ResearchHigh Magnetic Field X-ray Magnetic Circular Dichroisma New Microscopic Magnetization Probe for Any Magnet
A novel tool to evaluate a site and element selective
magnetic moment has been developed by combining
synchrotron radiation and high magnetic fields. X-ray
magnetic circular dichrosim: XMCD is a key method forspintronics materials, however, had been limited inferromagnets. The present technique breaks this limitation
and realizes the “XMCD for any magnet”.
A synchrotron X-ray is a powerful tool to investigate
materials for the strong intensity and the tunability in X-ray
regime. These features make it possible to perform thevarious types of spectroscopy such as X-ray absorption(XAS) and XMCD. These methods are unique because ofelement and site selective microscopic probing. For example,
XMCD has been established as the microscopic magnetization
probe for magnetic materials. One of the most crucial limits of
XMCD is that the method can be used only for ferromagnets.
To widen the application of XMCD, we have developed ahigh magnetic field XMCD. The idea is very simple and isstraightforward. In a very strong magnetic field, a substantial
magnetic moment is induced in any magnet and thus XMCD
can be measured in most of magnetic materials.
Figure 1 shows the mini magnetic field generator used for
XMCD experiment up to 40 T. Thanks to the extremely small
size, the magnet and the capacitor bank are portable andthus the combination with X-ray spectrometer is easy. In fact,
the capacitor bank is as small as a small refrigerator and thestoring energy is only 10 kJ. Even such small system, a highmagnetic field up to 40 T can be achieved.
The first experiment is made for the EuNi2 (Si0.18Ge0.82) 2,
which shows the magnetic field induced valence statetransition. It is non-magnetic at zero field and the magnetic
interaction is antiferromagnetic. Thus a conventional XMCD
cannot be applied for this material. Because of the verystrong magnetic field of our instrument, the substantial
magnetic moment is induced and the clear MCD signals areobserved. It is the first XMCD experiment up to 40 T.
By analyzing the XMCD spectra, we can deduce theFig. 2 XMCD spectra of Eu intermetallic compound at L2 andL3 edges. The signals grow as a function of magnetic field
intensity [1].

polarizations of rare earth element at different component
such as 4f and 5d. Also the important parameters such as
inter-band mixing and exchange couplings can be also
evaluated. These facts show that the method is very uniquein the field of magnetism.
By using the high magnetic field, XMCD can be measured
many of antiferromagnet and paramagnet. It would open the
new field for X-ray spectroscopy.
References[1] Y. H. Matsuda, Z. W. Ouyang, H. Nojiri, T. Inami, K.
Ohwada, M. Suzuki, N. Kawamura, A. Mitsuda and H. Wada,
Phys Reu. Lett. (in print)
Key Words
High Magnetic Field, XMCD, Magnetism
Contact toHiroyuki Nojiri (Magnetism Division)e-mail: nojiri@imr.tohoku.ac.jp

Fig. 1 A pulsed magnetic field generator XMCD. A magnetic fieldas high as 40 T can be generated.

KINKEN Research Highlights 2009 IMR

Innovative Electronic Materials

27Research

Infrared Optical Probe of Carrier-Doping in Organic Mott Insulator
Modulation of the band-filling in the Mott insulator could
produce the novel interesting strongly correlated electronic
states. X-ray irradiation for the molecular materials could bea new way of the carrier-doping into the Mott insulators. We
can obtain rich information about the correlated states fromthe Infrared optical properties

28

Innovative Electronic Materials

C

BEDT-TTF molecule

e- charge transfer

ClN

x-ray irradiation

Cu
C

Cu[N(CN)2]Cl layer(accepter)

Fig. 1 Crystal structure of κ-(BEDT-TTF)2Cu[N(CN)2]Cl. The
two-dimensional conduction plane consists of BEDT-TTF
donor molecules, which is sandwiched by the insulating
Cu[N(CN)2]Cl anion molecule layers.

100
80
R (%)

Organic charge transfer salts based on the BEDT-TTF
molecule have been recognized as one of the highly
correlated electron system. Among them, κ- (BEDT-TTF) 2X
with X = Cu (NCS) 2, Cu[N (CN) 2]Y (Y = Br and Cl), etc. haveattracted considerable attention from the point of view of thestrongly correlated electron system. The strong BEDT-TTF
dimer structure makes the conduction band effectively halffilling. In such strongly correlated electron systems, Mott
insulating phase appears and the first order Mott insulator –metal transition takes place by applying hydrostatic pressure,which must broaden the conduction bandwidth with respect
to the effective Coulomb repulsion energy on the dimer. Thusthe κ- (BEDT-TTF) 2X family has been considered to be thebandwidth controlled Mott system in comparison to the filling
controlled one in the inorganic perovskites such as High-Tc
copper oxides.
X-ray irradiation usually induces disorders in a crystal, forexample, displacement of the atomic position. In the case ofmolecular materials, the irradiation produces molecular
defects, which are generated by the radiolysis under ionizing
radiation. This kind of molecular defect permanently remains,while the irradiation damage in inorganic materials is only
due to atomic displacements which can be restored by aproper heat treatment. These defects and disorders makethe electrical conductivity worse in general because ofincreasing the electron scattering. Increase of the conductivity
by x-ray irradiation, however, has been found in organic Mott
insulator κ-(BEDT-TTF)2Cu[N(CN)2]Cl [1]. The irradiationinduced defects expected at the donor and/or anion molecule
sites might cause a local imbalance of the charge-transfer inthe crystal (Figure 1). Such local modulation of the chargetransfer comes into being the effective doping of carriers into
the half-filling Mott insulators. In order to investigate thechange of the electronic state by possible carrier-doping
induced by x-ray irradiation into the organic dimer-Mott
insulators, infrared optical reflectivity spectra were measured
in typical bandwidth controlled Mott insulator κ-(BEDTTTF)2Cu[N(CN)2]Cl [2].
In the optical reflectivity spectra (Figure 2) of κ-(BEDTTTF)2Cu[N(CN)2]Cl after x-ray irradiation by using thetungsten tube (40kV, 20mA), it was apparently observed thatthe spectral weight was transferred from the high- to lowenergy far infrared region. This means that the interband
transitions in dimer bands and Hubbard bands in the mid
infrared region are suppressed drastically and the low-energy
Drude-like part is enhanced by way of compensation. The
observed optical spectra suggest that the Mott insulator
changes into essentially a metal due to small shift of thecarrier number from the half-filling in the conduction band by
x-ray irradiation.
As for the future application of this x-ray irradiation
technique, a conductive circuit and dots can be madeartificially on the molecular crystals by controlling the local

BEDT-TTF layer(donor)S

60

590 h 590 h
165 h 165 h
60 h
60 h
0h
0h

T=4K
E//c

40
20
0
0

2000
4000
6000
ω (cm-1)(cm-1)
wave number

8000

Fig. 2 Optical reflectivity spectra of κ-(BEDT-TTF)2Cu[N(CN)2]
Cl at 4 K. Reflectivity in far infrared region increases withincreasing the x-ray irradiation time. Concurrently we observea decrease of the magnitude of the interband transition in the
mid infrared region around 3500-4000 cm-1.
irradiated position, which will be useful for fabricating theorganic electronic devices [3].
References[1] T. Sasaki, H. Oizumi, N. Yoneyama and N. Kobayashi, J.
Phys. Soc. Jpn. 76, 123701 (2007).
[2] T. Sasaki, N. Yoneyama, Y. Nakamura, N. Kobayashi, Y.
Ikemoto, T. Moriwaki and H. Kimura, Phys. Rev. Lett. 101,
206403 (2008).
[3] N. Yoneyama, T. Sasaki, N. Kobayashi, Y. Ikemoto, T.
Moriwaki and H. Kimura, Solid State Commun. 149, 775 (2009).
Key Words
Organic Conductors, Optical Conductivity, X-ray Irradiation
Contact toTakahiko Sasaki (Low Temperature Physics Division)e-mail: takahiko@imr.tohoku.ac.jp

IMR KINKEN Research Highlights 2009

Research

As an in-house collaboration with Kawasaki-group (WPIAIMR and IMR) and Nojima-group (IMR), we developed a
new electrochemical technique at solid/liquid interfaces.
Using the electric double layer as a capacitor, we havefabricated a field effect transistor device, with which wedemonstrated electric field induced phase transitions,involvinginsulator-metaltransitionandevensuperconductivity. This transistor can be a versatile method
to create and control new states of matter.
The electric double layer formed at an electrochemicalinterface between liquid and solid is attracting considerable
interest from the view point of charge capacitor applications.
However, their ability of high density charge accumulation
can be used as a transistor with high capacity and highmaximum carrier density, which might provide a significant
impact on solid state physics.
When voltage is applied between two electrodes in anelectrochemical cell, ions in electrolyte move towardcorresponding electrodes driven by the electric field. Finally,ions are stabilized right above the electrode surface to form
an electric double layer (EDL). Figure 1 shows a schematic
drawing of EDL for the case of polymer electrolyte, consistingof polymer solvents and KClO4 solute. EDL is a kind of
capacitor, which produces an electric field in the order of 10
MV/cm, which is difficult to achieve in solid capacitors. This
capacitor device, called electric double layer capacitor(EDLC) is well known for its capability of high density charge
accumulation, and is already on market as a high density andhigh speed capacitor. When one of the electrodes is replaced
by a semiconductor with a source and drain electrodes, thisdevice works as a field effect transistor, which can be called
an electric double layer transistor (EDLT). This electrochemicaltransistor device has been investigated for application to ion
sensors or for reducing operation voltages in organic
transistors. Since 2005, we have been investigating EDLT
devices aiming at accumulating high density carriers andhopefully inducing electronic phase transitions using organic
semiconductors [1]. Recently, we started to apply thistechnique to oxide semiconductors in collaboration with Prof.
Kawasaki’s group, and have successfully demonstrated theSheet carrier density (1014 cm-2)

Electric Double Layer Transistor
4

Ionic Liquid/ZnO

3
2
1

Electrolyte/STO[3]Electrolyte/ZnO [2]0Gate voltage (V)Fig. 2 Gate voltage dependence of carrier density
accumulated at EDLT of oxide semiconductor, which was
determined by Hall effect measurements. Ionic liquid,
specifically DEME-TFSI, displays an significant improvementin carrier density over that for polymer electrolyte.
electric field induced insulator-metal transition in ZnO [2],followed by superconductivity in SrTiO3 [3]. Particularly, thelatter is the first electric field induced superconductivity
without any help of chemical doping, which has been a targetof solid state physicists for about half a century.
For expanding electric field induced phase transitions toother materials, the increase of carrier density is of criticalimportance. For this purpose, we introduced ionic liquid which
is a kind of melt salt at room temperature. Figure 2 displays
gate voltage dependence of the carrier density determined byHall effect measurements on ZnO EDLT devices [4]. The
results uncovered that the charge density accumulated withionic liquid is several times larger than that with polymer
electrolyte. The maximum carrier density achieved in Fig. 2
allows us to anticipate to realize electric field induced
superconductivity in other materials. These results strongly
imply that EDLT could be useful for searching novel states ofmatter and offers a novel direction in materials research at theelectrochemical interface between ionic conductors (generally
liquid) and electronic conductors (solid).
Reference[1] H. Shimotani et al., Appl. Phys. Lett. 86, 022104 (2005).
[2] H. Shimotani et al., Appl. Phys. Lett. 91, 082106 (2007).
[3] K. Ueno et al., Nat. Mater. 7, 855 (2008).
[4] H. T. Yuan et al., Adv. Funct. Mater. 19, 1046 (2009).
Key Words
Field
EffectTransistor,
Superconductivity

Electrochemical

Device,Contact toFig. 1 Schematic drawing of interface between polymer
electrolytes and semiconductors under a voltage bias. Solvatedcations and accumulated electrons at solid surfaces form anelectric double layer with an approximate thickness of 1 nm.

KINKEN Research Highlights 2009 IMR

Yoshihiro Iwasa (Low Temperature Condensed State Physics
Division)e-mail: iwasa@imr.tohoku.ac.jp

Innovative Electronic Materials

29ResearchMonolayer Segregation of Dopant Atoms at the Interface between Gate Oxide and
Si Substrate in MOSFET Observed by Laser 3D Atom Probe Method
Laser assisted 3D atom probe was applied to analyze
three-dimensional dopant distribution in Si substrate ofmetal-oxide-semiconductor field effect transistor (MOSFET)
structure. Monolayer segregation of As atoms at the interface
between gate oxide and Si substrate was clearly observed,
which is a candidate of the origin of variability in transistor
characteristics. This technique is also useful to study
degradation of nuclear materials due to impurity segregation
on grain boundaries and interfaces.

30

Innovative Electronic Materials

Fig. 1 3D elemental map of the MOSFET structure sample.
As (yellow), B (white), O (blue), and Si (magenta). For visualclarity, only 5% of the Si atoms are plotted.

Gate Oxide[×10 ] 1
20

3]

As the minimum feature size of metal-oxide- semiconductor
field effect transistor (MOSFET) decreases to 100 nm or less,variability in MOSFET characteristics has become a serious
problem. The major factor is supposed to be random
distribution of discrete dopant in the channel region.
Therefore, the information on the exact location of each
dopant in the channel region is strongly desired. In this work[1], dopant distribution in MOSFET channel was observedwith atomic scale resolution using laser-assisted threedimensional local electrode atom-probe (3DAP) (IMAGO:
LEAP3000X).
The sample in this study is laterally uniform and has thedummy structure of MOSFET which consists of polycrystalline
Si gate, gate oxide, and Si substrate. After cleaning thesurface of Si substrate, As atoms were implanted at theenergy of 70 keV with the dose of 2x1014cm2. For recovering
the implanted damage, a rapid thermal annealing was carriedout at 950 °C for 60 s. Next, gate oxide of 2nm thickness andpolycrystalline Si gate of 150nm thickness were formed. B
atoms were implanted at the energy of 10 keV with the doseof 3x1015cm2 for gate pre-doping. Finally, spike annealing for
1050°C was carried out to activate the implanted impurities.
The needle sample for 3DAP analysis was prepared using a
focused-ion-beam system. The base temperature of thesample during the 3DAP measurement was kept at 30 K.
Figure 1 shows a 3D elemental map of the sample. The
box sizes in the figure are 60x60x125nm3. 70 nm of thepolycrystalline Si layer and 50 nm of the Si substrate acrossthe gate oxide were analyzed. For Si, 5% of atoms are plottedin this figure to make the map clear. The MOSFET structureof the polycrystalline Si gate, the gate oxide, and the Si
substrate structure are observed. As atoms implanted in the
Si substrate and B atoms implanted in the polycrystalline Sigate were observed.
Figure 2 shows a one-dimensional As atom distribution in
the depth direction. The As atom distribution is almost
consistent with the result measured by the SIMS in the regionof the Si substrate. However, at the interface between the gate
oxide and the Si substrate, the As concentration determinedby the 3DAP is higher than the SIMS results. This result
indicates that the As atoms segregate at the interface. Thissegregation can be confirmed by the enlarged view of the 3D
elemental map around the interface shown in Fig. 3. It is clearlyobserved that the As atoms are located just at the interface
with higher concentration. This monolayer segregation isimportant to understand the chemical and electrical states of
the As atoms in the MOSFET, which may affect thresholdvoltage, effective mobility, and gate oxide reliability. Moreover,the influence of the segregation will become more serious to
the device behavior in further downsizing MOSFETs.

0.8

Gate

Substrate
LEAP
SIMS

0.6
0.4
0.2
0

60

80
100
Depth [nm]120Fig. 2 1D As atom distribution in the depth direction from the
3DAP and SIMS analyses.

Fig. 3 Enlarged view of the 3D elemental map around thegate oxide. As (yellow) and O (blue).
References[1] K.Inoue, F.Yano, A.Nishida, T.Tsunomura, T.Toyama,
Y.Nagai, M.Hasegawa: App. Phys. Lett. 92 (2008) 103506.
Key Words
Laser 3D Atom Probe, Interface Segregation
Contact toYasuyoshi Nagai (Irradiation Effects in Nuclear and Their
Related Materials Division)e-mail: nagai@imr.tohoku.ac.jp

IMR KINKEN Research Highlights 2009

Research

Ternary uranium compounds U2XSi3 (X=transition metal)
have attracted much interest in the last decade. The considerable
changes of magnetic properties in these systems have been
demonstrated to relate with the character of the X atom and thearrangement of non-magnetic atoms (X and Si) in X-Si network.
For examples, Spin glass (SG) behavior, paramagnetic properties
and ferromagnetic cluster glass behavior have been observed
for the compounds with X= Pd, Rh and Fe, which crystallize inthe hexagonal structure with perfectly disordered, partiallydisordered and perfect order arrangement of X and Si atoms,
respectively. For U2CuSi3, it is known as a special and interestingcase in the family of compounds U2XSi3 relevant to its
controversial magnetic properties and crystal structures. U2CuSi3
was first reported to crystallize in the tetragonal α-ThSi2-type
structure exhibiting re-entrant SG behavior, and in the later
literature it was considered as a ferromagnetic material with the
hexagonal AlB2-type structure.
We have systematically measured the basic physicalproperties of U2CuSi3 on a well-annealed polycrystalline
sample, which was confirmed to crystallize in the tetragonal
α-ThSi2-type structure after annealed at 800°C for 240 h [1].
Figure 1 presents the low temperature dc susceptibility(χ=M/H) data measured in a field of H=100 Oe. Withdecreasing temperature, the χZFC (T) curve shows a sharp
peak near Tf~18.9 K, suggesting a certain kind of magnetic
phase transition at this temperature. However, no peak isobserved in the χFC curve and evident magnetic irreversibility
manifesting as the bifurcation between the χZFC and χFC
curves appears below a temperature Tir, similar to that usuallyobserved in SG materials. In addition, no any indication of amagnetic phase transition into a long-range order around Tf(~18.9 K) can be observed in both the specific heat C (T)(inset (a) of Fig. 1) and the electrical resistivity ρ(T) (inset (b)0.020

C (J/K/mol)

0.012
0.008

136

H=100 Oe

132

0.004
Tf

ZFC

0.000
0

10

Tir

20

ρ (µΩ cm)

FC

0.016

M/H (emu/g)

40
30
20
10
0
0

128
0

30

T (K)

(a)
Tf
10

20

(b)

5

30

T (K)

40

Tf
T (K)

10 15 20 25

40

50

60

Fig. 1 Temperature dependences of field-cooled (FC) andzero-field-cooled (ZFC) dc susceptibility (Χ=M/H) of U2CuSi3
in an applied field of 100 Oe. The insets (a) and (b) show thetemperature dependences of specific heat and electricalresistivity, respectively, for the U2CuSi3 sample.

KINKEN Research Highlights 2009 IMR

χac' (10−3emu/g)

Ternary nonmagnetic atom disorder (NMAD) uranium
compound U2CuSi3 is confirmed to crystallize in the tetragonal
α-ThSi2-type structure after annealed at 800ºC for 240h. Ac
susceptibility measurements reveal an evident spin glasstransition for this compound at a static spin freezing temperature
TS=18.3K. The presence of frustrated magnetic interactions in
U2CuSi3 is discussed in a “magnetic cluster model”.

4

χac" (10−4emu/g)

Spin Glass Behavior in NMAD Uranium Compound U2CuSi3

4

0.1Hz
1Hz
10Hz
100Hz
300Hz
500Hz
1000Hz

3
2
1

(a)
0.1Hz
1Hz
10Hz
100Hz
300Hz
500Hz
1000Hz

3
2
1
0
16

18

(b)

20
T (K)

22

Fig. 2 Real (a) and imaginary (b) components of the ac
susceptibility of U2CuSi3 vs. temperature at various frequencies.
of Fig. 1) curves. These results suggest the absence of longrange spatial magnetic order in the vicinity of Tf.
Figure 2 shows the in-phase χ’ac (T,ω) as well as the outof-phase χ”ac (T,ω) components of the ac susceptibility
versus temperature between 16 and 23 K. Both the χ’ac andχ”ac curves exhibit a characteristic pronounced maximum
with amplitude and position depending on the frequency ω ofthe applied ac magnetic field. As ω increases, the peak
position in χ’ac and χ”ac shifts to higher temperatures. Such a
feature can be considered as the most striking evidence for
SG state in U2CuSi3. The initial frequency shift of the peak
position is determined to be δTf=ΔTf/ (TfΔlogω) =0.009. Thisvalue is comparable to the typical values reported forcanonical SG systems. From the dynamical analyses of theac susceptibility data, the static spin freezing temperature TS,
critical exponent z.ν and activation energy Ea are determined
to be 18.3 K, 8.1 and 3.1 kBTS, respectively.
It is well known that “randomness” and “frustration” arethe necessary conditions for SG state. To understand theexistence of frustrated magnetic interactions in U2CuSi3, weconsidered that statistical arrangement of nonmagnetic Cu
and Si atoms could destroy long-range magnetic correlation
between U atoms in U2CuSi3 and lead to the formation ofindividual spins or finite-size granules with net magnetic
moments (magnetic clusters). These clusters should also
randomly distribute in the sample and interact on each otherat low temperature causing the formation of frustrated
magnetic moments. Below a freezing temperature Tf, thesefrustrated magnetic moments could be frozen-in along
random directions to form a spin glass state similar to what
happen in amorphous or diluted metallic SG materials.
References[1] D. X. Li, S. Nimori, T. Yamamura and Y. Shiokawa, J.
Appl. Phys. 103, 07B715 (2008).
Key Words
Spin Glass, Susceptibility, Frustrated Magnetic Interactions
Contact to
Dexin Li (Radiochemistry of Metals Division)e-mail: dxli@imr.tohoku.ac.jp

Innovative Electronic Materials

33Research

Room Temperature Coulomb Oscillation of a Proton Dot in
Ni-Nb-Zr-H Glassy Alloys with Nanofarad CapacitancA dc current-induced voltage oscillation was observedat room temperature in (Ni36Nb24Zr40)90.1H9.9 glassy alloy
ribbons of about 1-mm width and 30-μm thickness and anelectrode distance of 20 mm [1]. The I-V characteristic
provided evidence of the Coulomb staircase at ~300 K,
suggesting the existence of macroscopic proton dot
tunneling along the Zr(Nb)-H- -H-Zr(Nb) atomic bond array,
where is the vacancy barrier among clusters. The frequency
decreased remarkably with increasing capacitance (C) andresistance (R) at room temperature. Thus the (Ni36Nb24Zr40)
90.1H9.9 glassy alloy can be regarded as a dc/ac converting
device with a large number of nF capacitance.
Quantum dot tunnelling is one of the topics currently
attracting a great deal of interest in the field of physics. If
room-temperature macroscopic quantum dot tunnelling isrealized, it will lead to epoch-making developments in the
manufacture of electronic devices. Although the challenges
in realizing quantum dot tunnelling at room temperature havebeen carried out by various research groups, no research
work has achieved a success for the SETs, on the millimeter
size, as far as we know. We investigate an effect of Zr content
on Coulomb oscillation in the millimeter sized Ni-Nb-Zr-H
glassy alloys in anticipation of room-temperature Coulomb
oscillation.
We measured I-V characteristics at temperatures ranging
from 8 K to 412 K, because a stepwise increase of the current
I upon increasing the applied voltage V is expected for tunnel
barriers [2, 3]. Fig.1 shows a typical Coulomb staircase,indicative of quantum dot tunnelling, as can be seen from
“Coulomb gap” shown by a hyperbolic curve in I-R
characteristics at 300 K (insert). The width ΔV = 0.10 mV ofthe current plateaus is a direct measure of the charging
energy: ẹΔV = e2/C, from which we deduce the total

Fig. 2 Capacitance dependence of frequency for various
resistances in (Ni36Nb24Zr40)90.1H9.9 glassy alloy. Insert:
Oscillation circuit used in study. R, C and E are resistance,
capacitance and dc voltage source, respectively.

capacitance C = 1.60 fF. To obtain information on the tunnel
barrier height and width, the conductivity was plotted as afunction of the inverse temperature (1/T), the Arrhenius plot
in Fig.1, and measured for the fixed E =0.10 mV. It can beseen that there are two distinct temperature regions. At atemperature below ~300 K, the current is almost constant,whereas it increases noticeably with increasing temperature.
The former behavior is that of tunnelling, whereas the latter isan activation process which arises from the thermionicemission over the tunnel barrier.
Since the alloy (Ni36Nb24Zr40) 90.1H9.9 causes dc currentinduced ac oscillation at room temperature, we concluded
this study by investigating the RC effect on the oscillation in
the dc/ac circuit. The capacitance dependence of frequency
for various resistances at room temperature is shown in
Fig.2, along with the frequency circuit. In the capacitanceregion over 100pF, the frequency decreases remarkably withincreasing resistance from 900kHz.
References[1] M.Fukuhara and A.Inoue, J.Appl.Phys., 105, 063715(2008).
[2] M.Fukuhara A.Kawashima, S.Yamaura and A.Inoue,
Appl.Phys.Lett., 90, 203111(2007).
[3] M.Fukuhara and A.Inoue, Europhus.Lett., 83, 36002(2008).
Key Words
Nano Quantum Dot Tunnelling, Electronic Device

Fig. 1 I-V characteristics at temperatures ranging for(Ni36Nb24Zr40)90.1H9.9 glassy alloy at 8, 50, 100, 150, 200,
250, 300, 350 and 412 K. Insert: the voltage-controlled I-R
characteristics at 300 K. Arrhenius plot of the conductivity as
a function of the inverse temperature.

34

Innovative Electronic Materials

Contact toMikio Fukuhara (Research and Development Project on
Advanced Metallic Glasses, Inorganic Materials and Joining
Technology)
e-mail: fukuhara@imr.tohoku.ac.jp

IMR KINKEN Research Highlights 2009