bluuebunny/crossref_metadata_2025 huggingface dataset:
Corrugation-Pitch-Modulated Distributed Feedback Lasers with Ultranarrow Spectral Linewidth
Authors: Okai Makoto , Suzuki Makoto , Tuyoshi Taniwatari Tuyoshi Taniwatari , Naoki Chinone Naoki Chinone
Published: October 2002

We demonstrate that the spectral linewidth of distributed feedback (DFB) semiconductor lasers can be reduced by suppressing the longitudinal spatial hole-burning (SHB) effect. We confirm that the minimum spectral linewidth of lattice-matched multiple-quantum-well λ/4-shifted DFB (lattice-matched MQW-λ/4-DFB) lasers is limited by the SHB effect and we show that a corrugation-pitch-modulated (CPM) grating structure reduces the SHB effect while maintaining stable single-mode oscillation: at an output power of 25 mW, a lattice-matched MQW-CPM-DFB laser gives a spectral linewidth of 56 kHz. We further introduced the strained MQW structure into the CPM-DFB laser to obtain a narrower spectral linewidth. Introducing a 1.0% compressively strained MQW active layer into a CPM-DFB laser gives a spectral linewidth of 3.6 kHz at 55-mW output power and a linewidth floor (residual linewidth for extrapolated infinite output power) of 2 kHz and results in a linewidth-power product of 140 kHz·mW.
Electronic Structure Calculational Studies on Corrosion of Stainless Steel in Liquid Metal
Authors: Kimichika Fukushima Kimichika Fukushima , Hiroshi Endo Hiroshi Endo
Published: October 2002

The mechanism of element-selective corrosion of austenitic stainless steel in liquid sodium has been investigated using the molecular orbital method. Electronic states were calculated for the elements Cr and Ni substituted for an atom at the Fe(001) surface. The energy differences between the 3d orbitals for Fe, Cr and Ni cause charge transfers from Cr to Fe and from Fe to Ni. These charge transfers indicate that the charged element is apt to be attacked selectively by an oppositely charged atom. Following this, a calculation was carried out for an oxygen impurity associated with an Na atom on top of Cr, and for an Na atom coupled with an O atom on top of Ni at the Fe(001) surface exposed to sodium. The result indicates that an O anion will bring about selective Cr release, and that a positively charged Na will cause Ni to transfer selectively into sodium.
Schottky and Metal-Insulator-Semiconductor Diodes Using Poly(3-hexylthiophene)
Authors: Kuo Chung S. , Wakim Fahd G. , Sengupta Sandip K. , Tripathy Sukant K.
Published: October 2002

The semiconducting polymer poly(3-hexylthiophene) (P3HT) has been previously used to fabricate Schottky barriers and metal-insulator-semiconductor (MIS) tunnel diodes using indium as the blocking contact. When P3HT is doped with FeCl3, the conductivity increases and the polymer behaves as a p-type semiconductor. Schottky junctions fabricated on the doped material exhibited higher rectification ratios than equivalent junctions fabricated on undoped material. An indium contact evaporated on FeCl3-doped P3HT film gave the current-voltage ( I-V) characteristics of a minority carrier tunnel diode. Similar I-V characteristics were observed when a thin insulating polymer film was placed between the indium contact and the doped P3HT film.
Changes in Physical Property of Epoxy Resin with Absorption of Methyl Alcohol and Water
Authors: Wada Ken , Hiroshi Nohara Hiroshi Nohara , Ryuichi Shintani Ryuichi Shintani
Published: October 2002

Changes in physical properties with absorption of methyl alcohol and water were investigated. Upon CH3OH absorption, a boundary front appeared between the shell and core. The change in physical properties with absorption depended on the solvent and the volume absorbed. For example, when CH3OH of about 11 wt% was absorbed, Young's modulus decreased from 3.0×108 to 4.9×106 N/m2. In the case of H2O absorption (1 wt%), Young's modulus changed only slightly to 1.7×108 N/m2. The glass transition temperature T
g shifted down to room temperature upon CH3OH absorption, but did not shift upon H2O absorption.
Growth Conditions and Some Properties of TmB4and TmAlB4Single Crystals Obtained from High-Temperature Aluminium Metal Solution
Authors: Okada Shigeru , Kudou Kunio , Yu Yang , Lundström Torsten
Published: October 2002

TmB4and TmAlB4single crystals were obtained by the high-temperature aluminium solution method using thulium oxide powder and crystalline boron powder as starting materials. The optimum conditions to obtained relatively large crystals mentioned above were found to include soaking temperature 1500°C, soaking time 10 h, cooling rate 50°C·h-1and the atomic ratios of starting materials: B/Tm=5.5, Al/Tm=119.25 for TmB4; B/Tm=2.0, Al/Tm=119.25 for TmAlB4. In the case of TmB4, polyhedra single crystals were obtained. The ternary single crystals TmAlB4were generally obtained in the form of prismatic shape extending in the <001> direction or with well developed (100) faces. The as-grown TmB4and TmAlB4single crystals were used for chemical analysis and measurements of unit cell dimensions. Densities, microhardness and electrical resistivity of the as-grown crystals was studied.
Infrared Thermal Chemical Vapor Deposition of Thin SiN Film on InP: Dependence of Deposition Rate and Film Characteristics on Pressure and Gas Flux Ratio
Authors: Shin-ichiro Uekusa Shin-ichiro Uekusa , Yoshichika Mizuno Yoshichika Mizuno
Published: October 2002

The dependences of the film deposition rate and the film characteristics on the pressure and the gas flux ratio ( NH3/Si2H6) are investigated. A thin SiN film is deposited on InP substrate in the very wide pressure range from 1 to 100 Torr and in the very wide gas flux ratio range from 50 to 1300. The film thickness, the refractive index of the films and the capacitance of the MIS diodes are measured. The film surface morphology is observed by microphotography. As a result, it is shown that the deposition rate increases drastically as the pressure increases, that the film surface becomes smooth in the gas flux ratio range from 50 to 500 at 5 Torr, and from 800 to 1300 at 10 Torr, and that the minimum values of the refractive index and the surface state density (N
SS) of the film deposited at 10 Torr and flux ratio of 1000 are 2.01 and 2.21×1011 cm-2eV-1, respectively.
Wetting Kinetics and the Interfacial Interaction Behavior between Electroless Ni–Cu–P and Molten Solder
Authors: Chwan-Ying Lee Chwan-Ying Lee , Kwang-Lung Lin Kwang-Lung Lin
Published: October 2002

Formation of intermetallic compounds and wetting kinetics between an electroless Ni–Cu–P deposit and molten solder were investigated. The microstructure and phase of the interface were investigated with the aid of scanning electron microscopy (SEM) and X-ray diffractometry (XRD). Intermetallic compounds Ni3Sn4 and Ni3Sn2 were formed between Ni–Cu–P deposit and solder with Cu existing in the intermetallic layer. The contact angles of molten solder on a Ni–Cu–P deposit, measured with the sessile drop method, decrease with increasing temperature and time. The activation energy for wetting of molten solder on a Ni–Co–P deposit was estimated to be 193.7 kJ mol-1.
Production Mechanism of a Large-Diameter Uniform Electron Cyclotron Resonance Plasma Generated by a Circular TE01 Mode Microwave
Authors: Hirotsu Nobuyoshi , Yamaguchi Toru , Hidaka Ryota , Tanaka Masayoshi , Kawai Yoshinobu
Published: October 2002

To clarify the production mechanism of a large-diameter uniform electron cyclotron resonance (ECR) plasma generated by a circular TE01 mode microwave experimentally, the wave propagation characteristic in the plasma is measured with an interferometer. It is shown that a microwave introduced into the chamber is transformed mainly into an electron cyclotron wave and then entirely absorbed around the resonance point. Furthermore, it is experimentally proven that the correspondence between the radial distribution of the electric field intensity of injected microwaves and that of waves propagating in plasma may depend on the magnetic field intensity around the injection point. It is also confirmed that it is necessary to optimize the magnetic field configuration to generate a uniform ECR plasma since the absorption region of microwaves is as wide as from ω/ω
c
e
∼0.65 to adjacent to the resonance point.
Density Distributions in Cylindrical and Rectangular Plasma Sources
Authors: Hitoshi Nihei Hitoshi Nihei
Published: October 2002

The plasma density distributions in plasma sources with cylindrical and rectangular configurations are obtained by solving the diffusion equation based on a plasma model. In this model, the initial density distribution is given at the upper stream of each source, and the side walls of the plasma chambers are surrounded by magnetic multipole fields in order to obtain a uniform high-density plasma on the target wall. The results give the density distributions in the sources and the plasma particle fluxes flowing into the target walls. The forms of the initial density distribution in the upper stream of each source are also discussed. Calculated examples are shown for cylindrically unsymmetric and rectangular configurations. The equations derived in this paper are useful for the design of plasma sources capable of generating a uniform high-density plasma over a wide area.
Rejection Band in Waveguide Filled with Cold Magnetoactive Plasma
Authors: Alexov Emil G. , Kapchinskii Stefan T. Ivanov
Published: October 2002

A rejection band in the spectrum of the eigenmodes of a waveguide filled with cold collisionless magnetoactive plasma has been found. This rejection band lies above the upper hybrid frequency. The width of the rejection band has been investigated varying the values of the magnetic field, the plasma concentration and the waveguide radius. It is shown that the rejection band at low plasma concentration can be used for creating a microwave attenuator controlled by external magnetic field.
A Monte Carlo Simulation of Langmuir Probe Methods for Plasmas Having RF Amplitude Oscillations
Authors: Matsuoka Akio , Kondoh Yoshiomi , Onozato Atsushi , Tsurubuchi Iwao , Sato Koichi , Minoru Sugawara Minoru Sugawara
Published: October 2002

A Monte Carlo simulation model to analyze Langmuir probe characteristics is developed for an ideal plane probe in plasmas having rf oscillations of space potential only. When the oscillation amplitude is larger than electron temperature, plasma parameters determined with this model agree with those predicted by the simple probe theory with space potential oscillations. Space potential shifts and deformed probe characteristics for an rf discharge are explained by profiles of space/time electron density, energy and potential gained from these probe simulations with rf space potential oscillations.
Carrier Injection Characteristics of Organic Electroluminescent Devices
Authors: Egusa Syun , Miura Akira , Azuma Nobuhiro Gemma
Published: October 2002

The junction characteristics of metal/organic (M/Org) and organic/organic (Org/Org) interfaces, composing an organic electroluminescent (EL) device, M/Alq3/Diamine/ITO, were studied by measuring the displacement current characteristics of M/Org/Org/ SiO2/Si structures. The M/Alq3 junction was found to be both electron and hole injective, depending on the metal electrode. As for the Alq3/Diamine interface, it was found that two band offsets (Φ VB and Φ CB) existed for respective valence and conduction bands. Φ VB was not very large, and holes in Diamine were able to pass through into the adjacent Alq3 layer by applying a forward-bias, but Φ CB was so large that the electrons in Alq3 were blocked. Based on the standpoint that characteristics of the organic thin-film devices are governed by those junctions, we discussed carrier-injection mechanism, and explain the efficient EL emission.
Ionization Potential of Ni Obtained from the Observation of High Rydberg Series
Authors: Toshiaki Ishikawa Toshiaki Ishikawa
Published: October 2002

A series of the Rydberg states of Ni with quantum numbers n
′= 17 to 34 produced by a three-step selective excitation process using three tunable dye lasers are measured by a photoionization technique. It is found that the least squares fitting of the Rydberg-Ritz formula to the observed Rydberg series yields the ionization potential of E
i= 61616.3 cm-1±2.5 cm-1.
Shock Tube Using Free Piston Driven by Detonation Waves
Authors: Kunio Terao Kunio Terao , Tomonobu Furushoh Tomonobu Furushoh
Published: October 2002

In order to improve and simplify the Stalker tube, a shock tube having a free piston driven by detonation waves is developed and examined. The free piston accelerated in a long vacuum tube enters into the He shock driver gas with a velocity higher than 300 m/s, producing a shock wave at its front. Due to the repeating shock wave reflections between the piston and diaphragm set at the end of the driver-gas tube, the He driver gas is compressed and heated to a pressure and temperature much higher than those produced by isentropic compression. Applying this driver gas of high pressure and temperature, strong shock waves having a Mach number from 10 to 15 are produced in argon in the low-pressure tube. The results also suggest that much stronger shock waves can be produced in low-pressure argon by enlarging the size and honing the inner sides of the tubes.
Problem of Acoustic Absorption Measurement by Composite Oscillator Method: Low-Temperature Internal Friction Peaks in Quartz
Authors: Toshio Kosugi Toshio Kosugi
Published: October 2002

It is demonstrated that accurate measurements of internal friction can be made by a two-component composite oscillator method (COM), which was first proposed by Schwarz [Rev. Sci. Instrum. 48 (1977) 111]. The problems concerning COM are also discussed; in particular, the influence of the internal friction peaks in quartz used as a piezoelectric transducer is discussed for the first time.
Raman Scattering Study of Boson Peaks in Cesium Borate Glass
Authors: Kodama Seiji Kojima
Published: October 2002

The composition dependence of Raman spectra was measured to study the borate anomaly in cesium borate glass. The changes of structural groups were estimated by the internal vibrational bands. The boson peak of pure borate glass is well fitted only by the function deduced from the disorder-induced model, whereas that of cesium borate glass cannot be fitted in the same manner. This strongly suggests that the disorder induced-model cannot be applied to the binary system which contains many types of structural groups.
Dynamics of V2O5 Sol by Measurement of Ultrasonically Induced Birefringence
Authors: Keiji Yasuda Keiji Yasuda , Tatsuro Matsuoka Tatsuro Matsuoka , Shinobu Koda Shinobu Koda , Hiroyasu Nomura Hiroyasu Nomura
Published: October 2002

Ultrasonically induced birefringence of the divanadium pentaoxide ( V2O5) sol was investigated as a function of the ultrasonic amplitude, temperature and concentration. The birefringence of the sol was proportional to the volume fraction and the square of ultrasonic amplitude. Orientational relaxation times were also evaluated from the analysis of the transient birefringence spectrum. Temperature and concentration dependences of the orientational relaxation times were interpreted in terms of the change in the solution viscosity and shown to follow the Debye-Einstein equation. The particle length of V2O5 sol estimated from the experimental results was on the same order as that obtained from the transmission electron micrograph.
Propagating Properties of Surface Wave in Sol-Gel Transition of Tungstic Acid
Authors: Motonaga Kazuhiro , Okabe Hirotaka , Matsushige Kazuhiro Hara
Published: October 2002

The gelation process of tungstic acid was investigated by observing surface waves at two points on a sample surface. We used a deflected-light detection system, in which the surface waves were excited with a PZT bimorph vibrator. From the propagation time (δt) between the two isolated measuring points, surface wave velocity was calculated. We also estimated attenuation of the surface wave from the ratio of the observed amplitudes at the measuring points. Around the gelation time (t
g), which was determined by the tilting test, a marked increase in the surface wave velocity was observed. The attenuation coefficient showed frequency dispersion in the frequency range from 20 to 60 Hz, which reached a maximum value around t
g.
Diffraction Effect on Phase Deviation Caused by Nonlinear Interaction between Two Sound Waves in Measuring Spatial Distribution of Nonlinearity Parameter B/A
Authors: Akihito Kato Akihito Kato , Yoshiaki Watanabe Yoshiaki Watanabe
Published: October 2002

This paper discusses the diffraction effect appearing in the phase deviation by the nonlinear interaction of sound by sound. The correction method for the diffraction effect in measuring spatial distribution of nonlinearity parameter B/A was also examined. The diffraction wave from the edge of the transducer was considered in the measurement system for the spatial distribution of B/A, in which a transducer is located in the path of another wave. The diffraction effect on the phase deviations was theoretically estimated. Numerical calculation and experiments using a simple model clarified the diffraction effect on the spatial distribution of B/A. The method for quantitative estimation and elimination of the diffraction effect was proposed. The optimal conditions for the measurement were also investigated.
Linear Array Probe Using Biconcave Transducers
Authors: Hidekazu Tai Hidekazu Tai , Tsutomu Kobayashi Tsutomu Kobayashi
Published: October 2002

Recently, ultrasonic transducers with high resolution have been required in the field of ultrasonic diagnosis. The biconcave transducer treated in this paper will be suitable for this purpose, because this transducer has the features of focusing and damping effects, in the case of the radiation of ultrasonic pulse waves. These features are expected to lead to high lateral and time resolutions for the detection of a small object. We try to fabricate a probe of the linear array type using the biconcave transducers for ultrasonic diagnostic equipment, then some of its characteristics are investigated to determine whether this probe is suitable for the detection of a small object by the pulse echo method.
New Airborne Ultrasonic Transducer with High Output Sound Pressure Level
Authors: Okada Hirofumi , Kurosawa Minoru , Ueha Sadayuki , Masuda Michiyuki
Published: October 2002

To design a higher output ultrasonic sensor, reduction of stress in a piezoelectric element is required. For this purpose, a new transducer with vibrating parts for an ultrasonic sensor is proposed in this paper, in which we utilize an annular piezoelectric element bonded on three kinds of plates, stainless steel, titanium and aluminum, vibrating at its fundamental flexural mode. Our fabricated model gave a 10 to 20 dB higher output sound pressure level compared with a conventional enclosed-type ultrasonic transducer. From the results of our study, the output sound pressure level can be increased much more by selecting the material of the vibrating plate.
Ultrasonic Micromanipulation of Small Particles in Liquid
Authors: Masao Takeuchi Masao Takeuchi , Kazuhiko Yamanouchi Kazuhiko Yamanouchi
Published: October 2002

New ultrasonic micromanipulation techniques for small particles in liquid based on the forces due to radiation pressure of high-frequency ultrasound are proposed, using VHF-range leaky wave transducers. The proposed manipulator has the advantages of the efficient generation of high-frequency ultrasonic waves into very small quantities of liquid containing small particles such as biomaterials, and the isolation of electrodes of the transducer from the liquid. Transportation and trapping of 100-µm-diameter small glass spheres in water are confirmed by preliminary experiments at a frequency of 49 MHz and acoustic intensity of about 8 mW/mm2.
Ultrasonic Plastic Welding Using 90 kHz Upper and Lower Vibration Systems
Authors: Tsujino Jiromaru , Ishii Yasuhiro , Toshiyuki Shiraki Toshiyuki Shiraki , Hiroyuki Yamazaki Hiroyuki Yamazaki
Published: October 2002

Direct and transmission welding characteristics of an ultrasonic plastic welding system using 90 kHz upper and lower vibration systems are studied. By using high frequency, welding characteristics of plastic specimens may be improved because ultrasonic vibration absorption by plastic material increases as vibration frequency increases. The 90 kHz ultrasonic vibration source designed consists of a radial-to-longitudinal vibration direction converter with four bolt-clamped Langevin-type piezoelectric ceramic (lead-zircon-titanate; PZT) transducers of 15 mm in diameter. The 90 kHz welding equipment consists of two vibration sources positioned at upper and lower parts and a welding frame. In the case of direct welding of various sheet specimens, the required total velocity of 90 kHz upper and lower welding tips is less than 60% that of 27 kHz welding tips. Direct and transmission welding characteristics of a 90 kHz welding system with two vibration sources are significantly improved compared with those of conventional systems.
A Self-Oscillation-Type Ultrasonic Linear Actuator
Authors: Kohji Toda Kohji Toda , Hiroshi Tokumaru Hiroshi Tokumaru
Published: October 2002

A cylindrical piezoelectric ceramic vibrator with two half-moon-shaped electrodes on a flat surface is described as a key device for constructing a linear actuator. The unidirectional mechanical force, arising from two coupled vibration modes, on the side surface of the ceramic column plays the role of a stator for the actuator operation. A practical power-feeding circuit composed of the piezoelectric ceramic column with three electrode terminals and a transistor for power amplification is demonstrated successfully under a stable, continuous actuator operation. The size of the ceramic vibrator used for the present linear actuator is 10 mm in diameter and 10 mm in length. The directionality of linear actuator operation is changeable. The response time to the steady state from zero is on the order of ms.
Effects of Ultrasound on Extraction of Saponin from Ginseng
Authors: Li Hui , Etsuzo Ohdaira Etsuzo Ohdaira , Masao Ide Masao Ide
Published: October 2002

We performed a study of the effects of ultrasound on the extraction of saponin from Panax ginseng C. A. Meyer. In this study, the extraction of saponin was examined as functions of irradiation time (0.5 to 6 h) and acoustic pressure (0 to 90 kPa). It has been observed that the yields of both total extract and saponin are larger with ultrasonic irradiation than those without ultrasonic irradiation; the increase in yield of total extract is approximately 15 wt%, and that of saponin is approximately 30 wt% at an acoustic pressure 67 kPa. In addition, the yield increases with the acoustic pressure. It is also demonstrated that saponin was not resolved in the acoustic intensity range of this experiment. The enhancement in liquid-solid extraction caused by ultrasound can be attributed to the phenomenon of cavitation.
New Application of Shear Horizontal Surface Acoustic Wave Sensors to Identifying Fruit Juices
Authors: Jun Kondoh Jun Kondoh , Showko Shiokawa Showko Shiokawa
Published: October 2002

The objective of this paper is to present a new application of shear horizontal surface acoustic wave (SH-SAW) devices on 36° rotated Y-cut X-propagating LiTaO3 for a sensing system that can identify liquid samples, such as fruit juices. Theoretical sensor sensitivity for acoustoelectric interaction with a liquid loaded on the SAW propagation surface was derived and confirmed with experimental results. The results strongly suggested that by employing SH-SAW devices with different center frequencies the sensor can recognize many liquid samples without a film coated on the substrate surface. In the experiment, the sensing system which identifies fruit juices was fabricated using three SH-SAW devices with center frequencies of 30, 50, and 100 MHz. Identification of samples, eleven kinds of fruit juices, was achieved by classification in principal component analysis and discriminant analysis. Since the SH-SAW sensor without a coating film has intrinsically good reproducibility and stability, it is effective for identification and quality control of liquid samples.
Power Difference in Spectrum of Sound Radiation before and after Break of Phantom by Piezoelectric Extracorporeal Shock Wave Lithotriptor
Authors: Hiroshi Kanai Hiroshi Kanai , Yun-Seok Jang Yun-Seok Jang , Noriyoshi Chubachi Noriyoshi Chubachi , Yoshikatsu Tanahashi Yoshikatsu Tanahashi
Published: October 2002

This paper investigates the difference in the spectrum of sound radiated before and after the break of a phantom at a focal point of the piezoelectric extracorporeal shock wave lithotriptor (ESWL) in order to identify the break time or to examine whether a calculus exists exactly at the focal point or not. From the preliminary experiments using a piece of chalk as a phantom of a calculus to measure the sound radiated when impact is applied to the chalk by an impact hammer, it is found that the bending vibration component of the vibration is exhibited in the spectrum of sound. However, for small-sized chalk shorter than 3 cm, the peak frequency of the bending vibration is higher than 20 kHz. From the experiments using a piezoeletric ESWL, it is found that there is clear difference in the power spectra among the sound radiated before the break, that radiated just after the break in the breaking process, and that radiated when the chalk does not exist at the focal point of the ESWL. These characteristics will be effective for the examination of the existence of the calculus at the focal point.
Three-Dimensional Echography by a Spherical Pulsed Wave
Authors: Hirofumi Tojo Hirofumi Tojo , Osamu Oshiro Osamu Oshiro , Kunihiro Chihara Kunihiro Chihara , Masato Asao Masato Asao
Published: October 2002

We developed a new ultrasonic imaging system to obtain a three-dimensional echogram in a blood vessel. The method makes it possible to detect the echo signal from objects rapidly without scanning using a ring array probe. The experiments are performed on a sliced ham and a rabbit heart. The results show that a 3-mm-diameter hole in the ham can be detected and that the three-dimensional structure in the left ventricle can be reconstructed by this system.
Reconstruction of Three-Dimensional Images of Surface Acoustic Waves by Means of Computer-Controlled Laser Probe
Authors: Yoshimine Tatsuki , Katoh Hideki , Igari Takahiro , Kavalerov Vadim G. , Mitsuteru Inoue Mitsuteru Inoue , Toshitaka Fujii Toshitaka Fujii
Published: October 2002

A computer-controlled laser probe surface-acoustic-wave (SAW) observation system was constructed, which facilitates reconstruction of 3-dimensional images of travelling Rayleigh SAWs. Vivid images of a propagating single SAW and two colliding SAWs on a glass plate were observed by this system. The system is thus used as a powerful tool for elucidating the dynamic behaviors of SAW, especially for identification of surface acoustic solitons.
An Investigation on Practicability of Reflection Mode Diffraction Tomography
Authors: Hamamoto Kazuhiko , Shiina Tsuyoshi , Ito Masayasu
Published: October 2002

Reflection mode diffraction tomography is expected to reconstruct a more quantitative and higher resolution image than pulse-echo ultrasonic imaging. It is, however, necessary for its practical use, e.g., in medical applications to consider the influences of the lack of low frequency information, insonifying angle restriction, finite aperture and noise. In this work, these effects are investigated using the reconstruction algorithm which we have proposed combined with the maximum entropy method and a priori information on objects in order to evaluate the practicability of reflection mode diffraction tomography. Results reveal that it is possible to reconstruct quantitative and high resolution images under practical conditions of measurement because the algorithm works as reducing noise and restoring low frequency information.
Image Reconstruction of Ultrasonic Diffraction Tomography from Data Acquired with Transmitter and Receiver Arrays
Authors: Hiroaki Kataoka Hiroaki Kataoka , Tomoki Yokoyama Tomoki Yokoyama , Koichi Mizutani Koichi Mizutani , Keinosuke Nagai Keinosuke Nagai
Published: October 2002

In this paper we propose a new method of data acquisition and image reconstruction for ultrasonic diffraction tomography. We introduce transmitter and receiver arrays to speed up the data acquisition. We design the arrays to obtain a large amount of data with a comparatively small number of transducer-elements. We also discuss the imaging algorithm from data thus acquired. The imaging capability of the method is confirmed by numerical simulation.
Optical Probe Detection of High-Frequency Surface Acoustic Waves Generated by Phase Velocity Scanning of Laser Interference Fringes
Authors: Nishino Hideo , Tsukahara Yusuke , Nagata Yoshihiko , Koda Toshio , Yamanaka Kazushi
Published: October 2002

Laser-generated high-frequency surface acoustic waves (SAWs) and their optical detection for noncontact and nondestructive materials evaluation were presented. Scanning interference fringes (SIF) produced by intersecting two coherent pulsed laser beams on a tested object with different frequencies were used as a thermoelastic source to generate a 110 MHz SAW. The SAW was detected by the optical knife edge method using another continuous wave (CW) laser as a probe beam. Estimation of the SAW amplitude was carried out and the amplitude enhancement effect of the phase velocity scanning (PVS) method was verified. As a result, the SAW amplitude of 1.4 nm was obtained on an aluminum specimen with 0.71 MW/cm2power density of second-harmonic waves (532 nm) of a Q-switched Nd:YAG laser. An application to anisotropic SAW velocity measurement on a silicon (100) surface was carried out.
Defects in SiO2/Si Structures Probed by Using a Monoenergetic Positron Beam
Authors: Uedono Akira , Wei Long , Ohji Shoichiro Tanigawa
Published: October 2002

Defects in SiO2/Si specimens were probed by using a monoenergetic positron beam. Doppler broadening profiles of the annihilation radiation were measured as a function of incident positron energy for SiO2(100 nm)/Si specimens fabricated by wet, dry and ultradry oxidation. The diffusion of positrons in the Si substrate was found to be enhanced by an electric field caused by positive charges near the SiO2/Si interface. The Doppler broadening profile corresponding to the annihilation of positrons in the Si substrate with the SiO2film grown by wet oxidation was found to be broader than those in the specimens fabricated by dry or ultradry oxidation. This was attributed to the fact that the concentration of oxygen clusters in the Si substrate for the specimen fabricated by wet oxidation was higher than those for the specimens fabricated by dry or ultradry oxidation.
Confirmation of Aluminum-Induced Negative Charge in Thermally Oxidized Silicon Wafers Using AC Surface Photovoltage Method
Authors: Munakata Hirofumi Shimizu
Published: October 2002

The ac surface photovoltage (SPV) technique is applied for detecting the polarity of charge in thermally-oxidized silicon (Si) wafers, in which aluminum (Al) is deliberately incorporated in the native oxide. Upon thermal oxidation, most of the Al is contained in the oxide and it segregates at the very top of the oxide layer. With the increase of Al concentration in the oxide, ac SPV appears and increases for oxidized n-type Si wafers, whereas in p-type Si it decreases, indicating that Al acts as a negative charge by forming the (AlOSi)-network and compensates the positive fixed oxide charge. With the removal of the surface layer, for n-type Si, ac SPV disappears, whereas for p-type Si, it appears because the net positive fixed oxide charge becomes dominant.
Piezoelectric Sensor for Detecting Force Gradients in Atomic Force Microscopy
Authors: Toshihiro Itoh Toshihiro Itoh , Tadatomo Suga Tadatomo Suga
Published: October 2002

This paper presents a piezoelectric sensor for detecting force gradients in the noncontact atomic force microscope (AFM). To simplify the force gradient detecting system of the noncontact AFM, the direct sensing cantilever with a ZnO piezoelectric film has been developed. The signal related to the vibration amplitude of the cantilever end is measurable by detecting the charge induced by the piezoelectric effect. The gradient of the force between the tip of the vibrating cantilever driven by an external oscillator and the sample modifies the vibration amplitude of the lever, hence inducing a change of the piezoelectric charge signal. We have adapted the transfer matrix method for calculating the change of the piezoelectric charge due to the gradient of the force. The piezo-electric signal trace has been recorded as a function of sample displacement. We have converted the recorded data to force gradients using a transfer matrix.
High-Performance In0.3Ga0.7As/In0.29Al0.71As/GaAs Metamorphic High-Electron-Mobility Transistor
Authors: Win Pascal , Druelle Yves , Cordier Yvon , Adam Didier , Favre Jacques , Alain Cappy Alain Cappy
Published: October 2002

A new high-electron-mobility transistor (HEMT) using InAlAs/InGaAs grown by molecular beam epitaxy on GaAs has been successfully realized. This device, having an In content close to 30%, presents several advantages over conventional pseudomorphic HEMTs on GaAs as well as over lattice matched HEMTs on InP. High electron mobility with high two-dimensional electron gas density ( 25000 cm2/V·s with 3×1012 cm-2 at 77 K) as well as high Schottky barrier quality (V
b=0.68 V with η= 1.1) has been obtained for this material system. A 0.4-µm-gate-length device showed an intrinsic transconductance as high as 700 mS/mm with
f
t=45 GHz and f
max
=115 GHz while a minimum noise figure of N
F
min
=1.1 dB at 18 GHz has been obtained with a 0.2 µm device. This performance is, to the authors' knowledge, the first reported for submicrometer-gate metamorphic InAlAs/InGaAs/GaAs HEMTs.
Light Trapping for Thin-Film Silicon Solar Cells Fabricated on Insulator
Authors: Sasaki Hajime , Morikawa Hiroaki , Matsuno Yoshinori , Deguchi Mikio , Ishihara Takashi , Kumabe Hisao , Murotani Toshio , Shigeru Mitsui Shigeru Mitsui
Published: October 2002

We have developed a new solar cell using thin-film silicon supported by a silicon substrate etched in a grid form. The light-trapping structures of this cell have been studied by considering rear surface light reflections, electrical power loss and mechanical strength. High rear reflectance can be obtained by employing a multi-layer rear electrode. The pattern of the rear substrate is designed to provide sufficient mechanical strength and to minimize the electrical power loss, taking account of the current flow path. A conversion efficiency of 14.2% for a practical size of 10×10 cm2 is obtained by applying these calculated parameters using a single-crystal silicon substrate.
Dynamic Thermal Response of Photomasks Caused by Excimer Laser Pulse
Authors: Akira Chiba Akira Chiba , Yaichiro Watakabe Yaichiro Watakabe
Published: October 2002

Theoretical calculations have been performed to obtain information on the dynamic thermoelasticity in photomasks during pulsed exposure due to a KrF excimer laser stepper. A dynamic model based on lumped heat capacity and in-plane stress systems has been proposed. The calculations were performed at an 8 µ J/cm2 energy density with pulse duration of 15 ns. It was found that the displacement caused by thermal expansion takes place at a 10 µ s time lapse after pulsed exposure, while there is no influence on the printed feature shift. Since the resonance frequency of 7.14 kHz is higher than the practical pulse repetition frequency of 200∼800 Hz, the photomasks cannot receive thermal damage due to the resonance. Therefore, excimer laser lithography based on pulsed exposure will be a useful method for fabricating sub-half-micron LSI devices.
Critical Current Dependence on Deformation Kinetics in Textured YBa2Cu3OxSuperconductor
Authors: Zhang Youhe , Selvamanickam Venkat , Dominic F. Lee Dominic F. Lee , Kamel Salama Kamel Salama
Published: October 2002

The dependence of critical current on the deformation kinetics has been examined in melt-textured YBa2Cu3Oxsuperconductors that were subjected to uniaxial high temperature deformation. TheJcof the deformed superconductors is found to increase with deformation time at all magnetic field orientations with respect to thea-bplane. The rate of increase inJcis found to subside after 12 h of deformation. The deformation time dependence ofJchas been analyzed within the framework of high temperature creep, and is found to be very similar to the deformation time dependence of mechanical strain. The rate ofJcincrease in the secondary creep stage is found to be significantly higher in the orientation ofH//cresulting in a lower anisotropy with increasing deformation time. TheJccharacteristics suggest that an anisotropic defect structure is created after longer periods of deformation, and that the defects responsible for flux pinning are introduced by thermal activation.
Characterization by Chemical Etching for Superconducting Bi2Sr2CaCu2O8Crystals Grown by CO2-Laser Melting
Authors: Ishida Katsuei , Tsutsumi Takuya , Iida Masamori , Nakada Ichiroh , Kuroda Kazuo
Published: October 2002

Single crystals are grown directly from the melt in a rough size of (0.5–1.5)×(0.2–0.5)×(0.05–0.1) mm3. Comparing a pair of opposite surfaces created by cleaving, it has been recognized that the microstep line structure with the unit cell steps is generated at the instant of cleaving the crystal. With the aid of chemical etching it has further been clarified that the cleavage plane fractures into terraces hemmed by unit cell steps at crossing spiral dislocations. Simultaneously it has been proved that beak-pits observed among etch figures indicate the outcrop of dislocations. In addition it has been revealed by etching that stacking faults in a plane are involved in the crystal along the crystallographica-axis.
Emission Energy Shift in GaInAs/GaInAsP Strained Quantum-Box Structures Due to 0-Dimensional Quantum-Box Effect
Authors: Hideki Hirayama Hideki Hirayama , Kazuhisa Matsunaga Kazuhisa Matsunaga , Masahiro Asada Masahiro Asada , Tsukasa Kakinuma Tsukasa Kakinuma , Machiya Kumazawa Machiya Kumazawa
Published: October 2002

We report, for the first time, the emission energy shift in GaInAs/GaInAsP quantum-box (QB) structures due to an obvious 0-dimensional quantum-box size effect. Ga1-xInxAs QBs withx=0.33 (tensile), 0.53 (unstrained), and 0.70 (compressive) were embedded in a GaInAsP (band-gap wavelength of 1.1 µm) optical absorption layer. These QB samples were fabricated by 2-step organometallic vapor-phase-epitaxy (OMVPE) growth, cross line lithography with electron-beam-exposure (EBX) direct writing, and the wet chemical etching process. The pitch of the QB array was 100 nm. The size of the boxes was controlled by changing the EB line dose, and measured by scanning electron microscope (SEM) to be 152–402nm2. Photoluminescence spectra at liquid helium temperature were measured. The emission peak of unstrained (US)-QB samples shifted from that of the reference quantum-film (QF) sample due to an obvious 0-dimensional quantum-size effect. This QB effect was investigated for US-, tensile (T)- and compressive-strained (CS)-QB structures systematically. Energy shift obtained for the CS-QB sample (ΔE=45–63 meV) is much larger than those for US-QB (9–19 meV) and TS-QB (19–23 meV) samples with the same box size (S=252nm2) by factors of 3–4 and 2–3 times, respectively. This is because of the reduction of the lateral hole effective mass in the compressive-strained case. From these results, we found that compressive-strained structure is expected to be more advantageous for low-threshold QB lasers.
Plasma-Sheath Boundary in Plasmas Containing Thermal and Beam Electrons
Authors: James W. Bradley James W. Bradley , Hiroshi Amemiya Hiroshi Amemiya
Published: October 2002

The behaviour of the plasma-sheath boundary in the presence of beam electrons with finite temperature is modelled assuming a criterion for sheath formation. Solutions for the sheath edge potential are found from two separate treatments; a charge balance model and a dispersion relation description of the plasma. Ion saturation currents and floating potentials are determined as a function of the beam-plasma parameters. The results of this investigation can be used to predict the plasma properties at the surface of a substrate in process plasma discharges containing thermal electron beams.
Microwave Measurements of Low Pulp Concentration in Papermaking Process
Authors: Shigeru Nakayama Shigeru Nakayama
Published: October 2002

A method of microwave measurements of low pulp concentrations in the papermaking process is developed using a coaxial cavity resonator with an inner slot antenna. We measure the attenuation of the resonant peak of the cavity resonator which is related to the pulp concentration. The pulp concentration up to 10.1% is measured, and then the linear relationship between the attenuation and low pulp concentrations down to 0.6% is determined. By this method, a low pulp concentration can be measured within the standard deviation of 0.03% by linear approximation.
Modified Lumped Parameter Method for Measurements of Dielectric Susceptibility in Ferroelectrics
Authors: Li Shaoping , Sheen Jyh , Jang Sei-Joo , Bhalla Amar S. , Robert E. Newnham Robert E. Newnham , L. Eric Cross L. Eric Cross
Published: October 2002

The transmission techniques for dielectric measurements can be classified into two categories; one belongs to the lumped capacitance method and the other is related to the distributed parameter method. In reality, however, the dielectric dispersion for high dielectric constant materials in the frequency range 1 MHz–5 GHz could not be made accurately by using the transmission techniques. In this work, a modified lumped parameter method has been discussed. We call this modified method as the quasi lumped parameter method which is especially suitable for the microwave measurements of dielectric dispersion for high dielectric materials in a particular frequency region. The proposed method combines some features of both the lumped parameter method and the distributed parameter method. By using this measurement method, the measurements of dielectric dispersions are presented for several ferroelectric materals, such as Pb(Zr1-
x

Ti

x

)O3, and BaTiO3 in the frequency domain from 1 MHz to 1 GHz.
Blister Formation at Photoresist-Substrate Interface
Authors: Nagata Hitoshi , Kawai Akira , Takata Hiroaki Morimoto
Published: October 2002

We report the formation mechanism of a blister at the photoresist-substrate interface during exposure to ultraviolet (UV) light. It is found that the blister formation strongly depends on the following factors: (i) photoactive-compound (PAC) concentration of the photoresist film and (ii) adhesion energy between the photoresist film and the substrate. Formation parameter U, which represents the difference between the adhesion energy and the strain energy of the photoresist film, can be utilized for predicting the blister formation.
Effects of External Body Accelerations on Blood Flow
Authors: Srivastava Lalit M. , Edemeka U. E. , Srivastava Vijai P.
Published: October 2002

A mathematical model of blood flow in single arteries and arterioles subject to both the pulsatile pressure gradient due to normal heart action and a single cycle of body acceleration is presented. The body acceleration is such that it increases from zero to a maximum value at a uniform rate, remains constant at this maximum value for some time and thereafter returns to zero at a uniform rate. To account for the red cells in blood, blood is considered to be a two-phase fluid, that is, a suspension of red cells in plasma. Numerical results are presented for the effects of body acceleration on flow variables, such as, flow rate, velocity, acceleration and shear stress corresponding to the flow of blood in the human aorta and arterioles.
Scanning Tunneling Microscope Observation of Si(111)–3×1–Ag Structure
Authors: Ohnishi Hideaki , Katayama Itsuo , Ohba Yasuyuki , Kenjiro Oura Kenjiro Oura
Published: October 2002

A scanning tunneling microscope has been used to study the Si(111)-3×1-Ag surface. The 3×1-Ag surface has been observed to consist of a bright row and small protrusions; the bright row points in the <1̄10> direction and the protrusions point in the <123̄> and <213̄> directions. The width of 3×1-A
g domains, nucleated on the Si-7×7 terraces, has been found to be (21n-2)a, where n is an integer (n=1, 2,···) and a is the lattice constant of Si (a=3.84 Å). Detailed investigation on domain boundaries reveals that both sides of the 3×1-Ag domain face the unfaulted halves of the 7×7 structure. Moreover, two types of domain boundaries have been observed: one which runs across the corner holes, and another is that runs apart from the corner holes, leaving a narrow 7×7 terrace of one adatom width. Possible structural models for the 3×1-Ag surface are proposed based on the present STM results.
Atomic Force Microscopy in Ultrahigh Vacuum
Authors: Franz Josef Giessibl Franz Josef Giessibl
Published: October 2002

Since its invention in 1986, atomic force microscopy (AFM) has been used mainly in ambient conditions. Recent advances in instrumentation have fostered the application of AFM in ultrahigh vacuum (UHV). AFM experiments performed in UHV have led to a better understanding of the tip-sample interaction. This article reviews the theory related to achieving true atomic resolution of AFM in UHV in both contact- and noncontact-modes. Preliminary experimental results with unprecedented resolution on KCl and Si (111)7×7 achieved by noncontact AFM in UHV are presented.
Tip-Induced Surface Disorder on Hydrogen-Terminated Silicon(111) Surface Observed by Ultrahigh-Vacuum Atomic Force Microscopy
Authors: Kageshima Masami , Yamada Hirofumi , Morita Yukinori , Tokumoto Hiroshi , Nakayama Kan , Akira Kawazu Akira Kawazu
Published: October 2002

A sequence of images of a hydrogen-terminated Si(111) surface showing its change to disordered structure observed with an ultrahigh-vacuum atomic force microscope (UHV-AFM) are presented. This phenomenon is in striking contrast with the stability of this surface seen in the previous observations. A change of the chemical nature of the AFM tip is likely to have caused this difference. The silicon oxide layer on the tip is considered to have been removed due to an accidental crash, and consequently the exposed silicon reacted with the sample.
Time Dependent Dielectric Breakdown of Thin Silicon Oxide Using Dense Contact Electrification
Authors: Fukano Yoshinobu , Hontani Koji , Uchihashi Takayuki , Okusako Takahiro , Chayahara Ayumi , Sugawara Yasuhiro , Yamanishi Yoshiki , Oasa Takahiko , Seizo Morita Seizo Morita
Published: October 2002

We achieved time dependent dielectric breakdown (TDDB) measurement of a thin silicon oxide microscopically using contact electrification. By increasing the external bias voltage, TDDBs of the oxide layer without and with oxide surface roughening were observed sequentially. Charge-to-breakdown in the contact electrification was estimated to be on the order of 10-5∼10-6 C/cm2. This value is higher than that of electrified charge density in the absence of external bias voltage, but is much smaller than the value of ∼5×10-1 C/cm2 obtained in the conventional TDDB measurement using a metal-oxide-semiconductor (MOS) capacitor. From calculation of the number of injected charges per atom, TDDB measurement using contact electrification is expected to provide a more quantitative evaluation of charge-to-breakdown than that using a MOS capacitor.
Atomic Force Microscopy Studies of Tabular AgBr Emulsion Grains
Authors: Nozoye Hisakazu , Takada Hiroshi
Published: October 2002

The (111) faces of photographic tabular emulsion grains (AgBr microcrystals) have been studied by atomic force microscopy (AFM). The oriented single layers of tabular emulsion grains were formed on indium tin oxide (ITO) bases, and atomic images of the surfaces of microcrystals were observed in air as well as in water. Although the atomic images of (111) surfaces of tabular emulsion grains observed in water coincide with the ideal atomic arrangement of the (111) face of an AgBr crystal, those observed in air do not.