very close to the TEM
results; further work is needed to clarify thediscrepancy with the AFM study.

References[1] V. S. J. Craig, Soft Matter 7, (2011), 40.
[2] D. Lohse and X. Zhang, Rev. Mod. Phys. 87,(2015), 981.
[3] J. R. T. Seddon, D. Lohse, J. Phys. Condens.
Matter 23, 133001 (2011).
[4] X. H. Zhang, N. Maeda, V. S. J. Craig, Langmuir
22, (2006), 5025.
[5] H. Teshima, T. Nishiyama, K. Takahashi, J.
Chem. Phys. 146, (2017), 014708.
[6] T. Nishiyama, Y. Yamada, T. Ikuta, K. Takahashi,
Y. Takata, Langmuir 31, (2015), 982.
[7] K. Takahara and S. Suzuki, J. Appl. Phys. 130,(2021), 025302.
[8] K. Takahara and S. Suzuki, e-J. Surf. Sci.
Nanotechnol., (accepted).
[9] K. Yasui, T. Tuziuti, W. Kanematsu, K. Kato,
Phys. Rev. E 91, (2015), 033008.
[10] H. Takahashi, J. Surf. Sci. Soc. Jpn 25, (2004),
224.

4. Conclusion
We performed direct cross-sectional observationof bubbles formed in situ by electron irradiation.
Regardless of the size of the bubbles, they were nearly
hemispherical in shape, consistent with the bubbles atthe edges of the window reported previously. These79

Part 3. List of Publications

NewSUBARU Operation RoomList of publications
Papers1.

“In situ water radiolysis in a scanning electron microscope and observation of micro- andnanobubbles formation”
Koji Takahara and Satoru Suzuki
J. Appl. Phys. 130, 025302-1-8 (2021)

2.

“Properties and Classification of Diamond-Like Carbon Films”
Naoto Ohtake, Masanori Hiratsuka, Kazuhiro Kanda, Hiroki Akasaka, Masanori Tsujioka,
Kenji Hirakuri, Atsushi Hirata, Tsuguyori Ohana, Hiroshi Inaba, Makoto Kano, and Hidetoshi
SaitohMaterials 14, 315 (2021)

3.

“Effect of Soft X-Ray Irradiation on Film Properties of a Hydrogenated Si-Containing
DLC Film”
Kazuhiro Kanda, Ryo Imai, Shotaro Tanaka, Shuto Suzuki, Masahito Niibe, Takayuki
Hasegawa, Tsuneo Suzuki, and Hiroki Akasaka
Materials 14, 924 (2021)

4.

“Performance of BL07A at NewSUBARU with installation of a new multi-layered-mirror
monochromator””
Shotaro Tanaka, Shuto Suzuki, Tomohiro Mishima, and Kazuhiro Kanda
J. Synchrotron Rad. 28, 618-623 (2021)

5.

“Soft X-ray absorption and emission spectra of nanographene prepared from pentacene
with hot mesh deposition and soft X-ray irradiation”
Akira Heya, Masahito Niibe, Kazuhiro Kanda, Ryo Yamasaki, and Koji Sumitomo
Jpn. J. Appl. Phys. 60, 045506 (2021)

6.

“Space Exposure of Amino Acids and their Precursors during the Tanpopo Mission”
Kensei Kobayashi, Hajime Mita, Yoko Kebukawa, Kazumichi Nakagawa, Takeo Kaneko,
Yumiko Obayashi, Tomohito Sato, Takuya Yokoo, Saaya Minematsu, Hitoshi Fukuda,
Yoshiyuki Oguri, Isao Yoda, Satoshi Yoshida, Kazuhiro Kanda, Eiichi Imai, Hajime Yano,
Hirofumi Hashimoto, Shin-ichi Yokobori, and Akihiko Yamagishi
Astrobiology 21, 1479-1493 (2021)

7.

“In situ X-ray diffraction study on structural changes of neutron-irradiated highlyoriented pyrolytic graphite under room-temperature compression and decompression”
Syusaku Nakamura, Wataru Nakamura, Shunjiro Fujii, Shin-ichi Honda, Masahito Niibe,
Mititaka Terasawa, Yuji Higo, and Keisuke Niwase
Diamond Relat. Mater. 123, 108828 (2022)8.

“Photocatalytic Activity Enhancement of Anatase/Rutile-Mixed Phase TiO2 Nanoparticles
Annealed with Low-Temperature O2 Plazma”
Retsuo Kawakami, Yuki Mimoto, Shin-ichoro Yanagiya, Akihiko Shirai, Masahito Niibe,
Yoshitaka Nakano, and Takashi Mukai
Phys. Status Solidi A 218, 2100536 (2021)

83

Ⅲ

9.

Ⅲ

“A novel measurement approach for near-edge x-ray absorption fine structure:Continuous 2π angular rotation of linear polarization”
Yoshiki Kudo, Yasuyuki Hirata, Masafumi Horio, Masahito Niibe, and Iwao Matsuda
Nucl. Inst. Meth. Phys. Res. A 1018, 165804 (2021)

10. “Electronis strucuture of a borophene layer in rare-earth aluminum / chromium boride
and its hydrogenated derivative borophane”
Masahito Niibe, Mathis Cameau, Nyuyen Thanh Cuong, Omeji Ilemana Sunday, Xiaoni Zhang,
Yuki Tsujikawa, Susumu Okada, Kunio Yubata, Takahiro Kondo, and Iwao Matsuda
Phys. Rev. Mater. 5, 084007 (2021)
11. “In situ observation of Transtormation of neutron-irradiated highly oriented pyrolytic
graphite (HOPG) by X-ray diffraction under high-pressure and high-temperature
treatment”
Shin-ichi Honda, Yuji Higo, Keisuke Niwase, Masahito Niibe, Mititaka Terasawa, Eiji Taguchi,
and Syusaku Nakamura
Jpn. J. Appl. Phys. 60, 095002 (2021)
12. “Liquid Mixing Evaluated Using Entropy in a Lab-on-a-disc Platform”
A. Yamaguchi, A. Ishimoto, S. Saegusa, M. Sugiyama, S. Amano, and Y. Utsumi
Sensors and Materials 12, 4371-4382 (2021)
13. “Development of Microfluidic Device Coupled with Post-wall Waveguide for Microwave
Heating at 24.125 GHz”
Kaito Fujitani, Mitsuyoshi Kishihara, Tomoyuki Nakano, Ryota Tanaka, Akinobu Yamaguchi,
and Yuichi Utsumi
Sensors and Materials, 33, 4399-4408 (2021)
14. “Transporting Powder with Surface Acoustic Waves Propagating on Tilted Substrate”
T. Saiki, Y. Takizawa, T. Kaneyoshi, K. Iimura, M. Suzuki, A. Yamaguchi, and Y. Utsumi
Sensors and Materials, 12, 4409-4426 (2021)
15. “Manipulation of Powder with Surface Acoustic Wave Actuator to Control Standing andTraveling Modes”
Yukako Takizawa, Yusuke Fukuchi, Kazuya Hamaguchi, Satoshi Amaya, Yuichi Utsumi,
Masahiro Takeo, Kenji Iimura, Michitaka Suzuki, and Tsunemasa Saiki
Sensors and Materials 33, 4427–4439 (2021)
16. “Fabrication of Ni-W micro-gears using LIGA Process”
K. Tamada, S. Amano, K. Okamoto, M. Takeuchi, A. Yamaguchi, Y. Utsumi, and T. Yamasaki
Sensors and Materials 12, 4455-4460 (2021)
17. “Observation of individual resonances in magnetic vortex core gyration using
time-resolved magneto-optical Kerr microscope with picosecond laser diode illumination”
T. Ogasawara and A. Yamaguchi
Jpn. J. Appl. Phys. 61, 018001 (2021)

8418. “Enhancedment in spin-orbit torques by change in uniaxial in-plane magnetic anisotropyof Py/Pt bilayers on single crystal 128° Y-cut LiNbO3 substrate”
M. Ito, A. Yamaguchi, D. Oshima, T. Kato, M. Shima, and K. Yamada
Appl. Phys. Lett. 119, 152407 (2021)
19. “X-ray photoemission spectroscopy study of uniaxial magnetic anisotropy induced in a Ni
layer deposited on a LiNbO3 substrate”
Akinobu Yamaguchi, Takuo Ohkochi, Masaki Oura, Keisuke Yamada, Tsunemasa Saiki, Satoru
Suzuki, Yuichi Utsumi, and Aiko Nakao
Nanomaterials 11, 1024 (2021)
20. “Effect of atomic Hydrogen Exposure on Hydrogenated Amorphous Carbon Thin Films”
Yuichi Haruyama, Daiki Morimoto, Akira Heya, Koji Sumitomo, Seigo Ito, Kumiko Yokota,
and Masahito Tagawa
Jpn. J. Appl. Phys. 60, 125504 (2021)
21. “Pencil graphite rods decorated with nickel and nickel–iron as low-cost oxygen evolution
reaction electrodes”
Ramón Arcas, Yuuki Koshino,Elena Mas-Marzá, Ryuki Tsuji, Hideaki Masutani, Eri
Miura-Fujiwara, Yuichi Haruyama, Seiji Nakashima, Seigo Ito, and Francisco
Fabregat-Santiago
Sustainable Energy & Fuels. 5, 3929-3938 (2021)
22. “Development of a high-power EUV irradiation tool in a hydrogen atmosphere”
Tetsuo Harada, Shinji Yamakawa, Mitsunori Toyoda, and Takeo Watanabe
Jpn. J. Appl. Phys. 60, 087005 (2021)
23. “Modified-edge-support heat treatment method of polyimide for crystalline, large-area,and self-standing ultrathin graphite films”
Kensuke Murashima, Yuki Kawashima, Shuhei Ozaki, Atsushi Tatami, Masamitsu Tachibana,Takeo Watanabe, Tetsuo Harada, and Mutsuaki Murakami
Carbon 181, 348-357 (2021)
24. “Affinity Analysis of Photoacid Generator in the Thin Film of Chemical Amplification
Resist by Contact Angle Measurement”
Shinji Yamakawa, Ako Yamamoto, Seiji Yasui, Takeo Watanabe, and Tetsuo Harada
J. Photopolym. Sci. Technol. 34, 111-115 (2021)
25. “The Measurement of the Refractive Index n and k Value of the EUV Resist by EUV
Reflectivity Measurement Method”
Yosuke Ohta, Atsushi Sekiguchi, Tetsuo Harada, and Takeo Watanabe
J. Photopolym. Sci. Technol. 34, 105-110 (2021)
26. “Study on Fabrication of X-ray collimators by X-ray lithography using synchrotron
radiation”
S. Saegusa, N. Narukage, Y. Utsumi, and A. Yamaguchi
J. Photopolym. Sci. Technol. 34, 213-218 (2021)

85

Ⅲ

27. “Fundamental Evaluation of Resist on EUV Lithography at NewSUBARU SynchrotronLight Facility”
Takeo Watanabe, Tetsuo Harada, Shinji Yamakawa
J. Photopolym. Sci. Technol. 34, 49-53 (2021)

Ⅲ

28. “A Global Shutter Wide Dynamic Range Soft X-Ray CMOS Image Sensor With
Backside-Illuminated Pinned Photodiode, Two-Stage Lateral Overflow Integration
Capacitor, and Voltage Domain Memory Bank”
Hiroya Shike, Rihito Kuroda, Ryota Kobayashi, Maasa Murata, Yasuyuki Fujihara, Manabu
Suzuki, Shoma Harada, Taku Shibaguchi, Naoya Kuriyama, Takaki Hatsui, Jun Miyawaki,
Tetsuo Harada, Yuichi Yamasaki, Takeo Watanabe, Yoshihisa Harada, and Shigetoshi Sugawa
IEEE Trans. Electron Devices 68, 2056-2063 (2021)
29. “Anisotropic pyrochemical dry etching of fluorinated ethylene propylene induced by
pre-irradiation with synchrotron radiation”
Kaito Fujitani, Masaya Takeuchi, Yuichi Haruyama, Akinobu Yamaguchi, and Yuichi Utsumi
AIP Advances 11, 025104 (2021)
30. “Trial Fabrication and Evaluation of PTFE Substrate Integrated Waveguide Butler Matrix
for Short Millimeter-Wave”
Mitsuyoshi Kishihara, Kaito Fujitani, Akinobu Yamaguchi, Yuichi Utsumi, and Isao Ohta
IEICE Tech. Rep. 121, 5-10 (2021)
31. “In situ Fluorescence Yield Soft X-ray Absorption Spectroscopy of Electrochemical Nickel
Deposition Processes with and without Ethylene Glycol”
Akinobu Yamaguchi, Naoya Akamatsu, Shunya Saegusa, Ryo Nakamura, Masaru Kato, Ichizo
Yagi, Tomoko Ishihara, and Masaki Oura,
RSC Advances 12, 10425-10430 (2022)
32. “Physically Unclonable Functions Taggant for Universal Stegranographic Prints”
T. Fukuoka, Y. Mori, T. Yasunaga, K. Namura, M. Suzuki, and A. Yamaguchi
Scientific Reports 12, 985 (2022)
33. “Analysis of DNA Radiation Damage by Soft X-Ray Irradiation”
Kazuki Yoshida,, Naoto Matsuo,, Kazushige Yamana, Koji Sumitomo, Akira Heya, Tetsuo
Harada, Tetsuo Tabei, Abstracts of IEICE TRANSACTIONS on Electronics (Japanese Edition),
J105-C, 74-77 (2022)

86Books1.

“Nanomagnetic Materials: Fabrication, Characterization and application“
A. Yamaguchi, A. Hirohata, B. Stadler, (Editor&Author) , Elsevier, 2021 (ISBN978-0128223499)

Proceedings
1.

“Construction of a Compact Electron Injector Using A Gridded Rf Thermionic Gun And
A C-Band Accelerator“
T. Inagaki, T. Fukui, T. Hara, T. Hiraiwa, H. Maesaka, H. Tanaka, T. Asaka, H. Dewa, N.
Hosoda, E. Iwai, C. Kondo, T. Magome, T. Ohshima, T. Sakurai, K. Yanagida, S. Inoue, K.
Kajimoto, Y. Minagawa, S. Nakata, T. Seno, H. Sumitomo, R. Takesako, S. Tanaka, R.
Yamamoto, M. Yoshioka, and S. Hashimoto
IPAC2021, WEPAB039 (2021)

2.

“Commissioning of the new 1.0GeV electron linac for NewSUBARU storage ring”
Takahiro Inagaki, Toshihiko Hiraiwa, Hirokazu Maesaka, Toru Hara, Hitoshi TanakaA), Takao
Asaka, Hideki Dewa, Naoyasu Hosoda, Eito Iwai, Chikara Kondo, Tamotsu Magome, Takashi
Ohshima, Tatsuyuki Sakurai, Kenichi Yanagida, Yousuke Hamada, Takashi Sugimoto, Toshiro
Itoga, Noriyoshi Adumi, Satoshi Hashimoto, Hitoshi Fujii, Shinobu Inoue, Kazuyuki Kajimoto,
Yasuyuki Minagawa, Shotaro Nakata, Hiroshi Sumitomo, Shinichiro Tanaka, Ryo Yamamoto,
Masamichi Yoshioka, Nobuyuki Nishimori, Kota Ueshima, Yuji Hosaka, and Taiki Iwashita
Proc. of 18th. Particle Accelerator Society in Japan Annual Meeting, TUOB03, p.102 (2021)

3.

“Present status of the NewSUBARU synchrotron light facility”
Satoshi Hashimoto, Hitoshi Fujii, Hamada Yousuke, Yasuyuki Minagawa, Kazuyuki Kajimoto,Shoutarou Nakata, Hideyuki Hirayama, and Shinichirou Tanaka
Proc. of 18th. Particle Accelerator Society in Japan Annual Meeting, THP057, p.978 (2021)

4.

“Operation status and high power rf conditioning results of C-band main accelerator at
NewSUBARU injector”
Takahiro Inagaki, Takao Asaka, Chikara Kondo, Takashi Ohshima, Eito Iwai, Masamichi
Yoshioka, Hiroshi Sumitomo, Yasuyuki Minakawa, Kazuyuki Kajimoto, Shinichiro Tanaka, andSatoshi Hashimoto
Proc. of 18th. Particle Accelerator Society in Japan Annual Meeting, THP033, p.895 (2021)

5.

“Damage-Less Removal of Surface Contamination Using Atomic Hydrogen Generated on
Heated Tungsten Mesh”
Akira Heya, Tetsuo Harada, Masahito Niibe, Koji Sumitomo, and Takeo Watanabe
Proc. SPIE, 11908, 119080S (2021)

6.

“Hydrogen damage and cleaning evaluation of Mo/Si multilayer using high-power EUV
irradiation tool”
Tetsuo Harada, Ayato Ohgata, Shinji Yamakawa, and Takeo Watanabe
Proc. SPIE 11908, 119080U (2021)

87

Ⅲ

Ⅲ

7.

“Beyond EUV measurement at NewSUBARU synchrotron light facility”
Takuto Fujii, Shinji Yamakawa, Tetsuo Harada, and Takeo Watanabe
Proc. SPIE 11908, 119080T (2021)

8.

“Ultra-low density, nanostructured free-standing films for EUV Pellicles”
Márcio D. Lima, Takahiro Ueda, Luis Plata, Yang Yang, Vincent Le, Nicklas Keller, Chi Huynh,
Tetsuo Harada, Takeshi Kondo
Proc. SPIE 11517, 1151709 (2021)

9.

“Fundamental research activities on EUV lithography at NewSUBARU synchrotron lightfacility”
Takeo Watanabe, Tetsuo Harada, and Shinji Yamakawa
Proc. SPIE 11908, 1190807 (2021)

88International Meetings
1.

“Space Exposure of Amino Acids and Amino Acid Precursors in the Tanpopo and the
Tanpopo 2 Missions”
Hirofumi Hashimoto, Hajime Mita, Shin-ichi Yokobori, Kazuhiro Kanda, Akihiko Yamagishi,
Hiromi Shibata, Itsuki Sakon, Tomohiro Sato, Kazumichi Nakagawa, Yoko Kebukawa, IsaoYoda, Hajime Yano, Miki Nakayama, Hitoshi Fukuda, Yoshiyuki Oguri, Satoshi Yoshida,
Takuya Yokoo, Kai Terasawa, and Jun-ichi Takahashi
43rd Connecting space research for global impact Scientific Assembly (COSPAR2021), Online,
2021/1-2

2.

“Hydrogen damage and cleaning evaluation of Mo/Si multilayer using high-power EUV
irradiation tool”
Tetsuo Harada, Ayato Ohgata, Shinji Yamakawa, and Takeo Watanabe
Photomask Japan 2021, Online, 2021/4

3.

“Beyond EUV measurement at NewSUBARU synchrotron light facility”
Takuto Fujii, Shinji Yamakawa, Tetsuo Harada, and Takeo Watanabe
Photomask Japan 2021, Online, 2021/4

4.

“Damage-less removal of surface contamination using atomic hydrogen generated onheated tungsten mesh”
Akira Heya, Tetsuo Harada, Masahito Niibe, Koji Sumitomo, and Takeo Watanabe
Photomask Japan 2021, Online, 2021/4

5.

“Fundamental research activities on EUV lithography at NewSUBARU synchrotron lightfacility”
Takeo Watanabe, Tetsuo Harada, and Shinji Yamakawa
Photomask Japan 2021, Online, 2021/4

6.

“Aqueous-soluble Ink including Nano Beacon”
Akinobu Yamaguchi, Yuichi Utsumi, Kyoko Namura, Motofumi Suzuki, and Takao Fukuoka
Pittcon 2021, L51-03, Oral, 2021/3

7.

“X-ray radiolysis-induced-photochemical Reaction at Interface between liquid andsubstrate”
Shunya Saegusa, Naoya Akamatsu, Ikuya Sakurai, Ikuo Okada, Yuichi Utsumi, and Akinobu
Yamaguchi
2021 International Conference on Electronics Packaging (ICEP 2021), TB3-2, Oral, 2021/5

8.

“Affinity Analysis of Photoacid Generator in the Thin Film of Chemical Amplification
Resist by Contact Angle Measurement”
Shinji Yamakawa, Ako Yamamoto, Seiji Yasui, Takeo Watanabe, and Tetsuo Harada
ICPST-38, Online, 2021/6

9.

“The Measurement of the Refractive Index n and k Value of the EUV Resist by EUV
Reflectivity Measurement Method”
Yosuke Ohta, Atsushi Sekiguchi, Tetsuo Harada, and Takeo Watanabe
ICPST-38, Online, 2021/6

89Ⅲ

10. “Fundamental Evaluation of Resist on EUV Lithography at NewSUBARU SynchrotronLight Facility”
Takeo Watanabe, Tetsuo Harada, and Shinji Yamakawa
ICPST-38, Online, 2021/6

Ⅲ

11. “EUV Resist Development Program at NewSUBARU”
Takeo Watanabe, Shinji Yamakawa, and Tetsuo Harada
2021 EUVL Workshop, Online, 2021/6
12. “In-situ X-ray diffraction study on structural changes of neutron-irradiated highlyoriented pyrolytic graphite under room-temperature compression and decompression”
S. Nakamura, M. Ichikawa, W. Nakamura, S. Fujii, S. Honda, M. Niibe, M. Terasawa, Y. Higo,and K. Niwase
4th International Conf. On New Diamond and Nano Carbon, Online, 2021/6
13. “Study on spin-orbit-torque induced magnetization modulation using planar Hall effect incross-shaped multilayer wires”
A. Yamaguchi, N. Matsumoto, W. Yoshikawa, and Y. Fujii
Micro and Nano Engineering Conference (MNE) 2021, Turin, Italy, (Hybrid), Poster, 2021/9
14. “X-ray-induced photo-processes for functional nano/microstructures and materials inaqueous liquid solutions”
A. Yamaguchi, S. Saegusa, I. Sakurai, I. Okada, M. Ishihara, and Y. Utsumi
Micro and Nano Engineering Conference (MNE) 2021, Turin, Italy, (Hybrid), Poster, 2021/9
15. “pH dependence of X-ray-induced synthesis and immobilization of nickel
nano/microparticles”
S. Saegusa, I. Sakurai, I. Okada, M. Ishihara, Y. Utsumi, and A. Yamaguchi
Micro and Nano Engineering Conference (MNE) 2021, Turin, Italy, (Hybrid), Poster, 2021/9
16. “Structural and Electrical Properties of Nanographene Prepared from Pentacene by Hot
Mesh Deposition and Soft X-ray Irradiation”
Akira Heya, Masahito Niibe, Kazuhiro Kanda, Ryo Yamasaki, and Koji Sumitomo
28th International Workshop On Active-Matrix Flatpanel Displays and Devices, Online,
2021/6-7
17. “The measurement of the refractive index n and k value of the EUV resist by EUV
reflectivity measurement method”
Yosuke Ohta, Atsushi Sekiguchi, Tetsuo Harada, and Takeo Watanabe
MNC 2021, Online, 2021/10
18. “Fundamental Study of the Origin of the Stochastics in EUV Resist”
Takeo Watanabe, Tetsuo Harada, and Shinji Yamakawa
MNC 2021, Online, 2021/10
19. “Anisotropic pyrochemical dry etching of fluorinated ethylene propylene initiated byirradiation of synchrotron radiation”
K. Fujitani, Y. Haruyama, A. Yamaguchi, S. Amano, and Y. Utsumi
MNC 2021, Online, 2021/10

9020. “Photobacterical Activity of Anatase Titanium Dioxide Nanoparticles Annealed with theAssistance of Nonequilibrium Atmospheric-Pressure Oxygen Plasma”
R. Kawakami, Y. Mimoto, A. Shirai, S. Yanagiya, M. Niibe, Y. Nakano, and T. Mukai
42nd International Symposium on Dry Process (DPS2021), Online, 2021/11
21. “Nonequilibrium Atmospheric-Pressure O2 Plasma-Asssisted Annealing Effect on
Photocatalytic Activity of Anatase/Rutil-Mixes Phase TiO2 Nanoparticles”
Y. Mimoto, R. Kawakami, S. Yanagiya, M. Niibe, Y. Nakano, and T. Mukai
42nd International Symposium on Dry Process (DPS2021), Online, 2021/11
22. “In situ formation of micro- and nanobubbles by water radiolysis in a scanning electron
microscope”
Koji Takahara and Satoru Suzuki
9th International Symposium on Surface Science (ISSS-9), Online, 2021/11-12
23. “Cross-sectional Observation of Micro- and Nanobubbles Formed In-situ in a ScanningElectron Microscope”
Koji Takahara and Satoru Suzuki
9th International Symposium on Surface Science (ISSS-9), Online, 2021/11-12
24. “Elimination of the charging effect in nea-ambient-pressure hard X-ray photoelectron
spectroscopy”
Kento Takenaka, Kenta Adachi, Koji Takahara, Hirosuke Sumida, and Satoru Suzuki
9th International Symposium on Surface Science (ISSS-9), Online, 2021/11-12
25. “Soft X-ray L-emission spectra of S, Cl and K elements obtained by high energy
resolution spectrometer”
Masahito Niibe and Takashi Tokushima
9th International Symposium on Surface Science (ISSS-9), Online, 2021/11-12
26. “Soft X-ray Absorption, Emission and Photoelectron Spectroscopy of Ammmonia Borane(NH3BH3)”
Masahito Niibe, Yuichi Haruyama, and Seigo Ito
9th International Symposium on Surface Science (ISSS-9), Online, 2021/11-12
27. “Removal of Si Native Oxide by Irradiating Atomic Hydrogen”
D. Morimoto, A. Heya, K. Sumitomo, S. Ito, S. Suzuki, and Y. Haruyama
9th International Symposium on Surface Science (ISSS-9), Online, 2021/11-12
28. “Effect of Atomic Hydrogen Exposure on Hydrogenated Amorphous Carbon Films”
Yuichi Haruyama, Daiki Morimoto, Akira Heya, Koji Sumitomo, Seigo Ito, Kumiko Yokota,
and Masahito Tagawa
9th International Symposium on Surface Science (ISSS-9), Online, 2021/11-12
29. “Biomimetic Diamond-like Carbon Coating on a Lumen of Small-diameter Long-sized
Tube Functionalized by Oxygen Plasma Treatment”
Yuichi Imai, Tatsuyuki Nakatani, Kazuhiro Kanda, Shinsuke Knitsugu, Yasuhiro Fujii, Daiki
Ousaka, Susumu Ouzawa, and Tomio Uchi
Material research meeting 2021 (MRM2021), Yokohama, 2021/12

91

Ⅲ

30. “Totally-viewed structural analysis on DLC films using low energy positron beam, soft
x-ray beam and high energy ion beam”
Kazuhiro Kanda, Masahito Niibe, Hiroki Akasaka, Tsuneo Suzuki, Fuminobu, Hori, Atsushi
Yabuuchi, and Atsushi Kinomura
International Chemical Congress of Pacific Basin Societies 2021 (Pacifichem2021), Online,
2021/12

Ⅲ

31. “Formation and robustness of complex amino acid precursors with large molecularweights in space”
Kensei Kobayashi, Soushi Kuramoto, Tomohito Sato, Yoko Kebukawa, Hajime Mita, Hitoshi
Fukuda, Yoshiyuki Oguri, Kazuhiro Kanda, and Hiromi Shibata
International Chemical Congress of Pacific Basin Societies 2021 (Pacifichem2021), Online,
2021/12
32. “Study of electrochemical reaction of nickel sulfamte with ethylene glycol using X-ray
absorption fluorescence spectroscopy”
N. Akamatsu, S. Saegusa, R. Nakamura, Y. Utsumi, M. Kato, I. Yagi, T. Ishihara, M. Oura, andA. Yamaguchi
Pacifichem 2021, Oral, 2021/12
33. “Synthesis and deposition of nano/micro-copper particles using X-ray
radiolysis-induced-photochemical reaction”
A. Yamaguchi, I. Sakurai, I. Okada, M. Ishihara, and Y. Utsumi
Pacifichem 2021, Poster, 2021/12
34. “Study on X-ray-radiolysis-based deposition of nano/micro-copper particles as three
dimensional additive manufacturing process”
A. Yamaguchi, I. Sakurai, U. Okada, A. Yamaguchi, M. Ishihara, and Y. Utsumi
Pacifichem 2021, Poster, 2021/12
35. “Simulation verification of forward/reverse analysis in big data of 4D-XPS measurements”
Satoshi Toyoda, Masashi Yoshimura, Hirosuke Sumida, Susumu Mineoi, Masatake Machida,
Akitaka Yoshigoe, Akira Yoshikawa, Satoru Suzuki, and Kazushi Yokoyama
27th Workshop on Electron Device Interface Technology (EDIT27), Online, 2022/1

92

Academic Degrees
Master of Engineering
Takuto Fujii (University of Hyogo)“Improvement of optical system for the carbon region and Beyond-EUV utilization at BL-09
beamline of NewSUBARU”
Naoya Akamatsu (University of Hyogo)“Creation of microsystems for controlling chemical reactions”
Kaito Fujitani (University of Hyogo)“Microfabrication of fluorine resin FEP by Synchrotron Radiation photochemical reaction andapplication to microwave-induced chemical reaction chip”
Shota Matsuo (University of Hyogo)"Advanced Electron Beam Anomaly Detection with Machine Learning at NewSUBARU”

93

ⅢLASTI Annual Report Vol. 23 (2021)
February 2023, Published byLaboratory of Advanced Science and Technology for Industry
University of Hyogo
3-1-2 Kouto, Kamigori-Cho, Ako-gun, Hyogo 678-1205, JAPAN
Phone: +81-791-58-0249 / FAX: +81-791-58-0242

Editorial board
Takeo Watanabe (Editor in Chief)
Akinobu Yamaguchi
Koji Nakanishi
Yuichi Haruyama