bluuebunny/crossref_metadata_2025 huggingface dataset:
Difference in Simulated Low-Frequency Sound Propagation in the Various Species of Baleen Whale
Authors: Tsuchiya Toshio , Naoi Jun , Futa Koji , Kikuchi Toshiaki
Published: February 2005

Whales found in the north Pacific are known to migrate over several thousand kilometers, from the Alaskan coast where they heartily feed during the summer to low latitude waters where they breed during the winter. Therefore, it is assumed that whales are using the “deep sound channel” for their long-distance communication. The main objective of this study is to clarify the behaviors of baleen whales from the standpoint of acoustical oceanography. Hence, authors investigated the possibility of long distance communication in various species of baleen whales, by simulating the long-distance propagation of their sound transmission, by applying the mode theory to actual sound speed profiles and by simulating their transmission frequencies. As a result, the possibility of long distance communication among blue whales using the deep sound channel was indicated. It was also indicated that communication among fin whales and blue whales can be made possible by coming close to shore slopes such as the Island of Hawaii.
A New Nonlinear Dynamic Analysis for Myocardial Tissue Characterization: Studies on the Method of Surrogate Echo Data
Authors: Sonoyama Teruyuki , Harada Akimitsu , Yamamoto Kazuhiro , Masuyama Tohru
Published: February 2005

The purpose of this study is to quantify the characterization of myocardial tissue using the method of surrogate echo data and chaos analysis. Myocardium RF ultrasonic echo signals were obtained from healthy subjects and patients with dilated cardiomyopathy (DCM). This surrogate method is a null hypothesis test to differentiate a deterministic process from a stochastic one using translation error. The result of the translation error from the obtained data was about half of that from the surrogate data sets. Since the obtained data showed a higher degree of determinism, we confirmed that myocardial dynamics is dominated by a deterministic process, and found that there are significant differences in deterministic values between healthy subjects and DCM patients. These results suggest that the proposed nonlinear dynamic analysis from the reconstructed echo signals is useful in myocardial tissue characterization.
Activation of Electrode Surface on Silicon Solar Cell Using Dielectric Barrier Discharge
Authors: Sakoda Tatsuya , Matsukuma Kunihiro , Araki Ichiro , Sung Youl-Moon , Terakawa Takeshi , Furukawa Katsuhiko
Published: February 2005

To yield an activated electrode surface on a silicon solar cell, a surface treatment was examined using a dielectric barrier discharge instead of a wet cleaning technique. After the dry cleaning process using the dielectric barrier discharge, the surface state and the fill factor of the solar cell were evaluated. The results showed that the dielectric barrier discharge plasma could effectively activate the electrode surface of the solar cell in a relatively short time. Additionally, it was found that the surface treatment on finger electrodes played an essential role in the improvement of the fill factor.
Nonequilibrium Occupancy of Dangling Bond Defects in Undoped Amorphous Silicon Studied by Subgap-Light-Induced Electron Spin Resonance
Authors: Hattori Kiminori , Abe Syuya , Okamoto Hiroaki
Published: February 2005

A detailed investigation of the nonequilibrium occupancy of band tail states and dangling bond (DB) states in undoped amorphous silicon has been performed using the subgap-light-induced electron spin resonance (subgap LESR) technique. Measurements performed over a wide range of excitation intensities and temperatures reveal a systematic change of the LESR line-shape. Lowering the excitation intensity transforms the superposition of band-tail electron and hole absorption lines, corresponding to the creation of these carriers, into a reversed single DB line, corresponding to the annihilation of neutral DB states. The LESR behavior is reasonably well interpreted in terms of the charge neutrality requirement for band-tail carriers and charged DBs under illumination. A careful inspection of the experimental results on the basis of numerical calculation as well as analytical consideration proves that neutral DBs predominantly occur in thermal equilibrium, and that the ratio of charged to neutral defect density is not more than 10%.
Variable Body Effect Factor Fully Depleted Silicon-On-Insulator Metal Oxide Semiconductor Field Effect Transistor for Ultra Low-Power Variable-Threshold-Voltage Complementary Metal Oxide Semiconductor Applications
Authors: Ohtou Tetsu , Nagumo Toshiharu , Hiramoto Toshiro
Published: February 2005

We propose the concept of a variable body effect factor Fully Depleted Silicon-On-Insulator Metal Oxide Semiconductor Field Effect Transistor (FD SOI MOSFET) in which the body effect factor is varied by the substrate depletion capacitance. In this device, both higher drive current in the active mode and low leakage current in the standby mode can be obtained in the variable threshold voltage scheme. In the active mode, the body effect factor is reduced by the substrate depletion capacitance and the drive current increases. In the standby mode, the substrate is inverted or accumulated, and the depletion layer capacitance is neglected, resulting in a larger body effect factor that suppresses the standby subthreshold current. We demonstrate the validity of the proposed scheme with two-dimensional simulations and experiments.
Electron Transport Properties in Lightly Si-doped InGaN Films Grown by Metalorganic Vapor Phase Epitaxy
Authors: Wang Chengxin , Maeda Narihiko , Tsubaki Kotaro , Kobayashi Naoki , Makimoto Toshiki
Published: February 2005

The electronic properties of Si-doped InGaN thin films with different In compositions were investigated. The samples were grown by metalorganic vapor phase epitaxy (MOVPE), and then evaluated using photoluminescence, X-ray diffraction and variable temperature Hall effect measurements. The Si donor activation energy was found to decrease with the increase in In composition of InGaN as a result of shrinking bandbap energy, and determined to be 17 meV, 10 meV and 6 meV for 4%, 9% and 13% of In compositions through the least square fitting of experimental carrier concentrations versus temperatures. InGaN alloy with 9% of In composition exhibited the best electronic properties with the lowest compensation ratio and the highest mobilities among those three samples over the whole range of measurement temperature. The relatively high mobility of 227 cm2/Vs at room temperature was achieved in this sample. Scattering mechanism in InGaN alloy was also studied using a simple model.
Two-Dimensional Electron Gas Recombination in Undoped AlGaN/GaN Heterostructures
Authors: Martínez-Criado Gema , Miskys Claudio , Karrer Uwe , Ambacher Oliver , Stutzmann Martin
Published: February 2005

The radiative recombination of a two-dimensional electron gas (2DEG) was investigated in Al0.30Ga0.70N/GaN single heterostructures (SHs) without intentionally doping the barrier material, i.e., where the 2DEG appears at the interface due only to polarization effects. In addition to the typical excitonic transitions and the LO-phonon replicas originating from the GaN flat-band region, the photoluminescence spectra displayed three well-defined transitions. Their small binding energies and the observed blue shift with the excitation density suggested the association of these new emissions to quasi-2D excitons. On the basis of the thermal and excitation power dependences, the transitions were assigned to interface excitonic lines. Applying a weak electric field parallel to the growth direction, which depletes the triangular well, corroborated the 2DEG nature.
Effect of Oxygen Impurity on the Production of Room-Temperature Stable Metastable Defects in n-Type Silicon Implanted with Hydrogen Ions at 88 K
Authors: Tokuda Yutaka , Sugiyama Takahide , Iwata Hiroyuki , Ishikko Masayasu
Published: February 2005

The effect of oxygen impurity on the production of room-temperature stable metastable defects has been studied in n-type silicon implanted with hydrogen ions at 88 K. Deep-level transient spectroscopy measurements have been performed for implanted epitaxial-(Epi) and Czochralski-grown (CZ) samples. It is found that three metastable defects (E
c–0.29, 0.41 and 0.55 eV) are observed in implanted CZ samples as already reported, while no production of metastable defects is revealed in Epi samples. This indicates that metastable defects are hydrogen-related defects involving oxygen.
Michelson Interferometer-Type Wavelength Converter Integrated with Multimode Interference Coupler; Fundamental Characteristics
Authors: Yoshioka Keitaro , Miyazaki Kohji , Utaka Katsuyuki , Uchida Kei , Matsumoto Atsushi
Published: February 2005

We proposed and investigated a Michelson interferometer-type wavelength converter with a multimode interference coupler (MIWC-MMIC) as one of the key devices in future DWDM photonic switching networks. The MIWC-MMIC is compact and efficient due to its Michelson interferometer-like structure, which uses an MMIC simultaneously as input and output-side couplers. The dependence of the output characteristics on structural parameters, such as the power-division ratio of the MMIC and the reflection coefficient at semiconductor optical amplifier (SOA) ends, was analyzed to optimize the structure for operation with a low excess loss and a low signal light power. The device was actually fabricated and its preliminary static characteristics were measured. The cross modulation of the converted light by 9.0 dB was attained by introducing a signal light with a power of about -5 dBm.
Low-Fire Processing of CaTiO3 with 2ZnO–B2O3 Glass
Authors: Huang Chiao-Chan , Jean Jau-Ho
Published: February 2005

The effects of 2ZnO–B2O3 (2ZB) glass addition on the densification and dielectric properties of CaTiO3 (CT) have been investigated. With the 2ZB glass content greater than 20 vol%, the densification temperature can be greatly reduced from 1300°C for pure CT to 875–925°C for CT+2ZB dielectric ceramics. The above result is attributed to a chemical reaction taking place at the interface of 2ZB/CT during firing. The Ca in CT dissolves into 2ZB, forming a new glass of CaO–ZnO–B2O3 at 840–860°C which enhances the densification kinetics of 2ZB+CT dielectric ceramics. For the samples with 20–40 vol% 2ZB, the resulting 2ZB+CT ceramics have a dielectric constant of 60-90 and dielectric loss of less than 0.15% at frequencies below 13 MHz.
A Consideration of the Deposition Process of Polypyrrole Ultrathin Films on the Positively Charged Substrate
Authors: Onoda Mitsuyoshi , Shinkuma Akira , Tada Kazuya , Shirashige Michihiro
Published: February 2005

In in situ polymerized polypyrrole (PPy), the deposition process strongly depends on the nature of the substrate surface. That is, for a surface that is negatively charged, there is a linear correspondence between dipping time and the amount of PPy deposited on the substrate. However, in the case of a positively charged surface, there is an apparent rest period of approximately 10–20 min, during which no PPy is deposited. From optical absorption spectroscopy and photoelectron emission studies etc., it became clear that oligomers of pyrrole were adsorbed on the positively charged surface during the rest period, as a result the polymerization reaction of PPy could proceed.
SiO2 Hole Etching Using Perfluorocarbon Alternative Gas with Small Global Greenhouse Effect
Authors: Ooka Masahiro , Yokoyama Shin
Published: February 2005

The etching of contact holes of 0.1 µm size in SiO2 is achieved using, for the first time, cyclic (c-)C5F8 with a small greenhouse effect in the pulse-modulated inductively coupled plasma. The shape of the cross section of the contact hole is as good as that etched using conventional c-C4F8. It is confirmed that Kr mixing instead of Ar in the plasma does not change the etching characteristics, although lowering of the electron temperature is expected which reduces the plasma-induced damage. Pulse modulation of the plasma is found to improve the etching selectivity of SiO2 with respect to Si. Langmuir probe measurement of the plasma suggests that the improvement of the etching selectivity is due to the deposition of fluorocarbon film triggered by lowering of the electron temperature when the off time of the radio frequency (rf) power is extended.
Preparing Single Ions in m=0 States in the Lamb-Dicke Regime
Authors: Kajita Masatoshi , Matsubara Kensuke , Li Ying , Hayasaka Kazuhiro , Hosokawa Mizuhiko
Published: February 2005

When a trapped ion is used for optical frequency standards, it is usually cooled by laser radiation and then pumped to the m=0 state. However, simple laser cooling cannot be applied to some ion species due to the formation of the dark state. This paper shows theoretically that such ions can also be cooled to the Doppler limit and can be prepared in the m=0 state by three laser beams with different polarizations and frequency detunings.
Picogram Mass Sensor Using Resonance Frequency Shift of Cantilever
Authors: Sone Hayato , Fujinuma Yoshinori , Hosaka Sumio
Published: February 2005

A microsensor with a picogram mass sensitivity has been researched using the resonance frequency shift of an atomic force microscope (AFM) cantilever. The mass change of the water molecules adsorbed on the cantilever was measured by analyzing the resonance frequency shift using a laser beam deflection detection system. As experimental results, a sensitivity of about 2 pg/Hz was obtained. The mass change due to increasing humidity showed that the mechanism of water molecular growth changed from an island growth to a layer growth. The critical point of the mechanism change was a humidity of about 60%. The adsorbed mass corresponds to a water layer of about 12 monolayers.
Characterizing Optical Constants of Thin Films for Vacuum Ultraviolet Lithography Applications
Authors: Fan Wonder , Chen Hsuen-Li , Wu Chi-Lung , Chang-Liao Kuei-Shu
Published: February 2005

The determination of optical constants of thin films is an important requirement for the study of masks, antireflective coatings, and resist materials used in the vacuum ultraviolet (VUV) lithography process. We demonstrate a simple method for determining optical constants by measuring the reflectance of thin films with different incidence angles. In order to obtain accurate optical constants, the measurement of reflectance, incidence angles and thickness should be confirmed carefully. In addition, thickness measurements are not important for thick high-absorption films. The measured reflectance should be modified by the surface roughness of thin films particularly in vacuum ultraviolet regimes. The optical constants of various materials were obtained experimentally by this method without using complicated mathematics models.
Impact of Latent Image Quality on Line Edge Roughness in Electron Beam Lithography
Authors: Yoshizawa Masaki , Moriya Shigeru , Nakano Hiroyuki , Shirai Yuichi , Morita Tatsuo , Kitagawa Tetsuya , Miyamoto Yasuyuki
Published: February 2005

The impact of latent image quality on line edge roughness (LER) in 100, 50 and 2 keV electron beam lithography was investigated. There is a minimum LER of about 2 nm achievable with current resist systems though the LER increases as a result of the amplification of bandwidth of the threshold level by the slope of the quasi-beam profile (QBP), which is a latent image profile in which the line spread function is assumed to be Gaussian. A plausible cause of the minimum LER is the domain size of resist materials such as polymer/monomer aggregation. Analysis of the LER dependence on the 1/slope revealed the origins of the bandwidth of the threshold level: variation of the latent image profile in terms of image blur and intensity. Independent of the electron energies and resists used, the resolution of an isolated line was proportional to the blur of the QBP with an intrinsic resolution of the resists about 5 nm which has been ignored for photolithography.
Nanoscale Device Modeling and Simulation: Fin Field-Effect Transistor (FinFET)
Authors: Kim Kidong , Kwon Ohseob , Seo Jihyun , Won Taeyoung
Published: February 2005

The device performance of nanoscale fin field-effect transistor (FinFET) was investigated by numerically solving coupled Poisson-Schrödinger equations in a self-consistent manner. The number of fins was varied in order to optimize the current driving capability of FinFET. The simulation results were compared with the experimental results in order to verify the validity of the proposed quantum mechanical approach. Device optimization was theoretically performed in order to suppress the short-channel effect in terms of subthreshold swing, threshold voltage roll-off, and drain-induced barrier lowering. Quantum mechanical simulation results were also compared with the results from the classical approach in order to understand the influence of electron confinement. Our simulation results indicate that quantum mechanical simulation is essential for the realistic optimization of the FinFET structure.
Nanoscale Variable Resistance Using Interlayer Sliding of Multiwall Nanotube
Authors: Akita Seiji , Nakayama Yoshikazu
Published: February 2005

We have proposed nanoscale variable resistors using a sliding mechanism of an interlayer of individual multiwall carbon nanotubes. The resistor was fabricated using a combination of a well-controlled electrical breakdown process and a manipulation process using a scanning electron microscope. The two-terminal resistance of the processed nanotube increases exponentially with the sliding distance under a low bias voltage and is proportional to the sliding distance under a high bias voltage.
Ab initio Investigation of the Early Stage of Nano-scale Thin Film Growth: Al and Co Adatoms on Co (111) Surface
Authors: Kim Chiho , Kim Sang-Pil , Kim Yoon-Suk , Kim Hanchul , Chung Yong-Chae
Published: February 2005

We considered the diffusion behavior which occurred in the initial stages of thin film deposition for the fabrication of a tunneling magneto-resistance (TMR) junction with the use of the density functional theory (DFT). An Al adatom deposited on the Co (111) substrate had the most stable configuration when it was adsorbed on the hcp site and the energy barrier for the diffusion to the neighboring fcc or hcp site was sufficiently low for the Al adatom to move freely. The energy barrier for the Co on the Co substrate was approximately 1.6 times higher than that for the case of Al on a Co substrate. The energies for the step down (step energy barrier) of an adatom from the top of the adatom trimer were estimated as 0.54 eV and 1.09 eV for Al/Al trimer/Co and Co/Co trimer/Co, respectively.
Multiple Flow Switch Using Stepwise Sheath Flow
Authors: Kanai Masaki , Otsuka Shin-ichiro , Nakanishi Hiroaki , Shoji Shuichi
Published: February 2005

In this paper we present a concentration-conservative flow switch using a sheath flow. A novel concept of stepwise flow was proposed to prevent the sample dilution during flow switching. Computational fluid dynamics (CFD) simulations revealed that the stepwise flow suppressed a back flow of the sample reagent that caused the sample dilution. Based on the CFD simulation results, the prototype devices of the flow switch utilizing the stepwise flow were designed. Using fabricated devices, reduction of the sample dilution by the stepwise flow was confirmed. In order to reduce the switching time, pneumatic microvalves were integrated with the flow switch. Its characteristic of the switching time was evaluated experimentally. The switching time was about 130 ms, which was reduced to less than half compared to the case of using off-chip valves. In the case that the sample flow rate is 1 µL/min, it is expected that the flow switch will achieve fluid sampling with the accuracy of the order of nanoliters.
Characteristics and Modeling of a Nonplanar Nonrectangular Metal Oxide Semiconductor Field Effect Transistor for Charge Sensing in the Si Micro-Fluidic Channel
Authors: Lim Geunbae , Kim Dong-Sun , Lyu Hong-Kun , Park Hey-Jung , Shin Jang-Kyoo , Choi Pyung , Lee Jong-Hyun , Lee Minho
Published: February 2005

In this work, a nonplanar, nonrectangular metal-oxide-semiconductor field effect transistor (MOSFET) with an asymmetrical channel structure for sensing charge in the Si micro-fluidic channel was fabricated, and the electrical characteristics of the fabricated three-dimensional (3-D) MOSFET were measured. The device was formed in the convex corner of a Si micro-fluidic channel using tetramethyl ammonium hydroxide (TMAH) anistropic etching solution, so that it would be suitable for combination with a micro-fluidic system. We approximated the nonplanar, nonrectangular 3-D MOSFET to a two-dimensional rectangular structure using the Schwartz-Christoffel transformation. The LEVEL1 device parameters of the 3-D MOSFET were extracted from the measured electrical device characteristics and were used in a simulation program with integrated circuit emphasis (SPICE) simulation. The measured and simulated results for the 3-D MOSFET were compared and found to show good agreement. We also investigated the feasibility of the proposed 3-D MOSFET as a charge sensor for detecting charged biomolecules.
Fabrication of Polycrystalline Silicon Field Emitter Arrays with Hafnium Carbide Coating for Thin-Film-Transistor Controlled Field Emission Displays
Authors: Nagao Masayoshi , Sacho Yutaka , Sato Takanobu , Matsukawa Takashi , Kanemaru Seigo , Itoh Junji
Published: February 2005

Hafnium Carbide (HfC)-coated polycrystalline silicon (poly-Si) field emitter arrays (FEAs) were fabricated on an oxidized silicon wafer. The HfC coating layer was deposited by inductively coupled plasma-assisted magnetron sputtering. The effect of the HfC thickness on the emission characteristics was investigated by depositing 15-nm- and 30-nm-thick HfC on the tip. The thinner HfC could effectively improve the emission characteristics of poly-Si FEA, while the thicker one degrades the emission. Two methods of tip sharpening were also investigated: one is thermal oxidation sharpening which is commonly used for Si FEA fabrication, and the other is Ar ion sputtering. The apex radius of the thermally oxidized FEA was much smaller than that of the sputter-sharpened one. However, some irregularly shaped tips were found in the oxidized FEA, which are responsible for gate current. The detailed fabrication and emission characteristics, including gate current, will be reported.
A Novel Wet Etching Process of Pb(Zr,Ti)O3 Thin Films for Applications in Microelectromechanical System
Authors: Zheng Kelu , Lu Jian , Chu Jiaru
Published: February 2005

The wet etching of Pb(Zr,Ti)O3 (PZT) thin films has gained considerable attention in microelectromechanical systems (MEMS) since it is economical and effective compared with dry-etching methods. In this paper, a novel wet-etching process is proposed for PZT thin film patterning using 1BHF:2HCl:4NH4Cl:4H2O solution as the etchant, where NH4Cl is used as an additive to decrease the undercutting of the obtained PZT pattern. According to energy dispersion spectroscopy (EDS) analysis and X-ray diffraction (XRD) patterns, PbClF particles were left as residues on the substrate after etching using 1BHF:2HCl:4NH4Cl:4H2O solution. Therefore, an additional 2HNO3:1H2O etching process was applied to convert PbClF to PbCl2, which can be dissolved completely in deionized water. This process exhibits a high etching rate (0.016 µm/s) and good selectivity over the photoresist and Pt bottom electrode. Using this technique, PZT patterns with acceptable undercutting (1.5:1) can be obtained.
Nucleation of W during Chemical Vapor Deposition from WF6 and SiH4
Authors: Kajikawa Yuya , Tsumura Takeshi , Noda Suguru , Komiyama Hiroshi , Shimogaki Yukihiro
Published: February 2005

A gas mixture of tungsten hexafluoride (WF6) and silane (SiH4) is generally used to form the initial layer of tungsten (W) on titanium nitride (TiN). However, the nucleation mechanism is still not clear, thus making it difficult to optimize such processes for complete filling of via holes. Therefore, in this study, we examined the nucleation process by laser-reflection measurements, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). These measurements indicate that W nucleation has two stages: monolayer formation followed by nucleation of three-dimensional (3D) islands. The monolayer formation can be expressed as Langmuir-type adsorption, and proceeds with the reduction of WF6 by Ti on TiN substrates. After monolayer formation, nucleation of 3D islands occurs and islands rapidly grow. These processes were quantitatively modeled using a simple rate equation. The results of our model agree well with our measurements of the deposited amount and coverage of islands.
High-Beam-Current Microcolumns with Large Apertures
Authors: Park Sung-Soon , Kim Dae-Wook , Ahn Seungjoon , Kim Young Chul , Choi Sang-Kook , Kim Dae-Yong , Kim Ho Seob
Published: February 2005

High-beam-current microcolumns with large apertures were fabricated using a new process to improve etch uniformity and the quality of apertures of microlens. The properties of microcolumns were examined by varying the beam energy from 200 to 800 eV. The probe beam current of the sample was measured to be up to ∼5 nA at a total beam current of ∼1 µA and a working distance of ∼1 mm. The microcolumns readily distinguished carbon nanotube (CNT) sample wires with a diameter of 100 nm. The fabrication processes and the properties of high-beam-current microcolumns are presented.
Analyses of Alignment Measurement Error
Authors: Sugaya Ayako
Published: February 2005

In the progress of ULSI, alignment technology must have a high accuracy in all processes, even if the alignment mark is asymmetric and/or with a low step height. To satisfy such requirements, the alignment measurement errors and the pattern shape are studied and analyzed mathematically. In order to obtain a solution for these errors, our developed alignment technique, focus optimization of a field image alignment sensor (FFO), is studied and analyzed. The phase shift of diffraction rays obtained by FFO removes the image distortion caused by the asymmetrical distribution of the diffraction rays, and realizes alignment with a high accuracy. These analyses lead to a deep understanding of the alignment measurement errors and FFO effects. The advantages of FFO for future-generation ULSI production are confirmed.
Organic Photonic Crystal Band Edge Laser Fabricated by Direct Nanoprinting
Authors: Yokoo Atsushi , Suzuki Hiroyuki , Notomi Masaya
Published: February 2005

A direct nanoprinting technique is used to fabricate a pit arrangement on the surface of an organic amorphous emissive layer. A pit arrangement with a closely packed hexagonal pattern with a 400 nm pitch is successfully fabricated within 60 s. Pit depth is more than 70 nm and depends on press pressure. The fabricated structure is considered to be a photonic crystal band edge laser, and laser oscillation is confirmed by optical excitation. It is also confirmed that the oscillation threshold can be controlled simply by changing the press pressure used in the direct nanoprinting procedure. The results show that the use of the direct nanoprinting technique enables the fabrication of organic nanostructure devices such as photonic crystal band edge lasers with an organic emissive material.
Fabrication of Mold Master for Spiral Microcoil Utilizing X-Ray Lithography of Synchrotron Radiation
Authors: Mekaru Harutaka , Kusumi Shinji , Sato Noriaki , Yamashita Michiru , Shimada Osamu , Hattori Tadashi
Published: February 2005

To produce three-dimensional and precise microstructures on a small curved surface, we developed a high-precision 3-dimensional X-ray lithography technique. We succeeded in the production of a master of a metallic mold used for mass producing a spiral microcoil with a diameter of 0.48 mm and a length of 1 mm using this technique. An exposure stage controllable by piezoelectric elements and stepping motors was developed. The adhesion between a resist material and a substrate material was enhanced. We investigated about the effect that X-ray diffraction rounds the edge of a pattern, and a process flow was produced. This product has polymethylmethacrylate (PMMA) spiral microstructures with a line width of 10 µm, a thickness of 10 µm, and a pitch of 20 µm.
Migration-Enhanced Epitaxy of Cubic BN: An Ab Initio Study
Authors: Koga Hiroaki , Miyazaki Tsuyoshi , Watanabe Satoshi , Ohno Takahisa
Published: February 2005

Migration-enhanced epitaxy (MEE) is shown to be promising as a nonenergetic epitaxial growth method of cubic BN (cBN) for the first time, by examining the deposition of N (B) atoms on the B (N) surface of cBN(001) with ab initio calculation. We find that MEE has the potential for realizing the layer-by-layer epitaxial growth of cBN on cBN(001), owing to the epitaxial nature of monolayer deposition, the saturation of N adsorption at monolayer coverage, the high mobility of a B adatom on a B island which favors the formation of a flat B surface, and the B–N exchange reaction which repairs the defects created by the excess N (B) adatoms on the N (B) surface.
Structure and Magnetic Properties of Iron Nitride Films Prepared by Reactive dc Magnetron Sputtering
Authors: Naganuma Hiroshi , Nakatani Ryoichi , Endo Yasushi , Kawamura Yoshio , Yamamoto Masahiko
Published: February 2005

We have investigated the structure and magnetic properties of iron nitride films prepared by reactive dc magnetron sputtering with an argon gas flow rate of 12 sccm and a nitrogen gas flow rate varied between 0–10 sccm. Under the above conditions, the nitrogen concentrations in the iron nitride films were changed from 0 to 33 at.%. The phase and structure of the films changed from α-Fe, amorphous matrix with nanocrystallites of ε-Fe3N, ε-Fe
x
N (2<x≦3) to ζ-Fe2N phase as the nitrogen concentration of the iron nitride films increases, and these changes in the phase almost correspond to the Fe–N phase diagram. The saturation magnetization of the iron nitride films decreases as the nitrogen concentration increases up to 31 at.%, and disappears at 33 at.%. A relatively low coercivity of 9 Oe is observed at the nitrogen concentrations from 11 to 18 at.%. From the results of structural analysis and magnetic measurements, it is confirmed that the coercivity of the iron nitride films mostly correlates with the changes in grain size.
Simultaneously Gain-Flattening and Gain-Clamping Technique for Erbium-Doped Fiber Amplifiers by Backward Injection of a Fabry–Perot Laser Light
Authors: Yeh Chien-Hung , Lai Kuo-Hsiang , Lee Chien-Chung , Chi Sien
Published: February 2005

An active control technique of obtaining simultaneously gain-flattened and gain-clamped spectra for erbium-doped fiber amplifiers (EDFA) has been proposed and experimentally demonstrated by injecting Fabry–Perot (F–P) laser light into the EDFA. In the demonstration, our EDFA module could simultaneously reduce gain variation from 10.8 dB to 1.1 dB for a 10 dB input power change and reduce gain flatness from 11.6 dB to 2.0 dB over the operating wavelength range of 1528 nm to 1560 nm.
Electronic Structures of Polyheterole Monomers, Oligomers, Polymers and Their Block Copolymers
Authors: Narita Yuki , Hagiri Ikuya , Takahashi Norihiko , Takeda Kyozaburo
Published: February 2005

We have theoretically investigated the electronic structures of polyheterole, monomers, oligomers, polymers and their block copolymers. We considered here the poly-homo-heteroles (X) of borole (B), pyrrole (N), phosphole (P), furan (O), thiophene (S), selenophene (Se), and tellurophene (Te). Based on the Hückel approach, we first predicted the electronic structures of those homogeneously catenated heteroles and extracted their electronic characteristics by the Hartree–Fock ab initio method. Then, we studied the electronic structures of those block copolymers having a heterogenous catenation of the BX- or BXB-types.
Microstructure and Microwave Dielectric Properties of SnO2-Added Ba(Zn1/3Ta2/3)O3 Ceramics
Authors: Kim Min-Han , Kim Beom-Jong , Nahm Sahn , Lee Woo-Sung , Yoo Myong-Jae , Kang Nam-Kee , Lee Hwack-Joo , Kim Young-Sik , Ryou Sun-Youn
Published: February 2005

The Ba(Zn1/3Ta2/3)O3 (BZT) ceramic normally has a 1:2-ordered hexagonal structure, but it changes to the 1:1-ordered cubic structure with the addition of SnO2. When SnO2 was added to the BZT ceramics, grain growth occurred and the liquid phase formed. The liquid phase was responsible for the grain growth. The Q×f value of the BZT ceramic significantly increased with the addition of a small amount of SnO2. Since the degree of 1:2 ordering and the relative density decreased with the addition of SnO2, the enhancement of the Q value cannot be explained by the 1:2 ordering and the relative density. On the other hand, the improvement of the Q value could be related to the increase in the grain size because the average grain size increased with the addition of SnO2. However, when a large amount of SnO2 was added, the Q value was very low. The low Q value was explained by the low relative density and the presence of a large amount of Ba3Ta5O15 phase.
Electric-Field-Induced Layer Rearrangement in the Smectic A Phase of Nonsymmetric Dimeric Liquid Crystal
Authors: Jo Jae Shin , Nakajima Takaaki , Ozaki Masanori , Yoshino Katsumi , Narumi Tsuyoshi , Dewa Harutada , Yoshizawa Atsushi
Published: February 2005

A field-induced smectic layer rearrangement has been investigated in the smectic A phase of non-symmetric dimeric liquid crystals possessing cyanobiphenyl and phenylpyrimidine groups. The dimerization of mesogens likely lowers the stability of smectic layer structures, and smectic layers are rearranged by applying a low electric field in both planarly and homeotropically aligned cell geometries.
Crystal Orientation Change of Ni Films by Sputtering in Ar-N2 Mixed Gases
Authors: Kawamura Midori , Iibuchi Kyouhei , Abe Yoshio , Sasaki Katsutaka
Published: February 2005

Changing the crystal orientation of Ni films by the effect of reactive gas is attempted. It is known that (111)-oriented Ni film is usually obtained by sputtering in pure Ar gas. However, we report that almost single-oriented (100) Ni films are prepared by rf sputtering when a small amount of N2 (1% < N2 flow ratio < 7%) is mixed with Ar gas. By electrical resistivity measurement and Auger electron spectroscopy (AES), the presence of nitrogen in the (100) Ni films is not observed. Consequently, it is found that nitrogen influences the crystal orientation at the growing film surface but is not incorporated into the films. This enables us to prepare Ni films with either (111) orientation or (100) orientation by sputtering in a controlled manner without a postannealing process.
Characteristics of Parallel Internal-Type Inductively Coupled Plasmas for Large Area Flat Panel Display Processing
Authors: Kim Kyong Nam , Lee Young June , Jung Seung Jae , Yeom Geun Young
Published: February 2005

The development of a large-area high-density plasma source is desired for various plasma processes from microelectronics fabrication to flat panel display (FPD) device fabrication. In this study, using a parallel internal-type (double comb-type) inductively coupled plasma source having the size of 1020 mm×830 mm, high density plasmas on the order of 2.2×1011 cm-3 could be obtained with Ar at 5000 W inductive power. Plasma uniformity on the substrate in the size of 920 mm×730 mm decreased with the increase in inductive power and was about 8% when the inductive power was 5000 W. When SF6 was used to etch SiO2 using the source, the SiO2 etch rate higher than 2000 Å/min with an etch uniformity of about 6% could be obtained at 5000 W inductive power, -350 V bias voltage, and 15 mTorr operating pressure.
Monodisperse Metallic Iron Nanoparticles Synthesized from Noncarbonyl Complex
Authors: Yamamuro Saeki , Ando Toshinari , Sumiyama Kenji , Uchida Testuo , Kojima Isao
Published: February 2005

Highly monodisperse, metallic iron nanoparticles were prepared by the alcohol reduction of a nontoxic metal precursor (Fe(III) acetylacetonate) in an organic solvent at elevated temperatures. In order to obtain a metallic iron phase and minimize iron oxide ones, a relatively high molar ratio of the reducing agent to the precursor is required. Compared with a single-step reaction, a two-step seed-mediated synthesis results in the systematic control of particle diameter while maintaining monodispersity. The standard deviation of particle diameter is less than 10%, which is sufficiently small to lead to ordered self-assemblies.
Scanning Probes of Nonlinear Properties in Complex Materials
Authors: Shao Rui , Bonnell Dawn A.
Published: February 2005

Nonlinear materials have found wide applications in electronic devices. Of special importance and interest are those with varistor-type grain boundaries and those displaying large piezoelectric and electrostrictive responses to external fields. To access the local properties of these materials, we have designed two new contact mode scanning probe techniques. The first technique referred to as nanoimpedance microscopy/spectroscopy, which incorporates impedance spectroscopy with a conducting AFM tip as an electrode, has been demonstrated on measuring local grain boundary properties of a ZnO varistor, as well as the contact quality between AFM tip and a ferroelectric sample. The other technique referred to as second harmonic piezoresponse force microscopy developed to measure the electrosctriction has been demonstrated on ferroelectric polymer thin film. A theoretical model has been presented to describe the contrast formation of the second harmonic as well as the first harmonic (piezoresponse) images and to explain the observed hysteretic field dependence of the second harmonic amplitude signal.
Effects of Substrate Temperature on the Initial Growth of Titanium Silicides on Si(111)
Authors: Hsu H. C. , Hsu H. F. , Chiang T. F. , Liao K. F. , Chen L. J.
Published: February 2005

The growth of titanium silicide was investigated in sub-monolayer Ti deposited on Si(111)-7×7. The formation of nanorod and cluster structures was observed for 600 and 700°C deposited samples. In samples heated to 800°C, titanium silicide structures transformed to clusters. C49-TiSi2 nanorods were found to orient along three equivalent Si<220> directions with C49-TiSi2(200)∥Si(220). Deposition of sub-monolayer Ti at a high temperature was found to contribute to the lowering of the formation temperature of C49-TiSi2. The lowering of C49-TiSi2 growth temperature on heated substrate is attributed to smaller lattice mismatch between C49-TiSi2(200) and Si(220).
Development of Confocal Laser Scanning Microscope/Atomic Force Microscope System for Force Curve Measurement
Authors: Kodama Takashi , Ohtani Hiroyuki , Arakawa Hideo , Ikai Atsushi
Published: February 2005

We developed a confocal laser scanning microscope (CLSM) / atomic force microscope (AFM) system by combining an inverted CLSM with an AFM for simultaneous spectroscopic measurement and force curve measurement in liquid. We observed resonance energy transfer from donor dyes attached to an AFM probe to acceptor dyes immobilized on the substrate surface. We simultaneously performed the spectroscopic measurement of contact area and force curve measurement and demonstrated the experimental technique and its validity with these experimental results.
Dual-Bias Modulation Method for Scanning Tunneling Spectroscopy
Authors: Muranaka Masayuki , Takahashi Takuji
Published: February 2005

We proposed a novel method for scanning tunneling spectroscopy, in which a difference in differential conductance (dI/dV) between two d.c. biases was extracted using a double lock-in technique. We investigated some experimental parameters to be optimized, and finally obtained the spectra of dI/dV differences on self-assembled InAs quantum dot structures. As a result, we observed different conductance gaps attributable to a difference between the band gaps of the quantum dot and the surrounding wetting layer, and observed some peaks in the spectra on the dot as well. In addition, reasonable current-voltage curves were numerically reproduced from the measured dI/dV spectra.
Versatility of Self-Oscillation Technique with Mechanical-Acoustic Excitations for Frequency Modulation Atomic Force Microscope in Liquids
Authors: Okajima Takaharu , Tokumoto Hiroshi
Published: February 2005

We demonstrated that a cantilever with a small spring constant could be self-oscillated in liquids using a commercial atomic force microscope (AFM) employing a mechanical-acoustic excitation and that the present AFM system can image biological samples such as protein and deoxyribonucleic acid (DNA) in an aqueous solution in regions of slight contact. The present study together with the previous one [T. Okajima et al., Appl. Surf. Sci. 210 (2003) 68.] indicate that a self-oscillation technique with mechanical-acoustic excitations is a versatile method for frequency modulation (FM)-AFM in liquids, although the vibration properties of the cantilever in liquids, which affect the sensitivity of FM detection, have to be more optimized. It was also demonstrated that a noncontact force such as an electrostatic force was detected by the present FM-AFM.
Investigations of Nanoparticles by Scanning Near-Field Optical Microscopy Combined with Kelvin Probe Force Microscopy Using a Piezoelectric Cantilever
Authors: Satoh Nobuo , Kobayashi Kei , Watanabe Shunji , Fujii Toru , Horiuchi Toshihisa , Yamada Hirofumi , Matsushige Kazumi
Published: February 2005

A microfabricated cantilever with a lead zirconate titanate (PZT) piezoelectric thin film used as an integrated deflection sensor was applied to dynamic-mode atomic force microscopy (AFM). This probe can be used for scanning near-field optical microscopy (SNOM) and Kelvin-probe force microscopy (KFM). We adopted a frequency modulation (FM) detection method not only to stabilize imaging conditions in dynamic-mode AFM but also to enhance sensitivity for the detection of electrostatic forces in KFM measurement. We investigated local optical and electrical properties of gold and polystyrene nanoparticles dispersed on an indium tin oxide (ITO) substrate. We successfully identified the species of each particle by different contrasts obtained in SNOM and KFM images.
Picogram Mass Sensor Using Piezoresistive Cantilever for Biosensor
Authors: Sone Hayato , Okano Haruki , Hosaka Sumio
Published: February 2005

A harmonic vibrator using a piezoresistive cantilever has been developed for a picogram mass biosensor. We constructed a prototype vibrator sensor using the cantilever, Wheatstone bridge circuits, positive feedback controller, a piezoactuator and a phase-locked loop (PLL) demodulator. As experimental results, a mass sensitivity of 2.2 pg/Hz was obtained from water molecular adsorption on the cantilever. We confirmed that the mechanism of water molecular growth has 2 modes, island growth and layer growth. The critical point of the mechanism change was a humidity of about 42%. At the critical point, the adsorbed mass corresponds to the water layer of about 13 monolayers.
Influence of Hot Carrier Diffusion on the Density Limitation of Optical Data Storage
Authors: Laurenzis Martin , Först Michael , Bolivar Peter Haring , Kurz Heinrich
Published: February 2005

Hot carrier diffusion (HCD) in Ge-Sb-Te phase change materials for re-writable optical data storage applications may limit the resolution of blue laser recording and cause additional cross-talk. As simulation studies show, the high optical excitation energy and small optical focus size characteristic of blue laser data storage formats lead to significant hot carrier diffusion prior to the energy transfer to the crystal lattice. As a consequence, the optical energy is deposited in an area larger than the laser spot size, leading to enhanced intertrack cross-talk and thermal cross-erase that reduces the quality of high-density optical storage. Therefore, the fundamental limit of resolution for re-writable optical storage systems is no longer determined by the laser focus size alone, but also by additional nonequilibrium HCD effects.
A Magnetic Coil Suitable for Magneto-Optical Recording with a Large Working Distance
Authors: Yoshikawa Hiroyasu , Matsumoto Tsuyoshi , Fujimaki Tohru , Tezuka Koichi
Published: February 2005

A first surface magneto-optical (MO) system has a high storage density and a high data-transfer rate. The high-density recording is achieved using a blue laser and lenses that have a high numerical aperture (more than 0.85) and that are integrated with a magnetic-field modulation coil. If the working distance is more than 30 µm, the optical head can be controlled by using a mechanical actuator, for which many existing technologies are available. We have developed a magnetic coil suitable for working distances of up to 30 µm. First, we analyzed the relationship between the properties of a magnetic layer and a magnetic field and then from our analysis derived three design concepts. We then designed a magnetic coil with a fan-shaped magnetic layer composed of stick-shaped magnetic bodies and heat sinks; testing showed that it can be driven at a data transfer rate of 80 Mbps and that it has a wide temperature margin.
Blu-ray Disc/Digital Versatile Disc Recording and Reproducing Compatible Use Technology in the 2nd Generation Pick Up for Blu-ray Disc
Authors: Morishita Ichiro , Shindo Hiroyuki , Takeya Noriyoshi , Jeong Hoseop , Yoon Yonghan , Chang Incheol , Kim Hyungjin , Lee Dongwoo , Kyong Chonsu
Published: February 2005

We developed a 2nd generation pick up for the Blu-ray disc (BD), which makes possible recording and reproducing on both BD and digital versatile disc (DVD), and has a size for audio and visual (AV) and personal computer (PC) applications. These properties are realized by a single objective lens and a newly developed hologram element. The next generation optical disc system, which is expected to enable over 15 GB recording and reproducing on an optical disc, is also expected to record and reproduce on DVD or compact disc (CD), using one pick up. In order to satisfy such demand, we have developed an objective lens with a long working distance and proposed a BD/DVD/CD compatible use technology. This paper reports the details of how we achieved a proper sized AV/PC for common use, BD/DVD recording and reproducing compatible use and the dual layer disc in the 2nd generation pick up for BD.
Domain Wall Displacement Detection Magnetooptical Drive for Mobile Use, with 15 Gbit/inch2 Recording Density and 24 Mbps Data Transfer Rate
Authors: Nagura Chihiro , Torii Shinnosuke , Ishii Kazuyoshi , Nagatsuka Osamu , Nishikawa Koichiro , Miyaoka Yasuyuki , Suzuki Kazunori , Koyama Osamu
Published: February 2005

We have developed a domain wall displacement detection (DWDD) magnetooptical drive for the 2-inch-diameter disc with 3 GB capacity. The newly developed magnetic head and the drive circuit realize the high efficiency of 1.84 Oe/mA and the high speed switching of 13.5 ns. An optical pickup (OPU) with wavelength of 660 nm and numerical aperture (NA) of 0.6 is sufficiently compact to approach the innermost disc radius of 11 mm, and the overall weight is 3.2 g. The volume and power consumption of the entire drive system are 35.5 cc and 0.78 W respectively, and they are adequate for use in mobile storage devices. Furthermore, we have confirmed a complete read/write performance with 15 Gbit/inch2 recording density and 24 Mbps data transfer rate.