bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of Resistivity of Polycrystalline Si Films by Solid-Phase Recrystallization (SPR)
Authors: Mizushima Ichiro , Tabuchi Wataru , Kuwano Hiroshi
Published: February 2005

The effect of the grain size after solid-phase recrystallization (SPR) on the resistivity of polycrystalline Si (poly-Si) films was investigated in detail. SPR poly-si films were obtained by amorphization by Si ion implantation and by subsequent recrystallization by low-temperature furnace annealing. Resistivity could be precisely controlled by choosing the doping concentration and by full amorphization and recrystallization at a fixed temperature. This was due to the controlled increase in grain size and the decrease in trapping state density per unit volume. An advanced model on the resistivity was proposed in which the resistivity dependence on the dopant concentration was well explained. It was indicated that the grain boundary of SPR poly-Si films exhibits the same electrical characteristics as that of as-deposited films.
Working Principles of an Ion Flyer Composed of Needle and Ring Electrodes
Authors: Murakami Hiroyuki
Published: February 2005

The working principles of an ion flyer are explained phenomenally using a simple model composed of a needle electrode and a ring electrode. A positive or negative DC voltage in the region of 0–20 kV is applied to the needle electrode, and the ring electrode is earthed. Thrust, discharge current, and beam current are measured under air pressure in the region of 20–101 kPa. The maximum thrust is 4.6 mN for the applied voltage 20 kV under atmospheric pressure. This ion flyer is useful in a low-gravity or zero-gravity state in an air atmosphere.
Application of a Frame Transfer-Type CCD as an X-ray Image Sensor
Authors: Tsunemi Hiroshi , Mizukata Katsuya
Published: February 2005

We report here the result of an application of a CCD for optical use in the several keV region at working temperature below -30degC. The CCD we used is a product of TI Japan Corporation of a frame transfer-type device. We could take X-ray images at energies of about 8 keV and 1.5 keV for various objects. We found that this device could yield sufficient information for a two dimensional image down to individual pixel size (11.5×27 µm). We measured the pulse height distribution of X-rays of the 2–8 keV region in a photon counting mode. The energy resolution was kept constant about 400 eV (FWHM) by picking up the events absorbed in the depletion layer (about 3 µm).
Characteristics of Double Probe in Negative Ion-Containing Plasmas
Authors: Amemiya Hiroshi
Published: February 2005

Analysis of current-voltage characteristics of a generalized asymmetric double probe is made for plasmas containing negative ions. Characteristics are insensitive to negative ions up to a critical negative ion density ratio (>0.9), and tend to obey the tanh formula below this ratio. This critical value increases with higher negative ion mass. Applicability to negative-ion diagnostics is also considered.
Epitaxial Growth of Superconducting Nb3Ge Films on YSZ Single-Crystal Substrates
Authors: Asano Hidefumi , Tanabe Keiichi , Katoh Yujiro , Michikami Osamu
Published: February 2005

Yttria-stabilized cubic zirconia (YSZ:(ZrO2)1-m
(Y2O3)
m
)) single crystals are used as substrates for epitaxial growth for A15 Nb3Ge owing to the good lattice parameter matching. It is demonstrated that by means of magnetron sputtering, highly oriented crystallizes of A15 Nb3Ge grow epitaxially with the orientation relationship (100)A15∥(100)YSZ. The epitaxy considerably reduces the initial transition region usually observed for high-T
c Nb3Ge deposited on sapphire substrates. Tunneling as a function of thickness, used for material diagnosis, also shows an improvement in the quality of the epitaxial films, especially in the initial deposition layers.
Temporal Changes of Molecular Alignments of Nematic Liquid Crystals
Authors: Yamashita Masafumi , Tako Toshiharu , Ishiguro Kozo
Published: February 2005

Temporal changes of the molecular alignments on nematic liquid crystals are considered dynamically on the basis of experimental results, computer simulations of conoscopic figures and the Voigt model in viscoelastic theory. By assuming the molecular alignments of liquid crystals to follow the modified trapezoidal approximation model, the conoscopic figures obtained from the computer simulations agree semi-quantitatively with those from the experiments. It becomes clear from the Voigt model that the sharpness of isogyre of the conoscopic figures depends on the number of aligned thin molecular layers corresponding to the applied voltage; this is reconfirmed from computer simulations of the conoscopic figures.
Effect of Hydrogen Dilution on Structure of a-Si:H Prepared by Substrate Impedance Tuning Technique
Authors: Matsuo Shinji , Ueda Masato , Imura Takeshi , Osaka Yukio
Published: February 2005

The effect of hydrogen dilution of a source gas, SiH4, on structural inhomogeneity has been studied for hydrogenated amorphous silicon films prepared under the mode involving a high deposition rate by the substrate impedance tuning technique. As the silane fraction decreases from 100% to 1% with hydrogen dilution, the SiH bonding configuration gradually changes into the dihydride (SiH2) group; finally, the films become microcrystalline. On the other hand, the state density in the mid gap and the spin density, related to the structural disorder, have minima at silane fractions of 100% and 10%. These results seem to be consistent with a two-phase model suggested for high rate films, with an emphasis on a different medium range disorder between the films prepared at high and low deposition rates.
Simultaneous Measurement of Microscopic Image and Discharge Pulses at the Moment of Electrical Tree Initiation
Authors: Hozumi Naohiro , Okamoto Tatsuki , Fukagawa Hiromasa
Published: February 2005

This paper reports some experimental results concerning the tree initiation from a semiconductive needle electrode in polyethylene under a 50 Hz AC voltage. With a newly developed measuring system, the correspondence between partial discharge pulses and tree initiation and growth up to 10-20 µm in length was clarified for the first time. Tree observation and pulse measurement were made simultaneously. At the moment of tree initiation, positive pulses (current from the needle towards the grounding electrode) of 0.05-0.1 pC were first observed. A very small shade of the initial tree was observed when continuous positive pulses appeared; it grew rapidly to about 10 µm in length, along with the positive and negative pulses. After the tree branched, the growth rate dropped for a while. In many cases, the negative pulses disappeared during this stage.
Oxygen Ordering in YBa2Cu3O6+x
Authors: Nakamura Keikichi , Ogawa Keiichi
Published: February 2005

The orthorhombic and tetragonal phase relation, i.e. the order-disorder phase transformation in YBa2Cu3O6+x
, has been studied by employing statistical thermodynamics, and the equilibrium value of order parameter -1≦s≦1 has been determined as a function of the temperature and oxygen concentration. In the above-mentioned treatment, plus and minus signs of s in the ordered state (|s|≠0) are found to describe the degree of order in the twin related crystals. The calculated properties are compared with the experimental data, i.e. the temperature dependence of oxygen occupancy at a constant oxygen pressure and the concentration dependence of axial lengths, a and b, at room temperature. The agreement is excellent for both cases when the axial lengths at room temperature are measured for the samples with oxygen removed or doped at low temperatures. The statistical thermodynamical expression for further ordering has also been derived.
Longitudinal Mode Competition and Asymmetric Gain Saturation in Semiconductor Injection Lasers. II. Theory
Authors: Ogasawara Nagaatsu , Ito Ryoichi
Published: February 2005

Gain saturation in semiconductor lasers is analyzed using a density matrix formalism. A refined treatment of the density matrix formalism reveals that nonlinear gain has a component which is asymmetric with respect to the lasing frequency. The asymmetric component originates from refractive-index modulation due to a carrier-density pulsation induced by the optical-intensity beat. Based on the analysis, mode competition behavior is numerically examined using appropriate values of the linewidth enhancement factor and the intraband relaxation time. It is shown that the output power decreases at mode jumping from a shorter to a longer wavelength mode while it increases at mode jumping toward shorter wavelengths. The results agree with the features of the mode competition behavior observed in transverse-mode-controlled AlGaAs lasers.
Decarbonization by Using ECR Plasma
Authors: Ishibe Yukio , Kokai Hideki , Oyama Hitoshi , Sakamoto Yuichi
Published: February 2005

Decarbonization rates were measured by the use of ECR plasmas of H2 or O2. The rates are 2.0×1016 m-2s-1 for H2 and 2.4×1018 m-2s-1 for O2 at the same pressure of 1.6×10-2 Pa.
The rate for O2 is two orders of magnitude higher than that for H2. These results are analyzed depending on the equilibrium theory and the processing of decarbonization can be explained.
Relation between the Powder Charge and the Shape of the Pipe in Pneumatic Conveyance
Authors: Masui Noriaki
Published: February 2005

The electrification of a polymer powder transported though U-bend pipes was studied at particle speeds of ν=17.6 m/s and 26.4 m/s, and a solid load p=0.017 kg / m3. The charge / mass ratio, q, of powder passing through the U-bend pipes (seven different radii of curvature) depended on the flow pattern of the powder particles after their first collision with the inner wall of the bend of the pipe.
Electron-Phonon Scattering in Semiconductor Superlattices in a Quantizing Magnetic Field
Authors: Kubakaddi S. S. , Mulimani B. G. , Sankeshwar N. S.
Published: February 2005

Total electron-phonon scattering rates are obtained in an ideal superlattice in a quantizing magnetic field. The dispersion of an electron along the superlattice axis is assumed to be of a tight-binding type. Compact analytical expressions are possible for acoustic and nonpolar optical phonon scattering. The numerical results for acoustic and nonpolar optical phonon scattering rates are presented for the GaAs/Ga1-x
Al
x
As superlattice and the effect of miniband width parameters on these scattering rates is discussed.
Etch Rate Distribution over Silicon Wafers in EPW Solutions
Authors: Matsuoka Masakuni , Araki Yasushi , Yoshida Yukoh
Published: February 2005

Anisotropic etching of silicon wafers in ethylenediamine-pyrocatechol-water (EPW) solutions was carried out to reveal the distribution of etch rates over the wafer. The etch depth, i.e., the etch rate on the wafers, was found to vary within a few percent about the average value, and the standard deviation depended on the etch conditions such as temperature and flow patterns in the solution. The distribution was shown as a map and statistically analyzed. The major factor affecting the distribution was found to be the mass transfer in the solution via flow patterns in the solution.
Ferrite Plating of (Fe, Ni, Zn)3O4 Films in Aqueous Solution by an “Improved” Spray-Spin-Coating Method
Authors: Itoh Tomoyuki , Abe Masanori , Tamaura Yutaka
Published: February 2005

Polycrystalline films of Zn- and/or Ni-bearing spinel ferrites were prepared at 80degC by ferrite plating based on an “improved” spray-spin-coating method. A reaction solution with a low pH value (i.e., ∼5.2) was used, thus enabling the use of oxygen-containing water instead of oxygen-free water. This saved the labor of preparing the oxygen-free water. The experimental method is thus “improved” over the previous one which required oxygen-free water. The composition parameter, x, in the Fe3-x
Zn
x
O4 films is much larger than the corresponding one, x', in the reaction solution (x/x'=∼5), while x is smaller than x' in the Fe3-x
Ni
x
O4 films (x/x'=∼0.4). Even prepared at 80degC, all films were of good crystallinity and of good magnetic property comparable to those prepared at higher temperature, as revealed by X-ray, magnetic and Fe57 Mössbauer measurements.
Origin of Hysteresis-like Behavior in Flow Transition in Simulations of the Czochralski Method with Tetradecane
Authors: Kimura Hiroshi
Published: February 2005

A hysteresis-like behavior in the flow transition is experimentally discussed in terms of interactions of the natural convection with the forced convection from the viewpoint of crystal growth from a melt.
On the Uniformity of Thin a-Si:H Films Prepared in an RF-Glow Discharge System
Authors: Myburg G. , Swanepoel R.
Published: February 2005

The present work reports a study of the uniformity of 500- to 4000-nm-thick a-Si:H films deposited by glow discharge from undiluted pure monosilane. The techniques chosen to study the uniformity of these films encompassed the obtaining of reflection interference patterns and transmission spectra (400 nm\leqslantλ\leqslant900 nm) of the film-substrate configuration. The film thickness d, the homogeneity parameter Δd and the optical properties such as n(λ), α(λ) and E
0 were calculated from the transmission data. Five preparation parameters, pressure, rf power, gas flow rate, substrate temperature and geometry of the anode were varied. The influence of a sixth parameter, film thickness, was also studied. The results showed that large variations occurred in the film thickness from point to point on a single film. In contrast to this, the other optical parameters n(λ), α(λ) and E
0 remained constant.
Photoluminescence Properties of Nitrogen-Doped ZnSe Films Grown by Low-Pressure MOVPE
Authors: Yoshikawa Akihiko , Muto Shin-ichiro , Yamaga Shigeki , Kasai Haruo
Published: February 2005

Nitrogen-doped ZnSe layers were grown on (100) GaAs by low-pressure MOVPE using dimethylzinc and hydrogenselenide as reactants. Ammonia was used as a dopant source. The ZnSe films were characterized mainly by measuring photoluminescence at low temperatures, where ammonia-gas flow rate was changed. It has been reconfirmed that nitrogens can be incorporated into ZnSe as shallow acceptors with activation energy of about 100–110 meV. However, in heavily doped ZnSe films, it has been found that the nitrogens are no longer shallow acceptors, but deep centers associated with Y lines, and other types of deep centers are introduced.
Modulated Structures in Superconductor Tl-Ba-Ca-Cu-O Oxides: Crystal Structure of Tl2Ba2CuO6+x Phase
Authors: Iijima Sumio , Ichihashi Toshinari , Shimakawa Yuichi , Manako Takashi , Kubo Yoshimi
Published: February 2005

A crystal structure of Tl2Ba2CuO6+x
oxide, which was not a superconductor, was studied by an electron microscope. The unit cell parameters are a=b=3.85 Å and c=23.02 Å. The crystal was found to be one of a series of compounds expressed by Tl2Ba2Ca
n
Cu
n+1O2(3+n)+n
in Tl-Ba-Ca-Cu-O (TBCCO) oxide systems. The crystal has an incommensurate superstructure modulation in the (100) planes, whose occurrence is different from the (110) plane modulation found in Bi-Sr-Ca-Cu-O (BSCCO) systems. The modulation takes place in the BaO-TlO-TlO-BaO slabs with a period 6.6×a along the [100] direction.
Characterization of a Non-Superconducting Cuprate, Bi2Sr2YCu2O8.5
Authors: Tamegai Tsuyoshi , Watanabe Akiko , Koga Kei-ichi , Oguro Isamu , Iye Yasuhiro
Published: February 2005

A new Bi-containing cuprate, Bi2Sr2YCu2O8.5, was found in the course of substitution study for high T
c compounds Bi2Sr2CaCu2O8+y
. Bi2Sr2YCu2O8.5 is a semiconductor and undergoes an antiferromagnetic transition at about 13 K which is considered to originate from the ordering of Cu in the CuO2 planes. An electron diffraction study revealed the existence of a superstructure. The unit cell taking account of the superstructure is 1×8×1 of the original unit cell (5.47×5.43×30.18 Å3). Analogy of three kinds of oxide systems, (La1-x
Sr
x
)2CuO4, YBa2Cu3O6+x
, and Bi2Sr2Ca
x
Y1-x
Cu2O8+y
, is discussed.
Highly Uniform, High-Purity GaAs Epitaxial Layer Grown by MBE Using Triethylgallium and Arsenic
Authors: Saito Junji , Ono Katsuji , Nanbu Kazuo , Ishikawa Tomonori , Kondo Kazuo
Published: February 2005

We studied the growth of undoped GaAs epitaxial layers by molecular beam epitaxy using triethylgallium (TEG) and arsenic (As4). The variations in layer thickness over the 3-inch GaAs substrate decreased as the TEG flow rate increased. The carrier concentration of the undoped GaAs epilayer decreased as the As4 pressure increased at a constant TEG flow rate and the material converted from p- to n-type conductivity. The Hall mobility of the free carriers in the n-type film was 81,300 cm2/Vs (77 K) at a carrier concentration of n=4.1×1014 cm-3. This indicates a low level of compensation in the epilayer.
A New Solid State Cell with LiI as Solid Electrolyte
Authors: Franco J. I. , González O. A. , Walsöe de Reca N. E.
Published: February 2005

A new solid and miniaturized cell of the type Li/LiI/CTC (where CTC is a charge transfer complex formed by an organic compound and iodine) is proposed. It can be employed to feed low-power devices.
Process and Resistivity Studies of the High-Tc Superconductors in Tl-Ca-Ba-Cu-O
Authors: Liu R. S. , Lee W. H , Wu P. T. , Chen Y. C. , Chang C. T.
Published: February 2005

We report a method of sample preparation of thallium containing superconducting oxide system and the effects of subsequent heat treatment on superconducting properties of the compounds with the nominal composition TlCa3BaCu3O
y
, Tl2CaBa2Cu2O
y
and Tl2Ca2Ba2Cu3O
y
. Zero resistance at 123 K and the onset of superconductivity around 155 K have been achieved. In this paper, the optimum processing variables and the X-ray diffraction results are discussed.
Incorporation of Constituent Atoms of Transparent Conductive Films into Hydrogenated Amorphous Silicon via Gas Phase
Authors: Hirao Takashi , Yoshioka Yoshiaki , Kitagawa Masatoshi , Miyauchi Michihiro , Matsuda Akihisa , Tanaka Kazunobu , Wasa Kiyotaka
Published: February 2005

Thin films of hydrogenated amorphous silicon (a-Si:H) were deposited on single-crystal silicon (c-Si) surrounded by ITO or SnO2 films as a function of substrate temperature. It was found that In atoms are incorporated in the a-Si:H films on c-Si while Sn atoms are hardly detected. The concentrations of In atoms in the a-Si:H films on c-Si and ITO films are in the range of 1017–1018/cm3 and 4×1017–1020/cm3, respectively, in the temperature range studied (room temperature-280°C. Annealing steps subsequent to the a-Si:H deposition without substrate heating resulted in a slight change in the concentration profile of In atoms. It is deduced that the In atoms resulting from the reduction of ITO films by SiH4-H2 plasma are incorporated into the a-Si:H films on c-Si via a gas phase. The gas-phase doping is markedly dependent upon the atomic species and deposition temperature. This may also be one of the important mechanisms responsible for the In incorporation into a-Si:H films on ITO films.
Preparation and Properties of Tl-Ca-Ba-Cu-O
Authors: Takahashi Kazuhiko , Nakao Masao , Dietderich D. R. , Kumakura Hiroaki , Togano Kazumasa
Published: February 2005

The superconducting properties, T
c and J
c, of compounds in the Tl-Ca-Ba-Cu-O system were investigated on bulk specimens sintered at temperatures between 890°C and 940°C. It was determined that 910°C was the optimum temperature for the formation of the high-T
c phase. This heat treatment temperature produces the maximum values of T
c (zero-resistance) and J
c (77 K, 0 T), 118 K and 600 A/cm2, respectively. The results of X-ray diffraction and magnetic susceptibility measurements show that the volume fraction of high-T
c phase is maximized at this temperature.
Effects of Lattice Mismatch on Crystallographic Properties of ZnS Grown on GaP and GaAs by MOCVD
Authors: Mitsuishi Iwao , Mitsuhashi Hiroshi , Kukimoto Hiroshi
Published: February 2005

The unusual phenomenon that largely lattice-mismatched ZnS layers grown on GaAs by MOCVD show better surface morphology and crystalline quality than less mismatched ZnS layers on GaP has been investigated by X-ray diffraction measurements. The results indicate that this phenomenon can be ascribed to the strain-relaxation taking place at an earlier stage of epitaxial growth on GaAs than on GaP substrates.
A New Method for Measurement of MOSFET Channel Length
Authors: Jain Sanjay
Published: February 2005

We use the transresistance r≡g

m
/g
2 to measure channel length of MOSFET's with arbitrary parasitic source-drain series resistance. The channel length error due to the bias dependence of series resistance is completely eliminated by extrapolation to zero gate drive. The final accuracy is limited by sourcedrain asymmetry and errors in threshold voltage measurement; measurements on 0.5 µm lightly-doped drain MOSFET's indicate it is about 3 nm and a factor of seven better than previous methods.
New Stable Icosahedral Al-Cu-Ru and Al-Cu-Os Alloys
Authors: Tsai An-Pang , Inoue Akihisa , Masumoto Tsuyoshi
Published: February 2005

A thermodynamically stable quasi-crystalline single phase with an icosahedral structure was found to be formed at atomic compositions of Al65Cu20Ru15 and Al65Cu20Os15 in conventionally solidified and fully annealed states as well as in a rapidly solidified state. The quasi-crystalline nature determined by X-ray diffractometry is the highest for the fully annealed ingot, indicating the existence of a truly equilibrium icosahedral structure. The stable quasi-crystals appear to have a growth morphology of pentagonal dodecahedron with an average size of 0.03 mm in a fully annealed state.
Complex Susceptibility of Bi, Pb-Sr-Ca-Cu-O Superconductors
Authors: Mazaki Hiromasa , Takano Mikio , Takada Jun , Oda Kiichi , Kitaguchi Hitoshi , Miura Yoshinari , Ikeda Yasunori , Tomii Yoichi , Kubozoe Tadayoshi
Published: February 2005

In terms of complex susceptibility χ=χ'-iχ'', we measured the superconducting transition of the Bi, Pb-Sr-Ca-Cu-O systems, which were prepared by partial substitution of Pb for Bi. The observed χ of the disk samples shows that they contain both the bulk phase and the Josephson-like coupling phase, being similar to other oxide superconductors. From measurements of the powdered samples, we find that the system mostly consists of the high-T
c phase, of which the onset temperature lies in the range of 115–120 K. The low-T
c phase (80 K) is still involved, but the amount is roughly estimated to be 5% or less.
An XPS Study of the Passivating Oxide Layer Produced on GaAs (001) Substrate by Heating in Air above 200°C
Authors: Contour J. P. , Massies J. , Fronius H. , Ploog K.
Published: February 2005

The passivating oxide layer resulting from a high-temperature (250°C in air) GaAs substrate preparation procedure has been analysed by X-ray photoelectron spectroscopy. It is shown that the protective film obtained from heating a semi-insulating substrate in clean air to 250°C is mainly gallium oxide whereas it is an arsenic-rich mixture of As and Ga oxides after the standard preparation procedure. At this temperature, the oxidation steady-state conditions are reached after 5 minutes of heating. The higher the passivating temperature, the lower the arsenic content of the oxide layer.
Strong Flux Pinning by Cracks in Films of Superconducting Oxide
Authors: Matsushita Teruo
Published: February 2005

The possibility of flux pinning by cracks along basal planes in single-crystalline films of a superconducting oxide is theoretically investigated. For a single-crystalline film with thec-axis parallel to a substrate, the transport current can flow along the basal plane without an influence of the cracks, while the cracks act as strong pinning centers that prevent fluxoids from moving along thec-axis due to the Lorentz force. The critical current density in YBaCuO atT=77 K andB=5 T is estimated as 1.7×1010A/m2in the case of a mean interval of the cracks of 50 nm. This value is larger than that in Nb3Sn at 4.2 K.
Preparation of a-Si:H Films Resistive to the Staebler-Wronski Effect
Authors: Yamazaki Motoharu , Ohagi Hideki , Nakata Jun-ichi , Imao Shozo , Shirafuji Junji , Fujibayashi Keiji , Inuishi Yoshio
Published: February 2005

Undoped a-Si:H films with much reduced sensitivity to the optical degradation (Staebler-Wronski effect) were prepared by the combination of conventional plasma CVD starting from pure silane and subsequent lamp annealing at 450∼500°C for 10∼15 min in nitrogen. It was observed that both the photoconductivity and the ratio of photoconductivity to dark conductivity was not appreciably degraded by the lamp annealing, indicating the absence of the unintentional doping which often appears in a-Si:H prepared by conventional plasma CVD with high substrate temperature and in µc-Si:H from highly diluted SiH4 with H2.
Production of a Large-Diameter Uniform ECR Plasma with a Lisitano Coil
Authors: Yonesu Akira , Takeuchi Yoshiaki , Komori Akio , Kawai Yoshinobu
Published: February 2005

A large-diameter uniform plasma was demonstrated to be produced by electron cyclotron resonance heating with a slotted Lisitano coil of 40 cm diameter. The diameter of the realized uniform plasma was found to be almost equal to that of the Lisitano coil. It was also suggested that the microwave is propagated in the whole region inside the Lisitano coil, and produces the uniform plasma.
Suspension Spinning of Bi-Sr-Ca-Cu-Oxide Superconductor
Authors: Goto Tomoko , Takeuchi Katsuhiko
Published: February 2005

Suspension spinning of Bi1Sr1Ca1Cu2 oxide was examined to prepare a long filament with high-T
c. The various starting powders were suspended in PVA solution. The viscous suspension was extruded as a filament and subjected to heat treatment to remove volatile components and to generate oxide in the superconducting phase. The filament obtained was about 300 µm in diameter and had a mixed phase of high-T
c at 115 K and low-T
c at 80 K. Superconductivity exceeding the liquid nitrogen temperature was detected for the filament through the starting powder prepared by coprecipitation of the oxalates.
Optical Absorption of YBa2Cu3O7-δ and ErBa2Cu3O7-δ Crystals due to Interband Transition
Authors: Wang Xiao-lei , Nanba Takao , Ikezawa Mikihiko , Hayashi Shigeyuki , Komatsu Hiroshi
Published: February 2005

Reflectivity in the a-b plane of single crystals of orthorhombic YBa2Cu3O7-δ and ErBa2Cu3O7-δ has been measured at room temperature in the photon energy region from 0.05 to 30 eV and the spectra of absorption and energy loss function have been obtained by the Kramers-Kronig analysis. General features of the structure in the spectra of the Y-compound in the interband transition region from 1 to 8 eV are consistent with those calculated by Zhao et al. based on the energy band theory, but peaks in the observed absorption spectrum are shifted by 1 to 2 eV to the high energy side compared with the calculation.
Detection of the Polarization Rotation of Reflected Light Using an Optical Feedback Effect in a Laser Diode
Authors: Toda Tsuyoshi , Ogasawara Nagaatsu , Ito Ryoichi
Published: February 2005

It is shown that the polarization state, the light-current characteristics and the terminal voltage of a buried-heterostructure laser are changed by altering the polarization direction of a laser beam which is reflected back on the laser diode itself. This phenomenon is utilized to detect time-varying polarization rotations of reflected light.
Dynamical X-Ray Diffraction Profiles for Asymmetric Reflection form Crystals under Grazing Incidence Conditions
Authors: Sakata Osami , Hashizume Hiroo
Published: February 2005

Dynamical X-ray diffraction during total external reflection has been studied by measuring rocking curves from Bragg planes nearly perpendicular to the flat surface of a germanium single crystal. The rocking-curve profiles for both the diffracted and specular beams observed from slightly asymmetric Bragg planes were found to be quite different from those from the symmetric plane. Experiments using a parallel X-ray beam and a surface passivated sample confirmed the rocking-curve features arising from the excitation and de-excitation of the wave fields in shallow surface layers of the bulk crystal.
Low-Temperature Pretreatment in Chemical Vapor Deposition of a Silicon Film for Solid-Phase Epitaxial Growth
Authors: Ishii Kenichi , Hayashi Yutaka
Published: February 2005

A low-temperature pretreatment of a crystalline silicon substrate for solid-phase epitaxy of a CVD a-Si film on the substrate was studied. It was found that chlorine mixed with hydrogen etches the surface of the silicon substrate at a reduced pressure and a low temperature, e.g. 540°C. This low-temperature etching process was used as an in-situ surface cleaning process prior to CVD of an a-Si film on the silicon substrate at the same temperature. Vertical and lateral solid-phase epitaxial (L-SPE) growth was successfully obtained with this in-situ pretreatment. Using this L-SPE film, XMOS transistors were fabricated.
Smectic Layer Structure of Thin Ferroelectric Liquid Crystal Cells Aligned by SiO Oblique Evaporation Technique
Authors: Ouchi Yukio , Lee Ji , Takezoe Hideo , Fukuda Atsuo , Kondo Katsumi , Kitamura Teruo , Mukoh Akio
Published: February 2005

Smectic layer structures were studied by high-resolution X-ray analysis for two kinds of cells aligned on SiO obliquely evaporated film; the glass plates were fabricated for the evaporation direction to be the same (parallel) or to be the opposite (antiparallel). For parallel cells, a chevron layer structure was formed. The temperature dependence was similar to that of a rubbing cell, although the chevron structure with a small layer tilt existed even in the SmA phase. For antiparallel cells, on the other hand, the smectic layer was uniformly tilted and the layer tilt angle showed weaker temperature dependence than that of the parallel cells.
The Contact Resistance in the Pressed Powder of YBa2Cu3O7-δ
Authors: Fujita Hiroshi , Ohmichi Toshiyuki , Oda Yasukage
Published: February 2005

The apparent electrical resistivity of YBa2Cu3O7-δ powder just pressed into a pellet was measured in order to study the contribution of the grain boundary. The resistivity was found to behave as ρ=A exp
[-B
T]; (A, B>0) over a wide temperature range, even below the superconducting transition temperature, T
c, where each grain is superconducting. The result suggests the existence of a large potential barrier at the grain boundary.
Synthesis of Superconducting YbBa2Cu3O7-δ Thin Films by Electron Beam Deposition
Authors: Mukaida Masashi , Yamamoto Masafumi , Tazoh Yasuo , Kuroda Ken'ichi , Hohkawa Kohji
Published: February 2005

Superconducting YbBa2Cu3O7-δ thin films were synthesized by oxygen annealing of the sequentially deposited metal films of Yb, Ba, and Cu formed by electron beam evaporation. The obtained onset temperature of superconducting transition was 81.3 K with a transition temperature width of 2.6 K. The Yb-Ba-Cu oxide films studied by X-ray diffraction consisted of only the 1-2-3 phase and showed a preferred orientation along the a-b plane on MgO single-crystal substrates.
Improvement of the Interface Properties of Fluoride/GaAs(100) Structures by Postgrowth Annealing
Authors: Kim Kwang Ho , Ishiwara Hiroshi , Asano Tanemasa , Furukawa Seijiro
Published: February 2005

The postgrowth annealing technique has been shown to be useful for improving the interface properties of fluoride films grown on GaAs(100) by molecular beam epitaxy. Annealings typically at 800°C–850°C for 1 min reduce the interface state densities of the fluoride/GaAs interface to about 5×1011/cm2eV (derived from the 1 MHz capacitance-voltage measurement) in both n- and p-type substrates. Photoluminescence intensity of the CaF2-coated GaAs was compared before and after annealing. Ambient dependency during annealing was also investigated by measuring the structural and electrical properties of the films.
Oxygen Content and Transition Temperature (Tc) in Ba2-xLn1+xCu3O7-δ (Ln=Sm, Eu)
Authors: Maruyama Satoshi , Kodama Takahiro , Kobayashi Makoto
Published: February 2005

The relationship between oxygen stoichiometry and transition temperature (T
c) has been studied in Ba2-x
Ln1+x
Cu3O7-δ (Ln=Sm, Eu). T
c decreases with the increase of x and oxygen content. Furthermore, T
c does not show any clear dependence on the average copper valence estimated from the oxygen content.
Bulk Superconductivity in the New Orthorhombic (Tl, Pb)-Ca-Sr-Cu-O System
Authors: Tai M. F. , Wang W. N. , Ku H. C.
Published: February 2005

Bulk superconducting phases with compositional ratios (2122) and (2021) in the new (Tl, Pb)-Ca-Sr-Cu oxide system were reported. A two-step superconducting transition with onset temperatures of 118 K and 88 K were observed from electrical resistivity measurements. Magnetic susceptibility data indicate that bulk transition starts at 112 K. Superconductivity is highly reproducible and more stable than its Tl-Ca-Ba-Cu oxide homologs. Power X-ray diffraction profiles and EDAX analysis indicate the existence of two orthorhombic (pseudotetragonal) phases with c=29.08 Å (Bi2CaSr2Cu2O8-type) and c=24.09 Å (Bi2Sr2CuO6-type) with a possible incommensurate superstructure along the b-axis.
Nonexistence of Long-Range Order in Ga0.5In0.5P Epitaxial Layers Grown on (111)B and (110)GaAs Substrates
Authors: Gomyo Akiko , Suzuki Tohru , Iijima Sumio , Hotta Hitoshi , Fujii Hiroshi , Kawata Seiji , Kobayashi Kenichi , Ueno Yoshiyasu , Hino Isao
Published: February 2005

It has been found that Ga0.5In0.5P layers grown at 700°C on (111)B and (110)GaAs substrates do not show {1/2, 1/2, 1/2} superlattice (SL) formation, in contrast to that for the layers grown on (001)GaAs. The band-gap energy for these layers, which show no SL and are lattice-matched to GaAs, was estimated to be 1.918±0.002 eV at room temperature.
Direct Observation of a-Si:H/a-Si1-xCx:H Multilayers and Their Electrical Properties
Authors: Itoh Haruo , Matsubara Sunao , Muramatsu Shin-ichi , Nakamura Nobuo , Shimada Toshikazu , Shimotsu Teruho
Published: February 2005

Very clear transmission electron microscopy (TEM) patterns of ultrathin a-Si:H/a-Si1-x
C
x
:H multilayers have been observed. TEM photographs show rapidly increasing interface roughness as the number of multilayers increases. The a-Si:H/a-Si1-x
C
x
:H heterojunction interfaces are the main causes of this roughness. In addition, the dependence of the optical gap, activation energy, and conductivity on a-Si:H well later thickness is investigated. These results cannot be explained by the quantum effect alone.
New Method of Frequency Stabilization of Semiconductor Lasers
Authors: Uehara Kiyoji , Katakura Kazunori
Published: February 2005

It is demonstrated that the frequency of a semiconductor laser driven by a constant current can be stabilized by controlling the operating temperature so as to give a constant operating voltage. Since the operating voltage is a direct monitor of the operating temperature, the frequency thus stabilized is insensitive to ambient temperature variations. For hermetically unsealed near-infrared lasers the frequency stability is within ±350 MHz under normal laboratory conditions and the shift is only 500 MHz for a 10°C variation in the ambient temperature. A resettability of ±350 MHz is obtained with an adjustment-free operation.
Determination of Band Discontinuity in Amorphous Silicon Heterojunctions
Authors: Hayashi Tsukasa , Miyazaki Seiichi , Hirose Masataka
Published: February 2005

A new procedure of determining the band offset in semiconductor heterojunctions has been developed. The valence band spectra for ultrathin amorphous silicon nitride (a-Si1-x
N
x
:H) or silicon carbide (a-Si1-x
C
x
:H) deposited on hydrogenated amorphous silicon (a-Si:H) have been measured by X-ray photoelectron spectroscopy. It is demonstrated that the empirical deconvolution of measured spectra yields the valence band discontinuity in a-Si1-x
N
x
:H/a-Si:H and a-Si1-x
C
x
:H/a-Si:H systems.
CPA Density of States of Strongly Correlated Two-Dimensional Electrons in High-Tc Superconducting Compounds
Authors: Inada Yasuzi , Ishii Chikara
Published: February 2005

The density of states of two-dimensional tight binding electrons in the CuO2 plane of the high-T
c compounds (La1-x
M
x
)2CuO4 is calculated in the framework of the single-site coherent potential approximation (CPA), taking account of both effects of strong correlation and random distribution of hole sites introduced by dopant divalent atoms M(=Ba, Sr). The calculated density of states at the Fermi level shows correct x-dependence observed in the susceptibility measurements.
Depletion-Discharge Transient Spectroscopy: Direct Determination of the Density of Deep Emission States in Amorphous Semiconductors
Authors: Nakayama Yoshikazu , Akita Seiji , Kawamura Takao
Published: February 2005

An analysis was made of the depletion-discharge process observed in amorphous semiconductors, where the dark decay of the surface potential V was caused by a sweep out from the bulk of only one sign of the charge carriers thermally generated from deep states in the bulk and a simultaneously progressive formation of the space charge of the opposite sign. It is shown that the distribution of the density of deep emission states can be directly determined from a plot of t|dV/dt| for t<t
d (t
d: the depletion time) and t[d(1/V)/dt] for t>t
d vs ln
(t) using a deconvolution technique.
The Orthorhombic to Tetragonal Transition under Controlled Oxygen Content in High-Tc Superconductor YBa2Cu3Oy
Authors: Nakanishi Shigemitsu , Kogachi Mineo , Sasakura Hiroyuki , Fukuoka Nobuo , Minamigawa Shinnosuke , Nakahigashi Kiyotaka , Yanase Akira
Published: February 2005

The orthorhombic to tetragonal phase transition in YBa2Cu3O
y
(y=6.9-Δ
y) compounds under fixed oxygen content and its relation to superconductivity were investigated by means of X-ray diffraction and resistivity measurement. In the quenching method, the phase transition was observed at about Δ
y=0.62 (800°C quenching temperature). In the region Δ
y=0.62–0.69, the high-temperature tetragonal phase transformed into the low-temperature orthorhombic phase by slow cooling, but at Δ
y>0.69 such a transformation was not observed. No essential difference in T
c was observed between different phases having the same oxygen content in the region Δ
y>0.5.
High-Resolution Electron Microscopy of Planer Defects and Dislocation in Ba2YCu3Oy
Authors: Matsui Yoshio , Takayama-Muromachi Eiji , Kato Katsuo
Published: February 2005

Two types of planar defects in Ba2YCu3O
y
(y is around 6.9), previously reported [Y. Matsui et al.: Jpn. J. Appl. Phys. 26 (1987) L777] are re-examined by high-resolution transmission electron microscopy. The first is due to additional [CuO] one-dimensional chains inserted in the basal plane to form double chains, and the second to additional [CuO2] layers inserted near the Y layers to form double pyramids. The local formation of the latter type of planar defect may possibly be the origin of the edge-dislocation with Burgers vector [100] or [010].
Structure and Composition Analysis of High-Tc Superconducting Bi-Ca-Sr-Cu-O Oxide by High-Resolution Analytical Electron Microscopy
Authors: Bando Yoshio , Kijima Tsuyoshi , Kitami Yoshizo , Tanaka Junzo , Izumi Fujio , Yokoyama Masato
Published: February 2005

The chemical composition and the crystal structure of the Bi-Ca-Sr-Cu-O oxide with a high-T
c of about 75 K have been studied by the combined techniques of crystal structure imaging and spectroscopic microanalysis using a 400 kV high-resolution analytical electron microscope. The crystal is orthorhombic with lattice parameters a=0.54 nm, b=2.70 nm and c=3.06 nm. The chemical composition is assigned as Bi2Ca
x
Sr
z
Cu2O
y
, where x and z are approximately 1.0 and 1.5, respectively. The structure image reveals that the structure is comprised of a bismuth oxide layer interleaved with an oxygen deficient perovskite-like layer. It is suggested that a nearly commensurate superstructure based on the perovskite-type structure is formed.
Effect of Overcoating with Dielectric Films on the Superconductive Properties of the High-Tc Y-Ba-Cu-O Films
Authors: Ichikawa Yo , Adachi Hideaki , Mitsuyu Tsuneo , Wasa Kiyotaka
Published: February 2005

The high-T
c Y-Ba-Cu-O superconductive thin films were coated with dielectric films of Nb2O5 and Al2O3 using an rf-magnetron sputtering technique. The coating with dielectric films lowered the zero-resistance temperature of the Y-Ba-Cu-O films. The Auger analyses for these overcoated Y-Ba-Cu-O films suggested that internal diffusion appeared between the Y-Ba-Cu-O films and the dielectric films. It was also found that the crystallinity of the Y-Ba-Cu-O films was degraded due to the overcoating of the dielectric films.
Magnetic Susceptibility of Fe-Doped YBa2Cu3O7-δ
Authors: Noguchi Satoru , Inoue Jun , Okuda Kiichi , Maeno Yoshiteru , Fujita Toshizo
Published: February 2005

Magnetic properties of YBa2(Cu1-x
Fe
x
)3O7-δ with 0≦x≦0.085 were investigated by dc- and ac-magnetic susceptibility in a temperature range from 4.2 to 300 K. The susceptibility in the normal state follows the Curie-Weiss law χ=C/(T-\varTheta)+χ0 with constant paramagnetism χ0. The effective magnetic moments estimated from the Curie constant are 3.4∼4.0 µB/Fe, which are consistent with the magnetic moment obtained in the Mössbauer experiments. From the ac susceptibility in the superconducting state, a decrease of volume fraction of superconductivity was observed with increasing Fe-concentration.
Magnetic and Superconducting Properties of Ba2HoCu3O7-y under High Magnetic Field
Authors: Ishii Takao , Sugiyama Kiyohiro , Fuke Hiroyuki , Date Muneyuki , Kinoshita Kyōichi , Watanabe Takao , Matsuda Azusa , Yamada Tomoaki
Published: February 2005

The magnetic and superconducting properties of Ba2HoCu3O7-y
are examined using a pulsed magnetic field up to 55 tesla. Magnetic Ho3+ ions in Ba2HoCu3O7-y
show paramagnetic behavior. No magnetic ordering is observed down to 1.3 K. The temperature dependence of the upper critical field is measured by the magnetoresistance method. The H
c2(0) deduced from the present experiment assuming the dirty limit is 104 tesla.
Electron-Cyclotron-Resonance Microwave Plasma Oxidation of Er1Ba2Cu3Oy Superconductive Ceramics
Authors: Minomo Shoichiro , Taniguchi Michio , Ishida Yuji , Sugiyo Masato , Takahashi Tetsuro , Tonouchi Masayoshi , Kita Sadamu , Kobayashi Takeshi
Published: February 2005

An electron-cyclotron-resonance (ECR) microwave plasma was introduced to the forced oxidation of high-T
c Er1Ba2Cu3O
y
superconducting ceramics in oxygen pressure as low as 0.9 Pa. The negative bias (-40 V) application to the specimen greatly helped the progress of the plasma oxidation as compared with the positive bias (+30 V) one. The accumulation of the oxygen atoms ionized positively is thought to be responsible for the observed bias effect. A higher substance temperature and input microwave power also enhanced the plasma oxidation. A 30-minute oxidation was sufficient to obtain the superconductivity with T
c≧92 K.
Superconducting Properties of Ba-Y-Cu-O Tape Prepared by the Doctor Blade Process
Authors: Togano Kazumasa , Kumakura Hiroaki , Shimizu Hitoshi , Irisawa Naoshi , Morimoto Takeshi
Published: February 2005

Ba2YCu3O7 superconducting tape was successfully fabricated by the so-called doctor blade casting process. A zero-resistance state was achieved at 91.5 K for the tape heat-treated at 1000°C. The highest J
c was about 110 A/cm2 at 77 K and in zero magnetic field. The green sheet in an as-cast state has sufficient flexibility to be wound into a small diameter, making possible the winding and the sintering processes in future applications for superconducting coil.
S-N-S Josephson Junction Consisting of Y-Ba-Cu-O/Au/Nb Thin Films
Authors: Akoh Hiroshi , Shinoki Fujitoshi , Takahashi Masayuki , Takada Susumu
Published: February 2005

An S-N-S Josephson junction consisting of Y-Ba-Cu-O/Au/Nb thin films has been fabricated by making use of the proximity effect. The ac-Josephson effect can be confirmed by the observation of the Shapiro steps in this S-N-S junction under microwave radiation. In addition, the effects of the magnetic field and temperature on the critical current have been demonstrated, which indicates that the junction behaves phenomenologically as a Josephson junction.
Submillimeter-Wave Response of Nb-YBaCuO Point-Contact Josephson Junctions
Authors: Imai Syozo , Tozawa Tadayuki , Oya Gin-ichiro , Sugai Tokuko , Takeuti Yosihisa , Mikoshiba Nobuo
Published: February 2005

Shapiro steps in the submillimeter-wave (SMMW) range were observed in junctions made of a high-T
c superconductor, YBa2Cu3O
x
(YBaCuO), and niobium. Junctions were made by pressing a Nb needle on a sintered YBaCuO disk. Shapiro steps up to the fifth order were observed for SMMWs of wavelength 871.6 µm (frequency 344.0 GHz). The dependence of the Shapiro step width on the SMMW power is in accordance with the Bessel function dependence. For SMMWs of wavelength 570.6 µm (525.4 GHz), Shapiro steps up to the second order were observed.
Observation of GdBa2Cu3O7-δ Ceramic Microstructure
Authors: Matsuda Motohide , Kikuchi Akira , Maeda Takao , Ishii Mamoru , Iwai Yutaka , Takata Masasuke , Yamashita Tsutomu
Published: February 2005

The microstructures of high-T
c superconductor GdBa2Cu3O7-δ prepared under various sintering conditions were observed by using SEM and EPMA. The second phase was found on the grain boundaries of the samples sintered at temperatures higher than 970°C. The phase was confirmed to consist of more Ba and less Gd in comparison with the composition of the grain.
Preparation of BiSrCaCu2Ox Films with Tc>77 K by Pyrolysis of Organic Acid Salts
Authors: Nasu Hiroyuki , Makida Seigo , Ibara Yoshikazu , Kato Takeshi , Imura Takeshi , Osaka Yukio
Published: February 2005

High-T
c superconducting BiSrCaCu2O
x
films with T
c(end)>77 K were prepared on yttria-stabilized zirconia substrates by pyrolysis using Bi-, Sr-, Ca- and Cu-2-ethylhexanoates. The observed T
c(onset) and T
c(end) were 97 K and 79 K, respectively, and thus T
c(end) is higher than liquid nitrogen temperature. From X-ray diffraction patterns of these films, the superconducting crystal phase is mostly characterized by the c-axis perpendicular to the substrate.
Ba Isotope Effect in a Ba2YCu3O7-δ Superconductor
Authors: Hidaka Takehiko , Matsui Toshimi , Nakagawa Yoshihiko
Published: February 2005

The Ba isotope effect in Ba2YCu3O7-δ ceramic superconductors was studied by the Meissner effect. 134Ba-rich Ba (the weight of 134Ba being about 2.8 atomic units lighter than that of naturally obtained Ba) was introduced to obtain an isotope shift in T
c. No clear shifts in T
c are observed over the experimental resolution limit of temperature measurement.
Absence of Solid Solution of the Type, Y(Ba2-xREx)Cu3O7±δand Its Possible Implications
Authors: Sampathkumaran E. V. , Suzuki Atsushi , Kohn Kay , Shibuya Takashi , Tohdake Ayako , Ishikawa Masayasu
Published: February 2005

The results of X-ray diffraction and resistivity measurements of the specimens Y(Ba2-xREx)Cu3O7±δ(RE=Ce, Pr, Eu and Gd;x\lesssim0.4) are presented. The results suggest that the RE ions are not soluble with Ba in this series. This indicates that RE-Ba ionic size differences alone cannot explain the solubility behaviour normally observed in REBa2Cu3O7±δcompounds. We propose that O-O repulsive interaction plays a major role in deciding the solubility limits.
Superconductivity, Structure and Oxygen Content of Fe-Doped Ba2YCu3Oy
Authors: Obara Haruhiko , Oyanagi Hiroyuki , Murata Keizo , Yamasaki Hirofumi , Ihara Hideo , Tokumoto Madoka , Nishihara Yoshikazu , Kimura Yoichi
Published: February 2005

The crystal structure and superconductivity of Ba2Y(Cu1-x
Fe
x
)3O
y
have been studied along with its compositional analysis, especially that of oxygen. This system shows an orthorhombic-to-tetragonal phase transformation and has been extensively investigated by several groups. In the present study we observed that with an increasing Fe concentration x, the superconducting transition temperature T
c decreases slowly correlating with the difference of the lattice constants, b-a, in the orthorhombic phase region and decreases rapidly from x>0.04∼0.05 in the tetragonal phase region, while y is almost constant.