bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiation Field Prediction System Using Solutions of Exterior Steady-State Radiation Problem
Authors: Shuji Miyoshi Shuji Miyoshi , Tomoki Yokoyama Tomoki Yokoyama , Akio Hasegawa Akio Hasegawa
Published: October 2002

We have been studying a radiation field prediction system for an acoustic source that has an arbitrary shape. First, the nearfield sound pressure distribution around the source is measured and the normal velocity distribution over the surface of the source is predicted using the equivalent phased array method (EPAM). Then, radiation characteristics of the source, such as the pressure field, are predicted using the combined Helmholtz integral equation formulation(CHIEF). First in this paper, EPAM based on solutions for the exterior steady-state acoustic radiation problem is described. This method is applicable for predicting the normal surface velocity for sources that have an arbitrary shape. Then, an experimental example using a cylindrical source is presented. The predicted result of the pressure field is shown, and then the validity of this radiation field prediction system is confirmed by comparing the predicted pressure field with the actual field. The influence of the aperture restriction for the measurement contour on the surface of normal velocity predicted by EPAM is discussed. It is found that the error between the predicted and the ideal velocity distribution becomes smaller as the measurement contour covers the cylinder.
An Eulerian Scheme for Direct Numerical Simulation of Multibubble Dynamics in an Acoustic Field
Authors: Masato Ida Masato Ida , Yoshiki Yamakoshi Yoshiki Yamakoshi
Published: October 2002

An Eulerian numerical scheme for the direct simulation of bubble dynamics in an acoustic field is proposed. The compressible Navier-Stokes equation with a surface tension term is used as a governing equation. The convection terms in the equation are solved using the hybrid interpolation-extrapolation scheme which stably provides a nonsmoothed solution of density interface between bubbles and a surrounding material. The acoustic terms in the equation are solved by the generalized Crank-Nicholson method which is an implicit method and has a temporally second-order accuracy under the low-Courant-number condition and is applicable to high-Courant-number computation. Using this scheme, some typical results of single- and multibubble phenomena are given.
Quenching Mechanism of Multibubble Sonoluminescence at Excessive Sound Pressure
Authors: Shin-ichi Hatanaka Shin-ichi Hatanaka , Kyuichi Yasui Kyuichi Yasui , Toru Tuziuti Toru Tuziuti , Teruyuki Kozuka Teruyuki Kozuka , Hideto Mitome Hideto Mitome
Published: October 2002

Decrease in luminous intensity of multibubble sonoluminescence (MBSL) at excessive ultrasonic intensity is studied in connection with the behavior of cavitation bubbles. The intensity of MBSL from aerated distilled water in a rectangular vessel with six transducers, in which a standing wave field was established, was measured while the voltage applied to the transducers was increased. The corresponding change in the distribution of cavitation bubbles in the field was observed. The distributions of bubbles were compared with those of MBSL using an intesified charge-coupled device (ICCD) camera, and the bubble motion was observed with a high-speed camera. It is clarified that the expulsion of bubbles from the pressure antinode in the field is responsible for the decrease in MBSL intensity at high ultrasonic intensity. The expulsion is caused by the primary Bjerknes force which changes from an attractive force to a repulsive one depending on pressure amplitude and bubble radius, assisted by coalescence of bubbles due to the secondary Bjerknes force.
Experimental Study on Acoustic Streaming in Water Containing Microcapsules
Authors: Okabe Takeru , Sakamoto Shin-ichi , Watanabe Yoshiaki
Published: October 2002

Microbubbles strongly affect the sound field in a medium and various phenomena are caused by this sound field. In particular, in this study, the influence of microbubbles on acoustic streaming in water is quantitatively investigated by an experimental method. In order to ensure a constant distribution of microbubbles in water with time, and to appreciate the quantity of the microbubbles, water containing a certain amount of microcapsules packed in a cell is prepared. The streaming velocities are measured using a laser Doppler velocimeter (LDV). The observed results evidently show that the acoustic streaming velocity in water increases due to the microcapsules, and fluid-dynamic nonlinearity affects both velocities with and without microcapsules at a high sound pressure. This nonlinearity controls the velocity with microcapsules at a low sound pressure and also causes the dependence of the ratio between the streaming velocities of the medium with microcapsules and that without microcapsules on the sound pressure.
Power and Information Transmission to Implanted Medical Device Using Ultrasonic
Authors: Kawanabe Hideyuki , Katane Tamotsu , Saotome Hideo , Saito Osami , Kobayashi Kazuhito
Published: October 2002

Using ultrasonic, we propose here a novel method of transmitting power and information to implanted medical equipment. The proposed system is composed of two piezo oscillators and has the following functions: transmission of power and control information to an implanted device, and transmission of the information acquired by an implanted device to the outside of a living body. With amplitude shift keying (ASK), 9.5 Kbps is obtained for the proposed information transmission system.
A New Method for Simultaneous Determination of Anisotropic Thermal Conductivities Based on Two-Dimensional Analysis
Authors: Fujishiro Hiroyuki , Okamoto Tatsuya , Ikebe Manabu , Hirose Koichi
Published: October 2002

A new experimental setup and analysis method for simultaneous determination of the anisotropic thermal conductivities (κ
x
, κ
y
) is proposed for materials with uniaxial anisotropy or a layered structure. By applying heat power diagonally through the sample from a heater to a cold finger, temperature differences (ΔT

x
, ΔT

y
) along the two directions were monitored. The monitored temperature differences were compared with ΔT

x

′ and ΔT

y

′, which were calculated by solving a two-dimensional heat diffusion equation. Calculations were repeated until ΔT

x

′ and ΔT

y

′ agreed with ΔT

x
and ΔT

y
, to determine κ
x
and κ
y
. This technique was applied to a carbon-fiber-reinforced plastic (CFRP) from 40 K to 200 K and a satisfactory agreement was achieved with the κ
x
and κ
y
values and those determined from independent measurements of κ
x
and κ
y
.
Time-Frequency Analysis of the Blood Flow Doppler Ultrasound Signal
Authors: Yasuaki Noguchi Yasuaki Noguchi , Eiichi Kashiwagi Eiichi Kashiwagi , Kohtaro Watanabe Kohtaro Watanabe , Fujihiko Matsumoto Fujihiko Matsumoto , Suguru Sugimoto Suguru Sugimoto
Published: October 2002

Power spectral analysis is extensively used to interpret ultrasound data. However, the technique is useful only when the data can be treated as stationary. Ultrasound data are mostly nonstationary. Thus, a short time Fourier transform (STFT or spectrogram) is widely used to analyze spectral components which change with time. However, the STFT has a low accuracy in both time and frequency domains. Currently, Cohen's class time-frequency (TF) analysis is popular for analyzing nonstationary signals. The authors recently proposed a new kernel (named a figure eight kernel). In order to apply the TF analysis with the new kernel to a blood flow signal, experimental data were obtained from the carotid artery by an ultrasound Doppler monitor (Toitsu, Japan). To analyze the data, three kernels were used: (1) a Wigner kernel, (2) a Choi-Williams kernel, and (3) a figure eight kernel. Using our new figure eight kernel, the demodulation accuracy was improved and blood flow components were observed.
Imaging System for Intravascular Ultrasonography Using Pulse Compression Technique
Authors: Hu Zhiqiang , Moriya Tadashi , Tanahashi Yoshikatsu
Published: October 2002

We have developed an imaging system that applies FM-chirp pulse compression technology for use in intraductal ultrasonography, or intravascular ultrasonography. The pulse compression technique attempts to raise resolving power by using average power effectively under peak power restriction. This paper describes a method that use pulse compression technology in intravascular ultrasonography. In this paper, the following are reported: 1) A method to use the FM-chirp pulse compression technique in an imaging system is proposed. 2) A transmission line suited for intravascular ultrasonography is constructed using the L(0, 1) mode of the Pochhmmer-Chree wave propagating in a fused quartz rod coated with carbon. 3) A receiving signal from a target is compressed to give a shot pulse.
Estimation of Characteristics of Echo Envelope Using RF Echo Signal from the Liver
Authors: Tadashi Yamaguchi Tadashi Yamaguchi , Hiroyuki Hachiya Hiroyuki Hachiya , Naohisa Kamiyama Naohisa Kamiyama , Kazuki Ikeda Kazuki Ikeda , Norifumi Moriyasu Norifumi Moriyasu
Published: October 2002

To realize quantitative diagnosis of liver cirrhosis, we have been analyzing the probability density function (PDF) of echo amplitude using B-mode images. However, the B-mode image is affected by the various signal and image processing techniques used in the diagnosis equipment, so a detailed and quantitative analysis is very difficult. In this paper, we analyze the PDF of echo amplitude using RF echo signal and B-mode images of normal and cirrhotic livers, and compare both results to examine the validity of the RF echo signal.
Fundamental Study of Bone-Mimicking Phantom Using Apatite
Authors: Hirai Takuya , Ohdaira Etsuzo , Masuzawa Nobuyoshi , Itoh Katsuhiko , Matozaki Takeshi
Published: October 2002

Because of the success of the ultrasonic method for diagnosing osteoporosis, the challenge to obtain ultrasonic images of the inner part of bone has begun. Since ultrasonic imaging of the inner part of bone is very difficult, further research is necessary. The goal of this study is to develop a bone-mimicking phantom for use in the visualization of bone by ultrasound. The developed phantom using apatite and polyvinyl alcohol (PVA) as materials with consideration of the periosteum showed fairly good agreement with real bone.
Measurement of Acoustic Property Distributions of Diseased Heart and Liver Tissues
Authors: Hideaki Shigemoto Hideaki Shigemoto , Terukazu Sugimoto Terukazu Sugimoto , Hiroyuki Hachiya Hiroyuki Hachiya , Masaaki Ebara Masaaki Ebara , Hiroyuki Fukuda Hiroyuki Fukuda , Kazuki Kato Kazuki Kato , Hiromi Ando Hiromi Ando
Published: October 2002

Acoustic properties of living tissues are an important parameter for quantitative estimation of the tissue structure. It is very important to determine the relationship between the physical and the chemical change of tissue structure and the change of acoustic properties. In this paper, using a new system with high density measuring points, we present the relationship diagram between the speed of sound and attenuation of human heart and liver tissues at 25 MHz. To compare normal and diseased tissues, we investigate the relationship between the sound speed and the attenuation of tissue. A characteristic relationship of the tissue is found in cirrhotic liver and aortic regurgitation tissue.
Optimization of Focal Position of Ultrasonic Beam in Measurement of Small Change in Arterial Wall Thickness
Authors: Masaru Watanabe Masaru Watanabe , Hiroshi Kanai Hiroshi Kanai
Published: October 2002

We have previously developed a method for measurement of a small change in thickness of the arterial wall during a single cardiac cycle [H. Kanai, M. Sato, Y. Koiwa and N. Chubachi: IEEE Trans. UFFC 43 (1996) 791]. The resultant change in thickness is shown to be useful for the in vivo assessment of the regional elasticity of the arterial wall. Although the accuracy of the measurement of the change in thickness is found to be within 1 µm, it is affected by the interference of ultrasonic pulses. In this study, we simulate the propagation of ultrasonic pulses transmitted and received by a linear probe. In the simulation experiments, the ultrasonic pulses generated by a computer are reflected by a tube, which has a small change in wall thickness of 10 µm. The optimum focal position of the ultrasonic beam is determined by evaluating the root-mean-square (rms) error in the measured change in thickness.
High-Precision Motion Estimate of Soft Tissue in the Physiologaical State Using Two-Dimensional Complex-Valued Wavelet Transform of Speckle Echo
Authors: Shin-ichi Yagi Shin-ichi Yagi , Kouji Kitamura Kouji Kitamura , Shin Akimoto Shin Akimoto
Published: October 2002

In contrast with tissue elasticity imaging, a nonquantitative but high-resolution and real-time image of abdominal tissue strain could be a promising diagnostic tool for ultrasonic visualized palpation using a conventional array transducer. In order to realize the 2D strain imaging, accurate estimation of the lateral displacement perpendicular to the beam axis is required, which overcomes the limitation of the 2D cross-correlation method affected by the data window which determines the spatial resolution and computing efficiency of the estimation. The hierarchical 2D wavelet coefficients of successive complex-valued echo frames were applied to realize the excellent performance of the 2D motion estimate in accuracy, variance, spatial resolution and computational cost. The resultant total performance of this algorithm is evaluated on the basis of physiological free motion to obtain clinical data of hepatocellular carcinoma.
Low-Frequency Scattering Component for Quantitative Circular-Scanning Ultrasonic Diffraction Tomography
Authors: Toyokatsu Miyashita Toyokatsu Miyashita
Published: October 2002

We present a theory of circular-scanning ultrasonic diffraction tomography along with simple preliminary experimental results. Images of cross-sectional structures of objects achieved by diffraction tomography have a high resolution, which is finer than a wavelength of the probing wave, in the presence of diffraction, reflection, and refraction phenomena.
We investigate the spatial resolution and quantitative reconstruction of the object function, focusing on the role of the low-frequency component of the scattered wave, and show a simple method of extrapolation to determine the lacking low-frequency component. Additionally, we present numerical investigations on the quantitative accuracy of the reconstruction of a complex object function, introducing new numerical phantoms for the circular scanning diffraction tomography like Shepp and Logan's phantoms which are utilized in the numerical investigations of X-ray CT and MRI.
Size Effects of a Temperature Detector in an AC Calorimetric Thermal Diffusivity Measurement
Authors: Hatta Ichiro , Yamane Tsuneyuki
Published: October 2002

In an ac calorimetric thermal diffusivity measurement in which the amplitude and/or the phase of ac temperature is measured as a function of the distance between the ac heating position and the temperature detecting position, thermal diffusivity is obtained with high accuracy. It is well known that the method named “a distance-variation method”, in which the measurement is performed by changing the distance, has various advantages. We exhibit another advantage that not only the size of the temperature detector but also the distribution of its sensitivity does not affect the measurement at all.
Three-Dimensional (3D) High-Frequency Ultrasound Images of Skin and an Eye
Authors: Kumi Kamada Kumi Kamada , Osamu Oshiro Osamu Oshiro , Kunihiro Chihara Kunihiro Chihara , Wojciech Secomski Wojciech Secomski , Andrzej Nowicki Andrzej Nowicki
Published: October 2002

This report describes the three-dimensional (3D) visualization of skin and an eye using high-frequency ultrasound. A high-frequency ultrasound image has high resolution of the order of 10 µm and demonstrates the detailed internal structure of an organ. Therefore it is suitable for visualizing the structure of organs such as skin and the eye. The method of 3D visualization of skin and an eye we used is as follows. Initially, a high-frequency ultrasound image was obtained by using a transducer made of lead zirconate titanate (PZT) ceramics with a central frequency of 32 MHz. The spatial resolution of the image is 25 µm. Next, we applied a binarization procedure to the image and reconstructed a 3D image using a volume-rendering technique. From the results, we were able to separately image each layer of the skin and recognize the stratum corneum, epidermis and dermis. Moreover, we obtained images of the structure of the eye, that is, cornea and iris.
Influence of the Applied Cooling Rate on the Type Conversion of Platinum Diffused N-Type Silicon
Authors: Ventura Laurent , Pichaud Bernard , Lanois Frédéric , Lhorte André
Published: October 2002

In this work we show that the temperature and the applied cooling rate during a platinum diffusion process strongly influence the electrical conductivity in weakly phosphorus doped silicon. Diffusions were done in the range of 800–950°C for several hours. Spreading resistance profile analyses clearly show an n-type to p-type conversion under the surface when samples are slowly cooled (5°C/min). Only a compensation of the phosphorus donors is observed when samples are quenched. This mechanism is reversible. Five Pt related deep levels, including the acceptor level at 0.23 eV from the conduction band, are observed. One of them is located at 0.427 eV from the valence band and can be related to the acceptor state at the origin of the type conversion mechanism. This acceptor state can be associated with a complex defect based on the association of a substitutional Pt atom with interstitial atoms (Pt, O) or intrinsic point defects.
Intrinsic Gettering in Nitrogen-Doped and Hydrogen-Annealed Czochralski-Grown Silicon Wafers
Authors: Goto Hiroyuki , Pan Lian-Sheng , Tanaka Masafumi , Kashima Kazuhiko
Published: October 2002

The properties of nitrogen-doped and hydrogen-annealed Czochralski-grown silicon (NHA-CZ-Si) wafers were investigated in this study. The quality of the subsurface was investigated by monitoring the generation lifetime of minority carriers, as measured by the capacitance-time measurements of a metal oxide silicon capacitor (MOS C-t). The intrinsic gettering (IG) ability was investigated by determining the nickel concentration on the surface and in the subsurface as measured by graphite furnace atomic absorption spectrometry (GFAAS) after the wafer was deliberately contaminated with nickel. From the results obtained, the generation lifetimes of these NHA-CZ-Si wafers were determined to be almost the same as, or a little longer than those of epitaxial wafers, and the IG ability was proportional to the total volume of oxygen precipitates [i.e., bulk micro defects (BMDs)], which was influenced by the oxygen and nitrogen concentrations in the wafers. Therefore, it is suggested that the subsurface of the NHA-CZ-Si wafers is of good quality and the IG capacity is controllable by the nitrogen and oxygen concentrations in the wafers.
Theoretical Analysis of Placement Error due to Absorber Pattern on Extreme Ultraviolet Lithography Mask
Authors: Chiba Akira , Takahashi Masashi , Yamanashi Hiromasa , Hoko Hiromasa , Hoshino Eiichi , Hirano Naoya , Lee Byoung Taek , Ogawa Tarou , Ito Masaaki , Okazaki Sinji
Published: October 2002

The pattern placement accuracy of an extreme ultraviolet lithography (EUVL) mask strongly depends on the stresses present in the multilayer and absorber films, since film stress causes both out-of-plane and in-plane distortions. To analyze this elastic deformation, we have developed simulation models that handle the interaction between the multilayer and absorber patterns. The models are based on two-dimensional theories of bending plates and plane stress. The numerical calculations employ the finite difference method and the successive over-relaxation method. To examine the validity and accuracy of the models, the deformation of EUVL masks using simple absorber patterns was calculated. For the calculations, we assumed a standard 6 inch quartz substrate with a reflective coating. The influence of the absorber pattern on placement error was investigated by simulations, and it was found that the absorber pattern is the main factor determining the pattern placement accuracy of an EUVL mask.
Dependence of Fractal Formation on Thickness Ratio and Annealing Time in Au/Ge Bilayer Films
Authors: Chen Zhiwen , Tan Shun , Zhang Shuyuan , Hou Jianguo , Wu Ziqin , Sekine Hisashi
Published: October 2002

The dependence of the fractal formation on the thickness ratio and the annealing time in Au/Ge bilayer films has been investigated by transmission electron microscopy. The experimental evidence indicates that the polycrystalline Ge fractal clusters with various sizes, density, and fractal dimension are formed after crystallization of amorphous Ge. It is found that the fractal formation is sensitively dependent on the thickness ratio of Au and Ge. The random successive nucleation mechanism can be used to explain the behavior of the fractal formation.
Design of Ferroelectric Diode for High-Current Matched Electron-Beam Generation
Authors: Hayashi Yasushi , Flechtner Donald , Golkowski Czeslaw , Ivers Jim D. , Nation John A.
Published: October 2002

An electron gun using a ferroelectric cathode with a two-stage compression system has been designed. The performance of the beam generated by the gun has been investigated by simulation and experiment. When the applied diode voltage is 440 kV, a beam current of 230 A is obtained. The waveform of the beam current follows the diode voltage reasonably well, and their flat top overlaps for about 200 ns. Faraday cup measurement shows that the beam radius is 4.1 mm after second-stage compression, and the axial variation of the beam radius has been minimized.
Design of Transverse Muon-Cooling Channels for a Neutrino Factory
Authors: Kim Eun-San , Yoon Moohyun
Published: October 2002

Ionization cooling is the preferred method for transverse cooling of a muon beam in a neutrino factory. In this paper, we design two different cooling channels, a DF0F0 channel and an alternating solenoid channel, and show that the transverse beam emittance through these cooling channels is cooled down by a factor of 7.7 and 6.5, respectively. The cooling channel design has been carried out by invoking the ICOOL program. Transmission efficiency, transverse beam emittance, growth of longitudinal bunch length, and momentum spread are investigated. It is shown that these two cooling channels provide adequate cooling performance, satisfying the so-called Palmer, Johnson and Keil (PJK) parameter for a neutrino factory. It is also shown that the numerical results agree well with those of analytical formulae.
Properties of a Flux Dam Inserted in the Pickup Coil of a High-Tc Superconducting Quantum Interference Device Magnetometer
Authors: Enpuku Keiji , Nakahodo Atsushi , Hotta Masahiro , Hijiya Shintaro , Tokimizu Daishi , Kuroda Daisuke
Published: October 2002

The properties of a flux dam inserted in a pickup coil of a high-T
c superconducting quantum interference device (SQUID) are studied. First, the effect of thermal noise at T=77 K on the magnetic flux entry into in the pickup coil through the flux dam is discussed. It is shown that the thermal noise causes the flux entry even when the circulating current in the pickup coil is less than the critical current of the flux dam. The behavior of this thermally activated flux entry is analyzed using the so-called potential-barrier model. It is shown that the flux entry into the coil proceeds logarithmically with time, indicating the necessity of a long waiting time in the use of the flux dam. It is also shown that the critical current of the flux dam must be large enough to obtain a quasistable state, i.e., a state where no thermally activated flux entry occurs during the measurement time. The critical current should be larger than 50 µA in the magnetic field under operation. Next, in order to satisfy this requirement, the magnetic field dependence of the critical current of the flux dam is studied when the flux dam is made of a wide bicrystal junction. It is shown that the magnetic field dependence of the wide junction can be explained reasonably well if we take into account the so-called overlap-type-junction model and the flux-focusing effect of the bicrystal junction. The obtained results will be useful in the design of the flux dam.
On Magnetization Reversal of Co–Cr Films with Perpendicular Anisotropy
Authors: Kitakami Osamu , Shimada Yutaka
Published: October 2002

Based on a simple consideration, we show that the slope of the easy-axis loop for perpendicular magnetization films is dominated by the lateral size of a reversal unit. From the analyses of the slopes of Co–Cr films, we have estimated the lateral size of a reversal unit. The size becomes very large for the films grown and annealed at low temperatures, indicating that there are strong exchange interactions between constituent magnetic grains due to insufficient magnetically induced phase separation. We have also found a close relationship between the coercivity and the lateral size of a reversal unit. All these results are discussed.
Noise Reduction in the Measurement of Light Intensity by means of Correlated Twin Photons
Authors: Kazuyuki Muroo Kazuyuki Muroo , Yoshihiro Kajimura Yoshihiro Kajimura , Yoshitaka Takubo Yoshitaka Takubo
Published: October 2002

We investigated statistical fluctuations in the numbers of photons contained in the correlated twin photon beams generated by an optical parametric process. The coincidence between the signal- and idler-photoelectron pulses from a pair of avalanche photo-diodes was measured. The measured fluctuation in the number of signal-photons coinciding with idler-photons was equal to the standard deviation of a binomial distribution and was smaller than that of a Poisson distribution. We determined that even when the quantum efficiency of the photon detectors was much lower than unity, the uncertainty in the number of photons obtained with the twin photon beams was smaller, by a factor of 1/√2, than that with a classical light beam.
Growth, Thermal and Laser Properties of Neodymium-doped Sodium Yttrium Double Tungstate Crystal
Authors: Cheng Zhenxiang , Zhang Shujun , Fu Kun , Liu Junhai , Chen Huanchu
Published: October 2002

In this paper, the neodymium-doped sodium yttrium double tungstate crystal [Nd:NaY(WO4)2, designed as Nd:NYW] has been grown by the Czochralski method. The data of thermal expansion and specific heat of the crystal have been measured. The thermal expansion coefficients along X and Z direction are α1=3.5×10-6/K and α2=1.77×10-5/K, respectively. The specific heat is 0.5132 J/g·K. The measured absorption spectra around 800 nm at room temperature show that the crystal has different absorption peaks, 801.25 nm for π polarization and two peaks 804.04 nm and 812.26 nm for σ polarization. The peak absorption coefficients are 9.37 cm-1 (π) and 3.95 cm-1 (σ at 804.04 nm). The fluorescence at room temperature show that the strongest fluorescence is centered at 1060.12 nm. The laser at 1060 nm is demonstrated pumped by a Ti:saphiere laser at 801 nm. The slope efficiency is 38.1%.
Monolithic Formation of Metal Organic Chemical Vapor Deposition Grown Multi-wavelength Vertical Cavities with Highly Strained GaInAs/GaAs Quantum Wells on GaAs (311)B
Authors: Arai Masakazu , Nishiyama Nobuhiko , Azuchi Munechika , Matsutani Akihiro , Koyama Fumio , Iga Kenichi
Published: October 2002

We have demonstrated the monolithic integration of multi-wavelength vertical cavities with highly strained GaInAs/GaAs quantum wells on a patterned GaAs (311)B substrate. Using a patterned substrate, the resonant wavelength can be controlled in the range from 1.13 µm to 1.145 µm. The obtained result may open up the field of multi-wavelength surface emitting lasers emitting in the 1.1–1.2 µm band enabling their use in wavelength division multiplexing local area networks (WDM-LANs).
Half Wavelength Pattern Replication Using a Projection Lens with an Ultra High Numerical Aperture and Thin Resist Process
Authors: Horiuchi Toshiyuki , Narita Tsuyoshi
Published: October 2002

Applicability of a projection lens with an ultra high numerical aperture of 0.85 is investigated. Shorter wavelength exposure systems and various resolution enhancement techniques such as phase shifting masks, off-axis illumination and multi reticle exposure methods are researched. However, minimization of LSI patterns following the conventional trends is becoming increasingly difficult. Hence, various other ideas should be introduced and put to practical use simultaneously. When applying such a lens, it is anticipated that the depth of focus will become very small, especially for short wavelength exposure. For this reason, a thin resist with a thickness of 0.15–0.2 µm is adopted. A manufactured test exposure system is used for the experiments, and wafers are exposed by a halogen lamp illumination system with a central wavelength of 480 nm. As a result, half-wavelength 0.24 µm line-and-space patterns are printed successfully and significantly better than those obtained by the conventional trends, and 0.21 µm patterns are almost resolved. Depth of focus for the 0.24-µm patterns is about 1 µm. The combination of ultra high numerical aperture exposure and thin resist process will be a superior option for further minimization of LSIs.
Zeeman Effect of Shallow Bound Exciton Lines in CuGaS2
Authors: Tamao Matsumoto-Aoki Tamao Matsumoto-Aoki , Takahiro Shimojo Takahiro Shimojo , Hiromichi Kumakura Hiromichi Kumakura , Hisao Uchiki Hisao Uchiki , Seishi Iida Seishi Iida
Published: October 2002

The behavior of two shallow bound exciton absorption lines in a magnetic field was investigated for a CuGaS2 single bulk crystal. Upon application of a magnetic field perpendicular to the c-axis, both partially allowed absorption lines split into two components with an apparent g-value of 4. When the temperature was reduced under the applied magnetic field, the lower energy line of each pair decreased in intensity. Such behavior of bound exciton lines, in energy splitting and intensity ratio of split lines under different magnetic fields and at different temperatures, is shown to be consistent with the calculated absorption spectra for excitons bound to neutral centers using known band parameters of CuGaS2. The observed nearly isotropic apparent g-value of around 4, which is the sum of electron and hole g-values, is interpreted in terms of nondegeneracy of the valence band top and larger crystal field splitting compared to spin-orbit splitting for CuGaS2. The good agreement between the calculated and observed features clearly indicates that the binding centers are neutral.
Morphological and Optical Characteristics of Y2O3:Eu Phosphor Particles Prepared by Flame Spray Pyrolysis
Authors: Kang Yun Chan , Seo Dae Jong , Park Seung Bin , Park Hee Dong
Published: October 2002

Y2O3:Eu phosphor particles were prepared by flame spray pyrolysis and compared with the particles prepared by general spray pyrolysis. The particles prepared by flame spray pyrolysis had a spherical and dense morphology and were finer than the particles prepared by general spray pyrolysis. Flame temperature was an important factor in the preparation of the phosphor particles by flame spray pyrolysis. To obtain Y2O3:Eu particles with a uniformly dense structure, a sufficiently high temperature to form monoclinic phase was required. Too low flame temperature generated nonspherical and hollow particles with cubic phase because the particles did not melt completely, and too high flame temperature of flame generated many nanoparticles due to evaporation. After stepwise post-treatment of as-prepared particles with monoclinic phase and the dense structure, Y2O3:Eu phosphor particles with high brightness and cubic phase were obtained. The Y2O3:Eu phosphor particles prepared by flame spray pyrolysis showed 120% photoluminescence intensity in comparison with the particles prepared by general spray pyrolysis.
Nonlinear Optical Absorption in the AgOx-Type Super-Resolution Near-Field Structure
Authors: Ho Fu Han , Lin Wei Yi , Chang Hsun Hao , Lin Yu Hsaun , Liu Wei-Chih , Tsai Din Ping
Published: October 2002

Nonlinear optical absorption in the AgO
x
-type super-resolution near-field structure [glass/ZnS–SiO2 (170 nm)/AgO
x
 (15 nm)/ZnS–SiO2 (40 nm)] was investigated using a confocal Z-scan technique with a continuous He–Ne laser. The transmittance Z-scan shows that the sample undergoes a phase transition with increasing incident laser power. The phase transition of the sample with higher incident laser power is due to permanent local structure damage caused by the laser heating process.
Ab Initio Pseudopotential Calculations of Electronic Structure of Off-Stoichiometric ZnO
Authors: Ni Hai-Qiao , Lu Yong-Feng , Ren Zhong-Min
Published: October 2002

We have investigated the electronic structure and valence electron density distribution of ideal-stoichiometric and off-stoichiometric ZnO. The ab initio pseudopotential calculation is carried out in the framework of the density function theory within the local density approximation. In calculating the Zn pseudopotential, the errors, particularly those of elements that have 3d electrons, introduced by the frozen-core approximation and linearizing the exchange-correlation potential, were corrected. The electronic structures of ideal-stoichiometric and off-stoichiometric ZnO shows a trend of increasing conductivity introduced by excess Zn, which is consistent with the experimental results. The calculated valence electron density distribution reveals the strong ionic characteristic Zn–O bond in ideal-stoichiometric and off-stoichiometric ZnO.
Frequency Scan Spectra of Surface Plasmons Excitation in an Arbitrary Multilayer System
Authors: Liao Chih-Hsiung , Shyu Jiann-Shing
Published: October 2002

In this paper, we have derived approximate formulas from the Fresnel formulas and pole expansion for the reflectivity and resonant frequency in an arbitrary multilayer system. In accordance with the results of simulation, we conclude that the resonant wavelength increases when the incidence angle decreases and the resonant frequency increases when the metal thickness increases. Moreover the sensitivity of the resonant frequency versus the metal thickness is very large when the metal thickness is modulated from 10 nm to 60 nm. One can make use of these properties to fabricate the instrument of the metal film measurement. Besides, the resonant frequency is a function of the environment dielectric constant. One can apply the property to the chemical sensor based on surface plasmons (SPs) measurement.
Transmission Electron Microscopy and Atomic Force Microscopy Studies of an Al–Pd–Mn Thin Film Prepared by a Combined Technique of Vacuum Deposition and Thermal Annealing
Authors: Saito Kaichi , Yoneshima Masakazu , Sugawara Shigeo , Kamimura Yasushi , Edagawa Keiichi
Published: October 2002

A thin-film sample of Al–Pd–Mn ternary alloy has been produced by a vacuum deposition technique using dual evaporation sources, followed by thermal annealing. The microstructure of the film has been examined by transmission electron microscopy (TEM) and by atomic force microscopy (AFM). The TEM observations reveal that the film has a granular texture of highly ordered icosahedral phase islands embedded in the matrix consisting mainly of multiple-twinned crystals exhibiting a pseudo-tenfold symmetry. It is shown by AFM that the icosahedral islands form protuberant structures with the average height of approximately 50 nm.
Growth of SixGe1-x (x \fallingdotseq0.15) Bulk Crystal with Uniform Composition Utilizing in situ Monitoring of the Crystal-solution Interface
Authors: Usami Noritaka , Azuma Yukinaga , Ujihara Toru , Sazaki Gen , Miyashita Satoru , Murakami Yoshihiro , Nakajima Kazuo
Published: October 2002

A new growth system, which allows in situ monitoring of the crystal-solution interface, was developed and applied to grow Si
x
Ge1-x
(x\fallingdotseq0.15) bulk crystal with uniform composition by the multicomponent zone-melting method. By utilizing the system, the dynamical change of the growth rate was evaluated from the nonlinear upward shift of the interface as a function of the growth time. Based on the monitoring, an attempt was made to balance the pulling rate of the ampoule with the growth rate of the crystal, which led to the suppression of the upward shift of the growth interface. Consequently, the compositional uniformity of the crystal in the growth direction was markedly improved.
Study of Inhomogeneous Radial Distribution of Defects in As-grown and Annealed Czochralski Silicon Crystals by Multi-chroic Infrared Light Scattering Tomography
Authors: Ma Minya , Irisawa Toshiharu , Ogawa Tomoya , Frigeri Cesare
Published: October 2002

Multi-chroic infrared light scattering tomography (MC-IR-LST) and transmission electron microscopy (TEM) were used to systematically investigate the inhomogeneous radial distribution of defects in as-grown and annealed Czochralski silicon (CZ-Si) crystals. A new defect morphology of dark stripes observed for the first time by the MC-IR-LST system in a special region in the as-grown CZ-Si crystal. After annealing the crystal at 1150°C for 16 h in an O2 atmosphere, dark stripes that became scattered in width and deep in contrast were clearly visible in an OSF-ring area. The location of these stripes in the as-grown crystal coincided with that in the annealed CZ-Si crystal, where many stacking faults and oxygen-precipitate-related polyhedral defects were revealed by TEM analysis. This means that the dark stripes were generated during crystal growth as original grown-in defects. Quantitative measurement of the inhomogeneous radial distribution of defects in the annealed crystal was made and the characteristics of the defects in different regions of the crystal were analytically discussed.
Control of High Pretilt Angle for Nematic Liquid Crystal Using In Situ Photoalignment Method on Homeotropic Alignment Layer
Authors: Hwang Jeoung-Yeon , Seo Dae-Shik
Published: October 2002

Pretilt angle generation and liquid crystal (LC) aligning capabilities for nematic (N) LC using an in situ photoalignment method with obliquely polarized UV exposure of the polyimide (PI) surface for homeotropic alignment were studied. The high pretilt angle of 30° for NLC with obliquely polarized UV exposure for 10–20 min on the PI surface can be achieved. The exposure energy of UV used was 15.5 mW/cm2 at 365 nm. The pretilt angle generated in NLC using the in situ photoalignment method was higher than that generated using a conventional photoalignment method on a homeotropic alignment layer. Lastly, we suggest that the generation of pretilt angle in NLC with obliquely polarized UV exposure during imidization of the polymer for homeotropic alignment is a promising method to generate a high pretilt angle.
Low-Temperature Formation of Device-Quality SiO2/Si Interfaces Using Electron Cyclotron Resonance Plasma-Enhanced Chemical Vapor Deposition
Authors: Higashi Seiichiro , Abe Daisuke , Inoue Satoshi , Shimoda Tatsuya
Published: October 2002

Low-temperature formation of SiO2/Si interfaces using electron cyclotron resonance (ECR) plasma-enhanced chemical vapor deposition (PECVD) was investigated. It was found that the density of interface trap states (D
it) decreased with decreasing substrate temperature during film deposition and performing the post deposition annealing at 333°C in N2 or H2O atmosphere. The average D
it was 3 to 4×1011 cm-2 eV-1 when the substrate temperature was 300°C, while decreasing the substrate temperature to room temperature decreased it to 1.8×1010 cm-2 eV-1. These results indicate that device-quality-SiO2/Si-interface formation is possible using low-temperature processes of ECR PECVD and post deposition annealing.
Advanced Micro-Lithography Process with Chemical Shrink Technology
Authors: Ishibashi Takeo , Toyoshima Toshiyuki , Yasuda Naoki , Kanda Takashi , Tanaka Hatsuyuki , Kinoshita Yoshiaki , Watase Natsuo , Eakin Ron
Published: October 2002

We have developed an advanced micro-lithographic process for producing 0.1 µm contact holes (CH). A chemical shrink technology, resolution enhancement lithography assisted by chemical shrink (RELACS) utilizes the cross-linking reaction catalyzed by the acid component existing in a predefined resist pattern. This “RELACS” process is a hole shrinking procedure that includes simple coating, baking, and rinse steps applied after conventional photolithography. We evaluated the dependency of CH shrinkage on resist formulation. Though the acetal type KrF positive resist (low activation energy system) can achieve around 0.1 µm CH after RELACS processing under the optimized condition, the acrylate type positive resist (high activation energy system) showed less shrinkage under the same process condition. The shrinkage performance of the RELACS process largely depends on the resist chemistry used as the underlying layer. The results of these studies are discussed in terms of the influence of the base polymer on shrinkage performance and tendency.
Cryogenic Ion Trap for Minimization of Trapped Ion Loss
Authors: Okada Kunihiro , Wada Michiharu , Nakamura Takashi , Katayama Ichiro , Boesten Ludwig , Ohtani Shunsuke
Published: October 2002

A cryogenic linear ion trap was developed for the minimization of the loss of trapped Be+ ions. Buffer gas cooling as well as laser cooling for light element ions was tested in the cryogenic trap. The lifetime for the He-gas-cooled Be+ ions was longer than 15 min with a liquid-He-cooled trap, although they are known to be difficult to cool with a buffer gas in a conventional trap. A laser-cooled ion crystal was maintained for approximately 30 min without any ion loss.
A Method of Closed Orbit Correction under Constraint Conditions
Authors: Kim Kukhee , Choi Jinhyuk , Lee Tae-Yeon , Kim Guinyun , Cho Moohyun , Namkung Won , Ko In Soo
Published: October 2002

We have developed the correction algorithm of the closed orbit distortion (COD) under the constraint condition where beam positions at particular points are not changed. The new algorithm is based on the modified PSINOM algorithm including the regularization process in order to avoid the inversion problem of the ill-posed response matrices. We have confirmed that the COD is well corrected with no orbit leak in the simulation and is in good agreement with the experiment.
Improvement in Image Reconstruction of Scanning Near-Field Millimeter-Wave Microscopy Using a Metal Slit-Type Probe
Authors: Nozokido Tatsuo , Kudo Hiroyuki , Bae Jongsuck , Mizuno Koji
Published: October 2002

Improvements in image reconstruction of scanning near-field millimeter-wave microscopy using a metal slit-type probe have been demonstrated. A conjugate gradient method in combination with preconditioning and regularization has been used during the image reconstruction process to take into account the sensitivity distribution of the slit-type probe. The reconstructed images show that the image degradation that occurs due to the sensitivity distribution can be corrected.
Monolithic-Disked High-Voltage Vacuum Interface for High-Energy KrF-Laser Amplifiers
Authors: Okuda Isao , Owadano Yoshiro
Published: October 2002

Design and experimental results of the vacuum interface in the 3-kJ-class KrF-laser amplifier in our laboratory are reported. With the uniform field distribution throughout the disk-shaped interface, electrical stress on the diaphragm is alleviated with no grading rings and the inductance due to the insulator is reduced. High-voltage pulses (600 kV/270 ns) can be handled with stability. Application of this interface design to still larger amplifiers is also discussed.
High-Power and Low-Noise Photodetector for Interferometric Gravitational Wave Detectors
Authors: Mio Norikatsu , Ando Masaki , Heinzel Gerhard , Moriwaki Shigenori
Published: October 2002

We have developed a photodetector for interferometric gravitational wave detectors which can detect high power light with low intrinsic noise. The detector is designed to detect a laser power of more than 100 mW at 1.064 µm with a single InGaAs photodiode. Using a resonant circuit, low intrinsic noise is achieved; the noise-equivalent photocurrent is 132 µA. By using a photocurrent limiter used in the circuit, we confirmed that even with high power (2 W) incident on the diode, the diode was undamaged.
Scanning Tunneling Microscopy Characterization of Aromatic Molecules Stabilized by a Buffer Layer of Alkane Derivatives
Authors: Lei Shengbin , Xu Bo , Wang Chen , Xu Qingmin , Wan Lijun , Bai Chunli
Published: October 2002

Using lamellae of 1-octadecanol and stearic acid as a buffer layer, aromatic molecules such as copper phthalocyanine (CuPc) and nitrobenzene were immobilized on the surface of highly oriented pyrolytic graphite (HOPG), and been characterized by scanning tunneling microscopy (STM). These molecules crystallized in two dimensions on top of the monolayer of alkane derivatives, and high-resolution images of these molecules were obtained. An additional advantage is that the buffer layer underneath does not change the electronic properties of the immobilized molecules. The mechanism of the immobilization of the buffer layer is considered to be the cutting down of charge transfer between the aromatic molecules and graphite. These results proved that this strategy could be used as a general method to immobilize organic species on a substrate surface.
Scanning Tunneling Microscopy Barrier-Height Imaging of Shockley Dislocations on a Au(111) Reconstructed Surface
Authors: Shu Kurokawa Shu Kurokawa , Yasuharu Yamashita Yasuharu Yamashita , Akira Sakai Akira Sakai , Yukio Hasegawa Yukio Hasegawa
Published: October 2002

We have carried out a scanning tunneling microscopy barrier-height (STM-BH) imaging of a reconstructed Au(111) surface and found that the BH locally decreases on herringbone reconstruction ridges, or Shockley dislocations. The observed lowering of the BH can be explained by the formation of an electric dipole at a dislocation core, which was theoretically predicted by Cottrell et al.. (Philos. Mag. 44 (1953) 1064) in their theory on the electric interaction between solutes and dislocations.
A Single Vacancy Chain and its Bundle in Magnesium Oxide as Line-Type Lattice Defects
Authors: Kizuka Tokushi , Kawasaki Masahiro
Published: October 2002

One-dimensional atomistic holes, i.e., a single vacancy chain and its bundle penetrating a magnesium oxide film were individually produced by convergent electron beam irradiation inside a high-resolution transmission electron microscope. The width of these imperfections ranged from 0.21 nm to 0.42 nm and was less than that of a unit cell of the NaCl structure. The imperfections were line-type lattice defects.
Quantum Size Effects in Low-Temperature Growth of Pb Islands on Si(111)7×7 Surfaces
Authors: Su Wei-Bin , Chang Shih-Hsin , Chang Chia-Seng , Chen Lih Juann , Tsong Tien T.
Published: October 2002

Flat-top Pb islands with critical and magic thickness have been observed in the Pb/Si(111)7×7 system at 200 K by scanning tunneling microscopy. The growth behavior, different from that in the Stranski-Krastanov mode, arises from a quantum size effect. Quantized states are detected in the current–voltage (I–V) spectra on the Pb islands of varying thickness. Our observation of asymmetrical and oscillatory relaxation in the island thickness reveals that the charge distribution of confined electrons can influence the interlayer spacing. A simple model based on the infinite potential well can explain well all of our results.