bluuebunny/crossref_metadata_2025 huggingface dataset:
Double-Layered Garnet Films on Glass Substrate for High Carrier-to-Noise Ratio on Magnetooptical Recording
Authors: Akiyoshi Itoh Akiyoshi Itoh , Katsuji Nakagawa Katsuji Nakagawa
Published: February 2005

With a double-layered garnet film prepared on glass substrate, an excellent carrier-to-noise ratio has been achieved as high as 53 dB at 515 nm wavelength which has not been reported before for the garnet films fabricated on glass substrates. The doubled film consists of an underlayer fabricated by pyrolysis and a top layer deposited by sputtering. The underlayer was designed to accommodate small grain size by doping with Rb. The grain size of the top layer is as small as that of the underlayer and this provides a low noise level with a high carrier level.
Carbon Modulation-Doped P-AlGaAs/GaAs Heterostructures Grown by Metalorganic Chemical Vapor Deposition
Authors: Toshiki Makimoto Toshiki Makimoto , Shi Shya Chang Shi Shya Chang
Published: February 2005

Carbon atoms are used as a p-type dopant for modulation-doped p-AlGaAs/GaAs heterostructures grown by metalorganic chemical vapor deposition. Carbon impurities are effectively doped into AlGaAs layers by flow-rate modulation epitaxy, which is a modified method of metalorganic chemical vapor deposition. A mobility of 6.0×104 cm2/V·s is obtained at 13 K for a sheet carrier concentration of 4.1×1011 cm-2, indicating that a high quality two-dimensional hole gas is realized by abrupt heterointerfaces and sharp carbon doping profiles.
Low-Temperature Electron-Beam-Assisted Dry Etching for GaAs Using Electron-Stimulated Desorption
Authors: Heiji Watanabe Heiji Watanabe , Shinji Matsui Shinji Matsui
Published: February 2005

Low-temperature electron-beam(EB)-assisted dry etching for GaAs is developed to achieve highly anisotropic etching by reducing the side-etching caused by Cl2 gas etching. An extremely high etching rate ratio (EB-assisted etching/Cl2 gas etching) is achieved at a substrate temperature of -170°C. The mass spectra of the etching products during EB-assisted dry etching and Cl2 gas etching are measured. These correlate well with etching rate measurements.
Metalorganic Chemical Vapor Deposition of GaAs on (111)B Substrates by Using Diethylgalliumchloride
Authors: Okamoto Kotaro , Osamu Ito Osamu Ito , Ko-ichi Yamaguchi Ko-ichi Yamaguchi
Published: February 2005

Metalorganic chemical vapor deposition (MOCVD) of GaAs was carried out on (111)B just and 1°-misoriented substrates by using diethylgalliumchloride (DEGC). A smooth surface morphology was obtained for (111)B just substrates above the growth temperature of 620°C, while giant steps were observed for 1°-misoriented-(111)B substrates. The occurrence of the step bunching on the misoriented substrates was due to the reevaporation enhancement effects (REE) of GaCl precursors supplied from DEGC.
Metalorganic Vapor Phase Epitaxial Growth for High Electron Mobility Transistor LSIs
Authors: Ohori Tatsuya , Tomesakai Nobuaki , Suzuki Masahisa , Kazumi Kasai Kazumi Kasai , Junji Komeno Junji Komeno
Published: February 2005

We report on metalorganic vapor phase epitaxy (MOVPE) for high electron mobility transistor (HEMT) LSI. It is shown that the layers grown by a low-pressure barrel reactor with a large-area growth capacity (twelve 3-inch wafers) have an excellent reproducibility both for thickness and donor concentration with nearly ±1%. We applied MOVPE-grown wafers to fabricate a HEMT 64 kb SRAM with 0.6 µm gates and obtained a typical address access time of 1.2 ns at a power dissipation of 5.9 W.
High-Pressure Synthesis of Superconducting (Ba1-xSrx)2Cu1+yO2+2y+δ(CO3)1-y (0.35≤x≤0.6, y≈0.1)
Authors: Kyoichi Kinoshita Kyoichi Kinoshita , Tomoaki Yamada Tomoaki Yamada
Published: February 2005

A new copper-oxide superconductor containing carbon (Ba1-x
Sr
x
)2Cu1+y
O2+2y+δ(CO3)1-y
(0.35≤x≤0.6, y≈0.1), which is structurally related to Sr2CuO2CO3, was synthesized under high oxygen pressures of more than 5 atm. The onset temperature for superconduction T
c(onset) increased with oxygen partial pressure (P
O2
) during synthesis. Optimum P
O2
was about 50 atm and (Ba0.55Sr0.45)2Cu1.1O2.2+δ(CO3)0.9 synthesized under 50 atm O2 showed a T
c(onset) of about 40 K and a T
c(zero) of about 26 K.
GaAs Schottky Photodiode Fabricated on Glass Substrate Using Epitaxial Lift-Off Technique
Authors: Fumihiko Kobayashi Fumihiko Kobayashi , Youichi Sekiguchi Youichi Sekiguchi
Published: February 2005

We report on a substrate-side-illuminated GaAs Schottky photodiode fabricated on a glass substrate using the epitaxial lift-off technique. An external quantum efficiency in excess of 70% was observed at a wavelength of 780 nm. This is approximately 1.6 times higher than that of a conventional photodiode which has an absorption layer of the same thickness and is illuminated through a semitransparent Schottky window.
Red Shift of Photoluminescence and Absorption in Dilute GaAsN Alloy Layers
Authors: Weyers Markus , Michio Sato Michio Sato , Hiroaki Ando Hiroaki Ando
Published: February 2005

We present the first report on the optical properties of dilute GaAS1-x
N
x
alloys (0<x<0.015). The layers have been grown by plasma-assisted metalorganic chemical vapor deposition (MOCVD). The grown layers show a systematic red shift of the band-edge luminescence with increasing N content. The assignement of the photoluminescence to band-edge transitions and not to isolated N-N pair emission is verified by the characteristics of the optical absorption.
Multi-Atomic Steps on Metalorganic Chemical Vapor Deposition-Grown GaAs Vicinal Surfaces Studied by Atomic Force Microscopy
Authors: Makoto Kasu Makoto Kasu , Takashi Fukui Takashi Fukui
Published: February 2005

We studied MOCVD-grown GaAs (001) vicinal surfaces by atomic force microscopy (AFM) and observed multi-atomic steps (multisteps) of several-monolayers height. The multisteps become straight as the AsH3 partial pressure increases and when the misorientation direction is [1̄10]. As growth proceeds, first, multisteps, i.e., step bunches, form and then the average distance between multisteps saturates. The multistep straightening and the multistep formation mechanisms are discussed.
Residual Stress of a-Si1-xNx:H Films Prepared by Afterglow Plasma Chemical Vapor Deposition Technique
Authors: Nagayoshi Hiroshi , Morinaka Haruji , Kamisako Koichi , Kuroiwa Koichi , Shimada Toshikazu , Yasuo Tarui Yasuo Tarui
Published: February 2005

Relationships between residual stress and other film properties of amorphous silicon nitride films deposited by microwave afterglow plasma of NH3 and by photochemical vapor deposition have been studied. There are differences in the dependence of N-H and Si-H bond density and residual stress on the film composition between the films deposited by the two methods. The residual tensile stresses in both films, however, reach a maximum value of 7-9×109 dyn/cm2 when the N-H bond density is nearly equal to the Si-H bond density. The residual stress can be reduced by adjusting the N-H and Si-H bond density while maintaining the high breakdown field strength and high resistivity.
The Possibility of Proximity Effect in Pb/LaNiO3(thickness: 59 nm)/Bi-Sr-Ca-Cu-O Trilayer Junction
Authors: Akio Enomura Akio Enomura
Published: February 2005

A Pb(superconductor)/LaNiO3(thickness: 59 nm)/Bi-Sr-Ca-Cu-O (high T
c superconductor) trilayer junction was prepared on a (100) MgO single crystal and the current(I)-voltage(V) characteristics were examined. Judging from the nonlinear I-V curve, it was tentatively concluded that LaNiO3 is one of the barrier materials which has a long range proximity effect.
Practical Properties of Rhodium-Iron Thermometers with Fused-Silica Coil Frames Down to 2.3 K
Authors: Osamu Tamura Osamu Tamura , Hirohisa Sakurai Hirohisa Sakurai
Published: February 2005

Thermometric properties of the recently proposed rhodium-iron (mole fraction 0.5%) wire resistance thermometers with fused-silica coil frames are investigated down to 2.3 K. The thermometers annealed between 800°C and 900°C are calibrated down to 2.3 K with an accuracy of 1 mK by a simple method using a reference function and three reference temperatures, 4.2 K, 13.8 K and 24.5 K, which are the most convenient calibration points in this temperature region. The stabilities in thermal cycling between 4.2 K and room temperature and the self-heating effects due to the measuring current are reasonable for the same accuracy.
Surface Cleaning of AlGaAs Substrates by Hydrogen Electron Cyclotron Resonance (ECR) Plasma
Authors: Kondo Naoto , Yasushi Nanishi Yasushi Nanishi , Masatomo Fujimoto Masatomo Fujimoto
Published: February 2005

Surface cleaning of AlGaAs substrates by hydrogen electron cyclotron resonance (ECR) plasma is carried out. Plasma is transported to the substrate surface by a divergent magnetic field. In situ reflection high-energy electron diffraction (RHEED) observation reveals that surface cleaning of AlGaAs can be successfully performed at a temperature as low as 500°C. From secondary ion mass spectrometry (SIMS) measurements, oxygen concentrations at the interface between the AlGaAs substrate and the GaAs layer grown after plasma cleaning are found to decrease as the substrate temperature decreases. At 500°C, flat surfaces with streaked RHEED patterns and clean interfaces with neither carbon nor oxygen accumulations can be obtained by hydrogen ECR plasma cleaning.
Conductance Oscillations in a Quantum Wire with a Stub Structure due to Quantum Interference
Authors: Aihara Kimihisa , Masafumi Yamamoto Masafumi Yamamoto , Takashi Mizutani Takashi Mizutani
Published: February 2005

Y-shaped structures of a quantum wire with a stub were fabricated in a split gate configuration. Periodic oscillations in the conductance versus split gate voltage curve were observed for the Y-shaped structure of a quantum wire with a stub. In contrast, aperiodic conductance oscillations were observed in a Y-shaped branch in which the reflection wall in the stub had been removed. The distinct difference between the characteristics of these structures suggests that the observed periodic oscillations were caused by quantum interference in the stub. In addition, the calculated gate voltage period based on a model that attributes conductance oscillations to quantum interference in the stub is in good agreement with the experimental period.
Resolution Improvement of the Patterson Map of Tl(BaSr)CaCuO “1212” Phase Superconductor by the Maximum Entropy Method
Authors: Kuroda Masanori , Kenryo Fujise Kenryo Fujise , Kiyoshi Yokogawa Kiyoshi Yokogawa
Published: February 2005

Based on the maximum entropy method (MEM), calculation of the Patterson map of a Tl(BaSr)CaCuO (1212) phase superconductor has been carried out. The resulting Patterson map is of high quality and much superior compared to the map obtained by conventional direct Fourier synthesis. It was proposed that the MEM Patterson map was suitable to obtain the structural model for the Rietveld method in the thallium system superconductor. Further work is in progress to better understand the Patterson map of another type of thallium based superconductor.
Molecularly Doped Polymers as a Hole Transport Layer in Organic Electroluminescent Devices
Authors: Kido Junji , Hongawa Kenichi , Kohda Masafumi , Okuyama Katsutoshi Nagai
Published: February 2005

Electroluminescent devices were fabricated using polycarbonate or poly(methyl methacrylate) molecularly doped with triphenyldiamine derivative as the hole transport layer and tris(8-quinolinolato)aluminum(III) complex (Alq) as the emitting layer, respectively. A cell structure of glass substrate/indium-tin-oxide/doped polymer/Alq/Mg:Ag was employed. Hole injection from the electrode through the doped polymer layer and concomitant efficient electroluminescence from the Alq layer were observed. Bright green emission with a luminance of 7700 cd/m2 was observed at a drive voltage of 14 V from the cell with the doped polycarbonate layer.
Growth of TiO2 Plate Single Crystals by the Edge-Defined, Film-Fed Growth Process
Authors: Machida Hiroshi , Keigo Hoshikawa Keigo Hoshikawa , Tsuguo Fukuda Tsuguo Fukuda
Published: February 2005

TiO2 plate single crystals, up to 20 mm×1.8 mmn×90 mm in size, were successfully grown by the edge-defined, film-fed growth (EFG) method. Iridium was found to be a suitable die material; the die configuration and growth conditions are given. The growth characteristics and the optical quality of crystals obtained are reported.
Simulation of Time Decay for Photoluminescence Emitted from Silicon Crystals Excited by Short Laser Pulse
Authors: Thölmann Karsten , Yamaguchi Masakazu , Akihiro Yahata Akihiro Yahata , Hiromichi Ohashi Hiromichi Ohashi
Published: February 2005

The time decay for photoluminescence (PL) emitted from silicon crystals excited by a short laser pulse has been simulated for the first time on the basis of two simplified approximations in order to obtain both bulk carrier lifetime (τb) and surface recombination velocity (S). One approximation is that the PL intensity is proportional to the normalized (averaged) excess carrier densities, whereas the other is that it is proportional to the recombination rate. We compared simulated results with experimental ones and obtained better coincidence in the case of the latter rather than the former approximation, which means that the Buczkowski et al.'s algorithm for obtaining both τb and S [J. Appl. Phys. 69 (1991) 6495] cannot be applied to the PL decay method. Therefore, a new algorithm has been developed in this present work.
Growth of Large Isometric YBa2Cu3Ox Single Crystals from Coexisting Region of Solid with Melt in Y2O3 Crucibles
Authors: Asaoka Hidehito , Takei Humihiko , Iye Yasuhiro , Tamura Masafumi , Minoru Kinoshita Minoru Kinoshita , Hiroyuki Takeya Hiroyuki Takeya
Published: February 2005

Large isometric single crystals of oxide superconductor YBa2Cu3O
x
(YBCO) have been grown from a mixed region of solid Y2BaCuO5 and melt. The crystals possess sharp, shiny habits with a maximum thickness of about 7 mm along the c-axis. The best growth condition is that wherein the solvent composition is 7BaCuO2·11CuO which is close to the binary eutectic of BaCuO2-CuO, and the optimum concentration of the growth system is that wherein the ratio of YBCO to 7BaCuO2·11CuO is 64:36. The use of a Y2O3-crucible prevents contamination from containers during growth, and facilitates the synthesis of high-purity crystals. Temperature gradient and seed crystals are both effective for controlling nucleation. The annealed crystals show a sharp superconductive transition at 91 K. The temperature dependence of the resistivities is found to be metallic in the ab- as well as the c-direction. Sufficient diamagnetism is manifested as a sharp transition at T
c and a complete shielding effect below T
c.
A Low-Threshold 1.3 µm GaInAsP/InP Flat-Surface Circular Buried Heterostructure Surface Emitting Laser
Authors: Baba Toshihiko , Matsuoka Kazuyoshi , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

The liquid phase epitaxy regrowth process of the GaInAsP/InP flat-surface circular buried heterostructure (FCBH) has been improved and a perfectly buried microsize active region of 8 µm in diameter and 1.2 µm in depth was realized with good reproduclbility. Low-threshold (I
th=52 mA) lasing operation of a 1.3-µm-range FCBH surface emitting laser with a pair of dielectric micromirrors was achieved in a pulsed condition at 0°C.
Characterization of Deformed and As-cast Microstructure of Copper-Aluminium-Iron Alloys (α-Phase)
Authors: Pal Hiranmay , Swapan Kumar Pradhan Swapan Kumar Pradhan , Madhusudan De Madhusudan De
Published: February 2005

The microstructure of aluminium iron bronze, having nominal compositions Cu-1.5Fe-5Al, Cu-1.5Fe-10Al and Cu-1.5Fe-15Al (in at.%) has been characterized in the deformed and as-cast state by employing X-ray diffraction line profile analysis, microhardness studies, optical and scanning electron microscopy and magnetic susceptibility studies. From X-ray studies the stacking fault density <α> has been found to increase with increasing Al concentration relative to binary Cu-Al depicting the influence of small presence of Fe in the ternary alloys. The X-ray results further predict that stacking fault energy is lowered due to the influence of small presence of Fe. The results of the microhardness studies corroborate the findings of the X-ray study. Optical and scanning electron microscopy (SEM) studies reveal the grain and grain boundary structures containing Fe-rich precipitates. These precipitates are primarily responsible for the ferromagnetic behaviour of the materials.
Molecular Beam Epitaxy of SnSe2: Chemistry and Electronic Properties of Interfaces
Authors: Shimada Toshihiro , Ohuchi Fumio S. , Koma Atsushi
Published: February 2005

A layered material SnSe2 was grown epitaxially on various layered materials (MoS2, NbSe2, graphite), while reacting with Al2O3(0001) substrates. The films were characterized by means of X-ray photoemission spectroscopy, reflection high energy electron diffraction, and scanning tunneling microscopy. The observed band bending was consistent to the work function difference between the film and the substrate, indicating the Schottky limit property of the junctions. Applications of this system are discussed.
Measurement of Ge/Si Ratio of SiGe-Layer on Si Substrate Using Total-Reflection X-Ray Fluorescence
Authors: Yasuo Kunii Yasuo Kunii
Published: February 2005

The analysis of the Ge/Si ratio and the depth profile in a SiGe/Si sample has been performed using the recently developed total-reflection X-ray fluorescence (TXRF) apparatus. The TXRF measurement procedure is nondestructive, highly sensitive, requires no preparation, uses cassette-to-cassette operation, and provides depth information. It is used here to measure the Ge/Si ratio of SiGe molecular beam epitaxy (MBE) layers. The relationship between sample structure and the dependence of Ge-Lα and Si-Kα peak intensities on the glancing angle is studied. The Ge-Lα/Si-Kα peak intensity ratio is found to correspond to the Ge/Si atomic ratio as measured by Auger electron spectroscopy (AES).
Gain Measurement of a Free Electron Laser with an Optical Klystron on the UVSOR Storage Ring
Authors: Takano Shiro , Hiroyuki Hama Hiroyuki Hama , Goro Isoyama Goro Isoyama
Published: February 2005

We have conducted experiments to measure the gain of a free electron laser (FEL) with an optical klystron (OK) on the UVSOR storage ring. A conventional undulator has been remodeled into the OK in order to increase the gain. The FEL gain at a wavelength of 488 nm has been measured as a function of N
d, which is the number of wavelengths of light passing over an electron in a dispersive section of the OK. The measured gain curve is in good agreement with that calculated according to Madey's theorem from a measured spectrum of spontaneous radiation. The measured instantaneous peak gain is 0.4% for an average beam current of 10 mA/bunch, which agrees well with the gain calculated theoretically. The gain with the OK is enhanced by a factor of five compared with that with the conventional undulator.
Spherical and Chromatic Aberration Correction using Aperture Lens -Computer Simulation-
Authors: Mamoru Nakasuji Mamoru Nakasuji , Hiroyasu Shimizu Hiroyasu Shimizu
Published: February 2005

The electron trajectories from a Pierce-type electron gun are calculated. The aperture lens which is formed by an anode hole acts as a concave lens and produces negative-sign spherical and chromatic aberrations. The negative-sign focal length which is calculated by the trajectories coincides with the value calculated by the formula derived by Davisson and Calbick 60 years ago. For an electrode of practical size, the negative-sign spherical and chromatic aberration coefficients are on the order of 100 to 102 m and of 10-3 to 10-1 m, respectively. It is shown that when the electron beam from this type of electron gun is focused by a magnetic lens, most of the spherical aberration is compensated. These aperture lenses are expected to improve the characteristics of the charged particle beam systems.
Adenovirus Structure as Revealed by X-Ray Crystallography, Electron Microscopy, and Difference Imaging
Authors: Phoebe L. Stewart Phoebe L. Stewart , Roger M. Burnett Roger M. Burnett
Published: February 2005

The three-dimensional structure of human type 2 adenovirus was studied by combining X-ray crystallography and electron microscopy in a novel way. The 2.9 Å crystal structure of the major capsid protein, hexon, was positioned into a three-dimensional image reconstruction of the intact virus that was derived from cryo-electron micrographs. A three-dimensional difference map was generated by subtracting 240 copies of the crystallographic hexon from the density of the intact virus. This map revealed several minor structural proteins acting as “cement” to stabilize the assembly. The current state of structural knowledge concerning the location of the polypeptide components and the viral DNA is presented.
Chemical Dynamic Behavior at Solid Surfaces
Authors: Kenzi Tamaru Kenzi Tamaru
Published: February 2005

The orthodox approaches to elucidate the mechanisms of chemical reactions on solid surfaces have been discussed. Since catalysis is a dynamic process, it should be elucidated only through dynamic approaches. The importance of in situ studies of catalytic reactions and “isotope jump method” have been emphasized by the author for the first time, and some of the examples, such as “adsorption-assisted desorption” and isotope exchange reactions of carbon monoxide on ruthenium single crystal surfaces, are explained. Some methods to identify catalytic active sites at atomic scale in the future have been imagined.
Preparation of Bismuth Silicate Films on Si Wafer by Metalorganic Chemical Vapor Deposition
Authors: Kim Jonghee , Tsurumi Takaaki , Hirano Hideyuki , Kamiya Toshio , Nobuyasu Mizutani Nobuyasu Mizutani , Masaki Daimon Masaki Daimon
Published: February 2005

Thin films of crystalline Bi4Si3O12 were prepared by metalorganic chemical vapor deposition for use as capacitor layers in DRAM or buffer layers for epitaxial growth of various oxide crystals on Si wafer. This film was formed at 650-820°C by the reaction between SiO2 layer on Si and mixed gas of Bi vaporized from triphenylbismuth and O2. The films deposited at 760°C had a flat and homogeneous surface with a preferred orientation of crystals perpendicular to the film surface. The remaining SiO2 was observed between deposited film and Si. For the formation of homogeneous film without underlying SiO2, the growth rate of bismuth silicate should be faster than the deposition rate of Bi2O3 as well as the oxidation rate of Si substrate.
Electro- and Thermomigration of Metallic Islands on Si(100) Surface
Authors: Ichinokawa Takeo , Haginoya Chiseki , Inoue Dai , Kirschner Hiroshi Itoh
Published: February 2005

Electro- and thermomigration of metallic islands of µm size formed by vapor deposition on the Si(100)2×1 surface have been investigated using an ultrahigh-vacuum scanning electron microscope (UHV-SEM) at substrate temperature higher than the melting point of the islands. The direction of electromigration versus the electric current depends on the type of metal, whereas the direction of thermomigration is always from the cold to hot side independent of the type of metal. The velocity of islands is approximately proportional to the island radius and increases exponentially with temperature for both cases. The activation energies of electro- and thermomigration are approximately 0.6 eV for Au-Si islands having a eutectic composition. The driving forces which act on the islands are discussed based on the diffusion theories for electro- and thermomigration.
Deposition of SiO2 Films from ArF Laser Photolysis of Si2H6/N2O Mixtures in a Parallel Irradiation Configuration
Authors: Tsuji Masaharu , Itoh Naoki , Minoru Sakumoto Minoru Sakumoto , Yukio Nishimura Yukio Nishimura
Published: February 2005

Deposition of SiO2 thin films by the unfocused ArF excimer laser photolysis of Si2H6/N2O mixtures in a parallel configuration has been studied in the low substrate-temperature range of 30-400°C. The refractive index of oxide films agreed with that of stoichiometric SiO2 in the substrate-temperature range of 50-400°C. Basic properties of the deposited films were studied as a function of the substrate temperature, the deposition time, the laser repetition rate, the total pressure, and the N2O/Si2H6 flow ratio. The maximum growth rate was ∼70 Å/min at a substrate temperature of 400°C, a laser repetition rate of 50 Hz, a total pressure of 1 Torr, and a N2O/Si2H6 flow ratio of ∼1200.
Coverage-Dependent Growth Structures of Sodium on the GaAs(110) Surface
Authors: Bai Chunli , Hashizume Tomihiro , Dong-Ryul Jeon Dong-Ryul Jeon , Toshio Sakurai Toshio Sakurai
Published: February 2005

The geometry and the coverage-dependent growth structures formed by Na deposition on the GaAs(110) surface were studied by a field-ion scanning tunneling microscope (FI-STM) in an ultrahigh-vacuum. In the low-coverage regime at 300 K, Na adatoms reside on a bridge site encompassing one Ga and two As surface atoms to form linear chains along the substrate [11̄0] direction. The Na-Na nearest-neighbor distance in this low-density chain structure is 0.8 nm. With slightly larger Na coverages, the chains became disordered. Some of them were packed closer to form domains showing a local 2×2 structure. None of high-density 2D ordered structures or low-density zigzag chains were observed, in contrast to the Cs/GaAs(110) system. Additional Na adsorption resulted in the formation of three-dimensional disordered clusters. The saturation coverage of Na adsorption on the GaAs(110) surface was determined to be about 0.1 ML (1 ML=2 Na per substrate unit cell). The I-V curve recorded over the clean surface was consistent with published data for n-GaAs(110), while no evidence of metallic characteristics was found in the I-V curves recorded over the various Na-covered surfaces.
Surface Structure and Electronic Property of Reduced SrTiO3(100) Surface Observed by Scanning Tunneling Microscopy/Spectroscopy
Authors: Tanaka Hiroyuki , Matsumoto Takuya , Tomoji Kawai Tomoji Kawai , Shichio Kawai Shichio Kawai
Published: February 2005

We have obtained the scanning tunneling microscopy (STM) images and scanning tunneling spectroscopy (STS) data with atomic-scale resolution for a SrTiO3(100) surface annealed in ultrahigh vacuum (UHV) at 1200°C. A √5×√5-R26.6° surface superstructure indicating oxygen vacancy ordering has been observed. The STS data provide evidence for a localized surface state arising from oxygen vacancies at 1.35 eV below the Fermi level. STM images of the √5×√5 structure correspond to the surface orbital of the ordered Ti-oxygen vacancy complex.
Scanning Tunneling Microscopy of Oxygen and Sodium Adsorption on the Si(111) Surface
Authors: Jeon Dong-Ryul , Hashizume Tomihiro , Sakurai Toshio
Published: February 2005

The surface structure and the insulator-metal transition of the Na overlayer on the Na-induced Si(111)3×1 surface was studied using scanning tunneling microscopy and spectroscopy. The results suggested that this reconstruction was caused by the conversion of the 7×7 structure to the bulk-terminated 1×1 structure and a monolayer of Na adatoms arranged in the 3×1 periodicity at a coverage of 2/3 monolayer. When oxygen was adsorbed on this surface the surface morphology hardly changed up to several hundred Langmuir. This surface passivation arose from the removal of Si dangling bonds by the Na adatoms. Upon further Na evaporation onto the Si(111)3×1-Na surface at room temperature we could grow an epitaxial Na double layer and a multilayer through an island formation. Oxygen adsorption on the Na double layer, and a multilayer resulted in cluster formation. This result indicated that more than two layers of alkali overlayer was needed to promote the chemical activity on a silicon surface.
Electronic and Geometric Structures of Fullerenes and Metallofullerenes
Authors: Saito Susumu , Sawada Shin-ichi , Oshiyama Noriaki Hamada
Published: February 2005

We report the electronic and geometric structures of certain fullerenes and metallofullerenes. First, results on all the possible candidates for C84 are shown. Their geometries have been optimized by means of the empirical model potential and their electronic structure has been obtained by means of the generalized tight-binding model. Comparison of the density of states (DOS) with the experimental photoemission spectrum shows the preference of one candidate proposed according to the ring-stacking growth model as a major C84 isomer. The present results on C84 are found to be able to give a conclusive answer for the C84 structure after the separation of isomers in the near future. Next, we show the electronic structure of the endohedral metallofullerene C60 Ca obtained using the local-density approximation in the density-functional theory. Finally, the growth model and the geometry of the metallofullerene LaC82 are presented.
Comparison of Atomic Force Microscopy and Nanoscale Optical Microscopy for Measuring Step Heights
Authors: Hiroshi Komatsu Hiroshi Komatsu , Satoru Miyashita Satoru Miyashita
Published: February 2005

Comparison of measured step heights was carried out by means of nanoscale optical microscopes and an atomic force microscope (AFM) using a Frank spiral as a standard reference. It was found that the individual step height of the spiral was about 16.5 nm as obtained using two-beam interferometry, but AFM showed the height as 23.45-18.98 nm. This discrepancy was discussed briefly.
Single-Electron-Charging Effect Controlled by the Distance between a Substrate and a Liquid-Crystal Molecule
Authors: Nejoh Hitoshi , Ueda Masahito , Masakazu Aono Masakazu Aono
Published: February 2005

Single-electron-charging effects in a minuscule liquid-crystal molecule cannot be described in terms of a single-parameter-the capacitance. We performed a molecular-orbital-calculation to explain unequal Coulomb-staircase-edge spacings observed at room temperature. Since Coulomb blockade is a phenomenon associated with electron tunneling, it is describable using a transition probability from the initial state to the final state, where the initial state is the state before an electron enters into a molecule and the final state is the state after an electron enters into the molecule. When the applied electric field strength to the molecule overcomes an energy increase in the final state, the transition probability increases abruptly. This causes the Coulomb staircase edges. The effective charge confined within a molecule is determined by the distance between a molecule and a substrate.
Sensitivity of Residual Stress to Moisture Penetration on Optical Thin Films
Authors: King Hong-Jueng , Lee Bor-Ming , Shao Ching-An , Chou Chien , CHiang Fu-Pen
Published: February 2005

A Michelson-type, whole-field residual stress measurement method has been set up. From this method, two-dimensional out-of-plane partial slope contours of optical thin films were obtained. The linear and the rotational mismatch techniques in the experiment help to improve the sensitivity of measurement and determine the signs of residual stress. Whether aluminum film, the most popular material used in reflective optical components, is coated with protective layers (SiO or MgF2) or not, exposure to the background humidity is unavoidable because moisture penetrates into aluminum film. In this paper, we point out that the residual stress of aluminum film changes drastically because of moisture absorption. This highly sensitive residual stress measurement method also shows that protective layers cannot prevent moisture penetration.
Preparation and Characterization of Electrodeposited CuInSe2 Thin Films
Authors: Sudo Yoshihiro , Saburo Endo Saburo Endo , Taizo Irie Taizo Irie
Published: February 2005

CuInSe2 thin films were prepared on SnO2-coated glass by electrodeposition from aqueous solution containing CuCl2, InCl3 and SeO2. The deposition was carried out by varying cathode potential. It was found that the Cu/In ratio which influences CuInSe2 characteristics greatly can be controlled by the cathode potential. Annealing of as-deposited films in N2 atmosphere at 350°C was found to result in the formation of CuInSe2 films having a chalcopyrite structure. With the use of these annealed CuInSe2 thin films, CdS/CuInSe2 thin-film solar cells were formed as a preliminary step and the conversion efficiency of 1.49% was obtained.
Neutron Structural Studies of Superconducting Bi2Sr2CuO∼6 and Bi2-xPbxSr1.8La0.2CuO6+δ (x=0.0 and 0.2)
Authors: RajagopaL Hariharasubramoniaiyer , Sequeira Anisbert , Yakhmi Jatinder Vir , Sastry Pamidi Venkata Purna Siva Sankara , Iyer Ranga Mahadeva
Published: February 2005

We have investigated the influence of incorporation of La- and Pb-ions on the structural features of Bi-2201 system by Rietveld refinement of the neutron diffraction patterns of samples with three different compositions, viz. (A) Bi2Sr2CuO∼6 with T
c

R=0=9.5 K; (B) Bi2Sr1.8La0.2CuO6+δ with T
c

R=0=16.5 K; and (C) Bi1.8Pb0.2Sr1.8La0.2CuO6+δ with T
c

R=0=21 K. The large fraction of vacancies observed at Bi-, Sr-, Cu- and O(2)-sites in the sample A get filled up on substitution of La in the sample B. However, these vacancies reappear to a smaller extent for the sample C. The O(3)-ions belonging to the Bi-double layer are found to be disordered for all the three samples, though the nature of the disorder is highly sensitive to the type of substitution. A correlation exists between bond valence of the Cu-sites and the measured T
c-value of the three samples.
Growth of Superconductive Bi2Sr2CaCu2Ox Film by Liquid Phase Epitaxy
Authors: Yamaguchi Toshinao , Fumito Ueda Fumito Ueda , Masaaki Imamura Masaaki Imamura
Published: February 2005

The growth of Bi-Sr-Ca-Cu-O film by means of liquid phase epitaxy was studied in detail using KCl as a flux. The “2212” phase was difficult to grow on the MgO substrate by means of this method. However, stable growth of the “2212” phase was obtained when the GGG (gadolinium gallium garnet) substrate was used. The film showed high c-axis orientation and good superconductive characteristics.
Characterization of a Longitudinally Pumped CW, Room-Temperature Operation of Tm3+:YVO4 Laser
Authors: Ohta Kei , Saito Hideaki , Obara Minoru , Djeu Nicholas
Published: February 2005

Spectroscopic measurements were carried out to identify the fundamental optical properties of the Tm3+:YVO4 crystal (5 at.% Tm3+ ion concentration) as a laser medium. Absorption spectra, emission cross section versus wavelength of the 3F4-3H6 laser transition, and effective radiative lifetimes closely related to the laser diode pumping kinetics were derived from the measurements. We developed a rate equation model to describe the laser oscillation characteristics in terms of the lasing spectra. The theoretical results agreed well with the experimental results.
Double Heterostructure Pb1-xSrxS/Pb1-ySryS Lasers Prepared Using Hot Wall Epitaxy
Authors: Mohammadnejad Shahram , Aikawa Kazunori , Akihiro Ishida Akihiro Ishida , Hiroshi Fujiyasu Hiroshi Fujiyasu
Published: February 2005

Pb1-xSrxS/Pb1-ySryS double heterostructure (DH) lasers were prepared for the first time using a hot wall epitaxy (HWE) system and their operating characteristics were determined. Under pulsed measurement conditions, the operational wavelength for the lasers became as low as 2.07 µm at 140 K. This wavelength is the shortest wavelength ever reported for a IV-VI compound semiconductor laser.
SrS:Ce Thin-Film Electroluminescent Devices Fabricated by Post-Annealing Technique and Their Electrical Properties
Authors: Okamoto Shinji , Takao Kuki Takao Kuki , Takeo Suzuki Takeo Suzuki
Published: February 2005

A postannealing technique has been used to make double-insulating SrS:Ce thin film electroluminescent (EL) devices. This technique has the effect of lowering the substrate temperature during SrS:Ce deposition, and also of improving the luminance and emission color with blueshift. Using this technique, the controllability of thin film processing and reproducibility of the devices have also been improved. A suitable annealing temperature is about 720°C. The device has a luminance of 320 cd/m2 and improved color coordinates, x=0.18 and y=0.35, using a 1-kHz drive frequency. The devices have also been evaluated as to EL properties and film crystallinity. In particular, a novel way of directly measuring the transient electric field across the active layer has been proposed.
Growth Mechanism of ZnS:Mn Films Obtained by Hydrogen Plasma Sputtering and Its Application to a Thin-Film Electroluminescent Device
Authors: Sakama Hiroshi , Ohmura Masanori , Tonouchi Masayoshi , Miyasato Tatsuro
Published: February 2005

ZnS:Mn electroluminescent (EL) devices were fabricated by the technique of hydrogen plasma sputtering (HPS). ZnS films were grown by HPS followed by annealing at 500°C for 1 h in a vacuum. Greater brightness was obtained when the growth of ZnS:Mn film was performed at 30°C than at 200°C. From the results of scanning electron microscopy (SEM) and electron probe microanalysis (EPMA), it was found that the quality of ZnS:Mn film deposited at 200°C is poor due to the lack of sulfur atoms. The films grown at 30°C are sulfur-rich and have better crystallinity. Manganese concentration of the HPS film increases with decreasing sputtering pressure. The growth rate shows the similar tendency with decreasing the pressure, which is explained by the glow discharge theory.
Structural and Electrical Properties of Lead-Zirconate-Titanate Thin Films Prepared by Multitarget Reactive DC Magnetron Cosputtering
Authors: Kim Kwang-Young , Kim Sung-Tae , Woong-Kil Choo Woong-Kil Choo
Published: February 2005

We have investigated the structural and electrical properties of lead-zirconate-titanate (PZT) thin films prepared on Pt/Ti/SiO2/Si substrates by multitarget reactive DC magnetron cosputtering. Film composition has been controlled by independently varying the DC power applied to the Pb, Zr and Ti targets. A single perovskite phase with a pseudocubic structure has been obtained with postannealing at 550°C in oxygen. The structure, composition and chemical state have been examined as a function of annealing temperature. The 0.65 µm- and 2.1 µm-thick films annealed at 550°C have dielectric constants of 178 and 497 at 100 kHz, remanent polarizations of 1.7 µC/cm2 and 2.4 µC/cm2 and coercive fields of 7.8 kV/cm and 8.4 kV/cm, respectively.
Diffusion of Point Defects in Silicon Crystals during Melt-Growth. II -One Diffusor Model-
Authors: Habu Ryuichi , Kojima Kiyoshi , Harada Hirohumi , Tomiura Azusa
Published: February 2005

We introduce the phenomenological equations which describe the diffusion of one species of point defects in silicon single crystals during melt-growth. The chemical potential of point defects frozen into the crystal during CZ crystal growth is estimated, and the formation mechanism of the OSF-ring in CZ crystal is discussed with the equations thus developed. It was shown that the phenomenological diffusion equations can explain well the dependence of the location of the OSF-ring in CZ-crystals on crystal growth rate, and disappearance of the OSF-ring at low growth rate. The OSF-ring is proposed to be generated at the peak of the chemical potential of point defects frozen into the crystal.
New Microwave Launcher for Producing ECR Plasmas without Window Contamination I. Excitation of Electron Cyclotron Wave
Authors: Tanaka Masayoshi , Tamaoki Makoto , Higashi Seiichiro , Matsuoka Morito , Akio Komori Akio Komori , Yoshinobu Kawai Yoshinobu Kawai
Published: February 2005

A new microwave launcher with a reflector plate is experimentally examined. The reflector plate covers the microwave window and prevents particles from depositing onto the window surface. Two types of launchers are tested in terms of achieved density, excited wave mode and microwave reflection. It is found that the Type-II launcher is capable of exciting an electron cyclotron wave and produces dense plasmas of 1012 cm-3 density.
Simultaneous Measurements of Plasma Potential and Density Fluctuations in a Bumpy Torus by a Heavy Neutral Beam Probe
Authors: Iguchi Harukazu , Takasugi Keiichi , Shoji Tatsuo , Junji Fujita Junji Fujita , Hideo Ikegami Hideo Ikegami
Published: February 2005

A heavy neutral beam probe was developed for simultaneous measurements of local space potential and density fluctuations in a plasma. It was applied to both electron cyclotron heated (ECH) and radio frequency heated (RF) plasmas in the bumpy torus NBT-1M, and the feasibility of this method was successfully demonstrated by observing a low frequency m=1 interchange mode which was rotating poloidally at a frequency near the E×B drift frequency. It was shown that use of this probe results in extension of the range of fluctuation measurement by beam probe technique to relatively low temperature plasmas. It is applicable to a plasma with a strong RF field with which Langmuir probes cannot be used.
AC Conduction Rule for a Gaseous Mixture
Authors: Masumi Sato Masumi Sato
Published: February 2005

The AC conduction rule for ions in a binary gaseous mixture is derived using the Langevin model for charged particle transport in an oscillating electric field. The complex mobility \dotµ=µr+jµi of the ion obeys simple sum rules expressed only in terms of mobilities at the source frequencies ω=0 and ∞. Specifically, µr and µi at high ω vary almost linearly with the portion of the mixture as do µr
-1 and ||
µi||
-1/2 at low ω according to Blanc's law.
Absorbed-Current Polarization Detector with Fe(110) Target
Authors: Takashi Furukawa Takashi Furukawa , Kazuyuki Koike Kazuyuki Koike
Published: February 2005

A new polarization detector for low-energy electrons is developed. It uses the spin dependence of the current absorbed by the target. Fe(110) is used as the target in order to provide high detection efficiency. A lock-in technique is used for high S/N detection of the spin dependence of the absorbed current. Basic performance is determined by applying the detector to a spin-polarized scanning electron microscope for magnetic domain observation. Results demonstrate that magnetic domain images can be obtained using the new detector.
Calculation of the Response of a Miller Exponential Signal Correlator to ODLTS Signals
Authors: Butcher Dimitri Alexiev
Published: February 2005

A theoretical derivation of the response function of a Miller exponential signal correlator to a optical deep level transient signal is presented for the calculation of trap energy and capture cross-section in high resistivity semiconductors.
Chaos in Excitable Lipid Membranes
Authors: Saida Yoshinori , Matsuno Tetsuya , Kiyoshi Toko Kiyoshi Toko , Kaoru Yamafuji Kaoru Yamafuji
Published: February 2005

An artificial excitable lipid membrane, which is composed of a porous filter filled with lipids, exhibits self-sustained oscillation of the membrane potential by DC electric current imposed across the membrane. The system yielded various electric oscillatory responses to sinusoidal AC electric currents superimposed on the DC current. At adequate frequency and amplitude of the sinusoidal stimulation, the oscillation was entrained (or synchronized) to the stimulation; the oscillation was desynchronized when the parameter (frequency or amplitude) was deviated to some extent from the initial value. Aperiodic oscillations appeared for parameter values located between entrained regions. Detailed analyses revealed that the aperiodic oscillations were chaotic, which was first shown quantitatively in artificial membrane systems.
Production of Ultra-Narrow Velocity Distributions of Slow Atoms with the Zeeman Tuning Technique
Authors: Sérgio Zilio Sérgio Zilio , Vanderlei Bagnato Vanderlei Bagnato
Published: February 2005

We have demonstrated the production of an atomic beam with a very narrow velocity distribution through the use of the Zeeman tuning technique together with a stimulated Raman transition. Such a beam has a reasonable density and may be useful for the study of collisions involving low velocity atoms.
Aggregation Trends in Some Macromolecules by Photon Correlation Spectroscopy
Authors: Brahm Pal Singh Brahm Pal Singh , Subhash Chopra Subhash Chopra
Published: February 2005

The experimental results for heat aggregation behavior in some macromolecules of significant biological importance, e.g., phycobilisomes (PBS) and insulin are reported. The heat aggregation studies on PBS were performed only in the neutral medium pH 7.5 and very dilute concentration regime (0.23 to 1.8 gL-1). The aggregation and dissociation trends in PBS were found to be linear with temperature upto 55°C. Insulin also in very dilute concentration showed the linear aggregation tendency with temperature up to 35°C but on temperature reversal (self-cooling) insulin showed the hysteresis like behavior unlike the PBS. The hysteresis like behaviour at pH 7.5 was found to be predominantly large. In both cases the polydispersity observed in correlation spectra was quite low.
Influence of Boron in Semi-insulating GaAs Crystals on Their Electrical Activation by Si-Ion Implantation
Authors: Okubo Seiichi , Otoki Yoohei , Watanabe Masatoshi , Kuma Shoji
Published: February 2005

The influence of boron on the activation of silicon ions implanted in semi-insulating GaAs crystals grown by liquid encapsulated Czochralski (LEC) method from As-rich melt was investigated using crystals with the same carbon concentration and the same deep donor (EL2) concentration. The resistivity of the crystal was not affected by the boron concentration. The sheet resistivity of the implanted layer, however, became higher with increase of the boron concentration. An analysis of the electrical properties of the implanted layer suggested that the occupation rate of the implanted silicon at As site (SiAs), which decides the acceptor level, increased with the boron concentration. The dependence of this occupation rate was influenced by the annealing temperature for activation in the region of low boron concentration under 15×1016 cm-3.
Current-Voltage Characteristics of p-p Isotype InGaAlP/GaAs Heterojunction with a Large Valence-Band Discontinuity
Authors: Itaya Kazuhiko , Masayuki Ishikawa Masayuki Ishikawa , Gen-ichi Hatakoshi Gen-ichi Hatakoshi
Published: February 2005

Current-voltage characteristics of p-InGaAlP/p-GaAs heterojunctions have been investigated. A heterospike at the heterointerface of InGaAlP/GaAs generated a large voltage drop, which strongly depended on the Al composition and the acceptor concentration of InGaAlP layer. Insertion of an intermediate layer of InGaP, which had an intermediate band gap between those of InGaAlP and GaAs, significantly reduced the voltage drop by an order of 103. These experimental results were in good agreement with the theoretical calculation accounting for a large valence band discontinuity between InGaAlP and GaAs.
Applicability of TiN Adhesion Layer Formed by Nitridation of Sputtered Ti Film to Blanket CVD-W Contact Filling
Authors: Chen Shih-Chang , Sakamoto Akihiro , Tamura Hiroyuki , Masaki Yoshimaru Masaki Yoshimaru , Masayoshi Ino Masayoshi Ino
Published: February 2005

TiN film formed by rapid thermal nitridation (RTN) of sputtered titanium (Ti) was used as the adhesion layer for chemical vapor deposition (CVD) blanket tungsten (BLK-W) in a very high-aspect-ratio contact filling process. In contact holes, both TiN and TiSi2 layers, which formed simultaneously during RTN become thin in proportion to the decrease of the Ti film thickness because of the increase of the contact aspect ratio. Therefore, contact resistance increase and barrier effect degradation of the TiN adhesion layer during subsequent BLK-W film deposition are of concern when employing RTN of sputtered Ti film as the formation process technique in VLSI's. This study focused on the applicability of a TiN adhesion layer formed by RTN of sputtered Ti film to BLK-W contact filling technology in very high-aspect-ratio contacts.