bluuebunny/crossref_metadata_2025 huggingface dataset:
Nuclear Magnetic Resonance Study of Molecular Motions in Poly(γ-n-alkyl L-glutamate)s
Authors: Kakizaki Maeko , Katsura Toshihiko , Hideshima Teruo
Published: November 2005

The temperature dependence of the NMR line-width and second moment of poly(γ-n-alkyl L-glutamate)s having methyl, ethyl, n-propyl, and n-butyl groups were measured at temperatures ranging from -150°C to 150°C. Three motional narrowing processes were found and are ascribed to the motions of the main chain (the α-process), the side chain as a whole (the β-process), and part of the side chain (the γ-process). The correlation spectra for the β-process in these samples were determined, and the shapes of the spectra were compared with each other, with those of the dielectric-relaxation spectra of the same samples, and with those of the dielectric-relaxation spectra of the β-process in poly(n-alkyl methacrylate)s caused by the motion of similar side chains. It is shown that the shapes of these spectra are the same irrespective of the difference in side-chain length and in main-chain conformation.
Real-Time X-Ray Topographic Observation of Crystal Growth of Gallium from Melt
Authors: Kobayashi Tatsumasa , Nishikawa Yoshitaka , Imura Toru
Published: November 2005

The growth of gallium single crystal of 99.9999% purity from the melt was observed by real-time X-ray topography. At the solid-liquid interface, (010), (011), (101) and (111) facets were observed. Dislocations, which intersected the facets and propagated into a newly grown crystal, did not influence the faceted growth. The growth mechanism of the faceted growth of gallium is deduced from continuous observation of the growth process.
Annealing Effects in Aluminum Films Vacuum-Deposited on Room-Temperature Substrate
Authors: Kawakita Kazuhiko
Published: November 2005

Aluminum films were vacuum-deposited on glass substrates at 27°C, and the annealing effects of the films were examined. The electrical resistivity decays were measured during the annealing, and the grain size of the films was also investigated by electron microscopy. The activation energy of the resistivity decay at temperatures between 27°C and 130°C was 0.9∼1.2 eV, and the resistivity decrease due to the annealing was attributed to the annihilation of the dislocations. The dislocation density in the deposited films was estimated to be 5×1011 cm-2.
Furthermore, the specific grain boundary resistivity in the deposited films was estimated to be 3×10-12 Ω·cm2.
Study of Edge Effect in Photoacoustic Microscopy
Authors: Hangyo Masanori , Nakashima Shin-ichi , Sugimoto Shigeki , Yamaguchi Tsutomu , Mitsuishi Akiyoshi
Published: November 2005

The edge effect in microphone photoacoustic microscopy has been studied experimentally. It has been observed that the amplitude of the photoacoustic signal is enhanced nearly exponentially when the exciting laser spot approaches the sample edge. The phase also shows a characteristic shift near the edge. The features of this edge effect are well explained quantitatively by the theory developed by Thomas et al. which takes account of the three-dimensional heat flow in solids. The advantage of the phase image over the amplitude image is also discussed.
Switching Process in Ferroelectric Triglycine Selenate
Authors: Sangunni K. S. , Ravi R. , Bhat H. L. , Narayanan P. S.
Published: November 2005

Triglycine selenate (TGSe) is isomorphous with Triglycine sulphate and is ferroelectric below 22°C. It is interesting to study the switching process in TGSe in the ferro-state with a view to comparing the results with TSG. The switching process was studied by applying electrical square pulses to produce fields up to 5 kV/cm on the sample, and measuring the parameters characterizing the transient current flowing in the sample, according to the Merz method. The temperature range in which the process was studied was 15°C to -20°C. The results were analysed by applying the Pulvari-Kuebler theory and the parameters α the activation field and µ the mobility of the domains were evaluated. It is found that µ varies with temperature in TGSe in a manner similar to TGS. µ is lesser for TGSe than for TGS for the same shift of temperature from T
c. The switching behaviour of γ-irradiated TGSe is qualitatively similar to that of unirradiated crystal eventhougth the process gets slowed down as a result of irradiation.
AC Reignition Voltage on Partially Contaminated Insulator Surfaces
Authors: Kaga Akio , Sato Masashi , Akagami Hideo
Published: November 2005

In an attempt to clarify flashover phenomena on contaminated insulator surfaces, the authors have investigated the relations between the ac reignition voltage and the arc voltage characteristics at 50 Hz power frequency. The present paper discusses some of the characteristics of partially contaminated surfaces. As reported before for contaminated surfaces, the reignition voltage in each half cycle decreases with the number of reignitions, reaches a minimum, and then increases again. This characteristic is due to the thermal ionization of Na atoms diffused and accumulated in the discharge space by alternate reignitions. A similar tendency has been observed on partially contaminated surfaces. On the partially contaminated surface, however, the value of the reignition voltage depends upon whether the gap ends are contaminated or not. As a result, the critical flashover current on a contaminated insulator surface could be estimated.
Structure and Mechanism of Formation of Drawing- or Radiation-Induced Defects in SiO2:GeO2 Optical Fiber
Authors: Watanabe Yuichi , Kawazoe Hiroshi , Shibuya Kiyoshi , Muta Ken-ichi
Published: November 2005

The structure, mechanism of formation and thermal reaction of electronic defects associated with Ge in GeO2-doped silica fiber induced by fiber-drawing or γ-irradiation were studied by detecting ESR hyperfine structures due to 73Ge. The present assignment of the drawing-induced center to the Ge-E' center was confirmed from the estimated spin density on a 4s atomic orbital of 73Ge(\cong30%). The radiation-induced center was found to have a larger spin density on a 73Ge-4s orbital(\cong35%) than the drawing-induced center, and in the structural model proposed for the center, the unpaired electron is trapped on a GeO4 group (Ge electron trapped center: GEC). Most of the GECs induced by γ-irradiation at 77 K were bleached out by annealing at RT in dry fibers, while some of the GECs changed into Ge-E' centers in irradiated GeO2-SiO2 glass containing a considerable number of OH groups.
Radiation Effects on Pure Silica Core Optical Fibers by γ-Rays: Relation between 2 eV Band and Non-Bridging Oxygen Hole Centers
Authors: Nagasawa Kaya , Hoshi Yutaka , Ohki Yoshimichi , Yahagi Kichinosuke
Published: November 2005

The defect center causing the 2 eV absorption band induced in pure silica core fibers by 60Co γ-rays is discussed. The 2 eV band and non-bridging oxygen hole center (NBOHC, SI–O·) show almost the same thermal annealing characteristics. The peak wavelength of the 2 eV band in low-OH (≦6 ppm) fibers is 630 nm, but shifts to shorter wavelengths according to the amount of OH group the sample contains, and appears at 600 nm in high-OH (≧700 ppm) fibers. The peak shape is broader in high-OH fibers than in low-OH fibers. This shift and broadening is attributable to a hydrogen bond between NBOHC and a hydrogen atom. Based on the above results, the defect center responsible for the 2 eV band is considered to be NBOHC.
Optimum Design of Exploding Pusher Target to Produce Maximum Neutrons
Authors: Kitagawa Yoneyoshi , Miyanaga Noriaki , Kato Yoshiaki , Nakatsuka Masahiro , Nishiguchi Akio , Yabe Takashi , Yamanaka Chiyoe
Published: November 2005

Exploding pusher target experiments have been conducted with the 1.052 µm GEKKO MII two beam-glass laser system to design an optimum target, which couples to the incident laser light most effectively to produce the maximum number of neutrons. Since hot electrons preheat the shell completely in spite of the strongly nonuniform irradiation, a simple model can design the optimum target, in which the shell/fuel interface is accelerated to 0.5 to 0.7 times the initial radius within a laser pulse. A 2-dimensional computer simulation supports this target design. The scaling of the neutron yield N with the laser power P is N∝P
2.4±0.4.
A Metal-Insulator-Semiconductor (MIS) Device Using a Ferroelectric Polymer Thin Film in the Gate Insulator
Authors: Yamauchi Noriyoshi
Published: November 2005

A nonvolatile MIS memory device using a ferroelectric polymer thin film in the gate insulator is proposed. In the gate electrode of the device, a ferroelectric polymer thin film is sandwiched between two insulator films to prevent carrier injection into the polymer thin film. Al-SiO2-P (VDF/TrFE)-SiO2-Si capacitors were fabricated to evaluate the basic characteristics of the device by C-V measurement, and ferroelectric polarization reversal was observed in the capacitors. Based on the C-V measurements, MIS transistors were fabricated using a process which virtually self-aligns the effective gate area to the source/drain. It was shown that the MIS transistor could be electrically programmed and erased. The on/off ratio of the transistor was greater than 106.
Effect of Higher-Order Spherical Aberration Term on Transfer Function in Electron Microscopy
Authors: Uchida Yuji , Fujimoto Fuminori
Published: November 2005

The effect of the higher-order spherical aberration coefficient on the transfer function in transmission electron microscopy was calculated. In order to simplify the system, the optical illumination system was assumed to be perfectly coherent and axially symmetric. The result shows that the effect of the fifth-order spherical aberration coefficient, C5, on the usual transfer function with the third-order spherical aberration coefficient C5≡C3=0.5 mm for 100 keV electrons cannot be neglected, if high-order Bragg reflections from net planes with smaller lattice spacings than 0.1 nm are utilized for lattice imaging. The effect of the higher-order term due to the defocussing on the transfer function is also discussed.
Superconductor-Base Hot-Electron Transistor I. Theory and Design
Authors: Tonouchi Masayoshi , Sakai Hiroyuki , Kobayashi Takeshi
Published: November 2005

This paper proposes a theoretical design for a superconductor-base hot-electron transistor (Super-HET), a new device which can be regarded as one of the ultimate hot-electron transistors. Our study reveals that a Super-HET with a GaAs/Nb-based compounds/InSb/metal structure has excellent characteristics, although it works only in a limited temperature range. The total current transmission coefficient and the maximum oscillation frequency are predicted to be more than 96% and in excess of 1000 GHz, respectively. The estimation and design are performed taking into account the quantum mechanical reflection effect, the hot-electron mean free path in superconductor and semiconductor, Monte Carlo simulation, and unilateral power gain.
Microstructures of Hydrogenated Silicon Films Prepared by Ion Plating
Authors: Shimizu Hideki , Mizuno Satoshi , Noda Mikio
Published: November 2005

Hydrogenated Si are prepared by ion plating in a pure hydrogen atmosphere and their microstructures are investigated by using a transmission electron microscope and a Fourier-transform infrared spectrometer. The structures of such films change from amorphous to microcrystalline when the RF input power is increased or when the bias voltage of substrates is increased from a negative to a positive value. The structures are also affected by the electrical conductivity of the substrates. When insulating substrates are used, the films tend to have the microcrystalline-type structures due to an accumulation of positive charge. Mass and optical emission spectroscopy suggest that such trends regarding crystallization occur due to an increase in H radicals and a decrease in ionic species impinging onto a substrate during deposition.
Energy Dependence of Angular Distributions of Sputtered Particles by Ion-Beam Bombardment at Normal Incidence
Authors: Matsuda Yoshinobu , Yamamura Yasunori , Ueda Yasutoshi , Uchino Kiichiro , Muraoka Katsunori , Maeda Mitsuo , Akazaki Masanori
Published: November 2005

The angular distributions of sputtered Fe-atoms were measured using the laser fluorescence technique during Ar-ion bombardment for energies of 0.6, 1, 2 and 3 keV at normal incidence. The measured cosine distribution at 0.6 keV progressively deviated to an over-cosine distribution at higher energies, and at 3 keV the angular distribution was an over-cosine distribution of about 20%. The experimental results agree qualitatively with calculations by a recent computer simulation code, ACAT. The results are explained by the competition between surface scattering and the effects of primary knock-on atoms, which tend to make the angular distributions over-cosine and under-cosine, respectively.
Two Step Adsorption Process of Hydrogen on Ni(111) Surface
Authors: Inoue Masahiko , Ueda Kazuyuki
Published: November 2005

The adsorption of H2 on an Ni(111) surface at room temperature has been studied by different surface analytical techniques, i.e., LEED, AES and SES for measurements of Δφ, TDS and ESD. The ESD ion intensity, as a function of H2 exposure, showed a maximum value at ∼8 L, giving evidence for a two-step adsorption process, which has not been observed on an Ni(111) surface before.
A change in the work function for H2 exposure has been found to follow that of the ESD ion intensity very well. The secondary electron yield, first, decreases up to ∼8 L, corresponding to an increase in the work function. It then increases monotonically up to ∼100 L. An Ni MVV Auger signal was found to be so sensitive to H2 adsorption that the intensity decayed monotonically by nearly 40% for a monolayer coverage of H2. These results can be consistently explained by a two-step adsorption process.
Phosphorus Acceptor Levels in ZnSe Grown by Molecular Beam Epitaxy
Authors: Yao Takafumi , Okada Yasumasa
Published: November 2005

A new doping technique for phosphorous using a Zn3P2 source has been developed. From an extensive study of the electrical properties of ZnSe doped with P, it has been found that the doped P induces point defects in excess of the doped P atoms which lowers the electron concentration and the electron mobility much more than expected. From an investigation of the low-temperature PL spectra, it was found that P forms a shallow acceptor with an activation energy of 80-92 meV in MBE-grown lightly P-doped ZnSe, and at the same time a deep acceptor with an activation energy of 0.6-0.7 eV in heavily P-doped ZnSe.
Twisted Non-Circular Coil System in a Toroidal Helical Axis Stellarator
Authors: Harafuji Kenji , Sasaki Norihiko
Published: November 2005

Design studies for vacuum magnetic field configurations were made numerically for a toroidal plasma confining system with a three-dimensional magnetic axis (the helical solenoid). The purpose of this paper is to suggest favourable configurations which possess magnetic wells (a depth greater than 1.0%), a low aspect ratio (∼ 10) equal to that of existing and proposed planar axis stellarators, and modest variations of Q=\intdl/B for reducing Pfirsh-Schlüter currents. It is shown that promising configurations satisfying the requirements described above can be created only by modular toroidal field coils with moderate non-circular deformations, slight twistings and adequate swings.
Noise Reduction in Real Time X-Ray Images
Authors: Tsuda Motohisa , Kimura Yutaro
Published: November 2005

The signal-to-noise ratio of real-time digital X-ray imaging systems consisting of an X-ray image intensifier-television chain was investigated while concentrating on the effect of the X-ray quantum nature.
Along with conventional signal accumulation, logarithmic conversion and subtraction, a new technique called the peak hold method is introduced. Theoretical and simulational studies were made with practical parameters. Theory and simulation showed good agreement.
An accumulation of signal is most effective for improving the signal-to-noise ratio; the peak-hold method comes next. The peak hold method, however, offers a new image-display mode. Moreover, this method is superior to signal accumulation for specific conditions.
A Hole Trap Center Related to the 2.361 eV Bound Exciton Emission in ZnTe Single Crystals
Authors: Takeda Fuminori , Matsuura Koichi , Kishida Satoru , Tsurumi Ichiro , Hamaguchi Chihiro
Published: November 2005

The heat-treatment effects of ZnTe single crystals which contain a low concentration of Te inclusions were investigated by photoluminescence, optical-absorption and admittance spectra measurements. A correlation between the 2.361 eV bound exciton emission and hole traps located at 0.39 eV above the valence band is reported.
Limits on the Performance of Quantum-Controlled Devices
Authors: Noguchi Shoichi , Oya Gin-ichiro
Published: November 2005

A new concept, “figure of device”, is introduced to describe the fundamental limits on the performance of fluxon and photon devices, quantum-controlled logic devices which promise to be the ultimate high-speed logic devices in computers of the future.
A Simple Method to Determine λ from Isothermal Capacitance Measurements
Authors: Tomokage Hajime , Miyamoto Tokuo , Morooka Masami , Yoshida Masayuki
Published: November 2005

A simple method is proposed to determine λ from isothermal capacitance measurements of a Schottky barrier without knowing the energy levels of the traps or the position of the Fermi level. The trap concentration is determined from only three values of the capacitance. The Au concentration in an Au-diffused Au-Si Schottky diode is measured to verify the method.
Room Temperature Pulsed Oscillation of GaAlAs/GaAs Surface Emitting Junction Laser Grown by MBE
Authors: Iga Kenichi , Nishimura Takayuki , Yagi Katsumi , Yamaguchi Takao , Niina Tatsuhiko
Published: November 2005

GaAlAs/GaAs surface emitting (SE) junction lasers have been fabricated by molecular beam epitaxy (MBE). It is easy for the MBE method to obtain a good flatness of grown surfaces to be utilized as reflective mirrors, and to control the thickness of the grown layer more precisely, compared with liquid phase epitaxy (LPE). We report on the room-temperature pulsed oscillation of a SE laser grown by MBE. The threshold current was as low as 450 mA, and single-mode operation was achieved at λ = 8735 Å.
Negative Resistance in a Planar p+-i-n+ Diode with Junction Gate
Authors: Choe Il Yong , Akiba Yukio , Kurosu Tateki , Iida Masamori
Published: November 2005

A variation of a threshold voltage regarding the location of a p+-i junction gate under an open-gate condition was experimentally studied. From a determination of the potential distribution between the anode and cathode, it was found that a virtual negative-resistance region exists in the anode-to-gate region. In addition, an improved current-voltage characteristic was observed in a planar p+-i-n+ diode with a guard ring formed around the cathode.
Recovery Characteristics of Radiation Damage in MOS Devices
Authors: Ushizaka Hironori , Shimaya Masakazu , Shiono Noboru
Published: November 2005

Experimental evidence of a larger threshold-voltage (V
T) recovery for an n-channel MOSFET than for a p-channel MOSFET, after receiving ionizing radiation, is presented. Annealing of a parasitic leakage current, generated only for n-channel MOSFETs due to a field inversion during irradiation, is shown to be the main cause for a channel-type dependence for V
T recovery.
Bias Effects on Morphology and Growth Rate of Glow Discharge a-Si:H Films in a Triode System
Authors: Pyon Ryun Gill , Aozasa Masao , Ando Keiichi
Published: November 2005

We investigated the positive and negative bias effects on the morphology and the growth rate of a glow-discharge a-Si:H film prepared using a triode system. The growth rate increased with the magenitude of the bias, irrespective of its polarity. A columnar structure is promoted if the film is prepared with, an applied positive bias. The film is favorably densified if it is prepared with an applied moderate negative bias. An extremely high negative bias, however, leads to the formation of unfavorable nodules on the film surface. The configurational change of the incorporated hydrogen by the bias is discussed in terms of an inhomogeneous structure composed of a grain-boundary like region and a grain-like region.
Reduction of a Highly-Resistive Layer at an Interrupted-Interface of GaAs Grown by MBE
Authors: Iimura Yasufumi , Takasugi Hidetoshi , Kawabe Mitsuo
Published: November 2005

The desorption of Ga atoms from GaAs films at high substrate temperatures was utilized as an etch-back method for the reduction of highly-resistive layers formed around growth-interrupted interfaces in Si-doped GaAs.
The mechanism of the reduction of the highly-resistive layer was studied by a C-V carrier profiling technique, secondary-ion mass spectroscopy and deep-level transient spectroscopy, and was clarified as being due to compensation by Si atoms accumulated on the GaAs surface during the thermal etching procedure.
Photoelectric Properties of Copper Phthalocyanine Langmuir-Blodgett Film
Authors: Yoneyama Mitsuru , Sugi Michio , Saito Mitsuyoshi , Ikegami Keiichi , Kuroda Shin-ichi , Iizima Sigeru
Published: November 2005

Photovoltaic and structural characteristics of Langmuir-Blodgett film photocells have been studied using asymmetrically substituted copper phthalocyanine (asy-CuPc). By polarized-light absorbance measurements, each phthalocyanine molecule was found to be arranged in the film with its ring facing towards the dipping direction. The polarity of photoelectric characteristics showed typical features expected for an organic p-type Schottky diode, while the dark characteristics exhibited a reversed polarity. The maximum short-circuit photocurrent was on the order of 10-8 A/cm2 for 100 µW/cm2 monochromatic light, indicating the superiority of asy-CuPc as a film-forming molecule for photovoltaic LB films.
Three Midgap Levels in LEC n-GaAs Determined by DLTS Using Au and Al Schottky Barrier Diodes
Authors: Yahata Akihiro , Kikuta Toshio , Ishida Koichi
Published: November 2005

Midgap levels in n-GaAs have been studied in detail by DLTS and capacitance transient analysis using Au and Al Schottky barrier contacts. In addition to EL2, which we call EO1 here, two other midgap levels, EO2 and EO3, were observed. The variations of EO1 and EO2 concentrations did not correlate with the distribution of the optical absorption coefficient in a wafer, while that of the EO3 concentration exhibited good correlation. This suggests that EO3 is identical or related to the optically detected midgap level.
Morphological Studies of Surface Transformations in Amorphous Silicon Induced by Picosecond Laser Pulses
Authors: Kanemitsu Yoshihiko , Nakada Ichiroh , Kuroda Hiroto
Published: November 2005

Surface morphological changes of amorphous silicon are investigated using picosecond laser pulses at intensities near the melting threshold. At the small spot size, the surface becomes undulating. Well-marked boundaries are observed at irradiation of two-pulses separated by nanosecond time delays. The results suggest that anomalously rapid crystallization exists, and that shock stress is generated by ultra-rapid heating. Inhomogeneous melting as well as shock stress are important in the rapid crystallization at intensities below the amorphization threshold.
Anomalous Magnetic Behavior due to Reversible Fluxoid Motion in Superconducting Multifilamentary Wires with Very Fine Filaments
Authors: Sumiyoshi Fumio , Matsuyama Mikio , Noda Minoru , Matsushita Teruo , Funaki Kazuo , Iwakuma Masataka , Yamafuji Kaoru
Published: November 2005

It was found experimentally that the hysteresis loss in a superconducting multifilamentary wire was drastically decreased with the decrease of the filament diameter in spite of inappreciable change in the critical current density. This tendency is incompatible with the conventional theoretical prediction from the critical state model. In the present letter it is pointed out that this anomaly can be explained by taking account of a reversible motion of fluxoids in very fine filaments.
Atomic-Scale Structures of Top and Bottom Heterointerfaces in GaAs–AlxGa1-xAs (x=0.2-1) Quantum Wells Prepared by Molecular Beam Epitaxy with Growth Interruption
Authors: Tanaka Masaaki , Sakaki Hiroyuki , Yoshino Junji
Published: November 2005

We have studied microscopic structures of two different interfaces in MBE-grown GaAs–Al
x
Ga1-x
As quantum wells (QWs), and effects of growth interruption on the interface roughness. For QWs with x>0.5, the effective roughness of top (AlGaAs-on-GaAs) interfaces is drastically reduced down to less than 0.2 atomic layer by the growth interruption, whereas bottom (GaAs-on-AlGaAs) interfaces are unaffected and act as pseudo-smooth interfaces even without the interruption. However, for QWs with x<0.3, bottom interfaces are similar to top interfaces, and can be smoothed by the growth interruption. Microscopic models of various heterointerfaces are presented.
On the Possibility for Polarizing Slow Neutrons by Longitudinally Polarized Proton Filter
Authors: Hoshizaki Norio , Masaike Akira
Published: November 2005

It is shown that the low energy neutron beam can be polarized along the direction of the neutron beam using a longitudinally polarized proton filter. The polarizability of the neutron is nearly the same as in the case using the transversally polarized proton filter in the neutron energy region below 1 MeV and is higher in the energy region above 1 MeV. The difference of the polarizability between the two cases is estimated.
MBE Growth of InGaAlAs Lattice-Matched to InP by Pulsed Molecular Beam Method
Authors: Fujii Toshio , Nakata Yoshiaki , Sugiyama Yoshihiro , Hiyamizu Satoshi
Published: November 2005

High-quality InGaAlAs lattice-matched to InP was obtained by MBE with a pulsed molecular beam. Very narrow full width at half maximum (FWHM) of a photoluminescence spectrum at 4.2 K (4.5, 9.0, 10.3, 13.1, 16.2 meV) was obtained for In0.52(Ga1-x
Al
x
)0.48As(x=0, 0.25, 0.5, 0.75, 1). The dependence of the energy band gap of In0.52(Ga1-x
Al
x
)0.48As on Al composition, x, was found to be linear in the range of 0≦x≦1.
Fabrication of All-Nb Josephson Junctions Using Oxidized Zr Overlayers
Authors: Asano Hidefumi , Tanabe Keiichi , Katoh Yujiro , Michikami Osamu
Published: November 2005

Fabrication of all-Nb Josephson tunnel junctions using artificial barriers of oxidized Zr overlayers is described. Thin Zr overlayers are sputter-deposited onto polycrystalline Nb films and then thermally oxidized. The tunneling characteristics of these junctions are found to be greatly affected by the occurrence of Zr diffusion into the grain boundaries of the base Nb films during Zr deposition, which is confirmed by XPS analysis. Paying particular attention to the rapid substrate cooling, high quality junctions with V
m=47 mV are obtained.
EBIC Observation on the InP/InGaAs/InP Heterostructure Photodiode
Authors: Takanohashi Tsugunori , Osaka Fukunobu , Komiya Satoshi , Yamazaki Susumu , Nakajima Kazuo
Published: November 2005

An electron-beam induced current (EBIC) is measured on an InP/In0.53Ga0.47As/InP heterostructure photodiode which shows an anomalous photoresponse outside the photosensitive area. It is revealed that the EBIC response is extended in the lateral direction at the double heterojunctions when the punch-through occurs. The p-inversion of the heterojunction is discussed as the reason. The reverse bias dependence of the line-scan EBIC signal is explained by the hot carrier process.
Importance of Controlling Material Constants to Realize Bistable Uniform States in Surface Stabilized Ferroelectric Liquid Crystal Cells
Authors: Tsuchiya Tsuyoshi , Takezoe Hideo , Fukuda Atsuo
Published: November 2005

The director orientation structures in surface stabilized ferroelectric liquid crystal cells are calculated by minimizing the distortion free energy, F
d, and the surface energy, F
s. By taking account of K
2 ≠ K
3, it is shown that F
d itself stabilizes one kind of twisted state depending on the handedness of the inherent helicoid and the sign of K
3–K
2. It is possible that F
d and F
s favor different kinds of twisted states. This results in the potential conclusion that the critical thickness for realizing uniform states could be designed to be fairly large by the proper choice of material constants and surface conditions.
Improved Thermally Stimulated Current Spectroscopy to Characterize Levels in Semi-Insulating GaAs
Authors: Tomozane Mamoru , Nannichi Yasuo
Published: November 2005

Deep levels in semi-insulating GaAs were observed at low temperatures by means of improved thermally stimulated current (TSC) spectroscopy. The improvement was done by thinning the specimen and adding a guard ring electrode. The ionization energy of the levels was limited to below 0.7 eV. The concentration of 1013 cm-3 was easily measured with an electrode area of 5 mm2. Spectra by electron traps and hole traps were separated by changing the bias polarity.
The Effect of Reduction of Dislocation Density on the Lattice Distortions in Undoped GaAs Single Crystal Grown by LEC Method
Authors: Kitano Tomohisa , Ishikawa Tetsuya , Matsui Junji
Published: November 2005

Distributions were mapped of lattice inclination and lattice spacing in (001) undoped GaAs crystals using synchrotron plane wave X-ray topography. For a high dislocation density GaAs wafer, degree of lattice inclination is larger (Δθ≃±40 seconds) than that for a low dislocation density wafer (±5 seconds), whereas the variation of lattice spacing is of nearly the same order (Δd/d≃±1×10-5). Lattice spacing is small near the wafer center and large around the periphery for both the high and low dislocation density wafers.
Effects of Deep Impurities on Photoluminescence from Electron-Hole Droplets in Germanium
Authors: Nakata Hiroyasu , Ichikawa Yohei , Otsuka Eizo
Published: November 2005

Nucleation and decay kinetics of electron-hole droplets are investigated by photoluminescence measurements of germanium crystals doped with deep impurities, Be, Zn or Te, as well as with a shallow impurity Sb. Deep impurities decelerate the formation of droplets in contrast to shallow impurities, which accelerate the formation. The lifetime of droplets is shortened by doping deep impurities. Far-infrared absorption of droplets in Zn-doped germanium is also discussed.
An In-Doped Dislocation-Free GaAs Layer Grown by MBE on In-Doped GaAs Substrate
Authors: Takeuchi Hiroaki , Shinohara Masanori , Oe Kunishige
Published: November 2005

A dislocation-free GaAs epitaxial layer without propagating dislocations from a substrate or misfit dislocations is developed on an indium-doped semi-insulating GaAs substrate by molecular beam epitaxy (MBE). The epitaxial layer is doped with indium to reduce lattice mismatch between the layer and substrate. Photoluminescence measurements confirm that the indium-doped dislocation-free GaAs epitaxial layer has good photoluminescence efficiency. This dislocation-free GaAs epitaxial layer promises to play an important role in achieving a GaAs/AlGaAs optoelectric integrated circuit (OEIC).
Nb/Al-oxide/Nb and NbN/MgO/NbN Tunnel Junctions in Large Series Arrays for Voltage Standards
Authors: Niemeyer Jurgen , Sakamoto Yasuhiko , Vollmer Eckhard , Hinken Johann H. , Shoji Akira , Nakagawa Hiroshi , Takada Susumu , Kosaka Shin
Published: November 2005

Series arrays of 1440 Josephson tunnel junctions were fabricated out of Nb/AN-oxide/Nb- and Nb/NbN/MgO/NbN/Nb-sandwiches The arrays provide microwave-induced constant voltage steps of at least one volt. The good stability of hard superconductor tunnel junctions against room temperature storage and thermal cyling suggests that these arrays might be very useful for the constructions of practical lasting Josephson voltage standards of high precision.
DX Center-Like Trap in Selectively Si-Doped AlAs/GaAs Superlattices
Authors: Iwata Naotaka , Matsumoto Yoshishige , Baba Toshio , Ogawa Masaki
Published: November 2005

The behavior of a Si donor in selectively doped AlAs/GaAs superlattices(SLs) grown by MBE was investigated. It was found that Si atoms doped within ± monolayer from the AlAs/GaAs interfaces of the SL act as deep centers similar to the so-called DX center observed in mixed AlGaAs, while those confined in GaAs layers act as shallow centers. The fact led us to model the DX center as a Si donor having both Al and Ga at the second nearest-neighbor sites. The model consistently explains the DX center characteristics in mixed AlGaAs.
GaAs Substrate Material Assessment Using a High Lateral Resolution MESFET Test Pattern
Authors: Schink H. , Packeiser G. , Maluenda J. , Martin G. M.
Published: November 2005

The uniformity of the threshold voltage V
T of MESFETs fabricated on a variety of LEC-grown semi-insulating GaAs wafers was investigated. Microscopic uniformity data with a high lateral resolution of 10 µm are reported as well as macroscopic variations. It is demonstrated that the value of V
T can be a monotonic function of the FET position even for areas as small as 20 µm. Variations below 20 µm are superimposed.
On the macroscopic scale the typical W-shaped profile of V
T for Cr-doped GaAs over the wafer can be suppressed by the use of undoped GaAs even with conventional EPD. In low dislocation density In-doped GaAs the microscopic as well as the macroscopic scattering of V
T is drastically reduced.
Memory Effect in AC Thin Film ZnS:Mn Electroluminescent Devices Prepared by Metal Organic Chemical Vapor Deposition
Authors: Hirabayashi Katsuhiko , Kozawaguchi Haruki
Published: November 2005

AC thin film ZnS:Mn electroluminescent devices prepared by metal organic chemical vapor deposition have been found to exhibit a larger and more stable memory effect than devices prepared by EB-evaporation. The memory margin is about 15% of the threshold voltage for a device having an Mn concentration of 0.8 wt%. The memory margin is relatively stable. The results show that except for the first 300 hours, the brightness-voltage characteristic exhibits almost the same hysteresis shape during 2000 hours of aging at a constant brightness of 500 cd/m2, using a 5 kHz sinusoidal wave.
A New Partial Pressure Gauge for He and D2 Using Ion Backscattering Principle
Authors: Uritani Akira , Akaishi Kenya , Kubota Yusuke , Hori Yoichiro , Miyahara Akira
Published: November 2005

A new vacuum gauge which is capable of measuring partial pressures of He and D2 gases in their mixture was constructed. This gauge is operated with ion backscattering principle on a solid surface. The validity of the gauge for the partial pressure measurement is demonstrated experimentally and discussed.
Formation of Zn–O Complexes During the Molecular Beam Epitaxial Growth of GaP on Si
Authors: Kawanami Hitoshi , Ishihara Seiichi , Nagai Kiyoko , Hayashi Yutaka
Published: November 2005

Heteroepitaxial GaP films were grown on (100) oriented Si substrates by molecular beam epitaxy. During the growth, the substrates were irradiated with a Zn molecular beam. At growth temperatures lower than 450°C, a broad band luminescence due to Zn–O complexes was observed at room temperature.
A New Technique for the Formation of Ultrafine Particles by Sputtering
Authors: Yatsuya Shigeki , Kamakura Takanobu , Yamauchi Kenji , Mihama Kazuhiro
Published: November 2005

A gas evaporation technique using sputtering is newly developed. The characteristic of this new technique is the use of sputtering in an atmosphere of higher gas pressure such as 0.5 to 100 Torr than is used for ordinary sputtering. W, Ag and Cu are tested and their ultrafine particles are formed. WC1-x
particles are also prepared by reactive sputtering.
Composition-Dependent Appearance of Amorphous Phase in ZnSxO1-x System and its Stability
Authors: Takabayashi Akiharu , Iida Seishi
Published: November 2005

ZnS
x
O1-x
(x>0.3) films were prepared by r.f. sputtering of ZnS powder. This ZnS
x
O1-x
is amorphous in the range 0.3 < x < 0.5, and is a mixture of amorphous and crystalline phases in the range x < 0.5. The x-dependence of the amorphous phase is thought to be due to a large difference in the bond length between Zn–S and Zn–O. The amorphous structure has been found to be fairly stable. No X-ray diffraction line was observed after annealing at 400°C, though optical and electrical properties changed markedly. X-ray diffraction and photoluminescence properties have indicated that the photoluminescence is attributable to the amorphous structure.
Quench Characteristics and Operational Stability of the TOPAZ Thin Superconducting Solenoid
Authors: Yamamoto Akira , Mito Toshiyuki , Kimura Nobuhiro , Haruyama Tomiyoshi , Yamaoka Hiroshi , Araoka Osamu , Tadano Mikito , Suzuki Shoji , Kondo Yoshinari , Kawai Masanori , Kichimi Hiromichi , Doi Yoshikuni
Published: November 2005

A large thin wall superconducting solenoid magnet adopting a newly developed internal winding method has been constructed for the high energy particle detector “TOPAZ” at the TRISTAN e+e- collider. Various measurements were carried out on stability of such a thin solenoid in forced quench, sudden switch-off and forced mass flow during excitations. The results of these measurements are presented and evaluated.
Frequency Dependent Polarization Reversal and the Response Time of Ferroelectric Liquid Crystal by Triangular Wave Method
Authors: Bawa S.S. , Biradar A.M. , Chandra Subhas
Published: November 2005

Dynamic processes of molecular reorientation of thin (10 µm) well aligned film of ferroelectric smectic C (DOBAMBC) have been studied with a triangular wave by observing a current signal due to polarization realignment at different frequencies. The peak due to polarization reversal shifts along the abscissa axis with the increase in frequency of the triangular pulses. The peak originates from both a surface and interior molecular reorientation, switches amongst uniform up(UU) ↔ twisted(TI) ↔ uniform down(UD) states and shifts due to their composite response time. The method also provides an estimate for the response time by comparing the occurrence of the peak at two known frequencies.
Electron Energy Loss Spectra of In/Si(111) Superstructures
Authors: Hirayama Hiroyuki , Baba Shigeru , Kinbara Akira
Published: November 2005

Electron energy loss spectra (EELS) of Si(111) √3×√3–In, Si(111)√31×√31–In, Si(111)4×1–In superstructured surfaces were measured and compared with those of non-superstructured In/Si(111) surfaces. The shape of the loss spectrum of a superstructured surface is found to differ from that of a non-superstructured surface at coverages between 0.3 and 0.7 monolayers. The difference is discussed from the viewpoint of the surface electronic states.
A Solid Electrochromic Cell Using Lu-Diphthalocyanine and Lead Fluoride
Authors: Egashira Noritaka , Kokado Hiroshi
Published: November 2005

An all-solid state electrochromic display (ECD) cell consisting of lutetium diphthalocyanine (HLuPc2) was constructed using PbF2 as the solid electrolyte. The LCD cell having a structure, ITO/HLuPc2/PbF2/Au quickly changed its color from original green to orange when a positive voltage of 1–2 V was applied to the ITO electrode. The response time was less than 100 ms and the electrochromic reaction repeated well up to 105 times.
Formation of DX Centers by Heavy Si Doping in MBE-Grown AlxGa1-xAs with Low Al Content
Authors: Ishikawa Tomonori , Yamamoto Tohru , Kondo Kazuo
Published: November 2005

The dependence of shallow donors and DX centers on Si doping concentration in Al
x
Ga1-x
As layers grown by MBE has been investigated. In the shallow-to-DX transition region around x=0.2, the concentration ratio of DX centers to shallow donors was proved to have strong dependence on Si doping concentration. While few DX centers were observed in the samples with an Si concentration of about 1×1017 cm-3 DX centers became dominant above 1×1018 cm-3. These results can be explained by the effect of electron distribution between Γ-valley and DX center level.
Positional Stability of Focused Ion Beams
Authors: Arimoto Hiroshi , Morita Tetsuo , Miyauchi Eizo , Hashimoto Hisao
Published: November 2005

Probe position stability of focused ion beams in a 100 kV focused ion beam implanter has been investigated. The best result gave a steady probe ion beam with a fluctuation of about 0.1 µm. The ion beam position fluctuates with unstable ion emission. These fluctuations are due to the following two reasons. The first is the extractor voltage variation which is usually required to stabilize the ion emission (a kind of deflection effect). The second seems to be the movement of the Taylor cone itself whose apex represents the actual source position. The results suggest that the Taylor cone on a smaller emitter apex would hardly move, even if the ion emission is unstable.
Synthesis of Diamond Thin Films by Thermal CVD Using Organic Compounds
Authors: Hirose Yoichi , Terasawa Yuki
Published: November 2005

Diamond thin films have been formed by thermal chemical vapor deposition (thermal CVD) using the organic compounds such as CH3OH, C2H5OH, CH3COCH3C2H5OC2H5, and (CH3)3N. The films are grown on the silicon substrates with high growth rate (8–10 µm/h) under the pressure ranging 1–800 Torr. This growth rate is ten or several ten times faster than the CVD method using hydrocarbons such as CH4and C2H2. The films have good crystallinity and high quality in the sense of electron diffraction and Raman spectrum. The Vicker's hardness of the film is about 10000 kg/mm2and the gravity of that is about 3.52 g/cm3.
Twenty-Five Millisecond Resolution Time-Resolved X-Ray Absorption Spectroscopy in Dispersive Mode
Authors: Matsushita Tadashi , Oyanagi Hiroyuki , Saigo Satoshi , Kaminaga Ukyo , Hashimoto Hideki , Kihara Hitoshi , Yoshida Noboru , Fujimoto Masatoshi
Published: November 2005

The capability of an energy dispersive X-ray absorption spectrometer for time-resolved experiment was demonstrated by measuring X-ray absorption spectra with a time-resolution of 25 ms from two reacting solutions (0.3 M ferric nitrate (Fe(NO3)3) and 0.3 M hydroquinone (C6H4(OH)2)) mixed by the stopped-flow method. A real time observation of theenergy shift of the Fe K-absorption edge was successfully made after mixing the two solutions. The result suggests that the method is most suitable for the study of irreversible structural and chemical changes in various kinds of materials.
Preparation of Highly Photoconductive a-SiGex from Fluorides by Controlling Reactions with Atomic Hydrogen
Authors: Shibata Naoki , Tanabe Akihito , Hanna Jun-ichi , Oda Shunri , Shimizu Isamu
Published: November 2005

Highly photoconductive a-SiGe
x
alloys with an optical gap of 1.2–1.7 eV are prepared by plasma-induced decomposition of fluorides (SiF4 and GeF4) and the introduction of atomic hydrogens (hydrogen radicals). Two new preparing methods are proposed to attain high alloy quality by controlling the reactions for making precursors using hydrogen radicals. Attempts have been made to deposit alloys on a substrate apart from the plasma to avoid damage of the films by bombardment of the particles. By this means, highly photoconductive a-SiGe
x
:H(F) films with an optical gap of 1.4eV were obtained with high growth rates.
Accurate Determination of K1/ηsplay, K2/ηtwist and K3/ηbend in Nematic Liquid Crystalsby Using Photon Correlation Spectroscopy
Authors: Hirakata Jun-ichi , Chen Guo-ping , Toyooka Takehiro , Kawamoto Shunji , Takezoe Hideo , Fukuda Atsuo
Published: November 2005

A system based on photon correlation spectroscopy has been constructed using a microcomputer to measure the spectral width of Rayleigh light scattered from nematic liquid crystals. Maps in the (α, φ, θ=0° ) space have been devised to find the most suitable scatterinu geometries for the determination of K
1/ηsplay, K
2/ηtwist and K
3/ηbend, where α, φ and θ specify the scattering angle and the director direction. The ratios have been obtained as a function of T
NI–T for 4'-alkyl-4-cyanobiphenyls (n=5∼8).
Photoluminescence of the 78 meV Acceptor in GaAs Layers Grown by Molecular Bearn Epitaxy
Authors: Mihara Minoru , Mannoh Masaya , Shinozaki Keisuke , Naritsuka Shigeya , Ishii Makoto
Published: November 2005

The 1.44 eV photoluminescence peak of the 78 meV acceptor, previously known only in bulk GaAs crystals, has been observed in lightly Si-doped GaAs layers grown by molecular beam epitaxy. This observation provides strong evidence that the 78 meV acceptor is related to the Ga antisite defect (G
a
As).
Study on Fragmentation of Ionized Atom-Clusters by Time-of-Flight Mass Spectrometry
Authors: Saito Yahachi , Suzuki Mitsuru , Noda Tamotsu , Mihama Kazuhiro
Published: November 2005

Atom-clusters of Pb and PbS produced by nozzle beam expansion have been analyzed by time-of-flight mass spectrometry following the electron impact ionization. The dependence of the ion intensity on ionizing energy has shown occurrence of the fragmentation by electron impact. However, an ion retarding analysis has revealed that both Pb and Pb Scluster tons do not break during their flight in a drift tube. Therefore, the fragmentation has already finished prior to full acceleration of ions.
Dangling Bond Creation in Hydrogenated Amorphous Silicon by Light-Soaking
Authors: Shirafuji Junji , Shirakawa Kazuhiro , Nagata Shunsuke
Published: November 2005

It has been observed in glow-discharged undoped amorphous hydrogenated silicon (a–Si:H) films that the Fermi level position moves downwards and is pinned near the midgap by a low dose irradiation with gamma-rays. Films irradiated lightly with gamma-rays offer an opportunity for investigating Staebler-Wronski effect without any ambiguity due to Fermi level shift. Under the condition of the pinned Fermi level, we have confirmed a decrease in the electron lifetime and in parallel an increase in the ESR spin density relating to neutral Si dangling bonds after light-soaking.
The Origin of the DX Center in AlxGa1-xAs
Authors: Yamaguchi Eiichi
Published: November 2005

A new microscopic origin of the DX center in Al
x
Ga1-x
As is proposed on the basis of the scattering-theoretic method calculation. Calculated results show that the central cell potential of donors induces the deep levels attributed to the DX center. The theory satisfactorily explains the x- and pressure-dependence of the DX center energy levels in Al
x
Ga1-x
As.
A Consideration on Expression of the Elastic Free Energy of Chiral Smectic C Liquid Crystals
Authors: Akahane Tadashi , Nakagawa Masahiro
Published: November 2005

The effectiveness of the “nematic” expression of the elastic free energy in chiral smectic C liquid crystals is investigated. From the comparison with the phenomenological theory by Pikin and Indenbom, it is shown that the spontaneous twist parameter q
// and the spontaneous bend parameter q
⊥ involved in the “nematic” expression are related with the existence of Lifshitz's invariant and the flexoelectricity, respectively. Possibility of the evaluation of q
// and q
⊥ is discussed.
New Material for p-Type Window Layer in a-Si Solar Cells
Authors: Yoshida Toshihiko , Fukui Keitaro , Yamamoto Hideo , Matsumura Mitsuo
Published: November 2005

We have found a new wide band gap material and applied it as a window layer in a-Si solar cells. Films are deposited by rf-glow discharge method with NO/SiH4/H2 mixtures. IR spectra show that films contain Si, N, O and H (a-Si:O:N:H). Increasing NO/SiH4 ratio, the optical gap widen and the refractive index decreases. The performance of solar cells using an a-Si:O:N:H p-layer has been improved because of the increase in incident light into the i-layer. Moreover, the measurement of photodegradation indicates that the cell efficiency decreases by less than 1% under illumination with AM1 100 mW/cm2 for 10 hrs.
Hydrogen Evolution from Amorphous Si–N Films
Authors: Morimoto Akiharu , Kobayashi Isao , Kumeda Minoru , Shimizu Tatsuo
Published: November 2005

Hydrogen evolution experiments were carried out for a–Si1-x
N
x
:H films prepared by glow discharge decomposition. The H content increases with increasing N content in the range of x<0.4, accompanying a large change in the oscillator strength for Si–H IR wagging mode absorption. The ratio of the content of hydrogen evolved at low temperature to the content of hydrogen evolved at high temperature increases with the N content, suggesting that the structure becomesvoid-rich.