bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanoindentation Analysis of Al:ZnO Epitaxial Whiskers
Authors: Hidetoshi Saitoh Hidetoshi Saitoh , Yoshiaki Namioka Yoshiaki Namioka , Hironori Sugata Hironori Sugata , Shigeo Ohshio Shigeo Ohshio
Published: October 2002

An aggregation of well-organized ZnO whiskers epitaxially grown using a chemical-vapor deposition technique is one of the particularly simple and elegant examples of spontaneous pattern formation. In this study, we analyzed the breaking process of the epitaxial whiskers with and without Al doping using the nanoindentation technique. The whisker diameter and the number density of the whiskers were unchanged with increasing amounts of Al doped into the matrix. The relationship between the breaking load and the length of the whiskers follows Euler's equation, suggesting that the whiskers are destroyed through the bucking process. The degree of elastic deformation is higher for samples including 0.4 and 0.8 at.%Al and lower for those including 1.7 and 2.0 at.%Al than that for nondoped ZnO whiskers. This tendency is also found for the change in the critical load of whisker breaking.
Residual DC Characteristics in the In-Plane Switching Liquid Crystal Display by Voltage–Transmittance Hysteresis Method on Rubbed Polyimide Surfaces
Authors: Kim Hyang-Yul , Kim Jae-Hyung , Seo Dae-Shik
Published: October 2002

The residual DC phenomena in the in-plane switching liquid crystal display (IPS-LCD) by voltage–transmittance (V–T) hysteresis method on a rubbed polyimide (PI) surfaces were investigated. We found that the residual DC voltage in the IPS-LCD decreased with increasing concentration of cyano LCs. The residual DC voltage of the IPS-LCD can be improved by high polarity of cyano LCs.
Buffer Energy Nuclear Fusion
Authors: Ikegami Hidetsugu
Published: October 2002

A compact scheme of non-thermonuclear fusion is presented. Hydrogen ions are implanted directly from nonthermal discharge plasma or ion source into a surface of liquid Li metal at a buffer energy of a few tens keV where nuclear stopping occurs. The ions interact with Li atoms or mixed element atoms which are not being internally excited and tend towards the formation of united atoms at the minimum Gibbs free energy point. This leads to the enhanced rate of non-thermonuclear fusion of hydrogen ions due to cohesion in the liquid metal.
Heterodyne Fourier Transform Spectroscopy using Moving Diffraction Grating
Authors: Hirai Akiko , Zeng Lijiang , Matsumoto Hirokazu
Published: October 2002

New heterodyne white-light interferometry using a moving diffraction grating is applied to Fourier transform spectroscopy. The grating simultaneously acts as a beam splitter and a modulator, which realizes an optical frequency shift of incident light, which increases the sensitivity of measurement by heterodyne modulation. The technique was experimentally confirmed, and a spectrum of weak light was measured with high stability. This technique is expected to be effective, particularly in the infrared (IR) region where detector noise is dominant. Furthermore, reflective optical elements can be used for the proposed technique. The ease of fabrication of reflective optical elements compared to transmission elements is significant in the IR region.
Oxidation Properties of Hydrogen-Terminated Si(001) Surfaces Following Use of a Hyperthermal Broad Atomic Oxygen Beam at Low Temperatures
Authors: Tagawa Masahito , Yokota Kumiko , Ohmae Nobuo , Kinoshita Hiroshi , Umeno Masataka
Published: October 2002

The oxidation properties of an H-terminated Si(001) surface following the use of a hyperthermal broad atomic oxygen beam have been studied at low temperatures. Effects of sample temperature, flux and energy of the impinging atomic oxygen on the oxidation of silicon were investigated by X-ray photoelectron spectroscopy. It was confirmed that oxide growth at the surface was achieved even at room temperature and the oxide thickness reached a terminal thickness of a few nanometers depending upon the oxidation conditions. The oxidation process was divided into two stages: the fast oxidation stage and the subsequent slow oxidation stage. It was also confirmed that the reaction yield of atomic oxygen with Si increased with increasing translational energy. The characteristic feature of beam oxidation was explained by the effect of energy accommodation from the impinging oxygen atom to the surface silicon atom.
Single-Electron Signal Modulator Designed for a Flash Analog-to-Digital Converter
Authors: Yoshinao Mizugaki Yoshinao Mizugaki , Per Delsing Per Delsing
Published: October 2002

We demonstrate a 4-bit flash analog-to-digital converter (FADC) composed of a single-electron signal modulator (SESM) with a capacitive voltage divider (CVD). In the CVD, we utilize the self-capacitance of floating metal islands, and hence, maximum input impedance can be realized with the CVD. We also analyze the characteristics of the CVD with stray capacitance. The signals from the CVD are detected by four single-electron transistors (SETs), and their outputs, processed at quantizers, represent gray-coded digital signals. We designed two kinds of layouts for the CVDs, and fabricated two samples for each layout by photolithography, electron-beam lithography, and the shadow evaporation of aluminum. Measurements were executed at approximately 30 mK. Four-bit FADC operation was successfully simulated using experimental results. We also discuss the possibility of higher resolution with our circuit configuration.
Two-Dimensional Simulation of and Experiments on the Forward-Backward Modes Coupled Unstable Resonator
Authors: Sunako Katsuhiko , Endo Masamori , Yamaguchi Shigeru , Fujioka Tomoo
Published: October 2002

A new type of laser resonator, the forward-mode and backward-mode coupled unstable resonator, was two-dimensionally analyzed using a partially coherent input field. Under the optimum output power condition, the oscillating mode was annular even at the far field. The experiments with transverse electric atmospheric (TEA) CO2 laser qualitatively showed the same results as those calculated.
The Effect of Stress on Solid-Phase Epitaxial Regrowth in As+-Implanted Two-Dimensional Amorphized Si
Authors: Shin Yu Gyun , Lee Jeong Yong , Park Moon Han , Kang Ho Kyu
Published: October 2002

The effect of stress induced by a chemical-vapor-deposited (CVD) SiO2 film on the solid-phase epitaxial (SPE) regrowth in As+-implanted, two-dimensional amorphized Si has been studied. Trench structures were used to form the two-dimensional amorphous layer and to induce the stress in the Si substrate. As+ implantation at an energy of 80 keV with a dose of 3×1015/cm2 amorphized the silicon surface and produced a curved amorphous/crystalline (a/c) interface under the bottom corner of the trenches. At the trenches filled with the high-tensile-stress CVD SiO2 film, the regrowth of the amorphous Si layers was retarded and a notch remained in the a/c interface immediately under the bottom corner of the trench after annealing at 500°C for 4 h. The regrowth retardation and the remaining notch were explained by the effect of the stress induced by the CVD SiO2 film on the activation barrier of the SPE regrowth.
Adsorbed Water on a Silicon Wafer Surface Exposed to Atmosphere
Authors: Takayuki Takahagi Takayuki Takahagi , Hiroyuki Sakaue Hiroyuki Sakaue , Shoso Shingubara Shoso Shingubara
Published: October 2002

Adsorbed water on a silicon wafer surface exposed to atmosphere was investigated mainly by attenuated total reflection using Fourier-transform infrared spectroscopy. The atomically smooth hydrogen-terminated silicon wafer surface was shown to have no adsorbed water in room air. The water adsorbed on the chemically oxidized silicon wafer surface was shown to be covered by three adsorbed water-molecular layers comprising two molecular layers of liquid-phase water and one molecular layer which was directly hydrogen-bonded to the oxide surface under medium room-humidity condition. The former component reversibly adsorbs and desorbs depending on the atmospheric humidity at room temperature and the latter component desorbs in the temperature range between 100°C and 300°C.
Yb Fiber Laser Pumped Mid-IR Source Based on Difference Frequency Generation and Its Application to Ammonia Detection
Authors: Matsuoka Naoya , Yamaguchi Shigeru , Nanri Kenzo , Fujioka Tomoo , Richter Dirk , Tittel Frank K.
Published: October 2002

A Yb fiber laser pumped cw narrow-linewidth tunable mid-IR source based on a difference frequency generation (DFG) in a periodically poled LiNbO3 (PPLN) crystal for trace gas detection was demonstrated. A high power Yb fiber laser and a distributed feedback (DFB) laser diode were used as DFG pump sources. This source generates mid-IR at 3 µm with a power of ∼2.5 µW and a spectral linewidth of less than 30 MHz. A frequency tuning range of 300 GHz (10 cm-1) was obtained by varying the current and temperature of the DFB laser diode. A high-resolution NH3 absorption Doppler-broadened spectrum at 3295.4 cm-1 (3.0345 µm) was obtained at a cell pressure of 27 Pa from which a detection sensitivity of 24 ppm·m was estimated.
Novel Methods of p-type Activation in Mg-doped GaN
Authors: Takeya Motonobu , Ikeda Masao
Published: October 2002

We have developed two methods for the p-type activation of Mg-doped GaN; a low-temperature long-time annealing method and a RF input activation method. In the low-temperature long-time annealing method, hole concentration increased in proportion to the square root of annealing time. It took ∼ 80 h to obtain hole concentrations of ∼ 1018 cm-3 at 385°C annealed in air. In the RF input activation method, hole concentration increased with the product of RF input time and amplitude of the RF electric field. It took ∼ 70 s to get hole concentrations of ∼ 1018 cm-3 at a RF electric field of ∼ 21 kV/cm. No specific difference was observed for the optical and electrical properties as compared to those of thermally activated samples annealed between 475°C and 800°C in a N2 atmosphere. The photoluminescence (PL) intensity was found to decrease with increasing hole concentration in all activation methods. Nonradiative recombination process is thought to become dominant at hole concentrations over ∼ 2×1016 cm-3 independent of the activation method.
A Study on Thermal Stability of CoSi2 Employing Novel Fine-Grained Polycrystalline Silicon/CoSi2/Si (001) System
Authors: Bae Jong-Uk , Sohn Dong Kyun , Park Ji-Soo , Han Chang Hee , Park Jin Won , Kim Yeong-Cheol , Kim Jae Jeong
Published: October 2002

The cobalt silicide/fine-grained polycrystalline silicon (poly-Si) structure has been employed as gate electrodes in silicon-based very large-scale integration circuits. We have constructed a novel fine-grained poly-Si/cobalt silicide/silicon (001) structure to investigate the thermal stability of cobalt silicide at elevated temperatures. The dissociated cobalt atoms are observed to diffuse from fine-grained poly-Si/cobalt silicide and cobalt silicide/silicon (001) interfaces into the fine-grained poly-Si layer through poly-Si grain boundaries and the bulk cobalt silicide layer. The dissociated Si atoms at the cobalt silicide/silicon (001) interface are observed to grow epitaxilly on the silicon (001) substrate. This observation is consistent with previous results for circuits that employed amorphous Si instead of fine-grained poly-Si.
Recording Characteristics of Flux-detectable Magneto-optical Recording Media
Authors: Nemoto Hiroaki , Saga Hideki
Published: October 2002

We investigated the effect of an additional readout layer in TbFeCo-based bilayer media on the magneto-optical (MO) recording characteristics, by conducting experiments and calculations based on the Huth formula. The bilayer medium with an appropriate readout layer can have equivalent recording characteristics to those of a monolayer one. The designed bilayer medium showed sufficient performance for high-density MO recording, providing a sufficiently strong stray field for magneto-resistive detection. On the other hand, a monolayer medium with large magnetization resulted in poor recording performance due to its self-demagnetizing field. By comparing the recording characteristics, the guidelines for designing the bilayer structure were clarified.
Simple Formulas for Calculating Wave Propagation and Splitting in Anisotropic Media
Authors: Chang Chong-Min , Shieh Han-Ping D.
Published: October 2002

A general method for dealing with the propagation of waves in homogeneous anisotropic media is presented. The formulas were derived and applied to determine the reflected and transmitted waves resulting from a plane wave obliquely incident at an interface between two anisotroptic media with arbitrarily oriented principal axes. The validity of the formulas was also demonstrated by calculating the reflection and refraction at a biaxial–biaxial interface.
Monolithically Integrated Dual-Wavelength Self-Sustained Pulsating Laser Diodes with Real Refractive Index Guided Self-Aligned Structure
Authors: Onishi Toshikazu , Imafuji Osamu , Fukuhisa Toshiya , Mochida Atsunori , Kobayashi Yasuhiro , Yuri Masaaki , Itoh Kunio , Shimizu Hirokazu
Published: October 2002

Monolithically integrated 780-nm-band and 650-nm-band self-sustained pulsating (SSP) lasers, which are desirable for simplified optical pickups in digital versatile disk (DVD) systems, have been developed for the first time. The real refractive index guided self-aligned (RISA) waveguide structure is adapted to reduce absorption loss in the current blocking layers. In order to obtain stable SSP, a saturable absorber formed in the active layer outside the current stripe, and a saturable absorbing layer above the active layer are utilized for the 780-nm-band and 650-nm-band laser diodes (LDs), respectively. Relative intensity noise less than -130 dB/Hz is maintained at temperatures of up to 80°C at an output power of 7 mW for the 650 nm band and 10 mW for the 780 nm band, which suggests that stable SSP operations have been realized.
Design and Performance of a Diode-Pumped Nd:Silica-Phosphate Glass Zig-Zag Slab Laser Amplifier for Inertial Fusion Energy
Authors: Kawashima Toshiyuki , Kanabe Tadashi , Matsui Hiroki , Eguchi Takeyoshi , Yamanaka Masanobu , Kato Yoshinori , Nakatsuka Masahiro , Izawa Yasukazu , Nakai Sadao , Kanzaki Takeshi , Kan Hirofumi
Published: October 2002

A high-energy, high beam quality, diode-pumped 1053-nm Nd:silica-phosphate glass laser amplifier has been designed, constructed and tested in order to verify the conceptual design of HALNA (high average-power laser for nuclear-fusion application): a diode-pumped solid-state laser based on a water-cooled zig-zag slab optical geometry. This amplifier yields an 8.5 J output energy per pulse at 0.5 Hz in a 20 ns pulse of two times the diffraction limit beam quality with an optical-to-optical conversion efficiency of 10.9%. This is the first demonstration of a diode-pumped solid-state laser amplifier for the inertial fusion energy (IFE) driver. The detailed considerations on the optical and thermal designs of the novel amplifier architecture are discussed. The experimental results revealed that the primary requirements for the IFE driver, such as diode-pumping, energy storage and extraction efficiencies, and beam quality have been fulfilled.
Photoluminescence Quenching by Optical Bias in AlGaAs/GaAs Single Quantum Wells
Authors: Chavanapranee Tosaporn , Fujimoto Shin'go , Horikoshi Yoshiji
Published: October 2002

Anomalous photoluminescence characteristics are reported for AlGaAs/GaAs single quantum wells with one-monolayer-thick InAs inserted at the center of the GaAs well under an external electric field. The photoluminescence produced by exciting only the quantum well is strongly quenched when simultaneous excitation is performed using a high-energy light which can excite both the quantum well and the AlGaAs barrier layers. Since no prominent increase in the photocurrent accompanies the photoluminescence quenching, an efficient recombination center becomes operative under the simultaneous high-energy excitation. A carrier trapping center in AlGaAs which becomes active as a nonradiative recombination center after trapping carriers is considered to explain the observed result.
Optimum Designing of Single Crystalline Silicon Thin Film Solar Cells with Graded Active Layer
Authors: Yamamoto Yukie , Ishikawa Yasuaki , Uraoka Yukiharu , Fuyuki Takashi
Published: October 2002

A carrier density gradient was given to the p-doped active layer of a conventional p–n junction solar cell employing the concept of the p–i–n junction structure used in amorphous silicon solar cells. Single crystalline silicon thin film solar cells with graded carrier density in the active layer were analyzed to optimize the cell structure utilizing a two-dimensional device simulator. Two types of cell structures were designed. In the case of Cell1, the carrier density was fixed to be 1016 cm-3 on the back surface field (BSF) side and changed exponentially for the p–n junction side from 1013 cm-3 to 1018 cm-3. On the other hand, in the case of Cell2, the carrier density was fixed to be 1016 cm-3 on the p–n junction side and changed exponentially for the BSF side from 1013 cm-3 to 1018 cm-3. Improvement in short circuit current density and open circuit voltage was observed. Therefore, high efficiency was expected under an electric field, considering the carrier density gradient. In the case of a solar cell with a 5-µm-thick solar grade single crystalline silicon film, a conversion efficiency of about 14% was obtained for a flat surface solar cell.
GaInAsP/InP Distributed Reflector Lasers Consisting of Deeply Etched Vertical Gratings
Authors: Wiedmann Jörg , Kim Hyo-Chang , Ebihara Koji , Chen Bo , Ohta Masataka , Tamura Shigeo , Shim Jong-In , Arai Shigehisa
Published: October 2002

Deep-etching technology, which is a very simple fabrication process and requires only one lithography and one etching step without any regrowth, is applied to realize 1.5–1.55 µm wavelength GaInAsP/InP vertical grating (VG) distributed reflector (DR) lasers, which consist of a distributed feedback (DFB) region with the VG and a high-reflectivity distributed Bragg reflector (DBR) region. First, the coupling coefficient of the VG is theoretically estimated and fundamental lasing characteristics of the VG-DR lasers are investigated. Then, the fabrication process of the VG-DR lasers and the experimentally achieved fundamental lasing characteristics are given. A threshold current of 12.4 mA and a differential quantum efficiency of 42% from the front cleaved facet are achieved for a 220-µm-long and 5-µm-wide device. A submode suppression ratio (SMSR) of 33 dB at a bias current of 2.4 times the threshold is obtained.
Quasi-CW 110 kW AlGaAs Laser Diode Array Module for Inertial Fusion Energy Laser Driver
Authors: Kawashima Toshiyuki , Kanzaki Takeshi , Matsui Ken , Kato Yoshinori , Matsui Hiroki , Kanabe Tadashi , Yamanaka Masanobu , Nakatsuka Masahiro , Izawa Yasukazu , Nakai Sadao , Miyamoto Masahiro , Kan Hirofumi , Hiruma Teruo
Published: October 2002

We have successfully demonstrated a large aperture 803 nm AlGaAs diode laser module as a pump source for a 1053 nm, 10 J output Nd:glass slab laser amplifier for diode-pumped solid-state laser (DPSSL) fusion driver. Detailed performance results of the laser diode module are presented, including bar package and stack configuration, and their thermal design and analysis. A sufficiently low thermal impedance of the stack was realized by combining backplane liquid cooling configuration with modular bar package architecture. Total peak power of 110 kW and electrical to optical conversion efficiency of 46% were obtained from the module consisting of a total of 1000 laser diode bars. A peak intensity of 2.6 kW/cm2 was accomplished across an emitting area of 418 mm×10 mm. Currently, this laser diode array module with a large two-dimensional aperture is, to our knowledge, the only operational pump source for the high output energy DPSSL.
Photoluminescence from Thermally Oxidized Hydrogenated Amorphous Silicon Nanoball Films Fabricated by Double-Tubed-Coaxial-Line-Type Microwave Plasma Chemical Vapor Deposition System
Authors: Kato Isamu , Matsumoto Takayuki , Agnihotri O. P.
Published: October 2002

Using a double-tubed-coaxial-line-type microwave plasma chemical vapor deposition (MPCVD) system, hydrogenated amorphous silicon (a-Si:H) nanoball films, which include Si nanocrystals, can be fabricated. A high deposition rate of 1600 Å/s is achieved at a gas flow rate of 30 ml/min. Photoluminescence (PL) around 780 nm is observed at room temperature after the a-Si:H nanoball film is thermally oxidized in air or in pure oxygen gas. We have fabricated thermally oxidized a-Si:H nanoball films under various fabrication and oxidation conditions. As the substrate temperature during deposition becomes higher, the PL intensity decreases, and PL cannot be observed above 200°C. The PL intensity is the strongest when the substrate is set about 6 cm from the discharge tube end. As the discharge time increases, the film thickness increases and saturates, and consequently the PL intensity increases and also saturates.
First Principles Study on Li Deintercalation Effect in Orthorhombic LiMnO2
Authors: Nishidate Kazume , Baba Mamoru , Hasegawa Masayuki , Komaba Shinichi , Kumagai Naoaki
Published: October 2002

Density functional electronic structure calculations for orthorhombic LiMnO2 have been carried out applying spin polarized generalized gradient approximation. Structural stability during the initial deintercalation process of Li ions is analyzed by total energy difference resulting from changing the Li concentration x of orthorhombic LixMnO2 at ferromagnetic and antiferromagnetic initial spin configurations. Here, valence electrons of intercalated Li atoms transfer not only to O sites but also to Mn sites forming a high-spin Mn3+-derived e
g (d

x
2-y
2
) orbital. The Jahn–Teller distortion effect and lattice parameter changes associated with the Li deintercalation process are analyzed.
Thermal Behavior along Depth of Extreme Ultraviolet Lithography Mask during Dry Etching
Authors: Chiba Akira , Hoshino Eiichi , Takahashi Masashi , Yamanashi Hiromasa , Hoko Hiromasa , Lee Byoung Taek , Yoneda Takashi , Ito Masaaki , Ogawa Taro , Okazaki Shinji
Published: October 2002

The thermal response of an extreme ultraviolet lithography (EUVL) mask during dry etching was investigated through simulation. In order to estimate the power absorbed during dry etching, the temperature of a glass wafer was measured by observing the change in color of a heat-sensitive label. The experimental result was compared with the simulation result based on a lumped heat capacity model. The absorptance of power was found to be 0.25–0.35, and there was good agreement between the results of the experiment and simulation. To handle mask deflection caused by the temperature gradient, a first-approximation model based on spherical deformation and free boundary conditions was used. The temperature gradient in an EUVL mask that arises during dry etching was analyzed. Thermal deflection of EUVL masks was found to be much less when the masks were formed on an ultralow expansion (ULE) glass substrate or Si substrate rather than on quartz.
Two-Chord Interferometry Using a Pin Switch for Plasma Density Measurement
Authors: Yamada Takuma , Ejiri Akira , Shiraiwa Syun'ichi , Takase Yuichi
Published: October 2002

Microwave interferometry is a useful diagnostic for measuring the line-integrated density of plasmas. To obtain a detailed profile of the electron density, multi chord interferometry is indispensable. Using a pin switch, we have successfully measured the density along two chords by alternating the beam with a time interval of 2 µs for each chord. This method is very cost advantageous, because it requires only one set of sources and detection components. The system has been applied to Tokyo Spherical Tokamak-2 (TST-2) to measure two vertical chords at different major radii. It is shown that from the densities measured along the two chords, profile changes can be deduced.
Strong–Strong Beam–Beam Simulation for a Muon-Collider Ring
Authors: Hwang Il-Moon , Kim Eun-San , Yoon Moohyun
Published: October 2002

We have performed a strong-strong simulation to investigate the effect of a beam-beam interaction on the motion of circulating beams in a 50 GeV×50 GeV muon-collider ring. The phase-slip factor η1 in the muon-collider ring is approximately -1×10-6 so that the synchrotron motion is nearly frozen during the muon-storage time. Thus, the energy variation of a particle in the beam due to the beam-beam interaction accumulates from turn to turn, resulting in an increase in the energy spread of the beam. Through the strong-strong simulation, we have investigated the parametric dependencies of the energy spread and the beam size induced by the beam-beam interaction on various parameters. It is shown that the induced energy spread due to the beam-beam interaction affects the growth of the beam size. It is also shown that compensation of the energy spread by introducing one additional rf cavity in the ring can reduce the growth of the beam size.
Optimized Surface Pre-treatments for Cu Electroless Plating in ULSI Device Interconnection
Authors: Kim Jae Jeong , Cha Seung Hwan
Published: October 2002

We investigated the effects of under layer pretreatments on Cu electroless deposition to optimize the resistivity and morphology of the Cu. The pretreatments used in the Cu electroless plating process consisted of the removal of the titanium oxide layer on the barrier metal, TiN, and the deposition of Pd to activate the TiN diffusion barrier layer. Surface pretreatment using a 1%HF solution to remove the native Ti oxide formed on a TiN diffusion barrier layer showed a remarkable surface conditioning effect for the catalytic metal activation stage in Cu electroless plating, even in the absence of a wetting agent. Microcavities generated during Ti oxide etching are believed to be the key factor for the improved uniformity of the deposited catalytic metal on the pretreated TiN layer. Electroless plated Cu layers on non-uniform or rough Pd layers exhibited high resistivity and RMS roughness.
Deposition of Titanium Oxide Films with High Dielectric Constants on Silicon by an Ion Beam Assist Deposition Technique
Authors: Yokota Katsuhiro , Nakamura Kazuhiro , Sasakawa Tomohiro , Kamatani Toshihiko
Published: October 2002

Titanium-dioxide (TiO
x
) thin films were deposited on n-type Si wafers by an ion beam assist deposition technique utilizing an oxygen ion beam source and a Ti electron beam evaporator. The chemical structure of the TiO
x
thin films was determined by Rutherford backscattering spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy, which revealed that the TiO
x
thin films consisted of rutile TiO2 and O-deficient rutile TiO2 here and throughout. The TiO
x
films had high dielectric constants ranging from 30ε
0 to 160ε
0, which depended significantly on substrate temperature and oxygen ion energy.
Stress in Pulsed-Laser-Crystallized Silicon Films
Authors: Higashi Seiichiro , Ando Nobuyuki , Kamisako Koichi , Sameshima Toshiyuki
Published: October 2002

Stress in pulsed-laser-crystallized silicon films was investigated using high-resolution Raman scattering measurements. Film stress was evaluated based on the peak shift of transverse optical (TO) phonon of crystalline silicon in Raman scattering spectra. The tensile stress in laser-crystallized 50-nm-thick silicon films on glass substrates increased from 3.5×108 Pa to 9.7×108 Pa as the film deposition temperature increased from 200°C to 480°C. The peak shift of laser-crystallized microcrystalline silicon (µc-Si) films revealed that the tensile stress introduced by laser irradiation was 2.3×108 Pa at most. These results indicate that the strong tensile stress is introduced by the silicon film deposition rather than by the pulsed-laser crystallization. Also, the authors demonstrate that pulsed-laser crystallization maintains the existing stress at the growth initiation sites in the bottom region of silicon films.
Formation of Hard Amorphous Hydrogenated Carbon Films with Low Hydrogen Concentration and Their Erosion in Air
Authors: Maruyama Kazunori , Jacob Wolfgang , Roth Joachim
Published: October 2002

Hard amorphous hydrogenated carbon (a-C:H) films are prepared by radio-frequency plasma deposition from a mixture of CH4 and Ar. When these films are heated up to 1220 K under vacuum, they release Ar, a large amount of H2 and a small amount of hydrocarbon, but the thickness of the films does not decrease. In addition, their micro-Vickers hardness decreases, but they remain hard. If these hydrogen-free semihard a-C:H films are heated at 670 K in air for 1 h, they become soft and uptake oxygen and hydrogen. On the other hand, if the original hard a-C:H films are heated under similar conditions, they remain hard without releasing argon or uptaking oxygen. It is concluded that the reduction of hydrogen does not lead to the formation of new cross linking C–C bonds, and the pore size of the films increases after heating allowing the penetration of oxygen and water vapor into the films.
Analysis of Coaxial Periodic Dielectric Waveguides by an Extension of Floquet's Theorem
Authors: Toshihiro Hori Toshihiro Hori
Published: October 2002

The characteristics of coaxial periodic dielectric waveguides are treated by considering the scaling relation of transfer matrixes. First, analytical parameter conditions are introduced to make Floquet's theorem applicable. Next, the parameter conditions used for numerical calculations are found to yield the same transfer matrixes as analytical ones, when the core radii of the waveguides are much larger than the wavelengths and period lengths. Finally, analysis of eigen modes indicates that hybrid modes exist only when two dispersion equations are satisfied simultaneously.
Development of a Numerical Tool for Foil Acceleration by an Intense Pulsed Ion Beam
Authors: Harada Nobuhiro , Yazawa Masaru , Kashine Kenji , Jiang Weihua , Yatsui Kiyoshi
Published: October 2002

When we irradiate a foil with an intense pulsed ion beam, ablation plasma is created, and the foil is accelerated. In this study, we developed a numerical model of this phenomenon. We analyze the temperature and pressure of the ablation plasma, and the velocity of the accelerated foil by numerical simulation. It was possible for us to analyze the behavior and detailed results of the ablation plasma expansion and acceleration of the foil. We could also observe the processes of ablation plasma expansion and foil acceleration by back-lighting high-speed photography. The numerical results of foil velocity agree well with the experimental ones over a wide range of energy density values of an ion beam. We analyzed the time trend of the foil velocity, and we could observe that the foil is rapidly accelerated immediately after a delay.
Surface Passivation Effect of Silicon Substrates due to Quinhydrone/Ethanol Treatment
Authors: Takato Hidetaka , Sakata Isao , Shimokawa Ryuichi
Published: October 2002

A new technique of surface passivation of silicon substrates by quinhydrone/ethanol treatment has been investigated. To estimate the surface passivation effect, the lifetimes of the silicon substrates were measured using the microwave photoconductive decay method. The measured lifetimes were dependent on quinhydrone concentration and passivation time. The 0.01 mol/dm3 quinhydrone/ethanol treatment showed a good passivation effect, and a very low surface recombination velocity was obtained. The quinhydrone/ethanol treatment was a more effective passivation technique than the iodine/ethanol treatment. Therefore, the quinhydrone/ethanol passivation can be widely used for lifetime measurement.
Enhancement of Photoluminescence and Electrical Properties of Ga-Doped ZnO Thin Film Grown on α-Al2O3(0001) Single-Crystal Substrate by rf Magnetron Sputtering through Rapid Thermal Annealing
Authors: Jung Cho Jung Cho , Jongbum Nah Jongbum Nah , Min-Seok Oh Min-Seok Oh , Jae-Hoon Song Jae-Hoon Song , Ki-Hyun Yoon Ki-Hyun Yoon , Hyung-Jin Jung Hyung-Jin Jung , Won-Kook Choi Won-Kook Choi
Published: October 2002

Ga2O3 (1 wt%)-doped ZnO (GZO) thin films were deposited on α-Al2O3(0001) by rf magnetron sputtering at 550°C and a polycrystalline structure was obtained. As-grown GZO thin films show poor electrical properties and photoluminescence (PL). For the improvement of these properties, GZO thin films were annealed at 800–900°C in N2 atmosphere for 3 min. After rapid thermal annealing, deep-defect-level emission disappears and near-band emission is greatly enhanced. Annealed GZO thin films show very low resistivity of 2.6×10-4 Ω·cm with 3.9×1020/cm3 carrier concentration and exceptionally high mobility of 60 cm2/V·s. These improved physical properties are explained in terms of the translation of doped-Ga atoms from interstitial to substitutional sites.
Formation of Buried Oxide Layer in Si Substrates by Oxygen Precipitation at Implantation Damage of Light Ions
Authors: Ogura Atsushi
Published: October 2002

We have developed a novel Si-on-insulator fabrication technique in which light ions, such as H+ and He+, are implanted into a Si substrate instead of O+ implantation in the SIMOX (separation by implanted oxygen) process. The atmospheric oxygen atoms precipitate at the implantation damage during high temperature annealing in an oxydizing atmosphere. A continuous buried oxide layer was successfully formed in a Si substrate under the appropriate conditions, particularly a slow ramping rate and a high oxygen concentration in the atmosphere for the anneal.
GaAs Metal-Semiconductor Field-Effect Transistor with Surface Oxygen Implantation
Authors: Hsin Yue-Ming , Hsueh Kuang-Po , Hsu Chia-Jen , Wu Liang-Wen
Published: October 2002

Oxygen implantation has been employed to form a high-resistance region between the channel and the surface of GaAs metal-semiconductor field-effect transistors (MESFETs). Comparable DC and RF performances were achieved for MESFETs with and without oxygen implants; however, MESFETs with the extra oxygen-implantation demonstrated good breakdown performance, less frequency dispersion of drain current, and good time dependence of drain current at 150°C in air.
Influence of Crystallinity on the Bulk Laser-Induced Damage Threshold and Absorption of Laser Light in CsLiB6O10 Crystals
Authors: Kamimura Tomosumi , Ono Richi , Yap Yoke Khin , Yoshimura Masashi , Mori Yusuke , Sasaki Takatomo
Published: October 2002

The relationships among the bulk laser-induced damage threshold (LIDT), dislocation density and absorption of laser light in CsLiB6O10 (CLBO) were investigated. A newly developed synthesis process allows the growth of CLBO crystals with a LIDT of 2.5-fold higher than that grown by the conventional top-seeded solution growth (TSSG) technique. High-quality CLBO possesses lower dislocation density (6.6×103/cm2) than conventional CLBO (∼15.0×103/cm2). The absorption of laser light in CLBO was characterized by measuring the temperature increase on the crystal output surface during the generation of fourth-harmonic (@266 nm) light of Nd:YAG lasers. At a UV power of 5 W, the maximum temperature increase was 6°C for high-quality CLBO, which was ∼30% lower than that generated on conventional CLBO crystal. Thus, the reduction of dislocation density can suppress the absorption of laser light, which helps to enhance the resistance of CLBO against laser-induced damage and alleviate thermal dephasing during the high-power generation of UV light.
Femtosecond Multistep Laser Etching of Transparent Amorphous Organic Film
Authors: Hosokawa Yoichiroh , Yashiro Masaki , Asahi Tsuyoshi , Masuhara Hiroshi , Kadota Toshiaki , Shirota Yasuhiko
Published: October 2002

Novel laser etching was demonstrated by one-shot femtosecond laser ablation of a transparent organic amorphous film. The etch depth increased stepwise with increasing laser fluence and each step is constant and independent of the fluence, while the number of steps and etching area increase with the fluence. The successive depths were 270, 480, 690 and 820 nm, for which the thresholds were 180, 180, 210 and 290 mJ/cm2, respectively. A fifth step was not observed in the present fluence range. Both the etched surfaces and slopes between the steps are very smooth with a roughness of less than 10 nm. The mechanism is proposed and discussed in view of the optical interference effect and a possible application is mentioned.
AlGaN/InGaN/GaN Double Heterostructure Field-Effect Transistor
Authors: Simin Grigory , Hu Xuhong , Tarakji Ahmad , Zhang Jianping , Koudymov Alexey , Saygi Salih , Yang Jinwei , Khan Asif , Shur Michael S. , Gaska Remis
Published: October 2002

Novel, current collapse free, double heterostructure AlGaN/InGaN/GaN field effect transistors (DHFETs) are fabricated on the insulating SiC substrates. The simulations show that a combined effect of the bandgap offsets and polarization charges provides an excellent 2D carrier confinement. These devices demonstrate output RF powers as high as 4.3 W/mm in CW mode and 6.3 W/mm in the pulsed mode, with the gain compression as low as 4 dB.
Sacrificial Anodic Oxidation of 6H-SiC
Authors: Kato Masashi , Ichimura Masaya , Arai Eisuke
Published: October 2002

We formed oxide films on n-type 6H-SiC by an anodic oxidation method. As the electrolyte, a mixed solution of ethylene glycol, water and KNO3 was employed. By applying voltage with constant current to 6H-SiC, an oxide film was formed on the sample. The oxide was easily etched by HF. The formation rate for the anodic oxide was much higher than the typical thermal oxidation rate for 6H-SiC. By using this method for sacrificial oxidation before contact formation, Al ohmic contact resistance was reduced compared with those on an as-received surface.
Electron Spin Resonance Study of Low-Dimensional Magnetic Properties of MnF2–CaF2 Superlattices
Authors: Kuroda Shin-ichi , Marumoto Kazuhiro , Kihara Hideji , Ofuchi Hironobu , Tabuchi Masao , Takeda Yoshikazu , Banshchikov Alexandr Gavrilovich , Sokolov Nikolai Semenovich , Yakovlev Nikolai Leopoldovich
Published: October 2002

Electron-spin-resonance (ESR) studies were performed on short-period MnF2–CaF2 superlattices on Si(111) grown by molecular beam epitaxy. In the case of one to three MnF2 monolayers in the repeated unit of samples, angular dependence of ESR linewidth revealed the behavior characteristic of a two-dimensional (2D) magnet, where the linewidth minimum was observed for the angle between the plane normal and the external field of 55° (magic angle). At the same time, the antiferromagnetic transition of the bulk crystal at around 67 K, observed for thick MnF2-layer films, is seen to have disappeared in films of a few monolayers. These results indicate the development of well-defined 2D magnetic layers in the present superlattice structures with a few MnF2 layers.
Dramatic Improvement of Surface Wave Plasma Performance Using a Corrugated Dielectric Plate
Authors: Yamauchi Takeshi , Abdel-Fattah Essam , Sugai Hideo
Published: October 2002

Surface wave plasmas (SWPs) of large area and high density are conventionally produced under a flat dielectric window for microwave irradiation through slot antennas. However, the SWPs often show discontinuous jumps in plasma density, and they tend to localize near the slots in the case of electronegative gas discharge. In this letter we report that such problems can be avoided by using a corrugated dielectric window with a periodicity of ∼ 10 mm pitch and 5 mm depth. Compared with the conventional flat plate, the corrugated plate gives a widely spreading uniform plasma with higher power efficiency and no density jump. Three-dimensional numerical simulations of microwave excitation under the experimental conditions clearly show a dramatic change in the wave propagation along the corrugated surface, supporting the experimental observations.
New 300 kV Energy-Filtering Field Emission Electron Microscope
Authors: Bando Yoshio , Mitome Masanori , Golberg Dmitri , Kitami Yoshizo , Kurashima Keiji , Kaneyama Toshihiko , Okura Yoshihiro , Naruse Mikio
Published: October 2002

In order to observe high-spatial-resolution elemental images using inelastic electrons, a 300 kV energy-filtering transmission electron microscope with an omega-type energy filter has been developed. Some characteristic features of the new microscope are described. The accelerating voltage dependence of the inelastic images is calculated to confirm that the spatial resolution for the elemental images is improved with an increase in the voltage from 120 kV to 300 kV. It is shown that a single atomic layer of oxygen atoms in Al11O3N9 crystal is well imaged as a bright line with a periodic separation of 2.9 nm along the c-axis. The spatial resolution for the oxygen images is about 0.5 nm, which corresponds well with the theoretical calculation.
Low Temperature Growth of Polycrystalline Silicon Films by Hot-Wire Chemical Vapor Deposition Using SiCl4/H2 Gases
Authors: Wong Te-Chi , Wu Jih-Jen
Published: October 2002

Low-temperature growth of polycrystalline silicon films using SiCl4/H2 in a hot-wire chemical vapor deposition (HWCVD) reactor is reported here. Slightly (100) oriented polycrystalline silicon film with a crystalline fraction of 97% has been deposited at a hot wire temperature of 1900°C and a substrate temperature of 320°C. The average grain size of the film is 0.1 µm with a thickness of 0.5 µm. (110) Preferentially orientated silicon film with a 97% crystalline fraction is also deposited at a hot wire temperature of 1700°C and a substrate temperature of 290°C. A nanocrystalline film with a 57% crystalline fraction is formed when the substrate temperature is lowered to 150°C. The roles of Cl and H radicals in the formation of crystalline silicon films are discussed.
Indium–Tin–Oxide Thin Films Prepared by Dip Coating; Dependence of Resistivity on Film Thickness and Annealing Atmosphere
Authors: Seki Shigeyuki , Ogawa Makoto , Sawada Yutaka
Published: October 2002

Indium–tin–oxide (ITO) films were prepared by a dip coating method with novel solutions. The dip coating and heating in air at 600°C were repeated to obtain 3- or 10-layer films before annealing in N2–0.1%H2 atmosphere. A 10-layer film (7.0 at.%Sn, ∼ 250 nm-thick) showed the lowest resistivity (3.2×10-4 Ω·cm). Increase in film thickness was effective in improving both the carrier concentration (1.0×1021 cm-3) and the mobility (18.3 cm2·V-1·s-1) after annealing.
Nd3+:Y2O3 Ceramic Laser
Authors: Jianren Lu Jianren Lu , Junhua Lu Junhua Lu , Tomoyo Murai Tomoyo Murai , Kazunori Takaichi Kazunori Takaichi , Tomohiro Uematsu Tomohiro Uematsu , Ken-ichi Ueda Ken-ichi Ueda , Hideki Yagi Hideki Yagi , Takagimi Yanagitani Takagimi Yanagitani , Alexander A. Kaminskii Alexander A. Kaminskii
Published: October 2002

We have demonstrated CW one-micron laser oscillation in new ceramic laser material on the base of cubic Nd3+:Y2O3. Slope efficiency of 32% was achieved on an uncoated 1.5 at.% Nd3+:Y2O3 ceramic plate with size of φ14 ×2.7 mm under laser diode end-pumping.
670 nm Laser Light Propagation Characteristics of 10–1 µmφ Polystyrene Microsphere Array
Authors: Huang Fujun , Morita Shinzo
Published: October 2002

The light propagation characteristics of linear and curvilinear polystyrene microsphere arrays were studied experimentally and discussed analytically. The attenuation coefficients of 670 nm laser light propagation on the linear and curvilinear arrays for spheres of 10, 5, 2 and 1 µm diameters were measured to be 0.51, 0.48, 0.78 and 0.98 dB/sphere and 0.71, 0.67, 1.09 and 1.30 dB/sphere, respectively.
Near-Field Photocurrent Measurements of Si p-n Junction under the Reverse-Bias Condition
Authors: Fukuda Hiroaki , Ohtsu Motoichi
Published: October 2002

We measured the near-field photocurrent of the p-n junction on a Si substrate under the reverse-bias condition in order to estimate the dopant concentration of the p-n junction. The full-width at half maximum (FWHM) of the cross-sectional profile of the near-field photocurrent signal varied on changing the applied reverse-biased voltage according to the resulting change in the thickness of the depletion region. From the measured reverse-bias dependence of the FWHM of the cross-sectional profile, the local dopant concentration of the Si substrate was estimated as 3.5±0.4×1016 cm-3. This result shows good agreement with the value of dopant concentration (3.1×1016 cm-3) evaluated from the device fabrication conditions.
Epitaxial Growth of BaTiO3 Thin Film on SrTiO3 Substrate in Ultra High Vacuum without Introducing Oxidant
Authors: Shimoyama Kazuo , Kubo Kousuke , Maeda Tatsuro , Yamabe Kikuo
Published: October 2002

A high-quality BaTiO3 thin film on SrTiO3 substrate was obtained by shutting off the oxygen supply during growth. Epitaxial growth of BaTiO3 film was carried out with molecular-beam epitaxy (MBE) under extremely low oxygen partial pressure (pO2<1×10-8 Pa). Although only Ba and Ti metals were supplied without introducing oxidant during the growth, a clear reflection high-energy electron diffraction (RHEED) intensity oscillation from layer-by-layer growth of BaTiO3 was observed. Oxygen was automatically fed from the substrate during the growth. The deposited film was found to have an approximately stoichiometric composition and single-phase of BaTiO3 from the analyses of Auger electron spectroscopy (AES) and X-ray diffraction (XRD).
Direct Magnetic Imaging of Ferromagnetic Domain Structures by Room Temperature Scanning Hall Probe Microscopy Using a Bismuth Micro-Hall Probe
Authors: Sandhu Adarsh , Masuda Hiroshi , Oral Ahmet , Bending Simon J.
Published: October 2002

A bismuth micro-Hall probe sensor with an integrated scanning tunnelling microscope tip was incorporated into a room temperature scanning Hall probe microscope system and successfully used for the direct magnetic imaging of microscopic domains of low coercivity perpendicular garnet thin films and demagnetized strontium ferrite permanent magnets. At a driving current of 800 µA, the Hall coefficient, magnetic field sensitivity and spatial resolution of the Bi probe were 3.3 ×10-4 Ω/G, 0.38 G/√Hz and ∼2.8 µm, respectively. The room temperature magnetic field sensitivity of the Bi probe was comparable to that of a semiconducting 1.2 µm GaAs/AlGaAs heterostructure micro-Hall probe, which exhibited a value of 0.41 G/√Hz at a maximum driving current of 2 µA.
Suppression of Plasma Charging Damage in Sub-Micron Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) with Gate Oxynitride by Two-Step Nitridation
Authors: Tzeng Pei-Jer , Wu Bone-Fung , Chang-Liao Kuei-Shu
Published: October 2002

The two-step nitridation process of gate oxynitride in metal-oxide-semiconductor Field-Effect Transistors (MOSFETs) is utilized to demonstrate good electrical reliability in MOSFETs. The low temperature and short time of the second nitridation step can form a nitrogen pile-up at the poly-Si/oxynitride interface which leads to the reduction of detrimental species diffused from poly-Si to the oxynitride. This process reduces the plasma-charging damage even more as the charging effect is increased. Smaller characteristic degradation due to nitrogen pile-up at both sides of the gate oxynitride ensures better gate oxynitride integrity (GOI) in practical integration for ultra-large-scaled integration (ULSI) applications.
Highly Efficient Nd:Y3Al5O12 Ceramic Laser
Authors: Jianren Lu Jianren Lu , Mahendra Prabhu Mahendra Prabhu , Jie Song Jie Song , Cheng Li Cheng Li , Jianqiu Xu Jianqiu Xu , Ken-ichi Ueda Ken-ichi Ueda , Hideki Yagi Hideki Yagi , Takakimi Yanagitani Takakimi Yanagitani , Alexander A. Kaminskii Alexander A. Kaminskii
Published: October 2002

A highly efficient laser diode end-pumped polycrystalline 1% Nd:Y3Al5O12 (Nd:YAG) ceramic laser has been developed. It is comparable to a Nd:YAG single crystal laser in terms of efficiency. With 883 mW pumping, CW laser output of 499 mW at 1064 nm has been obtained, which corresponds to an optical-to-optical efficiency of 56.5%. The threshold is only 22 mW for a R=97% output coupler. Passively Q-switched operation has also been demonstrated using a Cr4+:YAG single crystal as a saturable absorber.