bluuebunny/crossref_metadata_2025 huggingface dataset:
Applying the Multiple Signal Classification Method to Silent Object Detection Using Ambient Noise
Authors: Mori Kazuyoshi , Yokoyama Tomoki , Hasegawa Akio , Matsuda Minoru
Published: February 2005

The revolutionary concept of using ocean ambient noise positively to detect objects, called acoustic daylight imaging, has attracted much attention. The authors attempted the detection of a silent target object using ambient noise and a wide-band beam former consisting of an array of receivers. In experimental results obtained in air, using the wide-band beam former, we successfully applied the delay-sum array (DSA) method to detect a silent target object in an acoustic noise field generated by a large number of transducers. This paper reports some experimental results obtained by applying the multiple signal classification (MUSIC) method to a wide-band beam former to detect silent targets. The ocean ambient noise was simulated by transducers decentralized to many points in air. Both MUSIC and DSA detected a spherical target object in the noise field. The relative power levels near the target obtained with MUSIC were compared with those obtained by DSA. Then the effectiveness of the MUSIC method was evaluated according to the rate of increase in the maximum and minimum relative power levels.
Convergence Property of Time Reversal Waves under Noisy Environment
Authors: Shimura Takuya , Ochi Hiroshi
Published: February 2005

We have studied on the convergence property of time reversal waves (which are equal to phase conjugate waves) in the ocean, particularly in time domain with various configurations of time reversal array (TRA) through simulations and tank experiments. In this paper, the property of time reversal waves under noisy environment is discussed. Simulations were carried out with various sound velocity profiles using the Pekeris solution of the normal mode method and the parabolic equation (PE) method, and tank experiments were also conducted to compare with the simulation results. Results revealed the following. Time reversal waves even at very low signal noise to ratio (SNR) can converge and send the desired signal to the focus at high SNR. The focusing effect of time reversal waves is higher when the horizontal range is extended. If the sound velocity profile is different, the focusing effects are not considerably affected.
Measurement of Elastic Moduli of the Arterial Wall at Multiple Frequencies by Remote Actuation for Assessment of Viscoelasticity
Authors: Hasegawa Hideyuki , Kanai Hiroshi
Published: February 2005

To characterize tissues in atherosclerotic plaques, we have developed a method, the phased tracking method, for measuring the strain (change in wall thickness) and elasticity of the arterial wall. However, some types of tissue, such as lipids and blood clots, cannot be discriminated from each other based only on elasticity due to the small difference in their elasticity. For more precise tissue characterization, we have measured the regional viscoelasticity. To obtain the viscoelasticity, in this study, elastic moduli at multiple frequencies were measured with ultrasound by generating the change in internal pressure due to remote cyclic actuation. Furthermore, the viscoelasticity of the arterial wall was estimated from the measured elastic moduli at multiple actuation frequencies.
In Situ Characterization of Microbubble Oscillation by Bubble Aggregation Pattern Analysis
Authors: Yamakoshi Yoshiki , Kurita Yasushi , Masuda Nobuyuki
Published: February 2005

When micro bubbles flow into an ultrasonic wave field, the microbubbles often produce bubble aggregation. The aggregated bubbles create an inherent aggregate pattern depending on the bubbles, ultrasonic wave frequency and sound pressure. To evaluate the microbubble aggregation, which is produced by ultrasonic waves, the Bjerknes force which is produced by aggregated bubbles is derived. We assume that 2n+1 bubbles are aligned with a separation shorter than the wavelength and that they oscillate independently producing secondary ultrasonic waves around the bubbles. The relative phase between the secondary wave radiation of the aggregated bubbles and the radial oscillation of a single neighboring bubble is an important parameter for characterizing the bubble aggregation. Based on this discussion, a novel method of measuring the relative phase between the secondary wave radiation and the radial oscillation is proposed. This method is applied to micro bubbles with polyvinyl chloride shells.
Apoptosis Induction in Cancer Cells by Ultrasound Exposure
Authors: Watanabe Akihiro , Kawai Kazuaki , Sato Toshio , Nishimura Hiroyuki , Kawashima Norimichi , Takeuchi Shinichi
Published: February 2005

The methods of suppressing cancer cell proliferation by ultrasound exposure were investigated to develop a new minimally invasive cancer treatment. A stainless-steel diaphragm with a bolt-clamped Langevin-type transducer (BLT) was attached to the bottom of a water tank in the ultrasound exposure system used in this study. Cancer cells of a mouse T lymphoma (EL-4) in a flask were exposed to ultrasound under various conditions of exposure time, ultrasound frequency, ultrasound waveform, and so forth. The number of cancer cells exposed to ultrasound decreased during the culturing process. In this study, it was proved by electrophoresis, enzyme activity measurement and morphological observation that cancer cell proliferation can be suppressed by apoptosis induction in cancer cells by ultrasound exposure.
Characterization and Device Application of Tensile-Strained Si1-yCy Layers Grown by Gas-Source Molecular Beam Epitaxy
Authors: Abe Katsuya , Yabe Chiaki , Watahiki Tatsuro , Yamada Akira , Konagai Makoto
Published: February 2005

Tensile-strained Si1-y
C
y
alloy films were grown on Si(001) by gas-source molecular beam epitaxy (GS-MBE). The substitutional C contents (Cs) were estimated from X-ray diffraction patterns and were found to decrease with increasing substrate temperature. The thermal stability of the Si1-y
C
y
alloy films was investigated by annealing experiments. The Cs value was also reduced at annealing temperatures higher than 850°C. Metal-oxide-semiconductor (MOS) transistors were fabricated using the strained Si1-y
C
y
channel layer grown by GS-MBE and the transistor characteristics were confirmed.
Characteristics of Spike-Free Single and Double Heterostructure-Emitter Bipolar Transistors
Authors: Lin Yu-Shyan , Hsu Wei-Chou , Jong Fuh-Cheng , Chiou Yu-Zung , Chen Yeong-Jia , Tang Jing-Jou
Published: February 2005

In this study, we propose single and double heterostructure-emitter bipolar transistors (SHEBTs and DHEBT, respectively) with undoped spacers inserted on both sides of the base. The spike-free HEBT is achieved by solving Poisson's equation. The SHEBT and DHEBT with 100 Å spacers exhibit common-emitter current gains of 200 and 120, along with offset voltages of 80 and 50 mV, respectively. Meanwhile, the current gains of the passivated SHEBT and DHEBT reach 360 and 180, respectively. The passivated SHEBT with 100 Å spacer exhibits a current gain over unity at ultralow current densities of 10-5 A/cm2. Additionally, experimental results for different spacer thicknesses demonstrate that the 100 Å spacer yields the highest current gain.
Analysis of Electron Statistics Involving Compensation and Deep-Dopant Effects for Phosphorus-Doped n-Type Diamond
Authors: Koide Yasuo
Published: February 2005

In order to understand carrier statistics in phosphorus-doped n-type diamond with an ionization energy of 0.6 eV, electron statistics involving compensation and the deep-dopant effect are theoretically analyzed. For n-diamond with a compensation ratio (c) larger than 1×10-4, the electron concentration (n) at room temperature (RT) is insensitive to the donor concentration (N
D) and decreases with increasing c value. On the other hand, for diamond with a c value smaller than 1×10-4, the n value at RT increases with increasing N
D value and is insensitive to the c value. Correspondingly, the length of Debye tailing (λ
n
) at RT decreases with increasing c value for n-diamond with c>1×10-4 and is insensitive to the c value for n-diamond with c<1×10-4. The n=1014 cm-3 and λ
n
=3 µm are predicted to be obtained at RT for diamond with a c value smaller than 10-5 and N
D of 5×1018 cm-3. However, it is found that an increase in temperature is effective in increasing the n value and reducing the λ
n
value. The n value as large as 1015 cm-3 and the λ
n
value as small as 100 nm are expected to be achieved at an elevated temperature of 473 K.
Novel Storage-Node Contacts with Stacked Point-Cusp Magnetron Sp-TiN Barrier for Metal–Insulator–Metal Ru/Ta2O5/Ru Capacitors in Gigabit Dynamic Random Access Memories
Authors: Kawagoe Tsuyoshi , Nakamura Yoshitaka , Kuroki Keiji , Asano Isamu , Goto Hidekazu , Nakanishi Naruhiko
Published: February 2005

We have investigated a mechanism for increasing the contact resistance (R
c) of the ruthenium (Ru) and the titanium nitride (TiN) barrier during the tantalum oxide (Ta2O5) oxidation annealing in the metal–insulator–metal (MIM) capacitors. It has been found that controlling the atomic ratio of Ti to N (Ti/N ratio) is a key to keeping the contact resistance low. Controlling the Ti/N ratio is easy for the sp-TiN, while it is difficult for the chemical-vapor-deposited TiN. On the basis of this result, we have proposed a novel Ru/TiN contact with a stacked-barrier structure fabricated by using the point-cusp magnetron (PCM) sputtering method. We have applied this structure to the MIM-Ru/Ta2O5/Ru capacitor in a gigabit DRAM with 0.10 µm design. In this capacitor, we have obtained the contact resistance of 10 kΩ·bit and the capacitor leakage current of 10-17 A/bit in the range of -1 to +1 V.
Grain Growth Simulation of Damascene Interconnects: Effect of Overburden Thickness
Authors: Jung Jung-Kyu , Hwang Nong-Moon , Park Young-Joon , Joo Young-Chang
Published: February 2005

We simulated grain growth in a damascene trench structure varying the overburden thickness, driven by the surface and the interface energy minimization. The modified Potts model based on the Monte Carlo method was implemented. To determine whether the trench evolved a bamboo microstructure or not, we analyzed the normalized number of the triple junction points per cross-section that approaches zero with completion of a bamboo. The results of both the simulation and the triple junction analysis suggest that only the trench whose depth is significantly thicker than the overburden thickness can evolve a bamboo. While the trench and the overburden evolve their microstructure independently at the initial stages, only the microstructure of the thick overburden continues to grow to the inside of the trench because of their large enough grain size. These may provide a clue to understand the dependence of the trench microstructure on the overburden counterpart.
Optical Compensation Method for In-plane Switching Twisted Nematic Mode
Authors: Oka Shinichirou , Kobayashi Kazuya , Iwamoto Yoshihisa , Toko Yasuo , Kimura Munehiro , Akahane Tadashi
Published: February 2005

We have proposed an in-plane switching twisted nematic (IT) mode. The characteristics of the IT mode are the wide viewing angle, the narrow cell gap error tolerance, and the relative fast response time. However, an IT mode needs a high electric field to obtain a high contrast ratio. To improve this situation, we propose a compensation method using a twisted nematic liquid crystal (LC) film or a twisted discotic LC film. Specifically, the latter can achieve the wide viewing angle, the high contrast ratio and the decrease in the driving voltage. In this paper, a compensation method using a film is suggested and evaluated by numerical calculation.
Nonlinear Equalizer for High-Density Optical Disc Reproducing Apparatus
Authors: Chekcheyev Sergey , Park Hyun-Soo
Published: February 2005

This paper presents an equalizer for a high-density optical disc reproducing apparatus. The equalizer ensures small bit error rate (BER) applying simple circuitry. The results of the experimental tests of the equalizer are described. The experimental comparison of the proposed equalizer with a known limit equalizer is given.
Asymmetric Two-Beam Coupling with High Optical Gain and High Beam Diffraction in External-Electric-Field-Free Polymer Composites
Authors: Tsutsumi Naoto , Shimizu Yusuke
Published: February 2005

This paper presents high-performance asymmetric two-beam coupling, beam diffraction and holographic recording in polymeric composites without poling and applying an external electric field. The polymer composites are based on poly(2-(9-carbazoyl)ethyl methacrylate) (PCzEMA) and poly(N-vinyl carbazole) (PVCz) as host matrices with 2,4,7-trinitro-9-fluorenone (TNF) as a sensitizer, four kinds of plasticizer; tricresyl phosphate (TCP), n-butyl benzyl phthalate (BBP), diphenyl phthalate (DPP), and dicyclohexyl phthalate (DCP); and (s)-(-)-1-(4-nitrophenyl)-2-pyrrolidine-methanol (NPP) as a nonlinear optical dye. The gain coefficient and diffraction efficiency increased markedly with increasing TNF and NPP concentrations. The highest net gain coefficient of 101.9 cm-1 with optical gain of 224 cm-1 and absorption coefficient of 122.1 cm-1 was obtained for PVCz/NPP/DDP/TNF (35/20/40/5), and the highest diffraction efficiency of 88% was achieved for PCzEMA/NPP/TCP/TNF (35/30/30/5) and PVCz/NPP/DDP/TNF (35/20/39/6) composites. The BBP plasticizer significantly enhanced the speed of two-beam coupling and diffraction grating formation for both PVCz and PCzEMA composites. Holographic images stored in the polymer composites were clearly read out using a probe beam. The key point for achieving the external-electric-field-free high performance of asymmetric energy transfer and diffraction efficiency is to have a high concentration of TNF (5 or 7 wt%).
Multilayered Unipoled Piezoelectric Transformers
Authors: Priya Shashank , Ural Seyit , Kim Hyeoung Woo , Uchino Kenji , Ezaki Toru
Published: February 2005

This study describes a multi-layer piezoelectric voltage and power transformer which has one direction poling, operates in a wide-frequency range and delivers both step-up and step-down voltages by inverting the electrical connections. In this design, the input and output electrodes are on the same side of the disk and are isolated from each other by a fixed gap. Investigations were performed on a disk of diameter 29.1 mm. The electrode pattern is a ring/dot structure, where a strip connects the dots. Various ratios of input to output area were studied and it was found that area ratio in the range of 2.8–3.3 or the output diameter in range of 13–15 mm yields high power and efficiency. The power density for the optimized single layer transformer was 40 W/cm3 while that for the 3-layer structure was 25 W/cm3. Though the power increased with multilayer structure, the effective power density decreased because of the interlayer constraints.
Low-Temperature Sintering of V2O5-Added and -Substituted ZnNb2O6 Microwave Ceramics
Authors: Wee Sung-Hun , Kim Dong-Wan , Yoo Sang-Im , Hong Kug Sun
Published: February 2005

The sintering behaviors and microwave dielectric properties of V2O5-added and -substituted ZnNb2O6 ceramics with columbite structure (abbreviated as ZNV and ZVN, respectively) have been investigated. It was found that the addition or substitution of V2O5 to ZnNb2O6 ceramics lowers the sintering temperature from 1150°C to ∼900°C, but the sintering mechanisms are different. The formation of a ternary liquid phase is attributed to enhanced sintering in ZNV samples. Interaction between ZnNb2O6 and V2O5 also led to the formation of a second phase, V3Nb17O50. In contrast, it has been observed that with up to 8 mol% substitution of V2O5 in ZnNb2O6, a complete solid solution is formed. The sintering temperature for the ZVN sample becomes lower due to the decreased temperature of liquidus according to the substitution of V for Nb ions. The microwave dielectric properties of ZNV samples are seriously degraded due to the presence of a V3Nb17O50 second phase. This was confirmed by measuring the dielectric properties of V3Nb17O50 second phase. However, V-substituted Zn(Nb0.94V0.06)2O6 samples sintered at 875°C for 2 h exhibit excellent microwave dielectric properties: Q×f of 65,000 GHz, ε
r of 24, and τf of -72 ppm/°C.
Thermoelectric Properties of Doped (ZnO)mIn2O3
Authors: Kaga Hisashi , Asahi Ryoji , Tani Toshihiko
Published: February 2005

The thermoelectric properties of layer-structured homologous compounds of (ZnO)
m
In2O3 (m is an integer) were investigated in terms of the detailed dependence of the molar ratio of ZnO to In2O3, n (=ZnO/In2O3), and of doping, such as with Ba2+, Ca2+, Sr2+, and Sn4+, for an In site. Except for the Ba and Sr dopings, all sintered specimens with n≥3 were found to be in the phases of (ZnO)
m
In2O3. The highest power factor apparently existed around n=3 while the thermal conductivity was minimum at the range from n=3.5 to 5. The Ca doping effectively reduced the thermal conductivity, resulting in a dimensionless figure of merit of 0.23 (at 1053 K) for n=3.5, which was relatively high among n-type oxides.
Control of Carrier Concentration in n-Type Hot-Pressed Bi1.8Sb0.2Te3 Alloys
Authors: Im Hee-Joong , Kim Dong-Hwan , Ahn Jeung-Sun , Iwasaki Hideo , Sano Seijirou , Je Koo-Chul , Mitani Tadaoki
Published: February 2005

We introduce an annealing method performed with only Bi powders at 673 K. With this method, the carrier concentration is controlled and the conductivity type can be changed by adjusting the annealing time. Most importantly, conductivity-type transition occurs in an annealing time of 48 hours. The thermoelectric properties of the alloys are measured and described as functions of carrier concentration and annealing time. n-Type hot-pressed Bi1.8Sb0.2Te3 alloys that deviated from the optimal figure-of-merit Z condition owing to high carrier concentration can be optimized by this annealing method.
Highly Precise Atomic Force Microscope Measurement of High-Aspect Nanostructure Free of Probe Bending Error
Authors: Hosaka Sumio , Terauchi Daisuke , Sone Hayato , Morimoto Takafumi , Kembo Yukio , Koyanagi Hajime
Published: February 2005

A new atomic force microscope (AFM) imaging has been used to study the bending of a sharpened and slim probe in the digital probing method (step-in mode) for the critical dimension (CD)-AFM technique. The bending of the AFM probe indicates a serious problem in measuring very fine patterns with a high aspect ratio with an error of less than 1 nm when we use the sharpened and slim probe. In our estimation, position errors Δr (in plane) and Δz (in perpendicular) rapidly increase with the slope angle and a controlled force. In experiments, we measured a degradation of the pattern profile as the controlled force increased in the AFM system. We have to control the probe at a force of <2 nN to be free of probe bending, when we measure very fine pit patterns with a size of <100 nm and an aspect ratio of >5 accurately.
Effect of Driving Frequency on the Electron Energy Probability Function of Capacitively Coupled Argon Plasmas Comparison between Simulation and Experiment
Authors: Takekida Hideto , Nanbu Kenichi
Published: February 2005

The effect of driving frequency in the range of 13–50 MHz on the electron energy probability function (EEPF) in capacitively coupled discharges is studied using particle-in-cell/Monte Carlo(PIC/MC) method. The EEPFs obtained from the simulation generally agree well with the measured data of Abdel-Fattah and Sugai. Detailed comparison shows, however, that the transition from the Druyvesteyn distribution to the bi-Maxiwellian type with increasing driving frequency is not as clear in the simulation as in the experiment.
Relationship between Photoluminescence Intensity of TiO2 Suspension Containing Ethanol and Its Surface Coverage on TiO2 Surface
Authors: Nakajima Hiromitsu , Mori Toshiyuki , Watanabe Mamoru
Published: February 2005

The photoluminescence (PL) of TiO2 suspensions containing ethanol in the concentration range from 5 to 100 ppm by volume was measured at room temperature. We found that the relationship between the PL of TiO2 in the presence of ethanol and the adsorption of ethanol onto the TiO2 surface can be described as a simple Langmuir isotherm by assuming that the PL intensity is proportional to the surface coverage of ethanol on the TiO2 surface.
Advantage of Thin-Film Filter for Reliable Photoemission Spectroscopy Using High-Flux Discharging Lamp
Authors: Yokoya Takayoshi , Tsuda Shunsuke , Kiss Takayuki , Shin Shik , Mochiku Takashi , Hirata Kazuto
Published: February 2005

An aluminum film with a thickness of 1500 Å has been used as a filter for the He Iα resonance line (21.2182 eV) from a microwave-driven high-flux discharging lamp to reduce the degradation of sample surfaces during photoemission spectroscopy (PES) measurements. A marked increase in the lifetime of sample surfaces, which overcomes a ∼90% intensity reduction, has been observed. The thin-film filter, if combined with a high-flux discharging lamp, provides clean vacuum ultraviolet lights for reliable PES measurements with an ultrahigh resolution.
Mechanical Vibration Model for Proteins and Nanoparticles Coupling with the Cell Membrane and its Application to Cell Treatment
Authors: Naruse Yujiro
Published: February 2005

The behaviors of proteins and nanoparticles coupling with the cell membrane were analyzed using an external mechanical vibration model. This model was based on a one-dimensional seismic vibration system. A simple equation was derived for the relationship between the amplitude of cell vibration and the amplitude of mobile protein or nanoparticle vibration in the cell membrane. Using this equation, the optimal frequency for the efficient vibration of mobile proteins or nanoparticles was found in the applications of in vivo and in vitro cell treatments.
Optical Characteristics of Two-Dimensional Photonic Crystals in Anodic Aluminum Oxide Films
Authors: Mizeikis Vygantas , Mikulskas Irmantas , Tomašiūnas Roland , Juodkazis Saulius , Matsuo Shigeki , Misawa Hiroaki
Published: February 2005

The optical properties of two-dimensional photonic crystals (PhCs) in anodic aluminum oxide (AAO) films obtained using a simple and low-cost pre-patterning procedure are described. The prepatterning of the initial Al film surface was carried out by imprinting with an optical diffraction grating; the anodization of the prepatterned sample led to the formation of a good quality, large-area PhC with a triangular lattice of air holes (lattice period a=0.48 µm, hole radius r=0.2 µm) in an AAO film. The optical transmission spectra of the sample were measured at visible wavelengths in the range of 0.4–1.0 µm for various incidence angles and linear polarizations of the probing light. The detailed analysis of the transmission data indicates a photonic band gap in the 0.9–1.0 µm wavelength range for light waves linearly polarized in the direction perpendicular to the axes of PhC pores.
The Extraction of Develop Parameters by Using Cross-Sectional Critical Shape Error Method
Authors: Kim Hyoung-Hee , Park Jun-Tack , Choi Jung-Wook , An Ilsin , Oh Hye-Keun
Published: February 2005

As the minimum feature size decreases, the gap between real experimental lithography process and simulated one increases. This gap should be reduced as small as possible by inserting the correct process parameters to simulation. Unfortunately, we do not have the exact simulation parameters in most cases and we need to get more accurate parameters. Among many methods to obtain the exact parameters, we used a new automatic cross-sectional critical shape error method to get the develop parameters by comparing the experimental scanning electron microscope image with the simulated image. This new bitmap masking technique is much faster than the conventional serial cross-sectional critical shape error method.
Enhanced Extreme Ultraviolet Lithography Mask Inspection Contrast Using Fabry-Perot Type Antireflective Coating
Authors: Cheng Hsu-Chun , Chen Hsuen-Li , Ko Tsung-Shine , Lai Lee-Jene , Ko Fu-Hsiang , Chu Tieh-Chi
Published: February 2005

In this paper, we describe two strategies for solving the low-contrast problem during extreme ultraviolet lithography (EUVL) mask inspection processes. One is the use of single-layer antireflective coating (ARC), and the other is the use of Fabry-Perot-type ARC. The materials of ARC are the same as those of buffer layers, such as SiO2 and Si3N4, which are easy to fabricate. Contrast can be increased up to >95% by adding ARC. For both absorbers, Single-layer Si3N4 ARC and Si3N4-based Fabry-Perot-type ARC show better performances than SiO2 ARC. Both types of ARC maintain a high contrast at 40% with a large thickness variation even until ±40%. Moreover, the top absorber in Fabry-Perot-type ARC has good conductivity that can eliminate electrical distortion, which is caused by electron charging during e-beam direct writing. The Fabry-Perot-type ARC structure has better contrast and thickness variation tolerance than the single-layer ARC structure. The film materials in Fabry-Perot structure can also be used for various absorber and dielectric materials.
Influence of Electron Scattering on Resolution in Low-Dose Electron-Beam Lithography
Authors: Kotera Masatoshi , Niu Hirohisa
Published: February 2005

The influence of electron scattering phenomena on the line edge roughness (LER) of a resist after development is discussed using an electron trajectory simulation. The energy range calculated is from 1 to 5 keV, the resist thickness ranges from 10 to 80 nm, and the electron dose ranges from 1 to 10 µC/cm2. In the variable threshold energy density model for obtaining a specific line width, the LER variation is obtained for various electron doses. If the dose is as large as 10 µC/cm2, it is found that it is possible to obtain a 30-nm-wide line, and if the PE energy is 2 keV or less, the LER becomes less than 5 nm. In the fixed threshold energy density model, the line width and the LER variation with electron dose are obtained for various resist thickness.
Growth of Silicon Nanocrystal Dots with High Number Density by Ultra-High-Vacuum Chemical Vapor Deposition
Authors: Naito Shinya , Satake Masaki , Kondo Hiroki , Sakashita Mitsuo , Sakai Akira , Zaima Shigeaki , Yasuda Yukio
Published: February 2005

Si nanocrystal growth using an amorphous Si (a-Si) layer pre-deposited on a SiO2 surface has been performed by ultra-high-vacuum chemical vapor deposition (UHV-CVD). It has been shown that high-density Si nanocrystals are formed by Si2H6 irradiation on to an a-Si surface and that Si atoms supplied from the a-Si layer contribute to the growth of Si nanocrystals. By changing the thickness of the a-Si layer, the number density and size of Si nanocrystals can be controlled systematically. A number density of 1.0×1012 cm-2 and an average diameter of 9.1 nm were achieved for Si nanocrystals on the SiO2/Si substrate in the case of using a 0.3-nm-thick a-Si layer. Si nanocrystals were successfully buried in a SiO2 matrix by post deposition processes and their diameters were found to range from 6 to 10 nm.
Three-Dimensional Simulation of the Effect of E-Beam Lithography Induced Line-Edge Roughness on N-Type Metal-Oxide-Semiconductor Transistor Electrical Characteristics for a 50 nm Technology
Authors: Scheiblin Pascal , Foucher Johann
Published: February 2005

Three-dimensional electrical simulations have been performed in the case of a 50 nm n-type metal-oxide-semiconductor transistor (NMOS) technology to show the effect of e-beam lithography induced line-edge roughness (LER) on the electrical characteristics of the device. It is shown that the periodic fluctuation of the LER induced significant three-dimensional effects only if its amplitude value causes the gate length to be locally reduced to about 30 nm, and when its spatial periodicity is lower than the average gate length. Otherwise, the transistor follows a two-dimensional behaviour.
Fabrication of Three-Dimensional Cu Coaxial Cable Using Porous Silicon Technology
Authors: Eun Duk-Soo , Shin Jang-Kyoo , Lee Jong-Hyun
Published: February 2005

This paper presents the fabrication of a three-dimensional Cu coaxial cable with a thick oxidized porous silicon (OPS) layer for application of microwave and RF integrated circuit technology. The structure was fabricated by hydrofluoric acid, nitric acid, acetic acid (HNA) etching, followed by the OPS process, electroplating and photoresist (PR) reflow. The return loss of the Cu coaxial cable on the OPS layer is -35.53 dB at 13 GHz and the insertion loss of Cu coaxial cable on OPS layer is -0.17 dB at 5.5 GHz. Therefore, the fabricated devices are expected to improve the characteristic of the insertion loss and the transmission line dispersion. Also, it is possible that the cable can be used as the microsize coaxial cable.
Development of Surface Micromachined Mechanism for Movement Translation and Displacement Amplification
Authors: Lee Chengkuo , Lai Yen-Jyh , Lin Yu-Shen , Wu Chia-Yu , Chen Chihchung , Tasi Ming Hung , Hung Shih-Yun , Huang Yi-Mou , Huang Ruey-Shing , Lin Min-Shyong
Published: February 2005

Characteristics of motion and movement are key concerns for microactuators and microrobots. We propose a new surface micromachioned mechanism to transfer small in-plane motion or displacement into the out-of-plane amplified rotation or amplified vertical projected displacement. We have demonstrated the concept of using this micromechanism to optical switch and variable optical attenuator (VOA) applications. Experimental data confirm its function of transferring and amplifying in-plane motion and movement into out-of-plane motion and movement. Preliminary results prove this mechanism can drastically reduce the driving voltage, thus the reported VOA device only requires 3 volts dc load to achieve 37 dB attenuation range.
Shrinking of Spin-On-Glass Films Induced by Synchrotron Radiation and Its Application to Three-Dimensional Microfabrications
Authors: Rahman Md. Mashiur , Tero Ryugo , Urisu Tsuneo
Published: February 2005

Photoinduced etching of siloxane-type spin-on-glass (SOG) by synchrotron radiation (SR) using a SF6/O2 etching gas and a Co contact mask has been investigated. The SOG film was etched by direct SR irradiation similarly to the case of thermally oxidized SiO2. We found that the indirect exposure to SR caused shrinkage of SOG under the Co mask. The shrinkage depth of SOG was attenuated by the thickness of the Co mask, but not eliminated even by a Co mask 350 nm thick, due to the high-energy photons (≥230 eV) being transmitted through the mask. The shrinkage phenomenon was successfully applied in the fabrication of a three-dimensional structure of the SOG thin film on Si(100). Atomic force microscopy observations showed that the surfaces were very smooth both on the completely etched Si area and on the shrunken SOG area. We investigated the mechanism of the shrinkage of SOG by Fourier-transform infrared spectroscopy.
Performance Enhancement of Vertical Tunnel Field-Effect Transistor with SiGe in the δp+ Layer
Authors: Bhuwalka Krishna Kumar , Schulze Jörg , Eisele Ignaz
Published: February 2005

The metal–oxide–semiconductor (MOS)-based vertical tunnel field effect transistor (FET) on silicon has been proposed earlier and which showed gate-controlled band-to-band tunneling from the valence band in the heavily doped δp
+ layer at source to the conduction band in the inversion channel. In this work, using 2D computer simulation, we further investigate the device performance enhancement with SiGe in the δp
+ layer. On-current as well as threshold voltage are seen to improve considerably and meet the roadmap technology requirements. We also show that unlike the conventional MOSFET, the subthreshold swing of the vertical tunnel FET is not limited to the theoretical value of 60 mV/dec at room temperature.
Grown-in Defects in Heavily Boron-Doped Czochralski Silicon
Authors: Yu Xuegong , Ma Xiangyang , Li Chunlong , Yang Jiansong , Yang Deren
Published: February 2005

Grown-in defects including oxygen precipitates and voids in heavily boron-doped (HB) Czochralski (CZ) and lightly boron-doped (LB) CZ silicon crystals are reported in this paper. It was found that heavy boron-doping enhanced oxygen precipitation during high-temperature annealing. Meanwhile, it was clarified that the amount of larger crystal originated particles (COPs) decreased, while that of smaller COPs increased on as-grown HB wafers, in comparison to LB wafers. Furthermore, the COPs on the HB wafers can be more readily annihilated at relatively lower temperatures. In HB CZ silicon, the heavy boron-doping, on one hand, reduces the initial concentration of vacancies incorporated in the crystal; on the other hand, it enhances oxygen precipitation at high temperatures around 1150°C, which consumes a portion of the incorporated vacancies during crystal growth, thus further reducing the amount of vacancies contributing to void formation.
Optical Properties of High Energy Tin (Sn5+) Ion Irradiated Metal-Organic Chemical Vapor Deposition Grown GaN on Sapphire
Authors: Perumal Premchander , Ganaprakasam Sonia , Krishnan Baskar
Published: February 2005

Unintentionally doped n-type GaN(0001) epitaxial layers grown by metal-organic chemical vapor deposition (MOCVD) on sapphire substrates have been irradiated with 75 MeV Tin (Sn5+) ion. Effect of different ion fluences at 1011, 1012 and 1013 cm-2 were studied by means of time correlated single photon counting (TCSPC), UV-visible optical spectroscopy and photoluminescence (PL) measurements at room temperature. The exponential decay of minority carrier life times was observed between 1910 and 1110 ps (pico-second) with increasing ion doses upto 1013 cm-2. High-energy irradiation with different ion fluences of GaN epitaxial layers creates midgap states in the material. Change in the absorption edges between 3.41 and 2.95 eV were observed by UV-absorption coefficient (α2) method on increasing fluences rate. Band-edge and yellow emissions were recorded for all GaN samples by transient steady state PL measurement at room temperature.
Direct Measurement of Electrical Hysteresis of Micron-Sized Pb(Zr,Ti)O3 Capacitors using the Constant Current Method
Authors: Wang Ding-Yeong , Chang Chun-Yen
Published: February 2005

In this paper, we introduce a constant current method (CCM) for directly measuring the electrical hysteresis of micron-sized Pb(Zr,Ti)O3 capacitors prepared on Pt/Ta/SiO2/Si substrates. The parasitic effect of the probing setup is found to possibly increase the maximum polarization as the capacitor's area is reduced. The CCM technique can be exploited to calculate the parasitic capacitance of the probe station and then easily construct the corrected hysteresis loops. Additionally, the dielectric constants of small capacitors were measured using an LCR meter, for comparison with the linear dielectric constant obtained from the high-field slope of the hysteresis loops with parasitic correction. Strong agreement was found between the measured dielectric constants and the results obtained from the hysteresis loops. These results indicate that the CCM technique represents an approach for investigating the ferroelectric characteristics of small ferroelectric capacitors.
High-Transmittance Pixel- and Common-Electrode Structures Design for In-Plane Switching Mode with Low Crosstalk
Authors: Lin Jiunn-Shyong , Yang Kei-Hsiung , Chen Shu-Hsia
Published: February 2005

The replacement of cathode ray tube (CRT) by thin-film-transistor liquid-crystal display (TFT-LCD) in TV applications requires the implementation of LC modes with wide viewing angles and excellent video display quality. Although the in-plane switching (IPS) mode has been known as an excellent technology for realizing wide viewing angles, it has a low aperture ratio that has been improved by Advanced Super-IPS (AS-IPS). In this paper, we propose a novel electrode structure that not only increases substantially the aperture ratio of the current AS-IPS but also reduces the crosstalk in terms of a capacitive coupling ratio from 1.2% to 0.05%.
β-phase Formation Behavior of Homogeneous Fe–Si Alloy Solidified in Short-Duration Microgravity
Authors: Nagai Hideaki , Nakata Yoshinori , Okutani Takeshi
Published: February 2005

We studied the β-phase formation behavior of Fe–Si alloy with a 1:2 atomic ratio solidified in short-duration microgravity. Electron probe microanalyzer (EPMA) observation revealed that the sample solidified in microgravity had a homogeneous structure and composition of Si/Fe = 2.0 (atomic ratio), and transmission electron microscope (TEM) observation indicated that 10- to 20-nm-size particles were combined in the solidified sample. This sample did not include copper as an accelerator of the β-phase formation. The peritectoid reaction (α-FeSi2 + ε-FeSi→β-FeSi2) was completed at a temperature of 1050 K to form single-phase β-FeSi2 in the solidified sample. The β-FeSi2 phase began to decompose the ε-FeSi phase and α-FeSi2 phase when the sample was heated to 1273 K, and many small precipitants appeared in the sample. These precipitants coagulated and grew into larger particles with increasing temperature.
Study of Interdiffused Layers Near the Surface of Multilayers by Total-Reflection Soft-X-ray Fluorescence Spectroscopy
Authors: Imazono Takashi , Hirayama Yushi , Ichikura Shigeru , Kitakami Osamu , Yanagihara Mihiro , Watanabe Makoto
Published: February 2005

Using soft-X-ray fluorescence spectroscopy with photon incidence at a critical angle of total reflection, it was made clear that SiO2 existed within a depth of a few nanometers from the surface of Fe/Si multilayers. It was generated by oxidation of the interdiffused Fe3Si layer nearest to the topmost Fe layer. Consequently, the Fe3Si layer was found to decrease in thickness. This result suggests that the total-reflection soft-X-ray fluorescence spectroscopy is fairly useful to analyze the chemical state of elements to a depth of a few nanometers from the surface.
Pulse Radiolysis Study on Proton and Charge Transfer Reactions in Solid Poly(methyl methacrylate)
Authors: Nakano Atsuro , Okamoto Kazumasa , Kozawa Takahiro , Tagawa Seiichi
Published: February 2005

Poly(methyl methacrylate) (PMMA) is a good matrix for a case study aimed at understanding reaction mechanisms of electron beam, X-ray and EUV resists. Radiation-induced reactions and proton dynamics of solid PMMA were studied under room temperature by pulse radiolysis. PMMA samples were doped with pyrene (Py), crystal violet lactone (CVL) or an anion scavenger to observe charge and proton transfer reactions in the solid matrix. The time-dependent behavior of ionic radicals was observed with the time resolution of 10 ns. The electron transfer from PMMA anion radicals to the anion scavenger or Py was observed in the time range of several hundred nanoseconds. The dynamics of protons generated in irradiated PMMA was traced using CVL. The growth of optical absorbance attributed to proton adducts of CVL was observed in the time range of several hundreds minutes. Protons derived from PMMA cation radicals have a long lifetime and migrated in the solid PMMA matrix.
A Hot Cathode Magnetron Gauge using a Divergence-Type Magnetic Field for Electric Field Control
Authors: Nishikawa Eiichi , Iwabuchi Takenori , Asamaki Tatsuo , Masui Noriaki , Miura Tsutomu
Published: February 2005

A new sensitive type of magnetron gauge has been developed in order to obtain a linear response of ion current, I
i, to pressure, P, with a high sensitivity over a wide range. The gauge is equipped with two ion collectors. The ratio of the ion currents of the two ion collectors is measured and kept constant by controlling the filament voltage, in order to keep the electric field constant within the anode over a wide range of pressure measurement. When a divergent-magnetic field is applied to this hot-cathode magnetron gauge, the slope of the plot of the filament voltage vs the ratio of the ion current of the two separate two ion collectors is improved from -0.28 to +1.1–+3.9 (V-1). When the diameters of the ion collectors were investigated, it was found that the current ratio η=1 was attained when the outer diameters of the ion collectors were identical, and their inner diameters were 2 and 8 mm respectively. With this configuration, ion current was directly proportional to pressure in the range of 1×10-8–1×10-4 Pa.
Modeling and Simulation of a Bird's-eye-Type Ferrite Electromagnetic Wave Absorber For an Anechoic Chamber
Authors: Yoon Hyun Jin , Kim Dong Il
Published: February 2005

The purpose of this study is to design and fabricate an electromagnetic (EM) wave absorber in order to achieve the wide-band characteristic. We proposed and modeled a bird's-eye-type EM wave absorber using the equivalent material constants method (EMCM), and we evaluated it through simulation using the finite difference time domain (FDTD) method. The numerical simulation showed that a bird's-eye-type periodic structure has a better wide-band reflection-reducing characteristic than that of the cutting-cone-type EM wave absorber. The validity of the proposed model was confirmed by comparison with a model with experimental results.
Boundary Detection Method for Ultrasound Diagnostic Images Using Region-Growing Approach
Authors: Oshiki Mitsuhiro , Shinomura Ryuuichi , Mitake Tsuyoshi , Sakurai Tomoo , Matsuura Shigeo , Harada Jyunta
Published: February 2005

We have proposed a boundary detection method for ultrasound diagnostic images using the Region-Growing method, which is mainly applicable to the detection of cysts. Region-Growing method, which extracts the region of interest using the image's brightness value, is optimized to be applicable to ultrasound diagnostic images. There are some cases in which the boundary is unclear in ultrasound diagnostic images, because the difference in acoustic impedance between two neighboring areas of tissue is small. In such cases, a satisfactory result cannot be obtained only by using the intensity value of the ultrasound diagnostic image. By applying the signal processing to enhance the brightness value transition, we can more easily find the boundary accurately. We adapted this method to be applicable to the diagnostic images of, for example, hyper, hypo, cystic, and mixed echoic lesions, and we confirmed that the boundary of the region of interest is obtained.
Schematics and Atomistic Simulations of Nanomemory Element Based on Carbon Tube-to-Peapod Transition
Authors: Kang Jeong Won , Hwang Ho Jung
Published: February 2005

We suggested and investigated a nonvolatile nanomemory element based on carbon nanopeapods using molecular dynamics simulations. The suggested system was composed of two carbon nanotubes and fully ionized endo-fullerenes. The two carbon nanotubes were placed face to face and the endo-fullerenes came and went between the two carbon nanotubes under alternatively applied force fields. Since the electronic properties of carbon nanotubes are changed by the endo-fullerene intercalation, the bit classifications can be achieved from the detection of these changes by the endo-fullerenes intercalation under the applied force fields. Since the endo-fullerenes encapsulated in the carbon nanotubes hardly escape from the carbon nanotubes, the proposed system can be considered to be a nonvolatile memory device. Several switching processes were investigated for external force fields and temperatures using molecular dynamics simulations.
Structure Identification of a C60 Dimer using Electrical Mobility Measurements
Authors: Tanaka Hideki , Takeuchi Kazuo
Published: February 2005

C60 particles were formed by a C60 vapor source equipped with an 241Am ionizer, and their mobility was measured using a differential mobility analyzer (DMA). Two distinct peaks for the C60 monomer and the C60 dimer were observed in the mobility spectra. When the measured mobility was compared with theoretical mobilities for several isomers of the C60 dimer, the C60 dimer was suggested to have the geometric structure of a [2+2] 66/66 cycloadduct C60 dimer. Selective formation of the [2+2] C60 dimer was also suggested when the peak profile for the C60 dimer was analyzed using the transfer function for the DMA. The formation mechanism of the [2+2] C60 dimer in the gas phase is discussed.
Friction and Pull-Off Forces on Submicron-Size Asperities Measured in High-Vacuum and in both Dry and Humid Nitrogen at Atmospheric Pressure
Authors: Ando Yasuhisa
Published: February 2005

Asperities having spherical peaks were fabricated on a silicon substrate using a focused ion beam. Pull-off and friction forces were measured on each asperity using atomic force microscopy (AFM) in a high vacuum (HV) of 2×10-5 Pa and in both dry and humid nitrogen at atmospheric pressure. The radius of curvature of the asperity peaks ranged from 70 to 610 nm. The probe of the AFM cantilever had a flat square tip, approximately 1×1 µm2 in area. The results showed that the pull-off force was roughly proportional to the radius of curvature of the asperity peaks in each atmosphere. The friction force was proportional to the pull-off force. The gradient of the friction force against the pull-off force was slightly higher in the humid nitrogen than in the HV, which suggests the viscous resistance of the capillary is part of the friction force. The friction force in HV increased with lower sliding velocities without heating the substrate, which suggests the capillary also has a lubricating effect that prevents direct solid contact.
Nanoscale Imaging of Biomolecules by Controlled Carbon Nanotube Probes
Authors: Chang Yuan Chih , Chang Chia Seng , Wang Dau Chung , Lee Ming-Hui , Wang Ting-Fang , Wu Mei-Yueh , Fu Tsu-Yi , Tsong Tien T.
Published: February 2005

We use a carbon nanotube (CNT) probe to observe the details in double-stranded deoxyribonucleic acid (DNA) and proteins under atomic force microscopy (AFM) tapping mode in air. The DNA has periodic helical turns of approximately 4 nm interval. Fine ring like and helical structures in the proteins adsorbed on graphite have also been resolved. These results cannot be reproduced using conventional AFM silicon probes. The superiority of the CNT probe applied with the AFM tapping mode lies in both the unique mechanical and chemical properties of the carbon nanotube, and in our ability to tailor the length and adjust the angle of the CNT probe attached to a commercial AFM tip.
Observation of Self-Assembled Monolayer Using the Lateral Resonance of the Cantilever in the Contact and Noncontact Regions
Authors: Hoshi Yasuo , Kawagishi Takayoshi , Kawai Shigeki , Kobayashi Dai , Kim Janggil , Cho Young-Hak , Takeuchi Shoji , Kim Beomjoon , Kawakatsu Hideki
Published: February 2005

A new imaging method utilizing the lateral resonance vibration of a cantilever in atomic force microscopy was applied to evaluate microcontact printed patterns of self-assembled monolayers. The lateral resonance vibration of a cantilever was excited by the feedback of the torsional signal detected optically to a shear piezo set at the base of the cantilever. The amplitude and frequency shift of the vibration were mapped as images in air and in vacuum. The phase-separated patterns of octadecanethiol and 16-mercaptohexadecanoic acid on gold substrates were observed in air using a contact-mode cantilever and -CH3-terminated cantilever, respectively. In most cases, amplitude mapping showed a similar contrast to friction force microscopy but with a better lateral resolution and contrast. In the case where the vibration amplitude was smaller than 3 nm, adhesive force was dominant on the image contrast. The observation using a noncontact-mode cantilever in vacuum gave a good contrast, where the tip-sample distance was controlled by maintaining a set lateral amplitude.