bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Surface Acoustic Wave Grating Waveguides Considering Velocity Dispersion Caused by Reflectivity
Authors: Kazuhiro Hirota Kazuhiro Hirota
Published: October 2002

Conventional surface acoustic wave (SAW) grating waveguide analyses ignore the changes in phase velocity in the grating region. In reality, velocity dispersion is caused by the reflectivity of finger electrodes, and phase velocity changes near the stop band.
In this paper, a new approximate analytical model of a SAW grating waveguide is proposed. This model considers the dispersion of phase velocity, by placing a wave number along waveguide of a transverse mode in such a way that it becomes a solution of the coupling-of-modes (COM) theory.
The results of the new model differ from those of conventional analyses. The frequency characteristics of 2-port resonators on 36.5°Y-X quartz and 45°X-Z Li2B4O7 are measured. Calculations using this new model show good agreement with measurements in terms of resonance frequencies and response levels, while those using conventional analyses vary largely. The adequacy of this model is confirmed by the experimental results.
A Design of Surface Acoustic Wave Wideband Single-Phase-Unidirectional Transducers Using Coupling-of-Modes Theory
Authors: Noritoshi Kimura Noritoshi Kimura , Masao Takeuchi Masao Takeuchi
Published: October 2002

To realize wideband surface acoustic wave (SAW) filters, a weighted
single-phase-unidirectional transducer (SPUDT) has been analyzed by
direct numerical analysis of the coupling-of-modes equations. It was
found that the directivity was obtained over a wide frequency range
when the reflection coefficient of the SPUDT was weighted using a sinc
function in order to distribute the positive and negative reflection
elements into the SPUDT; this was called a wideband SPUDT. This paper
also describes a high-performance wideband SPUDT, with both the reflection
and transduction coefficients weighted on 128°Y-X LiNbO3
substrates, and a new wideband natural-SPUDT (NSPUDT) on
50°Y-23°X La3Ga5SiO14 substrates,
which has recently attracted much attention for intermediate frequency
(IF) SAW filters.
Relationship between Horn Pressure and Welding Time in Ultrasonic Welding of Plastic Pipes Using Torsional Vibration
Authors: Suga Kenichi , Ohdaira Etsuzo , Masuzawa Nobuyoshi , Ide Masao
Published: October 2002

Application of ultrasonic welding to plastics has become common. Recently, an
ultrasonic welding method for long plastic pipes using torsional vibrations was developed.
Optimal welding conditions for this new method have not yet been clarified. This paper
reports the results of an investigation made in order to clarify the conditions, focusing on
the welding time and both horn pressure, static force that horns pinch pipe, and static
pressure which is added to welding surface. Experiments were performed on the welding
of acrylic resin and ABS resin pipes. It was found that welding time decreases
exponentially with increasing horn pressure and that increasing the static pressure reduces
the welding time. It was also found there is an optimum range of
horn pressures.
Suppression of Ultrasonic Cavitation in the Speed-Up of Permeability of Semipermeable Membrane
Authors: Irisawa Yuichiro , Ohdaira Etsuzo , Masuzawa Nobuyoshi , Ide Masao
Published: October 2002

Ultrasound is used to increase the diffusion speed in separation technologies using
semipermeable membranes. In this technology, increase of separation speed depends on
the ultrasonic pressure. At high pressure, cavitation is produced and this increases
degradation of the membrane. In this paper we report a cavitation-suppressed irradiation
of ultrasound under high-pressure region where cavitation is produced with conventional
irradiation. The method of suppressing cavitation in this study is by alternate switching of
the conventional single frequency wave and frequency modulated wave.
Effects of a Series Capacitor on the Energy Consumption in Piezoelectric Transducers at High Vibration Amplitude Level
Authors: Umeda Mikio , Nakamura Kentaro , Ueha Sadayuki
Published: October 2002

In this paper, a driving method for low-loss generation in piezoelectric transducers at a high vibration amplitude level is presented. First, we analyze the power consumption of several loss mechanisms of piezoelectric transducers using an electrical equivalent circuit model. In this model, loss due to piezoelectric effect is explicitly represented by a series resistor, and pure dielectric loss is separately denoted by a parallel resistor. Mechanical loss is represented by a series resistor in the mechanical arm. The reason for the high efficiency at the anti resonance frequency is explained by this analysis. Next, the effect of an external series capacitor is discussed by comparing the experiment with the calculation, based on the equivalent circuit model for the high vibration amplitude level. By using the external series capacitor, the loss generated at the high vibration amplitude was significantly reduced without a large increase in electrical impedance.
Numerical Analysis of Acoustical Propagation in Ocean with Warm and Cold Water Mass Used by The Three-Dimensional Wide-Angle Parabolic Equation Method
Authors: Tsuchiya Takenobu , Okuyama Takashi , Endoh Nobuyuki , Anada Tetsuo
Published: October 2002

The three-dimensional parabolic equation method (3DPE) is useful
for analyzing the three-dimensional transmission characteristics of
the propagation sound in the Pacific Ocean which has a spatial
temperature distribution caused by a warm or a cold water mass. Sound
pulses passing through a spatial water mass are curved not only in the
vertical direction but also in the horizontal direction because of the
temperature gradient of the water mass. In ocean acoustical
tomography, it is important to estimate the distribution of sound
pressure on the sound fixing and ranging (SOFAR) axis, because a small
number of sound sources and receivers are placed on the SOFAR axis. We
obtained accurate results of sound pressure distribution on the SOFAR
axis using three-dimensional (3-D) simulation, when the sound pulse
passed through a spatial water mass. The calculations of underwater
acoustical propagation for comparison in a cold or a warm water mass
were carried out using by the 3DPE method to compare with the
two-dimensional (2-D) calculation results. The maximum temperature
fluctuation at the center of the water mass was assumed to be varied
from -6.0 to 5.0°C. The propagation sound fields are a
larger extent than shown by the estimation results of
2-D simulation.
Computer Simulation of Tunneling Transfer and Formation of Resonant States in a GaAs/AlGaAs 2 Dimensional Electron Gas Disk
Authors: Mitsuru Ishida Mitsuru Ishida , Masahito Yamaguchi Masahito Yamaguchi , Nobuhiko Sawaki Nobuhiko Sawaki
Published: October 2002

The time-dependent 2-dimensional Schrödinger equation was
solved with the finite element method to investigate the electron
tunneling phenomena in a planar-type quantum disk with the electrodes
system. Tunneling time, which was determined at the electron
probability amplitude to reach a steady state, is longer
through a thin potential barrier than that through a thick barrier.
Mode formation process is analyzed with energy spectra in the
quantum dot. An ionized impurity introduced in the quantum
dot is shown to have a significant effect on the sequential
tunneling transfer through the dot.
Tissue Elasticity Reconstruction Based on 3-Dimensional Finite-Element Model
Authors: Yamakawa Makoto , Shiina Tsuyoshi
Published: October 2002

We describe a method of estimating the elasticity distribution in tissue based on
the 3-D finite-element model.
Generally, the elastic modulus is calculated from the strain and the stress.
The strain field can be estimated from the RF signals measured for pre- and postcompressed tissue, while it is impossible to directly measure
the stress field within the tissue. Therefore, we reconstruct the tissue elasticity distribution
by solving the inverse problem, that is, by estimating the elasticity
modulus from the axial strain field and the external pressure
distribution at the surface of the tissue. We have performed a simulation and a phantom experiment to demonstrate the ability of the proposed method.
The results verified that the method is able to detect tumors
more quantitatively than the conventional method based on the 2-D model,
even for lesions invisible in a B-mode image.
Annihilation Mechanism of Surfactant Microbubbles in a Blood Vessel Model by Ultrasound Exposure
Authors: Kawan Soetanto Kawan Soetanto , Tomohiro Saito Tomohiro Saito
Published: October 2002

In this study, the relationship between exposure to ultrasound and the lifetime of microbubbles in a blood vessel model is investigated. Microbubbles are produced from a surfactant solution, and the change in the number of microbubbles upon ultrasound exposure is measured. The experimental results confirm that the microbubbles collapse upon ultrasound exposure. Microbubble lifetime is shortest when the driving frequency of the ultrasound is equal to the frequency at which the maximum value of the ultrasound attenuation of the microbubble suspension is obtained.
Deposition of Ge1-xCx Alloy on Si by Combined Low-Energy Ion Beam and Molecular Beam Epitaxial Method
Authors: Shibata Hajime , Kimura Shinji , Fons Paul , Yamada Akimasa , Obara Akira , Kobayashi Naoto
Published: October 2002

A combined ion beam and molecular beam epitaxial method was
applied for the formation of a Ge1-x
C
x
alloy on Si(100)
using a low-energy (50–100 eV) C+ ion beam and a Ge molecular
beam. Ge1-x
C
x
alloys were formed up to x = 0.047. It was
revealed that the sticking coefficients of C+ ions into Ge were
∼53% and ∼34% at the ion energies of 100 eV and 50 eV,
respectively. This result suggests that the ratio of the number of
ions recoiling at the surface of the substrate to the number of
incident ions is higher for lower energy ions within the ion energy
range examined. Characterization of crystal structure by X-ray
diffraction suggests that the deposited films are single crystals
grown epitaxially on the substrate with twins on {111} planes. Study
of the C-1s chemical shift by X-ray photoelectron spectrometry in
the sample of x = 0.047 revealed that the total composition of C
atoms incorporated in substitutional and interstitial lattice sites is
about 72%, while that of C atoms incorporated in the form of
precipitate is about 28%. Lattice dynamical characterization by Raman
spectroscopy suggests that the deposited layers have been damaged by
ion irradiation.
Elongated shaped Si Island Formation on 3C-SiC by Chemical Vapor Deposition and Its Application to Antiphase Domain Observation
Authors: Yuuki Ishida Yuuki Ishida , Tetsuo Takahashi Tetsuo Takahashi , Hajime Okumura Hajime Okumura , Toshihiro Sekigawa Toshihiro Sekigawa , Sadafumi Yoshida Sadafumi Yoshida
Published: October 2002

We have investigated the early stage of Si growth on 3C-SiC. We found that adsorbed Si atoms on a 3C-SiC surface form elongated islands 2–3 µm long and parallel to the <110 > direction. The formation of anisotropic islands can be explained by the anisotropic diffusion constant of Si adatoms on a 3C-SiC surface. We proposed a novel method to observe antiphase domains (APDs) using this characteristic of Si island growth on 3C-SiC.
Improvement of Photo-Misalignment in Patterned Wafer Bonding Process for Silicon-on-Insulator Device
Authors: Lee Ki-Hong , Cha Gi-Ho , Bae Geum-Jong , Lee Kyung-Wook , Kim Il-Kwon , Lee Sang In , Lee Moon Yong
Published: October 2002

We have found that the photo-misalignment problem in patterned and bonded silicon-on-insulator
(PBSOI) was closely related to the bonding process. We examined the stress effect on photo-misalignment using a vacuum bonding system. Photo-misalignment was critically dependent on the
distance between bonding plates. Good alignment, which is less than
0.1 µm and has uniform direction
within a wafer, could be achieved with a 1.4 mm separation width
between bonding plates.
Tight-Binding-Calculation Method and Physical Origin of Reflectance Difference Spectra
Authors: Takashi Nakayama Takashi Nakayama , Misao Murayama Misao Murayama
Published: October 2002

The accurate tight-binding-calculation method of reflectance
difference (RD) spectra
is developed for surfaces and interfaces with various orientations,
taking into consideration the crystalline nature
and the finite size of the system adopted in the
calculation.
It is shown that
the bond-polarization picture, i.e., that every bond becomes
a unit of polarization, is applicable to the optical response
of surfaces and interfaces, and
the RD spectra are calculated by averaging the optical
responses of even and odd finite-layer systems.
The physical origins of the RD spectra are classified into two
groups; the RD spectra have either the peak shape or the
energy-derivative-of-peak shape
depending on whether the electronic states are localized or extended
around the surface/interface.
Model Study of Ballistic S-2DEG-S Josephson Field Effect Transistors
Authors: Wendin Göran , Shumeiko Vitaly S. , Samuelsson Peter , Takayanagi Hideaki
Published: October 2002

We analyze the variation of the critical Josephson current with gate voltage in a ballistic SNS heterostructure. With increasing gate voltage the number of bound Andrev levels increases, the junction becomes effectively long, and the critical current is suppressed.
Rewritable Optical Head Using ±First-order Diffracted Beams of a Holographic Optical Element
Authors: Tanaka Masahiko , Yamamoto Yuichiro , Takehara Shintaro , Hasegawa Hiroshi , Kobori Hiromichi
Published: October 2002

A new focusing error detection method using ±first-order diffracted beams
of a holographic optical element (HOE) is proposed. We fabricate the
proposed HOE and measured the focus offset between a land a groove.
According to the measurement results, the focus offset of the proposed HOE
was smaller than that of an astigmatic focusing error detection.
The Excitation Spectra of Two-Photon Induced Fluorescence in Xanthene Dyes
Authors: Wakebe Takanori , Keuren Edward Van
Published: October 2002

Two-photon excitation spectra of xanthene dyes in ethanol were
measured by observing fluorescence emission after excitation by light
with wavelengths from 780 to 1260 nm. The normalized spectra showed
large two-photon induced fluorescence at higher energies and two
moderate peaks near the one-photon absorption band. These features
agreed well with the two-photon excitation spectra reported by other
authors. The peaks near the one-photon absorption band may be due to a
two-photon allowed state overlapping the lowest singlet state or to
excitation to the lowest singlet state. We believe the latter is the
case; while a two-photon excitation is formally symmetry forbidden,
both interaction with the counterion in solution as well as vibronic
coupling will remove the symmetry, allowing this
transition. Comparison of the spectra of dyes with slightly different
structures supports this explanation. The input power dependence of
fluorescence irradiance was also measured and some deviation from the
expected quadratic dependence was observed in Rhodamine 6G and
Rhodamine B.
Bulk Boundary Condition for Numerical Solution of Simultaneous Diffusion Equations of Phosphorus and Point Defects in Silicon
Authors: Yoshida Masayuki , Takahashi Manabu , Tomokage Hajime
Published: October 2002

The bulk boundary condition for the numerical solution of the phosphorus diffusion
equation in silicon, which is based on the pair diffusion model of the vacancy mechanism, is
studied. The zero concentration-gradient condition of vacancy at a region more than two times
deeper than the phosphorus diffusion depth can be used in place of the equilibrium
concentration condition of vacancy at x=∞. The zero concentration-gradient condition is
applicable to diffusion equations based on the pair diffusion models of vacancy and
interstitialcy mechanisms.
Theory of Artificial Atoms and Molecules using Semiconductor Quantum Dots
Authors: Kawamura Kiyoshi , Eto Mikio
Published: October 2002

Physics of a quantum dot and a quantum dot dimer is reviewed with special emphasis on the importance of the Kondo effect and coherence of currents. A new formalism is proposed which enables us to calculate the current in the case where electrons change the quantum state in a quantum dot during their passage.
Preparation of Al–O–N Films by Electron Cyclotron Resonance Plasma-Assisted Chemical Vapor Deposition
Authors: Goto Takashi , Zhang Wei , Hirai Toshio
Published: October 2002

Al–O–N films were prepared by electron cyclotron resonance plasma-assisted chemical vapor deposition (ECR PACVD) using an AlBr3–N2O–N2–Ar–H2 gas system. The structure, composition, deposition rate and optical properties were investigated. The compositions were controlled by changing the N2O/(N2O+N2) flow rate ratio (R). The refractive index was varied from 1.60 to 2.10, and the cutoff photon energy at 10% transmittance (E
g/10) from 5.1 to 7.0 eV as the R changed from 0 to 1.0. The Al–O–N films were composed mainly of a mixture of Al2O3 and AlN. An aluminum oxynitride phase was also identified at R=0.2 to 0.53. The Al–O–N films contained a (001)-oriented hexagonal AlN phase at R=0.025, and the films were amorphous at R>0.05.
Physical Properties of Dense Plasma Produced by XeCl Excimer Laser in High-Pressure Argon Gases
Authors: Norio Tsuda Norio Tsuda , Jun Yamada Jun Yamada
Published: October 2002

When XeCl excimer laser light was focused in high-pressure Ar gas up to 150 atm, a hot and dense plasma developed not only backward but also forward. The physical properties of the plasma produced by an ultraviolet laser in high-pressure gases have not been studied yet except for the mechanism involved in its development. Interferometric and spectroscopic measurements were carried out. Electron density was measured using a Mach-Zehnder interferometer. When laser intensity was 2×1011 W/cm2 at the focal spot, electron density was proportional to the pressure and a fully ionized state was almost achieved up to 150 atm. Dense plasma with electron density of the order of 1027 m-3 was obtained. Electron density was highest at the focal spot and the forward electron density was higher than the backward one. Electron temperature was estimated from continuous intensities. Electron temperature at the focal spot of the order of 105 K was obtained. The electron temperature distribution differed from the electron density distribution, in which the backward electron temperature was higher than the forward one.
Detection Limit of Laser Thomson Scattering for Low Density Discharge Plasmas
Authors: Bowden Mark D. , Goto Yasunori , Uchino TsukasaHori , Muraoka Katsunori , Noguchi Masanori
Published: October 2002

Laser Thomson scattering is a method for measuring electron properties of plasmas.
Recent applications have showed that this method can be applied to much lower density
plasmas than was previously possible. In this paper, a formalism is given for estimating
the lower detection limit for different experimental arrangements and the lower detection
limit of electron density in low density discharge plasmas is presented. It is shown that
the intensity of the background plasma emission is the main factor that determines the
signal-to-noise ratio and hence the lower detection limit. The dynamic range for
measurements of electron energy distribution functions is also
discussed.
Effect of CF4 Addition on Downflow Ashing under Atmospheric Pressure
Authors: Kataoka Yoshinori , Saito Shuichi , Omiya Kayoko
Published: October 2002

We studied the rate increase of ozone ashing under atmospheric pressure. It
was verified that when an ozonizer discharge was used under atmospheric pressure,
the ashing rate increased to up to one and a half times the original rate with the
addtion of CF4. F element and C–F bonds, which might appear as a result of the
addition of CF4, were not detected on the resist surface by Fourier transform infrared
spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) analyses. On the other
hand, the formation of HF and an increase in CO and CO2 were observed by FT-IR
analysis of the excited gas. Therefore, the increased ashing rate with the addition of
CF4 is likely due to the active decomposition product which contains fluorine radicals
produced in the discharge. These active species are transported under atmospheric
pressure and cause H extraction from –OH groups which exist in the resist and result
in improved oxidative decomposition.
Conducting Polymer/Insulating Polymer Composite Films Prepared by the Molecular Self-Assembly Process
Authors: Mitsuyoshi Onoda Mitsuyoshi Onoda , Kazuya Tada Kazuya Tada , Hiroshi Nakayama Hiroshi Nakayama
Published: October 2002

By exposing low-density polyethylene to an atmosphere of fuming sulfuric acid, sulfonated low-density polyethylene (SPE) was prepared and the degree of surface sulfonation for the treated films was determined as the weight-increase per unit area. Polypyrrole (PPy) films were grown on the surface of SPE using the molecular self-assembly process and the properties of PPy/SPE composite films have been investigated. Functional applications of PPy/SPE composite films have also been proposed and in particular, the movement properties of actuators using PPy/SPE composite films have been mentioned.
Structure Transformation of the C Defects Observed at Low Temperature (80 K)
Authors: Hata Kenji , Morita Ryuji , Yamashita Mikio , Shigekawa Hidemi
Published: October 2002

The dynamical characteristics of the C defect at low temperature (80 K) were studied
by sequential scanning tunneling microscopy observations. We found that the C defect
frequently transforms into a another type of defect termed as the C2
LT defect. In addition,
the reversal C2
LT to C defect structural transformation was observed which implies that the
C2
LT defect is a metastable state of the C defect. The observed structural transformation was
completely different from that observed at room temperature. We interpret that structural
transformation associated with a change in the phase of the defect is suppressed at low
temperatures because it disturbs the ordering of the surrounding
buckled dimers.
Barrier-Height Imaging of Oxygen-adsorbed Si(001)2×1 and Ge(001)2×1 Surfaces
Authors: Shu Kurokawa Shu Kurokawa , Hiroshi Yamashita Hiroshi Yamashita , Jun Yoshikawa Jun Yoshikawa , Akira Sakai Akira Sakai
Published: October 2002

We have carried out barrier-height imaging of oxygen-adsorbed Si(001) and Ge(001) surfaces and investigated the adsorption-induced change in the barrier height at various oxygen-reacted sites. On Ge(001)2×1, we find that the most highly reactve site shows a large decrease (-1.6 eV in the occupied state) in barrier height. A similar but smaller decrease in barrier height is also observed at oxidized type-C defects on Si(001) 2×1. The observed low barrier height suggests that the oxygen-induced surface dipole at these reaction sites makes a negative contribution to the barrier height. It is also shown that the barrier-height difference between oxidized and unoxidized type-C defects can be used to distinguish them which show little difference in scanning tunneling microscopy (STM) contours.
Direct Observation of Strained Layer Formation at the Initial Stage of In Thin Film Growth on Si(100)
Authors: Kubo Osamu , Ryu Jeong Tak , Tani Hitoshi , Harada Toru , Katayama Mitsuhiro , Oura Kenjiro
Published: October 2002

The growth of In thin films on Si(100)2×1 substrates at
room temperature has been investigated mainly by scanning tunneling
microscopy (STM). In this study, we found that In atoms form a mixed
reconstruction phase of n×3 periodicity with 2×2
phase at coverage between 0.5 and 1.0 monolayer (ML), which has not
been observed so far. In atoms begin to form flat two-dimensional
(2D) islands above 1 ML. These islands have an apparent height of
about 7 Å and exhibit 2×1 periodicity associated with
the lattice constant of Si bulk crystal, indicating the formation of
a strained In layer. With increasing In coverage, the area of the
islands increases. At coverage above 3 ML, however, this layer
still does not dominate the entire surface and 2×2 and
n×3 phases still remain. We suppose that this layer plays an important role as the intermediate structure from 2D growth to 3D growth.
Photoinduced Current Properties of InAs-covered GaAs Studied by Scanning Tunneling Microscopy
Authors: Hiroshi Yamamoto Hiroshi Yamamoto , Itaru Kamiya Itaru Kamiya , Takuji Takahashi Takuji Takahashi
Published: October 2002

We performed simultaneous imaging of photoinduced current
and topography on an InAs-covered GaAs surface by scanning tunneling microscopy (STM)
under modulated laser irradiation
to investigate the difference in the electronic properties
between quantum dots and a wetting layer.
We also performed time-resolved tunneling current measurements to clarify the origin of the
photoinduced effects on its surface.
We observed a spiky transient current, resulting from photocarrier
separation by a built-in field in the surface depletion layer.
Images of the photoinduced current mainly originating from
the surface depletion were obtained at a chopping frequency of 900 Hz, and
both the photoinduced current images
and the
current transients observed at this frequency reveal that the surface depletion is more
suppressed under the dots than under the wetting layer.
Initial Stage of Nitridation of GaAs(001): Atomic Scale View
Authors: Imayoshi Takahiro , Oigawa Haruhiro , Shigekawa Hidemi , Tokumoto Hiroshi
Published: October 2002

The nitridation process of an As-terminated
GaAs(001)-β2(2×4) surface was studied by time-resolved
reflection high-energy electron diffraction (RHEED) and in
situ scanning tunneling microscopy (STM). On the intermediate
nitrided surface, a (3×4)-ordered phase was formed by the
rearrangement of the As-dimer pairs at 520°C. This phase
reverted back to the (2×4)-ordered phase below
400°C (reverse reconstruction by the re-adsorption of As
atoms). We propose a model to explain this behavior.
Phase Shift of an Electron Wave through a Quantum Dot and Aharonov-Bohm Effect
Authors: Asano Yasuhiro , Ohi Masafumi
Published: October 2002

The transmission coefficients of an electron wave passing through
an Aharonov-Bohm (AB) ring with a quantum dot
in one of its arms are studied numerically by the recursive
Green function method.
In addition to lead wires which are used as the
current-voltage probes, several lead wires
are attached to the AB ring in a simulation as they are in an experiment.
We discuss the relation ship between the effects of the additional lead wires
on the electron transmission and
the validity of a simple current formula which has been employed
in a number of studies.
We conclude that the simple current formula is valid when
the additional lead wires are strongly coupled to the AB ring.
Force Microscopy Study of SrTiO3(001) Surfaces with Single Atomic-Layer Steps
Authors: Iwahori Koichiro , Komeda ShunjiWatanabe , Saito MakiKawai , Kuwahara Yuji , Aono Masakazu
Published: October 2002

An atomically flat SrTiO3(001) surface was successfully
obtained by combining ultrasonic agitation and subsequent annealing at
1000°C in air. The topographic images taken using an atomic
force microscope revealed that the surface was composed of clear
atomic-steps and atomically smooth terraces. The steps were 0.2 nm
in height corresponding to half of the unit cell height of
SrTiO3, or the single atomic-layer height. The terraces were
categorized into two types; wide and narrow terraces appear
alternately. Surface composition analyzed by coaxial impact collision
ion scattering spectroscopy indicated that the topmost surface was
covered by domains of the SrO and TiO2 layers, where the latter
domain was dominant. The result suggests that the topmost surface of
the narrow terrace was terminated by SrO and the wide terrace by
TiO2. This was further examined by the use of a friction force
microscopy technique with which we were able to distinguish the
different surface terminations.
Application of Stacked ZnO Films as a Window Layer to Cu(InGa)Se2-Based Thin-Film Modules
Authors: Kushiya Katsumi , Sang Baosheng , Okumura Daisuke , Yamase Osamu
Published: October 2002

To overcome the disadvantages of DC sputtering while keeping its
advantages, a stacked structure of ZnO films as a window layer has
been developed for application to Cu(InGa)Se2 (CIGS)-based
thin-film modules. Application of multilayered, 2 wt%
Al2O3-doped ZnO (AZO) films prepared from a 2 wt%
Al2O3-doped ZnO ceramic target and use of a combination of
RF and DC sputtering techniques (i.e., sputtering conditions of RF
300 W/DC 1 A/DC 1 A) can lead to better crystallinity and
electrical properties and, as a result, an improved device performance
of CIGS-based thin-film modules. To improve the humidity resistance of
the ZnO window layer, which is the top layer of CIGS-based thin-film
modules, AZO is replaced with 5.7 wt% Ga2O3-doped ZnO
(GZO) prepared from a 5.7 wt% Ga2O3-doped ZnO ceramic
target. By adjusting the stacked structure and the layer thickness by
DC sputtering, an improvement in device performance, especially the
fill factor (FF), is achieved with the stacked structure of AZO
(base)/AZO (middle)/0.6 GZO (top) as the window layer, and a total
thickness of about 600 nm is realized, which means a thinner (about
60% of AZO top layer thickness) top layer.
Formation Mechanism of Antiphase Boundary Structure in Molecular Beam Epitaxy Grown InGaAs/(110)InP
Authors: Kangawa Yoshihiro , Kojima Chikako , Kuwano Noriyuki , Oki Kensuke
Published: October 2002

We have studied the morphology of antiphase boundaries (APBs) and their formation
mechanism in CuAu-I type ordered InGaAs grown on a vicinal (110)InP substrate. In InGaAs
grown at 380°C, APBs are formed parallel to (110) by the flow of one-monolayer steps. In
InGaAs grown at 450°C, the normal directions of APBs are slightly tilted toward [001] or [001]
from (110) and some APBs show a hairpin shape. New formation mechanisms of these APBs are
proposed.
Nitrogen Donor Concentrations and Its Energy Levels in 4H-SiC Uniquely Determined by a New Graphical Method Based on Hall-Effect Measurement
Authors: Hideharu Matsuura Hideharu Matsuura , Tsunenobu Kimoto Tsunenobu Kimoto , Hiroyuki Matsunami Hiroyuki Matsunami
Published: October 2002

This is the first report on the experimental results using the precise determination proposed in our previous papers. By means of this analysis, the concentrations and energy levels of dopants in a semiconductor can be uniquely determined using the temperature dependence n(T) of the majority-carrier concentration obtained experimentally from the Hall-effect measurement. In other words, the concentration and energy level of each dopant can be evaluated using the corresponding peak value and temperature of n(T)/k
T. In nitrogen (N)-doped 4H-SiC, the concentration and energy level of the shallow donor are 6.45 ×1015 cm-3 and E
C-0.0653 eV, respectively, and those of the deep donor are 3.04 ×1016 cm-3 and E
C-0.124 eV, respectively, where E
C is the bottom of the conduction band. The acceptor concentration is 6.14 ×1013 cm-3. These obtained values are found to be quite reliable.
Dissolution Rate Analysis of ArF Resists Based on the Percolation Model
Authors: Yamaguchi Atsuko , Takahashi Makoto , Kishimura Shinji , Matsuzawa Nobuyuki , Ohfuji Takeshi , Tanaka Tomoaki , Tagawa Seiichi , Sasago Masaru
Published: October 2002

We investigated the dissolution properties of ArF-resist base
polymers and ArF resist in order to study their development mechanism.
We measured the dissolution rate of methacrylate copolymers and a
resist as a function of the hydrophilic unit content, and simulated
dissolution phenomena by using percolation theory. The obtained
dissolution-rate curves had strong nonlinear dependence on hydrophilic
unit content. In the simulation analysis, base molecule diffusion
through the hydrophilic path was modeled as particle diffusion through
the percolation field. The diffusion constant was calculated by using
conventional and modified diffusion models. We suggest a new variable
to describe diffusion-path width in the modified model. The
simulation results indicate that our model reproduced the experimental
results better than the conventional model.
Effects of Phosphorus Dopant on the Thermal Stability of Thin Pd2Si and PtSi Silicide Films on (100) Si Substrates
Authors: Juang Miin-Horng , Ou-Yang Chang-I , Lin Cheng-Tung
Published: October 2002

The effects of phosphorus dopant on the thermal stability of thin Pd and Pt
silicide films on (100) Si substrates have been studied. For the samples formed by
implanting phosphorus dopant into thin Pd films followed by annealing, both the
thermal stability and the silicide conductivity of thin Pd2Si films are significantly
enhanced relative to the control samples without dopant incorporation. Large
improvements in the thermal stability and the silicide conductivity are dependent on
the formation of a textured Pd2Si structure. In addition, the Pt silicides formed by
implanting phosphorus dopant into thin Pt films followed by annealing also show
considerably improved thermal stability.
Si Deposition into Fine Contact Holes by Ultrahigh-Vacuum Chemical Vapor Deposition
Authors: Nakahata Takumi , Maruno Shigemitsu , Yamakawa Satoshi , Furukawa Taisuke , Tokuda Yasunori , Satoh Shinichi
Published: October 2002

An ultrahigh-vacuum chemical vapor deposition technique
with disilane (Si2H6) molecular flux is applied to fine contact
hole filling. Structural observations reveal that a completely
buried Si contact has a stacked structure, in which the lower
portion consists of pyramidal epitaxial Si, whose height depends
not only on the growth temperature and the Si2H6 flow rate but
also on the hole diameter, and polycrystalline Si is deposited
on the epitaxial Si. The mechanism of selective epitaxy is
interpreted in terms of incubation time and facet growth rate
depending on growth temperature and Si2H6 flow rate.
Annealing and Hydrogenation Behaviors of Electron-Beam Induced Defects in n-type Si
Authors: Ohmura Yamichi , Hayakawa Chiyuki , Suzuki Takao , Tajima Kenji
Published: October 2002

Deep level transient spectroscopy study shows that in electron-beam-irradiated
n-type Si, E1 level (O-V complex), E2 level (double negative
charge state of the divacancy) and E3 level (single charge state of the
divacancy) are hardly annealed at as low a temperature as 120°C, while
hydrogenation by boiling at 120°C (2 atm) dramatically reduces the
concentrations of these levels. A new level emerges near 0.33 eV below
the conduction-band edge E
c after boiling, which may be a
radiation-induced defect-hydrogen complex.
Experimental Investigation of CO2 Laser Assisted by Silent Discharge
Authors: Ling Yi-Ming , Xu Yi-Bo , Wu Xu-Feng , Jiang MeiXiao
Published: October 2002

A new type of CO2 laser tube has been designed by using a plasma tube having rectangular cross
section and is excited by both axial DC glow discharge and transverse high frequency (HF) silent
discharge. In this paper, the principle of the design is described briefly and its working characteristics,
including of breakdown, V-A, laser power and efficiency, are studied experimentally and compared
with those of CO2 laser excited by DC glow discharge only. Under the action of transverse HF silent
discharge, the laser power, the laser efficiency, the gas-filled pressure and the fraction of N2 in this
laser are increased significantly. In contrast, the breakdown voltage and the discharge voltage of this
laser tube are decreased.
Electrooptic Response of the Reflective Liquid Crystal Cell: Intensity and Phase Behaviors
Authors: Lee Geon Joon , Jo Jae Cheol , Lim Tong Kun
Published: October 2002

The electrooptic characteristics of a reflective mode,
45°-twisted nematic liquid crystal [E7] cell in the voltage
regions above and below Freedericksz transition threshold were
investigated for the intensity and phase of the reflected wave.
Oscillatory behavior in the parallel reflectivity was observed in the
regime of 2.96 π≥2β (phase retardation) ≥1.94 π.
This phenomenon was found to be due to the multiple reflections
between the glass-indium tin oxide interface and the aluminium
reflecting surface. In the regime of 1.94 π≥2β≥
0.72 π, a 100% modulation efficiency was achieved for the
perpendicular configuration. The phase characteristic of the
reflected wave was found to be closely related to the birefringence of
the liquid crystal layer.
Improving the Quality of Liquid-Crystal Projection Image by Multilevel Diffractive Grating Technique
Authors: Ko Fu-Jen , Wu Cheng-Ko , King Hong-Jueng , Wu Shiou-Yun , Shieh Han-Ping David
Published: October 2002

A technique using multilevel diffractive gratings to suppress
the discrete nature of liquid crystal display (LCD) projection images
is demonstrated. The multilevel diffractive gratings, having a cross
section similar to a staircase, are fabricated by VLSI processes and
plastic molding. Upon positioning the diffractive gratings on the
front surface of the LCD panel, the output light beams emitted from
each pixel are diffracted mainly into the zeroth and the ±first
diffraction order light beams of equal energy. The light beams
transformed by the diffractive gratings into orders higher than zeroth
are able to fill up the dead space between each subpixel, and generate
an array of images from each subpixel. As a result, the spatial
frequency of the color subpixel distribution within the whole image is
increased. Accordingly, the grain-like pixel structure in projection
images is removed, at a slight expense of image resolution.
Structure of Needlelike Defect in Homogeneously Aligned Cells of a Ferroelectric Liquid Crystal Mixture Studied Using X-Ray Microbeam
Authors: Takanishi Yoichi , Iida Atsuo , Ishikawa Ken , Takezoe Hideo , Fukuda Atsuo
Published: October 2002

Using a synchrotron X-ray microbeam, we analyzed the structure
of needlelike defects running parallel to the rubbing direction in virgin
homogeneously aligned cells of ferroelectric liquid crystals. It was
found that the local layer of the defect is perpendicular to the substrate
plane and the layer normal is tilted from the rubbing direction, which is
similar to the model proposed by Shao et al.. [Ferroelectrics 121 (1991)
127]. It was also found that the detailed structure depends on the cell
thickness.
In Situ X-Ray Topographic Study of Sweeping of Impurity Ions in Quartz Crystals
Authors: Sebastian M. T. , Becker R. A. , Klapper andH.
Published: October 2002

X-ray topographic studies were made on alpha quartz crystals with in situ electric field using graphite and silver electrodes at elevated temperatures in vacuum. A strong dark striation contrast appeared on the topographs near the anode side of the crystals when recorded with electric field along the c-axis. The effect is attributed to lattice deformation by space charge collection caused by the removal of the charge compensating impurity ions. The striation contrast disappeared as the temperature was raised above the stability range of the alpha phase. A strong contrast also appeared on the topographs near the cathode side of the crystals when silver electrodes were used. This contrast was due to the accumulation of the silver electrode material. The contrast at the anode end due to sweeping was predominant when the dc electric field was along the c-axis whereas the contrast near the cathode end was present irrespective of the direction of the electric field inside the crystals. Spotty contrast due to the
evolution of fluid inclusion with increasing temperature has also been observed in some crystals.
Lowering of Silicon Surface Cleaning Temperature by Irradiating Low Energy Electron Beams
Authors: Katsuhiro Yokota Katsuhiro Yokota , Kazuhiro Nakamura Kazuhiro Nakamura , Masashi Imai Masashi Imai
Published: October 2002

Thermal cleaning of Si surfaces for homo- and heteroepitaxial growth on Si substrates was performed at temperatures below 700°C by irradiating low energy and low intensity electron beams. In order to evaluate the cleaned Si surfaces, thin single-crystalline GaAs films were grown at 450°C using an organometal gas decomposition technique immediately after cleaning. No surface contamination, such as oxide and carbide, remained in the interface between the GaAs films and the Si substrates.
Influence of Creeping Distance and Gas Pressure on Negative Creeping Discharge for Composite Insulation Consisting of N2/SF6 and Solid Dielectric under Pulse Voltage
Authors: Ueno Hideki , Ohnishi Hiroshi , Tada Kazuya , Onoda Mitsuyoshi , Nakayama Hiroshi
Published: October 2002

Creeping discharge characteristics on negative polarity of a composite gas/solid
insulating system with N2/SF6 mixed gas have been studied by inserting a solid insulator
between a needle electrode and a plane electrode. In the case of the shorter creeping distance,
the flashover voltage on the negative needle increased with increasing SF6 gas content, which
was a positive effect of the SF6 gas mixture. When creeping distance was increased, a
considerable decrease in the flashover voltage on the negative needle under the gas pressures
P of 0.2 MPa and 0.3 MPa was observed by the addition of a small amount of SF6 into N2.
The effect of SF6 gas mixture for the flashover voltage on the negative needle changed from
positive to negative at a threshold creeping distance. Furthermore, the threshold creeping
distance depended on the gas pressure.
Selective Etching of GaN over AlxGa1-xN Using Reactive Ion Plasma of Cl2/CH4/Ar Gas Mixture
Authors: Basak Durga , Yamashita Kenji , Sugahara Tomoya , Nakagawa Daisuke , Fareed Qhalid , Nishino Katsushi , Sakai Shiro
Published: October 2002

Reactive ion etching (RIE) of GaN and Al
x
Ga1-x
N has been investigated using
Cl2, CH4 and Ar gas mixtures. It has been found that a variation in the CH4 percentage
in the gas mixture leads to a change in the etch rate of both GaN and Al0.85Ga0.15N with
a etch selectivity of 4.2:1 for GaN over Al
x
Ga1-x
N for an optimum value of 2.5% of
CH4. This gas composition also yields an anisotropic and smooth etching profile. An
etch rate of 257 nm/min of GaN has been obtained which is the highest value ever
reported with the RIE technique.
Reduction of Electron Temperature in rf Plasma Using Magnetic Filter
Authors: Nobuya Hayashi Nobuya Hayashi , Toshio Nakashima Toshio Nakashima , Hiroharu Fujita Hiroharu Fujita
Published: October 2002

The radio frequency (rf) plasma was adopted to reduce electron temperature, using a magnetic filter. Detection of electron energy distribution functions with a grid analyzer facing the plasma source and the magnetic filter revealed that only the low energy electrons passed through the magnetic filter and the high energy electrons were reflected by the filter. A reduction of the rf oscillating potential was also observed after passing through the filter, using a novel method with an emissive probe. The reduction rate, expressed as a function of the ion hole parameter around the magnetic filter, was found to be described by a fixed curve for various ion species and neutral gas pressures.
Characteristics of Very High Frequency Plasma Produced Using a Ladder-Shaped Electrode
Authors: Mashima Hiroshi , Murata Masayoshi , Takeuchi Yoshiaki , Yamakoshi Hideo , Horioka Tatsuji , Yamane Tsukasa , Kawai Yoshinobu
Published: October 2002

A very high frequency (VHF) excited H2 plasma is produced with a ladder-shaped electrode consisted of 17 rods and the plasma parameters are measured with
a movable Langmuir probe. When the discharge frequency (∼120 MHz) of the RF
power source is increased, the plasma density increases while the electron
temperature decreases. The position of the RF connections and the shape of the rod,
particularly at higher frequencies are found to affect the distribution of the ion
saturation current. The uniformity of the ion saturation current of ±17.2% over a
distance of 150 mm is achieved at 120 MHz.
Production of Large-Diameter Uniform Plasma in mTorr Range Using Microwave Discharge
Authors: Yasuyoshi Yasaka Yasuyoshi Yasaka , Daiki Nozaki Daiki Nozaki , Kazuya Koga Kazuya Koga , Makoto Ando Makoto Ando , Tetsuya Yamamoto Tetsuya Yamamoto , Naohisa Goto Naohisa Goto , Nobuo Ishii Nobuo Ishii , Tamotsu Morimoto Tamotsu Morimoto
Published: October 2002

A large-diameter uniform plasma is obtained by microwave discharge
without the use of magnetic fields at pressures in the mTorr range.
Microwave fields at 2.45 GHz are radiated from a multislotted
planar antenna located a short distance
above the glass window of a discharge chamber.
Overdense plasmas are produced with ± 3–4% uniformity of ion
saturation current over 30 cm diameter for wide ranges
of microwave power and gas pressure.
The discharge can be started up at pressures as low as 0.5 mTorr.
The efficient production of overdense plasmas
is investigated
by measuring microwave field propagation in the system.
Energy Control of Ions from a Capacitively Coupled Plasma Using RF Resonance Method
Authors: Naohiko Goto Naohiko Goto
Published: October 2002

Simulation results obtained, using a particle-in-cell simulation code show
that the RF resonance method can induce a strong electric field,
even in the bulk, which
maintains a high plasma density
under the condition that plasma
cannot be maintained
without resonance at a pressure of 0.133 Pa.
The high plasma density can be controlled by
magnetic flux density and applied voltage.
The magnetic flux density is a parameter which determines
the strength of the resonance
and the applied voltage increases the magnitude of the electric field
in the bulk.
A constant bulk condition, i.e., electron energy
and plasma density distribution in the bulk, is shown
to be realized for different combinations of the applied voltage and
magnetic flux densities
by adjusting the magnitude of the electric field in the bulk.
Voltage across the sheath varies
with the magnetic flux density.
Since the ion energy at the electrode depends on the sheath feature,
different ion energy distributions
at an electrode are obtained under a constant bulk condition.
Effects of Fluorocarbon Films on CF Radical in CF4/H2 Plasma
Authors: Toshihiko Arai Toshihiko Arai , Miki Goto Miki Goto , Keita Horikoshi Keita Horikoshi , Souichi Mashino Souichi Mashino , Satoshi Aikyo Satoshi Aikyo
Published: October 2002

The behavior of CF radicals in CF4/H2 plasma was studied as a function of the fluorocarbon film thickness grown on the inner wall in dc-pulsed CF4/H2 hollow cathode discharge plasma. Laser-induced fluorescence was used to examine the temporal behavior and radial distribution of the CF radical density. The thickness of the fluorocarbon films grown on the inner wall of the cylindrical hollow cathode was measured to investigate the influence of fluorocarbon film formation on the CF radical density in the plasma. For CF4/98%H2 discharge plasma, the radial distribution of the CF radical density deviated slightly from the zeroth-order Bessel function. The radial distribution of CF radical density changed to a uniform profile in CF4/98%H2 discharge plasma after exposure of the tube wall to CF4/20%H2 discharge.
Two-Dimensional Measurement of He Metastable Atom Density Profile in Front of Substrate in Electron Cyclotron Resonance Plasma Flow by Laser-Induced Fluorescence Spectroscopy
Authors: Mahiko Watanabe Mahiko Watanabe , Ken Takiyama Ken Takiyama , Hiroshi Toyota Hiroshi Toyota , Toshiatsu Oda Toshiatsu Oda
Published: October 2002

Two-dimensional measurement of He metastable atom distribution in the interacting region between plasma and substrate in ECR plasma flow was carried out by the forbidden laser-induced fluorescence technique. A sharp decrease was observed in the axial distribution of the metastable atom density in front of the substrate. It was also found that the radial density distribution was hollow-shaped in the region close to the substrate. This shape became shallower with increasing distance from the substrate. The mechanism involved in metastable atom destruction is briefly discussed.