Ⅲ-2

Materials SciencesⅢ -2. Materials Sciences

BL7U

Electron-Phonon Coupling Investigation in Highly Oriented Pyrolytic
Graphite by Angle-Resolved Photoelectron Spectroscopy
1

S. Tanaka1, M. Matsunami2,3 and S. Kimura2,3,4

The institute of Scientific and Industrial Research, Osaka University, Ibaraki 567-0047, Japan.
2
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.
3
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585,
Japan.
4
Graduate School of Frontier Biosciences, and Department of Physics, Osaka University, Suita 565-0871, Japan.
Electron-phonon coupling (EPC) plays animportant role in solid state physics. The EPC has
been analyzed via the self-energy " el ! ph ( E, T ) in thequasiparticle spectral function, which is determinedwith the integral of the Eliashberg function" 2 F (!!, q) with the energy and momentum of thephonon, by using the angle-resolved photoelectron
spectroscopy (ARPES). Here, we demonstrate anexperimental method in which the elemental processof EPC, that is a scattering of the electron by thephonon in the solid, can be investigated [1].
Figure 1(a) presents a series of surface-normal( ± 5! ) photoelectron spectra for HOPG (highlyoriented pyro-lytic graphite) at 50 K in the region
near the Fermi level with several photon energies (h!).
The feature that we focus on here is the step-likeedges located at either 154 meV or 67 meV withrespect to the Fermi level, those are clearly
demonstrated by the differentials of the photoelectron
intensity with the binding energy along with that of agold film as shown in Fig. 1(b). The "-band of thegraphite crosses the Fermi level at the K(H) point,and no electronic states are located near the Fermi
level at the #(A) point, that is observed in the present
spectra. We therefore conclude that the observed
electron emission is due to EPC and that the energyof the step matches the energy of the phonon that is
involved. The 154- and 67-meV steps are ascribed tothe transverse optical (TO), and the out-of-plane
acoustic (ZA) and/or out-of-plane optical (ZO)
phonon of graphite at the K(H)-point, respectively.
Figure 1 (c) plots the intensities of the steps at 154
and 67 meV in the surface-normal photoelectron
spectra as a function of the photon energy. These
intensities represent the electron-scattering intensities
from K(H) to #(A) by the phonons at the K(H) pointin the Brillouin zone. The black (red) solid line is theLorentzian curve, where the center and widthenergies are 11.05 and 0.92 eV (6.0 and 1.2 eV),
respectively. This h!-dependence indicates that the
final photoexcitation state is definitely defined by thephoton energy and that this state determines thephonon branch that can scatter the electron. Note that
this photon-energy dependence clearly demonstrates
that we are observing EPC among the electrons inbands of the solid. The photoexcitation process that

accompanies electron-phonon scattering is widely
known as the “indirect transition’’ that is often
observed in semiconductor materials.
The transition probabilities of the indirect transition
can be formulated as" " $ ' # (! $%& #$ ' #$ ' * )! !$ '& !#   % "
"

+!$'


" $' # "   ! "  ! """ " $ ' # * )! # # $ ' # # # $ ' # (! $%& !$ '   ! "  ! &# # "   % "(a)
Au (40K)(c)h!

154 meV
67 meV

11.5eV
13eV
11.1eV
8.7eV
6.3eV

200

0

Binding Energy (meV)

(b)

Au

-200

h!
11.5eVdN"
dE

11.1eV

Step Hight (Arb. Units)

Differencial (Arb. Units)

Photoelectron Intensity(Arb. Units)

where the matrix elements of the optical transition
and EPC among the electronic bands in graphite areincluded. This is the first measurement of the matrix
elements of the EPC by ARPES. Additional insights
about electron-phonon scattering in the solid will be
gained from further research using this method. A
comparison with the results of theoretical calculationsof the intensity of the electron-phonon interaction
while resolving the energy and momentum of all thecontributing electronic states and phonons will lead todeeper insight into EPC in solids.

6.3eV

200

0

Binding Energy (meV)

-200

6

8
10
12
14
Photon Energy (eV)16

Fig. 1. (a) Surface-normal photoelectron spectra ofgraphite at 50K. (b) Differentials of photoelectron
intensity with the binding energy. (c) Height of thesteps observed in the photoelectron spectra as afunction of the photon energy.
[1] S. Tanaka, M. Matsunami, and S. Kimura, Sci.
Rep. 3, 3031; DOI:10.1038/srep03031 (2013).

49

Ⅲ-2

Ⅲ -2. Materials Sciences

BL1B

Experimental Study of Electronic States on Solids Using THz Beamline
A. Irizawa

The Institute of Science and Industrial Research, Osaka University, Ibaraki 567-0047, Japan

Ⅲ-2

The optical study is one of the most powerful
techniques for the investigation of electronic states onsolids. There can be obtained the great deal of
information about the electronic band structure, thesymmetry of crystal structure, and the dielectric
property. In the respect of experimental affinity, theoptical study is extremely compatible with themultiple conditions such as low temperature, highmagnetic field, and high pressure. In the case ofstrongly correlated electron systems, it is well known
that the temperature is one of the decisive factors forthe electronic state. The considerable types of phasetransition are induced by the change of thetemperature. Particularly, the multiferroic compounds
can be controlled of its physical properties mutuallyby the external fields such as magnetic, electronic,
and elastic ones. The other particular condition, thepressure will directly affect the electron-electroninteractions through the change of lattice constants.
The beamline 1B in UVSOR is the new one adjusted
for the investigations at low temperature and at
extremely low-energy region of THz. There is
Martin-Puplett type interferometer moved from BL6B
and the cryostat covering the temperature between 10
K and 300 K. In this report, I tried to use this newly
installed beamline and aimed to get more low energy
spectra for samples we use to deal. In the beginning, I
prepared some typical compounds having absorption
bands in THz region for transmittance experiment.
However, the experiments were resulted inpreliminary ones. There were several problems in thealignment process of optical axis. Several upperstream mirrors were lost their original positions after
an electrical power down. Also step motion motors
for mirror alignment were not fixed even in motion
controlled mode. Therefore, every machine time after
several month was dedicated for find the light.
Fortunately a visible light was also on the same
optical axis, we can explore the THz light following it
as a loadstar. On the way, I believed to find the THz
light but it might not be true one. There were twodifferent type spectra, both the synchrotron light anda black body like light. The later one with rather
broad spectrum might be originated in thermally
activated mirrors or something near the optical axis
(unproved).
Next time, those problems accompanied by the firsttime experiment will be fixed and the study might beproceeded.

Fig. 1. Difference of light source spectra throughblank (vacuum) and water vapor (air). (But the light
was said to be ‘another’ origin.).

50

Ⅲ -2. Materials Sciences

BL1B

Teraheltz Spectra of Nano Porous GoldT. Awano

Department of Electronic Engineering, Tohoku Gakuin University, Tagajo 985-8537, Japan

It is well known that bulk Au is inert. However,Au nanoparticles with several-nanometer-scale
sizes are catalytically active for several chemical
reactions such as the decomposition offormaldehyde and oxidation of CO. The catalytic
activity depends on the size of nanoparticles. The
nanoparticles with diameters in the range of 2 to 5
nm show the highest activity for oxidation.
Nanoporous Au (NPG) with 10–50 nm pore size
also shows catalytic activity for oxidation.
Recently, TiO2 is being widely used forphotocatalysis of various materials. TiO2 has adifferent activity with crystal structure for different
wavelengths. It has been reported that composite
materials of TiO2 with Au or Pt nanoparticles
enhance TiO2 catalytic activity. TiO2 plays an activerole in the decomposition of water to generate OH
radicals. It is supposed that the plasmonic
electromagnetic effect of Au or Pt enhances thecatalytic activity of TiO2. In addition, since pores of
NPG are able to trap the TiO2 particles on its surface,
NPG seems to be a photocatalytic nanocomposite
because of enhancement of the catalytic activity by
the electromagnetic effect. We have found that NPG
acts as a promoter to produce OH radicals using TiO2.
We report optical properties of NPG in this paper toinvestigate electromagnetic and plasmonic origin of
the promotor effect [1].
Figure 1 shows THz-reflectivity spectra of the NPG
films on gold-evaporated substrate measured at BL1B.
These spectra were connected with other spectral
range between millimeter wave and UV. Dielectric
constants were obtained by K-K analysis.
Plasmon fitting by classical Drude model in energy
loss function spectra is shown in Fig. 2. In the Drude
model,# = # % (1 $

$p =

"p
2

2

" +!

4#Ne 2
m *"!

2

+i

!" p

Nano Porous Gold

11nm
20nm
25nm
33nm
42nm

REFLECTIVITY

1

0.9

Ⅲ-2

0.8

20

40
60
80
-1
WAVE NUMBER (cm )100Fig. 1. Reflectivity spectra of nano-porous gold
films on Au/SiO2 glass substrates.
100

42nm
33nm
25nm
20nm
11nm

Im(-1)

10-1

10-2

10-3

10-4
10-2

10-1
PHOTON ENERGY(eV)

100

Fig. 2. Drude curve fitting of the energy loss
function spectra of NPG membranes on quartz
substrates. Dashed lines show fitting curves foreach pore size sample.

2)" (" 2 + ! 2 )  

Table 1. Plasmon parameters.
pore size $p (eV) ! (eV)
"#
(nm)
42
2.3
0.06
2.2
33
2.4
0.01
9
25
2.3
0.025
4
20
2.6
0.02
8
11
3.6
0.03
10

 
where is the plasma frequency, ! is dumping factor
and "# is dielectric constant at high frequency. Energy
loss function, Im(1/"), is proportional to absorption
intensity by transverse wave. The plasmon fitting
parameters are summarized in Table 1. Systematic
decrease of the plasma frequency with pore size
increment was observed. Plasma frequency of bulk
gold is 8.6eV, therefore, these $p for pore samples aremuch small. The promoter effect seems to be relatedwith small values of these parameters. The origin ofpore size dependence of the promoter effect is still
not clear.

[1] S. Kuwano-Nakatani, Y. H. Han, T. Takahashi
and T. Awano, Advanced Electromagnetics 2 (2013)
5.

51

Ⅲ -2. Materials Sciences

BL2A

Fluorescence Yield XANES Measurement of Thin Film by Silicon-Drift
Detector
1
2

Advanced Key Technologies Division, National Institute for Materials Science, Tsukuba 305–0044, Japan
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara 252-5210,
Japan
3
Faculty of Science and Engineering, Waseda University, Shinjuku 169-8555, Japan

X-ray absorption near edge structure (XANES) is a
powerful tool to reveal local environments ofmaterials with an elemental selectivity. Since it isdifficult to prepare the suitable thin samples fortransmission mode in soft X-ray region, twoalternative techniques, total electron yield (TEY) andfluorescence yield (FY) were usually employed formeasurements. FY method gives bulk-sensitive
information while TEY does surface-sensitive one.
[1] For FY method, there are two suitable sample
conditions. One is thin and concentrated, and theother is thick and diluted. Otherwise FY spectra weredistorted by the “self-absorption effect”. In addition,
counting loss of a detector also affects XANES
spectra.
Recently, a silicon-drift detector (SDD), which is
high-efficient and energy-dispersive detector, wasintroduced in UVSOR and now we can measure
XANES by both TEY and partial fluorescence yield(PFY) at the same point sequentially. In this study,
we reported Si-K XANES of SiO2 film measured byboth of TEY and PFY.
Si-K XANES spectra were measured at BL2A in
UVSOR by TEY with drain current and PFY with
SDD. The X-ray fluorescence spectra were
deconvoluted with gauss functions. Incident X-ray
beam was monochromatized with a InSb-(111) (2d =7.481 Å) double crystals monochromator. The
samples were SiO2 glass, Si powder and a SiO2 film
formed on p-Si (SiO2/p-Si). The thickness of the film
was 1 µm.
Figure 1(a) shows Si-K XANES of SiO2/p-Si andreferences. The component of SiO2 was observed inboth of the TEY and the PFY spectra of SiO2/p-Si. In
the PFY spectrum, it was also found that acontribution derived from p-Si around 1840 eV(indicated an arrow). This indicated that PFY spectra
reflect on information below 1µm from the surface
for Si-K XANES.
Compared between the TEY and the PFY spectra,
the white line in the PFY spectrum of SiO2/p-Si wasunderestimated even if the contribution of p-Si wasremoved. This was the mainly caused by the counting
loss of SDD since dead time was around 10 % at thewhite line, as shown in Fig. 1(b).

3 (a)
2.8
2.6
2.4

: TEY (drain): PFY (SDD)

Si-K

SiO 2/p-Si

2.2

Intensity / arb. units

2
1.8
1.6

SiO 2 glass

1.4
1.2
1
0.8

Si powder

0.6
0.4
0.2
0
1820 1830 1840 1850 1860 1870 1880
20 (b)

Dead time / %Ⅲ-2

H. Murata1, K. Okada2,3, D. Kobayashi2, K. Hirose2 and T. Yamamoto3

1001820 1830 1840 1850 1860 1870 1880
Photon energy / eV

Fig. 1. (a) Si-K XANES of the SiO2/p-Si andreferences. (b) Dead time of SDD for SiO2/p-Si.
[1] T. Yamamoto and K. Kawabata, UVSOR Activity
Report 40 (2009) 126.

52

Ⅲ -2. Materials Sciences

BL2A

Soft X-Ray Photoluminescence and Photoluminescence Excitation Spectraof AlGdN around Gd MIV Edge
Department of Electrical and Electronics Engineering, University of Fukui, Fukui 910-8507, Japan2
Far-Infrared Region Development Research Center, University of Fukui, Fukui 910-8507, Japan

III-V nitride semiconductors doped with the rareearth elements are promising light emitting devices ina wavelength range from visible to ultraviolet. Gd3+
ion is known as the light emitting material having ~3.9 eV emission line by 6P7/2 (lowest excited state) !
8
S7/2 (ground state) 4f intra- transition. This emission
energy (3.9 eV) is higher than the band gap energy of
GaN, so we should use AlN or AlGaN as the host
semiconductor materials for Gd. In previous work [1],a sharp 3.9 eV line emission was clearly observed
from AlGdN, and its photoluminescence (PL)excitation (PLE) spectra in a energy range between 3
and 7 eV showed that the emission process was hostexcitation. We also showed that PLE spectra of this
3.9 eV line around Al K edge (1.55 ~ 1.6 keV) andGd MIV edge (1.2 ~ 1.25 keV) show very similar tototal electron yield (TY) spectrum [2]. They indicatethat there is a process which transfers energy fromband-to-band transition in the matrix to 4f
intra-transition of Gd3+ ion. They also indicate that
this 3.9 eV emission does not observed by the
intra-atomic 4f to 4f excitation of Gd3+, but clearlyobserved by the allowed intra-atomic 3d to 4f
excitation. Then, we carried out soft X-ray (SX) PL
measurements around both Al K edge and Gd MIVedge and their PLE measurements with TY
measurements to investigate the relaxation process of
excited inner core electrons.
AlGdN thin film was grown in a MBE system witha RF-plasma assisted radical cell on the Si-face of(0001)-oriented 6H-SiC substrate. The thickness ofthe sample is about 120 nm. Concentration of Gd3+
ions is 13% (Al0.87Gd0.13N). All SX-PL, PLE and TY
measurements were carried out at room temperature(RT) with a silicon drift detector (SDD).
Figure 1 shows the PL spectra of AlGdN at RT.
The excitation energy is 1215 eV. Peaks less than
1000 eV including the largest peak around 900 eV
and above the excitation energy are SX emission
lines of Cu sample holder and “sum peaks” by SDD
itself, respectively. Emission line due to Gd3+
intra-atomic transition is found around 1200 eV as asmall peak. This peak is observed only when the
excitation photon energy is near and higher than Gd
MIV edge energy. PLE spectrum of this peak and TY
spectrum are plotted in Fig. 2(a) and (b), respectively.
It is found that the spectrum feature of PLE spectrum

is very similar to that of TY spectrum which isclearly explained by the 3d104f 7 ! 3d 94f 8 transition
array [3].
Ⅲ-2  











 



 Energy
Photon（eV）Energy（eV）

Fig. 1. PL spectrum of Al0.87Gd0.13N at RT.



















1

K. Fujita1, K. Fukui1 and K. Yamamoto2















Energy
Excitation（eV）

Fig. 2. PLE (a) and TY (b) spectra of Al0.87Gd0.13N at
RT.
[1] K. Fukui et al., Phys. Stat. Sol. (c) 7 (2010) 1878.
[2] K. Fujita et al., UVSOR Activity Report 40(2012) 95.
[3] C. Bonnelle et al., J. Phys. B 10 (1977) 795.

53

Ⅲ -2. Materials Sciences

BL2A

Chemical State Analyses of Ag Species Loaded on Ga2O3 Photocatalysts
1

2

EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603
Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Nagoya 464-8603

CO2 reduction is important not only for the energy
storage as usable and value-added products but for
the abatement of CO2 as a greenhouse gas. Especially,
photocatalytic reduction of CO2 with water isenvironment-friendly and attractive as the artificial
photosynthesis. It has been reported that Ga2O3 shows
photocatalytic activity for CO2 reduction with waterto produce CO as well as for water splitting to H2 andO2, and Ag loading on Ga2O3 (Ag/Ga2O3) promotes
the CO2 reduction [1].
In the present study, Ag L3-edge XAFS
measurements were performed to clarify the chemical
states and the local structures of Ag species in
Ag/Ga2O3 samples.
The reaction tests were carried out with a fixed-bed
flow reactor. Photocatalysts (mass: 0.2 g) were put
into the reactor cell under flowing CO2 gas. When we
exposed this reactor cell to UV light for 1 h, a
NaHCO3 aqueous solution was added to this reactor
cell in dark condition. After an hour, UV lightirradiation was started. Analysis of products was
performed using a thermal conductivity detector gas
chromatography (TCD-GC, Shimadzu GC-8A).
X-ray
absorption
finestructure(XAFS)
measurements were carried out at the beam line 2A
station of UVSOR-II at the Institute for Molecular
Science and the beam line 6N1 station of Aichi
Synchrotron Radiation Center. Ag L3-edge XANES
spectra of the samples were measured at room
temperature in total electron yield mode and thefluorescent X-ray yield mode with a silicon drift
detector (Vortex Electronics).
The results of photocatalytic reduction of CO2 withwater are summarized in Table 1. All samples
exhibited photocatalytic activity for CO2 reduction to
produce CO, H2 and O2. The amount of CO
production over 0.1 wt% Ag/Ga2O3 is larger than thatover bare Ga2O3. It is confirmed that the Ag loading
promotes CO2 reduction.
Figure 1 shows Ag L3-edge XANES spectra ofsilver-loaded gallium oxide samples (Ag/Ga2O3)
together with those of Ag and Ag2O reference
samples. The spectrum feature in the post-edge region
reflects the local structure around the target Ag atom,that is, the coordination symmetry and electronic stateof the Ag atom. The XANES spectrum of 1 wt%
Ag/Ga2O3 [Fig.1 (b)] exhibits a sharp absorption(whiteline) at 3354 eV due to the oxidized Ag as wellas the fine resonance peaks at 3380, 3399 eVcharacteristic of the metallic Ag. This result suggeststhat Ag metal particles are partially oxidized in 1 wt%
Ag/Ga2O3. Note that the absorption peaks due to the

Ag metal and oxides are weak in the spectrum of 0.1
wt% Ag/Ga2O3 and indistinct broad feature isobserved. It seems that the Ag particles are atomicallydispersed by connecting directly to Ga2O3.
Table 1. The results of photocatalytic reduction of
CO2 with water over Ga2O3 and Ag loaded Ga2O3
catalysts.
photocatalystamount of CO(µmol/h)amount of H2(µmol/h)

Ga2O3

0.2

2.5

2.1

5.2

1.1

0.8

0.1 wt%
Ag/Ga2O3
1 wt%
Ag/Ga O
Intensity (arb. units)

Ⅲ-2

T. Yoshida1, M. Yamamoto2, N. Yamamoto2 and S. Yagi1

(d)
(c)
(b)
(a)

3340

3360

3380

3400

Photon energy (eV)Fig. 1. Ag L3-edge XANES spectra of (a) 0.1 wt%
Ag/Ga2O3, (b) 1 wt% Ag/Ga2O3, (c) Ag foil and (d)Ag2O.
[1] K. Koci, K. Mateju, L. Obalova, S. Krejcikova, Z.
Lacny, D. Placha and L. Capek, Appl. Catal., B:
Environ. 96 (2010) 239.

54

Ⅲ -2. Materials Sciences

BL2A

Local Structure Investigation of FAU Zeolite Prepared from Si Based
Waste Materials
1

M. Sato1, M. Togo2, Y. Inoue2, K. Hara2 and A. Nakahira1,2

Kansai Center for Industrial Materials Research, Tohoku University, Osaka 599-8531, Japan2
Department of Material Science, Osaka Prefecture University, Osaka 599-8531, Japan

Blast furnace slag (BF slag) is one of the industrial
waste materials, and efficient use of the BF slag has
been sought for a long time. BF slag is obtained as aby-product in an iron manufacturing process, andgeneration amount is about 25 million tons per year inJapan. It has been widely used as mixture material
and fine aggregate for cement, road bed, source ofrock wool, dressing and ground improvement
materials because of its hydraulic property. Since theconsumption amount of BF slag is smaller than its
generation amount, however, additional efficient useof BF slag has been strongly desired.
In a previous study, LTA Na-P1 and FAU typezeolite were successfully synthesized using BF slag
and some kinds of waste glass. To synthesize the
FAU zeolite in a single phase, optimum aging timeabout 150 hours was necessary, and the ratio between
Na-P1 and FAU zeolite changed strongly dependingon the aging time as shown in Fig. 1. Therefore, Si-K
and Al-K edge XAFS was measured to investigate theeffect of aging time to the local structure around both
atoms.
BF slag, waste glass, NaAlO2 and NaOH were usedas starting materials. Si/Al ratio was controlled ataround 2. The starting materials and 2 mol/L NaOH
solution were encapsulated into a Teflon vessel, andaged for several periods. After aging, they werehydrothermally treated at 368 K for 72 hours. After
that, obtained products were also filtered and dried at
323 K for overnight.
Al-K and Si-K edge XANES spectra of obtained
samples before and after hydrothermal synthesis were
measured by fluorescence mode using InSb
double-crystal monochrometer for Si-K and KTP
double-crystal monochrometer for Al-K at BL-2A
station of UVSOR.
Figure 2 shows Al-K edge XANES spectra ofsamples before hydrothermal treatment. Obtained
spectra of samples were resembled with starting
material and no changes were observed by aging.
This result indicates that the local structure around Al
atom does not changed during the aging. On the other
hand, Al-K edge XANES spectra of the sample afterhydrothermal treatment were resembled to that ofcommercial FAU zeolite. Similar results wereobtained in the case of Si-K edge XANES spectra.
From these results, the aging does not affect to the
local structure of Al and Si in sample and it issuggested that the frameworks of zeolite isdetermined at the point of nucleation duringhydrothermal synthesis.

Ⅲ-2

Fig. 1. Relationship between generation phase andaging time.

Fig. 2. Al-K edge XANES spectra of samples,
which before hydrothermal synthesis, prepared at
different aging period.

55

Ⅲ -2. Materials Sciences

BL2A

Partial Fluorescence Yield XANES Measurements for
Ultra-Dilute Dopants by Silicon-Drift Detector
Advanced Key Technologies Division, National Institute for Materials Science, Tsukuba 305–0044, Japan
2
Faculty of Science and Engineering, Waseda University, Shinjuku 169-8555, Japan

Incident: 2430 eV: raw data
: S-K!
: elastic

500 1000150020002500300035004000

In-L

S-K

Incident: 2490 eV
Al-K

3
2
1
0
0
3
2
1
0
0
3

Si-K

Intensity / cps

Fluorescence yield (FY) method of X-ray
absorption near edge structure (XANES) is suitablefor ultra-dilute dopants. In hard X-ray region, it ispossible to measure 10 ppm dopants [1]. On the other
hand, FY has following difficulties in soft X-ray
region: low fluorescence yield and overlap ofcharacteristic X-ray. Recent progress of light sourcesand detectors, such as top-up mode and energy
dispersive silicon drift detector (SDD), made us
enable to measure XANES of ultra-dilute dopants
even in soft X-ray region. In UVSOR, a SDD wasintroduced for soft X-ray spectroscopy.
Cubic boron nitride (c-BN) has a similar crystal
structure and features to diamond. It is a good matrix
for soft X-ray spectroscopy since it consists of only
light elements. It was interesting that a large
rare-earth cation, Ce3+, is substituted for N-site withsurrounding B vacancies [2] and thus it is essential toinvestigate local environments of dopants in c-BN. In
this report, we present an attempt of XANES
measurements for ultra-dilute dopants in c-BN bypartial fluorescence yield (PFY) with SDD.
S-K XANES spectra were measured by PFY with
SDD at BL2A in UVSOR. The X-ray fluorescence
spectra were deconvoluted by gauss functions. We
also consider the component of elastic scattering.
Incident X-ray beam was monochromatized with a
InSb-(111) (2d = 7.481 Å) double crystals
monochromator. The sulfur-doped c-BN (c-BN:S)
samples were synthesized under high-pressure andhigh-temperature conditions. Samples were mounted
by carbon tape on Al sample holder.
Figure 1 shows typical X-ray fluorescence spectraof c-BN:S at different incident energy. Besides
characteristic X-ray from the sample, B-K, N-K and
S-K, it was also observed additional characteristic
X-ray, C-K, O-K, Fe-L and so on. These derived fromthe optical and measurement system, such as achamber, a monochromator and carbon tape, forexample.
Since the sample contains only trace sulfur, the S-K
signals were weak, about 1 cps at the peak. However,long dwell time (20 sec/points, 3 h/spectra) enabled
us to obtain good XANES spectra, as shown in Fig. 2.
It was noted that total electron yield method withdrain current could not detect S-K XANES at all. A
detailed analysis of local environments of sulfur inc-BN is in progress using first-principles calculations.

500 1000150020002500300035004000
Incident: 2550 eV

2
1
0
0

500 1000150020002500300035004000
Photon energy / eV

Fig. 1. Typical X-ray fluorescence spectra of c-BN:S
measured by SDD at different incident energy.

Intensity / arb. units

Ⅲ-2

H. Murata1, T. Taniguchi1 and T. Yamamoto2

B-K
C-K
N-K
O-K
Fe-L

1

S-K
PFY

dwell time: 20 sec/pts
3 h/spectra

2440 2460 2480 2500 2520 2540
Photon energy / eV
Fig. 2. S-K XANES of c-BN:S measured by PFY
with SDD[1] I. Tanaka et al., Nat. Mater. 2 (2003) 541–545.
[2] R. Ishikawa et al., Phys. Rev. Lett. 110 (2013)065504.

56

Ⅲ -2. Materials Sciences

BL2A

Evaluation of Local Structures of Si for LTA Nano-Zeolite on the Grinding
Process
A. Nakahira1,2, T. Tagami1, H. Kanayama1, H. Sakaguchi1, K. Hara1, Y. Inoue1, M. Sato2
and H. Aritani3
1

Faculty of Engineering, Osaka Prefecture University, Gakuencho, Sakai 599-8531, Japan
2
Osaka Center, IMR, Tohoku University, Gakuencho, Sakai 599-8531, Japan
3
Saitama Institute of Technology, Fukaya 369-0293, Japan

Zeolites have the unique 3D micropore networks.
They are one of aluminosilicate minerals commonlyused as various commercial adsorbents and otherapplications. For example, zeolites are in fact widelyused in petroleum industry as a catalyst for the
preparation of advanced materials. Furthermore, they
are used to extract nitrogen purification from air toincrease oxygen content for both industrial andmedical purposes Recently, in addition, they areapplicable to water purification, and also Cs
purification in nuclear accidents. However, in order
to expand the applications of zeolite in various
industrial fields, furthermore modification of
microstructures and morphology is needed forzeolites. [1-3] For example, a lot of attentions arefocused on the synthesis of the finely nanosizedzeolite powders by various novel processing.
Although many novel processing are attempted tosynthesize the nano-sized zeolite powders, the finely
nano-sized zeolite powders were synthesized by themechanical mixing processing in this study. And
the local structures were investigated for finely
nano-sized zeolite powders prepared by themechanical mixing processing.
Commercial LTA type zeolite was prepared.
Nano-sized zeolite was synthesized by the following
method. The powder of this LTA type zeolites
powder was milled for 30 min and 120min by themechanical milling method with the high energy
forces. After the milled and ground nano-sized LTA
type zeolite powder were characterized by XRD
method, FT-IR and TG-DTA. The microstructures ofnano-sized LTA type zeolite powder were observed
by SEM. The local structures around Si for the
products of nano-sized LTA type zeolite powder werecharacterized by measuring X-ray adsorption nearedge structure (XANES) at BL02A in UV-SOR.
The evaluation of XRD for ground fine-zeolite andreference LTA was carried out. XRD results showedthat after the mechanical mixing processing for 30
min and 120min the ground products were also
identified to be LTA type. The results indicated thatthe obtained fine-zeolite products were LTA typezeolites. Products obtained after the mechanicalmixing processing had the average particle of a few
hundred nanometer in diameter, suggesting thenano-sized LTA zeoite powders were successfully

Normalized (a.u.)

obtained by after the mechanical mixing processing
for 2 hs
Figure 1 shows the XANES spectra of zeolites andreference materials. As shown in Fig. 1, XANES
spectra of sample obtained after the mechanicalmixing processing for 30 min to 120 min the same
spectra as the LTA without mechanical mixing. These
results suggest nano-sized LTA zeoite powders
possess the good crystallinity and also the same local
structure of Si after the mechanical mixing
processing.

(a)

(b)
(c)

180 1830 1850 1870

Energy / eV
Fig. 1. Si XANES spectra of zeolites and referencematerials. (a)commercial LTA, (b)30min, and(c)120min.
[1] C. D. Chang, A. J. Silvestri, Journal of Catalysis
47 (1977) 249–259.
[2] T. Wakihara, R. Ichikawa, J. Tatami, A. Endo, K.
Yoshida, Y. Sasaki, K. Komeya and T. Meguro, Cryst.
Growth Des. 11 (1977) 955–958.
[3] A. Nakahira, S. Nishimura, H. Aritani, T.
Yamamoto S. Ueda, J. Mater. Sci. 36 (2001) 1885-89.

57

Ⅲ-2

Ⅲ -2. Materials Sciences

BL2A

Ag-L and P-K Edge XAFS Measurement of Antibacterial HAp
1

Ⅲ-2

M. Sato1, H. Sakaguchi2, Y. Inoue2 and A. Nakahira1,2

Kansai Center for Industrial Materials Research, Tohoku University, Osaka 599-8531, Japan2
Department of Material Science, Osaka Prefecture University, Osaka 599-8531, Japan

Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) is a chief
component of our hard tissue and it shows excellent
biocompatibility and osteoconductivity. Therefore, it
has been widely used as an alternate of hard tissue inan orthopedic surgical procedure. However, bacterial
infection has been a major problem in orthopedic
surgery. Therefore, the development of a new implant
which can prevent a bacterial infection during surgery
is strongly desired.
There are many studies to provide an antibacterial
effect for implant by the doping of some kinds ofmetal elements. In these elements, silver, copper andzinc are understood to show and excellent
antibacterial effect with very small amount of use.
In this study, Ag doped HAp were prepared byconventional hydrothermal process, and local
structure around P and Ag atom was investigated by
XAFS measurement.
0.1 mol/L Ca(NO3)2, (NH4)2HPO4 and AgNO3,
solutions were used as starting materials. These
solutions were mixed up each other becoming theratio of Ca to P of 1.67 and the ratio of Ag changed
from 0.5 to 10 mol% for Ca of HAp in a Teflon
vessel, and pH of mixed solution was adjusted to 10.
After mixing, they were hydrothermally treated at
423 K for 24 hours. Obtained solutions were filteredand dried at 323 K for overnight.
Ag-L and P-K edge XANES spectra of obtained
Ag-HAp powders were measured in a total electron
yield mode and fluorescence mode by SDD detector
using InSb double-crystal monochrometer at BL-2A
station in UVSOR. For XAFS measurement,commercial HAp, AgNO3 and Ag3(PO4) were used as
references.
From the XRD analysis, HAp generated for all
samples as a main phase. In addition, metal Ag was
generated for the sample prepared at the ratio of Ag
more than 2 mol% for Ca of HAp. ICP measurement
showed that the actual amount of Ag in obtained
sample is about one tenth of additive amount.
Figure. 1 shows P-K edge XANES spectra ofsamples prepared in Ag ratio of 0.5 and 1 mol%.
Since obtained P-K edge XANES spectra of sample
was resembled that of commercial HAp, it is clarified
that the local structure around P atom does not change
by doping of Ag. From this result, the possibility ofAg substitution into HAp structure was suggested.
On the other hand, since we did not obtain the clear
spectra for Ag-L edge of sample in this measurement,
we will study continuously to obtain the clear Ag-Ledge XAFS spectrum.

Fig. 1. P-K edge XANES spectra of obtained
samples.
[1] M. Sato, S. Yamamoto, Y. Nishio, Y. Takamatsu
and A. Nakahira, UVSOR Activity Report 38(2011)115.
[2] M. Sato, Y. Kawabe, S. Misu, S. Hayashi and A.
Nakahira, UVSOR Activity Report 39 (2012)81.
[3] M. Sato, T. Nagayasu, S. Hayashi and A.
Nakahira, UVSOR Activity Report 40 (2013)126.

58

Ⅲ -2. Materials Sciences

BL2A

Investigation of Local Structure of Ca-Based Materials Synthesized from
Granulated Blast Furnace Slag
1

M. Sato1, M. Togo2, T. Morinaga2, S. Fujihara2 and A. Nakahira1,2

Kansai Center for Industrial Materials Research, Tohoku University, Osaka 599-8531, Japan2
Department of Material Science, Osaka Prefecture University, Osaka 599-8531, Japan

Blast furnace slag (BF slag) is one of the industrial
waste materials and generates about 25 million tons
per year in Japan. BF slag mainly consisted from
SiO2, CaO and Al2O. Fe, Ti and Mn are included as
trace elements. By focusing on this composition of
BF slag, it can be recognized that the ratio of Si, Ca
and Al is close to a tobermorite, and the ratio of Si
and Al is also close to a zeolite.
In a previous study, tobermorite, Ca-based layered
double hydroxide (LDH) and calcium phosphate weresuccessfully synthesized using BF slag. In thesematerials, tobermorite is one of the most important
calcium silicate materials and has been widely usedarchitectural materials such as autoclaved lightweight
concrete (ALC) and fire-resistant building materials.
Tobermorite has layer structure of that SiO4
tetrahedra sandwiches CaO sheet and cation exchange
ability by substituting a part of Si by Al ion.
It has been clarified that the Al substituted
tobermorite has selectivity for cation such as alkali
metal and alkali-earth metal ions.
Since tobermorite also has a high selectivity for Cs
ion, it has been suggested that can use for handling of
nuclear waste. Therefore, XAFS measurement was
conducted to investigate a local structure around Si
and Al atom of obtained tobermorite.
BF slag, quartz powder and CaO powder were usedas starting materials. BF slag was ball-milled to
become particle size less than 75µm. Ca/(Si+Al) ratio
was controlled in the range from 0.8 to 1.2 byaddition of quartz or CaO powder. Mixed powder anddistilled water was encapsulated into a Teflon vessel,
and then it was hydrothermally treated at 453 K for
24 and 48 h with rotation speed of 20 rpm. After that,obtained products were filtered and dried at 323 K for
overnight.
Al-K and Si-K edge XANES spectra of obtained
samples were measured by fluorescence mode by
SDD using InSb double-crystal monochrometer for
Si-K and KTP double-crystal monochrometer for
Al-K at BL-2A station of UVSOR.
From the Si-K edge XANES spectra, the spectrumof sample prepared at Ca/(Si+Al) = 1.0 was
resembled with that of commercial tobermorite, andsignificant change of spectrum by rotation during ahydrothermal synthesis did not observed .
Figure 1 shows Al-K edge XANES spectra ofsample prepared by hydrothermal synthesis using BF
slag. Obtained spectra showed similar trend to Si-K
edge XANES spectra, and local structure around Al

atom changed depending on the ratio between Ca and
Si+Al. These results suggested that the Al-substituted
tobermorite was synthesized by using BF slag, andthe possibility to use tobermorite as not only
architectural materials, but also environmental
purification materials was indicated.

Ⅲ-2

Fig. 1. Al-K edge XANES spectra of samples
prepared by static and rotary hydrothermal synthesisat 453 K for 48 h.

59

Ⅲ -2. Materials Sciences

BL2A

Structural Evaluation of Novel Piezoelectric Ceramics
A. Nakahira1,2, H. Kanayama1, T. Tagami1, S. Togo1, S. Fujihara1, T. Morinaga1,
M. Sato2 and H. Aritani3
1

Piezoelectric ceramics are widely used as
piezoelectric, electro-optic and non-liner optic
devices in modern society. Among piezoelectric
ceramics, PZT (Pb(Zrx,Ti1!x)O3) is used
extensively in the world, but it contains leaddamaging human health and environment. In orderto solve this problem of PZT, the development oflead-free piezoelectric ceramics are desired. Muchattention is attracted to niobium based complex
oxide, KNbO3 with the perovskite-type structure as
one of the promising ceramics instead of PZT
ceramics [1-3]. KNbO3 ceramics have the higher
curie temperature (435 °C) and energy conversion
rate (0.69) of KNbO3 than that of another post PZTmaterials.
KNbO3 was synthesized by the electrodereaction process in KOH solution as electrolyte
using metal niobium plate (10 " 20 " 0.2 mm) as
an anode and carbon (C) rod (#5 " 100 mm) as
cathode. The distance between Nb and C
electrodes was about 40 mm in the beaker. The
reaction was continued until Nb plate wascompletely dissolved under 100 mA / cm2 ofcurrent density supplied direct current power. Then,the precipitation obtained during the reaction was
filtered and collected by centrifugation. The solid
product was frequently washed and air-dried at
50 °C. For the comparison, KNbO3 (KN-ref) as areference material was prepared by the solid
reaction process at 1150 to 1250 °C. Products werecharacterized with some techniques such as XRD,
FT-IR, TG/DTA and the microstructures wereobserved with SEM. The local structures around K
for the products of the solid product powder werecharacterized by measuring X-ray adsorption nearedge structure (XANES) at BL02A station of
UVSOR in Okazaki.
As a result of XRD diffraction patterns and SEM
images, finely nano-sized KNbO3 powder was
synthesized in 1 M KOH solution. SEM
observations indicated that obtained KNbO3
powder with several hundred nanometer indiameter were synthesized. On the contrary,
KNbO3 (KN-ref) as a reference material preparedby the solid reaction process had the particle sizewith 5 to 10 micrometer in diameter, i.e.

micro-sized KNbO3 (KN-ref) powders. These
results suggest that the fine nan-sized KNbO3
powders were successfully obtained from theelectrode reaction process.
Figure 1 shows the XANES spectra ofsynthesized by the electrode reaction process
products (nano KN) and a reference material(KNbO3 : KN-ref). XANES spectra of sample
obtained the same spectra as the reference
micron-sized KNbO3 (KN-ref). These results
suggest the fine nano-sized KNbO3 powders
synthesized by the electrode reaction process
possess the good crystallinity and also the same
local structure of K–edge as the reference KNbO3(KN-ref).

Normalized Intensity (a.u.)

Ⅲ-2

Faculty of Engineering, Osaka Prefecture University, Gakuencho, Sakai 599-8531, Japan
2
Kansai Center, IMR, Tohoku University, Gakuencho, Sakai 599-8531, Japan
3
Saitama Institute of Technology, Fukaya 369-0293, Japannano KN
KN-ref.

3600 3610 3620 3630

Energy (keV)
Fig. 1. K-edge XANES spectra of nano-sized KNbO3
and a reference material (micro-sized KNbO3(KN-ref)).
[1] T. R. Shrout et al., Journal of Electroceramics 19(2007) 111-124.
[2] I. Nowak et al., Chemical Reviews 99 (1999)
3603-3624.
[3] C. H. Lu et al., Materials Letter 34 (1998)
172-176.

60

Ⅲ -2. Materials Sciences

BL3B
BL3B

Intrinsic Luminescence and Energy Transfer from Self-Trapped Excitons
Intrinsic Luminescence
EnergyTransferin Scandium andBoratesupon
Vacuumfrom
UV Self-trapped
Excitation Excitonsin Scandium Borates upon Vacuum UV Excitation
N. Kodama,
Kodama, A.
A. Abe,Abe, Y.
Y. Morisawa,
Morisawa, T.
T. Sakashita,
Sakashita andN.
and T.
T. Takahashi
Takahashi

Faculty of Engineering and Resource Science, Akita University, Akita 010-8502, Japan
Faculty of Engineering and Resource Science, Akita University, Akita 010-8502, Japan
Tb3+-doped LSB (Fig. 2(b)). This suggests efficient
appearance of intense emissions associatedwith Re3+
energy transfer fromthe STEs to the Re3+ ions. Re3+
3+
at 7.8 K for Sm -doped LSB (Fig. 2(a)), and at 14.9
doping also
caused a decrease in the decay times for
K for Tb3+-doped LSB (Fig. 2(b)). This suggests
the STE emissions, which is consistent with theefficient energy transfer from the STEs to the Re3+
decrease3+in the time-averaged STE emission intensity.
ions. Re doping also caused a decrease in the decay
This provides further evidence for energy transfer fromtimes for the STE emissions, which is consistent with
the STEs to the Re3+ ions. In the case of LSB at a
the decrease in the time-averaged STE emission
temperature of 293 K, the energy transfer rates
intensity. This provides further evidence for energy
determined from time-resolved 3+measurements weretransfer from the STEs to the Re ions. In the case of
1.6!106 s-1 (STE II) and 7.0!10-4 s-1 (STE III) for 5
LSB at a temperature of 293 K, the energy transfer
at.% Gd3+ doping, and 2.1!106 s-1 (STE II) andrates determined from time-resolved
measurementsfor 5 at.% Tb3+ doping.
8.0!10-4 (STE6 III)
were 1.6!10 s-1 (STE II) and 7.0!10-4 s-1 (STE III)The observed energy transfer rates are within anfor 5 at.% Gd3+ doping, and 2.1!106 s-1 (STE II) andorder ofmagnitude of estimates based on dipole8.0!10-4 (STE III) for 5 at.% Tb3+ doping.
dipole or dipole-quadrupole energy transfer. For both
The observed energy transfer rates are within an
LSB and YSB, the ratio of the STE II and III emission
order of magnitude of estimates based on
intensity in doped samples to that in undoped samples
dipole-dipole or dipole-quadrupole energy transfer.
gradually increased with temperature.
This
For both LSB and YSB, the ratio of the STE II and III
temperature dependence is shown in Fig. 3 for Sm3+emission intensity in doped samples to that inand Tb3+-doped LSB, and suggests that energy transfer
undoped samples gradually increased withfrom STEs to Re3+ ions is thermally activated andtemperature. This temperature dependence is shownprobably related 3+
to exciton mobility.
-doped LSB, and suggests
in Fig.
3 for Sm - and Tb3+5000
2500
251nm
! = 70 , 160 nm
that energy transfer from4000STEs
toT = 293K
Re3+ ions is
1500
3000
258nm related
 LuSc(BO ) to exciton
thermally
activated and probably YSc(BO )
2000
1000
mobility.
251 nm!ex = 70 , 160 nm

380 nm

500
100000324 nmλex = 70 , 160 nm
T = 7.8 K
250 300 350 400 450 500
Wavelength / nm

Fig. 1(a)

1500

1000
15000

ex

380 nm251 nm!ex = 70 , 160nm
324 nm
Tb3+ (5 D4"7FJ)

200

5000

 undoped
 5at.%Tb 10at.%Tb

J=5250 300 350 400 450 500/ nm
T = 7.8KWavelengthJ=4

Fig. 1(a)

J=3

J=6

3 2

3 2

1000
5000
0
251nm
λex = 70 , 160 nm
200
4000 300 400 500 600 700= 293K
Wavelength /Tnm
Fig. 1(b) ὼ LuSc(BO )
3000
258nm
3 2
ὼ YSc(BO3)2
2000
5000
!ex = 70 , 160 nm 4 G5/2"6HJ
1000
4000  undoped
J=7/2
0 1at.%Sm3000 200
600 700
T = 300
14.9K400 500J=9/2
Wavelength / nm
2000

Intensity / a.u.

Intensity / a.u.

500
2500
0
200
2000

Intensity / a.u.

T = 7.8 K

Intensity / a.u.

Intensity / a.u.

2000

Intensity / a.u.

The intrinsic luminescence characteristics were
The intrinsic luminescence characteristics
investigated for self-trapped excitons (STEs) in
were investigated for self-trapped excitons
polycrystalline samples of the binary scandium borates(STEs)in polycrystalline
samplesof the binary
YSc(BOandLaSc
3(BO3)4(LSB),
3)2(YSB),
scandiumborates
LaSc
3(BO3)4(LSB),
LuSc(BO3)2(LuSB), in which absorption of vacuum(YSB), lightand byLuSc(BO(LuSB),inYSc(BO3)2(VUV)
ultraviolet
the host3)2canfacilitate
3+ (VUV)
3+
which
absorptionofvacuumultraviolet
efficient energy transfer from the STEs to Re (Re =3+ by 3+light
, Gd the, or hostTb3+) canions.facilitate efficient energySm
3+ = Sm3+,(Remeasured
transferfromthe
STEsspectra
to Re3+Emission and excitationwere
at3+, or Tb3+) ions.
Gdtemperatures in the range 7.8-293 K using theEmissionSynchrotron
and excitation
spectrawere measured
atUltraviolet
OrbitalRadiation(UVSOR)
temperaturesin borates
the range
K usingthefacility.
All of thewere 7.8-293
found to exhibit
intenseUltraviolet
Synchrotron
Orbital(UVSOR)
intrinsic
emissionsin theUV Radiation
region under
VUV
facility. Allof andthe160borateswereto exhibit
excitation
at 70
nm, andthe founddecay times
wereintense intrinsic
emissionsin thewere
UV region
under
determined.
These
emissionsassignedto
VUV excitationofat STEs
70 andpossibly
160 nm,associatedand the decay
recombination
withtimes were
determined.
These emissions
bandgap
excitations,or to moleculartransitions inwere
the3assigned
torecombinationofSTEs
possiblyundopedLSB
BO3 group. The emission spectra for
associatedbandgapat excitations,to 7.8-293
molecular
under
VUVwithexcitation
temperaturesor ofK
3group.
Thebroademissiontransitionsin the BO
werecharacterizedby 3threedistinct
bandsspectra
at 253for (I),
undoped
LSBandunderatnm
323 nm (II),379 nmVUV(III), asexcitation
shown in Fig.
temperaturesof 7.8-293
K werecharacterizedby1(a).
These featuresare similar
to thosefound in thethree distinct
broad
at 253 nm(I),The323emission
nm (II),
emission
spectrafor bands
single-crystal
LSB.
and 379fornmundoped(III), asYSB
shown
Fig. at1(a).
Thesespectraand inLuSB
293 K
are
featuresinare
similarthose
found YSB,
in thetwo
emissionshown
Fig.
1(b). toFor
undopedbroad
spectra forsingle-crystal
LSB.
Thetemperatureemission spectra
emission
bands
were present
in therange
forundoped
YSB
and
LuSB
at
293
in
15-293 K, the first centered
258 K
nmare(I)shownand theFig. 1(b).
Fornm
undopedYSB, twoLuSB
broadexhibited
emissionasecond
at 320(II). Undoped
bands were
the temperaturesinglestrongpresent
broadin emission
at 250range
nm 15-293
in theK, the first centeredat 258K.
nm (I) and the second attemperature
range 14.9-293
320Fornm(II). LSB,
UndopedLuSBtimes
exhibiteda single
undopedthe decay
for emissions
I,strongemissionat 250nm 115in theII,and broad
III wereless than
10 ns,
ns temperatureand 3.4 µs,
range 14.9-293For
K. undoped YSB, the decay time forrespectively.
For
undopedemissionsI,emissions I LSB,
and theII decayweretimes
120 forand
550 ns,
II,
and
III
were
less
than
10
ns,
115
ns
and
3.4
µs,
respectively. By analogy with the STE states in alkali
respectively.
YSB, the IIdecay
time
forI
halides[1], the For
fast undoped
decay components
in LSBandemissionsI
andwereSTE
120
andwith550centerns,in
YSB originate
fromII singlet
statesrespectively.
analogy with The
the fast
STEcomponent
states in
and/or off-centerByconfigurations.
alkalihalides[1], thethe samefast origin,decay andcomponentsin
I in LSB
may have
may also II
have
LSB
and I in YSBfrom singlet
STE statesa contribution
fromoriginate
energy transfer
to impurities
orwith
off-centerIn configurations.
The
defectscenternear and/or
the STE.
contrast, the slow
fast
component
I
in
LSB
may
have
the
same
origin,components III in LSB and II in YSB are thought toandmay from
also ahave
a contribution
fromoff-center
energyoriginate
triplet
STE with an3+
transfer
to impurities
defectsnear
STE.
configuration.
Energy ortransferfromthetheSTEs
to ReIn
contrast,
the slow components
LSBandand293II inions at temperatures
between 7.8IIIorin14.9
K
YSB
are thoughtbytoaoriginate
a triplet
STE withwas evidenced
decreasefrom
in STEemissionsandanoff-center
Energywith
transfer
Gd3+
shorteneddecayconfiguration.
times in LSB doped
Sm3+, from3+
3+
3+
at withtemperatures
7.8 ortheSTEs
to YSBRe ions, and
doped
Gd . Thebetween
STE emission
or Tb
3+
14.9 and decreased
293 K waswith
evidenced
by Re
a decrease
in STE
concentration
intensity
increasing
emissionsshortened bydecay
times in LSB
doped
(1-40
at.%),and
accompanied
the appearance
of intense3+3+
3+
3+ doped with Gd3+.
,
Gd
or
Tb
,
and
YSB
with
Sm
at 7.8 K foremissions associated with Re
The3+STE
emissiondecreasedwithincreasing-dopedLSB intensity(Fig. 2(a)),
and at
14.9
K for
Sm
Re3+ concentration (1-40 at.%), accompanied by theFig. 1(b)1000

J=11/2

0.9
10000
0.8

䋭 undopedSTE䋭 5at.%Tb䋭 10at.%Tb

0.7
5000
0.6

T = 7.8K

0.5
0
200

Tb3+ (5 D4→7FJ)

J=6

J=5
J=4
J=3

50 100 150 200 250 300
300 Temperature
400500/ K 600 700
Wavelength / nm
Fig.3(a)

5000

0.6

Intensity / a.u.

Intensity
a.u.doped- to
STE intensity
ratio of/ Sm
undoped-LSB

15000
STE
1
λex = 70STE
, 160nm

STE intensity ratio of Tb doped-to
un doped-LSB

J=5/2
Fig. 15000
1. Emission spectra for undoped
samples
at excitation
00
200 300 400 500 600 700
700 160 nm: (a)
200
300
400
500 70600 andwavelengths
of
LSB
at
7.8
K, and (b) YSB
Wavelength / nm
Wavelength / nm
Fig.
2(a)K.
Fig.2(b)and LuSB atFig.
293
1(a)Fig. 1(b)

4000

0.5

3000

λex =STE
70 , 160 nm
ὼSTE
undopedὼSTE
1at.%Sm

4 G →6H
5/2
J

J=7/2

T = 14.9K

0.4

J=9/2

2000

0.3

1000

0.2

00

J=5/2
50

200

Fig. 2(a)

100

150

200

250

300Temperature
400 500
600/K/ nm
Fig.3Wavelength(b)J=11/2300

700

Fig.2(b)- too

STE intensity ratio of Sm doped- to
undoped-LSB

STE intensity ratio of Tb doped-to
un doped-LSB

Fig. 1 Emission spectra for undoped samples at
Fig. 2. Emission spectra for samples at 15 K and excitation3+
excitation
wavelengths
and and160Smnm:(a) LSB-dopedLSB,wavelengths of
70 and 160 nmof: (a) 70
undoped3+atand (b)YSB
and LSB.
LuSB at 293 K.
-dopedand7.8(b) K,
undopedand TbSTEΣ
Fig. 12 Emission
spectra for samples
at 15 K at
STEΣ
STEΤ
STEΤ
STEΥ
0.9
excitation
wavelengths of 70 andSTEΥ160 nm : (a)0.8
undopedand Sm3+-doped LSB, and (b) undoped and3+ 0.7
Tb -doped
LSB.
0.6
Fig. 0.530 Temperatureof ratio of STE
50 100 150 200 250 300 dependence
Temperature / K
intensity for
doped LSB to that for undoped
LSB: (a)Fig.3(a)Fig.3 (b)3+anddependence(b) Tb3+ of
doping.
Sm
Fig. 3. doping,Temperature
ratio of STE intensity for doped
doping, and
Tb3+
LSB K.Kan’noto that for et
undoped
LSB:&(a)Appl.
Sm3+ Chem.,[1]al., Pure
69 (b)(1997)
doping.
1227.
0.6

0.5
0.4

0.3
0.2

0

50

100 150 200
Temperature / K

250[1] K. Kan’no et al., Pure & Appl. Chem. 69 (1997) 1227.

61

300

Ⅲ-2

Ⅲ -2. Materials Sciences

BL3B

Analysis of Optical Properties for Pr3+-Doped Y3Sc2Al3O12
1

2

Ⅲ-2

S. Watanabe1, K. Ogasawara1, S. Ishii2 and M. Kitaura2

School of Science and Technology, Kwansei Gakuin University, Sanda 669-1337, Japan
Deptartment of Physics, Faculty of Science, Yamagata University, Yamagata 990-8560, JapanThe 4f-4f and 4f-5d transitions of lanthanide (Ln3+)
ions have drawn attention for potential application asluminescent materials. The garnet-type oxides are
chemically and structurally stable among inorganic
compounds. Therefore, to date, Ln3+-doped garnettype oxides have been widely used as commercial
materials. The analysis of the optical properties due tothe 4f-4f and 4f-5d transitions, however, remains
limited, since they originate in the complicatedmulitplet structures. In addition, the many-bodyeffects and relativistic effects coexist in these issues.
In this study, the optical properties of Pr3+-doped
Y3Sc2Al3O12 have been investigated, experimentallyand theoretically.
Pr3+-doped Y3Sc2Al3O12 polycrystalline sample wasprepared by the solid-state reaction. The
concentration of Pr3+ ion was 1 mol%. The
experimental excitation spectrum at 10 K was
measured monitoring the emission at 333 nm. We
analyzed the 4f2-4f15d1 transitions of Pr3+ ions in
Y3Sc2Al3O12 based on first-principles many-electron
configuration interaction calculations [1, 2].
Figure 1 shows the experimental excitation
spectrum and theoretical absorption spectrum for
Pr3+-doped Y3Sc2Al3O12. The fundamental absorptionof Y3Sc2Al3O12 host crystal is located above 6.7 eV.
This result agrees with the excitation spectrum of
non-doped Y3Sc2Al3O12 host crystal. Compared to thetheoretical 4f2-4f15d1 absorption spectrum of Pr3+, thepeaks at 4.2 – 6.0 eV can be attributed to the
4f2-4f15d1 transitions of Pr3+ ions The configuration
analysis of many-electron calculations clearly
indicates that the separations among main peaks are
due to crystal field splitting of the Pr-5d levels, while
splitting between the main peaks and subpeaks is due
to spin-orbit interaction of the Pr-4f levels. The
subpeaks are due to transitions to two-electron
excitation states based on a shake-up process.
Figure 2 shows the emission spectra for Pr3+-doped
Y3Sc2Al3O12 measured at 10 K under excitation at
various photon energies. The sharp peaks at 480 –800 nm originate in the 4f2intraconfigurationtransitions of Pr3+ ions, which can be attributed to the3
P0!3HJ transitions. The broad bands at 300 – 400
nm are considered to be either the excitonic emissionof Y3Sc2Al3O12 host crystal or the 5d-4f emission of
Pr3+ ions. Unfortunately, we have little informationon these bands. Further spectroscopy experimentsin the UV-VUV region are needed to assign theorigins of these two bands.

Fig. 1. Experimental excitation spectrum andtheoretical absorption spectrum for Pr3+-doped
Y3Sc2Al3O12.

Fig. 2. Emission spectra for Pr3+-doped Y3Sc2Al3O12.
[1] K. Ogasawara et al., Phys. Rev. B 64 (2001) 143.
[2] S. Watanabe et al., Phys. Rev. B 81 (2010)
125128.

62

Ⅲ -2. Materials Sciences

BL3B

Optical Spectra and Electronic Structure of SrCeO3 Crystals
H. Numata1, M. Kitaura1, S. Watanabe2, K. Ogasawa2, S. Kurosawa3,4, K. Yubuta3,
A. Ohnishi1 and M. Sasaki1
1

Department of Physics, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
Department of Chemistry, School of Science and Technology, Kwansei University, Sanda 669-1337, Japan
3
Institute for Materials Research, Tohoku University, Sendai 980-8679, Japan
4
New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8679, Japan

CeO2 is characterized by so-called mixed valency,
which is caused by mixing between 4f 0 and 4f 1L-1
configurations in the ground state, where L-1 denotes
the hole in the valence band mainly composed of
O-2p orbitals [1]. This feature comes fromhybridization between the Ce-4f and O-2p orbitals.
Indications of the mixed valency have been found inphotoemission and X-ray absorption spectra [2]. On
the other hand, it has been pointed out that thereflectivity spectrum also exhibits an evidence for themixed valency: A prominent reflectivity peak around
13 eV has been assigned to an appearance of 4f 2L-2
configuration.
SrCeO3 is also regarded as a mixed valent
compound [3], because of similarities inphotoemission and X-ray absorption spectra. In
addition, this material is known as one of typical
proton conductors. Despite the important material inboth of basic science and industrial application, thefundamental optical constant spectra such as
absorption and reflectivity spectra, and its electronic
structure have been few reported so far. One of thereasons for this is the difficulty for the crystal growthof SrCeO3. Recently, we have succeeded the crystal
growth of SrCeO3 by using a Floating zone technique.
In the present study, we have measured reflectivity
and absorption edge spectra of SrCeO3 crystals at 300
K. The results are shown in Fig. 1(a). As indicated bya red solid curve, the fundamental absorption starts at
2.2 eV. This energy is lower than that determinedfrom the diffuse refection spectrum [4]. The
reflectivity spectrum (red solid curve) consists ofthree parts: 3.4-6.3 eV (part I), 6.3-16.5 eV (part II),and 16.5-40 eV (part III). Referred to the calculated
energy band structure, the part I, II, and III are
assigned to O-2p!Ce-4f, O-2p!Ce-5d, Ce-5p!
Ce-5d transitions, respectively. The agreement
between experimental and theoretical spectra is good,as shown in Figs. 1(a) and 1(b). Several peaks in thepart II are due to the crystal field splitting of theCe-5d orbital. In the part III, a peak appears around27.9 eV. Considering the 5p55d1 configuration of a
Ce3+ ion, it is expected that the transition between 1P1
and 1S0 multiplets occurs in the part III. Thus, weassign the 27.9 eV peak to the 1S0!1P1 transition.
Drastic increase in reflectivity can be seen below 3.4
eV. This would be influenced by the reflection at theback of the crystal, because it occurs in the energy

region below the fundamental absorption edge. Since
the absorption coefficient is negligibly weak below
3.4 eV, the monochromatic synchrotron radiation
light can penetrate inside the crystal.
As mentioned above, it is expected that theexperimental reflectivity spectrum exhibits a peak
due to the excitation of the 4f 2L-2 configuration.
Actually, Fig. 1(a) shows such a peak around 12 eV.
On the other hand, Fig. 1(b) also exhibits a prominent
peak around 11.9 eV. Since the 11.9 eV peak isconnected to the critical point of the joint density ofstate, it is not likely to attribute the 11.9 eV peak in
Fig. 1(a) to the excitation of the 4f 2L-2 configuration.

(a) Experimental

!, R

R
!


(b) Calculated

R



2

0

10

20

30

40

PHOTON ENERGY (eV)Fig. 1. (a) Reflectivity (red line) and absorption adge
(blue line) spectra of SrCeO3 crystals, measured at
300 K. (b) Theoretical reflectivity spectrum (greenline).
[1] A. Fujimori et al., Phys. Rev. B 28 (1983) 2281.
[2] M. Niwano et al., J. Phy. Soc. Jpn. 57(1988)
1489.
[3] M. Matsumoto et al., J. Electron Spectrosc. Relat.
Phenom. 78 (1996) 179.
[4] F. Goubin et al., Chem. Mater. 16 (2004) 662.

63

Ⅲ-2

Ⅲ -2. Materials Sciences

BL3B

Energy Transfer from I! Centers to Au! Centersin Co-doped NaCl:I!, Au! Crystals
T. Kawai and K. Yuasa

Graduate School of Science, Osaka Prefecture University, Sakai 599-8531,

RT

Wavelength (nm)250
200
NaCl:AuAbsorption D2

NaCl:ILuminescenceC

3
Optical Density

Luminescence Intensity (arb. unit)

300

D1

2
1

A
4.0

5.0
6.0
Photon Energy (eV)0

7.0

Fig. 1. Luminescence spetrum (blue) of NaCl:I! andabsorption spectrum (red) of NaCl:Au! at RT.

Luminescence Intensity (arb. unit)

Ⅲ-2

mechanism from the I! center to the Au! center in the
co-doped NaCl:I!, Au! crystals, the measurements ofthe decay kinetics of the luminescence are needed.

Alkali halide crystals have the wide band-gap up to
the vacuum ultra violet energy region and are asuitable candidate host for doping of impurity ions.
Though many experimental investigations have been
performed on alkali halide crystals doped with
impurity ions, energy transfer between two kind of
impurity ions in co-doped alkali halide crystals arecomparatively less studied [1, 2]. In this study, we
have investigated the energy transfer from I! centers
to Au! centers in NaCl crystals co-doped with I! andAu! ions.
Figure 1 shows the absorption spectrum of
NaCl:Au! and the luminescence spectrum of NaCl:I!
at room temperature (RT). In NaCl:Au!, the A, C, D1,
and D2 absorption bands due to the Au! centers areobserved at 4.18, 5.54, 6.25, and 7.10 eV,
respectively [3]. In NaCl:I!, the luminescence banddue to the one-center type localized exciton appears
at 5.32 eV [4]. The 5.32 eV luminescence band in
NaCl:I! has an overlap with the C absorption band at
5.54 eV in NaCl:Au!. The fact indicates the potentialof the energy transfer from the I! center to the Au!
center in co-doped NaCl:I!, Au! crystals.
Figure 2 shows the excitation spectra in NaCl:Au!,
NaCl:I!, and co-doped NaCl:I!, Au! crystals at RT.
The 5.32 eV luminescence band in NaCl:I! isefficiently excited in the energy region between 6.5
and 7.2 eV, where the absorption band due to
one-center type localized exciton is located. In
NaCl:Au!, the luminescence band at 3.99 eV, whichcorresponds to the A’ luminescence band due to the
Au! centers, is efficiently excited at the A, C, D1, andD2 absorption bands. In the co-doped NaCl:I!, Au!
crystal, the excitation spectrum for the A’
luminescence band at 3.99 eV has the broad bandaround 6.66 eV in addition to the A, C, D1, and D2
bands. Since the 6.66 eV band corresponds to theexcitation band for the 5.32 eV luminescence band in
NaCl:I!, the fact implies the existence of the energy
transfer from the I! center to the Au! center in the
co-doped NaCl:I!, Au! crystal.
From the absorption intensity of respective
absorption bands, the concentrations of the I! and Au!
centers in the co-doped NaCl:I!, Au! crystal are
estimated to be about 3.01019 and 1.01015 cm!3,respectively. Thus, the average distance between theI! center and its nearest neighboring Au! center isabout 2.0 nm. The distance of 2.0 nm indicates thepotential of the energy transfer mechanism of Förster
type. In order to clarify the energy transfer

300
RT

Wavelength (nm)250
200
NaCl:I ,Au
for 3.99 eV-

NaCl:Ifor 5.32 eV-

NaCl:Au
for 3.99 eV

4.0

5.0
6.0
Photon Energy (eV)7.0

Fig. 2. Excitation spectra of NaCl:Au! (red), NaCl:I!
(blue), and co-doped NaCl:I!, Au! (purple).
[1] A. F. Muñoz and J. O. Rubio, Phys. Rev. B 38
(1988) 9980.
[2] A. Méndez, et al., J. Lumin. 79 (1998) 269.
[3] F. Fischer, Z. Physik 231 (1970) 293.
[4] I. Akimoto, et al., Phys. Status Solidi C 6 (2009)
342.

64

Ⅲ -2. Materials Sciences

BL3B

Photoluminescence Study on Structural Deformation of      
LaAlO3 Induced by Ion Implantation
M. Harima, Y. Horii, T. Morimoto and Y. Ohki

Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan
High permittivity (high-k) materials such as LaAlO3
or YAlO3 are expected as a gate insulator in advanced
MOS devices. In the manufacturing process ofsemiconductors, ion implantation through a gate
dielectric to a Si substrate is often used to adjust thethreshold voltage of a metal oxide semiconductor(MOS) device [1]. However, ion implantation may
induce localized electronic states in the forbidden bandand defects resulting from degradation of crystallinity.
In the present study, the effects of implantation of P+
or B+ ions on the structural change of single crystal
LaAlO3 were examined. Before and after ion
implantation, optical absorption, photoluminescence(PL) and X-Ray diffraction (XRD) were measured.
In Fig. 1, an optical absorption edge is seen at about
5.6 eV. This edge, which corresponds to the band gap
energy of LaAlO3, is scarcely affected by the ion
implantation.
Figure 2 shows PL spectra. As shown in Fig. 2(a), a
broad PL peak due to the oxygen vacancy appears ataround 2.8 eV [2]. The intensity of this PL, which is also
detectable in amorphous samples [3], scarcely changes
after the ion implantation. In addition, three sharp PL
peaks were detected at 1.62, 1.65, and 1.69 eV as shownin Fig. 2(b). The intensities of the three PLs become
smaller by ion implantation. These PLs are due to Cr3+
that are present in LaAlO3 as impurities [4]. It is known
that this type of PL appears only when the samples are
crystalline [5]. These results indicate that the ion
implantation degrades the crystallinity of LaAlO3.
Figure 3 shows in-plane XRD spectra. The XRD peakintensity at 2θ = 23.5ο is decreased by the ion
implantation. One important thing is that the depth
measurable by XRD is too shallow to evaluate thecrystallinity of the area where ions had passed through.
In this regard, PL measurements can cover the wholeion-implanted area.
To conclude, it has become clear that deformation of
crystal structure of LaAlO3 is induced by ion
implantation.

PL Intensity [arb. unit]

10

Absorbance4

6

beforeP ion implanted
B ion implanted

42
0
1.8 2.1 2.4 2.7

3

3.3 3.6 3.9 4.2

Detected Photon Energy [eV](a)

PL Intensity [arb. unit]

15
beforeP ion implanted
B ion implanted

10

5

0
1.5

1.6

1.7

Detected Photon Energy [eV]

1.8

(b)
Fig. 2. PL spectra induced by the irradiation of 5.0-eV (a)and 6.4-eV (b) photons observed before and after the
implantation of P+ or B+ ions at a fluence of 1015 cm-2.
Intensity [arb. unit]

12
10

beforeP ion implanted
B ion implanted

8
6
4
2
0
22

22.5

23

23.5

24

2! [degree]

24.5

25

Fig. 3. In-plane XRD patterns observed before and after
the implantation of P+ or B+ ions at a fluence of 1015 cm-2.
[1] B. Razavi and T. Kuroda, Design of Analog
CMOS Integrated Circuits (Tokyo; Maruzen, 2003).
[2] E. Hirata et al., Jpn. J. Appl. Phys. 49 (2010)
091102.
[3] H. Nishikawa et al., Phys. Rev. Lett. 72 (1994)
2101.
[4] D. Yamasaka et al., Jpn. J. Appl. Phys. 52 (2013)
071501.
[5] J. Heber et al., Z. Phys. 246 (1971) 261.

6
5

8

beforeP ion implanted
B ion implanted

32
10
1.5 2 2.5 3 3.5 4 4.5 5 5.5 6

Photon Energy [eV]Fig. 1. Optical absorption spectra observed before andafter the implantation of P+ or B+ ions at a fluence of 1015
cm-2. Note that the three spectra overlap each other.

65

Ⅲ-2

Ⅲ -2. Materials Sciences

BL3B

Observation of VUV Emission from Er/Nd:LuF3 Crystals
S. Kurosawa1,2, J. Pejchal2, M. Kitaura3, K. Fukui4, K. Nakagawa5, S. Watanabe6,
A. Ohnishi3, K. Ogasawara6, M. Hasumoto7 and M. Sakai7
1Institute for Materials Research, Tohoku University, Sendai 980-8679, JapanNew Industry Creation Hatchery Center, Tohoku University, Sendai 980-8679, Japan3
Deptartment of Physics, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
4
Department of Electrical and Electronics Engineering, University of Fukui, Fukui 910-8507, Japan
5
Graduate School of Human Development and Environment, Kobe University, Kobe 657-8501, Japan
6
School of Science and Technology, Kuwansei University, Sanda 669-1337, Japan
7
UVSOR facility, Institute for Molecular Science, Okazaki 444-8585, Japan2

Ⅲ-2

The development of new fast radiation detection
systems employing the vacuum ultraviolet (VUV)
scintillators has been started in the recent past. In
these systems, the fast VUV scintillators can becoupled with advanced VUV photodetectors, such as
position-sensitive gas electron multipliers (GEM),
micro-pixel
chambers
or
VUV-sensitive
photomultipliers with CsI-coated photocathodes [1,2].
One of the candidates considered for the VUVscintillator is the Nd-doped BaLu1.2Y0.8F8 (BaYLuF).
The fast VUV emission around 185 nm with a decay
time of several nanoseconds is due to the allowed
5d-4f transition of the Nd3+ ion. Even more favorable
properties, such as significantly elevated scintillation
efficiency and emission shifted to even shorter
wavelengths were found for LuF3 single crystals [3].
Shorter emission wavelength usually matches betterthe sensitivity of the mentioned VUV photodetectors.
Recently, we tried to improve the energy transferfrom the host matrix to the Nd3+ luminescence centerby Tm-codoping. As the Tm3+ 5d-4f emission
spectrum coincides with the Nd 4f-5d absorption
band, the energy would migrate over the Tm3+ 5dlevels to the Nd3+ ones. This was successfully proved[4], even though the improvement of the overall
scintillation efficiency was not significant.
Since Er3+ has also emission lines in the VUVregion, other co-dopant effect with Er is investigatedin this study; LuF3 codoped with 1-mol% Er / Nd 1
–mol% and 1 mol% Er doped LuF3 samples weregrown by micro-pulling down method. In order toshow the energy transfer, we measured the emission
spectra using BL3B beam line at UVSOR.
Figure 1 shows the emission spectra of the
LuF3Er1% sample excited at 135nm at 9K and
LuF3Er1%Nd1% excitd at 145nm at 9K. The result
for Er-doped sample shows presence of both low-spinand high-spin transitions at 160 and 165nm,
respectively. For the ErNd codoped sample no Er3+emission is observed at all, even though the sample isexcited in the Er3+ absorption band. This proves theenergy transfer from the Er3+ to Nd3+ ions.

Fig. 1. Emission spectra of the LuF3Er1% sample
excited at 135nm at 9K (a) and LuF3Er1%Nd1%
excitd at 145nm at 9K (b).
[1] R. Chechik, A. Breskin, Nucl. Instr. and Meth. A
595 (2008) 116-131 and references therein.
[2] S. Kurosawa, J. Pejchal et al., J. Instrumentation 7(2012) C03013.
[3] T. Yanagida, N. Kawaguchi, K. Fukuda et al.,Nucl. Instr. Meth. A 659 (2011) 258–261.
[4] J. Pejchal, K. Fukuda, M. Nikl et al., IEEE Trans.
Nucl. Sci. 59 (2012) 2177-2182.

66

Ⅲ -2. Materials Sciences

BL3B

Optical Spectroscopy of Rare-Earth Doped Y3Al5O12 (RE=Ce, Eu, Tb, Pr)
Single Crystals
M. Yamaga, K. Takagi, T. Kishita, D. Susuki and H. Watanabe

Department of Mathematical and Design Engineering, Gifu University, Gifu 501-1193, Japan
Current white LEDs with high efficiency andbrightness are composed of an InGaN-based blue
LED and a yellow phosphor in the powder form of
Ce3+-doped Y3Al5O12 (Ce:YAG). As the emission
from Ce:YAG lacks the red component of thespectrum, the white light has a low color-renderingvalue. In order to obtain warm white light and an
appropriate color rendering value, it is required to add
the red emission by codoping Ce3+ and otherrare-earth ions, such as Pr3+, Eu3+ and Tb3+. Suchenhancement of the red component may be achieved
through energy transfer between Ce3+ and codoped
ions.
Rare-earth doped YAG single crystals wereprepared using the Czochralski method by NIMS.
Optical measurements at 300 K were done at BL3B.
Figure 1 shows the optical absorption spectra of
Ce:Pr:YAG, Ce:Eu:YAG, Ce:Eu:Tb:YAG, andCe:YAG. The absorption spectrum of Ce3+ in YAG
consists of four bands with peaks at 205, 228, 340
and 458 nm, being due to the 4f!5d transitions of
Ce3+. In Ce:Pr:YAG, the intense broad bands at 237
and 290 nm other than the Ce3+ bands are due to the
4f!5d transitions of Pr3+. The fairly weak lines
around 600 nm is assigned to the 3H4 !1D2 transitionof Pr3+. The intense broad band below 240 nm in
Ce:Eu:YAG is due to the charge transfer transitions
to Eu3+ or the 4f!5d transitions of Eu3+, whereas thefairly weak line at 400 nm is due to the 7F0! 5D3
transition of Eu3+. In Ce:Eu:Tb:YAG, a new intense
broad band with a peak at 270 nm other than the
broad bands in Ce:Eu:YAG is due to the 4f!5dtransitions of Tb3+.
Figure 2 shows the emission spectra observed in (a)Ce:YAG, (b) Ce:Pr:YAG, (c) Ce:Eu:YAG, and (d)Ce:Eu:Tb:YAG. Excitation at 340 and 458 nm in
the Ce3+ absorption bands for (a) Ce:YAG produced
the broad emission bands with double peaks due tothe 5d!4f (2F5/2, 2F7/2) transitions of Ce3+. In (b)Ce:Pr:YAG, excitation at 610 nm, corresponding to
the 3H4!1D2 transition of Pr3+, produced the several
sharp emission lines in the range from 610 to 830 nm,
being assigned to the 1D2!3HJ (J=4,5,6) transitions.
The emission spectrum excited at 291 nm consists of
two broad bands at 320 and 380 nm, several sharp
weak lines in the wide range from 490 to 830 nm, andthe weak Ce3+ emission band. On the other hand,
excitation at 458 nm produced the weak Pr3+ emission
lines at 610, 640 and 830 nm other than the intense
In (c) Ce:Eu:YAG, theCe3+ emission band.
emission spectrum excited at 220 nm consists of the
weak sharp lines at 592, 609, 630, and 709 nm due tothe 5D0!7FJ (J=1,2,3,4) transitions of Eu3+. In (d)Ce:Eu:Tb:YAG, excitation at 271 nm produced theintense sharp lines at 385 nm and (490, 550, 590 andThese625) nm and the weak Ce3+ emission band.
sharp lines are assigned to the 5D3!7F6 and 5D4!7FJ(J=6,5,4,3) transitions in this series. The emission
spectrum excited at 220 nm consists of the sharp lines
from both Eu3+ and Tb3+ and the Ce3+ emission band.

Ⅲ-2

Fig. 1. Absorption spectra for rare-earth doped YAG
crystals.

Fig. 2. Emission spectra for rare-earth doped YAG
crystals.

67

Ⅲ -2. Materials Sciences

BL3B

Optical Properties of Amorphous Carbon Nitride Thin Films
1

Department of Electrical and Electronics Engineering, University of Fukui, Fukui 910-8507, Japan2
Far-Infrared Region Development Research Center, University of Fukui, Fukui 910-8507, Japan

Amorphous Carbon Nitride (a-CNx) is known tohave interesting mechanical, electrical and opticalproperties. In the case of optical properties, it isexpected that a-CNx becomes cheap white LED
material, because photoluminescence (PL) of a-CNx
spreads over the visible (VIS) region. However, PL
spectrum of a-CNx has sample preparation condition
dependences. Recently, it is found that laser
irradiated a-CNx thin film after depositing showsmuch higher PL intensity than that of as-deposited
a-CNx thin film [1]. Then, we have been measuringlaser irradiated a-CNx to investigate its luminescencemechanism and growth condition dependences byusing combined excitation emission (CEE)
spectroscopy.
All samples are deposited on Si substrates by the
RF-sputtering method at Ryukoku University. Their
thickness is about 1 um. Laser-irradiation time to
as-deposited samples is 240 minutes by using He-Cd
laser (325 nm) with 20 mW. All CEE spectra havebeen measured at BL3B [2].
Figures 1 and 2 show CEE spectra at 20 K of as
deposited (a-CNx(A)) and laser irradiated a-CNx thinfilms (a-CNx(L)), respectively. Higher intensity
regions are represented by warm colors. PL spectra
widely spread in VIS region, though their width
becomes narrower after laser irradiation. Photon
energies of PL peak and PL excitation of botha-CNx(A) and a-CNx(L) are ~3.3 eV and 4.5, 5.5 eV,
respectively. However, maximum intensity ofa-CNx(L) is 90 times larger than that of a-CNx(A).
Figure 3 shows emission spectra of a-CNx(A) anda-CNx(L) at the excitation energies of 4.6 eV and 5.5
eV. Asymmetric line shape of each spectrum can be
decomposed by two Gaussian type emission bands.
Higher energy side band has its peak at 3.5 eV in all
spectra. However, lower energy side peak shifts from
2.9 eV to 3.1 eV after laser irradiation. These higher
and lower energies are correspond to the energy gaps
between π* and π, σ* and NLP (nitrogen lone pair)bands, respectively, following from Nitta’s band
diagram [3]. According to C 1s XPS results,
contribution of sp2 bonding decreases and that of sp3
one increases after laser irradiation. Since these XPS
results are probably explain as the decrease of theoverlap between σ* and π* bands, and increaseenergy gap of NLP-σ* [4] after laser irradiation. Then,
it is supposed that the degree of hybridization of σ*and π* bands is important to understanding the effectof the laser irradiation.

6.0

0. 0002. 033E-15
4. 067E-15
6. 100E-15
8. 133E-15
1. 017E-14
1. 220E-14
1. 423E-14
1. 627E-14
1. 830E-14
2. 033E-14
2. 237E-14
2. 440E-14
2. 643E-14
2. 847E-14
3. 050E-14
3. 253E-14
3. 457E-14
3. 660E-14
3. 863E-14
4. 067E-14
4. 270E-14
4. 473E-14
4. 677E-14
4. 880E-14
5. 083E-14
5. 287E-14
5. 490E-14
5. 693E-14
5. 897E-14
6. 100E-14

Excitation Energy (eV)

5.5

5.0

4.5

4.0

3.5

3.0
2.0

2.5

3.0

3.5

4.0

4.5

5.0

Photon Energy (eV)Fig. 1. CEE Spectrum of as-deposited a-CNx.
6.0

0. 0003. 267E-13
6. 533E-13
9. 800E-13
1. 307E-12
1. 633E-12
1. 960E-12
2. 287E-12
2. 613E-12
2. 940E-12
3. 267E-12
3. 593E-12
3. 920E-12
4. 247E-12
4. 573E-12
4. 900E-12
5. 227E-12
5. 553E-12
5. 880E-12
6. 207E-12
6. 533E-12
6. 860E-12
7. 187E-12
7. 513E-12
7. 840E-12
8. 167E-12
8. 493E-12
8. 820E-12
9. 147E-12
9. 473E-12
9. 800E-12

Excitation Energy (eV)

5.5

5.0

4.5

4.0

3.5

3.0
2.0

2.5

3.0

3.5

4.0

4.5

5.0

Photon Energy (eV)Fig. 2. CEE Spectrum of laser irradiated a-CNx.
as-depo.
Exci 4.6eV

as-depo.
Exci 5.5eVIntensity (a.u.)

Ⅲ-2

D. Itoh1, K. Fukui1 and K. Yamamoto2

Laser irradiation
Exci 4.6eV

Laser irradiation
Exci 5.5eV

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Photon Energy (eV)Fig. 3. Emission Spectra of as-deposited and laser
irradiated a-CNx at the excitation energies of 4.6 and5.5 eV.
[1] M. Satake et.al., 2013 JSAP Autumn Meeting
28p-PB3-11.
[2] K. Fukui et.al., J synchrotron Rad. 21 (2014) 452.
[3] S. Nitta, Oyo Buturi 69 (2000) 7 (in Japanese).
[4] Y. Zhang et.al., Sci. Rep. 3 (2013) 1943.

68

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The Effect of PFI on the Microstructural Aggregates of PEDOT:PSS by
Scanning Transmission X-Ray Microscopy
12

M. W. Lin1, H. W. Shiu1, Y. L. Lai1, T. F. Guo2 and Y. J. Hsu1

National Synchrotron Radiation Research Center, Hsinchu, Taiwan 300, Republic of China
Department of Photonics, National Cheng Kung University, Tainan, Taiwan 701, Republic of China
resembles with our XPS findings, the adding PFI
re-arrange the distribution of PEDOT:PSS. It should
be noted that the obtained OD image was not divided
by the pre-edge image (for example at 160 eV) due tothe beamlight around 160 eV to 180 eV exists
periodic distribution of dark and bright. Again, theperiodic distribution minimizes the absorption
contrast attributed by the sample. Nonetheless, fromthe STXM results, we still found the PFI changes the
distribution of PEDOT:PSS. The result is important
to explain how the PFI influence the interplay of
PEDOT:PSS compositions.

A spin-casted conducting polymer PEDOT:PSS(poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)) forms a hole-injection layer
with a gradient work function tuned by
self-organization of the PFI, which resulted in aremarkably improved device efficiency of organic
light-emitting diodes and organic photovoltaics. Fromprevious X-ray photoelectron spectroscopy (XPS)
measurements, we found the sulfide component isincreased, while the PSS concentration decreases
after the addition of PFI. However, the PFI is rich at
the surface and its concentration gradually decreases
with depth. We therefore investigated whether if themorphology change of PFI aggregation on surface iscaused by the interplay between PEDOT:PSS and PFI.
To study the chemical morphology with several
blended polymers, the Scanning Transmission X-ray
microscopy (STXM) measurements were utilized to
explore the heterogeneous structure and chemical
properties of PEDOT:PSS:PFI composited polymers
at S L-edge.
Near-edge X-ray absorption fine structure(NEXAFS) taken at S L-edge (Figs. 2(a) and (b)) in
beamline BL4U identifies major characteristic peaks
for PEDOT:PSS and PFI unambiguously (Chemical
structures are shown in Fig. 1). The spectra of
PEDOT:PSS display strong intensity in the energy
range between 170 to 175 eV which are associatedwith the sulfonic acids groups, energy range between
165 to 170 eV corresponding to sulfur atoms in
PEDOT (Fig. 2(a)) . In Fig. 2(b), the PFI has a strong
absorption between 170 to 175 eV, which areassociated with the sulfonic acids in PFI. The 3D
optical density (OD) images were acquired todiscriminate the composition and structure change
caused by PFI. Figure 3 (a) and (b) exhibit OD
images of PEDOT:PSS and PEDOT:PSS:PFI,
extracted from 3D images, respectively. Despite
several large spots caused by dusts, the obtained
imaging at 166.8 eV (which is characteristic peak of
PEDOT) for PEDOT:PSS:PFI film(Fig. 3 (b)) has
denser dark particles in compared to pure
PEDOT:PSS film(Fig. 3 (a)). As a result, the additionof PFI tends to aggregate on surface. The obtained
data indicates that the blending of PFI on
PEDOT:PSS generates high concentration of
PFI-covered surface and cause the re-distribution of
sulfonic acids group in PEDOT:PSS. The OD
images for PEDOT:PSS and PEDOT:PSS:PFI arehence different. Also, the results from STXM greatly

Fig. 1. The chemical structures of conducting
polymers used in this study.
(a)

(b)

Fig. 2. S L-edge NEXAFS of the (a) PEDOT:PSS and(b) PFI.
(a)(b)

Fig. 3. The OD image for S L-edges extracted from
3D images of (a) PEDOT:PSS and (b)PEDOT:PSS:PFI.
[1] T. W. Lee, Y. Chung, O. Kwon, and J. P. Park ,Adv. Funct. Mater. 17 (2007) 390.

69

Ⅲ-2

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BL4U

Observation of the Origin of d0 Magnetism in ZnO Nanostructures Using
X-Ray-Based Microscopic and Spectroscopic Techniques
S. B. Singh1, Y. F. Wang1, J. W. Chiou2, W. F. Pong1, T. Ohigashi3 and N. Kosugi3
1

Department of Physics, Tamkang University, Tamsui 251, Taiwan
Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan
3
Editorial Board, UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan2

Ⅲ-2

In present report, efforts have been made to elucidate
the origin of d0 magnetism1,2 in ZnO nanocactus (NC) andnanowires (NW) using X-ray-based microscopic andspectroscopic techniques. The magnetic hysteresis curve
obtained in an applied field revealed that the saturation
magnetization in ZnO NC exceeded that of the NW.
Figure 1 shows the O K-edge scanning transmission X-ray
microscopy (STXM) and corresponding x-ray absorption
near-edge structure (XANES) spectra of the ZnOnanostructures. The experiments were performed at the
4U beamline. The O K-edge STXM stack mappings wererecorded at two randomly selected regions in ZnO NC(NC-1 and NC-2) and NW (NW-1 and NW-2)
respectively (see Figs. 1a-d). The insets in the figures alsopresent corresponding scanning electron microscopy
images that help to identify the regions and can be used toverify the STXM images. To overcome the signal-to-noise
ratio of the XANES spectra obtained from specificmapping areas in the STXM images, the O K-edge
STXM-XANES spectra in Fig. 1(e) were obtained as thesum of the XANES spectra in the regions that arebordered by yellow dashed lines, as shown in NC-1, NC-2,
NW-1 and NW-2. According to the dipole-transition
selection rule, the features at ~535-550 eV are attributed tothe electron excitations from O 1s-derived states to
2px,y-derived (along the bilayer) and O 2pz-derived (along
the c axis) states, which are approximately proportional tothe density of the unoccupied O 2p-derived states.3 The
intensities of the O K-edge STXM-XANES spectra ofNC-1 and NC-2 are clearly higher than those of NW-1
and NW-2. The STXM-XANES results consistently
demonstrate that the population of defects at the O sites in
ZnO NC is larger than in the NW and confirming theenhanced density of states of O 2p-derived states, as the
population of defects and dangling bonds at/above ECBM
or EF in ZnO NC exceeds that in the NW. The
experimental results are also consistent with themeasurements of extended X-ray absorption fine structure
spectroscopy, X-ray excited optical luminescence
spectroscopy and X-ray magnetic circular dichroism. The
STXM-XANES resesult strongly support the argumentsthat the origin of magnetization is attributable to the O 2p
orbitals rather than the Zn 3d orbitals.

70

Fig. 1. (a)-(d) O K-edge STXM images of two selected
regions in ZnO NC (NC-1 and NC-2) and NW (NW-1
and NW-2), respectively. (e) corresponding O K-edge
XANES spectra of regions bordered by yellow dashedlines in ZnO NC (NC-1 and NC-2) and ZnO NW (NW-1
and NW-2). The insets show the corresponding SEM
images.
[1] T. A. Dietl et al., Nat. Mater. 9 (2010) 965.
[2] S. Z. Deng et al., ACS Nano 4 (2010) 495.
[3] J. W. Chiou et al., Appl. Phys. Lett. 85 (2004) 3220.

Ⅲ -2. Materials Sciences

BL4U

STXM Study on Fluorescence Mechanism of Nanocarbon-Silica Composites
S. Kawasaki, Y. Ishii and H. Song

Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555, Japanwas occurred probably due to the charge transferfrom nanotubes to anthraquinone molecules.

Absorption Intensity / arb. units

In order to solve the energy and environmental
problems, we have to reduce our energy consumption.
For that purpose, it is highly expected to replace thenormal fluorescent lamps by LED lamps. However, it
is not a very easy task, because the present white
LED light does not have the same photoluminescenceprofile as normal fluorescent lamps have. To
reproduce the good profile, we need fluorescentmaterials which can emit good white light under
weak ultra-violet light produced by LED. Recently,
we found that a kind of mesoporous carbon-silica
composite can emit very broad white light.[1-3] The
detailed mechanism of the PL property is not clarified
yet. In order to elucidate the mechanism, electronic
structures of nanocarbon fragments included in thelight emitting mesoporous carbon-silica composites
should be investigated.
We prepared several kinds of chemically modified
nanocarbon materials such as oxidized carbon
nanotubes, oxidized graphenes, carbon nanotubes
including some functional molecules inside their
hollow cores and so on. Oxygen K edge X-ray
absorption spectra were observed using UVSOR
BL4U Scanning Transmission X-ray Microscopy(STXM).
STXM observations of several kinds of nanocarbon
materials were performed. Here, I report on theobservation of the carbon nanotube sample in whichanthraquinone molecules were encapsulated. The
encapsulation of anthraquinone was carried out by
exposing the SWCNT sample to anthraquinone gas inan evacuated glass tube. The open-end SWCNT
sample and the organic molecule powder sample in
the evacuated glass tube were heated at 200ºC for 10hours. After the heat-treatment, the SWCNT sample
was washed several times with ethanol in order toremove the physically adsorbed organic molecules on
the SWCNT surface. The encapsulation was
confirmed by XRD and N2 adsorption experiments.
Figure 1 shows STXM spectra of the anthraquinone
molecule sample and the the carbon nanotube sample
in which anthraquinone molecules were encapsulated(A@SWCNT). We could observe a peak of theanthraquinone sample at around 529 eV very clearly.
On the other hand, for the A@SWCNT sample, twopeaks were observed at around 529.2 eV and 531.5
eV. The latter peak was the absorption peak ofpolymer microgrids of TEM sample holder which
was used to mount the A@SWCNT sample.
Therefore, the peak position of anthraquinone
molecule shifted from 529 eV to 529.2 eV byencapsulating it in carbon nanotubes. The energy shift

(b)
Ⅲ-2

(a)

530

540

X!ray Energy / eV

Fig. 1. Oxygen K-edge X-ray absorption spectraof (a) the anthraquinone molecule sample and (b)the A@SWCNT sample.
[1] Y. Ishikawa, S. Kawasaki, Y. Ishii, K. Sato and A.
Matsumura, Jpn. J. Appl. Phys. 51, 01AK02, (2012)[2] Y. Ishikawa, K. Sato, S. Kawasaki, Y. Ishii, A.
Matsumura and S. Muto, physica status solidi (a) 209(2012) 1022.
[3] Y. Ishii, A. Matsumura, Y. Ishikawa and S.
Kawasaki, Jpn J. Appl. Phys. 50 (2011) 01AF06-1.

71

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X-Ray Linear Dichroism of Sodium Titanate Nanoribbons Measured
with in situ Azimuthal Sample Rotation in STXM
X. H. Zhu1, T. Ohigashi2, A. P. Hitchcock1, C. Bittencourt3, P. Umek4 and P. Krüger5
1

Ⅲ-2

Brockhouse Institute for Materials Research, McMaster University, Hamilton, ON L8S 4M1, Canada
2
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
3
University of Mons, 7000 Mons, Belgium
4Institute Jo!ef Stefan, 1000 Ljubljana, Slovenia
5
Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japanband). A similar apparent shift in the Ti 2p3/2 ! t2g
band was noted previously, and reproduced in thiswork (not shown). The Ti 2p and O 1s stacks can be
reduced to dichroic maps by fitting to spectra
characteristic of the sample parallel and perpendicular
to the fixed horizontal E-vector, as shown in Fig. 3
for one orientation of the O 1s data. Detailed analysis
and comparison to the results of multichannel
multiple scattering with atomic multiplet (Ti 2p)
and density functional (O 1s) calculations by Krüger(Chiba) is in progress.

Titanate nanostructures are potential active
materials in applications such as lithium ion batteries,
gas sensors, photocatalysts, and dye sensitized solar
cells [1]. This study used scanning transmission
X-ray microscopy (STXM) to investigate theelectronic structure of sodium titanate nanoribbons(NaTiOx-NR) prepared by hydrothermal treatment of
anatase TiO2 [2]. We measured the Ti 2p and O 1s
absorption spectra and X-ray linear dichroism (XLD)
of individual nanoribbons using a newly implemented
in situ azimuthal sample rotation device. While XLD
in NaTiOx-NR has been studied previously in a full
field microscope [3], the ability to examine XLD of
an identical nanostructure is an advantage of the
STXM approach. Figure 1 is a STXM image of thesample, and images of the 6 orientations at which Ti
2p and O 1s image sequences (stacks) were measured.
Figure 2 presents O 1s spectra of a small portion of
one nanoribbon extracted from the aligned opticaldensity (OD) O 1s stacks. Through careful energy
calibration an apparent energy shift in the lowest
energy band was identified. This shift is caused bydifferences in the XLD of two adjacent states (split t2g

Fig. 2. O 1s spectra as a function of angle between
sample and E-vector for the region in the green box.

Fig. 3. Color composite of component maps (holey
carbon support, parallel, perpendicular) from singularvalue decomposition analysis of an O 1s stack.
[1] D. Walsh et al., Titanate and Titania nanotubes.
(Cambridge Univ. Press, 2009)[2] P. Umek et al., J. Nanosci. & Nanotech. 7(2007) 3502.
[3] P. Guttman et al., Nature Photonics 6 (2011) 25.

Fig. 1. STXM OD image at 460 eV of the NaTiOx
nanorod sample. The yellow box is the area for
XLD study using in situ azimuthal rotation. Lower
panel is average O 1s stacks for the 6 orientations.

72

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BL4U

The Influence of N 2p Vacancy on the Electronic Structure of (p, n)-TypeGaN Nanowires Studied by Scanning Transmission X-Ray Microscopy
Y. F. Wang1, W. F. Pong1, L. W. Tu2, J. W. Chiou3, T. Ohigashi4 and N. Kosugi4
1

Department of Physics, Tamkang University, Tamsui 251, Taiwan
Department of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan
3
Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan
4
Editorial Board, UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
2

In this report, scanning transmission X-ray
microscopy (STXM) was utilized to investigate theeffect of N 2p vacancy on the electronic structure ofp- and n-type GaN, which were grown on the same
piece of nanowire top and bottom area, respectively.
As shown in Fig. 1, the scanning electron
microscope (SEM) measurement revealed that GaN
nanowires were ~1500 nm long and ~50 nm indiameter. Figure 2 presents the N K-edge STXM andcorresponding x-ray absorption near-edge structure(XANES) spectra of the (p, n)-type GaN. The
experiments were performed at the 4U beamline.
The N K-edge STXM stack mappings were recorded
at two selected regions in GaN nanowire top (p-type1 and p-type-2) and bottom (n-type-1 and n-type-2)
regions (see Fig. 2a). To overcome the signal-tonoise ratio of the XANES spectra obtained from
specific mapping areas in the STXM images, the N
K-edge STXM-XANES spectra in Fig. 2(b) wereobtained as the sum of the XANES spectra in theregions that are bordered by white color, as shown in
p-type-1, p-type-2, n-type-1, and n-type-2.
According to the dipole-transition selection rule, thefeatures at ~398-413 eV are attributed to the electron
excitations from N 1s-derived states to 2px,y-derived(along the bilayer) and N 2pz-derived (along the caxis) states, which are approximately proportional tothe density of the unoccupied N 2p-derived states.1
The intensities of the N K-edge STXM-XANES
spectra of p-type GaN are significantly higher thanthose of n-type GaN, which reflects the increase in
the number of unoccupied N 2p-derived states. In
other words, the STXM-XANES results demonstratethat the population of defects at the N sites in p-type
is larger than in the n-type and confirming theenhanced density of states of N 2p-derived states, as
the population of defects and dangling bonds
at/above ECBM or EF in p-type GaN exceeds that in
the n-type GaN. The STXM-XANES results
intensely support the arguments that the amount of N
2p vacancy affects the electric conductivity, carrier
concentration, and carrier mobility of p-type GaN
nanowires.

Ⅲ-2

Fig. 1. SEM image of the GaN nanowires. The pand n-type GaN were grown on the nanowire top andbottom area, respectively.

Fig. 2. (a) N K-edge STXM images of two selected
regions in GaN nanowire top (p-type-1 and p-type-2)
and bottom (n-type-1 and n-type-2), respectively. (b)The corresponding N K-edge XANES spectra of the
top (p-type-1 and p-type-2) and bottom (n-type-1 andn-type-2) regions.
[1] J. W. Chiou et al., Appl. Phys. Lett. 81 (2002)
3389.

73

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Comprehensive Characterization of Monolithic Polymers by Scanning
Transmission X-Ray Microscopy (STXM)
1Australian Centre for Research on Separation Science (ACROSS), School of Chemistry, University of Tasmania,
Private Bag 75, Hobart 7001, Australia
2
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan

Monolithic polymers are a new generation of
stationary phases for chromatography, offeringsignificant benefits over currently particle-basedmaterials. The main characteristic of these materials
is the presence of large through-pores which permits
the use of high flow rates at low backpressures [1].
However, improvements in this technology rely on
being able to accurately characterize the porous
structure and new characterization techniques areneeded to better understand the polymer morphology
and its optimization. In this sense, the relatively highpenetration power of X-rays would allow acomprehensive analysis of the radial and longitudinal
heterogeneity of the monolithic materials developedin our research group.
The characterization by STXM of polymer
monoliths was performed at the BL4U beamline of
the UVSOR synchrotron radiation facility. To obtaina suitable sample for STXM studies, the macroporous
methacrylatemonolithwithencapsulated
divinylbenzene (DVB) nanoparticles was embeddedwith an aliphatic epoxy resin specially designed for
STXM analysis [2]. The experiments were performedat the O 1s edge. Figure 1 shows the O 1s NEXAFS
spectra for the polymer monolith and the embedding
resin. The spectrum for the methacrylate scaffold hasa peak at 531 eV which is characteristic of the O
1s!"*C=O transition in esters. The O 1s spectrum of
the epoxy resin has little or no absorption at thisenergy and therefore there is good contrast between
the resin and the polymeric scaffold. The DVB
nanoparticles were not possible to be observed due tolack of contrast at the O edge.
Figure 2 shows color-coded composite maps of theporous polymer embedded with the epoxy resin.
These color coded composites display the spatial
distribution of the polymer scaffold relative to theembedding resin.
Ongoing studies in our research group are focusedin the characterization of polymer monoliths
containing nanostructures with different functionality
and the use of other photon energies (e.g. C 1s and N1s) to get a better understanding of the distribution of
the nanostructures within the polymeric scaffold.

Optical density per nanometer thickness

Ⅲ-2

D. Arrua1, T. Ohigashi2, Y. F. Wang2, J. Hoon1, N. Kosugi2 and E. Hilder1

resinmethacrylate polymer
530

540

550

Energy (eV)Fig. 1. NEXAFS spectra of the methacrylate scaffold(black) and the TTE epoxy resin (red).

Fig. 2. Color composite of STXM derived component
maps of methacrylate-based polymer (green) andTTE resin (orange).
[1] R. D. Arrua et al., Analyst 137 (2012) 5179.
[2] A. P. Hitchcock et al., J. Electron Spectrosc. 156(2007) 467.

74

Ⅲ -2. Materials Sciences

BL4B

O K-Edge XAS of Electrocatalytic Manganese Oxide
1

Y. Aoki1,2, K. Kikutani1, E. Tsuji1 and H. Habazaki1

Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan
2
PRESTO, JST, Kawaguchi 332-0012, Japan

In naturally occurring photosystem II (PSII), thewater oxidation reaction proceeds with extraordinaryhigh catalytic activity, where a µ-oxo bridged
tetrameric Mn cluster (Mn4CaO5) serves as themultielectron oxidation catalyst within a complex
protein environment [1, 2]. Thus, the Mn clusters ofphotosynthetic organisms have triggered extensive
research efforts to develop efficient water oxidation
catalysts composed of the inexpensive and abundantelement Mn. In a recent year, various manganeseoxides, such as MnO2, BaMnO3, LaMnO3 etc. has
been reported to show an excellent electrocatalytic
properties for oxygen evolution by electrochemical
water splitting [3, 4]. Suntivich et al reported thathole on oxygen make an important role for oxygen
evolution catalysis of manganese oxide [4]. Such ahole probably evolves by mixing of ligand-to-metal
charge transfer state related to the covalency of Mn-O
bonding. O K-edge XAS spectroscopy can direct
evidence of unoccupied state of solids. Accordingly,
it is of fundamental and technological important tostudy the manganese oxide system by using thistechnique in order to clarify the relationship between
oxygen hole and electrocatalysis. In this study, weinvestigate O K-edge spectra of various manganeseoxide and those of peroxide and superoxide.
Here, the O K-edge spectra of manganese oxides
KMnVIIO4, BaMnIVO3 and MnIVO2 were measured.
KMnO4 and MnO2 were purchased from Aldrich and
BaMnO3 was prepared by solid state reaction. The
spectra of MgO, BaO2 and KO2 were measured as areference of oxide (O2-), peroxide (O-) and superoxide(O2-). The powder specimens were attached to thefolder with carbon tape and to measure the adsorption
by total electron yield method.
O K-edge XAS spectra of the manganese oxide
samples were shown in Fig. 1(a). The Mn atoms in
MnO2 and BaMnO3 take octahedral coordination withoxygen atoms. Therefore, the two peaks near O
K-edge at around 529 and 531 eV can be assigned tothe transition anti-bonding t2g and eg states,
respectively. In case of KMnO4, the Mn-O clusters
take tetrahedral coordination, so that the peaks ataround 528 and 530 eV can be assigned to thetransition to anti-bonding t2 and e symmetric states,
respectively.
The O K-edge spectra are clearly changed bychanging oxidation state of oxide anions, as shown in
Fig. 1(b). The peroxide and superoxide show clear
pre-edge peak at around 529 eV, provably due to theantibonding O-O states, even though MgO does notshow pre-edge features because of strong ioniccharacter of Mg-O bonding.

Ⅲ-2

Fig. 1. O K-edge spectra of (a) various manganeseoxides and (b) oxides with various oxidation state of
O atoms.
[1] J. H. Alstrum-Acevedo et al., Inorg. Chem. 44(2005) 6802.
[2] G. C. Dismukes, R. Brimblecombe, G. A. N.
Felton, R. S. Pryadun, J. E. Sheats, L. Spiccia and G.
F. Swiegers, Acc. Chem. Res. 42 (2009) 1935.
[3] F. Jiao and H. Frei, Energy Environ. Sci. 3 (2010)
1018.
[4] J. Suntvichi et al., J. Phys. Chem. C 118 (2014)
1856.

75

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BL4B

Correlation between Oxygen Functional Groups and Magnetic Properties
in Graphene Oxides Using X-Ray Magnetic Circular Dichroism
Y. F. Wang1, S. B. Singh1, J. W. Chiou2, W. F. Pong1, Y. Takagi3 and T. Yokoyama3
1

Department of Physics, Tamkang University, Tamsui 251, Taiwan
Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan
3
Editorial Board, UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan2

Ⅲ-2

In present study, three different samples i.e.
graphene oxide (GO), medium reduce graphene
oxide (MRGO) and highly reduce graphene oxide(HRGO) where studied using x-ray magnetic
circular dichroism (XMCD) technique. Magnetic
study (M-H loop) shows room temperature
ferromagnetism in GO sample whereas gradualincreases of paramagnetic contribution wereobserved after photo-thermal reduction process (inMRGO and HRGO samples). Figures 1a and 1b
display the C and O K-edge XMCD spectra
respectively, with the photo-helicity of incident
x-rays parallel (µ+) and anti-parallel (µ-) to thedirection of magnetization of the GO sample. The
XMCD experiments were performed at the 4B
beamline. In Fig. 1a (top panel), spectral features
observed in the regions 283-289 eV and 289-315 eV
are ascribed to C 1s! "* and C 1s! #* transitions,
respectively. The difference was observed in both"*- and #*-states when applied the magnetic field in
opposite directions (see bottom panel). In Fig. 1b(top panel), spectral features observed in the regions
528-535 eV and 535-545 eV are ascribed to O 1s!
"* and O 1s! #* transitions, respectively. The
XMCD signal was also observed in O K-edge whenapplied the magnetic field in opposite directions(bottom panel, see Fig. 1b). The origin of XMCD
signal confirms that oxygen functional groups
playing important role in origin of magnetism in
GO sample. The presence of various oxygenfuntion groups were clearly observed in x-ray
photoelectron
spectroscopy
andscanning
transmission x-ray microscopy study in GO sample.
The presence of oxygen functional groups on GO
surface was related to ferromagnetism, whereas
consumption of oxygen function groups after
photo-thermal reduction process was related toparamagnetic contribution in MRGO and HRGO
samples.

Fig. 1. a) (Top panels) display the C K-edge x-ray
absorption near-edge structure (XANES) spectra of
GO sample, with the photo-helicity of incident
x-rays parallel (µ+) and anti-parallel (µ-) to thedirection of magnetization. Bottom panel represents
the XMCD spectra of GO sample. b) (Top panels)
display the O K-edge XANES spectra of GO sample,
with the photo-helicity of incident x-rays parallel(µ+) and anti-parallel (µ-) to the direction ofmagnetization. Bottom panel represents the XMCD
spectra of GO sample.
[1] M. Weser et al., Phys. Chem. Chem. Phys. 13(2011) 7534.
[2] A. Ganguly et al., J. Phys. Chem. C 115 (2011)
17009.

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BL4B

Investigation on Electrochemical Property of Al2O3-Coated Li-Excess
Mn-Based Layered Positive Electrode Material
1

T. Okumura1, M. Shikano1, K. Takada2 and H. Kobayashi1,2Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial Science andTechnology (AIST), Ikeda, 563-8577, Japan
2
Faculty of Chemistry, Materials and Bioengineering, Kansai University, Suita, 564-8680, JapanThe layered Li2MnO3-LiMO2 (M = transition metal)
materials are one of the promising positive electrodematerials for lithium secondary battery. Especially,it has been reported that Li[Mn0.56Ni0.17Co0.07Li0.2]O2
displayed an initial discharge capacity of ca. 280
mAh/g in the voltage range of 2.5 to 4.8 V andmaintained a reversible capacity of ca. 250 mAh/g
after 50 cycles.
On the other hand, thedecomposition of the electrolyte proceeded on thepositive electrode material above 4.5 V is a problem
to be solved for realizing long cycle life. Recently
several efforts have been made to improve the cycle
performance through surface modification of positiveelectrode materials, but limited efforts have been
made to improve the cycle performance throughsurface modification of Li-excess Mn-based layeredmaterials. In this paper, the effect of Al2O3-coating onelectrochemical
properties
wasstudiedinLi1.20Mn0.55Ni0.16Co0.09O2.
Surface modificated-Li1.20Mn0.55Ni0.16Co0.08O2 was
prepared by mechanochemical reaction with nanoAl2O3 using NOB-MINI (Hosokawa Micron Co.).
The particle morphology was measured by SEM.
Crystal and electronic structures were investigated bysynchrotron XRD (BL19B2 at SPring-8) and XAFS(BL7C at PF, BL4B at UVSOR, and BL27SU at
SPring-8) measurements. The crystal structure andbondlength were determined using the analysis
programs
RIETAN-FP
and
REX2000.
Electrochemical property was measured using cointype cells with Li/1M LiPF6 in EC:DMC(1:2)/samplesThe XRD and SEM results showed that the 5wt%
Al2O3-coated sample (Test conditions; 2000 rpm and5 min.) was well defined layered phase without
additional impurity peak and the Al2O3 particles withthe order of 10-20 nm were uniformly distributed
over the surface of Li1.20Mn0.55Ni0.16Co0.08O2 particles.
The hard X-ray XAFS results clarified that bothpristine and 5wt% Al2O3-coated samples showedalmost the same valence states of M cations. These
results indicated that the mechanochemical reaction
gave no damage to the bulk structure of
Li1.20Mn0.55Ni0.16Co0.09O2. On the other hands, thesoft X–ray XANES results clarified that the surfaceof Li1.20Mn0.55Ni0.16Co0.09O2 was covered by Al2O3
particles as shown in Fig. 1. Electrochemical tests
showed that the cycle dependence of discharge
capacity retention at 318 K was improved for the
5wt% Al2O3-coated sample as shown in Fig. 2. In

this paper, it is revealed that the mechanochemical
Al2O3-coating process is an effective way of
improving the cycle performance at high temperature.

Ⅲ-2

Fig. 1. Mn L-edge XANES spectra for pristine andAl2O3-coated samples together with Al2O3.

Discharge capacity retention / %

110
105
100
95
90

: pristine sample: Al2O3-coated sample

85
80
5

10

15

20

Cycles25

30

35

Fig. 2. Cycle dependence of discharge capacity
retention at 318 K for pristine and Al2O3-coatedsamples.
[1] A. Ito et al., J.Power Sources 183 (2008).
[2] H. Kobayashi et al., Solid State Ionics
DOI: 10.1016/j.ssi.2013.09.045.

77

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BL4B

Valence State Analysis of Mn and Fe Ions in Bi4Ti3O12
K. Nishimura1, T. Yoshioka1 and T. Yamamoto1,2

12

monochromatized by a varied-line-spacing planegrating (800 lines/mm). Energy resolution (E/!E) of
the incident beam was set to 3000.
Observed Mn- and Fe- L2,3 XAS are shown in Figs.
1(a) and (b), respectively, with those of metal oxides
for comparisons. Mn-L3 XAS of Mn-doped Bi4Ti3O12
shows similar profile as that of MnO2, whichindicates that valence state of Mn ions in Bi4Ti3O12
are 4+. On the other hand, that of Fe ions can be
determined as 3+ by the same comparisons in Fig.
1(b).
In summary, we have successfully determined thevalence states of doped dilute Mn and Fe ions in
Bi4Ti3O12 by XAS analysis.

Dilute Magnetic Materials (DMMs) have been
extensively investigated because of their potential
applications in spintronics. Recently, it was reported
that Bi4Ti3O12 doped with dilute Fe ions show both
ferroelectric and ferromagnetic properties, i.e.,
multiferroic property, at room temperature [1].
Although it is essential to know the local environmentof doped magnetic ions for the understandings of themechanism of room-temperature ferromagnetism,such analysis has often been skipped for DMMs. We
have studied Mn and Fe codoped In2O3 by the
analysis of X-ray absorption spectra (XAS) [2, 3]. In
the current study, the valence state of Mn and Fe ionsin Bi4Ti3O12 is investigated by the Mn- and Fe-L2,3
XAS measurements.
All the samples were synthesized by the solid-state
reaction method changing concentrations of doped
Mn and Fe ions. Reagent grade powders of Bi2O3,
TiO2, Mn2O3 and Fe2O3 were mixed and ground in an
agate mortar, which were calcined at 1023 K for 5
hours in air. Resultant powers were remixed andreground, and pressed into a cylindrical pellet form,
which were sintered at 1223 K for 5 hours in air.
Mn- and Fe-L2,3 XAS were collected at BL4B in
UVSOR by total electron yield method. Sample
powers were mounted on the first Cu-Be dinode ofthe electron multiplier using carbon adhesive tape.
Synchrotron radiation from the storage ring was

(a)

(b)
Intensity (arb. units)

Bi4(Ti0.95Fe0.05)3O12!-Fe2O3

Fe3O4

Bi4(Ti0.95Mn0.05)3O12

FeO

705

Intensity (arb. units)

Ⅲ-2

Faculty of Science and Engineering, Waseda University, Shinjuku 169-8555, Japan
Institute of Condensed-Matter Science, Waseda University, Shinjuku 169-8555, Japan

Mn3O4

MnO

650

Energy (eV)

655

720

725

[1] X. Q. Chen et al., Solid State Comm. 150 (2010)1221.
[2] T. Okazaki et al., Solid State Comm. 151 (2011)
1749.
[3] S. Nishida et al., UVSOR Activity Reports 2012,(2013) 99.

Mn2O3

645

715

Energy (eV)Fig. 1(b). Observed Fe-L2,3 XAS of Fe-doped
Bi4Ti3O12 and those of Fe oxides.

MnO2

640

710

660

Fig. 1(a). Observed Mn-L2,3 XAS of Mn-doped
Bi4Ti3O12 and those of Mn oxides.

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BL5U

Electronic Structures of the ZrNiSn Half-Heusler Thermoelectric Material
1

H. Miyazaki1, T. Nakano2, M. Inukai2, K. Soda3 and Y. Nishino2

Center for Fostering Young and Innovative Researchers, Nagoya Institute of Technology, Nagoya 466-8555,
Japan
2
Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555, Japan3
Department of Quantum Engineering, Graduate School of Engineering, Nagoya University, Nagoya 464-8603,
Japan
Half-Heusler MNiSn and MCoSb (M = Ti, Zr, Hf)alloys with a valence electron count of 18 areconsidered to be semiconductors with a narrow bandgap [1] and a promising class of thermoelectricmaterials with their large dimensionless figure of
merit ZT [2, 3]. Numerous half-Heusler ZrNiSn-based
alloys have been investigated, and ZT values of 0.52
(p-type) and 1.0 (n-type) (at 1000 K) have beenreported for the Zr0.5Hf0.5CoSb0.8Sn0.2 [2] andZr0.4Hf0.6NiSn0.98Sb0.02 [3] alloys, respectively.
Although the optimization of the thermoelectricperformance of half-Heusler ZrNiSn-based alloys has
been extensively investigated, the mechanism bywhich the thermoelectric properties are improved has
not been clarified. To clarify the origin of the large
thermoelectric properties, we investigate theelectronic structures of the ZrNiSn alloy byphotoemission spectroscopy (PES).
Soft X-ray and ultraviolet PES measurements were
performed using the BL27SU and BL5U beamlines at
the SPring-8 and UVSOR-III synchrotron radiation
facilities. Clean surfaces for the PES measurements
were obtained by in-situ fracturing with a knife edge
at 10 K under ultra-high vacuum. The Fermi level(EF) and total energy resolution were determined by
the Fermi edge of evaporated gold films. The totalenergy resolutions were set to 160 and 50 meV at theexcitation photon energies (hν) of 1000 and 50 eV,
respectively.
Figure 1(a) shows the photon-energy-dependent
valence band spectra and density of states (DOS)determined by electronic band structure calculations
using a theoretical lattice parameter of a = 6.154 Å.
The experimental spectra are normalized with respect
to their integrated intensity on the whole valenceband up to EB = 12 eV. The overall features of thephotoemission spectra of ZrNiSn are in good
agreement with the DOS results, even though a shift
to higher binding energies is observed compared withthe predicted values. Figures 1(b) shows thephotoemission spectra near EF at hν = 50 for the
ZrNiSn alloy and a Au film. The intensity of thephotoemission spectra of the Au film gradually
decreases from 0.4 eV to a value near the EF andchanges as a Fermi distribution curve at the EF. The
bandgap was not observed in the photoemission
spectra within the total energy resolution of thepresent measurements. The observed intensity at EF

and the inflection point suggests the existence of asemi-metallic in-gap state, that is to say, pseudo-gap,
which is inconsistent with the predicted
semiconductor-like band structure for the ZrNiSn
alloy [1].
Thus, an improvement in the thermoelectric
properties can be achieved by material design basedon the pseudo-gap electronic structure of half-Heusler
ZrNiSn-based alloys.

Fig. 1. (a) Photoemission spectra at excitation-photon
energies hν of 50 and 1000 eV, and calculated DOS
for the ZrNiSn alloy. (b) hotoemission spectra near
the Fermi edge at hν = 50 eV for the ZrNiSn alloy
and a Au film.
[1] J. Tobola et al., J. Phys. Condens. Mat. 10 (1998)
1013.
[2] S.R. Culp et al., Appl. Phys. Lett. 93 (2008)
022105.
[3] C. Yu et al., Acta Mater. 57 (2009) 2757.

79

Ⅲ-2

Ⅲ -2. Materials Sciences

BL5U

Metal-Insulator Transition in Pyrite-Type Ni1-xCuxS2
K. Usui1, S. Osawa2, H. Kondo1, M. Kato1,2, J. Iwasaki3, K. Niwa2,3, K. Kusaba2,3,
M. Hasegawa2,3 and K. Soda1,2
1

Department of Quantum Engineering, Graduate School of Engineering, Nagoya University,
Nagoya 464-8603, Japan2
Department of Physical Science and Engineering, School of Engineering, Nagoya University,
Nagoya 464-8603, Japan3
Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University,
Nagoya 464-8603, Japan

Ⅲ-2

Pyrite-type transition-metal dichalcogenides MX2
exhibit rich variety of electronic and magnetic
properties due to the electron correlation andhybridization effects. In particular, NiS2 is classified
as a charge-transfer-type insulator [1], while CuS2 is ap-band metal, showing superconductivity [2]. It isinteresting to clarify the effects of solid solution
between insulating NiS2 and metallic CuS2 on theelectronic structure and related properties. In thisstudy we have studied the valence band spectra near
the Fermi level EF of Ni1-xCuxS2 to clarify the originof the x-dependence of their electronic properties.
Photoelectron measurements were carried out at 10
K in angle-integrated mode. Specimens of NixCu1-xS2
were polycrystals synthesized under a high pressureof 6.5 GPa at a temperature of ~920 K with use ofmulti-anvil cell. Their clean surfaces were prepared
for the measurement by scraping them with adiamond file. Total energy resolution was estimatedas ~0.1 eV at the excitation photon energy of 60 eV.
The origin of the binding energy EB was set to the
Fermi energy EF determined by measuring the Fermiedge of an evaporated Au film on the sample holder.
Typical valence-band spectra near EF of NixCu1-xS2
are compared with each other in Fig.1. Numerals in
the right-hand side of the figure show the intensity at
EF normalized with the intensity (i.e. the edge jump)
linearly extrapolated from the spectral intensity
between EB = 0.2 ~ 0.3 eV to EF. The normalized
intensity at EF is ~0.5 of the edge jump for CuS2,
indicating its metallic nature, gradually decreases
with the Cu content x decreasing, and becomes ~0.2
for NiS2, suggesting that NiS2 has a semimetallic orsemiconducting (insulating) feature, as reported [2, 3].
For NiS2, fine structures are also recognized near EF,
which might imply that NiS2 is not a simple
semiconductor.
Figure 2 shows the electric conductivity at 300 K
for Ni1-xCuxS2 in comparison with the spectral
intensity at EF. The conductivity decreases graduallyas the Cu content x reduces from 1 to 0.1, and thensteeply from x = 0.1 to 0, qualitatively consistent withthe x-dependence of the spectral intensity at EF; themetal-insulator transition occurs between x = 0 and
0.1. Here we propose a mechanism for the
metal-insulator transition as follows; holes are

injected into the S3p-derived fully-occupied valenceband of Mott-insulating NiS2 from the metallic
S3p-band (or states) of CuS2. Hence the substitutionof Cu for Ni may make Ni1-xCuxS2 metallic in a wide
Cu content x range.
Cu and Ni 2p core-level spectroscopy will provide
further support to the above-mentioned mechanism.

Fig. 1. Photoelectron spectra near EF of Ni1-xCuxS2.

Fig. 2. Electric conductivity and spectral intensiy at
EF of Ni1-xCuxS2.
[1] J. Kunes et al., Phys. Rev. B 81 (2010) 025122.
[2] H. Ueda et al., Phys.Rev.B 65 (2002) 155104.
[3] K. Mamiya et al., Phys. Rev. B 58 (1998) 9611.

80Ⅲ -2. Materials Sciences

BL5U

Angle-Resolved Photoemission Study of Insulator-to-Metal Transition of
Sm1-xYxS1

M. Kaneko1,2, M. Sato3, T. Ito1,4, K. Imura3, T. Hajiri1,2,
M. Matsunami2,5, S. Kimura2,6, H. S. Suzuki7 and N. K. Sato3

Graduate School of Engineering, Nagoya University, Nagoya 464-0818, Japan
2
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
3
Graduate School of Science, Nagoya University, Nagoya 464-8603, Japan
4
Nagoya University Synchrotron Radiation Research Center, Nagoya University, Nagoya 464-8603, Japan
5
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585,
Japan
6
Graduate School of Frontier Biosciences and Physics Department, Osaka University, Osaka 565-0871, Japan
7
National Institute for Materials Science, Tsukuba 305-0047, Japan
Samarium monosulfide (SmS) is a prototypicalvalence fluctuating compound that exhibits aninsulator (black) – to – metal (golden) phasetransition by applying external pressure [1]. To
elucidate the origin of this anomalous phase transition,
the experimental investigation of the electronic
structure across the phase transition has been desired.
By using the three-dimensional (3D) ARPES at
UVSOR-III BL5U, we investigated the electronic
structure near the Fermi level (EF) of Sm1-xYxS, where
the similar black-golden phase transition has beenrealized by the substitution of Sm by yttrium in SmS
at ambient pressure [2]. For example, the color andelectronic properties of Sm1-xYxS changes from x = 0:
black insulating (BI) (x = 0), black metallic (BM) (x =0.03, 0.13), to golden metallic (GM) phase (x = 0.25,
0.32, 1).
Figure 1 shows the band structure near EF aroundthe X point of Sm1-xYxS obtained by the present
3D-ARPES experiment. From the comparison with
our previous study [2], the electronic structure near
EF of Sm1-xYxS consists of the Sm2+ 4f multiplet
structures and the electron-pocket at the X point with
Sm (Y) d character appearing at the metallic phase.
With increasing x, the Sm2+ 4f multiplet structure
gradually shifts to lower binding energies.
4 f feature at the
Furthermore,, we found that the Sm 4f

black phase (x = 0 ~ 0.13) shows sizable dispersion(dashed line), while one at the golden phase (x = 0.25,0.32) is non-dispersive. With respect to the electron
pocket (circles), we found that there exists anomalous
narrowing of the Sm 5d feature at the BM phase,
while the electron pocket shows a free-electron likeparabolic dispersion at the GM phase. Furthermore,
the high-energy shift of the electron pocket becomesintensively small from BM to GM phase. Taking
account that the x = 1 (YS) is a reference of thelocalized Sm3+ electron system, the present ARPES
observation of the dispersive (non-dispersive)features of Sm2+ 4f multiplet structure as well as thenarrowing (free-electron like dispersion) of Sm 5delectron pocket at the BM (GM) phase might suggest
the change of Sm 4f electron character from itinerant
to localized one across the BM-GM phase transitionof Sm1-xYxS.
[1] P. Wachter: in Handbook on the physics andchemistry of rare earths, edited by K. A. Gschneidner,
Jr. et al., (North-Holland, Amsterdam, 1994), Vol. 19,
p. 383.
[2] K. Imura et al., J. Korean Phys. Soc. 62 (2013)2028.
[3] V. N. Antonov et al., Phys. Rev. B 58 (1998)
6807.

Fig. 1. Band structure of the Sm1-xYxS (x = 0 (a), 0.03 (b), 0.13 (c), 0.25 (d), 0.32 (e), and 1 (f)).
Dashed lines (open circles) are guide for Sm 4f (Sm 5d (Y 4d)) features, respectively.
81

Ⅲ-2

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BL5U

Angle-Resolved Photoemission Study on LuPtSb
E. Tsuiki1, M. Kaneko1, T. Hosokawa1, T. Ito1,2, T. Hajiri1,3, S. Kimura3,4, M. Matsunami3,5,
K. Imura6 and S. Suzuki7
1

Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
Nagoya University Synchrotron Radiation Research Center, Nagoya University, Nagoya 464-8603, Japan
3
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
Graduate School of Frontier Biosciences and Physics Department, Osaka University, Osaka 565-0871, Japan
5
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585,
Japan
6
Graduate School of Science, Nagoya University, Nagoya 464-8603, Japan
7
National Institute for Materials Science, Tsukuba 305-0047, Japan
2

Intensity (arb.units)by the large electron-pocket appearing symmetricallywith respect to the ! point. Thus the experimental
electronic structure near EF of the LuPtSb shows
strong contrast to the calculation where the zero-gap
states at EF form a point-like FS at the BZ center. To
elucidate the effect of the FS formation at LuPtSb to
the systematic change of the electronic structure ofhalf-Heusler ternary compounds, systematic ARPES
study on the trivial border system, YPtSb etc., isintended.
LuPtSb, 61eV, 16K
(a)
(b)

!
2.0

1.0

EF

Binding Energy (eV)Fig. 1. (a) fcc Brillouin zone of LuPtSb. (b)ARPES
spectra along cut1 from Fig.1(a) obtained by using h" =61eV photons.
(b)
LuPtSb
16K

-8.0

-4.0

0

4.0

Wave Vector (-1)

Binding Energy (eV)(a)
Binding Energy (eV)Ⅲ-2

Several years ago, new kind of functional materials
that are neither the metal nor the insulator, so called
Topological Insulator, were discovered. In
topological insulators, the bulk properties arecharacterized as semimetal or insulating, while thesurface ones, as unique metal. In the surface metallic
state, the band shows linear (Dirac cone) dispersion
between the bulk, which in fact observed byangle-resolved photoemission spectroscopy (ARPES)
on TlBiSe2 [1].
Semi-metallic half-Heusler compound XYZ (X,Y:
Rare earth or transition element, Z: pnictogen) withthe lattice distortion have been expected to be a
topological insulator [2]. By changing combination of
X, Y, and Z atoms,
the ground state changes fromtopologically trivial (semiconducting) to non-trivial(semi-metallic) as the characteristic energy difference
between the !6 and !8 bands changes from negative
to positive. Furthermore, it is predicted that there is apossibilityofcontrolling
functionalities(superconductivity, magnetism, and abnormal carrier)in addition to the topologically insulating states. On
the other hand, there are few experimental evidencesof the existence of the topologically trivial to nontrivial border at the electronic structure of halfHeusler ternary compounds so far.
In this study, we have performed angle-resolved
photoemission spectroscopy (ARPES) on LuPtSb, ,which has been expected to be located on the nontrivial border [2, 3], to clarify the intrinsic electronic
structure of this system as the starting point.
Figure 1(b) shows ARPES spectra along cut1
passing through the ! point in the fcc Brillouin zone
(BZ) (Fig. 1(a)) of LuPtSb obtained by utilizing h! =61 eV photons. To show the dispersive features clear,
the second-derivative ARPES intensity plot of Fig.
1(b) is shown in Fig. 2 (a). We found that thehighly-dispersive features around the ! point seems
to be similar between the experiment and thecalculation (Fig. 2(b)).
On the other hand, we found two types of Fermi
surfaces (FSs) around the BZ center and boundary,respectively. The former is formed by the small
electron-pocket whose bottom merges with thehole-like dispersion around 100 meV, while the latter

Wave Vector (-1)

X

Fig. 2. (a) Second-derivative ARPES image of Fig. 1.
Thick lines are guide for eyes. (b) Band structure
calculation of LuPtSb along the ! KX line.
[1] T. Sato et al., Phys. Rev. Lett. 105 (2010) 136802.
[2] S. Chadov et al., Nature Mat. 9 (2010) 541.
[3] W. Al-Sawai et al., Phys. Rev.B 82 (2010)
125208.

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BL5U

Photoemission Study of MgxZn1-xO Synthesized under High Pressure
K. Takahama1, R. Eguchi2, D. Shimada3, M. Kato1, K. Niwa2,3, K. Kusaba2,3, M. Hasegawa2,3
and K. Soda1,3
1

Department of Quantum Engineering, Graduate School of Engineering, Nagoya University,
Nagoya 464-8603, Japan2
Department of Physical Science and Engineering, School of Engineering, Nagoya University,
Nagoya 464-8603, Japan3
Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University,
Nagoya 464-8603, Japan

Wide band-gap semiconductor ZnO and its related
solid solutons have received much interest for avariety of applications such as electronic andoptoelectronic devices, catalysts, gas sensors, andtransparent conductive films. Under high pressures,
ZnO crystalizes in NaCl structure (B1) with a band
gap EG of 2.45 eV and can form solid solutions with
B1-type MgO of EG ~ 7.7 eV in wide concentration
range. Hence it is expected from band structure
calculations [1] that the band gap of MgxZn1-xO may
increase with x. Thus we have investigated theelectronic band structure, in particular band gap, of
n-type semiconductor MgxZn1-xO by use ofphotoelectron spectroscopy.
Photoelectron measurement was performed at room
temperature. Specimens of B1-type MgxZn1-xO weresynthesized at high temperatures of 1173 K underhigh pressure of 6.5 GPa, and their clean surfaces forthe photoelectron measurement were prepared byscraping them with a diamond file. The origin of thebinding energy EB was set to the Fermi energy EF ofan evaporated film on the sample holder.
Figure 1 shows valence-band spectra of MgxZn1-xO
recorded with weak photon intensity to prevent fromthe charging-up effect as possible. Spectral intensities
are normalized with the integrated intensity up to EB= 20 eV. Densities of states (DOS) for B1-type
MgxZn1-xO are calculated by a full-potential
linearized augmented plane wave (FLAPW) methodwith WIEN2k code [2] and GGA-PBE approximation[3] for the exchange-correlation energy and they arealso presented for comparison in the figure, where theDOS’s are plotted as a function of energy relative tothe conduction minimum (CVM) indicated by abroken line and are shifted by 5 eV towards the highbinding energy side (in the lower abscissa), comparedto the experimental spectra.
Overall spectral features agree fairly well with thecalculated DOS except for a band at EB ~ 15 eV, theorigin of which is unknown at present. Taking
account of the n-type semiconductor, the band gap
can be estimated from the binding energy of thevalence band onset, which is indicated by arrows in
Fig.1. Observed band gaps are about 2~3 times larger
than calculated ones, as known as the underestimationof the band gap by the band structure calculation [4].

As is already reported [1], the calculated band gap
increases gradually with the Mg content x. For cubic
MgxZn1-xO epitaxial films (x > 0.6), it has beenreported that EG > 6 eV [5]. However, the present
experimental band gap seems almost unchanged orslightly decreased as x is increased. At present thisdiscrepancy has not been clarified yet; it might arise
from the Fermi level pining due to surface defectstates such as those of oxygen deficiency.
Charging-up effects might smear out fine structures
and the band onset. Further study is intended on thedependences on specimens and the content x.

Fig. 1. Photoelectron spectra and calculated densitiesof states of MgxZn1-xO.
[1] F. Z. Aoumeur-Benkabou et al., Model. Num.
Sim. Mater. Sci. 2 (2012) 60.
[2] P. Blach et al., Comput. Phys. Commun. 59(1990) 399-415.
[3] J. P. Perdew et al., Phys. Rev. Lett. 77 (1996)
3865.
[4] D. Fritsch et al., Appl. Phys. Lett. 88 (2006)
134104[5] S. Choopun et al., Appl. Phys. Lett. 80 (2002)
1529.

83

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BL5U

Resonance Photoemission Study on Electronic Structure of Fe2-xVAl1+x
1

S. Osawa1, Y. Yamada2, H. Miyazaki3, M. Kato1, Y. Nishino2 and K. Soda1

Department of Quantum Engineering, Graduate School of Engineering, Nagoya University,
Nagoya 464-8603, Japan2
Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology,
Nagoya 466-8555, Japan
3
Center for Fostering Young and Innovative Researchers, Nagoya Institute of Technology,
Nagoya 466-8555, Japan

Ⅲ-2

Heusler-type intermetallic compound Fe2VAl andrelated alloys have attracted much attention as
thermoelectric materials with a pseudogap around the
Fermi level EF in its electronic structure [1]. In
Fe2-xVAl1+x, both the p-type and n-type thermoelectric
powers are enhanced on the off-stoichiometric change
in the Fe/Al ratio, while the semiconductor-like
temperature dependence of the electrical conductivity
is observed for x > 0.08; it can be explained bythermal excitation between the pseudogap likesemiconductor and the weak localization caused by
the random occupation of the excess Al at the Fe
sub-lattice for x > 0.12 [2]. Analysis of the core-level
spectra suggests that the V3d states may appear justbelow EF. Thus we have performed the Fe3p-3d
resonance photoemission study to clarify the V3d
partial density of states (DOS) by suppressing the
Fe3d states on the anti-resonance as well as the Fe3d
partial DOS by the on-resonance enhancement.
The photoemission measurement was carried out at
7 K with the energy resolution of ~70 meV in anangle integrated mode. Polycrystalline specimens of
Fe2-xVAl1+x were in situ fractured with a knife edge toprepare clean surfaces for the measurement. Origin of
the binding energy EB is set to EF by measuring a
Fermi edge of a gold film evaporated onto the sample
holder.
Figure 1 shows typical on-resonance (recorded at
the excitation photon energy h! of 55 eV) andanti-resonance (at h! = 52 eV) valence-band spectra
for x = 0, 0.08 and 0.18. Here, the spectra are
subtracted backgrounds due to the secondary
electrons from by an iteration method [3] andnormalized with the intensity of the V3d-derived
band at EB = 1.5 eV, although the hybridized Fe3d
states contribute to the band at 1.5 eV in the
on-resonance spectra.
As seen in Fig. 1, the Fe3d-derived bands arelocated around EB = 0.7 and 3 eV; they are enhanced
at h! = 55 eV, compared to the V3d-derived band at
1.5 eV, due to the Fe3p-3d resonance. The band at EB~ 6 eV in the anti-resonance spectra is attributed tothe s-like hybridized states; it is shifted to the highbinding energy side and enhanced in the on-resonancespectra, which is ascribed to the Auger-like emission
near the 3p-3d resonance. Small shift of the main 3d
valence-band as a whole is recognized to the lowbinding energy side with x increased. This is due tothe decrease in the valence electron counts by
substitution of the excess Al for Fe, as expected in arigid band model [1]. On the other hand, theanti-resonance spectra show that the spectral intensity
near EF is increased with x, while the intensity at EF,
in particular for x = 0.08 and 0.18, does not change somuch for the on-resonance spectra. Thus the V3dstates grow just below EF with increasing x (x > 0.08),
as suggested [2], although the surface states may
affect the spectra [4]. The Fe3d-derived states are also
increased near EF for x = 0.08 and 0.18 in comparison
with Fe2VAl.
These states near EF act as the impurity states at theedges of the semimetallic conduction and valencebands, leading to the weak localization and themobility gap. This also suggests the importance of therelaxation time factor for thermoelectric properties aswell as the factors of DOS and its energy derivative.

Fig. 1. Valence-band spectra of Fe2-xVAl1+x.
[1] Y. Nishino, IOP Conf. Series: Mater. Sci. Eng. 18(2011) 142001.
[2] K. Soda et al., J. Phys. Soc. Jpn. in press.
[3] K. Soda et al., J. Phys. Soc. Jpn. 60 (1991) 3059.
[4] H. Miyazaki et al., J. Vac. Sci. Technol. A 24
(2006) 1464.

84

Ⅲ -2. Materials Sciences

BL5B

Reflectance Measurement of Fluoride Output-Coupler for Cavity
High-Harmonic Generation in VUVK. Wakui, K. Hayasaka and T. Ido

National Institute of Information and Communications Technology, Tokyo 184-8795, Japan
Intracavity high-harmonic generation of nearinfrared femtosecond (fs) frequency combs using apassive enhancement cavity has extended accessible
wavelength of frequency combs, realizing precision
spectroscopy in the extreme ultraviolet [1]. Lower
harmonics at 150-200 nm vacuum ultraviolet (VUV)
also attract interests because conventional optics arebarely available using fluoride material. In addition,
each comb components are well separated thanks tohigh repetition rate, and rather small phase shift fromthe nonlinear media maintains the regular comb
structures in this wavelength. Therefore its
application to a precision spectroscopy at the VUVwavelengths is anticipated.
Among various important atomic transitions, thetime and frequency community has been interested in
the use of 1S0 ! 1P1 transitions in alkaline-earth-likeions for state detection in the optical clock based on
the proposal by Dehmelt in 1982 [2]. Moreover, aclock transition in a single thorium nucleus has been
intensively studied for realizing hyper-accurate
frequency standard [3]. However, they all exist in
VUV region and the direct excitation has never beenrealized because of the difficulty in development ofcontinuous-wave (CW) coherent laser source in thatwavelength range. Alternatively, the single
frequency-comb component of the high-rep VUV
combs may be able to act as a “quasi-CW” laser andthus to work as a state detection laser. In the case ofsuch ions including Al+, a simple estimation indicatesthat single-mode VUV power in the order of 10 pW
might yield fluorescent photons sufficient for thestate detection. The single comb components of thehigh-rep VUV combs may supply this level of
average intensity. This approach also opens a way tosimultaneous detection of multiple ions, which may
overcome limited stability of the single-ion clocks.
Indium ion (115In+) provides an ideal test bed for thisapproach [4], where the 159 nm radiation generated
as the 5th harmonic of a Ti:S laser can excite the 1S0! 1P1 transition. In our intracavity HHG setup withthe repetition rate of 110 MHz, a total averageintensity in the order of 10 µW may provide sufficientfor In+ detection, whereas it has been limited to 1.5µW in our previous report [5].
The output coupling of high harmonics from thecavity is the key to scale up the yield of intracavity
HHG. Several methods were previously demonstratedusing e.g. bulk sapphire windows as Brewster plates[6, 7], a diffraction grating carved onto a NIR mirror[8], and on an anti-reflection-coated grazing

incidence plate [9]. Here, we design and demonstrate
a new type of VUV output-coupler (VUV-OC). The
VUV-OC consists of a SiO2 substrate of ~100 um
thickness with a fluoride-multilayer coating on one ofits surfaces. The VUV-OC’s reflectance is designed
to be >80% at 153-163 nm and >90% at 159 nm forp-polarized VUV light, while it works as a Brewster
plate at the incident angle of ~55 degree, that
corresponds to a Brewster angle to SiO2 at 795 nm.
We confirmed the reflectance in VUV using thebeamline facility (BL5B) in UVSOR. As shown in
Fig. 1, the reflectance of ~90% was measured at 159
nm as designed. We also demonstrate an efficient
output-coupling method using the VUV-OC for our
HHG experiment. The final yield of the HHG
currently amounts to 4.2 µW at 159 nm, which isalmost three times larger than previous work in spiteof ~20% reduction of the NIR inside the cavity.

Incident angle
55
60 

45 
50 

65 

Fig. 1. Reflectance of the fluoride output coupler.
[1] A. Cingös et al., Nature 482 (2012) 68.
[2] H. Delmelt, IEEE Trans. Instrum. Meas. 83(1982) IM-31.
[3] E. Peik and Ch. Tamm, Europhys. Lett. 61 (2003)
181.
[4] K. Hayasaka, Appl. Phys. B 107 (2012) 965.
[5] K. Wakui, K. Hayasaka and T. Ido, Proc. SPIE
8132, Time and Frequency Metrology III, 813204(2011).
[6] R. J. Jones, K. D. Moll, M. J. Thorpe and J. Ye,
Phys. Rev. Lett. 94 (2005) 193201.
[7] Ch. Gohle et al., Nature 436 (2005) 234.
[8] D. Yost, T. Schibli and J. Ye, Opt. Lett. 33 (2008)
1099.
[9] Y. Y. Yang et al., Opt. Express 19 (2011) 1954.

85

Ⅲ-2

Ⅲ -2. Materials Sciences

BL5B

Reflectance of Hypothetical Meteors in EUV Spectral Range
T. Hamaguchi, M. Kuwabara, K. Isashiki, K. Uji and I. Yoshikawa
Graduate School of Science, the University of Tokyo, Hongo 113-8654, Japan

Reflectance

40
45
50
60
70
80

0.1

0.05

0
26

28

30
32
Wavelength [nm]34

Fig. 2. NWA 4423 reflectivity.
0.008

40
45
50
60
70
80

0.006

ReflectanceⅢ-2

We have measured the surface reflectivities in the
EUV spectral ranges, of two examples (NWA 4423
NWA 645) which are hypothetical meteors. We haveselected (3, 5) among the combinations of (G,M) andalways employed Al/Mg/Al filter to avoid thehigher-order spectral contamination. Each result isshown in Fig. (Fig. 2 shows the reflectivity of NWA
4423, Fig. 3 is NWA 645). Please note that thestatistical error of NWA 4423 reflectivity
measurement is over-plotted, but it is so small(approximately 1/1000) that you might not identify it.
These measurements will be useful, when thealbedo of solid planets needs to be studied.

0.004
0.002
0
26

Fig. 1. Two examples of hypothetical meteors (left)
NWA 4423, (right) NWA 645.

28

30
32
Wavelength [nm]Fig. 3. NWA 645 reflectivityt.

8634

Ⅲ -2. Materials Sciences

BL6B

Far-Infrared Reflective Study of Alkali Niobate Ceramics
T. Yamazaki, M. Kato, K. Tsuchida and K. Kakimoto

Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan
Alkali niobate ceramics are one of the promising
candidates for lead-free piezoelectric materials.
Especially, Li(Na,K)NbO3 solid solution shows
excellent piezoelectric properties and high Curie
temperature. In our previous work, we demonstrated
that the small ionic diameter Li substitution induces
monoclinic Pm phase using synchrotron X-ray,
EXASF and FT-IR analyses. It is expected that Pm
phase involves piezoelectric properties. The present
work reports the spectroscopic characterization of Pm
phase using infrared (IR) technique.
The Li0.02(Na0.5K0.5)0.98NbO3 (LNKN02) ceramics
were obtained by conventional solid state reaction.
The surface of the LNKN sample was mirror polished
for IR reflectivity measurement. The spectra werecorrected by using Michelson interferometer (Bruker,
IFS66v). The measured reflectivity data was fittedusing the equation (1) and (2), as mentioned below.

Ⅲ-2

Fig. 1. The reflectivity spectra of LNKN02.

Where, !! is the high- frequency dielectric constant,"p and "o are the plasma and longitudinal frequencies,
and # is the damping constant.
The reflectivity spectra of LNKN02 in thetemperature range from 10 to 290 K are shown in
Fig.1. Remarkable difference in spectra is foundbelow 30 K. Figure 2 shows the imaginary part ofcomplex dielectric constant, which was calculated byfitting result using equations (1) and (2). Five peaks
were assumed around 600 cm-1 using (Na0.5K0.5)NbO3(NKN) data[1] and group factor analysis. Three peaks
are related to Bmm2 phase which represents NKN and
two peaks are related to Pm phase. The Pm ratio
calculated by fitting peaks area was about 26 % at
290 K. Figure 3 shows the calculated Pm ratio for
LNKN02 ceramics at various temperatures. The Pm
ratio is found to independent of temperature with thedecrease in temperature from 290 to 190 K. At 170 K,
Pm ratio increased suddenly and further temperatureinduces the decrease in Pm ratio gradually. Finally,
the Pm ratio decreases about 10 % at 30 K. It cantherefore be suggested that LNKN02 ceramics
indicate two phase transitions from 290 to 10 K
which is different from those of the pure NKN phase.

Fig. 2. The imaginary part of complex dielectric
constant for LNKN02 at 290 K

Fig. 3. Temperature dependence of the Pm ratio for
LNKN02 ceramics.
[1] M. D. Fontana et al., Phys. Stat. Sol. (b) 103(1981) 211.

87

Ⅲ -2. Materials Sciences

BL6B

Final State of Ultrashallow Thermal Donors
Formed in Carbon- and Hydrogen-Doped Czochralski Silicon Crystals
A. Hara and T. Awano

Department of Electronic Engineering, Tohoku Gakuin University, Tagajo 985-8537, Japan
USTD-A and USTD-B are generated in the initialstage of annealing at 480°C and eliminated after
long-term annealing at the same temperature. Thus,
these are not the final states of USTDs, butintermediate products. The USTD-C and USTD-D are
believed to be the final states of USTDs, because all
experimental results show the survival of only thesetwo peaks. The final form of these two USTDs is
consistent with the generation of two STD(H)s in theinitial stage. These results support our proposedmechanism of formation.
1.4

(a)

3.2

2p0

USTDs
2p

A
B
C

3.0
2.8
2.6

D

 



 



2.4
2.2
2.0

 



 



510-40h1.0
480-40h0.8

0.6

450-40h

0.4
0.2

0.0

1.8



2.0
 





1.8

 

1.2
1.0

 



 



0.8
0.6
0.4

+650-15min.

+640-15min.

1.4+620-15min.

1.2
1.0

+600-15min.

0.8+550-15min.

0.6

0.2

STD(H)s

100

150

2p0

2p

200

250

Wave number (cm-1)



1.6



Transmittance (arb. unit)

1.4



Wave number (cm-1)

(c)



1.6

0.0

(b)

1.2

3p

Transmittance (arb. unit)

3.4

Transmittance (arb. unit)

Ⅲ-2

In the past, we have reported on ultrashallow
thermal donors (USTDs) formed in carbon- andhydrogen-doped Czochralski silicon (CZ Si) crystals
after annealing at 480°C [1,2]. In this study, weevaluated the final state of USTDs.
Carbon-doped CZ Si samples were doped withhydrogen by annealing them in wet oxygen at 1300°C
for 60 min. The samples were then cooled to room
temperature by rapidly exposing them to air. For
carbon doping, the Si melt for preparing the ingot wasdoped with carbon powder during CZ Si crystal
growth. Transmission spectra were obtained using thefar-IR spectrometer of the BL6B beamline at theliquid-He temperature using a flowing cryostat.
Figure 1(a) shows the spectra of USTDs andshallow thermal donors (STD(H)s) after annealing at
480°C for various durations. It has been reported that
STD(H)s are hydrogen-like donors and are generated
in hydrogen-doped CZ Si crystals at approximately
450°C [3]. USTD-A and USTD-B are generated in an
initial stage of annealing at 480°C and eliminatedafter long-term annealing at the same temperature.
Finally, the intensities of only two peaks, namely,
USTD-C and USTD-D, are remarkable at 480°C-65h.
Figure 1(b) shows USTDs formed after annealing for
40 hours at 450°C, 480°C, and 510°C, respectively.
The spectrum of the USTDs at 450°C-40h is nearly
the same as that at 480°C-20h in Fig. 1(a). Moreover,the spectrum at 510°C-40h is nearly the same as thatat 480°C-65h in Fig. 1(a), and only two peaks,
USTD-C and USTD-D, are remarkable. Figure 1(c)shows the spectra of the USTDs at 480°C-40h
followed by additional annealing at each temperature
higher than 480°C for 15 min. The spectrum withadditional annealing at 550°C is nearly the same asthat at 480°C-52h and the spectrum at 600°C is nearly
the same as that at 480°C-65h. Also, in this case, only
two peaks, namely, USTD-C and USTD-D, areremarkable, and their intensity decreases withannealing above 620°C.
As mentioned in our previous report, our model for
generating USTDs comprises the following: in thefirst stage, STD(H)s are generated at high formation
speeds and, in the second stage, carbon modulates theelectronic structure of STD(H)s. The fact that similar
spectra are obtained with short-duration annealing
with increasing annealing temperature indicates that
thermally activated processes are concerned with thegeneration of USTDs. According to our model,
carbon acted as a modulator and had to migrate to
STD(H)s. It is a thermally activated process.

0-40h

0.4

3p

300

0.2
0.0









Wave number (cm-1)

Fig. 1. (a) Annealing behavior of USTDs at 480°C;(b) temperature dependence of USTDs with annealingfor 40 h; (c) annealing behavior of USTDs after 40 hfollowed by additional annealing for 15 min at ahigher temperature than 480°C.
[1] A. Hara, T. Awano, Y. Ohno and I. Yonenaga,
Jpn. J. Appl. Phys. 49 (2010) 050203.
[2] A. Hara and T. Awano, UVSOR Activity Report40 (2013) 103.
[3] R. C. Newman, J. H. Tucker, N. G. Semaltianos, E.
C. Lightowlers, T. Gregorkiewicz, I. S. Zevenbergen
and C. A. J. Ammerlaan, Phys. Rev. B 54 (1996)
R6803.

88

Ⅲ -2. Materials Sciences

BL6B

Electronic States on Solids Probed by a FIR-THz Light Using the
Synchrotron Radiation
A. Irizawa

The Institute of Science and Industrial Research, Osaka University, Ibaraki 567-0047, Japan
Optical study is one of the most powerful
techniques for investigating electronic states on solids.
There can be obtained the great deal of information
about the electronic states, a band structure, asymmetry of crystal structure, and a dielectric
response. In view of experimental affinity, the optical
study is extremely compatible with multiple
conditions such as low temperature, high magnetic
field, and high pressure. The observation of electronic
states can be concluded with only optical operations.
In the case of strongly correlated electron systems, itis well known that the temperature is one of thedecisive factors for the electronic state. The
considerable types of phase transition are induced by
the change of the temperature. Particularly, themultiferroic compounds can be controlled of its
physical properties mutually by the external fields
such as magnetic, electronic, and elastic ones. The
other particular condition, the pressure will directly
affect the electron-electron interactions through thechange of lattice constants. The beamline 6B in
UVSOR is adjusted for the investigations at low
temperature and high pressure in the extremely
low-energy region of FIR-THz. There equips two
type interferometers of both Michelson andMartin-Puplett type. In this report, we have
performed the optical transmittance measurements inthe longest wavelength region for several compounds
having peculiar absorption bands there.
The selected experimental components are theMichelson type interferometer and the Si-bolometer
detector with the liquid-He flow type cryostat forcontrolling the temperature from 300 K down to 13 K.
The transmittance was obtained from the ratio of
optical transmission spectra between the sample andpolypropylene as a matrix for samples. The
concentration of samples is around 5%wt for thematrix. They were installed on the sample holder andthe transmittance was measured through the tapered
hole of 4mm in diameter.
The transmittances are obtained in the energy range
between 40 and 600 cm-1 as shown in Fig. 1. Here wecan confirm the red shift of absorption bands withincreasing temperature. The transmittances are nearly
1 at lower energies and go down to zero in higher
energies. It means that both CuO and Cu2O are
insulating and the gaps are around there. Small
amount of CuO can be recognized in Cu2O, but the
samples are almost single phases. We notice that theshift of absorption bands around 150 cm-1 between
CuO and Cu2O. This must be due to the difference ofbonds between Cu and O and is originated in the
difference of valence. At the same time, experiments
in THz region using FEL in Osaka University are in
execution. The information obtained using FT-IR isuseful for the high power light source experiments.

Ⅲ-2

Fig. 1. Temperature change of transmittance of CuO
and Cu2O at the FIR-THz region.

Fig. 2. Expansion near the absorption bands at 300 K.

89

Ⅲ -2. Materials Sciences

BL6B

Macroscopic Randomness of Carrier Density in Sm0.83Y0.17S
1

Ⅲ-2

S. Kimura1, K. Imura2 and N. K. Sato2

Graduate School of Frontier Biosciences and Department of Physics, Osaka University, Suita 565-0871, Japan2
Department of Physics, Nagoya University, Nagoya 464-8603, Japan
reflectivity of the golden area at 3000 cm-1 in Fig. 1c3
is similar to the black area but the part at the rightlower side has a stripe pattern despite the constant
black phase in the visible image. This suggests thatthe inhomogeneity of carrier density appears in theblack phase.

Inhomogeneity or randomness of samples isimportant to investigate the origin of the physicalproperties of materials because local distortion
becomes a trigger of a phase transition [1]. The originof the insulator-to-metal transition, namely
black-golden phase transition (BG transition), of SmS
by applying an external pressure is under debate [2],one of candidates of such phenomena, i.e., the BG
transition originates from inhomogeneity and/or
spatial distribution of distortion. However, it isdifficult to obtain the information of local electronic
structures of samples. In the study, to obtain thespatial distribution of carrier density in the vicinity of
the BG transition, the spatial distribution of theinfrared reflectivity spectrum of Sm0.87Y0.17S, which
is located near the BG transition at ambient pressure[3].
The experiment was performed at the infrared
imaging end station of BL6B using a 16-channel
linear array MCT detector [4]. The spatial resolution
and the sampling points were set to be about 6 µm
and 64!64 points, respectively. The total
measurement time was about 40 min.
Figure 1a is a visible image of Sm0.87Y0.17S. Almost
all the area is black (black phase), but tiny areas arechanged to gold (golden phase), which indicates thecoexistence of both phases. Reflectivity spectra taken
at the four different points on the sample are shown in
Fig. 1b. The spectra are much different from one
another, two of four spectra have a bending part
indicated by arrows, which wavenumber corresponds
to the plasma edge of free carriers (!p). !p2 is
proportional to the carrier density. Other two spectra
have the plasma edge above the accessible
wavenumber of 6000 cm-1, but the intensity at around6000 cm-1 corresponds to the carrier density owing to
the spectral shape of a free carrier Drude formula.
The images at several wavenumbers are shown in
Figs. 1c1"1c4. The image at the wavenumber of 800
cm-1 shown in Fig. 1c1 is almost monochrome except
for low reflectivity at cracks on the sample. Thisimplies that the plasma edge of the monochrome area
is located at the wavenumber above 800 cm-1. At
higher wavenumbers, the image becomes more
inhomogeneous. The image at 3000 cm-1 in Fig. 1c3
is the most inhomogeneous owing to the distributionof the wavenumber of the plasma edge around 3000
cm-1. In addition, the difference of the golden areafrom the black area in the visible image of Fig. 1a isonly observed in the image at 5700 cm-1 in Fig. 1c4.
In comparison with the visible image in Fig. 1a, theFig. 1. (a) Visible image of a measured sample of
Sm0.83Y0.17S. (b) Four spectra at different positions on
the sample. Reflectivity intensities at 800 cm-1 (c1),1600 cm-1 (c2), 3000 cm-1 (c3), and 5700 cm-1 (c4).
[1] e.g. L. Zhang, C. Israel, A. Biswas, R. L. Greene
and A. de Lozanne, Science 298 (2002) 805.
[2] P. Wachter, In Handbook on the Physics andChemistry of Rare Earth (North-Holland, 1994) 19(1994) 383.
[3] K. Imura, T. Hajiri, M. Matsunami, S. Kimura, M.
Kaneko, T. Ito, Y. Nishi, N. K. Sato and H. S. Suzuki,
J. Korean Phys. Soc. 62 (2013) 2028.
[4] S. Kimura, T. Katsumata and J. Koshobu,
UVSOR Activity Report 40 (2013) 45.

90

Ⅲ -2. Materials Sciences

BL7U

Observation of the Phonon Dispersion in Single-Crystalline Graphite byAngle-Resolved Photoelectron Spectroscopy
1

S. Tanaka1, M. Matsunami2,3 and S. Kimura2,3,4

The institute of Scientific and Industrial Research, Osaka University, Ibaraki 567-0047, Japan.
2
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.
3
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585,
Japan.
4
Graduate School of Frontier Biosciences, and Department of Physics, Osaka University, Suita 565-0871,
Japan.
Recently, we demonstrated an experimental method
using the angle resolved photoelectron spectroscopy
in which the elemental process of EPC(electron-phonon coupling), that is a scattering of theelectron by the phonon in the solid, can beinvestigated in HOPG (highly oriented pyro-lytic
graphite) [1]. Since HOPG is polycrystalline material,
the dispersion of the phonon involved could not
discussed in detail in the previous work. Here, wereport the phonon dispersion of the graphite involvedin the indirect transition in single-crystalline graphite.
Figure 1(a) presents a series of angle-resolved
photoelectron spectra of graphite at 12 K in the region
near the Fermi level with the photon energies of
11.1eV, which gives a resonant enhancement in theintensity of step-like edges near 160meV[1]. Here wefocus on these step-like edges, which are provided by
the energy-shift from the Fermi-edge due to theelectron-phonon scattering from the K(A)-point of theBrillouin zone, where the !-band crosses the Fermi
level in graphite. The energy of the step, therefore,
matches the energy of the phonon that is involved[1].
Two possible scattering geometry when the electron
at the K and K’ points are scattered into the point on
the "-K line, along which the ARPES is measured,are displayed in Fig. 1(b). According to theseschemes, phonon dispersions along the K’-"(1) andK-M(2) lines are probed simultaneously in the present
case. We applied the least squares method to fit the
ARPES data by a phenomenological step-function as(XC - x ) ,f ( x ) = y0 + c(X C - x ) + [a (XC - x ) + b] 1 - erf
2w[shown as grey lines in Fig.1(a)] in order to obtain avalue (XC) of an energy for the step with respect to
the Fermi level. The results are shown as dots in Fig.
1(c) for two directions of the phonon momentum
vector simultaneously. Solid lines are results of
GW-calculation for LO (longitudinal optical), LA(longitudinal acoustic), and TO (transverse optical)
phonon branches. Dotted line presents that of the
LDA-calculation of the TO branch [2]. Note that
there are no practical differences reported between
GW and LDA calculations for LO and LA branches.
It is obvious that only the TO branch calculated with
GW-method agrees with the experiments. It is known

that the difference between the LDA and GW
calculations is usually caused by the Kohn anomaly,
which is due to the electron-phonon coupling in thesolid.
An important feature we should point out is the factthat the LO- or LA-phonon branches are not observed
here. This indicates that the probability of the indirecttransition accompanying with the electron scatteringby the LO- and LA- phonons are significantly smaller
than that by the TO-phonons. It is difficult to ascribe
these to the dipole selection rule, since the K5
symmetry of the LO and LA-phonons and the K1
symmetry of the TO phonon cannot be distinguishedwhen the initial state of the indirect transition is theK6 symmetry as in this case. Therefore, it should be
attributed to the difference in the magnitude of thematrix element for the electron-phonon scattering ofthese phonon modes.
(1)

(b)

(a)

Photoelectron Intensity (Arb. Units)"

Electron emission
angle (deg) along "-K
180

31.9
28.5
25.0
21.5
14.8
11.9
-200

-100

0

Photon Energy (meV)

49.8
38.2

K

K'

q

h!=11.1eV
Photon incident angle=20o

k

"

K'

k

M
K

K'

(c)

TO(LDA)

170
160

(2)
q

LO
LA
TO(GW)

150
140

Binding Energy (meV)

-0.5

"

0.0

0.5

#
q// (Å-1) from K

PhotonIncident
Angle
50o
65o
65o
80o
35o
20o
5o

M

Fig. 1. (a) Angle-resolved photoelectron spectra of
single-crystalline graphite. (b) Two possible
electron-phonon scattering geometry when theelectron at the K and K’ points is scattered into thepoint on the "-K line. (c) Phonon dispersion derived
from the ARPES (dots), GW-calculation (solid lines)
and LDA-calculation (dotted lines)[2].
[1] S. Tanaka, M. Matsunami and S. Kimura, Sci.
Rep. 3, 3031; DOI:10.1038/srep03031 (2013).
[2] A. Grüneis et al., Phys. Rev. B. 80 (2009) 085423.

91

Ⅲ-2

Ⅲ -2. Materials Sciences

BL7U

Photoemission Studies on Rashba & Dresselhaus Effect Systems

1

W. Jung1, S. Cho1, Y. Kim1, B. Kim1, Y. Koh1,
J. Seo1, M. Matsunami2, S. Kimura2,3 and C. Kim1

Institute of Physics and Applied Physics, Yonsei University, Seoul, Korea
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
3
Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan2

Ⅲ-2

better than 5%10&11 Torr. ARPES spectra wereacquired with a hemispherical photoelectron analyzer(MBS A-1). We used linearly polarized as well as left
and right circularly polarized (LCP and RCP) lightwith the photon energy in the range of 9−34 eV.
As for the OAM textures, we used circularly
polarized light on GaAs, InP, InAs of zinc blendesemiconductors. Figure 1 shows so obtained ARPES
data. Clear band dispersions are observed. Circulardichroism data (LCP-RCP data) shows complex
pattern, implying a complex OAM textures in thematerial. All these prove that there is significant
OAM in the material. This is rather surprising,considering the strong crystal field in the system.
On the other hand, we could not reach the !-pointwith low-energy photons due to the limitation of thebeam line in spite of the importance of the !-point
data. It is expected that three-dimensional bulk band
structure of GaAs and InSb should give us new
information. Therefore, we will perform thethree-dimensional ARPES to obtain the complete
bulk electronic structure.

Topological insulators with strong spin-orbit
coupling have recently been studied in our group. [1,2]. We found existence of orbital angular momentum(OAM) through theoretical calculation as well as
circular dichroism ARPES experiments. [1, 2] The
OAM is found to greatly affect the surface electronic
structure. We expect that OAM also greatly affect theelectronic structures of semiconductors such as CdTe,
InSb and GaAs that possess inversion symmetry
breaking (ISB) and resulting electric field.
Semiconductor materials have recently been
extensively studied for their spintronic applications.
An important example is spin-field-effect transistor(spin-FET) proposed by Datta and Das [3] in the lightof controllability of spin precession motion ofelectrons through the Rashba and Dresselhaus
spin-orbit coupling effects. [4, 5, 6]. As we expect
OAM in these materials greatly affects the electronic
structure, it is also expected that OAM has strong
influence on Rashba and Dresselhaus effects,
therefore in turn on the spintronic properties.
Compound semiconductors such as InSb, CdTe,
GaAs have zinc blende structure with ISB in the bulk.
They have three hole bands at the !-point (occupied
states). They are heavy and light hole bands with
J=3/2, and a split off band with J = 1/2. The energy
splitting (") between J=3/2 and 1/2 states due tospin-orbit coupling is the order of hundred meV. To
explain this band splitting they normally apply
Dresselhaus Hamiltonian. Then the effective
one-body Hamiltonian becomes:                 



Fig. 1. ARPES results from GaAs (110) bulk statemeasured with 21 eV photons at the !-point.

Here, HD is the Hamiltonian for the Dresselhaus
effect, # is Pauli matrix, and $ the material dependent
spin-orbit coupling constant. However, we believe it
is OAM instead of the spin that determines the energy.
Therefore, we expect an OAM pattern similar to aspin pattern. To study the OAM pattern insemiconductors, we have performed circulardichroism ARPES on semiconductors.
CdTe single crystals were purchased as wafers.
ARPES measurement was performed at the beam line
7U of UVSOR-III. Samples were cleaved in situ atroom temperature and the chamber pressure was[1] S. R. Park et al., PRL 107 (2011) 156803.
[2] B. Y. Kim et al., PRB 85 (2012) 195402.
[3] S. Datta et al., Appl. Phys. Lett. 56 (1990) 665.
[4] Y. A. Bychkov et al., JETP Lett. 39 (1984) 78.
[5] J. Schliemann et al., PRL. 90 (2003) 146801.
[6] X. Cartoixà, D et al., APL. 83 (2003) 1462.

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Low-Photon-Energy Polarization-Dependent Angle-Resolved Photoemission
Study on Quasi-One Dimensional Organic Conductor (TMTSF)2SbF6
M. Mitamura1, T. Hajiri1,2, T. Ito1,3, S. Kimura2,4 and T. Nakamura4,5
1

Graduated School of Engineering, Nagoya University, Nagoya 464-8603, Japan
2
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
3
Nagoya University Synchrotron Radiation Research Center, Nagoya University, Nagoya 464-8603, Japan
4
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585,
Japan
5
Institute for Molecular Science, Okazaki 444-8585, Japanin Fig. 2 (b) is weak, we found slight increase of thespectral weight around 0.3 eV with increasing !bc
from 5° to -15° (see Fig. 3). We expect that theobserved change of the spectral weight in Fig.3 issuggestive of the existence of the weak interchain
coupling in (TMTSF)2SbF6. To elucidate the role ofthe interchain coupling in the anomalous properties,
the further study is intended.

The Bechgaard salts (TMTSF)2X (where X is oneof the anions PF6, ClO4, etc.) belong to a family ofhighly anisotropic organic conductors [1]. The quasione-dimensional (Q1D) structure of these materials
allows for a variety of ground states from a
Peierl’s-like spin density wave (SDW) insulator to ametallic state, to a superconducting state, as anion
and/or pressure are changed [1].
In this study, we have performed polarization
dependent
angle-resolved
photoemission
spectroscopy(ARPES)onsingle-crystalline(TMTSF)2SbF6 to clarify the effects of the Q1D
TMTSF molecular chain and the interchain couplingon the electric structure. ARPES measurements were
performed at UVSOR-III BL7U by utilizing thebulk-sensitive low photon energy (h! = 8 eV) as wellas the micro focus beam (15!100 µm2).
Figure 1 (a) and (b) shows the polarizationdependent ARPES images near the Fermi level (EF)along TMTSF-chain direction (a-axis) measured at T
= 30 K with p (E // a) and s (E a) polarized
photons, respectively. In Fig. 1 (a), we found ahighly-dispersive feature which approaches EF aroundk = 0.2 Å-1. On the other hand, the dispersive feature
becomes intensively weak in Fig. 1 (b). Taking
account of the selection rules associated with the porbital of TMTSF molecules, initial states with theeven- (odd-) symmetry with respect to a mirror plane
are selectively observed with p- (s-) polarized light.
Thus the observed dispersive feature increasing with
p-polarization geometry can be ascribed to the porbital which forms the Q1D TMTSF chain along
a-axis.
Figure 2 (a) and (b) shows the angle (!bc)
dependent ARPES spectra near EF measured with pand s polarized photons, respectively. We found astrong reduction of spectral weight near EF as
increasing (decreasing) !bc from the normal emission
angle (!bc =0°) in Fig. 2 (a). Since the mirror planesymmetry of p-polarization geometry does not changewith !bc, the observed reduction might come from thedecreasing mean free path for the intrachain p orbital.
On the other hand, the cross section for the interchain
orbital will be changed with !bc in s-polarizationgeometry. Though the change of the spectral weightFig. 1. ARPES images of (TMTSF) 2 SbF 6 along
TMTSF-chain direction measured at T = 30 K with 
p (a) and s (b) polarized light. Dashed line is guidefor TMTSF band dispersion.

Fig. 2. Interchain angle-dependence of EDC at k = kF
(0.2 Å-1) of (TMTSF)2SbF6 measured at T = 30 K
with p (a) and s (b) polarized light.

Fig. 3. !bc dependence of the ARPES spectral weightaround 0.3 eV in Fig. 2 (b).
[1] T. Ishiguro et al., Organic Supercondutors(Springer - Verlag, Berlin, 1998).

93

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High-Resolution ARPES Study of SnTe(111): Observation of Two Types of
Dirac-Cone Surface States
Y. Tanaka1, T. Shoman1, K. Nakayama1, S. Souma2, T. Sato1, T. Takahashi1,2,
M. Novak3, K. Segawa3 and Y. Ando3

Department of Physics, Tohoku University, Sendai 980-8578, JapanWPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
3
Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan
1

2

Ⅲ-2

Topological crystalline insulators (TCIs) are a newclass of topological materials where an invertedbulk-band gap leads to unusual gapless surface states(SSs) that are protected by point-group symmetries of
the crystal, in particular, mirror symmetry [1, 2]. The
TCI phase has been experimentally verified on the(001) surface of the narrow-gap semiconductor SnTe,in which characteristic double-Dirac-cone SSs areobserved on the projection of the (110) mirror plane[3]. While the existence of topologically protected
Dirac-cone SSs is theoretically guaranteed on any
surface containing a mirror plane, it has not been
experimentally verified whether the topological SSs
indeed exist on other surface-plane orientations like(111) and how the surface band structure depends on
the symmetry of each surface orientation. This point
is of crucial importance for understanding theinterplay between the crystal symmetry and the
topological protection in TCIs.
In this study, we have performed angle-resolved
photoemission spectroscopy (ARPES) on the (111)
surface of SnTe whose bulk and surface Brillouinzones (BZs) are displayed in Fig. 1(a). By utilizing
the high-resolution and variable-photon-energy (hν)
capabilities of the beamline BL7U, we have succededin revealing two types of mirror-symmetry-protected
Dirac-cone SSs, which originate from the bulk-bandinversion at the L points [4].
Figure 1(b) represents Fermi-surface mapping
results on the (111) surface of SnTe with hν = 23 eV.
We identify bright intensity centered at theΓ point aswell as relatively weak intensity at theΜ point,
which reflects the periodicity of the (111) surface.
The observed intensity at EF around theΓ point
originates from a linearly dispersive hole-like bandnear EF as seen from Fig. 1(c). The near-EF band
dispersion [Fig. 1(d)] extracted from the numericalfittings of the MDCs with two Lorentzians reasonably
overlaps with each other within the experimental
uncertainties irrespective of photon energies. This
result strongly suggests the existence of a Dirac-cone
SS centered at theΓ point. We also found a linearly
dispersive hole-like band which crosses EF aroundtheΜ point as displayed in Fig. 1(e). The hν
independence in the dispersion [see Fig. 1(f)]demonstrates that the observed linearly dispersive
band originates from a Dirac-cone SS centered atΜ,

indicating that there exist four Dirac cones in thesurface BZ, one centered atΓ and three atΜ. As
seen from Fig. 1(a), the (110) mirror plane of the bulk
BZ lies along theΓ−Μ line of the surface BZ. Sincea single L point at which bulk-band inversion takes
place is projected onto either theΓ orΜ points, asingle Dirac cone is produced centered at thosetime-reversal-invariant momenta (on the projection of
the mirror plane), consistent with the present
observation. The present ARPES result on the (111)
surface, together with our previous study on the (001)surface [3], establishes an essential role of the crystal
mirror symmetry and the bulk-band inversion inrealization of the TCI phase.

Fig. 1. (a) Bulk fcc BZ and corresponding hexagonal(111) surface BZ of SnTe. Green shaded area
represents the (110) mirror plane. (b) ARPES intensity
mapping at EF at T = 30 K plotted as a function of
in-plane wave vector. (c) Intensity plot of the second
derivatives of the momentum distribution curves(MDCs) across the cut crossing theΓ point for hν =23 eV. (d) Comparison of the band dispersions fordifferent photon energies extracted by fitting the
MDCs. (e) and (f) Same as (c) and (d), respectively,
but measured along the cut crossing theΜ point.
[1] L. Fu, Phys. Rev. Lett. 106 (2011) 106802.
[2] T. H. Hsieh et al., Nature Commun. 3 (2012) 982.
[3] Y. Tanaka et al., Nature Phys. 8 (2012) 800.
[4] Y. Tanaka et al., Phys. Rev. B 88 (2013) 235126.

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An ARPES Study of the Electronic Structure of CsBi4Te6
S. T. Cui1, S. Kong1, G. B. Zhang1, Z. Sun1, C. Xiao2, Y. Xie2, M. Matsunami3 andS. Kimura3,4
1

National Synchrotron Radiation Laboratory, University of Science and Technology of China,
Hefei, Anhui 230029, People’s Republic of China
2 Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China,
Hefei, Anhui 230026, People’s Republic of China
3
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
Topological insulators are a new quantum state ofmatter with gapless surface states inside of the bulk
energy gap. (Bi, Sb)2(Te, Se)3 series of compounds
have been extensively studied as topologicalinsulators. On the other hand, (Bi, Sb)2(Te, Se)3 series
have been widely used as thermoelectric materials.
Indeed, the excellent properties of thermoelectricmaterials are mainly due to the nature of the novel
electronic structures of these topological insulators.
Thus, it is an interesting topic to search (Bi, Sb)2(Te,Se)3-derived thermoelectric materials for topologicalinsulators.
CsBi4Te6 is an excellent thermoelectric material [1],with thermoelectric properties better than (Bi, Sb)2(Te,Se)3 at low temperature. Recently, it has also beenfound that a slight hole-doping can induce
superconductivity in this compound [2]. Figure 1
shows the crystal structure of CsBi4Te6. In thismaterial, the Bi2Te3 framework is reconstructed, so
CsBi4Te6 bears no resemblance to the corresponding
binary compound. Thus it is important to investigate
whether this excellent thermoelectric material canhost topological insulating states. Moreover, it is ofgreat interest to study whether the topologicalinsulator
statescancoexistencewithsuperconductivity in this material.
We performed ARPES experiments on CsBi4Te6 at
BL7 of UVSOR at T=30K, with 20 meV energy
resolution and 0.5o angular resolution, under anultrahigh vacuum of 6×10-11 mbar.
Figure 1 shows the electronic band structure over alarge energy scale near the zone center. The band
structure calculations show that CsBi4Te6 is anarrow-gap semiconductor [3], while the electricalconductance measurements show that this material
bears metallic properties. The inset of Fig. 1(a)exhibits evident spectral weight near the Fermi level,
which is consistent with the metallic conductivity inthis material [3]. These metallic spectral weight
however could arise from the conduction band withslight electron doping.
A close inspection of the near-EF states can reveal
more details of the electronic structure. Figure. 2(b)shows the spectral weight distribution in the yellow
frame in Fig. 2(a). It is very interesting that there
likely exists Dirac-cone-like spectral weight within

the band gap of this material. Although moreexperiments should be carried out to reveal the true
nature of these states, it is possible that novel
electronic states may exist in this thermoelectricmaterial.

Fig. 1. The crystal structure of CsBi4Te6 looking
down the b axis.

Fig. 2. (a) Band structure of CsBi4Te6. (b) Near-EF
Dirac-cone-like dispersions, which were taken fromthe yellow frame in (a).
[1] D. Y. Chung et al., Science 287 (2000) 1024.
[2] C. D. Malliakas et al., J. Am. Chem. Soc. 135(2013) 14540.
[3] D. Y. Chung et al., J. Am. Chem. Soc. 126 (2004)
6414.

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Three-Dimensional Anisotropic Superconducting Gap of Over-Doped
BaFe1.8Co0.2As2
T. Hajiri1,2, T. Ito1,3, M. Matsunami2,4, B. H. Min5, Y. S. Kwon5 and S. Kimura2,4
1

Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
2
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
3
Nagoya University Synchrotron Radiation Research Center, Nagoya University, Nagoya, 464-8603, Japan
4
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585,
Japan
5
Department of Emerging Materials Science, DGIST, Daegu 711-873, Republic of Korea

Ⅲ-2

In iron pnictide superconductors, one of the most
attractive issues is the position of nodes in thethree-dimensional (3D) electronic structures, because
the position of nodes is the most important
information for the origin of the superconductivity as
well as the symmetry of the superconducting (SC)order parameter. Angle-resolved photoemission
spectroscopy (ARPES) is one of the most powerfultools to investigate the SC-gap structures. Importantly,
the SC-gap structure in the 3D momentum space canbe revealed by ARPES using synchrotron radiation.
In this report, we show the 3D-ARPES results of theover-doped BaFe1.8Co0.2As2 (Tc ~ 22.5 K) using
UVSOR BL7U “SAMRAI” end-station. In thismaterial, the nodal behavior was reported [1,2].
Figures 1(a) and 1(b) show the out-of-planeelectron Fermi surfaces (FSs) in the ΓMAZ plane andin-plane FSs determined by experiments, respectively.
The symmetrized ARPES spectra above Tc (T = 35 K)
and below Tc (T = 12 K) at several FS angles (θ )measured with the photon energy hν = 14 eV areshown in Figs. 1(c) and 1(d). At the outer electron FS
in Fig. 1(c), the spectral weight at Fermi level at |θ | =177.2° are suppressed with decreasing temperature,indicating the opening the SC gap. At |θ | = 92.3°,
however, no temperature dependence appears. In
contrast to the outer electron FS, the inner electron FS
shows substantially isotropic SC gaps as shown in Fig.
1(d). We summarized the θ-dependence of the
SC-gap size of both electron FSs around the A and M
points in Figs. 1(e) and 1(f), respectively. The only
outer electron FS has an anisotropic SC gap withnodes or gap minima around the longer axis of theellipsoid-shaped FS.
Focusing on the electron FSs at the intermediate
region between the M and A points taken at hν = 19
eV shown in Figs. 1(g) and 1(h), both electron FSs
show substantially isotropic SC gaps. Therefore, thenodes exist only around the longer axis of theellipsoid-shaped outer electron FS at around the M(hν = 24 eV) and A (hν = 14 eV) points. Our
observation suggests that the appearance ofsuperconductivity of this material originates from not
only spin fluctuation but also orbital fluctuation.

Fig. 1. (a) Out-of-plane electron FSs in the ΓMAZ
plane. (b) Schematic in-plane FSs. (c,d) Symmetrized
ARPES spectra taken at hν = 14 eV with selected θ ofthe outer and inner electron FSs, respectively. (e,f)θ-dependence of the SC-gap size around the M and A
points. (g,h) Same as (c,d) but taken at hν = 19 eV.
[1] D. -J. Jang et al., New J. Phys. 13 (2011) 023036.
[2] T. Hajiri et al., arXiv:1311.4990 (2013).

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Carrier Concentration Dependence of Superconducting Gap in
Bi2(Sr,RE)2CuO6+d (RE = La, Nd, Sm)
H. Sakamoto1, A. Yamamoto1, M. Matsunami2, S. Kimura2 and T. Takeuchi1,3,4,5
1

Department of Crystalline Materials Science, Nagoya University, Nagoya 464-8603, Japan
2
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
3
Ecotopia Science Institute, Nagoya University, Nagoya 464-8603, Japan4
Toyota Technological Institute, Nagoya 468-8511, Japan
5
Promoting Individual Research to Nurture the Seeds of Future Innovation, Japan Science and Technology
Agency, Tokyo 102-8666, JapanThe relation between the pseudogap and thestability of superconducting state had been
intensively discussed. Some experimental results
supported the scenario of the pseudogap as thepre-formed superconducting gap, but many otherexperiments suggested that the pseudogap developing
around the anti-node direction is caused by anunidentified mechanism that is different from the
Cooper pair formation and, therefore, prevents theelectrons near the anti-nodal region from forming the
Cooper pairs. The electrons near the node, on theother hand, are not affected by the pseudogap, and theBose condensation of the Cooper-pairs still takes
places to stabilize the superconducting state.
Despite a huge number of investigations being
performed after the discovery of high-Tc cuprate
superconductors, the collective excitation leading to
the formation of Cooper-pairs has not been fully
identified yet. In order to gain deep insight into suchcollective excitation, it is of great importance to knowthetemperature-,
momentum-,andcarrier
concentration- dependences of superconducting gap.
Unfortunately, however, the pseudogap developing at
the underdoped condition has made it difficult toreveal the temperature-, momentum-, and carrier
concentration- dependences of superconducting gap.
The relation between the carrier concentration
dependence of superconducting gap and the carrier
concentration dependence of Tc especially at theunderdoped region, on the other hand, has not been
fully investigated yet, because the highly developed
pseudogap covers the very wide momentum and thesuperconducting gap persists only in the limited
portion in the vicinity of nodal direction where theenergy-width of superconducting gap stays in verysmall values.
In this study, therefore, we carefully investigatedthe very small superconducting-gap Δ(φ ) = Δ0 cos φpersisting near the nodal direction ( φ = 0 ) for a seriesof Bi2(Sr,RE)2CuO6+d (RE = La, Nd, Sm)superconductors of various hole-concentrations bymeans of ultra-high-energy-resolution laser induced
ARPES. By additionally employing the synchrotron
radiation ARPES measurements at BL7U in UVSOR,
we investigated the shape of the Fermi surface andthe size of the pseudogap as a function of carrier
concentration.

Figure 1 shows the hole concentration dependence
Δ0
and Tc ofof superconducting gap
Bi2(Sr,RE)2CuO6+d (RE = La, Nd, Sm) determined bymeans of ARPES measurements. The pseudogap
develops when the rare earth element of small ionicradius is used for the substitute of Sr. The differencein Tc for the different series of Bi2(Sr,RE)2CuO6+d is,therefore, attributed to the development ofpseudogap.
The hole-concentration dependence of Δ0 shows
universal behavior regardless of the rare earth
element involved in the samples. It obviously
increases with decreasing hole concentration at
overdoped region. After becoming maximal at aroundp = 0.23 holes/Cu, it turns out to be reduced withdecreasing hole concentration. The value of p = 0.23
holes/Cu providing maximum Δ0 is definitely
different from p = 0.16 holes/Cu that has been
generally considered for the optimally doped
condition.
We should stress, as a consequence of this study,
that the formability of Cooper-pair is less sensitive toout-of-plane disordering. It is also very important tofind the collective excitation that can strongly affectthe energy and momentum of conduction electrons at
p = 0.23 holes/Cu.

Δ0 (meV)

25
20

(a)

15
10

La
Nd
Sm

5
0
40
T c (K)

30

(b)

20
10
0
0.0

0.1
0.2
0.3
0.4
0.5
Hole concentration, p (holes/Cu)

Fig. 1. Hole concentration dependence of (a)superconducting gap Δ0 and (b) Tc of
Bi2(Sr,RE)2CuO6+d (RE = La, Nd, Sm) determined bymeans of ARPES measurements and (b) that of.

97

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BL7B

Electronic Status of Ce3+ in Glass Host by Characterizing
Photoluminescence of Ce3+ Doped 20Al(PO3)3–80LiF Glass Scintillator
T. Shimizu1, Y. Minami1, R. Arita1, M. Tsuboi1, T. Nakazato2, T. Hori1,
K. Fukuda1, K. Yamanoi1, Y. Shinzato1, R. Sogi1, N. Sarukura1, H. Azechi1,
M. Cadatal-Raduban3, T. Murata4, S. Fujino5, H. Yoshida6, T. Suyama7, K. Fukuda7,
A. Yoshikawa8, N. Sato9, H. Kan9 and K. Kamata91

Institute of Laser Engineering, Osaka University, Suita 565-0871, Japan
Research Institute for Science & Technology, Tokyo University of Science, Noda 278-8510, Japan
3
Centre for Theoretical Chemistry and Physics, Institute of Natural and Mathematical Sciences, Massey
University, Albany, Auckland, 0632 New Zealand
4
Kumamoto University, Kumamoto 860-8555, Japan
5
Kyushu University, Fukuoka 812-8581, Japan
6
Ceramic Research Center of Nagasaki, Higashisonogi-gun 859-37, Japan
7
Hamamatsu Photonics K.K., Hamamatsu 430-8587, Japan
8
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
9
Furukawa Co. Ltd., Tokyo 100-8370, Japan2

Ⅲ-2

expanding of 5d bandwidth in Ce3+ with increasing of
Ce3+ concentration. The PLE spectra of samples,emission wavelength is 331 nm, at various temperatureare shown in Fig. 2. Both crystal show broad excitation
spectrum and the peak wavelength are around 270 nm.

The realization of nuclear fusion is highly expected tosatisfy the energy demand in the future. Fusion plasma
diagnostics at higher plasma areal density than 3 g/cm isone of the biggest breakthrough in nuclear fusion
research. Scattered-neutron diagnostics [1] utilizing
Pr3+-doped 20Al(PO3)3-80LiF (APLF+Pr) glass
scintillator is expected to achieve plasma areal density
measurement in fusion core. APLF+Pr, which have highsensitivity for scattered neutrons and fast response timeabout 5.4 ns, is the key factor of the measure. In addition,
recent research indicated that APLF+Ce also have great
characteristics as neutron scintillator [2]. In this work,
we report the optical properties of APLF+Ce at various
temperature for investigation of electronic status of Ce3+.
We have measured Photoluminescence (PL) spectra
and Photoluminescence Excitation (PLE) spectra of
APLF+Ce for 0.5 and 3.0 mol % Ce3+ concentrations at
30K, 100K, 200K, and 300K. APLF+Ce glass samples
which size are 25 mm in diameter and 10 mm inthickness are used. The experiment was conducted at
BL7B utilizing G2 grating. Each sample was put inside
a vacuum chamber maintained at a vacuum level of 10-6
Pa and was excited by the synchrotron radiation. An
optical fiber was used to guide luminescence from thesample to the spectrometer. The spectrometer consists ofa liquid nitrogen-cooled charge coupled device (CCD)
camera for PL measurement and a photomultipliertube(PMT) for PLE measurement. The temperature ofsamples was controlled by liquid helium cryostat andheater.
The PL spectra of APLF+Ce for 0.5 and 3.0 mol %Ce3+ concentrations excited by 220 nm radiation at 30 K
and 300 K are shown in Fig. 1. The luminescenceintensity of both samples remain nearly unaffected bytemperature change. The emission peak of APLF+0.5
mol % Ce3+ was around 330 nm wavelength. On theother hand, one of APLF+3.0 mol % Ce3+ was around343 nm wavelength. This difference result from2

Fig. 1. PL spectra of APLF+Ce.

Fig. 2. PLE spectra of APLF+Ce.
[1] M. Moran et al., Rev. Sci. Instrum. 75 (2004) 3592.
[2] IEEE TRANSACTIONS ON NUCLEARSCIENCE. 59 (2012) 2256.

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BL7B

Reflection Spectra of Ternary Zinc Bismuth Phosphate Glasses in the
Ultraviolet Region
N. Kitamura

National Institute of Advanced Industrial Science and Technology, Osaka 563-8577, Japan
Bismuth phosphate glasses, which have highrefractive index and low deformation temperature, arecandidate materials for producing high performance
optical components such as compact lenses anddiffractive optics. It is of interest that a zinc bismuth
phosphate glass system has two distinct glass-forming
regions; orthophosphate and isolated phosphate
structures are dominant in the region that the atomic
ratio O/P is higher than 3.5 and metaphosphate andpyrophosphate structures are dominant in the regionof O/P < 3.5[1, 2]. We have reported the glass
structure and local structure around bismuth ions in aprevious work [2, 3]. Absorption edge energy isrelated to the interconfigurational transition from 6s2
to 6s16p1 of the Bi3+ ion. However, the energy level inthe glass system is not clear yet. In the present study,
reflectivity of the bismuth phosphate glasses has beenmeasured to investigate compositional dependence ofthe band structure in the vacuum ultraviolet region.
Binary xBi2O3-(100-x)P2O5 glasses (x=15, 25 and30 mol%), ternary yZnO-(30-y/2)Bi2O3-(70-y/2) P2O5
glasses (y=10, 20 and 30 mol%) and 50ZnO-50 P2O5
glass were prepared by using a conventionalliquid-quench method. Reflectivity of opticallypolished samples was measured in the photon energy
region of 4-12 eV with an incident angle of 10˚ at theBL7B. Figure 1 shows reflection spectra of the binary
and un-doped ZnO-P2O5 glass. Distinct reflection
peak and broad contour were respectively observed ataround 5 eV and 6-8 eV by comparing the spectrum
for the undoped ZnO-P2O5 glass. The peak andcontour are assigned to the 6s2!6s16p1 transition in
the Bi3+ ion [2, 4]. We know that transitions from theground state (1S0) to excited states 3P0 and 3P2 are
spin-forbidden. Therefore, the lower distinct peak is
expected to the 1S0!3P1 transition and the next
contour could be due to the 1S0!1P1 transition. In thebinary Bi2O3-P2O5 glass system, the distinct peakshifted toward lower energy side with Bi2O3
concentration. Moreover, both the band structuretended to broaden with increasing the concentration.
It could be due to distortion of BiO6 tetrahedron
which was found in high energy diffraction
measurement [5].
On the other hand, reflection spectra of ternaryyZnO-(30-y/2)Bi2O3-(70-y/2) P2O5 glasses are shownin Fig. 2. As shown in the figure, the distinct peak did
not shifted with the change of Bi2O3 concentration,
while the intensity of the band increased with theconcentration. It was consistent with that theabsorption edge energy was less dependent on theconcentration in the ternary glass system with
O/P<3.5 [2]. The band structure of ternary glass with
O/P>3.5 will be measured in near future.
This work was supported by Nippon Sheet GlassFoundation for Materials Science and Engineering.
0.14
30Bi2O3-70P2O5
50ZnO-50P2O5

Reflectivity

0.12
0.10
0.08
0.06

25Bi2O3-75P2O5
15Bi2O3-85P2O5

0.04

4

5

6

7
8
9 10 11 12
Photon energy/ eVFig. 1. Reflection spectra of binary xBi2O3-(100-x)
P2O5 and ZnO-50P2O5 glasses.
0.14

30ZnO-15Bi2O3-55P2O5

Reflectivity

0.12

0.10

0.08

20ZnO-20Bi2O3-60P2O5
10ZnO-25Bi2O3-65P2O5

0.06
4

5

6

7

8

9

10

11 12

Photon energy/ eVFig. 2. Reflection spectra of ternary yZnO- (30y/2)Bi2O3-(70-y/2)P2O5 glasses.

[1] B. Elouadi et al., Phase Trans. 13 (1988) 219.
[2] N. Kitamura, K. Fukumi, J. Nakamura, T. Hidaka,
H. Hashima, Y. Mayumi and J. Nishii, Mater. Sci.
Eng. B 161 (2009) 91-95.
[3] N. Kitamura and K. Fukumi, J. Ceram. Soc. Jpn.
121 (2013) 355-360.
[4] G. Blasse and A. Bril, J. Chem. Phys. 48 (1968)
217-222.
[5] N. Kitamura, et al., 23th International Congress
on Glass 2013, in preparation.

99

Ⅲ-2

Ⅲ -2. Materials Sciences

BL7B

Anomalous Domain-Wall Conductance in Pyrochlore-Type Nd2Ir2O7 on the
Verge of the Metal-Insulator Transition
J. Fujioka1, K. Ueda1, Y. Takahashi1, T. Suzuki2, S. Ishiwata1, Y. Taguchi2, M. Kawasaki1,2
and Y. Tokura1,2
1100

eV. Below TN, the reflectivity in low energy region issignificantly suppressed, indicative of the opening of
the charge gap. Figure 1 (b) shows the real parts of
the optical conductivity spectra below 8 meV at 4 K.
Here, the black solid line denotes the conductivity for
multi-domain state [ " ut ' (! ) ] obtained at 0 T after
cooling under zero magnetic field(untrained state),
whereas the red one denotes the spectra for singledomain state[ " t ' (! ) ] obtained at 0 T once the field
applied(trained state). " ut ' (! ) shows Drude response
below 4 meV, whereas " t ' (! ) monotonicallydecreases as lowering energy. In order to examine thecharge dynamics of DW in more detail, we havededuced the real ( $" ' (! ) = " ut ' (! ) # " t ' (! ) ) andimaginary ( $" ' ' (! ) = " ut ' ' (! ) # " t ' ' (! ) ) part of the DW
optical conductivity spectra. Figure 1 (c) shows#" ' (! ) (red solid line) and #" ' ' (! ) (blue solidone). The broken lines corresponds to fitting 1 curvewith Drude model with scattering rate of 2 meV,
indicating that highly metallic state is realized at themagnetic DW. Such anomalous DW conductancecould be relevant with the topological edge state
relevant to WSM
1
0.8
0.6
0.4
0.2
0 -2
10

50 K
30 K
20 K
10 K

(a) Nd 2Ir 2O7$! (") (#-1cm-1)

10-1
100
101
Photon Energy (meV)85(b) Nd2Ir 2O7(c) Nd2Ir 2O7
4 K, 0 T
4 K, 0 T
46!'ut (")
3$!'' (")
4
2! 't ( ")21$!' (")
00
0 2 4 6 8
0 1 2 3 4 5 6
Photon Energy (meV) Photon Energy (meV)~The topological quantum phase of condensed
matter has been of great interest since the discoveryof the topological insulator. A spectacular feature of
topological insulator is the emergence of the
topologically protected surface state, whereas thebulk is characterized by a gapped electronic state.
Recently, Wan et al. have predicted another class of
unconventional topological quantum state, that is,
Weyl semimetal (WSM). WSM is a zero gap
semiconductor(semimetal) which is characterized by
the k-linearly dispersing bands near the Fermi energy
and by the emergence of topologically-protected edge
state at the sample surface.
Pyrochlore-type R2Ir2O7 (R = trivalent rare-earth or
Y ion) has attracted much attention since it is one ofthe promising candidates for the realization of WSM
due to the interplay between electron correlation andstrong spin-orbit coupling inherent to heavy 5delements. Among a series of R2Ir2O7, R = Ndundergoes metal-insulator transition accompanying
with all-in all-out type magnetic ordering at TN = 32
K, where all the spins on the vertices of tetrahedronpoint either inwards or outwards to its center. Recent
study suggests that its ground state could be a Mott
insulator in vicinity to WSM [2]. In order tocharacterize this unconventional phase, theobservation of edge state at sample surface ormagnetic domain wall (DW) is essential.
In this article, we report the spectroscopic
observation of metallic state at antiferromagnetic DW
in Nd2Ir2O7 [3]. The antiferromagnetic DW shows
Drude-like optical response with minimal damping
constant of ~ 2 meV, contrary to the fully-gappedelectronic structure in bulk.
We measured reflectivity spectra for polycrystals of
Nd2Ir2O7 between 12 meV and 5 eV using Fouriertransform spectrometer and grating-type spectrometerin temperature range between 5 K and 290 K. We
obtained the reflectivity between 5 and 40 eV at room
temperature by using synchrotron radiation at BL7B
in UVSOR. We determined complex optical constants
through the Kramers-Kronig transformation withproper extrapolations of reflectivity in the low andhigh energy regions. We also obtained the opticalconductivity spectra below 8 meV by the terahertz
time-domain spectroscopy in a transmission
configuration.
Figure 1 (a) shows the reflectivity spectra up to 40

Reflectivity

Ⅲ-2

Department of Applied Physics, University of Tokyo, Tokyo 113-8656, JapanRIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan!' (") (#-1cm-1)

2

Fig. 1. (a)Reflectivity and (b) (c) optical conductivity
spectra for Nd2Ir2O7 at various temperatures.
[1] X. Wan et al., Phys. Rev. B 83 (2011) 205101.
[2] K. Ueda et al., Phys. Rev. Lett. 109 (2012)
136402.
[3] K. Ueda et al., Phys. Rev. B 89 (2014) 075127.

Ⅲ -2. Materials Sciences

BL7B, BL8B

Measurement of Transmittance and Reflectance of LiTi2O4 and UPS
Measurement of Multi-Alkali Surface
R. Inagaki1,2, T. Konomi2, T. Tokushi2, M. Katoh2, E. Kako3, S. Yamaguchi3, Y. Kobayashi3,
N. Yamamoto4, M. Hosaka4, Y. Takashima4, S. Shiraki5, T. Hitosugi5, K. K. Rasika6
and Y. Okano7
1

Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
2
UVSOR facility, Institute for Molecular Science, Okazaki 444-8585, Japan
3
High Energy Accelerator Research Organization, KEK, Tsukuba, 305-0801, Japan
4
Nagoya University Synchrotron radiation Research center, Nagoya 464-8603, Japan
5
WPI-AIMR, Tohoku University, Sendai 980-8577, Japan
6
Graduate School of Advanced Integration Science, Chiba 263-8522, Japan
7
Laser center, Institute for Molecular Science, Okazaki 444-8585, JapanIn UVSOR, a VUV free electron laser based onsuperconducting linear accelerator with high pulse
repetition about 1MHz is being designed for the next
generation light sources. We are developing anelectron gun for the new accelerator by combining
superconducting RF cavity and photocathode. We
propose a back-illuminated multi-alkali photocathodewith transparent superconductor LiTi2O4 [1]. We
consider that to clarify the transmittance / reflectanceof the substrate and deposition state of multi-alkali is
important in making the photocathode.
In this study we measured the transmittance andreflectance of LiTi2O4 in R.T. and 25.5K at BL7B,
UVSOR-. Furthermore, we performed a Ultraviolet
Photoelectron Spectroscopy of gold surface wasdeposited multi-alkali (K2CsSb) at BL8B, UVSOR to elucidate the bonding state of alkali metal
atoms in the course of deposition.
Figure 1(a) shows a transmittance of LiTi2O4 of
70nm and 90nm thickness at R.T. and 25.5K. Figure1(b) shows a reflectance of LiTi2O4 of 70nm and90nm thickness at R.T. and 25.5K. The transmittanceat R.T. is about 70% in the range of 350nm and
600nm. These results are consistent with themeasurement results at Tohoku University [2]. At
25.5K, the transmittance of only substrate (MgAl2O4)
was higher than that of at R.T. in all measurement
wavelength range but transmittance and reflectance of
LiTi2O4 did not change significantly.
Figure 2 shows a spectrum of Au surface deposited
K2CsSb. The results suggests that three alkali metals
were not compounded, it was only stacked. This isbecause the substrate temperature during thedeposition was lower than the bonding temperature.
We plan to measure the transmittance andreflectance
below
superconducting
transition
temperature (<12K) and to perform a UPS in theactual deposition condition.
We are grateful to T. Hitosugi and S. Shiraki,
WPI-AIMR Tohoku Univ. for provision of LiTi2O4
samples.

Ⅲ-2

(a)
(b)
Fig. 1. (a) Transmittance comparison of 70nm and90nm thickness of LiTi2O4 at R.T. and 25.5K (b)Reflectance comparison of 70nm and 90nm thicknessof LiTi2O4 at R.T. and 25.5K.

Fig. 2. Spectrum of Au surface was deposited K, Cs
and Sb. (Black; Spectrum of Au, Red; Spectrum of
surface deposited Sb: 16nm, K: 16nm and Cs:
8nm, Green; Spectrum of surface deposited Cs;
8nm on the sample of the red line)[1] T. Hitosugi, N. Yamada, S. Nakao, Y. Hirose, andT. Hasegawa, Phys. Status Aolidi A 207, No.7,
1529-1537 (2010).
[2] A. Kumatani, T. Ohsawa, R. Shimizu, Y. Takagi,
S. Shiraki et al., Appl Phys. Lett. 101 (2012) 123103.

101

Ⅲ -2. Materials Sciences

BL7B

Ultraviolet Photoluminescence of Gd3+ in Inorganic Materials under
Vacuum Ultraviolet Excitation
Department of Materials Science, Graduate school of Engineering, Kyushu Institute of Technology, Kitakyushu
804-8550, Japan2
Department of Chemistry, Faculty of Science, Gakushuin University, Tokyo 171-8588, Japan

Several ions such as Gd3+, Ce3+, Pb2+, Bi3+ and Eu2+
are known as UV luminescent centers. Among them,
only the Gd3+ emission center gives a sharp emission
peak at approximately 310 nm in UV-B region. The
sharp emission, which is attributed to the inner shell
4f–4f transition from 6PJ to 8S7/2 in the Gd3+ ions, canbe used as a light source for not only lighting
application but also medical application such as
phototherapy for skin disease [1], transillumination
for DNA analysis [2]. Because Gd3+ doped phosphorsusually have large band gaps in the VUV region,
efficient UV emission from doped Gd3+ ionsnecessitates intense VUV excitation. In this study,
Gd3+ doped YAlO3 were prepared and thefundamental UV photoluminescence (PL) properties
were investigated by VUV excitation.
The polycrystalline samples of (Y1-xGdx)AlO3(x=0.00-0.30) were prepared by a polymerized
complexmethod,using
Y 2O 3,
Gd2O3,
Gd(NO3)3.6H2O, Al(NO3)3.9H2O as starting materials.
Citric acid monohydrate and propylene glycol (PG)
were used to form the polymerized complex gels. The
sample powders were obtained by heating at 1400 oC
in air. The obtained powders were pressed into pellets
and sintered at 1400 oC in air. The phases in thesamples were identified by the powder X-ray
diffraction (XRD) using a Rigaku RINT 2100
diffractometer (CuK! radiation). The emission andexcitation spectra were measured in the beamline
BL7B at the UVSOR facility.
Each sample was identified as a distorted
perovskite type phase with a space group Pnma.
Because the unit cell volumes increased with Gd3+
concentration x, it was confirmed that Gd3+ wasdissolved into the host lattices. Figure 1 shows PL
spectra observed in (Y1-xGdx)AlO3 at room
temperature along with the excitation energies forhost lattice as a function of x. All samples showed
Gd3+ emission peaks at 314 nm originating from 6P7/2
to 8S7/2 transition. The maximum PL intensity wasobserved at x=0.03 and concentration quenchingoccurred above x=0.03. The excitation energies forhost lattices, that gave the maximum PL intensity,
decreased with increasing x.
Figure 2 shows PL excitation spectra of(Y1-xGdx)AlO3. Intense peaks, that were assignable tohost excitation, were observed in the wavelength
range from 150 to 180 nm. The variation of the
wavelength probably indicates the decrease in theband gaps of the host materials. Although shoulder
peaks were observed at 120 nm and 200 nm, their

origins are unknown at the present time.
Consequently, (Y1-xGdx)AlO3 was found to exhibit
intense Gd3+ UV emission and showed promise as a
UV phosphor upon VUV excitation.
4.3

Energy (eV)

4.2

4.1

4

8.0
7.8
7.6



PL intensity (arb. units)

3.9
x=0.03!ex=155nm



x=0.10!ex=157nm

7.4
7.2
0.0

0.1

0.2

0.3

Gd concentration, xx=0.20!ex=170nm
x=0.30!ex=172nm

290

300

310

320

Wavelength (nm)Fig. 1. Gd3+ photoluminescence spectra in(Y1-xGdx)AlO3. Inset shows excitation energies forhost lattices as a function of x.
20 15

10

Energy (eV)"em=314nm

PLE intensity (arb. units)

Ⅲ-2

K. Ueda1, Y. Shimizu1, Y. Taira2 and Y. Inaguma2

Excitation energy (eV)

1

5

Host
x=0.03x=0.10x=0.20x=0.30

8

6

S7/2 ! IJ

50

100

150

200

250

300

Wavelength (nm)Fig. 2. PL excitation spectra of (Y1-xGdx)AlO3.
[1] R. P. Sonekar, S. K. Omanwar, S. V. Moharil, S.
M. Dhopte, P. L. Muthal and V. K. Kondawar, Opt.
Mater. 30 (2007) 622.
[2] S. Okamoto, R. Uchino, K. Kobayashi and H.
Yamamoto, J. Appl. Phys. 106 (2009) 013522.

102

Ⅲ -2. Materials Sciences

BL7B

Scintillation and Luminescence Properties of a Single CsCaCl3 Crystal
1

M. Koshimizu1, N. Yahaba1, R. Haruki2, F. Nishikido3, S. Kishimoto4 and K. Asai1

Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Sendai 9800-8579,
Japan
2
Advanced Science Research Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan3
Molecular Imaging Center, National Institute of Radiological Sciences, Chiba 263-8555, Japan
4
Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801,
Japan
Auger-free luminescence (AFL), or core-valence
luminescence, is a radiative electronic transition
between the valence band and the outermost coreband. This luminescence is observed only forinsulator crystals in which the band-gap energy islarger than the energy difference between the valenceband and the outermost core band. AFL is known to
be a fast luminescence process whose decay time
constant is typically of the order of nanoseconds orless. Therefore, insulator materials that exhibit AFL
are applicable as to fast-response scintillators.
Thus far, BaF2 has been the most successful
example of scintillators exhibiting AFL. Its
scintillation has a fast component corresponding to
AFL, whose decay time constant is as short as 0.8 ns[1]. Owing to this fast decay combined with relatively
high light yields, BaF2 has been used for applications
in which good timing characteristics are necessary.
However, its scintillation also has a long decay
component corresponding to self-trapped excitons(STEs). The decay time constant of the long
component has been reported to be 600 ns [1]. Thus,
the long component limits the usage of BaF2 inseveral applications, such as measurements with ahigh counting rate. AFL has also been observed inother binary halide crystals.
In this paper, we report the scintillation propertiesof a ternary halide crystal, CsCaCl3. The origin of thescintillation is discussed on the basis of theluminescence characteristics under VUV irradiation.
Figure 1 shows the luminescence time profiles for
excitation at 84 and 200 nm. For the excitation at 84
nm, we observed fast luminescence decay in theentire range of the broad band at 300 nm, and Fig. 1
illustrates the time profiles at short- andlong-wavelength regions of the band. The decay time
constant was estimated to be 2.3 ns, which isconsistent with the result reported in a previous paper[2].
Figure 2 shows the scintillation time profile of
CsCaCl3. The decay behavior was satisfactorily fittedwith a sum of two exponential-decay components anda time-independent component. The fast component
had a decay time constant of 2.3 ns, which isconsistent with that of the luminescence shown in Fig.
1. Thus, a fast scintillation component due to AFL
was successfully obtained. The fast component
accounts for 58% of the total scintillation. The slow
component had a decay time constant of 14 ns, and103

this component accounts for only 4% of thescintillation. The time-independent component
accounts for 38%, and this component is considered
to have a decay time constant much longer than 624
ns, which is the period of the successive X-ray pulses.
The components having a long decay time constant
are presumably ascribed to the luminescence at
defects or impurities and STE emission.

Fig. 1. Luminescence time profiles of CsCaCl3 underirradiation of VUV photons at 88 nm.

Fig. 2. Scintillation time profile of CsCaCl3.
[1] M. Laval, et al., Nucl. Instrum. Methods 206(1983) 169.
[2] I. A. Kamenskikh, et al., Rev. Sci. Instrum. 63(1992) 1447.

Ⅲ-2

Ⅲ -2. Materials Sciences

BL7B

Insulator-to-Metal Transition of Sm1-xYxS
K. Imura1, M. Saito1, M. Matsunami2,3, H. S. Suzuki4, S. Kimura2,3 and N. K. Sato1
1

Department of physics, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
2
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan3
School of Physical Sciences, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan
4
Nuclear Scattering Group, National Institute for Materials Science, Tsukuba 305-0047, Japan1.0

Sm1-xYxS
T = 300 K
x=0
0.17
0.33

Reflectivity

0.8
0.6
0.4
0.2
0.0
0.01

0.1
1
Photon Energy (eV)10Fig. 1. The reflectivity spectra as a function of photon
energy of Sm1-xYxS (x = 0, 0.17, 0.33) at T = 300 K.

10

T = 300 K

8

3

-1

-1

!1 (10 " cm )Ⅲ-2

structure is clearly observed at x = 0.17 and 0.33, andthe systems show metallic behavior. These results
indicate that the insulator-to-metal transition is not a
trigger of the BG transition of Y-substituted SmS.

Samarium monosulfide (SmS) is a prototypicalcompound that exhibits a phase transition by applying
external pressure. This phase transition isaccompanied by a color change from black to goldenyellow, namely black-to-golden (BG) transition [1]. It
is well known that the electrical resistivity shows anenergy gap of about Eg ~ 0.1 eV at ambient pressure.
Although this energy gap decreases as increasingpressure, it is still unsolved how energy gap changes
in the vicinity of the critical pressure of the BG
transition.
In order to study an electronic structure as well as amechanism of this phase transition, angle resolved
photoemission spectroscopy or optical conductivity
measurements are powerful techniques. However,pressure studies are very difficult for theseexperiments.
On the other hand, it has been reported that the BG
transition is also induced by site substitution [2].
Then we focused onto the Sm1-xYxS system andperformed optical conductivity measurement in orderto reveal the relationship between the insulator tometal transition and the BG transition.
A detailed description of single crystal growth of
Sm1-xYxS (x = 0, 0.17, 0.33) was shown in elsewhere[3]. The reflectivity measurement in the vacuumultraviolet, ultraviolet and visible region i.e., thephoton energy region of 1.2-25 eV, was performed at
the BL7B which consists of a 3-m normal incidence
monochrometer. The optical conductivity spectra
were obtained from the Kramers-Kronig (KK)
analysis of the reflectivity spectra.
The BG transition of Sm1-xYxS is observed in thevicinity of x = 0.17. Figure 1 shows photon energy
dependence of the reflectivity spectra [R(ω)] of x = 0(black color), 0.17 (black color) and 0.33 (gold color)at room temperature. The reflectivity in the infrared
region of x = 0 is low in the whole energy region
excepting a sharp reflection at !ω ~ 23 meV due to an
optical phonon, reflecting an insulating behavior ofpure SmS. At x = 0.17, however, a large reflectivity isobserved although the system is still in black phase.
The plasma edge of x = 0.33 is located at higher
energy than x = 0.17 reflecting an increasing ofcarrier density.
Figure 2 shows the optical conductivity [σ(ω)] as afunction of photon energy calculated using the KK
transformation from the reflectivity spectra. Closed
circles show the DC conductivity values. The Drude6
4

Sm0.67Y0.33S
Sm0.83Y0.17S

2
0
0.00

SmS
0.05
0.10
0.15
Photon Energy (eV)0.20

Fig. 2. Photon energy dependence of the opticalconductivity calculated using the Kramers - Kronigtransformation. Closed circles show DC conductivity
value obtained from the conventional 4 probe
method.
[1] P. Wachter, In Handbook on the Physics andChemistry of Rare Earth (North-Holland, 1994) 19(1994) 383.
[2] T. Penny and F. Holtzberg, Phys. Rev. Lett. 34(1975) 322.
[3] K. Imura, T. Hajiri, M. Matsunami, S. Kimura, M.
Kaneko, T. Ito, Y. Nishi, N. K. Sato and H. S. Suzuki,
J. Korean Phys. Soc. 62 (2013) 2028.

104

Ⅲ -2. Materials Sciences

BL7B

Anomalous Energy Transfer Route from Gd3+ to Ce3+ Ions in
Ce:Gd3Al2Ga3O12 Crystals
A. Sato1, M. Kitaura1, S. Kurosawa2,3, K. Kamada3, A. Ohnishi1, M. Sasaki1 and K. Hara4
1

Department of Physics, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
2
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan3
New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579, Japan
4
Research Institute for Electronics, Shizuoka University, Hamamatsu 432-8011, Japan

It is well known that the addition of Gd3+ ionsworks effectively for an enhancement of Ce3+ 5d-4f
emission in inorganic phosphors [1]. The
fundamental process is elucidated by the energy
transfer from
Gd3+ to Ce3+ ions (Gd3+!Ce3+energy transfer). The spectral overlap between the
Gd3+ 4f-4f emission and Ce3+ 4f-5d absorption bands
are necessary for the Gd3+!Ce3+ energy transfer, andthe route is usually opened from the lowest energy(4f)7 excited state of the Gd3+ ion to the (5d)1 excitedstate of the Ce3+ ion. Beside the spectral overlap, anappearance of phosphorescence in the Ce3+ 5d-4f
emission is also worthwhile to note. The Gd3+ 4f-4f
emission is electric-dipole forbidden, while the Ce3+
5d-4f emission is electric-dipole allowed. When the
Ce3+ 4f-5d excitation occurs through the energy
transfer from the Gd3+ ion excited, the decay curvefor the Ce3+ 5d-4f emission ranges from µs to ms.
The Ce-doped Gd3Al2Ga3O12 (Ce:GAGG) crystal
attracts much attention as an inorganic scintillator
for the detection of X- and "-rays [2]. So far, we haveinvestigated photoluminescence (PL) properties of
Ce:GAGG crystals at the BL3B beamline of UVSOR[3, 4]. The PL-excitation (PLE) spectra for the Ce3+
5d-4f emission exhibited narrow peaks around 4 and
4.5 eV, which are due to Gd3+ 4f-4f absorption. This
fact suggests that the Gd3+!Ce3+ energy transfer
process occurs in Ce:GAGG. This process is
supported by the existence of phosphorescence in the
decay curve for the Ce3+ 5d-4f emission.
In the present study, we have found an anomalous
Gd3+!Ce3+ energy transfer route in Ce:GAGG
crystals under the single bunch operation of UVSOR.
Figure 1(a) demonstrates that a fast rise component
with the lifetime of dozens of nanosecond appears in
only the decay curve for Ce3+ 4f-5d emission
measured under excitation in the Gd3+ 4f-4f
absorption around 4.5 eV. This component was notobserved under excitation in the Ce3+ 4f-5d
absorption (Fig. 1(b)) and host GAGG absorption(Fig. 1(c)). Furthermore, it was confirmed that thefast rise does not appear under excitation in the Gd3+
4f-4f absorption around 4 eV. Therefore, it is most
likely that the fast rise component is caused by the
excitation in Gd3+ 4f-4f absorption around 4.5 eV.
Details of such an anomalous energy transfer routeare unknown at present, so we are analyzing the routeusing the Dieke diagram.

(a)

Ⅲ-2
Intensity (arb. units)

(b)

(c)

0

20

40

60

80

100

Time (ns)Fig. 1. Decay curves for the Ce3+ 5d-4f emission fromthe Ce:GAGG crystal, which were measured at 11 K
under excitation at 4.5 eV (a), 3 eV (b) and 6.5 eV (c).
The concentration of Ce3+ ion was 1.5 mol%. The
decay curves were vertically shifted for clarity.
[1] M. Nikl et al., Appl. Phys. Lett., 77 (2000) 2159.
[2] K. Kamada et al., J. Cryst. Growth 352 (2012) 88.
[3] M. Kitaura et al., J. Appl. Phys. 115 (2014)083517.
[4] A. Satoh et al., Jpn. J. Appl. Phys. (in press).

105