Ⅲ-2

Materials SciencesⅢ -2. Materials Sciences

BL1B

Terahertz Reflectivity Spectra of Superionic Conductors
T. Awano

Faculty of Engineering, Tohoku Gakuin University, Tagajo 985-8537, Japan
Superionic conductors are solids which have highionic conductivity as liquids or electrolyte solutions. I
have measured their reflectivity spectra at millimeterwave and far-infrared region to investigate motions ofmobile and immobile ions [1-7]. Ionic plasmonic
feature in energy loss function spectra were observedin millimeter wave region of these superionic
conductors.
Terahertz spectral region is the frequency region
between vibration and translation motion of themobile ion. The “attempt mode” of conduction ion
were also observed in these superionic crystals. Thisvibrational mode is directly connected withtranslational movement of conduction ion. Namely,
silver ion surrounded by iodine tetrahedron try tomove out at this frequency, c.a. 20 cm-1.
On the other hand, the attempt mode was not clear
in AgI-based superionic conductive glasses.
Therefore, precise measurement of reflectivity spectraof these glasses was executed at the new terahertz
beam line BL1B.
Reflectivity spectra of (AgI)0.5(AgPO4)0.5 glassesand (AgI)0.75(Ag2MoO4)0.25 glasses were measured by
FARIS Martin-Puplett interferometer and QMC InSb
hot electron bolometer. The spectral region is suitable
for the observation of the attempt mode of silver ion.
Figure 1 shows spectra of four glass samples atroom temperature. The attempt mode was observed in#1 sample of each glass. In contrast, #2 samples
showed no such absorption at 20 cm-1. This difference
seems to be due to the difference of glass structure.
Much AgI-clusters may exist in the #1 glass samples.
Characterization of the glass structure is necessary to
make it clear.
Proton conductors are interested because of the use
in fuel cells. The Cs2(HSO4)(H2PO4) crystal is a
newly discovered room temperature proton
conductor[8]. It keeps high ionic conductivity once
after heating above 380 K. It is interesting to makeclear the mechanism of such conductivity dependenceby thermal history. Figure 2 shows reflectivity spectraof (AgI)0.5(AgPO3)0.5 glasses at room temperature.
Anisotropic peaks were observed as shown in the Fig.
2. The measurement of the change of these absorption
bands after the heating is underway.

(AgI) 0.5(AgPO 3)0.5 #1(AgI) 0.5(AgPO 3)0.5 #2(AgI) 0.75 (Ag2MoPO 4)0.25 #1(AgI) 0.75 (Ag2MoPO 4)0.25 #2

REFLECTIVITY

0.4

0.3

Ⅲ-2

0.2
10

20
-1
WAVE NUMBER (cm )Fig. 1. Reflectivity spectra of (AgI)0.5(AgPO3)0.5 and(AgI)0.75(Ag2MoO4)0.25 glasses.

REFLECTIVITY

0.4
0.3
0.2
0.1
0
10

Cs2(HSO 4)(H2PO4)

E // bE⊥b30
50 70 90
-1
WAVE NUMBER (cm )Fig. 2. Reflectivity spectra of Cs2(HSO4)(H2PO4)
crystal.
[1] T. Awano, T. Nanba, M. Ikezawa, T. Matsuyama
and H. Yamaoka, Solid State Ionics 53-56 (1992)
1269.
[2] T. Awano, Infrared Phys. Tech. 51 (2008) 458.
[3] T. Awano and T. Takahashi, J. Phys. Soc. Jpn. 79
suppl.A (2010) 118.
[4] T. Awano and T. Takahashi, Journal of Physics:
Conference Series 148 (2009) 012040.
[5] T. Awano and T. Takahashi, Proc. 13th Asian
Conference on Solis State Ionics, World Scientific(2012) 569.
[6] T. Awano, T. Nanba and M. Ikezawa, UVSOR
Activity Report 1992 20 (1993) 146.
[7] T. Awano, UVSOR Activity Report 2011 39(2012) 91.
[8] C. R. I. Chisholm and S.M. Haile, Acta Cryst.
B55 (1999) 937.

47

Ⅲ -2. Materials Sciences

BL1B

THz Spectra of Hole-Doped CeOs2Al10
1

H. Takao , S. Kamei1, Y. Yamada2, J. Kawabata2, T. Takabatake2 and S. Kimura3,1
1

Department of Physics, Osaka University, Toyonaka 56-0043, Japan
ADSM, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
3
Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan2

Ⅲ-2

Kondo insulators/semiconductors (KIs) arematerials with a tiny energy gap at the Fermi level(EF) owing to the hybridization between conduction
and localized 4f electrons, namely c-f hybridization.
Because of the strong c-f hybridization intensity, KIs
do
not
order
magneticallybythe
Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction.
However, recently observed KIs, CeM2Al10 (M = Ru,Os), have an antiferromagnetic magnetic ordering at
the temperature (T0) of about 27 K [1]. Since theordering temperature is too high compared with that
expected from the de Gennes factor [2], anothermechanism of the magnetic ordering besides the
RKKY interaction is anticipated.
One of such TIs, CeOs2Al10 has a clear energy gap
below the photon energy of about 50 meV [3]. T0 of
this material is strongly suppressed by the hole
doping due to the substitution of Os by Re,
Ce(Os1-xRex)2Al10, and disappears at x = 0.05 [4].
Then we have investigated the relation of the c-f
hybridization gap to the magnetic ordering using thematerial of x = 0.05.
CeM2Al10s have anisotropic crystal and electronic
structures as well as the anisotropic c-f hybridization
intensity [5]. The energy gap owing to the c-f
hybridization clearly appears along the c axis. Then
we measured the temperature-dependent polarizedreflectivity [R( , T)] spectra of x = 0.05 along the caxis at the beamline 1B using an automatic
measurement system [6].
The obtained R(, T) spectra divided by that at 80
K in the terahertz region of 3  10 meV (0.7  2.4
THz) are shown in Fig. 1. Since the spectrum at 80 K
is almost unity in this energy region because of its
metallic conductivity, the R(, T)/R(, 80 K) spectra
are nearly equal to R( , T). The R(, T) spectrum
strongly depends on temperature in this region. Thisorigin is considered to be the temperature-dependent
Drude weight due to carriers excited over an energy
gap. This is the evidence of the existence of theenergy gap.
The energy gap originates from the c-f
hybridization, which remains at x = 0.05 even though
the magnetic ordering disappears. This suggests thatthe c-f hybridization is not the sufficient condition forthe magnetic ordering. However, in the case of other
RM2Al10 (R = other rare-earth ions), which has no c-f
hybridization, magnetic ordering temperature obeys
the de Gennes factor indicating the RKKY interaction[2]. Therefore the c-f hybridization is basicallyneeded for the appearance of the high ordering
temperature T0. These facts suggest that the unusual
magnetic ordering of CeM2Al10 does not directly
originate from but indirectly relates to the c-f
hybridization.

Fig. 1. Temperaturedependenceofrelativereflectivity spectrum of Ce(Os0.95Re0.05)2Al10 divided
by that at 80 K in the photon energy region of 3  10
meV (0.7  2.4 THz).The observed Drude spectral
weight is suppressed with decreasing temperature.
[1] T. Nishioka, Y. Kawamura, T. Takesaka, R.
Kobayashi, H. Kato, M. Matsumura, K. Kodama, K.
Matsubayashi and Y. Uwatoko, J. Phys. Soc. Jpn. 78(2009) 123705.
[2] Y. Muro, J. Kajino, T. Onimaru and T. Takabatake,
J. Phys. Soc. Jpn. 80 (2011) SA021.
[3] S. Kimura, T. Iizuka, H. Miyazaki, A. Irizawa, Y.
Muro and T. Takabatake, Phys. Rev. Lett. 106 (2011)056404.
[4] J. Kawabata, T. Takabatake, K. Umeo and Y.
Muro, Phys. Rev. B 89 (2014) 094404.
[5] S. Kimura, Y. Muro and T. Takabatake, J. Phys.
Soc. Jpn. 80 (2011) 033702.
[6] S. Kimura, JASCO Report 50 (2008) 6 [inJapanese].

48

Ⅲ -2. Materials Sciences

BL2A

Local Structure Investigation around P Atom in Ag and Cu Doped
Hydroxyapatite
1

M. Sato1, H. Sakaguchi 2, Y. Inoue2 and A. Nakahira2,3

Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
Graduate school of Engineering, Osaka Prefecture University, Sakai 599-8531, Japan
3
Kansai Center for Industrial Materials Research, Tohoku University, Sakai 599-8531, Japan
2

Hydroxyapaite (Ca10(PO4)6(OH)2, HAp) is a chief
inorganics of our hard tissue and it has been widelyused in medical field as artificial hard tissue due to its
excellent biocompatibility and osteo-conductivity.
However, there is the most significant problem of
infection during the displacement surgery or after theoperation[1]. When such infections occurred, it isnecessary to repeat a surgery to replace the alternate
implants. This is a significant burden for patient. In
order to overcome these problems, imparting theantibacterial property to the implants is expected as
one of the efficient method, and the development ofalternate materials of hard tissue having antibacterial
property have been strongly desired [2]. Therefore,
Cu and Ag doped HAp, which are expected having an
excellent antibacterial property, has been prepared byhydrothermal technique to prevent some infections
during surgery, and the local structure around P atomof these sample was investigated by XAFS
measurement at BL-2A in UVSOR.
Ag and Cu doped HAp samples were prepared by
0.1 mol/L Ca(NO3)2, (NH4)2HPO4, CuCl2 and AgNO3
solutions, respectively. The Ca/P ratio was fixed at
1.67 and the amount of Ag and Cu changed in therange from 0 mol% to 10 mol% for Ca concentrationof HAp. The pH value of each solutions wereregulated by ammonia solution and tris buffer
solution, respectively. Obtained slurry was filtrated
and then dried at 323 K for overnight. The P K-edge
XAFS spectra was corrected in BL-2A of UVSOR.
The XAFS data of sample was obtained byfluorescence mode using InSb double crystal
monochrometer and SDD detector. In a present study,
unfortunately, the EXAFS spectra did not obtained
due to the influence of absorption of M-edge of Au
mesh which is using as an I0 measurement.
Figure 1 shows P K-edge XANES spectra of
Ag-HAp prepared by HT process. The obtained
XANES spectra resembled to that of commercial
HAp (HAp-200, Taihei Chemical Industrial Co., Ltd.),
and the shape of XANES spectra did not change byincreasing the Ag ratio. This result indicate that thesecondary phase such as silver phosphate does not
generate and the local structure around P atom does
not changed by Ag addition.
Figure 2 shows P K-edge XANES spectra of
Cu-HAp samples prepared by HT process. The P-K
edge spectra of sample showed similar spectra to
HAp-200 and Cu3(PO4)2. This result means that theadded Cu ion exists into HAp structure or forms

Cu3(PO4)2. It is thought that since the local structurearound P atom in both HAp and Cu3(PO4)2 resembles
each other, the obtained XANES spectra of HAp-200
and Cu3(PO4)2 had similar shape. Therefore, it isdifficult to decide that the Cu ion exists into HApstructure or forms Cu3(PO4)2 from P-K XANES
spectra only. In order to obtain the structural
knowledge of Cu-HAp in detail, the measurement in
EXAFS region is necessary in a future study. In Ag-Ledge measurement, good spectra could not obtain inthis measurement period.

Fig. 1. P K-edge XANES spectra of Ag-HAp
samples.

Fig. 2. P K-edge XANES spectra of Ag-HAp
samples.
[1] M. Stigter, J. Bezemer, K. de Groot and P.
Layrolle, Journal of Controlled Release 99 (2004)
127.
[2] L. Zhao, P. K. Chu, Y. Zhang and Z. Wu, Journalof Biomedical Materials Research Part B: Applied
Biomaterials 91 (2009) 470.

49

Ⅲ-2

Ⅲ -2. Materials Sciences

BL2A

Study of Formation Processes of Active Mo Species over
V-Doped Mo/H-AlGaMFI by Mo LIII-Edge XANES
1

H. Aritani1, S. Mogi1, N. Naijo1, T. Sugawara1, T. Kawai1 and A. Nakahira2

Department of Life Science & Green Chemistry, Saitama Institute of Technology, Fukaya 369-0293 Japan
2
Graduate School of Engineering, Osaka Prefecture University, Sakai 599-8531 Japan
Ga-free) catalysts show high activity only an initialstate, and large amount of deposited carbonaceous
species are shown over the catalysts. It is concluded
that Both Ga-doping onto H-MFI and V-doping with
Mo bring about the high and durable activity for
MTB reaction by way of stable Mo-carbonaceous
species without carbon deposition.

TEY

Mo/H-MFI
1.0
Mo/GaAlMFI[Al/Ga=100]
Mo-V/H-MFI [Mo/V=10]
Mo-V/GaAlMFI[Al/Ga=100, Mo/V=40]
-Mo2C (ref.)After 60 min.

0.5

0.0
2510

2515

2520

2525
2530
Energy / eV

2535

2540

After 200 min.

1.0

TEY

Ⅲ-2

Mo-modified H-MFI is a typical catalyst for MTB(Methane to Benzene) reaction, i.e., methane
dehydroarimatization. Although the MTB reaction isrevolutionary for direct conversion of natural gas,deactivation due to coking over the catalyst cannot be
avoided during the methane conversion. Clarificationof the deactivation process over the catalysts is one of
an important point for develop of highly active anddurable MTB catalysts. In this study, time course of
the formation and activation of active Mo species on
H-MFI supports is investigated. The effects of
Ga-doping onto MFI (GaAlMFI) support and Mo-V
co-doping on GaAlMFI are also studied.
Catalyst samples were prepared by impregnation ofeach H-GaAlMFI (Si/Al2=40) support with
MoO2(acac)2− VO(C5H7O2)3−CHCl3 solution (5wt%
as MoO3), and followed by dried and calcined at 773
K. GaAlMFI (Al/Ga=50-100) supports weresynthesized hydro- thermally at 413 K for a week,
and followed by ion-exchanging with NH4Cl andcalcined at 873 K. The catalytic MTB reactivity wasevaluated by means of fixed-bed flow reaction at
1023 K, as described in a separate paper [1]. Mo
LIII-edge 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, andnormalized XANES spectra and their derivatives arepresented. REX-2000 (Rigaku Co,) software wasused by normalization of each XANES spectrum.
Figure 1 shows the XANES spectra of various
Mo-V/GaAl-MFI catalysts after MTB reaction for 60
and 200 min. After the reaction for 60 min withhighly catalytic activity, the edge energy (shown in
Table 1) is almost as same as that of α-Mo2C over thewhole catalysts. At the same instant, the white lines
peaked at ca. 2524 eV can be shown, indicating theformation excess carbonized Mo species. It suggests
the formation of Mo-carbonaceous species incatalytically active state. After the reaction for
200min in deactivated state, the edge energy values
over Mo/H-MFI and Mo-V/GaAlMFI, which arehighly active and durable catalysts, are almost kept on
at ca. 2522 eV. For significantly deactivated catalysts,
Mo/GaAl-MFI and Mo/V-H-MFI, the edge energy
values are almost as same as that of α-Mo2C. Indeed,
the Mo-V/GaAlMFI is the most highly active anddurable catalyst for MTB, which is the least amountof deposited carbonaceous species analyzed bythermogravimetry. In contrast, Mo/H-MFI (V- and

0.5

0.0
2510

2515

2520

2525
2530
Energy / eV

2535

2540

Fig. 1. Mo LIII-edge XANES of Mo-V/H-GaAlMFI
catalysts after MTB reaction for 60 (top) and 200(bottom) minutes at 1023 K.
Table

1. Edge energy value of the catalysts after
MTB reaction for 60/200 min.

Catalyst
Mo/H-MFI40

Time / min.
60
200
Mo/Ga(100)Al-MFI40
60
200
Mo-V(10)/H-MFI40
60
200
Mo-V(40)/Ga(100)Al-MFI40
60
200
α-Mo2C

Edge Energy /eV2522.632521.75
2521.75
2522.35
2521.982523.52
2521.87
2521.652522.13[1] H. Aritani, H. Shibasaki, H. Orihara and A.
Nakahira, J. Environm. Sci. 21 (2009) 736.

50

Ⅲ -2. Materials Sciences

BL2A

Local Environment Analysis of Mg Ions Doped in CaZrO3:Tb
1

H. Fukaya1, Y. Kubo1 and T. Yamamoto1,2

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

2

ions. Such environment exists in CaZrO3 as Zr4+ site.
Finally, we could determine the local environment of
Mg ions in CaZrO3:Tb by the Mg-K XANES
analysis.

Phosphor is a very attractive material in the
combined use of the light emitting device (LED) andthen a lot of researches have been already carried out
for this material. One of the common strategies tosynthesize stable phosphors for the industrial
applications is the doping of the rare-earth ions in thematrix oxides. Among these, Tb doped CaZrO3 wasfound to show bright green-light emission by UV
irradiations [1]. In addition, it was reported that Mg
co-doping into this material can increase thebrightness of the green-light emission [1]. In order tounderstand the mechanism of this kind of change inbrightness, it is important to know the local
environment of doped ions in the matrix oxides. For
such purpose, XANES analysis is quite powerful andwe could successfully analyze wide variety offunctional materials [2, 3]. In the current study, local
environment of co-doped Mg ions in CaZrO3:Tb isinvestigated by the X-ray absorption near-edge
structure measurements at Mg K-edge.
Mg co-doped CaZrO3:Tb was prepared by theconventional solid-state reaction method. Reagent
grade CaCO3, ZrO2, Tb4O7 and MgO powders wereused as starting materials. These powders were
weighed changing the molar ratio of cations andmixed in an agate mortar. These mixed powders werepressed into cylindrical pellets, which were sinteredin air at 1673 K for 6 hrs. Resultant specimens wereground and were provided to photoluminescencemeasurements. A concentration of the dopants withthe most bright luminescence was 0.03 for both Tb
and Mg, i.e., CaZr0.94Tb0.03Mg0.03O3. This sample was
examined by the XRD measurements, which showed
its crystal structure is single-phased ans orthorhombic
perovskite structure without any precipitates.
Mg-K XANES spectra of Mg co-doped CaZrO3:Tb,
MgO and Mg(OH)2 were observed at BL2A in
UVSOR by total electron yield method. The incident
beam was monochromatized with aberyl (101̄0) (2d= 15.965 Å) double crystal monochromator. Sample
powders were put on the carbon adhesive tape, which
are attached on the first Cu-Be dinode of the electron
multiplier.
Observed Mg-K XANES spectra of Mg co-doped
CaZrO3:Tb (CaZr0.94Tb0.03Mg0.03O3) is shown in Fig.
1 together with those of MgO and Mg(OH)2. Mg-K
XANES profile of the Mg co-doped CaZrO3:Tb
shows similar one as that of MgO, but is quite
different from that of Mg(OH)2. From thiscomparison, it is suggested that the local environmentof Mg ions in Mg co-doped CaZrO3:Tb is similar tothat in MgO, which is the 6-coordination of oxygen

Mg co-doped CaZrO 3:Tb

Intensity (arb. units)

Ⅲ-2

MgO

Mg(OH) 2
1300

1310
1320
Energy (eV)1330

Fig. 1. Mg-K XANES spectra of Mg co-doped
CaZrO3:Tb, MgO and Mg(OH)2.
[1] Y. Shimizu et al., Mater. Sci. Eng. B 161 (2009)100.
[2] T. Yamamoto, et al., J. Phys.: Condens. Matter 21(2009) 104211.
[3] I. Tanaka et al., J. Am. Cer. Soc. 88 (2005) 2013.

51

Ⅲ -2. Materials Sciences

BL2A

Local Structure Analysis of the Charge-Discharge Process for Conversion
Reaction of the Binary Metal Oxide Containing Aluminum Ion by XAFS
Measurement
1

N. Sonoyama1, Y. Ogasawara1, T. Mizuno1 and T. Tukada2

Graduate School of Engineering Science, Nagoya Institute of Technology, Nagoya, 466-8555, Japan
2
Nagoya Institute of Technology Institute for Molecular Science, Okazaki 444-8585, Japan

Ⅲ-2

Tarascon et al. reported that 3d transition metaloxides (MO, where M is Fe, Co, Ni, and Cu etc.)
nanoparticles could reversibly react with lithium toachieve high theoretic capacities as high as 700 mAhg − 1 in 2000 [1–4]. The mechanism of the“conversion reaction” involves the formation anddecomposition of Li2O accompanied by a large
amount of lithium ion reaction toward metal oxide
nano particles. In this study, we have investigatedthe electrochemical reaction of Al3+ ion doped NiO
which was synthesized using layered doublehydroxide as a precursor by ex-situ XAFS
meaurement.
The solid solution of multiple metal oxides, AlIII
dissolved NiO was prepared according to the methodmen- tioned in the previous papers [9,10]. The ratioof divalent metal and other valent metals (Ni2+:Al3+)is 2:1 otherwise noted. X-ray absorption spectroscopy
measurements were performed at the BL-2 in
UV-SOR
underthevacuumcondition.
Measurements are carried out by fluorescence method
and photoelectric yield method. The electrochemical
reacted samples are removed from the cell and rinsed
with dimethyl carbonate and set in transfer vessel.
In Fig. 1, XANES spectra of as prepared Ni-Al
oxide comparing with alumina power and aluminum
foil. The absorption edge of as prepared Al-Ni oxideappeared at lower energy region than alumina power.
This would be brought by the crystal structure of
Ni-Al oxide.
In Fig. 2, XANES spectra of Ni-Al oxide reduced
by discharging until 30 mV. The XANES spectrumof Ni-Al oxide hardly changed in comparison withpristine sample. This result is inconsistent with theincreased capacity by aluminum introduction. Thissuggests that the reduction of aluminum ion is limited,
not until metal state.

Fig. 1. Al k edge XANES spectra of as prepared
Al-Ni oxide, Al foil and alumina.

Fig. 2. Al k edge XANES spectra of as prepared
Al-Ni oxide and reduced one.
[1] P. Poizot, S. Laruelle, S. Grugeon, L. Dupont and
J. Tarascon, Ionics 6 (2000) 321.
[2] P. Poizot, S. Laruelle, S. Grugeon, L. Dupont andJ.-M. Tarascon, Nature 407 (2000) 496.
[3] S. Grugeon, S. Laruelle, R. Herrera-Urbina, L.
Dupont, P. Poizot and J. M. Tarascon, J. Electrochem.
Soc. 148 (2001) A285.
[4] S. Laruelle, S. Grugeon, P. Poizot, M. Dollé L.
Dupont and J.-M. Tarascon, J. Electrochem. Soc. 149(2002) A627.

52

Ⅲ -2. Materials Sciences

BL2A

Evaluation of Local Structure of Si for Perlite Synthesized from Natural
MineralA. Nakahira1,2, S. Togo1, M. Kasai1,3, Y. Kobayashi3, T. Morinaga1, Y. Inoue1,
M. Sato4 and H. Aritani5
1

Faculty of Engineering, Osaka Prefecture University, Sakai 599-8531, Japan
2
Osaka Center, IMR, Tohoku University, Sakai 599-8531, Japan3
Mitsui Mining & Smelting Co., Ltd.. Perlite Division, Tokyo 141-8584, Japan
4
Institute of Materials Research, Tohoku University, Sendai 980-8577, Japan
5
Saitama Institute of Technology, Fukaya 369-0293, Japan

In general, perlite is considered to be a volcanic
glass typically formed by the hydration of obsidian.
Therefore, perlite minerals have a relatively highwater content and soften by heat-treatments on rotarykiln furnace around the temperatures range of1000 °C. Since on the heat-treatments water trappedin the perlite structure is vaporized, the rapid foam
phenomena for perlite material arise. As aconsequence, inorganic foam materials with uniqueporous-structures are easily produced in large
amounts. Perlite is one of most versatile natural
products. Large amounts of porous foam withamorphous structure is commercially useful for its
significantly light weight and low thermal
conductivity due to the unique porous structure andits compositions. These perlites are used in a lot ofcommercial fields as lightweight plasters, mortar,
concrete, tiles and thermal insulation materials. In
special, the large amounts of consumption of LNG
leads to the construction of LNG tanks andconsequently the usage of perlite for heat insulation
in LNG tanks rapidly increase. Furthermore, therecycle of waste material from perlite insulator in
LNG tanks emerges as a severe problem in Japan andother countries.
In order to solve the recycle of perlite waste after
insulator usage, we have continued to develop the
efficient use of perlite wastes. For example, perlite
wastes may be used for a silica source for inorganic
materials and ceramics like silica, mullite, zeolite,
glass and so on.
In this study, we attempted to investigate thestructure for naturally perlite products. However,perlite has amorphous structures and the detailed
characterization of perlite microstructures are
insufficiently carried out. In special, the relations of
perlite structure and synthetic parameter for usefulceramics are not well clarified.
Powders of natural perlite ore were prepared by thecrashers and the ball-milling process before the rotaryheat-treatments from natural ore minerals. Several
perlite powders were prepared for rotaryheat-treatments. Perlite powders were thrown into theheat-treatment furnace at 1073K to 1273K under air
atmosphere. Foamed perlites were crashed byball-milling and aligned to some grades of average

particle size.
Obtained products were characterized by XRD
method, FT-IR and TG-DTA. The microstructures of
products were observed by SEM. The local structures
around Si for the obtained products werecharacterized by measuring X-ray adsorption nearedge structure (XANES) at BL02A in UV-SOR.
Various foamed perlite powders were synthesizedthough heat-treatments at 1073 to 1273K in air
atmosphere. The evaluation of XRD for foamed
perlite powders was done. XRD results showed thatfoam products obtained from perlite powders were
amorphous. Figure 1 shows XANES spectra of
products and reference materials. As shown in Fig. 1,
XANES spectra of sample obtained the same spectra
as amorphous silica gel. These results suggest that
LTA products obtained from perlite possess the same
local structure of Si for commercial amorphous silica
gel.

Perlite source

喜多方真珠岩Commercial silica gel

シリカゲル

Heated perlite

ロカヘルプ439

1800

1850

1900

1950

2000

energy ［eV］

Fig. 1. Si XANES spectra of perlite and referencematerials: product and silica gel.

53

Ⅲ-2

Ⅲ -2. Materials Sciences

BL2A

XANES Aalysis of Methlylene Blue Adsorbed on WO3 Nanomaterials
T. Yoshida1, K. Komori2, M. Yamamoto2, C. Tsukada2, S. Yagi1, M. Yajima2, S. Kajita1 and
N. Ohno2
1

EcoTopia Science Institute, Nagoya University, Nagoya 464-8603, Japan
Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan

2

䢵䢰䢲

䢴䢰䢷

MB powder

I/I0 (a. u.)

䢴䢰䢲

䢳䢰䢷

MB aqueous
solution

䢳䢰䢲

䢲䢰䢷

䢲䢰䢲

䢴䢶䢸䢷

䢴䢶䢹䢲

䢴䢶䢹䢷

䢴䢶䢺䢲

X-ray energy (eV)

䢴䢶䢺䢷

䢴䢶䢻䢲

Fig. 1. S K-edge XANES spectra of a MB solid powder
and a MB aqueous solution.
䢷WO3(70)/W
In dark
under light䢶

I/I0 (a. u.)

Ⅲ-2

MB aqueous solutions under light irradiation or in thedark. The  *(S-C) peaks for both samples in thedark are much higher than the peak for MB molecule
in aqueous solution (Fig. 1). Such characteristicfeature of XANES spectra is similar to that of a MB
solid powder. Therefore, in the dark reaction, MB
molecules would be aggregated and stacked by -  interactions each other. The intensitiesof  *(S-C) and  *(S-C) peaks decrease by thelight irradiation for both samples, indicating the breakof S-C bonds of MB molecules adsorbed on thesamples. Thus, XANES measurements clearly
demonstrate the difference in the chemical state of
MB molecules between the photoinduced reaction
under NIR light irradiation and the adsorption
reaction in the dark.

Recently, formation of dendritic nanostructures
was found on W surface by He plasma irradiation incertain plasma conditions [1]. We have applied thedendritic nanostructured W to a photocatalyst which
can mineralize the organic compounds in water or
atmosphere under light irradiation.
In our previous research, we partially oxidized thesurface of the nanostructured W and obtained ananostructured WO3/W composite material. The
material showed photocatalytic decolorization
reaction of methylene blue (MB: C16H18ClN3S nH2O,n≈3) aqueous solution under near infrared lightirradiation. However, we should confirm whether MB
decolorizationreflects
thephotoinduced
mineralization of MB molecules or the sensitization
effect of MB adsorbed on WO3/W composite material.
Therefore, in the present study, we investigate thechemical state of MB molecules after photoinduced
reaction by XAFS measurements.
The dendritic nanostructure was fabricated by He
plasma irradiation to a monocrystal W plate. After theplasma irradiation, the surface of the sample waspartially oxidized on exposure to air at room
temperature. We prepared two samples in this manner
through the oxidation for 90 days, and the surface
oxidation ratios (x) of the samples were estimated by
XPS measurements as 70 %. Another two samples
with x =100 % were prepared by further
heat-treatment at 773 K for 2 hour in air. Thesesamples are referred to as WO3(x)/W.
S K-edge XANES measurements were conducted
for the adsorbed species on the surfaces ofWO3(70)/W and WO3(100)/W after photocatalytic
decolorization reaction of MB by total electron yieldor fluorescence X-ray yield method at BL2A in
UVSOR and BL6N1 in Aichi Synchrotron Radiation
Center.
Figure 1 shows S K-edge XANES spectra of a MB
solid powder and a MB aqueous solution. The peaks
at 2471.4 eV and 2473.4 eV are respectively assignedto  *(S-C) and  *(S-C) excitations [2].
Noticeable difference among the two spectra isobserved for the  *(S-C) peak. The XANES
spectrum of a MB powder shows a sharp  *(S-C)
peak, because MB molecules in the solid state arestacked each other by the  -  interaction [3] toform a high symmetric structure. On the other hand, *(S-C) peak is lower in the spectrum of a MB
aqueous solution rather than the solid state
Figure 2 shows S K-edge XANES spectra of thesurfaces of WO3(70)/W and WO3(100)/W kept with䢵

WO3(100)/W
In dark
under light

䢴

䢳

䢲

䢴䢶䢸䢷

䢴䢶䢹䢲

䢴䢶䢹䢷

䢴䢶䢺䢲

X-ray energy (eV)

䢴䢶䢺䢷

䢴䢶䢻䢲

Fig. 2. S K-edge XANES spectra of the MB adsorbates on
the surfaces of WO3(70)/W and WO3(100)/W.Thesesamples were kept with MB aqueous solutions under nearinfrared light for 225 min (black) or in the dark for 350 min(gray).
[1] S.Takamura, N. Ohno, D. Nishijima and S. Kajita, J.
Plasma Fusion Res. 1 (2006) 051.
[2] G. N. George et al., J. Phys. Chem. A 118 (2014) 7796.
[3] H. E. Marr III and J. M. Stewart, Acta Cryst. B29(1973) 847.

54

Ⅲ -2. Materials Sciences

BL2A

Local Structure Investigation around P Atom in Mn Substituted LiFePO4
1

M. Sato1, M. Togo 2, Y. Inoue2 and A. Nakahira2,3

Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
Graduate school of Engineering, Osaka Prefecture University, Sakai 599-8531, Japan
3
Kansai Center for Industrial Materials Research, Tohoku University, Sakai 599-8531, Japan
2

Lithium-ion battery has been used in many mobile
devices as high performance battery due to its highenergy density and repeatable property. However,there are some problems to be overcome such as astability in harsh environment and a significant costsaving. LiFePO4 is anticipated as a novel positiveelectrode material to reduce the materials cost and to
exhibit the high thermal stability. Among the 3dtransition elements, which are essential for thecathode active material, iron is the one of ideal
elements in terms of cost and resources. LiFePO4 hasreversible potential of 3.5 V and theoretical capacityof 170 mAhg-1, which are comparable energy density
to a bedded salt type LiCoO2. The doping ofmultiply-charged ion and the substitution of foreign
element to Fe site are to be a good approach to
improve the conductivity and to enhance the electrodepotential of LiFePO4. In this study, Mn substituted
LiFePO4 was synthesized by hydrothermal process,and the effect of Mn substitution on the local
structure around P atom was investigated by XAFS
measurement.
LiOH/H2O, (NH4)2HPO4, FeSO4/7H2O andMnSO4/5H2O were used as starting materials. Eachstarting materials were weighted to become a molar
ratio of Li : P : Fe : Mn = 2 : 1 : 1-x : x (x = 0, 0.25,
0.50, 0.75, 1.0). After measurement, they were put
into distilled water in a Teflon vessel and vigorously
mixed for a few minutes. Teflon vessel with mixed
solution was encapsulated into autoclave and washydrothermally treated at 473 K for 6 hours. Obtained
slurry was filtrated and then dried at 323 K for
overnight. The P K-edge XAFS spectra was corrected
in BL-2A of UVSOR. The XAFS data of sample wasobtained by fluorescence mode using InSb double
crystal monochrometer and SDD detector. In apresent study, unfortunately, the EXAFS spectra did
not obtained due to the influence of absorption of Medge of Au mesh which is using as an I0
measurement.
Figure 1 shows P K-edge XANES spectra of
LiMnxFe1-xPO4 (x = 0, 0.25, 0.5, 0.75, 1). Obtained
sample had similar XANES spectra to that ofcommercial LiFePO4, and the XANES spectra ofsample did not change by Mn addition. These results
indicate that the Mn based secondary phase such as
MnPO4 does not generated by Mn addition during a
synthesis and the local structure around P atom does
not change by Mn substitution.
Figure 2 shows P K-edge XANES spectra ofsamples after charge-discharge cycle test. The

shoulder was appeared around 2148 eV on the
XANES spectra of after 100 cycles, and it wasobserved more clearly after 1000 cycles. This result
indicate the generation of FePO4 phases and thequantitative increment of FePO4 phase withincreasing the cycles. Therefore, it is suggested thatthe reaction of eq.1 became difficult to occur by
repeating the charge-discharge cycle test.
Li1-xFePO4 + xLi+ + xe- → LiFePO4(eq.1)

Fig. 1. P K-edge XANES spectra of LiMnxFe1-xPO4
samples prepared by hydrothermal process. (a) x =0, (b) x = 0.25, (c) x = 0.5, (d) x = 0.75, (e) x = 1.

Fig. 2. P K-edge XANES spectra of samples after
charge-discharge cycle test. (a) 0 cycle, (b) 100 cycles,(c) 1000 cycles.
[1] Aniruddha Deb et al., J. Synchrotron Rad. 11(2004) 497.

55

Ⅲ-2

Ⅲ -2. Materials Sciences

BL2A

Structural Evaluation of Local Structure of Si for LTA-Type Zeolite from
Perlite Source
A. Nakahira1,2, M. Kasai1,3, S. Togo1, Y. Kobayashi3 and H. Aritani4
1

Faculty of Engineering, Osaka Prefecture University, Sakai 599-8531, Japan
2
Osaka Center, IMR, Tohoku University, Sakai 599-8531, Japan3
Mitsui Mining & Smelting Co., Ltd.. Perlite Division, Tokyo 141-8584, Japan
4
Saitama Institute of Technology, Fukaya 369-0293, Japan

Ⅲ-2

Perlite is a volcanic glass that is typically formedby the hydration of obsidian. Perlite with a relatively
high water content softens at temperatures of 1000 °C
and water trapped in the perlite structure of thematerial vaporizes, leading to the expansion of thematerial and unique porous-structure. Because perlite
has a high water content and amorphous structure, it
is commercially applicable to many fields from theadvantage of its significantly light weight after foamprocessing. Many commercial applications for perlite
have been developed as lightweight plasters, mortal
and concrete, ceiling tiles and insulation materials.
In this study, we attempted to synthesize the zeolitefrom naturally perlite products. Zeolites have theunique 3D microporous networks. They are one ofaluminosilicate minerals commonly used as various
commercial adsorbents and other applications inpetroleum industry as a catalyst and oxygen
purification and water purification. In thisexperiments, perlite was used for a silica source forzeolite. Especially we focused on LTA-type zeolitewith low Si/Al zeolite having unique properties suchas high ion exchange capacity, catalytic activity, andsorption ability etc.[1-2] In case of synthesis ofzeolite, the microstructure of perlite plays animportant role for stability of many zeolite phase. As,
however, perlite has amorphous structures, therelations of perlite structure and synthetic parameter
for LTA-type zeolite are not well clarified.
Perlite powders were prepared by the ball-milling
process for rotary heat-treatments from natural
products.
Foamed perlites were crashed byball-milling and aligned to some grades of average
particle size. Sodium aluminate (NaAlO2) was used
as an alumina source and added into perlite powder
for the adjustment of Si/Al ratio. Perlite powder andsodium aluminate were mixed in NaOH solution andaged for 6 hours. Then mixed solution was poured
into vessel and heated at 363K Hydrothermal
synthesis for perlite was carried out at 363K for 24hours. After hydrothermal treatments under somesynthetic conditions, the products were filtered andsufficiently washed with de-ionized water and dried.
Obtained products were characterized by XRD
method, FT-IR and TG-DTA. The microstructures of
products were observed by SEM. The local structures
around Si for the obtained products werecharacterized by measuring X-ray adsorption nearedge structure (XANES) at BL02A in UV-SOR.
Various zeolites were synthesized thoughhydrothermal treatment of perlite with alkaline
solutions in order to facilitate effective use of the
discarded perlite. The evaluation of XRD for products
was carried out. XRD results showed that products
obtained from perlite powders with 2.5 micron of
average particle size were also identified to be LTA
type without another phase. These results indicatedthat the obtained fine-zeolite products were LTA typezeolites. Using perlites powders after the mechanicalmixing by ball-milling process monolithic LTA
zeolite powders were successfully synthesized byafter the mechanical mixing processing for 24 hours.
Figure 1 shows the XANES spectra of products
and reference materials. As shown in Fig. 1, XANES
spectra of sample obtained the same spectra as thecommercial LTA. These results suggest that LTA
products obtained from perlite possess the good
crystallinity and also the same local structure of Si forcommercial LTA.

Comercial LTA
ゼオライトA
ロカヘルプ439
Perlite source

LTA from perlite
パーライト－ゼオライト

1800

1850

1900

1950

2000

Energy ［eV］

Fig. 1. Si XANES spectra of zeolites and referencematerials: perlite, product and commercial LTA.
[1] D. Novembre, B. D.Sabatino, D. Gimeno and C.
Pace, “Synthesis and characterization of Na-X, Na-A
and Na-P zeolites andhydroxysodalite frommetakaolinite”, Clay Minerals 46 (2011) 339.
[2] G.M. Khan, D.M.Y. Arafat, S.M.S. Razzaque and
Md. S. Alam, Indian Journal of Chemical Technology
17 (2010) 303.

56

Ⅲ -2. Materials Sciences

BL2A

Studies on Electronic Structure of Aluminum Oxide Thin Film under
Voltage Applied Conditions by Near-Edge X-Ray Absorption Fine Structure
E. Kobayashi1, K. K. Bando2, O. Takahashi3 and T. Okajima1
1

Kyushu Synchrotron Light Research Center, Tosu 841-0005, Japan
National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8565, Japan
3
Institute for Sustainable Science and Development, Hiroshima University, Higashi-Hiroshima, 739-8526, Japan2

㻌

Aluminum oxide is recognized as an importantmaterial because it is the prototype of metal oxides
and of wide-gap insulator. The aluminum oxide isalso used in a wide field of industrial applications
such as an insulating material. However, there is noreport on the electronic structure of aluminum oxide
under voltage applied conditions. Although Al K-edge
NEXAFS spectra of aluminum oxide have beenobtained in total electron yield mode, the method isdifficult under voltage applied conditions. Then we
have observed an electronic state by detecting x-ray
fluorescence from the sample while scanning photon
energy.
Al K-edge NEXAFS spectra of aluminum oxidethin film were measured at the beamline 2A of the
UVSOR in the Institute of Molecular Science. An
alumina film was made on a stainless steel plate by
dip-coating with a diluted alumina sol (Kawaken Fine
Chemicals, F1000). The coated plate was dried at 333
K and calcined at 573 K in an oven. The NEXAFS
spectra were obtained using the partial fluorescence
yield (PFY) mode at room temperature.
Figure 1 shows the Al K-edge NEXAFS spectra ofaluminum oxide obtained from PFY mode at various
applied voltage. This sample was discharged at 160 V.
Two strong peaks are observed at around 1569.3 eV(A) and 1571.8 eV (B), respectively. The spectralfeatures are also similar to the obtained for Gibbsite[1]. The intensity of peak A and peak B change
gradually with applied voltage. Figure 2 shows theapplied voltage dependence of the intensity of peak A
and peak B for aluminum oxide thin film. The
intensity of the two peaks tends to become weak withincreasing applied voltage and the peaks become
broad. This result indicates that the content of anamorphous phase increased in alumina with applied
voltage.

A B

Intensity (arb. units)

V= 150 V㻌

Ⅲ-2

V= 0 V

1560

1570

1580

1590

1600

Photon Energy (eV)Intensity (arb. units)

Fig. 1. Al K-edge NEXAFS spectra of aluminumoxide thin film obtained from PFY mode at various
㻌applied voltage.

㻌peak B

peak A

0

40

80

120

160

Applied voltage (V)Fig. 2. Applied voltage dependence of the intensityof peak A and peak B for aluminum oxide thin film.
[1] C. S. Doyle et al., J. Synchrotron Rad. 6 (1999)
621.

57

Ⅲ -2. Materials Sciences

BL3B

Temperature Dependence of Self-Trapped Exciton Emission and Energy
Transfer in Binary Rare-Earth Borates upon Vacuum UV Excitation
N. Kodama, A. Abe, M. Kudo and T. Takahashi

Graduate School of Engineering and Resource Science, Akita University, Akita 010-8502, Japan

STEⅠ
STEⅡ
STEⅢ

50 100 150 200 250 300
Temperature / K

Fig. 2(a)

1.0

0.6
0.4

Fig. 3(a)λex = 160 nm

STEⅠ
STEⅡ
STEⅢ

0.2
0

0

STEⅠ
STEⅡ
STEⅢ

0

Fig. 3(d)Fig. 1(c)λex = 160 nm
STEⅠ
STEⅡ
STEⅢ

0.2
0

50 100 150 200 250 300
Temperature / K

0

50 100 150 200 250 300
Temperature / K

Fig. 3(b)

1.0
0.8
0.6
0.4

0.4
λex = 160 nm

0.2
0

0.4

Fig. 2(b)1.0

50 100 150 200 250 300
Temperature / K

50 100 150 200 250 300
Temperature / K

0.6

0.6

0.4

00

0.8

0.8

0.6

STEⅠ

500

1.0

λex = 160 nm

Rate of decrease in
STE intensity

1.0
0.8

λex = 160 nm

2500

50 100 150 200 250 300
Temperature / K

0.6

0

360

1000

0.8

50 100 150 200 250 300
Temperature / K

240 280 320
Wavelength / nm

Fig. 1(c)

1500

STEⅡ

0.2

0

14 K
50 K
78 K
150 K
200 K
240 K
293 K

2000

0.4

0.2

Intensity / a.u.

λex = 160 nm

STEⅠ

Rate of decrease in
STE intensity

Rate of decrease in
STE intensity

STEⅠ
STEⅡ
STEⅢ

3000

Fig. 2(b)1.0

λex = 160 nm

0.8

200

360

Fig. 1(b)Peak Intensity / a.u.

20000

240 280 320
Wavelength / nm

1400
1300
1200
1100
1000
300
250
200
150
100 0

Peak Intensity / a.u.

400

0

200

λex = 160 nm

1200
1000
800
600

Peak Intensity / a.u.

600

Fig. 1(a)

1400

14 K
45 K
77 K
100 K
125 K
160 K
180 K
200 K
220 K
240 K
260 K
293 K

Rate of decrease in
STE intensity

300 400 500
Wavelength / nm

15 K
45 K
77 K
100 K
125 K
160 K
180 K
200 K
220 K
240 K
260 K
293 K

Rate of decrease in
STE intensity200

λex = 160 nm

λex = 160 nm

Intensity / a.u.

Intensity / a.u.

λex = 160 nm

Rate of decrease in
STE intensity

Ⅲ-2

For a high RE3+ doping concentration (5%), the rate ofdecrease did not show notable changes, or gradually
decreased up to approximately 200 K, followed by agradual increase as temperature rose, whereas for low
Sm3+ doping (1%), the rate of decrease increased
monotonically with increasing temperature. These
results suggest that for the low RE3+ doping, thethermally assisted energy transfer process related to theexciton (STE) mobility was activated as the temperature
increased.
In the case of LSB at a temperature of 293 K, theenergy transfer rates determined from time-resolved
measurements were 1.9 × 106 s–1 (STE(II)) and 1.8 × 105
s–1 (STE(III)) for 5 at.% Sm3+ doping, 1.6 × 106 s–1(STE(II)) and 0.8 × 105 s–1 (STE(III)) for 5 at.% Gd3+
doping, and 2.2 × 106 s–1 (STE(II)) and 0.8 × 105 s–1(STE(III)) for 5 at.% Tb3+ doping. The energy transfer
rates in the YSB at 293 K were 1.9 × 107 s–1 (STE(I))
and 5.6 × 105 s–1 (STE(II)) for 5 at.% Gd3+ doping and6.5 × 106 s–1 (STE(II)) and 1.5 × 105 s–1 (STE(III)) for 1
at.% Tb3+ doping. The observed energy transfer rates
were the same magnitude as, or within an order ofmagnitude of, the estimates based on dipole–dipole
energy transfer.

We report the temperature and material dependence of
the intrinsic luminescence from self-trapped excitons(STEs) and energy transfer to RE3+ (RE3+ = Sm3+, Gd3+,
or Tb3+) ions observed in three kinds of undoped binary
borates LaSc3(BO3)4 (LSB), YSc(BO3)2 (YSB), andLuSc(BO3)2 (LuSB) under vacuum ultraviolet (VUV)
excitation. In addition, we examine the temperaturedependence and the dynamics of energy transfer fromSTEs in RE3+-doped LSB, YSB, and LuSB samples.
The time-resolved spectra were measured using apulse with a width of 10 ns from an F2 pulsed laser
operating at 157 nm, and the decay times were
determined.
Figures 1(a), 1(b), and 1(c) show the temperaturedependence of the luminescence spectra in undoped
LSB, YSB, and LuSB, respectively. As can be seen, at
293 K, three, two, and one distinct emission bands wereobserved for LSB, YSB, and LuSB, respectively, andwere located at energies corresponding to the STE bands.
The peaks of the STE luminescence bands in all samples(LSB, YSB, LuSB) shifted to longer wavelengths withincreasing temperature from 15(or14) to 293 K.
Figure 2 shows the temperature dependence of the
STE intensities for the undoped samples. In the undoped
LSB, the STE(I) intensity decreased gradually from 15
to 160 K, and then remained nearly constant.
Accompanying this decrease in the STE(I) intensity, theintensities of STE(II) and (III) increased, reached theirmaxima at 180 K, and then decreased monotonically forhigher temperatures. This decrease in the STE(II) andSTE(III) intensity likely resulted from a thermal
quenching process, such as an intrinsic quenching or apartial energy transfer to nonradiative “killer” centers
due to the presence of defects or impurities. Undoped
YSB exhibited an STE(I) intensity that increased
gradually as the temperature increased to 125 K, above
which the intensity decreased. The STE(II)luminescence appeared at 180 K, and the intensity
increased with increasing temperature to 293 K. In the
undoped LuSB, the intensity of STE(I) passed through amaximum at 200 K, which is similar to the temperaturedependence of the STE(II) and STE(III) luminescencefor LSB and that of STE(I) for YSB. As the STE(I)emission intensity decreased in LSB and YSB, theSTE(II) and STE(III) emission intensity increased,accompanied by the appearance of the STE(II)emissions. These facts suggest that there are multiple(three in LSB, two in YSB) local minima on the
adiabatic potential energy surfaces, i.e., the barriers forthe exciton self trapping in LSB and YSB. Multi-steptransitions correspond to the evolution from STE(I) to
STE(II) and further to STE(III).
Figure 3 compares the temperature dependence of therate of decrease in the STE(I), (II), and (III) emissions in
the RE3+-doped and undoped samples of LSB and YSB.

STEⅠ

0

50 100 150 200 250 300
Temperature / K

Fig. 3(e)λex = 160 nm
STEⅠ
STEⅡ

0.2
0

0

50 100 150 200 250 300
Temperature / K

Fig. 3(f)Fig. 1. Temperaturedependenceof
intrinsic
luminescence spectra in (a) undoped LSB, (b) YSB,
and (c) LuSB in the range 15(or 14)–293 K.
Fig. 2. Temperature dependence of STE intensity for
undoped samples: (a) LSB, (b) YSB, and (c) LuSB.
Fig. 3. Temperature dependence of rate of decrease
in STE(I), (II), and (III) emissions in Re3+-doped andundoped samples for LSB and YSB: (a) 1%
Sm-doped LSB, (b) 5% Sm-doped LSB, (c) 5%
Gd-doped LSB, (d) 5% Tb-doped LSB, (e) 5%
Gd-doped YSB, and (f) 5% Tb-doped YSB.

58

Ⅲ -2. Materials Sciences

BL3B

Charging States of Oxygen Vacancies in Yttria-Stabilized Zirconia
Analyzed by the Decay of Photoluminescence
S. Kaneko, T. Morimoto and Y. Ohki
Waseda University, Tokyo 169-8555, Japan

release of electrons needs a certain long time, the
2.8-eV PL must have a large decay constant like 0.3
ms when it is originated from the F centers.

In yttria-stabilized zirconia (YSZ), ZrO2 is partly
replaced by Y2O3. This means that oxygen vacancies
are present in YSZ with the same ratio as that of Y2O3
[1]. In order to examine the electronic energy
structure of the oxygen vacancy in YSZ, the decaying
behavior of photoluminescence (PL) was observed in
YSZ.
It has been known that the PL with a peak energyof 2.8 eV appearing in YSZ as shown in Fig. 1 is dueto the oxygen vacancy and that the oxygen vacancy
can take three different charging states [1-3].
However, the charging state from which the PL isemitted is unclear.
Using the single-bunch mode of synchrotron
radiation at BL3B line in the UVSOR facility as an
excitation photon source, we observed the decay of
the 2.8-eV PL excited by 5.2-eV photons in a
ns-range. As shown in Fig. 2(a), the decay constant of
the PL can be estimated as 7 ns. In addition, we
measured the decay in a ms-range using afluorescence spectrometer FP-8500 (Jasco). As shownby the black open circles in Fig. 2(b), the 2.8-eV PL
decays with a lifetime of around 0.3 ms. Note that red
open squares show the decay in intensity of theexcitation photons induced by the movement of amechanical shutter.
When an oxygen atom is removed from a certain
site, the site would be effectively charged positively.
There- fore, the site attracts electrons. Regarding this,the oxygen vacancy capturing no electrons is called
the F2+ center, while the ones capturing one and twoelectrons are called the F+ center and the F center,
respectively.
The PL, which has been attributed to oxygen
vacancies, has been reported for many oxides. It has
been known that the F centers in alumina [4] andYAlO3 [5] induce phosphorescence with a time
constant of the order of ms, while the F+ centers havebeen assigned to the origin of fluorescence with atime constant of the order of ns. Taking these facts
into account, the 2.8-eV PL in YSZ would be
ascribable to both the F+ and F centers.
However, it is unlikely that both the F+ and F
centers with different charging states emit photons
with the same energy. In this regard, we assume thefollowing luminescent mechanism as a plausiblemodel. Namely, the 2.8-eV PL in YSZ is induced by
the F+ centers with the decay constant of 7 ns. One
important fact is that the F+ centers can be generated
if one electron is released from the F centers in
addition to those originally present in YSZ. If the

Ⅲ-2

Fig. 1. Distribution of PL energy and PL excitationenergy observed for YSZ at 10 K.
PL intensity [normalized]

1.0
0.8
0.6
0.4
0.2
0.0
-5

0

5
Time [ns]

10

15

(a)
Intensity [normalized]

10
1
10-1
10-2
10-3
0

1

2
3
Time [ms]

4

5

(b)
Fig. 2. Decay profiles of the 2.8-eV PL observed in
YSZ; (a) in a ns range and (b) in a ms range (○) incomparison with the decay of excitation photons withan energy of 5.2 eV (□), normalized by theirrespective initial values.
[1] J. M. Costantini, et al., J. Nucl. Mater. 440 (2013)508.
[2] H. Nakajima, et al., J. Alloys Compd. 408 (2006)
728.
[3] T. Morimoto, et al., Jpn. J. Appl. Phys. 47 (2008)
6858.
[4] A. I. Surdo, et al., Radiat. Meas. 33 (2001) 587.
[5] Y. V. Zorenko, et al., Opt. Spectrosc. 96 (2004)
532.

59

Ⅲ -2. Materials Sciences

BL3B

Band Gap of B1-Type MxZn1-xO (M = Mg, Mn, Fe, Co, Ni)
Synthesized under High Pressures
1

K. Takahama1, K. Usui1, D. Shimada2, M. Kato1, K. Niwa2, K. Kusaba2,
M. Hasegawa2 and K. Soda1

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

Ⅲ-2

Wide gap semiconductor ZnO is one of promisingmaterials for light emitting devices, transparent
conducting electrodes, catalysis, solar cells, and so on[1]. There have been many proposals and efforts forcontrolling such as a band gap width and energy
positions of conduction band minimum and valenceband maximum, and hence its functional properties,
by forming mixed crystals with other metal oxides [2,3]. Recently B1(NaCl)-type mixed crystals MxZn1-xO(M = Mg, Mn, Fe, Co, Ni) have been successfully
synthesized under high pressures [4], where ZnOtransforms the B4(wurtzite)-type structure to B1-type.
In this report, we have investigated their reflectancespectra to estimate their band gaps.
Measurement of reflectance spectra was performed
at BL3B for polycrystalline specimens of about 1 mm
in thickness and ~2 mm in diameter synthesized at1173 K under a pressure of 6.5 GPa with DIA-type
cubic anvil cell. The band gaps were estimated with
the Tauc plot for an indirect transition [5].
Figure 1 compares the estimated band gap (redcircle) with those experimentally evaluated fromvalence band photoelectron measurements (PES, blue
circles) [6, 7] for the present specimens as well as
experimental values of ZnO and MgO (black circles)
in ref. [3] and calculated with the first principle
calculations [2, 7, 8]. Here, theoretical direct andindirect band gaps are shown by solid and brokenlines, respectively, which were calculated with fullpotential linearized augmented plane wave methodwith generalized gradient approximation (GGA) by
Perdew-Burke-Ernzerhof (PBE) and Engle-Vosko(EV) [2] and with full potential linear muffin-tin
orbital method (LMTO) [8]. Experimental results arealso presented by open black circles for B1-type
MgxZn1-xO films grown by pulsed laser deposition[9].
The present band gaps agree quantitatively wellwith those obtained by PES and qualitatively withtheoretical predictions, taking into account that theunderestimation of the band gap is well known forthese calculations. The agreement of both the present
and PES experimental estimations of the band gap
indicates the n-type nature of the specimens, which
was assumed for the previous estimation from PES.
For x = 0.75, band gaps for the bulk specimens are
considerably different from those reported for thefilm. This may be due to effects of Zn as an impurity
for the Mg-rich films or different crossover between
indirect and direct band gaps of the films on asubstrate from the bulk specimens, although thereason has not been clarified at present yet.
Results will be reported elsewhere on other mixed
crystals.

Fig. 1. Band Gaps of B1-type MgxZn1-xO.
[1] H. Q. Ni et al., J. Appl. Phys. 91 (2002) 1339.
[2] B. Armani et al., Compt. Mater. Sci. 40 (2007) 66.
[3] D. K. Kanan and E. A. Carter, J. Phys. Chem. C
116 (2012) 9876.
[4] D. Simada, Master thesis (Nagoya University,2013).
[5] J. Tauc et al., Phys. Status Solidi 15 (1966) 627.
[6] K. Takahama et al., UVSOR Activity Report 201341 (2014) 83.
[7] K. Soda et al., Aichi SR Report (2013) 2504026.
[8] F. Z. Aoumeur-Benkabou et al., Model. Num. Sim.
Mater. Sci. 2 (2012) 60.
[9] R. Schmidt-Grund et al., AIP Conf. Proc. 772(2005) 201.

60

Ⅲ -2. Materials Sciences

BL3B

Energy Transfer from Tl+ Centers to In+ Centersin Co-Doped NaCl:Tl+, In+ Crystals
A. Iguchi and T. Kawai

Graduate School of Science, Osaka Prefecture University, Sakai 599-8531, Japantransfer mechanism from the Tl+ centers to the In+
centers in the co-doped NaCl:Tl+,In+ crystals, themeasurements of the decay kinetics of theluminescence are needed.

340

320

Lumi. Int. (arb. umit)

RT

Wavelength (nm)
300
280

260
0.2
C

+

NaCl:Tl
A' lumi.

Optical Density

Alkali halide crystals have the wide band-gap up to
the vacuum ultraviolet energy region and are asuitable candidate host for doping of impurity ions.
Among a lot of impurity ions, Tl+-type ions that havethe ns2 electronic configuration in their ground state
are well-known as impurity ions doped in alkali
halides[1,2]. Although many experimental studies
have been performed on Tl+-type centers in alkali
halides, energy transfer between Tl+-type centers inalkali halides are comparatively less studied. In thisstudy, we have investigated the energy transfer fromTl+ centers to In+ centers in NaCl crystals co-dopedwith the Tl+ and In+ ions at the BL-3B line of
UVSOR.
Figure 1 shows the absorption spectrum of
NaCl:In+ and the luminescence spectrum of NaCl:Tl+
in the energy range from 3.6 to 4.8 eV. In NaCl:In+,
the A absorption band having doublet structure andthe B absorption band appearing as a shoulder are
observed at 4.1 and 4.6 eV, respectively. The C
absorption band is located around 5.1 eV in thehigher energy region than the B absorption band. In
NaCl:Tl+, the A’ luminescence band due to the Tl+
centers is observed around 4.25 eV. The A’
luminescence band in NaCl:Tl+ has an large overlap
with the A absorption band in NaCl:In+. The factindicates the potential of the energy transfer from theTl+ centers to the In+ centers in co-doped NaCl:Tl+,
In+ crystals. According to the Förster model[3,4], thecritical distance between both centers for resonant
energy transfer is estimated to be 17.5 Å from theoverlap with the luminescence and absorption bands.
Figure 2 shows the excitation spectra in NaCl:Tl+,
NaCl:In+, and co-doped NaCl:Tl+,In+ crystals at room
temperature (RT). The A’ luminescence band in
NaCl:Tl+ is efficiently excited in the energy region
around 4.8 eV and 6.1 eV, where the A, B, and C
absorption bands of the Tl+ centers are located. In
NaCl:In+, the luminescence band at 3.00 eV, whichcorresponds to the A’ luminescence band of the In+
centers, is efficiently excited at the A, B, and C
absorption bands of the In+ centers.
In the co-doped NaCl:Tl+,In+ crystal, the excitation
spectrum for the A’ luminescence band of the In+
centers has the broad band around 6.10 eV in addition
to the A, B, and C bands of the In+ centers. Since the6.10 eV band corresponds to the excitation band for
the A’ luminescence band in NaCl:Tl+, the fact
implies the existence of the energy transfer from theTl+ centers to the In+ centers in the co-doped
NaCl:Tl+, In+ crystal. In order to clarify the energy

B

0.1
+

NaCl:InA abs.

0
4.0
4.2
4.4
4.6
4.8
Photon Energy (eV)Fig. 1. Luminescence spectrum (blue) of NaCl:Tl+
and absorption spectrum (red) of NaCl:In+ at RT.

Luminescence Intensity (arb. unit)

3.6

3.8

Wavelength (nm)
250
200

300
RT

+

NaCl:Infor 3.00 eV
CIn
ATl

AIn
4.0

BIn

NaCl:Tl +,In+for 3.00 eV

BTl

NaCl:Tl +CTl for 4.27 eV

5.0
6.0
Photon Energy (eV)7.0

Fig. 2. Excitation spectra of NaCl:Tl+ (blue),
NaCl:In+ (red), and co-doped NaCl:Tl+, In+ (purple).
[1] A. Ranfagni et al., Advances in Physics 32 (1983)
823.
[2] P. W. M. Jacobs, J. Phys. Chem. Solids 52 (1991)
35.
[3] T. Förster, Disc. Faraday Soc. 27 (1959) 7.
[4] D. L. Dexter, J. Chem. Phys. 21 (1953) 836.

61

Ⅲ-2

Ⅲ -2. Materials Sciences

BL3B

Luminescence Band with a Zero-Phonon Line in NaCl:Tl+ Crystals
T. Kawai

Graduate School of Science, Osaka Prefecture University, Sakai 599-8531, Japan
state of 3T1u has the shorter decay time constant of a
few ten nanoseconds. The fact implies that the
time-resolved luminescence spectroscopy would
allow us to decompose the A' luminescence band into
the slowly decaying luminescence band and the fastdecaying luminescence band, which correspond to theluminescence bands from the relaxed excited states of3
A1u and 3T1u, respectively. In order to confirm theabove idea, we are planning to perform a timeresolved luminescence spectroscopy.

Wavelength (nm)
200

250

Optical Density

2

NaCl:Tl
10 K

+

C
1
0
4.5

A
B
5.0

5.5
6.0
6.5
Photon Energy (eV)

7.0

7.5

Fig. 1. Absorption spectrum of a NaCl:Tl+ crystal.

Wavelength (nm)
280
270
260

290

Intensity (nomalized scale)

Ⅲ-2

Tl+ centers in alkali halide crystals are well-known
as a strong electron-phonon interaction system andexhibit the broad luminescence band with a large
Stokes shift. Though lots of the optical studies havebeen performed for the Tl+ centers in alkali halides[1,2], the optical measurements with high-resolution
are considerably less. We have performed the opticalmeasurements with high-resolution for NaCl:Tl+
crystals at the BL-3B line of UVSOR.
Figure 1 shows the absorption spectrum up to thevacuum ultraviolet energy region at low temperature
in NaCl:Tl+. The broad absorption bands called A, B,
and C are observed at 4.87, 5.77, and 6.19 eV,
respectively. The A, B, and C absorption bands are
attributed to the intra-ionic transitions from theground 1A1g state to the excited 3T1u, 3T2u+3Eu, and1T1g states in the Tl+ centers, respectively[1,2].
Figure 2 shows the luminescence and absorption
spectra measured by high-resolution spectroscopy inthe vicinity of the A band in NaCl:Tl+. The broad
luminescence band called A' appears with a Stokes
shift. It should be noted that the A' luminescence bandhas a weak zero-phonon line at 4.622 eV. On theother hand, the A absorption band has no zero-phononline and no overlap with the A' luminescence band.
This odd spectra can be explained on the basis of afact that the A' luminescence band is composed of
two luminescence bands.
In general, the A' luminescence band of the Tl+
centers comes from the radiative transitions from therelaxed excited states of 3A1u and 3T1u. The excited
3
A1u state is located at the slightly lower energy
position than the 3T1 state. Since the transition fromthe 1A1g state to the 3A1u state is strongly forbidden,
the absorption band due to the 3A1u state is not
usually observed on the absorption spectrum.
Therefore, the A absorption band observed in theabsorption spectra comes from the transition from the1
A1g state to the 3T1u state. On the other hand, theradiative transition from the relaxed excited state of3
A1u occurs with the long decay time constant of afew milliseconds. If the lattice-relaxation of theexcited 3A1u state is considerably smaller than that of
the excited 3T1u state, the luminescence band from therelaxed excited state of 3A1u would appear at thehigher energy position than that from the excitedrelaxed state of 3T1u. Then, the luminescence bandwith a zero-phonon line might be observed with anapparent Stokes shift, as shown in Fig. 2. Therefore,
the zero-phonon line at 4.622 eV in NaCl:Tl+ is
attributed to the radiative transition from the 3A1u
state.
The luminescence band from the relaxed excited

1

0
4.2

NaCl:Tl+

10 K

A' lumi.
A abs.

4.3

4.4

4.5 4.6 4.7 4.8
Photon Energy (eV)

4.9

Fig. 2. The A’ luminescence band and the Aabsorption band obtained by using a high-resolution
spectroscopy.
[1] A. Ranfagni et al., Advances in Physics 32 (1983)
823.
[2] P. W. M. Jacobs, J. Phys. Chem. Solids 52 (1991)
35.

62

Ⅲ -2. Materials Sciences

BL3B

Anomalous Excitons and Screenings Unveiling Strong Electronic
Correlations in SrTi1-xNbxO3
P. K. Gogoi1,2,3, L. Sponza4, D. Schmidt1, T. C. Asmara1,2,3, C. Diao1, J. C. W. Lim1,2,
S. M. Poh1, S. Kimura6, P. E. Trevisanutto1,3,5, V. Olevano7 and A. Rusydi1,2,3
1Singapore Synchrotron Light Source, National University of Singapore, 117603, Singapore
2
NUSNNI-NanoCore, National University of Singapore, 117576, Singapore
3
Department of Physics, National University of Singapore, 117542, Singapore
4
Laboratoire des Solides Irradiés, École Polytechnique, CNRS, F-91128 Palaiseau, France
5
Centre for Advanced 2D Materials and Graphene Reseach Centre, National University of Singapore, 117546,
Singapore
6
Graduate School of Frontier Biosciences, and Department of Physics, Osaka University, Suita 565-0871, Japan
7
Institut Néel, CNRS, BP 166, F-38042 Grenoble, France
Strong electronic correlations in transition metaloxides are known to drive rich phenomena such as
superconductivity, colossal magnetoresistance andmetal insulator transitions [1]. An example of a modeltransition metal oxide is the perovskite-type SrTiO3(STO). Indeed, STO in various bulk forms andrecently its heterostructures with other oxides, haveshown exotic phenomena such as superconductivity,
magnetisms,
metal-insulatortransitions
andtwo-dimensional electron gas. However the role ofelectronic correlations, particularly electron-hole(e-h) and electron-electron (e-e) interactions, remains
unclear. Then we measured the temperaturedependence of the optical conductivity spectra of
STO and SrTi1-xNbxO3 with x = 0.005 (STNO) andobtained the spectral weight transfer.
In Fig. 1a (1b), the real part of the opticalconductivity, is plotted for STO (STNO) for
temperatures of 4.2, 200 and 350 K. The energy range
is divided into 9 separate ranges for convenience ofanalysis. As can be seen in Fig. 1c (1d) the spectral
weight of the first excitonic region (Ex1) (shown asRegion 2) decreases monotonically with a slight dip
in the temperature range of 75  150 K. STO has aphase transition from cubic to tetragonal around 105
K with a very slight change of the c axis [2]. These
dips, both in STO and STNO, could be due to thisphase change which has been reported to occur over arange of 60 K previously [3]. Here the spectral weightof the band-edge region (shown as Region 3) remains
almost constant for both STO and STNO. A similar
trend is seen for the second excitonic region (Ex2)(shown as Region 5) and the corresponding next
region (shown as Region 6) respectively in Fig. 1e(1f). Also plotted are the spectral weight functions forthe energy range before the excitonic region in thiscase (as Region 4). Importantly it has opposite
spectral weight transfer as that of the excitonic region
and it is seen that the spectral weight for Region 4
and Region 5 are almost conserved together. These
spectral weight analysis sheds further light on thevarious general aspects of the excitonic effects
present in STO and STNO.

Ⅲ-2

Fig. 1. Real part of the optical conductivity andspectral weight transfer. Real part of the opticalconductivity at selected temperatures for (a) STO and(b) STNO. Temperature dependence of spectral
weight for the first direct inter-band (Region 3)transition and for associated excitonic spectra aroundpeaks Ex1 (Region 2) for (c) STO and (d) STNO.
Temperature dependence of spectral weight forregions around and including excitonic peak Ex2 for(e) STO and (f) STNO.
[1] D. N. Basov et al., Rev. Mod. Phys. 83 (2011)
471.
[2] K. A. Müller, W. Berlinger and F. Waldner, Phys.
Rev. Lett. 21 (1968) 814.
[3] K. W. Blazey, Phys. Rev. Lett. 27 (1971) 146.

63

Ⅲ -2. Materials Sciences

BL3B

Ultraviolet Photoluminescence of Gd3+ in Gd3+-Pr3+ Co-Doped Yttrium
Aluminate under Vacuum Ultraviolet Excitation

samples agreed well with the one for a Pr3+ single
doped sample that monitored Pr3+ 5d-4f emission at
243 nm. As the result, the Gd3+ emission mechanism
in Gd3+-Pr3+ co-doped samples was found to beconsiderably different from that in the Gd3+ single
doped one. The Gd3+ emission in Gd3+-Pr3+ co-doped
samples occurred through energy transfer from Pr3+ to
Gd3+, even on the excitation of the host lattices.

It is known that a Gd3+ center shows a sharp
emission peak at approximately 310 nm in UV-B
region, which is attributed to the 4f–4f transition from
6
PJ to 8S7/2 states. The sharp emission from Gd3+ isanticipated as a new light source for medical
application such as phototherapy for skin disease [1]and transilluminator for DNA analysis [2]. In the
recent studies, Pr3+ co-doping was found to give alarge excitation band for Gd3+ emission in somematerials such as LaPO4 [2] and YAlO3 [3]. Although
the excitation band is considered to be derived fromthe Pr3+ 4f-5d absorption, the details are unknown yet.
In this study, Gd3+ and Pr3+ co-doped YAlO3 wereprepared and the fundamental UV photoluminescence(PL) properties were investigated by VUV excitation.
The polycrystalline samples of (Y1-x-yGdxPry)AlO3(x=0.00-0.07 and y=0.00-0.03) were prepared by apolymerized complex method, using Y2O3, Gd2O3,
Pr6O11, Al(NO3)3.9H2O as starting materials. Citricacid monohydrate and propylene glycol were used toform the polymerized complex gels. The sample
powders were obtained by heating at 1400 °C in air.
The obtained powders were pressed into pellets andsintered at 1400 °C in air. The phases in the samples
were identified by the powder X-ray diffraction(XRD) using a Rigaku RINT 2500 diffractometer(CuKα radiation). The emission and excitation
spectra were measured at the beamline BL3B in
UVSOR.
Each sample was identified as a distorted
perovskite type phase with a space group Pnma.
Because no impurity phases were observed in their
XRD patterns, it was confirmed that both Gd3+ andPr3+ were dissolved into the host lattices. Figure 1
shows PL spectra observed in (Y1-x-yGdxPry)AlO3 atroom temperature along with the PL intensities as afunction of x or y. All Gd3+ doped samples showed
Gd3+ emission peaks at 314 nm originating from 6P7/2
to 8S7/2 transition. The maximum PL intensity wasobserved at x=0.07 and y=0.03. It is noteworthy thateven a small amount of Pr3+ co-doping such as
y=0.01 enhanced the Gd3+ emission.
Figure 2 shows PL excitation spectra of(Y1-x-yGdxPry)AlO3. An intense band, that was
assignable to host lattice excitation, was observed at
157 nm for a Gd3+ single doped sample. In contrast,
another intense band was observed at approximately
220 nm for Gd3+ and Pr3+ co-doped samples. The
shape of the excitation spectra for Gd3+-Pr3+ co-doped

3+

Gd

6

8

P7/2- S7/2

3+

Gd

6

0.8

λex=215nm
λem=314nm

0.6
0.4

3+

0.0

3+

Gd x%-Pr 3%

0.2

3+

3+

Gd 7%-Pr y%
0

2

4

3+

3+

6

8

10

Gd3%-Pr3% (λex=215nm)
Gd7%-Pr3% (λex=277nm)

320

340

360

Wavelength (nm)3+12

Gd , Pr concentration x, y

Gd7%-Pr3% (λex=215nm)

8P5/2- S7/2

300

1.0

㻌

PL intensity (arb. units)㻌

380

Fig. 1. Gd PL spectra in (Y1-x-yGdxPry)AlO3.Inset
shows the PL intensities as a function of Gd3+ andPr3+ concentration x, y.

PLE intensity (arb. units)

Ⅲ-2

Department of Materials Science, Graduate school of Engineering, Kyushu Institute of Technology, Kitakyushu
804-8550, Japan2
Department of Chemistry, Faculty of Science, Gakushuin University, Tokyo 171-8588, Japan

Integrated PL int. (arb. units)

1

K. Ueda1, Y. Shimizu1, A. Takiguchi1, Y. Taira2 and Y. Inaguma2

HLGd3%(λem=314nm)
Pr3+
4f-5d

Gd7%-Pr3%(λem=314nm)
Gd3%-Pr3%(λem=314nm)
Pr3% x 3(λem=243nm)
Gd3+

8

150

200

250

S7/2-6IJ

300

Wavelength (nm)Fig. 2. PL excitation spectra of (Y1-x-yGdxPry)AlO3.
Only the spectrum of (Y0.97Pr0.03)AlO3 is magnified.

[1] R. P. Sonekar, S. K. Omanwar, S. V. Moharil, S.
M. Dhopte, P. L. Muthal and V. K. Kondawar, Opt.
Mater. 30 (2007) 622.
[2] S. Okamoto, R. Uchino, K. Kobayashi and H.
Yamamoto, J. Appl. Phys. 106 (2009) 013522.
[3] Y. Shimizu, Y. Takano and K. Ueda, J. Lumin. 141(2013) 44.

64

Ⅲ -2. Materials Sciences

BL3B

Excitation and Emission Spectra of Ce3+ in Ba3Y2B6O15
M. Yoshino, M. Hotta and S. Watanabe

Graduate School of Engineering, Nagoya University, Nagoya 464-8603, JapanThe trivalent lanthanide ions (e.g., Nd3+, Er3+,
Yb3+) in Oxide crystals have drawn attentions due totheir application for luminescent materials in NIR to
UV regions such as solid-state lasers or phosphors.
The trivalent cerium ion, Ce3+, has also attracted
attentions as luminescence centers. In this work, the
4f-5d excitation spectra and emission spectra for Ce3+
in Ba3Y2B6O15 crystal have been measured. For thecomparison, the excitation spectra and emission
spectra for Pr3+-doped Ba3Y2B6O15 have been alsomeasured. The Ce doped and Pr doped samples areproduced by solid state reactions. The concentrationof dopants in the samples are 0.5 and 1.0 mol%.
Figure 1 shows the excitation spectrum monitored
440 nm for Ba3(Y0.995Ce0.005)2B6O15. The peaks B andC originate in the absorption of the 4f-5d transitionsof Ce3+. The peak A originates in the absorption of the
Ba3Y2B6O15 host crystal. The peaks related to theabsorption in the host and the 4f-5d transition oflanthanide ion are seen also in the excitation spectrum
for Pr3+-doped sample. They are shown as A and B in
Fig. 2, respectively. The emission spectra for Ce3+ in
Ba3Y2B6O15 are shown in Fig. 3 and 4. The emission
intensity in 0.5 mol% sample is higher than in 1.0
mol% sample due to the concentration quenching.
Each emission spectra have shoulder and may consistof two peaks due to the two final states of 4f energy
levels. As shown in Fig. 4, the shape of the twoemission spectra with excited in other Ce3+ absorption
wavelength, 336 and 356 nm, are different. From thisresult, these two transitions occur in Ce3+ on the
different sites. On the other hand, similarity in theemission excited with 336 and 187 nm indicates
preferential energy transfer from host to Ce3+ in theparticular site.

Ⅲ-2

Fig. 2. Excitation spectrum of Ba3(Y0.995Pr0.005)2
B6O15.

Fig. 3. Emission spectra of Ce-doped Ba3Y2B6O15.

Fig. 4. Emission spectra of Ba3(Y0.995Ce0.005)2B6O15.
Fig. 1. Excitation spectrum of Ba3(Y0.995Ce0.005)2
B6O15.

65

Ⅲ -2. Materials Sciences

BL3B

Optical Spectroscopy of Nd and Cr Codoped Y3ScxGayAl5-x-yO12
Single Crystals
M. Yamaga, T. Kishita, S. Fujiwara, Y. Takeda and A. Ogata

Department of Mathematical and Design Engineering, Gifu University, Gifu 501-1193, Japan-1

Absorption coefficient (cm )40

Nd:CrYGAG

20

Nd:CrYAG

Nd:CrYSAG

0300 400 500 600 700 800 900

Wavelength (nm)Fig. 1. Absorption spectra for three ganet crystals.

Nd:Cr:YGAG

Intensity (a.u.)10

Nd:Cr:YAG

10

Nd:Cr:YSAG
10

600

700

800

900

1000

Wavelength (nm)Fig. 2. Emission spectra for three garnet crystals.

Nd:Cr:YGAG
Nd:Cr:YAG
Nd:Cr:YSAG

Intensity (a.u.)

Ⅲ-2

Garnet crystals codoped with Nd and Cr are a
candidate of solar-pumped laser materials. In orderto improve pumping efficiency of Nd3+ luminescenceand energy transfer of Cr3+ to Nd3+, substitutional
disordered crystals Y3ScxGayAl5-x-yO12 were prepared.
The prepared garnet crystals were denoted by YAG(x=0, y=0),YSAG (x=0.2, y=0), YGAG (x=0, y=0.2).
The substitution produces inhomogeneous broadening
Enhancementof the Nd3+ and Cr3+ optical spectra.
of overlapping between the Cr3+ absorption and solar
spectra and between the Cr3+ luminescence bands andthe Nd3+ absorption lines lead to an increase of thepumping efficiency and the energy transfer rates,
respectively.
Figure 1 shows the absorption spectra of
Nd:Cr:YGAG, Nd:Cr:YSAG in comparison with thatof Nd:Cr:YAG. The base lines are shifted for clarity.
The sharp lines observed in the ultraviolet (UV),visible, and near infrared (IR) regions for three
crystals are due to the optical transitions from the 4I9/2
multiplet ground state of Nd3+ to the multiplet excitedstates. Three broad bands with peaks at 270, 430, and
600 nm are assigned to the optical transitions fromthe 4A2 ground state of Cr3+ to the 4T1(2), 4T1(1), and4
T2 excited states, respectively. The difference in theabsorption spectra of (Nd:Cr:YGAG, Nd:Cr:YSAG)
and Nd:Cr:YAG in Fig. 1 is inhomogeneous
broadening of the Nd3+ lines in Nd:Cr:YGAG or
Nd:Cr:YSAG caused by substitution of Ga3+ or Sc3+
for Al3+, respectively. The absorption coefficients of
Cr3+ bands and Nd3+ lines in Nd:Cr:YGAG and
Nd:Cr:YSAG were (2.5, 0.7) or (0.7, 0.1) times
compared with those in Nd:Cr:YAG, respectively.
This estimated ratios are nearly equal to theconcentration ratios of Cr and Nd contained in thesesamples, respectively.
Figure 2 shows the normalized luminescence
spectra excited at 430 nm in the 4T1(1) absorption
band of Cr3+ for three crystals. These spectra consistof sharp intense R lines around 690 nm andphonon-absorbed and phonon-emitted side bands
around 678 and 707 nm of Cr3+ and weak near IR
lines around 885 nm due to the optical transitions
from the metastable 4F3/2 excited state of Nd3+ to the4
I9/2 lowest state.
Figure 3 shows the excitation spectra of the Nd3+
luminescence lines at 885 nm for three crystals. The
excitation spectra are the superposition of the Cr3+
absorption bands and the Nd3+ absorption lines. The
observation of the Cr3+ bands in the Nd3+ excitation
spectrum gives evidence on the energy transfer from
Cr3+ to Nd3+.

300

400

500

600

700

800

Wavelength (nm)Fig. 3. Excitation spectra for three garnet crystals.

66

Ⅲ -2. Materials Sciences

BL3B

Relaxed Exciton Luminescence of RbCl Heavily Doped with RbI
N. Ohno and K. Sakae

Graduate School of Engineering, Osaka Electro-Communication University, Neyagawa 572-8530, Japan
Extensive studies have been made on luminescencearising from localized relaxed excitons in alkali
chlorides containing iodine impurities. Dilute I–doped crystals stimulated with VUV light or X-rays
produces characteristic luminescence bands. The
luminescence bands have been well explained interms of localized relaxed excitons at ICl– molecule(I– monomer) and a complex of two iodine ions (I–dimer) [1,2]. However, optical and luminescence
properties of heavily iodine-doped alkali chloride
crystals have not been examined sufficiently so far.
Recently our group have studied luminescence
properties of KCl heavily doped with KI as reported
in ref. [3]. The present report describes the results of
RbCl heavily doped with RbI.
The crystals of RbCl:I were grown by the
Bridgeman method from reagent grade RbCl addedwith an appropriate amount of RbI (up to 5 mol %).
The optical measurements were made at 15 K at
BL3B station.
In dilute crystals, the photoluminescence spectra
were almost the same as those of the previous studies[4,5]: three luminescence bands peaking at 2.46 eV(monomer emission), 4.38 eV (dimer emission) and at
5.76 eV (NE emission). Photoexcitation spectra forthe dimmer emission are shown in Fig. 1 for various
RbI mol % crystals detected at 4.38 eV. The each
spectrum has been normalized at unity at the
maximum. The excitation peaks at 6.25 and 6.78 eVof 0.01 mol % crystal move toward the lower energy
side with increasing RbI concentration. The low
energy shift of the excitation bands suggests that
there coexist dimers, trimers and lager sizes of I – ions
(RbI cluster) in heavily-doped RbCl:I crystal as canbeen observed in heavily-doped KCl:I [3].
The luminescence energies of the trimers andclusters of I – ions in heavily doped RbCl:I crystals
are expected to be different from that of I– dimers. We
have examined the photoluminescence spectra excited
at various photon energies. The results for 1 mol %crystal are shown in Fig. 2. It is clearly confirmedthat the peak energy of the luminescence band moves
towards the low energy side when excited with lower
photon energy. These luminescence bands aresupposed to be the composite bands due to radiativeannihilation of the relaxed exciton at dimers, trimers
and clusters of I – ions [3].
In RbCl crystals containing RbI around 1 mol %,there exists a small amount of dimer centers ascompared with monomers, and moreover the amountof trimers and clusters of RbI is extremely smallerthanthose of monomers and dimers. However, theNormarized Intensity

luminescence intensities of such large-sized centers
are found to be comparable with that of the dimer
emission. This fact suggests that the excitons trappedin RbI clusters in heavily doped RbCl:I crystals
would give the high luminescence efficiency.

1

RbCl:I
3mol%
1mol%
0.01mol%

0
5.5

6.0

6.5

7.0

7.5

Photon Energy [eV]Normarized Intensity

Fig. 1. Photoexcitation spectra of RbCl:I crystals
detected at 4.38 eV for various RbI mol % at 15 K.

RbCl:I

6.08eV
6.02eV
5.96eV
5.90eV
5.85eV
5.80eV

1

0
3.8

4.0

4.2

4.4

4.6

4.8

Photon Energy[eV]Fig. 2. Photoluminescence spectra of RbCl:I (1mol %) crystal excited with various photon energies at
15 K.
[1] N. Nagasawa, J. Phys. Soc. Jpn. 27 (1969) 1535.
[2] K. Kan’no, K. Tanaka and T. Hayashi, Rev. Solid
State Sciences 4 (1990) 383, and references therein.
[3] A. Ohno and N. Ohno, Phys. Status Solidi C 8(2011) 112.
[4] O. Arimoto, K. Sasaki, H. Nakatani, K. Kan’no
and Y. Nakai, J. Lumin. 31&32 (1984) 333.
[5] K. Kan’no, H. Nakatani, T. Mukai, O. Arimoto,and Y. Nakai, J. Phys. Soc. Jpn. 55 (1986) 2433.

67

Ⅲ-2

Ⅲ -2. Materials Sciences

BL3B

Near Band Edge Absorption Spectra and Green Band Excitation Spectrumof Boron-Doped Diamond Films
1

Department of Electrical and Electronics Engineering, University of Fukui, Fukui 910-8507, Japan
2
FIR Center, University of Fukui, Fukui 910-8507, Japan3
Department of Electronics, Tokai University, Hiratsuka 259-1292, Japan

Boron (B) is one of the best elements for p-type
impurity of the diamond semiconductor devices.
Boron-doped diamond (BDD) is also known as theblue diamond. Then, we have been measuring the
CEES (Combined Excitation Emission Spectroscopy)
around the band-gap (excitation energy 4.5 ~ 7.0eV)
in order to clarify the electron state of BDD whose B
concentrations is in the metal like - semiconductortransition region. In this study, we have focused on
the CEES pattern differences of between BDDs andnon B doped diamond (substrate) around the H3emission band which consists of several sharp peaks
and has the maximum peak at 2.47 eV.
The BDD films used in this study are grown on
Ib-synthesized diamond substrates by the MPCVD(Microwave Plasma Chemical Vapor Deposition)
method and their B concentration are 1000, 5000 and
10000 ppm [1]. All CEES measurements including
the diamond substrate (0 ppm) have been performed
at BL3B (and BL7B).
Figure 1 show the CEES patterns of both 1000
ppm and 10000 ppm BDD samples at 9 K. The
horizontal and the vertical axes correspond to theemission photon energy and the excitation photon
energy, respectively. Strong emissions around 2.4eV
at low excitation photon energy region (<~6.0eV) are
H3 emission band which are due to the nitrogen
dimer defect (H3) centers in the substrate. The drastic
intensity increases of the H3 emissions at 5.5 eV in
Fig. 1 suggest that the indirect band gap locates atabout 5.5 eV. On the other hand, at high excitation
photon energy region (>~6.0eV), no H3 emission
band has been observed in any samples without 0ppm, because the excitation light cannot reach
substrates through BDD thin films due to the strong
absorption of BDD at high excitation photon energy
region. However, 1000 ppm only show a different
Gaussian type emission band whose peak locates at
2.3 eV. This emission band is probably assigned as
the Green emission band that is often observed in the
BDD. Figure 2 shows the excitation spectrum of theGreen emission band. We believe that this is the firstexcitation spectrum of this emission band.
From the above description, the excitation photon
energy dependence of the H3 emission band intensity
represents the photon energy dependence of thetransmittance of the BDD thin film. Then, we try to
make the near band edge absorption spectra of the
BDD thin films. Figure 3 shows the absorption

spectra of 1000 ppm, 5000 ppm and 10000 ppm BDD
thin films.

Fig. 1. CEES patterns of 1000 ppm (left) and 10000ppm (right) BDD samples at 9 K.

Integrated Intensity (a.u.)

3.6

1000 ppm

2.4

1.2

0.0

5.6

5.8

6.0

6.2

6.4

6.6

6.8

7.0

Excitation Photon Energy (eV)Fig. 2. Excitation spectrum of the Green emission
band.
Absorption Coefficient -1/2 (x102 cm-1/2)

Ⅲ-2

S. Kondou1, K. Fukui1, K. Yamamoto2 and T. Inushima3

1.41000 ppm
5000 ppm
10000 ppm

1.1

0.7

0.3

0.0
5.5

5.6

5.7

5.8

5.9

6.0

6.1

6.2

6.3

6.4

6.5

Excitation Energy (eV)Fig. 3. Absorption spectra of 1000 ppm, 5000 ppm
and 10000 ppm BDD thin films.
[1]A. Ogasawara, T. Inushima, T. Shiraishi, S. Ohya,
S. Karasawa and H. Shiomi, Diamond Related Mater.
6 (1997) 835.

68

Ⅲ -2. Materials Sciences

BL3B

Optical Properties of SrCeO3 Crystals
1

H. Numata , M. Kitaura2, S. Watanabe3, S. Kurosawa4, K. Yubuta4 and A. Ohnishi2
1

School of Science and Technology, Yamagata University, Yamagata 990-8560, Japan2
Department of Physics, Faculty of Science, Yamagata 990-8560, Japan3
Department of Materials, Physics and Energy Engineering, Graduate School of Engineering, Nagoya
University, Nagoya 464-8063, Japan
4
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
From analogy with CeO2, the electronic state of
SrCeO3 is considered to be in the mixed-valence state
due to mixing between 4f0 and 4f1L-1 configurations,where L-1 denotes the hole in valence band mainlycomposed O-2p orbitals [1]. The mixed valence state
results from hybridization between O-2p and Ce-4f
orbitals. Basically, Ce-4f electrons have localized
character. However, it is considered that they haveitinerant character, owing to the mixed valence state.
Since either localization or itinerancy should bereflected in the conductive behavior of Ce-4f
electrons, photoconductivity experiment is favorable
to investigate the dynamical behavior of Ce-4f
electrons in photoexcited SrCeO3. As a first step, we
havemeasured
photoabsorption(PA),photoluminescence (PL), PL excitation (PLE) spectraof SrCeO3 crystals, in order to obtain fundamental
optical properties. These data provide us information
on creation and relaxation processes of Ce-4f
electrons and O-2p holes.
SrCeO3 crystals were grown in air by a Floatingzone method. They were annealed under oxygen
atmosphere for 24h at 1070K. Crystal surfaces weremechanically polished. Experiment was performed at
the beamline BL3B in UVSOR facility. PA spectra
were obtained by detecting incident and transmitted
light with a calibrated silicon photodiode. PL and
PLE spectra were measured using the combination ofa grating monochromator and a CCD detector or aphotomultiplier, respectively. PLE spectra werecorrected for the energy distribution of excitation
light source.
Figure 1 shows PA (green line), PL (blue line) andPLE (red line) spectra, which were measured at 9 K.
The PA spectrum exhibits the fundamental absorption
edge at 2.46 eV. According to the electronic structure
calculation reported previously, such a rapid increaseis ascribed to the formation of the charge transfer(CT) excitons which are composed of Ce-4f electronsand O-2p holes. A PL band appears around 2.30 eV
under excitation at 4.81 eV. A similar band isobserved in PL spectra of Sr2CeO4 [4]. The PLE
spectrum for the 2.30 eV band shows that it is excitedin the energy region above 3.46 eV. The intensity of
the 2.30 eV band reaches the maximum at 4.07 eV,
and is gradually decreased with increasing photon
energy.
The 2.30 eV band is excited in the fundamental
absorption region. This result suggests that the 2.30

eV band is an intrinsic feature in SrCeO3. This bandhas the Stoke shift of 0.30 eV. It is likely to consider
that the 2.30 eV band originates from the relaxedstate of a CT exciton, which may localizes on aoctahedral (CeO6)8- complex ion.
The threshold for excitation of the 2.30 eV band is
not agreement with the fundamental absorption edge.
Such a disagreement implies that CT excitonsannihilate nonradiatively under photoexcitation near
the fundamental absorption edge. There are two
possible explanations for this. One is that CT excitonstransfer their energy to lattice imperfections before
lattice relaxation. The other is that CT excitons
immediately relax to the ground state without
emitting 2.30 eV band. The missing of 2.30 eV bandis an open problem to be solved, and details of it will
be clarified by photoconductivity experiment.

Fig. 1. PA (green line), PL (blue line), and PLE (redline) spectra of SrCeO3 crystals measured at 9K.
[1] A. Fujimori et al., Phys. Rev. B 28 (1983) 2281.
[2] M. Niwano et al., J. Phy. Soc. Jpn. 57 (1988)
1489.
[3] H. Numata et al., UVSOR Activity Report 201341 (2014) 63.
[4] L. V. Peterson et al., J. Electrochem. Soc. 147(2000) 4688.

69

Ⅲ-2

Ⅲ -2. Materials Sciences

BL3B

VUV Absorption Spectra of Alanine Single Crystals
S. Tanaka, M. Kitaura, A. Ohnishi and M. Sasaki

Department of Physics, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan

Ⅲ-2

Amino acids are simple chiral molecules with Land D-forms. Protein molecules are composed of only
L-amino acids. This is called “homochirality”, which
has attracted much attention in relation to the mysteryof life. It has been generally accepted that thehomochirarity of proteins come from the creation of
L-amino acids by circularly polarized VUV light inouter space region. So far, VUV absorption spectra ofamino acids have been studied using their aqueous
solutions [2] and thin films [3]. To our knowledge,
there is no report on VUV absorption spectra ofamino acid single crystals. In the present study, VUVabsorption spectra of alanine crystals have beenmeasured to provide the true absorption spectrum ofit, and to verify the validity of natural circlulardichloism spectra already reported [4].
The alanine single crystals were obtained by theslow evaporation from saturated aqueous solution ofcommercial L-alanine regent (SIGMA-ALDRICH,
purity > 99.5%). The photograph of an alanine single
crystal used in our experiment is shown in Fig. 1. The
crystal structure of alanine is orthorhombic, andorthogonal crystalline axes exist in the cleavage place.
They were distinguished by two polarizers arranged
in a cross Nicole alignment. However, it could not be
determined which are they among a, b and ccrystalline axes.
Figure 2 shows the VUV absorption spectra of analanine single crystal for different configurations oflinearly polarized light. These data were obtained by
the Kramers-Kronig analysis from the VUVreflectivity spectra in 5-30 eV range measured atroom temperature. A number of peaks are observe in
5-10 eV range. They show remarkable linear
dichroism, which has not been found in Refs. 2 and 3.
A broad peak is observed in around the 14.0 eV. This
peak has been reported in Ref. 4. The VUVabsorption spectra of an alanine crystal are shown inan expanded scale of 5-12 eV. They are composed ofpeaks around 6.0, 6.8, 7.5, 8.0, 9.2, and 10.0 eV. In
Ref. 4, the natural circular dichroism spectrum of a
L-alanine deposite thin film exhibited peaks at 6.8
and 8.0 eV and dips at 6.2 and 7.5 eV. Since theenergies are in good agreement with those ofabsorption peaks in Fig. 3, we can say that there is no
doubt on the validity of natural circular dichroism
spectra in Ref. 4.

Fig. 1. Photograph of an alanine crystal used in our
experiment.

Fig. 2. VUV absorption spectra of an alanine crystal,
which were obtained by the Kramers-Kronig analysis
from reflectivity spectra in 5-30 eV range measured
at room temperature.

Fig. 3. VUV absorption spectra of an alanine crystal
in an extended scale of 5-12 eV.
[1] P. A. Snyder et al., Biopolymers 12 (1973) 975.
[2] T. Inagaki et al., Biopolymers 12 (1973) 1353.
[3] M. Tanaka et al., J. Electron Spectrosc. Relat.
Phenom. 181 (2001) 177.
[4] F. Kaneko et al., J. Phys. Soc. Jpn. 78 (2009)013001.

70

Ⅲ -2. Materials Sciences

BL3B

Temperature Dependence of Absorption Spectra
for Ce3+-Doped Y3Al5O12 Single Crystals
1

S. Watanabe1, M. Nakaya1, J. Onoe1, M. Kitaura 2, K. Kamada3 and A. Ohnishi2

Department of Materials, Physics and Energy Engineering, Graduate School of Engineering, Nagoya
University, Nagoya 464-8603, Japan2
Department of Physics, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan3
New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579, Japan

Ce3+-doped Y3Al5O12 (Ce:YAG) have been widely
studied for application as a yellow phosphor used inwhite light LEDs. The basic research on opticalproperties for Ce:YAG is important issues fordevelopment of luminescent materials. In addition,
the detailed analysis based on a first-principles
calculation is useful for understanding the opticalproperties of luminescent materials.
In this study, we have performed experimental andtheoretical investigation of the temperaturedependence of the 4f-5d absorption spectra for
Ce:YAG single crystals.
The single crystals of Ce:YAG were grown by the
micro pulling down method. The concentration of
Ce3+ was 1 mol%. The 4f-5d absorption spectra were
measured at 9 and 312 K. These absorption spectra
were analyzed by using a first-principles
configuration interaction calculation [1,2]. The effectsof lattice relaxation due to the substitution of Y3+ by
Ce3+ were considered using the optimized structure
estimated by a first-principles DFT calculation.
Figure 1 shows the experimental 4f-5d absorption
spectra of Ce:YAG at 9 and 312 K, respectively.
Three major peaks A, B and C were observed in both
spectra. These peaks can be attributed to the Ce3+
4f-5d absorption peaks. The peak intensities depend
upon temperature. As shown in Fig. 1, the intensity ofpeak B at 9 K increases, compared with that at 312 K.
In order to investigate the effects of thermal
excitation, we calculated the oscillator strengths forthe transitions from two different initial states since
the Ce3+ 4f5/2 level slightly splits due to the crystal
field. Figure 2 shows the theoretical 4f-5d absorption
spectra of Ce:YAG. Figure 2(a) shows the oscillator
strengths from the lowest 4f5/2 level, and Fig. 2(b)shows the oscillator strengths from the higher-lying
4f5/2 level which is 0.108 eV higher than the lowest
level. The oscillator strength of the peak B for thetransition from the higher-lying 4f5/2 level issignificantly strong, compared to that from the lowest
level. This result clearly indicates that the origin of
the strong temperature dependence of the peak B in
the experimental spectra can be ascribed to thechange of re-distribution of electron population inside
the 4f5/2 level by the initial state due to the thermal
excitation.

A
C

B

Ⅲ-2

312 K
A
C
B

9K

Fig. 1. Experimental absorption spectra of Ce:YAG
at 9 and 312 K.

B

(b)
C

A

C

A

(a)

B
Fig. 2. Theoretical absorption spectra of Ce:YAG. (a)Oscillator strengths from the ground state of 4f5/2
level. (b) Oscillator strengths from second-lowest 4f5/2
level.
[1] K. Ogasawara et al., Phys. Rev. B 64 (2001) 143.
[2] S. Watanabe et al., Phys. Rev. B 81 (2010)
125128.

71

Ⅲ -2. Materials Sciences

BL3B

Two-Band Luminescence from an Intrinsic Defect in Spherical andTerraced MgO Nanoparticles
1

Ⅲ-2

P. V. Pikhitsa1, C. Kim1, S. Chae1, S. Shin1, S. Jung1, M. Kitaura2,
S. Kimura3, K. Fukui4 and M. Choi1

Global Frontier Center for Multiscale Energy Systems, Division of WCU Multiscale Mechanical Design, Schoolof Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-744, Korea
2
Deparment of Physics, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
3
UVSOR Facility, Institute for Molecular Science and the Graduate University for Advanced Studies, Okazaki444-8585, Japan
4
Department of Electrical and Electronics Engineering, Faculty of Engineering, University of Fukui, Fukui
910-8507, Japan

Magnesium oxide nanocubes obtained by the
self-combustion of Mg metal have long exhibited
only a broad 2.9 eV cathodoluminescence (CL) band
owing to oxygen vacancies (F centers). In our work, aroom-temperature ultraviolet 4.8 eV CL band has
been observed coincident with a 2.5 eV band of thesame intensity from an unexplored intrinsic defect in
MgO terraced nanocubes and nanospheres produced
from Mg metal during combustion in an H2/O2 flame.
Synchrotron radiation excitation spectra reveal thatthe excitation energy at the onset of both bands is justabove the bandgap energy of 7.7 eV, where electrons
and holes are generated (see Fig. 1).
Figure 1 compares the PL spectra, taken at 8 K, forphoton excitation energies swept through theforbidden band and up to 10 eV from the UV-MgO(Fig. 1(a)) and the non-UV-MgO cubes (Fig. 1(b)). It
is clear that the two PL bands observed in CL arise
simultaneously at 7.7 eV and persist as the excitationenergy sweeps deeper into the conduction band (Fig.
1(a)). This is a strong indication that both bands(marked by red circles in Fig. 1(a)) have the same
origin and that electrons and holes from theconduction band are solely responsible and necessary
for the excitation of the two bands, similar to theelectron and hole “shower” in CL, when it isunderstood that a photon of 8 eV leads to theformation in MgO of a conduction electron and a holethat do not undergo transformation into a self-trappedstate.
We determine that a defect, responsible for bothemission bands, creates proximal anion-cation
vacancy pairs named P centers that may appear
instead of F centers because of changes in the MgOnanoparticle growth conditions.
The discovery of two-band room-temperature CL
from spherical and terraced MgO nanoparticles may
find applications in defect-center lasers based upon
MgO and in spectral transformers.1 The two-band CL
may also have applications in the geosciences
because its presence or absence should be useful todistinguish the history of MgO formation in the
Earth’s mantle or in planetary nebula.

Fig. 1. Photoluminescence spectra vs. excitationenergy from synchrotron radiation (intensity grows
from blue to red). (a) Red circles marking correlated
emission bands at 4.8 eV (upper) and 2.5 eV (lower)
from UV-emitting MgO. The F+ band at 420 nm isfrom the non-UV-MgO present in the powder sample.
(b) Emission from non-UV-MgO cubes, where the F+band at 420 nm is present but the 4.8 and 2.5 eVbands are absent. (c) CL spectrum for UV-MgO taken
at 79 K (blue) and the deconvoluted spectral peaks(red and green curves). The additional two-band
spectrum (green curve) is compared with (d) the
two-band synchrotron radiation spectrum (notcorrected for intensity magnitude) excited at 8 eV and8 K taken from (a).
[1] A. Lushchik, E. Feldbach, R. Kink, Ch. Lushchik,M. Kirm and I. Martinson, Phys. Rev. B 53 (1996)
5379.

72

Ⅲ -2. Materials Sciences

BL4U

Scanning Transmission X-Ray Microscopy Study on Fluorescence
Mechanism of Nanocarbon-Silica Composites
S. Kawasaki, H. Song and Y. Takeuchi

Nagoya Institute of Technology, Nagoya 466-8555, Japan

Intensity /arb. units

Mesoporous carbon-silica (MPCS) composites
synthesized by tri-constituent co-assembly method
have fascinating nano-space structures. We haveinvestigated Li-ion battery anode and EDLC
electrode properties of the composites. In the courseof the investigation we found that mesoporous
carbon-silica composites exhibit very intense visible
photoluminescence under low-energy ultra-violet
light irradiation.[1-5] Now, a class of stable, efficient,
inexpensive and less toxic photoluminescentmaterials
which emit
white
light
under
long-wavelength UV light is strongly required toreplace fluorescent lamps by LED lamps. The
composites we synthesized satisfy the requiredconditions and are the promising materials from theenvironmental point of view. However, detailed
mechanism of the fluorescence property of MPCS has
not been understood well. Then, in order tounderstand the mechanism, we performed scanningtransmission
x-ray
microscopy(STXM)
measurements of MPCS samples.
MPCS samples were prepared by tri-constituent
co-assembly method. Tetraethyl orthosilicate (TEOS)
and resol are used as silica and carbon sources,
respectively. Tri-block co-polymer (BASF F-127)
was used as a soft template. Carbonization was donein nitrogen atmosphere at 1170 K. Oxidation was
done in air at 720 K. The obtained MPCS samples
were characterized by TEM, SEM, XRD, Raman, andN2 adsorption measurements. STXM measurements
were performed at BL-4U of UV-SOR of Institute for
Molecular Science, Okazaki, Japan.
Figure 1 shows the observed C K-edge X-ray
absorption spectrum of MPCS sample. For usual bulk
carbon samples, sharp π* absorption peak is observedat around 285 eV. However, as shown in Fig. 1, for
MPCS sample, the peak at around 285 eV is verybroad and the peak-top is observed at about 288 eV.
The cluster size of nanocarbons remained in MPCS
sample after the oxidation treatment should be verysmall. If π conjugation scale is decreased, π-π* gapshould be widen. This would be the reason why thepeak-top of π* absorption of MPCS sample isobserved at higher energy than usual bulk carbon
samples. To confirm the validity of this hypothesis,
we should perform STXM measurements of several
kinds of MPCS samples having different carbon
cluster sizes.

Ⅲ-2

285

290

295

300

Photon energy /eV

Fig. 1. Carbon K-edge X-ray absorption spectra ofmesoporus carbon-silica composite sample.
[1] Y. Ishii, A. Matsumura, Y. Ishikawa and S.
Kawasaki, Jpn J. Appl. Phys. 50 (2011) 01AF06-1.
[2] Y. Ishikawa, K. Sato, S. Kawasaki, Y. Ishii, A.
Matsumura and S. Muto, physica status solidi (a) 209(2012) 1022.
[3] K. Sato, Y. Ishikawa, Y. Ishii, S. Kawasaki, S.
Muto and Y. Yamamoto, Jpn. J. Appl. Phys. 51 (2012)08240.
[4] Y. Ishikawa, S. Kawasaki, Y. Ishii, K. Sato and A.
Matsumura, Jpn. J. Appl. Phys. 51 (2012) 01AK02.
[5] Y. Ishii, Y. Nishiwaki, A. Al-zubaidi and S.
Kawasaki, J. Phys. Chem. C 117 (2013) 18120.

73

Ⅲ -2. Materials Sciences

BL4U

The Effect of Carbon Bombardment of ZnO Probed by
Scanning Transmission X-Ray Microscopy
Y. F. Wang1, S. H. Hsieh1, J. W. Chiou2, W. F. Pong1, T. Ohigashi3 and N. Kosugi3
1

Department of Physics, Tamkang University, Tamsui 251, Taiwan
Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan
3
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan2(a) NW(b) NC

2 μm

2 μm

2 μm

2 μm

2 μm

(c) C:NW

2 μm

1 μm

1 μm

1 μm

1 μm

0.5 μm
0.25

2 μm

2 μm

2 μm

2 μm

0.5 μm

0.5 μm

0.5 μm

0.5 μm(d) C:NC
1 μm(e)
O K-edge

0.25━ NW-Thin━ NW-Thick

0.20

(f)
O K-edge━ NC-Thin━ NC-Thick

0.20━ C:NW-Thin━ C:NW-Thick

0.15━ C:NC-Thin━ C:NC-Thick

0.15

Intensity (a.u.)

Intensity (a.u.)

Ⅲ-2

In the present work, the effect of carbon
bombardment of ZnO nanowires (NW) andnanocactus (NC) has been studied using X-ray-based
microscopic and spectroscopic techniques. Figures1(a-d) display the O K-edge scanning transmission
X-ray microscopy (STXM) stack mappings of
randomly selected sample regions of ZnO NW and
NC before and after carbon bombardment (C:NW
and C:NC). The stack mappings are decomposed into
blue, yellow, red and green maps (right panels),
which correspond to the regions that are associatedwith different thickness and spectroscopic variationsof the samples. Overall, the divisions of the
mappings into thick (green), thin (red), carbon lacing(yellow) and background (blue) regions weregenerated via principle component analysis (PCA)
for cluster analysis based on spectroscopic
differences. The O K-edge STXM-XANES (X-ray
Absorption Near-Edge Structure) spectra in the Figs.
1(e) and 1(f) are the sum of the corresponding
XANES spectra of the thick (green) and thin (red)regions of ZnO NW and NC before and after C
bombardment, respectively.
As displayed in Figs. 1(e) and 1(f), according to
the dipole-transition selection rule, the near featuresat ~535-550 eV in the O K-edge STXM-XANES
spectra are attributed to the electron excitations fromO 1s-derived states to 2pσ-derived (along the bilayer)
and O 2pπ-derived (along the c axis) states, which areapproximately proportional to the density of theunoccupied O 2p-derived states. The O K-edge
STXM-XANES spectra clearly reveal that theintensities of near features in the thin regions arehigher than those in the thick regions of ZnO
NC/NW and C:NC/C:NW. The enhanced intensitiesof the near features in the O K-edge STXM-XANES
spectra can result in a higher population of defects inthe thin or surface/edge regions because of the nonstoichiometric chemical composition or dangling
bonds.[1]Additionally, the intensities of near features of
ZnO C:NC/C:NW samples (after C bombardment)
are also higher than those in ZnO NC/NW samples(before C bombardment), further suggesting that thebombarding C atoms may play an important role toenhance density of the unoccupied O 2p-derived
states.

0.10

0.05

0.00

0.10

0.05

0.00
530

540

550

Photon Energy (eV)

560

530

540

550

560

Photon Energy (eV)Figs. 1. (a)-(d): O K-edge scanning transmission Xray microscopy (STXM) stack mappings of
randomly selected sample regions of ZnO NW and
NC before and after carbon bombardment (C:NW
and C:NC). The spatial distribution of background(blue), carbon lacing (yellow), thick (green) and thin(red) regions of samples. (e) and (f): The O K-edge
STXM-XANES spectra are the sum of thecorresponding XANES spectra between the thin(red) and thick (green) regions of ZnO NW and NC
before and after C bombardment, respectively.
[1] S. B. Singh et al., Nanoscale 6 (2014) 9166.

74

Ⅲ -2. Materials Sciences

BL4U

Chemical Redox of Mesoscopic NiO/CH3NH3PbI3 Perovskite
Heterojunction by Scanning Transmission X-Ray Microscopy
M. W. Lin1, K. C. Wang2, L. T. Chang1, Y. L. Lai1, T. Ohigashi3, N. Kosugi3,
P. Chen2 and Y. J. Hsu1,21National 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, Japan2

The corresponding micro NEXAFS spectra as the
cross marks shown in Figure 1 are displayed in Figure
2a and 2b for O K-edge and Pb N-edge, respectively.
In comparison with pristine NiOnc (as shown in theinset of Figure 2b), the spectra show decreased peakintensity at 532.1 eV and broader peak width between
535-545 eV. The micro NEXAFS of Pb N-edge in
Figure 2c express similar shape and intensity. Our
results suggest that the redox is occurred atheterojunction and the formation of perovskite is
located in the mesoporous structure of NiOnc.

Organometal trihalide perovskite-based solar cells
have exhibited high power conversion efficiencies
when incorporated into mesoscopic NiO (NiOnc)
hole-transport layers [1]. Herein we studied the origin
of such high efficient carrier transport in terms ofelectronicandchemicalproperties
ofheterojunction
by
x-ray
perovskite-NiOnc
photoelectron spectroscopy (XPS), Near-edge X-ray
absorption fine structure (NEXAFS), and scanningtransmission X-ray microscopy (STXM).
From our previous studies, we found a pronounced
chemicalredox
between
CH3NH3PbI3
perovskite-NiOnc heterojunction that PbI2 is oxidized
to PbO and subsequently produce hole-dopant
CH3NH3PbIO at the heterojunction. From the O
K-edge spectra in an auger-electron-yield (AEY)
mode, we observed an extra distinct peak at 535 eV for
ITO/NiOnc/CH3NH3PbI3 in comparison to pristine
NiOnc. This additional peak is apparently produced by
the contact reaction at heterojunction of
NiOnc/CH3NH3PbI3. As a results, the generation ofhole-doping CH3NH3PbIO at NiOnc/perovskite
heterojunction plays a critical role to facilitate thecarrier transport, and thus enhance the solar cell
efficiencies.[2]To further confirm the redox reaction at NiOnc andCH3NH3PbI3 perovskite heterojunction, chemicalmaps of oxygen distributions within microaggregatesof SiN/NiOnc/CH3NH3PbI3 are studied by STXM.
Figure 1 displays the STXM images of
SiN/NiOnc/CH3NH3PbI3, which are optical density(OD) maps obtained at (a) 532.1 eV and (b) 535.1 eV,
the characteristic absorption peaks of NiOnc andCH3NH3PbIO, respectively as mentioned above. The
Pb OD map of the SiN/NiOnc/ CH3NH3PbI3 as shownin Figure 1b is obtained at 610 eV. These image
mappings of O and Pb on SiN/NiOnc/CH3NH3PbI3show similar elemental distribution in morphology
and size except the contrast. As a result, we anticipate
that the Pb is bonded with O and located on themesoporous structure of NiOnc. The image acquired at532.1 eV which is composed of major characters of O
2p and Ni 3d orbitals, exhibits weaker image contrast
than that obtained at 535.1 eV, indicating the NiOnc is
involved in the interfacial redox reaction atheterojunction. The more redox occurs, the lower the
peak intensity of 532.1 eV and thus the weaker thecontrast displays.

(a)

(b)

(c)

Fig. 1. The OD images of O K-edge at (a) 532.1 eV,(b) 535.1 eV, and (c) Pb N-edge at 654 eV from
SiN/NiOnc/CH3NH3PbI3.

(a)

(b)

(c)

Fig. 2. Micro-NEXAFS spectra of the O K-edge and
Pb N-edge extracted from the Figure 1a, 1b, and 1c,
respectively. The inset in Figure 2a shows the O
K-edge NEXAFS of pristine NiOnc.
[1] K. C. Wang, J. Y. Jeng, P. S. Shen, Y. C. Chang, E.
W.-G. Diau, C. H. Tsai, T. Y. Chao, H. C. Hsu, P. Y.
Lin, P. Chen, T. F. Guo and T. C. Wen, Sci. Rep. 4(2014) 4756.
[2] Ming-Wei Lin, Kuo-Chin Wang, Yu-Ling Lai,
Takuji Ohigashi, Nobuhiro Kosugi, Peter Chen,
Tzung-Fang Guo and Yao-Jane Hsu, “Chemical
Redox of Mesoscopic NiO/CH3NH3PbI3 Perovskite
Interfaces for High Efficient Solar Cell”, inpreparation.

75

Ⅲ-2

Ⅲ -2. Materials Sciences

BL4U

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

Monolithic polymers are a new generation of
stationary phases for chromatography, offeringsignificant benefits over currently particle-basedmaterials. The main characteristic of these materials
is the presence of large through-pores which permits
the use of high flow rates at low backpressures [1].
However, improvements in this technology rely on
being able to accurately characterize the porous
structure and new characterization techniques areneeded to better understand the polymer morphology
and its optimization. In this sense, the relatively highpenetration power of X-rays would allow acomprehensive analysis of the radial and longitudinal
heterogeneity of the monolithic materials developedin our research group.
The characterization by STXM of polymer
monoliths was performed at the BL4U beamline of
the UVSOR synchrotron radiation facility. To obtain asuitable sample for STXM studies, the macroporous
styrene-divinylbenzene (Sty-DVB) monolith withencapsulated hydroxyapatite (HAP) and titanium
dioxide (TiO2) nanoparticles was embedded with an
aliphatic epoxy resin specially designed for STXM
analysis [2]. The experiments were performed at the
C-K, Ca-L and Ti-L edges. Figure 1 shows the
NEXAFS spectra for both the HAP and TiO2
nanoparticles. Both spectra show several peaks wich
are a result of the combination of spin-orbit splitting
between the 2p and 3d orbitals [3, 4].
The spectrum of the Sty-DVB polymer has a peakat 285.2 eV which corresponds to the C 1s→π*C=Ctransition of aromatic systems (spectrum not shown).
These
spectrocopic
differences
allowedidentification and mapping of each type ofnanoparticle within the polymer monolith. Figure 2
presents STXM optical density (OD) images at threedifferent energies of a monolith containing 5% wt/wt
of each nanoparticle. It is possible to see the HAP
nanoparticles at 349 eV (Fig. 2. panels a and d), theTiO2 nanoparticles at 460.4 eV (Fig. 2. panels b ande) and the polymer scaffold at 285.2 eV (Fig. 2.
panels c and e). These OD images display the spatial
distribution of each type of nanoparticle within thepolymeric scaffold.
Ongoing studies in our research group are focusedin the application of these composite materials as
solid supports for liquid chromatography and solid
phase extraction.

Optical density

3

2

1

0
340
2.0

345

350

355

360

480

490

Energy (eV)

1.5

Optical density

Ⅲ-2

D. Arrua1, C. Desire1, A. Khodabandeh1, T. Ohigashi2, N. Kosugi2 and E. Hilder1

1.0

0.5

0.0
450

460

470

Energy (eV)Fig. 1. NEXAFS spectra of HAP (top) and the TiO2(bottom) nanoparticles.

Fig. 2. STXM optical density (OD) images at (a andd) 349, (b and e) 460.4 and (c and f) 285.2 eV. Scalebars = 5 μm (a-c) and 1 μm (d-e).
[1] R. D. Arrua et al., Analyst 137 (2012) 5179.
[2] A. P. Hitchcock et al., J. Electron Spectrosc. 156(2007) 467.
[3] S. Hanhan et al., J. Electron Spectrosc. Relat.
Phenom. 172 (2009) 44.
[4] H. Zhang et al., J. Chem. Phys. 136 (2012)
174701.

76

Ⅲ -2. Materials Sciences

BL4B

O K-Edge Spectroscopy of High Valence State Mn(V) Oxides
Y. Aoki, T. Kobayashi, K. Kuroda, E. Tsuji and H. Habazaki

Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan
In naturally occurring photosystem II (PSII), thewater oxidation reaction proceeds with extraordinaryhigh catalytic activity, where a μ-oxo bridged
tetrameric Mn cluster (Mn4CaO5) serves as themultielectron oxidation catalyst within a complex
protein environment [1,2]. Thus, the Mn clusters ofphotosynthetic organisms have triggered extensive
research efforts to develop efficient water oxidation
catalysts composed of the inexpensive and abundantelement Mn. In a recent year, various manganeseoxides, such as MnO2, BaMnO3, LaMnO3 etc. has
been reported to show an excellent electrocatalytic
properties for oxygen evolution by electrochemical
water splitting [3, 4]. Suntivich et al reported thathole on oxygen make an important role for oxygen
evolution catalysis of manganese oxide [4]. Such ahole probably evolves by mixing of ligand-to-metal
charge transfer (LMCT) state which tends to be
involved in high valence state metal oxides due to thecovalency of metal-O bonding. In fact, it is reported
high valence state MnV=O intermediates are involved
during water oxidation cycle (S-cycle) and make an
impoirtant role for O-O bond formation from twowater molecules [5].
Ba3Mn2O8 is Mn(V) oxides and is thermally stablein ambient atmosphere. Recently, we found that
Ba3Mn2O8 electrodes facilitate O-O peroxide species
under the anodic polarization in neutral solutions.
K-edge XAS spectroscopy can direct evidence ofunoccupied state of solids. Accordingly, it is offundamental and technological important to study the
manganese oxide system by using this technique inorder to clarify the relationship between oxygen holeand electrocatalysis. In this study, we investigate O
K-edge spectra of Ba3Mn2O8 samples treated byanodic polarization at various potentials.
Ba3Mn2O8 powders were prepared by calcining
BaCO3 and MnO2 mixture at 950C in dry air.
Ba3Mn2O8-base electrodes were prepared by mixing
Ba3Mn2O8 and carbon powders with a teflon binderand uniaxialy-pressed at 100 MPa. The electrodes
were polarized at a constant anodic potential with an
Ag/AgCl (sat. KCl) reference electrode in neutral
NaClO4 solution (0.1 M).
O K-edge XAS spectra were recorded in a total
electron yield mode by measuring bulk current
through the irradiated samples. The spectra of themanganese oxide samples were shown in Fig. 1. The
Mn atoms in Ba3Mn2O8 take tetrahedral coordination
with oxygen atoms. Therefore, the pre-edge peaks ataround 529 eV can be assigned to the transition toanti-bonding t2g states. In case of KMnO4, the Mn-O
clusters take tetrahedral coordination, so that thepeaks at around 530 eV can be assigned to thetransition to anti-bonding t2 states. The apparentchanges in O K-edge spectra are not observed in thesamples after the polarization at various potentials, as
shown in Fig. 1. This might be due to thedeterioration of the polarized specimens by exposing
to air.

Ⅲ-2

Fig. 1. O K-edge spectra of Ba3Mn2O8 treated byanodic polarization in neutral solution at various
potentials.
[1] J. H. Alstrum-Acevedo et al., Inorg. Chem. 44(2005) 6802.
[2] G. C. Dismukes, R. Brimblecombe, G. A. N.
Felton, R. S. Pryadun, J. E. Sheats, L. Spiccia and G.
F. Swiegers, Acc. Chem. Res. 42 (2009) 1935.
[3] F. Jiao and H. Frei, Energy Environ. Sci. 3 (2010)
1018.
[4] J. Suntvichi et al., J. Phys. Chem. C 118 (2014)
1856.
[5] F. A. Armstrong, Phil. Trans. R. Soc. B 363 (2007)
1263.

77

Ⅲ -2. Materials Sciences

BL4B

XANES Analysis of Valence State of Co Doped in CeO2
1

T. Oomori1, K. Tarui1 and T. Yamamoto1,2

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

2

Normalized Intensity [arb.unit]

Ⅲ-2

A lot of researches on dilute magnetic materials(DMMs), which are processed by doping dilute ( afew at%) magnetic elements into the non-magnetic
materials, have been carried out after the discovery of
the ferromagnetism in InAs:Mn [1]. Among DMMs,
there are two type of the models for the doped
magnetic ions, i.e., substituted and precipitated ones.
In order to understand the mechanism of theappearance of ferromagnetism in DMMs, it isessential to know the local environment of the doped
magnetic elements. We have successfully studied thevalence state of Mn and Fe ions by measuring the Mn
and Fe-L3 X-ray absorption near edge structure(XANES) analysis at BL4B in UVSOR [2]. In thepresent study, charge state of doped Co in Co-doped
which
shows
room-temperature
CeO2,
ferromagnetism, was investigated by the XANES
analysis at Co-L3 edge.
Co doped CeO2 was prepared by the conventional
solid-state reaction method. Reagent grade CeO2 andCo3O4 powders were used as starting materials. These
powders were firstly weighed with a molar ratio of
Ce:Co = 0.95:0.05, which are mixed and ground in an
agate mortar and fired in air at 1273 K for 10 hours.
After cooling down to the room temperature, these
specimen was annealed in Ar(97%)-H2(3%)
atmosphere at 723 K for an hour. Co-L3 XANES
spectra of Co-doped CeO2, Co-foil and Co3O4 were
measured at BL4B in UVSOR by total electron yield
method. The incident beam was monochromatizedwith a varied-line-spacing plane grating (800lines/mm). Energy resolution (E/ΔE) of the incident
beam was set to 3000. Sample powders and foil wereput on the carbon adhesive tape, which are attachedon the first Cu-Be dinode of the electron multiplier.
Prior to the XANES analysis, synthesized
specimen was examined by the X-ray diffraction. No
extra peaks appeared after doping the Co and peak
position did not change. If Co is substituted at Ce site,
peak position should change, because ionic radius of
Co is much smaller than that of Ce ion. This result
suggests Co exists as nano-sized precipitates.
Observed Co-L3 XANES spectra of Co3O4, Co-foiland Co-doped CeO2 are shown in Fig. 1. Finestructures of the reference samples, i.e., Co andCo3O4, show different profiles and we can clearly
distinguish these two. A profile of Co-L3 XANES of
Co-doped CeO2 show similar profile as Co-foil, shidh
suggests that doped Co exists as metallic charge state.
Combining the results by XRD and XANES, we canconclude that doped Co exists as nano-sized metallic
precipitate.

Co3O4

Co-foilCo-doped
CeO2
775

780

785

790

Energy [eV]Fig. 1. Co-L3 XANES spectra of Co3O4, Co-foil andCo-doped CeO2.
[1] H. Ohno et al., Phys. Rev. Lett. 68 (1992) 2664.
[2] T. Okazaki et al., Solid State Comm. 151 (2011)
1749.

78

Ⅲ -2. Materials Sciences

BL4B

Investigation on the Surface Structure of LiNbO3-Coated LiCoO2
Using the Soft X-Ray XANES Measurement
H. Kobayashi, T. Okumura and M. Shikano

Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial Science andTechnology (AIST), Ikeda, 563-8577, Japansurface structure of coated samples.

Normalized Intensity (Arb. Unit)

Realization of the all-solid-state Li-ion battery(LIB) consisting of non-flammable inorganic solid
electrolytes is desired because of their high safety.
To improve energy and power densities of the
all-solid-state LIB, the decrease of the interfacial
resistance between the electrode and solid electrolyte
is required as well as the synthesis of solid electrolytewith high Li-ion conductivity. It has been reported
that Li4Ti5O12-coated LiCoO2 reduced the interfacial
resistance between LiCoO2 positive electrode andsulfide electrolyte and enhanced the rate capability to
be compatible to that of commercial LIB with liquid
electrolyte [1]. Recently we also reported that themechanochemical Al2O3-coating process was aneffective way of improving the cycle performance athigh temperature in the cell of Li/1M LiPF6 in
EC:DMC (1:2)/Li1.20Mn0.55Ni0.16Co0.09O2 [2]. In thispaper, LiNbO3-coating LiCoO2 was prepared andthese surface structure were investigated using thesoft X-ray XANES measurement.
LiNbO3-coated LiCoO2 were prepared with an
ethanol solution of ethoxides of Li and Nb using
tumbling fluidized bed granulating-coating machines(POWREX Co.) and heated for 30 min. in air
between 573 and 773 K. The particle morphology
and containing transition metal were confirmed by
SEM and EDAX measurements.
Electronic
structures were investigated by XANES measurement
at the beamline BL4B in UVSOR.
The SEM and EDAX results clarified that the sizesof pristine LiCoO2 particles were in the range of 1-10µm (an average particle size: 6 µm) and no transition
metal except Co was observed. The EDAX results
showed the existence of Nb in the LiNbO3-coated
LiCoO2 particles, but gave no information of the
distribution of Nb on the surface of LiNbO3-coated
LiCoO2 particle. Therefore, the soft X–ray XANES
was measured to check the surface structure on
LiCoO2. The Co L-edge XANES spectra clarified
that the samples after heat treatment showed weakerintensities of the A and B peaks compared with thepristine sample as shown in Fig. 1. The O K-edge
XANES spectra clarified that the shape of the C andD peaks for the samples after heat treatment wasclose to that of LiNbO3 with increasing heattemperature as shown in Fig. 2. These results
indicated that the surface of LiNbO3-coated LiCoO2
after heat treatment at 773 K was covered uniformly
by LiNbO3 layer and that the soft X-ray XANES
measurement was an effective way of confirming the

Co L-edge
LIII

LII

A

B

Ⅲ-2

After
773 K
After
673 K
After
573 K
Pristine

770

775

780

785

790

795

800

Normalized Intensity (Arb. Unit)

Energy / eV
Fig. 1. Co L-edge XANES spectra for pristine and
LiNbO3-coated samples after heat treatment.

O K-edge

CD

LiNbO3
After
773 K

After
673 K
After
573 K
Pristine

520

530

540

Energy / eV

550

560

Fig. 2. O K-edge XANES spectra for pristine and
LiNbO3-coated samples after heat treatment together
with LiNbO3.
[1] N. Ohta et al., Adv. Mater. 18 (2006) 2226.
[2] H. Kobayashi et al., Solid State Ionics 262 (2014)43.

79

Ⅲ -2. Materials Sciences

BL4B

Perpendicular Magnetic Anisotropy in Mn4N Studied by X-Ray Magnetic
Circular Dichroism
G. Shibata1, J. Okabayashi2, A. Chikamatsu3, A. Fujimori1 and T. Hasegawa3
1

Department of Physics, The University of Tokyo, Tokyo 113-0033, Japan
Research Center for Spectrochemistry, The University of Tokyo, Tokyo 113-0033, Japan3
Department of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan2

Ⅲ-2

Transition-metal nitrides such as Co4N, Fe4N, and
Mn4N have been investigated as novel materials forapplications in spintronics devices because of theroom-temperature
ferroorferrimagnetism.
Especially, the perpendicular magnetic anisotropy(PMA) in metallic Mn4N is one of the interesting
topics since it has benefits of enhanced thermal
stability and low current magnetization switching.
Anti-perovskite type Mn4N consists of two kinds ofinequivalent Mn sites (MnA: 3.85 μB/f.u. and MnB:
-0.9 μB/f.u.) which occupy the corner andface-centered positions of the unit cell with tetragonal
distortion. The large PMA energy of 0.16 MJ/m3 in
Mn4N was reported at room temperature [1].
However, the origin for the appearance of PMA in
Mn4N has not been clarified yet. For fundamental
understanding of PMA in Mn4N, the electronic andmagnetic structures have to be clarified explicitly. In
order to investigate PMA energy, it is necessary toevaluate the orbital magnetic moments along paralleland perpendicular directions to the surface. Here, wereport the x-ray magnetic circular dichroism (XMCD)
of Mn4N in order to discuss the origin of PMA.
Samples were grown by pulsed laser deposition
method on MgO (001) substrates. The 40-nm-thick
Mn4N was deposited under the substrate temperatureof 500 °C. Although there is a lattice mismatch of
7.0 % at the interface, coherent growth was observedby transmission electron microscope [1]. It is reported
that the 4-nm-thick MnOx layer is formed on the
Mn4N surface [1]. In order to suppress the formationof such an oxidization layer, the sample surface wascapped with 2-nm-thick Al2O3. The saturation
magnetic field of the Mn4N thin film along themagnetically hard axis was estimated to be ~ 3 T [1].
XMCD measurements were done at UVSOR BL-4B
under the conditions of 5 K [2]. A magnetic field of±5 T using a superconducting magnet was appliedalong the incident polarized soft x-ray, which isenough to saturate the magnetization along themagnetically hard axis direction. The total electron
yield mode was adopted. Normal incidence (NI) andgrazing incidence (GI) geometries were employed todeduce the anisotropic orbital magnetic moments.
Figures 1(a) and 1(b) show Mn L-edge x-ray
absorption spectra (XAS) and XMCD in the NI and
GI setups, respectively.
In XAS, a shoulder
structure is observed at 632 eV. In the Mn L3 XMCD
spectra, in addition to the negative XMCD peaklocated at the main absorption peak (628.5 eV), a
positive XMCD signal is observed around 630 eV. In
Mn4N, two kinds of XMCD components originatingfrom the MnA and MnB sites are overlapped
antiferromagnetically, which brings the complicated
XMCD spectral line shapes. Since the decomposition
into each component has not succeeded yet,magneto-optical sum rules cannot be applied at thismoment. The asymmetry in XMCD between the L3and L2 peaks at the NI setup is larger than that in the
GI setup, suggesting that the anisotropic orbital
magnetic moments are induced. These results suggestthat the anisotropic orbital magnetic moments might
be related to the PMA in this system as explained by
Bruno’s relationship [3]. In order to deduce the site
specific spin and orbital magnetic moments, we areplanning to measure the substitution dependence of
XMCD spectral line shapes in (Mn1-xMx)4N (M =nonmagnetic metal), which will provide information
about the electronic states and magnetism of each Mn
site.

Fig. 1. X-ray absorption spectra (XAS) and XMCD
of Mn4N thin film at the Mn L edge in (a) normal
incidence (NI) and (b) grazing incidence (GI) setups
at 5 K and 5 T.
[1] X. Shen, A. Chikamatsu, K. Shigematsu, Y.
Hirose, T. Fukumura and T. Hasegawa, Appl. Phys.
Lett. 105 (2014) 072410.
[2] T. Yokoyama, Y. Takagi and K. Nakagawa, Int.
Rev. Phys. Chem. 27 (2008) 449.
[3] P. Bruno, Phys. Rev. B 39 (1989) 865.

80

Ⅲ -2. Materials Sciences

BL4B

Investigating Orbital Magnetic Moments in Spinel-Type MnV2O4Using X-Ray Magnetic Circular Dichroism
1

J. Okabayashi1*, S. Miyasaka2, K. Hemmi2, K. Tanaka2,3, S. Tajima2,
H. Wadati4, A. Tanaka5, Y. Takagi3 and T. Yokoyama3

Research Center for Spectrochemistry, University of Tokyo, Tokyo 113-0033, Japan2
Department of Physics, Osaka University, Toyonaka 560-0043, Japan
3
Institute of Molecular Science, Okazaki, 444-8585, Japan
4
Institute for Solid State Physics, University of Tokyo, Kashiwa, 227-8581, Japan
5
Department of Quantum Matter, Hirshima University, Higashi-Hiroshima 739-8530, Japan
Couplings between orbital and spin degrees of
freedom in transition metal (TM) oxides exhibit awide variety of interesting physical phenomena
studied in strongly correlated electron systems. The
orbital degeneracy of t2g or eg orbitals, split by the
crystal field in TM oxides, gives rise to the orbital
ordering phenomena in perovskite-type Mn or V
oxides accompanied by Jahn-Teller distortion.
Spinel-type MnV2O4 is a good candidate to study
orbital ordering since orbital magnetic moments of
Mn2+ (d5) are nearly quenched with relatively large
spin moments in high spin states. An unresolved issue
related to orbital ordering of spinel-type vanadiumoxides is the relationship between the orbital
magnetic moments in vanadium sites and orbital
ordering. In this study, we investigated the element
specific electronic and magnetic properties of
MnV2O4 using XAS and XMCD, and examined therelationship between orbital magnetic moments andorbital ordering.
Single crystals were grown by the floating-zone
method. Details of the sample preparation and thefundamental physical properties are described in Ref.
[1]. The magnetic and orbital ordering temperaturesof MnV2O4 were estimated to be 59 and 54 K,
respectively. The XAS and XMCD measurements
were performed at BL-4B, UVSOR, Institute of
Molecular Science. Total photoelectron yield modeby directly detecting the sample current was adopted.
A magnetic field of ±5 T was applied along thedirection of the incident polarized soft x-ray.
Figure 1(a) shows XAS, XMCD, and the integrated
XMCD spectra of V L2,3-edge regions taken at 5 K,
which is sufficiently lower than the orbital orderedtransition temperature. The resulting residuals fromthe XMCD integrals for both L2 and L3 edges areshown at the bottom of Fig. 1 (a), suggesting that thefinite values of orbital magnetic moments remained inthe V3+ states. Using the integrals over XAS spectra
and assuming that the V 3d electron number to be 2,
we deduced the orbital magnetic moments (ml) to beless than 0.01 μB/(V atoms) from the orbital sum rule.
This value is close to zero but finite. This result
indicates that unquenched orbital magnetic moments
contribute to complex wave functions in V sites.
Figure 1(b) shows the calculated XAS and XMCD
spectra of V L-edges obtained using the clustermodels with configuration interaction. In the case of
V L-edges, qualitatively similar spectral line shapeswith both XAS and XMCD spectra in Fig. 1(a) werereproduced by the cluster-model calculation.
Tetragonal local lattice distortion around the V sites
must also be considered. The t2g states are split into
two levels by the tetragonal distortion and the lowest
xy states are occupied by one of the electrons. The
other electron occupies the yz or zx states. We
determined the tetragonal distortion value for the V
3d states (Dtet) to be 0.02 eV in order to reproduce thecomplicated XMCD spectral line shapes qualitatively.
The existence of the small but finite orbital magnetic
moments in the V sites can be explained by the (i)complex orbital ordering as discussed in the case of
FeV2O4, (ii) domain formation, and (iii) mixing of thereal and complex orbital orderings due to the trigonal
distortion around the V sites [2].
(b)䣚䣃䣕䢢䣋䣰䣶䣧䣰䣵䣫䣶䣻

䢪䣣䢫
䢲䢰䢴䢲
䢲䢰䢳䢷
䢲䢰䢳䢲

䣘䢢䣎䢯䣧䣦䣩䣧䢢
䣚䣃䣕



䢲䢰䢲䢷

䢯䢵

䣚䣏䣅䣆䢢䣋䣰䣶䣧䣩䣴䣣䣮䢢 䣺䢳䢲 䢢 䣚䣏䣅䣆䢢䣫䣰䣶䣧䣰䣵䣫䣶䣻

䢯䢵

䣺䢳䢲 䢢

䢲䢰䢲䢲

䣘䢢䣎䢯䣧䣦䣩䣧䢢䣚䣏䣅䣆

䢳䢷
䢳䢲
䢷
䢲
䢯䢷
䢴䢲
䢳䢷
䢳䢲
䢷

䣘䢢䣎䢯䣧䣦䣩䣧䢢䣚䣏䣅䣆䢢䣫䣰䣶䣧䣩䣴䣣䣮

䢲

䢷䢳䢲

䢷䢳䢷

䢷䢴䢲

䢷䢴䢷

䢷䢵䢲

䣒䣪䣱䣶䣱䣰䢢䣇䣰䣧䣴䣩䣻䢢䢪䣧䣘䢫

Fig. 1. V L-edge XAS, XMCD, and XMCD
integrated spectra in MnV2O4 (a). Cluster model
calculations are also shown in (b).
[1] K. Henmi et al., J. Phys. Soc. Jpn. 81 (2012)
SB030.
[2] J. Okabayashi et al., submitted.
*e-mail: jun@chem.s.u-tokyo.ac.jp

81

Ⅲ-2

Ⅲ -2. Materials Sciences

BL5B

Study of Ultrafast Spin-Switching of a Ferrimagnetic Alloy
by Resonant Magneto-Optical Kerr Effect1

S. Yamamoto1, M. Taguchi2, Y. Kubota1, S. Ito1, M. Hasumoto3,
E. Shigemasa3 and I. Matsuda1

Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan
2
Nara Institute of Science and Technology (NAIST), Ikoma 630-0192, Japan
3
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan

Ⅲ-2

A crystal of GdFeCo is a ferrimagnetic metallic
alloy, composed of rare-earth and transition metal
sublattices that couple anti-ferromagnetically. It has
been reported that the material shows ultrafast
spin-switching by irradiation of a femtoseconds-pulseof either circularly or linearly polarized infrared light.
Recently, we have carried out time-resolved
measurement of resonant magneto-optical Kerr effect(RMOKE) [1] at the Fe M-shell absorption edge bysoft x-ray free electron laser and succeeded in directly
detecting dynamic variations of magnetic signal
during the spin-switching. However, the RMOKE
data have lacked spectroscopic information to make aproper interpretation of the phenomena.
In the present research, we carried out the RMOKE
experiment at BL-5B at UVSOR to measure spectraof absorption intensity and Kerr rotation angle of acrystal of GdFeCo. Kerr rotation angle wasdetermined by the rotating-analyzer ellipsometry
method (Fig. 1). Figure 2(a) shows a schematic
drawing of the sample system. A 20 nm-thickGd21(Fe90Co10)79 film was grown on a Ta/Si(SiO2)
substrate and capped with a 2 nm-thick Ta layer.
Figure 2(b) shows absorption spectrum of the
GdFeCo sample that shows peaks of various
core-levels of Ta, Fe, and Co atoms. In themeasurements, perpendicular magnetic field of +/0.5 T was applied with a permanent magnet. As
shown in the figure, the simulated Fe 3p spectra,
based on the resonant scattering theory [1], almost
completely reproduces spectral feature of the Fe 3p
absorption peak. The Kerr rotation angles (θk’s) of the
Fe M-shell absorption edge were evaluated as in Fig.
2(c). The θk value becomes as large as 3-4 degrees atthe photon energy (hν) around 50 eV and it isreasonably reproduced by the simulation [1]. The
discrepancy at hν > 60 eV is likely due to thecontribution from the Co 3p level that has not been
considered in the calculation. On the other hand, thedifference at the pre-edge in Fig.2(c) seemingly
originates from the film structure that has beenreported previously in the Ni nanofilm [1]. The
smaller θk value of the Fe M-edge, compared with the
Ni M-edge, was likely due to the smaller spin-orbit
interaction for the lighter element.

Fig.1. (a) Geometry for rotating-analyzer ellipsometry(RAE) to measure the polar MOKE. The light beamis p-polarized by the surface, and the magnetic field(B) is applied along the surface normal. (b) Typicalresults of the intensity variation with rotation angle, χ.
The Kerr rotation angle, θk, can be determined from2θk= |θ(+B) − θ(−B)|.
(a)Fig.2. (a) Schematic drawing of the GdFeCo sample
system. (b) The absorption spectrum at hν=30-70
eV.(c) Photon energy dependence of the Kerr-rotation
angle (θk).
[1] Sh. Yamamoto et. al., Phys. Rev. B. 89 (2014)064423.

82

Ⅲ -2. Materials Sciences

BL6B

Infrared Spectroscopy of Photo-Induced Defects in Ce3+:GAGG Crystals
R. Inaba1, M. Kitaura1, K. Kamada2, S. Kurosawa2,3, A. Ohnishi1 and K. Hara4
1

Department of Physics, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan2
New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579, Japan
3
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
4
Research Institute of Electronics, Shizuoka University, Hamamatsu 422-8529, JapanThe Ce-doped Gd3Al2Ga3O12 (Ce:GAGG) crystal
was developed as a scintillator for radiation detector.
These crystals exhibit a high light yield, high-energy
resolution, and short decay time, as compared to otherinorganic scintillator crystals [1]. On the other hand,
it has been pointed out that trapping of photo-excited
carriers due to crystal defects causes the occurrenceof phosphorescence and decrease in light yield [2,3].
In order to improve the performance of scintillators, itis necessary to clarify the origin of crystal defects. We
have measured infrared (IR) absorption spectra of
Ce:GAGG crystals under UV-irradiation.
Ce:GAGG crystals were grown from a melt inoxygen or hydrogen atmosphere by the CZ method.
The concentration of cerium ion was set to 1.0 mol%.
Experiment was performed at the beamline BL6B.
The UV-irradiation was performed at 3.31 eV with apicosecond light pulser, which is located in the Ce3+
4f 5d2 absorption band. The sample temperature
was set to 9K.
Figure 1 shows stationary IR absorption spectra ofoxygen- and hydrogen-annealed Ce:GAGG crystals.
As indicated by a blue line, the IR absorption
spectrum of oxygen-annealed Ce:GAGG crystal isstructureless. On the other hand, one can see a broadband above 6000 cm-1 in the IR absorption spectrum
drawn with a black line.
Figure 2 shows IR absorption spectra of an
oxygen-annealed Ce:GAGG crystal. A black line
represents the IR absorption spectrum without
UV-irradiation. When UV-irradiation is turned on, theIR spectrum exhibits a broad band above 6000 cm-1,
as indicated by a blue line. This band is the same as
the stationary IR absorption band for ahydrogen-annealed Ce:GAGG crystal, which wasshown in Fig. 1.
The UV-irradiation at 3.31 eV results in thecreation of excited electrons in the conduction band
and Ce4+ ions [2-4]. The excited electrons will be
captured immediately by lattice imperfections [2].
Therefore, it is likely that the photo-induced IRabsorption band in Fig. 1 is caused by the formationof trapped electrons.
There are few candidates for the origin of trappedelectrons in multicomponent oxides with garnet
structure. The present experiment demonstrates thatthe photo-induced IR absorption band for an
oxygen-annealed Ce:GAGG crystal is the same as thestationaryIR
absorption
band
for
a
hydrogen-annealed Ce:GAGG crystal. In general, it

has been accepted that oxygen vacancies are easily
introduced in hydrogen-annealed oxide crystals. On
this basis, we assign the photo-induced IR absorption
band to electrons trapped at oxygen vacancies. Thisfinding is valuable as a guiding principle to growhigh-quality scintillator crystals.
A part of this work was carried out under the
Cooperative Research Project Program of the
Research Institute of Electrons, Shizuoka University.

Fig. 1. Stationary IR absorption spectrum of oxygenand hydrogen-annealed Ce:GAGG crystals measured
at 9K.

Fig. 2. IR absorption spectrum of an oxygenannealed Ce:GAGG crystal measured at 9K under
UV-irradiation (blue line). The data obtained underunirradiation was also shown (black line).
[1] K. Kamada et al., J.Cryst.Growth 352 (2012) 88.
[2] M. Kitaura et al., J. Appl. Phys. 115 (2014)083517.
[3] A. Satoh, et al., Jpn. J. Appl. Phys. 53 (2014)
05FK01.
[4] P. Dorenbos, J. Lumi. 134 (2014) 310.

83

Ⅲ-2

Ⅲ -2. Materials Sciences

BL6B

Formation Mechanism of Ultrashallow Thermal Donors
Formed in Carbon- and Hydrogen-Doped Czochralski Silicon Crystals
AA. Hara and T. Awano

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

2.8
2.7

2p0

2.6

USTDs
Group-1
Group-2

480℃-65h

2p0

2.5

2p＋－ 2p＋－

2.4

2.3

480℃-52h

2.2
2.1
2.0

480℃-40hTransmittance (arb. unit)

1.9
1.8
1.7

480℃-30h

1.6
1.5
1.4

480℃-20h

1.3
1.2

480℃-10h

1.1
1.0
0.9

480℃-5h0.8
0.7

480℃-3h

0.6
0.5
0.4
0.3
0.2

STD(H)s

100

150

2p0

2p＋－

200

Wave number (cm-1)

3p＋－

250

300

Fig. 1. Variation in USTD and STD(H) spectra incarbon- and hydrogen-doped CZ Si as function of
annealing duration at 480 °C.
8All
STD(H)s1s-2p± Group-1 of USTDs
1s-2p± Group-2 of USTDs

7
6

Intensity (arb. unit)

Ⅲ-2

STD(H) line areas showed a weak dependency on theannealing time when the duration was longer than 10
h at 480 °C. This result supports our model, whichshows that STD(H)s are changed to USTDs.
In summary, we validated our model for theformation mechanism of USTDs based on thevariations in the area intensities of USTDs and
STD(H)s using curve fitting. In the first stage,
STD(H)s form at a high rate; in the second stage,
carbon modulates the electronic structure of STD(H)sby combining with them to form USTDs.

We previously reported on ultrashallow thermal
donors (USTDs) in carbon- and hydrogen-doped
Czochralski silicon (CZ Si) crystals [1]. The
following formation mechanism was tentatively
proposed: in the first stage, STD(H)s are formed at ahigh rate; in the second stage, carbon diffuses in athermally activated process via an interstitial orinterstitialcy mechanism and modulates the electronic
structure of STD(H)s by combining with them toform USTDs. In this study, we evaluated theformation process of USTDs in order to clarify thepreviously proposed model.
Figure 1 shows the behavior of USTDs and
STD(H)s after carbon- and hydrogen-doped CZ Si
crystals were annealed at 480 °C for various durationsof time [1]. USTDs were slowly generated, and theirspectral intensity increased with the annealing time
up to 40 h. However, some lines for the group-1
USTDs began to reduce their intensity after further
annealing, and a strong line eventually became
dominant. In contrast, one strong line was dominant
in the group-2 USTDs. The STD(H) line intensities
were strong even after short-term annealing for 3 h
and were maximized after annealing for 10 h. This
indicates that the formation speed of STD(H)s is very
high compared to that of USTDs. It is significant that
the STD(H) lines began to decrease in intensity when
the annealing continued beyond 10 h.
To investigate the generation of USTDs andreduction of STD(H)s at 480 °C for various annealing
times, as shown in Fig. 1, we used Lorentzian curve
fitting to examine the variation in area intensity ofeach line. For the group-1 USTDs, an area intensityof 1s–2p± lines was used. For the group-2 USTDs,
1s–2p0 lines were used for curve fitting because of thefollowing reasons. The 1s–3p± spectral lines of thegroup-1 USTDs and 1s-2p0 lines of the STD(H)soverlapped with the 1s–2p± lines of the group-2
USTDs. According to the effective mass theory, theratio of intensity between the 1s–2p0 and 1s–2p± lines
should be 4:10. Thus, we determined the area
intensity of the 1s–2p± lines of group-2 to be 2.5
times the area intensity of the 1s–2p0 spectral lines
derived from curve fitting. The curves of the 1s–2p±
STD(H) lines were fitted by using two main peaks
and five satellite lines.
Figure 2 summarizes the variation in area intensityof the 1s–2p± lines for the group-1 and group-2
USTDs and the STD(H)s; the figure also shows thesum of these donors as a function of the annealing
time at 480 °C. The summation of the USTD and

5
4
3
2
1
0

0

10

20

30
40
50
Annealing time (h)6070Fig. 2. Variation in spectral intensity area for
STD(H)s, group-1 and group-2 USTDs, and the sumof these as function of annealing duration at 480 °C.
[1] A. Hara and T. Awano: UVSOR ACTIVITYREPORT 2013 41 (2014) 88.

84

Ⅲ -2. Materials Sciences

BL6B

Domain Structure of Alkali Niobate Piezoelectrics
by Far-Infrared Reflective Method
Y. Taniguchi, T. Yamazaki, M. Kato and K. Kakimoto

Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan
Orthorombic (Na,K)NbO3(NKN) piezoelectrics
have attracted much attention as substitute materials
for Pb(Zr,Ti)O3. We have examined that Li-doped
NKN revealed the existence of a monoclinic Pm
phase, and concluded that the Pm phase is the main
factor of good piezoelectric properties[1][2].
However, there is no detailed report about the domain
structure of NKN, which could explain the origins of
the improved properties. Electrical measurements,
like the impedance measurement, allow only for theevaluation of grains and grain boundaries. However,
it is impossible to evaluate domains and domain walls.
Therefore, spectroscopic methods need to be used,because they provide the structural deformation of theperovskite structure at a local scale about NbO6
octahedron and alkali-ion movements. Via Raman
spectroscopy, large changes in the vicinity of domain
walls have been obtained, both in the Raman shift andits peak intensity. In this work, we evaluated thedomain wall from the change of the permittivity using
Infrared(IR) reflectivity measurements.
crystals
were(Na0.55K0.45)(Nb0.995Mn0.005)O3
prepared by the floating zone method. The obtained
crystals were orthorhombic and had stripe domains
with a width of ~ 50 μm. The samples were cut andpolished for IR measurements. By means of a FT-IR
spectrometer(Bruker,
VERTEX
70v),
IRmeasurements were performed every 10 μm verticallyto the domain structure by using a line mapping
technique. The spectra were fitted by the following
equation:ε (ω) = ε∞ + Σn ω2pn / ω2on - ω2 - nγnωFigure 2 shows the permittivity of Mn-NKN crystals
at different positions. With the diameter of 0.25 mm,
the permittivity ε’ showed a maximum value at the 0μm position. The main reason for this behavior could
be the multitude of the polar axis at the domain wall.
This result suggests that the domain wall could be
evaluated via the increase of the permittivity during
IR reflectivity measurement.

Ⅲ-2

Fig. 1. IR reflectivity spectra of Mn-NKN crystals at
R.T. using the aperture diameters of 0.5 mm and 0.25mm

(1)

where, ε∞ is the high-frequency dielectric constant,ωp and ωo the plasma and longitudinal frequencies,and γ the damping constant. The complex dielectric
function is related to the reflectivity spectrum by theequation
R = |√ε (ω) – 1 / √ε (ω) + 1|2(2)
Fig. 2. Permittivity of Mn-NKN crystals at R.T. atdifferent positions for the aperture diameters of 0.5mm and 0.25 mm

Figure 1 shows the IR reflectivity spectra of
Mn-NKN crystals at R.T. using two apertures ofdifferent diameter. The spectra in the case of theaperture with a diameter of 0.5 mm showed nochange. In comparison, when the diameter is 0.25 mm,
the spectra slightly changed with the position of themeasurement. This result shows that the structureevaluation of domains and domain walls is enabled
by using the aperture with the smaller diameter.

[1] T. Nishi, K. Tsuchida, K. Kato, N. Kato, M.
Watanabe and K. Kakimoto, UVSOR Activity Report
2012 40 (2013) 140.
[2] T. Yamazaki, M. Kato, K. Tsuchida and K.
Kakimoto, UVSOR Activity Report 2013 41 (2014)87.

85

Ⅲ -2. Materials Sciences

BL6B

Spatial Distribution of Carrier Density of Sm1-xYxS (x = 0.17)
S. Kamei1, H. Takao1, Y. Ohtsubo2,1, H. Miyazaki3, K. Imura4, N. K. Sato4 and S. Kimura2,1
1

Department of Physics, Osaka University, Toyonaka 56-0043, Japan
Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan3
Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555, Japan
4
Department of Physics, Nagoya University, Nagoya 464-8603, Japan2

Ⅲ-2

Physical properties of some materials are
drastically changed at the first-order phase transition
by tuning external parameters of temperature,pressure, magnetic field, and chemical pressure. At
the first-order transition, phase separations as well asphase coexistence are sometimes observed [1]. Since
the phase separation is strongly related to the originof the first-order transition, the origin of the phaseseparations is under debate in some materials.
Samarium monosulfide SmS is known to be amaterial with a pressure-induced first-orderinsulator-to-metal transition accompanied with thecolor change from black to golden-yellow, namely
black-golden phase transition (BG transition), at thecritical pressure of about 0.7 GPa [2]. The origin of
the BG transition is known as the valence transition
from Sm2+ with larger ionic radius to Sm3+ withsmaller radius owing to the external pressure. When apart of Sm2+-ions are replaced to Y3+-ions of smaller
ionic radius, namely Sm1-xYxS, a similar BG
transition is realized at ambient pressure [3]. At theborder of the BG transition of x ~ 0.17, the black andgolden phase separation (BG separation) is observed[4]. To investigate the origin of the BG separation, we
measured a micro X-ray fluorescence (XRF) imaging(10-μm step) of Y Kα line to check the spatial
distribution of Y-atoms. In addition, to clarify the
relation of the insulator-to-metal transition to the BG
transition, the carrier density distribution was alsomeasured by using an IR micro-imaging (6.25-μm
step, about 26,000 points in total) [5]. The obtainedreflectivity spectra at all measured points were fitted
by the combination of the Drude and Lorentz
functions using a nonlinear least-square method andthe spatial distribution of the effective carrier density(Neff) in the Drude function was mapped on thesample surface.
Figure 1a shows the visible image of the BG
separation of Sm0.83Y0.17S. Some golden-yellow areas,
which indicate the appearance of the golden phase,are observed. The spatial distribution of the Y-ion
probed by the XRF imaging is shown in Fig. 1b. The
spatial distribution is almost flat on the whole sample
surface except for the sample edge. The Y-ion
distribution at golden-yellow areas is similar to that at
black areas (for instance, the open solid circles in Fig.
1). This implies that the BG transition as well as the
BG separation does not originate from the spatialconcentration distribution of Y-ions.
Figure 1c shows the spatial distribution of Neff. Neffat the golden-yellow area reasonably increases fromthat at the black area. However, we can recognize thatsome part of the black area has larger Neff than theother black area (for instance, the open dashed circle
in Fig. 1), i.e., the metallic conduction appears evenin the black phase. This result suggests that theinsulator-to-metal transition of Sm1-xYxS does not
relate to the BG transition.
[1] e.g. L. Zhang et al., Science 298 (2002) 805.
[2] P. Wachter, In Handbook on the Physics andChemistry of Rare Earth, edited by K. A. Gschneidner
et al., (North-Holland, Amsterdam, 1994), Vol. 19, p.
383.
[3] K. Imura et al., J. Korean Phys. Soc. 62 (2013)
2028.
[4] S. Kimura et al., UVSOR Activity Report 2013 41(2014) 90.
[5] S. Kimura et al., UVSOR Activity Report 2012 40(2013) 45.

Fig. 1. (a) Visible image of a measured sample of Sm0.83Y0.17S. (b) Spatial distribution of the intensity of the YKα line probed by X-ray fluorescence imaging. (c) Spatial distribution of the effective carrier density (Neff) fromthe Drude and Lorentz fitting of reflectivity spectra. Open solid (red) and dashed (blue) circles indicate thepoints of a typical golden phase area and a black phase area with different carrier density, respectively, discussed
in the text.

86

Ⅲ -2. Materials Sciences

BL7U

Local Electron-Phonon Coupling in Organic Single Crystals:
Angle-Resolved Ultraviolet Photoemission Study
1

F. Bussolotti1, J. Yang2, T. Yamaguchi2, Y. Nakayama2, H. Ishii2, M. Matsunami1,
N. Ueno2 and S. Kera1,2

Department of Photomolecular Science, Institute of Molecular Science, Okazaki 444-8585, Japan,
Department of Nanomaterial Science, Graduate School of Advanced Integration Science, Chiba University,
Chiba 263-8522, Japan2effects are substantially temperature independent in
the [307K–110K] temperature range (kT < 26meV) as
the rubrene intramolecular vibrations (hν0rub=130
meV) cannot be excited when kT << hν0rub.
According to our ARUPS results, the electronic
band structure of rubrene SC is significantly affectedby local electron-phonon coupling effects. The mostsalient spectral features come from the interaction ofelectrons with high-frequency intramolecularvibrations which causes the appearance in (i) kinkstructure in the electron band dispersion and (ii)scattering of higher binding energies electrons.

A detailed understanding of the electronic andtransport properties of organic semiconductors is
crucial for the optimization of any real organic-based(opto)electronic devices. Despite huge research
efforts important open issues still remain, as mainly
related to the role played by the electronic
delocalization and electron-phonon coupling effects
on the charge transport mechanism in organic
materials [1]. In this work, we clearly revealed theimpact of electron phonon-coupling on the electronic
band dispersion of rubrene single crystals (SCs) byangle-resolved ultraviolet photoelectron spectroscopy(ARUPS).
The ARUPS study was conducted at BL7U. The
photon energy (hν) was set to hν= 8 eV. During
photoemission measurements the SCs were
continuously irradiated with laser light (photon
energy=3.06 eV, power=14 mW) to avoid sample
charging [2]. The energy and angular resolution was
10 meV and 0.15o respectively.
Figure 1(a) shows the UPS spectra of the highest
occupied molecular orbital (HOMO) of rubrene SC as
acquired along the ΓY symmetry direction at 307 K(room temperature). In particular, a “kink”-like
dispersive behavior is observed at θ~20o. This
striking spectral feature is more clearly revealed by
the E(k//) band mapping of the HOMO band
dispersion [Fig. 1(b)]. The kink structure is centeredat k//kink = ~0.23 Ǻ-1 with an energy width of ~130
meV, which nearly coincides with the characteristicenergy of the rubrene intramolecular vibrations(hν0rub = 130 meV) [3]. Upon crossing the kinkstructure (from Γ to Y) a clear broadening of the
HOMO peak is observed [Fig. 1(c), left panel].
The occurrence of kink structures in the electronic
band dispersions of organic molecular solids wastheoretically predicted by Ciuchi et al. [4] as a resultof the interaction of electrons with high frequency
intramolecular vibrations [4]. This local electronphonon coupling introduces “cuts” in the electronic
band dispersion at multiple of the intramolecularvibrational energy, resulting in kink structures as
those observed in the present rubrene SC.
According to the above picture, electron-phonon
scattering events are allowed only for k// > k//kink (i.e.
at higher binding energies) where they cause theobserved increase of the HOMO linewidth [Fig. 1(c),left panel]. These local electron-phonon coupling

Fig. 1. (a)θ-dependence of the HOMO-UPS spectraof rubrene single crystal along ΓY direction (seeinset) (hν=8 eV). (b) E(k//) map of the HOMO band
dispersion (second derivative intensity plot, ΓY
direction). (c) E(k//) map of the HOMO band
dispersion at 307 K, 150 K and 110 K. The spectral
intensities were normalized to the intensity of the
HOMO peak.
[1] N. Ueno et al., Prog. Surf. Sci. 83 (2008) 490.
[2] S. Machida et al., Phys. Rev. Lett. 104 (2010)
156401.
[3] S. Duhm et al., Adv. Mat. 24 (2012) 901.
[4] S. Ciuchi et al., Phys. Rev. Lett. 106 (2011)
166406.

87Ⅲ-2

Ⅲ -2. Materials Sciences

BL7U

Valence Band Dispersion of the Pentacene Single Crystal
1

Ⅲ-2

Y. Nakayama1, M. Yamamoto2, Y. Mizuno2, M. Matsunami3, H. Ishii2,4 and N. Ueno2

Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science,
Noda 278-8510, Japan
2
Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan
3
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
Center for Frontier Science, Chiba University, Chiba 263-8522, Japan

Pentacene (C22H14) is one of the most vigorously
studied organic semiconductors because a practicalmagnitude of the field effect mobility of conductive
holes (μh > 1 cm2V-1s-1) at room temperature (RT)was discovered for the first time for organic thin filmtransistors [1]. In particular, the single crystal phaseof pentacene is attracting notable interest because
further greater μh (35 cm2V-1s-1 at RT and over 50
cm2V-1s-1 at 225 K) was reported [2]. As a primaryfactor for such excellent electric conduction
properties, the valence band dispersion structures ofthe pentacene single crystal (Pn-SC) have been
intriguing researchers of fundamental as well as
applied science fields. However, experimental
demonstration of the valence band structures of
insulating organic semiconductor single crystal
samples has been problematic due to “sample
charging”.
Photoconductivityoforganic
semiconductors provides one solution against thisdrawback, actually k-integrated density-of-states of
the Pn-SC were disclosed by means of photoelectron
spectroscopy under laser light illumination [3,4]. In
the present study, we elucidated the valence band
structures of the Pn-SC by a photoconductivity-assisted angle-resolved ultraviolet photoelectron
spectroscopy (ARUPS) technique.
Oblong plates (typically several mm2 wide and afew μm thick) of the Pn-SC produced by a physicalvapor transport technique were selected and posted
individually onto conductive carbon tape to prepare
specimens. Ag glue was additionally pasted at the rimof each crystal to ensure good electric conductivity.
ARUPS measurements were carried out at BL7U in
UVSOR, where the excitation photon energy (hν) was
set at 10 eV in this study. In order to cancel sample
charging, the sample was shined by continuous wave
laser light (405 nm) during the measurements [5].
Figure 1(a) shows the ARUPS spectra taken at RT
toward a diagonal direction of the surface Brillouinzone of the Pn-SC where the widest energy dispersionof the valence band is theoretically expected [6]. The
upper and lower valence bands originating from thehighest occupied states of two crystallographicallyinequivalent pentacene molecules exhibit clear energy
dispersion to split each other by tilting thephotoelectron take-off angle (θ) from the surface
normal. It is worth mentioning that this dispersion
direction is opposite to that of another crystalline
polymorph (so called “thin-film” phase) of pentacene,

where the two bands split at the Γ point (normal
emission) and degenerate each other for the grazing
emission [7], but agrees with the trend of one otherphase (“bulk” phase) [8]. Cooling the sample
temperature down to 115 K resulted in expansion of
the band width by ca. 20 % as shown in Fig. 1(b) and(c), which should be attributed to reduced
electron-phonon coupling at lower temperature [9].

Fig. 1. (a) ARUPS spectra of a Pn-SC sample. (b)and (c) Temperature dependent evolution of UPS
spectra (green: RT, light blue: 211 K, blue: 115 K) atelectron take-off angles of 30° and 0°, respectively.
[1] Y.-Y. Lin et al., IEEE Electron Device Lett. 18(1997) 606.
[2] O. Jurchescu et al., Appl. Phys. Lett. 84 (2004)
3061.
[3] A. Vollmer et al., Euro. Phys. J. E 17 (2005) 339.
[4] Y. Nakayama et al., Jpn. J. Appl. Phys. 53 (2014)
01AD03.
[5] S. Machida et al., Phys. Rev. Lett. 104 (2010)
156401.
[6] H. Yoshida et al., Phys. Rev. B 77 (2008) 235205.
[7] M. Ohtomo et al., Appl. Phys. Lett. 95 (2009)
123308.
[8] H. Kakuta et al., Phys. Rev. Lett. 98 (2007)
247601.
[9] N. Koch et al., Phys. Rev. Lett. 96 (2006) 156803.

88

Ⅲ -2. Materials Sciences

BL7U

Angle-Resolved Photoemission Study on
Quasi-One Dimensional Organic Conductor (TMTTF)2PF6
T. Ito1,2, M. Mitamura1, H. Horikawa1, T. Hajiri1, S. Kimura3,4 and T. Nakamura5
1

Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
Nagoya University Synchrotron Radiation Research Center, Nagoya University, Nagoya 464-8603, Japan
3
Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
4
Department of Physics, Osaka University, Suita 565-0871, Japan
5
Institute for Molecular Science, Okazaki 444-8585, Japan

2

The Bechgaard salts (TMTCF)2X (C = S, Se; X =PF6, AsF6, etc.) belong to a family of
quasi-one-dimensional (Q1D) organic conductors.
These materials allow for a variety of ground statesfrom antiferro magnetism, a Peierl’s-like spin density
wave, to a superconducting state by tuning thechemical pressure with the combination of
TMTSF/TMTTF and anion X [1].
In this study, we have performed temperaturedependent
angle-resolved
photoemission
spectroscopy(ARPES)onsingle-crystalline(TMTTF)2PF6 to clarify the relation between theelectric structure and the thermodynamic properties.
ARPES measurement were performed at UVSOR-Ⅲ
BL7U by utilizing the bulk-sensitive low photon
energy (hν = 8eV) as well as the micro focus beam
(15×100 μm2).
Figure 1 (a) and (b) shows the ARPES spectra andimage along the ΓX direction of (TMTTF)2PF6 at T =30 K (charge ordering state: CO). We found highly
dispersive band (h) folded around k = 0.27 Å-1 (redarrow) at 0.4 eV, the dispersive broad feature (s) andthe broad shoulder (p) below the Fermi level (EF).
From the comparison with the previous ARPES studyon (TMTSF)2X [2, 3], we have expected that theobserved three features are attributed to holon, spinon
and polaron band, respectively. It should be noted thatthe holon/spinon bands shift away from EF relative to(TMTSF)2PF6 in consistent with the insulating
properties of (TMTTF)2PF6 at CO states.
Figure 3 shows temperature dependent ARPES
spectrum at k = 0.27 Å-1 from T = 30 K (CO), 100 K,
200 K (charge localization state: loc) to 300 K(metallic state: M) [4]. With increasing temperature,
the main peak at 0.4 eV becomes weak and almost
disappears at T = 300 K. As a result, the band
structure at the metallic state dominates with thehigh-energy bound states (loc in Fig. 1) below 1 eV.
On the other hand, we found that the spectral weightat EF increases from T = 30 K to 300 K, which isconsistent with the thermodynamic properties of(TMTTF)2PF6. We have found the good
reproducibility of the observed temperaturedependence with decreasing temperature, which
ensure the less radiation damage effect during thepresent ARPES measurement.

Ⅲ-2

Fig. 1. ARPES spectra (a) and image of(TMTTF)2PF6 along ΓX direction at T = 30
K.Dashed lines are guide for eyes.Red arrow
indicates the top of the holon dispersion.

Fig. 2. Temperature dependent ARPES spectrum of(TMTTF)2PF6 at the top of the holon dispersion (k =0.27 Å-1).
[1] T. Ishiguro et al., Organic Superconductors(Springer-Verlag, Berlin, 1998).
[2] S. Hirate et al., UVSOR Activity Report 2011 39(2012) 97.
[3] M. Mitamura et al., UVSOR Activity Report 201240 (2013) 110.
[4] E. Rose et al., J. Phys.: Condens. Mat. 25 (2013)
014006.

89

Ⅲ -2. Materials Sciences

BL7U

Carrier Concentration Dependence of Superconducting Gap of
Bi1.7Pb0.4Sr2Ca1-xYxCu2O8+δ
1

H. Sakamoto1, A. Yamamoto2 and T. Takeuchi2,3Department of Crystalline Materials Science, Nagoya University, Nagoya 464-8603, Japan2
Toyota Technological Institute, Nagoya 468-8511, Japan
3
Promoting Individual Research to Nurture the Seeds of Future Innovation, Japan Science and Technology
Agency, Tokyo 102-8666, Japan

Ⅲ-2

concentration at overdoped region and turns out to be
reduced with decreasing hole concentration after
becoming maximal at around p = 0.23 holes/Cu.
Notably,Δ0 (p)
ofpresent
samples(Bi1.7Pb0.4Sr2Ca1-xYxCu2O8+d) shows a fairly different
behavior from the universal curve observed forBi2(Sr,RE)2CuO6+d. The much larger magnitude of Δ0(p) of the present samples than that of
Bi2(Sr,RE)2CuO6+d would be closely related with thedifference in the maximum critical temperature: Tc-max~ 90 K of Bi1.7Pb0.4Sr2Ca1-xYxCu2O8+d and Tc-max ~ 40
K of Bi2(Sr,RE)2CuO6+d.
It would be more important to note that Δ0 ( p) ofpresent samples shows a shape peak at around p~0.16
while that of Bi2(Sr,RE)2CuO6+d exhibits a shallow
hump in the Δ0 p plot. The mechanism leading to
the different carrier concentration dependence of Δ0(p) would be closely related to the difference in
critical temperature of Cooper-pair formation.

Despite a huge number of investigations being
performed after the discovery of high-Tc cuprate
superconductors, the collective excitation leading to
the formation of Cooper-pairs has not been fully
identified yet. In order to gain deep insight into suchcollective excitation, it is of great importance to know
the temperature-,
momentum-, and carrier
concentration- dependences of superconducting gap.
Unfortunately, however, the pseudogap developing at
the underdoped condition has made it difficult toreveal the temperature-, momentum-, and carrier
concentration- dependences of superconducting gap.
In this study, therefore, we carefully investigated theenergy-width of superconducting-gap Δ(φ, p) Δ0(p)cosφ forBi1.7Pb0.4Sr2Ca1-xYxCu2O8+d
using
ultra-high-energy-resolution laser induced angle
resolved photoemission spectroscopy (ARPES)
measurements. Here φ and p indicate the angle fromthe (0, 0)-(π, π) direction and the introduced
hole-concentration from the half-filled condition at p
= 0. By additionally employing the synchrotron
radiation ARPES measurements at BL7U in UVSOR,
we estimated the carrier concentration of theemployed samples using the area surrounded by the
Fermi surface.
Figure 1 shows a symmetrized kF-ARPES spectrumof Bi1.7Pb0.4Sr2Ca0.9Y0.1Cu2O8+d at φ≈23 ° as a typicalexample. The magnitude of Δ(φ, p) was defined as
the energy difference between two peaks in asymmetrized spectrum. The magnitude of Δ(23°, p) of
Bi1.7Pb0.4Sr2Ca0.9Y0.1Cu2O8+d was determined to be~56 meV. In the same manner as, Δ(23°, p), Δ(φ, p)
was precisely determined at various angles of φ.
By plotting Δ(φ, p) as a function of cosφ, wequantitatively evaluated Δ0 ( p) for there different
samples possessing different value of p. The
determined Δ0 (p) was plotted in Fig. 2. as afunction of p together with those previously
determined for Bi2(Sr,RE)2CuO6+d (RE = La, Nd,Sm).
We found, in our previous study, that Δ0 ( p) of
Bi2(Sr,RE)2CuO6+d falls on a universal curve
regardless of the rare earth elements involved in thesamples: it obviously increases with decreasing holeFig. 1. Symmetrized ARPES spectrum at kF
measured for Bi1.7Pb0.4Sr2Ca0.9Y0.1Cu2O8+d at aroundφ = 23. The temperature of measurement was ~13 K.

Fig. 2. Hole-concentration dependence of Δ0
determined for Bi1.7Pb0.4Sr2Ca1-xYxCu2O8+d andBi2(Sr,RE)2CuO6+d .

90

Ⅲ -2. Materials Sciences

BL7U

Angle-Resolved Photoemission Study of Heusler-Type Fe2V1+xAl1-x Alloys
H. Miyazaki, K. Ando, W. Nagasaka and Y. Nishino

Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555, Japan
Band structure calculations of Fe2VAl alloy havepredicted that a pseudo-gap is formed around the
Fermi level [1]. Because of the possession of a sharp
pseudo-gap across the Fermi level, Fe2VAl-based
alloys have attracted a great deal of interest as
potential
candidates
fornext-generation
thermoelectric materials [2]. The peak temperature of
the n-type thermoelectric power factor of previous
Fe-based Heusler alloys is around 300 - 400 K [3].
For the application of thermoelectric materials topower generation, it is desirable that the peaktemperature of both the n- and p-type be increased to400-600 K. Recently, the substitution of Al or V
atoms with V or Al atoms in the off-stoichiometric
Fe2V1+xAl1-x compounds has proven to improvesignificantly the p- and, especially, n-type
thermoelectric properties, such as electronic
resistivity and Seebeck coefficient, and allows a shiftof the peak performances towards interesting higher
temperatures (300 - 600K) [4]. In order to clarify theorigin of the improvement in the thermoelectric
properties for the off-stoichiometric Fe2V1+xAl1-x
alloys,we thus performed high-resolution
three-dimenional
angle-resolved
photoemission
spectroscopy(3D-ARPES)
measurements
toinvestigate the change in the electronic structure dueto the V/Al off-stoichiometry.
SR-PES measurements were carried out in thebeamline BL7U of the UVSOR-III. Photoemission
spectra were recorded at 10 K. Clean surfaces for
3D-ARPES measurements were obtained by in-situ
fracturing with a knife edge at 10 K under ultra-highvacuum. Fermi level and total energy resolution were
determined by the Fermi edge of evaporated gold
films. The total energy and momentum resolutions forthe 3D-ARPES measurement were set to 15 meV and
0.006 Å-1 at the X point (hν= 26 eV).
Figure 1(a) and (b) shows the second derivative
3D-ARPES images of Fe2V1.03Al0.97 (electron-doping)and Fe2V0.97Al1.03 (hole-doping) alloys along X-Γ line,
respectively. We observed three dispersion of theband around X point, which is consistent with theband structure calculation. All bands of Fe2V0.97Al1.03
alloy shift to lower binding energy side compared tothat of Fe2V1.03Al0.97 alloy. This indicates that, thenumber of valence electrons around Fe, V and Al
atoms decreases with increasing Al content (holedoping), and that the core level of Fe, V and Al
gradually shifts to lower binding energy side becauseof the chemical potential shift. However, the energy
dispersion (~30 meV) of Fe2V1.03Al0.97 alloy issmaller than that (~70 meV) of Fe2V0.97Al1.03 alloy.
This result indicates that the electronic structure near

the Fermi level is modified due to theoff-stoichiometric effect and the pseudo-gap widens.
According to band structure calculations, a wider
pseudo gap leads to a further shift in the peaktemperature of the maximum thermoelectric power tothe higher temperature side [5]. Therefore, it isthought that the origin of the improvement in n-type
Seebeck coefficient and its peak temperature should
be attributed to the modification in the electronic
structure due to the off-stoichiometric effect.

Fig. 1. Second derivative 3D-ARPES images of
Fe2V1.03Al0.97 (electron-doping) and Fe2V0.97Al1.03(hole-doping) alloys along X-Γ line. The dashed lines
indicate the the peaks in the second-derivative spectrathat correspond to the shoulder and peaks in the
spectra.
[1] G. Y. Guo, G. A. Botton, and Y. Nishino, J. Phys.:
Condens. Matter 10 (1998) L119.
[2] Y. Nishino, The Science of Complex Alloy Phases(Warrendale: TMS) (2005) 325.
[3] Y. Nishino, S. Deguchi and U. Mizutani, Phys.
Rev. B 74 (2006) 115115.
[4] H. Miyazaki, S. Tanaka, N. Ide, K. Soda and Y.
Nishino, Mater. Res. Express 1 (2014) 015901.
[5] D. Do, M. Lee and S. D. Mahanti, Phys. Rev. B
84 (2011) 125104.

91

Ⅲ-2

Ⅲ -2. Materials Sciences

BL7U

Angle-Resolved Photoemission Spectroscopy of YbB12 (001) Surface
K. Hagiwara1, J. Kishi1, Y. Ohtsubo2,1, H. Miyazaki3, T. Ito4, M. Matsunami5,
F. Iga6 and S. Kimura2,1
1

Department of Physics, Osaka University, Toyonaka 560-0043, Japan
Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan3
Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555, Japan
4
Department of Materials Engineering, Nagoya University, Nagoya 464-8603, Japan
5
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
6
Department of Physics, Ibaraki University, Mito 310-0056, Japan2

Ⅲ-2

Ytterbium dodecaboride YbB12 is known as one of
typical Kondo insulators/semiconductors (KIs),
which has a tiny energy gap owing to thehybridization between conduction and localized 4f
electrons, namely c-f hybridization [1]. Since so many
experimental and theoretical studies on the physicalproperties have been performed over three decades,
the overall physical properties have been reveled. The
electronic structure has also been investigated byusing optical conductivity [2], angle-integrated
photoemission
spectroscopy(AIPES)[3],time-resolved AIPES [4], and so on. However, theband dispersion as well as E-k curves probed byangle-resolved photoemission spectroscopy (ARPES)
along the high symmetry lines has never beenclarified experimentally because the sample cannot becleaved along principal axes. Here, we report the
ARPES result of a well-defined surface of YbB12.
A single crystalline sample was fabricated by afloating-zone method. The sample was cut along the(001)-plane and polished up to a mirror surface byusing a diamond lapping film sheet. The clean sample
surface was obtained by annealing indirectly heatedby SiC plate at the sample temperature of 1250 Cunder an ultra-high vacuum better than 510-8 Pa.
The obtained low-energy electron diffraction (LEED)
image is shown in Fig. 1. The LEED image indicatesthe square lattice pattern that is the same as the bulk
crystal.
The obtained ARPES image near the Fermi level(EF) at the excitation photon energy of 16 eV isshown in Fig. 2. The observed highly dispersive
bands at the binding energy below 0.3 eV mainly
originates from the Yb 5d conduction band because of
the higher cross-section at the photon energy than
expected other bands, for instance Yb 4f. The peaksof momentum-distribution curves (MDCs) andenergy-distribution curves (EDCs), which indicate thetrace of the band dispersion, are plotted by open
circles and triangles, respectively. The trace indicatesthat the conduction band becomes gentle below thebinding energy of 0.1 eV suggesting that the
conduction band is hybridized to localized Yb 4f
bands located near EF. The energy gap between thebonding and antibonding states of the c-f
hybridization is expected to be about 50 meV, whichis consistent with that observed in the opticalconductivity spectrum [2].

Fig. 1. LEED pattern of the YbB12 (001) surface with
an electron energy of 26.3 eV. Spots represent
diffractions of 1×1.

Fig. 2. ARPES image of the YbB12 (001) surface
along the (100) direction at the excitation photon
energy of 16 eV. Open circles and triangles are peaks
taken from the MDCs and EDCs, respectively.
[1] F. Iga et al., J. Magn. Magn. Mater. 177–181(1998) 337.
[2] H. Okamura et al., J. Phys. Soc. Jpn. 74 (2005)
1954.
[3] T. Susaki et al., Phys. Rev. Lett. 77 (1996) 4269.
[4] M. Okawa et al., arXiv: 1407.0578.

92

Ⅲ -2. Materials Sciences

BL7U

Quadratic Fermi Node in a 3D Strongly Correlated Semimetal
T. Kondo1, M. Nakayama1, R. Chen2, J. J. Ishikawa1, E.-G. Moon2,
W. Malaeb1, Y. Ishida1, M. Matsunami3, S. Kimura3,4,
S. Nakatsuji1, L. Balents5 and S. Shin1
1

ISSP, University of Tokyo, Kashiwa, 277-8581, Japan
Physics Department, University of California, Santa Barbara, California 93106, USA
3
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
5
Kavli Institute for Theoretical Physics, Santa Barbara, California 93106, USA

2

Following the discovery of topological insulators,
the next frontier is the regime in which bothspin-orbit coupling and correlation effects are strong.
Theory has suggested that the pyrochlore iridates(Ln2Ir2O7; Ln=rare earth elements), a family of cubic
5d transition metal oxides, realize both bandinversion [1,2], the essential ingredient of topologicalinsulators,
andstrongcorrelations.
Thephenomenological suggestion is that the Fermi
surface of Pr2Ir2O7 contains a single Fermi node at theΓ point protected by cubic and time-reversal
symmetries, which emerges as the touching point of
two quadratically dispersing “conduction” and“valence” bands [Fig.1(a) and Fig.2(e)]. If theassumption is correct, the Pr2Ir2O7 could be a “parent”
state tunable to new-types of strongly correlated
topological phases [Fig.1(b)-(d)] [1,2]. As the ionicradius of Ln site increases (for example, Ln=Nd andEu), the all-in-all-out antiferromagnetic orderemerges, which causes the time-reversal symmetry
breaking in bulk. This could provide a realization of
Weyl fermions that obeys a two-component Diracequation. It was also predicted to establish
remarkable topological properties manifested bysurface states in the form of Fermi arcs. The
pyrochlore iridates study therefore has enormous
potential to open up the next frontier of condensed
matter physics.
By ARPES, we have experimentally realized the
Fermi node state in Pr2Ir2O7 [see Fig.2]. A parabolic
band-dispersion approaches EF with increasing
photon energies (or kz values), and finally touches itat the Γ [Fig.2 (e)]. With a further increase of kz, thedispersion gets away from EF again, which signifies
that the 3D band structure of Pr2Ir2O7 has a single
Fermi point. Other scans of different kz values up to
the L point revealed no other states touching or
crossing EF [Fig.2(c)]. This satisfies the charge
neutrality, and it could be a further evidence for therealization of the Fermi nodal state. As demonstrated
in Fig.2(e), we found that our ARPES data is
consistent with the result of band calculations.

Ⅲ-2

Fig. 1. Schematic diagram illustrating (a) the
quadratic Fermi node state of Pr2Ir2O7 and its role asa parent of (b)-(d) interacting topological phases.

Fig. 2. (a) Brillouin zone. ARPES intensity maps
around Γ (b) and L (c). (d) Band dispersion around Γ,
divided by the Fermi function. (e) Comparison
between ARPES data and band calculation.
[1] D. Pesin et al., Nat. Phys. 6 (2010) 376.
[2] E.-G. Moon et al., Phys. Rev. Lett. 111 (2013)
206401.

93

Ⅲ -2. Materials Sciences

BL7U

ARPES Study on the Stripe-Ordered (La,Nd,Sr)2CuO4 Superconductor
1

K. Tanaka1, M. Matsunami1, S. Miyasaka2 and S. Tajima2

UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan2
Department of physics, Osaka University, Toyonaka 560-0043, Japan

Ⅲ-2

The “stripe order” is a periodic modulation of
one-dimensional charge and spin densities observedin some hole-doped transition metal oxides. It wasobserved by means of neutron scattering, X-ray
diffraction and so on [1,2]. In hole-doped La-214
cuprates, such as La2−xBaxCuO4 (LBCO) andLa2-x−yNdySrxCuO4 (LNSCO), represent this charge
and magnetic order coexisting with superconductivity.
Recently direct evidence for new charge density wave
(CDW) order in YBa2Cu3O7-δ (YBCO) has been
observed in high magnetic field using nuclear
magnetic resonance [3] and in zero-field diffraction,with resonant soft x-ray and hard x-ray scattering(RSXS) [4]. Since the superconductivity often
emerges in the proximity of, or in competition with,symmetry-breaking
groundstatessuchasantiferromagnetism or CDW, the stripe order also has
attracted much interests again.
Despite the intense interest and volume of research,
there were not many angle-resolve photoemission(ARPES) studies on stripe samples. There were only
a few studies on LBCO samples [5,6], which ismainly because it is hard to obtain a sharp peak in
ARPES spectrum to discuss the detail of thesuperconducting gap size. Moreover, the carrier
concentration and the strength of the stripe orderchange simultaneously by changing Ba concentration
x in LBCO, which makes it difficult to understand theeffect of the stripe order on the electronic structure,
because the electronic structure is sensitive to thecarrier concentration in cuprates. To figure out the
intrinsic electronic structure of the stripe order, wechoose LNSCO system, where the strength of the
stripe order solely can be controlled by Ndconcentration y. In this study, to clarify the intrinsic
electronic structure of the stripe order, we tried toseek the best ARPES measurement condition for
LNSCO samples, namely, an energy and apolarization of the incident light.
LNSCO single crystal (x = 0.16, y = 0.1) was
grown by a traveling solvent ﬂoating-zone (TSFZ)
method. As-grown sample was annealed on the gold
plate in O2 atmosphere at 800 degree for 1 week andquenched to the room temperature to make the holeconcentration uniform. Superconducting transition
temperature of the sample was determined as T= 35 K
from the onset in the magnetization measurements.
The ARPES measurements were carried out atbeamline BL7U of UVSOR-III at the Institute for
Molecular Science, using an MBS A-1 analyzer. Theenergy resolution was set to 10 meV and the angularresolution was about 0.17°. The Fermi level (E F) was

calibrated using an evaporated gold ﬁlm.
Figure 1 shows photon energy dependence ofspectra from 14 eV to 40 eV at nodal kF at 1st
Brillouin Zone (BZ) taken at temperature 12 K. Herethe polarization of the light was set along (π,0)-(0,π)
direction. One can clearly see the peak structure at
photon energy 20 and 36 eV. In those photon energies,
the Fermi arc can be clearly seen in the Fermi surface
mapping (not shown). We also performed
measurements with polarization along (0,0)-(π,π)
direction, however, there were almost no peak and thewhole spectral intensity was suppressed. This
polarization dependence is consistent with previous
calculation [5].
We clarify that the photon energies of 20 and 36 eV
can be used for LNSCO measurements at BL7U to
perform the detailed superconducting gap study.

Fig. 1. Photon energy dependence of ARPES spectraof La1.74Nd0.1Sr0.16CuO4 at nodal kF at 1st BZ taken at
temperature 12 K.
[1] J. M. Tranquada et al., Nature, 375 (1995) 561.
[2] M. Hucker et al., Phys. Rev. B 83 (2011) 104506.
[3] T. Wu et al., Nature, 477 (2011) 191.
[4] G. Ghiringhelli et al., Science 337 (2012) 821.
[3] T. Valla et al., Science 314 (2006) 1914.
[4] R. H. He et al., Nature Physics 5 (2009) 119.
[5] A. Bansil et al., Phys. Rev. Lett. 83 (1999) 5154.

94

Ⅲ -2. Materials Sciences

BL7U

ARPES Studies of Hydrogen Exposed MoS2
1

1

S. Cho , B. Kim , B. Kim1, Y. Kim1, Y. Koh1, J. Seo1, J. Kwon1, M. Matsunami2, K. Tanaka2,
S. R. Park3 and C. Kim1
1

Institute of Physics and Applied Physics, Yonsei University, Seoul, Korea
Editorial Board, UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan3
Department of physics, Incheon National University, Incheon 406-772, Korea

2

Therefore we assume that the bulk MoS2 turns into
the one of multilayer near surface after high pressurehydrogen treatment.

The physics associated with transition metal
dichalcogenides (TMDCs) is one of the mostintriguing issues in condensed matter physics. Thesematerials have several interesting aspects interphysical properties, especially the direct to indirect
band gap transition from monolayer to bulk and spinband splitting at the K-point. [1,2] There are manystudies on the electronic structures of the monolayer
TMDCs because of the direct band gap. [3,4,5] At
these days, monolayer MoS2 with direct band gap canbe manufactured and it is interested in a variety ofareas, such as field effect transistor, optoelectronic
applications and so on. But thorough systematicstudies on the electronic structures of bulk TMDCs
regarding those issues have not been done.
In the early 21 century, molybdenum disulfide(MoS2) was used by catalyst for hydrodesulfurization
which mean capture and remove sulfur from thecrude oil called thiophene by hydrogen sulfide.
During this process, there is intermediate state that
only sulfur released from MoS2 such as defect state.
We mainly interested in this intermediate state which
was known for the mid gap state between conduction
band and valence band. [6]We bought the MoS2 single crystal from the SPI
then we made the cell with low vacuum. For thehydrogen treatment, we put the MoS2 in the cell andflow the hydrogen under 20 bar pressure at about
350K for 10 hours. [7] Samples were cleaved in situ
at room temperature and the chamber pressure wasbetter than 5×10−11 Torr. ARPES spectra wereacquired with a hemispherical photoelectron analyzer(MBS A-1). We used linearly polarized light with
40eV photon energy.
We present the electronic structure studies ofhydrogen exposed MoS2 by angle resolved
photoemission in UVSOR. Figure 1a is the Γ-K finecut raw data of hydrogen exposed MoS2. To see band
dispersion more clearly, Fig. 1b is shown as thesecond derivative data of Fig. 1a. In the K-point,
there is a band splitting about 170meV due to strong
spin-orbit coupling. [8] It is well matched bytheoretical prediction for size of band splitting. The
dotted white lines in Fig. 1b are guide to the eye
indicating the band dispersions. It was recently
reported that the number of band in topmost valenceband at Γ-point are corresponding to be the number oflayers. [3] The bulk MoS2 case, it has a one thickband at Γ-point. In our data of Fig. 1b, the valenceband at Γ-point shows five distinguished dispersions.

Ⅲ-2

Fig. 1. (a) Γ-K fine cut raw data of hydrogen
exposed MoS2. Right side is intensity plot of raw
data. (b) Γ-K fine cut second derivative data ofhydrogen exposed MoS2. Right side is sign plot of
second derivative data.
[1] Q. H. Wang et al., Nat. Nanotelnol. 7 (2012) 699.
[2] Z. Y. Zhu et al., PRB. 84 (2012) 153402.
[3] Y. Zhang et al., Nat. Nanotechnol. 9 (2014) 111.
[4] B. Radisavlievic et al., Nat. Nanotechnol. 6 (2011)147.
[5] H. J. Conley et al., Nano Lett. 13 (2013) 3626.
[6] D. Liu et al., Appl. Phys. Lett. 105 (2014)
213508.
[7] B. H. Kim et al., RCS Advances 3 (2013) 18424.
[8] J. E. Padilha et al., PR 90 (2014) 205420.

95

Ⅲ -2. Materials Sciences

BL7U

Non-Uniform Temperature-Dependent Band Shift of an Iron Pnictide
Superconductor LiFeAs
T. Hajiri1,2, T. Ito1,3, M. Matsunami2,4, B. H. Min5, Y. S. Kwon5, K. Kuroki6 and S. Kimura2,6,7
1

Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
2
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
3
Nagoya University Synchrotron Radiation Research Center, Nagoya University, Nagoya, 464-8603, Japan
4
School of Physical Sciences, SOKENDAI(The Graduate University for Advanced Studies), Okazaki 444-8585,
Japan
5
Department of Emerging Materials Science, DGIST, Daegu 711-873, Republic of Korea
6
Department of Physics, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan
7
Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan

Ⅲ-2

Iron pnictide superconductors are recently attracted
in the change of physical properties above
superconducting temperature (Tc), such as thein-plane anisotropic resistivity [1], the softening of
the C66 mode [2], the orbital-polarized electronic
structure between dxz and dyz orbitals [3], and theappearance of a pseudogap [4]. Thus, it is consideredthat the electronic structure as well as the physicalproperty above Tc is closely related to the appearanceof the superconductivity, the electronic structure
above Tc should be investigated to elucidate the originof the superconductivity of the iron pnictides. In thisreport, we show the temperature-dependent
angle-resolved photoemission spectroscopy (ARPES)
results of LiFeAs (Tc ~ 19.7 K) using UVSOR BL7U“SAMRAI” end-station.
Figures 1(a)-1(d) show the ARPES image at the Γ(hν = 23 eV) and Z (hν = 35 eV) points along the Γ-M
and Z-A directions at T = 100 K (above Tc) and 12 K
(below Tc) taken by using S polarization. There are
two hole bands at both of the Γ and Z points; theouter and inner hole bands are attributed to dxy and dyz
orbitals, respectively [5]. Figures 1(e) and 1(f) show
the comparison of each band dispersion at two
temperatures of T = 100 and 12 K at the Γ and Z
points, respectively. At the Γ point in Fig. 1(e), theobserved two bands do not shift with temperature. At
the Z point in Fig. 1(f), on the other hand, the innerhole band rigidly shifts to the higher binding energy
side by 28 meV with decreasing temperature, though
the outer hole band has almost no temperaturedependence. Figures 1(g) and 1(h) show thetemperature-dependent ARPES images divided by a
Fermi-Dirac function at the Γ and Z points,
respectively. It is clear that the energy of the top of
the inner hole band at the Z point shifts below T = 40
K, but that at the Γ point is constant with temperature.
Recent ultrafast optical measurement reports anappearance of the pseudogap like feature below T =55 K due to antiferromagnetic fluctuations [6]. Indeed,
the spin fluctuation is enhanced with decreasing
temperature below about T = 50 K [7]. Thesetemperatures are consistent with that of an appearanceof the orbital-dependent band shift, i.e., the band shift

is considered to be strongly related to the spin
fluctuation.

Fig. 1. (a-d) ARPES images along Γ-M/Z-A
directions obtained by using S polarization at T = 100
and 12 K. (e, f) Comparison of each band dispersion.
(g, h) Temperature-dependent ARPES images divided
by a Fermi-Dirac function.
[1] M. Nakajima et al., Phys. Rev. Lett. 109 (2012)
217003.
[2] M. Yoshizawa et al., J. Phys. Soc. Jpn. 81 (2012)024604.
[3] M. Yi et al., Proc. Natl. Acad. Sci. 108 (2011)
6878.
[4] T. Shimojima et al., Phys. Rev. B 89 (2014)
045101.
[5] T. Hajiri et al., Phys. Rev. B 85 (2012) 094509.
[6] K.-H. Lin et al., arXiv:1407.3539 (2014).
[7] L. Ma, J. Zhang, G. F. Chen and W. Yu, Phys. Rev.
B 82 (2010) 180501(R).

96

Ⅲ -2. Materials Sciences

BL7U

Angle Resolved Photoemission Spectroscopy of Iron Pnictide
Superconductor NdFeP1-xAsx(O,F)
1

A. Takemori1, S. Miyasaka1, M. Uekubo1, T. Kobayashi1, S. Tajima1, T. Hajiri2,3,
M. Matsunami3,4 and K. Tanaka3,4

Department of Physics, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan
Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Nagoya
464-8603, Japan
3
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585,
Japan2

polarization configuration, the bands with dxz and dz2
orbital characters have been observed, and the dxz
band exists very near Γ point. As shown in this figure,the dxz band crosses the Fermi energy and resultantly
the dxz hole Fermi surface exists around Γ point at
x=0.4. The energy level of dxz band decreases withincreasing As concentration x, and this band almost
sinks below Fermi energy around Γ point in the x=0.8
sample. With further increasing x, this dxz Fermi
surface completely disappears at x=1.0. The clear
changes of Fermi surfaces and electronic structures
around x=0.8 are related with the x-dependentchanges of transport and other properties, and support
the scenario of two Tc-rising mechanisms and two
Fermi surface states in this system.

The iron-based superconductors are multiband
systems and have various Fermi surface states. These
compounds show unconventional superconductivity
with high superconducting transition temperature (Tc)
and have been extremely investigated by many
experimental and theoretical groups. Recently, we
studied the transport properties in 1111-type P/As
solid solution system, RFeP1-xAsxO1-yFy (R=La, Pr andNd). The results have indicated that this system has
two different Tc-rising mechanism, related to two
different Fermi surface states and nesting conditions
below and above x=0.6~0.8. [1, 2] To clarify
x-dependent change of electronic structures andFermi surfaces, we have investigated the angle
resolved photoemission spectroscopy using single
crystals of NdFeP1-xAsx(O,F) with x=0.4, 0.8 and 1.0
for F concentration y~0.1.
The single crystals of NdFeP1-xAsx(O,F) weregrown by high pressure technique using cubic anvilpress and self-flux method. [3] Tc of the single
crystals in the present work were 12 K for x=0.4, 23
K for x=0.8 and 44 K for x=1.0, respectively. The
angle resolved photoemission spectroscopy were
measured at BL7U of UVSOR facility in Institute for
Molecular Science. The measurements of Fermi
surfaces and electronic band dispersion around Γ andM points were performed at 12 K using incident lightwith the energy of 36 eV.
The results of the angle resolved photoemission
spectroscopy indicate the existence of three hole andtwo electron Fermi surfaces in x=0.4, and two holeand two electron Fermi surfaces in x=0.8 and 1.0
samples. These Fermi surfaces have two dimensionalfeatures (cylindrical shapes), and the hole andelectron Fermi surfaces are located around Γ and M
points, respectively. The present experiments haveclearly revealed that the change of Fermi surface state
occurs around x=0.8. The orbital characters of these
Fermi surfaces and electronic bands have been
assigned by the polarization-dependent angle resolved
photoemission spectroscopy [4], and the dxz bandparticularly shows the systematic and important x
dependence. Figure 1 shows the band dispersion
around Γ point of NdFeP1-xAsx(O,F) with x=0.4, 0.8
and 1.0 by the P-polarization measurement. In thisFig. 1. Band dispersions along Γ-M direction of
NdFeP1-xAsx(O,F) with (a) x=0.4, (b) 0.8 and (c) 1.0
by the P-polarization configuration measurement. [4]The broken red lines are guide for eyes and indicate
the bands with dxz and dz2 orbital characters around Γpoint.
[1] S. Miyasaka et al., J. Phys. Soc. Jpn. 82 (2013)
124706.
[2] K. T. Lai et al., Phys. Rev. B 90 (2014) 064504.
[3] A. Takemori et al., JPS Conf. Proc. 1 (2014)
012111.
[4] Y. Zhang et al., Phys. Rev. B 83 (2011) 054510.

97

Ⅲ-2

Ⅲ -2. Materials Sciences

BL7U

Polarization Dependent ARPES Study on Iron-Based Superconductor
KxFe2-ySe2
1

The Graduate School of Natural Science and Technology and Research Laboratory for Surface Science, Okayama
University, Okayama 700-8530, Japan
2
Research Center of New Functional Materials for Energy Production, Storage, and Transport, Okayama
University, Okayama 700-8530, Japan
3
National Institute for Material Science, Tsukuba 305-0047, Japan
4
Department of Physics, Osaka University, Toyonaka 560-0043, Japan
with tuning the photon polarization at BL-7U of
UVSOR, and confirmed the reproducibility of theobservation of the hole-like band, as shown in Fig 1.
We acknowledge M. Matsunami and K. Tanaka fortechnical assistance in this photoemission experiment.

An accurate description of the overall electronic
structure is extremely important for understanding themechanism of superconductivity. For iron-arsenide
superconductors, their Fermi surface (FS) topology
consists of hole- and electron-like FSs at the Brillouinzone center and corner, respectively. Theoreticalstudies based on weak-coupling approach haveproposed that spin fluctuations arising from the FS
nesting can realize a s± superconducting state [1,2]. A
nearly isotropic s-wave superconducting gap and aspin resonance peak at the nesting vector measured
by ARPES and neutron scattering measurements [3,4],
respectively,
areconsistent
with
the
s±
superconducting state.
However, this theory has faced a serious challengeever since the discovery of alkali-metal doped
iron-selenide superconductors (AFS), where only
electron-like FSs with nodeless superconducting gap
have been observed by ARPES [5-7]. These results
are not consistent with the d-wave symmetry
expected by some of weak-coupling theories [8-10].
Therefore, it remains open whether the
weak-coupling theories are suitable for explaining thesuperconductivity in AFS.
The low-lying electronic structure in iron-basedmaterials consists of multi-band with different orbital
character. Due to the photoemission selection rule, thespectral intensity of the bands exhibits photon
polarization dependence. Moreover, in severaliron-based superconductors, it has been reported thatthe strength of band intensity also depends on the
excitation photon energy. So, there is a possibility
that a hole-like FS actually exists and has eluded
previous ARPES experiments because of thesignificant photon polarization and/or photon energy
dependence of spectral intensity. Previously, we
performed ARPES measurements with careful tuningof photon energy and photon polarization on a highquality single crystal of K0.62Fe1.7Se2 [11], and we
succeeded to observe a hole-like band withapproaching EF in two different momentum regions
around the Γ point, suggesting the possible presenceof a hole-like FS in KxFe2-ySe2 [12].
In the present research, we performed thetemperature-dependent ARPES study on KxFe2-ySe2

40

E - EF (meV)Ⅲ-2

M. Sunagawa1, K. Terashima1,2, M. Tanaka3, H. Takeya3, Y. Takano3,
K. Suzuki4, H. Usui4, K. Kuroki4, T. Wakita1,2, Y. Muraoka1,2 and T. Yokoya1,2

0
-40
-80

-120
-0.6 -0.4 -0.20

0.2 0.4-1

Wave Vector (A )Fig. 1. ARPES E-k map along Γ-X line taken with
p-polarized 23 eV photon at T = 80 K. In Fig.1, redarrow indicates the new hole-like band.
[1] I. I. Mazin et al., Phys. Rev. Lett. 101 (2008)
057003.
[2] K. Kuroki et al., Phys. Rev. Lett. 101 (2008)
087004.
[3] P. Richard et al., Rep. Prog. Phys. 74 (2011)
124512.
[4] A. D. Christianson et al. Nature 456 (2008) 930.
[5] M. Xu et al., Phys. Rev. B 85 (2012) 220504.
[6] D. Mou et al., Phys. Rev. Lett. 106 (2011)
107001.
[7] X. –P. Wang et al., Europhys. Lett. 99 (2012)
67001.
[8] I. I. Mazin, Phys. Rev. B 84 (2011) 02459.
[9] M. Khodas et al., Phys. Rev. Lett. 108 (2012)
247003.
[10] A. Kreisel et al., Phys. Rev. B 88 (2013) 094522.
[11] T. Ozaki et al., Europhys. Lett. 98 (2012) 27002.
[12] M. Sunagawa et al., submitted.

98Ⅲ -2. Materials Sciences

BL7U

CD-ARPES Studies on Rashba & Dresselhaus Effects
1

W. Jung , S. Cho1, Y. Kim1, B. Kim1, J. Seo1, J. Kwon1, M. Matsunami2, K. Tanaka2,
S. R. Park3 and C. Kim1
1

Institute of Physics and Applied Physics, Yonsei University, Seoul, Korea
Editorial Board, UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan3
Department of physics, Incheon National University, Incheon 406-772, Korea

2

Semiconductor materials have recently been
extensively studied for their spintronic applications.
An important example is spin-field-effect transistor(spin-FET) proposed by Datta and Das [1] in light ofcontrollability of spin precession motion of electrons
through the Rashba and Dresselhaus spin-orbit
coupling effects. [2,3,4]. Based on previous work,orbital angular momentum (OAM) plays a vital rolein the Rashba effect. We expect OAM in thesematerials also has strong influence on the Dresselhaus
effect, therefore, in turn on the spintronic properties.
Compound semiconductors such as CdTe and InSb
have zinc blende structure with inversion symmetry
breaking (ISB) in the bulk. They have three holebands at the valence band top located at the Γ-point.
They are defined as heavy and light hole bands with
J=3/2, and a split off band with J = 1/2. The energy
splitting (Δ) between J=3/2 and 1/2 states due tospin-orbit coupling is on the order of hundred meV.
To describe the complex spin configuration of thesebands, they normally apply Dresselhaus Hamiltonian.
However, the conventional Dresselhaus Hamiltonian
does not consider OAM. Therefore, we aimed toinvestigate the OAM configuration in these bands of
CdTe by using circular dichroism (CD) ARPES. We
also performed density function theory calculation totheoretically study the role of OAM in the Rashba
and Dresselhaus effect in these materials.
CdTe single crystals were purchased as wafers.
ARPES measurement was performed at the beam line
7U of UVSOR-III. Samples were cleaved in situ atroom temperature and the chamber pressure wasbetter than 5×10−11 Torr. ARPES spectra wereacquired with a hemispherical photoelectron analyzer(MBS A-1). We used horizontally polarized as well as
left- and right-circularly polarized (LCP and RCP)
light.
The dispersion of heavy and light hole bands areclearly seen in Γ-X high symmetry cut data taken byhorizontal polarized light with 24 eV photon energy
as shown in Fig. 1a. Figure 1b is the CD-pattern. The
CD-pattern is defined as the subtraction data from
RCP and LCP (RCP-LCP). The dotted black line is a
guide to the eye, indicating the dispersion of the lighthole band. We can only confirm the CD-pattern oflight hole band because the heavy hole band is notclearly seen in low photon energy region. The
CD-pattern of light hole band seems to havemirror-symmetry breaking about the Γ-point.
The above observation means that the OAM has

similar textures to the spin textures of Dresselhaus
type, implying the existence of OAM in this system.
It also implies that OAM plays an important role in
the Dresselhaus effect. To confirm more precise
OAM texture, we will obtain the energy constantcontour data using CD-ARPES.

Ⅲ-2

Fig. 1. ARPES results from CdTe (110) bulk statemeasured with 24 eV photon (a) and CD pattern of
one with 9.75 eV (b) at the Γ-point.
[1] S. Datta et al., Appl. Phys. Lett. 56 (1990) 665.
[2] Y. A. Bychkov et al., JETP Lett. 39 (1984) 78.
[3] J. Schliemann et al., PRL. 90 (2003) 146801.
[4] X. Cartoixà, D et al., APL. 83 (2003) 1462.
[5] S. R. Park et al., PRL 107 (2011) 156803.
[6] B. Y. Kim et al., PRB 85 (2012) 195402.

99

Ⅲ -2. Materials Sciences

BL7B

Electronic Structures and Reflectance Spectra of AZnF3 (A=Na, K, Rb)
Single Crystals
S. Ishii1, S. Tanaka1, A. Yamaji2, S. Tanaka3, S. Kurosawa2,4, S. Watanabe5, M. Kitaura1,
A. Ohnishi1 and M. Sasaki1
1

Department of Physics, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
2
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan3
Department of Electric and Electronic Engineering, Faculty of Science and Engineering, Kinki University,
Higashi-Osaka 577-8502, Japan
4
New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579, Japan
5
Department of Materials, Physics and Energy Engineering, Graduate School of Engineering,
Nagoya University, Nagoya 464-8063, Japan

Ⅲ-2

Studies on Auger-free luminescence (AFL) are ofimportance in both sides of basic science andindustrial application. In this viewpoint, we havelooked for new types of AFL materials so far [1, 2].
The present study is an extension of such previous
studies; the possibility of AFL in AZnF3 (A=Na, K,
Rb) crystals has been investigated by measurementsof reflection and x-ray photoelectron spectroscopy(xps) spectra.
The crystals of NaZnF3, KZnF3, and RbZnF3 weregrown from melt by a micro puling-down method.
Reflectance spectra of NaZnF3, KZnF3, and RbZnF3
crystals are shown in Figs. 1(a)-1(c), respectively.
These data were measured at 8 K. The lowest energy
reflectance peak due to excitonic transition locatesaround 10 eV. Since the peak position is independentof alkali metals, it is likely that such excitonic
transition occurs by F 2p  Zn 4s transitions. The
reflectance spectrum of NaZnF3 is structureless in theenergy region above 10 eV, and is different from thereflectance spectra of KZnF3 and RbZnF3. According
to Ref. 3, the outermost core bands of NaZnF3,
KZnF3, and RbZnF3 are mainly of alkali p orbitals.
The binding energies are estimated to be 25, 12, and 9eV, respectively. In NaZnF3, the electronic transition
from the outermost core band does not occur in theenergy region below 30 eV, and thus the reflectancespectrum exhibits only tail. In KZnF3 and RbZnF3,
the transitions from outermost core bands areobserved as many peaks in the reflectance spectra.
There is a general rule on the occurrence of AFL. It
is observed in the case that the band gap energy islarger than the energy difference between the valenceband top and the outermost core band top. This rule issatisfied in KZnF3. Although KZnF3 is expected to be
an AFL material, AFL has not yet been found atpresent.

Fig. 1. Reflectance spectra of NaZnF3 (upper),KZnF3 (middle), RbZnF3 (lower) single crystals
measured at 8 K.
[1] A. Ohnishi et al., J. Lumi. 132 (2012) 2639.
[2] M. Kitaura et al., Phys. Status Solidi C 10 (2008)993.
[3] J. F. Moulder, W. F. Stickle, P. E. Sobol and K. D.
Bomben, Hand- book of X-Ray Photoelectron
Spectroscopy, edited by J. Chastain Perkin-Elmer
Corporation, Eden Prairie, MN, 1992.

100

Ⅲ -2. Materials Sciences

BL7B

Luminescence and Scintillation Properties of CdF2 Crystal
T. Yanagida1,2, Y. Fujimoto2, M. Koshimizu2 and K. Fukuda3
1

Kyushu Institute of Technology, Fukuoka 808-0196, Japan
Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan3
Tokuyama Corp., Shunan 745-8648 Japan

2

Auger-free luminescence (AFL) is a luminescenceprocess in which a valence electron radiatively
recombine with an outermost core hole. Typical decay
time constant of the AFL is subnanosecond or on theorder of nanoseconds. Owing to the fast decay,
insulator crystals exhibiting the AFL is often used as
fast scintillators. The AFL has been observed invarious insulators, mainly halide crystals.
Among the halide crystals, the occurrence of the
AFL was predicted in CdF2 [1]. Scintillation
properties of CdF2 crystals have been reported inseveral papers [2-4]. Fast scintillation components
has been observed, however, the ascription of thesecomponents to the AFL is not conclusive. In thisreport, the luminescence and scintillation propertiesof a single crystal of CdF2, with an emphasis on theluminescence properties under vacuum ultraviolet(VUV) photon irradiation.
Single crystal of CdF2 was grown by Tokuyama
Corp. The luminescence and excitation spectra of
CdF2 was obtained by using VUV light as an
excitation source at BL7B, UVSOR. Temporalprofiles of photoluminescence was obtained at
UVSOR operated in a single bunch mode.
Radioluminescence (RL) spectrum was obtained
under X-ray irradiation. Temporal profile ofscintillation was obtained by a single photon counting
technique using a pulsed X-ray as an excitation
source.
Figure 1 shows the RL spectrum. We observed aprominent band at 420 nm and a shoulder at ca. 350
nm.
Figure 2 shows the excitation spectra monitored at
350 nm. The excitation band maxima were locatedbetween 200 and 300 nm. This is also the case for themonitoring wavelength of 420 nm. Taking into
account the band gap energy, this excitation band isjudged to be located within the band gap. In addition,
the band was hardly observed under VUV irradiation.
Figure 3 shows the temporal profile ofluminescence at 420 nm. A fast component wasobserved. The fast components in scintillation can be
ascribed to this luminescence component.
The results mentioned above indicate that the fast
scintillation component in CdF2 cannot be ascribed to
the AFL but to the defects or impurities.

3100

Intensity (a.u.)

3080
3060
3040

3020
3000
2980

Ⅲ-2
200

300

400

500

600

700

Wavelength (nm)Fig. 1. Radioluminesence spectrum.
3.60E+05

Intensity (a.u.)

3.40E+05
3.20E+05

3.00E+05
2.80E+05
2.60E+05
2.40E+05
2.20E+05
2.00E+05

50

100

150

200

250

300

350

Wavelength (nm)CountsFig. 2. Excitation spectra monitored at 350 nm.
100
90
80
70
60
50
40
30
20
10
0

10

20

30

40

50

60

70

80

90

100

Time (ns)Fig. 3. Temporal profile of luminescence at 420 nm.
[1] J. Andiessen, P. Dorenbos and C. W. E. Van Eijk,
Radiat. Meas. 24 (1995) 347.
[2] R. V. Jones and J. H. Pollard, Proc. Phys. Soc. 79(1962) 358.
[3] S. E. Derenzo, W. W. Moses, J. L. Cahoon and R.
C. C. Perera, IEEE Trans. Nucl. Sci. 37 (1990) 203.
[4] E. Radzhabov and R. Shendrik, IEEE Trans. Nucl.
Sci. 61 (2014) 402.

101

Ⅲ -2. Materials Sciences

BL7B

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

National Institute of Advanced Industrial Science and Technology, Ikeda 563-8577, Japan
0 100
20

80

ZnO

40

60

60

P2O5

40

80
100

0

20

40

Bi2O3

60

80

Fig. 1. Glass forming region and chemicalcompositions of glass of the present system.
0.14

Bi 1S0→3P1
Bi 1S0→1P1

Reflectivity

0.12

30
20

0.10
x=10
0.08

xZnO-(30-x/2)Bi2O3-(70-x/2)P2O5

4

6

8

10

12

14

Photon energy/ eV

1618

Fig. 2. Reflection spectra of ternary(30-x/2)Bi2O3-(70-x/2)P2O5 glasses.

xZnO-

0.18
0.16

Reflectivity

Ⅲ-2

Bismuth phosphate glasses, which have highrefractive index and low deformation temperature, arecandidate materials for producing high performance
optical components such as compact lenses anddiffractive optics. It is of interest that a zinc bismuth
phosphate glass system has two distinct glass-forming
regions; orthophosphate and isolated phosphate
structures are dominant in the region that the atomic
ratio O/P is higher than 3.5 and metaphosphate andpyrophosphate structures are dominant in the regionof O/P < 3.5[1,2]. We have reported the glass
structure and local structure around bismuth ions in aprevious work [2,3]. However, the energy level in theglass system is not clear yet. In the present study,
reflectivity of the bismuth phosphate glasses has beenmeasured to investigate compositional dependence ofthe band structure in the vacuum ultraviolet region.
Ternary xZnO-(30-x/2)Bi2O3-(70-x/2) P2O5 glasses(x=10, 20 and 30 mol%) and (85-3x/2)ZnO-xBi2O3(15+x/2)P2O5 glasses (x= 15, 20 and 25 mol%) wereprepared by using a conventional liquid-quench
method. Nominal chemical compositions are plottedin the glass forming region of the present system asshown in Fig. 1. Reflectivity of optically polishedsamples was measured in the photon energy region of
4-18 eV with an incident angle of 10˚ at the BL7B.
Figure 2 shows reflection spectra of the binary andun-doped xZnO-(30-x/2)Bi2O3-(70-x/2) P2O5 glasses.
Distinct reflection peak and broad contour wererespectively observed at around 5 eV and 6-8 eV. The
peak and contour are assigned to the 6s2→6s16p1
transition in the Bi3+ ion [2, 4]. We know thattransitions from the ground state (1S0) to excitedstates 3P0 and 3P2 are spin-forbidden. Therefore, thelower distinct peak is expected to the 1S0→3P1
transition and the next contour could be due to the1
S0→1P1 transition. K-K transformed absorption
peaks having Gaussian shape have been fitted to thesereflection spectra by least square method. The firstpeak assigned to the 1S0→3P1 transition was located at
4.9 eV and the position was almost constant in spiteof large change in ZnO and Bi2O3 concentration.
On the other hand, reflection spectra of ternary
glassesare(85-3x/2)ZnO-xBi2O3-(15+x/2)P2O5
shown in Fig. 3. The first peaks located around 4.2eV
and shifted toward lower energy side with theincrease of ZnO content. In the previous work [5], wehave found that the fraction of the Bi-O bond having
short length in BiO6 polyhedra increased withincreasing ZnO content. The low energy shift of thefirst band might be due to the change in local
structure around bismuth ions.

0.14
x=10
0.12

20

0.10

30

0.08
0.06

(85-3x/2)ZnO-xBi2O3-(15+x/2)P2O5
4

6

8

10

12

14

Photon energy/ eV

1618

Fig. 3. Reflection spectra of ternary (85-3x/2)
ZnO-xBi2O3-(15+x/2)P2O5 glasses.
[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] G. Blasse and A. Bril, J. Chem. Phys. 48 (1968)
217.
[5] N. Kitamura, et al., 23th International Congress
on Glass 2013, in preparation.

102

Ⅲ -2. Materials Sciences

BL7B

Control of Spectral Response Using Compound Fluoride Materials
CaxSr1-xF2
S. Otani, H. Ishikawa, M. Yanagihara and S. Ono
Nagoya Institute of Technology, Nagoya 466-8555, Japan

Vacuum ultraviolet (VUV) light source is used invarious applications such as surface treatment, opticalcleaning of semiconductor substrates and sterilization.
Accordingly, the detector for monitoring the lightsource is also required. Currently, many researchersdeveloped VUV detectors based on oxide, nitride anddiamond. However, the detectors require the filtersfor cutting off deep-UV when being used formonitoring of the light source. On the other hand, ourgroup is proceeding to development of the VUVdetectors using fluorides [1, 2]. Some fluorides haveextremely wider band gap than oxides and nitrides sothat they transmit deep-UV region [3]. Until now, weachieved filterless VUV detectors by applying suchfluorides. And spectral response of the detectors
varies according to band gap of the material.
Therefore, we may realize the detectors possessing
arbitrary response region by controlling band gap of
the material. Here, we report on controlling band gapof compound fluoride materials CaxSr1-xF2 andspectral response of filterless VUV photoconductive
detectors.
CaxSr1-xF2 crystals were grown by Bridgman
method and they were controlled composition ratio as
Ca0.85Sr0.15F2 and Ca0.5Sr0.5F2. The transmission
spectrum of CaxSr1-xF2 crystals was measured inbeamline BL7B at the UVSOR facility. Absorption
coefficient was calculated by measuring transmission
spectrum of UV region, as shown in Fig. 1. Herewith,band gaps of Ca0.85Sr0.15F2 and Ca0.5Sr0.5F2 were
calculated as 10.09 eV and 9.93 eV, respectively.
Therefore, band gap of CaxSr1-xF2 is expanded byincreasing composition ratio of CaF2 in the crystals.
Filterless VUV photoconductive detectors were
fabricated by depositing a pair of interdigitatedaluminum electrodes on the crystals. Spectral
responses of the detectors were also measured inbeamline BL7B at the UVSOR facility. The detectorsof Ca0.85Sr0.15F2 and Ca0.5Sr0.5F2 responded until
below 151 nm and 156 nm, respectively. The resultshows the response region of the detectors shift to theshort-wavelength by expanding band gap of thecrystals.
In summary, we found capable of controlling thesize of band gap of CaxSr1-xF2 crystals. Additionally,
the spectral response change of filterless VUVphotoconductive detectors was observed by using
CaxSr1-xF2 crystals.

103

Ⅲ-2

Fig. 1. Transmission spectrum of CaxSr1-xF2 crystals.

Fig. 2. Spectral responses of the detectors using
CaxSr1-xF2.
[1] M. Ieda, T. Ishimaru, S. Ono, K. Yamanoi, M.
Cadatal, T. Shimizu, N. Sarukura, K. Fukuda, T.
Suyama, Y. Yokota, T. Yanagida and A. Yoshikawa,
Jpn. J. Appl. Phys. 51 (2012) 022603.
[2] T. Ishimaru, M. Ieda, S. Ono, Y. Yokota, T.
Yanagida and A. Yoshikawa, Thin Solid Films 534(2013) 12.
[3] S. Ono, R. E. Ouenzerfi, A. Quema, H. Murakami,
N. Sarukura, T. Nishimatsu, N. Terakubo, H.
Mizuseki, Y. Kawazoe, A. Yoshikawa and T. Fukuda,
Jpn. J. Appl. Phys. 44 (2005) 7285.

Ⅲ -2. Materials Sciences

BL7B

Optical Spectroscopy of Ba(Fe1-xCox)2As2 in Vacuum-Ultraviolet Energy
RegionM. Nakajima, S. Miyasaka and S. Tajima

Department of Physics, Osaka University, Toyonaka 560-0043, Japan

Ba(Fe1-xCox)2As2

0.2

x=0

0.1

Reflectivity

0
0.2

(a)
x = 0.1

0.1
0
0.2

(b)
x = 0.25

0.1
0
0

(c)
10

20
Energy (eV)30

Fig. 1. Reflectivity spectra of Ba(Fe1-xCox)2As2 up to
35 eV for (a) x = 0, (b) 0.1, and (c) 0.25.

Ba(Fe1-xCox)2As2
x = 0.25
0.2

0.2

0.1

Reflectivity

Ⅲ-2

similar, but fine structures are smeared for E//c,indicating that these structures result from excitations
parallel to FeAs layers. The most prominent
difference is observed for the 7-eV peak. The clearer
peak for Ec implies that the in-plane response isdominant for the transition from As4s to Fe3d.

Iron-based superconductors show high transition
temperatures as high as 55 K, which is the second
highest record after cupper-oxide high-temperature
superconductors, and have attracted much attention.
BaFe2As2 is one of the representative parent
compounds of iron-based superconductors andexhibits a magnetostructural phase transition at T =140 K. With Co substitution for Fe, the magnetostructural order is suppressed and superconductivity
emerges. Thus, how the electronic structure evolves
with doping (chemical substitution) is one of the mostimportant issues, and the investigation of theelectronic structure over wide energy range by themeasurements of the reflectivity spectra is essential.
In this beamtime, we measured reflectivity spectraof single-crystalline Ba(Fe1-xCox)2As2 (x = 0, 0.1, and0.25) for an energy range from 2 eV to 35 eV at room
temperature using BL7B. The measurement was
performed for x = 0.25 using the light polarized
parallel and perpendicular to FeAs layers (denoted asEc and E//c, respectively) and for x = 0 and 0.1
using the light of Ec. Reflectivity measurement inthis energy region is necessary to understand thecomprehensive electronic structure including valencebands away from the Fermi energy and to obtainreliable optical parameters derived from the
Kramers-Kronig transformation for multi-band/orbital
systems such as iron-based materials [1] or copperoxides [2], since a number of intraband and interband
excitations overlap in the same energy region andextend up to 10 eV or higher.
Figure 1 shows the in-plane reflectivity spectra(Ec) for x = 0, 0.1, and 0.25. For all the threecompositions, three distinct reflectivity edges areclearly observed at < 2, ~ 10, and ~ 25 eV. Each edge
indicates the end point of a series of intraband orinterband excitations. The lowest-energy edge
corresponds to the plasma edge of free carriers. In thepresent energy range, the lower limit of which is ~ 2
eV, only a tail of the edge is seen. With Co doping, anenergy showing a dip shifts to a higher energy region,
indicating that Co substitution increases electron
carrier density. The second edge probably
corresponds to the transition from As4s to Fe3d. A
height of a peak at ~ 7 eV decreases with increasing
the Co content. This might result from a Lifsitz
transition due to electron (Co) doping. The formationof the third edge observed at ~ 25 eV is contributedby the excitations involving all the valence electrons.
Polarization dependence of the reflectivity spectra
for x = 0.25 is shown in Fig. 2. An overall feature is

E//c

0.1

0

Ec
0
0

10

20
Energy (eV)30

Fig. 2. Reflectivity spectra of Ba(Fe0.75Co0.25)2As2
for the polarization parallel and perpendicular to the
FeAs layers. The spectrum for E//c is offset to avoid
overlapping.
[1] M. Nakajima et al., Proc. Natl. Acad. Sci. U.S.A.
108 (2011) 12238.
[2] S. Tajima et al., J. Opt. Soc. Am. B 6 (1989) 475.

104

Ⅲ -2. Materials Sciences

BL7B

Influence of Niobium Concentration on the Reflection Spectra for Ternary
Niobium Bismuth Phosphate Glasses
N. Kitamura1, K. Fukumi1, Y. Hisano2, N. Hirao2, S. Tuji2, A. Uchiyama2 and H. Kozuka2
1

National Institute of Advanced Industrial Science and Technology, Ikeda 563-8577, Japan
2
Kansai University, Suita 564-8680, Japan

105

might be due to the distortion of NbO6 polyhedra
which was found by Raman, FT-IR and XAFS
measurements of these glasses [3].
This work was supported by Nippon Sheet GlassFoundation for Materials Science and Engineering.
xNb2O5-(100-x)Ba(PO3)2 glass

Reflectivity

0.20

Ⅲ-2

x=0

0.15
15

0.10

35
50

8

10 12 14 16 18 20 22 24

Photon energy/ eVFig. 1. Reflection spectra(100-x)Ba(PO3)2 glasses.

ofternaryxNb2O5-

xNb2O5-50BaO-(50-x)P2O5 glass

0.20

Reflectivity

BaO-Nb2O5-P2O5 glass is one of niobium
phosphate glass systems having a wide glass forming
region with high Nb2O5 contents1). In this system,
NbOx polyhedra construct glass network structurewith PO4 tetrahedra. Since the glass shows highrefractive index due to high niobium concentration. It
is of interest for the application to optical glasses inprecision optical devices. However, the glass withhigh niobium content gives yellowish and blue
colours and the relationship between opticalproperties, such as refractive index, dispersion,
absorption edge, etc., and structure around niobium
ions or connection of niobium-oxygen polyhedra in
the network structure are not clear yet. In the present
study, reflectivity of the bismuth phosphate glasses
has been measured to investigate compositional
dependence of the band structure in the vacuum
ultraviolet region.
Ternary xNb2O5-(100-x)Ba(PO3)2 glasses (x=0, 15,35 and 50 mol%) and ternary xNb2O5-50BaO-(50-x)
P2O5 glasses (x=0, 10, 20 and 30 mol%) wereprepared by using a conventional liquid-quench
method. Reflectivity of optically polished samples
was measured in the photon energy region of 4-25 eV
with an incident angle of 10˚ at the BL7B. Figure 1
shows reflection spectra of the xNb2O5-(100-x)
Ba(PO3)2 glasses. Strong reflection peak was
observed at around 9.5eV and 22 eV, and a weakshoulder at 12-18 eV was observed for the glasses
with low Nb2O5 content. The peak are assigned to thetransition from O 2p and P 3p states to Nb 4d and Ba
5d states from a report of DFT calculation for barium
niobium phosphate compounds [2]. The origin of thehigher band at 22 eV is not clear yet. The weakshoulder around 12-18 eV suppressed with increasing
Nb2O5 content. Therefore, the shoulder could be dueto the Ba 5d state. In a crystal which NbO6 polyhedra
construct chain-like structure, Ba 5d state locates athigher energy side than Nb 5d state [2]. This does notcontradict the present results. The 9.5 eV peakbecame broad with the increase of Nb2O5 content.
Low energy shift of absorption edge and yellowish
color [3] might be due to the broadening of this band.
On the other hand, reflection spectra of ternary
xNb2O5-50BaO--(50-x) P2O5 glasses are shown in Fig.
2. As shown in the figure, the similar peaks andshoulder were observed. The weak shoulder around12-18 eV suppressed with increasing Nb2O5 content.
The 9.5eV band broadened with the increase of
Nb2O5 content too. The broadening of the 9.5eV band

x=0

0.15
10

0.10

8

20
30

10 12 14 16 18 20 22 24

Photon energy/eVFig. 2. Reflection spectra of
50BaO- (50-x) P2O5 glasses.

ternaryxNb2O5-[1] N. Shchegl ova and T. V. Avlas, Fiz. Khim.
Stekla 16 (1990) 879.
[2] I. Cho et al., Eur. J. Inorg. Chem. 2011 (2011)2206.
[3] N. Kitamura et al., Extended abstract 1st Int. Nat’l.
Conf. Phosphate glasses, Pardvice, 2014.

Ⅲ -2. Materials Sciences

BL8B

Ultraviolet Photoelectron Spectra of Ce2@C80 and La2@C80
1

Ⅲ-2

T. Miyazaki1, S. Okita1, T. Ohta1, H. Yagi1, R. Sumii2, H. Okimoto3, Y. Ito3,
H. Shinohara3 and S. Hino1

Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577, Japan
2
Institutes for Molecular Science, Okazaki 444-858, Japan
3
Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
than the HOMO-1 or -2, whereas that of La2@C80
locates rather close to the HOMO-1. From these data,
present findings suggest that the simulated spectra
obtained from D3d geometry reproduced the UPS of
Ce2@C80 and La2@C80 very well.
The UPS of La2@C80 are the same as those of
Ce2@C80, both have the same electronic structure.
Comparison of the UPS with theoretically generated
simulation spectra indicates that the most plausible
structure of Ce2@C80 and La2@C80 has D3d symmetry.
Charge population analysis suggests Ce26+@C806- andLa26+@C806- oxidation state.

Fullerene cages often encapsulate metal atoms. C80
endohedral fullerenes attract attention because of thereasons such as empty Ih-C80 is not stable and cannot
be isolated [1] but it becomes stable upon
encapsulation of metal atoms [2]. Early theoretical
calculation on La2@C80 suggested that entrapped two
La atoms rotated in the D2h-C80 cage. Vibrationalmode analysis using DFT calculation of La2@C80
suggested D3d symmetry that is the global minimum
in total energy. Ce2@C80, was isolated and its
predicted geometry was not D2h but D3d. The reason
of Ce2@C80 having D3d geometry was attributed to
specific bonding condition of Ce atoms to the cage:
they bonded to C atoms on the opposite side of C6
axis of C80. We succeeded to measure ultraviolet
photoelectron spectra (UPS) of La2@C80 and
Ce2@C80. In this report their UPS will be presented
and they are compared with simulated spectra
obtained from DFT calculation.
The UPS were measured using a photoelectron
spectrometer at BL8B2 of UVSOR.
Energycalibration of the spectra was carried out using the
Fermi edge of a gold-deposited sample disk before
the UPS measurements of La2@C80 and Ce2@C80.
Molecular orbitals of La2@C80 and Ce2@C80 were
calculated with a Gaussian 03 program module. Theirgeometry was optimized at the Hartree-Fock level
using the CEP-31G basis set. Simulated spectra
generated by broadening the calculated Eigen values
at the Hartree-Fock level with Gaussian functions of
0.2 eV full width at half maximum.
Figure 1 shows the UPS of La2@C80 and Ce2@C80
obtained with hv= 30eV. The spectral onset of
La2@C80 and Ce2@C80 was 0.77 and 0.89 eV below
the Fermi level, respectively. Except for the onset
energy, their UPS are almost identical. There are 10
structures labeled A to J in their UPS. Their relative
intensity is almost the same. The bars in Fig. 1
indicate the calculated
ionization energies(Eigenvalues of occupied states). Scale of thesimulated spectra and Kohn-Sham orbital energies isshifted by 4.4 eV for an easy comparison. The
simulated spectra generated from D3d and D2hgeometry seem to reproduce the UPS; the first four
structures A － D are well reproduced and deeper
structures F – J are also reproduced reasonably well.
Only attractive difference in the simulated spectra
might be associated with the position of the HOMO;
the HOMO of Ce2@C80 appears at slightly shallower

Fig. 1. Simulation spectra from the optimized D3dstructure and ultraviolet photoelectron spectra of
La2@C80 and Ce2@C80.
[1] F. H. Hennrich, et al., Angew. Chem. Int. Ed. 35(1996) 1732.
[2] M. M. Alvarez, et al., J. Phys. Chem. 95 (1991)
10561.

106