bluuebunny/crossref_metadata_2025 huggingface dataset:
Electroluminescence in Undoped GaAs/AlAs Superlattice due to Avalanche Breakdown
Authors: Domoto Chiaki , Ohtani Naoki , Vaccaro KazuyoshiKuroyanagi , NorifumiEgami NorifumiEgami
Published: October 2002

We have observed electroluminescence (EL) in an undoped
GaAs/AlAs superlattice (SL) originating from avalanche breakdown. From
EL and photocurrent-voltage characteristics, we found that a large
number of electrons were injected into Γ2 states in the SL by
avalanche breakdown under a high electric field. The EL spectra
revealed two peaks: one having a longer wavelength originated from the
radiative recombination process between Γ1 and hh1 states,
while the other peak originated from the recombination between
Γ2 and hh1 states.
Gate-Length Dependence of Optical Characteristics in Optically Controlled MOSFET
Authors: Yuichi Nitta Yuichi Nitta , Tomonari Yamagata Tomonari Yamagata , Kazuhiko Shimomura Kazuhiko Shimomura
Published: October 2002

The gate-length dependencies of the optical response characteristics in an optically
controlled metal oxide semiconductor field effect transistor (MOSFET) have been measured. This device was fabricated as an integrated
structure of the absorption region and MOSFET region using the direct wafer-bonding
technique. By reducing the gate length of the MOSFET region, the transconductance of
the FET channel was increased, and a high current modulation and responsivity was
obtained by irradiation of 1.5 µm wavelength light.
Acoustic Properties of β-In2S3 Thin Films Prepared by Spray
Authors: Amlouk M. , Saïd M. A. Ben , Kamoun N. , Belgacem S. , Brunet N. , Barjon D.
Published: October 2002

β-In2S3 thin films have been prepared on pyrex glass substrates by
the spray pyrolysis technique at 340°C. We have analyzed by acoustic
microscopy and particularly by acoustic signature V(z) these films with
various thickness (0.3–2.5 µm). The acoustic signature, performed at
130 and 570 MHz allows us to reach elastic properties of β-In2S3 material
and especially Young's modulus. Its value (443 GPa) is of the same order
of those of ceramics. Besides elastic properties and using scanning
electron microscopy (SEM) and atomic force microscopy (AFM)
investigations, we have shown that the V(z) signature gives valuable
information about the defects in the material. Finally, the experimental
results have been discussed related to the dispersion curves of velocity
of the first mode of β-In2S3/pyrex system.
Growth of ZnO by Molecular Beam Epitaxy Using NO2 as Oxygen Source
Authors: Keiichiro Sakurai Keiichiro Sakurai , Daiji Iwata Daiji Iwata , Shizuo Fujita Shizuo Fujita , Shigeo Fujita Shigeo Fujita
Published: October 2002

Nitrogen dioxide was applied for molecular beam epitaxy of
ZnO on (0001) sapphire substrates.
Equipped with liquid nitrogen cryoshrouds,
the pressure inside the chamber was kept below
1×10-7 Torr during growth.
The samples were characterized by reflection high energy electron
diffraction, X-ray diffraction, photoluminesence
and scanning electron microscopy.
The ZnO crystals clearly showed
excitonic optical properties up to room temperature.
Effects of low-temperature buffer layers for better
surface morphology and reproducibility were also investigated.
Enhanced Ultraviolet Emission in Polysilane Light-Emitting Diodes by Inserting a SiOx Thin Layer
Authors: Xu Yonghua , Fujino Takahiro , Watase Seiji , Naito Hiroyoshi , Oka Kunio , Dohmaru Takaaki
Published: October 2002

Bilayered polysilane light-emitting diodes (LEDs) have been fabricated by inserting a SiO
x

thin layer between the cathode and a poly(methylphenylsilane) (PMPS) film employed as an
emission material. The SiO
x
layers were prepared by O2 plasma treatment of the PMPS film
surfaces. It was found that the external quantum efficiency was significantly enhanced by this
treatment. The enhancement may be caused by the increased electron injection due to the
tunneling effect and the reduced hole current due to the blocking effect by the thin SiO
x
layer.
Experiments also showed that the weak visible emission invariably observed from single-layer polysilane LEDs was almost completely eliminated. It is concluded that the visible
emission is caused by the erosion of the PMPS surfaces occurring due to the collision with hot
metal particles during the vacuum deposition of the cathode, and this erosion is avoided by
the SiO
x
layer.
Anomalous Electrochemical Behavior of N-Type GaN Films on α-Al2O3 Substrates
Authors: Yamamoto Akio , Tsuji Yasuyuki , Hashimoto ToshimitsuSugiura
Published: October 2002

The anodic behavior of n-type GaN films grown on α-Al2O3(0001)
substrates has been studied. During the galvanostatic anodization of a
GaN sample, electrode potential in the dark is low at the beginning of
the anodization and suddenly becomes very high as the anodization
proceeds. After the electrode potential becomes high, the sample shows
a marked effect of ultraviolet light irradiation. The low electrode
potential at the initial stage of the anodization is interpreted to be
due to the selective etching of low-quality and/or
high-carrier-density parts in a GaN film. Due to the selective removal
of a part of a GaN film near the film/α-Al2O3 substrate interface as
one of the low-quality and/or high-carrier-density parts, the film is
peeled off from the substrate after the anodization. The peeling
suggests that the film contains a low-quality and/or
high-carrier-density part in the vicinity of the substrate.
Fabrication and Characterization of Planar Diamond Electron Emitters
Authors: Kawamura Hideki , Maki Tetsuro , Kobayashi Takeshi
Published: October 2002

A planar electron emitter was fabricated employing chemical vapor deposited (CVD) diamond particles. This device is composed of isolated particles of CVD diamond selectively deposited on a pair of patterned Pt films separated 4 micrometers from each other. Field emission current from the diamond particles was observed when the voltage was applied between the Pt films. The mechanism of electron emission from the diamond particles used in this device was discussed by comparing with the electron emission from a continuous diamond film. It was found that the effective work functions differ between the isolated particles and the continuous films. This result suggests a difference in the emission site of electrons.
Properties of Metal-Semiconductor Interfaces Formed on n-Type GaN
Authors: Hasegawa Hideki , Koyama Yuji , Hashizume Tamotsu
Published: October 2002

Properties of metal/GaN Schottky diodes formed by the
conventional vacuum deposition process and a novel in situ
electrochemical process are investigated by detailed I–V, C–V and
X-ray photoelectron spectroscopy (XPS) measurements with a special
focus on the correlation between the contact formation process and the
behavior of Schottky barrier height. Schottky diodes formed by vacuum
deposition pretreated with a warm NH4OH solution showed nearly ideal
thermionic emission I–V characteristics with Schottky barrier height
(SBH) values weakly dependent on metal work function with the slope
factor of about 0.1. On the other hand, Schottky diodes formed by the
in situ electrochemical process also showed high-quality nearly ideal
thermionic emission I–V characteristics, but they realized strongly
metal-work-function-dependent SBH values. The slope factor, S, was as
large as 0.49. These results could not be explained by the recently
proposed formula based on the metal induced gap state (MIGS)
model. They are explained here from the viewpoint of the disorder
induced gap state (DIGS) model.
First Demonstration of Rectifying Property of P-I-N Heterojunctions Fabricated by Tri-Layered Semiconducting Oxides
Authors: Sugiura Masanori , Uragou Kazuyuki , Tachiki MakotoNoda , Kobayashi Takeshi
Published: October 2002

We have fabricated semiconducting oxide p-i-n diodes in order to
explore minority carrier injection effects in oxide materials. The
diodes comprised p-La0.85Sr0.15MnO3/i-SrTiO3/n-La0.05Sr0.95TiO3. All
oxide layers were grown epitaxially by the eclipse pulsed laser
deposition method on (100) SrTiO3 substrates. The diodes showed good
rectifying properties, and from the flat-band capacitance measurement,
we obtained a diffusion potential of about 0.2 V for these diodes in
agreement with the calculated results. In the lower temperature
regime, the space-charge-limited-current property was pronounced,
arising from residual traps inside the i-SrTiO3 layer. The backward
current was mostly due to tunneling through the i-SrTiO3 layer,
showing no meaningful expansion of depletion regions in both p- and n-oxide layers.
In-Situ Monitoring of In0.53Al0.13Ga0.34As/In0.52Al0.48As 1.55 µm Vertical Cavity Surface Emitting Laser Structure Grown by Metal Organic Chemical Vapor Deposition
Authors: Baek Jong-Hyeob , Lee Bun , Han Won Seok , Cho Hyung Koun , Smith Jason M. , Choi In Hoon
Published: October 2002

A 1.55 µm vertical cavity surface emitting laser (VCSEL) structure was grown by low pressure metalorganic chemical vapor deposition method. In-situ laser reflectometry with a wavelength near resonant position of VCSEL structure was employed to monitor the optical thickness over the whole growth time. The distributed Bragg reflectors (DBR's) were grown with alternate In0.53Al0.13Ga0.34As and In0.52Al0.48As quarter lambda wavelength layers. The growth time of each layer in the DBR was determined through real time feedback of growth monitoring in the growth of In0.52Al0.48As and In0.53Al0.13Ga0.34As buffer layers prior to beginning the subsequently grown DBR structure. The oscillatory reflection signals by the laser operating at 1.53 µm gave information for the position of stop band in the reflectivity spectrum of the VCSEL structure. The reflectivity spectrum of VCSEL structure showed excellent square-shaped flat band wider than 50 nm where the reflectivity reached a plateau as expected by the in-situ monitoring data.
Pulsed Laser Deposition of Low-Resistivity Indium Tin Oxide Thin Films at Low Substrate Temperature
Authors: Adurodija Frederick Ojo , Izumi Hirokazu , Ishihara Tsuguo , Yoshioka Hideki , Matsui Hiroshi , Motoyama Muneyuki
Published: October 2002

Indium tin oxide (ITO) thin films were grown on SiO2 glass
and silicon (Si) substrates from a 95 wt% In2O3–5 wt%
SnO2 sintered ceramic target by pulsed laser deposition
(PLD). The films were deposited under different oxygen pressures
(P
o2) of 5×10-3 to 5×10-2 Torr at
room temperature (RT) and 200°C. P
o2 was found to
have a critical influence on the optical and the electrical properties
of the ITO films. Under a P
o2 of 1×10-2 Torr,
ITO films with resistivity as low as 4.5×10-4 and
1.8×10-4 Ωcm were obtained on glass at RT and
200°C, respectively. Moreover, by increasing the substrate
temperature (T
s) to 350°C, the resistivity was
further reduced to 1.3×10-4 Ωcm. Optical
transmittance in visible light greater than 85% was attained in all
the films deposited under P
o2 above 5×
10-3 Torr. However, a reduction in the transmittance to less than
80% was observed as P
o2 decreased. The films deposited at
RT were amorphous, whereas those produced at 200°C were
polycrystalline.
Effects of Initial Thermal Cleaning Treatment of a Sapphire Substrate Surface on the GaN Epilayer
Authors: Kim Jong-Hee , Choi Sung Chul , YounChoi Ji , Kim Ki Soo , MoYang Gye , Lim Chang-HeeHong , Lee Hyung Jae
Published: October 2002

We investigated the effects of the in situ thermal
cleaning treatment of a (0001) sapphire substrate surface in hydrogen
ambient on the structural, optical, and electrical properties of
epitaxial GaN films grown by metalorganic chemical vapor deposition
(MOCVD). Hall effect, X-ray diffraction (XRD), and photoluminescence
measurements of GaN films grown at 1040°C clearly indicate
that the film quality is strongly affected by the thermal cleaning
treatment of the substrate surface. GaN films under the optimized
thermal cleaning treatment at 1070°C for 10 min showed
minimum full-widths at half maximum (FWHMs) of 273 arcsec and
728 arcsec for (002) and (102) XRD peaks, respectively. In addition,
the FWHM of the band-edge emission peak was as narrow as 28.3 meV,
and the intensity ratio between the band edge emission and the yellow
band emission was as high as 100 at room temperature. It was also
found that the roughness of sapphire surface was reduced after the
thermal treatment.
Surface Structure of ZnO Single Crystals Analysed by Ion Scattering Spectroscopy
Authors: Maki Hideyuki , Ichinose Noboru , Sekiguchi Shoichi , Ohashi Naoki , Nishihara Takaharu , Haneda Hajime , Tanaka andJunzo
Published: October 2002

A ZnO crystal of wurtzite-type structure has polar surfaces of (0001)
and (0001), which are terminated by Zn and O ions, respectively.
Observation conducted by atomic force microscopy showed that step/terrace
structures were formed on the (0001) and (0001) surfaces, whose step height
was predominantly half of lattice parameter, c
0. The ionic arrangement of
the surfaces was determined by coaxial impact-collision ion scattering
spectroscopy (CAICISS); the CAICISS spectra had a periodicity of 60° for
azimuth angle dependence. From the analyses of CAICISS spectra it was
shown that the (0001) and (0001) surfaces had a single dangling bond, and
no ionic distortion occurred.
Interactions between Bias Magnetic Tape and Amorphous Magnetostrictive Strip used as a Magnetic Tag Device
Authors: Suenaga Wataru
Published: October 2002

The magnetic characteristics of a magnetic tag device composed
of a magnetostrictive strip and a bias magnetic tape were investigated
with the purpose of finding the optimum material properties for use as
a remote readable data carrier. We found that the magnetostrictive
strip in the device assumes a maximum magnetomechanical coupling
coefficient at an optimal strength of bias magnetic field, that varies
along the length of the strip and is generated by the magnetic tape
with appropriate thickness. The results are explained by a simple
model where the strip is regarded as a linear array of rectangular
domains. The model leads to the following conclusions: (1) the average
direction of the local magnetization of a domain is determined by the
bias magnetic field generated by the magnetic tape, and (2) an optimum
value of the magnetic tape thickness exists, which gives the maximum
coupling coefficient irrespective of the characteristics of the
amorphous alloy strip. The most appropriate bias magnetic field by the
magnetic tape is about 850 A/m in this study.
Measurement of the Spin Hamiltonian Parameters of Cu2+ Ion in Zn2+-Doped CaCd(CH3COO)4·6H2O
Authors: Oguama Ferdinand A. , Shields Howard W.
Published: October 2002

The spin Hamiltonian parameters (g
∥, g
⊥, A
∥ and A
⊥) of Cu2+ in Zn2+-doped
CCDAH
have been determined in the temperature range of 300 K to 15 K. The temperature
variation of the normalized intensity of the Cu2+ hyperfine lines was also studied in the
above temperature range. Our data show that g
∥, A
∥ and A
⊥ values are unaffected by the
presence of Zn2+ impurities in the crystal, while the g
⊥ changes significantly from the
corresponding values previously reported for pure CCDAH (i.e., without Zn2+
doping).
While g
∥ varied slightly with temperature (from 2.366 at 300 K to 2.351 at 15 K),
g
⊥
remained virtually unaffected by temperature.
Thermal Aging Effect in Poled Ferroelectric SrBi2(Ta,Nb)2O9 Capacitors
Authors: Shimada Yasuhiro , Noma Atsushi , Nakao Keisaku , Otsuki Tatsuo
Published: October 2002

Changes in the electrical properties of poled ferroelectric
SrBi2(Ta,Nb)2O9 (SBTN) thin-film capacitors caused by
high-temperature storage were studied. Current–voltage (J–V)
characteristics of SBTN capacitors before and after high-temperature
storage indicated that the current in SBTN is predominantly carried by
electrons and limited by electrode interfaces. The voltage shift in
the polarization–voltage (P–V) curve caused at high temperatures
was ascribed to a bulk effect because there were no definite changes
in the interface-limited J–V characteristics before and after
high-temperature storage. Assuming the pinning of domains by capturing
electrons emitted from traps distributed in the energy gap, we
describe the decay in switchable polarization with the power of
time. The activation energy for the decay in switchable polarization
associated with electron capture was determined to be 0.23 eV based
on the temperature dependence of the decay in switchable
polarization.
Effect of Oxygen to Argon Ratio on Growth of Bi4Ti3O12 Thin Films on Ir and IrO2 Prepared by Radio-Frequency Magnetron Sputtering
Authors: Jo W. , Cho S. M. , Lee H. M. , Kim D. C. , Bu J. U.
Published: October 2002

Bismuth titanate, Bi4Ti3O12, thin films were grown on Ir/SiO2/Si and IrO2/SiO2/Si substrates by radio-frequency magnetron
sputtering. Crystallinity and surface morphology of the heterostructures
were characterized over a wide range of oxygen mixing ratio (OMR) during the
deposition. X-ray fluorescence spectra reveal that the cation content of the
films is dependent upon the OMR, suggesting that control of Bi to Ti ratio
is possible by oxygen content of sputtering ambient. Polarization reversal
properties of the BTO films show P
r = +15 µC/cm2 and +12 µC/cm2, respectively.
Pyroelectric Properties of La-modified Lead Titanate Thin Film Detectors
Authors: Wang Chih-Ming , Chen Ying-Chung , Lee Maw-Shung , Chiou Chien-Chih , Huang Yao-Te
Published: October 2002

High-performance pyroelectric infrared (IR) detectors have been fabricated without the back side etching process using La-modified lead titanate (PLT) thin films. PLT thin films were deposited on (111)-oriented Pt thin film on SiO2/Si(100) substrates by a diol-based sol-gel process. The randomly oriented PLT thin film exhibits a relatively small dielectric constant and a large pyroelectric coefficient without poling treatment. The pyroelectric characteristics of point detectors with various La contents as a function of modulation frequency are compared. It was found that the PLT(10) detector has a large voltage responsivity of 3330 (V/W) at 20 Hz. The specific detectivity (D
*) at 100 Hz is 6.2×107 cmHz1/2/W. The results showed that Pb1-x
La
x
Ti1-x/4O3 thin film with x=0.10 [PLT(10)] was most suitable for use as a pyroelectric IR detector.
Deep Levels in Hg0.766Cd0.234Te Grown by Metal-Organic Chemical Vapor Deposition
Authors: Yoshino Junya , Morimoto Jun , Wada Hideo
Published: October 2002

The deep levels in Hg0.766Cd0.234Te grown on Si substrates by metal-organic chemical vapor
deposition (MOCVD) have been studied. Spectral analysis of deep level transient spectroscopy
(SADLTS) was used to evaluate the deep levels for this device. Three levels (LM1, LM2 and LM3)
were confirmed in this device. The values of activation energy and capture cross section for these
levels were as follows: LM1 (21 meV, 6.1×10-18 cm-2), LM2 (21 meV, 1.3×10-18 cm-2) and LM3 (35 meV, 9.8×10-18 cm-2). The midgap level in p-HgCdTe reported by several authors could not be
confirmed in this work.
Characterization of the Local Layer Structure at a Broad Wall in a Surface Stabilized Ferroelectric Liquid Crystal during Electric Field Application Using Synchrotron X-Ray Microdiffraction
Authors: Iida Atsuo , Noma Takashi , HirokatsuMiyata HirokatsuMiyata
Published: October 2002

The local layer structure response to the electric field was characterized at and around
the broad wall of a zig-zag defect in a surface stabilized ferroelectric liquid crystal cell by a
synchrotron X-ray microbeam. The rocking curves were measured as a function of the applied
voltage and the frequency. The broad peak appearing in the rocking curve at the broad wall
changed into a single, sharp peak when the electric field was applied to the cell, while the
rocking curve returned to the initial profile when the electric field was switched off. This
observation suggests that the pseudo-bookshelf structure at the broad wall becomes the
bookshelf structure with the application of electric field. The frequency dependence of the
rocking curve profile indicates the relaxation time of the local layer response to the electric
field. At a high electric field, a stripe texture comprised a pair of pseudo-bookshelf
structures, each of which tilted in the opposite direction with respect to the rubbing direction,
was generated from the broad wall.
Mechanical Activity of a Chiral Slab Sandwiched between Achiral Half-Spaces
Authors: Hsia Shao-Yi , Yang Shiuh-Kuang
Published: October 2002

A plane wave propagating in effectively chiral composites (ECC) has been
asymptotically investigated. In general, the ECC can be fabricated by embedding
a helical arrangement of microstructures in the soft matrix. Such a material is
mirror asymmetric or chiral; therefore, six independent wave numbers can be
found. They are associated with two sets of nondispersive longitudinal fields and
four sets of dispersive circularity polarized transverse fields. In this work, we
study the reflected and transmitted fields of a normally incident plane wave
propagating at achiral-chiral-achiral interfaces. The numerical study indicates
that the longitudinal wave is unaffected by the sandwiched chiral layer, while the
polarization of the transverse transmitted wave is significantly influenced by it.
Furthermore, when a normally incident SV-wave (vertical shear wave) propagates
in the upper half-space, the coupled SV- and SH-waves (horizontal shear wave)
can be found in the lower half-space. The polarization of the transmitted field is
affected by the handedness of the intermediate chiral layer.
Synthesis of (Ba,Sr)TiO3 Thin Films by Plasma-Activated Pulsed Laser Deposition Technique
Authors: Arakawa Taro , Arai Naonori , Yin Huaqing , Kaneda Hisayoshi , Sugahara Masanori , Haneji Nobuo
Published: October 2002

We report the synthesis of (Ba,Sr)TiO3 (BST) thin films using plasma-activated pulsed laser
deposition (PA-PLD) in oxygen ambient. In the PA-PLD system, an RF inductive coil was
placed between a target and a substrate, to which RF power of about
50 W was supplied. A SiO2
tube was positioned in the coil to confine the plasma particles. The BST films were deposited on
SrTiO3 (100) substrates at various temperatures by PA-PLD and the conventional PLD method.
X-ray diffraction results show that the films deposited by both methods were highly oriented in
the (100) direction, and the crystallinity of conventional PLD films was slightly better than that
of PA-PLD films. However, atomic force microcopy observation showed the surface
morphology of the PA-PLD films was smoother than that of conventional PLD films. The
leakage current characteristics of PA-PLD films were also effectively improved compared to
those of conventional PLD.
Total Cross Section of Electron Stimulated Desorption of Hydrogen from Hydrogen-Terminated Ge/Si(001) as Observed by Time of Flight Elastic Recoil Detection Analysis
Authors: Fuse Takashi , Fujino Toshiaki , Ryu Jeong-Tak , Katayama Mitsuhiro , Oura Kenjiro
Published: October 2002

We have performed time of flight elastic recoil detection analysis (TOF-ERDA) measurements to investigate the hydrogen desorption cross section of
electron stimulated desorption (ESD) from a hydrogen-terminated
Ge/Si(001) surface. These results showed that TOF-ERDA measurement was
valid for quantitative analysis of surface hydrogen. The desorption cross
sections were determined for incident electron energy ranges of 35–200 eV.
It was found that the threshold electron energy of ESD was about 30 eV. The
desorption cross sections indicated the dependence of irradiated electron
energy. This meant that the ESD mechanism was related to the core band
excitation.
Initial Stage of Ni Growth on the Mo(110) Surface
Authors: Tsunematsu Hiroshi , Gotoh Yoshihiko
Published: October 2002

Surface structures of Ni adsorbed on the Mo(110) surface have been studied using reflection high energy electron diffraction (RHEED). The surface phase diagram of Ni on the Mo(110) surface for annealing temperature vs Ni coverage has been completed. Both a two-dimensional layer and three-dimensional islands were observed in a thickness region of more than 1 ML (1 ML = 2.0 Å) and at annealing temperatures between 650°C and 850°C showing the Nishiyama-Wassermann orientation relationship on the Mo(110) substrate. The structure of the two-dimensional layer has a unit mesh of the distorted Ni(111) plane which is expanded by 0.9% in the [011]Ni direction and by 3% in the [112]Ni direction. The three-dimensional islands observed in the coverage of less than 15 ML have an atomic arrangement with a nearly six-fold symmetric structure of the distorted Ni(111) layer which is expanded uniformly by 3%. Both the layer and islands are commensurate with the Mo(110) lattice to form long-range-ordered structures.
Direct Measurements of Femtosecond Energy Dissipation Processes of Hot Electrons in a Gold Film
Authors: Akihide Hibara Akihide Hibara , Tomohiro Morishita Tomohiro Morishita , Isao Tsuyumoto Isao Tsuyumoto , Akira Harata Akira Harata , Takehiko Kitamori Takehiko Kitamori , Tsuguo Sawada Tsuguo Sawada
Published: October 2002

Energy dissipation processes of hot electrons in a gold thin film were measured by a femtosecond time-resolved transient reflecting grating method. The processes were analyzed using the two-temperature model and the theory of the transient grating method. It was found that the electron-phonon coupling and thermal diffusion processes could be investigated independently. Temperature dependence of the electron-phonon coupling factor and the thermal conductivity was investigated quantitatively. The results suggested that the nonthermal states of hot electrons still contribute to the dissipation processes on time scales of several picoseconds.
Generation of Uniform Magnetic Field for Cs Fountain Frequency Standard
Authors: Yasuhiro Fukuyama Yasuhiro Fukuyama , Takayuki Kurosu Takayuki Kurosu , Shin-ichi Ohshima Shin-ichi Ohshima
Published: October 2002

We developed a magnetic shield and generated a uniform magnetic field for an atomic fountain time and frequency standard at the National Research Laboratory of Metrology in Japan.
The shielding factor was 8000 and the uniformity of the generated magnetic field was 0.2%, both of which are sufficient for the magnetic field to realize a required accuracy of 1 ×10-16.
Composite Materials with Ultrasonically Induced Layer or Lattice Structure
Authors: Saito Mitsunori , Itagaki Kazuhiro , Hayashi Kiyohiko , Tsubata Kimiaki
Published: October 2002

Polymer composites with periodic layers or lattice structures
were fabricated with polysiloxane resin and acrylic particles. The
particles were kept arranged by ultrasonic standing waves during
solidification of polysiloxane resin. A pair of transducers were
placed face-to-face for excitation of a strong and uniform standing
wave. A two-dimensional lattice structure was fabricated by
solidification in two orthogonal standing waves.
Theoretical Considerations of Electron Transport in Single and Multiple Quantum Dots
Authors: Ferry David K. , Akis Richard , Holmberg DragicaVasileska , Bird FuadBadrieh
Published: October 2002

There are a variety of situations in which carriers sit in small 3-D quantum boxes containing a small number of electrons per box. These dots are characterized by periodic, oscillatory fluctuations in their magnetoconductance, which replicate the partial density of states in the dot itself. Hence, the measured magnetoconductance is a reflection of the energy spectrum of the dot. This carries over to arrays of dots, with the exception that new “superlattice” behavior can be observed in these structures. In this paper, we discuss recent quantum mechanical calculations of the properties of single dots and arrays of dots, and compare the results with experimental observations.
Microscopic Brillouin Scattering Study of Relaxation Phenomena in Low Molecular Weight Alcohols of Ethanol and Methanol
Authors: Ahart Muhtar , Jiang Fuming , Mikami Masayuki , Park In-Sung , Kojima Seiji
Published: October 2002

The temperature dependence of the longitudinal acoustic (LA) mode of ethanol and methanol is measured by means of a combination of a microscope and a Brillouin scattering equipment in the backward scattering geometry from room temperature to -190°C. The linewidth of Brillouin components of the samples shows attenuation maxima at temperature T
m ≈-100°C. The relaxation time changes with temperature gradually, even around the glass transition temperature T
g, it keeps and the value is at about 10-9s and 10-10s for methanol and ethanol, respectively. Its temperature dependence is compared with the α-relaxation measured by the dielectric method. It is found that the relaxation time related to the LA-mode is much shorter than that related to the α-relaxation for both alcohols. These results indicate that this fast relaxation occurs locally in comparison with the α-relaxation.
Brillouin Scattering Studies of Liquid-Glass Transition in Normal- and Iso-Propanols
Authors: Takagi Yasunari , Yano Toru , Kojima Seiji
Published: October 2002

The liquid-glass transition in the isomer of n- and iso-propanols has been investigated in detail from temperature and pressure dependences of Brillouin scattering spectra. The temperature dependence of spectra was measured with 90°scattering and their pressure-dependence was observed in the backward geometry using the microscopic Brillouin scattering equipped with the diamond anvil cell. The fitting analyses were performed using the spectral function based on the viscoelastic theory and the Vinet equation. Large differences as for velocity and density at glass transition (T

g
and P

g
), existed between the isobaric-cooling and isothermal-pressure processes in iso-propanol, the same as in n-propanol; V(P

g
) ≫V(T

g
) and ρ(P

g
) ≫ρ(T

g
). It was found that there is a little, but fine difference between two isomers due to a slight difference in molecular structures.
Brillouin Scattering in Optical Fibers
Authors: Kosugi Jun-ich , Takagi Yasunari
Published: October 2002

Microscopic Brillouin scattering in various optical fibers has been studied with edge illumination of a backscattering geometry. In the Brillouin scattering from thin samples, two inner scattering angles exist between incident and scattered light because of reflections inside the samples. The refractive indices were estimated from the angular dependence of two Brillouin peaks. It was found that these values had a tendency to be slightly larger than those of raw bulk materials.
Generation of Bessel Beam from Equiamplitude-Driven Annular Transducer Array Consisting of a Few Elements
Authors: Hiroyuki Masuyama Hiroyuki Masuyama , Tomoki Yokoyama Tomoki Yokoyama , Keinosuke Nagai Keinosuke Nagai , Koichi Mizutani Koichi Mizutani
Published: October 2002

We present a method for generating a nondiffraction
beam using an annular transducer array.
In this method, each element is driven with equiamplitude
and with an antiphase from its neighboring elements.
Theoretical and experimental analyses of an array of this
type have been carried out, and the feasibility of this method is
confirmed.
The beam from a continuous wave is shown using radiated pressure
magnitude distributions and it is shown that there exist most
suitable values of the width and number of elements.
When the array is driven by a burst signal,
the beam propagates as a plane wave which has an amplitude
corresponding to the zeroth-order Bessel function of the
first kind, J
0.
Since this beam is realized by an annular array consisting of
a few elements,
it suggests the possibility of a transducer of this form
developing into a source
which generates nondiffraction beams.
Effect of Process Parameters on Ultrasonic Separation of Dispersed Particles in Liquid
Authors: Hatanaka Shin-ichi , Taki Tomohito , Kuwabara Mamoru , Sano Masamichi , Asai Shigeo
Published: October 2002

The effects of process parameters on ultrasonic separation of dispersed particles in a liquid
using a standing-plane-wave field are discussed on the basis of experimental and theoretical results.
Numerical solution of the equation of motion of a fine particle in a standing-wave field indicates
that the inertia term can be neglected during conventional ultrasonic separation of fine particles.
Analytical solutions for the particle speed, the position at which particles are coagulated, and the
minimum power for separation, have then been derived to incorporate key process parameters.
Experiments are carried out to observe transitional coagulation of polystyrene particles in an
aqueous sugar solution with the incidence of standing ultrasonic plane wave, in terms of the
density difference as well as the acoustic energy density exerted. Experimental results agree well
with the theoretical predictions. The time required for coagulating and for the separation of
particles is shortened in the case that particles coalesce.
Experiments on Monopole Ultrasonic Pulse Radiated from Piezoelectric Polymer Film Transducers
Authors: Yoshida Yasuo , Kimoto Noriaki , Imano Kazuhiko , Inoue Hiroshi , Murata Kenji
Published: October 2002

We found experimentally that short monopole ultrasonic
pulses can be radiated from a piezoelectric polymer film transducer
driven by a step-function voltage with a fast rising time and low
output impedance. We clarified that the pulse width of the received
ultrasonic monopole pulse depends on the rising time of step-function
driving voltage, and is limited by transmission time (T

h
) in the
thickness direction of the film.
An Ultrasonic Imaging System Using a Matrix-Type Transducer Array
Authors: Michitoshi Noguchi Michitoshi Noguchi , Koichi Mizutani Koichi Mizutani , Keinosuke Nagai Keinosuke Nagai , Yoshinari Yamashita Yoshinari Yamashita
Published: October 2002

We propose a method for imaging an object's surface using a matrix-type transducer array. The matrix-type transducer array has a simple structure with some line-electrode fingers on both sides of a piezoelectric ceramic plate. By a combination of electrical-mechanical scanning, we image of an object's surface using data of distance between the transducer and the object. The ultrasonic probe used in the present system requires without beam forming and no signal processing for focusing. We measure two objects: one has a multilayered structure consisting of three differently sized aluminum plates, the biggest plate having an area of 150 mm × 80 mm and 0.8–1.5 mm thickness; and the other is a radio-wave-absorbent block 100.5 mm × 100.5 mm × 18.5 mm in size with 5 × 5 holes in a grid made of ferrite. The ultrasonic probe operates at a frequency of 3.5 MHz and the sensing distance between the transducer and the measured object is about 80 mm. At this distance, the diameter of the ultrasonic beam launched from the transducer is about 13 mm. We obtained a height resolution of ±0.2 mm and a spatial resolution of about 3.0 mm.
New Method for Measurement of Contact Angle (Droplet Free Vibration Frequency Method)
Authors: Shigeyuki Yamakita Shigeyuki Yamakita , Yoshikazu Matsui Yoshikazu Matsui , Showko Shiokawa Showko Shiokawa
Published: October 2002

We propose a new method for measuring the contact angle of a water droplet on a solid surface from the free vibration frequency. The method involves a new technique for vibrating a small droplet using surface acoustic waves (SAWs). We investigated experimentally the relationship between the contact angle of a water droplet on a SAW substrate and the free vibration frequency. The experimental results were compared with that of the theory based on normal-mode analysis and excellent agreement was obtained. The relationship was used to measure the contact angle of a water droplet on an arbitrary solid surface and to evaluate the solid surface condition.
Inspection Method for Detection of Defects in Sewage Pipes Renewed by Sewage Pipe Renewal Method
Authors: Tanigawa Hiroshi , Watanabe Yoshiaki , Imagawa Akira
Published: October 2002

A new nondestructive inspection method for the detection of
defects in a mortar layer of a sewage pipe renewed by the sewage pipe
renewal method is proposed. The mechanical admittance of the injected
material is observed at the inner surface. The mechanical admittance
of a normally constructed point shows that the magnitude increases in
proportion to the frequency. However, the frequency characteristic of
mechanical admittance exhibits resonance when there is a defect under
the measuring point, and the mechanical admittance is also higher than
that of a normally constructed point throughout the measuring
frequency. A defect index which shows the maximum displacement per
unit force against frequency is presented in order to estimate the
defect size. When there is a 150-mm-square defect 30 mm below the
inner surface of a renewed sewage pipe, the defect index is 10 times
as high as that in which there is no defect.
Linear Conductance through Parallel Quantum Dot Dimer below the Kondo Temperature
Authors: Kawamura Tomosuke Aono
Published: October 2002

The conductance through two quantum dots connected in a series is examined below the Kondo temperature as a function of the gate voltage attached to the dots. The ratio of the tunneling coupling between two dots to the level broadening characterizes the transport properties. When the ratio is less than unity, each dot accommodates one electron and forms the Kondo resonant state with an external lead at a sufficiently low gate voltage. In the valence fluctuating regime, the number of electrons in the dots decreases from two to zero whereas the conductance is suppressed. The corresponding range of the gate voltage is nearly the level broadening. When the ratio is larger than unity, the Kondo resonances are split into the bonding and antibonding peaks. The valence fluctuating regime is extended over the tunneling coupling between the two dots.
Characteristics of M-Sequence Signal in an Inhomogeneous Medium
Authors: Kohji Futa Kohji Futa , Nobuaki Takahashi Nobuaki Takahashi , Toshiaki Kikuchi Toshiaki Kikuchi , Hiroshi Ochi Hiroshi Ochi
Published: October 2002

One often observes fluctuation or disappearance of pulses in a series of received signals in the ocean.
In ocean acoustic tomography (OAT), pulses are detected with cross-correlation coefficients between a received signal and the replica of a transmitted M-sequence signal.
We study the influence of phase variation of an M-sequence signal on the coefficients through computer simulation.
It is found that the coefficients rapidly become small as the phase shift increases.
As a result, we should consider phase shift of signals in the analysis of received pulses in OAT.
Brillouin Scattering Study on the Elastic Properties of Epoxy Adhesive Layer
Authors: Yamura Hiroshi , Matsukawa Mami , Ohtori TakahikoOtani
Published: October 2002

Wave properties (wave velocity and attenuation) in epoxy
adhesive layers during cure were investigated. Longitudinal and shear
wave properties in the GHz region were measured by the Brillouin
scattering technique using 90°A-scattering geometry. The longitudinal
and shear wave properties showed similar changes during cure. Compared
with the ultrasonic wave properties in the MHz region, a clear
frequency dispersion could be seen during cure, in the glass
transition region. It is supposed that this dispersion results from a
strong α relaxation. Longitudinal modulus and shear modulus were also
obtained from the longitudinal and shear wave velocities. The
longitudinal modulus was always proportional to the shear modulus
during the entire curing process.
Optical Wavelength-Separation and Time-Response Characteristics of Collinear Acoustooptic Switches for Wavelength-Division-Multiplexing Photonic Switching Systems
Authors: Nobuo Goto Nobuo Goto , Yasumitsu Miyazaki Yasumitsu Miyazaki
Published: October 2002

Collinear acoustooptic (AO) switches are investigated for use in wavelength-division-multiplexing networks and photonic switching systems. Preliminary experiments of wavelength-selective switching with AO switches consisting of Nb2O5/Ta2O5/proton-exchanged LiNbO3 on LiNbO3 substrates are described. The optical multilayered channel waveguides are formed in a rib structure. The switching characteristics such as extinction ratio and crosstalk are found to strongly depend on the rib height in the branching region. The required conditions of the waveguide parameters are discussed. The wavelength dependence of the switching characteristics is also discussed.
Effect of Fracture Dynamics in Thin Plate on the Waveform and Radiation Pattern of the Lamb Waves
Authors: Sato Teruyoshi , Takemoto Mikio , Ono Kanji
Published: October 2002

Since the acoustic emission (AE) due to fractures in
thin-wall structures is monitored as Lamb waves, advanced
signal analyses are required for evaluation. The present
study aims to estimate the fracture kinematics (crack normal
and displacement discontinuity vectors) in thin plates by
radiation pattern analysis of the zeroth-order symmetric
Lamb waves (S
0-Lamb). We monitored in-plane profiles of
the S
0-amplitudes and polarities produced by six types of
surface and buried Mode-I, II and mixed-mode fractures
simulated with a line pulse laser and slender piezo-elactric
Pb(Zr-Ti)O3 (PZT) elements. The Mode-I fracture showed an
elliptical amplitude profile with the largest amplitude in
the crack-opening direction, while the mixed-mode fracture
as well the Mode-II fracture showed a connected
rugby-ball-shaped pattern, or a two-quadrant profile of
S
0-polarities with the largest amplitude in the displacement
discontinuity direction. The radiation pattern was
demonstrated to be utilizable for estimating the fracture
kinematics. For studying the fracture kinetic or crack
generation velocity, we determined the overall transfer
function of the system by the Gauss-Zeidel deconvolution of
the wave generated by PZT elements whose out-of-plane
displacement was measured using a laser interferometer. The
source dynamics (kinematics and kinetics) of
hydrogen-induced blistering (HIB) in a ferritic steel plate
was estimated by radiation pattern analysis and source
simulation. HIB was found to be caused by surface-normal
cleavage fracture with source rise times from 0.6 to 1.0 µs.
The estimated crack size agreed fairly well with the
postmortem blister size.
Homogeneity Evaluation of LiNbO3 and LiTaO3 Single Crystals for Determining Acoustical Physical Constants
Authors: Izumi Takanaga Izumi Takanaga , Junji Hirohashi Junji Hirohashi , Jun-ichi Kushibiki Jun-ichi Kushibiki
Published: October 2002

The homogeneity of surface acoustic wave (SAW) grade LiNbO3 and LiTaO3 single crystals, which are used to accurately measure acoustical physical constants, is evaluated using several specimens, by measuring the leaky surface acoustic wave (LSAW) velocity, longitudinal velocity, density, lattice constant, and Curie temperature. The specimens are taken perpendicular to the pulling-axis direction of each crystal. The variations of LSAW and longitudinal velocities along the pulling-axis direction are at most 1 m/s, and the corresponding changes of chemical composition ratio are estimated to be about 0.02 Li2O-mol% for both LiNbO3 and LiTaO3 crystals. The evaluation proves that the crystals employed can be regarded as homogeneous within the measurement accuracy, when the effect of the variations in the crystals on the constant determination is investigated.
Broadband Transducers Using Effectively Graded Piezoelectric Plates for Generation of Short-Pulse Ultrasound
Authors: Ken Yamada Ken Yamada , Jun-ichi Sakamura Jun-ichi Sakamura , Kiyoshi Nakamura Kiyoshi Nakamura
Published: October 2002

Broadband ultrasound transducers that utilize piezoelectric materials having an effectively graded piezoelectric parameter and/or an excitation electric field applied across the piezoelectric material are investigated. These transducers are constructed by forming a number of fine V-grooves on one surface of a piezoelectric plate. The broadband frequency characteristic of the proposed transducer is demonstrated by experiments of wave generation in water. Analysis by the finite-element method proves that even-order resonance modes are also excited in the plate with a grooved configuration.
Vibratory Gyro-Sensor Using Vertically Set Quartz Crystal Trident-Type Tuning Fork Resonator
Authors: Shiratori Norihiko , Ohnishi YoshiroTomikawa
Published: October 2002

In this study we deal with a new type of vibratory gyro-sensor using a vertically
set quartz crystal trident-type tuning fork resonator. The sensor is made of X-cut
quartz crystal wafer formed by rotating 2° about the X-axis, applying the wire saw
cutting method. The slits that form three arms are cut along the Y-axis direction. In
such a trident-type tuning fork resonator, two resonance vibration modes are used:
one has vibrational displacement in the vertical direction (X-axis) of the tuning fork
plane and the other has that in the horizontal direction (Z
′-axis). When an angular
rate (Ω
Y
′
) around the Y
′-axis is applied to the trident-type tuning fork gyro-sensor
vibrating in the V-MODE, Coriolis forces, due to the Ω
Y
′
, are applied on the three
arms in the X
′-axis direction and the H-MODE vibration is induced. Therefore, the
angular rate (Ω
Y
′
) can be determined by detecting the signals of H-MODE vibration.
The experimental results have proved that the vibratory gyro-sensor that uses such a
quartz crystal tuning fork resonator has good characteristics.
Quartz-Crystal Tuning-Fork Tactile Sensor
Authors: Itoh Hideaki , Nomura Masataka , Katakura Naoya
Published: October 2002

Sensing behavior of a quartz-crystal tuning-fork tactile sensor
was tested using several types of materials (metals and slide glass)
and several sheets of sandpaper of different roughnesses fixed on
copper or aluminum plates with acrylic resin paste. Sensing
mechanisms on the longitudinal plane wave transmission model are
discussed. For materials with roughnesses in the range of sandpaper
roughnesses, this sensor functions as a simple roughnesses sensor in
a stationary state.
Multilayer Ceramic Resonators using the Piezoelectrically Stiffened Length Mode Vibration
Authors: Inoue Jiro , Unami Toshihiko
Published: October 2002

Multilayer ceramic resonators that utilize the piezoelectrically stiffened length
mode vibration and have a much smaller size than any other vibration mode resonators,
are developed. Characteristics related to the internal and external electrodes such as
bandwidth and capacitance, are analyzed by the finite element method. According to the
results, resonators and ladder filters are investigated and their superior characteristics
are demonstrated.
Analysis of Surface Acoustic Wave Properties of the Rotated Y-cut Langasite Substrate
Authors: Bungo Akihiro , Jian Chunyun , Yamaguchi Kunio , Sawada Yoshihisa , Uda Satoshi , Pisarevsky Yuri P.
Published: October 2002

The propagation characteristics of Rayleigh waves on a Y-rotated
La3Ga5SiO14 (langasite) substrate are evaluated with the use of newly obtained
material constants. The calculated phase velocity, the power flow angle (PFA), the coupling
electromechanical coefficient (K2), the temperature coefficient of delay (TCD) and
the diffraction coefficient (γ) are shown as contour maps. The revised numerical
calculations were in much better agreement with the experimental results of the
temperature characteristics on the langasite substrate with Euler
angle (0°, 140°, φ). Moreover, the temperature characteristics as a function of the metal thickness
were experimentally investigated. It was found that a thicker metal leads to a
lower turnover temperature. Finally, an example of the frequency response of the
transversal filter designed for IS95 is shown.