bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Design of Optical Configuration of Transflective Liquid Crystal Displays using Antiferroelectric Liquid Crystals and Frustelectric Ferroelectric Liquid Crystals
Authors: Park Won Sang , Kim Sung-Chul , Lee Seo Hern , Hwang Yong Suk , Lee Gi-dong , Yoon Tae-Hoon , Kim Jae Chang
Published: October 2002

We propose an optical configuration of transflective antiferroelectric liquid crystal (AFLC) and frustelectric ferroelectric liquid crystal (FR-FLC) display modes using a half-wave LC cell in which the in-plane tilt angle is 22.5°. It is composed of two polarizers, an AFLC or FR-FLC cell, two achromatic quarter-wave films, and a transflective film layer. In the case of using it in the reflective mode, it provides a high brightness and a high contrast ratio, and in the case of using it in the transmissive mode, it also provides a high contrast ratio. By fabricating modes of a transflective liquid crystal display (LCD) with a half-wave retardation, we demonstrated high brightness as well as high contrast ratio of a half-wave by the commercial simulator (DIMOS).
Effect of Plasma Off Time on the Structure and Electrical Properties of Hydrogenated Amorphous Silicon Carbide Films Prepared by Pulse-Modulated Plasma Deposition
Authors: Tabata Akimori , Sekito Makoto , Mizutani Teruyoshi , Suzuoki Yasuo
Published: October 2002

Hydrogenated amorphous silicon carbide (a-Si1-x
C
x
:H) films were prepared by pulse-modulated rf plasma deposition under the conditions of a constant peak-to-peak rf voltage, a constant plasma-on-time and various plasma-off-times. The infrared absorption spectra showed that the peak of C–H
n
wagging mode had the highest intensity, except for that of Si–H
n
wagging mode, although for a-Si1-x
C
x
:H films prepared using a continuous wave plasma this peak is scarcely observed or very small and is always smaller than that of Si–CH3 wagging mode. The carbon content increased with increasing the plasma off time, indicating that the intake of carbon atoms occurred mainly during the plasma off time. The photoconductivity and photosensitivity slightly increased with increasing the plasma off time although the carbon content also increased.
Growth and Characterization of ZnCdSe/BeZnTe II–VI Compound Type-II Superlattices on InP Substrates and Their Application for Visible Light Emitting Devices
Authors: Che Song-Bek , Nomura Ichirou , Takada Tomoyuki , Kikuchi Akihiko , Shimomura Kazuhiko , Kishino Katsumi
Published: October 2002

ZnCdSe/BeZnTe II–VI compound superlattices (SLs) were grown on InP substrates by molecular beam epitaxy for the first time. In the X-ray diffraction studies, definite satellite peaks were observed for each sample, which indicates that fine periodic SL structures were obtained. For SL samples with several layer thickness combinations, wide-range visible emissions from 740 to 507 nm were observed during photoluminescence (PL) studies at 15 K. Comparison of PL emission properties at 15 K for a ZnCdSe/BeZnTe SL and ZnCdSe bulk samples showed the superior emission intensity of the SL sample. A double hetero-structure (DH) consisting of ZnCdSe/BeZnTe SLs and BeZnTe cladding layers was fabricated. In the PL spectrum of the DH sample at 15 K, sharp emission peaks at 517 and 604 nm were observed. Visible light emitting diodes were fabricated by applying ZnCdSe/BeZnTe SLs as the active layer, and were evaluated under pulsed current injections at room temperature. A single-peak yellow-green emission around 562 nm was obtained.
Magnetic Properties and Magnetic Entropy Changes of Annealed and Melt-spun DyCo2 Alloy
Authors: Wang Dunhui , Tang Shaolong , Liu Haidong , Li Shandong , Zhang Jianrong , Du Youwei
Published: October 2002

Structure and magnetic properties of annealed and melt-spun DyCo2 alloy were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magneometer (VSM). They both crystallize in the MgCu2-type structure. Curie temperature (T
C) of them vary slightly, while their coervicities change remarkably. Annealed DyCo2 alloy has a rather large magnetic entropy change (|ΔS
M|) near T
C. The magnetization of melt-spun DyCo2 alloy changes gradually in the vicinity of T
C. This fact leads to a relatively small |ΔS
M| in melt-spun DyCo2 alloy, but the temperature range of |ΔS
M| is widen, which is more effective in utility.
Magnetic Properties of Co/Si(100) Thin Films Studied using Magnetooptic Kerr Effect Technique
Authors: Wu Yueh-Er , Tsay Jyh-Shen , Chen Shu-Chenms , Fu Tsu-Yi , Shern Ching-Song
Published: October 2002

Magnetic properties of cobalt films grown on a Si(100) substrate were investigated using the magnetooptic Kerr effect technique. The longitudinal coercivity for the films with a thickness range from 2.4 to 17.7 nm is observed to be approximately 55 Oe. The easy axis of magnetization is in the surface plane. Because of silicide formation at the interface and a short absorption length for light in condensed matter, the Kerr intensity is not completely proportional to the film thickness. Thermal evolution for the Co/Si(100) system was systematically investigated. A higher thermal stability is concluded for a thicker cobalt film. At a low temperature, the Kerr intensity is nearly maintained constant upon annealing treatment. This is expected to be due to the Co–Si compound at the interface blocking further interdiffusion.
Switching Time of Optical Memory Devices Composed of Photonic Crystals with an Impurity Three-Level Atom
Authors: Nihei Hiroyuki , Okamoto Atsushi
Published: October 2002

We calculate the switching time of an optical memory device composed of three-dimensional photonic crystals with an impurity three-level atom, that is, a photonic memory device. We determine the switching time to be a function of the overshoot and the time constant of a decaying oscillation of the upper level population of the impurity atom. The analytical solutions for the overshoot and the time constant are given by using the Euler approach. Using these functions, we calculate the switching time for the Rabi frequency and the transition frequency of the impurity atom. Our results show that the switching time is improved by changing the transition frequency from inside the photonic band gap to outside it and/or by increasing the Rabi frequency, where the transition frequency and the Rabi frequency can be controlled by a small power field. We determine suitable ranges of these frequencies for realizing a high-speed photonic memory device, which are important for atomic-scale optical systems such as high-density integrated optical circuits and quantum computers.
Compensation for Third-Order Nonlinearity with Initial Phase Mismatch in Second-Harmonic Generation of Ultrahigh Intensity Laser Pulses
Authors: Harimoto Tetsuo , Aoyama Makoto , Yamakawa Koichi , Yonemura Motoki
Published: October 2002

It has been demonstrated that an initial phase mismatch in type I second-harmonic generation processes with ultrahigh intensity laser pulses can be used to compensate for third-order nonlinearity not only in temporal profiles but also in spatial distributions of fundamental and second-harmonic pulses. The spatial profile of the second-harmonic pulse shows a good reappearance of the input fundamental pulse throughout the compensation for the third-order nonlinearity.
New Degradation Mechanisms of Width-Dependent Hot Carrier Effect in Quarter-Micron Shallow-Trench-Isolated p-Channel Metal-Oxide-Semiconductor Field-Effect-Transistors
Authors: Chung Steve S. , Chen Shang-Jr , Yang Wen-Jei , Yih Cherng-Ming , Yang Jiuun-Jer
Published: October 2002

In this study, width-dependent hot-carrier degradation in the p-channel metal-oxide-semiconductor field-effect transistors (p-MOSFETs) with shallow-trench-isolation (STI) is presented. Results show an enhanced drain current degradation with reducing the gate width. A new model and mechanism are proposed to explain the width-dependent hot-carrier (HC) degradation for p-MOSFETs. Based on a two-dimensional channel shortening concept, a new model is developed. The mechanical stress enhanced oxide damage at the STI edge, which will induce channel shortening, is the dominant mechanism for the drain current degradation of the devices after hot-carrier stress. This is a crucial issue for present and future complementary metal-oxide semiconductor (CMOS) ultra-large-scale integration (ULSI), and in particular for high-density dynamic random-access memory (DRAM), fabricated using STI technologies.
Material Design for the Fabrication of p-type SrTiO3
Authors: Betsuyaku Kiyoshi , Tanaka Hidekazu , Katayama-Yoshida Hiroshi , Kawai Tomoji
Published: October 2002

We have carried out ab initio electronic structure calculations based on the local density approximation for N doped, and N and Nb codoped SrTiO3 using a full-potential linearized augmented plane wave method. N impurities form shallow acceptor levels by codoping with Nb donors. It was found that codoping with N acceptors and Nb donors in the ratio of 2:1 was suitable for the fabrication of low-resistivity p-type SrTiO3. Moreover, we suggest an experimental method appropriate for achieving N and Nb codoping.
Studies on Electrical Discharge Effects in a Foaming Environment
Authors: Pawlat Joanna , Hayashi Nobuya , Yamabe Chobei
Published: October 2002

A new apparatus called foaming column, which is potentially useful for polluted gas treatment, was constructed. Foam was created without addition of foaming agents, using only the kinetic energy of gas flow. During experiments, large quantities of gas and a small amount of pure water were required to generate foam between the main electrodes. Electrical discharge was obtained in the unique foaming environment. Various oxidants such as ozone, OH radicals and hydrogen peroxide were generated as an effect of electrical discharge. Several kinds of electrode materials and electrode set-ups were tested. Using the needle-to-plate electrode, which was made of stainless steel, higher concentrations were obtained for all oxidants.
Enhancement of X-ray Emission from a Cooled Kr Gas Jet Irradiated by an Ultrashort KrF Laser Pulse
Authors: Miura Eisuke , Honda Hiroshi , Katsura Keisuke , Takahashi Eiji , Kondo Kiminori
Published: October 2002

X-ray emission from a cooled Kr gas jet irradiated by an ultrashort KrF laser pulse (10 mJ in 500 fs) was investigated. When the Kr gas temperature was -100°C, the yields of X-rays with wavelengths of 2–18 and 0.5–0.9 nm were estimated to be 0.53 mJ and 0.44 µJ per pulse, respectively. By decreasing the gas temperature from 20 to -100°C, the yields of the sub-keV and keV X-rays increased by factors of 1.8 and 6.5, respectively. The enhancement of the X-ray yields for the larger clusters formed by gas cooling was caused by the more efficient collisional ionization and excitation brought about by the longer period for which the high local density of the cluster was maintained.
Dual Damascene Etching Process Using Sacrificial Spin-on-Glass Film
Authors: Seta Shoji , Yoshida Yukimasa , Nakata Renpei , Ohiwa Tokuhisa
Published: October 2002

The dual damascene (DD) formation process for sub 0.2 µm feature size devices has been investigated. The via-first DD process, where via holes are first formed, followed by trench formation, used the antireflection film in via holes after the trench pattern lithography process. In subsequential trench etch process, crownlike etch residues of SiO2were formed around via holes due to etch inhibiting effect of antireflection films in via holes. A spin-on-glass (SOG) film is filled in via holes as a sacrificial film before trench pattern lithography was used. It could eliminate the crownlike etch residues because of the absence of an antireflection film in via holes. Moreover, it could give via holes a rounded profile at their top edges. This DD process used for fabricating films with no etch residues and rounded via holes reduces the aspect ratio of via holes and was confirmed to be effective for subsequential metal filling process.
Crystalline Structure and Surface Morphology of AlN Films Sputtered on Rotated Y-Cut Quartz (ST-Quartz)
Authors: Wu Sean , Wu Long , Shen Yu-Tang , Chang Feng-Chih
Published: October 2002

Highly c-axis-oriented and fine structural AlN films were successfully prepared on Rotated Y-cut q uartz (ST-quartz) by rf magnetron sputtering. The crystalline structure of the films was determined by X-ray diffraction (XRD) and the surface microstructure of films was quantitatively investigated using an atomic force microscope (AFM). Different rf powers (250 W, 350 W and 450 W) were used to deposit the films. The films prepared in the rf power range of 250–450 W were all polycrystalline hexagonal AlN and had fine surface morphology. The experimental results demonstrate that AlN films deposited in this research were fine structural piezoelectric films. The optimal AlN films prepared at 250 W had small average grain sizes (13.31 nm), uniformity, dense structures and a very smooth top surface (R
a=1.838 nm). It is suitable to use low power to deposit AlN films on ST-quartz.
Structural Changes in a Resist Resulting from Plasma Exposure during the Reactive Ion Etching Process
Authors: Tohno Ichiro , Saito Makoto , Omiya Kayoko , Kataoka Yoshinori
Published: October 2002

Structural changes in a resist resulting from plasma exposure during the reactive ion etching (RIE) process were studied using 13C-NMR analysis and Fourier transform IR spectroscopy (FT-IR). Two types of resist were chosen containing different amounts of diazonaphthoquinone derivative as an initiator with the same type of base polymer, cresol novolak resin. It was found that a slightly soluble layer was formed by the cross-linking reaction of the main chain of novolak resin as a result of plasma exposure in the case of the resist with a low amount of photosensitizer. The molecular weight concurrently decreased, probably due to the chain-scission of the main chain of novolak resin. On the other hand, in the resist containing a larger amount of photosensitizer, the molecular weight of the material increased, probably due to the occurrence of some type of cross-linking reaction such as thermal condensation. From these results, we obtained some guidelines for developing a resist stripping process without a residue.
Focusing Properties of Volcano-Shaped Dual-Gate Field Emitters
Authors: Nicolaescu Dan , Filip Valeriu , Itoh Junji
Published: October 2002

Field emitters are used as distributed electron sources in applications such as field emission displays (FEDs) and electron guns. In this study we analyze the deflection and focusing properties of volcano-shaped dual-gate emitters, which has been considered for the first time in this context. The structure considered has a volcano-shaped extracting gate, recessed with respect to the emitter, allowing the focusing gate to be more efficient. The simulation results have been obtained using the Simion 3D 6.0 software package. The analysis refers to the electron beam spot diameter on the anode plane as function of the focusing voltage and the position and size of the focusing gate. An optimal position and size of the focusing gate, which depends only slightly on the focusing voltage, has been shown to exist.
Amorphous Silicon and Tungsten Etching Employing Environmentally Benign Plasma Process
Authors: Kazushi Fujita Kazushi Fujita , Shigeto Kobayashi Shigeto Kobayashi , Masafumi Ito Masafumi Ito , Masaru Hori Masaru Hori , Toshio Goto Toshio Goto
Published: October 2002

A novel dry etching process for amorphous silicon (a-Si) and tungsten (W) for chemical vapor deposition (CVD) chamber cleaning has been performed by electron cyclotron resonance (ECR) O2 plasma employing a solid-material evaporation system where fluorocarbon species are produced from fluorinated ethylene propylene (FEP) by CO2 laser evaporation for preventing global warming. This process enables us to realize etching of materials without using any perfluorocompound (PFC) feed gases which have a high global warming potential (GWP). Etching characteristics together with diagnostics of the F atom density, CFx (x=1–3) radical densities, electron density and temperature have been investigated as functions of pressure. As a result, it was found that etching rates of a-Si and W films were determined based on the F atom density, ion flux and ion bombardment energy. Furthermore, etching rates of a-Si and W films increased by heating the fluorocarbon species before introducing them into the plasma reactor. Thus, high rates of etching of a-Si and W films were successfully achieved by this novel etching process compared with conventional etching using ECR plasma with CF4/O2 feed gases.
Fluid Analysis of the Effect of Ionization on Measurement of Plasma Flow in the Magnetized Presheath
Authors: Chung Kyu-Sun
Published: October 2002

A fluid model is developed to analyze the effect of ionization on the free presheaths in magnetized flowing plasmas. Analytic solutions are derived from one-dimensional fluid equations with an arbitrary ionization source. Contributions from ionization and shear viscosity are normalized by the free transport source due to the cross-field diffusion. An analytic relation between the sheath current ratio and the unperturbed flow velocity is determined in terms of ionization ratio and normalized shear viscosity. The deduced plasma flow velocity and density would be miscalculated in the strong plasma-neutral interacting presheath without the contribution of ionization to the presheath source.
Degenerate Four Wave Mixing of C2 in Forward Geometry: Spectral Lineshape Analysis and Temperature Determination
Authors: Ju Jung Jin , Ryu Jae-seok , Park Chul Woung , Hahn Jae Won
Published: October 2002

Forward phase-matched degenerate four-wave mixing (DFWM) spectrum of C2 molecules is studied to determine the temperature of a premixed oxyacetylene flame. Both theoretical calculation and experimental measurement of the d3Πg↔d3Πu swan band of C2 are performed at weak field intensity. The measured spectra excited with a narrow band optical parametric oscillator (OPO) showed good matches with the results of calculations. When a DFWM spectrum corresponding to the molecular transitions of both high (J=36–42) and low (J=8–15) rotational levels is used for a Boltzmann plot, we can determine the flame temperature of 3143 K with a very small temperature uncertainty of 1.6%. In addition, the uncertainty in temperature measurement caused by the line interference of the DFWM spectrum in the forward geometry is estimated to be only 0.5%, which is negligible for practical applications.
Single Electron Memory at Room Temperature: Experiment and Simulation
Authors: Bubanja Vladimir , Matsumoto Kazuhiko , Gotoh Yoshitaka
Published: October 2002

We study a single-electron room temperature memory device. The device was fabricated by a pulse mode atomic force microscopy nano-oxidation process on an atomically flat α-Al2O3 substrate. We model the operation using a Monte Carlo simulation. There is a general agreement between theory and experiment. The observed differences stem from noise and the uncertainty in determining the geometry of the fabricated circuit.
Color-Imaging Ellipsometer: High-Speed Characterization of In-Plane Distribution of Film Thickness at Nano-Scale
Authors: Tanooka Daisuke , Adachi Eiki , Nagayama Kuniaki
Published: October 2002

We have developed a new type of imaging ellipsometer that is capable of rapidly visualizing the in-plane distribution of film thickness at the nanometer scale and displaying the results as a color distribution. Simultaneous use of three different wavelengths was made possible by capture with a color charge-coupled devices video camera at an acquisition speed of 5–10 frame/s followed by rapid image processing. This instrument has two main advantages when compared with a monochrome-imaging ellipsometer. The first is the capability of visualizing the difference between thin and thick areas of a film in one frame of video-image. The second is the ability to calculate the in-plane distribution of film thickness from the intensities of the three wavelengths in one frame without mechanical movements of any of the optical elements of the ellipsometer. We have demonstrated the performance of this instrument by measuring the thicknesses of four different SiO2films simultaneously prepared on one Si substrate.
Multipole Analysis of Electromagnetic Field Generated by Single-Bunch Electron Beams
Authors: Tsuyoshi Suwada Tsuyoshi Suwada
Published: October 2002

A method to measure transverse beam sizes of charged beams is demonstrated using stripline-type beam-position monitors (BPMs). The method is theoretically described based on the multipole-moment analysis of an electromagnetic field generated by the charged beams. An experiment has been performed to verify this method using single-bunch electron beams at the KEK B-Factory (KEKB) injector linac. The experimental results show that according to the detection method using the BPMs, which takes into account the higher-order moments derived from the multipole-moment analysis, the analyzed beam sizes are consistent with those measured by wire scanners. In this report we describe in detail the experimental results using two kinds of stripline-type BPMs with four electromagnetic pickups along with the theoretical multipole analysis.
The Atlas High-Energy Density Physics Project*
Authors: Davis Harold A. , Keinigs Rhon K. , Anderson Wallace E. , Atchison Walter L. , Bartsch R. Richard , Benage John F. , Ballard Evan O. , Bowman David W. , Cochrane James C. , Ekdahl Carl A. , Elizondo Juan M. , Faehl Rickey J. , Fulton Robert D. , Gribble Robert F. , Guzik Joyce A. , Kyrala George A. , Miller R. Bruce , Nielsen Kurt E. , Parker Jerald V. , Parsons W. Mark , Munson Carter P. , Oro David M. , Rodriguez George E. , Rogers Harold H. , Scudder David W. , Shlachter Jack S. , Stokes John L. , Taylor Antoinette J. , Trainor R. James , Turchi Peter J. , Wood Blake P.
Published: October 2002

Atlas is a pulsed-power facility under development at Los Alamos National Laboratory to drive high-energy density experiments. Atlas will be operational in the summer of 2000 and is optimized for the study of dynamic material properties, hydrodynamics, and dense plasmas under extreme conditions. Atlas is designed to implode heavy-liner loads in a z-pinch configuration. The peak current of 30 MA is delivered in 4 µs. A typical Atlas liner is a 47-gram-aluminum cylinder with ∼4-cm radius and 4-cm length. Three to five MJ of kinetic energy will be delivered to the load. Using composite layers and a variety of interior target designs, a wide variety of experiments in ∼cm3 volumes will be performed. Atlas applications, machine design, and the status of the project are reviewed.
Generation of an Intense Electron Beam with Sub-Nanosecond Duration Using Multi-Stage Autoacceleration
Authors: Daisuke Hasegawa Daisuke Hasegawa , Keiichi Kamada Keiichi Kamada , Atsushi Kuraku Atsushi Kuraku , Ritoku Ando Ritoku Ando , Masaru Masuzaki Masaru Masuzaki
Published: October 2002

An intense relativistic electron beam with a duration of 0.8 ns was obtained by four-stage multicavity autoacceleration. The electron beam with an energy of 500 keV and a duration of 12 ns was injected into coaxial cavities connected in tandem with decreasing lengths. In addition, electrons in the last one 16th part of their duration were accelerated. The energy of the most accelerated part was 1.1 MeV when a single cavity was used at each stage. The energy increased to 1.3 MeV when cavities of the same length were introduced in each stage.
Beam Non-Uniformity Smoothing Using Density Valley Formed by Heavy Ion Beam Deposition in Inertial Confinement Fusion Fuel Pellet
Authors: B. Blagoev Jun Sasaki , Shigeo Kawata Shigeo Kawata
Published: October 2002

We study the beam nonuniformity smoothing effect of radiation transport in the density valley formed by an ion-beam deposition in a heavy ion-beam inertial confinement fusion pellet by numerical simulations. The simulation results show that the radiation energy is confined in the density valley, and the beam nonuniformity can be smoothed out by the radiation transport along the density valley. In addition, an estimation for the Rayleigh-Taylor instability during the implosion phase is also presented.
Characteristics of Multichannel Arc Gap
Authors: Furuya Seizo , Watanabe Yoshiya , Yoshikawa Takeshi , Takano Saburo , Irisawa Juichi
Published: October 2002

The characteristics of a multichannel arc gap are investigated experimentally in the voltage range of less than 45 kV using a ferrite sharpener. The gap comprises 12 or 24 steel needle electrodes and a brass rod electrode. We examined the characteristics of the number of arc channels when the following parameters were changed independently: (1) rise rate of voltage pulse applied to the gap, (2) length of feeders which transmit voltage pulse from the ferrite sharpener to each needle electrode, (3) gap length, (4) kind and pressure of intergap gas and (5) with and without UV irradiation.
Nonvolatile Two-Color Holographic Recording in Er-Doped LiNbO3
Authors: Tomita Yasuo , Hoshi Mitsunari , Steven Sunarno Steven Sunarno
Published: October 2002

We demonstrate nonvolatile two-color holographic recording in as-grown and reduced Er-doped LiNbO3. It is found that, unlike the case of near-stoichiometric LiNbO3 reported previously, the diffraction efficiency can be increased by a factor of ∼ 5 after the reduction treatment. The recording sensitivity and the figure of merit M/# for the reduced crystal are measured to be 9×10-4 cm/J and 0.02, respectively, with a 488-nm gating beam at an intensity of 1 W/cm2 and 780-nm writing beams at a total intensity of 2 W/cm2. Results of the light-induced absorption measurement suggest that the small polarons are responsible for the two-color photosensitivity in Er-doped LiNbO3.
Resistivity Increase in Ultrafine-Line Copper Conductor for ULSIs
Authors: Hinode Kenji , Hanaoka Yuko , Takeda Ken-ichi , Kondo Seiichi
Published: October 2002

The resistivities of copper (Cu) thin films and damascene Cu fine lines were precisely measured by utilizing Matthiessen's rule. It was shown that this measurement method can produce reliable values without requiring precise and detailed line-dimension measurements. It was found that the increase in resistivities of the fine lines is much more than that of the films, and this increase results in an electron mean free path of 45 nm. We propose a simple equation for expressing line resistivity in terms of both line width and line thickness.
Magnetic-Field-Induced Second-Harmonic Generation on Si(111)-7×7
Authors: Takanori Suzuki Takanori Suzuki , V. Venkataramanan V. Venkataramanan , Masakazu Aono Masakazu Aono
Published: October 2002

We report for the first time experiments showing a magnetic-field-induced enhancement of second-harmonic generation (SHG) on the Si(111)-7×7 surface. An externally applied magnetic field of 10 T increased the SHG intensity of a selected susceptibility tensor element by ≈ 100% at room temperature and by ≈ 500% at 120 K. The observed SHG enhancement is induced by the magnetization of the Si(111)-7×7 surface. The electron spins on the dangling bonds are suggested to be responsible for the magnetization.
Blue-Emitting Eu2+-Doped CaAl2O4 Phosphor Thin Films Prepared Using Pulsed Laser Deposition Technique with Post Annealing
Authors: Kunimoto Takashi , Kakehi Ken-nosuke , Yoshimatsu Ryo , Ohmi Koutoku , Tanaka Shosaku , Kobayashi Hiroshi
Published: October 2002

Blue-emitting Eu2+-doped calcium aluminate phosphor thin films were obtained using the pulsed laser deposition technique with post annealing. As-deposited films were amorphous and showed weak red Eu3+ photoluminescence (PL). By annealing in reducing atmosphere (N2/H2:2% mixed gas) at 950°C for 3 h, the film was crystallized and showed a PL emission band peaking at about 447 nm, which originated from the 4f65d to 4f7 transition of Eu2+ ion. It is considered that the deposited film consists mainly of CaAl2O4 and partly of other binary compounds of the CaO–Al2O3 system. It was determined that the PL intensity of Eu2+ in CaAl2O4 can be controlled by the laser fluence, target-substrate distance and injection gas.
Optimum Treatment for Improvement of Indium-Halo Structure for Sub-0.1 µm n-Type Metal-Oxide-Semiconductor Field-Effect Transistor
Authors: Yeh Wen-Kuan , Chou Jih-Wen
Published: October 2002

The effect of post-thermal annealing after indium-halo implantation on the characteristics and reliability of sub-0.1 µm n-type metal-oxide-semiconductor field-effect transistors (nMOSFETs) was studied for the first time. We found that the control of annealing time is more efficient than that of annealing temperature with respect to achieving junction and gate oxide integrities. The best results of device performance were obtained with post-annealing treatment performed at medium temperatures (e.g., 900°C) for a longer time.
Highly Coherent Soft X-Ray Generation by Macroscopic Phase Matching of High-Order Harmonics
Authors: Tamaki Yusuke , Itatani Jiro , Obara Minoru , Midorikawa Katsumi
Published: October 2002

Highly coherent high-order harmonics in the soft X-ray region are generated by macroscopic phase matching. The high fringe visibility, which indicates the degree of coherence, of 0.73 is obtained at the 27th harmonic of a Ti:sapphire laser (the corresponding wavelength is 29.6 nm) by optimizing the 10-mm phase-matched propagation in 30 Torr argon gas, while the visibility of the pump laser is 0.84.
Simulation of 3He Minority Ion Cyclotron Range of Frequency (ICRF) Heating in International Thermonuclear Experimental Reactor (ITER)
Authors: Matsumoto Hiroshi
Published: October 2002

3He minority ion cyclotron range of frequency (ICRF) heating in international thermonuclear experimental reactor (ITER) was simulated by the 1.5 D tokamak simulation code PRETOR and ICRF heating simulation code PION. It was found that the smaller the minority concentration ratio is, the better the heating efficiency in terms of fusion power production is. The overall heating efficiency is insensitive to the location of the resonance layer over a wide range of the minor radius position. Very efficient heating of the ITER plasma by 3He minority ICRF heating using three different resonant locations at the same time was demonstrated by the PRETOR/PION simulations.
Photonic Band Gap in Naturally Occurring Ordered Anodic Porous Alumina
Authors: Masuda Hideki , Ohya Masayuki , Asoh Hidetaka , Nishio Kazuyuki
Published: October 2002

The two-dimensional (2D) photonic band gap was observed in naturally formed anodic porous alumina. Anodizing of Al under appropriate conditions yielded the anodic porous alumina which had an ordered air-hole array with a multidomain triangular lattice. The transmission spectra of the multidomain triangular air-hole lattice of the anodic porous alumina showed a clear dip in transmission that corresponded to the 2D photonic band gap. The band gap properties of the polycrystalline-type air-hole lattice could be interpreted as being the sum of those for the single-crystalline-type air-hole arrays of anodic porous alumina prepared by an artificial process.
THz-Radiation Emitter and Receiver System Based on a 2 T Permanent Magnet, 1040 nm Compact Fiber Laser and Pyroelectric Thermal Receiver
Authors: Stock Hideyuki Ohtake , Makoto Yoshida Makoto Yoshida , Heirich Endert Heirich Endert
Published: October 2002

Thermal receiver detectable terahertz (THz) radiation is generated from InAs irradiated with a 1040 nm, 80 fs, 180 mW, 48-MHz-repetition-rate mode-locked fiber laser in a 2 T field by a compact permanent magnet. THz radiation is monitored by means of a deuterated triglycine sulfate (DTGS) pyroelectric thermal receiver. DTGS operates at room temperature and does not require time-gating adjustment or cryogen cooling with liquid helium. The THz-radiation emitter system, including the excitation laser head, is almost the same size as a conventional notebook computer.
Quick Fabrication of Gigantic Single-Crystalline Colloidal Crystals for Photonic Crystal Applications
Authors: Sawada Tsutomu , Suzuki Yoshihisa , Toyotama Akiko , Iyi Nobuo
Published: October 2002

Colloidal crystals are potentially mass-fabricative and the most accessible three-dimensional photonic crystals in the optical regime. We found that a centimeter-sized single-crystalline domain of a colloidal crystal, an ordered latex colloidal array, could be instantaneously tailored through a dynamic process, i.e., quenching nonequilibrium ordering in a concentrated suspension induced by a momentary shear-flow. The single crystal is obtained in an extremely simple manner in a tractable container with a fixed crystallographic orientation, and resulting samples are sufficiently stable against external disturbance for practical application. The proposed method will contribute to the evolution of photonic crystal research and applications.
Detection of Nanopipes in GaN Films by Localized Avalanche Breakdown Using NaOH Electrolyte
Authors: Ohkubo Mitsugu
Published: October 2002

Nanopipes in high-quality GaN films grown by metalorganic chemical vapor deposition (MOCVD) on a sapphire substrate were investigated by generating hollow etch pits. Hollow etch pits were formed on the surface of GaN films by localized avalanche breakdown using NaOH electrolyte. Using scanning electron microscopy (SEM) and atomic force microscopy (AFM), the relationship between hollow etch pits and crystalline defects in GaN films was investigated. It was found that hollow etch pits were formed at the nanopipes and electrical discharge occurred through these nanopipes at high electric fields, resulting in localized avalanche breakdown. Defect etching by localized avalanche breakdown was found to be a simple method to detect nanopipes in GaN films.
Influence of Inversion Domains on Formation of V-Shaped Pits in GaN Films
Authors: Li Hongdong , Wang Tao , Lacroix Yves , Jiang Nan , Sakai Shiro
Published: October 2002

The influence of inversion domains (IDs) on the formation of V-shaped pits in GaN films grown by metalorganic chemical vapor deposition has been investigated using transmission electron microscopy. It was found that IDs can induce V-shaped pits which have a large size distribution. Upon introducing InGaN/GaN multiple-quantum wells to observe various growth stages, our results showed that the origin of these ID-induced pits may be a delayed formation of the IDs during island-island coalescence at the initial stage of film growth, thus we need not adopt a general explanation based on the different growth rates for the two opposite polarities.
Electron Emission Sites on Carbon Nanotubes and the Energy Spectra
Authors: Oshima Chuhei , Matsuda Kohei , Kona Takayuki , Mogami Yuhta , Komaki Masashi , Murata Yoshitaka , Yamashita Tetsutane , Saito Yahachi , Hata Koichi , Takakura Akihiro
Published: October 2002

Two kinds of electron emission sites on carbon nanotubes have been clarified; one is a nanoprotrusion exhibiting deformed honeycomb structures composed of carbon hexagons,pentagons and possibly heptagons. The other is either an edged species or adsorbates. The emission spectra show two characteristic features; a broad main peak as compared with theoretical curves based on Fowler-Nordheim theory, and an additional shoulder at about 0.5 eV from E
F, of which the features are observed independent of the emission direction. The broad main peak may indicate that energy band bending occurs near the emission sites.
Electrical Characterization of Atomic-Scale Defects in an Ultrathin Si Oxynitride Layer
Authors: Miyata Noriyuki , Ichikawa Masakazu
Published: October 2002

We examined the local structures in an ultrathin Si oxynitride layer by using scanning tunneling microscopy (STM) and spectroscopy (STS). It was found that an atomic-scale structural change from an intrinsic Si–Si bond (defect) to a Si cluster (damaged region) takes place because of the electrical damage during the STM and STS observations. It was also found that N incorporation into the oxide suppresses the expansion of the damaged regions but increases the density of intrinsic defects.
Epitaxial Growth of Pure 28Si Thin Films Using Isotopically Purified Ion Beams
Authors: Nobuteru Tsubouchi Nobuteru Tsubouchi , Akiyoshi Chayahara Akiyoshi Chayahara , Yoshiaki Mokuno Yoshiaki Mokuno , Atsushi Kinomura Atsushi Kinomura , Yuji Horino Yuji Horino
Published: October 2002

Isotopically purified 28Si homoepitaxial films were grown by means of an ion-beam deposition (IBD) method with isotopically mass-selected negative 28Si- ion beams. The surface structural evolution during the film growth and the film structure after the growth were investigated using reflection high-energy electron diffraction (RHEED), cross-sectional transmission electron microscopy (TEM) and transmission electron diffraction (TED). The Si isotopic composition (28Si : 29Si : 30Si = 99.9982 : 0.0016 : 0.0002 at.%) of the resulting Si epitaxial film was determined by secondary-ion-mass spectrometry (SIMS).
Formation of GaN Self-Organized Nanotips by Reactive Ion Etching
Authors: Yoshida Harumasa , Urushido Tatsuhiro , Miyake Hideto , Hiramatsu Kazumasa
Published: October 2002

We describe a new method of forming self-organized GaN nanotips by reactive ion etching using chlorine plasma and its mechanism. Nanotips with a density of approximately 8×109 cm-2 have been formed after etching. The nanotips have diameters between 10 and 30 nm, a length of about 0.7 µm and a high aspect ratio. It is revealed that nanotip formation is attributed to a nanometer-scale mask with a high etch selectivity to GaN. The structure simulated using our formation mechanism is almost similar to the experimental nanotip structure. These results prove the validity of the formation mechanism by nanomasking effect of ionized SiO2 sputtered by Cl+ ions.
Scanning Tunneling Microscopy Observation of the Initial State of Oxidation in Ferromagnetic Tunnel Junctions
Authors: Masamitsu Hayashi Masamitsu Hayashi , Yasuo Ando Yasuo Ando , Terunobu Miyazaki Terunobu Miyazaki
Published: October 2002

The initial oxidation process of thin aluminum films used in ferromagnetic tunnel junctions was investigated by scanning tunneling microscopy (STM). The STM images reveal the progression of oxygen penetration into an aluminum film composed of small grains. The oxygen first covers the aluminum grain surface homogeneously. At the same time, the oxygen is inserted into the aluminum grain boundaries. As the oxidation proceeds, the oxygen penetrates inside the grain.
Manipulation of Insulated Molecular Wire with Atomic Force Microscope
Authors: Tomonori Akai Tomonori Akai , Takumi Abe Takumi Abe , Takeshi Shimomura Takeshi Shimomura , Kohzo Ito Kohzo Ito
Published: October 2002

Recently, we have reported the formation of an insulated molecular wire of a conducting polymer, emeraldine base polyaniline, and a molecular nanotube synthesized from α-cyclodextrin. In this study, we manipulated the insulated molecular wire with the cantilever tip of an atomic force microscope (AFM). We found that the insulated molecular wire was moved or cut off by the manipulation process. The results of manipulation with varying AFM tip loading forces indicated that the insulated molecular wire is cut off at loading forces larger than approximately 30 nN.
Facing Double Probe for Plasma Flow Measurement
Authors: Yoshifumi Saitou Yoshifumi Saitou , Akira Tsushima Akira Tsushima
Published: October 2002

A new diagnostic method for plasma flow measurement has been developed. The method uses a pair of facing electrodes connected to each other by a power supply. ItsV-Icharacteristic curve is similar to that obtained by the conventional double probe but is asymmetric due to plasma flow. This asymmetry gives information on the plasma flow, that is, a specific voltage without net probe current is related to the Mach number of the plasma flow.
Heteroepitaxial Lateral Overgrowth of GaN on Periodically Grooved Substrates: A New Approach for Growing Low-Dislocation-Density GaN Single Crystals
Authors: Detchprohm Theeradetch , Yano Masahiro , Sano Shigekazu , Nakamura Ryo , Mochiduki Shingo , Nakamura Tetsuya , Amano Hiroshi , Akasaki Isamu
Published: October 2002

Using periodically grooved substrates, we propose a new approach to the growth of low-dislocation-density GaN single crystal. Three different substrates of basal-plane sapphire, 6H-SiC(0001)Si and Si(111) were used. Each substrate's surface geometry was formed as periodical straight trenches oriented in either the <1100>GaN or <1120>GaN direction. No selective-growth mask of dielectric or metallic materials was deposited on any part of the substrates during the growth. The laterally grown area had etch pit densities of 4×106 cm-2 or less.
Thin-Filmed Riboflavin Devices and Their Applications in the Photodegradation of Chlorinated Organics
Authors: Fu Yun Jen , Wang Chong Mou
Published: October 2002

Although riboflavin could not proceed ground-state molecular interactions with 4-chlorophenol over a pH ranging from 4 to 10, it could photooxidize 4-chlorophenol as being brought to its excited state. According to the emission spectra, the Stern-Volmer quenching rate constant was estimated to be about 106 s eq-1 (τo ≈5 ns). In addition, riboflavin could absorb on indium-tin-oxide (ITO) conductive glass squares. Benefitted with this phenomenon, riboflavin-modified electrodes were prepared. These electrodes showed promise for the degradation of 4-chlorophenol and sodium 2,3-dichloropropionate in the presence of light. According to the flow-injection analysis performed with a thin-layered photochemical cell, the detection limits for 4-chlorophenol at pH 5 were estimated to be about 10-5 M.
Fabrication and Optoelectronic Properties of a Transparent ZnO Homostructural Light-Emitting Diode
Authors: Guo Xin-Li , Choi Jae-Hyoung , Tabata Hitoshi , Kawai Tomoji
Published: October 2002

A transparent ZnO homostructural light-emitting diode (LED) with a structure of Au electrode/p(i)-ZnO film/n-ZnO single crystal/In electrode was fabricated using the technique of N2O plasma-enhanced pulsed laser reactive deposition. The contact between the p(i)-ZnO layer and n-ZnO wafer was found to exhibit nonlinear and rectifying current–voltage (I–V) characteristics. A current injection emission with bluish-white light was clearly observed at room temperature, and its intensity increased with increases in the injected electric current.
Self-Diffusion in Extrinsic Silicon Using Isotopically Enriched 30Si Layer
Authors: Nakabayashi Yukio , Osman Hirman I. , Segawa Toru , Saito Kazumasa , Matsumoto Satoru , Murota Junichi , Wada Kazumi , Abe Takao
Published: October 2002

Si self-diffusion coefficients were measured in intrinsic and extrinsic silicon at 900°C using an isotopically enriched 30Si layer. 30Si profiles are determined by secondary ion mass spectrometry. Si self-diffusion is enhanced in a heavily B-doped sample, but differs little from intrinsic Si in heavily As or Sb-doped samples.
Mechanical Property Characterization of Boron-Doped Silicon by Berkovich-Type Indenter
Authors: Guolin Yu Guolin Yu , Junji Watanabe Junji Watanabe , Katsutoshi Izumi Katsutoshi Izumi , Kenshiro Nakashima Kenshiro Nakashima , Takashi Jimbo Takashi Jimbo , Masayoshi Umeno Masayoshi Umeno
Published: October 2002

The “true-hardness” of (100) single-crystal silicon has been measured as a function of boron doping concentration by nanoindentation with a pointed diamond indenter (Berkovich triangular pyramid). The boron-ion implanted silicon wafers in which the boron concentration is varied up to 2.0×1020 cm-3 are studied. The results reveal an increase in the hardness at high boron concentrations, and a hardness ratio of 1.5:1 between the heavily and lightly boron-doped silicon has been obtained.
Photo-Electrochemical Gate Recess Etching for the Fabrication of AlGaN/GaN Heterostructure Field Effect Transistor
Authors: Jae-Seung Lee Jae-Seung Lee , Jong-Wook Kim Jong-Wook Kim , Doo-Chan Jung Doo-Chan Jung , Chang-Seok Kim Chang-Seok Kim , Won-Sang Lee Won-Sang Lee , Jae-Hak Lee Jae-Hak Lee , Jin-Ho Shin Jin-Ho Shin , Moo-Whan Shin Moo-Whan Shin , Jae-Eung Oh Jae-Eung Oh , Jung-Hee Lee Jung-Hee Lee
Published: October 2002

This is the first report on wet gate recess etching for the fabrication of an Al0.2Ga0.8N/GaN heterojunction field effect transistors. Wet recess etching was performed using a photoresist etching mask without any additional dielectrics or metals. The recess-etched surface was smooth and had no etch pits. After recess etching of a 300-Å-thick n+-GaN cap layer, Schottky contact metals of Pt/Au were deposited on Al0.2Ga0.8N. Gate-to-drain breakdown voltage and gate leakage current at V
GD = -20 V were -80 V and -34 µA, respectively. The fabricated device exhibited a maximum drain current of 193 mA/mm and a maximum extrinsic transconductance of 62 mS/mm.
Violation of a Variant Selection Rule in Atomic Ordering Observed in Ga0.5In0.5P with Sb Added during Growth
Authors: Suzuki Tohru , Ichihashi Toshinari , Hsu Chung-Chi
Published: October 2002

A new relation between the direction of the substrate surface normal and that of triple-period-A (TP-A) ordering was observed in Ga0.5In0.5P grown on a vicinal (001) GaAs substrate misoriented towards the [-1-11]A direction. The crystal was grown with a very small amount of Sb added during metalorganic vapor phase epitaxy. To our knowledge, this relation of surface-step vs variant is, irrespective of the types of ordering and the kinds of alloys, the first case in which the ordering variant selection rule thus far observed is being violated. This indicates a new phase relation at each step between unit cells of a ×3 surface reconstruction on the upper terrace and those on the adjacent lower terrace, with respect to the <111> direction nearest to the surface normal. The cause of this new step-variant relation is suggested.
Bi-Substitution Effect in La–Sr–Mn–O Thin Films for Bolometric Applications
Authors: Hayashi Ken-ichi , Ohta Eiji , Wada Hideo
Published: October 2002

La0.7Sr0.3MnO3-δ (LSMO) films have a large temperature coefficient of resistance (TCR: defined as 1/R dR/dT) at near room temperature. Bi0.34La0.33Sr0.33MnO3-δ (BLSMO) film in which La in LSMO is substituted by Bi, was deposited at low temperature, 400°C, by a laser ablation method. The BLSMO film on the SiO2/Si (100) substrate is polycrystalline without any preferred orientations. The low-temperature deposition and the Bi substitution eliminate the Curie temperature of the BLSMO film, and raise its TCR. The film has a large TCR, more than 2%/K, in the wide temperature range of 10–150°C.
Gaseous Ultraviolet-Radiation Source with Electron Emitter
Authors: Seishiro Hashiguchi Seishiro Hashiguchi , Kunihide Tachibana Kunihide Tachibana
Published: October 2002

An ultraviolet (UV) source is proposed. It resembles a dc-type plasma display panel (PDP) but the applied voltage is well below the breakdown voltage and an electron emitter is used. The advantage of the new UV source is that it can reduce energy dissipation due to creation of ions. Numerical calculations with pure xenon show an efficiency of 11% for the applied voltage of 210 V. The emitter current of 1.3 mA/cm2 was needed to realize an UV-radiation energy equal to that of a conventional PDP. The efficiency increased with decreasing applied voltage while the emitter current increased to obtain the same amount of UV-radiation energy.
Formation of Rough GaN Surface by Hydrogen Plasma Treatment and Its Application to Field Emitter
Authors: Takashi Sugino Takashi Sugino , Takamitsu Hori Takamitsu Hori , Chiharu Kimura Chiharu Kimura , Tomohide Yamamoto Tomohide Yamamoto
Published: October 2002

N-type GaN layers doped with Si are grown on sapphire substrates with AlN buffer layers by the metalorganic chemical vapor deposition method. The electron density is 2×1017 cm-3. The GaN surface is treated with hydrogen (H2) plasma produced by supplying microwave power. Etching of GaN with H2 plasma leads to the formation of a roughened GaN surface. An enhancement of the electric field at the roughened surface makes it possible to reduce the average electric field between the anode electrode and the sample surface for electron emission. The turn-on electric field for the electron emission is estimated to be as low as 12.4 V/µm.