Preface
This annual report reviews the research activities of the Laboratory of Advanced
Science and Technology for Industry (LASTI) in the academic year of 2022 which is from
April 2022 to March 2023 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 2020.
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 Science and Technology for Industry,
University of HyogoiCONTENTS
Preface…………………………………………….………………………..iPart 1. Current Status of NewSUBARU
NewSUBARU Beamlines……………………………………………………………….1
Koji Nakanishi (LASTI/University of Hyogo)
Electron accelerators at NewSUBARU………………………………………….…….8Satoshi Hashimoto (LASTI/University of Hyogo)

Part 2. Research Activities
Development of Betatron Tune Correction System by Deep Learning Using Loss
Function with Quality Filter………………………………………………………….14
Hitoshi Fujii1, Kousuke Hirose2, and Satoshi Hashimoto1(1LASTI/University of Hyogo, 2Faculty of Engineering, University of Hyogo)
Increased LCS g-ray flux by optimizing laser optics at BL01……………………...17
Satoshi Hashimoto and Haruto Hirakawa(LASTI/University of Hyogo)
Cross section asymmetry of polarized γ-ray elastic scattering……………..….….20
M. Omer1, T. Shizuma2, M. Koizumi1, R. Hajima2, S. Hashimoto3, and
S. Miyamoto4(1Japan Atomic Energy Agency, 2National Institutes for Quantum Science andTechnology, 3LASTI/University of Hyogo, 4Institute of Laser Engineering,Osaka University)

Implementation of SERS active structures using boehmite in microfluidic
devices………………………………………………………………………………….23
Shunya Saegusa1, Masayuki Naya2, Takao Fukuoka1, Sho Amano1,

Yuichi Utsumi1, Akinobu Yamaguchi1(LASTI/University of Hyogo, 2Faculty of Science and Technology, Keio
University)
Study of Dihedral-Corner-Reflector-Array Fabrication Process Using Soft X-ray
Deep X-ray Lithography…………………………………………………………..….27
Taki Watanabe1, Sho Amano1, Shinya Izawa1, Satoshi Maekawa2,
Keisuke Yoshiki3, Akinobu Yamaguchi1, and Yuichi Utsumi1(1LASTI/University of Hyogo, 2Parity Innovations Co. Ltd.3Institute for
Research Promotion and Collaboration)
Upgrading to expand available X-ray energy range for energy device analysis in
BL05C, the NewSUBARU……………………………………..………………….…..31
Koji Nakanishi(LASTI/University of Hyogo)
Selective excitation of Si-H-DLC Films using BL07A for Monochromatized Soft Xray Irradiation…………………………………………………………………..……35
Tomohiro Mishima, Koji Nakanishi, Masahito Niibe, and Kazuhiro Kanda(LASTI/University of Hyogo)
Magnetic field correction of NewSUBARU short undulator (SU) and creation ofpeak energy prediction program with gap table………………………………….…37
Tomohiro Mishima, and Kazuhiro Kanda(LASTI/University of Hyogo)
Effect of Photon Energy on the Reduction of Graphene Oxide by Soft X-ray
Irradiation……………………………………………………………………….…….40
Akira Heya1, Akinori Fujibuchi1, Masahiro Hirata1, Kazuhiro Kanda2,
Yoshiaki Matsuo3, Junichi Inamoto3, and Koji Sumitomo1(1Department of Materials and Synchrotron Radiation Engineering, Universityof Hyogo, 2 LASTI/University of Hyogo, 3Department of Applied Chemistry andChemical Engineering, University of Hyogo)Effect of Atomic Hydrogen Exposure on Hydrogen-Free Amorphous Carbon
Films………………………………………………………………………...………….44
Yuichi Haruyama1, Daiki Morimoto1, Akira Heya2, Koji Sumitomo2, Noriaki
Toyoda2, and Seigo Ito2
(1LASTI/University of Hyogo, 2Graduate School of Engineering, University of
Hyogo)
Ultraviolet photoelectron spectroscopy study on d band center of Co and Ir
catalyst particle…………………………………………………………….………….46
Takahiro Maruyama1, 2, and Yuichi Haruyama3, 4(1Department of Applied Chemistry, Faculty of Science and Technology, Meijo
University, 2Nanomaterial Research Center, Meijo University,
3
LASTI/University of Hyogo, 4Department of Materials and Synchrotron
Radiation Engineering, Graduate School of Engineering, University of Hyogo)
NEXAFS Studies of Amorphous Carbon Nitride Thin Films Deposited by
Pressure-gradient RF Magnetron Sputtering………………………………...……..48
Masami Aono1, Kyoji Morita2, Tasuku Inoue2, and Kazuhiro Kanda3(1Department of Electrical and Electronics Engineering, Graduate School of
Science and Engineering, Kagoshima University,2Faculty of Engineering,
University of Hyogo,3 LASTI/University of Hyogo)
Laser irradiation effect on oriented sp2 bonded carbon structure in hydrogenatedamorphous carbon films…………………………………………………………..….52
Dai Harada1, Naoki Umada1, Yuko Aono1, Kazuhiro Kanda2, Masahito Niibe2,3,
Yuki Hirata4, Naoto Ohtake4, and Hiroki Akasaka1*(1Dept. of Mechanical Eng., Tokyo Institute of Technology, LASTI/University of
Hyogo,3Institute of Solid State Physics (ISSP), The University of Tokyo,
4
Institute of Innovative Research, Tokyo Institute of Technology)
NEXAFS Studies of Amorphous Carbon Nitride Thin Films Deposited by
Pressure-gradient RF Magnetron Sputtering…………………………………….…57
Masami Aono1, Kyoji Morita2, Tasuku Inoue2, and Kazuhiro Kanda3(1Department of Electrical and Electronics Engineering, Graduate School ofScience and Engineering, Kagoshima University, 2Faculty of Engineering,
University of Hyogo,3 LASTI/University of Hyogo)
Development of Reflection- and Projection-Type Soft-X-Ray Microscope (RPSXRM) for Resist-Thin-Film Observation…………………………………..………..61
Tetsuo Harada, Shuhei Iguchi, Shinji Yamakawa, and Takeo Watanabe(LASTI/University of Hyogo)

Analytical method to determine Fe3+/Fe2+ ratio in pumice: Oxidation process
pumice from 7.6 ka Mashu caldera-forming eruption…………………….………..63
Kyohei Sano1, Tetsuo Harada2, and Shinji Yamakawa2(1Graduate School of Regional Resource Management, University of Hyogo,
2
LASTI/University of Hyogo)
Total-Electron-Yield XANES Measurements of Inks Painted on Insulating Copy
Papers……………………………………………………………………………….....67
Miyu Mamezaki and Yasuji Muramatsu(Graduate School of Engineering, University of Hyogo)
In-situ XANES Measurements of Peptide Bonds in Thermal Denaturation ofProteins in Eggs……………………………………………………………..….…….70
Ikuya Shimogaki and Yasuji Muramatsu(Graduate School of Engineering, University of Hyogo)
XANES Spectra in the C K and N K Regions of Nitrogen-Containing Aromatic
Compounds……………………………………………………………………...……72
Saki Yamada and Yasuji Muramatsu(Graduate School of Engineering, University of Hyogo)
Annealing effect on the structure and physical properties of highly hydrogenateddiamond-like carbon film…………………………………………………….……..74
Daisuke Niwa1, Tomohiro Mishima1, Koji Nakanishi1, Naoki Fukumuro2,

Tsuneo Suzuki3, Kazuhiro Kanda1(1 LASTI/University of Hyogo, 2 Graduate School of Engineering, University of
Hyogo, 3 Nagaoka University of Technology)
Scanning electron microscopy of living biological samples……………………..….77
Tomoki Eguchi1, Yuhei Miki1, Hidehiro Ishizawa2, Masahiro Takeo2, andSatoru Suzuki1(1LASTI/University of Hyogo, 2Graduate School of Engineering, University of
Hyogo)

Analysis of emulsions by conventional scanning electron microscopy………...…..82
Masaki Nakamura, Satoru Suzuki(LASTI/University of Hyogo)

List of publications……………………………………………………………..……..86
PapersBooks
Proceedings
Reviews
International Meetings
Academic Degrees

Beamlines
Koji Nakanishi
LASTI, University of Hyogo
The arrangement of the beamlines in the NewSUBARU synchrotron radiation (SR) facility is shown 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 by soft/tender X-ray XAFS in 2008. A major upgrade
was started in 2020 for more effective use. The tender X-ray XAFS capabilities that are part of BL05 have been
upgraded and moved to BL06. BL06 was reconstructed as a tender X-ray XAFS beamline and will be further
upgraded in 2022 to enable soft/hard X-ray (1-10 keV) XAFS. A new high-vacuum measurement chamber forsoft X-ray XAFS and a load lock chamber with transfer vessel were installed in BL09A. BL09B beamline
branched from BL09 beamline for the usage of the EUV interference lithography to evaluate. And BL09C
beamline branched from BL09B beamline for the usage of the thickness measurement of the carbon
contamination originated to the resist outgassing during the EUV exposure.

Figure 1. Beamline arrangement in NewSUBARU.
I. BL01

1

BL01 is a beamline for research and developing new light sources. This beamline is one of two long straightsection on NewSUBARU. Optical klystron was installed at this straight section. Upstream side of this beamline(BL01B) is intended to be used for visible 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. 2Gamma-ray beamline hutch just outside of the storage ring tunnel was constructed in 2004
for gamma-ray irradiation experiments. Specification of this gamma-ray 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 fromdeep X-ray lithography, electroforming, and molding process is one of the promising candidates for such 3D
micofabrication. More than hundreds aspect ratio for microstructure can be attained by the usage of the higher
energy X-rays (4-15 keV) from synchrotron radiation (SR) with deeper penetration depth to the photosensitive
resist. In this system we have succeeded to enlarge the exposure area 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 thecase 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 and thinner absorber, since low energy X-rays has
low penetration depth. Based on this principle, the beamline for x-ray exposure have constructed with continuous
selectivity of X-rays from 100 eV to 15 keV by using the X-ray mirrors (plane and cylindrical mirror) and Be
film filters. The horizontal angle of the outgoing SR could be obtained up to 12.5 mrad, which corresponds tothe horizontal size of 220 mm (A4 horizontal size) at the exposure position. The second characteristic
performance of the beamline is the high efficiency differential pumping system. This was necessary for maintainthe vacuum difference between the storage ring (<10-9 Pa) and the end-station (<10-9 Pa) at which gasses for
substrate cooling will be introduced in the exposure apparatus.
The flexibility for the shapes and functions of microstructure will be enlarged by achieving 3D
microfabrication process using multi step exposure at various configuration between X-ray mask and substrates.
2

The relative positions between X-ray mask and substrates, tilt and rotation angle to the SR incident direction canbe 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, and repetition number. In order to decrease the heat loadof sample substrate suffered during SR irradiation helium introduction and substrate cooling mechanism werealso equipped. Specification of spectrometer is listed in Table 3.
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
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 finepattern less than 7-nm 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) reflectometer was UV – VUV reflectometer. At EUV lithography, outof-band radiation (100 – 300 nm) of EUV source degrades image quality. Thus, optics and resist property of outof-band region was essential to evaluate, for example EUV mask reflectivity, and EUV resist sensitivity. The
monochromator specification was shown in Table 4. The EUV microscope (3) has Schwarzschild optics, whichwere 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.
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

IV. BL05
BL05 was constructed in response to a demand in the industry, which is enhancement of the analysis ability inthe soft x-ray region with the development of nanotechnology. BL05 consists of two branch lines for use in thewide 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 is provided 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 and did not perform well enough for industrial and advanced
analysis. In order to solve these problems, a drastic upgrade was started in 2020.
New BL05A
The constant-deviation monochromator consisting of 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 optical system consists of a first mirror (M0), a second mirror (M1), an entrance
slit (S1), a pre-mirror (M2), and three kinds of plane grating (G), an exit slit (S2) and a focusing mirror (M3).
The including angle of the monochromator is 175°. Two measurement chambers for XAFS and PES are prepared3

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

Monochromator
Grating
Energy range
Resolution

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 (BL05B and BL05C)
BL06 had been constructed for irradiation experiments such as photochemical reaction, SR-CVD, photoetching, surface modification. BL06 for irradiation experiments was closed due to plans to build a new beamline
for XAFS measurement. An X-ray mirror, Golovchenko-type double crystal monochromator, measurement
systems and many other beamline components were relocated from former BL05A. The new BL06 will beequipped with two XAFS beamlines, one for XAFS in the 1-5 keV X-ray energy range (BL05B) and the otherfor XAFS in the 1-10 keV energy range (BL05C). BL05C was first set up to enable tender X-ray XAFS, and thenupgraded to enable hard X-ray XAFS in 2022. A Rh-coated collimating mirror with incident/reflected angle of0.28 degrees was selected for this beamline, which allows the photon energy of 1-10 keV. Table 6 shows the
monochromator specification of BL05C.
Table 6. Monochromator specification of BL05C
Double crystal monochromator
Beryl(10-10), KTP(011), quartz(10-10), InSb(111),
Monochromator crystals
Ge(111), Si(111), Si(220), Ge(220), Si(311), Ge(311)Energy range
1 - 10 keV
Monochromator

VI. BL07
This beamline was designed for the development of new materials by SR technology. This beamline consistsof two branch lines, which are provided with an incident beam from a 3-m-long undulator by switching the firstmirror. One of them is a high photon-flux beamline with a multilayered-mirror monochromator for the study of
SR-process (BL07A) and another is a high-resolution beamline with a varied line spacing grating monochromator
for the evaluation of nano-structure characteristics by SR-spectroscopy (BL07B). The useful range of emitted
photons from 50 to 800 eV is covered at both beamlines. The light source of BL07 is a 3-m length planar undulator,
which consists of 29 sets of permanent magnets, a period length of which is 76 mm. The incident beam from theundulator is provided for two branch lines by translational switching of first mirror.
1) BL07A
The multilayered-mirror (MLM) monochromator, which has high reflectivity in the soft X-ray region, wasinstalled 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 to use only first mirror (switching
mirror), M0, for focusing. The MLM monochromator is designed to cover 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 is estimated4

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 mAring current. Table 7 shows the summary of BL07A. In addition, X-ray fluorescence (XRF) apparatus using
spherical varied line spacing grating was mounted at the downstream of irradiation chamber. The poly capillary
was used to enhance beam-condensing efficiency. Measurement energy range was from 30 eV to 450 eV. ThisXRF apparatus was expected to utilize the chemical analysis on the light metals, Li and Be, and light elements,
B, C and N.
Two novel vacuum chambers were installed in 2019 for the measurement of inverse Compton scattering ofsoft X-rays. One large chamber with a size of W1120×D820×H610 mm3 was set up 16.7 m downstream of theundulator center. A multi-layer mirror was placed on high precision auto-stages inside this chamber with coolingwater circulation. The other chamber was installed 2.6 m upstream of the large mirror chamber, in order tomonitor radiated and reflected X-rays.

Energy 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 %

FilterMaterial

Thickness

Al

100 nm

None

-

Ag

100 nmCr
Ni

500 nm
500 nm2) BL07B
The constant-deviation monochromator consisting of a demagnifying spherical mirror and varied line spacing
plane grating (VLSPG), which can provide to high resolution, simple wavelength scanning with fixed slits, wasmounted on BL07B. The optical system consists of a first mirror (M0), an entrance slit (S1), a pre-mirror (M1),and three kinds of plane grating (G), an exit slit (S2) and two focusing mirrors (M2 and M3). The monochromator
is designed to cover the energy range 50-800 eV with three gratings, of which including angle are 168. The
VLSPG has been well known to obtain high resolution in extreme ultraviolet region by diminishing various kindsof aberration. The total resolving power about 3000 can be realized in the whole energy region. Table 8 shows
the specification of the monochromator.
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 and coherent photon
beams radiated from 11 m long undulator in NewSUBARU.
BL09 consists of M0 mirror, M1 mirror, G grating and M2 mirror. 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 monochromator is constructed by M1 and a plane grating. The maximum
acceptance of the undulator beam is 0.64 mrad in horizontal and 0.27 mrad in vertical. The acceptance can be5restricted by 4-jaw slits equipped at upstream of the M0 mirror.
1) BL09A
BL09A beamline is used for material analysis: X-ray absorption spectroscopy (XAS) and X-ray photoelectron
spectroscopy (XPS). In 2013, X-ray emission spectrometer (XES) was introduced at the end-station of the BL09A. The energy range and resolving 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 for theevaluation 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 for the usage ofthe thickness measurement of the carbon contamination originated to the resist outgassing during the EUV
exposure. Table 9 shows the specification of the monochromator.
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

VIII. BL10
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 vertical deflection andbeam convergence. A monochromator is constructed by M1 and a plane grating. At the beginning, the multilayer
reflectivity measurement was carried out at this beamline. The characteristics of this 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-line-spacing plane grating (VLS-PGM). The line density of themonochromator in central region of the gratings were 600, 1800 and 2,400 lines/mm. The reflectometer has a
two-axis vacuum goniometer. One axis carries the sample, which may be a mirror surface at the center of thereflectometer vacuum chamber (θ-motion). The other (φ-motion) carries the detector on a rotating arm. In addition,
there are linear motions to translate the sample in two orthogonal directions (x, y). All motors are controlled bycomputer. 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 most downstream of the BL10 beamline for the EUV mask defectinspection 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 elementswith 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.
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

6

IX. BL11
A beam line BL11 is constructed for exposure Hard X-ray Lithography (DXL) in the LIGA (German acronym
for Lithographite Galvanoformung and Abformung) process. LIGA process, that utilizes a useful industrial
application of SR, is one of the promising technologies for fabrication 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 with height 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 so on. This beam line was designed by thecriteria; photon energy ranges from 2 keV to 8 keV, and a density 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 submicron-scale structure and microstructure with high aspect ratio byselectivity of X-rays using movable mirror system. That is, LIGA process in NewSUBARU can provide the best
3D microfabrication because the BL11 and BL2 are complementary. The beamline BL11 is consisting of anabsorber chamber, a first-mirror chamber (M1), a 4-way slit chamber, a Be and polyimide window chamber, andan exposure chamber. The horizontal angle of the outgoing SR could be obtained up to 17.8 mrad, providing abeam spot size on the exposure stage ≥ 80 × 10 mm2. The micron-scale structure with high aspect ratio will beachieved using the toroidal typed mirror M1 which can produce a parallel collimated beam of X-rays. In addition,
the homogeneity of the beam is excellently controlled by a novel adding system.
Using the precision stage in the exposure chamber, the flexibility for the shaped and functions of
microstructure will be enlarged by achieving 3D microfabrication process using multi step exposure at various
configuration between x-ray mask and substrates. The exposure area of 200 mm × 200 mm is brought to fruition.
In order to decrease the heat load of sample substrate suffered during SR irradiation, helium introduction andsubstrate cooling system 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 from industries, it is necessary to advance technologicaldevelopment for analyzing beamlines (BLs) of NewSUBARU SR facility to advance integrated and strategic
development of analyzing technology. For this reason, the Research Center for Advanced SR Analysis waslaunched in August 2016. As an organization crossing in university courses, this center is consulted andadministered 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 X-rays. We aim to respond to various
analysis needs of the 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 the beamlines.

7

Electron accelerators at NewSUBARU
Satoshi Hashimoto
Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo

Abstract
We report the operational status of two accelerators, the 1.0 GeV electron linear accelerator and the
1.5GeV electron storage ring, at the NewSUBARU synchrotron light facility in FY2022. The reportcovers a wide range of topics, including research and development of accelerator systems,
improvements in beam performance, and aging equipment. We will also introduce free electron laser
experiments performed at beamline BL01. In addition, the development and application of Laser
Compton Scattered gamma-ray sources will be covered.

1. Introduction
The NewSUBARU synchrotron light facility1, 2 houses a 1.5 GeV electron storage ring, making it the largest
accelerator among universities in Japan. Over the course of more than 25 years, this facility has been utilized
not only for fundamental research but also for student education and industrial applications, leveraging its
high-quality soft X-rays. Synchrotron radiation science and accelerator science stand out as major focal pointsof our university.
In FY2020, we successfully constructed a new 1.0 GeV linac dedicated to complementing the
NewSUBARU ring. This achievement was made possible with assistance from the SPring-8 accelerator staff3,
4. Since FY2022, the storage ring has been in operation with the integration of the new injector5.
2. Overview of electron accelerators
Table 1. Performance of the new injector linac.
2.1. 1.0 GeV electron linear accelerator
Figure 1 illustrates the comprehensive
configuration of the injection linac, while
Table 1 provides an overview of the linear
accelerator's performance. An electron beam,
produced through a thermal-cathode RF
electron gun, is accelerated to 1.0 GeV via aseries of stages involving a buncher cavity, Sband, and C-band acceleration tubes.

RequireBeam Energy
Bunch charge
Normalized emittance
Energy spread
Energy stability
Bunch length
Injection efficiency

Measurement

1.0 GeV
100 pC<10 mm-mrad<±0.5%

1.0 GeV
100 pC<10 mm-mrad

5ps (FWHM)>90%

0.4% (STD)<1ps (FWHM)>90%

0.1% (FWHM)

Figure 1. Layout of the new 1.0 GeV electron linear accelerator for the NewSUBARU storage ring.

2.2. 1.5 GeV electron storage ring
The overall arrangement of the ring is depicted in Figure 2. The ring comprises 6 Double-Bend
Achromat (DBA) cells featuring inverse bending magnets. Each cell is separated by 6 straightsections, which serve as locations for an injection septum, an accelerating RF cavity, and three
undulators.
Two long straight sections of 15 m each, one with a 10.8 m long undulator (LU) and the8other with Laser Compton Scattered (LCS) gamma-ray generation and Free Electron Laser(FEL) serves a dual purpose. Our FEL generates ultrashort pulses. Details of the main
parameters of the ring are shown in Table 2. In particular, a key feature of this ring is theadjustable stored beam energy in the range of 0.5 to 1.5 GeV.

Figure 2. General layout of the NewSUBARU storage ring. Electron beams are injected from the
newly-constructed 1.0 GeV linac dedicated to the ring.

Figure 3. Operation time of NewSUBARU

in FY2022.

Table 2. 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

3. Operation Status in FY2022
Our facility provides two different modes of operation for user time: 1.0 GeV top-up mode and 1.5 GeV
current decay mode. Normal business hours are from 9:00 am to 9:00 pm on weekdays. The weekly scheduledesignates Mondays for machine research and development (R&D) activities. Tuesday is allocated 1.5 GeV
of user time, and Wednesday and Thursday are allocated an additional 1.0 GeV of user time. Friday is
specified as 1.0 GeV or 1.5 GeV user time.
Until FY2020, weekday evenings and weekends were available for ancillary machine research andadditional user time utilizing special modes such as single-bunch operation and operation with arbitraryelectron beam energy. However, from 2021, accelerator operation has been limited to the hours from 9:00
am to 9:00 pm on weekdays. This change is due to outsourcing the operation of the accelerator to a privatecompany.
Figure 3 shows the distribution of machine uptime in FY2022. The cumulative operating time of themachine during this period was 1,791 hours, equivalent to 90% of the operating time in FY2021 excluding
beam down time. The term "beam downtime" includes not only periods of mechanical failure, but also beamabort due to issues such as beam instability or mishandling. The total downtime experienced throughout
9

FY2022 was approximately 32 hours, or 1.7% of total operational hours. Additionally, 587 hours were spent
on tuning and machine study activities.
In FY2022, there was concern about a significant reduction in annual operating hours due to soaring
electricity costs. However, due to the implementation of subsequent measures, the user time decreased byonly 2% compared to the previous year.
- Bringing forward user usage end time (from 21:00 to 19:00)- Cost reduction by postponing regular inspections of accelerators- Subsidy from Hyogo Prefecture
4. Machine Trouble
The beam down time in FY2022 was 57 hours. Typical troubles
are as follows.
4.1. Failure of additional power supply for inverse bending
magnets
In NewSUBARU, the bending magnet power supply isconnected in series to the bending magnets and the inverse
bending magnets. However, when accelerating the beam, thecurrent flowing through the inverse-bending magnets is
insufficient, so an auxiliary power supply for the inversebending magnet is connected in parallel. After June 2022, this
auxiliary power supply failed, making it impossible to operate at
1.5GeV, and operating at 1.23GeV during acceleration.

Figure 4. Additional Power supply
for inverse bending magnets.

4.2. Failure of a power supply for bending magnets
Oscillation of the output current of the bending magnet power supply had occurred about once a year until
then, but from April to May 2023, current oscillation occurred frequently and beam abort occurred eighttimes. It was presumed that it was due to aging, but since the specific cause could not be identified, measures
such as cooling the board part inside the power supply with a spot cooler were taken. Oscillation has notoccurred since the end of May, but measures to prevent recurrence and replacement of the power supply arebeing considered.
4.3. Sudden blackout of the power supply of the bending magnet in the beam transport line
About once a year, the power supply of the bending magnet installed in the beam transport system from theinjector exit to the ring accelerator suddenly dropped to 0A during operation. In 2022, such a phenomenon

Figure 5. Oscillation of output current of the power supply for bending magnets.
10

occurred 10 times. There was no abnormality in the power supply inspection, but after replacing the I/O board
for remote control of the power supply, such a phenomenon began to occur on rare occasions.
4.4. Failure of magnet power supply for injector
In 2022, three injector electromagnet power supplies failed. Two of them were discovered during tuning of
the accelerator and immediately replaced with spare parts and restored. The failure of the remaining one wasdiscovered before the beam ejection in the morning and was replaced with a spare in about 30 minutes, so it
is not included in the beam outage time. Of the three failures, two were due to power supply fan failures andone was due to power communication board failures. Regarding the power supply that I had been using formany years, I replaced all the fans after receiving this trouble.
4.5. Vacuum trouble at the beamline BL02
In June 2022, the gate valve between beamline BL02 and the ring accelerator opened due to user error, despite
the poor vacuum in the beamline. As a result, a beam abort occurred due to deterioration of the vacuum levelof the accelerator. Since the Fast-Closing valve on the beamline side and the gate valve between theaccelerator cells automatically closed immediately, the decrease in the degree of vacuum on the acceleratorside was minimized. A TSP flash restored the vacuum and he resumed beam operation 2 hours after shutting
down the beam.
4.6. Injector RF reflection multi-occurrence
Since mid-2022, two of the four C-band accelerator tubes used in injector linacs have increased RF reflections
when boosting to set voltage. It took more than an hour before the start of beam injection in the morning, andthe start of user time was sometimes delayed. After July 2022, we lowered the ring energy from 0.98 GeV to0.95 GeV. This lowered the C-band setting voltage and reduced the frequency of the reflections, but did notcompletely eliminate the reflections. We are currently optimizing the output waveform of the SLED toprevent reflection, and plan to start operation in the fall of 2023.
5. Machine R&D
5.1. SC3 project (mono-cycle FEL)
We are actively working on the SC3 (Slippage-Controlled Coherent Radiation by Chirped Micro-bunching)project in collaboration with the RIKEN Synchrotron Radiation Center, the Graduate School of Materials
Science, University of Hyogo, and LASTI. This effort includes experimental verification of generating ultra
short radiation pulses spanning just a few wavelengths. These were achieved at the NewSUBARU facility
through the use of arbitrary taper undulators6, magnetic chicanes, and chirp seed lasers7. During FY2022, weFigure 6. RF power of C-babd klystron and vacuum pressure in accelerating tube.
11

achieved an important milestone by successfully generating microbunching within a single-electron bunchand subsequently observing coherent radiation8.
5.2. LCS gamma-ray: development of light source and its applications
BL01, a dedicated light source research and development (R&D) beamline, has served as a platform forvarious studies utilizing laser Compton scattered (LCS) gamma rays9-17. As shown in Figures 7 and 8, thisprocess involves the scattering of incident laser photons in the visible or infrared by high-energy electrons,
resulting in the emission of high-energy photons within the gamma-ray spectrum. Figure 9 shows a
representative spectrum of LCS gamma photons, showing the results of using a 532 nm wavelength laser
in combination with a 1.0 GeV electron beam. Our commitment to enhancing and exploiting gamma-ray
sources remains unchanged.
In FY2022, we performed optimization calculations for the incident laser optical system with the aimof increasing the intensity of gamma rays. Optimization of parameters such as waist position and beam
diameter of the 532 nm laser wavelength achieved significant enhancement, increasing the measured
gamma-ray intensity by about 30%9.
5.3. Application of machine learning to beam diagnostics
We used machine learning to analyze the frequency spectrum waveforms of electron beam betatronoscillations in real-time18,19. By learning in advance using several thousand waveform data, horizontal andvertical peak frequencies can be accurately evaluated from noisy waveforms as well as their reliability.
Offline analysis by machine learning was successful, so next is a test using a real beam.
5.4. Other accelerator study
In collaboration with KEK, we initiated the development of a novel beam monitor capable of assessing thetilt of the electron bunch through the electrical processing of the BPM (Beam Position Monitor) signal20.
Accelerator tuning was performed to facilitate beam injection and accumulation at various low energies.
As a result of this effort, we have successfully implanted and accumulated beams in the range of 1.0 to 0.65
GeV while maintaining high injection efficiency and beam intensity. Achieving top-up operation at these
versatile energies is important for photon energy
tuning of free electron laser (FEL) and laser
Compton scattered (LCS) gamma-rays, increasing
their applicability and practicality.
6. Summary
NewSUBARU's 1.0-GeV injector accelerator andstorage ring in FY2022 went smoothly despite someequipment troubles. We have a lot of experience inoperating the new injector. The stable supply ofhigh-quality electron beams from the injector has
Figure 7. General scheme of Laser Compton
improved the performance of the storage ring.
Scattering (LCS) gamma-ray generation at
Currently, it is difficult to secure the number ofBL01.
operating days in FY2023 due to soaring electricity
magnets.
rates. Nonetheless, our commitment to advancing
accelerator capabilities, pioneering new light sources,and expanding industrial support remains unwavering.
Our main goal is to be able to consistently provide

Figure 8. General scheme of LCS gammaray generation.

Figire 9. Typical measured LCS gamma-ray
spectrum at BL01.
12

high-quality synchrotron radiation despite these challenges.
Acknowledgement
We extend our heartfelt appreciation to the accelerator personnel at RIKEN SPring-8 center, JASRI, and SES
for their invaluable collaboration in facilitating the operation of the injector linac. We also wish toacknowledge Dr. Y. Minagawa, Mr. K. Kajimoto, Mr. H. Hirayama, Mr. S. Nakata, and Mr. A. Nakamura of
SES for their dedicated machine operation efforts. Furthermore, we express our profound gratitude to Mr. T.
Ushizawa and Dr. T. Sakurai of JASRI for their contributions towards maintaining stable accelerator
operations. A special note of thanks goes to Dr. Fujii of Kansai Medical University for his noteworthy
contributions to machine learning research. Lastly, our deepest appreciation is reserved for Prof. Miyamotoof Osaka University, whose leadership played a pivotal role in overseeing the construction of BL01.
References[ 1] A. Ando, S. Amano, S. Hashimoto, H. Kinosita, S. Miyamoto, T. Mochizuki, M. Niibe, Y. Shoji, M.
Terasawa, T. Watanabe and N. Kumagai: Journal of Synchrotron Radiation 5(3) 342-344 (1998).
[ 2] http://www.lasti.u-hyogo.ac.jp/NS-en[ 3] S. Hashimoto: LASTI Annual Report 2021, 23, p.1-5 (2022).
[ 4] 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: International Particle Accelerator Cpnference, IPAC2021, WEPAB039 (2021).
[ 5] S. Hashimoto, H. Fujii, T. Sakurai, T. Ushizawa, Y. Minagawa, K. Kajimoto, S. Nakata and H.
Hirayama: Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan, p.1119(2022).
[ 6] T. Tanaka, Y. Kida, R. Kinjo, T. Togashi, H. Tomizawa, S. Hashimoto, S. Miyamoto, S. Okabe and Y.
Tanaka: Journal of Synchrotron Radiation 28(2) 404-409 (2021).
[ 7] Y. Kida, S. Hashimoto, S. Miyamoto, T. Togashi, H. Tomizawa, S. Okabe, A. Gocho, K. Kaneshima,
Y. Tanaka and T. Tanaka: Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan,
p.75 (2022).
[ 8] T. Tanaka, Y. Kida, S. Hashimoto, S. Miyamoto, T. Togashi, H. Tomizawa, A. Gocho, K. Kaneshima
and Y. Tanaka: Phy. Rev. Lett., acceptted (2023).
[ 9] S. Hashimoto and H. Hirakawa: LASTI Annual Report 2022, 24 (2023).
[10] D. Filipescu, I. Gheorghe, K. Stopani, S. Belyshev, S. Hashimoto, S. Miyamoto and H. Utsunomiya:
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers,
Detectors and Associated Equipment, 1047, p.167885 (2022).
[11] T. Ari-Izumi, I. Gheorghe, D. Filipescu, S. Hashimoto, S. Miyamoto. H. Utsunomiya, J. Instrum. 18
T06005 (2023).
[12] T. Sanami, T. Tran, T. Nguyen, H. Yamazaki, T. Itoga, Y. Kirihara, Y. Namito, H. Nakashima, S.
Miyamoto, S. Hashimoto and Y. Asano: Proceedings of 19th Annual Meeting of Particle Accelerator
Society of Japan, p.70 (2022).
[13] T. Sanami, T. K. Tran, H. Yamazaki, T. Itoga, Y. Kirihara, Y. Namito, Y. Sakaki, S. Miyamoto and Y.
Asano: 15th international conference on nuclear data for science and technology (ND2022), EPJ Web
of Conferences 284, 01047 (2023).
[14] T. K. Tran, Y. Sakaki, T. Sanami, H. Yamazaki, Y. Namito, T. Itoga, Y. Kirihara, S. Miyamoto and Y.
Asano: 15th international conference on nuclear data for science and technology (ND2022), EPJ Web
of Conferences 284, 01048 (2023).
[15] T. K. Tuyet, T. Sanami, H and Yamazaki: 14th International Conference on Radiation Shielding and21st Topical Meeting of the Radiation Protection and Shielding Division, Seattle, WA September 25–
29 (2022).
[16] T. Sanami et al.: LASTI Annual Report 2022, 24 (2023).
[17] M. Omer et al.: LASTI Annual Report 2022, 24 (2023).
[18] H. Fujii, K. Watanabe and S. Hashimoto: Proceedings of 19th Annual Meeting of Particle Accelerator
Society of Japan, p.557 (2022).
[19] H. Fujii et al., LASTI Annual Report 2022, 24 (2023).
[20] T. Nakamura et al.: Proceedings of 20th Annual Meeting of Particle Accelerator Society of Japan,(2023).
13

Development of Betatron Tune Correction System
by Deep Learning Using Loss Function with Quality Filter
Hitoshi Fujii1, Kousuke Hirose2, and Satoshi Hashimoto1
1

Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo
2
Faculty of Engineering, University of Hyogo

Abstract
In the NewSUBARU synchrotron light facility, real-time observations and analyzes of betatronoscillation spectra are performed for tune correction. Here, the observed spectra are sometimes
obscured due to various reasons, and wrong betatron frequencies are estimated from such spectra,
in which case the tune correction fails. To avoid this, current tune correction systems use complex
algorithms with many parameters to be manually adjusted. However, this system cannot handle
various operation modes in NewSUBARU, and when updating devices such as electromagnets, it isnecessary to update the parameters of the system from scratch. Therefore, we proposed deep learning
using “loss function with quality filter” and developed a new spectral analysis method that is more
flexible and accurate than the current systems.

1. Introduction
The electron beam oscillates slightly in the horizontal and vertical directions from the design orbit in thestorage ring, which is called betatron oscillation. The number of the oscillations per round of the ring iscalled “tune”. The problem in stabilizing the electron beam is not the betatron oscillation itself, but thetune value. For example, if the tune is an integer, it means that the electron beam rounds exactly the same
trajectory every round. In this case, similar to resonance of pendulum, if there is even a small extra
magnetic field somewhere in the ring, the electron beam will be affected by the external force in the same
direction every round and the amplitude of the betatron oscillation reaches the vacuum chamber. As aresult, the lifetime of the electron beam is reduced or, in the worst case, the beam is completely lost (thesame problem occurs when the decimal part of the tune is described by a relatively simple fraction suchas 1/2, 1/3, etc.). It is impossible to completely remove the extra magnetic field in the storage ring.

Figure 1. An example of betatron oscillation spectrum. The vertical axis is signal intensity and thehorizontal axis is frequency index; frequency is represented by the index number of the array forsimplification.
14

Therefore, in order to stabilize the electron beam, a tune correction system is required to constantly
monitor the tune value (that can change) and maintain (previously researched) optimal values.
Figure 1 shows an example of a betatron oscillation spectrum. The two large peaks are the horizontal
and vertical components of betatron oscillations, respectively. Tune values are estimated by performing apeak extraction from the spectrum. At this time, it is not always possible to obtain a clear spectrum asshown in Fig. 1, and the quality of spectrum data may deteriorate for some reason (for example, at thetime of electron beam injection, acceleration, deceleration, etc.). In such cases, a wrong tune value may
be estimated and the system performs a wrong correction, resulting in the loss of the electron beam.
Therefore, before performing the tune correction, it is necessary to judge whether the spectrum issufficiently reliable (high quality) to be used for the correction. In the current correction system, thejudgement is made by a complicated algorithm with many thresholds such as the height, half-width andapproximate position of the spectral peak. In the system, however, when the outline of the observed
spectra changes significantly due to changes in driving conditions or equipment upgrades, all parametersof the system must be readjusted manually.
In this study, we proposed a “loss function with quality filter” for deep learning and developed a more
flexible spectral analysis method. With this method, it is possible to simultaneously judge the quality ofspectra that can be used for correction and estimate the tune values (peak positions of spectra) by using asingle network. There are almost no parameters that need to be manually adjusted.
2. Method
2.1. Definition of Loss Function
Training a network requires a large amount of teacher data which is a set of features (descriptors) andtarget variables (correct answer values). In many cases, there is only one target variable, but there may be
multiple targets. In our case, there are three targets in total: the quality value (reliability or clarity) and thepeak positions for horizontal and vertical component of the spectra. The features are the spectral data
itself. The spectral data can be collected easily, and all the collected spectra are annotated, i.e., given
correct labels of quality values and peak positions1,2. The loss function with quality filter is defined asfollows:
𝐿(𝑡𝑞 , 𝑦𝑞 , 𝒕, 𝒚) = 𝑙𝑞 (𝑡𝑞 , 𝑦𝑞 ) + 𝛼𝑡𝑞 𝑙(𝒕, 𝒚),(1)𝑙𝑞 (𝑡𝑞 , 𝑦𝑞 ) = −𝑡𝑞 ln 𝑦𝑞 − (1 − 𝑡𝑞 ) ln(1 − 𝑦𝑞 ),(2)where 𝑡𝑞 ∈ {0,1} is the correct value of the quality (a binary value of 0: low or 1: high). 𝑦𝑞 ∈ [0,1] isa quality value estimate by network. 𝑙𝑞 (𝑡𝑞 , 𝑦𝑞 ) is called the binary cross-entropy error and is often used
as a loss function for binary classification problems. In the present case, 𝑙(𝒕, 𝒚) is appropriate to use
2𝑙(𝒕, 𝒚) = (𝑡𝑥 − 𝑦𝑥 )2 + (𝑡𝑦 − 𝑦𝑦 ) .

(3)This is the sum of the residual sum of squares which is used as a loss function of regression problems
with multiple target variables. 𝑡𝑥 and 𝑡𝑦 are the peak positions of the horizontal and verticalcomponents, respectively. 𝑦𝑥 and 𝑦𝑦 are the estimated values of 𝑡𝑥 and 𝑡𝑦 respectively. 𝛼 is a
hyperparameter to balance the magnitude of 𝑙𝑞 and 𝑙. Here, the point is that the second term of 𝐿 is
multiplied by 𝑡𝑞 . This works as a filter, i.e., skips learning about 𝒕 in the case of low-quality (𝑡𝑞 = 0)data. As a result, if the quality of the data is so low that it is impossible to annotate 𝒕 even with the humaneye (only 𝑡𝑞 = 0 is known), it is enough to put dummy values in 𝒕.
2.2. Definition of Network
Figure 2 shows the network configuration. The basic structure is the same as AlexNet3 proposed for image
recognition, but one-dimensional convolutional layers are used. In addition, the output layer is branched
into two, one related to prediction of quality and the other related to prediction of peak positions. In otherwords, the network for quality prediction is also used for peak position prediction partially. This is more
15

Figure 2. Illustration of the architecture of our network. FN, FS, and S mean the number of filters, filter size,and stride size, respectively. The left-hand side of the output layer gives an estimation value for certainty
and the right-hand side gives estimation values for peak positions.

efficient than building two completely independent networks. Also, in general, branching the output layer
can be expected to suppress over-learning.
3. Results and Discussion
As a result of testing the above network using actual spectrum data, the success rate for the spectra withquality𝑡𝑞 = 0 (ratio of correctly judging the low values as low) was 0.900, and the success rate for the
spectra with quality at 𝑡𝑞 = 1 (ratio of correctly judging the high values as high) was 0.969. The
prediction accuracy (RMSE) of the peak positions for the spectra with 𝑡𝑞 = 1 was 7.189 for thehorizontal component and 2.482 for the vertical component. This means that the prediction errors of thepeak positions are about 1 % in the given range, and it can be seen that the peaks can be extracted withconsiderable accuracy. The details of the results are in reference 1.
4. Conclusion
We developed a new spectra analysis method by using deep learning with loss function with quality filter.
This method shows that even with a relatively shallow network, it is possible to simultaneously predict
the quality and peak positions from spectra with high accuracy. By incorporating this network into thecurrent tune-correction system, it is expected that a more flexible system can be constructed.
References[ 1] H. Fujii, K. Watanabe, and S. Hashimoto: PASJ2022, WEP019 (2022).
[ 2] https://github.com/Hitoshi-FUJII/GFit.
[ 3] A. Krizhevsky, I. Sutskever, and G. E. Hinton: Communication of the ACM 60 (6), 84–90 (2017).

16

Increased LCS -ray flux by optimizing laser optics at BL01
Satoshi Hashimoto and Haruto Hirakawa
Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo

Abstract
The NewSUBARU light source R&D beamline BL01 is one of the few Laser Compton Scattered(LCS) gamma-ray facilities in the world, capable of producing gamma-rays of excellent
performance. Increased gamma-ray intensity is important for users. By optimizing the laser opticalsystem, we succeeded in increasing the number of gamma-ray photons by about 30%.

1. Introduction
LCS gamma-rays have excellent properties such as energy tunability, high directivity, quasimonochromaticity, and polarization1,2. BL01 generates gamma-rays by colliding incident laser photons headon with relativistic electrons orbiting within a storage ring. For users3-8, increasing the intensity of gammarays (the number of photons) has major benefits,
such as shortening experiment time and improving
the signal-to-noise ratio. One way to solve thisproblem is to optimize the laser optics. By focusing
the laser beam to a small radius at the right location,1mefficient collisions between electrons and laser
532nm
10m
photons occur. Figure 1 shows the profiles of threelasers that have been in use for many years. It can be
E-beam(H)seen that the laser waist size is large due to long
distance transmission and the waist position of the
E-beam(V)laser does not match that of the electron beam. We
have optimized the optics of the Talon laser (532
Figure 1. Horizontal and vertical elcctron beamnm) and succeeded in improving the measured
radius and beam radius of three lasers used at
gamma-ray intensity by about 30%. This report
BL01.
describes the details.
2. Optimization of laser optics
2.1. Optimization calculation
Optimization calculations for laser optics were performed using one divergent lens and one convergent lensin the tunnel. For calculations, we used a Python code created by Hirakawa based on Gaussian optical theory.
The beam portion exceeding the aperture of the viewport or optical element on the optical path was treatedas a loss. Table 1 and Fig. 2 show the results of minimizing the beam waist and designing the waist position
to be in the center of the straight section. Before optimization (Fig.2-a), the beam waist was relatively large,
and the waist position was approximately 2.3 m away from the center of the straight section. As shown in
Fig.2-b, the beam waist is narrowed down by optimization using two lenses, and the waist position coincides
with the center of the straight section.
2.2. Estimation of gamma-ray flux
The number of LCS gamma-ray photons N is expressed by the following equation2.
Nγ = c(1 + β)

I P
σ ∫ L(z)dzeυ Ep c tot z(1)

where c is the speed of light,  is the normalized electron velocity, I the stored current value, e the elementarycharge, υ the electron velocity, P the incident laser power, E p the incident photon energy, and tot the scatteringcross section. L(z) represents the degree of overlap between the incident laser and the electron beam, and isexpressed by the following equation2.

171

L(z) =(2)2π√σx (z)2 + w(z)2 √σy (z)2 + w(z)2where σx(z) and σy(z) are the horizontal and vertical sizes of the electron beam, and w(z) the beam size of theincident laser. The effect of laser optics concerns only the integral term in eq. (2). Fig. 3 shows the laser
radius and L function in the straight sectiom of the storage ring. The gamma-ray intensity can be evaluatedusing the value obtained by integrating the L function over the laser pulse width (30 ns) centered on theposition where the L function was maximum. The calculation results showed that by optimizing the optics,
the gamma-ray intensity could be approximately doubled.
Table 1(a). Talon laser optics parameter before
optimization.
type
convergent
Lens 1
Focal length [m]5Position [m]7.152
Laser waist [mm]1.04
Laser waist pos.[m]20.05
E-beam waist pos. [m]
22.41

lens

Center of straightsection

Laser
(z=0)

Table 1(b). Talon laser optics parameter after
optimization.
type
divergent
Lens 1
Focal length [m]-0.2
Position [m]
6.84
type
convergent
Lens 2
Focal length [m]0.5Position [m]7.144
Laser waist [mm]0.46
Laser waist pos.[m]22.03
E-beam waist pos. [m]
22.41

Lens2

Lens1

Figure 2. Laser beam radius (a) before and(b) after the optics optimization. Laser
wavelength is 532 nm. Laser is located at
z=0. Dotted line denotes the center of thestraighr section og the ring.

after∫Ldz=1.02
before

L function

Figure 4. Measured gamma-ray spectra
bedore (blue) and after (orange) the optics
optimizarion.

∫Ldz=2.15
L function

Table 2. Typical parameters at -ray
measurement

Figure 3. Overlap function before (upper) andafter (lower) optimization of laser optics.
18[Electron]

0.95 GeV, 10 mA, Sigle bunch[Laser]532 nm, 15 W, 20 kHz[Collimator]

φ3 mm

3. Measurement of increased gamma-ray flux
The number of gamma-ray photons per second was measured
using a Ge detector and a multichannel analyzer. Typicalparameters during measurement are shown in Table 2. Fig. 4
shows the measured spectra of gamma-rays before and after
the optimization of the optical system. It can be seen that the
number of gamma photons is improved by about 30% despite
the same stored current and laser power.
The measured gamma-ray photon increase was smaller
than the calculated value. This may be due to insufficientprecision in laser beam alignment. In calculating the Lfunction, it is assumed that the electron beam orbit and the
Figure 5. Damaged Ag-coat Si mirror
incident laser optical axis are perfectly aligned. However, inin vacuum (left) and vaciim viewport
reality it is very difficult to match the two beam axes. To solve(right) for Talon laser.
this problem, we are preparing to remotely control the opticalelements inside the shield tunnel, which have been difficult toadjust.
Another cause is damage to the silver-coated mirror in vacuum and the vacuum viewport for laser
incidence due to synchrotron radiation. Figure 5 shows the Talon laser mirror and vacuum window that were
replaced in August 2023. Damage caused by synchrotron radiation is clearly visible on the Si mirror surface.
Clouding was also observed at the same location inside the vacuum window. The data shown in Fig. 4 wasmeasured with the damage shown in Fig. 5. The experiment, which will resume this fall, will use new opticalelements, so a larger gamma-ray flux is expected.
4 Summary
By optimizing the LCS gamma-ray laser optical system, we succeeded in increasing the number of gammaray photons by approximately 30%. Although further improvement could be expected from the calculation
point of view, it is thought that the accuracy of the optical axis alignment and dirt on the vacuum mirror andvacuum window were the factors. By improving these in the future, we aim to further improve the LCS
gamma ray intensity.
Acknowledgement
We are deeply grateful to Mr. H. Hirayama, Mr. S. Nakata, Mr. A. Nakamura, and Dr. Y. Minagawa of SES
for their efforts in BL operation. We would also like to thank Mr. T. Ushizawa and Dr. T. Sakurai of JASRI
for their great contributions in maintaining the safety interlock system. Finally, we would like to express my
deep gratitude to Prof. Miyamoto of Osaka University, who played a central role in overseeing theconstruction of BL01.
References[ 1] D. Filipescu, I. Gheorghe, K. Stopani, S. Belyshev, S. Hashimoto, S. Miyamoto and H. Utsunomiya:
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers,
Detectors and Associated Equipment, 1047, p.167885 (2022).
[ 2] T. Ari-Izumi, I. Gheorghe, D. Filipescu, S. Hashimoto, S. Miyamoto. H and Utsunomiya: J.
Instrum. 18 T06005 (2023).
[ 3] T. Sanami, T. Tran, T. Nguyen, H. Yamazaki, T. Itoga, Y. Kirihara, Y. Namito, H. Nakashima, S.
Miyamoto, S. Hashimoto and Y. Asano: Proceedings of 19th Annual Meeting of Particle Accelerator
Society of Japan, p.70 (2022).
[ 4] T. Sanami, T. K. Tran, H. Yamazaki, T. Itoga, Y. Kirihara, Y. Namito, Y. Sakaki, S. Miyamoto and Y.
Asano: 15th international conference on nuclear data for science and technology (ND2022), EPJ Web
of Conferences 284, 01047 (2023).
[ 5] T. K. Tran, Y. Sakaki, T. Sanami, H. Yamazaki, Y. Namito, T. Itoga, Y. Kirihara, S. Miyamoto and Y.
Asano: 15th international conference on nuclear data for science and technology (ND2022), EPJ Web
of Conferences 284, 01048 (2023).
[ 6] T. K. Tuyet, T. Sanami, H and Yamazaki: 14th International Conference on Radiation Shielding and21st Topical Meeting of the Radiation Protection and Shielding Division, Seattle, WA September 25–
29 (2022).
[ 7] T. Sanami et al.: LASTI Annual Report 2022, 24 (2023).
[ 8] M. Omer et al.: LASTI Annual Report 2022, 24 (2023).
19

Cross section asymmetry of polarized γ-ray elastic scattering
M. Omer1, T. Shizuma2, M. Koizumi1, R. Hajima2, S. Hashimoto3, and S. Miyamoto4
1

Japan Atomic Energy Agency
National Institutes for Quantum Science and Technology
3
Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo
4
Institute of Laser Engineering, Osaka University
2

Abstract
Nondestructive elemental analysis is highly valued in many fields, such as archeology, paleontology,
space sciences, nuclear security, and nuclear nonproliferation. These fields usually impose estimating
the elemental composition of bulk, large, and inhomogeneous samples nondestructively. Common
elemental analysis techniques such as X-ray fluorescence (XRF) may fail in such situations due to theself-absorption of low energy X-rays within thin layers of the sample. In the present study, we propose
a novel nondestructive method that may be useful in distinguishing the elemental composition of a given
sample based on the elastic scattering of linearly polarized and high-energy γ-rays. Linear polarizationof γ-rays causes asymmetry of the elastic scattering cross sections with respect to the polarization planeof the incident γ-rays. At specific γ-ray energies and scattering angles, the asymmetry ratio, R, of thecross sections in two orthogonal planes is characteristic of each element. Therefore, we anticipate that
R may be considered as a spectroscopic quantity that can be measured using in-beam γ-ray spectroscopy.

1. Introduction
Elastic scattering of polarized γ-rays by atoms is a complicated interaction comprising many scattering
processes such as Rayleigh scattering, nuclear Thomson scattering, and scattering by the strong Coulomb
field around the nucleus, known as Delbrück scattering. All of these scattering processes manifest theinteractions of γ-rays with charge collections (electrons and nucleus) and their electric field. Theoretical
calculations of the scattering amplitudes have been performed and are available for each process1-4. Some ofthe scattering amplitudes, such as nuclear Thomson, are proportional to Z2, where Z is the atomic number.
Other scattering amplitudes, such as Delbrück amplitudes, are proportional to higher orders of Z. Thus, thedifferential cross section of the elastic scattering interaction (d𝜎) is, in principle, a unique fingerprint of eachelement. However, d𝜎 is a superposition of the scattering amplitudes of all processes and must be added
coherently. At certain conditions, the superposition of the scattering amplitudes results in a considerable
asymmetry in the angular distribution of the scattered γ-rays. Figure 1 shows an example of such asymmetry
for lead and tantalum elements. This asymmetry may be used in identifying the element under consideration.
Furthermore, the asymmetry of the elastic scattering cross section may be employed to isolate Delbrück
scattering contribution by a precise selection of scattering conditions and photon energy5. Experimental
measurement of Delbrück scattering will provide a unique test of the nonlinear aspects of the quantum
electrodynamics6. In the past, elastic scattering experiments using linearly polarized γ-rays could not be
conducted due to the unavailability of perfectly polarized γ-rays. However, Laser Compton Scattering (LCS)
γ-ray sources provide such polarized γ-rays. An example of these LCS sources is the γ-ray beamline (BL01)
at the NewSUBARU facility.

Figure 1. The calculated asymmetry ratios for the scattering of linearly polarized 1500 keV (left) and 1600
keV (right) γ-rays by tantalum and lead atoms.
20

Figure 2. Experimental setup for the elastic scattering experiment of linearly polarized γ-rays, top view(left) and side view (right).
2. Experimental Methods
2.1. Photon scattering measurement
A 20×8∅ mm cylindrical Ta target was irradiated by linearly polarized γ-rays generated by laser Compton
scattering at the NewSUBARU facility. Approximately 5-W CO2 linearly polarized laser beam was allowed
to collide with 0.95-GeV electrons. The generated γ-rays are linearly polarized with a maximum energy of
1.62+0.02−0.18 MeV. The elastically scattered γ-rays were measured using a 140% high purity germanium detector
positioned horizontally at 15 cm from the center of the target and at 45º in the horizontal direction, as shownin Figure 2. The γ-rays’ polarization plane was controlled by a couple of CO2 laser polarizers as a surrogateof half-wave plates. The γ-ray beam flux and profile were measured by moving the HPGe detector in thebeam. Furthermore, the γ-ray beam flux was continuously monitored during the measurement by a large NaI
detector. The estimated flux of the γ-ray beam was approximately 5.7×104 γ/s in the case of verticallypolarized γ-rays. However, the flux of the horizontally polarized γ-ray dropped to approximately one fifth ofthe value of the vertically polarized flux. This reduction in the flux originates from the intensity loss of thelaser beam due to the rotation of the polarization plane.
2.2. Monte Carlo simulation of the beam profile
Accurate estimation of the γ-ray beam profile is required to extract the elastic scattering cross section. We
performed Monte Carlo simulations to obtain the γ-ray beam profiles using the LCS simulation models
developed7,8 in the Geant4 simulation toolkit9. The γ-ray beam profiles calculated by the simulation are
shown in Figure 3 for the horizontal and vertical polarization cases. The measured γ-ray profiles for the two
photon polarization states are also shown in Figure 3. Except for the drop in the intensity of the γ-ray beam,
there is no observed difference between the beam profiles due to polarization planes.

Figure 3. The simulated and measured LCS γ-ray beam profiles for the vertical and horizontal linear
polarization states.
21

Counts per keV

3. Results and Discussion
The γ-ray spectra of the elastically1800
scattered photons when the polarization isperpendicular (vertical) and parallel
Vertical Polarization
1600(horizontal) to the scattering plane areshown in Figure 4. The spectra are
1400
normalized to the flux of the γ-ray beammeasured vertically. Although the statistics
1200
of the measurement are not high, there is
Horizontal Polarization
an observed difference between the two
1000
measurements, which may indicate that800
there is a possible asymmetry in the
angular distribution of elastic scattering of600
polarized γ-rays. These results reveal thatthe asymmetry in the elastic scattering of
400
γ-rays with respect to the polarization
direction of the incident photon could be200
observed for tantalum atoms. However,much more γ-ray beam flux is required to
0
1500
1550
1600
1650
1700
1750
evaluate the asymmetry due to theEnergy (keV)polarization of γ-rays.
It should be noted that the spectra shown in
Figure 4. Results of the elastic scattering of linearly
Figure 4 represent the average of the elastic
polarized γ-rays by Ta target.
scattering cross section over the energy
distribution and the angular spread of thedetector used in the measurement. The energy distribution spans approximately 100 keV, from 1500 to 1600
keV, while the angular spread of the detector is approximately 30º. As shown in Figure 1, the asymmetry is
maximum at 51º and 48º for the energies of 1500 keV and 1600 keV, respectively. However, the asymmetry
drops significantly far from these two scattering angles. Therefore, we only observe a low asymmetry ratio
due to the energy and angular spreading of the γ-ray beam and scattering angle. In the future, higher γ-ray
beam flux will enable a measurement with a much lower angular spread, which may provide a more accurate
measurement of the asymmetry ratio.
4. Conclusion
Asymmetry of the elastic scattering cross section due to linear polarization of γ-rays could be measured
for the Ta target at 1.62 MeV. Statistical uncertainty can be improved by increasing the detection efficiency
and enhancing the γ-ray beam flux.
Acknowledgement
This work is a contribution of the Japan Atomic Energy Agency (JAEA) to the International Atomic Energy
Agency (IAEA) under the agreement of the coordinated research program (CRP), J02015 (Facilitation of
Safe and Secure Trade Using Nuclear Detection Technology - Detection of RN and Other Contraband).
References[1] M. Omer, and R. Hajima: New J. Phys., 21 (11), 113006 (2019).
[2] M. Omer, and R. Hajima: Nucl. Instrum. Methods Phys. Res. B, 405, 43-49 (2017).
[3] L. Kissel: Radiat. Phys. Chem., 59 (2), 185-200 (2000).
[4] H. Falkenberg et al.: At. Data Nucl. Data Tables, 50 (1), 1-27 (1992).
[5] J. K. Koga and T. Hayakawa: Phys. Rev. Lett., 118, 204801 (2017).
[6] J. Sommerfeldt, V. A. Yerokhin, Th. Stöhlker, and A. Surzhykov: Phys. Rev. Lett. 131, 061601 (2023).
[7] R. Hajima: Nucl. Instrum. Methods Phys. Res., Sect. A, 985, 164655 (2021).
[8] Gianfranco Paternò, Paolo Cardarelli, Matteo Bianchini, Angelo Taibi, Illya Drebot, Vittoria Petrillo, andRyoichi Hajima: Phys. Rev. Accel. Beams 25, 084601 (2022).
[9] S. Agostinelli, et al.: Nucl. Instrum. Methods Phys. Res., Sect. A, 506 (3), 250–303 (2003).

22

Implementation of SERS active structures using boehmite in
microfluidic devices
Shunya Saegusa1, Masayuki Naya2, Takao Fukuoka1, Sho Amano1, Yuichi Utsumi1, Akinobu Yamaguchi1
1

Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo
2
Faculty of Science and Technology, Keio University

Abstract
Surface-enhanced Raman scattering (SERS) is high sensitivity, label-free, and suitability for long-term
measurement. So, this measurement is expected to be applied to real-time measurements in bioanalysis
and environmental analysis. Especially, gold nanofève (GNF)-SERS structure deposited on a boehmite
substrate is capable to have high-sensitivity and high-resolution measurements in a wide area. We
improved the adhesion of the GNF-SERS active pattern by magnetron sputtering and integrated thissensor into a microfluidic system. To evaluate the performance of the system, 4, 4’-Bypiridine (4bpy)
was used for SERS measurement in the microchannel. This study shows that our microfluidic systems
with the GNF-SERS active patterned area have the adequate potential for application and developmentin environmental analysis.

1. Introduction
Surface Enhanced Raman Scattering (SERS) is a spectroscopic method that enhances weak Raman signals
by the enhancement of the electric field on the noble metal surface by Local Surface Plasmon Resonance(LSPR), and enables detection of single molecules1-8. SERS is characterized by its high sensitivity and labelfree measurement, and is also suitable for measurements that take a long time because it is less affected bylight fading than the fluorescence method. Because of the above features and the ability to measure samples
in water, SERS has been applied mainly to molecular imaging for bioanalysis 2,3. However, SERS active
structures have the disadvantage that they are difficult to fabricate extensively on substrates such as glass. In
this study, we have focused on an easy method to fabricate SERS-active structures of gold nanofibers (GNFs)
using the boehmite structure, which is an aluminum hydroxide 6-8. The GNF structures can be fabricated to
produce stronger localized electric field enhancement. This method can be used to construct nanoscale noble
metal gap structures with high-sensitivity and high-resolution measurement over large areas 6-8. The
conventional method of fabricating noble metal layers using electron beam oblique deposition has highreproducibility and high performance, but has problems in terms of adhesion and stacking area 7,8. Therefore,
we changed the noble metal layer fabrication method from electron beam deposition to magnetron sputtering
to investigate the SERS activity sensitivity and to evaluate the distance dependence of the SERS activity
from the substrate edge 6. In this paper, SERS structures were successfully implemented in a microfluidic
system 9 by patterning and fabricating them in the desired position and shape based on the above methods.
In order to evaluate the performance and characteristics of the microfluidic system, experiments wereconducted to see if the detection intensity changes with the time and concentration of specimen flow. If the
GNF-SERS structure, which enables single-molecule detection by spectroscopic methods, can be patterned
at a desired position and fabricated into a microfluidic system, it is expected to be developed into a molecularimaging system that can measure molecules for a long time, and applied to environmental analysis and drug
screening.
2. Experimental
2.1. GNF-SERS structure fabrication method
The GNF-SERS structure was fabricated through a two-step process of boehmite formation on the glass slide
surface and oblique sputtering of gold. The specific processes are as follows.
1) Boehmite formation
Formation of an Al layer of 84 nm on a glass slide using magnetron sputtering. The glass substrate isimmersed in deionized water heated to 100 ºC and heated for 10 minutes to progress the Al hydroxylation
reaction.
232) Diagonal sputtering of gold
As shown in Figure 1, for
GNF structure fabrication, theboehmite substrate is tilted 10
degrees and sputtered with
about 60 nm of Cr/Au while
covered with a cover. The
reason for covering thesubstrate in step 2) is to limit
the deposition direction. In
addition, we limited thelocation of the SERS structureformation using a metal mask.

Cover

Au

Figure 3. Schematic diagram of diagonal sputtering of gold.

2.2. Fabrication of flow channel structure
Polydimerthylsiloxane (PDMS) wasused as a component material for
microfluidic devices. PDMS can betransferred to micron-order structuresby molding with high accuracy and canbe easily sealed by surface treatment
with high adhesion to glass and othermaterials9.The mold master for molding
was made of resin and printed using a
3D printer as shown in Figure 2. The
mold was designed to allow SERS
measurement while mixing two liquids.
PDMS precursor (10:1 liquid mixture of
PDMS monomer and cross-linker) was
poured onto the prepared master, andheated on a hot plate at 100°C for 30
minutes. Finally, a UV ozone cleaner
was used to perform a 5-minute plasma
treatment on the bonding surface of the
SERS substrate and channel structure
before bonding.
2.3. Fluid Measurement
SERS measurement was attemptedusing the fabricated microfluidic
device. The measurement system isshown in Figure 3, in which purewater and 4,4'-Bipyridine (4bpy)
were used as the sample. The
measurement method was as follows:
4bpy and pure water were mixed andpumped through a syringe, and a
Raman spectroscopy module wasused to perform SERS measurements
by irradiating a laser beam.

Figure 2. Fabrication of SERS device.

Raman module

SERS device

Waste liquid

Figure 3. Schematic diagram of fluid measurement system.

24

(a)

(b)

Figure 4. SERS substrate (a) SERS image, (b) Optical photograph.

3. Results and Discussion
3.1. Fabricated SERS device
The fabricated SERS structure is shown in Figure 4 (a), confirming the formation of the GNF-SERS structure.
(4bpy) from our previous study up to 100 nM, confirming that the sensitivity is sufficient for application 6.
When the SERS structure is formed on the entire surface of a glass slide, the film thickness is uneven as
shown in Figure 4 (b), but SERS activity can be realized in 20 x 20 mm2 .6 The structure fabricated using a
metal mask made of an Al thin film (0.1 mm) is shown in Figure 6. The transfer was successful, and theincreased glass surface area is expected to improve adhesion to the PDMS and prevent water leakage.
3.2. Fabricated SERS device
4bpy (20 µM) and pure water were each pumped at a flow rate of 0.1 mL/min for 40 min. After 40 min ofpumping, the pumping was stopped for 10 min. Figure 5 shows the results of the pumping. Figure 6 shows
the change in peak intensity at 1614 cm-1. The intensity of the peak at 1614 cm-1 increased as the flow rate
was changed, and equilibrium was reached in about 15 minutes after SERS was reached. This indicates thatsample molecules accumulate. Therefore, if the sample molecules are adsorbable on the SERS substrate, they
can be detected at any low concentration if the flow is continued for an extended period of time. The fact that
the Raman intensity is maintained even after the fluid has been flowing for more than one hour indicates that

22000

Intensity(arb.unit)

Intensity(arb.unit)

0 min
10 min20 min30 min

18000
14000

10000
6000
2000
0

10

20
30
40
50
time(min)Figure 6. Change in peak intensity (1618 cm-1).
400

800

1,200
1,600
-1
Raman Shift(cm )2,000

Figure 5. Change in Raman spectra.

25the SERS structure can be used for long-term experiments. In addition, an increase in intensity was observed
after the syringe pump was stopped. This may be due to the decrease in flow rate, which reduced the amountof 4bpy detached by the flow and caused more 4bpy to adhere to the electric field enhancement area. Basedon the above, we believe that it is possible to develop analytical devices for long-term bioanalysis andenvironmental analysis by verifying the relationship between the change in saturation intensity with flow rate
and the arrival time of saturation intensity with concentration.
4. Conclusion
In this study, we implemented GNF-SERS with a Boehmite substrate in a microfluidic device and attempted
to measure SERS of fluids. As a result, we succeeded in measuring a fluid of 4bpy equivalent to 10 µM. It
was found that the intensity saturated as the sample molecules accumulated and became more numerous thanin the electric field enhancement area when the fluid continued to flow for a long period of time. The factthat SERS activity was always shown during the one-hour long experiment suggests the possibility of
application to real-time measurements in bioanalysis and environmental analysis.
Acknowledgement
This research and development were supported by Grant-in-Aid for Scientific Research (22H01920), Tokyo
Ohka Foundation for Science and Technology, and Hyogo Science and Technology Association. We would
like to express our deepest gratitude to the following organizations.
References[ 1] K. Kneipp, Y. Wang, H. Kneipp, L. T. Perelman, I. Itzkan, R. R. Dasari, and M. S. Feld: Phys. Rev.
Lett., 78, 1667 (1997).
[ 2] C. Zong, M. Xu, L. Xu, T. Wei, X. Ma, X. Zheng, R. Hu, and B. Ren: Chem. Rev., 118, 4946−4980(2018).
[ 3]
H. Wei, S. M. H. Abtahi, and P. J. Vikesland: Environ. Sci.: Nano, 2, 120 (2015).
[ 4] A. Yamaguchi, T. Fukuoka, R. Hara, K. Kuroda, R. Takahashi and Y. Utsumi: RSC Adv., 5, 73194(2015).
[ 5] N. Chen, T. Xiao, Z. Luo, Y. Kitahama, K. Hiramatsu, N Kishimoto, T. Itoh, Z Cheng, and K. Goda:
Nat. Comm., 11, 4772 (2020).
[ 6] T. Tanaka, S. Saegusa, M. Naya, T. Fukuoka, S. Amano, Y. Utsumi, A. Yamaguchi: J. Photopolymer
Sci. Technol., 35.3, 249-253, (2022).
[ 7] S. Saegusa et al.: IEEJ Trans. E 143(6), 120-125. (2023).
[ 8] M. Shiota, M. Naya, T. Yamamoto, T. Hishiki, T. Tani, H. Takahashi, A. Kubo, D. Koike, M. Itoh, M.
Ohmura, Y. Kabe, Y. Sugiura, N. Hiraoka, T Morikawa, K. Takubo, K. Suina, H. Nagashima, O.
Sampetrean, O. Nagano, H. Saya, S Yamazoe, H. Watanabe and M. Suematsu: Nat. Comm., 9, 1561,(2018).
[ 9] S. Yamazoe, M. Naya, M. Shiota, T. Morikawa, A. Kubo, T. Tani, T. Hishiki, T. Horiuchi, M. Suematsu,
and M. Kajimura: ACS Nano, 8, 6, 5622–5632, (2014).
[10] K. Gale, A. R. Jafek, C. J. Lambert, B. L. Goenner, H. Moghimifam, U. C. Nze and S. K. Kamarapu:
Inventions, 3, 60 (2018)26

Study of Dihedral-Corner-Reflector-Array Fabrication Process
Using Soft X-ray Deep X-ray Lithography
Taki Watanabe1, Sho Amano1, Shinya Izawa1, Satoshi Maekawa2, Keisuke Yoshiki3, Akinobu Yamaguchi1, andYuichi Utsumi1
1

Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo
2
Parity Innovations Co. Ltd.
3
Institute for Research Promotion and Collaboration

Abstract
We fabricated sectoral-pillar structures for Dihedral Corner Reflector Array (DCRA) using Deep Xray Lithography (DXRL) in New SUBARU Synchrotron Radiation Facility. We studied process
conditions such as a start timing of development after exposure and development temperature. We
succeeded in fabricating a structure without of micro-cracks on sidewalls of the pillar and indemonstration of floating image using the fabricated DCRA.

1. Introduction
In recent years with the COVID-19, demand for non-contact terminal operation to avoid contact infection,
has increased. To realize non-contact operation, a visible floating image and a sensor-based operation system
are required. A Dihedral Corner Reflector Array (DCRA), which consists of two right-angle plane mirrors togenerate floating image in the air, was proposed1-4.
Fig. 1(a) shows the principle of DCRA. In a DCR the total reflections of a light-ray occur by two mirrors.
Fig. 1(b) shows a path of light in XY plane of the DCR. When the angle of incidence is θ, the light from asource is reflected and returns to the source with an angle of 180° according to Equation (1)3. In three
dimensions, the light from the source does not return to the source but reaches a symmetry point for the
DCRA device face. This point is an observation point (Fig. 1(a)).
2θ+2(π/2- θ)= π(1)

By mounting many DCRs perpendicularly to a substrate, the real image can be formed at the observation
point. The image sharpness is determined by surface clearness and right-angle accuracy of the DCR walls.
However, it is not easy to produce such a microstructure with high precision by conventional machining.
Therefore, we propose the use of DXRL technology for DCRA production. DXRL has several advantages: it
is easy to fabricate microstructures with high aspect ratio, mirror surfaces can be machined with highprecision, and it is a mass-production technology that can reduce costs5-15. Furthermore, by changing thepattern of the X-ray mask, desired cross-sectional shapes can be easily created. DCR shapes createdpreviously were limited to square pillars or holes1, 3. In such shapes, the other two faces that do not contributeto required imaging may produce ghost. Therefore, in this study, we developed prototype pillar structureswith a sectoral cross section as shown in Fig. 2 by DXRL, in which all surfaces except the two cornerreflectors are curved. Shown in Fig. 2 is an X-ray mask used in DXRL.
(b)

Figure 1. (a) Principle of DCRA, (b) Trajectory of the ray.
27

Figure 2. Unique sectoral shaped x-ray mask.
2. Experimental
Exposure experiments were carried out in the NewSUBARU synchrotron radiation facility in the Universityof Hyogo. There are two modes of electron storage energy, 1.0 GeV and 1.5 GeV, but in this study, we usedthe 1.5 GeV mode, which has higher X-ray energy and allows deeper processing. In BL11, synchrotron
radiation X-rays are passedthrough a toroidal mirror and two Be filters to cut off energy components below
2 KeV. The spectrum at the exposure plane is shown in Fig. 3(a). The X- ray energy range is 3KeV-8KeV,
with a peak of approximately 6KeV. The beam pattern is shown in Fig. 3(b) and the beam is highly paralleledwith a divergence of 278 μrad in the horizontal direction and 14 μrad in the vertical direction7.
In this study, PMMA (CLAREX Precision Sheet, Nitto Jushi Kogyo Co., Ltd) pillar structures are tested.
The critical angle of PMMA was calculated to be 42.2° from Snell's law, and the aspect ratio should be 2 torealize a two-times reflections in DCR. The smaller DCR size causes the higher space-resolution, but theimage becomes darker because of diffraction, so there is an optimum size. There is an optimum DCR pitch
for a focal distance. Based on the above, we determined the dimensions of the device to be fabricated in thisstudy as shown in Table 1.
We used GG developer solution for the development and developed the PMMA samples for 24 hours.
The ingredients of the developer are shown in Table 2. The development temperature and the elapsed time tostart development were changed and their optimum conditions were researched.
(a)

(b)

Figure 3. (a) Photon intensity distribution as a function of photon energy at the beamline BL11, (b)beam shape7.

28

Table 1. Target values and Measurements of each dimension of the DCR (parameters are defined in Fig.
6).

X wall

Y wallUpper distance [μm]Lower distance [μm]Upper side length [μm]Lower side length [μm]Verticality [mrad]
Upper distance [μm]Lower distance [μm]Upper side length [μm]Lower side length [μm]Verticality [mrad]
Average height [μm]target value measurements
300
301.6
300
303.5
175
174.7
175
171
0
1.72
300
291.9
300
306.4
175
186
175
171.5
0
13.1
600
553

Table 2. Ingredients of the GG developer.
IngredientVol%

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

60

Tetrahydro-1, 4-oxazine

202-amino-ethanol-1

5

D. I. Water

15

3. Results and Discussion
We succeeded in fabricating a DCRA without micro-cracks on the pillar wall surface in the optimized
development condition. The unique sectoral shaped DCRA fabricated is shown in Fig. 4. The exposure
dose was 150 J/cm2. The developing conditions at this time were a developing solution temperature of
37.8°C and an elapsed time to start development of 15 minutes.
Using this DCRA, we observed a floating image as shown in Fig. 5. The DCRA size was 2 cm square.
The scale parameters of each part of DCRA are defined as shown in Fig. 6. The target dimensions
and measured values of the fabricated DCRA are summarized in Table 1. Although the floating image
was successfully formed using the fabricated new DCRA, there is still a problem to be solved to obtainclearer image. It is the verticality of the DCR pillar is poor. In Table 1, the verticality is clearly worseon the Y wall than on the X wall. We consider this cause is due to thermal inhomogeneous by X-ray
beam scanning. Since the X wall is perpendicular to the beam scan direction, similar thermal mass isgiven simultaneously, but since the Y wall is parallel, a continuous distribution of thermal mass is created.

Figure 4. The unique sectoral shaped DCRA
fabricated.

Figure 5. Floating image formed using the
fabricated DCRA.

29

Figure 6. Scale parameters of each part of DCRA.
4. Conclusion
In this study, we fabricated a new DCRA device that can generate a floating image in the air. In
conventional square DCRA, two surfaces that do not contribute to image formation may cause the generationof ghost images. Therefore, we fabricated a unique sectoral-pillar DCRA that is expected to generate lessghost. For this micro-fabrication, we studied the PMMA fabrication process by DXRL at a BL11 in
NewSUBARU. By trying various development conditions, we found the condition under which micro-cracks
on the pillar wall were not observed. Using the DCRA fabricated, floating imaging was observed. However,the verticality of the pillar still needs improvement. We will improve the exposure and development process
in order to establish a DCRA processing by DXRL.
References[ 1] A. Yamaguchi, S. Maekawa, T. Yamane, I. Okada, Y. Utsumi: Transactions of The Japan Institute ofElectronics Packaging. 8, 23 (2015).
[ 2] D. Miyazaki, N. Hirano, Y. Maeda, S. Yamamoto, T. Mukai, S. Maekawa: Applied Optic. 52, A282
(2013).
[ 3] J. G. Korvink, S. Haf, S. Maekawa: Nanotech Japan Bulletin. 7, No.4 (2014).
[ 4] S. Maekawa, Y. Hirai, O. Matoba: Proc. SPIE. 63920E (2006).
[ 5] Meyer: LIGA and its Applications, (2009).
[ 6] Y. Utsumi, T. Kishimoto, T. Hattori, H. Hara: Jpn. J. Appl. Phys. 44, 550 (2005).
[ 7] M. Takeuchi, A. Yamaguchi, Y. Utsumi: J. Synchrotron Rad. 26, 528 (2019).
[ 8] W. Ehrfeld, V. Hessel, H. Lowe, Ch. Schulz, L. Weber: Microsystem technologies. 5, 105 (1999).
[ 9] F. Perennes, B. Marmiroli, M. Matteucci, M. Tormen, L. Vaccari, E. Di. Fabrizio: J. Micromech.
Microeng. 16, 473 (2006).
[10] F. Karlsruhe: Sensors and materials, 10, 363 (1998).
[11] V. Saile, U. Wallrabe, O. tabata, J. G. Korvink: LIGA and Its Applications, Wiley‐VCH Verlag GmbH& Co. KGaA. 51 (2008).
[12] S. Lemke, P. Goettert, I. Rudolph, J. Goettert, B. Lochel: Proceedings MNE Conference. (2013).
[13] G. Feiertag, W. Ehrfeld, H. Freimuth, H. Kolle, H. Lehr, M. Schmidt, M. M. Sigalas, C. M. Soukouli,
G. Kiriakidis, T. Pedersen, J. Kuhl, W. Koenig: Appl. Phys. Lett. 70, 1441 (1997).
[14] B. Lai, D. C. Mancini, W. Yun, E. Gluskin: Microlithography and Metrology in Micromachining. 2,(1996).
[15] H. Scheunemann, B. Loechela, L. Jiana, D. Schondelmaier, Y. M. Desta, J. Goettert, Smart Sensors,
Actuators, and MEMS. (2003).

30

Upgrading to expand available X-ray energy range
for energy device analysis in BL05C, the NewSUBARU
Koji NakanishiLaboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo

Abstract
BL05C of the NewSUBARU synchrotron radiation facility, University of Hyogo (NS-BL05C) is
capable of performing XAS measurements of soft/tender X-rays in the 1-4 keV energy range, which
has been used for reaction mechanism analysis and degradation analysis of various energy devices(e.g., next-generation lithium-ion batteries, innovative secondary batteries, fuel cells, and waterelectrolysis devices). However, due to its available X-ray energy range, XAS measurement of 3dtransition metals, which are contained as a major component in electrode active materials, has notbeen possible so far. The hard X-ray XAS spectra of the K-edge of 3d transition metals obtained at
NS-BL05C are highly accurate and have been used in industrial applications such as energy devices,
The hard X-ray XAS spectra of 3d transition metal K-edge obtained at NS-BL05C are found to bevery accurate and useful for the analysis of real industrial samples such as energy devices.

1. Introduction
BL05C of the NewSUBARU synchrotron radiation facility (NS-BL05C) is a relocated, refurbished, andupgraded beamline from the former BL05A, where soft/tender X-rays were available1. It has been in
operation since FY2021 to contribute to industrial analysis, especially to the analysis of energy devices suchas lithium-ion secondary batteries (LIBs), next-generation LIBs, innovative secondary batteries, fuelcells, water electrolysis technology, and methanation technology. NS-BL05C is capable of X-ray absorption
spectroscopy (XAS) measurements using soft and tender X-rays in the 1-4 keV range, and has been used forindustrial analysis of lithium-ion secondary batteries (LIBs)2 and next-generation LIBs as well as
semiconductor-related products and glass-related products. The elements and X-ray absorption edges thatcan be analyzed at NS-BL05C are mainly the K absorption edge (K-edge) of period third periodic elements

Figure 1. Configuration of NS-BL05C.
31

(e.g., Mg, Al, Si, P, S, Cl, etc.) and the L absorption edge of fifth periodic elements (e.g., Sr, Zr, Nb, Mo, Ru,
Rh, Pd, Ag, etc.). However, these elements and X-ray absorption edges alone are not satisfactory for the
analysis of a wide variety of energy devices, and more elements were expected to be included in XAS
measurements. For XAS measurements, it is essential to extend the incident X-ray energy available at thebeamline to cover more elements and X-ray absorption edges to be measured. The K-edge of 3d transition
metals (TMs) is located in the hard X-ray region above 4 keV, and it is very important for the beamline
upgrading strategy to be able to measure them because they are found in many industrial samples.
Therefore, NS-BL05C was upgraded to be able to use hard X-rays above 4 keV by replacing the opticalsystem and installing a measurement hutch and a new detection system. Since the New SUBARU is asynchrotron radiation facility specializing in the use of soft X-rays, there has been no beamline available forhard X-rays with spectroscopy. The upgrade of NS-BL05C was challenging because there were no beamlinesthat could be referenced. The hard X-ray XAS spectra obtained as a result of this upgrade are described below.
2. Experimental details
All XAS measurements were performed at NS-BL05C. It mainly consists of a collimating mirror, aGolovchenko-type double crystal monochromator (DCM), an X-ray intensity monitor (I0 monitor), andvarious optical apertures and slits. In addition, a vacuum measurement chamber and a load-lock chamber for
sample introduction without air exposure are available for soft X-ray XAS, as well as a measurement hatch
for hard X-ray XAS shown in Fig. 1. In order to obtain 1-10 keV monochromatic X-rays, Beryl(10-10),
KTP(011), quartz(10-10), InSb(111), Si(111), Ge(111), Si(220), Ge(220), Si(311), Ge(311) are prepared forthe DCM and are exchanged depending on measurement conditions.
All powder samples were pelletized by mixing with boron nitride powder. All XAS spectra were obtainedby the transmission mode. To evaluate the XAS spectra observed at NS-BL05C, those observed at BL14B2of the SPring-8 (SP8-BL14B2)3 were used as reference spectra.
3. Results and Discussion
Figure 2 shows the V K-edge XAS spectra, EXAFS oscillations, and the Fourier transform of k2-weighted
EXAFS spectrum (radial distribution function) of V2O5 observed at NewSUBARU BL05C and SP8-BL14B2
for comparison4. The spectra of V2O5 observed at SP8-BL14B2 are also shown for comparison in Fig. 2. A
comparison of both spectra shows that they are in very good agreement. One slight difference is that the preedge peak is slightly higher in the XANES spectrum for SP8. This is presumably due to the slightly higher

Table 1. XAS conditions of observed and referenced V K-edge XAS spectra for V2O5.
Facility / Beamline
NewSUBARU / BL05C
SPring-8 / BL14B2 3

CrystalsGe(220)Si(111)

Scan
Step
Quick

Range
5400 – 6400 eV
5140 – 6970 eV

Points
476
4238

dwell
0.1 s
0.1 s

Total time
20 min.
8 min.

Figure 2. V K-edge XAS spectra, EXAFS oscillation, and the radial distribution functions for V2O5.

XAS data of “SPring-8 BL14B2” is referenced from MDR XAFS Database3.
32

resolution of SP8-BL14B2. This difference in resolution may possibly be due to differences in the
Table 2. XAS conditions of observed and referenced Mn, Co, Ni K-edge XAS spectra for

LiMn0.33Co0.33Ni0.33O2.
Facility
Beamline

Crystals

Scan

Edge

Range

Pointsdwell

Total time

NewSUBARU (NS)BL05C

Ge(311)

Step

Mn
Co
Ni

6433 – 7377 eV
7576 – 8370 eV8172 – 9164 eV

409
414
519

1s
1s
1s

16 min.
16 min.
21 min.

SPring-8 (SP8)BL14B2 4, 5

Si(111)Quick

Mn, CoCo, Ni

6204 – 8046 eV
7379 – 9224 eV

4262
4462

0.05 s0.05 s4 min.
4 min.

Figure 3. Mn, Co, Ni K-edge XAS spectra, EXAFS oscillation, and the radial distribution functions for

LiMn0.33Co0.33Ni0.33O2. XAS data of “SP8 BL14B2” is referenced from MDR XAFS Database4, 5.
33

crystallinity of the V2O5 reagents used in each measurement. Regarding EXAFS vibrations, the SP8-BL14B2
spectrum shows oscillation structures even at k > 16 Å, whereas the NS BL05C spectrum shows a disturbanceof the oscillation structures around k = 14.5 Å. This directly indicates the accuracy of the spectrum, indicatingthat SP8-BL14B2 has higher measurement accuracy. Regarding the radial distribution function, again, good
agreement is observed between the two, but the peak resolution appears to be higher for SP8-BL14B2 due tothe accuracy of the EXAFS vibrational structure. These results suggest that the XAS spectrum of NS BL05C
is slightly less accurate than that of SPring-8 BL14B2 in the range of 5-6 keV where the V K-edge exists, but
it is still effective enough for the analysis of actual industrial samples.
Figure 3 shows the Mn, Co, Ni K-edge XAS spectra, EXAFS oscillations, and the radial distributionfunctions of LiMn0.33Co0.33Ni0.33O2 observed at NS-BL05C and SP8-BL14B2 for comparison.
LiMn0.33Co0.33Ni0.33O2 is known to be a typical positive electrode material in present practical LIBs. With
respect to the XANES spectra in Fig. 3, the shapes of the two are almost identical, but the slight discrepancy
is thought to be due to the stoichiometric ratio and crystallinity of LiMn0.33Co0.33Ni0.33O2 used in themeasurements, as well as impurities in the LiMn0.33Co0.33Ni0.33O2. Regarding the EXAFS vibrations andradial distribution functions, the characteristics of the two are almost identical. This result indicates that the
XAS spectra obtained at NS-BL05C are sufficient for LIB analysis.
4. Conclusion
In order to expand the range of target elements for XAS measurements at NS-BL05C, which is capable ofsoft X-ray and tender X-ray XAS at 1-4 keV, the optics were replaced and a new measurement hutch was
installed. This has made it possible to use hard X-rays in the energy range of 4-10 keV. The K-edges of 3d
TMs in this energy range was measured and evaluated. As a result, it was found that the XAS spectra wereequivalent to those observed at SP8-BL14B2.
Comparing the differences in the measurement conditions between NS-BL05C and SP8-BL14B2, it could
be seen that the measurement times differ significantly. In other words, NS-BL05 is effective enough for themeasurement of the equilibrium state, but for the measurement of one spectrum in a short time, as in theoperando measurement, the measurement time needs to be shortened. To solve this problem, we are planning
to introduce a quick-scan system at NS-BL05C in the future.
Acknowledgement
A part of this study was supported financially by the NEDO RISING3 project.
References[ 1] K. Nakanishi: LASTI Annual Report 23 (2022) 27.
[ 2] K. Nakanishi, T. Mori, H. Ohzono, K. Kanda, S. Suzuki: Adv. X-Ray. Chem. Anal., Japan. 54 (2023)
185.
[ 3] XAFS spectrum of Vanadium(V) oxide: “https://mdr.nims.go.jp/concern/datasets/z890rw79s”,
MDR XAFS Database, National Institute for Materials Science, Japan.
[ 4] XAFS
spectrumofLithium
nickelmanganese
cobaltoxide:“https://mdr.nims.go.jp/concern/datasets/s7526f74k”, MDR XAFS Database, National Institute forMaterials Science, Japan.
[ 5] XAFS
spectrumofLithium
nickelmanganese
cobaltoxide:“https://mdr.nims.go.jp/concern/datasets/8049g725n”, MDR XAFS Database, National Institutefor Materials Science, Japan.

34

Selective excitation of Si-H-DLC Films using BL07A for
Monochromatized Soft X-ray Irradiation
Tomohiro Mishima1, Koji Nakanishi1, Masahito Niibe1, and Kazuhiro Kanda1
1

Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo

Abstract
Highly hydrogenated diamond-like carbon film containing Si (Si-H-DLC) films were irradiated withmonochromatized soft X-ray using BL07A, to clarify the photochemical reaction due to soft X-ray
irradiation on Si-H-DLC films. The irradiation of soft X-ray of 155 eV was found to oxidize the SiH-DLC film surface, on the other hand, the chemical state in the bulk of the film was unchanged.
The irradiation of soft X-ray of 290 eV showed almost no change in chemical state of both thesurface and the bulk. As a result, the soft X-ray irradiation effect on the Si-H-DLC films was foundto be dependent on the incident light energy.

1. Introduction
The energy of the inner-shell electrons depends on the element, which varies greatly from element to element,
allowing selective excitation. The K-shell energies of elements in the second and third periods are in the soft
X-ray region. BL07A is a beamline constructed to irradiate samples with high-brightness monochromatizedsoft X-rays by the combination of undulator and multilayer mirror monochromator1.
Diamond-like carbon film (DLC film) is an amorphous carbon film consisting of carbon atoms with sp2
hybridized orbitals, carbon atoms with sp3 hybridized orbitals, and hydrogen atoms. DLC films have various
excellent properties such as high hardness, low coefficient of friction, and gas barrier property, and are used
in a wide field of industries. Highly hydrogenated DLC (H-DLC) films, which contain more than 40 at. %hydrogen, maintain a low coefficient of friction even in a vacuum, and are therefore attracting attention as
solid lubricants for use in artificial satellites2. However soft X-rays penetrate in a vacuum such as outer space
unlike in the atmosphere. Therefore, it is necessary to investigate the soft X-ray resistance of H-DLC films
to use these films safely in space. Our group has been studying the effect of soft X-ray irradiation on H-DLC
films3. We have previously reported that H-DLC films exhibited volume loss and hydrogen desorption upon
soft X-ray irradiation3. In addition, we reported that H-DLC films containing Si (Si-H-DLC films) exhibited
suppression of hydrogen desorption upon soft X-ray irradiation4. To elucidate the soft X-ray irradiation effecton Si-H-DLC films more deeply, it is necessary to irradiate monochromatized soft X-rays to the Si-H-DLC
films and to clarify the energy dependence of the structural change process of the Si-H-DLC films.
In this study, Si-H-DLC films were irradiated with monochromatized soft X-rays at different energies,
and the chemical state changes of the films were discussed from the measurement of Si K-edge X-ray
absorption near edge structure (XANES) spectra.
2. Experimental
Irradiation experiments of synchrotron radiation were performed at BL07A, which has an undulator as a lightsource and a multilayer mirror monochromator to provide high-brightness monochromatic light, in the
NewSUBARU synchrotron radiation facility1. The undulator of BL07 is a 3 m short planner type undulator
consisting of 28 cycles of permanent magnets with a period length of 76 mm. The multilayer mirror
monochromator of BL07A is suitable for cutting out one harmonic of undulator light5. By using a undulator
and a multilayer mirror monochromator, a sample at the irradiation chamber of BL07A can be irradiated with
about 1014 photons/cm2 between 50 eV ~ 400 eV and about 1013 photons/cm2 between 400 eV ~ 800 eV6.
Si-H-DLC films (thickness: 522 nm, composition ratio: Si 40%, H 20%) were deposited on Si substrates
by plasma enhanced CVD. In this experiment, the samples were irradiated at 155 eV (photon flux density:
5.37×1011 photons/cm2), which corresponds to the L absorption edge of Si, and at 290 eV (photon flux
density: 1.05×1013 photons/cm2), which corresponds to the K absorption edge of C. Si K-edge XANES
measurements were performed at BL05C in the NewSUBARU synchrotron radiation facility. The lightsource of BL05C is a bending magnet and a double crystal monochromator is equipped.
3. Results and Discussion
The Si K-edge XANES spectra of the Si-H-DLC films recorded with the total electron yield method and the35Figure 1. Si K-edge XANES spectra recorded with the total electron yield (left) and the partial
fluorescence yield (right).
partial fluorescence yield method were depicted in Figures 1. The absorption spectrum with the total electron
yield method provides information on the surface of the sample, on the other hand, that of the partial
fluorescence yield method provides information on the bulk of the sample. In Figure 1, the black line is the
spectrum of the unirradiated sample, the blue line is the spectrum of the sample irradiated with 155 eV soft
X-ray, and the red line is the spectrum of the sample irradiated with 290 eV soft X-ray. The green line is the
spectrum of quartz as a reference, which is multiplied by 0.5 on the vertical axis. By comparing the shape ofeach spectrum, it was found that only in the spectrum of the sample irradiated with 155 eV soft X-ray has a
new peak at 1847 eV. The position of this peak at 1847 eV is consistent with that of the quartz. Therefore,
the change in the spectrum of the sample irradiated with soft X-rays at 155 eV can be attributed to theoxidation of silicon. By comparing the shape of each spectrum recorded by the partial fluorescence yield, it
was found that there was no significant change. It showed that the interior of the film was not changed ofchemical state by soft X-ray irradiation. Therefore, silicon oxidation is considerable to limit in the surface of
the Si-H-DLC film.
These results suggest that the irradiating of 155 eV soft X-ray mainly excited the L-shell electrons of Si
on the Si-H-DLC film surface, and the Si-C and Si-H bonds were broken, producing Si dangling bonds. And
then recombined with oxygen in the vacuum chamber or in the air after remove from the vacuum chamber.
The soft X-ray irradiation at 290 eV did not cause the aforementioned reaction, indicating that the soft X-ray
irradiation of the Si-H-DLC film was dependent on the incident light energy.
4. Conclusion
By irradiating Si-H-DLC films with monochromatized soft X-rays of different energies and comparing
XANES spectra, we found that the soft X-ray irradiation effect on Si-H-DLC films was dependent on theincident light energy. In addition, we found that Si-H-DLC films react with 155 eV soft X-ray irradiation,
which is less photon flux density than 290 eV soft X-ray irradiation. BL07A proved useful for studying
selective excitation reactions in the soft X-ray region.
References[ 1] K. Kanda, Y. Haruyama, M. Fujisawa, S. Matsui: Nucl. Instrum. Meth. A. 467-468, 500-503 (2001).
[ 2] C. Donnet, M. Belin, J.C. Augé, J.M. Martin, A. Grill, and V. Patel: Surf. Coat. Technol. 68-69, 626(1994).
[ 3] K. Kanda, K. Yokota, M. Tagawa, M. Tode, Y. Teraoka, S. Matsui: J. Appl. Phys. 50, 055801 (2011).
[ 4] K. Kanda, R. Imai, S. Tanaka, S. Suzuki, M. Niibe, T. Hasegawa, T. Suzuki, H. Akasaka: Materials.
14, 924 (2021).
[ 5] M. Okui, A. Shimoguchi, N. Yato, N. Murayama, I. Kikuchi, I. Tsuboki, K. Kanda: Journal of Physics.
2380, 012054 (2022).
[ 6] S. Tanaka, S. Suzuki, T. Mishima, K. Kanda: J. Synchrotron Rad. 28, 618-623 (2021).
36

Magnetic field correction of NewSUBARU short undulator (SU)and creation of peak energy prediction program with gap table
Tomohiro Mishima1, and Kazuhiro Kanda1
1

Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo

Abstract
The actual magnetic field strength of the BL07 undulator was determined from the analysis on
undulator spectrum measured at BL07B and the actual electron storage energy at 1.0 GeV operation.
Using the determined magnetic field strength, the program to predict the energy of the harmoniclight from the undulator gap length at both 1.0 GeV and 1.5 GeV operation has been created. This
program was already used by BL07A users for experiments.

1. Introduction
BL07A is a beamline designed to create functional materials by surface modification using soft X-ray
irradiation.1 At BL07, the light supplied from undulator is introduced into BL07A and BL07B by a switching
mirror. The undulator of BL07 is a 3 m short planar type undulator (SU) consisting of 28 cycles of permanent
magnets with a period length of 76 mm. BL07A is equipped with a multilayer mirror monochromator formonochromatic light irradiation, which is suitable for cutting out one harmonic of undulator light.2 By using
an undulator and a multilayer mirror monochromator, a sample at the irradiation position of BL07A can be
irradiated with about 1014 photons/cm2 between 50 eV ~ 400 eV and about 1013 photons/cm2 between 400
eV ~ 800 eV.3 On the other hand, multilayer mirror monochromator is low energy resolution, because it can
provide high-brightness light. Therefore, the exact spectral wavelength cannot be determined at this beamline,
and the energy of each harmonic of the undulator light must be predicted from the undulator gap.
The high-resolution spectra can be measured at BL07B, which is mounted a grating monochromator andundulator light is supplied from the same SU as BL07A. We developed a program to calculate the undulator
light energy from the undulator gap length for 1.0 GeV and 1.5 GeV operation, using undulation spectra
measured at BL07B, which Dr. Yuichi Haruyama provided us.
2. Undulator Principle
Consider the following magnetic field with sin-type variation in the vertical direction as the periodic static
magnetic field of an undulator, and consider the motion of electrons incident in the z-axis direction.4
2𝜋𝑧(1)
𝑯 = −𝒆𝒚 𝐻0 𝑠𝑖𝑛 ()
𝜆𝑢(ey : unit vector along y-axis H0 : strongest magnetic field in y-axis direction)
Solving the equation of motion (2) for an electron in a magnetic field in equation (1) yields (3), (4) as thesolution for electron β and position r.
𝑑𝒑(2)= −𝑒𝜷 × 𝑯
𝑑𝑡
(p = γmv = γmcβ γ : Lorenz factor)
2
2
′)
𝐾𝛽
𝐾
𝐾
𝑐𝑜𝑠(2𝜔0𝑡(3)
𝜷 = 𝒆𝑥𝑐𝑜𝑠(𝜔0𝑡 ′ ) + 𝒆𝑧 𝛽 [1 −
−
]
𝛾
4𝛾 2
4𝛾 2

𝒓 = 𝒆𝑥𝐾𝜆𝑢
2𝜋𝛾

𝑠𝑖𝑛(𝜔0𝑡 ′ ) + 𝒆𝑧 [{1 −𝐾24𝛾2} 𝛽𝑐𝑡 ′ −𝐾2 𝜆𝑢 𝑠𝑖𝑛(2𝜔0𝑡 ′ )
16𝜋𝛾2

(4)

]

(ex : unit vector along x-axis, ez : unit vector along z-axis)(𝜔0 = 2𝜋𝑐𝛽

1 − 𝐾2 /4𝛾2𝜆𝑢)

K in equations (3) and (4) is a parameter corresponding to the maximum bending angle of the electron
orbit, called the deflection constant, and is expressed as
𝑒𝐻0 𝜆𝑢(5)
𝐾== 0.934𝐵0 (𝑇)𝜆𝑢
2𝜋𝑚𝑐 2(B0(T) : Maximum flux density corresponding to H0 λu : Magnetic field periodic length = 0.76 [m])37For the NewSUBARU BL07 undulator, the undulator gap dependence of B0(T) and K from the magnetic
field measurement data can be approximated by the following equation.
𝜋𝑔(6)
𝐵0 (𝑇) = 2.064 × 𝑒𝑥𝑝 (−
)
𝜆𝑢
𝜋𝑔
(7)
𝐾 = 14.654 × 𝑒𝑥𝑝 (−)
𝜆𝑢(g : length of gap [m])The relation between undulator light energy and gap length was obtained from equation (7) and thefollowing equation.
𝐸
(8)
𝛾 =1+
𝑚𝑒 𝑐 2𝐾2𝜆(9)𝑊1 = (1 +
)× 2
2
2𝛾
1
(10)
𝐸1 =
𝑊1 × 100 × 8065.541(E : storage electron energy W1 : wavelength of primary light
E1 : peak energy of primary light)
3. Results and Conclusion
NewSUBARU is operated in two type modes of operation: 1.0 GeV operation and 1.5 GeV operation. The
actual electron storage energy for 1.0 GeV operation was obtained as 0.974 GeV by Dr. Shuji Miyamoto's
laser Compton backscattering experiments,5 but the actual electron energy for 1.5 GeV operation has not yet
been reported.
Figures 1 and 2 show the relation between the undulator gap and the peak energy of each order of light at
1.0 GeV operation. The dotted line is the value calculated by the above formula, and the solid line is the valueof the undulator spectrum actually measured at BL07B. From Figure 1, it was found that the dotted and solidlines are out of alignment. Therefore, we corrected the misalignment by applying a zero-order correction to
the coefficient 14.654 in Equation (7). As a result, as shown in Figure 2, the coefficient of 13.855 in equation(7) was the smallest deviation.
Figures 3 and 4 show the relationship between the undulator gap and the peak energy of each order lightat 1.5 GeV operation. The dotted line in Fig. 3 is calculated by the above formula with the coefficient of Eq.
(7) as 13.855 and the electron storage energy as 1.5 GeV, and the solid line is the value of the undulator
spectra measured at BL07B. From Figure 3, it is found that the dotted line and the solid line are out ofalignment. Here, we corrected the discrepancy between the dotted and solid lines by applying a zero-orderFigure 1. Relationship between undulator gap
and peak energy of each order light at 1.0 GeV
operation (before correction).

Figure 2. Relationship between undulator gap
and peak energy of each order light at 1.0 GeV
operation (after correction).
38

Figure 4. Relationship between undulator gap
and peak energy of each order light at 1.5 GeV
operation (after correction).

Figure 3. Relationship between undulator gap
and peak energy of each order light at 1.5 GeV
operation (before correction).

correction to the electron storage energy (E) in Eq. As shown in Figure 4, the case with 1.48 GeV had thesmallest deviation. It is clear that the above correction lowered the coefficient in equation (7) for obtaining
the K value from 14.654 to 13.855. This indicates that the magnetic field strength of the SU has decreased.
Using this result, a program was created to calculate the peak energies of the 1st, 3rd, 5th, and 7th orderphotons by inputting the gap length and a program to calculate the gap length from the peak energy.
Acknowledgement
Dr. Yuichi Haruyama of the Laboratory of Advanced Science and Technology for Industry, University of
Hyogo provided the data on BL07 undulator spectra measured at BL07B.
Dr. Shuji Miyamoto of the Laboratory of Advanced Science and Technology for Industry, University of
Hyogo provided the data on the actual electron energy for 1.0 GeV operation at NewSUBARU.
References[ 1] K. Kanda, Y. Haruyama, M. Fujisawa, S. Matsui: NIMA. 467-468, 500-503 (2001).
[ 2] M. Okui, A. Shimoguchi, N. Yato, N. Murayama, I. Kikuchi, I. Tsuboki, K. Kanda: Journal of Physics.
2380, 012054 (2022).
[ 3] S. Tanaka, S. Suzuki, T. Mishima, K. Kanda: J. Synchrotron Rad. 28, 618-623 (2021).
[ 4] H. Ooyanagi: Fundamentals of Synchrotron Radiation, Maruzen Publishing (1996).
[ 5] S. Miyamoto, H. Utsunomiya, T. Shima and S. Amano: SPring-8 Research Frontiers 2013, 153-154(2014).

39

Effect of Photon Energy on the Reduction of Graphene Oxide bySoft X-ray Irradiation
Akira Heya1, Akinori Fujibuchi1, Masahiro Hirata1, Kazuhiro Kanda2, Yoshiaki Matsuo3, Junichi Inamoto3, andKoji Sumitomo1
1

Department of Materials and Synchrotron Radiation Engineering, University of Hyogo
Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo
3
Department of Applied Chemistry and Chemical Engineering, University of Hyogo

2

Abstract
The photon-energy dependence of reduction of graphene oxide (GO) through soft X-ray irradiation
was investigated using photon energies of 300 eV for C 1s core electron excitation and 550 eV for
O 1s core electron excitation. GO was reduced by soft X-ray irradiation at 150 °C (300 eV) and at
60 °C (550 eV). The O-related peaks such as C-O-C in GO after soft X-ray irradiation were smallerat 550 eV than at 300 eV. This indicates that the excitation of the core-shell electrons of O enhances
the reduction of GO. It was found that the soft X-ray irradiation depends on the photon energy, inother words, the difference between C 1s and O 1s electron excitation.

1. Introduction
The reduction of graphene oxide (GO) is apromising low-cost method for fabricating
graphene field-effect transistors (FETs)1 andsensors2. However, the electrical property of
reduced GO is degraded compared to those ofideal graphene due to defects introduced during
reduction.
Soft X-ray irradiation to reduce GO is often
used, and it has been reported that the X-ray
induced reduction process is initiated by photoand secondary electrons.3,4 Our group has
investigated the reductions of GO using soft xrays and combined atomic hydrogen annealing(AHA) and x-ray methods.5 In the soft X-ray
reduction, to excite the C 1s core electron at
284.6 eV, the soft X-ray of 300 eV was irradiatedwith GO film. However, functional groups suchas C-O-C and O=C-OH remain after soft X-ray
irradiation. In contrast, the excitation of the O 1s
core electron at 532 eV might promote the GO
reduction.
In this study, to enhance the GO reduction,
the O 1s core electron at 532 eV was excited bysoft X-ray of 550 eV. The mechanism of GO
reduction by soft X-ray irradiation was discussed
from the comparison between 300 and 550 eV.
2. Experimental
Individual GO sheets were prepared from naturalgraphite flakes with large grain sizes (～100 m)
based on the Brodie’s method. A 5 mm × 5 mmarray of circular wells with diameters of 1, 2, 4,
and 8 m, named microwell (MW) substrate, wasFigure 1. C 1s XPS spectra of the pristine GO (a) andsoft X-ray irradiated GO (b). The C 1s spectrum aredecomposed to five peaks.

40

used for application to suspended graphene FETs.
The GO dispersed in 0.1 mL of solvent (0.006
mg/mL) was dropped onto the cleaned MW
substrate on a hot plate at 150 °C.
The irradiation of soft X-rays was performed
at BL07A of NewSUBARU.6 The light source of
BL07A was a 2.28 m undulator. The electronenergy of the storage ring was 1 GeV during theexperiments. The main photon energies were 300
and 550 eV. However, the soft X-ray irradiation
was carried out without a monochromator to selectthe photon energy. Therefore, the irradiated lightalso had higher-order X-rays with lower photon
density than the main photon energy. The
irradiation duration was 3600 s. The storage-ringcurrent and dose were 350 mA and 350 mA·h,
respectively. The saturated sample temperaturesduring irradiation at 300 and 550 eV were 150 and
60 °C, respectively.
The surface property was evaluated using Xray photoelectron spectroscopy (XPS). For XPS(ULVAC-PHI, PHI 5000Versaprobe), an energy
step of 0.2 eV, pass energies of 23.5 eV, dwell
times of 100 ms, and integration of 10 times wereused. A neutralizer gun was used to suppress the
charge. The binding energy was corrected byusing C-C bond peak as a 284.6 eV.
3. Results and Discussion
The C 1s XPS spectra of the pristine GO and soft
X-ray irradiated GO are shown in Fig. 1. The C 1s
spectrum consists of five 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).7 To
compare 300 eV and 550 eV, the C 1s peak was
Figure 2. (a) Peak area fraction of the C–OH, C–O–C,
decomposed to five peaks. The C-O-C peak at
C=O, and O=C–OH bonds estimated from C 1s
286.6 eV was reduced by soft X-ray irradiation.
spectra. (b) C–O/C–C ratio of the pristine GO, the soft
However, the C 1s spectra were different in the
X-ray irradiated GO.
region of C-OH, C-O-C, C=O, and O=C-OH
peaks. The peak area ratios of C–OH, C–O–C,
C=O, and O=C–OH bonds estimated from the C 1s spectra at various treatments are shown in Fig. 2(a). The
C–O/C–C ratio of the pristine GO, the soft X-ray irradiated GO are shown in Fig. 2(b). In this case, the C-C
peak area was obtained from the peak at 284.6 eV and the C-O peak area was the sum of C-OH, C-O-C, C=O,
and O=C-OH peaks.
The peak area ratios of the C–O–C and C=O at 550 eV were smaller than that at 300 eV. In contrast, the
C-OH and O=C-OH at 550 eV were larger than that at 300 eV. The C-O/C-C ratio were 0.75 and 0.59 at 300
and 550 eV, respectively. and reduced by 22 % by using a photon energy of 550 eV corresponding to O 1s
core electrons. It was confirmed that GO was reduced more at 550 eV than at 300 eV.
The difference in interaction of soft X-ray with core electrons between 300 and 550 eV is discussed basedon the effect of resonant Auger electrons.8 The electron excitation from C 1s and/or O 1s and the behavior of
the electron are shown in Fig. 3. As GO absorbs soft X-rays of 300 eV, the core-shell electrons of C 1s are
excited into an unoccupied orbital (*), referred to as spectator electron. The spectator electron in the valenceband then transfers to the C 1s core level. Auger electrons emit from the sample surface into vacuum. On theother hand, when the GO absorbs soft X-rays of 550 eV, the core-shell electrons of not only C 1s but also O
1s are emitted from the sample surface into vacuum. This suggests that the reduction of terminal groups suchas C-O-C in GO is facilitated by the simultaneous action of excitation of both C and O core-shell electrons.
The speculated reduction mechanism due to the soft X-ray irradiation is shown in Fig. 4. In the Figure,41

Figure 3. Electron excitation from C 1s and O 1s, and the behavior of electron.

Figure 4. The speculated reduction mechanism due to soft X-ray irradiation.

we focus on the C-O-C of the main bond. As the C and O atoms absorbs soft X-ray, the ionization occurs. As
the neighbor atom is also ionized, a Coulomb repulsive force is generated. The repulsive force enhances thebond breaking. At 300 eV, CO is desorbed in breaking the C-C bond. On the other hand, at 550 eV, the C andO atoms are ionized simultaneously. In this case, the O atom is desorbed. Since the ionization of O as well
as C is realized at 550 eV, the reduction of GO occurs more at 550 eV than at 300 eV.
As mentioned, the change in XPS spectra indicates that the C-O-C changed to C-OH. The following
reactions are considered.
42

C-O-C + h (300 eV) → C- + CO↑,(1)

C-O-C + h (550 eV) → 2C- + O↑,(2)

C- + H2O → C-OH + H.

(3)

The increase in the C–OH peak after the soft X-ray irradiation is related to the generation of dangling bonds(C-) in the r-GO flakes. The C–OH generation is attributed to the reaction with H2O in air, which occurs at
the dangling bonds during air exposure.
4. Conclusion
GO was reduced by soft X-ray irradiation at 150 °C (300 eV) and at 60 °C (550 eV). The GO was reduced
more at 550 eV than at 300 eV. The excitation of the core-shell electrons of O enhanced the reduction of GO.
The C-C and C-O bonds preferentially broke by soft X-rays of 300 and 550 eV, respectively.
Acknowledgement
The authors are grateful to Dr. A. Oshima of NTT Basic Research Laboratories for the supply of the MW
substrates. This work was supported by JSPS KAKENHI Grant Number JP22K04877.
References[ 1] D.-J. Kim, Y. Sohn, J.-H. Jung, O. J. Yoon, N-E Lee, J.-S. Park: Biosens. Bioelectron. 41, 621 (2013).
[ 2] K. Lee, Y. K. Yoo, M.-S. Chae, K.S. Hwang, J. Lee, H. Kim, D. H. and J. H. Lee: Sci. Rep., 9, 10297(2019).
[ 3] C.-Y. Lin, C.-E. Cheng, S. Wang, H. W. Shiu, L. Y. Chang, C.-H. Chen, T.-W. Lin, C.-S. Chang, andF. S.-S. Chien: J. Phys. Chem. C, 119, 12910 (2015).
[ 4] V. M. Mikoushkin, A. S. Kriukov, S. Yu. Nikonov, A. T. Dideikin, A. Ya. Vul, and O. Yu. Vilkov: J.
Appl. Phys., 124, 175303 (2018).
[ 5] A. Heya, A. Fujibuchi, M. Hirata, K. Kanda, Y. Matsuo, J. Inamoto, and K. Sumitomo: Jpn. J. Appl.
Phys., 62, SC1028 (2023).
[ 6] A. Heya, T. Oonuki, R. Utimi, K. Kanda, R. Yamasaki, and K. Sumitomo: Thin Solid Films 713,
138365 (2020).
[ 7] 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, 1789 (2012).
[ 8] K. Tanaka H. Kizaki, R. Sumii, Y. Matsumoto, and S. Wada: Radiat. Phys. Chem., 75, 2076 (2006).

43Effect of Atomic Hydrogen Exposure on Hydrogen-Free
Amorphous Carbon Films
Yuichi Haruyama1, Daiki Morimoto1, Akira Heya2, Koji Sumitomo2, Noriaki Toyoda2, and Seigo Ito2
1

Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo
2
Graduate School of Engineering, University of Hyogo

Abstract
The effect of atomic hydrogen exposure on hydrogen-free amorphous carbon films was investigatedby a soft X-ray photoelectron spectroscopy. From the dependence of the C 1s photoelectron spectraof hydrogen-free amorphous carbon films on atomic hydrogen exposure, it was shown that thecontents of the sp3 hybridized and the C-H bonded carbon atoms increased remarkably after
atomic hydrogen exposure. In addition, the surface coordination of C atoms in the hydrogen-free
amorphous carbon films after atomic hydrogen exposure was investigated from the photoelectron
emission angle dependence. It was found that the sp3 C atoms were dominant at the surface ofhydrogen-free amorphous carbon films after atomic hydrogen exposure.

1. Introduction
Since amorphous carbon films have interesting properties such as high hardness and a low friction coefficient,
they have been expected to be used as lubrication materials in space1. The properties of amorphous carbon
films have been related with not only sp2/sp3 ratio but also hydrogen contents in films2. It is reported that
amorphous carbon films are etched in the atomic hydrogen exposure and the etching rate is depending on thehydrogen contents in films3. In addition, it is also reported that the coordination of the carbon atoms in thehydrogenated amorphous carbon films is unchanged in the atomic hydrogen exposure4. As the systematicinvestigation of atomic hydrogen exposure on the amorphous carbon films is important, the effect of atomic
hydrogen exposure on the hydrogen-free amorphous carbon films was investigated by a soft X-ray
photoelectron spectroscopy.
2. Experimental
Hydrogen-free amorphous carbon films were produced by the gas cluster ion beam method5. Atomic
hydrogen was generated using a hot filament method3,4. W mesh composed of 0.03 mmφ wire at a density of
30 wires per inch was used as the filament and heated at a temperature of about 1700 °C. An Ar (95 %) andH2 (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 40 °C by use of a water-cooled sample holder. The distance between the sample and W meshwas 150 mm. Since the atomic hydrogen generation apparatus was connected to the photoelectron analysis
chamber through a gate valve, photoelectron spectroscopy spectra after atomic hydrogen exposure were
measured without exposing them to air. Photoelectron measurements were carried out at the beamline 7B of
NewSUBARU synchrotron radiation facility, University of Hyogo.
3. Results and Discussion
The C 1s core-level photoelectron spectrum of the hydrogen-free amorphous carbon film after atomic
hydrogen exposure is compared with that before atomic hydrogen exposure in Figure 1. Although the peak
was located at 284.4 eV before exposure, it shifted at 285.2 eV after hydrogen exposure. In addition, the widthof the peak became narrower and the spectral feature changed symmetric line shape after atomic hydrogen
exposure. The component at 284.4 eV was assigned to the C 1s electrons originating from the sp2 hybridized
carbon atoms while the component at 285.2 eV was assigned to the C 1s electrons originating from the sp3
hybridized and the C-H bonded carbon atoms5. Therefore, it was observed that the contents of the sp3
hybridized and the C-H bonded carbon atoms increased remarkably after atomic hydrogen exposure. In thecase of the hydrogenated amorphous carbon films4, no change in the spectral features of the C 1s core-level
photoelectron spectrum was observed from the atomic hydrogen exposure dependence. This indicates thatthe coordination of C atoms in the hydrogenated amorphous carbon film is not influenced by atomic hydrogen44

exposure. Thus, we obtained the different results, depending on the contents of the hydrogen in amorphous
carbon films.
Figure 2 shows the photoelectron emission angle dependence of C 1s spectra after atomic hydrogen exposureon the hydrogen-free amorphous carbon film. With increasing photoelectron emission angle, the peak at 284.6
eV decreased while the spectral feature of the main peak at 285.2 eV remained unchanged. This indicatesthat the concentration of the sp2 C atoms increased with the depth and the sp3 C atoms are dominant in thesurface of the hydrogen-free amorphous carbon film.

Figure 2. C 1s photoelectron spectra of
the hydrogen-free amorphous carbon film
as a function of the photoelectron
emission angle.

Figure 1. C 1s photoelectron spectra of
the hydrogen-free amorphous carbon film
before and after atomic hydrogen
exposure.

4. Conclusion
We investigated the effect of atomic hydrogen exposure on hydrogen-free amorphous carbon films was byusing a soft X-ray photoelectron spectroscopy. The coordination of carbon atoms in hydrogen-free
amorphous carbon films was found to be affected by atomic hydrogen exposure while that in hydrogenatedamorphous carbon films was unaffected by atomic hydrogen exposure. Thus, we obtained the different results,
depending on the contents of the hydrogen in amorphous carbon films. After atomic hydrogen exposure forhydrogen-free amorphous carbon films, the sp3 carbon atoms was dominant at the surface. In addition, it wasobserved that the content of the sp2 carbon atoms increased with the depth.
References[ 1] J. Robertson: Surf. Coat. Tech. 50, 185 (1992).
[ 2] C. Lenardi, P. Piseri, V. Briois, C. E. Bottani, A. Li Bassi, P. Milani: J. Appl. Phys. 85, 7159 (1999).
[ 3] A. Heya, T. Harada, M. Niibe, K. Sumitomo, T. Watanabe: J. Photopolymer Sci. and Tech. 33, 419,
(2020).
[ 4] Y. Haruyama, D. Morimoto, A. Heya, K. Sumitomo, S. Ito, K. Yokota, M. Tagawa: Jpn. J. Appl.
Phys. 60, 125504 (2021).
[ 5] Y. Haruyama, T. Kitagawa, K. Kanda, S. Matsui, T. Gejo, N. Toyoda, I. Yamada: Jpn. J. Appl. Phys.
47, 3380 (2008).

45

Ultraviolet photoelectron spectroscopy study on d band center ofCo and Ir catalyst particle
Takahiro Maruyama1, 2, and Yuichi Haruyama3, 4
1

Department of Applied Chemistry, Faculty of Science and Technology, Meijo University
2
Nanomaterial Research Center, Meijo University
3
Laboratory of Advanced Science and Technology for Industry, University of Hyogo
4
Department of Materials and Synchrotron Radiation Engineering, Graduate School of Engineering, Universityof Hyogo

Abstract
Co and Ir are efficient catalysts for single-walled carbon nanotube (SWCNT) growth, but the optimal
temperature for SWCNT growth with an Ir catalyst is above 800 °C, which is much higher than thatwith a Co catalyst. Here, we investigated the energy levels of d band centers of Co and Ir
nanoparticles by using ultraviolet photoelectron spectroscopy (UPS). Our result showed that the dband center of Co 3d level is ~0.8 eV lower than that of Ir 5d level. We consider that the wide
temperature range of SWCNT growth with a Co catalyst is related to the lower binding energy of dband center of a Co catalyst.

1. Introduction
Single-walled carbon nanotubes (SWCNTs) [1] have been expected for various applications in many fields
because they exhibit excellent properties. At present, chemical vapor deposition (CVD) is widely used for
SWCNT growth because of both its capacity for mass production and its cost-effectiveness. So far, manygroups reported growth of vertically aligned SWCNTs (VA-SWCNTs), so called, “SWCNT forests”, with Fe
and Co catalysts [2]. Recently we reported VA-SWCNT growth by alcohol catalytic CVD (ACCVD) with an
Ir catalyst [3]. However, the optimal temperature region for SWCNT growth with an Ir catalyst was above
800°C, which is much higher than that with iron-group metal catalysts.
In this study, we performed ultraviolet photoelectron spectroscopy (UPS) for Co and Ir catalysts toinvestigate their valence band structures, which are strongly related to the catalyst activity.
2. Experimental
Co and Ir particles were deposited on Al2O3/Si and SiO2(100 nm)/Si substrates, respectively, by using thepulsed arc plasma deposition method in a high vacuum. This is because SWCNT forests were obtained fromCo catalysts deposited on Al2O3/Si substrates, while SWCNT forests were grown from Ir catalysts on SiO2/Si
substrates. The particle sizes were mainly distributed between 1 and 3 nm. The samples were mounted in thesample preparation chamber of the end station of BL7B at NewSUBARU synchrotron light facility. Afterhydrogen treatments for cleaning the sample surface, they were transformed into the analysis chamber, and
UPS measurements were performed at room temperature. For reference, we measured UPS spectra for
Al2O3/Si and SiO2/Si substrates with no catalyst particles under the same excitation energy.
3. Results and Discussion
Fig. 1(a) and (b) shows valence band spectra of Co and Ir catalysts which were deposited on Al2O3/Si and
SiO2/Si substrates, respectively. The excitation energies used for UPS measurements were 58 and 70 eV for
Co/Al2O3/Si and Ir/SiO2/Si substrates, respectively. For comparison, the spectra of Al2O3/Si and SiO2/Si
substrates with no catalysts are also shown, as black lines. In the spectra of Co/Al2O3/Si and Ir/SiO2/Si
substrates, weak structures appeared below the Fermi levels, as shown with black arrows. These structures
are derived from the Co 3d band and Ir 5d band, respectively. To show the 3d and 5d derived bands clear, thedifferential spectrum between the Co/Al2O3/Si and Al2O3/Si and that between Ir/SiO2/Si and SiO2/Si areshown in the insets of Fig. 1(a) and (b). For Ir catalysts, one weak peak was seen at ~3.8 eV below the Fermi
level, corresponding to Ir 5d band. In the case of Co catalysts, two structures were seen at ~2.2 and ~5.0 eV
below the Fermi level. Farkaš et al. reported that the energy separation between the 3d spin-up and spindown electrons of Co clusters was ~2.7 eV [4]. Therefore, we consider that the two structures observed in
the in set of Fig. 9(a) corresponds to the energy bands of the up- and down-spin electrons of Co catalyst
particles. From the differential spectra, we estimated the position of d band center of Co and Ir catalysts
46

Figure 1. UPS spectra of (a) Co/Al2O3/Si and (b) Ir/SiO2/Si samples. For comparison, UPS spectra of
Al2O3/Si and SiO2/Si samples are shown in (a) and (b) respectively, by black lines. The differential
spectra between Co/Al2O3/Si and Al2O3/Si samples, and between Ir/SiO2/Si and SiO2/Si samples areshown in the insets of (a) and (b), respectively. The d band center position of Co 3d and Ir 5d are shownwith vertical bars in the insets.
because the d band center is strongly related to the dissociation reaction process of feedstock gas. The d band
center of Co 3d was ~3.42 eV below the Fermi level, while that of Ir 5d was ~4.22 eV. This indicates that thed band center of Co catalyst particles was ~0.8 eV lower than that of 5d band of Ir catalysts.
Previously, Wang et al. performed ab initio density functional theory (DFT) simulation for ethanol
decomposition reaction on (111) surface of various transition metals [5]. Assuming various reaction pathways,
they investigated a dissociation barrier for each reaction pathway, and pointed out that the overall dissociation
barriers decrease as the energy level of d band center of a metal approaches the Fermi level. Our UPS result
showed that the d band center of Co 3d level was ~0.8 eV closer to the Fermi level. We consider that such alower binding energy of d band center of 3d level of Co catalyst particles leads to the lower dissociation
barrier in the reaction of ethanol molecules on Co catalysts, resulting in the wide temperature range for
SWCNT growth.
4. Conclusion
We investigated the d band centers of Co and Ir catalysts particles by UPS measurements. We found that thed band center of Co 3d level was ~0.8 eV closer to the Fermi level, compared with that of Ir 5d level. Such alow energy position of Co 3d level would lead to the high efficiency of feedstock decomposition, resulting
in the wide temperature range of SWCNT growth by ACCVD.
Acknowledgement
This work was partly supported by JSPS KAKENHI (grant number 19H02563) and was also partly supported
by Meijo University Nanomaterial Research Center.
References[ 1] S. Iijima, and T. Ichihashi: Nature, 363, 603 (1993).
[ 2] H. Ohno, D. Takagi, K. Yamada, S. Chiashi, A. Tokura, and Y. Homma: Jpn. J. Appl. Phys., 47, 1956
(2008).
[ 3] T. Maruyama, T. Okada, K.P. Sharma, T. Suzuki, T. Saida, S. Naritsuka, Y. Iizumi, T. Okazaki, and S.
Iijima: Appl. Surf. Sci., 509, 145340 (2020).
[ 4] B. Farkaš, U. Terranova, and N.H. de Leeuw: Phys. Chem. Chem. Phys., 22, 985 (2020).
[ 5] J. J. Wang, C. S. Lee, and M. C. Lin: J. Phys. Chem. C, 113, 6681 (2009).

47

NEXAFS Studies of Amorphous Carbon Nitride Thin Films
Deposited by Pressure-gradient RF Magnetron Sputtering
1

Masami Aono1, Kyoji Morita2, Tasuku Inoue2, and Kazuhiro Kanda3
Department of Electrical and Electronics Engineering, Graduate School of Science and Engineering,Kagoshima University,
2
Faculty of Engineering, University of Hyogo
3
Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo

Abstract
Amorphous carbon nitride (a-CNx) thin films were deposited through radio frequency (RF)magnetron sputtering under increasing nitrogen gas pressure around a graphite target to provide
nitrogen radicals at high concentrations. The C K-edge near-edge X-ray absorption fine structure(NEXAFS) measurements were performed at NewSUBARU BL09A. To increase the gas pressurearound the graphite target, C K-edge NEXAFS spectra of the a-CNx films was changed. The nitrogencontent in the a-CNx films obtained from XPS analysis did not increase when the nitrogen gas
pressure around the graphite target was increased. The effect of nitrogen incorporation on the a-CNx
films was comparatively more effective at higher RF powers.

1. Introduction
Liu and Cohen discovered a new super-hard material based on theoretical calculations, generating interest in
carbon nitride compounds.1 They predicted -C3N4 based on -Si3N4.2 However, the growth of this hexagonal
crystal structure has not been corroborated, even 30 years after its prediction. Following the prediction of C3N4, several crystalline structures based on sp3C–N have been presented, such as -C3N4 and cubic-C3N4.3
Almost all the carbon nitrides prepared using thin film deposition techniques, such as chemical vapor
deposition (CVD), sputtering, and laser ablation, have amorphous phases due to the low thermal stability of
sp3C–N bonds.
Thin films of amorphous carbon nitride (a-CNx) comprise sp2– and sp3–hybridized carbon networks. aCNx films can be deposited using two typical deposition methods: plasma-enhanced CVD using hydrocarbon
gases and sputtering using graphite. NH3 and N2 are used as the nitrogen source. The range of nitrogenconcentration (x) is wide, depending on the deposition method and condition; however, the maximum x value
in most a-CNx films is approximately 0.5. Furthermore, a-CNx films deposited using the CVD method havea relatively lower nitrogen concentration and higher sp3-C bonds because it contains hydrogen as source
material.4-6 In contrast, a-CNx films prepared from graphite and N2 by physical vapor deposition have more
sp2-C bonds.7, 8 The nitrogen concentration of the sputtering film depends on the sputtering gas ratio of Ar
and N2.
a-CNx films can be deposited with a high nitrogen concentration using the nitrogen-radical sputtering
method proposed by Nitta et al.9,10 In this method, nitrogen radicals in the glow discharge of nitrogenmolecules react well with a carbon target at low energy.11 This method can produce a higher nitrogen content
than other techniques. The x value of a-CNx films deposited by nitrogen radical sputtering with hydrogenplasma etching is ~0.86.10
As essential technique to increase both the nitrogen content and sp3C bond in a-CNx films is increasing
the amount of high-energy nitrogen radical species. The mean free path of sputtered species on the growthsurface is short under low-vacuum conditions. Therefore, sputtering under higher-vacuum conditions isdesirable for the growth of high sp3–hybridized carbon films. However, the number of nitrogen radical
species is an important factor in increasing the nitrogen content. In the conventional sputtering method, thevacuum inside the growth chamber is uniform, and thus, generating excess nitrogen radicals is difficult.
Recently, the pressure gradient sputtering source has been developed for sputtering at a high vacuum withlow plasma damage.12 In magnetron sputtering using a pressure gradient sputtering source, a gas is locallyinjected near the sputtering target through the pressure gradient sputtering source, and the main vacuum valve
connected to the turbo-molecular pump is fully opened. This condition induces a pressure gradient with ahigh vacuum at the substrate position and a low vacuum around the target. Hence, the production of additional
nitrogen radical species around the target can be expected using the pressure gradient sputtering source. In
this study, a-CNx thin films were deposited using the pressure gradient and conventional sputtering modes48

with the same growth chamber, and the chemical bonding structure of the films was investigated to confirm
the effect of nitrogen radicals.
2. Experimental
2.1. Sample Preparation
a-CNx films were prepared from graphite with a purity of 99.95% and N2 with a purity of 99.99995%. The
substrates used were SiO2 glass and Si(100), which were cleaned ultrasonically in acetone and ethanol for 15
min each, before loading into the vacuum chamber.
In the sputtering system, the gas inlet can be changed between two modes, the conventional sputteringand pressure gradient modes, by operating valves. In the gas pressure gradient mode (GP), the sputtering gas
was injected near the target. Therefore, the gas pressure around the target was approximately one order ofmagnitude higher than that around the substrate holder. In comparison, the gas pressure in the chamber in theconventional sputtering mode (CS) was kept constant owing to the flow of N2 gas through the middle of thetarget and substrate holder.
The base pressure was under 1×10−3 Pa. For the film deposition, the N2 gas flow rate was 3 sccm, and theprocess pressure was maintained at 16 Pa (measured near the substrate holder). The samples obtained at RF
powers of 85, 130, 200, and 300 W by the conventional sputtering mode were denoted by CS85, CS130,
CS200 and CS300, respectively; the samples obtained using the gradient-pressure mode were denoted by
GP85, GP130, GP200, and GP300, respectively.
2.2. Characterizations
The atomic concentrations of the samples were obtained from the C1s, N1s, O1s, and Si2p core-level peaks using
X-ray photoelectron spectroscopy (XPS; Kratos Ultra 1, Shimadzu); Si was derived from the substrate.
Monochromatic Al K radiation (1486.6 eV) was used as the X-ray source. The pass energy and step size were 40
and 0.05 eV, respectively. The analysis area was 300 µm × 700 µm. In this study, the Ar+ bombardment etchingprocess was skipped because it could possibly destroy the chemical bonding structure between carbon and nitrogen.
The corresponding binding energies were calibrated with the C1s line at 284.5 eV for all cases, which could be
assigned to sp2 graphite like carbon.13

Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is sensitive to the local coordinationof the CN structure and a probe of the electronic structure of unoccupied orbitals of carbon. NEXAFS
measurements were performed using the BL09A at the NewSUBARU synchrotron facility of the Universityof Hyogo14, 15; the instrument has an 11 m undulator as a light source and a grating monochromator. The
electron energy of the storage ring during this study was 1.23 GeV. The samples deposited on a Si substrate
were mounted on a copper plate using a carbon conductive tape. The electrons emitted from the sample weredetected in the total electron yield (TEY) mode. The NEXAFS spectra of the C K-edge absorption were
measured using a grating of 1200 grooves/mm in the range of 275–330 eV. The energy resolution was
estimated to be less than 0.5 eV (full width at half maximum).
3. Results and Discussion

49

0.70
GP
CS

0.65

N/C

Figure 1 shows the nitrogen content (N/C) obtained from the C1s
and N1s core level XPS spectra. The GP and CS samples showeda similar N/C tendency as a function of the RF power. An increasein the RF power decreased the nitrogen content of the films inboth sputtering modes. GP85 and CS85 have almost the sameN/C ratio of 0.66, showing no significant influence of gas
pressure around the target. A comparing of GP300 and CS300
indicates that the N/C ratio of GP300 is slightly larger than thatof CS300. The slopes of the regression line of the GP and CS
samples were 0.4×10−3 and 0.5×10−3, respectively. The oxygen
content (O/C) of the samples were in the range of 0.09–0.14; theoxygen originates from the surface adsorption of O 2 and H2Oafter the deposition.
Figures 2 shows the TEY absorption spectra of the a-CNx
films and HOPG as a reference obtained using NEXAFS. The
NEXAFS spectra of the a-CNx film was without dependence on
the incident angle of X-ray to the film surface. HOPG showed
two strong peaks at approximately 285.5 eV (known as the *peak), and 292 eV corresponding to various * transitions.

0.60

0.55

0.50
50

100

150 200 250
RF power (W)

300

350

Figure 1. Nitrogen content (N/C) of aCNx films deposited using the gradientgas pressure (GP) and common
sputtering (CS) modes.23

Conversely, a fine structure comprising of at least six peaks, centered at 284.5 eV (C1), 285.8 eV (C2), 286.6 eV(C3), 288.2 eV (C4), 288.9 eV (C5), and 289.5 eV (C6), could clearly be seen in the spectra of the a-CNx films.
These spectral features are recognized in the C K-edge spectra of carbon-related materials and amorphous carbon
films containing nitrogen.
A comparing GP85 and CS85 shows, the presence of two remarkable points in the NEXAFS spectra, as shownin Fig. 2a: 1) several peaks appeared in a region of 284–285 eV in CS85 and 2) the C3 peak of CS85 has anextremely high intensity. The peaks in 284–285 eV can be assigned * transition. The spectral feature,
characteristic of the several peaks appearing in the region of 284−285 eV, is similar to the electron-energy-loss
spectra (EELS) of fullerenes in the energy region of the carbon K-absorption edge.16 The first large peak of C60
and C70 appears to be of lower energy than graphite, while several small peaks appear to be of lower energy than
the first large peak. These small peaks become one broad peak and a shoulder as the number of carbon atoms
increases from C60 to C84. In addition, pure carbon materials exhibit C1 and C5 peaks, such as fullerene andamorphous carbon, and these can be assigned to 1s→* transition and 1s→* transition of the C=C bond,respectively.17, 18 From these reports, the small peaks around the C1 peak of CS85 are due to existence from bending
graphene sheet-like imperfect fullerenes. The C2 peak is from the * states of the C–N single bond.19
The identification of the C3 peak is not in agreement with previous results. McCann et al. concluded that thepeak at approximately 286.6 eV corresponding to C3 in Fig. 8 is mainly due to C=N bonds in tetrahedral
amorphous carbon films with increasing nitrogen concentration (0 < x < 10.3 at.%).16 Point et al. concluded that
the C3 peak can be attributed to the sp2 carbon bonded to nitrogen atoms, which are generally isolated nitrogenatoms involved in C=N and C≡N bonds.20 Lutham et al. suggested that C3 is 1s→* transition of C=C–NH.21 The
sharp peak at 289.3 eV in CS85 is an unknown peak, although this position is closer to 289.6 eV, which is assigned
to the * excitation in diamond.18 The C4 peak is attributed to the sp2 carbon bonded to the nitrogen atoms
corresponding to the conjugated nitrogen involved in single bonds, i.e. N–C–N or N≡C–N.22
With increasing RF power, several small peaks appeared around the C1 peak similar to those in the NEXAFS
spectrum of CS85 as shown in Fig. 1b. At the edge of the spectra, GP85 had a relatively long tail starting from
283.0 eV and then gradually shortened up to 283.3 eV with increasing RF power. This is probably due to an
asymmetrically shaped fullerene-like structure, as mentioned above.
The C3 peak was noticeable and shifted toward the lower energy with increasing RF power. This is due todecreased intensities of the C2 and C4 peaks. Both peaks are attributed to bonding with nitrogen, and thus, the C3
peak is assigned as the C=C bond. With decreasing N/C, the carbon-to-carbon antibonding state becomes dominant
in the conduction band; thus, the antibonding state of C=C shifts toward lower energy.
Lutham et al. suggested that the peak position of C6 is the 1s→* transition of the N–C bond.21 In contrast,
MaCann et al. explained that C6 corresponds to a  transition of the C–H bonds.16 For the C6 peak, hydrogen is
not used in the deposition environment of GP samples, therefore this peak is attributed to the transition of 1s→ σ*
as in the case of diamond.18 The intensity of C6 peak increased with increasing RF power in GP samples as shownin Fig. 2b. Thus, the advantage of high RF power with GP mode was achieved to increase sp3C– N bond.

Figure 2. TEY X-ray absorption spectra in the C K-edge of a-CNx films and HOPG as a reference
obtained using NEXAFS: (a) GP85 and CS85 and (b) GP samples prepared with different RF
power.23
50

4. Conclusion
Amorphous carbon nitride (a-CNx) thin films were deposited using the gradient gas pressure sputtering method.
The films were also deposited through the common sputtering mode, that is, at a uniform gas pressure in thechamber. The effect of the gradient gas pressure on the nitrogen content (N/C) was minimal, as obtained from XPS
analysis results. The N/C ratios of the GP and CS samples were mostly the same at approximately 0.65 when the
RF power was 85 W but decreased to 0.57 and 0.55, respectively, with increasing RF power up to 300 W. The
chemical bonding structure of the films was investigated using NEXAFS measurements at NewSUBARU BL09A.
When comparing GP and CS samples deposited at 85 W, a reduction of the peak intensity corresponding to the *transition was observed in the NEXAFS spectrum of GP samples. The intensity of the peak, which is assigned to
the 1s→* transition of the N–C bond, increased with increasing RF power of GP mode. At the edge of NEXAFS
spectra, the tail gradually decreased with increasing RF power.

Acknowledgement
A part of this work was supported from Hyogo COE Research Program and JSPS KAKENHI (22H00267).

References[ 1]
A. Y. Liu, M. L. Cohen: Science, 245, 841 (1989).
[ 2]
A. Y. Liu, M. L. Cohen: Phys. Rev. B, 41, 10727 (1989).
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S. Matsumoto, E.-Q. Xie, F. Izumi: Diam. Relat. Mater., 8, 1175 (1999).
[ 4] E. F. Motta, I. Pereyra: J. Non-Cryst. Solids, 338-340, 525 (2004).
[ 5] P. Wang, T. Takeno, K. Adachi, H. Miki, T. Takaghi: Appl. Surf. Sci., 258, 6576 (2012).
[ 6] Y. Iwano, T. Kittaka, H. Tacushi, M. Soukawa, S. Kunitsugu, K. Takarabe, K. Itoh: Jpn. J. Appl. Phys.,47, 7842 (2008).
[ 7] H. Kinoshita, M. Kubota: Thin Solid Films, 518, 3502 (2010).
[ 8] M. Aono, T. Takeno, T. Takagi: Diam. Relat. Mater., 63, 120 (2016).
[ 9]
S. Nitta, in: S.R.P. Silva (Ed.), Amorphous Carbon, INSPEC, UK, 2002, p. 62–63.
[10] S. Nitta, M. Aono, T. Katsuno, Y. Naruse: Diam. Relat. Mater., 12, 219 (2003).
[11] N. Takada, K. Arai, S. Nitta, S. Nonomura: Appl. Surf. Sci., 113/114, 274 (1997).
[12] Y. Terai, K. Haraguchi, R. Ichinose, H. Oota, K. Yonezawa: Jpn. J. Appl. Phys., 62, SA1003 (2023).
[13] N. Hellgren, R. T. Haasch, S. Schmidt, L. Hultman, I. Petrov, Carbon, 108, 242 (2016).
[14] M. Niibe, M. Mukai, H. Kimura, Y. Shoji: Fourth Huntsville gamma-ray burst symposium, 705, 243(2004).
[15] M. Niibe, M. Mukai, S. Miyamoto, Y. Shoji, S. Hashimoto, A. Ando, T. Tanaka, M. Miyai, H.
Kitamura: Fourth Huntsville gamma-ray burst symposium, 705, 576 (2004).
[16] R. McCann, S.S. Roy, T, P. Papakonstantinou, I. Ahmad, P. Maguire, J.A. McLaughlin, L. Petaccia, S.
Lizzit, A. Goldoni: Diam. Relat. Mater., 14, 1057 (2005).
[17] Y. Zhou, J. Lin, Xue-Ying Nie, Xiu-Neng Song, Yong Ma, Chuan-Kui Wang: Spectrochim. Acta A, 229,
117904 (2020).
[18] J. Diaz, S. Anders, X. Zhou, E. J. Moler, S. A. Kellar, Z. Hussai: Phys. Rev. B, 64, 125204 (2001).
[19] B. Bouchet-Fabre, K. Zellama, C. Godet, D. Ballutaud, T. Mine’a: Thin Solid Films, 482, 156 (2005).
[20] S. Hosokawa, H. Sato, Y. Wang, E. Ohata, A. Fukushima: J. Electron Spectrosc., 137-140, 2357 (2004).
[21] K. G. Latham, M. I. Simone, W. M. Dose, J. A. Allen, S. W. Donne: Carbon, 114, 566 (2017).
[22] S. Point, T. Minea, B. Bouchet-Fabre, A. Granier, G. Turban: Diam. Relat. Mater. 14, 891 (2005).
[23] M. Aono, M. Terauchi, Y. K. Sato, K. Morita, T. Inoue, K. Kanda, K. Yonezawa: Appl. Surf. Sci., 635,
157677 (2023).

51

Laser irradiation effect on oriented sp2 bonded carbon structure
in hydrogenated amorphous carbon films
Dai Harada1, Naoki Umada1, Yuko Aono1, Kazuhiro Kanda2, Masahito Niibe2,3, Yuki Hirata4, Naoto Ohtake4,
and Hiroki Akasaka1*
1

Dept. of Mechanical Eng., Tokyo Institute of Technology
Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo
3
Institute of Solid State Physics (ISSP), The University of Tokyo
4
Institute of Innovative Research, Tokyo Institute of Technology

2

Abstract
The effect of laser irradiation on the sp2 orientation of a hydrogenated amorphous carbon film withan oriented sp2 carbon bonding structure was evaluated by X-ray absorption spectroscopy usingsynchrotron radiation. XAS measurements while changing the incident angle of X-rays, andevaluated the change in the orientation of sp2 carbon from the angle dependence of * peak at XAS
spectra. A hydrogenated amorphous carbon film was deposited from C 2H2 by the pulsed plasma
CVD method and a ytterbium-doped fiber pulsed laser with 1064 nm was irradiated at defocus
condition. The XAS spectra of the hydrogenated amorphous carbon films before and after laser
irradiations measured at an X-ray incident angle of 0-75°. From angle dependence of the intensityof * peak in hydrogenated amorphous carbon films, the sp2 orientation in the film became stronger
by laser irradiation. From the molecular structure and the angle dependence at HOPG as standard
sample, this indicates that the sp2 bonded carbons at the surface of these hydrogenated amorphous
carbon films were oriented perpendicular to the substrate, this perpendicular orientation wasincreased by laser irradiation.

1. Introduction
Hydrogenated amorphous carbon film consists of sp2 or sp3 hybridized bonding carbon and hydrogen. The
structure in hydrogenated amorphous carbon films is that these carbon bonding networks are terminated withhydrogen, and is often discussed in the ternary diagram in terms of sp2 or sp3 ratio and the amount ofhydrogen1, 2. ISO 20523:2017 has also been established by International Organization for Standardization(ISO) based on the consideration including of ternary diagram3. Recently, extremely small the oriented sp2
bonded carbon network structure in hydrogenated amorphous carbon film was detected by the X-ray incident
angle dependence of X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES)
measurements using synchrotron radiation X-rays4. Although this oriented sp2 structure is too small to be
detected by X-ray diffraction, it was indicated there is an extremely small graphene sheet-like structure fromresults both the angle dependence of XAS measurement and the results of Raman spectroscopy. And theorientation distribution and direction of the sp2 carbon structure depended on the source material.
Although hydrogenated amorphous carbon films are usually weak against heating and change thestructure5,6, the partial heating using laser irradiation improve the tribological properties. It was reported that
one of the structural changes was by sp2 increasing by laser irradiation7. It is possible that the orientation of
sp2 is also changed due to the structural change of sp2 carbon due to this local heating. In this study, XAS
measurements using synchrotron radiation X-rays with different incident angles were performed to detect theorientation of extremely small the sp2 bonded carbon network structure in hydrogenated amorphous carbon
film. Based on previous study, an oriented sp2 structure containing hydrogenated amorphous carbon films
were prepared and heated partially by laser irradiation, and we investigated how the orientation in thehydrogenated amorphous carbon film was changed.
2. Experimental
The hydrogenated amorphous carbon films were deposited by pulsed plasma chemical vapor deposition(CVD) method from acetylene (C2H2, 98 %)8. A pulsed power supply (TE-HV1000-TK: Tamaoki
Electronics) was used as a power source to generate plasma. The Silicon (100) substrate was placed on theelectrode in the vacuum chamber, which was evacuated to 5×10-3 Pa. Subsequently, argon (Ar, 99.995 %)52

were introduced into the chamber while controllingthe flow rates using a mass flow controller. The
Anatural oxidation layer at the substrate surface wasremoved by Ar ion irradiation for 30 min before thedeposition of the film. The flow rate of Ar and
X-raypressure of the reaction chamber were 20 cm3/min
and 2 Pa, respectively. The pulsed bias voltage of -3.5
kV, with a frequency of 14.4 kHz, was applied togenerate Ar plasma. After the cleaning, C2H2 wasintroduced into the vacuum chamber with a flow rateof 20 cm3/min. The pressure was adjusted to 3 Pa. A
pulsed negative bias voltage of -4.5 kV with afrequency of 14.4 kHz was applied to the substrate.
The thickness of the film deposited was adjusted by
Figure 1. The X-ray incident angle, α at
the controlling the deposition duration atmeasurement.
approximately 500 nm.
Laser irradiation was conducted to these depositedhydrogenated amorphous carbon surface using laser marking apparatus with an ytterbium-doped fiber pulsed
laser (LP-S; Panasonic). Its wavelength is 1064 nm. The energy density and irradiation time for one shot were0.1 J/cm2 and 20 μs, respectively. The laser irradiation area of the hydrogenated amorphous carbon film wascontrolled by dis tance between laser irradiation spots to 100 μm intervals using a galvanometer mirror scanner.
The sample was placed at a depth of 5 mm from the focal point under laser irradiation. A laser microscope(OLS4100; Olympus Co.) and an optical microscope (BX53; Olympus Co.) were used to observe the surface
shapes of laser-irradiated hydrogenated amorphous carbon films.

The XAS measurements for the hydrogenated amorphous carbon films using soft X-rays were carried out
at the beamline BL-09A of the NewSUBARU synchrotron radiation facility at the University of Hyogo9-12.
The samples were fixed to a copper plate holder, and was introduced into the vacuum chamber while
maintaining pressure of the order of 10-5 Pa. The synchrotron radiation extracted from an undulator, which is
the light source of BL-09A, was mo nochromated and introduced at the irradiation point of the sample. Xray absorption spectra was measured using a total electron yield (TEY) method by sample current
measurement13. The X-ray incident angle, α, for XAS measurement is defined as the angle measured fromthe film surface normal of the sample, as shown in Fig. 1. X-ray incident angle, α, was varied from 0 to 75°.
3. Results and Discussion
Figure 2 shows the photomicrographs before and after laser irradiation of the hydrogenated amorphous
carbon film surface. Before laser irradiation, the hydrogenated amorphous carbon film deposited onto the Si
substrate appeared completely smooth, observed under an optical microscope. The surface shape changed
after an area of the films were subjected to laser irradiation at an interval of 100 μm using a galvanometer
mirror scanner. From the photomicrographs after irradiation, circular shapes centered on the center point of
the laser irradiation were observed on the surface. Continuous circles were observed at irradiation intervalsof 100 µm. The center points of the circular irradiation areas matched the laser irradiation interval. The
surface topographies of the irradiated samples were obtained and characterized using a laser microscope. The

Figure 2. Photomicrographs; before (Left) and after (Right) laser irradiation.
53

Figure 3. Cross sectional profiles before (Left) and after (center) the laser irradiation area, and laser
microscopic images (Right) after irradiation.

images and the profiles at the center of the circular irradiation area are shown in Fig. 3. The films werechanged to hemispherical shape from flat by the laser irradiation.
First, an evaluation using XAS was performed to detect the orientation of these sp2 carbon network structures.

Figure 4. XAS spectra of hydrogenated amorphous carbon film before (Left) and after (Right) irradiation.

Figure 4 (Left) shows the XAS spectra of the hydrogenated amorphous carbon films before irradiation
measured at an X-ray incident angle of 0-75° and normalized at 295 eV. Absorption of C=C π* in the sp2
bonded carbon atoms was observed near the photon energy of 285 eV14,15. The broad peaks near 292-295 eVcorresponds to the C-C σ* in sp2 and sp3-bonded carbon atoms was also observed14, 16, 17. The XAS spectra
for the hydrogenated amorphous carbon films shows that the absorption intensity of π* band at 285 eV dependon the incident angle. Before laser irradiation, the intensity of π band depended on the X-ray incident angle.
The results indicate that the peak intensity corresponding to the π* band in XAS spectra was dependent on
X-ray incidence angle in the deposited hydrogenated amorphous carbon films, further indicating that oriented
sp2-bonded carbon networks were present in their film structures. Figure 4 (Right) shows the XAS spectra of
the laser-irradiated hydrogenated amorphous carbon films measured at an X-ray incident angle of 0-75° andnormalized at 295 eV. The XAS spectra for the laser-irradiated hydrogenated amorphous carbon film
presented the dependence of the absorption intensity of π* band at 285 eV on the incident angle. The oriented
sp2 -bonded carbon networks were present in the laser-irradiated hydrogenated amorphous carbon film
structures. These XAS measurements indicate that there are oriented graphene-like structures composed ofvery small sp2-bonded carbons in the hydrogenated amorphous carbon films, and these orientations maintainin the films after laser irradiation.
54

Figure 5. XAS spectra (Left) and X-ray incident angle dependence on peak intensity ratio of π*/* (Right) for
HOPG.

Next, the orientation angle of the sp2 carbons in hydrogenated amorphous carbon film was estimated fromcomparison of XAS spectra with HOPG as standard. The structure in HOPG is that sp2 bonded-graphenesheets are stacked completely parallel to the material surface. Thus, at the X-ray incidence angle α=0°, the
X-ray is incident perpendicular to the π electron cloud of the sp2 bonded carbon networks. And this angle has
the smallest absorption at π peak in XAS for HOPG. Figure 5 (Left) shows the XAS spectra of HOPG. The
absorption intensity increases rapidly as α increases owing to the π* peak. The sp2 orientation direction in
the hydrogenated amorphous carbon films was estimated in HOPG based on this tendency. The angle
dependence of the amount of X-ray absorbed was extremely small because the uniform electron distributionof sp3 bonded carbon compared to that of the sp2 bonded carbons. Hence, the change in intensity ratio of thepeak of π*/σ* against the X-ray incident angle was determined. From spectra shown in Fig. 4, the X-ray
incident angle dependence of the absorption intensity ratio of the peak at 284.5 eV was determined owing to
the absorption of sp2 bonded carbon. When the ratio against absorption ratio of 284.5 eV at X-ray incident
angle =0°, the absorption ratios were appeared the X-ray incident angle dependence as shown in Fig. 6.
Angle dependence of the intensity ratio in hydrogenated amorphous carbon was opposite trend as that of
HOPG, and the tendency became stronger by laser irradiation. From the molecular structure and the angle

Figure 6. X-ray incident angle dependence on π*/* for the films.
55

dependence at HOPG, this indicates that the sp2 bonded carbons at the surface of these hydrogenatedamorphous carbon films were oriented perpendicular to the substrate, this perpendicular orientation wasincreased by laser irradiation.
4. Conclusion
Using XAS with synchrotron radiation, a very small sp2 orientation in the hydrogenated amorphous carbon
films was detected and laser irradiation to hydrogenated amorphous carbon films effect to the orientation wasinvestigated. A hydrogenated amorphous carbon film was deposited from C2H2 by the pulsed plasma CVD method
and the pulsed laser with 1064 nm was irradiated at defocus condition. The XAS spectra of the hydrogenatedamorphous carbon films before and after laser irradiation measured at varying X-ray incident angle. From angle
dependence of the intensity of * peak in hydrogenated amorphous carbon films, the sp2 orientation in the film
became stronger by laser irradiation. By the comparison of the molecular structure and the angle dependence at
HOPG, the sp2 bonded carbons with perpendicular orientation was increased by laser irradiation.

Acknowledgement
Funding: The part of this research was funded by the JSPS KAKENHI Grant-in-Aid for Scientific Research(B) Grant No. 22H01355, and ENEOS TONENGENERAL Research/Development Encouragement &Scholarship Foundation. The XRD and Raman spectroscopy analysis was performed at the Materials
Analysis Division, Open Facility Center in Tokyo Institute of Technology.
References[ 1] N. Ohtake, M. Hiratsuka, K. Kanda, H. Akasaka, M. Tsujioka, K. Hirakuri, A. Hirata, T. Ohana, H.
Inaba, M. Kano, and H. Saitoh: Materials 14 315 (2021).
[ 2] J. Robertson, Diamond-like amorphous carbon. Mater. Sci. Eng., R37 129 (2002).
[ 3] Carbon Based Films—Classification and Designations ISO 20523:2017; The International
Organization for Standardization; Vernier: Geneva, Switzerland, 2017.
[ 4] N. Umada, K. Kanda, M. Niibe, Y. Hirata, N. Ohtake, and H. Akasaka: Diam. Relat. Mater., 131
109533(2023).
[ 5] H. Akasaka, S. Tunmee, U. Rittihong, M. Tomidokoro, C. Euaruksakul, S. Norizuki, R. Supruangnet,
H. Nakajima, Y. Hirata, and N. Ohtake: Diam. Relat. Mater., 101 107609 (2020).
[ 6] H. Akasaka, S. Kawaguchi, S. Ohshio, and H. Saitoh: Trans. Mater. Res. Soc. Japan, 36 505 (2011).
[ 7] D. Harada, S. Tunmee, C. Euaruksakul, U. Rittihong, H. Nakajima, Y. Aono, Y. Hirata, N. Ohtake, and
H. Akasaka: Diam. Relat. Mater., 131 109573 (2023).
[ 8] M. Tomidokoro, S. Tunmee, U. Rittihong, C. Euaruksakul, R. Supruangnet, H. Nakajima, Y. Hirata,
N. Ohtake, and H. Akasaka: Materials 14 2355 (2021).
[ 9] A. Ando, S. Amano, S. Hashimoto, H. Kinosita, S. Miyamoto, T. Mochizuki, M. Niibe, Y. Shoji, M.
Terasawa, and T. Wantanebe: Proc. the IEEE Particle Accelerator Conference, 12–16 757 (1997).
[10] S. Hashimoto, A. Ando, S. Amano, Y. Haruyama, T. Hattori, K. Kanda, H. Kinoshita, S. Matsui, H.
Mekaru, S. Miyamoto, T. Mochizuki, M. Niibe, Y. Shoji, Y. Utsumi, T. Watanabe, and H. Tsubakino:Trans. Mat. Res. Soc. Japan 26 783 (2001).
[11] K. Kanda, T. Ideta, Y. Haruyama, H. Ishigaki, and S. Matsui: Jpn. J. Appl. Phys. 42 3983 (2003).
[12] Y. Kato, K. Kanda, Y. Haruyama, and S. Matsui: Jpn. J. Appl. Phys. 43 3938 (2004).
[13] M. Niibe, T. Kotaka, and T. Mitamura: J. Phys.: Conference Series 425 132008 (2013).
[14] P. E. Batson: Phys. Rev. B 48 2608 (1993).
[15] M. Niibe, T. Tokushima, N. Takehira, and Y. Arakia: J. Electron Spectroscopy Related Phenomena,
220 118 (2017).
[15] J. Stöhr: NEXAFS spectroscopy, Springer series in surface sciences.
[16] S. Ohmagari, T. Yoshitake, A. Nagano, S. AL-Riyami, R. Ohtami, H. Setoyama, E. Kobayashi, and K.
Nagayama: J. Nanomater. 876561 (2009).

56

NEXAFS Studies of Amorphous Carbon Nitride Thin Films
Deposited by Pressure-gradient RF Magnetron Sputtering
1

Masami Aono1, Kyoji Morita2, Tasuku Inoue2, and Kazuhiro Kanda3
Department of Electrical and Electronics Engineering, Graduate School of Science and Engineering,Kagoshima University,
2
Faculty of Engineering, University of Hyogo
3
Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo

Abstract
Amorphous carbon nitride (a-CNx) thin films were deposited through radio frequency (RF)magnetron sputtering under increasing nitrogen gas pressure around a graphite target to provide
nitrogen radicals at high concentrations. The C K-edge near-edge X-ray absorption fine structure(NEXAFS) measurements were performed at NewSUBARU BL09A. To increase the gas pressurearound the graphite target, C K-edge NEXAFS spectra of the a-CNx films was changed. The nitrogencontent in the a-CNx films obtained from XPS analysis did not increase when the nitrogen gas
pressure around the graphite target was increased. The effect of nitrogen incorporation on the a-CNx
films was comparatively more effective at higher RF powers.

1. Introduction
Liu and Cohen discovered a new super-hard material based on theoretical calculations, generating interest in
carbon nitride compounds.1 They predicted -C3N4 based on -Si3N4.2 However, the growth of thishexagonal crystal structure has not been corroborated, even 30 years after its prediction. Following theprediction of - C3N4, several crystalline structures based on sp3C–N have been presented, such as -C3N4
and cubic-C3N4.3 Almost all the carbon nitrides prepared using thin film deposition techniques, such as
chemical vapor deposition (CVD), sputtering, and laser ablation, have amorphous phases due to the low
thermal stability of sp3C–N bonds.
Thin films of amorphous carbon nitride (a-CNx) comprise sp2– and sp3–hybridized carbon networks. aCNx films can be deposited using two typical deposition methods: plasma-enhanced CVD using hydrocarbon
gases and sputtering using graphite. NH3 and N2 are used as the nitrogen source. The range of nitrogenconcentration (x) is wide, depending on the deposition method and condition; however, the maximum x value
in most a-CNx films is approximately 0.5. Furthermore, a-CNx films deposited using the CVD method havea relatively lower nitrogen concentration and higher sp3-C bonds because it contains hydrogen as source
material.4-6 In contrast, a-CNx films prepared from graphite and N2 by physical vapor deposition have more
sp2-C bonds.7, 8 The nitrogen concentration of the sputtering film depends on the sputtering gas ratio of Ar
and N2.
a-CNx films can be deposited with a high nitrogen concentration using the nitrogen-radical sputtering
method proposed by Nitta et al.9,10 In this method, nitrogen radicals in the glow discharge of nitrogenmolecules react well with a carbon target at low energy.11 This method can produce a higher nitrogen content
than other techniques. The x value of a-CNx films deposited by nitrogen radical sputtering with hydrogenplasma etching is ~0.86.10
As essential technique to increase both the nitrogen content and sp3C bond in a-CNx films is increasing
the amount of high-energy nitrogen radical species. The mean free path of sputtered species on the growthsurface is short under low-vacuum conditions. Therefore, sputtering under higher-vacuum conditions isdesirable for the growth of high sp3–hybridized carbon films. However, the number of nitrogen radical
species is an important factor in increasing the nitrogen content. In the conventional sputtering method, thevacuum inside the growth chamber is uniform, and thus, generating excess nitrogen radicals is difficult.
Recently, the pressure gradient sputtering source has been developed for sputtering at a high vacuum withlow plasma damage.12 In magnetron sputtering using a pressure gradient sputtering source, a gas is locallyinjected near the sputtering target through the pressure gradient sputtering source, and the main vacuum valve
connected to the turbo-molecular pump is fully opened. This condition induces a pressure gradient with ahigh vacuum at the substrate position and a low vacuum around the target. Hence, the production of additional
nitrogen radical species around the target can be expected using the pressure gradient sputtering source. In
this study, a-CNx thin films were deposited using the pressure gradient and conventional sputtering modes
with the same growth chamber, and the chemical bonding structure of the films was investigated to confirm
57

the effect of nitrogen radicals.
2. Experimental
2.1. Sample Preparation
a-CNx films were prepared from graphite with a purity of 99.95% and N2 with a purity of 99.99995%. The
substrates used were SiO2 glass and Si(100), which were cleaned ultrasonically in acetone and ethanol for 15
min each, before loading into the vacuum chamber.
In the sputtering system, the gas inlet can be changed between two modes, the conventional sputteringand pressure gradient modes, by operating valves. In the gas pressure gradient mode (GP), the sputtering gas
was injected near the target. Therefore, the gas pressure around the target was approximately one order ofmagnitude higher than that around the substrate holder. In comparison, the gas pressure in the chamber in theconventional sputtering mode (CS) was kept constant owing to the flow of N2 gas through the middle of thetarget and substrate holder.
The base pressure was under 1×10−3 Pa. For the film deposition, the N2 gas flow rate was 3 sccm, and theprocess pressure was maintained at 16 Pa (measured near the substrate holder). The samples obtained at RF
powers of 85, 130, 200, and 300 W by the conventional sputtering mode were denoted by CS85, CS130,
CS200 and CS300, respectively; the samples obtained using the gradient-pressure mode were denoted by
GP85, GP130, GP200, and GP300, respectively.
2.2. Characterizations
The atomic concentrations of the samples were obtained from the C1s, N1s, O1s, and Si2p core-level peaks using
X-ray photoelectron spectroscopy (XPS; Kratos Ultra 1, Shimadzu); Si was derived from the substrate.
Monochromatic Al K radiation (1486.6 eV) was used as the X-ray source. The pass energy and step size were
40 and 0.05 eV, respectively. The analysis area was 300 µm × 700 µm. In this study, the Ar + bombardment etchingprocess was skipped because it could possibly destroy the chemical bonding structure between carbon and nitrogen.
The corresponding binding energies were calibrated with the C1s line at 284.5 eV for all cases, which could be
assigned to sp2 graphite like carbon.13

Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is sensitive to the local coordinationof the CN structure and a probe of the electronic structure of unoccupied orbitals of carbon. NEXAFS
measurements were performed using the BL09A at the NewSUBARU synchrotron facility of the Universityof Hyogo14, 15; the instrument has an 11 m undulator as a light source and a grating monochromator. The
electron energy of the storage ring during this study was 1.23 GeV. The samples deposited on a Si substrate
were mounted on a copper plate using a carbon conductive tape. The electrons emitted from the sample weredetected in the total electron yield (TEY) mode. The NEXAFS spectra of the C K-edge absorption were
measured using a grating of 1200 grooves/mm in the range of 275–330 eV. The energy resolution was
estimated to be less than 0.5 eV (full width at half maximum).
3. Results and Discussion
Figure 1 shows the nitrogen content (N/C) obtained from the C1s and N1s core level XPS spectra. The GP
and CS samples showed a similar N/C tendency as a function of the RF power. An increase in the RF power
decreased the nitrogen content of the films in both sputtering modes. GP85 and CS85 have almost the sameN/C ratio of 0.66, showing no significant influence of gas pressure around the target. A comparing of GP300
and CS300 indicates that the N/C ratio of GP300 is slightly larger than that of CS300. The slopes of theregression line of the GP and CS samples were 0.4×10−3 and 0.5×10−3, respectively. The oxygen content(O/C) of the samples were in the range of 0.09–0.14; the oxygen originates from the surface adsorption ofO2 and H2O after the deposition.
Figures 2 shows the TEY absorption spectra of the a-CNx films and HOPG as a reference obtained using
NEXAFS. The NEXAFS spectra of the a-CNx film was without dependence on the incident angle of X-ray
to the film surface. HOPG showed two strong peaks at approximately 285.5 eV (known as the * peak), and292 eV corresponding to various * transitions. Conversely, a fine structure comprising of at least six peaks,
centered at 284.5 eV (C1), 285.8 eV (C2), 286.6 eV (C3), 288.2 eV (C4), 288.9 eV (C5), and 289.5 eV (C6),
could clearly be seen in the spectra of the a-CNx films. These spectral features are recognized in the C Kedge spectra of carbon-related materials and amorphous carbon films containing nitrogen.
A comparing GP85 and CS85 shows, the presence of two remarkable points in the NEXAFS spectra, as
shown in Fig. 2a: 1) several peaks appeared in a region of 284–285 eV in CS85 and 2) the C3 peak of CS85
has an extremely high intensity. The peaks in 284–285 eV can be assigned π* transition. The spectral feature,
characteristic of the several peaks appearing in the region of 284−285 eV, is similar to the electron-energy58

0.70
GP
CS

N/C

0.65

0.60

0.55

0.50
50

100

150 200 250
RF power (W)

300

350

Figure 1. Nitrogen content (N/C) of a-CNx films deposited using the gradient gas pressure (GP) and common
sputtering (CS) modes.23

loss spectra (EELS) of fullerenes in the energy region of the carbon K-absorption edge.16 The first large peakof C60 and C70 appears to be of lower energy than graphite, while several small peaks appear to be of lower
energy than the first large peak. These small peaks become one broad peak and a shoulder as the number ofcarbon atoms increases from C60 to C84. In addition, pure carbon materials exhibit C1 and C5 peaks, suchas fullerene and amorphous carbon, and these can be assigned to 1s→π* transition and 1s→σ* transition of
the C=C bond, respectively.17, 18 From these reports, the small peaks around the C1 peak of CS85 are due toexistence from bending graphene sheet-like imperfect fullerenes. The C2 peak is from the π* states of the C–
N single bond.19
The identification of the C3 peak is not in agreement with previous results. McCann et al. concluded thatthe peak at approximately 286.6 eV corresponding to C3 in Fig. 8 is mainly due to C=N bonds in tetrahedral
amorphous carbon films with increasing nitrogen concentration (0 < x < 10.3 at.%).16 Point et al. concluded
that the C3 peak can be attributed to the sp2 carbon bonded to nitrogen atoms, which are generally isolated
nitrogen atoms involved in C=N and C≡N bonds.20 Lutham et al. suggested that C3 is 1s→π* transition of
C=C–NH.21 The sharp peak at 289.3 eV in CS85 is an unknown peak, although this position is closer to 289.6
eV, which is assigned to the σ* excitation in diamond.18 The C4 peak is attributed to the sp2 carbon bonded
to the nitrogen atoms corresponding to the conjugated nitrogen involved in single bonds, i.e. N–C–N or N≡C–
N.22
With increasing RF power, several small peaks appeared around the C1 peak similar to those in the
NEXAFS spectrum of CS85 as shown in Fig. 1b. At the edge of the spectra, GP85 had a relatively long tailstarting from 283.0 eV and then gradually shortened up to 283.3 eV with increasing RF power. This is

Figure 2. TEY X-ray absorption spectra in the C K-edge of a-CNx films and HOPG as a reference
obtained using NEXAFS: (a) GP85 and CS85 and (b) GP samples prepared with different RF power.23
59

probably due to an asymmetrically shaped fullerene-like structure, as mentioned above.
The C3 peak was noticeable and shifted toward the lower energy with increasing RF power. This is due
to decreased intensities of the C2 and C4 peaks. Both peaks are attributed to bonding with nitrogen, and thus,
the C3 peak is assigned as the C=C bond. With decreasing N/C, the carbon-to-carbon antibonding state
becomes dominant in the conduction band; thus, the antibonding state of C=C shifts toward lower energy.
Lutham et al. suggested that the peak position of C6 is the 1s→σ* transition of the N–C bond.21 In contrast,
MaCann et al. explained that C6 corresponds to a σ* transition of the C–H bonds.16 For the C6 peak, hydrogenis not used in the deposition environment of GP samples, therefore this peak is attributed to the transition of
1s→ σ* as in the case of diamond.18 The intensity of C6 peak increased with increasing RF power in GP
samples as shown in Fig. 2b. Thus, the advantage of high RF power with GP mode was achieved to increase
sp3C– N bond.
4. Conclusion
Amorphous carbon nitride (a-CNx) thin films were deposited using the gradient gas pressure sputtering
method. The films were also deposited through the common sputtering mode, that is, at a uniform gas pressurein the chamber. The effect of the gradient gas pressure on the nitrogen content (N/C) was minimal, as obtained
from XPS analysis results. The N/C ratios of the GP and CS samples were mostly the same at approximately
0.65 when the RF power was 85 W but decreased to 0.57 and 0.55, respectively, with increasing RF power
up to 300 W. The chemical bonding structure of the films was investigated using NEXAFS measurements at
NewSUBARU BL09A. When comparing GP and CS samples deposited at 85 W, a reduction of the peakintensity corresponding to the π* transition was observed in the NEXAFS spectrum of GP samples. The
intensity of the peak, which is assigned to the 1s→π* transition of the N–C bond, increased with increasing
RF power of GP mode. At the edge of NEXAFS spectra, the tail gradually decreased with increasing RF
power.
Acknowledgement
A part of this work was supported from Hyogo COE Research Program and JSPS KAKENHI (22H00267).

References[ 1] A. Y. Liu, M. L. Cohen: Science, 245, 841 (1989).
[ 2] A. Y. Liu, M. L. Cohen: Phys. Rev. B, 41, 10727 (1989).
[ 3] S. Matsumoto, E.-Q. Xie, F. Izumi: Diam. Relat. Mater., 8, 1175 (1999).
[ 4] E. F. Motta, I. Pereyra: J. Non-Cryst. Solids, 338-340, 525 (2004).
[ 5] P. Wang, T. Takeno, K. Adachi, H. Miki, T. Takaghi: Appl. Surf. Sci., 258, 6576 (2012).
[ 6] Y. Iwano, T. Kittaka, H. Tacushi, M. Soukawa, S. Kunitsugu, K. Takarabe, K. Itoh: Jpn. J. Appl. Phys.,47, 7842 (2008).
[ 7] H. Kinoshita, M. Kubota: Thin Solid Films, 518, 3502 (2010).
[ 8] M. Aono, T. Takeno, T. Takagi: Diam. Relat. Mater., 63, 120 (2016).
[ 9] S. Nitta, in: S.R.P. Silva (Ed.), Amorphous Carbon, INSPEC, UK, 2002, p. 62–63.
[10] S. Nitta, M. Aono, T. Katsuno, Y. Naruse: Diam. Relat. Mater., 12, 219 (2003).
[11] N. Takada, K. Arai, S. Nitta, S. Nonomura: Appl. Surf. Sci., 113/114, 274 (1997).
[12] Y. Terai, K. Haraguchi, R. Ichinose, H. Oota, K. Yonezawa: Jpn. J. Appl. Phys., 62, SA1003 (2023).
[13] N. Hellgren, R. T. Haasch, S. Schmidt, L. Hultman, I. Petrov: Carbon, 108, 242 (2016).
[14] M. Niibe, M. Mukai, H. Kimura, Y. Shoji: Fourth Huntsville gamma-ray burst symposium, 705, 243(2004).
[15] M. Niibe, M. Mukai, S. Miyamoto, Y. Shoji, S. Hashimoto, A. Ando, T. Tanaka, M. Miyai, H.
Kitamura: Fourth Huntsville gamma-ray burst symposium, 705, 576 (2004).
[16] R. McCann, S.S. Roy, T, P. Papakonstantinou, I. Ahmad, P. Maguire, J. A. McLaughlin, L. Petaccia, S.
Lizzit, A. Goldoni: Diam. Relat. Mater., 14, 1057 (2005).
[17] Y. Zhou, J. Lin, Xue-Ying Nie, Xiu-Neng Song, Yong Ma, Chuan-Kui Wang: Spectrochim. Acta A, 229,
117904 (2020).
[18] J. Diaz, S. Anders, X. Zhou, E. J. Moler, S. A. Kellar, Z. Hussai: Phys. Rev. B, 64, 125204 (2001).
[19] B. Bouchet-Fabre, K. Zellama, C. Godet, D. Ballutaud, T. Mine’a: Thin Solid Films, 482, 156 (2005).
[20] S. Hosokawa, H. Sato, Y. Wang, E. Ohata, A. Fukushima: J. Electron Spectrosc., 137-140, 2357 (2004).
[21] K. G. Latham, M. I. Simone, W. M. Dose, J. A. Allen, S. W. Donne: Carbon, 114, 566 (2017).
[22] S. Point, T. Minea, B. Bouchet-Fabre, A. Granier, G. Turban: Diam. Relat. Mater. 14, 891 (2005).
[23] M. Aono, M. Terauchi, Y. K. Sato, K. Morita, T. Inoue, K. Kanda, K. Yonezawa: Appl. Surf. Sci., 635,
157677 (2023).
60

Development of Reflection- and Projection-Type Soft-X-Ray
Microscope (RPS-XRM) for Resist-Thin-Film Observation
Tetsuo Harada, Shuhei Iguchi, Shinji Yamakawa, and Takeo Watanabe
Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo

Abstract
A reflection- and projection-type soft-X-ray microscope (RPS-XRM) was developed at the
NewSUBARU synchrotron light facility to observe the chemical state distribution of resist thin filmon the Si wafers. A capillary mirror was used to focus the soft X-ray on the wafer at oblique incidence.
Magnified projection image was observed on a CCD camera. The observation result of a chemically
amplified resists revealed the presence of aggregation structures, which would cause defect in EUV
lithography.

1. Introduction
In EUV lithography at a wavelength of 13.5 nm, the development of high-performance resists is very
important. In addition to achieve high resolution and high sensitivity, resists with small line width variationand few defects simultaneously are required. Local aggregation of resist components is considered to be oneof the causes of defect generation. Line width variations on the order of several micrometers scale have beenreported as local critical dimension (CD) uniformity based on CD-SEM observations, and it is thought that
resist aggregation occurs on the micrometer scale. Since the aggregation of resist components would becaused by the polarity of the functional groups and conventional microscopes cannot observe them at a fewµm size, soft X-ray observation is suitable for this purpose. Scanning soft X-ray microscopy (STXM) is
usually used for soft X-ray imaging. However, STXM cannot measure resist wafers coated in the actual
process. Therefore, we developed a reflection-and projection-type soft-X-ray microscope (RPS-XRM)1) toobserve the chemical state distribution of the resist on the wafer.
2. Experimental
A schematic view of RPS-XRM developed at the NewSUBARU synchrotron radiation facility beamline BL10 is shown in Fig. 1. The monochromator of BL-10 provides soft X-ray of 50 – 1,000 eV region. In thisstudy, we used around carbon K-edge region of 284 eV. A 100-µm-diameter pinhole is installed at thefocusing point as a virtual source using. The pinhole image was focused by a capillary mirror optic (Sigray)2),
which has an axially symmetric ellipsoidal shape. The focusing size evaluated by the knife-edge method wasaround 2 µm. In this microscope, the sample is placed horizontally on the optical axis and half of the lightfrom the capillary mirror is focused near the sample surface. The soft X-rays reflected by the sample are

Figure 1. Schematic layout of the RPS-XRM, and observation result example.
61

Figure 2. (a) Observation result image of CAR 50 nm thick resist at 287 eV. (b) Intensity profile at theindicated line position in (a).

magnified and projected onto a CCD camera. The angle of incidence is determined by the angle of incidenceof the mirror, with a maximum angle of 4.2° and oblique incidence.
On the lower energy side of the carbon absorption edge, such as 280 eV, where the absorption of the resist issmall, the surface reflection of the resist is weak and is mainly from the substrate silicon wafer. In this case, anabsorption image of the resist can be observed. On the high energy side, the absorption of the resist becomes larger
and all components reflected by the wafer are absorbed, resulting in the observation of the surface reflectance
distribution. The observed image is a sample image projected on a half arc corresponding to the acquisition angleof the focusing element. The observation magnification varies with the distance between the focal point and thesample reflection point and is usually in the range of 60 – 1000x.

3. Results and Discussion
The sample is a 50 nm thick chemically amplified resist (CAR) on a silicon wafer. The observation image is shownin Fig. 2(a). The observed energy is 287 eV. The stripe pattern is mainly derived from speckles from the substrateof the Si wafer. In order to compare in the observation photon energy, measured intensity profiles on the yellow
line in Fig. 2(a) are shown in 284 - 296 eV. The speckle shape is dominant in the profiles as well, but the shapediffers with energy around 70 pixel position; no aggregation is observed at 284 eV, but a change in the intensity
profile occurs, especially at 287 eV. The speckle distribution does not change significantly in this energy range.
Therefore, the change is sample-induced and is an aggregation structure of the functional groups in the resist. The
total length of the profile is 100 µm, so the aggregation structure is of the order of 10 µm. This aggregation wouldchange the local pattern formation characteristics and cause the local CD changes, which would change the local
defects formation characteristic.

4. Conclusion
The existence of large aggregation structures was revealed using RPS-XRM. This microscope can be used toobserve the chemical state distribution of not only resist but also functional thin films such as carbon in a wide
energy range of 50 eV-1,000 eV, and has a wide range of applications, including the ability to observe the chemical
state distribution of films that were thought to be uniform.

References[ 1] Shuhei Iguchi, Tetsuo Harada, Shinji Yamakawa, Takeo Watanabe, and Takeharu Motokawa: J.
Photopolym. Sci. Technol. 36 (2023) 25.
[ 2] R. J. Koch, C. Jozwiak, A. Bostwick, B. Stripe, M. Cordier, Z. Hussain, W. Yun, and E. Rotenberg:
Synchrotron Rad. News, 31 (2018) 50.

62

Analytical method to determine Fe3+/Fe2+ ratio in pumice:Oxidation process pumice from 7.6 ka Mashu caldera-forming
eruption
Kyohei Sano1, Tetsuo Harada2, and Shinji Yamakawa2
1

Graduate School of Regional Resource Management, University of Hyogo
Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo

2

Abstract
We conducted synchrotron analysis for pumices from Mashu caldera-forming activity andestablished the analytical method to determine the Fe3+/Fe2+ ratio in volcanic products using soft Xray synchrotron. To determine the Fe3+/Fe2+ ratio, we collected absorption spectra between 650 eV
and 750 eV with using the standard materials at room temperature using the BL-10 beamline at the
NewSUBARU, Laboratory of Advanced Science and Technology for Industry, University of Hyogo,
Japan. The soft X-rays were focused on 2.5 mm ×1.2 mm area. To construct the calibration curvefor Fe3+/Fe2+ ratio, standard materials are prepared by wet chemistry. Based on the calibration curve,
we estimated the Fe3+/Fe2+ ratio for Mashu caldera-forming eruption. In the Ma-i layer, Fe3+/Fe2+
ratio changes from 11.5 to 16.6 from lower to the upper layer. On the other hand, Fe 3+/Fe2+ ratio in
Ma-h layer changes from 9.2 to 13.1. These valuable Fe 3+/Fe2+ ratios are formed because of thechange of temperature of eruption cloud and eruption rate during eruption.

1. Introduction
Caldera-forming eruption including pyroclastic flow has a huge influence on human society and it isimportant to reveal the sequence of magma ascent process during the eruption for the risk management of
volcanic eruption. For the formation of pyroclastic flow, the stability of the eruption cloud is an essential
factor1. The entrainment of air into the eruption cloud originates the buoyancy because of the heating andthermal expansion of air. Such entrainment also causes the oxidation of pyroclasts. Thus, by analyzing thedegrees of oxidation based on the Fe3+/Fe2+ ratio in volcanic products, we can reveal the temperature conditionin volcanic clouds, and discuss the formation process of pyroclastic flow based on the temperature of volcanic
clouds. In this study, we conducted the synchrotron analyses for pumices from Mashu caldera-forming activity andconstructed the calibration curve to estimate the Fe3+/Fe2+ ratio.

Figure 1. Location of Mashu volcano and sampling point.

63

Figure 2. Columnar section and photographs pf Point 1 outcrop.
2. Experimental
2.1. Sample Preparation

Mashu Volcano is located in the east part of
Hokkaido, Japan. Approximately 7.6 ka, thecaldera-forming activity of Mashu Volcano started
as phreatomagmatic eruption (Ma-j) and followed
Plinian falls (Ma-i, -h, -g) and pyroclastic flow
(Ma-f)2 (Fig.2). In this study, we conducted thefield survey and collected samples for synchrotron
analysis. We sieved samples and picked up the
pumices larger than 4 mm. Samples were washed bya sonic wave washer and dried at 110°C. For thesynchrotron analysis, we used the powdered
pumices.
2.2. Analytical method
To determine the Fe3+/Fe2+ ratio of pumicesamples, we collected the absorption spectra
between 650 eV and 750 eV by using the standard
materials at room temperature using the BL-10
beamline at the NewSUBARU, Laboratory of
Advanced Science and Technology for Industry,
University of Hyogo, Japan. The soft X-rays werefocused on a 2.5 mm ×1.2 mm area. For the
standard material, pumice from the 7.6 ka Mashu

Figure 3. Samples for synchrotron analysis.

64

Figure 4. Representative spectra and separated Gaussian peak.
eruption and obsidian from Akaishiyama lava, Shirataki, Hokkaido, Japan3 were analyzed by wet chemical
analysis at JFE Tecno-Research Corporation. Samples were mounted on the analytical stage by carbon tape(Fig. 3).
3. Results
Figure 4 shows the representative analyticalresults. In the spectrum, peaks around 709 eV
and 723 eV reflect the L3 and L2 of Fe,
respectively4 (Fig. 4). Furthermore, we
identified the small peak around 713 eV, and we
considered that this peak reflects the Fe3+ of L34.
For the construction of the calibration curve, we
extracted the three Gaussian peaks on 709, 713,
723 eV, and collected the peak intensity and areaof each Gaussian peak. Using the intensity andarea values, we calculate the peak character asfollows;
𝑷𝒆𝒂𝒌 𝒄𝒉𝒂𝒓𝒂𝒄𝒕𝒆𝒓 = (I709 / I713 ) × A722 × A713
where I is the intensity, and A is the area of each
Gaussian peak. By compiling the peak character
values and Fe3+/Fe2+ ratio determined by wet
chemical analysis, we construct the calibration
curve for Fe3+/Fe2+ ratio by using the absorption
spectra (Fig.5). Constructed calibration curveshows that slope is 4.9 × 1010 and correlation
factor (R2) is 0.9, although some variation ofpeak character in same sample are observed.

Figure 5. Constructed calibration curve for Fe3+/Fe2+
ratio.

65

Figure 6. Fe3+/Fe2+ ratio for 7.6ka Mashu pumices estimated by soft X-ray synchrotron analysis.

4. Discussion
Based on the calibration curve, we estimated the Fe3+/Fe2+ ratio for Mashu caldera-forming eruption.
Figure 6 shows the estimated Fe3+/Fe2+ ratio for 7.6ka Mashu pumices. In the Ma-i layer, Fe3+/Fe2+ ratiochanges from 12 to 17 from lower to the upper layer. On the other hand, Fe3+/Fe2+ ratio in Ma-h layer
ranges from 7 to 12 (Fig. 6). In Ma-g layer, Fe3+/Fe2+ ratio drastically increase from 6 to 22 (Fig.6). We
considered that these variations in Fe3+/Fe2+ ratio reflect the change of eruption rate and temperature oferuption cloud during eruption.
The variability of peak character could be caused by the sample preparation. Powdered pumice is not
sieved and the amount of powder on the analytical stage is not constant. These preparations affect theelectrical conductivity of samples. Furthermore, we analyzed three times for each sample and the increaseof number of analyses enhances the accuracy.
5. Conclusion
In this study, we conducted the synchrotron analyses for pumices from Mashu caldera-forming activity andtried to establish the analytical method to determine the Fe3+/Fe2+ ratio. Fe3+/Fe2+ ratio for Mashu caldera-

forming eruption shows variability and we considered that these Fe3+/Fe2+ ratio reflect the change oferuption rate and temperature of eruption cloud during eruption.
Acknowledgement
This study was supported by ERI JURP 2021-KOBO21 in Earthquake Research Institute, theUniversity of Tokyo. Dr. Keiji Wada supported field survey in Mashu volcano. Wet chemical analysis forstandard materials were conducted by JFE Tecno-Research Corporation.
References[ 1] A. W. Woods: Bulletin of Volcanology. 50, 169-193 (1988).
[ 2] H. Kishimoto, T. Hasegawa, M. Nakagawa, K, Wada: Bulletin of the Volcanological Society of Japan.
54, 15-36 (2009).
[ 3] K. Sano: Journal of Regional Resource Management. 1, 35-43 (2021)[ 4] S.J. Brotton, R. Shapiro, G. Laan, J. Guo, P. Glans, J. M. Ajello: Journal of Geophysical Research.
112 (2007).
66

Total-Electron-Yield XANES Measurements of Inks Painted on
Insulating Copy Papers
Miyu Mamezaki and Yasuji Muramatsu
Graduate School of Engineering, University of Hyogo

Abstract
To non-destructively analyze components of inks painted on papers, X-ray absorption spectra (XAS)of the inks/papers have been measured using a total-electron-yield (TEY) method. TEY-XAS
measurements were performed in BL10 at the NewSUBARU. From the C K-, N K- and O K-XANES
spectra, ink-components dependent on colors and types of pens could be identified by the TEYXANES. It is therefore confirmed that components of inks painted on copy papers can be nondestructively detected by using the TEY-XAS method.

1. Introduction
Monitoring the sample current during X-ray irradiation is easy way to measure X-ray absorption spectra(XAS), which is called as a total electron yield (TEY) method. Although numerous XAS studies have used
the TEY method to examine electrically conductive materials, it is difficult to apply to insulating bulk
materials because electric charge-up distort the XAS. To avoid or suppress charge-up effects of insulating
bulk samples during X-ray irradiation, bulk samples are often powdered, and the powdered samples areplaced on conductive substrates. We have recently developed another method to easily observe the TEY of
insulating samples. In the method, insulating film samples are tightly placed on conductive substrates, andthe sample current generated by soft X-ray irradiation can be efficiently detected through the conductive
substrates [1]. The TEY-XAS measurements of various insulating samples such as papers, wiping clothes,and organic tapes were performed [2-4], which confirmed that the method would be a powerful tool to nondestructively measure TEY-XAS of insulating samples.
To further apply the present TEY-XAS method for a novel analytical tool, we have measured TEY-XAS
of various inks painted on copy papers.
2. Experimental
Samples used in the experiments are shown in Table 1. Commercially-obtained copy papers (denoted as CP)
were used for matrix sample. Types of writing pens were black oil-based ballpoint pen (BB), black gel
ballpoint pen (GB) and black pencil (PB). All writing pens were made in the same manufacturer.
The ink-painted CPs were cut into small pieces of about 5 mm square, after drying. Each ink was also
applied on a gold (Au) substrate to obtain XAS of the ink itself. The ink (X) painted on CP is denoted as
X/CP, and the ink coated on the Au substrate is denoted as X/Au. These samples were held on an aluminum
plate by conductive carbon tapes as shown in Figure 1. X-ray absorption near-edge structure (XANES) in the
C K, N K, and O K regions of the samples were measured in the XAS chamber at BL10/NewSUBARU [5].
3. Results and Discussion
3.1. TEY-XAS
TEY-XAS covering C K, N K, and O K regions of CP, X/CP, and X/Au samples are shown in Figure 2. The
black lines exhibit X/CP and red lines X/Au. TEY intensity on the vertical axis is described on the same scalefor each region. XANES spectra in the C K and O K regions can be clearly observed in all the samples.
Especially, C K- and O K-XANES spectra were observed in CP, reflecting the main component of cellulose.
Hence, the XANES profiles of CP will be significant backgrounds to identify the ink components in X/CP.
Although N K-XANE intensity was weak in all the samples, XANES profile can be slightly observed in the
400 – 410 eV region. The N K-XANES will also be useful to identify the ink components.
3.2. Comparisons in the C K- and N K-XANES between X/CP and X/Au
O K-XANES profiles of X/CP were as same as CP. Hence, it is difficult to identify the ink components on
X/CP from O K-XANES.
67

Table 1. Specifications of the samples.

Figure 3 shows the XANES spectra in the C K(a) and NK (b) regions with the black lines for CP
and X/CP, and with the red lines for X/Au. Because
XANES spectra of X/Au reflect the ink-only
XANES, spectra between the X/CP and X/Au werecompared to confirm the ink components on CP. In
the C K-XANES, CP-derived peaks were observedin X/CP. However, ink-derived characteristic
peaks were observed in the range of 287 - 293 eV,
which can be identified in X/Au. Additionally, theink-derived characteristic peaks were dependent
on writing pens. This suggests that the writing penscan be identified even in X/CP. In N K-XANES,
spectra of X/Au exhibit the small S/N ratio due to

Figure 1. Photo of the sample plate.

Figure2. TEY-XAS covering C K, N K, and O K regions of CP, X/CP, and X/Au.
68

Figure 3. Comparison between the X/CP (black lines) and X/Au (red lines) of XANES spectra in C K (a)and N K (b) regions.
some experimental errors. However, BB/CP, GB/CP, and PB/CP clearly exhibit characteristic peaks in N KXANES, which are dependent on writing pens. This suggests that types of writing pens will be identified
from N K-XANES as well as C K-XANES.
References[1] Y. Muramatsu and E. M. Gullikson: Anal. Sci., 36, 1507-1513 (2020).
[2] Y. Muramatsu, Y. Tani, Y. Tobita, S. Hamanaka, and E. M. Gullikson: Adv. X-ray Chem. Anal., Japan
49, 219-230 (2018).
[3] Y. Muramatsu, R. Maruyama, and E. M. Gullikson: Adv. X-ray Chem. Anal., Japan 51, 179-190 (2020).
[4] R. Maruyama and Y. Muramatsu: Adv. X-ray Chem. Anal., Japan 53, 243-256 (2022).
[5] T. Uemura, Y. Muramatsu, K. Nambu, D. Fukuyama, M. Kuki, T. Harada, T. Watanabe, and H.
Kinoshita: Adv. X-Ray Chem. Anal. Japan 46, 317-325 (2015).

69

In-situ XANES Measurements of Peptide Bonds in Thermal
Denaturation of Proteins in Eggs
Ikuya Shimogaki and Yasuji Muramatsu
Graduate School of Engineering, University of Hyogo

Abstract
We have recently measured in-situ XANES spectra of egg yolk and egg white during heating, andspectral changes were successfully observed due to thermal denaturation. To clarify the chemicaltransformation of proteins, XANES spectra of various related compound were measured and thethermal-denaturized XANES were analyzed through finger-print analysis. It is confirmed that
peptide-binding structures can transform in protein molecules during thermal denaturation.

1. Introduction
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, andhydrophobic 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 hydrate with thesolvent outside the structure. By heating, molecular structures of proteins drastically change.
Intramolecular bonds such as hydrogen bonds are broken and the steric structure disintegrates. This isthermal denaturation of proteins. Such the structures result in thermal denaturation are unique andinteresting. Although molecular structures in thermal denaturation of proteins have been commonly andwidely analyzed by using X-ray diffraction method, the detailed local structures and chemicaltransformations have not been well elucidated.
To clarify the chemical transformations of proteins from the view point of chemical bonds, we haverecently measured XANES spectra in the C K, N K, and O K regions of egg yolk and egg white during
heating, and have successfully observed spectral change in the XANES profiles due to the thermal
denaturation [1]. In the present study, we have measured protein-related compounds such as typical aminoacids, peptides involved in egg white, and some unsaturated fatty acids, to further analyze the in-situ
XANES spectra of the heated egg yolk and egg white,
2. Experiments
Protein-related reference compounds of unsaturated fatty acids, amino acids, and dipeptide werecommercially obtained. Unsaturated fatty acids were oleic acid, linoleic acid, α-linolenic acid, and γ-linolenic
acid. Amino acids were glutamic acid, aspartic acid, leucine, serine, valine, lysine, phenylalanine, alanine,arginine, and glycine. Dipeptide was alanyl leucine.
XANES measurements in the C K, N K, and O K regions were performed in BL10 using a total electron
yield (TEY) method at a room temperature [2].
3. Results and Discussion
Figure 1 shows C K-XANES spectra of egg yolk heated from RT to 180°C (a) [1] and unsaturated fatty acids(b) [3]. In egg yolk, intensity of shoulder peak at 287.7 eV decreased as the temperature increased. The 287.7
eV shoulder corresponds to the shoulders of unsaturated fatty acids. In the unsaturated fatty acids, theshoulder intensity is dependent on the degree of unsaturation. The shoulder at 287.7 eV is attributed to the
sp3-C in unsaturated fatty acids, and the intensity of the shoulder decreases as the sp2-C of C=C double bondincreases, while the sp3-C decreases. This suggests that sp3-C decreases in thermal denaturation of egg yolk.
Figure 2 shows C K-XANES spectra of egg white heated from RT to 180°C (a) [1] and dipeptide (alanylleucine) with the sum-spectrum of amino acids alanyl and leucine (b). In egg white, intensity of the π* peaknear 285 eV increased and the σ* peak at 288.3 eV decreased as the temperature increased. This suggeststhat sp2-C increases and sp3-C decreases in thermal denaturation of egg white. This corresponds to abovementioned egg yolk. A peak was also observed at 284.3 eV in 180°C-heating. Figure 2(b) shows the C KXANES spectra of alanyl-leucine, which has a peptide bond between alanyl and leucine amino acids, and ofalanyl and leucine amino acids. Although each alanyl and leucine amino acid has no peak at 284.3 eV, alanyl70

Figure 2. C K-XANES spectra of the egg
white heated up to 180˚C (a), and dipeptide
with two amino acids (b).

Figure 1. C K-XANES spectra of the egg yolk
heated up to 180˚C (a) and unsaturated fatty
acids (b).

leucine exhibited a peak at 284.3 eV. This means that
peptide bonds exhibit the 284.3-eV peak,corresponding to the 284.3-eV peak observed in yolk
white heated at 180°C. It is therefore confirmed that
peptide bonds can be formed in thermal denaturation.
Figure 3 shows N K-XANES spectra of egg yolk(a), egg white (b), and amino acids (c). Egg yolk andegg white exhibit a sharp peak at 401.5 eV, a main peakat 406.2 eV, and a broad peak near 412 eV. Comparedto the amino acids, the 401.5-eV peak corresponds toarginine, and the 406-eV peak almost corresponds tothese amino acids. Hence these spectral structures of
egg yolk and egg white agree to the elemental aminoacids. However, the 412-eV peak dependent on heating
temperature does not correspond to the amino acids.
This suggests that the 412-eV peak reflects peptide
bond formation and the thermal denaturation affects
peptide bonds in proteins of eggs.
References[ 1] Shimogaki and Y. Muramatsu: LASTI Annual
Report 23, 61-62 (2021).
[ 2] T. Uemura, Y. Muramatsu, K. Nambu, D.
Fukuyama, M. Kuki, T. Harada, T. Watanabe, H.
Kinoshita: Adv. X-Ray Chem. Anal. Japan 46,
317-325 (2015).
[ 3] R. Maruyama and Y. Muramatsu: Adv. X-Ray
Chem. Anal, Japan, 53, 243-256 (2022).
Figure 3 N K-XANES spectra of the egg yolk(a), egg white (b) heated up to 180˚C, comparedto amino acids (c).
71

XANES Spectra in the C K and N K Regions of NitrogenContaining Aromatic Compounds
Saki Yamada and Yasuji Muramatsu
Graduate School of Engineering, University of Hyogo

Abstract
XANES spectra in the C K and N K regions of aromatic compounds having various nitrogen
functional groups were measured to prepare an XANES database for a fingerprint analysis ofnitrogen-containing graphitic carbon materials. It can be found that carbon atoms directly bonded tonitrogen atoms exhibit characteristic peak structures between π* and σ* peaks in C K-XANES. In
addition, it was found that each nitrogen functional group exhibited a characteristic peak structure
in N K-XANES. Such the C K- and N K-XANES database will be useful for the fingerprint analysis
of nitrogen-containing graphitic materials.

1. Introduction
Nitrogen-containing graphitic carbon materials such as carbon nitride (CNx) films and polyacrylonitrile(PAN)-based carbon fibers have attracted much attention in carbon industries. CNx films are advanced
functional materials due to their high elastic recovery rate and mechanical properties. PAN-based carbon
fibers are used as composite materials due to their excellent mechanical, electrical and thermal properties.
Developments of such nitrogen-containing graphitic carbon materials require local structure analysis toclarify the electronic and chemical bonding states.
Soft X-ray absorption spectroscopy is a powerful tool for the local structure analysis of light-element
materials. We have previously reported that chemical state and quantitative analysis of nitrogen atoms ingraphitic carbon materials can be successfully achieved by X-ray absorption near-edge structure (XANES)
measurements in the C K and N K regions of reference aromatic compounds having various nitrogenatedfunctional groups [1, 2]. Additionally, XANES database of typical reference compounds will be useful for
finger-print analysis. Hence, in this study, XANES in the C K and N K regions of further aromatic compounds
having various nitrogenated functional groups were measured to prepare the XANES database forcharacterization of nitrogen-containing graphitic carbon materials.
2. Experimental
Figure 1 shows the reference aromatic compounds having typical nitrogenated functional (amine, imine)groups; aminopyrene (denoted by A1), carbazole (A2), dimethyltriphenylamine (A3), phenazine (I1),bathophenanthroline (I2), benzo[c]cinnoline (I3), 6-aminoquinoline (Al1), and 9H-pyrido[3,4-b]indole(AI2). These compounds were commercially obtained. These powder samples were held on the indium(In) substrate for XANES measurements. XANES measurements in the C K and N K regions were
performed at BL10 in NewSUBARU by using the total electron yield (TEY) method [3].

Figure 1. Nitrogen-containing aromatic compounds as reference compounds
72Figure 2. XANES spectra in the C K (a) and N K (b) regions of the reference compounds.
3. Results and Discussion
C K-XANES of the reference compounds is shown in Figure 2 (a). All compounds exhibit the π* peak around
285 eV and σ* peak around 293 eV, reflecting the electronic structure of sp2-C atoms in the aromatic
backbones. Some compounds exhibit the π* peak broadening or splitting. These π* peak profiles usuallyarise from edge carbon atoms terminated with hydrogen (H) atoms [4]. All compounds exhibit peak structuresin the 286 – 290 eV region. This suggests that the π* peaks can shift to the higher energy side due to theformation of hybridized orbitals in the C-N bonds. Hence, various characteristic peak structures can beobserved between π* and σ* peaks in C K-XANES. In other words, it is necessary to keep this point in mind
when analyzing C K-XANES of nitrogen-containing graphitic carbon materials.
N K-XANES of the reference compounds is shown in Figure 2 (b). All compounds exhibit characteristic
peak structures, dependent on nitrogenated functional groups. Compounds having imine nitrogen (I1-3, AI1,
AI2) show peak a around 399 eV. Compounds having amine nitrogen (A1-3, AI1, AI2) exhibit peak b around403 eV. It is therefore confirmed that the chemical states of nitrogen atoms can be analyzed from thefingerprint analysis using the N K-XANES of such the reference compounds.
References[ 1] T. Amano, K. Shirode, Y. Muramatsu, and E. M. Gullikson: Jpn. J. Appl. Phys., 52, 041304 (2013).
T. Amano, Y. Muramatsu, N. Sano, J. D. Denlinger, and E. M. Gullikson: J. Phys. Chem. C 116, 67936799 (2012).
[ 2] T. Uemura, Y. Muramatsu, K. Nambu, D. Fukuyama, M. Kuki, T. Harada, T. Watanabe, and H.
Kinoshita: Adv. X-Ray Chem. Anal. Japan 46, 317-325 (2015).
[ 3] Y. Muramatsu, K. Murayama, T. Okada, and T. Ooe: Anal. Sci. 37, 1617-1623 (2021).
73

Annealing effect on the structure and physicalproperties of highly hydrogenated diamond-like carbon film
Daisuke Niwa1, Tomohiro Mishima1, Koji Nakanishi1, Naoki Fukumuro2, Tsuneo Suzuki3, Kazuhiro Kanda1
1

Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo
2
Graduate School of Engineering, University of Hyogo
3
Nagaoka University of Technology

Abstract
The desorption process of highly hydrogenated diamond-like carbon (H-DLC) films due to theannealing was investigated by the measurement of the thermal desorption spectrum of H-DLC
film and the temperature dependence on several properties of H-DLC film. Hydrogen moleculeions were desorbed from the H-DLC film at around 360℃ and 450℃. On the other hand,hydrocarbon ions were desorbed around 450℃. Film thickness, hydrogen content, and thesp2/(sp2+sp3) ratio of carbon atoms varied significantly in the temperature region higher than
360℃.
1. Introduction
Diamond-like carbon (DLC) films are amorphous carbon films composed of triangularly coordinated (sp2)carbon atoms, tetrahedrally coordinated (sp3) carbon atoms, and hydrogen atoms. DLC films possess several
useful properties such as high hardness, wear resistance, biocompatibility, and gas barrier1. DLC films havealready been applied in a wide range of fields such as tools, artificial joints, and plastic bottles, mainly as
coating materials. Typical DLC films have a low coefficient of friction in the air and water. However, acoefficient of friction increases in the vacuum2. Highly hydrogenated diamond-like carbon (H-DLC) films,
that contain more than 40% hydrogen atoms, maintain a low friction coefficient in a vacuum and are expected
as solid lubricants in space3. However, H-DLC films were reported to desorb hydrogen at a relative lowtemperature region4. In this study, we performed a thermal deposition spectrometry (TDS) study of H-DLC
films to examine the temperatures at which various species desorb to investigate the decomposition processof H-DLC film. In addition, samples were prepared by stopping the temperature increase at several
temperatures, and a couple of properties were measured. The film thickness and hydrogen content of thesesamples were measured by the combination technique of Rutherford backscattering spectroscopy and elastic
recoil detection analysis (RBS/ERDA) and the sp2/(sp2+sp3) ratio of carbon atoms were evaluated by themeasurement of the X-ray absorption near edge structure (XANES).
2. Experimental
H-DLC films were deposited using methane and hydrogen gases by plasma enhanced-chemical vapor
deposition method. Si wafer was used as a substrate.
TDS spectra of 20 kinds of ions, mainly hydrogen molecule ions, and hydrocarbon ions, were measured using
a quadrupole mass spectrometer, BGM102(ULVAC). A temperature increase rate was 5°C/min and themeasured temperature range was from room temperature to 1100℃.
RBS/ERDA spectra were measured using a tandem electrostatic accelerator at the Nagaoka University ofTechnology. The film thickness was measured by RBS using He2+ ions with an energy of 2.0 MeV andhydrogen contents were measured by ERDA using He2+ ions with an energy of 2.3 MeV.
XANES measurements were performed at BL09A in NewSUBARU equipped with the grating
monochromator. The C-K edge XANES spectra were measured in the energy range from 270 eV to 380 eVwith the total electron yield method.
3. Results and Discussion
Figure 1 shows the TDS spectra of hydrogen molecule ion and methyl-, ethyl-, propyl-, and butylhydrocarbon ions from room temperature to 900°C for the H-DLC film. No peaks were observed above
900℃ in all spectra. Peaks were observed at 360°C and 450°C in the spectrum of the hydrogen moleculeion. It was considered that the peak at 360℃ was ascribed to the desorption of hydrogen molecules from the74

Figure 1. TDS spectra of H-DLC films

H-DLC film because this peak was not observed in the spectra of hydrocarbon ions. In the spectra ofmethyl ion, the peak was observed near 480°C, and in the spectra of other hydrocarbon ions, peaks appearednear 420°C. In other words, the desorption of carbon atoms from H-DLC film dominantly began in thetemperature region higher than 400℃. From these results, we prepared samples by the stopping oftemperature increase at several temperatures, such as 200°C, 360°C, 400°C, 450°C, 550°C, and 700°C todiscuss the temperature dependence of several film properties of H-DLC film.
Figure 2 shows the temperature dependence of thickness and hydrogen content of the H-DLC films obtained
from the RBS/ERDA study. The hydrogen content of the H-DLC film was about 50% before annealing anddecreased from 50 % at 360°C to 35% at 400°C by the temperature increase. On the other hand, the film
thickness was about 250 nm before annealing. In the temperature region lower than 360℃, the film thickness
was maintained at 250 nm and it started to decrease at 360℃. With a further increase in the annealing
temperature, the thickness decreased to 40 nm at 700℃.
Figure 3 shows the temperature dependence of the sp2/(sp2+sp3) ratio of carbon atoms which was estimatedFigure 2. Temperature dependence of the hydrogen content and thickness of the H-DLC films.
75

Figure 3. Temperature dependence of the sp2 /(sp2+sp3)of the H-DLC films.

from the C-K XANES spectrum. The sp2/(sp2+sp3) ratio can be extracted by normalizing the area of theresonance corresponding to the 1s→π* transitions at 285.3 eV with a large section of the spectrum [5]. The
absolute sp2/(sp2+sp3) ratio was determined by comparing it with that from the XANES spectrum of HOPG.
Before annealing, the sp2/(sp2+sp3) ratio of H-DLC film was about 40%. Above 400℃, the sp2/(sp2+sp3) ratio
increased. This increase was considerable to be due to the coupling of carbon double bonds by the desorptionof hydrogen. Films remaining above 550℃ were mostly graphitized.
4. Conclusion
The desorption process of highly hydrogenated DLC films due to increasing temperature was investigatedby the measurement of the TDS, RBS/ERDA, and XANES spectra. The results showed that hydrogenmolecules desorbed at 360℃, hydrocarbon molecules desorbed at about 450℃. Decreases in film thickness
and hydrogen content and increases in the sp2/(sp2+sp3) ratio started above 360℃.
Acknowledgment
I would like to thank Mr. Naoya Iida for helping with my XANES experiment and Mr. Sugimoto belongs to
Nagaoka University of Technology for helping RBS/ERDA experiment.
References[ 1] J. Robertson: Curr. Opin. Solid. State. Mat. Sci., 1, 557-561 (1996).
[ 2] J. Fontaine, C. Donnet, A. Grill, T. LeMogne: Surf. Coat. Tech., 146-147, 286-291 (2001).
[ 3] A. Wei, G. Ma, G. Li, Z. Li, C. Han, H. Zhao, W. Guo, Z. Xing, H. Wang: Diam. Relat. Mater., 135,
1-10 (2023).
[ 4] H. Li, Tao. Xu, C. Wang, J. Chen, H. Zhou, H. Liu: Thin. Solid. Films., 515, 2153-2160 (2006).
[ 5] K. Kanda, T. Kitagawa, Y. Shimizugawa, Y. Haruyama, S. Matsui, M. Terasawa, H. Tsubakino, I.
Yamada, T. Gejo, M. Kamada: Jpn. J. Appl. Phys., 41, 4295 (2002).

76

Scanning electron microscopy of living biological samples
Tomoki Eguchi1, Yuhei Miki1, Hidehiro Ishizawa2, Masahiro Takeo2, and Satoru Suzuki1
1

Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo
2
Graduate School of Engineering, University of Hyogo

Abstract
Scanning electron microscopy (SEM) is an effective analytical tool for observing and analyzing
micro- and nanostructures. However, it is very difficult to observe living biological specimens byusing a conventional scanning electron microscope because the specimens must be exposed to a
vacuum. In this study, we developed a cell that encapsulates biological specimens for analyticaltechniques in a vacuum, such as SEM. Using the developed cell, we succeeded in scanning electron
microscope observation and energy dispersive X-ray analysis of living molds using a conventionalscanning electron microscope.

1. Introduction
In recent years, numerous developments in image analysis equipment have given birth to the concept of animaging complex, in which various analysis devices are used to "deepen our understanding of life by looking
at it. Observation of living or wet samples is becoming increasingly essential. However, vacuum analyzers
used to observe and analyze microstructures must expose samples to a high vacuum environment (10-5 ~ 107 Pa). If biological specimens are exposed to this pressure, the gases and fluids in their bodies will be deprived,
their bodies will shrink, and their microstructures will be severely deformed. For this reason, someresearchers have developed instruments such as pre-drying biological samples after applying various
scientific pretreatments or using a low-vacuum SEM with a vacuum reduced to about 10-2Pa, but the former
results in a loss of microstructure and the latter results in a loss of resolution. However, the former resulted
in the collapse of microstructures, while the latter reduced the resolution. Against this background, it isextremely difficult to observe wet samples of living organisms at high magnification and resolution, muchless live organisms. To solve this problem, it is necessary to establish a means of observing living biologicalsamples with a vacuum analyzer. Although scanning electron microscopes aim to maintain living morphology
as much as possible by applying a number of treatments to biological samples before observation, the current
situation is that dead samples are observed1,2.
In this study, we developed a cell for sealing biological specimens that can be used in a vacuum analyzer.
Molds and Wolffia globosa were used as biological samples, and the objective was to observe live biologicalsamples using SEM as a vacuum analyzer. Using the developed cell, molds were observed by general-purpose
SEM and qualitatively analyzed by EDS.
2. Experimental
2.1. Sample Preparation
In this study, we used a Si membrane substrate (NTT-AT) with a SiN film as the electron permeable film. We
used a 1.5 mm × 1.5 mm window with a film thickness of 200 nm and Si chips with a thickness of 200 μm
or 381 μm. In the SEM observation of the cell, it is important to attach the sample to the film because thedepth of secondary electron generation in the SEM image detection is very shallow (10 nm).
This experiment was conducted at room temperature in vacuum using an SEM (JEOL, JSM6700F).
Observations were made using a secondary electron detection method. Basically, the observation was
performed at an acceleration voltage of 20 kV and an irradiation current of 0.25 ~ 0.35 nA, which waschanged as necessary. The magnification was set to about 100x.
2.2. Mold Cell Creation
Nutrition, moisture, and temperature are important factors for mold development and growth, and growth
can be observed in cells if these factors are sufficiently met. In this experiment, we used mold generated oncommercially available miso. To generate the mold, miso was placed flat on a petri dish, and gauze with purewater was placed on the side to maintain sufficient humidity. The petri dish was covered with a lid and placedin an incubator set at 25°C. After one week, mold gradually grew on the miso.
77

Figure 1. Schematic diagram of a vacuum analysis cell with mold encapsulation.
In order to observe mold growth in the cell, we attempted to grow mold on the membrane instead ofattaching mold directly to the membrane. Figure 1 shows a schematic diagram of the vacuum analysis cell inwhich the mold was encapsulated in this study. The cell is prepared by dropping a glucose solution, which isa nutrient for mold, onto the SiN film of a chip beforehand and allowing the chip to dry for 10 minutes. At
this time, a 200 nm thick SiN chip with a 200 μm thick SiN film was used for the chip. The mycelium andspore parts of the mold on the miso were taken out, placed on the copper tape, and the chip was covered fromthe top to seal it together with the atmosphere. Here, the Si chip was covered with Araldite (Huntsman), ahigh-performance epoxy-based rapid curing adhesive, to improve sealing.
To allow the mold to grow in the cells, the mold was provided with the conditions for growth: nutrientsfrom glucose, humidity from the moisture in the glucose solution in the cells, and sufficient temperature bystoring the cells in an incubator at 25°C.
2.3. Creating a cell of Wolffia globosa
Wolffia globosa is the world's smallest seed plant, consisting of a leafy body that is not divided into roots,
stems, or leaves. It is 0.8 mm × 0.4 mm in size, but there are individual differences before and after
division. Since it absorbs phosphorus hydrochloric acid and arsenic, it is expected to improve water
quality through environmental purification3 and as a raw material for biomass fuels4 and biomass plastics.
wolffia globosa reproduces through its unique division, which is a determining factor to demonstrate that
it is alive in the cell.
Figure 2 shows a schematic diagram of the vacuum analysis cell in which wolffia globosa wereencapsulated in this study. wolffia globosa cells were prepared by dropping Schenk & Hildebrandt Basal
Salt Mixture (PhytoTech LABS) as the culture medium onto a Si substrate. A single wolffia globosa wasplaced on top. The cell was sealed with a Si chip, taking care to fill the cell with wolffia globosa andculture medium. A 381 μm thick Si chip with a 200 nm thick SiN was used for the chip. As in the moldcell, the Si chip was covered with Araldite around the chip to improve sealing. The cells were introduced
into an incubator set at 25°C and irradiated with plant light for 24 hours.

78

Figure 2. Schematic diagram of a vacuum analysis cell with wolffia globosa encapsulation.

Figure 3. Optical microscopy of mold growing in a cell.
3. Results and Discussion
3.1. SEM Observation of Mold
Progressive observation of the cell revealed new mold from two locations at the edge of the aqueous glucose
solution on the membrane surface, as shown in Figure 3 when the magnification was increased, new moldcould also be seen at the back. When the focus was changed, each of them came into focus, indicating thatthe mold had become self-sustaining and formed mycelium and spores. Mold growth could be seen even after
sealing in the cell, indicating that the mold was alive inside the cell. The mold cell sample was observed
under an optical microscope (BX60M) before and after introduction into the vacuum, and there was no
noticeable damage to the sample, confirming that measurements can be made under vacuum. EDS mapping
did not show any noticeable problems.
Figure 4 shows the SEM image of the mold, and the mycelium and spores of the mold were also observed
by SEM. This indicates that the SEM observation of mold under atmospheric conditions was successful. The
diameter of the mycelium was about 10 μm and the spores were less than 100 μm in size.
The depth of secondary electron emission in the SEM is very shallow at 10 nm. Despite the 200 nm
thickness of the membrane, we are able to observe the mold on the membrane through the membrane, muchless the mycelium and spores of the mold that are free-standing from the membrane. This may be due to thefollowing reasons.
The primary electrons in this observation have sufficiently high energy (20 kV) to pass through the SiN
film. The secondary electrons are excited by the electrons inside the sample. The excited electrons affectother electrons, not the direct detection of the excitation energy from the spores. However, since this is onlya hypothesis, we will make observations on SiN of several thicknesses and compare the dependence on
acceleration voltage and irradiation current in order to elucidate the cause.
3.2. EDS Observation of Mold
Elemental mapping by EDS is shown in Figure 5. It can be seen that carbon and oxygen, the major elementsof the organism, as well as phosphorus and potassium, are observed along the mycelium and spores of the
mold.
79

Figure 4. SEM image of mold growing in a cell.

Figure 5. Elemental Mapping of Molds by EDS.
Figure 6 shows the EDS spectra of a mold sticking to the surface of the SiN film and the SiN film.
Nitrogen is known to be one of the most abundant elements in living organisms, although it is observed
throughout because it is also used as a material for the membrane. Therefore, a point analysis by EDS was
performed on the mold and nonmold areas on the membrane, respectively.
Although the same elements are observed from both, perhaps because the mold lives outside the SiN film

Figure 6. EDS spectra of a mold and the SiN film.
80

Figure 7. Optical microscopy of wolffia globosa growing in a cell.

surface, it can be confirmed that the carbon, nitrogen, oxygen, phosphorus, and potassium peaks are stronger
in the point analysis of the mold. This comparison indicates that the nitrogen peak is also strongly detectedin the film mold. Sodium and chlorine are thought to be derived from the salt content of miso, and since
soybeans, along with beef and fish, are among the foods that contain sulfur, they are thought to be derived
from miso.
3.3. Observation of the growth of wolffia globosa in a cell
Figure 7 shows the growth process of wolffia globosa observed in the cell. The cells were sealed withwolffia globosa and culture medium, and the progress was observed. After 10 days of encapsulation in thecell, division of wolffia globosa was observed, as shown in Figure 7 This occurs when wolffia globosa
proliferates, indicating that wolffia globosa is growing inside the cell and that it lives inside the cell for atleast 10 days. In the future, we would like to perform vacuum analysis of biological Sample, which is difficult
to measure under air because it lives in water, as wolffia globosa does.
4. Conclusion
In the present study, we developed a cell for encapsulating biological samples that can be used in a vacuum
analyzer. We succeeded in observing mold in the cell through a 200 nm thick SiN film, and found that thechip used in this study was effective in the development of this cell.
The mold was successfully observed growing in the cell using a commercially available miso, and thecell was used for SEM and EDS observations of the mold under atmospheric conditions. Although we wereable to confirm mycelium and spores in the SEM images, growth observation was the main focus of thisexperiment due to lack of biological knowledge, but we increased our prior knowledge of mold structure andgrowth process, and conducted observations by type, such as white mold and black mold However, we believethat we can deepen our understanding of molds by increasing our prior knowledge of the structure and growth
process of molds and observing different types of molds, such as white molds and black molds.
Although SEM observation of wolffia globosa has not been successful, we plan to develop a cell using a
jig for micro-XAFS in order to observe SEM, and at the same time, we plan to use other analytical instruments
such as X-ray CT at BL025 and photoemission electron microscopy (PEEM) at BL09A. In addition, since
wolffia globosa is known to absorb phosphorus hydrochloric acid and nitrogen, we will examine thepossibility of linking this to environmental issues such as water quality improvement through environmental
purification action by encapsulating what is considered to be those environmental pollutants with the culture
medium and observing the progress using EDS.
References[ 1] S. R. Aid. et al: Journal of Physics: Conference Series, 1447, 012034 (2020).
[ 2] Y. takaku, H. Suzuki et al. J. surf. Sci. Soc. Jpn., 36, No4, 201-206, (2015).
[ 3] X. Zhang, F.-J. Zhao et al.: New Phytologist, 182 421-428 (2009).
[ 4] Y. Hubenova, E. Hubenova, M. Mitov.: J. Elctrochem. Sci. Eng. 00 (2023).
[ 5] A. Yamaguchi et al.: J. Vac. Sci. Technol. B, in press.
81Analysis of emulsions by conventional scanning electron
microscopy
Masaki Nakamura, Satoru Suzuki
Laboratory of Advanced Science and Technology for Industry (LASTI), University of Hyogo

Abstract
Liquid samples, including emulsions, are difficult to observe under a vacuum like that of ascanning electron microscope. We applied the liquid cell preparation procedure reported in ourlaboratory in the past to observe emulsion samples using a conventional scanning electron
microscope (SEM). We also performed structural analysis using an energy dispersive X-ray
spectrometer. As a result, two types of emulsions were successfully observed in the SEM, and thedispersion of water and oil was confirmed.

1. Introduction
ater and oil are widely known as mutually immiscible relations. Both can be brought into a mixed state by
the introduction of surfactants having two properties, hydrophilic and lipophilic groups. A liquid in whichthese two solutions are dispersed is called an emulsion, and the process of bringing it into an emulsion stateis called emulsification. Emulsification technology is utilized in many fields, including cosmetics, foodproducts such as mayonnaise and butter, and adhesives.
The emulsified particles are called the dispersed phase and the medium in which the emulsified particles
are dispersed is called the continuous phase, and according to these types, there are four types of emulsions.1
The first is the O/W type, in which oil is dispersed in water. The second is W/O type, in which water isdispersed in oil. Then there are W/O/W type emulsions, in which W/O emulsions are dispersed as droplets inwater, and O/W/O compound emulsions, in which O/W emulsions are dispersed in oil.
Previous studies on emulsions have reported the observation of the microstructure of emulsions using cryoSEM method by Yamashita2 and TEM observation using gelatinized emulsions by Okamoto3. However, it isdifficult to observe liquid samples such as emulsions as they are under vacuum conditions such as in scanningelectron microscopy. Therefore, we applied the liquid cell preparation procedure4 reported in our laboratory
in the past to observe emulsion samples using a conventional SEM. We also used an energy dispersive X-ray
spectrometer (EDS) to evaluate the dispersion state of water and oil.
2. Experimental
2.1. Emulsion sample and liquid cell preparation method
Pure water, edible oil (Nissin Canola Oil, Nissin Oillio Group Corporation), and a detergent (Attack Zero,
Kao Corporation) were used for the emulsion solution in this study. A micropipette was used to add 1 mL ofwater, 1 mL of salad oil, and 100 μL of detergent in that order to make a sample. Figures 1 and 2 shows aschematic of the sample structure, and a photograph of the whole sample, respectively.
Copper foil (Niraco Corporation) was cut to a size that would fit into a sample holder for SEM observation

Figure 1. Schematic diagram of the prepared sample.
82

Figure 2. Completed sample.

Figure 3. Sample holder for SEM observation after liquid cell installation.

and used as the base. The copper foil was employed to minimize the effect of charge-up of the sample. A 1
μL drop of emulsion sample was dropped into the sample holder with a micropipette, and a Si chip with SiN
film (EM Japan Corporation), which is an electron permeable film, was placed on top. The Si chip with SiN
film was used in this study because the emulsion sample attached to the SiN film was confirmed by opticalFigure 4. EDS data for 20 nm and 200 nm film thickness. (a) Characterstic X-ray spectrum. (b) Enlarged
spectra near light elements.
83

Figure 5. (a) SEM image, (b) C distribution image, (c) O distribution image of emulsion sample.

Figure 6. (a) SEM image, (b) C distribution image, (c) O distribution image of emulsion sample.

microscopic observation of the emulsion sample.
In order to obtain a high probability of observation, a chip with 9 windows, a film thickness of 20 nm, anda frame of 100 μm was used. The window consists of 8 windows of 100 μm x 100 μm and 1 window of 100
μm x 350 μm.
2.2. SEM/EDS observation method and measurement conditions
The prepared sample was placed on a sample holder for SEM observation as shown in Figure 3 and fixedwith carbon tape. Colloidal graphite (EM Japan Co., Ltd.) was applied across the adhesive to reduce chargeup due to the adhesive between the copper foil and the chip. In this experiment, an SEM (JEOL, JSM6700F)
was used for observation in vacuum at room temperature. The acceleration voltage was 20~30 kV. During
the EDS measurement, the detector was placed close to the sample and mapping was performed for 30~45
minutes. After mapping was completed, a point analysis evaluation was performed.
3. Results and Discussion

We used EDS to compare the nitrogen spectra of SiN films on Si substrates. Figure 4 (a) shows the

spectrum up to 0~2.5 keV, and (b) shows an enlarged spectrum near nitrogen. In the nitrogen spectrum in (b),it was confirmed that nitrogen was almost undetectable in the thinner film. Although the emulsion sample
itself does not contain nitrogen, it is considered that nitrogen contained in the liquid sample can be detectedwith high accuracy by applying the thinner film to the observation of the liquid sample that contains nitrogen.
Figure 5 (a) shows the SEM image and (b) and (c) show the EDS mapping results. On the SiN film in (a),there are structures of various sizes ranging from 3 to 30 μm in size that are slightly darker than thesurrounding area, indicating weak detection of secondary electrons. The EDS mapping results show that theC-distributed image in (b) shows a strong intensity, while the O-distributed image in (c) shows a weakerintensity than the surrounding area. Since C is a constituent of oil, we observed an O/W type emulsion withoil dispersed in water.
Figure 6 (a) shows the SEM image and (b) and (c) show the EDS mapping results. Again, several structuresof 3 to 15 μm in diameter can be seen. The EDS mapping results show an oil structure in water, confirming
an O/W type emulsion. Furthermore, in the O distribution image in (c), the C intensity is strong outside of
the strong area, indicating that the O/W emulsion is dispersed in the oil, indicating an O/W/O complex
emulsion.
For O/W/O emulsions, point analysis evaluation by EDS was also performed. Figure 7 (a) shows the SEM
84

Figure 7. (a) SEM image of an emulsion sample noting the point analysis position. (b) Characterstic Xray spectrum.

image of the point analysis, and (b) shows the spectral distribution of characteristic X-rays from the point
analysis. The oil distribution points 1 and 3 show a strong C Kα line, while the carbon spectrum is almost
undetectable in 2. Since oxygen is also a constituent element of oil, it can be confirmed that the oxygen
intensities of 1 and 3 are respectively emitted. This indicates that the oxygen spectrum was strongly detected
at the location where water was distributed, confirming that oil and water were detected, respectively.
On the other hand, the point 1 was oil, but oxygen was detected more strongly. Possible causes include
signals from the surrounding water and the influence of signals from the lower part of the emulsion.
4. Conclusion
The objective of this study was to observe emulsion samples using a conventional SEM, and O/W emulsions
and O/W/O emulsions were successfully observed. Qualitative analysis evaluation by EDS point analysis
was also conducted to confirm the distribution of water and oil, respectively. The evaluation of SiN film
thickness showed that the application of a thin film to the observation of samples containing nitrogen
improves the accuracy of qualitative analysis of liquid samples. Furthermore, it was found that sealing ofviscous samples such as oil and detergent is possible, indicating that it can lead to the observation of all kindsof liquid samples.
Droplet size distribution (DSD) of emulsions is one of the important properties, and there is a view thatthe tolerance of emulsions is affected by the size distribution and the smaller the droplet is, the more stable
it is5. In the future, we aim to observe nano-sized emulsions. Also, we aim to observe nanobubbles and analyze
their behavior in emulsion solutions using ultrafine bubbles as a substitute for surfactants.
We are also developing a liquid cell for PEEM, which is considered to be difficult to fabricate, for PEEM,
which uses electron lenses to magnify and project the spatial distribution of photoelectrons with a spatial
resolution of several tens of nanometers6. The PEEM will be used to analyze all kinds of samples undervacuum conditions.
References[ 1] T. Suzuki: J. Soc. Cosmet. Chem. Jpn, 44, 103-117 (2010).
[ 2] M. Yamashita et al: J. Soc. Cosmet. Chem. Jpn, 32, 52-58 (1998).
[ 3] T, Okamoto et al: J. Macromolecular Science and Technology, 75, 290-292 (2018).
[ 4] K. Takahara et al: J. Appl. Phys, 130, 025302 (2021).
[ 5] M. Moradi, V. Alvarado, S. Huzurbazar: Energy Fuels, 25, 260-268 (2011).
[ 6] M. Kotsugi et al: J. Surface Science, 37, 3-8 (2016).

85

List of publications
Papers1.

“Spectral distribution and flux of γ-ray beams produced through Compton scattering of
unsynchronized laser and electron beams”
Dan Filipescu, Ioana Gheorghe, Kontantin Stopani, Sergey Belyshev, Satoshi Hashimoto, Shuji Miyamoto,and Hiroaki Utsunomiya
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors andAssociated Equipment 1047, 167885 (2022)2.

“Prediction model of elastic constants of BCC high-entropy alloys based on first-principles calculations
and machine learning techniques”
G. Hayashi, K. Suzuki, T. Terai, H. Fujii, M. Ogura, and K. Sato
Science and Technology of Advanced Materials: Methods 2, 381-391 (2022)

3.

“Difference in Ge and Ni Underlayer for Nanographene Synthesis Using Soft X-ray Irradiation Effectsof Ge and Ni catalytic underlayers to nanographene synthesis from pentacene-based film via soft Xray irradiation”
Akira Heya, Kazuhiro Kanda, Ryo Yamasaki, and Koji Sumitomo
Japanese Journal of Applied Physics 61, SC1057 (2022)

4.

“An experiment demonstrating the capability of a symmetrical layout type double crystal
monochromator controlled using electronic cam technology”
Masato Okui, Atsushi Shimoguchi, Naoki Yato, Norio Murayama, Isao Kikuchi, Ichiro Tsuboki, andKazuhiro Kanda
Journal of Physics: Conference Series 2380, 012054 (2022)

5.

“Anion Substitution at Apical Sites of Ruddlesden−Popper-type Cathodes toward High Power Density
for All-Solid-State Fluoride-Ion Batteries”
Yanchang Wang, Kentaro Yamamoto, Yoshihiro Tsujimoto, Toshiyuki Matsunaga, Datong Zhang, Zulai Cao,
Koji Nakanishi, Tomoki Uchiyama, Toshiki Watanabe, Tsuyoshi Takami, Hidenori Miki, Hideki Iba,
Kazuhiko Maeda, Hiroshi Kageyama, and Yoshiharu Uchimoto
Chem. Mater. 34, 609 (2022)

6.

“Observation of Solid-Liquid Interface Reaction Between High-Capacity Amorphous Si Film
Electrode for Lithium Ion Battery and LiPF6 Electrolyte Solution Using Soft X-ray Absorption
Spectroscopy”
Koji Nakansihi, Takuya Mori, Hiroshi Ohzono, Kazuhiro Kanda, and Satoru Suzuki
Adv. X-Ray. Chem. Anal., Japan 54, 185-192 (2023)

7.

“Evaluation of sample charging in near-ambient pressure X-ray photoelectron spectroscopy”
Koji Takahara, Kento Takenaka, Hirosuke Sumida, and Satoru Suzuki
Adv. X-ray Chem. Anal., Japan 54, 75-80 (2023)

8.

“Cross-sectional Observation of Micro- and Nanobubbles Formed In-situ in a Scanning Electron
Microscope”
Koji Takahara and Satoru Suzuki
e-Journal of Surface Science and Nanotechnology 20, 248-251 (2022)

9.

“Effects of sample-aperture cone distance on the environmental charge compensation in near-ambientpressure hard X-ray photoemission spectroscopy”
Satoru Suzuki, Kento Takenaka, Koji Takahara, and Hirosuke Sumida
86J. Electron Spectrosc. Relat. Phenom. 257, 147192-1-9 (2022)
10. “Soft X-ray Absorption/Emission Spectroscopy and Atomic Hydrogen Irradiation Effect of Ammonia
Borane”
Masahito Niibe, Yuichi Haruyama, Akira Heya, and Seigo Ito
e-Journal of Surface Science and Nanotechnology 20, 226-231 (2022)
12. “In situ XAFS study on chemical states of Co and Ir nanoparticles under conventional growth
condition of single-walled carbon nanotube via alcohol catalytic chemical vapor deposition”
Shusaku Karasawa, Kamal Prasad Sharma, Takahiro Saida, Shigeya Naritsuka, Yuichi Haruyama, Toru Asaka,
and Takahiro Maruyama
Chemical Physics Letters 808, 140135 (2022)
13. “Comparison of Photoresist Sensitivity between KrF, EB and EUV Exposure”
Yosuke Ohta, Atsushi Sekiguchi, Shinji Yamakawa, Tetsuo Harada, Takeo Watanabe, and Hiroki Yamamoto
Journal of Photopolymer Science and Technology 35, 49-54 (2022)
14. “Development of Selenonium PAGs in EUV Lithography toward High Sensitivity Achievement”
Tomohito Kizu, Shinji Yamakawa, Takeo Watanabe, Seiji Yasui, and Tomoyuki Shibagaki
Journal of Photopolymer Science and Technology 35, 55-59 (2022)
15. “Grazing-Incidence Soft-X-ray Scattering for the Chemical Structure Size Distribution Analysis in
EUV Resist”
Atsunori Nakamoto, Shinji Yamakawa, Tetsuo Harada, and Takeo Watanabe
Journal of Photopolymer Science and Technology 35, 61-65 (2022)
16. “Micro Stirrer with Heater Mounted on SAW Actuator for High-speed Chemical Reaction”
Masatoshi Takahashi, Akinobu Yamaguchi, Yuichi Utsumi, Masahiro Takeo, Satoshi Amaya, Hiroaki
Sakamoto, and Tsunemasa Saiki
Journal of Photopolymer Science and Technology 35, 147-151 (2022)
17. “Evaluation of Surface-Enhanced Raman scattering substrate consisting of gold nanoparticles grownon nanoarrays of boehmite fabricated using magnetron sputtering process”
Taku Tanaka, Shyunya Saegusa, Masayuki Naya, Takao Fukuoka, Sho Amano, Yuichi Utsumi, and Akinobu
Yamaguchi
Journal of Photopolymer Science and Technology 35, 249-253 (2022)
18. “Determination of radiation dose leading to molecular chain destruction of amino acids”
Shyunya Saegura, Ryo Nakamura, Naoya Akamatsu, Yuichi Utsumi, Tomoko Ishihara, Masaki Oura, andAkinobu Yamaguchi
Journal of Photopolymer Science and Technology 35, 255-260 (2022)
19. “Microtaggant Technology for Ensuring Traceability of Pharmaceutical Formulations: Potential for
Anti-counterfeiting Measures, Distribution and Medication Management”
Toshiya Yasunaga, Takao Fukuoka, Akinobu Yamaguchi, Noriko Ogawa, and Hiromitsu YamamotoYAKUGAKU ZASSHI 142, 1255-1265 (2022)
20. “Physical Stability of Stealth Nanobeacon using Surface-Enhanced Raman Scattering for Anticounterfeiting and Monitorring Medication Adherence: Depostion on Various Coating Tablets”
Toshiya Yasunaga, Takao Fukuoka, Akinobu Yamaguchi, Noriko Ogawa, and Hiromitsu Yamamoto
International Journal of Pharmaceutics 624, 121980 (2022)
21. “Uniaxial in-plane magnetic anisotropy mechanism in Ni, Fe, and Ni-Fe alloy films deposited on single
crystal Y-cut 128° LiNiO3 using magnetron sputtering”
87Masayoshi Ito, Shota Ono, Hayato Fukui, Keiichi Kogirima, Natusmi Maki, Tatsuo Hikage, Takeshi Kato,
Takuo Ohkochi, Akinobu Yamaguchi, Mutsuhiro Shima, and Keisuke Yamada
Journal of Magnetism and Magnetic Materials 564, 170177 (2022)
22. “Design and Fabrication of PTFE Substrate-Integrated Waveguide Butler Matrix for Short Millimeter
Waves”
Mitsuyoshi Kishihara, Kaito Fujitani, Akinobu Yamaguchi, Yuichi Utsumi, and Isao Ohta
IEICE Transactions on Electronics E106-C, 111-115 (2023)
23. “The effect of pH on X-ray-radiolysis-induced synthesis of nickel nanoparticles on lithium niobate
substrates”
Shyunya Saegusa, Ikuya Sakurai, Ikuo Okada, Yuichi Utsumi, Keisuke Yamada, Mutsuhiro Shima, Atsushi
Yamaguchi, Mari Ishihara, and Akinobu Yamaguchi
Materials Science & Engineering B 287, 116093 (2023)
24. “Development and evaluation of microwave microfluidic devices made of Polydimethylsiloxane”
Ryota Tanaka, Tomoyuki Nakano, Kaito Fujitani, Mitsuyoshi Kishihara, Akinobu Yamaguchi, and Yuichi
UtsumiJpn. J. Appl. Phys. 62, SG1027 (2023)
25. “Study on magnetization dynamics modulated by spin-orbit-torque in a Ni81Fe19/NiO/Ni81Fe19
multilayered wire”
Akinobu Yamaguchi, Nobuko Matsumoto, Wataru Yoshikawa, and Yasuhisa Fujii
AIP Advances 13, 025341 (2023)
26. “Oriented sp2 bonded carbon structure of hydrogenated amorphous carbon films”
Naoki Umada, Kazuhiro Kanda, Masato Niibe, Yuki Hirata, Naoto Ohtake, and Hiroki Akasaka
Diamond and Related Materials 131, 109533 (2023)

88Books1.

“Materials and Microfabrication for Biosensing “
Akinobu Yamaguchi
Edited by Editorial committee of Materials and Microfabrication for Biosensing
CORONA PUBLISHING, 2022 (ISBN 978-4-339-07278-5)

Proceedings

1.

“Application of laser inverse Compton photon on measurement of photoneutron production
double differential cross section“Toshiya Sanami, Tuyet Tran, Thuong Nguyen, Hirohito Yamazaki, Toshiro Itoga, Yoichi Kirihara,
Yoshihito Namito, Hiroshi Nakashima, Syuji Miyamoto, Satoshi Hashimoto, and Yoshihiro Asano
Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan, p.70 (2022)

2.

“Ultrashort laser light source for demonstrating the monocycle FEL scheme”
Yuichiro Kida, Satoshi Hashimoto, Shuji Miyamoto, Tadashi Togashi, Hiromitsu Tomizawa, Sumiyuki
Okabe, Aoi Gocho, Keisuke Kaneshima, Yoshihito Tanaka, and Takashi Tanaka
Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan, p.75 (2022)

3.

“Real-time analysis of betatron oscillation waveforms using machine learning at the
NewSUBARU storage ring”
Hitoshi Fujii, Keisuke Watanabe, and Satoshi Hashimoto
Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan, p.557 (2022)

4.

“Present status of the NewSUBARU synchrotron light facility”
Satoshi Hashimoto, Hitoshi Fujii, Tatsuyuki Sakurai, Takahiro Ushizawa, Yasuyuki Minagawa,Kazuyuki Kajimoto, Shotaro Nakata, and Hideyuki Hirayama
Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan, p.1119 (2022)

5.

“Current Status and Prospect for EUV Lithography”
Takeo Watanabe, Tetsuo Harada, and Shinji Yamakawa
RadTech Asia 2022, S4-01 (2022)

Reviews

1.

“Existence of nanobubbles and surface nanobubbles”
Satoru Suzuki
Vac. Surf. Sci. 65, 594 (2022)

2.

“Introduction to Laboratory of Advanced Science and Technology for Industry, University of
Hyogo”
Satoru Suzuki
Materia Japan 62, 131 (2023)

89International Meetings
1.

“An experiment demonstrating the capability of a symmetrical layout type double crystal
monochromator controlled using electronic cam technology”
Masato Okui, Atsushi Shimoguchi, Naoki Yato, Norio Murayama, Isao Kikuchi and Ichiro Tsuboki,
and Kazuhiro Kanda
14th International Conference on Synchrotron Radiation Instrumentation (SRI2021), Online, 2022/3-4

2.

“EUV Research Activities at NewSUBARU”
Takeo Watanabe, Tetsuo Harada, and Shinji Yamakawa
IEUVI Resist TWG Workshop 2022, Online, 2022/4

3.

“Hydrogen Cleaning Evaluation of Mo/Si Multilayer using an EUV Irradiation Tool at
NewSUBARU”
Tetsuo Harada, Shinji Yamakawa, and Takeo Watanabe
Photomask Japan 2022, Online, 2022/4

4.

“Development of Grazing-Incidence Coherent EUV Scatterometry Microscope for Resist
Pattern Observation”
Naoya Kawakami, Tetsuo Harada, Shinji Yamakawa, and Takeo Watanabe
Photomask Japan 2022, Online, 2022/4

5.

“Functionalization of an Inner-wall of Diamond-like Carbon Coated Small-diameter Long-sized
Tube by Oxygen Plasma Treatment”
Yuichi Imai, Tatsuyuki Nakatani, Shinsuke Kunitsugu, Kazuhiro Kanda, Yasuhiro Fujii, Daiki Ousaka,
Susumu Oozawa, and Tomio Uchi
2022 MRS Spring Meeting, Hybrid, 2022/5

6.

“Investigation of Free Volume in Diamond-like Carbon Films Using a Slow Positron Beam”
Kazuhiro Kanda, Tomohiro Mishima, Hiroki Akasaka, Fuminobu Hori, Atsushi Yabuuchi, and Atsushi
Kinomura
15th International Conference on New Diamond and Nano Carbons (NDNC2022), Kanazawa Bunka
Hall, Japan, 2022/6

7.

“Effects of Sample-Aperture Cone Distance on Environmental Charge Compensation in Hard
X-ray Photoelectron Spectroscopy”
Kento Takenaka, Koji Takahara, Hirosuke Sumida, and Satoru Suzuki
9th Int. Conf. on Hard X-ray Photoelectron Spectroscopy (HAXPES 2022), Online, 2022/6

8.

“Determination of radiation dose leading to molecular chain destruction of amino acids”
Shunya Saegusa, Ryo Nakamura, Naoya Akamatsu, Yuichi Utsumi, Tomoko Ishihara, Masaki Oura,
and Akinobu Yamaguchi
ICPST-39, Online, 2022/6

9.

“Evaluation of Surface-Enhanced Raman scattering substrate consisting of gold nanoparticles
grown on nanoarrays of boehmite fabricated using magnetron sputtering process”
Taku Tanaka, Syunya Saegusa, Masayuki Naya, Takao Fukuoka, Yuichi Utsumi, Sho Amano, andAkinobu Yamaguchi
ICPST-39, Online, 2022/6

10. “Micro Stirrer with Heater Mounted on SAW Actuator for High-speed Chemical Reaction”
Masatoshi Takahashi, Yuichi Utsumi, Akinobu Yamaguchi, Masahiro Takeo, Satoshi Amaya, Hiroaki
Sakamoto, and Tsunemasa Saiki90ICPST-39, Online, 2022/6
11. “Grazing-Incidence Soft-X-ray Scattering for the Chemical Structure Size Distribution Analysis
in EUV Resist”
Atsunori Nakamoto, Shinji Yamakawa, Tetsuo Harada, and Takeo Watanabe
ICPST-39, Online, 2022/6
12. “Development of Selenonium PAGs in EUV Lithography toward High Sensitivity Achievement”
Tomohito Kizu, Shinji Yamakawa, Takeo Watanabe, Seiji Yasui, and Tomoyuki Shibagaki
ICPST-39, Online, 2022/6
13. “Comparison of Photoresist Sensitivity between KrF, EB and EUV Exposure”
Yosuke Ohta, Atsushi Sekiguchi, Shinji Yamakawa, Tetsuo Harada, Takeo Watanabe, Hiroki
Yamamoto, Shinji Yamakawa, Ako Yamamoto, Seiji Yasui, Takeo Watanabe, and Tetsuo Harada
ICPST-39, Online, 2022/6
14. “Research Activities Including the Hydrogen Brittle Evaluation in EUVL at NewSUBARU”
Takeo Watanabe, Tetsuo Harada, and Shinji Yamakawa
2022 EUVL Workshop, Online, 2022/6
15. “Study on spin-orbit-torque-induced magnetization modulation using rectifying plannar Hall
effect”
Akinobu Yamaguchi, Nobuko Matsumoto, Wataru Yoshikawa, and Yasuhisa Fujii
Joint European Magnetic Symposia (JEMS2022), Warsaw, Poland, (Hybrid), 2022/7
16. “Photon Flux Density Dependence of Nanographene Synthesis by Soft X-ray Irradiation from
Pentacene-based Molecules Prepared on Ni Films by Hot Mesh Deposition”
Akira Heya, Kazuhiro Kanda, Ryo Yamasaki, and Koji Sumitomo
29th International Workshop on Active-Matrix Flatpanel Displays and Deviceses(AMFPD2022),
Ryukokou Univ., Kyoto, Japan, 2022/7
17. “Spin transport properties in multilayer including Pt and NiO layers”
Akinobu Yamaguchi
Joint European Magnetic Symposia (JEMS2022), Warsaw, Poland, (Hybrid), 2022/7
18. “Structural changes of highly hydrogenated DLC films by SR irradiation”
Kazuhiro Kanda, Daisuke Niwa, Tomohiro Mishima, Masahito Niibe, Hiroki Akasaka, Fuminobu
Hori, Atsushi Yabuuchi, and Atsushi Kinomura
ASIAN Conference on X-ray Absorption Spectroscopy 2022 (ACXAS2022), NongNooch PattayaInternational Convention and Exhibition Center, Pattaya, Thailand, 2022/8
19. “Current Status and Prospect for EUV Lithography”
Takeo Watanabe, Tetsuo Harada, and Shinji Yamakawa
RadTech Asia 2022, Tsukuba, Japan, 2022/8
20. “Comparative Study of Atomic Hydrogen Exposure on Hydrogenated and Hydrogen-Free
Amorphous Carbon Films”
Yuichi Haruyama, Daiki Morimoto, Akira Heya, Koji Sumitomo, Noriaki Toyoda, and Seigo Ito
22nd International Vaccum Congress (IVC-22), Sapporo, Japan, 2022/9
21. “Effect of Atomic Hydrogen Exposure on Hydrogen-Free Amorphous Carbon Films”
Yuichi Haruyama, Daiki Morimoto, Akira Heya, Koji Sumitomo, Noriaki Toyoda, and Seigo Ito
22nd International Vaccum Congress (IVC-22), Sapporo, Japan, 2022/9
9122. “Study on Microfluidic analysis system with molecular sensing based on Surface enhanced
Raman Scattering”
Akinobu Yamaguchi, Taku Tanaka, Shunya Saegusa, Masayuki Naya, Takao Fukuoka, Sho Amano,
and Yuichi Utsumi
SSDM 2022, Chiba, Japan, 2022/9
23. “Chemical Physical Unclonable Functions Taggant for Anti-Counterfeiting and Authentication
Systems”
Akinobu Yamaguchi, Toshiya Yasunaga, Yuichi Utsumi, Kyoko Namura, Momofumi Suzuki, andTakao Fukuoka
MNE2022, Leuven Belgium, 2022/9
24. “Fabrication and evaluation of SERS structures on boehmite using magnetron sputtering
method for molecular sensing”
Shunya Saegusa, Taku Tanaka, Masayuki Naya, Takao Fukuoka, Sho Amano, Yuichi. Utsumi, andAkinobu Yamaguchi
MNE2022, Leuven, Belgium, 2022/9
25. “Deviation of photoelectron intensity from the Lambert-Beer’s law in near-ambient pressure
hard X-ray photoelectron spectroscopy”
Kento Takenaka, Koji Takahara, Tomoki Eguchi, Hirosuke Sumida, and Satoru Suzuki
Int. Symp. on Atomic Level Characterizations for New Materials and Devices (ALC 2022), Okinawa,
Japan, 2022/10
26. “Optofluidic device with Gold-nanofève-based-SERS active nanostructure”
Shunya Saegusa, Taku Tanaka, Masayuki Naya, Takao Fukuoka, Sho Amano, Yuichi Utsumi,
and Akinobu Yamaguchi
13th Japan-China-Korea Joint Conference on MEMS/NEMS, Kagoshima, Japan, 2022/10
27. “On chip organic synthesis by microwave heating in a microchannel coupled with post-wall
waveguide”
Kaito Fujitani, Mitsuyoshi Kishihara, Ryota Tanaka, Tomoyuki Nakano, Akinobu Yamaguchi, andYuichi Utsumi
13th Japan-China-Korea Joint Conference on MEMS/NEMS, Kagoshima, Japan, 2022/10
28. “On-chip synthesis of metal complex by microwave heating in a microchannel embedded in
post-wall waveguide”
Kaito Fujitani, Mitsuyoshi Kishihara, Akinobu Yamaguchi, and Yuichi Utsumi
MNC 2022, Tokushima, Japan, 2022/10
29. “Development and evaluation of microwave microfluidic devices made of PDMS”
Ryota Tanaka, Tomoyuki Nakano, Kaito Fujitani, Mitsuyoshi Kishihara, Akinobu Yamaguchi, andYuichi Utsumi
MNC 2022, Tokushima, Japan, 2022/10
30. “Development of low-energy-electron-flood-exposure tool (LEEFET)”
Wataru Kusada, Shinji Yamakawa, Tetsuo Harada, and Takeo Watanabe
MNC 2022, Tokushima, Japan, 2022/11
31. “Study on spin-orbit-torque-induced magnetization modulation using rectifying plannar Hall
effect”
Akinobu Yamaguchi, Nobuko Matsumoto, Wataru Yoshikawa, and Yasuhisa Fujii
92

Magnetism and Magnetic Materials 2022, Online, 2022/10-11
32. “Fundamental Research for EUV Lithography at NewSUBARU Synchrotron Light Facility”
Takeo Watanabe
Materials Science, Engineering & Technology, Online, 2022/11
33. “In situ spectroscopic study of electrochemical deposition processes and molecular sensing using
microchemical systems”
Akinobu Yamaguchi, Takao Fukuoka, Masaru Kato, Ichizo Yagi, Masaki Oura, and Yuichi Utsumi
International congress on pure and applied chemistry (ICPAC), Kota kinabalu, sabah, Malaysia,
2022/11
34. “Technical issue of EUVL and prospect for EUVL and Beyond EUVL”
Takeo Watanabe
7th EUV-FEL Workshop, Tsukuba (hybrid), Japan, 2023/1
35. “Plasmonic Nanotags for On-dose-authentication of Medical Tablets”
Takao Fukuoka, Toshiya Yasunaga, Kyoko Namura, Motofumi Suzuki, and Akinobu Yamaguchi
Pittcon 2023, Philadelphia, USA, 2023/3

93

Academic Degrees
Master of Engineering
Naoya Kawakami (University of Hyogo)“Improvement of Sensitivity of Grazing-Incident Coherent-Scatterometry Microscope for Resist-Pattern
Defect Detection”
Koji Takahara (University of Hyogo)“Observation and shape control of surface microbubbles”
Taku Tanaka (University of Hyogo)“Fabrication of Imaging Substrates Surface Enhanced Raman Scattering (SERS) and its Mounting on Micro
Chemical Chips”
Ryota Tanaka (University of Hyogo)“Fabrication and evaluation of Microwave Chemical Synthesis chips combined with in situ Raman
spectroscopy”
Kozo Tamada (University of Hyogo)“High-Strength Ni-W Deposition Using the LIGA Process Development of Micro Gears and Micro
Turbines”
Tomoyuki Nakano (University of Hyogo)“Prototyping and Evaluation of Microwave Chemical Synthesis Chip for nano- and microbubble
generation”
Daiki Morimoto (University of Hyogo)“Effect of atomic hydrogen exposure on amorphous carbon films”
Taki Watanabe (University of Hyogo)“Moving Mask X-ray Lithography High Yield of Submicron Mist by Development and Research ofGenerating Nebulizer”

94Laboratory of Advanced Science and Technology for Industry,
University of Hyogo
3-1-2 Kouto, Kamigori, Ako-gun, Hyogo 678-1205 Japan
兵庫県立大学 高度産業科学技術研究所〒678-1205 兵庫県赤穂郡上郡町光都3-1-2