bluuebunny/crossref_metadata_2025 huggingface dataset:
Epitaxial Growth of GaAs at One to Two Monolayers per Cycle by Alternate Supply of GaCl3 and AsH3
Authors: Ishikawa Katsumi , Kobayashi Ryuji , Satoru Narahara Satoru Narahara , Fumio Hasegawa Fumio Hasegawa
Published: February 2005

Atomic layer growth of GaAs using GaCl3 and AsH3 was carefully investigated. Precise measurements revealed that the growth rate depended on the growth temperature and increased from 1 monolayer/cycle at 300°C to nearly 2 monolayers/cycle at 450°C for alternating supply of GaCl3 and AsH3, contrary to what we had previously reported. When the growth temperature was less than 300°C, GaAs deposited both on a GaAs substrate and on the SiO2 mask and the growth rate was about 0.7 monolayers/cycle. Raman spectra of the grown layers indicated that GaAs grown at above 300°C was a single crystal but that GaAs deposited below 300°C was polycrystalline.
Initial Growth Mechanism of Si on GaAs Studied by Reflection High-Energy Electron Diffraction Oscillations
Authors: López Máximo , Takano Yasushi , Kangsa Pak Kangsa Pak , Hiroo Yonezu Hiroo Yonezu
Published: February 2005

We have studied the initial growth mechanism of Si on GaAs(100) and GaAs(111)B substrates by observing the behavior of the reflection high-energy electron diffraction (RHEED) specular beam intensity and the changes in the RHEED patterns. During the growth on just exactly substrates, we infer two-dimensional growth with nucleation on the terraces from the presence of RHEED oscillations. For the growth of Si on GaAs(100), a flat surface with bilayer steps (single domain) was obtained at ∼0.8 monolayers (ML) of growth. This structure was conserved up to ∼3 ML by a bilayer growth mode. With further growth, monolayer steps were formed on the surface and a double domain structure was observed. It is suggested that this change could be related to an alteration of the Si surface migration due to the high strain energy caused by the 4% lattice mismatch. A model is presented which includes some of the possible reactions between Si, Ga and As at the interface.
Current Dependence of 1/f Noise in Junction Diodes*
Authors: Yang Shiyuan , Toru Mizunami Toru Mizunami , Keiji Takagi Keiji Takagi
Published: February 2005

Experimental evidence shows that the noise current is proportional to the flowing current. The samples are the P-N junction, and light-emitting and laser diodes. Noise analysis is carried out using Hooge's equation. The low-frequency noise agrees qualitatively with the analytical result.
Carrier Lifetime Depth Profile for Power Devices with Fast Turn-On Time Investigated by Photoluminescence Decay Method
Authors: Akihiro Yahata Akihiro Yahata , Minoru Kuriki Minoru Kuriki
Published: February 2005

A photoluminescence (PL) decay method has been used for the first time to investigate carrier lifetime depth profiles for a silicon power device with fast turn-on time. Minority carrier lifetimes were found to be 1 to 2 µs for nonirradiated samples and about 60 ns for 5×1013 cm-2 electron-irradiated samples.
Metallurgical Reactions and Their Relationships to Enhanced Mechanical Strength in Zr-Bearing YBCO Composite Superconductors
Authors: Oka Tetsuo , Itoh Yoshitaka , Yanagi Yousuke , TAnaka Hidehiko , Takashima Shin-ichi , Mizutani Uichiro
Published: February 2005

The metallurgical reactions occurring during partial melting of the Zr-bearing YBCO composite superconductors have been investigated in detail by analyzing the DTA, XRD spectra and SEM micrographs of samples subjected to various heat treatments. It is shown that Zr reacts preferentially with Ba to form BaZrO3. As a result, the 123-phase is partially disintegrated and yields CuO and the 211-phase as by-products. The CuO phase in contact with the 123-phase lowers the melting point of the 123-phase to 970°C. The Zr-bearing YBCO sample annealed above 970°C melts partially and contributes to the reduction of voids. In addition, fine BaZrO3 particles precipitated along the grain boundaries form complicated three-dimensional networks. This skeletonlike structure prevents the sample from collapsing during partial melting and reinforces the mechanical strength of composites.
Fabrication and Properties of MgO/Bi2Sr2CaCu2OxInterfaces Using Crystalline and Amorphous MgO Films Grown by the MBE Method
Authors: Yamano Koji , Shimaoka Kazuhiro , Takahashi Kazuhiko , Usuki Tatsuro , Yorinobu Yoshisato Yorinobu Yoshisato , Shoichi Nakano Shoichi Nakano
Published: February 2005

Tunnel-type junctions with pinhole-free crystalline and amorphous MgO barriers on the order of several nm were successfully fabricated on the cleavage plane of BSCCO single crystals. Both MgO films for the tunnel barriers were grown by the molecular beam epitaxy method. The superconducting gap parameters, Δ, of a BSCCO single crystal deposited with crystalline and amorphous tunnel barriers were estimated to be 25 meV and 38 meV, respectively, for the configuration of a Nb/MgO/BSCCO junction from dI/dV-Vcharacteristics. The possibility of different surface superconductivities for BSCCO single crystals was determined by the characterization of the MgO/BSCCO interface.
Completely Bi-Substituted Iron Garnet (BIG) Films Prepared by Electron Cyclotron Resonance (ECR) Sputtering
Authors: Mino Shinji , Matsuoka Morito , Tate Akiyuki , Atsushi Shibukawa Atsushi Shibukawa , Ken'ichi Ono Ken'ichi Ono
Published: February 2005

Completely Bi-substituted iron garnet (BIG) films were epitaxially synthesized on garnet substrates by electron cyclotron resonance (ECR) sputtering. The critical temperature for the epitaxial growth, crystallinities, and Faraday rotation θF of BIG films depend on the O2 gas flow rate. With an optimum flow rate of 7 sccm, single-crystal BIG films were obtained at temperatures above 390°C, and θF achieved its largest value of 8.4×104 deg/cm (λ=0.633 µm). The minimum ferromagnetic resonance (FMR) linewidth ΔH was 70 Oe; this is the smallest value ever reported. The uniaxial perpendicular magnetic anisotropy is mainly caused by the elastic deformation induced by the thermal expansion mismatch between the film and the substrate.
X-Ray Topographic Observations of Magnetic Domain Structures and 180° Walls in a (100) Crystal of Pure Iron under an External Magnetic Field
Authors: Akira Mihara Akira Mihara
Published: February 2005

Magnetic domain structure in a (100) crystal of pure iron of about 70 µm in thickness was investigated under an external magnetic field by X-ray transmission topography. Several kinds of images in the <100> directions were observed in the crystal under the magnetic field of about 20 Os. They are simple 180° wall images, wall images having a periodic intensity of contrast and wall images having <100> images. In particular, the 180° wall images having periodic contrast are observed in the crystal only under the magnetic field, and vanish after removal of the magnetic field. Furthermore, the magnetic domain structure under the magnetic field was discussed.
Linear and Nonlinear Optical Properties of 2-Cyano-3-(2-Methoxyphenyl)-2-Propenoic Acid Methyl Ester
Authors: Nakatani Hiroyuki , Hideki Hayashi Hideki Hayashi , Takahiro Hidaka Takahiro Hidaka
Published: February 2005

Single crystals of a new nonlinear optical organic material, 2-cyano-3-(2-methoxyphenyl)-2-propenoic acid methyl ester (CMP-methyl) were grown, and the linear and nonlinear optical properties were investigated in detail. CMP-methyl crystals belong to space group P21, and the lattice parameters are a=4.020 Å, b=9.984 Å, c=13.757 Å, β=92.25° and Z=2. The largest second-order nonlinear optical coefficient was measured to be d
22=29 pm/V. Crystals were of fairly good optical quality.
Blue-Light-Emitting Organic Electroluminescent Devices with Oxadiazole Dimer Dyes as an Emitter
Authors: Hamada Yuji , Adachi Chihaya , Tetsuo Tsutsui Tetsuo Tsutsui , Shogo Saito Shogo Saito
Published: February 2005

Multilayer thin-film electroluminescent devices with blue emission color have been fabricated using new oxadiazole dimer dyes for both emission and electron transport layers. Emission characteristics of three types of cells, SH-A: ITO/HTL/EML/MgAg, SH-B: ITO/EML/ETL/MgAg and DH: ITO/HTL/EML/ETL/MgAg, in which ITO, HTL, EML, ETL and MgAg represent indium-tin-oxide cathode, hole transport layer, emission layer, electron transport layer and magnesium-silver alloy anode, respectively, are compared. Luminances exceeding 1000 cd/m2 are observed and emission peaks are located at 470-480 nm. Among the three cells, the DH cell shows the best performance. The DH cell is stable for more than 40-day storage and can also be continuously driven for more than one hour at room temperature and 7 h at liquid nitrogen temperature.
Dielectric Spectroscopy of p-GaSe Single Crystals //cand ⊥c
Authors: Anis Muhammad Khalid , Hashmi Riaz Ahmad , Syed Navaid Yousuf Syed Navaid Yousuf , Shakeel Ahmed Ansari Shakeel Ahmed Ansari
Published: February 2005

Frequency dependence of the complex susceptibility for a Bridgman-Stockbarger (B-S) grown p-GaSe single crystal parallel toc-axis (//c) and perpendicular toc-axis (⊥c) over seven decades (10-3-104Hz), together with temperatures ranging from 300-450 K, has provided experimental data relating to the dynamic response of slow transition. The crystal has exhibited low-frequency dispersion (LFD) for //cand ⊥c, with a buried loss peak due to an unknown process, and no single mechanism appears to be responsible for this. The LFD activation energies for hopping charge carriers for //cand ⊥care found to be 0.66±0.02 eV and 0.79±0.02 eV, respectively. Only slight anisotropy in the dielectric response is observed in the measured temperature range.
Charging Characteristics of a Copolymer of Vinylidene Fluoride and Tetrafluoroethylene
Authors: Guo Yufeng , Hoshino Katsuyoshi , Jun-ichi Hanna Jun-ichi Hanna , Hiroshi Kokado Hiroshi Kokado
Published: February 2005

Corona charging characteristics of a copolymer of vinylidene fluoride and tetrafuoroethylene, poly(VDF-TFE), were investigated by electrophotographic measurements. A difference in the charging characteristics was found between poled and unpoled films. This was interpreted by dipole rotation which induces change in the bulk conductivity. By analysis of the voltage-current relationship and current-temperature relationship, it was concluded that the Richardson-Schottky process was dominant in the high field. Data on corona charging characteristics with different electrode configurations indicate the primary importance of hole injection from the electrode into the film. The corona charging characteristics of poly(VDF-TFE) film was shown to be controlled by changing the electrode materials.
Reverse Recovery Time of Junction Diodes with High Capture Rate of Minority Carriers in the Low Injection Level
Authors: Tomokage Hajime , Yamakawa Tetsuya , Morooka Tokuo Miyamoto
Published: February 2005

The reverse recovery time is calculated using a general expression for the net recombination rate through a recombination center. When the capture rate of minority carriers is high compared to that of majority carriers, the recovery time increases with the injection level even if the condition of low injection level is satisfied. This means that the apparent lifetime obtained from Kingston's relationship is larger than the true value. An approximate equation which relates the recovery time to the injection level is proposed.
Application of a Hall Accelerator to Diamondlike Carbon Film Coatings
Authors: Okada Morihiro , Toku Hisayuki , Yasushi Yamamoto Yasushi Yamamoto , Kiyoshi Yoshikawa Kiyoshi Yoshikawa
Published: February 2005

A Hall accelerator-type ion source for low-voltage continuous operation (hereafter called HALOC) without any exhaustible filaments, designed for film coating purposes, has successfully produced a large-area low-energy continuous beam of methane or oxygen. The thin film of carbon uniformly coated on a steel plate by the HALOC has been found to be a typical amorphous hard carbon film with high Vickers hardness, strong adhesion, and strong anticorrosion properties. The causes of strong adhesion of the film have been studied.
Operating Regions of a Gas-Puff Z-Pinch and Its X-Ray Radiation
Authors: Takasugi Keiichi , Takeuchi Atsushi , Hiroyuki Takada Hiroyuki Takada , Tetsu Miyamoto Tetsu Miyamoto
Published: February 2005

A z-pinch experiment is carried out with a hollow-shaped Ar gas puff. Three types of discharge are found depending on the delay time of discharge from gas-puff detection, and the pinch time is compared with the measured gas pressure profile. Strong X-ray radiation is emitted from spots, a cloud and the anode surface. The number of spikes in the X-ray signal is correlated with spot images of the X-ray photograph. An X-ray burst is sometimes observed in the short-delay-time operation.
Control of Hydrocarbon Radicals and Amorphous Carbon Film Deposition by Means of RF Whistler Wave Discharge
Authors: Mieno Tetsu , Shoji Tatsuo , Kadota Kiyoshi
Published: February 2005

Hydrocarbon radicals are produced and controlled by using a radio-frequency (RF) whistler wave discharge in a low-pressure region (∼0.1 Pa). Plasma density of 1010-1013 cm-3, at an electron temperature of 2-20 eV is obtained for the discharge of an admixture of Ar and a small amounts of source gases (CH4, C2H2, CO). Densities of CH and H radicals and deposition rate of amorphous carbon:H film increase with electron density, electron temperature and source gas pressure. Both neutral radicals and ionic radicals play an important role in the deposition, and the etching effect of H atoms reduces the deposition rate. A high deposition rate (90 µm/h for CO/Ar discharge) is obtained even for a low-neutral-pressure discharge.
Thin Films of (BEDT-TTF)2Cu(NCS)2 Prepared by an Electrodeposition Method*
Authors: Awano Hiroshi , Kawase Koji , Asai Masaru , Ohigashi Hiroji , Ohshima Shigetoshi , Akiyama Kimio , Kato Masanao
Published: February 2005

Thin films of (BEDT-TTF)2Cu(NCS)2 are prepared by the electrochemical oxidation of BEDT-TTF at a large current density. The films are composed of numerous platelets, which are set on edge and loosely packed on the anodes. The X-ray diffraction suggests that the product contains both amorphous regions and κ-type and other crystals. The ESR and conductivity are discussed in terms of the presence of amorphous regions.
Measurement of the Density of Liquid under Pressure by Means of Buoyancy
Authors: Nomura Motoyuki , Itoh Yoichiro , Takahashi Tsukasa Itoh
Published: February 2005

A simple method for obtaining the density of liquid under pressure by means of the measurement of the buoyancy of a weight hung on a thin, suspending wire in the sample liquid up to the pressures of 700 MPa at room temperature is presented. The buoyancy was obtained from the tension of the suspending wire through a repeated operation with the pressure vessel in a vertical position and then in a horizontal position. Moving the pressure vessel in a seesaw fashion around the horizontal position was effective in eliminating residual tension due to friction between the weight and the inner wall of the pressure chamber. A method to experimentally estimate the influence of pressure on the proportionality coefficient relating the resistance change of a suspending wire with the tension is presented.
Synthesis of Diamond Using Fe Catalysts by RF Plasma Chemical Vapor Deposition Method
Authors: Shimada Yoshihito , Nobuki Mutsukura Nobuki Mutsukura , Yoshio Machi Yoshio Machi
Published: February 2005

Diamond growth was examined on a Fe/Si substrate in rf CH4 plasma. The Fe film, evaporated on a Si wafer, promotes the growth of diamond. Although the density of the diamond particle grown on a Si substrate was on the order of 106 cm-2, the Fe film enhanced the density to an order of 107 cm-2. The particle size was increased with the increase in the Fe film thickness, and indicated a maximum value at around 500 Å. At an initial stage in the diamond growth, it was confirmed that C and Fe atoms diffused deeply into the Fe film and the Si substrate, respectively, which was confirmed by X-ray photoelectron spectroscope measurements. It was also observed that the diamond particles exist at the interface between the Fe film and Si substrate.
Laser Ablation Deposition: Mechanism and Application
Authors: Dieleman J. , E. van de Riet E. van de Riet , J. C. S. Kools J. C. S. Kools
Published: February 2005

Especially in the eighties and early nineties laser ablation has drawn increasing attention for application in thin film deposition (and etching). For a variety of inorganic materials, at the practically most interesting laser fluence values just above the ablation threshold, the pulsed ablation clouds arriving at the substrate consist mainly of ground state atoms (≥99%, E
kin∼a few eV), Rydberg atoms (∼0.1 to 1%, E
kin∼near 10 eV), positive ions (≤10-2%, E
kin∼a few tens eV), electrons and “droplets”. The atoms are strongly peaked along the target surface normal, while the angular distribution of the ions is largely isotropic. A hydrodynamic model describes the ablation cloud quite well. As compared to other advanced thin film deposition techniques, laser ablation deposition produces high-quality, stoichiometric films of even very complex materials at lower substrate temperatures.
Photoinduced Deposition of Aluminum Thin Film on Silicon Nitride and Oxide
Authors: Ouchi Hideki , Ishida Kenji , Hanabusa Mitsugu , Shogen Satoshi , Kawasaki Masahiro
Published: February 2005

Aluminum thin films were deposited via a photochemical surface reaction using dimethylaluminum hydride (DMAH) and a deuterium lamp on silicon wafers covered with silicon nitride and silicon oxide layers. Unlike deposition on uncovered silicon wafers, the dosing of DMAH at room temperature was not required. The dependence of the thickness of the deposit on substrate temperature, as well as on deposition time, was measured for photodeposition on the nitride layer. Scanning tunneling microscope images showed the formation of aluminum islands. An X-ray photoelectron spectroscopy (XPS) study indicated that the aluminum atom was bonded with carbon after adsorption at 230°C, and we speculated that the aluminum-methyl radical complex was photodissociated.
Deposition in Dry-Etching Gas Plasmas
Authors: Arai Shin , Kazunori Tsujimoto Kazunori Tsujimoto , Shin'ichi Tachi Shin'ichi Tachi
Published: February 2005

Polymer deposition on Si and SiO2 surfaces has been investigated in CH2F2, CHF3, CF4, and CHClF2 gas plasmas, using a microwave plasma etching system. The dependence of the deposition rate on gas pressure, RF bias power, and substrate temperature was measured at a temperature between -120°C and 150°C. The deposition rate increased with decreasing temperature in CH2F2, CHF3, and CHClF2 plasmas. The deposition of polymers occured only below -60°C in the CF4 plasma. The obtained dependence of the deposition rate on gas pressure was examined in terms of the volume of adsorbed particles. X-ray photoelectron spectroscopy measurement showed that the number of bondings between C and F atoms in deposited polymers increases with decreasing temperature and RF power, and increasing gas pressure.
Dependence of Residual Chlorine Amount on Al Grain Size
Authors: Aoki Hidemitsu , Ikawa Eiji , Kikkawa Takamaro , Teraoka Yuden , Nishiyama Iwao
Published: February 2005

From the investigation of the thermal desorption spectroscopy (TDS) results, it was found that the amount of residual chlorine on Al films increased with increasing Al grain boundary length after 60°C etching and rinsing. The aluminum surface morphology, which was observed by atomic force microscopy (AFM) after etching, indicated that the Al surface was etched along grain boundaries. Consequently, residual chiorine was trapped at the ditches of grain boundaries which were engraved by etching. In the case of -10°C etching, residual chlorine was hardly trapped at the ditches of grain boundaries because engraving along grain boundaries by etching was suppressed at low temperature.
Crystal Structure Change of GaAs and InAs Whiskers from Zinc-Blende to Wurtzite Type
Authors: Koguchi Masanari , Kakibayashi Hiroshi , Yazawa Masamitsu , Kenji Hiruma Kenji Hiruma , Toshio Katsuyama Toshio Katsuyama
Published: February 2005

Crystal structures of GaAs and InAs whiskers grown by metalorganic vapor phase epitaxy are evaluated by means of a transmission electron microscope. The whiskers are grown epitaxially on GaAs substrates with diameters of 20-100 nm and lengths of 1-5 µm. They have the following characteristics. 1) GaAs whiskers have layered structures with 2-30 nm period, that are the 111 rotating twins of the zinc-blende type. 2) InAs whiskers also have layered structures which consist of wurtzite and zinc-blende type crystals. The wurtzite type InAs is observed for the first time in this study. The volume ratio of these two types strongly depends on the growth conditions, such as substrate temperature and material gas pressure. This suggests that defect-free whiskers with a single phase that are useful for quantum wire devices can be grown by controlling the growth conditions.
Anodic Oxides on Hg1-xCdxTe Studied Using Angle and X-Ray Power-Dependent X-Ray Photoelectron Spectroscopy
Authors: Kengo Shimanoe Kengo Shimanoe , Masao Sakashita Masao Sakashita
Published: February 2005

The surface composition of the anodic oxidation film on Hg0.8Cd0.2Te (MCT) has been studied by means of angle and X-ray power-dependent X-ray photoelectron spectroscopy (XPS) techniques. The anodic oxidation film is composed of oxides and hydroxides, in which a tellurium oxide with a low valence is involved. The hydroxides are more predominant in the outermost layer. The low valence oxide (Te2+) is changed to a high valence oxide (Te4+) with X-ray power higher than 40 W. Furthermore, such high-power irradiation induces evaporation of mercury oxides and/or hydroxides and conversion of hydroxides to oxides. These changes are observed also in the spectrum obtained under monochromatized X-ray irradiation.
Conversion Efficiency Enhancement Technique for a Quasiphase Matched Second-Harmonic Generation Device
Authors: Shinozaki Keisuke , Takamori Takeshi , Watanabe Kenji , Toshiaki Fukunaga Toshiaki Fukunaga , Takeshi Kamijoh Takeshi Kamijoh
Published: February 2005

Conversion efficiency enhancement techniques have been demonstrated for quasiphase matched (QPM) second-harmonic generation (SHG). First, we describe a technique for confining the high fundamental optical power density in a waveguide with a domain-inverted grating (SHG waveguide), i.e., a technique for monolithic integration, the SHG waveguide, and a distributed Bragg reflector (DBR). A 40% increase in the conversion compared with a conventional device without a DBR was achieved under QPM conditions. We also describe a method of automatically satisfying QPM conditions, using a laser diode (LD) with antireflection-coated facets. We used the InP/InGaAsP LD and confirmed that the LD oscillated at a wavelength satisfying the QPM conditions. The normalized conversion efficiency was 4.1%·W-1·cm-2.
Theoretical Study of Subpicosecond Pulse Amplification in XeF(C-A)
Authors: Fumihiko Kannari Fumihiko Kannari
Published: February 2005

The feasibility of using XeF(C-A) excimer media as an amplifier for subpicosecond short pulse lasers is theoretically investigated. Numerical caculations by using a coherent interaction model show that as a result of both a large saturation energy density and bleaching of absorbers output energy densities of >100 mJ/cm2 are easily obtained. Influence of narrow band absorption of excited xenon metastable atoms on the amplifier gain and pulse waveform is also predicted.
Parallel Neighborhood Operation System by Optical Parallel Logic Gate and Optical Interconnection with Prisms
Authors: Kenji Ueyama Kenji Ueyama , Takumi Minemoto Takumi Minemoto
Published: February 2005

Parallel neighborhood operations are very useful for image processing. A system that optically implements the operations is presented. The system consists of an optical parallel logic gate, a simple multiple-imaging system and electronic feedback circuits. The experimental results of several binary image processings are presented by use of the system, and a new algorithm for extraction of corners is proposed.
Far-Infrared Reflectance Spectra of Heavily Doped p-GaAs for Various Hole Concentrations
Authors: Fukasawa Ryoichi , Wakaki Moriaki , Ohta Kimihiro
Published: February 2005

We report far-infrared reflectance spectra of Be-doped p-type GaAs for hole concentrations between 3.5×1018 and 2.9×1019 cm-3. The spectral features of p-GaAs are quite different from the typical spectra of n-GaAs. The spectral shape analysis indicates that the free hole damping constant is about 8 times larger than that of n-GaAs.
Polar Anchoring Strength and the Temperature Dependence of Nematic Liquid Crystal (5CB) Aligned on Rubbed Polystyrene Films
Authors: Seo Dae-Shik , Muroi Koh-ichi , Isogami Toh-ru , Hideaki Matsuda Hideaki Matsuda , Shunsuke Kobayashi Shunsuke Kobayashi
Published: February 2005

A characterization of rubbed polystyrene (PS) film in terms of the optical retardation measurement as a function of the rubbing strength (RS) has been made, and the alignment capability of the rubbed PS films for a nematic liquid crystal (5CB) has been investigated by measuring anchoring strength and its temperature dependence. It is shown that the liquid crystal (LC) molecules orient homogeneously in a direction orthogonal to that of rubbing, the anchoring strength of the rubbed PS films at the strongest rubbing strength for 5CB is about 70 times weaker compared to that for rubbed standard polyimide films, and the anchoring strength decreases with the temperature in a divergent fashion according to the increase of the extrapolation length toward the clearing point (T
c=35.3°C).
Influence of Calcining Temperature on CuO-Modified (Ba0.8Sr0.2)(Ti0.9Zr0.1)O3 Ceramics
Authors: Yang Cheng-Fu , Long Wu Long Wu , Tien-Shou Wu Tien-Shou Wu
Published: February 2005

The sintering of (Ba0.8Sr0.2)(Ti0.9Zr0.1)O3 (abbreviated as BSTZ) with different amounts of CuO, which is used as the liquid phase promoter for lowering the temperature required to densify BSTZ, is studied using two types of calcined powders. For 1050°C calcination, the calcined powder contains BaTiO3, SrTiO3 and some raw materials such as ZrO2 and BaCO3. With sintering, some residual raw materials form unknown phases or low-dielectric-constant compounds with CuO, causing the liquid phase effect of CuO to disappear. For 1170°C calcination, the calcined powder completely forms ABO3 phases containing (Ba, Sr)TiO3 and BaZrO3. The sintering temperature for densification of ceramics is lowered, and the firing characteristics critically depend on the amount of CuO added and the sintering temperature.
Effects of Sulfidization and Sintering Temperatures of CaLa2S4 Powder on Its Optical Property
Authors: Li Hsing Wang Li Hsing Wang , Min Hsiung Hon Min Hsiung Hon
Published: February 2005

Highly sinterable submicron CaLa2S4 powders were prepared by sulfidizing calcium and lanthanum alkoxides at 400°C to 1050°C for 48 h in pure H2S atmosphere for application in infrared transmitting window material for 8-14 µm wavelength. The CaLa2S4 powders had some residues of carbon and hydrogen after sulfidizing at or below 850°C. The CaLa2S4 powder without extrinsic absorption in the 2.5-7 µm range due to the contaimination was obtained by sulfidizing at 950°C for 48 h. The characteristic absorption bands of sulfite and sulfate at 9.2 and 11 µm were reduced in the pellet by eliminating the oxygen content in the sulfide by sulfidizing the powder at 1050°C for 48 h. It was shown that 1050°C was the optimum sulfidization temperature, while 1400°C was the optimum sintering and hot isostatic pressing (HIP) temperature to obtain a higher transmittance ceramic.
The JFT-2M TV Thomson Scattering System
Authors: Yamauchi Toshihiko , Dimock Dirck , Tolnas Edwin , COrso Vince , Leblanc Benoit , Shiina Tomio , Takahashi Akira , Felt Janet , Johnson David , Joseph Bartolick Joseph Bartolick , Richard Paladino Richard Paladino
Published: February 2005

It is the purpose of this report to present a detailed description of the TV Thomson scattering system on the JFT-2M tokamak, produced through the collaboration of the Princeton Plasma Physics Laboratory (PPPL), and the JFT-2M group of the Japan Atomic Energy Research Institute (JAERI).
Applicability of Laser Phase Contrast Method for the Measurements of Electron Density Fluctuations in High-Temperature Plasmas
Authors: Tanaka Kenji , Matsuo Keiji , Goto Koji , Bowden Mark , Muraoka Katsunori , Furukawa Takehiko , Sudo Shigeru , Obiki Tokuhiro
Published: February 2005

We have demonstrated the potential of the laser phase contrast (LPC) method for measurements of electron density fluctuations in high-temperature plasmas, by measuring the direction of propagation and intensity of fluctuations in Heliotron E.
Behavior of Reaction Products of Poly-Si in Electron Cyclotron Resonance Ion Stream Etching and Its Application to Stable and High-Selectivity Etching
Authors: Chiharu Takahashi Chiharu Takahashi , Seitaro Matsuo Seitaro Matsuo
Published: February 2005

Effects of reaction products (SiCl
x
) are investigated in electron cyclotron resonance (ECR) ion stream etching of poly-Si metal-oxide-semiconductor (MOS) gates in which Cl2 is employed as a main etching gas. Experiments using a gas mixture of Cl2-SiCl4 confirm that SiCl4 gas (i) promotes SiO2 etching to some extent, (ii) reduces the effect of added O2 which is utilized to lower SiO2 etch rate, and (iii) is approximately equivalent to the reaction products in etching characteristics. In Cl2 with proper amounts of SiCl4 and O2, the above results prove that the SiCl4 can control the change in etching characteristics caused by a decrease in the amount of the reaction products during overetching to proceed in a self-regulating manner toward the cessation of SiO2 etching. This results in stable etching conditions with high selectivity (poly-Si/SiO2) over 100.
Synchrotron Radiation-Assisted Silicon Film Growth by Irradiation Parallel to the Substrate
Authors: Nara Yasuo , Sugita Yoshihiro , Kei Horiuchi Kei Horiuchi , Takashi Ito Takashi Ito
Published: February 2005

Growth of silicon films by synchrotron radiation (SR) photolysis of Si2H6 is studied for temperatures below 500°C. SR is irradiated parallel to the substrate to grow silicon film over a large area and to avoid substrate heating and gas dissociation by photoelectrons. The thickness uniformity in a 2-inch wafer is over 50% while an SR cross section is about 1×10 mm. At substrate temperatures above 300°C, the hydrogen content of the film is low enough that epitaxial silicon film is successfully grown.
Current-Induced Degradation of AlGaAs/GaAs Heterojunction Bipolar Transistors and Its Suppression by Thermal Annealing in As Overpressure
Authors: Nakajima Osaake , Ito Hiroshi , Takumi Nittono Takumi Nittono , Koich Nagata Koich Nagata
Published: February 2005

Current-induced degradation of current-voltage (I-V) characteristics in AlGaAs/GaAs heterojunction bipolar transistors (HBTs) with Be-doped base layers is investigated. Large shifts of emitter-base on-voltage (ΔV
BE) are observed during high current operation. The behavior of degradation is qualitatively explained in terms of interstitial Be diffusion in combination with the electron-hole recombination process. Thermal annealing in As overpressure can successfully stabilize the characteristics. Degradation is not observed in AlGaAs/GaAs HBTs with C-doped base layers without the Zn diffusion process.
Effects of Interface Atomic Configurations on Electronic Structures of Semiconductor Superlattices
Authors: Oda Katsuya , Takashi Nakayama Takashi Nakayama
Published: February 2005

The electronic structures are calculated using the semiempirical s
p
3
s
* tight-binding method for [001] GaAs/ZnSe and GaAs/AlAs semiconductor superlattices which have several structures at the interface. The results of calculation show that in GaAs/ZnSe superlattices electrons and holes are localized around donor (Ga-Se) and acceptor (Zn-As) bonds at the interface, respectively, and that the band-gap energy changes largely (∼0.3 eV) with varying configuration of donor and acceptor bonds. In GaAs/AlAs superlattices, because the difference in ionicity between GaAs and AlAs is small, there is little difference in the electronic structures between superlattices with various interface structures.
Growth and Characterization of Titanium Silicide Films on Natural Diamond C(001) Substrates
Authors: Humphreys Trevor P. , Labrasca John V. , Turner Kevin F. , Nemanich Robert J. , Das Kalyankumar , Posthill John B. , Hunn John D. , Parikh Nalin R.
Published: February 2005

Initial results pertaining to the growth and characterization of TiSi2 films deposited on natural single crystal insulating and semiconducting diamond C(001) substrates are reported. The TiSi2 films were formed by the co-deposition of Si and Ti in ultra-high vacuum by electron-beam evaporation. From an analysis of the Raman scattering spectra, both the orthorhombic metastable C49 and stable C54 crystallographic phases of TiSi2 have been identified. As evidenced by scanning electron microscopy (SEM) and scanning tunneling microscopy (STM) the TiSi2 films exhibit a faceted surface morphology indicative of polycrystalline growth. Moreover, the TiSi2 films exhibit excellent adhesion properties with the underlying diamond substrate. Corresponding current-voltage (I-V) measurements conducted at room temperature have demonstrated rectifying characteristics for the TiSi2 films deposited on natural p-type semiconducting diamond substrates. Consistent with the small turn-on voltage of ∼0.2 V, the corresponding I-V measurements recorded at 400°C exhibit ohmic-like behavior. However, upon subsequent annealing of the TiSi2 contacts at 1100°C, stable rectifying I-V characteristics were observed in the 25-400°C temperature range.
Magnetoelastic Effect of 3.25%Si-Fe Single Crystal under Low Magnetic Field
Authors: Kenji Kashiwaya Kenji Kashiwaya
Published: February 2005

The effect of stress on magnetization and the dependence of magnetization on crystallographic orientation were investigated using single-crystalline and polycrystalline specimens. It was found that the magnetization curve shifts toward the high-magnetic-field side with the application of stresses, and this shift is proportional to the stress and has a strong dependence on crystallographic orientation. A model was proposed in which, as the domain observation testified, magnetization took place in such a manner that a certain domain structure satisfied the minimum free-energy condition. It explained the experimental results well. It may be concluded that magnetization under low magnetic field is attained with a balance between magnetoelastic and magnetization energies without increasing magnetostatic energy.
A High-Speed Si Bipolar Transistor with SAVEN (Self-Aligned device using VErtical Nitride)
Authors: Koo Yong Seo , An Sang Won Kang
Published: February 2005

This paper presents a new device called SAVEN (self-aligned device using vertical nitride) which has faster switching speed characteristics. To obtain this level of performance, SAVEN adapts the technology reducing the extrinsic base region by controlling the vertical nitride layer. Also, it uses the trench isolation and TiSi2 process of the n+ polysilicon emitter region. The emitter area is designed to be 1.0×4.0 µm2. DC characteristics of the fabricated transistor is evaluated and analyzed for the SPICE input parameters. The current gain of the butted npn transistor is around 100, and the breakdown voltage for the collector-to-emitter is 7.5 V. The junction capacitances of base-to-collector and collector-to-substrate are measured at 12 fF and 19 fF, respectively. These low values are due to the small extrinsic base width and elimination of the parasitic capacitance between the epitaxial layer and substrate. From the measurement of the current mode logic (CML) ring oscillator with 31 stages, the minimum propagation delay time per gate is 45 ps at 1.4 mW.
Effects of Silver and Y2BaCuO5Inclusions on the Transport Current Density and its Anisotropy of Oriented-Grained YBa2Cu3Ox/Silver Composites
Authors: Lee Dominic , Xavier Chaud Xavier Chaud , Kamel Salama Kamel Salama
Published: February 2005

Transport critical current density (Jct) measurements were performed on bulk oriented-grained YBa2Cu3Ox/Silver composites in the presence of a magnetic field (B).Jctof these composites exhibit strong anisotropic behavior when the angle between the applied field and thec-axis of the specimen is varied. TwoJctpeaks were observed; a sharp peak centered atBperpendicular to thec-axis and aJctvalue roughly 3 times higher than that of the minimumJctis found. Another broader and weaker peak is found to be centered atBparallel to thec-axis. This anisotropic behavior is detected at all field strengths investigated at 77 K. The effects of Ag as well as Y2BaCuO5(2-1-1) additions onJctwere also investigated. Relatively small amount of randomly distributed normal-phase particles are found to have negligible effect on theJctanisotropy. The large Ag inclusions are determined to be ineffective pinning centers andJctdecreases with Ag content. The 0.5 to 2 µm size 2-1-1 additions, however, appear to enhance theJctof the composites.
Focusing of Elliptical Gaussian Beams for Optical Head
Authors: Mitsushige Kondo Mitsushige Kondo
Published: February 2005

This paper deals with experiments and computations concerning the focusing of laser diode elliptical Gaussian beams truncated by a centered circular aperture. The spot diameter of the focused beam was calculated in relation to the truncation coefficient. The experimentally measured values of the spot diameter closely agree with the calculated values within the error of 4%. When the minor axis size of the elliptical beams fits the pupil rim of the objective lens, the experimental and the calculated results indicate that adjusting the minor axis of the spot fitting parallel to the tracks results in twofold increased playback frequency characteristics at the spatial frequency 0.85/µm and about 4 dB less cross talk than in the case of fitting perpendicular to the tracks.
Output Characteristics of a KrF Laser Dependent on the F2 Absorption in Inactive Regions
Authors: Shimada Yasuhiro , Miki Tadaaki , Mimasu Mutsumi , Naoki Kosugi Naoki Kosugi , Yoshiro Ogata Yoshiro Ogata
Published: February 2005

Dependence of the output power of a discharge-pumped KrF laser on the F2 absorption in inactive regions has been studied. The F2 absorption cross section at 248 nm was experimentally determined to be 1.6×10-20 cm2. A greater than 15% increase in the output was obtained by filling the inactive regions on the optical path with a rare-gas mixture.
High Dielectric Constant of RF-Sputtered HfO2 Thin Films
Authors: Hsu Chin Tsar , Yan Kuin Su Yan Kuin Su , Meiso Yokoyama Meiso Yokoyama
Published: February 2005

Hafnium dioxide (HfO2) thin films are deposited on indium-tin-oxide (ITO)-coated glass substrates by the radio-frequency (RF) sputtering method using a HfO2 sintered target. The deposition conditions, dielectric loss and dielectric constant of HfO2 films before and after heat treatment are studied. The best deposition conditions for HfO2 films are RF power 200 W, substrate temperature 100°C and sputtering gas pure Ar. The maximum dielectric constants are about 150 and 45 with 1 kHz signal excitation before and after annealing, respectively. They are higher than any ever reported.
Coexistence of Two Types of Nucleation Sites for Oxygen Precipitates in Czochralski Silicon
Authors: Hideki Yamanaka Hideki Yamanaka
Published: February 2005

We have found that the nuclei effective for annealing at 800°C are dominantly generated at two characteristic temperatures of 500°C and 650°C. Carbon-related oxygen aggregates, whose density increases with increasing carbon concentration, are generated at temperatures around 500°C. Thermal-donor-related oxygen aggregates which thermal donors grow into are additionally created at temperatures around 500°C. In low-carbon-content silicon, thermal-donor-related oxygen aggregates are dominantly created at 500°C. Another type of carbon-related oxygen aggregate is generated at temperatures around 650°C. The rapid nucleation in high-carbon-content silicon during annealing at 500°C for only 30 min is reasonably explained by considering that carbon-related oxygen aggregates formed at about 500°C are composed of Ci-O2complexes.
New Organic Material of Bis(benzylidene)cycloalkanone Derivatives for Efficient Optical Second-Harmonic Generation
Authors: Kawamata Jun , Inoue Kuon , Kasatani Hirofumi , Terauchi Hikaru
Published: February 2005

We have synthesized a series of bis(benzylidene)cycloalkanone derivatives with up to 30 members, and examined their conversion efficiencies of second-harmonic generation (SHG) and related characteristics. As a result, we find that a few derivatives exhibit prominent features in SHG. That is, 2,5-bis(4-methylbenzylidene)cyclopentanone, 2,5-bis(4-bromobenzylidene)cyclopentanone and 2,7-bis(4-methylbenzylidene)cycloheptanone are 30, 20 and 16 times more efficient in SHG, respectively than urea, and they presumably satisfy the criteria required for practical application, concerning phase matching, cutoff wavelength, stability and laser-power tolerance. The crystallographic structures of a few typical compounds are also presented. Furthermore, the difference in effectiveness of the present design principle compared with conventional ones is discussed.
Persistent Spectral Hole-Burning in Semi-Crystalline Matrices Doped with Tetraphenylporphine
Authors: Shimada Toshiyuki , Arishima Koichi , Nishi Toshihiro , Hiroyuki Suzuki Hiroyuki Suzuki , Hiroaki Hiratsuka Hiroaki Hiratsuka
Published: February 2005

We report persistent spectral hole-burning (PSHB) in semi-crystalline polymer matrices doped with tetraphenylporphine (TPP). The host matrices were polyethylene (PE) and butadiene rubber (BR). The holewidth in TPP/PE was smaller than that observed in poly (methyl methacrylate) (PMMA) doped with TPP at about 5.5 K. However, the irreversible hole broadening measured with thermal cycling experiments was greater in PE. A similar tendency was also observed for the holewidth and irreversible hole broadening in semi-crystalline and amorphous BR matrices. These results show that the existence of the crystalline region plays an important role in the properties of spectral holes.
A New Type of Refractometer for High-Temperature Use
Authors: Takamizawa Kanichiro , Sachihiko Ueno Sachihiko Ueno , Kohzoh Shiokawa Kohzoh Shiokawa
Published: February 2005

A new type of refractometer is proposed. Its design is based on the method of critical angles. Instead of visually detecting the position of the critical boundary, the refractometer measures the intensity of scattered light from a sample layer. The temperatures of the sample and the prism were controlled over a range up to 300°C. The apparent critical angle θc could be determined from the relationship between the scattering intensity and incident angle. Reliable data were obtained for a simple liquid. When the sample size was limited due to temperature homogeneity, the effect of the sample thickness on θc had to be taken into consideration. High-temperature measurements on polycarbonate were satisfactorily obtained.
A Drift Tube for Monitoring ppb Trace Water
Authors: Irie Takashi , Hasumi Yasuhiro Mitsui
Published: February 2005

This paper demonstrates the possibility of using a drift tube to monitor trace water in nitrogen gases for semiconductor fabrication processes. In the drift tube, ions are produced by corona discharge and drift at atmospheric pressure. The arrival-time spectra are observed for nitrogen gases with water concentrations at several ppb levels. The spectra show an obvious peak, which disappears when the water concentration increases to several tens of ppb. This suggests that the peak results from nitrogen cluster ions not reacting with water molecules. This is supported by the ion mobility calculated for the peak in the spectra, and also by related ion-molecule reaction kinetics. It is possible that the developed drift tube determines the water concentration at several tens of ppb levels or below from the intensity change in the arrival-time spectra.
Estimation of Terrestrial Magnetism on High-Gain Electron Synchrotron
Authors: Shuhei Nakata Shuhei Nakata
Published: February 2005

Terrestrial magnetism has a significant effect on low-energy electron beam dynamics in a circular accelerator and calculation of the field distribution is neccesary to estimate the COD (closed orbit distortion) and to improve the performance of the accelerator. To overcome the difficulty of the limitation of memory size for the calculation of field distribution in a real synchrotron, the surface magnetic charge method with the iteration technique is developed and the field distribution of the Mitsubishi Electric Corporation synchrotron is calculated. Using this iteration method the equation can be solved with a residual error of less than 1×10-5. The maximum value of COD in the vertical direction caused by the calculated field is 5 mm at the external terrestrial magnetism of 0.1 G. This value is 40% stronger than the simple estimation made under the assumptions that the magnetic field is zero inside the magnets and equal to the external field outside the magnets. This COD, which is twice the expected value by misalignment of the magnets, is caused by the coupling between the perturbation of harmonics 1 by the terrestrial magnetism and the vertical betatron oscillation (ν
y
=1.21) of the model synchrotron.
Improvement in the Sensitivity of PPMMA Electron Beam Resist by S and F Atom Doping
Authors: Madhukar Zambare , Suresh Gosavi , Sucheta Gorwadkar , Beena Kuruvilla , Sulabha Kulkarni , Gangal Shashikala Gangal Shashikala
Published: February 2005

The present work reports the dependence of sensitivity of plasma polymerized methyl methacrylate (PPMMA) as electron beam resist on S and F atom concentration in the films. Plasma polymerization of MMA is carried out in an inductively coupled reactor at different deposition conditions with and without SF6 doping. Ar is used as carrier gas. The bonding characterization of the films is done by IR and X-ray photoelectron spectroscopy (XPS) techniques. XPS data taken on films, deposited under different deposition conditions, is used to estimate the S and F concentrations. The electron beam delineation is done using scanning electron microscope (SEM), modified for electron beam writing. The self development sensitivity of PPMMA films doped with S and F atoms is found to be 2-3 times improved compared to undoped PPMMA and is also dependent on deposition conditions.
An Extremely Simple Device for Variable Temperature AC Magnetic Measurements
Authors: Rao T. V. Chandrasekhar , Salunke H. G. , S. B. Ota S. B. Ota , V. C. Sahni V. C. Sahni
Published: February 2005

An extremely simple device for making ac magnetic measurements between ambient and LN2 (liquid nitrogen) temperatures is described. It can be rigged up easily and there is no requirement of a temperature controller. The device is particularly suitable for characterizing high-T
c superconductors.
Donor-Acceptor Pair as Opposed to Anion Antisite Metastability in Bulk Semi-Insulating GaAs: Electron Paramagnetic Resonance and Photoconductivity Data Analysis
Authors: Benchiguer Taha , Mari Bernabé , Desnica Claude Schwab
Published: February 2005

We show that the time evolution of the paramagnetic signals and photoconductivity in the same semi-insulating GaAs material during illumination below the band gap at low temperature can both be analyzed within a charge transfer model. This model involves the formation of metastable donor-acceptor pairs due to free carrier trapping by initially ionized defects. This result again questions whether the common link between EL2 and the AsGa-related defects needs a configuration-related metastability.