bluuebunny/crossref_metadata_2025 huggingface dataset:
Epitaxial Growth of Bi-Sr-Ca-Cu-O Thin Films by Molecular Beam Epitaxy Technique with Shutter Control
Authors: Nakayama Yoshimi , Tsukada Ichiro , Maeda Atsutaka , Uchinokura Kunimitsu
Published: February 2005

Thin films of Bi2(Sr, Ca)3Cu2O
y
have been prepared in situ by a molecular beam epitaxy technique in an ozone atmosphere of 4×10-4 Pa. The molecular beams were shutter controlled and films were deposited layer by layer. In situ reflection high energy electron diffraction (RHEED) showed the formation of the perovskite-related structure even at the initial deposition (one unit cell). The resistance of one of the films became zero at 30 K without heat treatment in oxygen.
Flash Lamp Pumped Tunable Forsterite Laser
Authors: Sugimoto Akiko , Segawa Yusaburo , Yamaguchi Yasuhide , Nobe Yukio , Yamagishi Kiyoshi , Kim Pil Hyon , Namba Susumu
Published: February 2005

The flash lamp excited lasing of chromium doped forsterite (Cr:Mg2SiO4) was demonstrated for the first time. The maximum output was 4.95 mJ when the input energy was 283 J. The tuning range was from 1206 nm to 1250 nm.
Blue Electroluminescence of Thin-Film Diamond Made by the Hot-Filament Method
Authors: Taniguchi Yasushi , Hirabayashi Keiji , Ikoma Keiko , Kurihara Noriko Iwasaki , Matsushima Masaaki
Published: February 2005

Blue electroluminescence has been observed in thin-film diamond deposited on a substrate when a mixture of methane and hydrogen gases react under heat treatment by tungsten filament. The diamond active layer is sandwiched between metal oxide insulating layers (HfO2and Al2O3) which are formed by evaporation of metal oxides in oxygen plasma. Indium tin oxide film is used as a transparent electrode. The electroluminescence spectrum shows the peak at 435 nm and luminance is 3.6 cd/m2at an applied voltage of 400 V.
Preparation of Multilayers by Alternate Cycles of Chemical Adsorption and Electron Beam Irradiation
Authors: Ogawa Kazufumi , Mino Norihisa , Tamura Hideharu , Hatada Motoyoshi
Published: February 2005

Multilayers of ω-nonadecenyl trichlorosilane (V-NTS) have been prepared on SiO2/Al/Si substrates by repeated cycles of chemical adsorption (CA) of V-NTS in solution and activation of terminal double bond by electron beam (EB) irradiation. The terminal double bond facing the outside of a V-NTS monolayer on the substrate reacted to form imino and/or amino groups when the irradiations were carried out in nitrogen atmosphere. This method provides a simple and rapid method of preparing multilayers with fewer defects on a large scale, which is important to the construction of the three-dimensional molecular structure.
Electrical Characteristics of High-Mobility Fine-Grain Poly-Si TFTs from Laser Irradiated Sputter-Deposited Si Film
Authors: Serikawa Tadashi , Shirai Seiiti , Okamoto Akio , Suyama Shiro
Published: February 2005

Electrical characteristics of n-channel fine-grain polycrystalline silicon thin-film transistors (poly-Si TFTs) fabricated from a sputter-deposited Si film irradiated with laser light have been measured. The fine-grain poly-Si TFTs have attained a high mobility of 383 cm2/V·s despite a small grain size from 40 nm to several hundred nanometers. The high-mobility fine-grain poly-Si TFTs feature decreases in mobility with gate voltage and decreases in drain current with temperature in a manner similar to single-crystal MOSFETs. They also show a low carrier trap state density N
st at grain boundaries of 5.6×1011 cm-2. High mobility in the poly-Si TFTs is due to a low N
st.
InSb P-N Junction with Avalanche Breakdown Behavior
Authors: Tu S. L. , Huang K. F. , Yang S. J.
Published: February 2005

High quality InSb p-n junction is formed by Cd diffusion using a two temperature zone technique. The junction has a breakdown voltage of 14.4 V at 77 K, exceeding those of the state of art. I-V characteristics as a function of temperature are carefully studied. The reverse breakdown voltage of the p-n junction increases as the temperature is raised, indicating that the mechanism responsible for the breakdown is an avalanche, rather than a tunneling induced process. RA product of the diode is measured to be 1.2×106 Ω·cm2 at zero bias and remains fairly constant up to a reverse bias of 4 V.
Generation of Misfit Dislocations in Si1-xGex/Si Heterostructures
Authors: Fukuda Yukio , Kohama Yoshitaka , Seki Masahiko , Ohmachi Yoshiro
Published: February 2005

The mechanism for misfit dislocation generation in Si1-x
Ge
x
/Si heterostructures is investigated by transmission electron microscopy. It is found that the dislocations nucleate at the surface, then expand to the interface by glide processes to generate 60°-type misfit dislocations. The nucleated dislocations are V-shaped with a 60° angle at the apex. One dislocation segment is of the above mentioned type, and the other is a screw-type. The V-shaped dislocation is energetically more favorable than the semicircular one. Existing surface atomic steps are shown to lower the activation energy of the dislocation generation.
Effect of Low-Temperature Annealing on the Coupling at Grain Boundaries in Sb-Doped (Bi, Pb)2Sr2Ca2Cu3Oy Superconductors
Authors: Sato Ryuji , Komatsu Takayuki , Matushita Kazumasa , Yamashita Tsutomu
Published: February 2005

We examined the effect of further annealing at low temperatures in the range of 300°C to 700°C on the coupling at grain boundaries of the high-T
c phases in superconducting Sb-doped (Bi, Pb)2Sr2Ca2Cu3O
y
ceramics prepared by the melt-quenching method. It was found that the weak coupling at grain boundaries of the high-T
c phases was remarkably improved by annealing at 500°C under the presence of oxygen. The improved coupling at grain boundaries was again weakened by annealing at 600°C or 700°C due to the occurrence of a new reaction.
Relation between Cu L X-Ray and Cu 2p Photoelectron in YBa2Cu3Ox
Authors: Fujinami Masanori , Hamada Hiroki , Hashiguchi Yoshihiro , Ohtsubo Takashi
Published: February 2005

X-ray emission spectroscopy (XES) is applied to the study of the electronic structure o f Cu in YBa2Cu3O
x
superconductors. It is shown that the Cu Lβ/Lα intensity ratio of the orthorhombic sample is about 4% higher than that of the tetragonal sample. The origin of this difference can be discussed consistently using Cu 2p X-ray photoelectron spectroscopy (XPS) spectra, indicating that the effect of charge transfer from O 2p to the Cu 3d hole is comparatively small for the orthorhombic sample in generation of Cu 2p hole. It is confirmed that the probability of |2p3d10L> and |2p3d10L2 > in the intermediate state for the tetragonal becomes higher in L line X-ray emission than that for the orthorhombic. As the result, the population of MV for the orthorhombic becomes low and only the intensity of Lα line is decreased.
A Direct-Overwrite Scheme for Magneto-Optical Memory Systems with an In-Plane Magnetized Control Layer
Authors: Berg H. A. M. van den
Published: February 2005

The principles of a new direct-overwrite method for magneto-optical memory systems in which the conductive layer of the heatsink is magnetic with an in-plane easy axis parallel to the data tracks are investigated. Magnetic charge windows are created in the conductive layer along the data tracks on the flanks of the temperature profiles produced by the focussed laser energy. By varying the laser power, the charge and the associated field windows are modified and displaced with respect to the storage layer. Thus, the total field is reversed at the critical rim at which M in the storage layer is adjustable. Write fields larger than 40 kA/m can be realized.
Passive Mode Locking of a Flashlamp-Pumped Ti:Sapphire Laser
Authors: Oda Seiji , Segawa Yusaburo , Kodama Nobuhiro , Kim Pil Hyon , Namba Susumu
Published: February 2005

Passive mode locking with a saturable absorber was observed in a flashlamp-pumped titanium-doped sapphire laser. The peak wavelength of the absorption spectrum of the saturable absorber (IR-125 dye) was almost the same as that of the gain spectrum of the titanium doped sapphire. The pulse durations of the mode-locked laser were about 100 ps.
Observation of Quantum-Confined Stark Effect in a Graded-Gap Quantum Well
Authors: Ishikawa Takuya , Tada Kunio
Published: February 2005

A graded-gap quantum well structure where the band gap of the well is inclined along the growth direction has been fabricated, and its quantum-confined Stark effect has been observed experimentally. It has been confirmed that, in comparison with the conventional square-shaped quantum well, the graded-gap quantum well exhibits larger and nearly linear energy shift of the fundamental exciton absorption edge with applied field.
High Quality Silicon Epitaxy at 500°C using Silane Gas-Source Molecular Beam Technique
Authors: Hirose Fumihiko , Suemitsu Maki , Miyamoto Nobuo
Published: February 2005

High-quality silicon epitaxial films were successfully obtained at as low as 500°C using a SiH4 molecular beam technique in a UHV system. Perfect selective growth onto SiO2-patterned wafers, which allowed a precise measurement on epitaxial film thickness through the height of the step formed by the selective growth, was also observed. Detailed Arrhenius plots on the growth rate were thus obtained for the temperature range 500–800°C. The plots showed a break around 600°C, separating a lower- and a higher-temperature region with activation energies of 21 kcal/mol and 3.6 kcal/mol, respectively. Growth rate measurements with the silane pressure varied for 2.0, 3.0, and 4.0×10-4 Torr revealed first-order reaction kinetics for the lower-temperature region and a second-order nature for the higher-temperature region.
Annealing Effect on Lattice Distortion in Anodized Porous Silicon Layers
Authors: Sugiyama Hiroshi , Nittono Osamu
Published: February 2005

The annealing effect on the lattice distortion of porous silicon (PS) layers have been studied mainly by X-ray multiple-crystal diffractometry and infrared spectroscopy. The lattice spacing of PS layers changed with increasing annealing temperature and finally became smaller than that of the unanodized Si substrate above 350°C. The lattice contraction of PS layers was found to be strongly related to the desorption of hydrogen atoms from the PS layer. It is also shown that the lattice expansion of as-prepared PS layers is attributable to hydrogen atoms chemisorbed on the pore surfaces in the PS layer.
Anodic Oxidation of Aluminum by Electron Tunneling through Al/Cadmium-Stearate/Al Structure
Authors: Okazaki Choichiro , Kuniyoshi Shigekazu , Kudo Kazuhiro , Tanaka Kuniaki
Published: February 2005

The conduction of the monolayer Langmuir-Blodgett(LB) film consisting of Cadmium-Stearate(CdSt) may be explained by an electron tunneling process. The tunneling current through the Al/CdSt/Al sample showed a great decrease with time when a constant voltage was applied in air. Such a phenomenon seems to result from the growth of an Al2O3 layer by the anodic oxidation of the aluminum electrode enhanced by the electron tunneling.
Hot Electron Injection Characteristics in Asymmetrically Structured Submicron MOSFETs
Authors: Okabe Naoko , Takato Hiroshi , Oowaki Yukihito , Hamamoto Takeshi , Nitayama Akihiro
Published: February 2005

Gate current and substrate current characteristics of submicron NMOSFET with asymmetrical lightly doped drain (LDD) structures are studied. It is newly found that the gate current also has a double-hump phenomenon, as does the substrate current. This new phenomenon can be estimated from impact ionization and the hot-electron emission mechanism. Furthermore, it is newly clarified that the threshold voltage shift after DC stress can be well explained by the gate current over the whole range of stress conditions.
Processing Dependence on Microstructure and Superconducting Properties in the (Bi, Pb)-Sr-Ca-Cu-O System
Authors: Nozue Akiyoshi , Nasu Hiroyuki , Tanaka Katsuhisa , Kamiya Kanichi
Published: February 2005

An oxide superconductor in the (Bi, Pb)-Sr-Ca-Cu-O system has been prepared by the sol-gel method. The effects of heating schedule and starting compositions on the growth rate of the high-T
c phase and on the microstructure and superconducting properties of the obtained samples have been examined. It was found that a higher volume fraction increase rate of the high-T
c phase makes the grains smaller and T
c(end) lower. In other words, by forming the high-T
c phase with lower volume-fraction increase rates, superconducting bodies possessing high-T
c values have been obtained.
Growth of the High-Tc Phase in the Bi-Pb-Sr-Ca-Cu-O Superconducting Oxide System
Authors: Hayashi Yasushi , Kogure Hideo , Gondō Yasuo
Published: February 2005

We studied the effects of the sintering temperature and the cooling rate on the depth profiles of the fraction of the high-T
c phase in the Bi-Pb-Sr-Ca-Cu-O superconductors. We used X-ray diffraction patterns to estimate the fraction of the high-T
c phase. We found that the larger fraction of the high-T
c phase grew inside the samples. Such depth profiles can possibly be explained by the desorption of oxygen in heating and the absorption of oxygen in cooling.
Contact between High-Tc Superconductor and Semiconducting Niobium-Doped SrTiO3
Authors: Hasegawa Haruhiro , Fukazawa Tokuumi , Aida Toshiyuki
Published: February 2005

The contact between a high-T
c superconductor of Er-Ba-Cu-O and a semiconductor of niobium-doped SrTiO3 has been examined by current-voltage measurements. The rectifying characteristic has been observed at 277 K for a sample with niobium-0.05wt%-doped SrTiO3. The breakdown voltage decreases with decreasing temperature or increasing niobium impurity concentration, and the temperature dependence of the breakdown voltage becomes more gradual with increasing niobium impurity concentration.
Gradient Index Polymer Optical Waveguide Patterned by Ultraviolet Irradiation
Authors: Eguchi Shuji , Asano Hideki , Kannke Atsusi , Ibamoto Masahiko
Published: February 2005

A new fabricating technique which is capable of easy pattern formation in gradient index polymer optical waveguides is proposed. Waveguides are obtained by diffusion and fixing of monomers with low refractive indices into a gel patterned by ultraviolet irradiation. The gradient index profiles can be selectively formed in the irradiated parts due to the difference in diffusion rate of monomers between regions in the same substrate. Waveguide optical properties are also demonstrated.
Photoacoustic Spectroscopy on the Metallic Colloids in Ionic Crystal after Pulsed Electron Irradiation
Authors: Inabe Katsuyuki , Owaki Shigehiro , Takeuchi Nozomu
Published: February 2005

Thin single crystals of NaCl were deeply colored by intense electron irradiation. The PAS peak due to small Na colloids formed in the crystal is shown to agree well with the optical absorption peak in a spectrum of transmission method. Dependence of the PA signal on modulation frequency of the exciting light reveals thermal diffusion of Na colloids out of the crystal during the heat treatment at 463 K.
One Approach to Joining Plasma and Sheath
Authors: Kubota Tadahiro , Ohsawa Atsushi , Yamada Shinjiro , Ohuchi Mikio , Kaneda Teruo
Published: February 2005

This letter treats the problem of joining plasma and sheath transverse to the discharge axis. The balance equations of plasma are solved from the center of the plasma to the wall. The point joining plasma and sheath is decided so that the sheath equation becomes non-negative. It is thought that the results of this letter will be useful in the analysis of the probe diagnostics, plasma processing, etc.
0.1 µm Fine-Pattern Fabrication Using Variable-Shaped Electron Beam Lithography
Authors: Hashimoto Kazuhiko , Yasuda Masaaki , Hirai Yoshihiko , Kawakita Kenji , Nomura Noboru , Murata Kenji
Published: February 2005

It is shown that fine patterns with 0.1 µm feature size can be obtained based on a new method of multiple-shot exposure with a variable-shaped electron beam lithography system.
High Reliability of Ultrathin Improved SiN on Poly-Si
Authors: Miyatake Hisakazu , Ide Shigeaki , Komiya Hideo , Ohshima Masatoshi
Published: February 2005

Ultrathin, improved SiN film, which was formed by removing the top oxide from SiO2/SiN stacked dielectric film on poly-Si, was investigated in terms of electrical properties. As a result, the ultrathin, improved SiN (top-oxide-removed SiN; T.O.R.SiN) revealed 3.8 nm SiO2 equivalent thickness and was superior to SiO2/SiN in TDDB (time dependent dielectric breakdown). This T.O.R.SiN shows promise as a dielectric film for memory capacitors in DRAMs of more than 16M bits.
Silicon Nitride Films with Low Hydrogen Content, Low Stress, Low Damage and Stoichiometric Composition by Photo-Assisted Plasma CVD
Authors: Suzuki Nobumasa , Yoshikawa Toshiaki , Masu Kazuya , Tsubouchi Kazuo , Mikoshiba Nobuo
Published: February 2005

A photo-assisted plasma CVD method was developed to deposit high quality silicon nitride films. Nitrogen gas excited in a high density plasma kept apart from a wafer was effectively transported to the deposition chamber under the Knudsen pressure region and reacted with silane gas to generate intermediates. The adsorbed intermediates on the wafer were photo-excited to produce silicon nitride film. Silicon nitride films with the hydrogen content of 3–7 atm%, the density of 2.9–3.3 g/cm3, the tensile stress of 0.5–3.0×109 dyn/cm2 and the Si/N composition of 0.75 were successfully deposited at 300°C.
Synthesis of 110 K Bi(Pb)-Sr-Ca-Cu-O Oxide Superconductors
Authors: Narumi Shun-ichi , Ohtsu Hiroshi , Iguchi Ienari , Yoshizaki Ryozo
Published: February 2005

The synthesis of high-T
c Bi(Pb)-Sr-Ca-Cu-O superconductors is reported in this Letter. Zero resistance is attained at 110 K for the samples sintered at 845°C for 200–300 h. The best sample is obtained after 300 h sintering. The d
c magnetic susceptibility measurement shows the presence of 53% of a high-T
c phase and 4% of a low-T
c phase in terms of the sample-volume ratio. The T
c decreased from 110 K to 108 K after a few days, suggesting that the T
c=110 K state is metastable. The synthesis of the high-T
c phase is studied from the viewpoint of sintering time, gas atmosphere, quenching and annealing procedures, and the Pb content in the original mixed materials.
Surface Lattice Strain Relaxation at the Initial Stage of Heteroepitaxial Growth of InxGa1-xAs on GaAs by Molecular Beam Epitaxy
Authors: Nakao Hiroshi , Yao Takafumi
Published: February 2005

The surface morphology, surface lattice parameter, and growth mechanism of epilayers during molecular beam epitaxy are investigated using a reflection high-energy electron diffraction observation system. The intensity and half width of diffraction streaks, together with the surface lattice parameter of In
x
Ga1-x
As grown on (001)GaAs substrates are measured in situ. The growth of In
x
Ga1-x
As is conducted under an As-stabilized growth condition. The Stranski-Krastanov growth mode is dominant at the initial stage of heteroepitaxy. The surface lattice parameters of In
x
Ga1-x
As epilayers match those of GaAs below a critical thickness (h
c), while they show an abrupt increase toward a bulk In
x
Ga1-x
As lattice parameter beyond the h
c value. The observed h
c value almost coincides with the critical thickness for the transition of the growth mode from 2D to 3D.
Ferroelasticity in Superconducting YBa2Cu3OxSingle Crystals
Authors: Hatanaka Tatsuya , Sawada Akikatsu
Published: February 2005

YBa2Cu3Oxsingle crystals are found to show ferroelastic behavior at about 200°C when they are heated in a mechanically clamped state. Atomic movements associated with ferroelastic domain wall motion are reasonably explained by an order-disorder model for a tetragonal-orthorhombic phase transition.
Microstructural Study of the Y-Ba-Cu-O System at High Temperatures
Authors: Murakami Masato , Morita Mitsuru , Doi Kenji , Miyamoto Katsuyoshi , Hamada Hiroki
Published: February 2005

Phase relations for the Y-Ba-Cu-O system near 1:2:3 stoichiometric compositions at high temperatures have been studied through microstructural observation. It has been found that YBa2Cu3O
x
decomposes into a Y2BaCuO5(211) plus liquid (a mixture of BaCuO2 and CuO) phase at around 1050°C and the 211 phase further decomposes into Y2O3 plus liquid at around 1200°C. Even at 1500°C Y2O3 seems to be stable. On cooling Y2O3 reacts with the liquid to produce the 211 phase by peritectic solidification. At around 1000°C the 211 phase reacts with the liquid to produce the YBa2Cu3O
x
phase again by the peritectic reaction.
LEED-AES and XPS Studies of Bi-Sr-Ca-Cu-O Single Crystal Surfaces
Authors: Kishida Satoru , Tokutaka Heizo , Nakanishi Syuuichi , Nishimori Katsumi , Ishihara Naganori , Fijimoto Hiroshi
Published: February 2005

The well-defined clean surface in the 80K-phase Bi-Sr-Ca-Cu-O single crystal was obtained by cleaving it in air and heating it at 350°C in ultrahigh vacuum (UHV). The low-energy electron diffraction (LEED) pattern from the clean surface showed the perfect single domain of a 1×5 structure. From the Auger electron spectroscopy (AES) measurements, the cleaved surface might be a Bi-O layer and O atoms will be removed more easily than the other elements of Sr, Ca and Cu by Ar+ sputter etching. In the clean surface of the single crystal, Cu2+ was dominant. The X-ray photoelectron spectroscopy (XPS) spectrum of O 1s consists of the OH(∼531 eV) and OL(∼529 eV) components, and the OH component is smaller than the OL component.
Ion Irradiation Effect on Ba2YCu3O7 Superconductor
Authors: Shiraishi Kensuke , Itoh Hiroshi , Yoda Osamu
Published: February 2005

Single-phased Ba2YCu3O7-y
pellets were sequentially irradiated with 200 keV oxygen or nitrogen ions up to 1.5×1016 m-2 at room temperature, and electrical resistance was measured as a function of temperature. The superconducting transition temperature measured with current density greater than 30 kA·m-2 was increased by the ion irradiations to about 3×1015 m-2. The zero-resistance temperature measured with 121 kA·m-2 in current density was enhanced from 88.1–89.1 K to 90.4 K by oxygen ion irradiation to 1.6×1015 m-2, and then reduced to a level obtained in the nonirradiated condition after irradiation to about 1×1016 m-2.
Superconducting Film Prepared from Rapidly Quenched Amorphous Materials of Bi2Sr2Ca2-xCdxCu3Oy
Authors: Yoshimura Masahiro , Sung Tae-Hyun , Ishizawa Nobuo , Nakagawa Zenbe-e
Published: February 2005

The effect of Cd substitution for Ca in Bi2Sr2Ca2Cu3O
y
has been studied using the rapid-quenching-after-rapid-melting technique. The zero resistivity temperature T
c(endpoint) increased and tailing of transition vanished with increased doping of Cd. The film with the composition Bi2Sr2Ca1.6Cd0.4Cu3O
y
exhibited a T
c(endpoint) value of 87 K without tail. Further substitution of Cd for Ca brought about lowering in the T
c until finally no superconductivity transition was shown above 20 K, because a semiconducting phase with c
0=2.5 nm formed instead of a c
0=3.0 nm phase.
Formation of the High-Tc Phase of the Superconducting Bi-Pb-Sr-Ca-Cu-O Thin Film by the Laser Ablation Method
Authors: Tabata Hitoshi , Kawai Tomoji , Kanai Masaki , Murata Osamu , Kawai Shichio
Published: February 2005

Films of the Bi-Sr-Ca-Cu-O and the Bi-Pb-Sr-Ca-Cu-O superconductors have been synthesized by a laser ablation method. Pb doping decreases the melting temperature, making the formation of the high-T
c phase much easier. The properties and structures of these thin films are mainly controlled by the thermal treatment and the composition of the targets for ablation. By controlling these conditions, as much as 40% of the total volume of the high-T
c phase is obtained. A precursor state of the 80 K phase can be obtained even at 400°C by this laser ablation method.
Superconducting Properties of Y-Ba-Cu-O Thin Films Prepared by RF Magnetron Sputtering with a Grid Electrode
Authors: Takechi Kazushige , Shiota Tetsuyoshi , Hatou Tsunehiro , Inoue Masumi , Takai Yoshiaki , Hayakawa Hisao , Ohbayashi Kazushige
Published: February 2005

Y-Ba-Cu-O thin films were prepared by an RF sputtering method with a DC-biased grid electrode inserted between a target and a substrate. When the grid was negatively biased at about -70 V, as-sputtered superconducting films with a c-axis orientation were obtained, while the films prepared without the grid electrode but under the same condition showed neither superconductivity nor c-axis crystal orientation.
Effects of Ar Ion-Beam Etching on Gd-Ba-Cu-O Superconducting Thin Films
Authors: Enokihara Akira , Higashino Hidetaka , Kohiki Shigemi , Setsune Kentaro , Wasa Kiyotaka
Published: February 2005

The effects of Ar ion-beam etching were investigated for Gd-Ba-Cu-O superconducting thin films prepared on (100) MgO substrates at 650°C by rf magnetron sputtering. Etching at acceleration voltages below 2 kV did not change the zero-resistivity temperature and the critical current at 50 K in spite of a reduction of film thickness. A nonsuperconducting layer was formed near the surface. Surface analyses by X-ray photoelectron spectroscopy suggest that the crystal structure was deformed and the mean value of a Cu valence reduced to +1 by the Ar ion bombardment.
Magnetic Properties of Fe-Based Binary Crystalline Alloys Produced by Vapor Quenching
Authors: Kataoka Noriyuki , Hosokawa Masami , Inoue Akihisa , Masumoto Tsuyoshi
Published: February 2005

Structure and magnetic properties of Fe-M (M=Ti, Zr Hf, Nb or Ta) alloy films produced by rf sputtering haye been investigated in Fe-rich compositional ranges below 10 at%M. These alloy films have a nonequilibrium bcc phase with lattice parameters larger than that of pure Fe. They exhibit high saturation magnetization and soft magnetic properties. In particular, the bcc Fe94Zr6 film annealed at 673 K for 1 h exhibits a saturation magnetization of 2 T and a magnetostriction less than 1×10-6.
A Two-Band Hubbard Model for Clusters of Doped Copper Oxides and Other Metal Oxides: Populations of Holes and Spin Densities by the Full VB CI Method
Authors: Yamaguchi Kizashi , Nakano Masayoshi , Namimoto Hideo , Fueno Takayuki
Published: February 2005

The two-band Hubbard model for clusters of doped transition metal oxides is solved by the valence-bond (VB) full CI technique. It is found that the holes are mainly introduced upon oxygen sites of doped copper oxides, whereas they are localized on metal sites in the case of the Mott-Hubbard insulators such as iron and manganese oxides. The full VB Cl calculations indicate the important roles of both spin-flip (bitriplet) and spin-unflip (charge-transfer) excitations, which are responsible for electronic fluctuations (correlations) within doped copper oxides. Implications of these results are discussed in relation to the high-T
c superccnductivity.
High Quality Ferroelectric Liquid Crystal Display with Quasi-Bookshelf Layer Structure
Authors: Sato Yuzuru , Tanaka Taka-aki , Kobayashi Hidekazu , Aoki Kazuo , Watanabe Hiroshi , Takeshita Hiroshi , Ouchi Yukio , Takezoe Hideo , Fukuda Atsuo
Published: February 2005

We realized a surface stabilized ferroelectric liquid crystal display with high contrast ratio and high transmittance using a conventional rubbing method. Such remarkable electrooptical properties are based on the switching between uniform states in a cell treated with an AC electric field in the SmC*. It was confirmed by X-ray diffraction that the treatment caused a permanent change in the smectic layer structure from a chevron to a quasi-bookshelf structure. An example of multiplexing is also displayed.
Preparation of an Almost Single Phase Superconductor in the Nd-Ce-Sr-Cu-O System
Authors: Kosuge Michikazu
Published: February 2005

A superconducting oxide with the composition (Nd0.60Ce0.175Sr0.225)2CuO4-δ was obtained as an almost single phase. This superconducting phase has a tetragonal unit cell with lattice parameters a=3.8575 Å and c=12.507 Å. The crystal structure of this phase is different from both the Nd2CuO4 type structure and the K2NiF4 type structure. Magnetic susceptibility measurement shows that (Nd, Ce, Sr)2CuO4-δ is a bulk superconductor. The superconductivity of samples annealed at a high oxygen pressure was investigated. The onset critical temperature was insensitive to high oxygen pressure.
Luminescence Characteristics from Gaussian Shaped Quantum Wells
Authors: Yamaguchi Hiroshi , Horikoshi Yoshiji
Published: February 2005

Gaussian shaped quantum wells are fabricated by low temperature migration-enhanced epitaxy. Low temperature photoluminescence measurement shows the superior luminescence characteristics of Gaussian wells. Computer simulation using a one-dimensional tight-binding model shows that this effect is caused by the statistical cancellation of the influence from the surface roughness among the neighboring atomic layers.
Resistivity of Flame Plasma in an Electric Field
Authors: Ikuta Kazunari
Published: February 2005

A generalized Ohm's law is obtained for a flame plasma in an electric field for the study of arc resistivity in an electromagnetic launcher (EML). The resistivity of flame plasma is reduced by the particle source, which suggests the injection of premixed combustible fuel into the arc plasma as the particle source in order to reduce the arc voltage. Reduction of the voltage in the arc is desirable to reduce the damage of electrodes in EML since the electric field in the arc plasma energizes charged particles which can bombard the electrodes.
Electron-Beam-Induced Cl2 Etching of GaAs
Authors: Taneya Mototaka , Sugimoto Yoshimasa , Hidaka Hiroshi , Akita Kenzo
Published: February 2005

Electron-beam (EB)-induced Cl2 etching of GaAs is performed for the first time. Etching occurs only in the area exposed to both the Cl2 molecules and the EB. The etching rate is equal to that of a Cl2 gas phase etching. The morphologies of the etched surfaces are slightly rough, but the photoluminescence intensity of the processed sample does not change as compared with that of the unprocessed sample. The etching characteristics predict that surface adsorbates act as a mask for a gas phase etching and that the EB plays an important part in patterning of the adsorbate mask.
Superconductivity in a Ln-Pb-Sr-Ca-Cu-O System
Authors: Inoue Osamu , Adachi Seiji , Takahashi Yukihiro , Hirano Hirofumi , Kawashima Syunichiro
Published: February 2005

The superconductivity and crystal structure of a Ln-Pb-Sr-Ca-Cu-O system, where Ln=Y or lanthanide, have been studied. The maximum onset temperature and zero resistance obtained for a nominal composition of YbPbSr2Ca2Cu3O
x
were 78 K and 64 K, respectively. This ceramic is composed of a new phase which has a tetragonal symmetry with a=3.81 Å and c=15.7 Å, and a second phase, Yb2SrO4.
Structural Change on Poling in a Piezoelectric Copolymer of Vinylidene Cyanide with Vinyl Acetate
Authors: Kurihara Suomi , Takahashi Yoshiyuki , Miyaji Hideki , Seo Iwao
Published: February 2005

Structural change induced by an electric field in poly(vinylidene cyanide/vinyl acetate) is investigated by X-ray scattering. Upon poling with an electric field of 50 MV/m at 170°C (10°C below the glass transition temperature), the amorphous halo increases in intensity and becomes narrower in the direction parallel to the electric field; in the direction perpendicular to the electric field, no change is observed upon poling. The order induced by poling is discussed in connection with the piezoelectricity of the polymer.
Electron Channelling Effect in an Al-Fe-Cu Quasicrystal
Authors: Shindo Daisuke , Hiraga Kenji , Williams Tim , Hirabayashi Makoto , Inoue Akihisa , Masumoto Tsuyoshi
Published: February 2005

Strong electron channelling effect has been observed in a quasicrystal of Al-Cu-Fe alloy which has a near-perfect icosahedral symmetry and low phason density. When the electron beam was set parallel with one of the high symmetry zone axes such as the 5-fold and 2-fold, the intensities of the characteristic X-ray of Fe and Cu relative to that of Al were much stronger than under non-channelling conditions. This result directly indicates that both Fe and Cu atoms occupy their own definite atomic sites different from those of the host element Al.
Low-Temperature Surface Cleaning of GaAs by Electron Cyclotron Resonance (ECR) Plasma
Authors: Kondo Naoto , Nanishi Yasushi
Published: February 2005

Low-temperature surface cleaning of GaAs by electron cyclotron resonance (ECR) plasma is carried out. Pure hydrogen is used for the cleaning gas, and ECR plasma is transported to the substrate surface by a divergent magnetic field. In situ reflection high-energy electron diffraction (RHEED) observation reveals that surface cleaning of GaAs can be successfully performed at temperatures as low as 300°C. The interface between the substrate and GaAs grown layer prepared after plasma cleaning is found by SIMS measurement to be cleaner than that prepared by thermal treatment and MBE growth.
High-Quality SOI by Bonding of Standard SI Wafers and Thinning by Polishing Techniques Only
Authors: Haisma Jan , Michielsen Theo M. , Spierings Gijsbertus A. C. M.
Published: February 2005

A technology is described for Silicon-on-Insulator (SOI) wafer fabrication realized by Van der Waals wafer bonding followed by wafer thinning. The uniqueness of this procedure is that only standard silicon wafer material and standard grinding and polishing techniques, derived from optics and silicon-wafer manufacturing, are applied. Submicron precision concerning flatness and parallelism of a 10 cm diameter wafer pair is achieved. The present SOI layer thickness aimed at is 5 µm but thinner layers are feasible.
Growth of GaAs on Si Substrates by Metalorganic MBE Using Triethylgallium and Arsenic
Authors: Watanabe Yoshio , Uneta Makoto , Ohmachi Yoshiro
Published: February 2005

GaAs layers are epitaxially grown on (100) Si substrates by metalorganic MBE (MOMBE) using triethylgallium and solid arsenic. All epilayers show p-type conductivity caused by carbon incorporation. The reproducibly obtained single-domain GaAs epilayers have almost featureless morphology. The X-ray diffraction measurements indicate that the MOMBE-grown layer is of high crystalline quality. The 4 K photoluminescence spectrum exhibits a strong, excitonic transition peak with a linewidth of 4.9 meV. These results can compete with those reported previously for the MOCVD-grown GaAs on Si.
Compositional Disordering of In0.53Ga0.47As/In0.52Al0.48As Multiquantum Well Structures by Repetitive Rapid Thermal Annealing
Authors: Miyazawa Takeo , Suzuki Yasuhiro , Kawamura Yuichi , Asai Hiromitsu , Mikami Osamu
Published: February 2005

In0.53Ga0.47As/In0.52Al0.48As multiple-quantum well (MQW) structures were partially disordered using a dopant-free technique. MQW disordering was accomplished by deposition of a Si3N4 cap followed by repeating rapid thermal annealing (RTA) at 850°C for 1–5 s. The photoluminescence spectrum for the capped region is blue-shifted by 43 nm in the 1.5 µm wavelength region. However, this shift could not be achieved by conventional RTA. Optical transmission measurements indicate that the disordered region extends to an area deeper than 0.74 µm from the surface. The disordering mechanism is also discussed.
Synthesis and Properties of Superconducting Mixed Rare Earth LnBa2Cu3O7-x Compounds
Authors: Spencer Nicholas D. , Roe A. Lawrence
Published: February 2005

A solution-phase technique has been used to produce mixed rare earth compounds of formula LnBa2Cu3O7-x
(Ln-123) starting with the Monazite-derived mixture known as Didymium (Di) and with other artificially produced mixtures of La, Nd and Pr in comparable ratios. La-123, La-Nd-123, La-Nd-Pr-123 and Di-123 display very similar XRD powder patterns. However, while La-123 and La-Nd-123 show T
cs of 85–90 K and high superconducting fractions, the presence of ≈11%Pr in the Di-123 and in La-Nd-Pr-123 leads to drastic drops in T
c and superconducting fraction to ≈25 K and 10% respectively.
Annealing of (Nd, Ca)2CuO4 Compounds under High Oxygen Pressure
Authors: Hiratani Masahiko , Takeda Yasuo , Saitoh Shin'ichiro , Miyauchi Katsuki
Published: February 2005

The copper oxide, Nd2CuO4, is known to become an electron-doped superconductor with Ce4+ substitution. Since all other copper oxide superconductors belong to the p-type, the possibility of hole doping is investigated using 600 bar O2 annealing. In the Nd-Ca system, electroneutrality is still compensated for by vacancy formation even when annealed under 600 bar O2. However, when sintered in Ar, the same reduction state is achieved with Ca2+ substitution as that with Ce4+ substitution. Vacancy ordering and structural symmetry may be essential for the superconductivity.
Preparation of a 90 K Superconductor (LaBa2Cu3O7-y) with Ag-Related Additives
Authors: Mizuno Fumio , Masuda Hiromu , Hirabayashi Izumi , Tanaka Shoji
Published: February 2005

The orthorhombic LaBa2Cu3O7-y
compounds which show superconducting transitions over 90 K were synthesized with Ag-related additives by liquid phase sintering through the molten Ag. From the results of SEM coupled with X-ray microanalysis and X-ray photoemission, more than 90% of the Ag was incorporated as the metallic state in the grain boundaries. The superconducting volume fraction and critical current density were improved by the addition of Ag2O. Both of them had a maximum value at Ag2O contents, i.e. 12.5% to 25%.
Valence State of Cu in Nd2-xCexCuO4 System
Authors: Uji Shinya , Shimoda Masahiko , Aoki Haruyoshi
Published: February 2005

We present XPS studies of semiconducting Nd2-x
Ce
x
CuO4 (0≦x≦0.20) and superconducting Nd1.85Ce0.15CuO4-y
to clarify the location of the electron carriers. Examination of the Ce3d spectra shows that the Ce ions are donors of electron carriers. From the analysis of the Cu2p spectra, the Cu+ concentration is found to increase with the Ce concentration x. A definite increase in the Cu+ concentration due to the reduction procedure is found for the superconducting sample. The present results suggest that the conduction of the electron carriers takes place in the CuO4 square plane in this system.
Enhancement of Critical Magnetization Current by the Electron Irradiation in Ba2YCu3O7 Superconductor
Authors: Shiraishi Kensuke , Kato Takahiko , Kuniya Jiro
Published: February 2005

A single-phased Ba2YCu3O7-y
pellet was sequentially irradiated with 3 MeV electrons up to 2.25×1022 m-2 at about 370 K, and the magnetization measurements were carried out at 77 K in fields up to a corresponding magnetic flux density of 1.0 T. The critical current density estimated from the magnetization mesurement was enhanced by the electron irradiation; the enhancement was larger in higher magnetic fields. The current density at 1.0 T of 7.4 MA·m-2 was increased to 11.3 MA·m-2 by the electron irradiation to 1.75×1022 m-2, and then decreased upon further irradiation.
Magnetic Shield of High-Tc Oxide Superconductors at 77 K
Authors: Shigematsu Koji , Ohta Hiroshi , Hoshino Kazutomo , Takayama Hitoshi , Yagishita Osamu , Yamazaki Shigeru , Takahara Hidefusa , Aono Masakazu
Published: February 2005

Magnetic shielding effects of superconducting Y-Ba-Cu-O vessels have been studied. Magnetic fields inside a Y-Ba-Cu-O vessel in a superconducting state at 77 K were compared with those in a normal state at 290 K by measuring induced voltages in a pick-up coil inside the vessel. The ratio of the magnetic field at 77 K to that at 290 K was as good as 2×10-6 when a magnetic field of 0.03 mT at 1000 Hz was applied to the outside of the vessel. This attenuation ratio is good enough for neuromagnetic measurements with a SQUID magnetometer.
Preparation of Yb-Ba-Cu-O Superconducting Films Using an Arc Discharge Evaporation Method
Authors: Ishiwara Hiroshi , Nohira Hiroshi
Published: February 2005

We report a new process for preparing superconducting films of YbBa2Cu3O7-x
using DC arc discharge evaporation on insulating substrates such as SrTiO3(100) and MgO(100). The films were deposited without intentional heating and subsequently annealed typically at 950°C for 2 hours in O2 atmosphere. Although the as-deposited films were amorphous and insulators, the annealed ones on MgO substrates showed superconductivity with Tcend(zero resistivity)=78 K. However, the films on other substrates (Y-stabilized ZrO2, SrTiO3, and Al2O3) did not show superconductivity down to 30 K. It was found from X-ray diffraction analysis that the films on MgO were predominantly oriented with the c-axis perpendicular to the substrate.
Concentration Effect of Pb in Sputter-Deposited Bi-Sr-Ca-Cu-O Superconducting Thin Films
Authors: Hakuraku Yoshinori , Aridome Yoshinari , Miyagi Daisaku , Suresha Nadabar G. , Ogushi Tetsuya
Published: February 2005

Superconducting thin films of the Pb-doped Bi-Sr-Ca-Cu-O system have been prepared on MgO substrates by dc magnetron sputtering using a single sintered target. After deposition at 400°C and post-annealing at 850°C for 3 h in air, we have succeeded in obtaining highly c-axis oriented thin films which have shown zero resistivity at 115 K. In order to examine the effect of Pb concentration, composition analysis was performed by electron probe X-ray microanalysis. As a result, the composition of the as-sputtered films deposited below 400°C was almost the same as that of the targets, except for a slight decrease in the Bi concentration. Further, we found that the Pb-content of the film decreased quickly only during the early stage of annealing at 850°C and quite slowly thereafter.
Tailored Thin Films of Superconducting Bi-Sr-Ca-Cu Oxide Prepared by Excimer Laser Ablation Technique
Authors: Tabata Hitoshi , Kawai Tomoji , Kanai Masaki , Murata Osamu , Kawai Shichio
Published: February 2005

Site-selective substitution of Ba for Sr or Ca in a layered (Bi-Pb)2Sr2Ca1Cu2O
y
structure has been performed by a successive deposition method using pulsed excimer laser ablation. The introduction of Ba to the Sr site diminishes the superconductivity, whereas that to the Ca site improves the superconducting properties, resulting in a higher T
c value. The extent of this improvement is observed in the order of Ba>Sr>Ca, being consistent with the expansion of the lattice parameter of the c axis.
Preparation of Bi-Sr-Ca-Cu-O Superconducting Films by CVD
Authors: Yamane Hisanori , Kurosawa Hideyuki , Iwasaki Hideo , Hirai Toshio , Kobayashi Norio , Muto Yoshio
Published: February 2005

Bi-Sr-Ca-Cu-O (BSCCO) films were prepared on MgO(100) single-crystal substrates at 770°C by chemical vapor deposition using β-diketone metal chelates of Sr, Ca and Cu and Bi-triethoxide. The films were Bi2(Sr, Ca)3Cu2O
x
(c=30 Å) with c-axis orientation. The films showed superconducting transition onset at 90 K with zero resistivity at 74 K. The formation of films having high-T
c phase (Bi2(Sr, Ca)4Cu3O
x
, c=37 Å) was achieved when the films were annealed at 890°C for 5 h under 760 Torr of oxygen. The resistivity of the annealed films began to drop sharply at around 110 K and reached zero at 77 K.
Observation of High Laser Gain at 703 nm in a New Chemical System
Authors: Yoshida Sanichiro , Taniwaki Manabu , Sawano Tatsuo , Shimizu Kouki , Fujioka Tomoo
Published: February 2005

Visible stimulated emission has been observed in a chemically produced O4
* complex system. A maximum positive gain of 2.8% has been measured at 703 nm. Experimental results imply high possibility that a visible chemical laser might be realized by the present system.
Undershooting, Flip-Flop and Set-Reset Operations in Electrooptic Bistable Devices
Authors: Okada Masakatsu , Takizawa Kuniharu , Aida Tahito , Kikuchi Hiroshi
Published: February 2005

We show that the reset operation, switching from an upper stable state to a lower one in optical bistable devices, is achieved by means of a positive optical pulse through undershoot-switching, in contrast with conventional downward switching by means of optical pulses negative relative to an optical bias level. Flip-flop and set-reset operations are demonstrated by using only positive optical pulses in an electrooptic bistable device, in which similar operations can also be achieved by applying electric pulses on a biased optical input.
Bound-Exciton and Edge-Emission Spectra Associated with Li and Na Acceptors in ZnSe
Authors: Yamada Yoichi , Kidoguchi Isao , Taguchi Tsunemasa , Hiraki Akio
Published: February 2005

An alternative model for the radiative recombination process in ZnSe, responsible for the edge-emission bands associated with Li and Na acceptors, is tentatively proposed. This is derived from a recent experimental result showing that the energy level of a Na acceptor is shallower than that of a Li acceptor. The energy value of Na level is found to be 102 meV using results from direct observation of two-hole transitions. Significant Li contamination was observed in intentionally Na-doped ZnSe specimens which were heat-treated above 500°C. Both the Li bound exciton line and the related edge-emission band were found to decrease in intensity after prolonged exposure of the samples in air, whilst the Na bound exciton line remained constant.
Supplementary-Light Method for Measuring the Conversion Efficiency of Multijunction Solar Cells
Authors: Shimokawa Ryuichi , Nagamine Fumiaki , Nakata Minoru , Fujisawa Kazuya , Hamakawa Yoshihiro
Published: February 2005

We have developed a supplementary-light method for measuring the conversion efficiency of multijunction solar cells using component reference cells with filters, which is a simple and low-cost method. Comparing the device I-V parameters measured by this method with the same parameters measured actually under the reference spectrum, that is, our reference spectrum (AM1.5 solar simulator) or the near AM1.5 reference spectrum, we found that this method is capable of determining the multijunction cell efficiency with an error of less than 2–3%, mainly due to the FF deviation. Also, we have tried to evaluate multijunction cells under a single-source solar simulator by the conventional reference-cell method and found that this method gave an uncertainty of 5–6%.
Temperature-Dependent EXAFS Study on Supported Silver and Palladium Clusters
Authors: Yokoyama Toshihiko , Kimoto Sanae , Ohta Toshiaki
Published: February 2005

Temperature-dependent Ag and Pd K-edge EXAFS (extended X-ray absorption fine structure) spectra were measured for SiO2-supported small Ag and Pd metal clusters. EXAFS analysis using the cumulant expansion technique has revealed that the Debye temperature is significantly lower and the themal expansion coefficient is larger for the small metal clusters compared with the corresponding bulk metal. These observations can be explained by the simple concept that the surface metal atoms of the clusters have shallower and more anharmonic interatomic potentials.
Surface Roughness Evaluation of Multilayer Coated X-ray Mirrors by Scanning Tunneling Microscope
Authors: Nakajima Kunio , Aoki Sadao , Koyano Tamotsu , Kita Eiji , Tasaki Akira , Fujiwara Shiro
Published: February 2005

Multilayer X-ray mirrors have been deposited by electron beam evaporation in a high-vacuum system, and the surface irregularities have been investigated by means of a scanning tunneling microscope (STM), the X-ray reflectivity measurement and a stylus profilometer. A good correlation between the STM and the peak X-ray reflectivity has been demonstrated.
Semiconducting CdTe Microcrystalline-Doped SiO2 Glass Thin Films Prepared by Rf-Sputtering
Authors: Nasu Hiroyuki , Tsunetomo Keiji , Tokumitsu Yoji , Osaka Yukio
Published: February 2005

Semiconducting CdTe microcrystalline was successfully doped in SiO2 films by the magnetron rf-sputtering technique. The average size of the microcrystalline depended on the relative area and location of the CdTe chips on the target, as well as the postannealing time; and that of as-deposited films varied from 22 A to 62 A. From the optical absorption spectra, the absorption edge of the films clearly exhibited blue shifts compared to the bulk CdTe. Thus the quantum size effect could be found for these films.