bluuebunny/crossref_metadata_2025 huggingface dataset:
Compact Disk/Digital Video Disk(CD/DVD)-Compatible Optical Pickup Actuator for High Density and High Speed
Authors: Choi In-Ho , Chung Won-Eull , Kim Young-Joong , Eom In-Seop , Park Ho-Man , Kim Jin-Yong
Published: October 2002

An optical pickup actuator is an objective lens moving mechanism
that provides a means to accurately follow the disk displacement.
Recently, since drive speed and physical density of the optical
disc have become higher, better performance and higher precision
are required of the actuator.
Moreover, small and thin design has become desirable.
In addition, a compact disk/digital video disk
(CD/DVD)-compatible pickup may require different actuator design.
In this paper, we introduce an optimal design method that complies with
these requirements.
Sample actuators are made with optimally designed parameters.
The performance of the samples is evaluated and compared with simulated data.
The results prove the effectiveness and validity of the proposed method.
We expect them to be used in CD/DVD-compatible pickups.
Electron Cyclotron Resonance (ECR) Sputtered Antireflection Coatings on Laser Facets for Optical Memory Applications
Authors: Kim Young-Joo , Tateno Ryo , Ikura Tomowo , Matsuda Keita , Kawai Hideki , Suzuki Masahiko , Goto Kenya
Published: October 2002

Antireflection (AR) layer coated semiconductor laser diodes may have many applications,
particularly as external cavity diodes for optical memory heads. The electron cyclotron
resonance (ECR) sputtering system was used for preparing AR coatings which consist of both
SiO2 and Si3N4 phases. The refractive index and the thickness of the AR coatings were adjusted
by controlling numerous deposition parameters, including the relative flow ratio of O2 and N2
gas flow, the total gas flow rate, the RF and ECR power, and the deposition time. AR coated
AlGaAs laser diodes do not show a sharp threshold in the light output-current characteristic
curve and have good potential for application in the lensless optical floppy systems.
A Study of Asymmetry Compensation for Partial-Response Maximum-Likelihood Detection in Optical Recording Media
Authors: Masaki Kagawa Masaki Kagawa , Jun Nakano Jun Nakano , Toru Abiko Toru Abiko , Shuichi Igarashi Shuichi Igarashi
Published: October 2002

The partial-response maximum-likelihood (PRML) detection technique is effective for high-density recording media. In the field of magnetooptical recording media, it is mainly adopted in a magnetic field modulation recording system. For a light intensity modulation (LIM) recording system, however, signal asymmetry caused by the deviation from the optimum recording conditions easily deteriorates the PRML detection procedure. In this paper, we propose an “adaptive reference level technique”, which can greatly improve the write power tolerance. It is expected to suppress the influence of the signal asymmetry in the LIM recording system.
Donor Neutralization by Fluorine Containing Plasmas in Si-Doped n-Type GaAs Crystals
Authors: Wada Jun , Matsukura Yusuke , Ogihara Toshihiro , Furukawa Yukihiko , Tanaka Hitoshi
Published: October 2002

CF4, SF6 and CF4/O2 plasma-induced damage in silicon-doped n-type GaAs
crystals have been investigated by using Hall measurements, X-ray Photoelectron
Spectroscopy (XPS) analysis and Secondary Ion Mass Spectrometry (SIMS) analysis.
We observed that the carrier density degraded after plasma exposure and post
annealing. The degree of deactivation of carrier density with post annealing was
strongly dependent on the plasma chemistries and the self-bias Vdc of the plasmas.
From SIMS analysis, fluorine contamination was observed in the surface region of
GaAs crystals after CF4 plasma exposure. The internal diffusion of fluorine atoms
and the localization of fluorine atoms in n-type GaAs layers were observed after post
annealing at 400°C. From these results, we proposed a mechanism of plasma
induced damage in which internally diffused fluorine atoms neutralize the donor
silicon by forming a Si–F bond. We also evaluated the effective diffusion coefficient of
fluorine in GaAs as 1.5×10-11 cm2/s (at 400°C).
Crystallization and Conduction Mechanisms on Amorphous PbTiO3
Authors: Hyun Kim Seong , Gyu Chae Byung , Suk Yang Yong , Jae Lee Su , Pil Kim Jong , Takashige Masaaki , Su Jang Min
Published: October 2002

Glass system ofxPbTiO3–(100-x)B2O3(x= 50, 70, 80) was produced by twin-roller quenching method. Glass transition temperatures were 541.3°C, 440.0°C, and 467.8°C for thex=80, 70, and 50, respectively with heating rate of 10°C/min. Crystallization temperatures(activation energies) were 517.5°C (4.10 eV), 526.5°C (3.72 eV), 547.2°C (3.79 eV), and 557.5°C (3.97 eV), for the samples ofx=80,x=70, 1st crystallization ofx=50, and 2nd crystallization ofx=50, respectively. It was revealed that this sample crystallized two-dimensionally analyzed by modified Ozawa method. From the X-ray diffraction experiments of heat-treated samples ofx=70, the PbTiO3crystalline did not form a tetragonal phase right after crystallization temperature but a cubic phase. By further annealing the PbTiO3crystalline became a tetragonal ferroelectrics. From the temperature- and frequency-dependence of dielectric constants, it was revealed that two conduction mechanisms are responsible for the dielectric response, and the transition frequency was thermally activated. The activation energies above and below the crystallization temperature are 1.1 and 0.7 eV, respectively.
Enhancement of Mask Selectivity in SiO2 Etching with a Phase-Controlled Pulsed Inductively Coupled Plasma
Authors: Shin Kyoung Sub , Chi Kyeong Koo , Kang Chang Jin , Jung Chul , Jung Chan Ouk , Moon Joo Tae , Lee Moon Yong
Published: October 2002

We developed a new method to enhace the photoresist selectivity in SiO2 etching by
modulating both the source and bias powers and by controlling the phase difference between the
modulation functions. Enhancement of mask selectivity was observed in the pulse plasma,
especially in the out-phase condition. To understand the heavy polymerization in the out-phase
pulse plasma, we analyzed the ion energy distributions of CF
x

+(x=1, 2, 3) ions using the
energy-spectroscopic quadrupole mass spectrometer (QMS) and measured the waveforms of the bias
power with a high-voltage probe which was connected directly to the wafer. Two distinct
plasma potential distributions were obtained in the pulse plasma and the dc bias voltage (V
DC)
was maximum in the out-phase condition. The heavy polymerization in the out-phase condition
was explained as a result of high V
DC. We also investigated the emission intensity of the C2
(516.5 nm) line, and found that C2 species were precursors of the polymerization and
contributed to the heavy polymerization in the out-phase condition.
Structural Analysis for Water Absorption of SiOF Films Prepared by High-Density-Plasma Chemical Vapor Deposition
Authors: Tamura Takahiro , Sakai Junro , Inoue Yoichi , Satoh Makoto , Yoshitaka Hikaru
Published: October 2002

Fluorine-doped silicon oxide (SiOF) films, prepared by high-density-plasma
chemical vapor deposition, are investigated as to the effect of bond structure on
water absorption. In this investigation, two kinds of SiOF films, containing 12%
and 8% fluorine atoms, were compared with regard to the change in their bond
structure before and after accelerated water absorption. Fourier transform
infrared (FT-IR) spectra, thermal desorption mass spectroscopy (TDS) spectra
and Raman spectra studies clarified the following. (1) The SiOF film which
contains 12% fluorine atoms has more Si–F bonds than that containing 8%
fluorine atoms, but it has fewer 3-fold rings. (2) The SiOF film which contains 8%
fluorine atoms absorbs little water, and its Si–F bond does not change after
water absorption. (3) The 3-fold ring of the SiOF film which contains 12%
fluorine atoms has an unstable F–Si–O–Si bond structure. (4) The F–Si–O–Si bond
structure of the 3-fold ring is easily changed to the F–Si–OH and Si–OH bond
structures due to hydration, upon water absorption.
Nitrogen Effusion and Self-Diffusion in Ga14N/Ga15N Isotope Heterostructures
Authors: Ambacher Oliver , Freudenberg Frank , Dimitrov Roman , Angerer Helmut , Stutzmann Martin
Published: October 2002

Ga14N/Ga15N/Ga14N isotope heterostructures are used to study nitrogen self-diffusion
by secondary-ion mass spectrometry and thermally activated decomposition.
After interdiffusion of Ga14N and Ga15N layers at temperatures between 770°C and
970°C the diffusion profiles are measured. The isotope heterostructures are particularly
well suited for self-diffusion studies because the diffusion takes place at the interface inside
the GaN crystal, and therefore the analysis is free from perturbations such as surface
electric fields, mechanical stress or chemical potential gradients. The temperature
dependence of the nitrogen self-diffusion coefficient (D) in hexagonal GaN was determined
to be 1600 cm-2 s-1 exp [(-4.1±0.4) eV/k
B
T], leading to a self-diffusion entropy
S
SD of about 10k
B. The nitrogen flux through an isotope interface is compared with the
nitrogen loss from a free GaN surface in vacuum above the decomposition temperature,
to obtain information about the diffusion kinetics relevant for epitaxial growth and high
temperature device applications.
Characteristics of Self-Assembled InSb Dots Grown on (100) AlGaSb by Molecular Beam Epitaxy
Authors: Yano Mitsuaki , Seki Yoshitaka , Ohkawa Hiroyuki , Koike Kazuto , Sasa Shigehiko , Inoue Masataka
Published: October 2002

A self-assembling method to produce dense InSb quantum dots on
Al0.5Ga0.5Sb is reported. Samples were grown on (100)-oriented GaAs substrates by
molecular beam epitaxy and characterized by reflection high-energy electron diffraction,
atomic force microscopy, Raman spectroscopy and photoluminescence. Low-temperature
deposition of InSb combined with an in situ post annealing resulted in
small-sized three-dimensional islands as high as 1010 cm-2 acting as quantum dots,
while deposition at 400°C yielded much larger sized islands at low density. It is also
shown that the density and size of the islands are controllable by changing the
annealing conditions.
Laser-Induced Enhancement of Electron-Tunneling via an Excited State in an Asymmetric Coupled-Quantum-Well
Authors: Tsukada Noriaki , Gotoda Mitsunobu , Isu Toshiro , Nunoshita Masahiro , Nishino Taneo
Published: October 2002

Dynamical suppression and enhancement of electron tunneling in an asymmetric coupled-quantum-well
is predicted to occur when a laser field induces a photon-mediated resonant
tunneling between a ground state and an excited state.
Magnetic Anisotropy of Y2Co7B3 Compound
Authors: Maruyama Fumio , Nagai Hiroyuki , Amako Yasushi , Yoshie Hiroshi , Adachi Kengo
Published: October 2002

In order to study the contribution of the Co-sublattice to the magnetic anisotropy of Y2Co7B3, the 59Co NMR of R2Co7B3 (R=Y
and Nd) has been carried out at 4.2 K. The local anisotropy energy
per Co atom for Y2Co7B3 is calculated. The Co atoms at the 2c and 6i
1 sites contribute to the axial and planar anisotropies, respectively,
resulting in the axial anisotropy for Y2Co7B3.
Crystallization Time and High Resolution Electron Microscope Lattice Images of Phase Change Optical Discs Dynamically Laser-Annealed
Authors: Cho B. I. , Hong H. C. , Gill B. L.
Published: October 2002

It was demonstrated that a dynamic laser-annealing system (DLAS) could be
used for obtaining the crystallization time (t
x) for the phase change optical discs. In the DLAS,
the laser beams are irradiated onto the discs which are rotating at variable linear velocity (V)
with variable power. The measured crystallization time (t
x) for the disc ZnS–SiO2/Ge2Sb2.5Te5/ZnS–SiO2/Al–Ti (disc A) monotonously decreased from 480 ns to 206 ns as the laser power
increased from 300 mW to 900 mW. t
x for Ge2Sb2Te5/ZnS–SiO2 (disc B) more sharply reduced
from 400 ns to 200 ns than that for the disc A as the power increased from 200 mW to 400 mW. In the case of the disc B, t
x was determined to be 50 ns at an extrapolated 570 mW. The high resolution electron microscope (HREM) of the cross sectional lattice image revealed
that the dominant crystallized phase in the active Ge2Sb2Te5 layer was the stoichiometric GeTe.
The measured inter-planar spacing of 0.298 nm corresponded to the (202) plane. The Kink
bands and edge dislocations were also observed in the crystallized active layer. This was
attributed to the thermal stress due to the thermal expansion difference between the active layer
and the dielectric layer.
Effects of Cd-substitution Site on PbO Evaporation in Pb(Ni1/3Nb2/3)O3–PbZrO3–PbTiO3 Ceramics
Authors: Chung Hoon-Taek , Cho Jeong-Ho , Kim Ho-Gi
Published: October 2002

The effects of Cd2+ substitution site on PbO evaporation was investigated in
Pb(Ni1/3Nb2/3)O3–PbZrO3–PbTiO3 (PNN–PZ–PT) ceramics. Generally no vacancy change is
observed with substitution of the same charge valence ion. But in this case it was
found that Vpb vacancy could be created or annihilated by replacing of the same charge
valence ion due to the incomplete substitution. PbO evaporation was influenced by this
incomplete substitution. In case of A-site substituted sample PbO activity decreased due
to the increase of VA-site(Pb)
′′, and PbO was condensed from the atmosphere powder into
the sample, and in B-site substituted sample PbO activity increased, and the promotion
of PbO evaporation occurred.
Structure Modulation of Al0.5In0.5P Studied by Energy-Filtered Electron Diffraction and High-Resolution Electron Microscopy
Authors: Shindo Daisuke , Konno Yuichi , Lim Sung-Hwan , Gomyo Akiko
Published: October 2002

Structure modulation of a III–V alloy semiconductor Al0.5In0.5P was investigated by
electron diffraction and high-resolution electron microscopy (HREM). By utilizing an
energy filter, the background of the electron diffraction patterns was markedly reduced
and two types of the diffuse scattering were clearly revealed. One type of diffuse
scattering is situated at the midpoint of the fundamental reflections while the other type is
situated around the fundamental reflections. From the analysis of the HREM image, the
structure modulation is interpreted to result from the ordering and the concentration
modulation of Al and In. Furthermore, a structure model of Al0.5In0.5P is derived from the
HREM image, and diffraction intensity calculated based on the structure model shows
good agreement with the observed intensity.
Optical and Structural Quality of GaAs Epilayers from Gallium, Bismuth Mixed Solvents by Liquid Phase Epitaxy
Authors: Saravanan Shanmugam , Jeganathan Kulandaivel , Arokiaraj Jesudoss , Baskar Krishnan , Ramasamy Perumal , Jimbo Takashi , Soga Tetsuo , Umeno Masayoshi
Published: October 2002

Liquid phase epitaxy (LPE) of GaAs epilayers grown at 645°C was studied for different
Bi compositions in Ga solvent . Mixed solvents such as Ga+Bi were used to improve GaAs
epilayer quality. The grown layers were characterized by photoluminescence (PL) and etch pit
density (EPD) measurements. The Bi composition was varied from 0 to 100% in Ga. Good
quality epilayers were obtained for 100% Bi composition. PL investigations revealed that the
epilayer grown using equal atomic percentage of Ga and Bi had good crystallinity, which is
comparable with the 100%-Ga-grown epilayer. The PL measurements reveal that carbon
inclusion in the epilayer grown using 50% Ga and 50% Bi solution is comparably less than other
solvent compositions. The EPD was reduced to more than half order of magnitude when the
solvent was changed from Ga to Bi. The EPD results of epilayers grown using mixed solvents
are reported for the first time. The EPD of the GaAs epilayer grown using 50% Ga and 50% Bi
solution is markedly reduced compared to the other Ga+Bi mixed solvents, and it is almost
equal to the EPD of 100%-Bi-grown epilayers.
Observation of a Fringe Locking Phenomenon in a Self-Feedback Laser Diode Interferometer
Authors: Liu Jiyuan , Yamaguchi Ichirou
Published: October 2002

A fringe locking phenomenon in a two beam-laser diode interferometer with optical
feedback is observed. If a fraction of at least 0.1% of the laser diode output power is
returned to it, the fringes are locked even in the presence of the vibrations of an
interferometer mirror with an amplitude of two wavelengths and this locking can also be
maintained for mirror displacements over 20 mm. Dependence of the fringe phase
fluctuation on the frequency of vibration and the optical path differences of the
interferometer are experimentally studied. A theoretical model based on the equivalent
Fabry-Perot cavity for the laser diode interferometer is proposed and shows good
agreement with experimental results.
Barrier Metal Properties of Amorphous Tantalum Nitride Thin Films between Platinum and Silicon deposited using Remote Plasma Metal Organic Chemical Vapor Method
Authors: Han Chang-Hee , Cho Kwang-Nam , Oh Jae-Eung , Paek Su-Hyoun , Park Chang-Soo , Lee Sang-In , Lee Moon Yong , Lee Jong Gil
Published: October 2002

Amorphous TaN thin films have been prepared by remote plasma-assisted metal organic chemical vapor deposition using pentakis-dimethyl-amino-tantalum (PDMATa)
in hydrogen plasma. The dependence of film properties such as resistivity, impurity contents, and microstructures on deposition conditions is reported. All obtained
films have been tested as diffusion barriers between platinum and silicon in a stacked-capacitor type memory cell for future, high-density ferroelectric memories.
X-ray photoelectron spectroscopy (XPS) has been used to determine the nature of carbon incorporation into the film, which is responsible for the observed microstructure
of the deposited film. Recrystallization occurs at an annealing temperatures of 1000°C in an oxygen-containing (10%) ambient,
showing (111) TaN, [bcc] Ta, and orthorhombic Ta2O5. It was determined that a TaN barrier layer can be successfully applied as a barrier layer between platinum and silicon (700°C for 30 min in
an oxygen-containing ambient), preventing the silicidation reaction of silicon with a Pt electrode as well as the oxidation of the underlying capacitor electrode during the capacitor formation process.
Melting Induced by Epitaxial Stress
Authors: Bottomley D. J.
Published: October 2002

Unprecedented phenomena observed in the epitaxial growth of certain zincblende structure III–V compounds in the past several years are accounted for on the basis of the melting of the epitaxial layer due to the large magnitude of the epitaxial strain (3.2% to 7.3%). The cases considered include InSb on InAs, GaSb on GaAs, InAs on GaAs and InAs on InP. The molar Gibbs free energy of the stress-free liquid phase is compared with that of the stressed solid film. Melting is predicted for temperatures hundreds of degrees Kelvin lower than the atmospheric pressure melting point. The resulting molten material is an epitaxially stabilized supercooled liquid.
Size Control of CdS Quantum-confined Ultrafine Particles by Photocatalytic Polymer Coating
Authors: Hayashi Toyoharu , Mizuma Hirokazu , Yao Hiroshi , Takahara Shigeru
Published: October 2002

CdS quantum-confined ultrafine particles (Q-ufp) were prepared in colloidal solutions in
the presence of styrene monomer under photoirradiation. By means of transmission
electron microscopy analysis, it has been experimentally verified for the first time that
the prepared CdS Q-ufp were coated with polystyrene layer, and the particle size
distribution was controlled by selecting the wavelength of the irradiating laser light:
shorter wavelength light irradiation gave smaller CdS Q-ufp. A mechanism for particle
size control through photocatalytic polymer coating is discussed to explain the
experimental results; the particle size distribution or corresponding UV-vis absorption
spectra were simulated using the proposed model. As a result, the oxidation potential of
styrene monomer, relative to the highest occupied molecular orbital (HOMO) or the top of
the valence band of CdS Q-ufp which depends on the particle size, is important for
electron transfer necessary for initiating the polymer coating process.
Characteristics of the Species Ablated from Silicon Surface by Pulsed CO2 Laser Irradiation
Authors: H. Ogata Tetsuo Sakka
Published: October 2002

Laser ablation of silicon surfaces with various dopant concentrations is studied by the irradiation of pulsed CO2 laser. Silicon ions with the charge ranging from 1 to 4 au are observed in the emitted species. The fraction of the multiple charged ions increases with an increasing dopant concentration. The kinetic energy of Si ions, determined by the time-of-flight measurement, extends up to ∼300 eV, and is almost independent of the dopant concentration. The results can be explained by a positive charging of the irradiated spot during the laser irradiation.
The Correlation between an Electric Field and the Metastable Chlorine Ion Density Distributions in an Ultrahigh-Frequency Plasma
Authors: Toshiki Nakano Toshiki Nakano , Seiji Samukawa Seiji Samukawa
Published: October 2002

The electric field strength in an ultrahigh-frequency (UHF) plasma,
as well as in an inductively coupled plasma (ICP), is measured with an
electrostatic probe as a function of the radial and azimuthal positions
of the plasma reactor. On comparing the electric field distribution
with the radial density profile of metastable chlorine ions measured
by Doppler-shifted laser-induced fluorescence, the electric field
distribution is determined to be positively correlated to the
ionization rate distribution in the UHF plasma, while that in the
ICP seems to be less dependent on the electric field distribution.
This phenomenon probably arises due to the large difference in
the discharge frequency between the UHF plasma and the ICP.
No remarkable azimuthal dependence of the radial average
velocity and the temperature of the metastable Cl+ is
observed, indicating that the two-dimensionally uniform plasma
is produced by UHF power through a spokewise antenna.
Average Value Method: A New Approach to Practical Optical Computed Tomography for a Turbid Medium Such as Human Tissue
Authors: Ueda Yukio , Ohta Kazuyoshi , Oda Motoki , Miwa Mitsuharu , Yamashita Yutaka , Tsuchiya Yutaka
Published: October 2002

We propose a new algorithm for optical computed tomography to determine the
concentrations of absorber in turbid media such as human tissue. Our method does not
require the measurement of a reference phantom, so that it is free from significant
errors caused by geometric and structural differences between the target and reference
media. We use an imaginary reference medium for which the optical properties are
specified by the average or quasi-average values measured for the real target medium.
Since we can calculate the weight function and re-emission for such an imaginary
medium, tomographic images can be reconstructed based on the difference in values
measured for the target medium and determined for the imaginary reference. The
validity of our method was confirmed by measuring an 80-mm-diameter cylindrical,
tissue-like phantom containing three different absorbers. The image quality such as
image distortion and the capability for quantifying the concentrations of absorber are
also discussed.
Optimized Structures of Multilayer Soft X-Ray Reflectors in the Spectral Range of 30 to 300 Å
Authors: Dong-Eon Kim Dong-Eon Kim , Dong-Ho Cha Dong-Ho Cha , Sang-Won Lee Sang-Won Lee
Published: October 2002

For wavelengths in the spectral range of 30 to 300 Å,
the structures of multilayer (ML) soft X-ray reflectors for maximum reflectivity
at normal incidence were optimized. A dynamical theory
of X-ray scattering was employed in the calculation for ideal ML
structures. The calculation indicates that the optimization should be performed for a sufficiently large number
of bilayers. The structural parameters optimized for a small number of bilayers do not yield the best
performance. It is also observed that for a given number of bilayers, there exists a range of
structural parameters for equivalent performance. In the spectral
region considered, the maximum
reflectivities vary from 40 to 78% with respect to wavelength.
Feasible Conditions for Magnetostatic Wave Solitons
Authors: Lihong Li Lihong Li , Ken'ichiro Yashiro Ken'ichiro Yashiro , Sumio Ohkawa Sumio Ohkawa
Published: October 2002

Feasible conditions for magnetostatic wave envelope (MSWE)
soliton formation and propagation
have been discussed by quantitatively investigating
the decay features of MSWE solitons.
A normalized model equation has been derived from
the nonlinear Schrödinger equation
to analyze the decay features of MSWE solitons in detail.
With the normalized model equation, a numerical study on
the amplitude decay characteristics of MSWE solitons
and the broadening properties of
their full-width at half maximum (FWHM) has been performed.
The amplitude decay rate
of MSWE wave packets has been found to be
dependent on the input power level, so is
the broadening rate of their FWHM, and it should be emphasized that
the increase of input power has further been proved to have an effect
on the damping of MSWE solitons
which is equivalent to the decrease of loss.
Computer Experiments on Collisions of Solitons with Defects in Two-Dimensional Model Crystals
Authors: Tanaka Hideki , Ozawa Satoru , Hiki Yosio
Published: October 2002

Molecular dynamics computer simulation has been performed in order
to excite solitons in the two-dimensional mass-spring square-lattice
model crystals. Central forces were considered between the nearest
neighbor atoms in the crystal, and a lattice anharmonic potential up to
the fourth order was taken into account. An input pulse displacement was
given to the atomic rows in the crystal and the displacements of all the
atoms were computed. When the applied input pulse was large, multiple
solitons were produced. Collisions of the solitons with homogeneous and
inhomogeneous rows of mass defects were simulated in order to investigate
the characteristics of the defect-soliton interaction in the two-dimensional crystal. Collisions of solitons and phonons with a single
mass defect were also simulated in order to investigate the differences
in the characteristics of the two kinds of excitations.
Simulation of Viscoelastic Effects of Polymer Coatings on Surface Acoustic Wave Gas Sensor under Consideration of Film Thickness
Authors: Jun Kondoh Jun Kondoh , Showko Shiokawa Showko Shiokawa , Michael Rapp Michael Rapp , Stefan Stier Stefan Stier
Published: October 2002

In this paper an analysis of the responses of surface acoustic wave (SAW)
sensors coated with polymer films is described. Complex bulk and shear moduli are
utilized to represent viscoelastic properties of the polymer. Compared with the
experimental results, the calculated results strongly suggest that the real
part of the shear modulus mostly influences the velocity shift and attenuation
change in the sensor responses. In addition, using the real parts of the shear
modulus, the polymer films can be classified into three types: glassy films,
glassy-rubbery films and rubbery films. Simulations of gas sorption for
polymer films are performed. For glassy films, the SAW sensor response increases
with increasing film thickness, whereas for glassy-rubbery and rubbery films,
the relationship between the sensor sensitivity and film thickness is more
complicated. Therefore, an optimization of the properties and thickness of
films and the operating frequency is required for designing SAW gas sensors
with polymer coatings.
A Sensor for Thin Film Thickness Monitor Using Torsional Quartz Crystal Resonators of Stepped, Free-Free Bar-Type
Authors: Kawashima Hirofumi , Sunaga Kenji
Published: October 2002

This paper describes a quartz microsensor for monitoring thin
film thickness. A microresonator of free-free bar-type with stepped
vibration bar vibrating in torsion as well as that of tuning fork-type is
very available for monitoring thin film thickness because it has
excellent frequency temperature behavior over a wide temperature range of
room temperature to high one of about 200°C. In this paper, a
relationship of resonant frequency to thin film thickness of Au and Al
is theoretically and experimentally clarified for the microresonator, so
that the frequency deviation is proportional to the film thickness deposited
on the top of the arm, and the calculated values show good agreement
with the measured ones. This microresonator is, therefore, very
available for monitoring thin film thickness.
Trapped-Energy Vibratory Gyroscopes Using Rotated Y-cut LiNbO3
Authors: Kiyoshi Nakamura Kiyoshi Nakamura , Masahiro Ohsaki Masahiro Ohsaki
Published: October 2002

In a rotated Y-cut plate of class (3m) crystal such as LiNbO3
and LiTaO3, two orthogonal thickness-shear vibrations can be
excited independently, by electric fields perpendicular and parallel
to the plate surface.
Using the trapped-energy thickness-shear vibrations, vibratory
gyroscopes of easy support with no need of trimming are expected to be
realized. In this paper, a trapped-energy vibratory gyroscope using a
rotated Y-cut of LiNbO3 is proposed. It is shown experimentally that by choosing appropriate electrode dimensions the resonance frequencies of the two orthogonal thickness-shear vibrations
almost coincide with each other, and
the energy of the thickness-shear vibrations is trapped around the electrodes.
The basic characteristics of a vibratory gyroscope using a 163°
rotated Y-cut LiNbO3 plate, about 2 mm thick, is presented.
Behaviour of Leaky Surface Acoustic Wave Propagation at Discontinuous Region of Periodic Grating
Authors: Yasunori Sakamoto Yasunori Sakamoto , Ken-ya Hashimoto Ken-ya Hashimoto , Masatsune Yamaguchi Masatsune Yamaguchi
Published: October 2002

This paper describes the leaky surface acoustic wave (LSAW) propagation
characteristics at a discontinuous region in a grating structure. First, the dispersion
relation of LSAWs propagating under a multielectrode-type grating is analysed. Then, the
LSAW propagation on the discontinuous region is characterised by simply assuming that the
LSAW behaviour under periodic part of the structure is identical with that under a totally
periodic grating structure. It is concluded that the phase lag considerably decreases at
the discontinuous region. This suggests that the energy storing effect may be weakened at
the region where the periodic structure is broken. The simulation of one-port LSAW
resonators shows that device performances are sufficiently evaluated only by taking
account of the constant phase lag for a simulation tool based on the coupling-of-modes
theory.
Study on Surface Acoustic Wave Characteristics of SiO2/Interdigital-Transducer/ZnO/Diamond Structure and Fabrication of 2.5 GHz Narrow Band Filter
Authors: Nakahata Hideaki , Kitabayashi Hiroyuki , Uemura Tomoki , Hachigo Akihiro , Higaki Kenjiro , Fujii Satoshi , Seki Yuichiro , Yoshida Kentaro , Shikata Shin-ichi
Published: October 2002

Surface acoustic wave (SAW) characteristics of the SiO2/interdigital-transducer(IDT)/ZnO/diamond
structure were studied theoretically and experimentally. It was found that the 2nd
mode in this structure can provide a zero temperature coefficient of frequency (T
C
F) as well as
high velocity of 10,000 m/s and a large electromechanical coupling coefficient of 1.4%. Utilizing
this wave, a 2.5 GHz narrow-band SAW filter was successfully fabricated with IDTs of 0.9 µm
finger width, which resulted in superior characteristics for a retiming filter with a small insertion
loss of 6.7 dB, Q value of 660 and small frequency deviation of 100 ppm in the temperature range
from -40 to 85°C. The insertion loss is smaller than any other retiming filters which have ever been
reported with quartz, a conventional SAW material, and also the frequency deviation with
temperature is smaller than that in the case of ST-cut quartz.
Piezoelectric Properties of ZnO Films on a Sapphire Substrate Deposited by an RF-Magnetron-Mode ECR Sputtering System
Authors: Michio Kadota Michio Kadota , Makoto Minakata Makoto Minakata
Published: October 2002

Compared to conventional RF magnetron sputtering systems,
electron cyclotron resonance (ECR) sputtering systems are
characterized by the ability to generate high-density plasma
under low gas pressure. (1120)-plane oriented
epitaxial ZnO films were deposited on an R-plane sapphire
substrate using the RF-magnetron-mode ECR sputtering equipment.
As the results of the measurement, the films showed a good
orientation and excellent effective electromechanical coupling
factors (k
eff) for the Rayleigh surface acoustic wave (SAW)
and its high-order SAW waves. These coupling factors were equal
to or higher than the theoretical values k
eff obtained by the finite
element method (FEM) analysis using a single crystal material constant.
Superhigh Electromechanical Coupling and Zero-Temperature Characteristics of KNbO 3 and Wide Band Filter Applications
Authors: Hiroyuki Odagawa Hiroyuki Odagawa , Kazuhiko Yamanouchi Kazuhiko Yamanouchi
Published: October 2002

In this paper, a superhigh electromechanical coupling surface acoustic wave (SAW) propagating on a potassium niobate (KNbO3) substrate is described and its applications for low-loss, wide band and temperature stable SAW filters are investigated.
KNbO3 has large piezoelectric constants. We obtained the electromechanical coupling coefficient (K
2) of 0.53 for SAW in a Y-cut X-propagating substrate, theoretically and experimentally. It is observed to be about 10 times as large as that in LiNbO3. Moreover, we obtained the zero temperature characteristics around room temperature, in a rotated Y cut substrate.
The experimental results of the wide band SAW filters show low loss and stable temperature characteristics. The bandwidth is about 20% and the insertion losses are less than 2–6 dB. The simulation results of a ladder-type filter using the Y-cut KNbO3 show a bandwidth of 40%.
Three-Dimensional Sound Pressure Field Measurement Using Photoelastic Computer Tomography Method
Authors: Mihara Tsuyoshi , Hagiwara Kota , Furukawa Takashi
Published: October 2002

A photoelastic computer tomography method is developed to determine the three-dimensional
sound pressure distribution of a longitudinal wave. An acoustic wave emitted
from a probe gives a three-dimensional sound pressure distribution that depends on the
ultrasonic transducer used. Since the sound pressure distribution affects the results of
the ultrasonic measurements, the authors have experimentally studied the sound pressure
distribution using a photoelastic ultrasonic visualization system. Hence we have
developed a highly sensitive visualization system for the quantitative measurement of a
weak emitted wave. However, since this method utilizes photoelasticity, the estimated
sound field is limited to a two-dimensional one. In this study, the basic measurement
system and the analysis algorithm for ultrasonic visualization have been improved to
measure the three-dimensional propagation in solids using the computer tomography
technique based on the two-dimensional photoelastic ultrasonic visualization technique.
Using this system, three-dimensional sound pressure distribution of a commercial probe in
the near field and/or far field are measured and compared with the results of the
theoretical estimations.
Automatic Ultrasonic Measurement of Sound Velocity in Liquids by a Phase Difference Method
Authors: Kiyoshi Ikeda Kiyoshi Ikeda
Published: October 2002

The working of a novel ultrasonic technique for measuring the sound velocity in liquids, which automatically cancels the dependence of temperature by a phase difference method is described in this paper. This technique uses a very simple circuit system which treats only the continuous sinusoidal waves and is constituted of only analog circuits. The temperature-compensation factor in the designing of the temperature-compensation circuit is derived from the equation obtained for the ultrasonic velocity in sea water. This measuring system is shown to yield a 0.01% accuracy of velocity determination, independent of the temperature variation of ±1.0°C around 25.4°C for the NaCl solution.
Ultrasound Doppler Sinusoidal Shift Signal Analysis by Time-Frequency Distribution with New Kernel
Authors: Noguchi Yasuaki , Kohtaro Watanabe Kohtaro Watanabe , Eiichi Kashiwagi Eiichi Kashiwagi , Takeo Hamada Takeo Hamada , Ken Mariko Ken Mariko , Fujihiko Matsumoto Fujihiko Matsumoto
Published: October 2002

A Cohen's class time-frequency (TF) distribution has high resolution in time and frequency simultaneously on a TF plane. It is a powerful tool for nonstationary signal analysis of the type observed commonly in speech and biological signals. A kernel of high resolution was investigated for its applicability to biological signals. To apply the TF analysis with the new kernel to the analysis of a signal from a blood flow, an ultrasound Doppler sinusoidal shift signal was studied. Experimental data were obtained in olive oil by moving a steel ball to and fro by continuously irradiating it with ultrasound. The movement of the steel ball was controlled by various functions. Three kernels were used: (1) a Wigner kernel, (2) a Choi-Williams kernel, and (3) our new kernel. The demodulation accuracy with our new kernel was higher and negative components were smaller than with the Choi-Williams kernel.
Scanning Nonlinear Dielectric Microscope with Submicron Resolution
Authors: Yasuo Cho Yasuo Cho , Kaori Matsuura Kaori Matsuura , Jun-ichi Kushibiki Jun-ichi Kushibiki
Published: October 2002

A new probe using a tungsten needle for the scanning nonlinear dielectric microscope has been developed. This probe has a submicron resolution. This probe combined with a submicron stage is used to observe the distribution of domains in a lithium tantalate substrate with a proton exchanged inversion layer and also in polarized and depolarized lead zirconate titanate ceramics.
Three-Dimensional Ray Simulation of Sound Propagation in Ocean with a Geostrophic Current
Authors: Tsuchiya Takenobu , Ohtsuka Eiji , Fujii Taro , Endoh Nobuyuki
Published: October 2002

Acoustical ray theory is used to analyze the three-dimensional (3-D) transmission
characteristics of the propagation of sound in the Pacific Ocean. For the computer
simulation, it is assumed that there is a temperature gradient caused by the warm and cold
water mass. The temperature gradient also generates a non-acceleration current or the
geostrophic current. The maximum flow speed of the current varies from 0 to 1.35 m/s in
the area of study of 100 km square. Sound pulses projected from the source on the sound
fixing and ranging (SOFAR) axis reach the cylindrical receiving plane with a curved locus,
because of the influence of both temperature gradient and current. The propagation path and
propagation time are more affected than shown by the estimation results by two-dimensional
(2-D) simulation.
Reliability of GaAs Metal-Semiconductor Field Effect Transistors Grown on Si Substrates
Authors: Aigo Takashi , Takayama Seiji , Yabe Aiji , Tachikawa Akiyoshi , Moritani Akihiro
Published: October 2002

We report on the reliability of metal-semiconductor field effect
transistors (MESFETs) fabricated on GaAs/Si compared to that of
MESFETs on GaAs/GaAs, based on the results of the high-temperature
storage test under dc bias. The failure mode was the non-pinch-off
phenomenon with the increase in drain current for both types of
MESFETs. From the results of observation using a scanning electron
microscope and Auger electron analysis, gate metal dispersion and the
possibility of a reaction between the metal and the GaAs channel were
revealed for the failed devices. The mean time to failure for the
MESFETs/Si at a channel temperature of 130°C was predicted to be
1.28×106 h from the storage test, which was almost equal to that for
MESFETs/GaAs. This result indicates that the lifetime of MESFETs/Si is
comparable to that of MESFETs/GaAs, and the high density of
dislocations in the GaAs/Si does not affect the reliability of the devices.
Indium Incorporation Coefficients in the Growth of AlInGaAs/Al0.3Ga0.7As Quantum Wells by Molecular Beam Epitaxy
Authors: Chua Soo-Jin , Zhang Zhi-He
Published: October 2002

Using the emission wavelength and well thickness data of AlInGaAs/Al0.3Ga0.7As
quantum wells obtained from room temperature photoluminescence and transmission electron
microscopy, indium incorporation coefficients are determined for the growth of the quantum
wells by molecular beam epitaxy (MBE). At a growth temperature of 600°C, the indium
incorporation coefficient is found to be 0.54.
Magnetic Anisotropy of New Intermetallic Compound SmFe7
Authors: Samata Hiroaki , Fujiwara Nobuto , Nagata Yujiro , Uchida Takayuki , Lan Ming Der
Published: October 2002

We characterized the magnetocrystalline anisotropy of a novel intermetallic
compound, SmFe7, by means of torque measurement. Single crystal of SmFe7 was
grown by the self-flux method using Sm as a flux. From an analysis of the torque curves
in the (001) and (100) planes using the least mean squares method, we found that the
tetragonal anisotropy constants K
1, K
2 and K
3 of SmFe7 are -8.7±0.4 (×107 erg/cm3),
1.4±0.3 (×107 erg/cm3), and -2.7±0.1 (×106 erg/cm3) at 293 K, respectively. The
reliability of these values was confirmed using the results of magnetization measurements.
The huge magnetocrystalline anisotropy of SmFe7 is superior to that of Nd2Fe14B. SmFe7 appears to be a promising host material for a
high-performance hard magnet.
Vibration Detection Using Moving Grating Technique in Photorefractive Two-Wave Mixing
Authors: Oda Isao , Otani Yukitoshi , Liu Liren , Yoshizawa Toru
Published: October 2002

Optical interferometry using photorefractive two-wave mixing has been proposed for the
detection of small amplitude vibration. Sensitivity in this interferometry depends on spatial phase
difference between the interference fringe and the refractive index grating due to the photorefractive
effect. It is proposed to realize vibration detection in such a way that the moving grating technique is
applied to the photorefractive two-wave mixing. For this purpose, the optimum speed of movement is
discussed. On the basis of the Kogelnik's theory, a theoretical equation is derived about the
interference beam which is equivalent to an output signal. Although this is simple approach, our
theoretical equation is available for practical use in vibration detection using photorefractive two-wave
mixing.
Dielectric Properties of Pb(Zr, Ti)O3-Dispersed MgO Nanocomposite
Authors: Nagai Toru , Hwang Hae Jin , Yasuoka Masaki , Sando Mutsuo , Niihara Koichi
Published: October 2002

Ceramic nanocomposites with perovskite-type ferroelectric dispersoids have been
studied in order to introduce ferroelectricity and piezoelectricity into structural ceramics.
First, MgO matrix/BaTiO3 dispersed ceramic nanocomposites were fabricated, but the
piezoelectric coupling factor, k
p, of the nanocomposites was reduced to less than 5%.
In the present work, MgO matrix/Pb(Zr,Ti)O3 (PZT) dispersed ceramic nanocomposites
were studied to realize ceramic nanocomposites with larger k
p values than MgO/BaTiO3.
MgO/PZT ceramic nanocomposites were successfully fabricated by a pressure-less
sintering method. The MgO/PZT nanocomposites exhibited a D–E hysteresis loop, and
the ferroelectricity of the PZT dispersoid was confirmed. The tetragonality of the PZT
dispersoid was decreased in comparison to that of monolithic PZT ceramics, however, the
tetragonal-cubic phase transformation temperature of the PZT dispersoid was higher than
that of the monolithic PZT. The decrease in the tetragonality was correlated to the
incorporation of Mg ions into the PZT dispersoid. The MgO/PZT nanocomposites
exhibited piezoelectricity after poling, and the k
p value was about twice that of the MgO/BaTiO3 nanocomposites.
Crystallographic and Dielectric Studies in the Solid Solution System PbCo1/2W1/2O3–PbYb1/2Ta1/2O3
Authors: M. Knowles Yung Park
Published: October 2002

The crystal structures and dielectric properties of (1-x)PbCo1/2W1/2O3–xPbYb1/2Ta1/2O3 perovskites have been investigated as a function of temperature. A continuous series of solid solutions was found and the phase diagram was determined. Ordered end compositions with 0.0 ≤x < 0.2 and 0.8 < x ≤1.0 showed successive paraelectric-antiferroelectric-ferroelectric phase transitions with decreasing temperature. Diffuse paraelectric-ferroelectric phase transitions occurred for 0.2 < x < 0.8, with the low temperature ferroelectric phase having disorder on the B-sites occupied by Yb3+, Ta5+, Co2+ and W6+. Plots of polarisation as a function of applied electric field confirmed the nature of each crystallographic phase.
Ferroelectric Imaging: A Proposal for Formation of Long-Life Electrostatic Images
Authors: Matsumoto Takuji , Hoshino Katsuyoshi , Kokado Hiroshi
Published: October 2002

A novel imaging process based on the polarization reversal of a ferroelectric
polymer film (e.g. copolymer of vinylidene fluoride and tetrafluoroethylene) was
proposed and the basic requirements for polarization reversal were investigated
by D–E hysteresis measurements and also by time domain measurements of
switching transients. It was found that the permissible temperature for successful
image formation was 100°C. The decrease of the coercive field, however, was
only 15 MV/m, apparently not large enough in the temperature range between
20°C and 100°C for practical application. However, when the film was
subjected to pulse heating, such as flash light exposure (with a light-to-heat
conversion layer), the polarization was reversed even at temperatures as low as 55 or 60°C under the application of a low electric field (30 MV/m). The
mechanism which makes pulse heating effective in the latent image formation
was pursued and a model was proposed which assumed a local field
enhancement arising from a nonuniform temperature distribution in the film.
Excitation of the Alfvén Ion Cyclotron Mode Solely by the Ion Pressure Distribution
Authors: Nakamura Motoyuki , Ichimura Makoto , Tanaka Satoru , Kanazawa Seikou , Ishikawa Eiji , Satake Chikako , Takayama Seiichi , Motegi Shinji , Kumagai Akira , Hojo Hitoshi , Nakashima Yousuke , Kiwamoto Yasuhito , Saito Teruo , Tatematsu Yoshinori , Tamano Teruo , Yatsu Kiyoshi
Published: October 2002

The Alfvén ion cyclotron (AIC) mode is spontaneously excited due to a temperature anisotropy in the ion cyclotron range of frequency (ICRF) heating experiments in the GAMMA10 tandem mirror. The behavior of the AIC mode is studied when the second harmonic electron cyclotron resonance heating is applied additionally. It is confirmed experimentally, that the excitation of the AIC mode is determined solely by the ion pressure and the ion pressure distribution.
Determination of Cation Distribution in Mn–Zn–Fe Ferrite by X-Ray Anomalous Scattering
Authors: Okita Atsushi , Saito Fumikazu , Sasaki Satoshi , Toyoda Takeshi , Koinuma Hideomi
Published: October 2002

Site preferency of cations in Mn–Zn–Fe ferrite, Mn0.54Zn0.35Fe2.11O4, has been investigated using spherical single crystals with synchrotron X-rays. The anomalous scattering effect was applied to diffraction experiments in a four-circle diffractometry at wavelengths of 1.7535 and 1.2934 Å which are 0.01 Å longer than FeK- and ZnK-absorption edges, respectively. The two-wavelengths anomalous dispersion (TWAD) method allowed us to determine the cation distributions accurately with a large difference in atomic scattering factors. The result shows that all Mn and Zn ions fully occupy the tetrahedral A sites within the experimental errors, suggesting that Mn–Zn–Fe ferrite has the crystal structure of a typical normal spinel. The chemical formula is [Mn0.54Zn0.34Fe0.12]A[Zn0.01Fe1.99]BO4. The cell dimension anduparameter area=8.4727±0.0006 Å andu=0.2609±0.0002, respectively.