bluuebunny/crossref_metadata_2025 huggingface dataset:
Vacancy-Type Defects in Ion-Implanted Diamonds Probed by Monoenergetic Positron Beams
Authors: Uedono Akira , Kawano Takao , Tanigawa Shoichiro , Suzuki Ryoichi , Ohdaira Toshiyuki , Mikado Tomohisa , Fujii Satoshi , Shikata Shinichi
Published: October 2002

Vacancy-type defects introduced by 180-keV B+-, C+- and N+-ion implantation in synthesized diamonds (type Ib) were probed by the positron annihilation technique. For an unimplanted specimen, the diffusion length of positrons was shorter and the lifetime of positrons was longer than those for a type IIa specimen. These facts were attributed to the trapping or the scattering of positrons by nitrogen-related defects. For ion-implanted specimens, the depth distributions of vacancy-type defects were determined from measurements of Doppler broadening profiles of the annihilation radiation as a function of incident positron energy. The obtained profiles of defects were in agreement with those of an energy loss of ions calculated by the Monte Carlo method. From measurements of lifetime spectra of positrons, the dominant defect species introduced by the B+- or N+-ion implantation were identified as complexes of vacancy clusters and these impurities.
Circular Polarization of Photoluminescence Excitation Spectra of Strained GaAs Layer
Authors: Horinaka Hiromichi , Cho Yoshio , Nakanishi Tsutomu , Okumi Shoji , Togawa Kazuaki , Saka Takashi , Kato Toshihiro
Published: October 2002

Measurements of photoluminescence (PL) spectra and photoluminescence excitation (PLE) spectra were made on strained GaAs samples fabricated as a photocathode of spin-polarized electron source. PL and PLE due to the interband transition of the strained GaAs layer showed large polarization in comparison with those of the GaAs substrate. The increase of the hand gap and the splitting of the valence band were observed in luminescence polarization spectra of PLE although they are not clear in the original spectra. The spin polarization of conduction band electrons in the case of resonant excitation was estimated to be 72% from luminescence polarizations of PL and PLE spectra.
High-Performance Nitrided Oxides Fabricated by Very-Low-Pressure Nitridation Technique
Authors: Su Huan-Ping , Huang-Chung Cheng Huang-Chung Cheng
Published: October 2002

A novel and simple method is proposed to produce high-performance nitrided oxides. Thin oxides nitrided only in NH3 at 900° C for 1 h at 0.1 Torr have excellent interface stability, few electron traps, and excellent reliability. Although the nitrogen concentration [N] at the dielectric/Si substrate interface is kept at a low value, the hydrogen concentration [H] has been shown to be comparable to that of pure oxide at the beginning of the nitridation. Consequently, a high ratio of [N]/[H], which reflects the stable interface, can be attained at the initial stage of the very-low-pressure nitridation (VLPN). This is very different from the case of conventional low-pressure nitridation. The retarded formations of the interfacial Si3N4 and the surface nitrogen-rich oxynitrides are conjectured to be the main cause of reduction in the hydrogen content in the dielectrics during VLPN.
Due to the simplicity and wide process window, VLPN is promising for the future ultra-large-scale-integration (ULSI) technology.
Effect of Stress on Oxide Edge Shape of Local Oxidation of Silicon for Various Oxidation Temperatures
Authors: Okihara Masao , Kuroda Shigeki , Itoh Masahiro , Norio Hirashita Norio Hirashita
Published: October 2002

Transmission electron microscopy and oxidation simulation based on the viscoelastic model were used to study oxide edge shapes during the local oxidation of silicon. Upon reducing the pad oxide thickness, local retardation of oxide growth, resulting in pinched shapes, was observed at field oxide edges at oxidation temperatures below 1000° C, and {111} interfaces between silicon dioxide and silicon were found to be formed at temperatures above 1000° C. These characteristic shapes were discussed in terms of the viscous flow of oxide, the simulated uniaxial stress in oxide during oxidation and the distortion energy of the interface. It was concluded that pinched shapes were formed by the anisotropic diffusion of oxidants and {111} interfaces resulting from the reaction of minimizing the distortion energy of the interface.
Dependence of Photoluminescence of Porous Silicon on Angle of Radiation
Authors: Kimura Tatsuya , Nishida Hidekuni , Terui Syusuke , Takeo Suzuki Takeo Suzuki
Published: October 2002

Brightness of UV-excited porous silicon has been measured as a function of angle of radiation. It is revealed that the variation of brightness of porous silicon with angle of radiation completely violates Lambert's law of cosine. The origin of this property is discussed in relation to surface morphology.
Compositional Design and Properties of a Low-k Silica Dielectric for Multilayer Ceramic Substrate
Authors: Jean Jau-Ho , Tong-Hua Kuan Tong-Hua Kuan
Published: October 2002

Compositional design and properties of a low-dielectric-constant silica composite containing borosilicate glass, high-silica glass and gallium oxide are described. A cristobalite-free silica dielectric with a high sintered density, >95%, is obtained at temperatures less than 1000° C. An analytical approach assuming the mixing rule is used to design compositions with desirable properties, and validated by experimental results. Compositions with a thermal expansion coefficient compatible with Si and GaAs, and dielectric constants in the ranges of 4-5 and 5-6, respectively, at 1 MHz, are developed.
Electrically-Induced Memory Effect in Bacteriorhodopsin
Authors: Okazaki Choichiro , Kazuo Takeda Kazuo Takeda
Published: October 2002

Absorption spectrum of bacteriorhodopsin under an electric field was investigated. We found that the change driven by the field does not disappear even after removing the field at relative humidity below 5%. Furthermore, we found that the state induced by the electric field returns to the initial state with light illumination. We examined the effect of humidity on this phenomenon. As for a retinylidene chromophore, we suppose the following phenomenon may occur. The existence of water molecules promotes the hydration of the nitrogen atom in the retinylidene chromophore, and the pi-electrons in the chromophore are attracted to the nitrogen atom. Such a change is considered to be one cause that makes the electrically-induced state unstable at high relative humidity.
Stress-Induced Anomalous Growth in Lateral Solid-Phase Epitaxy of Ge-Incorporated Si Films
Authors: Oh Jeong-Hee , Kim Duck-Young , Hiroshi Ishiwara Hiroshi Ishiwara
Published: October 2002

Lateral solid-phase epitaxy (LSPE) characteristics of Ge-incorporated amorphous Si films which are deposited on SiO2/Si (100) structures with [010] seed openings are investigated. It has been found in P-doped amorphous Si films that the LSPE growth rate at 600° C is enhanced about sixfold by incorporation of 0.5 at.% Ge atoms, and that the maximum growth length is about 21 µ m. It has also been found that the growth in the film with 1 at.% Ge atoms stops for a few hours upon annealing at temperatures lower than 600° C at a length of about 2 µ m from the seed edge and it proceeds again as annealing time is extended. To clarify the origin of the anomalous growth rate, the residual stress in the films has been measured using microprobe Raman spectrometry, and it is concluded that the origin of the enhanced growth is the residual stress in the films. Finally, it is suggested that the Ge-incorporated stress effect may be explained by the critical thickness theory in pseudomorphic growth of Si1-
x

Ge

x

films on Si substrates.
Millimeter-Wave Phase-Imaging Interferometry Using Two-Dimensional Detector Array
Authors: Oyama Naoyuki , Mase Atsushi , Tokuzawa Tokihiko , Ito Yasuhiko , Itakura Akiyosi , Tamano Teruo , Harada Yasoo , Mizuno Koji
Published: October 2002

A millimeter-wave two-dimensional detector array has been newly developed for application to a phase-imaging interferometer installed in the GAMMA10 tandem mirror. The detector has 4×4 channels consisting of beam-lead GaAs Schottky barrier diodes bonded to bow-tie antennas on a quartz substrate. The imaging system is also applied to measurements of electron cyclotron emission, which provides the spatial profile of warm and hot electrons.
Effect of Current Ripple of Power Supplies on Electron Beam in Synchrotron
Authors: Hirofumi Tanaka Hirofumi Tanaka , Tetsuya Nakanishi Tetsuya Nakanishi
Published: October 2002

The effect of current ripple of quadrupole magnet power supplies has been studied from measurements and calculations in an electron synchrotron situated Mitsubishi Electric Corporation. The effect has been unexplainable as a quasi-static tune shift. The effect can be simulated fairly well with beam tracking in which the injection beam size and momentum spread are taken into account. Measured and calculated results have shown that the allowed current ripple of quadrupole defocus magnet (QD) where νx=2.26 and νy=1.18, is about ±0.6% in the synchrotron when 20% beam loss is permitted. A calculation has proven that compensation of chromaticities can reduce the effect when the momentum spread of the injection beam is large.
Low-Damage and Smooth Etching of GaAs by Using a Neon Ion Beam
Authors: Yuji Uenishi Yuji Uenishi
Published: October 2002

The irradiation damage to a GaAs etched by an ion beam was experimentally investigated by using different inert gases such as argon and neon. Etching damage was evaluated by measuring the current-voltage (I-V) characteristics of Schottky diodes fabricated on the etched surfaces. Surface roughness was observed by replica transmission electron microscopy. The I-V curve of a diode fabricated on an Ar-etched surface was found to be much more degraded than that of one on an Ne-etched surface. The Ne-etched surface was also found to be smoother than the Ar-etched surface. The reflectance of LD etched mirrors fabricated by both Ne and Ar ion beam etching was measured to examine the etched sidewall striation. The reflectance of Ne-etched mirror was 0.22 and that of the Ar-etched mirror was 0.07, whereas the ideal reflectance for a cleaved facet is 0.32. Ne ion beam etching can thus produce smoothly etched surfaces and sidewalls with low damage at a practical etch-rate.
Anisotropic Etching of n+-Polysilicon Using Beam Plasmas Generated by Gas Puff Plasma Sources
Authors: Oomori Tatsuo , Taki Masakazu , Nishikawa Kazuyasu , Ootera Hiroki , Kouichi Ono Kouichi Ono
Published: October 2002

Generation of pulsed chlorine beam plasmas using a nozzle beam system generated from an electron cyclotron resonance (ECR) discharge plasma source with a high-speed gas puff valve (gas puff plasma source) has been studied. Simulations of gas flow, and measurements of plasma parameters and their etching properties have also been discussed, comparing the experimental results with those of conventional ECR plasmas using an almost identical reactor. The time-averaged electron temperatures around a wafer were lower than those in the ECR plasmas for time-averaged pressure of 0.1-2 mTorr. The instantaneous ion energy distributions of the beam plasmas incident on the wafer had wider high-energy tails than those in the ECR plasmas. Thus, anisotropic etching profiles of n+-polysilicon were obtained at the position of the wafer (B

z
∼200 G) where notching phenomena were observed in the ECR plasmas.
Effect of N2 Addition on Aluminum Alloy Etching by Electron Cyclotron Resonance Reactive Ion Etching and Magnetically Enhanced Reactive Ion Etching
Authors: Kusumi Yoshihiro , Fujiwara Nobuo , Matsumoto Junko , Masahiro Yoneda Masahiro Yoneda
Published: October 2002

Aluminum alloy etching is an important process in ultra-large-scale integration (ULSI) fabrication. We investigated the effect of N2 addition to Cl2+BCl3 gas mixture on aluminum-copper alloy etching by electron cyclotron resonance reactive ion etching (ECR-RIE) and magnetically enhanced reactive ion etching (MERIE). In ECR-RIE, N2 addition was effective in suppressing residues and post-etch corrosion of aluminum alloy interconnects; on the other hand, in MERIE, N2 addition promoted the formation of residues and post-etch corrosion. This difference is probably caused by BCl
X

+ in plasma, because it was found by mass spectral analysis that N2 addition increased the amount of BCl
X

+ in plasma of ECR-RIE, but it decreased that in plasma of MERIE.
Multiphoton Ionization-Mass Spectrometric Study on Laser Ablation of Polymethylmethacrylate and Polystyrene at 308 nm
Authors: Tsunekawa Makoto , Nishio Satoru , Sato Hiroyasu
Published: October 2002

A multiphoton ionization-mass spectrometric study has been made on laser ablation of polymethylmethacrylate and polystyrene films by an excimer laser at 308 nm. “Unzipping” reactions occurred, i.e., neutral fragments ablating from the polymer surface were predominantly monomer and dimer methylmethacrylate and monomer and dimer styrene. Exponential dependence of fragment yields on ablating laser fluence and the Maxwell-Boltzmann-type velocity distributions of ablating species were found. They are due to an essentially thermal or photothermal ablation mechanism of these polymers in the experimental conditions.
Characteristics of Silicon Dioxide Film Prepared by Atmospheric-Pressure Chemical Vapor Deposition Using Tetraethoxysilane and Ozone with Alcohol Addition
Authors: Ikeda Koichi , Nakayama Satoshi , Masahiko Maeda Masahiko Maeda
Published: October 2002

We evaluate the characteristics of silicon dioxide film deposited by atmospheric-pressure chemical vapor deposition (APCVD) using tetraethoxysilane and ozone ( TEOS/O3) with alcohol addition and the role of the alcohol in the reaction system using ethanol- D6. The deuterium substituted ethanol, like normal ethanol, decreases the effective ozone concentration. Secondary ion mass spectroscopy (SIMS) analysis detects a uniform distribution of hydrogen and deuterium incorporated into the deposited film. Fourier transform infrared spectroscopy (FT-IR) spectra show the relationship between the content of the terminal groups in the film and the effective ozone concentration. Three states in thermal desorption spectroscopy (TDS) spectra are characterized: water absorbed after film deposition, water absorbed during film deposition, and terminal groups (i.e., Si-H and Si-OH) in the film in order of annealing temperature. Moreover, it is found that the third state contains two peaks due to deuterium substitution. One of the peaks in the third state is associated with the flowing-like profile formation.
Photoellipsometry Analysis of n-AlGaAs/GaAs Heterojunction Structures
Authors: Xiong Yi-Ming , Wong Cheong Chee , Tadashi Saitoh Tadashi Saitoh
Published: October 2002

Photoellipsometry, a new contactless spectroscopic method, was applied to n-AlGaAs/GaAs heterojunction structures. Two samples were measured and analyzed, each having an epitaxially grown AlGaAs layer of a thickness of about 100 nm, with a different Al composition and a different doping density, on top of an undoped GaAs substrate. The objective of this research was to determine surface built-in electric field strength, depletion width, broadening, and critical point energies of AlGaAs for each given sample. The measured spectra were analyzed using the Franz-Keldysh theory with the inclusion of field inhomogeneity and nonuniform broadening effects. Good agreement between the measured and calculated spectra indicates that theories and models used were appropriate for the samples investigated and that the calculated results were reliable.
Experimental Observation of Intersubband Excitations in Si-Doped GaAs/AlAs Multiple Quantum Wells
Authors: Matsumoto Toshiyuki , Haraguchi Masanobu , Fukui Masuo , Yamaguchi Masahito , Kubo Hitoshi , Hamaguchi Chihiro , Nakashima Shinichi
Published: October 2002

Experiments are carried out to observe optical phonon modes coupled with intersubband transition in doped GaAs/AlAs multiple quantum wells (MQW) by attenuated total reflection (ATR) and Raman scattering methods. A step due to intersubband transition is found at an energy corresponding to the calculated subband level in ATR spectra. Two peaks related to charge-density intersubband excitation are observed in the Raman spectrum. From these spectra, we evaluated the parameters of intersubband transitions and the sheet carrier density in the well region.
Secondary Retarded Effect in Layered High-Temperature Superconductors
Authors: Yamaguchi Yoichi , Tanaka Kazuyoshi , Yamabe Tokio
Published: October 2002

Assuming a weak electron-phonon coupling mechanism in the high-temperature superconductivity in copper oxides, the possibility of effective electron-electron interaction mediated by the secondary retarded effect associated with inter- CuO2 layer coupling has been examined. It is pointed out that under the appropriate phonon phase there is an attraction even for |ε

n,k±q
-ε

n,k
|>\hbarω
q
, circumventing the conventional BCS restriction.
Capacitance-Voltage Characteristics of Au/PrBa 2Cu 3Oy /YBa 2Cu 3Ox Structure Measured at 4.2 K
Authors: Toshiaki Ohmameuda Toshiaki Ohmameuda , Yoichi Okabe Yoichi Okabe
Published: October 2002

Capacitance-Voltage (C-V) characteristics of Au/PrB2Cu3Oy/YBa2Cu3Ox structure were studied. YBa2Cu3Ox and PrBa2Cu3Oy were deposited by rf magnetron sputtering. Deposition temperatures were 700°C for YBa2Cu3Ox and 690°C for PrBa2Cu3Oy. Capacitance was measured at liquid-helium temperature. At this temperature PrBa2Cu3Oy behaves as an insulator, and C-V characteristics of Au/PrBa2Cu3Oy/YBa2Cu3Ox as a MIS diode can be measured. From analyses of C-V characteristics, a depletion layer was found to exist near the PrBa2Cu3Oy/YBa2Cu3Ox interface when DC bias was zero. The acceptor density of this layer was calculated to be about 1016/cm3 from C-V characteristics.
Thermal Conductivity of Ribbonlike Carbon Films
Authors: Matsumura Yuji , Wang Shenglong , Shinohara Kouji , Hatta Ichiro
Published: October 2002

The thermal conductivity parallel to the surface of a ribbonlike carbon film (RCF) treated at various heat-treatment temperatures (HTTs) was obtained from ac calorimetric measurements. The thermal conductivity was found to increase with rising HTT. The thermal conductivity of RCF treated at a HTT of 2700° C was larger than that of pure copper. Both the crystallite size L
a and the orientation of the crystallite were largely dependent on thermal conductivity. The difference in thermal conductivity is explained in terms of the phonon scattering mechanism.
Theoretical Evaluation of Earth-to-Satellite Laser Long-Path Absorption Measurement of Atmospheric Trace Species in the Infrared Region
Authors: Sugimoto Nobuo , Minato Atsushi , Ozawa Kenichi , Saito Yasunori , Nomura Akio
Published: October 2002

Measurement of atmospheric trace species based on the earth-to-satellite laser long-path absorption method using continuously tunable infrared laser was theoretically studied. Optimum wavelengths for the measurement were systematically investigated in the infrared region for all molecules included in the HITRAN92 data base. It was shown that H2O, CO2, O
3, CH4, N2O and CO have strong absorption lines, and that the inversion method for retrieving vertical profiles can be applied. Also, it was shown that absorption lines of NO2, OCS, HCl, C2H6, HF, HNO3, NO, NH3, C2H2, H2CO, and HOCl have sufficient intensities for measuring column contents. Accuracy of column measurement of each molecule was estimated for a laser long-path absorption system using a geosynchronous satellite.
Characterization of ZnO/CdS/CuInSe 2 Thin-Film Solar Cells by Deep-Level Transient Spectroscopy
Authors: Konagai Shin'ichi Kuranouchi
Published: October 2002

Trap energy levels in CuInSe2 (CIS) films have been measured by means of deep-level transient spectroscopy (DLTS). ZnO/CdS/CIS solar cells with conversion efficiencies of 5–11% were used as samples. Hole traps were detected for all samples measured in this study. Activation energy of traps in each sample was estimated to be in the range from 78 to 226 meV, which is shallower than any other reported values. Characteristics of the trap were thought to depend on the fabrication process of CIS films.
Fourier Transform Infrared Spectroscopic Study of Oxide Films Grown in Pure N2O
Authors: Chao Tien Sheng , Chen Wen Ho , Lei Tan Fu
Published: October 2002

The properties of the oxide films grown by pure N2O were studied in this work. A two-layer model, considering a N2
O oxide with an oxy-nitride film at the interface, was used to describe the dependence of the main peak shift in a Fourier transform infrared (FTIR) spectrum on N2O thicknesses. The thickness of interfacial layer was determined by FTIR and multiple-angle incident ellipsometer. Both methods showed consistent results and the thickness of this layer is found to be 14-16 Å.
Cylindrical Liquid Crystal Lens and Its Applications in Optical Pattern Correlation Systems
Authors: He Zhan , Nose Toshiaki , Susumu Sato Susumu Sato
Published: October 2002

The optical characteristics of a cylindrical liquid crystal (LC) lens are investigated with voltages applied to LC cells. We show that the focusing performance of cylindrical LC lenses, such as focal length, can be varied by voltage application. With this kind of cylindrical LC lens, optical correlation architectures are achieved for the first time using a holographic matched spatial filter. The influence on correlation results of different reference light distributions from a LC lens under various applied voltages is also discussed.
Time-Lag Method and Transport Properties of Gel
Authors: Masayuki Tokita Masayuki Tokita
Published: October 2002

The probe diffusion process across poly(acrylamide) gel is studied. The concentration of probe molecules eluted from the gel is measured as a function of time. It is found that the time course of the concentration of the probe molecule that eluted out of the gel is proportional to the elapsed time after a certain time lag. The results are in good agreement with the theoretical prediction. The diffusion coefficient of the probe in the gel, as well as the permeation coefficient of the gel, is determined from the time lag and the slope of the elution curve.
Preparation of Ferroelectric Bi4Ti3O12 Thin Films with c-Axis Orientation by Atmospheric-Pressure Metal-Organic Chemical Vapor Deposition
Authors: Yoshimura Kuniaki , Ishinabe Minoru , Okamura Soichiro , Takeyo Tsukamoto Takeyo Tsukamoto
Published: October 2002

Ferroelectric Bi4Ti3O12 thin films were prepared by the metal-organic chemical vapor deposition (MOCVD) method at atmospheric pressure using Bi( o-C7H7)3 and Ti( i-OC3H7)2(DPM)2 as metalorganic sources. Assist Ar gas flow rate effects on the growth of the thin films were also examined. Thin films obtained were characterized by XRD analysis, SEM, AFM and D-E hysteresis loop observations. Most of the single-phase Bi4Ti3O12 thin films with c-axis orientation were deposited on Pt/Ti/SiO2/Si and Pt substrates above 500° C. Completely c-axis-oriented Bi4Ti3O12 thin films were prepared on Pt plates at 600° C, which showed good ferroelectric properties: remanent polarization of 1.0 µ C/cm2, coercive field of 18 kV/cm and leakage current on the order of 10-9 A/cm2.
Structure and Dielectric Properties of SrTiO3 Films Prepared by Pulsed Laser Deposition Technique
Authors: Yeh Ming-Hua , Liu Kuo-Shung , Lin I-Nan
Published: October 2002

Strontium titanate thin films have been prepared on Pt-coated and p-type bare Si(100) substrates by a pulsed laser deposition technique. Both the substrate temperature and the oxygen pressure substantially affected the crystal structure, microstructure and texture characteristics of the SrTiO3 films. The (110)-textured films were obtained at 650° C under oxygen pressure of 1 mbar. The apparent dielectric constants increased with the thickness of the films and was accounted for by the formation of the low-dielectric-constant interacting layer, which was connected with the SrTiO3 films in series. The true dielectric constant of the (110)-textured SrTiO3 films was estimated to be K
STO=239 (100 kHz).
Propagation Characteristics in a Transversely Magnetized 70 GHz Waveguide Containing a p-InSb Slab Carrying an Applied Current
Authors: Ishizuka Takehiko , Tetsuo Obunai Tetsuo Obunai
Published: October 2002

It has been experimentally observed that the 70 GHz millimeter-wave propagation characteristics in a transversely magnetized waveguide loaded with a p-type InSb slab are markedly varied by applying a current considerably smaller than that used in the previous studies employing n-InSb. It is suggested that the shift of the slow-surface-wave resonant magnetic field in this waveguide is responsible for the observed variation.
Surface Acoustic Wave Properties of Lithium Tantalate Films Grown by Pulsed Laser Deposition
Authors: Shibata Yoshihiko , Kuze Naohiro , Matsui Masahiro , Kanno Yasuhito , Kaya Kiyoshi , Ozaki Masaru , Kanai Masaki , Kawai Tomoji
Published: October 2002

Single-crystal films of lithium tantalate ( LiTaO3) have been grown on sapphire substrates (001), (110) and (012) by pulsed laser deposition. Surface acoustic wave (SAW) and optical properties of these films have been investigated. The refractive indices of a (012) LiTaO3 film are n
e=2.1712 and n
0=2.1651 at 632.8 nm. The SAW velocities of propagation (V
s), the temperature coefficients of the center frequency (TCF) and the electro-mechanical coupling coefficients (k
2) of the films have been measured, and theoretical calculations of V
s and k
2 have been done. Experimental V
s and k
2 coincide with calculated ones. Theoretical calculations show that LiTaO3 films deposited by pulsed laser deposition are superior materials for high frequency SAW devices.
Isotropic Photon Injection for Noninvasive Tissue Spectroscopy
Authors: Tsuchiya Yutaka , Ohta Kazuyoshi , Tsuneyuki Urakami Tsuneyuki Urakami
Published: October 2002

Isotropic photon injection is proposed as a practical technique for noninvasive tissue spectroscopy, where the photon migration is almost plane symmetric including that at photon incidence and detection points. In addition, the reciprocity theorem holds for the photon migration process within the medium. This condition is easily achieved using simple optical components. A boundary approximation for isotropic photon injection is developed to solve the photon diffusion equation. This approximation is applied to determine the diffuse photon emission from the surface of the medium for diffuse reflection and transmission in both the time and the frequency domains, as well as for the steady state. The predictions for temporal response and intensity of diffuse photon emission are in good agreement with the results of a Monte Carlo simulation.
Consideration of Optimal Magnet Coil Design Using Nb-Ti Superconductor for 200 MWe Magnetohydrodynamic Generator
Authors: Nishimura Ryo , Aoki Yoshiaki , Naoyuki Kayukawa Naoyuki Kayukawa
Published: October 2002

We report on the effect of the cross-sectional shape of a magnet coil upon the reduction of the magnetohydrodymanic (MHD) channel length. We have optimized a cross-sectional shape of a magnet coil, including an MHD channel, for a 200 MWe coal-fired Faraday-type MHD generator. It is shown that the channel length can be shortened by more than 30% and the stored energy of the magnet coil can be reduced in comparison with the case of the crescent-shaped coil producing a uniform magnetic field without the decrease of enthalpy extraction. Also, for a stand-alone commercial MHD/steam combined plant, it is estimated by this coil shape optimization that the capital cost can be decreased by more than 8% and the cost of electricity can be reduced by about 3%.
Phonon Hot Spot in Vitreous Silica
Authors: Hiroshi Ikari Hiroshi Ikari
Published: October 2002

Peak arrival times of heat pulse profiles in vitreous silica vary linearly with propagation distances in the energy range from about 20 W/mm2 to 160 W/mm2 at 2.3 K, suggesting the features of quasidiffusive propagation. These arrival times are, however, retarded with increasing pulse energy, which is inconsistent with the simple quasidiffusion picture. We explain this discrepancy in terms of a phonon hot spot which act to efficiently down-convert the high-frequency phonons very near the excitation spot.
Computer Experiment on Solitons in One-Dimensional Anharmonic Crystals
Authors: Ozawa Satoru , Hiki Yosio
Published: October 2002

Computer simulation has been carried out for visualizing solitons and phonons propagating in one-dimensional mass-spring model crystals using the molecular dynamics method. Lattice anharmonicity up to the fourth order in interatomic potential was taken into account. Two kinds of experiments were performed: multiple-pulse input applied to an isolated linear crystal, and single-pulse input applied to a circular crystal. The kinetic energies or displacements of atoms in the crystals were computed after the pulse application. In the first case, phonons were mainly produced together with a preceding soliton, while in the second case, solitons of opposite sign with small tails composed of phonons were produced. The propagation velocities were different for solitons and phonons, and were respectively quite stable and unstable for mutual collisions. The velocity of solitons was determined for various input pulse amplitudes and amounts of lattice anharmonicity. The velocity was found to be enhanced by the increase of the pulse amplitude and the strength of anharmonicity of crystal lattice.
RF Plasmas in Methane: Prediction of Plasma Properties and Neutral Radical Densities with Combined Gas-Phase Physics and Chemistry Model
Authors: Gogolides Evangelos , Mary David , Rhallabi Ahmed , Turban Guy
Published: October 2002

A combined plasma physics and chemistry simulator is presented and applied for rf methane discharge in the 100 mTorr pressure range. The simulator consists of a self-consistent fluid model for charged species physics, a public-domain Boltzmann equation solver for dc field calculation of the electron energy distribution function (EEDF), and a generalized one-dimensional gas-phase chemistry model. The methane discharge shows an electropositive and capacitive behavior analogous to that of noble gases, with negative ion densities one order of magnitude less than those of electrons. Electron densities and energies compare favorably with literature values of probe measurements. The high-energy tail of the EEDF in methane has fewer electrons than the Druyvensteyn or Maxwell distribution. The chemistry model was applied for four species, namely, CH4, CH3, CH2, and H, and the densities predicted are on the order of 1015, 1012, 1010, 1013atoms/cm3respectively, at 140 mTorr. Their density profiles compare favorably with literature experimental data. Detailed analysis of the contribution of each reaction, and sensitivity analysis reveals the major creation and loss pathways for each chemical species.
A Vibration Analysis of Torsional Quartz Crystal Resonators Taking Account of Lateral Motion
Authors: Kawashima Hirofumi , Kenji Sunaga Kenji Sunaga
Published: October 2002

This paper describes a torsional quartz crystal resonator taking account of lateral motion. The objective of this paper is to clarify a term of lateral motion, resonant frequency and frequency temperature coefficient of a torsional quartz crystal resonator which is caused by lateral motion. An equation of motion including lateral motion is, first, shown and from the equation of motion resonant frequency is given as a function of a term of lateral motion. The term of lateral motion is, next, calculated, so that the resonant frequency is found to be very dependent upon a thickness-to-width ratio R

z
x
and a thickness-to-length ratio R

z
y
. Finally, the first order temperature coefficient α varies with 1.3×10-7/° C in the experiments and 1.7×10-7/° C in the calculation according to a variation of R

z
y
=0.033 to 0.165, when R

z
x
=0.825.
Precise Determination of the Optimum Supporting Position of a Stress Compensated (SC) Cut Quartz Crystal Resonator Using a Semiconductor Pulsed-Laser System
Authors: Watanabe Yasuaki , Koyama Mitsuaki , Sekimoto Hitoshi , Yoshimasa Oomura Yoshimasa Oomura
Published: October 2002

This paper describes a precise method of determining the supporting position of a stress compensated (SC) cut crystal wafer using a semiconductor pulsed laser. Because the supporting position greatly influences the frequency stability against acceleration and/or external stress, an accurate determination method is required. The experimental results for circular SC-cut quartz resonators with various supporting positions demonstrate the validity of this technique.
Sonochemical Oxidation of Iodide Ions in Solution Undersaturated with Ambient Gases
Authors: Hiroyuki Kitano Hiroyuki Kitano , Shigeo Hayashi Shigeo Hayashi
Published: October 2002

Sonochemical oxidation of I3
- has been carried out in atmospheres of nitrogen, oxygen, air, and argon in the pressure range between 40 Torr and 760 Torr. The ambient gases have been dissolved by two methods: distillation and bubbling, with the former leading to undersaturation. Except for nitrogen, no simple relation exists between the reaction rates for the gas-undersaturated solutions, k
U, and those for the gas-saturated solutions, k
S. In some cases the values of k
U are five times greater than those of k
S in spite of the reversed order in the gas concentration.
Ultrasonic Joining of Polytetrafluoroethylene Sheets Using a Newly Designed 50 kHz Flexural-Mode Transducer System
Authors: Watanabe Yuji , Tsuda Yoneo , Eiji Mori Eiji Mori
Published: October 2002

Polytetrafluoroethylene (PTFE; Teflon TM) has been widely used because of its high-grade characteristics. We joined PTFE sheets using a 320 kHz longitudinal-mode transducer. However, spot size of the joints was very small. Therefore, we attempted to join PTFE sheets using a new 50 kHz flexural-mode transducer system with large diameter. Rubbing the tool end of the transducer on a PTFE sheet can increase the temperature rise of the PTFE sheet. In this paper, the design method of the 50 kHz transducer and the results of joining PTFE sheets of 0.2-0.8 mm thickness using the 50 kHz transducer are described.
Measurement on Specimen Acoustic Impedance in Ultrasonic Plastic Welding
Authors: Si Fu , Masao Ide Masao Ide
Published: October 2002

In this paper we present the experimental results of the time dependence of the specimen acoustic impedance. The experiment was carried out with the specimen in the ultrasonic plastic welding state, by the ultrasonic constant vibrational velocity method. In particular, the acoustic reactance was obtained by improving the conventional method of calculating acoustic stiffness. Furthermore, the acoustic impedance was measured for various vibration amplitudes and static clamping pressures. In this study, acrylonitrile butadiene styrene (ABS) resin rods were used as specimens. It was concluded from the results of experiment that the resistance and reactance could be determined individually by our method, and the absolute value of the impedance was calculated from the known resistance and reactance.
Measurement of Acoustic Nonlinearity Parameter of Liquids by the Observation of Waveforms
Authors: Sumio Takahashi Sumio Takahashi
Published: October 2002

A method for measuring the acoustic nonlinearity parameter of liquids by the observation of acoustic pressure waveforms has been presented. The crest of a finite amplitude acoustic wave advances from the crest of the sine wave as it propagates due to the nonlinearity of the liquid medium. By measuring the amount of advance, the sawtooth parameter and the nonlinearity parameter are obtained, using acoustic pressure amplitude, acoustic velocity, acoustic wavelength, acoustic frequency and the propagated distance. Measurements on six kinds of liquids were made and the results have been shown. The features of this method are the straightforwardness and the simplicity of the measurement.
Doppler Measurement of Moving Object Across the Ultrasonic Field Radiated from Circular Planar Transducer
Authors: Juei Igarashi Juei Igarashi , Tomoki Yokoyama Tomoki Yokoyama , Koichi Mizutani Koichi Mizutani , Keinosuke Nagai Keinosuke Nagai
Published: October 2002

We improve the procedure for measuring the velocity component of a moving object perpendicular to the direction of ultrasonic wave propagation. The conventional procedure uses a concave transducer. We adopt a circular planar transducer. The use of the transducer offers advantages. The both ranges of the distances between the path of the moving object and the transducer and between the path and the central axis of the transducer could be extended by using not the converging beam but the radiating one. However, this degrades the accuracy of the measurement. We derive the equation approximately representing the relationship between the velocity across the field radiated from the planar transducer and the bandwidth of the reflected wave. Then the field is exactly calculated for a concrete example to estimate the accuracy of the approximation. Finally an experiment is performed to confirm the validity of the discussion.
Effect of Wavefront Distortion by Propagation through Inhomogeneous Layer to the Directivity of Ultrasonic Transducer
Authors: Sugimoto Kazuko , Tabei Makoto , Ueda Mitsuhiro
Published: October 2002

Quantitative analysis of ultrasonic wavefront distortion caused by propagation through biological tissue is important for the development of both imaging and tissue characterization techniques. In this study, using a periodic phantom made of oil jelly, quantitative analysis was performed to investigate the relationship between wavefront distortion and the degradation of directivity caused by it. The effect of wavefront distortion due to biological tissue is also discussed.
3-Dimensional Image Reconstruction of Diffraction Tomography from Data Collected with Compound Scanned Pair of Transducers
Authors: Tomoki Yokoyama Tomoki Yokoyama , Koichi Mizutani Koichi Mizutani , Keinosuke Nagai Keinosuke Nagai
Published: October 2002

We extend our 2-dimensional method of ultrasonic diffraction tomography to 3 dimensions. We first derive the theory and the procedure which correspond to 3-D data collection. Then we propose two image-reconstruction methods: interpolation method and noninterpolation method. We also calculate the obtainable resolution of these imaging methods. We numerically simulate the diffraction of ultrasonic waves from the assumed object and calculate the data of diffracted waves. Using the data we finally reconstruct the 3-D images of the object to confirm the feasibility of our theory.
Influence of Local Feature of Electron Cyclotron Resonance Plasma on the Formation of Amorphous Hydrogenated Silicon Films
Authors: Chen Wei , Miyake Shoji , Ariyasu Tomio , Kyou Bunkei
Published: October 2002

Amorphous hydrogenated silicon (a-Si:H) film synthesis in an electron cyclotron resonance (ECR) plasma in silane and/or hydrogen diluted gases is studied in correlation with the local feature of the plasma. Experiments are carried out in a divergent magnetic field configuration at a gas pressure of 4 Pa, and the microwave power input is varied up to 500 W. The highest deposition rate is obtained just near the resonance point and the optical gap of the film has the lowest value at this position. The photoconductivity of the films is found to be strongly dependent on the axial distance L between the substrate and the resonance point. The optimum position for the formation of high-quality a-Si:H films is found in the axial direction, and it varies with input microwave power. The distance L which gives the maximum photoconductivity is shifted with input microwave power. For instance, at a microwave power P
µ of about 50 W the highest photoconductivity is obtained at L=6 cm, while at P
µ=100 W, the highest value is obtained at L=8 cm. This feature is attributed to the local behavior of the plasma production and decomposition of radical species near the resonance zone.
Pulsation Detection from Noisy Ultrasound-Echo Moving Images of Newborn Baby Head Using Fourier Transform
Authors: Masayoshi Yamada Masayoshi Yamada , Masayuki Fukuzawa Masayuki Fukuzawa , Yoshiki Kitsunezuka Yoshiki Kitsunezuka , Jun Kishida Jun Kishida , Nobuyuki Nakamori Nobuyuki Nakamori , Hitoshi Kanamori Hitoshi Kanamori , Takashi Sakurai Takashi Sakurai , Souichi Kodama Souichi Kodama
Published: October 2002

In order to detect pulsation from a series of noisy ultrasound-echo moving images of a newborn baby's head for pediatric diagnosis, a digital image processing system capable of recording at the video rate and processing the recorded series of images was constructed. The time-sequence variations of each pixel value in a series of moving images were analyzed and then an algorithm based on Fourier transform was developed for the pulsation detection, noting that the pulsation associated with blood flow was periodically changed by heartbeat. Pulsation detection for pediatric diagnosis was successfully made from a series of noisy ultrasound-echo moving images of newborn baby's head by using the image processing system and the pulsation detection algorithm developed here.
Three-Dimensional Display of Human Heart Motion Using Medical Ultrasonic Images
Authors: Masaaki Kurozumi Masaaki Kurozumi , Osamu Oshiro Osamu Oshiro , Kosuke Sato Kosuke Sato , Kunihiro Chihara Kunihiro Chihara , Taisei Mikami Taisei Mikami , Akira Kitabatake Akira Kitabatake
Published: October 2002

In this paper we report a method for displaying mitral valve motion of a beating heart in a three-dimensional (3-D) image reconstructed from twenty-eight different scanning plane tomograms, each of which consists of twenty successive ultrasonic B-mode images. A 3-D image consists of surface polygon sets to separate the internal and external regions of the heart. The 3-D image is smooth with lighting calculated from vertex normals of polygons. The 3-D mitral valve motion image is obtained from repeated 3-D images in phase in one cardiac cycle. In addition, we display stereoscopic heart images which have angular viewing separation for viewing images, and we obtain spatial relationships of heart anatomy from such images.
Effects of Couplers on Acoustic Velocity Measurement by Complex \mbV(z) Method
Authors: Nishida Masahiro , Matsumoto Tomio Endo
Published: October 2002

The effects of a coupling liquid on the measurement of acoustic velocities were theoretically and experimentally investigated. The reflectance function was obtained from complex V(z) curves measured with an amplitude- and-phase-measuring acoustic microscope. Theoretical and experimental analyses were performed for six different specimens with water and mercury as couplers. Longitudinal, transverse and Rayleigh wave velocities were successfully measured provided that the acoustic impedance of the specimen was larger than that of the coupler by a factor of one to five. Longitudinal and transverse velocities were measured even if the acoustic impedance of the specimen was less than that of the coupler.
Photoacoustic Spectra of Si Wafers at Liquid Helium Temperature
Authors: Hiroyuki Matsuyama Hiroyuki Matsuyama , Tetsuo Ikari Tetsuo Ikari , Hirosumi Yokoyama Hirosumi Yokoyama , Koji Futagami Koji Futagami
Published: October 2002

Photoacoustic (PA) measurements of p- and n-type Si single crystals are carried out at liquid helium temperature (4.2 K). Two small peaks around 1.2 eV are observed in both samples. The energy of the higher-energy peak at 1.21 eV agrees with the thresholds of free exciton absorption with the emission of TO momentum-conserving phonons. The lower-energy peak shifts to the higher energy side with the decrease of the excitation light intensity. The possibility of the formation of an electron-hole drop for the lower energy peak will be discussed to explain the experimental results.
Evaluation of Optical Absorption Coefficient of Si by Photothermal Spectroscopy Using Transparent Pyroelectric Transducer
Authors: Hata Tomonobu , Konishi Hideaki , Iwai Daisuke , Kimihiro Sasaki Kimihiro Sasaki
Published: October 2002

This paper concerns the evaluation of the optical absorption coefficient of Si by photothermal spectroscopy (PTS) using a transparent pyroelectric transducer ( LiNbO3). In the theoretical analysis the optical absorption of the transducer, the multiple reflection of the incident beam and the air gap are taken into account. The calculation method of the optical absorption coefficient is presented using the relationship between the experimental PT amplitude signal and the theoretical absorption coefficient. The validity of the analysis is confirmed experimentally.
Depth Dependence of Shear Wave Velocity in Sands
Authors: Kimura Masao , Sayuri Kawashima Sayuri Kawashima
Published: October 2002

In this study, the depth dependence of shear wave velocity in dry glass beads and sands is measured, and the empirical equations for shear wave velocity as a function of depth are obtained.
Asymptotic Representation of Sound Pulse Propagation in Shallow Water
Authors: Ohshima Kouji , Toyohiko Ishihara Toyohiko Ishihara
Published: October 2002

The purpose of the present investigation is to propose asymptotic representation for calculating the sound pulse in shallow water, with the sound velocity increasing exponentially from the sea surface to the bottom. We present the time-domain acoustical ray representation, obtained from the convolution of the time-domain Green's function, and the modulated pulse source function for calculation of the waveform at the observation point. Comparison of the ray solution with the reference solution obtained from the mode theory reveals the accuracy and the numerical efficiency of the ray representation. We clarify quantitatively the influences of the bottom losses on the waveform of the sound pulse.
Dependence of Time Dependent Dielectric Breakdown Characteristics on Mechanism for Silicon Epitaxial Growth on Misoriented Czochralski Silicon Crystal
Authors: Izunome Koji , Takeda Ryuji , Hayashi Kenro , Saito Yoshihiko , Fukui Hiroyuki , Kubota Hiroyasu , Tsuchiya Norihiko
Published: October 2002

The reliability of oxide films formed on the surface in a misoriented Si(100) epitaxial wafer was studied by time dependent dielectric breakdown (TDDB). The accidental failure of TDDB decreases with an increase in misorientation and a drastic change is found at misorientation of 0.08° or less. A model, consisting of island growth and lateral growth in the epitaxial growth, has been proposed to explain the observation. In this model, the dominant growth mechanism changes from the island growth to the lateral growth at critical misorientation 0.11°. The appearance of the island growth may give rise to a TDDB weak point and cause the accidental failure.
Improvement of Electrical Characteristics of Pt-Diffused Devices
Authors: Bei Deng Bei Deng , Chang Shu Chang Shu , Hiroshi Kuwano Hiroshi Kuwano
Published: October 2002

Improvement of the electrical characteristics of Pt-diffused p
+
n diodes is achieved by reducing Pt-induced adverse effects. Platinum diffusion induces diffusion of mobile Pt ions into SiO2 films and also changes the surface condition near the Si-SiO2 interface. The former makes the devices unstable and the latter causes increase of leakage current. It is found that mobile Pt ions can be fixed in phosphosilicate glass (PSG) by fabricating metal-phosphosilicate glass-oxide-silicon (MGOS) structures. The reduction of the leakage current is carried out by improving the surface condition near the Si-SiO2 interface. It is revealed that the Pt-diffused p
+
n diodes having a PSG film on SiO2 film and a (100) substrate instead of a (111) substrate, which is conventionally used in power devices, are useful for both the preservation of electrical stability and the reduction of leakage current.