Ⅲ-2

Materials Sciences

BL1UⅢ -2. Materials Sciences

BL1U

Study on Defects in Iron Formed under Hydrogen Embrittlement
Environment Using In-Situ Measurement Technique ofGamma-Ray Induced Positron Annihilation Lifetime Spectroscopy
A. Yabuuchi1, T. Hirade2, M. Fujinami3, R. Awaji3, N. Oshima4, K. Takai5, K. Sugita6
and Y. Taira6
Institute for Integrated Radiation and Nuclear Science, Kyoto University, Kumatori 590-0494, Japan
2
Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan3
Department of Applied Chemistry and Biotechnology, Chiba University, Chiba 263-8522, Japan
4
National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8568, Japan
5
Department of Engineering and Applied Sciences, Sophia University, Tokyo 102-8554, Japan
6
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan1

The incorporation of hydrogen into metals such as
steel is known to cause embrittlement of the metal. In aprevious study, vacancy clusters have been detected
near the hydrogen embrittlement fracture surface by
positron annihilation lifetime spectroscopy. However,conventional positron annihilation lifetime spectroscopy
requires measurements after hydrogen charging, andtherefore, in-situ positron annihilation lifetime
measurements were desired to understand defectbehavior during hydrogen charging. In this study, we
irradiated pure iron samples with high-energy pulsed
gamma-rays obtained from UVSOR and measured thepositron lifetimes in-situ during hydrogen embrittlement
tests or tensile tests using positrons induced inside thesamples.
Well-annealed pure iron tensile test pieces (10 mm
in width and 2 mm in thickness) were either (1)mounted in a 0.1 N NaOH aqueous solution containing
5 g/L NH4SCN and charged with cathodic hydrogenby applying a current density of 50 A/m2, or (2)mounted in a tensile testing apparatus and stretched toa nominal strain of 8% and held under a constant load.
The samples (1) and (2) were irradiated with a pulsed
gamma-ray beam for in-situ positron annihilation
lifetime measurements.
Figure 1 shows positron annihilation lifetime spectrum
obtained from a hydrogen-charged pure iron sample
mounted in NaOH aqueous solution. A lifetime
component of ~2 ns, corresponding to the annihilationof positrons in the aqueous solution, was observed with
non-negligible intensity, indicating that further
refinement of the measurement technique is needed.
Figure 2 shows positron annihilation lifetime spectra
obtained from a pure iron tensile-test piece under noload and under the load required for stretching to anominal strain of 8 %. The spectral shape clearly changed
by applying the load, indicating the appearance of adefect component. Furthermore, focusing on the change
in positron lifetime over time may reveal more thanwhat can be obtained by conventional positronannihilation lifetime spectroscopy. A more detailed
analysis of the obtained spectra is currently underway.

Ⅲ-2

Fig. 1. Positron annihilation lifetime spectrum obtained
from a hydrogen-charged pure iron sample mounted in
NaOH aqueous solution.

Fig. 2. Positron annihilation lifetime spectra obtained
from a pure iron tensile-test piece under no load (opensquares) and under the load required for stretching toa nominal strain of 8 % (open circles).

53 1 Ⅲ02-

BL6U Sciences
Ⅲ -2. Materials

BL6U

Momentum Microscope Study of a Kagome Superconductor CsV3Sb5
T. Kato1, K. Nakayama1,2, Y. Li3,4, Z. Wang3,4, Y. Yao3,4, F. Matsui5, T. Takahashi1,6,7
and T. Sato1,6,7

Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency(JST), Tokyo 102-0076, Japan
3
Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture andMeasurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100081, China
4
Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems, Beijing Institute of Technology,
Beijing 100081, China
5
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
6
Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
7
Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan
1

2

Ⅲ-2

The kagome lattice, consisting of a two-dimensional
network of corner-sharing triangles with 3d transition
metal ions, offers a fertile ground to explore exotic
quantum phenomena originating from electron
correlation and non-trivial band topology. Band
structure of a simple kagome lattice is composed of aflat band, a Dirac cone, and a saddle point. Owing tosuch a unique band structure, the kagome lattice shows
various interesting physical properties depending on theposition of the Fermi level (EF).
Recently, a new family of kagome metals AV3Sb5 (A =K, Rb, Cs) with a V kagome network has been discovered.
AV3Sb5 commonly exhibits superconductivity below Tc= 0.9-2.5 K and charge-density wave (CDW) below
TCDW = 78-103 K. To clarify the interplay amongsuperconductivity, CDW, and electronic states, we have
performed ARPES measurements of CsV3Sb5 (Tc = 2.5
K, TCDW = 91 K) by using momentum microscope at
BL6U in UVSOR [1].
Single crystals of CsV3Sb5 were synthesized withthe self-flux method. ARPES measurements were
performed using KREIOS 150 MM (SPECS) [2]. Theenergy resolution was set to be 35 meV.
Figure 1 shows the plot of ARPES intensity at EF as afunction of kx and ky at T = 120 K (above TCDW) measured
with 106-eV photons corresponding to the kz ~ 0 plane[3,4]. Photoelectrons in this wide momentum window
were simultaneously collected by using a momentum
microscope. One can recognize three types of Fermi
surfaces, a circular pocket and a large hexagonal
pocket centered at the Γ point and a small triangularpocket at the K point. The circular pocket at the Γ point
originates from an electron band with the Sb 5pz orbital.
On the other hand, the hexagonal pocket originatesfrom linearly dispersive bands with the dominant V
3dxz/yz orbital character. The triangular pocket at the K
point is associated with the Dirac-cone band with the
Dirac point at EB ~ 0.3 eV. This band is attributed to
the V 3dxy/x2-y2 orbital, and forms the saddle point
slightly above EF. Our high-resolution measurements
below TCDW (not shown) reveal the largest CDW-gap
opening on this saddle-point band. Therefore, thesaddle point plays a crucial role in stabilizing CDW in
AV3Sb5.

Fig. 1. ARPES-intensity map at EF plotted as a functionof kx and ky, measured at T = 120 K in CsV3Sb5. Red,
purple, and blue dashed lines are guides for the eyes totrace the experimental Fermi surfaces.

[1] T. Kato et al., submitted.
[2] F. Matsui et al., Jpn. J. Appl. Phys. 59 (2020) 067001.
[3] K. Nakayama et al., Phys. Rev. B 104 (2021) L161112.
[4] K. Nakayama et al., Phys. Rev. X 12 (2022) 011001.

54 2 Ⅲ02-

BL1U

Ⅲ -2. Materials Sciences

BL1U

Probing Vacancy-type Defects in Ce:LuAG Scintillators by GiPALS
Experiment and DFT Calculation
M. Kitaura 1, Y. Taira2,3 and S. Watanabe4

Faculty of Science, Yamagata University, Yamagata 990-8560, JapanUVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan3
School of Physical Sciences, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan
4
Institute of Innovative Research, Tokyo Institute of Technology, Tokyo 152-8550, Japan1

2

existence of Al vacancies was suggested in Y3Al5O12(YAG) [3].

Intensity (count)

Positron annihilation lifetime spectroscopy (PALS) isa unique experimental technique that can visualize theexistence of vacancy-type defects in solids. Taira et al.,one of the authors, have developed gamma-ray induced
PALS (GiPALS) using ultrashort pulsed gamma-rays
generated by 90-degree inverse Thomson scattering [1].
We applied this method to the visualization of negatively
charged cation vacancies, which trigger the formationof photocarrier traps associated with defect complexesof cation antisites and oxygen vacancies in
Ce:Gd3Al2Ga3O12 (Ce:GAGG) crystals [2].
In the present study, GiPALS experiment has been
performed at 300 K for Ce-doped Lu3Al5O12 (Ce:LuAG)
crystals, which have the same crystal structure as
Ce:GAGG. GiPALS spectra were analyzed according to
the two-state trapping model of bulk and defect states.
The lifetimes and relative intensities were determinedby the least-square fitting using two exponential decayfunctions. Using these parameters, bulk- and defectlifetimes were calculated, and were compared to thoseobtained from the theoretical calculation based on twocomponent density functional theory (TC-DFT).
Figure 1 shows the GiPALS spectrum of a Ce:LuAG
crystals. The data were obtained at 300 K. The GiPALS
spectra are reproduced by the sum of two exponential
decay functions drawn by blue broken lines. The
positron annihilation lifetime becomes longer at thenegatively charged vacancy site, compared to the bulk
state free from vacancy-type defects. Therefore, theshort and long lifetime components are attributed to thepositron annihilation at the bulk and defect states,
respectively. The lifetimes i and relative intensities Ii
were analyzed by the least square fitting of experimental
data. The values of i and Ii are listed in Table I. The
bulk lifetime B and trapping rate  were estimated to be1662 ps and (1.530.07)109 s-1, respectively. Table IIlists bulk B and defect lifetimes 24c, 16a and 24d,
obtained by the present TC-DFT calculation. The
subscripts indicate the Wyckoff positions of the latticesites introducing cation monovacancies in the TC-DFT
calculation. The experimental value of B is almost
agreement with the calculated one. This result indicatesthe validity of our experiment and analysis.
In Table I, the value of 2 corresponds to the vacancyrelated lifetime. This value is similar to those of 24d, and16a in Table II. Thus, it is more likely that Al
monovacancies are introduced at 16a and 24d sites. The

10

5

10

4

10
10
10
10

Ⅲ-2

3

2

1

0

0

1
Time (ns)2

Fig. 1. GiPALS spectrum of a Ce:LuAG crystal
measued at room temperature. Broken lines indicate
the components due to positron annihilation at bulk
and vacancy-related defect sites. The sum of them also
was indicated by a red line.
Table I. Lifetimes i, and relative intensities Ii for
GiPALS spectra of Ce:LuAG, analyzed using the twostate trapping model.
I1 (%)
I2 (%)
1 (ps)2 (ps)
Ce:LuAG1321451.00.8

2261

49.00.8

Table II. Bulk B and defect lifetimes 24c, 16a and24d, obtained by the present TC-DFT calculation. The
subscripts indicate the Wyckoff positions of the latticesites introducing cation monovacancies in the TC-DFT
calculation.
B(ps)
24c(ps) 16a(ps) 24d(ps)Lifetimes

162

274

239

233

[1] Y. Taira et al., Rev. Sci. Instrum. 84 (2013) 053305.
[2] K. Fujimori et al., Appl. Phys. Express 13 (2020)
085505.
[3] F. A. Selim et al., Results Phys. 5 (2015) 28.

55 3 Ⅲ02-

BL1U Sciences
Ⅲ -2. Materials

BL1U

LCS-gamma Induced Positron Annihilation Study for the Dynamics ofDefect Behavior in Bulk Materials

Ⅲ-2

F. Hori1, S. Araki1, K. Sugita2 and Y. Taira2

Department of Quantum and Radiation Engineering, Osaka Prefecture University, Sakai 599-8531, Japan
2
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
apparatus for tensile test. Figure 2 shows the results ofpositron lifetime and voltage change after stressapplied. The initial drastic change in stress is due toelastic deformation at a moment of stress apply, andthe subsequent slow increase is thought to be due tothe introduction of dislocations and hardening due toplastic deformation. After applying stress, positron
lifetime increased slightly but almost constant. Thischange corresponds to defect formation such as
dislocations and vacancies. However, that change did
not exactly match the stress change. Considering thatthe positron lifetime analysis is an average value, it isnecessary to do multi component defects analysis on
the positron data.

Fig. 1. Newly developed stress applying positron
lifetime in-situ measurement apparatus at BL1U.

7000
6000
5000
4000
3000
2000
1000
0

Voltage (mV)The behavior of hydrogen atoms is attracting
attention in a wide range of research fields such as
high-strength structural materials and hydrogenstorage materials. In such materials, hydrogen atom
diffuses and has various interaction with defects andsurface, consequently it is possible to make change theserious characteristic features. In particular, in the
corrosion process of high-strength materials underhigh pressure and chemically harsh environment, thepresence or absence of defects in the material isconsidered to have a great influence on the intrusionof hydrogen and oxygen and the interaction withconstituent atoms in the material. It has been almost
impossible to directly observe the atomic-level defects
behavior that occurs inside the material during
processes such as corrosion. This has been hamperedby the need for high-energy acceleration of charged
particles such as electrons, which are probes in various
analytical methods used for detecting defects at theatomic level, and high-energy X-rays. On the other
hand, positron annihilation methods are used defects
research in materials powerfully. In normal defects
research, a radioisotope (RI) and an accelerated slow
positron beam are generally used for positronannihilation experiments. The maximum energy ofpositron emitted from most standard positron sourceof 22Na is about 540 keV and almost positron beam isthe order of 100 keV so that possible research area isnear surface of materials. In order to investigate thedynamics of the internal defect behavior which is notpossible to detect without destructing the material,mega electron volts accelerated fast positron is neededor positron production in target materials is useful. By
utilizing high-energy gamma rays generated byinjecting a laser beam from the outside into theelectrons of the UVSOR synchrotron radiation storage
ring, positron experiments for detecting defectbehavior in bulk materials such as the latter become
possible. We have developed positron annihilation
Doppler broadening system using LCS gamma-beam
at NewSUBARU synchrotron facility and successfullymeasured defects in bulk materials [1]. However, thatbeam line was closed at 2020. In this study, we havedeveloped a device of in-situ measurement of positronannihilation lifetime while applying stress to bulk asample at UVSOR beam line BL1U as shown in Fig.
1. In this system, initial stress is applied for the sample
and left as it was. Stress is measured as a voltage fromthe load cell connected to the sample.
Fe sample, which is well annealed at 1073 K for 1 h
to remove residual defects, was mounted on thisPositron annihilation lifetime (ps)

1

120
110
100

before applying stress

0

2

4

6
time (h)810Fig. 2. Stress and positron lifetime change as a functionof time.
[1] K. Sugita, S. Miyamoto, M. Terasawa, A. Iwase, K.
Umezawa and F. Hori, AIP Conf. Proc. 2182 (2019)040007.

56 4 Ⅲ02-

BL1U

Ⅲ -2. Materials Sciences

BL1U

Effect of the Particle Size on the Positron Annihilation Lifetime
and Relative Intensity of CeO2 Nanoparticles
S. Dohshi1, K. Maeda1, Y. Taira2, H. Toyokawa3 and T. Hirade4

Osaka Research Institute of Industrial Science and Technology, Izumi 594-1157, JapanUVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
3
National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8568, Japan
4
Japan Atomic Energy Agency, Tokai 319-1195, Japan1

2

previously reported. Furthermore, as the particle size
decreases, the relative intensity of the longer lifetime
component (I2) of ca. 390 ps increases. The longer
lifetime component for CeO2 nanoparticles with aparticle size of 2.3 nm is found to be more than 90 %.
As particle size decreases, the ratio of surface to bulk
increases. The longer lifetime component of ca. 390 ps
observed in this experiment is dependent on theparticle size, suggesting the annihilation at the CeO2
surface. Theoretical calculations on the positronannihilation lifetime at CeO2 surface will be performedin the future.

Counts [arb. unit]

Recently, it has been reported that the presence ofoxygen vacancies in CeO2 catalysts affect theircatalytic activity such as automotive exhaust gas
purification, particulate matter and/or volatile organic
compound oxidation [1]. Therefore, it becomes more
and more important to analyze the presence and theconcentration of oxygen vacancies in CeO2 with highsensitivity.
Positron annihilation lifetime measurement is a
powerful tool for the detection of lattice defects such as
oxygen vacancies with high sensitivity. It was previously
reported that two lifetime components were observedfor CeO2 catalysts: shorter lifetime component of 170200 ps and longer lifetime component of ca. 400 ps [1].
Moreover, theoretical studies have estimated a positronannihilation lifetime of ca. 170 ps for the bulk of CeO2
without oxygen vacancies [2]. This lifetime is in good
agreement with the experimentally observed shorter
lifetime component. However, there is no theoreticalstudies about the longer lifetime component (ca. 400 ps),and various arguments such as annihilation in oxygen
vacancy clusters or at the surface have been
experimentally made about this lifetime component.
In this study, positron annihilation lifetimes of CeO2
catalysts with different primary particle sizes were
measured to discuss the longer lifetime component in
the positron annihilation for CeO2 catalysts.
The particle sizes, which calculated from XRD
analysis, of CeO2 nanoparticles used in this experimentwere 2.3 nm, 9.3 nm, 18.3 nm, and 26.7 nm, respectively.
We have set up a gamma-ray spectroscopy system at thelaser-Compton scattering (LCS) beamline of BL1U at
UVSOR-III [3], and measured the lifetime of theannihilation gamma-rays at room temperature using
BaF2 scintillation detector. We used the software
Lifetime9 (LT9) to analyze the spectra.
Figure 1 shows the positron annihilation lifetime
spectrum of CeO2 nanoparticle with a particle size of
2.3 nm. As shown in Fig. 1, this spectrum could be
fitted with two lifetime components; ca. 155 ps (τ1)
and ca. 390 ps (τ2). The positron annihilation lifetimes(τ1 and τ2) and relative intensities (I1 and I2; I2 = 100 –I1) analyzed using LT9 for CeO2 nanoparticles withdifferent particle sizes are listed in Table 1. Twolifetime components of ca. 170 ps and 390 ps wereobserved for all CeO2 nanoparticles. The shorter
lifetime component of ca. 170 ps is considered to beannihilation in the bulk of the CeO2 nanoparticles, as

10

4

10

2

10

0

0

1

2
Time [ns]34Fig. 1 Positron annihilation lifetime spectra of CeO2
nanoparticles with a particle size of 2.3 nm.
Table 1 Positron annihilation lifetime and relative
intensity of CeO2 with different particle size.
particle size
2.3 nm
9.3 nm18.3 nm26.7 nmτ1 [ps]155.0 ±17

τ2 [ps]388.2 ±1.5174.7 ±4.6176.7 ±7.8386.3 ±3.1
388.0 ±30

188.0 ±30408.0 ±21l2 [%]
93.5 ±0.785.1 ±5.966.3 ±1.153.6 ±4.0[1] X. Liu et al., J. Am. Chem. Soc. 131 (2009) 3140 .
[2] B. Barbiellini et al., Phys. Rev. Lett. 114 (2015)
147401.
[3] Y. Taira et al., Rev. Sci. Instr. 84 (2013) 053305.

57 5 Ⅲ02-

Ⅲ-2

BL2A Sciences
Ⅲ -2. Materials

BL2A

Mo LIII-Edge XANES Study of Highly Active MoCx Species in Mo-V
Modified H-MFI Catalysts for Methane Dehydroaromatization
K. Kuramochi1, R. Yamazaki1, Y. Sonobe3, Y, Uchimura2 and H. Aritani2,3Advanced Science Research Laboratory, Saitama Institute of Technology, Fukaya 369-0293 Japan
2
Graduate School of Engineering, Saitama Institute of Technology, Fukaya 369-0293 Japan
3
Faculty of Engineering, Saitama Institute of Technology, Fukaya 369-0293 Japan
Mo/V=40 (react. time.)
0 min.
5 min.
60 min.
105 in.
185 min.
-Mo2C (ref.)Mo metal (ref.)1.0

TEY (Normalized)

Ⅲ-2

For direct conversion from natural gases to usefulpetroleum compounds, innovative GTL (Gas To Liquid)catalysts are called for. A molybdenum- modified HMFI zeolite (Mo/H-MFI) catalyst is a typical MTB(Methane To Benzene; 6CH4 → C6H6 + 9H2) catalyst
with high activity for methane dehydroaromatization,
which is a noted GTL process. Over the Mo/H-MFI
catalysts, definite deactivation due to coke deposition
has been a serious problem for enhancement of MTB
reactivity, and thus, clarification of the deactivation
process over the catalysts is one of the important points.
A cause of the deactivation strongly depends on bothcoke deposition onto strong acid sites over H-MFI andstructural deactivation of carbonized Mo species. Oneof the most important subjects for catalytically highand durable activity is the elucidation of active Mocarbide sites. In this study, Mo LIII-edge XANES isapplied to characterize the active MoCx species on
Mo/H-MFI and Mo-V co-modified H-MFI.[1]Mo(5 wt%)/H-MFI (Si/Al2=23) and Mo-V/H-MFI(Mo/V=10-40) catalysts were prepared as describedin the previous paper.[2] The methane dehydroaromatization reactivity was evaluated at 1023 K. Mo
LIII-edge XANES spectra were obtained in BL2A of
UVSOR-IMS in a total-electron yield mode using InSb
double-crystal monochromator. A REX-2000 (Rigaku)
software was used for normalization of each XANES
spectra.
At Mo/V=40, maximum durability for catalytic MTB
reactivity was shown at 1023 K. For LIII-edge XANES
spectra over Mo-V/H-MFI catalysts as shown in Fig. 1,
deeply carbonized Mo species due to MoCx (x > 0.5) areformed. On the time course of the MTB reaction over
Mo-V/H-MFI (Mo/V=40), decrease of edge energy due
to rapid carburization of Mo ions is revealed in theinitial step. At 60 min., the catalytic MTB reactivity was
shown. After 105 min., the energy value relatively
approached the -Mo2C. Because deactivation of MTB
was shown after 60 min., the structural change due toformation of -Mo2C like species can be assigned thedecrease of active MoCx sites. The rate of deactivation
reduced by V co-modification, and thus, inhibition ofexcess carbonization by V co-modification is proposed.
The result is likely to relate to a suppression effect ofdeactivation. For stabilize the active MoCx species, V
co-modification is effective on Mo/H-MFI catalysts.

0.5

0.0
2520

2525
2530
Energy / eV

2535

Mo-V/H-MFI(23)V-free
Mo/V=40
Mo/V=10
-Mo2C (ref.)Mo metal (ref.)1.0

TEY (Normalized)

1

0.5

0.0
2520

2525
2530
Energy / eV

2535

Fig. 1. Mo LIII-edge XANES spectra of Mo-V/H-MFI(Si/Al2=23) [top] and the Mo/V=40 on the time courseof MTB reaction [bottom] at 1023 K. The references,
-Mo2C and Mo metal, are also shown in each figure.
Table 1. Edge energy values obtained by 1stderivatives of LIII-edge XANES (shown in Fig. 1).
Mo-V/H-MFI (React. 185 min.) Mo-V/H-MFI (Mo/V=40)
Catalyst

V-free
Mo/V=10
Mo/V=40
 -Mo2C
Mo Metal

Edge Energy/ eV2520.92520.72520.92521.02520.2Time onEdge Energy
Stream / min.
/ eV

0
5
60
105
185

2522.02520.72520.62520.92520.9[1] H. Aritani et al., UVSOR Activity Report 2020 48(2021) 57.; H. Aritani et al., UVSOR Activity Report2019 47 (2020) 50.
[2] H. Aritani et al., J. Environm. Sci. 21 (2009) 736.

58 6 Ⅲ02-

BL2A

Ⅲ -2. Materials Sciences

BL2A

Evaluation of the Electronic State of MgO by NEXAFS Spectroscopy
E. Kobayashi1, K. K. Okudaira2, S. Yoshioka3 and A. Inoishi4

Kyushu Synchrotron Light Research Center, Tosu 841-0005, Japan
2
Chiba University, Chiba 263-8522, Japan
3
Graduate School of Engineering, Kyushu University, Fukuoka 819-0395 Japan
4
Institute for Materials Chemistry and Engineering, Kyushu University, Kasuga 816-8580, Japan
1

Magnesium oxide (MgO) is used in various fields
such as catalysts, electrical insulator and heat-resistantmaterials. In the development of organic solar cells,
the introduction of a metal oxide layer improved
functionality and efficiency [1]. For example, an MgO
nanolayer is used as the electrode [1-3]. Therefore, it
is important to evaluate the electronic state of the
produced metal oxide.
We have been studying using Near-edge X-ray
absorption fine structure (NEXAFS) spectroscopy as amethod for evaluating electronic states. Usually, thespectrum is carried out by the electron yield (EY)
method and the fluorescence yield (FY) method. The
EY method is a surface-sensitive method, and the FY
method is a bulk-sensitive method.
In this paper, we investigated how the presence of
defects changes the electronic states of the metal oxidesurface and bulk.
The sample is MgO powder. Samples with defects
were prepared by mechanically crushing. NEXAFS
spectra of the MgO powders were measured at thebeamline 2A of the UVSOR in the Institute of
Molecular Science. For TEY, the drain current fromthe sample was measured. For PFY fluorescence Xrays were collected using an energy dispersible silicon
drift detector (SDD). All experiments were performedat room temperature.
Figure 1 shows the Mg K-edge NEXAFS spectra of
MgO powder obtained from TEY. The black line is theuntreated sample and the red line is the defective
sample. The overall shape of the NEXAFS spectrum
is very similar. The inset is an enlargement of the risingedge of the spectrum. The rise of the spectrum of
defect MgO shifted to the low energy side. This is dueto the presence of reduced MgO.
Figure 2 shows the Mg K-edge NEXAFS spectra of
MgO powder obtained from PFY. The black line is theuntreated sample and the red line is the defective
sample. The overall shape of the NEXAFS spectrum
is very similar, but distorted by defects. The risingedge of the spectrum is shifted to the low energy side
due to the defect, but it is smaller than that obtained by
TEY.
The NEXAFS results obtained by the TEY method
showed little difference between the untreated andcrashed samples. On the other hand, the NEXAFS
results obtained by the PFY method differed significantly.
Since the mechanical crashing was done in theatmosphere, the defects formed on the surface arechemically unstable and quenched. On the other hand,the defects inside the powder are retained.

Ⅲ-2

Fig. 1. Mg K-edge NEXAFS spectra of MgO byusing TEY.

Fig. 2. Mg K-edge NEXAFS spectra of MgO byusing PFY.

[1] H. J. Bolink, H. Brine, E. Coronado, and M.
Sessolo, J. Mater. Chem. 20 (2010) 4047.
[2] J. Ma, G. Yang, M. Qin, X. Zheng, H. Lei, C. Chen,
Z. Chen, Y. Guo, H. Han, X. Zhao, and G. Fang, Adv.
Sci. 4 (2017) 1700031.
[3] I. Ierides, I. Squires, G. Lucarelli, T. M. Brown,
and F. Cacialli, J. Mater. Chem. C 9 (2021) 3901.

59 7 Ⅲ02-

BL2A Sciences
Ⅲ -2. Materials

BL2A

Sintering Behavior of Mg-Doped Hydroxyapatite Nano Particles
H. Murata, R. Kawanabe and A. Nakahira

Department of Materials Science, Osaka Prefecture University, Sakai 599-8531, Japan

Ⅲ-2

Hydroxyapatite (HAp) is a main inorganic componentof human bones and teeth. It has good biocompatibility
and thus it is used as materials for artificial bones andteeth. HAp in human bodies is not pure but contains
various kinds of impurities. They affect properties of
HAp such as solubility in water, mechanical strengthand so on.
Artificial HAp was commercially available in various
forms, powders, granules, pastes and sintered bodies.
Doping into HAp have been attempted to control
properties of HAp. However, some dopants induce Ca
deficiency [1], which cause high-temperature instability.
In this study, local environment of Mg in hydroxyapatitewere investigated by X-ray absorption near edge
structure (XANES) to reveal their effects to sintering.
Mg-doped HAp (Mg-HAp) samples were preparedby the solution-precipitation method. Starting materials
were 0.10 mol/L of Ca(NO3)2 and (NH4)2HPO4 aqueous
solutions. The initial Ca/P molar ratio were set to 2.0,
which is larger than that of stoichiometric HAp, toprevent formation of Ca vacancies. The (NH4)2HPO4
aqueous solution was dropped into the Ca(NO3)2
aqueous solution under Ar atmosphere. Then, thesolution was sealed in a PFA bottle and it was matured
at 37 °C in a water bath for 72 h. After maturing,
samples were washed by ion-exchanged water, filtrated
and dried at 50 °C. A parts of samples were pressed into
pellets and sintered at 1000 °C for 6 h.
Samples were characterized by powder X-ray
diffraction (XRD), inductively coupled plasma opticalemission spectrometry (ICP-OES) and XANES. MgK XANES were collected at BL2A in UVSOR by thepartial fluorescence yield method using a silicon drift
detector. [2] Samples were mounted on a metal plateusing carbon tapes.
The XRD pattern of as-dried samples can be assigned
to that of hydroxyapatite. Although stoichiometric HAp
were obtained in the present condition, (Ca+Mg)/P
molar ratio of Mg-doped samples was smaller than thatof HAp, 1.67. This indicated that Mg2+ in HAp are also
associated with Ca vacancies and excess H [1].
Figure 1 shows Mg-K XANES of the samples. The
spectrum of the sintered Mg-HAp has different featuresfrom that of as-dried Mg-HAp. The peak A and C showsformation of MgO. The shoulder D can be assigned to
Mg-doped β-TCP. Therefore, Present Mg-HAp werepartially decomposed to MgO and β-TCP during
sintering. Since non-stoichiometric HAp are partiallydecomposed to CaO or β-TCP at 1000 °C [3], the low(Ca+Mg)/P molar ratio of the samples also cause thedecomposition. Therefore, Mg-HAp and CaCO3 weremixed to compensate lack of (Ca+Mg)/P molar ratio

and they were sintered. However, its Mg-K XANES
spectrum has the same features to that of MgO. This
result means Mg2+ are ejected from HAp during sintering.
High-temperature instability of Mg-HAp are not due tolow (Ca+Mg)/P molar ratio but fundamental character.

Fig. 1. Mg-K XANES of (a) as-dried and (b) sintered
Mg-HAp and (c) Sintered samples of mixture MgHAp and CaCO3, respectively. Spectra of MgO andMg-doped β-TCP were also shown as references.

[1] K. Matsunaga et al., Acta Biomater. 6 (2010) 2289.
[2] H. Murata, T. Taniguchi and T. Yamamoto, UVSOR
Activity Report 2013 41 (2014) 56.
[3] K. Shitara et al., J. Asian Ceram. Soc. 2 (2014) 64.

60 8 Ⅲ02-

BL2A

Ⅲ -2. Materials Sciences

BL2A

Local Structure around Mg in Mg1-xNixAl2O4
S. Yoshioka 1, K. Yasuda1, S. Matsumura1, E. Kobayashi2 and K. Okudaira3

Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka 819-0395, Japan
2
Kyushu Synchrotron Light Research Center, Tosu 841-0005, Japan
3
Graduate school of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan

Spinel oxides with the general formula AB2O4 can beformed with various kinds of divalent A and trivalent B
cations. Owing to their unique mechanical, electronic,
and magnetic properties, the spinel oxides have gained
considerable attention not only from the fundamental
research fields but also from the industrial application
point of view. Some spinel compounds accommodate alarge degree of cationic disorder. The cationic disordering
naturally affects the structural properties of the spinels.
For example, magnesium aluminate (MgAl2O4) andnickel aluminate (NiAl2O4) spinels are generally known
as normal and inverse spinel structures, respectively.
However, their inversion degrees for synthetic specimens
were also reported to be fluctuating between 0 and 1,
respectively, due to the cationic disordering. Recently,
the structure of Mg1-xNixAl2O4 was reported using
neutron total scattering to understand the cationicdisordering process [1]. X-ray absorption spectroscopy(XAS) is a powerful structure characterization methodthat uses an X-ray probe to reveal local atomic
coordination and electronic structures. In this study, we
focus on the local structures in MgAl2O4–NiAl2O4 solid
solutions, particularly cationic-disordered structures.
The polycrystalline samples of Mg1-xNixAl2O4 (x =0.0, 0.05, 0.2, 0.5, 0.8, 1.0) were synthesized by a solidstate reaction. They were sintered in air at 1300 ºC for
10 h followed by furnace. Mg and Al K-edge XANES
measurements were performed on BL2A beamline at
UVSOR Synchrotron Facility, Okazaki, Japan, using
the partial fluorescence yield method. A KTiOPO4
double-crystal monochromator gives Mg and Al Kabsorption edges in the energy regions 1290–1340 eV
and 1540–1610 eV, respectively. The measurements of
Mg and Al K-edge XANES spectra were carried out invacuum at a pressure and temperature of 1×104 Pa and
20 ºC, respectively. Fluorescence X-rays of Mg Kα andAl Kα were collected utilizing an energy-dispersible
silicon drift detector.
The Mg K-edge XANES spectra for Mg1-xNixAl2O4
are shown in Fig. 1 with the composition values x = 0,0.05, 0.2, 0.5, and 0.8. The intensity of each spectrum
was normalized to a value of 1 at the photon energy of1335 eV after the removal of the background intensity.
All the Mg K-edge XANESs show similar spectra andno significant energy shifts or relative intensity changes
at the major peaks are observed. It suggests that the local
structure of Mg remains unchanged for the whole
composition range of Mg1–xNixAl2O4, whereas the Mg
concentration changes with respect to x.

Mg K-edge

x=0.80Intensity (arb. units)1

x=0.50x=0.20x=0.05

MgAl2O4

1300

1310

1320

1330

Photon energy (eV)Fig. 1. Mg K-edge XANES spectra of Mg1-xNixAl2O4.

[1] E. O’Quinn et al., J. Am. Chem. Soc. 139 (2017)
10395.

61 9 Ⅲ02-

Ⅲ-2

BL2A Sciences
Ⅲ -2. Materials

BL2A

Local Structure Investigations of Zn in ZnAl2O4 Induced on Swift Heavy
Ion Irradiations
S. Yoshioka1, K. Yasuda1, S. Matsumura1, E. Kobayashi2 and K. Okudaira3

Department of Applied Quantum Physics and Nuclear Engineering Kyushu University, Fukuoka 819-0395, Japan
2
Kyushu Synchrotron Light Research Center (SAGA-LS), Tosu 841-0005, Japan
3
Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan

Ⅲ-2

Zinc aluminate oxide (ZnAl2O4) is one of thecommon spinel compounds. Since it shows a variety
of interesting physical and chemical properties, its
microstructure has been extensively investigated. A
cationic disordered ZnAl2O4 spinel is represented by
the formula of [Zn1–xAlx](ZnxAl2–x)O4, where thesquare brackets and the parentheses denote thetetrahedral and octahedral sites, respectively. The
variable x is called the inversion parameter, whichquantifies the cation disorder. Radiation with swift
heavy ions (SHIs) interacts with materials and causes
the structural change. It is therefore applied to material
processing, modifications, etc. SHI irradiation provides
high energy deposition through electronic stopping to
the materials. SHIs in insulating solid materials are
known to leave trails of damage along the ion pathwith a diameter of several nanometers. Structuralchange related to the cationic disorder has been also
observed in ZnAl2O4 with SHI irradiation usingtransmission electron microscopy observation. In thisstudy, we clarify local coordination of each cation
element, on which we conducted synchrotron radiationbased X-ray analysis.
Sintered ZnAl2O4 samples with the shape of 10 × 4 ×
0.5 mm were used in this study. These specimens were
irradiated with 340 MeV Au ions to fluences of 1 × 1012
cm-2 at the H1 beamline of the tandem ion accelerator
facility in the Japan Atomic Energy Agency (JAEA)Tokai. At the beginning of each paragraph, two spacecharacters should be inserted as an indent. Zn L2,3-edge
and Al K-edge XANES measurements were performedat the BL2A beamline of UVSOR Okazaki, Japan, using
the partial fluorescence yield method (PFY). A
Be3Al2Si6O18 (beryl) double-crystal monochromatorgives Zn L3-edge in energy regions 1000 -1070 eV. In
the cases of Al K-absorption edges, a KTiOPO4 doublecrystal monochromator scanned the energy region
1540–1610 eV. The samples were set with their surface
perpendicular to the incident X-ray beam. Fluorescence
X-rays of Zn Lα and Al Kα were collected using anenergy dispersible silicon drift detector (SDD). All
measurements of XANES spectra were carried out invacuum of 1 × 10–5 Pa at room temperature.
The XANES spectra with the Zn L3-edge are shownin Fig. 1 for the ZnAl2O4 samples before and after
irradiation with 340 MeV Au ions at fluences ranging
from 1 × 1011 to 1 × 1012 cm−2. The intensities of spectra
were normalized to a value of 1 at 1055 eV for Zn L3edge, after the removal of background intensities. As

shown in Fig. 1, Zn L3-edge XANES of the pristine
ZnAl2O4 sample shows fine structures such as peaks A
to H. The Zn L3-edge XANES of the ZnAl2O4 samples
have not changed drastically from that of the pristine
sample even with high fluence irradiation. However, theintensities at the peak B were decreased and spectral
shape between the peaks F and G as indicated an arrow
were slightly changed with increasing of the ion
fluences.

ZnAl2O4
1×1012 cm-2

Intensity (arb. units)

1

1×1011 cm-2

I
B

CD E

F

GH
pristine

A

1020

1030

1040

1050

Photon energy (eV)Fig. 1. Zn L3-edge XANES spectra of pristine andirradiated ZnAl2O4 with 340 MeV Au ions to fluencesof 1×1012 cm-2.

62 10 Ⅲ02-

BL2B

Ⅲ -2. Materials Sciences

BL2B

UPS Spectroscopy of TFP Doped P3HT/PCBM Thin Films
K. K. Okudaira and Y. Hoshi

Chiba University, Chiba 263-8522, Japan

Valence top region

Cutoff region
Intensity (arb. units)

(b)

(a)

TFP 7wt%
TFP 5wt%
TFP 0wt%

24

23.5

2

1

0

Binding energy (relative to EF) (eV)Fig. 1. UPS of secondary electron cutoff (a) andvalence top (b) region at hν = 28 eV for P3HT/PCBM
thin film with various TFP doping level.

TFP 5%

Intensity (arb. units)

Organic solar cells (OSC) based on blends ofpolymers and fullerence derivatives are promising
candidates for new renewable resource. However, thepower conversion efficiency of OSC is low forcommercial use. A bulk hetero-junction structurecomposed of poly (3-hexylthiophene (P3HT) anddphenyl-C61 -butyric-acid-methyl ester (PCBM)
showed an improvement of the efficiency. To achieve
higher efficiency, it is necessary to improve the excition/
charge transport. Recently, it was reported that byincorporating additives (i.e. doping) such as
tetrafluorophthalnitrile (TFP), P3HT/PCBM system
obtain high conversion efficiency [1]. In this study weobserved photon- energy dependent photoemission of
TFP doped P3HT/PCBM thin film to estimate thechange of the electronic structure.
Photoemission measurements were performed at thebeam line BL2B of the UVSOR storage ring at theInstitute for Molecular Science. Incident photon
energies of 28 eV 40 eV, and 90 eV were used. Incident
angle of photon and take-off angle of photoelectron are
60° and 0° with respect to surface normal, respectively.
At first RR-P3HT (Mn ~ 40000) was dissolved with
0.1wt% in chlorobenzene, followed PCBM adding
with weight ratio of 1:0.9 to P3HT. TFP with 5 wt%
and 7 wt% were then added to the P3HT/PCBM
solution, followed by stirring for 30 min. at 50 °C. The
solution consisting of P3HT/PCBM with or without
TFP was spin-cast on the cleaned ITO substrate.
Figures 1 (a) and (b) show the measured UPS spectraof the secondary electron cutoff and valence top region,
respectively. By TFP doping valence band top is shifted
to Ef about 0.2 eV. It is expected that the gap statesdevelop due to polaron and/or bipolaron onpolythiophene chains of P3HT by TFP doping [2].
Figure 2 shows the measured UPS spectra at hν = 28 eV,
40 eV and 90 eV. In the UPS at hν = 90eV, the relative
intensity of the peak at binding energy (EB) of 6.5 eV islarger than those at hν = 40 eV and 28 eV. By considering
the photoionization cross-section of S 3p and C 2s and2p [3], the peak at EB of 6.5 eV can be assigned to theπ state included S 3p orbital in thiophene ring. The
photon-energy dependent photoemission can provide
the precise information on the electronic structure.

hv=90eV

hv=40eV

hv=28eV

15

10

5

0

Binding energy (relative to EF) (eV)Fig. 2. photon-energy dependent photoemission of
P3HT/PCBM thin film with 5 wt% TFP doping level.

[1] S. Jeong et al., J. Nanosci. Nanotechnol. 14 (2014)9219.
[2] M. Lögdlund et al., Phys. Rev. Lett. 23 (1989) 1841.
[3] J.–J. YEH, Atomic Calculation of Photoionization
Cross-sections and Asymmetry Parameters, (Gordon
and Breach Science Publishers) (1993).

63 11 Ⅲ02-

Ⅲ-2

BL2B,Sciences
BL7U
Ⅲ -2. Materials

BL2B, BL7U

Valence and In-gap states of a Polyethylene Model Oligomer, C44H90, Film
Studied by Conventional and High-Sensitivity Photoelectron Spectroscopy
1

Ⅲ-2

R. Nakazawa1, M. Yoshizawa1, S. Kera2 and H. Ishii1,3,4

Graduate School of Science and Engineering, Chiba University, Chiba 263-8522, Japan
2
Institute for Molecular Science, Okazaki 444-8585, Japan,
3
CFS, Chiba University, Chiba 263-8522, Japan
4
MCRC, Chiba University, Chiba 263-8522, JapanThe electronic structures of materials are a key tounderstand and control the nature of materials. Not only
their highest occupied molecular orbital (HOMO) but
also weak density-of-states (DOS) in the energy gap has
been focused to discuss the practical electric properties.
Our research group has been developing high-sensitivity
photoelectron spectroscopy (HS-UPS) which enables todirectly probe such in-gap states of organic materials[1,2]. Recently, we have applied constant final state
photoelectron yield spectroscopy (CFS-YS) to organicand inorganic materials, and a very weak in-gap states
whose density is less than 10-6 of HOMO [3]. The
observed in-gap states are believed to be in relation todefect and disorder of the films. However, the origin of
in-gap states is still open question. To qualify the natureof the wave function of the in-gap states, photoelectron
spectroscopy using synchrotron radiation (SR) is suited
because of photon energy tenability and polarizabilityof light, although conventional SR light includes strayphotons to increase background intensity, leading to low
sensitivity. BL7U has a unique advantage that highsensitivity measurement is enable for less than 10 eV
photon energy. We can expect that photon energy
dependence and angular dependence of photo electron
could give a hint to identify the wave function of in-gap
states. In this study, a model compound of polyethylene,
tetratetarcontane (TTC, C44H90) was investigated toclarify the valence and in-gap states by using BL2B
(conventional UPS), BL7U(HS-UPS), and CFS-YS at
Chiba University. Polyethylene is a basic polymer andapplied to various products mainly as insulator. It is alsointeresting in relation to triboelectricity. The clarificationof in-gap states is useful to understand its insulating
nature.
TTC film was prepared by vacuum vapor deposition
on an ITO-coated glass substrate, and the film thickness
was 20 nm. The CFS-YS measurement was performed
at Chiba University. SR measurements were performed
at BL2B and 7U at UVSOR.
Figure 1 shows the UPS of TTC films for hν=120
eV@BL2B and 21.2 eV@Chiba U. The horizontal axis
is the ionization energy relative to the vacuum level.
The onset in 21.2 eV spectrum locates around 9 eV,
which is consistent with the reported value of 8.9 eV [4].
The onset region is enhanced for 120 eV spectrum
because of hν dependence of photo- ionization crosssection of the HOMO, giving the onset around 7.5 eV,
consistent with our CFS-YS results in the inset of Fig.
1. This result suggests that the reported ionizationenergy should be updated.
Figure 2 shows the results of HS-UPS at BL7U for
TTC film with and without anneal. The valence top
region in the figure exhibited the intensity difference.
Blue spectrum gives more intensity than red one,suggesting that the in-gap states seems to be reduced bydecreasing the degree of disorder due to annealing. The
obtained spectrum is compared with our CFS-YS result
as shown in the inset. The both spectra are very similar,
demonstrating the feasibility of high-sensitivity
measurement at BL7U. The angular dependence ofthe photoelectrons from the in-gap states (1 to 3 eV in
the binding energy in Fig. 2) were isotropic. Now weare going to check the photon energy dependence tosqueeze the information about the wave function natureof the in-gap states.

Fig. 1. UPS spectra of the TTC film for hν= 21.2 and120 eV. The inset shows CFS-YS curve (black dots).

Fig. 2 HS-UPS spectra of TTC film with and without
anneal. (The inset: CFS-YS result)[1] F. Bussolotti, J. Elect. Spec. Relat. Phenom. 204(2015) 29.
[2] T. Sato et al., Appl. Phys. Express 10 (2016) 011602.
[3] R. Nakazawa et al., Appl Phys Express 14 (2021)
071004.
[4] K. Seki et al., Chem. Phys. 105 (1986) 247.

64
III 02- 12 -BL3U

Ⅲ -2. Materials Sciences

BL3U

Structure Analysis on Helical Nanofilament of B4 Phase of Bent-core
Liquid Crystals Mixed with Rod-like Cholesteric Liquid Crystals by
Resonant Soft X-ray Scattering (RSoXS) at UVSOR
Y. Takanishi1, F. Araoka2 and H. Iwayama3,4Faculty of Science, Kyoto University, Kyoto, 606-8502, JapanRIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan1

2

Due to the new intermolecular interactions, frustrationand competition, soft matter is expected to have a new
structure and new functionality. Liquid crystal istypical one of soft matter, and it exhibits various mesophases due to such an effect. For example, bent-coremolecules show unique liquid crystalline phases called
B1~B8. The B4 phase was the lowest temperaturephase observed in the bent-core liquid crystals, and it
shows spontaneously chiral separated domains despiteof achiral molecules. After various experimental
results, it is found that this phase forms a nano-helicalstructure.
Recently one of authors (YT) studied the binary
system between a rod-like cholesteric liquid crystal(CLC) mixture and a bent-core liquid crystal showing
a B4 phase [1]. The structure of the binary systemcomposed of rod-like cholesteric liquid crystal
mixture and bent-core molecules was analyzed inorder to confirm whether nano-scale phase separation
as observed in the 5CB – P-8OPIMB binary system isformed. As a summary, a new smectic structure that
does not appear in only constituent molecules withwide temperature range was unexpectedly discovered.
This structure seems to be fundamentally composed ofrich concentration of rod-like molecules. On the other
hand, there remains an open question with respect tothe effect of the nano-helical filament of B4 phaseformed by the bent-core liquid crystal.
In resonant X-ray scattering, using X-ray whoseenergy is coincident with a certain atom absorption
edge, the structure factor becomes a tensor instead of
the scalar in conventional X-ray diffraction. Recently,
carbon K-edge resonant scattering has been applied to
study, and successful in obtaining the precise
structures of polymer blends, block copolymer, andliquid crystals. In this study, we report the local nanostructure analysis of B4 nano-helical filament using
resonant soft-X-ray scattering (RSoXS) technique.
Concentration dependence of rod-like molecules andtemperature dependence were measured, and themixing effect on the helicity and correlation of B4
nano-helical filament are discussed.
The experiment was performed at BL3U of UVSOR.
For the measurement, a new vacuum chamber for small
angle measurement was fabricated. Used achiral bentcore liquid crystal was P-8OPIMB, and a rod-likecholesteric liquid crystal (CLC) mixture was composedof a nematic mixture (ZLI-2293, Merck) doped with achiral rod molecule (MLC-6248, Merck). Samples usedwere filled in the isotropic phase between two pieces of
100 nm-thick Si3N4 membranes (NTT-AT). The
scattering was detected by CCD (ANDOR DO940PBN). Incident X-ray beam was tuned between 270~300
eV. Typical RSoXS image was shown in Fig.1, and in
this compound, carbon K-edge energy was 285.5 eV.
Figure 2(a) shows chirality concentration dependenceof helical half pitch of B4 phase. By mixing CLC
mixture, half pitch of nano-helical filament decreases
from ca.120 nm to ca.80 nm, but pitch is independent ofchirality. Figure 2(b) shows correlation length as afunction of chirality concentration of CLC. Correlation
length of mixtures is about three times longer than thatof pure P-8OPIMB, and slightly increases withincreasing the chiral dopant concentration. It suggeststhat helical pitch of the nano filament of bent-coremolecules rich region is spatially homogeneous due tothe influence of the rod-like molecule rich region.

Fig. 1. Typical 2D RSoXS image from the helicalnano-filament of the B4 phase.
(a)

(b)

Fig. 2. half pitch (a) and its correlation length (b) as afunction of chiral dopant concentration.

[1] Y. Takanishi, Soft Matter 17 (2021) 563.

65
III 02- 13 -Ⅲ-2

BL3B Sciences
Ⅲ -2. Materials

BL3B

Evaluation of Fluorescence Lifetimes of Wavelength Shifting Fibers
for High-energy Particle Experiments
K. Shintate, R. Abe, R. Ishiyama, T. Naitou, S. Nakamura, S. Sakano, J. Ohashi, Y. Tajima
and H. Y. Yoshida
Department of Physics, Yamagata University, Yamagata 990-8560, Japan

Ⅲ-2

Recently, operation of particle detectors at higher
counting rates has been required in a high-energy
physics experiment. To satisfy this requirement,
scintillators used in particle detectors need to have ashort fluorescence lifetime to allow fast time response.
For this purpose, we measured fluorescence spectra anddecay curves of newly developed wavelength shifting
fibers for the future project of neutral kaon rare decay
experiment [1]. The fluorescence decay curves were
measured by using light pulses from visible to near
ultraviolet under single bunch operation, which enables
a time-correlated single-photon counting.
Figure 1 shows the decay curve of a wavelength
shifting fiber Y-11 for the 500 nm band under excitation
at 424 nm at room temperature. The blue lines indicate
experimental data. The lifetime was analyzed by using
the data analysis framework ROOT [2].
We assumed that the obtained decay curves are
fitted with the formuladata. The fluorescence lifetimes of Y-11, YS4 and YS6,
determined from our analyses, are summarized in Table
1.

Fig. 1. Decay curve of Y-11 measured at room
temperature under excitation at 424 nm obtained forthe 500 nm photoluminescence band.

�𝐼𝐼�𝑡𝑡� � � 𝑃𝑃�𝑡𝑡 � �𝜃𝜃�𝑡𝑡 � � 𝑇𝑇� �𝐺𝐺�𝑡𝑡 � 𝑡𝑡 � � 𝑑𝑑𝑑𝑑 � ,

where

and

��

�

𝑡𝑡
𝑃𝑃�𝑡𝑡� � � 𝐴𝐴� exp �� �,
𝜏𝜏�
���

�

(� � 1, 2, 3 and 𝐴𝐴� � 1)

𝐺𝐺�𝑡𝑡 � 𝑡𝑡 � � � � �� exp ������𝑡𝑡 � 𝑡𝑡 � � �� ��
�.
2𝜎𝜎��

(� � 1, 2)𝐼𝐼�𝑡𝑡� represents the observed decay curve, and 𝑃𝑃�𝑡𝑡�
represents the true fluorescence decay curve. If the true
decay curve is composed of multiple components, it isdescribed as the linear combination of exponential
decay functions with the parameters of lifetime 𝜏𝜏� andinitial intensity 𝐴𝐴� . 𝜃𝜃�𝑡𝑡 � � 𝑇𝑇� � is a step function todecide the time origin 𝑇𝑇� . 𝐺𝐺�𝑡𝑡 � 𝑡𝑡 � � represents theresolution of the measurement system, the time
structure of the beam, and so on, and is given by a single
gaussian or a sum of two gaussians. The red line is thefitting curve which reproduce the experimental data.
The lifetime analyses of wavelength shifting fiber
YS4 and YS6 [3] were carried out by using the same
analysis method. The top of Fig. 2 shows the decay
curve of YS4 for the 500 nm band under excitation at
416 nm. The fitting curve reproduce the experimental

Fig. 2. Decay curves of YS4 (top) and YS6 (bottom)
measured at room temperature under excitation at 416
nm and 418 nm. The former and latter are obtained forthe 500 and 492 nm photoluminescence band.
Table 1. Fluorescence lifetimes of Y-11, YS4 and YS6,
determined from data analyses.
SampleλEX [nm]λEM [nm]τ [ns] (Ratio)

Y-11

424

500

6.44±0.00

YS4

416

500

1.37±0.00

YS6

418

492

1.27±0.00[1] J. Comfort et al., Proposal for 𝐾𝐾� → 𝜋𝜋 � 𝜈𝜈𝜈𝜈̅
Experiment at J-PARC (2006).
[2] R. Brun and F. Rademakers, Nucl. Instrum. Methods
Phys. Res. A389 (1997) 81.
[3] H. Nakamura et al., Europhys. Lett. 95 (2011) 22001.

66
III 02- 14 -BL3B

Ⅲ -2. Materials Sciences

BL3B

Thermoluminescence of LuAG Thick Film Scintillators Prepared via
Chemical Vapor Deposition Process
S. Matsumoto1, S. Kurosawa2,3 and A. Ito1

Graduate School of Environmental and Information Sciences, Yokohama National University,
Yokohama, 240-8501, Japan
2
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan3
New Industry Creation Hatchery Center (NICHe), Sendai 980-8579, Japan1

Scintillators are phosphor materials with conversion
ability from radiation such as X-rays, γ-rays, and αparticles into UV–visible photons [1]. Scintillators
have been used as radiation imaging systems coupledwith photon detectors such as position-sensitive CCD.
Recently, radiation imaging systems have been used infields including non-destructive testing, nuclear
medical imaging, and geological surveying [2–4].
Scintillator screens with excellent luminescence andemission wavelengths compatible with photon
detectors are required for radiation imaging. Tl+ doped
CsI films and Tb3+ -doped Gd2O2S (GOS) powder
phosphors are used as scintillator screens because of
their high luminescence yield and well-matchedemission band (500–800 nm) with CCD detectors [5].
Columnar and pixelated scintillators have beenutilized to improve light yield and spatial resolution.
Furthermore, thin scintillator screens of 10 μm or lesscan prevent light dispersion and are expected to be
used in microtomography techniques [6].
Lu3Al5O12 (LuAG)-based scintillator shows a highstopping power for radiation, excellent light yield, anda fast scintillation decay. Because of the excellent
hardness of LuAG, LuAG thick film with less than 10µm was hardly obtained via mechanical polishing.
Crystal growth from the vapor phase is a promisingprocess for the preparation of LuAG thick films.
However, the vapor-grown LuAG thick film was only
reported using the pulse laser deposition method, theresultant film was only 140 nm. In the previous work,
we have demonstrated the preparation of 5 µm-thickCe3+:LuAG films via a chemical vapor deposition
process at a high deposition rate [7]. The thick film
showed an excellent light yield and a fast decay timecompared with the Ce3+:LuAG grown single-crystal
by the melting-growth process. The reason for these
excellent scintillation properties is not well known.
Defect information is useful to explain the variation in
scintillation properties of crystals grown by different
methods. In this report, we have demonstrated thethermoluminescence (TL) properties for the sake ofobtaining the defects in the vapor-grown Ce3+:LuAG
thick film.
In BL3B of UVSOR facilities, we measured TL
properties from 18 K to 300 K (room temperature) for
vapor-grown Ce3+:LuAG film and melting-grownCe3+:LuAG single crystal. The crystals were irradiatedat 165 nm for 10 minutes at a low temperature of 14–18

K. After the irradiation, the sample temperature wasslowly raised and luminescence intensity was measured
the with a CCD detector.
The TL emission spectrum for the Ce3+:LuAG thickfilm at 220 K was similar to that for the Ce3+:LuAG
single crystal at 140 K as shown in Fig. 1 (a). Theseemission peaks were originating from 5d–4f transitionof Ce3+ ions. The TL glow curves of the thick film andsingle crystal are shown in Fig. 1 (b). The curve for the
single crystal had continuous emissions up to room
temperature while one peak was found at 140–150 K.
In contrast, the thick film had two bands at ~80 and
220 K in the curve. These TL results suggested thattypes and amounts of defects existed in the single
crystal scintillator were more and larger than those in
the film scintillator.

Fig. 1. (a) TL spectra and (b) glow curve of LuAG
thick film and LuAG single crystal.
[1] C.W.E. van Eijk, Phys. Med. Biol. 47 (2002) R85.
[2] D.R. Schaart et al., Phys. Med. Biol. 54 (2009) 3501.
[3] J. Glodo et al., Phys. Procedia. 90 (2017) 285.
[4] S. Yamamoto et al., Radiat. Meas. 115 (2018) 13.
[5] T. Yanagida et al., Radiat. Meas. 55 (2013) 99.
[6] T. Martin et al., J. Synch. Radiat. 13 (2006) 180.
[7] S. Matsumoto, A. Minamino, A. Ito, Sens. Mater. 33(2021) 2209.

67
III 02- 15 -Ⅲ-2

BL3B Sciences
Ⅲ -2. Materials

BL3B

Temperature Dependence of Photoluminescence Properties of Li2HfI6
2

Ⅲ-2

C. Fujiwara1, S. Kurosawa1,2 and A. Yamaji1

Insititute for Materials Research, Tohoku University, Sendai 980-8577, JapanNew Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579, Japan1

We have developed Cs2HfI6 (CHI) scintillator [1]for radiation monitoring in the Fukushima Daiichi
Nuclear Power Plant. CHI has an emission wavelengthof approximately 700 nm and light yield of 60,000
photons/MeV. Such a red emitting scintillator can be
attached to an optical fiber for use in remote radiation
monitoring [2]. However, CHI has low neutron
sensitivity, and neutron muttering is also required due
to nuclear debris including [3].
Most conventional neutron scintillators have anemission wavelength of 500 nm or less, and thesescintillation materials are not suitable for the remotemonitoring system with the optical fiber. We havedeveloped a neutron scintillator with red and infraredemission by replacing Cs in CHI with Li. Here, 6Li hasa large neutron capture cross section. In this study, wemeasured the temperature dependence of the luminescence
properties to estimate the band gap energy (Egap) andto discuss the luminescence mechanism.
A Li2HfI6 crystal specimen was synthesized by thevertical Bridgman growth method in our laboratory
using 99.9 %-pure LiI powders and 99 %-pure HfI4
powders. We measured the photoluminescence excitationand emission spectra at 15, 50, 100, 150, 200, 250, 300
and 350 K. Multi-Gaussian fit was operated on theobtained spectra to analyze emission bands.
Figure 1 show the photoluminescence excitationand emission spectra of Li2HfI6. At 15K, Li2HfI6 hadan emission band of ~660 nm. The photoluminescenceband stably existed from 15 K to 50 K. This emission
bands can be originating from charge transfer emission
or self-trapped exciton.
On the Other hands, Li2HfI6 had two emission bands
from 100 K to 250 K. The one band located at ~550 nm
was observed excited by ~305-nm photons. The otherband had the broad red emission peak at ~660 nm. At
The emission intensity of such bands gradually decreased
as temperature increase. No luminescence was observedat room temperature due to thermal quenching.
To determine the emission mechanism exactly, wemeasure the temperature dependence of decay time in
the future.

Fig. 1. Temperature dependence of photo-luminescence
spectra of Li2HfI6.

[1] S. Kodama, S. Kurosawa et al., Journal of Crystal
Growth, 492 (2018) 1.
[2] https://fukushima.jaea.go.jp/en/pamphlet/topics/
pdf/topics-fukushima070e.pdf.
[3] https://www.hitachi-hgne.co.jp/download/2017/2017news17_17-11-1a.pdf

68
III 02- 16 -BL3B

Ⅲ -2. Materials Sciences

BL3B

Reflectivity Spectra of Sm0.9Ca0.1S in Vacuum Ultra Violet Region
Y. Yokoyama1, K. Kishida1, F. Matsunaga1, M. Kanou1, K. Takano1, Y. Okamoto1,
H. S. Suzuki2, K. Takehana3, Y. Imanaka3 and K. Takenaka1
Department of Applied Physics, Nagoya University, Nagoya 464-8603, JapanThe Institute of Solid State Physics, The University of Tokyo, Kashiwa 277-8581, Japan
3
National Institute for Materials Science (NIMS), Tsukuba 305-0003, Japan1

2

spectrum of Sm0.9Ca0.1S also demonstrated an
appearance of the reflectivity dip around 40 meV,strongly suggesting further insulation by the Ca
doping. On the other hand, for the reflectivity spectrain the higher energy region (Fig. 2(b)), problems in thedata consistency remain. The reflectivity data above 5
eV must be reconsidered for precise discussion on thechanges in the electric state due to the Ca doping,whereas fine structures below 5 eV are reliable. To
elucidate the changes in the electronic states by thevalence transition induced by the electric field, it isnecessary to construct a measuring system that thereflectivity spectra in the wide energy region can becollected at the liquid nitrogen temperature and underthe electric field in the future.

 ( cm)

5

104
103
102
101
100
10-1
10-2
10

Sm1-xCaxS
0.10
x=0
0

100

200

300

400

Temperature (K)Fig. 1. Electrical resistivity of Sm1-xCaxS single crystals.

(b) 0.4

1
0.8
0.6
0.4
0.2
0

Sm1-xCaxS
x=0

295 K

0.10
0.01

0.1

1

Photon Energy (eV)

Reflectivity(a)Reflectivity

Samarium monosulfide (SmS), in which twoelectronic configurations (insulator (4f)6 and metal(4f)5(5d)1) of Sm energetically compete, is known asvalence fluctuation materials. The electronic state of
Sm undergoes the transition to (4f)5(5d)1 from the (4f)6state by applying pressure and chemical doping, while
the (4f)6 state is stable under ordinary pressure andtemperature condition [1]. It is promising to be applied
to materials for negative thermal expansion (NTE) andactuators by controlling these electronic states [2]since this phenomenon is accompanied by a large
volume change up to 10 %. To study changes in theelectronic states due to the valence transition, we
conducted systematic optical reflectivity measurementsof Sm1-xYxS single crystalline samples, covering wide
energy and compositional region [3]. It is clarified thata characteristic structure, which showed the changes
in electronic states induced by the valence transition,
became appeared in the optical spectra at Ycomposition of 0.28 [3]. For the application of theelectric-field-driven actuator, the changes in theelectronic state during the valence transition inducedby the application of the electric field must be studied.
It is also necessary that SmS can be applied electricfield enough to induce the valence transition.
In this work, we prepared a Sm0.9Ca0.1S singlecrystalline sample to enhance the insulation, andconducted the optical reflectivity spectral measurements
at room temperature at no electric field first. Normal
incident reflectivity spectra were collected at 295 K byusing a Fourier-type interferometer (0.005–1.6 eV)
and a grating spectrometer (1–3 eV) installed with amicroscope. For the measurements from visible to thevacuum-UV region (2–30 eV), we used synchrotron
radiation at BL3B of UVSOR, Institute for Molecular
Science.
Figure 1 shows the electrical resistivity of Sm0.9Ca0.1S
single crystal. By comparing to the non-doped SmS, it
is clearly shown that the electrical resistivity
significantly increased by more than two orders ofmagnitude. We succeeded in the valence transition to
the metallic phase of this sample by applying theelectric field of 300 V/cm at the liquid nitrogentemperature (data not shown). The optical reflectivity
spectra of Sm0.9Ca0.1S are shown in Fig. 2. The spectrain the lower energy region (Fig. 2(a)) show that both
Ca-doped and non-doped SmS are characteristic of theinsulator, in terms of low reflectivity in the far-IR
region except for phonon peak. The reflectivity

Sm1-xCaxS

0.3

295 K

0.2
0.1
0

0.10
0

5

x=0

10 15 20 25 30

Photon Energy (eV)Fig. 2. Optical reflectivity spectra of Sm1-xCaxS at 295
K: (a) from far-IR to visible and (b) from visible tovacuum-UV regions.

[1] A. Jayaraman et al., Phys. Rev. B 11 (1975) 2783.
[2] K. Takenaka et al., Sci. Rep. 9 (2019) 122.
[3] Y. Yokoyama et al., Phys. Rev. B 100 (2019) 245143.

69
III 02- 17 -Ⅲ-2

BL3B Sciences
Ⅲ -2. Materials

BL3B

Optical Investigation on Fluoro-olefins in VacuumUltraviolet for New Refrigerant Gas Development
K. Yamanoi1,2, Y. Sakata1, H. Iwayama3, Y. Hasumoto1,2, O. Yamamoto1,2 and M. Noumi1,2
Osaka university, Suita 565-0871, JapanDAIKIN Industries Ltd, Settsu 566-8585, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
1

2

Ⅲ-2

Chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), and hydrofluorocarbon (HFC) havebeen used as a refrigerant. These gases have high global
warming potential (GWP) over 100. Recently, thehydrofluoroolefin (HFO) gases are expected as new low
environmental load refrigerant due to its low GWPs
since olefin gas is unstable and easily decompose by
ultraviolet light in nature. In order to put HFO into
practical use as a refrigerant, it is necessary to clarify thephysical characteristics of HFO such as UV absorption
and decomposition process. In this study, we measured
the vacuum ultraviolet (VUV) light induced
decomposition of HFO.
The decomposition spectra measurements werecarried out in BL3B in UVSOR facility. Trans-C2H2F2
gas was flowed into vacuum chamber through thecapillary tube. The pressure in vacuum chamber was
kept less than 3×10-4 Pa. The VUV light from 8 to 30
eV was irradiated on sample gas and the ionizedmolecular fragments were detected TOF-mass
spectrometer shown in Fig. 1.
Figure 2 shows the decomposition spectra ofC2H2F2. We could clearly observe the ionizationenergies of each fragments. The decomposition fromC2H2F2 to CH2F2 and HF arise with 14.9 eV. Withhigher energy about 18 eV, the C2H2F2 dissociate to
CHF and CHF. From our previous results, the transC2H2F2 has the absorption from 135 nm (9.2 eV) to190
nm (6.5 eV) as shown in Fig. 3. The absorption at 145
nm is attributed to the stretching and twisting ofcarbon double band and the 190 nm is the transition
from π to π* in C=C bonds, respectively [1]. However
the ionization and decomposition threshold is quite
higher than these absorption. These results show thatthe higher photon energy over 14 eV is needed fortrans-C2H2F2 to be decomposed in the air. However,
we notice that other components exist such as oxygenand nitrogen which react with fluorocarbon in real case.
In conclusion, we could observe the opticalproperties and ionization energy of decomposition
process of C2H2F2 in VUV region. The results let us
know the UV- or VUV-induced decomposition
dynamics of fluoro-olefins as refrigerant in nextgeneration.

nozzleelectron detector

Beam

ion detector

Fig. 1. Schematic image of the experimental setup in
BL3B.

Fig. 2. Decomposition spectra of trans-C2H2F2.

Fig. 3 Absorption spectrum of C2H2F2.

[1] G. Belange et al., J. Chem. Phy 55 (1971) 2055.

70
III 02- 18 -BL3B

Ⅲ -2. Materials Sciences

BL3B

Absorption Bands of Tl+ Centers in CsI-based Ternary Crystals
S. Ito and T. Kawai

Graduate School of science, Osaka Prefecture University, Sakai 599-8531, Japanabsorption bands in CsI:Tl+ may be related to thecoordination states around the Tl+ ion.

300

280

Wavelength (nm)
260
240

220

10 K
CsI:Tl +Ⅲ-2
Optical Density (arb. unbits)

The optical properties of the Tl+ centers in alkali
halide crystals have been extensively investigated [1].
The Tl+ centers in alkali halide crystals with the NaCltype crystal structure exhibit the typical A, B, and C
absorption bands. On the other hand, the Tl+ centers incesium halide crystals with the CsCl-type crystal
structure have absorption bands different from thetypical A, B, and C bands; in particular, the appearanceof absorption bands in CsI:Tl+ is unusual [2,3]. It has
been regarded that the unusual absorption spectra of
the Tl+ centers in cesium halide crystals originate fromthe different ionic configurations around the Tl+ ion in
the NaCl- and CsCl-type crystal structures [2]. To
provide a better understanding of these observations,
we investigated absorption bands of CsCaI3:Tl+,
CsBa2I5:Tl+, Cs4CaI6:Tl+, and Cs4SrI6:Tl+ crystals, whichwere prepared by a cell method [4].
Figure 1 shows the absorption spectra of CsCaI3:Tl+,
CsBa2I5:Tl+, Cs4CaI6:Tl+, and Cs4SrI6:Tl+ crystals at 10
K. For reference, the absorption spectrum of CsI:Tl+ is
also demonstrated in the top of Fig. 1. In CsCaI3:Tl+, theabsorption bands having no extremely different
absorption intensity are observed at 4.54, 5.14, and 5.55
eV. A absorption band is observed at 4.32 eV for
CsBa2I5:Tl+. In Cs4CaI6:Tl+ and Cs4SrI6:Tl+, theabsorption band with a doublet structure is observed atabout 4.23 eV and the band with the largest absorption
intensity is observed at 4.94 eV. In addition, the weakabsorption bands are observed at about 5.18 and 5.33 eV.
The 4.23 eV band with a doublet structure and the 4.94
eV band in Cs4CaI6:Tl+ and Cs4SrI6:Tl+ may be assigned
to the A and C bands of the Tl+ centers, respectively,from the intensity ratio between them. On the other
hand, it is hard to assign the absorption bands of
CsCaI3:Tl+ and CsBa2I5:Tl+ to the A, B, and C bands,
just like the absorption bands in CsI:Tl+.
The CsI-based ternary crystals above have various
crystal structures; orthorhombic (CsCaI3) [5], monoclinic(CsBa2I5) [6], and trigonal (Cs4CaI6 and Cs4SrI6) [7]structures. In the host lattice, the Tl+ ions which replace
the Cs+ ion, have various coordinations of the I− ions.
That is to say, the Tl+ ions in the ternary iodide crystals
have different coordination of the I− ions from the Tl+
ion in the CsI crystal. Despite the difference of thecoordination, the absorption bands of CsI:Tl+ seem toappear at the energy positions which the absorption
bands of the Tl+ centers in the ternary iodides areobserved. For example, the lowest absorption band of
CsI:Tl+ is located at 4.27 eV, which is close to the lowest
bands of Cs4CaI6:Tl+ and Cs4SrI6:Tl+ in the energy
position. The 4.52 eV absorption band of CsI:Tl+ is
located at the energy position close to the lowest 4.54
eV band of CsCaI3:Tl+. The energy positions of the

CsCaI3:Tl+

CsBa2I5:Tl+

Cs4CaI6:Tl

Cs4SrI6:Tl
4.0

4.5

+

+

5.0
Photon Energy (eV)5.5

Fig. 1. Absorption spectra of CsI:Tl+, CsCaI3:Tl+,
CsBa2I5:Tl+, Cs4CaI6:Tl+, and Cs4SrI6:Tl+ crystals at
10 K.

[1] P. W. M. Jacobs, J. Phys. Chem. Solids 52 (1991)
35.
[2] S. Masunaga and M. Ishiguro, J. Phys. Soc. Jpn. 25(1968) 1337.
[3] T. Kawai, et al., Phys. Status Solidi B 227 (2001)
587.
[4] S. Hashimoto and M. Itoh, Jpn. J. Appl. Phys. 27(1988) 726.
[5] J. Grimm, et al., Inog. Chem. 45 (2006) 10905.
[6] B. Kang, et al., J. Phys. D: Appl. Phys. 49 (2016)
395103.
[7] L. Stand, et al., J. Cryst. Growth 486 (2018) 162.

71
III 02- 19 -

BL3B Sciences
Ⅲ -2. Materials

BL3B

Photoluminescence Properties of Cs2ZrI6
2

Ⅲ-2

S. Kodama1 and S. Kurosawa2

Saitama University, Saitama 338-8570, JapanNew Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579, Japan1

The intrinsic luminescent scintillators with thechemical formula of A2BX6 (A: monovalent cation, B:
tetravalent cation, X: halogen ion) are attracting large
attention due to their high light outputs and highenergy resolutions. We reported Cs2HfI6 and Rb2HfI6
as the novel red-emitting scintillators with the highlight output over 40,000 photons/MeV [1-5]. Whilethe candidate compositions of A2BX6 scintillators areactively studied, the detailed mechanism of intrinsic
luminescence is still unclear. We have studied thephotoluminescence properties of A2BX6 scintillators tounderstand the basic luminescence behaviors andcompare them with the that of conventional phosphorsusing the beamline of BL3B, UVSOR.
In the UVSOR activity report 2020, we reported the
low-temperature photoluminescence properties of
Cs2HfI6. Cs2HfI6 showed two photoluminescence bands
at 10K. The origin of each band was unclear. In order tocompare the effect of B cation on the photoluminescence
properties, we grew Cs2ZrI6 crystal and evaluated thetemperature dependence of photoluminescence emission
spectra. A single crystalline Cs2ZrI6 specimen was
obtained by the vertical Bridgman growth method in ourlaboratory from 99.95 %-pure ZrI4 and 99.999 %-pure
CsI powders.
Figure 1 shows the measured spectra of Cs2ZrI6. The
emission wavelength of Cs2ZrI6 was ~630 nm at 300 K,
and shifted towards shorter wavelength as cooled downreaching ~720 nm at 10K. Cs2ZrI6 had only one
photoluminescence band at all temperature, while
Cs2HfI6 had two bands at 10K. Therefore, the numbersof photoluminescence bands of Cs2BI6 were determined
to be two when B is Hf and to be one when B is Zr. The
tetravalent cation B might play the important roll in theluminescence phenomena of A2BX6 scintillators. For
future study, we would continue to study A2BX6
compounds to reveal the rolls of A, B and X ions.

[1] S. Kodama et al., IEEE Trans. Nucl. Sci. 67 (2020)
1055.
[2] S. Kodama et al., Appl. Phys. Express 13 (2020)
047002.
[3] S. Kodama et al., UVSOR Activity Report 2019 47(2020) 60.
[4] S. Kodama et al., UVSOR Activity Report 2020 48(2021) 65.
[5] S. Kodama et al., Rad. Meas. 124 (2019) 54.

Fig. 1. Temperature dependence of photoluminescence
excitation and emission spectra of Cs2ZrI6 at 10, 50,
100, 150, 200, 250, 300 and 350 K.

72
III 02- 20 -BL4U

Ⅲ -2. Materials Sciences

BL4U

Structural Analysis of Unvulcanized Rubber by Scanning Transmission Xray Microscopy
T. Ohigashi1,2,3, F. Kaneko4, H. Yuzawa1 and H. Kishimoto4

UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
Institute of Material Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801, Japan3
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
4
Sumitomo Rubber Industries Ltd., Kobe 651-0071, Japan
1

2

Reduction of consumption of limited resources is
nowadays a critical issue to maintain our daily life.
Rubber is one of the important resources and its demandis assumed to increase especially according to growth ofcar industries. Therefore, further improvement in wearand destruction-resistant of rubber is necessary to
reduce its consumption. Then, control of crosslinking of
sulfur in rubber is a key technology. Heterogeneity of
network of crosslinking in rubber has been confirmedby small-angle neutron scattering [1]. This heterogeneity
causes destruction of rubber because it gathers internal
stress under deformation. Therefore, dispersion of acrosslinking reagent in the rubber is important to makethe crosslinking network homogeneous.
To achieve the above goal, it is important to measure
the relationship between the dispersion and various
parameters of synthesis. Thus, this dispersion has been
conventionally tried to depict by using electron
microscopy. However, its observation was not easy
because the rubber contains only small amount of thecrosslinking agent. Moreover, the crosslinking agent is
consisted of light elements and is easily damaged byelectron beam. Then, scanning transmission X-ray
microscopy (STXM) can be an alternative approach.
STXM can probe the crosslinking agent by using nearedge X-ray absorption fine structure (NEXAFS). The
advantages of STXM are high spatial resolution
around 30 nm and much lower radiation damage thanthe electron microscopy. In this report, the distributionof crosslinking agent in unvulcanized rubber isinvestigated by STXM.
An ultra-thin section of the unvulcanized rubber of
250 nm thick was prepared as a sample by a cryo ultramicrotome. In the case of STXM observation, thesample was cooled down to ~ -90 degree with cryocooling setup to suppress the radiation damage [2].
Figure 1(a) shows an X-ray fluorescence image at
N-K line by using transmission electron microscopy
with an energy dispersive detector. Since signal
intensity of N-K line is low, the image is noisy anddoes not have any structures. Even though thedetection of the X-ray fluorescence brings highsensitivity to the analytical system, the crosslinking
agent could not be detected. We assumed that thecrosslinking agent was damaged by irradiation of theelectron beam.
The STXM image acquired at the X-ray energy of
401 eV is shown in Fig. 1(b). The observed image

shows many dark domains with high absorption. X-ray
absorption spectra of these dark domains (Fig. 2(a))
are compared with references of the crosslinking agent“A” and “B” by comparing with the reference spectra(Fig. 2(b)). Matrix of the rubber has quite lower
nitrogen signals than the dark domains, which implies
heterogeneity of the distribution of the crosslinking
agent. As a result of linear combination fitting, thesedark domains are consisted of the crosslinking agent“A” and “B”.
(a)

(b)

2 µm

5 µm

Fig. 1. (a) Images of unvulcanized rubber acquired bytransmission electron microscopy with an energy
dispersive detector acquired at N-K line and (b) thatby STXM at N-K edge (401 eV).
(a)

(b)

Fig. 2. (a) X-ray absorption spectra of the unvulcanizedrubber in the dark domain (solid line) and matrix(dashed line) in Fig.1(b) around N-K edge and (b)those of the crosslinking agents for “A” (solid line)and “B” (dashed line).

[1] Y. Ikeda, N. Higashitani, K. Hijikata, Y. Kokubo
and Y. Morita, Macromolecules 42 (2009) 2741.
[2] T. Ohigashi, F. Kaneko, Y. Inagaki, T. Yano, H.
Kishimoto and N. Kosugi, UVSOR Activity Report2017 45 (2018) 34.

73
III 02- 21 -Ⅲ-2

BL4U Sciences
Ⅲ -2. Materials

BL4U

C-K Edge Spectra of Bound-rubber Structure in SBR Materials
with Filler and/or Reagents
T. Ejima1, 2 and Y. Tamura2, 3, *SRIS, Tohoku University Sendai 980-8577, JapanIMRAM, Tohoku University, Sendai 980-8577, Japan3
JSR Corporation, Yokkaichi 510-8552, Japan
1

2

Ⅲ-2

Adding filler materials such as carbon black toelastomer materials such as synthetic rubber cansignificantly change mechanical properties: stressproperties, tensile strength, and abrasion resistance [1].
The factors that cause the changes in mechanicalproperties are not well understood, and the type andthe amount of filler materials added to obtain thedesired mechanical properties are known empirically.
In addition, it is known that the structure of anelastomer material differs at each scale and exhibits ahierarchical structure [2-4]. Among the hierarchicalstructure, we presume that the chemical state and the
3D structure of the bound-rubber structure formed
between filler particles at the nm scale determine theoverall mechanical properties. In the study, we will
add filler materials and/or reagents to elastomer
materials that the mechanical properties are known,
then the chemical states of the bound rubber structure
and its spatial distribution will be measured using the
STXM in BL4U. We believe that this process will
clarify the origin of the mechanical properties.
In the measurement, compounds were prepared froman elastomer material with a filler material and various
reagents, and styrene-butadiene rubber (SBR) andmodified SBR are used as the elastomer materials. The
fabricated compounds were cut into sections and usedin the STXM measurements. The measurement was
performed with a spatial resolution of 100 nm and an
exposure time of 2 msec per point. The obtained soft Xray images clearly distinguish the position of the added
filler material. Based on the preliminary NEXAFS
results, spectral measurements were performed focusing
on the difference between the π*- and the σ*- structuresof the C-K absorption edge. The obtained nanoscopic
spectra around bound-rubber structures in a same
compound showed a similar spectral shape with achange in peak intensity depending on the presence or
the absence of the filler and/or reagents. Different spectral
shape was observed around a bound-rubber structure
according to a modification of the SBR. An example ofthe spectral change in shape is shown in Fig. 1. By theenergy positions of the peaks, we estimate the origins ofpeaks as that: peak A is a transition from C1s orbital toπ* orbital due to the C=C bond, peak B is a transition to
C-H* orbital, and peaks C and C' are transitions to σ*
orbital [5].

Fig. 1. C-K edge spectra of SBR and modified SBR
with same filler and reagents. Curves are smoothing
results for guide to see.

[1] M. Ashida et al., J.Soc. Rubber Science andTechnology, Japan 49 (1976) 821.
[2] K. Nakajima, et al., Rub. Chem. Technol. 90 (2017)272.
[3] J. Kikuma, et al., J. Surf. Anal. 25, (2018) 34.
[4] Z. Martin, I. Jimenez, M.A. Gomez-Fatou, M. West
and A. P. Hitchcock, Macromolecules 44 (2011) 2179.
[5]J. Stoehr, "NEXAFS Spectroscopy", Springer- Verlag,
Berin Heiderberg GmbH (1992), Chap. 7 and 8.

*Present Address: ENEOS Materials Corporation,
Yokkaichi, Mie 510-0871, Japan74
III 02- 22 -BL4U

Ⅲ -2. Materials Sciences

BL4U

Analysis of Materials for Secondary Batteries by STXM
E. Hosono1,2,3, D. Asakura1,2,3, H. Yuzawa4 and T. Ohigashi4,5Global Zero Emission Research Center, National Institute of Advanced Industrial Science (AIST),
Tsukuba 305-8569, Japan
2
Research Institute for Energy Conservation, AIST, Tsukuba 305-8565, Japan
3
AIST-UTokyo Advanced Operando Measurement Technology Open Innovation Laboratory (Operando-OIL),
Kashiwa 277-8565, Japan
4
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
5
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
1

In order to improve the performance of secondary
batteries such as lithium-ion batteries (LIB) anddevelop innovative electrode materials, investigationon the electronic state of electrode materials undercharge/discharge condition is required. This is because
the electronic state determined by redox conditions is
one of the critical factors for the energy density suchas charge/discharge capacity and operating voltage ofbattery. Since soft X-ray absorption spectroscopy(XAS) is sensitive to the change of local electronic
state, it is suitable analytical method for electrodematerials [1,2].
In addition, study of facet is also important tocontrol of the stability of the interface between theelectrode active material and the electrolyte. To
elucidate the behavior of the facet, analysis for spatial
distribution of electronic state at interface is required.
For spatially selective analysis, various techniquesof electron microscopes have been developed. For
example, TEM-EELS and TEM-EDS are widely used
as elemental analysis with a high spatial resolution.
However, in order to understand the electronic state of
the active materials, synchrotron radiation soft X-ray
spectroscopy is advantageous in terms of the energy
resolution and lower beam (X-ray) damage than thedamage by electron beams in electron microscopes.
Moreover, the scanning transmission soft X-ray
microscopy (STXM) with a spatial resolution ofseveral tens of nm is highly effective for analyzing theelectronic-state distribution in one particle of theelectrode material because the particle size is in theorder of several micrometers.
So far, we have mainly focused on cathode materials
like transition-metal oxides, but now we apply STXM
analysis to 2D carbon materials used for the anode as
well. Figure 1 shows the STXM image of 2D carbon
nanosheets at 320 eV and the C K-edge XAS spectrumof selected area. Graphite-like π* and σ* peaks areobserved. We believe that STXM is important for
carbon materials as well because it enables analysis forthe distribution of local electronic structure to discuss
the stability of the material.

Ⅲ-2

Fig. 1. STXM image and spectrum of selected area.

[1] Y. Nanba et al., Chem. Mater. 28 (2016) 1058.
[2] D. Asakura et. al., ChemPhysChem. 17 (2016)
4110.

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BL4U

Probing the Electronic Structure of Ni-Co Binary Oxide/Graphene
Nanocomposites as Supercapacitor Electrodes by Scanning Transmission
X-ray Microscope
H. W. Chang1,2, T. C. Huang2, T. Ohigashi3, C. H. Chuang1, Y. C. Tsai4, C. L. Dong1 and W. F. Pong1
Department of Physics, Tamkang University, Tamsui 251, Taiwan
Department of Chemical Engineering, National United University, Miaoli 360302, Taiwan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
Department of Chemical Engineering, National Chung Hsing University, Taichung 40227, Taiwan
1

2

Ⅲ-2

Nickel and cobalt-based oxide are considered aspromising materials for supercapacitors owing to themultiple oxidation states and excellent electrochemical
redox activity. The conductive carbon materials (such asgraphite, carbon nanotubes, and graphene) serve as aconductive component can created the possibility toform the conducting interconnection between carbon
materials and transition metal oxides, allowing fast ionsand electrons transport inside interior space of transition
metal oxide pore/channel structure, thus dramaticallyenhanced the electrocatalytic activity. In this study, Ni-Co
binary oxide were synthesized on the graphene to obtain
Ni-Co binary oxide/graphene (NCG) nanocomposites as
supercapacitor electrodes. NCG nanocomposites were
tested with the applied voltage of 0.3 and -0.1 V toevaluate pseudocapacitive behavior toward studying thechange of the local chemical environment of a selected
element using STXM. Figure 1 show the optical density
images, STXM stack mapping, and XANES spectra of
NCG at C K-edge and O K-edge under applied voltage
of 0.3V and -0.1V. The C K-edge XANES spectra has
several distinct features (Ga, Gb, and Gc). Features Ga
and Gc at 284.6 and 290.9−291.9 eV are associated withthe transitions from C 1s to the unoccupied π* and σ*
orbitals, respectively, reflecting the bonding perpendicular
to the ring plane and within the ring plane. Features Gb
consist of three peaks Gb1 (286.3 eV), Gb2 (287.5 eV),and Gb3 (288.5 eV) correspond to C−O π* (hydroxyl or
ether), C=O π* (carbonyl groups), and O=C−O π*(anhydride, lactone, or carboxylic acids). The O K-edge
XANES spectra reveals Ha and Hb features at 532.8 and
540.0−545.0 eV. These features are associated with
C=O π* states of carbonyl groups and the O−H σ*, C−O
σ* and C=O σ* symmetry states from carbonyl,
carboxylic acid, and hydroxyl groups. The spectral
profile in Figs. 1(g) and (h) changes with the bias
potential applied from selected regions of the edges(yellow) and the center (red) that indicate favorable
structural and chemical reversibility during the charge/
discharge process, suggesting that the oxygen-containing
functional groups provide pseudocapacitance throughFaradaic reactions that occur near the surface of thegraphene-based materials: >C−OH ↔ C=O + H+ + e−,− COOH ↔ − COO + H+ + e−, and >C=O + e− ↔
>C−O− [1-3]. Further studies at Ni and Co L-edge are
expected to provide detail information of the energy
storage mechanisms.

Fig. 1. Optical density images of NCG under (a) 0.3
V and (d) -0.1 V. (b,e) C K-edge and (c,f) O K-edge
STXM. (g) C K- and (h) O K-edge STXM-XANES ofNCG from different regions (yellow and red).

[1] Han et al., Nat. Commun. 11 (2020) 1.
[2] Gandhiraman et al., J. Phys. Chem. C 118 (2014)
18706.
[3] Chang et al., J. Phys. Chem. C 120 (2016) 22.

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BL4B

Development of Reflection XMCD Measurement Setup for the Investigationof Inner Structures of Magnetic Thin Films at UVSOR BL4B
K. Yamamoto, H. Iwayama, O. Ishiyama and T. Yokoyama
Institute for Molecular Science, Okazaki 444-8585, Japan

Magnetic thin films/multilayers with complex depth
structures exhibit a wide variety of magnetic
phenomena due to the interactions between layers [1].
Furthermore, multilayer structures have been used torealize useful properties in recording media, which isan important application of magnetic materials. Direct
observation of the magnetic distribution in the depth
direction of such magnetic multilayers has been used
to elucidate the mechanism of evolution of magnetic
structures in thin films
We installed an experimental setup for reflectance xray magnetic circular dichroism (XMCD) method [2] inthe soft X-ray region at BL4B and experiments were
performed on test samples as shown in Fig. 1.
The sample and the detector can be rotatedindependently to obtain reflectivity. X-rays were detectedby a photodiode (AXUV100G, Optodiode inc.). The
magnetic field was about 0.35T, and measurements
were made at room temperature. The magnetic field wasapplied by two pairs of Nd magnets disposed oppositely.
The magnets can be rotated and the relative positional
relationship between the magnetic field and the sample
was kept constant. The setup is schematically depicted
in Fig. 2.
We used off-axis components of x-rays from thebending magnet to obtain circularly polarized light. The
x-rays are elliptically polarized. XMCD intensity wasmeasured by changing the direction of magnetic field.
The sample was CoFeB and an oscillating structure
was observed due to the interference of the cap layer
and the underlying layers. We observed the difference
corresponding to XMCD by changing the direction ofmagnetic field, which is consistent with the simulation
results. The same measurements were made around theabsorption edges and spectroscopic information was
extracted. These results can be reproduced by thesimulation based on the full matrix algorithm and themagnetooptical effects of the elliptically polarized xrays were treated explicitly. Although there have beenprevious studies using XMCD of reflectance, there arefew studies that extends this method to obtain
spectroscopic information. We also conducted
spectroscopic measurements and obtained photon
energy and reflection angle dependence to analyze thedepth-resolved magnetization information.

Ⅲ-2

Fig. 1. The experimental setup installed at BL4B.

Magnetic
thin films
X-rays2θ

θ
PhotodiodeFig. 2 The illustration for the XMCD reflectivity
measurements.

[1] F. Hellman et al., Rev. Mod. Phys. 89 (2017)025006.
[2]S. Macke and E. Goering, J. Phys. Condens. Matter.
26 (2014) 363201.

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BL5U

Dirac Fermions and Topological Phase Transition in XMg2Bi2 (X = Ba and Sr)
D. Takane1, Y. Kubota1, K. Nakayama1,2, T. Kawakami1, S. Souma3,4, K. Sugawara1,2,3,4,
S. Ideta5,6, K. Tanaka5,6, T. Takahashi1,3,4, K. Segawa7 and T. Sato1,3,4

Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency(JST), Tokyo 102-0076, Japan
3
Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
4
Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan
5
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
6
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
7
Department of Physics, Kyoto Sangyo University, Kyoto 603-8555, Japan
1

2

Ⅲ-2

The search for novel fermions is recently becoming
an exciting challenge in condensed-matter physics, as
highlighted by the discovery of two-dimensional (2D)
Dirac fermions in graphene and helical 2D Diracfermions at the surface of three-dimensional (3D)
topological insulators. The recent discovery of 3D Diracfermions in topological Dirac semimetals (TDSs)
further enriches the category of exotic fermions. TDSs
show exotic quantum phenomena such as high carrier
mobility and giant linear magnetoresistance governedby the linearly dispersive Dirac-cone energy band. Also,
TDSs provide a fertile playground for realizing a variety
of topological phases, e.g., by breaking the timereversal/crystalline symmetry or by chemical substitution.
However, despite many theoretical predictions for TDS
candidates, TDSs that have been experimentally verified
are still rare. Moreover, topological phase transition
from TDSs has been scarcely realized partly because of
the difficulty in substituting constituent elements ofknown TDSs. Thus, it is highly desired to explore new
TDS materials that overcome such difficulties.
Here we demonstrate that ternary compoundBaMg2Bi2 is a new TDS and serves as a useful platform
to study topological phase transition [1].
High-quality single crystals of XMg2Bi2 (X = Ba andSr) were synthesized by the self-flux method. ARPES
measurements were performed with micro-focused
VUV synchrotron light at BL5U. Prior to the ARPES
measurements, samples were cleaved in an ultrahighvacuum.
Figure 1(a) shows the ARPES intensity near EF
measured along a momentum (k) cut crossing the Γpoint. One can see linearly dispersive bulk valence band
(VB) which crosses EF. To search for a possible band
touching of VB and conduction band (CB) predicted in
the calculation, we deposited K atoms onto the surface
in an ultrahigh vacuum. One can clearly see in Fig. 1(b)that the hole bands in K-deposited BaMg2Bi2 are shifted
downward due to the electron doping to the surface.
Intriguingly, VB in the negative k region appears toalmost continuously disperse across k = 0 and cross EF at
positive k, without losing its intensity at k = 0, indicativeof the formation of Dirac-cone dispersion. In contrast to
the case of K-deposited BaMg2Bi2, the spectral weightassociated with the CB is absent and no Fermi-edge cutoff is observed in K-deposited SrMg2Bi2 [Fig. 1(c)].
This observation demonstrates that an intrinsic band gap
opens in SrMg2Bi2, suggesting the occurrence of
topological phase transition from the TDS state to theordinary insulator phase upon replacing Ba with Sr [Fig.
1(d)].

Fig. 1. (a)-(c) ARPES intensity plot near EF in
BaMg2Bi2, K-dosed BaMg2Bi2, and K-dosed
SrMg2Bi2. (d) Schematic band diagram of XMg2Bi2.

[1] D. Takane et al., Sci. Rep. 11 (2021) 21937.

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BL5U

Band-structure Reconstruction of Ca3Ru2O7 Induced by K Adsorption
M. Horio 1,2, T. Wada1, V. Granata3, R. Fittipaldi3, A. Vecchione3, K. Tanaka4,
I. Matsuda1 and J. Chang2
Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581, Japan
Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
3
CNR-SPIN, I-84084 Fisciano, Salerno, Italy
4
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan1

2

Application of external perturbations to Mott
insulators often leads to dramatic changes in theelectronic structure. For example, the Mott insulator
Ca2RuO4 can be metallized by chemical substitutions[1,2], physical pressure [3], and electric current [4].
Changing the number of the RuO2 layer in the unit cellfrom one (Ca2RuO4) to two (Ca3Ru2O7), the system canalso become metallic down to low temperatures [5].
Instead, Ca3Ru2O7 exhibit a first-order phase transition
at T = 48 K that involves lattice and spin degrees of
freedom [6]. At 48 K, antiferromagnetically orderedspins change their orientation from the a to b crystalline
axis and the lattice undergoes slight compression along
the c axis. This phase transition makes a significant
influence on the transport properties such as resistivity,
Hall effect, and Seebeck effect [7], suggesting dramaticchanges in the band structure near the Fermi level.
Indeed, our recent angle-resolved photoemission
spectroscopy (ARPES) study [8] has revealed a clear
band-structure reconstruction into a Dirac-semimetallic
state upon cooling across 48 K.
Recently, alkali-metal adsorption is being recognized
as an efficient way to dope a solid surface with electrons.
This methodology has been applied to Mott insulatorssuch as iridates [9] and cuprates [10] and the occurrenceof metal-insulator transition has successfully been
demonstrated through in-situ ARPES measurements.
With this technique, electrons can be doped at thesurface even in the case where bulk electron doping bychemical substitutions is impossible. Ca3Ru2O7 is one
such case where electron doping has never been realized.
We have dosed K on Ca3Ru2O7 and carried out
ARPES measurements at BL5U at T = 10 K. Figure 1
shows energy distribution curves in a wide energy range.
As K is adsorbed on the surface, a peak at the binding
energy of ~1.7 eV, which is a remnant of the lower
Hubbard band, loses its intensity and instead a spectral
weight accumulates at the Fermi level. This spectralweight re-distribution suggests that the electronic statechanges away from the Mott insulating state. Thechange is even more clearly seen in the ARPES spectrain Fig. 2. Notably, the hole-like dispersion around the Γpoint expands, which is opposite to what is expectedfrom electron doping. It is therefore likely that the effectof adsorbed K atoms goes beyond simple electron doping
to cause the observed band structure reconstruction.

Ⅲ-2

Fig. 1. Energy distribution curves recorded withvarying the K deposition level.

Fig. 2. Electronic structure change in Ca3Ru2O7 by K
adsorption. (a)-(c) ARPES spectra of pristine and Kdosed Ca3Ru2O7. (d) Momentum distribution curves(MDCs) at E-EF = -0.02 eV.

[1] S. Nakatsuji and Y. Maeno, Phys. Rev. Lett. 84(2000) 2666.
[2] H. Fukazawa and Y. Maeno, J. Phys. Soc. Jpn. 70(2001) 460.
[3] S. Ricco et al., Nat. Commun. 9 (2018) 4535.
[4]R. Okazaki et al., J. Phys. Soc. Jpn. 82 (2013) 103702.
[5] Y. Yoshida et al., Phys. Rev. B 69 (2004) 220411(R).
[6] Y. Yoshida et al., Phys. Rev. B 72 (2005) 054412.
[7] H. Xing et al., Phys. Rev. B 97 (2018) 041113(R).
[8] M. Horio et al., npj Quantum Mater. 6 (2021) 29.
[9] Y. K. Kim et al., Science 345 (2014) 187.
[10] C. Hu et al., Nat. Commun. 12 (2021) 1356.

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BL5U

Quadrupole Electronic Structure in Mn3-xGa Studied by Angle-resolved
Photoemission Spectroscopy
J. Okabayashi1, Y. Miura2, K. Tanaka3, K. Z. Suzuki4 and S. Mizukami4

Research Center for Spectrochemistry, The University of Tokyo, Tokyo 113-0033, Japan
2
National Institute for Materials Science (NIMS), Tsukuba 305-0047, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585
4
WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8579, Japan
1

Ⅲ-2

Magnetic ordered alloys have attracted significant
attention for use as spintronics materials because they
are highly likely to exhibit perpendicular magnetic
anisotropy (PMA). Tetragonal Mn3-xGa alloys arewidely recognized as hard magnets which exhibit highly
anisotropic, ferrimagnetic, and metallic properties [1].
We have investigated the mechanism of PMA and large
coercive fields in Mn3-xGa by x-ray magnetic circularand linear dichroisms (XMCD /XMLD) [2]. The origin
of PMA in Mn3-xGa alloys can be explained by thequadrupole contribution along the z-axis by the chargeasphericity. The specific crystalline structures provide theelongated c-axis direction, which induces the anisotropic
chemical bonding, resulting in the anisotropy of electron
occupancies in 3d states and charge distribution.
However, orbital magnetic moments in the Mn sites arealmost quenched because of half-filled occupation.
Although the site-specific charge distributions can beaccessed by x-ray absorption spectroscopies, the originof quadrupole-induced PMA from the viewpoint of theband structures in Mn3-xGa alloys is not fully understood.
Here, we employ the angle-resolved photoemission
spectroscopy (ARPES) to unveil the anisotropic band
structures in Mn3-xGa by the comparison with thedensity-functional theory (DFT) calculations.
30-nm-thick Mn3-xGa samples were prepared on
MgO (001) substrate using sputtering technique. On
the surface of Mn3-xGa layer, Mg and MgO capping
layers were deposited. The MgO layer was removed
by Ar-ion sputtering and the Mg layer was removed byannealing just before the ARPES measurements. We
construct the method to remove the Mg layer which
does not react chemically with Mn atoms at theinterface. Clear low-enegy electron diffraction (LEED)
patterns were also obtained.
ARPES was performed at BL5U, UVSOR, where
the photoemission chamber is connected to the sample
preparation chamber. The measurement conditions
were set at 15 meV energy resolution and 10 K. Linear
polarized beams of s- and p-polarization were used todetect the orbital symmetry. We employ the photon
energy ranges of 60 – 80 eV to enhance the Fe 3d
photo-ionization cross section, where the Γ-X(M) line
is scanned by the angular mode of ± 15°.
Figure 1 shows the Fermi surface mapping taken at
photon energy of 80 eV. Four-hold symmetric lines aredetected, which is consistent with the LEED patterns.

High intensity spots appear at both Γ and X points.
Nodal lines are also developed from each symmetricpoint. Energy-momentum (E-k) dispersion curves also
exhibit the intensities at Γ and X points with thedispersive bands. These bands are comparable with the
DFT calculation. The band from the Γ point has acharacter of yz orbital, which can be detected by the spolarized beam in vertical geometry.
We discuss the quadrupole formation. In the DFT
calculation, the virtual spin-flip transitions from occupied
up-spin yz to down-spin z2 orbitals correspond to thefinite matrix element to the PMA in the perturbation.
Therefore, occupied yz orbitals detected by ARPES
contribute to spin-flipped yz-z2 oblate quadrupolecharge distribution, resulting in the PMA. Ourfinding explains the origin of PMA in Mn3-xGa comesfrom not orbital moment anisotropy but elongatedcharge distribution through the spin-flipped transition in
specific orbitals, whose results are also supported by
XMCD and XMLD.

Fig. 1. ARPES images of Mn3Ga taken at hv=80 eV
using s-polarized beam. (a) The kx-ky mapping. (b)Band dispersions along Γ-X direction in primitive
Brillouin zone. Dot curves in (b) show the results of
DFT calculation.

[1] S. Mizukami et al., Scr. Mater. 118 (2016) 70.
[2] J. Okabayashi et al., Sci. Rep. 10 (2020) 9744.

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BL5U

Change of the Fermi Surface of Bi2Sr2CaCu2O8Observed by ARPES
1

Y. Tsubota1, S. Kumar2, Y. Miyai2, K. Tanaka3, S. Ishida4, H. Eisaki4, S. Nakagawa5,
T. Kashiwagi5, M. Arita2, K. Shimada2 and S. Ideta2

Department of Physics, School of Science, Hiroshima University, Higashi-Hiroshima 739-0046, Japan
Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8560, Japan
5
Division of Material Science, Tsukuba University, Tsukuba 305-8577, Japan2

It has been known that the cuprate superconductors
show a high superconducting (SC) transition
temperature (Tc) and exotic physical properties, on theother hand, the SC mechanism has been unclear yet. In
order to understand the mechanism of high-Tc cuprates,
Bi2Sr2CaCu2O8+δ (Bi2212) is one of the promising
candidates to study the electronic structure and reveal
the physical properties. Bi2212 has two CuO2 planes in
the unit cell and shows the high Tc around 95 K at the
optimally doped sample. Superconductivity occurs
upon hole doping into the CuO2 plane and the amountof hole doping can control Tc, and therefore, carrier
doping (hole/electron concentration) plays an important
key parameter in cuprates [1,2]. According to theprevious report, we consider that differences of theelectronic states in Bi2212 depending on the sample
with several compositions might exist, even thoughsamples are expected to be the same hole concentration,
where the optimally doped sample shows the maximum
Tc (Tc,max); however, the compositions are different,
which shows a different Tc,max [1,2]. Therefore, in thepresent study, we have performed an angle-resolved
photoemission spectroscopy (ARPES) measurements tostudy the Fermi surface changes of Bi2212 due todifferences in sample compositions.
We have demonstrated ARPES measurements toinvestigate the electric structure on wide momentum
space for Bi2212 with two compositions. ARPES
experiments were carried out at BL5U and we measured
two optimally doped samples: Bi2.3Sr1.7CaCu2O8+δ, (Tc ~85 K) and Bi2.1-xPbxSr2CaCu2 O8+δ (x = 0.66, Tc ~ 95 K)
in the SC and the normal states. High quality single
crystals of Bi2212 were cleaved in-situ in the ultrahighvaccume ~4×10-9 Pa.
Figures 1(a) and 1(b) show the Fermi surfaces taken
at hν = 60 eV and T = 30 K in the SC state forBi2.3Sr1.7CaCu2O8+δ and Bi2.1-xPbxSr2CaCu2O8+δ (x =0.66), respectively. Fermi surfaces are clearly observedin wide momentum space for both samples. In Fig. 1(a),in addition to the main Fermi surfaces as shown by a redarrow at -0.4 Å–1 in momentum space on the horizontal
axis, the spectrum at -0.2 Å–1 in momentum space isobserved, indicating that the modulation from the BiO
layer, so called replicas, is observed as shown by a blue
arrow. If replicas are observed in the ARPES results, wecannot understand the electric structure precisely inmomentum space because the main and replica bands

are overlapped. Figure 1(b) shows Fermi surfaces of
Bi2.1-xPbxSr2CaCu2O8+δ (x = 0.66). Substitution of the Bi
site with Pb suppresses the modulated structure from the
BiO layer and as a result, the replica is strongly
suppressed. In Fig 1(b), the replicas on Fermi surfaces
are well suppressed and the main bands are dominantly
observed.
We have analyzed the ARPES spectra around thenodal region for each sample and determined the
Fermi momentum (kF) for each Fermi surface byfitting of momentum-distribution curves (MDCs) witha Lorentzian. The kF’s are plotted as shown by red dots
(Fig. 1). As a result, we have found that two samples
with different compositions show that the distance
between two nodal points has a different value. Thismeans that the Fermi surface might change due todifferences in sample compositions. As a future work,
we will demonstrate ARPES experiments in a different
composition and doping level.

Fig. 1. Electronic structure of Bi2212. (a) Fermi surfacesof Bi2.3Sr1.7CaCu2O8+δ in the superconducting state (30K). (b) Fermi surfaces of Bi2.1-xPbxSr2CaCu2O8+δ (x =0.66) in the superconducting state (30 K). Main Fermi
surfaces are shown by a red arrow. Red dots are theFermi momentum estimated from the MDC peak near
the Fermi level.

[1] J. L. Tallon et al., Phys. Rev. B 51 (1995) 12911.
[2] I. M. Vishik et al, Proc. Nat. Acd. Sci. 6 (2012)
18332.

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CDW-induced Electronic Reconstruction in a Kagome Metal KV3Sb5
T. Kato1, K. Nakayama1,2, T. Kawakami1, A. Moriya1, Yongkai Li3,4, Z. Wang3,4, S. Ideta5,6,
K. Tanaka5,6, T. Takahashi1,7,8, Y. Yao3,4 and T. Sato1,6,7

Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency(JST), Tokyo 102-0076, Japan
3
Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture andMeasurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100081, China
4
Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems, Beijing Institute of Technology,
Beijing 100081, China
5
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
6
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
7
Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
8
Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan
1

2

Ⅲ-2
Recently, a new kagome-lattice material AV3Sb5 (A= K, Rb, and Cs) has been discovered. AV3Sb5
undergoes a charge-density wave (CDW) transition
below TCDW = 78-103 K, accompanied by the in-plane
unit-cell doubling with the 2×2 periodicity. This CDW
state shows an intriguing entanglement with thesuperconductivity (transition temperature Tc of 0.9-2.5
K) and non-trivial topological surface states. Also,
exotic properties, e.g., strong anomalous Hall effectand possible time-reversal symmetry breaking havebeen reported, highlighting the unconventional natureof CDW.
Despite intensive studies, the origin of CDW in
AV3Sb5 is highly controversial. In particular, the type ofstructural distortion responsible for the CDW has yet to
be clarified. First-principles calculations proposed two
types of distortions sharing the same space group toaccount for the in-plane 2×2 periodicity. One is the“Star-of-David” (SoD) distortion of V atoms. The otheris an inverse type of the SoD distortion, where V atoms
show an opposite displacement compared with the SoD
case, resulting in a periodic arrangement of triangularand hexagonal patterns, called “Tri-Hexagonal” structure.
It is experimentally highly controversial which distortion
actually takes place.
To gain insight into the origin of CDW from theelectronic structure perspective, we have performedhigh energy and spatial resolution ARPES of KV3Sb5 byusing a micro-focused beam at BL5U in UVSOR [1].
Figure 1 shows a side-by-side comparison of the
ARPES intensity plots along the M-M cut measured in
the normal and CDW states (left and right panels,
respectively). In the normal state, one can see a strong
intensity near the Fermi level (EF) at the M point,
together with a hole-like dispersion topped at slightly
below EF at the M point. One can recognize an obvious
difference in the intensity distribution in the CDW
phase. A new shallow holelike bands crossing EF
appear at the middle of the two M points, as also
identified from the momentum distribution curve at EF(white curves shown in the inset; folded bands arehighlight by white triangles). This indicates the CDWinduced band folding. A comparison of the observed
electronic reconstruction with the band structure
calculations assuming SoD/TrH structural distortion
would help to clarify the origin of CDW.

Fig. 1. ARPES intensity measured along the M-M cut
at T = 120 K (left) and 20 K (right), respectively. White
curve in the inset shows the MDC at EF.

[1] T. Kato et al., submitted.

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Electronic Structure of VNb3S6: a Transition-metal Intercalated NbS2
M. Horio 1, T. Wada1, S. Okazaki2, K. Tanaka3, T. Sasagawa2 and I. Matsuda1

Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581, Japan
Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
1

2

Transition-metal dichalcogenides MX2 host a richvariety of physical phenomena such as superconductivity[1] and charge density wave [2], and thus have attracted
intense interest for decades. In 1970-1980’s, there havebeen extensive attempts to modulate its electronic
structure by intercalation of 3d transition metals T [3].
Thus made TM3X6 takes crystal structure with broken
inversion symmetry and shows various types ofmagnetic order depending on the intercalated 3dtransition metal. Out of these, CrNb3S6 has been mostintensively studied because of the special type ofmagnetic order called chiral soliton lattice.
In Recent years, due to the breaking of both theinversion and time-reversal symmetry, TM3X6 isattracting interest from a topological perspective.
Especially, VNb3S6, which shows a ferromagnetic order
below TC ~ 44 K, has been theoretically predicted topossess a magnetically induced Weyl point. Indeed, arecent study has demonstrated large anomalous Hall
conductivity potentially associated with the proposed
Weyl point [4]. While there recently appears increasing
number of ARPES reports made for CrNb3S6 [5,6],
MnNb3S6 [7], FeNb3S6 [8], CoNb3S6 [8-10], andNiNb3S6 [7,8], to the best of our knowledge there havebeen no such studies on VNb3S6. We therefore attempted
an ARPES measurement to reveal the low-energy
electronic structure of VNb3S6.
Single crystals of VNb3S6 were grown by the chemical
vapor transport method from polycrystals with iodine as
the transport agent. ARPES measurements were
performed at BL5U of UVSOR at temperatures ranging
from 10 to 200 K.
Figures 1(a) and (b) show the Fermi surface and band
dispersions through the Brillouin-zone center of VNb3S6,
respectively, recorded at 10 K. From these, three holelike Fermi surface sheets centered around the zone
center can be clearly identified. This result is distinct
from the observations for the antiferromagnets FeNb3S6,
CoNb3S6, and NiNb3S6 [7-10], where there is only single
Fermi surface. Instead, the Fermi surface structure
resembles what was reported for the ferromagnet
CrNb3S6 [5,6]. In the case of CrNb3S6, from temperaturedependent systematic APRES measurements across TC[6], the emergence of multiple Fermi surface sheets has
been ascribed to the effect of ferromagnetism. In contrast,
as for VNb3S6, the band structure is remarkably robust
against temperature variations up to 200 K (Fig. 1), farabove TC ~ 44 K. Therefore, the peculiar band structure
is likely not rooted in magnetism. Comparisons with
first-principles band structure calculations both in themagnetic and non-magnetic states would pave the way
to understanding the origin of these observations.

Ⅲ-2

Fig. 1. ARPES results of VNb3S6. (a),(b) Fermi
surface and band dispersions, respectively, measured
at 10 K. The momentum cut for (b) is indicated in (a).
(c),(d) The same plots at 50 K. (e),(f) The same plots
at 200 K.

[1] T. Yokoya et al., Science 294 (2001) 2518.
[2] J. Wilson et al., Adv. Phys. 24 (1975) 117.
[3] S.S.P. Parkin et al, Philos. Mag. B 41 (1980) 65.
[4] S. Okazaki et al., JPS annual meeting (2021).
[5] N. Sirica et al., Phys. Rev. B 94 (2016) 075141.
[6] N. Sirica et al., Commun. Phys. 3 (2020) 65.
[7] C. Battaglia et al., Eur. Phys. J. B 57 (2007) 385.
[8] H. Tanaka et al., Phys. Rev. B 105 (2022) L121102.
[9]X. P. Yang et al., Phys. Rev. B 105 (2022) L121107.
[10] P. Popčević et al., arXiv:2111.12529

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Angle-resolved Photoemission Study of Zr3SnC2
1

Ⅲ-2

T. Ito1,2, M. Mita2, D. Pinek3, M. Nakatake4, K. Tanaka5,6 and T. Ouisse3

Nagoya University Synchrotron radiation Research center (NUSR), Nagoya University, Nagoya 464-8603, Japan
2
Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
3
Grenoble Alpes, CNRS, Grenoble INP, LMGP, F-38000 Grenoble, France
4
Aichi Synchrotron Research Center, Seto 489-0965, Japan
5
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
6
The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, JapanMAX phase compounds, i.e., Mn+1AXn where M is atransition metal, A belongs to groups 13-16 and X is the
C or N element, have recently been attracted muchattention due to their possible application for new classof two-dimensional systems called MXenes by removing
A atoms [1]. Zr3SnC2 is so called 312 MAX phase inwhich Zr3C2 layers separated by Sn layer, then two
dimensionality becomes higher than 211 phase. In
addition, relatively stronger spin-orbit interaction of Zr
and Sn 4d is expected to affect its physical properties.
In this study, we have performed angle-resolved
photoemission spectroscopy (ARPES) on MAX phasecompound Zr3SnC2 to directly investigate the electronic
structure of this system.
ARPES measurements were performed at the
UVSOR-III BL5U. Data were acquired at T = 30 K withhν = 82 eV which enables us to trace around the ΓKM
plane with inner potential of V0=17.7 eV estimated fromthe photon energy dependent measurement (not shown).
Figure 1 shows the obtained Fermi surface (FS)image on the ΓKM plane of Zr3SnC2. Along the ΓMand ΓKM high-symmetry lines (orange lines), we haveextracted the band structure image as shown in Fig. 2.
We have found that the electronic structure near the
Fermi level (EF) consists of two hole-pockets aroundΓ point and relatively intense dispersive feature justbelow EF around M point. While the former seems tobe similar with DFT calculation, the latter feature has
appeared in the blank of bulk DFT bands around theM(L) point. Therefore, we assigned the dispersive
feature around the M(L) point to be surface state. Fromthe band structure near EF (Fig. 3(a)), the observed
surface state was formed by characteristic saddle-like
dispersive feature (Fig. 3(b)), in which the saddlepoint locates around 150 meV at the M(L) point. Fromthe saddle-like dispersion, it has been expected that thenarrow dispersive feature along MK line forms pair oftriangular FS around M point, which has been clearlyobserved in Fig.1. To clarify the essential role of thesurface states, further studies with using liner/circularpolarization and spin-resolved ARPES are intended.

Fig. 1. Fermi surface image of Zr3SnC2. Orange thicklines indicate the high-symmetry lines on which the
ARPES image has been extracted in Fig. 2.

Fig. 2. Band structure (lower panel) and MDC spectraat EF (upper panel) along ΓM and ΓKM lines of Zr3SnC2.
Blue solid and dashed lines are DFT calculation along
the MΓK and AHL lines, respectively.

Fig. 3. (a) Band structure near EF around M point of
Zr3SnC2. (b) Example of saddle-like dispersive feature,in which M point corresponds to the saddle point.
[1] M. Basoum, MAX phases (Wiley, Weinheim 2013).

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Fermi Surface Measurements of TiSe2 with the CDW Transition
S. Tanaka 1, K. Ueno2 and K. Tanaka3

Sanken, The Institute of Industrial and Scientific Research, Osaka University, Ibaraki 567-0047, Japan.
2
Graduate School of Science and Engineering Saitama University, Saitama 338-8570, Japan.
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.

1studies for investigating the driving force of theinterlayer CDW transition in TiSe2 is under progresswith a help of the DFT calculation.

6.0

5.5

5.0

kz (Å-1)

-1.0

-0.5

kx (Å-1)

0.0(a)300KL2/c 

4.5

0.5

4.0

6.0

5.5

5.0

kz(Å-1)

Transition metal dichalcogenides (TMDs) are aclass of materials attracting high scientific interest in
recent years. They are layered materials where theinterlayer distance is considerably larger than theintralayer atomic distance yielding a quasi-two
dimensional character. Charge density wave (CDW)
transition, which is a transition accompanying aperiodical superlattice formation below the transition
temperature, is one of the typical phenomena of the
low-dimensional system, and has been attracted many
researchers. Among TMDCs, (1T-)TiSe2 exhibits very
unique character; its CDW transition provides the 2a
× 2b × 2c superlattice formation where the interlayer
periodic distortion occurs. Although several studies,including ARPES studies, have been made forrevealing the driving force of the CDW transition in
TiSe2, rather few were made for investigating theinterlayer interaction. In this work, we investigate thechange in the Fermi surface of TiSe2 along theinterlayer axis due to the CDW transition by measuring
the photon-energy dependent ARPES.
The experiments were carried out at BL5U of UVSOR.
The temperature of the cleaving/measurements ofsingle-crystalline TiSe2 were 300K and 10K, which arerespectively above and below the CDW transitiontemperature (about 200K). The (lateral) CDW formation
at 10K was examined by the folding of the valenceband from Γ(A) point to M(L) point in the ARPES
spectrum. Figure 1 show intensity maps of thephotoelectron at the Fermi level, demonstrating the
Fermi surface along the Γ-M-L-A plane. The horizontal
axis is along the Γ-M(A-L) line derived from theangular distribution of the photoelectron, and thevertical axis is along the inter-layer axis (kz) derived
from the photon-energy dependent measurements. For
deriving value of kz, the free-electron final state is
assumed, and 13.5eV is used as the inner potential
after the reference[1].
At 300K [Fig. 1(a)], the Fermi surface of theelectron-pocket near the M(L) point shows a tilted
elliptical shape. This structure is periodic (except thevariation of the intensity) along the kz axis with a 2π/c
distance which is the periodicity of the inverse lattice.
This is consistent with the DFT calculation (not shownhere). When the CDW transition occurs at 10K,
meanwhile, the periodicity of the Fermi surface along
the kz axis shrieks as half of that at 300K [Fig. 1(b)]. It
is due to the superlattice formation whose lattice
constant along the inter-layer axis c* = 2 × c. It is a veryclear evidence of the CDW transition of TiSe2
accompanies the periodic interlayer distortion. Further0kx(Å-1) 1(b)10K

L*








2/c*

L*


4.5

4.0

Fig. 1. Intensity maps of the photoelectron at the
Fermi level of TiSe2. The horizontal axis is along theΓ-M(A-L) line derived from the angular distribution of
the photoelectron, and the vertical axis is along kz axis
derived from the photon-energy dependent measurements.
The sample temperature is 300K (a) and 10K (b).

[1] M. D. Watson et al., Phys. Rev Lett. 122 (2019)076404.

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Temperature Dependence of Electronic Structure in Pb-doped La(O,F)BiS2
Superconductor
1

Ⅲ-2

N. Kataoka1, L. Y. Jun1, T. Setoguchi1, S. Demura2 and T. Yokoya1,3

Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
2
Nihon University, Tokyo102-8275, Japan
3
Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan

BiCh2 compounds are quasi-two-dimensional materials
with a layered structure typically represented by thecomposition of REO1-xFxBiCh2 (RE=rare earth; Ch=S,
Se). It can be doped electrons by replacing oxygen withfluorine atoms, and electron-doped samples exhibit
superconductivity below 2-10 K. Several experimental
and theoretical studies have indicated the possibility of
unconventional superconducting mechanisms [1]. Since
the superconducting transition temperature is sensitive
to the pressure applied to the BiCh2 planes, the effects
of many elemental substitutions have been intensively
studied [1-2]. Elemental substitution effects are importantfor understanding the superconducting mechanism,
although there are few reports on the electronic structure.
Pb-doped La(O,F)BiS2 shows an anomalous behavior
with a sharp decrease in electrical resistance around 100
K, but the origin of this behavior is unknown [2]. In thisstudy, we performed temperature-dependent angleresolved photoemission spectroscopy (ARPES)
measurements of Pb-doped La(O,F)BiS2 above andbelow the temperature at which an anomaly in electricalresistance appears in order to investigate the cause of
the anomalous electrical resistance.
The measurements were performed using the
LaO0.5F0.5Bi0.9Pb0.1S2 single crystals synthesized by
the flux method [2]. The temperature at which theanomaly appears is estimated to be about 100 K fromthe temperature dependence of the electrical resistance.
ARPES measurements were performed at BL5U of
UVSOR III. We used the 70 eV photons, and theenergy resolution was 35 meV. All samples werecleaved in situ on the (001) plane in an ultrahighvacuum of less than 5.0×10-9 Pa. The temperaturedependence of the electronic structure was measured
in the range of 50-150 K.
Figure 1 shows the Fermi surface mapping from the
ARPES intensity between ±25 meV of the Fermi
energy (EF) measured at 70 K and 150 K. Figure 2
shows the angle-integrated energy distribution curves(EDCs) in the X-M and Γ-X directions measured at 70
K and 150 K. The Fermi surface shape was found to
be in good agreement with the previously reported
La(O,F)BiS2 (F concentration = 0.5) [3], with nosignificant difference in the Fermi surface shape at 70
K and 150 K, respectively. On the other hand, the EDC
intensity in the X-M and Γ-X directions at 70 K
decreased from EF to around 0.2 eV and increasedaround 0.3-0.6 eV, compared to those at 150 K.
Reproducibility of the results were checked for several

samples. Therefore, this EDC change is considered to
be a change in the electronic structure due to an anomaly
in the electrical resistance.

Fig. 1 Temperature dependent Fermi Surfaces mapof LaO0.5F0.5Bi0.9Pb0.1S2 at (a) 70 K and (b) 150K.

Fig. 2 Angle-integrated EDCs in each direction (top:
X-M, bottom: Γ-X). Spectral intensities were normalized
by area intensity in the range EB = -0.1~0.8 eV. The
angles are integrated about ± 6° around the X point.

[1] Y. Mizuguchi J. Phys. Soc. Jpn. 88 (2019) 041001.
[2] S. Otsuki et al., Solid State Commun. 270 (2018) 17.
[3] K. Terashima et al., Phys. Rev. B 90 (2014)
220512(R).

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Evaluation of Self-Energy in Overdoped Bi2201 by Angle-Resolved
Photoemission Spectroscopy
Y. Miyai1, Shiv Kumar2, T. Kurosawa3, M. Oda4, S. Ideta2 and K. Shimada2

Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
3
Fuculty of Science and Engineering, Muroran Institute of Technology, Muroran 050-8585, Japan
4
Department of Physics, Hokkaido University, Sapporo 060-0809, Japan
1

2

High-Tc cuprate superconductors have attracted
much interest since their discovery in 1986 for theirhigh Tc as well as unusual physical properties such as
bad metal states and formation of density waves [1, 2].
However, the high-Tc mechanism has not been fully
understood yet, and therefore, it is necessary to study
the physical properties from the microscopic point ofview. Angle-resolved photoemission spectroscopy(ARPES) is one of the most effective and direct
experimental methods to investigate the electronic
structure in solids. ARPES spectra are related to theimaginary part of the one-particle Green’s function
and give the quasiparticle excitation spectrum. The
one-particle Green's function includes the self-energy
derived from the many-body interactions such as theelectron-phonon, electron-electron, and electronimpurity interactions. By analyzing the ARPES
spectral lineshape quantitatively, one can directly
evaluate the magnitudes of each many-body interaction.
The previous ARPES studies of cuprates have focusedon the investigation of the electron-boson interaction
at the vicinity of the Fermi level [3]. In the previous
studies, the real part of the self-energy due to theelectron-electron interaction was usually estimated bya line [4]. However, the energy dependence of the selfenergy due to the electron-electron interaction is nottrivial in the wide energy range. It is assumed to induce
a so-called “waterfall” structure or a sudden spectral
intensity suppression in the ARPES spectra [5]. To
understand the mechanism of the high-Tc cuprate
superconductivity, it is also important to quantify themagnitudes of the electron-electron interaction as wellas electron-phonon(boson) interaction [3].
In this study, to quantitatively evaluate the electronboson interaction and the electron-electron interaction
simultaneously, we have performed a high-resolution
ARPES study using synchrotron radiation on the Bibased high-TC cuprate (Bi,Pb)2Sr2CuO6+δ (Pb-Bi2201)
in the wide momentum and energy ranges. We haveselected overdoped Pb-Bi2201 with TC = 6K because
it has a relatively simple electronic structure whichallows us to precisely evaluate the self-energy in thenormal state (i.e., normal self-energy). While it has
been expected that heavily hole-doped cuprates would
behave as the 2D Fermi Liquid, ferromagnetic
fluctuation has been found recently [6].
Figures 1(a) and 1(b) show ARPES intensity plots

taken at hν = 60 and 75 eV, respectively. Based on thelineshape analyses using the tight-binding model (here
we only considered the x2-y2 band), we have evaluatedthe self-energy in the wide energy range. Figure 1(c)shows the simulation of the ARPES intensity plotusing the evaluated self-energy. We clarified that thereal part of the self-energy crosses the zero line at theenergy of E – EF ~ -0.5 and the imaginary part of selfenergy has the maximum at that energy (Dashed line
in Fig. 1). Because the imaginary part of the selfenergy gives the spectral linewidth, the waterfall
structure is caused by the suppression of the spectral
intensity due to the significant broadening of thelinewidth at E – EF ~ -0.5 eV due to the electron-electroninteraction. In order to further reproduce the spectral
intensity, the matrix element and contribution fromother bands at the bottom of the x2-y2 band is required.

Fig. 1. Electronic structure of Pb-Bi2201. (a), (b)ARPES intensity plots taken at hν = 60 and 75 eV,
respectively. (c) Simulated ARPES intensity plots
using the evaluated self-energy. A solid black curve isthe x2-y2 band in the tight binding model.

[1] P. Choubey et al., Proceedings of National Academyof Sciences. 117 (2020) 14805.
[2] Y. Y. Peng et al., Nature Materials. 17 (2018) 697.
[3]I. M. Vishik et al., Phys. Rev. Lett. 104 (2010) 207002.
[4] H. Anzai et al., Scientific Reports. 7 (2017) 4830.
[5] D. S. Inosov et al., Phys. Rev. Lett. 99 (2007) 237002.
[6] K. Kurashima et al., Phys. Rev. Lett. 121 (2018)
057002.

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Multi-atom Resonance Photoemission from the Valence Band of TiSe2
S. Tanaka1, K. Ueno2, K. Fukutani3 and F. Matsui3

Sanken,Osaka University, Ibaraki567-0047, Japan
Graduate School of Science and Engineering Saitama University, Saitama 338-8570, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
1

2

Ⅲ-2

“Multi-atom resonant photoemission” (MARPE),
which is an interatomic resonant photoelectron emission
from neighboring atoms of the core-excited atoms,
was reported first for the O1s photoelectron emission
at the Mn-2p excitation edge in MnO [1], and attracted
significant attention. In this report, we report the
MARPE effect on, for the first time, the valence bandin TiSe2 analyzed with the momentum-resolved
constant initial state (MR-CIS) spectroscopy using the“Momentum Microscope” apparatus recently installed
at BL6U in UVSOR-III, IMS [2].
Figure 1(a) shows a CIS spectrum of TiSe2 at the TiL3 edge for the whole valence band (0-5.5 eV). The
spectrum is well represented by two symmetric
Lorentzian peaks. Meanwhile, in Fig. 1(b), the MR-CIS
spectrum for a specific state [M-point at the binding
energy of 2.0 eV; shown in Fig. 1(c)] is well reproducedby the sum of two Fano-shaped strongly asymmetriccurves. According to our photon-energy dependent
ARPES studies and DFT calculations (not shown here),
this state is mainly provided by Se-4p, while most of thevalence band is provided by Ti-3d. The symmetricshape in Fig. 1(a) indicates that the interference between
the direct photoexcitation from Ti-3d and the intraatomic Auger process does not occur since the former
probability is so small at this photon energy range [3].
On the contrary, it is suggested that the probability ofthe photoemission from Se-4p is comparable to that of
the inter-atomic Auger decay of Ti-2p core hole, and theinterference yields the Fano-type asymmetric shape. It
should be noted that he Fano parameter q is negative inthe present case, contrary to the conventional resonant
photoelectron emission. More work will be needed toreveal the physical origin of negative q.

Fig. 1. (a) CIS spectrum for the whole valence bandat the Ti-L3 edge, (b) The MR-CIS spectrum at the
specific states (M-points at the binding energy of 2.0eV), which are shown as bright spots in thephotoelectron intensity map (c), where the hexagon is
the Brillouin zone of TiSe2.

[1] A. Kay et al., Science 281 (1998) 679;J. Electr.
Spectrosc. Rel. Phenom. 114-116 (2001) 1179.
[2] F. Matsui et al. J. Phys. Soc. Jpn. 90 (2021) 124710.
[3] J. J. Yeh and I. Lindau, Atom. Data and Nucl. Dat

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Temperature-dependent Electronic Structure of η-Mo4O11 Revealed by
Photoelectron Momentum Microscopy
T. Kobayashi1, E. Iwamoto2, K. Sakamoto2, F. Matsui3 and S. Suga4

Department of Material and Life Science, Osaka University, Suita 565-0871, Japan2
Department of Applied Phisics, Osaka University, Suita 565-0871, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
SANKEN, Osaka University, Ibakaki 567-0047, Japan1

η-Mo4O11 is a pseudo two-dimensional material thatconsists of alternating layers of octahedral structure,
which contributes to electrical conduction, andtetrahedral structure, which do not contribute toelectrical conduction. Owing to the connection ofoctahedral structure in a form of one-dimensional
chain, η-Mo4O11 can be classed as a material withhidden one-dimensionality. A two-step anisotropic
charge density wave (CDW) transition at 109 K (TC1)and 30 K (TC2) has been reported for this material bytemperature-dependent conduction measurement [1],and this transition was supported by the observation ofchange in lattice periodicity [2]. However, though agap opening and band folding is predicted in case of
CDW transition, such phenomena were not observedin the band structure [3]. Therefore we have performed
photoemission measurements of η-Mo4O11 at different
temperatures in order to observe traces of CDW in theband structure.
Figures 1 and 2 show the Fermi surface and the band
dispersion at ky=0 Å–1 measured at T=20 K. The thinsolid black lines in Figs. 1 and 2 represent the Brillouinzone boundaries. The Fermi surface in Fig. 1 looks
different from that reported previously in Ref. [3],probably due to the difference in the energy of theexcitation light. The energy used in the present study
would make the band visible only in the first Brillouinzone, but not in the second one. In other words, we can
explain the results in Ref. [3] by considering the bands
in the second Brillouin zone.
Figure 3 shows the photoelectron intensity
distribution near the Fermi level. As can be seen in thisfigure, no band gap opening or band folding can beobserved even when the temperature is varied acrossthe transition temperatures, and metallic electronic
states are always observed. This result suggests thatthe charge density wave transition in η-Mo4O11 may be
a metal-metal transition. The nesting vector determinedin previous studies is qc1=0.23b* and qc2=0.55a*+
0.47b*+0.28c*, suggesting that the charge density
wave phase has a fairly long period structure. As aresult of the minute modulation of each atom, weconsider that the band structure of the metallic phase
may not be much affected. This idea is consistent withthe slow increase of resistivity below TC1, and thedecrease in resistivity indicating the metallic characterof this material below TC2.

Ⅲ-2

Fig. 1. Fermi surface of Mo4O11 measured at T = 20 K.

Fig. 2. Band dispersion at ky=0 Å–1.

150 K
70 K
20 K

Fig. 3. Temperature-dependent photoelectron intensity
distribution near the Fermi level.

[1] H. Guyot et al., J. Phys. C 16 (1983) L1227.
[2] H. Guyot et al., J. Phys. C 18 (1985) 4437.
[3] G.-H. Gweon et al., Phys. Rev. B 72 (2005) 035126.

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Characterization of CVD Graphene on Ir(111)/α-Al2O3(0001)
by Photoelectron Momentum Microscope
E. Hashimoto1, K. Tamura1, H. Yamaguchi1, F. Matsui2 and S. Koh1

Department of Electrical Engineering and Electronics, College of Science and Engineering, Aoyama Gakuin
University, Sagamihara 252–5258, Japan
2
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan1

Ⅲ-2

Chemical vapor deposition (CVD) is a promising
method to synthesize high-quality transferrable graphenesheets for device applications. We have previously
reported growth of high-quality graphene on Ir(111)/αAl2O3(0001) by a low-pressure CVD method anddemonstrated the reusability of the substrates [1-2]. In
this study, we characterized the crystallinity ofgraphene/Ir(111)/α-Al2O3(0001) and the electronicinteraction between graphene and Ir(111) using
photoelectron momentum microscope (PMM) [3].
We carried out CVD growth of graphene on theIr(111)/α-Al2O3(0001) substrates, using CH4 and H2 asprecursors at 1000 °C. The gas flow rate of hydrogenand methane were 100 : 10 (#1), and 200 : 10 (#2),
respectively. For both #1 and #2, the 2D and G peaks
for graphene were observed in the Raman spectra. We
characterized the samples (#1 and #2) by valence-band
photoelectron spectroscopy (VB-PES) using PMM at
the linearly polarized soft X-ray beamline BL6U of the
UVSOR-III synchrotron.
Figures 1(a) and (b) show the Iso-energy crosssections of the 2D band dispersion at Fermi energy forsample #1 and #2, respectively. The distinct patterns
with 6-fold symmetry were observed, which suggeststhat the sharp pattern with a low background corresponds
to high single crystallinity of graphene. By comparing
the patterns for #1 and #2, we found that #1 had thehigher single crystallinity for several hundred µm2 and#2 included the 30° rotated domains (R30). The growthof R30 domains was promoted by the fast growth rate,
which was attributed to the higher hydrogen gas flowrate in the CVD growth condition for #2.
Figures 2(a)-(d) show the momentum-resolved VBP
spectra of graphene on Ir(111). No Dirac points wereobserved in the VBP spectra along the KΓK direction
because the Fermi level located below the Dirac points,
which suggests that the charge transfer from graphene
to Ir(111) occurred. The binding energy of the M saddle
point, which was evaluated from the VBP spectra alongMΓM direction, reflected the amount of charge transfer.
The binding energy of the M saddle point for #1 and #2
were 2.30 eV and 2.25 eV, respectively. The lower
binding energy for #2, i.e., the higher amount of chargetransfer, can possibly be attributed to the presence of therotated domains (R30) in #2. The binding energy for
R30 was reported to be 0.06 eV lower than that for theperfectly aligned domains [4].
Through this study, we found that the relationship ofcrystal orientations and the degree of electronicinteraction between graphene and the Ir(111) depended
on the CVD growth conditions of graphene, for which
PMM is a powerful complementary characterization
tool to conventional methods (e.g., Raman spectroscopy
and AFM) for comprehensive characterization ofgraphene/Ir(111).

Fig. 1. Iso energy cross sections of 2D band dispersion
at Fermi energy for (a) #1, (b) #2.

Fig. 2. Momentum-resolved VBP spectra of graphenefor (a) #1 along KΓK direction, (b) #1 along MΓM
direction, (c) #2 along KΓK direction, and (d) #2 alongMΓM direction.
[1] S. Koh, Y. Saito, H. Kodama, and A. Sawabe, Appl.
Phys. Lett. 109 (2016) 023105.
[2] A. Sakurai et al., Jpn. J. Appl. Phys. 59 (2020)
SIID01.
[3] E. Hashimoto et al., Jpn. J. Appl. Phys. (2022) inpress.
[4] E. Starodub et al., Phys. Rev. B 83 (2011) 125428.

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Ⅲ -2. Materials Sciences

BL6B

Vibrational Spectroscopy of Pentacene Single Crystals in the Mid to Far
Infrared Region and its Temperature Dependence
J. Miyamoto, A. Sugiyama, K.Yamauchi and Y. Nakayama

Department of Pure and Applied Chemistry, Tokyo University of Science, Noda 278-8510, Japan
Charge transport in organic semiconductor molecules
has become an important issue in the pursuit of organic
semiconductor devices with excellent efficiency.
However, the decrease in carrier mobility due tomolecular vibration is a particular problem for organic
semiconductors, and the elucidation of the vibrational
interactions that limit the charge carrier transport
efficiency is one of the most important subjects in thefield of organic semiconductors. In this study, we
carried out mid-to-far infrared absorption spectroscopyon the single crystal pentacene (C22H14), a typical ptype organic semiconductor material, and attempted to
track its temperature dependence.
First, single crystals of pentacene were preparedusing the physical vapor transport (PVT) method andfixed to chemical-vapor-deposited (CVD) diamondsubstrates (5 mm × 5 mm × 0.4 mm). Infrared (IR)absorption measurements were performed in atransmission configuration at room temperature (RT)or low temperatures (100 K, 40 K). A blank CVD
diamond substrate as a reference sample was alsomeasured in identical conditions.
The measurement results are expressed in the top
panel of Fig. 1 in terms of the IR absorbance which
was derived from the relative transmittance of thepentacene/diamond sample with respect to the blankdiamond sample. Quantum-chemical calculation
results (Gaussian09, b3lyp, 6-31g*) for intramolecularvibration modes and calculated intermolecular Ag and
Au phonon modes of the pentacene single crystals
taken from a literature [1] are shown in the lower
panels of Fig. 1. To track how the absorption intensityand peak positions change when the effect of thermal
vibration is reduced by cooling, the measurements
were performed at three different temperatures (RT,100 K, and 40 K). Figure 1 shows two peaks around460~500 cm-1 for the spectra at RT and 100 K.
Whereas, the calculation results predict three modes
around 480~500 cm-1, the former two modes were
presumed to be merged in the experimental spectra.
Although, the two peaks appeared in a low wavenumber
region compared to the calculated positions. On theother hand, the spectrum at 40 K exhibited a single peak,
instead of two, at approximately the same wavenumber
as the calculation results. The reason for this is unclear
at this stage, but may be attributed to changes inintermolecular interactions as previously reported as
shifts in Raman bands for amorphous thin-films of
N,N’-di-naphthaleyl-N,N’-diphenyl-1,10-biphenyl-4,4’diamine and copper-phthalocyanine [2].

For the spectral features below 200 cm-1 observed inFig. 1 are not able to be assigned to which vibrations
at this stage mainly due to a poor signal-to-noise ratio.
More accurate and reliable measurements in thiswavenumber region are future subjects to identify
plausible phonon/vibration modes that inhibit theelectrical conduction at RT.

Ⅲ-2

Fig. 1 Far-infrared spectra of a pentacene single crystal
sample measured in a transmission configuration at
various temperatures (RT, 100 K, 40 K). Calculated
intramolecular vibrational modes using the ab-initio
density functional theory and lattice phonons ofpentacene single crystals taken from Ref. [1] are alsopresented.

[1] A. Girlando et al., J. Chem. Phys. 135 (2011) 084701.
[2] T. Sugiyama and Y. Furukawa, Jpn. J. Appl. Phys. 45(2007) 3537.

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BL6B

Spectral Evidence of Current-Induced Local-to-Nonlocal Transition of SmS
H. Watanabe1,2, S. Tatsukawa2, K. Imura3, H. S. Suzuki4, N. K. Sato5 and S. Kimura1,2,6
Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
Department of Physics, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan3
Department of Physics, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
4
Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581, Japan
5
Aichi Institute of Technology, Toyota, 470-0392 Japan
6
Institute for Molecular Science, Okazaki 444-8585, Japan1

2

density could not be explained by the increase of lattice
temperature [5].
From these results, the current flow induces thedelocalization of electrons without increasing lattice
temperature. However, the golden-colored metallic
phase does not appear by the current. This result
suggests that the BGT needs other factors, such as
lattice deformation.

R (arb.units)

20

50K

(a)

15
10

0.0A
0.2A
0.6A
1.0A

5
30

R (arb.units)

Ⅲ-2

Samarium monosulfide SmS shows a pressureinduced insulator-to-metal transition from a blackcolored semiconductor to a golden-colored metal(BGT) [1,2]. Even though BGT was discovered morethan 50 years ago, its origin remains unclear. One
possible origin has been proposed as a transition
between the Bose-Einstein condensation (BEC) and the
BCS state of excitons [3], but no definitive evidence has
been obtained.
Recently, Ando et al. reported that the nonlinear
relationship between voltage (V) and electric current (I)occurs with increasing I at temperatures lower than 100
K, which suggests the electronic state changes byapplying current [4]. However, whether the currentinduced electronic state change is related to the BGT is
now under debate. To clarify the origin of the nonlinear
V/I curve and the link to the BGT, we investigate thecurrent and temperature dependence of the reflectivity
spectrum, which reflects electronic structure, in the nonlinear V/I region. We have already reported the rapid
increase of the effective carrier density at the nonlinear
V/I region by observing the THz reflectivity spectrum[5], which suggests the appearance of the currentinduced local-to-nonlocal transition of the electronic
structure. To clarify the whole picture of the currentinduced electronic structure change, we measured thecurrent dependence of the mid- and near-infrared
reflectivity spectrum using THz and IR microscopes at
BL6B.
The single crystalline SmS with a typical sample sizeof 1×1×1 mm3 was sandwiched by the electrodesconnected to the current source and mounted in a liquidhelium-cooled cryostat.
Figure 1 shows the I-dependent reflectivity spectra at
temperatures of 50 and 100 K. With increasing I, thereflectivity intensity below 0.1eV increases, suggesting
the carrier density increase. The peak at 0.6 eV
corresponds to the exciton peak of the direct bandgap at
the X point in the Brillouin zone [6,7]. The peak was
broadened and slightly shifted to the higher energy sidewith increasing I. The spectra at 50 K (a) and 100 K (b)qualitatively showed the same behavior. In the case of anormal insulator-to-metal transition, the bandgap size
decreases toward the metallic phase. However, thischange in Fig. 1 is the opposite of that expected. The
spectral shift is consistent with that with increasing
temperature [2]. Our THz reflectivity spectrum results
suggest that the current-induced increase of the carrier

25

0.4
0.8
Energy (eV)

1.2
100K

(b)

20
15

0.0A
0.2A
0.6A
1.0A

10
5

0.4
0.8
Energy (eV)

1.2

Fig. 1. Current dependence of mid- to near-infrared
reflectivity spectra of SmS at 50 K (a) and 100 K (b).
[1]A. Jayaraman et al., Phys. Rev. Lett. 25 (1970) 1430.
[2]T. Mizuno et al., J. Phys. Soc. Jpn. 77 (2008) 113704.
[3] B. I. Halperin and T. M. Rice, Rev. Mod. Phys. 40(1968) 755.
[4] H. Ando et al., JPS Conf. Proc. 30 (2020) 011132.
[5] H. Watanabe et.al., UVSOR Activity Report 2020
48 (2021) 81.
[6] S. Kimura et al., Physica B 403 (2008) 805.
[7]V. N. Antonov et al., Phys. Rev. B 66 (2002) 165208.

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BL6B

Structural Analysis of Fiber Biomaterials by Synchrotron-Radiation
Infrared Microspectroscopy
T. Kawasaki1, F. Teshima2 and K. Tanaka2

Accelerator Laboratory, High Energy Accelerator Research Organization, Tsukuba 305-0801, Japan
2
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan

1

Recently, fiber biomaterials such as cellulose fiberand peptide fiber have been getting attention in
medical and materials fields. The common feature in
their structures is a rigid sheet-like conformation, and
it is usually difficult to regulate the stacking format
without uses of extreme heating and organic solvents.
As an alternate approach, physical technique such as
high-power radiation can be proposed to control thefiber structure. Here, two-kinds of terahertz waves
were applied to regulate the cellulose fiber: one isterahertz free electron laser (THz-FEL) and the otheris submillimeter wave from gyrotron [1]. The THzFEL has a double pulse structure that is composed of
micropulse and macropulse where the duration of theformer is 10-20 ps and that of the latter is about 4 μs.
The oscillation wavelength covers from 30 to 300 μm,
and the irradiation power is given as avg. 5 mJ permacropulse. The submillimeter wave from the gyrotron
is a single pulse (1-2 ms half width) having 10 W power.
After the cellulose fiber was irradiated by the THz-FEL
that was tuned to 80 μm and the submillimeter wave thatwas tuned to 720 μm under atmospheric conditions atroom temperature, those samples were added on metalcoating plate and analyzed by using BL6B synchrotronradiation infrared microspectroscopy. The measurement
was performed by reflection mode with 64 scans.
In the FT-IR spectrum of cellulose (Fig. 1), strong
band at 1050 cm-1 and middle peak at about 1300 cm-1
were observed (Black). The former band corresponds
to stretching vibrational mode of glycoside bond (νCO), and the latter peak can be assigned to bending
vibrational mode of H-C-O, respectively [2]. After
THz-FEL irradiation (blue), the former peak wasdecreased and the latter peak was increased. On theother hand, the former peak was largely increased
accompanied by slight increase of the latter peak after
the submillimeter wave from gyrotron (red). These
spectral changes indicate that submillimeter wave
gave the irradiation effect on cellulose fiber opposite
to THz-FEL. Interestingly, when the cellulose fiber
was irradiated by submillimeter wave following THzFEL (green), the whole spectral pattern was almost thesame as that of the non-irradiation sample (black). One
interpretation on this phenomenon is that the cellulose
fiber was dissociated to the monomeric chain by the
THz-FEL irradiation, and the cellulose monomers werere-associated by the submillimeter wave radiation to
produce the original cellulose fiber.
We have ever found that amyloid fibrils that form
fiber structure like cellulose can be dissociated by the

THz-FEL and be promoted to form the aggregate by
the gyrotron. [3,4]. Therefore, it can be enoughconsidered that cellulose fiber can be dissociated andre-associated by those terahertz waves similarly withamyloid fibrils. The high-power terahertz waves canbe expected as a physical tool for regulation of thefiber biomaterials in future.

Fig. 1. Infrared spectra of cellulose fiber after
irradiation by terahertz waves. Black: non-irradiation;
blue: cellulose irradiated by THz-FEL; red: cellulose
irradiated by submillimeter wave from gyrotron; green:cellulose irradiated by submillimeter wave behind THzFEL.

[1] T. Kawasaki et al., J. Jpn. Soc. Infrared Science &Technology 31 (2022) 52.
[2] N. C. Carpita et al., Plant Physiol. 127 (2001) 551.
[3]T. Kawasaki, K. Tsukiyama and A. Irizawa, Sci. Rep.
9 (2019) 10636.
[4] T. Kawasaki et al., Biomed. Opt. Express 11 (2020)
5341.

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Ⅲ -2. Materials

BL7U

Low-energy ARPES Study of Iron-chalcogenide High-temperature
Superconductors
K. Nakayama1,2, T. Kato1, A. Moriya1, F. Nabeshima3, N. Shikama3, T. Ishikawa3, Y.
Sakishita3, S. Ideta4,5, K. Tanaka4,5, T. Takahashi1,6,7, A. Maeda3 and T. Sato1,6,7

1
Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency(JST), Tokyo 102-0076, Japan3
Department of Basic Science, University of Tokyo, Tokyo 153-8902, Japan
4
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
5
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
6
Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
7
Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan2

Ⅲ-2

Since the discovery of high-temperature
superconductivity in LaFeAs(O,F), iron-based compounds
are attracting great attention. Among known iron-based
superconductors, iron selenide FeSe is the structurally
simplest material. It exhibits various exotic properties
such as anisotropic superconductivity and electronic
nematicity without long-range magnetic order. These
properties are sensitive to chemical substitution, highpressure application, and/or carrier doping. Therefore,
FeSe provides an opportunity to investigate the interplay
between nematicity and superconductivity while
controlling some physical parameters. In particular,
isovalent-substituted FeSe1-xTex and FeSe1-xSx films
offer an excellent platform. Nematicity is realized in
FeSe (x = 0) as in bulk FeSe, and the highest Tc of 23 K
among non-carrier-doped FeSe-based compounds has
been reported at the critical Te concentration xc of ~0.2
at ambient pressure [1]. On the other hand, for the Ssubstituted counterpart, large Tc enhancement is absent
and possible emergence of magnetism has been reported[2]. Comparative studies on these contrasting behaviors
would provide a key to understand the origin of exotic
properties.
In this study, we performed low-energy angleresolved photoemission spectroscopy (ARPES) studyof FeSe1-xTex and FeSe1-xSx films. High-quality thinfilms were grown by the pulsed laser deposition
method. ARPES measurements were performed usinga MBS-A1 spectrometer at BL7U in UVSOR withenergy-tunable photons of 12-25 eV.
Figures 1(a) and 1(b) show a comparison of the
ARPES intensity around the Brillouin-zone center
measured in pristine FeSe and FeSe1-xSx films,
respectively. In pristine FeSe, highly dispersive holeband with the dominant Fe 3dxz/yz orbital character (blue)
crosses the Fermi level (EF) and a relatively flat bandwith the Fe 3dxy orbital (red) is located well below EF.
On the other hand, Se/Te substitution leads to an upward
energy shift of the dxy band, resulting in the appearanceof the dxy-orbital character at EF. The large electronmass of the dxy band enhances the density of states at EF,
which is likely responsible for the Tc enhancement. We
also determined the evolution of the electronic structure

upon Se/S substitution, and compared the results withthose on FeSe1-xTex films to elucidate the mechanismsof nematicity and superconductivity as well as the originof contrasting phase diagram between FeSe1-xSx and
FeSe1-xTex.

Fig. 1. (a) and (b) ARPES intensity plotted as afunction of binding energy and wave vector measured
in FeSe and FeSe1-xTex films, respectively. Blue andred curves are a guide for the eyes to trace the dxz/yz anddxy band dispersions, respectively.

[1] Y. Imai et al., Sci. Rep. 7 (2017) 46653.
[2] F. Nabeshima et al., J. Phys. Soc. Jpn. 87 (2018)073704.

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Ⅲ -2. Materials Sciences

BL7U

Elucidations of Electronic Structure and the Many-body Interactions ofOrganic Molecular Materials
K. Fukutani 1,2, Y. Hasegawa3, M. Murakami4, D. Okaue5, K. Fukui1,5, H. Ishii6,
K. Tanaka1,2 and S. Kera1,2,4
1
Institute for Molecular Science, Okazaki 444-8585, JapanThe Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan3
Department of Physical Sciences, Ritsumeikan University, Kusatsu 525-8577, Japan
4
Graduate School of Science and Engineering, Chiba University, Chiba 263-8522, Japan
5
Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan
6
Department of Applied Physics, University of Tsukuba, Tsukuba 305-8573, Japan2

As the sustainability of our global resources andenergy-harvesting rapidly becomes a central issue innavigating our technological advancements, thedevelopment of quantum devices made of organic
molecular materials, characterized by their low
fabrication cost using abundant elements and high biodegradability, is of paramount importance.
Among such organic molecular materials, single
crystalline rubrene (C42H28) is known to exhibit
exceptionally high carrier mobility (40 cm2/Vs [1]) andis considered as a promising semiconductor material forthe next-generation electronics.
However, despite the numerous superiorities mentioned
above, what should be the most fundamental building
blocks for the future development are still incomplete;that is, the understanding of the electronic structure andtheir interactions with phonons and molecular vibrations.
For the purpose of elucidating these aspects of organic
materials, angle-resolved photoemission spectroscopy(ARPES) is a premier experimental technique, which
can simultaneously reveal the energies and momenta ofthe transport carriers (i.e., electrons and holes). Indeed,
ARPES has been extensively utilized for rubrene andunveiled, for instance, the existence of discernable band
dispersions for HOMO-derived bands [2], and the band
gap induced by the interactions of electrons withmolecular vibrations, revealed in our recent work [3].
On the other hand, there remain numerous criticalquestions about this material that are yet to be answered,including whether or not there are two HOMO-derived
bands (as theoretically predicted), and whether there
exists an interplay between the modes of molecularvibrations and the directions of electron propagation.
In our attempt to give the answers to these questions,
we have utilized the BL7U at UVSOR to perform thehigh-resolution ARPES experiments.
For elucidating the many-body interactions, we have
utilized the low photon energy of hv = 8.0 eV tomaximize the momentum resolution. From the data wehave obtained (see Fig. 1), we observe a discernabledifference in the magnitude of the band gap formed by
the electronic interaction with the intramolecularvibrations at different locations of the Brillouin zone.
This is likely a signature of anisotropy in the electronmolecular-vibration interactions in the rubrene crystal.

Further quantitative analyses are expected to give us thefirst opportunity to understand the interplay between themolecular vibrational modes and the direction of electron
propagations in molecular crystals
Furthermore, the ARPES data obtained at higher
photon energy (see Fig. 2) show two different HOMOderived bands which are degenerate at their maximum
binding energy. These are in agreement with thecalculated band structure and are expected to serve as a
key for resolving the long-standing discrepancy between
the theoretical predictions and experimental observations
in rubrene band structure.

Fig. 1. ARPES second derivative plots obtained for(a) kx = 0 Å-1 (Γ-Y line) and (b) kx = 0.14 Å-1.

Fig. 2. ARPES plots for two HOMO-derived bands
with (a, b) wider and (c) narrower dispersions. The
dashed curves in (b), (c) are visual guides.
[1]J. Takeya et al., Appl. Phys. Lett. 90 (2007) 102120.
[2] S. Machida et al., Phys. Rev. Lett. 104 (2010)
156401; H. Ding et al., Appl. Phys. Lett. 96 (2010)
222106; Y. Nakayama et al., Appl. Phys. Express 5(2012) 111601.
[3] F. Bussolotti et al., Nat. Commun. 8 (2017) 173.

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BL7U

Dirac-cone and Saddle-point Energy Bands in a Kagome Superconductor
AV3Sb5
K. Nakayama1,2, T. Kato1, Y. Li3,4, Z. Wang3,4, K. Tanaka5,6, T. Takahashi1,7,8, Y. Yao3,4
and T. Sato1,6,7

1
Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency(JST), Tokyo 102-0076, Japan
3
Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture andMeasurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100081, China
4
Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems, Beijing Institute of Technology,
Beijing 100081, China
5
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
6
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
6
Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
7
Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan2

Ⅲ-2

Kagome lattice is an excellent playground to study
the physics intertwining electron correlation and nontrivial topology, owing to its peculiar band structure.
Theoretical studies on the kagome lattice predict theformation of nearly flat band, Dirac-cone band, andsaddle point van Hove singularity. When either ofthese bands is placed near the Fermi level (EF), various
unusual properties would be realized, e.g., Weyl
magnet, density wave orders, charge fractionalization,and superconductivity.
Recently, a new family of kagome-lattice materials
AV3Sb5 (A = K, Rb, and Cs) has been discovered. AV3Sb5
shows superconductivity with the superconducting
transition temperature Tc of 0.93–2.5 K, providing a rareopportunity to study superconducting properties in the
kagome lattice. AV3Sb5 also exhibits a charge-density
wave (CDW) transition at TCDW = 78–103 K, possibly
accompanied with time-reversal symmetry breaking. To
understand the origin of these exotic properties,
experimental investigations of electronic states are of
crucial importance [1].
In this study, we performed low-energy angleresolved photoemission spectroscopy (ARPES) studyof KV3Sb5 and studied the electronic states with a highmomentum resolution, which enables us to determine
momentum dependence of the CDW gap.
High-quality single crystals of KV3Sb5 were grownby the self-flux method. ARPES measurements were
performed by using a MBS-A1 spectrometer at BL7U
in UVSOR. Clean surfaces of the samples wereobtained by cleavage in an ultrahigh vacuum.
Figure 1 shows the ARPES intensity measured
along the ΓKM high-symmetry line of bulk hexagonal
Brillouin zone. One can identify an electron pocket
centered at the Γ point. This band is attributed to the
5p band of Sb atoms. One can also recognize linear
dispersions that produce multiple Dirac points near the
K point. These bands are attributed to the kagomelattice band with mainly V-3dxy character. One of the
Dirac-cone band (indicated by red arrow) shows aflattening with approaching the M point and forms asaddle-point dispersion. Upon decreasing thetemperature below TCDW, we found an opening of the
CDW gap on V-derived bands. Our detailed momentumdependent study demonstrates the largest gap opening
on the saddle-point band at the M point as well as theabsence of clear gap opening on the Sb-derived band.
Our observations suggest that the scattering between
the saddle-point bands and resultant large gap opening
stabilizes CDW, and Sb-derived parabolic band at theΓ point is likely responsible for the superconductivity
that coexists with CDW.

Fig. 1. ARPES intensity plotted as a function of binding
energy and wave vector measured in KV3Sb5.

[1] K. Nakayama et al., Phys. Rev. B 104 (2021)
L161112.

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BL7U

Angle-resolved Photoemission Study of TPP[FePc(CN)2]2
T. Ito1,2, T. Hoshina2, K. Tanaka3,4, M. Matsuda5 and N. Hanasaki6

Nagoya University Synchrotron radiation Research center (NUSR), Nagoya University, Nagoya 464-8603, Japan
2
Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
5
Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan
6
Department of Physics, Osaka University, Toyonaka 560-0043, Japan1

Molecular conductors are known to exhibit a variety
of properties ranging from magnetism tosuperconductivity, depending on the addition of
inorganic elements or the combination of cationic andanionic molecules. In particular, axially substituted metal
phthalocyanine (MPc, M = metal) molecules haveattracted attentions because of their unique physicalproperties such as a giant negative magnetoresistanceeffect [1]. Though their anomalous properties have been
expected to originate from strong π-d interactions, being
similar with those in strongly correlated transition metal,
the electronic structure of this system has never beenreported yet. In this study, we have investigated theelectronic structure of axially-substituted quasi-onedimensional(Q1D)
molecular
conductor
TPP[FePc(CN)2]2 single crystal by using angleresolved photoemission spectroscopy (ARPES).
ARPES measurements were performed at the
UVSOR-III BL7U. Data were acquired with hν = 40 eV
at T = 10 K. Measurement axis was set along 1D
conducting axis (//c). Needle-shaped single-crystals(typical size < 1 × 0.1 × 0.1 mm3) were cleaved in situ
along (110) plane. The relation between the cleavage
plane and conducting axis is shown in Fig. 1. To
minimize photoirradiation damage photon flux was
sufficiently reduced during all measurements.
Figure 2 shows valence band ARPES spectra of
TPP[FePc(CN)2]2 along the conducting axis. We havesuccessfully observed several peak structures (A-G)
from EF to 15 eV. Small background relative to peaks
suggests the cleanliness of the cleaved surface. Fromthe comparison of the ARPES spectra (Fig. 2) with thevalence band structure image (Fig. 3), peak B around
4 eV seems to show symmetric intensity reduction
together with sizable energy shift from Γ to Z point. In
addition, systematic energy shift has also beenrecognized around 5-7 eV (blue dashed lines). On theother hand, the energy shift of the peaks cannot be
observed at high-binding energy side (peaks E-G). We
expect that the observed change of ARPES spectra
originates from the energy dispersive feature on
TPP[FePc(CN)2]2.

Ⅲ-2

Fig. 1. Crystal structure of TPP[FePc(CN)2]2. Due tothe existence of the axial CN ligands, Pc units form a
one-dimensional chain along c axis, which corresponds
to π conducting axis.

Fig. 2. Valence band ARPES spectra along the ΓZline of TPP[FePc(CN)2]2. Blue and green dashed lines
are guide for dispersive and non-dispersive features.

Fig. 3. Valence band structure along the ΓZ line of
TPP[FePc(CN)2]2 .
[1] N. Hanasaki, et al., J. Phys. Soc. Jpn. 75 (2006)
033703.

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BL7U

Relationship between Chemical Pressure Effect and Electronic Structure in
R1-xCexOBiS2 (R=Nd, La)
1

Ⅲ-2

N. Kataoka1, T. Wakita1,3, Y. Hanada2, M. Nagao2 and T. Yokoya1,3

Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
2
University of Yamanashi, Kofu 400-8511, Japan
3
Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan

BiCh2 compounds are quasi-two-dimensional materials
with a layered structure typically represented by thecomposition of RO1-xFxBiCh2 (R=rare earth; Ch= S,
Se). It can be doped electrons by replacing oxygen withfluorine atoms or by introducing mixed valence R atoms
such as Ce and Eu into R sites. Electron-doped samples
show superconductivity below 2-10 K. Several
experimental and theoretical studies have indicated thepossibility of unconventional superconducting
mechanisms [1]. Since the superconducting transition
temperature (Tc) is sensitive to the pressure applied to
the BiCh2 planes, the chemical pressure effects of many
elemental substitutions have been intensively studied[1-3]. The chemical pressure effects are important forunderstanding the superconducting mechanism, although
there are few systematic reports on the electronic
structure. In R1-xCexOBiS2, the ratio of Ce4+ at the R site
is about 0.1~0.15 despite the composition, so theaverage ionic radius of the R site can be controlled while
keeping the electron doping level fixed [2,3]. Therefore,
it is the best material for investigating the relationshipbetween pressure and electronic structure in the BiCh2
systems. In this study, angle-resolved photoemission
spectroscopy (ARPES) measurements of R1-xCexOBiS2
were performed to investigate the relationship between
pressure and the electronic structure.
The measurements were performed using R1-x
CexOBiS2 (R=La, Nd; x=0.2~0.75) single crystals
synthesized by the flux method [2,3]. ARPES
measurements were performed at BL7U of UVSOR III,using 20 eV photons with an energy resolution of 15~20
meV. All samples were cleaved in situ on the (001)plane in an ultrahigh vacuum of less than 5×10-9 Pa.
Figures 1 (a) and (b) show the Fermi surfaces of
Nd0.7Ce0.3OBiS2 and La0.75Ce0.25OBiS2, respectively,and (c) and (d) show the respective band dispersions.
Nd0.7Ce0.3OBiS2 is a superconductor with Tc of ~5K,
while La0.75Ce0.25OBiS2 is non-superconductive at least
above 1.5K. Nd0.7Ce0.3OBiS2 and La0.75Ce0.25OBiS2
have inner and outer electron pockets, respectively,
centered at the X point. Nd0.7Ce0.3OBiS2 is a relatively
low-dimensional Fermi surface, with nested quadrilateralFermi surfaces on both the inner and outer sides. On
the other hand, La0.75Ce0.25OBiS2 has an inner Fermi
surface distorted into an elliptical shape extending inthe Γ-X direction (perpendicular to X-M-X direction).
The outer Fermi surface also seems to be distorted.
The difference in the shape of the Fermi surface may be,
to a first approximation, due to differences in electron

doping levels rather than chemical pressure. In fact, thesizes of the Fermi surfaces are different and there is adifference of about 0.1 eV in the energy at the bottom of
the band. Furthermore, their Fermi surface shapes are
similar for n = 0.125 and n = 0.25 electron doping levels[4]. In this regard, it may be possible here that the nested
Fermi surfaces are more favorable for achieving higher
superconducting transition temperatures, given that
Nd0.7Ce0.3OBiS2 has a higher superconducting transition
temperature. For a more comprehensive understanding,comparisons with other compositions of the material
should be made.

Fig. 1 (a) and (b) Fermi surfaces, as well as (c) and (d)band dispersions along X-M lines, for Nd0.7Ce0.3OBiS2
and La0.75Ce0.25OBiS2, respectively.

[1] Y. Mizuguchi J. Phys. Soc. Jpn. 88 (2019) 041001.
[2]Y. Hanada et al., Jpn. J. Appl. Phys. 58 (2019) 063001.
[3] Y. Fujita et al., ACS Omega 5 (2020) 16819.
[4] M. Ochi et al., J. Phys. Soc. Jpn. 85 (2016) 094705.

98 46 Ⅲ02-

BL7B

Ⅲ -2. Materials Sciences

BL7B

Photoluminescence Properties of Cs2ZnCl4 and Cs3ZnCl5 with Vacuum
Ultraviolet Excitation
K. Takahashi, M. Koshimizu, Y. Fujimoto and K. Asai

Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan

Auger-free luminescence (AFL) is owing to theradiative transition between the valence band and theoutermost core level. Generally, AFL is not efficientbecause the transition is competitive with the Auger
process, which is generally a much faster process thanthat of AFL. In other words, efficient AFL has been
observed in limited compounds such as alkaline- or
alkaline-earth fluorides or CsCl-based compounds.
In recent years, we have developed fast scintillators
exhibiting AFL on the basis of ternary CsCl-based
compounds, such as Cs2ZnCl4 [1], CsCaCl3 [2], andCs2BaCl4 [3]. Fast scintillation decay within 2 ns has
been achieved. The scintillation light yields of thesecompounds were less than 1,500 photons/MeV, which
is significantly smaller than those of Ce-doped
inorganic scintillators. Hence, we further investigatednovel compounds based on CsCl. As an example of thefurther investigation, we have recently reported thephotoluminescence and scintillation properties of
Cs3ZnCl5 in comparison to those of Cs2ZnCl4 [4]. In
the present report, we present the excitation spectra ofCs2ZnCl4 and Cs3ZnCl5, which clearly indicates thatthe emission was attributed to AFL.
Crystalline samples of Cs2ZnCl4 and Cs3ZnCl5 wereused for the measurements. The measurements of thephotoluminescence under irradiation with vacuum
ultraviolet light were performed at BL7B of UVSOR atroom temperature. The excitation wavelength between
50 to 200 nm was used for the measurements. The
photoluminescence from the samples were observedwith a CCD-based spectrometer via an optical fiber. The
photoluminescence spectra with different excitation
wavelengths were recorded. On the basis of thephotoluminescence spectra, the excitation spectra wereobtained.
To verify the origins of the emission bands at 260
and 310 nm of Cs2ZnCl4 and 240 and 290 nm of
Cs3ZnCl5 crystals, we obtained the excitation spectra
monitoring the wavelengths. Figures 1 and 2 present
the excitation spectra. The excitation spectra ofCs2ZnCl4 are well consistent with those in a previous
report [1]. A steep rise was observed in both excitation
spectra at around 90 nm, which corresponds to theexcitation of electrons at the outermost core level tothe conduction band. Hence, based on the excitation
spectra, the emission bands are attributed to AFL.

Ⅲ-2

Fig. 1. Excitation spectra of Cs2ZnCl4 for monitored
wavelengths of 260 and 310 nm [4]. Copyright (2020)
The Japan Society of Applied Physics.

Fig. 2. Excitation spectra of Cs3ZnCl5 for monitored
wavelengths of 240 and 290 nm [4]. Copyright (2020)
The Japan Society of Applied Physics.

[1] N. Yahaba, M. Koshimizu, Y. Sun, T. Yanagida, Y.
Fujimoto, R. Haruki, F. Nishikido, S. Kishimoto, andK. Asai, Appl. Phys. Express 7 (2014) 062602.
[2] M. Koshimizu, N. Yahaba, R. Haruki, F. Nishikido,
S. Kishimoto, and K. Asai, Opt. Mater. 36 (2014) 1930.
[3]K. Takahashi, M. Arai, M. Koshimizu, Y. Fujimoto,T. Yanagida, and K. Asai, Jpn. J. Appl. Phys. 59 (2020)
032003.
[4] K. Takahashi, M. Arai, M. Koshimizu, Y. Fujimoto,T. Yanagida, and K. Asai, Jpn. J. Appl. Phys. 59 (2020)
072002.

99 47 Ⅲ02-

BL7B Sciences
Ⅲ -2. Materials

BL7B

Investigation of Gamma-ray-irradiated Oxide Glasses for Deep Ultraviolet
Detector with High Efficiency
T. Shimizu, K. Shinohara, D. Umeno, K. Yamanoi and N. SarukuraInstitute of Laser Engineering, Osaka University, Suita 565-0875 Japan

Ⅲ-2

Vacuum ultraviolet (VUV) light is used in important
technological applications such as photochemical
processing, surface treatment, optical cleaning ofsemiconductor substrates, and sterilization. In particular,
it has been suggested that non-contact sterilization,
treatment, and processing could be advanced by using
VUV in the current corona disaster. For such recent
progress in VUV research and applications, it isnecessary to develop detectors in the short wavelength
range. In the development of VUV detectors, it isimportant to evaluate spectral characteristics in VUVregion.
Previously, we have studied fluoride crystals, suchas MgF2 and CaF2, for VUV optical devices [1,2].
Fluoride crystals are widely used in ultraviolet (UV)
optics because of their wide band gaps. And also wehave investigated fluoride glasses for VUV opticaldevices [3].
In addition, there are high expectations for material
modification by gamma-ray irradiation. We haveinvestigated the improvement of time resolution of
scintillators such as ZnO by gamma-ray irradiation.
Gamma-ray irradiation can be used as a post-processing
step and is expected to improve the performance ofvarious devices.
In our recent study, gamma-ray induced opticalproperty changes in non-doped and Ce-doped lithiumrich oxide glasses are investigated [4]. However, opticalproperties of these material in VUV region has not been
fully researched. Neutron measurements are importantin fusion experiments, and lithium-rich oxide glasses
are used as scintillator to detect neutrons. Evaluation of
VUV characteristics of scintillator material is important
to improve the performance of neutron detection. Inhigh dose rate environment such as nuclear fusion
experiment, optical materials are easily damaged. It isreported that Ce doping in the base material preventsdegradation of optical materials.
In this study, we measured transmittance of gammaray-irradiated oxide glasses from VUV to visible region.
We used a lithium borosilicate glass (LBS) and CeF3doped LBS. All glass samples were fabricated by themelt-quenching method [4]. To fabricate LBS, a
mixture of high purity 99.99% boric acid (H3BO3), highpurity silica (SiO2) and lithium carbonate (Li2CO3) was
melted at 1100 °C for 2 h under air atmosphere. Natural
Li was used for all sample fabrication. The melted glass
was quenched in air in a graphite mold and thenannealed at 500 °C for 3 h. The CeF3-LBS glasses were
fabricated using similar precursors with the addition of
CeF3 powder. Precursors for Ce-doped samples weremelted in an aluminum crucible for 3 h at 1200 °C andwere quenched in air in a graphite mold, then subsequently
annealed at 350 °C for 3 h. After fabrication, the nondoped glass samples were cut and polished into 10 mm
× 10 mm flat plates with thicknesses ranging from 3.8
mm to 4.2 mm. The Ce-doped samples were cut andpolished into 15 mm × 10 mm, with thickness ranging
from 3.1 mm to 3.8 mm. The glass samples were
irradiated with gamma rays carrying 1.17 and 1.33 MeV
energies from a cobalt-60 (60Co) source. The 60Co
source was calibrated with water and had a dose rate of
36.82 Gy/h at a distance of 1.0 m. The samples were set
approximately 10 cm away from the radiation source.
The irradiation was performed at room temperature andin ambient atmosphere.
Figure 1 shows measured transmittance of gammaray-irradiated LBS and CeF3-LBS. In both samples,high transmittance was measured even with VUV.
Although Ce was not seen to have much of an effect inthis measurement, it is expected to reduce the effect of
gamma irradiation.
In the future, we will compare more detailed
conditions and develop materials for high-efficiency
deep-ultraviolet photodetectors.

Fig. 1. Transmittance of gamma-ray-irradiated oxide
glasses.

[1] T. Shimizu et al., UVSOR Activity Report 47(2019) 107.
[2] K. Yamanoi et al., Opt. Mater. 36 (2014)769.
[3] T. Shimizu et al., UVSOR Activity Report 2020 48(2021) 88.
[4] Y. Lai et al., Radiat. Phys. Chem. 179 (2021)
109272.

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UVSOR User 4

UVSOR User 5