bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffusion Mechanism of Cd in InP and InGaAs
Authors: Ohtsuka Ken-ichi , Matsui Teruhito , Ogata Hitoshi
Published: February 2005

Cadmium was diffused into InP and InGaAs using Cd3P2 + P or Cd3P2 + Cd3As2 as the diffusion sources. Two diffusion fronts were observed. The diffusion characteristics for Cd3P2 + P sources are interpreted based on the interstitial-substitutional model, or its modification, the vacancy complex model. The charge state of the diffusing interstitial cadmium atom is a singly ionized donor. The chemical species of phosphorus which reacts with InP is P2 and gaseous Cd originates from solid-phase CdP2. For Cd3P2 + Cd3As2 diffusion sources, the effective diffusion coefficient and the surface acceptor concentration decrease with increasing the Cd3As2 weight fraction. The relative depth of the deeper diffusion front becomes more deep when the supply of vacancies is suppressed.
Analysis of Thermally Stimulated Current Spectroscopy in Semiinsulating GaAs. I. Initialization
Authors: Tomozane Mamoru , Nannichi Yasuo , Onodera Isao , Fukase Tadashi , Hasegawa Fumio
Published: February 2005

The operation of improved thermally stimulated current (TSC) spectroscopy is described and analysed. This method is suited for studying defects in semi-insulating (SI) GaAs at liquid-helium temperatures. This paper, the first in a series, presents an analysis of the first half process of TSC, that is, initialization, which consists of three stages: carrier generation, transport, and trapping. The initialization is analysed in terms of such parameters as electrode spacing, biasing voltage and polarity, excitation light energy and dose, and temperature. The analysis leads to new methods of determining the cross section of a deep level trap. From the photocurrent transient, the cross section was estimated for the dominant trap(s) as 5×10-15 cm2. Another method offers an estimation for nondominant trap levels.
Double Heterostructure GaAs Tunnel Junction for a AlGaAs/GaAs Tandem Solar Cell
Authors: Sugiura Hideo , Amano Chikao , Yamamoto Akio , Yamaguchi Masafumi
Published: February 2005

A double hetero (DH) GaAs tunnel diode which consists of a GaAs tunnel junction sandwiched between Al
x
Ga1-x
As layers has been grown by molecular beam epitaxy, and its annealing characteristics studied. DH tunnel diodes have the advantage that a decrease in the tunnel peak current density due to annealing is greatly suppressed compared to conventional GaAs diodes without AlGaAs layers. In-depth profiles of dopants indicate that the AlGaAs layers act as blocking layers against Be diffusion, which causes a degradation of the diodes. An Al0.4Ga0.6As/GaAs tandem solar cell incorporating the DH tunnel junction as interconnectors has achieved a conversion efficiency of 20%.
A Thick and Large Active Area Si(Li) Detector
Authors: Miyachi Takashi , Ohkawa Shoichi , Emura Tsuneo , Nishimura Makoto , Nitoh Osamu , Takahashi Kaoru , Kitamura Shoichi , Kim Yongcha , Abe Takao , Matsuzawa Hidemi
Published: February 2005

A 5 inch diameter, 3mm thick silicon detector has been fabricated using a nondetector grade crystal. The detector characteristics of the silicon detector were examined with infrared light as well as a hadron beam.
Magic Numbers and Critical Sizes of Tin Clusters Emitted from a Liquid Metal Ion Source
Authors: Watanabe Makoto , Saito Yahachi , Nishigaki Satoshi , Noda Tamotsu
Published: February 2005

Sn cluster ions from a liquid metal ion source have been analyzed by mass spectrometry. Discontinuous variations in ion intensity as a function of the cluster size were found atn=4 and 6 (magic numbers) for singly charged clusters, wherenis the number of atoms contained in the cluster. By comparing this with other studies for Si, Gee, and Sn clusters, it is concluded that the presently found magic numbers can be attributed to cluster stability. The critical size, above which multiply charged clusters are observed, wasn=3 and 4 for doubly and triply charged states, respectively. The critical sizes are also discussed using the Rayleigh limit for charged droplets.
Theoretical Study on the High-Energy Electron Energy Loss Spectroscopy Compared with X-Ray Absorption Spectroscopy. I. Deep Core Excitation from K and L2,3 Edge of Atoms
Authors: Fujikawa Takashi , Takatoh Shuji , Usami Seiji
Published: February 2005

In this series of papers we are investigating the magnitude of the dipole and non-dipole processes observed in the high-energy electron energy loss spectroscopy (EELS) related to deep core orbitals. The present paper describes the atomic excitation from deep K and L
2,3 edges. We discuss the amount of discrepancy which emerged in the intensity of electron scattering when only assuming a dipole interaction and its dependence on the scattering angle, excitation energy and type of excited core levels. From this discussion, one can justify the means to obtain the same electronic and geometric information by an analysis of electron energy loss fine structure and the near-edge structure observed in high-energy EELS for small-angle scattering.
Effect of Growth Temperature on InGaAsP/GaAsP Epitaxial Growth
Authors: Fujii Sadao , Tobita Manabu , Furuta Shigeru , Sakai Shiro , Umeno Masayoshi
Published: February 2005

The epitaxial growth condition of InGaAsP on GaAs0.61P0.39 is discussed in conjunction with a lattice latching effect which is shown to have a relationship with the solid composition of the epilayer. The growth temperature dependence of this relation is also discussed in terms of a theoretical calculation. The PL FWHMs of the epilayers depend on the solid composition but not on the growth temperature. This behavior is attributed to the compositional fluctuation, lattice latching effect and binodal instability of the epilayers.
The Role of EL2 Centres in Infra Red Images of Defects in GaAs Materials
Authors: Fillard Jp , Montgomery P. , Gall P. , Asgarinia M. , Bonnafe J.
Published: February 2005

Careful measurements of the changes induced by photoquenching in the infra red transmission image of GaAs wafers at Liquid Nitrogen temperature shows an important enhancement of the mean light level and disappearance of the usual fourfold feature; but it also shows that the contrast of the pattern (cell structure) is not affected at all. The contribution of EL2 centres to the image is questioned; it is deduced from these results that photoquenchable EL02 centres are slightly more abundant in the cells than in the walls. In large cell materials an intermediate zone is found surrounding the cells and containing higher EL02 densities. This sheds new light on the role of the dislocations; these results are discussed and compared with etching and luminescence images.
A Study on Etching Parameters of a Reactive Ion Beam Etch for GaAs and InP
Authors: Tadokoro Takashi , Koyama Fumio , Iga Kenichi
Published: February 2005

Some etching characteristics for GaAs and InP with Cl2 gas using a reactive ion beam etching (RIBE) system have been studied. The employed etching gas was ionized by electron cyclotron resonance (ECR) at a gas pressure of about 6×10-4 Torr; the applied microwave power was 300 W. The etch rate was measured as a function of the substrate temperature and the applied ion extraction voltage. At low temperatures, the etch rate of InP was proportional to the five halves of the extraction voltage. This agreed well with a theoretical consideration. The maximum etch rates for InP and GaAs were 2.0 and 1.2 µm/min, respectively, both at 200degC.
Improvement of Solar Cell Performance Using Plasma-Deposited Silicon Nitride Films with Variable Refractive Indices
Authors: Shibata Noboru
Published: February 2005

Silicon nitride films containing various amounts of Si or O atoms were prepared by controlling the operation parameters of the plasma-chemical vapor deposition in N2-diluted silane mixed with H2-diluted silane or with O2 under various mixing ratios. By this method, the refractive indices of silicon nitride films could be varied over a wide range. The refractive index of films containing oxygen atoms gradually changed through oxygenation; however, oxygen-free plasma-deposited silicon nitride (P-SiN) films containing various amounts of Si atoms were very stable. The spectral response of the reflectance was measured for the latter Si-rich P-SiN films in order to determine the appropriate conditions as antireflective coatings for P/N single crystal Si solar cells. As a result, Si-rich P-SiN antireflective films improved the conversion efficiency of Si solar cells by 40 to 50 or by 50 to 70%, depending on whether a single-layer or double-layer coating, respectively, was used.
Studies of Plane Type Defects in Ferroelectric Ca2Sr(C2H5CO2)6 Single Crystal by Light Scattering Tomography
Authors: Kimura Masanori , Motegi Hiroshi , Deguchi Kiyoshi , Nakamura Eiji
Published: February 2005

Crystal defects in ferroelectric Ca2Sr(C2H5CO2)6 have been studied in detail by light-scattering tomography. Most of the crystal defects observed have been found to be the plane type parallel to the {101} or the {110} planes. The shape of the {101} plane type defects is fundamentally a hexagon which satisfies “the law of constancy of facial angles.” The formation mechanism of the plane type defects is studied and discussed.
Hall-Effect Measurement on Polycrystalline SnO2 Thin Films
Authors: Fujisawa Akira , Nishino Taneo , Hamakawa Yoshihiro
Published: February 2005

Hall-effect measurements of F-doped polycrystalline SnO2 thin films have been performed in the temperature range from 4.2 to 300 K with samples having different sizes of grains involved in the material. The carrier concentration and mobility have been analyzed in terms of the transport mechanism in a degenerate semiconductor. From a comparison between the calculated and experimental carrier concentration, we have obtained the results that the effective mass of electrons is 0.935 m
0 and that the position of the Fermi level in the conduction band varies from 0.269 to 0.224 eV for a change in the carrier concentration from 5.70 to 4.31 (× 1020 cm-3). Based on an analysis of the Hall mobility, it has been found that scattering by neutral and ionized impurities dominates the mobility and that both the impurities are localized at grain boundaries involved in polycrystalline SnO2 films.
F/Tb Ratio Dependence of the Photoluminescent and Electroluminescent Characteristics in MOCVD-Prepared ZnS:TbFx Green-Emitting Electroluminescent Devices
Authors: Hirabayashi Katsuhiko , Kozawaguchi Haruki , Tsujiyama Bunjiro
Published: February 2005

The photoluminescent characteristics of MOCVD-prepared ZnS:TbF
x
films are highly dependent on x, while the eletroluminescent characteristics are independent of x. For photoluminescence excitation at 330 nm, which is indirect excitation from the ZnS host to the Tb center, the photoluminescent intensity increases rapidly with a decrease in x, while for the photoluminescence excitation at 377 nm, which is a direct excitation of the Tb center, the photoluminescent intensity is independent of x. On the other hand, the electroluminescent intensity of devices prepared using these films is almost independent of x. The difference in the site of the F ion between MOCVD- and sputtering-prepared films is discussed as well as the excitation mechanism for photoluminescence and electroluminescence.
Characteristics of Optical CCD as an X-Ray Image Sensor
Authors: Tsunemi Hiroshi , Mizukata Katsuya , Hiramatsu Makoto
Published: February 2005

We report here on the characteristics of a CCD for optical use in the several keV region. The CCD we used was an interline-transfer type device. We took X-ray images at energies of about 8 and 1.5 keV for various objects. We found that this device could yield sufficient information for a two-dimensional image. The spatial resolution is up to the individual pixel size(23×27 µm). The efficiency for X-rays is much superior to that of film. We measured the pulse-height distribution of X-rays in a photon-counting mode. We obtained a linear relation between the incident photon energy and the pulse height, while the energy resolution was kept constant. The effective depth of the depletion layer of this device was calculated as being about 3 µm from these measurements. We discuss the problems which must be faced in fabricating the CCD for X-ray use.
Analysis of ac Surface Photovoltages in Accumulation Region
Authors: Munakata Chusuke
Published: February 2005

Equations for ac surface photovoltages (SPVs) excited with a chopped photon beam (PB) in the accumulation region are proposed for such semiconductors as silicon and germanium. Following the previously reported half-sided junction model for the depleted or inverted region, equations for photocurrent density and surface impedance per unit area have been newly deduced. When the surface potential is highly negative in p-type semiconductors, the maximum ac SPV in the accumulation region is limited by the conductance due to majority carrier diffusion flow. This is compared with the strong inversion region, where the mathematically maximum SPV depends upon the minority carrier diffusion flow. The voltage ratio between the two maximum ac SPVs is the same as that previously reported using the different models for ac SPVs excited with a continuous PB.
Structure of Twisted States in Ferroelectric Liquid Crystals Studied by Microspectrophotometry and Numerical Calculations
Authors: Hiji Naoki , Ouchi Yukio , Takezoe Hideo , Fukuda Atsuo
Published: February 2005

The transmittance spectra of twisted states of surface stabilized ferroelectric liquid crystal cells were measured under a polarizing optical microscope. It was found that the two twisted states give different spectra, as expected by an apparent color difference. There were two cases; in one case the two spectra interchange by rotating a cell, while in the other case the two spectra do not interchange. We could simulate both cases by numerical calculations of the spectra using a smectic layer bend model. The spectral interchange could be analytically explained on the basis of the Jones retardation matrix method. A simple method for judging the condition of the interchange is proposed.
The Strength of Rubbing Worked on Polyimide Films for Aligning Nematic and Chiral Smectic Liquid Crystals: Controlling Pretilt Angles and Some Electrooptic Performances of LCDs
Authors: Kuniyasu Seiyu , Fukuro Hiroyoshi , Maeda Shigeo , Nakaya Kenji , Nitta Michio , Ozaki Norihiko , Kobayashi Shunsuke
Published: February 2005

The degree of work done on polyimide films in the rubbing process with a nylon fabric was detected and evaluated in terms of induced birefringence. Strong and weak rubbing (effecting two extremes) gave rise to the optical retardation of 1 degree and 0.1 degree, respectively, with a resolution of 0.1 degree. Generation of a pretilt angle of up to 10 degrees (even up to 30 degrees) for nematic liquid crystals was achieved by performing weak rubbing in a specially synthesized polyimide which was successfully used to fabricate supertwisted nematic liquid crystal displays. Fairly good bistability in a ferroelectric liquid crystal device was obtained by weak rubbing.
Characterization of a Controlled Clearance Piston Gauge Using Different Working Fluids up to 5 MPa
Authors: Sharma J. K. N. , Jain Kamlesh K. , Bandyopadhyay A. K.
Published: February 2005

A systematic study carried out to characterize the controlled clearance piston gauge in the pneumatic pressure region up to 5.09 MPa full-scale pressure using different working fluids such as argon, nitrogen, helium and hydrogen is described. The characterization was conducted/carried out by measuring the fall rate of the piston as a function of the jacket pressure (P

j
) in order to determine the stall jacket pressure (P

z
) corresponding to the zero clearance between the piston and cylinder. A comparatively greater reproducibility in the P

z
values is obtained for helium and hydrogen as compared to that of argon and nitrogen. The effects of the temperature of the operation on the fall rate in this piston gauge using gaseous nitrogen as the working fluid are also reported. It is observed that a small temperature fluctuation does not effect the overall uncertainly in the measured pressure.
Raman Spectral Behavior of In1-xGaxP (0<x<1)
Authors: Kato Takamasa , Matsumoto Takashi , Ishida Tetsuro
Published: February 2005

We report on a Raman study of In1-x
Ga
x
P over the whole range of alloy compositions, x. The additional peak, which appeared for x\lesssim0.98 and about which various interpretations have been proposed, is found to be constructed by two unresolved modes. The Raman spectra indicate that this alloy system has a modified two-mode behavior. The spectral half width of a TO mode broadened in the middle of the alloy composition. This is partly due to the strong two-acoustic-phonons scattering process.
Crystal Structure and Superconductivity Controlled by Cation Substitution and Oxygen Annealing in Y1-xCaxBa2Cu3Oy and YBa2-xLaxCu3Oy
Authors: Tokiwa Ayako , Syono Yasuhiko , Kikuchi Masae , Suzuki Reiko , Kajitani Tsuyoshi , Kobayashi Norio , Sasaki Takako , Nakatsu Osamu , Muto Yoshio
Published: February 2005

The effects of Ca2+ substitution for Y3+ and La3+ substitution for Ba2+ in YBa2Cu3O7 on the structural and superconducting properties were studied to control the average copper charge. Single-phase tripled perovskites were obtained for 0≦x≦0.2 and 0≦x≦1.0 for Ca and La doped series, respectively. A slight decrease of T
c with increasing x was found for small x values for both kinds of substituted specimens prepared by furnace cooling in air. Oxygen annealing experiments were also carried out. These suggested that the superconduction in the Y-Ba-Cu-O system cannot be interpreted only by oxygen content or average copper charge.
Synthesis of Bi-Sr-Ca-Cu-O Superconductor by Vacuum Calcination Method
Authors: Uno Naoki , Enomoto Noritsugu , Tanaka Yasuzo , Takami Hiroshi
Published: February 2005

The vacuum calcination method (VCM) was developed to synthesize Bi-Sr-Ca-Cu-O superconductive oxides through solid phase reaction. When Bi2O3, SrCO3, CaCO3, and CuO are used as raw materials in powder form in this method, the carbon content of the resultant calcined product was lower than that of the conventional method. The VCM process gave a higher ratio of high-T
c phase (110 K class) in comparison with the conventional method.
X-Ray Diffraction Study of a High-Tc Bi-Ca-Sr-Cu-O Superconductor Having Incommensurate Superstructure
Authors: Kawaguchi Kenichi , Sasaki Satoshi , Mukaida Hiromi , Nakao Masao
Published: February 2005

The incommensurate superstructure of a Bi-Ca-Sr-Cu-O single crystal has been investigated by the X-ray precession method. The specimen crystal showed superconductivity at 79 K. It was found that the crystal has orthorhombic symmetry and the space group obtained from reflections of the subcell is D2h
20-Bbmb or C2v
13-Bb2b, with the cell dimensions of a=5.42, b=5.42 and c=30.91(2) Å. The first- and second-order satellites were observed systematically along the b
* direction with intervals of (1/4.7)|b
*| and indicate a modulated structure.
Phase-Equilibrium Diagram in the Ternary System Y2O3-BaO-CuO
Authors: Oka Kunihiko , Nakane Kenji , Ito Masahiro , Saito Masatoshi , Unoki Hiromi
Published: February 2005

A phase-equilibrium diagram of the ternary system of Y2O3-BaO-CuO was investigated. The temperature vs concentration diagrams are given on four binary systems ranging from YBa2Cu3O7-y
to CuO, to BaCuO2·3CuO, to 3BaCuO2·4CuO and to 3BaCuO2·2CuO mixtures. A liquidus line required for the preparation of YBa2Cu3O7-y
single crystal from solution was found to be extremely narrow in concentration range.
Concentric Pregrooved Disk Fabricated by a Beam Scanning Method
Authors: Miyagi Masami , Iwasawa Akira , Funakoshi Nobuhiro
Published: February 2005

A new method for fabricating a concentric pregrooved disk has been developed. In this method, a recording laser beam is scanned by a galvano mirror to trace a concentric circle while the disk moves continuously. Because a pregroove is recorded within two disk revolutions, the recording time is less than half that of the conventional concentric pregroove fabrication method. This method achieves a precise track pitch with less than 0.04 micron deviation.
Superconductivity in Tl1.5SrCaCu2Ox
Authors: Nagashima Toshio , Watanabe Kenji , Saito Hiromichi , Fukai Yuh
Published: February 2005

We have discovered superconductivity in the Tl-Sr-Ca-Cu-O system. Depending on the method of sample preparation, a number of superconducting phases with different T
c's appeared. Resistivity data suggest that a T
c of about 100 K is to be attained in Tl1.5Sr1Ca1Cu2O
x
.
Anisotropic Upper Critical Fields of Highly Oriented Bi-Sr-Ca-Cu-O Thin Films Prepared by Coevaporation
Authors: Yoshitake Tsutomu , Satoh Tetsuro , Kubo Yoshimi , Manako Takashi , Igarashi Hitoshi
Published: February 2005

Two kinds of thin films with a zero resistance T
c of 82 K and 103 K, respectively were prepared on an MgO substrate by coevaporation in the Bi-Sr-Ca-Cu-O system. Both films have a strong preferred orientation with the c-axis perpendicular to the film plane. The upper critical field H
c2 was measured for these two films. The anisotropy, that is, the ratio of -dH
c2
⊥/dT to -dH
c2
///dT is about 20 for both the 85 K phase and 110 K phase and is larger than that of YBa2Cu3O
x
. The estimation of the values of H
c2
⊥(0) results in about 440 T for the 85 K phase and about 500 T for the 110 K phase.
Superconducting Bi-Sr-Ca-Cu-O Thin Films by Sputtering
Authors: Kato Takahiko , Doi Toshiya , Kumagai Teruo , Matsuda Shin-Pei
Published: February 2005

BiSrCaCu2O
x
thin films were prepared by rf magnetron sputtering. Superconducting transitions were observed for the films on MgO after postdeposition annealing at 870°C and above. The appearance of a superconducting transition at a temperature of about 120 K for the film necessitated annealing at close to, but not above, its melting point near 900°C: the appropriate annealing temperature range was from 875 to 900°C. It was noteworthy that the 910°C annealed film showed a superconducting characteristic as well as the 870°C annealed film, in spite of their crystal structures being entirely different. Besides annealing temperature, cooling rate from annealing temperature, film thickness and substrate dependences of superconductivity in the BiSrCaCu2O
x
thin film were also investigated.
Effects of Hydrogen Ion Implantation on Superconductivity in YBa2Cu3O7-x
Authors: Kato Takahiko , Usami Katsuhisa , Kuniya Jiro , Matsuda Shin-Pei
Published: February 2005

The effects of hydrogen ion implantation on superconductivity in YBa2Cu3O7-x
have been investigated using resistance-temperature curves and X-ray diffraction patterns. Both the temperatures of superconducting onset and zero resistance were lowered through hydrogen ion implantations. Superconductivity was observed even in a sample with a tetragonal structure besides an orthorhombic one (implanted to 7.6×1016 H+/cm2), but it disappeared by the implantations of 1.5×1017 H+/cm2 and above. Shrinkage in the lattice observed in the sample implanted to 7.6×1015 H+/cm2 and the shift of transition temperature, T
c(onset), through hydrogen ion implantations suggested that the implanted hydrogen atoms deoxidized the YBa2Cu3O7-x
compound.
Dispersion of Second-Order Nonlinear Optical Coefficient d11 of 2-Methyl-4-Nitroaniline (MNA)
Authors: Morita Ryuji , Kondo Takashi , Kaneda Yushi , Sugihashi Atsushi , Ogasawara Nagaatsu , Umegaki Shinsuke , Ito Ryoichi
Published: February 2005

Results of measurement of the dispersion of the second-order nonlinear optical coefficient d
11 of 2-methyl-4-nitroaniline (MNA) are presented over a wavelength range of 1.20 to 1.54 µm. Laser diodes are used as light sources. The nonlinear coefficient strongly depends on wavelength, exhibiting a resonance enhancement.
The Effect of Long-term Annealing on the Electrical Properties of SI-GaAs
Authors: Nakamura Yoshio , Ohtsuki Yasuo , Kikuta Toshio
Published: February 2005

The effect of long-term annealing on the electrical properties of semi-insulating (SI) GaAs has been investigated from the viewpoint of both carbon concentration and cooling process following high-temperature heat treatment. Resistivity decreased after slow cooling, but increased after fast cooling; these changes were enhanced in the low carbon concentration region. It was found that the change in electrical properties in the slow cooling process was strongly related to the increase in the donor located at 0.4 eV ∼0.5 eV below the conduction band.
Photoluminescence of Unintentionally Doped and N-Doped 3C-SiC Grown by Chemical Vapor Deposition
Authors: Okumura Hajime , Shinohara Mikiya , Muneyama Etsuhiro , Daimon Hiroshi , Yamanaka Mitsugu , Sakuma Eiichiro , Misawa Shunji , Endo Kazuhiro , Yoshida Sadafumi
Published: February 2005

Photoluminescence of unintentionally doped and N-doped 3C-SiC epilayers grown on Si by chemical vapor deposition was studied. It was found that N-doped samples have different emission lines from the bound exciton emissions observed in unintentionally doped 3C-SiC epilayers. This result suggests that the residual carriers in unintentionally doped n-type 3C-SiC cannot be attributed to nitrogen atoms, which is consistent with the results obtained from the temperature dependence of the carrier density of 3C-SiC.
An XPS Study of Blackening of Indium-Tin Oxide Film during Deposition of Dielectric Films by RF Magnetron Sputtering
Authors: Matsuoka Tomizo , Kuwata Jun , Fujita Yosuke , Abe Atsushi
Published: February 2005

The blackening phenomenon of an indium-tin oxide (ITO) film when Sr(Zr0.2Ti0.8)O3 dielectric film was deposited on it by the rf magnetron sputtering method has been examined by X-ray photoelectron spectroscopy. It was found that the blackening took place in the thin surface layer of the ITO film near the Sr(Zr0.2Ti0.8)O3/ITO interface and originated from preferential reduction of the Sn4+ ion to Sn0 rather than of In3+.
Superconducting Properties of Grain-Oriented YBa2Cu3O7-x Ceramics
Authors: Takenaka Tadashi , Noda Hideki , Yoneda Atsuhiko , Sakata Koichiro
Published: February 2005

A critical current density, J
c, is an important basic property of superconducting electronic applications. The high-T
c superconducting YBa2Cu3O7-x
(YBCO) ceramics can be given a preferred grain orientation by the hot-forging (H.F.) method, because the ceramics have a large anisotropic crystal structure. We confirmed that the grain-orientation effects on the superconducting properties of the H.F. YBCO ceramics enhance them. The grains in the H.F. ceramics were oriented so that the c-axis was in a forging direction. The grain-orientation factor, F(=0.3∼0.5), could be estimated by X-ray diffraction patterns. The J
c [=110 A/cm2] of the grain-oriented (H.F.) sample was elevated to one and a half times [=74 A/cm2] that of the nonoriented sample.
An ac Microcalorimetric Method for Precise Heat Capacity Measurement in a Small Amount of Liquid
Authors: Yao Haruhiko , Hatta Ichiro
Published: February 2005

Making the most of light-irradiation-type ac calorimetry, a microcalorimeter is designed for measuring the heat capacity of a 1- µl liquid sample. The heat capacity can be determined within an accuracy of 1%.
Chemical Interaction between Ba2YCu3O7-δ and Substrate Materials in the Solid State
Authors: Koinuma Hideomi , Fukuda Kunio , Hashimoto Takuya , Fueki Kazuo
Published: February 2005

The solid phase chemical reaction between Ba2YCu3O7-δ (BYCO) and substrate materials has been investigated quantitatively by X-ray diffraction and ac-susceptibility measurements. The twelve substrate materials examined can be classified into four groups in the order of chemical reactivity with BYCO:SrTiO3, MgO<YSZ, Stainless steel (SUS-316), ZrO2, TiO2, Al2O3<Si, amorphous SiO2<WC, Cr2O3, CaF2. X-ray analysis indicates that Ba in BYCO is primarily responsible for the reactions with substrate materials. The electronegativity of a component in the substrate has a qualitative correlation with the reactivity of BYCO toward the substrate materials.
Single-Crystal Growth of Bi2(Sr, Ca)3-dCu2Ox and its Superconductivity
Authors: Nomura Shunji , Yamashita Tomohisa , Yoshino Hisashi , Ando Ken
Published: February 2005

A single crystal of Bi2.2(Sr, Ca)3-d
Cu2O
x
was grown by a self-flux method using a solution containing excess Bi2O3 and CuO compared to the composition of Bi2(Sr, Ca)3-d
Cu2O
x
in the Bi-Sr-Ca-Cu-O system. The dimensions of the single crystal obtained were up to 7×5×1 mm3.
The critical temperature of the single crystal was 84 K which was determined by both magnetization and electrical resistivity measurements. The ratio of resistivities in the c-plane and along the c-axis was found to be approximately 35 at T
c onset.
Effect of Fluorine on Superconducting Properties of Ba-Y-Cu-O and Sr-Ba-Y-Cu-O Systems
Authors: Sugise Ryoji , Ihara Hideo , Yokoyama Yuko , Okumura Tomoyuki , Hirabayashi Masayuki , Terada Norio , Jo Masatoshi , Koshizuka Naoki , Hayashida Ichiro
Published: February 2005

Superconducting properties of Ba-Y-Cu-O-F and Sr-Ba-Y-Cu-O-F compounds were studied on the samples prepared by two different methods, a gas method and a powder method. The samples from the powder method showed superconductivity with a high T
c above 90 K. The samples from the gas method, however, showed a semiconductive resistivity versus temperature and did not show superconductivity. The difference between lattice constants a and b decreased with increasing fluorine content, which indicated the fluorine occupation at the a-site. The XPS spectra of Ba and Cu core levels indicated that the cause of the deterioration of superconductivity was the doping with fluorine.
The Orthorhombic-to-Tetragonal Phase Transition in Sputtered Gd-Ba-Cu-O Thin Films by Low Temperature Processing
Authors: Hayashi Shigenori , Kamada Takeshi , Setsune Kentaro , Hirao Takashi , Wasa Kiyotaka , Matsuda Akihisa
Published: February 2005

An orthorhombic phase observed in prepared films with a high superconducting transition temperature (T
c) was found to be transformed into a nonsuperconducting tetragonal phase when annealed in a vacuum. Subsequent annealing of these films in an O2 atmosphere restored the superconducting orthorhombic phase. However, the dependences of T
c and the c-axis lattice parameter on O2 annealing temperature suggest that the structural deformation takes place within the orthorhombic phase including the ortho-I-to-ortho-II phase transition. Preliminary results of an evolution study on oxygen are also given.
Tc of c-Axis-Oriented Y-Ba-Cu-O Films Prepared by CVD
Authors: Yamane Hisanori , Kurosawa Hideyuki , Iwasaki Hideo , Masumoto Hiroshi , Hirai Toshio , Kobayashi Norio , Muto Yoshio
Published: February 2005

YBa2Cu3O7-x
thin films (0.8 µm in thickness) with c-axis orientation were prepared at 900°C on yttria-stabilized zirconia substrates by chemical vapor deposition using metal chelates as source materials. The onset and completion of the superconductive transition occurred at 89 K and 80 K, respectively, for the film that received in situ oxygen treatment. The oxygen-treated film had metallic resistivity and the resistance ratio (R273 K / R100 K) was 2.
Oxygen Content and Phase Diagram of the High-Tc Superconductor Ba2ErCu3Oy
Authors: Liang Ruixing , Nakamura Tetsurō
Published: February 2005

The oxygen content of Ba2ErCu3O
y
was determined by both thermogravimetric measurement and iodometric titration analysis. Four distinct regions were found in the diagram of log
P
O2
-1/T plots. These regions were proposed to correspond to: the first orthorhombic phase (OI), the second orthorhombic phase (OII), the tetragonal phase (T) and the coexistence of two phases. The partial molar enthalpy of oxygen, ΔH̄O2
, was obtained as -194±6 kJ/mol for the OI phase, -166±4 kJ/mol for the OII phase and -142+4 kJ/mol for the T phase. A pseudobinary phase diagram was proposed based on the log
P
O2
-1/T plots, quenching investigation and high-temperature X-ray diffraction analysis.
Formation of Bi-Sr-Ca-Cu-O Thin Films by a Laser Sputtering Method
Authors: Kanai Masaki , Kawai Tomoji , Kawai Maki , Kawai Shichio
Published: February 2005

Oriented Bi-Sr-Ca-Cu-O thin films with their c-axis perpendicular to the substrate surface were formed by a laser sputtering method. Films formed are classified into three types: a semiconductor, an 80 K superconductor and a 120 K superconductor, with the long axis lengths of the unit cell to be 24.4 Å, 30.8 Å and 36.8 Å, respectively.
Raman Study of (LaBa)2CuO4 Single Crystals
Authors: Koshizuka Naoki , Unoki Hiromi , Oka Kunihiko , Hayashi Kunihiko , Okuda Takashi , Kimura Youichi
Published: February 2005

Raman scattering of La2-x
Ba
x
CuO4 (x=0, 0.016) single crystals at various temperatures has been studied for the frequency range between 100 and 5000 cm-1. Besides an A1g phonon peak at 430 cm-1, the 480 and 725 cm-1 peaks are ascribed to the disorder-induced phonon modes which are allowed by the breakdown of lattice translational symmetry. The 940, 1220, and 1445 cm-1 peaks are thought to be the phonon overtone and combination modes. A two-magnon peak observed at 2900 cm-1 at room temperature in a La1.984Ba0.016CuO4 sample with fresh surfaces is also discussed.
The Effect of (NH4)2S Treatment on the Interface Characteristics of GaAs MIS Structures
Authors: Fan Jia-Fa , Oigawa Haruhiro , Nannichi Yasuo
Published: February 2005

MIS capacitors prepared on the (NH4)2S-treated GaAs substrate showed a marked reduction in the density of the dominant pinning levels near 0.6 eV below the conduction band. The annealing effect on the interface characteristics was also investigated. Analyses by means of secondary ion mass spectroscopy (SIMS) and Auger electron spectroscopy (AES) indicate that sulfur atoms at the interface stabilize the oxygen-free GaAs surface both electronically and thermally.
Studies on the Fully Automatic Horizontal Lifting Deposition of LB Films Using Double Gates
Authors: Kato Teiji
Published: February 2005

A high performance instrument for fully automatic horizontal lifting deposition of LB films was developed. By use of double gates and by devising deposition cycles, this instrument worked very skillfully to prepare LB films of good quality. Ethylstearate and octadecylacrylate were deposited as X-type LB films having the higher molecular order of structure. LB films of cadmium and lanthanum salts of arachidic acid deposited by the fully automatic horizontal lifting method gave extremely higher order X-ray diffraction corresponding to Y-type structure. These results reveal that this instrument is useful for preparing LB films of good quality, especially for materials forming rather rigid monolayers.
Crystallographic Study in the Nd2CuO4-Sr2CuO3 System
Authors: Takahashi Koh , Okai Bin , Kosuge Michikazu , Ohta Masatsune
Published: February 2005

A crystallographic study was done in the Nd2CuO4-Sr2CuO3 system. Five phases were found in this system; A: Nd2CuO4, B: Nd2SrCu2O6, C: (Nd0.45Sr0.55)3Cu2O6-y
, D: (Nd1-x
Sr
x
)2CuO4-y
, and E: Sr2CuO3. Phases B and C possess Sr3Ti2O7-type structures, and phase D has the same structure as La2CuO4. No superconductivity was observed in any of the above-mentioned phases down to 4.2 K.
Time-Resolved X-Ray Diffraction from a Silicon Crystal Irradiated by a Q-Switched Nd:YAG Laser
Authors: Kojima Shigeru , Kawado Seiji , Ishikawa Tetsuya , Takahashi Toshio , Kikuta Seishi
Published: February 2005

Using a highly collimated and harmonics-free X-ray beam obtained from synchrotron radiation, we studied the time-change behavior of a nearly intrinsic rocking curve from a Si single crystal irradiated by a Q-switched Nd:YAG laser. Time-resolved measurements were carried out by two fast X-ray detector systems using a plastic scintillation counter. The change of the rocking curve profile revealed the thermal expansion of Si due to the laser irradiation and its recovery process.
Heteroepitaxial Growth and the Effect of Strain on the Luminescent Properties of GaN Films on (11 2̄0) and (0001) Sapphire Substrates
Authors: Amano Hiroshi , Hiramatsu Kazumasa , Akasaki Isamu
Published: February 2005

GaN films grown on (11 2̄0) and (0001) sapphire substrates are characterized by X-ray Bond's method and the low temperature photoluminescence measurement. The GaN films are found to be strained by the biaxial compressive stress. From the measured strain and the shift of PL peak energy, the deformation potential of GaN (the relation between the strain parallel to the c-axis and the band gap energy) is found to be 12 eV. The origin of this compressive stress is discussed.
High-Resolution Electron Microscopy of the Tweed Microstructure in an Fe-Pd Alloy
Authors: Muto Shunsuke , Takeda Seiji , Oshima Ryuichiro , Fujita Francisco Eiichi
Published: February 2005

The tweed microstructure, which appears prior to an fcc-fct martensitic transformation in Fe-Pd, was investigated by high-resolution electron microscopy. The <110 > diffuse streaking in the electron diffraction pattern was well reproduced by optical diffraction of the high-resolution electron micrograph, which confirmed the origin of the tweed structure to be static modulations of lattice planes. The high-resolution image is considered to reflect the existence of small fct embryos irregularly dispersed in the fcc matrix, which give rise to the tweedy contrast in bright-field images.
Glass-Former-Doped Superconductors
Authors: Masuda Yumiko , Ogawa Yayoi , Ikushima Akira J.
Published: February 2005

Y1Ba2Cu3O7-y
(YBCO) samples containing boric oxide as a glass-former were prepared by the melt-cast method and investigated by electric resistivity and X-ray diffraction. Superconducting transitions were observed in samples with less than 2 mol% boric oxide, whereas those with more than this amount did not show any superconducting transition down to 15 K. X-ray diffraction experiments indicated that reaction of boric oxide with other oxides composing YBCO did not form the superconducting structure. Recovery of the superconductivity was observed in the samples doped with 2.5 and 5 mol% boric oxide when a slightly excess amount of BaO2 was added.
Superconductivity of Screen-Printed YBa2Cu3Oy Thick Films on Y2BaCuO5 Substrates
Authors: Yoshiara Kiichi , Kagata Kenji , Yokoyama Shoichi , Hiroki Tsutomu , Higuma Hiroko , Yamazaki Teruhiko , Nakahigashi Kiyotaka
Published: February 2005

YBa2Cu3O
y
superconducting thick films have been prepared on Y2BaCuO5 substrate by the screen printing and sintering method. The critical temperature T
c and current density J
c at 77 K in an absence of magnetic fields were extremely high as compared with the films printed on the other ceramic substrates such as MgO, SrTiO3 and YSZ, and were 86 K and 3000 A/cm2, respectively.
Formation of Bismuth Strontium Calcium Copper Oxide Superconducting Films by Chemical Vapor Deposition
Authors: Yamane Hisanori , Kurosawa Hideyuki , Hirai Toshio , Iwasaki Hideo , Kobayashi Norio , Muto Yoshio
Published: February 2005

Superconducting films of bismuth strontium calcium copper oxides were prepared by chemical vapor deposition at 910°C and 1 Torr on MgO substrate using a bismuth alkoxide and β-diketonate chelates of Sr, Ca and Cu as source materials. In the film with T
c(zero) of 78 K, the predominant phase was Bi2(Sr, Ca)3Cu2O
x
with the c-axis perpendicular to the substrate.
Structure and Superconducting Properties of TlCan-1Ba2CunO2n+3 Thin Films with Zero Resistance at Temperatures above 100 K
Authors: Huang T. C. , Lee W. Y. , Lee V. Y. , Karimi R.
Published: February 2005

New superconducting TlCa
n-1Ba2Cu
n
O2n+3 thin films have been analyzed by the X-ray diffraction and four-point probe techniques. The films consist mainly of a single TlCa2Ba2Cu3O9 phase or a mixture of the TlCa2Ba2O9 and TlCaBa2Cu2O7 phases with the c-axis preferentially oriented perpendicular to the film surface. The TlCa2Ba2Cu3O9 film grown on an asymmetrically cut yttrium-stabilized ZrO2 (YSZ) substrate has the highest superconducting transition with on-set T
c near 120 K and zero resistance at 116 K. The TlCa2Ba2Cu3O9 film deposited on a SrTiO3 (100) substrate has a slightly lower transition with zero resistance at 104 K probably because of stacking faults. The film composed of both the TlCa2Ba2Cu3O9 and TlCaBa2Cu2O7 phases and grown on YSZ has a double transition with on-set T
c near 118 K and 107 K, and zero resistance at 102 K.
Fabrication of Superconducting Y-Ba-Cu Oxide Through an Improved Diffusion Process
Authors: Tachikawa Kyoji , Sadakata Nobuyuki , Sugimoto Masaru , Kohno Osamu
Published: February 2005

The formation of the YBa2Cu3O7-y
layer has been investigated by a modified diffusion process as a basic research for high-T
c superconductor fabrication. The starting materials were Y2BaCuO5 and barium cuprate (Ba:Cu=3:5), unlike the ordinary sintering technique. A dense layer of YBa2Cu3O7-y
was formed on Y2BaCuO5 substrate, and the starting barium cuprate layer was fully converted to the superconducting phase. X-ray diffractometry revealed that the layer consisted of an orthorhombic crystal structure. A zero resistance of 91.5 K and a critical current density of 1900 A/cm2 (77 K, 0 T) were achieved in the layer.
Microstructure and Superconducting Properties in YBa2Cu3O7-x Ceramics Doped with Nb2O5 and WO3
Authors: Kuwabara Makoto , Kusaka Narutoshi
Published: February 2005

The effect of the addition of Nb2O5 and WO3 on the microstructure and superconducting properties in YBa2Cu3O7-x
ceramics has been investigated. It has been found that the microstructures of the two YBa2Cu3O7-x
samples to which were added Nb2O5 and WO3 were both characterized by prism-like grains and grain boundary segregations of the added elements. The superconducting transition temperature (T
c) showed no considerable changes in both series of samples of Nb-doped and W-doped YBa2Cu3O7-x
ceramics, while the critical current density was found to be significantly improved in the doped materials (570 A/cm2 for one of the Nb-doped samples and 690 A/cm2 for one of the W-doped samples were obtained at 77 K and H=0 T) compared with that (420 A/cm2) in the undoped YBa2Cu3O7-x
ceramics. All samples used were sintered at 1000°C in flowing O2.
Y-Ba-Cu-O Thin Film on Si Substrate
Authors: Harada Keizo , Fujimori Naoji , Yazu Shuji
Published: February 2005

Superconducting Y-Ba-Cu-O thin films have been prepared by RF magnetron sputtering on Si(100) substrate with a buffer layer of ZrO2 or MgO. The film with a ZrO2 buffer layer exhibited a superconductive transition with zero resistance at 82 K. X-ray diffraction patterns indicated a preferential orientation where c-axes were perpendicular to the substrate.
Giant Faraday Rotation of Ce-Substituted YIG Films Epitaxially Grown by RF Sputtering
Authors: Gomi Manabu , Satoh Kensuke , Abe Masanori
Published: February 2005

Cerium substituted yttrium iron garnet films epitaxially grown by rf diode sputtering were found to have exceptionally large Faraday rotation in the visible and near infrared (1–2 eV). Faraday rotation at room temperature is enhanced in proportion to Ce content by a factor per Ce ion of 2×104 deg/cm for λ=633 nm and -1.3×104 deg/cm for 1150 nm. The latter factor is 5 times higher than that by Bi. The Ce-substituted YIG films are the most promising magneto-optical materials.
New Approach to Low-Temperature Epitaxial Growth of GaAs by Photostimulated Metalorganic Chemical Vapor Deposition
Authors: Kachi Tetsu , Ito Hiroshi , Terada Shigeo
Published: February 2005

The epitaxial growth of high-quality GaAs using trimethyl-gallium (TMG) and arsine (AsH3) at low temperatures (∼500°C) is reported. The growth has been performed with photostimulation using a CO2 laser and an ultrahigh-pressure Hg lamp. The CO2 laser irradiation absorbed by AsH3 was effective for enhancement of the growth rate at temperatures below 600°C and the ultraviolet light from the Hg lamp was effective for improvement of the quality of the growth layers. The measurements of the electrical and optical properties showed that high-quality epitaxial layers were obtained at the growth temperatures down to 500°C by this method.
Measurement of the SiH3 Radical Density in Silane Plasma using Infrared Diode Laser Absorption Spectroscopy
Authors: Itabashi Naoshi , Kato Kozo , Nishiwaki Nobuki , Goto Toshio , Yamada Chikashi , Hirota Eizi
Published: February 2005

The SiH3 radical is an important precursor in amorphous silicon thin film formation, but its density in silane plasma has never been measured. In this work, we have developed a method for measuring the SiH3 radical density using an infrared diode laser absorption method and have determined the density in a pulsed SiH4/H2 plasma.
Large Change of Electrical Conductivity and Absorption Spectrum of Poly(3-alkylthiophene) at the Solid-Liquid Phase Transition
Authors: Yoshino Katsumi , Park Dae Hee , Park Bok Kee , Onoda Mitsuyoshi , Sugimoto Ryu-ichi
Published: February 2005

Electrical conductivity of poly(3-alkylthiophene) such as poly(3-dodecylthiophene) and poly(3-docosylthiophene) decreases in a step-wise manner at the melting point. The absorption spectra also changes rapidly at the phase transition. These phenomena are discussed in terms of the increased energy band gap in the liquid state due to the decrease of the co-planarity of thiophene rings accompanied by remarkable conformation changes. Large hysteresis was also observed in the temperature dependence of conductivity and absorption spectra. Thermochromism in the premelting region can be explained by effective shortening of the conjugation length due to the introduction of torsion of the thiophene rings at several points on a conjugated chain.
Gas-Sensitive Optical Absorption of Ultrafine Silver Particles Dispersed in a Porous Silica Film
Authors: Yanase Akihisa , Komiyama Hiroshi , Tanaka Kazunobu
Published: February 2005

In situ, real-time measurements of the optical absorption of ultrafine silver particles of about 9 nm dispersed in a porous silica film are carried out under defined atmospheres over a temperature range of 300 K to 653 K. A reversible change in the optical absorption spectra resulting from the atmosphere exchange between 1% O2 and 20% CO is observed for the first time, which indicates a shape change of silver particles induced by the adsorption and desorption of oxygen.
Preparation of Y-Ba-Cu-O Superconducting Thin Film by Chemical Vapor Deposition
Authors: Shinohara Kazuhiko , Munakata Fumio , Yamanaka Mitsugu
Published: February 2005

Y-Ba-Cu-O film was prepared by chemical vapor deposition using tris(2,2,6,6-tetramethyl-3,5-heptanedionato)yttrium(III) (Y(DPM)3), bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)barium(II) (Ba(HFA)2) and bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)copper(II) (Cu(HFA)2). Superconducting transition was observed with T
c(onset)=83 K and T
c(R=0)=65 K for these CVD films after an annealing process. Typical films of Y-Ba-Cu-O on a (001) SrTiO3 substrate exhibited the presence of YBa2Cu3O
y
according to X-ray diffraction patterns.
Instantaneous Preparation of Superconducting Thick Films through Melts in the Bi-Ca-Sr-Cu-O System
Authors: Akamatsu Yoshinori , Tatsumisago Masahiro , Tohge Noboru , Tsuboi Shinzo , Minami Tsutomu
Published: February 2005

Thick films of Bi-Ca-Sr-Cu-O superconductors were instantaneously prepared by crystallization through melts on a MgO single-crystal substrate. It took only half an hour in annealing to obtain superconducting thick films with T
c (zero) of 93 K and T
c (onset) of 98 K. From the X-ray diffraction patterns of these films, it was found that the superconducting phase was strongly oriented along the c-axis perpendicular to the substrate.
Thermally Stimulated Luminescence from High-Tc Superconducting Tl-Ba-Ca-Cu-O System
Authors: Fujiwara Yasufumi , Tonouchi Masayoshi , Kobayashi Takeshi
Published: February 2005

We have succeeded in observing a characteristic X-ray excited thermally stimulated luminescence (TSL) from the high-T
c superconducting Tl-Ba-Ca-Cu-O system. The TSL glow curve consists of several peaks, indicating that some traps exist in this system, whose wavelength region ranges from the ultraviolet to visible region. Through analyses of the TSL glow peaks, the activation energies of the related traps are found to range from 0.1 eV to 0.3 eV. The cumulative X-ray irradiation time dependence of the TSL intensities has been systematically investigated.