bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Property and Network Structure of Porous Silica Films
Authors: Takada Syozo , Hata Nobuhiro , Seino Yutaka , Yamada Kazuhiro , Oku Yoshiaki , Kikkawa Takamaro
Published: February 2005

We investigated the relationship between Young's elastic modulus of a series of spin-on sol-gel silica films and the shift of the longitudinal-optical component of the asymmetric stretching vibration mode of Si–O–Si (LO4), by nanoindentation measurements and Fourier transform infrared reflection spectroscopy. With the increase of the annealing temperature from 673–1073 K in air, the position of the LO4 mode reflection peak shifted from 1203 to 1253 cm-1, in parallel with the increase of Young's elastic modulus. The correlation between the LO4 peak position and Young's elastic modulus was also confirmed among a set of silica films in which the preparation conditions and/or the postpreparation treatment conditions were varied. It was concluded that the shift of the LO4 mode peak position is a good measure of the skeletal silica mechanical property of porous silica films.
Pt/BaxSr(1-x)TiO3/Pt Capacitor Technology for 0.15 µm Embedded Dynamic Random Access Memory
Authors: Tsunemine Yoshikazu , Okudaira Tomonori , Kashihara Keiichiro , Yutani Akie , Shinkawata Hiroki , Mazumder Motaharul Kabir , Ohno Yoshikazu , Yoneda Masahiro , Okuno Yasutoshi , Tsuzumitani Akihiko , Ogawa Hisashi , Mori Yoshihiro
Published: February 2005

A novel capacitor technology has been developed for 0.15 µm embedded dynamic random access memory (DRAM). Platinum as electrodes and barium strontium titanate (BST) as dielectrics are used in the capacitor. The BST dielectrics is a stack of two layers. The nucleating bottom layer is deposited by sputtering and the top bulk layer is deposited by chemical vapor deposition (CVD). The two-step deposition process is established with high reliability without N2 high-temperature annealing. Moreover, both thermal stability and reductive stability of the BST capacitors are improved by introducing modulated oxygen-doping into the Pt top electrodes. The degradation mechanism of the BST capacitors by annealing in the back end process was revealed. Oxygen atoms doped into the top electrode diffuse to the interface between the bottom electrode and the metal nitride barrier layer, and oxidize the metal nitride. The modified BST capacitors maintained low leakage current and sufficient capacitance after 500°C N2 annealing and 400°C H2 annealing. These BST capacitors have been integrated into the 0.15 µm rule-embedded DRAM having a capacitor under bit-line (CUB) structure and four-level metallizations.
Yellow Luminescence Centers of GaN
Authors: Zhao Guangyuan , Hubbard Seth , Pavlidis Dimitris
Published: February 2005

The method for measuring Shockley–Read–Hall (SRH) lifetime of yellow centers of GaN was developed. The capture-section ratio (150) of hole to electron is extracted by comparing the experimental and theoretical results. A marked increase in the SRH lifetime (from 0.75 to 7.0 ns) with the increasing in Si doping density (from 1.5×1017 to 8.8×1018 cm-3) was observed, and it is attributed to some Si dopant substituting for the Ga vacancy. In addition, it is also found that the YL centers are an important factor limiting the performance of GaN-based devices.
Quantum-Beat Free-Induction Decay of Copper Ions in an Aqueous Solution: Fourier-Transform ESR Spectroscopy by Optical Means
Authors: Furue Shigenori , Nakayama Kazuyuki , Kohmoto Toshiro , Kunitomo Masakazu , Fukuda Yukio
Published: February 2005

The fast-spin dynamics of transition-metal ions in an aqueous solution at room temperature has been directly observed in the subnanosecond region by polarization spectroscopy using the pump-probe technique. The time evolution of the optically induced magnetization is monitored through the change in the polarization of the probe pulse. Quantum-beat free-induction decay signals in the ground state of copper ions in an aqueous solution of copper sulfate are observed in transverse magnetic fields. The Fourier transform of the observed signals gives the ESR spectra. From the magnetic-field dependence of the beat frequency, the g-value of copper ions is g=2.20±0.05. The observed line shape of the ESR spectra suggests that the hydrated copper complex rotates in the picosecond region. This all-optical method can be a powerful tool for the study of fast-spin dynamics in solutions.
New Frequency Stabilization Method of a Semiconductor Laser Using the Faraday Effect of the Rb-D2 Absorption Line
Authors: Nimonji Toshiya , Ito Shin-ichi , Sawamura Akihiko , Sato Takashi , Ohkawa Masashi , Maruyama Takeo
Published: February 2005

We have applied a precise amount of electrical feedback into laser injection current to stabilize the oscillation frequency of a semiconductor laser. This feedback method usually requires a small direct modulation to the laser injection current to obtain an error signal. This broadens the oscillation width of the laser diode, but certain applications, such as those related to coherent optical communications and measurements, require a narrower oscillation linewidth. Thus, we have attempted to obtain the error signal and stabilize the laser oscillation frequency in a narrower oscillation linewidth using the Faraday effect of the Rb absorption line. Our next task for the Faraday-effect-based method involves frequency stabilization, which we accomplish using a large frequency discrimination gain G
d. By incorporating our “PEAK” circuit, which utilizes the envelope detection method to determine the switching points between two different absorption signals, we increase G
d in our improved PEAK methods.
Optical Properties of Thin Amorphous Silicon Film on a Phase Shift Mask for 157 nm Lithography
Authors: Kim Sung Kwan , Kim Yang Soo , Choi Young Min , Choi Jong Wan , Hong Jongin , Shon Jung Min , Sung Tae-Hyun , No Kwang Soo
Published: February 2005

We introduced thin amorphous Si (a-Si) films to prevent the degradation of Si–O–N–F films that were fabricated for phase shift masks in 157 nm optical lithography. To investigate the optical properties of thin a-Si films, a spectroscopic ellipsometry (SE) analysis method was used. In SE analysis of thin a-Si films, the optical properties, such as absorbance and optical band gap, were analyzed using the two layer model of effective medium approximation (EMA) (a-Si+SiO)/a-Si/Cauchy model. To verify the validity of SE analysis, Si 2p peak and O 1s peak variations of a-Si films were analyzed by X-ray photoelectron spectroscopy (XPS) respect to sputtering time. By comparing the results of SE and XPS analyses, it was confirmed that SiO could represent the optical properties of an oxidized surface and that EMA(a-Si+SiO)/a-Si/Cauchy model was appropriated.
Parametric Fluorescence Generation in LiNbO3 Quasi-Phase Matched Waveguide Pumped by Semiconductor Laser
Authors: Kintaka Hiroki , Suhara Toshiaki
Published: February 2005

We designed and fabricated a device for parametric fluorescence generation in the 1.5 µm band. The parametric fluorescence generation by pumping with a semiconductor laser was obtained. The fluorescence wavelengths and the spectrum were in good agreement with the theoretical prediction. Measured fluorescence power 2.2 nW for 12 mW pumping was in the same order of magnitude with the theoretical prediction.
InGaAs/AlGaAs Quantum Well Laterally-Coupled Distributed Feedback Laser
Authors: Das Prodip Kumar , Uemukai Masahiro , Suhara Toshiaki
Published: February 2005

InGaAs/AlGaAs quantum well laterally-coupled distributed feedback (LC-DFB) laser is designed and fabricated by electron beam lithography and reactive ion etching. The LC-DFB laser eliminates the need of a crystal regrowth in a conventional DFB laser fabrication process. A single mode lasing at a wavelength of 967.8 nm with a side mode suppression ratio of 46 dB was achieved under CW operation at room temperature. The threshold current and maximum peak output power were 15 mA and 19 mW at 90 mA injection, respectively.
Fast Switching of Frequency Modulation Twisted Nematic Liquid Crystal Display Fabricated by Doping Nanoparticles and Its Mechanism
Authors: Miyama Tomohiro , Thisayukta Jirakorn , Shiraki Hiroyuki , Sakai Yoshio , Shiraishi Yukihide , Toshima Naoki , Kobayashi Shunsuke
Published: February 2005

The electrooptic characteristics of a twisted nematic (TN) liquid crystal display (LCD) fabricated by doping Ag nanoparticles protected with NLC, 5CB (K-15, Merck) molecules have been investigated, and it is shown that the device exhibits a unique electrooptic response characteristic that is sensitive to the high-frequency components of the operating voltage together with the conventional root-mean-square voltage response. We call this device frequency modulation (FM) TN-LCD. The FM-TN-LCD is switched by switching the frequency of the operating voltage while its amplitude is kept unchanged. As an example, the frequency switched from 20 Hz to 500 Hz or 50 Hz to 2 kHz, and the switching is performed with the time constant of 21 ms for the rising process and 3 ms for the falling process. This device shows a peculiar response to a burst AC square wave, where the decay time is reduced by several times compared to that of an undoped TN-LCD. The mechanism of the FM-TN-LCD is investigated through the study of its dielectric properties.
Low-Fire Processing of BaTiO3 with BaCuO2–CuO
Authors: Lei Cheng-Dao , Jean Jau-Ho
Published: February 2005

The effects of a liquid-phase-sintering aid, BaCuO2–CuO (BCC), on the densification and dielectric properties of BaTiO3 ceramics have been investigated. The densification temperature of BaTiO3 is greatly reduced from 1300–1350°C down to 1050°C in the presence of BCC. This is attributed to a chemical reaction taking place at the interface of BCC/BaTiO3 during firing. The BaTiO3 dissolves into BCC, forming crystalline phases of BaCuO2, CuO, Cu2O and Ba6Ti17O40, and this enhances the densification kinetics of BaTiO3. For the samples with 2.0–2.5 wt% BCC, a high relative sintered density of >95% is obtained at 1050°C, and the resulting dielectric ceramics have a dielectric constant and dielectric loss in the range of 2200–2400 and <3% at 1 MHz, respectively.
Structural Stability and the Correlation of Lattice Constant versus Tantalum Concentration of the Ag-Based Fcc Solid Solutions Studied by Molecular Dynamics Simulation
Authors: Shen Yi-Xiong , Kong Ling-Ti , Gong Hao-Ran , Liu Bai-Xin
Published: February 2005

Based on the cohesion energies and lattice constants of some Ag–Ta non-equilibrium solid phases obtained by ab initio calculations, an embedded atom method (EAM) potential of the equilibrium immiscible Ag–Ta system was derived. Applied the derived potential, molecular dynamics simulation was carried out to predict, at an atomic scale, the quantitative correlation of the lattice constant of the Ag-based solid solutions versus the Ta concentration. The simulation results predict that the fcc crystalline structure can be preserved in the Ag-based solid solutions until the Ta concentration reaches 10 at.% and that the correlation of the lattice constant of the Ag-based solid solutions versus the Ta concentration is in good agreement with that deduced by Vegard's Law only when the Ta concentration is less than 6 at.%.
Intrinsic Defects in ZnO Films Grown by Molecular Beam Epitaxy
Authors: Tatsumi Tomohiko , Fujita Miki , Kawamoto Noriaki , Sasajima Masanori , Horikoshi Yoshiji
Published: February 2005

We have investigated the intrinsic defects in ZnO films grown by molecular beam epitaxy by annealing them in O2 and N2 atmosphere. We found that there is a good correlation between the annealing condition and photoluminescence characteristics. The results of annealing experiments suggest that the photoluminescence at 3.358 eV is caused by the excitons bound to oxygen vacancies. The green-yellow emission at around 2.3 eV is also observed in as-grown ZnO epitaxitial films. This emission becomes weak and the electron concentration increases when ZnO films are annealed in O2 atmosphere at 1000°C or in N2 atmosphere at 700°C. Since the donor in undoped ZnO is related to the oxygen vacancy, the observed green-yellow emission at around 2.3 eV is probably caused by defects other than oxygen vacancies. Our experimental results imply that it is related to interstitial Zn.
Crystal Structure of Dioctadecyldimethylammonium-Au(dmit)2 Salt
Authors: Miura Yasuhiro F. , Horikiri Masashi , Honda Kazumasa , Shiro Motoo , Sasaki Katsunari , Sugi Michio
Published: February 2005

The crystal of the dioctadecyldimethylammonium-Au(dmit)2 (2C18-Au(dmit)2) salt has been found to be composed of alternate sheets of Au(dmit)2 anions and dioctadecyldimethylammonium cations with a pronounced interdigitation of the alkyl chains. The planar Au(dmit)2 anions are dimerized by face-to-face stacking and further forming extended columns along the a-axis with short side-by-side contacts by sulfur atoms.
Efficacy of Cathodically Electro-Cleaning Nickel Thin Film Nozzle Plate for Piezo Inkjet Printer Head*
Authors: Lee Sungkyu , Jang Kwang-Kyun , Ahn Jae-Hwan , Chung Hyungsik
Published: February 2005

A hydrophilic nickel nozzle plate for a piezo inkjet printer head with a minimum 5° water contact angle was obtained by (1) primary cathodic electro-cleaning of the detached nickel nozzle plate by applying a cathodic current density of 109.64 A/m2 for 60 s in a thoroughly preelectrolyzed 20 wt% NaOH solution maintained at 97°C, and (2) secondary (post-treatment) cleaning by 1 or 2 min scrubbing of the primary cleaned nickel nozzle plate using a wiper soaked with a newly formulated post-treatment cleaner with inhibitor and surfactant to remove surface oxides and corrosion product films. The successful achievement of the hydrophilic nickel nozzle plate surface is attributed to (1) thorough and careful preelectrolysis of the primary 20 wt% NaOH electrolyte cleaner solution to remove dissolved oxygen and plateable cations, preventing potential aqueous caustic corrosion of the nickel nozzle plate under the more severe corrosive environment at 97°C compared with that of 25°C, and (2) proper formulation of the post-treatment cleaner solution, particularly the selection of the nonionic block copolymer type surfactant which not only assisted in widespread penetration of the cleaner into the NiO scale but also further improved the corrosion prevention performance of the inhibitor. The effect of post-treatment cleaning was experimentally substantiated by measurement of the water contact angle on the post-treatment cleaned nickel nozzle plate surface.
Thermochemical Stability of IrO2 Bottom Electrodes in Direct-Liquid-Injection Metalorganic Chemical Vapor Deposition of Pb(Zr,Ti)O3 Films
Authors: Byun Kyung-Mun , Lee Won-Jong
Published: February 2005

The IrO2 film has been regarded as a leading candidate bottom electrode of ferroelectric capacitors in ferroelectric random access memories (FRAMs). We have addressed a new issue on the thermochemical stability of IrO2 bottom electrodes during the growth of Pb(Zr,Ti)O3 (PZT) ferroelectric films on such electrode using direct liquid injection metalorganic chemical vapor deposition (DLI-MOCVD). The IrO2 electrode thermally dissociated at elevated temperatures in vacuum ambient at a low oxygen pressure. It was also reduced by carbon and hydrogen dissociated from the solvent in liquid solution. The reduction of IrO2 by the solvent was more pronounced at lower temperatures, which is attributed to the longer residence time of solvent molecules on the IrO2 surface at lower temperatures. The reduction of IrO2 was also induced by the metal elements Zr and Ti in metalorganic precursors because they have higher chemical affinities with oxygen than Ir. The reduction by Zr and Ti metal elements was more pronounced at higher temperatures. The use of thin Pt interlayers is a promising solution for the prevention of the reduction of IrO2 electrode during the growth of PZT films.
Preparation and Characterization of RuOx Thin Films by Liquid Delivery Metalorganic Chemical Vapor Deposition
Authors: Kim Kyoung-Won , Kim Nam-Soo , Lee Hyung-Gyoo , Kim Yeong-Seuk , Kang Hee-Jae , Park Ju-Chul , Joung Yang-Hee , Kang Seong-Jun
Published: February 2005

RuO
x
films were deposited by liquid delivery metalorganic chemical vapor deposition method using a new Ru(C8H13O2)3 precursor for the advanced capacitor electrode in Gbit-scale dynamic random access memory. Deposition was carried out on a TiN barrier layer in the range of 250–400°C and the ratio of the O2 flow rate to the total flow rate of Ar and O2 was varied from 20 to 80%. RuO
x
thin films were annealed at 650°C for 1 min with Ar, N2 or NH3 ambient. Film characterization was performed in terms of resistivity, crystal structure, surface morphology, microstructure and film purity. The resistivity depended on the impurity, grain density and crystalline structure of the film. The oxygen used to form Ru the oxide was found to eliminate the carbon and hydrogen elements in an organic source. The O2 flow ratio that changes the crystal structure of the films from Ru to RuO2 was found to be 40%. The metallic Ru phase forming a RuO2/Ru bilayer at the RuO2/TiN interface was observed at O2 flow ratios of 50% and 60%. The X-ray diffraction results indicate that the RuO2 phase and the silicidation are not observed regardless of the ambient gases. Ar was more effective than N2 and NH3 as an ambient gas for the postannealing of the Ru films.
Effects of Extremely Low Frequency Magnetic Field on Neurite Outgrowth of PC12 and PC12D Cells and Evaluation by Image Analysis
Authors: Sakanishi Akio , Takatsuki Hideyo , Yoshikoshi Akio , Fujiwara Yasuyoshi
Published: February 2005

A pheochromocytoma cell (PC12), and its derivative (PC12D), differentiate to nervelike cells in culture with the nerve growth factor (NGF) and forskolin respectively. We introduced a morphological factor σ=L/2(πA)1/2 for quantitating neurite outgrowth under a microscope in the presence of extremely low-frequency (ELF) magnetic fields for 22 hours, where L and A are the contour length and the area of the cells in clump determined using an image-analysis system. ELF magnetic fields B
1 were generated with a single coil or double coils in Helmholtz configuration together with static fields B
0 of -53, -20 and 67 µT. σ increased with increasing NGF or forskolin level at B
0=-53 µT (geomagnetism), in agreement with the cytometric observation of micrographs. With the addition of an AC field B
1 at 60 Hz (100 µT > B
1 > 3 µT rms) to B
0, neurite outgrowth represented by σ was depressed for PC12 and stimulated for PC12D. We discuss the cyclotron resonance and the ion parametric resonance models.
The Fabrication of the Low Loss Transmission Line and Low Pass Filter using Surface Microelectromechanical Systems Technology
Authors: Lee Han-Shin , Shin Dong-Hoon , Kim Sung-Chan , Lim Byeong-Ok , Baek Tae-Jong , Ko Baek-Seok , Chun Young-Hoon , Kim Soon-Koo , Park Hyun-Chung , Rhee Jin-Koo
Published: February 2005

In this study, we first fabricated a new GaAs-based dielectric-supported air-gap microstrip lines (DAMLs) by the surface microelectromechanical systems (MEMS) technology, and then fabricated the low-pass filter (LPF) for the Ka-band using those DAMLs. We elevated the signal lines from the surface in order to reduce the substrate dielectric loss and to obtain low losses at the millimeter-wave frequency band with a wide impedance range. We fabricated LPFs with DAMLs for Ka-bands, and we were able to reduce the insertion loss of LPFs by reducing the dielectric loss of the DAMLs. Miniaturization is essential for integrating LPFs with active devices, so we fabricated a LPF with the slot on the ground metal to reduce the size of the LPF. We compared the characteristics of the LPF with a slot and the LPF without the slot.
Nonuniform Reactive Ion Etching of MnAs/GaAs Heterostructures: MnAs Nanodots and GaAs Nanocolumns
Authors: Takagaki Yukihiko , Wiebicke Edith , Däweritz Lutz , Ploog Klaus H.
Published: February 2005

Under certain conditions, the reactive ion etching of MnAs layers grown on GaAs substrates proceeds in a remarkably nonuniform manner. Mounds are formed on the surface of the MnAs layers during the etching. They eventually result in submicron-scale islands when the etch front reaches the MnAs/GaAs interface. Because of the one-order-of-magnitude smaller etch rate for MnAs than that for GaAs, GaAs columns having large height-to-width ratios are subsequently generated when the etching further progresses. The nonuniform etching takes place when the MnAs surface is partly covered with a resist, indicating the inhomogeneous migration of etching species is crucial.
Digital-to-Analog Converter Using Single-Electron Tunnel Junctions
Authors: Shin Mincheol , Choi Jung Bum
Published: February 2005

We have devised a novel digital-to-analog converter (DAC) based on parallel-coupled single-electron tunnel junctions and demonstrated its functionality by performing simulation studies of a 3-bit DAC. The main features of the single-electron DAC are its ease of expansion due to its relatively simple structure and robust-to-background-charge property due to the parallel coupling of single-electron tunnel junctions.
Vibration Characteristics of a Large-Capacity Complex Vibration Source Using a Titanium Alloy Complex Transverse Vibration Rod with Two Stepped Parts
Authors: Tsujino Jiromaru , Ueoka Tetsugi , Kikuchi Yuya
Published: February 2005

The configurations of large-capacity 27 kHz ultrasonic complex vibration sources with multiple longitudinal transducers are proposed and studied. Ultrasonic complex vibration systems are effective for various types of metal welding and essential for new applications in various industries. The large-capacity vibration source consists of a complex transverse rod with a welding tip (titanium alloy), a complex vibration rod with a flange and a stepped part for holding the system (stainless-steel), a one-wavelength longitudinal vibration disk (aluminum alloy) and six bolt-clamped Langevin type piezo-electric ceramic (PZT) transducers (BLTs) installed along the circumference of the disk at an angle difference of 60°. The vibration source is driven using three driving systems with three transformers at a phase difference of 120°, and the disk is driven in a circular locus. The transverse vibration rod installed at the center of the disk is driven transversally and the welding tip of the rod vibrates in a circular locus.
Configuration of a Transverse Vibration Rod Type Ultrasonic Motor Using Three Longitudinal Transducers Driven in Three Different Vibration Phases
Authors: Suzuki Atsuyuki , Kihara Masaki , Katsumata Yasuhiro , Kikuchi Naoki , Tsujino Jiromaru
Published: February 2005

The vibration and load characteristics of an ultrasonic motor using a circular vibration disk with three longitudinal transducers have been studied. Three bolt-clamped Langevin type piezoelectric ceramic (PZT) longitudinal transducers (BLT) 20 mm in diameter were installed along the circumference of the circular disk, and complex transverse vibration rods were installed normally in the center of the circular disk. A complex transverse vibration rods are driven simultaneously using three power amplifiers with a phase difference of 120°. The transducers could also be driven using only one power amplifier in the case where the resonance frequencies were slightly different. A rotor disk installed on the free edge of the transverse vibration rod was pressed statically to a driving surface using a system for inducing static pressure. A maximum torque over 0.12 Nm was obtained using three power amplifiers under a static pressure of 1.7 MPa. A maximum rotation of 280 rpm and an efficiency of 1.13% were obtained using one power amplifier under a static pressure of 1.4 MPa.
Evaluation of Young's Modulus for Polymer Thin Film on Isotropic Substrate by Complex V(z) Curve
Authors: Maebayashi Masahiro , Matsuoka Tatsuro , Koda Shinobu , Hashitani Ryuki , Nishio Tomohiro , Kimura Shin-ichi
Published: February 2005

The complex reflectance function of acoustic waves in the incidence angle range from 0 to 60° was calculated for polymer thin films on glass substrates with different Young's modulus and density values. A characteristic phase change of the complex reflectance function was observed due to the existence of the polystyrene thin film on the glass substrate. The phase change appeared when the thickness of the polymer thin film was more than 0.9 µm at 300 MHz. The normalized wave number of the characteristic phase change varied sensitively with Young's modulus and the density of the polymer thin film. The contour map of the normalized wave number was obtained from these results. The determination method of Young's modulus of the polymer thin film by the characteristic phase change was proposed.
Observation of Ultrasonic Relaxation due to Micelle-Monomer Exchange Process in Aqueous Solutions of Rodlike Micelles
Authors: Matsuoka Tatsuro , Masuda Yukihiro , Yamaguchi Tsuyoshi , Koda Shinobu
Published: February 2005

Ultrasonic absorption in aqueous solutions of sodium p-toluene sulfonate and dodecyltrimethyl ammonium bromide was measured in the frequency range from 0.2 to 7 MHz. The ultrasonic relaxation spectra showed a single relaxation process in both the spherical and rodlike micelle solutions, which was identified as the relaxation due to the micelle-monomer exchange process. The relaxation time and strength were discussed in terms of Teubner's theory.
High Coupling and Highly Stable Shear-Horizontal-Type Surface Acoustic Wave on Langasite with Au or Ta2O5 Thin Film
Authors: Kakio Shoji , Nozawa Masaya , Nakagawa Yasuhiko
Published: February 2005

In this study, the propagation characteristics of a pure shear-horizontal-type surface acoustic wave on rotated Y-cut 90° X propagation langasite (at Euler angles of (0°, θ, 90°)) with a high-density thin film, such as a gold (Au) film or a tantalum pentoxide (Ta2O5) dielectric film, are investigated. The theoretical analysis showed that, by loading with these films, coupling factor increases to about 1.0% for a certain condition. In fact, the measured coupling factors for θ=20° were 0.80% and 0.61%, for the samples with a Au film thickness of 0.015 wavelength (λ) and a Ta2O5 film thickness of 0.047 λ, respectively. For both films, the measured frequency shifts in the temperature change for θ=20° showed that a temperature characteristic with a zero temperature coefficient of delay in the same as the ST-90°X quartz with a free surface can be obtained by appropriately choosing the film thickness.
Experimental Consideration of Acceleration Sensor Utilizing Resonance Frequency Change of Flexural Vibrator
Authors: Takahashi Jun , Sugawara Sumio
Published: February 2005

In this paper, the characteristics of the acceleration sensor utilizing the resonance frequency change in the flexural vibrator are examined experimentally. The sensor sample was produced using stainless steel. It was confirmed that the relationship between the applied acceleration and the resonance frequency change becomes linear and almost coincides with the theoretical value by the finite element analysis. The sensor sensitivities of approximately 2800 ppm/G and 2150 ppm/G are measured in the cases of using the 1st and 2nd modes, respectively. It was clarified experimentally that the spurious vibrations do not appear in the vicinity of the resonance frequency f
0. Moreover, it is shown that this sensor can also be used as an inclination angle sensor.
Observation of the Roundtrips of Surface Acoustic Waves on a Single Crystal LiNbO3 Ball
Authors: Akao Shingo , Nakaso Noritaka , Ohgi Tsuneo , Yamanaka Kazushi
Published: February 2005

Propagation of surface acoustic waves (SAWs) was investigated on a single lithium niobate (LiNbO3) ball of 1 inch diameter. We found ten specific routes, on which the roundtrips of SAWs are observed, and one or more specific routes, on which the multiple reflections of bulk waves are observed. Since the temperature coefficient is similar on each route of the SAW, one route can be used to correct the temperature dependency of all other routes, and the other routes can be used as multiple-gas sensors by coating various reactive thin films along each route.
Detection of Internal Micro Defects by Nonlinear Resonant Ultrasonic Method Using Water Immersion
Authors: Ohara Yoshikazu , Kawashima Koichiro
Published: February 2005

A nonlinear resonant ultrasonic method using water immersion has been developed to detect micro defects in solids. This method allows us to reduce the strong nonlinearity of water and amplify the weak second harmonics generated at internal micro defects. In this method, both the fundamental and second harmonic frequencies are selected to match the resonant frequencies based on the resonant spectra of a sample. The detection of the micro defects in SiCf/Ti composite has been demonstrated.
Study on Range-Dependent Evolution of the Mode Eigenvalue by Using the Wigner Distribution Function
Authors: Matsumoto Sayuri , Ohta Kazuhiko
Published: February 2005

In an attempt to obtain the eigenvalues of local modes in a range-dependent ocean environment, the Wigner distribution function (WDF) is exploited in the range-wavenumber domain, instead of in the time-frequency domain, in analogy with time-dependent signal processing. In the first place, it is confirmed that the WDF can extract the exact eigenvalues for the acoustic field simulated in a horizontally stratified environment. Then, the WDF is applied to a range-dependent field simulated using the parabolic equation model. Consequently, the WDF peaks are recognized to evolve laterally in the same manner as local modes; however, some of the small peaks are difficult to identify due to the affection of false images generated in the WDF. As a result of applying a technique to enhance the amplitude of those peaks, their identification can be improved.
Consideration of Radiation Impedance Calculation Methods for Cylindrical Array Sound Source
Authors: Yokoyama Tomoki , Asami Tomohiro , Mori Kazuyoshi , Nakamura Toshiaki , Hasegawa Akio
Published: February 2005

In a phased array, the interval between the centers of the sound source elements which adjoin each other is set below half the wavelength in order to suppress the gratinglobe. At this interval, the array sound source can gain strong radiation power. The estimation of radiation impedance is important in the analysis of the radiation power. The Greenspon's method which is a radiation impedance calculation method of rectangular pistons on a cylinder is explained, and some defects of this method are clarified. For the evaluation of Greenspon's method, we introduce the combined Helmholtz integral equation formulation (CHIEF) method. The radiation impedance is calculated using both Greenspon's method and the CHIEF method, and the results are compared. On the basis of comparison of the radiation power measured while driving the cylindrical phased array with the theoretical value of radiation power determined using the caluculated value of radiation impedance, it is considered that Greenspon's method and the CHIEF method give accurate estimations.
Sound Pressure Fields Focused Using Biconcave Acoustic Lens for Normal Incidence
Authors: Nakamura Toshiaki , Sato Yuji , Kamakura Tomoo , Anada Tetsuo
Published: February 2005

The underwater imaging sonar system with an acoustic lens is again receiving considerable attention because it does not require a complex beam-forming circuit. The lens system used in this type of sonar was designed by the ray theory or by a hybrid method of the ray and wave theories. In this report, a basic analysis was performed by an analytical method using a wave theory and by a numerical method using the parabolic equation (PE) method, to determine the convergent characteristics of a biconcave lens. The pressure field focused by the biconcave lens was measured in a water tank. The biconcave lens used in the experiment is made of acrylic resin with a radius of 20 cm and a radius of curvature of 20 cm. Measurements was conducted in a water tank at a frequency of 500 kHz. Sound pressure fields around the focal region measured by the experiments agreed well with the calculated ones by the analytical and PE methods.
Improvement of Calculation for Radiation Impedance of the Vibrators with Cylindrical Baffle
Authors: Kim Jung-Soon , Kim Moo-Joon , Ha Kang-Lyeol , Kim Chun-Duck
Published: February 2005

In order to determine the size of the vibrating surface of an individual element and the spaces among elements in a cylindrically arrayed ultrasonic transducer, enormous calculations for mutual- and self-radiation impedances should be accomplished within a limited time. However, the direct application of the equation of Greenspon and Sherman to such numerical calculations requires a very long time to obtain high accuracy. In this study, an effective calculation algorithm was investigated by introducing subintervals into the integration of the Greenspon and Sherman's equation. As results, limits of subintervals improving computation time and accuracy were fitted as functions of the size of the vibrating surface of the element and the size of the baffle.
Optical Observation of Microcapsule Destruction in an Acoustic Standing Wave
Authors: Koyama Daisuke , Kiyan Wataru , Watanabe Yoshiaki
Published: February 2005

The destruction of microcapsules having an elastic thin shell is discussed. An optical observation of the capsule destruction using a high-speed video camera is carried out. As the driving pressure is increased, the microcapsules trapped at the antinode of an acoustic standing wave show circling movements, and then the microcapsules eventually collapse. At the moment of destruction, it is found that the microcapsules change in shape and the internal gas jets out of the capsule rapidly. The sound pressure threshold for the capsule destruction is the lowest under the resonant condition. The capsule destruction also depends on the existence of free bubbles in the surrounding media. It is found that the mechanism of capsule destruction can be categorized into two types: one is due to the increasing driving sound pressure and the other is due to the existence of the free bubbles in the surrounding media. It is considered that the destructions of multicapsules depend on some parameters; however, these two types of capsule destruction are dominant factors.
Real-Time Monitoring of Shear Wave Traveling in Liver Tissue In Vivo
Authors: Machida Hideyuki , Yagi Shin-ichi , Kondo Yuji , Murata Yutaka , Akimoto Shin
Published: February 2005

Real-time imaging of tissue dynamic response caused by internal or external stress forces acting across a living tissue is promising for improving diagnostic quality and accuracy of clinical palpation as an “ultrasonic visualized palpation”. Thus we have investigated a real-time imaging system of local tissue displacement along an ultrasonic beam scanned across the living tissue, which realized straightforward but tissue-oriented physiological and dynamic color imaging on a conventional B-mode screen. System performance is fairly supported by a flexible design of a digital signal processor for real-time local cross correlation between successive two-dimensional complex speckle echo frames. Propagation of shear waves raised by external stress in a tissue phantom was clearly observed, so that real-time observation of shear wave traveling across a physiological liver tissue locally stressed by heartbeats was studied. As a result, we could confirm the characteristic shear wave propagation pattern by internal stress synchronous with heartbeat.
Optoelectronic and Structural Properties of Undoped Microcrystalline Silicon Thin Films: Dependence on Substrate Temperature in Very High Frequency Plasma Enhanced Chemical Vapor Deposition Technique
Authors: Das Chandan , Jana Tapati , Ray Swati
Published: February 2005

The effects of substrate temperature on optoelectronic and structural properties of undoped microcrystalline silicon thin films have been investigated. The undoped silicon films have been deposited by the very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) technique using a SiH4 and H2 gas mixture at 105 MHz plasma excitation frequency and moderately low power density of 70 mW/cm2. The effect of the systematic variation of substrate temperature (from 180°C to 370°C) on film properties has been studied, while keeping the other parameters constant. The deposition rate is considerably high (2.6 Ås-1) at 180°C and remains almost constant over the whole temperature range. Dark conductivity for all the films lies around ∼10-6 Scm-1. Low subband gap absorption has been observed by photothermal deflection spectroscopy for these microcrystalline films. Increase of substrate temperature improves the microcrystallinity of the film, which is confirmed from structural studies. Crystalline grain size also increases with increase of substrate temperature and a maximum of 460 Å has been achieved at 370°C. A satisfactory correlation is observed among the results of different structural studies: Raman spectroscopy, infrared spectroscopy, X-ray diffraction, transmission electron microscopy and atomic force microscopy.
Simulation of Three-Dimensional Stress in GaAs Microchannel Epitaxy Layer on Si Substrates
Authors: Naritsuka Shigeya , Okada Masahide , Maruyama Takahiro
Published: February 2005

The stress in a GaAs vertical microchannel epitaxy (V-MCE) layer on Si was simulated using the finite element method. The stress in the V-MCE layer decreased with increasing distance from the heterointerface. In a thin V-MCE layer, tensile stress was produced by the difference in thermal contraction between GaAs and Si. The stress at the center of the top surface of the V-MCE layer rapidly decreased with increasing thickness of the layer (H). Also, the sign of the stress changed from tensile to compressive when H exceeded a critical value. As H increased further, the stress decreased, thus forming a peak in the compressive stress. The stress generally decreased whit increasing thickness of the V-MCE layer, but the stress canceled when the V-MCE layer reached a critical thickness in which the tensile stress was equal and opposite to the compressive stress from the bowing of the substrate. The simulation also gives the stress distribution in the V-MCE layer, which is very useful for optimizing V-MCE for device fabrication.
Fabrication of Multimode Polymeric Waveguides by Hot Embossing Lithography
Authors: Yoon Keun Byoung , Choi Choon-Gi , Han Sang-Pil
Published: February 2005

The fabrication of polymeric waveguides and the loss of waveguides were investigated for optical interconnection. Multimode polymeric waveguides were fabricated by hot embossing process. The replication of waveguide channels with hot embossing technology is of interest for single step processes that have to deliver a surface roughness far below the wavelength. Resulting waveguides exhibited a smooth surface profile and the square cross section of the core. The average propagation loss of these waveguides was approximately 0.2 dB/cm at 850 nm wavelength.
Microwave Dielectric Properties of A2P2O7 (A = Ca, Sr, Ba; Mg, Zn, Mn)
Authors: Bian Jian-jiang , Kim Dong-Wan , Hong Kug Sun
Published: February 2005

Microwave dielectric properties of A2P2O7 (A = Ca, Sr, Ba, Mn, Mg, Ba) ceramic materials were investigated by a network analyzer at the frequency of 10 GHz. It was found that A2P2O7 ceramics could be sintered at relatively lower temperature below 1150°C, although the thortveitite type series, Mn2P2O7, α-Mg2P2O7 and α-Zn2P2O7 with smaller ionic radii of A cations were hard to sinter to full density. The dielectric constant of A2P2O7 is lower than 10. The Q×f value increased according to the sequence of δ-Ba2P2O7, α-Sr2P2O7 and β-Ca2P2O7 in dichromatic type series, and the sequence of Mn2P2O7, α-Mg2P2O7 and α-Zn2P2O7 in thortveitite type series, respectively. The temperature coefficient of resonant frequency τf for all samples exhibits negative value. Larger τf for α-Zn2P2O7, α-Mg2P2O7 and δ-Ba2P2O7 is mainly due to their reversible phase transformations. The microwave dielectric properties were discussed from the point view of bond valence.
In Situ Monitoring of Silicon Membrane Thickness during Wet Etching using a Surface Acoustic Wave Sensor
Authors: Lee Chi-Yuan , Cheng Ying-Chou , Chen Yung-Yu , Chang Pei-Zen , Wu Tsung-Tsong , Chen Ping-Hei , Chen Wen-Jong , Pao Shih-Yung
Published: February 2005

In this paper, we propose a novel method using the surface acoustic wave (SAW) sensor for monitoring in situ the thickness of a silicon membrane during wet etching. Similar to pressure sensors and accelerometers, some micro-electro-mechanical systems (MEMS) devices require the thickness of silicon membranes to be precisely known. Precisely controlling the thickness of a silicon membrane during wet etching is important, because it strongly influences post-processing and device performance. Furthermore, the proposed surface acoustic wave sensor enables the thickness of a silicon membrane, from 50 µm to 80 µm, to be monitored in situ. In summary, the proposed method for measuring the thickness of a silicon membrane in real time from 50 µm to 80 µm, is highly accurate, is simple to implement and can be used for mass production. The principles of the method, detailed process flows, the set up for measuring thickness and simulation and experimental results are all discussed. The theoretical and measured values differ by an error of less than 2 µm; thus the experimental and theoretical values correlate well with each other.
A Simple Model for Solidification of Undercooled Metallic Samples
Authors: Saleh Abdala M. , Clemente Roberto A.
Published: February 2005

A simple model for reproducing temperature recalescence behaviour in spherical undercooled liquid metallic samples, undergoing crystallization transformations, is presented. The model is applied to constant heat extraction rate, uniform but time dependent temperature distribution inside the sample (even after the start of crystallization), a classical temperature dependent rate of nucleation (including contributions from different specific heats for different phases and also a catalytic factor to model the possibility of heterogeneous distributed impurities) and the solidified grain interface velocity is taken proportional to the temperature undercooling. Different assumptions are considered for the sample transformed fraction as function of the extended volume of nuclei, like the classical Kolmogoroff, Johnson–Mehl, Avrami one (corresponding to random distribution of nuclei), the Austin–Rickett one (corresponding to some kind of clusterized distribution) and also an empirical one corresponding to some ordering in the distribution of nuclei. As an example of application, a published experimental temperature curve for a zirconium sample in the electromagnetic containerless facility TEMPUS, during the 2nd International Microgravity Laboratory Mission in 1994, is modeled. Some thermo-physical parameters of interest for Zr are discussed.
Most Efficient Alternative Manner of Patterning sub-80 nm Contact Holes and Trenches with 193 nm Lithography
Authors: Hah Jung Hwan , Yoon Jin-Young , Hata Mitsuhiro , Kim Sang Wook , Kim Hyun-Woo , Woo Sang-Gyoun , Cho Han-Ku , Han Woo-Sung , Moon Joo-Tae , Ryu Byoung-Il
Published: February 2005

The patterning of sub-80 nm contact holes and trenches by ArF lithography is very challenging. To solve this problem, several technologies have been proposed, including thermal flow, resolution enhancement of lithography assisted by chemical shrink (RELACS), and shrink assist film for enhanced resolution (SAFIER). In this paper, we compare these processes in order to determine the advantages and disadvantages, and to gain an understanding on their mechanism on the basis of the performances of each process. Thermal flow shows a strong advantage in terms of simplicity, but it shows several disadvantages in terms of layout dependence, mask error enhancement factor (MEEF), and process window. RELACS is proven to be the most reliable, since there is a small shrink amount dependence on layout and temperature, but the limitation of shrink amount is an obstacle. Finally, SAFIER shows strong advantages in low MEEF, wide process window, and enhanced uniformity, with a weakness of the deformation in asymmetric pattern. It is considered that such performances are strongly related to the mechanism of each process, and therefore, the process should be used according to its own performances and mechanism. On the basis of the properties and relationship with the mechanism, the appropriate applications are recommended for each process.
Fabrication of 65-nm Holes for 157-nm Lithography
Authors: Kawaguchi Etsuro , Watanabe Kunio , Kurose Eiji , Furukawa Takamitsu , Itani Toshiro
Published: February 2005

We investigated the use of hole shrink processes along with a bilayer process as a fine-hole-pattern replication technique for 157-nm lithography. A siloxane-type resist and an organic underlayer were used in the bilayer process. The lithographic resolution limit was 90 nm in diameter with a 0.85-numerical-aperture 157-nm microstepper using an attenuated phase-shift mask. Using the bilayer process, we successfully transferred 85-nm-diameter hole patterns in the resist into a 400-nm-thick tetraethylorthosilicate (TEOS) layer. A thermal flow process and the Resolution Enhancement Lithography Assisted by Chemical Shrink (RELACS) process were used as the hole shrink processes to enhance the resolution. The 120-nm-diameter hole patterns in the resist were shrunk to 80 nm by the thermal flow process and to 65 nm by the RELACS process. In the RELACS process, the diameters of the shrunk hole were less dependent on the hole pitch than in the thermal flow process.
Quantitative Evaluation of Grid Size Effect on Critical Dimension Uniformity Improvement
Authors: Lee Doo-Youl , Lee Sung-Woo , Yeo Gi-Sung , Lee Jung-Hyeon , Cho Han-Ku , Han Woo-Sung
Published: February 2005

In order to control the on-chip linewidth variation (OCV) in logic devices, accurate optical proximity correction (OPC) is required, and the method to enhance its result is devised. The optical proximity behaviors are severely varied according to the optical and material conditions. The change in photoresist (PR) species deteriorates the OPC rule from 9.3 nm to 15.1 nm for two kinds of PR species. The illumination condition variation also deteriorates the optical-proximity-corrected (OPCed) results from 9.3 nm to 11.6 nm. To obtain accurate OPCed results, these conditions should be fixed. For improving the correction accuracy of the optical proximity, the OPCed grid size effect on the critical dimension (CD) uniformity is evaluated quantitatively. By adopting the OPC grid size of less than 1 nm, the correction resolution limited by the grid size is enhanced. The selective bias with the assist features is applied to the line-and-space (L/S) patterns varied by the space sizes. The selective bias rule is generated with a model using the different grid sizes of 1 nm and 0.5 nm. In the nominal CD of 87 nm, the 3σ values of the optical proximity effect are measured to be 14.6 nm and 11.4 nm for 1 nm and 0.5 nm grid sizes, respectively. The improvement of 9.2 nm is achieved, corresponding to nearly 39% enhancement. The CD uniformity dependence on the grid size was characterized in two-dimensional pattern on a real static random access memory (SRAM) pattern with the different grid sizes of 1 nm and 0.5 nm. The 3σ values of the uniformity are 9.9 nm and 8.7 nm in the case of grid sizes of 1 nm and 0.5 nm, respectively. Decreasing the grid size improves the uniformity by 4.7 nm, corresponding to 22% enhancement. By considering the mask error enhancement factor (MEEF), the enhanced amount is calculated to be 3.2 nm. The pattern fidelity improvement in the mask by reducing the grid size enhances the printing images, and decreases the measurement error using the in-line CD scanning electron microscope (SEM).