bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Undulator for Generating Variably Polarized Radiation
Authors: Sasaki Shigemi , Miyata Koji , Takada Takeo
Published: February 2005

A new undulator is proposed for generating variably polarized radiation. This undulator consists of two pairs of planar permanent magnet arrays above and below the electron orbit plane. The magnetic field of this undulator induces helical or sinusoidal electron orbit motion by shifting the relative positions of pairs of magnet arrays. It leads to the generation of circularly or linearly polarized undulator radiation.
Photonic Integrated Circuit Combining Two GaAs Distributed Bragg Reflector Laser Diodes for Generation of the Beat Signal
Authors: Maeda Minoru , Hirata Takaaki , Suehiro Masayuki , Hihara Mamoru , Akira Yamaguchi Akira Yamaguchi , Haruo Hosomatsu Haruo Hosomatsu
Published: February 2005

We have fabricated a photonic integrated circuit (PIC) that had two GaAs distributed Bragg reflector (DBR) laser diodes (LD) and a Y-branch coupler integrated by means of the compositional disordering of a quantum well. Using this PIC as an optical heterodyne sweeper, frequency characteristics of a GaAs Schottky photodiode were measured.
Raman Study of Epitaxial Ga2Se3 Films Grown by Molecular Beam Epitaxy
Authors: Yamada Akira , Kojima Nobuaki , Takahashi Kiyoshi , Okamoto Tamotsu , Konagai Makoto
Published: February 2005

Epitaxial Ga2Se3 films grown by molecular-beam epitaxy were characterized by Raman spectroscopy. Raman spectra of the obtained Ga2Se3 films showed two broad peaks at 250 cm-1 and 300 cm-1, and one sharp peak at 155 cm-1. The intensity of the sharp peak strongly depended on the VI/III ratio (Se beam flux/Ga beam flux), and maximum intensity was obtained for the film grown with a VI/III ratio of 150.
The experimental spectra were analyzed in terms of an axially symmetric lattice-dynamical model for the first time. It is determined from both calculation and experiment that the sharp peak at 155 cm-1 shows A1 symmetry, which originates in the vacancy-ordering of Ga2Se3.
Alignment of Nematic Liquid Crystals by Polyimide Langmuir-Blodgett Films
Authors: Murata Makoto , Awaji Hiroshi , Isurugi Masakazu , Masakazu Uekita Masakazu Uekita , Yoshihisa Tawada Yoshihisa Tawada
Published: February 2005

Nematic liquid crystals with a high degree of alignment were prepared using polyimide (PI) Langmuir-Blodgett (LB) films. Polyimides with a linear primary structure are favorable for attaining highly oriented PI LB films. Furthermore, orientation of the PI LB films is essential in order to achieve well-aligned nematic liquid crystal molecules.
Excitation Spectra of the Visible Photoluminescence of Anodized Porous Silicon
Authors: Motohiro Tomoyoshi , Kachi Tetsu , Miura Fusayoshi , Takeda Yasuhiko , Shi-aki Hyodo Shi-aki Hyodo , Shoji Noda Shoji Noda
Published: February 2005

Porous silicon samples, photoluminous in orange, pink or greenish yellow, were formed by anodization. The shapes and wavelength positions of their photoluminescence peaks were not influenced by the excitation wavelength. The photoluminescence intensity at any wavelength between 520 nm and 800 nm varied as a function of the excitation wavelength in accordance with the imaginary part of the spectral refractive index of bulk silicon. Thus, the excitation process responsible for the visible photoluminescence of porous silicon seems to be bulk-silicon-like.
Superconducting 2201 Phase in the Bi2PrxCa2-xCuOz System
Authors: Sasakura Hiroyuki , Minamigawa Shinnosuke , Teraoka Hiroshi , Hirose Akinori , Noguchi Satoru , Okuda Kiichi
Published: February 2005

A new Sr-free Bi cuprate superconductor has been synthesized in the Bi2Pr
x
Ca2-x
CuO
z
system. The superconducting phase was isostructural to the 2201 phase (Bi2Sr2CuO
z
). The almost-single phase was attained at the nominal composition of x=0.7∼0.8. The sample with x=0.7 showed a superconducting onset at about 12 K and zero resistivity at about 6 K. The crystal structure had a pseudotetragonal symmetry with a=0.5381 nm and c=2.381 nm.
Anomalous Thermal Expansion in La2-xSrxCuO4
Authors: Yasuhiro Ono Yasuhiro Ono , Shin-ya Narita Shin-ya Narita
Published: February 2005

Lattice constants of La2-x
Sr
x
CuO4 (x=0.05, 0.10 and 0.15) are precisely determined as a function of temperature from 13 K to room temperature by Rietveld analysis using X-ray powder diffraction data. In La1.95Sr0.05CuO4 and La1.90Sr0.10CuO4, unit cell volumes show a small change below 50 K and 70 K, respectively. Anomalous volume change around T
c found in La1.85Sr0.15CuO4 and La1.90Sr0.10CuO4 cannot be explained only by superconductivity. The comparison between lattice constants in all samples is suggestive of the structural phase transition preceding the appearance of superconductivity.
Fabrication and Superconducting Properties of AgCu Alloy-Sheathed BiSrCaCuO Oxide Tapes
Authors: Tanaka Yoshiaki , Asano Toshihisa , Yanagiya Tomoyuki , Fukutomi Masao , Kazunori Komori Kazunori Komori , Hiroshi Maeda Hiroshi Maeda
Published: February 2005

Ag-Cu alloy-sheathed BiSrCaCuO tapes have been successfully fabricated. Critical temperature higher than 100 K (T
c-onset) was obtained for the Ag-13 at%Cu alloy-sheathed tape of the (Bi, Pb)2Sr2Ca2Cu3O
x
phase. T
c
′s of ∼80 K were obtained for the Ag-Cu alloy tapes of the Bi2Sr2Ca1Cu2O
x
phase with Cu content less than ∼25 at%. Critical current density reached 3.5×104 A/cm2 at 4.2 K and 12 T for the Ag-10 at%Cu alloy-sheathed Bi2Sr2Ca1Cu2O
x
-phase tapes. Mechanical strength of the sintered tapes could be increased, as well as improvement in workability of the wires and tapes.
Novel Superconductive Delay Line Process Using High-Tc Superconducting Films
Authors: Nagai Yasuhiro , Suzuki Naobumi , Yoshihiro Kimachi Yoshihiro Kimachi , Osamu Michikami Osamu Michikami
Published: February 2005

This letter reports a novel process for fabricating long and large-area superconductive delay lines. This process makes it possible to repattern easily without degrading superconducting properties and to obtain low contact resistance. A contact resistance of less than 3×10-5 Ω·cm2 can be obtained at a relatively low baking temperature in air. The process was used to fabricate a practical superconductive delay line 160 µm wide and 40 cm long. This line had a low insertion loss of 0.068 dB/ns at 1 GHz and 77 K.
Highly Transparent Memory States by Phase Transition with a Field in Polymer Dispersed Liquid Crystal Films
Authors: Rumiko Yamaguchi Rumiko Yamaguchi , Susumu Sato Susumu Sato
Published: February 2005

Memory effects and PTF (phase transition with a field) effects are investigated in PDLC (polymer dispersed liquid crystal) films which show different three kinds of morphology. Highly transparent on states and memory states are obtained by PTF operation. The PTF effect is marked in PDLC films with complicated polymer structures.
Elimination of Negative Surface Leader by a Hollow Electrode
Authors: Murasaki Yoshiaki Yamano
Published: February 2005

In an insulator with a backing electrode, negative surface leaders appear under ac voltage in air. When a hollow-type electrode is used, the negative surface leader is almost eliminated. With optimal size of the hollow for elimination, the number of generated negative leaders is at least 1/100 less than that in the electrode without a hollow at 40 kVp. An increase in flash over voltage is also observed when the hollow electrode is used.
Crossed-Beam Study of Initial Vibrational Distribution of KrF Excimer Produced in the Reaction of Kr*+F2
Authors: Komatsu Haruko , Kano Satoru S. , Shimizu Hiroshi Takuma
Published: February 2005

The reaction of metastable Kr with F2 to form KrF excimer is studied using the crossed-molecular-beam technique. An emission spectrum of KrF* is obtained in the 210-265 nm region. The spectrum appreciably differs from a previous one that has been obtained in a flowing afterglow experiment. The vibrational distribution of KrF* formed by the crossed beam is well described by a linear surprlsal distribution with λυ=-4.0, while that from the flowing afterglow has been described with λυ=-2.5. It is found that vibrational levels with υ=50-90 are highly populated.
Imaging Conditions for Resolving Oxygen Atoms in ZrO2 by an Ultra-High-Resolution High-Voltage Electron Microscope
Authors: Shigeo Horiuchi Shigeo Horiuchi , Yoshio Matsui Yoshio Matsui
Published: February 2005

The imaging conditions for resolving oxygen atoms in ZrO2 are clarified based on real images by ultra-high-resolution high-voltage electron microscopy (UHR-HVEM) as well as on calculated ones by computer simulation. A defocus vs thickness map clearly defines an area of the so-called structure image, in which not only Zr but also oxygen atoms are resolved as dark spots. Additional areas with reversed contrast are noted. It is also revealed that defects of oxygen atoms can be imaged only in the structure image.
Current-Pressure Characteristics of Ar Field Ion Source at High Pressures
Authors: Mieko Sato Mieko Sato
Published: February 2005

The ion current characteristic of an Ar field ionization source as a function of pressure has been studied using a W tip. The characteristic at low pressures shows a linear relationship, while at high pressures it shows an anisotropic change. A Field Ionization Microscopy image in the latter case shows an extremely localized emission on {110} planes, which suggests the origin of the unusual characteristic at high pressures.
Structural Aspects of Heavily Carbon-Doped GaAs Grown by Metalorganic Molecular Beam Epitaxy (MOMBE)
Authors: Fujimoto Isao , Nishine Shiro , Yamada Takumi , Konagai Makoto , Takahashi Kiyoshi
Published: February 2005

X-ray diffraction analysis has clarified structural features of heavily carbon-doped GaAs films grown by metalorganic molecular beam epitaxy (MOMBE). X-ray quasi-forbidden reflection (XFR) intensity measurements have provided direct evidence that almost all the doped C atoms occupy As sites and cause large displacements of the nearest-neighbouring Ga and the second-nearest-neighbouring As atoms. X-ray rocking curve analysis has also shown that large lattice strain remains unrelaxed even for an epilayer far thicker than the critical thickness, although a high density of misfit dislocations has been observed by X-ray topography.
Enhancement of Electron Density in the Base of GaSb/InAs Hot Electron Transistor
Authors: Funato Kenji , Taira Kenichi , Fumihiko Nakamura Fumihiko Nakamura , Hiroji Kawai Hiroji Kawai
Published: February 2005

Electron density was measured in the InAs base of symmetric GaSb/InAs/GaSb hot electron transistors whose base widths were from 7 to 30 nm. The density was enhanced one order of magnitude at room temperature and 77 K, compared with bulk InAs. It has nonlinear dependence on the base width, and tends to saturate. These results suggest that electrons mainly originate from outside of the base. The enhancement of electron density reduces the base resistance without doping, and will benefit high-frequency performance. The measurement of magnetoresistance at 3 K reveals that the enhancement is partially caused by the electrons' flow from the GaSb valence band to the InAs conduction band.
Novel Dual Wavelength Electro-Optical Bistability in InGaAs/AlGaAs Multiple Quantum Wells
Authors: Giugni Stephen , Kawashima Kenji , Sano Kenzo Fujiwara
Published: February 2005

Novel dual wavelength electro-optical bistability has been demonstrated in a resistor biased InGaAs/AlGaAs multiple quantum well self electro-optic effect device by the use of n=1 and n=2 electron to heavy-hole exciton states. A new concept is proposed to obtain a dual wavelength optical set-reset latch in a single device structure, and the clear bistable operation is evidenced by photocurrent switching experiments. Advantages of this new device configuration are discussed.
Effect of Y Substitution for Ca in Bi2Sr2CaCu2O8+d Superconducting Films Prepared by Liquid Phase Epitaxial Method
Authors: Shin Jae Soo , Enomoto Hiroyuki , Takeshi Kishimoto Takeshi Kishimoto , Hajime Ozaki Hajime Ozaki
Published: February 2005

The effect of Y substitution for Ca on superconducting properties has been investigated in Bi2Sr2CaCu2O8+d
films prepared by liquid phase epitaxial method. The Y concentration in the film, x
S, increased in proportion to that in the solution, x
L, in the region of 0≤x
L≤0.2, and then it was saturated. The incorporation ratio of Y in solid and in liquid, x
S/x
L, for 0≤x
L≤0.2 was found to be about 3. The x
S dependences of the zero-resistance temperature and the carrier concentration showed that about half of the Y concentration incorporated in the films contributes to the effect of the Y substitution obtained in sintered materials.
High-Temperature Superconductivity and Normal-State Anomaly
Authors: Masanori Sugahara Masanori Sugahara
Published: February 2005

A conduction experiment on LaSrCuO shows that (i) the carrier density dependence of the collision frequency of holes in the normal state has dips when x
′=4-N
(N=1, 2, 3,···), where x
′ is the hole density per one CuO2 cell, and that (ii) superconductivity appears in the interval 4-2<x
′<4-1. A model is proposed in which the normal state of LaSrCuO is characterized by localized hole pairing with some hierarchic structures even up to 300 K.
A Calculation of Electronic States in YBa2Cu3Oy
Authors: Yamamoto Takeshi , Shinagawa Kiminari , Toshiaki Saito Toshiaki Saito , Tachiro Tsushima Tachiro Tsushima
Published: February 2005

To clarify the optical properties of the oxide superconductors with the Cu-O plane and chain, one-electron energy levels and transition energies of a (CuO5)8- cluster and a (CuO2)3- cluster in YBa2Cu3O6.0 are calculated using the unrestricted SCF-Xα SW method. In the (CuO5)8- cluster, the observed optical transitions at 1.7 eV, 1.8 eV, 2.4 eV, 3.0 eV and 4.1 eV are assigned to the charge transfer (CT) transitions from O 2p to Cu3d
x
2-y
2
and to the d-d transition from Cu 3d
x
z
+3d
y
z
to 3d
x
2-y
2
. In the (CuO2)3- cluster, the observed optical transitions at 4.1 eV and 4.5 eV are assigned to the internal transition from Cu 3d
z
2
to Cu 4p and to the CT transition from O 2p to Cu 4s, respectively. In addition, from the calculation on a hole-doped (CuO5)7- cluster in the YBa2Cu3O6.8, it is found that the transitions observed in the low-energy region may be assigned to the charge transfer transitions from O 2p to Cu 3d
z
2
, and to the d-d transition from Cu 3d
x
z
+3d
y
z
to 3d
z
2
.
Preparation of Ferromagnetic Organic Compounds by Pyrolysis of (2,4,6-Triphenoxy-1,3,5-Triazine/Melamine) in Ar Atmosphere Including a Trace of Dry Air
Authors: Araki Hisashi , Roh Young Bae , Nobuhiro Kuwamura Nobuhiro Kuwamura , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

Organic compound exhibiting strong ferromagnetism (saturation magnetization 10 emu·G/g) was prepared from a mixture of 2,4,6-triphenoxy-1,3,5-triazine (TPTA) and melamine (M) by pyrolysis at 950°C in Ar atmosphere including a trace of dry air. The electron spin resonance (ESR) signal of this material also exhibited remarkably large intensities (4.7×1023 spins/g) and peak-to-peak linewidth (804 G at 290 K or 1570 G at 100 K). The values of linewidth and of g-factor at 290 K are comparable to those of iron oxide and of iron, respectively.
Optically Pumped Blue Lasing in ZnSe-ZnMgSSe Double Heterostructures at Room Temperature
Authors: Okuyama Hiroyuki , Futoshi Hiei Futoshi Hiei , Katsuhiro Akimoto Katsuhiro Akimoto
Published: February 2005

We report the first operation of ZnSe-ZnMgSSe double-heterostructure photopumped blue lasers with a threshold excitation intensity at 150 kW/cm2 at room temperature. The lasing was confirmed by measuring the polarization. This result indicates that ZnMgSSe is a promising material for the cladding layer of a blue laser diode. Until now, no material had been lattice-matched to a GaAs substrate and had sufficient band-gap energy. If p-type and n-type doping is possible, this ZnSe-ZnMgSSe double heterostructure can be applied to a blue laser diode.
Plastic Fiber Optical Isolator and Current Sensor
Authors: Muto Shinzo , Seki Nobuo , Takashi Suzuki Takashi Suzuki , Toru Tsukamoto Toru Tsukamoto
Published: February 2005

The Verdet constant of poly-α-methylstyrene fiber doped with a biphenyl compound showed a value beyond 0.09 min·Oe-1·cm-1 at 488 nm. The optical fiber isolator for the 488-nm laser, which was constructed using the above plastic fiber and a pulse magnetic field, had about 20-dB isolation. This plastic fiber could also be used as an optical sensor head for monitoring higher current in a planar discharge circuit.
Irreversible Phase Transition in Nylon 6 Crystal Induced by Ultrahigh Electric Field
Authors: Itoh Takashi , Shimizu Hikaru , Kitagawa Motohiro , Osamu Yoshida Osamu Yoshida , Takashi Konishi Takashi Konishi
Published: February 2005

A steady and extremely high electric field up to 15 GV/m is applied to the solution-cast thin films of nylon 6 at temperatures below 473 K. It is found from IR spectroscopy, transmission electron microscopy and X-ray analysis that the α-form crystal of the polymer shows irreversible structural change into a polar smectic phase by applying electric fields on the order of 10 GV/m at temperatures between 453 and 468 K. An IR result suggests the possibility of ferroelectrics: the polarity of the polar phase is considered to be reversed at 468 K by applying an inverse field (15 GV/m) higher than the initial poling field (10 GV/m).
New Flip-Chip Bonding Technology for Superconducting IC
Authors: Ogashiwa Toshinori , Nakagawa Hiroshi , Akimoto Hideyuki , Takada Hiroyuki Shigyo
Published: February 2005

A new flip-chip bonding method for achieving superconducting electrical contacts has been developed by employing a rapidly solidified Pb-2Sn-0.1Cu-0.5Sb (wt%) alloy wire. The solder balls were made from the wire by means of arc discharge in Ar gas containing H2. The bumps were thermosonically fabricated on the Pb-20Sn film deposited on the mullite substrate. Subsequently, a Si chip coated with Nb/Au films was bonded on the substrate using those bumps by means of the thermal compression method. This method has a significant advantage of reducing the elevated temperature for flip-chip bonding to below 100°C.
Visible Photoluminescence from Si Microcrystals Embedded in SiO2 Glass Films
Authors: Osaka Yukio , Tsunetomo Keiji , Toyomura Fumitaka , Kohno Hiroaki Myoren
Published: February 2005

We report the observation of an efficient visible photoluminescence (PL) from Si microcrystals embedded in SiO2 glass films. The Si microcrystals were formed by the rf magnetron sputtering technique. The peak position of the PL spectra at 77 K shifts to a lower-energy side as the average diameter of the Si microcrystals increases.
Highly Resistive Iron-Doped AlInAs Layers Grown by Metalorganic Chemical Vapor Deposition
Authors: Ishikawa Hideto , Kamada Mikio , Hiroji Kawai Hiroji Kawai , Kunio Kaneko Kunio Kaneko
Published: February 2005

We report for the first time highly resistive iron-doped AlInAs layers grown by metalorganic chemical vapor deposition (MOCVD) using a popular iron doping source, (C5H5)2Fe. The linear relationship between Fe atom concentration of Fe-doped AlInAs layers, which was measured by SIMS analysis, and (C5H5)2Fe flow rate was obtained. To evaluate the effect of Fe doping quantitatively, samples of Si-doped n-AlInAs layers were prepared. The relation between carrier concentration and Fe atom concentration of the layers suggested that one Fe atom killed one carrier of n-type AlInAs. An Fe-doped AlInAs layer, with undoped AlInAs layers, which had a residual carrier concentration of 1∼2×1015 cm-3, showed highly resistive characteristics. We found a deep trap with an activation energy of 0.7 eV using photoexcited DLTS, which may cause compensation.
High Gain Npn AlGaAs/GaAs Heterojunction Bipolar Transistors Prepared by Molecular Beam Epitaxy
Authors: Wu Chung-Chang , Si-Chen Lee Si-Chen Lee , Hao-Hsiung Lin Hao-Hsiung Lin
Published: February 2005

The behavior of surface recombination current in AlGaAs/GaAs heterojunction bipolar transistors prepared by molecular beam epitaxy have been investigated. By using compositional grading of the emitter-base junction and emitter edge-thinning design, the 1-kT injection current can be increased whereas the surface recombination current is suppressed at the same time. Consequently, the maximum differential current gain reaches 4200 which, to our knowledge, is the highest reported to date for AlGaAs/GaAs heterojunction bipolar transistors prepared by molecular beam epitaxy.
A New Superconductor with Tc=47 K in the Bi-Sr-Cu-O System (Nominal Composition=Bi4Sr8+xCu5-xOy)
Authors: Tohru Den Tohru Den , Toshiaki Aiba Toshiaki Aiba
Published: February 2005

A new superconductive bismuth cuprate, with a nominal composition of Bi4Sr8+x
Cu5-x
O
y
, was discovered using resistivity and magnetization measurements. The onset transition temperatures of as-synthesized and He-annealed samples are 42 K and 47 K, respectively. This superconductive phase is very unstable at the synthesis temperature, and thus, changes into Bi4Sr8Cu5O19+α and Bi2Sr3Cu2O
y
with prolonged calcination. Because of this instability, a single phase cannot be obtained. X-ray diffraction measurements indicate the existence of a new phase with a large-value peak of d=19.8 Å.
RHEED Intensity Monitored Growth of Bi-Sr-Ca-Cu-O Superconductors
Authors: Sakai Shigeki , Yuji Kasai Yuji Kasai , Peter Bodin Peter Bodin
Published: February 2005

In order to fabricate Bi-Sr-Ca-Cu-O superconducting thin films, the molecular beam epitaxy (MBE) technique with in situ monitoring by reflection high-energy electron diffraction (RHEED) is used. By coevaporated growth of Bi2Sr2CaCu2O8 on LaAlO3 (100) substrates, RHEED intensity oscillation with a period corresponding to the growth of half a unit cell is observed. Out-of-phase oscillations are observed outside the specular spot. After the end of growth, a 10-minute RHEED intensity recovery at the specular spot is found. Possible mechanisms during and after growth are discussed.
Two-Dimensional Epitaxial Growth of Bi2Sr2CuOx on Tilted SrTiO3(001) Substrates Studied by Reflection High Energy Electron Diffraction
Authors: Ishibashi Takayuki , Song Kang-ho , Yoshitaka Okada Yoshitaka Okada , Mitsuo Kawabe Mitsuo Kawabe
Published: February 2005

Growth modes of Bi2Sr2CuO
x
(2201) thin epitaxial films have been studied by coevaporation technique in molecular beam epitaxy (MBE) on tilted SrTiO3(001) substrates with angles of 2°, 4°, and 6° toward [110]. Observation of RHEED intensity oscillations means that the growth proceeds by two-dimensional mode. After continued growth over 1.2 nm, clear RHEED patterns of the known superstructures were observed. For the 2° tilted substrates, the RHEED patterns indicated that most of the films consisted of untwinned structure with small portions of twinned structure. For 4° and 6°-tilted substrates, however, the RHEED patterns of untwinned structures were observed. Furthermore for 6°-tilted substrates, the RHEED patterns showed separated streaks, arising from the periodic step structures, which was not originally observed on the substrate surface.
Rotational Invariant Pattern Recognition Using Photorefractive Correlator
Authors: Chang Chi-Ching , Yau Yuh-Ping Tong
Published: February 2005

Real-time rotational invariant pattern recognition is demonstrated using the method of circular harmonic filtering (CHF) in a photorefractive crystal such a BaTiO3 to perform pattern recognition via four-wave mixing (FWM). Experimental results have shown that the recognition result is fully rotational and shift invariant.
Enhanced-Nitridation of Silicon by UV-Irradiation
Authors: Ishikawa Yutaka , Izumi Kobayashi Izumi Kobayashi , Ichiro Nakamichi Ichiro Nakamichi
Published: February 2005

Silicon can be directly nitrided at relatively low temperature under NH3 flow with UV-irradiation from a low-pressure mercury lamp. The typical thickness of film is 6.2 nm for nitridation of 1 h at 800°C. The thickness is saturated with an increase in nitridation time. The Auger electron intensity of nitrogen is about two times larger than that of oxygen at the surface of the film. The apparent peak of IR absorption by the Si-N bond is seen at a wave number of 835 cm-1.
Electrical and Optical Properties of ZnS:Sb, Te Grown from Sb0.4Te0.6 Solution
Authors: Nagano Masahiro , Kanie Hisashi , Yoshida Iwao , Aoki Masatoshi Sano
Published: February 2005

ZnS crystals doped with Sb and Te were grown from an Sb0.4Te0.6 solution by means of a temperature-difference method. The grown crystals were transparent and platelike with a cubic structure. The Te concentration in the grown crystals varied from 0.10 atom% to 0.20 atom% as the growth temperature rose from 700°C to 1000°C, whereas the Sb concentration was 0.01 atom% in the entire range of growth temperature. All the crystals showed n-type conduction. The resistivity of the crystals grown at 700°C was 104 Ω·cm. They showed blue luminescence at room temperature. The emission intensity was higher than that of ZnS:Te.
Evidence of Ga2Se3-Related Compounds on Se-Stabilized GaAs Surfaces
Authors: Takatani Shinichiro , Nakano Asao , Ogata Kiyoshi , Takeshi Kikawa Takeshi Kikawa
Published: February 2005

A Se-stabilized GaAs(001) surface is examined by extended X-ray absorption fine structure (EXAFS) analysis. The Se K-edge EXAFS shows components due not only to the first but also the second nearest neighbors, indicating that the Se atoms are incorporated into ordered atomic arrangements. Comparing the interatomic distances to those measured for Ga2Se3 and GaSe, it is concluded that the nature of the surface compound on the Se-stabilized GaAs surface is close to that of Ga2Se3.
Several Blue-Emitting Thin-Film Electroluminescent Devices
Authors: Miura Noboru , Ishikawa Tetsuo , Sasaki Takashi , Oka Toshiyuki , Ohata Hiroshi , Hironaga Matsumoto Hironaga Matsumoto , Ryotaro Nakano Ryotaro Nakano
Published: February 2005

Blue-emitting thin-film electroluminescent (EL) devices were studied. As the blue-emitting phosphor, thin-films in which the Tm3+ ion was doped into several hosts (ZnS, Y2O2S, CdF2, ZnF2 and YF3) and CaF2:Eu were investigated. Blue EL emission of Tm3+ ions arising from the 1D2→3H4 or 1G4→3H6 transition was observed in each Tm-doped device. The most dominant lines in these emissions varied with the kind of host materials. The CaF2:Eu thin-film also showed blue electroluminescence due to a parity-allowed 4f6(7F)5d→4f7(8S) transition of the Eu2+ ion.
Site Occupancy and Anharmonic Thermal Vibration in Superconductor Tl2CaBa2Cu2O8
Authors: Sasaki Satoshi , Kawaguchi Kenichi , Nakao Masao
Published: February 2005

Crystal structure analysis of Tl2Ca
n-1Ba2Cu
n
O2n+4 (n=2; I4/mmm) was performed using single-crystal X-ray intensity data up to sin θ/λ=1.37 Å-1. The cell dimensions are a=3.8471(6) and c=29.397(5) Å. The chemical formula determined by X-ray diffraction is (Tl0.864Cu0.136)2(Ca0.910Tl0.090)Ba2Cu2O8. The O(3) atoms occupy the 4e sites at (1/2, 1/2, z). Difference-Fourier syntheses showed the existence of anharmonic thermal vibration for Tl and Ba atoms, which was described by the Gram-Charlier series expansion of the Gaussian density function. The R value was 0.015 (R
w=0.014) for 637 reflections averaged from 43188.
Electron Diffraction and High-Resolution Electron Microscopy Study on the Structure of Solid C60
Authors: Hirotsu Takashi Ishiguro
Published: February 2005

The structure of solid C60 was studied by means of electron diffraction and high-resolution electron microscopy. From both the plan-view and sectional observations of platelike specimens, the solid C60 was concluded to have the fcc structure. The weak reflections, which have been viewed as those from the hcp structure, were found to be due to the effect of the Ewald sphere cutting of streaked intensity regions caused by the stacking disorder in the fcc structure.
Low-Field Giant Magnetoresistance in [Ni-Fe-Co/Cu/Co/Cu] Superlattices
Authors: Hiroshi Sakakima Hiroshi Sakakima , Mitsuo Satomi Mitsuo Satomi
Published: February 2005

[Ni-Fe-Co/Cu/Co/Cu] superlattices were prepared by RF sputtering. The superlattices showed low-field (<500 Oe) giant magnetoresistance (Δρ/ρ=15%) at RT when the Cu layer thickness was about 2 nm. The MR (magnetoresistance) ratio was found to oscillate with the Cu spacer layer thickness with a period of 1.1 nm, which implies RKKY (Ruderman-Kittel-Kasuya-Yosida)-like interlayer exchange coupling between the magnetic layers.
Study of Luminescent Region in Anodized Porous Silicons by Photoluminescence Imaging and Their Microstructures
Authors: Noguchi Nobuaki , Suemune Ikuo , Yamanishi Masamichi , Hua G. C. , Otsuka Nobuo
Published: February 2005

The luminescent region in anodized porous silicon was examined by means of a photoluminescence imaging technique. It was found for the first time that the luminescence in the visible region originates from the topmost surface layer. This was confirmed not only by the surface photoexcitation but also by the excitation of the cleaved edge. This topmost surface layer does not show any diffraction spots with transmission-electron microscopy and is regarded as an amorphous layer. The microstructure of this layer observed by means of secondary-electron microscope (SEM) consisted of microparticles with the dimensions of 5∼30 nm, where the lower dimension is limited by the SEM resolution.
Lattice Parameter Control of Epitaxially Grown Hexagonal LaF3 Films on GaAs(111) Substrates by Incorporation of Orthorhombic YF3
Authors: Aizawa Kouji , Herve Ricard Herve Ricard , Hiroshi Ishiwara Hiroshi Ishiwara
Published: February 2005

Control of lattice parameters of hexagonal LaF3 thin films has been attempted by incorporation of orthorhombic YF3, in order to realize lattice-matched epitaxial growth of the films on GaAs(111)B substrates. It has been found that the lattice parameter of the Y
x
La1-x
F3 film is equivalently matched to that of GaAs(111) around the mixing ratio x of 0.55. It has also been found from Rutherford backscattering spectroscopy that the channeling minimum yield of the epitaxial films on GaAs(111)B substrates is relatively low (the best value is 0.36), when the mixing ratio of YF3 is close to that of the lattice matching condition.
Reflection High Energy Electron Diffraction Study of Superstructures Induced on a Si(110) Surface by Al Adsorption
Authors: Youiti Yamamoto Youiti Yamamoto
Published: February 2005

Al adsorption induces superstructures on a clean Si(110) surface. The present reflection high energy electron diffraction study has revealed two superstructures, i.e., 3×8 and (3,3)×(2̄,1) structures. The former transforms to the latter at 780°C during annealing. A model for the 3×8 structure is made on the basis of the analysis of characteristic intensity distribution of the diffraction spots.
Fabrication of GaInAs/InP Quantum Wires by Organometallic-Vapor-Phase-Epitaxial (OMVPE) Selective Growth on Grooved Side Walls of Ultrafine Multilayers
Authors: Komori Kazuhiro , Hamano Akira , Arai Shigehisa , Suematsu Yasuyuki Miyamoto
Published: February 2005

A new fabrication method for high-density and small-size quantum-wire and quantum-box structures is proposed and demonstrated. Using this method, we realized GaInAs/InP quantum wires with very small size (6 nm×16 nm) and high density and observed room temperature photoluminescence.
Strained II-VI Quantum Well for a Room-Temperature Blue-Green Laser
Authors: Ahn Doyeol , Chuang Tae-Kyung Yoo
Published: February 2005

Theoretical study on the effects of the biaxial compressive strain on the optical gain of the strained-layer Cd
x
Zn1-x
Se-ZnS
y
Se1-y
quantum-well blue-green laser is presented for the first time with the band mixing effects taken into account. Calculated gain of a Cd
x
Zn1-x
Se-ZnS
y
Se1-y
quantum well shows a remarkable enhancement with increasing biaxial compressive strain (in abosulte value) of a quantum well. In particular, the linear gain becomes one third of that of a GaAs-AlGaAs quantum well with a same well width when the biaxial compressive strain is ζ=-45 meV, allowing the CdZnSe quantum well laser favorable for room-temperature operation.
Direct Observation of Oxygen Atoms in a Tetragonal YBa2Cu3O7.7 High-Tc Superconductor by Means of Ultra-High-Resolution High Voltage Electron Microscopy
Authors: Horiuchi Shigeo , Okai Yoshio Matsui
Published: February 2005

Using an ultra-high-resolution high-voltage electron microscope (UHR-HVEM) recently installed at National Institute for Research in Inorganic Materials, a tetragonal YBa2Cu3O7.7 crystal was observed for the [001] as well as [100] orientations with the accelerating voltage of 800 kV, where the damage due to electron irradiation is rather suppressed. Dark spots from oxygens were directly detected in addition to those of Y, Ba and Cu atoms. As a result, the crystal structure was confirmed to be similar to that of the tetragonal YBa2Cu3O7-x
(x>0.5) crystal so far known. Excess oxygens are considered to be accommodated in the otherwise vacant oxygen sites.
Initial Stage of SiO2/Si Interface Formation on Si(111) Surface
Authors: Hattori Takeo , Nohira Hiroshi , Yoshinari Tamura Yoshinari Tamura , Hiroki Ogawa Hiroki Ogawa
Published: February 2005

The initial stages of SiO2/Si interface formation on a Si(111) surface were investigated at 300°C in dry oxygen with a pressure of 133 Pa. It was found that the SiO2/Si interfacial transition layer is formed in three steps characterized by three different oxidation rates.
[110]-Directed Ridge Formation of Epitaxial Y3Fe5O12 Film Grown on [111]-Oriented Gd3Ga5O12
Authors: Katoh Yujiro , Sugimoto Naoto , Akiyuki Tate Akiyuki Tate , Atsushi Shibukawa Atsushi Shibukawa
Published: February 2005

An epitaxially grown Y3Fe5O12 (YIG) film on a [111] oriented Gd3Ga5O12 (GGG) substrate is processed to form a [110]-directed ridge pattern by argon ion-beam etching and subsequent soaking in phosphoric acid solution. The appearance of (210) faces strongly depends on the temperature at which the film is soaked in the solution. The etch rate of YIG film in the solution is about half that of GGG. A GGG perpendicular side wall is obtained under the YIG ridge after soaking at 140°C for 13 min. A circular near-field intensity pattern is observed at λ=1.55 µm for a 3-µm-wide buried YIG waveguide which is prepared by an ion-beam etching process with soaking in the solution.
AlInAs/InP Delta-Doped Channel Field Effect Transistor Grown by Organometallic Chemical Vapor Deposition
Authors: Jeong Yoon-Ha , Jeong Dong-Ho , Hong Won-Pyo , Caneau Catherine , Bhat Raje , Hayes John R.
Published: February 2005

We report on organometallic chemical vapor deposition (OMCVD)-grown AlInAs/InP field effect transistors (EET's), employing a delta-doped channel. The EET's, having a gate length of 1.0 µm, demonstrated excellent saturation characteristics and a broad plateau of transconductance around a peak value of 210 mS/mm. The transistors were also highly stable with no hysteresis or long-term drain current drift being observed.
Photoluminescence in Tb-Doped CuAlS2 Single Crystals
Authors: Kudo Yuki , Kojima Nobuaki , Takada Yasushi , Igor Aksenov Igor Aksenov , Katsuaki Sato Katsuaki Sato
Published: February 2005

Single crystals of CuAlS2 doped with Tb were prepared by the iodine vapor transport technique. These crystals showed bright yellow photoluminescence at room temperature when excited by the 365 nm line of a Hg lamp. The photoluminescence spectrum consists of a yellow broad band at 2.0 eV and sharp emission lines at 2.278 eV and 2.532 eV which are tentatively assigned to Tb3+ ion.
Using Tertiary Butylamine for Nitrogen Doping during Migration-Enhanced Epitaxial Growth of ZnSe
Authors: Suian Zhang Suian Zhang , Naoki Kobayashi Naoki Kobayashi
Published: February 2005

We report the first use of tertiary butylamine as a nitrogen source for doping nitrogen into ZnSe. Tertiary butylamine cracked at various temperatures from 550 to 850°C was supplied onto ZnSe grown by migration-enhanced epitaxy. Photoluminescence of the doped ZnSe films indicated that nitrogen concentration increases with increasing cracking temperature. Secondary ion mass spectrometry revealed that a uniform nitrogen concentration as high as 8×1018 cm-3 could be achieved. The results of site-selective doping onto Se and Zn surfaces during growth imply that nitrogen is more efficiently incorporated into ZnSe when the dopant is supplied at the same time that Se is supplied.
Evidence for Sterilization of Saccharomyces Cerevisiae K 7 by an External Magnetic Flux
Authors: Ito Tatsuya , Murayama Yuzo , Suzuki Masafumi , Yoshimura Noboru , Iwano Kimio , Kudo Kozo
Published: February 2005

A new process of sterilization on Saccharomyces cerevisiae proposed and experimentally demonstrated. This process consists of external magnetic flux and ferrite. Consequently, an alteration of yeast cells, caused by treatment with 2000 G magnetic flux and 6 g of ferrite, was detected through observation of the release of materials from yeast cells absorbing at 260 nm and microscopy of disrupted cells, cell debris, ghost cells and intracellular components. The same results were seen at 28°C and 4°C.
Leakage Current Reduction in Buried Heterostructure Tunable Twin-Guide Laser Diodes
Authors: Illek Stefan , Wolf Thomas , Borchert Bernd , Eberhard Veuhoff Eberhard Veuhoff , Josef Rieger Josef Rieger
Published: February 2005

An effective concept for leakage current reduction in tunable twin-guide (TTG) lasers is proposed. TTG lasers fabricated according to this modified design using a hybrid metalorganic vapour phase and liquid phase process achieve CW output power exceeding 25 mW and linewidth below 10 MHz within the tuning range of 2 nm.
Confinement Subbands in an InGaAs/GaAs Non-Square Quantum Well
Authors: Li E. Herbert , Joseph Micallef Joseph Micallef , Bernard L. Weiss Bernard L. Weiss
Published: February 2005

Calculations of the confinement subbands energy levels, interband transitions energy and related overlapping wavefunctions in a single In0.2Ga0.8As/GaAs non-square strained quantum well structure have been carried out for an error function confinement profile. The results indicate a squeezing of subband states during the latter stages of diffusion, and an enhancement of the off diagonal transitions overlapping wavefunction, during the mid stages of diffusion, which give rise to a relaxed selection rule.
Optical Transitions in RF Sputtered CuInxGa1-xSe2 Thin Films
Authors: Yamaguchi Toshiyuki , Matsufusa Jiro , Yoshida Akira
Published: February 2005

Thin films of CuIn
x
Ga1-x
Se2 were produced over the entire range of 0≤x≤1 by rf sputtering. The optical absorption coefficients of the CuIn
x
Ga1-x
Se2 thin films were determined from the measured transmittance and reflectance in the wavelength range of 400 to 2000 nm. The optical absorption spectra for sputtered CuIn
x
Ga1-x
Se2 thin films (x≠0) show three energy gaps, which are attributed to the fundamental edge, and band splitting by crystal-field and spin-orbit splitting, respectively. The primary transition energies exhibit bowing behavior expressed by the relationship E
g1=1.674-0.803x+0.130x
2. The second and third transition energies are 0.06-0.08 eV and 0.22-0.27 eV above the primary transition energies, respectively.
Selective Growth of GaAs by Molecular Beam Epitaxy
Authors: Sugaya Takeyoshi , Yoshitaka Okada Yoshitaka Okada , Mitsuo Kawabe Mitsuo Kawabe
Published: February 2005

Selective epitaxial growth of GaAs on patterned GaAs substrates covered with SiN
x
have been demonstrated at 580°C by using atomic hydrogen irradiation in molecular beam epitaxy. The mechanism of the selective growth is mainly due to the re-evaporation of GaAs from the mask, SiN
x
. Re-evaporation rate of GaAs from the SiN
x
surface is larger than that from the SiO2 surface, and hence the selective growth of GaAs can be more easily achieved using SiN
x
mask. The epitaxial patterns of GaAs have clear crystal facets. In the line and space patterns along [110], (11̄0), (111)B and (211)B faces appear and in the [11̄0] line, (311)A and (111)A faces appear. There are no edge peaking and the side wall definitely reflects the mask edge boundary.
High-Quality Carbon-Doped Boron Nitride Membrane for X-Ray Lithography Mask
Authors: Kishimoto Akihiko , Sakakihara Masahiko , Kawai Tetsurou , Oizumi Hiroaki , Kuniyoshi Shinji , Yamaguchi Sadae , Kozo Mochiji Kozo Mochiji
Published: February 2005

Carbon-doped BN (BNC) membrane was fabricated by low pressure chemical vapor deposition (LPCVD) at a high temperature (750°C). Here, CH3NH2 was used as the reactive gas instead of NH3. The newly developed BNC has tensile stress and is transparent to visible light. A very small hydrogen content (3.3%) leads to the construction of strong atomic networks of B, N, and C, as well as to highly improved radiation stability.
Characterization of Oxidized GaAs (001) Surfaces Using Temperature Programed Desorption and X-Ray Photoelectron Spectroscopy
Authors: Tone Kiyoshi , Yamada Masamichi , Yuichi Ide Yuichi Ide , Yoshifumi Katayama Yoshifumi Katayama
Published: February 2005

Temperature programed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) were carried out on oxidized GaAs (001) surfaces in order to obtain insight into the durability of the oxide masks used in in situ selective-area processing. The TPD spectra comprised three successive desorption peaks showing the desorption of arsenic at 390°C, Ga2O at 475°C, and both Ga2O and arsenic above 500°C. XPS revealed the disappearance of As oxide and an increase of Ga oxide during the first desorption. The coexistence of two forms of Ga oxide, i.e., Ga2O and Ga2O3, is suggested, and a mechanism of oxide desorption is proposed.
Enhanced Thermal Oxidation of Silicon in Steam Ambient by UV-Irradiation
Authors: Ishikawa Yutaka , Tsuyoshi Shibamoto Tsuyoshi Shibamoto , Ichiro Nakamichi Ichiro Nakamichi
Published: February 2005

Thermal oxidation of silicon can be markedly enhanced by UV-irradiation in steam ambient. The typical thickness of the oxide is about 65 nm at 500°C for 90 min. This value is nearly equal to that of usual oxidation in dry O2 at 1000°C, and is much thicker than those produced by other oxidation techniques at relatively low temperatures, such as by dry O2+UV and using oxygen plasma. The characteristics of the oxide films obtained by the present technique are similar to those of usual dry O2 oxidation performed at high temperatures.
Anisotropic Optical Transitions in Semiconductor Quantum Wells
Authors: Shunji Nojima Shunji Nojima
Published: February 2005

Calculations have been made of the in-plane behavior of optical transition matrix elements at the band edge for quantum well films of several crystallograhic directions. This calculation takes into account the multiplicity of the valence band including the split-off band. The (001) film shows in-plane isotropy, while the (110) and (311) films reveal marked and slight anisotropy, respectively. The (111) film exhibits isotropic behavior despite the fact that each state of the doubly degenerate subband in the valence band produces an extremely anisotropic optical transition.
Relationship between Surface Roughness and Barrier Uniformity
Authors: Matsui Toshiyuki , Suzuki Takeshi , Kimura Hiroshi , Tsuda Koichi , Megumi Nagano Megumi Nagano , Kazuo Mukae Kazuo Mukae
Published: February 2005

The relationship between the surface roughness of YBa2Cu3O
x
(YBCO) films and the uniformity of a barrier layer was studied using atomic force microscope (AFM) and tunnel junctions with an Au-LaSrGaO4 (LSGO)-YBCO layered structure. AFM images showed that the surface roughness of both (001)- and (013)-oriented films depended strongly on their thickness, and that roughness decreased with a reduction in thickness. When an LSGO barrier was formed on these YBCO films, barrier height increased from 24 mV to 1.3 V with reduction in the thickness of the YBCO film from 400 nm to 70 nm. This suggests that barrier uniformity was improved by reducing the roughness of the YBCO films.
Transmission Electron Microscopy Cross-Sectional Observation on Mechanically and Chemically Lapped Si (111) Surfaces
Authors: Wu Xiao-Jing , Horiuchi Shigeo , Shiwaku Hideaki , Hyodo Kazuyuki , Ando Masami
Published: February 2005

The (111) surfaces of Si single crystals, mechanically lapped by fine abrasives with different particle size or chemically etched, are observed from the cross-sectional direction by transmission electron microscopy (TEM). On the mechanically lapped surface the defect layers of several µm in thickness, containing blocks, grains and cracks along nearly {100}, {110} {111} and {112}, are formed. The size of grains as well as the misorientation between grains increases with increase of the particle size of abrasives. On the chemically etched surface, on the other hand, the defect density is so low that the crystal near the surface seems almost perfect. The prominent enhancement of X-ray integrated intensity from mechanically lapped surfaces can be related to the misorientation between grains.
Ion Beam Etching for InSb Photovoltaic Detector Applications
Authors: Chen Liang Po , Luo Jiunn Jye , Liu Tai Hwa , Yang Shu Ping , Yen Ming Pang Yen Ming Pang , Sheng Jenn Yang Sheng Jenn Yang
Published: February 2005

We first investigate the differences of the InSb mesa etching profiles between ion beam etching and 10:1 lactic:nitric acid chemical etching. The mesa profile obtained by chemical etching always shows the mesa edge trench structure which is due to diffusion limited mechanism. However this effect can be eliminated by ion beam etching. We also present the device characteristics of InSb mesa type photovoltaic detectors which are mesa etched by both techniques. Generation-recombination current, shunt current, and tunneling current are the major components of the reverse currents for both kinds of detectors. However, the detector fabricated on the ion beam etched surface shows lower dark current, which is due to higher shunt resistance, and higher breakdown voltage. These results can be explained by the effects of the different mesa edge profiles.
Low Temperature GaAs/Si Technology: from Si Substrate Preparation to the Epitaxial Growth
Authors: González Y. , L. González L. González , F. Briones F. Briones
Published: February 2005

An actual development of GaAs/Si technology is subjected entirely to reduce the temperature of the full growth process, from the Si surface preparation to the epitaxial growth itself. In this paper we demonstrate the successful combination of a low temperature Si surtace preparation process (400°C<T
Si<550°C) adequate for further III-V epitaxial growth with a low temperature growth process (T
g=300°C) using Atomic Layer Molecular Beam Epitaxy (ALMBE). Experimental results obtained on reflection modulator structures grown at T
g=300°C by ALMBE on low temperature prepared Si substrates permit an actual advancement towards monolithic integration of III-V devices to Si circuits.
In Situ Optical Monitoring of Growth Rate and Surface Roughness of YBa2Cu3O7-y Films in Chemical Vapor Deposition
Authors: Higashiyama Kazutoshi , Izumi Hirabayashi Izumi Hirabayashi , Shoji Tanaka Shoji Tanaka
Published: February 2005

An optical method for in situ monitoring of film thickness has been applied to growth of YBa2Cu3O7-y
films by chemical vapor deposition. Reflectivity change is monitored at an incident angle of 78° from the film growing on MgO(100) substrate. An oscillation in the reflection intensity resulting from interference inside the YBa2Cu3O7-y
layer is observed with the deposition time. The deposition rate calculated from the oscillation frequency agrees well with the value estimated from chemical analysis of the film. Increase of CuO precipitate with increasing Cu content in the film results in a corresponding decrease of the reflection intensity due to the scattering of laser light at the film surface. Therefore, this simple method provides an effective means for growth control of superconducting thin film by chemical vapor deposition.