bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature Dependence of the Reflected Trimethylgallium Flux Intensity from a GaAs Surface in Metal-Organic Molecular Beam Epitaxy Measured by Mass Spectrometry
Authors: Ohki Yoshimasa , Hiratani Yuji
Published: February 2005

Desorbed species from a substrate in metal-organic molecular beam epitaxy of GaAs using trimethylgallium (TMG) and As4 were studied by mass spectrometry. The observed Ga-containing species were mainly reflected TMG at all substrate temperatures ranging from 290 to 650°C. The TMG reflection decreased with an increase in the substrate temperature up to 520°C, indicating a decomposition of TMG on the GaAs surface. Above 520°C, the reflection of TMG increased and showed a small maximum at about 600°C. The temperature dependence of the reflected TMG accounts for the reported anomalous temperature dependence of the growth rate of GaAs by MOMBE.
OMVPE Growth and Characterization of GaInP on GaAs Using Tertiary Butylphosphine for the Phosphorous Source
Authors: Takeda Yoshikazu , Araki Soichiro , Takemi Masayoshi , Noda Susumu , Sasaki Akio
Published: February 2005

GaInP layers were grown on GaAs substrates by organometallic vapor-phase epitaxy (OMVPE) at atmospheric pressure using trimethylgallium (TMGa), trimethylindium (TMIn) and much less toxic tertiary butylphosphine (TBP) as source gases. Fairly smooth surfaces were obtained at the growth temperature of 65O°C and at the V/III ratio of 78. The electrical and optical characteristics are comparable to those obtained by OMVPE using phosphine as the phosphorous source and far better than the previous results obtained by OMVPE with TBP. The undoped epitaxial layers showed n-type conductivity with electron concentrations of 2–3×1017 cm-3.
High-Temperature Superconducting Tl-Ba-Ca-Cu-O Lenses for Relativistic Electron Beams
Authors: Ishibashi Yoshiharu , Osada Tomoaki , Matsuzawa Hidenori , Marumo Hiroshi , Yokozawa Tomohide , Kobayashi Yoshihiro , Kawamura Masanori , Ohishi Morihiro , Morimoto Nobuo , Nagakura Tomio , Tohyama Akio , Akitsu Tetsuya
Published: February 2005

Thallium-compound bulk lenses have the highest ability to focus relativistic electron beams (REBs, 0.87 kA, duration time of some nanoseconds) among the high-temperature superconducting Y-, Bi-, and Tl-compound bulk lenses (Supertrons). The REBs were focused to a diameter of less than 2 mm, the narrowest diameter ever achieved with Supertrons. The current densities on the beam axes were higher than 350 kA/mm2. A revised figure of merit was proposed to evaluate the superconducting lenses.
Flash-Lamp-Pumped Tunable Ti:BeAl2O4 Laser
Authors: Sugimoto Akiko , Segawa Yusaburo , Anzai Yutaka , Yamagishi Kiyoshi , Kim Pil Hyon , Namba Susumu
Published: February 2005

The tunable lasing operation of Ti:BeAl2O4 was demonstrated by flash-lamp pumping for the first time. The maximum output energy of 21.1 mJ was obtained when the input energy was 283 J. The tuning range was from 753 nm to 946 nm.
Ab Initio Study of Elementary Processes in Silicon Homoepitaxy–Adsorption and Diffusion on Si(001)
Authors: Miyazaki Takehide , Hiramoto Hisashi , Okazaki Makoto
Published: February 2005

Ab initio total-energy calculations of the reconstructed Si(001) with adatoms for various adsorption sites have been performed. The results are interpreted in terms of adatom-substrate interactions to understand microscopic mechanisms of the surface diffusion of Si adatoms. The spatial variation of the adsorption energy suggests strong anisotropy in the direction of the adatom diffusion on Si(001)–the most probable direction of diffusion is along the dimer rows. The surface dimer breaks when the adatom moves along the lateral projection of the dimer bond.
Preparation of Cubic Boron Nitride Films by RF Sputtering
Authors: Mieno Masahiro , Yoshida Toyonobu
Published: February 2005

Cubic boron nitride (c-BN) films have been prepared by sputtering of a hexagonal BN sintered target under a negative self-bias voltage applied to Si substrates and a sputtering gas composition of Ar/N2. A c-BN phase was found to be contained only in the films prepared in pure Ar discharge with a negative self-bias above a threshold value. Moreover, the ratio of c-BN to hexagonal boron nitride increased with increasing negative self-bias voltage. The films consisting mainly of the c-BN phase were easily peeled from Si substrates on exposure to air because of their strong compressive stress.
Additional Bias Effects on the Formation of Amorphous Hydrogenated Carbon Films by ECR
Authors: Kamata Kiichiro , Inoue Tohru , Maruyama Kazunori , Tanabe Isao
Published: February 2005

Amorphous carbon films with a significant hardness and low compressive internal stress (below 0.1 GPa) were produced by a low temperature chemical vapor deposition (CVD) process at 200°C utilizing an electron cyclotron resonance (ECR). The deposition rate and microhardness of the films formed on glass were 5 nm ·min-1and 18 GPa, respectively. The additional negative bias up to -200 V was effective to produce hard carbon films above 30 GPa, to increase the deposition rate and to decrease the H/C ratio of carbon films.
Determining Object Orientation with a Hierarchical Database of Binary Synthetic Discriminant Function Filters
Authors: Reid Max B. , Ma Paul W. , Downie John D.
Published: February 2005

An optical correlation-based system is demonstrated which recognizes an object and determines its angular orientation by traversing a hierarchical database of binary filters. The database architecture is made possible by the development of binary synthetic discriminant function filters.
Optical Implementation of Multiple-Valued and Continuous Logics
Authors: Mada Hitoshi
Published: February 2005

The optical implemention of the basic operations of multiple-valued and continuous logics is described. The basic operations are realized with optical devices, which are composed of a liquid crystal light modulator and an electric feed-back system. In the several basic operations, the bounded difference, which can express the other operations, plays an important role. We have demonstrated the logical sum using the bounded difference and algebraic sum.
Shift-Invariant Associative Memory Based on Anamorphic Incoherent Correlator
Authors: Takino Masato , Ohtsu Norihito , Yatagai Toyohiko
Published: February 2005

An architecture of optical associative memory based on 1-D incoherent correlation using an anamorphic optical system is proposed. The proposed associative memory system has a shift-invariant feature because cross correlation is used in the recording and recalling processes. Computer simulation of the shift invariance for the proposed associative memory system is described. To increase memory capacity, a position separation method is proposed. Experimental verification of autoassociation is presented.
Optimization of the Optical Interconnection between Microlens and Channel Waveguide Arrays
Authors: Liñares Jesús , Fuente Raul de la
Published: February 2005

Optical interconnection between a linear microlens array and a channel waveguide array has been optimized (aperture of microlenses and separation between arrays) for its use in integrated optical computing.
Growth Mechanism in Migration-Enhanced Epitaxy of AlAs on Misoriented GaAs(111)B Substrates
Authors: Takano Yasushi , Torihata Teiji , Kawai Takahiro , Pak Kangsa , Yonezu Hiroo
Published: February 2005

Reflection high-energy electron diffraction (specular beam intensity) in migration-enhanced epitaxy of AlAs and GaAs has been investigated. The step flow growth mode was realized in the migration-enhanced epitaxy of AlAs by using a 0.5° misoriented GaAs(111)B substrate. In AlAs growth, excess As adsorption occurred easily in comparison with that in GaAs MEE growth. The control of the number of As4 molecules per cycle was found to be important in obtaining a flat surface.
Negative Differential Resistance of Strain-Free InGaAs/AlAsSb Resonant Tunneling Barrier Structures Lattice-Matched to InP
Authors: Inata Tsuguo , Muto Shunichi , Nakata Yoshiaki , Fujii Toshio
Published: February 2005

We grew AlAsSb/InGaAs(4.40 nm) resonant tunneling barrier structures lattice-matched to InP substrates using molecular beam epitaxy. Peak-to-valley current ratios exceeding 10 at room temperature were achieved for the first time with fully lattice-matched resonant tunneling barrier structures (15 with a peak current density, J
p, of 2.37×103 A/cm2 and 11 with J
p of 1.51×104 A/cm2). These values are comparable to peak-to-valley current ratios in InGaAs/AlAs pseudomorphic resonant tunneling barrier structures with corresponding peak current densities.
P-Channel Polycrystalline Silicon Thin-Film Transistors on Glass Substrates
Authors: Yamaguchi Fuminori , Tanaka Seiya , Nitta Yoshiteru , Tomita Kenji , Doi Atsutoshi
Published: February 2005

A p-channel polycrystalline silicon thin-film transistor was fabricated at low temperature (<600°C) on a glass substrate for application to large-area display devices with CMOS peripheral circuits. An active layer was formed by laser crystallization of amorphous silicon film using a liquid encapsulation technique to increase the grain size. The gate insulator and source and drain contacts were made by plasma-enhanced chemical vapor deposition. A hole mobility of 43 cm2/(V ·s) was obtained by these methods.
Complex Susceptibility of La2-xSrxCuOy
Authors: Mazaki Hiromasa , Yoshimura Kazuyoshi , Yasuoka Hiroshi , Nishizawa Yoichi , Ueda Yutaka , Kosuge Koji
Published: February 2005

The superconducting properties of powdered La2-x
Sr
x
CuO
y
were investigated for various values of Sr and oxygen contents. The phase identification by an X-ray diffractometer indicates that the samples have a single-phase K2NiF4 structure. Measurements of the superconducting transition in terms of complex susceptibility χ=χ'-iχ'' have revealed that the sample with x\cong0.16 and y\cong4 has the highest T
c. The dependence of χ on the magnetic field amplitude shows different features crossing the value of x∼0.16, suggesting that for x>0.16, no intrinsic superconducting phase appears, but a low-T
c phase may exist for x<0.16.
TEM Observation of Interfaces between Y2BaCuO5 Inclusions and the YBa2Cu3O7 Matrix in Melt-Powder-Melt-Growth Processed YBaCuO
Authors: Yamaguchi Koji , Murakami Masato , Fujimoto Hiroyuki , Gotoh Satoshi , Koshizuka Naoki , Tanaka Shoji
Published: February 2005

We have conducted transmission electron microscopic observations along the [001] direction of the interfaces between Y2BaCuO5 inclusions and the YBa2Cu3O7 matrix in the YBaCuO crystals fabricated by the Melt-Powder-Melt-Growth process. Amorphous layers about 1 nm in thickness are observed at some interfaces. We could not find observable crystallographic defects at the interfaces.
Non-Alloyed Ge/Pd Contacts for AlAs/GaAs Resonant Tunneling Structures
Authors: Van Hoof C. , Van Hove M. , Jansen P. , Van Rossum M. , Borghs G.
Published: February 2005

Resonant AlAs/GaAs/AlAs tunneling diodes with very thin top contact layers have been fabricated using non-alloyed Ge/Pd/n ohmic contacts. The current-voltage characteristics of a set of resonant tunneling diodes that only differed in the thickness of the top contact layer clarify the action range of separate processes taking place during contact formation. Resonant tunneling performance is still observed in structures with contact layers as thin as 10 nm. Device applications that require the contacting of a very thin layer can therefore benefit most from this contact scheme.
Transport Critical Current Density of Polycrystalline YBCO in Zero Field Cooled and Field Cooled States: A Comparison
Authors: Mishra P. K. , Ravikumar G. , Chaddah P. , Kumar Shailendra , Dasannacharya B. A.
Published: February 2005

Magnetic field dependence of transport critical current density (J
c) of a polycrystalline YBCO superconductor in field cooled and zero field cooled cases have been studied experimentally. The measured J
c value when the sample was cooled in a field (FC) was always larger than that measured for a zero field cooled (ZFC) case in the same magnetic field. We also observe (i) a peak in the field dependence of the ratio of J
c in FC case to that of ZFC case and (ii) an anomalous rise in J
c in ZFC case with increasing field. These observations are explained as a signature of two types of regions (intergrain and intragrain) in sintered specimens.
Estimation of Respective Volume Fractions of High- and Low-Tc Phases in Inhomogeneous Oxide Superconductors
Authors: Ando Yoichi , Akita Shirabe
Published: February 2005

For Bi- or Tl-based oxide superconductors, several different phases usually coexist in a sample. We propose here a new way of quantitative estimation of the volume fraction of each phase. It is based on the fact that the ratio of the reversible magnetization of each phase varies with temperature and magnetic field. In this estimation, fundamental parameters such as penetration depth or upper critical field of each phase should be specified beforehand, and the sample is required to be roughly c-axis oriented.
Preparation and Superconducting Properties of La2-x(Ca1-ySry)1+xCu2O6-x/2+δ
Authors: Kinoshita Kyoichi , Shibata Hiroyuki , Yamada Tomoaki
Published: February 2005

Superconductivity has been detected in the Ca-based 2-1-2-6 compound La2-x
(Ca1-y
Sr
y
)1+x
Cu2O6-x/2+δ and the relationship between crystal structure and superconducting properties is investigated by varying x, y, and O2 pressure during synthesis. It is shown that the lattice parameter a is restricted to between 3.823 and 3.826 Å for the superconducting material, irrespective of x, y, and O2 pressure. For a fixed Sr content y, the smaller a is, the higher the T
c is obtained. On the other hand, lattice parameter c has no clear correlation with superconductivity.
The Synthesis of New Cubic Conductive Cu7-xO8-yMX (M=In, Sc, X=NO3, Cl) Compounds
Authors: Yazawa Ichiro , Sugise Ryoji , Terada Norio , Jo Masatoshi , Oka Kunihiko , Ihara Hideo
Published: February 2005

New cubic conductive Cu6O8-y
MX (M=In, Sc, X=NO3, Cl) compounds were synthesized for the first time. These compounds were prepared in the thermal decomposition process of a mixed copper and metal-element nitrate and chloride solution. The decomposition temperatures of the Cu6O8-y
MNO3 were raised by replacing the NO3
- ion by the Cl- ion. The lattice constant of the cubic compound was related to the value of the ion radius of M and X.
Fluorine-Doped Indium Oxide Thin Films Prepared by Chemical Vapor Deposition
Authors: Maruyama Toshiro , Fukui Kunihiro
Published: February 2005

Transparent conductive fluorine-doped indium oxide thin films were prepared by an atmospheric-pressure chemical vapor deposition method without using an oxygen donor. The raw materials were indium 2-ethylhexanoate and indium fluoride. The polycrystalline films were obtained at a reaction temperature in the range of 330–430°C. For the 57.8-nm-thick film deposited at 400°C, the resistivity was 2.89×10-4 Ω·cm, and the transmittance was more than 85% in most of the visible range (470–700 nm). The effects of fluorine doping on the deposition rate, structure and characteristics of the film were discussed by comparing the results with the corresponding values for nondoped indium oxide film.
Photoacoustic Response to X-Ray Absorption in Copper and Brass
Authors: Toyoda Taro , Masujima Tsutomu , Shiwaku Hideaki , Iida Atsuo , Ando Masami
Published: February 2005

The X-ray photoacoustic spectra of copper and brass (64.7 wt.% Cu and 35.3 wt.% Zn) have been measured at XANES (X-ray absorption near-edge structure) regions using synchrotron radiation. These spectra were compared with optical density of X-ray spectra. It is shown that the information derived from XANES is also included in the X-ray photoacoustic spectrum which reflects the heat production processes in copper and brass. However, the results showed that the increases and changes of the photoacoustic signal were different from those of the X-ray absorption coefficient at XANES regions.
Composition Dependence of Superconductivity of Tl-Bi-Pb-Ba-Sr-Ca-Cu-O System
Authors: Kuroda Masanori , Yokogawa Kiyoshi
Published: February 2005

The superconductivity of the (Tl
x
Bi
y
Pb
z
)2Sr2Ca2Cu3O
w
, (Tl
x
Bi
y
Pb
z
)2Ba2Ca2Cu3O
w
, and (Tl
x
Bi
y
Pb
z
)2Ba1Sr1Ca2Cu3O
w
systems was studied. The critical temperature (T
c) of the systems was determined to be a function of the intended chemical composition of (Tl
x
Bi
y
Pb
z
). The superconductive compounds with the maximum T
c of 93 K were found in the wide region in the (Tl
x
Bi
y
Pb
z
)2Sr2Ca2Cu3O
w
system, those with the maximum T
c of 102 K were also found in Bi-Tl region in the (Tl
x
Bi
y
Pb
z
)2Ba1Sr1Ca2Cu3O
w
system and those with the maximum T
c of 110 K were observed in the Tl region in the (Tl
x
Bi
y
Pb
z
)2Ba2Ca2Cu3O
w
system.
Crystal Structure of (Pb/Cu)SrLaCuOy Superconductor
Authors: Adachi Seiji , Setsune Kentaro , Wasa Kiyotaka
Published: February 2005

The crystal structure of a new superconducting lead cuprate, (Pb/Cu)SrLaCuO
y
, has been investigated. The Rietveld refinement for powder X-ray diffraction data of a ceramic sample was performed. It revealed that the structure is composed of (Pb/Cu)-O single layers and Cu-O6 octahedrons. The properties of block layers between the apexes of two Cu-O6 octahedrons in p-type cuprate superconductors are discussed.
Optical Configurations for Solving Equations Using Nonlinear Etalons
Authors: Lu Xuenong , Honda Toshio , Ohyama Nagaaki , Wu Minxian , Jin Guofan
Published: February 2005

Based on the characteristics of ZnSe optical bistable etalons, we propose an all-optical parallel method which can add multiple input laser beams and perform the multiplication of two multibit binary numbers. By changing the mounted angles of nonlinear etalon devices, more complicated functions can be obtained. With the use of these functional systems, the possibility of solving linear equations mainly based on iterative methods is then described. Some simple experimental results are also presented.
Growth of CuGaS2 Single Crystals by Traveling Heater Method
Authors: Miyake Hideto , Sugiyama Koichi
Published: February 2005

Growth of bulk CuGaS2 single crystals by the traveling heater method (THM) with In solvent has been investigated. The THM growth was performed at 1050°C, where the In solution saturated with stoichiometric CuGaS2 solute is a single liquid phase. The obtained single crystals were solid solutions CuGa
x
In1-x
S2, and the mole fraction 1-x of CuInS2 was 0.02–0.03 along the entire crystal length. The photoluminescence spectra show a weak near-band-edge emission peak and two strong and broad low-energy emission peaks.
Spontaneous Hydrogenation of Ti Films Evaporated on NaCl Substrates I
Authors: Yamada Yukio , Kasukabe Yoshitaka , Nagata Shinji , Yamaguchi Sadae
Published: February 2005

The depth profiles of hydrogen concentration in Ti-evaporated films on NaCl substrates have been measured with the elastic recoil detection analysis technique using a 2.7 MeV 4He+ beam. It has been revealed that the Ti film absorbs hydrogen escaped from the substrate. The hydrogen concentration in the film decreased with increasing substrate temperature. It is pointed out that the epitaxial growth of substances with a great affinity for hydrogen, evaporated on NaCl or deliquescent alkali halide substrates, should be re-examined from the point of view of hydrogenation on the substrate.
Acid Vapor Treatment of Fatty Acid Salt LB Films–Evidence for Conservation of the Lamellar Structure–
Authors: Saito Mitsuyoshi , Tabe Yuka , Saito Kazuhiro , Ikegami Keiichi , Kuroda Shin-ichi , Sugi Michio
Published: February 2005

The width of each (0, 0, l) X-ray diffraction peak of a fatty acid salt LB film has been found to be invariant with the treatment with hydrochloric acid vapor in the first stage when the peak height decreases drastically. The IR measurements indicated that each fatty acid molecule in the LB film remains unchanged both in orientation and in conformation. These findings strongly suggest that the LB lamellar structure is conserved with the metal ions liberated from the original sites of the material.
Spontaneous Hydrogenation of Ti Films Evaporated on NaCl Substrates II
Authors: Kasukabe Yoshitaka , Yamada Yukio
Published: February 2005

The growth and structure of Ti films evaporated on ultra-high-vacuum- and air-cleaved NaCl substrates at room temperature have been studied by reflection high-energy electron diffraction. The 2 nm-thick film on the former showed bcc- and CaF2-type (TiH1.5) reflections while that on the latter showed TiH1.5 ones immediately after the evaporation. Judging from the lattice parameter (0.33 nm), the bcc crystallite was analyzed to be β-Ti. This is the first observation of β-Ti grown in evaporated Ti films. The β-Ti changed into TiH1.5 with time. This spontaneous hydrogenation mechanism of the evaporated Ti films is discussed.
Electron Cyclotron Emission Measured in Lower Hybrid Current Drive Plasma on WT-3 Tokamak
Authors: Sugawa Masao , Dodo Taro , Sugaya Reiji , Ide Shunsuke , Tanaka Hitoshi , Maekawa Takashi , Terumichi Yasushi , Tanaka Shigetoshi
Published: February 2005

Electron cyclotron emission from the lower hybrid current-driven WT-3 was measured along the vertical chord where the toroidal field is constant. Measurements show that the tail electron with the energy of 110 keV carrying the plasma current is generated, and the initial process (\lesssim10 ms) after the injection of the lower hybrid wave follows the quasi-linear theory. On a longer time scale (≃40 ms), energetic tail electrons are scattered to the perpendicular direction in velocity space by the collision with the bulk, and the effective temperature of tail electrons increases up to about 60 keV.
Ion Bernstein Wave Experiment on JFT-2M Tokamak
Authors: Tamai Hiroshi , Ogawa Toshihide , Matsumoto Hiroshi , Odajima Kazuo , Aikawa Hiroshi , Hoshino Katsumichi , Kasai Satoshi , Kawakami Tomohide , Kawashima Hisato , Kondoh Takashi , Matsuda Toshiaki , Miura Yukitoshi , Mori Masahiro , Nakazawa Ichiro , Ogawa Hiroaki , Ohasa Kazumi , Ohtsuka Hidewo , Sengoku Seio , Shoji Teruaki , Suzuki Norio , Uesugi Yoshihiko , Yamamoto Takumi , Yamauchi Toshihiko , Maeda Hikosuke
Published: February 2005

The ion Bernstein wave (IBW) is launched into the JFT-2M tokamak plasma in order to investigate the antenna loading resistance and the heating effect. Antenna loading resistance increases as the scrape-off electron density increases, in the same manner as that of fast wave antennas. Although the hydrogen ion temperature increases due to the IBW, most of the wave power is absorbed by the peripheral electrons. This is mainly due to the antenna location, which is at an oblique angle to the midplane. Peripheral electron heating induces the enhanced radiation loss, and IBW power of only about 120 kW can be launched because of the radiation limit.
Enhancement of Transport Critical Current Density of Ba2YCu3O7-δ Thin Film by 28 MeV Electron Irradiation
Authors: Terai Takayuki , Masegi Tamaki , Takahashi Yoichi , Enomoto Youichi , Kubo Shugo
Published: February 2005

Effect of 28 MeV electron irradiation was investigated on the critical current density (J
c) of high-T
c superconductor Ba2YCu3O7-δ thin films. For the film irradiated with a fluence of 4.7×1016 electrons/cm2, J
c determined from I-V characteristics at temperatures from 75 to 85 K was enhanced by about 8%. The enhance ratio of J
c due to irradiation increased with fluence over the range investigated, while the critical temperature (T
c) was unchanged. The temperature dependence of J
c was not affected by electron irradiation.
In Situ Optical Monitoring of the GaAs Growth Process in MOCVD
Authors: Makimoto Toshiki , Yamauchi Yoshiharu , Kobayashi Naoki , Horikoshi Yoshiji
Published: February 2005

A new optical method for in situ monitoring of epitaxial growth is proposed and applied to the growth of GaAs by metalorganic chemical vapor deposition. The growth process is investigated using optical reflection while triethylgallium and arsine are alternately supplied to the growing surface. Linearly polarized 325-nm He-Cd laser light is irradiated at a 20° angle with respect to the (001)-oriented GaAs substrate surface. Laser light with a polarization E vector that is perpendicular to the substrate surface is more efficiently reflected during the triethylgallium flow period than during the arsine flow period due to the different optical absorption between Ga- and As-atomic surfaces. Therefore, we call this the “surface photo-absorption” (SPA) method. This method provides a means for real-time control and in situ study of epitaxial growth by metalorganic chemical vapor deposition. A strong and persistent oscillation in the reflection intensity is observed when triethylgallium and arsine are alternately supplied.
Defect-Free LB Films by the “Isobaric Thermal Treatment” of Barium Arachidate Monolayers
Authors: Kato Teiji , Ohshima Katsunori
Published: February 2005

“Isobaric thermal treatment”, i.e., temperature rises and falls of monolayers under a constant surface pressure, makes monolayers and resultant LB films densify and be free from defect. This was confirmed by the copper electroplating of the one-layer LB films and by the observation of optical microphotos of the LB samples. The number of defects per unit area detected by the copper electroplating method decreased monotonously with increasing attained temperature from thermal treatment. It was shown experimentally that the number of defects in LB films of barium arachidate became almost zero when the monolayer was isobaric thermally treated up to 55°C at 15 mN/m.
Investigation on the Microstructure of Hydrogenated Amorphous Carbon Films by Electron Energy-Loss Spectroscopy
Authors: Yamazaki Hisashi , Katashima Mitsuhiro , Bekku Ichiro , Mihara Masahiro , Okuyama Naoki
Published: February 2005

Structure characterization of the hydrogenated amorphous carbon (a-C:H) films prepared by plasma CVD has been carried out by electron energy-loss spectroscopy (EELS). The EELS data are successfully resolved to the bulk contributions and the surface ones by using the curve fitting. The EELS spectra are discussed on the basis of the energy-loss function of graphite. The annealing may cause the increase in number of small linear or chainlike clusters of fused sixfold carbon rings rather than growth of their compact clusters.
Highly Sensitive Raman Spectroscopy by a Position-Sensitive Photomultiplier and a Triple-Stage Spectrograph with Stigmatic Optical Correction
Authors: Tanino Hiroshi , Okushi Hideyo
Published: February 2005

A Raman spectrometer with extremely high sensitivity was constructed through the use of a position-sensitive photomultiplier and a triple-stage spectrograph with stigmatic optical correction. Raman spectra of Si wafer were demonstrated with the low-level excitation intensity down to 10 nW. The longitudinal optical phonon spectrum of an individual 3-layer-thick AlAs thin film buried in GaAs was obtained for the first time. The system is useful for studying a small number of atoms and molecules of various surfaces, interfaces, and ultrathin layers.
Highly Beryllium-Doped GaInAs Grown by Chemical Beam Epitaxy
Authors: Uchida Toshi K. , Uchida Takashi , Yokouchi Noriyuki , Koyama Fumio , Iga Kenichi
Published: February 2005

Beryllium-doped GaInAs layers were grown on InP by chemical beam epitaxy and were electrically characterized. A hole concentration of as high as 2×1020 cm-3 at a growth temperature of 540°C was obtained without degrading the surface morphology. Highly doped growth was possible without changing any growth parameter. Hole concentrations were also investigated at different growth temperatures for a given Be cell temperature. Hole concentrations were found to increase with decreasing growth temperatures. Furthermore, we did not observe lattice mismatch (Δ
a/a<3×10-4) for any of the doped samples grown under the same growth condition as for undoped samples.
Mobility-Lifetime Product in Hydrogenated Amorphous Silicon
Authors: Könenkamp Rolf , Muramatsu Shin-ichi , Itoh Haruo , Matsubara Sunao , Shimada Toshikazu
Published: February 2005

We report an analysis of the carrier loss process in time-of-flight experiments on amorphous silicon solar cells. The electron mobility-lifetime ( µτ) product is determined by a transitory immobilization of the carriers in deep traps. The carriers can be recovered and collected when the experiment is extended into the ms time range. The collection efficiency is shown to depend on the occupation of gap states. We discuss the discrepancy between µτ values obtained from time-of-flight and photoconductivity measurements and present an analysis which relates the time-of-flight µτ products to the density of shallow and deep states in a-Si:H.
High-Voltage Schottky Diodes on Boron-Doped Diamond Epitaxial Films
Authors: Shiomi Hiromu , Nishibayashi Yoshiki , Fujimori Naoji
Published: February 2005

High-voltage Schottky diodes have been fabricated on diamond epitaxial films with the structure: metal/undoped diamond/p+-type diamond. The films were epitaxially grown on synthesized single-crystal diamonds (100) by microwave plasma-assisted chemical vapor deposition (CVD) using H2 and CH4. B2H6 was used at B2H6/CH4=167 ppm for p+ diamond. Al Schottky electrodes and Ti ohmic electrodes were formed by an e-beam evaporation method and a thermal evaporation method, respectively. The forward current was independent of temperature because of the Fermi degeneracy in p+-type diamond. These diodes had a breakdown voltage of 520 V.
Low Surface Resistance of Screen-Printed YBa2Cu3O7-x Thick Films
Authors: Ishii Osamu , Konaka Tsuneo , Sato Makoto , Koshimoto Yasuhiro
Published: February 2005

This letter describes the surface resistance of YBa2Cu3O7-x
thick films which are screen printed on Ag-coated Y2O3-stabilized ZrO2 substrates. The surface resistance decreases with decreasing YBa2Cu3O7-x
film thickness. The 7 µm-thick film shows the lowest surface resistances (8.2 m Ω at 17 GHz and 48 m Ω at 50 GHz at liquid nitrogen temperature) which are lower than those of pure Cu. These markedly low surface resistances are attributed to the enhanced growth and c-axis orientation of YBa2Cu3O7-x
grains.
High-Oxygen-Pressure Synthesis of Superconducting Tetragonal YBa2Cu3O7.7
Authors: Okai Bin
Published: February 2005

A tetragonal form of YBa2Cu3O
y
whose lattice parameters were a=3.8715 Å and c=11.6506 Å was prepared at a high oxygen pressure of 6 GPa and 1050°C. Using the value of oxygen content determined by oxygen analysis measurement, the tetragonal YBCO was expressed as YBa2Cu3O7.7. If the oxygen is assumed to be divalent as usual, the average valence of Cu becomes 2.8. The onset of the superconducting transition temperature was 92 K, nearly the same as usually obtained with YBCO; however, the volume fraction of superconductivity was a third of the usual YBCO.
Formation of 2223 in Bi(Pb)-Sr-Ca-Cu Oxide Resulting from the Reaction of (Bi, Pb)2Sr2Cu1Ox, (Bi, Pb)2Sr2Ca1Cu2Ox, Ca2CuO3 and CuO
Authors: Fukushima Kensuke
Published: February 2005

The reaction of (Bi, Pb)2Sr2Cu1O
x
(2201), (Bi, Pb)2Sr2Ca1Cu2O
x
(2212), Ca2CuO3 and CuO is studied to clarify the transformation mechanism through which the high T
c phase (2223) forms. Before and during the formation of 2223, the following change occurs: 1) Ca and Cu contents in 2212 increase and the c-lattice constant of 2212 decreases; 2) a Ca-rich Sr-Ca-Cu phase (Sr-Ca-Cu I) and a Ca-poor one (Sr-Ca-Cu II), which form before the formation of 2223, react with the above-mentioned 2212 and transform it to 2223.
Bi-Based Superconducting Thin Films Prepared by a Combination of Metalorganic Deposition (MOD) and a Diffusion Process
Authors: Yaegashi Seiji , Green Mark , Murakami Hirohiko , Nishino Junya , Shiohara Yuh , Tanaka Shoji
Published: February 2005

Bi-based superconducting thin films have been prepared by a combination of metalorganic deposition (MOD) and a diffusion process. The films derived from a layer of Bi/Sr/Ca/Cu=2/2/1/3 and a layer of Ca/Pb=2/1 after firing for only 4 h yielded a nearly single-phase layer of the 2223 (high T
c) phase. It was found that Ca2PbO4 played a very important role in the formation of the 2223 phase in short firing times, acting as a souce of Ca ions to react with the 2212 phase and CuO.
Purification and UV-VIS Light Absorption Property of Source Materials for CVD of High-Tc Superconducting Films
Authors: Hashimoto Takuya , Kitazawa Koichi , Suemune Youichi , Yamamoto Takakazu , Koinuma Hideomi
Published: February 2005

Purification and spectral properties of source materials for CVD of high-T
c superconducting films have been investigated quantitatively. Based on elemental analysis, TG, IR spectroscopy, and 1H-NMR spectroscopy, sublimation was verified to be satisfactory for the purification of Bi(C6H5)3, Ca(DPM)2, and Cu(DPM)2 (DPM: dipyvaloylmethane). Sr(DPM)2 was not sufficiently purified by the sublimation alone, but recrystallization from an ethanol solution in advance improved the purity of the sublimate, as verified by a significant decrease in the sublimation temperature. The UV-VIS spectra revealed that Bi(C6H5)3, Sr(DPM)2, Ca(DPM)2 and Cu(DPM)2 had high absorption coefficients at wavelengths around 254 nm, suggesting high possibilities of their photochemical decomposition by light irradiation from a low-pressure mercury lamp.
Noncentrosymmetric Langmuir-Blodgett Film of Phenylpyrazine Derivative Applicable to Nonlinear Waveguides
Authors: Era Masanao , Nakamura Ken-ichi , Tsutsui Tetsuo , Saito Shogo , Niino Hiroyuki , Takehara Kenji , Isomura Kazuaki , Taniguchi Hiroshi
Published: February 2005

Thick noncentrosymmetric LB films of more than 200 bilayers (thickness of more than 1 µm) were successfully fabricated with an alternating deposition of a phenylpyrazine derivative and arachidic acid monolayers. The alternating LB films were transparent from visible to near infrared region. Spectroscopic and X-ray diffraction studies on the alternating LB films proved that molecules were predominantly oriented normal to the film plane in the LB film. Further, the quadratic dependence of second-harmonic (SH) intensity on film thickness was confirmed in the LB films in the wide range of thickness from 1 to 200 bilayers. From the SH generation measurement, the alternating LB films were found to have fairly large second-order nonlinear susceptibility, which was estimated to be 1×10-7 esu.
Under Field Oxide Dopant Enhancement (UFDE) for CMOS and BiCMOS Technology
Authors: Lee Jong Ho , Park Young June , Lee Jong Duk
Published: February 2005

A structure with n-type dopant enhancement only under field oxide in an n-well and its implementation are proposed. This technique was applied to 3 µm CMOS and BiCMOS technology, and it was shown that CMOS and BiCMOS latch-up and collector resistance of the bipolar transistor were improved by adopting this technology. Problems with regards to this technology are also addressed.
A New Mechanism of Failure in Silicon p+/n Junction Induced by Diffusion Barrier Metals
Authors: Igarashi Yasushi , Yamaji Tetsuo , Nishikawa Satoshi
Published: February 2005

The mechanism of failure of p+/n and n+/p junctions under Al-Si/TiN/Ti and Al-Si/ZrN/Zr systems at contact holes has been investigated. When the total force of the barrier metal in the metallization system, which is defined as the product of the film stress and the film thickness, is larger than 3×105 dyn/cm, the junction leakage current increases on p+/n diodes, but not on n+/p diodes after annealing at 500°C. This increase is caused by the formation of dislocation loops in p+-Si. The formation depends on the annealing temperature, the total force of barrier metal and the B concentration.
Planarized Deposition of High-Quality Silicon Dioxide Film by Photoassisted Plasma CVD at 300°C Using Tetraethyl Orthosilicate
Authors: Suzuki Nobumasa , Masu Kazuya , Tsubouchi Kazuo , Mikoshiba Nobuo
Published: February 2005

High-quality SiO2 films were deposited by a photoassisted plasma CVD method using tetraethyl orthosilicate (TEOS) at 300°C. Oxygen gas was excited in a high-density plasma which was kept apart from the substrate. Excited oxygen reacted with TEOS gas to generate reactive intermediates. The adsorbed intermediates migrated sufficiently for conformal coverage on the substrate surface and were photoexcited to produce SiO2 films. Al steps were successfully planarized with the high-quality SiO2 film. The planarization was explained to be attained by low activation energy for migration using a site-by-site migration model.
Near-Room-Temperature Photopumped Blue Lasers in ZnSxSe1-x/ZnSe Multilayer Structures
Authors: Nakanishi Koichiro , Suemune Ikuo , Masato Hiroyuki , Kuroda Yasuhide , Yamanishi Masamichi
Published: February 2005

Photopumped blue laser oscillation was achieved up to near room temperature (280 K) in a ZnS0.18Se0.82/ZnSe multilayer structure grown by MOVPE. This significant improvement in the lasing temperature is attributed to the higher heterobarrier which prevents thermoionic emission and to the multilayer structure which has an average lattice constant matched to the GaAs substrate at the growth temperature of 515°C. The threshold excitation optical power density below 200 K where the thermoionic emission is negligible is less than 50 kW/cm2, which corresponds to a current density of 14 kA/cm2.
Switching Characteristics of InGaAs/InP Multiquantum Well Voltage-Controlled Bistable Laser Diodes
Authors: Uenohara Hiroyuki , Iwamura Hidetoshi , Naganuma Mitsuru
Published: February 2005

Voltage-controlled optical bistability in In0.53Ga0.47As/InP multiquantum well (MQW) laser diodes is demonstrated for the first time by using the quantum confined Stark effect (QCSE) and saturable absorption of a two-dimensional exciton. Optical bistability is obtained in a wide range of control voltages from +0.7 V to -0.6 V. Switching operation is achieved by injecting a set light pulse and applying reverse bias reset voltage to the saturable absorption region. Turn-on time is 300 ps with input light of 6 mW, and turn-off time of 260 ps is obtained by reducing the stray capacitance in the saturable absorption region.
Dry Etching of InGaAsP/InP Structures by Reactive Ion Beam Etching Using Chlorine and Argon
Authors: Nishibe Tohru , Nunoue Shin-ya
Published: February 2005

Very smooth InGaAsP/InP surfaces and sidewalls were obtained by using the enhanced sputtering effect of Ar addition to Cl2 etching gas in RIBE. The substrate temperature was raised to 180°C in order to remove involatile chlorides and impurities. Moreover, a vertical sidewall with no lateral etching under the mask was realized at the same time. This enables submicron dry etching for heterostructure devices.
Pressure Effects on Tc of Superconductor YBa2Cu4O8
Authors: Yamada Yuh , Matsumoto Takehiko , Kaieda Yoshinari , Mōri Nobuo
Published: February 2005

The enhancement of the superconducting transition temperature by pressure was studied up to 2 GPa for an YBa2Cu4O8 compound which was synthesized by using the canned HIP technique. The value of dT
c/dP was found to be 5.5 K/GPa. From the experiments of the specimen in which YBa2Cu4O8 and Y2Ba4Cu7O14 compounds coexist, dT
c/dP for Y2Ba4Cu7O14 was also shown to be 5.5 K/GPa. The result for the YBa2Cu4O8 compound is explained by the pressure induced carrier (hole) redistribution on the basis of the calculation of the Madelung energy.
Preparation of Bulky Bi(Pb)-Sr-Ca-Cu-O Superconductor by Magnetized Twin-Roll
Authors: Kawahara Nobuaki , Kawabata Sanemasa , Enami Hiroyoshi , Shinohara Toshiyuki , Hoshizaki Hiroki , Hasegawa Masashi , Asai Shigeo , Imura Toru
Published: February 2005

A highly oriented (Bi, Pb)2Sr2Ca2Cu3O
x
bulk superconductor has been prepared by magnetized twin-roll processing. In these bulks, plate-like crystal grains were highly oriented by a magnetic and mechanical force. The grain c-axes were parallel to the magnetic field and pressing directions. In fact, both critical current density (J
c) and orientation degree of the sample rolled under 2 T were higher than those of the sample rolled with no magnetic field. The magnetized twin-roll processing is effective not only in enhancing grain-orientation but also in packing to improve J
c.
Preparation and Crystal Structures of Bi-Based Layered Oxides Including Fe
Authors: Shoda Kaoru , Tsutsumi Masayuki , Matsui Yoshio , Horiuchi Shigeo
Published: February 2005

Three phases of bismuth iron oxides with layered structures were prepared in Bi-Sr-Ca-Fe-O, Bi-Sr-Fe-O and Bi-Ca-Fe-O systems. Phase A (c\fallingdotseq32 Å) is formed in the first system. High-resolution transmission electron microscopy is used to examine the structural modulation. The structure of the subcell is similar to that of Bi2Sr2CaCu2O
x
but the modulation periodicity is different, i.e. 4.5 times that of the subcell in the b direction (commensurate-type). For the second system, phase A as well as B (c\fallingdotseq40 Å) arises. The latter is with the isostructure of Bi2Sr2Ca2Cu3O
x
. The modulation periodicity is about 4.5. Phase C (c\fallingdotseq22 Å) appears in the third system and the subcell structure is similar to that of Bi2Sr2CuO
x
. The modulation periodicity is 3.5. All of these phases are electrically nonconductive.
Fabrication of SiC Blue LEDs Using Off-Oriented Substrates
Authors: Matsushita Yasuhiko , Nakata Toshitake , Uetani Takahiro , Yamaguchi Takao , Niina Tatsuhiko
Published: February 2005

SiC blue LEDs were fabricated by the dipping technique, using 6H-SiC substrates whose (0001̄)C face varied toward the [112̄0] or [101̄0] direction. The surface morphology of the epitaxial layers on the off-oriented substrates was a striped pattern perpendicular to the off-axis direction. By using off-oriented substrates, the degradation of SiC blue LEDs can be greatly reduced. High-efficiency blue LEDs (12 mcd at 20 mA) were fabricated by increasing the amount of Al dopant in the n-type layer.
Direct Evidence for the Negative-U Property of the DX Center as Studied by Hydrostatic Pressure Experiments on GaAs Simultaneously Doped with Ge and Si
Authors: Fujisawa Toshimasa , Yoshino Junji , Kukimoto Hiroshi
Published: February 2005

DX centers in GaAs codoped with Ge and Si have been investigated under a hydrostatic pressure, where Ge acts as a DX center, and Si as a shallow donor. It is demonstrated that the number of electrons trapped by the Ge DX center at 22 kbar increases with Si concentration and tends to saturate at a certain value. The behavior substantiates the negative-U model of the DX center, where two electrons are bound to a DX center.
Confirmation of P-Type Conduction in Li-Doped ZnSe Layers Grown on GaAs Substrates
Authors: Yahata Akihiro , Mitsuhashi Hiroshi , Hirahara Keijiro , Beppu Tatsuro
Published: February 2005

Hall effect measurements were carried out for Li-doped MOCVD ZnSe layers whose GaAs substrates were removed. This made it possible to obtain the original p-type properties for the layers. Hole concentration, Hall mobility and specific resistivity were 4.1×1016 cm-3, 24 cm2/V ·s and 6.4 Ω·cm, respectively. Furthermore, the characteristics for the GaAs inversion layers, which were changed from semi-insulating to p-type by Zn diffusion from the ZnSe layers, were estimated by comparing the results of samples without GaAs substrates with those with GaAs substrates.
Synthesis of YBa2Cu4O8 Powders by Sol-Gel Method under Ambient Pressure
Authors: Murakami Hirohiko , Yaegashi Seiji , Nishino Jun'ya , Shiohara Yuh , Tanaka Shoji
Published: February 2005

The 124 superconductor YBa2Cu4O8 was synthesized using a sol-gel method with starting solutions contained stoichiometric compositions of Y/Ba/Cu=1/2/3 and 1/2/4. Heattreatment was done below 800°C in 1 atm oxygen atmosphere; neither special equipment nor additives were required. Our result suggests that the 123 phase is thermodynamically metastable in the temperature region that had been thought to be the equilibrium region of 123-orthorhombic phase.
The High Field Magnetic Dependence of Critical Current Density at 4.2 K for Ag-Sheathed Bi2Sr2CaCu2Oy Superconducting Tape
Authors: Enomoto Noritsugu , Kikuchi Hiroyuki , Uno Naoki , Kumakura Hiroaki , Togano Kazumasa , Watanabe Kazuo
Published: February 2005

Critical current density (J
c) at 4.2 K and its dependence on applied magnetic field was measured for Ag-sheathed Bi2Sr2CaCu2O
y
superconducting tape. The specimen showed a strong grain alignment which could be attained by adjusting the conditions of heat treatment. The degree of crystal orientation (F) was evaluated to be up to 95% by XRD for this specimen. In the case of magnetic field applied in a direction parallel to the tape, the J
c initially decreased with the magnetic field from 1.2×105 A/cm2 at 1 T to 5×104 A/cm2 at 10T and then remained almost constant up to 23 T. As the F value decreased from 95%, J
c also decreased. The pinning force (F
p) of the 95%-F-value tape was estimated to be about 1×1010 N/m3 at 23 T. This value is larger than those of conventional low-T
c superconductors.
Properties of Ag-Sheathed Bi-Pb-Sr-Ca-Cu-O Superconducting Tapes Prepared by the Intermediate Pressing Process
Authors: Yamada Yutaka , Jikihara Kazunori , Hasebe Tsuginori , Yanagiya Tomoyuki , Yasuhara Seiji , Ishihara Mamoru , Asano Toshihisa , Tanaka Yoshiaki
Published: February 2005

The influence of an intermediate pressing process on the superconducting properties of Ag-sheathed Bi-Pb-Sr-Ca-Cu-O superconducting tapes has been investigated. The critical current density (J
c) was improved by the effect of the uniaxial pressing and by a sintering process after the initial sintering. The maximum transport J
c at 77.3 K under zero magnetic field was indicated as 2.36×104 A/cm2, and that at 4.2 K under zero magnetic field was indicated as 1.5×105 A/cm2. The magnetic field dependence on the J
c at 4.2 K was summarized as follows: 5×104 A/cm2 (I⊥H, C-axis⊥H, 10 T) and 3×104 A/cm2 (I⊥H, C-axis//H, 10 T).
ESR Absorption in a High-Tc Bi(Pb)-Sr-Ca-Cu-O Superconductor
Authors: Nishida Akihiko , Horai Kazumi
Published: February 2005

ESR absorption at 22.9 GHz of the high-T
c phase of a Bi(Pb)-Sr-Ca-Cu-O ceramic superconductor has been studied under two different spectrometer modes: a conventional field-modulation mode and a direct reflection-amplitude mode. Owing to the effect of hysteresis in the microwave response, the field modulation did not provide the proper field derivative of ESR absorption. By employing the direct mode, we were able to obtain more reliable data for the temperature dependence of the g value, linewidth and integral intensity. The spin susceptibility followed the Curie-Weiss behavior with the negative Weiss temperature around -4 K.
Ultralow Resistivity in Langmuir-Blodgett Heterofilms
Authors: Hino Taro
Published: February 2005

Resistivity of LB heterofilms with the double layer consisting of arachidic acid (nonpolar) and TCNQ-derivative (polar) LB films was investigated at room temperature. As a result, ultralow resistivity of 10-8∼10-9 Ω·cm was measured in the direction of the film surface. Furthermore, very high current density of about 4.1×105 A/cm2 was observed. Such ultralow resistivity and very high current density seem to be due to the two-dimensional potential well with electron gas generated in the LB heterofilms.
The Effect of High Energy Electron Beam Bombardment on Single Crystal Bi2Sr2CuO6 Surfaces
Authors: Bocquet A. E. , Ogawa Susumu , Suga Shigemasa , Eisaki Hiroshi , Takagi Hidenori , Uchida Shin-ichi
Published: February 2005

XPS has been used to investigate the degradation of single crystal Bi2Sr2CuO6 surfaces induced by high-energy electron irradiation. For 1500 eV electrons, exposure at an incident current of 100 µA for 20 minutes causes negligible damage, while longer exposure times, or higher incident currents of 360 µA, cause a reduction of the surface copper species to monovalency. X-ray BIS spectra have been recorded for both fresh and damaged surfaces.