bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and Magnetic Properties of Bi1.5Pb0.5Sr2Ca2Cu3Ox Superconductors
Authors: Murayama Norimitsu , Sudo Eiichi , Awano Masanobu , Kani Keiko , Torii Yasuyoshi
Published: February 2005

New high-T
c superconductors were prepared by the partial substitution of Pb for Bi in Bi2Sr2Ca2Cu3O
x
. The X-ray diffraction analysis of Bi1.5Pb0.5Sr2Ca2Cu3O
x
showed that most of the sintered sample was in the 105 K phase. The lattice parameters were a=5.410 Å and c=37.18 Å. The transition temperature was 105 K. The lower critical field, H
c1, was 6 Oe at 77 K which was much smaller than that of YBa2Cu3O7-y
(52 Oe). The volume fraction of the 105 K phase was estimated to be about 80%.
Growth and Domain Structures of Ba2YCu3O7-y Single Crystals
Authors: Hayashi Kunihiko , Tokumoto Madoka , Takahashi Kazuhiro , Suzuki Yoshishige , Murata Keizo , Ihara Hideo , Koshizuka Naoki , Kimura Yo-ichi
Published: February 2005

Crystallographic and superconducting properties of single crystals of Ba2YCu3O7-y
grown by the flux method are studied. The single crystals were superconductors in as-grown atates. Domain observation by an interference microscope revealed that there were a few kinds of single crystals with a single domain and a few with several domains. A single-domain crystal had a tetragonal structure and a T
c onset of ∼45 K while a multidomain crystal had an orthorhombic structure and a T
c onset of ∼95 K. The latter crystal with no twins had several rectangular shape domains. It is thought that long one-dimensional chains of oxygens with a few 100 µm in length were realized in each domain of the crystal. The reason for the appearance of such domain structures is discussed.
Formation of a 100 K Superconducting Bi(Pb)-Sr-Ca-Cu-O Film by a Spray Pyrolysis
Authors: Nobumasa Hitoshi , Shimizu Kazuharu , Kitano Yukishige , Kawai Tomoji
Published: February 2005

A 100 K superconducting Bi(Pb)-Sr-Ca-Cu-O film was formed on a MgO(100) single crystal by a spray pyrolysis method. Fifteen hours heating of the as-sprayed film at 845°C in air was enough to give the superconducting film with a T
c zero higher than 100 K. An X-ray diffraction pattern showed that this film mainly consisted of the high-T
c phase with the orientation of the c-axis perpendicular to the surface.
Characterization of Ultrathin CaF2 Films Heteroepitaxially Grown on Si(111) Surfaces
Authors: Ando Koji , Saiki Koichiro , Sato Yasuhiro , Koma Atsushi , Asano Tanemasa , Ishiwara Hiroshi , Furukawa Seijiro
Published: February 2005

Ultrathin CaF2 films heteroepitaxially grown on Si(111) substrates have been characterized by low-energy electron energy loss spectroscopy and Auger electron spectroscopy. The measured specimens were transferred from the growth chamber to an analyzing chamber located at a distant facility without suffering any contamination by use of a newly developed portable vacuum chamber. It has been proved from the measurements that a CaF2 film of good quality grows even from the very initial stage of epitaxy.
Homogeneous Langmuir-Blodgett Film of Double-Chain Ammonium Amphiphile Complexed with Anionic Polymer
Authors: Shimomura Masatsugu , Fujii Koichi , Karg Peter , Frey Wolfgang , Sackmann Erich , Meller Paul , Ringsdorf Helmut
Published: February 2005

Heterogeneous textures suggesting the coexistence of a fluid and a solid phase were found both in a surface monolayer and in a deposited Langmuir-Blodgett (LB) film of double-chain ammonium amphiphiles by fluorescence microscopy. Although an annealing of the surface monolayer at 40°C allowed crystal growth, the heterogeneous phase separation remained in the LB film. A drastic change of the fluorescence image shows that the recrystallization of the complexed monolayer with anionic polymers conducted the homogeneous monolayer.
Determination of Nonstoichiometry in YBa2Cu3O7-x
Authors: Yamaguchi Shu , Terabe Kazuya , Saito Akihiko , Yahagi Sinichiro , Iguchi Yoshiaki
Published: February 2005

Oxygen nonstoichiometry of the YBa2Cu3O7-x
phase has been determined for between 200 to 850°C and oxygen partial pressure of 1.0 to 3.0×10-4 atm by thermogravimetric measurements. Values of the partial molar enthalpy of oxygen were estimated. The stable region of the orthorhombic phase was suggested to expand at lower temperatures.
Correlation between Si-H2 Bond Density and Electron Drift Mobility in a-Si:H Films Prepared by Photochemical Vapor Deposition
Authors: Kamimura Takaaki , Nozaki Hidetoshi , Sakuma Naoshi , Ito Hiroshi
Published: February 2005

The correlation between Si-H2 bond density and electron drift mobility in a-Si:H films has been investigated by using the dependence of the film properties on the silane gas pressure in mercury-sensitized photochemical vapor deposition. It was found that the electron drift mobility decreased with increasing the Si-H2 bond density, when the hydrogen contents were about the same amount.
Indium-Tin Oxide Thin Films Prepared by Thermal Decomposition of Metallic Complex Salts
Authors: Maruyama Toshiro , Kojima Akira
Published: February 2005

Transparent conductive indium-tin oxide thin films were prepared by thermal decomposition of metallic complex salts. The films of high transparency and low electric resistivity (4.23×10-4 Ω·cm) were obtained by dip coating glass substrates with raw-material solution followed by heating at 500°C for 20 min in an inert atmosphere.
In-Plane Photocurrent Spectroscopy of Undoped GaAs/AlAs Quantum Well Heterostructures
Authors: Fujiwara Kenzo , Tsukada Noriaki , Nakayama Takashi
Published: February 2005

Photocurrent conducting parallel to the undoped GaAs/AlAs quantum well layers increases due to the increased number of photogenerated carriers by excitonic resonance absorption. This offers a simple and sensitive means to measure excitonic absorption spectral features without substrate removal and allows us to observe a sharp resonance absorption peak with a 15 meV linewidth at room temperature for the lowest heavy-hole free-excitonic transition in a 7.0 nm-wide GaAs single quantum well. Heavy-hole free-excitonic transitions associated with up to third-order quantized states are also observed.
Thermal Stability of the High-Tc Superconductor in the Bi-Sr-Ca-Cu-O System
Authors: Endo Hozumi , Tsuchiya Jun , Kijima Naoto , Sumiyama Akihiko , Mizuno Masaaki , Oguri Yasuo
Published: February 2005

In order to examine the thermal stability of the high-T
c phase (T
c∼110 K) in the superconducting Bi-Sr-Ca-Cu-O system, thermal analyses under various oxygen partial pressures were made at a temperature range of 800 to 900°C. The high-T
c phase disappeared under oxygen partial pressures of 0.02 and 0.1 atm at 870°C and under higher oxygen partial pressures than 0.2 atm at a temperature range of 880 to 900°C.
Under oxygen partial pressures higher than 0.2 atm at 870°C, the amount of the high-T
c phase was markedly increased from the possible disproportionation reaction of the low-T
c phase (T
c∼80 K).
Temperature Dependence of Some Fundamental Physical Quantities in YBa2Cu3O7
Authors: Yasuda Takashi , Horie Yuuji , Youssef Ahmed A. A. , Kondo Ryuji , Shiraki Kazuyuki , Fukami Takeshi , Mase Shoichi
Published: February 2005

The resistivity and Hall coefficient of YBa2Cu3O7 were measured as a function of temperature. The data obtained were analyzed with a conductivity model of a diffusion type: σ
x
x
=n
e
2
D/2k
B
T. It is found that the carrier concentration n of hole type varies as n=n
0[1+αT] with the magnitude ratio αT>1 at T>T
c, and consequently the diffusion constant D varies as D∝1/n. Therefore, in terms of the relaxation time τ, it becomes 1/τ=A
T+B
T
2. The origin of two terms is discussed.
Substrate Damage Prevention and Simultaneous ZMR in Stacked SOI Layers
Authors: Theunissen M. J. J. , Baumgart H. , Haisma J. , Mulder J. M. L. , Rutten W. P. M.
Published: February 2005

This letter describes a multilayer structure which has successfully been used for recrystallization of thin polycrystalline silicon films on silicon dioxide, preventing at the same time the formation of thermal misfit dislocations in the underlying silicon substrate. A CO2 laser beam having a round spot with a Gaussian intensity distribution was used in the zone-melting process which resulted in a simultaneous recrystallization of two levels of polysilicon. The lower silicon film is of good crystalline quality and of significantly improved flatness.
Epitaxial Growth of CdTe by H2 Sputtering
Authors: Nishibayashi Yoshiki , Tokumitsu Yoji , Saito Koji , Imura Takeshi , Osaka Yukio
Published: February 2005

CdTe films can be grown epitaxially on InSb(100) by chemical sputtering in H2. The crystalline quality of the epitaxial layers is improved when the substrate temperatures are in the range of 200 to 250°C at a high rf discharge power of 400 W. In channeling experiments employing Rutherford backscattering spectrometry, the χmin (aligned yield/random yield) in the film prepared at 270°C and 400 W is 9.5%. A lattice strain of 0.05% is obtained from the results of X-ray diffraction. These values show that the crystalline quality of the epitaxial film grown by H2 sputtering is superior to the film grown by Ar sputtering.
Temperature-Scaling Theory for Low-Temperature-Operated MOSFET with Deep-Submicron Channel
Authors: Yi You-Wen , Masu Kazuya , Tsubouchi Kazuo , Mikoshiba Nobuo
Published: February 2005

A novel principle is suggested for the optimum design of deep-submicron channel MOSFET operated at liquid-nitrogen temperature. Current-voltage characteristics of MOSFET are scaled down in proportion to operation temperature, while the distribution of the mobile carrier is kept constant. The results of a two-dimensional simulation confirm our scaling theory. A combination scaling law is also suggested which comprises the temperature-scaling law and a dimensional scaling law.
Emission from Pulsating Combustion of Silane at a Reduced Pressure
Authors: Suga Shinsuke , Koda Seiichiro
Published: February 2005

A pulsating combustion was found to continue successively, after a mixture of flowing SiH4/He and O2 was ignitied by appropriate means in a Pyrex vessel at a total pressure of ca. 400 Pa. Light emission in the UV and visible region was spectroscopically resolved to be composed of band emissions of SiO(\TildeA-\TildeX) and OH(\TildeA-\TildeX), as well as a broad emission in the visible region. These findings were discussed from the mechanistic viewpoints of silane combustion and chemical vapor deposition of SiO2 films.
Improvement of Projectile Velocity and Impact Rate on a Target by Two-Stage Plasma Accelerator
Authors: Tamura Hideki , Sawaoka Akira B. , Igenbergs Eduard B.
Published: February 2005

A new two-stage plasma accelerator was tested to conduct the hypervelocity acceleration of microprojectiles. The accelerator consisted of a gas gun as the first stage and a plasma accelerator as the second stage. It was confirmed that the two-stage operation performed well at any timing started by the laser trigger system. It was found that the velocity of projectiles was increased in the two-stage operation and that the velocity greatly depended on the position at the beginning of acceleration. The impact rate of projectiles on a target was also markedly increased.
Soft Mode Contribution around Sm A-Sm C* Phase Transition Temperature under DC Bias Field in Ferroelectric Liquid Crystal
Authors: Ozaki Masanori , Hatai Takashi , Yoshino Katsumi
Published: February 2005

The relaxation of the soft mode is observed both in the Sm A and Sm C* phases by eliminating the contribution of the Goldstone mode under a dc bias field. Three relaxations are observed in the Sm C* phase at the frequency range below 10 MHz. The temperature dependence of the dielectric constant originating in the soft mode shows a sharp peak at the phase transition temperature between the Sm A and Sm C* phases, and shows Curie type behavior. An anomalous dip just below the peak of the dielectric constant is also observed at very high frequencies.
Ionic States of Copper Atoms in YBa2Cu3-xO7-y
Authors: Sasaki Satoshi , Inoue Zenzaburo , Iyi Nobuo , Takekawa Shunji
Published: February 2005

The number of electrons around Cu atoms of tetragonal YBa2Cu2.933O6.38 gas been calculated from the charge integrations by direct Fourier summations of X-ray diffraction data. The atomic charges estimated from the total number of electrons belonging to the Cu1 and Cu2 atoms are +0.98(8) e and +1.78(7) e, suggesting univalent (3d
10) and divalent (3d
9) ionic states, respectively. The respective ionic states accord with the observations of the spherical electron distribution (Cu1) and of localized electron (Cu2).
Zinc Diffusion Across the Heterojunction in InP/InGaAsP Heterostructures
Authors: Jung H. , Marschall P.
Published: February 2005

The influence of temperature treatment on the p-doping concentrations near the interfaces of an InP/InGaAsP heterostructure has been investigated. During this treatment a significant out-diffusion of Zn from the p-InP layer into the adjacent InGaAsP layers took place. Due to different segregation coefficients of Zn in InP and InGaAsP an out-diffusion of Zn from the InP into the InGaAsP layer also occurred when the p-doping in InP is lower than in InGaAsP. In InP/InGaAsP lasers such an out-diffusion of Zn into the active InGaAsP layer usually leads to enhanced threshold currents.
Zn and Si Doping in {110} GaAs Epilayers Grown by Metalorganic Chemical Vapor Deposition
Authors: Okamoto Kotaro , Furuta Mamoru , Yamaguchi Ko-ichi
Published: February 2005

Zn and Si doping are examined for {110} GaAs epilayers by introducing diethylzinc and silane during the course of metalorganic chemical vapor deposition. Hole concentrations of Zn doped {110} epilayers show a saturation around 1.5·1019 cm-3, which is one sixth of the hole concentration of {100} epilayers, and the occurrence of the saturation is due to interstitially incorporated Zn atoms. Electron concentration of Si-doped {110} epilayers are lower than those of {100} epilayers, which suggests that incorporation of Si atoms into As sites occurs more frequently for {110} epilayers than for {100} epilayers.
Gas-Temperature-Controlled (GTC) CVD of Aluminum and Aluminum-Silicon Alloy Film for VLSI Processing
Authors: Sekiguchi Atsushi , Kobayashi Tsukasa , Hosokawa Naokichi , Asamaki Tatsuo
Published: February 2005

In order to investigate the feasibility of CVD metallization for IC manufacturing processes, Al and Al-Si film depositions on silicon (100) wafers were studied using a precursor gas of triisobutylaluminum with and without disilane. A new mechanism for the gas temperature controller (GTC) was provided in the process chamber so as to activate the gas thermally just prior to its arrival at a heated substrate. The typical deposition rate was 700 nm/min. Without post-annealing, an alloy of Al-0.4%Si was obtained. Specific resistivity was 3.0 µΩ·cm, and specularity was about 60% at 550 nm for the GTC-CVD films of 1 µm thickness.
Growth of SiO2 Thin Film by Selective Excitation Photo-CVD Using 123.6 nm VUV Light
Authors: Inoue Kohji , Okuyama Masanori , Hamakawa Yoshihiro
Published: February 2005

A new technology for low-temperature growth of high-quality silicon dioxide (SiO2) film on silicon has been developed. The technology is photo-CVD using 123.6 nm light of a Kr resonance lamp from Si2H6 and O2, in which only Si2H6 can be selectively excited but not O2. The amounts of Si-OH bondings in the SiO2 films deposited by the 123.6 nm light are much lower than those by the other VUV lamps. The interface state density of the Si-MOS diode is extremely low, and its minimum value is 2×1010 cm-2 eV-1 near the Si midgap for the SiO2 film deposited at a substrate temperature of 145°C.
Structural and Photoluminescence Characterization of CdS/GaAs Films and CdS-ZnS Strained-Layer Superlattices Grown by Low-Pressure MOCVD Method
Authors: Endoh Yasuyuki , Kawakami Yoichi , Taguchi Tsunemasa , Hiraki Akio
Published: February 2005

Single-crystalline CdS films have been epitaxially grown on (100) and (111)A and B GaAs substrates at temperatures between 200 and 350°C by a low-pressure metalorganic chemical-vapor-deposition (MOCVD) method using (CH3)2Cd and H2S gases. The (100)-oriented film exhibits perfectly cubic modification, but contains dislocations and stacking faults. Moreover, the films on (111)A and B substrates show pure hexagonal growth. In particular, the photoluminescence (PL) spectrum at 4.2 K of the film grown on the (111)A substrate is characteristic of a hexagonal wurtzite crystal and is dominated by the presence of the strong I
2 (neutral-donor bound exciton) line at 2.547 eV and I
1 (neutral-acceptor bound exciton) line at 2.534 eV, and a donor-acceptor pair (I
E) band at 2.447 eV. CdS-ZnS strained-layer superlattice has for the first time been fabricated on GaAs substrate by MOCVD. The structural and 4.2 K PL properties are also presented.
A New Photobleachable Positive Resist for KrF Excimer Laser Lithography
Authors: Endo Masayuki , Tani Yoshiyuki , Sasago Masaru , Ogawa Kazufumi , Nomura Noboru
Published: February 2005

A new photobleachable positive resist for KrF excimer laser lithography has been developed. The resist is composed of 2-diazo-1,3-dicarbonyl compound as the alkaline dissolution inhibitor and an alkaline-soluble styrene polymer as the mainpolymer. The new positive resist had excellent properties of photobleaching and dissolution kinetics. We achieved high aspect ratio half-micron pattern fabrication in 1.0 µm thickness with little loss of resist thickness using this new resist.
Charge Losses of N-Doped Trench Cells
Authors: Risch Lothar , Maly Rotraud , Bergner Wolfgang , Kircher Roland
Published: February 2005

N-doped trench cells exhibit increased charge losses during the refresh time interval when the cell plate voltage is reduced below 2.5 V. This effect is attributed to tunneling of electrons from the valence band of the n-region into the conduction band thus contributing to the leakage current of the cell. This is verified by numerical simulations which indicate that tunneling will occur preferently at the upper corners of the trench. The tunneling current is calculated based on a modified WKB-approximation using 2D potential and imref distributions.
Reversible Tc Change in Bi-Sr-Ca-Cu-O Thin Films by UV Photo and Thermal Annealings
Authors: Kawasaki Masashi , Nagata Shunroh , Takeuchi Kou , Koinuma Hideomi
Published: February 2005

UV light irradiation in oxygen atmosphere was found to cause a change of critical temperature in Bi-Sr-Ca-Cu-O thin films. The change was observed to be reversible between 80 K after thermal annealing and 60 K after photo irradiation. It accompanied a change in the lattice constant, suggesting that further oxygen incorporation into the 80 K phase thin films occurred by the UV light irradiation.
Threading Dislocation Density Reduction in GaAs on Si Substrates
Authors: Nishioka Takashi , Itoh Yoshio , Sugo Mitsuru , Yamamoto Akio , Yamaguchi Masfumi
Published: February 2005

The effects of annealing and insertion of strained intermediate layers on the reduction of threading dislocation density are investigated through etch-pit density evaluation. A model to explain the efficiency of the reduction techniques is proposed, which is that larger forces exerted on the dislocation lines lead to more effective dislocation reduction. This indicates that thicker layers in the annealing process and thicker strained intermediate layers within the critical thickness for dislocation generation give rise to better dislocation reduction effects.
Cation Contents and Superconducting Properties of the High-Tc Phase of Bi-Pb-Sr-Ca-Cu-O Ceramics
Authors: Murayama Norimitsu , Awano Masanobu , Sudo Eiichi , Torii Yasuyoshi
Published: February 2005

Energy dispersive X-ray analysis was carried out on samples with the starting compositions of Bi1-x
Pb
x
Sr0.8CaCu1.4O
y
(x=0.15, 0.20, 0.25). The Bi and Pb contents in the high-T
c phase were about 80% of the starting contents. A narrow range of solid solutions exists in the Bi-Pb-Sr-Ca-Cu-O system. It seems that Pb does not enter the Cu or Ca site. The temperature dependence of the initial magnetization curve was measured. The slope of the curve at 100 K was lower than that at 77 K. Therefore, it seems that superconducting phases with T
c's lower than 100 K exist, although these phases show the same X-ray diffraction pattern as the high-T
c phase.
YBa2Cu3Oy Superconducting Thin Film Obtained by Laser Annealing
Authors: Aizaki Naoaki , Terashima Koichi , Fujita Jun-ichi , Matsui Shinji
Published: February 2005

A rapid and low-temperature process to obtain YBa2Cu3O
y
superconducting thin film was studied using a laser annealing technique. As-deposited thin film prepared by ion beam sputtering was converted into the superconductive film using argon laser beam processing, where melting, quenching to 400°C and annealing at 400°C in air were carried out. The onset critical temperature was 80 K and the end-point critical temperature was 60 K. Structure, composition and surface morphology were studied by X-ray diffraction, electron probe micro-analysis and scanning electron microscope.
A Method of Quantitative Contamination with Metallic Impurities of the Surface of a Silicon Wafer
Authors: Hourai Masataka , Naridomi Toshio , Oka Yasunori , Murakami Katsumi , Sumita Shigeo , Fujino Nobukatsu , Shiraiwa Toshio
Published: February 2005

A method of quantitative and uniform contamination of the surface of a silicon wafer with a metallic impurity in low-level quantities using spin coating with a contaminated aqueous solution was developed. Fe, Ni, Cu and Al were examined and the quantities of these metallic impurities on the surface were controlled by the concentration of metal ions in the contaminated solution. Using this method, the influence on the recombination carrier lifetime was quantitatively investigated. A significant degradation of the recombination lifetime was observed for more than 1011 atoms/cm2 of impurities Cu, Ni and Fe on the surface.
A Unified Analysis on Hot Carrier Generation in p-Channel and n-Channel MOSFET's
Authors: Saito Kazuyuki , Yoshii Akira
Published: February 2005

This paper shows hot carrier generation in p-channel and n-channel MOSFET's. In the gate current analysis, the electron temperature in the pMOSFET, which is 2430 K at V
ds=-5 V, and 2650 K at V
ds=-6 V, is determined experimentally. Moreover, it is shown that electrons strongly interact with holes. From the substrate current analysis of nMOSFET's and pMOSFET's using the equation I
sub=M
I
d exp
[-βl/(V
ds-V
dsat)], it is confirmed that the effective length of the velocity saturation region l has the same value in pMOSFET's and nMOSFET's, and the temperature of the majority carrier in the nMOSFET is 1.47 times higher than that in the pMOSFET under the same drain voltage. The value of 1.47 is nearly equal to the ratio of the optical phonon mean free path for holes to that for electrons, which is 1.38.
RHEED Intensity Observation during TEGa-As4 Alternate Supply Growth of GaAs
Authors: Uneta Makoto , Watanabe Yoshio , Ohmachi Yoshiro
Published: February 2005

The RHEED intensity variation during the growth of GaAs with an alternating supply of TEGa and As4 is investigated. The measurements of the RHEED intensity recovery after supplying As4 molecules on the Ga-deposited surface and the growth rate of GaAs in the alternating TEGa and As4 supply mode demonstrate that the Ga deposition time T0, at which the RHEED intensity rises to a maximum, corresponds exactly to the Ga monolayer formation time. Using T0 as a measure of the Ga monolayer formation time, the decomposition rate of TEGa molecules is investigated as a function of the substrate temperature. The TEGa decomposition reaction takes place in the substrate temperature range of 350–450°C. The growth rate measurement shows that the decomposition rates are same on the As- and Ga-terminated surface.
Chloride VPE of AlxGa1-xAs by the Hydrogen Reduction Method Using a Metal Al Source
Authors: Hasegawa Fumio , Katayama Koji , Kobayashi Ryuji , Yamaguchi Hiromu , Nannichi Yasuo
Published: February 2005

VPE of AlGaAs by the chloride transport method using separate Al and Ga metals has been demonstrated for the first time. AsCl3 instead of toxic AsH3 was used as the arsenic source. Mirror-like surfaces with growth rates of 1–2 µm/hr were obtained. Background doping levels range in the order of 1018 cm-3, probably due to the reaction between AlCl3 and the quartz reactor. Band-edge emissions were observed in the photoluminescence spectra.
Direct Evidence for the Absence of 1/ω Type Anomalous Frequency Dependence of the Shear Viscosities of Smectic-A Liquid Crystals
Authors: Yamamoto Jun , Okano Koji
Published: February 2005

By measuring the shear mechanical transfer function of the smectic-A phases of octylcyanobiphenyl (8CB) and octyloxycyanobiphenyl (8OCB) in the low frequency range from 1 Hz to 1 kHz, it was demonstrated directly that the Martin-Parodi-Pershan shear viscosities η2 and η3 of smectic-A liquid crystals do not diverge as 1/ω at low frequencies ω contrary to the case of bulk viscosities.
Highly Conducting and Transparent SnO2 Thin Films Prepared by RF Magnetron Sputtering on Low-Temperature Substrates
Authors: Minami Tadatsugu , Nanto Hidehito , Takata Shinzo
Published: February 2005

Highly conducting and transparent thin films of undoped tin oxide (SnO2) are prepared on unheated substrates (≦90°C) by rf magnetron sputtering under an applied external dc magnetic field. The lowest resistivity obtained is 1.9×10-3 Ωcm. The SnO2 films with a sheet resistance below 200 Ω/s
q and an average visible transmittance (between 400 and 700 nm) above 85%, and below 300 Ω/s
q above 80% (including organic film substrate) can be obtained for the films deposited on glass substrates and organic film substrates, respectively.
Specific Heat on Metamorphic and Iron-Doped GdBa2Cu3O7-δ
Authors: Oota Akio , Kojima Teruhisa
Published: February 2005

Magnetic ordering and lattice properties were studied through low-temperature specific heat on metamorphic and Fe-doped GdBa2Cu3O7-δ. The orthorhombic to tetragonal (O-T) phase transition due to an increase of the parameter δ in GdBa2Cu3O7-δ causes a decrease of the Debye temperature θD, together with the rapid drop of superconducting transition temperature T
c, while causing no significant change in the Néel temperature T
N. This is compared with the result for GdBa2(Cu1-x
Fe
x
)3O7-δ, where the values of T
N and θD as well as T
c are insensitive to the variation of x during the course of O-T transition.
Preparation of High-Tc Superconducting Films by Q-Switched YAG Laser Sputtering
Authors: Komuro Shuji , Aoyagi Yoshinobu , Morikawa Takitaro , Namba Susumu
Published: February 2005

A laser sputtering technique using visible light from a Q-switched YAG laser is proven to be of use for high-T
c Y-Ba-Cu-O superconducting film fabrication. The obtained films reveal onset T
c of 98 K and offset T
c of 90 K, which are very similar to the bulk target material. The compositional ratios of Ba/Y and Cu/Y in as-sputtered films are found to be in perfect agreement with those in the bulk target material for a used laser power range. These results are well explained by a cluster model for the sputtering process.
High-Resolution Electron Microscopy of Modulated Structure in the New High-Tc Superconductors of the Bi-Sr-Ca-Cu-O System
Authors: Matsui Yoshio , Maeda Hiroshi , Tanaka Yoshiaki , Horiuchi Shigeo
Published: February 2005

Both high-T
c (105 K) and low-T
c (75 K) superconducting oxides recently reported by Maeda et al. (Jpn. J. Appl. Phys.: in press) are examined by transmission electron microscopy with an EDX analysis. The chemical compositions are estimated to be Bi4Sr3Ca3Cu6O
x
and Bi4Sr3Ca2Cu4O
y
for high- and low-T
c samples. The diffraction patterns and high-resolution structure images show that the compounds have layered structures with alternate Bi2O2 layers and perovskite ones in a c-direction. A high-resolution image projected along the a-axis clearly shows the presence of the modulated structure with lattice curving.
Possible Model of the Modulated Structure in High-Tc Superconductor in a Bi-Sr-Ca-Cu-O System Revealed by High-Resolution Electron Microscopy
Authors: Matsui Yoshio , Maeda Hiroshi , Tanaka Yoshiaki , Horiuchi Shigeo
Published: February 2005

A model for the modulated crystal structure (Matsui et al.: Jpn. J. Appl. Phys. in press) in high-T
c superconductor in a Bi-Sr-Ca-Cu-O system is proposed based on the high-resolution electron microscope images. Ideally, it is body-centered orthorhombic with a=0.54, b=5a=2.7 and c=3.08 nm. The Bi2O2 layers do not form complete sheets, but contain occupational and/or positional fluctuation of Bi-sites to form “Bi-concentrated bands” which extend in the a-direction. Contraction of lattice planes along the b-axis is induced in the Bi-concentrated bands, causing compensating expansion in the remaining Bi-deficient ones.
Preparation of High-Tc Bi-Sr-Ca-Cu-O Superconducting Thin Films by AC Sputtering
Authors: Koinuma Hideomi , Kawasaki Masashi , Nagata Shunroh , Takeuchi Kou , Fueki Kazuo
Published: February 2005

Thin films of Bi-Sr-Ca-Cu-O superconductors were prepared on a polycrystalline YSZ substrate by the 50 Hz ac sputtering method. A pair of targets with various compositions were used in this apparatus. The films deposited without intentional heating were amorphous insulators. When the films were annealed at temperatures ranging from 750°C to 900°C, X-ray diffraction analysis showed that they had highly oriented periodic superstructures with various planar spacings. A specimen annealed at 800°C for 120 min has T
c(onset) and T
c(zero resistive) of 115 K and 73 K, respectively.
Appearance of Superconductivity in Tetragonal Nd1.5Ba1.5Cu3Oy
Authors: Tsurumi Shigeyuki , Iwata Tsunekazu , Tajima Yukimichi , Hikita Makoto
Published: February 2005

Temperature dependence of magnetic susceptibility for superconducting Nd1.5Ba1.5Cu3O
y
(T
c∼6 K) was measured. The susceptibility of the normal state follows the Curie-Weiss law with µeff=3.0 µB which is smaller than that of the Nd3+ free ion. Susceptibility decreases below 40 K due to the Meissner effect and then increases due to the magnetic effect of the Nd+3 ions.
ESR and X-Ray Diffraction Studies on Ba-Y-Cu-O Superconductors
Authors: Morimoto Akiharu , Maeda Toshihiro , Moto Akihiro , Kumeda Minoru , Shimizu Tatsuo
Published: February 2005

ESR, X-ray diffraction and resistivity measurements were carried out for as-sintered Ba2Y1Cu3Ox, quenched Ba2Y1Cu3Oxand as-sintered Ba2Y1Cu3OxFy. The ESR spin density is found to be a good measure for the amount of an impurity phase Ba1Y2Cu1O5. A decrease in the sintering temperature reduces the amount of the impurity phase. A transition from a superconducting orthorhombic to a nonsuperconducting tetragonal structure induces no large change in the ESR signal. It is also found that an as-sintered Ba2Y1Cu3OxFysuperconductor shows a strong ESR signal originating mainly from the impurity phase.
Quantitative Photoacoustic Imaging of Biological Tissues
Authors: Nagai Satoshi , Izuchi Masaya
Published: February 2005

It is shown that quantitative photoacoustic images can be obtained by measuring the phase-lag under rear-surface illumination. The images reflect only thermal diffusivities of samples. Special attention is focused on thin samples of biological tissues and good correlation is observed between thermal and optical properties.
Fabrication of Y-Cu Liquid Metal Ion Source
Authors: Ochiai Yukinori , Kojima Yoshikatsu , Matsui Shinji
Published: February 2005

Y-Cu liquid metal ion source (LMIS) has been successfully fabricated using Y67-Cu33 (atomic%) alloy, which has a 760°C eutectic point. Tip materials used as needle and heater are W and Ta. It was observed that Cu+ and Y+ were dominant ion species emitted from this LMIS. Ion beam current stability and lifetime were better when Ta was used as a tip material than when W was used. It was observed that the liquid metal ion source lifetime was over 20 h.
Electrooptic Bistability of a Ferroelectric Liquid Crystal Device Prepared Using Polyimide Langmuir-Blodgett Orientation Films
Authors: Ikeno Hidenori , Oh-saki Akitoshi , Nitta Michio , Ozaki Norihiko , Yokoyama Yasuaki , Nakaya Kenji , Kobayashi Shunsuke
Published: February 2005

Excellent bistability was demonstrated in a ferroelectric liquid crystal electrooptic device prepared using polyimide Langmuir-Blodgett films for the orientation of the liquid crystals without performing rubbing.
Structural and Electrical Anomalies of Ba2YCu3O7-y at the Oxygen Stoichiometry of 6.48
Authors: Ono Akira , Kobayashi Michiko , Nozaki Hiroshi , Matsui Yoshio
Published: February 2005

Ba2YCu3O7-y
(7-y\fallingdotseq6.48) was prepared by quenching a specimen from 735–738°C in air, and subsequently annealing at 420°C in a sealed gold capsule. The material may have been a superconductor for about 3 min after the opening of the gold capsule, but it changed to a nonsuperconducting material with high electrical resistivity by the reaction with moisture in air. The lattice constants of the material are abnormal, and a superstructure was observed for 30–40% of the particles by electron microscopy.
Observations of Dislocations in White Tin Using High-Resolution Electron Microscopy
Authors: Ojima Kozo , Taneda Youji
Published: February 2005

End-on dislocations in white tin crystals have been examined using high-resolution electron microscopy. The experimental lattice images indicated the dissociation of a perfect dislocation lying in the (100) plane. The imperfect dislocation formed by the dissociation had a Burgers vector ½[010].
Interface Stress at OMVPE-Grown ZnSxSe1-x/GaAs:Cr Heterostructure
Authors: Tonami Yoshiyuki , Nishino Taneo , Hamakawa Yoshihiro , Sakamoto Takao , Fujita Shigeo
Published: February 2005

The interface stress at OMVPE-grown ZnS
x
Se1-x
/GaAs:Cr (x=0.03∼0.14) heterostructures has been investigated using the Cr-related photoluminescence line at 0.839 eV from GaAs:Cr substrates. From analysis of the shift of the Cr-related luminescence line, it has been found that the GaAs substrates at the heterointerface suffer compressive stress almost independent of the composition of ZnS
x
Se1-x
epitaxial layers. Such compressive stress at the GaAs substrates can be explained as being due to the difference between the thermal expansion coefficients of ZnS
x
Se1-x
and GaAs; the thermal stress introduced in cooling from the growth temperature (500°C) of ZnS
x
Se1-x
on GaAs.
Superconductivity of Bi0.25-ySr0.25-yCa2yCu0.5Ox (y=0.1, 0.125, 0.15)
Authors: Sumiyama Akihiko , Yoshitomi Toshihiko , Endo Hozumi , Tsuchiya Jun , Kijima Naoto , Mizuno Masaaki , Oguri Yasuo
Published: February 2005

Resistivity and magnetic susceptibility of superconducting Bi0.25-y
Sr0.25-y
Ca2y
Cu0.5O
x
(y=0.1, 0.125, 0.15) have been measured and compared with the results of X-ray powder diffraction. The volume fraction of the low-T
c phase (T
c∼75 K) decreases as the Ca concentration is increased and superconductivity attributed to the high-T
c phase (T
c>100 K) is observed. Resistivity of Bi0.125Sr0.125Ca0.25Cu0.5O
x
shows a sharp transition above 100 K and becomes zero at 97 K.
X-Ray Diffraction Study on the Crystal Structure of Nd1+xBa2-xCu3O7-δ
Authors: Takita Kôki , Katoh Hideo , Akinaga Hiroyuki , Nishino Makoto , Ishigaki Tōru , Asano Hajime
Published: February 2005

Crystal structures in the Nd1+x
Ba2-x
Cu3O7-δ system have been investigated by X-ray powder diffraction combined with Rietveld analysis. The compound NdBa2Cu3O7-δ is isomorphic with orthorhombic YBa2Cu3O7-δ. With the increase of x the orthorhombic distortion decreases, and the compound becomes tetragonal at x=0.2. The tetragonal structure is isomorphic with the tetragonal form of YBa2Cu3O7-δ. T
c of the compounds with x=0 and 0.05 is above 90 K, which decreases monotonically with x and the compound becomes semiconducting at x=0.4.
“Incipient Orthorhombic” Phase in Ba2YCu3O7-x Ctystals
Authors: Ichihashi Toshinari , Iijima Sumio , Kubo Yoshimi , Shimakawa Yuichi , Tabuchi Junji
Published: February 2005

Twinning in a wide oxygen-deficiency range of Ba2YCu3O7-x
crystals (0.15<x<0.78) prepared by a quenching method was examined by electron optical methods. Prior to the complete tetragonal-orthorhombic phase transformation, an “incipient orthorhombic” phase was observed in the x=0.78 specimen, whose crystal was not a superconductor. The incipient orthorhombic phase is considered as having finely dispersed domains in a tetragonal crystal. The incipient phase was also observed in a 5% Co-doped Ba2YCu3O7-x
crystal, which is a superconductor with a T
c value of 60 K. Lowering of T
c values due to Co-dopants seems to be attributed to development of the incipient orthorhombic phase.
Sputter Deposition of BiSrCaCuO Thin Films
Authors: Fukutomi Masao , Machida Junichi , Tanaka Yoshiaki , Asano Toshihisa , Maeda Hiroshi , Hoshino Kazutomo
Published: February 2005

The sputter deposition of superconducting Bi-Sr-Ca-Cu-O thin films was studied with particular reference to the relation between the deposition conditions and the superconducting properties of the films obtained. After annealing, the films sputtered from a sintered Bi1.3Sr1Ca1Cu1.5O
x
target exhibited superconductivity with zero-resistance at 83 K. The possibility of obtaining high-T
c superconducting film without post-deposition annealing was also demonstrated.
Cross-Sectional TEM Observation of Ba2YCu3O7-x Film on SrTiO3
Authors: Tomita Masato , Hayashi Takayoshi , Takaoka Hidetoshi , Ishii Yoshikazu , Enomoto Youichi , Murakami Toshiaki
Published: February 2005

Ba2YCu3O7-x
(BYCO) films epitaxially grown on (100) SrTiO3 substrates were examined by cross-sectional TEM. Near the film/substrate interfaces, the films consist of crystal grains whose boundaries have a regular atomic arrangement over the entire boundary area (coherent boundaries). The c axis of each crystal grain is oriented parallel to one of the three <100 > axes of the SrTiO3 substrate. Lattice constants measured with electron diffraction are a=b=c/3=0.390 nm. There are no mixed or amorphous layers at the interfaces.
Preparation of Superconducting Bi-Ca-Sr-Cu-O Printed Thick Films Using a Coprecipitation of Oxalates
Authors: Nakamori Tomohiro , Abe Hitoshi , Takahashi Yoshiro , Kanamori Takashi , Shibata Susumu
Published: February 2005

Bi-Ca-Sr-Cu-O thick films were prepared by printing using a coprecipitation of oxalates on (100) single-crystal MgO. We have obtained a superconducting thick film with T
c (extrapolated to zero-resistance) of 105 K, T
on of 115 K and T
off of 80 K, and it appears to be strongly oriented along the c-axis perpendicular to the substrate.
Upper Critical Field of New Oxide Superconductor Bi-Sr-Ca-Cu-O
Authors: Kumakura Hiroaki , Shimizu Hitoshi , Takahashi Kazuhiko , Togano Kazumasa , Maeda Hiroshi
Published: February 2005

The upper critical field H
c2 of Bi-Sr-Ca-Cu-O superconducting material, with a resistive transition above 100 K, was investigated by observing variations in resistivity with temperature down to 50 K and with magnetic fields up to 12 T. The slope of the critical field, the change in H
c2 with temperature, was -1.5 T/K for the midpoint of the transition. The values of H
c2 at 77 K and 0 K were estimated by extrapolation to be 41 T and 108 T, respectively.
Effect of Pressure on Superconducting Transition Temperatures in the Bi-Sr-Ca-Cu-O System
Authors: Okai Bin , Kosuge Michikazu , Takahashi Koh , Ohta Masatsune
Published: February 2005

Superconducting transition temperatures were measured under pressure for the Bi-Sr-Ca-Cu-O system. The transition temperature near 80 K (T
c1) slightly increases with pressure: dT
c1/dp=0.06 K/GPa (onset), while T
c near 110 K (T
c2) decreases with pressure: dT
c2/dp=-0.2 K/GPa (onset) and -0.3 K/GPa (complete). The negative pressure-dependence was discussed with regard to the resonating-valence-bond theory.
The Effect of Scanning Electron Beam Annealing on the Reverse Current in Ti-GaAs Schottky Diodes
Authors: Meglicki Zdzislaw , Nener Brett D. , Prasad Krishnamachar , Sharda Hemlata , Faraone Lorenzo , Nassibian Armenag G.
Published: February 2005

The effects of scanning electron beam annealing of Ti-GaAs Schottky diodes on the reverse diode characteristics are observed and discussed. Significant reductions in the values of the saturation current, the generation current and the shunt current are attributed to the low-energy secondary excitations generated by electron bombardment.
Heavily Sn-Doped GaAs Buffer Layers for AlGaAs/GaAs HBTs
Authors: Ito Hiroshi , Ishibashi Tadao
Published: February 2005

The Sn atom profile in MBE grown GaAs with a buried, heavily doped layer was characterized using SIMS analysis. Sn carryforward was prevented by decreasing either the growth temperature or doping concentration. Bulk resistivity of 0.0006 Ω·cm with a free carrier concentration of 1×1019 cm-3 and specific contact resistance of 1.6×10-7 Ω·cm2 were obtained with samples grown at 600°C. To confirm the feasibility of the heavily Sn-doped buffer layer, an AlGaAs/GaAs heterojunction bipolar transistor was fabricated. A current gain of 120 and base-collector junction breakdown voltage of 16 V were obtained.
EXAFS Studies of Amorphous Nickel-Zirconium Alloys
Authors: Maeda Hironobu , Fukunaga Toshiharu , Suzuki Kenji , Osamura Kouzo , Hida Moritaka , Terauchi Hikaru , Kamijo Nagao
Published: February 2005

Extended X-ray absorption fine structure (EXAFS) measurements have been made on the zirconium K absorption edge in amorphous NixZr1-xalloys withx=0.33, 0.50 and 0.67. The aim of this study is to understand the local structure vs composition in this system. It has been revealed as follows: (a) the bond length are 2.57 Å for the Zr-Ni pair and remain constant over the whole concentration range; (b) the second peak of the radial structure function consists of two component atoms, zirconium atom and nickel atom.
Molecular Beam Epitaxial Growth of (AlyGa1-y)0.5In0.5P on (100) GaAs
Authors: Hayakawa Toshiro , Takahashi Kosei , Sasaki Kazuaki , Hosoda Masahiro , Yamamoto Saburo , Hijikata Toshiki
Published: February 2005

High-quality (Al
y
Ga1-y
)0.5In0.5P layers lattice-matched to a (100) GaAs substrate have been grown by molecular beam epitaxy with the dimetric phosphorus (P2) beam. The line width of a room temperature photoluminescence spectrum of an undoped layer of Ga0.5In0.5P and (Al0.33Ga0.67)0.5In0.5P is as narrow as 36.5 and 40.6 meV, respectively. The former is comparable to the line width reported on high-quality liquid-phase epitaxial layers. An n-Al0.44In0.56P layer (Si=2×1017 cm-3) lattice-mismatched to a GaAs substrate has shown a fairly intense room-temperature photoluminescence comparable to the edge emission of an n-(Al0.65Ga0.35)0.5In0.5P lattice-matched to a GaAs substrate.
Properties of a-SiN0.7:H Films in High Electric Field
Authors: Maeda Keiji , Fukuda Kaichi , Matsumura Kunio , Ibaraki Nobuki
Published: February 2005

To understand the mechanism of transport in a high electric field, various properties of a-SiN0.7:H films deposited by rf glow discharge were investigated. The results are explained by a model in which two kinds of centers with different barrier heights are subject to Poole-Frenkel ionization. Either one of these centers contributes to the current, depending on the temperature. Above room temperature, the center contributing to Poole-Frenkel current is the neutral Si dangling bond, where the Fermi level is located. Below room temperature, the center can be associated with the negatively charged Si dangling bond, which behaves as an electron trap for photoconductivity. Based on this understanding of energy levels subject to Poole-Frenkel ionization, field enhancement of the photocurrent was expected and actually observed for the first time.
Stability of Electrical and Photovoltaic Characteristics of HBr Solution-Doped Polyacetylene
Authors: Lee M. S. , Tzeng J. S. , Chen Y. C. , Shiramatsu T.
Published: February 2005

Polyacetylene was doped with hydrogen bromide (HBr) solution. The electrical conductivity of the solution-doped polyacetylene increased by an order of six from 5×10-9 S/cm to 4×10-3 S/cm. Here the stability of HBr-doped polyacetylene is discussed with respect to the changes in conductivity due to heat treatment and exposure to air, in comparison with I2-doped polyacetylene. The HBr-doped polyacetylene is slightly more stable than the I2-doped polyacetylene. The Al/cis-[CH(HBr)
y
]
x
/Au M-S Schottky barrier solar cell was fabricated, and its properties were investigated. The maximum energy conversion efficiency of the cell was 0.9% under the illumination of an incident light intensity of 10 mW/cm2.
Nonvolatile Memory Based on Reversible Phase Transition Phenomena in Telluride Glasses
Authors: Gosain Dharam Pal , Nakamura Minoru , Shimizu Tomoyasu , Suzuki Masakuni , Okano Shuichi
Published: February 2005

The phase transitions from amorphous to crystalline states, and vice versa, by applying electrical pulses were studied for sandwich structures of metal/Ge
x
Te100-x
thin film/metal. A systematic study of the crystallization temperature in Ge
x
T100-x
(5\leqslant x \leqslant 30) thin films has been carried out. In some compositions, more than 104 repetitions of amorphous to crystalline states, and vice versa, were attained by the application of electric pulses. A model is proposed to explain the results observed.
Preparation of c-Axis-Oriented PbTiO3 Thin Films by MOCVD under Reduced Pressure
Authors: Okada Masaru , Takai Satoru , Amemiya Mitsuo , Tominaga Koji
Published: February 2005

Ferroelectric PbTiO3 thin films were prepared by a simultaneous deposition of TiO2 and PbO on heated substrates under the reduced pressure of 6 Torr. Titanium tetraisopropoxide and tetraethyl lead were used as source materials. The deposition behaviors of TiO2 and PbO were examined independently. Homogeneous nucleations of the reaction species in the vapor phase were depressed under the reduced pressure. The films obtained at 500° to 650°C of consisted of PbTiO3 of the single perovskite phase, and highly c-axis oriented and epitaxal films were grown on MgO(100). The deposition rate of the film available by adjusting the source temperature and the flow rate of the carrier gas is 50 to 1000Å/min, the maximum value of which is ten or more times that obtained by the conventional sputtering method.
Effects of Excited Plasma Species on Silicon Oxide Films Formed by Microwave Plasma CVD
Authors: Fukuda Takuya , Ohue Michio , Momma Naohiro , Suzuki Kazuo , Sonobe Tadashi
Published: February 2005

By using a microwave plasma deposition system, effects of highly excited plasma species on the film formation of silicon oxide have been studied and the roles of excited ion and radical species have been investigated by emission spectra of the excited plasma species. A strong correlation was confirmed between film quality and the amount of highly excited ion species transported to the substrate. Furthermore, high quality films could be formed by increasing the amount of the excited species.
Schottky Interface Formation between LaB6 and GaAs(001) Covered with a Native-Oxide Layer
Authors: Yokotsuka Tatsuo , Narusawa Tadashi , Nakashima Hisao
Published: February 2005

The influence of native-oxide layers on LaB6–GaAs(001) interface formation has been studied by X-ray photoelectron spectroscopy (XPS). LaB6 deposition reduces the GaAs native-oxide layer, and subsequent heat-treatment enhances the reduction. The behavior of band-bending of the LaB6–GaAs interface due to heat-treatment is similar to the case of the freshly MBE-grown surface.
Thermodynamical Analysis and Luminescence Properties of Vapor-Grown ZnSxSe1-x II–Bypass Flow Effect–
Authors: Goto Hideo , Zhou Jun , Sawaki Nobuhiko , Akasaki Isamu
Published: February 2005

The improved vapor phase epitaxial growth technique is applied to the growth of a ZnS
x
Se1-x
layer on a Gap substrate. It is predicted by a thermodynamical analysis and confirmed experimentally that the ZnS molar fraction x can be controlled over a wide range by varying the amount of hydrogen fed through a bypass tube to dilute the source gas without changing the source and/or the substrate temperature. The photoluminescence spectra of the ZnS
x
Se1-x
/GaP (0.50<x<1.0) sample exhibit only a strong edge emission at room temperature, showing that the epitaxial layers are of high quality.