bluuebunny/crossref_metadata_2025 huggingface dataset:
New Process of Self-Organized Interconnection in Packaging Using Conductive Adhesive with Low Melting Point Filler
Authors: Yasuda Kiyokazu , Kim Jong-Min , Yasuda Masahiro , Fujimoto Kozo
Published: February 2005

A model experiment of the novel self-organized joining process using conductive adhesive with low melting point alloy was demonstrated to break through the limitation of conventional solders and adhesives used in electronics packaging. Basic properties of the adhesive paste, joint morphology, the formation of the conduction path, and the self-organization characteristics were examined. Melting fillers were preserved in their initial spherical form in resin without oxygen-reduction capability, although enlargement of the alloy domain occurred in the case of oxygen-reduction polymer. The formation of the conduction path could be controlled accurately by varying the resin performance and the process parameters such as the gap distance of the joint and the volume fraction of filler. Self-organization due to capillary wetting of melting alloy was observed on the copper-line-patterned glass-epoxy substrate. The pair of lines on the faced substrates was selectively interconnected with an alloy joint.
Effect of High-Resistivity Si Substrate on Antenna Transmission Gain for On-Chip Wireless Interconnects
Authors: Watanabe Shinji , Rashid A. B. M. Harun-ur , Kikkawa Takamaro
Published: February 2005

Characterization of small integrated dipole antennas on high-resistivity Si substrates for use in on-chip wireless interconnection was performed and results were compared with those obtained by 3-dimensional (3D) finite-element simulation. The integrated antennas on standard P-type Si substrates with resistivities of 10 Ω·cm, 79.6 Ω·cm, 132 Ω·cm and 2.29 kΩ·cm, and one high-energy proton-implanted Si substrate were measured. When antenna length was 3.0 mm and antenna distance was 3.0 cm on a 10-Ω·cm-resistivity Si substrate, the antenna transmission gain was -43 dB. The antenna transmission gain was improved to -24 dB on the 2.29 kΩ·cm Si substrate. By using high-resistivity Si substrates, signal transmission via integrated antennas becomes possible.
Electrical Properties and Gas Response in Alternate Layer-by-Layer Films of Copper Phthalocyanine Dyes
Authors: Kato Keizo , Watanabe Naoki , Katagiri Shigenobu , Shinbo Kazunari , Kaneko Futao , Locklin Jason , Baba Akira , Advincula Rigoberto C.
Published: February 2005

Alternate layer-by-layer (LbL) films were fabricated using two kinds of copper phthalocyanine (CuPc) dyes and the electrical properties due to NO2 gas adsorption were investigated. Water-soluble CuPc dyes, that is, cationic Alcian blue, pyridine variant (AB) and anionic copper phthalocyanine-3,4',4'',4'''-tetrasulfonic acid, tetrasodium salt (CuPcTs) were used for the alternate LbL films. Successive depositions of the CuPc alternate LbL films were confirmed using UV-visible absorption and ellipsometry measurements. The average thicknesses of the AB and CuPcTs monolayers were estimated to be 0.7 nm and 0.4 nm, respectively. The fundamental electrical properties were examined for the CuPc alternate LbL films with Au gap electrodes and the properties in the direction parallel to the surfaces of the LbL films were measured. The conduction currents were considered to be dominated by hopping conduction. The response to NO2 gas was also measured and the large increase in conduction currents due to NO2 gas adsorption was observed. The magnitude of the conduction current after 30 min exposure to 100 ppm NO2 gas was 103–104 times larger than that in N2 gas.
Fabrication and Characteristics of Increased Efficiency of Layered Polymeric Electroluminescent Diodes
Authors: Hino Yuichi , Yamazaki Masayoshi , Kajii Hirotake , Ohmori Yutaka
Published: February 2005

We fabricated polymer electrophosphorescent organic light-emitting diodes (PHOLEDs) with a layered structure using water-soluble materials and a poly(n-vinylcarbazole) (PVCz) host doped with fac-tris(2-phenylpyridyl)Ir(III) (Ir(ppy)3). The 3-layered structure of PHOLEDs exhibit emission from Ir(ppy)3 (the emission maximum was observed at 520 nm) and show a significantly improved current efficiency of 21.0 cd/A and a luminous power efficiency of 5.2 lm/W (peak external quantum efficiency of about 6.0% has been realized compared to the conventional PHOLEDs with 2-layered structure. Furthermore, the 4-layered structure of PHOLEDs using tris(8-hydroxyquinoline)aluminum (Alq3) as electron transport layers exhibited a current efficiency of 28.1 cd/A and a luminous power efficiency of 6.0 lm/W (peak external quantum efficiency of about 8.0%). Our results suggest that the layered structure using water-soluble materials improves device performances and is effective for facilitating the fabrication by a wet process.
Self-Aligned Organic Field-Effect Transistors Using Back-Surface Exposure Method
Authors: Hyodo Takahiro , Morita Fumiya , Naka Shigeki , Okada Hiroyuki , Onnagawa Hiroyoshi
Published: February 2005

Self-aligned organic field-effect transistors using the back-surface exposure method were investigated. Using the back-surface exposure method, source and drain electrodes were self-aligned to the gate electrode. The overlapping length of the gate-source and the gate-drain electrodes was as small as 0.8 µm. Excellent field-effect operation was obtained with small parasitic resistance, where the maximum field-effect mobility was 0.12 cm2/Vs. The on-off ratio was 104, threshold voltage was -1.0 V, mutual conductance was 1.8 mS and subthreshold slope was 0.5 V/decade. Combined with capacitance measurement, the estimated cutoff frequency was 0.18 MHz.
Low-Birefringence Thermally and Environmentally Stable Slab Waveguide Planarized by Hot Embossing
Authors: Hasui Kenjiro , Tomiki Masahiro , Okamoto Naomichi
Published: February 2005

Slab optical waveguides made of “hot-embossing-able” phenyl and methyl silsesquioxane were fabricated. A wide range of refractive index control, from 1.46 to 1.56 at 0.63 µm was attained with high-precision controllability of precursor composition, ±0.5×10-3. A low birefringence, less than 7×10-4, was obtained. Despite the low birefringence, the refractive index of the waveguide was constant after heating at 200°C in an oxidizing atmosphere for 500 h. No difference in refractive index against the prolonged exposure of damp heating at 90°C and 90% relative humidity for 780 h was obtained. Radiative striation due to spin coating was successfully eliminated with planarization of the waveguide with hot embossment using a planar mold. The propagation loss of the planarized slab waveguide was measured to be less than 0.10 dB/cm at 0.63 µm of the transverse-electric mode. This material is considered to be suited for use in a cost-effective waveguide device.
Waterproof Anti Reflection Films Fabricated by Layer-by-Layer Adsorption Process
Authors: Fujita Shiro , Shiratori Seimei
Published: February 2005

To decrease light reflection from the surface of cathode-ray tube (CRT) and liquid crystal display (LCD), anti reflection (AR) technology has been investigated. In this work, we demonstrate the use of high-quality two-layer AR films (luminous reflection under 1.0) using numerous micropores to create a low-refractive-index layer, which was fabricated by a layer-by-layer (LBL) self-assembled polyelectrolyte adsorption process and a brief exposure to acidic aqueous solution. Accordingly, high-quality AR film, whose luminous reflection is approximately 0.5, was realized by LBL adsorption using a very low-refractive-index layer with numerous micropores. Also, we created waterproof AR film by means of a thermal treatment. We propose a new method of fabricating AR films.
Characterization of Hydrogen-Treated Pentacene Organic Thin Film Transistors
Authors: Yang Jung-Yen , Suen Shich-Chang , Whang Wha-Tzong
Published: February 2005

The electrical characteristics of hydrogen-postannealed and hydrogen-plasma-treated pentacene thin film transistors (TFTs) have been investigated. Experimental results have shown that the hydrogen-treated TFTs have improved field-effect mobility and a higher current on/off ratio, compared to untreated devices. The on/off current ratio of the hydrogen-treated devices was markedly increased. However, the TFTs treated with hydrogen plasma have degraded field-effect mobility, compared to hydrogen-postannealed devices.
Characteristics of High-Resolution Hemoglobin Measurement Microchip Integrated with Signal Processing Circuit
Authors: Noda Toshihiko , Takao Hidekuni , Ashiki Mitsuaki , Ebi Hiroyuki , Sawada Kazuaki , Ishida Makoto
Published: February 2005

In this study, a microchip for measurement of hemoglobin in human blood has been proposed, fabricated and evaluated. The measurement principle of hemoglobin is based on the “cyanmethemoglobin method” that calculates the cyanmethemoglobin concentration by absorption photometry. A glass/silicon/silicon structure was used for the microchip. The middle silicon layer includes flow channels, and 45° mirrors formed at each end of the flow channels. Photodiodes and metal oxide semiconductor (MOS) integrated circuits were fabricated on the bottom silicon layer. The performance of the microchip for hemoglobin measurement was evaluated using a solution of red food color instead of a real blood sample. The fabricated microchip exhibited a similar performance to a nonminiaturized absorption cell which has the same optical path length. Signal processing output varied with solution concentration from 5.32 V to 5.55 V with very high stability due to differential signal processing.
Three Growth-Temperature-Dependent Regions for Nitrogen Incorporation in GaNAs Grown by Chemical Beam Epitaxy
Authors: Sun Yijun , Yamamori Masayuki , Egawa Takashi , Ishikawa Hiroyasu
Published: February 2005

The effects of growth temperature on nitrogen incorporation in GaNAs grown by chemical beam epitaxy are studied from 340 to 515°C. Generally speaking, with increasing growth temperature, nitrogen content decreases. However, three distinct growth-temperature-dependent regions for nitrogen incorporation with activation energies of 0.59, 0.05, and 0.95 eV can be identified at low, middle, and high growth temperatures, respectively. At low and high growth temperatures, the growth temperature dependences of nitrogen incorporation are due to triethylgallium (TEG)-pyrolysis- and nitrogen-desorption-controlled processes, respectively, while a TEG-transportation-limited process is observed at middle temperatures. Atomic force microscope (AFM) results also show that there are three different surface morphologies for GaNAs grown at different growth temperatures. Based on X-ray diffraction (XRD) and AFM results, the best growth mechanism is determined, and high quality GaN0.007As0.993/GaAs triple quantum wells are obtained.
Influence of Growth Temperature on Quaternary AlInGaN Epilayers for Ultraviolet Emission Grown by Metalorganic Chemical Vapor Deposition
Authors: Liu Yang , Egawa Takashi , Ishikawa Hiroyasu , Zhang Baijun , Hao Maosheng
Published: February 2005

A set of AlInGaN epilayers with the same alloy compositions (Al ∼9%, In ∼2%) were grown at temperatures widely ranging from 780 to 940°C by metalorganic chemical vapor deposition (MOCVD) for ultraviolet (UV) application. A clear growth mode transition from three-dimensional to two-dimensional growth with the increased temperature was observed for the first time by means of atomic force microscopy (AFM). In comparison with the low-temperature (LT) grown AlInGaN, the high-temperature (HT) grown one exhibited high crystalline quality, which was also verified by the results of X-ray diffraction (XRD) and photoluminescence (PL). Therefore, the high-temperature growth of AlInGaN is strongly recommended, particularly for UV application. Further investigation was performed on these samples by using temperature dependent PL measurements, which indicated that the poor crystalline quality of LT-grown AlInGaN was due to the improper incorporation of Al and the facile formation of nonradiative recombination centers at low growth temperatures.
DC and Noise Characteristics of 4H-SiC Metal–Semiconductor–Metal Ultraviolet Photodetectors
Authors: Chiou Yu-Zung
Published: February 2005

Nickel (Ni)/indium-tin-oxide (ITO) layers were proposed and deposited on SiC epitaxy layers using a DC sputtering system to improve the effective barrier height and transmittance. SiC-based metal-semiconductor-metal (MSM) ultraviolet (UV) photodetectors were also fabricated using Ni/ITO as contact electrodes. The leakage current of SiC MSM PDs was only 2.4 nA/mm2 even at a -40 V bias. With an even larger 40 V applied bias, the photocurrent-to-dark-current contrast almost reached 4 orders of magnitude. The peak of spectrum responsivity of 4H-SiC MSM photodetectors was 0.07 A/W at a 5 V bias, which corresponds to an internal quantum efficiency of 33%. Furthermore, for a given bandwidth of 500 Hz, the corresponding noise equivalent power (NEP) and normalized detectivity D
* were calculated to be 1.33×10-10 W and 3.35×109 cmHz0.5W-1.
Fabrication and Characterization of Metal/Ferroelectric/Semiconductor Field Effect Transistor with the Ag/Bi4Ti3O12/p-Si(100) Structure
Authors: Yu Jun , Wang Hua , Zhao Bairu , Wang Yunbo , Guo Dongyun , Gao Junxiong , Zhou Wenli , Xie Jifan
Published: February 2005

Metal–ferroelectric–semiconductor field-effect-transistors (MFS-FETs) with the Ag/Bi4Ti3O12/p-Si (100) structures were fabricated. The I
ds–V
g hysteresis curve of the FET shows the counter-clockwise direction, which demonstrates the charge of channel conductivity due to the ferroelectric polarization of Bi4Ti3O12 and the memory window with a gate voltage of ±6 V was 1.2 V. The current ratio of I
ds(on) to I
ds(off) was over two orders in magnitude at zero gate voltage which indicates the MFS-FET can be used in nondestructive readout (NDRO) applications.
Fabrication of 50 nm Trigate Silicon On Insulator Metal–Oxide–Silicon Field-Effect Transistor without Source/Drain Activation Annealing
Authors: Im Kiju , Cho Won-Ju , Ahn Chang-Geun , Yang Jong-Heon , Oh Jihun , Lee Seongjae , Hwang Hyunsang
Published: February 2005

This paper presents the electrical characteristics of trigate silicon-on-insulator (SOI) n-type metal–oxide–silicon field-effect transistor (n-MOSFET) devices with a gate length of 50 nm, a channel width of 100 nm, and a channel thickness of 30 nm. The source and drain of these trigate SOI n-MOSFETs were formed by ion-shower doping at 250°C. In particular, activation annealing after ion-shower doping was excluded in order to improve the lateral steepness of the source/drain junction. Without any additional thermal processes, a low sheet resistance (R
s) of 1.2 kΩ/□ was obtained by ion-shower doping, and trigate MOSFETs showed satisfactory electrical characteristics. Since the short-channel effect was suppressed and the ratio of maximum drain current to minimum drain current (I
max/I
min) as ∼105, it is thought that the ion-shower doping process is effective for fabricating short-channel trigate SOI MOSFET devices.
Effect of TiN Substrate Plasma Treatment on Copper Chemical Vapor Deposition
Authors: Chang Chun-Li , Lin Cheng-Li , Chen Mao-Chieh
Published: February 2005

In this study, we investigated copper chemical vapor deposition (Cu CVD) on TiN substrates with respect to the effects of various plasma treatments. The Cu films deposited on the Ar-, H2-, and Ar+H2-plasma-treated TiN substrates all exhibit favorable properties over films deposited on the as-deposited TiN substrate. These include a smaller wetting angle of Cu nucleation and thus a smoother film surface, and an increased (111)-preferred orientation. However, the Cu films deposited on the plasma-treated substrates all exhibit a slightly higher resistivity, presumably due to a small grain size. With postdeposition thermal annealing at 400°C, the surface roughness of the Cu films and the Cu(111)/Cu(200) reflection ratio were both improved. We consider that a combined process including an Ar+H2 plasma substrate treatment prior to Cu film deposition and a postdeposition thermal annealing is favorable for achieving a low surface roughness and high (111)-oriented Cu film deposition.
Long-Time Annealing and Activation Energy of the Interdiffusion at AlOx/Co-Fe/Ir-Mn Interfaces
Authors: Saito Yoshiaki , Amano Minoru , Nishiyama Katsuya , Asao Yoshiaki , Tsuchida Kenji , Yoda Hiroaki , Tahara Shuichi
Published: February 2005

Dual-spin-valve-type double magnetic tunnel junctions (double MTJs) of sputtered Ir–Mn/CoFe/AlO
x
/CoFeNi/AlO
x
/CoFe/Ir–Mn were fabricated using photolithography and ion-beam milling. The double MTJs were subjected to long-time annealing at various temperatures (185–400°C) in order to investigate the thermal stability due to the interdiffusion. Magnetoresistance (MR) ratio and resistance were measured at room temperature before and after annealing. The thermal changes of MR ratio are well-explained by considering three phenomena with effective activation energies of 2.6 eV, 0.26 eV, and 1.9 eV. These values are in good agreement with the activation energies of the interdiffusion based on the vacancy mechanism. The three phenomena with the effective activation energies are well-explained by considering the interdiffusion and redistribution of O and Mn at the AlO
x
/Co–Fe/Ir–Mn interfaces. Based on the effective activation energies, it is evaluated that there would be no significant changes in the MR ratio in MTJs with CoFe(3 nm)/IrMn pinned layers for a period of more than 10 years at 160°C.
Effective Algorithms and Their Applications in Fiber Transmission Systems
Authors: Liu Xueming , Lee Byoungho
Published: February 2005

A class of fast and accurate algorithms for solving differential equations are proposed and derived. The proposed methods are considerably more accurate and more stable than classical numerical methods, and they can obtain a significantly faster speed, a higher accuracy and a larger stability region in parallel. Two kinds of basic equations, the fiber amplifier propagation equations and nonlinear Schrödinger equations, in the fiber transmission systems are effectively solved by use of these methods. Numerical simulations show that the proposed methods can increase the accuracy by more than an order of magnitude in comparison with the classical fast methods for solving Raman amplifier propagation equations, and shorten the central processing unit (CPU) time by a factor of ∼2 to ∼6 compared with the symmetrized split-step Fourier method for solving nonlinear Schrödinger equations.
Characterization of a Pico-Second Phase Conjugate Nd:YVO4Laser System
Authors: Imaizumi Toru , Goto Masato , Ojima Yasukuni , Omatsu Takashige
Published: February 2005

We present a full characterization of a pico-second pulse generation from a Nd:YVO4double-pass amplifier with a phase-conjugate mirror based on a photorefractive BaTiO3crystal with an external loop geometry. With this system, 7.4 W diffraction-limited pico-second output was generated. A corresponding optical extraction efficiency of >20% was achieved.
High-Precision Measurement of the Wavelength of a Nickel-like Silver X-ray Laser
Authors: Hasegawa Noboru , Kawachi Tetsuya , Utsumi Takayuki , Sasaki Akira , Tanaka Momoko , Kado Masataka , Sukegawa Kouta , Peixiang Lu , Kishimoto Maki , Renzhong Tai , Nagashima Keisuke , Koike Masato , Daido Hiroyuki , Kato Yoshiaki
Published: February 2005

We conducted high-precision measurements of the wavelength of a 4d
1
S
0→4p
1
P
1 line of a nickel-like silver X-ray laser. The Lyman series lines of hydrogen-like helium ions emitted from low-density plasmas were used as wavelength references, and the wavelength of the X-ray laser line was determined to be 13.887 nm (±0.002 nm). The experimental results were compared with Multiconfiguration Dirac–Fock calculations and were found to agree with theoretical wavelengths.
Entropy Production due to Time Exponentially Varying Laser Pulse: Convective Boundary Condition Case
Authors: Yilbas B. S.
Published: February 2005

Laser pulse heating with convective boundary at the surface finds applications in laser gas-assisted processing. Thermodynamic irreversibility associated with the thermal system can be quantified through entropy production. Consequently, in the present study, analytical formulation of entropy production is carried out for exponentially varying time laser pulse heating with convective boundary condition at the surface. Entropy ratio (ratio of entropy produced to its counterpart corresponding to the no-convection-boundary situation at the surface) is introduced. It is found that entropy production is low in the early heating period. The influence of heat transfer coefficient on entropy production is significant in the surface region, which becomes more pronounced as the heating period progresses.
Ultracompact Gain Block with Bi2O3-Based Erbium-Doped Fiber
Authors: Sugimoto Naoki , Ochiai Katsuhiro , Hirose Takeshi , Ohara Seiki , Fukasawa Yasuji , Hayashi Hideaki , Furuki Kenji , Tojo Makoto , Tanaka Yuichi
Published: February 2005

An ultracompact gain block with Bi2O3-based erbium-doped fiber (Bi-EDF) is presented. The ultracompact gain block includes two pump LDs, two isolators, a photodiode, dichromatic mirrors and a Bi-EDF 23 cm long in the amplifier package with a size of only 45×43×10 mm. We can obtain a net gain of 25 dB and output power of 10 dBm at 1560 nm in the C-band region.
Improved Data Disturbance Effects in 1T2C-Type Ferroelectric Memory Array
Authors: Kim Hyun-Soo , Yamamoto Shuu'ichirou , Ishiwara Hiroshi
Published: February 2005

The data disturbance characteristics in writing operations were investigated in a 1T2C-type ferroelectric memory array. On the basis of the analysis, a modified V/3-rule data writing method for reducing the data disturbance effect was proposed and verified experimentally. It was found that the current on/off ratio was maintained sufficiently to distinguish stored binary data, even after the application of 104 disturbance pulses, which were generated during writing operation for other cells. It was also found that the proposed data writing method is effective in reducing the data disturbance effect.
Microstructures and Microwave Dielectric Properties of (1-x)MgO·xBaO·TiO2 Ceramics
Authors: Chen Hsun-Chin , Weng Ming-Hang , Hung Chen-I , Houng Mau-Phon
Published: February 2005

The microstructures and microwave dielectric properties of (1-x)MgO·xBaO·TiO2 ceramics (x=0.005, 0.01, 0.03, and 0.05) prepared by a conventional solid-state reaction method and sintered at temperatures from 1280°C to 1400°C were investigated. Some minor phases were observed in (1-x)MgO·xBaO·TiO2 under different sintering conditions. The dielectric constant and Q×f of the specimens increased with an increase in x. In the (1-x)MgO·xBaO·TiO2 system, the temperature coefficient of resonant frequency could be controlled by varying x and can lead to a zero τ
f
. For practical applications, 0.97MgO·0.03BaO·TiO2 ceramics sintered at 1320°C have excellent microwave dielectric properties: ε
r=20.6, Q×f=32600 GHz and τ
f
=+4.47 ppm/°C.
A Comparison of Different Mathematical Treatments for Solving the Inverse Problem in Focused Laser Intensity Modulation Method
Authors: Petre Anca , Marty-Dessus Didier , Berquez Laureut , Franceschi Jean-Luc
Published: February 2005

Focused laser intensity modulation method (FLIMM) is a non-destructive technique for determining the polarization and/or space charge profiles in thin dielectric polymers. However, this requires to solve a Fredholm integral equation of the first kind which is an “ill-posed” problem. The aim of this paper is to evaluate different mathematical methods and to choose the one most adapted to our experimental needs. After a brief introduction to the FLIMM, various mathematical methods are described and compared. These procedures were used to calculate the polarization profiles in multilayered samples of polyvinylidene fluoride (PVDF). Thus we can make a comparison between well-known theoretical profiles and the results obtained using the different implemented methods. Due to the computation particularities and in order to obtain a good spatial resolution, two methods were preferred. The approximation method has been chosen for the study of a zone close to the surface sample. For a more in-depth analysis, Tikhonov procedure will be used.
Position Dependent Stress Distribution of Indium-Tin-Oxide on Polymer Substrate by Applying External Bending Force
Authors: Park Jun-Baek , Hwang Jeoung-Yeon , Seo Dae-Shik , Park Sung-Kyu , Moon Dae-Gyu , Han Jeong-In
Published: February 2005

In this paper, we investigated the position-dependent stress distribution of indium–tin–oxide (ITO) film on a polycarbonate (PC) substrate by applying an external bending force. It was found that crack density is maximum at the center position and decreases toward the edge. In accordance with crack distribution, it was observed that the change is electrical resistivity of ITO islands is maximum at the center and decreases toward the edge. From the result that crack density increases at the same island position as face-plate distance (L) decreases, it is evident that more stress is imposed on the same island position as L decreases.
Mechanism for Sustainment of High Density in Surface Wave Plasma
Authors: Omaru Takuro , Komiyama Fumiyuki , Kogoshi Sumio
Published: February 2005

Through particle-in-cell Monte Carlo Collision simulations, it has been predicted that high-energy electrons produced by electron plasma waves, which are resonantly excited at approximately the cutoff density by an evanescent E-field of a surface wave parallel to the density gradient, may sustain high-density plasma. The effective collision frequency at a resonant point is in fairly close agreement with the prediction of Aliev et al. [Plasma Source Sci. Technol. 1 (1992) 126].
A Flashover Prediction Method for Contaminated Insulators using a Stochastic Analysis of Leakage Current
Authors: Song Young-Chul , Park Jae-Jun , Choi Doo-Hyun
Published: February 2005

In this paper, we present the results of a new stochastic analysis of the leakage current on contaminated insulators under salt fog conditions. The stochastic analysis of the leakage current was conducted using a Hilbert transform and the level crossing rate. The Hilbert transform is used for the leakage current envelope, while the level crossing rate is used to convert the upper envelope into a cdf. Using a new defined weighting factor, the resulting cdfs show a probability that the stages until flashover can be discriminated from each other. Therefore, the proposed method is effective for flashover prediction and for monitoring the contamination conditions of outdoor insulators.
Microwave Synthesis of Iridium(III) Complexes: Synthesis of Highly Efficient Orange Emitters in Organic Light-Emitting Devices
Authors: Saito Kaori , Matsusue Noriyuki , Kanno Hiroshi , Hamada Yuji , Takahashi Hisakazu , Matsumura Takeko
Published: February 2005

Microwave synthesis of tris-ortho-metalated Ir(III) complexes was performed and resulted complexes were applied to the electrophosphorescent devices. For synthesis of Ir(ppy)3, the product was obtained by 30 min. microwave irradiation. That is microwave irradiation reduced the reaction time to 1/20 of that under conventional heating. Furthermore, we succeeded the rapid microwave synthesis of tris(2-phenyl-1-quinoline)iridium(III), Ir(phq)3, which is hard to synthesis by conventional method. An electrophosphorescent device with Ir(phq)3 as a dopant in emitting layer was developed. It demonstrated a high-efficient orange emission with maximum luminous efficiency of 33.4 cd/A and a power efficiency of 11.7 lm/W at 800 cd/m2. The color of emission corresponds to CIE coordinates x=0.56, y=0.43. The device showed a projected operational lifetime, namely T
1/2, of 6500 h at an initial brightness of 1500 cd/m2 under constant dc drive.
Hybrid Fiber-Optic Current Sensor Using Two Faraday Glass-Slab Magnetic Field Sensors
Authors: Lim Choong Soo , Oh Kijang , Kim Dalwoo , Cho Kyuman
Published: February 2005

A novel hybrid fiber-optic current sensor using two Faraday glass slab (FGS) magnetic field sensors is presented. Using the geometry that a current-carrying wire is placed in between two FGS sensors, we are able to construct a very reliable, easy-to-use, remote sensor for measuring the electrical current in the wire. Common mode interferences caused by the other currents are minimized by differentially processing magnetooptic signals.
Surface Plasmon Resonance Intensity in Ex Situ Analysis of Protein Arrays Using a Wavelength Interrogation-Based Surface Plasmon Resonance Sensor
Authors: Yuk Jong Seol , Yi Sun-Ju , Han Jeong-A , Kim Young-Myeong , Ha Kwon-Soo
Published: February 2005

We have investigated the properties of the surface plasmon resonance (SPR) spectra obtained by scanning each spot of protein arrays using a wavelength interrogation-based SPR sensor (custom-made). The surface structure of each protein array consists of glass/metal/proteins/air (ex situ). The analysis of serial spectra showed marked increases in SPR intensity and wavelength at the boundary area of protein array spots, which were mainly caused by the background signal from the glass substrate. However, at the central area, protein interaction caused an increase in SPR wavelength, and a decrease in SPR intensity. There was no significant difference between the central and boundary areas in terms of the roughness and thickness of the gold film. These results suggest that SPR intensity is a good indicator for distinguishing psuedosignals from real signals of biospecific interactions in the analysis of protein arrays using wavelength interrogation-based SPR sensors.
Quantum Transport Through Multiterminal Phenalenyl Molecular Bridges
Authors: Wang Liguang , Tagami Katsunori , Tsukada Masaru
Published: February 2005

The quantum transport properties of multiterminal molecular bridge systems are theoretically studied with the Green's functions method based on an empirical tight-binding model. As an illustrated example, we adopt a phenalenyl molecule which has a nonbonding singly occupied molecular orbital (SOMO). For a comparative study, first the two-terminal molecular bridges, then the three- and four-terminal molecular bridges are calculated. For the two-terminal case, we find that the transmission spectra significantly depend on the terminal sites connected to the leads. For example, the transmission spectrum has a peak at E=0.0 (SOMO level) as long as both the source and drain are connected to the α sites, but otherwise a dip structure appears at this energy. As a general trend, even when the third and fourth terminals are connected, the transmission spectra do not change considerably from the corresponding spectra of the two-terminal cases. However, some attractive aspects, such as the disappearance of the dip at the SOMO level and a shift in the location of the large loop current, are newly found.
Si Nanocrystals Embedded in Si Suboxide Matrix Grown by Laser-Assisted Chemical Vapor Deposition at Room Temperature
Authors: Lee Ching-Ting , Lin Chun-Hung
Published: February 2005

We present a novel laser-assisted chemical vapor deposition (LACVD) system for growing Si nanocrystals embedded in a Si suboxide matrix at room temperature. Varying growth gas ratio caused the observed photoluminescence (PL) light emission to vary from 1.65 eV to 1.92 eV without post-annealing. A phase-separated model and PL measurements were used to identify Si nanocrystals embedded in Si suboxides.
Cesium Primary Frequency References
Authors: Jefferts Steven R. , Heavner Thomas P. , Donley Elizabeth A.
Published: February 2005

Primary frequency standards with stated inaccuracies of δf/f∼10-15 or slightly better are in use today in several national timing laboratories. These standards, which are the most accurate in the world today, use laser-cooled cesium atoms to obtain this level of performance. We discuss the operation of these standards as well as possible future improvements that should see the inaccuracy of the realization of the second fall to the 10-16 level over the next 5–10 years.
Computer Experiments on Scattering of Atomic Excitations by Defects in Model Crystals
Authors: Komuro Ryoichi , Itaba Masanori , Minato Atsushi , Ozawa Satoru , Hiki Yosio
Published: February 2005

A molecular dynamics computer simulation has been carried out for a monatomic, anharmonic, and two-dimensional hexagonal model crystal. Central forces between the nearest neighbor atoms and anharmonic forces up to the third order are considered. Pulse input displacements are applied to the line of atoms at one end of a rectangular crystal, and the atomic excitations propagating in the crystal are observed. The excitations are shown to be phonons or solitons when the applied pulse is small or large, respectively. A mass defect – an atom of which the mass is lighter or heavier than that of the lattice atoms – is placed near the center of the crystal. The excitation is scattered by the defect, and the simulations are made for various cases of large and small inputs, and light and heavy mass defects. The obtained results are represented using two-dimensional maps. The intention of the study and the significance of the results are briefly discussed.
Effect of Decentering Ratio Fluctuation of Annular Array Element in Direction-Variable Type Sound Sources
Authors: Masuyama Hiroyuki , Mizutani Koichi , Nagai Keinosuke
Published: February 2005

On a direction-variable beam generated from an annular transducer array, the effects imparted to the shape of the beam when the decentering ratio of each element in the source is fluctuated are examined. A nondiffracting beam propagating with a sharp profile is formed by an annular transducer array in which each element has a width corresponding to the J
0 function. The sound source constructed by this method has clearances between each neighboring element, and the radiation direction of the beam becomes variable by utilizing these clearances in order to decenter the elements. Numerical calculations are carried out using five kinds of arrays the fluctuation of decentering ratio of each element of which differs. A slight deviation and bending in radiated beams appear, and these could be regarded as originating from the fluctuation of the decentering ratio in individual elements.
Impulse Representation of Sound Field due to a Rigid Wedge
Authors: Lawu Tjundewo , Ueda Mitsuhiro
Published: February 2005

An impulse representation for calculating a diffraction wave due to a rigid wedge is described. The method is an approximation of the Biot-Tolstoy rigorous closed-form solution for the diffraction of point source radiation by an infinite rigid wedge. The band-limited time-domain function can be reconstructed to the original waveform if it satisfies the sampling theorem, which assumes that sampling takes place at the lowest permissible sampling rate. Therefore, if the energy is concentrated between the first sampling intervals immediately after the rise time of the time-domain function, the rigorous solution can be approximated as a delta function. This paper shows the description methods of the diffraction field near the ridge in three-dimensional space. Using the proposed impulse representation, numerical simulation was performed and the calculation accuracy was examined.
Analyses of Acoustic Streaming Generated by Four Ultrasonic Vibrators in a Vessel
Authors: Nakagawa Masafumi
Published: February 2005

When ultrasonic waves are applied, the heat transfer at a heated surface in water increases markedly. The origin of this increase in heat transfer is thought to be due to the agitation effect from the microjets of cavitation and from acoustic streaming. The method in which four vibrators are used has the ability of further enhancing heat transfer. This paper presents the method using four vibrators to eject an acoustic stream jet at a selected position in the vessel. Analyses of this method are performed to establish it theoretically and to compare with an experiment previously conducted. The analyses shown in this research indicate that the aspects of acoustic streaming generated by the four vibrators in the vessel can be correctly predicted and provide a foundation for the development of using this method for the enhancement of heat transfer.
Leveling Viscous Fluids Using Ultrasonic Waves
Authors: Ampo Keisuke , Nakamura Kentaro , Ueha Sadayuki , Tanaka Shinobu
Published: February 2005

In this paper, we propose a method for leveling viscous fluids–photoresist, for example–on substrates using ultrasound. We expect this technology to supersede the spin-coat method, particularly for large substrates. Ultrasonic leveling using standing waves is presented first, followed by a leveling method using traveling waves. The uneven thickness distribution produced through slit nozzle application can be eliminated using the proposed method. The experimental evaluation of these methods was performed, and the results demonstrate the positive effect on the surface nonflatness of a photoresist. In particular, the traveling wave method has an advantage of the freedom of orientation of the slit nozzle movement.
High-Speed Thin Ultrasonic Spindle Motor and Its Application
Authors: Aoyagi Manabu , Suzuki Fumihiro , Tomikawa Yoshiro , Kano Ichiro
Published: February 2005

In this paper, we report an ultrasonic motor capable of high-velocity revolution applicable for long continuous high operation as a microfan. This study is a response to the new challenge of developing a new field of applications for an ultrasonic motor. Ultrasonic motors using a longitudinal-flexural coupling-vibration mode of a thin plate with a vibrating piece or step-horn are considered. A stator vibrator consists of a metal plate sandwiched by two thin unipoled piezoelectric ceramic plates, the electrodes of which are not divided, and this ultrasonic motor can be driven by a single ac source. Not only the coupling between a longitudinal vibration and flexural one but also the transformation of a longitudinal vibration velocity by a vibrating piece λ/4 long and step-horn λ/2 long are used. They will be effective at making the rotary speed fast. As a result, an ultrasonic motor 0.55 mm thick rotated a shaft 1.5 mm in diameter over 8,000 rpm under conditions of an applied voltage of 30 Vp-p and an input power of only 0.16 W.
Piezoelectric Linear Motor Using (R,1)-((1,1)) Mode Disk Equipped with T-Type Support Jigs for Realizing its Fine Performance
Authors: Masuda Takahiro , Tomikawa Yoshiro , Takano Takehiro
Published: February 2005

A piezoelectric linear motor using a (R,1)-((1,1)) mode disk has practical requirements, such as high-speed movement, high thrust characteristic and simple construction of thin shape. However, two resonance vibration modes, namely, (R,1) and ((1,1)), do not have vibration nodes common to their movement, and therefore, a stable support of the motor could not be realized. Thus, we devised a new stator vibrator to which a stable and good support method can be applied. That is, the construction is such that it is equipped with T-type support jigs on the two positions of the disk circumference. This structure suffers almost no influence from the support, because the resonance frequencies of T-type support jigs are made equal to the frequencies of the two resonance modes of the stator vibrator. In this paper, we deal with this new type of linear motor using the (R,1)-((1,1)) mode disk and report on the simulated and measured characteristics of the proto type motor.
Evaluation of Domain Boundary of Piezo/Ferroelectric Material by Ultrasonic Atomic Force Microscopy
Authors: Tsuji Toshihiro , Ogiso Hisato , Akedo Jun , Saito Shigeru , Fukuda Kenji , Yamanaka Kazushi
Published: February 2005

Ultrasonic atomic force microscopy (UAFM) was used to investigate the elasticity variation on domain boundary (DB) in lead zirconate titanate (PZT). The UAFM imaged the change in contact stiffness not only among grains but also on the DB. According to an analysis, the contact stiffness of the DB was approximately 10% lower than that within the domain. This is the first direct evidence of the variation of the elasticity due to the DB. The implication of this finding is that the low stiffness at the DB may affect the piezoelectricity of PZT and the easy mobility of the DB under a stress and electric field, which are important for not only actuator applications but also high-speed writing memory applications.
Brillouin Scattering Study on the Opto-Acoustic Properties of Thin Piezoelectric Polymer Films
Authors: Tomohiro Shin-ichi , Matsukawa Mami , Otani Takahiko , Ohtori Norikazu
Published: February 2005

Reflection-induced ΘA Brillouin scattering (RIΘA) is introduced to investigate the opto-acoustic anisotropy of uniaxially stretched polyvinylidene fluoride (PVDF) films (0.04 mm in thickness). Although the films are not perfectly transparent, their elastic and optical anisotropy could be investigated nondestructively. The optical anisotropy, which is observed as birefringence, showed a clear decrease near the Curie temperature (T
c).
Simulation of Ultrasonic Wave Propagation in Model Composite Materials
Authors: Chang Junjie , Ni Qing-Qing , Iwamoto Masaharu
Published: February 2005

The use of ultrasonic wave technology was anticipated as an important technology in monitoring the health of composite materials and/or structures. However, the propagation of ultrasonic wave becomes very complicated in polymer-based composite materials due to reflection, transmission, dispersion and other behaviors, which may occur at the interface of the matrix and reinforcements. Therefore, in this study, the elastic wave motion equation is evaluated using finite element analysis; then the propagation of ultrasonic waves in several model composite materials was simulated. The influences of the fiber/matrix interface, fiber size and other fiber properties on wave propagation were clarified. Moreover, the complicated propagation resulting from reflection, transmission and refraction on the fiber/matrix interface was visualized, and the influences of the arrangement of the fibers, the debonding position at the interface, and the volume fraction of fiber are discussed.
Estimation of Schottky Contacts to Porous Si by Photoacoustic Spectroscopy
Authors: Kawahara Toshio , Funaki Shingo , Okamoto Masaki , Inoue Yoshihiro , Tahira Kenichiro , Okamoto Yoichi , Morimoto Jun
Published: February 2005

The photoacoustic (PA) spectra of porous Si (PS) were measured using a microphone under various surface treatments such as vibration during anodisation, vibration during rinsing, and acid surface treatment before contact deposition. The Fourier transform infrared (FTIR) spectra were also compared for the estimation of surface conditions. To obtain good contacts for electroluminescence (EL) devices, where a large injection current during operation is required, the vibration during rinsing in distilled (DI) water and hydrochloric (HCl) acid surface treatment are important. The PA signals increase with such vibration because of the enhancement of the pressure effects in pores of PS. Moreover, the decrease in PA signals caused by the surface change of pores can be also observed with the surface treatments. As the good contacts are obtained both by the vibration and surface treatments, the surface states in the pores seem to be important for the contacts to PS. This process can be monitored by PA spectroscopy in a noncontact manner because the PA signals from the PS are enhanced in the pores by the pressure effects, and PA spectroscopy can be sensitive to the change in surface of pores of PS.
Photoacoustic Spectra from Co Doped ZnO with Different Grain or Cluster Sizes
Authors: Inoue Yoshihiro , Miyauchi Yoshiko , Kimura Akitsugu , Kawahara Toshio , Okamoto Yoichi , Morimoto Jun
Published: February 2005

Photoacoustic (PA) spectra for Zn1-x
Co
x
O mixed-crystal powders with various Co concentrations and sintering temperatures were measured. The PA spectra showed three peaks of Co2+ absorption between 560 nm and 660 nm. On the other hand, the PA spectra between 800 nm and 1000 nm were almost flat, and these are expected to be dominated by light scattering effects. The PA spectra were normalized by using the Co2+ absorption peaks in order to compare the sample size and the PA signals intensity, and the sintering temperature dependence of the PA spectra is discussed. The PA signal intensity decreased with the increase of the sintering temperature. The decrease of the PA spectra seems to be caused by small light scattering effects for the large clusters under higher temperature sintering, where the grains and clusters size increase. We could evaluate the grain growth in the sintering processes by PA spectroscopy in a noncontact mode.
Finite-Difference Time-Domain Analysis of Wavelength-Selective Characteristics in Weighted Acoustooptic Switches for Wavelength-Division-Multiplexed Photonic Routing
Authors: Goto Nobuo , Miyazaki Yasumitsu
Published: February 2005

Waveguide-type acoustooptic (AO) switches can switch optical waves wavelength-selectively for wavelength-division-multiplexed (WDM) signals. The switches can be expected to be used in WDM photonic networks. In this paper, finite-difference time-domain (FDTD) analysis is presented for wavelength-selective switching with a collinear weighted AO device consisting of an optical directional coupler, input/output Y-branches and a tapered surface acoustic wave (SAW) waveguide. The FDTD simulated results are compared with the result from the coupled mode theory. It is shown that a sidelobe level as low as -20 dB in the filtering characteristics is realized by using weighted AO interaction. It is also shown that the sidelobe structure is affected by the characterisitcs of the input Y-branch.
Piezoelectric Photothermal Study of the Optical Absorption Spectra of Microcrystalline Silicon
Authors: Wang Ping , Tada Masaki , Ohta Masashi , Sakai Kentaro , Fukuyama Atsuhiko , Ikari Tetsuo
Published: February 2005

The piezoelectric photothermal (PPT) signals from hydrogenated microcrystalline silicon (µc-Si:H) films were measured and the effects of the deposition rate on the optical properties were investigated. Increasing the deposition rate resulted in (i) a decrease in optical absorption coefficient, (ii) a shift in effective energy gap to the higher photon energy side, and (iii) a increase in the density of localized states originating from a structural disorder. These results led to a reduction in the photovoltaic conversion efficiency of the solar cells for high-deposition-rate samples. The usefulness of the PPT method for investigating the optical properties of thin and transparent µc-Si:H films was also demonstrated.
Multiplexed Fiber Bragg Grating Vibration Sensor with Temperature Compensation Using Wavelength-Switchable Fiber Laser
Authors: Tanaka Satoshi , Ogawa Takanari , Yokosuka Hiroki , Takahashi Nobuaki
Published: February 2005

A wavelength-switchable and tunable fiber ring laser has been proposed to implement an optical source of a fiber Bragg grating (FBG) vibration sensor array based on intensity modulation technique. The laser consists of an erbium-doped fiber amplifier (EDFA) and an optical switch with tuning FBGs, in which the lasing output is coupled out from a selected tuning FBG and serves as an optical source of one of the multiplexed FBG vibration sensor elements. By changing the channel of the optical switch, the lasing wavelength can be chosen for the sensing FBG of the respective sensor element. In addition, the temperature effects on the sensor outputs due to environmental temperature can be eliminated when the temperature changes are applied commonly to both the tuning and sensing FBGs. In the experiment, multipoint vibration detection with a temperature-insensitive operation is successfully demonstrated by constructing two sensor elements arranged in parallel.