bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication and Characteristics of an Integrated DFB Laser/Amplifier Having Reactive-Ion-Etched Tilted End Facets
Authors: Nakano Yoshiaki , Hayashi Yohichi , Chen Nong , Sakaguchi Yasuyuki , Tada Kunio
Published: February 2005

We describe the fabrication and characteristics of a DFB laser monolithically integrated with an optical traveling-wave amplifier prepared using OMVPE/LPE hybrid growth. A unique feature is its 7°-tilted end facets formed by reactive ion etching for reduction of optical crosstalk. Owing to the low reflectivity of the facets, the elemental devices operate with little interference.
Optimization and Characterization of InAs/(AlGa)Sb Heterojunction Field-Effect Transistors
Authors: Yoh Kanji , Moriuchi Toshiaki , Inoue Masataka
Published: February 2005

We report the structural optimization and characterization of (AlGa)Sb/InAs quantum well heterojunction field-effect transistors based on molecular beam epitaxy (MBE). A 1.7- µm-gate-length InAs-channel FET with optimized heterostructure showed a transconductance of more than 460 mS/mm (V
ds=0.5v) at room temperature. Higher transconductance and drain current increase in the higher lateral electric field region (V
ds>0.8v) corresponds to the increased carrier concentration measured by the pulsed high-field Hall-effect method on ungated samples.
Room-Temperature Synthesis of ZnS:Mn Films by H2 Plasma Chemical Sputtering
Authors: Tonouchi Masayoshi , Sun Yong , Miyasato Tatsuro , Sakama Hiroshi , Ohmura Masaki
Published: February 2005

Thy hydrogen plasma chemical sputtering technique has been employed to deposit polycrystalline ZnS and ZnS:Mn films. The X-ray diffraction measurements and the electron probe X-ray microanalysis indicated that the highly crystallized ZnS films composed of near-stoichiometric ZnS grains were grown at 20°C in the pressure range from 300 Pa to 800 Pa, and the Mn-doped ZnS films were also deposited from the Mn-doped ZnS targets. The plasma state during the sputtering has been diagnosed by analyzing the spectral intensity emitted from Zn atoms. It is revealed that the growth rate is closely correlated with the optical emission from the Zn particles.
Control of GaAs on Si Interface Using Atomic Layer Epitaxy
Authors: Kitahara Kuninori , Ohtsuka Nobuyuki , Ueda Osamu , Funagura Makoto , Ozeki Masashi
Published: February 2005

We controlled the initial stage of GaAs growth on Si by using atomic layer epitaxy (ALE) supplying source gases as a pulsed jet. The heterointerface was investigated with relection high-energy electron diffraction specially developed for vapor phase epitaxy. Auger electron spectroscopy and X-ray diffraction were also used for study. It was shown that the species of the prelayer (As, Ga, and Al) and thin ALE buffer layer (GaAs and AlAs) determines the coverage of the initial growth on Si and crystalline quality of GaAs epitaxial layers even at a thickness of 3 µm. The best results were obtained by using the AlAs buffer layer on the As prelayer deposited at 850°C.
Electrical Properties of Gallium Fluoride(GaF3)/GaAs Interface with and without Sulfur Treatment
Authors: Ricard Herve , Kim Kwang Ho , Aizawa Kouji , Ishiwara Hiroshi
Published: February 2005

The electrical properties of gallium fluoride (GaF3) films deposited on GaAs are investigated. It has been found that deposited GaF3 films are good insulators with a dielectric constant of 6.6 and a resistivity of 2×1013 Ω·cm. It has also been found that the interface properties are good enough to generate inversion carriers either when a GaF3 film is deposited onto a homoepitaxial GaAs layer without breaking the vacuum or when the film is deposited on a sulfur-treated surface.
Preparation of As-Deposited Yb-Ba-Cu-O Superconducting Films by DC Arc Discharge Evaporation Method
Authors: Nohira Hiroshi , Ishiwara Hiroshi
Published: February 2005

A new process using DC arc discharge evaporation is presented for preparing as-deposited superconducting Yb-Ba-Cu-O films on insulating substrates. In this method, it is necessary to alternate the applied bias direction periodically during film deposition in order to obtain stoichiometric composition films. It was found from SIMS analysis that the periodic change of the composition did not diffuse out in the film even after annealing at 800°C for 2 h. Thus, the alternation period was shortened to about 1 nm. The resultant film deposited on SrTiO3(100) at 700°C showed zero resistivity at 75 K.
Flat Panel Light-Emitting Sounder Using Thin-Film EL Devices with a Ceramic Insulating Layer
Authors: Minami Tadatsugu , Miyata Toshihiro , Kitamura Kentaro , Takata Shinzo , Fukuda Ichiro
Published: February 2005

Sound emission has been achieved from an EL device consisting of a ZnS:Mn thin-film phosphor and a thick piezoelectric BaTiO3 ceramic insulator. The BaTiO3 ceramic, serving not only as the insulating layer of the EL device but also as the substrate, functioned as the sounder. A high sound pressure level as well as a high luminance was obtained in the device driven with audio-frequency voltages: above 90 dB in a flat panel speaker composed of four sound-emitting EL devices with a maximum luminance of 8000 cd/m2. Test results have shown that the sound emission is related to the electroluminescence.
Plastic Deformation of Al-Ru-Cu Icosahedral Quasicrystals
Authors: Shibuya Tadaharu , Hashimoto Tatsuo , Takeuchi Shin
Published: February 2005

Polycrystalline specimens of Al68Ru15Cu17 icosahedral quasicrystals are brittle below 1000 K but plastically deformable above 1000 K with the flow stress sensitively depending on the strain-rate. The activation analyses show that the activation volume is less than 1 nm3 at high stress and 10 nm3 at low stress. The obtained activation enthalpy is anomalously high, ∼10 eV at low stress, and the pre-exponential factor is unreasonably large, suggesting that the simple Arrhenius rate equation is not appropriate for describing the deformation of quasicrystals. Discussion on the special feature of dislocation motion in quasicrystals is given.
Degradation by Mechanical Grinding and Recovery by Annealing in the Superconducting Phases of the Bi-Pb-Sr-Ca-Cu-O System
Authors: Kanai Tsuneyuki , Kamo Tomoichi , Matsuda Shin-Pei
Published: February 2005

It has been found that mechanical grinding may severely degrade phases from the superconducting to nonsuperconducting; i.e., a sample with 73 vol% of the high-T
c phase (105 K phase), 18 vol% of the low-T
c phase (75 K phase) and 8 vol% of a nonsuperconducting phase resulted in a sample with 98 vol% of a nonsuperconducting amorphous phase after grinding for 62 min. Susceptibility analysis showed that the high-T
c phase changed into a nonsuperconducting amorphous phase more easily than the low-T
c phase by mechanical grinding. It was also found that the degraded sample did not recover easily to the initial state compared with another kind of amorphous sample which was prepared by melt quenching and was initially free of the high-T phase. A process which includes such a crystal grinding causing the degradation of the superconducting phases may not therefore be appropriate for fabricating practical superconducting wires or sheets.
Superconductivity and Crystal Structure of the Y1Ba2Cu3O7-y-WO3 System
Authors: Matsumoto Yasukuni , Irie Fujio
Published: February 2005

The relationship between the superconductivity and crystal structure of the Y1Ba2Cu3O7-y
-WO3 system has been studied. Tungsten oxide has various oxidized states, and mixed WO3 in YBCO easily donates its oxygen atoms to YBCO. It is found that the orthorhombic structure of YBCO is modified by mixing of WO3. The lattice constant a increases with increasing concentration of WO3, while the others, b and c, do not significantly change. Although the atomic arrangement in the Cu(2)-O plane of YBCO is consequently modified, superconducting transition temperature T
c is kept nearly constant.
Catastrophic Local Degradation of YBa2Cu3Oy Epitaxial Film Induced by High Electric Field Application
Authors: Kabasawa Uki , Asano Katsunori , Iyori Masahiro , Hirata Satoshi , Sakuta Ken , Fujiwara Yasufumi , Kobayashi Takeshi
Published: February 2005

This letter describes the first observation of catastrophic local degradation of epitaxially grown YBa2Cu3O
y
film due to pulsed high electric field application in the normal conduction state. In the degraded samples, a damaged region like a crack appears which was not seen in the sound stage. Cathodoluminescence image observation, which reflects the distribution of defects inside MgO substrates, suggested that the local degradation of YBa2Cu3O
y
film occurred where defects in the substrate materials were aggregated.
In Situ Fabrication of Reproducible YBCO/Au Planar Tunnel Junctions with an Artificial MgO Barrier
Authors: Furuyama Masafumi , Iguchi Ienari , Shirai Koji , Kusumori Takeshi , Ohtake Hiroaki , Tomura Shoji , Nasu Masako
Published: February 2005

The in situ fabrication of YBCO (YBa2Cu3O
y
)/MgO/Au epitaxial planar tunnel junctions with a thin MgO barrier utilizing an electron-beam coevaporation technique is reported. The thickness of the MgO barrier is 3–12 nm and the tunnel resistance shows a strong dependence on barrier thickness. The fabricated tunnel junctions are highly reproducible and controllable. The observed tunnel characteristics contain the gap opening at about 20 mV and the anomaly around zero bias. The tunnel characteristics using the degraded films are also reported.
Contribution of the Si s Electronic State to the Density of State of CoSi2 at Fermi Energy by Soft X-Ray Emission Spectroscopy
Authors: Iwami Motohiro , Nakamura Hatsuo , Hirai Masaaki , Kusaka Masahiko , Azuma Yuhko , Akao Fumio
Published: February 2005

A clear modification is observed between an electron-excited Si L2.3 valence band (VB) soft X-ray emission spectrum (SXES) for CoSi2 and the one for Si. From this fact, it is concluded that a fair amount of the Si s electronic state is included in the upper half, especially at the Fermi edge, of the VB density of state (VB-DOS) of CoSi2. This fact is a clear contrast to many proposals given so far, where it is claimed that the upper part of the VB-DOS of CoSi2 is constructed only by the electronic states due to Co(3d)-Si(3p) hybridization.
Natural Superstep Formed on GaAs Vicinal Surface by Metalorganic Chemical Vapor Deposition
Authors: Fukui Takashi , Saito Hisao
Published: February 2005

GaAs surfaces and AlAs/GaAs interfaces grown on GaAs vicinal (001) substrates by metalorganic chemical vapor deposition (MOCVD) are observed by transmission electron microscopy (TEM). Under high As pressure, step flow growth is obtained. However, under very low As pressure, supersteps with about 20-monolayer step height are formed during AlAs/GaAs multilayer growth. The mechanisms of superstep formation are discussed. These supersteps can be applied to the new-type quantum well wires with 10 nm dimension without using patterned substrates.
X-Ray Photoelectron Spectroscopy Study of Cu Implanted in LiNbO3
Authors: Saito Yukinori , Takada Akio , Suganomata Shinji
Published: February 2005

Cu+ ions were implanted into LiNbO3 with doses of 3×1016–5.7×1016 ions/cm2 at an energy of 30 keV. The LiNbO3 implanted with Cu+ ions showed a blue-green color. Optical absorption spectra and XPS (X-ray photoelectron spectroscopy) valence-band spectra were measured for as-implanted and annealed samples. The absorption peak at ∼640 nm was decreased by annealing at relatively low temperatures of 150∼200°C. It was found that upon annealing, while no apparent change in the binding energy of Cu2p3/2 was observed, the peak position of Cu3d was slightly shifted to higher binding energy and the full width at half maximum of the peak was slightly narrowed compared to that of the as-implanted samples. This change in the valence-band spectrum may be due to variation of the electronic state of Cu3d related to the colorations.
Compensation Mechanism in Heavily Si-Doped GaAs Grown by MBE
Authors: Uematsu Masashi , Maezawa Koichi
Published: February 2005

The concentrations of Si-related sites in heavily Si-doped GaAs grown by MBE at 450°C and 65O°C are investigated by laser Raman spectroscopy. Almost all of the Si atoms are incorporated on Ga sites in both samples. However, in the 650°C sample, about one third of the Si atoms on Ga sites (SiGa) associate with Ga vacancies (VGa) to form the SiGa-VGa acceptors, which dominate the compensation mechanism.
Preparation of Highly Oriented Microstructure in the (Bi, Pb)2Sr2Ca2Cu3Ox Sintered Oxide Superconductors
Authors: Jain Kiran , Suri D. K. , Nagpal K. C. , Rao S. U. M. , Das B. K.
Published: February 2005

High T
c superconductors of the nominal composition of Bi1.6Pb0.4Sr2Ca2Cu3O
y
were successfully prepared by the conventional ceramic technique. The high T
c phase was predominant in all the samples giving zero resistance at 104 K. Drastic changes in density, as well as other material properties were obtained through a slight modification in the powder preparation process. Single-phase high T
c samples with a critical current density of 1000–1200 A/cm2 (at 77 K) were prepared by sintering in air for 250 h at 845°C. Most of the grains were aligned with their c-axis normal to the pellet surface.
Preparation of a New Superconductor Sr2Y0.7Ca0.3Cu2.35Pb0.65Oy
Authors: Ono Akira , Uchida Yoshishige
Published: February 2005

The superconducting oxide in the Sr-Ca-Y-Pb-Cu-O system was identified and prepared as a single phase. The compound examined has a tetragonal cell with a=3.815 Å and c=11.85 Å. The T
c was 17 K for the sample quenched from 860°C to 77 K, and below 4.2 K for the sample annealed in air at 400°C.
Reduced Pressure MOCVD of C-Axis Oriented BiSrCaCuO Thin Films
Authors: Hamaguchi Norihito , Vigil J. , Gardiner R. , Kirlin P. S.
Published: February 2005

BiSrCaCuO thin films were deposited on MgO(100) single crystal substrates by metalorganic chemical vapor deposition at 500°C and 2 Torr using fluorinated β-diketonate complexes of Sr, Ca and Cu and triphenylbismuth. An inverted vertical reaction chamber allowed uniform film growth over large areas (7.7 cm diameter). The as-deposited films were amorphous mixtures of oxides and fluorides and a two step anealing protocol (750°C+850–870°C) was developed which gives c-axis oriented films of Bi2Sr2Ca1Cu2O
x
. The post-annealed films showed onsets in the resistive transition of 110 K and zero resistivity was achieved by 83 K. Critical current densities as high as 1.1×104 A/cm2 were obtained at 25 K.
Preparation of Single Phase (Bi0.8Pb0.2)2Sr2Ca2Cu3Oy Films with Preferential Orientation of C-Axis by Laser Ablation Method
Authors: Youssef Ahmed A. A. , Fukami Takeshi , Yamamoto Takashi , Mase Shoichi
Published: February 2005

By a laser ablation method using an Ar-F excimer pulsed laser, (Bi0.8Pb0.2)2Sr2Ca2Cu3O
y
(H-BSCC) films have been prepared in almost single phase on MgO(100) substrates. As-deposited films on substrates at room temperatures did not show any diffraction peaks of X-ray powder analysis. As-deposited films were treated thermally and the optimum conditions to obtain H-BSCC films in almost single phase were confirmed. Essential conditions were the temperature just below the melting point of H-BSCC, and heating for a prolonged duration together with a bulk sample of the same composition as that of the target.
Microbridges Made of Y-Ba-Cu Oxide Films with an Artificial Weak-Link Structure
Authors: Matsuda Mizushi , Matachi Atsushi , Hashimoto Norio , Kuriki Shinya
Published: February 2005

We have fabricated Y-Ba-Cu oxide (YBCO) thin-film microbridges having a restricted region with an artificial weak-link structure where Au has been diffused into or reacted with the YBCO at some grain boundaries. In these microbridges, we have confirmed a microwave response exhibiting current steps and linear or exponential-like temperature dependence of the critical current near T
c. In contrast to this, microbridges without an artificial weak-link structure are virtually responsive to the microwave, and their temperature dependence of the critical current is like that of a granular microbridge.
XPS Studies of a-Si1-xCx:H Prepared from C2H4/SiH4 Gas Mixtures
Authors: Suzuki Yoshiko , Meikle Scott , Fukuda Yasuo , Hatanaka Yoshinori
Published: February 2005

Hydrogenated amorphous silicon carbon alloy films (a-Si1-x
C
x
:H) with optical band gap 2.4 eV and x=0.5, deposited in a radio frequency (13.56 MHz) plasma of H2/C2H4/SiH4 gases have been examined using X-ray photoelectron spectroscopy (XPS). From the Cls and Si2p core level spectra it was found that films grown using a smaller SiH4/C2H4 ratio had a larger concentration of Si-C bonds. Further, spectrum shifts caused by slight Ar sputtering of as-deposited films suggested that the formation of Si-C bond occurs at the surfaces. Finally, valence band spectra showed that films with high Si-C bond density had a steep valence band edge typical of high quality films.
Nonresonant Multiphoton Ionization of He and Ne Atoms
Authors: Kokubun Kiyohide , Ichimura Shingo , Shimizu Hazime
Published: February 2005

The nonresonant multiphoton ionization of high-ionization-potential atoms, He and Ne, was successfully observed using a commercial high-power ArF excimer laser. The experimental results are presented.
Fusible Conducting Polymer Poly(3-alkylfuran) and Its Novel Electrical and Optical Properties
Authors: Nishioka Yoshinori , Yoshino Katsumi
Published: February 2005

Fusible and soluble polyfuran derivatives such as poly(3-alkylfuran) were prepared. The melting point decreases with increasing alkyl chain length. The band gap of poly(3-alkylfuran) is much smaller than that of nonsubstituted polyfuran. A drastic absorption spectrum change upon doping and solvatochromism has been observed.
Gel Characteristics of Polyaniline and Its Anomalous Doping Effect
Authors: Oka Osamu , Morita Shigenori , Yoshino Katsumi
Published: February 2005

Polyaniline gel has been prepared from soluble polyaniline. Remarkable shrinkage of the gel has been observed upon increase of the concentration of water in N-methyl-2-pyrrolidone. However, the temperature dependence of the volume of polyaniline gel is anomalous. Shrinkage of the volume of the gel has also been observed upon acid doping. On the contrary, the volume was expanded by iodine doping. These characteristics are discussed in terms of intermolecular hydrogen bonding.
Electronic Transport in Graded-Period Delta-Doped Superlattice
Authors: Liu W. C. , Wang R. L. , Lour W. S. , Sun C. Y. , Hong C. C.
Published: February 2005

The electronic transport properties in a graded-period delta-doped superlattice have been studied. A novel negative differential conductivity (NDC) performance is exhibited due to the avalanche multiplications in the superlattice periods. Holes, created by the avalanche multiplications, play an important role in the transport characteristics. An interesting hysteresis phenomenon is also exhibited owing to the “trapped” holes. The significant control voltage ratio, V
S/V
H, of the studied structure introduces a good potential for application on the switching field.
Comparison of Silica- and Alumina-Based Spin-on Sources for P-Contact Diffusion of Zinc into InGaAs
Authors: Franz G. , Amann M.-C. , Thulke W. , Weber R. , Kaumanns R.
Published: February 2005

Alumina- and silica- based spin-on sources for p+-doping of InGaAs contact layers are compared. Shallow diffusion profiles with hole concentrations up to 2×1020/cm3 were obtained. Higher doping levels and improved long-term stability of the spin-on solution were achieved with the alumina-based source.
Hydrogenated Amorphous Silicon Carbide/Silicon Metal-Base Transistor
Authors: Jwo Shin-Cherng
Published: February 2005

A novel a-SiC:H/a-Si:H metal-base transistor has been successfully fabricated on an ITO/glass substrate by plasma-enhanced chemical-vapor deposition (PECVD). The operating characteristics of the transistor effect and evidence for true injection have been observed. The measured common-base current-transfer ratio is 9.75% at a collector field of 7.5×104 V/cm and an emitter current of 0.2 mA. The ballistic mean free path in Pt obtained from the current-transfer ratio is 97 Å.
Properties of Pb-Doped Bi-Sr-Ca-Cu-O Superconductors Prepared by a Hot-Press Method
Authors: Yoshizaki Ryozo , Ikeda Hiroshi , Yoshikawa Kozo , Tomita Nobuyoshi
Published: February 2005

Pressure effect during sintering (hot pressing) on the superconducting properties, focusing particularly on the critical current density J
c, has been studied for the high-T
c-phase Pb-doped Bi-Sr-Ca-Cu-O system. The properties are compared with those for the samples before the pressing or with intermediate-pressing at room temperature. The transport J
c observed by resistive transition measurement at 77.3 K was 7,000 A/cm2 at H=10 Oe for the hot-press sample, 6,260 A/cm2 for the intermediate pressed sample at H=0 and around 500 A/cm2 for the nonpressed one at H=0. The magnetic hysteresis loops were measured at 5 K and 77.3 K, and the hot-pressed sample showed larger hysteresis than that for the intermediate-pressed one.
ESR and Nonresonant Microwave Absorption of YBa2Cu3O7-δSingle Crystal
Authors: Tagaya Kimihito , Fukuoka Nobuo , Nakanishi Shigemitsu
Published: February 2005

ESR measurements were performed for a single crystal of YBa2Cu3O7-δover a temperature range from 77 K to room temperature. ESR signals of Y2BaCuO5and CuO were observed and investigated. Nonresonant microwave absorption was observed below the superconducting critical temperature of 93 K and was also investigated. The principal values of lower critical field were determined.
The Effect of Magnetic Field on the Critical Current of YBa2Cu3Ox Ceramics
Authors: Zhukov A. A. , Moshchalkov V. V. , Komarkov D. A. , Shabatin V. P. , Bush A. A. , Gordeev S. N. , Shelomov D. V.
Published: February 2005

Three magnetic field ranges corresponding to different critical current density J
c behavior have been discovered. They correlate with grain magnetization changes. The first field range corresponds to the grain Meissner phase, the second one to the partial penetration of magnetic fluxoids into a grain, and the third one to the complete vortex penetration. For the first interval, the dependence J
c(H)=J
c(0)/[1+(H/H
0)2] is valid. The inverse critical current density is shown to depend linearly on the sample cross-section due to the magnetic field self-induced by the flowing current.
Synthesis and Characterization of Single-Phase (Tl1-xBix)Sr2Ca2Cu3Oy Ceramics
Authors: Inoue Osamu , Adachi Seiji , Kawashima Syunichiro
Published: February 2005

The synthesis and characterization of the “1223” phase in a Tl-(Bi)-Sr-Ca-Cu-O system are described. Almost-single-phase (Tl1-x
Bi
x
)Sr2Ca2Cu3O
y
ceramics (x≦0.25) were obtained by using Tl2O3 and Tl2O as Tl sources. The zero-resistance temperature of the so-called “1223” phase reached 115 K for the nominal composition of Tl2Bi0.25Sr2Ca2Cu3O
y
ceramic. The Bi addition stabilized the “1223” phase and improved the superconductivity.
Degradation Phenomena in High-Power Single Quantum Well AlGaAs Ridge Lasers
Authors: Gfeller F. R. , Webb D. J.
Published: February 2005

Degradation studies with over 235,000 device hours have been performed on single quantum well AlGaAs lasers with uncoated and half-wavelength Al2O3 coated facets at stress levels ranging from below threshold up to optical power densities of 23 mW per µm facet width. The effectiveness of facet protection has been investigated with respect to gradual degradation and catastrophic failures. Lasers with facet protection showed gradual degradation rates as low as 0.18%/kh at power densities of 10 mW/ µm, and lifetime improvement factors up to 27,000 at 16 mW/ µm compared to uncoated facets.
Acoustic Emission Caused by Structural Changes in Amorphous Ni-P Alloy
Authors: Yamamoto Motokazu , Shirai Koichi , Yamana Masao , Kashiwazaki Naoya , Watanabe Nobuyoshi
Published: February 2005

Acoustic emission (hereafter referred to as AE) resulting from the heating of amorphous Ni-P alloy (hereafter referred to as a-Ni-P) prepared by plating was detected. AE is observed at certain temperatures, i.e., at 280°C, 320°C, 360°C and 410°C, when a-Ni-P (Ni: 84.9 wt%, P: 15.1 wt%) is heated. From the results of several experiments, it is confirmed that AE is related to structural changes in a-Ni-P. The method employing AE to observe structural changes in a-Ni-P features highly sensitive detection of the structural changes.
Microwave Plasma Source for Ion Sources with Multipolar and Axial Magnetic Fields
Authors: Nihei Hitoshi , Morikawa Junji , Inoue Nobuyuki
Published: February 2005

A microwave (2.45 GHz) plasma source for ion sources has been constructed and its chracteristics have been examined. It consists of the part of the source generating a plasma and that making the plasma uniform. The experiments have been conducted in four kinds of magnetic field configurations generated by solenoid coils and arrays of permanent magnets. The plasma parameters have been measured with a Lngmuir probe located at 2 cm above a plasma grid. The uniform plasma over an area of 8∼10 cm·φ in diameter and the density of 2.6×1011 cm-3 has been produced. The magnetic field intensity near the plasma grid is nearly zero.
Coaxial Laser Fluorescence System by Two-Photon Excitation for Atomic Hydrogen Detection in High-Temperature Plasmas
Authors: Kajiwara Toshinori , Takeda Kazuyuki , Muraoka Katsunori , Okada Tatsuo , Maeda Mitsuo , Akazaki Masanori
Published: February 2005

A coaxial laser fluorescence system using two-photon excitation of hydrogen atoms from their ground states to 3s, 3d states and H
α fluorescence observation was proven to have sufficient performance for local density measurements of hydrogen atoms in the periphery of high-temperature plasmas. The detection limit estimated against the H
α background radiation was shown to be adequate for the purpose.
Fast Optical Switching in Polymer Waveguide Using Ferroelectric Liquid Crystal
Authors: Ozaki Masanori , Sadohara Yutaka , Hatai Takashi , Yoshino Katsumi
Published: February 2005

A fast electro-optical switching in polymer waveguide has been demonstrated using ferroelectric liquid crystal. In this device, the surface stabilized ferroelectric liquid crystal layer is used as the active material with the passive polymer waveguide. The switching time is of the order of several microseconds.
Liquid Phase Epitaxy of InGaP on GaAs (100) Substrates at Low Growth Temperatures down to 630°C
Authors: Kato Takamasa , Matsumoto Takashi , Ogura Hiroyuki
Published: February 2005

InGaP layers were grown on GaAs (100) substrates by liquid phase epitaxy. The growth temperature (T
G) was varied from 738 to 630°C. Layer qualities such as the surface morphology and photoluminescence characteristics were investigated. They became inferior with decreasing growth temperature when T
G was lower than 700°C. The growth period required to grow a smooth surface was found to be shortened for T
G's below 650°C.
Effect of Surface Phosphidization on GaAs Schottky Barrier Junctions
Authors: Sugino Takashi , Yamada Takashi , Shirafuji Junji
Published: February 2005

Phosphidization of GaAs surface has been attempted by exposing to the plasma of PH3 and H2 gases. The presence of P atoms near the GaAs surface is confirmed by secondary ion mass spectroscopy analysis. The barrier height of Schottky junctions formed on the phosphidized GaAs surface varies depending on metal work functions in contrast to the conventional case of a rather constant barrier height independent of metal species. The density of the surface state is estimated to be 1.3×1013 cm-2·eV-1 from the dependence of the barrier height on the metal work function.
Study on the Crystal Structure of CdInGaS4 and Cd3InGaS6 by Computer Simulation Method
Authors: Matsushita Hiroaki , Nomura Shigetaka , Ando Shizutoshi , Endo Saburo , Irie Taizo
Published: February 2005

The crystal structures of CdInGaS4 and Cd3InGaS6 were studied by a computer simulation method using the experimental X-ray powder diffraction pattern. The ratio of the Van der Weals length between three “packs” in CdInGaS4 was determined to be 2.75:4.5:2.75. It is concluded that Cd3InGaS6 is not a single compound but has a laminated structure composed of CdS and CdInGaS4. In order to interpret the ratio of the intensity of diffraction lines, a type of stacking of Cd and S layers is proposed.
How to Compare Jc among Different-Sized Samples: Part II–An Extension to Thin Film Superconductors–
Authors: Adachi Gin-ya , Imai Hisao , Imanaka Nobuhito
Published: February 2005

J
c evaluation was examined by taking into account the sample thickness of bulk to thin film Bi superconductors. The J
c characteristics can be directly compared between the superconductors of various sample thicknesses by this evaluation.
Irreversibility of Critical Current Observed in Oriented YBa2Cu3Ox Ceramic Samples
Authors: Zheng Xu-guang , Kuriyaki Hisao , Hirakawa Kazuyoshi
Published: February 2005

Irreversibility of critical current was observed in oriented YBa2Cu3O
x
superconducting ceramic samples. In the transport measurement, the apparent J
c determined from V-I characteristics showed an increase of nearly 10% during the current cycling. As the result of a comparison study with conventionally sintered samples, weak intersections existing between oriented blocks were supposed responsible for this phenomenon.
Superconductivity in “1201” Lead Cuprate
Authors: Adachi Seiji , Setsune Kentaro , Wasa Kiyotaka
Published: February 2005

A new member of lead cuprates whose crystal structure consists of the (Pb/Cu)-O single-layer and Cu-O6 octahedron, called the “1201” structure, has been synthesized. At a nominal composition of Pb0.6SrLaCu1.5O
y
, an almost single-phase sample (tetragonal a=0.378 nm, c=0.867 nm) was obtained, and superconductivity with the T
c(zero) of 25 K was observed.
Structural Study of Tl2Ca3Ba2Cu4Ox Single Crystal by Transmission Electron Microscopy
Authors: Kotani Toshihiro , Nishikawa Takeshi , Takei Hiromi , Tada Koji
Published: February 2005

The microstructure of Tl2Ca3Ba2Cu4O
x
(2324-phase) single crystals grown by the slow-cooling method was investigated using transmission microscopy. These single crystals showed superconducting onset transition temperatures of 113 to 115 K, and lattice constants were a=b=3.85 Å and c=42.0 Å by X-ray diffraction measurement. The high-resolution transmission electron microscopy (TEM) observations revealed intergrowths of Tl-O single-layered structures, 1324 and 1425, with stacking spacings of 19 Å and 22 Å, in addition to a 2223 phase of 36 Å.
Oxygen Absorption Isotherms and Phase Diagram of YBa2Cu3Oy
Authors: Kanematsu Kazuo
Published: February 2005

Isothermal oxygen absorption experiments were carried out for YB2Cu3O5.98, and X-ray examination were performed for the oxides with various oxygen contents. The phase diagram of YBa2Cu3O
y
was determined from the isotherms with the help of X-ray results.
Preparation of Bi-Sr-Ca-Cu-O High-Tc Superconducting Fibers by Pyrolysis of Organic Acid Salts
Authors: Nasu Hiroyuki , Shoyama Masashi , Nozue Akiyoshi , Kamiya Kanichi , Shiono Takeo
Published: February 2005

Bi-Sr-Ca-Cu-O high T
c superconducting solid fibers were successfully obtained by pyrolysis of organic acid salts. The addition of oxide powder and the covering of fibers with hydroxypropylcellulose were necessary to prevent the deformation of fibers drawn from the liquid. The T
c(end) of the fibers was 60 K and the strength was 7.5 MPa after the fibers were heated at 800°C for 24 h. X-ray diffraction patterns showed the formation of the Bi:Sr:Ca:Cu=2:2:1:2 phase.
Preparation of YBa2Cu3O7-y High Tc Thin Films on NdGaO3 Substrate by Laser Ablation
Authors: Mukaida Masashi , Miyazawa Shintaro , Sasaura Masahiro , Kuroda Ken'ichi
Published: February 2005

As-grown thin films of YBa2Cu3O7-y
with a smooth surface were obtained on lattice-matched NdGaO3 substrates by ArF laser ablation deposition. The as-grown thin film has a zero-resistance temperature (T
c) at 90 K. The full width at half-maximum (FWHM) of the X-ray diffraction peak (005) of the thin film was as narrow as 0.12 degrees. These results suggest that the as-grown YBa2Cu3O7-y
films on NdGaO3 substrates were high-quality single crystals. NdGaO3 substrates are thought to be a promising substrate for epitaxial growth of YBa2Cu3O7-y
high T
c thin films.
Preparation of Ag-Sheathed (Tl, Bi)-Ca-Sr-Cu-O Superconducting Wire
Authors: Torii Yasuko , Kugai Hirokazu , Takei Hiromi , Tada Kouji
Published: February 2005

In the Tl-Bi-Ca-Sr-Cu-O system, Tl-O single layered superconducting phases of (Tl, Bi)CaSr2Cu2O
x
and (Tl, Bi)Ca2Sr2Cu3O
x
have been obtained. We prepared Ag-sheathed wire using the oxide powder of the (Tl, Bi)Ca2Sr2Cu3O
x
phase with T
c of 113 K. With a decrease in the thickness of the rectangular wire specimen, J
c at 77 K increases rapidly, reaching a maximum value of 1.45×104 A/cm2 at 0.05 mm in thickness. The crystal structure, morphology and microstructure of the superconducting core of the wire were observed using XRD, SEM and TEM to investigate the cause of the J
c enhancement.
Recovery of Transient Gain in an Open-Cycle FAF CO2 Laser Amplifier Using Gold Catalyst
Authors: Tsuchida Eiichi , Sato Heihachi
Published: February 2005

Using a gold catalyst placed inside the gas-circulating portion of a FAF CO2 laser amplifier, its transient gain has been significantly improved in an open-cycle operation. Several insertion schemes of the Au catalyst have been examined so as not to spoil the advantages of the FAF system. The periodic doughnut shape of the catalyst has thus far been found to be the most appropriate scheme, resulting in about 12% gain recovery at the steady-state condition. Based on the mass-spectrum analysis of the dissociated CO2 molecules, the gain recovery due to this catalytic effect is theoretically discussed.
Sensitization of Photochromism in Polydiacetylene Films by Phthalocyanine Layer
Authors: Fukagai Kazuo , Ishikawa Ken , Kanetake Tatsuo , Koda Takao , Koshihara Shin-ya , Tokura Yoshinori
Published: February 2005

A sensitization effect has been observed in the photochromism of vacuum-deposited polydiacetylene (PDA-12, 8) films with a lead phthalocyanine underlayer. The threshold photon energy of photochromism has been found to be extended from about 2.0 eV in the PDA film to the near infrared region by the sensitization. Transient changes in optical absorption in the sensitized PDA film by a pulsed-light excitation indicate that the response time of photochromism is shorter than 10 ns.
Spontaneous Formation of Quasi-Bookshelf Layer Structure in New Ferroelectric Liquid Crystals Derived from a Naphthalene Ring
Authors: Takanishi Yoichi , Ouchi Yukio , Takezoe Hideo , Fukuda Atuso , Mochizuki Akihiro , Nakatsuka Masakatsu
Published: February 2005

A quasi-bookshelf layer structure has been obtained by a conventional rubbing method at room temperature in a FLC mixture composed of naphthalene-derived liquid crystals. This layer structure is spontaneously formed due to a unique temperature dependence of the interlayer spacing; X-ray diffraction indicates that the layer spacing decreases from 34 to 33.5 Å and then increases to 33.8 Å with decreasing temperature in SmC*. Contrary to the unusual behavior of the layer spacing, the director tilt angle determined optically shows ordinary temperature dependence and attains a relatively large value, 17°, at room temperature.
Interference-Free Determination of the Optical Absorption Coefficient and the Optical Gap of Amorphous Silicon Thin Films
Authors: Hishikawa Yoshihiro , Nakamura Noboru , Tsuda Shinya , Nakano Shoichi , Yasuo Kishi Yasuo Kishi , Yukinori Kuwano Yukinori Kuwano
Published: February 2005

A new method to determine the optical absorption coefficient (α) of thin films is presented. α of hydrogenated amorphous silicon (a-Si:H) based alloys can be accurately determined from transmittance (T) and reflectance (R) by using T/(1-R), which almost completely eliminates disturbance from the optical interference effect. The method is applicable to any thin films, as long as the film is a single layer. Based on the interference-free α, various methods to determine the optical gap (E
OPT) of a-Si:H, a-SiC:H, and a-SiGe:H films are discussed. The (nαhν)1/3 plot and the (αhν)1/3 plot are most suitable for characterizing these films. The well-known (αhν)1/2 plot is less suited for detailed discussion of the E
OPT than the cube root plot, because the plot includes a large ambiguity in the E
OPT. The effect of the optical interference effect on the determination of the E
OPT is also discussed.
Analytical Study on Hole Transport of p-Diphenylaminobenzaldehyde-diphenyl Hydrazone Dispersed Molecularly in Polymeric Matrix
Authors: Takashi Kitamura Takashi Kitamura , Masaaki Yokoyama Masaaki Yokoyama
Published: February 2005

The hole drift mobility of DPH (p-diphenylaminobenzaldehyde-diphenyl hydrazone) dispersed molecularly in a polymeric matrix was analyzed in the framework of small polaron hopping model. The dependence of the zero-electric field hole mobility on molecular spacing of dopant R, exhibited a transition from adiabatic to non-adiabatic small polaron hopping regime with increasing R, different from the reported result for DEH (p-diethylamino-benzaldehyde-diphenyl hydrazone), one of hydrazone derivatives, which showed non-adiabatic small polaron hopping independently of R. The difference in the hopping behavior was discussed in terms of the molecular structure of dopants.
Distribution of Internal Bias Field in L-α-Alanine-Doped Triglycine Sulfate Crystal
Authors: Noriyuki Nakatani Noriyuki Nakatani
Published: February 2005

Distribution of internal bias field E
b was investigated in an LATGS crystal grown from TGS solution containing 10 mol% L-α-alanine. As the crystal was of single domain, the field E
b was oriented in one definite direction all over the crystal. The intensity of E
b distributed over a wide range of 30 to 500 kV/m or more, and distinctly depended on the crystal growth sector. The distribution showed the polar symmetry 2, similarly to the crystal form of LATGS. Generally speaking, E
b in the -b side of the seed crystal was more intense than in the +b side. The spontaneous polarization and the coercive field did not show a significant distribution in the crystal.
Local Structures of Carbon Thin Films Synthesized by the Hot Filament Chemical Vapor Deposition Method X-Ray-Absorption Near-Edge Structure and Raman Spectroscopic Studies
Authors: Edamatsu Kunishige , Takata Yasutaka , Yokoyama Toshihiko , Seki Kazuhiko , Tohnan Masanao , Okada Tadashi , Toshiaki Ohta Toshiaki Ohta
Published: February 2005

Various carbon thin films synthesized by the hot filament chemical vapor deposition (CVD) method with various methane concentrations in hydrogen (1.0-12.5 vol.%) and temperatures of Si substrate (770-1000°C) were characterized by X-ray-absorption near-edge structure (XANES) and Raman spectroscopies as well as by scanning electron microscopy (SEM) and X-ray diffraction. Based on these results, the structural change of carbon thin films is deduced as a function of methane concentration and substrate temperature. Comparison between the Raman and XANES spectra demonstrates the usefulness of XANES spectroscopy for the characterization of carbon thin films and the complementary character between these spectroscopies.
Statistics of Kinetic Secondary Electron Emission with Stochastic Elastic Collision of Ions in Solids
Authors: Kaoru Ohya Kaoru Ohya , Ichiro Mori Ichiro Mori
Published: February 2005

Electron emission statistics for H+ impact on Au in the energy range 1 keV-40 keV are investigated using a Monte Carlo calculation with the kinetic emission model. The factor f
0/ε evaluated by fitting the calculation to experimental electron yield increases with increasing impact energy, and it approaches an energy-independent value as recognized by many investigators because of the decrease of large-angle elastic scattering of H+ in Au (f
0: the transmission probability through the surface, ε: the average energy deposited to produce an electron). Special features of the emission statistics are a large probability to produce no electron for keV energy, a smaller probability for no electron with increasing energy, and higher (lower) yield than the inverse cosine law for tens keV (keV) with oblique incidence.
Secondary Electron Emission from a Hydrogen-Implanted Graphite by Low-Energy Electron Impact
Authors: Ohya Kaoru , Kenji Nishimura Kenji Nishimura , Ichiro Mori Ichiro Mori
Published: February 2005

For a plasma-surface interaction, the influence of an implantation of hydrogen atoms on the secondary electron emission of graphite bombarded by low-energy (<500 eV) electrons is investigated by using a Monte Carlo simulation. The results show that the secondary electron yield increases and the backscattering yield decreases; the incident-angle dependence of the former is little enhanced and the dependence of the latter is largely enhanced.
Development of Laser Imaging Method for Measurements of Electron Density Fluctuations in Plasmas
Authors: Matsuo Keiji , Tanaka Kenji , Akazaki Katsunori Muraoka
Published: February 2005

A generalized analysis of the laser imaging method is presented for measurements of long-wavelength electron density fluctuations in plasmas, so as to enable its application to practical situations, such as oblique incidence of laser light and identification of the position of the fluctuations. Experimental verification of the more salient features of the theory is also described.
Sulfite Radicals in Irradiated Calcite
Authors: Kai Ayako , Miki Toshikatsu
Published: February 2005

Radiation-induced radicals in calcite doped with SO3
2-, SO4
2- or PO4
3- were investigated with electron spin resonance (ESR). An axially symmetric ESR signal (g
⊥=2.0038 and g
//=2.0024) was enhanced by doping with SO3
2-. We suggest that SO3
- radical ions are responsible for the signal.
Study on Electrically Plastic Devices Made with Electropolymerized Films
Authors: Iseki Masahiro , Koichi Kuhara Koichi Kuhara , Atsuo Mizukami Atsuo Mizukami
Published: February 2005

Electrochemical deionization of an electrolyte solution in a micro-cell was accomplished by using an electrode coated with polypyrrole (PPy) having anion-capturing ability and an electrode coated with PPy having cation-capturing ability. The change in the ionic conductivity of the cell during electrolysis was simultaneously observed with a separate pair of bare electrodes. This cell system simulates the synaptic plasticity observed in the connection between neurons, where the efficiency of the signal transmission changes as a function of the frequency of the stimulus signal. We call this cell system an “electrically plastic device”. In addition, we constructed and studied a cell system with a summation function which was produced by dividing the PPy electrodes into three separate electrode.
A Fourier Transform Infrared Spectrometer with a Composite Interferometer for Soft Mode Studies
Authors: Wada Mitsuo , Shirawachi Kikuo , Nishizawa Seiji
Published: February 2005

The Fourier transform infrared spectrometer has a new design of composite construction which allows it to be alternatively utilized for both the amplitude-divided two-beam interferometer and the polarization-divided two-beam one. A wide range of spectral wavenumbers to 4 cm-1 can be covered with changes of beam splitters, light sources and detectors except for a change of the main optical configuration. By means of the spectrometer with a silicon bolometer, the soft phonon mode which associates the structural phase transition has been measured in ferroelectric Li2Ge7O15 single crystals. The performance of the spectrometer for soft mode studies is estimated.
Effect of Sample Edge in ac Calorimetric Method for Measuring Thermal Diffusivity of Thin Films with High Thermal Diffusivity
Authors: Yuqin Gu Yuqin Gu , Ichiro Hatta Ichiro Hatta
Published: February 2005

In the ac calorimetric thermal diffusivity measurement of a thin film with high thermal diffusivity, the reflection of ac temperature waves at the edge of the film is no longer disregarded. From a theoretical consideration, the condition required for the measurement on such a sample is proposed.
Direct Observation of Gaussian-Type Energy Distribution for Hot Electrons in Silicon
Authors: Sekido Mamoru , Kenji Taniguchi Kenji Taniguchi , Chihiro Hamaguchi Chihiro Hamaguchi
Published: February 2005

Measurement of photon emission spectra from metal Oxide Semiconductor Field Effect Transistors (MOSFETs) and reverse biased pn junctions at room temperature reveals that electron energy distribution is expressed by a Gaussian distribution function rather than the commonly used Maxwellian distribution function at high electric field: Gaussian distribution function decreases more rapidly in the high energy tail than the Maxellian distribution for the same average energy. The energy relaxation time, τe=0.17 ps, extracted from the optical measurements is much shorter than calculated values by Monte Carlo simulation, τe0.5∼1.0 ps, while it is longer than the recently reported experimental values (τe0.06∼0.10 ps). The discrepancy between the relaxation time obtained here and from other experiments is due to the fact that Maxwellian distribution has been erroneously assumed to evaluate the energy relaxation time in the high-energy tail in the previous works.
A New Thinning Method for Obtaining Less than 100-nm-Thick Si Film on Wafer Bonding
Authors: Kazuo Imai Kazuo Imai
Published: February 2005

This paper proposes a new wafer thinning method in bonding silicon-on-insulator (SOI) technology. With this new method, thermal oxidation is performed on thin boron-doped Si films after highly selective back-etching to reduce the boron concentration in the film. The boron concentration in the silicon layer on oxide can be decreased more than 2 figures under proper thermal oxidation conditions. A 90-nm-thick silicon layer with 4×1017/cm3 boron concentration was formed on an insulator by this method. Transmission electron microscope (TEM) observation shows that the silicon layer has a highly crystalline quality. It is also found that the reflow of borophosphosilicate glass (BPSG) can effectively fill in the small surface gaps during wafer bonding.
Photoemission Study on Initial Oxidation of Si Surfaces by Super-Pure Oxygen Gas
Authors: Oshima Masaharu , Sugahara Hirohiko , Kawamura Naoki , Yabumoto Norikuni , Minegishi Kazushige
Published: February 2005

Initial oxidation processes of clean Si(100) surfaces oxidized by super-pure and normal-grade oxygen gases are analyzed by synchrotron radiation photoemission spectroscopy to investigate the effect of water molecule impurities on oxidation features. A significant difference in initial oxidation rate between the two oxygen gases is found for the sputter-cleaned Si(100)2×1 surface and the Ag-deposited Si(100) surface. Furthermore, the band bending relaxation during oxidation is observed only for the normal-grade oxygen gas with about 70 ppm water impurity. These oxidation enhancement and band bending relaxation phenomena can be attributed to water molecule impurities.
Thermodynamical Properties of I-III-VI2-Group Chalcopyrite Semiconductors
Authors: Matsushita Hiroaki , Saburo Endo Saburo Endo , Taizo Irie Taizo Irie
Published: February 2005

Melting points and transition points of I-III-VI2-group compounds and their solid solutions were determined exactly. The heats of fusion and transition were also estimated. The melting points of I-III-VI2-group compounds and solid solutions depend on mean atomic weight and ionicity. It is found that the melting points are influenced by lattice strain. Heats of fusion and transition of I-III-VI2-group compounds depend on mean atomic weight, ionicity and u-parameter, the trends of which are in contrast to those for III-V-group compounds. Heats of fusion and transition of their solid solutions are much smaller than those for the end-member compounds.