bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Oxygen Partial Pressure on the Solubility of Y2O3 in the High TC Phase of Bi-Pb-Sr-Ca(Y)-Cu-O Superconducting Oxide
Authors: Iwai Yutaka , Kobayashi Takahiro , Takata Hiroshi Saito
Published: February 2005

The solubility of Y2O3 in the high T
C phase (2223 phase) of (Bi, Pb)-based superconducting oxides was investigated to examine the possibility of substitution of Y3+ for Ca2+. Under P
O2
=0.21 atm, approximately x=0.02 (x=Y/Ca+Y) of Y2O3 was found to be soluble. The solubility was measured as a function of the oxygen partial pressure (P
O2
) at 790°C. Under lower P
O2
, the Y-substituted 2223 phase was unstable and decomposed partially into the 2212 phase. The stable area of the 2223 phase was narrowed and the solubility of Y2O3 in the 2223 phase was decreased with decreasinff P
O2
. Electrical resistivity was increased and T
C,zero was decreased by doping with Y2O3.
Electron Irradiation Effects on Electrical Properties of a Bi1.4Pb0.6Sr2Ca2Cu3O10 Superconductor
Authors: Shiraishi Kensuke , Kato Hiroshi Itoh
Published: February 2005

A Bi1.4Pb0.6Sr2Ca2Cu3O10 ceramic was sequentially irradiated with 1 MeV electrons at a dose rate of 1.1, 5.5 or 27.5×1015 m-2·s-1 to a dose of 8.0×1019 m-2 at ambient temperature, and the electrical resistivity was measured as a function of temperature. In the specimen irradiated at 1.1×1015 m-2·s-1, the superconducting transition temperature measured with 125 kA·m-2 in current density increased from 90.7-92.5 K to 96.3 K at 1.0×1019 m-2, and then gradually decreased upon further irradiation. The normal-state resistivity was, concurrently, decreased by the irradiation to 1.0×1019 m-2, and then increased almost linearly with electron dose.
Crystallization of Amorphous Silicon with Clean Surfaces
Authors: Sakai Akira , Ono Haruhiko , Ishida Koichi , Niino Taeko , Tatsumi Toru
Published: February 2005

Crystallization of amorphous Si (a-Si) on SiO2 layers in ultra-high vacuum (UHV) was examined by transmission electron microscopy (TEM) and reflection high energy electron diffraction. The SiO2 growth, the a-Si deposition on the SiO2 layer, and the annealing for the crystallization were successively carried out in a UHV molecular-beam-epitaxy chamber. It has been found that the initial nucleation and the grain growth occur at the surface of the a-Si layer, in contrast with the nucleation at the a-Si/SiO2 interface ordinarily observed in the previous studies. Cross-sectional TEM observations revealed a novel mode of crystallization which resulted in the formation of mushroom-shaped Si grains at the a-Si surface. The mechanism of the crystallization was also discussed.
Carbon Incorporation in (AlGa)As, (AlIn)As and (GaIn)As Ternary Alloys Grown by Molecular Beam Epitaxy
Authors: Hiroshi Ito Hiroshi Ito , Tadao Ishibashi Tadao Ishibashi
Published: February 2005

Carbon incorporation in III-V ternary alloys, (AlGa)As, (AlIn)As and (GaIn)As, for the entire composition range is investigated using solid-source molecular beam epitaxy. On the binary corners, carbon-doped GaAs and AlAs show p-type conduction, while carbon-doped InAs shows n-type conduction. At a constant doping level, conduction-type inversion is found to occur in the (GaIn)As layer at an InAs mole fraction of about 0.6 and in the (AlIn)As layer at about 0.9. Hall mobilities and free carrier concentrations decrease around the compositions where the conduction-type inversions occur. The conduction-type inversion phenomena and the behavior of carrier mobilities are explained in terms of a self-compensation mechanism.
Hydrogenation of InP by Phosphine Plasma
Authors: Sugino Takashi , Hiroyuki Yamamoto Hiroyuki Yamamoto , Junji Shirafuji Junji Shirafuji
Published: February 2005

Hydrogenation of an InP surface has been attempted by the glow discharge of phosphine (PH3) gas diluted with Ar. Atomic P in the PH3 plasma is effective in suppressing the preferential etching of P at the InP surface which occurs easily by the exposure to the H2 plasma. The mirror surface of InP is found to be maintained after the plasma exposure even at 250°C. It is verified by secondary ion mass spectroscopy analysis that H atoms with a density higher than 1×1018 cm-3 diffuse into the bulk InP to 500 nm in depth. An enhancement of the photoluminescence (PL) intensity occurs on the hydrogenated surface, and a complete recovery of the PL intensity is observed after annealing at 350°C for 3 min. In the case of exposure to the PH3 and H2 mixture plasma, an increase of the H2 flow rate leads to further enhancement of the PL intensity which is attributed to the band bending at the surface due to an introduction of P vacancies.
Room-Temperature Self-Electrooptic Effects of GaAs/AlAs Asymmetric Coupled Quantum Wells
Authors: Abe Yuji , Tokuda Yasunori , Kyozo Kanamoto Kyozo Kanamoto , Noriaki Tsukada Noriaki Tsukada
Published: February 2005

Two unique functions of wavelength-selective spectral response and optically induced multistability have been demonstrated at room temperature by using self-electrooptic effects of a GaAs/AlAs asymmetric coupled double quantum well structure with carefully designed well widths and barrier thicknesses. Also, a brief discussion is presented on the effect of well widths and barrier thicknesses on the anticrossing properties of the coupled quantum wells.
Improvement of the Safe Operating Area for P-Channel Insulated-Gate Bipolar Transistors (IGBTs)
Authors: Ueno Katsunori , Hoshi Yasuyuki , Iwamuro Noriyuki , Naoki Kumagai Naoki Kumagai , Osamu Hashimoto Osamu Hashimoto
Published: February 2005

A p-channel insulated-gate bipolar transistor (IGBT), which is supposed to be useful for many applications especially for inverters, is developed. The SOA (safe operating area) of p-channel IGBTs is narrower than that of n-channel IGBTs because of the positive-feedback mechanism between a high rate of the avalanche multiplication of electrons and a high current gain h
fe of the wide-base npn transistor. The effect of the high resistivity of the p-base, which affects the avalanche breakdown, is examined by the numerical analysis and device fabrications. It is demonstrated that utilizing the high-resistivity (over 300 Ω·cm) p-base is effective to suppress the electric field and improve the SOA without a substantial increase of the on-state voltage drop.
Superconductivity and Chemical Composition of the High-Tc Phase (Tc∼111 K) in the Sb-Pb-Bi-Sr-Ca-Cu-O System
Authors: Kijima Naoto , Gronsky Ronald , Endo Hozumi , Oguri Yasuo , Mckernan Steffen K. , Zettl Alex
Published: February 2005

A superconducting phase with a critical temperature of 111 K in the Sb-Pb-Bi-Sr-Ca-Cu-O system has been synthesized by means of a long firing period. Its crystal structure is similar to the high-T
c phase (107 K) in the Pb-Bi-Sr-Ca-Cu-O system, and its average chemical composition is 4.3%, 2.6%, 19.2%, 21.4%, 15.8% and 36.9% for Sb, Pb, Bi, Sr, Ca and Cu, respectively. The summation of the Sb concentration and the Ca concentration is approximately the same for all the samples of this phase, implying that Sb substitutes for Ca, and oxygen atoms are introduced to compensate the oxygen deficiency in the central Cu-O layer sandwiched by the two Ca layers in the crystal structure of the high-T
c phase.
Fabrication of Thick Bi1.4Pb0.6Sr2Ca2Cu3Ox Superconducting Tapes by an Extrusion Method Using Paraffin Wax
Authors: Suzuki Suguru , Kato Hiroki , Iwashita Kenji , Minoru Takahashi Minoru Takahashi , Yasuo Hikichi Yasuo Hikichi
Published: February 2005

Thick Bi1.4Pb0.6Sr2Ca2Cu3O
x
superconducting tapes, which can flow practically high critical currents, are obtained continuously by the following process: (1) calcined Bi1.4Pb0.6Sr2Ca2Cu3O
x
particles, mixed with paraffin wax, are extruded through a nozzle to align platelike particles unidirectionally; (2) the paraffin wax, used as a matrix for workability, alone is burned out, taking care not to destroy the extruded configuration; (3) the burned out tapes are pressed to realize the denser configuration; and then (4) annealed at 850°C for 100 h in air.
Formation of Bilayer Shallow MoSi2/CoSi2 Salicide Contact Using W/Co-Mo Alloy Metallization
Authors: Fann-Mei Yang Fann-Mei Yang , Mao-Chieh Chen Mao-Chieh Chen
Published: February 2005

A very simple process to form a bilayer shallow MoSi2/CoSi2/Si silicided contact using W/Co54Mo46/Si bilayer alloy metallization has been developed. Two-step annealing in a conventional flowing-nitrogen furnace is employed. The first annealing is performed at a temperature of 500-600°C, with the W film passivating the underlying Co-Mo alloy layer from being oxidized and consuming some Co. A shallow contact is feasible by selectively etching away the remaining outer layer of the Mo-dominant Mo-Co alloy (or W-Co alloy) phase to deduct the metal source which would finally be transformed into silicides. Silicide lateral growth which is observed during the silicidation of Co on Si does not occur in the present system. This is presumably because the formation of CoSi2 is not preceded by Co2Si or CoSi due to the nonrich Co source in the Co-Mo alloy system. The second annealing performed at a higher temperature of 700-950°C is to further transform the CoSi2 and mixed-silicide layers obtained after the first annealing into separate layers of MoSi2 and CoSi2.
Influence of Spatially Exponential Carrier Generation on Shot Noise in Linearly Graded Junctions
Authors: Kazuhiro Sasaki Kazuhiro Sasaki , Kazunori Sato Kazunori Sato
Published: February 2005

An expression is developed for the suppression factor of noise due to spatiaily exponential carrier generation in the depletion region of linearly graded p-n junctions. Under the assumption that the generation rate is expressed asU(x)=U0exp (-x/a) and the noise spectrum asS(ω)=2qIΓ2, it is found that the value of the noise suppression factor Γ2lies between 26/35 and unity, and depends only on the ratio of characteristic lengthato the width of the depletion region of the junction.
Preparation of (Fe/Fe-N)/(Si-O) and (Fe/Fe-N)/(Si-N) Multilayered Films by Sputtering, ECR Plasma Nitridation and ECR Plasma CVD
Authors: Ono Hideaki , Fujinaga Masashi , Takaharu Yonemoto Takaharu Yonemoto , Tsugio Miyagawa Tsugio Miyagawa
Published: February 2005

Structures and soft magnetic properties of (Fe/Fe-N)/(Si-O, -N) duplex structure multilayered films were studied. The films were prepared by alternation of Fe RF-sputtering, N2 plasma nitridation and Si-O and Si-N electron cyclotron resonance (ECR) plasma chemical vapor deposition (CVD). Magnetic multilayers of Fe/Fe-N were magnetically isolated by 1 to 5 layers of nonmagnetic Si-O, -N to advance high-frequency permeability. High-frequency permeability was increased by lamination of Si-N layers, but Si-O lamination deteriorated soft magnetic properties of the Fe/Fe-N multilayers by oxygen contamination during the Si-O deposition process. At optimum lamination structure of (Fe/Fe-N)/(Si-N), µ′>3500 (20 MHz) was obtained.
Low-Loss Channel Waveguides in MgO:LiNbO3 and LiTaO3 by Pyrophosphoric Acid Proton Exchange
Authors: Yamamoto Kazuhisa , Kiminori Mizuuchi Kiminori Mizuuchi , Tetsuo Taniuchi Tetsuo Taniuchi
Published: February 2005

The characteristics of proton-exchanged MgO-doped LiNbO3 (MgO:LiNbO3) and LiTaO3 waveguides fabricated by the pyrophosphoric acid process are reported. Using this process, low-loss (0.4 dB/cm) channel waveguides in MgO:LiNbO3 have been realized at 633 nm without annealing. The optical damage in MgO:LiNbO3 waveguides at 441.6 nm wavelength is lower than that obtained in LiNbO3. For LiTaO3, by annealing, low-loss (0.3 dB/cm) channel waveguides can be fabricated by pyrophosphoric acid proton exchange. No optical damage was observed in the LiTaO3 waveguides even when the incident power was above 1 mW at 442 nm.
Magnetron Sputter-Deposited Al2O3/SiO2 Multilayer Coatings for Kilowatt Excimer Lasers with High Repetition Rates
Authors: Iwabuchi Takashi , Mutoh Katsuhiko , Furuya Nobuaki , Yuka Yamada Yuka Yamada , Takeo Miyata Takeo Miyata
Published: February 2005

The authors describe the multilayer coatings deposited using a magnetron sputtering method and their characteristics. In Al2O3/SiO2 multilayer mirrors fabricated on Si and SiC substrates, reflectivities of more than 99% are obtained both in XeCl and KrF excimer-laser wavelength regions. For antireflective windows, a reflectivity of 1% is obtained in SiO2/Al2O3/SiO2 trilayer systems coated on both sides of a CaF2 substrate in the two wavelength regions. In XeCl laser-beam irradiation tests, the fabricated multilayers show higher optical damage thresholds than do typical commercial mirrors. Furthermore, the multilayers show no reflection spectral change, even when heated to 800°C.
Comparison Between Experiment and Simulation in a Real-Time Joint Transform Correlator
Authors: Juvells Ignacio , Arturo Carnicer Arturo Carnicer , Santiago Vallmitjana Santiago Vallmitjana
Published: February 2005

A joint transform correlator which operates in real time with a liquid crystal television has been made for pattern recognition purposes. Discrimination is improved by means of saturation effects. A digital simulation of this process has been carried out with the same limitations of resolution and dimensions of experimental architecture. A comparison between the experiment and simulation shows good agreement.
N-Type Doping Properties and Electronic States of Poly(2,5-thienylene vinylene)
Authors: Onoda Mitsuyoshi , Morita Shigenori , Iwasa Toshinori , Yoshino Hiroshi Nakayama
Published: February 2005

Evidence for electrochemical n-type doping of poly(2,5-thienylene vinylene) (PTV) is obtained fromin situmeasurements of a cyclic voltammogram, optical absorption spectrum and electron spin resonance. Bipolaron levels in the gap states appear upon n-type doping and the electronic band scheme of PTV is discussed.
Local Structures of RbBrxCl1-x and CuBrxCl1-x Solid Solutions Studied by Temperature-Dependent Br K-Edge Extended X-Ray-Absorption Fine-Structure Spectroscopy
Authors: Sato Hitoshi , Yokoyama Toshihiko , Ono Izumi , Kentaro Kaneyuki Kentaro Kaneyuki , Toshiaki Ohta Toshiaki Ohta
Published: February 2005

Local structures of RbBr
x
Cl1-x
and CuBr
x
Cl1-x
(0.1≦x≦1.0) solid solutions were investigated by means of temperature-dependent extended X-ray-absorption fine-structure (EXAFS) spectroscopy and compared with the results of AgBr
x
Cl1-x
(0.05≦x≦1.0) and AgBr
x
I1-x
(0.6≦x1.0). The mixing ratio, x, and temperature dependences of the
bromine-cation distance R(x) show significant differences among these solid solutions. In AgBr
x
Cl1-x
and AgBr
x
I1-x
, d
R(x)/dx i
s
s
t
r
o
n
g
l
y
t
e
m
p
e
r
a
t
u
r
e-d
e
p
e
n
d
e
n
t; dR(x)/dx i
s
l
a
r
g
e
a
t
l
o
w
t
e
m
p
e
r
a
t
u
r
e
a
n
d
i
t
b
e
c
o
m
e
s
s
m
a
l
l
e
r
a
s
t
h
e
t
e
m
p
e
r
a
u
t
r
e
i
n
c
r
e
a
s
e
s. I
n
c
o
n
t
r
a
s
t, dR(x)/dx i
n
R
b
B
r_xC
l_1-x s
h
o
w
s
l
i
t
t
l
e
t
e
m
p
e
r
a
t
u
r
e
d
e
p
e
n
d
e
n
c
e
a
n
d
m
a
i
n
t
a
i
n
s
a
n
e
a
r
l
y
c
o
n
s
t
a
n
t
v
a
l
u
e
c
l
o
s
e
t
o
t
h
o
s
e
o
f
s
i
l
v
e
r
h
a
l
i
d
e
s
a
t
l
o
w
t
e
m
p
e
r
a
t
u
r
e. T
h
e
m
a
g
n
i
t
u
d
e
o
f dR(x)/dx i
n
C
u
B
r_xC
l_1-x i
s
v
e
r
y
s
m
a
l
l
a
n
d
i
s
a
g
a
i
n
i
n
d
e
p
e
n
d
e
n
t
o
f
t
e
m
p
e
r
a
t
u
r
e. T
h
e
d
i
f
f
e
r
e
n
t
b
e
h
a
v
i
o
r
i
s
d
i
s
c
u
s
s
e
d
f
r
o
m
t
h
e
v
i
e
w
p
o
i
n
t
o
f
s
t
r
u
c
t
u
r
a
l
a
n
d
d
y
n
a
m
i
c
a
l
p
r
o
p
e
r
t
i
e
s.
p-Type Characteristics of Cu-Doped CdS Thin Films
Authors: Kashiwaba Yasube , Itaru Kanno Itaru Kanno , Toshio Ikeda Toshio Ikeda
Published: February 2005

The characteristics of Cu-doped CdS films have been studied. Cu was easily diffused into CdS films when CdS was deposited on a Cu film successively at 200°C. The resistivity of the films increased initially with increasing Cu doping, but decreased for values of the Cu/Cd atomic ratio over about 0.5%. The Seebeck coefficient changed from negative to positive, and the Hall coefficient also changed from negative to positive with increasing Cu doping. I-V characteristics of a cell with a CdS(Cu-doped)/CdS(non-doped) film structure showed rectification. Thus, Cu-doped CdS films show p-type characteristics. It is proposed that the Cu compensates the donor due to S-vacancies, and the conductivity type of the CdS films was converted to p-type.
Position Linearity and Resolution of Large Position-Sensitive Silicon Detector with a Highly Uniform Thickness
Authors: Hasebe Nobuyuki , Doke Tadayoshi , Kashiwagi Toshisuke , Kataoka Satosi , Kikuchi Jun , Moriya Hitoshi , Nishijima Kyoshi , Crawford Henry J.
Published: February 2005

Large two-dimensional position-sensitive silicon detectors (PSDs) with good position linearity, resolution and thickness uniformity have been developed. The PSDs have an effective area of 62 mm×62 mm and a thickness of 500 µm. The non-linearity and position resolution for the whole sensitive area are found to be less than 0.26 mm in rms and 0.44 mm in fwhm, respectively, when an energy of 157 MeV is deposited in the detector and a shaping time constant of 12 µs is used in the pulse processing. The non-uniformity of detector thickness is ≤0.1% in rms. The PSDs recently developed are good enough to separate iron isotopes in a telescope aboard the GEOTAIL spacecraft scheduled to be launched at July in 1992.
Modulation of Electron Velocity Distribution Function by Moving Cathode Sheath in a Low-Pressure rf Discharge
Authors: Okuno Yoshihiro , Yasunori Ohtsu Yasunori Ohtsu , Hiroharu Fujita Hiroharu Fujita
Published: February 2005

Interaction between a moving collisionless cathode sheath and bulk electrons in a completely asymmetrical rf glow discharge is studied numerically. The incident electron velocity distribution function, assumed to be Maxwellian, is found to be modulated markedly by the interaction with the rf sheath expanding and contracting symmetrically in time. An electron beam toward the bulk plasma with sufficiently high velocity for ionization of atoms is generated during the sheath expansion. The modulated distribution function and the beam velocity are almost independent of the voltage applied on the cathode, although a slight extension of the tail and a slight increase in the beam velocity are observed with increases in voltage.
A Study on the Characteristics of Low-Energy Ion-Beam-Assisted Deposition of Tungsten
Authors: Young-Bum Koh Young-Bum Koh , Kenji Gamo Kenji Gamo
Published: February 2005

The characteristics of the low-energy ion-beam-assisted deposition (IBAD) of tungsten films was investigated. Hexacarbonyl tungsten (W(CO)6) and a 0.5 keV Ar+ beam were used for deposition. X-ray photoelectron spectroscopy (XPS) demonstrated that the W(CO)6 adsorbed on the substrate was decomposed and metallic tungsten was formed by ion beam irradiation. Quadrupole mass spectrometer and XPS analyses showed that the CO molecule was mainly dissociated from the W(CO)6. The deposition rate of tungsten films was proportional to the ion current density and the deposition yield was ∼1.7 atoms/ion. The deposited film consists of ∼76% tungsten and has a resistivity of ∼600 µQ·cm.
An Atomic Beam Collimator for Cs Beam Frequency Standards
Authors: Kenji Hisadome Kenji Hisadome , Masami Kihara Masami Kihara
Published: February 2005

It is necessary to predict the directivity of atomic beam collimators when designing Cs beam frequency standards. This paper presents an improved beam collimator theory. Collision processes are not neglected in this theory. This theory can analyze the temperature characteristics of a Cs atomic beam collimator of various lengths. Systematic experiments using three atomic beam collimators (lengths of 17, 34, and 50 mm) are performed. Beam profiles and peak beam intensities are compared with calculated values. Beam profiles calculated with this theory agree well with the measured profiles.
An Optical Absorption Property of Highly Beryllium-Doped GaInAsP Grown by Chemical Beam Epitaxy
Authors: Yokouchi Noriyuki , Uchida Takashi , Miyamoto Tomoyuki , Inaba Yuichi , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

The optical absorption property of highly beryllium (Be)-doped GaInAsP (λg=1.31 µm, p=2×1019 cm-3) grown by chemical beam epitaxy (CBE) was investigated. The absorption coefficient was estimated from the transmissivity of a Fabry-Perot resonator formed by selective etching of an InP substrate. We found a fairly large absorption (α\cong400 cm-1) in Be-doped material in the longer wavelength region (λ>1.35 µm).
Irradiation-Temperature Dependence of the Light-Induced Effect in a-Si Solar Cells
Authors: Nakamura Noboru , Takahama Tsuyoshi , Isomura Masao , Nishikuni Masato , Tarui Hisaki , Wakisaka Kenichiro , Tsuda Shinya , Nakano Shoichi , Yasuo Kishi Yasuo Kishi , Yukinori Kuwano Yukinori Kuwano
Published: February 2005

The irradiation-temperature dependence of light-induced degradation has been studied at temperatures between 300 K and 25 K. Although Si-H2 bonds have a strong influence on degradation at an irradiation temperature of 300 K, their influence is reduced at low irradiation temperatures. Si-H2 bonds are thought to have a stabilization effect on newly created defects. Also, the hydrogen atom itself was found to have an influence on light-induced degradation in a-Si solar cells with low Si-H2 bond density or in the region of low irradiation temperatures below about 60 K.
Anomalous Dopant Redistribution in Nd:YAG Laser Annealed Low Energy Ion Implanted Silicon
Authors: Harish Chinnaswamy Mohan , Kumar Vikram , Anantharamaiah Prabhakar Anantharamaiah Prabhakar
Published: February 2005

CW Nd:YAG laser (1.065 µm wavelength) anneal of B11 and BF2 implanted silicon yields sheet resistance values matching those of the thermally annealed ones. The samples annealed at low laser powers show a narrowing of the secondary ion mass spectroscopy (SIMS) dopant profile compared to the as implanted cases, accompanied by a shift in the profile peak towards the bulk. The anomalous dopant redistribution when annealing is done at low laser powers is explained on the basis of a new phenomenon, termed damage enhanced diffusion.
Application of Irradiation-Then-Anneal Treatment on the Improvement of Oxide Properties in Metal-Oxide-Semiconductor Capacitors
Authors: Jin-Jenn Lin Jin-Jenn Lin , Jenn-Gwo Hwu Jenn-Gwo Hwu
Published: February 2005

The improvement in electrical characteristics of oxides, including oxide leakage current, radiation hardness, and hot-carrier resistance, in metal-oxide-semiconductor (MOS) capacitors by irradiation-then-anneal (ITA) treatments is studied. The ITA treatment is performed by Co-60 irradiation with a suitable dose followed by annealing in pure nitrogen at 400°C for 10 min. It is found that samples receiving ITA treatments exhibit better performance in oxide properties than those not receiving an ITA treatment. For the examination of oxide leakage current, the charge-then-decay method is employed. Devices with two ITA treatments exhibit a very slow gate voltage decay behavior even in a moist environment. Both the radiation hardness and the hot-carrier resistance are improved by the ITA treatment. The gate area dependence and the total dose effect in ITA treatment are also discussed.
Ab Initio Cluster Study of the Interaction of Hydrogen with the GaAs(100) Surface
Authors: Nonoyama Shinji , Yoshinobu Aoyagi Yoshinobu Aoyagi , Susumu Namba Susumu Namba
Published: February 2005

The GaAs(100) surface is modeled, using a cluster to study the interaction with hydrogen. On the basis of ab initio theory including electron correlations, the most stable structures for the As-terminated surface with adsorbed hydrogen atoms are established. The optimized structure of the modeled cluster without the adsorbate is also obtained. From the computational results of total energy, the activation energy of the dissociation of the hydrogen molecule on the surface was estimated. The cluster with adsorbed hydrogen atoms is more stable than that without hydrogen, although the approach of the hydrogen molecule toward the surface causes an increase in the total energy.
Grain Delamination of Ag-Doped YBa2Cu3O7-x Superconductor
Authors: Wen-Cheng Wei Wen-Cheng Wei , Wen-Hwa Lee Wen-Hwa Lee
Published: February 2005

Silver-added YBa2Cu3O7-x
(Y123) composites have been prepared for study of the effects of noble metal on the fracturing of Y123 grains. The microscopic results show that the planar-type microcracks are frequently found in large Y123 grains, which are delaminated by a uniaxial pressure as low as 150 MPa. Planar-type microcracks, characterized by the Wulff Net operation, are laid on the basal (001) plane which is the weakest plane in the Y123 crystal system. The formation of glassy material above eutectic temperature, the effect of Ag on green density, eutectic liquid, and the reaction of Ag grains with glassy material will be discussed. Moreover, compression tests of Ag/Y123 depict that more than 20 vol% silver additive can improve the ductility of the composite and prevent delamination of large Y123 grains.
Dependence of Magnetic Shielding Property on Critical Current Density
Authors: Ishii Mamoru , Tsukamoto Keizou , Shimojima Hiromasa , Yamagishi Chitake , Takata Masasuke , Yamashita Tsutomu
Published: February 2005

Bi(Pb)-Sr-Ca-Cu-O superconducting tubes with different critical current densities were fabricated to examine the effect of the critical current density on the magnetic shielding property. The shielding magnetic flux density, at which the flux started to penetrate into the tube center, was proportional to the critical current density at zero magnetic field. These experimental results agreed with the calculations based on the critical state model.
Critical Current Distribution in Composite (NbTi)3Sn Wires
Authors: Masaichi Umeda Masaichi Umeda
Published: February 2005

Critical current distributions in superconducting composite wires of Nb3Sn alloyed with Ti were studied using the second-derivative analysis of the flux flow voltage state. Specimens were prepared for a reaction time of 1 to 8 days at a heat treatment temperature of 675°C and measurements were carried out with short samples. It has been shown that the critical current distributions were mainly determined by variations in the areas and the thermodynamic critical fields of the Nb3Sn filaments.
Pinning Mechanism Studies on the Nb/Al2O3 Superconducting Multilayer
Authors: Obi Yoshihisa , Ikebe Manabu , Hiroyasu Fujimori Hiroyasu Fujimori
Published: February 2005

The transport critical current J
c of the Nb/Al2O3 superconducting multilayer films has been measured at 4.2 K and 1.5 K under both the parallel and the perpendicular magnetic fields to the film plane. From the obtained J
c values, the pinning force density F
p in the parallel (F
p//) and the perpendicular (F
p⊥) directions is estimated. F
p⊥ enhancement is drastic in comparison with F
p// but F
p// itself is also remarkably enhanced by the multilayer structure. The pinning mechanisms are discussed in reference to the pinning function curve F
p//,⊥ (h). It has been found that for F
p⊥ of multilayers showing quasi-two-dimensional superconductivity the temperature scaling law breaks down. F
p// of all multilayers roughly obeys the scaling law and shows some characteristics of usual core pinning.
Effect of Intergrain Exchange Interaction on Magnetic Properties in Isotropic Nd-Fe-B Magnets
Authors: Hirotoshi Fukunaga Hirotoshi Fukunaga , Hiroshi Inoue Hiroshi Inoue
Published: February 2005

The effect of intergrain exchange and magnetostatic interactions on remanence and coercivity is calculated numerically for an isotropic Nd-Fe-B model magnet composed of 8000 grains. The intergrain exchange interaction affects the magnetizing process markedly when the grain size L is small, but the magnetostatic interaction does not have substantial effects. The calculated remanence which takes the intergrain exchange interaction into account increases with decreasing L from M
s/2 (M
s: the saturation magnetization) to M
s and agrees roughly with the experimental results. The calculated coercivity decreases with decreasing L from 0.48H
A (H
A: the anisotropy field) to 0. Our results suggest that the large remanence above M
s/2 observed experimentally in isotropic Nd-Fe-B magnets can be explained by the intergrain exchange interaction between Nd2Fe14B grains.
1.5 µm GaInAs/AlGaInAs Graded-Index Separate-Confinement-Heterostructure Quantum Well Laser Diodes Grown by Organometallic Chemical Vapor Deposition
Authors: Kasukawa Akihiko , Bhat Rajaram , Caneau Catherine , Andreadakis Nicholas C. , Pathak Bhadresh , Zah Chung-En , Mark. A. Koza Mark. A. Koza , Tien-Pei Lee Tien-Pei Lee
Published: February 2005

Very low threshold current densities of 640 A/cm2, 400 A/cm2 and 200 A/cm2 were obtained in 1.5 µm GaInAs/AlGaInAs lattice matched, compressive and tensile strained-layer quantum well laser diodes (SL-QW LDs) respectively, grown by organometallic chemical vapor deposition, with continuously graded-index separate-confinement-heterostructure. The polarization of output power for a tensile SL-QW LD showed transverse magnetic (TM) mode, while that for a lattice matched and a compressive SL-QW LDs showed transverse electric (TE) mode. A very low threshold current of 3.6 mA was obtained in a buried heterostructure compressive SL-QW laser diode grown by two-step organometallic chemical vapor deposition.
Dielectric Properties of Polymer-Liquid Crystal Composites
Authors: Deeleep K. Rout Deeleep K. Rout , Sukhmal C. Jain Sukhmal C. Jain
Published: February 2005

Dielectric properties of two polymer-liquid crystal composites, comprised of the polymer, poly (methyl methacrylate) (PMMA), and liquid crystal, octyl cyanobiphenyl (K-24) and a biphenyl-terphenyl mixture (E-8), are reported as function of frequency (100 Hz-1.0 MHz) and temperature (20-80°C). Two distinct dispersion regions in dielectric permittivity are observed; one at ∼500 Hz due to space charge relaxation at the liquid crystal droplet-polymer interface and the other at ∼50 kHz due to dipolar relaxation. Correspondingly, dissipation factor `D' peaks are also seen in the low- and high frequency regions. Temperature variation studies show that the low-frequency dispersion becomes more and more prominent with increasing temperature, attains a maximum at ∼55°C and then disappears completely beyond 72°C. Correspondingly, `D' also shows a broad peak at ∼55°C. The above results are explained in terms of the Maxwell-Wagner interfacial polarization which arises due to the presence of liquid crystal or liquid microdroplets of higher conductivity in a resistive polymer matrix. Dielectric behavior of polymer-liquid crystal composites is not so much affected by the mesophase transitions, as by the glass transition temperature of the polymer.
The Ratio of Rhombohedral and Tetragonal Phases on the Morphotropic Phase Boundary in Lead Zirconate Titanate
Authors: Wenwu Cao Wenwu Cao , L. Eric Cross L. Eric Cross
Published: February 2005

A method is introduced to determine the statistical distribution of energetically degenerate but geometrically inequivalent states in a temperature induced phase transition in solids. The method has been employed to calculate the ratio of the rhombohedral and tetragonal phases in the Pb(Zr
x
Ti1-x
)O3 solid solution of the morphotropic phase boundary (MPB) composition. Our results indicate that the MPB determined by Jaffe, Cook and Jaffe [Piezoelectric Ceramics (Academic Press, London, 1971) p. 136] from structural measurements should be shifted to the rhombohedral side, which is more consistent with the MPB determined from dielectric measurements.
Photoacoustic Spectroscopy on the Nonuniformity of Na Cluster Concentration in Electron-Irradiated NaCl Single Crystal after Heat Treatment
Authors: Jr. Vivencio N. Abastillas , Katsuyuki Inabe Katsuyuki Inabe , Nozomu Takeuchi Nozomu Takeuchi
Published: February 2005

Thin single crystals of NaCl were deeply colored by intense electron irradiation to introduce Na clusters in the crystal, and were heat treated at 473 K. Dependence of the photoacoustic (PA) signal on the absorption coefficient and on modulation frequency reveals a smaller concentration of clusters near the heated surface compared with the other surface. Recombination of hole centers with the Na clusters is suggested from temperature dependence of the Na cluster concentration.
Dielectric and Ferroelectric Hysteresis Loop Measurements for Ultrathin VDF/TrFE Copolymer Films Evaporated Under Electric Field
Authors: Nagamori Tomomi , Horiuchi Toshihisa , Hara Kazuhiro , Matsushige Kazumi
Published: February 2005

Dielectric and Ferroelectric (D-E) hysteresis loop measurements were conducted for evaporated organic thin films by utilizing a newly developed sample cell. A vinylidene fluoride-trifluoroethylene (VDF/TrFE) copolymer sample with 54 mol% VDF content clearly exhibited a ferroelectric nature when an electric field of 30 MV/m was applied during the evaporation process.
Investigations of Soft-Mode and Electroclinic Response in a Ferroelectric Liquid Crystal with Ps≈5 mC/m2
Authors: Skarp Kent , Andersson Gunnar , Hirai Toshihiro , Yoshizawa Atsushi , Hiraoka Kazuyuki , Takezoe Hideo , Fukuda Atsuo
Published: February 2005

Measurements of the soft-mode and electroclinic behavior in the smectic A*-phase of a compound with very high spontaneous polarization (about 5 mC/m2 (0.5 µC/cm2) in the smectic C*-phase) are presented. It is found that for large induced tilt angles, one observes a strip texture giving rise to a strong characteristic light scattering. Once created this periodic stripe pattern remains even when the field is turned off. Furthermore, the electric field-induced modulation of the pattern allows scattering intensity modulation, resulting in anomalous electroclinic behavior.
Monte Carlo Simulation of Diffusion Process on Quasi-Lattice
Authors: Sasajima Yasushi , Sakayori Kazuhiko , Minoru Ichimura Minoru Ichimura , Mamoru Imabayashi Mamoru Imabayashi
Published: February 2005

The characteristics of the diffusion process of quasicrystals are studied for one-dimensional and two-dimensional models by the conventional Monte Carlo simulation. For the one-dimensional model, the tracer diffusion coefficients of an isolated particle are calculated for the three types of lattice models, i.e., single crystal, binary solid solution and quasicrystal. The characteristics of diffusivity of the one-dimensional quasicrystal model are derived from comparisons among the three types of models. For the two-dimensional model, the characteristics of diffusivity of a quasicrystal are discussed in comparison with those of the honeycomb lattice. In particular, the concentration dependence of diffusivity on the two-dimensional Penrose lattice is calculated and the effects of interatomic potential are discussed.
Selective Epitaxial Growth of Si and Si1-xGex Films by Ultrahigh-Vacuum Chemical Vapor Deposition Using Si2H6 and GeH4
Authors: Aketagawa Ken-ichi , Tatsumi Toru , Hiroi Masayuki , Niino Taeko , Junro Sakai Junro Sakai
Published: February 2005

Aiming at the precise profile control of Si1-x
Ge
x
, selective epitaxial growth (SEG) conditions and Si1-x
Ge
x
growth were investigated by ultrahigh-vacuum chemical vapor deposition (UHV-CVD) using Si2H6 and GeH4. As long as the total amount of Si2H6 did not exceed the critical amount, Si- and Si1-x
Ge
x
-SEG were both achieved independent of source gas flow rate and substrate temperature. The Ge fraction x of Si1-x
Ge
x
could be decided by the flow rate ratio between Si2H6 and GeH4, independent of substrate temperature. Fast gas flow switching realized the formation of a Si(120 Å)/Si1-x
Ge
x
(69 Å) strained layer superlattice at 587°C.
Direct Monte Carlo Simulation of Incident-Angle Dependence of Secondary Electron Emission from Aluminum
Authors: Kawata Jun , Ohya Kaoru , Mori Ichiro
Published: February 2005

A direct Monte Carlo simulation of secondary electron emission from Al is carried out in order to describe its dependence on the incident angle. The results show that the dependence of the electron yield at low energy is under the inverse cosine of the angle measured from the surface normal. At high energy, however, it is slightly over the inverse cosine at least for angles of less than 60°. These are mainly caused by small penetration and large backscattering of primary electrons for high incident angles. The calculation describes the experiment better than the conventional simulation based on continuous slowing-down approximation. Furthermore, the energy and angular distributions of emitted secondary electrons are insensitive to the incident angle.
In electron emission statistics at higher energies than an energy where the secondary electron yield is maximum, the probabilities for no emission and high n electron emission (n>2) are larger than the Poisson distribution, being enhanced for high incident angle due to the backscattering.
A Discussion on the “Ultralow Resistivity” with Drs. Hino and Kushida
Authors: Huanchun Zhou Huanchun Zhou
Published: February 2005

The ultralow resistivity in Langmuir-Blodgett heterofilms reported by T. Hino and M. Kushida is deliberated in this paper. A false ultralow resistivity may be caused by the very thin and nonuniform top Au films and by the miscounting the total current, I, as the current in the top Au films only.
Ion Collection from Laser-Induced Plasma Using Positively Biased Wire Electrode
Authors: Ogura Koichi , Takashi Arisawa Takashi Arisawa , Takemasa Shibata Takemasa Shibata
Published: February 2005

In atomic vapor laser isotope separation (AVLIS), an ion collection method which has a short collection time and low applied potential is required. We demonstrated that by using a positively biased wire electrode, the ions are collected from the laser-induced plasma in a shorter time at the same applied potential or at lower electric potential in the same collection times compared with the conventional parallel electrode method. The ion collection times could be estimated using simple one-dimensional models for both the wire electrode method and the parallel electrode method.
Kinetic Calculations in Plasmas Used for Diamond Deposition
Authors: Bou Pierre , Jean Claude Boettner Jean Claude Boettner , Lionel Vandenbulcke Lionel Vandenbulcke
Published: February 2005

Kinetic calculations in microwave discharges have been carried out for experimental conditions currently employed to grow diamond layers. The effects of plasma parameters such as the nature of the electron energy distribution function (eedf), the electron density (N
e), and the electron temperature (T
e) have been investigated. It has been pointed out that ion-molecule reactions do not notably modify the plasma composition in the range of electron density 1010-2×1012 cm-3. In addition, the plasma chemistry is greatly influenced by the amount of H atoms present in the discharge. Finally, the hydrocarbons produced in the discharge have been classified into two categories, CH
x
(0≦x≦3) radicals and C2H
y
(0≦y≦6) neutrals, and diamond deposition can be related to plasma compositions.
Investigation of Thermal Coefficient for Polycrystalline Silicon Thermal Sensor Diode
Authors: Yeh Ching-Fa , Shyue-Shyh Lin Shyue-Shyh Lin , Geun-Pin Yang Geun-Pin Yang
Published: February 2005

Thermal sensors utilizing p-n junction diodes built into the polycrystalline silicon layer are developed. The effective factors influencing the thermal coefficient of polycrystalline silicon thermal sensor diodes are clarified. It is found that diodes with a light boron dose have a larger thermal coefficient than those with a heavy boron dose. The plural p-n diodes connected with more cascade series number have a larger thermal coefficient than ones with less cascade series number. The periphery of the thermal sensor seems to have little effect on the thermal coefficient. In addition, the thermal coefficient will become higher as a larger forward current is selected. The thermal coefficient of the sensor with a boron dose of 1×1015 cm-2 will reach a saturation value of -2 mV/K when the forward current is above 2 µA.
Detection of Fine Particles in Liquids by Laser Breakdown Method
Authors: Fujimori Haruo , Matsui Tetsuya , Ajiro Taiko , Yokose Kenji , Hsueh Yu-Ming , Shigeru Izumi Shigeru Izumi
Published: February 2005

Basic characteristics of a particle detection method using laser breakdown were studied for a system of polystyrene standard particles dispersed in ultrapure water. The method was able to detect 0.02 µm particles. The detection sensitivity decreased with the particle size due to size dependence of the laser breakdown threshold. The plasma emission delay time from the laser pulse decreased with particle size (9.8±0.8 ns for 0.04 µm, 5.7±0.8 ns for 3.0 µm). The above results suggested the possibility of concentration and size measurement of fine particles in liquids by the proposed method.
Responses of Monolayer Membrances of Thiol-Containing Lipids to Odor Substances
Authors: Miyazaki Yoshio , Hayashi Kenshi , Toko Kiyoshi , Nakashima Kaoru Yamafuji
Published: February 2005

It is known that thiol-containing compounds form monolayer membranes on a gold surface via chemisorption from organic solvents in terms of a strong connection ability between thiol and the metal. Here we prepared different kinds of thiol-containing lipids and fabricated monolayer membranes on the gold disk electrode whose surface structures were similar to biological membranes. Responses of this lipid-coated electrode to odor substances were examined by an electrochemical method of a cyclic voltammetry. Blocking ability for the redox reaction of Fe(CN)6
3- was found to change upon adsorption of odor substances into monolayer membranes. The order of threshold values to detect the odorants was β-ionone<β-citral<chloroform≦n-amyl acetate; this order was the same as that in the human olfactory sense. The present study indicates that the monolayer membrane of thiol-containing lipids can be useful as a transducer of an odor sensor.
Effects of Annealing on Proton-Exchanged LiNbO3 Waveguides Fabricated Using Octanoic Acid
Authors: Pun Edwin Yue Bun , Chan Po Shuen Chung
Published: February 2005

Annealing properties of proton-exchanged optical planar waveguides in z-cut LiNbO3 fabricated using octanoic acid have been studied systematically. Waveguide propagation losses decrease with annealing time, and variations in the surface refractive index and waveguide depth with annealing time follow a power law relationship. The annealing process is shown to be an effective means of improving and modifying waveguide properties.
Laser-Beam Direct Writing of TiO2 Channels for Fabrication of Ti:LiNbO3 Waveguides
Authors: Haruna Masamitsu , Yasuaki Murata Yasuaki Murata , Hiroshi Nishihara Hiroshi Nishihara
Published: February 2005

A novel photoresist-free process used for fabrication of Ti:LiNbO3 waveguides is proposed and demonstrated. In this process, smooth waveguide patterning of TiO2 channels can be performed by laser-beam (LB) direct writing at up to 0.2 mm/s, where Ti film deposited on LiNbO3 is thermally oxidized in air by the focused Ar+ laser beam. LB writing has sufficiently high accuracy for waveguide patterning because the Ti film thickness is usually below 0.1 µm. Unlike the previously reported resist-free processes, the process demonstrated here does not require any specific tools or materials, and can provide Ti:LiNbO3 waveguides more easily. It was also confirmed that there are no marked differences in guiding properties between two Ti:LiNbO3 waveguides fabricated by the proposed resist-free process and the standard process based on waveguide patterning in photoresist as thick as 1 µm.
Design of 3-dB Integrated Optical Couplers in Asymmetric Branching Waveguides
Authors: Chan Hau-Ping , Po-Sheun Chungs Po-Sheun Chungs , Edwin Yun-Bun Pun Edwin Yun-Bun Pun
Published: February 2005

We present here a study of phase-front accelerator (PFA) effects on the operation of integrated optical asymmetrical Y-branch waveguides. The use of a PFA sector and the careful design of waveguide parameters will give equal power division between the two asymmetric branch outputs under nonadiabatic conditions (i.e., power-dividing behaviour). In addition, the transmission loss is significantly reduced in such a design structure when compared to conventional Y-branch waveguides, particularly when the half-branching angle is larger than 1°.
Optical Switch-Off Effect Using Excited State Absorption of Erbium-Doped Fibers
Authors: Maeda Yoshinobu , Migitaka Masatoshi
Published: February 2005

Optical switch-off in which the constant signal light is suddenly decreased at 1.4 and 25.0 W/cm2 was demonstrated with an erbium-doped fiber using a single-wavelength control light. Discontinuous phenomena of optical switch-off have hysteresis and occur at a minimum or inflection point in the transmission curve. Negative intensity dependence, which causes the transmission to decrease as the laser intensity is increased, was observed at 787 nm, but not at 808 nm. Numerical analyses were carried out using a four-level double-absorption model. As a result, it was found that these phenomena take place because the absorption cross section from 4I13/2 to 2H11/2 is larger than that from 4I15/2 to 4I9/2.
Parallel Optical Walsh Expansion in a Pattern Recognition Preprocessor Using Planar Microlens Array
Authors: Murashige Kimio , Akiba Atsushi , Toshihiko Baba Toshihiko Baba , Kenichi Iga Kenichi Iga
Published: February 2005

We have developed a parallel optical preprocessor for a pattern recognition system using a planar microlens array and a Walsh orthogonal expansion spatial filter. We experimentally demonstrated the parallel optical Walsh expansion of multiple images made by the planar microlens array with good accuracy, which assures 99% recognition of simple numeral characters in the system. In order to enlarge the tolerance of the recognition rate against the deformation of input patterns, we propose a novel selection method of Walsh expansion coefficients. From the computer simulation, we confirmed that 5% transverse shifts and 20° rotation of input patterns are allowable with the optimization of the spatial filter using this method.
Novel Use of Thermoplastic Plates for Rewritable Holographic Stereograms
Authors: Kenji Kinoshita Kenji Kinoshita
Published: February 2005

Thermoplastic (TP) plates have been used as a recording material for rewritable holographic stereograms (HSs). This novel application has made it possible to automatically control the entire process of HS synthesis without chemical development, showing that the developed HSs have high potential for 3-D display. The HS has been recorded on a TP plate of 76×76 mm2 in 130 s, using a liquid crystal television panel as a spatial light modulator for ray-traced 30-frame images. The TP plate has the capability for multiple use (more than 20 times) for HS synthesis. A reconstructed image has been observed with a good stereoscopic effect by means of He-Ne laser illumination.
Pulse-Field-Assisted Wafer Bonding for Silicon on Insulator
Authors: Yoshihiro Arimoto Yoshihiro Arimoto , Fumitoshi Sugimoto Fumitoshi Sugimoto
Published: February 2005

We have developed a pulse-field-assisted bonding technique to give void-free, low-temperature wafer bonding for SOI (silicon on insulator). We bonded a pair of oxided wafers by applying pulses of a few hundred volts across the wafers at 800°C in a 0.1 Pa nitrogen ambient. To reduce the volatile materials on the surfaces of wafers, which cause voids at low temperature, we heated the wafers at reduced pressure. The impulsive electrostatic force deforms the insulating oxide and allows bonding despite surface roughness and wafer warpage. Our pulse-field-assisted bonding reduces both the bonding temperature and time. We obtained a bond strength of over 1700 kgf/cm2after thermal treatment at 800°C for 1 min. This paper also discusses surface roughness, voids, and bond strength.