Ⅲ-2

Materials SciencesⅢ -2. Materials Sciences
BL1B
BL1B

Terahertz Spectroscopy of Ionic Liquids
T. Awano

Faculty of Engineering, Tohoku Gakuin University, Tagajo 985-8537, Japan

N
O
F3

S

-

O

S
O

O
CF

Fig. 1. Ionic structures of [DEME] (a) and [Tf2N] (b).

-1

ABSORPTION COEFFICIENT (cm )

150

100

[DEME][BF4]
298K
258K
158K
for 86K

Ⅲ-2

50

0
20

30
40
50
-1
WAVE NUMBER (cm )60

Fig. 2. Absorption increment spectra of [DEME][BF4] against the absorption spectrum at 86 K.

ABSORPTION COEFFICIENT (cm -1)

We have observed millimeter wave absorption
bands in AgI-superionic conductive glasses previously[1,2]. These bands were also observed in CuIsuperionic glasses at slight different peak positions[3].
These bands seems to be due to collective motion of
conductive ions, although how conduction ions moves
in correlation is not clear.
Ionic liquid is molten salt at room temperature
because of large radius of component ions. Figure 1
shows molecular structures of [DEME] (a) and [Tf2N](b). It is interesting to compare ionic motion in ionicliquids with those in superionic conductor forinvestigation of dynamics of mobile ions. In
superionic conducting glasses, only cation is movable.
Temperature dependence of absorption spectra ofionic liquids in spectral range between 20 to 60 cm-1
have measured to investigate change of dynamics ofions in process of change of state from liquid to solid.
Transmittance spectra of one and two filter papers with
the ionic liquid of the same quantity per the paper were
measured. Absorption spectra were obtained bysubtracting each other. To eliminate interference
structure remaining in the spectra, absorption
difference spectra between each spectrum and that at
86 K are shown in Figs. 2 and 3.
There observed some slight structures in theabsorption spectra in terahertz region contrary to thepreviously reported THz-TDS result[4]. Temperaturedependence of the absorption spectra showed similartendency as the results in the millimeter wave region,that were obtained using coherent millimeter wave at
the LINAC of the Kyoto University Research Reactor
Institute[5]. Absorption intensity of [DEME][BF4],
which becomes solid (crystal) under 282 K, drasticallydecreased at that temperature. On the other hand, thatof [DEME][Tf2N], which becomes solid (glass) under
182 K decreased gradually. Absorption intensity of allother ionic liquids measured in this study decreased
like these ones, concerning with the transition
temperature of melting point or glass transition
temperature.

20[DEME][Tf 2N]

298K
227K
158K
for 86K

10

0
20

30
40
50
-1
WAVE NUMBER (cm )60

Fig. 3. Absorption increment spectra of [DEME][Tf4N] against the absorption spectrum at 86 K.
[1] T. Awano and T. Takahashi, J. Phys. Conf. Ser. 148(2009) 012040.
[2] T. Awano and T. Takahashi, J. Phys. Soc. Jpn. 79(2010) Suppl. A, 118.
[3] T. Awano and T. Takahashi, Proc. 13th Asian Conf.
Solid State Ionics (2012) 569.
[4] T. Yamada, Y. Tominari, A. Tanaka and M. Mizuno,
J. Phys. Chem. B 119 (2015) 15696.
[5] T. Awano and T. Takahashi, KURRI Prog. Rep.
2015, CO4-1.

49
Ⅲ2-1

Ⅲ -2. Materials Sciences
BL1B
BL1B

Optical Conductivity Spectra of Electron- and Hole-doped Anisotropic
Kondo Semiconductor CeOs2Al10 in the THz Region
S. Kimura1, 2, H. Takao2, J. Kawabata3, Y. Yamada3 and T. Takabatake3, 4Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
Department of Physics, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan3
Department of Quantum Matter, ADSM, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
4
Institute for Advanced Materials Research, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
1

2

Ⅲ-2

An anisotropic Kondo semiconductor CeOs2Al10
exhibits an unusual antiferromagnetic order at rather
high transition temperature T0 of 28.5 K [1]. Two
possible origins of the magnetic order have been
proposed so far, one is the Kondo coupling of thehybridization between the conduction (c) and the 4f
states and the other is the charge-density wave/chargeordering along the orthorhombic b axis [2,3]. To clarify
the origin of the magnetic order, we have investigatedthe electronic structure of hole- and electron-doped
CeOs2Al10 [Ce(Os1-yRey)2Al10 and Ceσ (Os1-xIrx)2Al10,
respectively] by using optical conductivity [σ(ω)]
spectra along the b axis.
σ(ω) spectra, which were derived from the KramersKronig analysis of reflectivity spectra, along the b axis
at T = 10 K in ħω < 100 meV are shown in Fig. 1(a). In
this region, it should be noted that a very sharp peakowing to a transverse optical phonon is observed ataround 25 meV in all samples. Except for the sharp peak,
one Drude component owing to carriers and threeinterband transition peaks are observed in all samples.
To clarify the change of the spectra by increasing x
and y, we adopt the Drude-Lorentz fitting method. Theσ(ω) spectra are fitted by using the combination of one
Drude and three Lorentz functions. The obtained valuesof the effective electron number N* together with T0 andγ are plotted in Fig. 1(b) as functions of Re (y) and Ir (x)concentrations. Firstly, the carrier density (N* of Drude
component) is almost proportional to the electron
specific heat coefficient γ. Secondly, the intensity of thec-f hybridization gap (N* of Δc-f) at ħω ∼ 50 meV
continuously decreases from y = 0.10 to x = 0.12 via x =y = 0. On the other hand, the intensity of the charge
excitation (N* of Δ0) observed at ħω ∼ 20 meV has the
maximum at x = y = 0 as similar with the doping
dependence of T0. The fact that the charge excitation isstrongly related to the magnetic order strengthens thepossibility of the charge density wave/charge orderingas the origin of the magnetic order [4].

Fig. 1. (a) σ(ω) spectra along the b axis at T = 10 K and
the fitted lines of one Drude and three Lorentz
functions. The three Lorentz functions are assumed asa peak (Δ0, solid line) appearing below the magnetic
ordering temperature T0, the interband transition in thec-f hybridization gap (Δc-f, dashed line), and higher
interband transition from lower energy side (IB, dotdashed line). (b) Obtained effective electron numbers(N*s) of the Drude, Δ0, and Δc-f components, which areplotted together with T0 and the electronic specific heatcoefficient as functions of the Re (y) and Ir (x)concentrations.
[1] A. M. Strydom, Physica B 404 (2009) 2981.
[2] S. Kimura, T. Iizuka, H. Miyazaki, A. Irizawa, Y. Muro
and T. Takabatake, Phys. Rev. Lett. 106 (2011) 056404.
[3] S. Kimura, T. Iizuka, H. Miyazaki, T. Hajiri, M.
Matsunami, T. Mori, A. Irizawa, Y. Muro, J. Kajino and
T. Takabatake, Phys. Rev. B 84 (2011) 165125.
[4] T. Yoshida, T. Ohashi and N. Kawakami, J. Phys. Soc.
Jpn. 80 (2011) 064710.

50
Ⅲ-2-2

Ⅲ -2. Materials Sciences
BL2A
BL2A

Local Structural Evaluation of Alloy Nitrides Extracted by Electrolytic
Extraction Method
M. SatoInstitute for Materials Research, Tohoku University, Sendai 980-8577, Japan
It is well known that the martensite phase obtainedby quenching is hard but brittle. Therefore the balance
between hardness and toughness is adjusted by thesubsequent tempering treatment. At that time,
cementite is precipitated in case carbon steel, and Fe4N
is precipitated in case of nitrogen steel [1, 2].
Although it is known that alloying elements
partially dissolve in solid solution in these precipitates,
there is little knowledge on the chemical state of thesesubstitution elements in the precipitates. In this study,changes in the chemical state of the substitutional
elements before and after tempering treatment were
investigated by XAFS measurement.
Fe-1mass%Si and Fe-1mass%Mo alloys were usedas starting materials. They were homogenized at 1523
K for 24h and furnace-cooled until room temperature.
Fe-1Mo-0.3N and Fe-1Si-0.3N alloys were preparedby nitriding and quenching process using NH3/H2
mixed gas at 1273 K for 1 h. Then Fe-1Mo-0.3N and
Fe-1Si-0.3N alloys were tempered at 773 K for 1 h.
and precipitates generated during tempering wereextracted using Iodine-alcohol procedure. The Si Kedge and Mo LⅢ-edge XANES spectra were correctedby fluorescence method using InSb double crystal
monochrometer and silicon drift detector (SDD) at
BL-2A in UVSOR, respectively. Obtained data wereanalyzed using Athena software.
Figure 1 shows Si K-edge XANES spectra of (a) ~(c) references and (d) ~ (f) samples. Since the obtained
spectrum from the as-quenched sample mainly had thesimilar shape with that of the Si powder (see Fig 1(a)and (d)), and it was suggested that Si atoms aresubstituted into the Fe structure. However, peak was
observed around 1844 eV, which is consistent with thewhite line of SiO2, suggesting a partial oxidation ofsample. In case of the tempered sample, a new peak
appeared around 1842 eV consistent with the whiteline of Si3N4 in addition to the above peaks. On theother hand, the spectrum of the extracted residue
showed two peaks around 1842 and 1844 eV, and thesepeak positions were consistent with the white line of
Si3N4 and SiO2, respectively.
Figure 2 shows Mo LⅢ-edge XANES spectra of (a)reference and (b) ~ (d) samples. No change in spectral
shape was observed before and after tempering. This
result indicate that local structure around Mo atom
does not change by tempering treatment. However, thespectrum of the extracted powder sample showedchemical shift to the high energy side, implying the
precipitation of Mo compounds. From this result, it
was suggested that a trace amount of Mo isprecipitating as compounds such as Mo nitrides etc. In
the future, detailed examination will be carried out by
analysis of the EXAFS region and calculation using
FEFF code.

Ⅲ-2

Fig. 1. Si K-edge XANES spectra of samples. (a) Si,(b) SiO2, (c) Si3N4, (d) as quenched Fe-1Mo-0.3N alloy,(e) tempered Fe-1Mo-0.3N alloy and (f) extracted
residue.

Fig. 2. Mo LⅢ-edge XANES spectra of samples. (a)Mo foil, (b) as quenched Fe-1Mo-0.3N alloy, (c)tempered Fe-1Mo-0.3N alloy and (d) extracted residue.
[1] L. Cheng and E. J. Mittemeijer, Met. Trans. A 21A(1990) 13.
[2] L. Cheng, A. Bottger and E. J. Mittemeijer, Met.
Trans. A 23A (1992) 1129.

51
Ⅲ-2-3

Ⅲ -2. Materials Sciences
BL2A
BL2A

Characterization of MTB-Active Mo-Carbide Species Supported on H-MFI
Catalysts by Mo LIII-edge XANES1

Ⅲ-2

H. Aritani1, S. Mogi1, R. Yamazaki1, M. Akutsu1, K. Kawashima1,
M. Tsutsumi1 and A. Nakahira2

Graduate School of Engineering, Satama Institute of technology, Fukaya 369-0293 Japan
2
Graduate School of Engineering, Osaka Prefecture University, Sakai 599-8531 JapanFor direct conversion of LNG (Liquified natural gas)
to useful organic compounds, Mo-modified H-MFI is atypical catalyst for MTB (Methane to Benzene) reaction,i.e., methane dehydroarimatization. The MTB reaction
is very unique and useful for industrial methane
conversion, however, coke deposition over the catalyst
cannot be avoided during the reaction.[1] At the sametime, active Mo species should be changed structurally
because of excess carburizaiton on both Mo species andacid sites of H-MFI.[2] For obtaining the durable MTB
reactivity, the deactivation process over the catalysts is
one of an important point to develop the industrial MTB
catalysts. In this study, time course of thecharacterization of active Mo species for MTB (manly
Mo2C species) on H-MFI zeolites in various Si./Al2
ratios is investigated by means of Mo LIII-edge XANES.
Catalyst samples were prepared by impregnation ofeach H-MFI (Si/Al2=28 and 40) support with
MoO2(acac)2−CHCl3 solution (in 5wt% as MoO3), andfollowed by dried and calcined at 773 K. The H-MFI
supports were synthesized hydrothermally at 413 K fora week, and followed by ion-exchanging with NH4Cl
and calcined at 873 K. The catalytic MTB reactivity
was evaluated by means of fixed-bed flow reaction at
1023 K, as described in a separate paper [1]. Mo LIIIedge XANES spectra were measured in BL2A of
UVSOR-IMS in a total- electron yield mode using
InSb double-crystal monochromator. Photon energy
was calibrated by using Mo metal-foil, and normalized
XANES spectra and their derivatives are presented.
REX-2000 (Rigaku Co.) software was used bynormalization of each XANES spectrum.
Figure 1 shows the time course of the Mo LIII-edge
XANES spectra over MTB-active Mo/H-MFI (inSi/Al2 ratios are 28 and 40) catalysts during thereaction. For Mo/H-MFI in Si/Al2=28, higher MTB
activity and lower deactivation are shown than in
Si/Al2=40. For these catalysts, edge energy of LIIIXANES becomes lower by proceeding the MTB
reaction. This result indicates that a carbonization ofmolybdenum species advanced according to thereaction time. On the other hand, the MTB reactivity
has been maximized at 30-55 minutes over Mo/H-MFI(Si/Al2=28-40) catalysts. For the XANES spectrum,
metallic Mo species can be seen at 30-90 minutes overthese catalysts. The result suggests the formation ofactive Mo species as well-dispersed metallic ones. For
Mo/H-MFI (Si/Al2=40), the XANES spectra at 180
minutes (well-deactivated) shows the formation of α-

Mo2C species with higher edge energy than that ofmetallic one. In contrast, the XANES spectra of Mo/HMFI (Si/Al2=28) shows excess carbonized Mo species
at 180 minutes. These results suggest the relationshipbetween the formation of α-Mo2C species anddeactivation of Mo species for MTB reaction. For
obtaining more details, metal-ion promoted Mo/HMFI catalysts have been employed to characterize thehighly active Mo species for MTB. This study is now
in progress.

Fig. 1. Time course of the Mo LIII-edge XANES
spectra over Mo/H-MFI [Si/Al2 ratios are 28 (top) and40 (bottom)] catalysts during the MTB reaction.
[1] H. Aritani, H. Shibasaki, H. Orihara and A. Nakahira,J. Environm. Sci. 21 (2009) 736.
[2] H. Aritani, S. Mogi, N. Naijo, T. Sugawara, A. Akutsu,
K. Kawashima and A. Nakahira, UVSOR Activity Report
43 (2016) 49.

52
Ⅲ-2-4

Ⅲ -2. Materials Sciences
BL2A
BL2A

XAS Analysis of Charge State of Eu in Ba2EuxBi(2-x)O6 Double Perovskite
A. Kamata1 and T. Yamamoto1, 2Faculty of Science and Engineering, Waseda University, Tokyo 169-8555, Japan
Institute of Condensed-Matter Science, Waseda University, Tokyo 169-8555, Japan
1

2

Ⅲ-2

Fig. 1. Schematic illustration of double perovskite
structured BaBiO3. Green, blue, yellow and red balls
denote Ba2+, Bi3+, Bi5+ and O2- sites, respectively [1].

Ba2EuxBi(2-x)O6
x = 0.25

Intensity [arb.units]

Bithmus is an interesting elements, which can stably
exist as various charge states, 3+ and 5+ for Bi.
Especially, both of Bi3+ and Bi5+ can exist in one
material, e.g., in BaBiO3 with the ratio of Bi3+:Bi5+ =1:1. This is simply because of keeping the charge
neutrality in the material. When the Bi3+ and Bi5+ exist
periodically, say 3+,5+,3+,5+, …, superlattice should
be constructed, one of which is shown in Fig. 1 drawn
with VESTA [1]. This structure is called as double
perovskite structured BaBiO3. It was reported that thisdouble perovskite structure can be stabilized with thedoping of rare-earth ions. In the case of Ce doping,
however, no double perovskite structure appeared. [2]Although it is essential to know substition site andcharge state of doped rare-earth, such have not beenclearly understood yet. In the current study, charge
state of Eu ions in BaBiO3 has been examined with EuM5 X-ray absorption spectrum (XAS) measurements.
All the samples were fabricated with the solid-state
reaction method. Reagent grade powders, Ba(CO)3,
Bi2O3, Eu2O3 were ground and mixed in an agate
mortar in air for 30 min. with ethanol, which were
calcined at 1073 K for 6 hours in air. Resultant
powders were ground and mixed again, which werepressed into a pellet form (10 mm). These pellets
were sintered in air at 1123 K for 12 hours.
Crystal structures of synthesized materials were
examined by the conventional powder X-ray diffraction
technique with Cu-Kα X-rays, which showed all thesamples have double perovskite structure.
Eu-M5 XAS were measured at BL2A in UVSOR
with the total electron yield method. Samples powders
were put on the carbon adhesive tape, which wereattached on the first Cu-Be dinode of the electron
mutiplier. Synchrotron beams were monochromatizedwith beryl (10-10)double- crystal monochrometar.
Observed Eu-M5 XAS of Eu-doped BaBiO3 areshown in Fig. 2 together with that of Eu2O3. All the EuM5 XAS are almost identical and similar to that of
Eu2O3. From the comparison with the standard oxide,in which Eu ions exist as trivalent, we can safely
determine the charge state of the Eu ions in BaBiO3 istrivalent.

x = 0.50
x = 0.75
x = 1.00
Eu2O3

1120

1130
Energy[eV]1140Fig. 2. Observed Eu-M5 XAS spectra of Ba2EuxBi(2-x)O6
and Eu2O3.
[1] K. Momma and F. Izumi, J. Appl. Crystallogr. 44(2011) 1272.
[2] A. Matsushita et al., Jpn. J. Appl. Phys. 51 (2012)
121802.

53
Ⅲ-2-5

Ⅲ -2. Materials Sciences
BL2A
BL2A

Structural Evaluation of AlPO-5 with Si
A. Nakahira1, 2, M. Togo1, T. Takahashi1, T. Minami1, C. Takada1, M. Matsumoto1,
M. Iida1 and H. Aritani3

Faculty of Engineering, Osaka Prefecture University, Sakai 599-8531, Japan
Trans-Regional Corporation Center for Industrial Materials Research (IMR), Tohoku University, Sakai
599-8531, Japan
3
Saitama Institute of Technology, Fukaya 369-0293, Japan1

2

characterized by XRD method, FT-IR and TG-DTA.
The microstructures of product powder were observed
by SEM. The local structures around Si for the productsof samples were characterized by measuring X-ray
adsorption near edge structure (XANES) at BL02A in
UVSOR.
The evaluation of XRD was carried out for various
products synthesized by the static hydrothermal
process. According to XRD results, products preparedby this hydrothermal process at 473K with thecolloidal silica and fumed silica (0.3) as a siliconsource and TEAOH as a SDA were identified to be
SAPO-34. And similarly products with high contentsof 0.6 for silica were composed of SAPO-34. Figure 1
shows the XANES spectra of various SAPO-34
samples with colloidal silica and fumed silica (0.6). As
shown in Fig. 1, XANES spectra of sample obtainedby hydrothermal process were quite similar.
Furthermore, SAPO-34 with the high contents ofcolloidal silica and fumed silica as a silicon source
were similar to SAPO-34 with low content of silica.

Normalized Intensity (a. u.)

Ⅲ-2

In recent years, the micro- and meso-porous inorganic
materials attract much attention with growing concern
about a lot of environmental problems. Although
especially porous aluminophosphate (AlPO-n) is one ofunique microporous materials, these materials have low
catalytic ability. In order to achieve the catalytic
activities of AlPO-n, various heterovalent elements havebeen incorporated into the framework of AlPO-n. These
modified AlPO-n were generally found to incorporate
negative charges in the framework, and extraframework cations are present to balance the charges.
For example, AlPO doped with Si, that is “SAPO-n”,
was synthesized to achieve the catalytic properties. In
the so-called SAPO-n, a portion of P(V) is replaced by
Si(IV). In special, SAPO-34 has attracted muchattentions on the MTO (methanol to olefin) reaction
because of high specific surface area, adsorptive
capacities, and excellent catalytic activities.
The purpose in this study was to evaluate the local
structure of SAPO-34 synthesized by the statichydrothermal process at 473 K using various starting
materials and organic-structure-directing-agents (SDA)
like tetraethylammonium hydroxide (TEAOH). The
effect of synthetic condition parameters (starting
materials, SDA, temperature, and time, etc) on the
microstructure for various SAPO-34 samples wasinvestigated.
All chemicals were analytical reagent-grade, and theyused without further purification. The reagants usedwere γ-alumina, phosphoric acid, morpholine, andvarious silicon sources (TEOS, SiO2, colloidal silica,and fumed silica etc). SAPO-34 were synthesized fromstarting gel with the composition of Al2O3 : P2O5 :TEAOH : SiO2 : H2O =1.0 : 1.6 : 4.0 : (0.3~0.6) : 140.
γ-alumina was first mixed with TEAOH as a SDA anddeionized water at room temperature. Various silica
sources were then added into the mixture. Finally,
phospholic acid was added dropwise to the resultant
solution. The reaction mixture was further stirred for 1
h prior to being transferred into a stainless steel
autoclave. The crystallization was conducted in an oventhrough the static hydrothermal process withpreprogrammed heating profiles at 473 K for 24 h. Inorder to investigate the influence of hydrothermal
synthetic conditions the samples were characterized.
After all of the ground product powders werecolｌoidal Silica 0.6（D）
coｌloidal Silica 0.3（C）
Fumed Silica 0.6（B）
Fumed Silica 0.3

（A）
1820

1840

1860

1880

1900

Photon Energy / eV

Fig. 1. Si-K XANES spectra of various products
synthesized by the hydrothermal process at 473 K. (A)fumed silica of 0.3, (B) fumed silica of 0.6, (C)colloidal silica of 0.3, and (D) colloidal silica of 0.6.

54
Ⅲ-2-6

Ⅲ -2. Materials Sciences
BL2A
BL2A

Soft X-ray Irradiation Effect on the Local Structural Deformation in a
Molecular Conductor
T. Sasaki

Instutute for Materials Research, Tohoku University, Sendai 980-8577, Japan
It has been known that X-ray irradiation to the organic
materials causes molecular defects and disorder. We
have investigated the X-ray irradiation effect widely inthe series of molecular materials κ-(BEDT-TTF)2X
showing superconductivity or Mott insulating state fromthe viewpoint of the relation between the correlated
electronic states and randomness [1, 2]. Recently, weinvestigated the local structure deformation induced by
X-ray irradiation in κ-(BEDT-TTF)2Cu[N(CN)2]Br
using density functional theory based first-principles
calculations [3]. The crystal structure is shown in Fig. 1.
The calculations demonstrate that the structure change
due to X-ray excitation can be predicted by introducing
a core-hole at specific light atoms of anion moleculeswith infinite lifetime. Formation of the bond-shifted
structure around dicyanamide group (NC-N-CN) in theanion layer was expected as a possible irreversible
molecular defect leading to permanent irradiation
damage.
In this study, soft X-ray irradiation experiments inorganic conductor κ-(BEDT-TTF)2Cu[N(CN)2]Br was
carried out in order to prove the calculation results.
BL2A soft X-ray beamline was used for the irradiation.
Beryl crystal was used for the monochromator at thesoft X-ray photon energy of 1000 eV. The energy
monochromatic soft X-ray was directory irradiated tothe small single crystal surface in a vacuum chamberat room temperature. Total irradiation time was 52
hours. To determine the defect sites in the crystal,change of the molecular vibration modes wasmeasured by means of the infrared optical reflectanceexperiments.
Figure 2 shows the mid-infrared reflectivity spectra(E//a and E//c) of the crystal at 300 K before (black) andafter 52 hours irradiation (red). Peak structures atapproximately 1390 (Fig. 2(a)) and 2150 cm−1 (Fig.
2(b)) have been assigned to the vibration modes related
to the dicyanamide group in the anion molecules,
which have been significantly suppressed by white Xray irradiation by using the tungsten tube with 40 kV
in the lab experiments [1]. In the present SR soft X-ray
irradiation, however, no detectable change wasobserved in the both vibration modes. Some possible
reasons are expected such as short irradiation time,
weak intensity, small penetration depth, and so on. We
will check these points carefully for making next plans,
including soft X-ray absorption experiments on the
crystals irradiated by using the tungsten tube inadvance to detect a defect structure consisting
dicyanamide group.

Ⅲ-2

Fig. 1. Crystal structure of κ-(BEDT-TTF)2Cu[N(CN)2]Br.

Fig. 2. IR optical reflectivity of κ-(BEDT-TTF)2Cu[N(CN)2]Br before and after 52 hours soft X-ray
irradiation.
[1] T. Sasaki, Crystals 2 (2012) 374.
[2] T. Furukawa et al., Phys. Rev. Lett. 115 (2015)
077001.
[3] L. Kang, K. Akagi, K. Hayashi and T. Sasaki,
submitted.

55
Ⅲ-2-7

Ⅲ -2. Materials Sciences
BL2A
BL2A

Al K-edge XANES of AlN Films Doped with 3d Transition Metals
N. Tatemizo and S. Imada

Faculty of Electrical Engineering and Electronics, Kyoto Institute of Technology, Kyoto 606-8585, Japan

Ⅲ-2

Recently, the doping of semiconductors with 3dtransition metals (3d-TMs) has been extensively
investigated in order to realize semiconductors
exhibiting additional electronic states and having
improved properties. At high concentrations (~10%),the 3d-TMs’ orbitals will start to overlap with one
another, to form an impurity band. Such an impurity
band well apart from the conduction band (CB) and thevalence band (VB) can intermediate optical excitationsof electrons from the VB to the CB when the impurity
band is partially filled by electron. This is so called anintermediate band (IB) material proposed by Luque etal., for use in absorption layers of solar cells toincrease their conversion efficiency [1].
For wurtzite III-nitrides, such as AlN and GaN, thedoped 3d-TMs can not only form impurity bands in theband gap but also reconstruct the intrinsic VB and CB
when the 3d-TMs occupy III element sites due to noncentrosymmetry of the site. This can result in band gap
narrowing of the semiconductors. In fact, it wasreported that the band gap energy of GaN doped with
9% Cr, is 3.1 eV, whereas that of un-doped GaN is 3.4
eV [2].
Expecting both the band gap narrowing effect andsub-bandgap absorptions such as VB-IB and IB-CB, wechose AlN (Eg = 6.2 eV) as a base semiconductor forour study. In our previous study, it was shown that (i) the
AlCrN films demonstrate distinctive optical absorption
properties in the ultraviolet-visible-infrared region asshown in Fig. 1. and (ii) the top of valence band of
wurtzite AlCrN (up to 17.1% Cr) contains considerable
Cr d component via various photoemission spectroscopies
and ab initio calculations [3].
In wurtzite AlN, main component of the bottom of
the conduction band is Al s and p states, while that of
the top of the valence band is N p [4]. To investigate
effects of the 3d-TM doping on the conduction band of
AlN, we carried out Al K-edge XANES measurements.
Figure 2 shows Al K-edge XANES spectra and adifferential spectrum of AlCrN with 10.46% Cr andun-doped AlN films. The electric field of the incident
light was parallel to the c-plane of wurtzite structure.
There are two features in the spectra: (i) the peakintensities of main edge (1558.5 and 1564.5 eV) in the
AlCrN are lower than those of the AlN, and (ii) a small
shoulder or tail is observed at around 1555eV. The
former implies decrease of Al p local DOS in thisenergy region due to disorder associated with random
distribution of Cr. The latter implies formation ofunoccupied DOS under the bottom of the CB. Both thefeatures in the Al K-edge XANES suggest that Cr
atoms distribute homogeneously in the films. Further
investigations such as incident angle and concentration

dependences of the Al K-edge XANES measurements
will reveal the effect of 3d-TM doping to the CB
structure of the films.

Fig. 1. Absorption coefficient α spectra of AlN and
AlCrN films (7.7%) with the solar spectral irradiancefor air mass of 1.5. The noise at high α region in the
spectra is because of the high absorbance; transmitted
light was too faint to detect.

Fig. 2. Al K-edge XANES spectra of AlN and AlCrN(10.46%) films on SiO2 substrates. The lower panel isdifferential spectra of AlCrN and AlN.
[1] A. Luque et al., Phys. Rev. Lett. 78 (1997) 5014.
[2] S. Sonoda, Appl. Phys. Lett. 100 (2012) 202101.
[3] N. Tatemizo et al., J. Phys.: Condens. Matter 29(2016) 085502.
[4] E. Ruiz et al., Phys. Rev. B 49 (1994) 7115.

56
Ⅲ-2-8

Ⅲ -2. Materials Sciences
BL2A
BL2A

Evaluation of Local Structures of P for CePO4A. Nakahira1, 2, M. Togo1, T. Minami1, C. Takada1, M. Matsumoto1, M. Iida1 and H. Aritani 3
1
Faculty of Engineering, Osaka Prefecture University, Sakai 599-8531, Japan
Trans-Regional Corporation Center for Industrial Materials Research (IMR), Tohoku University, Sakai
599-8531, Japan
3
Saitama Institute of Technology, Fukaya 369-0293, Japan2

characterized by measuring X-ray adsorption nearedge structure (XANES) at BL02A in UV-SOR.
The evaluation of XRD done for various products.
According to XRD results, products prepared byhydrothermal process at 423K was mainly composed ofhexagonal CePO4, although ones by soft chemical
process at 358 K and room temperature were composedof monoclinic CePO4. Figure 1 shows the XANES
spectra of various CePO4 samples. As shown in Fig. 1,
XANES spectra of sample obtained by hydrothermal
process and soft chemical process were quite different.
Furthermore, there was slight difference for CePO4
samples by soft chemical process at between 358 K androom temperature. In addition, the effect of synthetic
condition parameters (processing, temperature, andPO4/Ce on the microstructure for various CePO4
samples was confirmed.

Normalized Intensity (a.u.)

In recent years, the research about rare earth
phosphate materials with unique electronic transition
are active for various application as magnetic materials,
catalysts, and high performance luminescent devices
etc. In special, much interest has been focused on thesynthesis and luminescence of nano-sized rare earth
orthophosphates for their potential application in
optoelectronic devices and biological fluorescencelabeling device. Among them, CePO4 nanoparticles
and nanowires have been expected to be used asluminescent probe for selective sensing. CePO4 is oneof quite unique rare earth phosphate material,
hexagonal CePO4 and monoclinic CePO4 (natural
monazite). In special, the development and research on
nano-sized CePO4 material (nanorods, nanowires, andnanofiber etc) with a variable size attract muchattention. For example, monoclinic CePO4 generally
exists as natural monazite, bulk materials of which
could be prepared via the solid state reaction andhydrothermal method at high temperature. In this study,
the purpose was to evaluate the local structure of
CePO4 synthesized by hydrothermal process at 423 K
and soft chemical process at room temperature. The
effect of synthetic condition parameters (synthesis
processing, temperature, time, aging etc) on the
microstructure for various CePO4 samples wasinvestigated.
All chemicals were analytical reagent- grade, andthey used without further purification. In a typicalsynthesis, Ce(NO3)3 solution with 0.05 mol/Lconcentrations were prepared. Into them, the cerium
nitrate solution was added slowly to 6 mol/L oforthophosphoric acid solution while kept under stirring.
The as-obtained solution with a different reactant
PO4/Ce molar ratio was transferred into a stainlesssteel autoclave with an inner teflon vessel (28 ml). And
the hydrothermal treatment was carried out at 423 K
for 24 h. Furthermore, the soft chemical process wasdone at 358 K and room temperature using the samechemical solutions as hydrothermal treatments. Afterhydrothermal process and soft chemical process, theas-synthesized precipitates were separated by filtration,
washed with deionized water several times and ethanol,and dried at 343 K for 12 h. After drying, the products
were ground with Al2O3 mortal. The final products
appeared as light green solid powder. After all of theground product powders were characterized by XRD
method, FT-IR and TG-DTA. The microstructures of
product powder were observed by SEM. The local
structures around Si for the products of samples were

(A)
(B)
(C)

2140

2160

2180

2200

Photon Energy / eV
Fig. 1. P-K XANES spectra of various CePO4 samples.
(a) hydrothermal process at 423 K, (b) soft chemical
process at 358 K and (c) soft chemical process at room
temperature.

57
Ⅲ-2-9

Ⅲ-2

Ⅲ -2. Materials Sciences
BL2B
BL2B

Ultraviolet Photoelectron Spectra of Lu2@C90

Ⅲ-2

T. Miyazaki1, K. R. Koswattage2, H. Shinohara3 and S. Hino4

Faculty of Science, Research Laboratory for Surface Science, Okayama University, Okayama 701-8530, Japan
2
Institutes for Molecular Science, Okazaki 444-858, Japan
3
Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
4
Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577, JapanThe synthesis and separation of higher fullerenes
and endohedral fullerenes are remarkable resultsbrought by the investigation of the structure and theelectronic structure. Until now, there have been a lot ofattempts to synthesize and isolate endohedral
fullerenes contains mono-metal atom, di-metal atoms,
metal nitrides and metal–carbon clusters. This
encapsulation modifies the electronic structure of thefullerene cage by changing the encapsulated atom(s).
We have succeeded to measure ultraviolet
photoelectron spectra (UPS) of Lu encapsulated C82
fullerenes: Lu@C82, Lu2@C82, Lu2C2@C82 [1]. In thecurrent report, the UPS of Lu2@C90 will be presented.
The UPS of the endohedral fullerene were measured
using a photoelectron spectrometer at BL2B ofUVSOR. Energy calibration of the spectra was carriedout using the Fermi edge of a gold-deposited sample
disk before the UPS measurements of Lu2@C90. All
spectra were normalized by the peak height of thestructure α.
Figure 1 shows the UPS of Lu2@C90 obtained withhν = 25–55 eV. The spectral onset of Lu2@C90 was
0.99 eV below the Fermi level, which was muchsmaller than that of empty C90 (1.23 eV), which means
encapsulation of metal atom inside the cage contributeto narrow the band gap of fullerene, but Lu2@C90 isstill semi-conductive. There are 10 structures labeled
A–D, α–δ, X and Y in the UPS of Lu2@C90. The
intensity of these structures changed, when theincident photon energy was tuned, which was a typicalbehavior of fullerenes. From the UPS comparison of
the other endohedral fullerenes, their structures α–δappeared in the deeper binding energy region (Eb > 5eV) of the UPS of Lu2@C82 is due to σ-electrons that
constitute the C90 skeletal C–C bonds. Structureslabeled A–D appeared in the upper binding energy
region (Eb < 5 eV) of the UPS are derived from πelectrons. On the other hand, there are two structures
X and Y in the 9–11 eV region. They are not observed
when the incident photon energy is less than 35 eV, butthey are distinct and their intensity becomes stronger
in accordance with the increase of the incident photon
energy. This behavior is quite different from that ofother endohedral fullerenes and seems to be thecharacteristic ones to the entrapped Lu atom [1].
Possibly structures X and Y is due to Lu4f7/2 andLu4f5/2. The ionization potentials of Lu 4f7/2 and 4f5/2
of Lu metal are 7.5 eV and 8.9 eV, respectively [2].
Structures X and Y of Lu2@C90 appear at 9.8 eV and11.2 eV, respectively, which are higher than those of

Lu metal by 2.3 eV. Lu atom is electron wanting state.
Hence the ionization potential of entrapped Lu 4f
levels moves to deeper level. Thus, the entrapped Lu
atom donates electrons to the cage and the oxidation
state of Lu atom might be +3.

Photoelectron Intensity

1

Lu2@C90
D

C B
A
h =
55 eV

X
Y

  

50 eV


45 eV
40 eV
35 eV

 -bond

14

12

30 eV

 -bond108
64
Binding Energy

2

25 eV
0

Fig. 1. The incident photon energy dependent UPS of
Lu2@C90 at hν = 25–55 eV.
[1] T. Miyazaki, R. Sumii, H. Umemoto, H. Okimoto,T. Sugai, H. Shinohara and S. Hino, CPL 555 (2012)
222.
[2] M. Cardona and L. Ley (Eds.), Photoemission in
Solids. I: General Principles, Springer-Verlag, Berlin,
1978.

58
Ⅲ-2-10

Ⅲ -2. Materials Sciences
BL3B
BL3B

Radiative Decay of Intrinsic Luminescence from Self-Trapped Excitons in
Orthoborates with Plural Nonequivalent BO33- Groups upon VUV Excitation
N. Kodama, H. Kubota, M. Kudo and T. Takahashi

Graduate School of Engineering Science, Akita University, Akita 010-8502, JapanThe electronic structure of complex oxoanions, such
as BO33-, PO43-, and SiO44-, is expected to exhibit
peculiar features. Until now, there has been very little
work focusing on statistical fluctuations in the local
structure of low-symmetry complex rare-earth oxides
with plural nonequivalent oxoanions of the BO33group. We focused on three types of orthoborates withdifferent numbers of nonequivalent BO33- oxoanion
groups. The first type includes YSc(BO3)2 (YSB) [1]and Sr6YSc(BO3)6 (SYB) with one BO33- group; thesecrystals are characterized by a statistical fluctuation in
the local structure surrounding BO33- groups caused bydisorder of Y3+ and Sc3+ ions. The second type consistsof rare-earth orthoborate crystals, such as LaSc3(BO3)4(LSB) [1] and Ca4LaO(BO3)3 (CLOB), with two
nonequivalent BO33- groups. CLOB belongs to a classof double borates with oxygen as a foreign anion. The
third type is Ba3Y (BO3)3 (BYB) with threenonequivalent BO33- groups.
We report on intrinsic luminescence spectra anddecay characteristics of STEs in these crystals. In
addition, we discuss the correlation between intrinsic
luminescence bands associated with STEs and thenumber of nonequivalent BO33- groups in YSB, SYB,LSB, CLOB, and BYB, from the viewpoint of the local
structure, symmetry, and environment of BO33- groups.
Luminescence and excitation spectra of STEs in
YSB, SYB, LSB, CLOB, and YSB polycrystals were
measured at twelve temperatures in the range of 8(11)293 K using the undulator beamline BL3B at the
UVSOR facility. The decay characteristics of theluminescence on the nanosecond scale were measured
using a time corrected single photon counting method
under excitation with single bunched pulses fromUVSOR. The excitation spectral intensity for theorthoborates increased rapidly below about 200-210
nm. The broad excitation bands were assigned tobandgap excitations or molecular transitions of theBO33- group. All samples were found to exhibit
multiple STE luminescence bands in the UV region
under VUV excitation at 70 and 160 nm.
The luminescence spectra of YSB and SYB at 11
and 8 K, respectively, consisted of two broad bands
associated with STE(I) and (II) with peaks at 251 and274 nm, and 288 and 337 nm. The spectra of LSB and
CLOB at 11 K consisted of two broad bands with peaks
at 245 and 303 nm, and 281 and 364 nm, respectively,
again associated with STE(I) and STE(II) in two setsof nonequivalent BO33- groups. On the other hand, as
shown in Fig. 1(e), BYB exhibited three distinct broad
bands at 8 K: an intense luminescence band with apeak at 306 nm, a short-wavelength shoulder with apeak at 246 nm, and a band with a long-wavelength tailand a peak at 389 nm. These three intrinsic bands are
assigned to STE(I), STE(II), and STE(III) in three setsof nonequivalent BO33- groups. In LSB, CLOB, and
BYB, the number of intrinsic luminescence bands
coincides with the number of nonequivalent BO33groups, whereas in YSB and SYB two bands appear,
despite the presence of only one BO33- group. The

number of bands is inconsistent with the number of
nonequivalent BO33- groups. A possible interpretation
for this discrepancy is that there are two types of BO33groups with different geometries, presumably causedby random disorder of Y3+ and Sc3+ ions.
Figures 1(a)-(f) show decay curves for the UV bands
at 8 K for YSB, LSB, CLOB, and BYB, respectively.
All samples exhibit a fast and a slow component due
to high-spin and low-spin STEs associated with thetwo possible spin orientations for the exciton electronhole pair of alkali halides [1]. For YSB, the decay
times for STE(I) luminescence at 240 nm are 350 ps
and 4.3 μs. For LSB, the decay times for STE(I)luminescence at 260 nm are 1.2 ns and 184 ns, andthose for STE(II) at 330 nm are 1.8 ns and 180 ns. For
CLOB, the decay times for STE(I) luminescence at
270 nm are 1.7 ns and 2.0 μs, and those at 400 nm for
STE(II) are 2.0 ns and 2.0 μs. For BYB, the decay
times for STE(I) luminescence at 400 nm are 1.7 ns
and 2.0 μs.
The fast decay components for STE(I) in YSB andBYB originate from singlet STE states in BO33- groups
with D3 and Cs symmetry, respectively. The fast decay
components for STE(I) and STE(II) in LSB and CLOB
may also originate from singlet STE states the BO33groups with C1 and Cs symmetry, respectively. In
contrast, the slow decay components for STE(I) in
YSB, LSB, CLOB, and BYB, and those for STE(II) in
LSB and CLOB are attributed to triplet STEs in BO33groups in which singlet STE states occur.

Fig. 1. Decay curves for STE luminescence at 8 K at(a) 240 nm for YSB, (b) 260 nm for LSB, (c) 330 nm
for LSB, (e) 270 nm for CLOB, (e) 400 nm for CLOB,
and (f) 400 nm for BYB.
[1] N. Kodama, K. Yanagidaira and T. Takahashi, UVSOR
Activity Report 43 (2016) 53.
[2] T. T. Williama and K. S. Song, J. Phys. Chem. Solds.
51 (1990) 679.

59
Ⅲ-2-11

Ⅲ-2

Ⅲ -2. Materials Sciences
BL3B!"#!$$
BL3B
 

Excitation
Process of Pr3+
in Lu3Al5O
by VUV Photons!Ions
12
""Crystals

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Kitaura1,.:.1.
K. Kamada2,%B?<@.D.
S. Kurosawa1,2.;1"5;6@56
and A. Ohnishi1

Facultyof Science, Yamagata University, Yamagara 990-8560, Japan"#$%&'()*+),$-./$.0)1#2#3#'#)4/-5.67-'(0)1#2#3#6#)889:;<=90)>#?#/)
New
Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579, Japan
A.B)C/D%7'6()E6.#'-*/)F#'$G.6()E./'.60)H*G*I%)4/-5.67-'(0),./D#-)8;9:;<J80)>#?#/)
)
1!

2@

Ⅲ-2

The
impact 2E06A.A6<;
excitation <3
of 5<A
hot =5<A<0.??62?@
photocarriers D6A5
with&52 6:=.0A
impurity-localized
6:=B?6AF9<0.96G21 electrons
2920A?<;@ in
6; crystalline
0?F@A.996;2 solids@<961@ has
5.@
been
studied with the use of synchrotron radiation (SR)/22;@AB1621D6A5A52B@2<3@F;05?<A?<;?.16.A6<;%$
[1].
a ;B:/2?
number <3
of ?29.E.A6<;
relaxation =.A5D.F@pathways 0<:=2A2
compete, - Since%6;02 .
under
B;12? excitation
2E06A.A6<; with
D6A5 vacuum
C.0BB: ultraviolet
B9A?.C6<92A (VUV)
('(
photons=5<A<;@ from3?<: SR,%$ theA52 relaxation?29.E.A6<; of<3 hot
5<A photocarriers=5<A<0.??62?@
becomes
process <3
of 6:=B?6AF
impurity/20<:2@ complicated.
0<:=960.A21 The&52 =?<02@@
excitation
2E06A.A6<; by/F VUV('( photons=5<A<;@ still@A699 remains?2:.6;@ obscure,</@0B?2
despitethe /.@60
basic @B/720A
subject 0<;02?;6;4
concerning /<A5
both @612@
sides <3of
12@=6A2 A52
fundamental
and applied physics.
3B;1.:2;A.9.;1.==9621=5F@60@
95O
"12
The
crystal <3of =?.@2<1F:6B:1<=21
praseodymium-doped B
Lu3Al&52 0?F@A.9
(Pr:LuAG)
has been utilized as the scintillator for the#?B5.@/22;BA696G21.@A52@06;A699.A<?3<?A52
detectionof X- or γ-rays. VUV excitation spectra for
12A20A6<;<3)<?I?.F@('(2E06A.A6<;@=20A?.3<?
5d-4f+9B:6;2@02;026;#?B0?F@A.9@5.C2
luminescence in Pr:LuAG crystals havethePr3+D
A52#?
been
However, A52
the =?<02@@
process <3
of #?
Pr3+-
/22; reported?2=<?A21 ,[2, 3].
- <D2C2?
excitation
by VUV photons has not been discussed in
2E06A.A6<;/F('(=5<A<;@5.@;<A/22;16@0B@@216;
detail.
12A.69 The&52 information
6;3<?:.A6<; on<; this
A56@ process=?<02@@ provides=?<C612@ us
B@
hints
to obtain high-quality Pr:LuAG scintillators.
56;A@A<</A.6;5645>B.96AF#?B@06;A699.A<?@Themain aim of the present study is to clarify the&52:.6;.6:<3A52=?2@2;A@AB1F6@A<09.?63FA52
processesof electron-hole (e-h) relaxation in undoped=?<02@@2@<32920A?<;5<92.G?29.E.A6<;6;B;1<=21
in Pr:LuAG crystals.
2E06A.A6<;6;#?B0?F@A.9@
LuAG
crystals and Pr3+-excitation
B0?F@A.9@.;1#?
The
undoped LuAG and Pr:LuAG crystals were grown&52B;1<=21B.;1#?B0?F@A.9@D2?24?<D;
by/F theA52 micro:60?< pulling=B996;4 down
1<D; (μ–PD)
JH# method.
:2A5<1 The&52
6<;@ wasD.@ set@2A 0.8
 mol%.
:<9 In
; theA52
concentration
0<;02;A?.A6<; of<3 Pr#?3+ ionspresent=?2@2;A experiment,
2E=2?6:2;A we
D2 measured:2.@B?21 excitation
2E06A.A6<; spectra@=20A?.
forthe excitonic luminescence peaking at 4.96
eV and3<?A522E06A<;609B:6;2@02;02=2.86;4.A
2(.;1
5d-4f+9B:6;2@02;02.A
luminescence at 3.87
eV. The data were2(&521.A.D2?2
thePr3+D
A52#?
corrected
for the distribution of excitation light source.
0<??20A213<?A5216@A?6/BA6<;<32E06A.A6<;9645A@<B?02
Figureshows excitation spectra for the excitonic
64B?2 1@5<D@2E06A.A6<;@=20A?.3<?A522E06A<;60
5d-4f+9B:6;2@02;02
luminescenceluminescence(blue line) and Pr3+D
9B:6;2@02;02/9B296;2.;1#?
(redline). &52The 3B;1.:2;A.9
fundamental ./@<?=A6<;
absorption 2142
edge <3
of?21 96;2
undopedLuAG crystals was determined around 6.83
B;1<=21B0?F@A.9@D.@12A2?:6;21.?<B;1eV.
The excitonic luminescence is excited in the region2(&522E06A<;609B:6;2@02;026@2E06A216;A52?246<;
above
the fundamental absorption edge. The intensity./<C2A523B;1.:2;A.9./@<?=A6<;2142&526;A2;@6AF
isalmost kept constant in the 11-18
eV range, and it is
6@.9:<@A82=A0<;@A.;A6;A52
 2(?.;42.;16A6@
gradually
4?.1B.99F increased
6;0?2.@21 in
6; theA52 18-26
  eV2( range.
?.;42 The&52
thresholdenergy is higher than the sum of the lowest
A5?2@5<912;2?4F6@56452?A5.;A52@B:<3A529<D2@A
exciton
2E06A<; creation
0?2.A6<; energy
2;2?4F (6.83  eV)2( and.;1 theA52 band-gap/.;14.=
energy(7.932(,eV [4]).
In this case, hot photoelectrons
2;2?4F
-;A56@0.@25<A=5<A<2920A?<;@have
5.C2 theA52 kinetic
86;2A60 energies
2;2?462@ enough
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2E06A2 valence
C.92;02
electrons
into the conduction band minimum through2920A?<;@6;A<A520<;1B0A6<;/.;1:6;6:B:A5?<B45
inelastic
scattering with them. Consequently, it is most
6;29.@A60@0.AA2?6;4D6A5A52:<;@2>B2;A9F6A6@:<@A
likelythat the multiplication of electronic excitations
96829FA5.AA52:B9A6=960.A6<;<32920A?<;602E06A.A6<;@(MEEs)
In <?12?
order A<to </A.6;
obtain @ is
6@ realized?2.96G21 above./<C2 18 eV.
2( ;moredetail information on the process of the MEEs,:<?212A.696;3<?:.A6<;<;A52=?<02@@<3A52
@
ultraviolet
B9A?.C6<92A photoemission=5<A<2:6@@6<; experiment
2E=2?6:2;A are.?2 now;<D in6;
progress.
=?<4?2@@
5d-4f+9B:6;2@02;026@2E06A216;A52?246<;
luminescence is excited in the region
The
Pr3+D
&52#?
below
the fundamental absorption edge, in which the/29<DA523B;1.:2;A.9./@<?=A6<;21426;D5605A52
absorption occurs. In the region above the+D./@<?=A6<;<00B?@;A52?246<;./<C2A52
Pr#?3+ 4f-5d
fundamental
absorption edge, the excitation spectrum
3B;1.:2;A.9./@<?=A6<;2142A522E06A.A6<;@=20A?B:
5d-4f+9B:6;2@02;026@@6:69.?A<A5.A3<?A52
luminescence is similar to that for theforthe Pr3+D
3<?A52#?

excitonic
luminescence :2;A6<;21
mentioned ./<C2&56@?2@B9A
above. This result
2E06A<;60 9B:6;2@02;02
ionsindicatesthat no direct (elastic) excitation of Pr3+6<;@
6;160.A2@A5.A;<16?20A29.@A602E06A.A6<;<3#?
byhot photoelectrons occurs in Pr:LuAG crystals. One/F5<A=5<A<2920A?<;@<00B?@6;#?B0?F@A.9@";2
maynotice the spectral overlap between the excitonic:.F;<A602A52@=20A?.9<C2?9.=/2AD22;A522E06A<;60
absorption, implying the+D./@<?=A6<;6:=9F6;4A52
luminescenceand Pr3+ 4f-5d
9B:6;2@02;02.;1#?
ions. However, theenergytransfer from the host to Pr3+6<;@<D2C2?A52
2;2?4FA?.;@32?3?<:A525<@AA<#?
5d-4f+9B:6;2@02;026@</@2?C21B;12?2E06A.A6<;
luminescence is observed under excitationPr#?3+D
above
the fundamental absorption edge, even when the./<C2A523B;1.:2;A.9./@<?=A6<;21422C2;D52;A52
excitonic
luminescence is completely quenched at 300
2E06A<;609B:6;2@02;026@0<:=92A29F>B2;0521.A
K.
fact 2E09B12@
excludes A52
the =<@@6/696AF
possibility <3
of A52
the 2;2?4F
energy This&56@ 3.0A
ions. Thus, the following
transferfrom the host to Pr3+6<;@&5B@A523<99<D6;4
A?.;@32?3?<:A525<@AA<#?
by VUV2E06A.A6<;/F('(process
is most suitable for the Pr3+-excitation=?<02@@6@:<@A@B6A./923<?A52#?
photons.
=5<A<;@ The&52 e-h.G pairs=.6?@ created
0?2.A21 under
B;12? MEEs
@ are.?2
ions, and the excited states of Pr3+6<;@
ionscapturedby Pr3+6<;@.;1A522E06A21@A.A2@<3#?
0.=AB?21/F#?
are
The 2E06A21
excited @A.A2@
states ?29.E
relax 6;A<
into A52
the 4?<B;1
ground.?2 formed.
3<?:21 &525d-4f+9B:6;2@02;02
luminescence.
states,giving rise to the Pr3+D
@A.A2@46C6;4?6@2A<A52#?





Fig.
64 1. Excitation
E06A.A6<; spectra@=20A?. for3<? theA52 4.96
 eV2( (blue
/9B2 line)
96;2
andeV bands (red line). These data were obtained.;13.87
2(/.;1@?2196;2&52@21.A.D2?2</A.6;21
at
8 K. The former and latter correspond to the excitonic.A&523<?:2?.;19.AA2?0<??2@=<;1A<A522E06A<;60
5d-4f+9B:6;2@02;02?2@=20A6C29F
luminescence, respectively.
luminescenceand Pr3+D
9B:6;2@02;02.;1#?
[1]For example, M.6A.B?..')#&B:6
Kitaura et al., J. Lumi. 172 (2016), -<?2E.:=92243.
[2]
A. *<@568.D.
Yoshikawa etTran. !B09
Nucl. %06
Sci. 55, - 
.') al.,#& IEEE &?.;
(2008)
 1372.
 [3]
Y. Zorenko et al., J. Lumi. 179(2016), -*+<?2;8<.')#&K0)B:6
496.

[4]
P. Dorenbos, J. Lumi. 134 (2013)310.
, -#<?2;/<@B:6

60
Ⅲ-2-12
%&$

Ⅲ -2. Materials Sciences
BL3B
BL3B

Effects of Annealing and Mg-codoping on Luminescence Properties of Ce
Doped Garnet-Based Scintillator Grown by Micro Pulling Down Method
H. Yamaguchi1, K. Kamada2, 3, S. Kurosawa3, Y. Shoji1, 2, Y. Yokota3, Y. Ohashi1,
A. Yamaji1 and A. Yoshikawa1, 2, 3
Tohoku University, Institute for Materials Research, Sendai 980-8577, Japan
2
C&A Corporation, T-Biz, Sendai 980-8579, Japan
3
Tohoku University, New Industry Creation Hatchery Center, Sendai 980-8579, Japan
1

Recently, cations (B, Ca, Ba) codoping effects on
scintillation mechanism and annealing effects on
defect structures for Ce: Gd3Ga3Al2O12 (GGAG) has
been reported [1], where further improvement of
scintillation properties were also reported. In addition,
Mg2+ codoping effects on shallow electron traps for
Ce:GGAG by the UV-induced absorption spectroscopy
against the thermoluminescence (TL) glow curve wasreported [2]. In this study, we investigated the Mg
codoping effect on the shallow traps of defectcomplexes related to oxygen vacancies for themulticomponent garnet-based scintillators bymeasuring the TL glow curves.
We prepared Mg codoped and non codoped
Ce:(Lu,Gd)3Ga3Al2O12 single crystals grown by the
micro-pulling-down method, and TL spectra for thesesamples were measured and evaluated within 7.5-300
K at BL3B of the UVSOR facility. The size and weightof each crystal were similar and the TL glow curves
were normalized to the background intensity.
Figure 1 (a) - (b) show the TL glow curves for the
Mg/non codoped Ce:(Lu,Gd)3Ga3Al2O12 single crystals
under 210-190 nm excitation in the temperature rangeof 7.5-300K. Since absorption edge shifted from 210 nm
to approximately 190 nm with increasing the Lu
concentration, the 210-190 nm photons were selected as
an exaction source accordingly.
2 or 3 glow peaks were observed in this temperature
range of TL glow curves, which difference is mostprobably due to the difference of Ce concentration in
the grown crystals. It was also found that the peakintensity around 300 K relatively strengthened withincreasing the Lu concentration. Moreover, in case ofhigh Lu concentrated crystals (x = 3), its intensity
around 300 K significantly weakened by Mg codoping.
Therefore, these results implies that Mg codoping
affected the suppression of electron traps effectively inthe higher Lu concentrated crystal.

Ⅲ-2

Fig. 1. The TL glow curves of Mg/non codoped
Ce:(LuxGd3-x)Ga3Al2O12 single crystals; (a) x = 0, (b)x = 1, (c) x = 2, (d) x = 3.
[1] M. Tyagi et al., J. Phys. D; Appl. Phys. 46 (2013)
475302.
[2] M. Kitaura et al., Applied Physics Express 9 (2016)072602.

61
Ⅲ-2-13

Ⅲ -2. Materials Sciences
BL3B
BL3B

Determination of the Bandgap Energy of Gd Admixed Lu2Si2O7 Scintillator
Crystals Using the UVSOR Facility
T. Horiai1, S. Kurosawa2, 3, A. Yamaji1, H. Chiba1, S. Kodama1, Y. Shoji1, 4, Y. Ohashi1,
K. Kamada2, 4, Y. Yokota2, A. Yoshikawa1, 2, 4 and M. Kitaura3
Institute for Materials Research, Tohoku University, Sendai 980-8577, JapanNew Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579, Japan3
Department of Physics, Yamagata University, Yamagata 990-8560, Japan
4
C&A Corporation, Sendai 980-8579, Japan
1

2

Ⅲ-2

Scintillator is a material that converts ionizing
radiation such as alpha-rays, gamma-rays and X-ray toa visible/UV lights, and can be applied in oil welllogging, high energy physics and nuclear medicine [1,2]. Especially, pyrosilicate type scintillator, forexample Ce-doped Lu2Si2O7 (Ce:LPS), Ce-doped
Gd2Si2O7 (Ce:GPS) and Ce-doped (Gd, La)2Si2O7(Ce:La-GPS) were promising materials with high light
output, fast scintillation decay and stable light output
until high temperature (150ºC) [3-5]. These
scintillation properties were good for application in oil
well logging, where the scintillator is often exposed tohigh temperatures (~200ºC) under Earth surface.
Ce:GPS has been found to melt incongruantly, andtherefore it could not be grown by conventional
techniques from the melt [6]. On the other hand, thecomposition of Ce:LPS melts congruently and can begrown relatively easily [7]. Although Ce:LPS has large
intrinsic gamma-rays background due to 176Lu.
In this study, we focused on the Gd admixed Ce:LPS,
because Gd is good constituents for the material
without intrinsic background when compared to Lu,
and estimated the bandgap energy of Gd admixed
Lu2Si2O7 scintillator crystals.
We prepared undoped Lu2Si2O7 (LPS) and (Lu0.95
Gd0.05)2Si2O7 (LPSGd5%)single crystals grown by the
micro-pulling-down method, and UV absorption edge
for these samples were evaluated with a photo diode(IRD, AXUV 100) at BL3B of UVSOR. The bandgap
energies were calculated from the UV absorption edge.
We succeeded in growing the transparent samples
by the μ-PD method (Fig. 1). From the result of thepowder X-ray diffraction analysis, the crystal phase of
these samples matched the previous result on LPS(JCPDS No. 35-0326). In addition, the crystalline
structure of these crystals were determined to be
monoclinic with space group of C2/m.
Figure 2 shows the UV absorption spectra, and thesignificant change due to Gd admixed was notobserved. From this figure, the UV absorption edge
wavelength were around 178 nm. The bandgap energyof LPS and LPSGd5% were calculated about 6.96 and6.95 eV, respectively. Thus, the bandgap energy of
LPSGd5% was remained high value, and this result
suggested temperature dependence of light output wasalso good.

Fig. 1. Photograph of after polished samples,(a) Lu2Si2O7, (b) (Lu0.95 Gd0.05)2Si2O7.

Fig. 2. UV absorption spectra.
[1] C.L. Melcher, J.S. Schweitzer, R.A. Manente andC.A. Peterson, J. Crystal Growth 109 (1991) 37.
[2] C.L. Melcher, J. Nuclear Medicine 41 (2000) 1051.
[3] L. Pidol, A. Kahn-Harari, B. Viana, E. Virey, B.
Ferrand, P. Dorenbos, J.T.M. de Haas and C.W.E. vanEijk, IEEE Trans. Nucl. Sci. 51 (2004) 1084.
[4] S. Kawamura, J.H. Kaneko, M. Higuchi, T.
Yamaguchi, J. Haruna, Y. Yagi, K.susa, F. Fujita, A.
Homma, S. Nishiyama, K. Kurashige, H. Ishibashi and
M. Furusaka, IEEE Trans. Nucl. Sci. 54 (2007) 1383.
[5] S. Kurosawa, T. Shishido, T. Sugawara, A. Nomura,
K. Yubuta, A. Suzuki, R. Murakami, J. Pejchal, Y.
Yokota, K. Kamada and A. Yoshikawa, Nucl. Instrum.
Methods Phys. Res. A 772 (2015) 72.
[6] N.A. Toropov, F.Y. Galakhov and S.F. Konovalova
Russ. Chem. Bull. 10 (1961) 497.
[7] A.N. Christensen, Zeitschrift fur Kristallographie
209 (1994) 7.

62
Ⅲ-2-14

Ⅲ -2. Materials Sciences
BL3B
BL3B

Temperature Dependence of Luminescent Properties for Un-doped Cs2HfCl6
S. Kodama1, S. Kurosawa2, 3, A. Yamaji1, J. Pejchal4, R. Král4, Y. Ohashi1,
K. Kamada2, 5, Y. Yokota2, M. Nikl4 and A. Yoshikawa1, 2, 5

Institute for Materials Research (IMR), Tohoku University, Sendai 980-8577, JapanNew Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai 980-8579, Japan
3
Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
4
Institute of Physics, CAS, Cukrovarnická 10, 162 00 Prague, Czech Republic
5
C&A Corporation, Sendai 980-8577, Japan
1

20000

Intensity (a.u.)

Halide scintillation materials are expected to havehigh light output due to smaller band gap energy thanthat for the oxide materials [1]. Indeed, Tl:NaI [2,3],
Ce:LaBr3 [4] and Eu:SrI2 [5] have good light output.
However, almost all halide materials have strong
hygroscopic nature. Although these scintillators arepacked in a hermetic sealing, aging degradation would
be caused by remaining moisture in the package ordamage of the package.
Recently, a non-hygroscopic halide material,
Cs2HfCl6, was reported by Burger et al. [6], and thismaterial has a high light output of 54,000
photons/MeV and good energy resolution of around
3 % (FWHM for 662 keV gamma-ray). Moreover,Cs2HfCl6 emits ~440 nm blue light under ~250 nm
excitation [7]. This emission is considered to be of Zrrelated defect origin while the other component ofemission spectra located within 360-400 nm comesfrom self-trapped exciton (STE) luminescence on[HfCl6]2- anion complex [8]. However, the details of its
luminescence mechanism have not been investigatedyet. Here, we investigated temperature dependence ofphotoluminescence spectra for undoped Cs2HfCl6.
Un-doped Cs2HfCl6 were synthesized from 99.9%pure (Zr-free) HfCl4 and 99.999%-pure CsCl. Then, themixed powders were put into a quartz-glass ampoule andthe crystal was grown by the vertical Bridgman growthmethod. The procedure is in detail described in [9].
The obtained single crystal was cut and polished tomeasure its photoluminescence spectra. We evaluatedthe temperature dependence in BL3B beamline at
UVSOR. Cs2HfCl6 was excited by 250 nm UV light,
and spectra were measured with a spectrometer(spectoropro-300i, Acton research). The chamber wascooled by liquid helium, and the spectra were
measured from 8 to 300 K.
We succeeded in growing the undoped Cs2HfCl6
single crystal. Obtained photoluminescence spectra at
8, 100, and 300 K for Cs2HfCl6 are shown in Fig. 1.
The intensity of luminescence decreased withdecreasing temperature. We summarized the intensity
versus temperature of undoped Cs2HfCl6 in Fig.2. In
addition, emission peak shifted from 454 nm (at 300
K) to 441 nm (at 6 K). Given the fact that under 250
nm excitation rather Zr-impurity related defectemission peaking around 435 nm is excited at room
temperature [7] the temperature dependence measured
here is related to the same defect rather than to STE..

300K
100K
8K

15000
10000

Ⅲ-2

5000
0

300

400

500

600

Wavelength [nm]700Fig. 1. Photoluminescence spectra of Cs2HfCl6 at 300,
100 and 6 K.

Peak imtensity (a.u.)

2

20000
15000
10000
5000
0

0

50 100 150 200 250 300
Temperature [K]Fig. 2. Temperature dependence of emission intensity
obtained as peak position at 454 nm From Fig. 1.
[1] P. Dorenbos, NIMA486 (2002) 208.
[2] E. Sakai, IEEE TNS 1 (1987) 418.
[3] Bicron Co., physical properties of common inorganic
scintillators (2001) 3101.
[4] E.V.D. van Loef et. al., NIMA486 (2002) 254.
[5] Y. Yokota et. al., JCG 375 (2013) 49.
[6] A. Burger et. al., App. Phys. Lett. 107 (2015) 143505.
[7] K. Saeki et al., Appl. Phys. Ex. 9 (2016) 042602.
[8] B. Kang et al., J. Phys. Chem. C 120 (2016) 12187.
[9] S. Kodama et al., J. Lumin. in prep.

63
Ⅲ-2-15

Ⅲ -2. Materials Sciences
BL3B
BL3B

Evaluation of Ce:(Gd, La)2Si2O7 Scintillator Using an UVSOR Beam Line
-FY2016S. Kurosawa1, 2, A. Yamaji3, T. Horiai3, S. Kodama3, T. Chiba3, C. Tanaka3, Y. Shoji3, 4,
Y. Ohashi3, Y. Yokota1, K. Kamada1, 4, A. Yoshikawa1, 3, 4 and M. Kitaura2
1

Ⅲ-2

New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai 980-8579, Japan
2
Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
3
Institute for Materials Research (IMR), Tohoku University, Sendai 980-8577, Japan
4
C&A Corporation, Sendai 980-8577, Japan

Scintillators are used in various fields such as
medical imaging, astronomy, oil well ligging and so on.
Recently, scintillation properties of (Ce0.01, Gd0.90,
La0.09)2Si2O7 (Ce:La-GPS) have been reported. The
Ce:La-GPS crystal had a light output of approximately
35,000 photons/MeV, FWHM energy resolution of
5.0% at 662 keV [1, 2]. Moreover, the light output over
35,000 photons/MeV was found constant in thetemperature range from 0 to 423 K. In addition,
FWHM energy resolution of Ce:La-GPS (roughly 7–8%) at 662 keV remained constant up to 373 K [3].
Thus, this crystal can be applied to oil well logging orother radiation detection application at hightemperature conditions.
Up to now, the bandgap energy of La-GPS has been
not measured for La-GPS yet. In order to reveal themechanism of the thermal quenching, the evaluation of
the bandgap energy is required. Thus, in this paper, thebandgap energy was measured at low temperature (7K)
using UVSOR beam line BL3B.
To evaluate the bandgap energy, pure La-GPS was
prepared by the micro-pulling down method. Using
this sample and the BL3B, we measured thetransmittance spectrum as showin in Fig. 1. From thisdata, the band gap energy was estimated to be
7.130.01 eV. Compared with other oxide scintillators,
La-GPS was found to have wider bandgap. On theother hand, the light output of Ce:La-GPS was larger
than most of oxide scintillators with narrower
bandgaps than La-GPS.
Light output (light yield Y) was related to bandgap
energy (Egap) in following equation:

���ΕγS Q�Εgap(0 < η, Q, S 1) ,where S, Q, Eγ and β are the transfer efficiency fromthe electron-hole pair into the luminescence center, thequantum yield of the final luminescence process in
Ce3+ emission center, incident gamma-ray energy andthe ratio between the energy needed to create one
electron-hole pair and Egap [4]. Usually β is used as
constant (~2.5) , and η denotes generation coefficientfor electron-hole pair. The value of ηSQ for Ce:LaGPS was found to be higher than for the otherscintillators.

The quantum yield (Q) of Ce:-LaGPS was estimatedto be around 0.8 using an integrating sphere and aspectrometer (Hamamatsu C9920-02G), and this issimilar value to other oxide scintillator, where typicalvalue of Q for oxide conventional scintillator is 0.60.8. Thus, it implies that Ce:La-GPS has good transfer
efficiency or/and good electron-hole pair generation
efficiency.

Fig. 1. Transmittance of pure La-GPS as function of
wavelength. The small window marked (*) denotes
enlarged view arond the absorption edge.
[1] A. Suzuki et al., Applied Physics Express 5 (2012)
102601.
[2] S. Kurosawa et al., Nucl. Inst. and Meth. in Phys.
Res. A774 (2014) 30.
[3] S. Kurosawa et al., Nucl. Inst. and Meth. in Phys.
Res. A772 (2015) 72.
[4] R. H. Bartrama and A. Lempicki, 1996 Journal of
Luminescence 68 (1996) 225.

64
Ⅲ-2-16

Ⅲ -2. Materials Sciences
BL3B, BL7B
BL3B, BL7B

Temperature Dependence of the PL Spectra ofLaser Irradiated a-CNx Thin Films
K. Nakamura1, F. Sawa1, K. Fukui1 and K. Yamamoto2

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
behavior as the resulting from single thermal
quenching mechanism.
In summary, we measured temperature dependenceof PL spectra of laser irradiated a-CNx thin films. The
a-CNx thin films show a broad visible range emission
band, which consist of various emission bands.
However, their thermal quenching mechanisms are
relatively simple.

010 K
020 K
040 K
060 K
100 K
120 K
150 K
200 K
220 K
240 K
260 K
280 K
300 K
320 K

Intensity (a.u.)

Amorphous carbon nitride (a-CNx) is known to haveinteresting mechanical, electrical and opticalproperties. In the optical properties, a-CNx shows abroad emission at visible region. Since a-CNx is
composed only of carbon and nitrogen, it is expected
as an inexpensive white light emitting material.
However, photoluminescence (PL) spectra of thesamples evaporated under same conditions are, insome cases, different with each other, because theoptical properties of a-CNx are sensitive to the
preparation conditions. Recently, it is found that laser
irradiated a-CNx thin films in the atmosphere after
depositing show much higher PL intensity than thoseof as-deposited a-CNx thin films, and their PL spectra
have better reproducibility [1, 2]. In this report, weshow temperature dependence of the PL spectra byusing laser irradiated a-CNx thin films.
All samples on Si substrates are deposited by the
RF-sputtering method at Ryukoku University [1]. The
sputtering conditions of the graphite target in eachsample under low pressure nitrogen gas environment
were kept constant, and the RF power was changed to
40 W, 60 W and 100 W. Beam diameter of laserirradiation is about 1.2 mm, and irradiation time is 240
minutes by using He-Cd laser (325 nm) with 20 mW.
All PL measurements have been performed at BL3B
and BL7B from 10 to 320 K. The excitation energy of
PL measurements is fixed at 4.6 eV, where excitation
spectra of all samples have maximum intensities.
Figure 1 shows the PL spectra of RF power 60 W aCNx thin film at from 10 K to 320 K. It is found that a
broad PL is observed from 1.6 to 4.0 eV, and broadness
is independent on temperature. However, PL intensity
gradually decreases with increasing temperature, andthe peak energy of PL spectrum gradually shifts to thehigher photon energy side with increasing temperature.
These trends are also observed in both 40 W and 100
W a-CNx thin films. They suggest that the relaxation
mechanism of PL in a-CNx thin films does not change
at least below room temperature. However, both peakshift and intensity decreasing reveal that this broad PL
peak consists of many emission bands, which arecontinuously distributed from 1.6 eV to 4.0 eV [2].
Figure 2 shows temperature dependence of thenormalized PL intensity of 60 W a-CNx at emission
photon energy 2.43, 2.50, 2.55, 2.65, 2.76, 2.89, 2.97,
3.05 eV, respectively. Intensity normalization carriedout to the intensity at 10 K. Temperature dependences
show roughly similar with each other and relatively
simple behavior, although it is difficult to explain this

1.6

2.0

2.4

2.8

3.2

Photon Energy (eV)

3.6

4.0

Fig. 1. Temperature dependence of the PL spectra ofa-CNx 60 W.

Normalized Intensity (a.u.)

1

0

50

100

150

200

250

300

Temperture (K)Fig. 2. Temperature dependence of the PL intensity ateach emission photon energy.
[1] M. Satake et al., 2013 JSAP Autumn Meeting 28pPB3-11.
[2] K. Nakamura et al., UVSOR Activity Reports 43(2016) 61.

65
Ⅲ-2-17Ⅲ-2

Ⅲ -2. Materials Sciences
BL3B
BL3B

Photoluminescence and Excitation Spectra of Ce3+, Eu3+ Singly Doped
Lu3Al4.75Si0.25O11.75N0.25 Phosphors in VUV-Vis Region
K. Asami, K. Yasuda, J. Ueda and S. Tanabe

Graduated School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan

Ⅲ-2

The Ce3+ doped garnet phosphors are attracting
much attention in the application for white lightemitting diodes (LEDs) and scintillators [1].
Commercial white LED is composed of a blue LED
and yellow phosphor such as Y3Al5O12:Ce3+ (YAG:Ce)[2]. YAG:Ce phosphor has strong absorption in therange of blue LED wavelength (λ:~ 450 nm) andshows broad yellow luminescence with high quantum
yield (~90%). However, the generated whit light
exhibits a low color rendering and high color
temperature due to color deficiency in the red spectral
region. In order to realize the redshift of emission,
there are many reports to expand crystal field splittingof Ce3+ by substitution of the cation at each site [3].
Recently, it is reported that N3- ligands which is lower
electronegativity than O2- ligands incorporate into
YAG and Lu3Al5O12 (LuAG) hosts to replace O2anions and Si4+ was used as a charge compensation [4].
Setlur et al. have proven that Lu3(Al,Si)5(O,N)12:Ce3+
phosphor shows a very broad and warmer emission
spectrum and the lower thermal quenching [5]. To
investigate
theelectronic
structureof
Lu3Al4.75Si0.25O11.75N0.25 (LuASONG), we measured
photoluminescence and excitation (PL & PLE) spectraof both Ce3+ and Eu3+- singly doped phosphors at
UVSOR BL3B. Ce3+, Eu3+ singly doped LuASONG
phosphors are prepared by solid state reaction methodwith N2 atmosphere. Samples are identified as garnet
structure by XRD.
Figure 1 shows the PLE and PL spectra of Ce3+- doped
LuASONG phosphor at 10 K. In PLE spectrum, the hostexciton peaks are observed at around 170 nm and threebands derived from Ce3+ are observed at 220 nm (4f-5d3,
4, 5), 350 nm (4f-5d2) and 450 nm (4f-5d1). From the hostexciton peak, the bandgap energy is estimated to be 7.92
eV, which is almost the same as that of LuAG (7.94 eV)[5]. In PL spectrum, two emission bands are observed ataround 500 and 560 nm, which are attributed to 5d14f(2F5/2) and 4f(2F7/2), respectively. These emission bands
are longer wavelength than that of LuAG slightly. From
there results, the substitution of Si4+-N3- bonds for Al3+O2- bonds increases crystal field strength and causes
redshift of emission.
Figure 2 shows PLE and PL spectra of Eu3+- doped
LuASONG phosphor at 10 K. The strong broad bandis located at around 230 nm, which is attributed tocharge transfer transition (CTS) of Eu3+. The sharp
emission peaks (5D0-7F1,2,4 and 5D1-7F4) due to theintra-4f transitions of Eu3+ are observed in the range of
580-720 nm. CTS energy of LuASONG (5.26 eV) is
lower than that of LuAG (5.53~5.65 eV) [6,7]. CTS

energy is equivalent to the bandgap between Eu2+ 4f
ground state and valence band edge which p state ofanion forms. By substitution of Si4+-N3-, p state of N3interacts with the top of VB. Therefore, CTS energy ofoxynitride garnet is lower than that of oxide garnet.

Fig. 1. PLE and PL spectra of LuASONG :Ce3+.

Fig. 2. PLE and PL spectra of LuASONG :Eu3+.
[1] Z. Xia and A. Meijerink, Chem. Soc. Rev. 46 (2017)275.
[2] G. Blasse and A. Bril, Appl. Phys. Lett. 11 (1967) 53.
[3] C. C. Chiang, M. S. Tsai and M. H. Hon, J. Electrochem.
Soc. 155 (2008) B517.
[4] J. Liu, X. Wang, T. Xuan, C. Wang, H. Li and Z. Sun,
J. Lumin. 158 (2015) 322.
[5] A. A. Setlur, W. J. Heward, M. E. Hannah and U.
Happek, Chem. Mater. 20 (2008) 6277.
[6] P. Dorenbos, J. Lumin. 134 (2013) 310.
[7] L. Li and S. Zhang, J. Phys. Chem. B 110 (2006) 21438.

66
Ⅲ-2-18

Ⅲ -2. Materials Sciences
BL3B, BL7B
BL3B, BL7B

Total Photoelectron Yield Spectroscopy on 3d Transition Metal Doped AlN
Films
1

N. Tatemizo1, S. Imada1, F. Sawa2, S. Hirata2 and K. Fukui2

Faculty of Electrical Engineering and Electronics, Kyoto Institute of Technology, Kyoto 606-8585, Japan
2
Faculty of Electrical and Electronics Engineering, University of Fukui, Fukui 910-8507, Japan

It is well known that 3d-transition metals (3d-TMs)
can form impurity levels in the band gap of asemiconductor and these levels can accept and/or
donate electrons when irradiated with light ofappropriate energy. At high concentrations, the 3dTMs’ orbitals will start to overlap with one another, toform an impurity band. Such an impurity band wellapart from the conduction band (CB) and the valenceband (VB) in a heavily doped semiconductor canintermediate optical excitations of electrons from the
VB to the CB. This is so called an intermediate band(IB) material proposed by Luque et al., for use inabsorption layers of solar cells to increase theirconversion efficiency [1].
Based on this hypothesis, we have synthesized andinvestigated 3d-TM-doped AlN films for artificial
photochemical system. It is indispensable to reveal
potential energies of VB, IB and CB with respect to thevacuum level if the potentials have ability for the wateroxidation and hydrogen reduction potentials.
To investigate the potentials of the electron occupied
states (VB and/or a part of IB), we carried out total
photoelectron yield spectroscopy (TPYS) [2] for the
3d-TM doped AlN films deposited on Ti metal
substrates. As show in Fig. 1. electrical contacts withthe film were made both back (thorough the Ti
substrate) and front (a Cu metal plate with hole). A
photoelectron corrector was set in front of the film witharound 1mm interspace. A negative bias was applied tothe sample against the grounded photoelectron
corrector. The number of photoelectrons was obtainedby measuring the current needed to compensate for thephotoexcited holes at the sample with an ammeter. The
photoemission yield was measured as a function ofincident photon energy.
Figure 2 shows TPY spectra of AlCrN with 17.3, 9.3
and 2.2% Cr and un-intentional doped AlN films. It isclear that the AlCrN films with high Cr concentrations
have threshold at around 5.5 eV. This result agrees wellwith the level of Cr4+/3+ [3, 4] and imply a partiallyfilled IB is formed in the energy gap of AlN. We haveobtained different thresholds for different 3d-TM
elements, which means the potential of IB can becontrolled via choice of 3d-TM elements, and adjust
the band structure for the effective photoconversion.
To reveal all potentials of the electron occupied bandof the films, we will extend the energy region of themeasurements to larger one.

Ⅲ-2

Fig. 1. Schematic of sample setting for the TPYS
measurements.

Fig. 2. Total photoelectron yield spectra of AlCrN(Cr: 17.3, 9.3 and 2.2 %) and un-intentional doped AlN
films deposited on Ti metal substrates. The inset ismagnified view of near thresholds of AlCrN films.
[1] A. Luque et al., Phys. Rev. Lett. 78 (1997) 5014.
[2] M. Honda et al., J. Appl. Phys. 102 (2007) 103704.
[3] U. Gerstmann et al., Phys. Rev. B 63 (2001) 1.
[4] N. Tatemizo et al., J. Phys.: Condens. Matter 29(2017) 085502.

67
Ⅲ-2-19

Ⅲ -2. Materials Sciences
BL3B
BL3B

Optical Properties of Ag− Centers Doped in NaI Crystals
T. Kawai and S. Watanabe

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

Wavelength (nm)
400
300
-

NaI:Ag 6K

1

C abs.

Optical Density

Lumi. Int. (arb. unit)

600 500

A' lumi.

0.5

C' lumi.

2.0

2.5

3.0
3.5
4.0
4.5
Photon Energy (eV)5.0

0Fig. 1. Luminescence (blue) and absorption (red)spectra of NaI:Ag− crystals at 6 K.

450

400

NaI:Ag6K-

Lumi. Int. (arb. units)

Ⅲ-2

Ag− centers doped in alkali halide crystals belong to
the family of the so-called Tl+-type centers and exhibit
the optical bands called A, B, and C, which are
attributed to intra-ionic transitions from the 1A1g
ground state to the 3T1u, 3T2u +3Eu, and 1T1u excitedstates, receptively [1-3]. Though optical studies on theAg− centers doped in various alkali halide crystals
have been widely performed, no study on the Ag−
centers doped in NaI crystals has been reported until
now. In this study, optical properties of the NaI:Ag−
crystals have been investigated at low temperature.
NaI:Ag+ crystals were grown by the Bridgman
method from NaI powders containing AgI powders.
The conversion from the Ag+ to Ag− ions in the crystals
was achieved by an electrolytic coloration technique.
The optical measurements were performed at the BL3B line of UVSOR.
Figure 1 shows the absorption and luminescence
spectra of the NaI:Ag− crystals at 6 K. A remarkableabsorption band with a half-width of 0.15 eV isobserved at 3.96 eV. The Ag− centers doped in KI, RbI,
and CsI crystals exhibit the C absorption bands at
3.985, 3.888, and 3.770 eV, respectively [1, 2]. As
compared with these values, the band peaking at 3.96
eV in NaI:Ag− is assigned to the C absorption band.
In the NaI:Ag− crystals, the excitation on the Cabsorption band induces the two luminescence bands
peaking at 2.50 and 3.48 eV at 6K. The excitation
spectra for the 2.50 and 3.48 eV luminescence bands
are shown in Fig. 2. Both luminescence bands are
efficiently excited at the C absorption band. Therefore,
the 2.50 and 3.48 eV luminescence bands are assigned
to the A’ and C’ luminescence bands which are
attribute to the radiative transitions from the relaxed
excited states of 3T1u and 1T1u, respectively. In addition
to the C band, the excitation spectrum for the A’
luminescence band has an excitation band around 2.92
eV. The excitation band would correspond to the A
band due to the transition from the 1A1g to 3T1u states.
The energy positions of the A, B, and C bands of theAg− centers doped in alkali iodide crystals are
summarized in Table 1.
It should be noted that the band-shapes of theexcitation spectra around the C absorption band are
different between the A’ and C’ luminescence. The
excitation band for the A’ luminescence roughly reflect
the C absorption band, while that for the C’
luminescence is located on the slightly lower energy
side of the C absorption band. The difference of theexcitation band-shape would be concerned with therelaxation processes from the excited states of 3T1u and
1
T1u. Further studies will probably be necessary.

A
×20
3.0

Wavelength (nm)
350

300

C

for 2.50 eV
3.5
4.0
Photon Energy (eV)for 3.48 eV
4.5

Fig. 2. Excitation spectra detected at 2.50 eV (blue)and 3.48 eV (red) of NaI:Ag− crystals at 6 K.
Table 1. Energy positions (eV) of the bands of theAg− centers doped in alkali iodide crystals.
crystal
A
B
C
Ref.
NaI
2.92
−
3.96
this workKI
2.878 2.981 3.985
[2]
RbI
−
−
3.888
[1]
CsI
2.776 2.865 3.770[2][1] W. Kleemann, Z. Physik 214 (1968) 285.
[2] W. Kleemann, Z. Physik 248 (1970) 362.
[3] S. Shimanuki, J. Phys. Soc. Jpn. 35 (1973) 1680.

68
Ⅲ-2-20

Ⅲ -2. Materials Sciences
BL3B
BL3B

Energy Transfer from I− Centers to Eu2+ Centersin Co-Doped NaCl:I−,Eu2+ Crystals
O. Yagi and T. Kawai

Optical Density

1.2

RT

-

2+

NaCl:I
NaCl:Eu
Absorption Luminescence

0.8
0.4
0.0

3.0

4.0
5.0
6.0
Photon Energy [eV]Fig. 1. Luminescence spectrum (blue) of NaCl: I− andabsorption spectrum (red) of NaCl: Eu2+ at RT.

Luminescence Intensity [arb.units]

Alkali halide crystals have the wide band-gap up to
the vacuum ultraviolet energy region and are suitable
candidate hosts for doping of impurity ions. Thoughmany 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 is
comparatively less studied [1, 2]. In this study, we haveinvestigated the energy transfer from I− centers to Eu2+
centers in NaCl crystals co-doped with I− and Eu2+ ions.
Figure 1 shows the absorption spectrum of
NaCl:Eu2+ and the luminescence spectrum of the
NaCl:I−. NaCl:Eu2+ produces two broad absorption
bands in the uv-visible energy region, which are due totransitions from the 4f 7 ground state to the t2g and eg
components of the 4f 65d excited state [3]. The samples
were annealed for 2h at 600ºC and quenched to disperse
precipitations, because Eu2+ ions in the alkali halides are
well-known to produce precipitations. NaCl:I− shows
the luminescence band appearing around 5.2 eV, whichis called the NE luminescence band and comes fromthe one-center type exciton localized mainly on thecentral site of a substituted I− impurity with smalllattice relaxation [4]. The NE luminescence band in
NaCl:I− has a large overlap with the absorption banddue to the eg component in NaCl:Eu2+. This factindicates the potential of the energy transfer from theI− centers to the Eu2+ centers in co-doped NaCl: I−,Eu2+
crystals. According to the Förster model [5, 6], thecritical distance between both centers for resonant
energy transfer is estimated to be about 1.8 nm fromthe overlap with the luminescence and absorption
bands.
Figure 2 shows the excitation spectra in NaCl:I−,
NaCl:Eu2+, and co-doped NaCl:I−,Eu2+ crystals. The
NE luminescence band in NaCl:I− is efficiently excitedin the energy region around 6.7 eV, which corresponds
to the absorption band of the I− centers. In NaCl:Eu2+,
the luminescence band at 2.9 eV, which comes fromthe Eu2+ centers, is efficiently excited at the absorption
bands of the Eu2+ centers.
In the co-doped NaCl:I−,Eu2+ crystals, the excitation
spectrum for the 2.9 eV luminescence band of the Eu2+
centers has the broad band around 6.7 eV in addition to
the absorption bands of the Eu2+ centers. This result
implies the existence of the energy transfer from the I−
centers to the Eu2+ centers in the co-doped NaCl:I−,Eu2+
crystals. In order to clarify the energy transfer
mechanism from the I− centers to the Eu2+ centers in the
co-doped NaCl:I−,Eu2+ crystals, the measurements of the
decay kinetics of the luminescence are needed.

Lumi.Int. [arb.unit]

Graduate School of Science, Osaka Prefecture University, Sakai 599-8531, JapanRT NaCl:Eu2+ NaCl:I-,Eu2+
for 2.9eV

3.0

4.0

for 2.9eV

5.0

6.0

-

NaCl:Ifor 5.2eV

Photon Energy [eV]7.0

Fig. 2. Excitation spectra of NaCl: Eu2+ (red), NaCl:I− (blue), and co-doped NaCl: I−, Eu2+ (purple) at RT.
[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] J. E. Muñoz-Sautiuste and J. Garcia-Sole, Phys. Rev.
B 38 (1988) 10874.
[4] I. Akimoto et al., Phys. Status Solidi C 6 (2009) 342.
[5] T. Förster, Disc. Faraday Soc. 27 (1959) 7.
[6] D. L. Dexter, J. Chem. Phys. 21 (1953) 836.

69
Ⅲ-2-21

Ⅲ-2

Ⅲ -2. Materials Sciences
BL3B
BL3B

Luminescence and Photoexcitation Spectra of TlBr-TlI Mixed Crystals
N. Ohno1 and K. Matsui2

Fundamental Electronics Research Institute, Osaka Electro-Communication University, Neyagawa 572-8530, Japan
2
Graduate School of Engineering, Osaka Electro-Communication University, Neyagawa 572-8530, Japan

Ⅲ-2

Thallous halide crystals are compound semiconductors attractive for fabrication of γ ray detectors.
They exhibit high stopping power due to high atomic
number and high density [1]. TlCl and TlBr crystalize
in cubic CsCl-type structure, while the stable form of
TlI is orthorhombic structure below 170ºC [2] and is
cubic CsCl-type one above it [3, 4]. Therefore, it isdifficult to grow a large-sized single crystal of TlI
under atmospheric conditions. In the present study,
mixed crystals of TlBr-TlI in cubic CsCl-type structure
have been grown and examined to reveal the opticalproperties such as absorption, reflection spectra, andphotoluminescence, luminescence excita- tion spectra
at low temperatures.
The crystals TlBrxI1-x were grown by the Bridgeman
method from appropriate amounts of TlBr and TlI after
distillation and purification. A plate of the sample cut
from as-grown crystals was polished with alumina
abrasive plastic film, then etched in methyl alcohols
containing dilute bromine. The optical measurements
were made at 10 K at the BL3B station.
Figure 1 shows luminescence spectra (blue curves)of TlBrxI1-x mixed crystals of different compositions at
10 K. On exciting TlBrxI1-x with light at the energy
above the indirect absorption edge [4, 6], a Stokesshifted broad luminescence bands are observed foreach crystal. Photoecitation spectra for the luminescence band are shown by black curves in the figure.
The luminescence bands are found to be efficiently
stimulated at the energy between the fundamental
absorption edge transition and the direct exciton
transition by indicated by arrows. As clearly seen in
Fig.1, the excitation edge for the luminescence bandmoves to the lower energy with increasing iodine
concentration x. In pure TlBr (x=1.0), the excitationedge at 2.64 eV is ascribed to the indirect-forbidden
exciton transition [5]. At x=0.4, the absorption edge islocated at around 2.0 eV. Below x ≤ 0.3, no luminescence band was observed, which is caused by the phasetransition of the crystal; in iodine-rich mixed crystal,the cubic phase is unstable below the room
temperature [4].
In TlBr (x=1.0), the spectral shape of the broad
luminescence band is almost Gaussian as previously
observed in lightly doped TlBr [5]. The broad band has
been identified as annihilation of relaxed excitons dueto the impurity-induced self-trapping. It is worth
noting that the amount of the Stokes shift and the widthof the observed luminescence band in mixed crystals

becomes small as the iodine concentration x isincreased as clearly seen in the figure. Therefore, withadding iodine ions in TlBr, the lattice relaxation of theself-tapped excitons becomes small, which is ascribedto the weak exciton-phonon interaction.

1 TlBr 10 K

0
1 TlBr0.8I0.2

Intensity (arb. unit)

10
1 TlBr0.6I0.4

0

1 TlBr0.4I0.6

0
1.5

2.0

2.5

Photon Energy (eV)3.0

Fig. 1. Luminescence (blue) and photoexcitation(black) spectra of TlBrxI1-x at 10 K.
[1] K. Hitomi, T. Shoji and K. Ishii, J. Crystal Growth379 (2013) 93.
[2] N. Ohno and M. Itoh, J. Phys. Soc. Jpn. 62 (1993)
2966.
[3] K. Heidrich, W. Staude, J. Treusch and H. Overhof,
Solid State Commun. 16 (1975) 1043.
[4] A. Fujii, J. Phys. Soc. Jpn. 58 (1989) 2173.
[5] K. Takahei and K. Kobayashi, J. Phys. Soc. Jpn. 44(1978) 1850.
[6] N. Ohno and K. Matsui, UVSOR Activty Report 43(2016) 65.

70
Ⅲ-2-22

Ⅲ -2. Materials Sciences
BL4U
BL4U

Improved Photoelectrochemical Performance of Au@TiO2-coated Fe2O3
Nanorods Studied by Scanning Transmission X-ray Microscopy
Y. R. Lu1, 2, Y. F. Wang1, Y. C. Huang1, 2, J. W. Chiou3, C. L. Dong1, W. F. Pong1,
T. Ohigashi4 and N. Kosugi4
Department of Physics, Tamkang University, Tamsui 251, Taiwan
Department of Electrophysics, National Chiao Tung University, Hsinchu 300, Taiwan
3
Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan
4
Institute for Molecular Science, Okazaki 444-8585, Japan1

2

Since Fujishima and Honda had found thephotoelectrochemical (PEC) water splitting could bemade directly by TiO2 under UV irradiation thirty
years ago, this direct solar fuel conversion is regarded
as one of the most promising clean and renewableenergy resource. The main drawback of TiO2 is thebandgap is too large so it can only absorb the UV light.
Hematite (α-Fe2O3) is a promising material for solar
water splitting owing to its smaller band gap energy
about 2.1-2.3 eV, which can capture 40% of incident
sunlight. However, it is only suitable for oxygen
evolution half reaction and electron-hole recombinesvery easily due to its intrinsic short hole diffusion
length and poor electron conductivity. Doping is aneffective way to adjust the band edge and overcome
the charge transfer ability in hematite.[1-2] In addtion,
by taking advantage of plasmonic effect caused bymetal nanocrystals, the PEC performance could befurther improved. In this work, the hematite nanorods
coated with a thin layer of TiO2 with/without Au
nanoparticles embbeded in between have been studied
by STXM to elucidate the correlation between the
PEC properties and interfacial electonic structures.
Figures 1 present the O K-edge (left panel) and Fe
L-edge (right panel) STXM stack mappings of
selected single nanorod of bare-, TiO2 coated and Au
embedded TiO2-coated Fe2O3. The stack mappings
display yellow, red and green areas, corresponding to
the different regions that are associated with different
regions and chemical properties of the nanorods.
Figures 1 also present the XANES spectra, whichcorrespond to their stack mappings. While there is no
significant difference of XANES of Ti L-edge (notshown here) could be revealed, the variation of both
O K-edge and Fe L-edge are observed. Spectroscopic
results indicate the surface region contains more
defects compared with core region, which enhance thedensity of states both in O and Fe sites. However, theTiO2 layer and embedded Au nanoparticles may
inhibit the charge recombination.
The enhanced PEC performance of TiO2-coated
Fe2O3 with Au nanoparticles embedded is likely to be
not only the plasmonic effect caused by Au
nanoparticles, but also the intrinsic improvement ofcharge transfer ability that is attributable to embedded
Au nanoparticles.

Ⅲ-2

Fig. 1. O K-edge (left panel) and Fe L-edge (rightpanel) scanning transmission X-ray microscopy image
and its corresponding stack mappings of selected
single (top) bare-, (middle) TiO2-coated, and (bottom)
TiO2/Au- coated Fe2O3 nanorod.
[1] Y. Fu et al., Chem Nano Mat 2 (2016) 704.
[2] Y. Fu et al., Phys. Chem. Chem. Phys. 18 (2016)5203.
[3] Y. R. Lu et al., to be submitted.

71
Ⅲ-2-23

Ⅲ -2. Materials Sciences
BL4U
BL4U

Structural Identification of Cellulose Nanocrystal/Nanofibril Hybrids andComposites Using Soft X-ray Techniques
1

Ⅲ-2

M. Y. Ismail1, M. Huttula2, M. Patanen2, H. Liimatainen1, T. Ohigashi3 and N. Kosugi3

Fibre and Particle engineering unit, University of Oulu, P.O. Box 3000, 90014 University of Oulu, Finland
2
Nano and Molecular Systems unit, University of Oulu, P.O. Box 3000, 90014 University of Oulu, Finland
3
UVSOR Synchrotron, Institute for Molecular Science, Okazaki 444-8585, Japan

Nanocellulose hybrids are high strength materials
consisting of cellulose nanofibrils or nanocrystals
embedded in a continuous biopolymeric matrix withadditives such as mineral nanoparticles. In the present
work, the structure of the hybrid formed of nanosilica,
nanocellulose (cellulose nanofibrils) and chitosan
matrix is studied. The critical factors affecting themechanical performance of these materials are theinteraction between the constituents and their spatial
distribution. So far, these properties have mainly been
analysed using electron microscopy techniques (TEM
and SEM), but they possess limited ability to localize
nanocellulose and biopolymers within the hybrid
structure (e.g. to determine interactions between minerals
and nanocelluloses). Therefore, novel methods aredesired to better address the structural details of thehybrids. Previously, soft X-ray spectroscopy has
shown to be able to identify the localized distributionof biopolymers, but based on our best knowledge thismethodology has not been used for nanocellulose
hybrids. This report shows significant new outcomeson structural characteristics of nano-scale hybrids
based on nanocelluloses.
Chitin is one of the most abundant natural
biopolymers and it is used for the production of
chitosan by deacetylation [1]. Chitosan is antibacterial,
non-toxic, and biodegradable; thus, it can be used forthe production of biodegradable films which arepotential green alternatives for commercially available
synthetic counterparts. However, poor mechanical andthermal properties of chitosan restrict its wide spread
applications. Consequently, hybrids fabricated from
chitosan matrix reinforced by nanofibers are attractive
materials to develop sustainable products [2].
The aim of the present work was to obtain a nanoscale spatial distribution of constituents within the
hybrid. The hybrids had constant nanocelluloses:
chitosan ratio of 50:50, and variable nanosilica content(5-30%). The samples (thickness of 100 nm) wereprepared from solution casted hybrid films using an
ultramicrotome. Pure nanocellulose, nanosilica andchitosan samples were used as references.
The samples were exposed to soft X-ray radiation at
BL4U beamline at UVSOR synchrotron. The
absorption at carbon 1s-edge was recorded forinvestigation of the nanocellulose and the matrix
distribution, with photon energies between 280 and
300 eV. The Si 2p absorption edge around 100 to 130
eV was utilized for the same spatial parts of the sample
for observing the distribution of nanosilica on the

hybrid.
Figure 1 presents examples of the image data of the
30% nanosilica sample. In the first preliminaryinterpretation the nanosilica (Si2p on leftmost) appears
to be concentrated on the fiber bundles of the sample.
The nanocellulose fibers were found to provide
somewhat characteristic absorption structure (Fig.2.),
matching the intense absorption patterns on the Fig.1.
Similarly the appearance of smaller “dots” ofnanosilica on the fibers were also found in the sample
containing only 5% of the nanosilica.
The obtained data seem to provide a strong evidenceof the agglomeration of the nanosilica at the nanofibers.
Indications on the spectral changes in the Si richregions suggest also possible chemical binding
mechanism of the nanoselluloce and nanosilica. The
present data will give valuable information of behaviorof the additive mineral which will affect themechanical properties of composite hybrid materials.

Fig. 1. STXM images for 30% nanosilica sample.

Fig. 2. The
C1snanocellulose fibers.

absorption

referencefor[1] Abdul Khalil H.P.S. Chaturbhuj K. Saurabha, Adnan
A.S., et al., Carbohydrate Polymers 150 (2016) 216.
[2] R. J. Moon, A. Martini, J. Nairn, J. Simonsen and
J. Youngblood, Chemical Society Reviews 40 (2011)
3941.

72
Ⅲ-2-24

Ⅲ -2. Materials Sciences
BL4U
BL4U

Dopant Effect of Lead(II) Thiocyanate (Pb(SCN)2) for FA0.9Cs0.1PbI3
Perovskite Solar Cells
M. W. Lin1, M. H. Li2, H. W. Shiu1, Y. L. Lai1, T. Ohigashi3, N. Kosugi3, P. Chen2
and Y. J. Hsu1, 2
National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan
Department of Photonics, National Cheng Kung University 701, Tainan, Taiwan
3
Institute for Molecular Science, Okazaki 444-8585, Japan1

spectra exhibit dissimilar in peak ratio and shape
between 5% and 10% Pb(SCN)2 doped sample. It
implies that the interaction between mp-TiO2 andperovskite may be play a key role in determining the
PCEs performance.
In conclusion, STXM results clear show thatmorphology variation attributed by TiO2 andPb(SCN)2, and also illustrate that an importantchemical interaction between mp-TiO2 and perovskite.
(a)

(b)

(c)

Fig. 1. The SEM image of (a) FA0.9Cs0.1PbI3, (b) 5%
Pb(SCN)2 doped- FA0.9Cs0.1PbI3, and (c) 10% Pb(SCN)2
doped- FA0.9Cs0.1PbI3.
(a)

(b)

(e)

（d）
2.4

5.0

5% Pb(SCN)2

N-C/400.7 eV

10% Pb(SCN)2

2.2

1.8

N-H/405 eV

1.6
1.4
395

4.0

t2g/457.9 eV

3.5

2.0

5% Pb(SCN)2

4.5

Intensity

Thiocyante (Pb(SCN)2), as a dopant in perovskite
FA0.9Cs0.1PbI3 (FA: HC(NH)2), and mesoscopic titania(mp-TiO2) as scaffold/electron-transport layer showhigh power conversion efficiencies (PCEs) up to
15.1%. Herein we studied the origin of such high PCEs
in terms of morphology and chemical structure of mpTiO2/Pb(SCN)2 doped- FA0.9Cs0.1PbI3 heterojunction
by scanning electron microscopy (SEM) and scanningtransmission X-ray microscopy (STXM).
In SEM studies (Fig. 1), the Pb(SCN)2 dopedFA0.9Cs0.1PbI3 displays much larger perovskite crystalline
than FA0.9Cs0.1PbI3. More than 70% of the larger crystals
in 5% Pb(SCN)2 doped- FA0.9Cs0.1PbI3 crystals exhibita size distribution in the range of 0.8-1 μm size.
Increasing Pb(SCN)2 dopant to 10% in FA0.9Cs0.1PbI3,
the size of perovskite crystals decrease to the 0.5 μm anddisplay homogeneous distribution. The large crystals in
the perovskite bulk film are beneficial for chargetransport in the perovskite,1 that is possible to explain
5% Pb(SCN)2 doped- FA0.9Cs0.1PbI3 has best PECs thanthe others.
To further examine the effects of adding Pb(SCN)2on the crystalline morphology, chemical maps of N Kedge and Ti L-edge were acquired to obtain the
distributions of micro-aggregates of SiN/mp-TiO2/5%
and 10% Pb(SCN)2 doped- FA0.9Cs0.1PbI3 by STXM.
Figure 2 displays the STXM images of SiN/mpTiO2/5% Pb(SCN)2 doped- FA0.9Cs0.1PbI3 (Fig. 2(a)),
Pb(SCN)2
dopedand
SiN/mp-TiO2/10%
FA0.9Cs0.1PbI3 (Fig. 2(b)) which are optical density(OD) maps obtained at 403.5 eV for N K-edge and 457
eV for Ti L-edge, the characteristic absorption peaks of
FA0.9Cs0.1PbI3 and mp-TiO2, respectively. The N
mapping on above samples show similar distribution
in morphology and size to SEM results. The 5%
Pb(SCN)2 doped- FA0.9Cs0.1PbI3 shows grain size of~1 μm, and decrease to 0.5 μm when 10% Pb(SCN)2
doped. However, we notice some additional line shapeand large aggregation as shown in red color in thecomposite images, that is determined as TiO2
nanoparticles which are in a uniform diameter of 2–5
μm and appear to be more uniformly dispersed in thesample of 5% Pb(SCN)2 doped- FA0.9Cs0.1PbI3. It
suggests 5% Pb(SCN)2 dopant has effective chargetransfer between perovskite and TiO2. Fig. 2(c) and (d)show the micro-scpectra of N K-edge and Ti L-edge
extracted from 5% and 10% Pb(SCN)2 dopedFA0.9Cs0.1PbI3 film. We notice that both N and Ti

Intensity

2

10% Pb(SCN)2
eg/459.5 eV

3.0
2.5
2.0
1.5
1.0

400

405

410

415

Photon energy (eV)

420

425

450

455

460

465

470

475

Photon energy (eV)Fig. 2. OD mapping of Ti L-edge (red) and N K-edge(green) of (a) SiN/mp-TiO2/5% Pb(SCN)2 dopedFA0.9Cs0.1PbI3, and (b) SiN/mp-TiO2/10% Pb(SCN)2
doped- FA0.9Cs0.1PbI3. (c) and (d) micro-spectra of N
K-edge and Ti L-edge extracted from (a) and (b),respectively.
[1] Z. Xiao, et al., Adv. Mater. 26 (2014) 6503.
[2] M.-W. Lin, et al., Adv. Mater. Interfaces 3 (2016)
1600135.

73
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Ⅲ -2. Materials Sciences
BL4B
BL4B

Valence State Analysis of Fe Ions in LaGaO3
2

Ⅲ-2

Y. Osada1 and T. Yamamoto1, 2Faculty of Science and Engineering, Waseda University, Tokyo 169-8555, Japan
Institute of Condensed-Matter Science, Waseda University, Tokyo 169-8555, Japan
1

Solid Oxide Fuel Cell (SOFC) has been widely
studied because of its importance as one of the energy
sources. Among the SOFCs, LaGaO3 has been
extensively investigated because of its high oxygen ion
conductivity. In order to increase its ionic conductivity,
incorporation of Sr2+ and Mg2+ ions in LaGaO3 were
proposed, so-called LSGM, which can produce oxygen
vacancies in the material to keep the charge neutrality.
It was reported that additional incorporation of Co ionsin LSGM increase ionic conductivity. [1] Although it
is quite important to know the charge state of suchtransition elements in LSGM for the understanding ofincrease of ionic conductivity owing to the additional
ion incorporation, such investigations have not yet
been carried out. In the current study, valence state of
the Fe ions in LaGaO3 was examined as a proto-type
experiment by measuring the Fe-L3 X-ray absorption
spectrum (XAS).
All the samples were synthesized with theconventional solid-state reaction method changing theconcentration of Fe ions, i.e., x = 0, 0.05, 0.1 and 0.15
in LaGa1-xFexO3. High purity powders of La2O3,
Ga2O3 and Fe2O3 were used as starting materials. For
precise weighing, La2O3 were dried at 773 K for 30
min. in air prior to weighing. These powders weremixed in an agate mortar for 30 min., which were
calcined in air at 1273 K for 6 hours. Resultant
powders were ground again in an agate mortar, whichwere pressed into a pellet form (10 mm). Finally,
these pellets were sintered in air at 1773 K for 6 hours.
The synthesized specimens were characterized by
the powder X-ray diffraction with Cu-Kα X-ray
irradiation, which showed all the samples were
crystallized in a single-phased orthorhombic
perovskite structure.
Cell volumes were obtained from the observed XRD
patterns, which are shown in Fig. 1. As shown in thisfigure, cell volumes increase as increment of Feconcentration, which suggests that Fe ions substitute at
Ga3+ site as divalent or trivalent ions from a viewpointof ionic radius. [2]Fe-L3 XAS were recorded at BL-4B with the total
electron yield method. Incident beam was
monochromatized with the varied-space grating (800lines/mm), which was irradiated onto the sample.
Sample powders were put on the carbon adhesive tape,which was attached on the first dinode of the electron
multiplier.
Observed Fe-L3 XAS of Fe ions incorporated in
LaGaO3 were shown in Fig. 2 together with those of

Fe oxides. Fe-L3 profile of Fe ions in LaGaO3 arequite similar, which suggests that local environment
and valence state of the Fe ions are almost identical. In
addition, the profile is close to that of α-Fe2O3, which
can confirm the valence state of Fe ions in LaGaO3 istrivalent.

Fig. 1. Cell volumes of Fe incorporated LaGaO3,
LaGa1-xFexO3.

Fig. 2. Observed Fe-L3 XAS spectra of Fe doped
LaGaO3 and Fe oxides.
[1] T. Ishihara et al., Chem. Mater. 11 (1999) 2081.
[2] R.D. Shanon, Acta Crystallogr. A32 (1976) 751.

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BL4B
BL4B

Thickness Dependence of Spin and Orbital Magnetic Moment of Ultrathin
Magnetic Films: Au/Fe/Au and MgO/Fe/Au
S. Yamamoto1, K. Yamamoto1, Y. Hirata1, K. Fukuta2, D. Oshima3, T. Kato2, S. Iwata3,
H. Wadati1 and I. Matsuda1

Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581, Japan
Department of Electrical Engineering and Computer Science, Nagoya University, Nagoya 464-8603, Japan
3
Nagoya University, IMaSS, Nagoya 464-8603, Japan
1

2

Interface magnetism has been one of the central
topics for investigating fundamental magnetic
properties. They range from the relation between thedimensionality and the magnetic structure to thecontrol of magnetism by the electric field rather thanby electric current or magnetic field. Thinner magnetic
film systems have a larger contribution from theinterface to the magnetism. Furthermore, it is expectedthat an interfacial spin-orbit interaction enhances theperpendicular magnetic anisotropy (PMA) of magnetic
layers. However the effect of spin-orbit interaction oninterface magnetism has not been investigatedsystematically so far [1].
In our previous study, we have investigatedinterfacial perpendicular magnetic anisotropy (PMA)
energy of an ultrathin magnetic system, Au/Fe/Au,
comparing with a reference system, MgO/Fe/Au [2].
By utilizing a torque magnetometer, it was revealed
that PMA energy in the Au/Fe/Au system had a smaller
interfacial PMA energy (455 μJ/cm2) than that in the
MgO/Fe/Au system (696 μJ/cm2). In order to reveal
the origin of the interfacial PMA for both systems, wemeasured thickness dependence of Fe 2p X-ray
absorption spectroscopy (XAS) and X-ray magnetic
circular dichroism (XMCD) at BL4B in UVSOR.
Samples were fabricated using a molecular beam
epitaxy method before the beamtime. All of the layers
were evaporated at room temperature using electron
beam evaporator in an ultrahigh vacuum (7.0E-8 Pa).
The epitaxial growth was confirmed by observing
RHEED pattern during evaporation for both magnetic
systems. The sample structure is Au(2 nm)/Fe(0.29 –1.4 nm)/Au(25 nm)/Cr(5 nm)/MgO(001) (substrate,
0.5 mm) for Au/Fe/Au system. The top Au layer avoids
oxidation of magnetic layer. The MgO/Fe/Au system
has a similar structure except for being MgO layer witha thickness of 2 nm inserted between top Au and Fe
layer. We confirmed that the Fe layer had not oxidizedin the measurement by Fe 2p XAS measurements.
Measurements were conducted with a total-electron
yield mode at 10 K. The samples were cooled downwith a liquid He. External magnetic field, ± 2 T wasapplied parallel to the incident light. The sample
surface was perpendicular to the incident light. The
XAS (XMCD) was extracted from the sum(difference) of absorption spectra measured under
applying positive and negative external field. By
applying magneto-optical sum-rule for 2p edge

XMCD, the spin and orbital magnetic moment wereextracted. The Fe thickness dependence of themagnetic moment is shown in Fig. 1. In the figure,magnetic moment is expressed in the unit of μB/hole.
We adopted this notation because in the ultrathin
magnetic films, the hole number is not trivial.
Furthermore, spin magnetic moment (mspineff) includes
magnetic dipole moment. It indicates that in both
systems, larger orbital moments were observed with
reducing Fe film thickness with respect to the value ofbulk bcc Fe. On the other hand, the spin magnetic
moment does not depend on the Fe film compared tothe orbital moment. It was shown that the PMA
originates from the orbital moment in both systems.
The variation of orbital magnetic moment of Au/Fe/Au
was smaller than that of MgO/Fe/Au system, which
was consistent with our previous measurements ofinterfacial PMA energy.

Fig. 1. Fe thickness dependence of (a) orbital (morb)and (b) spin (mspineff) magnetic moment. The dashedline shows correspondent value for bulk bcc Fe.
[1] C. A. F. Vaz et al., Rep. Prog. Phys. 71 (2008)056501.
[2] J. Okabayashi et al., Appl. Phys. Lett. 105 (2014)
122408.

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BL5U
BL5U

Electronic Structure of Ba0.75K0.25Fe2As2 Observed by ARPES
2

Ⅲ-2

S. Ideta1, M. Nakajima2 and K. Tanaka1

National Institutes of Natural Science, Institute for Molecular Science, Okazaki, 444-8585, Japan
Department of Physics, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan

1

Iron-based superconductors have a complex phase
diagram with the antiferromagnetic (AFM) transition
and the structural phase transition. Recently, nematicity,
defined as broken rotational symmetry [a trigonal(C4)to-orthorhombic (C2) structural transition], has shedlight on the understanding of the mechanism on the ironbased superconductivity [1-4]. In hole-doped BaFe2As2(Ba122) system, inelastic neutron diffraction
experiments of Ba1-xNaxFe2As2 and Ba1-xKxFe2As2 (KBa122) have shown the magnetic order without C4
symmetry breaking [5, 6]. This indicates that themagnetism can survive even in the absence of orbital
order. Besides, the superconductivity is suppressed
between the superconductivity and the C4-magnetic
phase. The electronic structure at the C4 magnetic phasehas been unclear yet, and it would give us a great interest
to elucidate the mechanism of the hole-doped Ba122.
Here, we have investigated the electronic structure of
detwinned Ba0.75K0.25Fe2As2 to elucidate the occupieddxz and dyz states, reflecting the nematic ordering [3, 4].
As a first step, we demonstrated an angle-resolved
photoemission spectroscopy (ARPES) experiment toconfirm the electronic structure of the twinned K-Ba122(x ~ 0.25) with the C4-magnetic phase as shown in Fig.
1(a).
High-quality single crystals of Ba0.75K0.25Fe2As2 (Tc~ 25 K) were grown by self-flux technique. ARPES
experiments were carried out at BL 5U of UVSOR
using the linearly polarized light of hν = 32 eV-60 eV
photons. Temperature was set at T = 5 and 45 K andclean sample surfaces were obtained for the ARPES
measurements by cleaving single crystals in-situ in an
ultrahigh vacuum better than 1×10-8 Pa.
In order to confirm the electronic structure of KBa122 (x ~ 0.25) in the kz direction, we have performed
FS mapping as shown in Fig. 1(b). From the threedimensional shape of the FS, we found that the innerpotential is V0 ~ 15.6 eV which is similar to theprevious ARPES study [7].
Figure 1(c) shows the ARPES intensity mapping in
the two-dimensional kx-ky plane taken at hν = 60 eV
corresponding to the Z point. The electronic structure
does not show clearly the band folding due to the spindensity-wave formation. We consider that we would
need to study the temperature dependence andunderstand the band folding in detail.
In summary, we have performed an ARPES study of
K-Ba122 (x ~ 0.25) and measured in- and out-of-plane
ARPES intensity maps. We found that the innerpotential is V0 = 15.6 eV which is similar to theprevious ARPES study and the electronic structure
shows almost the same. We will demonstrate an

ARPES study in detail using detwinned K-Ba122 andthe temperature dependence in future work.

Fig. 1.(a) Phase diagram of hole-doped Ba1-xKxFe2As2
taken from Ref. [6]. TN, Ts, and Tc denote the temperatureof the magnetic, structural, and superconducting phasetransition, respectively. T1 and T2 show the C4-magnetic
phase and superconductivity-induced reentrance of theC2-SDW phase, respectively. (b) ARPES intensity map
taken at hν = 60 eV (T = 45 K), corresponding to the Zpoint (left) and FS mapping in the k||-kz mapping takenfrom hν = 32 eV–56 eV (right) (T = 5 K).
[1] R. M. Fernandes et al., Nat. Phys. 10 (2014) 97.
[2] R. M. Fernandes et al., Phys. Rev. Lett. 111 (2013)
127001.
[3] T. Shimojima et al., Phys. Rev. B 90 (2014) 12111(R).
[4] Y. Ming et al., PNAS 108 (2011) 6878.
[5] L. Wang et al., Phys. Rev. B 93 (2016) 014514.
[6] A. E. Böhmer et al., Nat. Commun. 6 (2015) 7911.
[7] Y. Zhang et al., Phys. Rev. Lett. 105 (2010) 117003.

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BL5U

Electronic Structure of MAX Phase Compound Cr2AlC Studied by Angleresolved Photoemission Spectroscopy
T. Ito1, 2, T. Fujita2, D. Pinek3, M. Nakatake4, S. Ideta5, K. Tanaka5 and T. Ouisse3
1

Synchrotron Radiation Research Center, Nagoya University, Nagoya 464-8603, Japan
2
Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
3
Université Grenoble-Alpes, CNRS, LMGP, F-38000 Grenoble, France
4
Aichi Synchrotron Research Center, Seto, 489-0965, Japan
5
Institute for Molecular Science, Okazaki 444-8585, JapanMAX phase compounds, i.e., Mn+1AXn where M isa transition metal, A belongs to groups 13-16 and X is
the C or N element, have recently attracted muchattention due to their possible application to the
production of a new class of two-dimensional systems
called MXenes, obtained by removing the A atom
planes [1]. On the other hand, the bulk electronic
structure of MAX phase has been studied mostly
through ab initio, density functional theory (DFT)
calculations, mainly due to a lack of single crystalline
samples. In this study, we have for the first time
performed angle-resolved photoemission spectroscopy(ARPES) on single crystals of the MAX phasecompound Cr2AlC [2] in order to directly investigate
the bulk electronic structure of this system.
ARPES measurements were performed at thebeamline BL5U of UVSOR-III. Clean surfaces wereobtained by in situ cleaving.
Figure 1 shows the Fermi surface of Cr2AlC along
ΓMK plane obtained by using hν = 65 eV photons. The
photon energies corresponding to high-symmetry kz
points were obtained by using normal-emission
ARPES, where the inner potential has been estimatedto be 15.5 eV. The band structure along the ΓK cut(orange line in Fig. 1) is shown in Fig. 2(a) together
with the band calculation (Fig. 2(b) [3]). From thepresent ARPES study, it has been found that theelectronic structure near the Fermi level (EF) of Cr2AlC
consists of a few closed electron-like Fermi surfaces(FS’s) around the Γ point (e, e’) as well as hole-like FS
around the M point (h). From the comparison with theband structure calculations [3], we have found that theobserved Fermi surface topology seems to beconsistent with the calculation. On the other hand, we
have found the qualitative difference of the band widthof the electron pockets, possibly due to some mass
enhancement (m*/mcal. ~ 2) of the carriers.

Ⅲ-2

Fig. 1. Fermi surface image of Cr2AlC along ΓMKplane. Orange line corresponds to ARPES cut shownin Fig. 2 (a).

Fig. 2. (a) Band structure of Cr2AlC along ΓK line.
Dashed lines are guide for the eye. (b) Band structure
calculations of Cr2AlC [3].
[1] M. Barsoum, MAX phases (Wiley, Weinheim, 2013).
[2] T. Ouisse et al., J. Cryst. Growth 384 (2013) 88.
[3] S. Cui et al., J. Solid State Chem. 191 (2012) 147.

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BL5U
BL5U

Search for a Nematic State in the Cuprate Superconductor Bi2212 byAngle-resolved Photoemission Spectroscopy
S. Nakata1, M. Horio1, K. Koshiishi1, K. Hagiwara1, C. Lin1,
S. Ideta2, K. Tanaka2, D. Song3, Y. Yoshida3, H. Eisaki3 and A. Fujimori1

Department of Physics, University of Tokyo, Tokyo 113-0033, JapanUVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
3
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan
1

2

Ⅲ-2

In cuprate superconductors, to understand the originof the pseudogap region in the phase diagram remains amost significant issue. Recently, experimental evidence
for several kinds of order (e.g. charge density wave, spin
density wave, electronic nematic order) has beenreported in the pseudogap region [1]. Electronic
nematicity, which does not break the translational
symmetry but breaks the fourfold rotational symmetryof the lattice, has been reported below the pseudogap
temperature and may play an important role in thepseudogap region [2]. For instance, evidence forelectronic nematicity appeared in YBa2Cu3O6+x fromtransport [3, 4], neutron scattering [5] and magnetic
susceptibility [6] measurements and in Bi2SrCaCu2O8+δ
from resistivity measurement [7].
Electronic nematicity has been discussed also in Febased superconductors [8] and studied by angleresolved photoemission spectroscopy (ARPES) [9],which is the most direct way to reveal the electronic
structure. However, at the moment, there has been noreport that reveals the electronic nematicity in cuprates
by ARPES. We performed ARPES measurements inorder to study the electronic nematicity in cuprates.
Furthermore, by ARPES one can investigate whether
the electronic nematicity is specific to the pseudogap
state or remains in the superconducting state.
Bi1.7Pb0.5Sr0.9CaCu2O8+δ (Pb-Bi2212) single crystal
samples were grown by the floating-zone method. It
was nearly optimally doped sample and Tc was 91 K.
ARPES measurements were carried out at UVSOR
BL5U. We used linearly polarized light with hν = 60
eV. The total energy resolution was set at 10 meV. The
samples were cleaved in-situ under the pressure of ~ 2
× 10-8 Pa. In order to obtain big signals of electronic
nematicity, mechanical strain was applied in the
direction of the Cu-O bond.
Figure 1 shows Fermi surface plots determined frommomentum distribution curves at the Fermi level taken
at 200 K, 100 K, 50 K and 5 K. In order to detect thepossible anisotropy of the Fermi surface, we usedtight-binding fitting function with x and y axis
anisotropy (ε(kx,ky) = -2t[(1+δ)coskx+(1-δ)cosky] –4t’coskxcosky -2t’’(cos2kx+cos2ky) + E0). Figure 2
shows the temperature dependence of the anisotropy
parameter δ, representing anisotropy in the tightbinding parameter. So far, we have not been able toidentify definitive evidence for electronic nematicity
due to the lack of accuracy. Further measurements withimproved accuracy are necessary.

Fig. 1. Fermi surface plots (red points) and fitting
curves (blue line) at (a) 200 K, (b) 100 K, (c) 50 K and(d) 5 K, respectively.

Fig. 2. Temperature dependence of δ representing theanisotropy of the nearest-neighbor tight-binding
parameter t.
[1] B. Keimer et al., Nature 518 (2015) 179.
[2] S. A. Kivelson et al., Nature 393 (1998) 550.
[3] Y. Ando et al., Phys. Rev. Lett. 88 (2002) 137005.
[4] R. Daou et al., Nature 463 (2010) 519.
[5] V. Hinkov et al., Science 319 (2008) 597.
[6] Y. Sato et al., JPS fall meeting (2016) 14pJC-5.
[7] K. Ishida et al., JPS fall meeting (2016) 14pJC-12.
[8] S. Kasahara et al., Nature 486 (2012) 382.
[9] M. Yi et al., PNAS 108 (2011) 6878.

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BL5U
BL5U

Preparation of Au(111) Reconstructed Surfaces
Toward the Understanding of Fe/Au Spin-orbit Coupled Interfaces
J. Okabayashi1*, S. Ideta2 and K. Tanaka2

Research Center for Spectrochemistry, University of Tokyo, Tokyo 113-0033, Japan
2
UVSOR, Institute of Molecular Science, Okazaki 444-8585, Japan1

The gold Au(111) surfaces are investigatedextensively by means of scanning tunneling microscopy
and angle-resolved photoemission spectroscopy(ARPES) because this surface exhibits the large
Rashba-type spin-orbit splitting. Large spin-orbit
interaction in the heavy element of gold brings the wide
varieties for the topological physics and spin-orbit
coupled sciences not only in the bulk but also in thesurface and interfaces. The Rashba splitting of 110 meVin Au(111) surface was reported firstly by LaShell et al.
[1]. Recently, the interfaces between Au(111) and otherheavy elements such as Bi or Ag have been researched
extensively [2, 3]. On the other hand, the interfaces
between Au(111) and functional molecules are also
investigated [4]. Here, we focus on the interfaces
between ferromagnetic materials and Au(111) interfaces
because the thin Fe layers on the heavy elements exhibit
the perpendicular magnetic anisotropy (PMA) throughthe spin-orbit interaction.
In the research fields of spintronics, the spin-orbit
coupling between the ferromagnetic 3d transition metal
Fe or Co and 5d heavy elements of non-ferromagnetic
materials such as Pt and Au has been utilized for the
PMA through the proximity at the interfaces. It isbelieved that the future researches concerning not only
spins but also orbitals are recognized as the orbitornics.
Therefore, to clarify the origin of the PMA at theseinterfaces is a crucial role for future spin-orbitronics.
The relationship between Au(111) Rashba-type spinorbit interaction and PMA in 3d TMs has not beenclarified explicitly. In order to investigate the orbitalresolved states in the Fe films showing the PMA,
ARPES at the interfaces becomes the powerful
techniques through the photon-energy and polarization
dependences in each 3d orbital. By using ARPES, we
aim to understand the orbital-resolved electronic
structures at the magnetic interfaces on Au(111)
Rashba-type surfaces in order to develop the researchesof novel PMA using spin-orbit coupled interfaces.
In the project proposed in 2016, we planned toprepare the clean Au(111) surface for the deposition of
Fe. The single-crystalline 200-nm-thick Au(111) films
grown on mica (Phasis, Switzerland) were used as
substrates. At the beamline 5U in UVSOR, we
performed the Ar-ion sputtering at 1 kV accelerating
voltage and subsequent annealing at 500 °C under thehigh vacuum conditions with repeated cycles. After the
preparation, the samples were transferred to the ARPES
chamber. We performed ARPES at 160 K using thephoton energy of 45 eV because of the large crosssection of Au(111) surface states.
We successfully detected the band dispersions in theAu(111) surface states are shown in Fig. 1. The
parabolic dispersions derived from the surface states areobserved. Clear Rashba splitting in the mapping of
surface states can be observed.
Considering this experiment, we plan to detect more
precise band dispersions and the modulation of thesebands by the ultra-thin Fe deposition. In order to achieve
the purpose, we will perform the following tasks;(i) the preparation of clear Au(111) surface and theobservation of low-energy diffraction patterns(ii) the determination of precise Fe deposition rates(iii) Au deposition onto the Fe layers.
After performing above tasks, the spin and electronic
states in the Rashba-type spin-orbit coupled interfaces
combining both ARPES and X-ray magnetic circulardichroism are clarified.
We acknowledge the fruitful comments anddiscussion with Assistant Professor H. Yamane in IMS.

Fig. 1. ARPES of Au (111) surface states near the
Fermi level.
[1] S. LaShell et al., Phys. Rev. Lett. 77 (1996) 3419.
[2] C. Tusche et al., Ultramicroscopy 159 (2015) 620.
[3] B. Yan et al., Nature Commun. 6 (2015) 10167.
[4] H. Yamane, Molecular Science 9 (2015) A0078.
*e-mail: jun@chem.s.u-tokyo.ac.jp

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BL5U
BL5U

Photoemission Study on Sm-oxide Thin Films Prepared by Molecular Beam
Epitaxy
H. Miyazaki1, Y. Sakai1, K. Yoshikawa2 and N. Nishino1

Department of Physical Science and Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan
Department of Environmental and Materials Engineering, Nagoya Institute of Technology, Nagoya 466-8555,
Japan

1
2

Ⅲ-2

Topological insulators are materials which exhibit afundamentally new physical phenomena that were firstpredicted by theorists [1]. Recently, SmO is predicted tohave a topological nontrivial ground state at ambientpressure [2], and we succeeded to fabricate SmO thinfilms by molecular beam epitaxy method controlled
precisely adjusting the substrate temperature andoxygen partial pressure. However, the valence state of
Sm is important for whether it is a topological insulator.
In this report, we have performed in-situ photoemission
spectroscopy (PES) on SmO thin films.
Sm-metal and Sm-oxide thin films have been grownby molecular beam epitaxy (MBE) method. We
evaporated Sm-metal and Sm-oxide thin films onto Ystabilized ZrO2 (100) substrates at 800 °C without
oxygen gas and under the oxygen pressure of 1.0 x 10-5
Pa, respectively. The PES measurements were performedat the beamline 5U of UVSOR-III, the Institute for
Molecular Science, combined with the molecular beam
epitaxy system, as shown in Fig. 1.
Figure 2 shows the PES spectra of Sm-metal andSm-oxide thin films recorded at hν = 60 eV and 180
eV. The experimental spectra are normalized withrespect to their integrated intensity on the wholevalence band up to EB = 15 eV. The peaks and shoulder
observed around 7.5, 10, and 12 eV at hν = 180 eV are
steeper than those at hν = 60 eV. If the photon energy
is increased from 60 to 180 eV, the atomic crosssections of the O 2p and Sm 4f states change by 0.07
and 0.5 times, respectively [3]. As a result, the partial
DOS originated from the Sm 4f state is expected to beenhanced compared with that from the O 2p state andthe peaks and shoulder observed around 7.5, 10, and
12 eV are attributed to the Sm 4f state and the peakaround 6.0 eV is attributed to the O 2p state. Thishypothesis is consistent with the past PES results of
Sm2O3 and the valence state of Sm 4f state is the 4f 3+
state.
Sm 4f 3+ valence state originates from Sm2O3 havebeen observed in PES, despite Sm 4f 2+ valence statefrom SmO expected from the results of X-ray
diffraction measurement. There is a contradiction
between the results of PES and XRD measurements.
Considering that the surface of the Sm-metal thin filmis oxidized, one possibility is that the surface of thethin films has been oxidized during the transfer of thesample from MBE chamber to PES system. In order todiscuss the essential surface electronic structure of thinfilms, further MBE system improvements are needed.

Fig. 1. Photo of the in-situ MBE system combined to
UVSOR-III BL5U beamline.

Fig. 2. Photon-energy
dependenceofthephotoemission spectra of Sm-metal and Sm-oxide thinfilms.
[1] C. L. Kane and E. J. Mele, Phys. Rev. Lett. 95(2005) 146802.
[2] D. Kasinathan et al., Phys. Rev. B. 91 (2015)
195127.
[3] J. J. Yeh and I. Lindau, At. Data Nucl. Data Tables
32 (1985) 1.
[4] G. Dufour et al., Chem. Phys. Lett. 42 (1976) 433.

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BL5U

Angle Resolved Photoemission Spectroscopy Study of Fermi Surface andSuperconducting Gap in NdFeAs(O,F)
Z. H. Tin1, T. Adachi1, A.Takemori1, S. Ideta2, 3, K. Tanaka2, 3, S. Miyasaka1 and S. Tajima1

Department of Physics, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan
2
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan3
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
1

Since the discovery of iron-based superconductors in
2008, intensive research has been going on in order tofind out the origin of superconductivity. Among various
families of Fe-based superconductors, 1111 system suchas RFeAs(O,F) (R=rare-earth elements) achieves thehighest Tc~ 55K [1]. In spite of highest Tc, 1111 system
is not the popular research target among iron-based
superconductors. The main reason is that it is very
difficult to synthesize the single crystal of 1111 system.
In our previous study, we have been able to grow the
single crystal of NdFe(P,As)(O,F) and observe theevolution of Fermi surfaces with the isovalent doping ofAs site to P. In order to clarify the pairing mechanism,
we have measured the superconducting gap of
NdFeAs(O,F) single crystal by using angle resolved
photoemission spectroscopy (ARPES) method.
The single crystals of NdFeAs(O,F) were grown by
self-flux method under high pressure [2]. Tc of thesingle crystal was 41K. The ARPES were measured at
BL5U in UVSOR facility.
Figure 1 shows the mapping of the Fermi surfaces(FSs) around Γ point, in horizontal (P) and vertical (S)polarized photon configurations. In these mapping,
two hole FSs (inner and outer) were clearly observed
around Γ point. Figure 2 shows kz dependence of both
FSs. Both of the FSs showed less dispersive feature
along the kz direction, which is consistent with the bandcalculation [3].
Superconducting gap was measured in kx-ky
momentum space around Γ point. Figure 3 shows theangle dependence of superconducting gap values on the
inner and outer FSs around Γ point. Both two hole FSs
have a nodeless superconducting gap of ~17.0meV 27.7meV on the outer FS and ~16.1meV - 23.3meV on
the inner FS. These correspond to large gap ration,
2Δ/kTc = 8-12 and 9-15, respectively.

Ⅲ-2
Fig. 1. Fermi surface mapping around Γ point in
NdFeAs(O,F) single crystal in S (left panel) and P (rightpanel) polarization configurations, respectively.

Fig. 2. The kz dependence of Fermi surfaces in
NdFeAs(O,F) single crystal in S (left panel) and P (rightpanel) polarization configurations, respectively.

Fig. 3. The angle dependence of superconducting gap
values on the inner (left panel) and outer Fermi
surfaces (right panel) around Γ point, respectively.
[1] Ren Zhi-An et al., Chinese Phys. Lett. 25 (2008) 2215.
[2] A. Takemori et al., JPS Conf. Proc. 1 (2014) 012111.
[3] H. Usui et al., Supercond. Sci. Tech. 25 (2012) 084004.

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BL6B

UV-Induced Absorption Spectra for Cerium-doped Gd3Al5-xGaxO12 Crystals
M. Kitaura1, K. Kamada2, S. Kurosawa1, 2, A. Ohnishi1 and K. Hara3

1
Faculty of Science, Yamagata University, Yamagata 990-8560, JapanNew Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579, Japan
3
Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8011, Japan2

Ⅲ-2

The cerimu-doped Gd3Al2Ga3O12 (Ce:GAGG)
crystal is known one of high performance scintillators[1]. This material is characterized by high light yield andgood energy resolution, and the scintillation properties
are superior to other inorganic scintillators. However,there is a serious problem for Ce:GAGG that Ce3+
emission accompanies not only phosphorescence but
also afterglow [2]. Since these components impede
scintillation application requiring high-speed response,
they must be suppressed as small as possible.
Most of scintillator crystals necessarily include latticeimperfections, which are unavoidably introduced in theprocess of the crystal growth. Such imperfections create
donor- and acceptor-like levels near valence andconduction bands, and they act as traps for photocarriers.
The traps are responsible for the occurrence ofphosphorescence and afterglow. It is therefore necessary
to clarify the origin of the traps degrading the scintillation
response.
Recently, we have demonstrated that the defectcomplexes including oxygen vacancies form trappedelectron centers in Ce:GAGG crystals [3]. We also
explained that the trapped electron centers are introduced
as charge compensators for cation deficiency. However,
the origin of the trapped electrons center remains
unsolved.
We show absorption spectra of cerium-doped
Gd3Al5-xGaxO12 mixed crystals induced underirradiation with UV-light at 375 nm for 10 min. The
data allow us to see the effect of x on the electronic
structure of trapped electron centers, and they areavailable to identify the origin of trapped electron
centers. In the present experiment, we used the single
crystals of Ce:Gd3Al5-xGaxO12 grown by the micropuling down (μ-PD) method. The concentration of
cerium ions was set 1.0 mol%. The single crystals of x
< 2.5 could not be obtained, because they contain thesecondary phase with perovskite structure. The
absorption spectra were measured under UV-irradiationand non-UV-irradiation. Here, the difference between thetwo is called as UV-induced absorption spectrum.
The UV-induced absorption spectra for x=3.0, 3.5,
4.0, and 5.0 are shown in Fig. 1. The data wereobtained at 12 K. The absorption spectra cannot be
obtained in the range below 1500 cm-1, because ofstrong Reststrahlen reflection. The UV-induced
absorption spectrum for x=3 exhibits a prominent bandat around 12000 cm-1. This feature is good agreementwith our previous data in Ref. 3, in which theprominent band was assigned to trapped electron
centers associated with oxygen vacancies. This band is

weakened for x=3.5. Another band also appears in therange below 4000 cm-1, together with the 12000 cm-1
band. This band is gradually increased with x.
The present results reveal that two kinds ofabsorption bands are replaced with increasing x. This
fact suggests that gallium and aluminum ions are alsoessential for the formation of trapped electron centers,
together with oxygen vacancies. The disappearance ofthe 12000 cm-1 band may occur also by the loweringof the conduction band minimum with increasing x [4].
Further investigations are needed to clarify the originof the trapped electron centers responsible for the UVinduced absorption bands.

Fig. 1.
UV-induced
absorption
spectraof
Ce:Gd3Al5-xGaxO12 crystals (x=3.0, 3.5, 4.0, and 5.0)
measured at 12 K. The longitudinal axis represents thedifference in absorption coefficient between theabsorption spectra measured under UV-irradiation andnon-UV-irradiation.
[1] K. Kamada et al., J. Cryst. Growth 352 (2012) 88.
[2] M. Kitaura et al., J. Appl. Phys. 115 (2014) 083517.
[3] M. Kitaura et al., Appl. Phys. Express 9 (2016) 072602.
[4] P. Dorenbos, J. Lumi. 134 (2013) 310.

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BL6B
BL6B

Ground-State Splitting of Ultrashallow Thermal Donors in Silicon
A. Hara and T. Awano

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

Ⅲ-2

Fig. 1. Temperature dependence of the absorption
coefficient. The vertical axis is ln[Trans.(T)/Trans.(15K)], where Trans.(T) represents the transmittance attemperature T K. (b) Magnified image of spectra A andB.
0.0

ln{-ln[Trans.(T)/Trans.(15 K)]}

We had found ultrashallow thermal donors (USTDs)
in carbon-doped and hydrogen-doped Czochralski
silicon (CZ Si) crystals.[1] To the best of our knowledge,
these are the shallowest energy levels among previously
reported donors in Si crystals. We found new peaks withincreasing measurement temperature.
To evaluate the relationship between the absorption
coefficient of the new peaks and the measurement
temperature, we analyzed the temperature dependence of
the absorption coefficient. We assumed that absorption
coefficient at 15 K to be zero to simplify the analysis, andthat absorption coefficient is proportional to N0×exp(−ΔE/kBT), where ΔE, N0, and kB are the activationenergy for occupying the new peak state, the total
population, and the Boltzmann constant, respectively.
Figure 1(a) plots ln[Trans.(T)/Trans.(15 K)] at various
measurement temperatures T (in units of kelvin), where
Trans.(T) represents the transparent coefficient at T K.
Figure 1(b) shows a magnification around spectral peaks
A and B. Because we assumed the absorption coefficientof the new peaks at 15 K to be zero, the vertical values
are correlated with their absorption coefficient at T K.
Figure 2 plots the variation of the intensity of peak B in
Fig. 1(b) as a function of 1/T. The vertical axis expresses
ln{-ln[Trans.(T)/Trans.(15 K)]}. The gradient of thiscurve is −ΔE/kB, implying ΔE = 6 meV. This magnitude
is reasonable because we observed the new peaks with athermal energy of kBT (T = 20–40 K), of 2–4 meV. The
reduction of the absorption coefficient above 40 K is
attributed to the excitation of electrons to the conduction
band.
We propose the following model to explain theorigin of the new peaks (A and B). These lines areassociated with the excitation of electrons from theupper level of the ground state to the original 2p0, 2p+−,
and 3p+− states of the USTDs, arising from the level
splitting of the ground-state. This model is consistent
with the thermal excitation energy of 6 meV required
to generate new peaks because the optical energy-level
splitting between the upper level of the ground state
and the ground state is approximately 4 meV.
Ground-state splitting indicates that the wave
functions of the ground state of the USTDs arecomposed of linear combinations of the wave functionsof the conduction-band minimum.
In summary, the ground-state splitting of the USTDs
was observed. This is the direct evidence that the
ground state of the USTDs is composed of linear
combinations of wave functions of the conduction
band minimum.

Excitation to C.B.

-0.5
-1.0

6 meV

-1.5
-2.0
-2.5

0

0.01

0.02

0.03
0.04
1 / T (K-1)

0.05

0.06

Fig. 2. Temperature dependence of the absorption
coefficient of the new shallow donor. The vertical axis
is ln{-ln[Trans.(T)/Trans.(15 K)]}. The gradient reflects
the thermal activation energy.
[1] A. Hara, T. Awano, Y. Ohno and I. Yonenaga, Jpn. J.
Appl. Phys. 49 (2010) 050203.

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BL6B
BL6B

Far-Infrared Reflective Analysis
for Unipolar Fatigued Alkali Niobate Piezoceramics
H. Nishiyama, N. Matsubara, K. Yoshida, D. Ando, T. Fuchigami and K. Kakimoto
Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan�

Measured points
for each samples

Fitting curve
VirginAs-poled
Fatigued

250

500

R

1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0

Wave number [cm-1]

200

�
���

�
����
− � � − ��� �

VirginAs-poled
Fatigued

100

(1)

�

Figure 1 shows FIR reflectivity spectra for NKNadditive. Peak shifts and a change of waveforms wereobserved in all wavenumber range after polarization(As-poled) and fatigue treatment (Fatigued). Figure 2
shows real part (ε’) and imaginary part (ε’’) ofpermittivity calculated from the FIR reflectivity spectra
shown in Fig.1. The ε’’ peak shifted from 88.2 cm-1 to53.8 cm-1 with increasing intensity from 54.9 to 450.5
after polarization treatment. After the fatigue treatment,
the peak shifted to 65.4 cm-1 with decreasing intensity

0

-100

where, ε∞ is the high-frequency dielectric constant, ωpand ωTO are the plasma and transverse optic frequencies,and γ is the damping constant. The complex dielectric
function ε*(ω) = ε’(ω) – iε’’(ω) is related to thereflectivity R by Fresnel equation:�� ∗ (�) − 1� (2)�(�) � ��� ∗ (�) + 1

750

Fig. 1. FIR reflectivity spectra for NKN-additive. Dotlines indicate measured points. Colored lines indicate
fitting curves for each measured points.

ε’�(�) � �� + �

to 109.3. A similar tendency was observed in the ε’. On
the assumption that the ε’’ peak relates to the Slatermode (Nb-O vibrations), these results imply reductionof Nb-O ionic polarization getting back to the virginstate. Thus, we believe that FIR analysis is useful as anexperimental method to reveal the fatigue mechanismsof the electromechanical property.

ε’’

Ⅲ-2

Electromechanical property of piezoceramics changes
due to a long-term and repeated exposure to high unipolarelectric fields. Although some fatigue mechanisms of theelectromechanical property have been discussed based ona change of domain structure [1], an experimental fact has
not been showed directly. Previously, we have reported
that it is possible to clarify the difference in permittivity ε’of piezoceramics by analyzing IR reflectivity spectra [2].
In this study, we thought it was possible to clarify thechange of domain structure before/after fatigue
experiment by investigating the difference of thepermittivity in alkali niobate piezoceramics with farinfrared (FIR) reflectivity analysis. Especially, we
focused on ionic polarization in perovskites because
FIR analysis has been used to explain soft-mode theory
for displacive type of ferroelectric perovskites [3].
Alkali niobate piezoceramic, Li0.06Na0.52K0.42NbO3
with additives (Li2CO3, SiO2, MnCO3, and SrZrO3)(NKN-additive), was polarized in silicon oil under DC
field up to 4 kV/mm. Fatigue tests was carried out for
specimens under unipolar triangle waves up to 106 cycles
by applying electric field of 0 - 3 kV/mm with a frequencyof 50 Hz. FIR measurement was conducted by a FT-IR
spectrometer (Bruker, VERTEX 70v). A beam splitterand detector were used a Mylar 6 μm and Si bolometer,
respectively. The spectra were fitted to obtain complex
permittivity according to Drude-Lorentz equation:

400
300
200
100
0
0

VirginAs-poled
Fatigued

50

100

150

Wave number [cm-1]

200

Fig. 2. Real and imaginary part of permittivity for
NKN-additive calculated from FIR reflectivity spectra.
[1] F-Z. Yao et al., Appl. Phys. Lett. 103 (2013) 192907.
[2] Y. Taniguchi and K. Kakimoto, Jpn. J. Appl. Phys.
54 (2015) 10ND09.
[3] J. L. Servoin and F. Gervais, Phys. Rev. B 21 5 (1980)
2038.

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BL7U
BL7U

ARPES Study of Possible Topological Superconductor Tl0.5Bi2Te3
C. X. Trang1, Z. Wang2, D. Takane1, K. Nakayama1, S. Souma3, 4, T. Sato1, 4, A. A. Taskin2,
Y. Ando2 and T. Takahashi1, 3, 4

Department of Physics, Tohoku University, Sendai 980-8578, Japan
Institute of Physics II, University of Cologne, Köln 50937, Germany
3
WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
4
Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan1

2

The discovery of topological insulators (TIs), in
which a gapless topological surface state (SS) with a
Dirac-cone energy dispersion appears at the edge orsurface, has stimulated intensive investigations into aneven more exotic state of matter, a topologicalsuperconductor (TSC). TSCs generically possess agapless Andreev bound state at the edge or surface
which consists of Majorana fermions [1]. Owing to thepeculiar characteristics of Majorana fermions and thepotential application to a fault-tolerant quantum
computer, TSC is one of the emergent topics in current
condensed-matter physics. It has been suggested that asuperconductor derived from a TI is a promising
candidate for a TSC because of the strong spin-orbit
coupling that would lead to unconventional electron
pairing. However, only a limited number of candidate
materials, such as CuxBi2Se3, Cux(PbSe)5(Bi2Se3)6, andSrxBi2Se3, have been discovered and their topologicalproperties are still under intensive debate. It is thus ofgreat importance to explore new platforms of TSCs
and establish the electronic structure to investigate thepossible topological superconductivity.
In this study, we report high-resolution angleresolved photoemission spectroscopy (ARPES) on a
new TSC candidate, Tl0.5Bi2Te3 (Tc = 2.28 K) [2], which
is derived from thallium (Tl) doping into a prototypical
TI, Bi2Te3. By utilizing energy-tunable photons fromsynchrotron radiation, we determined the bulk andsurface electronic states and found that Tl0.5Bi2Te3
provides an excellent platform to realize topologicalsuperconductivity [3].
Figure 1(a) shows the experimental Fermi surface(FS) measured with hν = 21 eV whose k cut nearlycrosses the Z point of the bulk Brillouin zone. The FS
consists of three large and three small pockets slightly
away from the Z point. These FSs commonly have ahole-like character as recognized from the Fermi level(EF) crossing of the valence band (VB) in Fig. 1(b).
This demonstrates that Tl doping leads to a direct hole
doping into the VB top. Besides the M-shaped VB
feature, we found a V-shaped electron-like band in thevicinity of EF inside the valley of the VB. This tiny
feature is assigned to a topological SS. This indicatesthat the band-inverted nature is conserved even uponTl doping. As shown in Fig. 1(c), we were able to trace
the dispersion of the SS up to ~0.2 eV above the VB
top simply by keeping the samples in a vacuum of 2 
10-10 Torr for 12 h, which resulted in a significant

downward surface band bending. Since the surface
chemical potential can be systematically controlled by
the surface-aging technique, it is possible to wellisolate the topological SS from the bulk bands in boththe k space and the energy axis by controlling thestrength of the surface band bending. This is in favorof the realization of 2D topological superconductivity
in the topological SS through the proximity effect fromthe SC bulk. In this regard, the TlxBi2Te3 systemprovides an excellent platform to realize the 2D
topological superconductivity.

Fig. 1. (a) APRES intensity at EF in Tl0.5Bi2Te3 plotted
as a function of 2D wave vector. (b) and (c)Experimental band dispersion along yellow line in (a)measured just after cleaving (fresh) and 12 h aftercleaving (aged), respectively.
[1] Y. Ando, J. Phys. Soc. Jpn. 82 (2013) 102001.
[2] Z. Wang et al., Chem. Mater. 28 (2016) 779.
[3] C. X. Trang et al., Phys. Rev. B 93 (2016) 241103(R).

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BL7U

Slater to Mott Crossover in the Metal to Insulator Transition of Nd2Ir2O7
M. Nakayama1, T. Kondo1, Z. Tian1, J. J. Ishikawa1, M. Halim1, C. Bareille1, K. Kuroda1,
T. Tomita1, S. Ideta2, K. Tanaka2, M. Matsunami3, S. Kimura4,
L. Balents5, S. Nakatsuji1 and S. Shin1
1
ISSP, University of Tokyo, Kashiwa 277-8581, JapanUVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan3
Toyota Technological Institute, Nagoya 468-8511, Japan
4
Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
5
Kavli Institute for Theoretical Physics, Santa Barbara, California 93106, USA2

Ⅲ-2

The 5d iridium oxides (iridates), having comparable
scales for their kinetic energy, Coulomb interaction, andspin-orbit coupling, provide an excellent platform forstudying new types of strongly correlated phenomena.
Amongst them, the pyrochlore iridates (Ln2Ir2O7, where
Ln is a lanthanide), endowed with frustrated geometry
and cubic symmetry, have a particularly fascinatingphase diagram. Pr2Ir2O7, with the largest Ln ion, is ametallic spin liquid and exhibits an anomalous Hall
effect. For Ln ions with a smaller ionic radius, anantiferromagnetically ordered insulating phase appears
at low temperature.
Theoretically, topological band structures have been
ascribed to the Ln2Ir2O7 series. The metallic phase ispredicted to exhibit quadratically, dispersing conduction
and valence bands touching at the Γ point close to the
Fermi level (EF). We have recently identified thisstructure by angle-resolved photoemission spectroscopy(ARPES) in Pr2Ir2O7 [1]. Theory predicts that such aquadratic Fermi node state may be converted into
various topological states such as a topological insulator
or a Weyl semimetal by appropriate symmetry breaking.
Antiferromagnetism in these materials is of the Ising
type, consisting of an “all-in–all-out” (AIAO)
configuration of Ir moments on alternating tetrahedra.
This can be considered an “octupolar” spin order which
breaks time-reversal but preserves cubic symmetry, anddoes not enlarge the unit cell. Early density functional
studies predicted the magnetic state to be a Weyl
semimetal, and general arguments imply that, if aquasiparticle picture applies at low energy in theantiferromagnetic phase, and the magnetic ordering isweak, it must exhibit Weyl points and cannot have a true
gap. Nevertheless, optical and transport measurements
indicate a gapped insulating ground state for Nd2Ir2O7,
despite its low antiferromagnetic–metal-insulator (MI)transition temperature TMI ≈ 30 K and proximity tometallic Pr2Ir2O7. This begs the question of whether the
weakness of the order, the quasiparticle assumption, or
both, break down in this system. More generally, we
seek to understand the influence of the MI transition on
the conduction electrons.
We use ARPES to investigate the evolution of theelectronic structure through the MI transition in
Nd2Ir2O7, which is the most suitable member of theseries for such study because its low TMI minimizes
thermal broadening. Although the layered iridates havebeen extensively studied by photoemission, ours is thefirst study across a MI transition in any iridate, since thelatter occurs only in the pyrochlores. Using high-quality
single crystals, we are able to directly measure both thesingle particle excitations of the metallic and insulatingphases. Our data in Fig. 1 indicate that Nd2Ir2O7 displays
a dramatic Slater to Mott crossover with reducing
temperature [2]. This implies that Weyl fermions, if they
exist, may do so only in a narrow region of temperatureslightly below TMI, in which the order is, indeed, weakand quasiparticles can survive.

Fig. 1. Temperature evolution of ARPES dispersion
map across Γ showing a quadratic Fermi node state in
the metallic phase of Nd2Ir2O7, and its destruction uponcooling below TAF.
[1] T. Kondo et al., Nat. Commun. 6 (2015) 10042.
[2] M. Nakayama et al., Phys. Rev. Lett. 117 (2016)056403.

Ⅲ-2-3886

Ⅲ -2. Materials Sciences
BL7U
BL7U

d-wave Superconducting Gap Observed in the Protect-annealed Electrondoped Cuprate Superconductor Pr1.3-xLa0.7CexCuO4
M. Horio1, K. Koshiishi1, S. Nakata1, K. Hagiwara1, S. Ideta2, K. Tanaka2, A. Takahashi3,
T. Konno3, T. Ohgi3, T. Adachi4, Y. Koike3 and A. Fujimori1
Department of Physics, University of Tokyo, Tokyo 113-0033, JapanUVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan3
Department of Applied Physics, Tohoku University, Sendai 980-8579, Japan
4
Department of Engineering and Applied Sciences, Sophia University, Tokyo 102-8554, Japan1

2

The symmetry of the superconducting (SC) gap
provides a strong clue for the origin of unconventional
superconductivity. As for the electron-doped cuprate
superconductors, most of the previous studies havesupported d-wave symmetry [1, 2], and large contributionof antiferromagnetic (AF) spin fluctuations to thesuperconductivity has been proposed.
Recently, a new annealing method, which is called
protect-annealing, has enabled superconductivity inelectron-doped cuprates with lower Ce concentration
than that in previous studies [3]. This is probably
because the impurity apical oxygen atoms which
stabilize short-range antiferromagnetic (AF) order
have been efficiently removed by the improved
annealing. Our recent ARPES study on protect-annealed
Pr1.3-xLa0.7CexCuO4 (PLCCO, x = 0.10) has revealed
strong suppression of the AF pseudogap, suggesting a
dramatic reduction of the AF spin correlation length
and/or the magnitude of the fluctuating magnetic
moments [4]. In order to investigate the nature of the SC
state with a high Tc and suppressed antiferromagnetism,
we have performed ARPES measurements on protectannealed PLCCO (x = 0.10, 0.15) single crystals anddirectly observed a momentum-dependent SC gap.
Single crystals of PLCCO with x = 0.10 (samples#1-#3) and 0.15 (samples #4 and #5) were synthesized
by the traveling-solvent floating-zone method andwere protect annealed for 24 hours at 800 °C. After theannealing, samples with x = 0.10 and x = 0.15 showed
Tc’s of 27 K and 22 K, respectively. ARPES
measurements were performed at beamline 7U of
UVSOR facility. Linearly polarized light with hν =16.5 eV was used for the measurements. The totalenergy resolution was set at 8 meV. Considering therelatively quick surface degradation which is typicalfor electron-doped cuprates, ARPES spectra wererecorded within 4 hours after cleavage at only one
momentum position at two temperatures below andabove Tc for each sample.
Figure 1(a) shows energy distribution curves (EDCs)of PLCCO (x = 0.10) at the Fermi wave vector (kF) near
(π/2, π/2) and (0.3π, π), which are in the nodal andantinodal regions, respectively, in the case of dx2-y2-wave
paring. We compared the spectra taken above and below

Tc and estimated the magnitude of the leading-edge shift
Δshift caused by the opening of SC gap. EDCs near (π/2,π/2) taken above and below Tc cross almost at EF andΔshift is as small as 0.3 meV. On the other hand, thosenear (0.3π, π) cross appreciably below EF and a leadingedge shift of 1.3 meV was observed, which is also
confirmed in the measurements on another x = 0.10
sample as shown in Fig. 1(b). The same tendency also
applies to the x = 0.15 samples (Fig. 1(c)).
The present result suggests that dx2-y2-paring, whichis associated with strong electron correlation and AF
spin fluctuations, persists after the strong reduction of
AF correlation length and/or magnitude of thefluctuating magnetic moment by protect annealing.
The short-range AF order induced around the apicaloxygen atoms is harmful for superconductivity, but it
is still possible that electron correlation itself drive thedx2−y2-wave SC state in the electron-doped cuprates.

Fig. 1. Leading-edge shift observed in PLCCO samples.
EDCs of (a) samples #1 and #2 with x = 0.10, (b) sample#3 with x = 0.10, and (c) samples #4 and #5 with x = 0.15
measured at temperatures above (red curves) and below(blue curves) Tc. Insets indicate the kF positions where the
EDCs were taken.
[1] G. Blumberg et al., Phys. Rev. Lett. 88 (2002) 107002.
[2] H. Matsui et al., Phys. Rev. Lett. 95 (2005) 017003.
[3] T. Adachi et al., J. Phys. Soc. Jpn. 82 (2013) 063713.
[4] M. Horio et al., Nat. Commun. 7 (2016) 10567.

87
Ⅲ-2-39

Ⅲ-2

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BL7U

Electronic Structure of FeS
J. Miao1, X. H. Niu1, D. F. Xu1, Q. Yao1, Q. Y. Chen1, T. P. Ying1, S. Y. Li1,2, Y. F. Fang3,
J. C. Zhang3, S. Ideta4, K. Tanaka4, D. L. Feng1,2 and F. Chen31

Ⅲ-2

State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials,
Fudan University, Shanghai 200433, People's Republic of China
2
Collaborative Innovation Center of Advanced Microstructures, Nanjing, 210093, China
3
Materials Genome Institute, Shanghai University, Shanghai 200444, People's Republic of China
4
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan

Among all the iron-based superconductors, the ironchalcogenide FeSe has the simplest layered structure
yet extraordinarily rich physics [1]. The mostremarkable one is the interfacial superconductivity ashigh as 65 K in FeSe monolayer thin film grown on
SrTiO3 (001) substrate, which has attracted great
attention of the community [2].
As a counterpart, the bulk FeSe processes a
superconducting transition temperature of about 8K. It
will be further enhanced by hydrostatic pressure, surface
dosing or liquid gating to around 40K [3-5]. Element
substitution in the bulk is another effective way to
explore the properties of FeSe. Recently, it was foundthat by dilute S doping, the transition temperature of
FeSe1-xSx is first enhanced, then decreases upon further
substitution. The end member of this series, FeS, is still
superconducting with a Tc of 4.5 K[6-7]. The presenceof superconductivity in FeS is quite surprising, since S
substitution is expected to significantly reduce theelectron correlations which are crucial for theunconventional superconductivity. To address thissurprise, we performed angle-resolved photoemission
spectroscopy (ARPES) at BL7U to examine theelectronic structure of FeS.
Here we report the electronic structure of FeS. Our
high-resolution ARPES studies show two hole-like (αand β) and two electron-like (η and δ) Fermi pockets
around the Brillouin zone center and corner,
respectively, all of which exhibit moderate dispersion
along kz. However, a third hole-like band (γ) is notobserved, which is expected around the zone centerfrom band calculations and is common in iron-based
superconductors. Since this band has the highest
renormalization factor and is known to be the mostvulnerable to impurities, its absence in our data is likely
due to impurity scattering and yet superconductivity can
exist without coherent quasiparticles in the γ band. Thismay help resolve the current controversy on the
superconducting gap structure of FeS. Moreover, bycomparing the β bandwidths of various ironchalcogenides, including FeS, FeSe1-xSx, FeSe, andFeSe1-xTex, we find that the β bandwidth of FeS is thebroadest. However, the band renormalization factor of
FeS is still quite large, when compared with the bandcalculations, which indicates sizable electron
correlations. This explains why the unconventional
superconductivity can persist over such a broad range of
isovalent substitution in FeSe1-xTex and FeSe1-xSx.

Fig. 1. (a) Photoemission intensity distributions alongthe Γ-M direction taken with s- and p-polarized
photons, respectively. (b) Corresponding energy
distribution curves of data in panel (a) taken with spolarized photons. (c) Left panel: the band structure of
FeS measured by ARPES. Right panel: the calculated
FeS band structure along Γ-M reproduced from Ref.
[8]. All the ARPES data were taken with 30 eV photons.
[1] F. C. Hsu, J. Y. Luo, K. W. Yeh, et al., Proc. Natl.
Acad. Sci. U.S.A. 105 (2008) 14262.
[2] Q. Y. Wang, Z. Li, W. H. Zhang, et al., Chin. Phys.
Lett. 29 (2012) 037402.
[3] S. Medvedev, T. M. McQueen, I. A. Troyan, et al.,Nature Mater. 8 (2009) 630.
[4] B. Lei, J. H. Cui, Z. J. Xiang, et al., Phys. Rev. Lett.
116 (2016) 077002.
[5] C. H. P. Wen, H. C. Xu, C. Chen, et al., Nat.
Commu. 7 (2016) 10840.
[6] X. F. Lai, H. Zhang, Y. Q. Wang, et al., J. Am.
Chem. Soc. 137 (2015) 10148.
[7] U. Pachmayr, N. Fehn, and D. Johrendt, Chem.
Commun. 52 (2016) 194.
[8] A. Subedi, et al., Phys.Rev. B 78 (2008) 134514.

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BL7U

High-Resolution ARPES Study of Topological Line-Node Semimetal HfSiS
D. Takane1, Z. Wang2, S. Souma3, 4, K. Nakayama1, C. X. Trang1, T. Sato1, 4,
Y. Ando2 and T. Takahashi1, 3, 4
1Department of Physics, Tohoku University, Sendai 980-8578, Japan

Institute of Physics II, University of Cologne, Köln 50937, Germany
WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
4
Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
2

3

Topological semimetals are recently attracting agreat deal of attention. In contrast to conventional
semimetals with a finite band overlap between valenceband (VB) and conduction band (CB), topologicalsemimetals are categorized by the band- contacting
nature between the VB and CB in the Brillouin zone
(BZ); point-contact (Dirac/Weyl semimetals) or linecontact (line-node semimetals; LNSMs). The existenceof three-dimensional Dirac semimetals was first
confirmed in Cd3As2 and Na3Bi, where the VB and CB
contact each other at the point (Dirac point) protected byrotational symmetry of the crystal. Recent studies on
noncentrosymmetric transition-metal monopnictides(TaAs family) have clarified pairs of bulk Dirac-conebands and Fermi-arc surface states, supporting their
Weyl-semimetallic nature. While the existence ofDirac/Weyl semimetals with point nodes has been
confirmed experimentally, the experimental studies of
LNSMs with line nodes are relatively scarce despite
many theoretical calculations.
Recently, it was theoretically proposed that ZrSiO
with PbFCl-type crystal structure (space groupP4/nmm) and its isostructural family WHM [W = Zr,
Hf, or La; H = Si, Ge, Sn, or Sb; M = O, S, Se and Te;
see Fig.1 (a) for crystal structure] may host the LNSM
phase protected by a glide-mirror symmetry of thecrystal [1]. In this study, we performed high-resolution
angle-resolved photoemission spectroscopy (ARPES)
on HfSiS. By utilizing energy-tunable photons fromsynchrotron radiation, we determined the overall VB
structure and revealed the LNSM nature of HfSiS.
HfSiS crystal consists of a stack of S-Hf-Si-Hf-S fivesquare nets along c axis. A natural cleaving plane isindicated by an orange square in Fig. 1(a). The lowenergy electron diffraction (LEED) measurement on thecleaved surface shows a clear 11 pattern [see Fig. 1(b)],demonstrating high-quality nature of the cleaved surface.
Figures 1(c) and 1(d) show the ARPES-intensity plot
and the corresponding second-derivative-intensity plot,
respectively, in the VB region as a function of wave
vector and binding energy (EB) measured along the ΓM
cut at hν = 21 eV with linear polarization. One can notice
several dispersive bands; hole-like bands (α) at the Γpoint with the top of dispersion at 3 eV, an undulating
band (β) with the top of dispersion at 1.6 eV midway
between Γ and M, and linearly dispersive bands (γ, δ)
within 1.6 eV of the Fermi level (EF). These bands arewell reproduced in the band calculation [1]. According

to the band calculation, the γ and δ bands are attributed
to the electron-like Hf 5d and the hole-like Si 3p bands
at Γ, respectively. These bands intersect each other near
EF to form line nodes in the case of negligible spin-orbit
coupling (SOC) [1]. In fact, through the band-structure
mapping over entire BZ, we have observed the diamondshaped quasi-two-dimensional Fermi surface hosting line
nodes. Therefore the present observation supports the
LNSM nature of HfSiS.

Fig. 1. (a) Crystal structure of HfSiS. (b) LEED pattern
on a cleaved surface measured with a primary electronenergy of 90.5 eV. (c) and (d) Plots of ARPES intensity
and corresponding second- derivative intensity,
respectively, in the VB region measured at T = 40 K
along the ΓM line with linearly polarized 21-eV photons.
[1] Q. Xu et al., Phys. Rev. B 92 (2015) 205310.

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BL7U

Electronic Structure of Triple-layer Cuprate Superconductor
Bi2Sr2Ca2Cu3O10+δ Observed by ARPES
S. Ideta1, T. Yoshida2, S. Ishida3, K. Takashima4, S. Uchida3, 4, A. Fujimori4 and K. Tanaka1
National Institutes of Natural Science, Institute for Molecular Science, Okazaki, 444-8585, Japan
Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan
3
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan
4
Department of Physics, University of Tokyo, Tokyo 113-0033, Japan
1

2

Ⅲ-2

Effects of interlayer interaction between CuO2 planes
which may contribute the enhancement of criticaltemperature (Tc) in the multi-layer high-Tc cuprate
superconductors (HTSCs) have been investigated toelucidate the mechanism of superconductivity [1].
While it has been well known that the number of doped
carriers and the number of CuO2 planes are one of theessential factors to control the Tc of cuprates,
unexpectedly Tc does not decrease in the overdoped
Bi2Sr2Ca2Cu3O10+δ (Bi2223) [2]. In spite of extensive
studies both experimentally and theoretically [3-7], themicroscopic origin of the high-Tc superconductivity inthe triple-layer HTSCs still remains unclear.
We reported that the electronic structure of Bi2223
by ARPES showed two bands originating from theouter and inner CuO2 planes [8-10], and recently wealso observed the third band caused by the triple-layer
splitting [11]. Here, we report an ARPES study on
overdoped Bi2223 using low-energy photons and thelinearly polarized synchrotron light. In this study, we
found that each band shows a superconducting (SC)gap with different magnitude.
Single crystals of Bi2223 (Tc ~ 110 K) were grownby the travelling solvent floating zone method. ARPES
experiments were carried out at BL 7U of UVSOR
using hν = 7 eV - 8.5 eV photons. The total energy
resolution was set at 7 - 8 meV. Temperature was set at
T = 12 K and clean sample surfaces were obtained bycleaving single crystals in-situ in an ultrahigh vacuum
better than 710-9 Pa. The samples were aligned by
Laue diffraction and set so that the direction of Cu-O[(π, 0)-(π, π)] was perpendicular to the electric field
direction of the incident light.
In order to estimate the SC gap of overdoped Bi2223,
symmetrized energy-momentum (E-k) plots in theoffnodal region taken at different photon energies arepresented in Fig. 1. Black bars show the peak positionof the energy-distribution curve (EDC) indicating the
SC gap size. The SC gap estimated along the Fermi
surface (FS) is plotted as a function of the d-waveorder parameter in Fig. 1(c). The SC gaps of the innerplane band (IP) and outer-plane-antibonding band
(OP-AB) show almost the same magnitudes (ΔIP ~ 50
meV and ΔOP-AB ~ 40 meV) as the previous ARPES
study [8]; however, that of the outer-plane-bonding
band (OP-BB) shows a smaller gap size at the antinode(ΔOP-BB ~ 20 meV). This result indicates that the large

SC gap of OP-AB may contribute to the higher Tc in
the overdoped Bi2223.
As future work, we need to investigate the Fermi arc
length in order to determine how much these three bands
contribute to the superconductivity. Also, theoreticalwork to interpret the different SC gap magnitude of thethree bands should be done.

Fig. 1. Symmetrized E-k plots in the Cu-O bonddirection taken at hν = 8 and 7.5 eV (T = 12 K) and SC
gap anisotropy. IP, OP-AB, and OP-BB indicate theinner, middle, and outer bands, respectively.
[1] J. M. Wheatley et al., Nature 333 (1988) 121.
[2] T. Fujii et al., Phys. Rev. B 66 (2002) 024507.
[3] E. Pavarini et al., Phys. Rev. Lett. 87 (2001) 047003.
[4] S. Chakravarty et al., Nature 428 (2004) 53.
[5] S. Okamoto et al., Phys. Rev. Lett. 101 (2008) 156401.
[6] D. L. Feng et al., Phys. Rev. Lett. 88 (2002) 107001.
[7] T. Sato et al., Phys. Rev. Lett. 91 (2003) 157003.
[8] S. Ideta et al., Phys. Rev. Lett. 104 (2010) 227001.
[9] S. Ideta et al., Phys. Rev. B 85 (2012) 104515.
[10] S. Ideta et al., Physica C 470 (2010) S14-S16.
[11] S. Ideta et al., Activity repot 43 (2015) 45.

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Self-Energy in the Superconducting States of the High-Tc Cuprates
Bi2Sr2CaCu2O8+δ
D. Ootsuki1, K. Yamawaki1, D. Shimonaka1, D. Shibata1, H. Eisaki2, T. Sasagawa3,
A. Fujimori4, S. Ideta5, K. Tanaka5 and T. Yoshida1

Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8562, Japan
3
Materials and Structures Laboratory, Tokyo institute of Technology, Yokohama 226-8503, Japan
4
Department of Physics, University of Tokyo, Tokyo 113-0033, Japan
5
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan

1

2

Angle-resolved
photoemission
spectroscopy(ARPES) can directly detect the spectral function
A(k,ω) and, hence, one can determine the self-energy
Σ(k,ω). From the discovery of the kink structure in thehigh Tc-cuprate superconductors, a considerable
number of studies have been conducted on the selfenergy in the nodal region where the superconducting
gap closes [1, 2]. On the other hand, the self-energy inthe anti-nodal region in the superconducting states also
has many information of the formation of Cooperparing. Several studies have reported the self-energy inthe anti-nodal region in the superconducting state andpointed out that there is a bosonic structure [3, 4].
However, the origin of the bosonic mode has not beenclarified yet.
In the present study, we have performed an ARPES
study of the over-doped Bi2-xPbxSr2CaCu2O8+δ (PbBi2212) in order to determine the self-energy in the
superconducting state. Here, we have applied KramarsKronig relation to A(k,ω) for deducing the self-energy
Σ(k,ω) in a wide energy range [3, 5]. ARPES experiment
was carried out at BL7U of UVSOR. All the data weretaken with the photon energy hν = 22.7 eV. The totalenergy resolution was ~10 meV. The single crystal PbBi2212 was cleaved in the pressure better than 1.6×10-8
Pa. The measurement temperature were T = 16 K and
110 K.
Figure 1 shows the spectral function A(k,ω), the realpart ReΣ(k,ω) and the imaginary part ImΣ(k,ω) of theself-energy deduced from ARPES spectra using the
Kramers-Kronig transformation. A sharp quasiparticle
peak appears corresponding to the gap opening in the
superconducting state in Fig.1 (a). In the imaginary
part of the self-energy ImΣ(k,ω), the peak at EF
increases from the nodal to anti-nodal regions, whichindicates the d-wave superconducting gap. In the antinodal region, the dip structure around 50 meV are
observed in the spectral function, compared with thatin the normal state. This dip structure in A(k,ω)
corresponds to the drop in the imaginary part ImΣ(k,ω)
and is suppressed in going from the anti-nodal region
to the nodal region. Also, the same energy scale ~50
meV appears in the ReΣ(k,ω) below Tc, particularly inthe anti-nodal direction.

In summary, we have deduced the self-energy in the
superconducting states and found a characteristicenergy scale ~50 meV, corresponding to the peak-dip
hump structure of the spectral function. Since thecharacteristic structure evolves in the anti-nodal region,
the observed energy scale may be relevant to the signalof the Cooper paring.

Fig. 1. (a) Spectral function A(k,ω) for the overdoped Pb-Bi2212. (b),(c) The real part ReΣ(k,ω) andimaginary part ImΣ(k,ω) of the self-energy deduced
from the ARPES spectra using the Kramers-Kronigtransformation.
[1] P. D. Johnson et al., Phys. Rev. Lett. 87 (2001) 177007.
[2] A. Lanzara et al., Nature 412 (2001) 510-514.
[3] M. R. Norman et al., Phys. Rev. B 60 (1999) 7585.
[4] J. M. Bok et al., Sci. Adv. 2 (2016) e1501329.
[5] S. Aizaki et al., Phys. Rev. Lett. 109 (2012) 056401.

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Superconducting Gap of Sr1-xCaxFe2(As1-yPy)2 (x = 0.08, y = 0.25)
Revealed by Angle Resolved Photoemission Spectroscopy
T. Adachi1, S. Ideta2, 3, K. Tanaka2, 3, Z. H. Tin1, S. Miyasaka1 and S. Tajima1

Graduate School of Science, Department of Physics, Osaka University, Toyonaka 560-0043, Japan
2
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan3
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan1

Ⅲ-2

It is essential for elucidating the superconducting
mechanism to evaluate the anisotropy of superconducting
gap sizes in k-space. In our measurement performed lastyear, the topology of Fermi surfaces and thesuperconducting gap sizes on some points of Fermi
surfaces in Sr1-xCaxFe2(As1-yPy)2 (x = 0.08, y = 0.25) havebeen clarified. In this material, we have detected the gap
minimum, which is possibly a node, in the outer electron
Fermi surface around X point [1]. On the other hand,according to tight binding model + RPA calculation [2],it has been pointed out that there are superconducting
gap nodes in the outermost hole Fermi surface among
three hole Fermi surfaces around Z point in phosphorus
doped 122 systems.
In this measurement, we observed the electronic
structure, particularly the superconducting gap structureof hole Fermi surfaces near Z point of Sr1-xCaxFe2(As1-yPy)2(x = 0.08, y = 0.25, Tcmax=32K). Figure 1(a) shows Fermi
surface mapping around Z point. We observed three holeFermi surfaces around Z point, indicated by broken lines
in Fig. 1(a). The superconducting gap values have been
estimated at the points on these Fermi surfaces, which
are indicated by dots in Fig. 1(a).
Figure 1(b) shows the superconducting gap value
around Z point as a function of Fermi surface angle θFS.
Here, θFS is restricted between 0 and 90 degrees
reflecting the C4 rotational symmetry of the crystal
structure. The superconducting gaps on hole Fermi
surface show small anisotropy but any node likebehavior has not been detected. Considering the present
and previous our results, only spin fluctuation due toFermi surface nesting is not sufficient to explain the
superconducting gap structures of phosphorus doped
122 systems. Our experimental results indicate that it isneeded to take into account of the hybridization between
the two electron pockets which makes the interlayer
hopping finite, or the multiorbital effects such as orbital
fluctuation due to interorbital quadrupole interaction[3, 4].

Fig. 1. (a) Fermi surface mapping around Ζ point in
Sr1-xCaxFe2(As1-yPy)2 (x = 0.08, y = 0.25). Three holeFermi surfaces are indicated by the broken lines. The
dots indicate the point, where the superconducting gap
is estimated. θFS is Fermi surface angle. (b)Superconducting gaps around the Ζ point as a functionof θFS.
[1] T. Adachi et al., UVSOR activity report 43 (2016).
[2] K. Suzuki et al., J. Phys. Soc. Jpn. 80 (2011) 013710.
[3] M. Khodas et al., Phys. Rev. B 86 (2012) 144519.
[4] T. Saito et al., Phys. Rev. B 88 (2013) 045115.

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BL7B

Luminescence Properties of Ce- or Nd-doped SrAl2O4 Crystals with
Vacuum Ultraviolet Excitation
D. Nakauchi1, M. Koshimizu2, T. Yanagida1, G. Okada1, Y. Fujimoto2 and K. Asai2
Nara Institute of Science and Technology, Ikoma 630-0101, Japan
Graduate School of Engineering, Tohoku University, Sendai 9808579, Japan
1

2

Luminescence materials based on SrAl2O4 haveextensively studied from a viewpoint of long-term
persistent phosphors. In such usage, trap sites forelectron-hole pairs are introduced by co-doping strategy.
On the other hand, we recently reported excellent
scintillation properties of Ce-, Eu-, or Nd-doped
SrAl2O4 [1–3]. The band gap energy of SrAl2O4 isreported to be 6.5 eV, which corresponds to the energyof a photon with wavelength of 190 nm [4]. Therefore,vacuum ultraviolet (VUV) light is a suitable tool for
analyzing the luminescence properties in the case of
host excitation. In this report, we present theluminescence properties of Ce- or Nd-doped SrAl2O4
crystals with an emphasis on those with VUV excitation.
Undoped, Ce-doped, and Nd-doped crystals weregrown in a floating zone method. Luminescence spectrawith VUV excitation were measured at the Beamline 7B
at UVSOR. X-ray-induced radioluminescence (RL)
spectra were obtained using a CCD detector equippedwith a monochromator.
Figure 1 shows the X-ray-induced RL spectrum of
1.0% Ce-doped SrAl2O4 crystal. A broad emission bandat 380 nm is attributed to 5d-4f transition of Ce3+ ions.
Figure 2 shows the excitation spectrum of a 1.0% Cedoped SrAl2O4 crystal. The monitored wavelengths
correspond to the 5d-4f transition of Ce3+ ions. 4f-5dtransitions are clearly observed at 120 and 150 nm, in
addition to a band-edge at 180 nm.
Figure 3 shows the photoluminescence spectra ofundoped and Nd-doped SrAl2O4 crystals with excitation
at 160–180 nm. The observed bands for the Nd-doped
samples can be attributed to self-trapped excitons
perturbed by Nd3+ ions.

Ⅲ-2

Fig. 2. Excitation spectra of 1.0% Ce-doped SrAl2O4
crystal. The monitored wavelengths correspond to the
5d-4f emission of Ce3+ ions.

Fig. 3. Photoluminescence spectra of undoped and Nddoped SrAl2O4 crystals with excitation at 160–180 nm.
[1] D. Nakauchi, G. Okada, M. Koshimizu and T.
Yanagida, Nucl. Instrum. Methods Phys. Res. B 377(2016) 89.
[2] D. Nakauchi, G. Okada, M. Koshimizu and T.
Yanagida, J. Lumin. 176 (2016) 342.
[3] D. Nakauchi, G. Okada, M. Koshimizu and T.
Yanagida, J. Rare Earths 34 (2016) 757.
[4] D. Jia, X.-J. Wang, W. Jiad and W. M. Yen, J. Lumin.
122–123 (2007) 311.

Fig. 1. X-ray-induced RL spectra of 1.0% Ce-doped
SrAl2O4 crystal.

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Optical Properties of Pr3+ and Ce3+ Co-doped APLF Glass
as a Fast Neutron Scintillator
T. Shimizu1, Y. Minami1, M. J. F. Empizo1, M. V. Luoug1, T. Taniguchi1, A. Shiro1,
J. Watanabe1, K. Yamanoi1, N. Sarukura1 and T. Murata2
Institute of Laser Engineering, Osaka University, Suita 565-0871, Japan
Faculty of Education, Kumamoto University, Kumamoto 860-8555, Japan

1

2

Ⅲ-2

Neutron detection plays an important role in oursociety. Several characteristic parameters can beobtained by measuring neutrons which are generated
by the fusion reaction and then elastically scattered in
the high-density fusion plasma. On the other hand,neutron detection is considered as one of the nondestructive methods to inspect forms of infrastructure.
Scintillator materials which are able to detect anddiscriminate neutrons should then be developed to beable to satisfy the demand.
The complex fluoro-oxide glass, 20Al(PO3)3-80LiF(APLF) has been investigated as a candidate neutron
scintillator material due to its high 6Li content and fast
decay times [1]. APLF glasses doped with Pr and Ceions exhibit less than 30-ns decay times with optical, xray, and radioactive excitation. With broadband energy
neutron excitation from 252Cf, Pr-doped and Ce-doped
APLF glasses have fast decay times of 5.3 and 28.9 ns,
respectively, which are faster than a conventional
scintillator, GS2 [2]. But like most scintillator materials,
the fast lifetimes come at the expense of the emission
intensities. To achieve fast decay times and highconversion efficiencies, we then devise a way to codope APLF glass with Pr and Ce. In this study, weinvestigate the optical properties of Pr/Ce-doped APLF
glasses with different concentrations using the BL7B of
UVSOR.
The optical properties of the Pr/Ce-doped APLF
glasses were characterized using room-temperature
photoluminescence (PL) and photoluminescence
excitation (PLE) spectroscopies. Three samples wereprepared, namely: (1) APLF glass doped with 1.0 mol%Pr and 2.0 mol% Ce (APLF+1.0Pr/2.0Ce); (2) APLF
glass doped with 1.5 mol% Pr and 1.5 mol% Ce or(APLF+1.5Pr/1.5Ce); and, (3) APLF glass doped with
2.0 mol% Pr and 1.0 mol% Ce or (APLF+2.0Pr/1.0Ce).
All samples were cut into 20-mm diameter cylinders
with 8-mm thickness and were polished on both sides toan optical finish.
Figure 1 shows the PL spectra of the Pr/Ce-doped
APLF glasses with 200-nm excitation. The emission
peaks, which shift to lower wavelengths withdecreasing Ce concentration, correspond to the interconfigurational 5d-4f transition of Ce3+. In addition, allsamples exhibit small emission peaks, whichcorrespond to the 4f5d  3H4, 1S0  3F4, and 1S0 
1G4 transitions of Pr3+. The intensity of these emission
peaks increases with increasing Pr concentration.
Figure 2 shows the PLE spectra of the Pr/Ce-doped
APLF glasses monitored at their dominant peakemissions (~ 340 nm). This glasses exhibits a broad
excitation channel and a peak at 270 nm regardless of
the Pr and Ce concentration. These results suggest thatthe ~ 340-nm emission (5d-4f Ce3+ transition) has
efficient excitation with 270 nm as evidenced by the
PL spectra of the Pr/Ce-doped APLF glasses with 270nm excitation in Fig. 2. On the other hand, the PLE
spectra monitored at around the emissions
corresponding to the Pr3+ transitions are not recorded
because of their weak intensities.
The effect of co-doping on the optical properties of
APLF will be elucidated in the future.

Fig. 1. PL spectra of Pr/Ce-doped APLF glasses with
200-nm excitation.

Fig. 2. PLE monitored at ~ 340 nm and PL spectra with
270-nm excitation of Pr/Ce-doped APLF glasses.
[1] Y. Arikawa et al., Rev. Sci. Instrum. 80 (2009)
113504.
[2] Y. Arikawa et al., Rev. Sci. Instrum. 81 (2010)
106105.

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Excitation and Emission Spectra of Pr-doped SrY2O4
M. Yoshino, S. Nishiki and S. Watanabe

Graduate School of Engineering, Nagoya University, Nagoya 464-8603, JapanThe trivalent lanthanide ions (e.g., Ce3+, Nd3+, Er3+) in
oxide crystals have drawn attentions due to theirapplication for luminescent materials in NIR to UV
regions such as solid-state lasers, phosphors or
scintillators. The trivalent praseodymium ion, Pr3+, hasalso attracted attentions as luminescence centers. In thiswork, the excitation spectra and emission spectra for Pr3+
in SrY2O4 crystal have been measured. The Pr-doped
SrY2O4 samples are synthesized by solid state reactions.
The samples are annealed in N2-H2 atmosphere in orderto reduce Pr4+ to Pr3+. The concentration of Pr in thesamples are 0.2, 1.0 and 5.0 mol%.
The excitation spectrum monitored at 518 nm
emission is shown in Fig. 1. The peak near 200 nm
relates the absorption from the optical transition
around the band edge in SrY2O4. This corresponds tothe peak in the spectrum monitored at 423 nm in pureSrY2O4 [1]. The absorption around 315 nm and 273 nm
originate the 4f-5d transitions of Pr3+. The emission
spectra at 315 and 273 nm excitation in 300 K areshown in Fig. 2 and Fig. 3, respectively. Peaks A, B, C
exist in the each spectra. On the other hand, peak D
appears only in 273 nm excitation and has different
dependency to Pr concentration compared with theother peaks. The intensity of D decrease with Pr
concentration while it decreases after the increase in A,
B and C. The emission spectra at 273 nm excitation indifferent temperatures are shown in Fig. 4. It is foundthat the peak D has also different dependency totemperature compared with the peaks A, B and C.

Ⅲ-2
Fig. 2. Emission spectra of SrY2O4:xPr.
(λex= 315 nm, 300 K)

Fig. 3. Emission spectra of SrY2O4:xPr.
(λex= 273 nm, 300 K)

Fig. 1. Excitation spectrum of SrY2O4:0.010Pr.
Fig. 4. Emission spectra of SrY2O4:0.002Pr.
(λex= 273 nm)[1] M. Yoshino, S. Watanabe and Y. Ichikawa, UVSOR
Activity Report 36 (2009) 122.

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Optical Conductivity of Zn-Ag-Sc Quasicrystal and Approximant Crystal
1

Ⅲ-2

K. Imura1, M. Hayashi1, S. Kimura2, 3 and N. K. Sato1

Department of physics, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
2
Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan3
Department of Physics, Osaka University, Toyonaka 566-0043, Japan

Quasicrystal (QC) is a solid in which constituent
atoms are arranged according to a special rule “quasiperiodicity”. QCs show a sharp x-ray diffraction
pattern as shown in usual crystals, however, peculiar
five or ten folded rotation symmetry is observed which
is forbidden to normal crystals [1]. Therefore, theelectronic state of the QC is considered to be different
from the normal one; however, it has not been clarified
experimentally yet. Zn-Ag-Sc QC which has an
isostructural to a typical binary icosahedral Cd-Yb QC[2], and Zn-Ag-Sc approximant crystal (AC), which
has locally the same structure as QC are target
materials of this study.
Polycrystalline Zn-Ag-Sc QC and AC wereobtained by annealing method using an evacuatedquartz tube. The reflectivity measurement in thevisible, ultraviolet, and vacuum-ultraviolet region i.e.,
the photon energy region of 1.2-30 eV, was performedat the BL7B which consists of a 3-m normal incidence
monochrometer at room temperature. Low-energy
reflectivity (0.01-1.5 eV) has been carried out by using
a Michelson-type rapid-scan Fourier spectrometer at
selected temperatures from 10 to 300 K. The opticalconductivity spectra σ(ω) were obtained from the
Kramers-Kronig analysis (KKA) of the reflectivity
spectra extrapolating to zero-energy (DC) limit
assuming Hagen-Rubens relation.
Figure 1 shows an incident energy dependence of thereflectivity R(ω) at several temperature. Comparing
between QC and AC, R(ω) of QC is higher than AC in awide energy region and some broad structures areobserved at around 0.09, 1 and 3 eV.
Figure 2 shows optical conductivity spectra σ(ω) of AC
at several temperatures from 10 to 300 K obtained by
KKA. σ(ω) slightly increases as decreasing temperature
which is consistent with the DC conductivity as shown in
the inset of Fig. 2. It does not seem to reach the DC valueeven if it is extrapolated smoothly.
σ(ω) decreases as increasing photon energy at wholetemperatures. This energy dependence is qualitatively
different from icosahedral-QC Al-Cu-Fe: the σ(ω)
increases linearly from DC limit to near-IR region [3].
An understanding of this difference may give important
information to elucidate the electronic state of the QC.
In order to clarify the low-energy electronic state,further experiments are needed.

Fig. 1. Incident photon energy dependence of thereflectivity of Zn-Ag-Sc quasicrystal (T = 300 K)
and 1/1 approximant crystal (T = 10, 20, 50, 100,
200, 300 K).

Fig. 2. Incident photon energy dependence of the
optical conductivity of Zn-Ag-Sc 1/1 approximant
crystal. Closed circles show DC conductivity
measured by conventional four terminal method.
[1] D. Shechtman, I. Blech, D. Gratias and J. W. Cahn,
Phys. Rev. Lett. 53 (1984) 1951.
[2] H. Takakura, C. P. Gomez, A. Yamamoto, M. Boissieu
and A. P. Sai. Nature Matter. 6 (2007) 58.
[3] C. C. Homes, T. Timusk, X. Wu, Z. Altounian, A.
Sahnoune and J. O. Strom-Olsen, Phys. Rev. Lett. 67(1991) 2694.

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Effects of Fluorine Substitution on the Bi 6s-6p Transition of Zinc Bismuth
Phosphate Glass
N. Kitamura-1-1(55-x)ZnO-xZnF2-20Bi2O3-25P2O5 Glass

4

5
10
15

x=0

3

20

Ⅲ-2

2
1
Eabs

0

1.61.7 3.0

3.5

Photon energy/ eVFig. 1. Absorption spectra of (55-x)ZnO-xZnF220Bi2O3-25P2O5 glasses.[4]BiF312%ZnF2 sub.glass
8%ZnF2 sub.glass

0.15

Reflectivity

Bismuth phosphate glasses, which have high refractive
index and low deformation temperature, are candidate
materials for producing high performance opticalcomponents such as compact lenses and diffractive 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 theregion that the atomic ratio O/P is higher than 3.5 andmetaphosphate and pyrophosphate structures are
dominant in the region of O/P < 3.5 [1, 2]. We havereported the glass structure and local structure aroundbismuth ions in a previous work [2, 3]. Recently, we
found that the absorption edge of the glasses in the region
O/P<3.5 shifts higher energy side by substituting ZnF2 forZnO [4], as shown in fig. 1. In the present study,
reflectivity of the fluorine substituted bismuth phosphateglasses has been measured to make clear the band
structure in the vacuum ultraviolet region.
Ternary 55ZnO-20Bi2O3-25P2O5 glass was used a baseglass. Fluorine doping was performed by substituting
ZnF2 for ZnO in the mixture of starting materials (ZnO,
Bi2O3, and Zn(PO3)2). Fluorine content was determinedby the electron probe micro analysis (EPMA). Two
samples, 8%ZnF2 (x=10 in fig.1) and 12%ZnF2 (x=20 in
fig. 1) substituted glasses, were used for reflection
measurement. Reflectivity of optically polished samples
was measured in the photon energy region of 3.6-25 eV
with an incident angle of 10˚ at the BL7B.
Figure 2 shows reflection spectra of the un-substituted
55ZnO-20Bi2O3-25P2O5 glass, and 8% and 12% ZnF2
substituted glasses. Spectra for polycrystalline samples of
BiF3, ZnF2 and ZnO were also shown in the figure.
Distinct reflection peak and broad contour wererespectively observed at around 4.5 eV and 5-10 eV. The
peak and contour are assigned to the 6s2→6s16p1
transition in the Bi3+ ion [2, 4-6]. We know that transitions
from the ground state (1S0) to excited states 3P0 and 3P2
are spin-forbidden, but transition to 3P2 level would beallowed by spin-orbit coupling [6]. Therefore, the lower
distinct peak is expected to the 1S0→3P1 transition and thenext contour could be due to the 1S0→3P2 and 1S0→1P1
transition at least. The peak of BiF3 was located at about
5.0 eV. The lowest peak at 4.5eV for the glass sample
shifted toward higher energy side by the substitution, andthe magnitude of the peak shift was about 0.3 eV by the
12%ZnF2 substitution. It was very consistent with theabsorption edge shift (~0.3eV). It was deduced that someof substituted fluorine ions would terminated to bismuthions directly for oxygen ions.

Molar extinction coefficient /cm mol lNational Institute of Advanced Industrial Science and Technology, Ikeda 563-8577, Japan

0.10

No sub. glass
ZnO

0.05
4

6

8

10

12

ZnF2

14

Photon energy/ eV

1618

Fig. 2. Reflection spectra of 8% and 12% fluorine (ZnF2)
substituted 55ZnO-20Bi2O3-25P2O5 glass. Spectra of un-

substituted glass, polycrystalline BiF3, ZnO and ZnF2
also shown.

[1] B. Elouadi et al., Phase Trans. 13 (1988) 219.
[2] N. Kitamura et al., Mater. Sci. Eng. B 161 (2009) 91.
[3] N. Kitamura and K. Fukumi, J. Ceram. Soc. Jpn.
121 (2013) 355.
[4] N. Kitamura et al., J. Non-Crysta. Solids 357 (2011)
1188.
[5] G. Blasse and A. Bril, J. Chem. Phys. 48 (1968)
217.
[6] R. H. P. Awater and P. Dorenbos, J. Lumin. 184(2017) 221.

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