bluuebunny/crossref_metadata_2025 huggingface dataset:
Generation of a Large Electron Beam for Plasma Processing
Authors: Sugai Hideo , Yabuoshi Noriyuki , Toyoda Hirotaka
Published: February 2005

A large-diameter (∼16 cm) electron beam in a range of energy from 5 to 30 eV was extracted from an ECR microwave plasma in order to control active species in plasma processes. The measurement of the electron energy distribution function revealed that the beam energy was linearly proportional to an externally applied bias. On the other hand, the beam flux turned out to be limited to 10–20% of the random thermal flux of electrons in the source plasma. The rate of production of radicals by the energetic beam was calculated and founed to be large enough for the beam source to be used in CVD or etching processes.
MBE Grown Undoped Superlattice Gate and Modulation-Doped Buffer Structure for Power FET Applications
Authors: Liu W. C. , Hsu W. C. , Lour W. S. , Wang R. L. , Chang C. Y.
Published: February 2005

A new power FET with a hybrid (MESFET and MD) operation mechanism has been fabricated successfully. The insertion of a modulation-doped (MD) structure between the AlGaAs buffer and GaAs active layer gives high output current and high transconductance. By reducing the gate length to 1 µm, transconductance of up to 340 mS/mm can be expected. Furthermore, the use of an undoped AlGaAs/GaAs superlattice “gate insulator” provides low leakage current and much higher gate breakdown voltage (>30 V). From the experimental results, it is obvious that the proposed structure is suitable for high power applications.
The Occurrence of Superconductivity in the TlBa2CuO5-δ-Type (1021) System
Authors: Ku H. C. , Tai M. F. , Shi J. B. , Shieh M. J. , Hsu S. W. , Hwang G. H. , Ling D. C. , Watson-Yang T. J. , Lin T. Y.
Published: February 2005

Stable and reproducible superconductivity in the Tl(Ba2-x
La
x
)CuO5-δ (0.0≤x≤0.6) system with the tetragonal TlBa2CuO5-δ-type (1021) structure was reported. A Prototype compound TlBa2CuO5-δ had shown a metastable superconducting onset around 25 K, with zero resistivity at 10 K. With partial substitution of La for Ba ions, T
c (50% resistivity drop) increases to 45 K, T
c0 (zero resistivity) to 42 K and onset around 50 K. A diamagnetic signal was observed with onset as high as 57 K. Tetragonal lattice parameters decrease with the increasing La concentration due to the partial replacement of larger Ba2+ ions by smaller La3+ ions. The Pairing field energy of 170 K and electron-elementary excitation coupling constant λ of 0.76 were derived from the BCS-like T
c formula through comparison with other single Tl-O layer systems TlCa
n-1Ba2Cu
n
O2n+3-δ.
Phase Diagram and Crystal Growth of Superconductive (NdCe)2CuO4
Authors: Oka Kunihiko , Unoki Hiromi
Published: February 2005

Single crystals of (NdCe)2CuO4 have been grown by the travelling-solvent floating-zone (TSFZ) method. The single crystal grown in a deoxidized atmosphere exhibits superconductivity. Part of the crystallographic phase diagram of the Nd2O3-CuO system has been derived by conventional means to determine the concentration and temperature range of the liquidus line.
Effect of Annealing on Superconductivity in Bi-Pb-Sr-Ca-Cu-O System
Authors: Matsuda Motohide , Kikuchi Akira , Tanaka Masasuke , Ishii Mamoru , Yamashita Tsutomu , Koinuma Hideomi
Published: February 2005

The effect of annealing on the superconductivity in the Bi-Pb-Sr-Ca-Cu-O system was investigated. The tailing phenomenon was observed in the R-T curves for all samples annealed at temperatures in the range of 600°C to 825°C though the as-sintered sample showed a superconducting transition above 100 K. This phenomenon was enhanced in the sample annealed at 700°C.
Ba2Y1Cu3O7-y Oxidation by Thermodynamic Nonequilibrium High-Temperature (TNH) Plasma
Authors: Takagi Shinji , Sekiguchi Atsushi , Hosokawa Naokichi , Terada Norio , Jo Masatoshi , Ihara Hideo
Published: February 2005

In order to obtain high-T
c superconducting Ba-Y-Cu-O materials, we have studied a method used to supply the oxygen content using a thermodynamic nonequilibrium high-temperature (TNH) plasma. Compared with the usual glow discharge, very-high-density atomic oxygen was observed in the TNH plasma. Treatment of the TNH plasma showed the recovery of quenched samples from the tetragonal structure to an orthorhombic 90-K superconductor within 30 min at 300°C. This is superior to usual oxidation techniques of an atmospheric oxygen anneal and a glow discharge plasma from the viewpoint of short period and low temperature.
Oxygen K-Edge Fine Structure of Tl1Ba2Can-1CunO2n+3 Studied by Electron Energy Loss Spectroscopy
Authors: Shindo Daisuke , Sato Hiroshi , Liedl Gerald L. , Perry Darold , Hiraga Kenji , Hirabayashi Makoto , Nakajima Satoru , Kikuchi Masae , Syono Yasuhiko , Hojou Kiichi , Soga Takeshi
Published: February 2005

The fine structures of the oxygen K-edge in the Tl1Ba2Ca
n-1Cu
n
O2n+3 with single Tl-O layers were investigated by electron energy loss spectroscopy (EELS). The peak corresponding to the hole state near the Fermi energy was sensitive to the number of Cu-O layers and the direction of momentum excitation. It was shown that the hole content in Tl1Ba2Ca
n-1Cu
n
O2n+3 decreases with the increase of n (n=2–4) and that most holes exist in the O 2p
x,y
orbitals of 2-dimensional Cu-O planes.
Superconducting Thin Film of (Nd, Ce)2CuO4-y
Authors: Saitoh Shin'ichiro , Hiratani Masahiko , Miyauchi Katsuki
Published: February 2005

Superconducting (Nd, Ce)2CuO4-y
thin films are prepared on MgO substrates using rf-magnetron sputtering. The resistivity drop is observed at around 10 K in the as-deposited film. After annealing at 1070°C in Ar, resistivity drops at 19 K and reaches zero at 14 K. The onset temperature in the magnetic susceptibility measurement is 12 K.
Preparation of a Bi-Sr-Ca-Cu-O High-Tc Superconductor by the Reaction of a Cu-Free Precursor with Cu Plate
Authors: Yoshimoto Mamoru , Hashimoto Takuya , Koinuma Hideomi
Published: February 2005

A Bi-Sr-Ca-Cu-O high-T
c superconducting layer was formed on a metallic copper substrate by the reaction between calcined Bi2SrCaOp powder or thick film and surface-oxidized copper plate, The reaction proceeded at an oxidized copper surface to form a triple layer structure composed of Bi2Sr2CaCu2O
x
, CuO
q
, and Cu. The use of Bi in excess of the high-T
c phase stoichiometry (Bi/Sr/Ca=1/1/1) was essential for the formation of the superconducting Bi-Sr-Ca-Cu-O layer.
Effect of Flux Creep on Current-Voltage Characteristics of Superconducting Y-Ba-Cu-O Thin Films
Authors: Enpuku Keiji , Kisu Takanobu , Sako Ryuichi , Yoshida Keiji , Takeo Masakatsu , Yamafuji Kaoru
Published: February 2005

Temperature dependence of current-voltage characteristics of Y-Ba-Cu-O thin films is studied experimentally. The observed results are analyzed with the flux creep model, and good agreement is obtained between the theory and the experiment. Using the flux creep model, the pinning potential, U, is obtained as U(T=0)\gtrsim77 meV for thin films with j
c(T=0)\gtrsim2×107 A/cm2. The temperature dependence of U is also obtained, and the result is discussed based on the pinning theory.
Static SIMS Studies of Superconducting YBa2Cu3O7-y Thin Films
Authors: Seo Satoru , Chang Jon-Chi , Matsui Masakazu , Takami Hirosi
Published: February 2005

Static secondary ion mass spectrometry (SIMS) has been used for the first time to study the Cu-O binding situation of YBa2Cu3O7-y
thin films. The CuO4 square-planar and CuO5 polyhedra units, the concentration of which depends upon the oxygen content of the YBa2Cu3O7-y
structure, were confirmed in the mass spectra with either 0.5 keV Ar+ or O2
+ bombardment. Also, a depth analysis of these molecular ions in the films was carried out.
Growth Temperature Dependence of Electrical Properties of LPE-Al0.1Ga0.9Sb Characterized by p-n Junction Current Transport
Authors: Kitamura Noboru , Takeda Yoshikazu , Sasaki Akio
Published: February 2005

Al0.1Ga0.9Sb p-n junctions were fabricated by liquid phase epitaxy (LPE) at 300–500°C and investigated to characterize electrical properties of Al
x
Ga1-x
Sb. The growth temperature dependences of current-voltage (J–V) characteristics and their stability showed that the diodes grown at 400°C had the best electrical properties. The reverse current density was interpreted by a simple tunneling model. The excess current was observed in the low forward voltage region at both 77 K and 300 K. The slope of log J
f–V
f characteristic in the high forward bias region did not depend on the measurement temperature. The experimental results showed that the current in the Al0.1Ga0.9Sb p-n junctions was attributable to the bulk characteristic of the junction and that the tunneling current was dominant. The tunneling current is due to the high residual acceptor density in the diode grown at high growth temperatures, while it is attributable to the increase of electronic states in the band gap in the diode grown at low temperatures.
Evaluation of Epitaxial ZnTe Films Prepared by RF Sputtering by Means of Ion Beam Channeling
Authors: Tokumitsu Yoji , Kawabuchi Akira , Kitayama Haruyuki , Imura Takeshi , Osaka Yukio , Nishiyama Fumitaka
Published: February 2005

Epitaxial films of Zinc telluride are deposited by rf sputtering on the clean surface of GaAs(100), InP(100) and GaSb(100) substrates, which have lattice mismatches with ZnTe of 7.6, 3.8 and 0.1%, respectively. Ion-channeling measurements are carried out to evaluate the crystalline quality of the ZnTe films. The defect density in the films greatly depends on the lattice mismatch between ZnTe and the substrates. The epitaxial films with thicknesses of 130 to 150 nm on GaAs, InP and GaSb give minimum aligned yields X
min of 32, 18 and 8%, respectively. The value of X
min of the film on GaSb is fairly small, comparable to the value for the single crystal. The dependences of the dechanneling probability on the incident-beam energy indicate the presence of dislocation lines.
Stoichiometry of Ta–N Film and Its Application for Diffusion Barrier in the Al3Ta/Ta–N/Si Contact System
Authors: Sasaki Katsutaka , Noya Atsushi , Umezawa Toshiji
Published: February 2005

In order to obtain a stable contact structure applicable to Si–LSI thin film technology, we have produced the contact structure of Al3Ta/Ta–N/Si by interposing the Ta–N film as a diffusion barrier between Al3Ta film and Si substrate. The contact structure was heat-treated at various temperatures in vacuum, and the behavior of mass transport across the interfaces of both Al3Ta/Ta–N and Ta–N/Si caused by the heating process was examined by Auger depth analysis. Also, on the basis of X-ray diffraction and XPS analysis, the barrier properties of the Ta–N film were examined with respect to the crystalline state and the chemical bonding state of the film. It is revealed that the thermal stability of this contact structure is closely related to the stoichiometry of the Ta–N film used as a diffusion barrier.
Effects of Starting Materials and Preparation Conditions on Superconducting Properties of Ba2YCu3O7-δ Compounds
Authors: Ohshima Shigetoshi , Okuyama Katsuro
Published: February 2005

Three different types of CuO powders prepared by the neutralization method (CuO-I), the autoclave method (CuO-II) and the electrolysis method (CuO-III) were used to study the effect of starting materials on the superconducting properties of Ba2YCu3O7-δ compounds. T'cs measured by the electrical method are almost the same among the Ba2YCu3O7-δ compounds prepared from these CuO powders; however, J
c and T
c as measured by ac susceptibility were quite different. The J
c value for the samples prepared using CuO-II was higher than that for the samples prepared using CuO-I and CuO-III. Optimum formation conditions to obtain the high J
c samples were also investigated.
Epitaxial Growth of MgO Layer on Y1Ba2Cu3O7-y Thin Film
Authors: Tanaka Saburo , Nakanishi Hidenori , Higaki Kenjiro , Itozaki Hideo
Published: February 2005

A MgO/Y1Ba2Cu3O7-y
(YBCO) structure on a MgO(100) substrate was prepared by a reactive vacuum evaporation method. The MgO layer with (100) orientation was obtained on each of the (001) and (100) YBCO thin films at the substrate temperature of 400°C. The crystallinity of the MgO layer as a function of the MgO thickness was investigated. The randomness of the crystallinity became smaller with a decrease in the thickness. The (100) epitaxial MgO layer without other orientations was obtained at a thickness of 5 nm. Structures of both YBCO/MgO/YBCO(001) and YBCO/MgO/YBCO(100) were studied. From the result of the cross-sectional TEM observation, it was confirmed that for both the (001) and (100) base YBCO layers, top YBCO layers with the same orientation were epitaxially grown via the intermediate MgO layer with a thickness of 5 nm.
Frequency-Dependent Switching Behavior under Triangular Waves in Antiferroelectric and Ferrielectric Chiral Smectic Phases
Authors: Lee Ji , Chandani A. D. L. , Itoh Keizou , Ouchi Yukio , Takezoe Hideo , Fukuda Atsuo
Published: February 2005

A realistic model structure of the ferrielectric phase is proposed by taking into account the apparent tilt angle measurements. On the basis of the model, the electric and optical responses are investigated in the ferrielectric SmCγ
* as well as in the antiferroelectric SmCA
* phases of MHPOBC (C8H17O---COO--COOC*H(CH3)C6H13) under triangular waves of various frequencies. At low frequencies, D-E curves show double and triple hysteresis loops characteristic of the antiferroelectric and the ferrielectric phases, respectively. T (transmittance)-E curves also reveal similar hysteresis loops. With increasing frequency, the direct switching between the two ferroelectric states occurs without passing through the antiferroelectric state or the ferrielectric states. The complicated frequency dependence is interpreted based on the spatially inhomogeneous domain switching.
Effect of Degree of Imidization in Polyimide Thin Films Prepared by Vapor Deposition Polymerization on the Electrical Conduction
Authors: Ito Yasuhiko , Hikita Masayuki , Kimura Toyoaki , Mizutani Teruyosi
Published: February 2005

Polyimide (PI) thin films of about 300 nm in thickness are fabricated by vapor deposition polymerization (VDP) from pyromellitic dianhydride (PMDA) and 4,4'-diaminodiphenylether (DDE). The structure of the films obtained is analyzed by means of infrared absorption spectra (IR spectra) and X-ray diffraction. The IR spectra show that the films are changed into PI by curing through the precursor, polyamic acid (PAA). The relation between the imidization of the films and the electrical conduction is examined. The results show that as imidization caused by curing the films proceeds, the current is decreased. It is therefore suggested that the residual PAA in PI thin films affects the electrical conduction. An attempt is also made to apply a model of ionic hopping conduction to the electrical conduction data.
Effect of Impurity Segregation on Crystal Morphology of Y-Bar Synthetic Quartz
Authors: Iwasaki Fumiko , Shinohara Armando H. , Iwasaki Hideo , Suzuki Carlos K.
Published: February 2005

The effects of Al and H impurities on the crystal morphology of Y-bar synthetic quartz were studied. The growth velocities perpendicular to the Y-axis were evaluated in relation to the Al and H impurity segregations on the growth interfaces. It was found that the -X-growth region has the highest H content and shows the lowest growth velocity, due to the effect of H2O adsorbed on the growth interface in hydrothermal solution. Therefore, the -X-face, (1̄1̄20), always becomes larger in size. Al has a selective effect on the (112̄2) and (1̄1̄22̄) faces to suppress the growth velocities and thus is important for crystal morphology. The growth velocities perpendicular to these faces, however, are controllable by the Al impurity content in the nutrient.
Pyrolysis Mechanism of Fatty Acids for Thin Solid Films Prepared by Physical Vapour-Deposition
Authors: Ushikusa Toshiaki
Published: February 2005

The pyrolysis mechanism and thermostability of the series of saturated and unsaturated fatty acids, used as molecular of organic thin solid films, were studied using a thermogravimeter. The weight loss of saturated fatty acids was caused by evaporation of the molecules, although it was accompanied by a slight decomposition of the molecules in air flow. In cases of unsaturated fatty acids, evaporation of the molecules decreased and it decomposed with an increase in the number of double bonds. The thermostability of fatty acids, measured with the initial temperature of weight loss, was enhanced with an increase in the number of carbon atoms in the case of saturated fatty acids. On the other hand, thermostability of the unsaturated fatty acids reduced with an increase in the number of double bonds.
Mechanical Transfer Function of Thin Smectic A Slab having Homeotropic Structure
Authors: Okano Koji , Yamamoto Jun
Published: February 2005

We derive a formula which expresses the low frequency longitudinal mechanical transfer function of thin smectic A slab having homeotropic structure in terms of the layer compression modulus and the viscosity coefficients.
A corresponqing formula for thin homeotropic nematic slab is also given.
Perovskite Formation of Pb(Mg1/3Nb2/3)O3 and Pb(Fe1/2Nb1/2)O3 Film by Sol-Gel Method
Authors: Okuwada Kumi , Nakamura Shinichi , Imai Motomasa , Kakuno Keiichi
Published: February 2005

Dielectric thin films of Pb(Mg1/3Nb2/3)O3 and Pb(Fe1/2Nb1/2)O3 were prepared by sol-gel method. The Pb(Mg1/3Nb2/3)O3 perovskite film was formed by heat treatment at over 600°C and oriented on substrates whose interplanar spacings were close to that for the perovskite. On the other hand, Pb(Fe1/2Nb1/2)O3 perovskite appeared at below 500°C. It was not oriented in spite of having almost the same lattice parameters. Transmission electron microscopy revealed that Pb(Mg1/3Nb2/3)O3 perovskite nucleation occurs at specific places on the substrate, while Pb(Fe1/2Nb1/2)O3 occurs randomly in the film. The grain of these films grew larger than 0.1 µm, and the dielectric constant was 1800 for the PMN film.
Oxygen-Sensitive Surface Layer in Pt/TiO2 Composite Film
Authors: Ono Hiroshi , Morisaki Hiroshi , Horiike Akio , Yazawa Kazuhiko
Published: February 2005

It is shown that the surface resistance of Pt/TiO2 composite films is sensitive to oxygen gas at temperatures higher than 130°C. The measured potential distribution along the film surface suggests that there is an oxygen-sensitive high resistance layer in the surface region. According to the results of an ESCA analysis, the high resistance is due to the Pt-free surface layer formed on the Pt/TiO2 granular metal layer.
Substrate Misorientation Effect on Be Transport during MBE Growth of GaAs
Authors: Mochizuki Kazuhiro , Goto Shigeo , Kakibayashi Hiroshi , Kusano Chuushiro
Published: February 2005

The Be transport during MBE growth of GaAs has been studied. The Be surface segregation was clearly separated from the Be diffusion by using misoriented as well as nominal (100) substrates. The Be profiles measured by SIMS showed that the surface segregation was suppressed by the substrate misorientation even when the anomalous diffusion took place. The CAT observation revealed that the Be-induced disordering of superlattices occurred for 6×1019 cm-3 doping. The width of the disordered region was found to depend on the substrate misorientation, which was due to the misorientation dependence of the surface segregation. The step exchange model has been successfully employed to account for these results.
Low-Frequency Noise in GaAs
Authors: Yang Shiyuan , Mizunami Toru , Takagi Keiji
Published: February 2005

Low-frequency noise measurements were carried out on GaAs devices in the frequency and temperature ranges from 10 Hz to 100 kHz, and from 77 K to 300 K, respectively. The noise spectra are considered to be superpositions of generation-recombination noise components caused by traps. The activation energies of these traps are determined from the temperature dependence of the noise.
Shock-Induced Changes in La2CuO4, La2NiO4, La2-xSrxCuO4 and La2-xSrxNiO4 Single Crystals
Authors: Takeya Hiroyuki , Takei Humihiko , Jang Wen-Jye , Syono Yasuhiko , Kikuchi Masae , Kusaba Keiji
Published: February 2005

Shock loading experiments up to 70 GPa have been carried out on single crystal specimens of La2CuO4, La2NiO4, La2-x
Sr
x
CuO4 and La2-x
Sr
x
NiO4. An apparent lattice expansion after compression was observed in La2CuO4. In contrast to this, no cell volume change was detected in La2NiO4 while the Sr-doped crystals showed slight expansion. This contrast is attributable to a difference in the crystal structure: La2CuO4 is orthorhombic with a puckering structure of the CuO6 octahedra, whereas the others are tetragonal with no puckering.
Levitation Forces, Relaxation and Magnetic Stiffness of Melt-Quenched YBa2Cu3Ox
Authors: Moon F. C. , Chang P.-Z. , Hojaji H. , Barkatt A. , Thorpe A. N.
Published: February 2005

Measurements of levitation forces on melt-quenched and free sintered YBa2Cu3O
x
superconductors show that melt-quenched samples produce forces from 96-170% higher than sintered specimens. The force increases are correlated with higher magnetization values for the melt-quenched material. Similar increases in the magnetic stiffness were also measured. Vertical levitation force relaxation showed less than 5% decrease in one hour. These results have important favorable implications for application to superconducting bearings.
Magnetic Properties of High-Tc Bi1.4Pb0.6Ca2Sr2Cu3Oy Superconductor
Authors: Lee Sang-Geun , Park Chong-Yun , Kim Young-Cheol , Yi Kyung-Soo , Jang Min-Su , Yu Seong-Cho
Published: February 2005

Magnetization measurements were performed on Bi1.4Pb0.6Ca2Sr2Cu3O
y
superconductor with T
c=108 K using a vibrating sample magnetometer in fields up to 18 kOe. The magnetization M(T) is linearly increased in a temperature range of about 15 K below T
c, and the temperature dependence of H
c2 is obtained from the onset of diamagnetism. From the upper critical field slope ∂H
c2/∂T, the zero-temperature upper critical field H
c2(0) is estimated about 61 T. Also, the lower critical field H
c1(0) is 111 Oe using the magnetization measurement M(H). From the magnetic critical fields H
c2 and H
c1, we estimate the superconducting parameters: the coherence length ζ0=23 Å, the penetration depth λ0=2600 Å, the Ginzburg-Landau parameter κ=113 and the jump in the specific heat ΔC/T
c≃2 mJ/molK2.
Realization of Fast InGaAs Photoconductive Response by Ion Implantation and Annealing with No Degradation of Peak Responsivity
Authors: Kimura Tadamasa , Yamamura Shin'ichi , Koike Ken'ichi , Morita Tetsuo , Yugo Shigemi , Kamiya Takeshi
Published: February 2005

Fast and efficient InGaAs photoconductive responses were obtained by B-ion implantation and subsequent rapid thermal annealing (RTA). Undoped, n-type (n=5×1015 / cm3), 0.5 µm thick InGaAs layers were epitaxially grown on semi-insulating InP:Fe substrates. These layers were homogeneously implanted with B ions at multiple energies. Thereafter, they were subjected to RTA in a halogen lamp furnace. The photoconductive impulse response of these layers to a 1.3 µm light pulse showed an improved FWHM (full width at half-maximum) of 0.7 ns at a dose of 1.9×1013 B/cm2 and RTA at 800°C with scarcely degraded responsivity, in contrast to the FWHM of more than 1.6 ns for original samples. It was interpreted that this improvement might be obtained due to both hole trap annihilation by the implantation itself, resulting in a removal of the long tail, and the recovery of degraded carrier mobilities by post-implantation annealing.
Incident Angle Dependence of Secondary Electron Emission from Copper with Multiple Elastic Scattering of Primary Electron in the Muffin-Tin Potential
Authors: Ohya Kaoru , Kawata Jun , Mori Ichiro
Published: February 2005

A Monte Carlo simulation of the secondary electron emission from a copper metal bombarded with low-energy electrons is carried out for analyzing its dependence on the angle of incidence. For the simulation, the differential cross section and the mean free path of the elastic collision of low-energy electrons in bulk copper are calculated with the muffintin approximation for a crystal potential. The mean free path (m.f.p.) is larger than the nearest-neighbor distance even at very low energy (10 eV), while the m.f.p. with an isolated atom potential is smaller than the distance at any energy of less than 1120 eV. The calculated angular dependence of the secondary electron yield is more consistent with an experimental dependence than that for the isolated atom potential.
Plasma Parameters in a Rectangular Tube Positive Column Neon Plasma
Authors: Kaneda Teruo , Ohsone Yasufumi , Chang Jen-Shih
Published: February 2005

Plasma parameters in a rectangular discharge tube positive column neon plasma have been studied experimentally. The results show that the axial electric field and the electron temperature decrease with increasing gas pressure and discharge tube minor axis, and decreasing discharge tube minor-to-major axis ratio for fixed minor axis. Plasma density profiles also show that the effect of metastables becomes important when gas pressure increases.
Construction of a Soft X-Ray Emission Spectroscopy (SXES) Apparatus and Its Application for Study of Electronic and Atomic Structures of a Multilayer System
Authors: Iwami Motohiro , Hirai Masaaki , Kusaka Masahiko , Kubota Masaru , Yamamoto Sekika , Nakamura Hatsuo , Watabe Hirokuni , Kawai Masao , Soezima Hiroyoshi
Published: February 2005

A soft X-ray emission spectroscopy (SXES) apparatus was constructed using a grating monochromator. The resolution was sufficient to show differences in valence electronic structures of Si compounds including pure Si crystal. A nondestructive analysis of a Ni/Si(111) specimen with heat treatment was carried out using either a clear difference in Si L2,3 SXES spectra of Ni silicide and Si single crystals or the fact that the soft X-ray production depth increases in a solid with increasing energy of a primary electron, E
p. The electronic and atomic structures of the surface and interface of specimens adopted were clarified with E
p varying between 1.5 and 10 keV.
Measurement of Soft X-Ray Absorption by Al, Cr, and Ni Using Synchrotron Radiation
Authors: Fujisaki Hisao , Nakagiri Nobuyuki , Nagata Hiroshi , Kihara Naoto , Miyahara Tsuneaki
Published: February 2005

The X-ray absorption of thin films of Al, Cr, and Ni was measured using synchrotron radiation to determine their mass absorption coefficients. The wavelength region was 1.25-6 nm. Sample films were prepared on a polycarbonate membrane by evaporation deposition in the same chamber used for the X-ray absorption measurements in order to avoid sample oxidation and/or the introduction of impurities from air. Plots of the mass absorption coefficients calculated from the X-ray absorption data against wavelength showed that anomalous deviations occurred in several wavelength regions where the curves should be monotonic. Such deviations can be attributed to the second-order light included in the incident light.
Theoretical Study on High-Energy Electron Energy Loss Spectroscopy Compared with X-Ray Absorption Spectroscopy III. Effects of Double Elastic Scattering
Authors: Yikegaki Tetsuro , Yiwata Noriyuki , Fujikawa Takashi , Usami Seiji
Published: February 2005

We investigate the effects of multiple elastic scattering in high-energy electron energy loss spectroscopy (EELS) before and after deep core excitation based on the previous theory developed by the present authors. In addition to simple surfaces, which include only one kind of atomic element, more complex systems like adsorbed system O/Ni(001) and clean surface NiO(001) are studied for two different modes: the grazing incidence and small takeoff angle detection mode and the backward scattering reflection mode. The calculated results show that multiple elastic scattering gives rise to a small effect in this high-energy region, ε
p
=2-3 keV, which is especially small for the surfaces composed of light atoms. In the reflection mode, additional oscillation is observed for any surface except diamond. Careless analysis of the oscillation could give us incorrect information about the bond distance around an excited atom.
Deep Impurity Levels of Cobalt in Silicon
Authors: Nakashima Hiroshi , Tsumori Yasuo , Miyagawa Tsuyoshi , Hashimoto Kimio
Published: February 2005

It has been believed until now that cobalt in silicon forms an acceptor level at around E
c–0.53 eV and a donor level at around E
v+0.35 eV. However, it is found that an acceptor level at E
c–(0.40±0.02)eV and a donor level at E
v+(0.23±0.01) eV are attributed to the amphoteric cobalt levels from the DLTS measurements for the samples diffused with cobalt deposited from the evaporation of a pure cobalt wire. The former levels (0.53 eV and 0.35 eV) are observed only for the samples prepared by the cobalt deposition from a tungsten filament wrapped with cobalt wire, and the tungsten contamination is regarded to be the cause of these levels.
Photoluminescence Study of AlxGa1-xSb Grown by Liquid-Phase Epitaxy
Authors: Kitamura Noboru , Higuchi Kenji , Uekita Hiroshi , Ichimura Masaya , Usami Akira , Wada Takao
Published: February 2005

The dependences of PL of Al
x
Ga1-x
Sb on growth temperature, AlSb composition, excitation laser power, and donor impurity doping were investigated. Two main emissions and one additional peak, except for the band edge emission, were observed. The experimental results were interpreted with the residual acceptor level of E
v+30 meV and one defect level which was located at the energy of 70–120 meV, depending on AlSb composition, below the Γ conduction band edge. The PL spectra in undoped layers suggested that the emission at E
g–(70 to 120) meV (emission C) was different from one related to the double charged states of residual acceptors. In donor-doped layers, however, the emission which implied the possibility of the residual acceptor being doubly ionizable was observed close to emission C.
Electrical and Optical Characteristics of an a-Si:H/c-Si Heterojunction Switch
Authors: Chen Yu-Wen , Fang Yean-Kuen , Lee Hong-Da , Chang Chun-Yen
Published: February 2005

A novel structure of a three-terminal a-Si:H(p+-i-n)/c-Si(p-n) heterojunction threshold switching device is developed. The device can be controlled both by a voltage-controlled mode and a current-injection mode. The voltage control gain and current triggering capability are 0.9 and 5×10-3 V/µA, respectively. When this switching device is operated as an optical switch, the light triggering sensitivity is 5.8×10-3 V/µW.
Gap States in a-SiGe:H Examined by the Constant Photocurrent Method
Authors: Watanabe Takeshi , Azuma Kazufumi , Nakatani Mitsuo , Shimada Toshikazu
Published: February 2005

Gap states in a-SiGe:H alloys were examined by the deconvolution analysis of subgap absorption spectra obtained by the constant photocurrent method. A broad distribution of defect states was found in a-SiGe:H alloys by the analysis postulating a Gaussian distribution of defect states. Analysis postulating two Gaussian peaks suggested that defects in a-SiGe:H can be divided into Si- related and Ge-related types. The energy positions of two defect peaks relative to the conduction band edge were almost constant irrespective of the optical gap of alloy films, and the position of one peak agreed with the defect peak in a-Si:H. The other peak which locates around 0.75 eV below the conduction band edge appeared when Ge was introduced into a-Si:H. The ratio of these two peaks exhibited a fairly good correlation to the Ge/Si ratio of alloys.
The Energy Gap Temperature Coefficient in the Nonisoelectronic Solid Solutions of the Type A4B6–A2B6
Authors: Baleva M. , Sendova M.
Published: February 2005

The analytical expression for the compositional and temperature dependence of the energy gap in quaternary solid solutions Pb1-x
Cd
x
S1-y
Se
y
, obtained by Koguchi et al. [Jpn. J. Appl. Phys. 28 (1989) 1170] has been discussed. Theoretical and experimental arguments have been adduced to prove the compositional dependence of the gap temperature coefficient, which had not been taken into account by Koguchi et al. Also concerns the refractive index compositional dependence.
Preparation, Superconducting and Normal State Transport Properties of Granular, n-Doped Ln2-xCexCuO4-δ, Ln=Nd, Sm
Authors: Ströbel J. P. , Klauda M. , Markl J. , Saemann-Ischenko G.
Published: February 2005

We report on superconducting and normal state transport properties of the electron-doped cuprates Ln2-x
Ce
x
CuO4-δ with Ln=Nd, P Sm. Irreversible behaviour of bulk samples after applying a magnetic field at low temperatures is observed. This feature as well as the two step transition in R(T) and the `semiconducting' behaviour of the polycrystalline samples above T
c is explained in terms of granularity. Phase-diagrams for both Nd2-x
Ce
x
CuO4-δ and Sm2-x
Ce
x
CuO4-δ are presented. There is evidence for a solubility limit of Ce-ions in Sm2CuO4 within the superconducting concentration range. We show results for the Hall-coefficient, which is negative all over the investigated temperature range. The preparation process has been monitored by means of X-ray analysis and TGA/DTA.
Annealing Effect on Sputtered CoCr Films
Authors: Uchiyama Yoichi , Ishibashi Kazuo , Sato Hiroshi , Ueda Toshifumi , Hwang Uee-Myung
Published: February 2005

Changes in structure of sputter-deposited CoCr films are discussed in conjunction with those in magnetic properties by means of annealing. At an annealing temperature of 400°C, drastic changes are observed with respect to crystallinity, saturation magnetization, and perpendicular anisotropy. Then at an annealing temperature of 480°C, the film structure becomes homogeneous. Furthermore, the films made especially at a high substrate temperature of 220°C are suggested to be composed of at least two regions with different lattice coherency along the film thickness; such a structure contributes to a large value of the perpendicular coercivity and, together with segregation, to the perpendicular anisotropy.
An Optical Parallel Computing System with Electronic Feedback Circuits
Authors: Chen Jing , Ueyama Kenji , Yoshida Kazuaki , Yanagi Yasuhiro , Minemoto Takumi
Published: February 2005

A hybrid optical computing system having a parallel optical logic gate and electronic feedback circuits is proposed. With this system, various repeated parallel computations can be performed.
Effect of Dipoles on Electrical Conduction in Polymers: I. Numerical Calculation
Authors: Kaneko Kazue , Suzuoki Yasuo , Mizutani Teruyoshi , Ieda Masayuki
Published: February 2005

Current-time (J-t) characteristics for polar polymers were simulated by using a simple one-carrier model including dipoles with the relaxation time τ. When τ was much smaller than the carrier transit time t
0 under an average field, either the current showed a peak resembling a space-charge-limited-current (SCLC) peak in a nonpolar material even when the injection field was not reduced to zero, or the current did not show any peak but increased or decreased monotonically to reach the steady state. However, the peak appeared later than the SCLC peak time. When τ>t
0, the current increased after t
0 due to the virtual increase of the dielectric constant with time. From the shape of experimental J-t curves for polar polymers, ranges of τ and t
0 can be determined.
Native Defects in III–V Ternary Alloy Semiconductors Grown from Liquid-Solutions
Authors: Ichimura Masaya , Wada Takao
Published: February 2005

A thermodynamic model of native defects developed by Van Vechten was extended and applied to III–V ternary alloy semiconductors grown from a liquid solution. Antisites and vacancies were taken to be dominant defects. In order to guarantee the solvability of the mass action equations, the equilibrium of defect-formation reactions and the liquid-solid phase equilibrium were considered with consistency; that is, the same thermodynamic data were used in calculations of the phase diagrams and the defect concentrations. In addition, the effects of the nonideality of the alloy were taken into account in the calculation of the free energies of the reactions. The Al-composition dependence and temperature dependence of the native defect concentrations in Ga1-x
Al
x
As were calculated as an example.
Light-Induced Desorption of Cs from the Cs–Sb Photoemissive Cathode
Authors: Hirohata Toru , Mizushima Yoshihiko
Published: February 2005

We have confirmed the desorption of Cs atoms from Cs–Sb photocathodes by external irradiation. The desorbed species are estimated as cesium by a work function of the captive filament method. This light-induced desorption is made predominant by the irradiation of infrared light (hν<1 eV), but not by visible light. To explain this phenomenon, the authors have calculated an adiabatic potential diagram of Cs adsorption on a Cs–Sb cathode surface, which safely explains the light-induced desorption.
Origin of Anomalous Corrugation Height of STM Images of Graphite
Authors: Sugawara Yasuhiro , Ishizaka Tatsuya , Morita Seizo
Published: February 2005

To clarify the origin of the anomalous corrugation height of STM images of a graphite under a constant current mode, we carefully investigated the variation of the tunneling current and forces between the lever and graphite during lateral scans. In the case of an unoxidized Pt lever, the variations of the sample displacement, the lever deflections and the apparent corrugation height were almost independent of the measuring tunneling current. On the other hand, in the case of a slightly oxidized W lever, the variation of the sample displacement, the lever deflection and the apparent corrugation height increased with increasing tunneling current. We also found a tendency that for the W lever, an apparent corrugation height increases monotonously with the increase of the force variation. We concluded that the anomalous corrugation height of STM images of a graphite surface was enhanced by the oxide layer of the tunneling tip.
Gamma-Ray Measurement of 152Eu Produced by Neutrons from the Hiroshima Atomic Bomb and Evaluation of Neutron Fluence
Authors: Kato Kazuo , Habara Minoru , Aoyama Tetsuhisa , Sakata Hidefumi , Yoshizawa Yasukazu
Published: February 2005

The 152Eu/Eu ratios were measured in a tombstone exposed to neutrons of the Hiroshima atomic bomb near the hypocenter. Measurements of 152Eu gamma rays were performed for europium samples chemically isolated from numerous rock specimens taken from the tombstone. A reliable attenuation curve of the 152Eu/Eu ratios was obtained. The curve suggests that the thermal neutron component was relatively small and the average incident angle of neutrons to the tombstone was roughly 45°C from the perpendicular downward direction. It revealed to us several important pieces of information concerning the energy and angular distributions near the Hiroshima bomb hypocenter.
Effect of Argon Atmosphere on Self-Absorption of a Spectral Line in Laser Microprobe Analysis
Authors: Kuzuya Mikio , Mikami Osamu
Published: February 2005

The effect of the reduced argon atmosphere on the self-absorption of a spectrum was studied with the use of a normal laser microprobe by changing the gas pressure and the observation height of spectral lines. At 150 Torr, a spectral line virtually free of self-absorption and a resultant high emission intensity were obtained about 1.5 mm above the sample surface. Using this condition, the linear calibration curve with unit slope was obtained for the analysis of copper (concentration:1–20%) in aluminium samples.
Oxygen Gas Response of Layered Compound CuFeTe2
Authors: Kuriyaki Hisao , Kishiro Koichi , Hirakawa Kazuyoshi
Published: February 2005

The electrical properties of layered compound CuFeTe2 are studied under intercalation and deintercalation conditions of intercalant gas. The resistivity perpendicular to the layer responds to oxygen gas at room temperature. It is found that CuFeTe2 is a favorable material for oxygen sensors which operate even at low temperatures below 100°C.
An Application of Quadrupole to the Handling and Selection of Laser Fusion Fuel Containers
Authors: Tajima Tsuyoshi , Norimatsu Takayoshi , Izawa Yasukazu
Published: February 2005

An application of two-dimensional quadrupole to the handling and selection of laser fusion fuel containers is presented. The system, which was combined with microcomputer-based image processing, demonstrated its practical feasibility.
Effects of Carbon Atoms on the Defects in Czochralski-Grown Silicon Formed by Annealing
Authors: Fukuoka Noboru , Atobe Kozo , Honda Makoto
Published: February 2005

The effects of carbon atoms on defect formation in annealings were studied. The results suggest that a defect associated with the photoluminescence line at 0.767 eV (P-line) captures the carbon atom preferentially in the formation process. By assuming that the defect is Ci-O2(Ci: interstitial carbon atom, O: oxygen atom), the experimental results on the 0.767 eV line can be explained. It is reported that the new donor formation is suppressed in a sample that does not contain carbon atoms, but the obtained value for the new donor concentration is 2 × 1015/cm3in carbon-lean Czochralski-grown sample (carbon concentration <1015/cm3).
Optical Stabilizer and Directional Coupler Switch Using Polymer Thin Film Waveguides with Liquid Crystal Clad
Authors: Muto Shinzo , Nagata Takashi , Asai Keisuke , Ashizawa Hideaki , Arii Kohzoh
Published: February 2005

Two types of optical functional devices with a polymer thin film core and liquid crystal clad, to which an electric voltage can be applied, have been fabricated. One type operates as an optical stabilizer and the other operates as an optical directional coupler switch since laser light propagation in these devices can be controlled electrically.
Fluorescence from Resins for Oil Painting under N2 Laser Excitation
Authors: Miyoshi Tadaki
Published: February 2005

Time-integrated and time-resolved fluorescence spectra were measured at 300 K in resins under N2 laser excitation. Fluorescence spectra of mastic and dammar are similar to those of varnishes which contain these resins. Fluorescence from lac dye is observed in shellac.
Ferroelectric Liquid Crystal Display Using Tristable Switching
Authors: Yamada Yuichiro , Yamamoto Norio , Mori Kahoru , Nakamura Koji , Hagiwara Takashi , Suzuki Yoshiichi , Kawamura Ichiro , Orihara Hiroshi , Ishibashi Yoshihiro
Published: February 2005

Smectic layer structure and switching behavior in antiferroelectric liquid crystals TFMHPOBC, TFMHPDBC and MHPOBC were studied. At the phase transition point between SmC* and SmCA
*, discontinuity in the leaning angle and the layer spacing was observed. In the SmA phase, diffraction peaks attributable to the focal conic texture and the planar layer structure were observed, implying that the bookshelf structure and the focal conic texture coexist. Using the tristable switching, we designed the fundamental waveforms for multiplex driving and constructed a prototype antiferroelectric liquid crystal display which works at room temperature.
Growth of Ga0.47In0.53As/InP Double-Heterostructure Wafers by Chemical Beam Epitaxy (CBE)
Authors: Uchida Takashi , Uchida Toshi K. , Mise Kazuaki , Yokouchi Noriyuki , Koyama Fumio , Iga Kenichi
Published: February 2005

GaInAs/InP wafers with a thick active layer (0.5-2.0 µm) were grown by chemical beam epitaxy (CBE). Stripe-contact lasers were fabricated to evaluate these wafers. The lowest normalized threshold current density obtained was 7.9 kA/cm2·µm for devices with a 2.0 µm thick active layer. This value is almost acceptable for application to surface emitting lasers.
Population Inversion in a Recombining Helium Plasma Mixing with Hydrogen Molecular Gas in a TPD-I Machine
Authors: Furukane Utaro , Sato Kuninori , Oda Toshiatsu
Published: February 2005

A high potentiality of plasma cooling and its mechanism are theoretically revealed for a helium plasma which comes into contact with hydrogen molecular gas in the TPD-I machine. The stationary population inversion between the levelsn=2 and 3 of the He+ion, which is due to mixing of the stationary high-temperature helium plasma and the hydrogen molecular gas, is simulated and discussed in comparison with cooling due to the mixing of the plasma and the atomic hydrogen gas. The calculation also shows that the gain per unit length of the He II 164 nm line is ∼ 2 cm-1for the laser oscillation under optimum initial helium plasma (Te∼ 30 eV andne∼ 3.5 × 1016cm-3) contacted with hydrogen molecular gas at a pressure of 0.1 Torr.
Heat Deposition on the Partial Limiter
Authors: Itoh Kimitaka , Nagasaki Kazunobu , Itoh Sanae-Inoue
Published: February 2005

The effect of the partial limiter in the outermost magnetic surface of toroidal plasmas is studied. The power deposition on the partial limiter and its effect on the temperature profile are analysed. Interpretation in terms of the perpendicular heat conductivity is also discussed.
Thomson Parabola Ion Analyzer with Quick Data Acquisition
Authors: Yamamoto Toshikazu , Ishii Katsunobu , Hirano Katsumi
Published: February 2005

A Thomson parabola ion analyzer with a newly developed ion detector system is designed for quick data acquisition and is successfully used to obtain the energy distribution of a pulsed ion beam ranging from 100 to 1000 keV. The detection system consists of an MCP (microchannel plate), a phosphor screen and an image processing system in which a CCD camera, image memory and personal computer are employed. Sensitivity calibration of the detection system is carried out. The dynamic range of the ion energy analyzer is evaluated as a function of incident ion energy.
Diagnostic Study of VHF Plasma and Deposition of Hydrogenated Amorphous Silicon Films
Authors: Oda Shunri , Noda Jun'ichirou , Matsumura Masakiyo
Published: February 2005

The role of the excitation frequency in processing plasma is investigated through comparative experiments of VHF and RF plasma by means of plasma diagnostics and deposition charaterisitcs of a-Si:H films. Electron temperature, electron density and the shape of the tail of the electron energy distribution function (EEDF) are evaluated from the Langmuir probe measurement. EEDF is also discussed based on optical emission spectra measured by He, H2SiH4plasma. The frequency effect is explained in terms of the effect of ω/ν on EEDF. Structural and electrical properties of a-Si:H films deposited both by VHF and RF plasma are also investigated. The favorable condition for obtaining device-quality a-Si:H films is discussed in connection with the plasma structure.
High-Quality n-GaInAs Grown by OMVPE Using Si2H6 by High-Velocity Flow
Authors: Miyamoto Yasuyuki , Kohtoku Masaki , Yamaura Shinji , Furuya Kazuhito
Published: February 2005

High-quality n-GaInAs grown by OMVPE using Si2H6 is reported. The crystal quality was improved by high-velocity flow and was evaluated based on the sharp peak in X-ray diffraction measurement and large small-signal current gain of the hot electron transistor.
Microstructure and Superconductivity in Bi–Sr–Ca–Cu–O System Doped with Pb and Sb
Authors: Xu Qinlun , Chen Zhaojia , Meng Guangyao , Peng Dingkun
Published: February 2005

A series of samples Bi
x
Pb
y
Sb0.1Sr2Ca2Cu
z
O
w
has been produced by two methods. X-ray diffraction patterns revealed that there was a nearly single 2223 phase with a small amount of monoclinic phase in both two kinds of samples. The samples made by the oxalate coprecipitation technique had T
CO=102 K. The A.C. magnetic susceptibility showed only one sharp transition at 110 K. For samples prepared by a mixture of powders, the electrical resistance began to drop at 140 K, reaching zero at 92 K. Their A.C. magnetic susceptibility showed sharp transition at 135 K, and no transition at 110 K. The monoclinic particles were segregated on the surface of the samples. The intergrowth of 2223 and monoclinic phases at their boundaries caused the partial distortion of the 2223 phase. The distorted 2223 phase might be responsible for the 130 K superconductivity.