bluuebunny/crossref_metadata_2025 huggingface dataset:
Steam Laser Cleaning of Plasma-Etch-Induced Polymers from Via Holes
Authors: Lee Yuan Ping , Lu Yong Feng , Chan Daniel S. H. , Low Teck Seng , Zhou Mei Sheng
Published: October 2002

As the wafer industry enters into submicron processes and below, the demand for new
cleaning technology after plasma etching increases. The cleanliness of via holes becomes
very crucial for the success of low-resistance interconnecting high-density ultra-large-scale
integrated devices. In this study, a relatively new approach in removing the sidewall and
bottom polymers resulting from reactive ion etching of via holes, using dry and steam laser
cleaning techniques is investigated. The presence of a layer of isopropanol (IPA) film on the
wafer surface during excimer laser irradiation is found to improve the removal efficiency
greatly even at fluences as low as 80–100 mJ cm-2–much lower than the damage threshold of
the underlying Al–Cu metal film with titanium nitride anti-reflective coating of 250–280 mJ cm-2. The explosive evaporation of IPA and the creation of bubbles at the liquid-substrate
interface were proposed to be the reason for the improvement. Experimental results show
however that the presence of a layer of acetone film does not improve but even impedes the
laser cleaning process. An explanation is offered for this phenomenon in terms of the
difference in the absorbance of the two liquids at the laser wavelength.
Epitaxial Growth of SrF2 on ZnSe(100) Epitaxial Films
Authors: Mohammad Mustafa Sarinanto Mohammad Mustafa Sarinanto , Kazuo Tsutsui Kazuo Tsutsui
Published: October 2002

Epitaxial SrF2 films were grown on ZnSe(100) epitaxial substrates using molecular beam epitaxy (MBE), and their crystallinity dependent on growth temperature was characterized using X-ray diffraction and Rutherford backscattering spectroscopy. SrF2 film with good crystallinity was obtained at the growth temperature of 250°C.
Negative Temperature Coefficient of Electrical Resistivity in B2-Type Ti–Ni Alloys
Authors: Kakeshita Tomoyuki , Fukuda Takashi , Tetsukawa Hiroki , Saburi Toshio , Kindo Koichi , Takeuchi Tetsuya , Honda Makoto , Endo Shoichi , Taniguchi Toshifumi , Miyako Yoshihito
Published: October 2002

A negative temperature coefficient of electrical resistivity (TCR) has been observed in Ti50-XNi50+X(at.%;X=1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5) in the temperature range between 20 and 350 K. The resistivity vs temperature curve has no hysteresis and the relative resistivity at 20 K (ρ20 K/ρ350 K) decreases with increasing Ni content. X-ray diffraction and magnetic susceptibility measurements show that a negative TCR is not caused by structural phase transition nor by magnetic transition. The Debye temperature of Ti48Ni52, obtained from the analysis of specific heat measurements, is quite low (217 K) and its spin relaxation process has a time duration between 400 µs and 20 ms, suggesting that some lattice instability exists. Based on these results, the origin of a negative TCR is discussed.
Application of Extended Finite-Difference Time-Domain Method to Two-Dimensional Dynamic Analysis of a Piezoelectric Vibrator
Authors: Yosihiro Yamada Yosihiro Yamada , Masahiro Sato Masahiro Sato
Published: October 2002

We propose a new algorithm that simulates the dynamic response of a piezoelectric vibrator. We derived this algorithm by incorporating new terms corresponding to the electric fields in the conventional finite-difference time-domain (FD-TD) method for elastodynamics. The FD-TD method, which is widely used to analyze electromagnetic waves or elastodynamics, requires less computation than the finite element method (FEM).
Effects of Annealing in Ar Gas on Ferroelectric Properties of SrBi2Ta2O9 Thin Films
Authors: Ohfuji Shin-ichi , Itsumi Manabu
Published: October 2002

The effects of annealing processes at 700°C in Ar gas, added prior to
the oxidizing processes of SrBi2Ta2O9 (SBT) films at the lowered
temperature of 700°C, are investigated in terms of the ferroelectric
properties of the films. SBT films 200 nm thick were spin-coated on
Pt(200 nm)/Ti(30 nm)/SiO2(200 nm)/Si substrates by using the chemical
liquid deposition method. The annealing was found to be effective in
obtaining a large saturated polarization and a remanent polarization 2P
r of
more than 10 µC/cm2 with leakage current less than 1×10-6 A/cm2 at the
process temperature of 700°C. Structural and compositional analyses
suggest that some Bi atoms in the films become free of oxygen and arrive
at the lattice sites as a result of the annealing in non-oxidizing Ar gas for
periods shorter than 100 s. Consequently, the crystallization of SBT
layered structures may be promoted even at temperatures as low as 700°C.
Computer Simulation of Core Structure of Screw Dislocations in C60 Crystals Using Girifalco Potential
Authors: Shigeru Tamaki Shigeru Tamaki , Naoki Ide Naoki Ide , Isamu Okada Isamu Okada , Kenichi Kojima Kenichi Kojima
Published: October 2002

The equilibrium molecular configuration around a 1/2[101] screw dislocation
in C60 crystals in a fcc phase
was calculated by means of molecular dynamics.
The molecules were assumed to be rigid and
the spherical intermolecular potential derived by Girifalco was utilized.
The dislocation was found to dissociate into
two Shockley partials.
The partial dislocation had a spreadout core and the width of
the Burgers vector density at the half-peak height reached 13 times the magnitude
of the Burgers vector.
Atomic Peening Effect of Ambient Gas on Platinum Films Grown on Amorphous Substrates by Pulsed Laser Deposition
Authors: Koo Tae Yeong , Lee Ki-Bong , Jeong Yoon-Hee , Kang Kwang Yong
Published: October 2002

The effects of substrate temperatures and ambient gas pressures
on the preferred orientation of platinum films deposited on
amorphous SiO2/Si(100) substrates by the pulsed laser deposition
method were studied.
Even at room temperature, platinum films could be grown under
vacuum with (111) preferred orientation.
The increase of substrate temperature to 600°C induced
the additional (100) orientation.
While the presence of ambient oxygen or nitrogen gas suppressed
(111) orientation at room temperature, it had the opposite
effect of enhancing (111) orientation and suppressing (100)
orientation at 600°C.
The effect of ambient gas pressure at high temperatures on the
selective enhancement of platinum film crystallinity on
SiO2 is proposed to be due to the atomic peening effect of
gas molecules.
Gas-Puff Z-Pinch Plasmas Driven by Inductive Energy Storage Pulsed Power Generator
Authors: Murayama Koichi , Shinkai Toshinori , Katsuki Sunao , Akiyama Hidenori
Published: October 2002

An inductive energy storage pulsed power generator is used as a power source of gas-puff
z-pinch plasmas to investigate the effect of the steepened current rise on the intensity of soft X-rays
and the spatial reproducibility of the hot spots. Furthermore, two kinds of electrodes, which are
solid and mesh type, are used to investigate the influence of the incident gas distribution on the z-pinch
plasmas. In the case of the solid electrode, the axial symmetry of the plasma column during
pinching and the spatial reproducibility of the hot spots is improved not only by the steepened
current rise but also the induced pulsed voltage. On the other hand, the improvement in the plasma
column and the reproducibility due to the inductive pulsed power generator is unclear in the case of
mesh electrode. In this experiment, the uniform gas distribution has priority over the current rise
time and the induced pulsed voltage.
Cascade-Like Temporal Evolution of Plasma Discharge by an Electron Beam
Authors: Masao Sugawa Masao Sugawa , Shohei Utsunomiya Shohei Utsunomiya , Shigeru Isobe Shigeru Isobe , Tsunehiro Maehara Tsunehiro Maehara , Reiji Sugaya Reiji Sugaya
Published: October 2002

An electron beam (0.5–1.5 keV, ≤5 mA)
is injected into argon gas (10-4–5 × 10-4 Torr)
in a magnetic field (50–300 G). The discharge via a gas
breakdown occurs cascade-like in time.
Observation of temporal evolutions of
frequency spectra (20 MHz–3.0 GHz) of unstable waves,
as well as the measurements of plasma density and temperature,
indicate that the gas break down
is based on the cyclotron damping of unstable electron
cyclotron harmonic waves in an electron beam-plasma system.
Upgrade of RIKEN 18 GHz Electron Cyclotron Resonance Ion Source Using an Electrode at Floating Potential
Authors: Nakagawa Takahide , Biri Sandor , Kidera Masanori , Miyazawa Yoshitoshi , Hemmi Masatake , Chiba Toshiya , Inabe Naohito , Kase Masayuki , Kageyama Tadashi , Kamigaito Osamu , Goto Akira , Yano Yasushige
Published: October 2002

We have observed the enhancement of the Ar11+ beam intensity from
the RIKEN 18 GHz electron cyclotron resonance ion source (ECRIS) when
using the electrode at the floating potential. We have successfully obtained
the beam intensity of 280 eµA for Ar11+ at an extraction voltage of 15 kV.
Atomic Scale Simulation of Point Defects Diffusion and Reactions Using Transputers
Authors: Djafari-Rouhani Mehdi , Idrissi-Saba Hafida , Gue Anne Marie , Estève Alain , Estève Daniel
Published: October 2002

The diffusion and agglomeration of point defects under high energy electron irradiation have been examined
by the means of parallel computing. The whole process is divided into independent diffusion processes running in
parallel and communications between these processes to represent the reactions. We have calculated the
concentration of point defects and extended defects and the size of the latter, and compared them to the results of the
chemical reaction rate theory and to experimental data. Furthemore, we have shown that under high irradiation rates,
small deviations due to the random nature of the process may, in some circumstances, lead to catastrophic situations
as the result of enhancement of the reactions due to local interactions.
Quantitation of Absorbers in Turbid Media Using Time-Integrated Spectroscopy Based on Microscopic Beer-Lambert Law
Authors: Zhang Hedong , Miwa Mitsuharu , Yamashita Yutaka , Tsuchiya Yutaka
Published: October 2002

Based on the microscopic Beer-Lambert law, two practical time-integrated spectroscopy (TIS)
methods, called dual-wavelength spectroscopy method, and dual-wavelength and dual-site spectroscopy
method, are described to determine the absolute concentration of an absorber in variously shaped turbid
media. We demonstrate, for the first time, the validity of the TIS methods by means of experiments in
which the absolute concentrations of an absorber in a tissue-like phantom were determined with errors less
than several percent. The advantages and disadvantages of both methods are also discussed.
The Influences of Temperature and Residual Gas on the Wettability of Aluminum Melt on Sapphire
Authors: Wu Hsien-Nan Ho
Published: October 2002

The wettability of aluminum melt on sapphire is shown to be sensitive to melt oxidation at liquid-solid interface. The oxidation is controlled by extruding a fresh droplet of liquid metal onto the substrate placed in a vacuum better than 10-6 mbar. The substrate temperature can reach up to 950° C. In the absence of oxidation the contact angle remains constant at 90° when the substrate temperature is lower than 800° C. It decreases to 75° at 850° C.
Trace Heavy Element Analysis Using X-Ray Fluorescence with Quasi Monochromatic High-Energy Photons: Iodine in an Environmental Sample
Authors: Harada Masaaki , Sakurai Kenji
Published: October 2002

X-ray fluorescence with high-energy photon excitation is a
promising method for heavy element analysis. For trace
determination, however, it is necessary to optimize the excitation
spectrum. In this study, quasi monochromatization by a primary-beam filter and by a secondary target is quantitatively studied in
order to detect an important bioelement, iodine, in an environmental
sample. The primary-beam-filter technique gives the lowest
detection limit, which is 1/5th the limit given by white excitation.
Formation of a Negative Photoresist Thin Film by Spin Coating
Authors: Yada Toshio
Published: October 2002

Experimental film formation of a rubber-based negative photoresist
by spin coating relative to that of a diazoquinone sensitized
positive photoresist was investigated. The baked film
produced with the negative photoresist is thinner than that produced
with the positive photoresist in the first stage of the
spinning in spite of the heavy wet weight due to the low solid
content, but becomes thicker in the later stages in spite of the
light wet weight due to the high solid content. The thickness
deviation of the baked film of the negative photoresist is larger
than that of the positive photoresist during the entire spinning
process because the negative photoresist always had a high viscosity
during the spinning process. The solvent evaporation rate
of the negative photoresist is higher than that of the positive
photoresist up to the intermediate stages of the spinning due to
the higher vapour pressure and activity.
Propagating Property of Surface Waves and Viscoelasticity near the Gelation Point
Authors: Hirotaka Okabe Hirotaka Okabe , Keiichi Kuboyama Keiichi Kuboyama , Kazuhiro Hara Kazuhiro Hara , Shoich Kai Shoich Kai
Published: October 2002

We studied the properties of surface waves during the gelation process of tungstic acid gel and gelatin.
The experimental results agreed qualitatively with the known theoretical results of the viscoelastic
model in an equilibrium system except in the vicinity of the gelation point.
Near the sol–gel transition point of tungstic acid gel, we found interesting features in the time
variation of the velocities, namely, the velocities of surface waves had a
maximum near the gelation point, decreased once rapidly, and again
increased gradually as the gelation proceeded.
On the other hand, the velocity of gelatin
just decreased slightly near the gelation point.
The reason for the velocity increase before the gelation point is possibly
caused by the increase of the effective surface tension coupled with the
elasticity of the networks. However, further investigation is necessary to clarify the mechanism of this particular property of tungstic acid gel.
Band Gap of Porous Silicon Estimated by Photoacoustic Spectra
Authors: Toshio Kawahara Toshio Kawahara , Kiyotaka Sato Kiyotaka Sato , Noriko Yamaguchi Noriko Yamaguchi , Jun Morimoto Jun Morimoto , Kenichi Tahira Kenichi Tahira , Toru Miyakawa Toru Miyakawa
Published: October 2002

The conditions under which photoacoustic (PA) measurements of porous Si samples can yield reliable results on the widening of their band gaps are studied.
The enhancement of the PA signals observed from porous Si samples is stronger than those from the powdered ones.
Although this enhancement makes the observation of both the magnitude and phase of the PA signals easy, it also causes an apparent shift in the observed gap of the samples with a thin porous Si layer on the Si substrate.
A simplified two layer model is examined, including the effect of scattering to separate this effect.
The results of the samples with a thicker porous Si layer reveal the real shift of the band gap.
Piezoelectric Sensors Using Rubber Sensing Film
Authors: Hohkawa Kohji , Kaneko Atusi , Koh Keishin , Suzuki Hiroji , Komine Kenji , Eguchi Tomohiro
Published: October 2002

Piezoelectric sensors, consisting of multiple-crystal oscillators or surface acoustic
wave (SAW) devices, are effectively used as highly functional and highly sensitive
chemical sensors which identify unknown or target materials in gasses and liquids. We
present the results of a basic study on applying rubber materials as the sensing films of the
piezoelectric sensors and a simple method of preparing crystals with sensing films of
various characteristics. We verified the feasibility of the materials used as sensing films of
the piezoelectric sensors. We made several films with different adhesive natures by
bonding reactive materials on the surface of the rubber films instead of preparing various
kinds of monomers. We also present the results of the basic characteristics of SAW sensors
with rubber films.
Electromechanical Coupling Coefficients for a New H-Type LiTaO3 Piezoelectric Gyroscope
Authors: Tanaka Hiroshi , Wakatsuki Noboru
Published: October 2002

In this paper, the electromechanical coupling coefficients (k
2) for the piezoelectric gyroscope
are investigated and compared with the experimental data using the finite element method (FEM).
The conventional fork type LiTaO3 piezoelectric gyroscope has an unnecessary k
2 of the driving
electrode to the f

z
mode and the detecting electrode to the f

x
mode, due to asymmetrical electrodes
on the right and left arms. Therefore, we propose a new H-type gyroscope of a driving fork type
resonator and a detecting H-type resonator. The obtained experimental data of the input impedance
of the driving and detecting electrodes of the new H-type sample concurred with the FEM analysis.
Consideration on Temperature Characteristics of Sensitivity in Quartz Tuning Fork Gyroscope
Authors: Kudo Subaru
Published: October 2002

The temperature characteristics of the double resonant frequencies of a
quartz tuning fork gyroscope are analyzed by means of the finite element
method. The temperature characteristics of the sensitivity of the
gyroscope are calculated and the relationships between the variations in
sensitivity and the frequency deviations are considered. The possibility
of quantitative analysis of temperature characteristics of the sensitivity
of gyroscope is shown.
Piezoelectric Resonance Properties of a β Phase Quartz Plate
Authors: Noge Satoru , Uno Takehiko
Published: October 2002

We have previously reported an artificial twinning (x-axis inversion)
technique for rotated Y-cut quartz plates. The twinning is produced by
mechanical stress through a thin metal film deposited on the plate. Such a
twinning phenomenon occurs at a considerably lower temperature than the
α-β transition temperature, T
c, of 573°C. This paper presents the electromechanical properties of quartz at a temperature region higher than
the twinning temperature. Degeneration of the piezoelectric resonances
corresponding to the x-axis inversion area and the non-inversion area are
observed at a temperature between the twinning temperature and T
c. The
elastic stiffness constants c
55 and c
66, estimated from the degeneration mode
resonance frequency, agree with these for the β phase. This suggests that the
α-β transition occurs by the thin metal film at a considerably lower temperature
than T
c of 573°C. An intense piezoelectric response with a high quality
factor above 20,000 is observed from the degeneration temperature to
above 660°C.
10 GHz Range Low-Loss Ladder Type Surface Acoustic Wave Filter
Authors: Hiroyuki Odagawa Hiroyuki Odagawa , Jamil A. Qureshi Jamil A. Qureshi , Toshiyasu Meguro Toshiyasu Meguro , Kazuhiko Yamanouchi Kazuhiko Yamanouchi
Published: October 2002

A low-loss 10 GHz range surface acoustic wave (SAW) filter is investigated. It is fabricated on 128° Y-X LiNbO3 using the electron beam direct writing and lift-off process. The Al electrode with a width of 95 nm and a thickness of 30 nm is obtained successfully. In order to simulate the characteristics of a ladder type filter with an equivalent circuit model, the parameters of an equivalent circuit model for a thick Al film in the 5 GHz range (thickness is 0.08 λ, λ= 0.75 µm, λ is the wavelength of SAW) is determined experimentally. The experimental results of the ladder type filter in the 10 GHz range show low loss characteristics. The minimum insertion loss of 3.7 dB is obtained.
Model for Operation Mechanism of Acoustooptic Modulator with Two Interdigital Transducers
Authors: Michio Ohki Michio Ohki , Kohji Toda Kohji Toda
Published: October 2002

A model for the operation mechanism
of an acoustooptic modulator (AOM)
with two interdigital transducers (IDTs) is
described.
The 1st IDT in the AOM drives an acoustic wave
on a piezoelectric substrate
and the 2nd IDT controls reflection of the wave
and modulation of a light intensity by controlling
an electrical terminal condition at the 2nd IDT.
An acoustooptic (AO) interaction is performed
in a medium in contact with the substrate, using
wave radiation from the substrate to the medium.
An operation model of this AOM assumes the following.
(1) Interference of acoustic waves in the substrate
determines the characteristics of the device,
where a phase of the
reflection is controlled by the 2nd IDT.
(2) Resonance effect inside the IDT makes
the equivalent propagation length of the acoustic wave
longer, which influences the frequency
characteristics of the interference intensity,
accompanied with an amplification of the confined wave.
Heteroepitaxial Growth of CdF2Layers on CaF2/Si(111) by Molecular Beam Epitaxy
Authors: S. Sokolov Akira Izumi
Published: October 2002

The effects of growth temperature and structural perfection of the CaF2buffer layer on the crystallinity of CdF2layers grown on CaF2/Si(111) substrates by molecular beam epitaxy (MBE) were investigated by double-crystal X-ray diffractometry (XRD). The crystal perfection of CdF2layers grown on pseudomorphic CaF2layers was considerably better than that of CdF2layers grown on relaxed CaF2layers. It was shown that epitaxial CdF2films with high structural quality can be grown on the pseudomorphic CaF2layer at growth temperatures as low as 50°C.
Characteristics of Ultrasonic Motors Driven in a Vacuum
Authors: Ishii Takaaki , Matsuo Eiichi , Nakamura Kentaro , Ueha Sadayuki , Ohnishi Kazumasa
Published: October 2002

Ultrasonic motors are driven by the frictional force between a rotor and a stator, and
therefore, the contact surfaces are affected by ambient atmosphere. One example of
severe driving conditions is a vacuum. First, friction materials, carbon fiber
reinforced plastics and carbon metal, which have already been used for ultrasonic
motors driven under atmospheric pressure conditions were tried out under two
different vacuum pressures. Ceramic materials such as Al2O3, Si3N4 and SiC, have
recently been tried out under two different vacuum pressures. The characteristics of
motor, friction and wear such as rotor speed, maximum torque, friction coefficient
and wear height, were measured and the feasibility of using the ultrasonic motor in
vacuum was discussed.
Effect of Pressing Force Applied to a Rotor on Disk-Type Ultrasonic Motor Driven by Self-Oscillation
Authors: Kusakabe Chiharu , Tomikawa Yoshiro , Takahashi Sadayuki , Takano Takehiro
Published: October 2002

In this paper the relationship between the pressing force
applied to a rotor and the rotation characteristic of an
ultrasonic motor driven by self-oscillation are discussed.
The motor used here is an in-phase drive-type ultrasonic
motor using two degenerate bending vibration modes of a disk.
The picking-up electrical signal caused by self-oscillation
is positively fed back into the piezoelectric ceramics for
driving through an operational amplifier and a step-up
transformer. The pressing force applied to a rotor was measured
using a force gauge coupled to the shaft of the ultrasonic
motor. As a result, it was confirmed that the selection of the
picking-up position for the feedback signal is important for a
stable starting and running of the disk-type ultrasonic motor
driven by self-oscillation.
Properties of Ambient Air Aged Thin Porous Silicon
Authors: Chang Sung-Sik , Yoon Sang Ok , Choi Gwang Jin , Kawakami Yoichi , Kurokawa Sue , Sakai Akira
Published: October 2002

Thin porous silicon (PS) exhibits the red and blue luminescence bands without any rapid thermal oxidation. In addition, ambient air aged thin PS displays the increase of blue photoluminescence (PL) band with the reduction of the red PL band. Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) have been performed both on freshly prepared and ambient air aged anodically etched PS samples. STM studies of these samples reveal the porous structure and displays less than 5 nm feature size for visible luminescing samples. STS analysis of freshly prepared PS shows the expected increase in band-gap energy compared with unetched silicon. The ambient air aged PS which exhibits both red and blue PL reveals an electronic structure similar to that obtained from STS.
Control of a Standing Wave Field Using a Line-Focused Transducer for Two-Dimensional Manipulation of Particles
Authors: Kozuka Teruyuki , Tuziuti Toru , Mitome Hideto , Fukuda Toshio
Published: October 2002

Control of the positions of particles using acoustic radiation pressure in water was
studied to develop a noncontact micromanipulation technique. In this paper a method to
transport the particles two-dimensionally using an ultrasonic standing wave field between a line-focused transducer with multiple electrodes and a reflector placed at the focal line is described.
When alumina suspension of mean diameter 16 µm was poured into the standing wave field of
2.1 MHz, the particles were trapped and agglomerated at sound pressure nodes existing at half
wavelength on the sound beam axis near the reflector. Changing the frequency alters the wave-length and hence the interval of agglomeration. Therefore the trapped particles were transported
along the sound beam axis. When the next electrodes were driven, the standing wave field
shifted laterally and the trapped particles moved to the corresponding nodal points. Thus two-dimensional transportation was realized using the line-focused transducer. A sound field
generated by the line-focused transducer was discussed based on numerical calculations to
design an optimum shape of a transducer for manipulation.
Influence of Static Prestress on the Characteristics of Bolt-Clamped Langevin-Type Transducers
Authors: Kazunari Adachi Kazunari Adachi , Isao Ogasawara Isao Ogasawara , Yasutaka Tamura Yasutaka Tamura , Munekazu Makino Munekazu Makino , Naoyoshi Kato Naoyoshi Kato
Published: October 2002

Bolt-clamped Langevin-type transducers (BLTs) are widely used as powerful
vibration sources in high-power ultrasonic applications. In the structure
of a BLT, static compressional prestress is imposed on piezoelectric
ceramic elements by clamping, to compensate for their weakness to tensile
stress. Nevertheless, no report has been made about the clamping effects
on the characteristics of a BLT with a reasonable estimation of the prestress.
Previous works on material property change of piezoelectric ceramics caused
by static compressional stress have always presumed a groundless uniformity of
stress distribution in the objects examined. The authors have investigated
the effects by some experiments and numerical simulations with the use
of the finite-element analysis system to estimate precisely the prestress.
As a result of these experiments, the prestress has been
found to reduce the electromechanical coupling factor of the BLT. Estimation
of the prestress is considered indispensable for designing BLTs, although
the microscopic mechanism of the piezoelectricity reduction is
not yet clarified.
Dependence of Permeability of Semipermeable Membranes on Frequency of Ultrasonic Irradiation
Authors: Yamaguchi Ryoichi , Ohdaira Etsuzo , Masuzawa Nobuyoshi , Ide Masao
Published: October 2002

The use of ultrasonic irradiation to increase the diffusion speed in separation
technologies using semipermeable membranes has been attempted. Such studies
have been carried out around the relatively low frequency of 28 kHz. This paper
reports studies of the frequency dependence of the diffusion speed for ultrasonic
irradiation in the frequency range of 28 kHz to 1 MHz. The diffusion speed was
maximized at 400 kHz, and the increase compared to that at 28 kHz was 42% at a
pressure of 60 kPa.
Ultrasonic Welding of Plastic Pipes Using Torsional Vibration
Authors: Masuzawa Nobuyoshi , Hori Kiichi , Ide Masao
Published: October 2002

In recent years, the application of ultrasonic welding to plastics has become
common. In this paper a method for ultrasonic welding of plastic pipes using torsional
vibrations is reported. In this method torsional vibrations are applied to the welding pipe
from the circumferential direction with horns placed near the welding surface. Static
pressure is independently applied from the vibrations to the welding surface. It was
observed that acrylic resin pipes could be effectively welded by the proposed method.
An Optimization Method for Ultrasonic Beamforming with a Synthetic Aperture
Authors: Ayumu Matani Ayumu Matani , Kunihiro Chihara Kunihiro Chihara
Published: October 2002

Ultrasonic beamforming with a synthetic aperture is widely used in underwater and underground visualizations, but often suffers from visualization results with elliptically symmetric artifacts, due to lack of measurement points or transducers. We propose a newly-developed optimization method for ultrasonic beamforming. The aim of this method is to sharpen the distribution of the point spread function with a limited number of transducers. The characteristic of the point spread function is useful for evaluating the beamforming performance. This optimized beamforming method employs a visualization result by the conventional beamforming method as the initial guess. In the recursive calculation of this optimization method, the initial visualization result is modified by reducing and enhancing the weights of the discretized points in the measurement area. To evaluate this method, we tested it using a computer simulation and an actual measurement experiments, with a limited number of transducers. As the results of the experiments, this method successfully derives a sharp distribution of the point spread function.
A Simplified Elastic Stiffness Estimation of Unidirectional Carbon-Fiber-Reinforced Coupon Using the In-Plane Velocity Anisotropy of Lamb Waves
Authors: Yoshihiro Mizutani Yoshihiro Mizutani , Mikio Takemoto Mikio Takemoto
Published: October 2002

We propose a simplified method for estimating the five elastic stiffnesses of a unidirectional carbon-fiber-reinforced plastic (UD-CFRP) coupon from the velocity anisotropy of laser-excited Lamb waves. This method utilizes the in-plane orientation dependence of the Rayleigh wave velocities which are estimated from the velocity dispersions of the zero-th-order antisymmetric Lamb (A0-Lamb) wave. We estimated the five elastic stiffnesses of UD-CFRP coupons by utilizing the simplex-assisted inverse scheme, and compared the obtained values with those determined by the strain gauge method. The proposed method was found to be
effective for estimating the stiffnesses of anisotropic materials. However, the inverse scheme must be modified to improve the accuracy of measurement of some stiffnesses.
Kinetic Model of Gas Heating of Laser-Produced Plasmas by CO2 Laser in Atmospheric Air
Authors: Takahashi Akihiko , Nishijima Kiyoto
Published: October 2002

A kinetic model was developed for theoretical investigations on laser-induced breakdown and gas heating in an N2/O2 gas mixture. This model calculates particle densities, electron energy, electron rate coefficient, vibrational temperature, gas temperature, and the other plasma parameters. The gas temperature was calculated from the potential differences in all chemical reactions. The analyses were performed for an N2/O2 mixture of 1 atm irradiated with a O2 laser. The results show that the electron density of 1023 m-3 is the threshold of electrical breakdown and gas heating, and that the electron-ion recombination and the collisional de-excitation of vibrationally excited N2(X1Σg
+) have a strong effect on the gas heating.
Longitudinal and Shear Wave Velocities of Gel-Clay Mixtures
Authors: Kimura Masao , Ishikawa Tomotaka , Kawashima Sayuri
Published: October 2002

In this study, the acoustic wave velocities of gel-clay
mixtures and gel-saturated porous media are studied. First the
longitudinal and shear wave velocities of these media are
measured. In the case of gel-diatomite mixture, the
longitudinal wave velocity rapidly decreases, as the diatomite
weight percent increases over 10%. Finally it is found that the
gel-diatomite mixture with the longitudinal wave velocity of
about 250 m/s and the shear wave velocity of about 8 m/s, can be
obtained.
Effects of Mutual Interactions on a Phased Transducer Array
Authors: Tomoki Yokoyama Tomoki Yokoyama , Mitsuru Henmi Mitsuru Henmi , Akio Hasegawa Akio Hasegawa , Toshiaki Kikuchi Toshiaki Kikuchi
Published: October 2002

In the conventional design method of the SONAR array system, variations of the transducer's velocity occur because the acoustic interactions between transducers are not considered. This research was conducted first, to analyze the acoustic interaction effects on the vibration velocity of transducers using an equivalent circuit. Then, we studied the acoustic interaction effects on the amplitude and phase of the velocity, the radiation power outputs and the far-field directivity pattern in the case of a phased array. It is obvious that there have been drastic effects on the radiated field from the phased array operated at the resonance frequency.
Formation of Silicon-Based Thin Films Prepared by Catalytic Chemical Vapor Deposition (Cat-CVD) Method
Authors: Matsumura Hideki
Published: October 2002

This paper is a review of the catalytic chemical vapor deposition (Cat-CVD) method and properties of silicon-based thin films, such as amorphous-silicon (a-Si), polycrystalline-silicon (p-Si) and silicon nitride (SiN
x
) films,
prepared by the Cat-CVD method. In the Cat-CVD method, also known as
the hot-wire CVD (HWCVD) method, deposition gases are decomposed by
catalytic cracking reactions with a heated catalyzer placed near the
substrates, so that films are deposited at low substrate temperatures
around 300°C without any help from the plasma. After explaining the
deposition system and deposition mechanism, the properties of Cat-CVD a-Si, p-Si and SiN
x
films are described and the results are compared with
those obtained by the conventional plasma CVD (PCVD) method. The
superiority of the Cat-CVD method over the PCVD method is demonstrated.
Analysis of Oxygen Evaporation Rate and Dissolution Rate Concerning Czochralski Si Crystal Growth: Effect of Ar Pressure
Authors: Huang Xinming , Saitou Keijirou , Sakai Susumu , Terashima Kazutaka , Hoshikawa Keigo
Published: October 2002

A small sessile drop sample and a small crucible sample were used for
measuring oxygen evaporation rate and dissolution rate. Dependence of the
oxygen evaporation rate (from surface of silicon melt) and dissolution rate
(from silica glass to silicon melt) on Ar pressure from 20 to 3800 Torr was
investigated at different temperatures. The oxygen evaporation rate and
dissolution rate increased monotonically with decreasing Ar pressure, and
increased remarkably with increasing temperature. The relationship between
the oxygen dissolution rate and the interfacial phase of the brownish rings has
also been investigated. The interfacial phase disappeared when the oxygen
dissolution rate was sufficiently high.
Defects in the Oxidation-Induced Stacking Fault Ring Region in Czochralski Silicon Crystal
Authors: Harada Kazuhiro , Tanaka Hideo , Watanabe Toshihiko , Furuya Hisashi
Published: October 2002

We have examined the defects in the oxidation-induced stacking fault (OSF) ring region in the as-grown Czochralski silicon crystals subjected toin situannealing by the halt of pulling during crystal growth using secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM) in order to investigate the nature of OSF nuclei. Oxygen aggregates were observed in the ring region in the crystals held for 4 h and 16 h using SIMS. The aggregate density in the crystal held for 16 h corresponded to the density of the grown-in defects without a flow pattern revealed by non-agitated Secco etching. TEM observation indicated that one of the grown-in defects in the ring region in the crystal held for 4 h was oxygen precipitate with a dislocation loop. OSF density decreased with holding time and density of another defect which was not an OSF increased with holding time in the ring region held at temperatures below about 1060°C. We believe that the OSF nuclei were oxygen precipitates and the dislocation loop was appeared around the precipitate during the halt of pulling process, so that OSF nuclear density was decreased.
Scaling Relations for the Production and Acceleration of a J × B Driven Rotating Plasma
Authors: Takashi Ikehata Takashi Ikehata , Yasuhito Igarashi Yasuhito Igarashi , Naoyuki Sato Naoyuki Sato , Toshio Tanabe Toshio Tanabe , Hiroshi Mase Hiroshi Mase
Published: October 2002

The density and velocities (rotational and axial) of a rotating plasma driven by the J ×B Lorentz force and their parametric dependence on radial current I and axial magnetic field B
z are investigated in ranges of 3–11 kA and 0–3.6 kG, respectively. Results are compared with those from a simplified single-fluid model that describes the motion of an incompressible plasma with uniform density under the existence of ion production by electron-impact ionization and ion loss by convection to electrodes. In the experiment, argon plasmas are produced by the pulsed discharge (28 µs) of a coaxial plasma gun and are accelerated in both the azimuthal and axial directions by J ×B
z and J ×B
θ forces, respectively, where B
θ is induced by I. Typical values of the plasma density n, the rotational frequency ω and the axial velocity v
z are ∼1021 m-3, ≃1 ×106 rad/s and ≃2 ×104 m/s, respectively, at I=9 kA and B
z=3.6 kG. Scaling laws derived from the experiment: n ∝I
2
B
z
0, ω∝I
1
B
z
1
n
-1 and v
z ∝I
2
B
z
0
n
-1, are found to agree well with predictions of the model. As a result, plasma production and acceleration are found to be strongly related to each other.
Rugged Surface Polycrystalline Silicon Film Formed by Rapid Thermal Chemical Vapor Deposition for Dynamic Random Access Memory Stacked Capacitor Aplication
Authors: Lin Mark , Chang Chun Yen , Huang Tiao Yuan , Kuo Uin Jack
Published: October 2002

Polycrystalline silicon films with a rugged surface (rugged poly-Si), deposited by a
single-wafer rapid thermal chemical vapor deposition (RTCVD) system suitable for 12
inch wafer fabrication, are studied and the films have been successfully applied to bottom
storage electrodes for stacked capacitors in dynamic random access memory cells. Our
data show that the rugged poly-Si is actually formed by the nucleation generation on the
amorphous silicon surface and subsequent crystalline growth during the annealing step
following deposition. We also determined that a wide temperature window exists for the
formation of rugged poly-Si (i.e., ±15°C) using RTCVD, which is wider than that using
low pressure chemical vapor deposition (LPCVD) (i.e., ±3°C) and ultra high vacuum
chemical vapor deposition (UHVCVD) (i.e., ±10°C). Stacked capacitors fabricated
using rugged poly-Si and thin silicon oxide/silicon nitride dielectric film show that for a
rugged poly-Si storage electrode with a 60 nm top-layer and 645°C annealing, an
effective surface area of approximately 2.9 times that of a conventional poly-Si film
electrode is obtained.
Γ-X Tunnelling in GaAs/AlAs/GaAs Heterostructure
Authors: Khanin Yurii , Vdovin Evgenii , Novoselov Konstantin , Dubrovskii Yurii , Omling Pär , Carlsson Sven-Bertil
Published: October 2002

Tunnelling, via X-valley related states, is investigated in GaAs/AlAs/GaAs single-barrier structures.
The features in the tunnel current, which are experimentally observed, are associated with resonant
tunnelling through the X-valley AlAs quantum well states derived from the conduction band minima,
both perpendicular (X
x
and X
y
) and parallel (X
z
) to the (100) growth direction and the Si-donor
states linked to the X valley. Tunnelling through the impurity states associated with X
z
and X
x
y

valleys are observed for the first time.
Near-Ohmic Contact of n-GaAs with GaS/GaAs Quasi-Metal-Insulator-Semiconductor Structure
Authors: Okamoto Naoya , Takahashi Tsuyoshi , Tanaka Hitoshi , Takikawa Masahiko
Published: October 2002

We report on the current-voltage (I–V) characteristics of a metal/ultrathin GaS (thickness<100 Å)/n+-GaAs (carrier concentration=2×1018 cm-3) quasi-metal-insulator-semiconductor (QMIS)
structure. The GaS was grown by molecular beam epitaxy (MBE) employing the precursor
tertiarybutyl-galliumsulfide-cubane ([(t-Bu)GaS]4). The I–V characteristics of the QMIS structure
depend on the work function of various metals (Au, Al, Ti). We discovered that a QMIS structure
leads to a reduction of Schottky-barrier height itself. Furthermore, we demonstrated near-ohmic
contact (contact resistivity=3.7×10-3 Ωcm2) for a Ti/97-Å-thick GaS/n+-GaAs QMIS structure.
From the relationship between the semiconductor barrier height and the metal work function, we
determined that Fermi level pinning was almost eliminated by GaS passivation.
Suppression of Effects of Parasitic Metal-Oxide-Semiconductor Field-Effect Transistors on Si Single-Electron Transistors
Authors: Fujiwara Akira , Takahashi Yasuo , Namatsu Hideo , Kurihara Kenji , Murase Katsumi
Published: October 2002

Si single-electron transistors (SETs), which are fabricated in ultrathin Si of a
silicon-on-insulator substrate by pattern-dependent oxidation, are accompanied by
parasitic metal-oxide-semiconductor field-effect transistors (MOSFETs) on both sides of
the SET. While the Si island of a SET is formed by design in a one-dimensional Si wire,
the parasitic MOSFETs are inevitably formed in two-dimensional Si pad layers, between
which the Si wire runs, because the poly-Si gate covers the Si pad layers as well as the Si
island. Electrical characteristics of the device are strongly affected by these parasitic
MOSFETs because of their relatively high resistance or the Coulomb blockade effect due
to multiple islands unintentionally formed in the pad Si layers. We found that backgate
voltage is useful for reducing or analyzing such parasitic effects. We propose a new
fabrication technique; the use of a SiN mask for oxidation avoids unnecessary thinning of
pad Si layers and parasitic effects can be suppressed.
Annealing Behavior of Deep Trap Level in p-GaTe
Authors: Shigetomi Shigeru , Ikari Tetsuo , Nakashima Hiroshi
Published: October 2002

The deep levels in GaTe single crystal have been
investigated by deep-level transient spectroscopy measurements.
The hole-trapping level is detected at 0.8 eV above the valence
band. It is found that the deep level is associated with the
defect or defect complex and the concentration increases with
increasing annealing temperature.
YBa2Cu3O7-z/Pr0.5Ca0.5MnO3-y/YBa2Cu3O7-z Sandwich Type Josephson Junctions
Authors: Sakai Joe , Hioki Jun-ichi , Ohnishi Takaaki , Yamaguchi Toru , Imai Syozo
Published: October 2002

YBa2Cu3O7-z
/Pr0.5Ca0.5MnO3-y
/YBa2Cu3O7-z
sandwich type junctions
are fabricated using pulsed laser deposition and photolithography processes.
Clear Shapiro steps are observed under microwave irradiation. Along with the
magnetic field response, the results prove the existence of a Josephson effect at
this junction. A superconductor-insulator-superconductor (S-I-S)-like
transfer process is suggested from the temperature dependence of I
c and R
n.
Dry Etch Process in Magnetic Neutral Loop Discharge Plasma
Authors: Chen Wei , Itoh Masahiro , Hayashi Toshio , Uchida Tajiro
Published: October 2002

Magnetic neutral loop discharge (NLD) plasma, which has attractive characteristics in terms of plasma production and spatial controllability, was successfully applied to a high-rate etch process with satisfactory uniformity. In the application to the SiO2 etch process, an etch rate of about 1 µm/min was obtained with C4F8 gas pressure of 0.4 Pa, and the uniformity was better than 3% for the 6-inch wafer. A highly selective process was achieved by mixing C4F8 with H2. At a gas flow ratio of H2/(H2+C4F8)×100=65%, the obtained selectivity of SiO2/Si was higher than 100 and the etch rate of SiO2 was sustained on the order of 800 nm/min, where 13.6 MHz rf power was supplied in the continuous wave (CW) mode.
Electronic Structures and Optical Properties of GeTe and Ge 2Sb 2Te 5
Authors: Yamanaka Shozo , Ogawa Shuichiro , Morimoto Isao , Ueshima Yasuhiro
Published: October 2002

The optical properties of GeTe and Ge2Sb2Te5 have been studied by means of the
density functional theory (DFT) in the local density approximation (LDA). The
electronic band structures were obtained by two methods, the plane wave (PW) and
spherical wave (SW) expansions of the wave functions. GeTe was calculated to be
semiconductive, and Ge2Sb2Te5 to be semimetallic. The frequency dependent optical
constants such as refractive index and extinction coefficient were calculated and
compared with those obtained experimentally. The origin of the peaks in the extinction
coefficient spectra was assigned in terms of the transitions between Ge, Sb and Te p
states. Dynamical calculations with respect to Ge2Sb2Te5 have also been performed in
order to obtain an understanding of its structural features. The displacements of the
Te atoms were found to be larger than those of the Ge and Sb atoms.
Magnetic Field Effect on Laser Isotope Separation Based on Polarization Selection Rules
Authors: Niki Hideaki , Kitazima Iwao , Izawa Yasukazu
Published: October 2002

Excitation dynamics of atoms by linearly polarized lasers were analyzed for
J=2→2→1→0 multistep transition under a magnetic field. The time evolution of
the population in each magnetic substate was calculated by solving the rate
equations under the condition where the atomic alignment is gradually destroyed
by the precession motion of the angular momentum around the magnetic field.
Isotopic selectivity in the laser isotope separation based on the polarization
selection rules was discussed. It has been found that a relatively small
magnetic field may cause a degradation of selectivity in the case of Gd and the
magnetic field should be kept as small as the terrestrial magnetic field when
the laser polarization is perpendicular to the magnetic field.
Effects of the Annealing Temperature and CdCl2 Treatment on the Photovoltaic Properties of the CdS/CdTe Solar Cell
Authors: Lee Jae-Hyung , textscLee Ho-Yeol , Park Yong-Kwan , Shin Sung-Ho , Park Kwang-Ja
Published: October 2002

Effects of the annealing temperature and CdCl2 treatment of CdTe films prepared by vacuum evaporation
on structural properties of the CdTe films and photovoltaic properties of thin film CdS/CdTe solar
cells were investigated. The crystal structure of as-deposited CdTe films was zincblende type with
preferential orientation of the (111) plane parallel to the substrate. The preferential orientation
of the (111) plane in CdTe films decreased, and the grain size of CdTe films increased with the increase
of the annealing temperature and the CdCl2 treatment. As increasing annealing temperature, the
conversion efficiency of the CdS/CdTe solar cells without and with CdCl2 was increased due to increasing grain size and improving crystalline of CdTe films. However, the efficiency of cells annealed
at the temperature of higher than 500°C for cells without CdCl2 treatment and 450°C for cells with CdCl2
treatment was reduced because of increasing reverse saturation current density and series resistance.
Dielectric and Conduction Properties in Nickel Doped Barium Strontium Titanate Ceramics
Authors: Hafid Mustapsha , Moudden Souhaila , Proust Chantal , Husson Elisabeth , Takeoka Shinsuke , Nishida Sousuke , Fukami Tatsuo , Sheng Jianxin
Published: October 2002

Electrical properties of defect structure in Ni-doped (Ba1-x
Srx)TiO3 ceramics were studied by means of electron spin resonance (ESR), thermally stimulated current (TSC), dielectric and conduction measurements. A set of experimental results revealed that the nickel cations were located on the B-site of the perovskite in the form of Ni2+ and mainly Ni3+ leading to a slight increase of the diffusion characteristics of the para-ferroelectric transition and that the enhanced electric conduction observed at high temperatures is due to oxygen vacancy migration towards the cathode.