bluuebunny/crossref_metadata_2025 huggingface dataset:
CoCr-Polyethylene Co-Evaporated Films
Authors: Maro Tsuyoshi , Kitakami Osamu , Fujiwara Hideo
Published: February 2005

This is a report on CoCr-polythylene films synthesized by co-evaporation of CoCr and polyethylene. Through structural and magnetic analyses of CoCr-polyethylene co-evaporated films, it is found that by including amounts of polyethylene, CoCr films become amorphous and their magnetic properties change from hard to soft to superparamagnetic as the amount of polyethylene in the films increases. The results indicate that amorphous metallic alloys can be produced from combinations of metals and polymers as well as by the conventional methods.
Effect of Annealing on Photoluminescence Properties in Ar+-Ion Irradiated MOCVD-Grown ZnSe Films
Authors: Sekoguchi Maki , Taguchi Tsunemasa , Hiraki Akio
Published: February 2005

Ion irradiation and subsequent thermal annealing effects have, for the first time, been investigated on photoluminescence properties at 4.2 K of ZnSe films grown on (100) GaAs and Ge substrates by metalorganic chemical-vapour deposition (MOCVD). After irradiation of Ar+-ion beams with a total dose of about 1015 cm-2 at 50 KeV, the deep-level emission bands newly appear in the vicinity of about 570 nm, while the excitonic emission lines become extremely weak in intensity or vanish completely. It is found that the photoluminescence spectra in ZnSe/Ge are almost completely recovered by annealing at 350°C. On the contrary, in the case of ZnSe/GaAs, the deep-level emission bands around 570 nm become much greater in intensity after the anneal. It is therefore suggested that the 550, 570 and 600 nm bands which occur in the irradiated ZnSe/GaAs, are derived from complex defects associated with radiation-induced Zn vacancies and/or donor impurities out-diffused from the substrate.
Modification of Surface Layers by Irradiation with a Long-Pulse Intense Ion Beam
Authors: Nakagawa Yoshiro , Ariyoshi Takeshi , Itami Masao , Fujii Yasuo
Published: February 2005

The effects of irradiation produced by long-pulse, intense ion beams on metal surfaces (Al, stainless steel and Ti) and silicon surfaces were investigated. These beams were comprised of proton or carbon ions with pulse widths of ∼300 ns, current densities of \lesssim1 kA/cm2 and energies of ∼80 keV. The observed molten surface structures and recrystallized layers (20 µm depth) indicated that the surfaces reached high temperatures as a result of the irradiation. Changes in the X-ray diffraction patterns also indicated recrystallization by a rapid heating of the surfaces. Titanium carbide was produced by carbon-ion irradiation on a titanium surface; this process was verified by ESCA measurements.
Tristable Switching in Surface Stabilized Ferroelectric Liquid Crystals with a Large Spontaneous Polarization
Authors: Chandani A. D. L. , Hagiwara Takashi , Suzuki Yoshi-ichi , Ouchi Yukio , Takezoe Hideo , Fukuda Atsuo
Published: February 2005

A new switching process was observed in surface stabilized ferroelectric liquid crystals. The switching is associated with a third stable state in addition to the well-known bistable states. The appearance of the third state is characteristic of materials with a large spontaneous polarization and is caused by minimizing induced polarization charges. The switching between each bistable state and the third state exhibits a sharp dc-threshold and hysteresis, suggesting a possible application for a switching device.
Preparation of YBa2Cu3O7-y Thin Films by Heat-Oxidation of Vacuum-Deposited Multilayer Metallic Films
Authors: Futamoto Masaaki , Honda Yukio
Published: February 2005

YBa2Cu3O7-y
polycrystalline films have been prepared by heating the multilayer metallic films at 910°C in an oxygen atmosphere. The zero resistance temperature of 0.5 µm-thick YBa2Cu3O7-y
film is 88 K on SrTiO3(100) and 78 K on MgO(100) substrates. The electrical resistance of the film formed on an Al2O3(11̄02) substrate does not disappear at the solidification temperature of nitrogen (63 K). Impurity elements which diffused from the substrates into the superconductive thin films lower the critical temperatures. The crystallization mechanism is discussed based on the microstructural analysis.
New Electrooptic Switching in Ferroelectric Liquid Crystal Cells
Authors: Ouchi Yukio , Takezoe Hideo , Fukuda Atsuo , Kondo Katsumi , Kitamura Teruo , Yokokura Hisao , Mukoh Akio
Published: February 2005

A new type of the director orientation structure was proposed and the associated new switching process was discussed in a homogeneously aligned ferroelectric liquid crystal cell. The cell had a helicoidal structure and the director on each surface aligned in the same direction. An apparent uniform state was obtained except around the disclination lines. The disclination behavior plays an important role in the switching process and provides several advantages such as a memory effect and nucleation control for a display application.
Solid Composition of In1-xGaxAs Grown by the Halogen Transport Atomic Layer Epitaxy
Authors: Koukitu Akinori , Nakai Hideo , Saegusa Akihiko , Suzuki Takeyuki , Nomura Okio , Seki Hisashi
Published: February 2005

The growth of In1-x
Ga
x
As by halogen transport atomic layer epitaxy (ALE) is described. The vapor-solid distribution relation for the group III elements is experimentally obtained. A model which assumes the Langmuir-type adsorption for the group III monochlorides is developed. It is shown that the solid composition grown by halogen transport ALE is determined by the competitive adsorption of GaCl and InCl on the substrate.
Epitaxy of Au and Ag on Cleaved (10, 0) Surface of MoS2
Authors: Ikarashi Nobuyuki , Kobayashi Kunio , Hasegawa Tsuyoshi , Yagi Katsumichi
Published: February 2005

It is well known that Ag and Au grow on cleaved (00, 1) surfaces of MoS2 with the (111) orientation. However, particles of Au and Ag grown along <10, 0 > crystal edges of cleaved MoS2 thin films show the (110) and (100) orientations. These orientations are found through high resolution TEM images of individual fine particles. A small misfit at the interface of the (10, 0) plane of MoS2 and (100) or (110) plane of metals is found to be the reason for these anomalous epitaxial orientations. These particles are good samples for studies of surfaces by the plan-view imaging method.
High Critical Current Density of Y-Ba-Cu Oxide Wire without a Metal Sheath
Authors: Kohno Osamu , Ikeno Yoshimitsu , Sadakata Nobuyuki , Goto Kenji
Published: February 2005

A critical current density of around 1000 A ·cm-2 in Y-Ba-Cu oxide wire sheathed with silver has previously been reported. In order to obtain a higher critical current density, it has been found that the metal sheath of a wire must be dissolved and thereafter the core heat-treated in ambient flowing oxygen. The maximum critical current density of a 0.72 mm diameter wire was found to be 3900 A ·cm-2 at the nitrogen temperature.
A Simple Way to Reduce Hysteresis and Creep When Using Piezoelectric Actuators
Authors: Kaizuka Hiroshi , Siu Byron
Published: February 2005

We present a simple way to compensate for hysteresis and creep in piezoelectric actuators. By inserting a capacitor in series with the piezoelectric actuator, we find a reduction in the size of the hysteresis loop. For a suitable small capacity in series, creep is eliminated.
Superconducting Properties of Tetragonal Nd1.5Ba1.5Cu3Oy: The Effects of Annealing under High Oxygen Pressure
Authors: Tsurumi Shigeyuki , Iwata Tsunekazu , Tajima Yukimichi , Hikita Makoto
Published: February 2005

Superconductivity in tetragonal Nd1.5Ba1.5Cu3O
y
was observed by annealing at 450°C under high oxygen pressure. Slight changes in the crystal structure parameters were observed by Rietveld refinements of the X-ray powder diffraction data. The (Ba, Nd)-(Ba, Nd) distance became shorter, and the O(2) atom site shifted from the Cu(1)-O plane toward the Cu(2)-O plane, due to the increase of the oxygen atoms at the O(1) site. The occurrence of superconductivity is considered to be correlated with the increase in carriers which are introduced by the oxygen atoms at the O(1) site.
Preparation of High-Tc Tl-Ba-Ca-Cu-O Superconductors
Authors: Usui Toshio , Sadakata Nobuyuki , Kohno Osamu , Osanai Hiroshi
Published: February 2005

Bulk superconductors of the Tl-Ba-Ca-Cu-O system have been investigated to clarify their superconducting properties; these were found to be significantly sensitive to the sintering temperature and the composition of the oxides. Zero-resistance was achieved at 118 K for Tl2Ba2Ca2Cu3O
x
sintered at 880°C for 1 h in O2. In addition, an ac susceptibility result also supports its superconductivity with high critical temperature.
Two-Step Superconducting Transition of a Bi-Sr-Ca-Cu-O System
Authors: Mazaki Hiromasa , Ishida Takekazu , Sakuma Takashi
Published: February 2005

The ac susceptibility χ=χ'-i χ'' was used for examining the superconducting nature of a two-step transition in a Bi-Sr-Ca-Cu-O specimen. The X-ray diffraction pattern indicates that the crystalline habit of our specimen is tetragonal (a=3.81 Å, c=30.7 Å). Although both bulk and weakly coupled components appeared in the lower-T
c phase of the sintered pellet, the latter phase was fully depressed by pulverization. The pulverization remarkably altered the transition profile of the higher-T
c phase. The implications of these results are discussed.
Critical Behavior of Electrical Resistivity of Y1Ba2Cu3O6+x in the Vicinity of Structural Phase Transition Temperature
Authors: Sugawara Kazushi , Okibayashi Katsushi , Kataoka Shoei
Published: February 2005

The electrical resistivity, R, and its temperature derivative, dR/dT, have been measured for Y1Ba2Cu3O6+x
as a function of temperature from 400°C up to 750°C. Both R and dR/dT reveal anomalous increments between about 450°C and 580°C. The increments in resistivity (excess resistivity), Δ
R, and dR/dT have peaks at around 550±20°C. From the thermogravimetric measurements for the Y1Ba2Cu3O6+x
samples, an anomaly was found to occur near the structural phase transition temperature. A possible origin of the anomaly is also discussed.
Anomalous Magnetic Properties of Y2Cu2O5 Compound in a Weak Magnetic Field
Authors: Moshchalkov V. V. , Snigirev O. V. , Avdeev L. Z. , Brandt N. B. , Volkozub A. A. , Gippius A. A. , Muttik I. G. , Tretiakov Yu. D. , Graboy I. E. , Kaul A. R. , Khanin V. V. , Shpanchenko R. V. , Hyan Ho Hyu
Published: February 2005

Measurements of magnetic susceptibility χ(T, H
0) of the single phase Y2Cu2O5 compound in weak H
0=(0.05∼2 Oe) and moderate (H
0≤500 Oe) magnetic fields are reported. Quite surprisingly, in weak magnetic field H
0=0.05 Oe, a diamagnetic χ(T) response of about 2% of χideal(-1/4π) is observed below T≈150 K. At temperatures T∼13 K the Y2Cu2O5 diamagnetism is strongly enhanced up to χ(T=10 K, H
0=0.05 K)=26%·χideal. The sharp diamagnetic χ(T) minimum at T=5∼13 K is suppressed by the external magnetic field, and for H≥0.4 Oe this minimum is transformed into a paramagnetic χ(T) maximum. In moderate magnetic field H
0=500 Oe, a cusp on the χ(T, H
0) curve is observed. This peak corresponds to the transition from the paramagnetic Curie-Weiss χ(T)∼1/(T+θ) to a simple paramagnetic Curie χ(T, H
0)∼1/T behavior.
Fluorescence EXAFS Study of Zn-Doped LEC InP Crystal
Authors: Kitano Tomohisa , Watanabe Hisao , Matsui Junji
Published: February 2005

Interatomic distance between Zn impurity atom and P host atom in LEC InP:Zn was determined by extended X-ray absorption fine structure by monitoring the Zn Kα fluorescence yield. The measured Zn-P interatomic distance remained the value of 2.42 Å, which was in excellent agreement with the distance 2.41 Å calculated from Pauling's tetrahedral radii for zincblende structure. From XANES spectra, strong lattice distortion was observed around the Zn atom.
The VPE Growth of GaAs by the Pulsed Introduction of H2
Authors: Koukitu Akinori , Ihana Tsuneaki , Hashimoto Sakae , Suzuki Takeyuki , Seki Hisashi
Published: February 2005

The epitaxial growth of GaAs is reported using pulsed VPE. In this method, epitaxial layers are grown intermittently by the pulsed introduction of H2 and the thickness of epitaxial layers is controlled by the number of pulse cycles. It is shown that the epitaxial growth of an angstrom order is possible by the pulsed VPE.
Characterization of Te Precipitates in CdTe Crystals
Authors: Wada Morio , Suzuki Junichi
Published: February 2005

Te precipitates in CdTe crystals grown by the Bridgman method have been investigated using Auger electron spectroscopy, transmission infrared microscopy and etching techniques. The transmission infrared microscopy shows that Te precipitates with dimensions of several micrometers have well-defined crystallographic facets and are found to decorate dislocations; the density of the precipitates (<1 µm in diameter) is of the same order of the etch pit density, which suggests there exists a strong correlation between the presence of the precipitates and the dislocations.
Chemical Kinetic Analysis on the Growth Mechanism of Diamondlike Films from a CH3OH–H2Mixture
Authors: Matsui Yasuji , Sahara Mieko
Published: February 2005

The reaction kinetics describing the CH3OH decomposition in CVD conditions are studied by the comparison between the measured and the simulated time-varying gas concentrations. The chemical kinetic calculation for the deposition of the diamondlike film by the conventional tungsten filament method is carried out by making use of a simplified one-dimensional model, and it is shown that CH3is the mainC-containing radical. The overall sticking probability of CH3is roughly estimated as β(CH3)=10-2for the silicon substrate heated to 1000 K.
Improvement of SiO2/Si Interface Properties Utilising Fluorine Ion Implantation and Drive-in Diffusion
Authors: Ohyu Kiyonori , Itoga Toshihiko , Nishioka Yasushiro , Natsuaki Nobuyoshi
Published: February 2005

Thermal drive-in diffusion of ion-implanted F atoms has been employed to fluorinate SiO2/Si interfaces and thereby improve their electrical properties. The interface state density can be lowered with little fixed charge generation. Correspondingly, pn-junction surface leakage current decreases. Furthermore, the interfaces can be hardened against hot-electrons due to Fowler-Nordheim current injection and avalanche current at the junction surface. As a result, a fluorinated MOSFET shows higher hot-carrier immunity. It is pointed out that there is an optimal F dose for these improvements to be achieved.
Scanning Tunneling Microscopy of Ga0.47In0.53As/InP Multiquantum Well Structures in Air
Authors: Kato Takashi , Osaka Fukunobu , Tanaka Ichiro
Published: February 2005

Scanning tunneling microscope (STM) images of Ga0.47In0.53As/InP multiquantum well (MQW) structures in air showed a corrugated pattern. This corrugation turned out to be not geometrical but rather to arise from a difference in tunneling conductance between the GaInAs and the InP layers. The amplitude of the corrugations was affected by various factors such as contamination and atmospheric humidity.
Field Desorption Processes of Pd Adlayer and Adatom on W(011), (112) and (111)
Authors: Okuno Kimio , Kim Hyunwoo
Published: February 2005

Field desorption of Pd on W(011),(112) and (111) has been studied to determine the characteristic behavior of adsorbed Pd by field emission and field ion microscopies. The results indicate that the field emission current variations at room temperature in the field desorption process can be classified into three regions: (1) the field desorption of the Pd overlayer atFdes=10–28 V/nm, (2) a region where further field desorption does not occur atFdes=30–37 V/nm and finally, (3) a region where the monolayer of Pd suddenly startes to be desorbed in the critical fieldFdes>∼38 V/nm. Binding energies for the overlayer and the monolayer of Pd were found to be 2.9–4.8 eV and 5.72 eV, respectively. Adsorbed Pd at various stages of the field desorption processes was also observed with a field ion microscopy.
Te–K EXAFS Study on the Local Structure of Amorphous TexC1-x Alloys
Authors: Tsunetomo Keiji , Sugishima Tatsumi , Imura Takeshi , Osaka Yukio
Published: February 2005

Te K-edge EXAFS (extended X-ray absorption fine structure) of trigonal Te and amorphous Te
x
C1-x
alloy films prepared by the rf sputtering technique have been measured in order to determine the local structure around Te atoms. EXAFS parameters (backscattering amplitude and phase function) are determined for Te atoms. The Debye-Waller factors are also obtained for trigonal Te and the Te
x
C1-x
alloys. The average coordination number of a Te atom in amorphous Te
x
C1-x
is found to be smaller than in trigonal Te with the disappearance of interchain coupling in these amorphous alloys. Further, the Te–Te distance in a-Te
x
C1-x
is gradually shortened with an increase of the carbon content compared with that in trigonal Te.
Modes and Forms of Discharge in a Minute Space with the Application of a DC Magnetic Field from the Standpoint of the Optical Responses
Authors: Ueda Hiroyuki , Miyawaki Sawami , Iida Yukio , Morita Masanobu
Published: February 2005

The features of the discharge modes and the discharge forms in a minute space with the application of a D
C magnetic field are described from the standpoint of the wide-band optical and video frequency responses. The optical detections due to collision ionization caused by an electric field of optical signals become conspicuous in the longer wavelength range, while with the photoionization of excited atoms, they become conspicuous in the shorter wavelength range. The equivalent circuit of discharge is analyzed with the video frequency responses of the optical analog signals and the optical digital signals, and it is shown that the contraction of the discharge forms caused by the application of a magnetic field to the discharge plasma exerts an influence on the constants of the equivalent circuit.
Electromagnetic Picture of Inertial Forces
Authors: Agu Masahiro , Yamada Mitsuru
Published: February 2005

It is found from the equation of motion of a massive particle in a general noninertial frame that inertial forces on the particle can be regarded equivalently as the electromagnetic Lorentz force. Here the vector potential corresponds to the local velocity of the noninertially moving frame and the scalar potential to the local kinetic energy of the frame. The above consideration is applied to a rotating system with time-dependent angular velocity. As another application, on regarding a locally disturbed medium which carries an elastic wave as a noninertial frame, we derive Maxwell-like equations for the fields.
On the Electron Photoionization Cross-Section of EL2 in GaAs
Authors: Winnacker A. , Zach F. X.
Published: February 2005

From an analysis of literature data as well as our own measurements it is shown that the recently published electron photoionization cross-section σ
n

0(λ, T) of the EL2-as determined by photocapacitance techniques-includes major contributions of the intracentre transition cross-section σ
n

*(λ, T). So the σ
n

0(λ, T) as determined by photocapacitance measurements is essentially identical to the σ
n
(λ, T) observed in optical absorption experiments and can be used in the analysis of the latter.
Effect of Double-Layered SiO2–Si3N4 Films on Formation of Stacking Fault-Free Region in Silicon
Authors: Kakishita Kazuhiko , Otani Akihiko , Ohta Eiji , Sakata Makoto
Published: February 2005

We have studied the effect of surface conditions on the formation of a stacking fault-free region. The specimens with and without double-layered SiO2–Si3N4 films were heat-treated at 750°C for 64 h and then annealed in vacuum at 1050–1150°C for 0.5–128 h. In the specimens with double-layered films, a stacking fault-free region was formed beneath the Si–SiO2 interface, while it was formed beneath the surface in the bare specimens. Its thickness increased depending on the annealing time, t
0.6±0.1. The thickness of the stacking fault-free region in the bare specimens was two to three times wider than that in the specimens with double-layered films. This difference can be explained using a model in which the Si–SiO2 interface acts as a sink of self-interstitials and the bare surface acts as not only a sink of self-interstitials, but also as a source of vacancies.
Metallurgical Studies and Optimization of Critical Crrent Density in Bi–(Pb)–Sr–Ca–Cu–O Superconductors
Authors: Sekine Hisashi , Ogawa Keiichi , Inoue Kiyoshi , Maeda Hiroshi , Numata Koichi
Published: February 2005

The Bi–(Pb)–Sr–Ca–Cu–O superconductor has been fabricated into tapes without a sheath and into multifilamentary wires and tapes with a Ag sheath. Superconducting properties, workability, the possibility of forming the superconducting phase in a long wire, morphology, effects of compacting and effects of c-axis alignment, to name a few, have been studied. Tape specimens prepared by combination and repetition of cold work (or cold press) and sintering showed a critical current density, J
c, as high as 5×103 A/cm2 at 77 K with good reproducibility and reliability, although these specimens are sufficiently thick (0.5–1.0 mm). (Generally, J
c, at the zero field is inversely proportional to thickness.) For these tape specimens (with Cu sheath), sintering and J
c measurement were performed after the Cu sheath was removed. X-ray analysis showed that most of these tape specimens consisted purely of the high-T
c phase (∼107 K). In these specimens, the c axis tended to align well. This c axis alignment may be a reason for the enhancement in J
c. On the other hand, the tape specimens cold-worked and sintered only once showed J
c as small as 102 A/cm2 the c axis showing no sign of the c axis alignment. A 1330-filament Bi–Pb–Sr–Ca–Cu–O wire with a Ag sheath has been successfully fabricated. This multifilamentary wire shows a critical temperature, T
c of ∼105 K. A multifilamentary tape specimen fabricated by a combination of cold working and sintering showed a J
c of 1.05×103 A/cm2 at 77 K.
Formation of Cubic SiC Crystals by Gas-Phase Reaction
Authors: Omori Mamoru , Takei Humihiko , Fukuda Tsuguo
Published: February 2005

Cubic SiC crystals of 4 mm in maximum edge length were produced by heating a mixed powder hexagonal SiC and SiO2 around 2350°C. In this condition, a Si element produced by the reduction of SiO2 played an important role in the growth of the cubic type crystal.
Microscope observation of the as-grown surface of crystals revealed that the recrystallization from the hexagonal-to-cubic types occurred through a gas phase, i.e. a vaporization-deposition process.
Molecular Beam Epitaxial Growth of InxGa1-xAs and InxAl1-xAs on Si Substrates
Authors: Fukunaga Toshiaki , Hashimoto Akihiro , Watanabe Nozomu
Published: February 2005

Surface morphologies of In
x
Ga1-x
As and In
x
Al1-x
As (X∼0.53) layers grown on Si (100) substrates by molecular beam epitaxy are investigated. It is found that the In
x
Al1-x
As/In
x
Ga1-x
As multiquantum wells buffer layer and the substrate misorientation play an important role in the reduction of the surface roughness. The surface morphologies of In
x
Ga1-x
As and In
x
Al1-x
As on Si compare well with that of GaAs on Si.
High-Temperature Magnetic Susceptibility of YBa2Cu3Oy
Authors: Kimishima Yoshihide , Akutsu Kenji , Kittaka Hideyoshi
Published: February 2005

The DC magnetic susceptibility χ was measured for sintered YBa2Cu3O
y
from 77 K to 800∼900 K in heating “up” and cooling “down” processes. After subtracting the contribution of isolated Cu spins, the χ of the “down” process, in which y∼6, showed a rapid decrease as temperature decreased at about 300 K (T
0), and this χ behavior proved the existence of long-range antiferromagnetic ordering below T
0 in y∼6 system.
Semi-Insulating P0-Region in Si-Doped GaAs Diodes
Authors: Park Seounghwan , Choe Byungdoo
Published: February 2005

Variations of the thickness of the P0-region as a function of Si doping levels in Si-doped GaAs diodes are studied. The thickness gradually decreases as the Si concentration increases. The results are well explained in terms of the variation of the Si concentration gradient near the p-n junction.
Improved Magnetron Sputtering Systems Using Ring-Type Permanent Magnets
Authors: Ohnuma Toshiro , Ishii Motohiko , Kuroko Takashi
Published: February 2005

With the use of a ring-type permanent magnet, spatial profiles of the density profile etc. in the target area are investigated in RF-magnetron plasmas for thin films. As a result, “improved” magnetron-type sputtering systems are realized which can be used in larger areas. In particular, improvements in the density profiles in the target area are described in such improved magnet systems.
Electrochromis in Thermally Oxidized Iridium Oxide Films in LiClO4/Propylene Carbonate
Authors: Sato Yoshiyuki
Published: February 2005

Iridium oxide films prepared by thermal oxidation of iridium carbon composite films show persistent electrochromic (EC) behavior in a propylene carbonate solution containing 1 M LiClO4 and 0.8–1.0 wt% water. By treatment in aqueous 0.5 M H2SO4 before hand, the EC behavior of the film has been improved. The charge capacity and corre-sponding transmission variation of the film were 9.5 mC/cm2 and in the range from 0.69 to 0.50, respectively.
A Study of Vacancy-Type Defects in B+-Implanted SiO2/Si by a Slow Positron Beam
Authors: Uedono Akira , Tanigawa Shoichiro , Sugiura Jun , Ogasawara Makoto
Published: February 2005

Variable-energy (0∼30 keV) positron beam studies have been carried out on 80 keV B+-implanted SiO2(43 nm)/Si specimens. Doppler broadening profiles of the positron annihilation as a function of the incident positron energy were shown to be quite sensitive for the detection of vacancy-type defects introduced by B+-implantation. The average depth of the defected regions was found to shift towards the surface of the specimen with increasing the dose of B+ ions. This effect is attributed to the accumulation of vacancy-type defects at the SiO2/Si interface. Dominant defect species were identified as vacancy clusters by their annealing stage.
Mass Spectrometric Studies on Silicon Doping of OMYPE GaAs
Authors: Mashita Masao
Published: February 2005

The doping of OMVPE GaAs with silicon through use of disilane has been studied as a function of arsine concentration, alkylgalliums (trimethylgallium and triethylgallium), gas flow rate, reactor pressure, and temperature, using a low pressure reactor. Reaction products were analyzed by quadrupole mass spectroscopy (QMS). The apparent activation energy for disilane decomposition was investigated, and reactions concerning disilane were discussed. A new mechanism in which Si doping was accomplished by the SiH3AsH2 decomposition on adsorption sites was then proposed. This mechanism can qualitatively explain dependences of doping on flow speed, growth temperature, and AsH3 concentration. In addition, it also accounts for the difference in Si doping sites between OMVPE and MBE GaAs layers.
Nonempirical Calculation of Ill–V Ternary Semiconductor Phase Diagrams
Authors: Mohri Tetsuo , Koyanagi Kiyoshi , Ito Tomonori , Watanabe Katsuya
Published: February 2005

Nonempirical calculation of a phase diagram for the III-V ternary semiconductor is attempted. The atomic interaction energies are obtained based on the results of pseudopotential perturbation calculation, while the entropy term is evaluated by the tetrahedron approximation of the cluster variation method. Phase diagrams of pseudobinary GaSb–In–Sb and GaP–LnP are obtained, and both are characterized as the phase separation type. The origin of the asymmetry of the solubility line is discussed.
Effect of Deposition Temperature on the Properties of Magnetron Sputtered Hydrogenated Amorphous Silicon Films
Authors: Banerjee Ratnabali , Das Debajyoti , Batabyal A. K. , Barua A. K.
Published: February 2005

Hydrogenated amorphous silicon films have been prepared by planar rf magnetron sputtering method. The effect of deposition temperature and the hydrogen dilution on the optoelectronic as well as structural properties of the films have been investigated. Parametric variations have yielded films with a wide spectrum of optoelectronic properties. Two useful results have come out of this study. First–the attractive optoelectronic properties obtained for films deposited near room temperature. This may be important from the viewpoint of potential utilisation in photovoltaic devices, where a high deposition temperature is liable to induce diffusion between the intrinsic and doped layer. The second interesting result is the realisation of undoped a-Si:H with wide optical band gap (∼1.9–2.0 eV) showing high photoconductivity (∼10-5–10-6 Ω-1 cm-1) and large ratio of photoconductivity to dark conductivity (∼104–105). This suggests an alternative to the p-type a-SiC:H films as a window layer in a-Si solar cells, after p-type doping.
Temperature Dependence of the Center Wavelength of Narrow Band Filters Made of AgGaSe2, CuGaS2 and CuAlSe2
Authors: Horinaka Hiromichi , Okudo Takafumi , Yamamoto Nobuyuki
Published: February 2005

The temperature tuning of filters made of AgGaSe2, CuGaS2 and CuAlSe2 is investigated in the temperature range of 77 K∼520 K. The center wavelength of the CuGaS2 filter moves monotonically toward a longer wavelength with temperature from 633 nm to 661 nm, while that of the CuAlSe2 filter moves from 528 nm to 544 nm. The AgGaSe2 filter exhibits a small temperature dependence near room temperature. Its center wavelength shifts from 820 nm at 77 K to 811 nm at 350 K and from 811 nm at 400 K to 814 nm at 520 K. The dependence of the center wavelength on the lowest band gap and the anisotropy in transition strength is discussed.
InP Grown on Si Substrates with GaP Buffer Layers by Metalorganic Chemical Vapor Deposition
Authors: Kohama Yoshitaka , Kadota Yoshiaki , Ohmachi Yoshiro
Published: February 2005

InP epilayers are grown on Si substrates with buffer layers of InAs, GaAs, or GaP. The buffer layers are grown on Si below their crystallizing temperatures, and then InP epilayers are grown on top of them using a conventional two-step growth method. GaP is the best of the three buffer layer materials and the optimum thickness is about 17 nm. The InP epilayers grown on Si with GaP buffer layers have higher crystalline quality than either those grown directly on Si or those grown with GaAs intermediate layers. The full width at half maximum of the (400) reflection obtained from annealed 7.8-µm-thick InP epilayer is as small as 240 arcseconds and the etch pit density is 3.0×107 cm-2
Cascade Model for Reduction of Field-Effect Mobility of Electrons in Lightly Doped Channel of Submicron Gate Si Thin-Film Field-Effect Transistors
Authors: Hatori Fumitoshi , Asada Kunihiro , Sugano Takuo
Published: February 2005

Polycrystalline silicon accumulation-type thin-film field-effect transistors (TFTs), whose channel lengths range from 20 µm to 0.3 µm, have been fabricated, and reduction of the field-effect mobility of electrons has been observed in the lightly doped channel of submicron-gate TFTs. This phenomenon was well understood by assuming the diffusion of donor ions from the source and the drain to the channel which raised the barrier height between polycrystalline Si grains near the source and the drain. A model for device performance was built by cascading two Si TFTs with different channel doping levels. Considering that the shape of the depletion region on the surface of polycrystalline Si grains in channels is modulated by the gate voltage, the drain current-voltage characteristics were calculated, and found to be in good agreement with the experimental results.
Electrical, Magnetic and Superconducting Properties of the High-Tc Superconductor Bi2Sr2Ca1-xRExCu2O8+δ (RE=Nd and Pr)
Authors: Koyama Kuniyuki , Kanno Satoshi , Noguchi Seiichiro
Published: February 2005

Structure, resistivity and susceptibility have been studied in the Bi2Sr2Ca1-x
RE
x
Cu2O8+δ (RE=Nd and Pr) system. The samples with 0≦x≦1 have a single phase of the Bi2Sr2CaCu2O8+δ structure. The oxygen concentration, 8+δ, is estimated as about 8.3 which is independent of the RE composition x. The T
c increases slightly with x in the range of x≦0.10 and remains constant (∼85 K) for 0.10≦x≦0.25, then decreases linearly with x for 0.25≦x≦0.55. Superconductivity disappears for the samples with x≧0.55 in both cases. The Nd and Pr ions in the samples were both determined to be trivalent from the susceptibility data. The results show that the hole concentration in [Cu–O] plays a most significant role in the occurrence of superconductivity in the Bi–Sr–Ca–Cu–O system.
Microstructure and Superconductivity in Epitaxial MgO/NbN Multilayers
Authors: Nagaoka Shiro , Hamasaki Katsuyoshi , Yamashita Tsutomu , Komata Toranosuke
Published: February 2005

The aim of this investigation is to achieve high transition temperature, low resistivity films under conditions suitable for use in all-NbN Josephson junction fabrication. For this purpose, the heteroepitaxy of NbN on MgO films is investigated. For substrate temperature of 200°C or thereabouts, polycrystalline MgO films of (200) orientation were formed on (100) silicon, (11̄02) α-Al2O3, and fused silica. Based on XTEM, HEED and X-ray data, heteroepitaxial growth ((100)NbN//(100)MgO) was obtained in NbN films and NbN/MgO/NbN trilayers deposited on (200) oriented MgO films. The epitaxial NbN films of 10 nm thickness had high transition temperatures of about 14 K, and relatively low residual resistivities of less than 200 µΩ·cm. Using the GL relationships, we calculated the Ginzburg-Landau parameters, λ(0) and ξ, of our NbN films in the dirty limit. The calculated ξ(4.2 K) and λ(0) are ∼4.5 nm and ∼300 nm, respectively.
Method for Estimating Accurate Deep-Trap Densities from DLTS of Junctions Containing Several Kinds of Deep-Traps
Authors: Nakashima Hiroshi , Hashimoto Kimio
Published: February 2005

The density of a deep trap is estimated from the peak height of the DLTS signal and the steady-state capacitance on a reverse-biased semiconductor junction. When several kinds of traps exist in the depletion region and the trap densities are not much smaller than the net shallow-level density, a considerable error appears in the trap-density estimations. For such a case, it is necessary to solve exactly Poisson's equation for the depletion region in transient sequence to deduce the trap densities. A method for accurate trap-density evaluation is introduced, and the results of the analysis for the DLTS spectrum of a gold-doped n-type silicon Schottky diode are discussed.
Electronic Dielectric Constants of Crystalline and Amorphous GeSb2Te4 and Ge2Sb2Te5 Semiconductors
Authors: Yokota Ryosuke
Published: February 2005

It is found that Phillips' spectroscopic theory of bonding for determining the zero-frequency electronic dielectric constant ε
0 can apply to crystalline and amorphous GeSb2Te4 and Ge2Sb2Te5 semiconductors. These compounds are assumed to be composed of GeTe and Sb2Te3 and have the remarkable characteristic that n
2 measured at 0.83 µm (n: refractive index) in the crystalline state is 2.2times larger than that of the amorphous state. The ε
0 values of these semiconductors in crystalline and amorphous state have been calculated from their short-range structural data. In all compounds, a good agreement with ε
0 values which correspond to n
2 at 0.83 µm has been obtained.
A Method for Determination of Elastic Constants K1, K2, K3 of a Nematic Liquid Crystal Only Using a Homogeneously Aligned Cell
Authors: Koyama Kazuo , Kawaida Masahiro , Akahane Tadashi
Published: February 2005

It is shown that three Frank elastic constants K
1, K
2 and K
3 of a nematic liquid crystal can be determined by measuring the capacitance change with a magnetic field of a homogeneously aligned cell. The splay elastic constant K
1 is determined from the threshold magnetic field strength H
c1 when the magnetic field is applied normal to the cell. The bend elastic constant K
3 is determined from the slope of the linear dependence between the inverse of the capacitance 1/C and the inverse of the magnetic field strength 1/H in the high field region H/H
c1> 3. The twist elastic constant K
2 is determined from the threshold field strength when the magnetic field is applied oblique to the cell normal but perpendicular to the initial director. In these procedures, principal dielectric constants ε
//, ε
⊥, dielectric anisotropy Δ
ε, anisotropy of the magnetic susceptibility Δχ can be determined simultaneously.
Structural and Mechanical Properties of Cr2CO Films
Authors: Kado Tetsuo , Noda Yukio
Published: February 2005

Thin films of chromium oxycarbide(Cr2CO) were prepared on SUS 304 stainless steel and slide glass by plasma decomposition of hexacarbonylchromium with hydrogen carrier gas. The structure of the film was investigated in detail by X-ray diffraction. It was found that the structure of Cr2CO was fcc and that the (111) plane was highly oriented on the substrate surface. The characteristics of Vickers hardness, electric conductivity and deposition rate strongly correlated to the X-ray intensity of the particular Bragg scattering.
Measurements of Backscattered Electron Energy from CRT Shadow Mask Coatings by Calorimetric Method
Authors: Koitabashi Masayasu , Yamamoto Morio , Kimura Hiroshi , Shimoji Sadao , Watanabe Tetsuya
Published: February 2005

A calorimetric method is developed for measuring the total energy of the backscattered electrons from the coatings of a CRT shadow mask. We measured the energy from the heater input power in order to maintain thermal equilibrium between the sample under the electron bombardment and the cooled black wall. Measurements were carried out on the coatings of Bi2O3 and Fe3O4. About 21% of the incident primary energy was carried away by the backscattered electrons for Bi2O3 and 11 % for Fe3O4. These values agree with the previously reported values obtained by the retarding potential method.
Experimental Study on the Deposition Profile of the ICRF Power and Electron Thermal Diffusivity
Authors: Ogawa Yuichi , Ando Ritoku , Kako Eiji , Kawahata Kazuo , Kawasumi Yoshiaki , Morita Shigeru , Watari Tetsuo , Akiyama Ryuichi , Hamada Yasuji , Hirokura Satoru , Masai Kuniaki , Matsuoka Keisuke , Mohri Akihiro , Noda Nobuaki , Ogawa Isamu , Ohkubo Kunizo , Sato Kuninori , Tanahashi Shugo , Taniguchi Yoshiyuki , Toi Kazuo
Published: February 2005

In ICRF heating experiments the deposition profile of the rf power directly coupled with electrons has been derived experimentally, and the electron thermal diffusivity has been evaluated. The rf power delivered to electrons is estimated to be \hatPe∼60% of the radiated power from antennas. It is found that the deposition profile is relatively broad (Prf,e(r)=Prf,e(0)(1-(r/a)2)kwithk=1.8), and this is interpreted in terms of characteristics of the mode-converted ion Bernstein wave. With the deposition profile experimentally obtained, the electron thermal diffusivity χehas been calculated, resulting in χe∼0.65 m2/s at n̄e=9×1019m-3.
Electron Orbit Analysis in a Localized Plasma-Beat Wave and a Plasma Fiber Accelerator
Authors: Osuga Toshiaki , Mima Kunioki , Takabe Hideaki
Published: February 2005

The particle orbit in a plasma fiber accelerator and/or a localized plasma-beat wave is numerically investigated to evaluate trapping efficiency. In the present plasma fiber accelerator, the phase velocity of the acceleration field is assumed to be constant and the field profile is very different from the plane geometry because of a small focal spot. Therefore, most of the injected electron orbits are bent by the transverse acceleration field. As the result of the orbit analysis, it is found that only a few percent of 0.5 MeV injected electrons can be trapped in the acceleration field and become more than 10 MeV.
Estimation of Plasma Elongation and Position on Noncircular Tokamak TRIAM-1M
Authors: Moriyama Shin-ichi , Nakamura Kazuo , Kawasaki Shoji , Jotaki Eriko , Nagao Akihiro , Nakamura Yukio , Hiraki Naoji , Itoh Satoshi
Published: February 2005

A method of estimating the plasma elongation and position using the magnetic field picked up by magnetic coils is described. The method is based on the approximate solution for the Grad-Shafranov equation including the effect of the eddy current on the resistive shell. When this method was applied to noncircular plasmas on TRIAM-1M, the analytical results were found to be in good agreement with the plasma shape observed by a TV camera and with the outermost magnetic surface obtained through the calculation of an MHD equilibrium code. This approach is suitable for the real-time analysis and feedback control of plasma shape in a noncircular tokamak.
Soft X-Ray Spectrum Measurement of the Ultralong Discharge in the TRIAM-1M Tokamak
Authors: Nagao Akihiro , Jotaki Eriko , Moriyama Shin-ichi , Nakamura Kazuo , Nakamura Yukio , Hiraki Naoji , Itoh Satoshi
Published: February 2005

In order to evaluate the electron temperature and the effective charge number (Zeff) of the ultralong discharge by a lower hybrid current drive in the TRIAM-1M tokamak, the soft X-ray energy spectrum is measured by the pulse height analysis system. The accuracy of the electron temperatures determined by the soft X-ray spectrum measurements is confirmed by comparing with the temperature obtained by the Thomson scattering system for OH plasmas. We obtained a bulk electron temperature of about 1.5 keV and aZeffvalue of about 2 during the long-term discharge. It was found that the impurities observed in the spectrum wereKα-lines of Fe, Cr and Ni originating from the stainless-steel limiter and they did not increase during the long-term discharge. Thus we obtained clean plasmas with relatively high temperature by a lower hybrid current drive.
Emission Cross Sections of the Fragments in Dissociative Excitation of Germane by Electron Impact
Authors: Kono Kyaw , Goto Toshio
Published: February 2005

A study of photon emission induced by electron impact on the GeH4 molecule was conducted using an electron beam collision apparatus. The optical excitation functions of Ge I, Ge II, GeH, and H excited fragments were measured in the 0–100 eV electron energy range. The appearance potentials of the fragment emissions were determined and these values were compared with the dissociation limits of the possible processes. The absolute emission cross sections of excited fragments were measured by means of the helium bench-mark cross sections.
Development of a Non Contact Temperature-Monitoring System for TEM Specimen
Authors: Shigenaka Naoto , Hashimoto Tuneyuki , Fuse Motomasa
Published: February 2005

A non contact temperature-monitoring system was developed to measure the specimen temperature inside a TEM connected to an ion accelerator. An optical fiber was inserted through the TEM column, and an infrared pyrometer was used to measure the specimen temperature. Performance tests confirmed that the system could monitor the temperature range between 150 and 800°C.
Effect of Taste Substances on Aperiodic Oscillation of an Electric Potential in a Synthetic Lipid Membrane
Authors: Hayashi Kenshi , Toko Kiyoshi , Yamafuji Kaoru
Published: February 2005

A correlation dimension and a distribution pattern of spectrum intensities of a self-sustained electric oscillation were studied for an aperiodic oscillation induced by an application of electric current on a membrane of a synthetic lipid, dioleyl phosphate. The estimated dimension showed a remarkable deviation in the presence of taste substances such as quinine (above a certain threshold value) from that in the absence of these taste substances; this deviation was accompanied by a change in spectrum pattern. The present result indicates that the two variables extracted from the aperiodic oscillations will be useful as sensing information in a chemical taste sensor using lipid membranes.
Capacitance-Voltage Characteristics of ZnO MIS Diodes
Authors: Kanai Yasuo
Published: February 2005

The experimental results for the measurements of the capacitance-voltage characteristics of ZnO MIS diodes are reported. A distinct difference is found between the C-V characteristics for the Zn surface and O surface of ZnO crystals. A difference in the work functions of the electrode metals of the MIS diode is also found in the C-V characteristics.
Axicon-Focused Noncritically Phase-Matched Second-Harmonic Generation
Authors: Tanuma Ryohei , Kasai Takeshi
Published: February 2005

This paper describes second-harmonic generation where a conical axicon focuses a 1.06-µm YAG-laser-radiated beam into a MgO:LiNbO3 crystal, and a frequency-doubled beam is generated along the cone axis. This method can reduce a 90°-phase-matching temperature to room temperature. We obtained the matching temperatures of 35–36°C and 58–59°C by exchanging two axicons with different base angles, whereas 102°C in their absence.
Growth of Amorphous SiN Films by Chemical Vapor Deposition Using Monomethylamine
Authors: Yasui Kanji , Katoh Hirohisa , Komaki Kazuki , Kaneda Shigeo
Published: February 2005

Chemical vapor deposition of silicon nitride film has been studied by using SiH4 and NH2CH3 as source gases for the deposition temperature region of 700∼900°C. The deposition rate was somewhat larger than that of the case using SiH4 and NH3 gases. The film deposited at 900°C had a particularly smooth specular surface.
Contact Lithography Modelling Using Statistical Experimental Designs
Authors: Pommereau Frédéric , Iost Michel , Rabinzohn Patrick
Published: February 2005

A Statistical Experimental Design Methodology has been applied to contact lithography modelling for GaAs technology. The AZ 4000 resists have been used with three thicknesses 1, 2 and 3 µm. A standard process with UV4 and UV3 exposures and a post exposure bake process with UV4 exposure have been modelled. Two optimisations of the UV4 process leading to vertical profiles and an optimization of the PEB process leading to a lift-off profile are presented.
Structural and Magneto-Optical Properties of Bi-Substituted Garnet Films Prepared by Pyrolysis from Organic Solution
Authors: Cho Jaekyong , Gomi Manabu , Abe Masanori
Published: February 2005

Bi1.5Dy1.5Fe4AlO12 films were prepared by pyrolysis from acetylacetonic solution of metal nitrates. The solution was chemically stable and had good wettabiiity on glass substrates without any surface pretreatment. Film structure and the shape of the Faraday rotation hysteresis loop markedly depended on drying conditions, especially on the initial temperature T
i of the drying process. The best T
i was 130°C. The crystallized film dried at T
i=130°C had crystalline grains uniform in size (diameter ∼0.5 µm) and exhibited Faraday rotation hysteresis loops with an excellent squareness and a large coercive force (1.7 kOe).
Observation of Chaos in an Inhomogeneously Pumped Self-Pulsating Semiconductor Laser
Authors: Liu Hai-Feng , Kamiya Takeshi
Published: February 2005

Chaos was observed in an inhomogeneously excited self-pulsating semiconductor laser under periodic current modulation. By varying the dc bias, it was found that the laser changed its state from simple modulation at external frequency through quasi-periodicity to chaos. The presence of chaos and the route to chaos were simulated by a set of multimode rate equations incorporating the gain compression effect. This analysis revealed that the carrier storage associated with intracavity saturable absorber is responsible for the appearance of chaos in self-pulsating semiconductor lasers.