bluuebunny/crossref_metadata_2025 huggingface dataset:
Superconducting YBa2Cu3Ox Thin Film Growth on a Vicinal Surface of NdGaO3 Substrate
Authors: Mukaida Masashi , Shintaro Miyazawa Shintaro Miyazawa , Masahiro Sasaura Masahiro Sasaura
Published: February 2005

Surface morphology is observed for a superconducting YBa2Cu3O
x
(YBCO) thin film grown on a 1.7° off angle vicinal surface of lattice-matched NdGaO3 substrate. Ragged step-like edges are clearly observable with exclusions in the front of the edges. The height of a step is measured to be 20 Å∼30 Å and is calculated from the vicinal angel and the terrace width to be 23±2 Å, indicating an evidence for a doubled periodicity of YBCO crystal c-axis unit length of ∼12 Å.
Preparation and Properties of ZrF4-Based Fluoride Glass Films by Plasma-Enhanced Chemical Vapor Deposition
Authors: Fujiura Kazuo , Nishida Yoshiki , Kenji Kobayashi Kenji Kobayashi , Shiro Takahashi Shiro Takahashi
Published: February 2005

ZrF4-based binary glass films are for the first time synthesized by plasma-enhanced chemical vapor deposition (PCVD) and their optical transmission spectrum is measured from the UV to near IR region. The films are pore-free and transparent. No absorption band caused by OH or other impurities can be observed in the near IR region. Weak absorption bands attributed to defect centers, which are induced by plasma bombardment, are observed in the UV to visible region.
A Simple Magnetization Technique for Determining Critical Currents in Superconducting Thin Films
Authors: Scharen M. J. , Cardona A. H. , Sun J. Z. , L. C. Bourne L. C. Bourne , J. R. Schrieffer J. R. Schrieffer
Published: February 2005

We demonstrate a simple technique for determining the critical current density (J
c) of superconducting thin films from remanent magnetization measurements. The technique provides a rapid, non-destructive measurement of J
c for films of arbitrary size. J
c values of both in-situ grown high-temperature superconducting thin films were determined with this technique. These J
c's were compared to direct measurements on microbridges patterned on the same film. For homogeneous films, the J
c values obtained by the two techniques agree to within a factor of 2.
A New Type of Heterojunction a-Si Photodiode for Lensless Contact-Type Image Sensor
Authors: Shindoh Yasuyuki , Haga Koichi , Yamamoto Kenji , Murakami Akishige , Watanabe Masafumi Kumano
Published: February 2005

Using boron-doped and nondoped a-SiO
x
:H layers as photoreception windows, an ITO/a-SiO
x
(B):H/a-SiO
x
:H/a-Si:H/Cr heterojunction photodiode is constructed. The collection efficiency for photocarriers is improved over the wavelength range of visible light by this structure. The photo/dark current ratio of 5×103 is obtained at an applied voltage of -5 V. The photocurrent retains over 80% of its initial value over 2×104 seconds under the irradiation of AM1. With this photodiode, a lensless contact-type image sensor is realized with 8 bits/mm, A4 size and 2.5 ms/line.
Photoluminescence in Hydrogenated Amorphous Carbon Films Prepared at Room Temperature
Authors: Ohtani Noboru , Katsuno Masakazu , Futagi Toshiro , Ohta Yasumitsu , Hidenori Mimura Hidenori Mimura , Kazuhiko Kawamura Kazuhiko Kawamura
Published: February 2005

Hydrogenated amorphous carbon (a-C:H) films were prepared at room temperature from the decomposition of a mixture of ethylene C2H4 with hydrogen by capacitively coupled rf-glow-discharge chemical vapor deposition. These films showed intense visible photoluminescence in which the intensity varied markedly with such preparation conditions as the fraction of ethylene in the raw gas. It has also been found that the films are gradually oxidized in air even at room temperature. To examine the origin of the intense photoluminescence, the chemical bonding structure of the a-C:H films and its changes after exposure to air have been explored from infrared absorption measurements. Through these investigations, it has become evident that the intense photoluminescence is closely related to polyethylenelike structures existing in the film.
Effects of Substrate Materials and Their Properties on Photoassisted Metalorganic Vapor Phase Epitaxy of ZnSe
Authors: Tamotsu Okamoto Tamotsu Okamoto , Akihiko Yoshikawa Akihiko Yoshikawa
Published: February 2005

Effects of substrate materials and their properties on photoassisted MOVPE of ZnSe using DMZn and DMSe as reactants have been investigated. For GaAs substrates, the presence of a thin predeposited ZnSe buffer layer and its quality greatly affect the subsequent film growth. However, for InP substrates, no essential effect of the buffer layer has been observed. Furthermore, in both substrates, the conduction type makes no significant difference to the results of photoassisted MOVPE. These results can be interpreted by a proposed growth model in which photoinduced excess holes in the ZnSe layer contribute to the film growth.
Exciton-Forming Vibronic Optical Subbands and Their Inhomogeneous Broadening in Trans-Polyacetylene
Authors: Kubo Takaya , Hideo Takezoe Hideo Takezoe , Atsuo Fukuda Atsuo Fukuda
Published: February 2005

A method has been established to prepare as-grown, about-10-µm-thick (CH)
x
films which show a reflection spectrum with two conspicuous triplet structures, one at 1.57, 1.69 and 1.81 eV originating from trans-form segments and the other at 2.07, 2.24 and 2.41 eV from cis-form segments. These exciton-forming vibronic optical subbands of triplet structure usually become somewhat blurred after the completion of cis-trans conversion; thermoreflectance measurements have been performed to restore the triplet structure clearly. By comparing the inhomogeneous broadening of the exciton-forming vibronic optical subbands in trans-(CH)
x
with that in poly(p-phenylenevinylene), the possibility of observing the luminescence spectra from trans-(CH)
x
segments under quasi-resonant conditions has been discussed.
Phase-Matched Second-Harmonic Generation in Ferroelectric Liquid Crystal
Authors: Ozaki Masanori , Utsumi Manabu , Gotou Tatsuya , Kazuhiro Daido Kazuhiro Daido , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

The profile of the phase-matching behavior of second-harmonic generation in ferroelectric liquid crystal has been found to be strongly dependent on cell thickness. A sharp angular phase-matching curve of the second-harmonic generation with the full width at half-maximum of ∼1° is observed even in the liquid crystal. The effective nonlinear optical coefficient d
eff at the phase-matching condition is determined. The temperature dependence of the phase-matching behavior in the ferroelectric phase has also been studied.
Mass Spectrometric Study and Modeling of Decomposition Process of Tris-Dimethylamino-Arsenic on (001) GaAs Surface
Authors: Hamaoka Kazuhiko , Suemune Ikuo , Fujii Kazuyuki , Koui Tomoaki , Akihiro Kishimoto Akihiro Kishimoto , Masamichi Yamanishi Masamichi Yamanishi
Published: February 2005

Decomposition process of a new arsenic precursor, As[N(CH3)2]3, for metalorganic molecular beam epitaxy (MOMBE) was studied. It was found that a Ga-stabilized (4×2) GaAs surface turned to an As-stabilized (2×4) surface at a low substrate temperature of ∼400°C and with a low As[N(CH3)2]3 pressure of ∼10-7 Torr when it was supplied without thermal precracking. This is a marked contrast to conventional As[C2H5]3 with which the As-stabilized GaAs surface is never formed without precracking. The decomposition process was modeled assuming an intermediate-state species adsorbed on the GaAs surface based on a quadrupole mass spectrometric study. The measured temperature dependence was very well explained with the present model.
Shape of the GaInAs/InP Multiquantum Well Potential Observed by Scanning Tunneling Microscopy
Authors: Takashi Kato Takashi Kato , Fukunobu Osaka Fukunobu Osaka
Published: February 2005

Under an ultrahigh vacuum (UHV) environment, a cross-sectional observation of a non-doped n-Ga0.47In0.53As/InP multiquantum well (MQW) structure was performed using scanning tunneling microscopy (STM). The STM image of the non-doped MQW structure was compared with the STM image of a highly-doped n-GaInAs/InP MQW structure. As a result, it has become clear that the STM images of the MQW structures reflect the shape of the MQW potential which varies with the doping concentration.
All-Solid-State Glucose Sensor Using Proton-Conductive Thick Film
Authors: Matayoshi Naoko , Norio Miura Norio Miura , Noboru Yamazoe Noboru Yamazoe
Published: February 2005

A solid-state glucose sensor using a proton-conductor thick film was investigated as a possible approach to a miniaturized enzyme sensor. A planar-type electrochemical cell, (reference electrode) Au|antimonic-acid thick film (proton conductor)|Pt-GOD (sensing electrode), was fabricated on a porous alumina substrate. When measured in a phosphate buffer solution of pH 7.0 at 30°C, the emf of the sensor varied logarithmically with a change in glucose concentration in the range from 5×10-4 to 4×10-2 M, following a Nernst equation. The 90% response time was about 1 min. The glucose sensitivity was fairly stable for 10 days. The Nernst slope (-54 mV/decade) was very close to that (-55 mV/decade) of the responses to H2O2, indicating that the glucose-sensing signal was generated by responding to the H2O2 produced by the enzymatic reaction of glucose.
Effect of Coating on the Blue-Green Color Imparted to LiNbO3 by Cu Ion Implantation
Authors: Saito Yukinori , Akio Takada Akio Takada , Shinji Suganomata Shinji Suganomata
Published: February 2005

LiNbO3 was implanted with Cu+ ions in the dose range 1016 to 1017 ions/cm2 with an energy of 30 keV. It was found that the blue-green color imparted to LiNbO3 by Cu+ ion implantation was very sensitive to temperature. The temperature dependence of the fading time was measured. Depth profiles of some elements of LiNbO3 just after Cu+ ion implantation and after heating at 200°C for 3 min in air were measured. A large depletion of oxygen around the range of the Cu+ ions is also related to the color tone. Coating the surface of LiNbO3 with a film such as SiO2 just after Cu+ ion implantation is very effective in preventing the color from fading.
Metalorganic Molecular Beam Epitaxy of Zn1-xCdxSySe1-y Quaternary Alloys on GaAs Substrate
Authors: Ichino Kunio , Wu Yi-hong , Kawakami Yoichi , Shizuo Fujita Shizuo Fujita , Shigeo Fujita Shigeo Fujita
Published: February 2005

The successful growth of Zn1-x
Cd
x
S
y
Se1-y
(ZnCdSSe) quaternary alloys by metalorganic molecular beam epitaxy (MOMBE) is reported. Layer-by-layer growth was confirmed for the first time by monitoring the intensity oscillation of a specular beam in a reflection high-energy diffraction (RHEED) pattern. ZnCdSSe layers coherently grown on GaAs exhibited good crystallographic and optical properties.
Power-Law I-V Characteristics in the Superconducting Transition Region of Bi-Sr-Ca-Cu-O Single Crystal under Magnetic Fields
Authors: Ando Yoichi , Motohira Naofumi , Kitazawa Koichi , Takeya Jun-ichi , Akita Shirabe
Published: February 2005

The resistive state in single-crystal Bi2Sr2CaCu2O
y
with field applied perpendicular to the c-axis has been studied to investigate the origin of the Lorentz-force-independent dissipation. It was observed that the current-voltage characteristics obey a power law in the higher current density region in our experiment (J≥20 A·cm-2), and that the power-law exponent and the resistivity show an unusual dependence on the magnetic field. These observations strongly suggest that a Kosterlitz-Thouless-type mechanism plays an essential role in the Lorentz-force-independent dissipation.
Magnetic Instability in High-Jc Y1Ba2Cu3O7 Prepared by Quench-Melt-Growth Process
Authors: Watanabe Kazuo , Kobayashi Norio , Awaji Satoshi , Kido Giyuu , Nimori Shigeki , Kimura Keiichi , SAwano Kiyoshi , Yoshio Muto Yoshio Muto
Published: February 2005

Magnetisation measurements of quench-melt-growth-processed Y1Ba2Cu3O7 were performed in high fields of up to 23 T at 4.2 K by a sample extraction method. Many flux jumps were observed in the magnetization curve. It was demonstrated that high-T
c oxide superconductors with very large J
c of 107 A/cm2 in fields at 4.2 K gave rise to magnetic instability due to the low specific heat.
Nondestructive Observation of Si0.5Ge0.5/Ge/Si1-xGex Heterostructure Using Soft X-Ray Emission Spectroscopy
Authors: Hirai Masaaki , Kusaka Masahiko , Iwami Motohiro , Nakamura Hatsuo , Murakami Eiichi , Nakagawa Kiyokazu
Published: February 2005

In-depth observation of a Si1-x
Ge
x
heterostructure grown by the molecular beam epitaxy (MBE) method was carried out using electron-excited soft X-ray emission spectroscopy (SXES) nondestructively. Si-L2,3 emission band spectra showed a clear modification between those for Si1-x
Ge
x
alloys and the one for single-crystal Si. The difference in the spectral shape was utilized for the nondestructive study of a Si-Ge heterocontact system in combination with the energy dependence of the X-ray production depth of an energetic electron in a solid.
Structure Control of GaN Films Grown on (001) GaAs Substrates by GaAs Surface Pretreatments
Authors: Shinji Fujieda Shinji Fujieda , Yoshishige Matsumoto Yoshishige Matsumoto
Published: February 2005

Two types of cubic and hexagonal GaN films were deposited on (001) GaAs substrates. The film structure proved to be controlled by GaAs pretreatments. By performing a N2H4 (hydrazine) pretreatment of GaAs substrates, the GaN films, which were otherwise hexagonal similarly to ordinary films on sapphire substrates, became cubic. A surface cubic nitride layer was found to be formed on the pretreated GaAs by a RHEED (reflection high-energy electron diffraction) observation, which is thought to be the substantial substrate for the following growth of a cubic GaN film.
Grazing Incidence X-Ray Diffraction Study of Arachidic Acid Monolayer on Cyanine Dye Aqueous Solution
Authors: Matsushita Tadashi , Iida Atsuo , Takeshita Kunikazu , Saito Kazuhiro , Kuroda Shin-ichi , Oyanagi Hiroyuki , Sugi Michio , Furukawa Yukito
Published: February 2005

The angle and direction of tilt of arachidic acid molecules on the surface of 10-4M cyanine dye aqueous solution were determined as a function of surface pressure from the intensity profile along the Bragg rod obtained in a grazing incidence diffraction experiment using synchrotron X-radiation. Experimental data were interpreted by a model in which molecules tilt toward next nearest neighbors in a two dimensional hexagonal lattice at low surface pressures and stand upright at high surface pressures above 35 mN/m. The dependence of lattice spacings of (1, 0), (0, 1) and (1, -1) molecular rows on the angle of molecular tilt was qualitatively explained by this model.
Laser Cooling of a Helium Atomic Beam
Authors: Norio Morita Norio Morita , Mitsutaka Kumakura Mitsutaka Kumakura
Published: February 2005

The laser cooling of a helium atomic beam in the 2s3S1 metastable state has been demonstrated. Using a single-mode LNA (La1-x
Nd
x
MgAl11O19) laser resonant with the 2s3S1-2p3P2 transition, the metastable atoms are cooled by the Doppler cooling method combined with the Zeeman-tuning technique. To monitor the velocity distribution, the Doppler profile of the 2p3P2-3d3D3 transition is observed. As a result, the most probable velocity of the metastable helium atoms, which is initially 750 m/s, is decelerated to 90 m/s.
A Method of Producing High-Quality Linear Field Gradient for Magnetic Resonance Imaging Using Straight Current Lines
Authors: Masahiro Furusawa Masahiro Furusawa , Motoji Ikeya Motoji Ikeya
Published: February 2005

A new method for generating a highly linear field gradient in a large space is described. The coil system consists of N equispaced parallel current lines placed on a cylinder perpendicular to the static magnetic field. The wires generate a gradient of any accuracy depending on N and in any direction in a plane perpendicular to the cylinder axis by controlling the current of each wire independently. The accuracy of the gradient using 16 infinite-length wires is less than 0.3% in the 60% region in diameter of the cylinder. An ESR-CT image of a DPPH test sample was obtained using this system of 16 wires.
Si Wafer Bonding with Ta Silicide Formation
Authors: Fukuroda Atsushi , Sugii Toshihiro , Yoshihiro Arimoto Yoshihiro Arimoto , Takashi Ito Takashi Ito
Published: February 2005

Bonded SOI wafers with a Ta silicide layer are fabricated. The 0.08-µm-thick Ta film sputtered on an oxidized Si wafer
is bonded to another Si wafer with a native oxide. When the wafers are uniformly bonded by pulse-field-assisted bonding, Ta silicide forms at the interface. The buried Ta silicide layer is 0.12 µm thick and the sheet resistance is 9 Ω/\Box. From a SIMS analysis, Ta decreases rapidly in Si. This proves that a pure SOI layer for devices can be obtained.
A Unified Circuit Model for the Polysilicon Thin Film Transistor
Authors: Izzard M. J. , P. Migliorato P. Migliorato , W. I. Milne W. I. Milne
Published: February 2005

This paper describes a unified approach to modelling the polysilicon thin film transistor (TFT) for the purposes of circuit design. The approach uses accurate methods of predicting the channel conductance and then fitting the resulting data with a polynomial. Two methods are proposed to find the channel conductance: a device model and measurement. The approach is suitable because the TFT does not have a well defined threshold voltage. The polynomial conductance is then integrated generally to find the drain current and channel charge, necessary for a complete circuit model.
GaN Growth Using GaN Buffer Layer
Authors: Shuji Nakamura Shuji Nakamura
Published: February 2005

High-quality gallium nitride (GaN) film was obtained for the first time using a GaN buffer layer on a sapphire substrate. An optically flat and smooth surface was obtained over a two-inch sapphire substrate. Hall measurement was performed on GaN films grown with a GaN buffer layer as a function of the thickness of the GaN buffer layer. For the GaN film grown with a 200 Å-GaN buffer layer, the carrier concentration and Hall mobility were 4×1016/cm3 and 600 cm2/V·s, respectively, at room temperature. The values became 8×1015/cm3 and 1500 cm2/V·s at 77 K, respectively. These values of Hall mobility are the highest ever reported for GaN films. The Hall measurement shows that the optimum thickness of the GaN buffer layer is around 200 Å.
C-V Analysis of Electrical Properties for PN Heterointerface in InP/InGaAsP Double-Heterojunction Laser Diode
Authors: Yamamoto Norio , Kiyoyuki Yokoyama Kiyoyuki Yokoyama , Mitsuo Yamamoto Mitsuo Yamamoto
Published: February 2005

Electrical properties at the pn heterointerface in a double-heterojunction (DH) laser diode (LD) has been studied based on capacitance-voltage (C-V) measurement. A self-consistent numerical program, which solves Poisson's equation and current continuity equations, has been used to calculate bias dependent capacitance values. Comparing the calculated results with measured values, we can determine an electrically active dopant concentration around the active layer from 1015 to 1016 cm-3 and the detailed profile of electrically active dopant due to Zn diffusion from the doped buffer layer. It was also found that this analysis has its sensitivity in clarifying the existence of a 100-Å thick transition layer at the pn heterointerface.
Soft Magnetic Properties of bcc Fe-M-B-Cu (M=Ti, Nb or Ta) Alloys with Nanoscale Grain Size
Authors: Suzuki Kiyonori , Makino Akihiro , Akihisa Inoue Akihisa Inoue , Tsuyoshi Masumoto Tsuyoshi Masumoto
Published: February 2005

The changes in microstructure and magnetic properties upon crystallization were investigated for melt-spun amorphous Fe-M-B-Cu (M=Ti, Nb or Ta) quaternary alloys. A mostly single bcc phase with nanoscale grain size of about 10 nm was formed by annealing the amorphous Fe-M-B-Cu alloys for 3.6 ks in the range of 750 to 950 K. The crystallization-induced bcc alloys were found to exhibit a high permeability (µe) of from 10000 to 20000 at 1 kHz, combined with a high saturation magnetization (B
s) of from 1.40 to 1.55 T. These values are superior to those for amorphous Fe-Si-B alloys which are a known soft magnetic material with high B
s.
Magnetic and Magnetotransport Properties of CoxFe1-x/Cu Multilayers
Authors: Yoshiaki Saito Yoshiaki Saito , Koichiro Inomata Koichiro Inomata
Published: February 2005

We have investigated the magnetic and magnetotransport properties of (Co
x
Fe1-x
/Cu) multilayers prepared by ion beam sputtering. We found that (Co
x
Fe1-x
/Cu) multilayers are new ones with large magnetoresistance in the range between x=0.6 and 1.0. We also found that the 27.2% magnetoresistance ratio could be observed for the magnetic field under the 0.9 kOe when (FeCo910 Å/Cu10 Å)15 was deposited on the MgO(110) single-crystal substrates. In this system, saturation field H
s decreases substantially when crystal anisotropy is utilized.
Optogalvanic Wavelength Calibrator for an Automatic Tunable Laser System
Authors: Oki Yuji , Izuha Tatsuya , Maeda Mitsuo , Honda Chikahisa , Hasegawa Yoshio , Futami Hiroshi , Izumi Jun , Matsuda Keiichi
Published: February 2005

A simple, fully-automatic wavelength calibrator using the optogaivanic (OG) effect is demonstrated with an automatic dye laser system developed for analytical spectroscopy. When a target wavelength is put into the keyboard, the computer scans the laser wavelength, and takes OG signals of the hollow cathode lamp which is installed in the laser system. Then the wavelength of the laser is tuned to the target, comparing with the reference OG line. The reproducibility in the absolute wavelength calibration is demonstrated to be better than ±1 cm-1 over a wide spectral range from 220 nm to 740 nm. The calibration time is less than thirty seconds.
Green Electroluminescence from ZnS-CuGaS2 Heterojunction Diode in DC Operation
Authors: Kobayashi Satoshi , Youichi Momiyama Youichi Momiyama , Futao Kaneko Futao Kaneko
Published: February 2005

The dc green electroluminescence (EL) from the ZnS-CuGaS2 heterojunction diode is described in the temperature range of 93-291 K. The EL spectrum at 93 K which consists of the only band peaking at 514 nm resembles the photoluminescence (PL) spectrum. At elevated temperatures, another emission band emerges at the shorter-wavelength side of the main band. The main peak position shifts toward the longer-wavelength direction with increasing temperature and reaches 529 nm at 291 K. The EL intensity, which rises steeply with the current, decreases with increasing temperature.
Auger Electron Spectroscopy Study on the Characterization and Stability of the Cu9Al4/TiN/Si System
Authors: Atsushi Noya Atsushi Noya , Katsutaka Sasaki Katsutaka Sasaki
Published: February 2005

Diffusion barrier properties of TiN films to silicon and the Cu9Al4 compound have been studied using Auger electron spectroscopy. The experimental results indicate that the TiN layer of 800 Å is effective as a diffusion barrier at 670°C. It is found that the reaction of Al in the compound with Ti in the barrier results in the failure of the system due to intermixing of elements at 700°C. The failure temperature of 700°C, which is higher than that of aluminum or copper metallization, is due to the stability of the Cu9Al4 compound itself.
Evaluation of the Electron Cyclotron Resonance Plasma Process Using a Microwave Twin-Lead Line Probe
Authors: Hiroshi Nishimura Hiroshi Nishimura , Seitaro Matsuo Seitaro Matsuo
Published: February 2005

A plasma measurement method using a parallel twin-lead line probe is developed. An accurate measurement of process plasma such as electron cyclotron resonance plasma can be made even in the presence of an external magnetic field by this method. Measurement errors are estimated to be less than ±10% considering the influence of the electron density distribution and the multiple reflection between the plasma boundaries. The density of electron cyclotron resonance plasma is measured by the method and a high ionization degree of 1 to 10% is confirmed.
Effect of the Blending of Binder Polymers on Recording Sensitivity of Dye/Polymer Optical Recording Media
Authors: Nobuyuki Matsuzawa Nobuyuki Matsuzawa , Jun'etsu Seto Jun'etsu Seto
Published: February 2005

We studied the effect of blending binder polymers on the recording sensitivity of dye/polymer optical write once media. We found that the change in the surface entropy due to mixing is responsible for the change in the recording sensitivity after mixing. It is also indicated that for polymer pairs having complete miscibility or the lower critical solution temperature, the recording sensitivity becomes lower; for polymer pairs having complete immiscibility or the upper critical solution temperature, the recording sensitivity becomes higher compared to the value obtained by assuming that the recording sensitivity is linear to the weight ratio of blended polymers.
Jc Measurements and the Observation of Flux Movements and Flux Jumps in Quench-and-Melt Growth YBCO by a Pulsed Magnetic Field
Authors: Takizawa Takeo , Kosaka Masashi , Kanbara Kohji , Morita Mitsuru , Sawano Kiyoshi
Published: February 2005

An observation of the flux motion in a ring-shaped quench-and-melt growth (QMG) YBCO has been attempted under a pulsed magnetic field in a temperature range from T
c down to 25 K. The transport critical current density (J
c) is estimated from the magnetic field where the flux just enters into the central hole of the sample ring. At low temperatures, the flux jump is clearly observed and its interpretation is made in terms of the traditional stabilization theory. In a thin sample, a peculiar flux motion suggesting the undulation of flux lines is observed.
Study on the Structural Characteristics of Bi-Sr-Ca-Cu-O Single Crystals Using the Method of Crystal Rotation
Authors: Lei Shi , Yunlan Huang , Yunbo Jia , Jiang Lu , Guien Zhou , Genda Gu , Yuheng Zhang
Published: February 2005

The structural characteristics of single crystals of the Bi-Sr-Ca-Cu-O 2212 superconducting phase have been studied by using the setup of Weissenberg photograph and the plane film. It is observed that the lattice points have been stretched extensively along the c
* direction to form reciprocal poles by rotating the crystal around the a axis. It is proved that the single crystal is not a normal definite three-dimensional lattice. It is a stacking layer structure with a two-dimensional lattice. A two-dimensional superlattice on the (001) is formed by a three-dimensional crystal, which is broken up by “Bi-concentrated bands”, and a one-dimensional lattice along the [001] direction with period c=15.40 Å, or c=30.80 Å is formed by the interval arrangement of the two-dimensional superlattices of perovskite-like layers and “Bi-concentrated bands” with each other. It is the crystal structural characteristics of the Bi-Sr-Ca-Cu-O high-T
c superconductor that the two-dimensional lattice and one-dimensional lattice are independent of each other, which is closely related with the superconductivity.
InGaAs/InP Gain-Coupled Distributed Feedback Laser with a Corrugated Active Layer
Authors: Inoue Takeshi , Nakajima Shin-ichi , Luo Yi , Oki Tokukoh , Iwaoka Hideto , Nakano Yoshiaki , Tada Kunio
Published: February 2005

With InGaAs/InP materials, we have fabricated gain-coupled distributed feedback lasers having grating corrugation on the active layer itself, using two-step organometallic vapor phase epitaxy. Single longitudinal mode properties have been achieved. Self-consistent calculation of coupling coefficients and threshold gain difference for these lasers has also been carried out.
Electric-Field-Induced Apparent Tilt Angle and Devil's Staircase in SmCα
* of an Antiferroelectric Chiral Smectic Liquid Crystal
Authors: Hiraoka Kazuyuki , Takanishi Yoichi , Skarp Kent , Hideo Takezoe Hideo Takezoe , Atsuo Fukuda Atsuo Fukuda
Published: February 2005

The SmCα
* phase which was discovered between SmA and SmC* in 4-(1-metylheptyloxycarbonyl) phenyl 4'-octyloxybiphenyl-4-carboxylate (MHPOBC) has been studied by means of electric-field-induced tilt angle measurements and conoscopic observation. The induced tilt angle increases not smoothly but stepwise in SmCα
* and its neighboring SmA temperature ranges, suggesting successive structural changes, namely, Devil's staircase. According to the conoscopic figures, the existence of the ferrielectric orientation was confirmed. Devil's staircase observed as a result of changing field strength was discussed in comparison with that induced by changing temperature.
The Characterization of Traps in Semi-Insulating Gallium Arsenide Buffer Layers Grown at Low Temperature by Molecular Beam Epitaxy with an Improved Zero-Bias Thermally Stimurated Current Technique
Authors: Lau Wai Shing , Chong Tow Chong , Tan Leng Seow , Chuen Hang Goo Chuen Hang Goo , Kian Seng Goh Kian Seng Goh
Published: February 2005

An improved zero-bias thermally stimulated current (TSC) technique was successfully applied to characterize the traps in semi-insulating gallium arsenide buffer layers grown at low temperature by molecular beam epitaxy (MBE) for the reduction of backgating in gallium arsenide based integrated circuits. Conventional TSC technique is not suitable because of the strong leakage current in those buffer layers. Special precaution is needed to suppress the leakage current even when the bias is nominally zero. An electron trap with an activation energy of 0.52 eV was found in annealed buffer layers. In addition, a continuum of states, which were attributed to the interface states at the interface of arsenic precipitates and bulk gallium arsenide, was also detected.
Particle Acceleration by Longitudinal Field in Two Superposed Laser Beams
Authors: Kazuo Sakai Kazuo Sakai
Published: February 2005

Results have shown that a longitudinal electric field is produced by superposing two laser beams. The variation of particle energy in the longitudinal field is discussed, and a new scheme of particle acceleration by the longitudinal field is proposed.
Emission Spectrochemical Analysis of Food Material Using TEA CO2 Laser-Induced Shock Wave Plasma
Authors: Kagawa Kiichiro , Deguchi Yoji , Ogata Akira , Kurniawan Hendrick , Takagi Noriko Ikeda
Published: February 2005

A new method for spectrochemical analysis of food materials is presented using a Transverse Excited Atmospheric (TEA) CO2 laser. Milk powders containing different amounts of Ca are mixed with KBr powder, and compressed to make pellets. The pellets are bombarded by the TEA CO2 laser (300 mJ, 100 ns) under the surrounding gas of 300 Pa. The shape of the luminous plasma is hemispherical. This plasma is excited by the shock wave induced by the laser bombardment. It is proved that the relative intensity of the Ca 422.6-nm emission line to that of the K 404.4-nm emission line is proportional to the Ca content. This method has a bright prospect as a direct analytical method of food materials.
Adsorption and Decomposition of Organometallics on GaAs Surfaces in Low-Pressure Metalorganic Chemical Vapor Deposition
Authors: Michio Sato Michio Sato , Markus Weyers Markus Weyers
Published: February 2005

To determine the mechanism of surface reactions during metalorganic chemical vapor deposition, we perform mass spectrometric studies of the products desorbed from a GaAs surface upon pulsed supply of the reactants. We find that the surface after trimethylgallium (TMG) exposure is terminated by CH3 and that the desorption of the CH3 from the surface is activated by the presence of As. The adsorption of triethylgallium (TEG) is inhibited on a CH3-terminated surface whereas TEG is decomposed both on As-rich and on Ga-rich surfaces. The effect of CH3 termination is highlighted by the complete inhibition of triethylaluminum decomposition when it is introduced together with TMG.
Role of the Hole Diffusion Current on the Theory of Conduction in ZnO Varistor
Authors: Kim Myung-Sik , Kim Hyung-Hwan Oh
Published: February 2005

We propose a new model which enables us to explain the highly nonohmic varistor behavior, C-V characteristic, and the role of CoO additive: In the new model, the highly nonohmic varistor conduction process is associated with the hole diffusion current due to the gradient of the holes in ZnO grain, which may be caused by moving holes to the depletion region of the forward biased Schottky barrier from the depletion region of the reverse biased Schottky barrier by tunneling process. As this hole diffusion current is strongly limited by the electron-hole generation rate, it is necessary to increase the electron-hole generation rate for the enhancement of the nonlinearity in I-V characteristic of ZnO varistor. Co ions do this role, i.e., the electron-hole generation rate is increased with CoO concentration in ZnO varistor.
End-Point Detection Method in Etch-Back Planarization Process for Josephson Integrated Circuits
Authors: Inoue Takashi , Mutsuo Hidaka Mutsuo Hidaka , Shuuichi Nagasawa Shuuichi Nagasawa
Published: February 2005

We report here the use of a Nb or Si thin layer as an end-point marker for etch-back end-point detection. This has improved the controllability of the end point and has successfully reduced the variations in the final junction height between each etch-back planarization process down to + / - 10 nm over the insulator. As a result, we have achieved high reliability in ensuring an electrical contact between junctions and the upper wiring, in preventing interlayer leakages between the lower and the upper wirings, and in controlling the thickness of the insulator according to the designed inductance values of the wiring.
Blue Electroluminescent Diodes Utilizing Poly(alkylfluorene)
Authors: Ohmori Yutaka , Uchida Masao , Keiro Muro Keiro Muro , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

Blue electroluminescent diodes utilizing poly(alkylfluorene) have been demonstrated for the first time. A Schottky-type electroluminescent diode of poly(9,9-dihexylfluorene) is driven at ∼10 V and has a peak emission wavelength of 470 nm at room temperature.
Discontinuous Radial to Axial Transformation of Director Configuration in a Cylindrical Nematic Cavity
Authors: Bau-Jy Liang Bau-Jy Liang , Shu-Hsia Chen Shu-Hsia Chen
Published: February 2005

The optical patterns of a nematic liquid crystal confined to a closed cylindrical cavity are observed through crossed polarizers. This optical pattern exhibits an annular phenomenon when the radius of the cylinder is varied. The minor dependence of the width of the bright annulus on the radius of the cavity is presented. The formation of the disclination ring is numerically studied and found to be the physical mechanism of the annular phenomenon. The characteristic length defined as the distance from the ring defect to the laterally cylindrical boundary is nearly invariant and is characterized to be the width of the bright annulus.
Selective Growth of GaAs/Si by One-Step Low-Pressure Metalorganic Chemical Vapor Deposition
Authors: Kiyotaka Sato Kiyotaka Sato , Kenji Togura Kenji Togura
Published: February 2005

Selective heteroepitaxy of GaAs on Si(100)<011>4°-off substrates using SiO2 masks was carried out by one-step low-pressure metalorganic chemical vapor deposition. Good selectivity of depositions was realized even if the thickness of SiO2 was at least 100 Å. Swells at the edge of the GaAs layers were hardly observed. The cross section of the GaAs layers revealed flat surfaces regardless of the opening window width. Exactly GaAs(100)-oriented planes inclined 4° to the top GaAs surface were observed only on the tilted side of opening windows on a Si(01̄1) cross section. This suggests that two-dimensional growth was dominant under the conditions in this study.
The Effects of AsH3 Preflow Conditions at Low Temperature on the Morphology of GaAs Buffer Layers for GaAs/Si Grown by Metalorganic Chemical Vapor Deposition
Authors: Asai Koyu , Kazuhisa Fujita Kazuhisa Fujita , Yasunari Shiba Yasunari Shiba
Published: February 2005

In the two-step growth of GaAs on Si, the effects of AsH3 preflow conditions (preflow time and preflow rate) at a low temperature (450°C) on the morphology of GaAs buffer layers (GaAs islands) have been investigated with scanning electron microscopy. As the preflow time or preflow rate was increased, the islands were aligned parallel to the step edges of the misoriented Si surface, and Si surface coverage was increased. These results indicate that the sufficient AsH3 preflow to the Si surface at low temperatures forms both multilayer steps on the Si surface for GaAs island nucleation and a stable GaAs/Si interface.
Faraday Effect of Cd0.55-yHgyMn0.45Te Thin Films
Authors: Takashi Inukai Takashi Inukai , Ken'ichi Ono Ken'ichi Ono
Published: February 2005

The energy gap (E
g) and the Verdet constant were examined for quaternary Cd0.55-y
Hg
y
Mn0.45Te thin films with y≤0.11. As the Hg content increases, the E
g decreases and the S-shaped dispersion of the Verdet constant spectrum shifts to a lower photon energy. The magnitude of the Verdet constant for the film with E
g=1.78 eV (y=0.11) is about 1.9 times larger than that for the Cd0.8Mn0.2Te film with E
g=1.78 eV. It is thought that the large Faraday effect of the Cd0.55-y
Hg
y
Mn0.45Te films in the lower-photon-energy region is based on the large Zeeman splitting enhanced by Mn2+, as in the case of ternary Cd1-x
Mn
x
Te.
Annealing out of Thermal Process-Induced Defects at InP(110) Surfaces-A Novel Method
Authors: Yamada Masao , Green Albert M. , Herrera-Gomez Alberto , Tom Kendelewicz Tom Kendelewicz , William E. Spicer William E. Spicer
Published: February 2005

A novel method which can anneal out defects of InP(110) surfaces due to phosphorous loss is proposed. InP(110) surfaces become phosphorous deficient and the surface Fermi level of p-InP is pinned at 0.55 eV (±0.05 eV) above the valence band maximum with vacuum annealing at around 200°C. A few monolayers of Sb are deposited on the surface, then annealed at above 200°C for 10 minutes. This produces a well-ordered Sb epitaxial monolayer which effectively caps the InP surface, preventing phosphorous desorption from the surface and chemical reactions between overlayers and InP. Thereby the surface returns to approximately the flat band condition. The Sb capped samples can be annealed without phosphorous loss.
Faraday Rotation and Elliptization of Electron Cyclotron Emission on Reactor-Grade Tokamak Plasma
Authors: Sato Masayasu , Nagashima Akira , Shinichi Ishida Shinichi Ishida , Nobuaki Isei Nobuaki Isei
Published: February 2005

The effects of the polarization state evolution on two-dimensional electron cyclotron emission (ECE) measurements along horizontal lines of sight for a reactor-grade plasma are studied. In order to investigate the polarization evolution, the propagation of ECE through the plasma is calculated. The final polarization states are very different from the initial states. The exact electron temperature is obtained in a reactor-grade plasma by measuring the polarization states described by the Stokes parameters.
Confirmation of the Correlation between the Electrical Hysteresis and Silicon Dangling Bond Density in Silicon Nitride by UV Irradiation of Nearly Hysteresis Free Metal-Nitride-Silicon Capacitors
Authors: W. S. Lau W. S. Lau , C. H. Goo C. H. Goo
Published: February 2005

Previously, Lau [W. S. Law: Jpn. J. Appl. Phys. 29 (1990) L690] has pointed out that part of the hysteresis ΔV
+ in MNS (Metal-Nitride-Silicon) capacitors is correlated to the spin density measured by electron spin resonance and the other part of the hysteresis ΔV
- is correlated to defects close to the nitride/silicon interface. The spin density was thought to originate from silicon dangling bonds in the silicon nitride. 254 nm ultraviolet irradiation, which was known to be capable of producing silicon dangling bonds in silicon nitride, was found to induce a large ΔV
+ in nearly hysteresis free MNS (Metal-Nitride-Silicon) capacitors, thus confirming that ΔV
+ is correlated to silicon dangling bonds.
Effects of the Fermi Level on Defects in Be+-Implanted GaAs Studied by a Monoenergetic Positron Beam
Authors: Uedono Akira , Wei Long , Tabuki Yasushi , Kondo Hitoshi , Tanigawa Shoichiro , Wada Kazumi , Nakanishi Hideo
Published: February 2005

Vacancy-type defects in 60-keV Be+-implanted GaAs(100) were studied by a monoenergetic positron beam. The depth distribution of vacancy-type defects in an n-type specimen (Si, 1×1016 Si/cm3) was obtained from measurements of Doppler broadening profiles of the positron annihilation as a function of incident positron energy. The dominant defect species was identified as a divacancy from the characteristic value of the line-shape parameter S. These defects, however, could not be observed in the p-type specimen (Zn, 3×1018 Zn/cm3). This fact can be attributed to the recombination of vacancy-type defects and interstitial Ga atoms introduced by the Fermi level effect.
Classification of Inhomogeneities in Hydrogenated Amorphous Silicon
Authors: Muramatsu Shin-ichi , Matsubara Sunao , Watanabe Takeshi , Shimada Toshikazu , Kamiyama Tomoaki , Suzuki Kenji , Matsuda Akihisa
Published: February 2005

This paper presents studies of medium range order (MRO) of a-Si:H by small-angle X-ray scattering (SAXS) measurements. Device-quality a-Si:H films prepared by different preparation methods show differences in thermal evolution characteristics of hydrogen and scaling features in SAXS spectra. This suggests that a-Si:H can have several kinds of microstructures, and can therefore be classified by MRO.
Newly Designed Hg Cell for Molecular Beam Epitaxy Growth of CdHgTe
Authors: Haseyama Ken , Sugiura Osamu , Haga Ryou , Satoshi Sugahara Satoshi Sugahara , Masakiyo Matsumura Masakiyo Matsumura
Published: February 2005

We have designed and constructed a new pressure-controlled Hg cell for molecular beam epitaxy growth of CdHgTe. It generates a stable Hg flux by regulating the vapor pressure with a capacitance manometer / reservoir heater feedback loop. The Hg flux intensity was controlled up to 2.4×1016 cm-2·s-1 by changing the vapor pressure in the Hg reservoir. This Hg cell has the capability to switch the flux on and off and to degas the Hg without introducing Hg into the growth chamber, through the use of valves. A single-crystalline Cd
x
Hg1-x
Te film with the composition of x=0.21 was grown using an MBE system equipped with this new Hg cell.
Doping Effects of Metallic Elements on the Superconductivity in the Tl-Ba-Ca-Cu-O System
Authors: Jyodoi Kouki , Sonoda Akihisa , Sigeyuki Yasuyama Sigeyuki Yasuyama , Akira Ohyoshi Akira Ohyoshi
Published: February 2005

The effects of various metallic dopants on the superconductivity of the Tl-Ba-Ca-Cu-O system have been investigated. Metals (Zn, Cd, Al, In, Pb and Bi) control the rate of solid-state reaction and the volatility of Tl components. Increases in the electrical conductivity at room temperature and the superconducting volume fraction were achieved as the result of metallic doping. It is considered that metals promote the intergranular coupling of the superconductive particle and annihilate the ceramic pores in the sintering process.
Fermi Surfaces of Alkali-Metal-Doped C60 Solid
Authors: Hamada Noriaki , Saito Susumu , Miyamoto Yoshiyuki , Oshiyama Atsushi
Published: February 2005

We present the first-principles electronic-structure calculation which provides outstanding features in the Fermi surface of K
x
C60. We have found that there exist two main Fermi surfaces: One is a hole pocket around the center of the Brillouin zone, and the other a large hole surface extending to the zone boundary. We have also found Fermi-surface nesting resulting in a peak at q=(1, 0, 0)2π/a in the susceptibility χ(q), which may induce an instability in this exotic material.
Solid-Phase Epitaxy with X-Ray Irradiation to Grow Dislocation-Free Silicon Films at Low Temperatures
Authors: Sato Fumio , Chikawa Katsuyuki Goto
Published: February 2005

Amorphous silicon films with a thickness of 300 nm were deposited on silicon wafers. They were irradiated on a water-cooled specimen holder by X-rays using synchrotron radiation. The irradiation effect was investigated by Raman spectroscopy and electron microscopy. It was found that the irradiation at room temperature greatly enhanced homogeneous nucleation in post-annealing at 600°C. X-ray irradiation with a 54-pole wiggler heated the films up to about 500°C, and dislocation-free films were grown epitaxially within 10 min. This irradiation effect on crystal growth is explained by assuming that vacancy-interstitial pairs are formed with X-ray irradiation by Auger processes.
Crystallization of Amorphous In2O3 Films during Film Growth
Authors: Shigetoshi Muranaka Shigetoshi Muranaka
Published: February 2005

The effect of the film thickness on crystallization of amorphous indium oxide films was investigated using transmission electron microscopy and electron diffraction. Films of different thicknesses, 10-60 Å, were reactively evaporated on SiO substrates at 200°C. The results showed that the amorphous films crystallized markedly with increasing film thickness above 40 Å, while below the thickness of 40 Å, the films partially crystallized from pre-existing crystallites. Concurrently, the microstructure of the films became almost continuous above the thickness of 40 Å.
X-Ray Characterization of Lapped Surfaces of Si and Ge Single Crystals at 33.17 keV
Authors: Shiwaku Hideaki , Hyodo Kazuyuki , Ando Masami
Published: February 2005

X-ray characterization of lapped surfaces of Si and Ge monochromator crystals was performed at 33.17 keV. From comparison of the integrated intensity and FWHM (full width at half-maximum) of those crystals versus the particle size of lapping abrasives, Si crystal lapped with abrasive of #3000 showed a very high reflectivity of 78% and a reasonably narrow FWHM of 12.4 arcsec. This lapped crystal provides ten times the X-ray integrated intensity of the etched one and retains energy resolution of 33 eV (ΔE/E=9.9×10-4), which meets the requirements for imaging in intravenous
coronary angiography utilizing an enlarged monochromatic beam from an asymmetrical cut Si crystal surface.
Transport Critical Current Properties of Silver-Sheathed Bi-Based Superconducting Tapes and Coils at 4.2 K
Authors: Shibuta Nobuhiro , Ueyama Munetsugu , Hidehito Mukai Hidehito Mukai , Ken-ichi Sato Ken-ichi Sato
Published: February 2005

Transport critical current properties of silver-sheathed bismuth-based superconducting tapes and coils were investigated at 4.2 K and up to 25 T. Critical currents showed isotropic properties when the direction of the applied magnetic field changed from parallel to the tape surface to perpendicular, i.e., J
c of 8.9×104 A/cm2 for H//tape and 6.6×104 A/cm2 for H⊥ tape at 23 T. Critical current properties of a three-double-pancake coil were consistent with those of short specimens, showing little change at from 5 to 23 T.
Self-Limiting Adsorption of SiCl2H2 and Its Application to the Layer-by-Layer Photochemical Process
Authors: Yasuo Takahashi Yasuo Takahashi , Tsuneo Urisu Tsuneo Urisu
Published: February 2005

Adsorption of SiCl2H2 on the Ge(100) clean surface is investigated by X-ray photoelectron spectroscopy and thermal desorption spectrum measurement. It is concluded that the adsorption is self-limiting at temperatures below 350°C, and that the surface is reactivated by synchrotron radiation. The sequential processes of self-limiting adsorption of SiCl2H2 and synchrotron radiation are promising for development of Si atomic layer epitaxy.
Indium Composition Dependent Threshold Current Density in Strained InGaAs/AlGaAs Quantum Well Lasers
Authors: Sugimoto Mitsunori , Hamao Noboru , Hiroyuki Yokoyama Hiroyuki Yokoyama , Kenichi Nishi Kenichi Nishi
Published: February 2005

The dependence of threshold current density on indium composition in strained InGaAs/AlGaAs quantum well lasers is examined. A threshold current density (J
th) as low as 115 A/cm2 is obtained in a chip with a 500 µm long cavity at a lasing wavelength of 950 nm. The J
th for a strained InGaAs QW was found to be 35% less than that for a GaAs QW laser with the same cavity length. Time resolved photoluminescence measurement revealed that the improvement in the nonradiative carrier lifetime for quantum wells with higher indium composition was limited to a J
th improvement of only 10%. Calculation suggests that the most likely reason for the major portion of the J
th improvement is gain enhancement due to a reduction in heavy hole mass.