bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel Damascene Gate Metal–Oxide–Semiconductor Field-Effect Transistors Fabricated by In situ Arsenic- and Boron-Doped Epitaxy
Authors: Kikuchi Yoshiaki , Tateshita Yasushi , Miyanami Yuki , Wakabayashi Hitoshi , Tagawa Yukio , Nagashima Naoki
Published: July 2010

A new concept planar metal–oxide–semiconductor field-effect transistor (MOSFET) which was fabricated by in situ doped selective Si epitaxy, has been proposed. Owing to the ultra-shallow junction, the short-channel effects were improved, and the drive current was increased by the gate overlapped structure as well. The characteristics of this new concept MOSFET were improved compared with those of a conventional MOSFET because of improvements in short-channel effects and parasitic resistances.
Low-Temperature Sintered Pb(Zr,Ti)O3–Pb(Mn,Sb)O3–Pb(Zn,Nb)O3for Multilayer Ceramic Actuators
Authors: Wan Dandan , Li Qian , Choi Joo-Young , Choi Ji-Won , Yang Ying , Yoon Seok-Jin
Published: July 2010

A quaternary 0.90Pb(Zr0.48Ti0.52)O3–0.05Pb(Mn1/3Sb2/3)O3–0.05Pb(Zn1/3Nb2/3)O3(0.90PZT–0.05PMS–0.05PZN) piezoelectric ceramic was synthesized by a conventional method, and CuO was adopted to lower its sintering temperature. The crystal structure, micromorphology, and electrical properties were studied in terms of CuO content. The results indicate that 1.0 wt % CuO addition significantly improves the sinterability of 0.90PZT–0.05PMS–0.05PZN ceramics, lowering the sintering temperature to 900 °C and maintaining moderate electrical properties:d33=306 pC/N,Qm=997,kp=53.6%, tan δ=0.50%, andε33T/ε0=1350. The low-temperature sintering behavior could be explained by the formation of a transient liquid phase by CuO during sintering. Moreover, the endothermic peak at about 950 °C in the differential thermal analysis (DTA) curve of the raw ceramic powder provides further evidence of an amorphous phase. To obtain better piezoelectric properties, La2O3was selected as the donor dopant for the 0.90PZT–0.05PMS–0.05PZN + 1.0 wt % CuO system. Our study demonstrates that La2O3is very effective in improving piezoelectric properties, markedly increasingd33andkpwithout decreasingQm. Finally, 0.5 wt % La2O3added 0.90PZT–0.05PMS–0.05PZN + 1.0 wt % CuO ceramics show excellent electrical properties:d33=355 pC/N,Qm=936,kp=58.4%, tan δ=0.32%, andε33T/ε0=1590, which are quite suitable for multilayer piezoelectric ceramic actuators.
Step and Flash Imprint of Fluorinated Silicon-Containing Resist Materials for Three-Dimensional Nanofabrication
Authors: Takei Satoshi
Published: July 2010

Advanced fabrication of multiple-level three-dimensional nanostructures by step and flash nanoimprint lithography was studied. This study has been shown to be applicable to future nanofabrication endeavors in the industrial production of electronic devices and optical materials. Step and flash nanoimprint technologies using the newly fluorinated silicon-containing resist materials to prevent resist pattern collapse, contamination problem of the quartz template, and defect problems were demonstrated. High-quality nanoimprint patterning of 65 nm dense lines and other multiple-level three-dimensional nanostructures was achieved using the proposed material design and under ultraviolet nanoimprint conditions. The developed fluorinated silicon-containing resist material as a hard mask layer with a nonsilicon spin-on carbon material was found to be useful in producing high-aspect-ratio patterned structures by step and flash nanoimprint lithography.
Characteristics of Electrically Switchable Wettability Surfaces of Liquid Crystal and Polymer Composite Films
Authors: Chiu Ya-Ping , Shen Cheng-Yu , Lin Yi-Hsin
Published: July 2010

Experimentally, the electrically controllable surface wettability of liquid crystal and polymer composite film has been demonstrated. In the work, scanning probe microscopy has been used to investigate the surface characterization of liquid crystal molecular units at a polymer surface under external voltages applied. The surface morphologies as well as the sensitivity of measurement to surface adhesive force on the nanoscale are determined quantitatively for such unique nano-sized liquid crystals/polymer composite films. The surface wettability of the films deduced from the local adhesion properties demonstrated the electrical control of surface wettability properties, suggesting that the interfacial liquid-crystal molecular alignment of the films with external voltage applied should have significant influence on the modification of the surface characterization of liquid crystals.
Design of the Ring Remote Phosphor Structure for Phosphor-Converted White-Light-Emitting Diodes
Authors: Lin Ming-Te , Ying Shang-Ping , Lin Ming-Yao , Tai Kuang-Yu , Tai Sheng-chieh , Liu Chih-Hsuan , Chen Jyh-Chen , Sun Ching-Cherng
Published: July 2010

A phosphor-converted light-emitting diode structure with an increased phosphor extraction efficiency owing to the ring remote phosphor structure achieves a maximum luminous efficacy of 145 lm/W at 20 mA and a maximum luminous flux of 132 lm at 400 mA. The ring remote phosphor structure consists of an inverted cone lens encapsulant and a surrounding ring remote phosphor layer. Ray-tracing simulations demonstrate that the phosphor extraction efficiency of the ring remote phosphor structure exceeds 93%. A high phosphor extraction efficiency is achieved by decreasing the re-emitting light from the ring remote phosphor layer to the absorptive light-emitting diode (LED) chip. Our results further demonstrate that the ring remote phosphor structure device has a radiation pattern as a bi-wing, which is more appropriate for solid-state lighting owing to the low glare.
Effect of Ridge Growth on Wafer Bowing and Light Extraction Efficiency of Vertical GaN-Based Light-Emitting Diodes
Authors: Ryu Jae Hyoung , Chandramohan S. , Kim Hyung Gu , Kim Hee Yun , Kim Hyun Kyu , Han Nam , Kang Ji Hye , Uthirakumar Periyayya , Suh Eun Kyung , Hong Chang-Hee , Cho Hyun Kyong , Song Hyun Don , Kwon Ho-Ki
Published: July 2010

In this paper we report on the selective area growth (SAG) of vertical GaN-based light-emitting diodes (LEDs) by low-pressure metal-organic chemical vapor deposition (MOCVD). SAG, under optimized growth conditions, leads to ridge-shaped epilayers with a smooth top surface, devoid of any surface defect structures. The final ridge-shaped vertical LED structures, after the removal of the sapphire substrate by laser lift-off (LLO), exhibit a smaller bowing effect than conventional vertical LED structures. The suppression of lateral strain in the epilayers is responsible for the smaller bowing effect because of the reduction in lateral dimensions. Consequently, the use of SAG LEDs can achieve a 21% higher light output power than conventional vertical LEDs, indicating a significant improvement in light extraction efficiency due to the light guiding pathways offered by the ridge-shaped geometry of the LED structures.
Vertical GaN-Based Light-Emitting Diodes Structure on Si(111) Substrate with Through-Holes
Authors: Wei Jingting , Zhang Baijun , Wang Gang , Fan Bingfeng , Liu Yang , Rao Wentao , Huang Zhicong , Yang Weimin , Chen Tufu , Egawa Takashi
Published: July 2010

A novel vertical GaN-based light-emitting diode (LED) structure on a Si(111) substrate with through-holes was reported in this letter. The through-holes were formed by dry etching from the n-GaN layer to the Si substrate. Metals connecting the n-GaN layer and Si substrate were used to fill the holes. The series resistances induced by the AlN buffer layer and other interlayers were shorted by the metals filling the holes. Compared with those of the conventional LED structure, the series resistance and operating voltage at 20 mA were reduced from 26 to 22.5 Ω, and from 4.4 to 4.0 V, respectively. Light output intensity shows an increase of 29%.
Perpendicular Magnetic Anisotropy of Iron–Cobalt Silicide Nanowires on Si(110)
Authors: Ohira Yutaka , Tanji Takayoshi
Published: July 2010

Ferromagnetic nanowires (NWs) of Fe–Co silicide have been formed successfully by the codeposition of Fe and Co onto a clean Si(110) surface at 750 °C in an ultrahigh vacuum (UHV). NWs up to 3.0 µm long are self-aligned along the Si[110] direction, owing to the low symmetry of the ideal Si(110) surface. Transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) reveal that NWs have a fluorite structure including both Fe and Co. Electron holography (EH) reveals that the magnetization of an NW is perpendicular to its long axis and is ca. 0.6±0.1 T at room temperature (RT).
Accurate Analytical Model for Current–Voltage and Small-Signal Characteristics of AlmGa1-mN/GaN Modulation-Doped Field-Effect Transistors
Authors: Hosseini Seyed Ehsan Abtahi , Hosseini Seyed Ebrahim
Published: July 2010

In this paper, a simple and accurate analytical model for current–voltage and small-signal characteristics of Al
m
Ga1-m
N/GaN modulation doped field-effect transistor (MODFET) devices is presented. For the charge control model, Fermi potential variation with sheet carrier concentration, the infiltration of a two-dimensional electron gas wave function into the spacer layer, and the effects of spontaneous and piezoelectric polarizations at the heterointerface are considered. Also, parasitic source/drain resistances have been incorporated in the analysis. In addition, a suitable drift velocity model and the gate voltage dependence of low-field mobility are used to provide simple and accurate equations for the different characteristics of AlGaN/GaN MODFET devices. By implementing the model in the MATLAB environment, current–voltage characteristics, transconductance, output conductance, capacitance–voltage characteristics, and cutoff frequency have been calculated. A comparison of simulation results with published experimental data for Al0.15Ga0.85N/GaN shows excellent agreement, thereby proving the validity of the model.
Anomalous Substrate Current in Metal–Oxide–Semiconductor Field-Effect Transistors with Large Channel Width
Authors: Abe Kazuhide , Sasaki Tadahiro , Itaya Kazuhiko
Published: July 2010

Anomalously large substrate current has been observed in a metal–oxide–semiconductor field-effect transistor (MOSFET) with a large channel width of 1600 µm. The magnitude of the substrate current per unit channel width is approximately 2 orders larger than that of a MOSFET with a channel width of 100 µm when they are compared at the maxima. Furthermore, the substrate current measured as a function of gate voltage could not be fit to a typical simulation model based on the conventional theory of impact ionization. In addition to the substrate current, anomalies were also observed in the drain current and the gate leakage current measured simultaneously with the substrate current. To explain the interrelation of the anomalous phenomena, we have introduced a hypothesis in which two modes of impact ionization are excited in the respective voltage regions generating electron–hole pairs in specific directions.
Large Area Fabrication of Moth-Eye Antireflection Structures Using Self-Assembled Nanoparticles in Combination with Nanoimprinting
Authors: Nakanishi Tsutomu , Hiraoka Toshiro , Fujimoto Akira , Okino Takeshi , Sugimura Shinobu , Shimada Takuya , Asakawa Koji
Published: July 2010

A moth-eye structure, which suppresses the reflection on a surface, was fabricated on the entire surface of a large silicon wafer by the formation of a self-assembled particle monolayer as a dry-etch mask formed by our embedded particle monolayer (EPM) method. We optimized the shape of moth-eye structures by optical calculation and improved the fabrication procedure to allow formation over a large area. As a result, we succeeded in fabricating a moth-eye structure on the entire surface of a 12-in. silicon wafer and the surface reflectance was reduced to less than 0.8% in the visible light range. A large nickel mold, which is able to transfer the pattern to an 8-in. display, could be formed using the 12-in. silicon substrate as a master. A moth-eye film was fabricated by UV nanoimprinting using the nickel mold and the high antireflection performance was confirmed. The fabrication cost of the moth-eye structure over a large area would be markedly reduced by the use of the self-assembly technique in combination with nanoimprinting.
Correlation between Segregation of Rare Earth Dopants in Melt Crystal Growth and Ceramic Processing for Optical Applications
Authors: Chani Valery I. , Boulon Georges , Zhao Wei , Yanagida Takayuki , Yoshikawa Akira
Published: July 2010

The paper deals with segregation of rare earth doping cations in solid-state hosts. Increased concentration of Ce3+ and Nd3+ on the grain boundaries of transparent garnet optical ceramics was recently reported. These experimental results correlate well with low segregation coefficients of Ce3+ and Nd3+ large rare earth cations and the higher segregation coefficients for small rare earth cations like Yb3+ in the garnet structure observed in the melt crystal growth and thin film liquid phase epitaxy from flux. Thus, the segregation in solid-state grain growth is qualitatively similar to that observed in the melt/flux growth of the garnet single crystals. The data on segregation in the melt/flux crystal growth are widely available and can be used for preliminary estimation of the dopant distribution in the ceramics produced from the solid state. This information could help to predict distribution of doping cations in the solid state hosts that is important in development of uniform and highly efficient optical materials.
Low-Resistivity and Adhesive Sputter-Deposited Cu–Ca Films with an Intermediate Oxide Layer
Authors: Mori Satoru , Kawai Akira
Published: July 2010

We investigated a method of producing low-resistivity and adhesive sputter-deposited copper alloy films with an intermediate oxide layer that retains its adhesion after hydrogen annealing for applications of electric interconnections for thin film circuits and liquid crystal displays. The formation of an intermediate copper oxide layer between a copper film and a substrate by sputter deposition in the presence of oxygen enhances adhesion. However, when such films are exposed to hydrogen at elevated temperatures, hydrogen penetrates the films and reduces copper oxide. This reaction generates water molecules, which aggregate at the interface between the copper film and the substrate. As a result, microvoids form at the interface, degrading the film adhesion. Sputter-deposited films with an intermediate oxide layer produced from a Cu–Ca target are adhesive even after hydrogen annealing. As films deposited in pure argon have low resistivities, it is possible to form low-resistivity and adhesive metallization.
Effect of Carrier Gas (Ar and He) on the Crystallographic Quality of Networked Nanographite Grown on Si Substrates by Photoemission-Assisted Plasma-Enhanced Chemical Vapor Deposition
Authors: Sumi Haruki , Ogawa Shuichi , Sato Motonobu , Saikubo Akihiko , Ikenaga Eiji , Nihei Mizuhisa , Takakuwa Yuji
Published: July 2010

In this study, networked nanographite is formed on a Si substrate without any metal catalysts by photoemission-assisted plasma-enhanced chemical vapor deposition. We investigated the carrier gas dependence of the crystallographic quality of networked nanographite when Ar and He are used as the carrier gases. When Ar is the carrier gas, Raman spectroscopy and grazing incident X-ray diffraction show that the crystallographic quality deteriorates makedly with decreasing growth temperature, indicating that amorphous carbon is deposited at low temperatures (below ∼500 °C). On the other hand, when He gas is used as a carrier gas, a high quality nanographite can be grown even at temperatures as low as room temperature. Thus, there is a significant difference in the temperature dependence of crystallographic quality for the two carrier gases.
Effects of Optical Parameters in a Free-Electron Laser Oscillator
Authors: Nam Soon-Kwon , Nfor Julius
Published: July 2010

We have developed a three-dimensional simulation code to study free-electron laser optical resonator parameters for a proposed far-infrared free-electron laser facility. We have investigated the effects of Rayleigh length, electron beam spot size, power extraction, and waist position by using the modified coupled equations, including a wave equation that is expanded in axisymmetric Gauss–Laguerre modes. The modified coupled equations are also used in the simulation to obtain the effects for fundamental and higher order modes. The optimum value for the oscillator mirror radius of curvature is found, and the effects of Rayleigh length, electron beam spot size, power extraction, and waist position in a free-electron laser oscillator with a short undulator are investigated.
Evaluation of the Validity of Crystallization Temperature Measurements Using Thermography with Different Sample Configurations
Authors: Aono Yuko , Sakurai Junpei , Shimokohbe Akira , Hata Seiichi
Published: July 2010

We describe further progress of a previously reported novel crystallization temperature (T
x) measurement method applicable for small sample sizes. The method uses thermography and detects T
x as a change in emissivity of thin film amorphous alloy samples. We applied this method to various sample configurations of Pd–Cu–Si thin film metallic glass (TFMG). The validity of the detected T
x was determined by electrical resistivity monitoring and differential scanning calorimetry (DSC). Crystallization temperature can be detected in all sample configurations; however, it was found that the magnitude of the detected change of emissivity at T
x depended on the sample configuration. This emissivity change was clear in the absence of a higher emissivity material. The results suggest that this method can achieve high-throughput characterization of T
x for integrated small samples such as in a thin film library.
Appropriate Laser Focusing Configuration for Number Density Measurement of Water Droplets in an Aerosol by Laser-Induced Breakdown Method
Authors: Yashiro Hidehiko , Sasaki Fumio , Kakehata Masayuki
Published: July 2010

The number density of water droplets in an aerosol can be experimentally evaluated by a laser-induced breakdown method with different focal configurations. The detection volume is evaluated from the intensity ratio between the breakdown threshold and the actual laser irradiation and focal parameters. The number of droplets in a volume is evaluated from the breakdown probability. The number density is determined by the experimentally observed detection volume and the number of droplets. Theoretical calculations indicate that an appropriate focus configuration in which breakdown is generated at a laser intensity over three times the breakdown threshold reduces the measurement error of the volume, and an appropriate breakdown probability reduces the sampling error due to the limited number of laser shots. These findings are consistent with the experimental results in terms of the difference in the measured number density with different focal configurations and the nonlinear increase of the number of droplets as a function of the volume. These results also indicate the appropriate detection range of the number density of droplets for a certain focus configuration and the accuracy of the experimental results.
Elastic Properties of Lithium Germanate Glasses Studied by Brillouin Scattering
Authors: Kaneda Kazuhiro , Matsuda Yu , Kojima Seiji
Published: July 2010

To investigate the correlation between structural changes and physical properties, the elastic properties of lithium germanate glasses, xLi2O·(100-x)GeO2 represented as a function of Li2O mole fraction, have been studied in the composition range 6≤x≤36 mol % by Brillouin scattering spectroscopy. Raman spectra have also been measured to clarify the composition variation of structural changes. Several elastic properties, such as sound velocity and elastic modulus, have been determined from the Brillouin shift. The longitudinal and transverse sound velocities increase up to about x=20 mol %, and above x=20 mol %, they become nearly constant. Elastic moduli, such as longitudinal modulus (L) and shear modulus (G), increase gradually up to x=22 mol % and then decrease with a further increase in Li2O content. It is considered that such behaviors are due to the change in the coordination number of germanium atoms and the formation of nonbridging oxygen. Differently from other elastic moduli, Poisson's ratio (σ) shows a similar behavior to sound velocity.
Annealing Effect on Acoustic Property of Fe/Pt Superlattice Studied by Picosecond Ultrasound
Authors: Nakamura Nobutomo , Uranishi Atsuyoshi , Wakita Mamoru , Ogi Hirotsugu , Hirao Masahiko
Published: July 2010

Fe/Pt superlattices deposited on glass substrates were annealed after deposition, and the relationships among annealing temperature, out-of-plane longitudinal-wave elastic constant, and the attenuation of a GHz longitudinal acoustic pulse propagating in the superlattices were studied using picosecond ultrasound. Picosecond ultrasound generates and detects GHz longitudinal acoustic pulses using ultrashort pulse lights, and is capable of evaluating the acoustic property of a superlattice thinner than 100 nm without touching the specimen. The elastic constant of an as-deposited superlattice was smaller than those of bulk Fe and Pt; it increased as annealing temperature increased. The attenuation also increased as annealing temperature increased. The frequency dependence of the attenuation indicated the formation of FePt alloy at interfaces at 300 °C. Thus, we confirmed that the investigation of acoustic properties using picosecond ultrasound can be a powerful tool for evaluating the structural evolution in superlattices.
Fabrication and Evaluation of Highly Oriented Ta2O5 Piezoelectric Thin Films Prepared by Radio Frequency Magnetron Sputtering
Authors: Kakio Shoji , Mitsui Takeshi , Tsuchiya Akinori , Nakagawa Yasuhiko
Published: July 2010

Highly X-axis-oriented tantalum pentoxide (Ta2O5) piezoelectric thin films were deposited on a SiO2 substrate using an RF-magnetron sputtering system with a metal tantalum target and an O2-radical source. The degree of orientation, Rayleigh-type surface acoustic wave properties, and surface morphology were evaluated. The deposition condition with the substrate temperature T
S of 700 °C and O2 flow rate of 10 ccm was found to be optimum for obtaining a strongly piezoelectric property. Under the optimum condition, the coupling factor of the oriented Ta2O5 thin film with a normalized thickness h/λ of 0.21 was determined to be 0.88% and was 75% of the reported value. The diffraction angle of the preferential peak under the optimum condition was equal to that of the (200)-plane spacing d
(200) in the unit cell of monoclinic Ta2O5. A larger plane spacing with Δd/d
(200)=2.9% exists preferentially at T
S=600 °C, and the piezoelectricity is considered to be zero or very weak. When T
S was higher than 700 °C and the O2 flow rate was more than 8 ccm, a smooth surface with the rms roughness of approximately 8–10 nm was obtained. A correlation was found in which a strongly piezoelectric property was obtained when the thin film had a smooth surface.
Plate Waves in Locally Resonant Sonic Materials
Authors: Hsu Jin-Chen , Wu Tsung-Tsong
Published: July 2010

Plate wave propagation in two-dimensional locally resonant sonic materials (LRSMs) is theoretically analyzed. The well-known plane wave expansion method for a periodic elastic structure recast based on the Mindlin plate theory and a finite element (FE) method are employed to calculate the frequency band structures of plate waves. The results of the two methods are compared. The FE method is further used to analyze the resonant eigenmodes and attenuation spectrum of the plate waves propagating through a finite LRSM. Numerical results show that complete band gaps of plate waves exist in the frequency range of two orders of magnitude smaller than those in typical sonic crystals where complete band gaps are produced by Bragg scattering. The attenuation spectrum of plate waves in a finite-size LRSM containing eight rows of locally resonant unit structures is in good agreement with the band gaps predicted using the frequency band structure.
Liquid Jet Breakup by High-Frequency Pressure Modulation
Authors: Takeuchi Atsushi , Yamada Tatsuya , Sakai Keiji
Published: July 2010

We developed a system for the mass production of µm-size liquid particles. Liquid jet is emitted by a glass nozzle with a constant pressure and the additional pressure modulation induced by an ultrasonic transducer causes a slight periodical change in jet radius: the modulation spontaneously evolves and the jet breaks up into µm particles. By applying the modulation at a frequency higher than 100 kHz to the nozzle with an inner diameter of 8 µm, we succeeded in producing pl-size particles at a rate of 105 particles/s. We also demonstrated the ability of our system to produce microcapsules by the collision of liquid particles.
Destructive Inspection of Weld Defect and its Nondestructive Evaluation by Photoacoustic Microscopy
Authors: Shiraishi Daijiroh , Kato Ryosuke , Endoh Haruo , Hoshimiya Tsutomu
Published: July 2010

In this study, the nondestructive evaluation (NDE) of an internal defect introduced in the welded region of an aluminum plate has been demonstrated by photoacoustic microscopy (PAM). The internal defect is a blowhole and an incomplete fusion, which were formed in the weld metal during welding. Experiments were carried out at different modulation frequencies. Furthermore, a stereoscopic image of the fractured specimen was obtained by destructive inspection using scanning laser microscopy (SLM) and compared with a photoacoustic (PA) amplitude image. The size of the internal weld defect measured by both methods was approximately the same.
Proposal of Novel Method to Measure Young's Modulus of Materials Using Change in Motional Capacitance of the Electrical Equivalent Circuit of Quartz-Crystal Tuning-Fork Tactile Sensor at Resonance
Authors: Itoh Hideaki , Hatakeyama Naoki
Published: July 2010

We propose a novel method to measure the Young's modulus of materials using the change in motional capacitance of the electrical equivalent circuit of a quartz-crystal tuning-fork tactile sensor at resonance before and after the sensor's base coming into contact with materials with different Young's moduli, such as silicon rubbers and plastics. How to measure the Young's modulus of materials using the change in motional capacitance is investigated experimentally and theoretically. By our calculation of motional capacitance and from contact experiments on silicon rubbers and plastics, we found that there was a possibility to measure the Young's modulus of materials using the relationship between the change in motional capacitance and their Young's modulus.
Flow Velocity Measurement Using an Orthogonally Radiated Ultrasonic Beam
Authors: Igarashi Juei , Mizutani Koichi , Wakatsuki Naoto
Published: July 2010

A method of measuring flow velocity using an orthogonally radiated ultrasonic beam based on Doppler spectra is discussed. We run numerical simulations of an ultrasonic wave scattered by particles and received at a circular planar transducer when particles flow perpendicular to the axis of the transducer. It is observed that spectrum bandwidth varies depending on flow velocity as the simulation is validated using an experimental result. In particular, when the beam diverges, the spectrum bandwidth is consistent with the amount of Doppler shift that is supposed to occur owing to the velocity of the particles. The simulation also shows that the spectrum bandwidth when multiple particles continuously flow along a line at a constant velocity is consistent with that when a single particle flows. Furthermore, in the case of multiple flow paths having positional variations in terms of both the distance from the transducer to the path and the offset of the path from the axis of the transducer, the bandwidth is still consistent with the case of a single flow path. This result implies the expansion of the applications of the proposed velocimetry such as to flow running in a pipe with a finite radius.
Optimal Transducer Arrangement for Temperature Distribution Measurement in Arbitrary Convex-Shaped Space by Acoustic Computerized Tomography
Authors: Minamide Ayumu , Wakatsuki Naoto , Mizutani Koichi
Published: July 2010

We study the optimal transducer arrangement for measuring temperature distribution in an arbitrary convex-shaped space by acoustic computerized tomography (A-CT) using flexibly arranged transducers. The transducer arrangement is optimized by the combined use of two methods, namely, real-coded genetic algorithm (RCGA) and simulated annealing (SA). By RCGA, the optimized arrangement is globally searched and then locally searched by SA. A fitness function of these methods is defined to evaluate the distribution of projection data in θ–r space. By use of this function, we aim to obtain better projection data sets by two-dimensionally interpolating the projection data. By numerical simulations, we confirmed the adequacy of our method and the optimized transducer arrangement.
An Improvement of Absorbing Boundary Condition Based on Algorithm of Constrained Interpolation Profile Method for Finite-Difference Time-Domain Acoustic Simulation
Authors: Harada Yoshifumi , Okubo Kan , Tagawa Norio , Tsuchiya Takao
Published: July 2010

In this study we examined an improved reasonable absorbing boundary condition (ABC). We examined ABC on the basis of the algorithm of the constrained interpolation profile (CIP) method for finite-difference time-domain (FDTD) acoustic simulation. Analysis of one-dimensional sound propagation with CIP-ABC was implemented. The results obtained in this study clarified that improved CIP-ABCs have better absorption performance than first-order Mur's ABC. That is, CIP-ABCs maintain a reflection coefficient that is lower than that of Mur's ABC in all frequency ranges.
Defect Detection in Square Billet Using Time-of-Flight of Longitudinal Waves
Authors: Mitsui Hideto , Mizutani Koichi , Wakatsuki Naoto
Published: July 2010

We investigate defect detection using the time-of-flight (TOF) of longitudinal waves in an experiment. The apparent sound velocity is reconstructed using the TOF measured by the transmission method. The defects are visualized as a decrease in apparent sound velocity because the TOF increases owing to diffraction at the defects. In addition, the effects caused by the frequency of the input signal and the transducer size are evaluated by calculation prior to the experiment. Wave propagation is calculated by the transmission-line matrix method. As a result, the proposed method could detect defects of 2.8 mm when the frequency was 2.0 MHz and transducer diameter was 5 mm by calculation. The defect detection was evaluated in an experiment using a transducer whose diameter was 5 mm. The defects could be identified and their location conformed to the setup. Therefore, the proposed method could detect defects by experiment as well as calculation.
Distinguishing Buried Objects in Extremely Shallow Underground by Frequency Response Using Scanning Laser Doppler Vibrometer
Authors: Abe Touma , Sugimoto Tsuneyoshi
Published: July 2010

A sound wave vibration using a scanning laser Doppler vibrometer are used as a method of exploring and imaging an extremely shallow underground. Flat speakers are used as a vibration source. We propose a method of distinguishing a buried object using a response range of a frequencies corresponding to a vibration velocities. Buried objects (plastic containers, a hollow steel can, an unglazed pot, and a stone) are distinguished using a response range of frequencies. Standardization and brightness imaging are used as methods of discrimination. As a result, it was found that the buried objects show different response ranges of frequencies. From the experimental results, we confirmed the effectiveness of our proposed method.
A Study of Vibratory Tactile Sensor Using a Horn-Type Longitudinal Bar Resonator
Authors: Kudo Subaru
Published: July 2010

Piezoelectric vibratory tactile sensors have been studied for measuring the softness and hardness of an object. In this research, a novel piezoelectric vibratory tactile sensor with a horn-type longitudinal bar resonator was investigated. For improving the sensitivity of the vibratory tactile sensor, the shape of the longitudinal bar resonator was calculated by the finite element method. The sensitivity of these tactile sensors with modified resonators was experimentally shown. It was clarified that the sensitivity of the tactile sensor was increased by modifying the shape of a resonator. Then, in order to reduce the vibration displacement at the supporting point on the tactile sensor, vibration displacement analysis was performed. The dimensions of the resonator, which were not affected by the conditions of the supporting points, were determined. This horn-type longitudinal bar resonator is expected as a novel tactile sensor with high performance.
Equivalent Circuit Analysis and Design of Multilayered Polyurea Ultrasonic Transducers
Authors: Aoyagi Takahiro , Koyama Daisuke , Nakamura Kentaro , Tabaru Marie
Published: July 2010

In this paper, we carried out equivalent circuit analysis for a multilayered transducer including the backing and load effects. The calculated resonance frequencies showed good agreement with previously measured values. The improved multilayered transducers in this study exhibit good characteristics for output sound pressure when loaded with water. We also demonstrated designs for a four-layer polyurea transducer with a frequency of up to 220 MHz. As a result, designs for a wide frequency range can be obtained by varying the polyurea thickness.
New Design of the Kerfs of an Ultrasonic Two-Dimensional Array Transducer to Minimize Cross-Talk
Authors: Lee Wonseok , Roh Yongrae
Published: July 2010

The transducer under consideration is a planar two-dimensional (2D) array transducer working at 3.5 MHz. The transducer is composed of 17×17 piezoelectric elements separated by major and minor kerfs. Through finite element analyses (FEA), the performance of the 2D array transducer was investigated in relation to the acoustic impedance and structure of the kerfs. Based on the analysis results, three new types of kerfs were proposed to reduce the cross-talk. Detailed material properties and structures of the new kerfs were determined to provide the lowest cross-talk level and highest pulse–echo sensitivity while preserving a desired acceptance angle at the center frequency of 3.5 MHz. The results in this work can contribute to developing a 2D array transducer which would result in having a higher signal-to-noise level, which in turn will lead to better ultrasonic imaging.
Development of 170 MHz Electrodeless Quartz-Crystal Microbalance Immunosensor with Nonspecifically Immobilized Receptor Proteins
Authors: Ogi Hirotsugu , Nagai Hironao , Fukunishi Yuji , Yanagida Taiji , Hirao Masahiko , Nishiyama Masayoshi
Published: July 2010

Staphylococcus aureus protein A (SPA) shows high nonspecific binding affinity on a naked quartz surface, and it can be used as the receptor protein for detecting immunoglobulin G (IgG), the most important immunoglobulin. The immunosensor ability, however, significantly depends on the immobilization procedure. In this work, the effect of the nonspecific immobilization procedure on the sensor sensitivity is studied using a home-built electrodeless quartz-crystal microbalance (QCM) biosensor. The pure-shear vibration of a 9.7-µm-thick AT-cut quartz plate is excited and detected in liquids by the line antenna located outside the flow channel. SPA molecules are immobilized on the quartz surfaces, and human IgG is injected to monitor the binding reaction between SPA and IgG. This study reveals that a long (nearly 24 h) immersion procedure is required for immobilizing SPA to achieve the tight biding with the quartz surfaces.
Electromechanical Characteristics of Exponentially Tapered Piezoelectric Bimorph Actuators
Authors: Kim Jungsoon , Kim Moojoon , Lee Huiuk , Ha Kanglyel
Published: July 2010

In order to investigate the most effective shape for a piezoelectric bimorph actuator, equations giving the free input admittance for an exponentially tapered vibrator were derived. Five piezoelectric bimorph actuators with different shapes were fabricated and their characteristics were analyzed using the derived equations and by measurements. The experimental and theoretical results were in good agreement, and they suggested that the resonant frequency and displacement can be controlled by the tapered shape.
Quantitative Analysis of Power Leakage in an Film Bulk Acoustic Resonator Device at the Antiresonance Frequency
Authors: Thalmayr Florian , Hashimoto Ken-ya , Ueda Masanori , Omori Tatsuya , Yamaguchi Masatsune
Published: July 2010

In this paper we analyze for the first time quantitatively the acoustic losses in a film bulk acoustic wave resonator (FBAR), which are expected to deteriorate the device performance. To this end, we regard the effective acoustic admittance, conduct laser probing measurements and finite element modeling (FEM). For our device under test (DUT) at the anti-resonance frequency, we compare the relative power of observable modes in the active and passive area and point out the relevant energy loss mechanism in terms of a single mode. By scattering analysis of the resonator's border region, we can identify the respective excitation mechanism within the active area and therefore can consider specific countermeasures to improve the device performance. Practically applied for the first time, the utilized methods and the overall procedure are explained in detail and are applicable to investigate acoustic energy loss as well at other frequencies as in other devices.
Large-Area Growth of In-Plane Oriented (1120) ZnO Films by Linear Cathode Magnetron Sputtering
Authors: Kawamoto Takayuki , Yanagitani Takahiko , Matsukawa Mami , Watanabe Yoshiaki , Mori Yoshikazu , Sasaki Sho , Oba Masatoshi
Published: July 2010

(1120) textured ZnO films are good candidates for shear-mode piezoelectric devices. In the previous deposition techniques of these films, there have been two problems related to their practical application. These problems are as follows: (i) highly oriented films can be obtained only in a small area and (ii) the crystallite c-axis of in the films is radially oriented in the substrate plane. To resolve these problems, the sputtering deposition technique using a linear cathode has been proposed. The in-plane and out-of-plane orientations of the films were quantitatively determined by pole figure analysis. As a result, we have demonstrated the formation of in-plane unidirectionally oriented (1120) ZnO films over the entire area of 4-in. silicon wafers.
Simple Simultaneous Modulation for Red, Green, and Blue Laser Lights Using Surface-Acoustic-Wave-Driven Acoustooptic Modulator
Authors: Kakio Shoji , Shinkai Susumu , Nakagawa Yasuhiko
Published: July 2010

An acoustooptic modulator (AOM) driven by a surface acoustic wave (SAW), in which laser light of the three primary colors, red, green, and blue (RGB), can be modulated by the same modulator at the same driving frequency, was investigated. To suppress the light power leaked to the outside of the waveguide, a waveguide-type AOM with a 3.5-µm-deep waveguide was fabricated. The RGB laser lights were modulated with the diffraction efficiencies of 73–85% and a driving SAW power of less than 0.2 W at the same driving frequency of 245.5 MHz. By combining the AOM module, laser sources, WDM couplers, and fiber delay lines, a simple simultaneous modulation for RGB laser lights was proposed and constructed. On the basis of the designed properties, the switching time of the output signal from the constructed system equipped with the AOM with the three-finger-pair interdigital transducer (IDT) was demonstrated to be 28 ns.
Acoustic Wave Devices Composed of Periodically Poled Z-Cut LiTaO3 Plate Using Edge Reflection
Authors: Kadota Michio , Ogami Takashi , Yamamoto Kansho , Cho Yasuo
Published: July 2010

The excitation method using the periodically poled (PP) structure has several merits suited for high-frequency devices in comparison with the excitation method using a conventional interdigital transducer (IDT). For example, a simple photolithography process, absence of short circuit caused by metallic powder, and a strong electric power durability can be expected. Although transducers using PP plates or PP films have been reported, none of the resonator-type devices using them has been. The authors attempted to fabricate PP resonators and resonator filters by applying an edge reflector to the fabrication of PP structure devices. As the result, a resonator having an impedance ratio of 33 dB and a resonator filter having an insertion loss of 2.6 dB and a relative 3 dB bandwidth of 2.2% were realized.
Estimation of Sonochemical Reactions under Single and Dual Frequencies Based on Energy Analysis
Authors: Son Younggyu , Lim Myunghee , Cui Mingcan , Khim Jeehyeong
Published: July 2010

Sonochemical reactions were quantified using KI dosimetry and analyzed based on calorimetry and electric energy consumption under single (35, 72, 170, 300, 500, and 1000 kHz) and dual (35/35, 35/72, 35/170, 35/300, 35/500, and 35/1000 kHz) frequency conditions. For single-frequency conditions, ultrasonic energy under calorimetry decreased as the applied frequency increased, while there was no significant change with the applied frequency for dual-frequency conditions. A synergistic effect was observed in the dual-frequency mode not considering the energy consumption; however, double the electric energy consumption in the dual mode was considered as the main reason for high performance. It seemed that calorimetry was not adequate for determining the optimal condition even though it was based on the direct measurement of the temperature in the solution. For electric energy analysis, there was no significant synergistic effect for dual-frequency applications and some single-frequency applications were superior to their dual-frequency counterparts.
Investigation of Output Signal from Cavitation Sensor by Dissolved Oxygen Level and Sonochemical Luminescence
Authors: Uchida Takeyoshi , Sato Hidenobu , Takeuchi Shinichi , Kikuchi Tsuneo
Published: July 2010

We investigated the relationships between the broadband integrated voltage (BIV) calculated from the high-frequency components of broadband noise produced by acoustic cavitation in an output signal, the dissolved oxygen (DO) level which is one of generation conditions for cavitation, and sonochemical luminescence which is a chemical reaction induced by cavitation. As a result, BIV was changed by the DO level in distilled water. Also, a correlation was found between BIV and sonochemical luminescence. This indicated that BIV has the potential to be used as an index of the amount of generated cavitation.
Effects of Salt and pH on Sonophotocatalytic Degradation of Azo Dye Reactive Black 5
Authors: Son Younggyu , Cho Eunju , Lim Myunghee , Khim Jeehyeong
Published: July 2010

The effects of salt and pH on the sonophotocatalytic degradation of azo dye Reactive Black 5 (RB5) were investigated. The applied frequency was 35 kHz, and 254 nm UVC lamps and TiO2 were used. At salt concentrations of 0, 50, 500, and 5000 mg/L, salt acted as an inhibitor or a OH radical scavenger under neutral pH condition and there was no significant difference in the removal trends for salt-added conditions. Under acidic condition, adsorption of RB5 on the surface of TiO2 was observed before the start of the sonophotocatalytic process and it was revealed that adsorption of RB5, negatively charged dye anions, could be enhanced under acidic condition because the charge of the TiO2 surface was changed from negative to positive at a pH of 6.6. This enhancement under acidic condition was observed during the entire operation time. In the comparison of the pH and salt effects, the enhancement by acidic pH control was larger than the inhibition by the effect of salt as a radical scavenger.
Sonophotochemical Degradation of Bisphenol A with Solid Catalysts
Authors: Lim Myunghee , Son Younggyu , Park Beomguk , Khim Jeehyeong
Published: July 2010

In order to investigate the degradation of bisphenol A (BPA) solution under sono, photo, sonocatalytic, photocatalytic and sonophotocatalytic processes, the BPA concentration and the total organic carbon (TOC) concentration were analyzed. The degradation rate of BPA was higher at high frequency (1 MHz) than at low frequency (300 kHz). At high frequency the acoustic period is shorter, and a high H2O2 concentration is therefore produced in aqueous solutions, which can enhance the degradation rate. The degradation rates of BPA were 0.0060, 0.0258, and 0.0451 min-1 under the sonocatalytic (1 MHz), photocatalytic and sonophotocatalytic processes respectively. The combined system of the sonochemical and photocatalytic processes can enhance the degradation rate of BPA compared with individual processes (sono and photocatalytic processes). The order of degradation of BPA (CuO>ZnO≈TiO2) and TOC (TiO2>ZnO>CuO) differed for each of the three types of catalysts. The separation characteristics of catalysts were dissimilar for each of the two frequencies.
Ultrasonic Polymerization of N-Isopropylacrylamide below and above Critical Temperature
Authors: Yanagida Hirotaka , Umeki Erika , Tamura Yasutaka , Saitoh Tadashi , Takahashi Tatsuhisa , Ikegami Masanaga , Minagawa Keiji
Published: July 2010

Poly(N-isopropylacrylamide) is a well-known thermosensitive polymer exhibiting a phase transition at 32 °C. Here, ultrasonic polymerization of the monomer, N-isopropylacrylamide, in an aqueous solution is reported as a novel reaction. Ultrasound irradiation of an N-isopropylacrylamide aqueous solution for approximately 30 min produced the polymer. The yield and molecular weight (M
w) of the polymer were measured for various temperatures and monomer concentrations. At 15 °C (below the critical temperature), the reaction yield did not increase after 1 h. At 33 °C (above the critical temperature), however, polymerization continued even 6 h after sonication, producing twice the yield obtained at 15 °C. The M
w of the polymer obtained at 33 °C was 5 ×104 g/mol, approximately five times that at 15 °C.
Elimination of Two Hormones by Ultrasonic and Ozone Combined Processes
Authors: Cui Mingcan , Son Younggyu , Lim Myunghee , Na Seungmin , Khim Jeehyeong
Published: July 2010

A direct ultrasonic (US) and ozone (O3) combination (US/O3) process for the removal of two hormones, estrone (E1) and estriol (E3), in aqueous solutions was investigated. These two hormones were detected in a wastewater treatment plant effluent in Korea. It was found that the ultrasonic/ozone process showed a higher removal performance than the US and O3 process even though the O3 process also showed approximately the same removal efficiency after 60 min. Chemical oxygen demand/total organic carbon (CODcr/TOC) ratios for E1 and E3 decreased, indicating that biodegradability could be increased significantly in the US/O3 process. The optimal pH condition was determined above the neutral pH condition.