bluuebunny/crossref_metadata_2025 huggingface dataset:
A Rigorous Solution of Two-Dimensional Diffraction Based on the Huygens-Fresnel Principle
Authors: Nonogaki Saburo
Published: February 2005

The problem of two-dimensional diffraction of light by a slit is solved rigorously on the basis of Huyagens-Fresnel principle assuming the amplitude of a secondary wavelet emitted from an infinite strip of infinitesimal width on the slip aperture to be proportional to cos
(θ/2)/√r, where θ is the angle of diffraction and r the distance from the strip. The solution of the problem where a plane-wave of light is normally incident on a slit in a perfectly black screen is expressed in terms of the Fresnel integral. With slight modification, the method is also applicable to the diffraction in a light-absorbing medium.
Refractive Index Ellipsoids of a Polycarbonate Magneto Optical Memory Disk Substrate
Authors: Shirouzu Shigenori , Shigematsu Kazuyoshi , Sakamoto Shuji , Nakagawa Takashi , Tagami Sanae
Published: February 2005

To investigate the generating mechanism of optical anisotropy in a polycarbonate (PC) magneto optical memory disk substrate, refractive index ellipsoids were measured for as-molded and annealed disk substrates. The shape of the refractive index ellipsoid for the as-molded disk substrate was muffin-shaped; that is, the thickness direction was substantially smaller than the other directions. Even after an annealing process to remove residual stress in the disk substrate, the shape of the ellipsoids remained anisotropic and muffin-shaped. This fact suggests that the molecular orientation of constructive units with anisotropic refractive indices is mainly responsible for the optical anisotropy in this PC substrate.
Refractive Index Anisotropies of Constructive Units in Polycarbonates
Authors: Shirouzu Shigenori , Shigematsu Kazuyoshi , Sakamoto Shuji , Nakagawa Takashi , Tagami Sanae
Published: February 2005

The following methods were considered for decreasing refractive index anisotropies (RIA) of constructive units in bisphenol-A polycarbonate: 1) Substitution of side-chain methyl groups with atomic groups of large RIA to cancel those in constructive units. 2) Substitution of side-chain methyl groups by other alkyl groups to change conformations of main-chain phenyl groups in constructive units. Utilizing the above methods, polycarbonate systems with constructive units with low RIA were obtained.
Optical Recording Materials Based on TeOx Films
Authors: Kimura Kunio
Published: February 2005

TeO
x
films containing Ge, Sn or Pd were prepared for application in optical recording media by electron-beam coevaporation of Te, TeO2 and additional elements. Since these films exhibited large differences in optical constants between the amorphous and crystalline states, they are thought to be potentially useful for optical recording materials. The addition of Ge, Sn or Pd increased the transformation temperatures from the amorphous to the crystalline state in comparison with pure TeO
x
films. The time required for crystallization was shortened to 300 ns by the addition of Ge, Sn and Pd, while pure TeO
x
films required about 30 sec. The TeO
x
–Pd film showed excellent stability. The phase transformation mechanism of these films from the amorphous to crystalline states is discussed.
The Concentration and Wavelength Dependence of Faraday Ellipticity in Magnetic Fluids
Authors: Yusuf Nihad A.
Published: February 2005

Faraday ellipticity in Fe3O4 particle magnetic fluids with different concentrations has been measured. The results show that Faraday ellipticity increases with the field and tends to saturate at high fields. The results also show that Faraday ellipticity increases with the concentration and tends to saturate at higher fields for higher concentrations. Moreover, measurements of Faraday ellipticity over the wavelength range 450–650 nm in a dilute Fe3O4 particle magnetic fluid have been undertaken. The results in agreement with the theory show an enhancement of Faraday ellipticity near the wavelengths λ=611 nm and λ=500 nm.
Highly Oriented Polycrystalline Si Film on Quartz Grown from Si3H8 by Thermal and Photo-CVD
Authors: Fujiki Noriaki , Nakatani Yoshiki , Inoue Kohji , Okuyama Masanori , Hamakawa Yoshihiro
Published: February 2005

Si films deposited on quartz plates grown from Si3H8 by thermal and photo-CVD have shown a strong crystalline orientation and are preferentially grown as (110) planes at substrate temperatures below 560°C, but turn to (100) above 575°C. In the transition region, an enhancement of <100>-orientation occurs with increasing H2 partial pressure and Si3H8 flow rate, but <110>-orientation occurs at extremely high H2 pressure and Si3H8 flow rates. Surface morphologies have also been investigated, and pyramidal texture, dome like structure and random roughness are found in <100>- and <110>-oriented films and non oriented crystalline film, respectively. The mechanism of the preferred orientation is discussed, taking into consideration the bonding structure of the crystal plane and that of decomposed species in the vicinity of the surface.
Silicon Selective Epitaxial Growth and Electrical Properties of Epi/Sidewall Interfaces
Authors: Ishitani Akihiko , Kitajima Hiroshi , Endo Nobuhiro , Kasai Naoki
Published: February 2005

Facet formation and stacking fault generation in silicon selective epitaxial growth are studied. On selective epilayer surfaces, a {311} facet and a {111} microfacet are formed on a {100} and a {111} substrate, respectively. In selective epilayers, stacking faults are observed adjacent to the sidewall Facet-free and stacking-fault-free selective epilayers are obtained using the <100>-orinted sidewall at low growth temperatures. These results are explained by an epitaxial growth model at hollow bridge sites. Electrical properties of the interfaces between the selective epilayer and the sidewall are also studied. The <100>-oriented SiO2 sidewall has better electrical characteristics than other sidewall orientations and sidewall materials.
Effect of a Frenkel Pair Generation-Annihilation Term upon Diffusion Equations of Self-Interstitials and Vacancies
Authors: Okino Takahisa , Yoshida Masayuki
Published: February 2005

The diffusion equations for the self-interstitials and vacancies in Si, which contained the Frenkel pair generation-annihilation term, were solved. Two cases were found for the solutions. The first case is that self-interstials and vacancies reach their local equilibrium state before they reach the center of the specimen by the diffusion from the surface. The second case is the reverse of the first. It was concluded that the Frenkel pair generation-annihilation term could not be neglected even after self-interstitials and vacancies had reached their local equilibrium states. In this paper, several approximate solutions are also shown.
Searching a Fractal Basis for Low-Frequency 1/f Fluctuations –MOSFET Structure in Case
Authors: Yadava R. D. S.
Published: February 2005

We present here a first fractal theory of 1/f
α noise in MOSFET structures. Inhomogeneous distribution of fixed charges in the gate oxide is assumed to be statistically self-similar, and to produce a fractal interface potential at the oxide-semiconductor interface. The interface is modelled as a special Sierpinski carpet having fractal dimension between 1 and 2. The carpet patches of each stage of fractal's construction are assigned a uniform interface potential which scales by a constant amount ψ0 at successive stages. This amounts to scaling the interface states time constant by a factor exp
±q|ψ0|k
T at each stage. In framework of this model, we studied the low frequency behaviour of the interface states admittance under weak depletion and strong inversion conditions of the interface. Interface states charge fluctuation is held responsible for generating 1/f
α noise. In a MOSFET, it manifests through the fluctuations in channel carrier density and surface recombination velocity, and in a MOS capacitor, through direct induction across the oxide capacitance. Frequency exponent is found to be

α= 1 ±\frac{kT}{q|\psi_{0}|}ln
a
2-d

where a-length scale factor and d-fractal dimension. Thus it assumes values on either side of unity depending upon the type of the substrate and sign of ψ0. The theoretical predictions are in good agreement with the experiments. For a soft modulation and even distribution of the interface potential the noise spectrum approaches towards perfect 1/f, and any deviation is distinctly linked with the interface fractality. In essence, we have searched sufficient ground to believe that fractals are at the root of 1/f
α noise generation. Further, based on this theory we suggest that the noise spectra with α≠1 should be termed `fractal 1/f noise'.
CAMAC Data Taking System for Experiments Using Continuous Ion Beams from a Cyclotron
Authors: Yasue Masaharu , Ikeoa Masaru , Sakurai Mikio , Yoshida Koichi , Tsukahara Makoto
Published: February 2005

The CAMAC system, composed of a front-end processor and a super minicomputer, was realized for nuclear physics experiments using continuous ion beams from a cyclotron and was found to be applicable to measurements at a high counting rate of up to 100 kB/s by transferring of the block data between the two processors. The large scaled central computer also became useful for on-line analyses of data obtained at a high rate.
Optical Studies of Doping-Characteristics in Boron-Doped a-Si:H Films Prepared by the Photo-CVD Technique
Authors: Mizukawa Satoshi , Sato Katsuaki , Yasuhiro Kazumichi , Isawa Mikio , Kuroiwa Koichi , Tarui Yasuo
Published: February 2005

We measured subgap optical absorption and photoluminescence spectra in boron-doped a-Si:H films prepared by photochemical vapor deposition (photo-CVD) techniques. We estimated the Urbach energy (E
0) and the density of defect states (N
s) from the subgap optical absorption spectra; the value of N
s was estimated from PL spectra. We conclude that N
s is approximately proportional to a square root of the boron doping level (B2H6/SiH4) and that E
0 increases linearly with an increase in the doping level. It is found that the doping mechanism proposed by Street applies to the photo-CVD films.
Diffusion of Metal Ions and Stimulated Currents into a-As2Se3 Thin Films
Authors: Kim Dae Young , Onari Seinosuke , Arai Toshihiro
Published: February 2005

The current-voltage characteristics of a-As2Se3 vacuum-evaporated films doped with Cu, Ag or Au metal have been investigated by a bias-voltage scanning method at several temperatures. The diffusion current of metal ions by an electric field was observed in the I-V characteristics. A stimulated current, which was generated by the interaction between metal ions and charged dangling bonds of the chalcogenide atoms, was observed. Electrical conductivity in chalcogenide glass due to the hopping of the doped metal ions is discussed along with the current by the carriers induced by the diffusion of the metal ions.
Effects of Substitution by Sc on Superconductivity and Chemical Structures in Y–Ba–Cu–O Systems
Authors: Mori Natsuki
Published: February 2005

The electrical conduction and chemical properties in Y–Ba–Cu–Sc oxide systems in which Sc was partially added in place of Y or Cu were investigated. These systems show a high-T
c superconductor-semiconductor transition with increasing Sc concentration. The superconducting samples are in the orthorhombic phase of the 123 compounds with unidentified structures which grow with increasing Sc concentration. Photoemission studies reveal that the Cu core-level spectra in the superconducting phase consist of bivalent and trivalent states, whereas the monovalent state becomes evident in the semiconducting phase. It was found that the T
c's of the systems correlate well with the average valence of Cu ions.
Stress-Released MBE Growth on GaAs on Si (001) with a Si-GaAs Superlattice Buffer
Authors: Ogasawara Kazuto , Ishikawa Tomonori , Kondo Kazuo
Published: February 2005

We investigated the GaAs heteroepitaxial layers on Si substrates by RHEED, TEM, and wafer warpage measurements. To reduce the tensile stress in thick GaAs heteroepitaxial films, Si-GaAs superlattice buffer layers were introduced pseudomorphically. The tensile stress due to thermal expansion coefficient mismatch balanced with compressive stresses due to lattice constant mismatch.
The TM010 Microwave Cavity Made of YBa2Cu3O7-d
Authors: Minehara Eisuke , Nagai Ryoji , Takeuchi Manabu
Published: February 2005

The cavity made of bulk YBa2Cu3O7-d
was resonant at 7 GHz in the TM010 mode without any dielectric interior. At 25 K the quality factor was measured to be just around 105 (the maximum of 2×105 by reducing microwave power) which represents an improvement by a factor of several hundreds from the normal state at 100 K.
Soft X-Ray Lasing in an Al Plasma Produced by a 6 J Laser
Authors: Hara Tamio , Ando Kozo , Kusakabe Naoto , Yashiro Hidehiko , Aoyagi Yoshinobu
Published: February 2005

For the first time, amplified spontaneous emission of Al ions was observed in a recombining plasma produced by a low-power driving laser of only 6 joules. It had a high gain of 3.4 cm-1 for a soft X-ray wavelength of 105.7 Å of Al XI. This lasing was achieved by tightly focusing a pumping glass laser to a line 40 µm wide and 12 mm long onto a slab target. This result can pave the way to a low-power-pumped X-ray laser.
Enhancement of Quantum-Confined Stark Effect in GaAs-AlGaAs Quantum Wells by Quantization along the [111] Axis
Authors: Kajikawa Yasutomo , Sugiyama Nao-haru , Kamijoh Takeshi , Katayama Yoshifumi
Published: February 2005

Photoluminescence measurements have been performed in (100)- and (111)-oriented GaAs-AlGaAs quantum well structures (QWS) subject to an electric field perpendicular to the well plane. In the (111) QWS, the energy shift of the heavy hole exciton induced by an electric field was found to be larger than that in the (100) QWS having the same well width. This difference of electric field dependence between (100) and (111) QWS is well explained by theoretical calculations that consider the anisotropy of the heavy hole mass. Emission due to a “forbidden” transition has been also observed in the (111) QWS.
Anisotropic Lateral Growth of GaAs by Molecular Beam Epitaxy
Authors: Kawabe Mitsuo , Sugaya Takeyoshi
Published: February 2005

A large anisotropy of the lateral growth rate on (001) GaAs is observed in molecular beam epitaxy of GaAs. The growth rate along [11̄0] is much larger than that along [110], which is contrary to that of metal-organic chemical vapor deposition. The growth rate along [11̄0] increases with increasing substrate temperature or decreasing As4 pressure. These results and the fact that the surface diffusion constant of Ga along [11̄0] is larger than that along [110] indicate that the lateral growth is limited by the surface diffusion of Ga. A model taking account of the diffusion length and terrace widths is shown to explain the anisotropic growth rate.
New Fabrication Technique of Quantum Wire Structures with Dimensions Precisely Controlled by the CBE Method
Authors: Iimura Yasufumi , Shimomura Satoshi , Nagata Kou , Den Shouji , Aoyagi Yoshinobu , Namba Susumu
Published: February 2005

A quantum wire structure of GaAs with a line width of below 100 nm has been successfully grown by the chemical beam epitaxial technique using the cleaved face of a GaAs/AlAs multiquantum well (MQW) structure. Before GaAs growth, an ultrafine ridge pattern defined by the (001) MQW structure was made by the thermal etching method. GaAs layers grown on the patterned substrate exhibit a mesa-shaped structure, with sidewalls of (111)A and (1̄1̄1)B facets. This method for making quantum wires is compatible with currently available growth techniques, and is readily applicable to one-dimensional lasers etc.
Re-Examination of Carrier Trapping Models for Light-Induced Changes in Hydrogenated Amorphous Silicon
Authors: Sakata Isao , Ishida Takeshige , Okazaki Satoru , Yamanaka Mitsuyuki , Hayashi Yutaka
Published: February 2005

Light-soaked states in hydrogenated amorphous silicon (a-Si:H) are not recovered by near-infrared or visible light illumination. Simple trapping of photogenerated carriers in the gap states of a-Si:H can, thus, be ruled out as the main process which initiates the light-induced changes. The carrier trapping accompanying the change in the atomic configuration, on the other hand, cannot be excluded as the initial process of the changes. The illumination on the light-soaked states may induce the simultaneous bond reconstruction with detrapping. The efficiency of this process has been estimated to be less than 10-5.
Pinning Strength of Bi-Sr-Ca-Cu-O Superconductor after Ion Irradiation
Authors: Takamura Saburo , Aruga Takeo , Hoshiya Taiji
Published: February 2005

The temperature dependence of critical current was measured after removing an applied magnetic field in Bi-Sr-Ca-Cu-O films after He ion irradiation at room temperature. The curve was remarkably different from the temperature dependence of critical current without magnetic field. The difference between the temperature dependence of critical current after removing an applied magnetic field and without magnetic field is due to the presence of pinning denters produced by irradiation.
Single High-Tc Phase Region of the Bi-Pb-Sr-Ca-Cu-O System
Authors: Sasakura Hiroyuki , Minamigawa Shinnosuke , Nakahigashi Kiyotaka , Kogachi Mineo , Nakanishi Shigemitsu , Fukuoka Nobuo , Yoshikawa Masatoshi , Noguchi Satoru , Okuda Kiichi , Yanase Akira
Published: February 2005

The phase diagram in the superconducting Bi1.68Pb
v
Sr
x
Ca
v
Cu
z
O
w
(v=0.28, 0.32) system was investigated by means of X-ray diffraction and electrical resistivity for samples calcined in air. The results revealed that the phase was classified into four regions, a single 110 K-phase region, two types of two-phase regions (110 K phase+Ca2CuO3 and 110 K phase+80 K phase) and a three-phase region (110 K phase+Ca2CuO3+80 K phase). The single 110 K phase with a T
c of about 106–108 K exists in a fairly wide composition range, especially in the Bi1.68Pb0.32Sr1.75Ca
y
Cu
z
O
w
system, 1.75≦y≦1.85 and 2.65≦z≦2.85. This means that the single 110 K phase can be easily obtained, even by the usual calcination in air in the Bi-Pb-Sr-Ca-Cu-O system.
The Fabrication and Characterization of Superconducting Tl0.5Pb0.5(Ca1-xMx)Sr2Cu2Oy Compounds with M=Mischmetal
Authors: Liu R. S. , Wang W. N. , Wu S. F. , Wu P. T.
Published: February 2005

Bulk superconductivity with T
c(zero) up to 101 K in Tl0.5Pb0.5(Ca1-x
M
x
)Sr2Cu2O
y
system with M=mischmetal and x=0, 0.05, 0.1, 0.2, and 0.3 was observed. The powder X-ray diffraction profiles indicate a single phase, P4/mmm tetragonal crystal structure with a=3.80±0.02 Å and c=12.05±0.02 Å for Tl0.5Pb0.5(Ca1-x
M
x
)Sr2Cu2O
y
compounds. T
c(zero)'s were found to be 78, 91, 101, 98, and 87 K for x=0, 0.05, 0.1, 0.2 and 0.3 respectively. The sample of Tl0.5Pb0.5(Ca0.9M0.1)Sr2Cu2O
y
was found to be the most homogeneous both in composition and structure. Meissner signal of this sample indicates the T
c onset around 100 K and mass diamagnetic susceptibility - χg at 10 K is 1.3×10-3 emu/g·G (field-cooled at 100 G).
Crystallization from a Glassy State in the Bi-Sr-Ca-Cu-O System
Authors: Takei Humihiko , Koike Masayoshi , Takeya Hiroyuki , Suzuki Kunio , Ichihara Masaki
Published: February 2005

The crystallization process of glassy mixtures of Bi-Sr-Ca-Cu-O was investigated by annealing the melt-quenched specimens. Apparent crystallization of Bi2(Sr, Ca)2CuO
x
(A-phase) containing a stacking fault along the c-plane was observed by high resolution electron microscopy on the specimens annealed at 500°C for 6 h in air, where very broad peaks appeared in the X-ray diffraction patterns. With increasing the annealing temperature, crystals of both the A and Bi2(Ca, Sr)3Cu2O
x
(B-) phases grew together, and the A-phase disappeared only when the annealing temperature reached higher than 800°C. A tentative phase relation is discussed on the basis of the present results.
Superconductivity in the Nd-Ba-Ca-Cu-O System
Authors: Taguchi Isao
Published: February 2005

High-temperature superconductivity has been found in ceramic oxides with nominal compositions of Nd2-x
Ba
x
CaCu2O
y
(x=1.0, 1.2). Resistivity measurements show that the T
c is about 80 K for Nd0.8Ba1.2CaCu2O
y
. X-ray diffraction patterns suggest that the superconducting phase is described as a new compound NdBaCaCu3O
y
which is isomorphic with the superconducting oxide CaBaLaCu3O
y
.
Synthesis of Metastable GexSn1-x Alloys by Chemical Sputtering in H2
Authors: Ishida Kouichi , Myoren Hiroaki , Yamamoto Masaki , Imura Takeshi , Osaka Yukio
Published: February 2005

Thin films of metastable alloy Ge
x
Sn1-x
(0≦x≦1) are formed by chemical sputtering in H2 on glass and semiconducting crystalline substrates. X-ray diffraction indicates the formation of microcrystalline Ge
x
Sn1-x
alloy films with a diamond structure. Ge
x
Sn1-x
films deposited on InSb(x=0) and GaSb(x=0.47) substrates with lattice matches consist of polycrystals and are shown to have a crystal orientation nearly aligned to the substrate by RHEED observations. The chemical sputtering technique is appropriate for synthesizing Ge
x
Sn1-x
alloys which might have potential as direct and narrow band gap materials.
A Liquid Encapsulated Laser Recrystallization for Silicon-on-Insulator Structures
Authors: Doi Atsutoshi , Asakawa Toshifumi , Namba Susumu
Published: February 2005

Seedless recrystallization of capped and uncapped silicon-on-insulator structures has been demonstrated using a new fabrication method in which the conventional laser melting technique was combined with a liquid encapsulating technique. Substantial increase in the grain size was observed in polycrystalline silicon films fabricated by the new method. The stabilization of the recrystallization process was likely due to features of the liquid encapsulation technique: i.e., effective heat release from the surface of molten silicon, resulting in control of vertical temperature profile.
The Effect of Hydrogen Plasma on the Low Temperature Epitaxial Growth of InSb
Authors: Ohshima Tomoyuki , Yamauchi Satoshi , Hariu Takashi
Published: February 2005

InSb layers have been epitaxially grown on (100) semi-insulating GaAs by plasma-assisted epitaxy (PAE) in hydrogen plasma at a temperature as low as 270°C. It was found that higher rf power should be applied to plasma for the epitaxial growth of InSb layers at lower temperatures than at higher temperatures, and when higher rf power is applied, the optimum Sb/In supply ratio to obtain PAE-InSb with electronic property comparable to those growrn at higher temperatures, shifts to lower value.
Magnetic Analysis of Quadrupole Lens for MeV Ion Microprobe
Authors: Inoue Ken-ichi , Takai Mikio , Ishibashi Kiyotaka , Kawata Yutaka , Namba Susumu
Published: February 2005

The magnetic field in a quadrupole magnet has been studied using a 3-dimensional numerical method. The profile of pole-edges for a MeV ion microprobe system was optimized by evaluating the higher-order harmonic components. The dependence of the cut-off angle for the hyperbolic pole of the quadrupole magnet on the uniformity of the field gradient was revealed. Moreover, it was found that the higher-order harmonic contaminant fields can be significantly suppressed by rounding the edges of the poles along the beam axis.
Properties of Ga1-xInxN Films Prepared by MOVPE
Authors: Nagatomo Takao , Kuboyama Takeshi , Minamino Hiroyuki , Omoto Osamu
Published: February 2005

Epitaxial films of the solid solution Ga1-x
In
x
N (up to X=0.42) have been fabricated on (0001) sapphire substrates by metalorganic vapor phase epitaxy (MOVPE) at 500°C. The properties of the films have been studied by the reflection high-energy electron diffraction technique, X-ray diffraction, and electrical and optical measurements. The fundamental absorption edge of the film decreases linearly with composition (up to X=0.42) from 3.20 eV to 2.01 eV at room temperature.
Strain-Induced Energy Shift of Photoluminescence Spectra in MOCVD-Grown ZnTe Films on (100) GaAs Substrates
Authors: Ekawa Mitsuru , Taguchi Tsunemasa
Published: February 2005

It has been revealed that heteroepitaxial ZnTe films grown on (100) GaAs substrates by low-pressure metalorganic chemical vapour deposition (MOCVD) receive considerably biaxial tensile stress. In order to characterize the effect of strains on the optical properties, the dependence of the 2.32 eV donor-acceptor pair and oxygen-bound-exciton emissions on film thickness was investigated in the range of 1 to 8 µm. It was found that photoluminescence (PL) peaks shift toward the lower-energy side and that full-width at half-maximum (FWHM) values of both PL and X-ray diffraction peaks decrease with increasing film thickness, suggesting that the film quality significantly depends upon its thickness.
XPS Study on the Formation Process of the High-Tc Phase in the Bi-Pb-Sr-Ca-Cu-O System
Authors: Shin Jae Soo , Enomoto Hiroyuki , Takauchi Hideki , Takano Yoshiki , Mori Natsuki , Ozaki Hajime
Published: February 2005

X-ray photoemission spectroscopy (XPS) measurements were carried out to investigate the changes in the Cu ion valency through the formation of the high-T
c phase in the Bi-Pb-Sr-Ca-Cu-O superconducting system. The Cu2+ composition increased rapidly in the initial stages of sintering and became saturated, whereas the Cu+ and Cu3+ compositions showed a systematic change, within a certain sintering time, dependent on the sintering temperature. It was found that these changes in the Cu ion valency reflect the structural change in the formation of the high-T
c phase in this system.
Preparation of High-Tc Superconducting Bi-Pb-Sr-Ca-Cu-O Filament by the Suspension Spinning Method
Authors: Goto Tomoko
Published: February 2005

A high-T
c superconducting Bi-Pb-Sr-Ca-Cu-O filament was successfully prepared using a combined technique of suspension spinning and densification of the pyrolyzed filaments by two stages of pressing and sintering. Zero electrical resistivity was achieved at 99 K and the maximum J
c of the filament was 1210 A/cm2 at 77 K, 0 T. The filament consisted of a single high-T
c phase and the grains were oriented with the c-axis perpendicular to the longitudinal direction of the filament. The filament exihibited a tensile strength of 55 MPa and an elongation of 1.1%.
A Novel GRIN-SCH-SQW Laser Diode Monolithically Integrated with Low-Loss Passive Waveguides
Authors: Hirata Takaaki , Maeda Minoru , Hosomatsu Haruo
Published: February 2005

We propose a novel fabrication process for monolithic multielement laser diodes and demonstrate the performance of a monolithically integrated passive waveguide laser as compared with a conventional laser fabricated under the same procedures. This process, which is based on silicon ion implantation and two-step MOVPE growth, is suitable for integrating optical elements like gratings and rib waveguides. We also demonstrate that the COD level of the window structure laser fabricated by this process is more than 1.3 W in pulsed operation.
Visual Observation of a Pressure-Driven Crystal Growth
Authors: Takano Kaoru J. , Nishida Satoshi , Wakatsuki Masao
Published: February 2005

Visual observation of crystal growth at high pressure was realized by the use of a diamond anvil cell. With a eutectic system of meta- and para-xylenes, phase equilibrium pressures were determined at various compositions and temperatures. Stepwise changes in pressure were applied to drive and observe even rapid growth of a crystal at a constant supersaturation. The growth form and the growth rate were observed in relation to both the composition of the solution and the magnitude of the excess pressure. Results are promising in terms of its application to various cases.
Low-Temperature Thermal Oxidation of Silicon in N2O by UV-Irradiation
Authors: Ishikawa Yutaka , Takagi Yukio , Nakamichi Ichiro
Published: February 2005

A new thermal oxidation method using UV-irradiation has been proposed. Silicon dioxide of 3.5–4.0 nm thickness can be formed in 0.5 h at 200–500°C under N2O flow with UV-irradiation. Oxide formed by the present method is determined to be silicon dioxide. The fixed charge density at the Si/SiO2 interface is relatively low for 500°C oxidation. It is estimated to be about 2×1011 cm-2 without any thermal annealing.
Polyacetylene Film with Fibrils Aligned across the Thickness Synthesized with a Liquid Crystalline Catalyst under Magnetic Field
Authors: Tsuji Taishi , Negishi Masataka , Yao Kenji , Kubo Takaya , Takezoe Hideo , Fukuda Atsuo , Scheuble Bernhard S.
Published: February 2005

Polyacetylene film with aligned fibrils across the film thickness was synthesized using a liquid crystalline catalyst under a magnetic field. The morphology observed by an electron microscope was characteristic in the fibril thickness (no less than 1 µm in diameter) in addition to the fibril orientation. The presence of well developed fibrils across the film thickness suggests the possibility of intrafibrillar electric measurements.
Preparation of 95 K Bi2CaSr2Cu2O8+δ Superconductor from Citrate Precursors
Authors: Wang N. H. , Wang C. M. , Kao H.-C. I. , Ling D. C. , Ku H. C. , Lii K. H.
Published: February 2005

Highly crystalline single phase “2122”, Bi2CaSr2Cu2O8+δ, sample with δ=0.25 has been prepared from citrate precursors with pyrolysis. Stable and bulk superconductivity with T
c(onset)=99 K and T
c(zero)=95 K was reproducibly detected by the magnetic susceptibility and electrical resistivity measurements, respectively.
Flux Creep in Sintered Superconducting Y-Ba-Cu-O
Authors: Matsushita Teruo , Funaba Seiji , Nagamatsu Yoshiyuki , Ni Baorong , Funaki Kazuo , Yamafuji Kaoru
Published: February 2005

The flux creep rate in sintered superconducting Y-Ba-Cu-O was measured at 77 K and in fields of up to 0.1 T. The pinning potential mainly caused by flux pinning inside grains was 0.25 eV at B=50 mT and decreased monotonically with increasing magnetic field. The obtained results can be explained by the theoretical model with observed intragrain current density. This theoretical model suggests that the flux creep at high fields is notable even if a superconducting wire with the critical current density of 2×1010 A/m2 at B=5 T is realized.
Preparation of a Bi-Sr-Ca-Cu-O Superconductor by the Arc-Melting Technique
Authors: Koo H. S. , Liu R. S. , Wang W. N. , Lan S. D. , Wu S. F. , Wu P. T.
Published: February 2005

High-T
c superconducting Bi-Sr-Ca-Cu oxide was prepared by the arc-melting technique and post annealing treatment. The as-melted sample was in a crystalline phase and showed semiconducting behavior, but post heat treatment at various annealing temperatures resulted in superconductors with different critical transition temperatures. The best sample, annealed at 860°C for 10 h, showed a zero-resistance temperature of 82 K and a critical current density, which was calculated from the magnetization measurement at 5 K with 5 kOe applied magnetic field, was 8000 A/cm2. XRD analysis, magnetization data and the packing-density measurement all indicated that the arc-melting and post annealing-treatment-prepared samples have better superconducting properties than those prepared by the solid-state reaction.
Bridge Type Josephson Junctions in MO-CVD Thin Films
Authors: Noge Satoru , Yamashita Tsutomu , Wang Zhen , Matsui Toshiaki , Kurosawa Hideyuki , Yamane Hisanori , Hirai Toshio
Published: February 2005

Using Y1Ba2Cu3O7-x
thin films, bridge type Josephson junctions are fabricated. Thin films of Y1Ba2Cu3O7-x
on (100) MgO substrates are deposited by the MO-CVD method. These films exhibit zero resistance at 86 K, and a critical current density of 104 to 105 A/cm2 at 77 K. The effect of radio frequency irradiations to the bridge are investigated. Sharp microwave-induced steps are observed up to 800 µV at 77 K for X band irradiation. Clear Shapiro steps are also observed at the millimeter (101 GHz) and submillimeter frequency (303 GHz). The results demonstrate that the thin film bridges made by MO-CVD show an ideal ac Josephson effect.
Dominant Factors Influence the Bistability of Surface-Stabilized Ferroelectric Liquid Crystal Devices
Authors: Yang K. H. , Chieu T. C.
Published: February 2005

The bistability of surface-stabilized ferroelectric liquid crystal (FLC) devices using ion-free FLC mixtures has been analyzed as a function of the spontaneous polarization, the thickness of the insulating alignment layer, and the percentage of chiral dopants in the achiral host. A memory time that scales with the rotational viscosity of the FLC was defined to characterize the bistability. In one of the most favorable cases, we predict that bistability can be maintained with a spontaneous polarization as high as 100 nC/cm2 and a rotational viscosity of 40 mPas using a pure single FLC compound aligned either by conductive alignment layers or shear alignments.
Measurement of Refractive Indices of Ferroelectric SmC* Liquid Crystal by the Fabry-Perot Interference Method
Authors: Kawaida Masahiro , Yamaguchi Tomomi , Akahane Tadashi
Published: February 2005

The wavelength and temperature dependences of the principal refractive indices (n

e
and n

o
) of a ferroelectric SmC* liquid crystal were measured by using the Fabry-Perot interference technique in the surface stabilized cell. The refractive indices have a normal wavelength dispersion similar to a nematic liquid crystal. The refractive indices for about 630 nm wavelength in the SmC* phase gradually increase as the temperature rises and then remain almost constant in the SmA phase. The layer tilt (i.e., molecular tilt from glass plate) due to the chevron structure in the SmC* phase was also taken into account for the evaluation of n

e
.
Applicability of the Soft X-Ray Standing-Wave Method to Surface Structure Determination
Authors: Yokoyama Toshihiko , Takata Yasutaka , Yoshiki Masahiko , Ohta Toshiaki , Funabashi Manabu , Kitajima Yoshinori , Kuroda Haruo
Published: February 2005

The applicability of the soft X-ray standing-wave (SW) method to surface structure determination is discussed by investigating the SW signals of c(2×2)Cl/Ni(100). The measurements of reflectivities for Ni(200) Bragg reflection at nearly normal incidence make it possible to determine the mosaic width (0.3°) of the Ni(100) crystal employed, and the Cl-K fluorescence yield spectrum reveals that Cl atoms are located 0.04Å above the Ni(200) lattice plane. The experimental and analytical error is estimated to be 0.04Å, which allows us to discuss detailed surface structure.
Measurements of Near-Infrared Absorption in Thin GaAs Wafers
Authors: Yamada Kohji , Watanabe Kazuo , Hoshikawa Keigo
Published: February 2005

The accuracy of near-infrared absorption coefficients for EL2 concentration determination by transmittance measurement in thin GaAs wafers is investigated. Using wafers having the same absorption coefficients but varying in thickness, we found that the error in absorption coefficient is larger than 30% in 0.4 mm-thick wafers when reported reflectance derived from refractive index is used in the calculation. We therefore propose to use an appropriate reflectance which is determined by measuring the transmittance of different thickness wafers. Adopting the appropriate reflectance, the error is reduced to less than 2%.
MOVPE Growth of AlGaAs/GaAs Heterostructures for HEMT LSI
Authors: Itoh Hiromi , Tanaka Hitoshi , Ohori Tatsuya , Kasai Kazumi , Mitani Eizo , Suzuki Masahisa , Komeno Junji
Published: February 2005

We have developed an MOVPE technique capable of mass-producing HEMT LSI quality AlGaAs/GaAs selectively doped heterostructures by a barrel-type reactor. The reactor grows six three-inch wafers at a time. The uniformities of layer thickness and donor concentration are ±2.1% and ±2.0% across a three-inch wafer, respectively. The wafer-to-wafer uniformities for six wafers are ±2.3% for thickness and ±1.7% for donor concentration. The fabricated ring oscillator circuits having a quarter-micron gate showed an average delay time of 11.6 ps/gate with a standard deviation of 0.46 ps over an entire three-inch wafer.
An Improved Calculation for Differential Voltage Capacitance Spectroscopy
Authors: Tezuka Toshikazu , Sato Kazunori
Published: February 2005

An improved method is presented for the extraction of the differential capacitance of a forward-biased Schottky-barrier diode. The present method has been applied to the capacitance measurement of Mo-nSi diodes with great success. The correction of the capacitance is much appreciable in the higher-conductance region compared to the results obtained by the existing theory.
Joining of Hot-Pressed Bi-Pb-Sr-Ca-Cu-O Superconductor
Authors: Murayama Norimitsu , Kodama Yasuharu , Wakai Fumihiro , Sakaguchi Shuji , Torii Yasuyoshi
Published: February 2005

Hot-pressed Bi0.85Pb0.15Sr0.8CaCu1.4O
y
superconductors were joined without an interfacial layer at 780°C at a pressure of 25 kg/cm2 in air for 30 min. Then the joined sample was annealed at 830°C in air for 40 h. No appreciable void was observed at the joining interface. The resistivity in the normal conducting state and the T
c of the joined sample were almost equal to those of the base sample. However, the J
c of the joined sample and the base sample were 241 A/cm2 and 375 A/cm2 at 77 K in zero magnetic field, respectively. The decrease in J
c seems to be due to a weak link at the joining interface.
Characteristics of 325-nm CW Oscillation of a Hollow Cathode He-Cd+ Laser
Authors: Fuke Akira , Tokita Yasuhiro , Masuda Katsuhiko
Published: February 2005

A hollow-cathode He-Cd+ laser oscillates with 12 lines. The oscillation line at 325 nm could emit only by pulse oscillation using the conventional hollow cathode. The 325 nm line is promising in the measurement and chemical analysis fields. Simultaneous oscillation of both the line at 325 nm and one or more lines in the visible light range are desired as well. The authors utilized the hollow-cathode He-Cd+ laser of 61 cm in cathode length used for high-power white light laser oscillation to enable 325-nm single-light oscillation to be emitted continuously with a power of 18 mW.
Crystallization Characteristics of Phase-Change Media by Laser Pulse-Train Irradiation
Authors: Tanabe Takaya , Iijima Tetsuo , Funakoshi Nobuhiro
Published: February 2005

A pulse-train method, which uses a laser beam as a highly frequent pulse train, is investigated to crystallize phasechange optical disk media. In this method, the laser power for crystallization can be controlled more easily than in conventional DC-irradiation. This method is especially effective for media with a narrow power margin for crystallization.
Adsorption of Cytochrome c to Flavin Monolayers
Authors: Kawakubo Hiroaki , Isoda Satoru , Maeda Mitsuo
Published: February 2005

Adsorption of cyt c molecules to flavin monolayers was analyzed by Gibbs' adsorption isotherm, and the effect of ionic strength on the adsorption was studied by reflection spectroscopy. Cyt c molecules adsorbed the most to the flavin monolayer which has two carbonyl groups. It was concluded from these analyses that the adsorption of cyt c to flavin monolayers depends mainly on the electrostatic interaction between positive charges on the surface of the cyt c molecule and negative charges of the flavin monolayer.
Generation of Electron Cyclotron Resonance Plasma in the VHF Band
Authors: Oda Shunri , Noda Jun'ichirou , Matsumura Masakiyo
Published: February 2005

A novel processing plasma in the VHF region (144 MHz band) is described. Optical emission spectroscopy has been employed as a diagnostic tool of the plasma. The advantage of the VHF plasma is enhanced in the ECR mode by applying magnetic field. ECR plasma with a large area uniformity has been obtained at a magnetic field of as low as 51 G. By using the ECR mode, the discharge condition has been significantly expanded to a lower pressure range and lower power density region. The ECR-VHF plasma has been successfully applied for the deposition of amorphous silicon films.
Laser-Assisted MOMBE Growth of GaAs Using Tri-Isobutyl Gallium
Authors: Yamada Takeshi , Iga Ryuzo , Sugiura Hideo
Published: February 2005

Growth rate enhancement of GaAs films is studied using tri-isobutyl gallium (TIBGa) and triethylgallium (TEGa) by Ar+ laser-assisted metalorganic molecular beam epitaxy (MOMBE). TIBGa grows GaAs films at substrate temperatures approximately 50°C lower than does TEGa. The laser power required to enhance the growth rate for TIBGa is two-thirds that for TEGa. The carbon concentration of a film grown with TIBGa is one-tenth that of one grown with TEGa. Thus, the use of TIBGa has two advantages over TEGa: less laser power required to enhance growth rate, and less carbon in the film.
12 GHz High Power GaAs/Si MESFETs
Authors: Charasse M. N. , Bartenlian B. , Gérard B. , Hirtz J. P. , Laviron M. , Parscau A. M. de , Derevonko M. , Delagebeaudeuf D.
Published: February 2005

GaAs power MESFET structures have been grown by MBE on Si substrates. Growth specifications are the nucleation of GaAs on Si by migration enhanced epitaxy and the annealing of the first few hundred angstroms-thick GaAs layer before using standard MBE growth conditions for GaAs. A standard process with an air bridge source interconnection and 0.8 µm gate length has been achieved. 1 W output power with a 1 dB compressed gain of 5 dB and 1.6 W with a 1 dB compressed gain of 9 dB are obtained at 12 and 5 GHz, respectively. The power and the gain are equivalent to the same GaAs/GaAs MESFETs. The drain efficiency is 35%, which is excellent.
Nonresonant Microwave Absorption of Single Crystals in the Bi-Sr-Ca-Cu-O System
Authors: Tagaya Kimihito , Fukuoka Nobuo , Nakanishi Shigemitsu
Published: February 2005

A nonresonant microwave absorption was observed for single crystals in the low-Tcphase of the Bi-Sr-Ca-Cu-O system, and a critical field in the resonance was investigated. This field may be the lower critical field. The anisotropy of critical field was uniaxial along thec-axis, and its principal values were determined to be 26 and 36 Oe at 77 K for thec-axis and thec-plane, respectively. Further, the lower critical field at 0 K was roughly estimated.
Effect of 120 MeV 16O Ion Irradiation at Liquid Nitrogen Temperature on Superconducting Properties of Bi-Pb-Sr-Ca-Cu-O
Authors: Iwase Akihiro , Watanabe Mitsuo , Iwata Tadao , Nihira Takeshi
Published: February 2005

Bi-Pb-Sr-Ca-Cu-O superconductor is irradiated at liquid nitrogen temperature with 120 MeV 16O ions up to the fluence of 3.5×1014/cm2. Transition temperature T
c and critical current I
c at 77.3 K decrease with increasing ion fluence. Annealing of the specimen up to 300 K after irradiation causes a slight recovery of T
c and I
c. However, recovery of the electrical resistance above 100 K is not observed.
The Oxygen Potentials in the Y2O3-BaO-CuOx System
Authors: Borowiec K. , Kolbrecka K.
Published: February 2005

The oxygen potential for some chosen four and three-phase combinations has been measured at 750–1000°C using solid ZrO2+CaO electrolyte. On the basis of log P
O2
values, the Gibbs energies of reactions for many possible reactions in the system were obtained. The reactions with the Y2BaO4 on the left sides exhibit negative entropy due to decomposition of Y2BaO4 below about 850°C. The positive entropy for several reactions clearly indicates that ternary cuprates such as Y2BaCuO5, YBa2Cu3O
x
, YBa4Cu3O
x
and Y3Ba8Cu5O
x
are entropy-stabilized compounds. These cuprates become increasingly less stable with decreasing temperature and on cooling there are temperature limits below which these cuprates are metastable.
Improvement of Surface Flatness on BiSrCaCuO Film
Authors: Nagai Yasuhiro , Tsuru Koji
Published: February 2005

This paper reports on the improvement of the surface flatness on BiSrCaCuO films. By keeping the film surface in contact with a MgO(100) plane during annealing, it is possible to greatly improve the surface flatness at each annealing temperature. The smooth surface is mainly made up of several-µm platelike crystals approximately 60 nm thick. The average surface roughness is determined by the annealing temperature, regardless of film thickness, in the range of 0.1–1.5 µm. As the critical temperature and surface morphology change due to the contacted MgO crystal plane, the improvement of surface flatness is considered to result from the crystal growth restriction on the film surface in contact with a MgO(100) plane.
Transmission Loss Characteristics of a Fluoride Optical Fiber in the Near-Ultraviolet to Mid-Infrared Wavelength Region
Authors: Kanamori Terutoshi , Oikawa Kiyoshi , Terunuma Yukio , Kobayashi Kenji , Takahashi Shiro
Published: February 2005

A fluoride optical fiber with low impurity and defect content has been fabricated using high-purity raw materials and a dry fluorination method. The 160-meter-long fabricated fiber shows a minimum transmission loss of 1.2 dB/km at a 2.30-µm wavelength and transmission losses of less than 10 dB/km in the 0.8–2.7 µm wavelength region. It seems that the transmission loss in the 0.3–0.4 µm wavelength region is dominantly due to Rayleigh scattering, and that a weak absorption tail with lower loss than that in pure silica glasses is the second major loss factor in this region.
Crystallization Characteristics of Phase-Change Optical Disks
Authors: Iijima Tetsuo , Tanabe Takaya , Funakoshi Nobuhiro
Published: February 2005

A new crystallization method for erasing recorded amorphous marks in phase-change optical disks, based on irradiation with a high power laser beam producing temperatures above the melting point of the media is proposed. Erased medium reflectivity for a prepared Sb56Te44 disk shows an intermediate value between the crystalline and amorphous states, which corresponds to a residual signal of less than -35 dB. The reflectivity after erasing is constant over a wide range of erasing power.
13C NMR Analysis of Molecular Motions of a Ferroelectric Liquid Crystal
Authors: Yoshizawa Atsushi , Kikuzaki Hiroshi , Hirai Toshihiro , Yamane Mamoru
Published: February 2005

We report on the NMR observation of local molecular motions and microscopic environment of a ferroelectric liquid crystal, 4-(2-methyloctanoyl)phenyl 4'-nonylbiphenyl-4-carboxylate, obtained from variable-temperature solid-state 13C CP/MAS NMR analysis. Based on the analysis of NMR spectra and relaxation times, we show that the molecular motion of the asymmetric carbon does not change during the phase transition from SA to SC
* and that the mobility of the polar group adjacent to the asymmetric carbon decreases remarkably during the phase transition.
GaAs P-N Junction and Doping Superlattices Grown by Laser-Assisted MOVPE
Authors: Ban Yuzaburoh , Ishizaki Mamoru , Asaka Tatsuya , Koyama Yoshihisa , Kukimoto Hiroshi
Published: February 2005

A GaAs p-n junction and a GaAs doping superlattice (nipi structure) have been fabricated by switching the ArF excimer laser light on and off during MOVPE growth while simultaneously using an n-type doping source of tetramethylsilane (TMSi) and a p-type doping source of dimethylzinc (DMZn). The current-voltage characteristic of the p-n junction showed good diode properties with a breakdown voltage of about 26 V and a built-in voltage of 0.8 V. The formation of the doping superlattice was confirmed by secondary ion mass spectrometry (SIMS) analysis of the impurity depth profile and photoluminescence peak shift with excitation intensity.
Anomalous Distribution of In Atoms in GaAs during Migration-Enhanced Epitaxy
Authors: Yamaguchi Hiroshi , Horikoshi Yoshiji
Published: February 2005

An InAs monolayer is grown between GaAs layers using migration-enhanced epitaxy. The surface chemical characteristic during growth is investigated by reflection high energy electron diffraction. When the substrate temperature is about 500°C, the oscillation amplitude of reflected electron beam after growth of one monolayer of InAs vanishes during the growth of GaAs over more than 20 atomic layers. High-resolution secondary-ion mass spectroscopic analysis of the fabricated structures indicates that the anomalous distribution of In atoms with a gradual slope towards the growth direction occurs when the substrate temperature is 500°C. The experimental results are explained in terms of the replacement of In atoms in the InAs monolayer by the newly deposited Ga atoms.