bluuebunny/crossref_metadata_2025 huggingface dataset:
Reflection High-Energy Electron Diffraction Intensity Oscillations during GexSi1-x MBE Growth on Si(001) Substrates
Authors: Sakamoto Kinihiro , Sakamoto Tsunenori , Nagao Satoru , Hashigutchi Gen , Kuniyoshi Katsuya , Bando Yoshio
Published: November 2005

Reflection high-energy electron diffraction (RHEED) intensity oscillations during the heteroepitaxy of Ge
x
Si1-x
on a Si(001) substrate were observed for the first time. The oscillation amplitude decreased rapidly during Ge
x
Si1-x
growth due to the three-dimensional growth, which had a strong dependence on the Ge mole fraction. The layer thickness of Ge
x
Si1-x
/Si strained-layer superlattices was controlled precisely by monitoring the RHEED intensity oscillation. The interface roughness of Ge
x
Si1-x
/Si heterojunctions was examined by the observations of RHEED intensity oscillations and high-resolution transmission electron microscope images.
Out-Diffusion of Chromium and 0.839 eV Luminescence Center in GaAs
Authors: Hus Jun-Tsung , Nishino Taneo , Hamakawa Yoshihiro
Published: November 2005

We have studied the diffusion of Cr atoms in GaAs:Cr by a new photoluminescence technique which involves measuring the Cr-related luminescence intensity. The results on the intensity profiles after thermal annealing are discussed in terms of the substitutional-interstitial dissociative mechanism. The experimental observation that redistributed profiles have an abnormal peak at the near-surface region in those wafers annealed at over 900°C for 6h, has been shown to be caused by the in-diffusion of arsenic vacancies from the surface. The Cr-related luminescence intensity was re-examined as a function of the arsenic pressure during the annealing of GaAs wafers; the results show that the in-depth profiles can be well understood in terms of the diffusion of Cr and arsenic vacancies; also, the luminescence ceter is a CrGa–VAs complex.
Preparation, Magnetic and Magneto-Optic Properties of Small-Crystallite MnBi Films
Authors: Masuda Morio , Izawa Ichiro , Yoshino Seiji , Shiomi Shigeru , Uchiyama Susumu
Published: November 2005

MnBi composite films were prepared by annealing Bi–Mn multilayers which were deposited in vacuum by repeating an alternate evaporation of Bi and Mn metals. They were found to have a crystallite size of about one thousand angstroms and, moreover, to exhibit an orientation of the C-axis perpendicular to the film plane, as observed in MnBi single layers. A structure analysis by electron microscopy and a significant increase in the coercive force suggest that they have a multilayer structure. Their large coercive force enabled us to write-in reversed magnetic domains (as small as 1.2 µm in diameter) by the irradiation of a single-pulse Baser beam. No significant difference was found in the magnetization, Kerr rotation or reflectivity between composite MnBi films and single-layer MnBi films.
Thermo-Dynamic Discussions for the Chalcogenide Films of Reversible Optical Disk
Authors: Okuda Masahiro , Rhee Jung Chul , Matushita Tatsuhiko
Published: November 2005

Thermodynamic discussions concerning the melt and solidification of binary and thernary chalcogenide films as well as the temperature distribution in a film during write-erase cycles are presented. For a reversible optical disk, a very high-rate temperature change (108°C/s) and a high-temperature gradient (8.5×106°C/cm), compared with the usual metal alloy experiments, were experienced. In a Se–Te (isomorphous) system, the Te concentration increases at the circumference due to segregation. Thus, an isomorphous system is not adequate for reversible memory materials. On the other hand, in an eutectic system, segregation has not occured and, thus, many cycle operation is possible.
Variation of Ion Current Flowing into Double Probes with Coating of Organic Thin Film in rf Discharge Plasma
Authors: Yamaguchi Shinji , Sawa Goro , Ieda Masayuki
Published: November 2005

The current-voltage(I
d–V
d) characteristics of double probes coated with an ethylene plasma polymerized(PPE) film were investigated in ethylene and nitrogen plasma produced by rf discharges. Since the probes were coated, the I
d–V
d curve exhibited a hysteresis and the ion current was observed to decrease. On the basis of the shape of the hysteresis in the saturation region, we found a way to clarify whether the observed ion current was real or not. As a result, we could confirm that the coating of probes actually causes a decrease in the ion current ΣI
p. Furthermore, a comparison between coated probes and a clean metal probe furnished with an external C–R parallel circuit has revealed that the decrease in ΣI
p arises from the direct contact of plasma with the PPE film, indicating that the ion current from plasma into dielectrics is smaller than that into metal.
A Numerical Study on Gaseous Reactions in Silane Pyrolysis
Authors: Yuuki Akimasa , Matsui Yasuji , Tachibana Kunihide
Published: November 2005

A simple gaseous reaction model involving 11 elementary reactions for 10 chemical species is proposed for silane and disilane pyrolyses at 550–750 K; its appropriateness is examined by a calculation based on an one-dimensional nonsteady condition which includes gaseous reactions, diffusional transport and radical adsorptions. The calculated results show that the model can successfully explain the experimental behavior of a gas composition concerning the time lag of hydrogen molecule production as well as the temperature and pressure dependences of the saturated higher silane concentrations.
The reaction model is applied to a SiH4–H2–N2 system; it predicts that dilution with hydrogen or the premixing of c.a. 4% of disilane is useful for obtaining a spatially uniform deposition rate in a flow-type CVD reactor.
Design of a Wien Filter Type Heavy Ion Beam Probe System for the Measurement of Plasma Potential
Authors: Fujita Hideki , Adati Keizô , Kumazawa Ryuhei , Okamura Shoichi , Sato Teruyuki
Published: November 2005

This paper describes the design of a Heavy Ion Beam Probe (HIBP) system to measure the two-dimensional plasma potential profile in the central mirror region of an open ended plasma confinement device (RFC-XX-M). This HIBP system incorporates three novel features. The first is a Wien filter-type guide field that reduces the required beam acceleraltion voltage. The second is a set of deflecting electrodes located at the exit position of the secondary ion beam that steers all secondary ions into the analyzer at the same angle. And the third is a new method of absolute calibration.
Alloy Scattering Mobility in III–V Ternary Alloy Semiconductors with Nonrandom Atom Arrangerment
Authors: Ichimura Masaya , Sasaki Akio
Published: November 2005

The alloy scattering mobility is theoretically analyzed for III–V ternary alloy semiconductors by taking the nonrandom atom arrangements into account. Differences from the mobility in a random arrangement are calculated. Warren-Cowley's short-range order parameter is used for describing the atom arrangement. The results show that even a rather low degree of ordering or clustering greatly influences alloy scattering.
Phase Transition of Lipid Multilamellar Aqueous Suspension under High Pressure. IV. Chain Packing Conformation of Dipalmiloyl Phopholipid in Temperature Range between Pre- and Sub-Transition
Authors: Utoh Shigenori , Takemura Tetuo
Published: November 2005

Wide-angle X-ray scattering (WAXS) measurements for a lipid multilamellar aqueous suspension have been studied using computer profile analyses; these suggest that in the temperature range between the pre- and sub-transition, hydrocarbon chain packing conformation does not have a single structure with quasi-hexagonal or orthorhombic symmetry. Under atmospheric pressure there exists a sharp X-ray reflection at about 4.2 Å, followed by a more diffuse peak at a higher angle within this intermediate zone. With increasing pressure these two reflection peak heights indicate changes that are independent of each other; one has a decreasing and the other an increasing tendency. Thus, a comparison of the WAXS profile under atmospheric pressure with that under 300 MPa obviously shows a reversal in these two peak heights. As a result, the iea that the pre- and sub-transition intermediate is composed of a two-component system with the same hexagonal symmetry is introduced.
Quasiparticle-Injected Superconducting Weak Links and Their Application to dc SQUID
Authors: Kojima Kazuyoshi , Nara Shigetoshi , Hamanaka Koichi
Published: November 2005

Quasiparticle-injected superconducting weak links of lead alloy were fabricated under various conditions. The resistance of the weak links depends on the indium concentration of the weak link; a larger indium concentration gave a larger normal resistance. By applying the weak links of this large normal resistance to dc superconducting quantum interference devices (SQUID), a larger output voltage (∼30 µV), comparable to that of a conventional resistively shunted dc SQUID, could be obtained.
A Parametric Study of the Etching of Silicon in SF6Microwave Multipolar Plasmas: Interpretation of Etching Mechanisms
Authors: Petit B. , Pelletier J.
Published: November 2005

A parametric study of the etching of silicon has been performed in a Microwave Multipolar Plasma using an Electron Cyclotron Resonance excitation. The evolution of the anisotropy and etch rate is measured as a function of the SF6pressure, ion energy (<100 eV) and ion current density collected on the silicon wafers. For a given ion current density and ion energy, perfect anisotropy is obtained below a critical SF6pressure whereas the etch rate, independent of ion energy and current density, increases proportionally with the SF6pressure in the domain investigated. These results, corroborated by the mass spectrometry analysis of the reaction products are explained through the diffusion model recently proposed for plasma etching.
Characterisation of Nitrides Prepared by Ion Beam Enhanced Deposition of Aluminium, Silicon and Titanium
Authors: Fatkin James , Kohno Akio , Kanekama Norio
Published: November 2005

The composition and ultramicrohardness of thin films deposited by electron beam evaporation of aluminium, silicon and titanium, with a simultaneous 20 keV nitrogen ion bombardment, were investigated. The friction coefficient and wear resistance against steel were also measured. Only \leqslant50% of the incident nitrogen ions were incorporated during deposition. Under our experimental conditions, titanium oxycarbonitride and aluminium-nitrogen films containing 10–20% oxide were formed. Silicon reacted to produce a relatively pure substoichiometric SiN
x
random bonding alloy, which showed excellent wear resistance. Titanium oxycarbonitride films exhibited low friction against steel and a hardnesses approaching that of bulk TiN.
High Field Properties of Superconducting Nb3Ge Films Prepared by Chemical Vapor Deposition
Authors: Suzuki Mitsumasa , Watanabe Yuji , Anayama Takeshi , Watanabe Kazuo , Noto Koshichi
Published: November 2005

The superconducting critical current densities J
c of Nb3Ge films prepared by chemical vapor deposition have been investigated in magnetic fields parallel and perpendicular to the film plane up to above 20 T. The J
c and its field dependence are strongly influenced by any change in the microstructure of films deposited at different deposition temperatures T
d. Films deposited at a low T
d of 800°C exhibit a high J
c below 20 T and show a slight difference between parallel and perpendicular field dependences of J
c. As T
d is increased to 900°C, the J
c of films is appreciably lowered over the entire field range and the difference between two field dependences of J
c is remarkably enlarged. The upper critical field H
c2 of these films has been obtained by extrapolating the Kramer plot of J
c
1/2
H
1/4 versus H to J
1/2
c
H
1/4=0, and were estimated to range from 28 to 31 T at 4.2 K.
Characterization of Silicon Implanted with Focused Ion Beam by Raman Microprobe
Authors: Mizoguchi Kohji , Nakashima Shin-ichi , Fujii Akihito , Mitsuishi Akiyoshi , Morimoto Hiroaki , Onoda Hiroshi , Kato Tadao
Published: November 2005

Damage to silicon implanted with Si++, Au++ and Be++ ions using focused ion beams has been evaluated by a Raman microprobe technique. A quantitative evaluation of damage to ion-implanted silicon was made by comparing the intensities of Raman scattering from implanted and unimplanted areas. The minimum dose at which damage is detectable by Raman measurements is 9×1011 ions/cm2 for Au++, 7.5×1012 ions/cm2 for Si++ and 7.5×1013 ions/cm2 for Be++. From the depth distribution of the damage measured using laser lines of different wavelengths, it is inferred that damage at the near-surface region in Be++ implanted silicon is reduced by self annealing during high-dose-rate implantation and that a channeling effect causes the saturation dose in Be++ implantation to be higher than that in other ion implantations.
Emission Properties of Electrodeless Argon Gas Discharge in VUV Region
Authors: Shao Chun-Lin , Jimbo Takashi , Umeno Masayoshi , Hattori Shuzo
Published: November 2005

The dependences of the VUV light intensity from an electrodeless Argon gas discharge on various parameters such as the gas pressure, gas flow rate, input voltage, input current and discharge current were investigated. These data can be utilized in designing this type of VUV light source. The peak intensity of the light in the 50 to 110 nm wavelength region was estimated to be about 1.8×10-4 W/cm2 at the output aperture of the discharge tube.
Electrochromic Characteristics of Organic Materials with a Simple Molecular Structure
Authors: Nakamura Kenichi , Oda Yasuhiro , Sekikawa Toshikazu , Sugimoto Mitsuhiro
Published: November 2005

Electrochromic characteristics of familiar organic materials with relatively simple molecular structures, such as dimethyl terephthalate, are described. Coloration occurred at the cathode of all cells examined; the color spontaneously bleached upon removing the voltage. Electrochemically induced optical absorption was measured for organic compounds with various types of terminal groups. As a result, the induced color was found to depend upon the type of terminal groups as well as its position placed in the compound. The time response of the optical density during a coloration and bleaching sequence was also investigated. An empirical formula fitting with the observed response curves is proposed.
Imaging Characteristics of a Replicated Wolter Type. I. X-Ray Mirror Designed for Laser Plasma Diagnostics
Authors: Aoki Sadao , Shiozawa Munehisa , Kamigaki Keiji , Hashimoto Hiroshi , Kokaji Masahiko , Setsuhara Yuichi , Azechi Hiroshi , Yamanaka Masanobu , Yamanaka Tatsuhiko , Izawa Yasukazu , Yamanaka Chiyoe
Published: November 2005

A Wolter type-I X-ray mirror designed for laser plasma diagnostics has been fabricated by the replication method. A master mandrel has been ground by a diamond grinder and polished by a computer-controlled machine. The replicated mirror coated with gold can be used for X-rays longer than 2.5 Å. X-ray imaging tests were performed with a laboratory X-ray source.
Growth of Hydrogenated Amorphous Silicon by an Inductive Coupling Glow Discharge Reactor
Authors: Yokota Katsuhiro , Nakayama Shuuichi , Ohno Yoshikazu , Katayama Saichi
Published: November 2005

Hydrogenated amorphous silicon (a-Si:H) films were prepared using an inductively coupling glow discharge reactor as a function of the position of the substrate in the reactor. The growth rate of the films had a maximum at a position in the tube around which the working coil was wound and had values slightly smaller than the maximum over a wide region extending from the lower end of the rf working coil towards the down-stream region. A maximum of dark and photoconductivities was obtained on a film prepared in the down-stream region.
Magnetic Properties of Plastically Deformed Iron Single Crystals II
Authors: Maruyama Hiroko , Nosé Hiroshi
Published: November 2005

Magnetization curves of single crystals (picture-frame shapes) elongated along the [001] and [011] axes under various conditions were measured at low temperatures down to -196°C. It was found that their coercive forces H
c increase as the temperature is decreased. If the origin of H
c is some type of induced anisotropy caused by a magnetoelastic interaction, the temperature dependence of H
c would mainly be due to the magnetostriction.
Time-of-Flight Counters for VENUS Detector
Authors: Hemmi Yasuo , Kikuchi Ryusaburo , Kubo Kiyoshi , Kurashige Hisaya , Miyake Kozo , Nakamura Teruo , Sasao Noboru , Tamura Norio , Yamada Yoshikazu , Daigo Motomasa , Kondo Takahiko
Published: November 2005

A time-of-flight counter system has been installed in the VENUS detector of the TRISTAN experiment at KEK. A time resolution of about 200 ps was obtained for a long scintillator of 466 cm. The system is being successfully operated in experiments.
Low-Threshold AlGaAs/GaAs MQW Laser Diode Fabricated on Si Substrates by MOCVD
Authors: Shiraishi Hiroyuki , Yamada Ryuzo , Matsui Nobuyuki , Umeno Masayoshi
Published: November 2005

We report the room-temperature pulsed operation of AlGaAs/GaAs multi-quantum well (MQW) laser diodes (LD's) fabricated on Si substrates by metallorganic chemical vapor deposition (MOCVD). The lowest threshold current was 115 mA at room temperature (at 293 K). This is the lowest value of reported laser diodes on Si.
Atomic Displacements at Surface of Si-Wafer(111)
Authors: Kashihara Yasuharu , Kawamura Kazuo , Kashiwagura Nobuo , Harada Jimpei
Published: November 2005

The rod shaped distribution of X-ray scattered intensity observed from the (111) surface of Si-wafer shows asymmetry in its intensity profile with respect to the Bragg point. Such asymmetry is closely related to the lattice distortion near the crystal surface. From the analysis of the observed asymmetric intensity distribution the Si lattice plane at the interface region between the Si-wafer and the adsorbed amorphous SiO2 layer is shown to be expanded by about 3% from the bulk spacing.
Fusibility of Polythiophene Derivatives with Substituted Long Alkyl Chain and Their Properties
Authors: Yoshino Katsumi , Nakajima Shigeaki , Sugimoto Ryu-ichi
Published: November 2005

Conducting polythiophene derivatives with substituted long alkyl chain such as poly(3-octylthiophene), poly(3-dodecyl-thiophene) and poly(3-dococylthiophene) etc. Have for the first time been found to be fusible by heating in a relatively low temperature range. The film formed by the hot press method at a temperature above the softening point from the powder sample exhibits a drastic change of properties upon doping just as in the case of conducting polymer films prepared by other methods.
Preparation and Properties of Three Types of Orthorhombic Superconductor Ba2YCu3-xO7-y
Authors: Ono Akira , Ishizawa Yoshio
Published: November 2005

Three types of the orthorhombic superconductor were recognized based on crystallographic data; they were prepared in air by annealing coarse-grained Ba2YCu3-x
O7-x
at different temperatures before quenching into air. Annealing at higher temperature produced the superconductor with larger c cell dimension. The c cell dimension at room temperature showed a strong correlation with superconductivity. Superconducting transition temperature increases abruptly with decreasing c cell dimension in the range of 11.71 to 11.68 Å. The c cell dimension is about 11.70 Å for the superconductor exhibited zero resistance at 77 K.
Structure of High-Tc Superconductor YBa2Cu3O6.6 at Low Temperatures
Authors: Katano Susumu , Funahashi Satoru , Hatano Takeshi , Matsushita Akiyuki , Nakamura Keikichi , Matsumoto Takehiko , Ogawa Keiichi
Published: November 2005

A single-phase YBa2Cu3O6.6 shows a sharp superconductive transition at 94 K. The crystal structure of this compound has been determined by the Rietveld profile analysis of neutron powder diffraction data measured at 10 K and 120 K. The space group Pmmm is confirmed, and the positions and occupations of oxygen atoms are established. No phase transitions or other structural anomalies were observed in relation to the superconductive transition.
Metal Schottky Barriers on Hydrogenated Amorphous Ge/Si Superlattices
Authors: Wronski C. R. , Hicks M.
Published: November 2005

The barrier heights and junction properties of Pt Schottky barriers on hydrogenated amorphous Ge/Si superlattices have been characterized for films with individual layer thickness from ∼5 to 30 Å. The electronic properties of these junctions, which allow efficient extraction of photogenerated carriers, are explained in terms of the quantum shifts in the conduction band and the densities of gap states in the Ge layers.
Infrared Reflection Spectra of High Tc Superconductor YBa2Cu3Ox Sintered at Various Temperatures
Authors: Onari Seinosuke , Iioka Mitsuru , Ohshima Ken-ichi , Arai Toshihiro , Sakudo Tunetaro
Published: November 2005

The infrared reflection spectrum of the tetragonal YBa2Cu3O
x
sintered at 1000°C exhibits Reststrahlen vibration, and spectra of the orthorhombic YBa2Cu3O
x
sample sintered at 900°C and 600°C exhibit the characteristics of free electrons. The large differences in the free electron concentration may, however, also be influenced by the oxygen concentrations.
Synchrotron Plane Wave X-Ray Topography of 6 inch Diameter Si Crystal
Authors: Kitano Tomohisa , Ishikawa Tetsuya , Matsui Junji , Akimoto Koichi , Mizuki Jun'ichiro , Kawase Yutaka
Published: November 2005

A precision three horizontal axis diffractometer system with large crystal stage was developed. It was used for a synchrotron plane wave X-ray topographic camera for a 6 inch Si wafer. A surface sensitive topograph was taken under the condition of specular reflection by (+, +) double crystal arrangement. Change in lattice distortions as small as 0.2 arc second was detected under the condition of plane wave X-ray topography by (+, +, -) triple crystal arrangement.
Secondary Defects of As+ Implanted Silicon Measured by Thermal Wave Technique
Authors: Ishikawa Katsuya , Yoshida Masakatsu , Inoue Morio
Published: November 2005

As+ implanted layers have considerable residual defects even after annealing treatment. The evaluation of the defects of impurity layers has been very important for such micro-devices as VLSI, and TEM analysis has been extensively investigated. In this paper, As+ implanted silicon after annealing was measured by the thermal wave technique. Samples of doses higher than 1×1015 cm-2 have more highly increased secondary damage. The defects can be annealed out considerably at 800°C, and higher temperature annealing is very effective to decrease this secondary damage.
Superconductivity of Multiphase Mixtures in Y-Ba-Cu-O Compounds
Authors: Yamaya Kazuhiko , Kodaira Kohei , Higuchi Mikio , Ishibashi Teruo , Ido Masayuki , Nomura Kazushige , Sambongi Takashi
Published: November 2005

We have investigated the superconductivity and phases of various compositions of (Y
z
Ba1-z
)
x
CuO
y
using resistance and susceptibility measurements and X-ray diffraction. It has been found that (Y
z
Ba1-z
)
x
CuO
y
compounds are classified into two groups with a high (91 K) and a low (65 K) superconducting transition temperature according to the amount of orthorhombic phase in samples.
Amorphous Silicon Superlattice Thin Film Transistors
Authors: Tsukude Masaki , Akamatsu Susumu , Miyazaki Seiichi , Hirose Masataka
Published: November 2005

A new type of thin film transistor (TFT) has been fabricated using hydrogenated amorphous silicon (a-Si:H)/silicon nitride (a-Si1-x
N
x
:H) multilayer structures. The field effect mobility of the superlattice TFT was 0.74 cm2/Vs, while that of an a-Si:H TFT with the active layer produced by the same deposition conditions as the superlattice was 0.13 cm2/Vs. The increase in the field effect mobility for the superlattice was interpreted in terms of the quantum size effects in the a-Si:H potential well.
Initial Stage and Domain Structure of GaAs Grown on Si(100) by Molecular Beam Epitaxy
Authors: Kawabe Mitsuo , Ueda Toshio , Takasugi Hidetoshi
Published: November 2005

The initial stage of GaAs epitaxial growth on Si(100) has been studied by RHEED and AES. On exposure to a As4 flux, the Si surface is covered with one or two monolayers of As which are stable up to 700°C, while Ga on Si desorbs even at 500°C. There are two kinds of Si-As reconstruction, which depend on the temperature of Si exposed to As4 flux. One is 1×2 for high temperature (>600°C) and the other is 2×1 for low temperature (<450°C) when the Si substrate has 2×1 reconstruction. The surface reconstructions of GaAs grown on Si(100)-As 1×2 and Si(100)-As 2×1 are perpendicular to each other, which indicates that the domain direction of GaAs to Si substrate is different depending on the initial growth temperature.
Liquid Quenched Superconductor Ba-Y-Cu-O with Tc,zero=88 K and AC Josephson Effect at 77 K
Authors: Komatsu Takayuki , Imai Kouji , Matusita Kazumasa , Takata Masasuke , Iwai Yutaka , Kawakami Akira , Kaneko Yasuhisa , Yamashita Tsutomu
Published: November 2005

A superconducting Ba-Y-Cu-O with T
c,zero=88 K was prepared by a liquid quenching method, in which the melt of nominal composition Ba2YCu3O7-δ was first quenched and then the sample was annealed at 900°C for 48 h in air. AC Josephson effect was observed at 77 K in point-contacts made of the present samples. This new method is applicable to the preparation of superconducting thin films, wires, tapes and superconduciting cavities.
High Resolution Electron Microscopy of Crystal and Defect Structures of the High-Tc Superconductor Ba2YCu3O7-δ
Authors: Hirotsu Yoshihiko , Nakamura Yoshio , Murata Yuzo , Nagakura Sigemaro , Nishihara Takaharu , Takata Masasuke
Published: November 2005

Structural study of the superconducting oxide Ba2YCu3O7-δ has been made at room temperature by high resolution electron microscopy. The orthorhombic structure was confirmed by the direct imaging of metal atoms. Planar defects with stacking sequence of metal-oxygen planes in the La2CuO4 type of structure were observed. Depending on the selected arca in electron diffraction, the axial ratio b/a was found to vary in a range from 1.003 to 1.018. Black and white contrasts appearing alternately along the twin boundaries are discussed in relation to the lattice distortion and the oxygen deficiency in the Cu-O layer.
Oxygen Effect on the Superconductivity of Ba2YCu3O7-y
Authors: Nozaki Hiroshi , Ishizawa Yoshio , Fukunaga Osamu , Wada Hiroaki
Published: November 2005

The correlation of superconducting properties of Ba2YCu3O7-y
to the oxygen deficiency y has been investigated using samples quenched in different temperatures in air. The magnitude of the superconducting diamagnetism at 77 K rapidly decreases with increasing y. The variations of T
c and ΔT
c (transition width) are presented and discussed in terms of the occupancy and distribution of oxygen atoms in the Cu layer between the Ba layers.
Analysis of Dopant Diffusion in Molten Silicon Induced by a Pulsed Excimer Laser
Authors: Sameshima Toshiyuki , Usui Setsuo
Published: November 2005

Dopant diffusion calculations explain well the mechanism of the non-equilibrium incorporation of boron from the silicon surface into the molten silicon induced by a pulsed excimer laser. When a high-power laser causes the melt front to proceed into the substrate faster than 8 m/s, p+ doped regions are formed only near the surface of the molten region because dopant atoms cannot diffuse sufficiently fast for the junction depth to reach the maximum melt depth.
Thermo-Photometric Study on Phase Transitions in Sputter-Deposited Ag-Zn Alloy Thin Films
Authors: Maeda Yoshihito , Minemura Tetsuroh , Andoh Hisashi
Published: November 2005

The behavior and kinetics of transitions between β', ζ and β phases in a sputter-deposited Ag-50 at %Zn alloy thin film were examined by thermo-photometric technique observing the change of reflectivity with temperature and time. Good observation was made easily and determined activation energy for the β'→ζ transition was 220.6 kJ/mol. It seems that the ζ phase should nucleate at the grain edge or the grain boundary of the β' phase after site saturation under a zero nucleation rate.
High-Tc Y-Ba-Cu-O Thin Films Prepared by Dual Magnetron Sputtering
Authors: Asano Hidefumi , Tanabe Keiichi , Katoh Yujiro , Kubo Shugo , Michikami Osamu
Published: November 2005

Y-Ba-Cu-O thin films (200-300 nm thick) have been magnetron-sputtered on heated sapphire substrates. By means of dual sputtering configuration with a Cu and sintered Y-Ba-Cu-O target, films having compositions closer to Y1Ba2Cu3O
y
are reproducibly obtained at a substrate temperature of about 600°C. They have a nearly single-phase perovskite-like structure with highly c-axis preferred orientation and show a T
c onset of 90 K. Remarkable improvement in the zero resistivity temperature (up to 73 K) is achieved by subsequent annealing of these films at 550-650°C, while annealing at higher temperatures leads to T
c degradation.
Superconductivity in Metamorphic Phases of Ba2ErCu3O7-δ
Authors: Takabatake Toshiro , Nakazawa Yasuhiro , Ishikawa Masayasu
Published: November 2005

We have confirmed the presence of three metamorphic phases of Ba2ErCu3O7-δ, which correspond to those of Ba2YCu3O7-δ. In addition to the high T
c (92 K) orthorhombic phase, we obtained another orthorhombic phase and a tetragonal phase by rapid quenching. The former has a lower T
c value of 50 K and the latter is semiconducting. Both the temperature dependence of resistivity and the T
c value of each phase are similar to those of the yttrium system. It is likely that the common relation between the structure and superconducting properties exists for other rare earth systems as well.
Local Structure in Orthorhombie and Tetragonal Ba2YCu3O7-y: The Role of Oxygen Vacancies for High Tc Superconductivity
Authors: Oyanagi Hiroyuki , Ihara Hideo , Matsubara Toshiya , Matsushita Tadashi , Hirabayashi Masayuki , Tokumoto Madoka , Murata Keizo , Terada Norio , Senzaki Kiyoshi , Yao Takafumi , Iwasaki Hiroshi , Kimura Yoichi
Published: November 2005

Cu valency and local structure in the orthorhombic and tetragonal phases of high T
c superconductor Ba2YCu3O7-y
(0.03<y<0.64) have been studied by the near-edge and extended X-ray absorption fine structure (EXAFS). Oxygen vacancies on the z = 1/2 plane modify both Cu valency and local structure. The near-edge spectra show that Cu ions at Cu1 sites in tetragonal Ba2YCu3O7-y
are monovalent. From the temperature dependence of the Cu-O distance and its mean relative displacement, it is suggested that the breathing mode Cu-O stretching vibration is slightly suppressed in the tetragonal phase, which may degrade superconducting properties.
Preparation and Characterization of Ba-Y-Cu-O Single Crystals
Authors: Hayashi Kunihiko , Murata Keizo , Takahashi Kazuhiro , Tokumoto Madoka , Ihara Hideo , Hirabayashi Masayuki , Terada Norio , Koshizuka Naoki , Kimura Yoichi
Published: November 2005

Single crystals of Ba2YCu3O7-y
were prepared from molten Ba-Y-Cu-O. The shape of the crystals was thin rectangular slab and the size of the largest crystal was 1.5×1.5×0.04 mm3. The crystals were characterized by resistivity measurement, Meissner effect study and structure analysis. Superconductivity was found with transition temperature of about 90 K by resistivity measurement. The resistivity parallel to the c-axis is 30-90 times larger than in-plane resistivity just above T
c. The Meissner effect was also observed in the same sample. The unit cell was orthorhombic with space group Pmmm and the lattice parameters a = 3.857(1), b = 3.865(1) and c = 11.723(4) Å.
The β-Form-Random Coil Transition of Polypeptide in Solution
Authors: Kamashima Kazuo
Published: November 2005

The β-form-random coil transition of polypeptide in solution was studied. From optical rotatory dispersion and viscosity measurements on poly-s-carbobenzoxy-L-cysteine in chloroform-dichloroacetic acid mixed solvents at various temperatures, this polypeptide was found to show a small thermal transition between a β-form and a random coil. Changes in viscometric behavior with solvent composition are also reported.
Electric Field Induced Reflection in GaInAsP/InP MQW Structure
Authors: Kikugawa Tomoyuki , Ravikumar K. G. , Shimomura Kazuhiko , Izumi Akira , Arai Shigehisa , Suematsu Yasuharu , Ohki Yoshimasa
Published: November 2005

Reflection of light due to the electric field effect was seen for the first time in GaInAsP/InP MQW structures through the observation of an interference pattern between the transmitted and reflected light; this was caused by a change in the refractive index and absorption coefficient in the MQW layers due to the partial application of an electric field to the MQW layers. The observed data were fitted with the theoretical simulations and the refractive index change was predicted to be about 0.025% at -5 V. This is a promising step towards the realization of the intersectional optical switch.
3d-Transition Metal Related Photoluminescence in In1-xGaxP Alloys
Authors: Shirakata Sho , Nishino Taneo , Hamakawa Yoshihiro , Kato Takamasa , Ishida Tetsuro
Published: November 2005

Photoluminescence spectra related to a series of 3d transition metals (V, Cr, Co and Ni) in In1-xGaxP alloys have been systematically measured at liquid He temperature. The spectra in In1-xGaxP have shown broad bands without characteristic zero-phonon lines which can be observed in both GaP and InP. In particular, Co-related spectra in In1-xGaxP (0.74<x<1) have been precisely investigated and analyzed, the results showing that such broad bands are due to the perturbation by disordering of Ga and In atoms in the cation sublattice of In1-xGaxP alloys.
Stabilization of Tunable Diode Lasers for Spectroscopy of Low Density Gases
Authors: Okude Shin'ichiro , Matsushima Fusakazu , Shimizu Tadao
Published: November 2005

A simple but efficient method for stabilizing tunable diode lasers (TDL) has been developed to improve the sensitivity of spectroscopy of low density gas. The same spectral line itself to be measured is broadened by pressure and is used as a frequency discriminator in the loop of stabilization. The frequency tuning range is wide enough to obtain a correct profile of the spectral line. A demonstrative observation has been done on the v
2asQ(7,6) transition of NH3(929 cm-1). With the TDL stabilization, the fluctuation of the TDL frequency is reduced to less than 1 MHz in several hours.
Mechanism of High-Tc Oxide Superconductivity
Authors: Soda Toshio
Published: November 2005

The mechanism of recently discovered high-T
c Y-Ba-type copper oxide superconductors is proposed by the two-conduction-band model of heavier and lighter electrons, taking into account the infrared divergent effect due to the Fermi surface of the lighter electrons. The interaction between two heavy electrons, via a screened Coulomb interaction between a heavier and a lighter electron, turns out to be attractive when half their relative momentum is the Fermi momentum, though modified largely by the on-site and screened Coulomb interactions. T
c is estimated to be of the order of one hundred degrees Kelvin, depending on the magnitudes of the two bandwidths.
Complex Susceptibility of High-Tc Superconductor ErBa2Cu3O6+x
Authors: Ishida Takekazu , Mazaki Hiromasa
Published: November 2005

The magnetic response of ErBa2Cu3O6+x
has been studied in terms of complex susceptibility χ=χ'-iχ''. In the superconducting transition, χ' reflects the Meissner effect and χ'' forms a single peak. Careful measurements revealed that the onset temperature of χ' is slightly higher than that of χ'' and there exist two superconducting phases. χ' and χ'' of the lower phase are very sensitive to the field amplitude. The upper phase may be interpreted as a bulk superconductivity while the lower phase corresponds to a weak coupling between bulk superconducting inclusions.
Analysis of the Atomic Structure of the Si(111)√3×√3-Bi Surface by X-Ray Photoelectron Diffraction
Authors: Park Chong Yun , Abukawa Tadashi , Higashiyama Kazuyuki , Kono Shozo
Published: November 2005

It is found by X-ray photoelectron spectroscopy and LEED that the saturation coverage of Bi is one monolayer for the Si(111)√3×√3-Bi surface. Azimuthal dependence of Bi 4d photoelectron diffraction has been measured for the Si(111)√3×√3-Bi surface and analyzed kinematically. The results of the analysis have confirmed the presence of Bi-triplets with sides of 3.1 Å as proposed by X-ray diffraction. It is further found that the Bi-triplets form an overlayer on the substrate.
Crystal Structure of Ba2HoCu3O7-x Determined by Neutron Powder Diffraction
Authors: Asano Hajime , Takita Kôki , Ishigaki Tōru , Akinaga Hiroyuki , Katoh Hideo , Masuda Kohzoh , Izumi Fujio , Watanabe Noboru
Published: November 2005

The crystal structure of the high T
c superconductor Ba2HoCu3O7-x
has been determined by Rietveld analysis of TOF neutron powder diffraction data. This compound is orthorhombic (space group: Pmmm) with lattice parameters a = 3.8851 Å, b = 3.8205 Å and c = 11.6822 Å. It is isomorphic with Ba2YCu3O7-x
. Ba and Ho atoms are ordered in a sequence of Ba-Ho-Ba along the c-axis, oxygen atoms on a z = 1/2 plane are missing, and an oxygen site at (1/2, 0, 0) is selectively occupied. The chemical composition of the present sample has been determined to be Ba2HoCu3O6.96.
High-Resolution Transmission Electron Microscopy of a Coincidence Site Boundary in BaTiO3 Ceramics
Authors: Fujimoto Masayuki
Published: November 2005

A triple grain junction including a Σ=5 coincidence site boundary showing a small deviation from the perfect mismatching observed in normally prepared BaTiO3 ceramics was detected by electron diffraction. The periodicity of the atomic coincidence site structure of the boundary was observed using high-resolution transmission electron microscopy. A Σ=5 coincidence site lattice (CSL) related to the Σ=5 twist structure was revealed in the high resolution image. Furthermore, the CSL structure was confirmed by the optical diffraction pattern obtained from the negative of the high-resolution image.
Coercivity of Surface Grains of Nd-Fe-B Sintered Magnet
Authors: Hirosawa Satoshi , Tokuhara Kohki , Sagawa Masato
Published: November 2005

To investigate magnetic hardening mechanisms in sintered Nd-Fe-B magnets, magnetic hysteresis loops of sintered Nd15Fe77B8 magnets 100 µm thick, the surfaces of which are sputter-deposited with Nd or Tb metal, were measured at various steps in the sample preparation procedures. The surface grains in as-polished magnets have a very small coercivity of approximately 150 kA/m. Sputter deposition of Nd or Tb metal on the polished magnets and a subsequent heat treatment have resulted in a dramatic improvement of coercivity of the surface grains.
High Tc Superconductivity of a Melt-Spun Er1Ba2Cu3 Oxide Ribbon
Authors: Matsuzaki Kunio , Inoue Akihisa , Kimura Hisamichi , Shimizu Koichi , Masumoto Tsuyoshi
Published: November 2005

An Er1Ba2Cu3 oxide ribbon with a nonequilibrium crystalline structure was prepared by melt-spinning. Heating of the oxide ribbon in air resulted in the structural change to an orthorhombic phase accompanied by the oxygen absorption of about 21% at about 650 K. The Er1Ba2Cu3O
y
ribbon annealed at 1173 K for 5 h in air was found to exhibit high T
c superconductivity with onset at 92.5 K and zero resistance at 88 K. It is thus concluded that the application of melt-spinning to an Er1Ba2Cu3 oxide is useful for the production of oxide ribbon exhibiting high T
c superconductivity.
Simple Resonant-Cell for Photoacoustic Study of Liquids
Authors: Choi Pak-Kon , Takagi Kenshiro
Published: November 2005

An acoustically-resonant photoacoustic cell has been designed which is useful for optical spectroscopy and trace analysis for liquid samples. The cell is simple, easy to use and corrosion-free. Acoustic characteristics of the cell are described. High sensitivity is demonstrated by detecting a small amount of permanganate ion (MnO4
-) with the concentration down to 8×10-8 M.
Optical Multistability by a Liquid Crystal Light Modulator
Authors: Mada Hitoshi , Nakajima Yasunari , Ozawa Takao
Published: November 2005

Optical multistability is demonstrated using a liquid crystal light modulator operated in the electrically controlled birefringence mode. The experimental setup is composed of He-Ne lasers, a homogeneously aligned nematic liquid crystal cell sandwiched between two polarizers, and a mirrorless electrical feedback system. Eight-valued optical memory, multistability, and threshold characteristics were obtained in the input-output properties. A method to construct the two-dimensional device is also proposed.
Structural and Resistivity Changes in YBa2Cu3Oy Ceramics by Heat-Treatment in Air
Authors: Leng Song , Narita Nobutaka , Higashida Kenji , Mazaki Hiromasa
Published: November 2005

Effect of heat-tretment in YBa2Cu3O
y
ceramics was investigated using the methods of electrical resistivity, TG, DTA and X-ray diffraction. In the heating process, a mass increase and a resistivity decrease are observed in the sample in the temperature range 630-780 K. Heat-treatment in air at temperatures above 780 K causes the marked increase of resistivity as well as the decrease of oxygen content. The YBa2Cu3O
y
compound is decomposed gradually above 1200 K and completely at around 1290 K. The degradation and recovery of structural and transport properties by heat-treatment in air are also reported.
Frequency Dependent Conductivity in Lightly Doped Polypyrrole
Authors: Hirai Yoshinori , Tanaka Hajime , Nishi Toshio
Published: November 2005

Frequency (f) and temperature (T) dependence of electrical conductivity σ(f, T) in lightly doped polypyrrole is presented. The behavior of σ(f, T) is different from those of disordered semiconductors and insulating polymers, with considerably strong temperature and frequency dependence of σac.σac changes with ∝f
0.7. These results can be described by slightly modified Kivelson's model, that is, the interpolaron hopping process between the polaron and bipolaron states.
Raman Scattering in Single Crystal Ba2YCu3Oy
Authors: Yamanaka Akio , Minami Fujio , Watanabe Kenji , Inoue Kuon , Takekawa Shunji , Iyi Nobuo
Published: November 2005

A Raman scattering study was performed in a variety of single crystals of both tetragonal and orthorhombic Ba2YCu3O
y
structures at room temperature. It is found that Raman spectra observed in the tetragonal crystal are much different from those in the orthorhombic one. Three modes with 500 cm-1 580 cm-1 and 637 cm-1 in energy in the orthorhombic crystal are tentatively assigned to be the copper-oxygen vibrational modes. The 500 cm-1 mode is assigned as the oxygen-stretching mode in Cu-O-Cu bond along the c-axis and its frequency is found to shift to 470 cm-1 in the tetragonal crystal.
Crystal Structure of the High Tc Superconductor LnBa2Cu3O7-δ (Ln=Sm, Eu and Gd)
Authors: Asano Hajime , Takita Kôki , Katoh Hideo , Akinaga Hiroyuki , Ishigaki Tōru , Nishino Makoto , Imai Mitsugu , Masuda Kohzoh
Published: November 2005

The crystal structure of the high T
c superconductor LnBa2Cu3O7-δ (Ln=Sm, Eu and Gd) has been determined by Rietveld analysis of X-ray powder diffraction data. The compounds crystallize in an oxygen-deficient layered perovskite structure with space group Pmmm. The structure is isomorphic with YBa2Cu3O7-δ. The Ln and Ba atoms have an ordered arrangement, oxygen on a z=1/2 plane is missing and the oxygen site on the basal Cu plane is selectively occupied.
Antiferromagnetism and Superconductivity of La2CuO4
Authors: Nishihara Yoshikazu , Tokumoto Madoka , Murata Keizo , Unoki Hiromi
Published: November 2005

Magnetic susceptibility and electrical resistivity have been measured for stoichiometric and La deficient La2CuO4, and 57Fe doped La2CuO4. In all the samples the magnetic susceptibility shows two cusps around 220 and 110 K. From the temperature dependence of resistivity R(T) and the Mössbauer effect of 57Fe doped in La2CuO4, it is concluded that the cusp of susceptibility at 220 K corresponds to the antiferromagnetic transition. The slope of resistivity |d
R/d
T| becomes small below this temperature with decreasing temperature. The hyperfine field of iron is 395 kOe at 77 K. The La deficient sample exhibits superconductivity below 35 K.
Cleaning of MBE GaAs Substrates by Hydrogen Radical Beam Irradiation
Authors: Takamori Akira , Sugata Sumio , Asakawa Kiyoshi , Miyauchi Eizo , Hashimoto Hisao
Published: November 2005

Hydrogen radical beam cleaning of substrates for GaAs MBE growth has been studied. The cleaning effects of carbon and oxygen contaminated by exposure to air and a lower-grade vacuum were investigated using Auger electron spectroscopy (AES), capacitance-voltage (C-V) carrier profiling, and secondary ion mass spectrometry (SIMS). AES signals of contaminants decreased to the detection limit with hydrogen radical irradiation. Carrier depletion around the growth interface was also reduced with decreasing carbon density.
Growth of YBa2Cu3Ox Single Crystals with Superconducting Transition above 90 K
Authors: Takei Humihiko , Takeya Hiroyuki , Iye Yasuhiro , Tamegai Tsuyoshi , Sakai Fumiko
Published: November 2005

Single crystals of high-temperature superconductor YBa2Cu3O
x
have successfully been prepared using a CuO flux method. Two types of crystals of a mm-size are obtained: irregular blocks with the (001) habit and thin plates with the well-developed (001) plane. EPMA shows that the ratio Y/Ba/Cu is 1.0/1.9/2.9 and no apparent difference in metal composition is observed between the two. Electrical resistivity measurements show that the block crystals are metallic and exhibit a sharp superconducting transition at 91.3 K, whereas the plates are semiconducting and show no superconducting behavior above 4.2 K.
Y-Ba-Cu-O/Nb Tunnel Type Josephson Junctions
Authors: Inoue Atsuki , Takeuchi Kiyoshi , Ito Hiroyuki , Nakayama Akiyoshi , Okabe Yoichi , Kawasaki Masashi , Koinuma Hideomi
Published: November 2005

Y-Ba-Cu-O/Au/AlO
x
/Nb tunnel type Josephson junctions were fabricated and their current-voltage relation exhibited typical characteristics of Josephson tunnel junctions such as supercurrent, hysteresis and rf-induced voltage steps at 4.2 K.
Improved Self-Aligned Structure for GaAlAs High-Power Lasers
Authors: Yoshizawa Misuzu , Uomi Kazuhisa , Ohishi Akio , Ono Yuuichi , Kawano Toshihiro , Nakashima Keiichi , Kajimura Takashi
Published: November 2005

An improved self-aligned structure using two-step MOCVD technique is developed for GaAlAs high-power lasers. This structure is characterized by the introduction of a GaAlAs layer having low AlAs mole fraction at the regrowth interface to avoid the formation of native oxide film. The lasers operate at levels up to 100 mW in the stabilized fundamental transverse mode under CW operation at room temperature and show high reliability.
Twinning of High-Tc Ba2YCu3O7-x Oxides
Authors: Iijima Sumio , Ichihashi Toshinari , Kubo Yoshimi , Tabuchi Junji
Published: November 2005

Orthorhombic crystallites of the high-Tc superconductor Ba2YCu3O7-x
oxide prepared by the standard sintering technique are heavily laminated by twinning on (110) lattice planes. Upon heating these crystals under a vacuum in an electron microscope, the orthorhombic structure transformed irreversibly to a tetragonal one. Between these two forms, a transitional orthorhombic form was observed. This irreversible transformation seems to be caused by a lack of oxygen in the evacuated microscope.
Madelung Potentials in YBa2Cu3Ox (x=7 and 8)
Authors: Iguchi Eisuke , Yonezawa Yoshiyuki
Published: November 2005

Calculations of Madelung potentials of ions in YBa2Cu3O8 reveal that the oxygen ions which are found experimentally to have small occupation factors are quite unstable. The most stable ionic configuration of YBa2Cu3O7, which contains a Cu3+, two Cu2+ ions and an oxygen vacancy per “molecule” in the structure of YBa2Cu3O8, has been obtained by calculating the Madelung energies per YBa2Cu3O7 molecule for several ionic positions. These calculations determine the most stable Cu3+ position and also show that the unstable oxygen ions in YBa2Cu3O8 become remarkably stabilized in YBa2Cu3O7.