bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancement of the Capture Rate of Carriers in (111)-Oriented GaAs/AlGaAs Quantum Well Structures
Authors: Hayakawa Toshiro , Kondo Masafumi , Suyama Takahiro , Takahashi Kosei , Yamamoto Saburo , Hijikata Toshiki
Published: February 2005

A detailed analysis on the dependence of the photoluminescence spectrum on the excitation density in (111)- and (100)-oriented single-quantum-well (SQW) structures is presented. The results show that the capture rate of photo-excited carriers in the barrier region by the SQW and the radiative recombination rate in the SQW are enhanced in (111)-oriented SQW structures compared to those in (100)-oriented ones.
Rare-Earth(RE)–Barium Solubility Behaviour in Y(Ba2-xREx)Cu3O7+δand Sm(Ba2-xREx)Cu3O7+δ
Authors: Suzuki Atsushi , Sampathkumaran E. V. , Kohn Key , Shibuya Takashi , Tohdake Ayako , Ishikawa Masayasu
Published: February 2005

The lattice constants and the superconducting transition temperatures of the series Y(Ba2-xREx)Cu3O7+δ(RE=Pr, Eu, and Gd;x≦0.4) show that the solubility of RE with Ba is practically absent for Eu and Gd, whereas a small solubility of Pr cannot be ruled out. The degree of RE-Ba solubility limit in the Y-based systems is significantly smaller relative to that in the respective RE based series. This observation could be consistently understood by our earlier proposal on the RE-Ba solubility dependence on the degree of O-O repulsive interaction. Our results also indicate that Pr is trivalent in these oxides, contrary to a previous report.
Preparation and Superconducting Properties of Tetragonal Ba2YCu3O7-y and Ba2EuCu3O7-y with Low Oxygen-Defect Concentration (0.05<y<0.20)
Authors: Kinoshita Kyoichi , Matsuda Azusa , Ishii Takao , Suzuki Naobumi , Shibata Hiroyuki , Watanabe Takao , Yamada Tomoaki
Published: February 2005

Tetragonal phases of Ba2YCu3O7-y
and Ba2EuCu3O7-y
with low oxygen-defect concentration (0.05<y<0.20) are prepared by synthesis under high oxygen pressure (3–8 atms). As oxygen pressure increases during sintering, the crystal structure of synthesized samples changes from the orthorhombic to tetragonal phase and superconductivity is suppressed. Substitution of Y and Eu for Ba is observed to accompany the change to the tetragonal phase. Disordering of oxygen vacancies and such substitution may be vital for the absence of superconductivity because no strong correlation between T
c and oxygen-defect concentration is observed.
YBCO Superconducting Coils Operated at Nitrogen Temperature
Authors: Tanaka Yasuzo , Yamada Kiyoshi , Sano Takayuki
Published: February 2005

Trial coils of YBa2Cu3O
x
superconductor were prepared from oxide superconducting powder and binder mixtures. The critical temperature of the wire was more than 86 K in the four-probe measurement. Magnetic fields, 21.1 gauss, and 350 gauss were generated by dc operations at 77 K and 4.2 K, respectively. A critical current density in the coil was of 1,330 A/cm2, corresponding to a level of 77 K and zero magnetic field. Experimental results show that an oxide superconducting magnet with an appropriate protection circuit is feasible and stable at liquid nitrogen temperature.
Assignment of the Powder X-Ray Diffraction Pattern of Superconductor Bi2(Sr, Ca)3-xCu2Oy
Authors: Onoda Mitsuko , Yamamoto Akiji , Takayama-Muromachi Eiji , Takekawa Shunji
Published: February 2005

The powder X-ray diffraction pattern of superconductor Bi2(Sr, Ca)3-x
Cu2O
y
was assigned taking into account the satellite reflections arising from an incommensurate modulated structure. All reflections are indexable with h a*+k b*+l c*+m k, provided that the wave vector k of the modulated structure is b*/4.8. The result shows that many satellites can be observed and some satellite intensities are strong.
Crystal Structure Variations due to Multiplicity in CuO2-Ca-CuO2 Slabs in Superconductive Tl-Ba-Ca-Cu-O Oxides
Authors: Iijima Sumio , Ichihashi Toshinari , Shimakawa Yuichi , Manako Takashi , Kubo Yoshimi
Published: February 2005

Structural variations in crystals for Tl-Ba-Ca-Cu-O oxides with T
c above 100 K were examined by an electron microscope. Common phases for these oxides were found to be Tl2Ba2CaCu2O8+x
and Tl2Ba2Ca2Cu3O10+x
. Variations in these structures result from multiplicity in (CuO2-Ca-CuO2)×n slab (designated CC
n
with n=integer), whose composition is represented by Tl2Ba2Ca
n
Cu
n+1O2(3+n)+x
. It is shown, for the first time, that slab thicknesses CC
n
have been observed for structures with n=1 to 6. The structural variation is also caused by two kinds of BaO-TlO-BaO and BaO-TlO-TlO-BaO slabs.
Heterogeneous Distribution of Magnetic Flux on Ba2YCu3O7-xSuperconductors
Authors: Osamura Kozo , Tomii Yoichi , Matsukura Norikazu , Ochiai Shojiro
Published: February 2005

Applying the decoration method, the macroscopic heterogeneity of magnetic flux distribution has been directly observed on the surface of Ba2YCu3O7-xsuperconductors. Its heterogeneity was clarified as correlating with the microstructual imperfections like twinned structure, grain boundary and pore, with respect to the anisotropic and heterogeneous superconducting properties.
Optical Degradation of a-Si:H films with Different Morphology
Authors: Ohagi Hideki , Yamazaki Motoharu , Nakata Jun-ichi , Imao Shozo , Shirafuji Junji , Fujibayashi Keiji , Inuishi Yoshio
Published: February 2005

The optical degradation (Staebler-Wronski (SW) effect) of a-Si:H films prepared by plasma CVD has been studied in connection with the morphological inhomogeneity of the films. The relative degradation rate of cubic photoconductivity α widely varied with deposition substrate temperature T
s and had its maximum at T
s=200∼250°C. In the films of both the lower and higher T
s, α decreased due to the increase of stable dangling bonds in the former and the decrease of weak bonds in the latter. The SW effect was hardly observed in µc-Si:H deposited from highly diluted silane with hydrogen.
Numerical Analysis of the Dynamic Characteristics of Amorphous Silicon Thin-Film Transistors
Authors: Yue Jin-hai , Oda Shunri , Matsumura Masakiyo
Published: February 2005

The dynamic characteristics of amorphous silicon thin-film transistors have been analyzed numerically. Electrons accumulated at the semiconductor/gate-insulator interface move toward the opposite interface formed by the semiconductor and substrate as soon as the pulsive gate voltage returns to a low value. All excess electrons are quickly swept out from the active region to either the source or drain, resulting in a large voltage change of the pixel. The gradual decrease of the gate voltage is an effective solution for reducing the voltage change.
Measurements of Energy Distributions in ECR Plasma
Authors: Amemiya Hiroshi , Shimizu Kazuo , Kato Shigeki , Sakamoto Yuichi
Published: February 2005

The electron energy distribution is measured in an ECR device for H2 and N2 plasmas as a function of pressure. The maximum measurable energy and the high-energy tail increase with decreasing pressure. However, the energy distribution at the high-energy part progressively departs from a Maxwellian shape as the pressure is increased. The electron temperature obtained from the low-energy part increases with decreasing pressure. The positive ion temperature is of the order of a few eV and increases with the electron temperature. A mechanism of ion acceleration should exist.
High Quality Amorphous Silicon Films Prepared by Atmospheric-Pressure Photo-CVD
Authors: Kim Woo Yeol , Konagai Makoto , Takahashi Kiyoshi
Published: February 2005

We have prepared undoped a-Si:H films by atmospheric-pressure mercury-sensitized photo-CVD for the first time. The maximum deposition rate of 45 Å/min has been obtained by optimizing the mercury reservoir temperature and the flow rate of SiH4. The maximum ratio of the photoconductivity (AM-1, 100 mW/cm2) to the dark conductivity was 6×106 with an optical handgap of 1.78 eV. The concentration of oxygen in the films prepared by the atmospheric-pressure photo-CVD was 2×1018 cm-3 which is much lower than that of films grown by low-pressure photo-CVD.
Highly Ordered Icosahedral Quasicrystal of Al-Cu-Fe Alloy Studied by Electron Diffraction and High-Resolution Electron Microscopy
Authors: Hiraga Kenji , Zhang Bo-Ping , Hirabayashi Makoto , Inoue Akihisa , Masumoto Tsuyoshi
Published: February 2005

An icosahedral quasicrystal in a conventionally solidified Al-Cu-Fe alloy has been examined with electron diffraction and high-resolution electron microscopy. Diffraction and Kikuchi patterns taken with the incident beam exactly parallel to the 5- and 3-fold symmetry axes show strict 5- and 3-fold rotational symmetry. Any systematic shift of diffraction spots, which often appears in rapidly solidified quasicrystals, was not observed at all. A high-resolution electron micrograph taken with the incident beam parallel to the 5-fold axis shows no existence of phason strains in the icosahedral quasicrystal.
Surface Segregation at Boron Planar Doping in Silicon Molecular Beam Epitaxy
Authors: Tatsumi Toru , Hirayama Hiroyuki , Aizaki Naoaki
Published: February 2005

When a 1.0 monolayer coverage of boron atoms was evaporated on a Si(100) clean surface, followed by a 200 Å n--type Si epitaxial layer, about 70% of the boron atoms were activated. However, using Auger analyses, it was found that surface boron segregation occurred during this process and the boron profile was smeared. In the case of Si(100) substrate, boron atoms were incorporated into the growing Si film in proportion to the surface boron density. On Si(111), surface boron atoms did not incorporate in proportion to the surface boron density and boron segregation had a large growth temperature dependence. This difference is explained using the existence of a √3×√3R30° surface superstructure of boron only on the Si(111) surface.
Epitaxial Growth Mechanism of the (100) As Surface of GaAs–The Effect of Positive Holes–
Authors: Tsuda Minoru , Morishita Mutsuo , Oikawa Setsuko , Mashita Masao
Published: February 2005

The mechanism of the monoatomic layer epitaxy (ALE) on the (100) As surface of GaAs crystals was elucidated in terms of the elementary reactions which control the epitaxial growth. A positive hole plays an important role in ALE. The potential energy hypersurface and the chemical structure changes following the progress of the elementary reaction with a positive hole were described.
Chemical Etching of High-Tc Superconducting Films in Feliox-115 Solution
Authors: Tonouchi Masayoshi , Sakaguchi Yoshiyuki , Kobayashi Takeshi
Published: February 2005

A new chemical etching technique of high-T
c superconducting Y-Ba-Cu-O and Er-Ba-Cu-O films has been developed by employing a novel etchant Feliox-115. It offered a diffusion-limited etching. The rate (at 20°C) and the activation energy of Y-Ba-Cu-O dissolution were, respectively, 0.5 µm/min and 0.32 eV. The Er compound was etched off more preferentially than the Y one: The etching rate of the former was nearly twice as high as the latter. The degradation of T
c induced during this process was at most 4 K.
A Pseudopotential Approach to the Formation of Group IV Interstitial in III-V Semiconductors
Authors: Ito Tomonori
Published: February 2005

Formation of neutral group IV interstitial atoms in III-V semiconductors is investigated using a pseudopotential perturbation approach. The interstitial sites of group IV atoms in III-V semiconductors are specified by the atomic volume ratio \varOmegaIV/\varOmegaIII-V and bulk modulus ratio B
IV/B
III-V between III-V and IV semiconductors. The favored interstitial site is found to change from hexagonal to tetrahedral with an increase in \varOmegaIV/\varOmegaIII-V and decrease in B
IV/B
III-V. The calculated formation energies of group IV interstitial in III-V semiconductors imply that interstitial Sn is formed more easily than interstitial Si and Ge.
Nonrepetitive Measurements of Wave and Plasma Parameters along a Low Frequency Surface Wave-Produced Plasma Column by an Interferometer Method
Authors: Nonaka Shigehiko , Yamaguchi Hiroshi
Published: February 2005

An interferometer method for surface wave-produced plasma column study was developed into the nonrepetitive and simplest form. The principle was applied to the successive measurements of both wave and plasma parameter variations along a low frequency (28 MHz) surface wave-produced plasma column. The interferogram obtained by experiments could be used for the simplest point-determinations of the wave number, attenuation coefficient and plasma density variation along the plasma column. The electron-neutral collision frequency and the electron temperature were estimated from the wave attenuation.
Characterization of Boron-Doped Diamond Film
Authors: Okano Ken , Naruki Hidetoshi , Akiba Yukio , Kurosu Tateki , Iida Masamori , Hirose Yoichi , Nakamura Terutaro
Published: February 2005

Diamond films doped with boron were fabricated by the thermal filament CVD method. Powdered B2O3 was used as the doping source. The films were identified as diamond by means of several methods including Raman spectroscopy. The resistivity of the films was inversely proportional to the B/C ratio over four orders. The temperature dependence of current was measured and to fit this result to the theoretical calculation, the activation energy was evaluated.
Lasertron: A Pulsed rf Source Using a Laser-Triggered Photocathode
Authors: Yoshioka Masakazu
Published: February 2005

A new pulsed rf source, the “lasertron”, is being developed as a possible rf power source for future electron-positron linear colliders. In a series of systematic studies, a prototype lasertron was fabricated and tested. A peak power of 80 kW was attained at a 2.856 GHz rf frequency with a 1 µs time duration. This paper describes the results of experimentation on the lasertron, including the development of the photocathode and the laser system. Test results are compared with the analysis of beam dynamics in the lasertron.
Self-Development Properties of Nitrocellulose (Dependence on Ion Energies)
Authors: Kaneko Hidehiko , Yasuoka Yoshizumi , Gamo Kenji , Namba Susumu
Published: February 2005

The dependence of self-development properties of nitrocellulose on ion energy was investigated in order to clarify the mechanism for the self-development of nitrocellulose. Experimental results were studied comparing the calculated electronic and nuclear stopping powers and projected range. It was concluded from the study that it was difficult to remove nitrocellulose film through self-development when it was irradiated with light ions such as He+ and Ne+ which have small nuclear stopping powers. As such, irradiation with ions which have sufficient nuclear stopping power, such as Ar+, is required in order to completely remove nitrocellulose through self-development.
Stress-Induced Perpendicular Magnetic Anisotropy in PtMnSb Thin Films
Authors: Sugimoto Naoto , Inukai Takashi , Matsuoka Morito , Ono Ken'ichi
Published: February 2005

Stress-induced perpendicular magnetic anisotropy is studied for PtMnSb thin films deposited on various substrates having different expansion coefficients. The magnetostriction constant λ of PtMnSb thin film is -30 × 10-6. The film's perpendicular magnetic anisotropy constant K
u increases as tensile thermal stress in the film plane increases.
Measurement of Laser Damage Threshold of 355-nm Antireflection Coating
Authors: Tamura Shigeharu , Kimura Saburo , Sato Yoshiyuki , Otani Minoru , Yoshida Hidetsugu , Yoshida Kunio
Published: February 2005

The laser damage thresholds of various types of antireflection (AR) coatings for an UV (355-nm) laser system were measured. Among them, the coatings consisting of two low-index materials, SiO2 and MgF2, had the highest average thresholds: 2.1 J/cm2 fused silica substrates and 2.6 J/cm2 sapphire substrates. The SiO2/MgF2 coating is hopeful for UV laser component.
Contribution of Thermal SiO2 Layers on Si Wafer Back Surfaces to Photoconductive Decay Time Measured with Microwave Reflection from Front Surfaces
Authors: Munakata Chusuke , Honma Noriaki , Tamura Hiroshi , Yagi Kunihiro
Published: February 2005

Two p-type silicon wafers, 420 µm in thickness, have been provided with different surface recombination characteristics. It is found that the back surface oxide layer greatly contributes to the photoconductive decay time in the wafer whose surface recombination rate is not large. However, the decay time is independent of the back surface oxide layer when the time is short because of the surface recombination.
The Determination Method of Accurate Electron Temperature by a Triple Probe in Plasma with Contaminants
Authors: Okano Daisuke
Published: February 2005

With respect to obtaining an accurate electron temperature by a triple probe in a plasma containing contaminating particles, a method of determination is proposed through calculations. This method is based on the existence of various contact potential differences due to deposition of either electronegative or electropositive material on the surfaces of the probes.
Properties of High-Quality Flexible Graphite Film and Its Preparation by the Pyrolytic CVD Method
Authors: Fukuda Masahiko , Mizogami Shigeyoshi , Yoshino Katsumi
Published: February 2005

Pyrolytic chemical vapor deposition (CVD) of hydrocarbon containing oxygen atoms yields free-standing conductive carbonaceous films of 450 S/cm. With further heat-treating at a higher temperature, the obtained film is converted to high quality graphitized film with a conductivity of 1.6×104 S/cm for the 2800°C treatment, which is of the same order of magnitude as that of highly oriented pyrolytic graphite (HOPG). The electrical conductivity and thermoelectric power of the films are examined as a function of the heat-treatment temperature. The temperature dependence of thermoelectric power is also confirmed to be the same as that of HOPG.
Thermally Activated Deformation of KCl and KCl-KBr Single Crystals at Low Temperatures between 1.8 and 70 K
Authors: Kataoka Toshihiko , Sumida Takashi , Azuma Kensaku , Yamada Tomoharu
Published: February 2005

The critical-resolved shear stress and the strain-rate dependence of flow stress for KCl pure crystals and KCl-1, 4, 22 and 48 mol% KBr solid-solution crystals were measured over a temperature range between 1.8 K and 70 K. The activation analyses of the results showed that an Arrhenius rate equation for plastic deformation appeared to hold above 15 K for KCl and KCl-1 and 4 mol% KBr and above 25 K for KCl-22 and 48 mol% KBr, but not below these temperatures. Such discrepancy of the Arrhenius rate equation has been interpreted by the fluctuation of activation enthalpy due to random distribution of solute atoms. In the present interpretation the pre-exponential factor of the Arrhenius rate equation should have a strong temperature-dependence, especially in the low-temperature range, which agrees well with experimental results.
TeGeSnAu Alloys for Phase Change Type Optical Disk Memories
Authors: Ohno Eiji , Yamada Noboru , Kurumizawa Toshimitsu , Kimura Kunio , Takao Masatoshi
Published: February 2005

TeGeSnAu thin films were studied for phase change type rewritable optical disk material. Addition of Au to TeGeSn thin film shortened crystallization time. The crystallization time of Te60Ge4Sn11Au25 thin film was about 0.3 µs and was less than one 100th of that of Te80Ge5Sn15 thin film. Formation of a simple cubic structure with no atomic diffusions had caused the fast crystallization. The obtained optical disks showed high recording/erasing sensitivity, cyclability and thermal stability. The TeGeSnAu alloys will be applicable to rewritable optical disks with high data transmission rates.
Vibrational and Rotational Energy Distributions in a Hot Cl2 Molecular Beam
Authors: Hiraoka Susumu , Suzuki Keizo , Nishimatsu Shigeru
Published: February 2005

Vibrational and rotational energy distributions of a hot Cl2 (Cl2
*) molecular beam, which is used for a semiconductor device etching process, is studied by a laser-induced fluorescence method. The Cl2
* beam is produced by free jet expansion of a Cl2 gas heated in a quartz furnace. It is found that the hot molecular beam is a transition flow between a continuum free jet and an effusive flow. The vibrational and rotational energy distributions can be described by Boltzmann functions of well-defined temperatures. The vibrational temperature is rather close to the furnace exit temperature, while the rotational temperature is cooled to 150–250 K during the isentropic free expansion. These results show that furnace exit temperature is crucial to the production of a highly reactive hot molecular beam of large vibrational energy.
Optical Constants of CVD-SiC Mirrors Produced by Different Processes from 200 to 1000 eV
Authors: Yanagihara Mihiro , Sato Shigeru , Koide Tsuneharu , Takeda Shigekatsu , Iijima Akio
Published: February 2005

The optical constants of seven CVD-SiC mirrors produced by different processes have been measured in the soft X-ray region (200-1000 eV) by means of the reflectance method. In spite of the difference in the production process, no dependence of the optical constants on the samples was found. The photon-energy dependence of the optical constants for CVD-SiC is represented in terms of power formulas over a range of 300-1000 eV. It is also found that the rms surface roughness estimated by the reflectance method is always larger than the value measured with a WYKO optical profilometer.
Spectral Characteristics of Linewidth Enhancement Factor α of Multidimensional Quantum Wells
Authors: Miyake Yasunari , Asada Masahiro
Published: February 2005

We calculated spectral characteristics of the linewidth enhancement factor α for multidimensional quantum-well lasers. By increasing the quantization dimension, the wavelength dependence of α becomes stronger and its value around the maximum gain becomes smaller. For a quantum box, α is almost zero at the gain peak, and becomes negative at a shorter wavelength. The negative α yields the possibility of long-distance high-capacity optical fiber communication.
Laser-Induced Fluorescence of Pearls a Shells of Genus Haliotis and Their Comparison to Other Species Used in Pearl Culturing
Authors: Miyoshi Tadaki , Matsuda Yasunori , Akamatsu Shigeru
Published: February 2005

To determine the parentage of pearls nondestructively, the measurement of fluorescence spectra was applied to several kinds of pearls as well as shells. The fluorescence spectra of pearls and shells of genus Haliotis (abalone) were also measured together with those of other species of mother oysters used in pearl culturing. Experimental results indicate that some differences in the spectra make it possible for pearls of genus Haliotis to be distinguished from those of other mother oysters.
White Light Emitting Thin Film Electroluminescent Cells with SrS:Pr,Ce Active Layer and Their Application to Multicolor Electroluminescent Devices
Authors: Abe Yoshio , Onisawa Ken-ichi , Tamura Katsumi , Nakayama Takahiro , Hanazono Masanobu , Ono Yashimasa A.
Published: February 2005

White light emission with a maximum luminance of 950 cd/m2 under a 1 kHz sinusoidal wave drive condition was obtained from a SrS:Pr,Ce thin film electroluminescent (TFEL) cell. The EL spectrum was found to be composed of emissions from Pr3+ and Ce3+ ions. Spectral change was studied by varying the concentration of activator ions and the luminance for a unit concentration of Ce3+ ions was estimated to be three times as large as that of Pr3+ ions. By using color filters on the SrS:Pr,Ce TFEL cell, multicolor (red, blue, green) EL devices with suitable color coordinates and balanced luminance levels were developed.
ZnS:TbOF Thin-Film Green Electroluminescent Panels Fabricated by Two-Target Sputtering
Authors: Okamoto Kenji , Yoshimi Takuya , Nakamura Kimiaki , Kobayashi Tetsuya , Sato Sei , Miura Shoshin
Published: February 2005

We developed a two-target rf-magnetron sputtering system to reproducibly fabricate bright ZnS:TbOF thin-film green electroluminescent panels. ZnS and Tb are sputtered from independent targets, and the substrate moves between these targets. This results in good controllability of both ZnS thickness and Tb doping concentration. To improve luminance, we have developed a TbOF target to form efficient TbOF complex centers, and used an Ar/He mixture to avoid sputtering damage to the ZnS host. We made a prototype 640 × 200 thin-film green electroluminescent panel to demonstrate large-area capability of this system. We also made a multicolor thin-film electroluminescence panel by arranging ZnS:TbOF and ZnS:Mn active layer segments laterally.
Photocurrent-Voltage Characteristics of a Potassium Tantalate Single Crystal
Authors: Yamaichi Eiji , Ohi Kikuo
Published: February 2005

The photocurrent-voltage characteristics of a potassium tantalate(KTaO3) single crystal with electrodes of Pb–Sn alloy were measured. The characteristics obey Ohm's law at room temperature. However, the photocurrent at low bias is limited by the barrier formed at the electrodes at low temperatures, and the characteristics are in good agreement with the calculated results using a model in which the back-to-back Schottky barrier-type junctions are formed on the sample. The diffusion potential V
D increases with the intensity of exciting light and with decreasing of the temperature. These results are explained by the density of the free electrons in photoexcited KTaO3. The photocurrent at low bias increases several times when voltage of over 1 V is applied to the sample. This is explained by the capture of holes in deep traps near the cathode.
Crystal Structure of Proton-Exchanged Layers on Single Crystals of LiNbO3
Authors: Ito Masao , Takei Humihiko
Published: February 2005

The crystal structure of proton-exchanged layers on single-crystal LiNbO3 was analyzed using the X-ray precession method. It was found that the layers were of single crystals, and that the structures varied depending on the orientation of the LiNbO3 wafers: on the (014̄) wafers, an orthorhombic phase appeared, whereas a hexagonal phase was obtained on the Z-cut (001) wafers. This suggests that the exchange reaction proceeds topotactically: protons replace Li ions with small changes in the atomic framework of oxygen and niobium.
A Scanning Total Reflection Method for Refractive-Index Profiling
Authors: Zhu Xiaofan , Iga Kenichi
Published: February 2005

A simple index-distribution measurement method using scanning total reflection (STR) is presented. On the basis of preliminary experiments, its accuracy confirmed to be 0.1% with a spatial resolution of 2 µm. Further considerations show that the theoretical limits of these values can be better than 0.01% and 1 µm, respectively. The results of rod lenses measured by the STR method and the interference method coincided well, and good measurement reproducibility was confirmed. The index profile of a planar microlens was measured and the result was found to coincide with a theoretically predicted result.
Effect of Stray Carriers on the Separation of Electron and Hole Traps in TSC
Authors: Fukase Tadashi , Nie Heng-Yong , Nannichi Yasuo
Published: February 2005

Separation of the electron and hole traps in semi-insulating GaAs by changing the polarity of bias voltage in the thermally stimulated current measurement is done more distinctly when the photo excitation for initialization is confined to the thinned region of the improved specimen, rather than illumination over the whole front surface as previously reported. It was found that this rambling component of the transient current was suppressed by applying an electric field in the order of 103 V/cm.
Field-Effect Study of the Staebler-Wronski Effect in Hydrogenated Amorphous Silicon
Authors: Bautista Ma. Lourdes B. , Enomoto Hiroyuki , Ozaki Hajime
Published: February 2005

The Staebler-Wronski effect (SWE) exhibited by a-Si:H was studied by the field-effect (FE) technique. A new method for the determination of the flat band voltage (V
FB) using the third differential coefficient of the FE curve was proposed. The computer time in the calculation of V
FB was shortened considerably by this method, coupled with the self-consistent method. A peak was observed clearly in the density of states curve just above the Fermi level, and it was found to change reversibly in the cycle of illumination and annealing. This peak was identified via FE measurements as the D- dangling bond states induced from the D0 dangling bond states.
Dependence of Resistivites of Cadmium Telluride on Residual Gas Pressure in Ampoules during Preparation
Authors: Yokota Katsuhiro , Yoshikawa Toshiharu , Inano Sigeru , Katayama Saichi
Published: February 2005

Resistivities of cadmium telluride (CdTe) grown by the Bridgman method varied largely with residual gas pressure in ampoules used for preparation. Spectroscopy of residual gas in the ampoules and measurements of photoluminescences and infrared absorptions for grown CdTe crystals revealed that the resistivity increased as the concentration of oxygen incorporated from the atmosphere into CdTe during preparation decreased.
Surface Morphology and Crystal Structures of As-Grown BiSrCaCuO Thin Films Prepared by RF Magnetron Sputtering from Three Targets
Authors: Kuroda Ken'ichi , Kojima Kazuyoshi , Tanioku Masami , Yokoyama Kazuo , Hamanaka Koichi
Published: February 2005

As-grown superconducting BiSrCaCuO thin films were grown at 650°C on MgO(100) substrates by RF magnetron sputtering from three targets. The substrate was rotated over the three targets: Bi3Sr2Ca2Cu3O
x
, Bi2Sr3Ca3Cu3O
x
and Bi2Sr2Ca2Cu4.5O
x
. By adjusting the staying time of the substrate over each target, it was possible to precisely control the chemical composition of the thin film. This paper describes the superconducting properties, surface morphology and crystal structures of sputtered films formed by varying the staying time. X-ray diffraction measurement showed that the crystal structure could be changed by varying the staying time. The film with the optimum composition showed zero resistivity at 75 K and had an exceedingly smooth surface. This film had the mixed phase which is considered to be a stacked structure consisting of a high-T
c phase and a low-T
c phase.
Equivalence and Accuracy of MOSFET Channel Length Measurement Techniques
Authors: Jain Sanjay
Published: February 2005

It is shown that the MOSFET channel length measurement techniques of Terada and Muta, Peng et al., Whitfield, Suciu and Johnston, and De La Moneda et al. are actually equivalent, i.e. merely different expressions of the same formula for channel length in terms of measured resistance, and that some of the transresistance methods of Jain, although not equivalent, are also related to the same formula. The accuracy of this formula is evaluated for the general case and related to the error components due to source and drain resistance asymmetry, short channel geometry effect, and variation of series resistance with bias. No independent error component due to field-induced mobility degradation is found. Finally the errors in the methods of Terada and Muta, Chen et al., Sheu et al., Wordeman et al. and Jain, are determined and compared. The gate transresistance technique is found to be the most accurate method.
Crystal Structure and Thermal Conductivity of Gd3(Ga1-xAlx)5O12 Garnets
Authors: Kimura Hideo , Numazawa Takenori , Sato Mitsunori , Maeda Hiroshi
Published: February 2005

Single crystals of Gd3(Ga1-x
Al
x
)5O12 garnets with x=0.0, 0.1, 0.2, 0.3 and 0.4 have been grown using the Czochralski method. Crystal structure analysis and thermal conductivity measurement have been performed. Aluminum ions tend to occupy the 16a site with gadolinium ions; the ions are distributed randomly even when x is 0.4. The thermal conductivity is changed with an increase in the x, which is affected by the distribution randomness of the crystal structure.
Liquid Crystal Polarizers with Axially Symmetrical Properties
Authors: Yamaguchi Rumiko , Nose Toshiaki , Sato Susumu
Published: February 2005

Liquid crystal polarizers are prepared by using a common linear polarizer, a nematic liquid crystal and PVA-coated glass substrates. The surface of one substrate is treated for unidirectional molecular orientation and the other substrate is treated for concentrically circular molecular orientation. The liquid crystal cell has axially symmetrical polarization properties, that is, a concentrically circular or radial polarization can be achieved.
Third Harmonic Generation in Precursor Route Poly(p-Phenylene Vinylene)
Authors: Bradley Donal D. C. , Mori Yasushi
Published: February 2005

From third harmonic generation measurements on unoriented thin films and with excitation at 1.064 µm we have determined a third order nonlinear susceptibility χ(3) (-3ω; ω, ω, ω) of 7.5 ×10-11 esu for poly(p-phenylene vinylene) [PPV]. In addition, the effect of increasing π-electron conjugation has been investigated for samples at different stages in the thermal conversion from saturated precursor to fully conjugated polymer. χ(3) increases in magnitude with increasing conversion as is expected for a nonlinearity originating in the conjugated π-electron system.
Optoelectric Characteristics of a-Si/a-SiC Superlattice-Structure Films and Devices Fabricated by the Photo-CVD Method
Authors: Tarui Hisaki , Matsuyama Takao , Okamoto Shingo , Takahama Tuyoshi , Nakamura Noboru , Tsuda Shinya , Nakano Shoichi , Ohnishi Michitoshi , Kuwano Yukinori
Published: February 2005

a-Si/a-SiC superlattice-structure films fabricated by a photo-CVD method were investigated as a wide-bandgap material and applied to window layers of a-Si solar cells. As for carrier transport properties vertical to the interfaces in the dark, I-V characteristics based on tunneling emission and Frenkel-Poole emission were observed with low and high bias voltage regions, respectively. Under illumination of AM-1, 100 mW/cm2, ohmic emission was observed in the same bias voltage region. As for device characteristics, a p/i/n a-Si solar cell whose p-layer was a superlattice-structure was studied. A remarkable increase in the collection efficiency of the cell was found, and it is explained by a calculation by assuming that the superlattice-structure p-layer is an active photogenerating layer. To confirm this, a superlattice-structure p/n diode was fabricated, and it was found that the peak value of the collection efficiency of the diode was five times greater than that of a conventional p/n diode. A conversion efficiency of 11.2% was obtained for a glass/TCO/p-superlattice-structure/i/n/metal a-Si solar cell with p-type doping gas of B(CH3)3.
Formation of As-Grown YBaCuO Thin Films by RF Magnetron Sputtering from Three Targets
Authors: Kuroda Ken'ichi , Kojima Kazuyoshi , Tanioku Masami , Yokoyama Kazuo , Hamanaka Koichi
Published: February 2005

As-grown YBaCuO thin films with 500 Å thickness have been formed at 620°C on MgO(100) substrates by RF magnetron sputtering from three targets: Y1.5Ba2Cu3O
x
, Y1Ba3Cu3O
x
and Y1Ba2Cu4.5O
x
. The chemical composition can be precisely controlled by this method. A smooth surface was obtained by adjusting the chemical composition. Zero resistivity was observed at 81 K for the best superconducting film. The films with a slightly Cu excessive composition showed somewhat higher T
c(zero) than the stoichiometric film. X-ray diffraction spectra of sputtered films did not change distinguishably upon varying of the chemical composition when the value of Ba/Y ranged from 1.5 to 2.3 and the value of Cu/Y ranged from 1.8 to 3.3. The c-axis of the film was highly oriented normal to the substrate surface, and the c-axis lattice constant was equal to that of a bulk sample.
Josephson Junctions with Links of Super-Normal Bilayer
Authors: Takatsu Motomu , Okabe Yoichi
Published: February 2005

Josephson junctions with links of super-normal bilayer are proposed as reproducible Josephson weak links. By an analysis using Ginzburg-Landau equations, the effective coherence length of the super-normal bilayer is estimated to become longer than that of the superconductor. Junctions are fabricated using Nb/Cu bilayers, and exhibit good electrical properties. Critical current dependence on Cu thickness agrees qualitatively with the result of analysis.
InGaAsP/InP Etched Mirror Lasers Fabricated by Inclined RIE
Authors: Saito Hideho , Noguchi Yoshio
Published: February 2005

The results of an etching study on InP crystal by inclined RIE, using TiO2 mask and Cl2-Ar mixture gas, are described. Fabrication of vertical etched facets for lasers and the origins of a fine striation pattern on the vertical etched facet are investigated. Influences on the facet reflectivity of the etched mirror lasers by the facet roughness and inclination are discussed both theoretically and experimentally. InGaAsP/InP lasers with both facets etched were fabricated by inclined RIE. Typical CW threshold currents of these etched-mirror lasers range from 20 to 30 mA at 25°C and the light-output power from one facet exceeds 25 mW. Results of the 6050-h aging test at 50°C and about 5 mW show that InGaAsP/InP etched-mirror lasers can be excepted to be highly reliable.
X-Ray Diffraction and Dielectric Studies on the K2BiNb5O15-K2LaNb5O15 System
Authors: Shimazu Masaji , Tanokura Yasuo , Tsutsumi Sadao
Published: February 2005

Sintered solid solutions in the K2BiNb5O15 (KBIN)-K2LaNb5O15 (KLN) system have been synthesized. The KBIN-KLN system has continuous solid solutions over the whole range, which have the tungsten bronze type of structure with pseudotetragonal symmetry. The a-axis decreases with the increase of La content while the c-axis increases. The Miller indices h
k
l of KBIN in the X-ray powder diffraction pattern have been assigned, and the lattice parameters are a≈b=17.8676 Å and c=7.8451 Å. The temperature dependence of dielectric constant has been observed. The curve of dielectric constant displays a very diffuse maximum at a temperature which corresponds to the ferroelectric transition temperature (T
c). The T
c varies from 372°C (KBIN) to a temperature lower than 0°C (KLN) with the increase of La content.
Production of Metallic Small Particles by Vacuum Evaporation
Authors: Sako Sanshiro
Published: February 2005

A multilayer film of metallic small particles was produced by the alternate evaporation of metal and LiF on a substrate. The process of the production was automatically carried out by the use of a deposition controller which also controlled the sequence of the process in addition to the evaporation rate and film thickness. By several hundreds or thousands of repetitions of alternate evaporations, we can obtain a sufficient amount of small particles to determine their physical properties. This method makes it possible to produce well-defined small particles because the production process under high vacuum suppresses the effect of surface oxidation, and the particle size and particle number density are controlled with high accuracy.
Investigation of a Langmuir Film Using a Current-Measuring Technique: Influence of the Behavior of Monolayers at the Edge of the LB Trough
Authors: Iwamoto Mitsumasa , Majima Yutaka
Published: February 2005

Using a current-measuring technique, we investigated the abrupt change of a current observed at the liquid-to-solid phase transition in a current-area (I-A) isotherm of a fatty acid monolayer at the air/water interface. The change occurred when an electrode suspended in air was not electrically shielded. It was found both experimentally and theoretically that the behavior of the monolayer at the edge of the trough plays a very important role in the abrupt change described above.
Deviation from an Inverse Cosine Dependence of Kinetic Secondary Electron Emission for Angle of Incidence at keV Energy
Authors: Ohya Kaoru , Kawata Jun , Mori Ichiro
Published: February 2005

Incident angle dependence of kinetic secondary electron emission from metals resulting from incidence of keV ions is investigated by computer simulation with the TRIM Monte Carlo program of ion scattering in matter. The results show large deviations from the inverse cosine dependence, which derives from high-energy approximation, because of a series of elastic collisions of incident ions with metal atoms. In the keV energy region, the elastic collisions have two different effects on the angular dependence for relatively high-energy light ions and for low-energy heavy ions: they result in over- and under-inverse-cosine dependences, respectively. The properties are observed even with an experiment of the keV-neutral incidence on a contaminated surface. In addition, the effects of the thin oxide layer and roughness on the surface are examined with simplified models.
A Spin-Frozen Polarized Target of Proton and Deuteron
Authors: Ishimoto Shigeru , Hiramatsu Shigenori , Isagawa Shigeru , Masaike Akira , Morimoto Kimio
Published: February 2005

A spin-frozen polarized target of proton and deuteron was constructed for the measurement of spin dependent parameters of hadron-hadron scatterings at the 12 GeV KEK proton synchrotron. The target was also used for experiments at LAMPF-HRS. As the proton and deuteron targets, 1,2-propanediol and fully deuterated propanediol (D-8) with stable Crv complex (EHBA) were used, respectively. The characteristics and performance of the targets are described. Data on the nuclear spin lattice relaxation time (T
ln) with proton beam give us information on the Kapitza resistance between the target material and liquid 3He/4He mixture.
First Negative Corona Pulses in 70% N2+30%SF6Mixture
Authors: Černák Mirko , Kaneda Teruo , Hosokawa Tatsuzo
Published: February 2005

Waveforms of the first negative corona current pulses in a 70% N2+30% SF6mixture at pressures of 13.33, 26.66 and 40 kPa have been studied as a function of overvoltage ranging from 0 to 100%. Near the corona threshold, the pulses, taking the form of a simple hump, are governed by the secondary electron emission due to a positive-ion impact. At moderate overvoltage, the formation of a double-peaked pulse was observed. This phenomenon can be explained in terms of the effect of photoemission and secondary electron emission. At higher overvoltages, peculiar current waveforms were observed. This phenomenon was explained by the association of the development of a cathode-directed streamer and its interaction with a cathode surface.
Ion Kinetic Effect on Fusion Reaction Rate
Authors: Nishikawa Takeshi , Takabe Hideaki , Mima Kunioki
Published: February 2005

The non-Maxwellian effect of D-T ions in an inertially confined plasma was studied, and it was found that the reduction of the fusion reaction rate due to such a non-Maxwellian effect in the recent high-neutron-yield implosion experiments is not so drastic. Although the nonuniformity effect actually seems to be the main reason for explaining the difference of the neutron yield between the experiment and the 1-D simulation, the difference of a factor of 0.6∼0.7 in neutron yield can be explained by taking account of such a non-Maxwellian effect.
Computer Aided Proximity Effect Correction System in Photolithography
Authors: Hirai Yoshihiko , Nomura Noboru , Misaka Akio , Hayama Shigeru , Yamashita Kazuhiro , Harafuji Kenji
Published: February 2005

Reflected light from step coverage causes fatal pattern defects in photolithography. The resist pattern defects are caused by the extra exposure from the highly reflective stepped substrate, such as breaks in the pattern of the aluminum layer. The problem is significant when the patterns in the different layers are near each other. We named this problem the proximity effect. The specific design rules such as the space between the resist pattern and the steps on the substrate are evaluated by simulation and experiment. Based on the evaluated results, we propose a computer aided proximity effect correction system to verify the pattern layout and eliminate the proximity effect. The effectiveness of the system is confirmed experimentally.
The Effects of Secondary Electrons from a Silion Substrate on SR X-Ray Lithography
Authors: Ogawa Taro , Mochiji Kozo , Soda Yasunari , Kimura Takeshi
Published: February 2005

The effects of secondary electrons from an Si substrate have been investigated quantitatively in SR lithography. It is confirmed that secondary electrons from an Si substrate produce undercuts of 0.1 µm in depth in the replicated resist patterns. The Si KLL Auger electron proves to be the main cause of this problem. This is ascertained through analysis of many kinds of secondary electrons. Moreover, eliminating the wavelength which excites the Si 1s electron from the exposing SR is one promising way to lessen this problem. The resolution of SR lithography is also confirmed to improve to less than 0.1 µm in the practical wavelength, if secondary electrons from the substrate are effectively minimized.
New Evaluation Approach of Alignment Signal from Resist-Coated Patterns
Authors: Kuniyoshi Shinji , Fujimoto Kooji , Kimura Takeshi
Published: February 2005

A new evaluation approach of alignment signals from resist-coated patterns using a linear Fresnel zone plate alignment method is described. In most alignment methods, signals are greatly influenced by resist topography on the target pattern. For calculations of alignment signals, Fraunhofer diffraction from the target pattern and optical path change through the resist materials are considered. In order to determine resist topography on the pattern, a mass transport method is introduced. Based on these results, a target pattern of shallow step depth (0.09 µm) is selected as the best target for alignment, and an alignment accuracy of 0.09 µm (3σ) is obtained.
Focused Ion Beam Lithography with Transition Metal Oxide Resists
Authors: Koshida Nobuyoshi , Ohtaka Koichi , Ando Masanobu , Komuro Masanori , Atoda Nobufumi
Published: February 2005

The microlithographic behavior of inorganic resists for focused ion beam (FIB) has been studied for thin amorphous films of WO3, MoO3, V2O5, a mixture thereof and Ta2O5 using 20∼70 keV Ga+ FIB. The exposure characteristics, composition at the film surfaces and electrical properties have been investigated in order to evaluate the mechanism of the microlithographic behavior. A study of line exposure indicates that the resolution of these resists is determined by the FIB diameter owing to their high contrast. It is also demonstrated that this resist work is directly applicable to fine patterning of W and Mo.
Image Reversal Characteristics of a Novel Silicone-Based Positive Photoresist (SPP) in Near UV Lithography
Authors: Tanaka Akinobu , Ban Hiroshi , Kawai Yoshio
Published: February 2005

The image reversal characteristics of SPP, which is composed of an alkali-soluble silicone polymer (APSQ) and a diazonaphthoquinone photosensitizer, have been studied. The mechanism of SPP image reversal in near UV lithography is the acid-catalyzed condensation of the silanol groups in the APSQ during postexposure baking. SPP is a dual-mode resist which can accommodate both a standard positive resist process and an image reversal process in near UV lithography. The sensitivity is much higher in the latter process.
Effect of the Structure of a Photoactive Compound on the Dissolution Inhibition Effect
Authors: Kishimura Shinji , Yamaguchi Atsumi , Nagata Hitoshi
Published: February 2005

The dependence of the dissolution rate of unexposed resist on the concentration of a developer was investigated using a practical resist composition and its film. From the results, the mechanism of the dissolution inhibition effect was discussed. The lower the average value of esterification of a photoactive compound becomes, the higher the dissolution rate becomes and the larger the dependence of the dissolution inhibition effect on the concentration of the developer becomes. The number of all hydroxyl groups in photoactive compounds plays the main role in the dissolution inhibition effect greater than the influence of the number of all hydroxyl groups in the novolak resin, which are out of the interaction with naphthoquinonediazide sulfonyl moieties in the photoactive compound, i.e., “masking effect”.