bluuebunny/crossref_metadata_2025 huggingface dataset:
Superconducting Bi-Sr-Ca-Cu-O Thin Films Prepared by Thermal Decomposition of Metallic Complex Salts
Authors: Maruyama Toshiro , Higashi Seiji
Published: February 2005

Superconducting Bi-Sr-Ca-Cu-O thin films of zero-resistivity temperature 79 K and critical current 38 A/cm2 (at 77 K) were synthesized on polycrystalline MgO substrate by thermal decomposition of naphtanic acid salts. For obtaining the film of zero-resistivity temperature above 77 K, postdeposition annealing at 820°C for 30 min was necessary.
Radiation Effect of YBa2Cu3O7-y Irradiated by γ-Rays and 14 MeV Neutrons
Authors: Kato Teruo , Watanabe Mitsuo , Kazumata Yukio , Naramoto Hiroshi , Iwata Tadao , Ikeda Yujiro , Maekawa Hiroshi , Nakamura Tomoo
Published: February 2005

High-T
c superconductor YBa2Cu3O7-y
was irradiated by γ-rays and 14 MeV neutrons to a dose up to 2.5×109 rad and 2×1015 n/cm2, respectively. No significant effects on the critical temperature were found in these irradiations, but the resistivity at 273 K changed slightly. It was concluded from this experiment that electronic process was not very influential in changing the T
c and the effects of 14 MeV neutrons on defect formation were assumed to be comparable to those of inpile neutrons.
Fabrication and Characterization of Multilayer Zone Plate for Hard X-Rays
Authors: Saitoh Kazuya , Inagawa Konosuke , Kohra Kazutake , Hayashi Chikara , Iida Atsuo , Kato Norio
Published: February 2005

A zone plate for 8 keV X-rays with alternative WSi2 and C layers was fabricated using a DC planer magnetron sputtering. The zone plate had 20 pairs of a high aspect ratio for hard X-rays. Its thickness was about 50 µm. An X-ray interference pattern through the zone plate was observed using monochromated synchrotron X-rays, and a focusing property of the zone plate was confirmed. The focal length was about 67 mm and the spot size (FWHM) was smaller than 8 µm.
Plasma Ion-Doping Technique with 20 kHz Biased Electron Cyclotron Resonance Discharge
Authors: Kitagawa Masatoshi , Matsuo Naoto , Fuse Genshyu , Iwasaki Hiroshi , Yoshida Akihisa , Hirao Takashi
Published: February 2005

Boron ions have been successfully doped into crystalline silicon substrates using AC(20 kHz)-biased microwave electron cyclotron resonance plasma, as functions of microwave power and AC bias power. Diborane gas diluted with hydrogen was used as a gas source. A sheet resistance of 10100 kΩ/\Box, junction depth of 0.1 µm and boron concentration at the silicon surface of 1018 atoms/cm3 were attained using this technique.
High Temperature Operated Enhancement-Type β-SiC MOSFET
Authors: Fuma Hiroo , Miura Atsushi , Tadano Hiroshi , Sugiyama Susumu , Takigawa Mitsuharu
Published: February 2005

Enhancement-type β-SiC MOSFETs have been fabricated on a single crystalline β-SiC layer grown on a 3-inch Si(100) substrate by chemical vapor deposition. The MOSFETs fabricated by applying the reactive ion etching technique show reasonable I-V characteristics at room temperature. The saturation tendency of the drain currents has been observed at a drain voltage as high as 18 V. The MOSFETs operate even at 350°C.
Very-Low-Temperature Epitaxial Silicon Growth By Low-Kinetic-Energy Particle Bombardment
Authors: Ohmi Tadahiro , Matsudo Kiyohiko , Shibata Tadashi , Ichikawa Takeshi , Iwabuchi Hiroshi
Published: February 2005

Low-kinetic-energy Ar ions have been utilized to control the kinetics of thin film growth as well as to perform very effective predeposition substrate surface cleaning. As a result, epitaxial silicon layers with a perfect crystallinity are grown on silicon substrates at a temperature as low as 350°C. The resistivity of an as-grown epitaxial silicon film as low as 0.0018 Ωcm has been obtained, showing the impurity activation without any heat treatment. A p-n junction formed by growing an n-type epitaxial silicon layer directly on a p-type substrate at 350°C exhibited a low reverse current of 1.88×10-9 A/cm2 at a reverse bias of 5 V.
A High Integrity and Low Resistance Ti-Polycide Gate Using a Nitrogen Ion-Implanted Buffer Layer
Authors: Kobushi Kazuhiro , Okada Shozo , Kameyama Shuichi , Tsuji Kazuhiko
Published: February 2005

A new titanium-disilicide/polysilicon gate system using a nitrogen ion-implanted buffer layer which has high dielectric strength and low resistivity has been developed. The buffer layer of a nonstoichiometric silicon nitride layer approximately 30 nm-thick is formed with a N2
+ dose below 5.0×1016 cm-2 at an acceleration energy of 15 keV. This layer can prevent intermixing of a titanium-disilicide film and a polysilicon film even after high-temperature annealing. Therefore, it can improve dielectric strength without increasing series resistances through those films.
The Dielectric Reliability of Very Thin SiO2 Films Grown by Rapid Thermal Processing
Authors: Fukuda Hisashi , Iwabuchi Toshiyuki , Ohno Seigo
Published: February 2005

Very thin SiO2 films, 3–10 nm in thickness, have been formed on silicon by rapid thermal processing (RTP), and their dielectric reliability has been investigated in comparison with furnace-grown oxides. The SiO2 films grown by RTP are superior to furnace oxides on both the dielectric breakdown and the Si-SiO2 interface characteristics. On the RTP SiO2 films, quantum oscillation in MOS tunneling is clearly observed at 300 K. The Si-SiO2 interface roughness is estimated from the Fowler-Nordheim plot. These results indicate that the Si-SiO2 structure is ordered within one monolayer.
Multi-Step Bidirectional NDR Characteristics in Si/Si1-xGex/Si DHBTs and Their Temperature Dependence
Authors: Xu D. X. , Shen G. D. , Willander M. , Hansson G. V.
Published: February 2005

Novel bidirectional negative differential resistance (NDR) phenomena have been observed at room temperature in strained base n-Si/p-Si1-x
Ge
x
/n-Si double heterojunction bipolar transistors (DHBTs). A strong and symmetric bidirectional NDR modulated by base bias, together with a multi-step characteristic in collector current I
C vs emitter-collector bias voltage V
CE, was obtained in the devices with very thin base. The temperature dependence of the NDR and the multi-step I
C-V
CE characteristics has been measured to identify the possible transport mechanism. The physical origins of these phenomena are discussed.
Extremely Sharp Photoluminescence from InGaAs/GaAs Quantum Wells Grown by Flow-Rate Modulation Epitaxy
Authors: Sato Michio , Horikoshi Yoshiji
Published: February 2005

InGaAs/GaAs quantum well structures are grown by a modified MOCVD method, called flow-rate modulation epitaxy (FME), in which organometals and arsine are alternately fed into a reaction chamber. These structures exhibit low-temperature photoluminescence with very narrow linewidths. The linewidth of single quantum well is 0.4 meV, the best reported value for any quantum wells. Exciton structures of multiple quantum wells are clearly observed. This extremely sharp photoluminescence shows that FME can grow atomically flat InGaAs/GaAs interfaces by enhancing the surface migration of isolated In and Ga.
Characterization of Nitrogen-Doped ZnSe and ZnS0.06Se0.94 Films Grown by Metal-Organic Vapor-Phase Epitaxy
Authors: Suemune Ikuo , Yamada Kouichi , Masato Hiroyuki , Kanda Takashi , Kan Yasuo , Yamanishi Masamichi
Published: February 2005

The relations of doped nitrogen (N) and deep-level emissions such as Y lines (477 nm) and self-activated (SA) emissions (∼580 nm) were investigated in detail by photoluminescence measurements mainly in ZnS0.06Se0.94 films lattice-matched to GaAs. The Y and SA emissions in the N-doped ZnS0.06Se0.94 films both showed appearance of a `threshold' for the incident optical power, indicating the existence of the activation energy on these lines. Persistent photoconductivity was observed for the first time in the N-doped ZnS0.06Se0.94 films which corresponds with the above new finding. The electrical property of the lattice-matched ZnS0.06Se0.94 film was p-type with a carrier concentration of 7×1015 cm-3 which is the highest carrier concentration ever reported with N-doping, while the lattice-mismatched ZnSe film was highly resistive. It was pointed out that the partial incorporation of the doped N-into the defect sites related to the Y line is still compensating the p-type property, even in the lattice-matched films.
Development of an Innovative 5 µm φ Focused X-Ray Beam Energy-Dispersive Spectrometer and its Applications
Authors: Yamamoto Naoki , Hosokawa Yoshinori
Published: February 2005

A 5.7 µm φ X-ray microbeam spectrometer has been developed. It incorporates an approximately parabolic inner-surface X-ray guide tube made of glass and a Li-diffused Si X-ray detector with a large area of 200 mm2, developed to detect weak X-rays. An energy-dispersive spectrometer incorporating these components can simultaneously measure diffraction X-rays for observing local reactions and residual stresses, and fluorescent X-rays for analyzing least-amount-of-impurity elements in microregions during ULSI processing (\lesssim900°C).
Three-Dimensional Quantum Well Effects in Ultrafine Silicon Particles
Authors: Furukawa Shoji , Miyasato Tatsuro
Published: February 2005

The mostly crystallized Si:H having a wide optical band gap and showing a visible photoluminescence at room temperature, has been fabricated by means of a planar magnetron rf sputtering technique in hydrogen gas onto a low temperature (about 100 K) substrate. The materials consist of very small crystalline silicon particles (average diameters: 2–5 nm) surrounded by =SiH2 groups. The observed macroscopic physical properties are explained by the three-dimensional quantum size effects in the ultrafine silicon particles.
Effect of Oxygen Deficiency on Tc of Oxide Superconductor La1.1Ba1.9Cu3Oy
Authors: Takayama-Muromachi Eiji , Uchida Yoshishige , Fujimori Atsushi , Kato Katsuo
Published: February 2005

The effect of oxygen deficiency on T
c of La1.1Ba1.9Cu3O
y
was examined by ac susceptibility measurements. The results indicate that superconductivity of the La-containing compound is much more sensitive to the oxygen deficiency than is that of YBa2Cu3O
y
. We suggest that the suppression of T
c in the La-containing compound is not due to the oxygen defects in the 1D Cu-O layer but to those in the rock-salt-type BaO layer, which leads us to propose the possibility of the superconductivity occurring in the BaO layer.
Three Classes of New Chiral Dopants: Synthesis and Physical Qualification as Dopants for Practical FLC-Mixtures
Authors: Dübal H. R. , Escher C. , Günther D. , Hemmerling W. , Inoguchi Yoshio , Müller I. , Murakami Mikio , Ohlendorf D. , Wingen R.
Published: February 2005

Three classes of new chiral dopants were synthesized and their properties in a non-chiral host mixture were measured. An extremely large spontaneous polarization (77 nC/cm2 at 25°C) was induced by 10% dopant in one case. Molecular mechanics calculations reveal that such a high polarization is predominantly obtained by steric hindrance around the chiral center. This steric effect also influences other physical properties such as helical twisting power. In addition the relationship between electro-optical properties and spontaneous polarization (Ps) are studied. It is apparent that higher Ps does not always improve switching time and bistability.
New Amorphous Mg-Ce-Ni Alloys with High Strength and Good Ductility
Authors: Inoue Akihisa , Ohtera Katsumasa , Kita Kazuhiko , Masumoto Tsuyoshi
Published: February 2005

New Mg-based amorphous alloys with high strength and good ductility were produced in the Mg-Ce-Ni system by melt spinning. The tensile fracture strength ( σf) and Vickers hardness reach 750 MPa and 199 DPN for Mg80Ce10Ni10. The specific strength defined by the ratio of σf to density is as high as 27, being considerably higher than the highest value (≃20) for conventional Al-based alloys. The high-strength Mg-base amorphous alloys are expected to attract much attention as a new type of high-strength material with low density.
Al-Ge-Mn and Al-Cu-Ge-Mn Quasi-Crystals with Coercivity at Room Temperature
Authors: Tsai An-Pang , Inoue Akihisa , Masumoto Tsuyoshi , Kataoka Noriyuki
Published: February 2005

Icosahedral quasi-crystals with coercivity at room temperature are found in rapidly solidified Al-Ge-Mn and Al-Cu-Ge-Mn alloys with compositions ranging form 20 to 25 at%Ge, 22.5 to 25%Mn and 0 to 10%Cu. The highest Curie temperature is 533 K for Al52.5Ge22.5Mu25 and 467 K for Al40Cu10Ge25Mn25. The magnetization ( σ20) of the Al-Ge-Mn alloys in a field of 20 kOe at room temperature increases from 0.2 to 0.5 emu/g with increasing Ge and Mn contents and the coercivity (H
c) is in the range of 0.7 to 1.1 kOe. The replacement of Al by 10%Cu is found to bring about significant increases of σ20 and H
c to 3.9 emu/g and 1.8 kOe.
Superconducting and Magnetic Properties in Metamorphic Phases of GdBa2Cu3O7-δ
Authors: Oota Akio , Kiyoshima Yoshio , Sasaki Yoshinobu , Shimono Akira
Published: February 2005

Superconducting and magnetic properties were studied on samples of GdBa2Cu3O7-δ in the ortho-I, ortho-II and tetra-II phases, where ortho-I is typical of the 90 K-superconductor. The ortho-I sample shows a value of T
c=92.7±0.3 K and the Meissner flux expulsion near 100% at T=79.0 K. Ortho-II has a value of T
c=49.0±5.0 K, while tetra-II shows no superconductivity until 4.2 K. The susceptibility data for ortho-I between 100 and 700 K provides the effective magnetic moment 7.38µB, which is slightly smaller than 7.94µB for a free trivalent ion of Gd.
Geometrical Relations of Various Modulated Structures in Bi-Sr-Ca-Cu-O Superconductors and Related Compounds
Authors: Matsui Yoshio , Horiuchi Shigeo
Published: February 2005

Geometrical relations of the three types of modulated structures in Bi-based superconductors are discussed. The constituent blocks of width B
s, wavelength of wavy perovskite and BiO layers, are packed in various ways to form various structures. Body-centered orthorhombic structures in Bi-Sr-Ca-Cu-O superconductors are derived by B
s/2 displacements between upper and lower blocks, whereas the B-centered monoclinic structure in the Bi-Sr-Cu-O one is derived by nearly B
s/4 displacement. Another orthorhombic structure, recently found in Bi-Pb-Sr-Ca-Cu-O superconductor, is possibly due to the simple arrangements of blocks with no mutual displacement.
Properties of Bi-Sr-Ca-Mg-Cu-O Superconductors
Authors: Moroishi Keiji , Ogawa Yayoi , Ikushima Akira J.
Published: February 2005

The superconducting properties of Bi1Sr1-x
Ca1-x
Mg2x
Cu2O
y
(0≦x≦0.33) were investigated. Electrical resistivity and X-ray diffraction suggest that, with increased Mg concentration, the fractions of low-T
c phase (80 K phase), high-T
c phase (110 K phase) and CuO in the superconductors are unchanged, decreased and increased, respectively.
Ag-Sheathed Tl-Ba-Ca-Cu-O Superconductor Tape with Tc≈120 K
Authors: Okada Michiya , Nishiwaki Ryou , Kamo Tomoichi , Matsumoto Toshimi , Aihara Katsuzo , Matsuda Shinpei , Seido Masahiro
Published: February 2005

Ag-sheathed Tl2Ba2Ca2Cu3O10 tapes with a T
c of 120 K were fabricated by cold rolling. The tapes annealed at an optimized condition yielded J
c=6700 A/cm2 (77 K/0 T) and 100 A/cm2 (77 K/1 T). The J
c's of the TBCCO tapes were twice as high as those of YBCO tapes in the absence of external magnetic fields, and about ten times as high as those of YBCO in the presence of magnetic fields.
Erbium Implanted in III–V Materials
Authors: Rochaix C. , Rolland A. , Favennec P. N. , Lambert B. , Corre A. Le , L'Haridon H. , Salvi M.
Published: February 2005

Erbium impurities were implanted in binary, ternary and quaternary III–V semiconductors. The main erbium emission centered at 1.54 µm is an invariant for III–V semiconductors having a band gap energy higher than the intrashell transition energy of Er 4f electrons (0.805 eV). The erbium emission is independent of the emission temperature from 2 K to 300 K.
Annealing Effect of Magneto-Optical Kerr Rotation for PtMnSb Compound
Authors: Takanashi Kōki , Fujimori Hiroyasu , Watanabe Jun , Shoji Masuhiro , Nagai Aisaku
Published: February 2005

The polar magneto-optical Kerr rotation angle ( θK) was obtained in the 400 nm–1000 nm wavelength range for bulk PtMnSb, one of the Clb-type Heusler compounds. The θK spectrum in the as-polished state was almost the same at that reported by van Engen et al. After annealing at higher temperatures than 400°C, however, the values of θK were strongly enhanced, although the change in the spectrum of reflectance was very small. From the surface analysis using Rutherford back scattering and Auger electron spectroscopy, it is considered that the enhancement is not attributed to the formation of the oxydized overlayer.
New Quaternary Semiconductor Material Pb1-xMnxS1-ySey for Mid-IR Lasers
Authors: Koguchi Nobuyuki , Takahashi Satoshi , Kiyosawa Teruo
Published: February 2005

The energy gap and the refractive index of a new quaternary semiconductor material Pb1-x
Mn
x
S1-x
Se
y
are determined experimentally. The compositional and temperature dependence of the energy gap of this material is E(x, y, T)=3.93x-0.186y-17.3x
2+0.0373y
2+x
y+0.271+(4×104+2.65×10-7
T
2)1/2 (eV). The refractive index decreases as the manganese content increases, and increases with the selenium content. It becomes evident that this new quaternary solid solution is a suitable material lattice-matched to PbS for the confinement layers of double-heterostructure lasers.
Emission of Doubly Charged Dimer Ions from Liquid-Metal Ion Sources
Authors: Umemura Kaoru , Kawanami Yoshimi , Ishitani Tohru
Published: February 2005

Emission of doubly charged ions, M2
2+, from liquid-metal ion sources (LMISs) is observed. The Sb2
2+ peak is confirmed in the mass spectrum of ions emitted from LMIS using gold antimonide (Au-Sb) alloy. The Sb2
2+ intensity is about 18% of the (Sb++Sb2
2+) intensity after isotope correction and accounts for approximately 3% of total emission intensities at a total ion current of 20 µA. The Sb2
2+ ions emitted from platinum antimonide (Pt-Sb) LMIS, on the other hand, have only several tenths of 1% of the (Sb++Sb2
2+) intensity. A strong dependence of Sb2
2+ intensity upon the source matrix is found.
Recrystallization Mechanism for Solid Phase Growth of Poly-Si Films on Quartz Substrates
Authors: Nakamura Akira , Emoto Fumiaki , Fujii Eiji , Uemoto Yasuhiro , Yamamoto Atsuya , Senda Kohji , Kano Gota
Published: February 2005

The recrystallization mechanism for solid-phase growth of poly-Si films amorphized by ion implantation on quartz substrates is clarified on the basis of an experimental finding obtained through the TEM observation. It is found that the {110} textured nucleation occurs. The preferential growth in the <112 > directions along twin boundaries then leads to the formation of the dendritic structure.
Effects of PAsxNy Deposition Conditions and the Cd Concentration in the Substrates on the Characteristics of In0.53Ga0.47As Metal-Insulator-Semiconductor Field Effect Transistors
Authors: Iwase Yoshimichi , Kawahara Akifumi , Arai Fusako , Sugano Takuo
Published: February 2005

Effects of the deposition temperature of PAs
x
N
y
films and the Cd concentration in the substrates on the electrical characteristics of In0.53Ga0.47As metal-insulator-semiconductor field effect transistors were investigated. It was found that the effective mobility of electrons increases with the decreases of the deposition temperature of the film and the decrease of Cd concentration in the substrate, and has exceeded 2000 cm2/Vs at room temperature. The drain current drift of the MISFETs was suppressed within 10% of the initial value in 103 s, by using in-situ vapor phase etching before the film deposition.
Quasi-One-Dimensional Channel GaAs/AlGaAs Modulation Doped FET Using a Corrugated Gate Structure
Authors: Okada Makoto , Ohshima Toshio , Matsuda Manabu , Yokoyama Naoki , Shibatomi Akihiro
Published: February 2005

This paper reports on the fabrication and characterization of a modulation-doped GaAs/AlGaAs FET with a corrugated gate structure in which the electron gas confinement has been changed from two-dimensional to quasi-one-dimensional with a negatively biased gate voltage. We observed enhanced field effect mobility and transconductance oscillations in a strictly-confined one-dimensional channel regime.
Integration of a GaAs SISFET and GaAs Inversion-Base Bipolar Transistor
Authors: Matsumoto Kazuhiko , Hayashi Yutaka , Kojima Takeshi , Nagata Toshiyuki , Yoshimoto Tomomi
Published: February 2005

The first integration of a GaAs FET-type device and a GaAs bipolar transistor-type device was achieved using the GaAs SISFET and GaAs inversion-base bipolar transistor (GaAs IBT). The GaAs SISFET showed the transconductance of g
m=80 mS/mm and 190 mS/mm at 300 K and 77 K, respectively. The GaAs IBT showed the current gain of β=18 and 13 for the common emitter configuration at 300 K and 77 K, respectively.
Field-Drifting Resonance Tunneling Through a-Si:H/a-Si1-xCx:H Double Barrier in the p-i-n Structure
Authors: Jiang Y. L. , Hwang H. L.
Published: February 2005

An a-Si:H/a-Si1-x
C
x
:H double-barrier structure was imbedded in the i layer of a p-i-n structure. The effects of photoinduced carriers tunneling through the double-barrier structure were examined. Distinct current bumps at room temperature were observed for the first time. The results support the resonance tunneling of carriers in the multilayer which provides further direct evidence of the quantum size effects of amorphous silicon-based superlattice structures.
Preparation of Ba-Y-Cu-O Superconducting Films by Laser Ablation with and without Laser Irradiation on Growing Surface
Authors: Otsubo Shigeru , Minamikawa Toshiharu , Yonezawa Yasuto , Maeda Toshihiro , Moto Akihiro , Morimoto Akiharu , Shimizu Tatsuo
Published: February 2005

Superconducting Ba-Y-Cu-O films were prepared by the excimer laser ablation method. Films with a good superconducting property were prepared on various substrates with substrate temperatures T
s of 650°C∼800°C without a high-temperature annealing. In particular the film (1.7 µm thick) prepared on crystalline Si without a buffer-layer exhibits zero resistance at 82 K. To reduce T
s, we examine the effect of the laser irradiation onto the growing film surface. We found that excimer laser irradiation onto the growing film surface improves the superconducting properties of the films prepared at a lower T
s.
High-Quality Zinc Sulfide Thin Films Grown by MOCVD Using Carbon Disulfide as A Sulfur Source
Authors: Takata Shinzo , Minami Tadatsugu , Miyata Toshihiro , Nanto Hidehito
Published: February 2005

High-quality zinc sulfide (ZnS) films are prepared by a low-pressure metalorganic chemical vapor deposition technique using carbon disulfide (CS2) as a new sulfur source material. In the diethylzinc-CS2 system, the ZnS films are grown on the substrates at a temperature above about 200°C. The ZnS films with a strongly preferred orientation are grown on glass substrates at a temperature of 325–425°C and with an atomic ratio of supplied sulfur to zinc of 18–22.
Photoluminescence Properties of Li-Doped ZnSe Films Grown by Metalorganic Chemical Vapor Deposition
Authors: Yoshikawa Akihiko , Muto Shin-ichiro , Yamaga Shigeki , Kasai Haruo
Published: February 2005

Lithium-doped ZnSe films have been grown by atmospheric metalorganic chemical vapor deposition. Dimethylzinc and dimethylselenide were used as source materials and cyclopentadienyl lithium was used as a dopant. The films have been characterized by a low-temperature photoluminescence. It is shown that the lithium acts as a shallow acceptor in ZnSe with an activation energy of about 101–118 meV. Furthermore, it is shown that the intensity of emission from deep centers, such as so-called self-activated and copper-green emission, is remarkably reduced in lithium-doped ZnSe films.
Electroluminescence in Organic Films with Three-Layer Structure
Authors: Adachi Chihaya , Tokito Shizuo , Tsutsui Tetsuo , Saito Shogo
Published: February 2005

We have succeeded in the fabrication of a stable organic electroluminescent (EL) device with a three-layer structure; hole transport layer/emitting layer/electron transport layer. The EL device was prepared by vacuum evaporation. Efficient carrier double injection into the emitting layer was realized by the use of separate hole and electron transport layers. Bright EL emission was observed in a darkened room at the dc bias voltage of 50 V. Stable emission lasted for more than five hours at this condition. The emission spectrum could be changed with variation of the organic material for the emitting layer.
Relation between Spontaneous Polarization and Rotational Viscosity in Enantiomeric Mixtures of Ferroelectric Liquid Crystals
Authors: Chandani A. D. L , Ouchi Yukio , Takezoe Hideo , Fukuda Atsuo
Published: February 2005

Spontaneous polarization P
s and rotational viscosity of the C-director ηc were measured in two series of mixtures of L- and D-enantiomers of ferroelectric liquid crystals. It was confirmed that ηc is independent of optical purity, while P
s depends on it almost linearly. The results of ηc are totally different from the recent results achieved by Dubal et al., who showed that high P
s accompanies high ηc. An explanation is given for the discrepancy, suggesting that the present results are more reliable.
The Effect of Photochemical Surface Passivation on 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 effect of photochemical surface passivation on Ti-GaAs diodes is demonstrated and discussed. The procedure described can be used to prepare a stable and repeatable GaAs surface for device processing. It is also compatible with lift-off technique.
Preparation of High-Tc Bi-Sr-Ca-Cu-O Superconductors
Authors: Togano Kazumasa , Kamakura Hiroaki , Maeda Hiroshi , Takahashi Kazuhiko , Nakao Masao
Published: February 2005

A sharp resistive superconducting transition above 100 K has been achieved for Bi-Sr-Ca-Cu-O superconductors. The resistance at 100 K was estimated to be less than 10-6 Ω cm in a zero magnetic field.
Formation and Decomposition of Superconducting BiSrCaCu2Ox Ceramics
Authors: Inoue Osamu , Adachi Seiji , Kawashima Syunichiro
Published: February 2005

Phase changes of superconducting BiSrCaCu2O
x
ceramics against temperature and atmosphere have been studied. Phases of high-T
c superconducting BiSrCaCu2O
x
ceramics sintered at 850°C in air were decomposed by low-temperature annealing, therefore the phases are not stable at low temperatures. The formation of these phases depended on the sintering atmosphere.
Identification of the Superconducting Phase in the Bi-Ca-Sr-Cu-O System
Authors: Takayama-Muromachi Eiji , Uchida Yoshishige , Ono Akira , Izumi Fujio , Onoda Mitsuko , Matsui Yoshio , Kosuda Kosuke , Takekawa Shunji , Kato Katsuo
Published: February 2005

In order to identify the superconducting phase in the Bi-Ca-Sr-Cu-O system, phase search experiments were performed. The results of power X-ray study, EPMA study, specific gravity measurements and oxygen analysis revealed that the compound having the composition Bi2(Ca, Sr)3Cu2O9 or Bi2(Ca, Sr)3-Δ
x
Cu2O9-Δ
y
is responsible for the high-T
c superconductivity. Two possible structure models, which are closely related to the structure of the bismuth titanate Bi4Ti3O12, are proposed for this compound.
High-Temperature Superconductivity Caused by the Interaction between Holes and Optical Mode Phonons
Authors: Sugahara Masanori , Akeyoshi Tomoyuki
Published: February 2005

The interaction between carriers and optical mode phonons has been considered as one of the possible mechanisms of high-T
c superconductivity in ceramic superconductors. Criticism of the mechanism based on the geometrical properties of the Cu-O 2D lattice is re-examined. It is pointed out that the phonon exchange by hole carriers in the filled band which are made with the gap formation in the half-filled p-d hybridizing electronic state can cause the high-T
c superconductivity even when the special properties of the 2D lattice are taken into consideration.
Effect of Annealing on the Transition Temperature and the Upper Critical Magnetic Field of the YBa2Cu3Ox Superconductor
Authors: Umakoshi Yukichi , Hamada Kohtaro , Yamane Toshimi
Published: February 2005

The effect of the cooling rate on T
c and H
c2 of YBa2Cu3O
x
was studied. The significant decrease of T
c for samples quenched in air or in ice water was found to be affected by the oxygen deficiency and/or the coexistence of tetragonal and orthorhombic phases. When the sample was cooled in furnace from 600°C∼400°C, a decrease of T
c and H
c2 was also observed, however, the oxygen content did not change. The degradation of superconductivity of the samples cooled in the furnace after reheating may be due to the formation of new imperfect twin bands.
Interference Phenomena of Diffraction Waves Originating on the Boundary of a Small Obstacle
Authors: Itô Hiroshi , Kanai Norikane
Published: February 2005

Existence of boundary diffraction waves originating at every point of the outline of an obstacle illuminated by coherent light is studied experimentally. Optical fringes appearing in the shadow region of the obstacle are recognized to be made by interference of this kind of wave.
Influence of the Ring-Substitution on the Second Harmonic Generation of Chalcone Derivatives
Authors: Fichou Denis , Watanabe Toshiyuki , Takeda Takeshi , Miyata Seizo , Goto Yoshitaka , Nakayama Masaharu
Published: February 2005

Several chalcone derivatives exhibiting second harmonic generation up to 5 times that of urea under IR-excitation have been synthesized by varying the substituents on both phenyl-rings.
Partial Discharge in a Void Filled with Sulfur Hexafluoride and Formation of Sulfide
Authors: Tsujikawa Yukihiro , Onoda Mitsuyoshi , Nakayama Hiroshi , Amakawa Kiyoshi
Published: February 2005

The deterioration products formed due to partial discharge in a void filled with sulfur hexafluoride (SF6) were analyzed. The SF6 content in the void decreased with ageing; after about 15 h of ageing, the SF6 content was about 15%. Then, after 24 h of ageing, spots of powder formed on the void surface. When the powder was exposed to air, it changed into a colorless liquid. It was determined that this liquid was sulfuric acid (H2SO4) and thus, the powder was sulfur trioxide (SO3).
Observation of Electrochemical Polymerization Pattern of Conducting Polymer and Its Interpretation by Fractal Dimension
Authors: Fujii Masaharu , Yoshino Katsumi
Published: February 2005

Characteristic growth patterns of conducting polymers prepared by the electrochemical polymerization method have been found to be strongly dependent on the polymerization conditions and undergo dramatic change during their growth. In polypyrrole, three types of growth one-, two- and three-dimensional growth, have been observed depending on the condition. These are discussed in terms of fractal dimension.
Depth Profiling of Superstructures by µ-AES Utilizing Angle-Lapped Specimens
Authors: Matsunaga Fumiko , Kakibayashi Hiroshi , Nagata Fumio
Published: February 2005

Line scanning of an angle-lapped specimen by microprobe Auger electron spectroscopy ( µ-AES) is proposed for depth profiling of superstructures. A multilayer structure enlarged several hundred times is exposed on an angle-lapped surface, and depth profiling is carried out using electron beam scanning. This method makes it possible to measure the compositional depth profiles of a large depth region that is over several thousand Å within only several minutes. The composition profile of Ga in a GaAs/Al
x
Ga1-x
As superstructure is measured with the depth resolution of 80 Å. The thinnest detectable GaAs layer is 15 Å.
Nanometer-Area Electron Diffraction of Interfaces of Semiconductor Superlattices
Authors: Tanaka Nobuo
Published: February 2005

A new method for analyzing interfaces of semiconductor superlattices such as GaAs/Ga1-x
Al
x
As is reported: An electron probe of 1–2 nm in size of formed in a transmission electron microscope is incident in the [100] direction on a {110} cleaved crystal of the superlattices and scanned around the interfaces like the cross-sectional observation. The nanometer-area diffraction patterns are recorded continuously by scanning the probe. The local compositional and structural information of the interfaces in the superlattices can be obtained using the method.
Aluminum-Based Amorphous Alloys with Tensile Strength above 980 MPa (100 kg/mm2)
Authors: Inoue Akihisa , Ohtera Katsumasa , Tsai An-Pang , Masumoto Tsuyoshi
Published: February 2005

New Al-based amorphous alloys with high strength and good ductility were produced in an Al-Y-Ni system by liquid quenching. The tensile fracture strength ( σf) and Vickers hardness reach 1140 MPa and 300 DPN for Al87Y8Ni5. The specific strength defined by the ratio of σf to density is as high as 38, being much higher than that for conventional alloy steels. The high-strength Al-base amorphous alloys are expected to attract strong attention as a new type of high-strength material with low density.
Growth of GaAs on Preferentially Etched GaAs Surfaces by Migration-Enhanced Epitaxy
Authors: Kawashima Minoru , Horikoshi Yoshiji
Published: February 2005

The migration mechanism of surface adatoms during migration-enhanced epitaxy is quite different from that expected in conventional molecular beam epitaxy. This difference is clearly demonstrated in the cross-sectional views of GaAs layers grown on preferentially etched, undercut-mesa stripes. Definite crystal facets of (110) appear in the layers grown by migration-enhanced epitaxy, in contrast to the (111)B facets in the layers grown by molecular beam epitaxy. The migration mechanisms of these two growth methods are discussed in order to interpret the differences in the facetting characteristics.
Atomic Layer Epitaxy of GaAs Using Solid Arsenic and DEGaCl
Authors: Sasaoka Chiaki , Yoshida Masaji , Usui Akira
Published: February 2005

ALE growth of GaAs was reported using solid arsenic and DEGaCl. An abrupt shutoff of arsenic vapor was successfully achieved and monolayer growth was obtained independent of DEGaCl partial pressure. Grown surfaces were mirror-like at growth temperatures of 400∼550°C. Grown layers showed p-type conductivity. The carrier concentration of the grown layers was rather low compared with that reported in DEGaCl-AsH3 ALE. QMS measurements of the DEGaCl decomposition rate suggest that DEGaCl completely decomposes to GaCl before reaching the substrate, which is considered to result in lower carbon contamination.
Density of Mid-Gap States for Undoped a-Si1-xGex:H and a-Si:H Determined by Steady-State Heterojunction-Monitored Capacitance Method
Authors: Matsuura Hideharu
Published: February 2005

A simple technique has been described for determining the density of mid-gap states of highly resistive amorphous semiconductors, using amorphous/crystalline heterojunction structures. The technique has been tested and applied on undoped hydrogenated amorphous silicon films and silicon-germanium alloy films, covering the optical gap range of 1.30 to 1.76 eV. Those densities obtained from this technique have been found to be densities of singly-occupied dangling bonds.
Density-of-State Distribution for Undoped a-Si:H and a-Si1-xGex:H Determined by Transient Heterojunction-Monitored Capacitance Method
Authors: Matsuura Hideharu
Published: February 2005

A novel technique has been proposed for determining the density-of-state (DOS) distribution in the mobility gap of highly resistive amorphous semiconductors, using amorphous/crystalline heterojunction structures. This technique has been tested and applied on undoped hydrogenated amorphous silicon (a-Si:H) films and silicon-germanium alloy (a-Si1-x
Ge
x
:H) films, covering the optical gap range (E
0) of 1.55 eV to 1.76 eV. For undoped a-Si:H (E
0=1.76 eV), the peak of the mid-gap DOS distribution has been located at 0.85 eV below the conduction band mobility edge, with a value of 5.6×1015 cm-3eV-1.
Preparation of High-Tc Superconducting Bi-Ca-Sr-Cu-O Ceramics by the Melt Quenching Method
Authors: Komatsu Takayuki , Imai Kouji , Sato Ryuji , Matusita Kazumasa , Yamashita Tsutomu
Published: February 2005

Superconducting Bi-Ca-Sr-Cu-O ceramics with T
c(onset)=102 K and T
c(zero)=92 K were prepared by a melt quenching method, in which the melt of nominal composition BiCaSrCu2O
x
was first quenched and then annealed at 800∼850°C for 24 h in oxygen atmosphere. It was found that the rapidly cooled samples after annealing show high T
c and sharp superconducting transition, but the samples slowly cooled in the furnace after annealing show low T
c and broad transition with a tail. The critical current density at 77 K in the zero magnetic field for the rapidly cooled sample after annealing at 800°C was 102 A/cm2.
Large Anisotropy of the Upper Critical Magnetic Field in Single Crystal Bi-(Sr, Ca)-Cu-O
Authors: Hidaka Yoshikazu , Oda Migaku , Suzuki Minoru , Maeda Yasushi , Enomoto Youichi , Murakami Toshiaki
Published: February 2005

Single crystals of a recently discovered high-T
c Bi-(Sr, Ca)-Cu-O compound have been obtained. EPMA analysis exhibited that the compositional ratio of the crystal is 2-3-2. X-ray diffraction and transmission electron diffraction analysis revealed that the crystal has a layered structure characterized by orthorhombic symmetry with the lattice constant a=5.405 Å, b=5a and c=30.69 Å. The upper critical magnetic field H
c2 has been measured for the superconducting single crystal. The anisotropy between the c-axis and the basal plane is much larger than that of Ba2YCu3O7-y
or (La1-x
Sr
x
)2CuO4-y
. The slope of temperature dependence of H
c2 along the c-axis is -0.32 T/K, while that along the basal plane is -14±3 T/K. The coherence length along the c-axis is estimated to be 1.0±0.1 Å, and that in the basal plane is 42 Å. The anisotropy factor is 44±9. These values suggest that the two-dimensionality in electronic structure for this superconductor is much stronger than other high-T
c oxides.
High-Tc Superconducting Glass Ceramics Based on the Bi-Ca-Sr-Cu-O System
Authors: Komatsu Takayuki , Sato Ryuji , Imai Kouji , Matusita Kazumasa , Yamashita Tsutomu
Published: February 2005

Various superconducting glass ceramics based on the Bi-Ca-Sr-Cu-O system with T
c(onset)=80∼95 K and T
c(zero)=63∼78 K were prepared by a melt-quenching method. The melt-quenched samples of Bi1.5CaSrCu2O
x
and Bi1.5Ca1.5SrCu2O
x
were found to be a glass with a glass transition of about 425°C; these samples became high-T
c superconductors by annealing at 820°C.
Synthesis of a Tl-Ba-Ca-Cu-O Superconductor and Its Properties
Authors: Itoh Takao , Uchikawa Hiroshi , Sakata Hiroyuki
Published: February 2005

Tl-Ba-Ca-Cu-O superconductor has been synthesized by means of the solid-state reaction, Tl2O3+BaCuO2+Ca2CuO3. The resultant bulk superconductor was found to show the onset T
c at 126 K, with the superconducting critical current density or over 100 A/cm2 at 105 K.
Superconductor with a Layered Structure in Bi-Sr-Ca-Cu Oxides
Authors: Ohta Masatsune , Takahashi Koh , Kosuge Michikazu
Published: February 2005

One of the high-T
c superconducting phases in Bi-Sr-Ca-Cu oxides has been found to be Bi4Sr3Ca2Cu4O
y
with a pseudo-tetragonal structure which belongs to the family of complex bismuth oxides with layered structures. The superconducting transition takes place at 80 K (midpoint), with a long tail of residual resistance down to 20 K. A partial drop of resistance at 108 K was also observed with nominal composition Bi:Sr:Ca:Cu=2:3:4:8.
An X-Ray Diffraction and Electron Microscopic Study of a New High-Tc Superconductor based on the Bi-Ca-Sr-Cu-O System
Authors: Syono Yasuhiko , Hiraga Kenji , Kobayashi Norio , Kikuchi Masae , Kusaba Keiji , Kajitani Tsuyoshi , Shindo Daisuke , Hosoya Syoichi , Tokiwa Ayako , Terada Shoji , Muto Yoshio
Published: February 2005

Observed high-resolution images of a new high-T
c superconductor based on the Bi-Ca-Sr-Cu-O system (T
c above 70 K) indicated a structure derived from the Bi4Ti3O12 type in which doubled bismuth oxide layers alternate with double perovskite layers along the c-axis. The orthorhombic unit cell dimensions showed an approximate relation of a=√2a
p, b=5√2a
p and c=8a
p, where a
p=3.82 Å, the cell parameter of a cubic perovskite. At least a quarter of the oxygen should be deleted in accordance with the average copper valence of less than 3 and two-dimensional Cu-O layers are supposed to be responsible for the high-T
c superconductivity.
Superconducting Phases with Tc above 100 K in the Tl-Ba-Ca-Cu-O System
Authors: Kubo Yoshimi , Shimakawa Yuichi , Manako Takashi , Satoh Tetsuro , Igarashi Hitoshi
Published: February 2005

Superconductivity above 100 K was observed in Tl-Ba-Ca-Cu oxides. DC resistivity, ac susceptibility, EPMA and X-ray diffraction studies revealed that two superconducting phases with different T
c's of ∼110 K and 100 K exist in this oxide system. The 110 K phase is Tl2Ba2Ca2Cu3O
x
(2223 phase) with a 5.45×5.45×35.6 Å tetragonal unit cell, while the 100 K phase is Tl2Ba2Ca1Cu2O
x
(2212 phase) with a 5.45×5.45×29.3 Å tetragonal unit cell. The crystal structure of the 2212 phase seems quite similar to that of Bi2Sr2Ca1Cu2O
x
, and the 2223 phase structure can be derived by inserting another Cu and Ca layer into the 2212 phase.
Effect of Magnetic Field and High Pressure on the Superconductivity of the New High-Tc Oxide Bi-Sr-Ca-Cu-O
Authors: Matsumoto Takehiko , Aoki Haruyoshi , Matsushita Akiyuki , Uehara Mitsuru , Mori Nobuo , Takahashi Hiroki , Murayama Chizuko , Maeda Hiroshi
Published: February 2005

The electrical resistances of the multiphase new high-T
c superconducting oxides Bi-Sr-Ca-Cu-O have been measured in the magnetic field and under hydrostatic pressure. The resistances decrease in two steps around 80 K and 110 K, which are believed to correspond to the presence of phases with different T
c's. The effect of the magnetic field on the superconductivity is similar to that in the Y-Ba-Cu-O and La-Ba(Sr)-Cu-O systems. However, the superconducting transition is not affected appreciably by the pressure. The results are deduced to be due to the anisotropic structure of the high-T
c phase.
Correlation of Tc with Hole Concentration in Copper-Oxide Superconductors; Hall Effect Measurement in Nd1+xBa2-xCu3O7-δ
Authors: Takita Kôki , Akinaga Hiroyuki , Katoh Hideo , Masuda Kohzoh
Published: February 2005

Hole concentration compensation effect in Nd1+x
Ba2-x
Cu3O7-δ and a simple correlation of T
c with the hole concentration in copper-oxide-type superconductors, proposed in a previous paper by the present authors, have been supported by the Hall effect measurement. The effective hole concentration p
H (=1/R
H
e) deduced from the Hall coefficient, R
H, decreases with increasing x. The plot of T
c against p
H obtained in the present system is very similar to that of oxygen-doped YBa2Cu3O7-δ in spite of that the two systems differ in the oxygen content, δ. This suggests that the hole concentration is a more essential parameter than the oxygen content δ, in determining the superconductivity of copper-oxide superconductors.
Preparation of Ba2YCu3Ox Superconducting Films by Laser Evaporation and Rapid Laser Annealing
Authors: Minamikawa Toshiharu , Yonezawa Yasuto , Otsubo Shigeru , Maeda Toshihiro , Moto Akihiro , Morimoto Akiharu , Shimizu Tatsuo
Published: February 2005

A Ba2YCu3O
x
superconducting film was prepared by laser evaporation and rapid laser annealing followed by 450°C furnace annealing in flowing O2. This is the first report on the preparation of a superconducting film by laser annealing. This technique supplies the first step in the preparation of superconducting films on various kinds of substrates without a prolonged high-temperature treatment.
Preparation of New High-Tc Superconducting Oxide Bi-Sr-Ca-Cu-O Thin Film by Electron Beam Deposition Technique
Authors: Kuroda Kenichi , Mukaida Masashi , Yamamoto Masafumi , Miyazawa Shintaro
Published: February 2005

Thin films of Bi-Sr-Ca-Cu-O superconducting oxide were prepared by electron beam deposition of Bi, SrF2, CaF2 and Cu on (100) MgO substrates followed by annealing in oxygen gas flow. Onset transition temperature is 110 K, and resistance drops to less than 5% of the value in the temperature range T
c+4 K, although zero resistance is observed at 60 K. Between 110 K and 60 K, there exist at least 2 resistance drops, indicating multiphase superconductors with different T
cs. X-ray diffraction analysis reveals that the films are highly oriented so that the c-axis is normal to the substrate and has a length of 30.605 Å.
Formation of High-Tc Superconducting BiSrCaCu2Ox Films on ZrO2/Si(100)
Authors: Nasu Hiroyuki , Myoren Hiroaki , Ibara Yoshikazu , Makida Seigo , Nishiyama Yukio , Kato Takeshi , Imura Takeshi , Osaka Yukio
Published: February 2005

High-T
c superconducting BiSrCaCu2O
x
films have been successfully prepared on Si(100) wafer coated with epitaxially grown tetragonal ZrO2 as a buffer layer. The films have been formed by pyrolysis of 2-ethylhexanoates. Regarding superconducting features, T
c(onset) observed is 97 K and T
c(end) is 50 K. From the X-ray diffraction patterns, the c-axis of the superconducting crystal phase mostly orients perpendicular to the substrate. These present results seem to prove the usefulness of ZrO2 layer on Si for the further application of high-T
c oxide films for a part of sophisticated electronics devices.
The Orthorhombic-Tetragonal Phase Transformation and Oxygen Deficiency in LnBa2Cu3O7-δ
Authors: Nakabayashi Yukinobu , Kubo Yoshimi , Manako Takashi , Tabuchi Junji , Ochi Atsushi , Utsumi Kazuaki , Igarashi Hitoshi , Yonezawa Masatomo
Published: February 2005

The orthorhombic-tetragonal phase transformation in LnBa2Cu3O7-δ (Ln=Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb) was studied using careful isobar TG measurements under an oxygen partial pressure of 1 atm. As the atomic number within the lanthanide series increases, the transformation temperature tends to increase as well. This tendency is strongly related to the spacing of the nearest-neighbor oxygen atoms and is successfully interpreted in terms of the repulsion energy between them on the basis of a simple order-disorder transformation model proposed in our previous paper.
C-Axis-Oriented Superconducting Oxide Film by the Sol-Gel Method
Authors: Shibata Shuichi , Kitagawa Takeshi , Okazaki Hisaaki , Kimura Takao
Published: February 2005

In R-Ba-Cu-O systems (R=Y, Nd, Y-Nd), c-axis-oriented superconducting oxide films with T
c(zero)=90 K have been fabricated on yttrium-stabilized zirconia substrates. Oxide pastes for printing on the substrates are made by the sol-gel method using liquid alkoxides. Starting paste compositions that are Cu-rich and R-poor are found to be suitable for forming the c-axis-oriented superconducting oxide film.
Blue and Green Cathodoluminescence of Synthesized Diamond Films Formed by Plasma-Assisted Chemical Vapour Deposition
Authors: Kawarada Hiroshi , Nishimura Kazuhito , Ito Toshimichi , Suzuki Jun-ichi , Mar King-Sheng , Yokota Yoshihiro , Hiraki Akio
Published: February 2005

Cathodoluminescence study of synthesized diamond films formed by magneto-microwave plasma CVD and usual microwave plasma CVD has been carried out for the first time. The visible luminescence spectra of these diamond films show that peaks occur at different energies between 2.4–2.8 eV (green to purple-blue by visual inspection), depending on the deposition conditions. These spectra can be classified into so-called “band A” luminescence commonly observed in all types of bulk diamond. The growth sectors of {100} (bright visible emission) and {111} (dark) can be differentiated by the intensity of luminescence. These features are analogous to the luminescent properties of high-pressure synthesized diamond.