bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical Properties of an 80 K-Superconductor: Bi-Sr-Ca-Cu-O Ceramics
Authors: Maeda Atsutaka , Yabe Tomoaki , Ikuta Hiroshi , Nakayama Yoshimi , Wada Takahiro , Okuda Shigeru , Itoh Takao , Izumi Mitsuru , Uchinokura Kunimatsu , Uchida Shin-ichi , Tanaka Shoji
Published: February 2005

The magnetization curve, tunneling spectra, and normal-state susceptibility were measured in well-characterized single-phase 80 K superconductor, Bi-Sr-Ca-Cu-O ceramic samples. The obtained result is very similar to that of other copper-oxide superconductors.
Single Crystal ESR Study of Y2BaCuO5
Authors: Kobayashi Tadashi , Katsuda Hiratoshi , Hayashi Kunihiko , Tokumoto Madoka , Ihara Hideo
Published: February 2005

Single-crystal ESR measurements were made in insulating Y2BaCuO5. The principal values of the g tensor of Cu2+ ions in Y2BaCuO5 are g

X
=2.050(4), g

Y
=2.094(4) and g

Z
=2.222(4), which reflects the rhombic symmetry. The principal X-axis is parallel to the crystallographic c-axis, the Y to the b, and the Z to the a. The crystal habits with Miller indices and the crystallographic axes are shown. The temperature dependence of the ratio of the ESR intensity to that of DPPH at room temperature, which agrees well with that observed for the magnetic susceptibility, is also reported.
New Amorphous Al-Y, Al-La and Al-Ce Alloys Prepared by Melt Spinning
Authors: Inoue Akihisa , Ohtera Katsumasa , Masumoto Tsuyoshi
Published: February 2005

New amorphous alloys in Al-M (M=Y, La or Ce) binary systems have been formed in the compositional ranges of 9 to 13 at% Y and 7 to 10 at% La or Ce by liquid quenching. Crystallization temperature, Vickers hardness and electrical resistivity at 293 K of the binary amorphous alloys increase with an increase of Y, La or Ce content from 437 to 516 K, 116 to 216 DPN and 54 to 93 µΩcm, respectively. The first amorphization for the Al-M binary alloys is important for subsequent development of Al-based amorphous alloys with high specific strength.
Study on the Si(111) √3×√3-Ag Surface Structure by X-Ray Diffraction
Authors: Takahashi Toshio , Nakatani Shinichiro , Okamoto Naoko , Ishikawa Tetsuya , Kikuta Seishi
Published: February 2005

The surface structure of Si(111) √3×√3-Ag has been analyzed from the X-ray intensity versus energy curves measured both for the integral- and fractional-order spots. A modified trimer model with three Ag atoms in the √3×√3 unit cell is proposed, in which triangles made of Ag atoms are chained in a honeycomb arrangement. The distances between the nearest neighbor Ag atoms are about twice the van der Waals radius. The height of the Ag layer measured from the ideal first Si layer is 2.9±0.1 A. The center of each triangle coincides with the position of the honeycomb protrusion observed by scanning tunneling microscopy.
Possible Organic Analogues to Copper Oxides: Applications of a J-Model
Authors: Yamaguchi Kizashi , Takahara Yoichi , Fueno Takayuki , Nakasuji Kazuhiro , Murata Ichiro
Published: February 2005

Ab initio MO calculations were carried out for diradical, polyradical and cation-radical states of azomethyne-ylide dimer and clusters. The calculated results were applied to a molecular design of possible organic analogues to copper-oxide chains and planes in YBa2Cu3O
x
and related species. These organic analogues have molecular skeletons similar to those of conducting polymers and graphite, although their electronic structures are quite different because of electron and spin correlations.
Electron Conduction in an Atomic-Layer-Doped GaAs Plane
Authors: Makimoto Toshiki , Kobayashi Naoki , Horikoshi Yoshiji
Published: February 2005

Electronic transport characteristics in Si atomic-layer-doped GaAs are investigated using Hall measurements. In the uniformly Si-doped GaAs crystals, the carrier concentration varies very little throughout the whole temperature range, while the atomic-layer-doped GaAs layer exhibits a strong temperature-dependent electron concentration with a minimum value around 100 K. The temperature dependence of the sheet resistance of the Si atomic-layer-doped GaAs is quite different from that of the uniformly Si-doped GaAs. The observed characteristics are interpreted by considering parallel conduction in the Si atomic-layer-doped GaAs. We propose a hypothetical model that the electrons are confined by a local potential well structure due to the random distribution of Si atoms in the atomic-layer-doped plane. Using this model, we also discuss the discrepancy reported so far between the doped layer thickness evaluated from magnetoresistance measurements and that from C-V profiling measurements.
High-Tc Superconductor Prepared by Oxidation of a Mechanically Alloyed Nonequilibrium fcc Ba2YCu3 Phase
Authors: Matsuzaki Kunio , Inoue Akihisa , Masumoto Tsuyoshi
Published: February 2005

A nonequilibrium fcc Ba2YCu3 phase was prepared in an immiscible Ba-Y-Cu system by mechanical alloying (MA). Heating of the nonequilibrium phase powder in air resulted in the structural change to an equilibrium metallic phase at about 440 K, followed by the oxidation into Ba2YCu3O
y
at temperatures above 470 K. The Ba-Y-Cu oxide prepared by oxidation of the pressed product of the fcc alloy powder exhibited high-T
c superconductivity with zero resistance at 89 K. Thus, MA is useful for the preparation of a high-T
c oxide superconductor through the formation of the homogeneously mixed fcc phase of immiscible elements.
XPS Measurement of YBa2Cu3Oy Compounds Heated at Various Temperatures
Authors: Watanabe Hiroyuki , Ikeda Koji , Miki Hirofumi , Ishida Kohtaro
Published: February 2005

Temperature dependences of XPS spectra of orthorhombic and tetragonal YBa2Cu3O
y
compounds were measured. Variation of satellite peaks of Cu 2P for the superconducting compound coincided with a change of Cu valence which was deduced from the oxygen content. For the nonsuperconducting compound, no distinct change in XPS spectra was observed up to 770 K. The XPS spectra of O 1S showed three different states of oxygen atoms in the compound. Analyzing the temperature dependence of these peaks, they were attributed to the three oxygen configurations around copper: the octahedral, pyramidal and square planar.
Preparation and Properties of Single Crystals of the High-Tc Oxide Superconductor in the Bi-Sr-Ca-Cu-O System
Authors: Ono Akira , Sueno Shigeho , Okamura Fujio Peter
Published: February 2005

Single crystals of the superconductor in the Bi-Sr-Ca-Cu-O system were prepared by the Bridgman method. Platy crystals annealed at various physical conditions were examined by electrical resistivity measurements and single crystal X-ray diffraction studies. The superconducting transition temperature (T
c) depended on the annealing temperatures and oxygen pressure. Corresponding to annealing conditions, single crystal X-ray diffraction patterns on (h
k1)* Layer precession photographs systematically changed at room temperature. This may be related to the slight differences of the cell parameters of each specimen.
Transition to an Insulator from a Superconductor due to Substitution of Ca by Rare-earth Elements in Bi4Sr4RE2Cu4O16+δ (RE=Nd, Eu, Y)
Authors: Fukushima Noburu , Niu Hiromi , Ando Ken
Published: February 2005

X-ray diffraction analyses and electrical properties were determined for Bi4Sr4RE2Cu4O16+δ, where RE=Nd, Eu and Y. Samples sintered at 920°C showed identical XRD patterns with that of superconducting Bi4Sr4Ca2Cu4O16+δ, however, their electrical properties were insulating. Oxygen content for the Y-substituted sample Bi4Sr4Y2Cu4O
y
was y=16.75 and the Cu average valence was 1.875. The compounds seem to correspond to the ground state of Bi4Sr4Ca2Cu4O16+δ, where no holes are doped in Cu-O levels, equivalent to the reduced semiconductor REBa2Cu3O6 in REBa2Cu3O7-δ systems.
Structural Properties of Two Superconducting Phases in the Bi-Sr-Ca-Cu-O System
Authors: Kijima Naoto , Endo Hozumi , Tsuchiya Jun , Sumiyama Akihiko , Mizuno Masaaki , Oguri Yasuo
Published: February 2005

X-ray powder diffraction patterns and transmission electron diffraction patterns of superconductors with the nominal composition of BiSrCa3Cu4O
x
have been observed and compared with the results of the magnetic susceptibility. Unit cell dimensions of high-T
c phase (T
c∼107 K) are a=5.40 Å, b=27.0 Å, c=36.8 Å, indicating a pseudotetragonal symmetry. High resolution structure image of the high-T
c phase shows that there are layer structural units with 15.4 Å and 22.5 Å in thickness, in addition to the main layer structural unit with a thickness of 18.4 Å.
Crystal Substructure of the Bi-Sr-Cu-O System
Authors: Sawa Hiroshi , Fujiki Hideo , Tomimoto Koukichi , Akimitsu Jun
Published: February 2005

A substructure with a pseudotetragonal unit cell is proposed for a low-T
c superconducting oxide Bi-Sr-Cu-O system on the basis of Rietveld analysis of powder X-ray diffraction data. It is a layered structure having the composition Bi2Sr2CuO
y
. The relationship between the crystal structure of the Bi-Sr-Ca-Cu-O system and that of Bi-Sr-Cu-O system was discussed.
High Tc Phase of Bi-Sr-Ca-Cu-O Superconductor
Authors: Nobumasa Hitoshi , Shimizu Kazuharu , Kitano Yukishige , Kawai Tomoji
Published: February 2005

High T
c superconducting phase above 100 K in a Bi-Sr-Ca-Cu-O superconductor was found to appear in proportion to the time of the sintering just below the melting temperature. The changes of the magnetic susceptibility for this high T
c phase corresponded well to the behavior of 4.8° peak in X-ray diffraction pattern taken with Cu-Kα, which indicated that the high T
c phase contains triple Cu-O layers sandwiched by two Bi2O2 layers. The mechanism of the high T
c phase formation is proposed such that a disproportionation into triple and single Cu-O layers occurs from 80 K phase with double Cu-O layers to form the high T
c and a semiconducting phase, respectively.
Sputtered Tl-Ca-Ba-Cu-O Thin Films with Zero Resistivity at 98 K
Authors: Nakao Masao , Yuasa Ryohkan , Nemoto Masaaki , Kuwahara Hideki , Mukaida Hiromi , Mizukami Atsuo
Published: February 2005

Superconducting Tl-Ca-Ba-Cu-O thin films were prepared by rf magnetron sputtering from a sintered Tl3Ca2Ba2Cu3O
x
target. After post-annealing, films grown on (100) MgO substrates exhibited the best superconducting properties with an onset temperature as high as 110 K and zero resistivity at 98 K. No resistive tails were observed at measuring current densities of 0.5–5 A/cm2. X-ray diffraction patterns indicated that the major phase of the films is Tl2Ca1Ba2Cu2O
x
.
Ba-Y-Cu-O Thin Films Fabricated by Dip Coating Using Concentrated Mixed Alkoxide Solution
Authors: Nonaka Toshihisa , Kaneko Kimiyoshi , Hasegawa Tetsuya , Kishio Kohji , Takahashi Yasutaka , Kobayashi Keisuke , Kitazawa Koichi , Fueki Kazuo
Published: February 2005

Superconducting oxide thin films of Ba2YCu3O
x
were fabricated on polycrystalline zirconia ZrO2-Y2O3 (PSZ) substrates for the first time by a dip coating technique using an ethanol solution of highly concentrated mixed alkoxides of the component metals (0.6 mol/l). The thickness of the films prepared ranged 2.1–0.8 µm and the best sample showed T
c(onset)=94 K and T
c(zero)=60 K.
Effect of Argon Ion Bombardment on Internal Stress in Evaporated Co-Cr Film
Authors: Awano Haruo , Sato Takanori
Published: February 2005

The amount of Ar in evaporated Co-Cr film increases linearly with increasing argon ion flux density divided by the deposition rate of Co-Cr. The tensile internal stress decreases and then becomes compressive as the amount of Ar increases. The average energy imparted to Co and Cr atoms by argon ion bombardment during deposition is estimated to be about 17 eV at the point at which tensile internal stress becomes compressive. This energy is about 100 times that imparted during vacuum deposition. The number of cracks decreases and the spacing of the (00 ·2) planes increases as the tensile internal stress decreases.
n-InSb Point Contact Warm Carrier Infrared Laser Detectors
Authors: Yasuoka Yoshizumi , Okuda Takahisa , Inoue Narumi
Published: February 2005

Point-contact warm carrier devices were fabricated using n-type InSb instead of p-type Ge. The incident angle dependence of the detected voltage was measured at 10.6 µm and 118 µm laser radiations. It was confirmed that the detected signal of the fabricated devices was due to the induced current by antennae and not due to the photon-drag effects.
Effect of Heat Treatment on the Crystalline Quality of ZnSe Epilayers Grown by Metalorganic Vapor Phase Epitaxy
Authors: Yodo Tokuo , Yamashita Ken
Published: February 2005

Thermal stability of ZnSe epilayers grown at the low growth temperatures of 250–300°C by MOVPE depends heavily on growth conditions, particularly the reactor pressure. The high density of deep centers is generated from the surface and diffuses into the epilayer by treating the epilayer at a temperature above 600°C under H2 atmosphere only. However, the increase of deep centers is effectively prevented by mixing dimethylzinc (DMZ) in the atmosphere even at the high temperature of 700°C. Probably, the partial pressure of Zn vapor in the ambience would suppress the generation of Zn vacancies at the high temperature.
Temperature and Composition Dependences on the Electrical Properties of As-grown ZnHgTe Crystals Grown by the Travelling Heater Method
Authors: Sasaki Tokuhito , Taguchi Tsunemasa , Hiraki Akio
Published: February 2005

Temperature dependence on the electrical properties of unintentionally-doped Zn
x
Hg1-x
Te bulk crystals, grown by the travelling heater method with a Te solvent, has been investigated by means of the Hall measurements at temperatures in the range 77 to 300 K. The crystals grown from x=0.02 to 0.8 at about 700°C, exhibited typically n-type conduction at 300 K. In particular, the electron Hall mobility of x=0.2 was about 104 cm2/(V ·s) at about 150 K, and from its temperature dependence a donor level was located at about 12 meV below the conduction band. The electron mobility at 300 K decreased remarkably due to alloy scattering with increasing composition x. We observed anomalous behavior in the temperature dependence of the hole mobility above x=0.33; a maximum value was reached at about 4×103 cm2/(V ·s) at 77 K.
Modulation-Doped In0.5Al0.5P/GaAs Field-Effect Transistors
Authors: Ohba Yasuo , Watanabe Miyoko O. , Kawasaki Hisao , Kamei Kiyoo , Nakanisi Takatosi
Published: February 2005

In0.5Al0.5P/GaAs modulation-doped field-effect transistors (MODFETs) have been fabricated to study the applicability of In0.5(Ga1-x
Al
x
)0.5P/GaAs heterostructures to electronic devices. A DC transconductance of 250 mS/mm and a noise figure of 1.7 dB with associated gain of 10 dB at 12 GHz were obtained for a MODFET with a 0.25 µm-long and 200 µm-wide gate. Improvements in the performance are expected by Al-composition optimization for the InGaAlP. These results show the promising potential of In0.5(Ga1-x
Al
x
)0.5P/GaAs MODFETs as high-frequency and high-speed devices.
Time-Resolved FT-IR Study of Electric-Field Induced Homogeneous-to-Homeotropic Transition of Nematic 4-Pentyl-4'-cyanobiphenyl
Authors: Toriumi Hirokazu , Sugisawa Hisashi , Watanabe Hiroshi
Published: February 2005

A time-resolved FT-IR study of electric-field induced homogeneous-to-homeotropic transition of nematic 4-pentyl-4'-cyanobiphenyl (5CB) is reported. A homogeneous 5CB sample exhibits a bond orientational order parameter S
b=0.40 for the C ≡N stretching band and for the phenyl C–C stretching band, both polarized parallel to the para-axis of the cyanobiphenyl core. Transition to the homeotropic structure under a DC pulse field requires an induction period of ca. 5 ms, and takes place in the 5∼10 ms region. The potential applicability of the FT-IR time-resolved spectroscopy in the study of dynamic properties of liquid crystals is emphasized.
New Icosahedral and Amorphous Phases in Mg-Al-Ag System Prepared by Liquid Quenching
Authors: Inoue Akihisa , Nakano Koh , Bizen Yoshio , Masumoto Tsuyoshi , Chen Ho Sou
Published: February 2005

New icosahedral (I) and amorphous (Am) phases in the Mg-Al-Ag system have been produced by liquid quenching. Their formation extends in wide ranges of 30 to 67%Al and 3 to 30%Ag for the I-phase and 5 to 30%Al and 3 to 30%Ag for the Am-phase. Thus, the change of the ratio of Al to Al+Mg brings about a drastic structural change. The decomposition temperature and electrical resistivity at 273 K are 435 to 540 K and about 130 µΩcm for the I-phase and 352 to 412 K and about 80 µΩcm for the Am-phase and the I-phase alloys have a higher thermal stability and higher resistivity than the amorphous alloys.
Epitaxial Lateral Overgrowth of GaAs by LPE
Authors: Nishinaga Tatau , Nakano Tsuyoshi , Zhang Suian
Published: February 2005

Epitaxial lateral overgrowth (ELO) of GaAs on SiO2 film was successfully performed by LPE. It was found that the lateral overgrowth on (111)B substrate was the slowest when the stripe opening in SiO2 film oriented in the <1̄10 > and equivalent directions, while it was the fastest when the stripe oriented in the <112̄ > and equivalent directions. In the latter case, a large lateral to vertical growth velocity ratio (up to 50) of epitaxial GaAs was achieved. RC etching revealed that the etch pit density in the lateral epitaxial GaAs was found to be extremely low.
Preparation of Black Phosphorus Single Crystals by a Completely Closed Bismuth-Flux Method and Their Crystal Morphology
Authors: Baba Mamoru , Izumida Fukunori , Takeda Yuji , Morita Akira
Published: February 2005

Needle-shaped and film- or plate-shaped black phosphorus single crystals were prepared by an improved bismuth-flux method. The conversion of red phosphorus to white phosphorus and the growth of black phosphorus single crystals from the solution of white phosphorus in liquid bismuth were performed in an evacuated quartz-glass apparatus without breaking the vacuum. Needle crystals measured about 5 mm in length and 10 to 100 µm in thickness. The thickness of film or plate crystals ranged from 1 to 10 µm and the width was usually above 100 µm, generally increasing with decreasing thickness. Some crystal morphologies were observed and analyzed crystallographically.
High Efficiency Amorphous Silicon Solar Cells with “Delta-Doped” P-Layer
Authors: Kazama Yoshiyuki , Seki Kazuhisa , Kim Woo-Yeol , Yamanaka Satoshi , Konagai Makoto , Takahashi Kiyoshi
Published: February 2005

Novel a-Si p-i-n solar cells with “delta-doped (δ-doped)” p-layers were shown to enhance the hole concentration of the p-layers. A high photoconductivity of 1 ×10-4 Scm-1 (AM1, 100 mWcm-2) was obtained using a δ-doped p-layer. The existence of δ-deped boron layers was confirmed by cross-sectional TEM (transmission electron microscope) observations. A conversion efficiency of 11.5% was obtained for glass/TCO/p-i-n/Al solar cells with δ-doped p-layers. The photovoltaic characteristics of δ-doped p-layer solar cells exhibited a high open-circuit voltage of over 0.9 V, which is higher than that of solar cells with a conventional a-SiC p-layer. We furthermore investigated the stability of solar cells with δ-doped p-layers.
Numerical Study of Amorphous Silicon Based Solar Cell Performance Toward 15% Conversion Efficiency
Authors: Yamanaka Satoshi , Konagai Makoto , Takahashi Kiyoshi
Published: February 2005

A detailed theoretical analysis of a-Si based solar cells has been performed using a comprehensive computer simulation model in order to clarify the factors limiting the cell performance. We simulated how the solar cell characteristics are influenced by the variations of various factors. As a result, it was found that the solar cell performance was seriously affected by low conductivity in the a-SiC p-layer and the density of D-states in the i-layer. Based on all of the theoretical results, we predict that a conversion efficiency of over 15% can be potentially realized for the a-Si based single-junction solar cell when the enhancement of the carrier concentration in the p-layer (greater than 1018 cm-3) and the decrease of the density of D-states in the i-layer (to about one fifth of the present state-of-the-art value) are achieved and the device structure is optimized.
Thermo-Optic Effect in Smectic-Cholesteric Mixed Liquid Crystals
Authors: Nawa Nobuhiko , Liu Wen-rui
Published: February 2005

In this paper attention has been focused on the thermo-optic effect observed in the cooling process from the cholesteric phase to the smectic A phase. The transmission of the final smectic A texture depends on the initial cholesteric texture. From the microscopic observation, it is found that the focal conic texture in the cholesteric phase changes to the transparent smectic homeotropic texture, while the planarlike texture in the cholesteric phase changes to the smectic scattering texture. This causes different types of thermo-optic effects. The relaxation occurring just below the transition temperature plays an important role in the thermo-optic effect. The characteristics of the thermo-optic effect relating to the cooling rate and the cell parameters are also investigated.
Surface Diffusion Length of Gallium during MBE Growth on the Various Misoriented GaAs(001) Substrates
Authors: Shitara Tomoya , Nishinaga Tatau
Published: February 2005

The previous theoretical work on MBE of GaAs, which is based on the 2D-nucleation and surface diffusion, has been expanded to take into account the surface diffusion of arsenic as well as that of gallium. MBE experiments were carried out on the GaAs(001) substrates which were misoriented from (001) toward [110], [1̄10], or [100]. By measuring the critical temperature at which RHEED intensity oscillation begins to appear, the critical conditions for the mode transition were obtained. With the present theory and the experimental data, the surface diffusion length of gallium is evaluated and the origin of its anisotropic behavior of gallium is discussed.
Simple Gas Sensor Using Dye-Doped Plastic Fibers
Authors: Muto Shinzo , Ando Akitoshi , Ochiai Tatsuo , Ito Hiroshi , Sawada Hitoshi , Tanaka Akira
Published: February 2005

We report the fully optical sensing of low-level alkalescent gas and acid gas realized by the combination of dye-doped plastic fibers operating as the gas sensitive fiber and the fiber light source. This simple system was demonstrated to be capable of achieving a detection sensitivity below 10 ppm for both of ammonia and hydrochloride gases.
Nitridation Perturbed Tin Diffusion in Silicon
Authors: Marioton B. P. R. , Gösele U.
Published: February 2005

The influence of surface nitridation on the diffusion of tin in silicon at 1100°C has been investigated. Nitridation, which is associated with vacancy generation, has been found to enhance tin diffusion. This is expected since the large tin atoms should prefer to diffuse via vacancies. Based on the value of the vacancy supersaturation generated by nitridation of bare silicon reported in the literature, it is estimated that 33% of tin diffuses via vacancies. However, the actual percentage may be higher, since the high tin concentration may influence the nitridation-induced vacancy generation. The influence of oxidation, also studied, did not yield meaningful results.
Excitonic Effects in the Optical Spectrum of InP
Authors: Adachi Sadao
Published: February 2005

A calculation of the real (ε
1) and imaginary (ε
2) parts of the dielectric function of InP at energies below and above the fundamental absorption edge is presented. This model includes the E
0, E
0+Δ
0, E
1, E
1+Δ
1 and E'0 (E'0+Δ'0) gaps as the main dispersion mechanisms. The model is also made to account for the excitonic effects at these critical points (CP's). A model analysis indicates that the inclusion of the excitonic effects in our one-electron model corrects the strength of the peaks in the correct direction with experimental information. Detailed analyses are presented for InP in the temperature range between 30 and 740 K, and results are in satisfactory agreement with the experimental data over the entire range of photon energies (0.0-6.0 eV). The temperature dependence of the strength and the broadening parameters at each CP are also given and discussed.
Perpendicular Magnetic Anisotropy in Sputtered CoPd Alloy Films
Authors: Hashimoto Shunichi , Ochiai Yoshitaka , Aso Koichi
Published: February 2005

Magnetic properties of CoPd alloy films prepared by rf magnetron sputtering were studied as a function of the Pd content. CoPd alloy films showed extraordinarily large magnetostriction the order of 10-4in a Pd-rich composition, and it was found that the perpendicular magnetic anisotropy was related to the magnetostrictive effect. The CoPd alloy films can be considered to be perpendicular magnetic recording material.
Diamagnetic Properties of TlBaCaCuO Superconducting Thin Films
Authors: Hatta Shin-ichiro , Ichikawa Yo , Adachi Hideaki , Wasa Kiyotaka
Published: February 2005

The diamagnetic properties of superconducting TlBaCaCu oxide thin films with (2212) phase were studied, using an rf SQUID susceptometer. The remanent magnetization was observed up to 98 K, which is higher than the zero-diamagnetization temperature in a magnetic field. In the hysteresis curve, diamagnetization remains during increasing of the external field, compared to the results for other oxide superconducting films. The remanent magnetization is decreased almost linearly with rising temperature. In the flux creep model, the activation energy of relaxation in remanent magnetization for this specimen was estimated to be about 0.1 eV.
Wide-Wavelength InGaAs/InP PIN Photodiodes Sensitive from 0.7 to 1.6 µm
Authors: Kagawa Shuzo , Inoue Kouichi , Ogawa Isao , Takada Yuji , Shibata Tomohiro
Published: February 2005

We have developed, for the first time, a wide-wavelength InGaAs/InP PIN photodiode for optical communication systems from 0.7- to 1.6-µm wavelength. The diode has a planar structure with an InP/InGaAs/InP double-hetero epitaxial wafer grown by chloride VPE. To obtain a highsensitivity to 0.7-µm wavelength light, we introduced a very thin InP cap layer (0.06 µm) and a shallow pn junction (0.27µm). Using this structure, we obtained a quantum efficiency of 76% for 0.78-µm light and 81% for 1.3-µm light. Dark current and capacitance are only 30 pA and 0.53 pF at 5 V. The frequency response is flat up to 1 GHz above 5 V at 0.78 µm.
Electronic States of Zn in GaAs and a Consideration on Its Anomalous Diffusion Phenomena
Authors: Fukushima Kimichika , Adachi Hirohiko
Published: February 2005

Electronic states of impurity zinc atoms in gallium arsenides (GaAs) are calculated for model clusters by means of the DV-Xα molecular orbital computational method. The result shows that the bond between the Zn in an interstitial site and the surrounding As atoms is weaker than that in a substitutional site, indicating that the Zn in GaAs has a tendency to diffuse through the interstitial sites. It is also found that the interstitial and the substitutional Zn atoms interact rather strongly to form the σ bond of 4p orbitals. This suggests that the mobility of the substitutional Zn becomes smaller by the bonding interaction with the substitutional Zn which is less mobile. These effects qualitatively explain the strong concentration dependence of zinc diffusion in GaAs.
Computer Simulation of the Growth of Ni on a Ni(111) Surface
Authors: Kaneko Takeo , Kageyama Kensuke , Sasaki Tsutomu , Yamamoto Ryoichi
Published: February 2005

We simulated the growth of metal films and investigated the relationships between their change of surface step densities and growth conditions. We modeled surface migration by the Arrhenius relation and considered two cases of decomposition of clusters. In the first case, no decomposition of cluster takes place, and in the other case cluster decompositions are taken into account. When the substrate temperature was above 430 K, clear periodic oscillations of the number of steps on the surface were observed in both cases. The amplitude of the oscillation for the no-decomposition model was larger than that in the decomposition case. However, the number of steps was smaller and the growing surface was flatter in the latter case.
Radiation Damage of Silicon Junction Photodiodes by Evaporation Neutrons from Nuclear Spallation Reactions with 12 GeV Protons
Authors: Arima Tatsumi , Asano Yuzo , Hasegawa Masami , Mori Shigeki , Kondo Takahiko , Noguchi Masaharu , Ohsugi Takashi , Taketani Atsushi
Published: February 2005

Radiation damage effects of silicon PIN photodiodes were studied by using evaporation neutrons from nuclear spallation reactions of a copper target with 12 GeV protons. Photodiode samples were placed in the backward direction from the copper target and neutron flux was determined by the foil activation method. The average neutron energy was estimated to be about 6 MeV. The damage effects were observed in terms of the increase of leakage current with reverse voltage which is expected to be approximately proportional to radiation dose of neutrons. The present result of the leakage current constant is of the order of 3 to 4 times those measured by using identical photodiodes exposed to reactor neutrons with the average energy of about 2 MeV. The observed energy dependence of the leakage current constant can be qualitatively explained by the NRT model.
Development Methods for Submicron Optical Lithography
Authors: Endo Masayuki , Sasago Masaru , Nakagawa Hideo , Ueno Atsushi , Nomura Noboru
Published: February 2005

The effects of development methods on resist pattern fabrication have been examined. The automated immersion, puddle and spray development methods can be compared and characterized. The immersion development could fabricate high-aspect-ratio 0.6 micron line-and space patterns and had the largest process latitude for submicron optical lithography. The spray development has been found not to be good except for sensitivity.
Extended Appearance Potential Fine Structure Analysis of Zinc Oxide
Authors: Konishi Ryōsuke , Arioka Masato , Sasakura Hiroshi
Published: February 2005

We attempted to analyze the fine structure above Zn-M2,3 appearance potential spectra of transparent conductive (TCO) ZnO thin film. The analysis was done in two different cases. One in which the effect on the fine structure from the Zn-M1 edge is considered and the other is in which it is not. From the results of the analyses, it can be considered that there is no effect from the Zn-M1 edge. The nearest-neighbor atomic spacing of the TCO ZnO film is 0.202 nm. This value is in good agreement with that of SEELFS.
Analysis of Chemical Amplification Resist Systems Using a Kinetic Model and Numerical Simulation
Authors: Fukuda Hiroshi , Okazaki Shinji
Published: February 2005

A kinetic model for chemical amplification resist systems, including a post exposure baking (PEB) process, is proposed. A negative tone EB resist SAL601 (Shipley) subjected to excimer laser exposure is investigated to examine the validity of the model. It is shown that the model can well explain the resist's crosslinking and development characteristics over a wide range of exposure and PEB conditions. Using the model, the catalytic chain length and process optimization are discussed from an analytical approach. Application of the model to resist profile simulation is also shown. The simulated resist profiles exhibit good agreement with the real resist pattern profiles.
Characteristics of Adhesion between Photoresist and Inorganic Substrate
Authors: Nagata Hitoshi , Kawai Akira
Published: February 2005

The adhesion of positive photoresist film to some inorganic substrates used as LSI substrate material in dry and wet conditions has been investigated based on surface chemistry. The method of surface energy treatment is used to predict the adhesion energy. The contact angle method is used to measure the surface energy of each substrate. The correlation between the value of two components of surface energy, the polar and the dispersion parts, and adhesion strength is discussed. It is important to control the polar part of surface energy of a substrate in order to achieve high adhesion strength.
Low Temperature Silicon Surface Cleaning by HF Etching/Ultraviolet Ozone Cleaning (HF/UVOC) Method (I) –Optimization of the HF Treatment–
Authors: Suemitsu Maki , Kaneko Tetsuya , Miyamoto Nobuo
Published: February 2005

Several variations of fluoric acid (HF) treatments of silicon substrates were examined for their adaptability as a pretreatment method for a silicon epitaxy process. Treatments with and without distilled, deionized (DI) water rinse, of different HF concentrations, and of different methods of HF supply were tested and their residual carbonic impurity contents were measured using RHEED. As a result, HF treatments by themselves were found to be insufficient in passivating the surface dangling bonds irrespective of the method of HF supply: dipping into the solution or exposure to the vapor. The optimum procedure of HF treatment thus proposed is a succession of (a) HF dipping, (b) DI-water rinsing, (c) nitrogen-gas blowing, and (d) UV-ozone cleaning.
Superconductive Wire Bonding with High Reliability at 4.2 K
Authors: Ogashiwa Toshinori , Inoue Akihisa , Masumoto Tsuyoshi
Published: February 2005

A superconductive bonding technique for superconducting electronic devices such as the DC-SQUID was developed by using a rapidly solidified Pb76In20Au4 (at%) wire. The wire was bonded on the Nb pad coated with 30 nm-thick Au film to form the superconducting connection operating at 4.2 K. Mechanical stability of the wire bond parts remains unchanged by 15 thermal cycles in the temperature range 4.2 to 273 K. No appreciable degradation of the superconducting connection is observed even after the thermal cycling. These results lead us to expect that the present bonding technique will be useful in practical applications.
Chevron Layer Structure and Parabolic Focal Conics in Smectic A Liquid Crystals
Authors: Ouchi Yukio , Takanishi Yoichi , Takezoe Hideo , Fukuda Atsuo
Published: February 2005

The smectic A layer structures of homogeneously aligned 8CB and 4O.8 liquid crystals have been studied by X-ray diffraction analysis. It has been confirmed that the homogeneously aligned SmA cell is frequently characterized by the chevron layer structure with an array of elongated parabolic focal conics or by the tilted layer structure with the undulation pattern texture. This behavior is caused by the layer thinning and is generally affected by the cell thickness. The layer tilt angle of the chevron structure often depends on a phase sequence and a thermal history; for example, when a homogeneously aligned 4O.8 cell has cooled down to a SmB phase from a SmA phase, the layer tilt angle in the SmA phase in the heating process becomes two times larger than that in the cooling process.
Patterning Characteristics of ITO Thin Films
Authors: Inoue Mayumi , Matsuoka Tomizo , Fujita Yosuke , Abe Atsushi
Published: February 2005

The relationship between patterning characteristics and other (such as microstructural and electroptical) characteristics which depend on sputtering conditions, especially the substrate temperature and oxygen partial pressure, was investigated in ITO films prepared by the rf magnetron sputtering method. Sputtering conditions that satisfied both the patterning and electroptical characteristics were found to exist and ought to be precisely controlled since the postannealing of ITO films does not necessarily improve the patterning characteristics. The films showing superior patterning characteristics had dense microstructures without pores and simultaneously exhibited fairly low etching rates and low resistivities.
Epitaxial Growth of ZnTe on GaAs(100) by RF Sputtering
Authors: Tokumitsu Yoji , Kitayama Haruyuki , Kawabuchi Akira , Imura Takeshi , Osaka Yukio
Published: February 2005

ZnTe is deposited epitaxially by rf sputtering on the clean surface of GaAs(100) substrate from which the surface native oxides have been etched away by H2 plasma treatment. The crystalline quality of ZnTe films, which depends on the substrate temperature, is evaluated by means of optical measurements and RHEED pattern observation. A ZnTe film prepared at a substrate temperature of 320°C is deposited epitaxially.
Preparation and Formation Process of TlBa2Can-1CunOy
Authors: Sugise Ryoji , Ihara Hideo
Published: February 2005

The Tl–Ba–Ca–Cu–O compounds, TlBa2Ca
n-1Cu
n
O
y
(n = 1–5), with a single Tl–O layer and multiple Cu–O layers per unit cell were prepared. The formation process of these phases was studied. The numbers of Cu–O and Tl–O layers were influenced by the thallium content. Control of the thallium content was essential to prepare the desired phases in the Tl–Ba–Ca–Cu–O system. The value of T
c increased with increasing number of Cu–O layers (1≤n ≤4). At n=5 T
c was lower than that at n =4. Therefore, the highest T
c value was obtained at n=4.
Stabilization of a CW Mode-Locked YAG Laser Using Feedback with an Acousto-Optic Modulator
Authors: Matsumoto Takahiro , Baba Motoyoshi , Kuga Takahiro , Matsuoka Masahiro
Published: February 2005

We have achieved reduction of the power fluctuation of the second harmonic of a cw mode-locked YAG laser from 5% to less than 0.1% using a feedback loop with an acoustic loss modulator inside the laser cavity. By using the second harmonic of this laser as a pumping source, we have also reduced the output power fluctuation of a synchronously pumped dye laser at low frequencies.
Dependence of Spatial Gain Distribution on Gas-Flow Velocity and Discharge Current in a Fast-Axial Flow CO2 Laser Amplifier
Authors: Tsuchida Eiichi , Sato Heihachi
Published: February 2005

Taking into account the radial distributions of the gas-flow velocity v, the discharge current I
dis, the gas temperature T and the effective pumping rate ηe, we theoretically derive the gain coefficient γ as a function of the radial distance from the plasma-tube axis for a fast-axial flow (FAF) CO2 laser amplifier. For various combinations of v and I
dis, the calculated γ's are compared with the experimental results corresponding to both laminar and turbulent flows, resulting in good agreement in both cases. Increase of v leads to a linear enhancement of γ: for example, γ becomes about two times larger with increasing v from 80 to 180 m/s, while there is an optimum current near 45 mA to provide the highest gain in our FAF system. It is especially noteworthy that the high-gain region tends to spread towards an area far off-center of the discharge tube axis with increasing v, and its spreading area becomes significantly broader at a turbulent flow greater than v = 170 m/s.
High-Field Dielectric Dissipation Property in Low-Density Polyethylene Film
Authors: Tokoro Tetsuroh , Nagao Masayuki , Kosaki Masamitsu
Published: February 2005

The high-field dielectric dissipation factor (tan
δ) of low-density polyethylene (LDPE) films was studied as a function of the applied ac field and the voltage application period. The measurements were made at room temperature by means of a current comparator-type capacitance bridge. As the applied ac field increased, the high-field tan
δ increased gradually. With the voltage application period, the high-field tan
δ first increased and then decreased, exhibiting a peak. This time variation of tan
δ was accelerated with increase in the applied electric field. These characteristics of the high-field tan
δ in LDPE films are discussed on the bases of the carrier generation in the bulk due to the modified Poole-Frenkel effect, the carrier injection from the electrodes, the trapping of the carriers and the formation of the space charge layer in front of the electrodes.
Anodically Electrodeposited Iridium Oxide Films (AEIROF) from Alkaline Solutions for Electrochromic Display Devices
Authors: Yamanaka Kazusuke
Published: February 2005

Anodically electrodeposited iridium oxide films from alkaline solutions were investigated for application to electrochromic devices. Micro-crystalline (diameter: 15Å) films obtained by the electrolysis of aqueous alkaline solutions containing iridium chloride, oxalic acid and potassium carbonate showed good electrochromic reaction reversibility. The coloration efficiency of the films was about one third that of typical evaporated tungsten oxide films, and the response rate measured by the amount of injected charge was about double. The cycle lives of the cells, composed of electrodeposited films, 1M H3PO4-NaOH (pH=3∼5), and an activated carbon cloth, were more than 8 × 106 with a 0.6 V, 1 Hz continuous square wave.
Removal of Zig-Zag Defects in Surface-Stabilized Ferroelectric Liquid Crystal Cells
Authors: Bawa S. S. , Saxena Kanchan , Chandra Subhas
Published: February 2005

We have succeeded in eliminating the zig-zag type of defects of surface-stabilized ferroelectric liquid crystal cells by applying an alternating electric field of suitable frequency to polyamide-coated rubbed glass plates. This has been achieved in those cases of sample thickness in which the oscillatory movement in the hairpin texture associated with the zig-zag defects occurs on the application of the ac field. The sample shows uniform contrast, remains defects free even after the removal of the field, and exhibits the characteristics of fast-switching bistable SSFLC displays.
Microscope Observation of the Process of the Pressure-Induced Phase Transition of RbCl by Means of a Diamond Anvil
Authors: Okano Yoji , Nomura Motoyuki
Published: February 2005

A precision driver for the diamond-anvil cell in which the diamond-anvil cell was thrust up with the external load created by the compressed gas was built. Using the new driver, clamping of the diamond-anvil cell was executed successfully at the desired magnitude of the external load, which was confirmed by the measurement of the volume of RbCl as a test sample charged in the diamond anvil mounted on the four-circle automatic X-ray diffractometer. The microscope observation of RbCl was made at each stage of the phase transition through the diamond anvil. It was confirmed that the crystalline nuciei appearing at the initial stage of the phase transition were spread over the entire surface of the sample with the increment of the external load.
Nickel Suilicide Phase Transformation during Post-Annealing and Related Schottky Characteristics
Authors: Kikuchi Akira
Published: February 2005

Nickel silicide was formed by heat-treating Ni film on single-crystal Si. X-ray diffraction and resistivity measurements revealed that heat treatment at 300°C resulted in the formation of Ni-rich silicides, which were converted to NiSi during post-annealing above 400°C. Schottky barrier height of Ni silicide was examined in relation to phase differences. Barrier height was found to be unaffected by silicide phase.
Improvement of Ge/AlGaAs Air-Exposed Interfaces Grown by MBE and Their Application to n+-Ge Gate AlGaAs/GaAs MISFETs
Authors: Maezawa Koichi , Mizutani Takashi
Published: February 2005

The properties of air-exposed Ge/AlGaAs hetero-interfaces were studied with the aim of improving them. Based on C-V measurements of n+-Ge gate MIS diodes it was found that the thermal etching of a 30 nm GaAs cap layer, which passivates the AlGaAs surface during air-exposure, drastically improves the interface properties. It was also found that the dominant factor determining the properties of the air-exposed hetero-interfaces is not the thermal etching temperature itself but the etching depth. The reduction mechanism of the interface charges is discussed based on SIMS and TEM measurements. It is shown that structural imperfections such as interface disorder and/or dislocations play an important role in determining the interface properties. The above results were successfully applied to an n+-Ge gate MISFET using a pattern inversion process.
Surface Residence Time Measurements of Ba Atoms by Molecular Beam Relaxation Spectrometry
Authors: Yaguchi Tomio , Yamamoto Shigehiko
Published: February 2005

Molecular beam relaxation spectrometry has been applied to measure the residence time of Ba atoms on such refractory metal surfaces as W and W-26Re, which are commonly used as substrates for dispenser cathodes. It is found that there are at least two chemisorption states on both metal surfaces, which yield different residence times at the same temperature. The chemisorption energies of Ba on W-26Re surface are found to be 2.4 and 0.4 eV respectively. The dependency of the residence time (signal phase shift) on the Ba impinging flux suggests the existence of a third adsorption state. In the dispenser cathode operation temperature range, 900–1200°C, the role of the highest energy chemisorption sites is crucial in determining the surface coverage of the mono-atomic order layer, the electric dipole of which reduces the work function, thus enhancing electron emission of dispenser cathodes.
Diffusion Properties of Mg in AlxGa1-xAs
Authors: Mukai Seiji , Kaneko Yasuyuki , Nukui Toru , Mori Masahiko , Watanabe Masanobu , Itoh Hideo , Yajima Hiroyoshi
Published: February 2005

Mg is diffused into Al
x
Ga1-x
As layers at 785°C from a Ga solution containing 0.1 wt% Mg and saturated with As. Secondary ion mass spectroscopy and differential Hall measurement reveal that the depth profile consists of a high-Mg-concentration region near the surface and a lower-concentration plateau inside. Diffusion into GaAs, Al0.5Ga0.5As, and Al0.7Ga0.3As for 20 min results in diffusion fronts at about 2, 4, and 6 µm from the surface. The depth with a fixed hole concentration varies in proportion to the square root of the diffusion time both in GaAs and Al0.35Ga0.65As.
671 nm GaInAsP/AlGaAs Visible DFB Lasers with Ridge-Waveguide Structure Grown by LPE
Authors: Chong Te-Ho , Kishino Katsumi
Published: February 2005

A transverse-mode controlled distributed feedback (DFB) GaInAsP/AlGaAs laser with a ridge-waveguide structure emitting at 671 nm in wavelength, fabricated by two-step liquid phase epitaxy was demonstrated for the first time. The third order grating with 2910 Å period on the GaInP guide layer was employed for the light feedback. Fundamental transverse mode operation in TE was observed at the current level more than 1.3 times the threshold. The DFB mode operation in a single longitudinal mode was maintained in the temperature range of 35°C, with a lasing wavelength shift as small as 0.04 nm/deg.
Hign-Power Long-Cavity T3 Laser with a Very Narrow Beam
Authors: Shima Akihiro , Yamawaki Takeshi , Saito Hiroyuki , Matsubara Hiroshi , Kumabe Hisao , Susaki Wataru
Published: February 2005

A 790 nm AlGaAs laser with a thin tapered thickness active layer (T
3 laser), whose cavity length is 350 µm, has been developed. As the beam divergence of the laser becomes narrower, the threshold current does not increase. Both the current density and the thermal resistance can be reduced by extending the cavity length of the laser. The laser emitted a light output power over 100 mW even at 80°C and proved to have a fundamental transverse mode at least up to 120 mW. The stable 50 mW operation at 50°C over 2000 hours has been confirmed.
Effects of Hg Annealing on Photoluminescence Spectra of CdTe Crystals and MOCVD-Grown CdTe/GaAs Films
Authors: Ohba Katsuhiko , Taguchi Tsunemasa , Onodera Chikara , Hiratate Yukio , Hiraki Akio
Published: February 2005

Annealing effects on CdTe crystals and CdTe/GaAs films in Hg have been investigated through the spectral changes of PL (photoluminescence) at 4.2 K. Before annealing, the PL spectrum of CdTe crystals or films is dominated by the excitonic-emission lines, the edge-emission band and two broad bands. After annealing, a marked decrease in intensity of the broad and edge-emission bands in the bulk crystals is observed, while an increase in intensity of the broad bands in the MOCVD-grown CdTe is significant. We will point out from the PL investigations that the Hg annealing plays an important role in the improvement of both the surface and bulk properties.
Photoconductivity of O2-Doped Poly-p-Phenylene Sulfide Films
Authors: Takimoto Akio , Tanaka Eiichiro , Watanabe Masanori
Published: February 2005

The photoconductivity of O2-doped PPS was studied. The oxygen doping was performed by annealing in pure oxygen at a temperature below the melting point of PPS. The photoconductivity of the doped PPS was four orders of megnitude larger than that of pristine PPS. The photo- and dark conductivity were reversible for oxygen doping and deoxidization.