bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Expansion Coefficients of High-Tc Superconductors
Authors: Hashimoto Takuya , Fueki Kazuo , Kishi Akira , Azumi Tadahiko , Koinuma Hideomi
Published: February 2005

High-T
c superconducting oxides were confirmed to have much higher thermal expansion coefficients than various substrate materials. The difference in thermal expansion between superconductor and substrate materials corresponded well with the crack size formed in the film. Thermal expansion of Ba2YCu3O7-δ abruptly changes at about 350°C and 650°C, which reflects the change of oxygen concentration and the phase transition, respectively. The expansion pattern varied considerably by the substitution of yttrium by ytterbium, suggesting a difference in the kinetics of oxygen uptake and secession between the two superconductors.
Selective Growth of Polycrystalline Silicon by Laser-Induced Cryogenic CVD
Authors: Tanaka Takeshi , Deguchi Koji , Miyazaki Seiichi , Hirose Masataka
Published: February 2005

Spatially selective cryogenic chemical vapor deposition of polycrystalline silicon has been achieved in the area irradiated with ArF excimer laser beam. Photodissociation reactions of adsorbed Si2H6 on a cooled substrate and subsequent excitation of the polymerized matrix results in polycrystalline silicon formation.
Microcharacterization and Novel Device Applications of Semiconductor-Metal Eutectic Composites
Authors: Ditchek B. M. , Yacobi B. G.
Published: February 2005

Semiconductor-metal eutectic composites, such as Si-TaSi2, which consist of an aligned array of metallic rods permeating a semiconductor matrix, are electronic materials that offer a variety of novel device applications. Advantages of utilizing the volumetric nature of these devices in high voltage, high power transistors and high quantum efficiency photodiodes are demonstrated.
Photochemical Vapor Deposition of Si/Si1-xGex Strained Layer Superlattices at 250°C
Authors: Yamada Akira , Jia Ying , Konagai Makoto , Takahashi Kiyoshi
Published: February 2005

Si/Si1-x
Ge
x
strained layer superlattices have been successfully grown by mercury-sensitized photochemical vapor deposition at a very low temperature of 250°C. Lattice strain and lattice dynamics of the superlattices were examined by Raman scattering and X-ray diffraction measurements and it was found that the in-plane lattice constant of the superlattices was commensurate with the lattice constant of a silicon substrate. Direct observation of superlattice structures was carried out by transmission electron microscopy measurement.
Correlation between Photoluminescence and Surface-State Density on GaAs Surfaces Subjected to Various Surface Treatments
Authors: Hasegawa Hideki , Saitoh Toshiya , Konishi Seiichi , Ishii Hirotatsu , Ohno Hideo
Published: February 2005

Relationship between band edge photoluminescence (PL) and surface states is rigorously analyzed on computer, using the disorder-induced gap state (DIGS) model, and is compared with experiments on GaAs surfaces subjected to various treatments. It is shown that PL intensity is directly correlated with the effective surface recombination velocity, but is not necessarily directly correlated with the surface-state density (N
ss) itself. PL enhancement by photochemical oxidation and by Na2S deposition is proposed to be due to a fixed negative charge, whereas photochemical treatment in HCl leads to significant reduction in N
ss.
Self-Limited Growth in InP Epitaxy by Alternate Gas Supply
Authors: Sakuma Yoshiki , Kodama Kunihiko , Ozeki Masashi
Published: February 2005

Self-limited growth in InP epitaxy was investigated by alternately exposing the substrate to (CH3)3In(TMIn) and PH3. The growth proceeded in the atomic layer epitaxy (ALE) mode at a low temperature of 350°C. The growth rate saturated at about 0.5 monolayers (ML)/cycle, independent of the mole fractions and the exposure times of TMIn and PH3. The surface morphology and thickness uniformity were greatly improved by ALE, indicating the superiority of ALE in the fabrication of ultrathin layers and abrupt interfaces.
High-Temperature Resistivity Measurements of YBa2Cu3O7-x
Authors: Yamaguchi Shu , Terabe Kazuya , Imai Atsuo , Iguchi Yoshiaki
Published: February 2005

The high-temperature resistivity of YBa2Cu3O7-x
was measured by a DC four-probe technique at partial oxygen pressures (p
O2
) of 1.0, 0.2, 0.053, 0.013 and 0.006 atm. The determined resistivity values increased with increasing temperature and decreasing p
O2
in accordance with the increase of the oxygen deficiency. The discontinuous change of the slopes d(log
ρ)/d(1/T) was observed at temperatures 20–95°C lower than those reported for the orthorhombic-to-tetragonal transition.
Ultraclean Technique for Silicon Wafer Surfaces with HNO3-HF Systems
Authors: Takizawa Ritsuo , Nakanishi Toshiro , Honda Kouichirou , Ohsawa Akira
Published: February 2005

We have developed a wafer cleaning technique called the slight etch (SE) using an HNO3 and trace HF mixture. A 30 nm surface removal by the SE reduces the surface Fe concentration by one tenth, compared to conventional RCA and all measured elements below a concentration of 1010 cm-2, without roughness degradation. The ultraclean surface results in a significant improvement in the C-t retention time and defect density of SiO2. Since the etch selectivity of silicon for the oxide is more than 10, this cleaning is also ideal for wafers with patterned oxides.
Early Stage of Silicon Oxidation Studied by in situ X-Ray Photoelectron Spectroscopy
Authors: Takakura Masaru , Ogura Tsuyoshi , Hayashi Tsukasa , Hirose Masataka
Published: February 2005

In this study, a clean silicon surface is oxidized in a UHV chamber and the surface suboxide compositions are analyzed using in situ X-ray photoelectron spectroscopy. It is found that the predominant suboxides are Si2O3 and SiO irrespective of crystallographic orientations in the early stages of oxidation. This is interpreted in terms of a significant number of atomic steps existing on the clean Si surface. The observed chemical shift of O(1s) core level signal is explained by the partial charge transfer from the first and second nearest-neighbor silicon atoms to oxygen.
Novel High-Performance N-AlGaAs/InGaAs/N-AlGaAs Pseudomorphic Double-Heterojunction Modulation-Doped FETs
Authors: Nishii Katsunori , Matsuno Toshinobu , Ishikawa Osamu , Yagita Hideki , Inoue Kaoru
Published: February 2005

High-current driving pseudomorphic N-AlGaAs/InGaAs/N-AlGaAs double-heterojunction modulation-doped FETs (DH MODFETs) with high K-values have been successfully fabricated using an improved layer structure. The structure has been made by simply incorporating a thin N-AlGaAs layer at the heterointerface between the InGaAs and GaAs buffer layers of a conventional GaAs/InGaAs/N-AlGaAs pseudomorphic MODFET structure. A very high transconductance of 835 mS/mm and a K-value of 698 mA/(V2·mm) were achieved at room temperature for a 0.35 µm-gate FET. Microwave results showed an f

T
of 64 GHz.
Superconducting Lines Fabricated from Epitaxial Y-Ba-Cu-O Films
Authors: Tsuge Hisanao , Matsui Shinji , Matsukura Noritsugu , Kojima Yoshikatsu , Wada Yoshifusa
Published: February 2005

High-T
c superconducting lines as narrow as 0.8 µm, have been fabricated from Y-Ba-Cu-O films. The films were epitaxially grown on MgO (100) substrates heated at 740°C, by rf magnetron sputtering. The lines were patterned using focused ion-beam lithography and ion-beam etching. The resulting superconducting lines, 1.3 µm wide and 2 mm long, showed a zero resistance temperature of 81 K and a critical current density of 1.5×104 A/cm2 at 77.3 K with smooth surfaces.
Saturation of Optical Degradation in a-Si:H Films with Different Morphologies
Authors: Ohagi Hideki , Nakata Jun-ichi , Miyanishi Atsushi , Imao Shozo , Jeong ManU , Shirafuji Junji , Fujibayashi Keiji , Inuishi Yoshio
Published: February 2005

The saturation effect of the optical degradation in hydrogenated amorphous silicon films (a-Si:H) deposited at various temperatures T
s has been studied by means of photoconductivity measurements. It was confirmed that the saturation is mainly related to the simultaneous annealing at a higher light-soaking temperature T
1 (≧20°C) as well as the depletion of the weak Si-Si bonds at lower T1 (≦0°C). The weak bond density (1016∼1018/cm3) estimated from the low-temperature saturation effect decreases with increasing T
s corresponding to the growth of Si clusters.
GaAs and In0.53Ga0.47As MIS Structures Having an Ultrathin Pseudomorphic Interface Control Layer of Si Prepared by MBE
Authors: Hasegawa Hideki , Akazawa Masamichi , Matsuzaki Ken-ichirou , Ishii Hirotatsu , Ohno Hideo
Published: February 2005

A novel compound semiconductor MIS structure using an ultra-thin partially oxidized MBE Si film as a pseudomorphic interface control layer (ICL) is reported for GaAs and InGaAs. As an outer insulator layer, a silicon dioxide or silicon nitride film is deposited in-situ by a low-temperature photo-CVD process using an ArF excimer laser. While the GaAs MIS structure exhibited strong Fermi level pinning, the InGaAs MIS structure showed completely “unpinned” behavior with a very small hysteresis after annealing. The difference is qualitatively explained by a band line-up of the constituent materials.
Silicon Dioxide Thin Films Prepared by Thermal Decomposition of Silicon Tetraacetate
Authors: Maruyama Toshiro , Aburai Koji
Published: February 2005

Silicon dioxide thin films were prepared by thermal decomposition of silicon tetraacetate. Acetone solutions of the precursor material were applied to a glass substrate, then heated at 300–500°C for 20 min in an air atmosphere. This method was superior to the sol-gel method in the stability of the raw solution and in the low heat-treatment temperature.
Identification of the Superconducting Phase in the Nd-Ce-Sr-Cu-O System
Authors: Takayama-Muromachi Eiji , Matsui Yoshio , Uchida Yoshishige , Izumi Fujio , Onoda Mitsuko , Kato Katsuo
Published: February 2005

Phase search experiments were performed to identify the superconducting phase in the Nd-Ce-Sr-Cu-O system. A single phase superconductor was obtained form the nominal composition (Nd0.66Ce0.135Sr0.205)2CuO
y
. It has a tetragonal cell with a=3.8558(1) and c=12.487(1) Å. From powder X-ray diffraction and electron microscopic observations, it was confirmed that the metal positions in this phase are identical to those in the K2NiF4 structure but with cationic order of Nd(Ce) and Sr. Three structure models including oxygen positions are proposed and discussed. Although we could not be absolutely conclusive, the structure which consists of alternative stacking of K2NiF4- and Nd2CuO4-type slabs seems to be most likely.
Evaluation of Oxygen Nonstoichiometry in High-Tc Superconductors
Authors: Parashar D. C. , Rai J. , Gupta Prabhat K. , Sharma R. C. , Lal K.
Published: February 2005

A sensitive method has been developed for the determination of oxygen nonstoichiometry in YBa2Cu3O6.5+x
superconductors to critically examine the orthorhombic phase containing low-T
c or high-T
c superconducting material. Oxygen is evolved on reacting a few mg of powdered sample with dilute nitric acid in helium atmosphere in a closed circuit in a specially designed glass sampler and analyzed by gas chromatographic techniques using a thermal conductivity detector. In the samples analyzed, the x value varies from 0.47 to 0 indicating the change from the high-T
c to the low-T
c orthorhombic phase. The accuracy of the measurement is better than 3%.
Preparation of Tl2Ba2Ca2Cu3Oy Thick Films from Ba-Ca-Cu-O Films
Authors: Sugise Ryoji , Hirabayashi Masayuki , Terada Norio , Jo Masatoshi , Kawashima Fumiyuki , Ihara Hideo
Published: February 2005

The preparation of Tl2Ba2Ca2Cu3O
y
thick films from spin-coated Ba-Ca-Cu-O films in the presence of thallium oxide vapor was studied. The starting Ba-Ca-Cu-O films were prepared by pyrolysis of organic acid salts. The preparation of the Tl2Ba2Ca2Cu3O
y
thick films was carried out for cases of the presence of Tl2O3 powder and of mixed powders of Tl2O3, BaO2, CaO2 and CuO. A Tl2Ba2Ca2Cu3O
y
film with T
c onset=126 K, T
c mid=115 K and T
c zero=108 K was obtained. Control of the thallium content of the films was more easily accomplished when using the mixed powders of Tl2O3, BaO2, CaO2 and CuO than when using Tl2O3 powder alone.
Time-Dependent Photoconductivity in CdIn2S4
Authors: Takizawa Takeo , Takeuchi Hidemi , Kanbara Kohji
Published: February 2005

To investigate the photoresponse due to defect levels in CdIn2S4, the measurement of photocurrent was carried out as a function of light intensity and time. It was found that the photocurrent showed a strong dependence both on time and light intensity, indicating the existence of photoactive levels at the top of the valence bands.
Effect of S, Se and Te Addition on the Superconductive Properties of Ba2YCu3O7-y
Authors: Kambe Shiro , Kawai Maki
Published: February 2005

An addition of a small amount of sulfur or selenium in Ba2YCu3O7-y
lead to the formation of the phase whose c-axis was 11.62 Å, which is much shorter than that observed in sulfur-free Ba2YCu3O7-y
. This phase increased the T
c(zero) value, accompanied by the sharpening of the transition width within 1 K.
Bubble-Free Silicon Wafer Bonding in a Non-Cleanroom Environment
Authors: Stengl R. , Ahn K.-Y. , Gösele U.
Published: February 2005

Bubble-free bonding of 4-inch silicon wafers on either silicon or quartz wafers is achieved outside a cleanroom. Two wafers are stacked horizontally in a rack with the two mirror-polished surfaces facing each other. In order to avoid wafer contact during hydrophilization, cleaning, and drying, the wafers are separated in the rack by teflon spacers introduced at the wafer edges. After drying the wafers by a spin dryer, the spacers are removed and bonding occurs. Using this procedure we are also able to monitor the bonding process between quartz and silicon wafers at different temperatures. We find that the initial wafer bonding process at room temperature stops operating at temperatures above 200°C.
A Model to Explain the Effective Passivation of the GaAs Surface by (NH4)2Sx Treatment
Authors: Nannichi Yasuo , Fan Jia-Fa , Oigawa Haruhiro , Koma Atsushi
Published: February 2005

A model is presented to explain why and how the GaAs surface is passivated and stabilized by (NH4)2S
x
treatment. Natural oxide, together with a thin layer of GaAs, is removed and the fresh GaAs surface is covered with a monoatomic layer of sulfur which has no dangling bonds. On this surface, foreign atoms are prohibited from chemical adsorption. Thus, the As and Ga vacancies which are, according to Spicer's “unified defect model”, the cause of the interface trap level are not introduced. The present model of the passivation successfully interprets different experimental data on the surfaces treated with solutions of sodium sulfide and ammonium sulfide with and without excess sulfur.
Interpretation of Magneto-Optical and Reflectivity Spectra in Compositionally Modulated Multilayered Fe/Cu Films
Authors: Sato Katsuaki , Kida Hiroyuki , Katayama Toshikazu
Published: February 2005

Anomalous behavior of magneto-optical Kerr spectra in compositionally modulated multilayered Fe/Cu films is analyzed using virtual optical constant calculations. Calculated spectra are in good agreement with experimental results published previously. The enhancement of the Kerr rotation in Fe/Cu films around the absorption edge of Cu is interpreted in terms of the existence of hybrid plasma in these materials.
Metastable Behavior of the DX Center in Si-Doped GaAs
Authors: Fujisawa Toshimasa , Krištofik Jozef , Yoshino Junji , Kukimoto Hiroshi
Published: February 2005

The DX center in Si-doped GaAs was found through a high-pressure technique to show metastable behavior. This center is located above the conduction band at atmospheric pressure and in the band gap under high hydrostatic pressure. We found that the emission rate of the metastable DX center in GaAs is extremely small at low temperatures. These results support the large lattice relaxation model of the DX center.
Heterointerface Field Effect Transistor with 200 A-Long Gate
Authors: Ishibashi Akira , Funato Kenji , Mori Yoshifumi
Published: February 2005

AlGaAs/GaAs heterointerface field effect transistor (FET) with a gate-length comparable with electron de Broglie wavelength has been fabricated for the first time by the electron-beam-induced resist process, which demonstrates the possibility of `universal' FET. The transconductance maximum is found to be at the gate length three times as large as the channel depth.
Liner Implosion Experiments with a Pipe Foam Target on Pulsed Power Transformer
Authors: Yugami Noboru , Umehara Satoshi , Zakou Akira , Miyamoto Shuji
Published: February 2005

Liner implosions using a newly designed pulsed power transformer have been studied. The transformer generates a 1 MA current pulse with a 250-ns rise time. The mass and initial radius of the liner has been optimized. An aluminum L-shell radiation with a peak power of 20 GW in a 40-ns pulse width was measured. This radiation can be used as the pump radiation of an Al/F X-ray laser scheme. In experiments with pipe-foam targets at the axis of cylindrical symmetry, the linearity of the aluminum plasma implosion was improved. The radiation from the inside of the target was observed by a time-integrated X-ray pinhole camera.
Dependence of Absorption Spectra and Solubility of Poly(3-alkylthiophene) on Molecular Structure of Solvent
Authors: Yoshino Katsumi , Love Peter , Onoda Mitsuyoshi , Sugimoto Ryu-ichi
Published: February 2005

Solvatochromic shifts of spectra of solutions of poly(3-hexylthiophene) and poly(3-docosylthiophene) have been analyzed in terms of Taft linear solvation energy relationships. Color changes of solutions of the former at 25°C are primarily due to changes in normal solute-solvent interactions. On the other hand, color changes of solutions of poly(3-docosylthiophene) appear to be due to configurational changes of the polymer chain. Solubility of the polymer is affected by solvation of the alkyl groups, electron donating or Lewis basicity properties of the solvent, polarity, and molecular volume of solvent molecules.
Interface State Generation Mechanism in MOSFET's during Substrate Hot-Electron Injection
Authors: Yasuda Naoki , Nakamura Hiroshi , Taniguchi Kenji , Hamaguchi Chihiro , Kakumu Masakazu
Published: February 2005

Substrate hot-electron injection reveals that there exist two modes in interface state generation. Mode A, generated at the low gate oxide field (<3.5 MV/cm), is due to the head-on collision of hot electrons. The critical energy for mode A generation is 3.5 eV. The physical mechanism of mode B, generated at the high oxide field (>3.5 MV/cm), is attributed to hole trapping.
Relation between Ge(2) Center and 11.9 mT Hyperfine Structure of ESR Spectra in Ge-Doped Silica Fibers
Authors: Nagasawa Kaya , Fujii Takashi , Ohki Yoshimichi , Hama Yoshimasa
Published: February 2005

The nature of the Ge(2) center and ESR hyperfine structure with a splitting of 11.9 mT, observed in germanium-doped silica fibers, is studied experimentally. It is considered that the Ge(2) center has a structure of –O–Ġe=O and that the 11.9 mT hyperfine structure is due to a structure of H–Ġe=O. The former is a precursor of the latter, i.e., the latter is yielded through chemical reaction of the former with hydrogen molecules.
A New Transverse-Mode Stabilized InGaAlP Visible Light Laser Diode Using p-p Isotype Heterobarrier Blocking
Authors: Itaya Kazuhiko , Ishikawa Masayuki , Watanabe Yukio , Nitta Koichi , Hatakoshi Gen-ichi , Uematsu Yutaka
Published: February 2005

A new waveguide structure for the InGaAlP transverse-mode stabilized visible laser diode has been successfully fabricated by a two-step MOCVD. A unique current confinement mechanism, using the voltage-drop difference between the isotype heterojunctions of p-GaAs/p-InGaAlP and p-GaAs/p-InGaP/p-InGaAlP was employed in this laser. A low cw threshold current of 40 mA, and a stable fundamental transverse-mode oscillation up to 5 mW were achieved. The oscillation wavelength was 668 nm. The lasers have operated over 1000 hours at 40°C, 3 mW.
CW Operation and Extremely Low Capacitance of TJ-BH MQW Laser Diodes Fabricated by Entire MOVPE
Authors: Shimoyama Kenji , Katoh Masanori , Suzuki Yoshihiro , Satoh Takuzoh , Inoue Yuichi , Nagao Satoru , Gotoh Hideki
Published: February 2005

Transverse junction buried heterostructure laser diodes using an MQW active layer have been successfully fabricated by an entire MOVPE. The employed MQW has five undoped GaAs wells, every thickness being 110 Å. While the barriers were undoped Al0.3Ga0.7As, each of thickness 190 Å. Further, several processes for fabricating the devices were improved. These TJ-BH MQW laser diodes displayed CW operation at room temperature with a threshold current of 9.5 mA and high uniformity of laser characteristics. Furthermore, they also exhibited extremely low capacitance, i.e., less than 0.05 pF at zero bias voltage.
Use of Ethyliodide in Preparation of Low-Resistivity n-Type ZnSe by Metalorganic Vapor Phase Epitaxy
Authors: Shibata Noriyoshi , Ohki Akira , Zembutsu Sakae
Published: February 2005

Ethyliodide is shown to be useful as a dopant for growing high-quality n-type ZnSe layers by metalorganic vapor phase epitaxy. Low-resistivity ZnSe single-crystal layers with ρ<0.002 Ω·cm and n>1019 cm-3 have been grown on (100) GaAs substrate. The grown layers, with an appropriate doping level (n∼1018 cm-3), show a strong blue near-band-edge photoluminescence at room temperature. The emission intensity from the layer is several hundred times stronger than that from the undoped ZnSe.
A Hall Element Yielding a Precise Field-Linear Hall Voltage up to a High-Field Region
Authors: Oguro Isamu , Sasaki Yoshisato , Itoh Kazuo , Tanuma Sei-ichi
Published: February 2005

A Hall element yielding a precise field-linear output up to 8 tesla has been developed using heavily As-ion implanted Si. The deviation from the linear relationship was less than 0.1% from 1.5 to 8 tesla at 4.2 K. The material design was so made that the conducting surface layer was thinner than 1 micron and the mobility and field product were smaller than 0.04 at 8 tesla.
Magneto-Inertia Confinement Approach (MICA) to Fusion in Dynamic Z-Pinch Formed from a Frozen Deuterium-Tritium Tube
Authors: Ikuta Kazunari
Published: February 2005

This paper reconsiders the magneto-inertia confinement approach to fusion in dynamic z-pinch with a new method of generating a hot plasma using a frozen deuterium-tritium (D-T) tube as an initial condition. If modern pulsed power technology can induce the high current of the order of 10 MA along the tube, the dense z-pinch plasma formed from the electro-magnetical implosion of thin tubular D-T ice with a radius of about 1 mm can satisfy the Lawson criterion for its 1 cm length.
Low-Energy Electron Energy Loss Spectroscopy on YBa2Cu3O7-y
Authors: Ando Atsushi , Saiki Koichiro , Ueno Keiji , Koma Atsushi
Published: February 2005

Electronic structures of the high-T
c superconductor YBa2Cu3O7-y
have been investigated by low-energy electron energy loss spectroscopy. Loss peaks due to interband transitions, plasmon excitation and core electron excitations have been observed. It has been found from the observed spectra that a high-density-of-state portion of the first conduction band is located at 2–4.7 eV above the Fermi level and that of the higher conduction band is located at around 10 eV above the first conduction band.
Sound Velocity and Attenuation in YBa2Cu3Oy
Authors: Suzuki Masaru , Okuda Yuichi , Iwasa Izumi , Ikushima Akira J. , Takabatake Toshiro , Nakazawa Yasuhiro , Ishikawa Masayasu
Published: February 2005

The sound velocity and attenuation in a sintered single phase YBa2Cu3O6.9 (denoted as orthor-I), which has a superconducting transition temperature, T
c of about 90 K, were measured and compared with those of the corresponding semiconductor YBa2Cu3O6.2 (denoted as tetra-II). The sound velocity in ortho-I has an additional increase below T
c, in contrast to that of tetra-II. This anomaly may imply a strong coupling between the lattice and electrons in this system. This cannot be explained by a simple thermodynamic analysis. The sound attenuation does not show any anomaly around T
c.
Preparation and Properties of Ba2YCu3O7-y Single Crystals Grown Using an Indium Oxide Flux
Authors: Ono Akira , Nozaki Hiroshi , Ishizawa Yoshio
Published: February 2005

Single crystals of Ba2YCu3O7-y
were prepared using an In2O3 flux. Considerable variations in 7-y exist among crystals from different batches, although the same annealing conditions were applied. Tetragonal phases were found to be quenchable at 630°C in air for certain single crystals, although tetragonal phases of highly aluminous sintered specimens were unquenchable below 700°C. These characteristics are explained by the variation of oxygen mobility among the single crystals which were controlled by aluminium impurities and certain defect structures.
Superconducting Properties in a Bi-Sr-Ca-Cu-O System
Authors: Adachi Seiji , Inoue Osamu , Kawashima Syunichiro
Published: February 2005

Superconducting properties in a Bi-Sr-Ca-Cu-O system have been studied. Two types of superconductors were observed: one has a transition temperature of 80 K, and the other has two transitions at 80 K and 110 K. XRD measurements suggest that the latter superconductor has at least two phases. The phase which seemed to be responsible for the superconductivity above 80 K was investigated by means of XRD, SEM and XMA.
Superconductivity and Substrate Interaction of Screen-Printed Bi-Sr-Ca-Cu-O Films
Authors: Hashimoto Takuya , Kosaka Tamio , Yoshida Yasuhiko , Fueki Kazuo , Koinuma Hideomi
Published: February 2005

Thick films of the Bi-Sr-Ca-Cu-O system have been prepared by the screen-printing and sintering method to show moderately high-T
c superconductivity. Electric properties and crystal structures of the films were strongly dependent on both the sintering temperature and substrate materials. Highly oriented films were obtained by sintering the films printed on YSZ and SrTiO3 substrates at 850°C. A film prepared on YSZ substrate showed superconductivity with the onset and zero resistivity temperature of 95 K and 68 K, respectively.
A Universal MO-VB Approach to Electron and Spin Correlations in Copper-Oxide Clusters: Néel Order, Spin Fluctuation and High-Tc Superconductivity
Authors: Yamaguchi Kizashi , Fueno Takayuki
Published: February 2005

The Hubbard model for the Cu4O4 cluster was solved analytically in order to clarify the interrelationships between molecular orbital (MO)- and valence-bond (VB)-type solutions. Both VB and MO models were complementarily applied to investigations of Néel order, spin fluctuation and magnetic excitations for copper oxides belonging to the intermediate correlation regime. Our previous J-model (Jpn. J. Appl. Phys. 26 (1987) L1362) for high-T
c superconductivity seems compatible with the spin fluctuations observed recently.
Preparation and Physical Properties of (PrxY1-x)1+δBa2-δCu3Oy
Authors: Okai Bin , Kosuge Michikazu , Nozaki Hiroshi , Takahashi Koh , Ohta Masatsune
Published: February 2005

The Pr-Y solid-solution of the “1-2-3” crystal structure is expressed as (Pr
x
Y1-x
)1+δBa2-δCu3O
y
, with δ ranging from 0 (x=0) to 0.06 (x=1); a small percentage of the Ba sites are occupied by Pr ions. This Pr-Y solid-solution for x>0.5 is nonsuperconducting and does not show metallic conduction. At the metal-semiconductor boundary (x=0.5), the average valence of the Cu ion is smaller by only ca. 0.1 than that of the 90 K superconductor YBa2Cu3O7 (x=0). The relation between the lattice parameters and ionic radii at the Y site is completely different from the empirical relation obtained so far for REBa2Cu3O
y
crystals (RE=Y and trivalent lanthanide elements).
Preparation of Superconducting Y-Ba-Cu-O Thick Film
Authors: Itoh Mineo , Ishigaki Hiroyuki
Published: February 2005

During sintering, superconducting copper-oxide films commonly have a high chemical activity with substrate materials, which results in poor superconductivity. In this research, the substrate is prepared by coating multiple non-superconducting Y-Ba-Cu-O films on alumina. The superconducting Y-Ba-Cu-O thick films were prepared by mixing powders Y2O3, BaCO3 and CuO, making a paste by mixing this noncalcined mixture with solvent, coating it on to a film-coated substrate using a painting or printing method, and then sintering the specimen. The thick films have positive superconductive characteristics at high temperatures.
Vertical Integration of GaAs/AlGaAs Laser Diode and Vertical JFET
Authors: Yoo Hoi-Jun , Kwon Young-Se
Published: February 2005

An embedded heterostructure laser and vertical JFET are integrated in a vertical configuration employing Zn diffusion and a selective liquid phase epitaxy method. The vertical JFET shares the current path with the laser, and can handle high power to effectively control the light output of the laser. Gate-voltage-controlled laser light output characteristics are demonstrated, and when V
DS=4.3 V, the modulation depth of the laser output is as large as 98% for the gate voltage of -4 V.
Lateral Growth on (110) GaAs Substrates by Metalorganic Chemical Vapor Deposition
Authors: Okamoto Kotaro , Furuta Mamoru , Yamaguchi Ko-ichi
Published: February 2005

Lateral growth was carried out on (110) GaAs substrates by metal-organic chemical vapor deposition (MOCVD). In the case of lateral layers extending over free GaAs surfaces, the lateral growth rate is highest in the [00 1̄] direction and lowest in the [001] direction; the dependences can be explained by the stability of the kink sites. In the case of lateral layers extending over SiO2 films, definite facets appear in [ 1̄11]A, [ 1̄10], and [ 1̄12] directions, and lateral layers extending in the [111]A direction show an extremely smooth surface and a plumb ( 1̄11)A plane at the front edge. The ratio of lateral length to thickness is 1.4, which coincides well with the ratio of monolayer space of the {111} surface to the {110} surface.
Characteristics of a Field-Effect Transistor Fabricated with Electropolymerized Thin Film
Authors: Oyama Noboru , Yoshimura Fumihiro , Ohsaka Takeo , Koezuka Hiroshi , Ando Torahiko
Published: February 2005

The preparation and characteristics of the solid-state field-effect transistor (FET) based on poly(p,p'-biphenol)(PBP) thin film prepared by electropolymerization of p,p'-biphenol are presented. The PBP-based FET displayed excellent drain current (I
D)-drain voltage (V
D) characteristics for various gate voltages. The I
D-V
D characteristics were analyzed as in a conventional MOS transistor.
Spectral Change of Polymer Film Containing Poly(3-Alkylthiophene) with Temperature and Its Application as Optical Recording Media
Authors: Yoshino Katsumi , Nakajima Shigeaki , Park Dae Hee , Sugimoto Ryu-ichi
Published: February 2005

A remarkable absorption spectral change has been observed in polymer films containing poly(3-alkylthiophene) with temperature which is explained in terms of the transition of conformation of poly(3-alkylthiophene) in polymer matrix. By quenching the sample from a high temperature, the high-temperature spectrum has been maintained even at room temperature. The spectral change by laser irradiation and its memory have also been confirmed. The applications of these phenomena as optical recording and memory elements are also proposed.
X-Ray Computerized Tomography Using Monochromated Synchrotron Radiation
Authors: Suzuki Yoshio , Usami Katsuhisa , Sakamoto Kozo , Kozaka Hiroshi , Hirano Tatsumi , Shiono Hidemi , Kohno Hideki
Published: February 2005

An X-ray computerized tomographic (CT) imaging system using monochromated synchrotron radiation has been constructed and its performance has been evaluated. Spatial resolution is about 125 µm. Several CT images have been taken. Element mapping in a test sample has also been obtained using the difference between two CT images at different X-ray energies just above and below the absorption edge of the element.
Electrooptic Characteristics of a Charge-Transfer Complex-Doped Surface-Stabilized Ferroelectric Liquid Crystal Device
Authors: Nitta Michio , Ozaki Norihiko , Suenaga Hitoshi , Nakaya Kenji , Kobayashi Shunsuke
Published: February 2005

Enhancement of bistability and response speed in a surface-stabilized ferroelectric liquid crystal (SSFLC) electrooptic device was realized by doping a charge-transfer complex (CTC) into an FLC host. These characteristics were found to be effective for pulsed voltage waveforms whose duration exceeded several 100 µs depending on LC materials and aligning polymer films. The polarity of the electrooptic response to the pulsed waveforms was shown to be inverted in comparison with an undoped device, depending on the polar nature of polyimide substrates.
Thermoelastic Strain in ZnSe Films Grown on GaAs by Metalorganic Vapor Phase Epitaxy
Authors: Shibata Noriyoshi , Ohki Akira , Zembutsu Sakae , Katsui Akinori
Published: February 2005

It has been observed that ZnSe lattices grown on (100) GaAs by metalorganic vapor phase epitaxy deform as growth temperature increases. The lattice parameter variation corresponds to calculated thermoelastic strain due to a mismatch in the thermal expansion coefficient between ZnSe and GaAs. In-plain tensile strain in ZnSe films is found to cause a spectral position shift in photoluminescence to longer wavelengths with increasing growth temperature. This shift can be explained by the dependences of energy gap variation on thermoelastic strain.
Growth of Oriented Si Film on Quartz from Si3H8 by Thermal and Photo-CVD Using a D2 Lamp
Authors: Okuyama Masanori , Fujiki Noriaki , Inoue Kohji , Hamakawa Yoshihiro
Published: February 2005

Polycrystalline Si films have been grown on fused quartz plates at 500–650°C from Si3H8 by thermal CVD and photo-CVD using a D2 lamp. The thermal and photo-CVD films prepared above 575°C are highly <100 >-oriented but the films at 545 and 560°C are <110 >-oriented. This tendency is more remarkable in the photo-CVD than in the thermal CVD. These orientations change little in depth, but the orientation horizontal to the film plane is random.
Detection of Sputtered Neutral Atoms by Nonresonant Multiphoton Ionization
Authors: Shimizu Hazime , Hashizume Hiroko , Ichimura Shingo , Kokubun Kiyohide
Published: February 2005

A nonresonant multiphoton ionization method was applied for the detection of sputtered neutrals using a time-of-flight mass spectrometer. The preliminary results for Cu, Ni and Cu-Ni alloy samples are reported from the viewpoint of a semiquantitative surface analysis. Photoions from pure elements were a reflection of their sputtering yield ratios. The estimated composition of an alloy during sputtering at room temperature is almost the same as that of bulk. On the other hand, anomalous copper-enriched flux was detected at 800 K, and the result was explained by the enhanced segregation and diffusion of copper through the ion-damaged surface layer.
Effect of Hydrogen Absorption on Superconductivity in YBa2Cu3O6.91 and GdBa2Cu3O6.89
Authors: Fujii Hironobu , Kawanaka Hirofumi , Ye Wei , Orimo Shinichi , Fukuba Hitoshi
Published: February 2005

Measurements of lattice constants and ac susceptibility have been performed on YBa2Cu3O6.91H
x
and GdBa2Cu3O6.89H
x
with x<2.0. The lattice constant a increases with increasing x, whereas the parameters b and c decrease slightly with x up to x=0.8. An orthorhombic to tetragonal transition occurs at x=0.80 for both the hydrides, after which the parameter c becomes almost constant for x up to x=1.8 in spite of the increase of the parameter a with x. The superconducting transition temperature T
c remains unchanged with x in the Y hydride system, while T
c decreases slightly with x up to x=1.0 in the Gd hydride system. The diamagnetic signal is weakened by hydrogenation for both hydrides.
Preparation of High-Tc (105 K) Superconducting Phase in Bi-Sr-Ca-K-Cu Oxide System
Authors: Honda Toshihisa , Wada Takahiro , Sakai Masayuki , Miyajima Masamichi , Nishikawa Norihiro , Uchida Shin-ichi , Uchinokura Kunimitsu , Tanaka Shoji
Published: February 2005

The preparation conditions of a high-T
c superconducting phase are investigated in a Bi-Sr-Ca-K-Cu oxide system. The high-T
c phase (T
c∼105 K) was formed at a temperature lower than 850°C in the sample of nominal composition BiSr2/3Ca2/3K2/3Cu2O
y
. The relation of the high-T
c phase formation and the liquid phase is briefly discussed based on the results of differential thermal analysis.
On the 110 K Superconductor in the Bi-Ca-Sr-Cu-O System
Authors: Takayama-Muromachi Eiji , Uchida Yoshishige , Matsui Yoshio , Onoda Mitsuko , Kato Katsuo
Published: February 2005

We found a new compound in the Bi-Ca-Sr-Cu-O system which has a different structure from the 80 K superconductor Bi2(Ca, Sr)3Cu2O
y
. The c-dimension of this compound is ∼37 Å and is ∼6 Å longer than that of Bi2(Ca, Sr)3Cu2O
y
. Although we have not obtained a single-phased sample yet, the clear correlation between the diamagnetic susceptibility just below 110 K and the content of this compound included in the sample strongly suggests that the compound with c≈37 Å is responsible for the superconductivity of T
c∼110 K.
Superconductivity and Microstructural Observation of Er0.5Y0.5Ba2Cu3O7-y
Authors: Wadayama Yoshihide , Kudo Kotaro , Nagata Akihiko , Ikeda Keisuke , Hanada Shuji , Izumi Osamu
Published: February 2005

The critical current density, J
c, of Er0.5Y0.5Ba2Cu3O7-y
was investigated in relation to its microstructure. An increase was observed in the J
c of a sintered sample prepared from a mixture of YBa2Cu3O7-y
and ErBa2Cu3O7-y
with sintering time of up to 10 h at 930°C. The insufficiently sintered sample had a BaCuO2 network in the grain boundaries possibly caused by partial melting of the 1:2:3 compounds. This phase disappeared with increased sintering time, which relates to an endothermic reaction. It is considered that the increase in J
c is due to an increase in the degree of sintering and to the disappearance of the highly resistive phase from the grain boundary.
High-Resolution Electron Microscopy of the High-Tc Superconductor Bi-Ca-Sr-Cu-O
Authors: Hiraga Kenji , Hirabayashi Makoto , Kikuchi Masae , Syono Yasuhiko
Published: February 2005

The arrangement of cation atoms in the observed high-resolution images of a superconductor Bi-Ca-Sr-Cu-O is interpreted well with the Bi4Ti3O12-type structure which consists of doubled slabs of the perovskite structure unit separated by double layers of Bi atoms. Some defects considered as intergrowths of polymorphic structures with different numbers of perovskite layers were observed. From the observed images and electron diffraction patterns, we proposed a structural model with an ordered arrangement of oxygen atoms.
Variation of Superconducting Properties with Hole Concentration in the Solid Solution Systems of Sm1+xBa2-xCu3O7-δ and Eu1+xBa2-xCu3O7-δ
Authors: Akinaga Hiroyuki , Katoh Hideo , Takita Kôki , Asano Hajime , Masuda Kohzoh
Published: February 2005

Superconducting transition temperatute T
c and the normal state resistivity of Sm1+x
Ba2-x
Cu3O7-δ and Eu1+x
Ba2-x
Cu3O7-δ are investigated by changing x in the range of 0∼0.40. According to the X-ray powder diffraction at room temperature combined with the Rietveld method, all the samples are single phase. For both compound systems, T
c of the samples with x=0 and 0.05 is above 90 K and decreases monotonically with x, and the compounds become semiconducting at x=0.40. The variation of T
c with x is insensitive to orthorhombic-tetragonal phase transition at around x=0.20. These results are very similar to those of Nd1+x
Ba2-x
Cu3O7-δ reported in a series of recent papers by the present authors, where it has been proposed that T
c has a simple correlation with hole concentration. This also suggests that a hole concentration compensation effect by excess trivalent Ln ions substituted for divalent Ba ions commonly occurrs in Ln1+x
Ba2-x
Cu3O7-δ (Ln=Nd, Sm and Eu).
YBa2Cu3Ox Superconducting Thin-Film Formation Studied by Rutherford Backscattering Spectroscopy for the Multilayer Deposition Method
Authors: Ohkubo Masataka , Hioki Tatsumi
Published: February 2005

YBa2Cu3O
x
thin films have been synthesized on MgO and Y-stabilized ZrO2 (YSZ) by multilayer deposition followed by annealing in oxygen. From Rutherford backscattering spectroscopy, it has been shown that interdiffusion among the layers occurs and then uniform YBa2Cu3O
x
films are formed by annealing at 900°C for 10 min. The YBa2Cu3O
x
phase grows with (001)-preferential orientation parallel to the substrate surface. For the films on YSZ, a zero-resistance temperature above 77 K has been achieved.
Y-Ba-Cu-O Superconducting Thin Films Prepared by Flash Evaporation
Authors: Hatou Tsunehiro , Takai Yoshiaki , Hayakawa Hisao
Published: February 2005

Superconducting thin films of Y-Ba-Cu-O oxides were prepared by a simple technique of flash evaporation. The critical temperature T
c(R=0) was 80 K in a ∼1 µm-thick film on a MgO substrate. The film showed a preferred c-axis orientation after annealing at 900°C and 600°C in oxygen.
Y-Ba-Cu Oxide Films Formed with Pulsed-Laser Induced Fragments
Authors: Eryu Osamu , Murakami Kouichi , Takita Kôki , Masuda Kohzoh , Uwe Hiromoto , Kudo Hiroshi , Sakudo Tsunetaro
Published: February 2005

For the formation of Y-Ba-Cu oxide films by pulsed-laser sputtering, the dependence on laser energy density was first investigated over a wide range from 0.6 to 3 J/cm2 at 1.064 µm. Rutherford backscattering spectrometry proved that the composition of deposited films strongly depends on the energy density. Films formed at a narrow window of laser energy density from the sputtering threshold of 0.6 J/cm2 to 0.8 J/cm2 showed superconductivity with a T
c onset at 81 K and zero resistance at 79 K in spite of an excess of Cu and Ba atoms after annealing in oxygen. The X-ray diffraction patterns showed that these films have highly preferred orientation of the c-axis, and scanning electron microscopy exhibited the texture of highly dense grains with large sizes of about 5 µm at the surface.
Preparation and Properties of Superconducting Bi-Sr-Ca-Cu-O Thin Films
Authors: Adachi Hideaki , Ichikawa Yo , Setsune Kentaro , Hatta Shin-ichiro , Hirochi Kumiko , Wasa Kiyotaka
Published: February 2005

Thin films of the superconducting Bi-Sr-Ca-Cu-O system have been prepared on MgO and SrTiO3 substrates by rf-magnetron sputtering and subsequent heat treatment. The films had preferred orientation and exhibited superconducting transition with zero- ρ temperature of around 70 K. Large resistivity drops at 110 K were observed only when the films were deposited at relatively high substrate temperatures (>600°C) and heat-treated.
Magnetic Properties of BiSrCaCu2Ox Superconductors
Authors: Uehara Mitsuru , Asada Yuji , Maeda Hiroshi , Ogawa Keiichi
Published: February 2005

Magnetization measurements have been performed for the newly found superconductor, BiSrCaCu2O
x
, which is composed of two phases, i.e., a high-T
c phase (105 K) and a low-T
c phase (75 K). The superconductor is found to be of type II and the lower critical field of the high-T
c phase is as small as 16.2 Oe at 77 K. The volume fraction of the high-T
c phase is as high as 21% in the present sample. The hysteresis observed in the magnetization vs field curve is much smaller in BiSrCaCu2O
x
than in YBa2Cu3O
y
, implying a small critical current density in the high-T
c phase.
A Compensation Temperature Induced by Transverse Fields in a Mixed Ising Ferrimagnetic System
Authors: Kaneyoshi Takahito , Sarmento E. F. , Fittipaldi I. P.
Published: February 2005

The magnetizations of a mixed Ising ferrimagnetic system consisting of spin-½ and spin-1 with different transverse fields are investigated. We find that a compensation point induced by the different transverse fields is obtained as well as the typical temperature dependences of magnetization usually found in crystalline ferrimagnetic alloys, although the system never exhibits any compensation point for the zero transverse fields.
Polarization-Independent and Optical-Damage-Insensitive LiNbO3 Interferometric Waveguide Modulator
Authors: Takizawa Kuniharu , Okada Masakatsu , Aida Tahito
Published: February 2005

A polarization-independent Mach-Zehnder interferometric light modulator consisting of z-propagation Ti-indiffused waveguides is fabricated on an x-cut LiNbO3 substrate in which electrically induced phase shifts are nearly identical for TE and TM modes. The optimum Ti-film thickness for making the modulator is determined by measurements on the electrooptic property of the waveguides. Using the modulator we have achieved an extinction ratio of ∼17 dB with a 14.5 V drive voltage for both modes and low sensitivity to optical damage at a wavelength of 633 nm.
GaAs Surface Cleaning with HCl Gas and Hydrogen Mixture for Molecular-Beam-Epitaxial Growth
Authors: Saito Junji , Nanbu Kazuo , Ishikawa Tomonori , Kondo Kazuo
Published: February 2005

GaAs surface cleaning with a hydrogen chloride gas and hydrogen mixture prior to molecular-beam-epitaxial growth has been investigated as a means of reducing the carrier depletion at the substrate-epitaxial layer interface. Reactive gas etching was performed at a substrate temperature of 500°C. The amount of carrier depletion, measured by a capacitance-voltage carrier profiling technique, decreased significantly from 1.2×1012 cm-2 to less than 1×1010 cm-2.
Thermochromism, Photochromism and Anomalous Temperature Dependence of Luminescence in Poly(3-Alkylthiophene) Film
Authors: Yoshino Katsumi , Nakajima Shigeaki , Park Dae Hee , Sugimoto Ryu-ichi
Published: February 2005

Thermochromism and anomalous temperature dependence of emission spectra have been observed in poly(3-alkylthiophene) films, and are explained in terms of the transition of poly(3-alkylthiophene) conformation. The spectral change by laser irradiation and its memory have also been confirmed. The application of this phenomenon as an optical active element is proposed.
Phase Transition of Y2BaCuO5
Authors: Nakahigashi Kiyotaka , Yoshiara Kiichi , Kogachi Mineo , Nakanishi Shigemitsu , Sasakura Hiroyuki , Minamigawa Shinnosuke , Fukuoka Nobuo , Yanase Akira
Published: February 2005

Phase transition of Y2BaCuO5 has been studied by X-ray diffraction, thermal gravimetric and differential thermal analyses. At temperatures higher than 1265°C in air, the transition has a body-centered cubic structure with a probable space group of Ia3 and the lattice constant of a=1.0602 nm. The transition temperature T
c(°) from the well known orthorhombic phase to the cubic one was changed depending heavily on the oxygen partial pressure P(atom) as T
c=1295+47.5 log
P.
Crystallographic Characterization of ZnSxSe1-x Epitaxial Films
Authors: Okamoto Keiichi , Itoh Nobuo , Ogawa Haruki , Kawabata Toshiharu , Koike Susumu
Published: February 2005

Crystalline quality of ZnS
x
Se1-x
films grown on GaAs substrates has been investigated in detail using the X-ray double-crystal method. Respective fluctuations in orientation and spacing of lattice planes are measured separately. It is shown that the crystalline quality of ZnS
x
Se1-x
films is noticeably affected by the fluctuation in orientation caused by lattice mismatch and partly by the fluctuation in spacing which may be associated with an inhomogeneous distribution of Se and S atoms. Improvement of the quality by lattice matching is due to a reduction of fluctuation in orientation.
Characteristic Secondary Electron Emission from Graphite and Glassy Carbon Surfaces
Authors: Ueno Keiji , Kumihashi Takao , Saiki Koichiro , Koma Atsushi
Published: February 2005

Secondary electron emissions (SEE) from graphite and glassy carbon surfaces have been measured. The spectra give several characteristic peaks whose energies are independent of incident electron energies from 20 to 2500 eV. It has been proved that the SEE spectra show good agreement with core electron excitation energy loss spectra and with the calculated density of state (DOS) of the conduction band. Thus, the SEE spectra directly reflect the conduction band DOS above vacuum level, and the difference between the spectra of graphite and glassy carbon comes from the difference in their conduction band structures.