bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Ultrasound on Driving Force of Diffusion Dialysis
Authors: Li Hui , Etsuzo Ohdaira Etsuzo Ohdaira , Masao Ide Masao Ide
Published: October 2002

In this paper, we discuss the effect of ultrasound on the driving force of diffusion dialysis which we demonstrate through experiments. The experiments were conducted using a cellophane membrane and 0.025 wt% NaCl solution at 25° C under ultrasonic irradiation of different sound pressures from 55 kPa to 100 kPa, at a frequency of 27.5 kHz. It was found that the amount of NaCl permeated decreases with increasing sound pressure when the diffusion direction is opposite to the irradiation direction of ultrasound.
Scanning Nonlinear Dielectric Microscope Using a Lumped Constant Resonator Probe and Its Application to Investigation of Ferroelectric Polarization Distributions
Authors: Yasuo Cho Yasuo Cho , Shigeyuki Atsumi Shigeyuki Atsumi , Kiyoshi Nakamura Kiyoshi Nakamura
Published: October 2002

A new probe using a lumped constant resonator for the scanning nonlinear dielectric microscope has been developed. This probe has sufficient resolution to observe the area distribution of ferroelectric polarization. Using this probe, the distributions of the domains in the thin film of a copolymer of vinylidene fluoride and trifluoroethylene and in a lithium niobate substrate with a titanium-diffused inversion layer are observed.
Optical Measurement System of Sound Pressure with Refracted Laser Light Propagated through an Acoustic Field
Authors: Kitsu Katsuo , Ikeno Yasunori , Tsuchiya Takenobu , Natori Nobuyuki Endoh
Published: October 2002

An optical measurement method using a laser beam is described for the quantitative measurement of acoustic fields. The light beam is refracted in the acoustic field because the distribution of densities forced by sound pressure generates a refractive index gradient in the medium. The characteristics of the acoustic field can be measured using a laser beam refracted by the acoustic field. To confirm the validity of the method, the acoustic field generated by a lead zirconate titanate (PZT) circular-plane transducer was measured for comparison with the characteristics obtained from a conventional hydrophone. We also measured harmonic contents, wave distortion due to the nonlinear effect of water, and subharmonics of the n/2 th order (n: integer) caused by cavitation in water.
Measurement of Ultrasonic Attenuation in Magnetic Fluid and its Application to Surface Profiling
Authors: Kazuhiko Imano Kazuhiko Imano , Hiroshi Inoue Hiroshi Inoue
Published: October 2002

The measurement of ultrasonic attenuation in a magnetic fluid (MF) is carried out to investigate the properties of frequency and magnetic field dependence in an ultrasonic propagation medium. The reference method for the ultrasonic attenuation measurement is explained and is executed by a pulse reflection system in the frequency range from 1 to 15 MHz. The magnetic field dependence of attenuation in a MF is measured with a pulse transmission system at a field strength from 0 to 0.2 T. Experimental results show that: 1) the attenuation constant divided by the frequency squared, α/f
2, is almost constant (0.5×10-15 s2/cm) over a frequency of 3.5 MHz. 2) Relative changes in attenuation, Δα, in the magnetic field are less than 2 dB over the frequency range from 1 to 15 MHz. Surface topographical profiling of drilled holes in an aluminum plate is carried out to demonstrate the usefulness of a MF as an ultrasonic propagation medium.
Molecular Arrangement Simulation of Pentacosadiynoic Acid Langmuir-Blodgett Films
Authors: Higashino Hidetaka , Mizoguchi Eriko , Ogawa Kazufumi
Published: October 2002

A simulation of the molecular arrangement of 10,12-pentacosadiynoic acid (PDA) Langmuir-Blodgett (LB) films has been carried out. The PDA molecules were optimized to local minimum energy structures by the molecular mechanics technique using Allinger's MM2 force field. The optimized molecules were arranged in the close-packed structures in a two-dimensional area where the closest atomic distances of the contacting molecules were restricted by the Van der Waals radii. The simulation results showed successful agreement with the reported experimental data.
Estimation of the Impulse Response for Diffracted Waves from a Semi-Infinite Plane by Virtual Discontinuity Principle of Diffraction
Authors: Ueda Kwanshin Park
Published: October 2002

The virtual discontinuity principle of diffraction (VDPD) is a new method for the analysis of field diffracted by three-dimensional objects that satisfy the wave equation and boundary condition for obstacles of arbitrary geometry. In this study, the temporal response of diffracted fields is analyzed using VDPD. The impulse response of waves diffracted by a semi-infinite plane is calculated using VDPD and geometrical-optics expression of acoustic fields, and compared with the exact solution. The profile of the impulse response by VDPD showed a good agreement with the exact solution, but the decay time of the impulse response, determined using VDPD, has a tendency to be shorter than the decay time determined from the exact solution.
Confirmation of the Distribution of Measured Values from an Ultrasound Fetal Heart Rate Monitor
Authors: Noguchi Yasuaki , Hamada Takeo , Matsumoto Fujihiko , Sugimoto Suguru , Yoshida Atsushi , Kobayashi Hisaaki , Kobayashi Mitsunao
Published: October 2002

To estimate the measurement error in an ultrasound fetal heart rate (FHR) monitor, we compared the differences in the distribution of the FHR measured with an ultrasound Doppler to the FHR measured with a direct fetal electrocardiogram. We confirm that (1) the distribution is very similar to Student's t distribution, and (2) the number of degrees of freedom in Student's t distribution has a significant impact on the evaluation of fit.
Evaluation of Mortar Layer Thickness on Concrete Boards Using the Surface Wave Velocity Dispersion Effect
Authors: Kato Hiroshi Kamata
Published: October 2002

A novel nondestructive test for the thickness of a mortar layer on the surface of a concrete building wall board is proposed in this paper. The method is based on the surface wave velocity dispersion effect in the mortar layer. The velocity of the surface wave varies from 1850 m/s to 1500 m/s at 77 kHz as a function of the thickness of the mortar layer from 10 mm to 30 mm.
Ultrasonic Flaw Detection for High Impedance Materials Using a Transmission Line Coupling Method
Authors: Hirokuni Yamaguchi Hirokuni Yamaguchi , Masasumi Yoshizawa Masasumi Yoshizawa , Norio Tagawa Norio Tagawa , Tadashi Moriya Tadashi Moriya , Shin-ichi Yagi Shin-ichi Yagi
Published: October 2002

A method for the detection of hidden flaws close to the surface of the sample is described. The method uses a fused quartz rod coupled to the sample. The flaw is measured as a variation in the acoustic impedance. The experimental detection of hidden flaws in glass and aluminum is demonstrated.
Dependence of the Photoacoustic Signal Intensity Spectra on Sintering Temperature for Ceramic CdS and CdS0.5Se0.5
Authors: Toyoda Taro , Hiroshi Fujimoto Hiroshi Fujimoto , Toshihiro Konaka Toshihiro Konaka
Published: October 2002

Photoacoustic spectroscopy is used to study the heat generated by nonradiative processes in ceramic CdS and CdS0.5Se0.5. It can provide information about optical absorption because the detection of signal is directly proportional to thermal energy induced by the absorbed photons. Photoacoustic spectra of ceramic CdS and CdS0.5Se0.5 depend on the sintering temperature. Photoacoustic signal intensities plotted semilogarithmically vary linearly with photon energy below the fundamental absorption edges. The steepness factor for CdS, which characterizes the slope of the semilogarithmically plot, decreases with increasing sintering temperature, indicating structural disorder. On the other hand, that of CdS0.5Se0.5 increases with increasing sintering temperature, indicating a decrease in structural disorder.
Observation of Photothermal Dielectric Signal for Powder
Authors: Yasuo Cho Yasuo Cho , Tomoyuki Kumamaru Tomoyuki Kumamaru , Teruaki Kasahara Teruaki Kasahara
Published: October 2002

A new photothermal dielectric (PTD) technique for measuring the thermal characteristics of powder is proposed. Using this technique, the PTD signal from a PZT powder is measured. The data shows that the average grain size of the powder can be estimated by using this PTD technique.
Brillouin Scattering from the Soft Optical Phonon in the Orthorhombic Form of a K 3Co 1-xFex(CN) 6 (x≤ 0.03) Crystal
Authors: Akira Yoshihara Akira Yoshihara , Makoto Kurosawa Makoto Kurosawa , Yoshiyuki Morioka Yoshiyuki Morioka
Published: October 2002

The soft optical phonon in the two-layer orthorhombic form of a K3Co1-x
Fex(CN)6 (x≤0.03) single crystal has been reinvestigated using a (3+3)-pass tandem Fabry-Pérot interferometer around the structural phase transition temperature. The soft phonon response can be well described using the phonon-relaxator coupled model. The soft phonon frequency ω∞/2π obeys the |T-T
c
±|1/2 law except in the vicinity of T
c=82.5 ±0.1 K; (ω∞/2π)2=1.20×103(T-82.1) (GHz2) for T>T
c and 4.55×103(83.0-T) (GHz2) for T<T
c. The soft phonon-relaxator coupling constant increases linearly above the T
c as the temperature decreases and the slope becomes steeper below T
c. The relaxation time is longer than 40 ps and independent of temperature above T
c, but becomes one order of magnitude shorter below T
c. The Fe3+ defects seem to be responsible for these unusual temperature dependences.
Effects of Thermal History on the Formation of Oxidation-induced Stacking Fault Nuclei in Czochralski Silicon during Crystal Growth
Authors: Harada Kazuhiro , Kida Hisashi Furuya
Published: October 2002

The formation of oxidation induced stacking fault (OSF) nuclei during Czochralski silicon crystal growth was investigated using crystals subjected to in situ annealing for either 1 or 4 hours by halt of pulling during crystal growth. The effects of in situ annealing at temperatures from about 1160° C to 1030° C can be summarized as follows. In positions held at about 1090° C and 1030° C, the radial distributions of OSFs, LSTDs (light scattering tomography defects), and OPs (oxygen precipitates after annealing) changed greatly. In the position held at about 1090° C, large LSTDs were formed but the OSF-ring disappeared in the region where it should have been present if pulling was not halted. In the position held at about 1030° C, the defects in the OSF-ring grew, its width increased, and the OP density both inside and outside the OSF-ring decreased with holding time. However, the radial distribution of defects at the position held at about 1160° C was similar to that for a reference crystal which was not subjected to halt of pulling. These results indicate that these defects were not formed until 1160° C, the large LSTDs were formed at 1160–1090° C, the OSF nuclei were formed at 1090–1030° C, and the OP nuclei inside and outside the OSF-ring were formed below 1030° C. We discussed the influence of point defects upon the formation of OSF nuclei.
Surface Wave Eigenmodes in a Finite-Area Plane Microwave Plasma
Authors: Ivan Ghanashev Ivan Ghanashev , Masaaki Nagatsu Masaaki Nagatsu , Hideo Sugai Hideo Sugai
Published: October 2002

The resonance frequencies of electromagnetic surface modes propagating along a plane dielectric-plasma interface are computed, taking into account the finite area of the latter. The analysis results in simple analytical formulae for estimating the plasma density at which a given mode can be expected to occur for given geometry and wave frequency. Comparison with measurements in large-area circular plasmas is made.
Metalorganic Vapor Phase Epitaxy of Thick InGaN on Sapphire Substrate
Authors: Shimizu Masaya , Kawaguchi Yasutoshi , Kazumasa Hiramatsu Kazumasa Hiramatsu , Nobuhiko Sawaki Nobuhiko Sawaki
Published: October 2002

Growth of thick InGaN films was performed on single crystal films of GaN or AlGaN and buffer layers of AlN, GaN or AlGaN by metalorganic vapor phase epitaxy (MOVPE). In the growth of InGaN on GaN or AlGaN films, smooth InGaN films with small indium mole fractions were grown in the initial growth stage caused by strong stress due to lattice mismatch. However, with an increase in thickness of the InGaN film surface became rough due to the generation of InGaN grains with large indium mole fractions. Smooth and thick (∼2 µ m) InGaN films with large indium mole fractions were grown on AlN, GaN or AlGaN buffer layers.
4.5 kV Injection Enhanced Gate Transistor: Experimental Verification of the Electrical Characteristics
Authors: Kitagawa Mitsuhiko , Hasegawa Shigeru , Inoue Tomoki , Akihiro Yahata Akihiro Yahata , Hiromichi Ohashi Hiromichi Ohashi
Published: October 2002

Experimental verifications are presented for the injection enhanced gate effects of a new metal oxide semiconductor (MOS) controlled power transistor. We call this transistor an “injection enhanced gate transistor” (IEGT). It was first experimentally confirmed that IEGTs achieve the same low on-state voltage drop as that of gate turn-off (GTO) thyristors without degradation of turn-off capability. The fabricated 4.5 kV IEGT with 8 µ m deep trench gates exhibited an on-state voltage of 2.5 V at 100 A/cm2, and the measured on-state voltage drop as a function of the trench gate structural parameter agrees well with the predicted values. By use of the fabricated IEGT, 4.2 kV self-clamped anode voltage switching operation was achieved at a turn-off current density of 65 A/cm2. The observed electrical characteristics of the fabricated IEGTs agree well with the predicted characteristics, and it was confirmed that high voltage and high power can be directly controlled by a MOS gate.
Effects of Nonlinear Wave Absorption on the Radiation Loss Fraction during Second Harmonic Minority Ion Cyclotron Resonance Heating Experiments in JT-60U
Authors: Saigusa Mikio , Moriyama Sinichi , Kimura Haruyuki , Hamamatsu Kiyotaka , Fujii Tsuneyuki , Hosogane Nobuyuki , Tatsuo Sugie Tatsuo Sugie , Hirotaka Kubo Hirotaka Kubo
Published: October 2002

The ratio of an increment in radiation power to ion cyclotron resonance heating (ICRH) power (ΔPradmain/PIC) decreased from about 40% to below 10% with increasing ICRH power in JT-60U. The most plausible mechanism for the anomalous behavior of ΔPradmain/PICis inferred to be nonlinear wave absorption, which was experimentally estimated from the time derivative of the diamagnetic stored energy at the turn-off timing of the ICRH pulse. Nonlinear wave absorption observed during the experiments supported the theoretical estimation using a full wave code incorporating the 1-D Fokker-Planck code.
GeO Desorption in Reactive Scattering of an Oxygen Molecular Beam with a Ge(100) Surface
Authors: Kamioka Isao , Kitajima Masahiro , Kawabe Takaya , Kazutaka G. Nakamura Kazutaka G. Nakamura
Published: October 2002

Reactive scattering of O2 with a Ge(100) surface has been studied using resonance enhanced multiphoton ionization (REMPI) at substrate temperatures between 870 and 1020 K. The first observation of the (2+1) REMPI of GeO is performed at around 297 nm. The desorption rate constant of GeO is determined by analyzing the GeO waveforms, and is estimated to be k=1017.6±0.4 exp
(-2.4±0.1 eV/k
B
T) [ s-1], and the large pre-exponential factor is well reproduced using a transition state theory calculation. The angular distribution of the GeO is found to be isotropic on the virgin surface and deformed on the highly etched surface.
Relation of Oxygen Content and Modulation Structure in Bi2201 System
Authors: Gaojie Xu , Zhiqiang Mao , Mingliang Tian , Guien Zhou , Yuheng Wu Ronghu
Published: October 2002

Two series of samples of Bi1.8Pb0.2Sr2CuO

y

and Bi1.9Sr1.6La0.4CuO

y

systems with different oxygen content were prepared. The microstructure of these samples was investigated by means of X-ray diffraction (XRD) and electron diffraction (ED). The analysis of XRD indicates that a progressive change in lattice parameters takes place with the removal of oxygen. The analysis of ED patterns reveals that for the Bi1.8Pb0.2Sr2CuO

y

system, the orthorhombic modulation (Pb-type modulation) is strongly related to the oxygen in Bi2O2 layers, which implies that the orthorhombic modulation is not compositional (Pb) modulation, and the periodic distribution of oxygen in Bi2O2 layers induced by Pb doping may be the real origin of orthorhombic modulation. While for the Bi1.9Sr1.6La0.4CuO

y

system, the monoclinic incommensurate modulation is independence of the variation of oxygen in Bi2O2 layers, which suggests that the intercalation or removal of extra oxygen atoms was only the result of the monoclinic modulation structure changing, and the crystal misfit between Bi2O2 layers and perovskite blocks was the real driving force of the Bi-concentrated band superstructural modulation.
Magnetic Properties of SmFe3 Single Crystal
Authors: Samata Hiroaki , Fujiwara Nobuto , Shimizu Yoshihiro , Nagata Yujiro , Uchida Takayuki , Lan Ming Der
Published: October 2002

SmFe3 single crystal was grown by a self-flux method using Sm as a flux, and its crystallographic and magnetic properties have been studied. SmFe3 crystalizes in the rhombohedral PuNi3-type structure and has lattice constants of a=0.5179 and c=2.4795 nm. The saturation magnetizations M
S at 5 K and 300 K are respectively 89.9 emu/g and 80.7 emu/g, and the Curie temperature is 644 K. The anisotropy constants K
1 and K
2 at 5 K are -2.69×107 and 11.9×107 erg/cm3 and at 300 K are 2.36×107 and 2.21×107 erg/cm3. While the easy direction of magnetization is parallel to the c-axis at 300 K, it lies on the surface of a cone below 160 K. The angle θ between the c-axis and the generatrix of the cone is about 31° at 5 K.
An Efficient Excitation of Iodine Atoms by Mixing of Two Microwave Discharged Flows of I2 and Oxygen Containing Singlet Oxygen
Authors: Kobayashi Takaomi , Satoh Naoto , Makoto Ishibashi Makoto Ishibashi , Nobuyuki Fujii Nobuyuki Fujii
Published: October 2002

Excitation of iodine atoms, i.e., the transition I2P1/2–I2P3/2, effectively occurred, when discharged iodine was mixed with a discharged oxygen flow containing singlet oxygen, O2(1Δ). We demonstrate that microwave discharge of molecular iodine is useful for the formation of atomic iodine and that the resultant atom is excited by O2(1Δ) in a two discharge-flow system.
A Simple Graphical Method for Evaluating the Polarization and Relaxation Times of Dipoles or Densities and Energy Levels of Traps in a Dielectric Film from Transient Discharge Current
Authors: Hideharu Matsuura Hideharu Matsuura
Published: October 2002

The purpose of this study is to propose a simple graphical method for determining the polarization and relaxation times of dipoles and for determining the densities and energy levels of traps in a dielectric film. Using the transient discharge current density J
dis(t) which flows in a capacitor consisting of a dielectric film between two electrodes, a function S(t) is defined as S(t) ≡t ·J
dis(t) exp
(1). For dipoles with discrete relaxation times (τ
i
) or for traps with discrete energy levels (ΔE
t i
) where the subscript i represents the i-th dipole or trap, S(t) has peaks corresponding to each τ
i
or ΔE
t i
. Using each peak, therefore, one can easily determine the dipole polarization (P
s i
) and τ
i
, or the trap density (N
t i
) and ΔE
t i
. By a simple curve-fitting procedure, moreover, one can easily evaluate the continuously distributed dipole polarization P
s(τ) or energetically distributed trap density N
t(ΔE
t).
Bistable Switching Effects and Thermal Storage of Polymer/Induced Smectic Phase Composite Film
Authors: Jenn Chiu Hwang Jenn Chiu Hwang , Yu Chyi Tsai Yu Chyi Tsai
Published: October 2002

The electrooptical effect of a composite (polymer/induced smectic phase formed by mixing low molecular weight nematic liquid crystals) has been studied. The low molecular weight nematic liquid crystal 4-cyano-4′-pentyloxy biphenyl 5OCB with a strong polar terminal group was miscible with the nematic liquid crystal 4-hexyloxyphenyl-4′-pentyl benzoate HPPB having a weak polar terminal group. This binary mixture formed an induced smectic phase over a wide range of concentration and temperature. The reversible transparent-opaque (light scattering) switching of the polymer/induced smectic phase composite was observed upon the application of electric fields with low and high frequencies, respectively. Both the transparent and opaque states of the mixture could be maintained stably, even after the electric field was turned off (memory effect). The response speed for bistable light switching could be remarkedly improved by reducing the 5OCB fraction, while maintaining an induced smectic state. Thermal writing and local erasure in polymer/induced smectic composite with a response time of ms at room temperature are realized with bistable and reversible light switching.
Preparation by a Sol–Gel Process and Dielectric Properties of Lead Zirconate Titanate Glass-Ceramic Thin Films
Authors: Kunio Saegusa Kunio Saegusa
Published: October 2002

Ferroelectric glass-ceramic thin films of PbZr0.5Ti0.5O3(PZT)–PbO–B2O3, PZT–PbO–SiO2 and PZT–PbO– SiO2–B2O3 were produced by a sol-gel process. A pin-hole-free thin film of 300–500 nm thickness on a Pt/Ti/ SiO2/Si substrate was obtained having a structure in which small PZT crystals developed in a glass matrix. A high PZT content, of more than 80%, was achieved at levels unattainable by a conventional glass-ceramics preparation method. The perovskite-type PZT crystallized at around 500° C in the pure PZT, PZT–PbO–B2O3, and PZT–PbO–SiO2–B2O3 systems and at around 700° C in the PZT–PbO–SiO2 system. The dielectric properties of the 0.835PZT–0.165(3PbO·SiO2·B2O3) film fired at 700° C with gold electrodes were ε=1000, and tan
δ=0.035.
Cation Distributions in Nickel Ferrites
Authors: Tsukimura Katsuhiro , Sasaki Satoshi , Kimizuka Noboru
Published: October 2002

Crystal structures of magnetite ( Fe3O4) and Ni-ferrites ( Ni0.4Fe2.6O4 and Ni0.6Fe2.4O4) were determined using X-ray single-crystal diffraction methods. The single crystals were grown hydrothermally at 673–743 K, and some of the crystals were heated at 1303 K. After the positional and thermal parameters were initially determined using the MoKα radiation data set, the cation distributions were determined using the synchrotron radiation data set. The synchrotron X-rays were tuned at a wavelength 0.015 Å longer than the Fe K-absorption edge. This allowed us to precisely determine the cation distributions with a large difference in scattering factors. Our structural analyses with the synchrotron radiation measurements show that all the Ni ions in the ferrites are involved in the octahedral B sites.
The Nickel/Diamond(100)–(2 × 1)H Interface Studied with Electron Spectroscopy
Authors: Michael Pitter Michael Pitter , Markus B. Hugenschmidt Markus B. Hugenschmidt , R. Jürgen Behm R. Jürgen Behm
Published: October 2002

The nickel/diamond(100)–(2 ×1)H interface has been studied using Auger electron spectroscopy, electron energy loss spectroscopy and low-energy electron diffraction. Deposition of ultrathin nickel films at room temperature results in the formation of disordered nickel islands, whereas heteroepitaxial growth is achieved during deposition at 520 K. At temperatures above 850 K nickel interaction with the uppermost diamond layers causes graphitization of the diamond surface, a process which starts only at temperatures above 1500 K on the clean diamond surface.
Enhancement of Electron Mobility in Quasi-One-Dimensional Structure
Authors: Shoko Niwa Shoko Niwa , Masahito Yamaguchi Masahito Yamaguchi , Takamasa Suzuki Takamasa Suzuki , Nobuhiko Sawaki Nobuhiko Sawaki
Published: October 2002

The electron mobility and energy relaxation phenomena in GaAs wires with geometrical width of 300–400 nm were investigated using the magnetotransport and photoluminescence (PL) intensity correlation method. The electron mobility at 4.2 K was analyzed with the Shubnikov de Haas effect. It was found that the narrower the wire width is the higher the electron mobility is. The femtosecond PL measurements were performed at 77 K. The rate of cooling with emission of LO phonons of photoexcited hot electrons was found to be lower in narrower wires. The electric field dependence of the PL spectra showed that the LA phonon scattering rate is also reduced in quasi-one-dimensional electron gas (Q-1DEG) structures.
Influence of Biased Electrode on Plasma Confinement in the Tohoku University Heliac
Authors: Inagaki Shigeru , Kitajima Sumio , Takayama Masakazu , Nakamura Eiji , Takeo Yoshida Takeo Yoshida , Hiroshige Watanabe Hiroshige Watanabe
Published: October 2002

Observations of an increase in electron density triggered by electrode biasing are reported in the Tohoku University Heliac (TU-Heliac). The biased electrode, which is located deep inside the plasma, induces a strong positive radial electric field, after which the line density increases by a factor of 2, the electron density profile steepens and the fluctuation level drops. We estimate the damping force opposing poloidal rotation experimentally and compare it with various versions of the neoclassical theory. The experimental results agree in that the measured damping force has a local maxima at |M
p|=1–2 and tends to be proportional to M
p in the high speed region (|M
p|>3–6), where M
p is the poloidal Mach number. For |M
p|<1–2, however, the dependence of the measured damping force on M
p differs a little from theoretical predictions.
Two-Dimensional Transport of Submicron Particles in Capacitively Coupled Plasma Reactor
Authors: Ryu-ichi Hashido Ryu-ichi Hashido , Masao Hasebe Masao Hasebe , Yoshiyuki Hosokawa Yoshiyuki Hosokawa , Nobuhiko Nakano Nobuhiko Nakano , Yukio Yamaguchi Yukio Yamaguchi , Toshiaki Makabe Toshiaki Makabe
Published: October 2002

We show a series of two-dimensional (2D) space distributions of submicron insulating particles in Ar rf-capacitively coupled plasma (CCP) as a function of time after injection by using a fluid model under the external conditions of 102sccm < flow rate < 105sccm and 10-8m < particle radius < 10-5m at 13.56 MHz in Ar. The final density profile is strongly dependent on the flow rate. For low flow rates, the profile of density is disk shaped at low pressure and dome shaped at high pressure. As the flow rate increases, the profile becomes ring shaped, and finally all particles are exhausted. There is a linear relation between the flow rate and the minimum radius of a particle which can be exhausted. It was found that high pressure, low voltage and strong gas flow are the most effective for the purpose of exhausting particles from the reactor.
Cross Section Measurements for Electron-Impact Dissociation of C 4F 8 into Neutral and Ionic Radicals
Authors: Hirotaka Toyoda Hirotaka Toyoda , Makoto Iio Makoto Iio , Hideo Sugai Hideo Sugai
Published: October 2002

The absolute cross sections for electron-impact dissociation of octafluoro-cyclobutane (C4F8) into the neutral radicals CF, CF2, CF3 and C3F5 are measured from the threshold to 250 eV. This measurement was accomplished by appearance mass spectrometry in a dual electron beam device. The threshold energies for the neutral dissociation into CF, CF2 and CF3 are 14.5, 10.5 and 12.8 eV, respectively. The cross sections for dissociation from C4F8 into CF2 and CF are much larger than those from CF4. Besides the neutral dissociation, the cross sections for the dissociative ionization of C4F8 are extensively measured for formation of CF+, CF2
+, CF3
+, C2F3
+, C2F4
+ and C3F5
+.
Concentration Dependence of Brownian Motion and the Viscosity of Hemoglobin Solutions
Authors: Okuda Masaaki Iino
Published: October 2002

Brownian rotational and translational motion of hemoglobin molecules and the viscosity of concentrated hemoglobin solutions are quantitatively described by modified hydrodynamics commonly applied to suspensions of macroscopic hard spherical particles. The modified hydrodynamic forms, including explicitly the volume fraction of the hydration shell, a crowding factor, and Einstein's coefficient, are found to reproduce well the concentration dependence of the kinetic parameters, such as the viscosity, protein rotational correlation time, and diffusion coefficient, for protein volume fractions from 0 to 0.34. It is also found that the apparent volume fraction of the hydration shell decreases with increasing protein volume fraction for protein volume fractions above 0.34, where the viscosity of the hemoglobin solution exceeds 0.1 Pa s, indicating that the viscosity of the hydration shell ranges from 0.1 Pa s to about 1 Pa s (300 ps–3 ns in NMR correlation time).
Nano-Fabrication on GaAs Surface by Resist Process with Scanning Tunneling Microscope Lithography
Authors: Katsuya Hironaka Katsuya Hironaka , Nobuyuki Aoki Nobuyuki Aoki , Hidenobu Hori Hidenobu Hori , Syoji Yamada Syoji Yamada
Published: October 2002

Recently scanning tunneling microscopes (STMs) have become important tools for nanometer scale fabrication. In order to make a nanoscale structure on a semiconductor surface, we attempted to lithograph very fine lines (possibly less than 10 nm) by using a resist process with an STM as an electron beam source. A diluted positive electron beam resist, poly-methyl methacrylate (PMMA), was first coated on a S-doped GaAs substrate. Using the STM in air, we approached a W-tip to the surface at a bias voltage of 10 V and a tunneling current of 0.5 nA, and made a line using by scanning the tip with various scan times. We then analyzed those lines made by the STM tip using an atomic force microscope (AFM) in air. After these processes, we deposited a Ti membrane on the sample surface by vacuum evaporation, then lifted it off. As a result, we confirmed that it was possible to make fine Ti lines as narrow as 50 nm by this process.
Atomic Force Microscopy Studies of Erythrocyte Membranes Immobilized by Centrifugation under Aqueous Conditions
Authors: Hideki Iwamoto Hideki Iwamoto , Nobuyuki Wakayama Nobuyuki Wakayama
Published: October 2002

Structural studies of human erythrocytes and corresponding membranes (erythrocyte ghosts and inside-out vesicles) immobilized by centrifugation under aqueous conditions using atomic force microscopy (AFM) are described. The samples immobilized by centrifugation on mica substrates provided much better images than those simply adsorbed on the substrates, and we obtained images of mesh-like structures and circular, plaque-like structures. Comparison of these structures using electron microscope images reported to date suggests that the observed structures seem to correspond to the cytoskeletal networks and the cell surfaces, respectively. Bundle structures, thought to be induced by the interaction between the AFM tip and the cytoskeletal networks, were occasionally observed. The centrifugal fixation method, which is described here for the first time, can easily immobilize biomembranes under aqueous conditions and is expected to enable the detailed observation of various types of living cells and biomembranes under physiological conditions.
Electric Field and Contact Interactions of Tip with Adenine Molecules on SrTiO3(100)-√ 5×√ 5 Surfaces
Authors: Akiyama Ryota , Matsumoto Takuya , Hiroyuki Tanaka Hiroyuki Tanaka , Tomoji Kawai Tomoji Kawai
Published: October 2002

We have performed tip-assisted migration of adenine molecules adsorbed on SrTiO3(100)-√ 5×√ 5 surfaces with scanning tunneling microscopy (STM) under ultrahigh vacuum (UHV) conditions at room temperature. The migration with stepwise current control reveals the difference in binding energy of adenine molecules adsorbed on various sites on √ 5×√ 5 surfaces. The adenine molecules easily migrate on the √ 5×√ 5 surface at room temperature and settle down at the trap sites of Sr atoms remaining on the surface. Quantitative analysis of migration probability as a function of tunneling current (I) and tip bias voltage (V
t) shows that the electric field effect is dominant at V
t≧4 V or I≧70 pA, while contact interaction is dominant at 0 V<V
t≦0.1 V for the tip-assisted migration in this system.
Electronic Structures of Few Electrons in a Quantum Dot under Magnetic Fields
Authors: Mikio Eto Mikio Eto
Published: October 2002

The many-body effect on the electronic structures of a few electrons confined in a quantum dot is calculated, under magnetic fields, by the exact diagonalization method. When the Coulomb interaction is comparable to the one-electron level spacings and the magnetic field is not too large, the peak positions of the Coulomb oscillation reflect a shell structure of the one-electron levels, which is in semi-quantitative agreement with experimental results [Tarucha et al.: Phys. Rev. Lett. 77 (1996) 3613]. Under strong magnetic fields, the correlation effect results in transitions of the ground state. These transitions can be observed as cusps of the magnetic-field dependence of the peak positions, in the presence of the Zeeman effect.
Magnetic Field Effects on Anisotropic Parabolic Quantum Dots
Authors: Akiko Natori Akiko Natori , Yuichiro Sugimoto Yuichiro Sugimoto , Masamichi Fujito Masamichi Fujito
Published: October 2002

The many-electron ground states of cylindrical parabolic quantum dots in magnetic fields parallel to the cylindrical axis are investigated by means of an unrestricted Hartree-Fock method. The many-electron eigenstates are assigned by two quantum numbers, L
z and S
z, the z-components of the total orbital angular momentum and the total spin, respectively. As the strength of the magnetic field increases, the spin state of the ground state changes from the paramagnetic to the ferromagnetic state according to Hund's rule. | L
z| of the ground state increases monotonically with magnetic field strength. In the extremely high-field region of complete spin polarization, | L
z| increases the electron number N by N. From the total energy of the ground state, the chemical potential and the magnetic susceptibility of quantum dots are calculated as functions of electron number up to 12. Magnetic field dependence of the chemical potential exhibits many cusps, caused by the transitions of many-electron ground states. The chemical potential depends on the vertical extent of a quasi-two-dimensional dot only in weak and intermediate fields where the spin polarization is incomplete, and it depends only slightly on the spin Zeeman term for GaAs dots. The magnetic susceptibility for an array of dots consists of two parts, paramagnetic and diamagnetic, and shows oscillation with electron number at low temperatures.
Gate Voltage Dependence of the Resistance of a Two-Dimensional Array of Small Tunnel Junctions
Authors: Hideto Kazawa Hideto Kazawa , Ryuta Yagi Ryuta Yagi , Keiji Ono Keiji Ono , Youiti Ootuka Youiti Ootuka , Shun-ichi Kobayashi Shun-ichi Kobayashi
Published: October 2002

We studied the gate voltage dependence of the resistance of a two-dimensional array of Al/AlOx/Al small tunnel junctions. The resistance exhibited periodic oscillations similar to those in a single electron transistor in both superconducting and normal states. The amplitude of the oscillation in the superconducting state was much smaller than that in the normal state.
Nanostructure Fabrication Using Selective Growth on Nanosize Patterns Drawn by a Scanning Probe Microscope
Authors: Sasaki Kentaro , Keiji Ueno Keiji Ueno , Atsushi Koma Atsushi Koma
Published: October 2002

A novel method of fabricating organic material nanostructures using selective growth on patterned layered material surfaces has been developed. First, an epitaxial monolayer film of layered semiconductor GaSe was grown on a cleaved face of MoS2. Then, nanosize patterns were drawn by scratching only the grown GaSe film using an atomic force microscope (AFM). Next, C60 molecules were deposited on the surface. It has been found that if a substrate temperature is appropriately chosen, C60 molecules nucleate only on the bare MoS2 surface and fill up the carved nanostructures. This combination of AFM lithography and selective growth enables the formation of C60 nanostructures as small as 10 nm.
Magnetotunnelling and Photoluminescence Spectroscopy of Self-Assembled InAs Quantum Dots
Authors: E. Itskevich Igor , Henini Thomas Ihn , Carmona Humberto de Andrade , Eaves Laurence , Main Peter Clifford , Maude Duncan Kennedy , Portal Jean-Claude
Published: October 2002

Self-assembled InAs quantum dots (QDs) in AlAs and GaAs matrices are investigated by tunnelling and optical spectroscopy. Tunnelling through an individual QD in the AlAs barrier of a n-i-n single-barrier device is used to probe the properties of both the emitter two-dimensional electron gas (2DEG) and the QD. The Landau fan of the 2DEG is mapped at magnetic field parallel to the tunnelling current, B\VertI, as well as the spin splitting in the QD at B⊥I. An electron g-factor in the QD is determined as ∣g∣=1.2±0.5. In the photoluminescence spectrum of InAs QDs in B up to 23 T, a strong anisotropy in the diamagnetic shift is found. The spatial extent of the carrier wave function in the dot is estimated as 60 Å. Under hydrostatic pressure up to 8 kbar, the pressure coefficient for the dot emission line is (9.1±0.2) meV/kbar, about 20% smaller than for the Γ-point bandgap in bulk GaAs.
Self-Organized CdSe Quantum Dots on (100)ZnSe/GaAs Surfaces Grown by Metalorganic Molecular Beam Epitaxy
Authors: Munetaka Arita Munetaka Arita , Adrian Avramescu Adrian Avramescu , Katsuhiro Uesugi Katsuhiro Uesugi , Ikuo Suemune Ikuo Suemune , Takahiro Numai Takahiro Numai , Hideaki Machida Hideaki Machida , Norio Shimoyama Norio Shimoyama
Published: October 2002

II–VI semiconductor low-dimensional structures, quantum dots, have been grown on GaAs substrates by metalorganic molecular beam epitaxy (MOMBE). Before the heteroepitaxial growth, atomically flat, As-stabilized GaAs surfaces were prepared by high-temperature As cleaning using tris-dimethylamino-arsenic (TDMAAs). CdSe thin films deposited on (100)ZnSe/GaAs surfaces have been investigated with atomic force microscopy (AFM) and were found to form three-dimensional islands with rather uniform size distribution. A large mismatch (∼7%) of lattice constants between CdSe and ZnSe pseudomorphically grown on GaAs possibly results in the Stranski-Krastanov growth mode. CdSe quantum dots with a diameter of 97±11 nm were successfully formed at 350°C.
Metalorganic Vapor Phase Eitaxy Growth Features of AlGaAs in Tetrahedral-Shaped Recesses on GaAs (111)B Substrates
Authors: Tomoko Tsujikawa Tomoko Tsujikawa , Wugen Pan Wugen Pan , Keishi Momma Keishi Momma , Masahiro Kudo Masahiro Kudo , Kunio Tanaka Kunio Tanaka , Hiroyuki Yaguchi Hiroyuki Yaguchi , Kentaro Onabe Kentaro Onabe , Yasuhiro Shiraki Yasuhiro Shiraki , Ryoichi Ito Ryoichi Ito
Published: October 2002

We have investigated the compositional modulation of AlGaAs layers grown in tetrahedral-shaped recesses (TSRs) on n-type GaAs (111)B substrates using scanning electron microscopy, photoluminescence and cathodoluminescence. Growth hardly occurred between the TSRs, and complicated facets were seen in the TSR. Gallium-rich regions were formed around the edges between sidewalls rather than at the center of sidewalls and at the bottom region rather than the top region. To observe the facetting process during growth, GaAs/AlGaAs multilayers were also grown in TSRs. Aluminum compositional modulation is dependent not only on the difference in migration distances of Ga and Al atoms but also on the differences in the incorporating process among different facets.
Highly Field Sensitive (150 Oe) Quadri-Valued Magnetooptical Media for High-Speed Overwriting
Authors: Takao Hiroki , Shimazaki Katsusuke , Ohta Norio , Yoshihiro Masafumi , Nobuyuki Nagai Nobuyuki Nagai , Susumu Imai Susumu Imai
Published: October 2002

For high-density and high-speed magnetooptical (MO) recording, the use of magnetic multi-valued (MMV) MO media has been proposed. [rf:1] A quadri-valued recording has been achieved using this media and a field modulation recording method. For practical use of this media, it is important to reduce the critical magnetic field to minimize the applied field for realizing the quadri-valued recording. We have achieved reduction of the critical magnetic field down to 150 Oe using a new coupled film, TbFeCo/GdTbFeCo.
Advantages of the Asymmetric Tunnel Barrier for High-Density Integration of Single Electron Devices
Authors: Matsumoto Yoshinari , Hanajiri Taturo , Toyabe Tohru , Sugano Takuo
Published: October 2002

The advantages of single electron devices with asymmetric tunnel barriers for high-density integration were demonstrated by computer simulation. Electron tunneling rates through the asymmetric potential profile of the tunnel barrier are dependent on the energy of the tunneling electron. This energy-dependent tunnel rate leads to two important advantages in single electron devices. First, an unintended tunneling caused by co-tunneling or thermal excitation in the Coulomb blockade region can be substantially suppressed, improving the reliability of the device performance. Secondly, the circuit design becomes simpler with unilateral electron tunneling. The advantages of asymmetric tunnel barriers are a breakthrough for the preventation of the difficulties associated with conventional single electron devices.
Luminescence of Excitons Localized by Monolayer Interface Fluctuations in ZnSe/MgS Superlattices Grown by Metalorganic Vapor Phase Epitaxy
Authors: Hiroyuki Nashiki Hiroyuki Nashiki , Ikuo Suemune Ikuo Suemune , Hideki Suzuki Hideki Suzuki , Katsuhiro Uesugi Katsuhiro Uesugi
Published: October 2002

Luminescence properties of ZnSe/MgS superlattices (SLs) grown by metalorganic vapor phase epitaxy (MOVPE) were characterized using photoluminescence (PL) and reflection measurements. At low temperature, PL peaks originating from localized excitons which were confined by monolayer fluctuations were clearly observed. It was found that the luminescence efficiency of localized excitons was very high, probably nearly 100%. The thermalization of localized excitons to free excitons with the increase of temperature leads to a blue shift of the PL peak energy and an abrupt decrease of the luminescence intensity. This decrease of the luminescence intensity is attributed to the capture of free excitons by nonradiative centers. A SL which shows luminescence from continuously distributed tailed states exhibited a temperature dependence much different from that of the above SLs which show luminescence from the localized excitons defined by the interface fluctuations.
Novel Erasable and Rewritable Optical Memory Utilizing Photostimulated Luminescence in Eu and Sm Codoped SrS Phosphor Ceramics
Authors: Nanto Hidehito , Douguchi Yoshiteru , Nishishita Jun-ichi , Kadota Mitsuteru , Kashiwagi Noboru , Nasu Toru Shinkawa
Published: October 2002

Photostimulated luminescence (PSL) in Eu and Sm codoped strontium sulfide (SrS:Eu, Sm) phosphor ceramics is studied in order to develop a novel erasable and rewritable optical memory utilizing the PSL. Intense PSL with a peak at about 600 nm is observed in SrS:Eu, Sm phosphor ceramics which are stimulated with infrared light after irradiation with ultraviolet (UV) light or visible light. The excitation and emission mechanisms of the 600 nm PSL are discussed. The PSL characteristics for the optical memory are reported.
Analysis of Amorphous Silicon Solar Cells by the Photocurrent-Separation Method
Authors: Okamoto Shingo , Yoshihiro Hishikawa Yoshihiro Hishikawa , Shinya Tsuda Shinya Tsuda
Published: October 2002

A simple but profitable analysis of amorphous silicon (a-Si) solar cells is conducted. The analysis is based on the principle of separating the output current I
out(V) into the dark current I
d(V) and photocurrent I
ph(V). The illumination-intensity dependence of I
out(V) can be calculated in the wide range of illumination intensities (from 1.1×10-2 to 5.1×102 mW/cm2 in this study), even if the effects of series and/or shunt resistance are considerable. The output current is also investigated in relation to the design of multi-junction cells. I
out(V) of multi-junction cells can be simulated precisely by separating the I
out(V), both before and after light soaking. The estimation of cell parameters from the separated I
ph(V) is also investigated. I
out(V) can be expressed by a relatively simple formula using only two fitting parameters: the mobility-lifetime products (µτ) and built-in potential of the junction (V
t). Good agreement between the results of the experiments and the calculations in this study suggests that the basic concept of the analysis, i.e. I
out(V) can be separated into I
d(V) and I
ph(V), is valid.
Performance and Reliability Trade-off of Large-Tilted-Angle Implant P-Pocket on Stacked-Gate Memory Devices
Authors: Shen Shih-Jye , Chen Hsin-Ming , Lin Chrong-Jung , Chen Hwi-Huang , Hong Gary , Charles Ching-Hsiang Hsu Charles Ching-Hsiang Hsu
Published: October 2002

In this paper, the effects of large-tilted-angle p-pocket (LAP) implantation on the performance and reliability of stacked-gate memory cell are investigated. The utilization of LAP process achieves the improved programming efficiency and reduced punchthrough susceptibility. The 45° LAP cell featuring a fastest programming speed, however, would not be desirable due to the seriously aggravated read current degradation, drain/read disturbance, and early snap-back breakdown. The cells with 0° and 30° tilted angle are the feasible cells with the moderate programming performance and acceptable reliability constraints. Furthermore, the 0° LAP cell is preferred for the fact that it exhibits the desirable read current than that in 30° cell. Based on the cell performance and reliability consideration, the 0° p-pocket implanted cell is the optimal angle among 0°, 30° and 45° for the future scaling of stacked-gate memory cell.
Effect of Hydrogenation on Photodarkening in CdS-Doped Glass
Authors: Tadaki Miyoshi Tadaki Miyoshi , Koji Nitta Koji Nitta , Ken-ichi Towata Ken-ichi Towata , Naoto Matsuo Naoto Matsuo
Published: October 2002

The effect of hydrogenation on photodarkening has been investigated in CdS-doped glass to investigate the nature of photoinduced defects using luminescence and electron spin resonance (ESR). Photodarkening disappears after hydrogenation. This indicates that the photoinduced defects are passivated by hydrogen. The possible structures of the defects are considered in this paper.
Chemical State of Phosphorus at the Silicon Surface
Authors: Sato Yoshiyuki , Yoshimura Yusuke , Ono Kanta , Fujioka Hiroshi , Oshima Satoshi Maeyama
Published: October 2002

We used synchrotron radiation photoelectron spectroscopy (SRPES) to investigate the chemical state of phosphorus that piles up at the silicon surface covered with a native oxide and found that the piled-up phosphorus does not make bonds with oxygen.
Refractive Index Profiles of Ion-Implantation Waveguides Formed on Lithium Niobate and Lithium Tantalate Crystals
Authors: Lu Fei , Meng Ming-Qi , Wang Ke-Ming , Chen Xiang-Dong Liu
Published: October 2002

The planar waveguides are formed by He ion implantation on lithium niobate and lithium tantalate crystals. The refractive index profiles in the waveguides are obtained and fitted. The He ion implantation results in the decrease of indices in the barriers both for lithium niobate and lithium tantalate. In the region of guide, the profiles of the extraordinary indices n
e in two crystals are significantly different. The probable reasons are discussed by use of 16O(α, α)16O 3.045 MeV resonance reaction.
Simultaneous Time- and Wavelength-Division Optical Digital Processing with a InP Buried Side-Injection-Light-Controlled Bistable Laser Diode
Authors: Nonaka Koji , Yoshio Noguchi Yoshio Noguchi , Takashi Kurokawa Takashi Kurokawa
Published: October 2002

An InP-buried side-injection-light-controlled bistable laser diode (SILC-BLD) has been fabricated for digital optical processing. Signal-regenerating wavelength conversion and optical demultiplexing for non-return-to-zero (NRZ) optical signals are simultaneously demonstrated with the module, which has integrated functions for gating input signals, digital regeneration, and bit memory characteristics.