bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth of Single Crystals in the Bi-Sr-Ca-Cu-O System Using KCl as a Flux
Authors: Shishido Toetsu , Shindo Daisuke , Ukei Kazutoshi , Sasaki Takahiko , Toyota Naoki , Fukuda Tsuguo
Published: February 2005

Single crystals of Bi2Sr2CaCu2O
x
having good crystallinity were successfully obtained. Nitrates of Bi, Sr, Ca and Cu were used as raw materials. Specially prepared solute calcined at low temperatures (below 500°C) were used with a KCl flux. The solvation of this solute to the KCl flux proceeded very smoothly. Single crystals having smooth surface were extracted from the KCl flux. Fundamental electrical and magnetic properties of the crystals have been investigated.
The Phase Decomposition of YBa2Cu3O6.9 Induced by HIP
Authors: Yamada Yuh , Yata Masanori , Kaieda Yoshinari , Irie Hirosada , Matsumoto Takehiko
Published: February 2005

Phase stability of the high-T
c oxide YBa2Cu3O6.9 (1-2-3 phase) has been studied under the pressure generated by canned HIP at various temperatures. Resistivity measurements in samples hipped at 930°C and 780°C show a degradation of electric properties, for example the broad transition at T
c and the rise in resistivity above T
c. The sample hipped at 830°C exhibits a sharp transition at a T
c of 80 K and low resistivity above T
c. X-ray analysis reveals that the original compound decomposes into the 2-1-1 phase in parts in the former, and into the 1-2-4 and 2-1-1 phases in the latter. This phase decomposition is explained by the rise in oxygen partial pressure during HIP.
Crystalline Phases Formed in the Partially Melted States of Bi-Sr-Ca-Cu-O
Authors: Oka Yoshio , Yamamoto Naoichi , Tomii Yoichi , Kitaguchi Hitoshi , Oda Kiichi , Takada Jun
Published: February 2005

Partially melted states of Bi-Sr-Ca-Cu-O were investigated by SEM-EDX analysis and X-ray measurements on rapidly quenched samples in which the partially melted states were preserved. The 30 Å phase was found to decompose into a Bi-rich liquid phase and crystalline phases of Sr-Ca-Cu-O in the partial melt. The crystalline phases were assigned to Sr1-x
Ca
x
CuO2 (x\fallingdotseq0.5) or (Ca1-x
Sr
x
)2CuO3 (x<0.1) depending on the starting compositions, and the Bi-rich liquid phase led to the 24 Å phase on crystallization.
New Phases in the Ferroelectric Liquid Crystal MHPOBC Studied by Differential Scanning Calorimetry
Authors: Fukui Minoru , Orihara Hiroshi , Yamada Yuichiro , Yamamoto Norio , Ishibashi Yoshihiro
Published: February 2005

Phase transitions of L- and D-enantiomers of 4-(1-methylheptyloxycalbonyl)phenyl 4'-octyloxybiphenyl-4-carboxylate (MHPOBC) were studied by the DSC method. Two new phases have been observed between the smectic A phase and the smectic C
* phase and between the smectic C
* phase and the third stable state (S
Y
* phase) in both L- and D-MHPOBC. The new phases disappear by the introduction of more than 3% D-MHPODC into L-MHPOBC and vice versa. A phase diagram was constructed for the enantiometric mixture of L- and D-MHPOBC.
Alkaline Metal Secondary Batteries Using Poly(2,5-pyridinediyl) as an Active Electrode Material
Authors: Yamamoto Takakazu
Published: February 2005

Poly(2,5-pyridinediyl) film serves as a good active material for positive electrodes of rechargeable polymer batteries, alkaline metal/MX(M=Na, Li; X=PF6, ClO4)/polymer batteries. Use of sodium as the alkaline metal affords an open circuit voltage (OCV) of 2.54 V and the battery shows almost 100% current efficiency. Use of lithium gives an OCV of 2.65 V.
Titanium Carbide Single-Crystal Tips for High-Resolution Scanning Tunneling Microscopy (STM)
Authors: Yata Masanori , Ozaki Motoyoshi , Sakata Shinichi , Yamada Tetsuo , Kohno Akio , Aono Masakazu
Published: February 2005

Titanium carbide (TiC) single-crystal tips that were sharpened by cleavage have been used to observe the atomic images of the cleaved surfaces of graphite in air. The obtained atomic images were essentially the same as those observed by the commonly used tungsten and platinum tips. However, the TiC single-crystal tips were much better than the tungsten and platinum tips in that atomic images of high resolution could almost always be observed. It was also found that the TiC single-crystal tips were resistant to the intentional and accidental touching to samples. This indicates that the TiC single-crystal tips are suitable for mechanical microlithography of materials in the nanometer scale.
Difference between the Face Up and Face to Face Methods in AsH3 Capless Annealing of LEC-GaAs
Authors: Nishitsuji Mitsuru , Hasegawa Fumio
Published: February 2005

In order to determine why the AsH3 capless annealing of ion implanted GaAs does not necessarily yield good reproducibility, conductive LEC-GaAs was annealed in AsH3/H2 flow with face up and face to face configurations. The surface carrier and EL2 concentrations decreased extensively when the wafer was annealed in the face up configuration, whereas they did not decrease for the face to face configuration. We found that a deep acceptor level, called HL2 or LPE-B, was introduced at the surface when the wafer was annealed in the face up configuration, even if a sufficient amount of As partial pressure was supplied. The introduction of this hole trap was more enhanced for an annealing in H2 than in Ar.
Resistive Transition in Magnetic Fields for a Single Crystal of a Tl-Ba-Ca-Cu-O Superconductor
Authors: Togano Kazumasa , Kumakura Hiroaki , Mukaida Hiromi , Kawaguchi Kenichi , Nakao Masao
Published: February 2005

Resistivity-versus-temperature curves are measured for the single crystal of a Tl-Ba-Ca-Cu-O superconductor in applied magnetic fields up to 12T. The resistive superconducting transition broadens extremely in the field perpendicular to the c-plane. The anisotropic factor of H
c2 is ∼4. The resistivity shows an exponential temperature dependence in the lower resistivity region, suggesting the occurrence of a thermally activated flux motion.
Improving Superconducting Characteristics of Tl-Sr-Ca-Cu-O by Doping with Pb and/or Rare-Earth Elements
Authors: Nagashima Toshio , Watahiki Masaya , Fukai Yuh
Published: February 2005

We have investigated the effects of doping Pb and/or rare-earth elements on the T
c of Tl-Sr-Ca-Cu-O. Depending on the amount of Pb doped, at least two superconducting phases were formed: the 1223 and 1212 phase having a T
c of 100 K and 60 K, respectively. The 1223 phase is stabilized by doping and increased in volume by annealing at 550°C. In the case of the rare-earth-doped one, the 1212 phase is stabilized and has a T
c of about 90 K. We also investigated the case of samples doped with both Pb and rare-earth elements. A nominal composition of Tl0.7Pb0.3La0.3SrCaCu1.8O
y
has a T
c of above 100 K, which is the highest of materials with 2-CuO2 layers.
Diffusion Bonding of Y-Ba-Cu-O High-Tc Superconductors
Authors: Mutoh Yoshiharu , Ebihara Takashi , Aizawa Takeshi
Published: February 2005

Diffusion bonding of Y-Ba-Cu-O ceramics without insert materials was accomplished under the conditions in which bonding temperatures ranged from 1173 K to 1223 K and bonding times were longer than 4 h. It resulted in T
c and shear strength of the bonded joints which were almost identical to those of the bulk.
Structure and Superconducting Properties of Bi-Sr-Ca-Cu-O Thin Films Annealed at Low Temperatures
Authors: Matsushima Tomoaki , Hirochi Kumiko , Adachi Hideaki , Setsune Kentaro , Wasa Kiyotaka
Published: February 2005

Thin films of the Bi-Sr-Ca-Cu-O system were prepared at substrate temperatures between 550°C and 600°C. The film deposited at 570°C showed an X-ray diffraction pattern of the high-T
c phase without other phases and had a zero-resistance temperature T
c at 23 K. After annealing at 570°C under the oxygen pressure of 1 atm, the zero-resistance T
c increased to 47 K, but under the pressure of 0.1 atm, the crystal structure was changed and Ca-Cu-O phase appeared. On as-deposited films prepared by a low-temperature process, structure and superconducting properties are easily affected by low-temperature postannealing.
Fabrication of Bi(Pb)SrCaCuO Thin Film of High-Tc Phase
Authors: Yotsuya Tsutom , Suzuki Yoshihiko , Ogawa Soichi , Imokawa Hirofumi , Yoshikawa Masahiro , Naito Makio , Takahata Ryoichi , Otani Kohei
Published: February 2005

Lead-added Bi-Sr-Ca-Cu-O (BSCCO) thin film of high-T
c phase has been successfully prepared by means of rf-magnetron sputtering and the post annealing process. The content of lead in the BSCCO thin film was decreased during an ordinary annealing process. In order to minimize the decrease of lead, the BSCCO thin film was placed on a bulk ceramics whose composition was similar to that of the film, and annealed for 50 hours at 855°C in air. As the result, the content of lead in the thin film was almost unchanged during the annealing process. The intensity ratio of the X-ray diffraction lines due to the (002) of high and low-T
c phases was about 4/1. The film showed a superconducting transition at 110 K; a long tail of some residual resistance remained down to 90 K.
C-Axis Lattice Spacing Control of As-Grown Bi-Sr-Ca-Cu-O Thin Films by Single-Target Excimer Laser Ablation
Authors: Ohya Seishiro , Kobayashi Ken , Hirabayashi Yasuo , Kurihara Yukio , Karasawa Shiro
Published: February 2005

As-grown c-axis-oriented thin films of Bi-Sr-Ca-Cu-O on MgO(100) substrates were prepared by simultaneous deposition using the pulsed excimer laser ablation technique. The c-axis spacing of lattice planes could be controlled by the variation of Ca and Cu contents using simultaneous deposition with single targets. As Ca and Cu contents increased, the peaks of the X-ray diffraction pattern approached that of (Ca0.86Sr0.14)CuO2; the n=∞ parent of the Bi2Sr2Ca
n-1Cu
n
O
y
superconductors with a lattice constant, 3.1995 Å, of the c-axis. After postannealing, films with T
c,end over 100 K were obtained.
Application of Reflectance Difference Spectroscopy (RDS) to Migration-Enhanced Epitaxy (MEE) Growth of GaAs
Authors: Briones Fernando , Horikoshi Yoshiji
Published: February 2005

Differences in the reflectance of light polarized along the [110] and [11̄0] directions of the (001) GaAs surface are detected with a simple optical setup and used as an in-situ analysis and control tool for migration-enhanced epitaxial growth. The reflectance difference (RD) signals during successive surface exposures to Ga and As4 beams at various substrate temperatures are analyzed and correlated to the surface reconstruction and the fractional surface coverage, on the basis of current models of the (001) GaAs surface and nucleation of Ga–Ga dimers. A new negative component of the RD signal is tentatively attributed to Ga nucleation and accumulation along [110] terrace edges. Finally, RD periodic signal analysis during a stationary MEE growth process is used to determine the most appropriate growth conditions.
Preparation of µc-Si:H/a-Si:H Multilayers and Their Optoelectric Properties
Authors: Nakata Masami , Shirai Hajime , Namikawa Tatsuru , Shimizu Isamu
Published: February 2005

A layered structure consisting of alternate sublayers of µc-Si:H and a-Si:H was fabricated by means of plasma enhanced CVD from fluorinated precursors, SiH
n
F
m
(n+m≤3), under the condition modified periodically by the addition of SiH
n
as an amorphousizing agent. The structure with repeated layers of 75 Å or less in thickness was confirmed by small-angle X-ray diffraction. High photoconductivity equivalent to that of a-Si:H was maintained in the layered structures in the period of 75 Å or less despite the marked increase in optical absorption in the near-IR region of 1.0 eV–1.5 eV resulting from the optical absorption of the µc-Si:H layers.
The Core-Shell Grain Resistance in the Reduced La-Doped (Ba, Sr)TiO3 Ceramics
Authors: Ho In-Chyuan , Fu Shen-Li
Published: February 2005

Based on the oxygen-vacancy diffusion, a core-shell model of grain resistance is proposed, for the reduced La-doped (Ba, Sr)TiO3 ceramics, to describe the charge-carrier distribution. Complex impedance analysis is adopted to determine the grain resistance and grain boundary resistance. After sintering at 1400°C in reducing atmosphere, the low grain resistance is attributed to the effective electron compensation in the grain core, while the higher grain boundary resistance is thought to be due to the lower charge-carrier concentration in the grain shell. In addition, reoxidation leads to further decrease of charge-carrier concentration on the grain shell by diffusing inward to the grain core.
DLTS Measurement on Electron-Irradiated GaAs-on-Si
Authors: Okamoto Hiroshi , Oh'hara Takahiko , Kadota Yoshiaki , Ohmachi Yoshiro
Published: February 2005

Three electron traps, E3*, E4*, and E5*, are observed in 1 MeV-electron-irradiated GaAs-on-Si by using DLTS measurement. The characteristics of these traps are similar to those of E3, E4, and E5 in irradiated GaAs-on-GaAs. The slightly lower activation energies and broader DLTS peaks of the traps in GaAs-on-Si than those in GaAs-on-GaAs might be caused by band-gap decrease and valence-band splitting of biaxially strained GaAs on Si.
Formation of As-Grown BiSrCaCuO Thin Films by Sputtering Three Targets Heavily Doped with Pb in Atmospheres of O2 and N2O/O2 Mixtures
Authors: Kuroda Ken'ichi , Kojima Kazuyoshi , Tanioku Masami , Yokoyama Kazuo , Kuroki Hiroshi , Hamanaka Koichi
Published: February 2005

As-grown BiSrCaCuO thin films have been formed on MgO(100) substrates at various temperatures by RF magnetron sputtering from three targets in atmospheres of neat O2 and N2O/O2 mixtures (1:1). The three targets had slightly different compositions heavily doped with Pb: Bi3Pb3Sr2Ca2Cu3O
x
, Bi2Pb2Sr3Ca3Cu3O
x
and Bi2Pb2Sr2Ca2Cu4.5O
x
. Both films formed in O2 and N2O/O2 mixtures at 660°C showed zero resistivity at 77–78 K. A film obtained at 540°C by N2O/O2 mixtures showed superconductivity, while a film obtained at the same substrate temperature by neat O2 did not.
Gas mixtures of N2O and O2 used instead of neat O2 as a sputtering gas were effective in lowering the growth temperature by 20–40 degrees.
Unique Method of Patterning Superconducting Thin Films by Selective Growth of Y–Ba–Cu–O
Authors: Hatano Toshikazu , Fujimaki Akira , Takai Yoshiaki , Hayakawa Hisao
Published: February 2005

A new method of patterning superconducting thin films by the selective growth of YBaCuO has been developed. Films deposited on MgO substrates are superconductive, while films on SiO2 films have the insulative properties. The results of X-ray diffraction and Auger electron spectroscopy analyses show that the insulative properties are due to the intermixing of YBaCuO films and SiO2 films. A superconducting line of 15 µm wide has the transition temperature of zero resistance at 72 K and the critical current density of 3.26×106 A/cm2 at 4.2 K.
Microwave Detector Using Granular-Type YBCO Superconductors
Authors: Yoshisato Yorinobu , Takeoka Akio , Ikemachi Takaaki , Niki Kazuya , Yokoo Toshiaki , Nakano Shoichi , Kuwano Yukinori
Published: February 2005

A highly sensitive microwave detector has been developed for the first time by granular-type bulk YBCO superconductors with fine particles. Particles with a size of about 1 µm, having a SNS-like grain boundary, were controlled by a coprecipitation method, followed by a sintering process. A new fabrication method for bulk superconductors was also developed to produce a precise microbridge-type structure. Sensitivity to microwave power below -40 dBm was obtained, and a direct mixing effect was obtained at a frequency of 8.6 GHz at the temperature of 77 K. It was confirmed that the Josephson effect of the detector at the SNS grain boundary formed in the sintering process for ceramics is the most responsive for microwave detection.
Enhanced Dislocation Mobility by Electron-Beam Irradiation in GaP
Authors: Maeda Narihiko , Takeuchi Shin
Published: February 2005

Mobility of α-dislocations under stress in Te-doped n-GaP has been measured by cathodoluminescence microscopy at high temperatures. The mobility is remarkably enhanced by electron-beam irradiation. The activation energy of the dislocation velocity without irradiation is 1.48 eV, while that under the electron-beam irradiation is only 0.37 eV.
Impurity and Defect Center Concentrations in High-Purity Quartz: Their Change Processes by Sweeping and Irradiation
Authors: Shimoda Yoshio , Uno Takehiko
Published: February 2005

Effects of sweeping (electrodiffusion) and radiation on high-purity quartz are investigated, focusing on changes in impurity and defect center concentrations. The quantitative correlation between impurity and defect centers is estimated. Sweeping replaces Al–M (M=Na, Li, or K) centers with Al–OH centers by dissociating alkali ions in Al–M centers. The Al–OH center is produced initially at the anode and proceeds to the cathode. The relationship between the Al–OH formation process and the alkali ion migration process is consistent, as confirmed by their distribution measurements in several swept samples. It is confirmed that the number of removed alkali ions corresponds to the concentration of Al–M centers dissociated by sweeping. Removed alkali ions are both sodium and lithium. Irradiation produces not only Al–OH centers but also Al–h centers. However, the Al–h concentration is far smaller than the Al–OH concentration.
Efficiency of Current Drive by Pulsed Injection of REB
Authors: Michishita Toshinori
Published: February 2005

A simple analysis based on a relativistic kinetic equation for REB dynamics combined with a set of circuit equations is performed for evaluating the efficiency of a current drive by a pulsed REB. A two-dimensional numerical result is given for the efficiency as wells as for the temporal evolutions of the REB momentum distribution function and the circuit quantities. A comparison of the numerical result with the analytical limit for efficiency is given. Optimization for the REB current drive in a reactor-grade tokamak is discussed.
Nickel/Vanadium and Nickel/Titanium Multilayers for X-Ray Optics
Authors: Nagata Hiroshi
Published: February 2005

Ni/V and Ni/Ti multilayers with 3–10 nm layer periods and 8 or 32 layer pairs were deposited with rf sputtering, and examined by X-ray diffraction and transmission electron microscopy(TEM). The increase of X-ray diffraction peak numbers proved that the sharper interfaces were formed under lower Ar pressure, and the estimated interfacial roughness for multilayers deposited at 2.1 Pa was 0.55 nm. The microcrystalline structure was observed by TEM in the Ni layer, and seemed to dominate the residual interfacial roughness.
Resolution Function and Recent Developments of the Multi-Analyser Crystal Spectrometer MAX
Authors: Todate Yoshiei , Tajima Keisuke , Ikeda Hironobu , Tomiyoshi Shoichi
Published: February 2005

The multi-analyser crystal spectrometer (MAX) installed at KENS has the unique capability of measuring collective excitations in single crystal samples with the time-of-flight method. We report the recent developments as well as the resolution function formulation of the spectrometer. The important characteristics of MAX which are useful in understanding the ability of the spectrometer are also described.
Oxide Resistance Characterization in MOS Structures by the Voltage Decay Method
Authors: Hwu Jenn-Gwo , Ho I-Hsiu
Published: February 2005

The resistances of the gate oxides in MOS structures are determined based on the voltage decay method proposed in this work. This method provides nondestructive measurement of the oxide. The oxide resistance obtained by this method can be as high as 1014 ohms. Also, the unreliability of the data obtained by the conventional method, i.e., by dividing the applied voltage by the measured current, is compared. It is found that samples having the same initial C-V behavior can show significant differences in their oxide resistances. The one having a high oxide resistance can sustain a higher breakdown voltage than that having a low oxide resistance. A possible mechanism of the oxide resistance and the usability of the voltage decay method are also discussed.
Highly Uniform Si-Doped GaAs Epitaxial Layers Grown by MBE Using a TEG, Arsenic, and Silicon System
Authors: Ono Katsuji , Saito Junji , Nanbu Kazuo , Kondo Kazuo
Published: February 2005

We studied the lateral thickness uniformity and carrier concentration in 3-inch Si-doped epitaxial layers grown by gassource MBE using triethylgallium, arsenic, and silicon. A variation in thickness and carrier concentration of ±1% over a 70-mm diameter was obtained by rotating the substrate. We proved that the thickness distribution depends primarily on the angular distribution of TEG molecules, as with the metal gallium source.
Effects of H2 and CO Additives on the O2 Accumulation in the TEA CO2 Laser
Authors: Uchida Yutaka , Oukuma Shinji , Sato Saburo , Goto Tatsumi
Published: February 2005

A change in gas mixture in a sealed-off TEA CO2 laser discharge was analyzed gas-chromatographically. It has been found that the addition of a small amount of H2 and CO will reduce the O2 formation in the mixture. In particular, when a mixture of N2:CO2:CO:H2:He=12:12:6:1.6:68.4% was used, a sealed-operation lifetime exceeding 5 × 105 shots without any oxygen formation was obtained. However, it has also been found that CO2 was decomposed by discharge and formed O2 was missing. No nitrogen oxide formation was recognized, implying that the missing oxygen was dissipated to some other reactions. Furthermore, notable differences in the change in the electrode surface, with addition of CO or H2 to the mixture, were recognized by visual observation. Hence, we proposed electrode surface reactions for the reduction in the O2 formation in the mixture.
Effect of Drawing on Ferroelectricity in Vinylidenefluoride-Trifluoroethylene-Hexafluoroacetone Copolymer
Authors: Maeda Kazuhiko , Tasaka Shigeru , Inagaki Norihiro
Published: February 2005

The ferroelectricity of drawn and undrawn vinylidenefluoride-trifluoroethylene-hexafluoroacetone (VDF-TrFE-HFA) copolymer was compared with that of P(VDF-TrFE) by differential scanning calorimetry, X-ray diffraction and dielectric constant. In the undrawn samples with identical VDF/TrFE composition, the Curie temperature (T
c) was independent of the presence of a HFA unit. However, the T
c of drawn P(VDF-TrFE-HFA) with 9 mol% of HFA content shifted to a temperature lower than 10°C. It was shown that a particular molecular reorganization was produced by drawing to form the ferroelectric crystal involving the HFA unit.
Electrical Conduction in Heat-Resistive Polyparabanic Acid (PPA) Films at High Temperatures
Authors: Miyairi Keiichi
Published: February 2005

The electrical conduction in PPA films was measured in the temperature range of 373-453 K. From the results of temperature, thickness, electrode material and voltage dependences, ionic conduction was proposed. Significant influence of the chemical structure on electrical conduction was observed. The jump distance changed with the chemical structure, while the potential barrier remained constant.
Structure of Crosslinked Poly(vinylidene Fluoride) Crystallized from Melt under Uniaxial Compression
Authors: Nabata Yoshiyuki
Published: February 2005

Crosslinked poly(vinylidene fluoride) (PVDF) of gel fractions from 0.17 to 0.85 was crystallized from melt under uniaxial compression at various compression ratios (C
R). The structure of the samples was studied by X-ray diffraction methods. The PVDF composed of form I and II crystals was obtained by this crystallization method. At the same time, orientation of the particular crystal planes of forms I and II parallel to the film plane appeared. The amount of form I and the degree of orientation increased with increasing C
R. In PVDF with a gel fraction of about 0.7, films mainly composed of form I crystals were obtained under high C
R.
Determination of Rate Controlling Step in CVD Processes with Gas Phase and Surface Reactions
Authors: Desu Seshu. B. , Kalidindi Surya R.
Published: February 2005

An analytical model incorporating the individual effects of gas phase and surface reactions in CVD processes is presented. It is shown that the rate controlling step in the CVD process can be determined from the trends exhibited by the deposition rate profiles. This is an important step in the optimization scheme to obtain the most uniform deposition profile. The results are first derived for a highly idealised simple CVD process with a single gas phase reaction and a single surface reaction. It is shown that despite these assumptions, the predictions work well for real CVD system such as pyrolysis of tetraethoxysilane.
A Useful Method for the Determination of the Total Electron Scattering Cross Section
Authors: Nishimura Hiroyuki , Sakae Takeji
Published: February 2005

A compact linear electron transmission apparatus has been constructed for the measurement of the total electron-scattering cross section for various atoms and molecules. The transmitted electrons are analyzed without a retarding potential. The effective scattering path length of electrons in the apparatus can be evaluated from measured currents. As a test of this method, the total electron-scattering cross section for CH4 has been measured in the energy range between 5 and 500 eV with a statistical uncertainty ≤5% for electrons below 250 eV and ≤7% for electrons above 250 eV. The results show E
-1/2 dependence at lower energies and a steeper decline at higher energies.
The Effect on Turn-On Voltage (VBE) of AlGaAs/GaAs HBT's due to the Structure of the Emitter-Base Heterojunction
Authors: Kusano Chushirou , Masuda Hiroshi , Mochizuki Kazuhiro , Kawada Masahiko , Mitani Katsuhiko
Published: February 2005

The effects on the turn-on voltage (VBE) of collector current in AlGaAs/GaAs HBT's due to Be diffusion and discontinuity in the conduction band are investigated. It is clarified that V
BE increases significantly with the decrease in saturation current due to Be diffusion into the AlGaAs emitter during MBE growth. It is also found that the V
BE's of HBT's with Al compositionally abrupt and graded emitter-base junctions and homojunction GaAs bipolar transistors are the same. These results indicate that the spike-like potential barrier at the heterojunction has no influence on the electron injection from emitter to base.
Characterization of GaAs and AlGaAs Layers Grown by Laser Atomic Layer Epitaxy
Authors: Miyoshi Tadaki , Iwai Sohachi , Iimura Yasufumi , Aoyagi Yoshinobu , Namba Susumu
Published: February 2005

Raman spectra were measured at 300 K to characterize GaAs and AlGaAs layers grown by laser atomic layer epitaxy. The quality of the GaAs patterned layer grown by laser scanning was uniform in spite of the laser intensity profile. The molar fraction of Al in the peripheral region of the AlGaAs layer is affected by the intensity profile of the laser beam.
Effect of Residual Strain on the Splitting of Excitonic Luminescence Lines in Epitaxially Grown ZnSe/GaAs
Authors: Ohishi Masakazu , Saito Hiroshi , Fujiwara Jun-ichi , Ohmori Kenzo
Published: February 2005

Polarization characteristics for excitonic luminescence lines of epitaxially grown ZnSe on GaAs demonstrate the splitting of the neutral donor-bound exciton as well as the free exciton due to the residual strain in the epilayer. The strain is interpreted well by the misfit of the calculated lattice constants between ZnSe and GaAs.
The Growth Mechanism of Diamond Crystals in Acetylene Flames
Authors: Matsui Yasuji , Yabe Hideki , Hirose Yoichi
Published: February 2005

To discuss the diamond growth mechanism in acetylene flames, numerical calculations are carried out, including both gaseous reactions in the boundary layer near a water-cooled substrate and overall surface reactions on a growing crystal. It is shown that stable species such as CH4 and C2H4 are rapidly produced in the layer, followed by the methyl radical formation according to the fast partial equilibrium of the reaction, CH4+H\rightleftarrowsCH3+H2. The comparison between the calculated and the measured CH4 concentrations upon the substrate has revealed that C-radicals adsorbed on the diamond surface are etched by H-atoms to form CH4, though the surface reactions do not have a significant effect on the gaseous concentrations. The dependences of the growth rate both on the substrate temperature and on the C2H2/O2 ratio are shown to be explainable by the CH3-precursor model.
Theoretical Analysis of a-Si:H Based Multilayer Structure Thin Film Transistors
Authors: Reita C. , Mariucci L. , Fortunato G.
Published: February 2005

In this paper we show that the experimentally observed increase in the field-effect mobility in superlattice TFTs can be accounted for by a simple classical model based on Poisson's equation, including the presence of interface states at every interface. The field-effect mobility enhancement is a direct consequence of the different potential and electric field distibutions among the various layers, if compared with a single layer structure with the same total active layer thickness. The results of the calculations fit well experimental data already reported. Furthermore, the analysis of the single layer structure shows a similar field-effect mobility enhancement, suggesting the reduction of the active layer thickness as a key factor.
Characterization of Distributed-Threshold-Voltage Transistors with Amorphous-Silicon
Authors: Berkel Cees van , Matsumura Masakiyo
Published: February 2005

Experimental characteristics have been presented for an `original' distributed-threshold-voltage thin-film transistor that features a reduced hole current and a very low minimum off-current, even at elevated temperatures. These properties are the result of an engineered change in the sheet conductivity along the channel which is characterized by a distribution in threshold voltage. This distribution is controlled in this paper by using a resistive gate and an offset voltage applied between both ends of the gate. The device characteristics are studied as a function of this offset voltage. The results show good agreement with theory for moderate gate voltage.
Elastic Recoil Detection Analysis of the Concentration and Thermal Release of Hydrogen in a-Si:H Films by the ECR Plasma CVD Method
Authors: Umezawa Kenji , Shoji Fumiya , Hanawa Teruo , Oura Kenjiro
Published: February 2005

For the a-Si:H films prepared by ECR plasma CVD, the hydrogen content and its variation associated with heat treatment have been studied by means of 6.06 MeV-19F-ERDA. It was found that as the deposition temperature was elevated from room temperature(RT) to 573 K, the hydrogen content in the film abruptly decreased. The activation energy for detrapping was estimated to be 0.84±0.02 eV for the Si-H bonds of two films prepared at RT and at 573 K. For a film prepared on a 5-in.-diameter Si wafer at RT, the film thickness was uniform in the error range of ±3% within the distance from the center to the edge of the wafer, while the hydrogen content fluctuated over the range of 20% near the edge.
Deposition of Y-Ba-Cu-O Thin Films by RF Magnetron Sputtering with a Grid Electrode: Plasma Parameters
Authors: Takai Yoshiaki , Takechi Kazushige , Inoue Masumi , Hayakawa Hisao
Published: February 2005

Sputtering conditions of Y-Ba-Cu-O films with a grid electrode were discussed from the measurements of plasma parameters. A grounded grid electrode and a suitable negative substrate bias voltage were effective for the growth of oxide superconductors especially at a lower substrate temperature around 550°C. These conditions reduced the density of high-energy charged particles near the substrate and also de-energized those particles. The grid electrode was still effective at a relatively high gas pressure above 10 Pa, although a slight modification was required for the grid configuration.
Electroless Cobalt Alloy Perpendicular Anisotropy Films Plated from a Simplified Malonate Bath
Authors: Homma Takayuki , Saito Keiichi , Osaka Tetsuya
Published: February 2005

The electroless-plated Co alloy films for perpendicular magnetic recording were prepared from a newly developed plating bath with simplified composition, and their magnetic and structural properties were investigated. The composition of the films changed with varying cobalt sulfate concentration in the plating bath. The films containing 10-30 at% of Co in deposits, which show high crystallinity and crystal orientation, have perpendicular magnetic anisotropy. Among them, the Co-24 at% film shows the largest perpendicular magnetic anisotropy. The film consists of hcp crystallites whose <002> axis orients perpendicular to the film plane, showing high crystallinity and the crystal orientation from the initial deposition stage with a thickness of 20 nm. It was confirmed that the films for the use of highly functional devices can be fabricated from the electroless-plating bath with simplified composition.
Very Short Electrical Pulse Generation by a Composite Planar GaAs Photodetector
Authors: Kamiyama Hiroyuki , Kobayashi Yuzuru , Nagatsuma Tadao , Kamiya Takeshi
Published: February 2005

Combining two metal-semiconductor-metal Schottky barrier photodiodes (MSM-PDs) monolithically, a composite photodetector is fabricated on a semi-insulating GaAs substrate. Upon illuminating each of them with subpicosecond optical pulses, electrical pulses with full width at half maximum (FWHM) less than 30 ps are generated. Delay time dependence of the waveform is investigated both experimentally and theoretically based on a dynamic equivalent circuit model.
Ionic Thermocurrent Measurements Following Different Schemes of Heating
Authors: Prakash Jai , Nishad A. K.
Published: February 2005

Equations for the depolarization current recorded following linear, reciprocal, quadratic and square root schemes of heating in ionic thermocurrent measurements have been derived. Methods for the evaluation of the dielectric relaxation parameters following the proposed schemes of heating have also been developed.
Determination of Capacitances and Conductances of the Constituent Phases from Dielectric Observations on Terlamellar Composite Systems
Authors: Kiyohara Kenji , Zhao Kongshuang , Asaka Kinzi , Hanai Tetsuya
Published: February 2005

A method of numerical calculation was proposed to derive the electrical capacitances and conductances of three constituent phases from observed dielectric parameters characteristic of the double relaxation pattern exhibited by a terlamellar composite system. Secondly, numerical estimation was carried out on the errors of capacitances and conductances of the constituent phases arising from misestimation of the observed dielectric parameters. Finally, dielectric measurements were made on a composite system where a Teflon film was sandwiched between two aqueous solutions. Reasonable values of the capacitances and the conductances of the three constituent phases were obtained by applying the method proposed. The present method may be of use for the evaluation of material separation films.
Study on the Light Scattering Mechanism at Precipitates on Dislocation Lines in an Indium Doped GaAs Crystal
Authors: Sakai Kazufumi , Ogawa Tomoya
Published: February 2005

The light intensities scattered from the precipitates on dislocations in an In-doped GaAs crystal were measured as a function of the temperature with three different frequencies of lasers. The scattered intensity showed a few peaks from 30 K to 260 K depending upon the wave length of the incident beams. The temperature dependence of resonance frequencies was obtained by Ogawa's resonance scattering model (R.S.M.) and compared with the experimental result.
Infrared Reflection Absorption in Vacuum-Deposited Polyethylene Film with Rough Surface
Authors: Maki Kunisuke , Kikuma Kazuhiro , Suzuki Yasushi
Published: February 2005

The thickness dependence of infrared reflection absorption (IR-RAS) is studied for vacuum-evaporated polyethylene(PE) film for an area 2 cm in diameter. The p-component of the intensity in IR RAS, I

A
P
, ls proportional to the thickness, d, as predicted theoretically when p-polarized infrared rays are incident at an angle of 70° . The s-component, I

A
S
, is also detected when s-polarized rays are incident although it is given numerically that I

A
S
is too small to detect. In particular, the amount of I

A
S
increases dramatically for the film with the rougher surface. For such film, the s-component also becomes large when p-polarized rays are incident. This means that the film is not optically homogeneous or isotropic. The usefulness of determining the thickness dependence of I

A
P
for thin film growth of polymeric materials is also discussed.
Radio Frequency Effect on the Ion Saturation Current
Authors: Rapozo Cândido da Cunha , Carneiro Lindolff Thadeu
Published: February 2005

We show analytically and experimentally that Bohm's theory on plasma probes can be modified to take into account the effect of the applied RF voltage on the ion saturation current. The experiment has been carried out in the mirror linear device LISA of the Universidade Federal Fluminense, where a helium low-density plasma has been produced by a radio-frequency source built at UFF with a power of 100 watts and a frequency of 28 MHz.
Analytic Expressions of Magnetic Multipole Field Generated by a Row of Permanent Magnets
Authors: Nihei Hitoshi
Published: February 2005

Analytic expressions of a magnetic multipole field generated by a row of permanent magnets which are arranged on a same plane have been obtained. Each magnet is replaced by two sheet currents flowing in opposite directions through each side of the magnet. The results have been compared with measured values and both have been in good agreement. These expressions are simple and very convenient for design of a plasma source surrounded by magnetic multipole fields.
Channeling Radiation from 1 MeV Electrons
Authors: Matsuhata Hirofumi , Kamiya Yoshihiro , Kajii Shinji , Fujimoto Fuminori , Komaki Ken-ichiro , Nakanishi Tsutomu , Horikawa Naoaki , Fukui Shuji , Gao Chan Ye
Published: February 2005

Channeling radiation from relativistic electrons channeled <111> zone axis of the germanium single crystal is measured by using 1 MeV electron microscope. The energy of channeling radiations is accordance with the theoretical results although the intensity of X-rays is weak.
Sub-Halfmicron Lithography Using a High-Contrast i-Line CEL
Authors: Tanaka Toshihiko , Uchino Shouichi , Hashimoto Michiaki , Hasegawa Norio , Fukuda Hiroshi , Okazaki Shinji
Published: February 2005

A newly developed, metal-free, water soluble i-line CEL and its patterning features are described. A, B and C parameters of CEL are 18 µm-1, 0.12 µm-1, and 0.09 cm2/mJ, respectively. CEL changes the γ value from 3 to 20. This CEL material makes patterns with an aerial image contrast of 0.4 possible. This result suggests that 0.3 µm microfabrication is possible with an i-line lithography that has a high numerical aperture lens.
Vacancy-Type Defects in As+-Implanted SiO2(43 nm)/Si Proved with Slow Positrons
Authors: Uedono Akira , Tanigawa Shoichiro , Sugiura Jun , Ogasawara Makoto
Published: February 2005

Variable-energy positron-beam studies have been made on 150-keV As+-implanted SiO2(43 nm)/Si specimens. From measurements of Doppler braodening profiles of the positron annihilation as a function of incident positron energy, it was found that the region of vacancy-type defects induced by As+-implantation extends far beyond the As-stopping profile. The dominant defect species was identified as a divacancy from the characteristic value of the line-shape parameter. The defect concentration of the damaged region for the specimens with the doses of 5×1014∼5×1015 As/cm2 was estimated as 1×1021 cm-3. The effect of isochronal annealing is also discussed.
Mechanical and Superconducting Properties of Ag/YBCO Composite Superconductors Reinforced by the Addition of Zr
Authors: Oka Tetsuo , Ogasawara Fumihiko , Itoh Yoshitaka , Suganuma Motohiro , Mizutani Uichiro
Published: February 2005

The composite high T
C superconductor Ag/YBCO reinforced by adding Zr has been synthesized by sintering a compressed mixture of Zr
x
YBa2Cu3O7-δ(0≤x≤1.0) and Ag powders at various ratios. The flexural strength in the Ag/ZYBCO reached its maximum value of 280 MPa at the composition x=0.8 and 33 vol.%Ag, being more than 5 times as large as that in the sintered YBCO. In addition, the presence of Ag can endow the plasticity while maintaining the superconducting transition temperature above about 80 K. Both the flexural strength and the Vickers hardness are enhanced in magnitude comparable to those for commercial alumina and magnesia. The enhanced mechanical strength is attributed to the unique microstructure, in which dispersed Ag particles remain intact with the Zr-bearing YBCO matrix, whereas CuO and BaZrO3 precipitates in the 123-phase matrix act to reinforce the ceramic without disrupting the superconducting channel.
Self-Aligned Ridge-Waveguide DFB Lasers Emitting at 1.55 µm: Ridge-Width Dependence
Authors: Sato Kenji , Kano Fumiyoshi , Kondo Yasuhiro
Published: February 2005

Self-aligned ridge-waveguide (SA-RG) DFB lasers emitting at 1.55 µm have been fabricated utilizing the MOVPE growth technique and a self-aligning process. The ridge-width dependence of the threshold current and the optical lateral mode is investigated. Ridge-waveguide lasers with a thin active layer of 0.1 µm for low threshold current provide sufficient index guiding. The fabricated SA-RG DFB laser has a threshold current of as low as 29 mA. The threshold current density increases as the ridge width becomes narrower than 10 µm. This is explained by the electron diffusion in the active layer and the diffusion length is experimentally estimated to be 2–5 µm. The measured far-field pattern parallel to the junction shows a single-lobe pattern at a ridge width of less than 10 µm.
Optical Recording Characteristics of Dye/Polymer Systems
Authors: Matsuzawa Nobuyuki , Tamura Shin-ichiro , Seto Jun'etsu
Published: February 2005

The influence of the molten polymer properties on the optical recording sensitivity was examined for cyanine dye/polymer systems. We obtained a linear relationship between the recording sensitivity and the surface entropy of the binder polymers and found that the non-Newtonian flow induced by the surface entropy is responsible for pit formation by laser marking.
New Liquid Crystal Polarized Color Projection Principle
Authors: Schadt Martin , Fünfschilling Jürg
Published: February 2005

A wide-aperture, color projection principle is presented whose functional parts, namely, polarizers, bandpass filters and electrooptical modulators, consist entirely of liquid crystal elements. The concept ideally enables one hundred percent input-output light conversion. The angular and wavelength dependences of planar cholesteric layers and layer combinations are shown. From them optical filter/polarizer elements result with adjustable center wavelengths and tunable bandwidths. The filters comprise novel cholesteric liquid crystals with a temperature dependence of their center wavelengths as low as 0.06 nm/°C. New, circularly polarized operating modes for twisted nematic (TN-LCDs) and other field effects exhibit not only low threshold voltages, but also voltage-transmission (reflection) characteristics whose slope is adjustable over a wide range. Thus, the new modes are applicable in high-information-content, actively addressed television TN-LCDs requiring gray scale, as well as in displays requiring large time multiplexing rates approaching those of supertwist LCDs.
Electronic Structures in Substituted Derivatives of Polypyrrole
Authors: Wang Shenglong , Kawai Tsuyoshi , Yoshino Katsumi , Tanaka Kazuyoshi , Yamabe Tokio
Published: February 2005

The electronic state of substituted derivatives of polypyrrole has been studied in both experiment and theory. The ionization potential of polypyrrole substituted by electron accepting group is larger than that of polypyrrole substituted by electron donating group. The result is explained based on the theoretical calculation results of electronic structure of model polymers.
Temperature-Dependent EXAFS Study on Supported Silver and Palladium Clusters: Comparison of Their Interatomic Potentials with Those of Bulk Metals
Authors: Yokoyama Toshihiko , Ohta Toshiaki
Published: February 2005

Temperature-dependent Ag and Pd K-edge extended X-ray-absorption fine-structure (EXAFS) spectra were measured for SiO2-supported small Ag and Pd metal clusters and their corresponding bulk metals. The EXAFS analysis using the cumulant expansion technique reveals that the Debye temperature is significantly lower and the thermal expansion coefficient is larger for the small metal clusters compared with the bulk metals. The EXAFS results thus obtained allow us to describe interatomic potential curves of the bulk metals and the metal clusters by use of a Morse potential function. The resultant dissociation energies of the small metal clusters are actually smaller than those of the corresponding bulk metals. It is quantitatively demonstrated that the surface metal atoms of the clusters have shallower and more anharmonic interatomic potentials.
Fabrication of X-Ray Mask Using W-CVD for Forming Absorber Pattern
Authors: Ohta Tsuneaki , Kawazu Yoshiyuki , Yamashita Yoshio
Published: February 2005

Tungsten chemical vapor deposition (W-CVD) using WF6 and H2 as reactants was applied to forming absorbers of X-ray masks for synchrotron radiation (SR) lithography. For this purpose, the properties of deposited W (CVD-W), such as stress, density and thermal stability, were examined. The stress can be minimized reproducibly to less than 1×108 dyn/cm2 by controlling the flow rate of WF6 at various substrate temperatures. This W film was thermally stable up to 200°C, and the density was 18.5 g/cm3. From these results, CVD-W was found to be suitable as an absorber material. For the formation of absorber patterns, filling SiO2 grooves with stress-reduced CVD-W was examined. The 0.2-µm-wide grooves were filled with CVD-W and absorber patterns were formed by etch-back. The X-ray mask was successfully fabricated by this developed process.
Effects of Photo- and Auger Electron Scattering on Resolution and Linewidth Control in SR Lithography
Authors: Deguchi Kimiyoshi , Ishiyama Toshihiko , Horiuchi Toshiyuki , Yoshikawa Akira
Published: February 2005

The effects of photo- and Auger electron scattering on resolution and linewidth control in X-ray lithography are quantitatively evaluated employing resist patterns replicated using a novel contact replication method. In this method, the effects of penumbral shadow and Fresnel diffraction can be neglected because exposure, development and SEM observation are carried out keeping the absorber pattern on the resist. The depth of the undercut of the resist pattern from the absorber pattern edge, which means the range of electron scattering in the lateral direction, increases from zero to the Bethe range as a function of exposure dose, and reaches 0.16 µm in SR lithography with spectra ranging from 0.2 to 1.4 nm. It is shown that the maximum range of photo- and Auger electron scattering does not determine the resolution directly, but rather affects the linewidth control.
ECR Plasma Etching with Heavy Halogen Ions
Authors: Fujiwara Nobuo , Sawai Hisaharu , Yoneda Masahiro , Nishioka Kyusaku , Abe Haruhiko
Published: February 2005

It is shown that the ECR plasma, which contains heavy halogen ions and other light ions, is effective as a dry etching technique for fabrication of VLSI devices. The ion temperature, which is one of the most important parameters for etching fine features, is greatly reduced by using a Cl2/He mixture gas and by controlling the pressure. By this method, strong anisotropic etching of poly-Si is realized with high selectivity to SiO2. Hydrogen halide gases are suitable gases for the ECR plasma etching process, because they produce heavy halogen ions and protons. In particular, using HBr or HI gas produces a strong anisotropic feature with no micro-loading effects. The ion temperature of Br+ ions and I+ ions is 1.0∼1.1 eV, which is about half that of Cl+ ions.