bluuebunny/crossref_metadata_2025 huggingface dataset:
Spontaneous Magnetization Phenomena in Pyrolyzed Organic Compounds Containing Nitrogen Atoms
Authors: Hisashi Araki Hisashi Araki , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

Organic compounds exhibiting spontaneous magnetization were obtained by the pyrolysis of 2,4,6-triphenoxy-1,3,5-triazine (TPTA)/benzoguanamine(BG), TPTA/melamine(M), BG/m-phenylenediamine(PDA), M/m-PDA and guanine(G). The magnetically active components of pyrolyzed TPTA/M, BG/m-PDA, M/m-PDA and G exhibit ferrimagneticlike behavior. The largest saturation magnetization M
s(2.25 emu·G/g) has been found in the magnetically active component of guanine pyrolyzed at 600^°C. S
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Quick and Quantitative Measurement of Oxygen Precipitates near Denuded Zone in Intrinsic-Gettering-Treated Czochralski-Si Wafers
Authors: Miyairi Hiroo , Isamu Suzuki Isamu Suzuki , Yūkichi Horioka Yūkichi Horioka
Published: February 2005

Defect profiles near the denuded zone in intrinsic-gettering (IG)-treated Czochralski (CZ) Si wafers, which had been immersed in Secco etching solution in advance, were measured using a wafer defect analyzer. It is clear that measurement of oxygen precipitates is completed near the denuded zone of 125-mm-diam Si wafers in a few hours, and that in the region of precipitate densities from 5×104 to 106 (cm-2) that were counted by means of Nomarski microscope, the systematical error of this wafer defect analyzer is smaller than 10%.
Trimethylgallium Reactions on As-Stabilized and Ga-Stabilized GaAs(100) Surfaces
Authors: Sasaki Masahiro , Kawakyu Yoshito , Hironori Ishikawa Hironori Ishikawa , Masao Mashita Masao Mashita
Published: February 2005

We compared the trimethylgallium (TMG) reaction on an As-stabilized surface of GaAs with that on a Ga-stabilized surface using a quadrupole mass spectrometer equipped with a cold aperture. It was found that, although TMG thermally decomposed on both the As-stabilized and Ga-stabilized surfaces, Ga-containing decomposition products did not desorb from the As-rich surface. A new growth mechanism for GaAs atomic layer epitaxy, related to this desorption difference, is also discussed.
Distribution of Oxygen Atoms in a YBa2Cu3O6.4 Superconductor Visualized by Ultra-High-Resolution Electron Microscopy
Authors: Shigeo Horiuchi Shigeo Horiuchi
Published: February 2005

Arrangements of oxygen atoms in a superconducting YBa2Cu3O6.4 crystal (T
c=27 K) have been visualized by ultra-high-resolution high-voltage electron microscopy. The crystal consists of major orthorhombic and minor pseudotetragonal regions. Oxygens in CuO
y
planes do not distribute homogeneously but are mostly concentrated in areas smaller than 100 Å in diameter, in which clusters of 8 to 30 Å are closely packed with an oxygen arrangement similar to that in YBa2Cu3O6.9 or YBa2Cu3O7.7 respectively. The volume ratio of these two types of clusters varies in each area, resulting in the local change of the crystal symmetry. The formation of these oxygen-rich areas as well as clusters must strongly affect the mechanism and properties of superconductivity.
Unit-by-Unit Process of Bi2Sr2CuOy Film Growth with Molecular Beam Epitaxy by Separated Evaporation/Oxidation/Crystallization Technique
Authors: Suzuki Kouji , Karaki Tetsuya , Iwashima Kenji , Shibata Miki , Okada Hiroyuki , Hiroyoshi Onnagawa Hiroyoshi Onnagawa , Kazuo Miyashita Kazuo Miyashita
Published: February 2005

Thin films of Bi2Sr2CuO
y
were grown with MBE (Molecular Beam Epitaxy) by the separated evaporation/oxidation/crystallization technique on a MgO (100) substrate. The proposed technique is the unit-by-unit process consisting of three steps: multilayer deposition of (Bi-Sr-Cu-Sr-Bi)×2, low-temperature oxidation (300°C) in low concentration O3 (O2/O3(0.3%)) atmosphere (5×10-5 Torr) and crystallization (750°C, 1×10-8 Torr). After growth of ten units, clear streaks on the RHEED pattern showing the twin structure and a fairly fine X-ray diffraction pattern were observed.
Dielectric Properties of SrTiO3 Epitaxial Film and Their Application to Measurement of Work Function of YBa2Cu3Oy Epitaxial Film
Authors: Hirano Takashi , Ueda Masakazu , Matsui Ken-ichi , Fujii Tatsuhiko , Ken Sakuta Ken Sakuta , Takeshi Kobayashi Takeshi Kobayashi
Published: February 2005

The dielectric properties of SrTiO3 epitaxial film were studied using film grown on oxide superconductor YBa2Cu3O
y
. They were, to a certain extent, similar to those of the single-crystal bulk in terms of both temperature and electric field dependence, though the value of the dielectric constant was low, particularly at cryogenic temperatures. The observed dielectric properties were analytically expressed. Using the dramatic field dependence of the dielectric constant of the SrTiO3 film in the Au-SrTiO3-YBa2Cu3O
y
metal-insulator-superconductor (MIS) structure, we determined the work function of (001)YBa2Cu3O
y
epitaxial film to be ∼6.1 eV.
Light-Induced Changes in Plasma-Deposited Hydrogenated Amorphous Silicon Prepared under Visible-Light Illumination Studied by a Constant Photocurrent Method
Authors: Sakata Isao , Mitsuyuki Yamanaka Mitsuyuki Yamanaka , Yutaka Hayashi Yutaka Hayashi
Published: February 2005

Experimental studies on the light-induced changes in plasma-deposited hydrogenated amorphous silicon prepared under visible-light illumination have clarified that (1) the type 2 defect state (ST2), previously found by the present authors (ref. 5), is not a latent site for the light-induced changes in this material; (2) the illumination on the growing surface can modify the surroundings of ST2; and (3) the light-induced increase of the density of neutral Si dangling bonds is small in the illuminated GD sample, especially in the initial stage of long exposure to light.
Spin-Polarized Electron Tunneling in Ni/Al2O3/Co Junction and Large Magnetoresistance of Ni/Co Double Layers
Authors: Suezawa Yoshitaka , Takahashi Fumiaki , Gondō Yasuo
Published: February 2005

The magnetic field dependence of the tunnel resistance of Ni/Al2O3/Co junctions and the resistance across the interfaces of Ni/Co junctions was studied. Both types of junctions showed the magnetic valve effect, in which junction resistances vary with the angle between the magnetizations of Ni and Co electrodes. For Ni/Co junctions, additional peaks were observed on the resistance versus magnetic field curves at the coercive fields of Co electrodes, suggesting the effect of magnetic domains formed in the junction area in the magnetization process. The relative change in resistance for the Ni/Co junction showed a large value of 16.4%.
Deep-Level Transient Spectroscopy of Interface States in ZnO/PrCoOx/ZnO Thin-Film Junctions
Authors: Yano Yoshihiko , Yukihiko Shirakawa Yukihiko Shirakawa , Hisao Morooka Hisao Morooka
Published: February 2005

Deep-level transient spectroscopy is successfully applied to detect interface states in ZnO/PrCoO
x
/ZnO thin-film junctions. The interface state is measured at 0.70 eV below the conduction-band edge. The junctions are equivalent to a model of a single grain boundary in a ceramic varistor.
Gas-Phase Nucleation in an Atmospheric Pressure Chemical Vapor Deposition Process for SiO2 Films Using Tetraethylorthosilicate (TEOS)
Authors: Adachi Motoaki , Okuyama Kikuo , Tohge Noboru , Shimada Manabu , Satoh Jun-ichi , Muroyama Masakazu
Published: February 2005

Formation of a SiO2 film on a substrate and generation of particles in the gas phase were examined simultaneously in an atmospheric-pressure chemical vapor deposition (APCVD) process using tetraethylorthosilicate (TEOS). The furnace temperature range where SiO2 films can be prepared without particle generation was found to be 700-740°C. The particles generated from the APCVD process were spherical, amorphous, and had a diameter smaller than 60 nm. The Fourier transform infrared and thermal desorption spectra showed that the particles contained a small amount of an ethoxy group and a relatively large amount of a hydroxyl group.
A New Type of Tunnel-Effect Transistor Employing Internal Field Emission of Schottky Barrier Junction
Authors: Hattori Reiji , Akihiro Nakae Akihiro Nakae , Junji Shirafuji Junji Shirafuji
Published: February 2005

A new type of tunnel-effect transistor, which has nearly the same structure as conventional metal-oxide-silicon field-effect transistors (MOSFET's) except for a Schottky barrier source contact and a low resistivity channel layer, has been proposed. The structure has the advantage of an easy fabrication process and is capable of submicron channel length without the short channel effect. In the proposed device the drain current is controlled by the gate bias through the tunnel injection of electrons at the Schottky barrier source contact. A 2-D device simulation has shown that this device can have a high transconductance of 138 mS/mm at a drain voltage of 2 V.
Flux Creep Characteristics after High-Temperature Magnetization in YBaCuO Superconductor
Authors: Sakamoto Nobuyoshi , Matsushita Tadahiro Akune
Published: February 2005

Flux creep characteristics at an operating temperature T
o have been investigated experimentally after temperature changes from the critical state, which were created by cooling a YBaCuO superconductor magnetized at higher temperatures T
o+ΔT (HTM). Drastic reduction in the creep rate by one order of magnitude was observed for ΔT\gtrsim3 K at T
o ranging from 40 to 77 K. A transient state with high HTM creep rate has also been observed at high operating temperature and is ascribed to flux profile variations induced by strengthened diamagnetic properties at low temperatures.
Electron Energy-Loss Spectra of Carbon Nanotubes
Authors: Kuzuo Ryuichi , Masami Terauchi Masami Terauchi , Michiyoshi Tanaka Michiyoshi Tanaka
Published: February 2005

Carbon nanotubes were investigated by means of electron energy-loss spectroscopy. Two peaks due to the π plasmon and the π+σ plasmon were observed. The energy of the π+σ plasmon peaks varied from 22.0 eV to 24.5 eV, which roughly agrees with the average plasmon energy of graphite. A shoulder due to single electron excitations was observed at 13 eV, which was not observed in graphite. There were two kinds of nanotubes which exhibited their respective π plasmon peaks at 5.2 eV and 6.4 eV. The peaks in the dielectric function obtained by Kramers-Kronig analysis of the spectra were broader than those of graphite probably due to the curving of the graphitic sheets.
Preparation of Thin Single Crystals of Diacetylene by Pseudo-Homo Epitaxy
Authors: Komatsu Kyoji , Okada Shuji , Hattori Yasuhiro , Matsuda Hiro , Minami Nobutsugu , Oikawa Hidetoshi , Katsumichi Ono Katsumichi Ono , Hachiro Nakanishi Hachiro Nakanishi
Published: February 2005

Thin single-crystal growth of diacetylene monomer between a substrate and a glass plate has been investigated from the molten state. Among five different substrates examined, polydiacetylene single crystal, having the characteristics of pseudo-homo epitaxy, attained the best performance of growth control to give thin single crystals with the size of over one mm2 as well as uniaxial orientation. The crystals were successfully converted into polymer thin single crystals, which were usefull enough for nonlinear optical device fabrication.
Normal-Incidence X-Ray Microscope for Carbon Kα Radiation with 0.5 µm Resolution
Authors: Murakami Katsuhiko , Oshino Tetsuya , Nakamura Hiroshi , Masayuki Ohtani Masayuki Ohtani , Hiroshi Nagata Hiroshi Nagata
Published: February 2005

An X-ray imaging microscope experiment was performed using Schwarzschild-type normal-incidence X-ray optics (×32, NA0.2) and 44.8 Å carbon Kα radiation. NiCr/C multilayers were employed for normal-incidence mirrors at this wavelength. A magnified image of a 1000 lines/mm transmission grating was taken on film and a 0.5 µm-wide pattern was successfully resolved.
Ge Distribution in Gen/Sim Strained-Layer Superlattices
Authors: Miki Kazushi , Unoki Shigeyuki , Matsuhata Hirofumi , Kunihiro Sakamoto Kunihiro Sakamoto , Tsunenori Sakamoto Tsunenori Sakamoto
Published: February 2005

Ge
n
/Si
m
strained-layer superlattices (SLSs) grown by molecular beam epitaxy were investigated by the X-ray diffraction method. The diffraction intensities of Ge4/Si12 SLSs were analyzed with surface segregation models. It has been found that surface segregation does not involve 1 ML but 2-3 ML of the Ge top layer, and that the smearing decay length is about 4.5 ML.
Photogeneration and Transport of Carriers in Strained Si1-xGex/Si Quantum Well Structures
Authors: Fukatsu Susumu , Noritaka Usami Noritaka Usami , Yasuhiro Shiraki Yasuhiro Shiraki
Published: February 2005

Generation and transport of carriers in strained Si1-x
Ge
x
/Si quantum well structures were investigated by photoluminescence measurement with varying temperature and excitation power. It was found that the majority of carriers giving luminescence were produced inside the substrate beyond 1 µm and subsequently transported to the quantum wells on the surface side when a visible wavelength excitation source was used. Consequently, the emission of the quantum well closest to the substrate dominated the spectrum under a low excitation condition. In contrast, the emissions of the quantum wells on the surface side were observed at higher temperatures or under intense photopump. The evolution of surface-side quantum well emission is interpreted in terms of carrier escape out of the substrate-side quantum well in the form of either thermal jump to the barrier band-edge or overflow due to population saturation.
Doping Profile Measurement of a Bonded Silicon-on-Insulator Wafer by Capacitance-Voltage Measurements
Authors: Nagai Kiyoko , Hidetaka Takato Hidetaka Takato , Yutaka Hayashi Yutaka Hayashi
Published: February 2005

Doping profile of a silicon-on-insulator (SOI) wafer formed by a direct bonding method was analyzed for the first time by capacitance-voltage (C-V) measurement techniques. The analysis is an extension of the conventional metal-oxide-semiconductor (MOS) diode theory based on nonuniform dopant impurity distribution. Boron concentration of the substrate (non-oxidized wafer) near the Si/SiO2 interface was higher than that of the bulk. Boron absorption into the oxide from both surfaces of the substrate and SOI layer was suggested.
Velocity Selective Absorption by a Long Lifetime Transition in a Ca Atomic Beam
Authors: Riehle Fritz , Morinaga Atsuo , Ishikawa Jun , Takayuki Kurosu Takayuki Kurosu , Nobuhiko Ito Nobuhiko Ito
Published: February 2005

Velocity-selective absorption by a long lifetime transition in a calcium atomic beam has been measured for two spatially separated counterpropagating laser beams. The observed variation of the absorbed power as well as of the Lamb dip depth with laser power and with velocity of the atoms is in agreement with calculations of Rabi cycles.
Numerical Study on Mode Structure of an Optically-Pumped 385 µm D2O Laser
Authors: Sasaki Koichi , Matsuoka Kanji , Masaaki Nagatsu Masaaki Nagatsu , Takashige Tsukishima Takashige Tsukishima
Published: February 2005

The temporal variation of the mode structure of an optically-pumped 385 µm D2O laser is studied numerically. A semiclassical laser theory is adopted to investigate coherent interaction between the laser fields and D2O molecules. The pump field is assumed to be a monochromatic emission of a pulsed CO2 laser at the 9R(22) transition line. Mode-shift phenomena are observed in the present numerical simulation, which have also been observed in the experiment.
Anomalous Hydrodynamic Behavior of Lyotropic Smectic Phases of Hydrated Phospholipid at Low Frequencies
Authors: Yamamoto Jun , Yuka Tabe Yuka Tabe , Koji Okano Koji Okano
Published: February 2005

We measured the frequency dependence of the longitudinal viscosity and the layer compression modulus of homeotropically aligned multilamellar film of hydrated dimyristoyl phosphatidylcholine (DMPC) at low frequencies from 10 Hz to 1 kHz, varying temperature (T) and relative humidity (RH) systematically. We have, for the first time, demonstrated unambiguously that in the L
α phase (the lyotropic smectic-A phase) the longitudinal viscosity diverges as 1/ω when the circular frequency goes to zero. In addition, we were able to construct the T-RH phase diagram of the L
α-L
β′
transition of hydrated DMPC, based upon the T and RH dependences of the layer compression modulus. The phase boundary thus determined agreed well with that obtained by X-ray scattering by Smith et al. (J. Chem. Phys. 92 (1990) 4519).
The Choke Mode Cavity
Authors: Tsumoru Shintake Tsumoru Shintake
Published: February 2005

A new simple RF structure is proposed for damped accelerating cavities in linear and circular particle accelerators. Almost all of the beam-induced higher-order modes are heavily damped through a radial transmission line terminated with a matched load. The accelerating mode is established by means of an imaginary short due to a choke structure. Preliminary measurements showed good damping properties, while a high Q accelerating mode was maintained. Because the structure has axial-symmetry, it is easy to fabricate, and is especially suitable for mass production of the disk-loaded accelerating structures for future e+e- linear colliders.
Observation of Wet Biological Specimen by Soft X-Ray Microscope with Zone Plates at UVSOR
Authors: Watanabe Norio , Taniguchi Mieko , Shimanuki Yoshio , Sugiyama Masaru , Ohba Akira , Kihara Hiroshi
Published: February 2005

With an environmental chamber (wet cell) using polypropylene foils as windows, wet specimens were observed at a wavelength of 4.6 nm with a zone plate imaging X-ray microscope installed at the beamline 8 A of UVSOR (synchrotron radiation facility at Institute for Molecular Science, Okazaki, Japan). Images of spicule of trepang, human blood cells and cultured protoplast of plant cell stained by methyl mercury were observed with good contrast.
Study of Radiation-Induced Reactions in Chemically Amplified Resists for Electron Beam and X-Ray Lithography
Authors: Kozawa Takahiro , Yoshida Yoichi , Tagawa Mitsuru Uesaka
Published: February 2005

The radiation-induced reactions of the onium salts in model compound solutions of chemically amplified electron beam (EB) and X-ray resists have been studied by means of nanosecond pulse radiolysis. It is found that the onium salts scavenge electrons and promote the generation of proton adducts. On the basis of experimental results, the reaction mechanisms of the chemically amplified EB and X-ray resists have been estimated. It can be presumed that proton adducts of basepolymers play an important role in acid generation.
Light-Induced Degradation and Recovery of Visible Photoluminescence in Porous Silicon
Authors: Nishitani Hikaru , Nakata Hiroyasu , Fujiwara Yasufumi , Tyuzi Ohyama Tyuzi Ohyama
Published: February 2005

We have investigated the light-induced degradation of visible photoluminescence (PL) and its recovery in porous silicon. It has been found that the exposure of the porous sample to UV and visible laser light results in the drastic quenching of the PL intensity. Furthermore, the PL intensity in the photodegraded sample is effectively recovered by annealing at low temperature up to 200°C, rather than by HF etching. Based on the recovery behavior of the PL fatigue through the low-temperature annealing, the origin of the visible luminescence in porous silicon is discussed.
Cracking of Saturated Hydrocarbon Gas Molecular Beam for Carbonization of Si(001) Surface
Authors: Yoshinobu Tatsuo , Mitsui Hideaki , Tarui Yoichiro , Takashi Fuyuki Takashi Fuyuki , Hiroyuki Matsunami Hiroyuki Matsunami
Published: February 2005

Carbonization of Si(001) surfaces by saturated hydrocarbon gas molecular beams in a high vacuum was carried out employing a thermal cracking technique. In the case of C3H8 and C2H6, the Si surfaces were carbonized at 750°C with a cracking temperature of 1300°C, and 3C-SiC layers were obtained. Decomposition of C3H8 by cracking was observed in quadrupole mass analyzer (QMA) measurements. In the case of C2H6, the effect of cracking was less obvious, and decomposed species were not observed except for H2 in QMA measurements. In the case of CH4, no effect of cracking was observed. This result seems to be related to the difference in the bond strengths of molecules.
On the Irreversibility Line in Superconductors
Authors: Kazuo Watanabe Kazuo Watanabe
Published: February 2005

The irreversibility lines have been comparatively investigated for conventional commercial (Nb, Ti)3Sn and high-TcY1Ba2Cu3O7superconductors. It is found that for both superconductors the irreversibility line obtained in magnetization measurements is related to the flux depinning fieldB*at which the transport critical current goes to zero. The relationship between the flux lattice melting and the flux depinning is proposed from the viewpoint of the field and temperature (B,T) phase diagram.
Fabrication of Step-Edge Junctions on the Concave or Convex Side of YBa2Cu3O7-x Film
Authors: Sugiura Masayuki , Kato Kei , Kunihiro Asada Kunihiro Asada , Takuo Sugano Takuo Sugano
Published: February 2005

Step-edge junctions using YBa2Cu3O7-x
(YBCO) film are fabricated with two types of patterns. One has the bridge structure only at the concave side of the edge and the other, only at the convex side. The steps are fabricated by etching MgO substrates with hydrochloric acid solution, and YBCO films are deposited using rf-sputtering and subsequent annealing. It is shown from the current-voltage (I-V) characteristics of these patterns at 4.2 K that the grain boundary required for the formation of step-edge junctions tends to be built up on the convex side of the step.
Visualization of Remanent Polarization in Ferroelectric Film and Its Application-Image Recording with Ferroelectric Film (II)
Authors: Guo Yufeng , Hoshino Katsuyoshi , Kokado Jun-ichi Hanna
Published: February 2005

A new technique for visualizing a remanent polarization (Pr) of the ferroelectric film was discovered: the oriented dipoles in the uniformly corona-poled thin film of a copolymer of vinylidene fluoride and tetrafluoroethylene (poly(VDF-TFE)) were visualized by using charged particles as the toner: the direction of the spontaneous polarization could be determined by the polarity of the toner. With this technique we illustrated the reorientation of the dipoles in a thermally depolarized area of the poled film as a function of time. Moreover we have applied this technique to the image recording system previously reported and have succeeded in simplifying the processes of the system and improving the memory lifetime markedly, up to 72 h.
Thermodynamical Models for Phase Changes between Tetragonal and Cubic Phases in ZrO2-CeO2 Solid Solution
Authors: Masatomo Yashima Masatomo Yashima , Masahiro Yoshimura Masahiro Yoshimura
Published: February 2005

The Gibbs energies of cubic (c-) and tetragonal (t-) phases in pseudobinary solid solutions of Zr1-X
Ce
X
O2 were assessed by two models. A regular solution model in which the Gibbs energy differences between c- and t-phases of end members were assumed to be linear functions of temperature, could not explain simultaneously the stable and metastable phase diagrams. A mathematical expression on the basis of Landau's theory for the second-order phase transition explained both of them.
A Theoretical Growth Curve of Defect Formation for Electron Spin Resonance and Thermoluminescence Dating
Authors: Motoji Ikeya Motoji Ikeya
Published: February 2005

A new method for evaluating the total dose of natural radiation (TD) directly from the theoretical growth curve of defect formation is proposed for dating and dosimetry with electron spin resonance (ESR) or thermoluminescence (TL). The defect production efficiency, a, and the insensitive volume around a defect, b, are evaluated from the growth curve by means of an additive dose at a high dose rate D
′ in the laboratory. The real TD is obtained from the growth curve calculated by solving the equation dn/dt=a
D(1-b
n/N
0)-n/τ-λn
2, where D is a natural dose rate, and τ and λ are the parameters for the first- and second-order annealing.
Behavior of Excess Arsenic in Undoped, Semi-Insulating GaAs during Ingot Annealing
Authors: Suemitsu Maki , Terada Koji , Masaaki Nishijima Masaaki Nishijima , Nobuo Miyamoto Nobuo Miyamoto
Published: February 2005

Densities of EL2 and other shallower intrinsic donors in undoped, semi-insulating GaAs crystals have been investigated before and after thermal treatments using infrared absorption, nuclear-magnetic resonance, and photoluminescence measurements. After annealing for 12 h at 1100°C, EL2 showed a decrease by 25-35%, while half of this reduction was recovered by a subsequent 800°C-0.5 h annealing. The total density N
XD for the shallower donors behaved quite conversely, maintaining the sum [EL2]+N
XD almost unchanged. This substantial conservation of the total donor density is understood by a rearrangement of dissolved excess arsenic atoms.
Effects of Optical Confinement in Textured Antireflection Coating using ZnO Films for Solar Cells
Authors: Takato Hidetaka , Yamanaka Mitsuyuki , Hayashi Yutaka , Shimokawa Ryuichi , Hide Ichiro , Gohda Shinji , Nagamine Fumiaki , Tsuboi Hideyuki
Published: February 2005

The effect of optical confinement in textured antireflection coating (AR coating) was investigated. Textured ZnO films prepared by metalorganic chemical vapor deposition were applied to solar cells as AR coating. The reflectance of the cells decreased as the grain size increased with film thickness, especially at long wavelength. This reduction in the reflectance caused an increase in short-circuit current and spectral response of the cells at near-infrared. The effect of optical confinement in the cell by this film was shown as far as long-wavelength range was concerned.
Improvement in the Output Characteristics of a Large-Bore Copper Vapor Laser by Hydrogen
Authors: Hayashi Kazuo , Iseki Yasushi , Suzuki Setsuo , Watanabe Ikuo , Etsuo Noda Etsuo Noda , Osami Morimiya Osami Morimiya
Published: February 2005

It has been experimentally confirmed that addition of about 1% hydrogen gas to the copper vapor laser (CVL) discharge improves the output characteristics of a large-bore CVL with 80 mm beam diameter and 1500 mm discharge length. The annular distribution of the beam intensity became uniform and the output power increased. The increase in the green laser power was larger than that in the yellow one. The hydrogen gas addition was effectual when the input power to the discharge was large and the copper temperature was high. A 120 W output power was obtained continuously for 26 hours.
Characterization of Depletion-Type Surface Tunnel Transistors
Authors: Tetsuya Uemura Tetsuya Uemura , Toshio Baba Toshio Baba
Published: February 2005

A depletion-type Surface Tunnel Transistor (D-STT) is proposed to increase the tunneling current compared to that of the enhancement-type STT (E-STT) previously reported. The most important feature of the D-STT is the use of a modulation doped structure in order to accumulate a high concentration of electrons under the gate. GaAs/AlGaAs D-STTs, which are fabricated by using an MBE regrowth technique, exhibit depletion-mode transistor action with a larger operation current than that displayed by the E-STT. This increase in current is due to a higher two-dimensional electron gas concentration at the i-GaAs surface. Moreover, the high gate leakage current which limits GaAs E-STT operation is reduced in the case of the D-STT by a factor of 106.
Texture Structure Analysis and Crystalline Quality Improvement of CeO2(110) Layers Grown on Si(100) Substrates
Authors: Inoue Tomoyasu , Ohsuna Tetsu , Yamada Yoshinori , Wakamatsu Kiyoshi , Itoh Youichi , Nozawa Takayuki , Sasaki Eiji , Yamamoto Yasuhiro , Sakurai Yoshinobu
Published: February 2005

The texture structure of epitaxially grown CeO2(110) layers on Si(100) substrates was investigated using high-resolution electron microscopy. Surface morphology observations using high-resolution secondary electron microscopy indicated that the layer reveals a surface morphology with stripes aligned in two perpendicular directions. High-resolution transmission electron microscopy analysis verified that the crystallographic in-plane directions of the two kinds of domains correlated with the two directional stripes are exactly perpendicular to each other. The texture structure is well explained crystallographically by the model, which has been proposed by the authors. It is found that silicon substrates with off-orientation of ∼0.17° lead to the predominance of one kind of stripes, which are aligned in the off-orientation direction. On the other hand, the population of the two kinds of stripes are nearly equal in the layer grown on substrates without off-orientation. The crystalline quality of the former is significantly improved, as normalized minimum yields in the ion channeling analysis of the former are more than 27% smaller than that of the latter.
Ti/Pt/Au Ohmic Contacts to n-Type ZnSe
Authors: Miyajima Takao , Hiroyuki Okuyama Hiroyuki Okuyama , Katsuhiro Akimoto Katsuhiro Akimoto
Published: February 2005

We report that a Ti/Pt/Au multilayered metal structure can make a nonalloy ohmic contact to n-type ZnSe with an electron concentration greater than 1019 cm-3. A specific contact resistance as low as 3.4×10-4 Ω-cm2 was achieved for Cl-doped ZnSe with an electron concentration of 2×1019 cm-3. We think that the lower contact resistance can be ascribed to the higher reactivity and adhesion of Ti metal with the surface of ZnSe at low temperature, and to the lower work function of Ti metal. The dominant current flow may be due to the quantum mechanical tunneling of electrons through the potential barrier at the ZnSe surface, because the specific contact resistance decreases with an increase in the electron concentration. A small improvement in the specific contact resistance was made by thermal annealing at a temperature of 250°C for 5 min, which yielded the lowest value of 1.1×10-4 Ω-cm2. With annealing at 300°C and below, the contact resistance was not drastically increased. The electrical properties of the contact are therefore thermally stable up to 300°C.
Structured Photoluminescence Spectrum in Laterally Anodized Porous Silicon
Authors: Fujiwara Yasufumi , Nishitani Hikaru , Nakata Hiroyasu , Ohyama Tyuzi
Published: February 2005

Visible photoluminescence (PL) has been systematically investigated in laterally anodized porous silicon. The PL peak position was dependent on the distance from the meniscus and shifted towards a shorter wavelength with increasing anodization current density. A PL spectrum exhibiting several structures was observed inside the mirrorlike region on the sample surface, which was interpreted by multiple reflection of the luminescence, not by the quantum size effects. Through the analysis of the PL spectrum, the Si density of the porous layer was roughly estimated to be 37% by means of the effective-medium model.
The Amplification Properties of a Highly Er3+-Doped Phosphate Fiber
Authors: Nishi Toshihiro , Nakagawa Koichi , Yasutake Ohishi Yasutake Ohishi , Shiro Takahashi Shiro Takahashi
Published: February 2005

The amplification properties of a highly Er3+-doped phosphate fiber were measured. Gain was observed in the wavelength region of 1.525-1.57 µm and the wavelength at maximum gain was 1.535 µm. Since the absorbed pump threshold obtained experimentally agreed with the calculated result, no cooperative upconversion process occurred in the 1.53 wt% Er2O3 fiber.
Thermal Chemical Vapor Deposition of Diamond from Methane-Hydrogen Gas System Pyrolized at Low Temperature (1450°C)
Authors: Kondoh Eiichi , Ohta Tomohiro , Tohru Mitomo Tohru Mitomo , Kenichi Ohtsuka Kenichi Ohtsuka
Published: February 2005

Thermal chemical vapor deposition (CVD) of diamond using a nozzle or a plate heated at much lower temperature than a conventional hot filament CVD was reported. The lowest temperature achieved for the pyrolysis of the material gas was 1450°C for the methane-hydrogen mixture system. The gas-phase chemistry was then discussed in relation to both the experimentation and the corresponding numerical simulation.
34 GHz Bandwidth GaAs High-Speed Schottky Barrier Photodiode Fabricated by Chemical-Beam Epitaxy
Authors: Sekiguchi Youichi , Kuwahara Tohru , Fumihiko Kobayashi Fumihiko Kobayashi , Shinji Iio Shinji Iio
Published: February 2005

A high-speed, high-sensitivity GaAs Schottky barrier photodiode grown by chemical-beam epitaxy (CBE) has been designed, fabricated, and characterized. Antireflection coatings utilizing Si and SiO2 films were optimally used to minimize reflection loss, thereby significantly improving sensitivity of the Schottky barrier photodiode. This device has a -3 dB cutoff frequency of 34 GHz, determined by an optical heterodyne technique, an external quantum efficiency of 41% at 780 nm wavelength, and a dark current of 100 pA (V
R=-2 V).
Temperature Dependence of Nucleation Density of Chemical Vapor Deposition Diamond
Authors: Hayashi Yasuaki , Drawl William , Messier Russel
Published: February 2005

The temperature dependence of the nucleation density of Chemical Vapor Deposition diamond was carefully investigated by ellipsometric monitoring. Substrates were pre-treated by rubbing with diamond powder and then by wiping off the residual powder until visually clean. Nucleation density was greater than 1010/cm2 in some ranges of temperature. It was also observed that nucleation density increased suddenly to 860°C and then gradually decreased in the range of higher temperatures. The results were explained by a change in the adsorption state of the precursor, from a physical to a chemical.
Solid Electrolyte Carbon Dioxide Sensor Using Sodium-Ion Conductor and Li2CO3-BaCO3 Electrode
Authors: Yao Sheng , Shimizu Youichi , Norio Miura Norio Miura , Noboru Yamazoe Noboru Yamazoe
Published: February 2005

A sodium-ion conductor (Na3Zr2Si2PO12: NASICON)-based CO2 sensor using a Li2CO3-BaCO3 electrode responded very well to CO2 in air over a wide temperature range of 270-600°C. The sensor responses, electromotive force (EMF), to varying partial pressure of CO2(P
CO2
) were in accordace with a 2-electron reaction of CO2. On the other hand, the sensor response to a fixed P
CO2
(2×10-3 atm) was almost independent of partial pressure of O2(P
O2
) at temperatures above 450°C, while at 305°C and below, it depended on P
O2
in a manner similar to a 2-electron reactionof O2. Thus, two types of sensing electrode reactions were indicated to occur depending on working temperature.
Scanning SCANIIR (Surface Composition Analysis by Neutral and Ion Impact Radiation) Microscope
Authors: Inoue Masahiko , Kunitomo Shinta , Satoshi Nishigaki Satoshi Nishigaki , Tamotsu Noda Tamotsu Noda
Published: February 2005

A scanning SCANIIR (surface composition analysis by neutral and ion impact radiation) microscope for lateral and in-depth composition analysis of insulators has been developed, employing a photon counting technique with a ratemeter. The spatial resolution of this system was estimated to be about 30 µm by observing Cu(I) 324.8-nm photon images of a 200-mesh circular-type Cu grid. The depth profile of a SiO2/Si interface was depicted using a Si(I) 288.2-nm photon, which yields in-depth resolution of approximately 40 nm.
Single-Shot Measurement of Spectral Reflectance of a Soft X-Ray Multilayer Mirror Using a Laser-Plasma X-Ray Source
Authors: Azuma Hirozumi , Watanabe Yoshihide , Kato Yoshiaki , Motohiro Tomoyoshi , Murai Shoji Noda
Published: February 2005

We propose a new experimental arrangement to measure spectral reflectance of multilayer coatings in the soft X-ray region in a single laser shot, where laser-produced plasma is used as a light source. Reflectivity measurement of a Mo/Si multilayer having a 2d spacing of 24 nm is presented.
Study of Low-Temperature Oxidation in Au/Si and Cu/Si Systems by 7-MeV Alpha Particle Backscattering Analysis
Authors: Li Jian , Hiroki Yonezawa Hiroki Yonezawa , Toshio Shigematsu Toshio Shigematsu
Published: February 2005

Low-temperature oxidation kinetics in the Au/Si and Cu/Si systems was measured by a 7-MeV alpha backscattering technique. The formation of a Si oxide layer near the surface in the Au/Si system is mainly controlled by intermixing between the Au and Si substrates. The formation of thick SiO2 in the Cu-Si interface at room temperature is a catalytic process due to the presence of a Cu3Si compound.
Epitaxial Growth and Properties of Ca1-xSrxCuO2 Thin Film (x=0.18 to 1.0) Prepared by Co-Deposition and Atomic Layer Stacking
Authors: Li Xiaomin , Kanai Masaki , Tomoji Kawai Tomoji Kawai , Shichio Kawai Shichio Kawai
Published: February 2005

Thin films of Ca1-x
Sr
x
CuO2 have been prepared on SrTiO3 (100) substrates by co-deposition of all elements and successive stacking of atomic layers. When all the elements are deposited simultaneously, Ca1-x
Sr
x
CuO2 films can be formed only within the narrow range of Sr concentration near x=0.2. On the other hand, by stacking atomic layers of Ca(Sr)O
x
and CuO
x
, the appropriate range becomes much wider and the formation of an infinite layer structure becomes possible, even in Ca free composition, SrCuO2. For the SrCuO2 thin film, a diamagnetic transition and decrease of resistance have been observed at 65 K.
Gamma Irradiation Effect on the Transport Critical Current Density of a Bi1.5Pb0.5Sr2Ca2Cu3Ox Ceramic
Authors: Shiraishi Kensuke , Sakamoto Hiroshi , Yano Koichi , Otoguro Yasuo
Published: February 2005

A Bi1.5Pb0.5Sr2Ca2Cu3O
x
ceramic was sequentially irradiated with 60Co γ-rays at a dose rate of 2.0 MR·h-1 up to a dose of 24 MR at ambient temperature, and the transport critical current density was measured as a function of temperature. The critical current density in zero field was decreased by 2 MR irradiation at temperatures below 65 K, and the radiation effect was more prominent at lower temperature. The radiation effect was enhanced and extended to higher temperature upon further irradiation; the decrease in the critical current density was apparent at temperatures below 77 K after γ-irradiation to 24 MR.
Magnetic Penetration Depths and Normal-State Resistivities of Epitaxial and Polycrystalline NbCxN1-x Films
Authors: Kohjiro Satoshi , Akira Shoji Akira Shoji , Shogo Kiryu Shogo Kiryu
Published: February 2005

We have studied the magnetic penetration depth λ and the normal-state resistivity ρ of epitaxial and polycrystalline NbC
x
N1-x
films as a function of film thickness t and sputtering gas pressure P during the deposition of the films. It was found that λ(∼200 nm) and ρ(∼50 µΩ·cm) of epitaxial films are almost independent of P and t, while λ(>300 nm) and ρ(>110 µΩ·cm) of polycrystalline films increase considerably with increasing P(>2 Pa) or decreasing t(<80 nm). The pressure and thickness dependence of λ and ρ of polycrystalline films can be explained by a model of Josephson coupling between grains.
Artificial Grain Boundary Junctions in BiSrCaCuO Thin Films with (11n) and (001) Orientation
Authors: Takami Tetsuya , Kuroda Ken'ichi , Kojima Kazuyoshi , Wada Osamu , Tanimura Junji , Kataoka Masayuki , Ogama Tetsuo , Koichi Hamanaka Koichi Hamanaka
Published: February 2005

Artificial grain boundary junctions in sputtered BiSrCaCuO films on SrTiO3 (110) substrates have been fabricated by controlling the orientation of the films using a MgO buffer layer. A grain boundary with large twist misorientation is formed along the edge of the MgO buffer layer that is placed perpendicular to the [001] direction of the SrTiO3 substrate. The grain boundary junctions thus obtained exhibited clear Shapiro steps in response to microwave irradiation (15.7 GHz). This indicates that the artificial grain boundaries obtained by controlling the orientation of the BiSrCaCuO films behave as a weak link.
Third-Order Optical Nonlinearities in Porphyrins with Extended π-Electron Systems
Authors: Hosoda Masahiro , Wada Tatsuo , Anthony F. Garito Anthony F. Garito , Hiroyuki Sasabe Hiroyuki Sasabe
Published: February 2005

The third-order optical susceptibilities |χ1111
(3)(-3ω; ω, ω, ω)| for spin-coated films of free-base (H2) and MnCl-octaethyl[18]porphyrins, and N,N′,N′′,N′′′-tetramethyl-octaethyl[26]porphyrin-bistrifluoroacetate are determined by optical third-harmonic generation measurements at a wavelength of 1907 nm. The |χ(3)| values are 1.9×10-12, 2.6×10-12, and 1.0×10-11 esu for H2-[18]porphyrin, MnCl-[18]porphyrin, and [26]porphyrin, respectively. The enhancement of third-order nonlinear properties in macrocyclic compounds is discussed in terms of an extended π-electron system.
Substrate Temperature Dependence of Transparent Conducting Al-Doped ZnO Thin Films Prepared by Magnetron Sputtering
Authors: Minami Tadatsugu , Sato Hirotoshi , Hideyuki Imamoto Hideyuki Imamoto , Shinzo Takata Shinzo Takata
Published: February 2005

A technique is demonstrated that improves the substrate spatial distributions of resistivity and film thickness of transparent conducting oxide thin films prepared using a conventional dc planar magnetron sputtering method. The spatial distributions of Al-doped ZnO (AZO) films are markedly improved by deposition onto substrates at temperatures above 300°C. Large-area AZO films with a resisitivity of 3-6×10-4 Ω·cm can be produced at a substrate temperature of 350°C.
Photo-Chemical Vapor Deposition of Al2O3 Thin Films with High Quantum Yield
Authors: Fukushima Yasumori , Higashino Tomohiko , Nobuo Matsumura Nobuo Matsumura , Junji Saraie Junji Saraie
Published: February 2005

Photo-Chemical Vapor Deposition (CVD) of Al2O3 thin films has been studied under low-pressure Hg lamp irradiation. The source material was aluminum-tri-isopropoxide. Under oxygen atmosphere the deposition rate was constant and about 200 Å/min in the temperature range of 230-360°C. The deposition rate showed saturation as the UV light intensity was increased, and the apparent quantum yield was found to be roughly close to unity. The interface state density of the Al/Al2O3/p-Si MIS structure was very low, which indicates the usefulness of low-temperature deposition.
Measurement of the Cl Atom Concentration in RF Chlorine Plasmas by Two-Photon Laser-Induced Fluorescence
Authors: Ono Kouichi , Tatsuo Oomori Tatsuo Oomori , Mutumi Tuda Mutumi Tuda
Published: February 2005

Two-photon laser-induced fluorescence has been employed to measure atomic chlorine concentrations in rf and rf magnetron discharges in Cl2. The spin-forbidden Cl transition 3p44sp(4S3/2o)←3p5(2P3/2o) was excited by two-photon absorption of 233.2-nm laser light, and the fluorescence decay to the 3p44s(4P5/2) level was observed at 725.6 nm. The same 233.2-nm laser radiation in low-pressure CCl4gases was found to induce relatively strong fluorescence of atomic Cl, resulting from laser-induced photodissociation followed by two-photon excitation. These fluorescence intensities in Cl2plasmas and CCl4gases were compared with the help of a rate equation analysis, to achieve absolute calibration.
Observation of the Ca 4s1S0-4p3P1 Transition in Continuous Free-Falling Cold Atomic Flow from an Atom Trap
Authors: Kurosu Takayuki , Makoto Morinaga Makoto Morinaga , Fujio Shimizu Fujio Shimizu
Published: February 2005

The 4s1S0-4p3P1 spectrum of Ca is observed using cold atoms continuously falling from a magneto-optical trap. The 4s1S0-4p3P1 and 4s1S0-4p1P1 transitions are alternately excited at a point 8 cm below the trap. From the depletion of the blue fluorescence in the 1S0-1P1 transition, the absorption signal of the 1S0-3P1 line is obtained.
Visible Observation of Metastable Helium Atoms Confined in an Infrared/Visible Double Resonance Trap
Authors: Mitsutaka Kumakura Mitsutaka Kumakura , Norio Morita Norio Morita
Published: February 2005

Using a visible probe laser exciting the 2p3P2→3d3D3 transition (λ=588 nm), we have demonstrated a visible observation of metastable He atoms magnetooptically trapped by an infrared laser resonant with the 2s3S1→2p3P2 transition (λ=1083nm). Detecting visible resonance fluorescence, only 104 atoms confined in a trap with a diameter of 1 mm have been sensitively observed even with the naked eye. It has been found that under a given condition the visible laser operates as a trapping laser and considerably extends the capture range of infrared laser detuning.
Phonon Effect on the Superconducting Transition Temperature of a Small Particle
Authors: Akira Tamura Akira Tamura
Published: February 2005

Using an elastic vibration model for phonons of a small metallic particle, size dependence of the superconducting transition temperature T
c is derived. It is shown that enhancement of T
c with decrease in particle size stems mainly from the associated increase of surface modes contribution. Comparison is made with other treatments and inconsistencies are noted.
Picosecond Repetitive Optical Switching Using Type II AlGaAs/AlAs Multiple Quantum Well Structures
Authors: Tomobumi Mishina Tomobumi Mishina , Yasuaki Masumoto Yasuaki Masumoto
Published: February 2005

Highly repetitive picosecond optical switching operation is demonstrated at room temperature using type II AlGaAs/AlAs multiple quantum well structures. The type II system realizes both large optical nonlinearity and rapid recovery of absorption saturation. More than 10 successive lps optical switchings are observed with a 12 ps interval at the energy density level of ∼1 µJ/cm2. The repetitive optical switching operation is based on the balance between the bleaching due to the phase space filling and the induced absorption caused by real space charge transfer.
Control of Polymer Orientation in Polymer Dispersed Liquid Crystal (PDLC)
Authors: Eiji Shimada Eiji Shimada , Tatsuo Uchida Tatsuo Uchida
Published: February 2005

It is considered that electrooptical properties of polymer dispersed liquid crystal (PDLC) strongly depend on the polymer network structure. Therefore, we have tried to control the orientation of the polymer network of PDLC, and we succeeded by means of photopolymerization of the nematic phase mixture of the monomer and liquid crystal material. In addition, the liquid crystal in the PDLC was roughly aligned parallel to the extended direction of the polymer network. This result predicts that uniform alignment of liquid crystal can be obtained by optimizing the polymerization condition.
Effect of Si Doping on Epitaxial Lateral Overgrowth of GaAs on GaAs-Coated Si Substrate
Authors: Seiichi Sakawa Seiichi Sakawa , Tatau Nishinaga Tatau Nishinaga
Published: February 2005

By adding an impurity, a GaAs(001) facet was successfully formed on the misoriented substrate and epitaxial lateral overgrowth (ELO) of wide area has been achieved. The largest ELO ratio obtained was 15 and in this case, the thickness of the vertical and lateral directions were 10 µm and 150 µm respectively. Molten KOH etching showed that a dislocation-free region was obtained, except in the region above the seed opening. The width of the dislocated region depends on the growth thickness. To obtain a wide dislocation-free region, it is concluded that the vertical growth rate should be suppressed as compared with the lateral growth rate.
Weak Guidance in Bent and Unbent Four-Layer Planar Waveguides-A Comparative Study of Dispersion Curves
Authors: Choudhury P. K. , Khastgir P. , Singh S. P. Ojha
Published: February 2005

A comparative study has been made of the dispersion curves of a four-layer bent and an unbent dielectric slab waveguide under the assumption of the weak guidance approximation. It has been noticed that the introduction of a slight bend to a planar waveguide results in mode-proliferation, and lower order modes show no cutoff at all. This anomalous behaviour of the dispersion curves is not seen in the case of an unbent waveguide structure.