bluuebunny/crossref_metadata_2025 huggingface dataset:
Ar Lowest Excited State Densities in Ar and Ar–Hg Hot Cathode Discharge
Authors: Yuasa Kunio , Yamashina Kazue , Sakurai Takeki
Published: October 2002

The densities of the Ar lowest excited levels in Ar and Ar–Hg gas-filled discharge lamps were measured using the absorption and laser-induced fluorescence methods from the positive column to the vicinity of the cathode. The lamp current was between 20 to 200 mA. A contour of the density distributions was obtained. Near the cathode, the exponential decay of these densities was observed within a distance of 20 mm from the cathode. This spatial decay characteristic can be explained by the result that the main deexcitation of the lowest excited atoms is caused by three-body and electron collision depopulation processes. In the Ar discharge, time-dependent density oscillations were observed in the positive column. High as well as very low (close to zero) densities were observed alternately. No density oscillations existed in the vicinity of the cathode. The behavior of the densities in such oscillations is also reported.
Optical High Voltage Measurement Technique Using Pockels Device
Authors: Josemir Coelho Santos Josemir Coelho Santos , Kunihiko Hidaka Kunihiko Hidaka
Published: October 2002

This paper describes a new optical high voltage measurement technique to realize optical voltage transformers (optical VTs) through which high voltages up to 400 kV can be directly measured. A prototype of an optical VT using Pockels device in a multi-segmented arrangement is designed based on the numerical calculation of the electric field distribution. The response characteristics of the developed prototype are examined for ac, dc, and lightning impulse voltages, and these experimental results showed good agreement with theoretical estimations. An oscillatory component appearing on the output signal of the sensor for the impulse voltage application is successfully eliminated using a fast Fourier transform (FFT) digital filter. It is also found that the sensor can respond to fast transients with a rising time of 40 ns, which defines the frequency response bandwidth of the system from dc to several MHz.
Scanning Tunneling Microscopy Observations and Analysis of Thermal Etching of Si(100) with Br and Cl
Authors: Weaver Celso M. Aldao
Published: October 2002

The surface morphologies that result from spontaneous etching of Si(100)-2×1 with Br and Cl have been studied using scanning tunneling microscopy. Layer-by-layer etching, which characterizes steady state removal, yields bounded surface roughness. The etch pits, step profiles, and Si regrowth structures produced in the range 700–900 K exhibit characteristic patterns that vary with temperature because they reflect atomic level interactions. The data obtained with scanning tunneling microscopy (STM) make it possible to examine these interactions and to extract information about etching dynamics.
Characterization of F 2 Treatment Effects on Si(100) Surface and Si(100)/SiO 2 Interface
Authors: Takeshi Kanashima Takeshi Kanashima , Yoshiaki Kurioka Yoshiaki Kurioka , Takaaki Imai Takaaki Imai , Hideaki Yamamoto Hideaki Yamamoto , Masanori Okuyama Masanori Okuyama
Published: October 2002

Effects of F2 treatment on the Si(100) surface have been characterized using infrared reflection absorption spectroscopy (IR-RAS). Hydrogen desorbs first from Si–H, and desorption from Si–H2 and Si–H3 follows subsequently, when the n-Si(100) wafer terminated by Si–H, Si–H2 and Si–H3 is exposed to F2 gas. Moreover, the hydrogen of Si–H2 desorbs faster on a terrace than on an edge. Finally, the Si(100) surface is covered by Si–F and Si–F2.
Extended X-Ray Absorption Fine Structure Study on Anharmonic Pair Potential in CuBr
Authors: Kamishima Osamu , Ishii Tadao , Hironobu Maeda Hironobu Maeda , Setsuo Kashino Setsuo Kashino
Published: October 2002

The Cu K-edge EXAFS (extended X-ray absorption fine structure) of CuBr has been measured at room temperature. An anharmonic pair potential for the Cu–Br bond introduced as Φ(u)=Φ0+(1/2!)αu
2+(1/3!)βu
3 in a central-field approximation is determined by numerical integration of the EXAFS function: obtained values of α and β are 2.28(4) eV/Å2 and -8(1) eV/Å3, respectively, and the Grüneisen parameter γ G=-(R
0/6)(β/α) is obtained as 1.5(2) using these values. These values are concluded to be reasonable from comparison with previously obtained Grüneisen parameters and from studying phonon dispersion relations.
Conformational Characteristics of Biphenylene-Ether-Ketone
Authors: Shirouzu Shigenori , Chino Shinji , Hayashi Mikiya , Ishii Tatsuo , Iga Toru , Yoshida Masahiro , Senda Norio
Published: October 2002

The characteristic ratio of Biphenylene-Ether-Ketone (BEK), a newly developed engineering plastic with high heat resistance (Tg: 181°C,Tm: 364°C), was calculated using rotational isomeric state theory.
An Analytical Fully-Depleted Silicon-on-Insulator Metal-Oxide-Semiconductor Field-Effect-Transistor Model Considering the Effects of Self-Heating, Source/Drain Resistance, Impact-Ionization, and Parasitic Bipolar Junction Transistor
Authors: Hu Man-Chun , Jang Sheng-Lyang , Chen Young-Shying , Shau-Shen Liu Shau-Shen Liu , Jien-Min Lin Jien-Min Lin
Published: October 2002

This paper presents a simple, complete, and analytical drain current model for submicrometer silicon-on-insulator metal-oxide-semiconductor field-effect-transistor (SOI MOSFET). The model applicable for digital/analog circuit simulation contains the following advanced features: precise description of the subthreshold, near threshold, and above-threshold regions of operation by one single expression; precise description of I–V and G–V characteristics in the saturation region; single-piece drain current equation smoothly continuous from the linear region to saturation region; considering the source/drain resistance; inclusion of important short channel effects such as velocity saturation, drain induced barrier lowering and channel length modulation; self-heating effect due to the low thermal conductivity of the buried oxide; impact-ionization of MOS devices and the parasitic bipolar junction transistor (BJT) effect associated with drain breakdown. The model predicts that the parasitic resistances are important for submicron and deep submicron SOI MOS devices, the effects of impact-ionization and parasitic BJT are important in saturation region at small gate source voltage V
GF, and self-heating effect is important in saturation region at large V
GF. The present model agrees well with experimental results of various dimensions.
Auto-doping of Carbon to AlAs Grown by Metalorganic Chemical Vapor Deposition using Trimethylaluminum and Tertiarybutylarsine
Authors: Shigeaki Sekiguchi Shigeaki Sekiguchi , Tomoyuki Miyamoto Tomoyuki Miyamoto , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: October 2002

Carbon (C) heavily doped AlAs has been grown by metalorganic chemical vapor deposition (MOCVD) using trimethylaluminum (TMAl) and tertiarybutylarsine (TBA) without any additional dopant sources. The hole concentration was controlled by changing only the V/III ratio. The highest hole concentration was 2.5×1019 cm-3. The decrease in the lattice constant of C-doped AlAs shows that the acceptor activation ratio is close to unity.
Reflective Direct-View and Projection Displays Using Twisted-Nematic Liquid Crystal Cells
Authors: Wu Shin-Tson , Kuo Chiung-Sheng Wu
Published: October 2002

Jones matrix method was used to optimize the twisted nematic liquid crystal cell parameters for reflective direct-view and projection displays. Twist angles ranging from 0 to 90° were investigated. From these analyses, two operation modes are found to have particularly important applications. The mixed-mode 90° twisted nematic cell exhibits an excellent contrast ratio for normally white direct-view and projection displays whereas the improved 45° twisted nematic cell shows an impressive light efficiency for normally black projection display.
A Novel Method for Determining the Cell Thickness and Twist Angle of a Twisted Nematic Cell by Stokes Parameter Measurement
Authors: Ying Zhou Ying Zhou , Zhan He Zhan He , Susumu Sato Susumu Sato
Published: October 2002

A novel method of determining the cell thickness and the twist angle of twisted nematic liquid crystal (TNLC) cells by measurement of the Stokes parameters of light transmitted through the cell is presented. The relationships of the Stokes parameters of transmission light to the cell thickness and the twist angle are reduced by use of Jones matrix representation. The cell thicknesses and twist angles of some TNLC cells are determined practically by this simple method. The experimental results indicate that this method is valid. Furthermore, some properties of this method are discussed and an accuracy analysis by theoretical calculation is undertaken.
Influence of Elastic Constants on the Optical Properties of Liquid Crystal Microlenses
Authors: Shin Masuda Shin Masuda , Michinori Honma Michinori Honma , Toshiaki Nose Toshiaki Nose , Susumu Sato Susumu Sato
Published: October 2002

Use of liquid crystal (LC) microlenses prepared from various types of LC materials is demonstrated for clarification of the influence of material parameters on the optical performance experimentally. Spherical aberration in the LC microlens is reduced by optimization of structure parameters, and the correlation between astigmatic aberration and elastic constants is investigated. The astigmatic aberration in the LC microlens strongly depends on the elastic constants and is explained by use of molecular orientation models calculated by a finite element method.
Reflection High Energy Electron Diffraction Intensity Oscillations in Fe3O4/MgO Superlattices Grown by Molecular Beam Epitaxy
Authors: Gung Chern Gung Chern , Yo Ren Chean Yo Ren Chean
Published: October 2002

Fe3O4/MgO superlattices are grown on MgO(001) substrates. Modulation coherency and sharp interface structures are observed by X-ray diffraction and reflection high energy electron diffraction (RHEED). The RHEED intensity oscillations of the specular and Bragg scattering provide direct evidence that structurally smooth interfaces can be maintained over many bilayers. Similar superlattices are also grown on an Fe-coated MgO(001) substrate for comparison and although the interface is relatively rough due to the misfit between the film and substrate, the modulation coherency is still maintained. RHEED intensity oscillations allow direct microscopic observations of the growth mode which is important for the further development of oxide superlattices.
Effect of NaOCl-Polishing on Metal Organic Chemical Vapor Deposition grown GaAs Surface on Si Substrate by Spectroscopic Ellipsometry and Atomic Force Microscopy
Authors: Guolin Yu Guolin Yu , Tetsuo Soga Tetsuo Soga , Junji Watanabe Junji Watanabe , Takashi Jimbo Takashi Jimbo , Masayoshi Umeno Masayoshi Umeno
Published: October 2002

NaOCl-polishing of a metal organic chemical vapor deposition (MOCVD)-grown GaAs surface on a Si substrate has been studied by spectroscopic ellipsometry (SE) and atomic force microscopy (AFM). The AFM results indicate that the root-mean-square (rms) roughness of the surface of polished samples is typically 0.3 nm which is about 1/10 that of unpolished samples. The SE data also clearly indicate that the maximum ε
2 (E
2) value is ∼24.5 for polished samples. The thickness of rough surface and void fraction (an effective medium of rough layer consisting of bulk GaAs and void) for unpolished samples are obtained by using the effective medium approximation (EMA) and the obtained dielectric functions from the respective polished samples. The surface thicknesses obtained using this method compare well with those obtained by AFM measurements.
Finite Element Analysis of Mechanical Couplings in a Tuning Fork Gyroscope
Authors: Subaru Kudo Subaru Kudo
Published: October 2002

The mechanical couplings of a tuning fork gyroscope are analyzed by a finite element method. The mechanical couplings due to anisotropy and asymmetrical structure are discussed based on differences in materials. These couplings are estimated by calculating the double resonant frequencies and vibrating modes of the gyroscope. It is possible to analyze quantitatively the couplings for the anisotropy and the asymmetrical structure of the gyroscope.
Temperature Stable Piezoelectric Ceramics for Cylindrical Vibrators of Vibratory Gyroscopes
Authors: Satoh Kaoru , Ise Osamu , Abe Hiroshi , Mitsuo Tamura Mitsuo Tamura , Etsuo Otsuki Etsuo Otsuki
Published: October 2002

The relationships between piezoelectric characteristics of a ceramic cylindrical vibrator and the performance characteristics of a vibratory gyroscope such as in terms of sensitivity and zero offset were assessed by means of an equivalent circuit model. It was confirmed that the temperature stability of the gyroscope depends on temperature variations of the mechanical quality factor (Q
m), the damped capacitance (C
d) and the resonant frequency (f
r). The piezoelectric characteristics were investigated in the ternary system of PbTiO3–PbZrO3–Pb(Mn1/3Sb2/3)O3. It was noticed that reduction of the Pb(Mn1/3Sb2/3)O3 proportion to less than 5 mol% and addition of MnO, Fe2O3 and Sm2O3 enhances the temperature stabilities of Q
m, C
d and f
r. Consequently, a material having ranges of temperature variations of Q
m, C
d and f
r of within +12 %∼-29 %, +16 %∼-9 % and +0.2 %∼-1.1 % respectively in the temperature range of -30° C∼+80° C was developed. Finally a gyroscope having a range of temperature variation of sensitivity of within ±10% and one of zero offset of within ±10°/s was obtained, which is applicable to direction sensors of car navigation systems.
Software for a Multilayered Surface Acoustic Wave Device Based on the Finite Element Method and Coupling-of-Modes Theory
Authors: Masanori Koshiba Masanori Koshiba , Naoki Shichishima Naoki Shichishima , Kazuhiro Ohbuchi Kazuhiro Ohbuchi , Yasuhide Tsuji Yasuhide Tsuji
Published: October 2002

A software package that provides an interactive and graphical environment for the design and modeling of multilayered surface acoustic wave (SAW) devices is described. The software is based on the finite element method (FEM) and the coupling-of-modes theory (COM). FEM is used to calculate the dispersion diagram of an infinite periodic array and the capacitance of one pair of interdigital transducers (IDTs). COM parameters are then determined using these calculated data. As a result of COM calculations, a 6-port circuit representation is obtained for basic device elements such as IDTs, grating or IDT reflectors and delay lines. The frequency response of SAW devices composed of these elements can be systematically evaluated by cascading the 6-port circuits. As an example, a high frequency SAW filter with a ZnO/diamond/Si structure is designed.
Surface Acoustics Wave Propagation Characteristics on a Langasite Crystal Plate
Authors: Hiroaki Satoh Hiroaki Satoh , Atsushi Mori Atsushi Mori
Published: October 2002

Propagation characteristics of a surface acoustic wave on a langasite ( La3Ga5SiO14) crystal plate are studied mainly in terms of the temperature coefficients of resonant frequency (TCF). The coefficients are measured from the first resonant frequencies of one-port surface acoustics wave (SAW) resonators. It is clarified that a (90°, 90°, 175°)-cut plate with the maximum theoretical coupling factor in the X-cut plate has a TCF of +25 ppm/°C at 20° C, a (90°, 90°, 25°)-cut plate has a turnover point of 0° C in the curve of relative resonant frequencies and a (90°, 90°, 15°)-cut plate with the maximum theoretical power flow angle of 13.3° in the X-cut plate has the minimum value of TCF in the wide temperature range of 50° C to 100° C. Experimental results suggest that the existence of the zero TCF substrate with k
2 of about 0.3% is expected.
Study of the Microscopic Surface Structure of a Quartz Substrate for Surface Acoustic Wave Devices
Authors: Noge Satoru , Araki Nobushige , Komine Kenji , Suzuki Hiroji , Shiraishi Hideya , Kohji Hohkawa Kohji Hohkawa
Published: October 2002

This paper describes the results of investigating the microscopic features of a commercially available 35°-rotated Y-cut (ST-cut) quartz surface using atomic force microscopy (AFM) and X-ray diffraction analysis. X-ray diffraction analysis suggests that distortions in the peaks are due to the existence of a dislocation or plane slip near the surface, but precise analysis was impossible in this experiment. Data from AFM showed that a flat area with an interesting particle image exists on the surface along with a heterogeneous damage layer at a depth of about 30 nm.
GHz-Range Conventional λ/4 Unidirectional Surface Acoustic Wave Transducers and Their Application to Low-Loss and Zero-Temperature Coefficient Filters
Authors: Hiroyuki Odagawa Hiroyuki Odagawa , Toshiyuki Kojima Toshiyuki Kojima , Toshiyasu Meguro Toshiyasu Meguro , Yasuo Wagatsuma Yasuo Wagatsuma , Kazuhiko Yamanouchi Kazuhiko Yamanouchi
Published: October 2002

A new fabrication technology using an oblique angled photo-lithography process for a conventional λ/4 type single phase unidirectional transducer (SPUDT) having a thin dielectric layer with a λ/8 shift from the electrode is proposed. This process does not require a precise alignment. This technique is also applied to a SiO2/LiNbO3 substrate with zero temperature coefficients. Experimental results using a conventional λ/4 type SPUDT filter show low-loss characteristics. A 2.2 dB insertion loss over 1 GHz-range is achieved in a simulation using an experimentally measured S parameter, assuming that ideal matching circuits are added in the electrical ports. The results also show the characteristics of low-loss filters with small temperature coefficients of 2.5 ppm/°C at 1 GHz.
Frequency Control Method of Magnetostatic Wave Oscillators Using External pin Diode Circuits
Authors: Koike Takuro , Tatsuya Hirao Tatsuya Hirao , Tomoyasu Ito Tomoyasu Ito
Published: October 2002

In this report we discuss the effects of additional electrodes, fabricated near the center electrode of a magnetostatic wave (MSW) straightedge resonator, on the frequency shifts of the MSW oscillator. By switching the pin diodes in the additional electrode circuits on and off, the resonant frequency can be shifted without changing the external magnetic field and the circuit parameters of a feedback load circuit. We constructed oscillators using this technique and could observe shifts of oscillatory peaks as predicted by our equivalent circuit model. Some interesting features of additional frequency shifts are also discussed.
Fabrication of Thin-Film Phase Grating Using Surface Acoustic Waves
Authors: Masahiko Watanabe Masahiko Watanabe , Mitsuhiro Yawata Mitsuhiro Yawata , Shouji Kakio Shouji Kakio , Yasuhiko Nakagawa Yasuhiko Nakagawa
Published: October 2002

By depositing a thin film on a substrate in which a standing surface wave is excited, we fabricated a phase grating in which variations in the film thickness as well as the refractive index occurred at half the wavelength of the surface acoustic waves. As no such phenomenon has been reported until now, its application for optical elements is expected.
Blood Concentration by Superposition of Higher Harmonics of Ultrasound
Authors: Kenji Yasuda Kenji Yasuda
Published: October 2002

A method for concentrating cells in blood using an acoustic radiation force generated by superposition of the higher harmonics on fundamental ultrasound has been investigated. From the theoretical estimation, the efficiency of concentration of blood cells in a chamber based on a rectangular acoustic radiation force slope calculated by integration of the higher harmonics of ultrasound was 17% better than that based on a sine wave, while the peak pressure was reduced to 82% of that in the sine wave case. Concentration of blood cells was also performed experimentally using superposition of higher harmonics on a 500 kHz sine wave. At a 1.2 m l/min fluid flow rate, the blood cells were concentrated on the pressure node within 9 s, with a cell distribution half-width of 348 µ m (i.e., 76% of blood cells concentrated within 23% of the chamber width), which is 5% narrower than that of the sine wave. Though the experimental result was insufficient for the realization of the theoretical estimation because of the incomplete synthesis of the desired waveform, these results suggest the potential usefulness of this superposition method for improving the concentration efficiency with maintenance of the width of the potential slope and reduction of peak pressure.
Magnification of Transportation Range Using Non-Contact Acoustic Levitation by Connecting Vibrating Plates
Authors: Hashimoto Yoshiki , Koike Yoshikazu , Ueha Sadayuki
Published: October 2002

The authors have identified a new acoustic phenomenon by which an object weighing several kilograms and having a planar shape can be levitated by radiation pressure above a set of vibrating plates. We propose to use this phenomenon for levitation and transportation systems for moving silicon wafers and liquid crystal devices (LCDs). In this report, the authors describe a method that increases the capability of the device to carry large objects by placing two vibrating plates in parallel and enlarges the transportation range by placing the vibrating plates in a series. The results show that a large object such as an LCD 250 mm square can be transported long distances limited only by the number of plates placed in series.
Energy Storage Characteristics of a Piezo-Generator using Impact Induced Vibration
Authors: Umeda Mikio , Nakamura Kentaro , Ueha Sadayuki
Published: October 2002

This paper presents theoretical and experimental considerations of the energy storage characteristics of a piezoelectric generator developed previously by the authors. In this paper, the oscillating output voltage induced by mechanical impact via the piezoelectric effect is rectified, and the electrical energy is stored in a capacitor. The effect of the capacitance of the capacitor and the initial voltage is investigated using an equivalent circuit model. A maximum efficiency over 35% has been achieved with a prototype generator.
Measurement of Leaky Lamb Wave Velocity Using Raman-Nath Diffraction
Authors: Ohki Michio , Inoue Masaru , Toda Kohji
Published: October 2002

A method of measuring the phase velocity of a leaky Lamb wave using Raman-Nath diffraction is investigated. Each mode of the wave with the different phase velocity in a substrate is radiated at each radiation angle into a load medium that is in contact with the substrate. An incident optical wave into the load medium can be diffracted by the radiated acoustic wave, and the diffraction image is formed in parallel to a wave vector of the radiated acoustic wave, reflecting the phase velocity of the leaky Lamb wave. By observing and processing the diffraction image stored in the form of digital matrix data, the phase velocity can be estimated. This method can be used to observe the dispersion of the phase velocity, the separation of plural modes excited at the same frequency, and the generation of the third harmonics of the wave number. This technique has the merit of measuring the leaky Lamb wave phase velocity separately, simply and precisely.
Ultrasonic Measurement of Concentration in Solutions by a Phase-Locked Loop Method
Authors: Kiyoshi Ikeda Kiyoshi Ikeda
Published: October 2002

In this paper we propose a new ultrasonic technique for measuring the concentration of solutions by a phase-locked loop method. This technique has a very simple circuit system which treats only continuous sinusoidal waves. We verify experimentally its validity and usefulness using NaCl solutions as test specimens. The accurate measurement of concentration is limited by slight changes in the temperature because of the strong temperature dependence of ultrasonic velocity in the solutions. A temperature-compensation factor for NaCl solutions is derived from the equation for ultrasonic velocity in sea water. We designed a circuit compensating for this effect and added it to the measuring system. This measuring system with the compensation circuit was shown to yield accurate values independent of a temperature variation of ±1.3°C around 25° C.
Improvement of Underground Image: Underground Imaging Using Shear Waves
Authors: Tsuneyoshi Sugimoto Tsuneyoshi Sugimoto , Hiroki Saito Hiroki Saito , Motoyoshi Okujima Motoyoshi Okujima
Published: October 2002

We previously proposed an underground imaging method using shear waves, but the resolution was insufficient. Therefore improvements in the resolution and the precision of depth direction were made by using a high-pass filter and peak position correction of the received wave.
Effect of Ultrasound Acoustic Characteristics in Cattle Liver under Ultrasound Exposure
Authors: Kawan Soetanto Kawan Soetanto , Yoshifumi Saisu Yoshifumi Saisu , Motoyoshi Okujima Motoyoshi Okujima
Published: October 2002

The effects of ultrasound exposure on the living body can be divided into thermal and non-thermal effects. In this study, the thermal effect was considered and temperature elevation due to ultrasound exposure was examined. First, experimental apparatus for measurement of temperature elevation was considered. Then, fundamental experiments to record the thermal effect of ultrasound waves on different substances were carried out. These included measuring the acoustic characteristics and temperature elevation of degassed water, tissue samples and samples made from agar, having properties similar to those of tissues. It was clarified on noted that the attenuation constant of tissue decreases after ultrasound exposure. Finally, it proposed that the viscosity of a target changes according to ultrasound exposure, and the proposition was investigated experimentally.
Simulations of Contrast Effects from Free Microbubbles in Relation to Their Size, Concentration and Acoustic Properties
Authors: Man Chan Man Chan , Kawan Soetanto Kawan Soetanto , Motoyoshi Okujima Motoyoshi Okujima
Published: October 2002

To gain a deeper insight into the diagnostic images produced by microbubbles as ultrasound contrast agents, the basic acoustical properties such as the scattering cross section, extinction cross section and the expected backscattered power from different sized microbubbles are calculated. The results proved that the ratio of scattering to extinction cross section, size and concentration of microbubbles are the factors determining the maximum backscattered power received from microbubble dispersions. When microbubbles decrease in size, the energy loss by microbubbles upon ultrasound exposure gradually changes from loss by scattering to loss by absorption. As a result, the concentration of microbubbles required to produce a B mode image of the comparable brightness is increased. However, an increased concentration of microbubbles does not necessarily produce a clearer image. In this paper, it is further established that an optimum concentration exists at which the microbubbles give maximum backscattered power. The optimum microbubble concentration and the maximum backscattered power also depend on the depth of the microbubbles in the microbubble dispersion. In addition, the concentration of microbubbles necessary to produce the maximum backscattered power during resonance is less than that at other frequencies.
A Method for 3D Measurement with High Resolution Using Ultrasound Spherical Waves
Authors: Ayumu Matani Ayumu Matani , Masayuki Nambu Masayuki Nambu , Atushi Kondo Atushi Kondo , Osamu Oshiro Osamu Oshiro , Kunihiro Chihara Kunihiro Chihara
Published: October 2002

Many methods for 3D measurement using ultrasound spherical waves with many ultrasound receivers have been proposed to date for use as sonars applied to fish-finders and underground locators. These methods, however, generated elliptically symmetric artifacts so that even a simply shaped object was revealed as distorted elliptic planes in 3D (lines in 2D) which made it difficult to recognize its shape. This paper describes a newly developed 3D measurement method using ultrasound spherical waves with an ultrasound ring-array probe. Our new method does not weight points aligned on an elliptic plane with the same value. This method is based not on a simple expansion method but on an optimization method. To evaluate the system and to compare it with the previous algorithms, a computer simulation assuming several point reflectors was performed. The results indicated that point reflectors were represented not in the elliptic planes but as points placed the assuming location. This method is especially useful for intravascular ultrasound frontal viewing.
Observation and Evaluation of Simulated Pitting Corrosion by Photoacoustic Imaging
Authors: Hiwatashi Yoichiro , Hoshimiya Haruo Endoh
Published: October 2002

Photoacoustic imaging of simulated pitting corrosions has been demonstrated. Simulated pittings, columnar holes, are fabricated on a pure aluminum plate by drilling, the diameters and depths of which are 0.2–1.0 mm and 0.5–1.5 mm, respectively. Nondestructive measurement of simulated pittings was carried out with both front and rear surface laser irradiation exitation. The signal intensity variation with hole diameter and depth is interpreted semi-quantitatively by means of a simple model. Heat flow from the bottom of a hole to the rear surface also contributes to the variation.
Heliconwave Plasma Which Contains Negative Ion
Authors: Horiike Haruo Shindo
Published: October 2002

In negative ion containing plasma, which is important in dry etching, dispersion of helicon wave is numerically investigated, and related plasma characters are discussed. In negative ion containing plasma, a cut-off newly appears at low frequency range and thus one of its important characters, that the phase velocity of helicon wave lowers with frequency, is lost. The fact states that the Landau damping cannot be a candidate for the production mechanism of heliconwave etching plasma in halogen gas. The skin depth of the wave in negative ion plasma is not shallow as in the electron plasma, and this fact may become important in case of realizing low damage etching.
Numerical Simulation of Plasma Chemical Vapor Deposition from Silane: Effects of the Plasma-Substrate Distance and Hydrogen Dilution
Authors: Motoaki Kawase Motoaki Kawase , Tsuyoshi Nakai Tsuyoshi Nakai , Akimasa Yamaguchi Akimasa Yamaguchi , Tomohiro Hakozaki Tomohiro Hakozaki , Kenji Hashimoto Kenji Hashimoto
Published: October 2002

Rf plasma chemical vapor deposition from silane was numerically analyzed. When a substrate was moved away from the plasma, gas-phase polymerization increased the contribution of oligomer radicals to film deposition. In addition, the contribution of silylene radicals became lower compared with that of silyl radicals. As a result of the trade-off between these two effects, an optimal plasma-substrate distance, where a high-quality a-Si:H film was obtained, appeared. Dilution of feed silane with hydrogen effectively reduced gas-phase polymerization and enhanced the generation of hydrogen radicals that create silyl radicals selectively through a reaction with silane. Improvement of the film quality as a result of plasma-substrate separation and hydrogen dilution was thus explained by the change in the composition of film precursors.
High Barrier Height Nickel/GaAs Schottky Diodes Fabricated by Addition of Pr2O3 into a Ga Melt for Liquid Phase Epitaxy
Authors: Chang Liann Be , Hung Thung Wang Hung Thung Wang , Li Chang Yang Li Chang Yang
Published: October 2002

A high Schottky barrier and low leakage current Ni/GaAs diode was fabricated by addition of an appropriate amount of Pr2O3 into a Ga melt for liquid phase epitaxy (LPE), which was brought about by removal of oxygen and sulfur impurities and induction of a slight increase in the concentration of carbon impurities at the grown surfaces. These effects not only enhanced the Schttky barrier height but also reduced the leakage current. Excellent properties of a Schottky barrier as high as 0.94±0.01 eV and an ideality factor as low as 1.02±0.01 were obtained.
Characteristics of Nonalloyed Pseudomorphic High Electron Mobility Transistors Using InAs/InxGa1-xAs (x=1→0)/AlyGa1-yAs (y=0→0.3) Contact Structures
Authors: Chen Sheu-Shung , Lin Chien-Cheng , Lan Wen-Ho , Tu Sun-Li , Peng Chin-Kun
Published: October 2002

A molecular beam epitaxy InAs/ In

x

Ga1-
x

As (x=1→0)/ Al

y

Ga1-
y

As (y=0→0.3) heterojunction was used as an ohmic contact structure to the GaAs-based pseudomorphic high electron mobility transistors (PHEMTs). This nonalloyed PHEMT had a specific contact resistance r
c of 1.05×10-7 Ω· cm2 and an extrinsic transconductance g
me of 272 mS/mm for devices with 1 µ m gate-length. Microwave measurements showed a current gain cut-off frequency f
t of 22 GHz and a maximum oscillation frequency f
max of 43 GHz. These results are comparable to our best conventional PHEMTs' alloyed at 450° C and 2 min duration. Meanwhile, a small-signal equivalent circuit model of the nonalloyed PHEMT has also been demonstrated.
Optical Parametric Amplification using the Phase Matching Retracing Behavior in MgO:LiNbO3 for Generation of Intense Widely Tunable Mid-infrared Pulses
Authors: Lin Shujie , Tanaka Yoshihito , Masakazu Aono Masakazu Aono , Takanori Suzuki Takanori Suzuki
Published: October 2002

We report on a new scheme for seeded optical parametric amplification using the phase matching retracing behavior in a 7% MgO:LiNbO3 crystal to generate picosecond widely tunable pulses in the mid-infrared range. A regeneratively amplified 2 ps Ti:sapphire laser and a tunable 3 ns narrow-band optical parametric oscillator serve as pumping and seeding sources, respectively. By setting the crystal at a phase matching angle very close to the retracing point of the crystal for a pumping wavelength of 778 nm, a wide tunability from 3.35 to 3.85 µ m of 2.3 ps pulses at a very intense constant pulse energy of 60 µ J has been demonstrated by varying only the seeding wavelength from the nanosecond optical parametric oscillator. The constant energy range could be blue- or red- shifted as a function of the pumping wavelength.
Azo-compound-aggregate Induced Photocarrier Generation in Layered Organic Photoreceptors
Authors: Tatsuya Niimi Tatsuya Niimi , Minoru Umeda Minoru Umeda
Published: October 2002

The extrinsic photocarrier generation between an azo compound and a carrier transport molecule was investigated using aggregate and non-aggregate azo compounds in order to elucidate the high yield of photocarriers based on aggregation. The differences between the two systems were compared in terms of geminate-pair formation and dissociation efficiencies. The efficiencies of charge separation for generation of geminate pairs, which are independent of an electric field, do not vary significantly. Charge separation occurs via a fixed energy state which appears due to relaxation from a higher excited state of the photoexcited azo compound. This suggests that charge separation occurs between the two closest neighboring molecules. However, the efficiencies of geminate pair dissociation into free carriers are quite different; the electric field dependence of the photocarrier generation efficiency of the system containing a non-aggregated azo compound is much larger than that containing an aggregated one. According to the Onsager theory, the geminate hole-electron distance for dissociation is estimated to be 26 Å for the former system and 140 Å for the latter system. It is concluded that the primary geminate pair, the two closest neighboring molecules, relaxes to a looser condition in terms of distance based on the aggregation.
High Temperature Characteristics of Strained InGaAs/InGaAlAs Quantum Well Lasers
Authors: Seoung-Hwan Park Seoung-Hwan Park
Published: October 2002

The effect of high temperature on the threshold current density and the optical gain of strained InxGa1-x
As/InGaAlAs quantum well (QW) lasers is investigated theoretically. These results are also compared with those of strained InxGa1-x
As/InGaAsP QW lasers. InGaAs/InGaAlAs lasers show lower values of the threshold current density than InGaAs/InGaAsP lasers in the investigated range of strain. Also, it is found that the better performance can be achieved in InGaAs/InGaAlAs lasers compared to InGaAs/InGaAsP lasers at high temperature. This is attributed to the reduced temperature dependence of the threshold carrier density N
th for InGaAs/InGaAlAs QW lasers. These results indicate that the carrier overflow problem can be reduced by using the InGaAlAs materials.
Electrooptical Properties of Vertically Aligned Twisted Nematic Cells with Negative Dielectric Anisotropy
Authors: Taiju Takahashi Taiju Takahashi , Susumu Saito Susumu Saito , Tadashi Akahane Tadashi Akahane
Published: October 2002

Two types of vertically aligned twisted nematic (VATN) liquid crystal (LC) cells in which a chiral nematic LC with negative dielectric anisotropy is used are proposed. In one type of the VATN cells, both substrate surfaces are treated by rubbing to obtain a slight tilt angle from the normal of each substrate, and in another one, only one substrate surface is treated by rubbing. In this study, some electrooptical properties are investigated experimentally and by simulations. Similar T–V characteristics were obtained for both types of cell in which d/P
0≈0.5 (ratio of the cell thickness to the equilibrium value of the chiral pitch). It is shown that these cells exhibit a good colorless black–white display image. The threshold voltage of VATN cells is expressed by π√{1-4(K
22/K
33)2(d/P
0)2}K
33/(ε
0 ∣Δε∣).
Amplitude Sensitive Optical Heterodyne and Phase Lock-in Technique on Small Optical Rotation Angle Detection of Chiral Liquid
Authors: Chou Chien , Huang Yeu-Chuen , Feng Ching-Mei , Chang Ming
Published: October 2002

A novel method in which an optical polarized heterodyne polarimeter and lock-in technique are used to measure low concentration glucose solution based on the detection of an amplitude sensitive heterodyning signal is proposed. The linearity and the sensitivity of the measurements are enhanced in comparison with those of conventional methods in which a Pockels cell, Faraday rotator, and rotating linear polarizer are used to modulate the incident light source. A pseudo heterodyning carrier and delayed optical heterodyning technique is also discussed in comparison with the proposed amplitude sensitive optical heterodyne method. During the detection of glucose solution, the measurable rotation angle reaches 10-4 deg and a sensitivity of a concentration to 10 mg/d l in 1 cm optical path length is obtained. Further improvements such as using a better intensity stabilized laser and a high extinction ratio Glan-Thompson polarizer will allow the detection sensitivity of the measuring optical rotation angle to reach 10-5 deg.
Optical Phase Change Disc without Bulk Laser Initialization and a Quick Bulk Initialization Structure
Authors: Tominaga Junji , Kikukawa Takashi , Takahashi Makoto , Tatsuya Kato Tatsuya Kato , Toshiki Aoi Toshiki Aoi
Published: October 2002

Optical phase change discs without bulk laser initialization were produced. When an Sb film was partially separated by more than 7 nm from a V added Ag–In–Sb–Te alloy film, the as-deposited reflectivity of the disc was almost the same as that of a disc with an initial alloy film after annealing by bulk laser erasing. Further, the recording and overwriting properties of the discs without bulk laser erasing were estimated. The recording jitter of the 1–7 frequency modulation signal increased during the first 2 or 3 overwriting iterations and then saturated at less than 3.5 ns until 30,000 overwriting iterations at a linear constant velocity of 12 m/s. Additionally, the disc could be initialized at the overwriting speed.
Properties of Highly Resistive and Nonstoichiometric GaAs Film Grown by Low-temperature Metalorganic Chemical Vapor Deposition Using Tertiarybutylarsine
Authors: Wen-Chung Chen Wen-Chung Chen , C.-S. Chang C.-S. Chang , Wei-Kuo Chen Wei-Kuo Chen
Published: October 2002

The properties of highly resistive and nonstoichiometric GaAs films grown by metalorganic chemical vapor deposition (MOCVD) at low temperature (LT) are studied by transmission electron microscopy (TEM), photoluminescence (PL), deep level transient spectroscopy, and double crystal X-ray and X-ray photoelectron spectroscopy. GaAs films are grown with source precursors of triethylgallium (TEGa) and tertiarybutylarsine (TBAs) at substrate temperatures of 425–550°C. The microstructure observed in the MOCVD GaAs film shows better film quality as the input V/III molar flow ratios increase. Furthermore, the growth rate and the shift of binding energy for the As 3d core level of the film are slightly increased with increasing V/III ratio, but the intensity of V As-related emission in PL is decreased. We suggest that the high resistivity of the LT-MOCVD film is due to structural defects caused by the nonstoichiometry of excess As atoms in the film.
Simulation Study of Noise Influence in 3-Dimensional Reconstruction using High-Angle Hollow-Cone Dark-Field Transmission Electron Microscope Images
Authors: Tsuneta Ruriko , Kuniyasu Nakamura Kuniyasu Nakamura , Hiroshi Kakibayashi Hiroshi Kakibayashi
Published: October 2002

Three-dimensional reconstruction of crystal structures by filtered convolution back projection of high-angle hollow-cone dark-field transmission electron microscope images (HADF images) of a specimen is investigated. To determine the distribution of Cu particles in Si crystal from reconstructed images, the necessary conditions are estimated. Undistorted distribution of particles is obtained from a simulated reconstruction when the specimen is inclined between ±50°, the inclination axis direction error is ±2° and Poisson noise is 30 db. Under these conditions, the distribution of Cu particles in a Si crystal is experimentally reconstructed.
Internal Bremsstrahlung Accompanying the 1S, 2S Electron Capture in 7Be
Authors: Abdelhady Yousef Abdelhady Yousef , Mamdouh Abdelrahman Mamdouh Abdelrahman , Nader Hasan Nader Hasan
Published: October 2002

The total internal bremsstrahlung (IB) spectra accompanying electron capture in 7Be is measured using a NaI (T1) scintillation spectrometer. Corrections for background and absorption are made. For analysis of the experimental data, a response matrix with dimensions of 46 energy bins and 140 channels is constructed. With the help of a detector assembly response matrix, the true IB energy spectrum is obtained by iterative unfolding of the pulse-height distribution for comparison with theoretical spectra. Also, the response matrix is used directly to fold the theoretical probabilities for comparison with the experimental pulse-height distribution. After all the necessary corrections are made, the experimental results are compared with the theoretical spectra reported by Morrison and Schiff and Martin and Glauber (1958). All the comparisons reveal that our experimental data are in agreement with both theories.
Electrical and Optical Properties of Conducting Polymer with Quinoid Structure
Authors: Kazuhisa Hosoda Kazuhisa Hosoda , Kazuya Tada Kazuya Tada , Tsuyoshi Kawai Tsuyoshi Kawai , Mitsuyoshi Onoda Mitsuyoshi Onoda , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Poly[α-(bithiophene-5,5'-diyl)-(p-(heptyloxy)benzylidene)-co-(α-bithiophene quinodimethane-5,5'-diyl)] (PBTHBQ), which is obtained from precursor poly[α-(bithiophene-5,5'-diyl)-(p-(heptyloxy)benzylidene)] (PBTHB) by oxidative dehydrogenation with 2,3-dichloro-5,6-dicyano-p-benzoquinone and contains alternating aromatic and quinoid thiophene rings in its main chain, has an optical absorption edge at about 1.4 eV, while the band gap of PBTHBQ was evaluated to be about 2.6 eV from the short-circuited photocurrent spectrum. The electrochemical and optical properties of PBTHBQ and PBTHB have been investigated by cyclic voltammetry, in situ optical absorption spectroscopy, photoconduction spectra measurements and electron spin resonance measurements. From these experimental results, electronic energy states of PBTHBQ and PBTHB were estimated. PBTHBQ was also found to be made from PBTHB by an electrochemical cycle.
Charge Dissipation on Chemically Treated Thin Silicon Oxide in Air
Authors: Uchihashi Takayuki , Nakano Akihiko , Ida Tohru , Andoh Yasuko , Kaneko Reizo , Sugawara Yasuhiro , Morita Seizo
Published: October 2002

We studied the microscopic charge dissipation of densely contact-electrified charges on silicon oxides with and without a trimethylsilyl (TMS) organosilane monolayer using a modified atomic force microscope in air. Here, the TMS film was used to change a hydrophilic surface to a hydrophobic one. As a result, for both of the deposited negative and positive charges, it was clarified that the TMS film can suppress the rapid dissipation induced by surface diffusion. For the positive charge, however, the TMS film enhanced the charge dissipation induced by recombination through the TMS film and silicon oxide.
Hydrogenated Silicon-Oxynitride Film Antireflective Layer for Optical Lithography
Authors: Ogawa Tohru , Gocho Tetsuo , Nakano Hiroyuki , Tsukamoto Masanori
Published: October 2002

We present a theoretical method for antireflective layer (ARL) optimization in optical lithography and report the performance of hydrogenated silicon oxynitride ( SiO

x

N

y

:H) film used as an ARL for krypton fluoride (KrF) excimer laser lithography. The optimum optical conditions of an ARL for tungsten silicide (W–Si) and aluminum silicon (Al–Si) substrates, which minimize the fluctuation of energy absorption in photoresists for photoresist thickness variations, are investigated. There are two types of optimum optical conditions, which give zero reflectance with the first and second cycle in thin film interference effects in an ARL, respectively. A type of SiO

x

N

y

:H, which can satisfy the optimum optical conditions of an ARL for W–Si and Al–Si substrates, was found from the standpoints of its spectroscopic characteristics. Refractive indices of SiO

x

N

y

:H film at the wavelength of 248 nm can be controlled by varying the deposition conditions in a plasma-enhanced chemical vapor deposition system. The variations in critical dimension caused by the thin-film interference effects in the photoresist for W–Si and Al–Si substrates are drastically reduced to within 0.02 µ m for 0.30 µ m patterns using this SiO

x

N

y

:H film. Moreover, these SiO

x

N

y

:H films can be left in the device structure without any influence on the electronic characteristics.
Effect of Wind Shear on the Film Thickness Distribution over Rotating Doughnut Disks
Authors: Shih-Chin Gong Shih-Chin Gong , Fu-Chu Chou Fu-Chu Chou
Published: October 2002

Spin coating has been extensively investigated. However, a numerical study of the wind shear effect on film thickness distributions over doughnut disks has not yet been performed. Also, the effect of a hub on the air shear flow over a rotating doughnut disk has not yet been addressed. In this study, we predict successive liquid surface contours on rotating doughnut disks. The results are compared with experimental data, and discrepancies between them are identified. We found that the discrepancies are caused mainly by the presence of a hub, and that the wind shear effect cannot be simply analyzed in terms of Cochran's solution.