bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribution of Amplitudes and Time Intervals between Partial Discharges
Authors: Jiří Macur Jiří Macur , Karel Domanský Karel Domanský
Published: February 2005

Measurement of the impulse noise of partial discharges (PD) in previous paper1) has been carried out. To make a relation between obtained experimental results on discharge pulses and geometrical properties of cavities which cause partial discharges a statistical theory has been proposed.
Pd-on-GaAs Schottky Contact: Its Barrier Height and Response to Hydrogen
Authors: Heng-Yong Nie Heng-Yong Nie , Yasuo Nannichi Yasuo Nannichi
Published: February 2005

A Pd-on-GaAs Schottky contact was prepared by depositing palladium using a tungsten heater, rather than electron-beam heating, onto a GaAs surface. The interface composition was investigated by sputter Auger electron spectroscopy. An intermediate layer resulting from the reaction of Pd and GaAs was observed under certain conditions. The Schottky barrier height estimated from the measurements of forward current-voltage (I-V) or reverse capacitance-voltage (C-V) characteristics was found to depend on the interface structure. The response of the Schottky contact to hydrogen was found to be correlated with the barrier height. We pointed out that hydrogen can be used as a probe to the interface structure, whether metallic Pd or an intermediate material of Pd-Ga-As is in contact with GaAs. The observation was consistent with both p- and n-type GaAs.
Structure and Thermal Stability of Amorphous Ni84Y8Kr8 Alloy
Authors: Ratag Victor M. , Nakahigashi Nobuyoshi Wakabayashi
Published: February 2005

The structural studies of amorphous Ni84Y8Kr8 alloy have been performed by means of X-ray diffraction combined with DTA/TG, TEM and SEM experiments. The local structure of this amorphous alloy appears to be well represented by a mixture of noncrystalline microstructures with short-range interatomic distances similar to crystalline Ni9.4Y, Ni and Kr. The X-ray diffraction pattern at 300°C demonstrated the occurrence of crystallization. Initially, the diffraction peaks can be indexed as a mixture of Ni9.4Y and Ni phases, and Ni9.4Y decomposes into Ni and Ni5Y at higher temperatures. X-ray diffraction measurements exhibit the formation of solid fcc Kr bubbles or precipitates above 540°C. The rapid release of Kr does not occur below 700°C.
X-Ray Photoelectron Spectroscopy Studies of 7 K-Phase Bi-System Single Crystals
Authors: Kishida Satoru , Tokutaka Heizo , Futo Wataru , Fujimoto Hiroshi , Katsumi Nishimori Katsumi Nishimori , Naganori Ishihara Naganori Ishihara
Published: February 2005

The Bi-system single crystals with c-axis unit cell length of ∼24 Å, i.e., Bi-Sr-Cu-O (BSCO), Bi-Pb-Sr-Cu-O (BPSCO), Bi-Sr-Ca-Cu-O (BSCCO), and Bi-Pb-Sr-Ca-Cu-O (BPSCCO) single crystals, were prepared using the starting materials of various compositions by the self-flux method. X-ray photoelectron spectroscopy (XPS) measurements from the air-cleaved surfaces of the single crystals were carried out. From the results of the surface composition analyses, we found that Pb occupied a part of the Bi site in the BPSCO single crystal and Ca occupied a part of the Sr site in the BSCCO single crystal. The chemical bond natures of Sr, Cu and O in the BSCO crystal seem to be changed by doping with Pb and/or Ca.
Preparation of Bi-Pb-Ca-Sr-Cu-O Superconducting Thick Films Using Spray-Pyrolyzed Fine Powders
Authors: Tatsumisago Masahiro , Tohge Noboru , Minami Tsutomu , Okuyama Kikuo , Adachi Motoaki , Inada Yoshikazu , Kousaka Yasuo
Published: February 2005

High-T
c superconducting thick films were prepared using fine powders obtained by spray pyrolysis. The 110 K phase was predominantly formed in the films heat-treated at 855°C. The films prepared using fine powders with an average particle size of 1.4 µm showed a higher T
c(zero) of 105 K compared with those using powders of 0.8 µm.
Second-Harmonic Generation in Langmuir-Blodgett Monolayer of a Two-Dimensional Charge-Transfer Molecule: N,N′-Dioctadecyl-4,6-Dinitro-1,3-Diaminobenzene
Authors: Nalwa Hari S. , Nakajima Kenji , Watanabe Toshiyuki , Nakamura Kazushi , Yamada Akira , Seizo Miyata Seizo Miyata
Published: February 2005

A new amphiphilic dye, N,N′-dioctadecyl-4,6-dinitro-1,3-diaminobenzene (DIODD), which is capable of forming Langmuir-Blodgett (LB) films, has been synthesized and represents a model for a two-dimensional charge transfer (2-D CT) molecule. The stable Langmuir-Blodgett monolayers of a 1:1 mixture of dye and arachidic acid were deposited onto a glass substrate. The Langmuir-Blodgett monolayers exhibited a well-defined fringing pattern resulting from second-harmonic generation. These experimental results have been analyzed in connection with theoretical calculations for the model compounds. Our theoretical calculations demonstrate the superiority of two-dimensional charge transfer molecules over one-dimensional charge transfer molecules in the case in which the LB molecules incline from the normal to the substrate. The molecular orientation of the DIODD molecule is close to the optimum orientation applicable for maximizing χ111
(2). Second-order nonlinear optical susceptibilities χ111
(2) and χ133
(2) determined by analyzing the data were 2.2×10-8 and 7.7×10-9 esu, respectively at a tilt angle of 60°. This work presents the first example of a two-dimensional charge transfer molecule displaying second-harmonic generation from a Langmuir-Blodgett monolayer.
Effects of Annealing Conditions and Substrate Materials on the Superconducting Properties of Ba2YCu3O7-y Films Prepared by the Dipping-Pyrolysis Process at 750°C
Authors: Manabe Takaaki , Kondo Wakichi , Susumu Mizuta Susumu Mizuta , Toshiya Kumagai Toshiya Kumagai
Published: February 2005

Superconducting Ba2YCu3O7-y
(BYCO) films were prepared on various substrates by the dipping-pyrolysis process. The effects of annealing parameters, environment and time were also investigated. The 2-µm-thick films of BaCO3-Y2O3-CuO mixture were heat-treated at 750°C under a low-oxygen partial pressure (p(O2)=2×10-4 atm) followed by annealing under higher-p(O2) atmospheres. The resulting films showed high superconducting transition temperatures; values of T
c,onset(s)'s were 89 K on SrTiO3(100), 86 K on LaAlO3(100), 86 K on yttria-stabilized zirconia (YSZ), 83 K on MgO(100), and 76 K on sapphire.
Electro-Optics of a Twisted Nematic Liquid Crystal Display by 2×2 Propagation Matrix at Oblique Angle
Authors: Hiap Liew Ong Hiap Liew Ong
Published: February 2005

We present a new 2×2 propagation matrix for calculating the electro-optics of a liquid crystal display as a function of applied voltage and viewing angle. The 2×2 matrix method is obtained with the use of a new 2×2 propagation matrix for obliquely propagating light in a layered-inhomogeneous anisotropic medium. We show that the transmissions in a 90° twisted nematic cell at various applied voltages and viewing angles that are computed by the 2×2 matrix method are in good agreement with the experimental results and with those computed by the 4×4 propagation matrix and by the generalized geometrical optics approximation.
Transport Critical Currents of Single-Crystal YBa2Cu3O7-δ Thin Films in Weak Magnetic Fields Applied at Varied Angles to Film Surface
Authors: Aomine Takafumi , Nishizaki Terukazu , Fujii Itsuhiro , Terashima Takahito , Iijima Kenji , Hirata Kazuto , Hayashi Katsuhiko , Yamamoto Kazunuki , Bando Yoshichika
Published: February 2005

The transport critical current density J
c of single-crystal YBa2Cu3O7-δ thin films has been measured in weak magnetic fields applied at varied angles to the film surface. There are samples with the hysteresis of J
c against H and with no hysteresis. The hysteresis occurs in fields not parallel to the direction of the transport current except near the critical temperature. The presence of the hysteresis is related to the value and the temperature dependence of electrical resistivity.
Preparation and Characterization of New Sb-Containing Ternary Sulfides with Layered Composite Crystal Structure
Authors: Gotoh Yoshito , Onoda Mitsuko , Junji Akimoto Junji Akimoto , Yoshinao Oosawa Yoshinao Oosawa
Published: February 2005

New Sb-Containing ternary sulfides with layered composite crystal structure have been prepared and characterized: (SbS)
n
TiS2, (SbS)
n
TaS2, (SbS)
n
(NbS2)2, and (SbS)
n
(TaS2)2; n≃1. On the basis of X-ray and electron diffraction patterns, it is suggested that the first and the second sulfides consist of a SbS and a TS2 (T=Ti or Ta) layers stacked alternately and that the third and the fourth sulfides consist of a SbS and two TS2 (T=Nb or Ta) layers stacked alternately. The in-plane electric resistivity of (SbS)
n
TaS2 showed metallic temperature dependence in the region of 4.2-300 K.
Numerical Study of Magneto-Plasma-Dynamic Thruster Onset Phenomena
Authors: T. S. Sheshadri T. S. Sheshadri
Published: February 2005

The occurrance of onset in (magneto-plasma-dynamic) MPD thrusters is investigated by means of a steady MPD formulation and an onset hypothesis. The onset boundary curve for Argon propellant is obtained and is found to be consistent with experimental observations. It is shown that in order to attain high specific impulse before occurrance of onset, it is necessary to increase the low temperature plasma electrical conductivity.
Excess Noise in Amorphous Selenium Avalanche Photodiodes
Authors: Ohshima Tetsuya , Tsuji Kazutaka , Sameshima Kenji , Hirai Tadaaki , Shidara Keiichi , Taketoshi Kazuhisa
Published: February 2005

Excess noise in amorphous Selenium avalanche photodiodes (a-Se APD) has been measured in a frequency range from 3 kHz to 30 kHz. The deduced excess noise factors, including dependences on photocurrent, frequency, applied electric field and the a-Se layer's thickness, agreed with McIntyre's theoretical values.
Relationship between Photodarkening and Light-Induced ESR in Amorphous Ge-S Films Alloyed with Lead
Authors: Masuda Atsushi , Minoru Kumeda Minoru Kumeda , Tatsuo Shimizu Tatsuo Shimizu
Published: February 2005

It had been reported that lead alloying causes the disappearance of PD in Ge-S films. However, it was confirmed that LESR continues to exist in spite of the disappearance of the PD. For Ge-S films without lead, the LESR was observed by irradiation, the intensity of which is not so strong as that giving rise to the PD. It also turned out that the density of defects, including neutral and charged ones at room temperature, remains constant after strong irradiation at low temperature. From these results, it has become apparent that in Ge-S system the PD does not originate from bond-breaking.
Comparison between ESR and CPM for the Gap States in a-Si-Ge:H
Authors: Kumeda Minoru , Awaki Narimasa , Yan Hui , Morimoto Akiharu , Watanabe Tatsuo Shimizu
Published: February 2005

Si dangling bonds and Ge dangling bonds in a-Si1-x
Ge
x
:H are separately estimated both by low-energy optical absorption measurements using a constant photocurrent method (CPM) and by ESR measurements. The ratio of the density of Si dangling bonds to that of Ge dangling bonds decreases with increasing germanium content, as expected. However, the ratio deduced from CPM is far larger than that deduced from ESR. Origins of the difference are discusssed.
Interface Modification by Hydrocarbon Gas Molecular Beams in Heteroepitaxy of SiC on Si
Authors: Yoshinobu Tatsuo , Takashi Fuyuki Takashi Fuyuki , Hiroyuki Matsunami Hiroyuki Matsunami
Published: February 2005

Carbonization of Si surfaces using hydrocarbon gas molecular beams was investigated. In the case of carbonizing bare Si surfaces with C2H2, single-crystalline 3C-SiC layers were obtained only in the narrow range of a substrate temperature near 780°C. Among various surface treatments, the existence of a surface oxide layer and temperature rise during carbonization is proved to be effective in reproducibly obtaining single-crystalline 3C-SiC layers.
Surface Morphology of Tl2Ba2Ca2Cu3Oy Thin Films Prepared by Thallium Diffusion Process
Authors: Adachi Seiji , Adachi Hideaki , Ichikawa Yo , Kentaro Setsune Kentaro Setsune , Kiyotaka Wasa Kiyotaka Wasa
Published: February 2005

The surface morphology of Tl2Ba2Ca2Cu3O
y
thin films prepared by the thallium diffusion process was studied. Ba-Ca-Cu-O rf-sputtered films were annealed with a powder mixture of Tl2O3, BaCuO2, Ca2CuO3 and CuO at a nominal composition of Tl1Ba1Ca3Cu3O
y
. The films obtained by two-step annealing (at 900°C for 8 h and at 930°C for 8 min) had uniform appearance over a rather large area and exhibited superconductivity of T
c (zero resistivity)=117 K.
NMR Study of Compositional Inhomogeneities in Sputtered Co-Cr Films
Authors: Koji Takei Koji Takei , Yasushi Maeda Yasushi Maeda
Published: February 2005

The development of compositional inhomogeneities in sputtered Co-22 at.% Cr films is studied as a function of substrate temperature using the spin-echo 59Co-NMR technique. It is observed that a highly Co-rich component grows as the substrate temperature increases from 30°C to 400°C. The Cr content of the Co-rich part in the film deposited at 400°C is estimated to be as low as 5-7 at.%. The results are consistent with the appearance of a clearly striped compositional microstructure which suggests compositional separation.
Mobility Enhancement of Textured ZnO Films by Ultraviolet Light Irradiation
Authors: Yamada Akira , Wenas Wilson W. , Yoshino Masahiro , Makoto Konagai Makoto Konagai , Kiyoshi Takahashi Kiyoshi Takahashi
Published: February 2005

We have grown high-conductivity textured ZnO films by the photo-MOCVD method using DEZ (diethylzinc) and H2O as reactant gases. It was found that the UV light irradiation during the growth was very effective in the improvement of electron mobility. The improvement of the electron mobility could be caused by the chemisorption of the oxygen at the grain boundaries. The boron-doped ZnO films were also grown by photo-MOCVD using B2H6 as dopant gas. The resistivity of the films grown with UV irradiation was one order of magnitude less than that grown without UV irradiation, and the minimum resistivity of 6.8×10-4 Ω·cm was obtained by the photo-MOCVD method.
Magnetic Softness of Fe-1.5 wt.%Si Single-Crystal Films Deposited on GaAs(111)
Authors: Akihiko Hosono Akihiko Hosono , Yutaka Shimada Yutaka Shimada
Published: February 2005

The magnetic softness of Fe-1.5 wt.%Si single-crystal films with (111) orientation was investigated. Fe-1.5 wt.%Si films deposited on GaAs (111) single-crystal substrates grow epitaxially with good (111) orientation parallel to the film plane. Coercivities of the Fe-1.5 wt.%Si films decrease as the film thickness decreases. A 300 Å-thick film exhibits coercivity of 0.7 Oe. The permeability of a 1000 Å thick film is 1400.
Detector Characteristics of a Vertical-Cavity Surface-Emitting Laser
Authors: Kosaka Hideo , Kurihara Kaori , Mitsunori Sugimoto Mitsunori Sugimoto , Kenichi Kasahara Kenichi Kasahara
Published: February 2005

The possibility of using a vertical-cavity surface-emitting laser (VCSEL) as a detector has been investigated. For a 100 Å In0.2Ga0.8As strained quantum-well-layer that serves as both an active and absorption layer, 26% absorption due to the effect of multireflection mirrors and an 8% absorption increase at the resonant wavelength by applying an electric field were demonstrated.
Optical Branching Device for Arrayed Waveguides
Authors: Moriki Kazunori , Aizawa Khoji , Ohnishi Yoshihumi , Iga Takeo Hattori
Published: February 2005

A new optical branching device for arrayed waveguides was proposed and experimentally demonstrated. This device consists of GaAlAs/GaAs waveguides. An input optical beam can be split into eleven waveguides. Moreover, it is shown that the phase relation between the lightwaves in branch waveguides is conserved.
Contrast Enhancement of SAL Resist by Reducing Residual Solvent at Prebake
Authors: Tetsuyoshi Ishii Tetsuyoshi Ishii , Tadahito Matsuda Tadahito Matsuda
Published: February 2005

An examination of prebake effects of a chemically amplified resist, SAL601-ER7, reveals that solvent retention in the film after prebake has a great effect on pattern contrast. By reducing residual solvent through a high temperature prebake (105°C), 0.8-µm lines and spaces can be obtained in a thick single layer resist of 1.8 µm and 0.1-µm feature patterns with an aspect ratio of 6 can be resolved.
Beryllium Doping for Ga0.47In0.53As/InP Quantum Wells by Chemical Beam Epitaxy (CBE)
Authors: Uchida Takashi , Uchida Toshikazu , Yokouchi Noriyuki , Miyamoto Tomoyuki , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

High-concentration modulation doping of beryllium (Be) for GaInAs/InP quantum wells (QWs) was achieved by chemical beam epitaxy (CBE) up to 1×1019 cm-3. The modulation-doped quantum well (MD-QW) structure showed strong photoluminescence intensity. Broad-contact separate-confinement-heterostructure (SCH) QW lasers were also fabricated to evaluate the quality of MD-QWs. The measured threshold current density was 1.5-2.0 kA/cm2 for devices with 200 µm width and 200-1000 µm cavity length. High concentration and modulation doping for GaInAs/InP lasers was demonstrated.
Thermal Equilibration of Defect Density in Hydrogenated Amorphous Silicon-Germanium Alloys
Authors: Yan Hui , Morimoto Akiharu , Minoru Kumeda Minoru Kumeda , Tatsuo Shimizu Tatsuo Shimizu
Published: February 2005

The ESR signal in a-Si1-x
Ge
x
:H alloy films after fast cooling from an elevated temperature was compared with that after slow cooling. The reversible thermally induced increase in the neutral dangling bond density of about 20% was observed at 250°C. The reversible thermally induced change in the dark conductivity (σd) was also observed by the same heat treatment as for the ESR measurement.
Digital Chemical Vapor Deposition of SiO2 Using a Repetitive Reaction of Triethylsilane/Hydrogen and Oxidation
Authors: Sakaue Hiroyuki , Nakano Masayuki , Tsutomu Ichihara Tsutomu Ichihara , Yasuhiro Horiike Yasuhiro Horiike
Published: February 2005

The extraction reaction of hydrogen in triethylsilane (TES) with hydrogen radicals generated by a remote plasma of H2 produces an organic Si film. Step coverage features of the film depend strongly on H2 concentration in the TES+H2 reaction system. A conformal profile has been achieved for 60% H2 at 250°C as a result of the low-viscosity nature of the film which includes C
x
H
y
groups. With the aim of filling a deep trench with hlgh-quality SiO2 film, digital chemical vapor deposition (CVD), which was carried out by repeating a cycle of the conformal deposition of the Si film and subsequent oxidation, was studied. The SiO2 film which was deposited at 250°C and with an initial thickness per cycle of 5 Å at a 1 s oxygen pulse offered a low concentration of organic species, and thus a relatively low BHF etch rate.
Gas-Sensitive Schottky Gated Field Effect Transistors Utilizing Poly(3-alkylthiophene) Films
Authors: Ohmori Yutaka , Takahashi Hiroyuki , Muro Keiro , Uchida Masao , Tsuyoshi Kawai Tsuyoshi Kawai , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

The gas sensitivity of Schottky gated poly(3-alkylthiophene) field effect transistors has been reported. The source-drain currents have been strongly influenced by air, water and chloroform gases. A large increase in transconductance of the (field effect transistor) FET is observed in chloroform gas. This is explained by the increase of the mobility with diffusion of chloroform molecules into the poly(3-alkylthiophene) films.
Laser Picosecond Acoustics in Thin Films: Effect of Elastic Boundary Conditions on Pulse Generation
Authors: Wright Oliver B. , Takao Hyoguchi Takao Hyoguchi , Katsuhiro Kawashima Katsuhiro Kawashima
Published: February 2005

Using the pump-probe technique with laser noise compensation, laser picosecond acoustic measurements were carried out for the amorphous sputtered thin films a-Ge and a-InSb on sapphire substrates with both pump and probe beams incident on the front side of the film. The contraints at the stress generation region were then changed using a pump beam incident on the substrate side of the a-Ge film, allowing background signals from non-acoustic sources to be greatly reduced. The symmetry of the detected echo pulse shapes are interpreted with a theoretical model.
Metalorganic Chemical Vapor Deposition of InAlP Using Tertiarybutylphosphine
Authors: Hori Hisao , Kawakyu Yoshito , Hironori Ishikawa Hironori Ishikawa , Masao Mashita Masao Mashita
Published: February 2005

The InAlP growth by metalorganic chemical vapor deposition using tertiarybutylphosphine is reported for the first time. Films with mirrorlike surface morphology were obtained at 650°C. In comparision with phosphine, tertiarybutylphosphine is more suitable for growth at lower temperature.
Heteroepitaxy of Layered Semiconductor GaSe on a GaAs(111)B Surface
Authors: Ueno Keiji , Abe Hideki , Koichiro Saiki Koichiro Saiki , Atsushi Koma Atsushi Koma
Published: February 2005

Growth of a III-VI compound semiconductor GaSe on a GaAs(111)B substrate has been tried by the molecular beam epitaxy technique. Although GaSe and GaAs have completely different lattice structures, it has been found that a good GaSe film having its own lattice constant grows with its c-axis normal to the GaAs substrate surface. The growth proceeds via van der Waals-like weak forces between each layer of GaSe, relaxing the lattice-matching condition drastically. The heteroepitaxial growth of GaSe will be applied to effective surface passivation of GaAs.
Microstructures and Jc-B Characteristics of Ag-Sheathed Bi-Based Superconducting Wires
Authors: Ueyama Munetsugu , Hikata Takeshi , Takeshi Kato Takeshi Kato , Ken-ichi Sato Ken-ichi Sato
Published: February 2005

We prepared silver-sheathed BiPbSrCaCuO wires by the powder-in-tube method. Maximum critical current densities at 77.3 K were 5.4×104 A·cm-2 in a zero magnetic field, 4.2×104 A·cm-2 at 0.1 T and 1.2×104 A·cm-2 at 1 T. At 77.3 K, as the J
c improves, the history effects decrease. J
c and J
c-B enhancements are due to the decrease and dispersion of nonsuperconducting phases, and to grain boundary improvements.
Structural Differences between Hydrogenated and Deuterated Amorphous Silicon Films Prepared by Plasma-Enhanced Chemical Vapor Deposition
Authors: McElheny Peter J. , Suzuki Atsushi , Mashima Satoshi , Hasezaki Kazuhiro , Satoshi Yamasaki Satoshi Yamasaki , Akihisa Matsuda Akihisa Matsuda
Published: February 2005

Hydrogenated and deuterated amorphous silicon films were investigated to determine the origin of the lower photodegradation rates reported for deuterated films. Deuterated layers were deposited onto hydrogenated films and were ineffective in changing the photodegradation rate, implying that hydrogenated and deuterated films exhibit structural differences related to the bulk. Deuterium effused as low as 250°C, compared with 325°C for hydrogen, and the deuterium effusion was greater at temperatures below 400°C. Raman scattering intensities of the TO band were also slightly broader and shifted to higher energy for the deuterated films.
Delayed Neutron Emission from a Plasma Focus with a Titanium Disc Affixed on its Central Electrode
Authors: Rout R. K. , Shyam A. , V. Chitra V. Chitra , M. Srinivasan M. Srinivasan
Published: February 2005

A low energy (2 kJ) plasma focus has been operated with central electrode end covered with 500 µm thick disk of titanium. When this electrode was suitably conditioned and the device was operated at negative voltage, neutron emission from the plasma focus was observed even ten seconds after the focus formation.
Noise Correlation of Magnetic Thin Film Media
Authors: Mian Guo , R. S. Indeck R. S. Indeck , M. W. Muller M. W. Muller
Published: February 2005

We have experimentally observed a linear relationship between the correlation coefficient of the noise voltages read on a saturated magnetic thin film rigid disk by a magnetic recording head at different radii, and the radial offset of the head between readings, in both longitudinal and perpendicular media. This linear relationship indicates that for the length of the data stream used in the experiments, the noise voltages from adjacent narrow longitudinal strips that could be denoted pseudo microtracks are uncorrelated. The experiments indicate that the correlation length between the pseudo microtracks is less than 0.5 µm. We have used the linear relationship as the basis for a track following scheme that follows an 11.3 µm wide track with 0.3 µm accuracy.
New Types of Nonlinear Optical Materials: Li3VO4- and Li3PO4-Type Structures
Authors: Shin'ichi Sakata Shin'ichi Sakata , Itsuhiro Fujii Itsuhiro Fujii
Published: February 2005

Li3VO4- and Li3PO4-type structure crystals are found as new types of nonlinear optical materials for second-harmonic generation (SHG). Their lattices are formed of only the MO4 oxygen tetrahedra, being different from other typical nonlinear optical materials that have previously been developed.
Characteristics of p-type ZnSe Layers Grown by Molecular Beam Epitaxy with Radical Doping
Authors: Ohkawa Kazuhiro , Takeshi Karasawa Takeshi Karasawa , Tsuneo Mitsuyu Tsuneo Mitsuyu
Published: February 2005

p-type ZnSe layers have been grown by molecular beam epitaxy using nitrogen radical doping. We have employed Pt as the electrode material for p-type ZnSe. The Pt electrodes markedly reduced contact resistances. The p-type conduction was confirmed by Hall measurement. Carrier concentration was 4.4×1015 cm-3. Hall mobility was as high as 86 cm2/V·s because of good crystallinity. The p-type ZnSe layers exhibited the 2.616-eV emission from recombination
between free electrons and acceptor holes (FA) in room-temperature photoluminescence measurement. The FA
emission provides evidence that the layers are p-type ZnSe.
Field Ion-Scanning Tunneling Microscopy Study of the Ag(110)-O System
Authors: Hashizume Tomihiro , Taniguchi Masahiro , Motai Kumi , Lu Hua , Tanaka Kenichi , Toshio Sakurai Toshio Sakurai
Published: February 2005

Atomic-resolution scanning tunneling microscope (STM) images of the Ag(110) clean surface were obtained successfully using a high-performance UHV-mode FI-STM. When the surface was exposured to oxygen, one dimensional linear chains with various separation widths were observed, corresponding to the (n×1) LEED patterns. It was concluded that those linear chains consist of Ag O Ag components, similar to the case of the Cu(110)-O system.
A New Superconducting Gradiometer Complex for Vector Detection of Weak Magnetic Field
Authors: Shirae Kimisuke , Matani Ayumu , Yoshida Minoru , Shinjiro Kiyono Shinjiro Kiyono , Hisao Furukawa Hisao Furukawa
Published: February 2005

We have devised a superconducting gradiometer complex which enables the second-derivative detection of the vector components of the magnetic field at a point. Consisting of the orthogonal pairs of parallel first-derivative gradiometers, the gradiometer complex detects only two components of the magnetic field at its center, and synthesizes the last component using the former results.
Electro-Optical Bistability and Multistability in GaAs/AlAs Superlattices with Different Miniband Widths
Authors: Kawashima Kenji , Fujiwara Kenzo , Yamamoto Teiji , Mitsuhiro Sigeta Mitsuhiro Sigeta , Kikuo Kobayashi Kikuo Kobayashi
Published: February 2005

We have studied room temperature operation of self-electro-optic effect devices utilizing Wannier-Stark localization in GaAs/AlAs superlattices by photocurrent spectroscopy. Correlation between device characteristics and superlattice structures is studied in detail. Bistable operation is obtained with a high on/off ratio in a particular range of miniband widths. We also show multistability due to higher-order Stark-ladder transitions in wider miniband superlattices.
Pb-Amount Dependence of Copper and Oxygen Valence in Pb-Doped Bi-Sr-Ca-Cu-O Superconductors
Authors: Yuan Liu Ren , Kurosawa Kou , Takigawa Yasuo , Okuda Masahiro , Naito Hiroyoshi , Nakahigashi Kiyotaka , Nakanishi Shigemitsu , Matsushita Tatsuhiko
Published: February 2005

X-ray photoelectron spectroscopic (XPS) studies are done on superconducting (Bi1-x
Pb
x
)2Sr2Ca2Cu3O
y
(x=0-0.4) containing various volume fractions of the 80 K and 110 K phases. Systematic changes in the Cu 2p and O 1s core-level emission spectra are observed as a function of x. The analyses of these XPS spectra reveal that Cu+, Cu2+, and O (off-plane), O (on-plane) ions exist in the superconductors. With increasing volume fraction of the 110 K phases in the samples, the ratios of Cu+/Cu2+ and O (off-plane)/O(on-plane) increase.
Fabrication of Thin Silicon Wires by Anisotropic Wet Etching of SOI Structures
Authors: Itoh Kazuo , Kazuaki Iwameji Kazuaki Iwameji , Yoshisato Sasaki Yoshisato Sasaki
Published: February 2005

A fabrication method of thin single-crystalline silicon wires on SiO2 is reported. The wires are fabricated by anisotropic wet etching of (110) and (100) SOI wafers. We obtained a thin (110) SOI wire of 0.2 µm width and 0.2 µm height with a rectangular cross section. Since the (110) SOI wires are enclosed by a pair of ultraflat {111} side walls parallel to each other, this method has the potential to form ultranarrow wires by careful control of the etching conditions.
Epitaxial Growth of ZnMgSSe on GaAs Substrate by Molecular Beam Epitaxy
Authors: Okuyama Hiroyuki , Nakano Kazushi , Takao Miyajima Takao Miyajima , Katsuhiro Akimoto Katsuhiro Akimoto
Published: February 2005

We propose a new material, ZnMgSSe, as the cladding layer of a blue-light laser diode. Band-gap energy can be varied from 2.8 to near 4 eV, maintaining lattice-matching to a (100)GaAs substrate. The band-gap energies of MgS and MgSe (zincblende structure) are estimated to be about 4.5 eV and 3.6 eV, and the lattice constants are 5.62 Å and 5.89 Å, respectively. The refractive index of ZnMgSSe lattice-matched to GaAs is smaller than that of ZnSSe lattice-matched to GaAs. ZnMgSSe meets the requirements of the cladding layer of ZnSSe for fabricating the blue-light laser diode.
Temperature Dependence of the Phase Coherence Length of High-Mobility AlGaAs/GaAs Quantum-Wire Rings
Authors: Aihara Kimihisa , Yamamoto Masafumi , Kazumi Iwadate Kazumi Iwadate , Takashi Mizutani Takashi Mizutani
Published: February 2005

The temperature dependence of the phase coherence length,Lφ, of high-mobility AlGaAs/GaAs quantum-wire rings was investigated through the Aharonov-Bohm (AB) magnetoresistance oscillations. The expression of the AB oscillation amplitude for the quasiballistic, multitransverse-mode quantum-wire rings was derived and used to extractLφfrom the experimental AB oscillation amplitudes. The phase coherence time, τφ, was estimated fromLφusing an expression for an intermediated region. It was found that below 2.0 K,Lφsaturates at 2.5 µm and τφsaturates at 24 ps. The temperature dependence of τφshowed approximatelyT-2dependence above 2.0 K, which is characteristic of electron-electron scattering in a pure system.
Influence of Strain on Electrical Properties of the Ge Channel in the Modulation-Doped p-Si0.5Ge0.5/Ge/Si1-xGex Heterostructure
Authors: Etoh Hiroyuki , Murakami Eiichi , Nishida Akio , Kiyokazu Nakagawa Kiyokazu Nakagawa , Masanobu Miyao Masanobu Miyao
Published: February 2005

The influence of strain on the electrical properties of the Ge channel in a modulation-doped p-Si0.5Ge0.5/Ge/Si1-x
Ge
x
heterostructure is studied in relation to the Si mole fraction (1-x) and the thickness of the Si1-x
Ge
x
buffer layer. In the range of 1-x≤0.25, the hole concentration and mobility increase with strain in the Ge channel. However, in the range of 1-x>0.25, they decrease with strain due to the large number of threading dislocations. It is also found that hole concentration and mobility increase with buffer layer thickness. As a result, a very high mobility of 7600 cm2·V-1·s-1 at 77 K is obtained at a Si mole fraction of 0.25 and buffer layer thickness of 1 µm.
High Performance 1.55 µm Quantum-Well Metal-Clad Ridge-Waveguide Distributed Feedback Lasers
Authors: Borchert B. , Stegmüller B. , Baumeister H. , Rieger J. , Veuhoff E. , H. Hedrich H. Hedrich , H. Lang H. Lang
Published: February 2005

We present results on high performance 1.55 µm InGaAs/InGaAsP multiple quantum well metal-clad ridge-waveguide distributed feedback lasers. The multilayer structure was grown entirely by low pressure metal-organic vapor phase epitaxy. For improved high speed modulation a small-area contact mask was used. As a result the following characteristics were obtained on the same device: 38 mW single-mode output power with a 3dB-bandwidth of 11 GHz and a linewidth of 3.5 MHz. Best values for the individual parameters are 71 mW, 11 GHz and 880 kHz.
Surface Tension Wave on Gelatin Gel
Authors: Kikuchi Hiroki , Keiji Sakai Keiji Sakai , Kenshiro Takagi Kenshiro Takagi
Published: February 2005

Thermally excited surface waves were measured on gelatin gel in a frequency range up to 800 kHz by a newly developed technique of light scattering. The observed frequency and dispersion showed that the wave propagating on the gel is a surface tension wave, not a surface elastic wave, in spite of the elasticity appearing in the sol-gel transition. The surface tension of the gelatin gel at 3.0 wt% and 20°C was observed from the frequency to be 32 mN/m. The shear viscosity of sol and gel determined from the damping constant over a wide frequency range suggested the existence of a relaxation process characteristic to each phase.
Novel Chemical Analysis for Thin Films: Scanning Electron Microscopy & Total-Reflection-Angle X-Ray Spectroscopy (SEM-TRAXS)-X-Ray Take-Off Angle Effect
Authors: Usui Toshio , Kamei Masayuki , Aoki Yuji , Tadataka Morishita Tadataka Morishita , Shoji Tanaka Shoji Tanaka
Published: February 2005

Scanning electron microscopy & total-reflection-angle X-ray spectroscopy (SEM-TRAXS) was applied for fluorescence X-ray analysis of 50 Å- and 125 Å-thick Au thin films on Si(100). The intensity of the AuM line (2.15 keV) emitted from the Au thin films varied as a function of the take-off angle (θt) with respect to the film surface; the intensity of AuM line from the 125 Å-thick Au thin film was 1.5 times as large as that of SiKαline (1.74 keV) emitted from the Si substrate when θt=0°-3°, in the vicinity of a critical angle for total external reflection of the AuM line at Si (0.81°). In addition, the intensity of the AuM line emitted from the 50 Å-thick Au thin film was also sufficiently strong for chemical analysis.
Improvement of Organometallic Vapor Phase Epitaxy Regrown GaInAs/InP Heterointerface by Surface Treatment
Authors: Suemasu Takashi , Yasuyuki Miyamoto Yasuyuki Miyamoto , Kazuhito Furuya Kazuhito Furuya
Published: February 2005

It is shown that the combined surface treatment of a (NH4)2S
x
treatment and preheating improves the regrown heterointerface of n-GaInAs/i-InP in organometallic vapor phase epitaxy (OMVPE). Properties of the regrown heterointerface were evaluated from voltage-current (V-I) characteristics of the n-GaInAs/i-InP/n-GaInAs tunneling diode. This surface treatment is useful for the fabrication of ultrafine-size structures of quantum-wire, -box and electron wave devices.
Magnetic Susceptibility of YBa2(Cu1-xFex)3Oy Prepared by Various Heat Treatments
Authors: Shibata Tomohiko , Katsuyama Shigeru , Kazuyoshi Yoshimura Kazuyoshi Yoshimura , Koji Kosuge Koji Kosuge
Published: February 2005

The magnetic susceptibility was measured for YBa2(Cu1-x
Fe
x
)3O
y
(0≦x≦0.10) prepared by the `usual' and `special' heat treatments. By the special heat treatment, we mean that the sample prepared by the usual method was reduced at 800°C in flowing N2 gas followed by reoxidation in flowing O2 gas below 400°C, stabilizing the orthorhombic phase to higher Fe concentrations. We estimated the effective magnetic moment per Fe in the Cu1 site, P
eff(1), from the magnetic susceptibility combined with the result of the Mössbauer effect measurement. The values of P
eff(1) could be calculated as 4.4 µB and 2.2 µB for the compounds with the `usual' and the `special' heat treatments, respectively. This smaller P
eff(1) may be attributed to the antiferromagnetic coupling between Fe spins within the process at high temperature.
Dynamic Behavior of Lipid across a Micropore during Self-Excited Potential Oscillation
Authors: Sha Seimei , Takamichi Nakamoto Takamichi Nakamoto , Toyosaka Moriizumi Toyosaka Moriizumi
Published: February 2005

This letter reports observation with an optical microscope on dynamic behavior of a lipid across the oil/water interface, which are formed at a micropore of 2 µm in diameter during self-excited potential oscillation. Periodical movement of dome-shaped body on the interface is observed, and its expansion and shrinkage are quite synchronous with the potential oscillation.
Strong Ultraviolet-Emitting ZnF2:Gd Thin Film Electroluminescent Device
Authors: Miura Noboru , Sasaki Takashi , Hironaga Matsumoto Hironaga Matsumoto , Ryotaro Nakano Ryotaro Nakano
Published: February 2005

A ZnF2:Gd thin film electroluminescent device was fabricated, and very strong ultraviolet (UV) emission was achieved from this device. This UV emission showed a sharp line at 311.5 nm assigned to the6P7/2→8S7/2transition of Gd3+ion. Blue photoluminescence was observed from the CaF2:Eu single crystal excited by the ZnF2:Gd electroluminescent device.
The States of Surface-Stabilized Ferroelectric Liquid Crystal with High-Pretilt Aligning Film
Authors: Koden Mitsuhiro , Shinomiya Tokihiko , Itoh Nobuyuki , Kuratate Tomoaki , Taniguchi Tsugiko , Awane Katsunobu , Tomio Wada Tomio Wada
Published: February 2005

Surface-stabilized ferroelectric liquid crystal with high-pretilt (about 15°) aligning film rubbed in parallel showed three types of states: C1-uniform (C1U), C1-twisted (C1T), and C2 states. In the C1 state, the uniform state (C1U) showing extinction positions and the twisted state (C1T) showing no extinction position were observed. On the other hand, the C2 state showed only one state showing extinction positions. The properties of these three states were investigated and their orientational model will be discussed in combination with the molecular orientation on the surface of the aligning film.
Interferometric Gravitational Wave Detector Using the Transmission Light of the Fabry-Perot Cavity
Authors: Ohashi Norikatsu Mio
Published: February 2005

We show here the feasibility of an interferometric gravitational wave detector using the transmission light of the Fabry-Perot cavity, which eliminates the effect due to the frequency noise of the light source. The characteristics of the detector are discussed.
In Situ Gravimetric Monitoring of the GaAs Growth Process in Atomic Layer Epitaxy
Authors: Koukitu Akinori , Ikeda Hitoshi , Hiroshi Yasutake Hiroshi Yasutake , Hisashi Seki Hisashi Seki
Published: February 2005

A gravimetric method for in situ monitoring of atomic layer epitaxy (ALE) is proposed and applied to the growth of GaAs by halogen transport ALE. An ALE growth system with an electrobalance is developed as a monitoring system. In the conventional method of measurement the growth rate of ALE is obtained as an average value, but the system can directly monitor the growth rate and the surface coverage in each cycle in actual ALE growth conditions. It is shown that the growth of the monomolecular layer unit occurs in each cycle in halogen transport GaAs ALE, and the gravimetric method makes in situ and real-time monitoring of growth rate possible on a submonolayer scale.
Preparation of YBa2CuZ3O7-x and YBa2Cu4O8 Thick Films by Gas Deposition Using Fine Powders
Authors: Murakami Hirohiko , Nishino Junya , Yaegashi Seiji , Yuh Shiohara Yuh Shiohara , Shoji Tanaka Shoji Tanaka
Published: February 2005

Superconducting thick films 1 mm wide and 25 µm thick were prepared on MgO substrates by gas deposition of YBa2Cu4O8 (124) fine powders. A 124 thick film with random grain orientation had a J
c of 490 A/cm2 at 36 K. A YBa2Cu3O7-x
(123) thick film produced by converting 124 into 123+CuO had a J
c of 1470 A/cm2 at 30 K.
Irreversibility Line in Polycrystalline Superconducting Bi-Pb-Sr-Ca-Cu-O with Oriented C-Axis
Authors: Matsushita Teruo , Otabe Edmund Soji , Nakatani Tatsuhiko , Ni Baorong , Umemura Toshio , Egawa Kunihiko , Wakata Mitsunobu , Utsunomiya Shin
Published: February 2005

The irreversibility line, i.e., a boundary between zero and nonzero critical current density in the magnetic field vs temperature plane, was measured for polycrystalline Bi-based superconductors of high T
c phase with oriented c-axis, and its anisotropy was discussed. Both the anisotropy with respect to the direction of the current and that of the magnetic field were small, and the quasitwo-dimensionality of the crystal structure did not play an important role. Although these results are affected by the weak link of grain boundaries, it is suggested that the flux pinning strength is the main determinant of the irreversibility line.
Effect of Y2BaCuO5 Particles on Pinning Characteristics of Y-Ba-Cu-O Prepared by Melt Powder Melt Growth Method
Authors: Ni Baorong , Kobayashi Masato , Funaki Kazuo , Matsushita Kaoru Yamafuji
Published: February 2005

Two kinds of YBaCuO bulk samples with different densities and sizes of 211 particles were prepared by the melt powder melt growth method. The magnetic field and temperature dependences of critical current density, J
c, were measured inductively. Strong dependence of J
c on size and density of 211 particles at higher temperatures was observed, while no relationship could be recognized between the two at lower temperatures. This result supports the expectation that nonsuperconducting particles such as the 211 phase act as dominant pinning centers at higher temperatures. A history effect was observed at 4.2 K, suggesting an existence of weak links.
Preparation and Superconducting Properties of TlBaSrCaCuO System
Authors: Masanori Kuroda Masanori Kuroda , Kiyoshi Yokogawa Kiyoshi Yokogawa
Published: February 2005

We report the effect of calcining and heating temperature on the structure and superconductivity of the Tl-based
superconductors, TlBaSrCaCuO. It was found that a CuO2 3-layer nearly single phase (1223 phase) was obtained at heating temperature over 865°C, and CuO2 2-layer phases (2212 and 1212 phases) were obtained at heating temperature under 860°C.
γ-Irradiation of Superconducting Bi-Sr-Ca-Cu-O and Its Lead-Dopes Varieties
Authors: De Amitabha , Nitya R. Das Nitya R. Das , Sudhindra N. Bhattacharyya Sudhindra N. Bhattacharyya
Published: February 2005

Effects of γ-ray irradiation on Bi2Sr2Ca2Cu3O
y
and Bi2-x
Pb
x
Sr2Ca2Cu3O
y
(x=0.1 and 0.2) superconductors have been studied using a 60Co γ-ray source up to a maximum dose level of 300 Mrads. On irradiation of the undoped variety, a small decrease in its T
c value is observed up to a certain dose level after which it has no effect on T
c. In the case of lead-doped samples with x=0.1 the irradiation effect is more pronounced (T
c decreases from 94 K to 84 K) than where doping of lead is higher, i.e., x=0.2 (T
c decreases from 96 K to 90 K), at a 100 Mrad dose level. The experimental results corroborate the X-ray powder diffraction data.
Magnetic Properties and Current-Voltage Characteristics of Anisotropic Y1Ba2Cu3O7-y / Native Barrier / Pb Josephson Planar Tunnel Junctions
Authors: Zhongmin Wen Zhongmin Wen , Ienari Iguchi Ienari Iguchi
Published: February 2005

The magnetic properties and the current-voltage characteristics of Y1Ba2Cu3O7-y
(YBCO) / native barrier / Pb Josephson tunnel junctions employing both the c-axis- and a, b-axes- oriented YBCO films are reported. The stable Fraunhofer-like patterns of Josephson critical current under the applied magnetic field are observed. The current-voltage curves of the junctions made of a, b-axes-oriented YBCO films exhibit hysteretic behavior typical of conventional Josephson tunnel junctions. The anomalous temperature dependence of Josephson critical current is also reported.
Tunable Laser Diode Having a Complementary Twin-Active-Guide (CTAG) Structure
Authors: Yamamoto Eiji , Suda Kazuya , Hamada Madoka , Seiji Nogiwa Seiji Nogiwa , Tokukoh Oki Tokukoh Oki
Published: February 2005

We propose a new type of tunable laser, the complementary twin-active-guide (CTAG) laser, and present the preliminary experimental results of its tuning characteristics. A wide continuous tuning range over 4 nm is obtained for the CTAG laser. In the CTAG laser, not only power reduction but also spectral line-width broadening during tuning are greatly improved in comparison to conventional TTG lasers and three-section DBR lasers.
Stimulation of Dog Heart by Pulsed Magnetic Fields
Authors: Yamaguchi Masuhiro , Ando Tomio , Goto Tsuneaki , Hosono Akihiko , Kawakami Tadashi , Okumura Fukuichiro , Syugyo Hitoshi , Takenaka Toshifumi , Isao Yamamoto Isao Yamamoto
Published: February 2005

A dog heart with normal activity has been successfully stimulated by strong pulsed magnetic fields. The magnetic stimulus delivered on the T-wave causes the first beat immediately after the stimulus to be missed.
Additivity of the Quantized Conductance of Multiple Parallel Quantum Point Contacts
Authors: Schmidt Poul Erik , Okada Makoto , Kinjiro Kosemura Kinjiro Kosemura , Naoki Yokoyama Naoki Yokoyama
Published: February 2005

We report on the first direct observation of the additivity of the quantized conductance for multiple parallel quantum point contacts. We have studied from 1 to 4 parallel quantum point contacts and find that the total conductance can be written in the form (2e
2
N
L
N
QPC/h) as a function of the applied gate voltage, where N
QPC is the number of parallel quantum point contacts. The processing of multiple parallel quantum point structures is also described.
Dependence of the Switching Current on the Pretilt Angle in the Surface-Induced Ferroelectric Phase of a Nematic Liquid Crystal
Authors: Mochizuki Akihiro , Kobayashi Katsusada Motoyoshi
Published: February 2005

The polarization switching current observed in a cell filled with a liquid crystal, which normally takes a nematic phase, aligned using highly polarized orientation films is shown to reveal a saturation versus the amplitude of the applied voltage depending on the pretilt angle. This behavior is explained by solving an equation for pretilted and anchored nematic medium having a longitudinal permanent dipole moment.
Investigation of Gas-Phase Reaction between Trimethylamine Alane and Triethylgallium in Chemical Beam Epitaxy
Authors: Kobayashi Fumihiko , Iio Shinji , Toru Kuwahara Toru Kuwahara , Youichi Sekiguchi Youichi Sekiguchi
Published: February 2005

We investigated the gas-phase reaction between trimethylamine alane (TMAA) and triethylgallium (TEG) in chemical beam epitaxy (CBE) using a quadrupole mass analyzer (QMA). When they were premixed to form a single beam, the overall intensity of the mass spectrum for the mixtures was much lower than that for each source, which was consistent with the observed growth rate of each layer. In contrast, such reduction was remarkably suppressed when they formed individual beams. These results indicated that gas-phase reaction to produce nonvolatile materials occurred in the premixing region. Therefore, premixing must be prevented during growth using TMAA and TEG.
Surfactant Epitaxy of Si on Si(111) Mediated by Sn
Authors: Shun-ichi Iwanari Shun-ichi Iwanari , Kunio Takayanagi Kunio Takayanagi
Published: February 2005

Surfactant epitaxy is studied by high-resolution reflection electron microscopy for the growth of Si on a Si(111) surface covered by a tin (Sn) layer. The growths on stepped surfaces occur chiefly by the step flow at substrate temperatures above ≃330°C. The Si atoms deposited on the Sn layer diffuse underneath the Sn layer to be incorporated with the bulk Si layer, so that the Sn layer is always located at the outermost surface to maintain the step flow as well. The growths with and without the Sn layer are studied comparatively to find an approximate relation, λc
2∼A exp (-E/k
T
c), between the critical step distance for the step flow, λc, and the substrate temperature, T
c. The step flow for the Si/Sn/Si occurs at much lower temperature and at much longer step distance than for the Si/Si: at 330°C, λc≃1240 nm for Si/Sn/Si, and λc≃175 nm for Si/Si.