bluuebunny/crossref_metadata_2025 huggingface dataset:
Self-Organized Gold Nanodots Array on a Silicon Substrate and Its Mechanical Stability
Authors: Gen Tsutsui Gen Tsutsui , Shujuan Huang Shujuan Huang , Hiroyuki Sakaue Hiroyuki Sakaue , Shoso Shingubara Shoso Shingubara , Takayuki Takahagi Takayuki Takahagi
Published: October 2002

The fabrication of a self-organized two-dimensional array of gold
nanodots encapsulated by alkanethiol on a silicon substrate is presented.
An experimental study on the mechanical stability of such a quantum
dot structure was carried out. The results of this work demonstrate
that gold nanodots encapsulated by alkanethiol can maintain their
position strongly on a silicon substrate rather than be destroyed
in a destructive environment. Therefore it is believed that such
a nanostructure is useful for the development of future nanoelectronics.
Oxidation and Disproportionation of Wüstite Studied by Mössbauer Spectroscopy
Authors: Kaori Mori Kaori Mori , Takuya Okada Takuya Okada , Yasuo Takagi Yasuo Takagi , Yoshihisa Takada Yoshihisa Takada , Tadashi Mizoguchi Tadashi Mizoguchi
Published: October 2002

Oxidation of wüstite (Fe1-δO) in air and
disproportionation into α-Fe and Fe3O4 in a vacuum-sealed tube at
temperatures below the transition temperature (843 K) were studied by
Mössbauer spectroscopy. The observed discontinuity of weight
increase during oxidation in air indicates a two-step process, i.e., the
first is the oxidation of Fe1-δO to Fe3O4 and the
second, that of Fe3O4 to α-Fe2O3. The change in the
fraction of components by annealing in a vacuum-sealed tube depends linearly on
the logarithm of the annealing time. The process is interpreted as
having a wide distribution of effective thermal activation energy.
Effects of Gravity and Magnetic Field in Production of C60 by a DC Arc Discharge
Authors: Aoyama Shoji , Mieno Tetsu
Published: October 2002

We have examined the dependence of the production of C60 on the direction of the arc current with respect to the direction of gravity in a DC arc discharge in a helium gas
atmosphere. The production rate decreases when the direction of the current is opposite to that of heat convection of the helium gas. When a DC magnetic field is
applied, the hot gas plasma in the arc region is jetted out by the J×B force. The production rates of carbon soot and C60 increase and depend little on the direction of gravity.
Control of Surface Recombination of Si Wafers by an External Electrode
Authors: Ichimura Masaya , Hirano Masashi , Kato Naoki , Arai Eisuke , Takamatsu Hiroyuki , Sumie Shingo
Published: October 2002

A transparent electrode was placed close to a Si wafer, and a negative or positive
voltage up to 2 kV was applied to the electrode with respect to the wafer. The wafer
was irradiated through the electrode with a pulsed laser, and the decay of the excess
carriers was monitored by the microwave reflectance photoconductivity decay (µ-PCD)
method. The carrier lifetime of p- and n-type as-polished wafers was increased by a
factor of 3 by application of a 2 kV negative voltage to the electrode. This showed that
the surface recombination velocity was controlled by the external electrode. A
different tendency was observed for the oxidized wafers, and these results were
explained by considering the surface charge and the surface state.
Analytical Modeling of Metal Oxide Semiconductor Inversion-Layer Capacitance
Authors: Miyazaki Khairurrijal , Takagi Shin-ichi , Hirose Masataka
Published: October 2002

Electron wavefunctions confined in a logarithmic potential well formed in the
inversion layer of a metal oxide semiconductor field-effect transistor (MOSFET) are
given on the basis of generalized Airy functions. The charge centroid of electrons in the
inversion layer has been calculated to derive the quantum mechanical inversion-layer
capacitance by taking into account higher subband states. It is shown that the present
analytical model can quantitatively explain the experimentally observed inversion-layer
capacitance.
Fabrication of 1×4 Optical Switch with Gain Using Dual InGaAsP/InP Laser Diode Amplifier
Authors: Min Lee Sang , Oh Kwang Ryong , Ho Kim Kang , Soo Kim Jeong , Goo Kang Seung , Kyu Song Min , Man Kim Hong
Published: October 2002

The fabrication and characterization of a 1×4 optical switch module are described. The switch consists of one pre-amplifier and four gate-amplifiers which are monolithically integrated with passive waveguides and splitters. We obtained very uniform characteristics for each path. The average values of fiber-to-fiber gains and extinction ratios were 7.4 dB and 54 dB, respectively, for TE polarized light at 50 mA gate current and 30 mA pre-amplifier current.
Order Parameter of Liquid Crystal on Polyimide with Polarized Ultraviolet-Light Exposure
Authors: Nishikawa Michinori , West John L.
Published: October 2002

We report a brief method of measuring the order parameter of liquid crystal (LC) depending
on the cell gap. The method utilizes polarized ultraviolet-light (UV) absorption of host-guest LC in
a wedge cell. We applied this method to evaluate the order parameters of LC on polarized-UV-exposed
polyimide (PI) films compared with those on rubbed PI films. The results suggest that the
order parameter of LC gradually decreases with decreasing cell gap. Furthermore, the relative
order parameters of LC on UV-exposed PI films show a stronger dependence on the LC layer
thickness than those on rubbed PI films.
Effect of Refractive Index Change on the Interference Modulation of Q Values in a Layered Cylindrical Microlaser
Authors: Hee-Jong Moon Hee-Jong Moon , Jonghoon Yi Jonghoon Yi , Jin-Tae Kim Jin-Tae Kim , Jongmin Lee Jongmin Lee
Published: October 2002

We observed the effect of refractive index change on the interference modulation of Q-values in a liquid-silica capillary tube.
The lasing peaks of whispering-gallery (WG) modes were modulated periodically due to
the interference effect. As the pump fluence increased,
the WG peaks showed a blueshift due to the decrease of the refractive index of liquid and
the constructive interference peak jumped to the neighboring red WG peak.
The interference period measured from the spectral behavior agreed with the formula predicted by the ray-optics model within the
experimental error.
Growth of “Oxide-Less” GaN Layer by Helicon-Wave Excited N2–Ar Plasma Treatment of Al/GaAs Structure
Authors: Nariaki Okamoto Nariaki Okamoto , Fumio Kasahara Fumio Kasahara , Hideaki Ikoma Hideaki Ikoma
Published: October 2002

Gallium nitride could be formed by direct nitridation of GaAs using the helicon-wave excited N2–Ar plasma at or near the grown insulative layer/GaAs interface. However, a fair amount of the oxides and the suboxide of Ga and As also existed in this insulative layer. In the present study, the Al/GaAs(100)structure, instead of a GaAs one, was exposed to the helicon-wave excited N2–Ar plasma. X-ray photoelectron spectroscopic measurements were performed to investigate the chemical composition and depth profile of the grown layer. The top Al film was completely nitrided and oxidized (due to residual oxygen), so that Al2O3 and AlN were formed. Under the Al2O3–AlN mixed film, a GaN layer was uniformly formed on GaAs. Oxides of Ga and As, such as Ga2O3, GaO, As2O3 and AsO were scarcely observed in the film. Thus, an “oxide-less” GaN layer was obtained. However, a small amount of elemental arsenic was detected in the GaN layer. Nitrogen atoms or ions are considered to diffuse into the Al film and react with GaAs to produce GaN. The presence of the grain boundaries in “Al” enhances the N2 diffusion. The oxides of Ga and As were probably eliminated by the reducing effect of Al.
Organic Light-Emitting Diode Using Eu3+ Polymer Complex as an Emitter
Authors: Zhao Dongxu , Li Wenlian , Hong Ziruo , Liang Chunjun , Zhao Dan , Peng Junbiao , Liu Xingyuan
Published: October 2002

A new fluorescent Eu3+ polymer complex with the trivalent europium (Eu3+) ion
directly bonded to a polymer chain was synthesized, and a new organic
electroluminescent (EL) device in which it is used as the emitting layer was fabricated
successfully for the first time. It was found that the EL and PL spectra of the
device and its film were different from each other; for the former, the emission peaks
lie at 595 nm and 657 nm, while it is at 618 nm for the latter. The difference between
EL and PL was also discussed.
Preliminary Study of Field Sequential Fullcolor Liquid Crystal Display using Polymer Stabilized Ferroelectric Liquid Crystal Display
Authors: Taiju Takahashi Taiju Takahashi , Hirokazu Furue Hirokazu Furue , Masahiro Shikada Masahiro Shikada , Noriyuki Matsuda Noriyuki Matsuda , Tomohiro Miyama Tomohiro Miyama , Shunsuke Kobayashi Shunsuke Kobayashi
Published: October 2002

Using a side-chain mesogenic polymer stabilized ferroelectric liquid crystal display (PS-FLCD) cell together with a two-dimensional array of red, green and blue light-emitting diodes (LEDs) as a modulated back light unit, we constructed a field sequential fullcolor (FSC) LCD. The PS-FLCD used in this research exhibits a high contrast ratio (230:1) with thresholdless monostability, grayscale capability, and a fast response speed (τ=40 µs). In the present research it is taken the advantages of the favorable characteristics of the PS-FLCD for implementing a FSC-LCD that has an 8×8 matrix format. The fabricated FSC-LCD, which is operated at the frame rate of 330 Hz, is shown to exhibit an excellent color gamut, color grayscale, and smearless moving color bars.
pH Distribution Around the Electrode During Electrochemical Deposition Process for Producing Bioactive Apatite
Authors: Ban Seiji , Maruno Shigeo
Published: October 2002

The pH distribution of an electrolyte around a cathode during the electrochemical deposition
of calcium phosphate was examined using a pH imaging microscope and discussed from an
electrochemical point of view. From the plot of the weight gain due to the deposits against
square root of the loading time, the critical time for deposition was determined at four levels
of current densities. OH- concentration around the cathode during the electrochemical
deposition was found to be pH 9.6 using the Sand equation on the basis of the critical time
and other constants. The pH distribution around the cathode was quite different for the
electrolytes with and without pH buffer.
Ultra-short Pulses of Synchrotron Radiation on Storage Rings
Authors: Katoh Masahiro
Published: October 2002

A method to produce a few pico- and possibly sub-picosecond pulses of synchrotron radiation on storage rings is proposed.
A transverse kick is given to an electron bunch by using an RF deflector. The kick angle is proportional to the longitudinal
distance from the bunch center. Each longitudinal segment of the bunch initiates betatron motion and emits photons in different
directions. These photons are introduced to a beam line which produces a difference in path length depending on their angles of
emission, such that the pulse length originating from the electron bunch length is canceled out. The final pulse length is limited
by the angular divergence of the radiation.
Enhanced Crystallinity at Initial Growth Stage of Microcrystalline Silicon on Corning #7059 Glass Using SiH2Cl2
Authors: Fukai Chisato , Moriya Yoshimizu , Nakamura Takuya , Shirai Hajime
Published: October 2002

The crystallinity at the initial growth stage of hydrogenated microcrystalline silicon
(µc-Si:H) was greatly improved on Corning #7059 glass substrate with
dichlorosilane (SiH2Cl2) as the starting gas using conventional (13.56 MHz)
capacitively coupled plasma-enhanced chemical vapor deposition system.
Deposition studies examined film thickness, substrate temperature, total pressure,
electrode distance and H2-dilution conditions as variables. Through Raman
spectroscopy, atomic force microscopy (AFM), spectroscopic ellipsometry, X-ray
diffraction (XRD) and Mie scattering measurements, it was found that ∼20 nm sized
crystalline Si particles were formed in the plasma region, resulting in the enhanced
crystallization from the initial growth stage. The growth kinetics of µc-Si:H from
SiH2Cl2, compared with that from SiH4, is described.
Impact Ionization in InAlAs/InP Single Channel Heterojunction Field Effect Transistors
Authors: Gautier-Levine Astrid , Teissier Roland , Nezzari Amar , Rao Elchuri , Décobert Jean , Pelouard Jean-Luc , Scavennec André
Published: October 2002

We report on experimental observation of impact ionization in InAlAs/InP heterojunction field effect
transistors (HFET) with an InP channel. The I
g(V
gs)
V
ds
static characteristics and electroluminescence
intensity are compared, exhibiting similar evolutions with bias conditions. These observations
indicate that minority carriers (holes) are generated in the structure, through an impact ionization
process. This process, unusual in InP channel FETs, is attributed to the staggered InAlAs/InP
interface.
Characterization of Molecular Orientation of Rubbed Polyimide Film by Grazing Incidence X-ray Scattering
Authors: Hirosawa Ichiro , Sasaki Nobuyoshi , Kimura Hiroshi
Published: October 2002

Molecular orientation in non-crystalline rubbed polyimide films for a
liquid crystal display device (LCD) was characterized by grazing incidence
X-ray scattering. The scattered X-ray intensity profiles clearly showed
anisotropy in the molecular orientation of the rubbed polyimide film. It was
clarified that the monomer units of the polyimide align in parallel to the
rubbing direction and that the average spacing between polyimide chains is
about 0.55 nm.
Suppression of Arsenic Loss by Phosphorus Co-Implantation in n+/p Shallow Junction Diffused from a CoSi2 Layer
Authors: Park Ji-Soo , Sohn Dong Kyun , Bae Jong-Uk , Park Jin Won
Published: October 2002

We propose phosphorus (P) co-implantation as a simple and effective method for
suppression of arsenic (As) loss from a junction formed by As implantation into a CoSi2
layer and drive-in annealing. With this method, the reverse leakage current of the n+/p
junction is lowered by more than two orders of magnitude without increasing the
junction depth. By comparing P and Si co-implantation, we find that the suppressed
dopant loss by P co-implantation can be attributed to the chemical species effect of P
rather than an increased damage/amorphization by P co-implantation.
Three-Step Molecular Beam Deposition of Crystalline Polydiacetylene Films on Semiconductor Substrates with Large Crystal Domains
Authors: Kondo Tsuyoshi , Ishii Akihiro , Munekata Hiroo , Takeda Kenji
Published: October 2002

We have developed a three-step molecular beam deposition method to obtain crystalline
polymer films directly on semiconductor substrates. This is exemplified by
alkyluretane-substituted polydiacetylene (PDA-4U4) films composed of lateral crystal
domains of one hundred square microns or larger on GaAs(100) substrates. Polarization
dependence of Raman scattering confirms each domain is formed by well-aligned crystalline
polymers. The blue-to-red thermochromic phase transition occurs at around 70°C, which is
lower than that reported for the PDA-4U4 bulk crystal (T
c=125°C).
Elimination of X-Ray Photoelectron Diffraction Effect of Si(100) for Accurate Determination of SiO2 Overlayer Thickness
Authors: Katayama Toshiharu , Yamamoto Hidekazu , Ikeno Masahiko , Mashiko Yoji , Kawazu Satoru , Umeno Masataka
Published: October 2002

The X-ray photoelectron diffraction (XPD) intensities from Si(100) substrates with
silicon oxides of various thicknesses are quantitatively analyzed based on the elastic attenuation
of XPD intensity from hydrogen-terminated Si(100) in the silicon oxide. The elastic attenuation
length of Si 2p photoelectrons excited by Al Kα in the silicon oxides is determined to be 2.9 nm, which reproduces the experimentally measured polar-angle intensity distributions from
Si(100) substrates with the silicon oxides. The thickness error obtained from conventional
angle-resolved X-ray photoelectron spectroscopy (AR-XPS) is maximum for a silicon oxide
thickness of 2 nm; however, by modified AR-XPS considering the XPD effect, the thickness
error of the apparent thickness is reduced by one-third for such silicon oxides.
Enhanced Electron Mobility in AlGaN/InGaN/AlGaN Double-Heterostructures by Piezoelectric Effect
Authors: Maeda Narihiko , Saitoh Tadashi , Tsubaki Kotaro , Nishida Toshio , Kobayashi Naoki
Published: October 2002

A striking effect of piezoelectric electron confinement on transport properites has been
observed for the first time in nitride double-heterostructures. The two-dimensional electron
gas mobility has shown to be drastically enhanced in the AlGaN/GaN/AlGaN double-heterostructure,
compared with that in the conventional AlGaN/GaN single-heterostructure. The observed mobility
enhancement results from the piezoelectrically enhanced electron confinement in the
double-heterostructure. The electron transport properties in the AlGaN/InGaN/AlGaN
double-heterostructure have also been examined for the first time. The increased capacity for
the two-dimensional electron gas density has been observed in addition to the enhanced electron
mobility. The AlGaN/(In)GaN/AlGaN double-heterostructures are promising for field effect
transistor applications because of their superior electron transport properties.
Laser-Induced Damage Threshold and Surface Processing of GaN at 400 nm Wavelength
Authors: Eliseev Petr G. , Sun Hong-Bo , Juodkazis Saulius , Sugahara Tomoya , Sakai Shiro , Misawa Hiroaki
Published: October 2002

The laser-induced damage of epitaxially grown GaN semiconductor material is investigated for the first
time by illumination
of the c-plane by sub-picosecond laser pulses at the wavelength of 400 nm. The surface damage
was investigated by optical and atomic force microscopies. The threshold fluence for ablation
damage is determined to be ∼5.4 J/cm2 for pulse width of 150 fs. An application
is demonstrated for laser-beam processing by the formation of clean dips on the GaN surface to depths of 240 nm in a single shot.
Magnetic Damping of the Temperature-Driven Convection in NaCl Aqueous Solution Using a Static and Homogeneous Field of 10 T
Authors: D. Durbin Gen Sazaki , Satoru Miyashita Satoru Miyashita , Toru Ujihara Toru Ujihara , Kazuo Nakajima Kazuo Nakajima , Mitsuhiro Motokawa Mitsuhiro Motokawa
Published: October 2002

Temperature-driven convection in 25 wt% NaCl
aqueous solution was observed in situ under a static and homogeneous
magnetic field of 10 T.
The convection in the solution was visualized using polystyrene latex particles
of 5 µm diameter.
A magnetic field of 10 T reduced the velocity of convection by a factor of two.
Magnetic damping of convection in an electrolyte solution could be a useful
technique to control the growth of crystals such as proteins.
Enhancement of Surface Productions of CFx Radicals by the Addition of H 2 into CF 4 Plasmas
Authors: Koichi Sasaki Koichi Sasaki , Hiroyuki Furukawa Hiroyuki Furukawa , Chihiro Suzuki Chihiro Suzuki , Kiyoshi Kadota Kiyoshi Kadota
Published: October 2002

Spatially resolved CF and CF2 radical densities
were measured in low-pressure,
high-density CF4 plasmas with the addition of H2 by
laser-induced fluorescence spectroscopy.
Hollow radial distributions (the densities in the outside
region were higher than those in the plasma column) were observed for
the radical densities.
Diffusion fluxes of the radicals from the outside region
to the plasma column were evaluated from the slope of the
hollow density distributions.
Linear correlations were found between the inward diffusion fluxes and
the gas-phase radical densities, suggesting that the gas-phase CF and
CF2 radical densities were determined not by the
electron-impact dissociation
of CF4 in the plasma column but by the production of radicals
in the outside region.
The source of the radicals in the outside region is the
surface of the chamber wall covered with
fluorocarbon film.
Line-Focus-Beam Acoustic Microscopy Detection of Variations of Growing Conditions of LiTaO 3 Crystals
Authors: Jun-ichi Kushibiki Jun-ichi Kushibiki , Tadashi Okuzawa Tadashi Okuzawa
Published: October 2002

Line-focus-beam (LFB) acoustic microscopy is applied to evaluate the homogeneities of optical-grade LiTaO3 single crystals, pulled along the crystallographic Y axis. Z-cut substrates prepared from three kinds of single crystals with different chemical compositions of 48.0, 48.5, and 49.0 Li2O-mol% as the starting materials, and one commercially available optical-grade congruent LiTaO3 single crystal, are examined by measuring the leaky surface acoustic wave (LSAW) velocities along the Y axis. Using the relationship between the LSAW velocities and chemical compositions obtained from the three crystals, some significant and characteristic velocity variations of 0.54 m/s along the pulling-axis direction and of at most 0.38 m/s along the diameter direction were observed on the congruent specimen surface, corresponding to the chemical composition changes of 0.017 and 0.012 Li2O-mol%, respectively. This is the first evidence to signify that the variations are in essence due to changes of the crystal growing conditions during the growth process.
Isotope Effects on the Dissociation of a Hydrogen–Carbon Complex in Silicon
Authors: Yoichi Kamiura Yoichi Kamiura , Kazuhisa Fukuda Kazuhisa Fukuda , Shigeki Ohyama Shigeki Ohyama , Yoshifumi Yamashita Yoshifumi Yamashita
Published: October 2002

We have found, by deep-level transient spectroscopy (DLTS), that the dissociation rate of a deuterium-carbon complex in silicon is about half that of a hydrogen-carbon complex, while the activation energies for the dissociation of both the complexes are the same. This clearly proves that both the complexes have the same atomic configuration and their dissociation is governed by the atomic jump of hydrogen (deuterium).
Key Molecular Structure Determination of Photoalignment Materials from the Effects of Linearly Polarized Deep UV Light on Several Polymers
Authors: Masaki Hasegawa Masaki Hasegawa
Published: October 2002

We studied the photoalignment of nematic liquid crystals by examining polyimide, polyester, polystyrene, polyvinylalcohol (PVA), and polymethylmethacrylate (PMMA) exposed to linearly polarized deep UV (LPDUV) light. Polystyrene aligned the liquid crystal parallel to its LPDUV polarization axis, while polyimide and polyester aligned the liquid crystal perpendicular to the polarization axis. Polyimide and polyester exhibited order parameter peaks for small dosages of LPDUV. PVA and PMMA did not align the liquid crystal. The presence of a phenyl ring is a key to the decomposition-type photoalignment, whose alignment direction depends on the position of the phenyl ring.
Optical Emission from a Pulsed Corona Discharge and Its Associated Reactions
Authors: Teich Fumiyoshi Tochikubo
Published: October 2002

In order to investigate some chemical reactions occurring in the early stage of pulsed corona discharges intended for the conversion of nitrogen oxides, we studied the time dependence of optical emissions. Special attention has been paid to the decay time constants of populations of species excited by radical-molecule reactions. By systematically changing the partial gas pressure of minor gas components, we estimate the reaction rate contributions of these particular gas constituents. We conclude that NO(B2Π) is predominantly excited by the reaction of N(2D) with N2O, while NO(A2Σ+) and OH(A2Σ+) are mainly excited by the energy transfer from N2(A3Σu
+). The rotational temperature in the active discharge zone was estimated to be about 500 K from the second positive and first negative band emissions of nitrogen.
Thermal Conductivity Measurement of Molten Silicon by a Hot-Disk Method in Short-Duration Microgravity Environments
Authors: Nagai Hideaki , Nakata Yoshinori , Tsurue Takashi , Minagawa Hideki , Kamada Keiji , Gustafsson Silas E. , Okutani Takeshi
Published: October 2002

The thermal conductivity of molten silicon was measured by a hot-disk method in
short-duration microgravity environments. The hot-disk sensor was made of
molybdenum foil cut in a conducting pattern and covered with an aluminum nitride
plate. Aluminum nitride has good resistivity against corrosion from silicon melt and
the molybdenum foil was protected from the molten silicon. The thermal conductivity
of molten silicon measured on the ground was estimated to be
45.6 W·m-1·K-1 at the melting point
(1687 K). The thermal conductivity of molten silicon measured in microgravity was
about 5% lower than that measured on the ground.
Chaotic Monte Carlo Computation: A Dynamical Effect of Random-Number Generations
Authors: Ken Umeno Ken Umeno
Published: October 2002

Chaotic maps with absolutely continuous invariant probability measures are implemented as random-number generators for Monte Carlo computation. We observe that such Monte Carlo computation based on chaotic random-number generators yields sometimes unexpected dynamical dependency behavior which cannot be explained by usual statistical arguments. Furthermore, we find that superefficient Monte Carlo computation with O(1/N
2) mean square error can be carried out as an extreme case of such dynamical dependency behavior. Here, such superefficiency sharply contrasts with the conventional Monte Carlo simulation with O(1/N) mean square error. By deriving a necessary and sufficient condition for the superefficiency, it is shown that such high-performance Monte Carlo simulations can be carried out only if there exists a strong correlation with chaotic dynamical variables. Numerical calculation illustrates this dynamics dependency and the superefficiency of various chaotic Monte Carlo computations.
Effect of Concentration-Dependence on Ion-Exchanged Channel Waveguide Profile
Authors: Kazuyoshi Hakamata Kazuyoshi Hakamata , Junko Ishizu Junko Ishizu , Tatsushi Kunou Tatsushi Kunou , Tomonori Ichikawa Tomonori Ichikawa , Yasuhiro Anma Yasuhiro Anma
Published: October 2002

An accurate simulation model of ion-exchange processes for fabricating
channel glass waveguides is presented. The simulation results are in good agreement with the experimental results because the simulation takes the concentration-dependent diffusion coefficient into account and applies the cubic-interpolation pseudoparticle (CIP) method for electromigration which can treat a sharp interface with a few grids. The simulation is then used to study optimum process conditions for a buried single-mode channel waveguide. It is demonstrated that an annealing process following field-assisted ion-exchange is useful in reducing the coupling loss to a single-mode optical fiber.
Optical Characteristics of Al2O3 Ceramics Doped with Cr at High Concentrations Prepared by Extrusion Molding Process
Authors: Murotani Hiroshi , Mituda Takahiko , Wakaki Moriaki , Kondou Yoshinori
Published: October 2002

Polycrystalline Al2O3 ceramics doped with Cr (sintered ruby) up to high concentrations (0.66, 0.76 and 0.97 wt%) were fabricated with an extrusion molding process using Al2O3 and Cr2O3 powders. It was found from absorption spectra that a high concentration of Cr ions was optically activated. The fluorescence spectrum of Cr ions in the sintered ruby corresponded to that of a single crystal.
Characterization of Ferroelectric BaSrTiO3 Thin Films Using a Flip-Chip Technique at Microwave Frequency Ranges
Authors: Sok Junghyun , Park Sang Jin , Lee Eun Hong , Hong Jin Pyo , Kwak Jun Sik , Kim Chae Ok
Published: October 2002

Microwave properties of ferroelectric Ba0.5Sr0.5TiO3 (BST) thin films were investigated utilizing a gold resonator combined with a
planar flip-chip structure. The resonator was designed to have bias
circuits at the zero field points in the microstrip line. The
dielectric properties, capacitance (C) and dielectric loss (tan
δ) of the BST film are characterized under the influence of an applied dc
voltage, V
b, at room temperature. The BST ferroelectric
capacitor with a capacitance of about 0.6 pF successfully controlled the
tunability of the resonance frequency in the resonator with a factor
of ∼2. In addition, dependence of the loss tangent and the
capacitance on the electrode were determined for both of the
SrRuO3/BST/LaAlO3 (SRO/BST/LAO) and BST/LAO structures. The use of a SRO buffer layer in the multilayer provided a low loss tangent of
about 3×10-3 at about 2 GHz and 80 V bias voltage. This low loss
seems to be related to the reduction of defect density in the
interfacial layer between the electrode and the ferroelectric thin film.
Crystal Structure and Microstructure of Nitrogen-Doped Ge2Sb2Te5 Thin Film
Authors: Jeong Tae Hee , Kim Myong R. , Seo Hun , Park Jeong Woo , Yeon Cheong
Published: October 2002

Ge2Sb2Te5 thin film is a promising candidate for recording material of phase-change optical disks, and nitrogen is doped into this film to increase overwrite characteristics. In this study, the crystal structure and the microstructure of nitrogen-doped Ge2Sb2Te5 thin film were investigated. In the annealed nitrogen-doped thin film, the characteristic face-centered cubic peaks on the X-ray diffraction pattern were broadened and shifted to a smaller angle with the increase of nitrogen content. In addition, a remarkably reduced grain size and a highly strained structure are seen in the transmission electron microscopy image. Doped nitrogen in Ge2Sb2Te5 thin film plays two roles. One is to distort the crystal lattice and induce a strain field in the film. The other is to refine the grain size of the film through precipitation. The crystal lattice is transformed from face-centered cubic to a hexagonal structure in nitrogen content above 20 at.%.
Ultrasonic Elastic Properties of Steel under Tensile Stress
Authors: Fukuhara Mikio , Sampei Asao
Published: October 2002

Longitudinal and transverse wave velocities, eight kinds of elastic parameters and dilational and shear dampings of chromium-molybdenum steel have been simultaneously measured at room temperature in terms of acoustoelasticity, by an ultrasonic pulse method. Young, shear and bulk moduli and Lamé parameter apparently decrease with increasing tensile stress, suggesting decrement of rigidity. However, decease in Poisson's ratio shows actual enhancement of rigidity due to lattice dilation, accompanied by decrease in longitudinal wave frequency, Debye temperature and Grüneisen parameter. As the stress increases, the dilational damping increases and then saturates over 600 MPa, while the shear one increases abruptly from 600 MPa. This abrupt increase indicates an increase in motion of dislocation for plastic deformation. The atomic dilation enthalpy shows the endothermal process in elastic field up to 750 MPa.
Elastic Anisotropy of Single Crystalline P[VDF/TrFE] Copolymer Films with 75/25 Mol Ratio
Authors: Leo Otani Leo Otani , Jun-Ichi Mawatari Jun-Ichi Mawatari , Akira Yoshihara Akira Yoshihara , Hiroji Ohigashi Hiroji Ohigashi
Published: October 2002

The in-plane elastic anisotropy of hypersonic sound velocities in single crystalline P[VDF/TrFE] copolymer films with 75/25 mol ratio have been studied by Brillouin light scattering in the ferroelectric phase at room temperature. Both as-grown and poled films give an identical anisotropy. To analyze the anisotropy, orientations of the ferroelectric domains with respect to the film coordinate are discussed using a Landau free-energy. We analyzed the in-plane anisotropy applying the individual domain (IDD) model and the effective elastic constant (EEC) model. A complete set of the crystallographic elastic constants was deduced for the IDD model. The EEC model gives four EECs, C
11
E, C
33
E, C
44
E and C
13
E. Both models can successfully reproduce the observed anisotropy.
Observation of a Sonoluminescing Bubble Using a Stroboscope
Authors: Kozuka Teruyuki , Hatanaka Shin-ichi , Tuziuti Toru , Yasui Kyuichi , Mitome Hideto
Published: October 2002

A method to observe sonoluminescing bubble motion has been
studied. By a single flash of a stroboscope much shorter than the
acoustic cycle, a charge coupled device (CCD) camera captures an
instantaneous image of the bubble, which includes the dancing
condition. Changing the flash timing of the stroboscope slowly made
it possible to observe periodical expansion and contraction of the
bubble. It is clarified that the bubble size and the phase at the
time the bubble collapses changes according to the amplitude of
sound pressure.
Existence of Hysteresis Based on Argon Rectification in Single Bubble Sonoluminescence
Authors: Asai Takamasa , Watanabe Yoshiaki
Published: October 2002

The existence of a hysteresis loop on the graph of single bubble sonoluminescence
(SBSL) intensity with respect to sound pressure is discussed. A theoretical estimation
was performed using the phase diagram of sound pressure and ambient radius for the
various concentrations of air in water. The existence of the hysteresis loop was
confirmed experimentally in the water at low air concentrations. Upon increasing the
concentration of air in water, the hysteresis became smaller, shifted to the lower
sound pressure range and eventually could not be observed. Taking these results into
consideration, the effect of argon rectification in the bubble on hysteresis is
discussed.
Effects of Ultrasonic Irradiation on Phenolic Compounds in Wine
Authors: Masuzawa Nobuyoshi , Ohdaira Etsuzo , Ide Masao
Published: October 2002

Red wine has been of interest recently because many
poly-phenols, that are considered to be good for health, are
contained therein. Since ultrasonic irradiation accelerates
maturation, its effects on phenolic compounds in wine were
investigated in this study. Effects were evaluated using the indices
developed by Glories. It was found that weak ultrasonic irradiation
promotes an increase in the amount of phenolic compounds in red
wine.
Temperature Self-Compensated Lithium Tantalate Piezoelectric Gyroscope for Higher Stability
Authors: Mitsuharu Chiba Mitsuharu Chiba , Noboru Wakatsuki Noboru Wakatsuki
Published: October 2002

We are studying the flexura H-type vibrational gyroscope using a LiTaO3 single crystal with large electromechanical coupling coefficients. The H-type LiTaO3 piezoelectric gyroscope sharply suppresses leakage output. As a result, temperature characteristics of drift and sensitivity can be calculated using an equivalent circuit deduced from the experiment. The resonant frequency and Q-value of the X mode are stable with the temperature. However, the resonant frequency and the Q-value of the Z mode show complicated fluctuations with temperature due to the effects of the support and other factors. As a countermeasure, the possibilities of applying an automatic temperature characteristic compensation method with the monitor transducer in the drive mode of operating in nonresonant drive and resonant detection were studied. By adding a new monitor that detects the vibrational mode of the drive, we can establish a stable reference signal for the synchronous detection of output. It is possible to greatly improve the temperature characteristics of sensitivity and drift.
Equivalent Network Analysis of Functionally Graded Piezoelectric Transducers
Authors: Jun-ichi Sakamura Jun-ichi Sakamura , Ken Yamada Ken Yamada , Kiyoshi Nakamura Kiyoshi Nakamura
Published: October 2002

The performance of ultrasound transducers composed of a piezoelectric plate with a graded parameter is studied theoretically using an equivalent network model formerly presented by the authors. Transfer functions and impulse responses are calculated for a model of a functionally graded piezoceramic transducer which has a water load on one side and a matched backing on the other side. The theoretical examinations of the plates with some typical distributions of the piezoelectric constant e
33 clearly show the effectiveness of the piezoelectrical grading.
Photoacoustic Microscope Using Linear-Motor-Driven Pulse Stages
Authors: Hoshimiya Tsutomu , Miyamoto Katsuhiko
Published: October 2002

A linear-motor-driven photoacoustic microscope, which realizes both rapid response and quiet environment for a gas-microphone detection system, is fabricated as a candidate for the optimum gas-microphone photoacoustic microscopy system.
Transmission Electron Microscopic Studies of YbBa2Cu3O7-δ Superconducting Final Films Formed on LaAlO3(001) Substrates by the Dipping-Pyrolysis Process
Authors: Shibata Junko , Yamagiwa Katsuya , Hirabayashi Izumi , Hirayama Tsukasa , Ikuhara Yuichi
Published: October 2002

We investigated the relationship between final heat-treatment
conditions and microstructures of YbBa2Cu3O7-δ
films formed on LaAlO3(001) substrates by the dipping-pyrolysis
process. First, we spin-coated the substrates with a solution
including metal organic compounds. Second, we heated them at 425°C
in air to form amorphous precursor films. Finally,
YbBa2Cu3O7-δ films were prepared by the
final heat-treatment of the precursor films at 750°C in an Ar gas
flow under various conditions of heating rate and holding time. The
microstructures of these final films were studied by transmission
electron microscopy. It has been found that a rapid heating rate is
necessary for the epitaxial growth of the superconducting films, and
that a long holding time is effective for the grain growth of the
crystals. The transmission electron microscopic studies revealed
different microstructures of the final films, although X-ray
diffraction patterns did not distinguish them.
Optical Bistability of the Negative Nonlinear Absorption Effect in Erbium-Doped Fibers Using a 1.5 µm Laser Diode
Authors: Maeda Yoshinobu
Published: October 2002

Optical bistability derived from the negative nonlinear absorption
effect was investigated in 470 ppm erbium-doped fibers using a 1.5 µm
laser diode. Optical bistability was observed in a laser intensity range of
0.3 W/cm2 to 2.5 kW/cm2 at a fiber length of 6 m. The transmitted
laser intensity (I
out), propagating through the fiber, decreased
exponentially in accordance with the well-known exponential law. However,
the amplitude of the optical bistability (ΔI
out) increased
logarithmically as the fiber length was increased. It was clarified that
ΔI
out was proportional to the product of exp
(-L)
and log
(L) as a function of the fiber length (L). The optical bistability
can be explained by considering an enhanced absorption model for a four-level
system of the Er3+ ion.
Parasitic Resistance Reduction in Deep Submicron Dual-Gate Transistors with Partially Elevated Source/Drain Extension Regions Fabricated by Complementary Metal-Oxide-Semiconductor Technologies
Authors: Sugihara Kohei , Miura Naruhisa , Furukawa Taisuke , Nakahata Takumi , Nishioka Yasutaka , Yamakawa Satoshi , Abe Yuji , Maruno Shigemitsu , Tokuda Yasunori
Published: October 2002

Deep submicron dual-gate metal-oxide-semiconductor field-effect transistors
(MOSFETs) with partially elevated source/drain (S/D) structures were fabricated using
complementary MOS (CMOS) technologies. In comparison with well-defined conventional
MOSFETs, it is revealed that the drivability is appreciably enhanced by the S/D
elevation and, further, that a p-channel MOSFET gains more from the S/D elevation than
an n-channel MOSFET. Investigation of the parasitic resistance is consistent with
the results of the transistor characteristics.
An Improved Theory for Direct-Tunneling Current Characterization in a Metal-Oxide-Semiconductor System with Nanometer-Thick Silicon Dioxide Film
Authors: Nakatsuji Hiroshi , Omura Yasuhisa
Published: October 2002

In this paper, we formulate an improved theory to characterize the direct
tunneling current for the metal-oxide-nondegenerate semiconductor system with a
nanometer-thick SiO2 film on the basis of the Wentzel-Kramers-Brillouin (WKB)
approximation. The theoretical expressions described herein incorporate the current
contribution stemming from the valence band-to-conduction band tunneling. Valence
band-to-conduction band tunneling predictions are verified by experiments. Simulation
results show that the effective mass of tunneling electrons is smaller than reported
to date because the electron density at the injection source is more restricted than
previously thought.
Chopping Frequency Variation of Photoacoustic Amplitude from Porous Silicon
Authors: Ohmukai Masato , Tsutsumi Yasuo
Published: October 2002

We investigated the possibility of applying photoacoustic (PA) spectroscopy to
the study of luminescent porous silicon. Since porous silicon is usually formed on a
silicon substrate, PA spectroscopy is useful for obtaining the absorption coefficient of
porous silicon without removing the substrate. In this article, we investigated the
chopping frequency dependence of the PA signal from porous silicon and showed that
the chopping frequency is critical for the exclusion of the PA signal from silicon
substrate.
Characterization of Single Grain Boundaries in a Bi-Doped ZnO Varistor Using a Focused Ion Beam System
Authors: Tanimura Junji , Wada Osamu , Kurokawa Hiroshi , Furuse Naomi , Kobayashi Masahiro
Published: October 2002

This report presents a new method for electrically characterizing single grain boundary junctions of ZnO varistors. For the first time to our knowledge,
a focused ion beam system was used to deposit tungsten microelectrodes on two adjacent ZnO grains. Gallium ions irradiated onto the ZnO surface lowered the
resistivity of the ZnO, and therefore highly nonlinear current-voltage (I–V) characteristics of single grain boundaries could be obtained after etching
the gallium-irradiated ZnO surface with HClO4 solution. Breakdown voltages in the I–V characteristics were observed in the range from 2.6 V to 3.2 V
within the same ZnO varistor. The grain boundary with the breakdown voltage of 3.2 V was structurally different from that of 2.6 V. The boundary with the
breakdown voltage of 3.2 V contained precipitates and a thin, amorphous Bi-segregated layer about 1 nm thick. On the other hand, the boundary with the voltage
of 2.6 V contained no precipitate but rather, a thin, amorphous Bi-segregated layer about 0.5 nm thick. It was suggested that the electrical characteristics
of grain boundary junctions within the ZnO varistors are strongly dependent upon the microstructure of the grain boundary.
Effect of Boron on Solid Phase Epitaxy of Ge on Si(111) Surface
Authors: Yamamoto Tomonori , Ikeda Makoto , Ezoe Kenji , Ishii Kunihiro , Matsumoto Satoru
Published: October 2002

The effect of boron(B) on the growth of Germanium(Ge) by solid phase epitaxy
(SPE) on Si(111) has been investigated using scanning tunneling microscopy in
ultra-high-vacuum (UHV) and atomic force microscopy in the tapping mode in air.
After annealing 1 mono-layer(ML) of amorphous Ge (a-Ge) at 500°C on a
√3×√3R30°-B surface, it is found that B segregates
to the Ge surface and induces the √3×√3R30° structure.
For 6 ML, the surface structures of Ge exhibit a mixture of 5×5 and
√3×√3R30° areas. The √3×√3R30°
areas show the presence of B, while the 5×5 areas show
the absence of B. Moreover, 3-dimensional(D) islands are formed only on the
5×5 areas of the surface. Another set of experiments is also performed,
i.e. 1/3 ML of B is deposited on top of a-Ge, followed by annealing at
500°C. This B-deposited Ge film grows in a layer-by-layer mode up to
10 ML. At larger Ge thicknesses, relaxed 3D islands of Ge are formed on
the surface as in normal Ge/Si heteroepitaxial growth. The promotion of
layer growth is attributed to the reduction of Ge surface mobility by
the B layer on the Ge surface.
InAs Quantum Dots Growth by Modified Droplet Epitaxy Using Sulfur Termination
Authors: Mano Takaaki , Watanabe Katsuyuki , Tsukamoto Shiro , Imanaka Yasutaka , Takamasu Tadashi , Fujioka Hiroshi , Kido Giyu , Oshima Masaharu , Koguchi Nobuyuki
Published: October 2002

We have applied the modified droplet epitaxy method using sulfur
termination to fabricate InAs quantum dots on GaAs(001) substrates
for the first time. It is observed that the S-terminated surface
effectively prevents the two-dimensional growth of InAs, forming
InAs nanocrystals. From the magneto-photoluminescence measurements
of this structure, three-dimensional quantum confinement effect was
confirmed. This modified droplet epitaxy method is promising for the
fabrication of quantum dots, not only in the lattice-matched system
but also in the lattice-mismatched system.
Self-Organized Nanostructures Generated on Au, Ag and Cu Surfaces by Low-Temperature Electron Irradiation
Authors: Niwase Keisuke , Phillipp Fritz , Seeger Alfred
Published: October 2002

We describe a new type of self-organized nanostructure for Au, Ag and Cu thin foils irradiated with high-energy electrons at around 100 K. The nanostructure appears on the electron exit surface and consists of aligned grooves which developed parallel to the surface, and nanoholes and hillocks which grew parallel to the electron beam. The groove pattern depends on the irradiation direction, the surface orientation, and the kind of metal. After about 1000 s of irradiation, penetration of the foil by grooves and holes occurs, finally leading to the formation of nanoslits or nanoparticles. These structures are probably the smallest ones generated so far on each metal surface. It is suggested that some irradiation-induced effects are closely related to the generation of nanostructures.
Study on Defects of Solar Cell Silicon Irradiated with 1 MeV Electrons by Positron Annihilation
Authors: Tamano Takuya , Hori Fuminobu , Oshima Ryuichiro , Hisamatsu Tadashi
Published: October 2002

In order to obtain information on the degradation of solar cells in artificial satellites as a result of cosmic ray radiations, positron annihilation lifetime experiments were performed for B-doped p-type Czochralski (CZ) silicon wafers irradiated at room temperature with 1 MeV electrons with fluences between 1014 and 1017 e/cm2. Positron lifetime measurements were done at 100 K to improve the trapping rates of positrons with defects. The mean lifetime of irradiated Si was shorter than that of unirradiated Si. We found that short lifetime defects (approximately 100 ps) existed, which could be associated with complexes of Si with interstitial oxygen atoms, doped B and vacancies resulting from irradiation. Lifetime components longer than those of the bulk accounted for the formation of thermal donors and divacancies.
Effects of Barrier-Metal Schemes of Tungsten Plugs and Blanket Film Deposition
Authors: Chang Hui-Lin , Jeng Pei-Ren
Published: October 2002

This work investigates the effects of various contact integration schemes on tungsten (W) plug formation. The deposition rate, surface morphology, sheet resistance and reflectivity of W deposited on various substrates are also characterized. Experimental results indicate that the titanium nitride (TiN) film which does not undergo post-rapid-thermal-processing (RTP) treatment has a higher W deposition rate than TiN film which under goes the post-RTP treatment. The W plug formed on chemical vapor deposition (CVD) TiN has easily found voids, which result in high contact resistance. To reveal the relationship of CVD TiN process conditions and W plug loss, process variables including film thickness, plasma ambient, in situ plasma treatment periods and cycles are tested. According to these results, plasma ambient has a strong influence on W plug loss during the etch-back process. In addition, the electrical characteristics of various contact integration schemes are examined in terms of both n+ and p+ contact resistance. This work also proposes a superior contact integration scheme to achieve low contact resistance and high production efficiency.