bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of the High-Tc Phase of Bi-Sr-Ca-Cu-O Superconductor
Authors: Endo Utako , Koyama Satoshi , Kawai Tomoji
Published: February 2005

Co-decomposition of mixed nitrates of Bi, Pb, Sr, Ca and Cu around 830°C under low oxygen pressure led to the formation of a high-T
c superconducting phase of Bi(Pb)-Sr-Ca-Cu-O with T
c(zero) at 107.5 K. A sample prepared by a conventional solid state reaction method under low oxygen pressure also showed the superconducting transition at 107.5 K. X-ray powder diffraction and magnetic susceptibility measurements on these samples revealed the high-T
c phase without 80 K or semiconducting phase. The reaction under low oxygen pressure has an effect to lower the temperature with broad ranges to render the high-T
c phase of the Bi-Sr-Ca-Cu-O.
Superconducting Films of YBa2Cu3Ox and Bi-Sr-Ca-Cu-O Fabricated by Electron-Beam Deposition with a Single Source
Authors: Terasaki Ichiro , Nakayama Yoshimi , Uchinokura Kunimitsu , Maeda Atsutaka , Hasegawa Tetsuya , Tanaka Shoji
Published: February 2005

Superconducting thin films of YBa2Cu3O
x
and Bi-Sr-Ca-Cu-O were made by electron-beam deposition with a sintered pellet as an evaporation source. With a c-axis orientation perpendicular to the substrates, YBa2Cu3O
x
grows on MgO(100) and Bi-Sr-Ca-Cu-O grows on SrTiO3(100), and the critical temperatures for zero resistivity were 78 and 72 K, respectively.
New Technique for Preparation of BiSrCaCuO Thin Films with Tc of 100 K and Above
Authors: Fukutomi Masao , Machida Junichi , Tanaka Yoshiaki , Asano Toshihisa , Yamamoto Takashi , Maeda Hiroshi
Published: February 2005

The successful growth of superconducting BiSrCaCuO thin films has been reported by a new process based on rf magnetron sputtering. The formation of a partially melted underlayer by controlling the substrate temperature during an early stage of the deposition process appeared to be responsible for a marked improvement in T
c. A zero-resistance temperature of 100 K and above was achieved with very high reproducibility when the film was deposited on MgO(100) substrate using a target of Bi1.3Sr1Ca1Cu1.5O
x
followed by annealing at 875°C for 0.5 h.
Electric Properties of the Y-Ba-Cu-O/Ag Interface
Authors: Mizushima Koichi , Sagoi Masayuki , Miura Tadao , Yoshida Jiro
Published: February 2005

The energy gap parameter 2 Δ induced in Ag, evaporated on an Y-Ba-Cu-O (YBCO) film, was determined by a quasi-particle tunneling experiment for a YBCO/Ag/PbO
x
/Pb junction. The energy gap 2 Δ was as large as 35 mV at 4 K and decreased almost linearly with an increase in temperature, vanishing at about 45 K. The same type of junction with a larger tunnel conductance showed a tunnel-type Josephson characteristic below the critical temperature of Pb.
X-Ray Absorption Studies of High-Tc YBa2Cu3Ox
Authors: Suzuki Yoshio , Sekiyama Hideo , Hirai Yasuharu , Hayakawa Kazunobu , Kajiyama Hiroshi , Hirano Tatsumi , Usami Katsuhisa , Takagi Kazumasa
Published: February 2005

The a Cu valency and local structure in high-T
c YBa2Cu3O
x
have been analyzed by X-ray absorption near-edge structure (XANES) and by extended X-ray absorption fine structure (EXAFS) techniques. The Cu valency is predominantly divalent. The evidence for trivalent Cu has not been observed. The radial distribution function around Cu ions indicates that an average of 4.1 oxygen atoms are present at 1.915 Å.
Direct Laser Beam Writing on YBaCuO Film for Superconducting Microelectronic Devices
Authors: Pandey H. C. , Jain Y. K. , Bhatnagar S. K. , Singh B. R , Khokle W. S.
Published: February 2005

Patterning of Y-Ba-Cu-O thin films has been accomplished using a pulsed Nd:YAG laser and a specially developed software for this purpose. Various structure of different dimensions and shapes have been generated. In contrast with other researchers this process does not require any mask and complete removal of the film material has been achieved. In addition the process does not suffer from the disadvantages/problems normally associated with photolithography, wet chemical etching and plasma etching of superconducting thin films. The process has tremendous potential particularly for fabricating superconducting microelectronic devices using Y-Ba-Cu-O thin films.
Thermal Variation of Imaginary Part of Permeability in Previously Photoexcited YIG Single Crystal
Authors: Hisatake Keizo , Matsubara Ikuya , Maeda Keiichiro , Fujihara Tutomu , Ichinose Noboru
Published: February 2005

A photoinduced decrease in permeability µ' is observed over 90% at 77 K in the highly pure single crystal of YIG grown by a floating zone method. Furthermore, an imaginary part of permeability µ'' is found to show an increase unlike µ' on illumination at 77 K and on warming the double peaks below 10 kHz. From the frequency dependence of these peaks, the activation energies obtained are 0.1 and 0.3 eV, respectively. The peak at lower temperature shows a maximum, whereas the other peak at higher temperature shows a monotonous increase with an increase of strength of illumination. These features have been discussed in terms of a two levels-two minima model.
Improvement in Soft Magnetic Properties of Heat-Treated Fe-C/Ni-Fe Multilayers
Authors: Kobayashi Toshio , Nakatani Ryoichi , Ootomo Shigekazu , Kumasaka Noriyuki
Published: February 2005

Ion beam-sputtered Fe-9 at%C/Ni-Fe multilayers are heat treated and the changes in their magnetic properties are examined. Relative permeability increases and coercivity decreases as the heat treatment temperature increases. The mean anisotropy field and magnitude dispersion also decrease with increasing temperature. The (110) plane distance decreases with the heat treatment, showing that compressive stress within the film is released. A film separated from the substrate has a decrease in the mean anisotropy field and magnitude dispersion. Thus, it can be concluded that heat treatment plays an important role in releasing stress.
Magnetic Transitions in the Y-Ba-Co-O System
Authors: Kimishima Yoshihide , Hirabayashi Shuichi
Published: February 2005

The DC magnetization M and magnetic susceptibility χ were measured for YBa2Co3O
y
sintered samples. The DC χ of a type 1 sample showed a ferromagnetic Curie-Weiss behavior in 100 K<T<350 K, and M increased steeply ferromagnetically at about 50 K. In the DC χ of the type 2 sample, the two anomalies appeared successively at 240 K and 280 K. The crystal field effect for the Co spin and the cancellation of magnetization were pointed out in this report.
A New Ray-Tracing Program Capable of Simulating Insertion-Device Synchrotron Radiation Sources
Authors: Muramatsu Yasuji , Ohishi Yasuo , Maezawa Hideki
Published: February 2005

A new ray-tracing program was developed to facilitate optical design of synchrotron radiation beam lines and monochromators. The program uses Monte Carlo modelling to simulate characteristics of insertion-device sources such as undulators and wigglers as well as those of normal bending magnets. The program is successfully applied to the optical design of monochromator systems for a new multipole wiggler/undulator beam line (BL16) at the Photon Factory.
Nature of Lattice Defects Induced by Excimer Laser Irradiation for Extrinsic Gettering
Authors: Sakai Akira , Ono Haruhiko , Ohshita Yoshio , Matsui Junji
Published: February 2005

Structure and thermal behavior of lattice defects in silicon induced by excimer laser irradiation, which is expected to be adopted as a new extrinsic gettering technique, were examined by transmission electron microscopy. Stacking fault tetrahedra and a peculiar type of dislocations which appeared in a V-shape were found in a melted and regrown layer of an as-irradiated sample. After subsequent heat treatment, slip dislocations were generated from the traces of laser beam shot and the stacking fault tetrahedra were mostly transformed into the V-shaped dislocations. These V-shaped dislocations were proved to be thermally stable and were expected to work as effective extrinsic gettering centers.
Application of Gd2O2S Ceramic Scintillator for X-Ray Solid State Detector in X-Ray CT
Authors: Yoshida Minoru , Nakagawa Manabu , Fujii Hideji , Kawaguchi Fumio , Yamada Hiromichi , Ito Yukio , Takeuchi Hiroshi , Hayakawa Takayuki , Tsukuda Yasuo
Published: February 2005

The quality of CT images depends on the characteristics of the X-ray detector. In place of conventional xenon ionization detectors, we have designed a highly efficient solid state detector with low detector noise by using a Gd2O2S ceramic scintillator.
Etching Technique to Reveal Dislocations in Thin GaAs Films Grown on Si Substrates
Authors: Nishikawa Hironobu , Soga Tetsuo , Mikuriya Nobuo , Jimbo Takashi , Umeno Masayoshi
Published: February 2005

Dislocations in GaAs and GaAs/Si are revealed by the etching technique at room temperature. The etchant is composed of H2O, K2Cr2O7, HNO3, HCl and H2SO4. The dislocation density of GaAs grown on Si by MOCVD using GaP and strained layer superlattices is about 1×106 cm-2.
Thermodynamic Analysis on Vapor Phase Epitaxy of GaAs by GaCl3 and AsH3 System
Authors: Koukitu Akinori , Hasegawa Fumio , Seki Hisashi
Published: February 2005

A thermodynamic analysis of the VPE growth of GaAs using GaCl3 and AsH3 is described. It is shown that most of the GaCl3 converts to GaCl and HCl at about 650°C and that the growth of GaAs is possible by the GaCl3 and AsH3 system without using a high temperature zone. The experimental features of the system can be explained well by equilibrium model.
Electromigration of Ag Ultrathin Films on Si(111) 7×7
Authors: Yasunaga Hitoshi , Sakomura Shigetoshi , Asaoka Takashi , Kanayama Seiji , Okuyama Naoki , Natori Akiko
Published: February 2005

Scanning Auger electron spectroscopy observation revealed that a patch of Ag thin film with a thickness of several monolayers spread on the cathode side over the clean surface of Si(111) 7×7 with the application of dc current to the Si substrate. The spread-out layer had the constant thickness of 1.0 monolayer (=7.8×1014 atom/cm2) with √3×√3 structure. On the anode side the edge of the patch made no significant movement but a mixed phase of √3×√3 and 3×1 with a thickness of 0.8 monolayer appeared and extended from the edge toward the cathode. The mass transport was correlated with changes in the structure of the overlayer.
Electronic States in Polythiophene and Poly(3-methylthiophene) Studied by Photoelectron Spectroscopy in Air
Authors: Yoshino Katsumi , Onoda Mitsuyoshi , Manda Yasuhisa , Yokoyama Masaaki
Published: February 2005

The difference of the energy of the top of the valence band in polythiophene and poly(3-methylthiophene) has been evaluated by photoelectron spectroscopy in air to be about 0.2 eV in coincidence with that obtained by cyclic voltammetry in electrolytes.
In the doped state of poly(3-methylthiophene) with BF4
-, the threshold energy of the photoemission has been found to decrease by about 0.4 eV compared with the undoped sample. This is discussed in terms of polaron state formation by doping.
Effects of Water on the Resistance-Temperature Characteristics of YBa2Cu3O7-y Oxides
Authors: Kishida Satoru , Tokutaka Heizo , Nishimori Katsumi , Ishihara Naganori , Watanabe Yoshihide , Noishiki Yoshio , Yamamoto Takayuki
Published: February 2005

We investigated the effects of water on the superconductivity of YBa2Cu3O7-y
specimens of different particle sizes and densities, which were prepared from the starting materials of Y2O3, Ba(NO3)2 and Cu(NO3)2·10H2O (referred to as specimen A) and Y2O3, BaCO3 and CuO (referred to as specimen B). The dependences of the T
c and the resistance at the normal state of specimens A and B on the time stored in water were different. This is thought to be caused by the differences of the particle sizes and the densities between specimens A and B. Large crevices were observed in the surfaces of specimens A and B stored in water. This may indicate that the corrosion products from the reaction with water are soluble in water.
The Superconductivity in the Bi-Sr-Ln-Cu-O System (Ln=Pr, Nd and La)
Authors: Den Tohru , Yamazaki Akira , Akimitsu Jun
Published: February 2005

The superconductivity in samples nominally described as Bi2(Sr1-x
Ln
x
)2Cu1+n
O
y
(Ln: lanthanide elements and yttrium: n=0 and 1) was investigated. The effect of an increasing T
C compared with that of Bi2Sr2CuO
y
was observed for Ln=La, Pr and Nd. The highest end-point of the transition temperature of Bi2(Sr1-x
Nd
x
)2CuO
y
was 20.4 K with x=0.25. Compounds described as Bi2(Sr0.95Ln0.05)2CuO
y
(Ln=Pr and Nd) had an onset T
C of about 60 K, and small but definite Meissner effects were also observed.
Upper and Lower Critical Fields of High-Tc Tl-Ba-Ca-Cu-O System
Authors: Iwasaki Hideo , Kobayashi Norio , Koike Yoji , Kikuchi Masae , Syono Yasuhiko , Noto Koshichi , Muto Yoshio
Published: February 2005

Magnetization and electrical resistance are measured on sintered Tl-Ba-Ca-Cu-O samples whose compositions are Tl:Ba:Ca:Cu=2:2:2:3, 2:2:3:3 and 2:2:1:2. The superconducting transition temperature T
c is 114 K for the 2:2:2:3 and 2:2:3:3 samples and is 98 K for the 2:2:1:2 sample. The difference in T
c comes from the numbers of perovskite-like layers between Tl2O2 layers. The upper critical fields H
c2 of the 2:2:2:3 sample increases linearly just below T
c (-(dH
c1/dT)
T
c
=13 kOe/K) and the lower critical field H
c1 increases monotonically with decreasing temperature down to 4.2 K (-(dH
c1/dT)
T
c
=4.5 Oe/K and H
c1(0)=500 Oe). From the results, some superconducting parameters such as ξ, κ, λ and H
c are calculated.
Critical Current Density of Bi-Pb-Sr-Ca-Cu-O Superconducting Ceramics
Authors: Matsuda Motohide , Iwai Yutaka , Takata Masasuke , Ishii Mamoru , Yamashita Tsutomu , Koinuma Hideomi
Published: February 2005

The critical current densities of Bi-Pb-Sr-Ca-Cu-O ceramics, which have a zero resistance state above 100 K, were studied. The critical current densities at 77 K under a zero magnetic field showed the low values (10∼20 A/cm2) in spite of T
c,zero=105 K and decreased drastically by applying the magnetic field.
Single Crystal X-Ray Structure Analysis of Bi2(Sr, Ca)2CuOx and Bi2(Sr, Ca)3Cu2Ox Superconductors
Authors: Imai Katsuhiro , Nakai Izumi , Kawashima Takuji , Sueno Shigeho , Ono Akira
Published: February 2005

Average crystal structures of Bi2(Sr, Ca)2CuO
x
and Bi2(Sr, Ca)3Cu2O
x
were analyzed using single crystal X-ray intensity data applying anisotropic temperature factors. Crystal data: Bi2Sr1.60Ca0.40CuO6, Bbmb, a=5.3826(8) Å, b=5.3761(11), c=24.384(7), R
w=0.108 for 282 reflections; Bi2.06Sr1.70Ca1.24Cu2O8, Bbmb, a=5.3946(8), b=5.3895(13), c=30.649(12), R
w=0.064 for 354 reflections. Precession photographs show that Bi2Sr1.60Ca0.40CuO6 has a monoclinic modulated structure and Bi2.06Sr1.70Ca1.24Cu2O8 has an orthorombic one. The incommensurate modulated structures were qualitatively illustrated by using a modulation wave model.
Simulation of Diffraction Intensity Distribution of a Superconductor Containing Stacking Faults in the Bi-Sr-Ca-Cu-O System
Authors: Onoda Mitsuko , Takekawa Shunji , Nozaki Hiroshi , Umezono Akihiko , Takayama-Muromachi Eiji
Published: February 2005

A superconducting material with a T
c∼110 K in the Bi-Sr-Ca-Cu-O system is liable to contain stacking faults as suggested by the broadened diffraction. The diffraction intensity is simulated by applying the matrix method based on assumed models of stacking faults. The calculated intensity distributions explain the features of the observed powder X-ray diffraction patterns of the high-T
c specimens.
Reproducible Processing for High-Tc Superconducting Tl-Ba-Ca-Cu-O-Phases
Authors: Itoh Mitsuru , Liang Ruixing , Urabe Kazuyori , Nakamura Tetsurō
Published: February 2005

In order to establish the reproducible processing for high-T
c superconducting Tl-Ba-Ca-Cu-O phases, three kinds of superconductive samples with different starting compositions of Tl:Ba:Ca:Cu=2:2:2:3, 2.5:2:2:3 and 3:2:2:3 were heat treated under various conditions. The optimum starting composition was found to be 2:2:2:3. A particular heat treatment of the 2:2:2:3 sample elicited polycrystalline materials showing a zero-resistance temperature at 120.3 K and an onset temperature of the diamagnetic shift at 127 K.
Effect of Substrate Temperature on the Crystalline State of Ba2ErCu3O7-x Superconducting Thin Films by rf Magnetron Sputtering
Authors: Mochiku Takashi , Kanke Yoko , Wen Zhongmin , Iguchi Ienari , Yamaka Eiso
Published: February 2005

The crystalline state of the Ba2ErCu3O7-x
thin films deposited at various substrate temperatures by rf magnetron sputtering are investigated. The as-sputtered films deposited above 650°C have a layered-perovskite structure which exhibits superconductivity by an annealing process in an oxygen flow. The annealed films have a better crystalline state and better superconducting properies than the films annealed after the deposition at lower substrate temperatures. The spatial distribution of the film composition across the thickness is also studied by Rutherford backscattering spectrometry.
The Effect of Annealing Time on the Superconductivity of Bi-Sr-Ca-Cu-O Film by High Pressure DC Sputtering
Authors: Lin R. J. , Wu P. T.
Published: February 2005

The strongly oriented superconducting Bi-Sr-Ca-Cu-O film on (100) MgO single crystal with T
c(onset)=104 K and T
c(zero)=80 K has been prepared by high pressure DC sputtering process. The superconductivity and the phases of the films annealed at 870°C are strongly related to the annealing time. The equilibrium phases are the semiconductor (peaks corresponding to the planar spacing d of 12.3 Å (2θ=7.2)) and a small fraction of insulator phases.
Superconducting YBa2Cu3O7-x Thin Films Prepared by Thermal Decomposition of Metallic Complex Salts
Authors: Maruyama Toshiro , Nishikawa Toshikazu
Published: February 2005

Superconducting YBa2Cu3O7-x
thin films of zero resistivity temperature 82 K were synthesized by thermal decomposition of naphtanic acid salts. For obtaining the film of zero resistivity temperature above 77 K, the film thickness above ca. 2 µm and adequate processing duration at 900°C were necessary.
Structural Distortions Induced by Pseudo Jahn-Teller Effect in the Y-Ba-Cu-O System
Authors: Bacci Mauro
Published: February 2005

Pseudo Jahn-Teller coupling constants are evaluated for the five-coordinated Cu2+ ion in the perovskite-like system YBa2Cu3O7-δ. On the basis of the obtained results rhombic static distortions are yielded in a very good agreement with the experimental data. The resulting electronic level scheme is then discussed in connection to the problem of the superconductivity in this material.
The Characterization of YBa2(Cu1-xCox)3Oy
Authors: Oda Yasukage , Toyoda Haruhisa , Kawaji Naoki , Nakada Ichiroh , Asayama Kunisuke
Published: February 2005

The detailed characterization of YBa2(Cu1-x
Co
x
)3O
y
has been made for various x values. The critical temperature is found to be constant in the small x region and then decrease linearly with x and abruptly vanish at a critical concentration. This result indicates a very different role of magnetic impurities in this compound compared with conventional superconductors. Two transition stages, which were independent of Co concentration, were observed in the ac susceptibility. This is concluded to be an intrinsic character of the Co substitution system. The results are discussed in comparison with other substitution systems.
The Formation Process of New High-Tc Superconductors with Single-Layer Thallium-Oxide, TlBa2Ca2Cu3Oy and TlBa2Ca3Cu4Oy
Authors: Sugise Ryoji , Hirabayashi Masayuki , Terada Norio , Jo Masatoshi , Shimomura Takehiko , Ihara Hideo
Published: February 2005

The formation process of new high-T
c superconductors with a single Tl-O layer, TlBa2Ca2Cu3O
y
(1223 phase) and TlBa2Ca3Cu4O
y
(1234 phase), was studied. The thallium content decreased continuously with increased sintering time. At the first sintering stage, the Tl2Ba2Ca2Cu3O
y
phase (2223 phase) was formed. Next, the 1223 phase was formed with the demise of the 2223 phase. Then, after further sintering, the 1234 phase was formed with the disappearance of the 1223 phase. These results indicate that one Tl-O layer of the double Tl-O layers of the 2223 phase evaporated owing to the volatility of the thallium component, and the 1223 phase was formed. Then the 1223 phase with three Cu-O layers changed to the stable 1234 phase with four Cu-O layers.
Analysis of the Linewidth of Distributed Feedback Laser Diodes Using the Green's Function Method
Authors: Kojima Keisuke , Kyuma Kazuo
Published: February 2005

To calculate the linewidth of distributed feedback laser diodes accurately, Green's function method was used. The discrepancy from the conventional theory is given by a correction factor, which is rather larger than unity with no mirror facets. The correction factor approaches unity by increasing the facet reflectivity or with a phase shifter.
Highly Efficient Second Harmonic Generation in p-Nitroaniline/Poly(lactone) Systems
Authors: Miyazaki Takeshi , Watanabe Toshiyuki , Miyata Seizo
Published: February 2005

The novel polymer system made up to the host-guest mixture of poly ( ε-caprolactone) and p-nitroaniline, spontaneously exhibits a large second harmonic generation (SHG) intensity 115 times as large as that of urea, or 3.3 times that of MNA. In addition, this material possesses good mechanical strength and long-term stability of the SHG activity over 1,000 hours.
Molecular Beam Epitaxial Growth of Stress-released GaAs Layers on Si(001) Substrates
Authors: Ogasawara Kazuto , Kondo Kazuo
Published: February 2005

The heteroepitaxial growth of GaAs on Si substrates was studied by RHEED, X-ray diffraction, and stress gauge measurements. The conditions for the pseudomorphic growth of GaAs monolayers on Si was determined. The monolayer growth technique was used for the two-step growth of thick GaAs layers on Si substrates. Stress-released 2 µm thick GaAs films were obtained at a growth temperature of about 420°C.
Simulation of the Ash Exhaust in a Fusion Engineering Reactor
Authors: Itoh Kimitaka , Ueda Noriaki , Itoh Sanae-I. , Sugihara Masayoshi
Published: February 2005

Numerical analysis of the plasmas in the divertor and scrape-off layer (SOL) of a fusion engineering reactor (FER) is made by using the two-dimensional time-dependent simulation code. The equation for plasmas in the SOL and divertor regions is solved for the given particle and heat sources from the main plasma, \varGammaoutandQT. For the given size of the pumping duct and the pumping speed, the necessary value of \varGammaoutfor the ash exhaust is discussed. Sufficient ash exhaust is possible under the condition which is consistent with the scaling law of the particle and energy confinement of the main plasma.
Formation and Phase Stability of Tetragonal Phase in Rapidly Quenched ZrO2-ErO1.5
Authors: Yoshimura Masahiro , Yashima Masatomo , Noma Tatsuo , Sōmiya Shigeyuki
Published: February 2005

In the system ZrO2-ErO1.5, inherent tetragonal phases of their contents of 4–12 mol.% ErO1.5 were obtained using a rapid quenching technique of their melts. The tetragonality (axial ratio c/a) decreased with ErO1.5 contents to the unity of the cubic phase with >14 mol.% ErO1.5. The transformability of these tetragonal phases into monoclinic phases correlates to the tetragonality.
Chemical State Mapping by X-Ray Fluorescence Using Absorption Edge Shifts
Authors: Sakurai Kenji , Iida Atsuo , Takahashi Mamoru , Gohshi Yohichi
Published: February 2005

Spatial distributions of chemical states of an element were determined by the measurement of X-ray fluorescence emission based on the selective excitation. Due to the chemical shifts of absorption edges, energy dependence of the fluorescent X-rays intensity near the edge is characteristic for the chemical state. There is a certain appropriate energy which selectively excites the specific valence state. Experimental results of the chemical state mapping of Fe-O and Cr-O systems are shown. The image reconstruction technique with the line shaped incident X-rays as well as the ordinary point-by-point scanning was employed.
Observation of Atomic Steps by Reflection Electron Holography
Authors: Osakabe Nobuyuki , Matsuda Tsuyoshi , Endo Junji , Tonomura Akira
Published: February 2005

Reflection electron holography has been carried out successfully for the first time. Two regions in a reflection electron image of a Pt(111) surface at glancing angle incidence are overlapped by means of an electron biprism to form an off-axis electron hologram. The optically reconstructed interferogram displays the phase distribution of the diffracted electron wave which reflects surface topography. This method has been proved to have high sensitivity of the order of 0.01 nm for quantitatively measuring surface undulation by observing mono-atomic-height surface steps.
Initial Stage of Phase Separation in a Binary Mixture of Poly(Vinyl Methyl Ether) and Water
Authors: Tanaka Hajime , Nishi Toshio
Published: February 2005

We report the initial stage of phase separation in a binary mixture of poly(vinyl methyl ether) and water under the off-critical temperature jump condition. We find the initial-stage spinodal decomposition described by Cahn's linear theory. The spatial scale of the initial fluctuation (about 10 µm) is much larger than that of usual binary mixtures. This unusual behavior can be qualitatively explained by the off-critical temperature jump of the long-range force system close to the spinodal line. The morphology is a droplet-like pattern initially, even in the spinodal decomposition, probably because of the highly asymmetric phase diagram.
New Amorphous Alloys with Good Ductility in Al-Ce-M (M=Nb, Fe, Co, Ni or Cu) Systems
Authors: Inoue Akihisa , Ohtera Katsumasa , Kita Kazuhiko , Masumoto Tsuyoshi
Published: February 2005

New Al-based amorphous alloys were formed in Al-Ce-M (M=Nb, V, Cr, Mn, Fe, Co, Ni or Cu) ternary systems by melt spinning. The compositional range is the widest for Al-Ce-Ni alloys and extends from 2 to 15 at% Ce and below 30%Ni. The Al-Ce-M (M=Nb, Fe, Co, Ni or Cu) alloys containing over 80%Al have good bending ductility. The crystallization temperature (T
x) and hardness (H
v) of the ductile alloys increase to 625 K and 400 DPN with increasing M and Ce content and the highest tensile strength reaches 935 MPa. The effect of M elements on T
x and H
v is interpreted by taking the bonding nature of Ce and M atoms into consideration.
Generation Kinetics of EL2 Centers in GaAs
Authors: Suezawa Masashi , Sumino Koji
Published: February 2005

The generation kinetics of EL2 centers is investigated by means of the optical absorption at low temperature with GaAs in which grown-in EL2 centers have previously been eliminated by annealing at 1200°C. An analysis of the experimental results with chemical rate equations shows that an EL2 center consists of at least three defects of elementary type. The activation energy for the generation of EL2 centers is determined to be about 2.5 eV. The results favor the picture that the kernel of an EL2 center consists of one AsGa antisite and two Ga vacancies.
Electronic States for Threefold- and Fivefold-Coordinated Si Atoms in Amorphous Si
Authors: Ishii Nobuhiko , Shimizu Tatsuo
Published: February 2005

The defect-state wave functions for threefold-coordinated and fivefold-coordinated Si atoms were calculated for small clusters by using the transferable nonorthogonal tight-binding method. The results show that the largest Si 3s orbital density of the unpaired electron for one atom is larger for the cluster with a fivefold-coordinated Si atom than for the cluster with a threefold-coordinated Si atom. A comparison with the observed results suggests that the ESR signal with g=2.0055 observed in a-Si:H does not originate from fivefold-coordinated Si atoms but from threefold-coordinated ones.
TEM Observations of Initial Crystallization States for LPCVD Si Films
Authors: Adachi Eimi , Aoyama Takashi , Konishi Nobutake , Suzuki Takaya , Okajima Yoshiaki , Miyata Kenji
Published: February 2005

Crystallization of LPCVD amorphous silicon films, especially the initial crystallization states, has been studied by transmission electron microscopy (TEM), X-ray diffraction and electron spin resonance (ESR) techniques. For longer annealing times at 600°C, the X-ray diffracted intensity (crystalline component) increased and the electron spin density (mainly amorphous component) decreased; TEM cross-sectional observations indicated that crystallization was initiated only at the film-substrate interface, as reported previously, on the basis of Raman scattering measurements.
The Influence of Growth Temperature and Thermal Annealing on the Stress in GaAs Layers Grown on Si Substrates
Authors: Ueda Takashi , Onozawa Sachiko , Akiyama Masahiro , Sakuta Masaaki
Published: February 2005

The stress in GaAs layers grown on Si substrates was studied. The GaAs layers were grown by the two-step growth sequence using reduced pressure MOCVD. The stress in the GaAs layers was found to be independent of growth temperatures and did not change after in situ thermal annealing. The value of the stress was smaller than that calculated with the bimetal model. The mechanism of the stress reduction by dislocation motion was proposed to explain these phenomena.
Oxygen-Enhanced Surface Segregation of Mn in Cu-Mn and Ag-Mn Alloy Films Studied by ISS/AES
Authors: Katayama Itsuo , Oura Kenjiro , Shoji Fumiya , Hanawa Teruo
Published: February 2005

The influence of oxygen contamination on the surface segregation of simultaneously deposited Cu-Mn and Ag-Mn thin-film alloys has been investigated by a combined use of low-energy ion scattering spectroscopy (ISS) and Auger electron spectroscopy (AES). It has been reported that (1) in both Cu-Mn and Ag-Mn systems, the surface segregation of Mn is enhanced by oxygen adsorption and (2) the oxygen-enhanced segregation is accompanied by the multilayer enrichment of Mn.
Analysis of Contamination Layer of InP During LPE Process by Synchrotron Radiation-Excited X-Ray Fluorescence
Authors: Iida Atsuo , Sakurai Kenji , Gohshi Yohichi , Komiya Satoshi
Published: February 2005

A Ga and As contamination layer formed on the corrugated InP substrate during the LPE growth process of DFB lasers is analyzed using the synchrotron radiation-excited X-ray fluorescence. Quantitative analysis shows that the concentrations of Ga and As are in the order of 1014 atoms/cm2 and both impurities are localized less than 50 Å from the surface. The effect of the surface corrugation on the quantitative analysis is also discussed.
Extended Hubbard Models for Transition Metal Oxides and Halides: Importance of Spin and Charge Fluctuations in Charge Transfer Metals
Authors: Yamaguchi Kizashi , Nakano Masayoshi , Namimoto Hideo , Fueno Takayuki
Published: February 2005

The atomic parameters used in the extended Hubbard (EHB) models for transition metal oxides were determined so as to reproduce ab initio results and experimental results. The EHB model was investigated in relation to classification of transition metal oxides into the Mott-Hubbard and charge transfer (CT) semiconductors. The model calculations indicate that both spin and charge fluctuations are of importance to the high-T
c superconductivity.
Enhancement of Jc in Y1-xCa1.1xBa2-0.1xCu3Oy
Authors: Okai Bin , Kosuge Michikazu , Takahashi Koh , Ohta Masatsune
Published: February 2005

With specimens of Y1-x
Ca1.1x
Ba2-0.1x
Cu3O
y
prepared under the same conditions, Y0.95Ca0.055Ba1.995Cu3O
y
possessed a larger superconducting critical current density J
c than the nondoped YBa2Cu3O
y
. The J
c of the former composition was 275 A/cm2 at 77 K, whereas it was 145 A/cm2 with the latter stoichiometric composition.
Crystal Structures of Tl-Ba-Ca-Cu-O Superconducting Phases Studied by High-Resolution Electron Microscopy
Authors: Hiraga Kenji , Shindo Daisuke , Hirabayashi Makoto , Kikuchi Masae , Kobayashi Norio , Syono Yasuhiko
Published: February 2005

Crystal structures of superconductors Tl2Ba2CaCu2O8 and Tl2Ba2Ca2Cu3O10, which show zero-resistivity at temperatures of 98 and 114 K, respectively, were studied with a high-resolution electron microscope having a resolution of 0.17 nm. High-resolution images clearly revealed arrangements of cations and oxygen vacancies in the superconductors. Computer image simulations provided evidence that a considerable amount of Tl atoms are substituted by Ca atoms.
Fabrication of Ag-Sheathed Ba-Y-Cu Oxide Superconductor Tape
Authors: Okada Michiya , Okayama Akira , Morimoto Tadaoki , Matsumoto Toshimi , Aihara Katsuzo , Matsuda Shinpei
Published: February 2005

Ba2YCu3O7-δ tapes were fabricated by cold rolling. The critical current density J
c apparently depended on the thickness of the tape and increased markedly with decreasing tape thickness. The maximum J
c of 3330 A/cm2 at 77 K in a zero magnetic field was achieved in an Ag-sheathed BYCO tape, 0.06 mm in thickness. The presence of a 20 mT magnetic field reduced the J
c value by 1/100.
Structural Investigations of High-Tc Superconducting Untwinned DyBa2Cu3O7-y Single Crystal by X-Ray Diffraction
Authors: Machida Mitsuo , Achiwa Norio , Koyano Nobumitsu , Shibuya Iwao , Hikita Makoto , Katsui Akinori
Published: February 2005

The crystal structure of high-T
c superconducting orthorhombic DyBa2Cu3O7-y
has been determined by X-ray diffraction using an untwinned single crystal. Fourier and difference Fourier analyses revealed exact occupancy factors of O(1) and O(2) in this crystal to be 0.84 and 0.08, respectively. The crystal has one of the highest orthorhombicity ever found with (a-b)/a=0.016, and hence, distinct structural differences of the a and b directions.
High-Resolution Electron Microscopy of Modulated Structure in 20 K Superconducting Oxide Bi2Sr2CuOy
Authors: Matsui Yoshio , Takekawa Shunji , Horiuchi Shigeo , Umezono Akihiro
Published: February 2005

The structure of the 20 K superconductor Bi2Sr2CuO
y
is examined by high-resolution transmission electron microscopy. A strongly modulated structure due to the periodic lattice distortions is observed. The unit cell is B-centered monoclinic with a
m=0.54, b
m=2.6, c
m=2.8 nm and α=116°, where b
m is incommensurate with the tetragonal subcell. The pseudo-orthorhombic setting of the unit cell, where A=a
m=0.54, B=b
m=2.6 and C=2c
m cos
α=5.0 nm, reported previously [Matsui et al.: Jpn. J. Appl. Phys. 27 (1988) L827], is considered convenient to compare the superstructure with the orthorhombic one of the 80 K superconductor Bi2Sr2CaCu2O
y
.
Preparation of Bi2Sr2CaCu2Ox Superconductors from Amorphous Films by Rapid Quenching after Rapid Melting
Authors: Yoshimura Masahiro , Sung Tea-Hyun , Nakagawa Zenbe-e , Nakamura Tetsuro
Published: February 2005

Complete amorphous films with the composition of Bi2Sr2CaCu2O
x
were successfully prepared by the rapid quenching after rapid melting technique without any containers. The evaporation loss was measured to be 0.237 wt%/sec or less at 1673–1773 K in the initial stage of melting. The amorphous materials were crystallized in the Bi2Sr2CaCu2O
x
phase above 1073 K through the Bi2Sr2CuO
x
phase crystallized above 733 K. The crystallized Bi2Sr2CaCu2O
x
film showed a superconducting transition at T
co=86.8 K and T
ce=66.7 K.
Large Magnetization in YBa2Cu3O7 Prepared by Sintering at High-Temperature
Authors: Kumakura Hiroaki , Takahashi Kazuhiko , Uehara Mitsuru , Togano Kazumasa
Published: February 2005

Magnetization and resistive J
c at 77 K were measured for YBa2Cu3O7 samples prepared by sintering above 950°C. Anomalously large magnetization was observed at a sintering temperature of 1030°C, although resistive J
c remained low. This large magnetization can be explained by both the improvement in pinning J
c of the compound and the coarseness of the YBa2Cu3O7 structure.
Photoacoustic Spectrum in Superionic Conductors Ag3SI and AgI
Authors: Kurita Mitsufumi , Nakagawa Kimio , Akao Fumio
Published: February 2005

The photoacoustic spectrum P(λ) of the superionic conductors β-Ag3SI and α-Ag3SI has been measured in the range 270≦λ≦1800 nm at room temperature. A difference in the band gap is observed in each specimen; in the annealed β-phase and in the quenched α-phase. These data can be interpreted on the basis of a simple band model in which Pantelides has shown that the band gap varies approximately with an equilibrium nearest-neighbor distance, d, as d
-2. As a result, Ag3SI (E

g
(β)=1.11 eV and E

g
(α)=1.47 eV) is found to have a small band gap in comparison with γ-AgI (E

g
=2.85 eV). Therefore, Ag3SI resembles a semiconductor and the electrons make a large contribution to the conductivity in comparison with AgI.
Oxygen Contamination in SrS:Ce Thin-Film Electroluminescent Devices
Authors: Okamoto Kenji , Hanaoka Kazutaka
Published: February 2005

Oxygen contamination in SrS:Ce thin-film electroluminescent devices was studied. We found that the luminance is reduced by the oxygen contamination in the SrS:Ce thin films and that oxygen concentration is strongly influenced by the evaporation rate. The source of the oxygen contamination is SrCO3 in the SrS:Ce pellet due to incomplete refining and/or reactions with atmospheric H2O and CO2. Significantly higher luminance has been obtained by reducing the SrCO3 concentration in SrS:Ce pellets.
In Situ Observation of Pulsed Laser Doping
Authors: Sameshima Toshiyuki , Tomita Hisashi , Usui Setsuo
Published: February 2005

Transient conductance measurements were used to study the rapid process of pulsed laser doping of silicon film. The use of a thin silicon-on-sapphire (SOS) film made it possible to measure the movement of the liquid-solid interface during melting and regrowth and to determine the point at which the carrier generation of dopant atoms diffused in the molten silicon begins. The results of the transient conductance measurements revealed that the recrystallization of molten silicon and the activation of dopant atoms diffused in the molten silicon occurred simultaneously.
Electrical and Photoluminescence Properties of Iodine-Doped ZnSe Films Grown by Low-Pressure MOVPE
Authors: Yoshikawa Akihiko , Nomura Hiroshi , Yamaga Shigeki , Kasai Haruo
Published: February 2005

Iodine-doped ZnSe films have been grown on GaAs by low-pressure MOVPE. It has been shown that the electrical properties of the films can be controlled over a wide range by using diluted ethyliodide as a dopant source. Effects on the properties of ZnSe films of the doping levels and the growth temperature have been investigated separately, using low-temperature photoluminescence as a characterization method. Furthermore, it has been found that the sticking coefficient of iodine remarkably decreases with temperature, resulting in a growth of lower carrier-concentration films at higher growth temperatures.
High-Tc Superconductor Produced by Oxidization of Melt-Spun Ag-Ho-Ba-Cu Alloy Ribbon
Authors: Matsuzaki Kunio , Inoue Akihisa , Masumoto Tsuyoshi
Published: February 2005

A (Ho0.17Ba0.33Cu0.5)50Ag50 alloy ribbon with a non-equilibrium structure was produced by melt-spinning. Heating of the alloy ribbon in air brought about the structural change to a stable metallic phase at about 610 K, followed by the formation of Ho1Ba2Cu3O6.7 and Ag in the range of 630 to 740 K. The mixed materials of Ho1Ba2Cu3O6.7 and Ag produced by oxidization of the melt-spun ribbon exhibited high-T
c superconductivity with onset at 90 K and zero resistance at 80 K. It is notable that the mixture of Ag enables us to produce an alloy ribbon by melt-spinning even in the Ho-Ba-Cu alloy system with large miscibility gap.
Structure and Melting Behavior of Poly(vinylidene fluoride) Crystallized by Pressure Quenching
Authors: Iwamoto Toshiyuki , Itoh Takashi , Ando Yutaka , Miyata Seizo , Konishi Takashi
Published: February 2005

Multiple melting behavior in Poly(vinylidene fluoride) crystallized by pressure quenching (0.1→600 MPa at 513 K) is analyzed by means of differential scanning calorimetry, X-ray diffraction and transmission electron microscopy (TEM). It is found that the endothermic peak at 477 K corresponds to the melting of the γ-form extended-chain crystal, and that at 479 K to the melting of an unknown phase ( γ'-form) similar to the γ-form crystal. The band structure is 80∼100 nm thick, which suggests the existence of extended-chain crystals, and is confirmed by TEM observation for both crystals of γ- and γ'-forms.
Low-Noise Infrared Detection System with InSb Photodiode for Infrared Astronomy
Authors: Murakami Hiroshi , Akiba Makoto , Matsumoto Toshio , Noda Manabu
Published: February 2005

We have developed a low-noise infrared detection system for astronomical observations in space. The circuit is a charge integrating amplifier with a newly developed low-capacity InSb photodiode operated at 4.2 K. The amplifier consists of JFETs operated at 70 K. The readout noise is about 80 electrons for an integration time τ=1 sec. The dark current noise is negligible. The noise equivalent power is 2×10-17 W/√Hz at τ=1 sec and lower than 10-17 W/√Hz for τ>10 sec.
Magnetic Field Penetration into La1.85Sr0.15CuO4
Authors: Ishida Takekazu , Mazaki Hiromasa
Published: February 2005

We examined the temperature dependence of the magnetic field penetration depth λ of La1.85Sr0.15CuO4 through variations of the ac susceptibility. The temperature dependence of λ cannot be understood by the conventional BCS theory. The analysis of the data indicates that the T
2 dependence of λ(T)-λ(0) is plausible at lower temperatures. This gives evidence of point nodes in the energy gap on the Fermi surface in this compound.
Effect of High Pressure on the Hyperfine Field and Curie Temperature of an Amorphous Fe86B14 Alloy
Authors: Oshima Ryuichiro , Nagatomo Shohei , Kurimoto Kazumi , Nasu Saburo , Endo Shoichi , Fujita Francisco Eiichi
Published: February 2005

In this paper, Mössbauer spectroscopy of an amorphous Fe86B14 alloy is carried out using a diamond-anvil type high-pressure cell under pressures up to 40 kbar at room temperature. The obtained high-pressure effect on the hyperfine field, ( dH
f/dp=-1.42 kOe/kbar, p≥6.5 kbar) is accounted for by the reduction of Fe atom magnetization at room temperature associated with an appreciable decrease of the Curie temperature, T
c, with increasing pressure. This indicates the Invar characteristics of this material. The pressure dependence of T
c is evaluated to be dT
c/dp=-3.1 K/kbar, which is smaller than that reported previously by magnetic measurements.
The Dependence of Field Effect Mobilities on Substrate Temperature for Amorphous Silicon Deposition for Amorphous Silicon Thin Film Transistors
Authors: Oyoshi Keiji , Kusuda Yukihisa , Yamaoka Tomonori , Tanaka Shuhei
Published: February 2005

We evaluated the field effect mobility ( µFE) for a-Si TFTs at different temperatures for a-Si deposition (T
sub). The µFE showed a maximum in the temperature range of 200∼250°C. We estimated the tail localized state distribution of the a-Si films for each T
sub value from theoretical curves modified by the measurement temperature dependence of µFE. The result of the fittings showed that the a-Si tail localized state was suppressed in the T
sub range 200∼250°C.
Gas-Phase and Surface Reactions in Xenon Lamp-Assisted Organometallic Vapor-Phase Epitaxy of ZnSe
Authors: Fujita Shizuo , Takeuchi Fumiyo Y. , Fujita Shigeo
Published: February 2005

In this paper, the influence of xenon lamp irradiation on gas-phase and surface reactions in organometallic vapor-phase epitaxy of ZnSe on GaAs is investigated. The irradiation only to the gas phase scarcely influences the growth rate, while irradiation to the growth surface is essential for growth rate enhancement. Numbers of incident photons and those of adhered molecules are found to be of the same order, i.e., most photons irradiated onto the substrate are associated with the epitaxial growth. The above experimental results strongly suggest that incident photons enhance some surface reactions, resulting in higher growth rates and lower growth temperatures compared with those reactions occuring under no irradiation.
X-Ray Powder Diffraction Study on the Occupancy of Oxygen Atoms in the YBa2Cu3Ox Compound
Authors: Ikeda Koji , Nagata Masakatsu , Ishihara Minoru , Kumazawa Shintaro , Shibayama Takashi , Imagawa Akihiko , Sugamata Tohru , Katoh Hiroyuki , Momozawa Nobuyuki , Umezawa Kikuo , Ishida Kohtaro
Published: February 2005

The crystal structure of an YBa2Cu3O
x
compound prepared under various quenching temperatures has been studied by X-ray powder diffraction techniques. The orthorhombic-to-tetragonal phase transition was observed with increasing quenching temperature. The change of oxygen content was determined by gravimetric measurement. Occupancies of the oxygen atoms sandwiched between Ba-O layers were determined by profile fitting on the weak diffraction peaks of 012 and 102 reflections.
Effect of Polymer Elongation on the Absorption Spectrum of Poly(3-alkylthiophene)
Authors: Yoshino Katsumi , Onoda Mitsuyoshi , Sugimoto Ryu-ichi
Published: February 2005

A remarkable absorption spectral change has been observed in ethylene propylene elastomer (EPR) films containing elongated poly(3-alkylthiophene). This change is explained in terms of the formation of new torsioned bonds between thiophene rings on the main polymer chains. This interpretation is also consistent with the anisotropy of the polarization dependence of absorption.
Analytical Electron Microscopic Study of High-Tc Superconductor Bi-Ca-Sr-Cu-O
Authors: Shindo Daisuke , Hiraga Kenji , Hirabayashi Makoto , Kobayashi Norio , Kikuchi Masae , Kusaba Keiji , Syono Yasuhiko , Muto Yoshio
Published: February 2005

Superconductors Bi-Ca-Sr-Cu-O containing high-T
c (110 K) and/or low-T
c (80 K) phases were investigated by analytical electron microscopy. In the sample containing the high-T
c phase, various stacking sequences formed with 2, 3 and 4 perovskite layers were observed by a lattice imaging technique. From EDX analysis, a considerable variation of composition with a higher Cu atomic fraction than that of low-T
c phase was detected. The structure of 3 perovskite layers is considered to be responsible for a superconducting transition at 110 K. A discrepancy between a volume fraction of the structure containing 3 perovskite layers and that of high-T
c phase expected from the magnetization experiment is discussed. Despite the differences of chemical composition and stacking period along the c-axis, a similar structural modulation with an incommensurate period along the b-axis was equally found in the high-T
c phase as the low-T
c phase.
A.C. Complex Susceptibility Measurement in Sintered Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O Superconductors
Authors: Kumakura Hiroaki , Togano Kazumasa , Takahashi Kazuhiko , Yanagisawa Eiji , Nakao Masao , Maeda Hiroshi
Published: February 2005

A.C. complex susceptibility χ'-i χ'' was measured as a function of temperature at various field amplitude for the sintered Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O in order to investigate the coupling properties of both polycrystalline compounds. The steps in χ'-T curves and the peaks in χ''-T curves were composed of two contributions for sintered bulk samples. One comes from the intergrain couplings, while the other is attributed to the bulk superconductivity. The amplitude dependence of the former contribution indicates that the coupling in the Bi compound is weaker than that in the Tl compound.
The High-Tc Phase with a New Modulation Mode in the Bi, Pb-Sr-Ca-Cu-O System
Authors: Ikeda Yasunori , Takano Mikio , Hiroi Zenji , Oda Kiichi , Kitaguchi Hitoshi , Takada Jun , Miura Yoshinari , Takeda Yasuo , Yamamoto Osamu , Mazaki Hiromasa
Published: February 2005

The preparation and characterization of Bi1.73Pb0.35Sr1.89Ca1.86Cu3O9.91, a lead-rich high-T
c phase, were studied (T
c(ρ=0)=105 K). This compound crystallized in a pseudotetragonal structure with a
t=0.541 nm and c
t=3.709 nm, while a unique one-dimensional modulation with a wavelength of 4.7 nm (≃8.7a) was found along the b axis using transmission electron microscopy. Such a lead-rich phase and a lead-free (or very poor) phase crystallizing in the well-known modulated structure (2.7 nm≃5a) were intergrown at intermediate compositions, such as Pb/Bi=1/9. Effects of annealing under different oxygen pressures were studied.