bluuebunny/crossref_metadata_2025 huggingface dataset:
Variation of Bending-Vibrator Characteristics when an Object is Brought into Close Proximity with the Vibrator End
Authors: Yamada Ken , Yamazaki Daisuke , Nakamura Kiyoshi
Published: February 2005

Evanescent acoustic fields which decay exponentially from the plate surface can be created in the vicinity of a piezoelectric bending vibrator. When an object is brought into this evanescent field, the electric admittance of the vibrator undergoes some change depending on the vibrator-to-object distance d. The authors' group has found so far that as an object comes into close proximity with the plate end, an unexpected phenomenon occurs such that the Q-factor which once decreased starts to increase in the range where d becomes small. In this study, this unique phenomenon is examined in detail by experiments and some new findings are shown on the variation of bending-vibrator characteristics. Also, theoretical explanations are given to conjecture the mechanism of this phenomenon by using a simple model.
Characterization of (112̄0) Textured ZnO Films Fabricated by RF Magnetron Sputtering
Authors: Yanagitani Takahiko , Tomohiro Shin-ichi , Nohara Takuya , Matsukawa Mami , Watanabe Yoshiaki , Otani Takahiko
Published: February 2005

Using a conventional RF magnetron sputtering system, we have obtained two types of ZnO films on various kinds of substrate. One is a film with the c-axes of crystallites unidirectionally aligned in the substrate plane {(112̄0) textured film}. The other is a film with c-axes parallel and perpendicular to the plane (mixed texture film). The former is expected to realize a shear wave transducer on the surfaces of various materials. The alignment of c-axes of crystallites in the plane was then carefully investigated by the X-ray pole figure analysis. The elastic anisotropy in the film has been successfully measured by the Brillouin scattering method. The (112̄0) textured film did not excite the elastic waves; however, comparatively strong shear waves were actually excited by the mixed texture film.
Effect of Tilted Edges on Coupled Vibrations of Doubly Rotated Quartz Plates
Authors: Sekimoto Hitoshi , Tamura Takashi , Goka Sigeyoshi , Watanabe Yasuaki
Published: February 2005

We numerically analyze the two-dimensional (2-D) coupled vibrations of a doubly rotated quartz plate with tilted edges. An efficient technique that uses a combination of 1-D and 2-D finite element methods is developed to solve coupled vibrations in the Y'-Z' cross section of a parallelogram shape. When the orientation of a quartz plate is described using the IEEE notation, as (YXwlt)φ/θ/ψ, the third rotation ψ about the plate normal is selected such that the Z'-width faces are parallel to the particle motion of a slow-shear wave propagating in the Y'-thickness direction. For SC-cut plates operating in the fundamental slow thickness-shear mode, we evaluate the effect of tilted edges on the frequency spectra and the first frequency-temperature coefficients, and verify the strong decoupling effect on the thickness-shear and face-shear modes. The optimal inclination angle of tilted edges for SC and FC cuts is appropriately defined as the equiphase plane of the main displacement of the face-shear traveling wave.
Surface Acoustic Wave Unidirectional Transducers Using Grating Substrates and Resonators Using λ-Period Reflectors
Authors: Yamanouchi Kazuhiko , Satoh Yusuke
Published: February 2005

Surface acoustic wave (SAW) filters employing a unidirectional interdigital transducer (UIDT) show low loss, wide band properties. In this paper we describe a new single phase unidirectional transducer (UDT) of about λ/4 electrode width with the best transducer efficiency. The new UDTs are fabricated on the very thin dielectric grating or very shallow groove grating SAW substrates. The electromechanical couplings (k
2) of electrodes on SiO2 gratings decrease rapidly for film thickness. Therefore the good properties of UDT are obtained for very thin SiO2 (about 0.3 µm and 0.03 µm at 100 MHz and 1 GHz, respectively). The calculation results show wide-band, low-loss filters with various k
2 materials. Also, the electrodes of λ/2 width have large reflection coefficients of SAW. The calculation and experimental results of SAW resonators with λ/2 electrode width and λ-period using susceptance changes are described.
Low Loss Intermediate-Frequency Resonator Filter Using Shear Horizontal Type Leaky Surface Acoustic Wave on α-Phase Heavy Metal Film/Quartz
Authors: Kadota Michio , Takata Eiichi , Nakagawa Masatoshi , Tose Makoto , Yamamoto Yasuji
Published: February 2005

By applying a new shear horizontal (SH)-type leaky surface acoustic wave (LSAW) excited by interdigital transducers (IDTs) and reflectors made of Ta or W on an ST-cut 90°X-propagation (direction perpendicular to X-axis) quartz substrate, we succeeded in fabricating very small resonator filters (1/5–1/4 of conventional device sizes). However, the Ta and W films used in our filters were β-Ta and β-W, which have resistances higher than that of an Al film. α-Ta and α-W films with very low resistivities have been successfully deposited in place of β-Ta and β-W films. The insertion loss of resonator filters consisting Ta- or W-electrode/ST-90°X quartz has been improved by 1.5–8 dB using the α-Ta or the α-W film electrode.
Transmission Characteristics of a Triple Tuned Coupled Band-pass Filter and Their Dependences on Terminating Resistances
Authors: Hirama Koichi , Nakagawa Yasuhiko
Published: February 2005

In this paper, we present the relationship between the transmission function and the terminating resistances of a triple tuned coupled band-pass filter. It is possible to estimate the change of the transmission function by changing only the terminating resistances continuously while keeping the other equivalent circuit parameters fixed. The following results were obtained. When terminating resistances are changed continuously over a wide range, the well-known equal ripple, maximally flat and flat delay characteristics appear dispersedly. There is a combination of parameters which shows the group delay resembling a Gaussian distribution. The group delay at the center frequency becomes minimum when the filter function exhibits the maximally flat in attenuation. It is convenient that the terminating resistances can be changed continuously as an independent variable, because it enables some evaluation criteria to be satisfied.
Ultra-Wideband Surface Acoustic Wave Devices Using Cu-Grating/Rotated-YX-LiNbO3-Substrate Structure
Authors: Hashimoto Ken-ya , Asano Hiroki , Omori Tatsuya , Yamaguchi Masatsune
Published: February 2005

This paper discusses the application of Love mode propagating on Cu-grating/rotated YX-LiNbO3-substrate structure to the development of ultra-wideband and low-loss RF surface acoustic wave (SAW) filters. Theoretical analysis suggested that high performance resonators with very small capacitance ratio would be realised using Cu gratings with a thickness of several percent of wavelength. It was also suggested that in particular, on 15°YX-LiNbO3-substrate structure, the spurious response due to Rayleigh mode could effectively be suppressed. An IDT-type one-port SAW resonator and a ladder-type SAW filter were fabricated on the Cu-grating/15°YX-LiNbO3-substrate structure, and their high performances are demonstrated with discussion.
Digital Subtraction Method in FM-Chirp Pulse Compression Method for Intraductal Ultrasonography
Authors: Tonegawa Yuya , Moriya Tadashi , Tagawa Norio
Published: February 2005

In pulse compression methods used with ultrasonography, when a small signal is reflected by a small target positioned near a large target, the small-target reflected signal can be obscured by the sidelobes of the large-target reflected signal. We apply a digital subtraction method using zero-padding to detect the small signal.
Evaluation of Closed Cracks by Model Analysis of Subharmonic Ultrasound
Authors: Yamanaka Kazushi , Mihara Tsuyoshi , Tsuji Toshihiro
Published: February 2005

Cracks in solids can be detected by ultrasound if they are open. However, their detection is not easy when they are closed with a closure stress, and thus it is a fundamental problem in ultrasonic testing. Subharmonics with half the input frequency is potentially useful in the detection and evaluation of such cracks, although quantitative analysis has not been established. In this work, we develop analytical and numerical theories accounting for the crack parameters, such as closure stress and crack surface conditions, for the first time. We proved their validity by comparison with experiments on a well-defined fatigue crack in aluminum alloy, finding reasonable agreements. Based on these theories, it will be possible to estimate important parameters of partially closed cracks by fitting measured waveforms to theoretical predictions, which solves the fundamental problem in ultrasonic testing of cracks.
Network-Controlled Measurement of Mean Spatial Temperature Using a Sound Probe with a Long Baseline
Authors: Mizutani Koichi , Itoga Kazuya , Kudo Kousuke , Okushima Limi , Wakatsuki Naoto
Published: February 2005

An acoustical method for temperature measurement of large-scale spaces in a wind field is described. The real-time thermometry in a long span of 100 m was realized by the adoption of a bidirectional sound probe as a temperature sensor and a wireless local area network for controlling sensors. The probe mainly consists of two loudspeakers and two microphones. An accurate mean spatial temperature was measured without the interference of the wind in the area by the bidirectional probe. We carried out numerical simulations to confirm the validity of our method. The mean temperature was satisfactorily measured by this principle under various distributions of wind velocity. In field measurements, mean spatial temperature along a 100-m-long baseline was measured by the system with a conventional thermometer as a reference. The temperature change over one hour at 30 s intervals was compared to the change in the reference temperature at the center of the baseline. The results indicated that the system recorded a long periodic change in air temperature without the effects of local turbulence and wind. The advantages of the proposed system compared to a conventional thermometer are real-time, wireless and noncontact measurements.
Temperature Measurement Using Acoustic Reflectors
Authors: Kudo Kousuke , Mizutani Koichi
Published: February 2005

In this paper, we describe temperature measurement using acoustic reflectors. The reflectors increased the number of sound paths to five. The temperature distribution was measured with one loud speaker (SP) and one microphone (MIC) utilizing a radial transmission of the SP and specular reflections of sounds. The propagation paths of the sounds could be used as the sound probes and their directions could be changed using the acoustic reflectors with plane surfaces. By adjusting the angles of the acoustic reflectors as the propagation paths reached one of the MICs, the temperature distribution of an arbitrary and partial space in the measurement object could be measured. The temperature distribution of a horizontal space partitioned into five unit cells was measured with one SP, one MIC and ten acoustic reflectors. The -6 dB beam width of the SP was approximately 80 deg, thus the received signals maintained sufficient amplitudes. Experimental results showed a good agreement with the temperature distribution results measured with thermocouples.
Micrometeorology Measurement by Acoustic Method
Authors: Mizutani Koichi , Taruishi Keigo , Hachisuka Yutaka , Kudo Kousuke , Ishii Masahisa
Published: February 2005

In this paper, we describe a visualization method of wind velocity and direction distributions for micrometeorology measurement. The wind velocity and direction were measured in a noncontact mode within a measurement area using acoustic probes, on the basis of differences of the time of flight of sound. To reconstruct a two-dimensional distribution, eight acoustic transducers were installed at equal intervals along the circumference of a turntable. The reliability of the system was tested in a wind tunnel. The test was performed for two patterns: increasing wind velocity under a constant wind direction, and rotating wind direction under a constant wind velocity. For the two experimental patterns, two-dimensional distributions of the wind velocity and direction could be reconstructed. Compared with a reference measured with an ultrasonic anemometer, our results showed good agreement.
Scanning Acoustic Microscope/Photoacoustic Microscope Operating on a Unified Software Environment
Authors: Miyamoto Katsuhiko , Suzuki Manabu , Sannomiya Toshio , Hoshimiya Tsutomu , Chubachi Noriyoshi
Published: February 2005

A scanning acoustic microscope (SAM) and a photoacoustic microscope (PAM) operating on a unified software environment was designed and fabricated. Welded steel plates, in which the welding condition was changed by varying the amount of current and its duration, were used as specimens. SAM and PAM measurements for this specimen were carried out, and the obtained images were compared. This system has the advantage of complementary measurement using both SAM and PAM.
Advantage of Multichannel Decision Feedback Equalizer on Underwater Acoustic Communication
Authors: Watanabe Yoshitaka , Ochi Hiroshi
Published: February 2005

Underwater acoustic digital communication was investigated by simulation under conditions of various distortions which seem to degrade communication performance, such as multipath or Doppler shift. M-sequence data was used as transmission data. The signal band was 20 kHz±4 kHz, and the modulation method was 16-quadrature amplitude modulation (16-QAM). The received data was demodulated using a multichannel decision feedback equalizer (DFE). In this paper, the effect of feedforward tap allocation on communication performance under an intensive multipath condition is considered. It became clear that the communication performance is advanced by utilizing multipaths, that this advantage is distinguished when the signal-to-noise ratio (SNR) of the input signal is small, that it is necessary to consider the trade-off between this advantage and the instability caused by a large number of taps, and that this advantage is available if ever there is Doppler shift or few multipaths.
Experiments on Acoustic Communication with Quadrature Amplitude Modulation in Multipath Environment
Authors: Ochi Hiroshi , Watanabe Yoshitaka , Shimura Takuya
Published: February 2005

An experiment on high-speed underwater acoustic data communication was carried out at real sea as a time-variant multipath channel. Demodulation was processed by a multichannel decision feedback equalizer (DFE) demodulator with adaptive filtering. The modulation method used was 16-quadrature amplitude modulation (16-QAM), transmitting rate was 32 k bit per second (bps), carrier frequency was 20 kHz, and bandwidth was 8 kHz (16–24 kHz). Good demodulation results were obtained at a sea trial despite the presence of high-level multipaths. At real sea, we proved that high-speed (32 kbps) acoustic communication can be realized even in a multipath fading channel with 16-QAM. Therefore, it is expected that the flexibility of the design of underwater equipment will be improved, because the influence of a circumferential structure can be neglected.
Cross-Sectional Elasticity Imaging of Carotid Arterial Wall in Short-Axis Plane by Transcutaneous Ultrasound
Authors: Nakagawa Nozomi , Hasegawa Hideyuki , Kanai Hiroshi
Published: February 2005

We have developed the phased tracking method [H. Kanai, M. Sato, Y. Koiwa and N. Chubachi: IEEE Trans. UFFC 43 (1996) 791.] for measuring the minute change in thickness during one heartbeat and the elasticity of the arterial wall with transcutaneous ultrasound. When this method is applied to a plane perpendicular to the axis of the artery (short-axis plane) using a linear-type probe, only an ultrasonic beam which passes through the center of the artery coincides with the direction of the change in thickness. At other beam positions, the wall motion cannot be accurately tracked because the direction of wall expansion slips off the beam. To obtain the cross-sectional image of elasticity in the short-axis plane using transcutaneous ultrasound, in this paper, the directions of ultrasonic beams are designed so that each beam always passes through the center of the artery; thus, they always coincide with the direction of the wall expansion. In basic experiments, the accuracy in elasticity measurement was evaluated using a silicone rubber tube. In in vivo experiments, the minute change in wall thickness was measured along each ultrasonic beam, and the cross-sectional image of elasticity was obtained in the short-axis plane with transcutaneous ultrasound.
Modified Ultrasound Source for Long Focused Second Harmonic Beam
Authors: Saito Shigemi , Kawagishi Tetsuya
Published: February 2005

With the aim of avoiding the concentration of second harmonic generation at the focus, a modified focusing source designed to minimize the fundamental amplitude at the focus is examined. The present source consists of two coaxially arranged confocal transducers: An inner disk transducer and an outer ring transducer whose areas are the same. They have been polarized in the thickness direction opposite to each other, and are connected in parallel. The theoretical and experimental results show that the second harmonic amplitude attains a maximum at three locations including two positions where the fundamental amplitude takes peak values. A relatively sharp second harmonic beam is demonstrated. Provided the radius of curvature is relatively small, since the three maximum positions are close to each other, the second harmonic beam effectively focuses long. Suppression of side lobes by weighting the source excitation is also discussed.
Unconstrained Evaluation System for Heart Rate Using Ultrasonic Vibrograph
Authors: Nagamune Kouki , Kobashi Syoji , Kondo Katsuya , Hata Yutaka , Taniguchi Kazuhiko , Sawayama Toshiyuki
Published: February 2005

Unconstrained health monitoring systems have received much considerable attention in medical applications, because such system can examine a subject without constraint. In this study, we propose a detection method based on a fuzzy logic for evaluating heart rate using our ultrasonic vibrograph. In the experiment for confirming heart rate, our method has been successfully used to detect the heart rates of four subjects, compared with a method using an electrocardiograph.
Myocardial Strain Imaging Based on Two-Dimensional Displacement Vector Measurement
Authors: Nitta Naotaka , Shiina Tsuyoshi
Published: February 2005

The abnormalities of myocardial wall motion caused by changes in wall stiffness often appear in the early stage of ischemic heart disease. Since the myocardium exhibits complex and large motion, a two-dimensional (2D) or three-dimensional (3D) assessment of stiffness distribution is required for accurate diagnosis. Although a 3D assessment is ultimately required, as a stepped approach for practical use, we propose novel methods for tracking the 2D motion using a one-dimensional (1D) phased array and for assessing myocardial malfunction by visualizing the invariant of a strain tensor. The feasibilities of the proposed methods were evaluated by numerically simulating the short-axis imaging of a 3D myocardial model. This model includes a hard infarction located between 1 and 3 o'clock, which is difficult to detect by conventional tissue Doppler and strain rate imaging, and the motions of the model were assigned by referring to actual myocardial motion. These results revealed that the proposed imaging methods clearly depicted the hard infarction area which conventional imaging could not detect.
Staebler-Wronski Effect in Hydrogenated Amorphous Silicon and Related Alloy Films
Authors: Shimizu Tatsuo
Published: February 2005

Hydrogenated amorphous silicon and related alloy films have attracted much attention because of the wide application of these films in devices such as thin-film transistors and solar cells. However, the degradation of these films caused by intense illumination is a serious shortcoming. In this review, various experimental results concerning this problem and various models for the photocreation of dangling bonds which is thought to be the main origin of the degradation are introduced and discussed. Degradation in the device performance, some efforts to overcome the degradation and some metastable defects other than photocreated ones are also briefly introduced.
Feed-Horn Antenna for Enhanced Uncooled Infrared Sensor Using Novel UV Lithography, Plastic Micromachining and Mesh Structure Bonding
Authors: Park Jong-Yeon , Kim Kun-Tae , Shin Hyun-Joon , Moon Sung , Pak James Jungho
Published: February 2005

In this paper, we report a uncooled infrared sensor coupled with a 3-dimensional (3D) feed-horn shape micro-electro-mechanical system (MEMS) antenna using novel UV lithography technique for fabricating a 3D feed-horn-shaped mold array, obtaining parallel light using a mirror-reflected parallel-beam illuminator (MRPBI) system and plastic micromaching. The microassembly of infrared detector and 3D feed-horn-shaped antenna arrays is difficult using the conventional MEMS bonding process. To overcome limitation, the proposed novel 3D MEMS bonding technique is mesh structure bonding (MSB) using microchannels with micromolding in capillaries by polydimethylsiloxane (PDMS). The feasibility of fabricating both a 3D feed-horn MEMS antenna and a mold array was demonstrated. As a result, it seems possible to use a 3D feed-horn-shaped MEMS antenna to improve uncooled infrared sensor performance and applications to fabricate MEMS device.
Effect of Phase Formation Behavior on Thermal Stability of Hafnium-Based Thin Films for Copper Interconnects
Authors: Lin Ming-Hong , Chiou Shi-Yung
Published: February 2005

Hafnium (Hf) and hafnium nitride (Hf–N) flims were deposited on silicon wafers using a magnetron sputtering system. The as-deposited Hf film has a hexagonal close packed structure and a low resistivity of 101 µΩcm. The phases form in the order of α-Hf → HfN0.4 → ε-Hf3N2 → fcc-HfN with increasing nitrogen concentration in the Hf–N film. The thermal stabilities of Cu/Hf–N/Si contact systems are evaluated by thermal stressing at various annealing temperatures. In Cu/Hf/Si, a reaction between the Hf barrier layer and the Cu layer is observed, and copper–hafnium compounds form after annealing at 550°C. Moreover, highly resistive copper silicide is found after 600°C annealing. No copper–hafnium or copper silicide compounds are found in the Cu/HfN0.47/Si contact system even after annealing at 650°C. Incorporating nitrogen into the hafnium diffusion barrier can suppress the formation of copper–hafnium compounds and copper penetration, thus improving the barrier's thermal stability.
Metal–Semiconductor–Metal AlN Mid-Ultraviolet Photodetectors Grown by Magnetron Reactive Sputtering Deposition
Authors: Chen Lung-Chien , Fu Ming-Song , Huang In-Lin
Published: February 2005

Metal–semiconductor–metal (MSM) AlN mid-ultraviolet (mid-UV) photodetectors were fabricated. AlN layers were grown on GaN substrates by magnetron reactive sputtering deposition. The AlN photodetectors exhibited a high responsivity at wavelengths from 210 nm to 190 nm, and the response tails off at a wavelength of 220 nm. The responsivities at 200 nm at biases of 5 V and 10 V were 1.08 and 3.51 A/W, respectively. When the reverse voltage was higher than 7 V, responsivity increased almost linearly with reverse voltage. The responsivity at 25 V was calculated to be approximately 14.9 A/W.
High Spin Polarization of Conduction Band Electrons in GaAs-GaAsP Strained Layer Superlattice Fabricated as a Spin-Polarized Electron Source
Authors: Matsuyama Tetsuya , Takikita Hisaya , Horinaka Hiromichi , Wada Kenji , Nakanishi Tsutomu , Okumi Shoji , Nishitani Tomohiro , Saka Takashi , Kato Toshihiro
Published: February 2005

We measured a spin-dependent luminescence from a GaAs–GaAsP strained layer superlattice and GaAs substrate to evaluate the spin polarization of conduction band electrons excited by circularly polarized light. The GaAs–GaAsP strained layer superlattice with a mixture of group-V elements, As and P, was considered as a suitable spin-polarized electron source because the discrepancy of the valence band was reported to be larger than that of the conduction band. The observed maximum circular polarizations of the luminescence from the GaAs–GaAsP strained layer superlattice and GaAs substrate were 68% and 15%, respectively. The dependence of the circular polarization of the luminescence on the excitation photon energy was well explained by the calculated band structure. The initial spin polarizations of conduction band electrons excited in the GaAs–GaAsP strained layer superlattice and GaAs substrate were estimated to be 95% and 46%, respectively, from the luminescence polarization, lifetime and spin relaxation time. The high initial spin polarization of conduction band electrons proved the high performance of a photocathode with the GaAs–GaAsP strained layer superlattice as the spin-polarized electron source.
Growth of High-Quality Single-Phase Bi2Sr2CaCu2Ox Whiskers by a New Growth–Melt–Regrowth Method
Authors: Sugimata Etsuro , Fujino Hidetoshi , Kume Eiji , Sakai Shigeki
Published: February 2005

High-quality and large single-phase Bi2212 whiskers are grown by a new growth–melt–regrowth method. The average composition of the Bi2212 whiskers and the maximum size of single-crystal domains are Bi2.15Sr2.08Ca0.90Cu2.00O
x
and 0.5 µm × 88 µm × 2 mm, respectively. The results of X-ray diffraction analysis and I–V characteristic measurement indicate that the crystallinity of the obtained Bi2212 whiskers is excellent.
Far-Field Spectral Intensity Characteristics of a Time-Dependent Gaussian Pulse from Two Types of Apodized Slits
Authors: Han Pin
Published: February 2005

The diffraction spectral intensity characteristics of a time-dependent Gaussian pulse from triangular and elliptic apodized slits in the far field are studied both theoretically and numerically. The apodization for the spectrum of the Gaussian pulse for both types can be observed as well as the red or blue shift of the spectral intensity maximum of the incident pulse. Also, the formulae used to determine the temporal intensity and energy distribution of the diffracted pulse on the observation plane are provided in this work.
GaInAsP/InP Partially Strain-Compensated Multiple-Quantum-Wire Lasers Fabricated by Dry Etching and Regrowth Processes
Authors: Yagi Hideki , Sano Takuya , Ohira Kazuya , Plumwongrot Dhanorm , Maruyama Takeo , Haque Anisul , Tamura Shigeo , Arai Shigehisa
Published: February 2005

This paper reports the structural properties and lasing characteristics of GaInAsP/InP multiple-quantum-wire lasers fabricated by electron beam lithography, CH4/H2-reactive ion etching and organometallic vapor-phase-epitaxial regrowth. Good size distributions of multiple-quantum-wire structures (wire widths of 18 nm and 27 nm in a period of 80 nm) have been obtained with standard deviations less than ±2 nm. We have confirmed that low-damage etched/regrown interfaces of quantum-wire structures can be realized by using a partially strain-compensated quantum-well structure. Threshold current densities of 5-quantum-well wirelike lasers (wire widths of 43 nm and 70 nm) were found to be lower than that of the quantum-film laser, fabricated from the same initial wafer, due to a volume effect at temperatures up to 85°C. Finally, room temperature (RT)-continuous wave (CW) operation of multiple-quantum-wire lasers (wire width of 23 nm in a period of 80 nm, 5-stacked quantum-wires) was achieved, and the good reliability of this quantum-wire laser was demonstrated for the first time by means of lifetime measurement under the RT-CW condition.
Total Refraction of P-Polarized Light at the Boundary of 90°-Domains in the Ferroelectric Crystal
Authors: Shichijyo Shiro , Hirohashi Junji , Kamio Hiroyuki , Yamada Kazuhiro
Published: February 2005

A 90°-domain structure was fabricated using electrical poling in ferroelectric birefringent KNbO3 crystal. The refraction and reflection characteristics of the light at the boundary of the 90°-domain structure were investigated, and the novel behavior of total refraction (no reflection) has been found for the P-polarized light throughout the entire range of incident angle (0≤θ≤90°). Strong refraction of the light was observed after it exited from the crystal output surface at the incidence parallel to the domain boundary. These behaviors were explained analytically.
1.3 µm Traveling-Wave GaInNAs Semiconductor Optical Amplifier
Authors: Hashimoto Jun-ichi , Koyama Kenji , Katsuyama Tsukuru , Iguchi Yasuhiro , Yamada Takashi , Takagishi Shigenori , Ito Masashi , Ishida Akira
Published: February 2005

We fabricated a GaInNAs semiconductor optical amplifier (SOA) by applying a facet coating to a buried-ridge-stripe GaInNAs laser. Due to a low reflectivity (<0.1%) and a wide bandwidth (70 nm) coating, Fabry–Perot (FP) modes of the GaInNAs laser were suppressed sufficiently, and thus a 1.3 µm traveling-wave GaInNAs SOA was realized for the first time. Peak chip gains of more than 9.6 dB and a 3-dB-gain bandwidth above 49 nm (9 THz) were obtained simultaneously with a cavity length between 600 µm and 900 µm. In addition, on/off ratios between 20 and 30 dB were obtained by switching the current on and off, which seems sufficient for the SOA to work as a switching device. With the temperature characteristics, we found that the ASE intensity and the gain coefficient of the GaInNAs SOA were much less dependent on temperature than those of conventional InP-based SOAs. These results demonstrate the superior temperature characteristics of the GaInNAs SOA compared with conventional InP-based SOAs.
Effect of Launching Angle of Light on Critical Micelle Concentration Determination Using an Optical Fiber Sensor Based on Adsorption Effect
Authors: Singh C. D. , Isobe Hirokazu , Fujinami Tatsuo , Ogita Masami
Published: February 2005

In this paper, an optical fiber sensor for the determination of critical micelle concentration (CMC) is described. The sensor is based on the adsorption effect. When the concentration of the surfactant solution reaches the CMC, the outputs from the fiber suddenly begin to increase due to the interaction between the evanescent wave and surfactant molecules. Using this phenomenon, the sensor is able to determine the CMC of the surfactant solution in real time. The effect of launching angle of the light and interaction length of the fiber in the sensing region on sensor sensitivity has been studied. It has been found that the selective rays launching close to the critical angle of the fiber and the long interaction length of the sensing region increase the sensor sensitivity.
Photochemical Modification of Silicone Films Using F2 Laser for Selective Chemical Etching
Authors: Okoshi Masayuki , Kimura Takeshi , Takao Hiromitsu , Inoue Narumi , Yamashita Tsugito
Published: February 2005

Silicone ([SiO(CH3)2]
n
) films were photochemically modified into SiO2 by irradiation with a 157 nm F2 laser. The dissociation of Si–CH3 bonds of silicone simply depended on the photon number of the F2 laser. The quantum yield of the modification was estimated to be approximately 1×10-2. Mechanisms of oxidation and O–H production in the modified films were clarified. The depth of the modification was not limited by the absorption coefficient of silicone because SiO2 of the modified films is transparent for the F2 laser. A fine pattern of the 1.5-µm-thick silicone films could be fabricated by immersing the modified samples in 0.2 wt% hydrogen fluoride solution.
Simulation of Ho:CaF2 Q-switched Tm:Y3Al5O12 Laser
Authors: Kuo Yen-Kuang , Chen Hsiu-Fen , Chang Yi-An
Published: February 2005

The optical performance of the Ho:CaF2 Q-switched Tm:YAG laser as a function of the initial population in the ground state of the Ho:CaF2 saturable absorber, pumping rate, and the reflectivity of the output coupler are studied numerically. The results obtained numerically are in good agreement with those obtained experimentally. For a typical laser configuration, a Q-switched laser pulse of 70 mJ in 45 ns is obtained.
Fast Wavelength Switching Based on a Fabry-Perot Laser Pair Using Optical Injection
Authors: Yeh Chien-Hung , Lee Chien-Chung , Chi Sien
Published: February 2005

We propose and experimentally demonstrate a new fast wavelength-selectable laser technique, which is based on Fabry–Perot (FP) lasers with external light wave injection. By using different bias currents of FP lasers, wavelength tuning can be realized. In the experiment, the tuning of three different wavelengths tuning, the side-mode suppression ratio of >20 dB, and the wavelength switching time of <2 ns were attained.
Defect-Free Bistable C1 Surface Stabilized Ferroelectric Liquid Crystal Display
Authors: Wang Chenhui , Wand Michael , Handschy Mark , Bos Philip J.
Published: February 2005

A defect-free, large memory angle, high contrast ratio and bistable surface stabilized ferroelectric liquid crystal (SSFLC) display, which has potential for electronic paper and liquid crystal on silicon (LCoS) applications, has been developed using an alignment layer of 5° obliquely evaporated SiO
x
. In this paper, optimized conditions for achieving a defect free device are presented.
Two Classes of Photonic Crystals with Simultaneous Band Gaps
Authors: Chern Ruey-Lin , Chang Chien-Chung , Chang Chien C. , Hwang Robert R.
Published: February 2005

In this study, we consider band structures of two classes of photonic crystals with two geometric parameters. The first class has a square lattice and is studied for dielectric contrast, centered at ε/ε
0=11.4 (GaAs-air). The second class has a hexagonal lattice and is studied for dielectric contrast, centered at ε/ε
0=13 (silicon-air). These examples have the following feature: the optimal (and largest) full band gap is obtained when both band gaps for E and H polarizations have the same (simultaneous) band edges. In addition, photonic crystals with two geometric parameters typically have much larger optimal band gaps than their counterparts with one geometric parameter.
Electrical Properties of and Conduction Mechanism in Ultrathin ZrO2 Films on Si1-yCy Heterolayers
Authors: Dalapati Goutam K. , Samanta Santanu K. , Chatterjee Somenath , Bose Probir K. , Varma Shikha , Patil Shivprasad , Maiti Chinmay K.
Published: February 2005

Ultrathin ZrO2 films with a dielectric constant of 20 have been deposited at 150°C on carbon-implanted solid phase epitaxy (SPE)-grown Si1-y
C
y
heterolayers by microwave plasma-enhanced chemical vapor deposition (PECVD) using zirconium tetra-tert-butoxide. The SPE-grown Si1-y
C
y
heterolayers and deposited ZrO2 films have been analyzed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) for chemical analysis. The fixed oxide charge density (Q
f/q) and interfacial trap density (D
it) of as-deposited ZrO2 films are found to be 2.6×1011 cm-2 and 5.6×1011 eV-1cm-2, respectively. The gate current of the ZrO2 layers is found to decrease after 400°C annealing in N2 for 30 min. The main conduction mechanism is dominated by Schottky emission in the ZrO2 films deposited on Si1-y
C
y
layers.
Optical and Thermal Properties of Si–O–C Films Grown by Organic Catalytic Chemical Vapor Deposition Using Organic Silicon
Authors: Yagi Tetsuya , Nakayama Hiroshi , Miura Yozo , Shimoyama Norio , Machida Eimei
Published: February 2005

Optical, thermal and mechanical properties of Si–O–C ternary alloy films grown by organic catalytic chemical vapor deposition (CVD) were studied in comparison with those of Si–O films grown by electron-beam evaporation and AlN grown by electron cyclotron resonance sputtering. Si–O–C with Si: 36 at.%, O: 46 at.%, and C: 18 at.%, grown using TEOS, shows a relatively high refractive index of around 1.9 and a small extinction coefficient of less than 0.01 at wavelengths between 500 nm and 1000 nm. The value of the extinction coefficient is roughly five times smaller than that of SiO films grown by electron-beam evaporation. The thermal conductivity of 0.64 W/m·K and the stress of the film are comparable with those of SiO. The results indicate that Si–O–C grown by organic catalytic CVD using TEOS is a promising material for optical applications such as laser diodes and semiconductor optical amplifiers.
Continuous Single-Step Fabrication of Nonaggregated, Size-Controlled and Cubic Nanocrystalline Y2O3:Eu3+ Phosphors Using Flame Spray Pyrolysis
Authors: Chang Hankwon , Lenggoro I. Wuled , Okuyama Kikuo , Kim Tae-Oh
Published: February 2005

Continuous single-step fabrication of cubic nanocrystalline Y2O3:Eu3+ phosphor particles using flame spray pyrolysis was successfully conducted without any post-heat treatments. The morphology of the as-prepared particles was spherical and nonaggregated. The mean size of as-prepared particles was easily controlled by adjusting the precursor concentration. On varying the overall concentration of the precursor solution from 0.01 to 0.5 M, the crystallite size and geometric mean particle diameter varied from 38.4 nm to 50.6 nm and 263 nm to 741 nm, respectively. XRD spectra of as-prepared particles indicated that all products, regardless of the precursor concentration, showed the cubic phase with high crystallinity without any post-treatments, although residence times in the flame were very short. Upon excitation with 254 nm light, all of the as-prepared particles showed bright red emission due to the 4f–4f transitions of Eu3+ ions, and the highest photoluminescent intensity at 611 nm was found at a Eu3+ content of about 12 mol%. These results indicate the possibility of the fabrication of cubic nanocrystalline Y2O3:Eu3+ phosphors with a high production rate and high purity.
Formation Mechanism for High-Surface-Area Anatase Titania Nanoparticles Prepared by Metalorganic Chemical Vapor Deposition
Authors: Sun Yijun , Egawa Takashi , Shao Chunlin , Zhang Liangying , Yao Xi
Published: February 2005

High-surface-area anatase titania nanoparticles are prepared by metalorganic chemical vapor deposition (MOCVD) using thermophoretic collection. Based on the dependence of X-ray linewidth (FWHM) on collection distance, a formation mechanism for the nanoparticles is proposed in which it is assumed that the relative changes in the grain size of and vacancy concentration in the nanoparticles are proportional to the velocity of the gas flow in the reactor. Three nondimensional equations that describe the dependence of the properties of the nanoparticles on collection distance are derived. This model explains well the effect of collection distance on X-ray linewidth, and it is not only in good agreement with XPS results but also consistent with TEM observations.
Internal Friction Originating from Random Magnetism
Authors: Tanji Toru , Moriwaki Shigenori , Mio Norikatsu , Tomaru Takayuki , Suzuki Toshikazu , Shintomi Takakazu
Published: February 2005

We investigated the relation between internal friction and magnetism due to a random arrangement of magnetic atoms by using the Mn–Cu–Ni–Fe alloy, called M2052. Its internal friction and dc susceptibility were measured as a function of the temperature from 4.2 K to room temperature. As for the internal friction, two peaks were observed at around 70 K and 270 K; the peak at the lower temperature was shifted by changing the measurement frequency. A comparison of the temperature dependency of the susceptibility and the internal friction indicated that freezing of the magnetic moments of ferromagetic clusters could cause low-temperature internal friction. We confirmed that relaxation related to the internal friction is consistent with magnetic relaxation in random magnetism.
Mechanical Properties of Extremely Thin B–C–N Protective Layer Deposited With Helium Addition
Authors: Miyake Shojiro , Wang Mei
Published: February 2005

With complex treatment, which includes plasma irradiation pretreatment and reactive sputtering treatment, a boron–carbon–nitrogen (B–C–N) film was deposited as an overcoat on a CoCrTa magnetic disk by RF sputtering using two semicircular targets. Nitrogen-containing carbon (C–N) and CN/BN layered films were deposited by controlling the time duration the substrate faced each of the graphite and hexagonal boron nitride (h-BN) targets. The effects of plasma irradiation produced from an argon and nitrogen (N2+Ar) mixed gas as well as a nitrogen and helium (N2+He) mixed gas on the mechanical properties of these films were evaluated in this work. Based on the results obtained in microwear and oscillation scratch tests, it is verified that the wear resistance of the B–C–N film formed in N2+He was improved and this film exhibited a high lubricant performance, with a low friction of µ=0.027, due to He addition.
Measurement of Linear Energy Transfer Distribution at CERN-EU High-Energy Reference Field Facility with Real-Time Radiation Monitoring Device III and Its Comparison with Dosimetric Telescope
Authors: Doke Tadayoshi , Fuse Tetsuhito , Hara Kenichiro , Hayashi Takayoshi , Kikuchi Jun , Suzuki Satoshi , Terasawa Kazuhiro
Published: February 2005

The distributions of linear energy transfer for LET (LETwater) in front of the 80-cm-thick concrete side shield at the CERN-EU high-energy reference field (CERF) facility were measured with a Si detector telescope named real-time radiation monitoring device-III (RRMD-III) covered with and without a 1 cm-thick acrylic plate. In these measurements, a difference of about 20% in the absorbed dose between the two LETwater distributions was observed as a result of protons, deuterons and tritons recoiled by neutrons. The LETwater distribution obtained using RRMD-III without the 1-cm-thick acrylic plate is compared with lineal energy distributions obtained using the dosimetric telescope (DOSTEL) detector under the same conditions. These dose equivalents are also compared with that obtained using HANDI TEPC which is used as the standard at the CERF facility.
Development of Proton Detection System with Thin Ruby Scintillator Insensitive to Neutrons and Gamma Rays for Neutron Lifetime Measurement
Authors: Hosono Yoneichi , Nihei Hitoshi , Nakazawa Masaharu
Published: February 2005

A proton detector for lifetime measurement of neutrons using a thin ruby scintillator which can be used under an environment of neutrons and γ-rays has been developed. The detector is almost insensitive to neutrons and γ-rays. This was confirmed by setting the detector adjacent to the ultra-cold neutron (UCN) facility installed in Kyoto University Reactor. When a single proton was injected into the scintillator, many scintillation signals were observed. The number of scintillation signals decreases with decreasing proton energy. Although the output signals generated by the scintillation and by the dark currents of a photomultiplier have approximately the same pulse heights, the proton can be detected by counting the signals within the time width corresponding to the decay time of scintillation. This neutron lifetime measurement system can be applied to the detection of particles other than protons.
Gravity Field Effect on Copper-Electroless Plating –Comparison with the Magnetic Field Effect
Authors: Oshikiri Yoshinobu , Sato Makoto , Yamada Akifumi , Aogaki Ryoichi
Published: February 2005

To compare the gravity field effect on copper-electroless plating with the magnetic field effect on the same reaction, the plating rates were measured under various vertical gravity fields. Consequently, considerably different results from those of the magnetic-field case, where the reaction was suppressed by the magnetic field, were obtained; the reaction was not suppressed but promoted by the gravity field. The total reaction rate increased with increasing gravitational acceleration, and followed the diffusion current equation in a vertical gravity field. The scanning electron microscope (SEM) observation also revealed the promotion by the gravity field, i.e., the increase of crystal sizes with increasing gravitational acceleration. This is because, in the magnetic field, the micro-magnetohydrodynamic (micro-MHD) flows interact with the nonequilibrium fluctuations accompanying the reaction. Therefore, it was concluded that the gravity convection cells occurring under gravity fields do not interact at least up to 170 G with the nonequilibrium fluctuations. At the same time, the density coefficients intrinsic to cathodic and anodic partial reactions were obtained by measuring current responses to sweeping gravitational acceleration, i.e., sweep gravitammetry. By comparing observed data with those calculated from the density coefficients, it was clarified that the autocatalytic process between the cathodic and anodic reactions is more accelerated by gravity convection than the intrinsic autocatalytic process without gravity convection.
Organic Thin Film Transistor-Driven Liquid Crystal Displays on Flexible Polymer Substrate
Authors: Kim Yong Hoon , Park Sung Kyu , Moon Dae Gyu , Kim Won Keun , Han Jeong In
Published: February 2005

In this report, organic thin film transistor (OTFT)-driven active-matrix liquid crystal display (AM-LCD) on flexible polymer substrate is demonstrated. A polymer material, poly (3-hexylthiophene) (P3HT) was used as the active layer and printed by a rubber stamp printing method using a prepatterned silicone elastomer stamp. With this method, the active layer was easily printed on the device without further patterning process. The saturation field-effect mobility of the rubber-stamp-printed TFT array was 0.025 cm2/V·s and the on/off ratio was 104. From the results, a 2'' OTFT-LCD panel with 35×24 pixels was successively fabricated and operated using a polycarbonate substrate. In addition, we investigated the reliability of the OTFT device under various conditions with or without a passivation layer to realize more stable devices.
Dispersion and Purification of Single-Wall Carbon Nanotubes Using Carboxymethylcellulose
Authors: Takahashi Teruo , Tsunoda Katsunori , Yajima Hirofumi , Ishii Tadahiro
Published: February 2005

We have developed a novel method for the purification of single-wall carbon nanotubes (SWNTs) that involves annealing in air and dispersing the SWNTs in an aqueous solution of carboxymethylcellulose (CMC). The purity of the resulting SWNTs was evaluated by analytical techniques such as electron microscopy, Raman spectroscopy, and thermogravimetric analysis (TGA). As a result, it was revealed that CMC functioned as an effective dispersion reagent in the exfoliation of the SWNT bundles and thereby, SWNTs with appreciably high quality were prepared.
A Stark Spectroscopic Study on a Flavin Langmuir–Blodgett Film
Authors: Isoda Satoru , Hanazato Yoshio , Ueyama Satoshi
Published: February 2005

The molecular orientation of a flavin Langmuir–Blodgett film was investigated by Stark spectroscopy. The first-harmonic Stark spectrum was found to be close to the first derivative of the absorbance, indicating that the flavin (isoalloxazine) ring took a specific orientation toward the direction of the applied electric field instead of a random orientation. From the analysis of the Stark spectrum, it was deduced that difference dipole moments for the S0 → S1 and S0 → S2 transitions were almost parallel to the substrate in the direction of approximately 35° from the long axis of the isoalloxazine ring.
Structural Characterization of a Mo/Ru/Si Extreme Ultraviolet (EUV) Reflector by Optical Modeling
Authors: Kang In-Yong , Kim Tae Geun , Lee Seung Yoon , Ahn Jinho , Chung Yong-Chae
Published: February 2005

The performance of a multilayer extreme ultraviolet (EUV) reflector has a direct bearing on process throughput and the cost of new technology. Using measured data from an experimentally manufactured reflector, we intend, in this work, to show that the reflectivity of the Bragg reflector can be characterized by using structural parameters such as the d-spacing, density, thicknesses of the interdiffusion layers and oxidation layer. This quantitative analysis of the reflectivity derived from the structural parameters can be utilized to optimize the optical properties of the existing Mo/Ru/Si system and to provide fundamental insights into the science involved in a Bragg EUV reflector.