bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Structure and Electronic States of V2O5 Surface Studied by Scanning Tunneling Microscopy/Spectroscopy
Authors: Sakai Yoshiyuki , Ehara Shaw
Published: October 2002

The surface structure and the surface electronic states of
V2O5 were investigated using scanning tunneling
microscopy/spectroscopy (STM/STS). The samples used in this experiment were prepared by annealing a cleaved crystal in an ultrahigh vacuum (UHV) to grow a reduced and lower oxide surface on its (001) plane. It was found that the crystal maintained the basic structure of V2O5 even after heat treatment, since the atomic images of the vanadyl oxygen alignments on the stoichiometric V2O5 (001) surface could be observed by STM on a few successively cleaved surfaces of the same sample. The STS spectra showed the local density of states peculiar to a reduced V2O5 surface, which were different from those of a stoichiometric V2O5 surface.
Two-Dimensional Effects on Measurement of Thermal Diffusivity by AC Calorimetric Method: I. Conditions for Precise Measurement
Authors: Hatta Ichiro , Fujii Kazuhiko , Takahashi AtsushiSakibara , Kaneda YukihiroHamada
Published: October 2002

In the application of an ac calorimetric method to precise thermal diffusivity
measurement of a thin material, one-dimensional temperature wave propagation is
required. In a relatively thick material, one-dimensional temperature wave propagation
is deformed and in the strict sense, two-dimensional temperature wave propagation
should be taken into account. In the present paper, we propose the condition of the
maximum thickness of a material required to measure thermal diffusivity within an
accuracy of ±2% in the framework of one-dimensional temperature wave propagation,
based upon the results obtained analytically for the two-dimensional temperature wave
propagation.
Approach to Next-Generation Optical Lithography
Authors: Keisuke Nakazawa Keisuke Nakazawa , Toshio Onodera Toshio Onodera , Masaru Sasago Masaru Sasago
Published: October 2002

We discuss the possibility of using optical lithography when the design size is below 130 nm. Our optical simulations at the laser wavelengths of KrF (248 nm), ArF (193 nm), F2 (157 nm), Kr2 (146 nm), ArKr (134 nm), Ar2 (121 nm), and the extreme ultraviolet (EUV) (13 nm) indicate that the ArF excimer laser can be used up to the 100 nm generation and that the lithographic tool most suitable for the 70 nm generation is an ArKr laser system with a numerical aperture larger than 0.65. They also indicate that EUV sources will be needed for the 50 nm generation and that high-contrast resists will be needed for the 70 nm generation and beyond.
Proposal of a Self-Heated Composite Touch Sensor for Material Discrimination
Authors: Yuji Jun-ichiro , Shida Katsunori
Published: October 2002

In this paper, a self-heated composite touch sensor with two kinds of sensing
mechanisms for material discrimination is described. One sensing mechanism is
pressure-conductive rubber sheet with a temperature dependence that
determines both the hardness and thermal property of a material. The other is a
pair of comb-shaped electrodes with a capacitive-inductive function to determine
both the dielectric and magnetic properties of a material. Through integrated use
of this sensor, discrimination of some typical sample materials with flat surfaces
was successfully performed.
Effects of Existence of Microbubbles for Increase of Acoustic Streaming
Authors: Sakamoto Shin-ichi , Watanabe Yoshiaki
Published: October 2002

The effects of the existence of microbubbles in water on the increase of acoustic streaming velocity are experimentally investigated. The harmonics
generated by the nonlinear vibration of microbubbles are regarded as the
increase factor of the velocity. The streaming velocity was measured using a
laser doppler velocimeter (LDV). To observe the effects of harmonics, a special tank was used. Microbubbles were generated by extracting water using the
syringe mechanism. Experimental results clearly show that the acoustic
streaming velocity is increased when microbubbles exist.
Surface Wave Velocity of Crosslinked Polyacrylate Gels
Authors: Matsuoka Tatsuro , Kinouchi Wataru , Nomura ShinobuKoda
Published: October 2002

Surface wave velocities of crosslinked polyacrylate hydrogels
were measured as a function of water content with different
compositions of sodium polyacrylate (NaPA) and polyacrylic acid (PAA).
The water content and composition dependencies of the surface wave
velocity were discussed.
Measurement of Fine-Particle-Velocity under Spatial Frequency Domain Using a Fourier Transform Spectrometer
Authors: Koichi Mizutani Koichi Mizutani , Masahiro Yamazaki Masahiro Yamazaki , Masahiro Yoshioka Masahiro Yoshioka , Keinosuke Nagai Keinosuke Nagai
Published: October 2002

A method for measuring fine-particle-velocity under a
spatial frequency domain using a Fourier transform
spectrometer is described. In the spatial frequency domain,
the spectrum of a particle increases in inverse proportion to
its size. We simultaneously approach the sampling of two-portion images of a fine-particle-flow with a short time difference, and estimate the moving velocity of the flow using autocorrelation from the recorded data. The experimental relation between the applied velocities of 5–20 mm/s to samples of 100–50 µm diameter transitory starch granules and the measured moving velocity agrees well. The advantage of this method is that it can be used for observing bubble oscillation, powder transportation and particle sizing.
An Optical Method for Measurements of Sound Waveform at the Focal Point of Focused Ultrasound
Authors: Miyaki Hironaka , Watanabe Yoshiaki
Published: October 2002

The sound waveform of focused ultrasound is measured at the focal point using optical beam refraction. Instead of a narrow light beam, an ordinary Gaussian laser beam whose diameter is 1 mm is used. An iris which has a small aperture is also applied to observe the refracted light. The signal obtained by the optical method was in agreement with the waveform measured by a poly vinylidene fluoride (PVDF) hydrophone.
Internal Magnetic Focusing in an Array of Open Quantum Dots
Authors: Ye Peide D. , Tarucha Seigo
Published: October 2002

The ballistic motion of electrons is studied in an array of open quantum dots. The submicron dots are fabricated by electron beam lithography and dry etching techniques. Pronounced oscillations are observed in the magnetoresistance which can be understood in terms of the commensurability effect between the ballistic trajectories and the geometry of the circular cavity or the internal magnetic focusing. By breaking the symmetry of the entrance/exit openings, or by inducing a large antidot at the center of the cavity, the commensurability effect disappears.
Observation and Nondestructive Evaluation of Grooved Plane with Defect Using Photoacoustic Microscope
Authors: Endoh Haruo , Sugawara Shin-ya , Hiwatashi Yoichiro , Hoshimiya Tsutomu
Published: October 2002

A nondestructive test of a grooved metal plane with a vertical defect was
performed using a photoacoustic microscope. A defect and a groove which was introduced
at the central portion of the defect, were processed by a machine or a mechanical cutter with
high accuracy. Processing of both amplitude and phase images facilitated detection of a
groove with a defect, which is difficult with conventional nondestructive evaluation (NDE)
techniques.
Modeling of Electron Transport in Corrugated Quantum Wires
Authors: Ochiai Yuichi , Lin L.-Hung , Ishibashi Kohji , Aoyagi Yoshinobu , Sugano Takuo , Holmberg Nicholas L. , Bird Jonathan P. , Vasileska Drgica , Akis Richard , Ferry David K.
Published: October 2002

We have studied the low-temperature magnetotransport in the singly and doubly corrugated wires. The application of a sufficiently negative gate bias might result in the formation of weakly coupled dots. In the structures considered here the corrugations act as weak perturbations on the quantum wire. Compared with the experimental results and the numerical simulations of the transports in these perturbed quantum wires, we show that oscillatory magnetoresistance features, observed in the doubly corrugated wire, arise from back-scattered orbits. The observation of wave function scarring in the quantum simulations is given the open nature of the weakly perturbed quantum wires.
10 GHz-Range Surface Acoustic Wave Low Loss Filter Measured at Low Temperature
Authors: Kazuhiko Yamanouchi Kazuhiko Yamanouchi , Hideyuki Nakagawa Hideyuki Nakagawa , Jamil Ahmad Qureshi Jamil Ahmad Qureshi , Hiroyuki Odagawa Hiroyuki Odagawa
Published: October 2002

The 10 GHz-range surface acoustic wave (SAW) is of great importance in the field of physical acoustics and application of SAW devices, for example, in mobile and wireless communications. The temperature dependency of the propagation attenuation at 10 GHz-range is measured using the three-transducer system with an electrode width of less than 0.1 µm, which is fabricated using an electron beam exposure and lift-off technique. The results show that the attenuation at room temperature is about 1.5 dB/(100 λ) at 10 GHz. Next, the temperature dependency of the insertion loss of a floating electrode reflection type unidirectional transducer (FEUDT) whose electrodes are respectively fabricated from Al and the superconductor Nb, is investigated experimentally. In the case of Al-FEUDT at 8 GHz, the insertion loss at a low temperature is about 8.5 dB, which is 3.4 dB lower than the insertion loss at room temperature. The main cause of decrease in the insertion loss is the decrease in the resistivity of the very thin and narrow metal electrodes. The results of Nb-FEUDT show a marked decrease in the insertion loss around the critical temperature T

c
=9.23 K.
Observation of Ultrathin Single-Domain Layers Formed on LiTaO3 and LiNbO3 Surfaces Using Scanning Nonlinear Dielectric Microscope with Submicron Resolution
Authors: Yasuo Cho Yasuo Cho , Kaori Matsuura Kaori Matsuura , Satoshi Kazuta Satoshi Kazuta , Hiroyuki Odagawa Hiroyuki Odagawa , Kazuhiko Yamanouchi Kazuhiko Yamanouchi
Published: October 2002

The formation of very thin domain layers on the surface of
multidomain lithium tantalate by heat treatment is observed by scanning
nonlinear dielectric microscopy. A similar phenomenon of forming a very
thin single-domain layer was also observed on the surface of periodically
polarized lithium niobate single crystal. By measuring the
thickness of the single-domain layers, the depth sensitivity of the scanning
nonlinear dielectric microscope with submicron resolution was estimated.
Fundamental Consideration of Piezoelectric Multilayer Actuators with Interdigital-Electrode-Type Structure
Authors: Watanabe Jyunichi , Someji Takahiro , Jomura Shigeru
Published: October 2002

This study deals with a piezoelectric multilayer actuator with an interdigital-electrode-type
structure. This type of actuator is usually badly damaged when large displacements are generated,
because of internal tensile stresses in the actuator. The effect of the number of ceramic layers in the
actuator on the internal stress was investigated with the help of finite element simulation and
experimentally fabricated actuators. Consequently, the actuator with less than 40 ceramic layers
could generate large displacements without destruction, while the magnitude of displacement for
the 40-layer actuator was 3.4 µm for an applied direct current
(DC) field of 150 V.
Improvement in Performance of Longitudinal and Torsional Vibrator Combination-Type Ultrasonic Motor
Authors: Manabu Aoyagi Manabu Aoyagi , Yoshiro Tomikawa Yoshiro Tomikawa
Published: October 2002

Longitudinal and torsional vibrator combination-type ultrasonic motors in which the torsional vibrator rotates as a rotor have the ability to produce high torque.
The purpose of this study is to further improve the performance of this type of motor.
The motor was newly designed and improved in regards to the longitudinal vibration mode and the output method of its mechanical power.
The longitudinal vibration mode, with one node on each of the longitudinal and torsional vibrators, is applied to control the friction force on the contact surface.
This mode can cause repulsive collision of both vibrators.
Consequently, the maximum torque and the maximum efficiency of the improved motor increased by 75% and 107%, respectively.
Moreover, the input electric power for the longitudinal vibrator was remarkably reduced.
Thus, improvement of this type of the ultrasonic motor was successful.
Cylindrical Micro Ultrasonic Motor Utilizing Bulk Lead Zirconate Titanate (PZT)
Authors: Morita Takeshi , Kurosawa Minoru Kuribayashi , Higuchi Toshiro
Published: October 2002

Ultrasonic motors are expected to be used as microactuators
because of their high torque, low speed and simple construction. We
have already reported cylindrical-shaped micro ultrasonic motors which
utilized a lead zirconate titanate (PZT) thin film. In this paper, we
discuss a micro ultrasonic motor composed of bulk PZT. The stator
transducer had dimensions of 2.4 mm in diameter and 10 mm
length. The maximum revolution speed was 650 rpm and the maximum
output torque was 0.22 mNm with the condition of 100 Vp-p
input voltage. The driving frequency was 85 kHz. The comparison
between the bulk PZT stator transducer and the previous PZT thin film
transducer was considered. From this consideration, the e
31
piezoelectric factor was determined to be the main factor for
different output torques. The bulk PZT motor was
applied to robot hands which was a simple procedure. A two axes hands application was successfully operated with a step motion and carried up to a 10 g load.
Estimation of the Stability of Acoustic Multipath in Long-Range Propagation at the Western Equatorial Pacific
Authors: Hiroyuki Hachiya Hiroyuki Hachiya , Toshiaki Nakamura Toshiaki Nakamura , Iwao Nakano Iwao Nakano
Published: October 2002

In this paper, we present the stability estimation results of the data collected during the sound transmission experiment performed by Japan Marine Science and Technology Center (JAMSTEC) in 1996 at the western equatorial Pacific.
The amplitude and the phase of a correlated signal were very stable within 50 s.
There was a small component of the acoustic changes with a period of less than 50 s due to the ocean-structure change.
The amplitude and phase, changed significantly within about 3 h.
The travel time could be estimated with an error of less than 0.3 ms.
The combined information of the amplitude and phase was effective for
identifying a ray and observing the ocean-structure change.
Evaluation of the Performance of Deep Sea Survey Sonars from the Results of Search for a Sunken Ship
Authors: Tsuchiya Toshio , Ochi Hiroshi , Shibata Jun Naoi andKatsura
Published: October 2002

The Japan Marine Science & Technology Center carried out a search for the
“Tsushima-maru,” a school children evacuation ship which was sunken during the World
War II. In this search, we first measured the bottom surface reflection intensity
over the entire sea, and narrowed down to a special point using the multi narrow
beam echo sounder (SEABEAM 2112.004) equipped to the vessel bottom. Then, the
vicinity of the investigated with a towing side scan sonar. Eventually, a TV camera
on board an remotely operated vehicle confirming the hull of the ship. The search
for the sunken ship was utilized to investigate the performance of the sonars. As
a result, resolution and detection abilities of various sonar were confirmed in actual
ocean operations.
Novel Approach for Lateral Current Confinement in Vertical Resonant Tunneling Devices
Authors: Gustafson Boel , Carlsson Niclas , Fukui Takashi , Litwin Andrei , Maximov Ivan , Sarwe Eva-Lena , Seifert Werner , Wernersson Lars-Erik , Samuelson Lars
Published: October 2002

We have used the Schottky depletion around overgrown tungsten
(W) features to define vertical conducting channels having submicron
lateral extension. In the first example, epitaxially buried lattices
of tungsten discs are used, which give rise to a semi-insulating
behavior in GaAs. A designed opening of n×n vacant disc
positions in this lattice defines a transport channel in the otherwise
semi-insulating material. A double barrier resonant tunneling (DBRT)
structure (GaInP/GaAs) is placed immediately below the disc lattice,
and the
current-voltage characteristics are investigated. In diodes with
submicron openings (0.7 µm×0.7 µm), a fine
structure including
additional current peaks is found, which is not
seen in
larger diodes. The magnetic field dependence of the current peaks is
investigated and discussed. As a second example, we report
on the fabrication of gateable zero-dimensional (0D) resonant
tunneling structures that are obtained using selective area growth in
openings (d=300 nm) in
an otherwise continuous W mask.
Hydrogen Plasma Passivation and Improvement of the Photovoltaic Properties of a GaAs Solar Cell Grown on Si Substrate
Authors: Wang Gang , Ohtsuka K. , Soga Tetsuo , Jimbo Takashi , Umeno Masayoshi
Published: October 2002

The effects of hydrogen (H) plasma passivation of metalorganic chemical
vapor deposition
(MOCVD) grown GaAs solar cells on a Si substrate have been studied. After
H plasma passivation
and postannealing in AsH3 ambient, the conversion efficiency of the GaAs
solar cell grown on a Si
substrate is increased from 16.3 to 17.2% at AM0. This improvement is
thought to be due to the
passivation of the defect-associated recombination centers by H plasma
exposure and the recovery
of the plasma-induced damages by postannealing the passivated solar cells
in AsH3 ambient at
450°C.
Low-Fire NiO–CuO–ZnO Ferrite with Bi2O3
Authors: Jean Jau-Ho , Lee Cheng-Horng
Published: October 2002

Additions of Bi2O3 were used to enhance densification and to promote grain
growth during sintering of NiO–CuO–ZnO ferrite. With a small amount of Bi2O3 (0.5–2.5 wt%) present as a sintering aid in NiO–CuO–ZnO ferrite, the densification rate and
final sintered density are greatly increased, but the activation energy of densification is
significantly reduced. The grain size of NiO–CuO–ZnO ferrite is significantly increased
with the presence of Bi2O3. These results are attributed to the occurrence of a chemical
reaction taking place at the interface of Bi2O3/NiO–CuO–ZnO ferrite, resulting in a
greater amount of liquid phase and good wetting during sintering. Microstructural
analyses show that the above interfacial reaction induces mutual dissolution between
Bi2O3 and ferrite, resulting in a reduction of initial magnetic permeability.
Surface Reflectivity of Graded-Index Layers Formed by Ion Exchange in Glass
Authors: Qing De-Kui , Yamaguchi Ichirou
Published: October 2002

In this paper, we theoretically analyze the reflectivity of a graded-index layer made by ion exchange in glass. We use two approaches, i.e., the matrix and the wave equation. The results of both approaches are in good agreement when refractive index profiles are approximated by a sufficient number of discrete layers. Calculated results show that when the effective thickness of an ion-exchanged layer is larger than the wavelength of incident light, the reflectivity is mainly determined by the refractive index at the surface, and the internal refractive index has little influence on the reflectivity. In other words, the measurable effective thickness from the surface reflectivity is below the wavelength of incident light. This thickness, however, is generally below the cutoff thickness, i.e., the minimum thickness enables graded-index layers to be used as optical waveguides. This indicates the difficulty of a nondestructive measurement of the refractive index profile of ion-exchanged optical waveguides based on their surface reflectivity. On the other hand, our results show that surface reflectivity can assist the inverse Wentzel- Kramers-Brillouin (WKB) method to accurately determine the refractive index at the surface of a gradient optical waveguide.
All-Optical Inverter Operating with a 1.5 µm Laser in Erbium-Doped Phosphate Glass
Authors: Maeda Yoshinobu , Akidzuki Yoshiki , Konishi Akio , Hashima Hidekazu , Wakabayashi Hajimu
Published: October 2002

The dependence of an all-optical inverter derived from the negative
nonlinear absorption effect on
both the modulation degree and frequency was investigated in erbium-doped
phosphate glass using
a 1.5 µm laser diode. With a decreasing degree of incident modulation, a reversed-phase
waveform was obtained in the transmitted laser at modulation degrees less
than 86%. The
reversed-phase transmitted waveforms were observed at modulation
frequencies from 10 Hz to 250 MHz and at wavelengths from 1530.0 to 1545.0 nm. The wavelength dependence
of the negative
nonlinear absorption effect agreed with the transmitted spectra for the
erbium-doped phosphate
glass. The negative nonlinear absorption effect for 1.5 µm can be explained
by considering an
enhanced absorption model for a four-level system of the Er3+ ion.
Femtosecond Dynamics of Carrier Relaxation and Exciton Formation in Zn1-XCdXSe/ZnSYSe1-Y Multiple-Quantum-Well Structures
Authors: andArao Nakamura Takashi Tokizaki
Published: October 2002

We have investigated the intraband carrier relaxation and exciton formation
dynamics in a Zn0.88Cd0.12Se/ZnS0.12Se0.88
multiple quantum well using a femtosecond pump and probe method.
We have analyzed the spectral shape of the exciton absorption band, and
obtained the temporal change of the homogeneous broadening.
The homogeneous width of the heavy-hole exciton absorption shows the delayed
rise of ∼1 ps and the two-component decay with decay times of
∼10 ps and ∼100 ps.
These behaviors are dependent on temperature and pumping wavelength.
The temporal behavior of the additional broadening has been explained by
the numerical simulation, taking into account the intraband carrier
relaxation and the exciton formation.
Electronic Properties and Mid-Infrared Transitions in Self-Assembled Quantum Dots
Authors: Leburton Jean-Pierre , Fonseca Leornado R. C. , Shumway John , Ceperley David , Martin Richard M.
Published: October 2002

We present a detailed model of the electronic properties of single and vertically
aligned self-assembled pyramidal InAs/GaAs quantum dots (SADs) which is based on
the self-consistent solution of three-dimensional (3D) Poisson and Schroedinger equations within the local (spin) density approximation. Nonparabolicity of the band
structure and a continuum model for strain between GaAs and InAs results in position and energy dependent effective mass. In single SADs, shell structures obeying
Hund's rule for various occupation numbers in the pyramids agree well with recent
capacitance measurements. The electronic spectra of SADs of various shapes have
been determined with intraband level transitions and mid-infrared optical matrix elements. In the case of two vertically aligned pyramidal SADs, we show that quantum
mechanical coupling alone between identical dots underestimates the magnitude of
the coupling between the dots, which in large part is due to piezoelectricity and size
difference between SADs.
Nonlinear Dielectric Investigation of Trifluoroethylene-Rich Copolymers of Vinylidene Fluoride
Authors: Kodama Hidekazu , Furukawa Yoshiyuki Takahashi andTakeo
Published: October 2002

Phase transition behavior in trifluoroethylene (TrFE)-rich copolymers of vinylidene fluoride (VDF) has been investigated by means of nonlinear dielectric spectroscopy. Unlike VDF-rich copolymers showing a single ferroelectric-to-paraelectric transition, TrFE-rich copolymers undergo two-stage transitions, loss of ferroelectric polarization at a temperatureTAand transition into a paraelectric motional phase at a temperatureTC. BetweenTAandTC, they exhibit theD–Edouble hysteresis loop characteristic of an antiferroelectric. Analysis of such a double loop allowed the estimation of antiferroelectric polarizationPAas well as ferroelectric polarizationPF. A comparison of the temperature dependences of reciprocal polarizabilities βn(n= 1, 2, 3) with those ofPFandPArevealed that β2is proportional toPFwhereas β1and β3are proportional toPF2+PA2. These results are consistent with phenomenological prediction for an antiferroelectric. It was concluded that TrFE-rich copolymers of VDF have an antiferroelectric-like phase consisting of all-trans molecules packed in a disordered manner.
Characterization of Sputtered Lead-Zirconate-Titanate Thin Films with Various Compositions
Authors: Sakoda Tomoyuki , Aoki Katsuhiro , Fukuda Yukio
Published: October 2002

Sputtered Pb(Zr,Ti)O3 (PZT) thin films with various compositions were characterized.
Comparing sputtered PZT films with sol-gel PZT films, it was found that the film
composition can be approximately estimated from the distance of the PZT (100) lattice plane.
The sputtered PZT thin films with a Ti-rich phase showed excellent ferroelectric properties.
The remanent polarization density, the coercive field and the saturation voltage of
300-nm-thick PZT capacitors with Zr/Ti=35/65 were 42 µC/cm2, 46 kV/cm and 3.2 V,
respectively. Those of 300-nm-thick PZT capacitors with Zr/Ti=30/70 were 42 µC/cm2, 48 kV/cm and
2.5 V, respectively. The polarization retention properties of PZT capacitors with a Ti-rich
phase are outstanding, and the value of the retained polarization density after 10
years is expected to be larger than 40 µC/cm2.
Three-Dimensional Fractal Analysis of Real Electrical Trees in Polyethylene
Authors: Hiroaki Uehara Hiroaki Uehara , Katsutoshi Kudo Katsutoshi Kudo
Published: October 2002

In this paper, real electrical trees in polymeric insulating
materials were discussed from the
viewpoint of their fractal characteristics. Experiments on real
electrical trees were carried out in the needle to plane electrode geometry
under ac voltage application. Samples in this investigation were made of
cross-linked polyethylene (XLPE). Two methods of
reconstructing three-dimensional (3D) patterns of real electrical trees were
developed. One is the computerized tomography method (CTM) and the other
is the serial sectioning method (SSM). The relationship between
tree characteristics and 3D fractal dimensions of tree patterns was studied.
The experimental
results showed that
the spatial tree patterns have a fractal characteristics and that the tree
characteristics can be characterized by fractal dimensions.
Growth Mechanism during Silicon Epitaxy by Photochemical Vapor Deposition at Low Temperatures
Authors: Abe Katsuya , Watahiki Tatsuro , Konagai AkiraYamada
Published: October 2002

The growth mechanism of Si epitaxial film at low temperatures on Si(100) by photochemical vapor deposition (photo-CVD) is analyzed theoretically by using reaction models both in the gas phase and on the surface. We discuss three surface reactions: the growth of Si from SiH3 radicals, the dangling bond termination by atomic hydrogen and the abstraction of bonding hydrogen by SiH3 radicals. The parameters of the surface-reaction model are estimated from the experimental results, assuming that the film structure is determined by the hydrogen surface-coverage ratio “θ”. The theoretical analysis explains well the experimental results of the Si films grown under various conditions.
Stress Characteristics of Multilayered Polysilicon Film for the Fabrication of Microresonators
Authors: Choi Chang Auck , Lee Chang Seung , Jang Won Ick , Hong Yoon Shik , Lee Jong Hyun , Sohn Byung Ki
Published: October 2002

Micro-polysilicon actuators, which are widely used in the field of
microelectromechanical system (MEMS) technology, were fabricated
using a novel stacking method. Polysilicon film was deposited to
have a symmetrical layer structure using a low-pressure chemical
vapor deposition (LPCVD) system. We have also measured the physical
characteristics using micromachined test patterns to verify the
minimal stress and stress gradient in the polysilicon layers,
according to the film stacking, doping, and thermal treatment
methods. Finally, the fabricated planar polysilicon resonators,
symmetrically stacked to 6.5 µm thickness, showed Q of 1270 and
oscillation amplitude of 5 µm under 1000 mTorr. The developed
micro-polysilicon resonator can be utilized in the fabrication
of both microgyroscopes and accelerometer sensors.
Effect of Electrode for Producing the Highly Charged Heavy Ions from RIKEN 18 GHz Electron Cyclotron Resonance Ion Source
Authors: Kurita Tetsuro , Nakagawa Takahide , Kidera Masanori , Miyazawa Yoshitoshi , Hemmi Masatake , Chiba Toshiya , Inabe Naohito , Kase Masayuki , Kageyama Tadashi , Kamigaito Osamu , Goto Akira , Yano Yasushige
Published: October 2002

We successfully produced the intense beam of highly charged Kr
ions using an electrode. Under the pulsed mode operation, we found
that the depth of the plasma potential dip strongly depends on the
duration of the microwave and takes about 40 ms to reach the
equilibrium state. Taking these results into account, we compared the
beam intensities of highly charged Kr ions with and without the use of
an electrode under the pulsed mode operation. We observed that the
density of highly charged Kr ions and ion confinement time increase
with increasing mirror magnetic field strength. The plasma potential
dip becomes shallower with insertion of the electrode. Consequently,
when we increase the mirror magnetic field strength and insert the
electrode into the plasma, the beam intensities of highly charged ions
increase.
Characteristics of RF Wave Propagation in Large-Diameter Plasma with Cusp Magnetic Field Configurations
Authors: andAtsushi Fukuyama Seiji Takechi
Published: October 2002

RF wave propagation, in the large-diameter (45 cm) plasma produced by a planar, spiral antenna, was investigated with the cusp magnetic field configurations. Measurements of the excited magnetic field amplitude and the phase were examined by a helicon wave dispersion relation, and the obtained results were consistent with the calculated ones by Transport Analyzing System for tokamaK/Wave analysis by Finite element method (TASK/WF) code. The wave characteristics depended on the gradient and the magnitude of the magnetic field near the line cusp position, and in the neighborhood of this position, this wave showed different behavior from the helicon wave observed in a uniform field.
Compensation of Linearization Approximation Error in Acoustic Inverse Scattering Problem: Quantitative Reconstruction of Attenuation and Sound Speed Images
Authors: Akira Yamada Akira Yamada
Published: October 2002

For the realization of the acoustic parameter quantitative reconstruction of biological tissues by ultrasonic diffraction tomography, the author recently developed the backward propagation Rytov approximation to overcome the limitation of the weak scattering condition of tissuelike objects. A sound speed image with sufficient quantitative precision was realized. The problem, however, was that the precision of the attenuation image was limited when the sound speed contrast of the object was large. In this paper, a method for compensating the weak scattering approximation error is presented so that a compatible reconstruction of both sound speed and attenuation images can be realized. From numerical verification, the precision of the attenuation image after compensation is verified to be more superior than that before compensation.
Evaluation of the Refrigeration in the Gifford-McMahon-Cycle Refrigerator Based on the Thermoacoustic Theory
Authors: Biwa Tetsushi , Ikuta Hiroshi , Mizutani Uichiro
Published: October 2002

We have measured the refrigeration of the Gifford-McMahon-Cycle
(G-M) refrigerator by using Pb, Er3Ni and NdAg as regenerator
materials. The magnetic intermetallic compounds Er3Ni and NdAg exhibit
a specific heat anomaly corresponding to the magnetic ordering at 7
and 22 K, respectively and possess a larger volumetric specific heat
at low temperatures than that of the conventional regenerator
materials Pb. We analyzed how the performance of the refrigerator is
influenced by the differences in the specific heat of the regenerator
materials based on the Tominaga thermoacoustic theory. We found that
the refrigeration performance, as well as the lowest temperature
reached in a given G-M refrigerator, is determined by the ratio of the
specific heat of the regenerator material over that of the helium gas,
and the volume expansion coefficient and mean temperature of the
helium gas. We can predict the lowest temperature attainable by a
given regenerator material in the ordinary G-M refrigerator only from
the temperature dependence of the
product of these parameters.
Two Theorems of Instability with Application to Gimbal Walk
Authors: Ge Zheng-Ming , Liu Wu-Pen
Published: October 2002

Two theorems of instability, different from the traditional Chetaev's instability theorem are
developed. The theorems determine the instability of autonomous and non-autonomous
dynamical systems by means of investigating the higher-order derivatives of the Lyapunov
function. Using the first theorem of these theorems, the walk of a free gyroscope, which has
not been verified by traditional stability theorem, can be solved by our theorem. Furthermore,
several dynamical systems are presented as examples of application of these two theorems.
They are the motion of a symmetric gyroscope with steady precession, the steady rotations of
a rigid body around the intermediate axis of its ellipsoid of inertia, the equilibrium of the
equations of Lotka-Volterra model of competition between two species, etc.
Effect of the Dipole-Dipole Interaction on the Self-Assembly of Cyclodextrin Inclusion Complexes
Authors: Yasuda Satoshi , Miyake Koji , Komiyama JunSumaoka , Shigekawa Hidemi
Published: October 2002

We performed scanning tunneling microscopy (STM) observations on self-assembled α-cyclodextrin (CyD) inclusion complexes on HOPG for the guest compounds of (1) H2O, (2) MeOH
(Methanol) and (3) p-NP (p-nitrophenol). The observed structures of α-CyD-H2O and α-MeOH
complexes were channel-like with twofold symmetry, however, α-CyD-p-NP showed a structure
different from that of the others, namely, a threefold symmetric arrangement. On the other hand,
the dipole moments calculated for α-CyD-H2O and α-MeOH complexes were similar and directed
from the secondary to the primary hydroxyl groups of the α-CyD. However, the dipole moment on
the α-CyD-p-NP complex was oblique to the axis for the other two complexes. Taking into account
this difference in the dipole moment and the hydrogen bonding between the CyDs, the structural
differences observed by STM could be explained comprehensively. The obtained results indicate
the existence of a high potential for the structural control of the self-assembled α-CyD complexes
by changing the guest compounds.
Bases of Chemical Force Microscopy by Friction: Energetics and Dynamics of Wearless Friction between Organic Monolayers in Terms of Chemical and Physical Properties of Molecules
Authors: Fujihira Masamichi , Ohzono Takuya
Published: October 2002

Molecular dynamics and simple phenomenological simulations are used to model the friction between two ordered monolayers of alkyl chains bound at their ends, i.e., pinned atoms, to rigid substrates. We could previously interpret the origin of friction differences in organic monolayer systems by comparing these two simulations. In the present work, insight given by such comparisons is described in detail. In particular, the molecular mechanism of energy dissipation, the origin of friction force microscopic image, the chain length dependence, the packing density (tilt angle) dependence, and anisotropy of friction due to sliding direction are discussed by taking into account the effects of the molecular properties on two simplified potentials of the monolayer films. One potential is due to the lateral collective deformation of a film, and the other is a corrugated interfacial potential between films facing each other. This interpretation of molecular lubrication mechanisms in terms of the chemical and physical properties of molecules using the simple phenomenological model can be extended widely to understand the bases of chemical force microscopy by friction force microscopy.
Reduction of Schottky Reverse Leakage Current Using GaAs Surface Cleaning with UVO3 Treatment
Authors: Tanimoto Takuma , Ohbu Isao , Ohta Hiroshi , Takatani Shinichiro
Published: October 2002

A GaAs surface-cleaning method using UVO3 treatment was developed.
The UVO3 treatment involves two processes: GaAs surface oxidation and
oxide removal. Surface oxidation is performed by using a mercury lamp at
high temperature, such as 180°C. GaAs oxide is removed by NH4OH
solution dipping. Spectroscopic ellipsometry and X-ray photoelectron
spectroscopy (XPS) study showed that thermally unstable As oxides exist on a
non-treated surface; however, surface GaAs oxides are almost completely
removed by this treatment. This cleaning method was applied in the field
effect transistor (FET)-gate-formation process and, consequently, Schottky
leakage current was significantly reduced.
Band-Tail Characteristics in Amorphous Semiconductors Studied by the Constant-Photocurrent Method
Authors: Tanaka Keiji , Nakayama Shin-ichi
Published: October 2002

Optical absorption edges in five chalcogenide glasses, Se, As2S(Se)3, and GeS(Se)2, and a-Si:H have been measured using the constant-photocurrent method at 10–400 K. In the chalcogenide glasses the weak-absorption tail detected by the method is much smaller than that evaluated from transmission spectra, while in a-Si:H the magnitudes are similar. Photoconductive Urbach tails in all the chalcogenide glasses blue-shift from the optical Urbach tails, and marked non-photoconducting spectral gaps appear. The width and the residual absorption of the spectral gap depend upon the dielectric constant and the average coordination number of atoms, respectively. These characteristics of the chalcogenide glass are discussed in comparison with those in a-Si:H and crystalline chalcogenide materials.
Direct Bonding of Gallium Arsenide on Silicon
Authors: Lee Ming-Kwei , Yeh Min-Yen , Guo Shyh-Jen , Huang Hung-Da
Published: October 2002

Direct bonding of gallium arsenide on silicon is studied. The technology
is expected to enable the easy integration of gallium arsenide optoelectronic
devices with silicon very-large-scale integrated circuits. The interface
quality of n-GaAs/p-Si can be improved with a thermal annealing process. It
is examined by the current-voltage characteristics of the n-GaAs/p-Si diode.
The bonding strength was found to be sufficiently high and could “high
enough to” withstand the subsequent grinding and polishing procedures of
the bonded wafers.
Magnetic Properties and Growth Behavior of Nd–Fe–B Films on Si(111)
Authors: Tsai Jai-Lin , Chin Tsung-Shune , Shih Shi-KunChen
Published: October 2002

NdFeB films were prepared by dc-magnetron sputter-deposition
onto Si(111) at 600 to 700°C. Anisotropic films with remanence ratio
larger than 0.67 and intrinsic coercivity greater than 7 kOe were
obtainable at a substrate temperature of 650°C on Si(111) using one of
W, Mo, or Pt as the underlayer. The mechanical polishing can reduce
the film thickness from about 850 nm to 150 nm, and the coercivity
remains 2–5 kOe. The coercivity of being strongly dependent on film
thickness can be explained by the domain-wall motion in films through
suitable modeling. The depth-profile and microstructure of the films
on different underlayers were explored by secondary ion mass
spectroscopy (SIMS) and high resolution transmission electron
microscopy. The Pt underlayer, being in fact a Pt/Ti/SiO2/Si(111), is
a sound barrier layer between the NdFeB film and Si(111) so that there
is negligible interdiffusion as evidenced by SIMS depth profile. The
formation of silicide was found in films with Mo or W underlayer
sputtered at 650°C. This can be observed from the overlap region
between the underlayer and Si(111) in the SIMS depth
profile. Diffusion coefficients of the Nd, Fe, B in Si(111) were also
quantitatively estimated.
Analysis of Confocal Push-Pull Detection of Tracking-error Signals of Optical Disk Player
Authors: Mizuno Takeshi , Doi Masato , Matsuda HironobuNarui
Published: October 2002

We previously reported a novel optical pick-up using a confocal
laser coupler (CLC) and the confocal push-pull (CPP) method of
detecting tracking-error signals. The CPP method is very stable in the
face of the lens displacement of the optical pick-up, but it remains
to determine whether the optical pick-up can be applied to optical
disk systems of various parameters. In this paper, the inherent
characteristics of the CPP method of detecting tracking-error signals
are discussed based on the results of numerical analysis and
experiments.
Derivation of Analytical Solution for Confocal Push-Pull Signals and Improved Confocal Push-Pull Detection Method Using Signal Processing
Authors: Mizuno Takeshi , Narui Hironobu , Matsuda Osamu
Published: October 2002

We clarified the inherent characteristics of the confocal push-pull (CPP) method of detecting tracking-error signals for an optical disk player before. We reported that CPP signals strongly depend on the parameters of the optical disk systems such as the groove/land ratio (duty ratio) and focus conditions, although CPP signals are very stable in the face of the lens displacement. In order to obtain stable tracking-error signals, it is necessary to improve CPP signals. In this paper, the analytical solution for CPP signals is reported and an improved CPP method using signal processing is proposed.
Antimony Aperture Properties on Super-Resolution Near-Field Structure using Different Protection Layers
Authors: Tominaga Junji , Fuji Hiroshi , Sato Akira , Nakano Takashi , Fukaya Toshio , Atoda Nobufumi
Published: October 2002

Modifying a rewritable digital versatile disc (DVD) structure by Sb and SiN thin films, near-field super-resolution was performed beyond the optical diffraction limit only using a
current DVD optical pickup. Using the wavelength (λ) of 635 nm and the lens numerical
aperture (NA) of 0.6, a mark size of 60 nm was recorded and detected at the double rotation
speed of Compact Disc. The super-resolution properties of Sb thin films sandwiched by
different dielectric layers of SiO2 and ZnS–SiO2 instead of SiN were also investigated. Super-resolution did not occur and the resolution was close to 200 nm, when using the ZnS–SiO2 layers.
A Pit-edge Confocal Push-Pull Tracking-error Signal Detection Method for an Optical Pick-up
Authors: Mizuno Takeshi , Narui Hironobu
Published: October 2002

We previously reported that the confocal push-pull (CPP) signals for the tracking-error signals of an optical disk player strongly depend on the parameters of the optical disk system, such as the groove/land ratio (duty ratio) and focus conditions, although CPP signals are very stable in the face of lens displacement. In this paper, improved CPP signal detecting at the pit-edge is reported. This new tracking-error detection method can be applied to an optical disk system in which the optical disk has a pit depth of λ/4n to λ/8n without any phase compensation.
Voltage Gain in GaAs-Based Lateral Single-Electron Transistors Having Schottky Wrap Gates
Authors: Satoh Yoshihiro , Okada Hiroshi , Jinushi Kei-ichiroh , Fujikura Hajime , Hasegawa Hideki
Published: October 2002

Gain characteristics of GaAs-based lateral single-electron transistors (SETs)
formed by putting two- or three-wrap gates (WPGs) on etched GaAs quantum wire
were investigated in detail theoretically and experimentally. The computer
simulation of potential distribution showed that the three-WPG SET allows
independent control of the dot geometry and the tunneling barrier profile and that
the three-gate device realizes much tighter control of the dot potential and a higher
voltage gain than the two-gate device.
Both two- and three-gate SETs were fabricated experimentally. These devices
showed clear Coulomb blockade oscillations which were visible up to 40 K. In
excellent agreement with the computer simulation, a high voltage gain of 1.3 was
achieved in the three-gate SET, whereas the gain of the two-gate SET remained
below unity. This is the first report on achieving a voltage gain higher than unity
in III–V SETs. This field effect transistor (FET)-like lateral SET structure seems
to be promising for the realization of III–V SET ultra large scale integrated circuits
(ULSIs).
Effect of Channel Coding in Digital Holographic Data Storage
Authors: Chiang Phua Jingfeng Liu , Chong Chong Tow , Yihong Wu Yihong Wu , Veerappa Boopathi Veerappa Boopathi
Published: October 2002

A random array exclusive OR modulation (REOM) channel coding technique is proposed for digital holographic data storage. The effect of channel coding on the system performance is analyzed through simulations. The performance of REOM is compared with that of other coding methods in terms of system raw bit error rate (BER) and signal-to-noise ratio (SNR). It is shown that REOM provides relatively uniform intensity distribution on the recording plane and therefore gives an improved performance.
A Novel Structure to Improve the Viewing Angle Characteristics of Twisted-Nematic Liquid Crystal Displays
Authors: Gong Shaoqin , Kanicki Jerzy , Xu Gang , Zhong JohnZ. Z.
Published: October 2002

A numerical simulation of a novel wide viewing angle twisted-nematic liquid crystal
display (TN-LCD) structure has been performed. The simulated results indicate that this new
structure can provide an excellent gray level separation and a 50 : 1 contrast ratio that extends up
to around ±60° along both the vertical (V) and horizontal (H) directions. No reverse image is
expected over the ±65°H/±80°V range. No excessively dark or excessively bright images are
observed over the entire viewing angle range of the display. The fabrication process to achieve
this novel structure is also proposed.
Synthesis of Single-Walled Carbon Nanotubes by AC Arc Discharge
Authors: Ohkohchi Masato
Published: October 2002

We evaporated carbon bilateral rods containing different catalytic metals by AC arc
discharge in He gas. No carbonaceous deposit was formed on either of the two electrodes,
which meant that all of the evaporated carbon became soot in which single-walled nanotubes
existed. It was clarified that the method is superior for high-efficiency synthesis of single-walled nanotubes.
Initial Stage of C60 Thin-Film Growth on YB66(001) Surfaces
Authors: Nakata Kazunari , Hirayama Hiroyuki , Takayanagi Kunio
Published: October 2002

Exposed B156 supericosahedra on a YB66(001) surface
were found align periodically in a two-dimensional square lattice.
On the YB66(001) surface, C60 molecules were deposited at
room temperature. The initial stages of C60 thin-film growth
on the YB66(001) surface were studied using a scanning tunneling
microscope (STM). In the submonolayer regime, the C60
molecule adsorbed strongly on the surface to show the stripe pattern
due to the inner molecule C=C bonds. The adsorbed
layer had no long-range ordering. The C60 molecules did not
favor the on-top site of the B156 supericosahedron. We propose a
model that the C60 molecule adsorbs on triangular sites made up
of the B12 icosahedra on each B156 supericosahedron on the
surface. Due to size frustration, the C60 molecule occupies
only one of two equivalent triangular sites. The model explains
the characteristics of the adsorption site and the arrangement of the
C60 molecules in the submonolayer regime. In the multilayer
regime, the dangling bonds of the surface were passivated by the
first layer, and overlayer growth was governed by van der Waals
interaction between C60 molecules. An island, the top of which
showed a hexagonal lattice, grew on the first layer. The hexagonal
lattice was rotated by 10° with respect to the underlying
square lattice of the YB66(001) surface.
Orientational Phase Transitions in Langmuir Monolayers
Authors: Jiang Min , Xing Ding Yu , Dong Jinming
Published: October 2002

A statistical mechanics approach is applied to studying orientational
phase transitions in Langmuir monolayers. The orientational phase
transition of rodlike molecules in the monolayer is attributed to a
competition between two types of forces experienced by the dipolar
molecules. One is the electrostatic attractive force between the dipolar
molecules and water surface, the other is the steric repulsive force
among the molecules. The consideration of finite steric repulsive potentials
makes the present theoretical result in qualitative agreement with the
existing experiments.