bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvement of TiN Flow Modulation Chemical Vapor Deposition from TiCl4 and NH3 by Introducing Ar Purge Time
Authors: Jun Keeyoung , Im Ik-Tae , Shimogaki Yukihiro
Published: February 2005

TiN films were deposited by using TiCl4/NH3 flow modulation chemical vapor deposition (FMCVD). FMCVD consists of repetitive TiN deposition periods by TiCl4/NH3, each of which is followed by Cl reduction period. TiN deposition periods are typically 3 s and Cl reduction periods are 1 s. The effect of the number of deposition/reduction cycles and the effect of the partial pressure of TiCl4 and NH3 on film uniformity and resistivity were investigated. For a total reduction period of 100 s, increasing the number of reduction periods from 100×1-s periods to 300×0.33-s periods decreased the step coverage. This decrease in coverage was due to residual TiCl4 during the Cl reduction period by NH3 that cleared out TiCl4 at a constant rate, independent of the length of the period of reduction cycle. An Ar purge cycle was used between the deposition and reduction cycles to allow the residual TiCl4 to clear out before the NH3 was used for the film reduction cycle. This significantly improved the film step coverage from 50% to over 90%. The minimum film resistivity occurred when the NH3 partial pressure was 0.25 Torr. NH3 partial pressure less than 0.25 Torr inhibited film reduction, and NH3 partial pressure higher than 0.25 Torr enhanced the deposition rate, which also inhibited film reduction. By using the optimum conditions determined in this study, we could obtain TiN films that had film resistivity of about 240 µΩ·cm and step coverage of about 98% at 410°C.
A New Voltage between Collector and Emitter (VCE) Sensing Scheme for Short-Circuit Withstanding Capability of the Insulated Gate Bipolar Transistor
Authors: Jeon Byung-Chul , Ji In-hwan , Ha Min-Woo , Han Min-Koo , Choi Yearn-Ik
Published: February 2005

A new protection circuit employing a voltage between collector and emitter (V
CE) sensing scheme for the short-circuit withstanding capability of insulated gate bipolar transistors (IGBTs) is proposed and verified on the basis of two-dimensional simulation and experimental results. Because the current path between the gate and the collector can be successfully eliminated in the proposed protection circuit, power consumption can be reduced and gate input impedance can be increased. The experimental results show that the proposed protection circuit can adjust the current saturation level of IGBTs and the short-circuit withstanding capability can be significantly enhanced.
Large-Scale Emulation of Quantum Computing Based on Nonzero State Transitions
Authors: Fujishima Minoru , Inai Kento , Kitasho Tetsuro , Hoh Koichiro
Published: February 2005

Quantum computing realizes high-speed calculation with massive-parallel computing of quantum state transitions. The quantum computing emulator, however, must be able to manipulate exponentially increasing states as the problem scale increases. To reduce the number of quantum states to be manipulated in the emulator, we have focused on the quantum-state transitions in a quantum computer. In this paper, an emulator representing the state transitions with the location of a nonzero quantum state is proposed. As a result, the emulation of larger-scale quantum algorithms can be realized with a finite amount of hardware.
Mechanical Property Control of Low-k Dielectrics for Diminishing Chemical Mechanical Polishing (CMP)-Related Defects in Cu-Damascene Interconnects
Authors: Hijioka Ken-ichiro , Ito Fuminori , Tagami Masayoshi , Ohtake Hiroto , Harada Yoshimichi , Takeuchi Tsuneo , Saito Shinobu , Hayashi Yoshihiro
Published: February 2005

The dielectric constant dependence of the mechanical strength and the adhesion strength is investigated using porosity-controlled low-k films, and a material parameter is clarified to suppress the chemical mechanical polishing (CMP)-related defects in Cu damascene interconnects. Mechanical strengths such as the modulus and hardness of low-k films decreased as the dielectric constant decreased. Adhesion energy between the low-k films and an upper hard-mask layer (HM) of PECVD-SiO2 strongly depends on the dielectric constant of low-k films, while adhesion energy between the low-k films and a lower etch stop layer (ES) of SiCN shows weak dependence. It was found that the adhesion energy between the upper SiO2 and the low-k film is a critical mechanical parameter for diminishing the CMP-related defects. Introducing a porous low-k film, methylsilsesquiazane (k=2.64), with high adhesion to the HM-SiO2, we successfully fabricated single damascene copper interconnects within an acceptable limit of CMP-related defects.
Influence of Structural Variation of Ni Silicide Thin Films on Electrical Property for Contact Materials
Authors: Okubo Kazuya , Tsuchiya Yoshinori , Nakatsuka Osamu , Sakai Akira , Zaima Shigeaki , Yasuda Yukio
Published: February 2005

The influence of crystallographic structural variation of Ni silicide thin films on the sheet resistance with annealing has been investigated. The agglomeration of NiSi and the phase transition to NiSi2 which occurred in the polycrystalline NiSi films have been revealed microscopically. It is found that degradation of the sheet resistance characteristic critically depends on the annealing time particularly at temperatures ranging from 650°C to 750°C. The enlargement of the Si-exposed region concomitant with the agglomeration of NiSi grains is a dominant factor responsible for the increase in sheet resistance and the activation energy of this process is estimated to be 2.8±0.4 eV. Furthermore, it is observed that the growth of epitaxial NiSi2 is initiated at the site where the agglomeration of NiSi grains results in the exposure of Si surfaces. The formation of the NiSi2 layer effectively suppresses the degradation of the film above 750°C.
Thermal Annealing Effect in GaInNAs Thin Films Estimated by Fluorescence X-Ray Absorption Fine Structure Spectroscopy
Authors: Uno Kazuyuki , Yamada Masako , Takizawa Toshiyuki , Tanaka Ichiro
Published: February 2005

The radiative efficiency of dilute nitride GaInNAs alloys is improved by thermal annealing. However, the band gap of these alloys is found to significantly blueshift. The structural changes of these alloys occur during thermal annealing. In this study, we studied the local atomic configuration around In atoms using fluorescence X-ray absorption fine structure spectroscopy. By comparing the radial distribution functions of as-grown and annealed GaInNAs thin films, it was found that the number of In atoms surrounding N atoms increases after thermal annealing.
40 GHz Actively Mode-Locked Distributed Bragg Reflector Laser Diode Module with an Impedance-Matching Circuit for Efficient RF Signal Injection
Authors: Arahira Shin , Ogawa Yoh
Published: February 2005

A 40 GHz actively mode-locked laser diode integrated with an electroabsorption modulator as a mode locker was developed. The laser was packaged in a module together with an impedance-matching circuit of double open stubs for efficient RF signal injection. A 13 dB improvement of the RF injection efficiency was successfully achieved compared with a conventional 50 Ω terminated circuit. Nearly transform-limited, picosecond (<3 ps) pulses were successfully generated with a low timing jitter of 0.15 ps. A wide locking bandwidth over 1.9 GHz (39 GHz–40.9 GHz) was achieved while retaining small variation of pulse widths and low relative intensity noise values of less than -130 dB/Hz. Such a wide locking range could fully cover an error in cavity length in the cleaving process and is very promising for cost-effective device fabrication.
Numerical Analysis of Waveguides in Three-Dimensional Photonic Crystal with Finite Thickness
Authors: Watanabe Yoshinori , Yamamoto Noritsugu , Komori Kazuhiro
Published: February 2005

The propagation losses of the straight waveguide in three-dimensional photonic crystals with finite thickness have been estimated by using the finite-difference time-domain method. It was confirmed that the propagation loss decreases almost exponentially as the thickness of the photonic crystal increases. The waveguide for the photonic crystal suspended in air has complicated transmission properties, although it achieves the efficient guiding of light. For the six-stacking-period- or 24-layer-thick photonic crystal suspended in air, the propagation loss of less than 1 dB/mm was evaluated in a wide wavelength range around 1.55 µm. Our results indicate that to obtain the loss of the same order, we can use photonic crystals surrounded on both sides by GaAs, which have an advantage in terms of stability for the construction of large-scale crystals, by increasing the thickness by one extra period.
AlGaAs/InGaAs DFB Laser by One-Time Selective MOCVD Growth on a Grating Substrate
Authors: Takasuka Yasuyuki , Tsuji Yasuhide , Yonei Kenji , Yamauchi Hiromi , Ogura Mutsuo
Published: February 2005

A gain-coupled distributed feedback (DFB) laser is realized using a high-density InGaAs/AlGaAs quantum wire (QWR) array formed within a finite area of 6×500 µm by electron beam lithography and one-time selective metalorganic chemical vapor deposition (MOCVD). The stable gain-coupled DFB mode is confirmed at 812 and 830 nm from the 360 and 370 nm pitch gratings, respectively. The mode analysis of the actual cross-sectional structure using a finite element method verified that modal gain has a single peak at the Bragg wavelength of the grating.
Generation of Local Magnetic Field by Nano Electro-Magnets
Authors: Kim Hyung Kwon , Hong Su Heon , Kim Bo Chang , Hwang Jong Seoung , Seong Shi Myoung , Park Tai Hyun , Hwang Sung Woo , Ahn Doyeol
Published: February 2005

Fabrication and characterization of nano electro-magnets are reported. The nano-transformer consisting of two concentric loops has been made and Faraday's induction experiment has been successfully performed. The mutual inductance value extracted from the measured induced current is consistent with the simulated results of mutual inductance between two macroscopic loops with nano-meter spacing. It is also demonstrated that only a small number of magnetic particles can be captured by controlling the design and current level of the electro-magnet.
Generation of Radiation Pressure in Thermally Induced Ultrasonic Emitter Based on Nanocrystalline Silicon
Authors: Hirota Jun , Shinoda Hiroyuki , Koshida Nobuyoshi
Published: February 2005

To confirm the applicability of thermally induced ultrasonic emission from nanocrystalline silicon (nc-Si) devices as radiation pressure generators, the dynamic response has been investigated under a pulse operation mode. The nc-Si emitter is fabricated on a p-type Si wafer by conventional electrochemical anodization with subsequent formation of the surface electrode. Due to the flat nature of the frequency response of this emitter, the device emits an acoustic wave with little distortion under the pulse-drive condition. It is shown that a significant radiation pressure of 34.5 Pa is generated by a concentrated burst-like electrical input, and that a beam located at a distance can be levitated as a result of the mechanical loading effect. This silicon-based emitter is attractive for applications to integrated nano- or micro-electromechanical systems.
Optical Characteristics of InAs/GaAs Double Quantum Dots Grown by MBE with the Indium-Flush Method
Authors: Yamauchi Shohgo , Komori Kazuhiro , Sugaya Takeyoshi , Goshima Keishiro
Published: February 2005

We fabricated InAs/GaAs double quantum dot (QD) structures by molecular beam epitaxy (MBE) with the Indium-Flush method, where the energy separation between the electron levels of two QDs was less than the longitudinal optical (LO) phonon energy with a different barrier thickness. We confirm the peak energy shift between the double QDs in the photoluminescence (PL) spectra and assign this shift to the wave function coupling effect between the double dots. We also measured the time resolved PL spectra and observed the carrier transfer from smaller QDs to larger ones in the time domain. By estimating the tunneling time between double QDs, we obtain a tunneling time that is longer than the exciton decay time in single QD. Additionally, we mention the fade-out of the electron LO phonon interaction with the electron wave function coupling between double QDs based on the result of photoluminescence excitation measurements. These results suggest that our structures are attractive for quantum information processing.
Cross-Sectional Channel Shape Dependence of Short-Channel Effects in Fin-Type Double-Gate Metal Oxide Semiconductor Field-Effect Transistors
Authors: Liu Yongxun , Ishii Kenichi , Masahara Meishoku , Tsutsumi Toshiyuki , Takashima Hidenori , Yamauchi Hiromi , Suzuki Eiichi
Published: February 2005

The dependence of short-channel effects (SCEs) on the cross-sectional channel shape of the fin-type double-gate metal oxide semiconductor field-effect transistors (MOSFETs) has been experimentally investigated from the viewpoint of fin fabrication. The three types of fin-type double-gate MOSFETs (FinFETs) with a rectangular-cross-section channel on a (110)-oriented silicon-on-insulator (SOI) wafer, and a triangular and trapezoidal channels on a (100)-oriented SOI wafer were fabricated using the same orientation-dependent wet etching process. The experimental results show that the SCEs in rectangular-cross-section silicon (Si)-fin channel devices are well suppressed compared with those in a triangular or a trapezoidal Si-fin channel device fabricated using a similar mask pattern, in the regimes of the gate length of less than 85 nm and Si fin height of larger than 65 nm. The presented experimental results are valuable for FinFET design and fabrication.
Synthesis and Thermal Conductivity Measurement of High-Integrity Ultrathin Oxygen-Implanted Buried Oxide Layers
Authors: Dong Yemin , Chen Jing , Chen Meng , Wang Xi , He Ping , Tian Lilin , Liu Litian , Li Zhijian
Published: February 2005

Ultrathin buried oxide (BOX) layers have been synthesized by low-dose and low-energy separation by implantation of oxygen (SIMOX) technique. The formed BOX layers were examined by transmission electron microscopy (TEM) and the results demonstrated that the BOX layers are of high integrity without any detectable silicon islands therein. A modified method was introduced to measure the thermal conductivity of the synthesized high-integrity BOX layers with different thicknesses. It is found that ultrathin SIMOX BOX layers exhibit a thermal conductivity of ∼0.92 Wm-1K-1, which is approximately 34% lower than that of bulk SiO2, 1.4 Wm-1K-1. In addition, the boundary thermal resistance of the Si/BOX interfaces was also measured.
Novel Capacitor Structure Using Sidewall Spacer for Highly Reliable Ferroelectric Random Access Memory Device
Authors: Kim Hyun-Ho , Park Jung-Hoon , Song Yoon-Jong , Jang Nak-Won , Joo Heung-Jin , Kang Seung-Kuk , Joo Seok-Ho , Lee Sung-Young , Kim Kinam
Published: February 2005

Since ferroelectric capacitors prepared by 1-mask etching are degraded after the etching, we systematically investigated the origin of the degradation. It was found that the major degradation originates from the formation of the nonstoichiometric and amorphorized Pb(Zr
x
Ti1-x
)O3 (PZT) layer on the sidewall of the PZT film during etching of the bottom electrode (BE). Therefore, to eliminate the undesired etch-damaged layer, we developed a novel etching technology using a ferroelectric (FE) sidewall spacer, which results in the enhancement of the remnant polarization after completing the capacitor etching process. Using the novel FE sidewall spacer, the sensing margin of bit-line-developed voltage was improved to 400 mV, which can guarantee highy reliable high-density ferroelectric random access memory (FRAM) devices.
Data Retention Improvement of Metal-Oxide-Nitride-Oxide-Semiconductor Memories Using Silicon-Tetrachloride-Based Silicon Nitride with Ultralow Si-H Bond Density
Authors: Nomoto Kazumasa , Asayama Goh , Kobayashi Toshio
Published: February 2005

We have improved the data retention of metal-oxide-nitride-oxide-semiconductor (MONOS) memories by reducing the Si-H bond density in silicon nitride. This marked improvement was achieved by depositing silicon nitride with NH3 and SiCl4 (silicon tetrachloride, STC), instead of with NH3 and the conventionally used SiCl2H2 (dichlorosilane, DCS). The Si-H bond density of the STC-based nitride was less than 1% that of the DCS-based nitride. We clarified that the improvement was due to the suppression of the leakage of trapped electrons through shallow traps which are related to Si-H bonds with an activation energy of 0.1–0.2 eV.
New Three-Dimensional High-Density Stacked-Surrounding Gate Transistor (S-SGT) Flash Memory Architecture Using Self-Aligned Interconnection Fabrication Technology without Photolithography Process for Tera-Bits and Beyond
Authors: Sakuraba Hiroshi , Kinoshita Kazushi , Tanigami Takuji , Yokoyama Takashi , Horii Shinji , Saitoh Masahiro , Sakiyama Keizou , Endoh Tetsuo , Masuoka Fujio
Published: February 2005

New three-dimensional Stacked-Surrounding Gate Transistor (S-SGT) flash memory architecture can achieve the cell area of 3.88F2 per bit using the 0.2 µm design rule. The new architecture is realized by stacking two select transistors and two memory cells vertically on each pillar located in a two-dimensional array matrix. Each gate and each interconnection of this new architecture are fabricated by the vertical self-alignment process and horizontal self-alignment process simultaneously using HTO conformal deposition and reactive ion etching (RIE) without using the photolithography process. The new three-dimensional S-SGT flash memory architecture is applicable to high-density nonvolatile memories as large as tera-bits and beyond.
Non-Recessed-Gate Enhancement-Mode AlGaN/GaN High Electron Mobility Transistors with High RF Performance
Authors: Endoh Akira , Yamashita Yoshimi , Ikeda Keiji , Higashiwaki Masataka , Hikosaka Kohki , Matsui Toshiaki , Hiyamizu Satoshi , Mimura Takashi
Published: February 2005

We fabricated non-recessed-gate enhancement-mode (E-mode) AlGaN/GaN high electron mobility transistors (HEMTs) with a gate length L
g of 120 nm. As gate metals, Ni/Pt/Au and Mo/Pt/Au were used. The Ni/Pt/Au-gate HEMTs with rapid thermal annealing (RTA) at 500°C were normally-off at a gate-source voltage V
gs of 0 V, indicating E-mode operation. Moreover, the Mo/Pt/Au-gate HEMTs also showed E-mode device operation without RTA. The fabricated E-mode HEMTs with both gate metals showed high RF performance. We obtained a cutoff frequency f
T of more than 50 GHz and a maximum oscillation frequency f
max of approximately 100 GHz.
Indium Content Dependence of Electron Velocity and Impact Ionization in InAlAs/InGaAs Metamorphic HEMTs
Authors: Ono Hideki , Taniguchi Satoshi , Suzuki Toshi-kazu
Published: February 2005

We have fabricated In
x
Al1-x
As/In
x
Ga1-x
As metamorphic high electron mobility transistors (MHEMTs) with x=0.36, 0.43, and 0.53 on GaAs, and lattice-matched (LM) HEMTs with x=0.53 on InP. Using the HEMTs, we have carried out systematic studies on the electron velocity and the impact ionization in the InGaAs channels with several indium contents. The electron velocity is determined by the gate length dependence of cut-off frequency. Although high-density crystalline defects propagate into the channels of the MHEMTs, the electron velocity is not affected by the defects. Impact ionization phenomena, which dominate on-state breakdown voltage, have been investigated by gate-current analysis in the prebreakdown regime of the HEMTs. We have estimated the characteristic electric field of the impact ionization for InGaAs. It has been found that the gate current due to the impact ionization of the MHEMT with x=0.53 is smaller than that of the LMHEMT, which is explained by the enhanced electron-hole recombination by the crystalline defects in the MHEMT.
Enhanced Red Emission from Fluorescent Organic Light-Emitting Devices Utilizing a Phosphorescent Sensitizer
Authors: Liu Shiyong , Feng Jing , Zhao Yi
Published: February 2005

Highly efficient red organic light-emtting devices that employ 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as a fluorescent dye, with a green phosphorescent-sensitizer, fac tris(2-phenylpridine) iridium (Ir(ppy)3) doped in a 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBi) host are demonstrated. The OLEDs at the concentration of 10:2 with red emission have the maximum brightness and luminance efficiency of 10000 cd/m2 (at 19 V) and 3.6 cd/A (at 5 V), respectively, which is higher than most of the fluorescent red organic light-emitting diodes (OLEDs). We attribute the improvement of the double-doped devices to the efficient energy transfer of both singlet and triplet excited states in the double-doped host to the fluorescent material using Ir(ppy)3 as a sensitizing agent.
Fabrication of High-Resolution Periodical Structure in Photoresist Polymers Using Laser Interference Technique
Authors: Shibata Shinya , Che Yanlong , Sugihara Okihiro , Okamoto Naomichi , Kaino Toshikuni
Published: February 2005

Periodical structures in the nanometer order, which are clearer and of superior aspect than those reported elsewhere, were fabricated. These structures were fabricated onto a positive-type photoresist film by a two-beam interference technique using a single-pulse Nd:YAG (355 nm) laser. A grating structure with a depth of more than 300 nm and period of 400 nm was formed, accompanied by wet development. Moreover, a 200-nm-period grating, which is close to the theoretical limit, was successfully fabricated with higher aspect.
Determining the Self-Assembling and Redox Process of a Viologen Monolayer by Electrochemical Quartz Crystal Microbalance
Authors: Ock Jin Young , Shin Hoon Kyu , Qian Dong Jin , Miyake Jun , Kwon Young Soo
Published: February 2005

Electrochemical and quartz crystal microbalance (EQCM) methods are used to probe the redox behavior of self-assembled monolayers of viologen derivatives with long alkyl chains and disulfide or thiol groups that provide for attachment to gold electrodes. The EQCM measurements revealed that cations exit and enter the viologen monolayer during reduction and oxidation, respectively. In this study, the self-assembly process of viologen was monitored using resonant frequency (ΔF) and resonant resistance (ΔR). The QCM measurements indicated a mass adsorption for viologen assembling on the gold surface with a frequency change of approximately 135 Hz and calculated its surface coverage (Γ) to be 3.5273×10-9 mol/cm2. Also, a reversible redox process was observed and analyzed with an ionic interaction at the viologen/solution interface using ΔF.
Resonant Cavity Thin Film Photodiode for Compact Displacement Sensor
Authors: Sasaki Minoru , Nakai Fuki , Mi Xiaoyu , Hane Kazuhiro
Published: February 2005

A new sub-wavelength thick photodiode for realizing a compact interferometer has been fabricated. The previous thin film photodiode has problems of low sensitivity and signal deformation caused by multiple reflections at interfaces. By setting the thin Si film to be λ/2 of the wavelength of incident light, the signal intensity increases due to resonant cavity enhancement. At the same time, the photocurrent signal shape is improved, because the resonant cavity works as an anti-reflection structure. The interference signal increases 32-fold, and its shape approaches a sinusoidal curve. The sensitivity obtained is about 10 mA/W. The noise of the 2nd order Fourier component in the interference signal is reduced from 41 to 25% at 632.8 nm and to 4.3% at 678.8 nm, showing good agreement with the theoretical estimation.
2-Step Growth Method and Microcrystalline Silicon Thin Film Solar Cells Prepared by Hot Wire Cell Method
Authors: Ide Yoshinori , Saito Yuji , Yamada Akira , Konagai Makoto
Published: February 2005

Hot Wire Cell (HW-Cell) method has been developed in order to grow microcrystalline silicon (µc-Si:H) thin films. The influence of various deposition parameters on the structural and electrical properties of the films was investigated to improve film quality. It was found that the concentrations of O and C atoms in µc-Si:H films could be reduced from the order of 1021 cm-3 to the order of 1020 cm-3 by decreasing the partial pressure of SiH4 from 100 mTorr to 3 mTorr. Then, a novel 2-step growth method was proposed in order to reduce the incubation layer in the initial growth of µc-Si:H i-layer. By using this method, J
sc largely increased (10.11 → 18.32 mA/cm2), and as a result, the conversion efficiency of 3.9% could be achieved. The influence of the incubation layer on solar cell performances was also investigated by a numerical analysis. To date, a conversion efficiency of 5.3% (V
oc: 0.48 V, J
sc: 20.56 mA/cm2, F.F.: 0.54, active area: 0.086 cm2, AM1.5) was obtained for µc-Si:H solar cells with an i-layer thickness of 1.0 µm. Furthermore, high-rate depositions were investigated and a maximum deposition rate of 11.5 nm/s could be achieved. µc-Si:H solar cells fabricated at a high deposition rate of 1.5 nm/s showed a conversion efficiency of 2.8% (V
oc: 0.42 V, J
sc: 12.31 mA/cm2, F.F.: 0.54, active area: 0.086 cm2, AM1.5).
Charge Compensation Mechanism Decreases Dielectric Loss in Manganese-Doped Pb(Fe1/2Nb1/2)O3 Ceramics
Authors: Fang Bijun , Shan Yuejin , Imoto Hideo
Published: February 2005

Mn-doped Pb(Fe1/2Nb1/2)O3 (PFN) ceramics are synthesized by the conventional solid-state reaction method via a B-site oxide mixing route. The pure perovskite phase of Mn-doped PFN is obtained up to 0.75 mol% of manganese doping. Due to manganese doping, dielectric loss of the obtained ceramics decreases continuously up to 3 mol% of manganese, although pyrochlore phase appears. The decrease of dielectric loss can be explained by the charge compensation effect caused by the substitution of Mn4+ for Fe3+ in the octahedral cage of the perovskite structure, which is confirmed by X-ray photoelectron spectrometry (XPS). That is, due to the substitution of Mn4+ for Fe3+ ions, the relative content of iron in different valence states changes, i.e., the relative content of Fe2+ ions increases with the amount of doped manganese. Therefore, the hole-conduction mechanism caused by the partial reduction of Fe3+ to Fe2+ in the PFN system weakens, which leads to the decrease of dielectric loss. The effect of manganese doping on the depression of mechanical vibration loss also provides some contribution to the decrease of total dielectric loss through pinning down the rotation of spontaneous polarization induced by combining Mn2+ (reduced of doped Mn4+ ions during sintering) with the oxygen vacancy (produced by the compensation effect) and standing near the domain boundary. The relative dielectric constant of the Mn-doped PFN ceramics also decreases continuously with the increase of manganese content, which is believed to be related to the reduction of space-charge polarization.
Structural Nonuniformity and Internal Stress in Chromium Films Deposited by Magnetron Sputtering
Authors: Shaginyan Leonid , Han Jeon Geon , Lee Hyuk Min
Published: February 2005

Using high-resolution transmission electron microscopy, selected area electron diffraction and X-ray diffraction methods, the microstructures and lattice parameters of different parts of Cr films deposited by magnetron sputtering under different deposition conditions have been studied. It was revealed that the microstructure and lattice parameter of the films deposited onto nonheated substrates vary in the film thickness direction. Lattice parameter a has a maximal value in the film-substrate interface region and gradually decreases towards the conventional value in the middle and upper film parts. In accordance with this, the internal tensile stress decreases, while the grain size increases in the direction from the substrate to the film surface. Elevation of the substrate temperature results in smoothing of nonuniformity of the film microstructure and stress distribution along the thickness. At a certain combination of a substrate temperature and bias voltage, unstressed large-grained films with uniform microstructure have been deposited. The model proposed for explanation of the obtained results is based on the supposition of dynamic elevation of condensation surface temperature during film growth that promotes the formation of the film with structure and stress nonuniformly distributed in the thickness direction.
Influence of Voids on the Accuracy of Measurement of Vacancy Concentration in NiAl and CoAl Intermetallic Compounds
Authors: Kodera Takuro , Matsui Masanori , Takama Toshihiko
Published: February 2005

The vacancy concentrations c
v in the B2-type alloys of Ni1-x
Al
x
(0.45≤x≤0.54) and Co1-x
Al
x
(0.46≤x≤0.52) were determined by the measurements of lattice constant with X-ray diffraction and bulk density ρA using the Archimedes method. The measurements were performed at room temperature for various sizes of powder samples. The obtained density of ρA increased with decreasing powder size, and the resultant vacancy concentration decreased. The size dependence of ρA and a scanning electron microscopic observation indicated that the increase in ρA was due to the presence of voids in the powder samples. The reliable values of c
v were estimated using a model that reduced the influence of voids. The effective formation energies of vacancy and antistructure atom were also estimated from the composition dependence of c
v. The results of the estimation showed that the Al antistructure is the ground state of the defect structure at 0 K.
Influence of the Beam Irradiation Conditions on an Si Film Melting-Crystallized by a Nd:YAG Pulse Laser Beam with Linear Polarization
Authors: Nakata Yasunori , Kaki Hirokazu , Horita Susumu
Published: February 2005

We investigated the influence of the irradiation conditions of the coherent length and the polarization of the laser beam, the incident angle θi, the pulse number, the fluence, the substrate temperature and the a-Si film thickness on the melting-crystallization of an a-Si film and the controllability of the periodic grain boundary location by using a linearly polarized laser beam. For formation of periodic grain boundary in the crystallized Si film, the linear polarization is key factor rather than the coherent length. Also, the a-Si film thickness should be around 60 nm for large optical absorption, and the high substrate temperature and the large pulse number are preferable. By using a p-polarized beam, the grain boundary width can be expanded proportional to 1/(1-sin
θi) roughly. In order to suppress the ablation of the film and to increase the productivity, the fluence should be adjusted precisely.
Preparation of Amorphous Hydrogenated Carbon Films by RF Sputtering at a Low-Hydrogen-Flow-Rate Region for Hydrogen-Reactive Substrates
Authors: Oshiro Takehiko , Yamazato Masaaki , Higa Akira , Maehama Takehiro , Toguchi Minoru
Published: February 2005

Amorphous hydrogenated carbon (a-C:H) films have been deposited by RF magnetron sputtering system in H2/He plasma. Hydrogen incorporated into the a-C:H film plays an important role in the release of internal stress in the film. On the other hand, hydrogen plasma has deoxidizing, etching and reduction effects on a substrate. Some oxides and compound semiconductors such as CdTe substrate receive serious damage during the deposition process of a-C:H film. Therefore, the amount of hydrogen radicals in sputtering plasma should be as small as possible for suppressing the damage. In this study, we investigate the effects of hydrogen incorporated to an a-C:H film which are deposited at a wide range of relative hydrogen gas flow rate (R
H) from 0.1% to 50%. It has been clarified that the a-C:H films deposited in low R
H have high quality and that the films can be grown on a CdTe substrate without etching by hydrogen ions and radicals at R
H=0.2% and the nearest-neighbor region.
In Situ Epitaxial Growth of Lead Zirconate Titanate Films by Bias Sputtering at High RF Power
Authors: Nam Song-Min , Tsurumi Takaaki
Published: February 2005

High-quality epitaxial lead zirconate titanate (PZT) films with high growth rate were successfully grown by bias sputtering on (001) MgO single crystal substrates using a composite ceramic target. The composite ceramic target composed of a PbO pellet on the center of Pb1.2(Zr0.4Ti0.6)O3 ceramics was necessary to stably obtain perovskite-phase PZT films under high RF power by sputtering. At high RF power, the application of DC bias voltages to the growing PZT films increased the growth rate and changed the Ti/Zr composition. In particular, the optimum negative bias voltage considerably improved the crystallinity and surface morphology of the films compared with the conventional sputtering process. The optimum negative bias voltage plays a role in suppressing the bombardments of the energetic negative oxygen ions on growing films and also in making low-energy positive ions assist help in crystallization.
Filtered Cathodic Vacuum Arc Process Conditions and Properties of Thin Tetrahedral Amorphous Carbon Films
Authors: Inaba Hiroshi , Furusawa Kenji , Sasaki Shinji
Published: February 2005

The properties of thin tetrahedral amorphous carbon films were evaluated for various deposition conditions using a filtered cathodic vacuum arc process. The most marked change observed in the properties of the films caused by varying the arc current and substrate bias was the change in the compressive stress of the films. It was found that C+ ion energy values ranging from 55 to 75 eV are optimum for obtaining very hard tetrahedral amorphous carbon coatings.
AC Mode Feedback and Gate Pulse Acquisition Methods for Scanning Near-Field Optical Microscope
Authors: Nakamoto Keiichi , Mooney Charles B. , Kitamura Shin-ichi
Published: February 2005

A scanning near-field optical microscope (SNOM) with a nanometer-size aperture cantilever is a new powerful tool for investigating the optical characteristics of specimen surfaces. We applied the AC-mode feedback and gate pulse acquisition methods in illumination/reflection-mode SNOM. The application of the AC-mode feedback method increased the optical intensity of reflected light from two-to seven fold that obtained by the contact-mode feedback method. The use of the gate pulse acquisition method reduced optical imaging artifacts originating from the topographical features of surfaces.
Sheath Equivalent Electrical Circuit Model for Transient Sheath Dynamics
Authors: Deka Utpal , Prakash Ram , Sarma Arun , Dwivedi Chandra Bhushan
Published: February 2005

This work presents a new alternate understanding and interpretation of the observed ion implantation current profile in transient sheath experiments. Two time-scale structure of the observed ion implantation current profile is clearly noted in constant phase of applied pulse voltage at the electrode. But no complete and self-consistent model calculation for theoretical explanation is available as yet. We treat the positive (ion-rich) sheath as an equivalent electrical series LCR circuit and use Kirchoff's law to arrive at a second order differential equation for theoretical description of the defined circuit. The Child law describes the expanding motion of transient sheath dynamics and monitors current in the circuit. Numerical solution of the defined driven circuit equation yields almost the same current profile as observed in the transient sheath experiments.
Electronic Structures of CF3
- for Studying Dissociative Electron Attachment to CF3 Radicals
Authors: Hayashi Daiyu
Published: February 2005

To elucidate the process of dissociative electron attachment (DA) to CF3 radicals, the potential energy surfaces of CF3, CF3
- and the electronic state CF3
-* temporally produced in DA are calculated at the MP2/6-311++G** level by Gaussian 98. The electron affinities (E
A) of the CF3, vibrational frequencies of CF3 and CF3
- are also calculated. Our results are in good agreement with the experimental values (cf. E
A=1.72 eV, experimental value = 1.7±0.2 eV). It is elucidated that the electron capture by CF3 under the adiabatic approximation occurs by the incident of a low-kinetic energy (∼0.6 eV) electron. DA to CF3 is a slightly endothermic process with 0.2–0.4 eV. It is concluded that CF3 radicals produce F- ions via DA with low kinetic energies. This process is considered to be very important in the kinetics of low-energy electrons in fluorocarbon plasmas.
Vacancy Cascades Following Inner-shell Ionization in Ar And Kr Determined Using Different Atomic Data
Authors: El-Shemi Adel Mohammedien
Published: February 2005

The charge state distribution of ions following K-shell ionization in Ar and Kr atoms is calculated using a Monte Carlo simulation technique. A computer program is written to trace successive X-ray and Auger transition probabilities, which fill vacancies in atomic configurations. The radiative and nonradiative branching ratios are evaluated. Electron shake-off probabilities due to atomic rearrangement after inner-shell ionization are considered in the calculation. The obtained results are compared with those determined experimentally and those calculated from the atomic data collected from different literature sources. It is found that using accurate atomic data leads to results that agree well with experimental values.
Comparison between Modern Violin Bridge and Baroque Violin Bridge by Photoelastic Observation and Frequency Analysis
Authors: Matsutani Akihiro
Published: February 2005

A comparison between the modern bridge and the baroque bridge of the violin by photoelastic observation was carried out. The relationship between the stress part and the hole is symmetric in the modern and baroque bridges. The measured spectral envelopes of baroque bridges are similar to those of modern bridges in D- or G-strings, and have peaks at a frequency higher than those of modern bridges in E-string. The visualization method as used in this study may provide hints for the design of violin bridges.
Construction of DNA-Au Nanoparticles Multilayer and Its Application to Detection of DNA Hybridization
Authors: Liu Hongchun , Yamaguchi Akira , Hayashida Masayuki , Matsuo Shigeki , Misawa Hiroaki
Published: February 2005

We have developed a sensitive detection system for DNA hybridization containing DNA-Au nanoparticles (DNA-GPs) multilayer which leads to the enhancement of the detection sensitivity of surface plasmon resonance (SPR) signals. The SPR angular shift, which is the difference in the SPR angles before and after hybridization, becomes amplified with increasing number of layers of the DNA-GPs. A similar increase in SPR angular shift was obtained for the target DNA with low concentration. The reason for the enhancement is attributed to the interaction between Au nanoparticles and the Au film, as well as the increase in immobilized probe DNA content on the substrate.
Removal of Liquid Leaked into Narrow Channel Using High-Intensity Aerial Ultrasonic Waves
Authors: Ito Youichi , Kotani Masayuki
Published: February 2005

We tried to remove a liquid leaked into a narrow channel immediately by radiating high-intensity aerial ultrasonic waves (at a frequency of 20 kHz) onto the liquid to atomize and disperse it into the atmosphere. Channels of 0.3 to 2 mm width and 1 to 10 mm depth with and without a bottom were used. The results of experiments showed that an ultrasonic radiation of 170 dB or more could remove a liquid in each of the channels immediately, by atomizing and dispersing it. The processes of atomization and dispersion of the liquid in each channel without a bottom largely varied, depending on the channel width and depth as well as the ultrasonic radiation intensity.
Examination of Disk-Type Multidegree-of-Freedom Ultrasonic Motor
Authors: Aoyagi Manabu , Nakajima Toshinori , Tomikawa Yoshiro , Takano Takehiro
Published: February 2005

A multidegree-of-freedom (MDOF) ultrasonic motor using the multimode of a disk vibrator is realized. A spherical rotor can rotate around arbitrary axes. However, at the beginning of research on the MDOF ultrasonic motor, the MDOF ultrasonic motor did not have any mechanisms for supporting a spherical rotor. Since the preload was given by only the rotor's own weight, the friction between the rotor and the stator vibrator was very small, but the torque characteristics of the MDOF motor were insufficient for practical use. The purpose of this study is to improve the motor performance further. In this paper, some support and preload mechanisms using a support plate were examined for the improvement of the motor performance. In addition to these methods, a sandwich structure in which two stator vibrators hold a spherical rotor is proposed. This structure has both a rotor support mechanism and a preload mechanism, and high torque by the torque composition of two stator vibrators can be obtained.
Configuration of a 30-mm-diameter 94 kHz Ultrasonic Longitudinal Vibration System for Plastic Welding
Authors: Hongoh Misugi , Yoshikuni Masafumi , Miura Hiroyuki , Miyamoto Rei , Ueoka Tetsugi , Tsujino Jiromaru
Published: February 2005

Vibration and welding characteristics of a 94 kHz ultrasonic plastic welding system are studied. The 94 kHz ultrasonic plastic welding systems consist of a 30-mm-diameter bolt-clamped Langevin-type PZT longitudinal transducers with four PZT rings, a stepped horn (vibration transform ratio N = 3.0) with a supporting flange at a nodal position and a catenoidal horn (N = 3.13) with an 8-mm-diameter welding tip. Maximum vibration velocity of the 94 kHz welding tip was 3.2 m/s (peak-to-zero value) at loaded condition. The welding characteristics of the 1.0-mm-thick polypropylene sheet specimens using the 94 kHz welding system were studied. Using the 94 kHz system, a weld strength of more than 370 N per one welded area was obtained at a vibration velocity of 2.7 m/sp-0 (peak-to-zero value), welding time of 0.8 s and static pressure of 600 kPa.
Observation and Nondestructive Evaluation of Tilting Surface Defects by Photoacoustic Microscopy
Authors: Endoh Haruo , Inomata Keita , Miyamoto Katsuhiko , Hiwatashi Yoichiro , Hoshimiya Tsutomu
Published: February 2005

In this study, the nondestructive testing (NDT) of tilting surface defects has been demonstrated using a photoacoustic microscope (PAM). The tilting surface defects were fabricated on a metal plane specimen by mechanical processing. The obtained signal strength distribution was affected by the tilt angle of the surface defects, and it is possible to estimate the tilt angle of the surface defects from the gradient of the obtained signal strength distribution.
Model of Contact Mechanism for Quartz-Crystal Tuning-Fork Tactile Sensor
Authors: Itoh Hideaki , Yamatani Masataka , Yoshida Shinobu , Fujiwara Yasunobu , Ishikawa Kiyoshi
Published: February 2005

The contact mechanism for a quartz-crystal tuning-fork tactile sensor has been investigated both theoretically and experimentally. We assume that the L-shaped right half of a quartz-crystal tuning fork is described by Sezawa's model and the torsion spring model. The frequency of the tuning-fork tactile sensor is analyzed by considering the lateral clamping force of an acrylic resin case and Winkler's foundation of the object in contact. The calculations are performed under two boundary conditions at one end of the bar which corresponds to the center of the base. Five metals (brass, copper, aluminum, stainless steel, and iron) are investigated in the present experiment. The calculated results are in reasonable agreement with the experimental ones.
Mode Decoupling Effect of Multistepped Bi-Mesa AT-Cut Quartz Resonators
Authors: Goka Shigeyoshi , Tamura Takeshi , Sekimoto Hitoshi , Watanabe Yasuaki , Sato Takayuki , Sato Kenji
Published: February 2005

In this paper, we calculated the mode-coupling characteristics of multistepped bi-mesa resonators and compared them with those of beveled resonators. Calculation results showed that increasing the number of mesa steps red to reduced coupling between the thickness-shear and thickness-flexure modes. These results indicate that the multistepped bi-mesa resonator has a good mode-decoupling effect, and its performance characteristics approach those of the beveled resonator.
LiTaO3 Shear Wave Resonator for Viscosity Measurement of Polymer Liquid in MHz Range
Authors: Bannai Mai , Wakatsuki Noboru
Published: February 2005

We are studying the response of a strip-type LiTaO3 shear wave resonator in polymer liquid in MHz range. The element size is small (1.0×7.4×0.49 mm3). The side surfaces of the resonator were covered with a highly viscous silicone rubber material. Using Newton fluid theory, the characteristic mechanical impedance of the shear wave in the liquid was derived for the equivalent circuit of the resonator. The analytical values of glycerin were roughly consistent with the experiment using only 0.1 cm3. The polymer liquid used for the measurement was silicone oil. The static viscosity was from 9.8 to 94,720 mPa·s. The resonance frequency change was from 0.05% to 0.07%. The resonance resistance change was from 57 Ω to 190 Ω. The experiment results were examined using Mason's equivalent circuit with Maxwell model of a viscoelastic polymer.
Finite Element Analysis of Viscoelasticity of Test Pieces for Tactile Sensor
Authors: Kudo Subaru , Akiba Yuuichi , Aoyagi Ryoji , Yoshida Tetsuo
Published: February 2005

In this paper, we present an analysis of the viscoelastic characteristics of a silicone rubber test piece for a tactile sensor using the finite element method. The calculated characteristics of stress relaxation and dynamic viscoelasticity agree well with the experimental values. The results can be used for designing a standard test piece for the evaluation of the measurement accuracy of a tactile sensor.
Arrayed Ultrasonic Transducers on Arc Surface for Plane Wave Synthesis
Authors: Kim Jung-Soon , Kim Jung-Ho , Kim Moo-Joon , Ha Kang-Lyeol , Yamada Akira
Published: February 2005

In ultrasonic computed tomography (UCT), it is necessary to synthesize a plane wave using waves emitted from sound sources arranged in the interior surface of a cylinder. In order to transmit a plane wave into a cylindrical surface, an ultrasonic transducer which has many vibrating elements with piezoelectric transverse effect arrayed on an arc surface is proposed. To achieve a wide beam width, the elements should have a small radiation area with a much narrow width. The measured electroacoustic efficiency for the elements was approximately 40% and the beam width defined by -3 dB level from the maximum was as wide as 120 deg. It was confirmed that plane wave synthesis is possible using the proposed transducer array.
A Basic Experimental Study for Imaging by Monopolar Pulse Radiated from Concave Polyvinylidene Fluoride (PVDF) Transducer
Authors: Ooyashiki Atsuko , Yoshida Yasuo , Inoue Hiroshi , Murata Kenji
Published: February 2005

Monopolar C-mode imaging using a concaved polyvinylidene fluoride (PVDF) transducer was developed. The basic characteristics of the spreading of the ultrasound field are measured and discussed with respect to the imaging, along with the spatial resolution, and the C-mode image of a printed circuit board (PCB) surface.
Finite Difference Time Domain Analysis for a Sound Field Including a Plate in Water
Authors: Saito Hideaki , Naoi Jun , Kikuchi Toshiaki
Published: February 2005

In marine research, measures against self-noise of an observatory ship are important. Generally, the self-noise is measured after the completion of ships. It is difficult to predict this noise level beforehand. Then, an attempt is made to determine the noise emitted from various elements of a structure. The finite difference time domain method is applied to obtain sound fields, including that of a plate in water. The time behavior of the sound wave emitted from a sound source placed near the upper part of a plate is investigated. As a result, the reflected and re-radiated waves from the plate including the head wave resulting from the longitudinal and traverse waves in the plate are able to be visualized. In the case of the plate with a branch plate, the suppression of the wave which propagates at the inside of the plate with the length of the branch plate is shown.