bluuebunny/crossref_metadata_2025 huggingface dataset:
Finite Element Method Aided Power Flow Mapping of an Ultrasonic Vibration Tool
Authors: Yoshikazu Koike Yoshikazu Koike , Kei Hiraizumi Kei Hiraizumi , Jun Sakai Jun Sakai , Kentaro Nakamura Kentaro Nakamura , Sadayuki Ueha Sadayuki Ueha
Published: October 2002

The power flow mapping of a loaded ultrasonic tool is necessary for designing the fatigue life of such a tool. As the power flow vector is defined as a tensor product of the vibration velocity and the stress tensor matrix, the entire vibration distribution of the tool is required. However, the three-dimensional (3D) measurement of the entire vibration distribution of the ultrasonic tool is impossible. In this paper, a newly proposed method for calculation of the power flow vector, in which the forced vibration analysis based on finite element method (FEM) is employed together with the partial vibration data measured at the surface of the ultrasonic tool, was applied to two types of rectangular parallelepiped ultrasonic tools. Reasonable power flow maps of both types of tools were successfully obtained.
Design of Weighted Reflectors and Their Application to Surface Acoustic Wave Bandpass Filter
Authors: Tatsuya Omori Tatsuya Omori , Motoyuki Tajima Motoyuki Tajima , Junichi Akasaka Junichi Akasaka , Ken-ya Hashimoto Ken-ya Hashimoto , Masatsune Yamaguchi Masatsune Yamaguchi
Published: October 2002

This paper proposes a method of designing surface acoustic wave (SAW) weighted reflectors using an adaptive nonlinear least-squares algorithm.
In the method, the total reflector length, the weighting function, the film thickness and pitch of the grating electrodes are all
simultaneously optimised. The optimally designed reflector possesses the stopband width of 4 MHz
at the centre frequency of 200 MHz with very steep response in the transition region and off-stopband reflectivities of nearly -80 dB.
The electrode width-weighted reflectors were fabricated and applied to filter devices employing a multistrip
coupler. The experimental result was in good agreement with theoretical prediction.
Transversely Coupled Resonator Filters Utilizing Reflection of Bleustein-Gulyaev-Shimizu Wave at Free Edges of Substrate
Authors: Michio Kadota Michio Kadota , Junya Ago Junya Ago , Hideya Horiuchi Hideya Horiuchi , Haruo Morii Haruo Morii
Published: October 2002

Smaller-sized and lower insertion loss surface acoustic wave (SAW) filters are urgently required for mobile telecommunications. We describe here that miniature, low-loss transversely coupled resonator filters without reflector electrodes could be realized and commercialized by utilizing the edge reflection of a Bleustein-Gulyaev-Shimizu (BGS) wave for the first time. The transversely coupled resonator filter has a narrower bandwidth than a longitudinally coupled one. A small, low-loss resonator filter for a first intermediate-frequency stage (first IF) of a spread spectrum (SS) codeless telephone system could be realized using a piezoelectric ceramic substrate with a coupling factor (k) of 0.20 and the transversely coupled resonator filter consisting of single finger electrodes. A filter for the first IF of the global system for mobile communication (GSM) requires a narrower bandwidth than SS codeless telephone, but a suitable substrate with a small coupling factor is not available. However, we could realize the small transversely coupled filter for GSM using split finger electrodes.
Mathematical Treatment of Mode Coupling between Two Plane Waves Using Unitary Matrix and Neumann Series
Authors: Michio Ohki Michio Ohki , Kohji Toda Kohji Toda
Published: October 2002

Mode coupling between two plane waves
through a spatial periodic structure
is discussed using a unitary matrix
and Neumann series; this differs
from the conventional methods which deal with
a difference or differential equation
as an eigenvalue problem.
The two modes are represented
by a two-component quantity,
which does not correspond to
the power flow as is involved in the conventional theory,
but to stored energy.
Phenomenon
due to multiple reflection or transmission
inside the periodic structure
is expressed
by a simple and unified matrix algebra,
which leads to the resonance characteristics
after the mode coupling.
Simulation of Multiaxial Angular Velocity Detection Using a Diaphragm Vibratory Gyrosensor
Authors: Hideki Tamura Hideki Tamura , Yoshiro Tomikawa Yoshiro Tomikawa
Published: October 2002

In this paper we deal with the simulation of multiaxial angular velocity detection for a vibratory
gyrosensor using a diaphragm vibrator with an additional inertia. The diaphragm vibrator is constructed
as a triple-mode resonator, and the inertia has vibrational motions in three degrees of freedom.
In this vibrator, two orthogonal forces are used to drive it, and therefore, the trajectory of the inertia
motion forms a circle. Under this condition, the three components of the applied angular velocities
individually change the trajectory. Therefore, we can determine these three components of the angular
velocities from their trajectory change. In the first part of this paper, we describe the theoretical
operation principle of the gyrosensor, and the second part contains the simulation of its vibrational
characteristics using the finite-element method, including the Coriolis force effect. The results indicate
that the multiaxial angular velocities can be detected.
Mechanical Displacement Measurement Using a Leaky Lamb Wave Delay Line Oscillator
Authors: Kohji Toda Kohji Toda , Takeshi Fujita Takeshi Fujita
Published: October 2002

A measurement technique for mechanical displacement using a liquid delay
line oscillator is described. The delay line is composed of a leaky Lamb wave
device with two interdigital transducers (IDTs), a liquid cavity as the propagation
medium for an ultrasound beam and an amplifier connected between two IDTs.
The IDT for leaky Lamb waves functions as a longitudinal wave radiator or
a detector of a reflected ultrasound beam from the surface of a wall in the liquid cavity.
The two lowest modes, S0 and A0, propagating in a thin piezoelectric ceramic plate
are useful for constructing the leaky wave transducer because of high transducer efficiency.
The acoustic delay length changes with mechanical displacement,
which results in a change of oscillation frequency. The basic performance of the delay
line oscillator is presented with the results of measurements in two operating modes, S0 and A0.
An Experimental Study of Ultrasonic Diffraction Tomography with Circular Scanning
Authors: Toyokatsu Miyashita Toyokatsu Miyashita , Akio Honda Akio Honda
Published: October 2002

We present an experimental result of a circular-scanning ultrasonic
diffraction tomography, where the transducer always faces towards
an object and moves around it.
Restricting the object in the far field of the incident cylindrical wave,
we have derived a reconstruction formula composed of a Fourier series
of Hankel transforms without any higher order Hankel functions
than the 0th order function.
Our simple experimental study for a small acrylic pipe in water shows a
promising quality of tomographic images.
Space Thermometry Using a Double Acoustic Delay Line Oscillator
Authors: Koichi Mizutani Koichi Mizutani , Eisuke Ishikawa Eisuke Ishikawa , Keinosuke Nagai Keinosuke Nagai
Published: October 2002

Acoustic thermometry in space using a double-delay line oscillator is described. The delay line oscillator is an important component in the sensor systems. In this paper, the adverse effect of a discontinuous oscillation was solved by adopting an acoustic technique which uses multiple oscillators. An experimental result at 40 kHz shows that the error in measured room temperature is 1.5% in a room 4,020 mm (D)×4,200 mm (W)×3,550 mm (H) with air conditioning. The acoustic thermometry proposed in this paper has advantages over conventional methods for such applications as atmospheric monitoring and air conditioning.
Detection of Inclusion in Molten Metal by Focused Ultrasonic Wave
Authors: Ihara Ikuo , Jen Cheng-Kuei , França Demartonne Ramos
Published: October 2002

An attempt for detecting impurity particles suspended in molten
zinc at 650°C has been made using a focused ultrasonic
pulse-echo technique with a clad metallic buffer rod. The focused
ultrasonic waves are generated by a spherical acoustic lens which is
fabricated at the end of the buffer rod. An experiment is carried
out at 10 MHz. The result shows that impurity particles in molten
zinc are detectable by using the presented focusing buffer rod.
A Real-Time Telemedicine System Using a Medical Ultrasound Image Sequence on a Low Bit-Rate Network
Authors: Toshiyuki Umeda Toshiyuki Umeda , Takatoshi Suenaga Takatoshi Suenaga , Tomohiro Kuroda Tomohiro Kuroda , Osamu Oshiro Osamu Oshiro , Kunihiro Chihara Kunihiro Chihara
Published: October 2002

A new telemedicine system that enables real-time telemedicine using a
medical ultrasound image sequence on a digital network of up to 128
kbps is proposed. This system compresses an image sequence by our
original joint photographic expert group (JPEG) compression library
that adapts for real-time and point-to-point communication. Moreover,
this system deals with three transmission modes to provide smooth
telemedicine and two kinds of transmission images. The three
transmission modes available include real-time teleconferencing
between the remote expert at a diagnosis site and the doctor and a
patient at a patient site, real-time remote instruction from the
remote expert to obtain an appropriate medical ultrasound image
sequence for the diagnosis and real-time transmission of the medical
ultrasound image sequence for the remote expert to make the diagnosis.
One transmission image contains an entire medical ultrasound image
with a low frame rate, therefore the remote expert can diagnose a
disease using this medical ultrasound image sequence that contains
tissue and other information. The other image is of the region of
interest (ROI) of a medical ultrasound image sequence for
diagnosis. The ROI is specified by the remote expert at the diagnosis
site to reduce the size of the medical ultrasound image. As a result,
the proposed system transmits the ROI with a high frame rate. Through
international telemedicine experiments using medical ultrasound image
sequence consulting experts, we can state with sufficient certainty
that the proposed system can provide the required performance to
enable medical experts to perform real-time telemedicine on a digital
network or over the Internet.
Compression and Transmission of RF Signals for Telediagnosis
Authors: Toshihiro Seko Toshihiro Seko , Motonori Doi Motonori Doi , Osamu Oshiro Osamu Oshiro , Kunihiro Chihara Kunihiro Chihara
Published: October 2002

Health care is a critical issue nowadays.
Much emphasis is given to quality care for all people.
Telediagnosis has attracted public attention.
We propose a new method of ultrasound image transmission for
telediagnosis.
In conventional methods, video image signals are transmitted.
In our method,
the RF signals which are acquired by an ultrasound probe,
are transmitted.
The RF signals can be transformed to color Doppler images or
high-resolution images by a receiver.
Because a stored form is adopted, the proposed system can be realized
with
existent technology such as hyper text transfer protocol (HTTP)
and file transfer protocol (FTP).
In this paper, we describe two lossless compression methods which
specialize in the transmission of RF signals.
One of the methods uses the characteristics of the RF signal.
In the other method, the amount of the data is reduced.
Measurements were performed in water targeting an iron
block and triangular Styrofoam.
Additionally,
abdominal fat measurement was performed.
Our method achieved
a compression rate of 13% with 8 bit data.
3-D Flow Visualization for Construction of the Model of the Blood Flow in the Heart
Authors: Masataka Imura Masataka Imura , Tomohiro Kuroda Tomohiro Kuroda , Osamu Oshiro Osamu Oshiro , Kunihiro Chihara Kunihiro Chihara , Joakim Brandberg Joakim Brandberg , Per Ask Per Ask
Published: October 2002

The authors have been developing a model of blood flow in the
heart.
The flow model of the heart enables us to estimate the entire blood flow
of the heart from a couple of 2-D color Doppler images.
Therefore, the load on patients is expected to be reduced.
To develop the model of the heart, precise observation
and an understanding of the blood flow are indispensable,
because the flow is strongly related to the diagnosis of
heart diseases.
The visualization method must have the following features:
(1) 3-D (2) objectivity (3) interactivity and (4) multi-aspect.
The authors have developed visualization methods
to meet the above-mentioned requirements and
evaluated the proposed methods with the in-vitro flow data set.
The results clearly reveal that the proposed system enables
the researchers of the modeling group to obtain
the state of entire flow, such as the occurrence of turbulence.
Reduction of Influence of Decrease in Signal-to-Noise Ratio in Measurement of Change in Thickness of Arterial Wall Due to Heartbeat
Authors: Hasegawa Hideyuki , Kanai Hiroshi , Hoshimiya Nozomu , Koiwa Yoshiro
Published: October 2002

To diagnose early-stage atherosclerosis, for the local evaluation of
the elasticity of the arterial wall it is necessary to increase the
spatial resolution in the axial direction of the artery to several
millimeters, which corresponds to the size of the lesion on the
surface of the arterial wall. For this purpose, we previously proposed
a method for measuring the small change in thickness of the arterial
wall during the cardiac cycle [H. Kanai et al..: IEEE Trans. UFFC 43 (1996) 791, H. Kanai et al..: IEEE Trans. UFFC 44 (1997) 752 and
H. Hasegawa et al..: Electron. Lett. 33 (1997) 340]. The
change in thickness cannot be measured from conventional B-mode or
M-mode images because of its small amplitude of less than 100
micrometers. Though the change in thickness is useful for in
vivo assessment of the local elasticity of the arterial wall, in some
cases successful measurements based on only two consecutive echos fail
because of the low signal-to-noise ratio (SNR) of the echos. To
realize the practical use of the proposed method, this problem must be
overcome. In this paper, we propose a method that is more robust in
the presence of noise. In this method, more than two echos are
employed to estimate their phase shift for reducing the influence of
low SNR. Simulations provide an optimal value of the estimation period
for each SNR. By evaluating the SNR of in vivo experimental
data, the optimal estimation period is determined. In in vivo
experiments using an optimal estimation period of 20 ms, the change in
thickness can be measured with good reproducibility even in the case
of a low SNR of 28 dB.
Effects of Denudation Anneal of Silicon Wafer on the Characteristics of Ultra Large-Scale Integration Devices
Authors: Cho Won-ju , Kuwano Hiroshi
Published: October 2002

The effectiveness of denudation annealing at high temperatures
on the characteristics of ultra large-scale integration (ULSI)
devices has been studied. The secondary-ion mass spectroscopy (SIMS)
profile showed that the oxygen atoms near the wafer surface diffuse
out during the denudation anneal and the amount of outdiffused
oxygen atoms increases with the increase of denudation annealing
temperature. The depth of the defect-free zone (DFZ) at the surface
region, the breakdown property of the thin gate oxide of 7 nm
thickness and the leakage current of PN junction diodes were greatly
improved following by the denudation annealing process at a high
temperature. It is found that the refresh properties of a 256 Mbit
dynamic random-access memory (256 M-DRAMs) were closely related to
the depth of the DFZ at the device surface and were improved by the
denudation annealing. Therefore, denudation annealing at high
temperatures is effective for the fabrication of reliable
quarter-micron level DRAM devices.
Chemical Reactions within Fe/AlN Layered Nanocomposites: A Simulation Study based on Crystal-Chemical Atomic Dynamics
Authors: Richard Dronskowski Richard Dronskowski , Bernhard Eck Bernhard Eck , Shinichi Kikkawa Shinichi Kikkawa
Published: October 2002

Layered nanocomposites made of metallic iron and aluminum nitride are subject to unexpected chemical reactions, resulting in a spontaneous formation of iron nitrides and a partial reduction to metallic aluminum. Since bulk thermochemical data are unable to rationalize the above finding, atomistic computer simulations based on the crystal-chemical atomic dynamics (CCAD) approach have been performed in the search for an explanation. The computational setup mimics a total number of about 1000 atoms moving over a time frame of 74 ps. When AlN molecules are sputtered on the iron surface under the experimental radio frequency (rf) conditions, the molecules are found to be chemically unstable upon hitting the surface, immediately breaking apart into individual atoms. Atomic nitrogen enters the Fe crystal to acquire quasi-octahedral coordination, leaving Al atoms behind on the surface. The reaction results in a stronger bonding of the nitride ion in the crystal compared to the covalently bonded nitrogen atom in the molecule. As a consequence, a small amount of Fe lattice expansion (2.5%) as well as a partial buildup of an iron/aluminum alloy is observed in the reaction zone near the surface of the bulk material.
Thermally Stable Tungsten Bit-line Process Flow for the Capacitor Over Bit-line-Type Dynamic Random-Access Memory
Authors: Lee Won-Jun , Hong Jeongeui , Rha Sa-Kyun
Published: October 2002

Thermally stable tungsten (W) bit-line process technology has been successfully
integrated for capacitor over bit-line (COB)-type dynamic random-access memory (DRAM).
Major parameters of the W bit-line process flow are demonstrated to be the Ti thickness,
the silicidation temperature and the dopant concentration. The minimum contact resistance
(<1000 Ω) of the W bit-line into the p+ active region has been obtained
by the silicidation of thin Ti (7 nm) at a high temperature (800°C) with the additional
ion implantation of BF2
+ after the contact formation. The effects of the process
parameters were explained in terms of the agglomeration of the Ti silicide and dopant
concentration in the silicon active region.
Surface Morphology Improvement of Metalorganic Chemical Vapor Deposition Al Films by Layered Deposition of Al and Ultrathin TiN
Authors: Ahn Seong-Deok , Lee Hyun-Bae , Kang Sang-Won
Published: October 2002

The surface morphology of aluminum (Al) films grown by metalorganic chemical
vapor deposition (MOCVD) has been improved by inserting a 1.0-nm-thick titanium
nitride (TiN) layer between 90-nm-thick Al layers. For multilayered Al/TiN film
depositions, dimethylaluminum-hydride (DMAH) and tetrakis(dimethylamido)titanium
(TDMAT) are used as metalorganic precursors. For uniform and conformal TiN layers
1.0-nm-thick atomic layer deposition (ALD) was carried out in the same reaction
chamber as the Al MOCVD. The surface morphology of the films was evaluated by
measuring the optical reflectance. In the early stage of Al MOCVD, the reflectance
versus film thickness curve shows a rapid decrease because of the scattering of
incident light from the Al nuclei, and then it increases sharply to a maximum
reflectance until the completion of island coalescence. However, it monotonically
decays again with Al thickness due to the nonuniform grain growth. By inserting a
1.0 nm TiN layer on the Al layer at the maximum reflectance, the reflectance is
restored again to the peak reflectance in the manner of a sinusoid waveform. Moreover,
the multilayered Al/TiN films have a strong (111) preferred crystal orientation, and
small and uniformly sized Al grains, which are expected to result in higher
electromigration resistance. Therefore, the combined deposition technique with Al
MOCVD and TiN ALD is considered a promising candidate to make Al MOCVD suitable for
future microelectronic applications.
Dark-Field Phase Shifter Edge Mask for Actual Logic Gate Patterns
Authors: Okamoto Yoshihiko , Fukumoto Keiko , Hotta Shoji , Fukuda Hiroshi
Published: October 2002

The fabrication of a dark-field phase shifter edge mask that
improved the lithography process latitude for fine transistor gate
patterns was examined. The applicability of this mask was confirmed
by analyzing of phase shift mask fabrication yield. The pattern
formation method used both a dark-field phase shifter edge mask and
a clear-field binary mask. It was clarified that the fabrication
yield of the phase shifter edge mask was dependent on the
transparent area of the phase shifter region. Clear-field phase
shifter edge masks were fabricated with difficulty because of
shifter defects. On the other hand, the fabrication yield of the
dark-field phase shifter edge mask was about two times that of the
clear-field phase shifter edge mask. This mask was applied to an
actual logic device. Resist patterns were fabricated with a line
width accuracy of 0.15±0.01 µm and a focus budget of
±0.4 µm. The dark-field phase shift mask exposure method
also improved the lithography process latitude significantly.
Characterization of Residues on Anhydrous HF Gas-Phase Etching of Sacrificial Oxides for Surface Micromachining
Authors: Jang Won Ick , Choi Chang Auck , Lee Jong Hyun , Jun Chi Hoon , Yang Haesik , Kim Youn Tae
Published: October 2002

We employed a newly developed anhydrous HF gas-phase etching (GPE) process for the removal of sacrificial oxides. The structural layers are P-doped multi-stacked polysilicon and silicon-on-insulator (SOI) substrates and sacrificial layers are chemical vapor deposition (CVD) tetraethylorthosilicate (TEOS) oxide, low-temperature oxide (LTO), phosphosilicate glass (PSG), and thermal oxides on silicon nitride or polysilicon substrates. The characteristics of residues on polysilicon or silicon nitride were scrutinized by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). After the GPE of CVD TEOS oxide, LTO, and PSG on the silicon nitride substrate, the polysilicon microstructures adhere to the underlying substrate because neither the SiOxNy layers nor the H3PO4(H2O) layer vaporize. We found that the etching of CVD TEOS oxide, LTO, and thermal oxide on a polysilicon substrate shows no residue and no stiction. Finally, the fabricated microstructures, symmetrically stacked to 6 µm thickness, operated at DC 4 V and AC 0.1 V in a vacuum chamber at 100 mTorr.
Observation of Less Heat Generation and Investigation of Its Effect on the Stability Range of a Nd:YAG Laser
Authors: Cheng Chao-Chia , Huang Tong-Long , Chang Sheng-Hsiung , Tsai Hung-Sheng , Liu Hai-Pei
Published: October 2002

In a Nd3+ laser rod, “less heat generation” due to intracavity beam reduces
the thermal lensing power, but this phenomenon has never been considered in previous
publications dealing with resonator stability. We observed this effect in a Nd:YAG
resonator specially designed to keep the beam divergence insensitive to thermal
lensing, and investigated how this effect affects the stability range of this resonator.
Femtosecond Interferometric Waveform Measurement of Photon Echoes Using a Collinear Geometry
Authors: Fuji Takao , Jordan Carsten , Yoda Takuya , Kondo Kiminori , Hattori Toshiaki , Nakatsuka Hiroki
Published: October 2002

A new method for waveform measurement of photon echoes using a modified Michelson interferometer has been developed. The experimental setup uses collinear geometry, and photon echo signals are detected using a double-phase modulation technique. The amplitude and phase of photon echoes and those of excitation pulses are simultaneously measured by this technique. The method has been applied to a photon echo experiment on a dye solution. The results are explained using a stochastic modulation model with an accumulation effect of population grating.
Construction of Small-Angle X-Ray Scattering Diffractometer Using Asymmetric Channel-Cut Monochromator
Authors: Kasahara Yasutoshi , Nishikawa Keiko
Published: October 2002

With the aim of easy use in a laboratory, a small-angle X-ray
scattering diffractometer was constructed by employing an asymmetric
channel-cut monochromator. The apparatus is very convenient and has
overall efficiency; namely, the measurable range from 0.01 to
0.4 Å-1 in scattering parameter s, proper s-resolution
and reasonable accumulation time.
Improvement of the Electrochemical Profiling Technique of Carrier Concentration in Cu(InGa)Se2 Thin Film Solar Cells
Authors: Shimizu Akira , Yamada Akira , Konagai Makoto
Published: October 2002

In our previous works, we measured the carrier concentration profile of Cu(InGa)Se2 (CIGS) films using the electrochemical capacitance–voltage (ECV) method with ethylenediaminetetraacetic acid (EDTA). However, we occasionally observed deposition of Se onto the CIGS films after the etching, which limited the reproducibility of the measurement. In this study, we tried to improve the ECV technique and successfully measured the carrier concentration profile for the film with a wide Cu/III ratio range by the addition of sulfurous acid into the EDTA electrolyte. Moreover, the results of these measurements revealed that the carrier (hole) concentrations of the CIGS films ranged between 1016 and 1018 cm-3 and that the carrier concentration changed with the growth conditions. Based on the above results, it is believed that this new measurement technique is a useful and powerful tool for characterization of CIGS thin films.
Operating Current Mode Dependence of Luminescence Properties of Rubrene-doped Yellow Organic Light Emitting Diodes
Authors: Tsujioka Tsuyoshi , Hamada Yuji , Takahashi Hisakazu
Published: October 2002

The operating current mode dependence of luminescence properties
of rubrene-doped yellow organic light-emitting diodes (OLEDs) was
investigated. The devices were driven by three types of constant
current mode: a simple direct current (DC) mode, a simple
alternating current (AC) mode and a pulsed current (PC) mode. The
device driven by the AC mode showed low energy efficiency because of
the existence of time intervals with no emission in spite of energy
consumption. The device driven by the PC mode showed the highest
efficiency and better stability compared with the devices driven by
the other modes.
Generation of 10 fs Pulses from a Diode-Pumped Kerr-Lens Mode-Locked Cr:LiSAF Laser
Authors: Uemura Sadao , Torizuka Kenji
Published: October 2002

We demonstrate 10 fs pulse generation from a diode-pumped
Kerr-lens mode-locked Cr:LiSAF laser without chirped mirrors on the
basis of an improved estimation of intracavity dispersion
compensation. This is, to our knowledge, the shortest pulse ever
produced from a mode-locked Cr:LiSAF laser.
DC Conduction in Polyethylene Films under High Electric Field after Annealing
Authors: Yan Ping , Zhou Yuanxiang , Yoshimura Noboru
Published: October 2002

It is well known that the electrical properties of polymers are significantly
influenced by the morphology. High-density polyethylene (HDPE) is a semicrystalline
polymer with crystalline and amorphous regions. HDPE specimens with different
crystallinities have been prepared by varying the annealing conditions. Based on the
conventional thermally activated electronic injection process, the dependence of DC
conduction on the crystallinity of PE has been studied. We calculated that with the
increase of crystallinity from 52.8% to 68.2%, values of the metal/dielectric contact
potential for samples of PE decrease from 2.75 eV to 2.24 eV. We presumed that
the morphological microstructure of the transcrystals in the electrode-polymer
interface is responsible for the difference between the potential energy of an electron
at the Fermi level in the metal electrode and that of one in the conductive state in the
polymer bulk.
Impedance Spectra near the Phase Transition Temperature of Potassium Lithium Niobate Crystals
Authors: Kim Jin Soo , Kim Jung-Nam
Published: October 2002

The impedance spectroscopy of potassium lithium niobate (KLN) crystals was investigated over the frequency range of 100 Hz to 1 MHz in the temperature region of room temperature to 600°C. Above and below the phase transition temperature, the AC complex impedance is explained by the Cole-Cole semi-circle, with a temperature-dependent factor indicating the degree of distribution of the relaxation time. However, near the phase transition temperature, a skewed semi-circle was found. The frequency dispersion of the AC complex impedance near the phase transition temperature is different from that above and below the phase transition temperature. The two distinct slopes and the differences in the frequency variation of the imaginary part of impedance suggest that two dispersion mechanisms are involved. In the vicinity of the phase transition temperature at a low frequency, the AC complex impedance is influenced by a mobile charge carrier.
Study of Crystal Growth Mechanism for Poly-Si Film Prepared by Excimer Laser Annealing
Authors: Matsuo Naoto , Aya Youichiro , Kanamori Takeshi , Nouda Tomoyuki , Hamada Hiroki , Miyoshi Tadaki
Published: October 2002

Recrystallization of polycrystalline silicon (poly-Si) film by excimer laser
annealing (ELA) is discussed by considering the experimental results that the three
stages of nucleation, textured grain growth and secondary grain growth were observed.
Although the phenomenon of nucleation in the amorphous silicon (a-Si) is understood by
considering crystallization from the super cooled liquid, the growth mechanisms of the
textured grain and secondary grain are not understood by this, because the melting
point of poly-Si which has already been formed on the entire surface during these
growth stages is higher than that of a-Si. The recrystallization mechanism considering
the dislocation movement is introduced to investigate the present phenomenon. It also
clarifies the reason why secondary grain growth occurs under the critical conditions of
laser irradiation energy and shot number. The feasibility of nucleation through the
super cooled liquid is also discussed.
Electrooptic and Dielectric Properties in Bent-Shaped Liquid Crystals
Authors: Zennyoji Masahito , Takanishi Yoichi , Ishikawa Ken , Thisayukta Jirakorn , Watanabe Junji , Takezoe Hideo
Published: October 2002

Electrooptic and dielectric properties were studied in the
antiferroelectric phase, B2, of bent-shaped liquid crystal
molecules. We have succeeded in selectively obtaining the
homogeneously chiral domain, the racemic domain, and the
intermediate domain in which layers with opposite chirality are
partially mixed, by properly choosing particular waveforms of the
electric field applied. Tristable switching was observed for all
domains under a triangular wave field. The switching current
profiles under a rectangular wave field indicate that the switching
time of homogeneously chiral domains is slower than that of racemic
domains. The magnitude of spontaneous polarization depends not on
temperature but on the carbon number of the terminal chain of the
molecules. Two relaxation modes were detected in dielectric
measurements, one of which was attributed to the distortion of the
antiferroelectric ordering.
Effects of Lanthanum on the Electrical Conductivity of CuO Ceramics
Authors: Suda Sei-ichi , Aoyama Takeshi , Kanamura Kiyoshi , Umegaki Takao
Published: October 2002

Lanthanum was dissolved in CuO and the effects of La on the electrical conductivity of CuO were investigated in order to control
the hole concentration and clarify the conduction mechanism of CuO
that exhibits a p-type semiconductivity. The maximum amount of La
dissolved in CuO was evaluated to be 0.5 mol% by powder X-ray
diffraction. The conductivities for La-doped CuO were investigated
by 4-probe and 3-probe methods. The temperature dependence of
conductivity showed that CuO has two conduction mechanisms in the
temperature range of 50°C to 900°C; conductivity at more
than 600°C was independent of atmosphere and the amount of La,
whereas conductivity below 500°C increased with an increase in
partial oxygen pressure (P
O2
) and amount of
La. Surface conductivity at 200°C was especially influenced by
P
O2
, and the sensitivity of surface conductivity to
P
O2
increased with doping of La into CuO. The doping
of La led to a change of chemisorbed oxygen species from O2
-
to O2- and resulted in an increase in sensitivity to
P
O2
.
Development of WO3 Thin Films Using Nanoscale Silicon Particles
Authors: Aliev Ali E. , Park Chul
Published: October 2002

The WO3-x
–0.1TiO2-y
thin films prepared by the sol–gel route exhibit
increased lifetime and stability. A sol–gel solution mixed with nanoscopic silicon oxide
particles (40 nm, 200 nm) was spin-coated onto an indium tin oxide (ITO)-covered glass
substrate followed by further surface development by chemical etching. A significantly
faster response time of the electrochromic cell due to the increase of the surface area
of the WO3/electrolyte interface and enhancement of the lithium ion diffusion rate
have been obtained. The coloration efficiency was found to be much higher in the areas
surrounding incorporated nanoscale particles.
Preparation of Al-doped PbTiO3 Thin Films by Metalorganic Chemical Vapor Deposition and Their Characterization
Authors: Aratani Masanori , Nagashima Kuniharu , Iijima Takashi , Mizuhira Manabu , Funakubo Hiroshi
Published: October 2002

Alminium-doped PbTiO3, Pb(Al, Ti)O3, thin films were
prepared by metalorganic chemical vapor deposition from the
Pb(C11H19O2)2–Al(O·n-C3H7)3–Ti(O·i-C3H7)4–O2 system. Al content of
the film could be controlled only by changing the input gas
concentration of Al(O·n-C3H7)3, and was independent of the deposition temperature from 400 to 620°C. Lattice parameter change
of the film showed that the solubility limit of Al atoms into
perovskite phase existed in the vicinity of 8 at.%. Leakage current
density of the film deposited on (111)Pt/Ti/SiO2/(100)Si substrate
decreased with increasing Al content up to 33 at.%. The thin film
with 4.1 at.% Al content showed ferroelectricity, and the twice the
values of remanent polarization (2P
r) and the coercive
field (2E
c) were 8.5 µC/cm2 and 90 kV/cm, respectively. The epitaxial Pb(Al, Ti)O3 thin film was deposited on (110)SrRuO3∥(110)SrTiO3 substrate, and the 2P
r and the 2E
c values were 27.5 µC/cm2 and 200 kV/cm, respectively.
High-Resolution Examination of Recording Marks in Phase-Change Media Using a Scanning Near-Field Optical Microscope
Authors: Toshiyasu Tadokoro Toshiyasu Tadokoro , Toshiharu Saiki Toshiharu Saiki , Keiichiro Yusu Keiichiro Yusu , Katsutaro Ichihara Katsutaro Ichihara
Published: October 2002

Recording marks in digital versatile disc-random access memory (DVD-RAM) were examined using a scanning near-field optical microscope (SNOM) incorporating an improved probe tip design. The marks were recorded on an experimental DVD-RAM medium with a track-pitch of 0.6 µm. The tip size of the SNOM was made wider than the track width in order to avoid optical ghosting arising from the track edge. The recording power was varied in order to investigate the dependence of the mark shape on power and it was found that the mark shape correlated well with the reproduced signal. The SNOM is considered to be a good candidate for a practical characterization tool for optical recording media.
Photovoltaic Effect in Heterostructure Consisting of Poly(p-phenylene vinylene) Derivative and Polypyridine
Authors: Tada Kazuya , Onoda Mitsuyoshi
Published: October 2002

The characteristics of a photovoltaic device based on a heterostructure consisting of poly(2-methoxy-5-dodecyloxy-p-phenylene vinylene) (MDOPPV) and polypyridine (PPy) have been studied. The heterostructure device shows a significant enhancement of the photovoltaic properties compared to the single-layer devices based on MDOPPV or PPy. For example, the device shows a significantly larger photocurrent than a device consisting only of MDOPPV. Moreover, notable quenching of the photoluminescence of the two polymers due to lamination has also been observed. These results indicate that a photoinduced charge transfer occurs between MDOPPV and PPy. However, the photoinduced charge transfer between these polymers cannot be explained by the bulk electronic energy structure of the polymers estimated from the optical absorption and the atmospheric photoemission spectra. A possible mechanism, which takes modulation of electronic energy structure at the interface due to a local lattice distortion into account, has been proposed. Another possible mechanism of the enhanced carrier generation based on the polarization at the MDOPPV/PPy interface is also mentioned.
Subgap Absorption Spectra in Polysilane Films
Authors: Tatsuo Fujii Tatsuo Fujii , Lujun Pan Lujun Pan , Yoshikazu Nakayama Yoshikazu Nakayama
Published: October 2002

The subgap absorption spectra of polysilane films have been measured by photothermal deflection spectroscopy using the deflection medium 1,4-butanediol. It has been revealed that poly(methylphenylsilane) (PMPS) films have a band tail with an exponential distribution rather than a Gaussian distribution and a low density of states in the midgap. The Urbach energy is estimated to be 30 meV. The photodegradation of PMPS films increases the subgap absorption, indicating defect generation. The defects are generated from the photoscission of σ bonds, which has a stretched exponential time dependence. The doping of C60to PMPS sensitizes the absorption in the visible region. The absorption increases proportionally to the doping ratio of C60in a range of three orders of magnitude. The absorption spectrum of the PMPS and C60mixture shows no interaction between the two ground states.
High-Sensitivity Method for Counting Low Concentrations of Particles in Liquids Using Centrifugation and Image Analysis
Authors: Yabusaki Katsumi , Saitoh Naoko , Hirono Taisuke , Matsui Hiroki , Okada Hiraki
Published: October 2002

A new method was developed for counting low concentrations of particles suspended in a liquid, and found to be limited only by Poisson statistics. The method, called the image cytometry-centrifugation (ICC) method, uses centrifugation to concentrate particles into a narrow observation area at the bottom of a specially designed cuvette, and then uses image analysis to measure the number of particles. Our method was used to count from 1 to 64 fluorescent beads suspended in 500 µl of liquid. By comparing the number of counted beads with the actual number of beads added to the liquid, we confirmed that the counting accuracy of the ICC method is limited by Poisson counting statistics.
Fabrication of Quartz Microcapillary Electrophoresis Chips Using Plasma Etching
Authors: Takekazu Ujiie Takekazu Ujiie , Toshiaki Kikuchi Toshiaki Kikuchi , Takanori Ichiki Takanori Ichiki , Yasuhiro Horiike Yasuhiro Horiike
Published: October 2002

In order to fabricate microcapillary electrophoresis (µ-CE) chips, high-rate quartz etching with high selectivity over the mask was studied using both C4F8/Ar and C4F8/SF6 high-density plasmas with Cr hard masks. Vertical quartz etching with high etch rate selectivity against the mask was attained using an 85%C4F8/15%SF6 inductively coupled plasma, where the quartz etch rate was 530 nm/min and the etch rate selectivity against the mask measured at the Cr top surface and the facet were 80 and 27, respectively. Deep quartz etching technology has been demonstrated by fabricating vertical trench features with 50 µm depth and 20 µm width, i.e., the aspect ratio of 2.5, which cannot be attained by means of the wet chemical etching technology conventionally used. Subsequently, fundamental performances of µ-CE chips fabricated using plasma etching were examined and compared with those fabricated by conventional wet etching. No significant difference was found in the separation performances between dry-etched and wet-etched chips, while the rectangular cross-sectional feature with high aspect ratio, which has become attainable for the first time by deep plasma etching technology, has been shown to be the most suitable for the optical absorption detection commonly used in capillary electrophoresis and liquid chromatography and for the image observation necessary for particle and/or cell electrophoresis. Furthermore, the advantage of pattern transfer with high resolution and high fidelity has been demonstrated by fabricating functional microstructures such as a slit or a filter within a capillary.
Nanolithography of Organic Polysilane Films Using Carbon Nanotube Tips
Authors: Ai Okazaki Ai Okazaki , Seiji Akita Seiji Akita , Hidehiro Nishijima Hidehiro Nishijima , Yoshikazu Nakayama Yoshikazu Nakayama
Published: October 2002

The patterning of polysilane films is performed by means of the contact-mode-Scanning Probe Microscope(SPM) lithography technique. Both a carbon nanotube tip
and a gold-coated Si tip are used. The polysilane film is directly patterned or
grooved when the tip is negatively biased. It is considered that the grooves are
fabricated by the scission of Si-Si bonds and volatilization of the species due
to the emanating of electrons from the scanning tip. Compared with gold-coated
Si tips, carbon nanotube tips produce narrower grooves with a higher scan speed
and have a longer lifetime. The maximum ratio of groove depth to width can be
obtained at a speed as high as 20 µm/s when using the carbon nanotube tip.
Atomic Force Microscopy of Living Cells
Authors: Ushiki Tatsuo , Yamamoto Susumu , Hitomi Jiro , Ogura Shigeaki , Umemoto Takeshi , Shigeno Masatsugu
Published: October 2002

This paper is a review of our results of the application of
atomic force microscopy (AFM) to the three-dimensional observation
of living cells. First, we showed AFM images of living cultured
cells in fluid. Contact mode AFM of living cells provided precise
information on the shape of cellular processes (such as spike-like
processes or lamellipodia) at the cellular margin. The contour of
cytoskeletal elements just beneath the cell membrane was also
clearly observable on the upper surface of the cells. Secondly, we
showed the data on the discrepancy between the AFM images of living
cells and fixed cells. These findings were useful for evaluating AFM
images of living cells. Finally, we described the time-lapse AFM of
living cells. A fluid chamber system enabled us to obtain AFM images
of living cells for over 1 h at time intervals of 2–4 min. A
series of these AFM images were useful for examining the movements
of cellular processes in relation to subcellular cytoskeletal
elements. Time-lapse movies produced by sequential AFM images also
gave a realistic view of the cellular dynamics.
Prospects and Problems of Single Molecule Information Devices
Authors: Wada Yasuo , Tsukada Masaru , Fujihira Masamichi , Matsushige Kazumi , Ogawa Takuji , Haga Masaaki , Tanaka Shoji
Published: October 2002

Current information technologies use semiconductor devices and magnetic/optical discs, however, it is foreseen that they will all face fundamental limitations within a decade. This paper reviews the prospects and problems of single molecule devices, including switching devices, wires, nanotubes, optical devices, storage devices and sensing devices for future information technologies and other advanced applications in the next paradigm. The operation principles of these devices are based on the phenomena occurring within a single molecule, such as single electron transfer, direct electron-hole recombination, magnetic/charge storage and regand-receptor reaction. Four possible milestones for realizing the Peta (1015)-floating operations per second (P-FLOPS) personal molecular supercomputer are described, and the necessary technologies are listed. These include, (1) two terminal conductance measurement on single molecule, (2) demonstration of two terminal molecular device characteristics, (3) verification of three terminal molecular device characteristics and (4) integration of the functions of “molecular super chip”. Thus, 1000 times higher performance information technologies would be realized with molecular devices.
Evaluations of Carrier Lifetime in Silicon Epitaxial Layers Grown on Lightly Doped Substrates
Authors: Takahashi Hidenori , Maekawa Takao
Published: October 2002

The recombination lifetime of excess carriers in silicon epitaxial wafers (p/p-and n/n-) with substrates of high resistivity has been analyzed based on a continuity equation. The solutions are derived for two cases of lifetime values. Under the conditions that the wafer surfaces are chemically passivated, and that the effects of recombination velocity and built-in potential at the interface of the epitaxial/substrate layer can be neglected, an approximate expression of effective lifetime can be derived from the solutions of the continuity equation. The result indicates that the effective lifetime is not only a function of the bulk lifetimes in both the epitaxial layer and substrate, but also a function of their thicknesses. The results of analytical solutions are applied to a commercially available silicon p/p-epitaxial wafer. The difference between the experimental and analytical results is discussed.
First Room-Temperature Continuous-Wave Operation of Self-Formed InGaAs Quantum Dot-Like Laser on Si substrate Grown by Metalorganic Chemical Vapor Deposition
Authors: Kazi Zaman Iqbal , Egawa Takashi , Jimbo Takashi , Umeno Masayoshi
Published: October 2002

The first room-temperature continuous-wave operation of a self-formed InGaAs quantum dot-like laser on a Si substrate fabricated by metalorganic chemical vapor deposition at atmospheric pressure is reported. This laser exhibits a threshold current density of 1.32 kA/cm2 and a lasing wavelength of 854 nm with a spectral width of 1.6 nm. A significant improvement in the reliability has been found due to the quantum dot-like active region in the laser which reduces the dislocation numbers and hence provides a laser with a long lifetime.
Deep Level in InP Crystal Grown by the Horizontal Bridgman Method under Controlled Phosphorus Vapor Pressure
Authors: Shimizu Atsushi , Nishizawa Jun-ichi , Oyama Yutaka , Suto Ken
Published: October 2002

InP crystals were grown by the horizontal Bridgman (HB) method under a controlled ambient phosphorus vapor pressure. The relationship between the phosphorus vapor pressure and crystal defects was investigated. Crystals grown under a lower phosphorus vapor pressure have an In-rich composition. P-vacancy related photoluminescence (PL) emission at 1.1 eV decreased in growth under a higher phosphorus vapor pressure. The ion density at E
c-1.1 eV also decreased according to results of photocapacitance measurement. It was considered that crystals became a P-rich composition from an In-rich one by growth under higher phosphorus vapor pressure of 23 or 29 atm. This corresponds to the results of coulometric titration analysis. In the InP crystal grown under the phosphorus pressure of 33 atm, the density of the deep level was undetectable by PL or photocapacitance measurement.
Magnetoluminescence Study of Annealing Effects on the Electronic Structure of Self-organized InGaAs/GaAs Quantum Dots
Authors: Goñi A. R. , Born H. , Heitz R. , Hoffmann A. , Thomsen C. , Heinrichsdorff F. , Bimberg D.
Published: October 2002

We have studied the effects of annealing a self-organized InGaAs/GaAs quantum dot sample between 580 and 700°C by magnetoluminescence measurements at 2 K and fields up to 15 T. High-excitation power density luminescence spectra reveal up to three features in addition to the ground-state emission arising from radiative recombination processes between excited states of the quantum dots. With increasing annealing temperature all emission lines shift to higher energies while varying their splittings indicating a systematic increase in volume and Ga content of the dots. From the diamagnetic shift and the Zeeman splitting of the ground-state emission we obtain an increase of the spatial extent of the exciton wave function but a decrease of the effective g-factor upon annealing. The magnetic field splittings of excited-state transitions exhibit a strong dependence on annealing and are well accounted for within a simple oscillator model with total angular momentum mainly determined by the dot envelope functions.