bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaction of Al3Ta Intermetallic Compound Film with Si
Authors: Noya Atsushi , Sasaki Katsutaka , Umezawa Toshiji
Published: February 2005

The interaction of deposited Al3Ta intermetallic compound film with a silicon substrate is studied by Auger electron spectroscopy in order to examine the suitability of film for use instead of aluminum as a metallization material. Penetration of aluminum into silicon and formation of aluminum spikes are completely blocked by a thin interfacial layer consisting of Ta and Si formed at the interface between Al3Ta and silicon. It is revealed that Al3Ta film is a useful material as a high-quality metallization for silicon devices.
The Effect of Pb Addition on Superconductivity in Bi-Sr-Ca-Cu-O
Authors: Oota Akio , Kirihigashi Akihiro , Sasaki Yoshinobu , Ohba Kentaro
Published: February 2005

The effect of Pb addition on superconductivity was studied on the systems with nominal compositions (BiPb
x
)2Sr2Ca2Cu3O
y
, (Bi1-x
Pb
x
)2Sr2Ca2Cu3O
y
and (Bi1-x
Pb
x
)2Sr2Ca2Cu3.6O
y
. The melting point decreases monotonically from ∼880 to ∼860°C as x increases from 0 to 0.45 in the systems, while the volume fraction of the high-T
c phase (HTP) and the offset value of T
c show a peak around x=0.2∼0.3. Further increase in x produces the Ca2PbO4, leading to the suppression of the HTP. The amount of Pb suitable for the formation of the HTP is limited by the competition between the reaction to form the HTP by the catalytic effect of Pb and the one to form the Ca2PbO4.
Superconducting Characteristics and Microstructure of Bi-Pb-Sr-Ca-Cu-O Ceramics
Authors: Kikuchi Akira , Matsuda Motohide , Takata Masasuke , Ishii Mamoru , Yamashita Tsutomu , Koinuma Hideomi
Published: February 2005

The influence of the processing on the superconducting characteristics was investigated for the new high-T
c Bi-Pb-Sr-Ca-Cu-O ceramics prepared under various sintering conditions. The critical temperature T
c,zero and the critical current density J
c at 77 K under zero magnetic field were strongly dependent on the sintering temperature. The maximum values of 105 K and 26 A/cm2 were obtained for the specimen sintered at 845°C. For the specimen sintered at 850°C, these values were lower although the volume fraction of the high-T
c phase was higher than that of the specimen sintered at 845°C. This difference was discussed in terms of the microstructure of the superconducting ceramics.
The Reversible Reactions in Tl-Ba-Ca-Cu-O System
Authors: Sugise Ryoji , Hirabayashi Masayuki , Terada Norio , Jo Masatoshi , Tokumoto Madoka , Shimomura Takehiko , Ihara Hideo
Published: February 2005

The reversible reactions in the Tl-Ba-Ca-Cu-O system were found. The phase transformations from the Tl2Ba2CaCu2O
y
(2212) phase to the Tl2Ba2Ca2Cu3O
y
(2223) phase and to the Ba-Ca-Cu-O mixed phases by heating in an oxygen atmosphere were observed. Moreover, the phase transformations from the Ba-Ca-Cu-O mixed phases to the 2223 and to the 2212 phases by heating in the presence of thallium oxide vapor were observed. Therefore, these phase transformations are reversible. These reversible reactions are very useful in stabilizing the structure of each superconductor.
Preparation of the High-Tc Superconducting Phase in Bi, Pb-Sr-Ca-Cu-O Films by Pyrolysis of 2-Ethylhexanoates
Authors: Nasu Hiroyuki , Kato Takeshi , Makida Seigo , Imura Takeshi , Osaka Yukio
Published: February 2005

The high-T
c superconducting phase of Bi, Pb-Sr-Ca-Cu-O was prepared in films by pyrolysis of 2-ethylhexanoates. The derived T
c(onset) was 115 K, and T
c(end) was 102 K. From X-ray diffraction patterns, the films contained about 65% of the high-T
c superconducting phaes. To increase the concentration of the high-T
c superconducting phase, the partial pressure of oxygen, annealing temperature and the addition of Pb in the starting solution played important roles.
Preparation of Superconducting Tl1Ba2Ca3Cu4Ox Thin Films by RF Magnetron Sputtering
Authors: Zhou Jun , Ichikawa Yo , Adachi Hideaki , Mitsuyu Tsuneo , Wasa Kiyotaka
Published: February 2005

Superconducting thin films of the Tl-Ba-Ca-Cu-O system with a single 1234 phase were prepared on a (100) MgO substrate by rf magnetron sputtering from a sintered Tl2Ba1Ca2Cu3O
x
target and subsequent annealing. X-ray diffraction analyses indicated that the films thicker than 5 µm which underwent annealing at 900–910°C contained the 1234 phase with a high degree of the c-axis orientation normal to their surface. The c-axis lattice constant was determined to be 19.05 Å. The best superconducting properties were obtained for the 5- µm thick films annealed 900°C for 1 min with an onset critical temperature at about 120 K and a zero-resistivity temperature at 113 K.
Degradation in Bi-Sr-Ca-Cu-O Thin Films Exposed to Water
Authors: Yoshikawa Kohta , Yoshida Masamichi , Nakano Motoo
Published: February 2005

A study of Bi-Sr-Ca-Cu-O thin films soaked in water demonstrated that film superconductivity was degraded by exposure to water. ICP analysis showed that Sr and Ca, but no Bi and Cu, largely dissolved. EPMA analysis indicated that dissolution took place mostly in nonsuperconducting grains. By contrast, XRD patterns showed no significant change after soaking. That is, superconducting grains were indeed stable, but nonsuperconducting grains were notably degraded in polycrystalline films, with a consequent lowering of overall superconductivity.
Anomalous Tc Alteration of Quenched Bi2Sr2CaCu2Ox
Authors: Ishida Takekazu
Published: February 2005

The full superconducting transition of a single-phase low-T
c specimen was investigated as a function of a quenching temperature T
q. The midpoint T
c varied from 68.8 K to 95.9 K. A surprising feature was that the T
c had a steep minimum at T
c=300°C. The oxygen stoichiometry did not seem to be a dominant factor for the determination of T
c. We speculate that the (BiO)2 layer was responsible for controlling the hole concentration of the CuO2 plane.
A Novel Amorphous-Silicon Field-Effect Transistor with Good Off-Characteristics
Authors: Uchida Yasutaka , Matsumura Masakiyo
Published: February 2005

This letter proposes a novel amorphous-silicon field-effect transistor whose local threshold voltage is distributed along the channel. A low off-current is the most important feature of the new device, while the on-current is as high as that of the conventional device. The superior off-characteristics of the novel device were verified experimentally.
The Doped Quantum Well Gate FET Fabricated by Low-Pressure MOCVD
Authors: Lin W. , Lei M. D. , Chang C. Y. , Hsu W. C. , Di L. B. , Kai F.
Published: February 2005

The doped quantum well FETs with Al0.5Ga0.5As/GaAs heterostructures have been fabricated using the low-pressure metalorganic chemical vapor deposition (LP-MOCVD) method. The conventional δ-doping thin layer in MODFET has been replaced with a doped Al0.5Ga0.5As/GaAs/Al0.5Ga0.5As quantum well. Doping level in the GaAs quantum well was varied to observe the effects on the 2-DEG density in the channel. The corresponding IDsat was increased from 12 mA to 27 mA at V

g
=0 V for increasing the doping level in the well.
Thin-Film Solid State Devices Based on Nonlinear Magnetostatic Waves
Authors: Boardman A. D. , Gulyaev Yu. V. , Nikitov S. A.
Published: February 2005

It is now well-known that a new class of solid-state devices can be constructed using linear magnetostatic guided waves (MSW) or surface waves (MSSW) as their basis. Such waves can propagate, for example, in ferrimagnetic materials in the high frequency part of the microwave spectrum and the technology now exists for the preparation of high quality thin-films of yttrium-iron-garnet (YIG). This fact permits the construction of devices in micro-minature form. In this paper, two important theoretical foundations are laid. The first concerns the generation of MSSW solitons on small samples of YIG and the second concerns nonlinear Bragg diffraction and TE-TM conversion of light by the grating presented by nonlinear MSSW to waves at optical frequencies. The potential these effects have for new microwave and magnetooptical devices is very briefly discussed.
Image Analysis of EL2 Distributions in LEC GaAs Si Materials
Authors: Fillard J. P. , Montgomery P. , Baroudi A. , Bonnafé J. , Gall P.
Published: February 2005

In a recent paper we showed that EL2 centers are not especially concentrated on dislocations as is the usual stated opinion. Photoquenching experiments and the analysis of infrared transmission images enable the identification of the local EL2° contribution in the cell pattern; a profile of the calculated EL2° quenched center densities was deduced showing a lower density in the walls and a higher density in an intermediate zone surrounding the inner cell. In this letter we propose a confirmation of this schematic distribution by extending the calculation to the complete image. A quantitative image of the EL2° densities is presented. A discussion is introduced which compares this new point of view with previous results reported in the literature, especially the conclusions on infrared luminescence images.
Enhancement of Heavy-Hole-Related Excitonic Optical Transitions in (111)-Oriented Quantum Wells
Authors: Hayakawa Toshiro , Takahashi Kosei , Suyama Takahiro , Kondo Masafumi , Yamamoto Saburo , Hijikata Toshiki
Published: February 2005

Photoluminescence excitation spectra have been measured at low temperatures on high quality GaAs/Al0.3Ga0.7As and GaAs/AlAs multiple quantum wells grown by molecular beam epitaxy along the [111] and [100] crystallographic axes. Comparisons of these spectra have shown clear evidence of the enhancement of the heavy-hole-related excitonic optical transitions relative to the light-hole-related transitions in (111)-oriented quantum wells in comparison with (100)-oriented quantum wells.
Superconductivity of the System Nd1+2xBa2(1-x)Cu3Oy (0≤x≤0.4): Effect of the Magnetic Nd3+ Ion Occupying the Ba-Site
Authors: Nozaki Hiroshi , Takekawa Shunji , Ishizawa Yoshio
Published: February 2005

A solid solution system Nd1+2x
Ba2(1-x)Cu3O
y
(0≤x≤0.4) was investigated through its magnetic susceptibility and electrical resistivity. In the system, trivalent Nd ions partly occupy the Ba2+ sites of the structure, depending on x. Superconductivity was observed in the range of x=0∼0.16 and the transition temperature decreased steadily with increasing x. The resistivity in a normal state varied from metallic to semiconductive in character with an increment of x. These phenomena are discussed from the viewpoint of how trivalent, magnetic Nd ions in the Ba-O layers affect superconductivity in the system.
Tape Conductor Fabrication Processes for High-Tc Ba2YCu3O7-y
Authors: Shimizu Hitoshi , Kumakura Hiroaki , Togano Kazumasa
Published: February 2005

Tape conductors of Ba2YCu3O7-y
were successfully prepared by a new surface-reaction technique of a Cu-electroplated Ag tape was coated with a fine mixture of BaCO3 and Y2O3 and heat-treated to form superconducting Ba2YCu3O7-y
. A zero-resistance state was achieved at temperatures above liquid nitrogen temperature. A critical current density of about 40 A/cm2 was obtained at 77 K in zero magnetic field.
Observations of Mixed-Phase Y-Ba-Cu-O Superconductors with a Scanning Electron Microscope at Low Temperatures
Authors: Tomii Yoichi , Ochiai Shojiro , Zhang Wei , Takayama Tomoo , Unesaki Teruyoshi , Nakagawa Isamu , Osamura Kozo
Published: February 2005

The microstructure of a Y2Ba3Cu5O
y
superconducting mixed-phase material with a critical temperature of 88 K was examined with a scanning electron microscope from room temperature to 85 K. Two regions were observed: a dark region constituted of superconducting YBa2Cu3O
y
and a bright region of Y2BaCuO
y
. The dark region became darker and the bright region became brighter with decreasing temperature. The SEM image was reversible with respect to temperature.
Photoluminescence Due to Lattice-Mismatch Defects in High-Purity ZnSe Layers Grown by Metalorganic Vapor Phase Epitaxy
Authors: Shibata Noriyoshi , Ohki Akira , Zembutsu Sakae , Katsui Akinori
Published: February 2005

High-purity ZnSe layers grown by metalorganic vapor phase epitaxy exhibit an unusually strong luminescence band at 2.60 eV (Y band), which is extremely sensitive to residual impurity concentration. Y emission depends on the lattice mismatch between the epilayer and substrate. The emission decreases with the use of a lattice-matched In
x
Ga1-x
As substrate. With the GaAs substrate, the emission intensity varies with layer thickness reflecting lattice relaxation in the ZnSe/GaAs structure.
Computer Simulation Analysis of the Planar Channeling Effect in Practical Ion Implantation
Authors: Kimura Yoshihide , Kang Hee Jae , Shimizu Ryuichi
Published: February 2005

The planar channeling effect in ion implantation was studied using computer simulation. The simulation code was a modified MARLOWE code which enabled dynamic processes of amorphization due to high-dose ion implantation to be simulated. We simulated the practical ion implantation of 100 keV Si+ ions in a 3 inch wafer of GaAs. Since an ion beam scans over a wide area, the angle of incidence of the ion beam changes from point to point on the wafer and results in considerable deterioration of uniformity in the ion-implanted depth, even though the angle of incidence was chosen so as to prevent the channeling condition from occurring during ion implantation. The result clearly indicates that a marked inhomogeneity in ion implantation takes place in the practical manufacturing processes.
Complex Susceptibility of the Oxide Superconductor BiSrCaCu2Ox
Authors: Ishida Takekazu , Mazaki Hiromasa
Published: February 2005

The magnetic response of a sintered BiSrCaCu2O
x
pellet has been studied in terms of the ac susceptibility χ=χ'-i χ''. Both the resistive and inductive transitions occur in two steps (at 110 K and at 82 K). From the field-dependent susceptibility, we revealed that both bulk and weakly coupled superconductive components contribute to the χ profile of the lower transition. This behavior is similar to that of other oxide superconductors.
Effects of Synthesis Conditions on the Properties of a Superconducting Bi-Sr-Ca-Cu-O System
Authors: Tanaka Yoshiaki , Fukutomi Masao , Asano Toshihisa , Maeda Hiroshi
Published: February 2005

With the aim of preparing a single, high-T
c phase in the Bi-Sr-Ca-Cu-O system, optimization of the composition and heat treatment have been studied. It was found that the temperature range at which the high-T
c phase forms, was very narrow (865–880°C) and a process of furnace-cooling was required to reduce a residual resistance due to the low-T
c phase. The high-T
c phase in this oxide system can easily form from a limited starting composition around Bi1Sr1Ca1Cu2O
x
. T
c values for the high-T
c phase do not change much from the initial composition or the heat treatment, while that for the low-T
c phase moves considerably from about 88 K down to below 20 K. Existence of new superconducting phases in the Sr-Ca-Cu-O system is mentioned.
Effect of Hole-Doping in High-Tc Ln1Ba2Cu3O7-δ (Ln=Nd, La, Pr)
Authors: Uwe Hiromoto , Sakudo Tunetaro , Asano Hajime , Han Tae-Su , Yagi Kazuhiro , Harada Ryusuke , Iha Michiaki , Yokoyama Yasuharu
Published: February 2005

Systems of solid solution Ln1-x
Ca
x
Ba2Cu3O7-δ (Ln=Nd, La, Pr) have been investigated in order to clarify the effect of hole-doping on the superconducting state. The transition temperature T
c decreases with increasing Ca-ion substitution in either Nd1-x
Ca
x
Ba2Cu3O7-δ or La1-x
Ca
x
Ba2Cu3O7-δ. Combined with the fact that the electron-doping in the system Ln1+x
Ba2-x
Cu3O7-δ (Ln=La, Nd, Eu) decreases T
c, the experiment indicates that the nondoped LnBa2Cu3O7-δ (Ln=Nd, La) has an optimum carrier concentration for T
c. For the nonsuper-conducting Pr1-x
Ca
x
Ba2Cu3O7-δ, the conductivity at 77 or 280 K exhibits a maximum at the formal valence of ca. 3 for Pr1-x
Ca
x
.
Structural Study on High-Tc Superconductor Bi2-x(Ca, Sr)3Cu2+xO9-y
Authors: Kajitani Tsuyoshi , Kusaba Keiji , Kikuchi Masae , Kobayashi Norio , Syono Yasuhiko , Williams Timothy B. , Hirabayashi Makoto
Published: February 2005

The crystal structure of the high-T
c Bi2-x
(Ca, Sr)3Cu2+x
O9-y
with x=0.2 and y=0.78 was studied by means of neutron and X-ray powder diffraction. Since the unit cell parameters were relatively large for powder diffraction analysis, an averaged structure was refined, assuming an orthorhombic sub-cell (a=5.39 Å, b=5.39 Å and c=30.37 Å) which corresponds to 1/5 of the unit cell: This is a derivative of Bi4Ti3O12. The double perovskite unit interleaved by the double bismuth layers is B-type, i.e. a CuO6 octahedron is surrounded by eight alkaline earth metal ions. The pyramidal CuO5 configuration is found in this oxide. The copper valency is estimated at about 2.3 on the basis of the determined chemical composition.
On the Fluorination Dependence of Tc in YBa2Cu3O7-δ
Authors: Hyland G. J.
Published: February 2005

It is shown, in terms of a model in which the superconducting carriers in YBa2Cu3O7-δ are holes in an oxygen band, that fluorination of the material can either increase or decrease the concentration of these holes depending on the amount of fluorine and where it is incorporated into the lattice. From the experimentally established dependence of T
c on δ in YBa2Cu3O7-δ–and consistent with its known structure–the likely range of T
c values corresponding to the different possible degrees of fluorination is calculated, and is found to cover the various experimental T
c values reported to date; the consequences of replacing fluorine with nitrogen are discussed.
Electrical Resistivity and Magnetic Susceptibility of YBa2Cu3O7-x at High Temperatures
Authors: Ohtani Tsukio , Okudo Tomoyuki , Tamaki Atsuhiro , Ueda Takeshi
Published: February 2005

A reversible transition was observed at around 650°C in both dc electrical resistivity ( ρ) and dc magnetic susceptibility ( χ) measurements. The transition was characterized by a shoulder-like increment in the ρ-T curve and a sudden change in the temperature gradient of χ, which is interpreted as the orthorhombic-to-tetragonal transition.
Superconductivity of Ba2Y(Cu, Ti)3Oy Oxide
Authors: Okura Kengo , Ohmatsu Kazuya , Takei Hiromi , Hitotsuyanagi Hajime , Nakahara Tsuneo
Published: February 2005

Samples of Ba2Y(Cu, Ti)3O
y
oxide were synthesized and the effect of substituting Cu with Ti was studied. In the Ba2Y(Cu3-x
Ti
x
)O
y
(0≦x≦0.9), specimens were obtained which indicated a T
c of over 80 K. In the composition BaαYCuβTi0.6O
y
(1.9≦α≦2.3, 2.3≦β≦3.5), some (Cu Ti)-rich samples indicated a T
c of over 95 K which was as high as that of the existing Ba2YCu3O
y
. Diamagnetic signals measured by AC susceptibility at room temperature were detected in some specimens. Zero electric resistance was observed (<10-4 Ωcm at our experimental resolution) up to 300 K in the composition Ba2YCu2.4Ti0.6O
y
sintered at 940°C.
Hole Concentration Compensation Effect and Superconducting Properties of Nd1+xBa2-xCu3O7-δ
Authors: Takita Kôki , Akinaga Hiroyuki , Katoh Hideo , Asano Hajime , Masuda Kohzoh
Published: February 2005

The superconducting transition temperature T
c and normal-state resistivity have been investigated as a function of x for the Nd1+x
Ba2-x
Cu3O7-δ system, whose crystal structures have been determined at room temperature by X-ray powder diffraction combined with the Rietveld method. T
c of the samples with x=0 and 0.05 is above 90 K, which decreases monotonically with x except for around x=0.25∼0.30 (T
c≃35 K) and the sample becomes semiconducting at x=0.40. The orthorhombic distortion of the compounds decreases with x and the compound becomes tetragonal at x=0.20. The variation of T
c with x is insensitive to the orthorhombic-tetragonal phase transition. A correlation of T
c with hole concentration in copper-oxide-type superconductors is discussed based on a possible hole concentration compensation effect of excess Nd.
1.55 µm Butt-Jointed Distributed Bragg Reflector Lasers Grown Entirely by Low-Pressure MOVPE
Authors: Tohmori Yuichi , Oishi Mamoru
Published: February 2005

1.55 µm distributed Bragg reflector lasers were fabricated entirely by low-pressure MOVPE growth. An active waveguide was connected to a passive waveguide by a butt-joint technique. In the butt-jointed structure, the optical field axis in the active region was matched to that in the passive region. Devices fabricated were operated at currents as low as 13 mA. Spectrum linewidth as narrow as 3.4 MHz was obtained at four times the threshold current.
Organic Electroluminescent Device with a Three-Layer Structure
Authors: Adachi Chihaya , Tokito Shizuo , Tsutsui Tetsuo , Saito Shogo
Published: February 2005

An electroluminescent device with a three-layer structure was constructed using an intensely fluorescent material, 12-phthaloperinone derivative, for the emitter material. The cell structure of Mg-electrode/amorphous electron-transport layer/polycrystalline emitting layer/amorphous hole-transport layer/Au-electrode was constructed on a glass substrate. Yellow EL emission was clearly observed in normal room lighting at the dc bias voltage of 60 V. The emission intensity was proportional to the injection current over a wide current range of 10-7 to 10-3 A/cm2. The EL intensity exceeded 1 µW/cm2 at the injection current of 2 mA/cm2.
Smectic C* Chevron Layer Structure Studied by X-Ray Diffraction
Authors: Ouchi Yukio , Lee Ji , Takezoe Hideo , Fukuda Atsuo , Kondo Katsumi , Kitamura Teruo , Mukoh Akio
Published: February 2005

Layer structures in chiral smectic C (S
C
*) phases were studied by high-resolution X-ray diffraction. The existence of a chevron layer structure was confirmed even in thick cells such as 350 µm and even in a compound with the phase sequence of N
*-S
C
*. Cells made by a SiO oblique-evaporation technique gave two diffraction patterns; a single peak was observed when the evaporation directions of top and bottom glasses were set in opposite directions (antiparallel), while two peaks were observed in the case of the glasses set in the same direction (parallel). Thus, the chevron structure was confirmed to exist quite generally except for in the SiO antiparallel cells.
Appropriate Pulling Axis Orientation to Suppress Slip Dislocation Generation during Czochralski Growth of Semiconductor Crystals
Authors: Kitano Tomohisa , Matsui Junji
Published: February 2005

The pulling axis orientation effect on dislocation density reduction is considered, based on the Schmid factor calculation under a uniform tangential stress field. The maximum Schmid factor converges at the 0.4536 value at <110 > orientation. The <110 > pulling axis is the best orientation to suppress slip dislocation generation. The feature of slip dislocation in a (110) wafer is also clarified from the calculation.
Glass Formation of High-Tc Compound BiCaSrCu2Ox by Rapid Quenching
Authors: Minami Tsutomu , Akamatsu Yoshinori , Tatsumisago Masahiro , Tohge Noboru , Kowada Yoshiyuki
Published: February 2005

A new high T
c compound, BiCaSrCu2O
x
, was successfully prepared in glassy form by a twin-roller quenching method for the first time. The rapidly quenched glass has a glass transition temperature of 390°C and a crystallization temperature (T

x
) of 444°C. Heat-treatment at higher temperatures above T

x
increased the crystallinity and at 850°C produced X-ray patterns identical to those of the starting compound. The resistivity of the sample heat-treated at 850°C shows the onset T
c at 88 K. These findings are expected to facilitate fiber drawing for such high T
c compounds.
Preparation of High-Tc Ceramic Superconductors Through Oxidation of Mechanically Alloyed Master Alloy Powders
Authors: Yamada Yuh , Murasaki Shun-ichi , Suganuma Motohiro , Mizutani Uichiro
Published: February 2005

The high-T
c ceramic superconductors YBa2Cu3O
x
and BiSrCaCu2O
x
are synthesized through oxidation of master alloy powders produced by mechanical alloying. The oxide YBa2Cu3O
x
undergoes the superconducting transition at 90 K with a width of about 2 K. The BiSrCaCu2O
x
oxide is found to consist of at least two different superconducting phases with T
c values of 110 and 75 K.
EXAFS Study on the Local Structure of a New High-Tc Superconductor in the Bi-Sr-Ca-Cu-O System
Authors: Maeda Hironobu , Koizumi Akihisa , Bamba Naruhiko , Takayama-Muromachi Eiji , Izumi Fujio , Onoda Mitsuko , Kuroda Yasushige , Maruyama Hiroshi , Yoshikawa Yuzo , Ishii Tadao , Hida Moritaka , Yamazaki Hitoshi
Published: February 2005

X-ray absorption spectroscopy has been used to study a new superconducting phase in the Bi-Ca-Sr-Cu-O system. X-ray absorption measurements at the Cu K-edge indicate that a copper ion is surrounded by five coordinated oxygen atoms, and that the Cu-O distance is 1.91 Å. Measurements at the Bi LIII-edge give the interatomic distance between bismuth and oxygen as 2.10 Å.
Microstructures in a Twinned Single Crystal of Tetragonal La1.5Ba1.5Cu3O7.11
Authors: Suzuki Kunio , Ichihara Masaki , Takeuchi Shin , Takeya Hiroyuki , Takei Humihiko
Published: February 2005

Microstructures in a single crystal of tetragonal La1.5Ba1.5Cu3O7.11 grown by a flux method have been studied using high-resolution electron microscopy. The crystal is composed of twin domains with the a- and c-axes mutually interchanged. In each domain, a high density of stacking faults with a fault vector of 1/3[001] and with a fault plane nearly parallel to {101} have been observed. These stacking faults are considered to be related to a compositional fluctuation in the crystal.
Structural Variations on Superconductor Tl-Ba-Ca-Cu-O Oxides
Authors: Iijima Sumio , Ichihashi Toshinari , Kubo Yoshimi
Published: February 2005

Two crystal structures for c 105 K Tl-Ca-Ba-Cu-O oxides, with lattice parameters a=b=5.44 Å, c=29.32 Å, and a=b=5.44 Å, c=35.68 Å, isostructural with Bi2CaSr2Cu2O8+x
and Bi2Ca2Sr2Cu3O10+x
, respectively, were found by electron microscopic observation. The stacking arrangements for the CuO2-Ca-CuO2 slabs and BaO-TlO-BaO slabs in their structures result in a series of phases and stacking disorder in this oxide system. Weak long-range-order, taking place in the BaO-TlO-TlO-BaO slabs in the a-c plane projection, was observed.
Neutron Diffraction Study of Nonstoichiometry in Ba1.5La1.5Cu3Oy
Authors: Izumi Fujio , Takayama-Muromachi Eiji , Kobayashi Michiko , Uchida Yoshishige , Asano Hajime , Ishigaki Tōru , Watanabe Noboru
Published: February 2005

The structure parameters of annealed and quenched samples of Ba1.5La1.5Cu3O
y
were refined by the Rietveld analysis of TOF neutron powder diffraction data. Partial occupation of an oxygen site at (0, 1/2, 0) causes nonstoichiometry in the oxide. The y values calculated from the occupation factors of oxygen at this site are 7.20 (annealed) and 6.76 (quenched), which are in fair agreement with those determined by iodometry: 7.15 (annealed) and 6.74 (quenched).
Twins and Intergrowth Defects in High-Tc Bi-Sr-Ca-Cu-O Superconductor Examined by High-Resolution Electron Microscopy
Authors: Matsui Yoshio , Maeda Hiroshi , Tanaka Yoshiaki , Takayama-Muromachi Eiji , Takekawa Shunji , Horiuchi Shigeo
Published: February 2005

Twinned structure with twin plane (510) and with the composition plane (001) is observed in a high-T
c Bi-Sr-Ca-Cu-O superconductor which is orthorhombic with a=0.54, b=2.7 and c=3.08 nm. Directions of “Bi-concentrated bands” in both twin individuals are perpendicular to each other. Local intergrowths of perovskite-related layers with 1.8 and 2.1 nm thickness are observed among the major layers of 1.5 nm. The material includes small amounts of crystal with c=3.6 nm, which may be responsible for the superconductivity at 105 K, as already suggested by Muromachi et al. (Jpn. J. Appl. Phys. 27 (1988) L556).
Growth and Very Anisotropic Upper Critical Field of Single-Crystal Bi2Sr2CaCu2Oy
Authors: Koike Yoji , Nakanomyo Takashi , Fukase Tetsuo
Published: February 2005

Flaky single crystals of a new high-T
c oxide Bi2Sr2CaCu2O
y
with dimensions of the order of 1×1×0.1 mm3 have been prepared using a CuO flux method. The electrical resistivity shows a sharp superconducting transition at 80.6 K. The upper critical field H
c2 was determined to be very anisotropic. The values of -dH
c2/dT for H//c-axis and H⊥c-axis are 0.39 T/K and 7.3 T/K, respectively. The ratio of -dH
c2
⊥/dT to -dH
c2
///dT is 19. The value of H
c2
⊥(0) for H⊥c-axis is estimated to be as large as 400 T. The Ginzburg-Landau coherence length along the c-axis at 0 K ξ//(0) is 2.1 Å, suggesting quasi-two-dimensional superconductivity.
Low Resistance Ohmic Contact for the Oxide Superconductor EuBa2Cu3Oy
Authors: Sugimoto Iwao , Tajima Yukimichi , Hikita Makoto
Published: February 2005

The ohmic contact between an oxide superconductor and a Au electrode was systematically studied under various temperature conditions. A low resistance ohmic contact below 7×10-8 Ωcm2 between the oxide superconductor EuBa2Cu3O
y
and a Au electrode is obtained by annealing at 300°C in an oxygen atmosphere. Under these conditions, the intrinsic electrical properties of the superconductor are not changed. In contrast, anomalous behavior is observed when using indium as the contact metal.
Light Irradiation Effect on the Preparation of High-Tc Yb-Ba-Cu-O Superconducting Thin Films
Authors: Nagata Shunroh , Kawasaki Masashi , Koinuma Hideomi
Published: February 2005

We have constructed a simple ac sputtering apparatus in which the growing film surface can be irradiated with light from a low-pressure mercury lamp. Yb-Ba-Cu-O thin films were irradiated by UV light at various steps of film preparation. The light irradiation was found to improve the superconductivity of the films, providing a promising method for decreasing the processing temperature of high-T
c superconducting oxide films. The pronounced irradiation effect at the post-annealing step suggests that the UV light primarily works to accelerate the incorporation of oxygen into the films.
A New Ferromagnetic Amorphous Oxide of the La-Sr-Mn-B-O System
Authors: Inomata Koichiro , Hashimoto Susumu , Nakamura Shiho
Published: February 2005

Amorphous 0.5La1-x
Sr
x
MnO3 0.5B2O3 (0.2≤x≤1.0) oxides were produced by melt quenching using a twin-roll technique. They were characterized by high crystallization temperatures above 920 K and transparency. Curie temperature is higher than 380 K over a wide range of Sr concentrations (0.3≤x≤1.0), thus differing from crystalline La1-x
Sr
x
MnO3 perovskite. The temperature dependence of magnetization in the amorphous state is similar to that for crystalline perovskite, suggesting ferromagnetism in the present amorphous oxides. The ferromagnetic behavior of the amorphous state may be explained by positive double-exchange interactions of Mn3+ and Mn4+ ions.
High Reliability in AlGaAs Laser Diodes Prepared by Molecular Beam Epitaxy on 0.5°-Misoriented (111)B Substrates
Authors: Hayakawa Toshiro , Takahashi Kosei , Suyama Takahiro , Kondo Masafumi , Yamamoto Saburo , Hijikata Toshiki
Published: February 2005

Slip lines in the molecular beam epitaxial wafer bonded with In during the growth have been eliminated by using (111)-oriented GaAs substrates instead of the usual (100)-oriented ones. AlGaAs double-heterostructure and quantum well lasers were grown on (100)- and 0.5°-misoriented (111)B substrates. The yield of reliable lasers is much higher for (111)-oriented devices than that for (100)-oriented ones, possibly due to the elimination of local defects such as slip lines.
Variation of Misfit Strain in ZnSe Heteroepitaxial Layers with Temperature, Layer Thickness and Growth Temperature
Authors: Matsumoto Takashi , Iijima Takayuki , Ishida Tetsuro
Published: February 2005

The temperature variation of misfit strain in ZnSe layers grown on GaAs(100) substrates has been measured at 80∼600 K for layer thicknesses of 0.2∼4.0 µm by X-ray diffraction. Layers as thin as 0.2 µm grow coherently on the substrate and the coherency holds even for low temperatures. Strain-free layers at room temperature include the two-dimensional expansive strain with ε
⊥≡(a
⊥-a
0)/a
0≈-0.03% at 80 K; layers including the two-dimensional compressive strain with ε
⊥≈+0.03% at room temperature become strain free at 80 K. The X-ray analysis is consistent with low-temperature reflection spectra.
EL2° Distribution in the Vicinity of Dislocations in GaAs-In Materials
Authors: Fillard Jp. , Gall P. , Asgarinia M. , Castagne M. , Baroudi M.
Published: February 2005

We have recently shown that, contrary to the well-reputed opinion, the EL2° centers in GaAs undoped materials are not especially concentrated on dislocations: the cell pattern, in particular, does not disappear after photoquenching at Liquid Nitrogen Temperature. In this paper we shall complete this study with details of the EL2° densities in the vicinity of individual dislocations in GaAs-In materials. Laser Scanning Tomography and Infra Red Transmission images will be analyzed complementarily. Grown-in axial dislocations appear to be surrounded by a wide EL2-rich cylindrical zone, whereas the dislocation itself is not to be considered as a large reservoir of gettered EL2 centers.
Nitrogen Doped p-Type ZnSe Layer Grown by Metalorganic Vapor Phase Epitaxy
Authors: Ohki Akira , Shibata Noriyoshi , Zembutsu Sakae
Published: February 2005

Nitrogen-doped ZnSe layers have been grown on (100) GaAs substrates by metalorganic vapor phase epitaxy using NH3 as the doping material. The N-doped layers exhibit a strong free-to-acceptor transition emission at 77 K and a strong acceptor bound-exciton emission line at 15 K. The layers with a high doping level, which exhibit broader excitonic emission lines, indicate p-type conduction with low resistivities from 102 to 103 Ω·cm, carrier concentrations of the order of 1014 cm-3 and mobilities from 20 to 50 cm2/Vs. Current-voltage characteristics of the N-doped ZnSe/n-GaAs heterojunctions conform to the p-type conduction.
Single-Crystal YBa2Cu3O7-x Thin Films by Activated Reactive Evaporation
Authors: Terashima Takahito , Iijima Kenji , Yamamoto Kazunuki , Bando Yoshichika , Mazaki Hiromasa
Published: February 2005

By means of the activated reactive evaporation, YBa2Cu3O7-x
single-crystal thin films with the c axis perpendicular to the substrate plane have been directly and epitaxially grown on the (100) surface of SrTiO3. The substrate temperature was kept below 600°C and the oxidation treatment was performed at below 500°C. The ac-resistive measurement for a film with 2000 Å thickness gave a sharp superconducting transition, where the endpoint was 90.2 K and Δ
T
c(10–90%)=1.7 K. From the complex susceptibility measurement we confirmed the Meissner effect as well as the structural uniformity of the specimen.
Humidity Sensor Using Antimony Phosphate Operative at a Medium Temperature of 150–250°C
Authors: Miura Norio , Mizuno Hiroshi , Yamazoe Noboru
Published: February 2005

A humidity sensor using a proton conductive antimony phosphate (HSb(PO4)2) operative at a medium temperature was developed. The sensor could detect water vapor pressure (P
H2O) in the range from 0.05 to 4.1 kPa at 150–250°C. Its humidity sensitivity (impedance change) was relatively high, especially in the low P
H2O range, i.e., lower than ca. 0.2 kPa. The 90% response time of the sensor to the change in P
H2O from 2 to 4 kPa was about 2 min. The sensor impedance was stable for a test period of 40 h under 3.3 kPa at 200°C. Moreover, the impedance was found to be affected only slightly by other coexistent reducible gases.
Magnetic Phase Transitions in 90 K Superconductors HoBa2Cu3O7-δ and GdBa2Cu3O7-δ Observed by ZF- µ+SR
Authors: Nishida Nobuhiko , Miyatake Hideaki , Okuma Satoshi , Kuno Yoshitaka , Watanabe Yasushi , Yamazaki Toshimitsu , Hikami Shinobu , Ishikawa Masayasu , Takabatake Toshiro , Nakazawa Yasuhiro , Kreitzmann Sydney R. , Brewer Jess H. , Huang Chao-Yuan
Published: February 2005

Freezing of holmium magnetic moments was observed below 3 K in a 90 K superconductor HoBa2Cu3O7-δ by zero-field positive muon spin relaxation (ZF-µ+SR) measurements. The ZF-µ+SR function revealed a marked change of µ+ local field from a critically fluctuating regime (4–7 K) to a quasi-static regime below 3 K (of nearly Gaussian distribution). The observation indicates that holmium magnetic moments are short-range ordered around 2 K. In contrast, a 90 K superconductor GdBa2Cu3O7-δ showed a zero-field spin precession at 2 K, indicating long-range ordering of gadolinium magnetic moments.
Production of Bi-Sr-Ca-Cu-O Glasses by Liquid Quenching and their Glass Transition and Structural Relaxation
Authors: Inoue Akihisa , Kimura Hisamichi , Matsuzaki Kunio , Tsai An-Pang , Masumoto Tsuyoshi
Published: February 2005

New BiSrCaCu2O
y
and Bi1.3SrCaCu2O
y
oxide glasses were produced by the single roller melt-spinning technique. The glasses were found to translate into a supercooled liquid accompanied with a distinctly appreciable glass transition at about 680 K, followed by crystallization at about 725 K. The increase in Bi content brought about a decrease in glass transition temperature and an increase in crystallization temperature, i.e. the extension of the supercooled liquid region. Specific heats of the glassy solid and the supercooled liquid and the difference in specific heat between the two states were measured for the two oxide glasses.
Development of a Compact Electron Beam Ion Source Cooled with Liquid Nitrogen
Authors: Okuno Kazuhiko
Published: February 2005

A small-sized EBIS type ion source (mini-EBIS) for production of highly charged ions has been developed. The whole system, namely, the electron gun, ion drift tube, electron collector, ion extraction lens and liquid nitrogen reservoir containing solenoid coil is housed in a vacuum envelope, 150 mmφ in diameter and 500 mm in length. The idea of cooling the solenoid to 77 K has proved very effective to miniaturize the solenoid and its power supply. Moreover, the wall of the liquid nitrogen reservoir exhibits a cryogenic pumping function at the ionization region. In the D
C ion extraction mode with an electron current of 15 mA at 2 keV, beam intensities obtained for C6+, N7+, O8+, Ne9+ and Ar16+ ions are at least 5×104, 3×104, 1×104, 5×103 and 3×103 counts per second, respectively.
An X-Ray Diffraction Study of Amorphous Ge0.13As0.17Te0.70
Authors: Ohkawa Yoshinori , Kahata Hisataka , Nakazato Masahiro , Wakabayashi Nobuyoshi
Published: February 2005

The radial distribution function for Ge0.13As0.17Te0.70 has been determined by conventional X-ray diffraction techniques. The results are analyzed on the assumption that the system is a mixture of amorphous As2Te3 and GexTe1-x.
Detection and Counting of Ultrafine Particles in Ultrapure Water Using Laser Breakdown Acoustic Method
Authors: Kitamori Takehiko , Yokose Kenji , Sakagami Masaharu , Sawada Tsuguo
Published: February 2005

Ultrafine particles, with a size and number density comparable to those of particulate impurities in ultrapure water, were counted individually by the proposed laser induced breakdown acoustic method. The detection conditions and counting efficiency of the particles were investigated theoretically, and the design conditions of the optical system for counting the ultrafine and ultradilute particles was obtained. Using 0.038 µm polystyrene ultrafine particles, which is one of the smallest standard particles on the market, particle counting at the number density of ultrapure water level, 102 particles per 1 ml, was demonstrated, and it was shown that the minimum detectable particle size was at least one order smaller than that of the conventional laser scattering method. The validity and applicability to in-line monitoring using a flow-type cell and size distribution measurements applying the pulse height distribution of the breakdown acoustic signals were also confirmed.
The Diffusion of Bismuth in Silicon
Authors: Ishikawa Yutaka , Yazaki Kazuyuki , Nakamichi Ichiro
Published: February 2005

The diffusion of bismuth into silicon from a spin-on source has been investigated at a temperature range of 1050–1200°C. The concentration profile of bismuth agrees with the complementary error function, and its diffusion coefficient shows a value similar to the values of phosphorus and boron. Its activation energy is estimated to be 2.50 eV. That is much smaller than the values of phosphorus, boron and arsenic.
Adsorption of Oxygen SnOx Thin Film
Authors: Konishi Ryōsuke , Furukawa Kimihiko , Matsubara Chihiro , Harada Hisamochi , Sasakura Hiroshi
Published: February 2005

The change in electrical resistance and the surface potential of SnOx thin film by the adsorption of oxygen were observed. At an oxygen pressure of 6.7×10-4 Pa, both changes result in a decrease. At further adsorption, the change in the electrical resistance ascends abruptly at about 10-2 Pa. These changes can be explained by devising a model of band bending.
Luminescence Circular Polarization of AgGaSe2 on Excitation of Circularly Polarized Light
Authors: Horinaka Hiromichi , Inada Hiroshi , Saijyo Takashi
Published: February 2005

Luminescence circular polarization on the optically isotropic face of the AgGaSe2 crystal, (001), is studied using a pulsed-dye laser. The photon energies of the pulsed-dye laser are set to 1.89 eV, 2.12 eV and 2.75 eV so as to excite the electrons to the lowest conduction band from the uppermost valence band, the upper two valence bands and all three valence bands, respectively. The luminescence circular polarization for excitation at 1.89 eV shows the opposite sign to that for excitation at 2.12 eV, as expected from the quasi-cubic model, but the maximum degree of luminescence circular polarization, 15%, is much smaller than the predicted value. It is confirmed that the built-in lattice compression diminishes the intensity of the transition probability for circularly polarized light on the optically isotropic face.
Preparation of Superconducting Y–Ba–Cu–O and Bi–Pb–Sr–Ca–Cu–O Compounds by Chelating Method
Authors: Fujisawa Tadashi , Takagi Akira , Honjo Tetzuji , Okuyama Katsuro , Ohshima Shigetoshi , Matsuki Kenzo , Muraishi Kazuo
Published: February 2005

Superconducting Y–Ba–Cu–O (YBCO) and Bi–Pb–Sr–Ca–Cu–O (BPSCCO) compounds were prepared by a chelating method with various chelating agents, such as nitrilotriacetic acid (NTA), hydroxyethylethylenediaminetriacetic acid (HEDTA) and ethylenediaminetetraacetic acid (EDTA). Above 600°C, the precursors YBCO and BPSCCO turned into a mixture of metal oxides and BaCO3, which finally transformed into the almost single phase of YBCO at 850∼930°C and into the high-T
c phase of BPSCCO at 840°C. The critical current densities of YBCO and BPSCCO in blocks of 1*4*15 mm3 were estimated to be as high as 350 and 500 A/cm2 at 77 K, respectively.
Self-Epitaxial Growth of Metastable A15 V3Al on Au-Coated Sapphire Substrates
Authors: Ohshima Shigetoshi , Ishida Hiroyuki , Wakiyama Tokuo , Okuyama Katsuro
Published: February 2005

The metastable A15 V3Al phase was obtained on glazed alumina (glass-coated alumina) and Au-coated sapphire substrates by sputtering using a composite target of Al and V. However, the metastable phase was not formed on sapphire or Ag-coated sapphire substrates. From the depth profile of the composition of the films prepared on glazed alumina substrates, it was found that Si and Ca atoms diffused into V–Al films from the glazed alumina substrate forming an A15 V3(Si, Ca) layer. The metastable A15 V3Al phase was grown self-epitaxially on such layers. The T
c value of the A15 V3Al prepared on glazed alumina substrates was higher than that prepared on Au-coated sapphire substrates. The maximum T
c of 13.8 K was obtained for the films prepared on glazed alumina substrates.
Anisotropy in Photocurrent Spectra of Poly(4,4'-oxydiphenylene pyromellitimide) Film
Authors: Iida Kazuo , Nohara Tsukasa , Nakamura Shuhei , Sawa Goro
Published: February 2005

The anisotropy of the photoconduction of polyimide was investigated in relation to the molecular orientation. The photocurrent as well as the molecular chain alignment was found to be anisotropic. A phenomenological model for the photocurrent in different directions of electric field was discussed. The photoconduction phenomena in the in-plane direction and that normal to the film plane were analyzed. The results are used as a foundation for comparing the conduction in the three directions. It was concluded that the anisotropy was caused by the alignment and orientation of the molecular planes as well as the molecular chains.
Optical Band Gap of Electron-Beam-Evaporated Doped Silicon Films
Authors: Fang P. H. , Chen Eryong , Kinnier J. H. , Miao Hong , Ma Jun
Published: February 2005

The optical band gap of electron-beam-evaporated silicon films doped with antimony and boron is determined in both amorphous and microcrystalline structures. The value in the amorphous structure is 1.5 eV for the Sb-doped case, the same as the intrinsic case, while for B-doping, the gap is sharply decreased to 1.0 eV. For the microcrystalline structure, the values are all 1.7 eV for Sb- and B- doped cases as well as the intrinsic case.
The Phase Diagram of the YO1.5–BaO–CuO Ternary System and Growth of YBa2Cu3O7 Single Crystals
Authors: Maeda Masaki , Kadoi Mikio , Ikeda Takuro
Published: February 2005

Phase equilibria relations in the YO1.5–BaO–CuO system at 900°C in air were investigated and the phase diagram of the subsystem YBa2Cu3O7–BaCuO2–CuO was determined by differential thermal analyses, quenching experiments, and X-ray diffraction measurements. Single crystals were grown by the slow cooling method and then characterized.
Enhanced Diffusion of Implanted Arsenic in Silicon at an Early Stage of Annealing
Authors: Sasaki Yoshisato , Itoh Kazuo , Tanuma Sei-ichi
Published: February 2005

The diffusion profiles of the heavily ion-implanted arsenic (As) in silicon by short annealing time were examined by Hall effect measurements in conjunction with anodization and layer removal. The arsenic diffusion profiles obtained by computer simulation were compared with the measured results. It is shown by this comparison that the diffusion of the arsenic atoms is enhanced at an early stage of annealing.
Silicon-on-Insulator Wafer Bonding-Wafer Thinning Technological Evaluations
Authors: Haisma J. , Spierings G. A. C. M. , Biermann U. K. P. , Pals J. A.
Published: February 2005

The realization of wafer-scale Silicon-on-Insulator by Van der Waals wafer bonding and subsequent thinning of one of the wafers is described for 100 mm wafers. The bonding of two silicon wafers is brought about by Van der Waals forces which are found to be sufficiently strong for a tight bond at wafer distances of less than 1 nm. This condition requires wafer surfaces which are extremely flat and free of dust particles. Usually the bonding susceptibility is enhanced by a short polishing step.
Van der Waals bonding (dipole bonding) is sufficiently strong to withstand the thinning procedure, but bonding is often enhanced by an anneal step (chemical bonding) before thinning. Four thinning procedures are described:
1.  Electroless chemical thinning: Selective etching of highly doped bulk material of an active wafer using an electrochemically controlled HF–HNO3–HAc–H2O etchant down to a low-dope, low etch-rate epilayer.
2.  Chemical thinning: Electrochemically controlled chemical etching of p-type bulk material of an active wafer down to a p/n junction, where electrochemical passivation of an n-type silicon epilayer occurs.
3.  Thinning down to a tribochemical polish stop: In this technique an active wafer is polished until grooves filled with Si3N4 are encountered. The removal rate then becomes small while SOI remains in the areas between the grooves.
4.  Polish without stopper: By adapting the existing optical polishing technology, extreme control of flatness and parallelism of wafer surfaces can be achieved. It then becomes possible to polish homogeneously down to SOI layers a few microns thick over a 100 mm wafer. In procedures 1 and 2 an acceptable surface quality is obtained by applying a final tribochemical polishing step. Experimental results of the four technologies are presented.
In these technologies, tribochemical polishing is crucial. The necessity of this polishing technology as an off-line facility is discussed in the broader context of ICs of the future.