bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Tc Superconductivity of La-Ba(Sr)-Cu Oxides. IV –Critical Magnetic Fields
Authors: Uchida Shin-ichi , Takagi Hidenori , Tanaka Shoji , Nakao Koichi , Miura Noboru , Kishio Kohji , Kitazawa Koichi , Fueki Kazuo
Published: November 2005

Magnetic field dependence of the resistivity was measured up to 33T for high T
c superconductors (La1-x
A
x
)2CuO4 with A=Ba and Sr. Although the transition from the superconducting to normal state was broad, the upper critical field defined as the field at 50% of the normal resistance was estimated to be larger than 50 T at liquid helium temperature. The critical field probably exceeds 10 T at liquid hydrogen temperature and also at liquid neon temperature for (La1-x
Sr
x
)2CuO4.
Drift Velocity and Pulse Response of Trapped Ions in a Circulating Electron Beam
Authors: Watanabe Ken-ichi , Miyahara Yoshikazu , Ohkuma Haruo , Shinoe Kenji
Published: November 2005

Response of trapped ions in a circulating electron beam to a sharp pulsed voltage applied to a clearing electrode was successfully observed with a NaI scintillator, detecting γ-rays caused by the trapped ions. It was found that velocity distribution of trapped ions is 3.3 times wider than the Maxwell-Boltzmann distribution of CO+ ions. The pulse response was also analyzed considering transmission, elimination and production of trapped ions.
Dispersion Relation of Optical Eigen Modes in Ferroelectric SmC* Distorted by an Electric Field
Authors: Kawaida Masahiro , Nakagawa Masahiro , Akahane Tadashi
Published: November 2005

The dispersion relations of optical eigen modes in ferroelectric SmC*, whose structure is distorted by a DC electric field perpendicular to the helical axis, are calculated by the 4×4 matrix method. When the effect of the spontaneous polarization on the elastic deformation is dominant over that of the induced polarization, or when the anisotropy of the dielectric constant ε
a<0, even if the latter is dominant, coupling between the slow (fast) forward mode and fast (slow) backward mode occurs as the electric field increases. When ε
a>0 and the induced polarization is dominant, such a coupling does not occur.
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 MOCVD. The lowest threshold current obtained in 7 µm-wide oxide stripe MQW LD's was 170 mA at room temperature (at 293 K). The average threshold current and peak wavelength among the tested 60 chips were 324 mA and 864.3 nm, respectively. The maximum differential quantum efficiency was 14.0%.
Stable Quasi-Crystals in Al75Cu15V10 Prepared by Crystallization of an Amorphous Phase
Authors: Tsai An-Pang , Inoue Akihisa , Masumoto Tsuyoshi
Published: November 2005

A mostly single icosahedral phase has been found to be formed by crystallization of an amorphous Al75Cu15V10 alloy prepared by liquid quenching. The crystallization-induced icosahedral phase is concluded to be a highly stable intermediate product because it remains stable up to high temperatures just below melting temperature (T
m) and changes to equilibrium Al2Cu and Al3V phases only after an annealing time of more than 30 h at 0.99T
m.
Doping Enhancement by Excimer Laser Irradiation in Gas Source Molecular Beam Epitaxy of GaAs
Authors: Kimura Kōzō , Horiguchi Seishi , Kamon Koichi , Shimazu Mitsuru , Mashita Masao , Mihara Minoru , Ishii Makoto
Published: November 2005

Ultraviolet ArF excimer laser irradiation is found to enhance the doping efficiency from disilane in gas source molecular beam epitaxial growth of n-GaAs. The enhancement is observed in two configurations in which the laser beam is directed either normal or parallel to the substrate surface. The increase in doping efficiency is caused by the photolytic decomposition of disilane.
Growth Rate Enhancement by Xenon Lamp Irradiation in Organometallic Vapor-Phase Epitaxy of ZnSe
Authors: Fujita Shigeo , Tanabe Akira , Sakamoto Takao , Isemura Masashi , Fujita Shizuo
Published: November 2005

The growth rate of ZnSe in organometallic vapor-phase epitaxy (OMVPE) using dimethylzinc (DMZ) and dimethylselenide (DMSe) as the source materials was substantially increased by irradiation from a xenon lamp. The growth temperature was reduced from 500°C to 300°C by keeping a constant growth rate of 1∼2 µm/h. Promotion of surface reaction due to irradiation was considered as one of the factors for the growth rate enhancement. The density of defects which causes deep level emissions was also successfully reduced. We suggest that this technique is very effective to obtain high-quality epilayers.
London Penetration Depth of YBa2Cu3O7-δ
Authors: Ishida Takekazu , Mazaki Hiromasa
Published: November 2005

We have measured the ac magnetic susceptibility of powdered YBa2Cu3O7-δ as a function of temperature. The temperature dependence of the London penetration depth estimated from the susceptibility data is quite different from that expected by the BCS theory. The result is well reproduced by the empirical formula λ(T)=λ(0)(1-T/T
c)-1/2, suggesting the existence of a gapless region on the Fermi surface in the high-T
c oxide superconductor.
2-D Oxygen Order in the 55 K-Superconducting Phase of Y-Ba-Cu-O
Authors: Inoue Masahiro , Takemori Tadashi , Sakudo Tunetaro
Published: November 2005

Considering the nearest- and two next-nearest-neighbor interactions, phase diagrams are presented for oxygens in the middle layer of Y-Ba-Cu-O. A simple estimate indicates it is likely that the oxygens in the 55 K-phase are formed from the 90 K-phase by removing all oxygen atoms from every other Cu-O chain.
Antiferromagnetic Transition in Y2BaCuO5
Authors: Kanoda Kazushi , Takahashi Toshihiro , Kawagoe Takeshi , Mizoguchi Tadashi , Kagoshima Seiichi , Hasumi Masahiko
Published: November 2005

Magnetism of a compound Y2BaCuO5 has been investigated by means of electron paramagnetic resonance (EPR) and static susceptibility measurements. An EPR absorption signal due to Cu2+ was observed. The temperature dependence of the integrated signal intensity follows a Curie-Weiss law, consistent with the results of static susceptibility. The Weiss temperature is -33±2 K. The EPR signal becomes appreciably broadened at low temperatures and disappears at about 20 K. This is indicative of an antiferromagnetic transition. A peak of static susceptibility is observed at 14 K.
Possibility of Two-Dimensional Superconductivity in (La, Ba)2CuO4 and (La, Sr)2CuO4 with High Critical Temperatures
Authors: Tanaka Shoji
Published: November 2005

The possibility of two-dimensional superconductivity in (La, Ba)2CuO4 and (La, Sr)2CuO4 is discussed based on experiments in magnetic susceptibility and upper critical magnetic field. Both results seem to indicate that two-dimensional superconductivity occurs below 20 K in these materials.
Negligible Photoconductivity Efficiency and Impurity Sensitive Absorption Fine Structure at the Low Energy Tail of π-π* Transition in Trans-Polyacetylene
Authors: Kubo Takaya , Sasaki Kozo , Takezoe Hideo , Fukuda Atsuo
Published: November 2005

Photocurrent spectra normalized by incident light intensity together with high-resolution optical absorption spectra have been obtained in the visible and near IR regions using carefully prepared very pure samples. The photocurrent efficiency is practically zero at the low energy tail of the π-π* absorption band and gradually increases with the photon energy, becoming very high on the high energy side. Oxygen doping produces a photocurrent peak at 1.4 eV and a corresponding series of sharp absorption bands which stick to the intrinsic absorption band edge.
Upper Critical Field and its Anisotropy of EuBa2Cu3O7-x and GdBa2Cu3O7-x Studied in Preferentially Oriented Pellets
Authors: Takita Kôki , Akinaga Hiroyuki , Masuda Kohzoh
Published: November 2005

Upper critical field H
c2 and its anisotropy are studied in disk samples of EuBa2Cu3O7-x
and GdBa2Cu3O7-x
. Preferentially oriented samples with c-axis perpendicular to the disk plane show anisotropic behavior of H
c2 for midpoints and almost isotropic behavior for the offset field. The critical field slopes (-dH
c2/dT) for offset field are 0.9∼1.1 T/K for both Eu-compound and Gd-compound. An analysis based on a model of a quasi-two-dimensional anisotropic superconductor suggests that the anisotropy factor ε is 0.16 for both materials. A degradation of the critical field values was observed in these materials in a shorter period of time after sintering than in the case of Y-, Ho- and Er-compounds.
31P Nuclear Magnetic Resonance Study of Local Bonding Configuration of Phosphorus in Amorphous Silicon-Hydrogen-Phosphorus Alloys
Authors: Hayashi Shigenobu , Hayamizu Kikuko , Yamasaki Satoshi , Matsuda Akihisa , Tanaka Kazunobu
Published: November 2005

31P nuclear magnetic resonance (NMR) spectra have been measured for amorphous hydrogenated silicon heavily doped with phosphorus. Phosphorus is enriched in the film during glow-discharge decomposition of the SiH4-PH3 mixture at a substrate temperature of 250°C by a factor of 3. 31P NMR results demonstrate that almost all the phosphorus atoms are bonded to three silicon atoms, and not to hydrogen or to other phosphorus.
Crystal Structures and Superconductivity in EuxBa3-xCu3Oy (1≤x≤1.5)
Authors: Iwata Tsunekazu , Hikita Makoto , Tajima Yukimichi , Tsurumi Shigeyuki
Published: November 2005

The Eu
x
Ba3-x
Cu3O
y
system has been investigated by X-ray powder diffraction analysis and electrical resistivity measurements. The region of solid solubility for Eu
x
Ba3-x
Cu3O
y
has been found to extend from x = 1.0 (the 123 phase) to x = 1.5 (the 336 phase). As x increases, the phase changes from orthorhombic to tetragonal around x = 1.25, resulting in a less metallic and lower T
c. Even in the tetragonal phase samples, at x = 1.25 and 1.33, superconductivity has been observed.
Anisotropic Optical Properties of (La1-xSrx)2CuO4 Single Crystal Thin Films
Authors: Suzuki Minoru , Oda Migaku , Enomoto Youichi , Murakami Toshiaki
Published: November 2005

Room temperature polarized reflection and transmission measurements in the 0.4 to 2.6 µm wavelength range for a superconducting (La1-x
Sr
x
)2CuO4 thin film single crystal with a (103) surface are reported. The reflectance for the a-axis (Cu-O plane) polarization is typical of a metal with a plasma frequency of 0.87 eV, while that along [301̄] is almost like a semiconductor, at least in the present wavelength range. The results provide direct evidence of the two-dimensional elecironic structure in this compound.
Potassium Grain Boundary Segregation and Site Occupancy in SrTiO3 Ceramics
Authors: Fujimoto Masayuki
Published: November 2005

The grain boundary segregation profile of potassium in SrTiO3 ceramics was revealed using HR-TEM (high-resolution transmission electron microscopy) and STEM (scanning transmission electron microscopy). HR-TEM showed precipitation-free grain boundaries in the specimen. STEM chemical analysis data, and K/Ti, K/Sr and Sr/Ti X-ray intensity ratios indicated a potassium segregation layer of less than 20 nm wide at the grain boundaries and Sr-site occupancy by potassium. These properties were considered responsible for the nonohmic current-voltage characteristic, i.e., varistor behavior, of the specimen.
Magnetic Field Effect on the Superconducting Transition in (RE)xBa1-xCuOy
Authors: Koike Yoji , Nakanomyo Takashi , Hanaguri Tetsuo , Nomoto Tetsuo , Fukase Tetsuo
Published: November 2005

The superconducting transition of (RE)
x
Ba1-x
CuO
y
(RE: Nd, Sm, Eu, Gd, Ho, Yb, Y; 0.25≦x≦0.40) has been studied in magnetic fields up to 6 T. Two-step transitions have been clearly observed in the magnetic fields for most of the samples. The samples are considered to be composed of the orthorhombic phase with a higher T
c around or below 90 K, and of the inhomogeneous quasi-tetragonal phase with a lower T
c around or below 60 K surrounding the former phase, though the composite ratio depends on the RE-concentration x. The RE-concentration dependence of the transition curve is closely concerned with the ion radius of RE.
The Oxygen-Deficient Perovskite Solid Solution Nd1+xBa2-xCu3Oy and Its Superconductivity
Authors: Takekawa Shunji , Nozaki Hiroshi , Ishizawa Yoshio , Iyi Nobuo
Published: November 2005

The Nd1+x
Ba2-x
Cu3O
y
system and its superconductivity were studied. This system forms a solid solution within the x range of 0.00 to 0.80. At room temperature, it has orthorhombic symmetry for x ranging from 0.00 to 0.14 and tetragonal symmetry for x not less than 0.20. All specimens at 900°C in air have tetragonal symmetry. It is a superconductor in the region of x less than 0.50. The superconducting onset temperature decreases from 93.5 to 40.0 K with increasing x. In comparison with the superconductivity of the La1+x
Ba2-x
Cu3O
y
system, there appears to be little influence of the magnetic ion Nd3+ on the T
c in the Nd1+x
Ba2-x
Cu3O
y
system.
Superconductivity in the Bi-Sr-Cu-O System
Authors: Akimitsu Jun , Yamazaki Akira , Sawa Hiroshi , Fujiki Hideo
Published: November 2005

A superconducting transition with an onset temperature near 8 K was observed for the Bi-Sr-Cu-O system through electrical resistivity and magnetic susceptibility measurements. The superconductivity is of a bulk nature and reproducible.
Isotope Effect in Superconducting YBa2Cu3O7-δ System
Authors: Katayama-Yoshida Hiroshi , Hirooka Tsuguyoshi , Mascarenhas Angelo J. , Okabe Yutaka , Takahashi Takashi , Sasaki Taizo , Ochiai Akira , Suzuki Takashi , Pankove Jacques I. , Ciszek Ted , Deb Satyen K.
Published: November 2005

An oxygen isotope effect is observed by a measurement of the resistivity when 16O is substituted for 18O in the YBa2Cu3O7-δ compound. The superconducting transition temperature T
c is lowered by 0.4 K upon substitution. The results suggest that the phonon related to oxygen in the two-dimensional CuO2 plane contributes to the mechanism of high-T
c superconductivity. When 63Cu is substituted for 65Cu, no appreciable isotope effect is observed.
Low Pressure Vapor Phase Epitaxy of High Purity ZnSe Using Metallic Zinc and Selenium as Source Materials
Authors: Matsumoto Takashi , Kobayashi Nobuo , Ishida Tetsuro
Published: November 2005

High-purity ZnSe layers have been grown on GaAs(100) substrates at 420°C by low pressure (∼21 kPa) vapor phase epitaxy using metallic zinc and selenium as starting source materials. Zinc vapor and H2Se gas produced by a reaction between selenium and hydrogen are transported into a crystal growth region by H2 carrier gas. Growth rates are 0.05∼0.3 µm/h, and dependent on source transport rates. When the source transport rates are controlled at Zn=Se=1∼3 µmol/min, free exciton emissions dominate 4.2 K photoluminescence spectra, and emissions due to donor-bound excitons and deep level defects become very weak.
Two Kinds of Switching Processes in Surface Stabilized Ferroelectric Liquid Crystals
Authors: Ouchi Yukio , Takano Hideo , Takezoe Hideo , Fukuda Atsuo
Published: November 2005

Two kinds of molecular reorientation processes in SSFLC cells were observed. One (a) is accompanied by the nucleation and growth of domains and the other (b) proceeds by uniform brightness change without any domain formation throughout a cell. In transmittance change, (a) and (b) are also explained by two-step and single-step switchings, respectively. The switching speed of the case (b) is one hundred times faster than that of the case (a) at a low electric field. The models for these switching processes are presented: an internal disclination model for case (a), and a cooperative director reorientation model for case (b).
Electron Microscopy of Composite Films of Titanium and Magnesium Oxide
Authors: Nagao Masaru , Tanaka Nobuo , Mihama Kazuhiro
Published: November 2005

Composite films of titanium and magnesium oxide are prepared by simultaneous deposition technique on sodium chloride (001) surfaces and characterized by electron microscopy and electron diffraction technique. Small crystallites of around 1 nm in size with the structure of titanium oxide with ordered vacancies embedded epitaxially in magnesium oxide single crystal films are observed in as grown films. The structure of the composite films remains unchanged by heat treatment at 500°C for a few hours. Heat treatment of the composite films at 1000°C for a few minutes brings about the formation of Mg2TiO4 with the spinel structure.
Quantum Well Width Dependence of Negative Differential Resistance of In0.52Al0.48As/In0.53Ga0.47As Resonant Tunneling Barriers Grown by MBE
Authors: Muto Shunichi , Inata Tsuguo , Sugiyama Yoshihiro , Nakata Yoshiaki , Fujii Toshio , Ohnishi Hiroaki , Hiyamizu Satoshi
Published: November 2005

The effect of quantum well width on the negative differential resistance (NDR) at 77 K of an InAlAs/InGaAs resonant tunneling barrier structure, lattice-matched to InP substrates and grown by MBE, was studied. The best NDR characteristics ever reported (peak-to-valley ratio of 11.4 with peak current density of 5.5×104 A/cm2) have been achieved for a resonant tunneling barrier diode with a thin quantum well width of 44 Å. A reduction of electron effective mass in the InAlAs barrier layer was also observed.
Light Emission from Quantum-Box Structure by Current Injection
Authors: Miyamoto Yasuyuki , Cao Ming , Shingai Yasushi , Furuya Kazuhito , Suematsu Yasuharu , Ravikumar K. G. , Arai Shigehisa
Published: November 2005

Light emitting from quantum-box structure by current injection was observed for the first time. GaInAsP/InP quantum-box structures were fabricated from one-dimensional quantum-well (quantum-film) structures grown by OMVPE. Holographic lithography, wet etching, and LPE regrowth techniques were employed. Three-dimensional quantum size effect was suggested by the wavelength shift of the light emission.
The Effect of Ultraviolet Irradiation on Electroless Plating Process of Nickel
Authors: Nakamichi Ichiro , Ishikawa Yutaka , Hirose Yoichi
Published: November 2005

The effect of irradiation of ultraviolet (UV) light on the nickel electroless plating process has been investigated. Both enhancement of plating rate and the quite opposite effect, suppression, are obtained. These effects may possibly be used for making metal film patterns on printed circuits.
Determination of Twist Elastic Constant K22 by Forced Rayleigh Scattering
Authors: Takezoe Hideo , Toyooka Takehiro , Hirakata Jun-ichi , Fukuda Atsuo
Published: November 2005

A novel method for determining the twist elastic constant K
22 is proposed. A critical magnetic field strength due to a Frederiks transition was detected by utilizing the anisotropy of diffusion constants of a dye by means of forced Rayleigh scattering technique. Measurements were made for 5CB and were compared with those made by other methods. It was found that the obtained values are comparable with those from other recent measurements.
DLTS Study of Electron Traps in n-GaAs Grown by Gas Source Molecular Beam Epitaxy Using Triethylgallium and AsH3
Authors: Kanamoto Kyozo , Kimura Kōzō , Horiguchi Seishi , Mihara Minoru , Ishii Makoto
Published: November 2005

Deep level transient spectroscopy has been carried out in n-GaAs grown by gas source molecular beam epitaxy (GSMBE) using triethylgallium (TEG) and AsH3. Seven electron traps have been observed, five of which correspond to those reported in n-GaAs grown by conventional MBE. The concentration of E
L2 was below the detection limit of about 1×1012 cm-3. The concentrations of the dominant traps, which correspond to M1, M2' and M4, decreased as the AsH3/TEG flow-rate ratio increased. High-quality GaAs layers with a total trap concentration as low as about 2×1013 cm-3 have been grown even at a low growth temperature of 550°C.
Electrical Characteristics of Focused-Be-Implanted GaAs Activated by Rapid Thermal Annealing
Authors: Uematsu Masashi
Published: November 2005

The electrical behavior of focused Be-implanted GaAs followed by rapid thermal annealing (RTA) is investigated by means of Hall-effect measurements. Focused Be ion implantation is carried out at energies of 50 to 200 keV. The electrical activation is found to decrease with higher implantation energies. The electrical properties indicate that the radiation damage induced by focused ion beam (FIB) is more difficult to be annealed out as the implantation energy increases. This behavior is different from that of unfocused ion beam (UIB) implants, which shows no significant dependence on implantation energy.
Photoluminescence Study of Undoped, Sn-Doped and S-Doped InP Single Crystals
Authors: Inoue Takayuki , Takahashi Junzo
Published: November 2005

Photoluminescence (PL) intensity distribution was measured at 4.2 K along the <011> direction across the wafer, to compare the etch-pit density (EPD) distribution for undoped, Sn-doped and S-doped InP. Exiciton, donor-acceptor and 1.06 eV peaks of the undoped InP have W-shapes corresponding to the EPD distribution. The 1.06 eV band seems to be related to In vacancies. The Sn-doped and the S-doped InP show broadened and shifted peaks to a higher energy side for near band-edge emissions. The PL intensity distributions and the EPD distributions are W-shaped for the Sn-doped and U-shaped for the S-doped InP, respectively.
Formation of Ti Hydride Ultrafine Particles and Transformation between TiH2 and Ti
Authors: Yanagida Akihiko , Yatsuya Shigeki , Mihama Kazuhiro
Published: November 2005

TiH2 ultrafine particles are formed by the H2 gas evaporation technique. The typical habit of the particles shows a dodecahedron. Through the habit, the growth is considered to be resulting from a martensitic transformation from a bcc structure to a CaF2 structure due to the hydrogen absorption. The desorption of H2 from the TiH2 particles by heat treatment in a vacuum brings about the formation of hcp Ti particles, while the absorption of H2 gas of Ti particles due to heat treatment in a H2 atmosphere leads to the formation of TiH2 particles with CaF2 structure, in both cases always accompanied by twin planes.
Preparation of Birefringent Plastic Optical Material
Authors: Muto Shinzo , Ichikawa Akio , Okuda Kenichi , Kawai Masato , Ito Hiroshi
Published: November 2005

A preparation method for birefringent plastic bulk material is presented. A plastic such as poly(α-methylstyrene) takes a birefringent orientation when a high dc electric field is applied to its molten phase. This phenomenon is maintained even in a solid phase after decreasing the temperature and hence the birefringent plastic material is formed. It is noticeable that the magnitude of birefringence in the bulk plastic prepared here is controllable.
Nonradiative e-h Recombination Characteristics of Mid-Gap Electron Trap in AlxGa1-xAs (x=0.4) Grown by Molecular Beam Epitaxy
Authors: Ando Koshi , Amano Chikara , Sugiura Hideo , Yamaguchi Masafumi , Saletes Anne
Published: November 2005

Nonradiative electron-hole(e-h) recombination characteristics have been investigated for a dominant mid-gap electron trap (0.86 eV) related to oxygen-complex defect center in MBE-grown Al
x
Ga1-x
As films(x=0.4) by means of an extended capacitance-transient spectroscopy technique. Direct evidence is presented to demonstrate that the 0.86 eV defect level plays an important role as an efficient electron-hole nonradiative recombination channel as well as an electron capture and emission center role accompanied with strong lattice relaxation.
Hole Transport in Silicon Thin Films with Variable Hydrogen Content
Authors: Shibata Naoki , Oda Shunri , Shimizu Isamu
Published: November 2005

The hole transport characteristics of Si:H(F) thin films with variable hydrogen contents, prepared by hydrogen-radical-enhanced chemical vapour deposition (HRCVD), were evaluated by the time-of-flight method. The drift mobility conforms with a multiple-trapping model derived from an exponential energy distribution of the valence band tail states, and increases as hydrogen contents decrease from 15 to 2 at.%. The characteristic temperatures provided by the above model show a significant decrease over the same compositional interval. These results were interpreted on the basis of the packing density of the films and the film growth processes during deposition.
Chemical Vapor Deposition of a-SiGe:H Films Utilizing a Microwave-Excited Plasma
Authors: Watanabe Takeshi , Tanaka Masahiro , Azuma Kazufumi , Nakatani Mitsuo , Sonobe Tadashi , Shimada Toshikazu
Published: November 2005

Hydrogenated amorphous silicon-germanium films were prepared by a chemical vapor deposition method utilizing a microwave-excited plasma produced at low gas pressures (∼10-3 Torr). Deposition methods in which SiH4 and GeH4 were decomposed by a plasma stream of Ar or hydrogen or by direct excitation were examined at 200°C and at the pressures optimized for the preparation of hydrogenerated amorphous silicon films. Highly photoconductive narrow gap films (an optical gap of 1.5 eV) with photoconductivity higher than 10-5 S/cm and photosensitivity of about 104 were obtained by these methods, keeping a high deposition rate.
Optical Properties and Lasing of Ti3+ Doped BeAl2O4
Authors: Segawa Yusaburo , Sugimoto Akiko , Kim Pit Hyon , Namba Susumu , Yamagishi Kiyoshi , Anzai Yutaka , Yamaguchi Yasuhide
Published: November 2005

The absorption and photoluminescence spectra of Ti3+ doped chrysoberyl (BeAl2O4) were studied, as well as its lasing operation. The photoluminescence spectrum of Ti:BeAl2O4 has two peaks at 750 nm and 850 nm and the lifetime of both these lines is 5.0 µs, which is longer than that of Ti3+ doped sapphire (Al2O3). With an excitation power of 15 mJ, lasing wavelength was 803±20 nm and the pulse duration was less than 80 ns.
Reduction in Threshold Current Density of Quantum Well Lasers Grown by Molecular Beam Epitaxy on 0.5° Misoriented (111)B Substrates
Authors: Hayakawa Toshiro , Kondo Masafumi , Suyama Takahiro , Takahashi Kosei , Yamamoto Saburo , Hijikata Toshiki
Published: November 2005

GaAs/AlGaAs graded-index, separate confinement heterostructure quantum-well lasers with an extremely low threshold current density (J
th) were grown by molecular beam epitaxy on 0.5° misoriented (111)B substrates. The J
th of these lasers was reduced by 20 A/cm2 compared with that of (100)-oriented devices, which results from the quantization along the <111> direction. The minimum J
th of 158 A/cm2 was achieved for a 490 µm long device.
Atomic Corrugation of Kish Graphite in Air Measured with Scanning Tunneling Microscope
Authors: Morita Seizo , Tsukada Shuichi , Mikoshiba Nobuo
Published: November 2005

Using a scanning tunneling microscope (STM), we have measured the atomic corrugation ΔZ of a Kish graphite in air. In the usual topographic mode, we found an anomalously large ΔZ up to about ΔZ=70 Å at the tunnel resistance of R
T=1 MΩ, which decreased to about 20 Å at R
T=100 MΩ as R
T increased. On the other hand, in a current mode, we found only a small modulation of the tunneling current ΔI
T/<I
T>=2∼5%, which corresponds to an atomic corrugation of ΔZ=0.01 Å∼0.02 Å. We interpret these results as evidence that a W tip was in mechanical contact with the Kish graphite and its surface was thereby contaminated.
Superconducting Properties of La1.85Sr0.15CuO4 Made by Hot-Press and Sinter Methods
Authors: Yoshizaki Ryozo , Iwazumi Toshiaki , Sawada Hideaki , Ikeda Hiroshi , Matsuura Etsuyuki
Published: November 2005

The superconducting transition properties were investigated by resistivity and magnetization in La1.85Sr0.1CuO4 for hot-pressed and sintered samples. The zero resistance at 34.5 K and the midpoint of the transition at 37.7 K were obtained in the sintered one with the onset temperature of 42 K. A single crystal was obtained in the hot-pressed one.
High Transition Temperature Superconductor: Y-Ba-Cu Oxide
Authors: Hikami Shinobu , Hirai Takashi , Kagoshima Seiichi
Published: November 2005

New material with high temperature superconductivity is discovered. This material is an oxide of the composition of yttrium, barium and copper. The observation of the superconductivity begins at 85K and completely vanishing resistance occurs at 45 K.
Fermi Surface Instability of Quasi-Two-Dimensional Tight Binding Electrons : A Possible Phase Diagram of (La1-xMx)2CuO4
Authors: Hasegawa Yasumasa , Fukuyama Hidetoshi
Published: November 2005

The Hartree-Fock instability against charge or spin density wave is examined as a function of the band filling for quasi-two-dimensional tight binding electrons in the tetragonal symmetry. It is found that the existence of the instability can be confined to the region close to the half-filling. The implication of the present result is discussed in the context of high T
c superconductor, (La1-x
M
x
)2CuO4, and it is indicated that the ground state for very small value of x will be the spin density wave (SDW) and that the superconductivity state is stabilized above some critical value of x of the order of 0.01.
High-Tc Superconductivity in New Oxide Systems
Authors: Hosoya Shoichi , Shamoto Shin-ichi , Onoda Masashige , Sato Masatoshi
Published: November 2005

Superconducting transitions have been observed by resistivity measurements for several specimens of L-M-Cu-O system with L being Yb, Lu, Y, La and the mixture of Yb and La, and M being Ba and mixture of Ba and Sr. The onset transition temperature T
c becomes very close to 100 K. Since Yb-Ba-Cu-O and Lu-Ba-Cu-O have almost the same transition temperatures (T
c>90 K), the magnetic moment of Yb atoms does not seem to destroy the superconductivity in the present system. This suggests that the superconductivity occurs in certain parts of the system which are, at least, far from the Yb atom sites. Therefore M-Cu-O or Cu-O system may have an essential role in the occurrence of the superconductivity.
Superconductivity of Y-Ba-Cu-O Compound above Liquid Nitrogen Temperature
Authors: Iguchi Ienari , Watanabe Hirohito , Kasai Yuji , Mochiku Takashi , Sugishita Akimitsu , Narumi Shun-ichi , Yamaka Eiso
Published: November 2005

A new ceramic Y-Ba-Cu oxide compound which exhibits superconductivity above liquid nitrogen temperature is presented. It is found that the compound of the form Y0.8Ba1.2CuO
y
exhibits superconducting onset at 92 K and complete zero resistance state at 77 K. The observed maximum critical current density is 14 A/cm2.
High-Tc Superconductor Ba0.5Y0.5Cu1Ox
Authors: Matsushita Akiyuki , Hatano Takeshi , Matsumoto Takehiko , Aoki Haruyoshi , Asada Yuji , Nakamura Keikichi , Honda Kinichi , Oguchi Tamio , Ogawa Keiichi
Published: November 2005

We report experimental results of resistivity, transition temperature and critical field for a new high-T
c superconductor Ba0.5Yn0.5Cu1O
x
. The onset temperature is found to be as high as 100 K and the end point to be 77 K. The superconducting transition has two components, a tail part on the lower temperature side of the transition region and a sharp drop on the higher temperature side. The end point of the higher component is estimated to be 88 K.
Preparation of a High Tc Superconductor by Oxidization of an Amorphous La1.8Sr0.2Cu Alloy Ribbon in Air
Authors: Matsuzaki Kunio , Inoue Akihisa , Kimura Hisamichi , Moroishi Keiji , Masumoto Tsuyoshi
Published: November 2005

A ductile La1.8Sr0.2Cu amorphous alloy with a long ribbon shape was prepared by melt spinning. Oxidization of the amorphous alloy ribbon at 1173 K for 1.2 ks in air results in formation of a tetragonal (La1.8Sr0.2Cu)
x
O
y
, oxide. Furthermore, the oxide ribbon was found to exhibit high T
c superconductivity with onset at 36 K, midpoint at 22 K and zero resistance at 9 K. It is therefore concluded that the new process consisting of the preparation of an amorphous alloy ribbon with good ductility, followed by the high temperature oxidization in air is useful for production of a superconducting oxide tape with high T
c.
Direct Evidence of Superconductivity of Y-Ba-Co Oxides –The Meissner Effect–
Authors: Minami Hidetoshi , Masumi Taizo , Hikami Shinobu
Published: November 2005

Direct evidence has been obtained of the existence of the perfect diamagnetism at least in parts of the high-T
c superconductors Y-Ba-Cu oxides at 4.2 K by using a microwave SQUID at 9 GHz.
Magnetic and Structural Properties of the High-Tc Superconductor Ho-Ba-Cu Oxide
Authors: Kagoshima Seiichi , Koga Kei-ichi , Yasuoka Hiroshi , Nogami Yoshio , Kubo Koichi , Hikami Shinobu
Published: November 2005

The title material is found to have the crystal structure same as another superconductor, Y-Ba-Cu oxide. The lattice has the face-centered tetragonal symmetry and the unit cell, whose parameters are a=b=7.81±0.02 Å and c=7.665±0.02 Å, contains eight units of the perovskite structure. The magnetic susceptibility obeys essentially the Curie-Weiss formula when sufficient fields are applied. For the fields less than 200 Oe the Meissner effect is observed up to about 70 K above which a finite resistance is found. The diamagnetic susceptibility at 4.4 K reaches about 50% of a perfect diamagnetism.
Crystal Structures of (La1-xMx)2CuO4-δ(M=Sr and Ba)
Authors: Onoda Masashige , Shamoto Shinichi , Sato Masatoshi , Hosoya Syoichi
Published: November 2005

Structure determinations of (La1-x
Sr
x
)2CuO4-δ and (La1-x
Ba
x
)2CuO4-δ(x≃0.075) are carried out by single crystal X-ray diffraction. The former is tetragonal with space group I4/m
m
m, while the latter is orthorhombic with Pccn. Both compounds have the K2NiF4-type layered perovskite structures formed by the linkage of CuO6 octahedra. The orthorhombic distortion in the compound with Ba is found to be mainly described by the rotation of CuO6 octahedra which corresponds to the R
25-mode of cubic perovskite lattice.
Properties of the Superconductor (Sr, Ca)-La-Cu-O System in Various Sintering Atmosphere
Authors: Saito Yoshitami , Noji Takashi , Endo Akihiko , Matsuzaki Nozomu , Katsumata Masao , Higuchi Naoaki
Published: November 2005

A sort of the layered perovskite (Sr1-z
Ca
z
)0.15La1.85CuO4-y
was prepared by a ceramic technique. Electrical resistance was measured for the various substitution ratio z. It exhibited the highest T
c value at z=0.03. The dependence of T
c upon the composition of sintering atmosphere (N2-O2 mixed gas) was also studied. At the oxygen partial pressure of 530 Torr, T
c exhibited the highest value.
Critical Temperature of Superconductivity Caused by Strong Correlation
Authors: Fukuyama Hidetoshi , Yosida Kei
Published: November 2005

The critical temperature of superconductivity based on a new mechanism proposed by Anderson and Hirsch is calculated by use of the Hubbard model and the coherent potential approximation to treat strong correlation. It is found that the critical temperature, T
c, has a maximum at around quarter-filling of the band with T
c∼te-c(U/t) where t and U are the transfer integral and the Coulomb interaction, respectively, and c is a constant of order unity.
Identification of Phases in High Tc Oxide Superconductor Ba0.7Y0.3Cu1Ox
Authors: Hatano Takeshi , Matsushita Akiyuki , Nakamura Keikichi , Honda Kinichi , Matsumoto Takehiko , Ogawa Keiichi
Published: November 2005

Crystal structures of a high-T
c oxide superconductor Ba0.7Y0.3Cu1O
x
have been identified using X-ray diffractometry and electron probe microanalysis. All the major diffraction peaks can be indexed in terms of the cubic and tetragonal phases. The lattice constant a
c is 3.884 Å for the cubic phase and the lattice constants a
t and c
t are 3.856 Å and 11.64 Å, respectively for the tetragonal phase. The identified phases have been confirmed on the scanning backscattered electron images of the sample and their chemical compositions have also been determined.
Anisotropie Properties of Superconducting Single-Crystal (La1-xSrx)2CuO4
Authors: Hidaka Yoshikazu , Enomoto Youichi , Suzuki Minoru , Oda Migaku , Murakami Toshiaki
Published: November 2005

Anisotropic electrical properties of single crystals of the recently-discovered superconducting La-Sr-Cu-O system are described. The resistivity along the c-axis of the K2NiF4 structure is 1.9×10-2 ohm-cm, 20 times larger than that along the a-axis. The second critical magnetic field H
c2 along the a-axis is estimated to be larger than that along the c-axis by a factor of more than 5. The results strongly indicate that the oxide system can be regarded as a pseudo-two-dimensional superconductor.
In Situ Deoxidation of GaAs Substrates by HCl Gas
Authors: Massies Jean , Contour Jean-Pierre
Published: November 2005

In situ chemical etching by HCl gas of GaAs {001} substrates for molecular beam epitaxy application has been studied by X-ray photoelectron spectroscopy. Oxide free surfaces are obtained for low HCl pressures (P∼0.1 Torr) at room temperature. The residual adsorbed chlorine is completely removed by annealing at 450°C under vacuum and a reconstruction characteristic of a clean GaAs surface is then observed by low energy electron diffraction. Preliminary results of GaAs molecular beam epitaxial growth on such HCl-treated surfaces indicate a significant decrease of the morphological defects concentration in the layers.
Preparation and Property of La1.85Sr0.15CuO4 Single Crystal
Authors: Iwazumi Toshiaki , Yoshizaki Ryozo , Sawada Hideaki , Uwe Hiromoto , Sakudo Tunetaro , Matsuura Etsuyuki
Published: November 2005

A single crystal of the high T
c superconductor, La1.85Sr0.15CuO4, was prepared using the solid phase reaction, and the magnetization was investigated. In the superconducting state, strong anisotropic diamagnetism was observed for external magnetic field parallel and perpendicular to the c-axis. This result supports the two-dimensional character of Sr-La-Cu-O system.
Effect of Lanthanide Ion Substitutions for Lanthanum Sites on Superconductivity of (La1-xSrx)2CuO4-δ
Authors: Kishio Kohji , Kitazawa Koichi , Hasegawa Tetsuya , Aoki Makoto , Fueki Kazuo , Uchida Shin-ichi , Tanaka Shoji
Published: November 2005

By substituting various lanthanide ions for La sites up to 90% level, the effect of foreign magnetic ions on the superconductivity of (La1-x
Sr
x
)2CuO4-δ was examined. None of the 4f transition metal ions at 5% substitution level substantially destroyed the superconductivity, while a strong correlation was observed between the total spin of the 4f magnetic ions and the superconducting critical temperature, suggesting the exchange interaction between the conduction electrons and the 4f shell spins.
Temperature Dependence of Infrared Spectra of (La1-xBax)2CuO4-y
Authors: Ohbayashi Kohji , Ogita Norio , Udagawa Masayuki , Aoki Yuji , Maeno Yoshiteru , Fujita Toshizo
Published: November 2005

Temperature dependence of the infrared spectra of (La1-x
Ba
x
)2CuO4-y
(x=0, 0.02, 0.06, 0.10, 0.20) have been measured in the energy region between 400 and 800 cm-1. For x=0 and 0.02, the crystal structure is orthorhombic at room temperature and becomes tetragonal (T

t
phase) at elevated temperature. For x=0.06, 0.10 and 0.20, the crystal structure is tetragonal (T

x
phase). It has been found that the infrared spectra are different for the T

t
phase and the T

x
phase. From the difference of the infrared spectra and the similarity of the X-ray diffraction patterns, the T

t
phase is concluded to be of the K2NiF4 type and the T

x
phase is expected to be of the Nd2CuO4 type.
Structure and Superconductivity in a New Type of Oxygen Deficient Perovskites Y1Ba2Cu3O7
Authors: Hirabayashi Masayuki , Ihara Hideo , Terada Norio , Senzaki Kiyoshi , Hayashi Kunihiko , Waki Shinya , Murata Keizo , Tokumoto Madoka , Kimura Youichi
Published: November 2005

We have succeeded in obtaining a new single phase of oxygen-deficient perovskite ABO3-x
type. The sample of nominal composition Y1/3Ba2/3CuO3-x
exhibits the superconductivity at 125 K and a zero resistance state at 83 K. X-ray diffraction patterns of this compound show the oxygen deficient tetragonal perovskite to be of a nearly single phase of the formula Y1Ba2Cu3O7. This structure is a layered perovkite which is associated with the high-T
c superconductivity.
High-Tc Superconductivity in New Oxide Systems II
Authors: Hosoya Syoichi , Shamoto Shin-ichi , Onoda Masashige , Sato Masatoshi
Published: November 2005

Superconducting transitions observed by resistivity measurements for several new systems of L-M-Cu-O, where L=Tm, Er, Ho, Dy, Eu and Lu, and M=Ba are reported. Although all of the elements L except for Lu have magnetic moment, the transition temperature T
c is as high as almost 100 K. This is suggestive that the M-Cu-O or Cu-O system has an essential role for the high-T
c superconductivity.
Upper Critical Field of SrxLa2-xCuO4-y
Authors: Ihara Hideo , Hirabayashi Masayuki , Terada Norio , Bushida Kenichi , Akimoto Makio , Kobayashi Norio , Toyota Naoki , Muto Yoshio
Published: November 2005

The electrical resistance of Sr
x
La2-x
CuO4-y
has been measured under magnetic fields up to 21.1 T between 4.2 and 50 K. The onset of T
c was 41.0 K in H=0 and 33.0 K in H=21.1 T. H
2c(0) is estimated to be 76 T according to the dirty limit theory of type II superconductivity. The H
c2 value is near the Pauli limit value and is higher than that (60 T) of PbMo6S8. Sr
x
La2-x
CuO4-y
is one of the highest-H
c2 superconductor as well as a high-T
c one.
Electronic Structures and Superconducting Mechanism of Ba2Y1Cu3O7
Authors: Ihara Hideo , Hirabayashi Masayuki , Terada Norio , Kimura Yoichi , Senzaki Kiyoshi , Akimoto Makio , Bushida Kenichi , Kawashima Fumiyuki , Uzuka Ryuichi
Published: November 2005

The high-T
c superconductor Ba2Y1Cu3O7 with the oxygen-deficient perovskite structure was prepared almost in a single-phase with T
co of 125 K, T
c of 95 and T
ce of 93 K. The XPS valence-band spectrum showed a relative large N(E
F), density of states at the Fermi level. The XPS Cu 2p3/2 peak is divided into three peaks which are attributed to monovalent, bivalent and trivalent Cu ions with the concentration ratio of 1:2:1. These results and the peculiar lattice structure lead to the T
c enhancement mechanism from the plasmon or exciton origin due to the Cu d-hole creation and annihilation resonating with vibration modes of the CuO5 and CuO4 clusters. The T
c value was calculated.
Pressure Dependence of Superconductivity of the 90 K-Superconductors, Ba-Y-Cu-O
Authors: Murata Keizo , Ihara Hideo , Tokumoto Madoka , Hirabayashi Masayuki , Terada Norio , Senzaki Kiyoshi , Kimura Yoichi
Published: November 2005

Pressure dependences of superconductivity as well as that of normal state conductivity of the 90 K-superconductors, Ba
x
Y1-x
CuO3-y
(x=0.6, y∼1) in ceramic form is reported. Change of the transition temperature with pressure is small and slightly negative as -0.25 K/kbar or less, contrary to the 40 K-superconductors, while the normal state conductivity at 300 K increases with pressure by 1.27%/kbar.
Upper Critical Fields of the 40 K- and 90 K- Superconductors, Sr-La-Cu-O and Ba-Y-Cu-O
Authors: Murata Keizo , Ihara Hideo , Tokumoto Madoka , Hirabayashi Masayuki , Terada Norio , Senzaki Kiyoshi , Kimura Yoichi
Published: November 2005

Superconducting transitions and the upper critical fields, H
c2 of 40 K- and 90 K-superconductors, Sr
x
La2-x
CuO4-y
(x=0.6, y∼1) and Ba
x
Y1-x
CuO3-y
(x=0.6) in ceramic forms, were studied by resistivity measurement. The onset of superconductivity of the former (latter) was 43 K(93 K), and the midpoint was 35 K(89 K). The slopes, -dH
c2/dT were 1.48 T/K at the onst, and 0.92 T/K(1.79 T/K) at the midpoints. The Ginzburg-Landau coherence length, ζGL, at 0 K is estimted to be 23 A (onset points) and 32 A (midpoints) for the former, and 14 A (midpoints) for the latter. The value of 14 A is close to lattice constant, 12 A. H
c2(T=0 K) is discussed in relation to the small value of ζGL. Two-step transition was observed.
AC Susceptibility of Superconducting La-Sr-Cu-O System
Authors: Oda Yasukage , Nakada Ichiroh , Kohara Takao , Fujita Hiroshi , Kaneko Tetuyuki , Toyoda Haruhisa , Sakagami Eiji , Asayama Kunisuke
Published: November 2005

The complex susceptibility χ'-iχ'' of the superconducting La1.8-Sr0.2-Cu1-O4 was measured. The complete Meissner effect of the whole volume was observed below 20 K, though the transition temperature of the resistance was 36 K (at the midpoint). Both χ' and χ'' are found to be very sensitive to the magnitude of the a.c. magnetic field. The measurements were made on several specimens prepared in different conditions. From these measurements it was concluded that the boundary and the surface of grains play an important role in the superconductivity in this system.
Raman Study of High Tc Superconductors (La1-xSrx)2CuO4
Authors: Sugai Shunji , Sato Masatoshi , Hosoya Shoichi
Published: November 2005

Lattice vibrations in high T
c superconductors (La1-x
Sr
x
)2CuO4 are investigated by Raman scattering using single crystals. In La2CuO4 the 664 and 153 cm-1 peaks are resonantly enhanced at low temperatures. The enhancement is caused by the electronic transition spanning the quasi-square Fermi surface to the nesting directions. The 664 cm-1 mode is assigned to the planar breathing mode which strongly interacts with electrons at the Fermi level and the 796 cm-1 mode in (La0.925Sr0.075)2CuO4 is tentatively assigned to the axial breathing mode.
Epitaxial NbN/MgO/Si(GaAs,InP) Tunneling MIS Schottky Diode Fabricated by Interrupted-Sputtering Method
Authors: Kobayashi Takeshi , Tonouchi Masayoshi , Sakaguchi Yoshiyuki , Yamashita Tsutomu
Published: November 2005

Epitaxial NbN/MgO/Si(GaAs or InP) MIS structures were prepared by the sputtering technique. Introduction of the interrupted-sputtering method facilitated the growth of epitaxial NbN/MgO/Si heterostructures for almost one monolayer MgO layer. GaAs and InP substrates, however, never fostered epitaxial overgrowth of NbN until the MgO layer became thicker than 3 nm. Diodes fabricated from these wafers exhibited good tunneling MIS Schottky characteristics.
Pressure Effect on the Lattice Constant and Compressibility of a Superconductor (La0.9Sr0.1)2CuO4-y
Authors: Takahashi Hiroki , Murayama Chizuko , Yomo Shusuke , Mōri Nobuo , Kishio Kohji , Kitazawa Koichi , Fueki Kazuo
Published: November 2005

(La0.9Sr0.1)2CuO4-y
with K2NiF4-type layered structure shows a superconducting transition at 37 K. The pressure effect on the lattice constants along a- and c-axis was measured at room temperature up to 70 kbar. Compression coefficients of a- and c-axis are found to be almost of the same value of (2.5±0.4)×10-4kbar.-1
Superconductivity Transition in High-Tc Y-Ba-Cu-O Mixed-Phase System
Authors: Takita Kôki , Ippōshi Takashi , Uchino Takashi , Gochou Tetsuo , Masuda Kohzoh
Published: November 2005

We report the results of temperature dependence of the resistivity in Y-Ba-Cu-O mixed-phase system for several samples with different composition and sintered at different temperatures. Two types of compounds were investigated, which have the nominal composition (Y1-x
Ba
x
)2CuO4-δ(Type I) or Y1-y
Ba
y
CuO3-δ(Type II) with x=0.45 or 0.40, y=0.6 and δ undetermined. Superconductivity transition was observed in all the samples around 90 K, although it was incomplete at 78 K in some Type I-samples. In a Type II-sample with nominal composition Y0.4Ba0.6CuO3-δ, in addition to this transition which is completed at 87 K, sharp reduction of resistivity was observed around 150 K, suggesting a possible existence of a new phase with higher T
c in this system.
Deposition of SrxLa2-xCuO4-y Thin Films by Sputtering
Authors: Terada Norio , Ihara Hideo , Hirabayashi Masayuki , Senzaki Kiyoshi , Kimura Youichi , Murata Keizo , Tokumoto Madoka
Published: November 2005

Superconducting Sr
x
La2-x
CuO4-y
thin films were deposited on heated substrate by sputtering. Crystalline films were obtained by setting substrate temperature T
c above 450°C. In this process, there were 2 peculiar features as follows; (1) deviation of film composition from that of target (such as Cu deficiency and excess of oxygen) and (2) change of target surface with an increase of the number of the deposition. Films of almost single phase of K2NiF4 structure were obtained by adjusting film composition and T
s above 550°C. Tc onset up to 42 K was obtained for as-deposited films, though its reproducibility was limited by the change of target.