bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical Results on Dopability in Large-Band-Gap II-VI Semiconductors
Authors: Chadi James D.
Published: October 2002

The difficulties in the p-type doping of ZnS and the n-type doping of ZnTe are well known
phenomena in the II-VI semiconductor community. We find extremely strong evidence from the
results of parameter-free first-principles calculations that the major source of doping difficulties in
II-VI semiconductors is the formation of self-compensating centers resulting from bond
rearrangement at dopants. The most important self-compensating center is identified. When the
formation energy of this center is endothermic, there is no problem with doping but when it is
exothermic, low resistance doping is not possible. The theoretical results on formation energies
and dopability are in excellent accord with experimental data.
Substrate Resistance Effect on Charge-Pumping Current in Polycrystalline Silicon Thin Film Transistors
Authors: Lee Ga-Won , Lee Jin-Woo , Han Chul-Hi
Published: October 2002

A model is proposed to explain the pulse transition time dependence of the charge-pumping current in polycrystalline silicon thin film transistors (poly-Si TFTs). When the gate pulse transition times are short, the charge-pumping current is increased abnormally due to the substrate resistance of poly-Si TFTs. The model is in good agreement with measured charge-pumping current, which enables accurate trap characterization.
Quantum Simulation of Resonant Tunneling Diodes: a Reliable Approach Based on the Wigner Function Method
Authors: Martín Ferran , García-García Joan , Oriols Xavier , Suñé Jordi
Published: October 2002

In this work, we demonstrate that the limitations of previous simulation tools for
resonant tunneling diodes based on the Wigner function approach, can be overcome by
coupling a classical Monte Carlo solver to the quantum Liouville equation, the former
being applied to regions far enough from the double barrier, where quantum effects are
not present. This allows us to extend the simulation domains up to hundreds of
nanometers, without paying a penalty in computational burden. It is shown that this
large domains are necessary to obtain an accurate description of device behavior. By
using physical parameters corresponding to those of actual devices, we have found
current oscillations and a plateaulike behavior in the negative conductance region in
accordance to experimental I-V characteristics obtained on resonant tunneling diodes.
Study of HF Defects in Thin, Bonded Silicon-on-Insulator Dependent on Original Wafers
Authors: Aga Hiroji , Nakano Masatake , Mitani Kiyoshi
Published: October 2002

To study the origin of HF defects in thin, bonded silicon-on-insulator (SOI) wafers fabricated by
the plasma assisted chemical etching (PACE) process, the dependence of HF defects on original wafers
[wafers fabricated by Czochralski method (CZ wafers), hydrogen-annealed CZ wafers and epitaxial
wafers] was investigated. It was shown that HF defect density was affected by the type of original wafer
used, and no HF defect was detected when epitaxial wafers were used as bond wafers. HF defects were
detected on 0.2 µm or thinner SOI wafers with CZ wafers. Crystal originated particles (COPs) at SOI
and buried oxide (SOI/BOX) interface were found to be the main origin of HF defects by inspecting light
point defects (LPDs) at the SOI/BOX interface.
Quantum Chemical Study of Silane Decomposition on Hydrogen-Terminated Si(001) Surfaces
Authors: Hiraoka Yoshiko S.
Published: October 2002

The mechanism of SiH4 adsorption to the bare Si defects in a
hydrogen-terminated Si(001) surface is analyzed using ab initio molecular
orbital calculations based on a cluster model. The energy barriers for
the dissociative adsorption of SiH4 are estimated to be 0.24 and 0 eV,
depending on the environment around the bare Si defects. This result
shows that the bare Si defects become the chemisorption sites of SiH4 in
chemical vapor deposition.
Measurement of Absorption Efficiency by a Leakage Power Analysis Method from an Efficient Nd:YAG Rod Laser Pumped by Diode Bars
Authors: Lee Jongmin , Moon Hee-Jong , Yi Jonghoon , Lee Sungman , Cha Byungheon
Published: October 2002

We proposed a leakage power analysis method to measure the absorption efficiency of a diode side-pumped Nd:YAG rod laser which was fabricated using a 3-fold symmetric gold-coated flow tube. The pump power from the 3 diode bar modules was coupled into the reflector through AR-coated windows. A maximum output power of 150 W with a slope efficiency of 47% was obtained from a Nd:YAG rod of 4 mm diameter at the diode pump power of 434 W, which corresponds to an optical efficiency of 34.6%. We investigated the thermally induced lens and pump light distribution of the 4-mm and 6-mm rods. The high slope efficiency originated from the wing-pumping scheme, uniform pump light distribution and the high absorption efficiency. By fixing the wavelength of the diode at 802.4 nm, we measured the absorption efficiency, using the leakage power analysis method, which agreed well with the results obtained using the Findlay-Clay method.
Therefore, the leakage power analysis method was demonstrated to be simpler and more reliable because it gives accurate values without the need to adjust diode wavelength.
An absorption efficiency of 94% was measured for the case of a 4-mm rod.
Electro-optical Performance of a Self-Compensating Vertically-Aligned Liquid Crystal Display Mode
Authors: Liu Weimin , Chen Jack Kelly andJ.
Published: October 2002

Very recently, a novel homeotropic nematic liquid crystal
display (LCD) with excellent grayscale performance has been
introduced. This rub-free mode adopts the homeotropic alignment in the
off-state and switching is controlled by an in-plane field. It has
electrically-induced dual domain-like director configuration. In this
work, we simulate the electro-optical behavior of this device to
optimize its performance. We investigate the dependence of
electro-optical performance on cell thickness and electrode gap
distance. The angular dependence is also studied, which shows the
effect of self-compensation. The viewing angle characteristics are
investigated in terms of transmission, contrast, gray scale, and
chromaticity. We find from modeling that the director configuration
above the electrodes is well behaved and masking of the electrodes is
unnecessary. In fact, this homeotropic mode has better performance if
the electrodes
are unmasked.
Experimental Study on Electron Beam Energy Recovery System Using a Laser-Heated Electron Gun and a Multistage Electron Collector for Highly Efficient Beam Application
Authors: Roy Prabir Kumar , Fujita Masayuki , Imasaki Kazuo , Moon Ahsa , Sano HidehiroTanaka , Tsunawaki Yoshiaki , Ohigashi Nobuhisa , Mima Kunioki , Nakai Sadao , Yamanaka Chiyoe
Published: October 2002

An experiment on electron beam energy recovery systems has been performed using a laser-heated electron gun and a multistage electron collector. Modeling of the laser heating indicates that the cathode temperature is proportional to the one-fourth power of laser power. The energy recovery efficiency of 99.8% of the designed collector is calculated using a computer code with a beam current of about 10 mA and -75 keV. In the first phase of the recovery experiment, potentials of the collector electrodes are provided through a voltage divider of several hundred megaohms. In order to overcome the drawback of voltage-divider resistance, two high-voltage power supplies are provided in the second phase of the experiment, and charge and energy recovery efficiencies are measured.
Photoluminescence Properties of Nonpolymeric Amorphous Dyes
Authors: Naito Katsuyuki , Yoko Watanabe Yoko Watanabe , SyunEgusa SyunEgusa
Published: October 2002

The relationships between optical properties and assembly states for
various nonpolymeric organic dyes have been investigated. Absorption photon
energies (ΔE
AB) for amorphous films were nearly equal to those for solution samples.
However, photoluminescence photon energies (ΔE
PL) for amorphous films were smaller
than those for solution samples and were nearly equal to those for crystalline samples.
Photoluminescence (PL) quantum yields (Q) for amorphous films were generally smaller than those for
crystalline and solution samples. PL decay time measurement indicates that
nonradiative deactivation processes in amorphous films are faster than those in
crystalline and solution samples. The relationship between the optical properties and
the molecular structures was investigated using the Pariser-Parr-Pople
configuration interaction (PPP-CI) MO method. Many nuclear
configurations probably exist for amorphous states and excitation energies are lost in
the presence of many rotational and vibrational sites.
Electroabsorption Spectra of Merocyanine J-Aggregate Langmuir-Blodgett Films
Authors: Saito Kazuhiro
Published: October 2002

Electroabsorption spectra were measured for Langmuir-Blodgett (LB)
films which contain a merocyanine J-aggregate monolayer. The LB films,
which possess asymmetrical molecular arrangement, were employed to
investigate linear electrochromism. A clear difference was observed in the
spectra between linear and quadratic electrochromism.
Intrinsic Reasons for Variations in Dielectric Properties of Ba6-3xR8+2xTi18O54(R=LA–Gd) Solid Solutions
Authors: Valant Matjaz , Suvorov Danilo , Rawn ClaudiaJ.
Published: October 2002

Studies of the temperature coefficient of permittivity of
Ba6-3x

R
8+2x
Ti18O54 (R=La–Gd) solid
solutions revealed a high degree of correlation with the ratio of mean
radii (r

A
/r

B
) of A- and B-site ions. Single-crystal X-ray
diffraction analyses of La, Sm and Pr analogues showed that
r

A
/r

B
can be further correlated to tilting of the TiO6
octahedra in the network of the Ba6-3x

R
8+2x
Ti18O54
crystal structure. Changes in the tilting of the octahedra induce
changes in the crystal field and subsequently, changes in the
temperature coefficient of permittivity as well as dielectric
loss. Variations in dielectric properties are limited by the
flexibility of the crystal structure. Variations in the tilting of the
octahedra resulting from changes in the composition are highly
anisotropic, which explains the markedly high electrical anisotropy of
Ba6-3x

R
8+2x
Ti18O54 solid solutions.
Effect of Soaking in Solvents on Molecular Orientation of Rubbed Polyimide Film
Authors: Hirosawa Ichiro , Matsushita Tomoharu , Miyairi Hiroshi , Saito Susumu
Published: October 2002

We used reflection ellipsometry and infrared absorption spectroscopy to
investigate the effect of soaking rubbed polyimide films in solvents. This enabled
us to clarify the influence of washing on polyimide films after rubbing, in the
fabrication process of liquid crystal display devices. It was found that soaking in
solvents caused disordering of the polyimide molecules, thinning of the
molecular ordered layer and increase of the tilt angle of principal dielectric axis
of the rubbed polyimide film. However, there was no indication that soaking in
solvents caused a chemical reaction in rubbed polyimide films.
Characteristics of Excimer Laser Induced Plasma from an Aluminum Target by Spectroscopic Study
Authors: Lu Yong-Feng , Tao Zi-Bo , Hong Min-Hui
Published: October 2002

Optical emission spectrum of Al plasma induced by a KrF excimer laser (248 nm)
in a vacuum chamber is investigated using an optical multichannel analyzer (OMA).
It is observed that different air pressures and delay times after the laser pulse play
important roles in the characterization of emission spectrum from Al surface. The
optimal conditions for spectroscopic study of Al plasma are estimated. A spectrum
self-absorption effect can be observed clearly from the calibrated spectral line profiles
at the initial stage of plasma expansion and high fluence. Assuming local
thermodynamic equilibrium (LTE) conditions, the plasma temperature and density are
estimated from two spectral lines (Al I, 309.2 and 396.1 nm) as a function of air
pressure, delay time and laser fluence. The plasma temperature is derived to be in the
range of 5500 to 10000 K using the relative intensities of the spectral lines. The
electron density is estimated from Stark broadening profiles of the spectral lines, and
found to range from 0.7×1018 to 3.5×1018 cm-3. The behaviors of the plasma
temperature and density reveal a 1-D plasma expansion at a delay time shorter than
200 ns and the plasma shielding effect at high fluence.
Charging of Glass Substrate by Plasma Exposure
Authors: Kitabayashi Hiroyoshi , Fujii Haruhisa , Ooishi Takayuki
Published: October 2002

It is probable that charge-up of a glass substrate during plasma
processing such as ashing and/or etching deteriorates the production
yield of thin-film transistor-liquid-crystal-display (TFT-LCD)
devices. In order to keep the production yield at a high level, it is
necessary to understand the charging mechanism of glass surface in
plasma and then offer countermeasures for the process. We measured the
surface potential of the glass substrate during plasma processing. We
exposed the glass substrate to plasma in a parallel-plate electrode
system by introducing Ar, O2 or SF6 gas into the plasma
reactor and exciting with 13.56 MHz RF or DC power supply. As a
result, we found that the charging of the glass substrate in plasma
depended considerably on the power source and the gas species.
We discussed the phenomenon in terms of the behavior of molecular ions
in plasma.
Atomic Force Microscopy Study on the Dissolution Processes of Chemically Amplified Resists for KrF Excimer Laser Lithography
Authors: Kanzaki Kenichi , Ohfuji Takeshi , Sasago Masaru , Tagawa Seiichi
Published: October 2002

The surface images of chemically amplified KrF excimer laser resists after development
were measured by atomic force microscopy (AFM). From the AFM images at various exposure
doses, the dissolution behavior of the polyvinylphenol-based KrF resists differed from that of
novolak-diazonaphthoquinone (DNQ) resists. An explanation for the different dissolution behavior
has been proposed by considering the difference in the mechanisms of formation of soluble sites
between chemically amplified resists and novolak-DNQ resists (non-chemically amplified resists).
In addition, AFM topographic images of the resists dissolving layer by layer were observed clearly in
the resist spin-coated on a Si wafer. The step heights of the layered structure observed by AFM are
in good agreement with the computed value of the distance between two adjacent nodes of standing
waves formed by KrF excimer laser exposure. The layered dissolution may be applied to the
processing of thin polymer films.
Brillouin Scattering Study of Elastic Properties of Transition-Metal Nitride Superlattices
Authors: Akira Yoshihara Akira Yoshihara , We-Hyo Soe We-Hyo Soe , Ryoichi Yamamoto Ryoichi Yamamoto
Published: October 2002

Surface acoustic waves of transition-metal nitride TiN/CrN superlattices prepared on MgO (001) and glass substrates have been examined by Brillouin scattering. The superlattices were capped by a 15-nm-thick Al layer to enhance the Brillouin scattering efficiency. Scattering from the Rayleigh wave and the longitudinal guided wave have been observed. The Rayleigh wave velocity is independent of the superlattice period in a range of 30 to 0.6 nm. On the other hand, the longitudinal guided mode velocities exhibit a softening of about 10% and show a minimum at around 5 nm and 3 nm of the superlattice periods for the glass and MgO substrate superlattices, respectively.
Chaos and Quantum Transport in Antidot Lattices
Authors: Ando Tsuneya , Uryu Seiji , Ishizaka Satoshi
Published: October 2002

A review of magnetotransport in antidot lattices mainly from a theoretical point of view is given.
The topics include various mechanisms proposed for the explanation of the origin of the commensurability peaks such as pinned orbits, runaway orbits, and diffusive orbits combined with a magnetic focusing effect.
Roles of quantum effects and antidot disorder are also discussed.
Second Harmonic Component in the Focused Ultrasound Diffracted by a Straight Edge
Authors: Saito Shigemi , Kim Jung-Soon
Published: October 2002

The influence of a diffracting edge inserted into the focal
region on the fundamental and second harmonic field is theoretically
and experimentally investigated. A straight edge of a rigid plate set
normal to the acoustic axis is assumed to diffract a focused Gaussian
beam. The second harmonic sound generated, both in front of and beyond
the edge, is taken into account to formulate the diffracted field
using Green's function for the governing approximate equation, where
the Fresnel approximation is employed for a focused Gaussian beam. In
the experiment, a straight edge of a steel plate is inserted into the
beam formed by a 1.9 MHz focusing Gaussian source of a concave
piezoelectric transducer with an asteroid electrode. The acoustic
field beyond the diffracting edge is observed with a needle type or a
concave hydrophone to have a reasonable agreement between the
theoretical and experimental results.
Sound Velocities in Polymer Blends and the Compatibility
Authors: Yamada Gen , Koda Shinobu , Nomura Hiroyasu
Published: October 2002

The longitudinal and transverse sound velocities in polymer blends of
polyvinylchloride with polystyrene or polymethylmethacrylate were measured as a
function of the polyvinylchloride content. The relationship between the sound velocity
and composition deviated slightly from linearity. The shear, bulk, Young's modulus
and Poisson's ratio were evaluated from the sound velocities and density. These
elastic properties changed monotonically with an increasing content of
polyvinylchloride. Young's modulus of polymer blends was analyzed on the basis of
compatible and incompatible models. The compatibility of the polymer blends was
discussed on the basic of the sound velocity measurement, thermal analysis, dynamic
thermomechanical analysis and acoustic micrography.
Effect of Ultrasound Frequency on Sonochemical Luminescence under Well-Determined Sound Pressure
Authors: Yanagida Hirotaka , Masubuchi Yuichi , Minagawa Keiji , Takimoto Jun-ichi , Koyama Kiyohito
Published: October 2002

By determining sound pressure using the Ramann-Nath parameter
and confirming sound form based on schlieren images, we
investigated the effects of ultrasound frequency on the sonochemical
luminescence of a luminol solution. Separating the effect into the
luminescence threshold of sound energy and the rate of luminescence
increase with respect to the sound energy, we found that the lower
the frequency is the lower the threshold and the higher the rate of
increase, and that only the standing-wave induces luminescence under
the conditions where the running-wave does not induce luminescence
at all.
Pressure Sensitivity of a Fiber-Optic Microprobe for High-Frequency Ultrasonic Field
Authors: Yasuto Uno Yasuto Uno , Kentaro Nakamura Kentaro Nakamura
Published: October 2002

An acoustic microprobe is required to measure high-frequency ultrasonic fields with good spatial resolution. An optical fiber microprobe was proposed in our previous study, which consists of a small optical cavity 100 µm long made at the end of the fiber. The optical path length of the cavity is changed by the applied acoustic field, and the
modulation of output light intensity is monitored at the other end of the fiber to derive information of the acoustic field. In the present study, the pressure sensitivity of the fiber-optic microprobe is discussed theoretically and experimentally. Mechanical deformation of the optical cavity by acoustic pressure is calculated by the finite element method (FEM), and the effect of the deformation on the optical property is analyzed for a low finesse microcavity.
Acoustic Measurement of Temperature Distribution in a Room Using a Small Number of Transducers
Authors: Funakoshi Koichi Mizutani , Keinosuke Nagai Keinosuke Nagai , Ken'ichi Harakawa Ken'ichi Harakawa
Published: October 2002

We propose a method for noncontact measurement of room temperature distribution using a small number of acoustic transducers. The sound propagation velocity is dependent on the air temperature, and it is acquired from the time of flight of sound. The mean temperature parallel to the sound probe is acquired using an acoustic delay line consisting of a pair of transducers. The measured object is a room of size 4,000 mm (D)× 4,200 mm (W) partitioned into a 3×3 grid, with 9 unit cells. By arranging a certain geometrical property of the sound propagation path, we can formulate an expression for the temperature distribution as a matrix function of the sound velocity. Twelve transducers are installed in contact with the four walls. We create a temperature gradient throughout the room using an electrical heat source. Experimental reconstruction results of the room temperature distribution were in agreement with the distributions estimated from the temperature profiles of the heat sources. This technique has the advantages of noncontact sensing, quicker response time and simpler calculation of room temperature distribution, in comparison with conventional temperature measurement systems.
Photoacoustic Studies of Annealed CdSxSe1-x (x = 0.26) Nanocrystals in a Glass Matrix
Authors: Shen Qing , Toyoda Taro
Published: October 2002

Photoacoustic (PA) spectroscopy is applied to study an optical
absorption of CdS
x
Se1-x
(x=0.26) nanocrystals in a glass matrix
annealed at 700°C for different time durations. As the annealing time
increases, a shift of the absorption peak (due to the quantum
confinement effect) to lower energy is observed in the PA spectra
at room temperatures. The observed absorption peak shifts are used
to evaluate the average size of CdS
x
Se1-x
nanocrystals in terms of a
simple model. The average radius increases from 2.3 to 4.7 nm as
the annealing time increases from 0 to 120 min. The PA signal
intensities plotted in the semilogarithmic scale vary linearly below
the fundamental absorption edges in accordance with the Urbach rule
for the optical absorption coefficient. The steepness factor (slope
of exponential optical absorption) of the PA spectra increases with
increasing annealing time. The change of the electronic states by
annealing is explained by considering that the contribution of the
surface states decreases with the increase of the nanocrystal size.
Underwater Acoustic Sensor Using Optical Fiber Bragg Grating as Detecting Element
Authors: Takahashi Nobuaki , Tetsumura Kanta , Takahashi Sumio
Published: October 2002

An underwater acoustic sensor using an optical fiber Bragg grating (FBG) in the reflection mode is examined to characterize the sensor under various conditions. For the fabrication of the sensor, one end of the FBG fiber pigtail is terminated by a low reflection facet such as an APC connector or an angled cut fiber and the output signal is extracted by an optical circulator of low back reflection. The sensor demonstrated as good performance of fundamental characteristics as a FBG acoustic sensor in the transmission mode. Considering many of the basic properties such as sensitivity, linearity, frequency response and compactness, an acoustic sensor using a FBG is as good as or better than a conventional PZT acoustic sensor.
Zero Field Magnetoresistance Peaks in Open Quantum Dots: Weak Localization or a Fundamental Property?
Authors: Akis Richard , Vasileska Dragica , Ferry David K. , Bird Jonathan P.
Published: October 2002

We have performed numerical simulations of the magnetotransport of open quantum dots with contacts supporting several modes.
We reproduce the zero field resistance peaks seen in experiments performed on such structures, a phenomenon previously attributed to weak localization. Our results, however, indicate that these peaks can have an entirely different origin, involving the zero field crossings of conductance resonance lines that reflect the underlying dot spectrum.
Even with significant ensemble averaging, the nature of these crossings largely determines the shape and width of the resistance peaks.
Ultrasonic Seam Welding System Using a Complex Vibration Circular Disk in Transverse and Torsional Vibrations
Authors: Tsujino Jiromaru , Ueoka Tetsugi
Published: October 2002

Ultrasonic seam welding of metal plate specimens using a 28 kHz complex vibration disk welding
tip vibrating in transverse and torsional vibration modes is studied. Conventional ultrasonic seam
welding equipment using one-dimensional vibration locus can only join metal foil or very thin plate
specimens and not join thick metal plate specimens. Using a complex vibration welding system
with a welding tip vibrating in elliptical or circular locus, thick plate specimens can be welded with a
more uniform and larger area weldment compared to a conventional ultrasonic welding system. An
ultrasonic seam welding system consists of a complex vibration disk welding tip which is driven by
a longitudinal vibration system through a longitudinal-torsional vibration converter. The disk
welding tip vibrates in elliptical locus. Aluminum plate specimens 0.3 mm and 3.0 mm in
thickness were successfully joined with such weld strengths that the specimens were broken at the
plate parts adjacent to the welded area under tensile strength test. Aluminum plates 50 mm in width
were successfully joined by the ultrasonic seam welding system.
Measurement of Microscopic Spatial Distribution of Acoustic Radiation Force Using Microspheres and Electrostatic Force
Authors: Yasuda Kenji
Published: October 2002

A simple method for measuring the microscopic spatial distribution of the
acoustic radiation force by exploiting the competition between the acoustical
radiation force and the electrostatic force on charged microspheres is investigated. First, the effective charge of polystyrene spheres is measured by
monitoring the mobility of the particles in the 1 Hz, 13.4 Vpp/mm alternating
electric field. Next, the shift of the particles away from the sound pressure
node with an increase in intensity of the electrostatic force is observed by optical
microscopy, and finally the acoustic radiation force is estimated. In the
experiment, the spatial distribution of the acoustic radiation force in the 500 kHz,
80 Vpp standing wave was proportional to the sine curve, and had the same
tendency as the result obtained from calculation. The intensity was 0.5 pN for
7 µm polystyrene spheres.
Conductance through Laterally Coupled Quantum Dots
Authors: Hiroaki Ueno Hiroaki Ueno , Katsuji Moriyasu Katsuji Moriyasu , Yuuko Wada Yuuko Wada , Shin-ichi Osako Shin-ichi Osako , Hitoshi Kubo Hitoshi Kubo , Nobuya Mori Nobuya Mori , Chihiro Hamaguchi Chihiro Hamaguchi
Published: October 2002

We fabricated laterally coupled quantum dots on a GaAs/
Al0.3Ga0.7As single quantum well, and studied their
transport properties. We focused on the geometrical dependence
of the conductance through laterally coupled quantum dots. The
quantum-dot-array pattern was defined by electron beam lithography and
deeply etched through the GaAs quantum well layer. We measured the
I–V characteristics of two different types of samples, which
consisted of ten quantum dots in straight and zigzag forms. For
the straight coupled quantum dots, we observed a single peak in the
conductance at zero applied bias. On the other hand, for the zigzag
coupled quantum dots, we observed double peaks in the conductance at
finite applied biases. The difference in I–V characteristics
is associated with a collimated electron beam entering into the
quantum dots.
A Low-Wear Driving Method of Ultrasonic Motors
Authors: Ishii Takaaki , Takahashi Hisanori , Ueha KentaroNakamura
Published: October 2002

The life of ultrasonic motors is limited by the wear of friction materials used for the contact
surfaces. In order to reduce the wear of the friction material, we have to reduce the sliding
speed between the sliding surfaces of the motor. In this report, we propose a new driving
method to reduce the sliding speed of the motor by shaping the vibration speed waveform.
The sliding loss was calculated and wear reduction effect was confirmed. A wear test was
carried out under no-load condition. This method prolongs the life of an ultrasonic motor by
about 3.4-fold. The results and wear reduction effects are also described.
Conductance through Atoms: Dot or Channel?
Authors: Nobuhiko Kobayashi Nobuhiko Kobayashi , Mads Brandbyge Mads Brandbyge , Masaru Tsukada Masaru Tsukada
Published: October 2002

We present a first-principles calculation of the transmission
eigenchannels of an Al atomic wire between jellium electrodes. We
show how the decomposition of electronic states into eigenchannels
can provide a transparent view of electronic transport in atomic-sized
systems. In particular, we show how local density of states
and current density resolved
into eigenchannels reflect the atomic orbitals of the single Al
atom. On the other hand, the eigenchannel density of states
has a one-dimensional (1D) band character for the straight three-atom wire.
From this we conclude that
the transport through the single Al atom in this case mainly has a
1D (channel) character in contrast to a zero-dimensional
resonant tunneling (dot) character.
The Signal to Noise Ratio of the 200 Hz Ocean Acoustic Tomography System
Authors: Nakamura Toshiaki , Fujimori Hidetoshi , Nakano Iwao
Published: October 2002

This paper describes the signal to noise ratio of the 200-Hz
ocean acoustic tomography system as determined by the result of the
performance test for tomographic monitoring conducted at the Kuroshio
extension east of the Izu-Ogasawara Trench for a 3 month period
between July and November 1997. After recovery of all the equipments, the retrieved data were read
from the hard disk in the transceiver and analyzed. The average value
of the signal to noise ratio in this experiment was approximately 20 dB which was an adequate value for the sound propagation up to 1000 km.
Applying the Hamiltonian Algorithm to Optimize Joint Photographic Expert Group (JPEG) Quantization Tables for Medical Ultrasonic Echo Images
Authors: Kazuhiko Hamamoto Kazuhiko Hamamoto , Hideaki Umemura Hideaki Umemura , Kazutaka Hirata Kazutaka Hirata , Jun-ichi Yamada Jun-ichi Yamada , andKazumasa Shinjo andKazumasa Shinjo
Published: October 2002

Storing digital medical images is standardized by the digital imaging and communications in Medicine (DICOM) report. Lossy pulse-echo ultrasonic image compression by a joint photographic expert group (JPEG) baseline system is permitted by it. Although significant compression is achievable by lossy algorithms, they do not permit the exact recovery of the original image. The objective of this study is to reduce the data volume and to achieve a low bit rate in the digital representation of pulse-echo ultrasonic images without a perceived loss in image quality. In image compression with a JPEG baseline system, it is possible to control the compression ratio and image quality by controlling quantization values. In this paper, we apply the Hamiltonian algorithm to optimize JPEG quantization tables. We construct the evaluation function involving the compression ratio and image quality. Results reveal that it is possible to optimize these quantization values by the Hamiltonian algorithm for lossy pulse-echo ultrasonic image compression.
Three-Dimensional Imaging System Using Ultrasonic Encoded Wavefront –High Speed Computation and Array Geometry
Authors: Tamura Yasutaka , Ito Tomoshi , Wada Noriaki , Fuwa Shingo , Yoshizawa Shigenori
Published: October 2002

We are developing a computed ultrasonic 3-D imaging system based on encoded wavefront transmission
which enables acquisition of 3-D images with a very high flame rate. We have developed an underwater
3-D imaging system based on the proposed method. In order to expand our system to various applications
including medical imaging, we are designing a new imaging system. The present data acquisition system
consists of multi channel A/D converters and a pulse-pattern generator. A transducer array is now under
development, with polymer and composite piezoelectric films. Computation is accelerated with a DSP
coprocessor board. In this paper, we describe high-speed 3-D image reconstruction using sector-like grid
geometry. Influence of the array configurations to artifact level are investigated using computer simulations.
Influence of Secondary Electron Detection Efficiency on Controllability of Dopant Ion Number in Single Ion Implantation
Authors: Takahiro Shinada Takahiro Shinada , Atsuki Ishikawa Atsuki Ishikawa , Makoto Fujita Makoto Fujita , Keisuke Yamashita Keisuke Yamashita , Iwao Ohdomari Iwao Ohdomari
Published: October 2002

The single ion implantation (SII) technique has been developed for the purpose of suppressing the fluctuation of the dopant ion number in semiconductor fine structures. It is based on a focused ion beam with a chopping electrode for the extraction of single ions, which enables implanting of dopant atoms one by one into a target. The influence of secondary electron detection efficiency, which is the key technology in SII, on the controllability of ion number has been investigated in this study. The measured sheet electron concentration coincides well with that estimated by taking the detection efficiency into account.
Simulation of High-Concentration Boron Diffusion in Silicon during Post-Implantation Annealing
Authors: Uematsu Masashi
Published: October 2002

We have simulated the transient enhanced diffusion (TED) and electrical
activation of high-concentration boron (B) in silicon during
post-implantation annealing. Based on the models for B diffusion, for TED
by self-interstitial clusters, and for B clustering, a unified simulation
is done, taking into account implantation-induced dislocations as a sink
for self-interstitials and the solid solubility limit of B. To establish
the initial profiles for higher doses, we used the maximum area density of
self-interstitials and B concentration effective for the TED and B
clustering. We have satisfactorily fitted B depth profiles at different
doses (5×1014–5×1015 cm-2) in a wide range of experimental conditions
(800–1000°C and 10 s–8 h).
Numerical Analysis of the Electrical Characteristics of Gate Overlapped Lightly Doped Drain Polysilicon Thin Film Transistors
Authors: Richard Ayres Alessandro Pecora , D. Brotherton Stanley
Published: October 2002

Polycrystalline silicon (polysilicon) thin film transistor (TFT) technology is emerging as a key technology for active matix liquid crystal displays, allowing the integration of both active matrix and driving circuitry on the same substrate. However, conventional self-aligned polysilicon TFTs present several undesired effects in the electrical characteristics, including large off-currents, kink effect and hot carrier instabilities. These effects are related to the presence of high electric fields at the drain junction and drain field relief is essential. Among the different structures proposed to reduce the drain field, the gate overlapped lightly doped drain (GOLDD) structure appears to have a number of advantages. In this work we investigate the electrical characteristics of GOLDD polysilicon TFTs by using 2-dimensional (2D) numerical analysis. From a close analysis of the output characteristics, we have distinguished two saturation regimes: the first related to the conventional formation of the pinch-off region near the LDD, the second one, occurring at higher source-drain voltages, related to the depletion of the LDD region. Impact ionization effects have been also analysed and kink effect in GOLDD structure has been found to be associated with the parasitic bipolar transistor action, similarly to silicon-on-insulator (SOI) devices. At very high source-drain voltages, avalanche breakdown occurs, due to impact ionization occurring at both channel/LD-region and LD-region/n
+ region junctions.
Radiative Centers in Layer Semiconductor p-GaSe Doped with Mn
Authors: Shigetomi Shigeru , Ikari Tetsuo , Nakashima Hiroshi
Published: October 2002

The emission bands of GaSe doped with Mn in the range of 0.1
to 1 at.% have been studied by photoluminescence (PL)
measurements. From the temperature dependence of the PL
intensity, the peak energy as a function of Mn concentration, and
excitation spectrum, we found that the emission band at 1.82 eV
is caused by the transition from the conduction band to the
acceptor level at 0.30 eV above the valence band.
Optical Design of High-Performance Beam Lines for X-Ray Lithography
Authors: Toyota Eijiro
Published: October 2002

In this paper is presented an optical design of high-performance beam lines for
synchrotron-radiation-based X-ray lithography. The optical system is composed of a single
toroidal scanning mirror and a movable beryllium window whose motions are synchronized. The
use of a toroidal scanning mirror is thought to cause excessive deformation of beam shape during
scanning and to suppress the light-condensing capacity. This problem has been solved by placing
the rotating center of the mirror near the light source point. Thus, intense illumination power can
be obtained. A beam reflected by the toroidal mirror forms an arc-shaped section, which causes
nonuniformity in the exposure intensity. A beryllium window foil with a specific curvature can
compensate the nonuniformity. A series of analytical studies and computer simulations have
proven the performance of the optical design.
Reduction of Inhomogeneous Broadening of Exciton Luminescence in CdxZn1-xSe Ternary Alloys and CdxZn1-xSe–ZnSe Multiple Quantum Wells Grown by Molecular-Beam Epitaxy under Se-Excess Supply
Authors: Masakatsu Fujimoto Masakatsu Fujimoto , Hiroshi Shigematsu Hiroshi Shigematsu , Kazuhiko Senda Kazuhiko Senda , Mitsutoshi Yoshikawa Mitsutoshi Yoshikawa , Hachiya Kubo Hachiya Kubo , Yoichi Yamada Yoichi Yamada , Tsunemasa Taguchi Tsunemasa Taguchi
Published: October 2002

Optical and structural properties of Cd
x
Zn1-x
Se ternary alloy layers grown by molecular-beam epitaxy (MBE) have been studied as a function of the Se/(Cd, Zn) beam pressure ratio (BPR). With increasing Se/(Cd, Zn) BPR, the inhomogeneous broadening of exciton luminescence and the rms roughness of surfaces decreased drastically. This indicates that Se-excess supply during MBE growth suppresses alloy composition fluctuation and also enhances two-dimensional growth nucleation. Furthermore, Cd
x
Zn1-x
Se–ZnSe multiple quantum well (MQW) structures have been fabricated under Se-excess supply. Biexciton luminescence from MQW structures was observed, even under a cw weak excitation condition (less than 100 mW/cm2). This observation reflects the finding that exciton lifetime increase as a result of the improvement of crystalline quality, which results in the enhancement of carrier accumulation.
Enhancement of the Laser Breakdown of Simple Gaseous and Liquid Materials under Intense Picosecond Double-pulse Excitation
Authors: Makoto Hosoda Makoto Hosoda , Shin-ichiro Aoshima Shin-ichiro Aoshima , Toshiaki Itoh Toshiaki Itoh , Yutaka Tsuchiya Yutaka Tsuchiya
Published: October 2002

We report the breakdown behaviors of simple gaseous and liquid materials
under double-pulse excitation from an intense picosecond Nd:YAG laser.
With an increasing in the separation time of the pulse pair,
a sharp increase in the intensity and decay time of a white-light emission
from the breakdown plasma was observed.
The further excitation of the preformed plasma by the second pulse
explains the origin of the phenomenon.
Effect of Oxidation on Chemical Bonding around 3d Transition-Metal Impurities in ZnO
Authors: Oba Fumiyasu , Tanaka Isao , HirohikoAdachi HirohikoAdachi
Published: October 2002

First-principles molecular orbital calculations for ZnO with 3d transition-metal (TM)
impurities ranging from Mn to Cu have been carried out in order to investigate the
relationship between TM impurities and oxygen adsorption in ZnO ceramics. Two kinds of
model calculations, i.e., the TM impurities with various formal charges in the bulk and
oxygen atom adsorption on the (1010) surface with TM impurities, were performed. For
bulk calculations, TM impurities form specific states within the band gap. The covalent
bonding around TM impurities is reinforced by the increase in formal charges. A similar
behavior is recognized for surface calculations. TM impurities at the surface are oxidized
by the adsorbed oxygen atom and the covalent bonding around TM impurities is reinforced.
On the other hand, the covalent bonding at the surface is weakened by oxygen adsorption
when TM impurities are absent. This result suggests that TM impurities enhance oxygen
adsorption at the ZnO surface. The mechanism may be similar at the grain boundary of
polycrystalline ZnO.
The Microwave Characteristics of Glass-BaTi4O9Ceramics
Authors: Yang Cheng-Fu
Published: October 2002

Microwave characteristics of BaTi4O9ceramics combined with different amounts of MgO–CaO–SiO2–Al2O3(MCAS) glass and sintered at different temperatures were examined. The temperature needed to densify the BaTi4O9dielectric is lowered with an increase of the content of MCAS glass. The densities and the dielectric constants of densified MCAS-BaTi4O9ceramics decrease with the an increasing amount of MCAS glass. The results of X-ray diffraction (XRD) patterns indicate that BaTi4O9and MCAS glass (cordierite phase) exist as two different phases. For BaTi4O9with 3 wt% addition of MCAS, the sintering temperature is lowered to 1200°C, and the ceramics have the optimum dielectric properties:Q=5720 (Q×f=42050),εrvalues=34.6, and τf=14.2.
Influence of Morphology on Electrical Properties of Syndiotactic Polypropylene Compared with Those of Isotactic Polypropylene
Authors: Dong Wook Kim Dong Wook Kim , Katsumi Yoshino Katsumi Yoshino , Takeo Inoue Takeo Inoue , Masaru Abe Masaru Abe , Nobutaka Uchikawa Nobutaka Uchikawa
Published: October 2002

The influence of morphology on the electrical properties of syndiotactic polypropylene (sPP) has been investigated in comparison with those of conventional isotactic polypropylene (iPP). The evolution of spherulite in sPP occurred at a lower temperature than in iPP, and the size of spherulites in sPP is much smaller than those of iPP, though the number of spherulites increases drastically. The influence of heat treatment on the electrical properties of sPP, such as conductivity and current density-electric field characteristics, is negligible in contrast to iPP, in which the conductivity increased drastically and breakdown strength decreased markedly due to growth of large spherulites upon heat treatment. These results are discussed in terms of morphological change upon heat treatment. As a result, sPP is confirmed to be an excellent candidate for a new insulating polymer for cables which can be used at a much higher operating temperature than that of widely used cables with cross-linked polyethylene (XLPE) (90°C), because of its thermal stability, stable electrical properties even following heating treatment and mechanical flexibility due to the small spherulite size and low crystallinity under any preparation and treatment conditions.
Microstructural Evolution under Polarization Switching of Ferroelectric Tin-modified Lead Zirconate Titanate Ceramics
Authors: Tsun Yung-Fu , Chou Chen-Chia
Published: October 2002

Electric fatigue properties of ferroelectric niobium-doped tin-modified lead zirconate titanate (PNZST) ceramics were investigated using polarization-electric field (P–E) measurements, and the corresponding microstructure evolution was studied employing transmission electron microscopy. The results show that domain boundaries are induced under repeated electric field application, and the microstructures become more complicated due to domain intersection. The mobility of domain boundaries degrades and the polarization of the material decreases because the intersection of domain boundaries introduces enormous strain fields and defects in the materials. A large number of dislocations and microcracks were observed in some regions when the specimens were repeatedly loaded for 106 cycles. In contrast, the remanent polarization of the ferroelectric PNZST degraded to 83% of its initial value and only half of the degraded polarization was recoverable after a refresh treatment, indicating that defects in grains play important roles in fatigue properties.
Minute Viscoelastic Observation in Isotropic-Nematic Phase Transition of 7CB with a Thousandth Kelvin Resolution
Authors: Ken-ichi Tozaki Ken-ichi Tozaki , Mitsunobu Kimura Mitsunobu Kimura , Satoshi Itou Satoshi Itou
Published: October 2002

The temperature dependence of the shear viscosity η for homeotropically aligned liquid crystals, 4-n-heptyl-4'-cyanobiphenyl (7CB) at 10 MHz was observed in the immediate vicinity of the isotropic-nematic phase transition with a thousandth Kelvin resolution by the piezoelectric composite resonator method. The transition process shows a clear hysteresis between heating and cooling processes. Furthermore, there is an interesting behavior of η only during the cooling process; the value of η suddenly decreases and then increases in a very narrow temperature region of 32 mK.
Chromium Carbide Thin Films Synthesized by Pulsed Nd:YAG Laser Deposition
Authors: Suda Yoshiaki , Kawasaki Hiroharu , Terajima Ryou , Emura Masanari
Published: October 2002

Chromium carbide thin films are synthesized on Si(100)
substrates by a pulsed Nd:YAG laser deposition method at different
substrate temperatures. Glancing-angle X-ray diffraction shows that a
crystalline chromium carbide film can be prepared at the substrate
temperature of 700°C. Grain size of the films, examined with
a field-emission secondary electron microscope, increases with
increasing substrate temperature.
Strain Relaxation in InGaAs Epilayers on GaAs by Means of Twin Formation
Authors: Moeck Peter , Mizuno Kaoru , Tanner Brian K. , Lacey Gales , Whitehouse Colin R. , Smith Gilbert W. , Keir Andrew M.
Published: October 2002

Strain relaxation in In0.045Ga0.955As epilayers grown by molecular beam epitaxy on (001) vertical gradient freeze Bridgman GaAs substrates has been assessed by monochromatic synchrotron X-radiation topography. A striation pattern parallel to the [110] direction was observed in every topograph of a sample grown with a non-uniform temperature distribution. Such a pattern has never been seen in specimens grown with a uniform temperature across the wafer. From a detailed analysis of the contrast, it is concluded that twins were formed. These twins, which were associated with oval defects, appear to relax the strain in the epilayer without misfit dislocation formation.
Temperature Dependence of the Optical Absorption Peaks at around 1990 cm-1 in Electron-irradiated Si doped with Hydrogen
Authors: Suezawa Masashi
Published: October 2002

We studied the temperature dependences of optical absorption peaks around 1990 cm-1 in
electron-irradiated Si doped with hydrogen. Contrary to a previous report, they are well separated
even at room temperature.
Comparison of Thin GaN and AlN Layers Deposited by Plasma Assisted Molecular Beam Epitaxy on 6H-SiC
Authors: Ferro Gabriel , Okumura Hajime , Yoshida Sadafumi
Published: October 2002

We have studied the effect of the deposition temperature and high temperature
annealing on the quality of thin GaN and AlN layers on 6H-SiC substrates. By systematic characterization using reflection high electron energy diffraction (RHEED) and atomic force
microscopy (AFM), we have shown that the two nitrides act differently in the early stage of
growth. GaN undergoes a Stransky-Krastanov transition enhanced by the post growth
annealing. AlN is less sensitive to the effect of annealing and the layers are comparatively
smoother than the GaN ones. GaN gives easily the cubic phase at low temperatures
whereas it is less feasible for AlN. For each material, better morphology and crystallinity
are achieved at the highest temperature studied (800°C) but AlN is preferable to GaN as no
islands are formed with AlN.
Epitaxial Growth of C54 TiSi2 on Si (001) as Revealed by High Resolution Transmission Electron Microscope
Authors: Huang Jen-Yun , Wu Shinn-Tyan
Published: October 2002

A high resolution transmission electron microscope has been applied to a cross-sectional
specimen to establish without ambiguity the epitaxial relationship between
C54 TiSi2 and Si (001) as TiSi2 [100] (022) ∥Si [110] (111). The straining of
the silicide film is also established by the displacement of the center of the zero-order
Laue zone of the film.