bluuebunny/crossref_metadata_2025 huggingface dataset:
Trabecular Pattern Analysis Using Fractal Dimension
Authors: Ishida Takayuki , Yamashita Kazuya , Takigawa Atsushi , Kariya Komyo , Itoh Hiroshi
Published: February 2005

Feature extraction from a digitized image is advantageous for the detection of signs of disease. In this work, we attempted to evaluate bone trabecular pattern changes in osteoporosis using the fractal dimension and the root mean square (RMS) values. The relationship between the fractal dimension and the 1st moment of the power spectrum is explored, and we investigated the relationship between the results of this analysis and the bone mineral density (BMD) value which was measured using dual-energy X-ray absorptiometry (DEXA). As a result, we were able to extract useful information, using the fractal dimension and the RMS value of the radiographs (lateral view of the lumbar vertebrae), for the diagnosis of osteoporosis. Abnormal clinical cases were separated from normal cases based on the evaluation values. Negligible correlation between the BMD value and these indexes was observed.
Dependence of Open Circuit Voltage of Amorphous Silicon Solar Cells on Thickness and Doping Level of the p-Layer
Authors: Isomura Masao , Takahama Tsuyoshi , Shinya Tsuda Shinya Tsuda , Shoichi Nakano Shoichi Nakano
Published: February 2005

We have focused on the thickness and the boron-doping concentration of the p-layer of amorphous silicon solar cells and systematically obtained data for open circuit voltage (V
oc) and the built-in potential to reveal the mechanism causing a high V
oc. A highly doped p-layer gives a higher built-in potential in the entire thickness range, but V
oc is limited by the carrier recombination caused by the doping-induced defects. A low-doped p-layer causes a higher V
oc in a sufficiently thick film because less carrier recombination occurs due to the lower density of the doping-induced defects. After light-soaking, significant V
oc degradation occurs with the low-doped p-layer. The light-induced defects are not negligible compared with the initial defects in the low-doped p-layer and thus more carrier recombination occurs. Moreover, some of the acceptors are compensated by light-induced defects. The highly doped p-layer, however, does not cause much V
oc degradation because the light-induced defects are negligible compared with the large number of doping-induced defects and acceptors. The experimental data show that the midgap defects induced by doping or light-soaking near the p/i interface cause the V
oc limitation.
Carrier Transport Properties of Sputter-Deposited CdS/CdTe Heterojunction
Authors: Tomita Yasuhiro , Hatanaka Toshiaki Kawai
Published: February 2005

CdS, CdTe and CdS/CdTe heterojunction films were deposited on glass substrates by RF sputter deposition using undoped CdS and CdTe targets, respectively. The deposited CdS and CdTe films have high resistivities greater than 106 Ω·cm and 109 Ω·cm, and preferential orientations at (002) and (111) planes, respectively. CdS/CdTe heterojunction film shows good rectification properties. The carrier transport properties of the CdS/CdTe heterojunction were investigated by means of current-voltage measurements at different temperatures. The forward current is classified into the tunneling-recombination current, recombination current, space charge limited current (SCLC) and trap filling of SCLC regions by considering applied voltage. The reverse current is dominated by the generation recombination current in the depletion region of the CdTe layer.
Superresolution in Optical Disk Systems with a Non-Linear Refractive Layer
Authors: Takuma Yanagisawa Takuma Yanagisawa , Seiichi Ohsawa Seiichi Ohsawa
Published: February 2005

We derived the optical transfer function in scanning optical microscopy which has the same properties as optical disk read-out systems, in the case where we observed an object coated with a non-linear refractive layer whose amplitude transmissivity depends on the incident light intensity, and showed that this cutoff frequency is higher than that of the case where we observed the object without the aid of a non-linear refractive layer.
Phosphorescence and Thermoluminescence of UV-Irradiated SrO Powders at Temperatures from 120 K to 350 K
Authors: Yasunori Yanagisawa Yasunori Yanagisawa , Kenji Sakamoto Kenji Sakamoto
Published: February 2005

Long-lived phosphorescence and thermoluminescence (TL) from UV-irradiated SrO powders under high vacuum are observed at low temperature. Phosphorescence decays following a t
-1 law below 160 K in the time range 10-103 s. The emission spectra of phosphorescence and TL have a peak at 2.7 eV. The luminescence is quenched by O2 gas exposure at low temperatures. On the basis of the phosphorescence decay and TL glow curves, plausible emission mechanisms are discussed in terms of a thermally assisted tunneling recombination model between distant electron and hole traps and a first-order decay model with an energy distribution of trap depth. The observations are well described by the recombination model.
Construction of Photosensor Utilizing Magnetic Semiconductor
Authors: Seki Kyoshiro , Nakayama Yasushige , Chiba Shigeki , Murakami Yoshitaka Tsunekawa
Published: February 2005

A photomagnetic semiconductor (PMS) is composed of a ferrimagnetic semiconductor and a radiant flux absorbent. The PMS is a pyromagnetic film utilizing temperature dependence of magnetic reluctance. When the PMS is irradiated with visible light, an absorbent captures the light energy and transfers thermal energy to a magnetic semiconductor, causing the reluctance change of the PMS. Therefore, the PMS acts as a photomagnetic transducer without windings for excitation or detection.
Spectroscopic Ellipsometry of Thin Copper Films on Glass Substrates
Authors: Takeshi Kawagoe Takeshi Kawagoe , Tadashi Mizoguchi Tadashi Mizoguchi
Published: February 2005

The complex reflectance ratio, ρ=R
p/R
s, for p- and s-polarized lights of copper island films with the mean mass thickness d
w of 4 to 16 nm on glass substrates was measured in the visible region by means of in-situ ellipsometry. The observed wavelength dependence of ρ was interpreted with the effective anisotropic continuous film model. The clear resonance peak of plasma oscillation in ε
x

′′ was observed at E≃1.8 eV, which corresponded to the mean distance between the particles of 7.5 nm in the film of d
w=4 nm. The estimated particle radius r was smaller by a factor of 10-1 or 10-2 than the island size directly observed by means of a scanning electron microscope.
Morphology of Extended Chain Single Crystals of Vinylidene Fluoride and Trifluoroethylene Copolymers
Authors: Hikosaka Masamichi , Sakurai Katsuyuki , Koizumi Hiroji Ohigashi
Published: February 2005

The morphology of extended chain crystals (ECCs) or extended chain single crystals (ECSCs) of vinylidene fluoride and trifluoroethylene copolymers, P(VDF/TrFE), with VDF molar content x\lesssim0.82 was observed by polarized optical microscopy and transmission electron microscopy. It was found that a thick isolated ECSC and thick stacked ECCs, about 0.3-0.8 µm thick, were formed when P(VDF/TrFE) was crystallized from the melt into the mobile hexagonal phase at atmospheric pressure or under high pressure, 80 MPa or 170 MPa. The isolated ECSCs were found for the first time on the copolymer. This confirmed the prediction of chain sliding diffusion theory proposed by Hikosaka that ECSCs or ECCs will be formed when polymers are crystallized from the melt into the mobile hexagonal phase.
Radiation Defects in Thermal-Donor-Doped Silicon
Authors: Fukuoka Noboru , Yoneyama Masahiro , Makoto Honda Makoto Honda , Kozo Atobe Kozo Atobe
Published: February 2005

The nature of radiation defects in thermal-donor-doped silicon crystals was studied by analyzing the deep level transient spectroscopy (DLTS) spectrum and carrier concentration. It is ascertained using the DLTS technique that the concentration of thermal donors decreased with annealing of A-centers. Namely, an A-center interacted with a thermal donor during annealing and both lost their electrical properties. The energy levels at E
c-0.17 eV, E
c-0.23 eV and E
c-0.43 eV were introduced in samples doped with group III atoms or group V atoms by irradiation. An E
c-0.27 eV level and E
c-0.21 eV level were generated during annealing at 240°C and 320°C, respectively. Sixty percent of the electrically active defects introduced by neutron irradiation were not annealed after 20 min at 400°C.
Improvement of Mislanding in Shadow Mask Cathode Ray Tubes (CRTs) by Electron-Reflecting Coatings
Authors: Yamamoto Morio , Koitabashi Masayasu , Kimura Hiroshi
Published: February 2005

Mislanding caused by thermal deformation of the shadow mask during CRT operation was effectively improved by an electron-reflecting coating formed on the shadow mask surface. Coatings with high atomic number materials such as Bi2O3, WO3, and W exhibit high electron reflectance and reduce the amount of mislanding by about 40% compared to a conventional mask, when the CRT screen was brought to the highest brightness condition. These improvements in mislanding were mainly due to the energy dissipated by the electrons reflected by the coating. The effects of coating characteristics on mislanding were made clear, and the mechanism of the improvement was discussed.
Density Distribution in a Plasma Source with Cylindrical Configuration
Authors: Hitoshi Nihei Hitoshi Nihei
Published: February 2005

The density distribution in a cylindrical plasma source is obtained by solving the diffusion equation based on a plasma model. In this model, the side wall of the cylindrical chamber is surrounded by magnetic multipole fields in order to obtain a uniform high-density plasma on a target wall. The form of the initial density distribution at the upper stream of the source is also discussed. Some calculated examples are shown. The results give the density distribution in the source and the plasma particle flux flowing into the target wall. The equations derived in this paper are useful for the design of a plasma source capable of generating a uniform high-density plasma over a wide area.
Measurements of Plasma Controlled by Compressed Magnetic Field Magnetron Sputtering Technique
Authors: Ido Shunji , Hijikata Yukihiro Ishida
Published: February 2005

Measurements of the electron density of plasma and the magnetic field were carried out in a compressed magnetic field-magnetron sputtering system using a non-ferromagnetic material target. The electron density has its maximum in the region where the lines of magnetic force are parallel to the target surface, where the peak of erosion profile is observed. It was found that the peak position of the profiles of electron density and erosion could be controlled using this system.
Ionized Cluster Beams: Physics and Technology
Authors: Isao Yamada Isao Yamada , Gikan H. Takaoka Gikan H. Takaoka
Published: February 2005

Ionized cluster beam (ICB) deposition has been used to form thin films of metals, insulators, semiconductors and organic materials which have unique characteristics when compared to films formed using other techniques. In addition, the use of gas-phase atoms in the form of accelerated clusters has recently shown promise for surface modification applications. A fundamental understanding of ICB deposition and related techniques requires investigations of (1) the mechanisms which lead to the growth of large vapor phase clusters, (2) techniques for determining the size distribution of large vapor clusters, (3) the initial stages of film nucleation, (4) film growth morphology related to lattice mismatch and ion beam parameters. Clarification of the role of clusters in ICB deposition has been greatly aided by atomic scale imaging by transmission electron microscopy and scanning tunnel microscopy in the early stages of film growth. Emphasis is given to the formation of high-quality, epitaxial metallic films. Several applications of ICB films with respect to microelectronics, optical mirrors, compound materials and organic materials are discussed with emphasis on the special characteristics of ICB films. Applications for gas-cluster processing are reviewed.
Overthreshold Nonlinearity of Parametric Sound Wave Phase Conjugation in Solids
Authors: Vladimir Preobrazhensky Vladimir Preobrazhensky
Published: February 2005

The nonlinear stage of acoustic wave phase conjugation over the threshold of absolute parametric instability is considered with respect to magnetic active media. The common case of nonlinear, nonstationary and spatially inhomogeneous parametric interaction is studied. Theoretical results are compared with experimental data on phase conjugate wave gain measurements in ferrite. It is shown that the pumping exhaustion mechanism of nonlinearity provides a reproduction of incident wave field distribution in the output of the active zone by parametric phase conjugation in the overthreshold regime of giant amplification in ferrite. The signal and fluctuation mode competition is shown to be essential for overthreshold limitation of phase conjugate wave amplitude.
Phonons in Nonlinear and Nonequilibrium Systems and Thermal Conductivity
Authors: Ohtsubo Yuuki , Norihiko Nishiguchi Norihiko Nishiguchi , Tetsuro Sakuma Tetsuro Sakuma
Published: February 2005

Heat transport and dynamical properties of a one-dimensional monatomic lattice with large quartic potentials are investigated using the molecular dynamics method. Energy is transported not only through diffusive processes but also nondiffusive processes. The nondiffusive energy flow is assigned to modified KdV solitons, which decrease with propagation distance due to collisions with thermally excited phonons with very short wavelength. The behavior of energy spreading resembles anomalous diffusion due to the nondiffusive current within a critical region N
cr or a critical time, τcr=N
cr/\tv, where v denotes the velocity of the soliton. The diffusive behavior of energy spreading recovers beyond that region. Fourier's law is confirmed in the regime, and the thermal conductivity is found to be independent of local temperatures.
Investigation of Disk Bender Low-Frequency Projector with Dual Radiation Surfaces
Authors: Yamamoto Mitsuru , Hama Yoshinori , Shiba Hiroshi , Watari Noriko , Takeshi Inoue Takeshi Inoue
Published: February 2005

A low-frequency disk bender projector with dual radiation surfaces was designed on the basis of finite element method (FEM) analysis and equivalent circuit analysis, in order to devise a miniature light weight projector with a high sound pressure level. These analyses suggest that a low-frequency, high-power, miniature and light weight projector can be realized. A trial projector was produced and evaluated. The resonant frequencies for the projector in air and water were 1315 Hz and 970 Hz, respectively. Experimental maximum transmitting voltage sensitivity was 132.2 dB re 1 µPa/V at 1 m.
Effects of External Modulation Signals on the Tracking of Resonance and Antiresonance of Piezoelectric Resonators
Authors: Shigeo Hayashi Shigeo Hayashi
Published: February 2005

The phase-locked loop developed previously for the tracking of resonance and antiresonance of piezoelectric resonators is examined with respect to the stability against external modulation signals in the form a sin 2πf
0
t. A PZT resonator with f
r=68.1 kHz and f
a=82.3 kHz is used as a sample. The critical amplitude a
c, beyond which phase lock is lost, is measured for each value of f
0. The value of a
c increases discontinuously at a critical frequency, f
c, of 150 kHz. In the freqeuncy range between f
c and 500 kHz hysteresis is found in the relationship between a and the width of the power spectrum. No hysteresis is found if f
0<f
c. This behavior can be explained by an inhomogeneous second-order differential equation.
Integrated Acousto-Optic Space Switch Modules with Applications to Multiport Optical Switching and Communications*
Authors: Chen S. Tsai Chen S. Tsai , Arjun Kar-Roy Arjun Kar-Roy
Published: February 2005

Integrated acousto-optic space switch (AOSS) modules, up to 8×8 in size, have been realized using multiple Bragg diffractions on Y-cut LiNbO3 substrates. The integrated AOSS modules consist of a new hybrid beam expanding/collimating lens, a large-aperture focusing lens, and a pair of multielement tilted surface acoustic wave (SAW) transducer arrays in a titanium-indiffused channel-planar-channel composite waveguide. The distinctive traits of the integrated AOSS modules as well as performance parameters such as crosstalk, insertion loss, RF drive power requirement, reconfiguration time and size limitations, are discussed. The experimental results of 4×4 and 8×8 modules are reported. The integrated AOSS modules can also be used in single-wavelength as well as wavelength-division-multiplexed multiwavelength networks involving both star and tree topologies.
Rotary Ultrasonic Motor Using Symmetric Contour Vibration of Rectangular Plate
Authors: Iijima Tamotu , Sano Kazuhide , Nakagawa Yasuhiko , Ito Hiroshi
Published: February 2005

By restraining the center point in the side of a rectangular plate, symmetrical contour vibration can be excited which has nodal points at the centers of the sides. If this contour mode is used instead of the longitudinal mode in an ultrasonic motor, the vibrator can be fixed at the center of the side and will withstand high rotor pressure.
Powder-Feeding Device Using Hollow Cylindrical Piezoelectric Ceramics
Authors: Kanbe Nobuhiro , Takano Yoshiro Tomikawa
Published: February 2005

This paper deals with a powder-feeding device using hollow cylindrical piezoelectric ceramics; the device is constructed so that the hollow cylindrical piezoceramics itself acts as an electrical excitation part as well as a powder-feeding part, and therefore its specific merits are small size and simple construction. Characteristics of the powder-feeding device are measured by changing the length of the silicone rubber cover as a guide for the powder supply or the electrode width for electrical excitation. The measured characteristics are compared with calculated characteristics, as to the propagated ultrasound wave number and elliptic motion of displacements of an infinite hollow cylinder.
Multilayer Piezoelectric Ceramic Actuator with Interdigital Internal Electrodes
Authors: Ōhashi Junichi , Yoshiaki Fuda Yoshiaki Fuda , Tomeji Ohno Tomeji Ohno
Published: February 2005

A multilayer piezoelectric ceramic actuator with interdigital internal electrodes has been developed. The internal electrodes of this actuator are line electrodes which are printed on piezoelectric ceramic green sheets and stacked such that alternating electrode lines are displaced by one-half pitch. This actuator is displaced at right angles to the stacking direction due to the piezoelectric longitudinal effect. Therefore, it is possible to prepare a long ceramic actuator, which will be highly reliable in applications. In this work, we have obtained a displacement of 50 µm/DC350V and a generative force of 34.3 MPa for a 74-mm-long actuator. The reliability of this actuator is confirmed to have a long life of more than 1000 hours using applied voltage of DC350V at 25°C and 60%RH.
Torsional Actuators Using LiNbO3 Plates with an Inversion Layer
Authors: Nakamura Kiyoshi , Takeshi Nakamura Takeshi Nakamura , Ken Yamada Ken Yamada
Published: February 2005

By utilization of a ferroelectric inversion layer formed in a LiNbO3 plate by heat treatment at just below the Curie temperature, a piezoelectric torsional actuator consisting of a single-crystal plate with no bonding layer can be obtained. The optimal cut suitable for generating torsional motion efficiently without causing bending motion is theoretically examined. It is experimentally demonstrated that torsional actuators fabricated using 140°-rotated Y-cut LiNbO3 plates with an inversion layer as thick as half the plate thickness exhibit no hysteresis and little creep. When an actuator with dimensions of 16×7.0×0.1 mm3 is used as a light deflector, a light beam deflection angle as large as 2.08° is obtained at an applied voltage of 220 Vp-p.
In Situ and Real-Time Measurement of Methane Concentration in Rice Paddy Field at Okayama University Using Tunable Diode Laser Absorption Spectrometry
Authors: Kagawa Naoki , Wada Osami , Hai Xu , Koga Ryuji , Sano Hiroya , Inubushi Kazuyuki
Published: February 2005

A transportable device based on absorption spectrometry was constructed and the atmospheric methane concentration over a rice paddy was measured. An open optical path of 50 m length was employed along with a PbSnTe diode laser. Diurnal change of methane concentration was recorded in association with meteorological parameters. Feasibility was proven for practical application to in situ study of atmospheric methane.
Novel Method for Detecting Resonant Frequency Shift in Atomic Force Microscopy
Authors: Keiji Takata Keiji Takata
Published: February 2005

This paper describes a simple method for detecting the resonant frequency shift caused by the forces between a sample and the tip of the cantilever in an atomic force microscope (AFM). This method is based on the fact that the impedance of a piezoelectric element reflects its mechanical resonant states and varies sensitively near the resonant frequencies as a function of frequency. A resonance shift therefore shifts the impedance curve. The forces are detected by sensing the impedance of a cantilever made of piezoelectric material which is vibrated near its resonant frequency. The tip-to-sample spacing is maintained by keeping changes in impedance constant. This method greatly simplifies the AFM, allowing us to use a scanning tunneling microscope as an AFM simply by exchanging the tip probe.
Optical Measurement of Acoustic Velocity and Poisson's Ratio in Disk Piezoelectric Transducer
Authors: Ohki Michio , Naomi Shima Naomi Shima , Tadashi Shiosaki Tadashi Shiosaki
Published: February 2005

The fiber-optic measurement of piezoelectric vibration in a disk transducer and the evaluation of acoustic velocity and Poisson's ratio are described. The amplitude and phase of the vibration can be measured locally by means of the optical method. The phase can change by π radians at both resonance frequencies independent of the position in the resonator and other frequencies dependent on the position. The latter frequencies can be measured only by means of the optical method, and the acoustic velocity and the Poisson's ratio can be calculated through measurement.
Frequency Characteristics of Scattering Sound Pressure from Pipe Containing Sediments
Authors: Ichihara Tadahiro , Kikuchi Toshiaki , Nakanishi Toshio Tsuchiya
Published: February 2005

For investigation of the ocean subbottom, in order to obtain a precise subbottom profile, it is important to determine the acoustic characteristics of sediments on the ocean subbottom. Thus, we propose a method for measuring the acoustic characteristics of sediments inside a pipe which is used in ocean bottom boring. The scattering sound pressure from a pipe containing sediments is applied to measure the acoustic characteristics of sediments. We show that these frequency characteristics have several peak frequencies which shift as functions of the sound speed and density of the sediments. The rate of increase of the peak frequency is constant for the variation in both the sound speed and density of the sediments.
Asymptotic Analysis of Acoustic Field by Geometrical Theory of Diffraction in Antiwaveguide Propagation
Authors: Toyohiko Ishihara Toyohiko Ishihara , Kouji Ohshima Kouji Ohshima
Published: February 2005

The asymptotic analysis of the antiwaveguide propagation of sound waves in continuously layered media is described. The geometrical theory of diffraction developed by Keller and collaborators is extended to account for the sound fields in the transition region near the limiting ray that grazes the sea surface. Included are normal-modes, acoustical rays and diffracted rays. Numerical comparisons with the normal-mode solution reveal the validity and utility of the asymptotic analysis studied in the present paper. The diffracted ray solution applied in the transition region near the geometrical shadow zone is the most satisfactory from the physical viewpoint.
Variation of Pressure Waveforms in Measurements of Extracorporeal Shock Wave Lithotripter
Authors: Naoto Inose Naoto Inose , Masao Ide Masao Ide
Published: February 2005

In this paper, we describe measurement of variation in pressure waveforms of the acoustic field of an extra-corporeal shock-wave lithotripter (ESWL). Variations in the measured acoustic fields and pressure waveform of an underwater spark-gap-type ESWL with an exhausted spark plug electrode have been reported by researchers using crystal sensors. If the ESWL spark plugs become exhausted, patients feel pain during kidney, biliary stone disintegration. We studied the relationship between exhaustion of electrodes and the variation of pressure waveforms and shock-wave fields of the ESWL using a newly developed hydrophone.
Measurements of Pressure of Extracorporeal Shock Wave Lithotripter Using Pressure-Sensitive Papers
Authors: Naoto Inose Naoto Inose , Masao Ide Masao Ide
Published: February 2005

This paper describes measurements of pressures at the focal region of the extracorporeal shock wave lithotripter (ESWL) using pressure-sensitive papers. At the focal region of ESWL, ordinary hydrophones are quickly damaged, because of very high pressures. Recently, measurements of pressure at the focal region of ESWL using pressure-sensitive paper have been advised. Therefore, we have studied the effectiveness of pressure-sensitive papers in the measurement of high acoustic pressures at the focal region of ESWL.
Determination of the Concentration of Magnetotactic Bacteria by Means of Susceptibility Measurements
Authors: Harasko Gerald , Pfützner Helmut , Rapp Eva , Futschik Karl , Schüer Dirk
Published: February 2005

High concentrations of magnetotactic bacteria are needed for their practical applications, as investigations of domains in soft magnetic materials. The present paper reports experimental studies, the initial aim of which has been to determine the concentration c of magnetotactic bacteria within a culture medium from the measured susceptibility χ. A pure culture of Magnetospirillum gryphiswaldense as well as a natural population of cocci were investigated. M. gryphiswaldense showed a linear relation of the measured χ with the concentration c. Cocci showed characteristics which complicate the determination of c. Problems of manipulation of cocci by means of magnetic fields are discussed. For an effective interpretation of χ attempts were made to divide natural populations in sub-populations of more uniform characteristics by a magnetophoresis technique and by changing the polarity of bacteria.
Observation of Leaky Surface-Skimming Compressional Wave Excited on Polymers Using Ultrasonic Micro-spectrometer
Authors: Ohira Katsumi , Koyama Yusuke Tsukahara
Published: February 2005

A new method for material characterization using an ultrasonic micro-spectrometer system is described. This system with spherical-planar-pair lenses can be used to directly estimate the reflection coefficient R(f, θ) for infinite plane waves at a local surface area on the solid. In this paper, the characterization is carried out by comparing the magnitude of the measured reflection coefficient ||
R(f, θ)||
and that of the calculated coefficient ||
R(f, θ)||
around the critical angle of the specimen's longitudinal wave. This method is very useful for materials such as polymers, with a low Rayleigh velocity, because the leaky Rayleigh wave is not excited; on the contrary, the leaky surface-skimming wave is sufficiently excited to be measured. Velocity and attenuation of the longitudinal wave and the transverse wave are also estimated by means of computer fitting.
Generation of 100-MHz-Band Rayleigh Waves by Phase Velocity Scanning of a Laser Interference Fringe
Authors: Nishino Hideo , Tsukahara Yusuke , Nagata Yoshihiko , Koda Toshio , Yamanaka Kazushi
Published: February 2005

We investigated the thermoelastic generation of Rayleigh waves in the 100 MHz frequency range using a scanning interference fringe (SIF) obtained by intersecting two laser beams with different frequencies. A long-pulse (140 ns) Q-switched Nd:YAG laser was used to generate Rayleigh waves on an aluminum specimen at various scanning velocities controlled by the intersection angle of the laser beams. It was found that the amplitude of the generated tone burst of Rayleigh waves followed a sinc function dependence over the scanning velocity with a peak at the Rayleigh wave velocity. The center frequency of the tone burst followed a linear dependence. Implications of these findings in the quantitative nondestructive evaluation of microdevice components are discussed.
Analysis of Pyroelectric Signal in Photoacoustic Spectroscopy Using a Transparent Transducer
Authors: Horita Susumu , Saikawa Takeshi , Hideaki Konishi Hideaki Konishi , Tomonobu Hata Tomonobu Hata
Published: February 2005

It is shown that a pyroelectric signal from a transparent transducer, Z-cut LiNbO3, depends on the surface state of the measured sample, a Si wafer. The signal of the Si wafer with the native oxide deviates markedly from the normal pyroelectric signal. Also, we develop a three-dimensional theory of 1he transparent pyroelectric transducer method in photoacoustic spectroscopy (PAS). We discuss the cases in which the pump beam illuminates the sample not only directly, but also through the transducer. It is shown that the theoretical calculation results are in good agreement with the experimental data of both PA amplitude and phase signals of Si. This result indicates that the validity of our theoretical model is verified experimentally.
Study on Photoacoustic Effect of Epoxy Resin on Backing Material by Scanning Photoacoustic Microscope
Authors: Tokunaga Yoshiaki , Minamide Akiyuki , Nakada Keimei Tamura
Published: February 2005

Amplitude and phase of a photoacoustic signal generated from an epoxy resin on backings (aluminum, white acrylic resin and black-coated white acrylic resin) were measured by a scanning photoacoustic microscope. The experimental results were as follows. The photoacoustic signals for light-reflective backings (aluminum and white acrylic resin) were generated from the epoxy resin on the backing, while photoacoustic signals for light-absorptive backing (black coated white acrylic resin) were generated from the backing itself.
High Voltage Transmission Electron Microscopy of Low Power Pulsed Laser Annealing of Zn+ Implanted GaAs
Authors: Pashov Nicolai , Kalitzova Maria , Vitali Gianfranco , Rossi Marco , Baither Dieter
Published: February 2005

Crystals of (100) GaAs implanted with Zn+-ions were treated by low-power pulsed-laser annealing (LPPLA) technique. The first investigations about the effect of this treatment on the damage structure distribution in the GaAs by means of high voltage transmission electron microscopy are shown. Typical rearrangement and accumulation trends of the initially uniformly dispersed damage clusters were established after the LPPLA. The morphology of gallium oxide films grown on the surface of GaAs during LPPLA treatment and their specific behavior under electron bombardment during the observation in the microscope are reported too.
Numerical Derivative Analysis of the Pseudodielectric Function of CdTe
Authors: Toshifumi Kimura Toshifumi Kimura , Sadao Adachi Sadao Adachi
Published: February 2005

The real (ε1) and imaginary (ε2) parts of the dielectric function for CdTe have been measured by spectroscopic ellipsometry in the 1.1-5.6-eV photon-energy range at room temperature. The measured spectra reveal distinct structures at energies of the E0, E
0+Δ0, E
1, E
1+Δ1 and E
2 oritical points (CPs). These data are analyzed by fitting the first-(dε/dE) or second-derivative spectra (d2ε/dE
2) with model dielectric functions (MDF) or standard critical-point (SCP) line shapes. It is found that both the MDF and SCP models successfully explain the measured derivative spectra. The MDF also shows excellent agreement with the experimental ε(ω) spectra, but the SCP does not. The CP energies determined here are: E
0=1.58 eV; E
0+Δ0=2.55 eV; E
1=3.55 eV; E
1+Δ1=4.13 eV; and E
2=5.13 eV.
Dependence of Piezoelectric and Pyroelectric Activities of Aromatic Polyurea Thin Films on Monomer Composition Ratio
Authors: Wang Xian-Shan , Iijima Masayuki , Yoshikazu Takahashi Yoshikazu Takahashi , Eiichi Fukada Eiichi Fukada
Published: February 2005

Thin films of aromatic polyurea were prepared by simultaneous deposition of 4,4'-diamino diphenylmethane (MDA) and 4,4'-diphenylmethane diisocyanate (MDI) on a polyimide film substrate. By changing the evaporation temperature of the monomers, the monomer molar ratio of MDA to MDI of the deposited film was varied to yield MDA-rich, balanced, and MDI-rich films. After poling, the balanced films exhibited the maximum values of pyroelectric and piezoelectric constants, which were stable up to 200°C. Elemental analysis confirmed that oligomers consisting of about five monomers were present in as-deposited films. In the balanced films, an exothermic peak appeared at about 110°C in the first run of DSC measurements and the IR absorption peak due to isocyanate groups disappeared after heat treatment. These results suggest that during the poling process polymerization of oligomers, which forms polar urea bonds, takes place at about 110°C under a high electric field. The large residual polarization thus produced leads to high pyroelectric and piezoelectric activities.
Numerical Simulations of DC Glow Discharge using Self-Consistent Beam Model
Authors: Seishiro Hashiguchi Seishiro Hashiguchi
Published: February 2005

Calculations are presented of helium dc glow discharges using a beam model, in which beam electrons represent nonequilibrium electron transport; cold electrons and ions are treated with an equilibrium continuum model. Calculated current densities ranged from 4.7 µA/(cm2·Torr2) (near the normal glow conditions) to 290 µA/(cm2·Torr2) (abnormal regime). High-density plasmas appeared in the negative glow; the peak density occurred at the position where the electric field changed from negative to positive. Calculations were also made using a continuum model with the local field approximation for electron transport; high-plasma density and electric field reversal were not predicted by the model. Calculations using the beam model show good agreement with recent experiments except at high current densities, where experiments showed complex phenomena.
Effect of RF-Biased Electrode on Microwave Plasma
Authors: Ohtsu Yasunori , Yoshihiro Okuno Yoshihiro Okuno , Hiroharu Fujita Hiroharu Fujita
Published: February 2005

The effect of an rf-biased electrode on a microwave plasma has been studied experimentally and compared with the results of a theoretical model considering the contribution of the rf sheath oscillation to rf plasma production. Conditions under which the rf electrode does not affect the microwave plasma, or acts only as “rf biasing,” are low voltage applied to the electrode, high microwave plasma density, and low rf driving frequency. These non interacting conditions are also related quantitatively. The theoretical model is found to account fully for the experimental results.
Multipoint Correlation Number Fluctuation Laser Velocimeter
Authors: Iwamoto Toshiyuki , Kanda Toshikazu , Norio Ogita Norio Ogita , Kohji Ohbayashi Kohji Ohbayashi
Published: February 2005

A multipoint correlation number fluctuation laser velocimeter (MNFLV) is developed, by which the number fluctuation signals are detected at multiple points in a flow and the photon correlation function is used for analysis of scattered light from particles suspended in fluids. The principle of the method is explained. Applications to pipe flows are carried out to demonstrate capability of the method. The method is particularly suited for quantitative characterization of turbulence as well as velocimetry.
Correction of the Self-Absorption Effect in Fluorescence X-Ray Absorption Fine Structure
Authors: Noma Atsuo Iida
Published: February 2005

The X-ray absorption fine structure (XAFS) measured with the X-ray fluorescence yield strongly depends on the concentration, thickness and detection geometry resulting from the self-absorption effect. A correction procedure for the self-absorption effect is presented using a simple theory of X-ray fluorescence yield and applied to X-ray absorption near-edge structure (XANES) of a thin iron foil and an iron compound. The accuracy of the self-absorption correction is discussed.
Characterization of Epitaxial Films of Layered Materials Using Moiré Images of Scanning Tunneling Microscope
Authors: Mori Tomohiko , Abe Hideki , Koichiro Saiki Koichiro Saiki , Atsushi Koma Atsushi Koma
Published: February 2005

Moiré-type modulated patterns have been observed in scanning tunneling microscope (STM) images of ultrathin epitaxial films of MoSe2 grown on MoS2 substrates, which arise from the existence of a very abrupt interface between two lattice-mismatched materials. Some distortions have been observed in the moiré patterns, reflecting the local lattice distortions in epitaxial films. It has been proven from a simple analysis that the moiré patterns enhance the distortions in the epitaxial films by a factor of 10 to 20, which enables the precise characterization of local lattice distortions in the epitaxial films.
Cleavage and Intercalation Properties of a Layered Compound, K4Nb6O17·3H2O, Studied with Atomic Force Microscopy
Authors: Nozoye Hitoshi Shindo
Published: February 2005

The surface structures of the title compound were studied with atomic force microscopy (AFM) after cleavage in air and after substitution of K+ with (CH3)4N+ (tetramethyl ammonium ion: TMA). Of the two interlayers, hydrated and anhydrated, cleavage in air occurred at the former when weak force was applied. Upon ion exchange at the hydrated interlayer with an aqueous solution of TMA, the niobate bilayer sheets broke free and slid against each other. The free bilayer sheets were mechanically weak enough to be scraped away by the stylus during scanning in the AFM measurement, which suggests the possibility of micromachining this material. Atom-resolved AFM images correspond to a regular arrangement of TMA with the methyl groups pointing in the directions of the crystal axes. This material can be used in constructing a two-dimensional assembly of organic molecules.
Scanning Tunneling Microscopy and Barrier-Height Observation of Stearic Acid Thin Films Prepared by Hot-Wall Technique
Authors: Sasaki Akira , Iwata Futoshi , Katsumata Akira , Fukaya Jisuke , Aoyama Hisayuki , Akiyama Tetsuo , Yoshio Nakano Yoshio Nakano , Hiroshi Fujiyasu Hiroshi Fujiyasu
Published: February 2005

Stearic acid thin films prepared by the hot-wall technique have been observed and barrier heights (φ) have been measured using scanning tunneling microscopy (STM), which is operated in air. Three kinds of substrates are used to prepare stearic acid films: highly oriented pyrolytic graphite (HOPG), gold thin film and indium-tin-oxide (ITO) film. X-ray diffraction analysis reveals that molecules in films are oriented normal to the substrate. The thickness of films we used is about 30 nm. Using STM and φ images of films, we confirmed that the film surface morphology varies with the kind of substrate. Islands of stearic acid are sparsely formed on the HOPG and gold thin film substrates; however, in the case of the ITO substrate, small islands (about 3 nm) nearly cover the entire substrate surface. Under certain circumstances, it is more effective to observe the stearic acid morphology in terms of values of φ with the STM images in the constant-current mode.
Wave Propagation and Plasma Uniformity in an Electron Cyclotron Resonance Plasma Etch Reactor
Authors: James E. Stevens James E. Stevens , Joseph L. Cecchi Joseph L. Cecchi
Published: February 2005

Wave propagation and absorption have been studied experimentally in an electron cyclotron resonance (ECR) plasma etch reactor operating at 2.45 GHz, with various microwave couplers. A coaxial rf probe was used to measure the wave amplitude along the reactor axis, and radial profiles of the plasma ion saturation current were determined by a Langmuir probe. A single mode whistler wave was detected, and wave absorption was found to occur at magnetic fields corresponding to an ECR frequency which is Doppler-shifted above the cold resonance. The radial uniformity of the plasma is strongly determined by the radial power distribution of the microwave coupler at lower magnetic fields where absorption occurs near the microwave window. Plasma radial transport also influences the resulting profile, especially for modes which are hollow in the center, such as the TM01. Under conditions where the waves propagate from the window without absorption for several wavelengths, the waves refract towards regions of lower density where subsequent ionization tends to correct non-uniform plasma profiles. A model is presented and yields predictions which are in good agreement with the data. The model allows calculation of wave trajectories by ray-tracing techniques and includes simple plasma transport and power deposition.
Estimation of Ion Incident Angle from Si Etching Profiles
Authors: Gotoh Yasushi , Tokuo Kure Tokuo Kure , Shin'ichi Tachi Shin'ichi Tachi
Published: February 2005

The distribution of angles of incident etching ions was measured using a test sample having an overhanging mask structure. The standard deviation of ion incident angles decreased with decreasing pressure of the etching atmosphere. With conventional reactive ion etchers, standard deviations of 3 to 8° were measured at pressures from 2.6 to 101 Pa. With a microwave plasma etcher, the measured deviation at 1.3 Pa was 2°. The aspect-ratio dependence of etching with SF6 may be caused by the insufficient radical supply, which becomes the rate-determining step for etching a high-aspect-ratio trench.
Ion-Beam-Assisted Etching in Ga+/GaAs/Cl2 System
Authors: Kosugi Toshihiko , Gamo Hiroaki Iwase
Published: February 2005

We have investigated the characteristics of ion-beam-assisted etching of GaAs by continuous and pulsed Ga+ beam irradiation in Cl2 ambient. A rate equation model was proposed to explain the measured etch yield. Due to pulsed beam irradiation, the etch yield increased to 500 atoms/ion with decreasing pulse duty ratio. This increase was explained by the accumulation of GaCl3 on the surface while the ion beam is off based on the rate equation model.
High-Fluidity Deposition of Silicon by Plasma-Enhanced Chemical Vapor Deposition Using Si2H6 or SiH4
Authors: Shin Hidetoshi , Hashimoto Makoto , Okamoto Katsuhiko , Seiichi Miyazaki Seiichi Miyazaki , Masataka Hirose Masataka Hirose
Published: February 2005

High-fluidity deposition of silicon thin films on fine-patterned surfaces has been achieved at a substrate temperature of -110°C from a Si2H6 plasma or a high-partial-pressure SiH4 discharge by using a conventional diode-type reactor. It is shown that the polymerization reaction forming higher silane radicals proceeds on the surface which suffers ion irradiation. The formation rate of the polymerized species competes with its decomposition rate induced by ion bombardment. The former is predominant when Si2H6 or high-partial-pressure SiH4 is used. Such polymerised precursors exhibit high fluidity which is favorable for planarizing the patterned surface.
Thin Film Deposition by Low Energy SiCln
+ Beam
Authors: Sakai Takayuki , Sakai Akira , Haruo Okano Haruo Okano
Published: February 2005

The reaction between mass-separated low-energy (30 eV) SiCl
n

+ ion beams and Si and SiO2 substrates was studied to investigate the influence of the number of Cl atoms in SiCl
n
species on their deposition characteristics. It has been found that the deposition yield of Si is positive (deposition) at n=1 and it becomes negative (etching) at n=3 on the Si substrate while it is nearly zero on SiO2. In the presence of O2 gas, the deposited species change to silicon oxides and the deposition of SiO2 also takes place on SiO2 with SiCl3
+. The etching of Si by SiCl3
+, however, takes place and the etching yield was found to be unaffected by O2. These results can be explained if adsorbed Cl atoms are assumed to desorb as SiCl2, leaving either Si or Cl on the substrate depending on the value of n. In the O2 ambience, the preferred bonding of Si with O leads to the deposition of SiO2, except in the case of SiCl3
+ on Si where excess Cl atoms react with Si.
Evaluation of Spatial Distribution of Hole Traps Using Depleted Gate MOSFETs
Authors: Yasuda Naoki , Toyoshima Yoshiaki , Hashimoto Kazuhiko , Kenji Taniguchi Kenji Taniguchi , Chihiro Hamaguchi Chihiro Hamaguchi
Published: February 2005

The distribution of hole traps in the gate oxide of metal-oxide-semiconductor field effect transistors (MOSFETs) is evaluated with capacitance-voltage measurements using depleted polysilicon gate MOSFETs. Nonavalanche hole injection from the substrate shows that the average distance of hole traps from the SiO2/Si-substrate interface is 3.7 nm for MOSFETs with a 10-nm gate oxide. The experiment of a Fowler-Nordheim electron injection after the hole injection indicates that electron traps created during the hole injection exist at a distance in the range of 2.5-6 nm from the SiO2/Si-substrate interface, suggesting that hole traps also exist in the same region.
Selective Deposition of Silicon by Mercury Sensitized Photochemical Vapor Deposition
Authors: Hiramatsu Masato , Ishida Arichika , Takaaki Kamimura Takaaki Kamimura , Yoshito Kawakyu Yoshito Kawakyu
Published: February 2005

The authors have developed a low-temperature process for selective deposition of silicon by mercury sensitized photochemical vapor deposition (Photo-CVD) without using ultraclean technology. It was found that hydrogen radical pretreatment was required to obtain selective deposition. There was an incubation period for not only SiO2 surface but also Si surface. It was confirmed that mercury sensitized Photo-CVD is a promising method for selective deposition process at low temperature using large-area glass substrate.
Photoluminescence and Its Excimer Laser Irradiation Effects in SiO2 Film Prepared by Photo-Induced Chemical Vapor Deposition
Authors: Kanashima Takeshi , Masanori Okuyama Masanori Okuyama , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: February 2005

Defects and other imperfections in photo-induced chemical vapor deposition (photo-CVD) SiO2 films have been characterized by photoluminescence excited by ArF and F2 excimer lasers. Photoluminescence peaks have been observed at around 2.7, 3.5 and 4.4 eV and are characteristic of both the deposition temperatures of photo-CVD and excitation energy. The intensity of the photoluminescence peak at around 2.7 eV initially increases with ArF excimer laser irradiation but decreases after about 2000 shots. On the other hand, it decreases monotonously with F2 excimer laser irradiation. The origins of these peaks have been discussed in terms of various dependences of photoluminescence and absorption spectra.
Effects of H2O on Atomic Hydrogen Generation in Hydrogen Plasma
Authors: Kikuchi Jun , Fujimura Shuzo , Masafumi Suzuki Masafumi Suzuki , Hiroshi Yano Hiroshi Yano
Published: February 2005

The effects of water vapor added to hydrogen plasma were investigated by measuring the relative concentrations of hydrogen atoms in the plasma and in the downstream. The added water vapor increased the concentration of hydrogen atoms in the downstream to an amount 80 times greater than that without addition of water vapor. The relative concentration of hydrogen atoms generated from water-vapor-added hydrogen gas was only slightly decreased in the downstream. To clarify the role of water vapor, we examined the behavior of oxygen atoms and OH radicals. As a result, it was revealed that water vapor passivated the quartz surface and the recombination of hydrogen atoms was prevented.