bluuebunny/crossref_metadata_2025 huggingface dataset:
Superconductivity in a New Oxide System of Eu-La-Ce-Cu-O
Authors: Yoshimoto Mamoru , Hashimoto Takuya , Takata Masasuke , Koinuma Hideomi
Published: February 2005

A Ce-doped Eu-La-Cu-O system was confirmed to be superconducting by the observation of the Meissner effect. Compounds with the nominal compositions of Eu2-x-y
La
y
Ce
x
CuO4-δ (x=0.1 to 0.2, and y=0.8 to 1.4) were prepared by sintering the constituent metal oxide powders in a stream of Ar. The XRD pattern of the compounds primarily exhibited the T'-phase (Nd2CuO4) structure. The measurements of resistivity and susceptibility indicate that the samples have T
c
onset in the range of 11 K to 18 K.
Metal-Insulator Transition in the Bi2Sr2Ca1-xYxCu2O8+y System
Authors: Tamegai Tsuyoshi , Koga Kei-ichi , Suzuki Kunio , Ichihara Masaki , Sakai Fumiko , Iye Yasuhiro
Published: February 2005

Metal-insulator transition driven by the change of the carrier concentration was investigated in the 80 K superconductor Bi2Sr2CaCu2O8+y
. The carrier concentration was controlled by the substitution of yttrium for calcium. Experimental results from structural, transport, and magnetic studies are discussed in comparison with other high-temperature superconductor systems, La2-x
Sr
x
CuO4 and YBa2Cu3O7-y
.
Magnetization of a YBa2Cu3O7 Crystal Prepared by the Quench and Melt Growth Process
Authors: Murakami Masato , Morita Mitsuru , Koyama Noboru
Published: February 2005

Magnetization measurements have been conducted on YBa2Cu3O7 samples fabricated by the quench and melt growth(QMG) technique using a vibrating sample magnetometer at 77 K. It has been found that the magnetization behavior of QMG-processed YBa2Cu3O7 can be understood in terms of Bean critical state model.
Preparation and Physical Properties of (Bi1-xLnx)2.2Sr1.8CaCu2Oy (Ln=La, Pr and Nd, x≦0.25)
Authors: Zhengnan QIAN , Okai Bin , Tanaka Junzo , Nozaki Hiroshi , Ohta Masatsune , Matsunaga Masahisa
Published: February 2005

Solid solutions (Bi1-x
Ln
x
)2.2Sr1.8CaCu2O
y
(Ln=La, Pr and Nd, x≦0.25) were prepared. Of these three Ln ions replacing Bi3+, Pr was not trivalent, the average valence of Pr being shown to be 3.5. With increase of x, the onset of superconducting transition temperature and hole concentration initially increase, then decrease steadily with increase of x equally for all the three series, irrespective of difference in lanthanide elements substituted.
Structure and Superconducting Properties of the Bi1.4Pb0.6Sr4-xCaxCu3.8Oy System (0≤x≤4)
Authors: Lee Hee-Gyoun , Kim Chan-Joong , Won Dong-Yeon
Published: February 2005

Samples of Bi1.4Pb0.6Sr4-x
Ca
x
Cu3.8O
y
(0≤x≤4) were prepared by sintering at various temperatures (805°C–870°C). The structure and superconducting properties of Bi1.4Pb0.6Sr4-x
Ca
x
Cu3.8O
y
were altered by varying the Sr/Ca ratio. For x=0 and 0.5, the c parameter of the unit cell was ∼25 Å and no superconductivity was observed down to 77 K. For x=1 and 1.5, the c parameter was ∼31 Å, and T
c end and T
c onset were 81 K and ∼90 K, respectively. For x=2 and 2.5, the c parameter was ∼37 Å and T
c end and T
c onset were 91 K and ∼105 K, respectively. For x=3 and 3.5, the c parameter was ∼31 Å and T
c onset was 80 K, but zero resistivity did not appear down to 77 K. On the basis of these results, the structure and superconductivity of the Pb-doped BiSrCaCuO system are discussed.
Growth Process of the (2223) Phase in Pb-Added Bi-Sr-Ca-Cu-O
Authors: Oota Akio , Ohba Kentaro , Ishida Akira , Kirihigashi Akihiro , Iwasaki Kiyotoshi , Kuwajima Hideaki
Published: February 2005

The growth process of the (2223) phase in Bi-Sr-Ca-Cu-O has been studied for oxides with nominal composition Bi2Pb0.6Sr2Ca2Cu3O
x
prepared by sintering at 835∼855°C for 5∼160 h in air. The partial melting which starts to occur at T
pm≃842°C enhances the growth rate of the (2223) phase and produces a nearly single phase within 40 h. However, it causes a disturbance in current paths and suppresses the value of T
c(ρ=0) below 100 K. The sample which has the highest T
c(ρ=0) and the nearly single (2223) phase is obtained by sintering at a temperature just below T
pm for a long period of time.
Smectic Layer Switching by an Electric Field in Ferroelectric Liquid Crystal Cells
Authors: Johno Masahiro , Chandani A. D. L. , Ouchi Yukio , Takezoe Hideo , Fukuda Atsuo , Ichihashi Mitsuyoshi , Furukawa Kenji
Published: February 2005

Switching between two different smectic layer structures, chevron and bookshelf geometries, was observed for the first time in ferroelectric liquid crystal cells. In the absence of an electric field, a chevron layer structure is formed, as in a usual smectic C
* phase. An electric field induces layer switching to a bookshelf geometry with a sharp DC threshold. Accompanying the layer switching, the projection of the director onto glass plates changes from the smectic layer normal to one of the uniform states when an electric field is applied. This optical change is equivalent to what is recognized as tristable switching.
Diamagnetic Properties of Nd-Ce-Cu-O Superconducting Thin Films with Electron Carriers
Authors: Hatta Shin-ichiro , Hayashi Shigenori , Adachi Hideaki , Wasa Kiyotaka
Published: February 2005

The diamagnetic properties of superconducting Nd-Ce-Cu-O films with n-type carriers were studied by an rf SQUID susceptometer. The specimen indicates remanent magnetization up to 25 K which is higher than the zero-resistance temperature by 3 K. The critical current density was calculated by Bean's formula to be 0.73×106 A/cm2 at 4.2 K. Although the transition temperature is relatively low, very strong magnetic relaxation was observed for this specimen. In the flux creep model, the activation energy was estimated to be about 0.01 eV which is much smaller than ErBaCuO or TlBaCaCuO film.
Some Correlations between the Temperature Dependence of Induced Cholesteric Pitch and the Chemical Structure of Chiral Compounds
Authors: Emoto Naoyoshi , Tanaka Masami , Saito Shinichi , Furukawa Kenji , Inukai Takashi
Published: February 2005

Cholesteric pitches induced in the nematic phase by chiral additives that have a 4'-alkoxy-4-biphenyl moiety and some other types of chiral compounds are studied. The relations of the pitch and its temperature dependence with the chemical structures of the additives are discussed. Modification of the temperature dependence of the threshold voltage of the twisted nematic display by use of chiral additives is described.
Adsorption of Oxygen on Electron-Bombarded CaF2(111) Surfaces
Authors: Saiki Koichiro , Sato Yasuhiro , Koma Atsushi
Published: February 2005

The effect of oxygen adsorption was investigated on both stoichiometric and damaged CaF2(111) surfaces. Oxygen is hardly adsorbed on a stoichiometric surface, while it is easily adsorbed on electron-bombarded surfaces. For the lightly bombarded CaF2(111) surface, oxygen occupied the fluorine vacant site. However, oxygen reacted with Ca atoms aggregated on the heavily damaged CaF2(111) surface and CaO formation was observed.
Bulk Superconductivity of the (Tl0.5Bi0.5)(Ca1-xYx)Sr2Cu2Oy System
Authors: Huang Y. T. , Liu R. S. , Wang W. N. , Wu P. T.
Published: February 2005

A family of (Tl0.5Bi0.5)(Ca1-x
Y
x
)Sr2Cu2O
y
compounds with x=0, 0.1, 0.2, 0.3, 0.5 and 0.7 were studied systematically. The major phase (above 90%) of all sintered samples was identified as (Tl, Pb)CaSr2Cu2O
y
, an isostructure of the 1122 phase. A maximum T
czero
up to 102 K was achieved at x=0.2, and semiconducting behavior was found at x=0.7. The magnetization measurement is consistent with the resistance data observed. The c-axis of a unit cell contracted significantly and monotonically as the Y substitution increased. It appears that the reduction of the interlayer distance as well as the excess positive charge introduced by substitution played an important role on superconductivity; the difference from a similar Y-substituted Bi2(Ca1-x
Y
x
)Sr2Cu2O
y
system was discussed.
Optimal Growth Conditions of AlGaAs/GaAs Quantum Wells by Flow-Rate Modulation Epitaxy
Authors: Yamauchi Yoshiharu , Makimoto Toshiki , Horikoshi Yoshiji
Published: February 2005

AlGaAs/GaAs single quantum wells with narrow photoluminescence linewidths were grown at 570°C by modified metal-organic chemical vapor deposition, flow-rate modulation epitaxy, using optimal arsine flow rates. The full widths at half maximum of low-temperature photoluminescence spectra strongly depended on arsine flow rates. Under optimal conditions, their values were 8.8, 6.7, 5.0 and 4.8 meV for 1.7, 3.4, 5.1 and 6.8 nm-wide wells, respectively. The resulting narrow photoluminescence linewidths indicate that the heterointerfaces are very flat on an atomic scale, probably as a result of enhanced surface migration of Ga and Al atoms.
Transformation of Superconducting Phases in (Bi, Pb)-Sr-Ca-Cu-O during Post-Annealing
Authors: Kao S. M. , Lin W. J. , Lu H. B. , Chiang C. I. , Wu S. C. , Yeh C. Y. , Lin I. N. , Young C. C. , Yao P. C. , Yang S. C. , Hsu S. E.
Published: February 2005

(Bi, Pb)SrCaCuO superconducting films have been successfully obtained from single-target DC sputtering, deposited on (100) MgO substrate, followed by an appropriate annealing treatment. By varying the post-annealing temperature and time, we can have 9 K (2201) or 80 K (2212) superconducting phase as desired. It is particularly interesting to find that the two phases can be transformed from one to the other reversibly, as confirmed by both crystal structure and transport measurement.
Superconducting Bi-Sr-Ca-Cu-O Thin Films Grown by Metalorganic Chemical Vapor Deposition at Different Temperatures
Authors: Natori Katsuaki , Yoshizawa Shun-ichi , Yoshino Junji , Kukimoto Hiroshi
Published: February 2005

Superconducting Bi-Sr-Ca-Cu-O thin films have been prepared on MgO substrates by metalorganic chemical vapor deposition using triphenylbismuth and β-diketonates of Sr, Ca and Cu as source materials. Superconducting properties, surface morphology and crystallinity of the as-deposited films are largely dependent on growth temperature. When the substrate temperature is at 800°C and over, as-deposited films show high c-axis orientation and zero resistance over 70 K. The best results to date, obtained from a film grown at 800°C show the T
c onset at 110 K and zero resistance at about 80 K. On the other hand, as the substrate temperature decreases below 800°C, the temperature exhibiting zero resistance and X-ray diffraction intensity are rapidly reduced.
Laser Etching of n-GaAs in Chlorides
Authors: Švorčík V. , Rybka V.
Published: February 2005

The HeNe laser-stimulated etching of n-GaAs in chlorides of group II metals was studied. It was shown that the etching rate of GaAs in agueous solutions depends on the size, mobility and charge of cations.
The Breakover Condition for the PNPN Structure
Authors: Chang David C. Y.
Published: February 2005

In this work, the breakover condition of the Shockley diode by the voltage triggering is studied. By replacing the current gain and the multiplication factor with their ac counterparts, an elegant definition of the breakover condition is presented and justified to be more general than previous definitions.
Large (6°) Off-Angle Effects on Sublattice Ordering and Band-Gap Energy in Ga0.5In0.5P Grown on (001) GaAs Substrates
Authors: Gomyo Akiko , Kawata Seiji , Suzuki Tohru , Iijima Sumio , Hino Isao
Published: February 2005

Effects of a large (6°) misorientation angle of (001) GaAs substrates on the <1/2, 1/2, 1/2 > superlattice (SL) formation and the band-gap energy (E
g) for Ga0.5In0.5P were studied. It was found that the [-1/2, 1/2, 1/2] SL formation is strongly enhanced and the [1/2, -1/2, 1/2] SL formation is virtually suppressed, for the case of 6° misorientation towards the [1̄10] direction. In the case of 6° misorientation towards the [110] direction, both SLs were formed, accompanied by significant disorders. The E
g values seemed to correspond well to the degrees of ordering; this is consistent with the previous observation.
Some Experiments on Flux Pinning in Pb Doped Bi-Sr-Ca-Cu-O System
Authors: Nagashima Toshio , Watanabe Kenji , Watahiki Masaya , Fukai Yuh
Published: February 2005

In order to investigate the mechanism of energy dissipation by irreversible motion of fluxoids, we performed two different types of experiments; the oscillating-pendulum in magnetic field and the magnetic hysteresis including both major and minor loops. Results obtained for Pb-doped Bi-Sr-Ca-Cu-O system at 77 K are presented and some preliminary discussions are made.
Effect of Alkyl Chain Length of Chiral Dopants on Rotational Viscosity of FLC Mixtures
Authors: Nishiyama Isa , Yokoyama Akihisa , Fukumasa Mitsuo , Yoshizawa Atsushi , Hirai Toshihiro
Published: February 2005

In binary mixtures consisting of a non-chiral Sc material and chiral dopants having a 2-methyl alkanoyl chiral part, the effect of alkyl chain length of the chiral dopant on rotational viscosity is investigated. FLC mixtures containing the chiral dopants with a long normal aliphatic chain exhibit low rotational viscosity, which is considered to be provided by the strong lateral intermolecular interaction. This consideration is supported by the fact that mixtures having a stable smectic phase, which is usually attributable to the strong lateral intermolecular interaction, show low rotational viscosity.
Hole Donors in the High-Tc Phase of a Bi-Pb-Sr-Ca-Cu Oxide Superconductor
Authors: Nobumasa Hitoshi , Arima Takahisa , Shimizu Kazuharu , Otsuka Yuji , Murata Yukio , Kawai Tomoji
Published: February 2005

The locations of Sr atoms in a crystal of the Bi-Pb-Sr-Ca-Cu oxide superconductor consisting of the high-T
c phase were studied by high-resolution analytical electron microscopy (HRAEM) with a spatial resolution of 17 Å using a probe 5 to 10 Å in diameter. The HRAEM showed that not only Pb atoms, but also Sr atoms were located in the Bi-O layers, indicating that these atoms might be hole donors in the Bi-Pb-Sr-Ca-Cu-O superconductor.
Crystal Structure and Characterization of the New Tl(La, Sr)2CuO5-Type Superconductor
Authors: Mochiku Takashi , Nagashima Toshio , Watahiki Masaya , Fukai Yuh , Asano Hajime
Published: February 2005

We have discovered a new superconductor Tl(La, Sr)2CuO5 with transition temperature of about 40 K. The crystal structure of this material was determined by Rietveld analysis of powder X-ray diffraction data. The result indicates Cu-substitution for the Tl site and/or deficiency in the Tl site, and location of La and Sr on the Sr site in the Tl-O monolayer TlSr2CuO5 compound: the compounds have general formulas Tl1-x
LaSrCu1+x
O5 and Tl1-x
LaSrCuO5. In both systems, superconducting properties were improved by Cu-substitution for the Tl site and deficiency of the Tl site.
Absorption and Desorption of Oxygen in Y1Ba2Cu3O7-δ
Authors: Umemura Toshio , Egawa Kunihiko , Wakata Mitsunobu , Yoshizaki Kiyoshi
Published: February 2005

The absorption and desorption velocities of oxygen in a Y1Ba2Cu3O7-δ sintered sample were measured by a thermogravimetric analysis when the atmospheric gas of nitrogen was exchanged for oxygen and oxygen for nitrogen. The weight change of the sample could be expressed by an exponential function of time in each process. In the absorption process of oxygen, the time constant was a complex function of the temperature, while in the desorption process, it was the monotonous temperature dependence. The diffusion constant and the activation energy were estimated at the temperature range of the tetragonal phase.
High-Resolution Transmission Electron Microscopy of Commensurate Modulation in Bi2Sr2CoOy
Authors: Matsui Yoshio , Kishio Kohji , Tomioka Yasuhide , Hasegawa Tetsuya , Ikeda Shozo
Published: February 2005

The modulated structure of Bi2Sr2CoO
y
was directly observed by high-resolution electron microscopy. The modulation periodicity is four times commensurate with the tetragonal subcell, as was pointed out by Tarascon et al. (to be published in Phys. Rev. B), while the average structure is identical to that of compositionally analogous superconductor Bi2Sr2CuO
y
which has an incommensurate modulation. Some of the weak satellite reflections appearing in the a
*-b
* diffraction pattern are, however, incompatible with the body-centered orthorhombic symmetry proposed by Tarascon et al., suggesting that weak additional modifications are induced in the structure.
Formation Process of Stacking Faults with Ringlike Distribution in CZ-Si Wafers
Authors: Hasebe Masami , Takeoka Yoshihiko , Shinoyama Seiji , Naito Shunta
Published: February 2005

In some large diameter CZ-Si wafers, stacking faults with ringlike distribution are observed after thermal oxidation. Although the stacking faults are formed through wafer thickness from surface into bulk after dry O2 or steam oxidation, no stacking faults are observed after N2 annealing or HCl+dry O2 oxidation. All the stacking faults, even in bulk, are therefore considered to be formed by the condensation of silicon self-interstitials generated at the surface during oxidation. The ringlike distribution is found to originate from grown-in oxygen precipitates observed right in the center of the stacking faults by transmission electron microscope.
Preparation of BaTiO3 Thin Film by Hydrothermal Electrochemical Method
Authors: Yoshimura Masahiro , Yoo Seung-Eul , Hayashi Motoo , Ishizawa Nobuo
Published: February 2005

BaTiO3 thin films have been prepared in situ on Ti metal substrates by a hydrothermal electrochemical technique, where a direct current has been passed between the anode, Ti plate, and the cathode, Pt plate, in high-temperature, high-pressure Ba2+ solutions. Dense thin films, 0.1∼0.3 µm thick, which consist of cubic BaTiO3 polycrystals without apparent pores or defects have been obtained under the following conditions: in 0.25∼0.5 N-Ba(OH)2 solutions above 100°C under saturated vapor pressures with the current density of 10∼100 mA/cm2 after 30∼80 min. These films are paraelectric with the dielectric constant of ≈300.
Doped Conducting Polymer Gel and Its Characteristics as Functions of Solvent, Temperature and Electrochemical Doping Potential
Authors: Yoshino Katsumi , Nakao Kenji , Morita Shigenori , Onoda Mitsuyoshi
Published: February 2005

Lightly doped poly(3-alkylthiophene) exhibits the characteristics of a polymer gel. The volume of the sample in chloroform shrinks drastically upon introduction of ethanol and also with decreasing temperature. The shrinkage ratio depends strongly on doping potential and therefore on the dopant concentration. The results are interpreted in terms of dopant-induced cross-linking formation between polymer main chains. The spectrum of the doped get also changes in association with the volume instability.
Lattice Images of Langmuir-Blodgett Films of Cadmium Arachidate Obtained by Superconducting Cryo-Electron Microscope
Authors: Inoue Takahito , Yase Kiyoshi , Okada Masakazu , Okada Shuji , Matsuda Hiro , Nakanishi Hachiro , Kato Masao
Published: February 2005

We have succeeded, for the first time, in the direct observation of lattice images of cadmium arachidate in LB films. We have demonstrated that the electron microscopic techniques including cooling of the specimeut to 4.2 K have great potential for determining the structure of beam-sensitive organic thin films at a molecular level.
Synthesis of Bi-Sr-Ca-Cu-O Ceramics with Large Intergrowth Defects
Authors: Adachi Seiji , Hirano Hirohumi , Takahashi Yukihiro , Inoue Osamu , Kawashima Syunichiro
Published: February 2005

Superconducting Bi-Sr-Ca-Cu-O ceramics with intergrowth defects larger than 1.8 nm in half of the c-axis length were synthesized at a nominal composition of Bi2Sr2Ca4Cu6.5O
y
. Electrical resistance and a.c. susceptibility for the ceramics were measured. No indication of a T
c higher than 110 K was obtained.
Crystallization Behavior and Partially Melted States in Bi-Sr-Ca-Cu-O
Authors: Oka Yoshio , Yamamoto Naoichi , Kitaguchi Hitoshi , Oda Kiichi , Takada Jun
Published: February 2005

High-temperature X-ray measurements were carried out on Bi-Sr-Ca-Cu-O. It was found that the 30 Å phase showed incongruent melting forming new crystalline phases which differed depending on the compositions. Crystallization from the melt by cooling first produced the 30 Å phase on solidification and then the 24 Å phase crystallized around 730°C. Crystallization from the glassy phase by heating started at 430°C and led to the 24 Å phase, which changed to the 30 Å phase above 800°C. As a rule, low-temperature crystallization from the amorphous phase takes place below 730°C to form the 24 Å phase in Bi-Sr-Ca-Cu-O.
Cross-Sectional Reflection Electron Microscopy of a GaAs-AlGaAs Single Quantum Well Structure
Authors: Yamamoto Naoki
Published: February 2005

The GaAs-AlGaAs single quantum wells (SQW's) grown on a slightly tilted substrate by MOVPE showed stripe patterns in the monochromatic cathodoluminescence images. These SQW's were examined by cross-sectional reflection electron microscopy (cross-sectional REM). The REM image of the cleavage surface normal to the SQW planes revealed a roughness of the SQW interfaces of about 2 nm in height indicating the existence of the nearly periodically aligned multilayer height steps.
How to Compare Jc Among Different-Sized Samples
Authors: Imanaka Nobuhito , Imai Hisao , Adachi Gin-ya
Published: February 2005

The J
c evaluation was examined on the assumption that a Joule heat caused by the current for resistivity measurement exceeds the sample thermal cooling from the liquid nitrogen refrigerant when current density (J
c) becomes more than a critical value for Bi-Pb-Sr-Ca-Cu-O superconductors or Au-mixed Bi-Pb-Sr-Ca-Cu-O composites. Re-examination revealed that a normalized J
c value was independent of the sample sizes. The calculation method proposed here allows J
c of different-sized samples to be directly compared.
Evaluation of Temperature and Magnetic-Field Dependence of Pinning Potential of High Tc Superconductors from Flux-Creep Resistivity Experiments
Authors: Enpuku Keiji , Yoshida Keiji , Takeo Masakatsu , Yamafuji Kaoru
Published: February 2005

A method is presented to evaluate the temperature T and magnetic-field B dependences of the pinning potential U directly from the flux-creep resistivity experiments. Using this method, we analyse the previous experimental results in YBaCuO single crystals. It is shown that the temperature and magnetic-field dependences of the potential obtained with the present method are different from the previous model, i.e., U(T, B)∝(1 - T/T
c)3/2/ B, where T
c is the critical temperature. It is also shown that the previous model can not explain these experimental results consistently.
Formation of the High-Tc Phase in Rapidly Quenched Bi-Pb-Sr-Ca-Cu-O Ceramics
Authors: Kanai Tsuneyuki , Kamo Tomoichi , Matsuda Shin-Pei
Published: February 2005

Amorphous ceramics with the composition of Bi2Pb0.4Sr2Ca2Cu3O
y
were prepared by rapid quenching. The change in crystalline structure during annealing and the effect of the “seeding” with the high-T
c phase were investigated. The volume fraction of the high-T
c phase increases with annealing time; however, the low-T
c phase reaches a maximum value of 38% for 1 h annealing and decreases on prolonged annealing. The formation rate of the high-T
c phase changes when the volume of the high-T
c phase reaches about 30%. TEM observation shows that the high-T
c phase is often located between the low-T
c phase and the nonsuperconducting phase. The addition of the seed crystals with the high-T
c phase is effective in forming the high-T
c phase in shorter annealing times, but a smaller volume fraction of the high-T
c phase was obtained after annealing for 50 h.
In Situ Growth of Superconducting Y-Ba-Cu-O Films on Si, SiO2, GaAs and Cu/Ag by the High-Pressure DC Sputtering Process
Authors: Lin R. J. , Wu P. T.
Published: February 2005

Superconducting Y-Ba-Cu-O thin films on Si, SiO2, GaAs and Cu/Ag substrates have been reproducibly prepared by the high-pressure DC sputtering process without further annealing treatment. The targets were Y-Ba-Cu-O compounds made by the solid-state reaction. The substrate temperature was lower than 450°C. The films (0.6–2 µm) consist of predominantly the superconducting phase of Y1Ba2Cu3O
x
and impurity phases such as CuO or a mixture of CuO and Y2Ba1Cu1O5. The best superconductivity of the films on Si is Tc(onset)=95 K and Tc(zero)=70 K. There are no microcracks on the film surface, and the interdiffusion between film and Si substrate is limited.
Sub-MHz Linewidth GaAs/AlGaAs GRIN-SCH-SQW DFB Laser Diodes with First-Order Gratings Fabricated by Electron Beam Lithography
Authors: Hirata Takaaki , Suehiro Masayuki , Maeda Minoru , Yamada Noriyuki , Hosomatsu Haruo
Published: February 2005

Narrow-linewidth GaAs/AlGaAs GRIN-SCH-SQW DFB laser diodes with first-order gratings are reported. The first-order gratings and the GRIN-SCH-SQW structures were fabricated using electron beam lithography and MOVPE. The narrowest linewidth achieved is 730 kHz for a 1 mm cavity length. We also report on problems with gratings fabricated by electron beam lithography.
Surface Analysis of YBa2Cu3Ox and Bi-Sr-Ca-Cu-O Superconductors by Auger Electron Spectroscopy
Authors: Tokutaka Heizo , Kishida Satoru , Nishimori Katsumi , Ishihara Naganori , Watanabe Yoshihide , Noishiki Yoshio , Kawai Tomoji
Published: February 2005

The YBa2Cu3O
x
superconductors show critical temperatures at around 90 K. Although they are prepared from the different starting materials, they however exhibit similar intensities of AES spectra. For the superconductors of Bi-Sr-Ca-Cu-O and (Bi, Pb)-Sr-Ca-Cu-O, the AES intensity ratios of Ca/Sr increase when their critical temperatures increase. When the AES intensity ratios are transformed into the composition ratios using the sensitivity factor, the volume fractions of the phases of the critical temperatures (7 K, 80 K and 110 K) can be estimated from these ratios and the ideal composition ratio of each phase.
Numerical Studies of Induced Emission and Saturation of Free Electron Lasers Using a CO2 Laser Wiggler
Authors: Taguchi Toshihiro , Mima Kunioki
Published: February 2005

Numerical studies of free electron lasers using a CO2 laser as an electromagnetic wiggler are performed in the Compton regime. Linear growth and nonlinear saturation processes are analyzed by the quasi-linear theory. The results show that it is possible to achieve a high gain and induce a quasi-linear saturation using the currently available relativistic electron beam and CO2 laser facilities.
High-Pressure Synthesis of Ca1-xSrxCuO2
Authors: Okai Bin
Published: February 2005

Conditions for high-pressure synthesis were examined for defect-type perovskite Ca1-x
Sr
x
CuO2 with planar [CuO2]∞ sheets. For x=0.2, the temperature of preparation ranges from 800°C to over 1000°C at 6 GPa, whereas it falls to around 800°C for SrCuO2. The lattice parameters increase linearly with increasing x.
Marked Reduction of the Surface/Interface States of GaAs by (NH4)2Sx Treatment
Authors: Fan Jia-Fa , Kurata Yasushi , Nannichi Yasuo
Published: February 2005

MIS capacitors have been fabricated on (NH4)2S
x
-treated GaAs using a SiO
x
insulator prepared by conventional resistive-heating evaporation. The MIS interface state density was found to be about 1.2×1011 cm-2·eV-1 in a wide range of the band gap, which is two orders of magnitude less than that on the as-etched GaAs.
Preparation of High-Tc Bi-Sr-Ca-Cu-O Films on MgO Substrates by the Liquid Phase Epitaxial (LPE) Method
Authors: Takeya Hiroyuki , Takei Humihiko
Published: February 2005

Thin films of high-T
c superconductor Bi2Sr2CaCu2O
x
were prepared on MgO(100) substrates by a liquid phase epitaxial method. Several kinds of fluxes were applied for preparation of Bi2Sr2CaCu2O
x
thin films, and KCl was found to be the best among them. The film consisted of two phases, Bi2Sr2CaCu2O
x
and Bi2Sr2CuO
x
. The onset T
c in the superconducting transition was at 95 K in an as-grown state, but zero resistivity was not observed over 50 K.
Effects of Trap State on Field-Effect Mobility of MOSFET's Formed on Large-Grain Polysilicon Films
Authors: Katoh Teruo , Hirashita Norio
Published: February 2005

Electrical characteristics of large-grain polysilicon transistors for various grain sizes were examined. The field-effect mobilities of poly-Si transistors were studied based on the thermionic emission model with potential barriers at grain boundaries. Electron mobility within the grains was evaluated and found to be 194 cm2/V·s. Our result indicates that, using the electron mobility within the grains, the thermionic emission model can be applied to poly-Si films with relatively large grain sizes.
Photoemission Studies of Mo6Se8, Ru6xMo6(1-x)Se8 and Nb6xMo6(1-x)Se8
Authors: Namatame Hirofumi , Soda Kazuo , Mori Tamiko , Fujisawa Masami , Taniguchi Masaki , Suga Shigemasa , Kitazawa Koichi , Tanaka Shoji
Published: February 2005

Ultraviolet photoemission spectra (UPS) have been measured on clean surfaces of Mo6Se8, Ru6x
Mo6(1-x)Se8 (with x=0.075, 0.1, 0.15) and Nb6x
Mo6(1-x)Se8 (with x=0.05, 0.075 and 0.1) The photon energy dependence of the intensity of the structure at the binding energy E
B=1.0 eV shows a remarkable resonance effect in the Mo 4p core excitation region. The spectra of different samples are normalized to the integrated intensity of the Se 3d core levels and the relative magnitude of the density of states (DOS) near the Fermi level of each of the samples is estimated. The results are consistent with those obtained by the specific heat measurements.
The Synthesis of Diamond Films at Lower Pressure and Lower Temperature Using Magneto-Microwave Plasma CVD
Authors: Suzuki Jun-ichi , Kawarada Hiroshi , Mar King-Sheng , Wei Jin , Yokota Yoshihiro , Hiraki Akio
Published: February 2005

Diamond films have been obtained using magneto-microwave plasma assisted CVD at 0.1 Torr. The reaction gas is a CO/H2 mixture. By setting the ECR condition at the deposition area, a high density plasma (1×1011 cm-3) is obtained around the substrate. The discharge area is quite uniform in the pressure. Diamond films are obtained on positively biased substrates. As the reaction pressure becomes lower, the substrate temperature for the diamond formation tends to decrease. The films were evaluated by SEM imaging, electron diffraction and Raman spectroscopy.
Transmission Electron Microscopic Study of the Surface and Interface of Carbonized-Layer/Si(100)
Authors: Iwami Motohiro , Hirai Masaaki , Kusaka Masahiko , Yokota Yasuhiro , Matsunami Hiroyuki
Published: February 2005

A heterojunction of carbonized-layer/Si(100) was studied by means of a transmission electron microscope (TEM). The surface layer was clarified to be well aligned to substrate Si(100) by a crosssectional TEM observation. Small misorientation was observed at the bottom of the carbonized layer. Either the surface or the interface of the overlayer had a rough structure with a thickness of a few nm. A plane-view observation revealed the existence of fine grains in the grown layer with a size of \lesssim10 nm, which rotated a little with respect to the substrate Si(100) and each other.
Radiative Relaxation of Vibration of the Nitric Oxide Molecule in Its Electronic Ground State (X2 Π)
Authors: Mizushima Masataka , Inagaki Keizo
Published: February 2005

An empirical adiabatic potential for the electronic ground state of the NO molecule (X2 Π) is obtained by fitting with the observed vibrational energy levels up to v=17 and the dissociation energy. Using thus calculated vibrational eigenfunctions and Billingsley's dipole moment function, we calculated the probabilities of the electric dipole transition among vibrational states up to v=40. Beside the conventional Δv=-1 transitions, many higherorder transitions are found to have reasonably large probabilities. Applying the result to the theory of Shuttle Glow, we predict that not only many infrared radiations, but also visible lights such as 0.570, 0.523, 0.484 µm lines have intensities near 1 µW per 1 m2 of the Shuttle's surface.
Effects of ECR Hydrogen-Plasma Treatment on Narrow-Stripe Polycrystalline Silicon Thin-Film Transistors
Authors: Takeshita Tatsuya , Unagami Takashi , Kogure Osamu
Published: February 2005

The characteristics of thin-film transistors (TFT's) have been examined to determine the effects of a narrow-stripe structure of polycrystalline silicon in the channel region and of a hydrogen-plasma treatment utilizing electron cyclotron resonance (ECR hydrogen-plasma treatment). After this treatment, the carrier mobility, even for small-grain poly-Si, achieves 11.3 cm2/(V·s) for the narrow-stripe TFT. This high carrier mobility can be obtained according to the remarkable reduction of the potential barrier height of poly Si, which is attained by making poly-Si narrow and by ECR hydrogen-plasma treatment.
Possible Existence of a Superconducting Phase in Highly Oxygen-Deficient YBa2Cu3Oy (y<6.5)
Authors: Mazaki Hiromasa , Ueda Yutaka , Aihara Yuji , Kubozoe Tadayoshi , Kosuge Koji
Published: February 2005

YBa2Cu3O
y
with various values of y was successfully prepared by slow cooling in Ar gas. The phase identification by an X-ray diffractometer indicates that the orthorhombic phase extends down to about y=6.2. Measurements of the superconducting transition in terms of complex susceptibility have revealed that the superconducting phase exists even for y<6.5, suggesting a possible existence of a lower T
c phase with a different vacancy-ordered structure in the Cul-O planes.
Epitaxial Growth of YBaCuO Films on Sapphire at 500°C by Metalorganie Chemical Vapor Deposition
Authors: Oda Shunri , Zama Hideaki , Ohtsuka Tomohiko , Sugiyama Kazuhisa , Hattori Takeo
Published: February 2005

Single crystalline films of YBaCuO have been epitaxially prepared for the first time on sapphire substrates at temperatures as low as 500°C by the metalorganic chemical vapor deposition method. The starting materials were Y(HFA)3, Ba(HFA)2, and Cu(AcAc)2. Deposition was carried out with an oxygen pressure of 10 Torr. Electron probe measurements and Auger electron spectroscopy suggest that the constituent of the film is YBa2Cu3O
x
. Carbon has not been detected in the film. Spots and streak patterns obtained in the electron diffraction measurements suggest high crystalline quality and smoothness of the surface.
Crystallinity and Morphology of Superconducting Thin Films Prepared by Sputtering
Authors: Tanaka Saburo , Itozaki Hideo
Published: February 2005

HoBaCuO superconducting thin films were prepared on MgO substrates by rf magnetron sputtering. The crystallinity and morphology of the thin films have been investigated. An amorphous thin film was crystallized by postannealing at 900°C, while an epitaxial grown thin film was obtained by substrate heating at more than 600°C.
STM Observation of Electroless-Plated Cobalt Alloy Thin Films
Authors: Osaka Tetsuya , Homma Takayuki , Itaya Kingo , Sugawara Shizuo
Published: February 2005

The microstructure of electroless-plated CoNiReP thin films in the initial deposition state were investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and scanning tunneling microscopy (STM). The films consisted of grains 30–50 nm in diameter. The result of STM observation presented a more detailed structure than that obtained by TEM and SEM. Also, the STM observation was effective in evaluating the minute structure of the films.
Transmission Loss Characteristics of Nd-Doped Silica Single-Mode Fibers Fabricated by the VAD Method
Authors: Shimizu Makoto , Hanawa Fumiaki , Suda Hiroyuki , Horiguchi Masaharu
Published: February 2005

This letter presents transmission loss characteristics of Nd-doped silica single-mode fibers. By performing a spectral deconvolution, it is clarified that the intrinsic origin of a transmission loss in the low-loss region for the Nd-doped fibers is the Rayleigh scattering loss.
A “Mechanical Aligning” Method for Preparing High-Jc YBa2Cu3Ox Superconductors
Authors: Zheng Xu-guang , Kuriyaki Hisao , Hirakawa Kazuyoshi
Published: February 2005

High-J
c YBa2Cu3O
x
ceramic samples were prepared by a mechanical aligning method which involved of large crystal growing and vibration aligning. In these samples, the crystal grains were found to be highly oriented and closely packed. Accordingly, the maximum critical current density was found to be 4200 A/cm2 at the liquid nitrogen temperature.
Compositional Dependences of the Superconducting Transition Temperatures of the Low-Tc Bi-Pb-Sr-Ca-Cu Oxides
Authors: Ono Akira
Published: February 2005

Supercondudting properties of (Bi, Pb)2(Bi, Sr, Ca)3Cu2O
y
were studied by electrical resistivity measurements. The oxygen contents of specimens were changed by annealing at different temperatures before rapid quenching. It was revealed that superconducting transition temperatures strongly depended on slight changes of oxygen deficiency which were controlled by changing the annealing temperature, the Ca/Sr ratio, and the Bi and Pb contents. Moreover, the effects of the annealing temperature on the T
c differed considerably among specimens with various cationic compositions.
Gold Gettering in Directly Bonded Silicon Wafers
Authors: Yang W.-S. , Ahn K.-Y. , Marioton B. P. R. , Stengl R. , Gösele U.
Published: February 2005

Gold gettering in directly bonded silicon wafers was investigated. Wafers of (100) orientation were rotationally misoriented against each other by 1° or 25° and bonded by annealing at 1100°C for 2 hours in nitrogen. Transmission electron micrographs had shown two different bonding interface structures depending on the rotational angle. The bonded wafers were gold-deposited on one side and annealed for 3 hours at 950°C or 1000°C in vacuum. The spreading resistance was measured and the result showed a double-U profile in both 1°-misoriented and 25°-misoriented samples. Our results show for the first time that the bonding interface acts as a gettering site and that the bonding interface might be used to artificially introduce gettering sites close to the regions in which devices would be fabricated.
Interface State Density Distribution in Amorphous/Crystalline Silicon Heterostructures
Authors: Iyer Suman B. , Kumar Vikram , Harshavardhan K. S.
Published: February 2005

We present the first report of the interface state density distribution in undoped hydrogenated amorphous silicon/crystalline silicon heterostructures. The observed MIS (metal-insulator-semiconductor) like high frequency C(V) variation in this structure is used to obtain interface state density distribution in heterostructures with a-Si:H layer prepared either by reactive sputtering or glow discharge technique.
The Strontium Content Dependence of Pressure Effect in (La1-xSrx)2CuO4
Authors: Tanahashi Nobukatsu , Iye Yasuhiro , Tamegai Tsuyoshi , Murayama Chizuko , Môri Nobuo , Yomo Shusuke , Okazaki Noriaki , Kitazawa Koichi
Published: February 2005

The enhancement of the superconducting transition temperature by pressure was studied up to ∼1.5 GPa for samples of (La1-xSrx)2CuO4with varying strontium contentx. Simultaneously measured Hall coefficients were found to be independent of pressure in the present range, ruling out a pressure induced carrier density change as an origin of theTcenhancement. The pressure coefficient ofTcwas found roughly the same for the two regimes. i.e. forx<0.08, whereTcincreases withx. and for 0.08<x<0.15 where it decreases withx. These results are discussed in the context of the current controversy over the nature of the electronic state in this class of materials.
Ferroelastic Domain Switching in YBa2Cu3Ox Single Crystals by External Stress
Authors: Hatanaka Tatsuya , Sawada Akikatsu
Published: February 2005

It is found that single-domain crystals of YBa2Cu3O
x
can be formed from multidomain crystals by making use of ferroelasticity. Ferroelastic domain switching is shown to take place upon application of the external compressive stress of about 1000 kgw/cm2 along a pseudotetragonal [100] axis at sample temperatures of about 200°C to 350°C.
Ag-Sheathed Bi-Pb-Sr-Ca-Cu-O Superconducting Wires with High Critical Current Density
Authors: Hikata Takeshi , Sato Ken-ichi , Hitotsuyanagi Hajime
Published: February 2005

Critical current density (J
c) and its dependence on magnetic field in Ag-sheathed Bi-Pb-Sr-Ca-Cu-O superconducting wire was improved by grain alignment and homogenization of the high-T
c phase (110 K). The maximum transport current density at 77.3 K in a zero magnetic field was increased to 6930 A/cm2. The magnetic field dependence of J
c (0.1 µV/cm criterion) was summarized as follows: 1660 A/cm2 (I ⊥H, a-b plane ∥H, 0.1 T), 900 A/cm2 (I ⊥H, a-b plane ⊥H, 0.1 T). We found that the grain boundaries were bonded strongly in the direction of alignment.
Forming Superconducting Tl-Ca-Ba-Cu-O Thin Films by the Diffusion Method
Authors: Lin R. J. , Wu P. T.
Published: February 2005

A new diffusion process has been developed for preparing superconducting Tl-Ca-Ba-Cu-O thin films (0.6∼2 µm) on (001)MgO and YSZ single-crystal substrates. The films have T
c(onset)=120 K and T
c(zero)=78 K. The superconducting phase of the films is highly oriented Tl1Ca1Ba2Cu2O
x
.
Low-Energy Electron Energy Loss Spectroscopy on Evaporated Films of Metal-Free and Metal Phthalocyanines
Authors: Tada Hirokazu , Saiki Koichiro , Koma Atsushi
Published: February 2005

Non-derivative energy loss spectra of low energy electrons reflected from the surface of evaporated films of phthalocyanines (MPc; M=H2, Cu, VO, Pb) have been measured in the loss energy region up to 30 eV. The observed peaks in the π-π* excitations region are in good agreement with the optical absorption maxima. Two broad structures are observed in common above 10 eV. The peak around 14 eV is considered to be due to the σ-σ* excitation. The collective excitation of valence electrons (plasmonlike oscillation) is observed at 20 eV. Electron radiation damage and the surface activity have also been investigated.
Cubic ZnCdS Lattice-Matched to GaAs: A Novel Material for Short-Wavelength Optoelectronic Applications
Authors: Fujita Shizuo , Funato Mitsuru , Hayashi Shigeo , Fujita Shigeo
Published: February 2005

We propose cubic Zn1-x
Cd
x
S epilayers lattice-matched to GaAs (x∼0.58) as a new candidate for short-wavelength optoelectronic applications. This material is expected to possess a wide bandgap corresponding to the blue-to-purple spectral region and a mismatch in the thermal expansion coefficient smaller than that of the ZnSSe/GaAs system (1/4 of the latter). The problem lay in whether we could obtain a cubic structure, since only a hexagonal structure has been prepared for ZnCdS. In this study, we report on the successful growth of a cubic material by organometallic vapor-phase epitaxy. The nearly lattice-matched epilayers (x≃0.50∼0.65) showed good crystallographic properties and strong blue or purple photoluminescence both at 4.2 K and at room temperature.
As-Grown Y-Ba-Cu-O Superconducting Thin Films Prepared by Magnetron Sputtering
Authors: Michikami Osamu , Asahi Masayoshi , Asano Hidefumi
Published: February 2005

YBa2Cu3O7-δ thin films were prepared on MgO(001) planes at 600°C by RF magnetron sputtering. These as-grown films were classified into 3 types: high-T
c, low-T
c and nonsuperconducting. In this report, film properties are discussed in relation to the annealing effect in an oxygen atomosphere and lattice parameters (co). By optimizing the sputtering conditions, c-axis-oriented superconducting films with an endpoint T
c above 80 K are obtained. These as-grown films are highly uniform and semi-transparent and have a room temperature resistivity of 0.3 mΩcm.
Optical Spectra of (Bi, Pb)2(Sr, Ca)4Cu3O10 Superconductors
Authors: Arima Takahisa , Nobumasa Hitoshi , Shimizu Kazuharu , Kawai Tomoji
Published: February 2005

Visible-to-near-infrared optical spectra of (Bi, Pb)2(Sr, Ca)
n+1Cu
n
O
y
superconductors (n=2, 3) have been measured by both reflection and transmission modes. The spectra of the n=2 and n=3 phase are quite different from each other. From the estimated plasma frequency ωp, the relation T
c∝ωp
2 reported previously on La-Sr-Cu-O and Y-Ba-Cu-O seems to be valid in (Bi, Pb)2(Sr, Ca)4Cu3O10. The origin of the optical transition appearing in the infrared region is discussed.
Profile-Imaging of Wavy Cleavage Surface of Bi2Sr2CaCu2Oy by High-Resolution Transmission Electron Microscopy
Authors: Matsui Yoshio , Maeda Hiroshi , Tanaka Yoshiaki , Horiuchi Shigeo
Published: February 2005

Profile-imaging of the (001) cleavage surface of Bi2Sr2CaCu2O
y
is performed by means of high-resolution transmission electron microscopy. The surface BiO layer suffers from structural modulation, almost in the same manner as (BiO)2 layers in the bulk structure [Y. Matsui et al., Jpn. J. Appl. Phys. 27 (1988) L372]. Small vertical fluctuation of the surface height, with a periodicity of 2.6 nm along the b axis, is observed. This wavy feature of the surface BiO layer is almost consistent with the recent scanning tunneling microscope (STM) study of Bi2Sr2CaCu2O
y
[M. D. Kirk et al., Science 242 (1988) 1673].
Fabrication of Flexible Ribbons of High-Tc Bi(Pb)-Sr-Ca-Cu-O Superconductors
Authors: Togano Kazumasa , Kumakura Hiroaki , Maeda Hiroshi , Yanagisawa Eiji , Irisawa Naoshi , Shimoyama Jun-ichi , Morimoto Takeshi
Published: February 2005

Thin ribbons (30 µm thick) of high-T
c Bi(Pb)-Sr-Ca-Cu-O superconductor have been successfully prepared by the combined process of doctor blade casting, cold rolling and sintering. A zero-resistance state has been achieved at 107 K. The highest J
c obtained so far is about 1850 A/cm2 at 77 K and in zero magnetic field. The ribbon has sufficient flexibility to be bent to about a 30 mm diameter even after the final sintering.
Epitaxy and Orientation of Eu1Ba2Cu3O7-y Films Grown In Situ by Magnetron Sputtering
Authors: Asano Hidefumi , Asahi Masayoshi , Michikami Osamu
Published: February 2005

Superconducting films of Eu1Ba2Cu3O7-y
have been grown in situ onto SrTiO3 and MgO (100) substrates by magnetron sputtering from a stoichiometric oxide target. The sputtering process results in the growth of epitaxial films with perfect a-axis orientation as well as perfect c-axis orientation. The orientation of the films can be controlled by the proper choices of substrate temperature, oxygen pressure, and film growth rate. The routine production of films showing T
c zero of 88–90 K is accomplished. In situ growth of the films with the particular orientation is of importance in the fabrication of multilayer structures such as tunnel junctions.
In Situ Reflection High Energy Electron Diffraction Observation During Growth of YBa2Cu3O7-x Thin Films by Activated Reactive Evaporation
Authors: Terashima Takahito , Iijima Kenji , Yamamoto Kazunuki , Hirata Kazuto , Bando Yoshichika , Takada Toshio
Published: February 2005

Epitaxial growth of (001) oriented YBa2Cu3O7-x
(YBCO) on SrTiO3(100) and MgO(100) by activated reactive evaporation was investigated by in situ reflection high energy electron diffraction (RHEED). RHEED observation of the YBCO films on both the substrates demonstrated the formation of the perovskite structure even at initial deposit. A sharp streak in every deposition stage revealed the layer-by-layer growth. The initial deposit on the substrate of MgO with the large mismatch of 9% kept the same in-plane lattice spacing as MgO. The lattice spacing converted from the bulk value of MgO to that of YBCO when the layer became thicker than 12 Å.
Thermal Desorption from Si(111) Surfaces with Native Oxides Formed During Chemical Treatments
Authors: Kobayashi Yoshihiro , Shinoda Yukinobu , Sugii Kiyomasa
Published: February 2005

The thermal desorption process during thermal cleaning of Si(111) surfaces with native oxides formed by various chemical treatments is studied using TDS (thermal desorption spectroscopy) under UHV. The reaction product of the process is identified to be SiO. The surface cleanliness after the cleaning is virtually independent of the oxide formation method. However, the desorption temperature of SiO strongly depends on the method. This dependence cannot be explained purely by SiO diffusion in the oxide film. It suggests that the interface structure between an oxide layer and a Si substrate significantly affects the desorption temperature of native oxides. A scheme for removing oxide film is proposed.