bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of Hydrogenated Amorphous Silicon Prepared by ECR Plasma CVD Method
Authors: Kitagawa Masatoshi , Setsune Kentaro , Manabe Yoshio , Hirao Takashi
Published: February 2005

Hydrogenated amorphous silicon (a-Si:H) films were prepared by the microwave electron-cyclotron-resonance (ECR) plasma CVD method using SiH4 gas without intentional substrate heating. The influence of the deposition conditions in the ECR plasma CVD method on the properties of a-Si:H films was studied and the properties were correlated with plasma optical emission spectra of similar deposition conditions. Photoconductivity of ∼10-6 (Ω cm)-1 under simulated AM1 (100 mW/cm2) illumination was obtained for the as-grown film with an optical gap of ∼2.1 eV at the SiH4 gaspressure of 2×10-4 Torr. The photoconductivities, the optical gaps and the B values estimated from optical absorption measurements were widely changed when SiH4 gas pressure condition was changed. Infrared absorption spectra also showed that the Si-H2 stetching mode at ∼2100 cm-1 and (Si-H2)
n
wagging mode at ∼845 cm-1 increased as SiH4 gas pressure increased. Measurements of optical emission spectra in the SiH4 ECR plasma showed that the emission intensity ratio of Si (288 nm) to SiH (414 nm) was larger than that in conventional RF plasma CVD, and that the photoconductivities and optical gaps increased as this ratio increased.
a-Si:H Deposition from SiH4and Si2H6rf-Discharges: Pressure and Temperature Dependence of Film Growth in Relation to α-γ Discharge Transition
Authors: Perrin Jérôme , Cabarrocas Pere Roca i , Allain Bruno , Friedt Jean-Marie
Published: February 2005

We present an interpretation of the pressure and temperature dependence of the growth kinetics of hydrogenated amorphous silicon (a-Si:H) in SiH4and Si2H6rf-glow discharges. At constant rf power, the a-Si:H deposition rate increases drastically at a given pressure depending on the nature of the gas and on the wall temperature. The threshold nature of this transition is attributed to the onset of an electron avalanche due to ion-induced secondary electron emission and ionization in the plasma sheaths close to the electrodes. We analyze the effect of various plasma parameters governing this α-γ discharge transition in terms of equivalent circuit of the discharge and power dissipation mechanisms. The ratio of a-Si:H deposition rates from SiH4and Si2H6rf discharges at the same rf power and flow rate is strongly dependent on the pressure because the α-γ transition occurs at a lower pressure for Si2H6than for SiH4. The transition is shifted to higher pressures as the temperature increases primarily because of the reduction of gas density, which explains contradicting results in the literature on the influence of temperature on a-Si:H deposition rate. At a given rf power and substrate temperature, the optical, structural and electrical film properties are correlated with the variation of deposition rate as a function of SiH4or Si2H6pressure.
Kerr Rotation Angle versus Gobalt Sublattice Magnetic Moment in RE-Co Sputtered Films
Authors: Honda Shigeo , Yoshiyama Masatoshi
Published: February 2005

Kerr rotation angles, θ
K, at 780 nm of an optical wavelength, λ, are measured at room temperature for RE(Gd, Tb, Dy, Nd)-Co sputtered films in a wide range of RE content. The absolute rotation angle |θ
K| decreases linearly with an increase in RE content. This compositional dependence of θ
K is analyzed using the mean field theory. From this analysis, it is found that the absolute value of θ
K is proportional to the Co sublattice magnetic moment, M
Co, with the coefficient of about 3.3 × 10-4 deg·cm3 / emu at δ = 780 nm. This linear relation indicates that θ
K of RE-Co films arises mainly from the Co moment, M
Co, at this wavelength. Furthermore, the Kerr rotations of Co-Ti, Co-Zr and Co-Cr sputtered films are measured. They are also proportional to the saturation magnetization, M
s, with the coefficients of values nearly equal to those of RE-Co films.
Magnetic Properties of Superconducting Pb-Bi System Alloy Filaments Produced by Glass-Coated Melt Spinning
Authors: Gotō Tomoko , Niimi Akira
Published: February 2005

The superconducting long filaments of Pb45Bi35 Sn20 and Pb45Bi40Te15 alloys with a high T
c of 10.1 and 10.2 K, respectively, were produced by glass-coated melt spinning. Magnetic measurements of the filaments were made in the temperature range from 2.1 K to the zero field transition temperature. The magnetic properties of both filaments exhibited similar behavior. The magnetic hysteresis and trapped flux of the filaments are small due to the thin sample size (such as 20 µm in diameter) and became much smaller through room-temperature annealing. Moreover, the B
c2, κ and T
c of the filaments decreased as the result of room-temperature annealing. κ was estimated from the equation B
c2=√2κB
c, where B
c2 and B
c are the upper critical field and the thermodynamic critical field, respectively. The B
c2 of filaments at various temperatures followed the de Gennes and Maki prediction for a dirty type-II superconductor.
Electrical and Optical Properties of Stannite-Type Quaternary Semiconductor Thin Films
Authors: Nakazawa Kentaro Ito
Published: February 2005

Quaternary stannite-type semiconductor films of Cu2CdSnS4 and Cu2ZnSnS4 with (112) orientation were deposited on heated glass substrates using atom beam sputtering. These p-type films showed resistivities which were decreasing functions of the substrate temperature up to 240°C. The films had an absorption coefficient larger than 1 × 104 cm-1 in the visible wavelength range. The direct optical band gaps of the (112) oriented polycrystalline films were estimated as 1.06 eV and 1.45 eV for Cu2CdSnS4 and Cu2ZnSnS4, respectively.
AC Field-Stabilization Phenomena of Ferroelectric Liquid Crystals
Authors: Umeda Takao , Nagata Tetsuya , Mukoh Akio , Hori Yasuro
Published: February 2005

AC field-stabilization phenomena of ferroelectric LC cells have been studied. The amplitude E
h of an AC electric field which is necessary for stabilizing an LC cell under a DC electric field with reverse polarity, has been obtained by theoretical discussions. E
h is expressed by the following equation:

E
h
2=E
ho
2+R·\frac{P_{\text{s}}{\cdot}E_{\text{b}}}{|\Delta\epsilon| \sin^{2}\theta_{t}}

where E
ho is the AC electric field which is necessary for stabilizing an LC cell without an electric field, P
s is the spontaneous polarization, E
b is the DC electric field, Δε is the dielectric anisotropy, θt is the tilt angle and R is a constant. This equation represents the experimental results well.
Modes in a Parallel-Plate Guide Filled with a Magnetoplasma
Authors: Miyahara Shunji , Kobayashi Sumio
Published: February 2005

The radio wave propagation in a parallel-plate guided magnetoplasma is studied. We introduce a classification chart consisting of five parameters to classify the propagation in the magnetoplasma and specify the dispersion patterns, and show that the chart is useful for the classification and understanding of the propagation. Electric field distributions of several modes identified in the parallel-plate guide are presented and their characteristics are also discussed.
RF Magnetron-Sputtered Si-Rich SiO2 Films on GdTbFe
Authors: Suzuki Akihiro , Matsuda Riki , Taki Kazunari , Watanabe Yumiko , Mizutani Shuzo
Published: February 2005

Si-rich SiO2 films have been produced by magnetron sputtering using a composite target. The magneto-optical properties in GdTbFe were successfully improved by using Si-rich SiO2 as a protective layer. In order to characterize the Si-rich SiO2 films and the interface in a Si-rich SiO2/GdTbFe structure, X-ray photoelectron spectroscopy (XPS) and Auger depth profiling were employed. Any excess Si in Si-rich SiO2 plays an important role in the improvement of the magneto-optical properties. It was revealed that Si-rich SiO2 comprised three components: elemental Si, SiO2 and SiO-like suboxide. The chemical shift of Si2p form the SiO2 component was measured with values of 3.25 eV. Auger and XPS measurements revealed that FeSi2 was formed at the interface. The FeSi2 layer works as a blocking layer against oxygen penetration.
Etch-Back Planarization Technique for Multilevel Metallization
Authors: Mayumi Shuichi , Fujiwara Kazuo , Nishida Shuichi , Ueda Seiji , Inoue Morio
Published: February 2005

In order to realize multilevel interconnections of VLSIs, problems in the conventional etch-back planarization of silicon oxide film have been clarified through a detailed study. Also, a new etch-back planarization technique has been developed using silicon nitride films, which is able to form very smooth surfaces. An end point detection for the etch-back is also proposed. This planarization technique and a newly developed method of “via hole making” have been successfully applied to Al three-level interconnections with a 2µm design rule.
AC Flashover Characteristics on Trapezoidal Contamination Models of Actual Insulators
Authors: Sato Masashi , Saito Hiroshi , Kaga Akio , Akagami Hideo
Published: February 2005

The fundamental characteristics of an ac contaminated flashover were investigated by using a simplified model which consists of a trapezoidal unit and a series of units in order to simulate the current density distribution on actual insulators. It is found that the lowest flashover voltage decreases with an increase in the voltage build-up rate, and after passing a minimum, tends to increase. Experiments also show that, if the leakage length is equal, a disc insulator string model having a metal plate on the connected area of units tends to flashover at a lower voltage than a long rod insulator model having no metal plate. The results are discussed according to the characteristics of the ac reignition voltage on contaminated surfaces in previous reports. It is deduced that the accumulation of Na ions in the discharge space at flashover dominates the reduction of contaminated flashover voltage.
Hydrogen Concentration and Bond Configurations in Silicon Nitride Films Prepared by ECR Plasma CVD Method
Authors: Hirao Takashi , Setsune Kentaro , Kitagawa Masatoshi , Kamada Takeshi , Wasa Kiyotaka , Tsukamoto Kazuyoshi , Izumi Tomio
Published: February 2005

The influence of deposition conditions on the hydrogen concentration and bond configurations in silicon nitride (SiN) films prepared by the electron cyclotron resonance plasma CVD(ECR P-CVD) method has been studied in comparison with those prepared by a conventional plasma CVD(P-CVD) method, by means of secondary ion mass spectrometry (SIMS), infrared absorption (IR) spectra and electron spin resonance (ESR).
SiN films deposited at low microwave powers and a relatively high SiH4 flow rate had higher H concentrations than those deposited at high microwave powers.
The hydrogen concentration was found to be in the range from 1.3×1022-5×1021/cm3 (13.8-4.7%) at microwave powers between 50 and 500 W.
The bond configurations in the films are markedly dependent upon the deposition conditions. SiN films with only N-H bonds are thermally stable, even after annealing at 900°C in a dry N2 atmosphere, while almost all the H atoms are lost after annealing for films with both N-N and Si-H bonds.
Annealing studies by ESR measurements revealed that the H concentration in the films has little influence on the spin density.
On the Existence and Origin of Elliptical Defects with Nucleus on Epilayers Grown by Molecular Beam Epitaxy
Authors: Mreira Marcus Vinicius Baeta , Oliveira Alfredo Gontijo de
Published: February 2005

Macroscopic elliptical defects with a nucleus on epilayers grown by molecular-beam epitaxy were analysed by scanning electron microscopy (SEM) and by Nomarski optical microscopy. The origin has been identified to be a macroscopic surface containation before growth.
Determination of the Townsend Primary Ionization Coefficient Using a Parallel Plate Avalanche Counter
Authors: Tsumaki Koji
Published: February 2005

Gas multiplication factors were obtained from the observed fast pulse of a parallel plate avalanche counter and the Townsend primary ionization coefficients for methane and isobutane were determined from the data over the ranges E/P=150–228 V/cm·Torr and 183–411 V/cm·Torr, respectively. The results for methane agreed well with the values obtained by Heylen.
Growth and Breakaway of Viscous Liquid Drops Hanging from a Tube
Authors: Watanabe Yoshio
Published: February 2005

When a liquid drop hanging from the end of a vertical tube is increased in volume at a constant rate, the growth of the drop is divided into two stages. Until the volume of the drop reaches a certain critical value, the drop increases its vertical length in a stable manner. After that, the vertical length increases in an unstable manner, and is finally broken away.
This experimental study is concerned with the effects of the increase rate of the drop volume and the viscosity of the drop substance upon the growth and the breakaway of the drop. The total volume of falling drops (a main drop and satellite drops) after breakaway increases with the increase rate of volume and the viscosity. Thus, the surface tension and the viscosity could be obtained by measuring the total volume of the falling drops for several increase rates of volume.
Effects of Reabsorption and Xenon on the Lifetime of the Excited Cesium Atom
Authors: Inoue Yukio , Iwazaki Ryuji , Hori Hirokazu , Sakurai Takeki
Published: February 2005

The effects of the reabsorption of radiation on the lifetime of the Cs 72P3/2 level were measured from the decaying waveform of fluorescence under various experimental conditions. Reabsorption does not have any influence on the lifetime when the experimental condition satisfies k
0
L<1, where k
0 is the peak absorption coefficient and L is the reabsorbing path length. A theoretical calculation based on a simple model agrees with the experimental results.
Allowed and Forbidden Transitions in ESR of Mn2+ in PbCl2 Crystals
Authors: Hirota Toyoharu
Published: February 2005

Single crystals of PbCl2 doped with Mn2+ have been investigated by ESR at X band and room temperature. The Mn2+ ion is found to be replaced for the Pb2+ ion. The spectrum can be described by a spin Hamiltonian for an ion in an orthorhombic crystal field. The parameters are found to be g

z
=1.9996±0.0002, g

y
=2.0004±0.0002, g

x
=2.003±0.001, D=-495.9±0.1 G, E=-137.0±0.1 G, A

z
=-84.8±0.2 G, A

y
=-85.2±0.2 G, A

x
=-85.2±0.5 G, a∼0 G and F∼0 G. The hyperfine structure splitting depends on the angle θ between the static magnetic field H and the z axis. the linear relation between the hyperfine constant A and the ionicity of the lattice holds even in PbCl2. The experimental angular variation of intensities is in good agreement with the calculation by numerical diagonalization. The measured intensity is asymmetric about the nuclear quantum number m=0.
Cation and Anion Displacements at Hetero-Interfaces of (GaAs)28(AlAs)24 Superlattice Layers
Authors: Kashihara Yasuharu , Harada Jimpei
Published: February 2005

By developing a new method of Fourier analysis the local cation and anion displacements in a superlattice, especially near the hetero-interface boundary between the GaAs and the AlAs, were determined from the X-ray integrated intensities of the satellite reflections observed around the two fundamental Bragg reflections, namely the 002 and 004 reflections. The interlayer distance of successive cation layers was found to be 2.827 Å in the GaAs region and 2.835 Å in the AlAs region, except near the hetero-interface boundary. The anion layers are, therefore, located at the mid-point between the cation layers in these regions. However, near the hetero-interface region, which consists of eight molecular layers, anion layers are not located at the mid-point between them but are slightly shifted to the GaAs side. The value of the shift at the boundary between GaAs and AlAs was 0.016 Å.
Monte Carlo Study of Hot Electron Transport in Quantum Wells
Authors: Tanimoto Hiroyoshi , Yasuda Naoki , Taniguchi Kenji , Hamaguchi Chihiro
Published: February 2005

Monte Carlo simulations of hot electron transport in AlGaAs/GaAs /AlGaAs quantum wells were carried out in order to clarify the drift velocity overshoot and steady state drift velocity versus the electric-field relation. In the simulations, we took into account the nonparabolic isotropic energy band structures. Results are given for GaAs well widths of 500 and 100 Å and an electron sheet density of 1.0×1012cm-2at 77 K. The drift-velocity overshoot reaches about 7×107cm/s at an electric field of 10 kV/cm in both quantum well structures. A negative differential mobility appears beyond 3 kV/cm in both structures due to electron transfer from the Γ valley to theLvalleys.
A Study of the Crystallographic and Luminescent Characteristics of ZnS:Mn Films Prepared by an RF Magnetron Sputtering Method for AC Thin-Film Electroluminescent Devices
Authors: Matsuoka Tomizo , Kuwata Jun , Nishikawa Masahiro , Fujita Yosuke , Tohda Takao , Abe Atsushi
Published: February 2005

Characteristics of ZnS:Mn films prepared by an rf sputtering method for electroluminescent devices were examined in detail; the features were clarified by a comparison with films produced by an electron-beam method. It was found that the incident species to the substrate during sputtering were composed of ZnS, Zn2, Zn2S, MnS and ZnMn in addition to Zn and S atoms; in the case of the electron-beam method, they were composed of Zn and S2. We confirmed that preparative, crystallographic, microstructural , chemical, and eventually electroluminescent characteristics in sputtered ZnS:Mn films were different from those in electron-beam films, according to the fundamental difference of the incident species to the substrate, which affected film growth.
Neutral Iron Generation with Sawtooth Oscillation in TEXTOR ICRF Heated Plasmas
Authors: Yamauchi Toshihiko , Schweer Bernd , Bay Helge L. , Höethker Klaus , Hintz Edward , Nieuwenhove Rudi Van
Published: February 2005

The emission of neutral iron atoms from a metal target in the shadow of the limiter was investigated during ICRF heating of the TEXTOR plasma, using laser induced fluorescence. By collecting the data over many similar sawtooth periods, the sawtooth oscillation of the neutral iron density was found for first time. The sawtooh oscillation of the netral iron density occurring during additional heating was in reverse phase to the neutral oxygen flux from the main limiter, but in phase with the central electron temperature. On the other hand, another case which was in contrast to the above case was found. The incident ion on the metal surface was studied.
X-Ray Photoelectron Spectra of an Electron-Beam Oxide Layer on GaSb
Authors: Wada Takao , Kitamura Noboru
Published: February 2005

A new oxidation method for GaSb that utilized a high energy electron-beam was investigated. The grown oxide layer was characterized by X-ray photoelectron spectroscopy (XPS) measurements. The oxidized Sb was distributed throughout the oxide layer and there was less pile-up of elemental Sb concentration at the oxide-semiconductor interface.
Measuring Methods of Plasma Parameters by a Differentiating and Modulating Double Probe
Authors: Amemiya Hiroshi
Published: February 2005

Methods for the (1) determination of the electron temperature by differentiation of the probe curve, (2) detection of a non-Maxwellian energy distribution and plasma inhomogeneity, (3) rapid measurement of the electron temperature by voltage modulation, and (4) measurement of the space potential are developed.
The Stark Modulation Spectrum of IBr Transition B'0+←X1Σ
Authors: Watanabe Akiyoshi , Takei Taka-aki , Sato Yoshi-ichi , Amako Yoshito
Published: February 2005

The Stark modulation technique was applied to the B'0+
v'=11←X
1Σv''=1 transition of IBr. The observed line shapes of R- and P-branches are composed of two different types; one is of an absorption type and the other of the derivative type. The relative amplitudes of both line shapes change characteristically according to the angle between the applied electric field and the light polarization. New rotational lines, otherwise forbidden in the transition, appeared under the applied electric field. Moreover, these field-induced lines always show the same absorption-type line shapes. Q-branch lines, in particular, are remarkably enhanced at the perpendicular polarization of light to the electric field.
These characteristic features of the Stark modulation spectrum have been explained by a perturbational treatment.
Anomalous Applied Voltage Dependence of the Switching Time in a Ferroelectric Liquid Crystal with Negative Dielectric Anisotropy
Authors: Nakamura Kohji , Orihara Hiroshi , Ishibashi Yoshiro , Yamada Yuichiro
Published: February 2005

We investigated the switching behavior of a ferroelectric liquid crystal with negative dielectric anisotropy in a high-applied-voltage region at various temperatures. It has been found that the switching time decreases with increasing applied voltage, but in higher-voltage regions it attains a minimum and then increases. By furthur increasing the applied voltage, the switching time attains a maximum and then decreases. The minimum of the switching time shifts towards a higher voltage with increasing temperature. It has been disclosed that the switching time falls on a universal curve when the switching time and the applied voltage are suitably scaled. The equation of motion with respect to the azimuthal angle φ of the n-director was introduced, and its analyses show qualitative agreement with the experimental findings.
Far-Infrared Optical Properties of Quenched Germanium; V. Uniaxial Stress Effects on the SA1 Acceptors
Authors: Hattori Takeshi , Yamano Koji , Mitsuishi Akiyoshi , Kamiura Yoichi
Published: February 2005

Far-infrared absorption spectra of quenched germanium were measured under a uniaxial stress along the <100>, <110> and <111> crystallographic orientations. It is concluded from the analyses of the number of the bands split with stress and from the feature of splitting of each band that the SA1 acceptor, which is the shallowest one in the quenched-in acceptors and has a ground state split into two levels without a uniaxial stress, is constructed from a defect in which the symmetric axis is along a <111> crystallographic axis. From the comparison between the results on the SA1 acceptors and the SA1Au and SA1Ag acceptors which are the perturbed SA1 acceptors, it is proposed that the SA acceptor is constructed from a pair of substitutional and interstitial atoms along the <111> axis and that SA1Au and SA1Ag acceptors are the defects consisting of the SA1 acceptor together with either Au or Ag impurities along the <111> axis, respectively.
Determination of Ion Temperature and Toroidal Rotation Velocity via Charge-Exchange Recombination Spectroscopy
Authors: Ogawa Hiroaki , Miura Yukitoshi , Kasai Satoshi
Published: February 2005

In JFT-2M plasmas spatially and temporally resolved ion temperature and toroidal rotation velocity were determined by measuring the Doppler-broadened profiles of spectral lines excited by charge-exchange recombination reaction between the neutral hydrogen beam (H0) and fully stripped ions (H+, C6+). The obtained ion temperature was in agreement with that measured by the neutral particle analyzer (NPA). These experimental results indicate that the charge-exchange recombination spectroscopy (CXRS) method is a powerful technique to measure hot and dense plasmas.
Forbidden Transitions of LiI in Laser-Induced Fluorescence Spectroscopy for the Measurement of Low-Frequency Electric Fields in Plasmas
Authors: Kawasaki Ken , Takiyama Ken , Oda Toshiatsu
Published: February 2005

Three forbidden transition (42P-22P, 42D-32D and 22P-42F) due to the Stark effect in the LiI energy system were theoretically investigated for the measurement of low-frequency electric fields in plasmas. Numerical results concerning the intensities of the forbidden transitions and the polarization characteristics are presented in which the effect of the electron spin is taken into account. The excitation of the levels of n=4 is supposed to be possible using tunable lasers and thus, the effect of laser polarization is also considered. The first two transitions (42P-22P and 42D-32D) are suitable for measuring a rather strong electric field (1 kV/cm) and can also be used to give the direction of the electric field in plasmas. The third transition is applicable to a weak-field measurement down to about 0.1 kV/cm.
Critical Transport Current Density in Sintered Oxide Superconductors with High Critical Temperature
Authors: Matsushita Teruo , Ni Baorong , Sudo Yasuo , Iwakuma Masataka , Funaki Kazuo , Takeo Masakatsu , Yamafuji Kaoru
Published: February 2005

Percolative critical transport current density in sintered Y–Ba–Cu–O superconductors is estimated by taking into account the effect of anisotropies in the upper critical field and the pinning structure. This value is much smaller than the estimate for the optimized situation, where misorientation between the magnetic field and anisotropic pinning structures does not occurs. As the volume fraction of the superconducting region becomes small, the critical transport current density decreases drastically due to a decrease in the percolation probability of the current. To improve the transport property, it is necessary to align the orientation of grains or to introduce isotropic pinning centers, in addition to increasing the superconducting volume fraction.
Ionization of Tetramethyltin in a Molecular Beam Injected Near a Metal Substrate in Vacuum with Laser Irradiation on the Substrate
Authors: Toya Kenzo , Kawasaki Masahiro , Sato Hiroyasu
Published: February 2005

Ionization of tetramethyltin, an organometallic compound, was observed when its molecular beam was injected near a metal substrate in vacuum and the laser light (the second or third harmonics of a Q-switched Nd:YAG laser) was irradiated on the surface of the metal substrate. Organometallic ions along with the substrate metal ions were observed with a quadrupole mass spectrometer. The role of a laser-irradiated metal surface in the ionization of an organometallic compound is discussed from the comparison of the appearance time (time delay necessary for an ion to be formed in or to arrive at the entrance region of the mass spectrometer after the irradiation of a laser pulse) of organometallic ions with that of substrate metal ions. The ionization of an organometallic compound by the reaction with translationally hot electrons ejected from a metal surface is concluded.
Characterization of Below-Gap Absorption in Semi-Insulating GaAs:Cr by Magneto-Circular Dichroism Spectrum
Authors: Sato Katsuaki , Iijima Tadashi , Nakajima Takeshi , Yahagi Koichi , Kobayashi Shunsuke
Published: February 2005

Magneto-circular dichroism (MCD) spectra in semi-insulating (SI) single crystals of GaAs:Cr have been measured between 0.7 and 1.4 eV with a magnetic field of about 106 A/m (13 kOe) at temperatures above 20 K. Relatively strong MCD signals were observed in the below-gap energy region where a strong photoionization absorption band appears. Assuming that this strong absorption is caused by the charge transfer transition from the top of the valence band to the Cr-related deep state, we have analyzed the observed data by a theoretical calculation using a model adopted by Martinez et al., from which the Cr-related state was located 0.89 eV above the top of the valence band. The spin-orbit parameter used for the fitting is much smaller than that expected from the splitting in the top of the valence band. Modification of the theory used in this analysis is required.
Structure Analysis of High-Tc Superconductor Bi-Ca-Sr-Cu-O by Processing of High-Resolution Electron Microscope Images
Authors: Shindo Daisuke , Hiraga Kenji , Hirabayashi Makoto , Kikuchi Masae , Syono Yasuhiko
Published: February 2005

A modulated structure in Bi-Ca-Sr-Cu-O was analyzed by image processing of high-resolution electron micrographs. The contrast of the modulated structure along the [010] direction with about 5a period was strongly enhanced by the processing. The structural modulation, mainly caused by the displacements of Bi atoms due to oxygen vacancies in the Bi4Ti3O12 derivative structure was clearly revealed. By combining the above result with processed images in other orientations, a realistic model of the modulated structure is proposed. It is demonstrated that the processing of high resolution images is useful in analyzing the complicated modulated structures such as observed in the new high-T
c superconductor Bi-Ca-Sr-Cu-O.
Polarization of λ=1.55 µm InGaAsP Ridge-Waveguide Lasers
Authors: Hartl Engelbert , Amann Markus-Christian
Published: February 2005

The influence of waveguide parameters on the polarization of the lasing mode is investigated for λ=1.55 µm InGaAsP-InP ridge-waveguide lasers. It is found experimentally that for weak index guiding the lasers are polarized TM, whereas for gain guided or strongly index guided devices the polarization is TE. This behaviour is in excellent agreement with calculations based on a recently developed ridge-waveguide laser model. It is demonstrated that stable TE or TM polarization can arbitrarily be established by means of an appropriate choice of the laser parameters.
Epitaxial Growth of Ba2YCu3Ox Thin Film on Epitaxial ZrO2/Si(100)
Authors: Myoren Hiroaki , Nishiyama Yukio , Nasu Hiroyuki , Imura Takeshi , Osaka Yukio , Yamanaka Shoji , Hattori Makoto
Published: February 2005

High-T
c superconducting Ba2YCu3O
x
films have been epitaxially grown on tetragonal ZrO2/Si(100) substrate by rf magnetron sputtering below 700°C. The slowly-cooled sample after deposition in a chamber involving O2 gas exhibits the superconducting transition above liquid nitrogen temperature. T
c(onset) and T
c(end) observed are 88 K and 82 K, respectively.
Fracture Toughness Measurements of Ba2YCu3O7-x Superconducting Oxide by Means of Indentation Technique
Authors: Ochiai Shojiro , Osamura Kozo , Takayama Tomoo
Published: February 2005

Fracture toughness of polycrystalline Ba2YCu3O7-x
superconducting compound was measured by means of indentation technique in air. The toughness value of the sample heat-treated at 1203 K for 28.8 ks was 0.71 MPa ·m1/2, but it became 0.87 MPa ·m1/2 through heat treatment at 1223 K for the same period and 1.37 MPa ·m1/2 by the addition of 0.1 mol of Ag2O for 1 mol of Ba2YCu3O7-x
. It was demonstrated that polycrystalline Ba2YCu3O7-x
can show higher fracture toughness than the single crystalline one (0.74 MPa ·m1/2) and the addition of Ag2O improves toughness.
Magnetic Property of YBa2Cu2CoOy
Authors: Kimishima Yoshihide , Hirabayashi Shuichi , Miyata Nahonori
Published: February 2005

The magnetic property of YBa2Cu2CoO
y
was studied by the measurement of DC magnetic susceptibility χ using a vibrating sample magnetometer (VSM). The temperature dependence of χ showed the antiferromagnetic Curie-Weiss behavior down to 10 K. The effective moment of this system is considered to be mainly due to the Co3+ spin on the site-1 which is the Cu-1 site in the YBa2Cu3O
y
system.
Mössbauer Effect of Icosahedral, Amorphous, and Crystalline Al-Cu-Fe Alloys
Authors: Kataoka Noriyuki , Tsai An-Pang , Inoue Akihisa , Masumoto Tsuyoshi , Nakamura Yoji
Published: February 2005

The local structure and magnetic properties of the icosahedral Al65Cu20Fe15, produced by liquid quenching and by conventional solidification and annealing, have been examined by the Mössbauer effect in comparison with the equilibrium tetragonal Al7Cu2Fe1 compound, nonequilibrium bcc Al63Cu23Fe14 and amorphous Al71Cu14Fe15 alloys. The atomic arrangement of the constituent elements has been found to be different in the two quasicrystals prepared by the different procedures.
SIMS and DLTS Measurements on Fe-Doped InP Epitaxial Layers Grown by MOCVD
Authors: Takanohashi Tsugunori , Nakai Kenya , Nakajima Kazuo
Published: February 2005

SIMS and DLTS measurements have been carried out on Fe-doped InP epitaxial layers grown by metalorganic chemical vapor deposition (MOCVD). Fe was doped with ferrocene Fe(C5H5)2 and smoothly distributed in the epitaxial layers. The solubility limit of Fe is 7×1016 cm-3 at a growth temperature of 650°C. A new electrically active defect was observed in InP doped with the excess concentration of Fe over the solubility limit.
Optical and Colorimetric Properties of an EC 8CB-Cell for the Transmission and Reflection Cell Types
Authors: Shimomura Teruo , Furuta Takashi , Eguchi Yoshihiro
Published: February 2005

An electrochromic (EC) cell with liquid crystal 8CB and electrolytic substance TBAI in propylene carbonate (PC) is evaluated for its optical and colorimetric characteristics in the isotropic phase. Adding a small amount of PC 0.2 wt%, we can drop the transition temperature from nematic to isotropic phases of the cell, compared to that of the cell which uses no PC. Optimum concentration for a good color switching is TBAI 3 wt%. The color difference between the coloration and bleached states is shown as the lightness index vs chromatic index in comparison with that of the WO3-cell.
Electrooptic Bistability and Threshold Characteristics of Ferroelectric Liquid Crystal Cell Possessing Polyimide Langmuir-Blodgett Film as an Aligning Layer
Authors: Nishikata Yasunari , Morikawa Atsushi , Takiguchi Yasuyuki , Kanemoto Akihiko , Kakimoto Masa-aki , Imai Yoshio
Published: February 2005

Ferroelectric liquid crystal cells with a high degree of bistability were prepared using the polyimide LB film as the aligning layer. The plots of the threshold voltages (V
th) and the pulse widths ( Δ
t), which were necessary to switch between the bistable states under the application of bipolar pulse voltages, displayed a hyperbola which was asymptotic to Δ
t=0 and V
th=constant (≠0).
Implications of Broad Raman Spectra of Sputtered SiGe Alloy Films
Authors: Hayashi Shinji , Fujii Minoru , Takanabe Tomoyuki , Yamamoto Keiichi
Published: February 2005

SiGe alloy films prepared by rf sputtering have been investigated by Raman spectroscopy and high-resolution electron microscopy. As-deposited films and films annealed at 600°C show broad Raman spectra usually attributed to continuous random network structures (amorphous). Electron diffraction patterns of the films are diffuse halos. However, high-resolution TEM images clearly show lattice fringes corresponding to microcrystals about 2 nm in size. The observed broad Raman spectra do not imply the continuous random structure of the films.
Observation of RHEED Intensity Oscillation in the Growth of Ag on Ag(100) Single Crystals
Authors: Suzuki Yoshishige , Kikuchi Hideyuki , Koshizuka Naoki
Published: February 2005

Oscillation of the reflection high-energy electron diffraction (RHEED) intensity has been observed during the MBE growth process of Ag on Ag(100) single crystals. The oscillation of the specular beam intensity is observed in the growth temperature range from 200 K to 480 K, but not observed above 500 K. Temperature dependence of the RHEED intensity oscillation is discussed on the basis of the step flow and roughening transition, and it is shown that the roughening transition is more important in the growth process of this system with high surface energy.
Diffusion of Constituent Atoms in P-type a-Si:H/SnO2 Interfaces
Authors: Kawabata Keishi , Shiratsuki Yoshiyuki , Miyazaki Seiichi , Hirose Masataka
Published: February 2005

Chemical states and impurity profiles in the p-type amorphous hydrogenerated silicon (a-Si:H)/SnO2 interface have been studied by X-ray photoelectron spectroscopy (XPS). It is found that a trace amount of reduced metallic Sn exists in a-Si:H, while molecular units such as SiO2, Si2O3, SiO and Si2O are incorporated not only in a-Si:H but also in SnO2, indicating that the mutual diffusion of silicon and oxygen in the interface takes place.
Josephson Junction and DC SQUID of Y-Ba-Cu-O Thick Film at 77 K
Authors: Lin A. Z. , Li H. Q. , Liu F. W. , Tang L.
Published: February 2005

YBa2Cu3O7-x
thick films were farbricated by the method of screen printing. Zero resistance temperature of 89 K and critical current density of 130 A/cm2 at 77 K of the films were obtained. The observation of ac Josephson effect at 77 K from weak link Junction of the thick film is reported. The successful dc SQUID operation at 77 K fabricated from the thick film is described. The observation of clear periodic patterns due to the macroscopic quantum interference effect assures promising application of this device at liquid nitrogen temperature.
Phase Compatibility and Superconductivity of Y-Ba-Cu-O Compounds
Authors: Wadayama Yoshihide , Kudo Kotaro , Nagata Akihiko , Ikeda Keisuke , Hanada Shuji , Izumi Osamu
Published: February 2005

Superconducting properties of Y-Ba-Cu-O compounds were investigated in relation to precipitation of second phases. Contour lines of J
c, T
c and diamagnetic signal intensities were presented in the YO1.5-BaO-CuO system. These superconducting properties decreased steeply with BaCuO2 precipitation, and the maximum J
c was obtained in the yttrium-rich composition of Y1.2Ba2Cu3O7-y
. It is considered, therefore, that the BaCuO2 precipitating around the YBa2Cu3O7-y
grains interrupt the superconducting current pass at the grain boundary. Yttrium-rich composition, which inhibits BaCuO2 precipitation, is effective for the preparation of the high-J
c sample.
Orthorhombic-Tetragonal Phase Boundary in YBa2Cu3O7-Δy
Authors: Kogachi Mineo , Nakanishi Shigemitsu , Nakahigashi Kiyotaka , Minamigawa Shinnosuke , Sasakura Hiroyuki , Fukuoka Nobuo , Yanase Akira
Published: February 2005

The orthorhombic-tetragonal phase boundary in the (Δ
y-T) diagram was determined by means of in situ X-ray diffraction methods for the YBa2Cu3O7-Δ
y
. To cover the oxygen content region as widely as possible, two different methods were adopted. The first was performed under the fixed oxygen partial pressure and the second under the fixed oxygen content (deficiency Δ
y) of the samples. The obtained phase boundary showed a peculiar shape which differed from that proposed previously, suggesting the existence of another orthorhombic (ortho II) phase in low temperature region.
Structural Study of Superconducting Tl-Ba-Ca-Cu-O System
Authors: Onoda Masashige , Kondoh Shinji , Fukuda Kenji , Sato Masatoshi
Published: February 2005

A crystal structure of Tl-Ba-Ca-Cu-O system with a superconducting onset transition temperature higher than 100 K which is systematically characterized by electron probe microanalysis and electron diffraction is determined by single crystal X-ray diffraction. The unit cell is described by a body-centered tetragonal lattice with space group I4/mmm. The structural unit consists of the seven oxide layers, -Ca-Cu-Ba-Tl-Tl-Ba-Cu-, stacked along the c-direction. The expected chemical formula is Tl1.95Ba2Ca0.85Cu2.18O8, which is slightly deviated from the stoichiometric composition Tl2Ba2CaCu2O8. It is suggested that the hole carrier of this system may be given by the nonstoichiometric composition of the cation.
Superconductivity in Ba3La2LuCu6Oy
Authors: Watanabe Takao , Kinoshita Kyoichi , Shibata Hiroyuki , Matsuda Azusa , Asano Yoshihiro , Yamada Tomoaki
Published: February 2005

Single-phase Ba3La2LuCu6O
y
(y∼14) is synthesized. Superconductivity is observed after annealing in oxygen at high pressure; it is a semiconductor without annealing. Power X-ray diffraction shows that annealing changes the crystal structure of Ba3La2LuCu6O
y
from tetragonal into orthorhombic. Magnetic susceptibility measurements show that T
c onset of the annealed sample is around 50 K and about 1% of the volume is superconductive. The analysis shows that the average Cu valence dependence on T
c of Ba3La2LuCu6O
y
and Ba2YCu3O7-y
differs.
Three Phases in BiSrCaCuO Thin Films Synthesized by the Multilayer Deposition Method
Authors: Ohkubo Masataka
Published: February 2005

Thin films of the BiSrCaCuO system have been synthesized by a multilayer deposition followed by annealing in oxygen. Three phases, two being pseudotetragonal with c lattice parameters of about 24 and 30 Å and one being an unestablished phase with T
c=100 K, have been confirmed in the thin films. The phase with c≃30 Å (T
c=80 K) remarkably crystallizes by annealing at a lower temperature (865°C) than those (≧870°C) for other phases. Both phases with c≃24 and 30 Å grow with (001)-orientation parallel to the substrate surface. The best film has a T
c(onset) of 80 K and a T
c(zero) of 70 K.
Spatial Distribution of Trapped Magnetic Flux in the High-Tc Superconductor Y1Ba2Cu3O7-δ. II. Comparison with the Critical State Model
Authors: Kisu Takanobu , Enpuku Keiji , Yoshida Keiji , Takeo Masakatsu , Yamafuji Kaoru
Published: February 2005

We measured spatial distributions of the trapped magnetic flux density B in polycrystalline YBaCuO superconductors. It is shown that the spatial distribution of B for external magnetic fields is similar to that predicted from the critical state model of the type II superconductor. Furthermore, the spatial gradient of B becomes steep in proportion to the coupling strength among superconducting grains. It is also shown that the spatial distribution of B changes when the grain-coupling strength is degraded by postannealing around 200°C.
Preparation of Superconducting Bi-Sr-Ca-Cu-O Printed Thick Films on MgO Substrate and Ag Metal Tape
Authors: Hoshino Kazutomo , Takahara Hidefusa , Fukutomi Masao
Published: February 2005

The thick films of Bi-Sr-Ca-Cu-O(BSCCO) systems have been prepared by a screen printing method on (100) MgO substrates, Ag and some metal tapes. The electrical resistivity and microstructure have been investigated as a function of the postprinting heat treatment. We have succeeded in obtaining a highly oriented thick film with the c-axis perpendicular to the MgO substrate. The film annealed at 885°C for 1 hr followed by annealing at 872°C for 72 hr shows zero resistance Tc(end) of 107 K, which corresponds to the superconducting transition of the high-T
c phase in BSCCO materials. By depositing BSCCO thick films on Ag metals tapes, highly oriented films have also been obtained, which have shown zero resistance at 76 K.
Large Area Doping Technique Using an Ion Source of rf Discharge with Magnetic Field
Authors: Yoshida Akihisa , Kitagawa Masatoshi , Setsune Kentaro , Hirao Takashi
Published: February 2005

A low energy broad ion beam doping technique has been developed. This technique enables the doping of impurities into semiconductor materials over a large area (370 mm φ) without mass separation and beam scanning. Diborane diluted in hydrogen was discharged by rf (13.56 MHz) power and magnetic fields. Ions from discharged gas were accelerated by an acceleration voltage of 1.5 kV and were implanted into silicon wafers. We confirmed that resistance uniformity in five pieces of 3in.-Si wafers simultaneously doped by this technique was ±3.44 percent.
Hot Isostatic Pressed Gd2O2S:Pr, Ce, F Translucent Scintillator Ceramics for X-Ray Computed Tomography Detectors
Authors: Ito Yukio , Yamada Hiromichi , Yoshida Minoru , Fujii Hideji , Toda Gyozo , Takeuchi Hiroshi , Tsukuda Yasuo
Published: February 2005

Translucent scintillator ceramics of Gd2O2S:Pr, Ce, F were fabricated using a hot isostatic pressing (HIP) technique. The optical transmission is about 60% of the incident light and the X-ray stopping power is also quite high. Owing to the enhancement of these properties by the HIP densification process, the highest light output from a 1 mm thick specimen combined with a silicon photodiode, when excited by 120 kV X-rays, has reached 1.8 times that of CdWO4 single crystals. The present ceramics are very promising candidates for scintillator materials in X-ray computed tomography (CT) detector applications.
Initial Oxidation Process of Anodized Porous Silicon with Hydrogen Atoms Chemisorbed on the Inner Surface
Authors: Kato Yoshihisa , Ito Toshimichi , Hiraki Akio
Published: February 2005

The initial stage of oxidation of anodized porous silicon (PS) at low temperature (\lesssim208°C) has been investigated using a conventional infrared (IR) spectroscopy technique. After the oxidation in air, four extra IR absorption peaks appeared in the Si-H stretching band (2000∼2300 cm-1). The origins of these peaks have been assigned as excitations of Si-H oscillators for various SiH
n
(n=1∼3) bonded by oxygen atom(s). The progress of the oxidation without breaking Si-H bonds was linearly dependent on the square root of the oxidation time, indicating a diffusion-limited process even for the initial stage. The activation energy of this process was 0.60 eV. The role of chemisorbed hydrogen atoms in the oxidation process is discussed.
Anomalous Temperature Dependence of Electrical Conductivity in Polythiophene Derivatives Substituted with Long Alkyl Chain
Authors: Yoshino Katsumi , Park Dae Hee , Park Bok Kee , Fujii Masaharu , Sugimoto Ryu-ichi
Published: February 2005

The electrical conductivity of poly(3-alkylthiophene)s such as poly(3-butylthiophene), poly(3-hexylthiophene), poly(3-octylthiophene), poly(3-decylthiophene) and poly(3-dodecylthiophene) increases with increasing temperature. However, after attaining a maximum value, it decreases with further temperature increases. Hysteresis has also been observed in the temperature dependence of conductivity during heating and cooling cycles. This anomaly is interpreted in terms of the strong influence of molecular conformation change on carrier scattering.
Single-Crystal X-Ray and Magnetization Study of the 106 K Bi-Sr-Ca-Cu-O Superconductor
Authors: Sueno Shigeho , Yoshizaki Ryozo , Nakai Izumi , Ohishi Kazumasa , Ono Akira
Published: February 2005

Single crystals of Bi2(Sr, Ca)4Cu3O
x
were studied by an X-ray precession camera together with the 232 and 221 phases. The 243 crystals were selected from two types of the specimens: (1) quenched from 810°C (T
c=80 K) and (2) annealed subsequently at 500°C for 4 hours (T
c=106 K). X-ray photographs revealed that the 243 phase has basically a 37 Å stacking unit along the c-axis with a remarkable stacking disorder. The direction of the modulation is not parallel to the b
*-axis but inclined 35.7° from the b
*-axis for the 243 phase. SQUID study revealed that the volume fraction of the 106 K phase at 50 K was about 57%.
Effect of Dopant Concentration on Oxidation-Induced Stacking Faults in Boron-Doped CZ Silicon
Authors: Chichibu Shigefusa , Harada Tsuyoshi , Matsumoto Satoru
Published: February 2005

The length of oxidation-induced stacking faults strongly depends on the boron concentration in extrinsic conditions at the oxidation temperature. This behavior can be interpreted by the generation of silicon self-interstitials by the Fermi level effect attributed to the heavy boron doping.
Dislocation Reduction in MBE-Grown Ge on Si(001) by in situ Thermal Annealing
Authors: Fukuda Yukio , Kohama Yoshitaka , Seki Masahiro , Ohmachi Yoshiro
Published: February 2005

The threading dislocation density in Ge layers grown by molecular beam epitaxy on Si substrates can be reduced by insitu thermal annealing during deposition. The Ge/Si interfaces of nonannealed and insitu annealed samples are observed by plan-view transmission electron microscopy to understand the dislocation-reduction mechanism. The results suggest the following: (1) the formation of dislocation networks and half-loops terminating at the interfacial misfit dislocation array is enhanced by the thermally induced strain of insitu annealing; (2) the dominant mechanism of dislocation reduction is the shrinkage of dislocation networks and half-loops into the interface; (3) dislocation line tension is the driving force of this shrinkage.
Bulk Nature of Quench-Enhanced Superconductivity in Bi2Sr2CaCu2Ox
Authors: Ishida Takekazu , Mazaki Hiromasa , Sakuma Takashi
Published: February 2005

The lower T
c of the Bi-Sr-Ca-Cu-O (BSCCO) system can be raised by more than 15 K by quenching. This characteristic has been confirmed for a stoichiometric 2212 compound. From the ac susceptibility measurement of the powdered specimens, we revealed that the observed T
c enhancement is not filamentary but has a bulk origin. X-ray diffraction study indicated that our specimens are almost single phase and the crystalline cage is not altered drastically by quenching.