bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Properties of Phase-change Recording Media: GeSbTe Films
Authors: Jong Chao-An , Fang Weileung , Lee Chain-Ming , Chin Tsung-Shune
Published: October 2002

Mechanical properties of as-deposited GeSbTe media on SiO2/Si(100) with different compositions and film thicknesses were successfully investigated by using the microcantilever method and nanoindentation. All the studied films show a compressive residual stress state, which increases proportionally to the elastic constant. Because of the accumulating effects during film deposition, the mechanical properties of these GeSbTe films can be greatly affected. As the film thicknesses were 20 and 25 nm, compared with the Ge4SbTe5 and Ge4Sb0.5Te5Bi0.5 films, the Ge2Sb2Te5 film has the highest residual stress value ranging from 3 MPa to 15 MPa. When the film thickness was 30 nm, the composition-induced stress relaxation occurred. Bi addition, which leads to lattice expansion in Ge4SbTe5 films, resulted in a decrease of stress. Compared with the Ge4SbTe5 and Ge4Sb0.5Te5Bi0.5 films, the Ge2Sb2Te5 film also has the lowest coefficient of thermal expansion (CTE) value ranging from 2×10-6 to 7×10-6/°C, and a lower CTE was obtained when the film thickness was increased. By nanoindentation, the Ge4SbTe5 film shows higher hardness and elastic constant than those of the Ge2Sb2Te5 film. The measured hardnesses for Ge2Sb2Te5 and Ge4SbTe5 films are 12 GPa and 18 GPa; and the reduced elastic modului are 120 GPa and 140 GPa, respectively.
Thermoelectric Properties of CeRu4P12 and CeOs4P12 with Filled Skutterudite-Type Structure
Authors: Chihiro Sekine Chihiro Sekine , Kimiya Akita Kimiya Akita , Norimasa Yanase Norimasa Yanase , Ichimin Shirotani Ichimin Shirotani , Ikuo Inagawa Ikuo Inagawa , Chul-Ho Lee Chul-Ho Lee
Published: October 2002

The thermoelectric properties of hybridized band-gap semiconductor CeRu4P12 and CeOs4P12 with the filled skutterudite-type structure have been studied. Skutterudites have been identified recently as promising candidates for thermoelectric applications such as in solid-state refrigeration or power generation. Polycrystalline samples of CeRu4P12 and CeOs4P12 were synthesized with a high-pressure cell under high temperature using a cubic-anvil high-pressure apparatus. The samples were characterized by X-ray diffractometry. The Seebeck coefficient, electrical resistivity, Hall coefficient and thermal conductivity were measured. The Seebeck coefficients of both compounds are significantly large and the power factor values are of the order of 10-3 W/mK2. The effect of hybridization between the Ce 4f and pnicogen p states or transition metal d states is important for determining the thermoelectric properties of this system.
Low Temperature Direct Crystallization of SrBi2(Ta1-xNbx)2O9 Thin Films by Thermal Metalorganic Chemical Vapor Deposition and Their Properties
Authors: Mitsuya Masatoshi , Nukaga Norimasa , Saito Keisuke , Osada Minoru , Funakubo Hiroshi
Published: October 2002

Directly crystallized SrBi2(Ta1-x
Nb
x
)2O9 (SBTN) films were deposited on (111) Pt/Ti/SiO2/Si substrates at 585–670°C by thermal metalorganic chemical vapor deposition (MOCVD). The crystalline SBTN film was directly deposited at 670°C irrespective of the deposition rate, but its leakage current markedly decreased when the deposition rate decreased from 5.0 to 2.1 nm/min. When the deposition rate was below 2.1 nm/min, an SBTN film with large ferroelectricity was deposited even at 585°C, and strong (103)-orientation was ascertained by an X-ray reciprocal space mapping method. This orientation is considered to locally epitaxially occur on a (111)-oriented Pt substrate. Twice the remanent polarization (2P
r) and twice the coercive field (2E
c) of the film deposited at 585°C were 12.2 µC/cm2 and 160 kV/cm, respectively. When the deposition temperature increased, the film became randomly oriented which was in response to the orientation change in the Pt substrate from single (111) to a mixed orientation of (111) and (100) orientations by heating before starting the film deposition. 2P
r and 2E
c of the film deposited at 670°C increased to 23.8 µC/cm2 and 190 kV/cm, respectively.
Sub-300 Å (Bax,Sr1-x)TiO3 Films by Metal Organic Chemical Vapor Deposition: Nanostructure, Step Coverage, and Dielectric Properties
Authors: Dey Sandwip K. , Majhi Prashant , Shin Yong-W. , Tang Derek , Kirby Aaron , Zhao Jun , Dornfest Charles , Lou Lee , Kher Shreyas
Published: October 2002

This is a preliminary report on the nanostructure and its evolution, step-coverage, and dielectric properties of sub-300 Å (Ba
x
,Sr1-x
)TiO3 films. The (001)-oriented polycrystalline films were deposited at 50–70 Å/min by metal-organic chemical vapor deposition (MOCVD) on (111) Pt-passivated Si substrates of 8-inch diameter. From the detailed nonstructural characterization of (Ba0.64,Sr0.36)TiO3 films, the orientation, cation stoichiometry, and an alternative but plausible mechanism of growth and the origin of roughness are forwarded. Additionally, the step-coverage in 2:1 to 5:1 aspect-ratio trenches, coupled with the frequency/voltage dependence of the dielectric properties of (Ba
x
,Sr1-x
)TiO3 films are reported. A 275 Å (Ba0.64,Sr0.36)TiO3 film exhibited a dispersionless dielectric permittivity and loss tangent of 260 and 0.003, respectively, and the permittivity (ε
r=340) of a 300 Å (Ba0.5,Sr0.5)TiO3 film reduced by 53% at a dc-bias of 3 V.
Crystallization of Ag–In–Sb–Te Phase-Change Optical Recording Films
Authors: Chou Lih-Hsin , Chang Yem-Yeu , Chai Yeong-Cherng , Wang Shiunn-Yeong
Published: October 2002

Crystalline phases formed on thermally annealed and laser-annealed Ag12.4In3.8Sb55.2Te28.6 four-element alloy films were observed to be different. After 1 h isothermal annealing at temperatures between 190°C and 450°C, hexagonal Sb and chalcopyrite AgInTe2 phases were observed, whereas laser annealing by initialization at laser power higher than 2.86 mW/µm2 yielded cubic crystalline Sb and AgSbTe2 phases. There was only one exothermic peak at 170°C determined by differential scanning calorimetry (DSC) measurement. Only the hexagonal Sb phase was observed by X-ray diffraction of samples subjected to DSC measurement. These experimental results suggest that the activation energy for crystallization derived from Kissinger's equation using DSC data may not be the same as that for crystallization during erasing of phase-change optical recording disks.
Valence Subband Structures and Optical Properties of Strain-Compensated Quantum Wells
Authors: Seko Yasuji , Sakamoto Akira
Published: October 2002

The strain compensation effects on the valence subbands and on the optical properties of GaInAs/AlGaInAs quantum well structures are theoretically studied for the first time. In the case of compressive-strained quantum wells, where the top valence subbands are always formed with heavy hole (HH) subbands, the compensatingly tensile-strained barriers shift the first light hole (LH) subbands upward increasing the valence band mixing between them, and significantly reducing the transverse electric (TE) gain. In contrast, in the tensile-strained quantum wells whose top valence subband is formed with LH subband, the compensatingly compressive-strained barriers shift the top LH subband downward and on some occasions the top LH subband is replaced with the first HH one. The increase of the TE gain is relatively small due to the strong valence band mixing. The strain of the barrier layers is found to play an important role in the valence subband structures and optical properties.
Development of a Decision Method for Optimum Ferromagnetic Board Arrangements to Reduce Toroidal Magnetic Field Ripple
Authors: Nakayama Takeshi , Abe Mitsushi , Takeuchi Kazuhiro , Miura Yukitoshi , Sato Masayasu
Published: October 2002

A new decision method for ferromagnetic board (FB) arrangements was developed to obtain the desired toroidal magnetic field (TF) distribution. An approximation, in which the magnetization vector is only pointed in the toroidal direction and its magnitude is magnetically saturated, was introduced to allow treatment as a linear problem. The desired thickness distribution of FBs could be obtained by calculating a generalized inverse matrix which transforms from the thickness distribution to the TF distribution due to FBs. We employed a singular value decomposition (SVD) method to calculate the generalized inverse matrix. The final TF distribution was confirmed by the general-purpose 3D non-linear magnetostatic field analysis code. This method was applied to the TF coils of JFT-2M. The maximum TF ripple in the whole plasma region could be reduced from 2.1% to 0.1%.
Fabrication and Characterization of Carbon Nanotube Triodes
Authors: Hong Wei-Kai , Chen Kuei-Hsien , Chen Li-Chyong , Tarntair Fu-Gow , Chen Kuo-Ji , Lin Jia-Bin , Cheng Huang-Chung
Published: October 2002

To achieve high emission current density, carbon nanotube triodes have been proposed using recessed oxide as the insulator between the gate and the carbon nanotubes to replace the conventional spacer. An anode current of 10 µA was achieved with a gate voltage of 98 V for a nanotube sample prepared with a growth time of 12 min. Carbon nanotubes synthesized with various growth times were analyzed using a scanning electron microscope and Raman spectroscopy. By increasing the growth time, longer carbon nanotubes were obtained. Effects of the length of the carbon nanotubes on the field emission of the triodes are discussed. Enhanced luminance was obtained as the anode voltage increased from 600 V to 1000 V. Such carbon nanotube triodes are promising for utilization in future field-emission displays.
Measurement of Diffusion of InCl3 in AgCl Single Crystal by Internal Friction
Authors: Tateno Hiroto , Kajihara Makoto , Iwashita Yoichiro
Published: October 2002

To study the behavior of divacancy and impurity, the diffusion process of InCl3 doped on the surface of a AgCl single crystal was measured by the internal friction and dielectric loss. All of the In3+ ions move to the dislocation core with a rate proportional to t
1/6 and the migration energy is 0.060 eV. The concentration in the dipole of In3+ ion and cation vacancy rapidly becomes zero at the critical temperature 566 K. Reorientation of the dipole and ionic conductivity gives an identical migration energy of 0.33 eV. The binding energy between the vacancy and the trivalent impurity E

b
is 0.10 eV.
Development of a Doppler Acoustic Imaging System for Borehole Wall to Evaluate Fluid Flow Distribution around Subsurface Fractures
Authors: Saito Jin , Niitsuma Hiroaki
Published: October 2002

We are in the process of developing a doppler borehole televiewer (DBHTV) which quantitatively evaluates the permeability of independent subsurface fractures in a borehole. The system employs an ultrasonic pulsed Doppler method, and is compatible with the conventional acoustic borehole imaging system called borehole televiewer (BHTV). Using the DBHTV, back-scattered waves from fine particles in the borehole fluid such as drill mud or cuttings in a water filled borehole are detected along with the reflected waves from the borehole wall, and the Doppler shift of the back-scattered waves is used to estimate the fluid velocity. A method to estimate the distribution of Doppler shift was examined using a laboratory experimental model. An attempt to locate the sampling volume and a method to quantitatively estimate the flow velocity by scanning the transducer are examined. This study shows that the location of permeable fractures, the distribution of fluid velocity and the fluid volume can be visualized using the DBHTV.
Diffusive Hydrophone for Ultrasonic Measurements
Authors: Ohta Haruyoshi , Shimizu Naomi , Kamakura Tomoo
Published: October 2002

Experimental performance of a newly developed diffusive hydrophone (DHP) is evaluated with respect to its sensitivity and spatial resolution. Although conventional hydrophones such as a polyvinylidene fluoride (PVDF) needle type hydrophone have been widely used in measurements of sound pressure, they have often failed to show sufficient sensitivity when their active elements are as small as 0.2 mm in diameter or below. The DHP allows precise use in sound field measurements with sufficient sensitivity. The basic operation of the DHP is discussed below, taking into account the spatial averaging effect that inevitably occurs over the hydrophone aperture.
Effect of Voltage Treatment on Modulation Frequency Dependence of the Photoacoustic and Photoelectrochemical Current Spectra of Highly Porous, Polycrystalline TiO2 Electrodes
Authors: Toyoda Taro , Sato Jun , Shen Qing
Published: October 2002

We report the effect of voltage on a concentrated KCl electrolyte applied to a highly porous TiO2 electrode during its final preparation process on the photoelectrochemical current (PEC) spectra. Optical absorption measurements were monitored by a photoacoustic (PA) method. The PA spectrum of the TiO2 electrode with the voltage treatment is similar to that without the treatment above the band-gap region. Below the band-gap region, the intensities of the PA spectrum of the TiO2 electrode with the voltage treatment are higher than those without the treatment, suggesting an increase of carrier concentration by the voltage treatment. The PEC spectra without the voltage treatment show a monotonic increase with the photon energy above the band-gap region. The PEC intensity with the voltage treatment increases rapidly immediately above the band-gap region and shows saturated values. The PEC intensity of the TiO2 electrode with the voltage treatment is approximately twice that without the treatment above the band-gap region. The increase of the PEC intensity implies an increase of carrier concentration due to partially reduced Ti ions. The modulation frequency dependence of the PEC intensity of TiO2 electrodes with and without the voltage treatment shows two types of exponential decay. The decay rate in the TiO2 electrode with the voltage treatment is slower than that without the treatment below the modulation frequency of 100 Hz. The decay rate with the voltage treatment agrees with that without the treatment above the modulation frequency of 100 Hz.
Morphology and Sound Velocity of Plasticized Polyvinylchloride Studied Using Scanning Acoustic Microscope
Authors: Yamada Gen , Koda Shinobu , Matsuoka Tatsuro , Nomura Hiroyasu
Published: October 2002

Morphology and sound velocity of plasticized polyvinylchloride were studied using scanning acoustic microscope. Pseudonetwork and well-dispersed domains were observed as acoustic images. The sound velocity of leaky surface skimming compressional waves in the two domains and the intermediate domain were evaluated by analysis of the V(z) curves. The sound velocity in the well-dispersed domains was faster than that in the pseudonetwork domains.
Observation of Branched Complicated Defect and its Nondestructive Evaluation by Photoacoustic Microscopy
Authors: Endoh Haruo , Yaegashi Naoto , Hiwatashi Yoichiro , Hoshimiya Tsutomu
Published: October 2002

In this study, the imaging of simulated branched complicated defects using a photoacoustic microscope has been demonstrated. A surface vertical defect is fabricated on a metal specimen surface by mechanical processing. The subsurface defect was made perpendicular to the surface defect by drilling. The surface defect and the subsurface defect were relevantly distinguishable in the photoacoustic amplitude image obtained using the photoacoustic microscope. The size of the subsurface defect and information on the undersurface structure were obtained.
Photoacoustic Spectra for Porous Silicon Using Piezoelectric Transducer and Microphone
Authors: Toshio Kawahara Toshio Kawahara , Masaki Okamoto Masaki Okamoto , Akitsugu Kimura Akitsugu Kimura , Jun Morimoto Jun Morimoto , Kenichiro Tahira Kenichiro Tahira , Toru Miyakawa Toru Miyakawa , Kenji Yoshino Kenji Yoshino , Tetsuo Ikari Tetsuo Ikari
Published: October 2002

Photoacoustic (PA) spectra are measured for porous Si (PS) using piezoelectric detectors (PPT) and compared with the microphone PA (MPA) spectra to examine the nonradiative properties of PS that has complicated nanostructures. Three peaks (peaks 1 and 2, and a small peak at 600 nm) are observed in samples 2 and 3 with porosities p=60 and 70%, respectively, while only a single peak (peak 1) is observed in sample 1 with p=30%. Peak 2 is related to the band gap of the Si substrate. In contrast, peak 1 seems to be due to the absorption change at the band gap unique to the PS. This band gap shifts to higher energy for PS samples with higher porosity. We propose that this band gap is defined by the largest size nanocrystals, where PS has nanocrystallite size distribution. The small peak at 600 nm is related to the PL peak and it is observed only in PPT spectra. These results suggest that different mechanisms are operating in PPT spectra and MPA ones for the enhancement of the PA spectra.
Photoacoustic Spectra of ZnO-CoO Alloy Semiconductors
Authors: Akitsugu Kimura Akitsugu Kimura , Yasuhiro Ohbuchi Yasuhiro Ohbuchi , Toshio Kawahara Toshio Kawahara , Yoichi Okamoto Yoichi Okamoto , Jun Morimoto Jun Morimoto
Published: October 2002

Photoacoustic spectra (PA) of Zn1-x
Co
x
O alloy semiconductors sintered as powdered samples were measured to estimate the optical absorption. Photoacoustic spectroscopy (PAS) is insensitive to the light scattering effects on the samples. CoO molecular percentages in the alloy were changed from 0 to 20 mol%. The samples were sintered at 600 or 950°C for 24 h in a quartz glass tube. From the PA spectra in the short wavelength region, we plotted (ρh ν)2 vs h ν and estimated the band-gap energy (E
g) of the alloy semiconductors, where ρ is the PA signal intensity and h ν is the excitation light photon energy. E
g of ZnO-CoO alloy decreases as the CoO content increase and reaches to 2.19 eV in the 20 mol% CoO sample. Although the band-gap variation in the lower-CoO-content samples (CoO content below 10 mol%) is large, it becomes small in the high CoO concentration samples. This result concurred with the result of dissolving CoO in ZnO as obtained by X-ray diffraction measurement.
Improvement of Underground Image (III): Underground Imaging Using Shear Waves
Authors: Natsuki Yoshizumi Natsuki Yoshizumi , Tsuneyoshi Sugimoto Tsuneyoshi Sugimoto
Published: October 2002

We have been studying an underground imaging method using shear-horizontal (SH) waves to detect buried relics and ruins at shallow depths. To improve the underground image, a deconvolution method has been introduced. An exploration experiment was conducted at a test site to confirm the validity of the method. As a result, we confirmed that the processing technique is effective for improvement of underground imaging at extremely shallow subsurfaces within a depth of 10 m.
Fiber Bragg Grating Vibration Sensor Using Incoherent Light
Authors: Takahashi Nobuaki , Yoshimura Kazuto , Takahashi Sumio
Published: October 2002

The operation of an optical fiber vibration sensor using two fiber Bragg gratings (FBGs) and incoherent light has been demonstrated, based on the intensity-modulation method. One FBG is used to make a narrow-band incoherent light source from a broad-band light source and the other is used for sensing the vibration of a solid. Stable and linear operation of the sensor is realized without optical isolators and fusion splicing. The developed sensor is expected to be temperature insensitive if the temperatures of the two FBGs are kept same during the operation.
Viscosity Measurements in Liquid Using Transversal Effects of Piezoceramic Disk-Type PZT Transducer in the Frequency Range of 70–430 kHz
Authors: Shin-ichi Momozawa Shin-ichi Momozawa , Kazuhiko Imano Kazuhiko Imano
Published: October 2002

Transversal effects of a piezoceramic disk-type Pb(Zr,Ti)O3 (PZT) transducer are newly introduced in the measurement of dynamic viscosity of liquid. The fundamental resonance (75 kHz) and the higher harmonic resonant frequencies (195, 310, 424 kHz) of the transducer are used in the experiments. The resonant resistance R
r and the resonant frequency shift Δf
r of transducer are measured with a water-glycerin mixtures (viscosity ηL:3∼490 mPa·s) and silicone oil (ηL:10 ∼1000 mPa·s) as the sample liquids. From the experimental results, it is gathered that 1) the resonant resistance R
r has a linear relationship to ηL
1/2, 2) the resonant frequency shift Δf
r does not show a linearity in the high viscosity range larger than 100 mPa·s. The viscosity measurement in the frequency range of 75∼424 kHz, which has not been explored previously, was successfully accomplished by our method.
Static and Dynamic Characteristics of Giant Magnetostrictive Materials under High Pre-Stress
Authors: Nakamura Toshiaki , Nakano Iwao , Kawamori Akiyoshi , Yoshikawa Takashi
Published: October 2002

We describe the static and dynamic characteristics of a giant magnetostrictive material under high pre-stress, using the pre-stress given to the giant magnetostrictive material as a parameter, and also evaluate material constants. Seven evaluation units, each having an optimum magnetic bias applied to vary the pre-stress given to the material from 15 MPa to 54 MPa, were used to measure the static and dynamic characteristics. As a result, the trends of equivalent circuit constants such as stiffness, internal resistance, and force factor in response to the increase in pre-stress for enhancing the output, were clarified. Furthermore, considering the linearity to the input level, the necessity of examining the optimum pre-stress region, in addition to the simple increase in pre-stress, was suggested.
H-Type Single Crystal Piezoelectric Gyroscope of an Oppositely Polarized LiNbO3 Plate
Authors: Ono Keisuke , Yachi Masanori , Wakatsuki Noboru
Published: October 2002

For obtaining greater accuracy and stability of piezoelectric gyroscopes, the authors have advanced the research on H-type LiTaO3 single-crystal piezoelectric gyroscopes, which combine the tuning fork vibration with H-type vibration. In this paper, the H-type LiNbO3 gyroscope of an oppositely polarized single crystal plate is reported. The electromechanical coupling factor of LiNbO3 is larger than that of LiTaO3 for the flexural vibration mode. Using an oppositely polarized plate, the electrode construction without a side electrode becomes possible. Therefore, the possibility of miniaturizing the H-type single-crystal piezoelectric gyroscope is examined to obtain the same sensitivity level. In the trial experiment, the dimensions of the LiNbO3 gyroscope were reduced to be 1/8 that of the LiTaO3 gyroscope.
Characteristics of Longitudinal Leaky Surface Wave Propagating on La3Ga5SiO14 Substrate
Authors: Hankun Zhang Hankun Zhang , Masao Murota Masao Murota , Yasutaka Shimizu Yasutaka Shimizu
Published: October 2002

The propagation characteristics of the longitudinal leaky surface wave propagating on a La3Ga5SiO14 substrate were theoretically investigated for all cuts and propagation directions. The results of temperature coefficient of delay (TCD), electro-mechanical coupling constant (K
2) and phase velocity were displayed on contour maps. Cuts with zero TCD were obtained at Euler's angle's of (20°,θ,ψ) and (30°,θ,ψ). Temperature dependence of fractional time delay (Δτ/τ) on (90°,90°,0°)-cut changes only by 18.5 ppm from -30°C to 110°C. This cut has very good temperature characteristics.
Effects of Dielectric Overlay upon Surface Acoustic Wave Propagation under Metallic Grating Structure
Authors: Shintaro Kondo Shintaro Kondo , Tatsuya Omori Tatsuya Omori , Ken-ya Hashimoto Ken-ya Hashimoto , Masatsune Yamaguchi Masatsune Yamaguchi
Published: October 2002

This paper describes surface acoustic wave (SAW) propagation under a periodic metallic grating structure overlaid with an SiO2 film. An analysis was made by modifying the software FEMSDA, in which the finite element method is applied to both the grating electrodes and SiO2 overlay. For Rayleigh-type SAW propagating on 128°YX-LiNbO3, changes in the reflection coefficient and effective velocity are calculated as a function of the SiO2 film thickness overlaying an Al grating structure. It is shown that the SiO2 film overlaying the top surface of the grating electrodes affects both the SAW reflection coefficient and effective SAW velocity more significantly than the film overlaying the electrode gaps.
Two-Color Reflection Multilayers for He-I and He-II Resonance Lines for Microscopic Ultraviolet Photoelectron Spectroscopy Using Schwarzschild Objective
Authors: Ejima Takeo , Kondo Yuzi , Watanabe Makoto
Published: October 2002

Two-color multilayers reflecting both He-I (58.4 nm) and He-II (30.4 nm) resonance lines have been designed and fabricated as reflection coatings of mirrors of Schwarzschild objectives used for microscopic ultraviolet photoelectron spectrometers. The multilayer was designed to consist of a top single layer and piled double layers so that its normal incidence reflectances for both He-I and He-II resonance lines are more than 20%. Multilayers of SiC(top layer)-Mg/SiC(double layers) and SiC(top layer)-Y2O3/Mg (double layers) are fabricated, and their reflectances for the He-I and He-II lines are 25% and 20%, and 23% and 26%, respectively.
Multi-Wavelength Separation Characteristics in Integrated Acoustooptic Devices for Photonic Switching System
Authors: Nobuo Goto Nobuo Goto , Yasumitsu Miyazaki Yasumitsu Miyazaki
Published: October 2002

Photonic switching systems in wavelength-division-multiplexed (WDM) networks are discussed. By employing collinear acoustooptic (AO) devices as wavelength selective functional devices, the system structure can be simplified with flexibility in wavelength assignment. As the AO devices, collinear AO wavelength separators and switches consisting of an optical directional coupler are investigated in integrated structures. Integrated optic devices such as WDM demultiplexers/multiplexers, wavelength-selective matrix-switches, and routers for delay time selection in buffer memories are described. Wavelength selective characteristics are theoretically estimated for a material combination of TiO2/Ta2O5/proton-exchanged layers on LiNbO3 substrates. The switching capacity in the switching system consisting of AO devices is evaluated. Issues for employing AO switching devices in WDM networks are also discussed.
A Study on the Acceleration of Electrolytic Refining of Copper Using Ultrasound
Authors: Ohdaira Etsuzo , Masuzawa Nobuyoshi
Published: October 2002

Copper is a useful metal widely used for electric materials, etc. In order to raise the copper purity, electrolytic refining is used. Since the long time is needed for the purification of this method, to shorten this time is desirable. In this study, ultrasonic irradiation was attempted to shorten this time. It was found that to shorten the refining time was possible by ultrasonic irradiation.
Effect of Ultrasound in High-Pressure Glow Discharge
Authors: Tetsuro Otsuka Tetsuro Otsuka , Kenji Teranishi Kenji Teranishi , Tomoo Nakane Tomoo Nakane
Published: October 2002

This paper deals with the influence of ultrasound energy in high-pressure glow discharge. A discharging unit was set inside an acoustic tube and glow discharge was produced between a positive needle electrode and a negative disk electrode. A high-intensity standing wave field was produced in the tube at the resonance frequency and sound pressure level was increased to 163 dB. As a result, the sound energy was affected by the glow discharge at the loop of particle velocity distribution, which means that the glow discharge was controlled by the sound energy only in terms of particle velocity.
Detection and Selective Focusing on Scatterers Using Decomposition of Time Reversal Operator Method in Pekeris Waveguide Model
Authors: Tomoki Yokoyama Tomoki Yokoyama , Toshiaki Kikuchi Toshiaki Kikuchi , Toshio Tsuchiya Toshio Tsuchiya , Akio Hasegawa Akio Hasegawa
Published: October 2002

The decomposition of the time reversal operator (DORT) method is a selective detection and focusing technique for the pulse-echo mode that uses an array of transmit-receive transducers. Because it is an application of the acoustic time reversal mirror, the irregular shape of the array and the aberration of the propagation medium are compensated and the selective focusing on targets is made possible. In this paper, we examined the application of this method to the underwater acoustics and the application to active sonar and communication are made possible. To clarify the relationship between the focusing effect of the DORT method and the sound propagation property in shallow water, we examined the selective focusing effect with respect to the propagation distance by using the cylindrical spread model without the sea surface and bottom and the Pekeris model, which is typical of shallow water models. There are few influences of the propagation distance on the focusing effect in shallow water model as a result, and it is shown that the focusing effect improves with the increase of the sound velocity of the bottom.
Numerical Analysis of a Single Solid Spherical Particle Falling in an Ultrasonic Standing Wave Field
Authors: Nomura Shinfuku , Murakami Koichi , Akao Hiroshi
Published: October 2002

The velocities of particle falling in a standing wave field through a vertical pipes filled with a stagnant liquid in are analyzed numerically for Reynolds number (Re)<1, for a wide range of pipe diameters. The equations of motion of a spherical particle in a viscous fluid are solved based on the Basset-Boussinesq-Ossen (BBO) equation to clarify the falling velocities in an infinite stagnant fluid, and two-dimensional hydrodynamic equations based on the cubic-interpolated pseudo-particle (CIP)-combined and unified procedure (C-CUP) method to clarify the effects of the walls of pipes. The velocity of a particle is periodically changed due to the influence of the radiation force of the standing wave. The average terminal velocity in a standing wave field is lower than that for which there is no ultrasonic field. As the particle diameter approaches the pipe diameter, the velocity of the particle approaches zero due to the influence of the pipe wall. The C-CUP method effectively simulates the behavior of a particle falling through a liquid-filled pipe in the standing wave field.
Effects of Bjerknes Forces on Gas-Filled Microbubble Trapping by Ultrasonic Waves
Authors: Yoshiki Yamakoshi Yoshiki Yamakoshi , Yoshiyuki Ozawa Yoshiyuki Ozawa , Masato Ida Masato Ida , Nobuyuki Masuda Nobuyuki Masuda
Published: October 2002

When gas-filled microbubbles flow into an ultrasonic wavefield, the microbubbles interact with the ultrasonic waves and aggregate into large masses of bubbles. Those bubbles are trapped against the surrounding liquid flow by ultrasonic waves. In this paper, the microbubble trapping by an ultrasonic wavefield are discussed both from theoretical and experimental viewpoints. Both, the microbubble aggregation by ultrasonic-wave secondary Bjerknes force and the microbubble trapping by ultrasonic-wave primary Bjerknes force are considered. The dynamics of microbubbles inside an ultrasonic wavefield are observed using two different types of gas-filled microbubbles with corresponding mean diameters of 20 µm and 1.3 µm.
Basic Investigation on Compression of I/Q Signals for Ultrasonic Diagnostic Equipment
Authors: Yuusuke Ohta Yuusuke Ohta , Kazuhiko Hamamoto Kazuhiko Hamamoto , Takashi Mochizuki Takashi Mochizuki
Published: October 2002

In ultrasonic diagnostic equipment, I/Q signals are usually used for the construction of B-mode images, displays in the M-mode, and the acquisition of Doppler information. On the other hand, the number of ultrasonic diagnostic equipment in which the digital technique is applied has continuously increased. Accordingly, it is important to understand how I/Q signals are digitized and compressed. In this study, the compression of I/Q signals by wavelet transform is attempted. First, the results are compared with those of a typical compression method by discrete cosine transform (DCT). The proposed method achieved a higher compression ratio than DCT under the same quality of the restored signal. Then, several types of mother wavelets (MWs) are tested. The MW can control the efficiency of compression. The result suggests that the most appropriate MW for I/Q signals compression exists.
Strain Estimation Using the Extended Combined Autocorrelation Method
Authors: Yamakawa Makoto , Shiina Tsuyoshi
Published: October 2002

We previously proposed the combined autocorrelation (CA) method to estimate the strain distribution in tissue. This method is based on the conventional Doppler method but overcomes the problem of aliasing, which is a weakness of the Doppler method. The ability of the CA method has been demonstrated with phantom experiments and in vitro measurements. However, we have to maintain the tissue displacement in the axial direction because the CA method is based on 1-D processing, and this is difficult to perform with the conventional compression system. Therefore, in this paper, we propose an extended CA method that is robust against sideslip. We also demonstrate the ability of this method with computer simulations.
Inverse Scattering Image Reconstruction from Reflection and Transmission Data Observation with Fixed Transmitter/Receiver Pair Transducer
Authors: Jung-Soon Kim Jung-Soon Kim , Akira Yamada Akira Yamada
Published: October 2002

The inverse scattering imaging method based on reflection and transmission observation data, which was previously developed by the present author, is anticipated for its practical advantage in which the necessary range of observation view can be reduced to half compared to the conventional full observation view. In this report, we propose a modified method, which involves data observation carried out while rotating an object under the fixed condition of a transmitter/receiver pair, and a reflector. The inverse scattering reconstruction procedure is developed by applying the mirror-image theory. A special feature of the present method which is stressed is its superiority for the limitation of the observation view range much smaller than 180 deg. The validity of the method is tested using simulation and experimental data from the triangular specimen. It is shown that the quantitative precision of the reconstructed sound speed images is fairly good even when the limited viewing range is less than 120 deg.
The Effect of Al Interlayer on TiSi2 Formation
Authors: Kishi Akira , Doi Tukasa , Ohnisi Shigeo , Awaya Nobuyoshi , Iguchi Katsuji , Sakiyama Keizoh , Maa Jer-Shen , Hsu Sheng Teng
Published: October 2002

Ti silicide technology using an Al/Ti bilayer is investigated to reduce TiSi2 sheet resistance on the arsenic (As)-implanted Si surface. A 38% reduction resulting in the sheet resistance value of 1.62 Ω/sq was obtained using the bilayer of 5 nm Al/55 nm Ti. The resistivity of the film is 14.3 µΩ·cm. These films showed a very smooth silicide/Si interface. X-ray diffraction observation shows a C54 phase with high (010) orientation. Void formation was not detected by transmission electron microscope (TEM) and scanning electron microscope (SEM) observations.
GaAsP pn Diode on Si Substrate Grown by Metalorganic Molecular Beam Epitaxy for Visible Light-Emitting Devices
Authors: Yoshimoto Masahiro , Itoh Mitsunari , Saraie Junji , Yasui Toshiyuki , Ha Sanghoon , Kurobe Tatsuro , Matsunami Hiroyuki
Published: October 2002

Luminescent GaAs1-x
P
x
(0.2<x<0.7) was grown on a Si substrate by metalorganic molecular beam epitaxy (MOMBE). The insertion of a GaP buffer layer grown at a low temperature was essential to obtain luminescent GaAsP on Si. The growth condition of the GaP buffer layer was optimized based on the results of atomic force microscopy, reflection high-energy electron diffraction, and X-ray diffraction. Chemical and thermal treatments of the Si substrate were also carefully examined to obtain a flat surface and a sharp X-ray rocking curve of the GaAsP epilayer. The GaAsP epilayer on Si emits photoluminescence ascribed to the donor acceptor pair emission at a low temperature, and to a band-edge emission at room temperature. The GaAsP epilayer was doped for both n- and p-types with carrier concentrations up to 2 ×1018 and 6 ×1019 cm-3, respectively. A GaAsP pn junction on a GaP substrate with a total thickness of 1.25 µm shows bright electroluminescence, indicating a tough nature against the large lattice mismatch. The preliminary GaAsP pn junctions on Si showed infrared and visible luminescence at room temperature.
Thermal Change of Unstable Stacking Faults in β-SiC
Authors: Shirahata Naoto , Kijima Kazunori , Ma Xiuliang , Ikuhara Yuichi
Published: October 2002

The thermal change of unstable stacking faults (USFs) in ultrafine and highly pure β-SiC powder synthesized by the plasma chemical vapor deposition (plasma-CVD) method was studied by high-resolution transmission electron microscopy (HR-TEM). The number of USFs, which were frequently observed in as-synthesized powder, decreased at elevated temperatures in an Ar atmosphere. In contrast, the number of general stacking faults (GSFs) increased with decreasing number of USFs. Moreover, a type of stacking fault that was geometrically more unstable than USF was observed in the specimen after heat treatment. In the present study, the annihilation process of USFs observed in the specimen before heat treatment is discussed.
Temperature Dependence of Surface Potential in a-Si:H pH-Ion Sensitive Field Effect Transistor
Authors: Chou Jung Chuan , Wang Yii Fang , Tsai Hsjian Ming
Published: October 2002

In this study, we focus on the investigation of the relationship between the a-Si:H/SiO2 gate pH-ion sensitive field effect transistor (pH-ISFET) and the Al/a-Si:H/SiO2 gate metal-oxide-semiconductor field effect transistor (MOSFET). The a-Si:H thin film was deposited by plasma-enhanced chemical vapor deposition (PECVD). The thickness of the a-Si:H thin film was 1000 Å. The aluminum gate electrode was deposited by a thermal evaporation system. We use the Keithley 236 current–voltage (I–V) measurement system to measure the drain-source current (I
DS) versus gate voltage (V
G) curves for the pH-ISFET and MOSFET. The surface potential of the a-Si:H sensing membrane can be calculated from the I
DS–V
G curves of pH-ISFET and MOSFET. That is, the semiconductor related terms of threshold voltage could be eliminated. Furthermore, we investigate the temperature dependence of the surface potential. From experimental results, we can observe that the pH sensitivity of the surface potential is increased with increasing temperature. We can also find the pHpzc (pH at the point of zero charge) of the a-Si:H pH-ISFET.
Electron Cyclotron Resonance Plasma Etching of n-SiC and Evaluation of Ni/n-SiC Contacts by Current Noise Measurements
Authors: Nobuhisa Tanuma Nobuhisa Tanuma , Satoshi Yasukawa Satoshi Yasukawa , Saburo Yokokura Saburo Yokokura , Sumihisa Hashiguchi Sumihisa Hashiguchi , Josef Sikula Josef Sikula , Toshiaki Matsui Toshiaki Matsui , Munecazu Tacano Munecazu Tacano
Published: October 2002

The Si surface of n-SiC is etched by an Ar electron cyclotron resonance plasma in order to smooth the as-received substrates. Low-frequency current noise characteristics of Ohmic contacts of the wide-band-gap semiconductor n-SiC are investigated. Ohmic contacts with a diameter of 200 µm have a minimum Ohmic contact resistance of the order of 10-4 Ω·cm2 at an alloying temperature of 1000°C for 30 min. These low resistance Ohmic contacts show typical 1/f current noise characteristics that increase with the square of the sample current I
2. A sample with a higher contact resistance exhibits, however, current noise power increase with increasing sample current I. The relevant total electron number between the electrodes of the bulk substrate is estimated from the resistance and by finite element method simulation, from which the Hooge parameter αH is estimated to be approximately 40.
A Void Free Soldering Process in Large-Area, High Power Insulated Gate Bipolar Transistor Modules
Authors: Onuki Jin , Chonan Yasunori , Komiyama Takao , Nihei Masayasu , Saitou Ryuuichi , Suwa Masateru , Morita Toshiaki
Published: October 2002

We have developed a new void free process for making the solder joint between the chip mounted AlN substrate and the metal substrate in large-area, high power insulated gate bipolar transistor (IGBT) modules. This new process consists of two steps. First, Ar+ were used to clean the surfaces of Ni plated film on a metal and AlN substrates which were then coated with 0.5-µm-thick Ag film. Second, 50 wt% Pb–Sn solder was sandwiched between the two substrates and heated to 503 K in a vacuum for 5 min before being cooled in a N2 atmosphere. By using this process, the area percentage of voids in a soldering area up to 130×190 mm2 can be reduced to less than 0.1%. IGBT modules made by this process were also found to exhibit satisfactory current-voltage characteristics.
A New Characterization Method of Photocatalytic Activity in Semiconductor Photocatalysts
Authors: Sumita Taishi , Yamaki Tetsuya , Yamamoto Shunya , Miyashita Atsumi
Published: October 2002

We propose a new simple method for characterizing photocatalytic activity by measuring photo-generated transient charge separation at the surface of semiconductor photocatalysts. In this method, the charge separation generated by a pulse dye laser is obtained as a function of the incident laser energy. Using this method, the photocatalytic activity and the type of surface reaction (reduction or oxidation) in titanium dioxide films were rapidly determined.
Ultra Short Two-Section Vertical Directional Coupler Switches with High Extinction Ratios
Authors: Cho Sung-Chan , Kim Boo-Gyoun , Moon Yong , Shakouri Ali
Published: October 2002

We show that both cross and bar states with high extinction ratios larger than 30 dB can be achieved at the same end of ultra short fused vertical directional coupler switches (FVCSs) with two sections by changing the refractive indices of cores and inner cladding layer less than 1%. The improvement of extinction ratios for various combinations of the refractive indices in a two-section FVCS is studied using the improved coupled theory and beam propagation method. Design guidelines to achieve high extinction ratios with large tolerances are presented.
Crystal Structure of Zirconium Oxide Deposited as Thin Films from Zr-acetylacetonate and Zr-ter-butoxide by Laser Chemical Vapor Deposition Technique
Authors: Watanabe Akio , Tsuchiya Tetsuo , Imai Yoji
Published: October 2002

Zirconium oxide films were prepared from gaseous zirconium-acetylacetonate (ZAC) and also from gaseous zirconium-ter-butoxide (ZTB) by ArF- and KrF-laser chemical vapor deposition (CVD) methods. In the case of ZTB, addition of oxygen to the source material was found to be useful for increasing the deposition rate. The films prepared from ZAC were found to consist of metastable tetragonal species of the oxide, while the films prepared from ZTB by ArF-laser CVD method were found to consist of monoclinic species of the oxide.
Effects of pH and Surfactant on the Ultrasound-Induced Chemiluminescence of Luminol
Authors: Miyoshi Norio , Hatanaka Shin-ichi , Yasui Kyuichi , Mitome Hideto , Fukuda Masaru
Published: October 2002

The pH dependence of the sonochemi-luminescence (SCL) of luminol at 141 kHz was investigated and compared to the effect of pH on its fluorescence emission intensity. From the fluorescence intensity, the pKa1
* and the pKa2
* values were determined to be 6.4 and 10.5 respectively, which was consistent with changes observed in the SCL intensity of luminol when the pH was varied. An inverse relationship was found to exist between the SCL and the fluorescence intensities against pH, i.e., the luminol SCL spectrum at pH=10.8 (mono-anionic form) had the same shape as the fluorescence emission spectra in acidic pH solutions, where luminol exists in either the mono-cationic or neutral form. The addition of an anionic surfactant, sodium dodecyl sulfate (SDS), significantly decreased the luminol SCL intensity at high pH. It is proposed that the generation of a negative electric potential at the surface of cavitation bubbles effectively prevented the negatively charged form of luminol from approaching the bubbles, thereby inhibiting the reaction of luminol with OH radicals.
Effect of Sr Substitution on Dielectric Characteristics of Ba4Nd2Ti4Ta6O30 Ceramics
Authors: Zheng Xing Hua , Chen Xiang Ming
Published: October 2002

The effect of Sr substitution for Ba on the dielectric characteristics of Ba4Nd2Ti4Ta6O30 ceramics was investigated together with the microstructures. The dielectric constant and dielectric loss increased with increasing Sr content, while the crystal parameters decreased. The temperature coefficient of the dielectric constant was improved slightly from -1500 ppm/°C to -1227 ppm/°C. There was a clear relationship between the dielectric constant, the temperature coefficient of the dielectric constant and the axial ratio 101/2
c/a.
Electrically Controlled Millimeter-Wave Transmission Properties of Stack-Layered Liquid Crystal Cells with Metal Substrates
Authors: Tanaka Masaki , Sato Susumu
Published: October 2002

Novel liquid crystal (LC) cells with a stack-layered structure using metal substrates, which have a large effective path length, are proposed for the millimeter-wave region. We adopt the finite-difference time-domain (FDTD) method to calculate the millimeter-wave transmission properties of the LC cells. The Floquet boundary condition is used to reduce the analysis to one unit cell, since the stack-layered structure cell has a periodicity. The transmission properties are measured from 47 to 53 GHz and 86 to 94 GHz ranges by applying a voltage to the LC cell, and transmission changes (∼ 50%) can be obtained. The transmission peak frequency shifts toward the lower frequency by increasing the applied voltage and agrees with that obtained by calculation. The dielectric and absorption anisotropies of nematic LC are estimated for these millimeter-wavelength ranges.
Boron-Doped Diamond Film Homoepitaxially Grown on High-Quality Chemical-Vapor-Deposited Diamond (100)
Authors: Wang Chunlei , Irie Masatake , Kimura Kenichi , Teraji Tokuyuki , Ito Toshimichi
Published: October 2002

In this study, high-quality homoepitaxial diamond (100) without any growth hillocks or abnormal particles has been investigated as a buffer layer for boron-doped diamond overgrowth to improve the electrical properties. For the undoped buffer layer used, very strong band-edge emissions were observed at room temperature (RT) in the cathodoluminescence (CL) spectra. After the overgrowth of B-doped homoepitaxial layer, CL characteristics and electrical properties were compared with cases when diamond buffer layers with inferior quality from the viewpoint of CL spectra were employed. The results showed that employing such a high-quality buffer layer led to an efficient acceptor doping of B atoms of 1.6×1019 cm-3 to the overgrown layer while the RT hole mobility was kept at 910 cm2/Vs, although bound-exciton CL peaks were well resolved only at lower temperatures. The usefulness of the high-quality buffer layer is discussed.
Observation of Etch Pits of β-FeSi2 Single Crystals
Authors: Udono Haruhiko , Isao Kikuma Isao Kikuma
Published: October 2002

We have observed etch pits of p-type β-FeSi2 single crystals grown by the temperature gradient solution growth method. Characteristic etch pits which depend on the surface orientation of the crystals were observed on the surface etched by diluted hydrofluoric acid and HF:HNO3:H2O=1:2:2–8 solutions. These etchants are suitable for the observation of etch pits and surface orientation of β-FeSi2 single crystals.