Highlight
BL4B

Electronic Structure of DNA Characterized by Resonant Photoemission
Spectroscopy

H. S. Kato1, M. Furukawa1, M. Kawai1, M. Taniguchi1,2, T. Kawai1,2,
T. Hatsui3, N. Kosugi3
1
RIKEN (The Institute of Physical and Chemical Research), Wako 351-0198 Japan
2
Institute of Scientific and Industrial Research, Osaka University, Ibaraki 567-0047 Japan
3
Institute for Molecular Science, Okazaki 444-8585 JapanThe characterization of electronic states near Fermi
level of DNA duplexes has been desired to clarify themechanisms of long-range charge migration in DNA,
from the viewpoint of not only biochemistry but also
molecular device materialization. Thorough stacking
orbitals of DNA bases (Fig. 1), the dc conductivity
model of DNA strands was proposed, over four
decades ago, on the basis of electric conductivity
measurements and a striking resemblance toconductive one-dimensional aromatic crystals. With
the recent progress in nanotechnology, in addition, theelectric conductivity of DNA has directly beenmeasured in molecular scale. However, thesecharacterizations of the electric property are still
indefinite, and there is no significant observation on
the electronic states near Fermi level of DNA for
understanding of the charge migration mechanism. In
this study, therefore, we carried out resonant
photoemission spectroscopy (RPES) experiments
near the Fermi level for both poly(dG)·poly(dC) (GC)and poly(dA)·poly(dT) (AT) DNA duplexes [1]. Since
N atoms are included in only bases in DNA duplexes,
the RPE spectra were obtained via the resonance from
N 1s to unoccupied states, and thus we could purely
extract the electronic orbital features of the bases inDNA.

Experimental
Experiments were performed at the beamline
BL4B of the UVSOR facility, in which theend-station (ultrahigh vacuum systems) is equippedwith an electron energy analyzer (Scienta SES200)
and a retarding-field electron detector for X-ray
absorption spectroscopy (XAS). The obtained RPE
intensities were normalized by the excitation lightintensity monitored as mesh current. We preparedthick GC- and AT-DNA films on SiO2/p-Si(111)substrates in the atmosphere. The film thickness
prepared was estimated to be 100 - 200 nm.
Comparing our observed Raman spectra [2] to thosepreviously reported, we confirmed that DNA in the
prepared thick films forms a mixture of A- andB-form double helixes. These samples wereintroduced into the ultrahigh vacuum via a sample
entry system from the atmosphere, without baking
procedures. Special care of freshness of DNA
samples was taken throughout the experiments, toavoid any chemical changes. At the experiments, thesample was frequently replaced with new one, at least
twice a day. This procedure also excluded
accumulation of X-ray radiation damages on thesurface. We confirmed suitable N 1s photoelectron
spectra [2] for each sample.

Results and Discussion
An N K-edge XA spectrum of GC DNA is shownin the inset of Fig. 2. In the XA spectrum, two 1s - S*resonant peaks at 399.7 eV and 401.9 eV and a broad
1s - V* resonant peak at 407 eV were observed. The
off- and on-RPE spectra near the Fermi level of GC
DNA are shown in Fig. 2 as a function of kinetic
energy. The RPE spectra were measured at eachresonant absorption peak marked on the XA spectrum
shown in the inset. On the comparison to the off-RPE(normal Auger) spectrum, the on-RPE (resonant
Auger) spectra are obviously involving additional
components which is attributed to the N-KLL Auger
electrons.
The resonant Auger signals could be extracted fromthe on-RPE spectra by subtracting the off-RPE
spectra in binding energy plots, as the dotted lines inFig. 2. The differential spectra commonly show abroad bump. Normally, the Auger electrons keep an
identical distribution in kinetic energy, independentlyof excitation photon energies. The obtained resonant
Auger signals were, however, strongly affected by

Fig. 1 Schematic structure of a DNA double helix.

90

Highlight
excitation energy; the lower photon energy lightprovides a higher kinetic energy distribution. This
indicates that the excited electrons locate in theunoccupied states for, at least, a time scale ofresonant Auger transition and affect its final state of
the transition.
In addition, an appended component was observedat the first S* resonance, as marked by a dagger in
Fig. 2. We attribute the additional component to thatof participant Auger transition. This finding again
indicates that the excited electrons locate in the S*
states for, at least, the time scale of Auger transition.
In the case of the molecules chemisorbed on metals,
such as CO/metals, their RPE spectra do not show thedrastic peak shift of Auger electrons in kinetic energy.
These are explained as that the molecular orbitals
rehybridized with metal electronic states aredelocalized, and the excited electrons in thechemisorbed molecules diffuse into the metal,
immediately. In contrast, all features of the observed
RPE spectra of DNA, as mentioned above, clearlyshow that the excited electron is localized at theexcited orbitals. In other words, the unoccupied statesof the bases in DNA duplexes are not delocalized.
The degree of the localization of excited electrons
can be determined from the peak shift of resonant
Auger signals, according to the report of Takata et al.
[3]. For Ni metal, the LMM Auger peaks show aconstant kinetic energy, i.e., normal Auger transition
behavior, under excitation above the photoabsorption
maximum. For the K2Ni(CN)4 ionic crystal in which
the Ni(CN)4 complex exists as a quasi-isolated ion, on
the other hand, the Ni-LMM Auger peaks show adownward shift as a function of photon energy withthe slope of 'KE/'hv = -0.55 ± 0.05. For thevaporized Ca atom [4], the slope of a resonant Auger
peak has been estimated to be -1, which would be thelower limit because of the condition ideally isolated.
The upper limit must be zero as results at the Ni
metal. In the case of DNA, the slope was estimated tobe -0.5 ± 0.2 from the Auger peak shift shown in Fig.
1C. It is concluded that the degree of the localizationof excited electrons at DNA bases is similar to that at
the Ni complex in the ionic crystal.
Regarding electron migration mechanisms in DNA
duplexes, several models have been proposed. Porath
et al. carried out the conductivity measurements of asingle GC DNA and described two antitheticalmodels, namely, the charge hopping model between
localized states and the charge transfer model throughdelocalized states [5]. They finally proposed that the
charge transfer model is adequate on the basis of theobserved voltage gap in I-V curves, although direct
evidence could not be obtained. Our results, incontrast, clearly show the feature of the localized
unoccupied orbitals of the bases in DNA. We hence
conclude that the hopping model for electric
conduction is pertinent when the electrons passthrough the unoccupied states of bases.
Finally, we collate our results with recent

biochemical research on charge migration in DNA
duplexes. In relation to the biochemical aspects of
DNA damage and repair, the charge migration
mechanisms in DNA duplexes have been extensively
discussed. In these arguments, the carrier is regarded
as a hole formed by oxidation and migrates throughthe bases in DNA duplexes. In spite of the detailed
analysis of the LUMO structure described above, the
HOMO structure cannot be directly revealed by
RPES. However, it is generally expected that theenergetically deeper orbitals are more compact than
the shallow ones. Hence, the observation of thelocalized LUMO suggests the localized HOMO in
DNA, which is consistent with recent findings; forthe long-range charge migration, the hole hopping
model between the localized DNA-base orbitals withshort tunneling has been inferred.
In summary, we characterized the electronic
structure near Fermi level of DNA duplexes using
RPES, in order to specify the charge migration
mechanism. On RPES, we observed the kinetic
energy shift of N-KLL resonant Auger electrons andthe intensity enhancement of valence electrons forboth GC and AT DNAs. These directly indicate thelocalized unoccupied orbitals of the bases. Hence, we
conclude that the charge hopping model is suitablefor electric conduction in DNA duplexes rather thanthe charge transfer model via delocalized states, whenelectrons pass through the S* states of DNA bases.

Fig. 2 Off- and on-RPE spectra of GC DNA. The
inset shows an N K-edge X-ray absorption spectrum.
[1] H. S. Kato, M. Furukawa, M. Kawai, M.
Taniguchi, T. Kawai, T. Hatsui, and N. Kosugi, Phys.
Rev. Lett. 93 (2004) 086403.
[2] M. Furukawa et al., (to be published).
[3] Y. Takata, T. Hatsui, and N. Kosugi, J. Electron
Spectrosc. Relat. Phenom. 101-103 (1999) 443.
[4] K. Ueda et al., Phys. Rev. A 54 (1996) 490.
[5] D. Porath, A. Bezryadin, S. de Vries, and C.
Dekker, Nature 403 (2000) 635.

91

BL1A

Mo LIII-Edge XANES Study of MoO3/H-MFI for GTL Catalysts

H. Aritani1, S. Koyama1, K. Otsuki1, M. Fukushi1, Y. Hoshino1, S. Shinohara1, A. Nakahira2
1
Department of Applied Chemistry, Saitama Institute of Technology, Okabe 369-0293, Japan
2
Faculty of Engineering & Design, Kyoto Institute of Technology, Kyoto 606-8585, JapanMo sites partly. These results exhibit the highly
reduction proceeds on H-MFI in Si/Al2= 90. Thesefeatures can also be seen after ethene
dehydroaromatization at 973 K. In fact, maximum
benzene yield was obtained for MoO3/H-MFI in Si/Al2
= 90. It is concluded that formation of well-dispersed
carbide species relates to the catalytic activity for
GTL.

MoO3-modified H-MFI zeolite (MoO3/H-MFI) is atypical catalyst for so-called GTL (Gas-To-Liquid)
one, which process needs to produce aromatics fromnatural gas. Because methane is a dominantcompound in natural gas, direct conversion frommethane to benzene is a catalytically desired process.
For MoO3/H-MFI catalyst system, Mo species are
reduced during the reaction at high temperature (ataround 973 K), and Mo-carbide species are formed
mainly as an active species for methane activation.
Then dehydrogenated methane is formed ascarbene-like species on reduced Mo species, andfollowed by production of benzene onto H-MFI. For
the catalytic process described above, redox behaviorof Mo ions is an important role for catalytic activity
for dehydroaromatization of methane. In particular,
formed Mo species after the reaction needs to analyze
for evaluation of catalytically active sites. Thus wecharacterized the active Mo spices on H-MFI supports
with various SiO2/Al2O3 ratios by means of Mo
LIII-edge XANES. In this report, local structure of
supported Mo ions and their redox changes after
dehydroaromatization of methane at 973 K for 3 h.
All the catalyst samples were prepared byimpregnation of each silica-alumina support with
AHM ((NH4)6Mo7O24•4H2O) solution, and followedby drying and calcination at 773 K for 3 h. Amount of
MoO3-loading is 7.5wt% in all the samples. H-MFI
supports were obtained by hydrothermal synthesis (at343 K) from sodium silicate and aluminum chloride
with TPABr template, and followed by filtration,
H+-ion exchanging with NH4OH solution, andcalcination at 773 K. Mo LIII-edge XANES spectra
were collected in BL1A beamline of UVSOR-IMS in
total-electron yield (TEY) mode. XANES spectra ofreference Mo compounds were shown in the previous
report.
Fig. 1 shows XANES spectra of MoO3/H-MFI withratiosbefore/after
methanevarious
Si/Al2dehydroaromatization. Before reaction, Mo species on
H-MFI are due to Mo6+ in all the ratios. It is likely thatcomponents of Mo6+O6 octahedra is larger than that of
Mo6+O4 tetrahedra in low Si/Al2 ratio. After thereaction of methane dehydroaromatization, edgeenergy of XANES spectra in all samples becomes low,indicating reduction of Mo ions. In case of H-MFI
with Si/Al2= 90, the spectrum is almost as same asthat of Mo2C, while Mo2C can not be detected by XRD.
It possesses the formation of well-dispersed
Mo-carbide species on H-MFI as highly reduced ones.
On the other hand, the spectrum in Si/Al2= 40 shows
Mo2C and another components. The spectrum in
Si/Al2= 1880 suggests formation of slightly reduced

Fig. 1 Mo LIII-edge XANES spectra of MoO3/H-MFI
with various Si/Al2 ratios before/after methane
dehydroaromatization at 973 K.

92

BL1A

1

X-Ray Absorption Near-Edge Fine Structure Study of
AlInN Semiconductors

Q. X. Guo1, J. Ding2, Y. Mitsuishi1, T. Tanaka1, M. Nishio1, H. Ogawa1
Department of Electrical and Electronic Engineering, Saga University, Saga 840-8502, Japan
2
Venture Business Laboratory, Saga University, Saga 840-8502, Japan

With a wide variable bandgap range, AlInN has
great potential for applications in light-emitting
diodes and laser diodes. This is particularly true,
because in their natural crystal structures both AlN
and InN have direct bandgaps. Moreover, Al0.83In0.17N
can be used as a cladding layer with no strain on a
GaN-based laser diode structure, leading to a
reduction of defects because it is lattice-matched to
GaN. In order to fulfill AlInN applications incommercially optical and electronic devices, many
fundamental properties of this material should beclarified. X-ray absorption near-edge fine structure(XANES) refers to the region of the x-ray absorption
spectroscopy spectrum dominated by strong
photoelectron scattering that extends about 40 eV
above an absorption edge, is a powerful tool toanalyze electronic structures of materials, because
spectral fine structure of XANES spectrum is very
sensitive to a change in chemical environment. In thisarticle, we report a characterization of AlInN using
x-ray absorption measurements at the Al- K edges.
The AlInN thin films were prepared on (0001)
sapphire substrates by reactive radio-frequency
magnetron sputtering in an ambient of argon andnitrogen. The sputtering chamber was evacuated to apressure of 10-7 Torr using a turbomolecular pumpbefore introducing the sputtering gas. The sapphire
substrates were chemically cleaned, degreased inorganic solvents, etched in an acid solution, and thenrinsed in deionized water. During the growth, thesubstrate temperature, total gas flow rate, andpressure were maintained at 100°C, 3 sccm, and 10
mTorr, respectively. The indium plate and thealuminum plate were separately mounted onto thetargets and the sputtered area was varied in order toobtain AlInN films with the desired composition.
The XANES experiments were carried out at beamline BL1A of UVSOR facility in the Institute for
Molecular Science, Japan. The XANES spectra werecollected by recording the total yield of secondary
electrons at room temperature. The photon flux was
obtained simultaneously by measuring the current ofan Au mesh located near the exit slit of themonochromator and used for normalization of the
XANES spectra. Figure 1 shows the Al K-edge
XANES spectra of AlxIn1-xN films at various Al
compositions x. As shown in Fig.1, all thecharacteristics of XANES spectra, including theposition and the slope of the absorption edge as wellas the energy positions and the intensities of theresonances, depend strongly on the composition. The
main peak labeled B is clearly observed in all samples

which include Al content. Its intensity increases withincreasing Al content, although no linear relationshipis observed because the intensity depends on both the
Al content and the sample thickness and size.
Therefore, we believe that the XANES spectrum canbe a fingerprint of the composition of the nitride
semiconductors since it is affected both by thecentral-absorbing atom and its neighboring atoms.
Here, we note that the peak positions (A, B, and C) in
Fig. 1 shift to lower energy with decreasing Al
content.
Next, the XANES spectra of Al K-edge in wurzite
AlInN was computed on the basis of theself-consistent-field real-space multiple-scattering(RSMS) theory calculations using the FEFF8 code.
We find that the experimental and theoretical XANES
spectra are in satisfactory agreement. Both theexperimental curve shape and peak positions arereasonably reproduced in the theoretical spectra
although there are some shifts in peak positions aswell as differences in intensity. This discrepancy may
be due to errors in the theory; for example, errors inthe self-energy or the neglect of nonsphericalcorrections to the potential.
In conclusion, we have carried out the XANES
measurements of AlInN at Al K-edge and theself-consistent-field real-space multiple-scattering
theory calculations using FEFF8 code. It wasdemonstrated that the Al K-edge XANES spectra of
AlInN are the fingerprints of their composition. The
theoretical results could give a reasonablereproduction of the experimental spectral structures.
This type of combined use of the experimental
XANES and the RSMS calculations must be a
powerful tool for systematic and qualitative analysisof the structural and electronic structures of nitride
semiconductors.
B
A
Intensity(arb. units)

C

x=1

x=0.4

x=0.25x=0.05
x=0

1560
1580
Energy (eV)1600

Fig. 1 Experimental Al K-edge XANES spectra for
AlxIn1-xN.

93

BL1A&8B1

Study on the Surface Structure of Cathode Electrode for
Li-Ion Battery Cells with High Power-Type

H. Kobayashi1, Y. Arachi2, S. Emura3
Research Institute for Ubiquitous Energy Devices, AIST, Ikeda, Osaka, 563-8577 Japan
2
Unit of Chemistry, Faculty of Engineering, Kansai University, Suita, Osaka, 564-8680 Japan
3
ISIR, Osaka University, Ibaraki, Osaka, 567-0047 Japan1

showed the shifts of LIII and LII peaks to higher energy
above 40qC, indicating the increase in the valence stateof Ni and Co on the surface. Figure 1 shows Ni L-edge
XANES spectra for the SOC100% cathode materials.
In addition, the O K-edges XANES spectra of
SOC100% sample after test at 60ºC showed the
additional peak similar to NiO together with pre-edge
peak originated from LiNi0.8Co0.2O2-based phase,indicating the existence of cubic phase on the surface.
These XANES results indicated that the surface
structure became to be different from bulk one after
pulse cycle tests. The TEY method using soft X-ray
gave us useful information to understand the origin ofbattery performance of battery performance.

Lithium ion battery has attracted the interest on theapplication for fuel cell vehicle (FCV) because of thepromising high-power sources. On the other hand, thebattery for FCV requires the long period life over 15
years. Therefore, the development of the estimation
method of the pulse cycle and calendar life has beenstrongly needed and several mechanisms have been
proposed to explain the deterioration in battery
performance. Although the deterioration in battery
performance has instinct problem on the electrodes,
the mechanism of deterioration on the electrodes isstill unclear. Detailed information on the change in theboth cathode and anode electrodes is very important inorder to determine the origin of battery performance ofelectrochemical performance of battery cell. In thisstudy, the XANES spectra about the cathode electrodeafter pulse cycle tests were collected by the total
electron yield (TEY) method and the relationships
between the changes in the surfaces and theirelectrochemical properties were studied.

Table1 Results of pulse cycle test.
20ºC
40ºC
40ºC
40ºC
60ºC

Experimental
We used the cylindrical battery cells of c.a. 400
mAh for this study. LiNi0.8Co0.2O2-based material andhard carbon were used for positive and negativeelectrode, respectively. Each cell was characterizedusing standard battery test procedure given in thepartnership for a new generation of vehicles (PNGV)
Battery Test Manual. We checked the changes in thecell capacity and DC resistance at every several cycles.
The SOC0% and SOC100% cathode electrodeobtained from the battery after PNGV tests were
washed with DMC and then Ni/Co L-edges and O
K-edge were measured by the TEY method on BL1A
or BL8B1 at UVSOR, respectively.

IPmax

DOD

Cycles

10C
10C
20C
10C
10C

3%
3%
3%
30%
3%

50000
50000
50000
3000
50000

Relative
Capacity
0.960
0.946
0.951
0.932
0.907

Relative DC
resistance
1.08
1.11
1.13
1.25
1.28

Ni L-edge<SOC100%>

LIII
LII

Peak Intensity (Arb.Unit)

NiO
LiNi0.8Co0.2O2
60°C(10C,DOD3%)
40°C(10C,DOD30%)
40°C(20C,DOD3%)
40°C(10C,DOD3%)

Results

20°C(10C,DOD3%)

The results after pulse cycle tests are summarized inTable 1. The decrease in capacity and increase in DC
resistance were observed with increasing temperature.
These results indicated that battery performance
deteriorated when battery cells were used at hightemperature. ICP and XRD results indicated that thevalence state of Ni and Co increased to higher valence
state for SOC0% samples and the valence state of Ni
and Co decreased to lower valence state for SOC100%
samples after the pulse cycle tests in this system, andshowed that no degradation of crystallinity andappearance of impurity phases were observed forcathode material. On the other hand, both Ni and Co
L-edges XANES results of SOC0% and 100% samples

840

850

860

870

880

Energy / eV

Fig. 1 Ni L-edge XANES spectra for the cathodematerials. NiO and LiNi0.8Co0.2O2 are given as
reference.

Acknowledgement
This work was supported by Ministry of Economy,
Trade and Industry (METI) and New Energy andIndustrial Technology Development Organization(NEDO).

94

BL1A&8B1

Crystal and Electronic Structures of the LiNi0.45Mn0.45Al0.10O2

H. Kobayashi1, I. Teshima2
1
Research Institute for Ubiquitous Energy Devices, AIST, Ikeda, Osaka, 563-8577 Japan2
Department of Molecular Science and Technology, Faculty of Engineering, Doshisha
University, Kyotanabe, Kyoto, 610-0321 Japan
L-edge XANES results showed that divalent nickel
metal is oxidized to tetravalent through trivalent after
charging, while the O K-edge showed no change over
the whole composition range. These results clarified
that the Li de-intercalation/ intercalation from
LiNi0.45Mn0.45Al0.10O2 proceeded mainly by thevalence state change of Ni without the contribution ofoxygen over the whole composition range.

LiNi1/2Mn1/2O2-based materials are one of thepromising cathode materials of lithium secondary
battery because of their large capacity and highthermal stability. Especially, LiNi1/3Mn1/3Co1/3O2
displays a reversible capacity of 170 mAh/g in thevoltage range 2.5 to 4.5 V and keep the layered
structure over 280 C° [1]. A lot of papers have reportedonelectrochemical
performanceoftheLi1-yNi1/2Mn1/2O2-based materials until now. We havestudied these materials from the perspective ofstructure and found the characteristic structural change
during Li de-intercalation for LiNi1/2Mn1/2O2 [2]. On
the other hand, the relationship between the crystal andelectronic structures are still ambiguous in thesesystems. Detailed information on the electronic
structures is very important in order to improve theelectrochemical properties of these materials and,
therefore, the crystal and electronic structures of
LiNi0.45Mn0.45Al0.10O2 were investigated in this study.

(a)Li1-yNi0.5Mn0.4Al0.1O2

LIII

Intensity (Arb. Unit)

LII

NiO
cycle
y=0.6
y=0.4
y=0.2

Experimental

y=0

LiNi0.45Mn0.45Al0.10O2 was synthesized in air at
1273 K for 24 h using appropriate molar ratios ofMn(CH3COO)2·6H2O,
LiOH·H2O,
Ni(CH3COO)2·6H2O, and AlNO3. The de-lithiatedsamples were prepared electrochemically usingincoin-type
cells
with
Li/1M
LiPF6
EC:DEC(1:1)/samples. Crystal and electronic
structures were investigated by synchrotron XRD(BL02B2 at SPring-8), XAFS (BL7C at PF), and thetotal electron yield (BL1A/BL8B1 at UVSOR)
measurements. The crystal structure was determinedusing the computer program RIETAN2000.

840

850

860

870

Energy / eV

Intensity (Arb.Unit)(b)

Results
LiNi0.45Mn0.45Al0.10O2 was single-phase andadopted the D-NaFeO2 structure. The Ni and Co
K-edge
XANES
spectrashowedthat
LiNi0.45Mn0.45Al0.10O2 can be represented as
Li(Ni2+0.45Mn4+0.45Al3+0.10)O2. Structural analysis usingsynchrotron XRD data demonstrated that the lattice
parameters of LiNi0.45Mn0.45Al0.10O2 are a = 2.881 Åand c = 14.31 Å and that the chemical composition canbe expressed referring to the Wyckoff positions 3a and3b with the space group R3m as [Li0.92Ni0.08]3a[Li0.08Mn0.45Ni0.37Al0.10]3bO2. The fraction of Ni on the
3a site is almost equal to be those observed forand
LiNi0.5Mn0.4Ti0.1O2[3].
LiNi0.5Mn0.5O2
correspondedtotheLi1-yNi0.45Mn0.45Al0.10O2
composition for showing a charge capacity of 170
mAh/g. Figure 1 shows the Ni L-edge and O K-edge
XANES spectra in Li1-yNi0.45Mn0.45Al0.10O2. The Ni

Li1-yNi0.5Mn0.4Al0.1O2

NiO
1cycle
y=0.6
y=0.4
y=0.2
O K-edge
530 535 540 545 550 555 560

Energy / eV

Fig. 1 Ni L-edge (a) and O K-edge (b) XANES
spectra in Li1-yNi0.45Mn0.45Al0.10O2.
[1] N. Yabuuchi and T. Ohzuku, J. Power Sources.
119-121 (2003) 171-174.
[2] H. Kobayashi, Y. Arachi, K. Tatsumi, and H.
Kageyama, J. Mater. Chem. 14 (2004) 40-42.
[3] H. Kobayashi, Y. Arachi, H. Kageyama, H.
Sakaebe, K. Tatsumi, D. Mori, R. Kanno, and T.
Kamiyama, Solid State Ionics. 175 (2004) 221-224.

95

BL1A

Investigation of Local Structure for Low Crystalline Calcium Phosphate
Prepared by Anodic Oxidation of Ti Metal

A. Nakahira1, H. Aritani2, K. Konishi1, S. Nishida1, K. Kubo1, S. Takaezoe1, M. Ohta1
1
Faculty of Engineering & Design, Kyoto Institute of Technology, Matsugasaki, Sakyo, Kyoto
606-8585, Japan
2
Faculty of Engineering, Saitama Institute of Technology, Okabe, Saitama 369-0293, Japan
Introduction

Results and Discussion

In biomaterials, hydroxyapatite and calcium
phosphates are expected to be used as an implantmaterial. Since especially, calcium phosphate andhydroxyapatite with low crystallinity, not highcrystallinity, are active for bone formation, thedevelopments of low crystalline calcium phosphateand hydroxyapatite are desired. On the other hand, Ti
metal is also one of the useful implant materials.
However, Ti metal has no bioactivity for boneformation in body. Therefore, the calcium phosphatecoating on Ti metal is important process for theachievement of the high bioactivity for Ti implants. In
general, coatings of calcium phosphate are carried out
by sol-gel coating and arc plasma methods. Recently,
many studies on anodic oxidation of Ti metal aretitanium oxide films prepared by are reported for novel
developments of titanium oxides and other oxides
coating on Ti metal. In addition, this anodic oxidation
method is considered to be useful to prepare thecalcium phosphate materials on Ti. In special, doping
some anions into oxide is easy to perform by anodic
oxidation methods.
In this study, the low crystalline calcium phosphatesamples were synthesized by an anodic oxidation of Ti
metal using the mixture of calcium salts and H3PO4
solution at room temperature. Because in medical
application, this low crystalline calcium phosphates
are more effective for the osteoconduction, comparedto high crystalline calcium phosphate, the informationof low crystalline calcium phosphates are considered
to be useful fordeveloping the high performance
implantmaterials.The purpose is to clarify the local
structure of P ion in low crystalline calcium phosphate.
The investigation of local structure for this low
crystalline calcium phosphate prepared by the anodic
oxidation method was carried out at BL1A in UVSOR.

The samples obtained by the anodic oxidationinthis experiment were identified to be a calcium
phosphate with low crystallinity by the results ofpowder X-ray diffraction analysis. P-K local structure
for this low crystalline calcium phosphate prepared by
the anodic oxidation method was examined at BL1A in
UVSOR. The XANES spectra of low crystalline
calcium phosphates obtained by anodic oxidation insolution mixed with GP and H2O are shown in Figure 1
(shown by GP-Anodic Oxidation in figure). All
spectra of low crystalline calcium phosphates
synthesized by anodic oxidation were similar,
although the low crystalline calcium phosphates
obtained by anodic oxidation at higher voltage of 50Vand 350V possess P5+. From these results of XANES
spectra at P-K edge, P local structures for low
crystalline calcium phosphates synthesized by anodic
oxidation method of Ti was similar to those of
Ca2P2O7., not hydroxyapatite (HAP).These results
will lead to thedevelopment of the high performance
implantmaterials.

CaHPO3(P3+)
Normalized intensity
2135

HAp(P5+)

Ca2P2O7(P5+)
Ti-GPCa
GP-anodic㓁ᭂ㉄ൻ

Oxidation

2140

2145
2150
Energy/eV

2155

2160

Fig. 1 XANES of P-K edge of low crystalline
calcium phosphates. GP-ampdic oxidation was the
sample synthesized by an anodic oxidation processing.
HAP shows hydroxyapatite. CaHPO3 and Ca2P2O7 arereference materials.

Experiment
Ti metal (10mm×10mm×0.4mm) was used as
an anode and carbon black (ĳ5mm×10mm, Toyocarbon) was used as a cathode. The distance between
electrodes was about 3cm. Ti substrate was polishedusing abrasive paper. Finally it was washed withdionized water and dried in atmosphere before it wasused as an electrode. After polishing, the Ti substrate
was soaked in solution mixed with glycerophosphoricacid calcium salt (GP) and H2O. Anodic oxidation
performed under 50V, 150V, 250V, and 350 V
supplied direct current power.

96

BL1A

Investigation of Local Structure of P-K Edge for Titania Prepared byAnodic Oxidation of Ti Metal

A. Nakahira1, H. Aritani2, K. Konishi1, S. Nishida1, K. Kubo1, S. Takaezoe1, M. Ohta1
1
Faculty of Engineering & Design, Kyoto Institute of Technology, Matsugasaki, Sakyo, Kyoto
606-8585, Japan
2
Faculty of Engineering, Saitama Institute of Technology, Okabe, Saitama 369-0293, Japan
Titaniumu oxide (titania) is one of useful materials
for photocatalyst, although titania is classified into
anatase-type, rutile-type, and brookite-type. Usually,various synthesis methods, such as sol-gel, sputtering,chemical processings, and so on, have been reported
by many researchers for the synthesis of titania.
Although, in general, the coatings of titania on Ti
substrate are carried out by sol-gel coating and arc
plasma methods, these coatings have such problems
that the strength between titania and Tiis weakandsometimes the delamination is generated between
titania and Ti. On the other hand, anodic oxidation
method of Ti metal is a unique method for preparationof strong titania coating on Ti metal. Furthermore, In
addition, this anodic oxidation method is considered tobe significantly useful to prepare the high performancetitania coating with doping some anions. Namely, it isexpected that such doping into titania is easy to
perform by this anodic oxidation methods. So, thisanodic oxidation will be applicable for themodification of titania by successful doping ofvarious ions into titania on titanium metal forphotocatalyst.
In this study,the various synthesis of titania dopedof P ion was attempted byan anodic oxidation of Ti
metal using the mixture of H3PO4 solution at various
temperatures ranging room temperature and 343 K.
The investigation of local structure, in main XANES,
for this P-doped titania prepared by the anodic
oxidation method in this study was carried out at
BL1A in UVSOR.

Results and Discussion
The samples obtained by anodic oxidation
processing at a voltage of 350 V were identified to beanatase with low crystallinity by powder X-ray
diffraction analysis. P-K local structure for these low
crystalline titania samples prepared by the anodic
oxidation method was examined at BL1A in UVSOR.
Figure 1 shows the results of XANES of P-K of sometitania samples prepared by anodic oxidation method
and also some reference materials. The XANES
spectra of titania obtained by anodic oxidation weresimilar to one of Ti3(PO4)4, although the position of its
peak was not agreement with ones of other references.
From these results of XANES spectra at P-K edge, P
local structures of titania with low crystallinity
prepared by onodic oxidation method was almost
similar to one of Ti3(PO4)4.

Normalized Intensity/a.u.

1

0.06M Ca-GP
0.06M Na-GP
0.25M H3PO4
Ti 3(PO4)4
HAP

0.5

0

Experiment2150

Ti metal (10 mm × 10 mm × 0.4 mm, Nilaco. Co.
ltd) was used as an anode and carbon black (ĳ5 mm ×
10 mm, Toyo carbon) was used as a cathode. Ti
substrate was polished using abrasive paper, washedwith deionized water and finally dried in atmosphere
before it was used as an electrode. The distance
between electrodes on anodic oxidation processing
was kept to be approximately 3 cm. Ti substrate wassoaked in solution mixed with glycerophosphoric acidsodium salt (Na-GP)and aqueous H3PO4at room
temperature.Other samples were synthesized in the
mixture of glycerophosphoric acid calcium salt
(Ca-GP) and aqueous H3PO4 solution at room
temperature.For comparison, Ti substrate was soaked
only in aqueous H3PO4 solution. Anodic oxidation
processing in this study was performed under a voltageof 350 V supplied with direct current power(TP0650-01, Takasago Seisakusho, Co. Ltd, Japan).

2160
Photon Energy /eV

Fig. 1 XANES of P-K of some titania samples
prepared by anodic oxidation method.Ca-GPsamples
were synthesized in the mixture of glycerophosphoricacid calcium salt (Ca-GP) and aqueous H3PO4
solutionat room temperature.Na-GPsamples weresynthesized in the mixture of glycerophosphoric acidsodium salt (Na-GP)and aqueous H3PO4 solutionatroom temperature.

97

BL1A

Characterization of Mixed Valence Complexes of Platinum
by an XAFS Method

H. Yamashige1, K. Kuroiwa2, T. Kurisaki1, H. Wakita1,3
Department of Chemistry, Faculty of Science, Fukuoka University, Nanakuma, Jonan-ku,
Fukuoka 814-0180, Japan2
Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu
University, Higashi-ku, Fukuoka 812-8581, Japan
3
Advanced Materials Institute, Fukuoka University, Nanakuma, Jonan-ku, Fukuoka 814-0180,
Japan
1

Normalized Intensity / a.u.

There has recently been much interest in the
one-dimensional(1D)
halogen-bridge
metal
complexes [1], because of their unique physicalproperties in the mixed-valence state or, equivalently,
the commensurate charge density wave (CDW) state.
In this work, we applied X-ray absorption finestructure (XAFS) spectroscopy to structure analysis ofthe1D
chloro-bridged
Pt
complexes:[PtII(en)2][PtIV(en)2Cl2]X4 (X= ClO4, Glu, Asp). The
X-ray absorption spectra were measured at BL1A of
the UVSOR in the Institute of Molecular Science,
Okazaki [2]. The energy of the UVSOR storage ringwas 750MeV and the stored current was 110-230 mA.
Cl K-edge absorption spectra were recorded in theregion of 2533-3733 eV by use of two Ge(111)crystals. The absorption was monitored by the total
electron yield using a photomultiplier. The Cl K
XANES spectrafor three Pt complexes are shown in
Fig. 1. A pre-edge peak and a main peak are observedin these spectra.

Normalized Intensity / a.u.

2790

a

b
c

2800

2810

d

e

2820

Photon energy / eV
Fig. 2 Observed and calculated Cl K-edge XANES
spectra of [PtII(en)2][PtIV(en)2Cl2](Glu)4.
Observed and calculated Cl K XANES spectra forthe [PtII(en)2][PtIV(en)2Cl2](Glu)4 complex are shownin Fig. 2.The two peaks are estimated to the electrontransition (pre-edge peak: Cl 1s to Pt 5d, main peak: Cl
1s to mixed orbital). As a result of many othercalculated data, the energy gap of two peaks is related
to the distance between Pt and Cl atoms.

ClO4
Glu
Asp
2800

2810 2820
Energy / eV

[1] P. Day, in H. J. Keller (eds.), Low Dimensional
Cooperative Phenomena (Plenum, New York, 1974)
191.
[2] S. Murata, T. Matsukawa, S. Naoè, T. Horigome, O.
Matsuodo, and M. Watatabe, Rev. Sci. Instrum. 63(1992)1309.

2830

Fig. 1 Observed Cl K-edge XANES spectra of[PtII(en)2][PtIV(en)2Cl2]X4,(X= ClO4, Glu, Asp).

98

BL5U

Three-Dimensional Band Dispersion of CeTe2

T. Ito1,2, H. J. Im2, S. Kimura1,2, Y. S. Kwon3
1
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
2
School of Physical Science, The Graduate University for Advanced Studies, Okazaki 444-8585,
Japan3
BK21 Physics Research Division and Institute of Basic Science, Sungkyunkwan University,
Suwon 440-746, Korea
Low-dimensional compounds have attracted muchattention
becauseof
theiranomalouselectronic/magnetic properties, especially thecoexistence of the charge density wave (CDW)
formation and the antiferro-magnetism. Since theiranomalous properties have been attributed to the low
dimensionality, in turn, the three–dimensionality at theelectronic structure is important to understand theessential nature of the anomalous properties.
Angle-resolved
photoemission
spectroscopy(ARPES) is one of powerful methods to directly
determine the electronic band structure as well as the
Fermi surface topology. However, there are few
examples of the ARPES determination of thethree-dimensional electronic structure by controllingthe excitation energy and the detecting angle. To
elucidate the three dimensionality at the electronic
structure of low-dimensional compounds, we have
performed the photon-energy dependent ARPES on
the quasi-two dimensional CeTe2, which crystallizes in
the layered structure formed by the planar Te(1) sheet
sandwiched by the corrugated CeTe(2) double layers[1].
Figure 1 shows the photon-energy dependence of
the ARPES spectra of CeTe2 at normal emission (k// =0 Å-1), obtained at UVSOR-II BL5U with usingsynchrotron radiation source. Since the control of thephoton-energy at k// = 0 Å -1 directly corresponds tothe trace of the electronic structure along *Z axis, wehave mapped out the dispersive feature of the ARPES
peaks as a function of photon energy and binding
energy. Here, we use the dispersion relation

highly-dispersive feature may suggest the possible
three-dimensionality on the electronic structure ofquasi-two dimensional CeTe2.

Fig. 1 Photon-energy dependence of ARPES spectraof CeTe2. Note that the spectrum with hQ = 21.2 eV isobtained by using the He ID resonance line.

,
where V is inner potential, EK is kinetic energy at EF
and T = 0°. At the left panel in Fig. 2, we show theexperimental band structure along *Z line where V a
15 eV is expected from the symmetry of thedispersive features. In Figs. 1 and 2, we clearly findthe two types of bands; one is almost non-dispersive
bands at 0.5 and 1.0 eV binding energies, and theother is the bands with a large dispersion from 1.0 eV(1.8 eV) to 1.5 eV (< 1.7 eV) along *Z line. From thecomparison with the band calculation of the referencecompound LaTe2 (right panel in Fig. 2), the former
has been attributed to the Te 5p orbital at the Te(1)plane (green lines), while the latter to one at the
CeTe(2) plane (blue lines). The observed

Fig. 2 (Left panel) Experimental band structure
along *Z high-symmetry line of CeTe2. Symbols anddashed lines are the ARPES peak positions and guidefor eyes, respectively. (Right panel) LDA bandcalculation along *Z high-symmetry line of LaTe2.
[1] M.H. Jung et al., Phys. Rev. B 62 (2000) 11609.

99

BL5U

Ce 4d - 4f Resonant Photoemission Spectroscopy on CeNi1-xCoxGe2

H. J. Im1, T. Ito1,2, B. K. Lee3, S. Kimura1,2, Y. S. Kwon3
1
School of Physical Science, The Graduate University for Advanced Studies, Okazaki 444-8585,
Japan
2
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
3
BK21 Physics Research Division and Institute of Basic Science, Sungkyunkwan University,
Suwon 440-746, Korea
the electronic structure around QCP. It has been
expected by the thermodynamic experiments that theCe 4f electronic structures show anomaly at QCP [1].
On the other hand, the Ce 4f electronic structures
around 2.2 and 0.3 eV in Fig. 1 show no anomalouschange between x = 0.2 and x = 0.4. We can say thatthe observed contradiction strongly suggests thecontinuous change of the Ce 4f electronic structuresfrom localized to itinerant regime, at least, in thevalence band region. To elucidate the relation
between the anomalous properties at QCP and thesystematic change of the Ce 4f electronic structures
through QCP, further studies (detailed analysis basedon SIAM, temperature dependent RPE experiments,etc) are intended.

CeNi1-xCoxGe2 were newly found Ce-based ternary
alloys, where the ground states continuously change
from a local-moment magnetism (x = 0 – 0.2) to anintermediate valence (x = 0.4 – 1.0) regimes through aquantum-critical point (QCP) (x = 0.3) by thehybridization between the Ce 4f and Ni/Co 3d stateswith the similar lattice constants in this series [1]. To
elucidate the systematic change of the electronic(magnetic) structure as a function of the d - fhybridization strength through QCP, we have
performed Ce 4d - 4f resonant photoemission (RPE)
spectroscopy on CeNi1-xCoxGe2 with varying the Co substitution from x = 0 to x = 1.0.
Polycrystalline CeNi1-xCoxGe2 were grown by thearc-melting and annealed at 900°C for 3 weeks in an
evacuated quartz tube. The Ce 4d – 4f RPE
measurements were carried out at UVSOR-II BL5U
with the energy resolution of about 150 meV at hQ=
122 and 115 eV which correspond to Ce 4d – 4f onand off- resonance energies, respectirvely. The cleansurfaces were prepared by fracturing thepolycrystalline samples in situ under vacuum of 2 x
10-8 Pa. The Fermi level of the sample was referred toa gold film evaporated onto the sample substrate.
Figure 1 shows the Co-substitution dependence of
the Ce 4d – 4f on- (upper panel) and off– (lower
panel) RPE spectra measured at T = 5 K. While theoff– RPE spectra are formed by the Ni/Co 3d main
peaks around 1.8/0.6 eV, the on– RPE spectra show
additional structures around 2 and 0.3 eV where thestrong Ce 4f character has been expected by thesingle-impurity Anderson model (SIAM) [2]. With
increasing Co– substitution, d - states shift from 1.8
to 0.6 eV in the off– RPES spectra and the spectral
weight at EF seems to be enhanced in consistent withthe corresponding LDA band calculation. On theother hand, the spectral weight of Ce 4f structurestransfers from 2.2 eV to 0.3 eV. From the comparison
with the SIAM calculation on the various kind of Ce–
based heavy fermion compounds [2], we haveassigned that the former Ce 4f structure comes fromthe Ce 4f0 final states with a localized Ce 4f character,while the latter from the Ce 4f1 final states with aitinerant (or strongly hybridized) Ce 4f electrons.
Thus, the systematic changes of the d – bands and theCe 4f states may be attributed to the increased d– f
hybridization strength from the localized CeNiGe2 tothe itinerant CeCoGe2.
Finally, we can briefly comment on the change of

Fig. 1 Co-substitution dependence of the Ce 4d - 4f
on - (Upper panel) and off – RPE spectra (lower
panel), obtained with using hQ = 122 eV and 115 eV
photons at T = 5 K, respectively.
[1] B. K. Lee et al., Phys. Rev. B (2005) in press.
[2] For example, D. Malterre et al., Adv. Phys. 35(1986) 275.

100

BL5U

Electronic Structure of Zr-TM-Al (TM = Ni, Cu) Bulk Metallic Glasses
K. Soda1, T. Suzuki1, H. Miyazaki1, M. Inukai1, M. Kato1, S. Yagi1, T. Takeuchi2, U. Mizutani1,
T. Taketomi3, M. Hasegawa3, T. Ito4, S. Kimura4
1
Graduate School of Engineering, Nagoya University, Furocho, Chikusa-ku, Nagoya
464-8603, Japan
2
Ecotopia Science Institute, Nagoya University, Furocho, Chikusa-ku, Nagoya 464-8603,
Japan
3
Institute for Materials Research, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577,
Japan
4
UVSOR, Institute for Molecular Science, Myodaijicho, Okazaki 444-8585, Japanintensity is reduced in comparison with Au below thebinding energy indicated by arrows, which suggeststhat a pseudo-gap in the sp bands of these glasses
may increase with the phase stability [1].
The present results show how the electronic statesof the metallic glasses contribute to their large glass
formation ability. Further systematic study is intended
for Zr-Ni-Al and Zr-Cu-Al metallic glasses withdifferent compositions.

Introduction
Bulk metallic glasses are new materials having
useful engineering properties such as high mechanicalstrength, good ductility, and high corrosion resistance.
In order to understand the origins of their large glass
formation ability and unique properties from themicroscopic point of view, we have studied theelectronic structure of bulk metallic glasses Zr-TM-Al(TM = Ni, Cu) by use of photoelectron spectroscopy.

Experimental
Photoelectron spectra were recorded under anultrahigh vacuum of 2 x10-8 Pa at low temperatureswith a high-resolution energy analyzer at BL5U. Totalenergy resolution and the origin of the binding energy
EB, i.e. the Fermi level EF, were determined by the
Fermi edge of an evaporated Au film.
Specimens were bulk metallic glasses Zr65Ni25Al10,Zr50Cu35Al15, Zr66.7Cu25.8Al7.5, and Zr55Al10Cu30Ni5 ina size of I mm x 3 mm and attached on a cupper
plate by conductive glue. Their supercooled liquid
regions 'Tx = Tx – Tg (Tx: crystallization temperature,
Tg: glass transition temperature), one of the parameters
representing the stability of these metallic glasses, are52.0 K, 61.8 K, 99.8 K and 87.9 K, respectively. Clean
surfaces for the measurement were prepared by in situ
scraping the specimen with a diamond file.

Fig.1 Valence-band spectra of Zr-TM-Al (TM = Ni,Cu) recorded with hQ = 40 eV.

Results and Discussions
Figure 1 shows typical valence-band photoelectron
spectra of the metallic glasses recorded at 30 K withthe excitation photon energy hQof 40 eV. They arenormalized by the intensity integrated up to thebinding energy EB of 10 eV. Three features around EB= 0.6 eV, 2.0 eV and 3.7 eV are ascribed to the Zr 4d,
Ni 3d and Cu 3d states, respectively. It seems that thepeak positions of the Zr 4d-derived bands, indicated byarrows in the figure, are located at the higher binding
energy as the metallic glass is more stable. This may
imply that the hybridization of Zr 4d states with thestates of its neighboring atoms, or the chemicalbonding around Zr, becomes strong with the stability.
Valence-band spectra near EF recorded with hQ = 18
eV are shown in Fig. 2 for the metallic glasses and areference Au. The detailed analysis shows that theFig.2 Valence-band spectra near the Fermi level of
Zr-TM-Al (TM = Ni, Cu) and Au recorded with hQ =18 eV.
[1] K. Soda et al., J. Electron Spectrosc. & Relat.
Phenom., in press.

101

BL5U

Surfaced Photo-Voltage Effect on Cr/GaAs(100) Surface
Studied by Combination of SR and Laser
K. Takahashi, Y. Nagata, S. Tokudomi, J. Azuma, M. Kamada
Synchrotron Light Application Center, Saga University, Saga 840-8502 Japan

Electronic non-equilibrium in the surface layer ofphoto-excited metal/semiconductor interfaces has
been attracting much interest from the basic scientificpoint of view and also from the practical applications
for photo-electronic or spin-electronic devices. In
order to elucidate the electronic non-equilibrium inthe surface layer of metal/semiconductor interfaces, it
is indispensable to understand the transient state ofphoto-excited semiconductor surface. In this work,
we have performed photoemission spectroscopy for
Cr/GaAs(100) surface with the combinational use ofsynchrotron radiation and laser.

components at lower binding energy. At the Cr
deposition of 0.5 nm, two reacted components areclearly observed at 0.76 and 1.02 eV lower binding
energies than the bulk component. The spectral
intensity of bulk component decrease with the Cr
deposition and two surface components disappear at
the Cr deposition of 0.2 nm.
As shown in Fig. 1, it is clearly seen that the peak
position of the Ga 3d spectrum is shifted to lower
binding energy under the laser excitation. From theconjunction with our previous studies for GaAs(100)clean surface, we have concluded that the present
core-level shift is originated from the surface
photo-voltage (SPV) effect. It is found that the Ga 3d
peak shows larger SPV shift than that for cleansurface at the Cr deposition of 0.05 and 0.10 nm. A
simple SPV formula derived from the depletion
approximation scheme with excess photo-carriers
suggests that the surface with larger band-bendingshows larger SPV value. The Cr deposition, as
mentioned above, leads the increase of the
band-bending. Thus, the small amount of Cr
deposition leads the increase of the SPV shift. On theother hand, the further depositions of Cr decrease the
SPV shift, while the band-bending value is larger thanthat of clean surface. The SPV value also depends onamount of the photo-excited carriers. It is consideredthat the small SPV values at large Cr coverage is dueto the lifetime of photo-excited carriers shorter thanthe pulse width of the probe light.

Experimental
Experiments were performed at BL5U. N-type(Si-doped, 3.0x1016 cm-3) and p-type (Zn-doped,
3.0x1018 cm-3) GaAs(100) wafers were used as thesubstrate. An As-capped GaAs(100) wafer was used
as n-type substrate. An As capping layer was removed
by heating the sample in the ultra-high vacuum. The
clean surface of p-type substrate was obtained by the
Ne+-ion sputtering and annealing cycles. We used themode-locked Ti:Sapphire laser (COHERENT Mira
900-F) which is synchronized with the synchrotron
radiation in the multi-bunch operation. The
time-resolved photoemission measurements in
nano-second region were performed by the so-called
pump-probe technique with the synchrotron radiationand laser. The laser light was transported to theviewport of the main experimental chamber using an
optical fiber. The laser light was then focused onto
the sample surface with a 3 mm radius spot. The
spatial overlap of the laser with the synchrotron
radiation was adjusted by eyes.

Results and Discussions
Figure 1 shows the Ga 3d photoemission spectrawith and without laser illumination measured at 80K.
The delay time between laser and SR is 0 ns. The Cr
coverage is also shown in the figure. These core-level
spectra were deconvolved into bulk, surface andeventually reacted components, using a least-square
curve fitting technique. The curve fitting parameters
for Ga 3d (Lorentzian width, spin-orbit splitting, andbranching ratio) were identical to those reported for
GaAs(100) clean surface [1]. The Ga 3d peak iscomposed of one bulk and two surface components
and reproduced well with same fitting parameters as
those reported in Ref. 1. The bulk and surface
components shift to 0.23 eV higher binding energies
at the Cr deposition of 0.05 nm. This energy shiftcorresponds to the increase of the band-bending. The
further deposition of Cr produces new reacted

Fig. 1 Ga 3d photoemission spectra with andwithout laser illumination.
[1] D. Mao et al., Phys. Rev. B 45 (1992) 1273.

102

BL5U

Photoelectron Spectroscopic Study of Fe Films on NEA Surface

N. Takahashi1, S. Nakanishi2, H. Itoh2, S. Koshiba2, T.-H. Shen3,
T. Zhang4, S. Tanaka5, K. Takahashi6, M. Kamada6
1
Department of Physics, Kagawa University, Takamatsu 760-8522, Japan2
Department of Advanced Materials Science, Kagawa University, Takamatsu 761-0396, Japan
3
Institute for Materials Research, University of Salford, Greater Manchester M5 4WT, UK
4Blackett Lab, Imperial College of Science, Technology and Medicine, London SW7 2BZ, UK
5
Research Center for Materials Science, Nagoya University, Nagoya 464-8602, Japan
6
Synchrotron Light Application Center, Saga University, Saga 840-8502, Japan
component is seen to grow at the lower energy side of
the As 3d peak. The Ga 3d peak appears to obtain ahigher energy side component whilst losing a lower
side one. Moreover, the width of the Cs 4d peak wasfound to decrease.
It was found that the Fe covered surface still has
NEA characteristics which is comparable to thestandard NEA, even in the thicker Fe coverage regionof about 100 Å. Furthermore, the change of NEA
intensity appears to be independent of the change of
the work function. The core level peak results imply
that the overlayer has a complicated structure,dependent on its depth from the top of the layer.

Experiment
All experiments were carried out at RT in UHVchamber with the base pressure of about 3 × 10-8 Pa. A
Zn doped (1 × 1019 atoms/cm3) p-GaAs(100) wafer
with (8×2) surface reconstruction was used as a
substrate. The NEA intensity was measured as theabsolute value of the photocurrent from the biased (-10V) sample while the He-Ne laser was on and off. Fe
was deposited on the NEA surface a total of 5 times,
yielding estimated coverages of 9.7 (after the first Fe
deposition, Fe#1), 29 (Fe#2), 68 (Fe#3), 97 (Fe#4) and115 Å (Fe#5). Photoelectron spectroscopy was carriedby using 100 eV.

100

N E A In te n sity
W o rk F u n c tio n

㪺㫃㪼㪸㫅

80

0

-1
60
40

-2

20

㪸㪽㫋㪼㫉㩷㪥 㪜 㪘 㩷㫋㫉㪼㪸㫋㫄 㪼 㫅㫋

0

0

-3

20

40

60

80

100

120

Work Function Lowering (eV)㩷

Relative NEA Intensity (%)

NEA (negative electron affinity) semiconductors
are used as efficient photocathodes, due to their highdegrees of polarization and efficiency. However, froma fundamental science point of view, the details of
NEA formation are not fully understood [1]. On theother hand, the study of magnetic thin films on
semiconductor substrates has been widely carried out
due to the applicability to magneto-electronics devices,such as the Spin Polarised Field Effect Transistor [2].
As a typical basis for such devices, the Fe/GaAs
system has been extensively studied for decades [3]because of its great promise in the possible use of
hybrid ferromagnetic metal-semiconductor structures
for applications. In this report, we present a study of a
Fe covered NEA.

F e th ickn e ss (Å )Fig. 1 The variation of the relative NEA intensity andthe relative work function lowering of the sample.
㩷

㩷

(a )

㩷

(b )

㩷

(c )

(d )
Fe#2

㩷

Fe#1

㩷

㩷

㩷

㩷

㩷

The relative NEA intensity is shown in Figure 1 as afunction of Fe coverage and is compared with thelowering of the work function. The intensity is kept at
50, 20 and 7 % of the maximum intensity obtained
from the pure NEA surface after Fe depositions Fe#1,#2 and #3, respectively. The intensity decreases withincreasing coverage, although the work function isalmost constant even at thicker coverages. This is ingood agreement with the literature [1] which suggeststhat the band bending is not a sufficient condition for
the amplitude of the NEA effect.
Figure 2 shows normalized core peaks from (a) Cs
4d, (b) As 3d and (c) Ga 3d levels. Spectra from thebottom to the top of each panel indicate different
stages of Fe growth (layers Fe#1 and Fe#2,
respectively) after NEA treatment. The Cs 4d and Ga
3d peaks shift to higher kinetic energies, and a new㩷Results and Discussion

NEA

16

18

20

22 54

56

76

78

90

92

94

96

K in e t ic E n e r g y ( e V )Fig. 2 Panel (a), (b) and (c) show core peaks from Cs
4d, As 3d and Ga 3d levels, respectively. Panel (d) is
the VB.
[1] ex, S. Moré et al., Surface Science 527 (2002) 41.
[2] S. Datta and B. Das, Appl. Phys. Lett. 56 (1990)
665.
[3] J. Shen et al., Surface Science 500 (2002) 300.

103

BL5U

Electronic Structure of Relevant Crystals of Bulk Metallic Glasses

T. Takeuchi1, S. Nakano2, T. Kondo2, T. Kitao2, T. Ito3, S. Kimura3
1
EcoTopia Science Institute, Nagoya University, Nagoya 464-8603 Japan2
Department of Crystalline Materials Science, Nagoya University, Nagoya 464-8603 Japan
3
Institute for Molecular Science, Okazaki 444-8585 Japan
Amorphous metals are generally produced by
rapidly solidification techniques, such as liquid
quenching and vapor deposition methods. These
techniques restrict the sample shape to ribbons or thinfilms. Recently, however, formation of amorphous
metals without rapidly quenching was reported for
Zr-based, Fe-based, and Pd-based alloy systems, andamorphous metals with bulk shape of nearly ten
centimeter in dimension had been produced. Since
amorphous phase are characterized by highmechanical strength and extremely soft magnetic
properties, amorphous phase with bulk shapeencourages us to utilize it in a large number ofapplications. Unfortunately, however, guiding
principles to produce “stable” amorphous phases andto control their physical properties have not been wellunderstood yet. In order to utilize them in many
applications, it is highly requited to investigate their“stabilization” mechanism.
To gain deep insight into the origin of theirstabilization mechanism, we have to evaluate the freeenergy of the bulk amorphous phases. Internalenergy and entropy should be equally taken into
account to estimate the free energy of the amorphous,
whereas the crystalline phases are stabilized
dominantly by the contribution of the internal energy.
If the covalent bonds associated with d-orbital of theconstituent transition-metal elements reduce theinternal energy of the relevant crystals, local atomic
arrangements (clusters) in the crystals especiallyaround the transition metal elements should be
regarded as the most important factor for the phasestabilization. This consideration lets us strongly
believe that the local atomic clusters in the relevant
crystals exist also in the corresponding amorphous
phase, and their random arrangements leads tosufficient reduction in the free energy both by the lowinternal energy and the large entropy.
In order to confirm validity of this idea, weanalyzed the local atomic clusters in the relevant
crystals of the Zr-Ni-Al amorphous phase. As thesimplest approximation, all coordination polyhedra
centered at a Zr atom in the crystalline phases are
picked up. Their compositions are calculated byassuming that the surrounding atoms supply 1/Z ofsingle element, where Z is the coordination number ofthe surrounding atom. We found as a result of thisanalysis that the composition of the most “stable”
amorphous phase is surrounded by compositions of
the local atomic clusters of the relevant crystals. The
entropy associated with the random arrangement of
the clusters was calculated on the basis of thewell-known Bragg-Williams approximation. The
resulting entropy possess its maximum value in thevicinity of the composition for the largest 'Tx = Tx Tg, where Tx and Tx represent crystallization
temperature and glass-transform temperature of theamorphous phase, respectively. This result strongly
suggests the crucial role of the entropy in reducing
free-energy of the bulk amorphous phases.
The internal energy associated with covalent
orbital was investigated using the DXVD cluster
calculation. The validity of the resulting energy levels
was confirmed by the high high-resolution
photoemission spectroscopy, HRPES. HRPES
measurements were carried out in the BL5U of the
UVSOR, Okazaki. The incident photon energy was
selected to be 20 a 40 eV, with which high-flux andhigh-energy resolution of 'E a 20 meV are
simultaneously obtained.
We confirmed that the calculated cluster levels
associated with d-orbital of the Zr atoms reproduce
well the energy levels of the d-orbital measured by
the HRPES. From the calculated cluster levels, totalenergy of the clusters was quantitatively evaluated.
We confirmed that the difference of the internalenergy among the all clusters stays within the energy
scale of ST at Tx a 700 K.

Intensity (arb. units)

Zr2NiAl3

5.0

4.0

3.0

2.0

1.0

0.0

Kinetic Energy (eV)Fig. 1 HRPES spectrum of the Zr2NiAl3 with hQ =20 eV at 20 K. Two peaks centered at 1.8 eV and 0.3
eV correspond to the Ni 3d and Zr 4d orbitals,
respectively. Widely extending d-orbitals are brought
about by the hybridization of d-orbitals withs,p-orbitals of the surrounding elements.

104

BL5U

Surface-Passivant Dependence of Photoemission Spectra of
Alkanethiolate-Passivated Au Nanoparticles on the HOPG Substrates
A. Tanaka1, M. Imamura1,2, R. Saito1,2
1
Department of Mechanical Engineering, Kobe University, Kobe 657-8501, Japan2
Department of Physics, Tohoku University, Sendai 980-8578, JapanThe chemically synthesized metallic nanoparticles
surface-passivated by various organic molecules are
attracting much interest from the viewpoints of both
fundamental and device physics, since they show thedistinctive physical and chemical properties found inneither bulk nor molecular/atomic systems. In order todevelop the future nanostructured devices using theseorganic-inorganic hybrid nanoparticles, it is especiallyindispensable to understand the interface features aswell as their electronic structures. In this work, wehave carried out a systematic photoemission study ofalkanethiolate- (AT-) passivated Au nanoparticles on
the HOPG substrates in order to characterize theirinterface features.
The synthesis procedure of AT-passivated Au
nanoparticles is described elsewhere [1]. We have used
the octanethiol (C8H17SH, OT), dodecanethiol(C12H25SH, DT), and hexadecanethiol (C16H33SH,
HDT) as the surface-passivants of AT molecules.
Photoemission measurements were performed at
BL5U of UVSOR Facility. Photoemission
measurements were performed with the incident
photon energy of 190 eV at room temperature. Further
ultraviolet photoemission measurements with the He I
resonance line (hQ = 21.2 eV) as the excitation source
were performed at Kobe University.
From the low-energy cutoff of the ultraviolet
photoemission spectrum due to the vacuum levelmeasured with He I resonance line (not give here), it
is found that the effective work functions of thepresent all AT-passivated Au nanoparticles with mean
diameters of 4 nm are smaller than bulk Au crystallite.
Moreover, these effective work functions are smaller
than the previously reported ones of self-assembled
monolayers of AT molecules on the Au surfaces [2],and exhibit no surface-passivant dependence. Thischange in the surface potential is considered tooriginate from the interface dipoles formation at AT
molecules-Au nanoparticle heterojunction. These
interface dipoles are considered to be composed of the
intrinsic dipoles of AT molecules (dipole moment of
the hydrocarbon tail region) and the dipoles inducedby charge transfer due to the Au-S chemical bonds
formation. In order to characterize the bonding nature
at the interface between AT molecules and Au
nanoparticle surface, we have performed the Au 4f
core-level photoemission measurements as shown in
Fig. 1. As previously reported [2, 3], Au 4f core-level
spectra of AT-passivated Au nanoparticles consist of
two components. The components with lower binding
energy (blue lines in Fig. 1) and higher binding energy(red lines in Fig. 1) originate from the inner Au atomsof Au nanoparticles (bulk component) and the surface
Au atoms of Au nanoparticles bonded tosurface-passivants of AT molecules (surface
component), respectively. As shown in Fig. 1, thechemical shifts of the surface components relative tothe bulk components are almost same among thepresent AT-passivated Au nanoparticles. This indicatesthat the charge transfer between the surface passivantsof AT molecules and Au nanoparticle surfaces and theresultant dipoles are almost same among the present
AT-passivated Au nanoparticles. Therefore, theintrinsic dipoles of AT molecules dominate thedependence of effective work function on thesurface-passivant molecules, and are almost sameamong the present AT-passivated Au nanoparticles.

Fig. 1 Au 4f7/2 core-level photoemission spectra ofvarious AT-passivated Au nanoparticles with mean
diameter of 4 nm on the HOPG substrates bulk Au
polycrystalline film for a comparison.
[1] M. Imamura and A. Tanaka, submitted.
[2] D. M. Alloway, M. Hofmann, D. L. Smith, N. E.
Gruhn, A. L. Graham, R. Colorado, Jr., V. H. Wysocki,
T. R. Lee, P. A. Lee, and N. R. Armstrong, J. Phys.
Chem. B 107 (2003) 11690.
[3] A. Tanaka, Y. Takeda, T. Nagasawa, and K.
Takahashi, Solid State Commun. 126 (2003) 191.
[4] A. Tanaka, Y. Takeda, M. Imamura, and S. Sato,Phys. Rev. B 68 (2003) 195415.

105

BL5B

Desorption of Ionized Clusters from Water Physisorbed on Solid Neon
T. Tachibana1, Y. Yamauchi1, T. Miura1, T. Hirayama2, M. Sakurai3, I. Arakawa1
1
Dept. Phys., Gakushuin Univ., Mejiro, Toshima, Tokyo 171-8588, Japan
2
Dept. Phys., Rikkyo Univ., Nishiikebukuro, Tokyo 171-8501, Japan
3
Dept. Phys., Kobe Univ., Rokkodai, Nada, Kobe 657-8501, Japan

There has been a growing interest in the propertiesof ice surface and ice particle for both fundamental andpractical points of view in the field of surface,environmental and planetary sciences. Understanding
electronic excitations and relaxation processes ofwater molecule is one of the most important subjects inthese fields. A variety of studies have been made onelectronand
photon-stimulated
desorption(ESD/PSD) atice surface [1, 2].
We have investigated the PSD of (H2O)nH+ fromwater physisorbed on solid Ne. From themeasurements of the desorption yield as a function of
the incident photon energy, the desorption of (H2O)nH+
is effectively and indirectly induced by themultiple-excitation and -ionization of rare gas
substrates. The direct excitation of the water molecule
does not induce noticeable desorption of (H2O) nH+.
The PSD-experiments have been carried out in an
ultra high vacuum system at the beam line 5B at
UVSOR in Institute for Molecular Science, Okazaki.
The mass spectrum of PSD ions was measured by atime-of-flight (TOF) technique. The desorption yield
was normalized by the light intensity, which wascontinuously monitored by the photoemission current
from a gold-plated mesh inserted in the beam lines.
The sample film was prepared on a Pt(111) substrate,
which was fixed to a liquid He cryostat and cooled
down to 6 K. The sample was irradiated by the photon
in the energy range between 6 and 1000 eV. The
incident angle of the photon beam was 20 deg from thenormal.
Photodesorption yield of (H2O)nH+ [n=2-5] fromwater adsorbed on Ne substrate in the 38-100 eV
photon energy is shown in Fig. 1. The desorption yield
increases gradually from 60 eV to 90 eV of theexcitation energy. The threshold of ESD (H2O)nH+
from ice surface was reported at 70 eV [1], however
we have not observed the threshold-like increase of theyield near 70 eV excitation energy. The increase of(H2O)nH+ desorption yield above 60 eV is probably
related to direct double photoionization of Ne because
the threshold energy is reported at 62.5 eV in the gas
phase [3]. This result leads us to the conclusion thatthe desorption of (H2O)nH+ is caused by themultiple-hole states of the rare gas substrates.

Fig. 1 (H2O)nH+ desorption yield [n=2-5] as afunction of the incident photon energy from water (0.2
ML) on solid Ne (100 ML) in the 40-90 eV energy
range at 6 K of the sample temperature.

[1] J. Herring, A. Aleksandrov, and T. M. Orlando,
Phys. Rev. Lett. 92 (2004) 187602.
[2] R. Rosenberg, V. Rehn, V. Jones, and A. Green,
Chem. Phys. Lett. 15 (1981) 488[3] R. Bartlett and P. J. Walsh, Phys. Rev. A 46 (1992)
5547.

106

BL8B1

Characterization of Carbon-Based Material Formed by
Focused-Ion-Beam Chemical-Vapor-Deposition

K. Kanda, J. Igaki, Y. Kato, R. Kometani, S. Matsui
University of Hyogo, Laboratory of Advanced Science and Technology for Industry, Kamigori,
Hyogo, 678-1205 Japan107

FIB-CVD DLC

Normalized Absorption (a.u.)

Nano-structure fabrication using focused ion
beam-chemical vapor deposition (FIB-CVD) has beenachieved in view of the production of the numerous
three-dimensional nano-tools [1]. The nano-structural
material formed by FIB-CVD was considered to becomposed of the carbon-based material, however the
structural properties has not been sufficiently
understood. In the present study, we will show that the
combination of Raman spectroscopy, near-edge x-ray
absorption fine structure (NEXAFS) spectroscopy andother analyses can provide useful information on the
structure of carbon-based material formed by
FIB-CVD method.
The NEXAFS measurement was performed at theBL8B1 stage of UVSOR in the Institute for Molecular
Science. The synchrotron radiation provided by the
0.75 GeV electron storage ring was dispersed by aconstant-deviation constant-length spherical grating
monochromator and was perpendicularly irradiated tothe sample film surface. The NEXAFS C K-edge
spectra were measured in the energy range 275-320 eVwith 0.5 eV FWHM resolution. The detection ofelectrons coming from sample was performed in the
total electron yield (TEY) mode. The intensity of theincident photon beams I0 was measured by monitoring
the photocurrent from a gold film. The absorption
signal was given by the ratio between the out-coming
electron intensity from the sample Is and the intensityfrom the gold film, I0.
Figure 1 depicts the NEXAFS carbon K-edge
spectrum of carbon material formed by 30 kV Ga+
FIB-CVD using Phenanthrene as a source gas. For
comparison,thespectraofcommercial
diamond-like-carbon (DLC) produced by ion-plating(IP) method and graphite are also depicted in the figure.
NEXAFS was useable for the characterization of
amorphous carbon materials [2]. Resonance peaks of
291.9 and 292.8 eV, which are characteristic ofgraphite, are not observed in the NEXAFS spectrum of
FIB-CVD DLC. The peaks at 295.1 eV and 297.8 eV
are assignable to resonance peaks to the V* states from1s level of carbon atom neighboring Ga atoms, which
are residue from ion beam. A resonance at about 285.4
eV is due to transitions from C 1s level to unoccupied
S* states of sp2 (C=C) sites. The sp2 content of the
DLC films formed by FIB-CVD method is smaller
than that of the IP DLC film. This result is consistent
with that the hardness measurement of the FIB-CVD
DLC (67 GPa) and IP DLC (26 GPa). As the result,
FIB-CVD method can construct ultra-hard structure,
because the deposited material by this method is DLC
with a high content of sp3 hybridized carbon.

IP DLC

Graphite

280

290
300
310
Photon Energy (eV)320

Fig. 1 NEXAFS spectra in the C K-edge of FIB-FVD
DLC, IP DLC and graphite: The pre-edge resonance at
285.4 eV is due to the C 1s o S* transitions. The
broad band between 290 and 310 eV is the result ofoverlapping C 1s level to V* unoccupied states of sp,
sp2 and sp3 sites. The sharp peak at 295.1 and 297.8 eV
at the spectrum of FIB-CVD DLC are assignable to 1so S* transitions of carbon atom neighboring Ga atom.
[1] R. Kometani et al., Jpn. J. Appl. Phys. 42 (2003)
4107.
[2] K. Kanda et al., Nucl. Inst. Meth. B 206 (2003)
880.

BL8B1N K XAFS Analysis of Some Porphyrin Compounds and Their Complexes

H. Yamashige1, T. Kurisaki1, H. Wakita1,2
1Department of Chemistry, Faculty of Science, Fukuoka University, Nanakuma, Jonan-ku,
Fukuoka 814-0180, Japan
2
Advanced Materials Institute, Fukuoka University, Nanakuma, Jonan-ku, Fukuoka 814-0180,
Japan
Metalloporphyrins, used as biomimetic catalysts,
are important prosthetic groups in enzymes, and offer
thepotentialforsubstrate
oxidation1.
Iron-porphyrins, in particular, have been used as
cytochrome P-450 models for oxidative catalysis
using a large variety of oxygen donors, such as
iodosylbenzene and hydrogen peroxide. The
introduction of electron-withdrawing substitutes at themeso-positions of Fe-porphyrin complexes affects thecatalytic activity of the oxidation reaction for
cytotoxin and pollution hazards. The chemical state of
Fe ions in Fe-porphyrin complexes withmeso-substitutes has been examined using IR, XRD,
NMR, EPR, Mössbauer, electron spectroscopy, MD,
and DFT calculations. Notwithstanding, it remains
unclear how the influence of electron-withdrawal istransmitted to the electron state of the center Fe ion ineach Fe-porphyrin complex. Elucidation of theelectron structure throughout a Fe-porphyrin complex
with meso-substitutes is an important task toward thedevelopment of stable and highly active Fe-porphyrin
complexes as oxidation catalysts.
X-ray absorption spectra of near C and N K
absorption edges were (XAFS) measured at BL8B1 of
the UVSOR in the Institute of Molecular Science,
Okazaki [2]. The energy of the UVSOR storage ringwas 750 MeV and the stored current was 110-230 mA.
The absorption was monitored by the total electron
yield using a photomultiplier. The C and N K XANES
spectra for tetraphenylporphyrin (TPP) are shown in
Fig. 1 and Fig. 2. The peaks which appeared at
approximately 282, 285, 395, 398, 400, and 405 eV in
each experimental spectrum are labeled A, B, C, D, E,
and F in the order of increasing energy. This work is to
examine electron structures of TPP, TCPP, and TSPP
using crosschecks of XANES data for C and N K
absorption edges in combination with DV-XD MO
calculations. These results indicated that ap-electron-withdrawing group on the phenyl group in
porphyrin compounds engenders a unique electronstate because of the electron-withdrawal strength
itself.
Crosschecks of XANES data for multi-element
absorption edges are important not only for porphyrin
compounds and complexes, but also for othernumerous metal complexes, especially those with alayer structure or chain structure, because they areclosely related to intermolecular interaction ofelectrons. This method is applicable to the design anddevelopment of new metal complexes with a usefulfunction by obtaining detailed information about theelectronic structure along with an electron statecalculation method, such as the DV-XD02 method.
An experimental setup of simultaneous measurements
of XANES, which we are currently constructing forthe laboratory users, will facilitate such studies.

B

Intensity / a.u.

A

TPP

Back ground

280

285
290
Energy / eV

295

Fig. 1 C K XANES spectra of TPP.

TPP

Intensity / a.u.

C D E

F

Back ground
noise

390

400
Energy / eV

410

Fig. 2 N K XANES spectra of TPP.
[1] J. H. Chou, H. S. Nalwa, and M. E. Kosal, The
Porphyrin Handbook vol. 7, ed. K. M. Kadish, K. M.
Smith, R. Guilard (Academic Press, San Diego, CA,
2000) 41.
[2] S. Murata, T. Matsukawa, S. Naoè, T. Horigome, O.
Matsuodo, and M. Watanabe, Rev. Sci. Instrum. 63(1992) 1309.

108

BL8B2Ultraviolet Photoelectron Spectra of Three Tm@C82 Isomers

S. Hino1,2, N. Wanita2, K. Iwasaki1, D. Yoshimura3,4, N. Ozawa5,
T. Kodama5, K. Sakaguchi5, H. Nishikawa5, I. Ikemoto5, K. Kikuchi5
1
Faculty of Engineering, Chiba University, Chiba 263-8522, Japan
2
Graduate School of Science & Technology, Chiba University, Chiba 263-8522, Japan
3
UVSOR, Institute for Molecular Science, Okazaki 444-8585, Japan
4
Research Center of Material Science, Nagoya University, Nagoya 464-8602, Japan
5
Department of Chemistry, Tokyo Metropolitan University, Tokyo 192-0397, Japan
exactly to be C2v (No. 9). There are three Cs and C2
cages for IPR satisfying C82 cage. The NMR could
not elucidate the exact cage structure for isomers I
and II. The UPS of three isomers can be well
reproduced by simulated spectra obtained with abinitio calculation assuming Cs (No. 4), C2 (No. 5) andC2v (No. 9) cage structures. Thus, cage structures ofthree isomers can be determined [4].

Abstract
Ultraviolet photoelectron spectra (UPS) of three
Tm@C82 isomers were measured with a synchrotron
radiation light source. The upper valence band spectra(0 – 5 eV) of three isomers are different each otherand they also differ from those of other trivalent
metal atoms encapsulated metallofullerenes such as
La@C82, Sc@C82 and Gd@C82. Resemblance of thespectra of Tm@C82 (II) and Ca@C82 (III) suggests
identical
cage
structures
of
these
two
metallofullerenes. The UPS are well reproduced bysimulated spectra obtained with ab initio calculation,
which indicates that isomers I – III have Cs (No. 4),
C2 (No. 5) and C2v (No. 9) cage structures.

h Q = 40 eVResults and Discussion
The spectral onsets of the UPS of three Tm@C82
isomers (I) – (III) are 0.85, 0.75 and 0.9 eV,
respectively, which is relatively large compared withthose of La@C82 [1] and Gd@C82 [2] but almost thesame as those of Ca@C82 isomers [3]. This finding isclosely related to the amounts of transferred electrons
from encapsulated metal atom to the fullerene cage.
The spectra obtained with 40 eV photon energy
show upper valence band very distinctly. As explicit
difference among the spectra lies mainly in the upper
valence band region (pseudo S-electron region) so that
40 eV UPS of three Tm@C82 isomers are shown in Fig.
1 for comparison. As for the deeper valence band
(mainly due to pseudo V-electrons) region there ishardly any difference among the three Tm@C82
spectra. This implies that electronic structures ofskeletal cage structures of three isomers are not so
different. As for the upper valence band region thesituation is quite different. Although onset positions ofthese spectra do not change so much, the first structureof each spectrum differs so much. Intensity ratio of
second and third structures of these spectra also differs.
The UPS of two Ca@C82 isomers are also shown in
Fig. 1. The UPS of Tm@C82 (II) and Ca@C82 (III) areessentially the same which indicates that these two
metallofullerenes have the same electronic structure
derived from the same cage structure.
The NMR analysis suggests symmetry of three
Tm@C82 isomers are Cs, C2 and C2v, respectively.
There are nine isolated pentagon rule (IPR) satisfying
cages for C82. There is only one C2v cage among themso that cage structure of isomer III can be determined109

photoelectron counts

Ca@C 82(IV)

Ca@C 82(III)

Tm@C 82(III)

Tm@C 82(II)Tm@C 82(I)

14

12

10

8

6

4

2

0 = EF

Binding Energy ( eV )Fig. 1 The UPS of three Tm@C82 isomers and two
Ca@C82 isomers.
[1] S. Hino et al., Phys. Rev. Lett. 71 (1993) 4261.
[2] S. Hino et al., Chem. Phys. Letts. 281 (1997) 115.
[3] S. Hino et al., Chem. Phys. Lett. 337 (2001) 165.
[4] S. Hino et al., Chem. Phys. Lett. 402 (2004) 217.

BL8B2

Epitaxial Growth of Copper Tatrakis(Thiadiazole)PorphyrazineFilm
K. Kanai1, E. Kawabe1, D. Yoshimura2, Y. Suzuki1, M. Fujimori1, H. Yoshikawa1,
K. Awaga1, K. Seki1,2,3
1
Graduate School of Chemistry, Nagoya University, Nagoya, 464-8602 Japan
2
Research Center for Material Science, Nagoya University, Nagoya, 464-8602 Japan
3
Institute for Advanced Research, Nagoya University, Nagoya, 464-8602 Japan
molecules have preferred orientation on the GeS(100)surface. From comparison between the observedTdependence of ARUPS spectra and theoretical
calculationby
independent
atomiccenterapproximation, CuTTDPz molecule is found to bealmost flatly lying. The role of intermolecularinteraction for both molecular arrangement andorientation will be discussed near future.

Introduction
Thin films of organic semiconductors have been
attracting much interest over the past decade for theirpotential technological applications. In organic
devices, such as organic field effect transistor andorganic light emitting diode, charge transport andluminescence properties are strongly affected by the
structural properties of the films. Thus, it is importantto understand the mechanism of molecularaggregation, packing, and orientation to control thestructure of the film for improvement of theproperties of such devices.
In this research, we focus on the epitaxial growthof phthalocyanine-based molecules, copper tGtrakis-(thiadiazole)porphyrazine (CuTTDPz) film on
GeS(100) surface. CuTTDPz is expected to havestronger inter-molecule interaction than that ofphthalocyanine because of the close contact between
the sulfur and nitrogen atoms of the thiadiazolegroup[1]. Comparison between CuTTDPz film and otherphthalocyanine film will provide insight into the roleof inter-molecule interaction on epitaxial growth oforganic thin films.

Fig. 1 LEED pattern of CuTTDPz film deposited on
GeS(001) surface. Primary energy is 40 eV and thethickness of the film is 0.4 nm. The black circles in
the figure represent diffraction spots from GeS(100).

Experimental
Low energy electron diffraction (LEED) was
performed to study the arrangement of CuTTDPz
molecules on GeS(100) surface. Angle-resolved
ultraviolet photoemission spectroscopy (ARUPS) was
performed to determine the molecular orientation of
CuTTDPz molecule on GeS(100) surface. ARUPS
experiment was done in UVSOR-II BL8B2 with
VG-CLAM4 analyzer. Clean GeS(100) surface wasobtained by cleaving the surface of GeS single crystal
under ultrahigh vacuum condition. The film of
CuTTDPz was in situ evaporated onto clean
GeS(100) surface.

Results and Discussion
Clear diffraction spots from CuTTDPz molecules
shown in Fig. 1 indicate epitaxial growth of
CuTTDPz molecules deposited on GeS(001) surface.
From this result, the unit cell of CuTTDPz film on
GeS(100) surface is estimated to be twice as large asthat of ZnPc.[2]Figure 2 shows the take-off angle Tdependence of
ARUPS spectra of CuTTDPz film deposited on
GeS(001) surface. The inset gives the measurement
geometry. ARUPS spectra show strong dependence
on T, especially in HOMOѽindicating that CuTTDPz

Fig. 2 ARUPS spectra of CuTTDPz film depositedon GeS(100) surface. Vertical bar points at the highest
occupied molecular orbital (HOMO) CuTTDPz.

[1] Y. Suzuki, et al, Chem. Eur. J. 10 (2004) 5158.
[2] E. Kawabe, unpublished.

110

BL8B2

Angle-Resolved UV Photoelectron Spectra of OTi-Phthalocyanine
Monolayer on Graphite

S. Kera1,2, H. Yamane1, H. Fukagawa1, T. Hanatani1, M. Ono1,
S. Nagamatsu1, T. Yokoyama1, D. Yoshimura3, K. K. Okudaira1, K. Seki2, N. Ueno1
1
Faculty of Engineering, Chiba University, Chiba 263-8522 Japan
2
Institute for Molecular Science, Okazaki 444-8585 Japan
3
Research Center for Materials Science, Nagoya University, Nagoya 464-8602 Japan
A few years ago, we succeeded to observe a very
sharp HOMO band with clear vibration satellites on awell-ordered Cu-phthalocyanine (Pc) on graphite [1].
After detecting the highly-resolved HOMO band, we
could discuss the complex nature of band width,shape and position in organic solid systems [1-3].
Very recently, we observed peculiar angular
distribution for OTiPc doublelayer/graphite system. It
may be related to a photoelectron scattering process
passing through a different local potential within thefilm. Photoelectron angular distribution involves
information on the initial wavefunction, and thus thequantitative analysis of the angular distribution
provides a detailed origin of the UPS bands, as well
as a geometrical structure of organic thin films [4]. In
this work, we measured take-off angle dependencies
of angle-resolved UPS (ARUPS) for well-defined
OTiPc monolayer precisely.

vacuum as illustrated in Fig. 1(b). Moreover, wefound that effects of a multiple scattering are
negligibly small for organic molecule, since our
SS/MO approximation is applicable well even for the
low-energy photoelectron (a 15 eV).
Now to compare impacts on a different local
potential, further experiments on the photoelectron
angular distribution both for the monolayer and the
doublelayer are in progress with theoretical
calculations.

Intensity (normalized to IR)(a) OTiPc(0.8MLE)/HOPG
o

D=70

hv

T

HOMO

T=0~60oExperiments
2.0

ARUPS spectra were measured at photon incidence
angle D = 70°, hQ = 20 eV, and T = 295 K. T
dependence of ARUPS spectra was analyzed using
the single-scattering approximation combined withmolecular orbital calculation (SS/MO) [4,5]. The
purified OTiPc was carefully evaporated onto the
HOPG. Characterization of the film growth of the
OTiPc/graphite has been carried out [6]. Coverage ofthe film can be estimated from the total shift of thevacuum level as discussed in the previous paper [3].
To obtain the well-ordered monolayer film,
subsequent annealing is performed at 420 K/2 h.

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

Binding Energy /eVș = 0°(b) HOMO-band intensity
30°: Experiments: SS/MO (ȕ=0° )60°hv= 20eV90°

Intensity (normalized)

Fig. 1 (a) Take-off angle (T) dependence of the
ARUPS of the 0.8-MLE-OTiPc on HOPG(0001). The
HOMO distribution of OTiPc is also shown. (b)Comparison between observed and calculated T
dependencies of the HOMO-band intensities with
SS/MO approximation for hQ = 20 eV and T= 0o.

Results and Discussion
Figure 1(a) shows T dependence of ARUPS of
OTiPc monolayer (annealed-0.8-MLE) on HOPG
surface. The intensity is normalized to the incidence
photon flux and the background is subtracted. The
HOMO band is assigned to a single S MO as in otherPcs (inset of Fig. 1) [1-3]. Very sharp asymmetric
HOMO
bands
are
detectedforallphotoelectron-take-off-angles (T= 0 a 60o).
Figure 1(b) shows the comparison between
observed and calculated T dependences of the
HOMO-band
intensities
with
the
SS/MO
(HF/STO-6G) for the molecular tilt angle E= 0o,which gave the best agreement with the observed T
pattern. It indicates that the OTiPc molecules orient
flat to the HOPG surface with O-atom protruding the[1] S. Kera et al., Chem. Phys. Lett. 364 (2002) 93.
[2] H. Yamane et al., J. Electron Spectrosc. Relat.
Phenom. 137-140 (2004) 223.
[3] There are some articles by us in IPAP conference
proceedings, in press.
[4] N. Ueno et al., J. Chem. Phys. 107 (1997) 2079.
[5] K. K. Okudaira et al., J. Appl. Phys. 85 (1999)
6453.
[6] S. Kera et al,: Jpn. J. Appl. Phys. 40 (2001) 783.

111

BL8B2

Electronic Structure of LiNi1-xMxO2 Mixed Oxides (I)T. Miyazaki1, H. Takeno1, D. Yoshimura2, T. Yamaguchi1
1
Department of Applied Chemistry, Faculty of Engneering, Ehime University,
Matsuyama 790-8577 Japan
2
Research Center for Materials Science, Nagoya University, Nagoya 464-8602, Japan112

of LiNi0.9Al0.1O2 was almost equal electronic structure
for LiNiO2, though the features in which all of thespectra were shifting to the high energy side wererecognized. It has been reported that the selectivity for
OCM reaction over LiNi0.9Ti0.1O2 and LiNi0.9Mn0.1O2
improved but LiNi0.9Al0.1O2 was remarkably being
decreased, when it tries to compare the OCM activityof these samples with those of LiNiO2. Comparing theelectronic structures of LiNiO2, LiCoO2 andLiNi1-xMxO2 (M = Ti, Al, Mn), several differenceswere found. These points should be examined in moredetail by the CIS spectra over a wide excitation photon
energy region.

eIntensity

An application of LiNiO2 has been studied as apositive electrode of lithium secondary battery on thebasis of the lamellar structure. And, the structure wasmaintained to over 1073 K under the oxidative
atmosphere. It was reported that the surface latticeoxygen of LiNiO2 had the catalytic property at around1000 K for the oxidative coupling of methane [1].
Ultraviolet photoelectron spectroscopy was applied inorder to discern the correlation of catalytic property
and electronic states near the top of the valence band
region. The valence band usually determines theelectronic properties and the catalytic activities of thematerials, therefore, it should be carefully investigated.
At this approach, ultraviolet photoelectron spectra
were measured as samples of LiNiO2, LiCoO2 andLiNi1-xMxO2 (M = Mn, Ti, Al) were replaced withother metallic element a part of Ni site in LiNiO2.
Then, the electronic structure was examined from theincident photon energy dependence of ultraviolet
photoelectron spectra in order to clarify the origin of
selective catalysis and electronic properties.
LiNiO2, LiCoO2 and LiNi1-xMxO2 (M = Ti, Al, Mn;
x = 0.1) were prepared from LiNO3, Ni(OH)2 andM(NO3)2 by the solid-state reaction. The UPS spectra
were measured using the angle resolved photoelectron
spectroscopy equipment at BL8B2. The UPS spectra
were measured for electrons emitted normal to thesample surface with an incident angle 45° of the lightbeam. The Fermi energy of the UPS system wasdetermined by using the Fermi edge of gold films. A
pure processing by Ar+ sputtering or the heating of
infrared radiation was carried out as a surface
pretreatment of these samples.
Figure 1 shows the UPS spectra of LiNiO2, LiCoO2,
LiNi0.9Mn0.1O2, LiNi0.9Ti0.1O2 and LiNi0.9Al0.1O2 at 60
eV of the incident photon energy. These spectra were
measured with reference to EF as the zero of theenergy scale. Several structures, denoted by thecharacters A䯹E, are observed at Eb = 1.6, 3.0, 4.9, 6.1
and 9.8 eV in the spectrum of LiNiO2. The structure
located at Eb = 3.0 eV of LiNiO2, observed clearly inthis study. In case of LiCoO2, there were four
structures on the top of the valence band. However, theB band was not clearly observed in those of LiCoO2.
Also, each band may be shifting to the high energy
side of 0.5 䱊 1.0 eV. The UPS spectra of
LiNi0.9Mn0.1O2, LiNi0.9Ti0.1O2, and LiNi0.9Al0.1O2, apart of Ni site were replaced with Mn, Ti, and Al, havebeen composed of five bands as well as LiNiO2. In thecase of LiNi0.9Mn0.1O2, it may be difference withelectronic structure of LiNiO2 that the relative
intensity of band B is to be conspicuous. The spectrum

d
c
b

C
E

20

15

10

B A

D

a
5

0

B in d in g E n r g y / e V

Fig. 1 The UPS spectra of a) LiNiO2, b) LiCoO2, c)
LiNi0.9Mn0.1O2, d) LiNi0.9Ti0.1O2, e) LiNi0.9Al0.1O2.
[1] T. Miyazaki et al., Res. Chem. Inter. 28 (2002)
479.
[2] T. Miyazaki et al., UVSOR Activity Report 2002
(2003) 197.

BL8B2

㩷 Photoemission Study of a Cu-Ga-Mg-Sc Icosahedral Phase

M. Mori1, R. Hashimoto1, S. Motomura1, D. Yoshimura2, S. Kashimoto3, T. Ishimasa3
1
Graduate School of Information Science, Nagoya University, Chikusa, Nagoya 464-8601
Japan
2
Research Center for Materials Science, Nagoya University, Chikusa, Nagoya 464-8603 Japan
3
Graduate School of Engineering, Hokkaido University,Sapporo 060-8628 Japan
pseudogap.

Introduction
Since the discovery of an icosahedral phase(i-phase) in Al-Mn alloys by Shechtman et al. [1],there have been reported a large number of studies
about the electronic properties of icosahedral
materials in spite of remaining the arrangement of theatoms in an i-phase unclear. By intuition thepseudogap structure can be interpreted in terms of thenearly-free-electron-like energy gap inferred from thestrong diffraction spots, which may be related to thestability of the i-phase.
A pseudogap-like anomaly in the DOS near EF was
directly confirmed with the photoemission study ofan Al-Cu-Fe i-phase by Mori et al. [2]. The CIS
spectra at the binding energy region between 0-2 eVshow a resonant characteristic near the 3d-electron
excitation of Fe atom in the i-phase.

Experimental and Results
The purpose is to observe the photoemission studyof a new Cu-Ga-Mg-Sc (CGMS) i-phase and the
Cu-Ga-Sc approximant crystal (CGS). The sample, an
Cu-Ga-Mg-Sc i-phase quasicrystal, was an ingot
prepared. It is well known that this is quite highquality of the quasicrystal. It was confirmed that the
specimen used with this study consists of only a new
I-type i-phase but does not contain the other phases.
Photoemission studies were performed with anangle-resolved spectrometer on beam-line BL8B2.
All measurements were carried out at room
temperature. The clean surface of the specimen was
obtained by scraping with a diamond file in a vacuumof 2-10 10-8 Pa. Immediately after this proccess, thesample was transferred to the UPS experimental
chamber and measured in a vacuum of 2-10 10-8 Pa.
The line shape near EF is like a plateau cut off at EF
shown in Fig. 1. We have tried the fitting of thephotoemission curve of the Al-Pd-Mn i-phase, using
the (flat DOS) * (Gauss distribution function typeresolution function. Using the fitting parameters of
the Au spectrum, we could get the solid curves oflower two spectra. The middle one is well fitted with
the CGS approximant crystal data. But the lower is
not fitted with the CGMS quasicrystal data. Thismeans that the CGMS quasicrystal has a pseudogapnear EF, and the CGS approximant crystal has not a
pseudogap. It shows that this experimental result iswell fitted as the quasicrystal has the pseudogap ofwidth 0.4 eV and depth 0.6. This experimental result
is the secondary example that the quasicrystal has theFig. 1 Photoemission spectra near EF measured atroom temperature. Each solid curve shows the fitted
curve of the DOS near EF without pseudogap. The
upper one is the spectrum of Au, and the middle isthat of CGS approxmant crystal and the lower is thatof CGMS i-phase quasicrystal.

[1] D. Shechtman, I. Blech, D. Gratias, J. W. Cahn,
Phys. Rev. Lett. 53 (1984) 1951.
[2] M. Mori, S. Matsuo, T. Ishimasa, T. Matsuura, K.
Kamiya, H. Inokuchi, T. Matsukawa, J. Phys.:
Condens. Matter 3 (1991) 767; ibid. 4 (1992) L157.

113

BL8B2

Possibility of Fermi Level Control Induced by VUV-Induced Doping:
UPS Study of Photodegraded PTFE Film
M. Ono1, H. Yamane1, H. Fukagawa1, S. Kera2, D. Yoshimura3,
E. Morikawa4, K. Seki3, N. Ueno1
1
Graduate School of Science and Technology, Chiba University, Chiba 263-8522, Japan.
2
Institute for Molecular Science, Okazaki 444-8585, Japan.
3
Research Center for Material Science, Nagoya University, Nagoya, 464-8602 JAPAN.
4
CAMD, Louisiana State University, Baton Rouge, LA 70806, U.S.A.

EF

E a kT § N a ·
¸
ln¨

2
2 ¨© n0 ¸¹§ 2Smh kT ·
2¨
¸
2
¹
© h

n0

…. (1),

3/2,
where Na is the concentration of acceptors, Ea is theenergy of acceptor level from top of the valance bandand mh is the effective mass of a hole in the valenceband. It should be noted that the Fermi level position is
proportional to logarithm of the concentration of theacceptor. Therefore it can be considered that the shiftof UPS spectra is caused by Fermi level shift. It is
expected that the radical generated by VUV light has
unoccupied electronic states in the PTFE band gap. In
addition the lifetime of radical is much longer (a1000h) than the measurement time (5 h). Hence it isconsidered that the radical acts as acceptor upon the
degradation of the PTFE film.
(a1,a2 and b) / eV

20

sub

Peak position from EF

36

Peak (c)(F 2s)

Peak (b)V(c-F)

16

14

34

Peak (a2)
F lone pair

32

12

30

Peak (a1)
F lone paor
10

8
14
10

(F 2s) / eV

Irradiation dosePTFE
/ photons (min)F Fpeak(a1, a2)
14C C
7.8 x 10 (0)15nF F
8.3 x 10 (2)16
1.6 x 10 (5)e1675eV 45°
2.7 x 10 (10)16
4.2 x 10 (20)16PTFE(25nm)/Au
6.7 x 10 (35) peak (b)17299K
1.0 x 10 (75)

18

38

sub

peak (c)charge-up effect, because the shift caused bycharge-up moves toward high binding energy side. In
Figure 2 the binding energy positions of the four peaks
are plotted against the irradiation dose. The binding
energy shifts of all peaks are proportional to logarithmof the irradiation dose with identical slope. In the caseof simple model which assumes only one acceptor
level the energy position of the Fermi level, EF, can be
expressed by following formulae under the
low-temperature approximation [2]:Peak position from EF

Intensity / arb. unit

Control of Fermi level is a fundamental andextremely important technique for the development ofsemiconductor devices. Control of the Fermi level inthe organic molecular film has been attempted byembedding metals or organic molecules. However, themethod of Fermi level control is not well established.
One of the most crucial problems is the difficulty to
prepare a homogeneously doped film, particularly inthe case of molecular doping.
The doping induced by high-energy photon
irradiation is an attractive method. If photoproducts
generated in the film can act as dopants, thehomogeneous doping can be achieved. In addition
concentration of dopants can be also controlled by theirradiation dose. As our attempt at the Fermi level
control by “high-energy radiation-induced doping”,
the photodegradation of polytetrafluoroethylene(PTFE, -(CF2-CF2)n-) film was studied [1]. As PTFE
has a wide band gap, energy shift of the Fermi levelcan be easily detected.
PTFE film prepared by vacuum deposition in the
UHV chamber was directly transferred to UPS
measurement chamber under UHV condition. The
75-eV photon beam was utilized for both UPS
measurement and photodegradation of the PTFE film.
The photon dose was estimated by measuring thenumber of electrons emitted from the gold mesh byincidence photon.
Figure 1 shows the photodegradation effect on the
UPS spectra of the PTFE film. During the VUVirradiation the UPS spectra are shifting toward low
binding energy side. This shift is not due to the

28

10

15

10

16

10

17

26

10

18

Irradiation dose / photons

Fig. 2 The binding energy positions of the UPS
peaks plotted against the irradiation dose.
0
40

30

20

10
sub

Binding energy from EF

0[1] M. Ono et al., Submitted to IPAP Conference
Proceedings.
[2] C. Kittel, Introduction to Solid State Physics,2nded. (John Wiley & Sons, New York, 1957).

/ eV

Fig. 1 VUV photodegradation effect on UPS
spectra of the PTFE film.

114