bluuebunny/crossref_metadata_2025 huggingface dataset:
Pressure Generation by Sintered Diamond Multianvils
Authors: Endo Shoichi , Akahama Yuichi , Utsumi Wataru
Published: November 2005

Pressure generation was attempted by multianvils made of sintered diamond in “6-8 type” double-stage system, and the results were compared with those by WC-Co anvils. Pressure smoothly increased up to 22 GPa (the maximum pressure examined) with the increasing load of the press, whereas plastic deformation of WC-Co anvils resulted in a remarkable decrease in efficiency at pressures higher than ∼15 GPa.
Preparation of Oriented Orthorhombic LnBa2Cu3O7-x Polycrystals
Authors: Omori Mamoru , Tomiyoshi Shoichi , Yamauchi Hiroshi , Kamiyama Takashi , Fukuda Tsuguo
Published: November 2005

Tetragonal YBa2Cu3O7-x
and DyBa2Cu3O7-x
crystals were ground to resemble plate-like powder. Pellets of oriented tetragonal polycrystals were prepared from this powder using a uniaxial press. The tetragonal pellet was transformed into oriented orthorhombic polycrystals. The orientation of crystals was investigated by X-ray diffraction measurement and observed by SEM images. Samples exhibited zero resistance above 90 K, with a transition width of 2.0 K.
Passivation Properties of Plasma CVD AlN Films for GaAs
Authors: Hasegawa Fumio , Takahashi Tsuyoshi , Kubo Kiyokazu , Ohnari Seinosuke , Nannichi Yasuo , Arai Toshihiro
Published: November 2005

Plasma CVD AlN films were examined as passivation films for the heat treatment of GaAs. It was found that when the AlN/GaAs was annealed at 850°C for 15 min. in H2 atmosphere, the film was more oxidized than when it was annealed in Ar atmosphere. No Raman peak shift and no TO phonon were observed when the AlN/GaAs was annealed in Ar atmosphere, whereas they were observed for the annealing in H2. These results suggest that the PCVD-AlN can be used as a passivation film for the annealing of GaAs after ion implantations, and that Ar is a beter ambient gas for the annealing.
Dependene of Focused Ion Beam Intensity Profile on Ion Species at Several Orders of Magnitude below the Peak Intensity
Authors: Miyauchi Eizo , Arimoto Hiroshi , Morita Tetsuo , Hashimoto Hisao
Published: November 2005

We have estimated the current intensity distribution of focused Be and Si ion beams emitted from a Au-Si-Be liquid metal ion source down to several orders of magnitude below the peak intensity. The distributions are indirectly measured from implantation-induced damage configurations formed on a GaAs by the ion beams. The diameters of the intensity distributions are more or less larger than the Gaussian profile, and they increase to several microns at six orders of magnitude below. Since the spread depends on ion species, charge, and ion emission current, the prevailing tail of velocity distribution of the FIB must be involved.
Formation of Superconducting Y-Ba-Cu-O Thin Films by the Solid Phase Reaction between BaCo3/Cu/Y2O3 Layers on Single Crystalline SrTiO3 Substrate
Authors: Sorimachi Yoshio , Kobayashi Akihito , Yamashita Tsutomu , Takata Masasuke , Miyauchi Shinnosuke , Tsubata Ichiro
Published: November 2005

Thin films of superconducting Y-Ba-Cu-O were formed on single crystalline SrTiO3 substrate by the solid phase reaction between BaCO3/Cu/Y2O3 layers. The layers were evaporated on the substrate by an electron-beam gun and heated at 900°C in oxygen atmosphere for an hour. Resistivities of the films were measured by the four-probe method and superconduction was observed at T
c=90 K (onset) and 50 K (end).
Growth Properties of AlxGa1-xAs Grown by MOVPE Using TEG and TMA
Authors: Shinohara Masanori , Imamura Yoshihiro , Yanagawa Fumihiko
Published: November 2005

Correlations of metalorganic gas flow rate ratio with solid phase composition and the growth rate of MOVPE-grown AlGaAs using TEG and TMA are investigated. The AlGaAs growth rate is low compared to the sum of individually grown GaAs and AlAs growth rates, and solid phase composition differs from that calculated from their growth rate ratios. These characteristics result from variations in GaAs and AlAs growth rates with vapor phase composition. The correlations among growth properties can be explained by considering the reaction between metalorganic gas sources which reduces the amount of metalorganics contributing to the growth.
Macroscopic Quantum Interference Effect for High-Tc YBaCuO and GdBaCuO Josephson Junctions
Authors: Sugishita Akimitsu , Yanagisawa Manabu , Iguchi Ienari
Published: November 2005

DC SQUID operation utilizing all ceramic YBa2Cu3O7-δ and GdBa2Cu3O7-δ Josephson junctions is reported. It is confirmed that the macroscopic quantum interference effect is observable up to 90 K, almost the transition temperature of bulk cermaics. The periodic patterns of GdBa2Cu3O7-δ SQUID are rather deformed; probably due to the presence of magnetic element Gd. The temperature dependence of Josephson critical current shows a nearly linear behavior down to low temperatures, in disagreement with Ambegaokar-Baratoff's calculation.
Annealing Effect of High-Tc Superconducting Y(Ba1-xSrx)2Cu3O7-y Ceramics
Authors: Wada Takahiro , Adachi Seiji , Inoue Osamu , Kawashima Syunichiro , Mihara Toshihiro
Published: November 2005

Annealing effect of high-T
c superconducting Y(Ba1-x
Sr
x
)2Cu3O7-y
[x=0, 0.1, 0.2] ceramics on the superconducting transition temperature and lattice constants has been studied. For well annealed Y(Ba0.8Sr0.2)2Cu3O7-y
ceramics, the superconducting transition onset temperature was 95 K and the offset temperature was 92 K. These transition temperatures are comparable to those of the YBa2Cu3O7-y
ceramics.
Preparation of Y-Ba-Cu-O Thin Films by Rf-Magnetron Sputtering
Authors: Ohkuma Haruo , Mochiku Takashi , Kanke Yoko , Wen Zhongmin , Yokoyama Shin , Asano Hajime , Iguchi Ienari , Yamaka Eiso
Published: November 2005

Thin films of Y-Ba-Cu-O compound are prepared by rf-magnetron sputtering technique. Superconductivity appears for those films annealed at 900-930°C. The best thin films exhibit superconducting onset at 86 K and complete zero resistance at 76 K. From the X-ray diffraction analysis, it is found that the films annealed at 920°C have a strong c-axis orientation perpendicular to the film surface. The observed X-ray intensities are in good qualitative agreement with the calculated ones. The results of SEM and Auger electron spectroscopy are also presented.
High-Tc Superconductivity of La-Ba-Cu Oxides. III –Electrical Resistivity Measurement
Authors: Uchida Shin-ichi , Takagi Hidenori , Kitazawa Koichi , Tanaka Shoji
Published: November 2005

Electrical resistivity of the high-Tc superconductor (La1-x
Ba
x
)2CuO4 is measured as a function of temperature. The resistivity becomes substantially zero below 25 K and the onset of the superconducting transition is observed at 35 K for one of the samples. In the higher temperature region a T-linear term dominates in the normal-state resistivity.
Atomic Images of Disordered Regions in Graphite Crystals Obtained with Scanning Tunneling Microscope
Authors: Morita Seizo , Tsukada Shuichi , Mikoshiba Nobuo
Published: November 2005

Using a scanning tunneling microscope (STM), we investigated atomic images of disordered regions in three different grades of graphite crystals in air: (1) single-crystal flake graphite (Kish graphite), (2) highly oriented pyrolytic graphite (HOPG) and (3) pyrolytic graphite (PG). In HOPG and Kish graphites, we found unusual super-structures of graphite crystal located near defects, though almost all the STM images showed defect-free graphite structures. In PG, we could find few regions of graphite structure with STM, though atomic images different from the graphite structure were obtained frequently.
Estimate of Attainable Critical Current Density in Superconducting YBa2Cu3O7-δ
Authors: Matsushita Teruo , Iwakuma Masataka , Sudo Yasuo , Ni Baorong , Kisu Takanobu , Funaki Kazuo , Takeo Masakatsu , Yamafuji Kaoru
Published: November 2005

Attainable critical current density in oxide superconductor YBa2Cu3O7-δ is estimated by an ordinary analyzing method in flux pinning phenomena with superconducting parameters obtained from a magnetization measurement. The pinning mechanisms considered here are an anisotropy in the upper critical field and an electron scattering effect for grain boundaries and twinning planes. While the elementary pinning force of these planar defects is small due to a small thermodynamic critical field at 77 K, a critical current density comparable to that of Nb-Ti at 4.2 K is expected to be attained by increasing the pin concentration.
Anomalous Temperature Dependence of Hc1 in High-Tc Superconductor YBa2Cu3O7-δ
Authors: Isikawa Yosikazu , Mori Katsunori , Kobayashi Koichi , Sato Kiyoo
Published: November 2005

Temperature dependence of magnetization curves was measured on a polycrystalline sample of high-T
c superconductor YBa2Cu3O7-δ. The lower critical field obtained from the magnetization curves has an anomalous temperature dependence, which may infer that a dimensional crossover occurs as observed in an artificial layered superconductor Nb/Cu.
Chemical-State Studies of Oxygen-Released Y-Ba-Cu Oxide
Authors: Sasaki Teikichi A. , Baba Yuji , Masaki Norio , Takano Ichiro
Published: November 2005

Thermal release of oxygen from a high-T
c compound, YBa2Cu3O7, and the subsequent changes of the chemical states were examined by a thermal desorption method and X-ray photoelectron spectroscopy. The former gives a spectrum with two peaks around 480°C and 700°C. The latter suggests that the 480°C peak corresponds to oxygens in the one dimensional CuO chains in the unit cell of the lattice, and the 700°C peak to one of the oxygens above and below the central copper atom. With the release of these oxygens, the copper atoms in the compound change from a pure Cu2+ state into a Cu1+ dominant state.
Low-Temperature Surface Cleaning of Si and Successive Plasma-Assisted Epitaxial Growth of GaAs
Authors: Gao Qing Zhu , Hariu Takashi , Ono Shoichi
Published: November 2005

Removal of native oxide on Si at a temperature as low as 500°C and the successive epitaxial growth of GaAs have been achieved in hydrogen plasma. Simultaneous supply of Ga or As during hydrogen plasma treatment has been found to be more effective in getting reproducible and successful epitaxial growth than simple hydrogen-plasma cleaning.
Compensating Piezoelectric Effect of Gate Metal and Dielectric Overlayer Stresses on GaAs MESFETs
Authors: Schnell R. D. , Schink H.
Published: November 2005

The orientation dependence of the threshold voltage V
T of GaAs MESFETs before and after passivation with a SiN
x
overlayer was investigated. [001] and [010] oriented FETs have the same V
T which does not change after passivation. [011] and [01̄1] oriented FETs show opposite V
T shifts relative to the [001] FETs. The sign of the shift is reversed by passivation. The measured stresses in the gate metal and dielectric overlayer are both tensile. A model of the piezoelectrically induced charges is extended to include the effects of both the gate metal and dielectric overlayer. Using the measured stress values, a good conformity between experimental results and model calculations is obtained. In particular it is demonstrated that the same stress in both layers produces piezoelectric charges of opposite sign in the MESFET channel region.
MOCVD Growth of InP on 4-inch Si Substrate with GaAs Intermediate Layer
Authors: Seki Akinori , Konushi Fumihiro , Kudo Jun , Kakimoto Seizo , Fukushima Takashi , Koba Masayoshi
Published: November 2005

This letter describes the heteroepitaxy of InP on Si by MOCVD. A new epitaxial structure with a thin GaAs intermediate layer (InP/GaAs/Si) is proposed to alleviate the large lattice mismatch (8.4%) between InP and Si. Using this structure, a 4-inch InP single crystal with a mirror-like surface and good thickness uniformity (Δd/d=±10%) was obtained. Residual stress in the InP film was 5.7±108 dyn/ cm2 for the InP/GaAs/Si structure, as compared to 8.3×108 dyn/cm2 for the InP directly grown on Si. This shows that the GaAs intermediate layer is also effective in reducing the residual stress in the InP epilayer.
Current Oscillation Related to N=3 Subband Levels up to Room Temperature in InGaAs/InAlAs MQW Diodes
Authors: Kawamura Yuichi , Wakita Koichi , Oe Kunishige
Published: November 2005

A clear current oscillation related to the n=3 subband levels was observed up to room-temperature in the forward I-V characteristic of the InGaAs/InAlAs MQW diodes, as well as a current oscillation related to the n=2 subband levels. A significant hysteresis characteristic was also observed for the current oscillation related to the n=3 subband levels at 77 K. The energy difference between the n=1 and n=2 subband levels estimated from the I-V characteristic agrees with that obtained from the absorption spectrum.
Preparation of a Thin Silicon Nitride Layer by Photo-CVD and Its Application to InP MISFET's
Authors: Takahashi Seiichi , Nakada Tokio , Kamimura Kiichi , Zama Hideaki , Hattori Takeo , Kunioka Akio
Published: November 2005

Thin silicon nitride (SiN
x
) layers have been successfully prepared by photochemical vapor deposition (photo-CVD) technique. Ellipsometric and X-ray photoelectron spectroscopic studies prove that the refractive index and concentration of nitrogen in the layer are strongly dependent on the substrate temperature. The interface state density at the SiN
x
/InP interface is estimated to be 8×1011 cm-2 eV-1 from the capacitance-voltage characteristics of InP MIS diodes. Using SiN
x
layer as a gate insulator, InP MISFET's were fabricated on semi-insulating InP substrates.
Generation of Quasi-Circularly Polarized Undulator Radiation with Higher Harmonics
Authors: Yamamoto Shigeru , Kitamura Hideo
Published: November 2005

Spectral and polarization characteristics of radiation from a relativistic electron travelling along a deformed helix constrained on a surface of an elliptic cylindroid are theoretically investigated. The present theory shows that the radiation has quasi-circular (elliptical) polarization with higher harmonics. It also gives the general expressions for the radiated electric field which contains both helical and plane undulator radiations as special cases.
A Quick Computation of Potential Distribution in a Highly Conductivity-Modulated Semiconductor and its Application to PCD Devices
Authors: Kusuda Yukihisa , Tanaka Shuhei , Asai Takahiro
Published: November 2005

The plasma-coupled device (PCD), which is a bipolar type functional device, has been applied to various image sensors. However, the PCD patterns cannot be designed by computer simulation because of the difficulty in calculating three-dimensional potential distribution in a highly-injected, highly conductivity-modulated semiconductor body. This letter proposes a new but practical simulation method in which some simple assumptions are employed. It is shown that the shape of the potential distribution and the conductivity modulation region around the ON-element of the PCD are consistent with the experimental observation.
Observation of Low Chirp Modulation in Long Wavelength InGaAs/InAlAs Multiple-Quantum-Well Optical Modulators
Authors: Wakita Koichi , Yoshikuni Yuzo , Nakao Masashi , Kawamura Yuichi , Asahi Hajime
Published: November 2005

Modulated light spectra are measured in long-wavelength InGaAs/InAlAs multiple-quantum-well intensity modulators under 990 MHz, large signal modulation. The linewidth broadening factor, α, is determined from the relation between the intensity modulation index and the sideband strength, relative to the carrier. The minimum α value is estimated to be 0.60, which is less than that reported in a bulk Franz-Keldysh modulator.
Superconductivity of Y1Ba2(Cu1-xFex)3Oy
Authors: Oda Yasukage , Fujita Hiroshi , Toyoda Haruhisa , Kaneko Tetsuyuki , Kohara Takao , Nakada Ichiroh , Asayama Kunisuke
Published: November 2005

A systematic study on the superconductivity of Y1Ba2(Cu1-x
Fe
x
)3O
y
has been made down to 30 mK for various x values. The critical temperature decreases linearly with x. The complete Meissner effect is retained down to 30 mK, up to about x=0.10. The crystal structure of the superconducting phase was found to transform from the orthorhombic to the tetragonal between x=0.02 and 0.05. It is concluded that a branching effect of a one-dimensional chain of Cu1-O through Fe impurities is essential for this structure transition. The supercurrent is considered to flow on the two-dimensional sheets of Cu2.
Effect of Co Substitution on Tc in YBa2Cu3-xCoxO7-y(x=0∼1)
Authors: Shindo Daisuke , Hiraga Kenji , Hirabayashi Makoto , Tokiwa Ayako , Kikuchi Masae , Syono Yasuhiko , Nakatsu Osamu , Kobayashi Norio , Muto Yoshio , Aoyagi Eiji
Published: November 2005

The crystal structure of YBa2Cu3-x
Co
x
O7-y
(x=0∼1) was investigated by X-ray and electron diffraction and the crystallographic site of Co atoms was directly determined by electron-channelling-enhanced microanalysis. It was shown that the structure is tetragonal based on the tripled perovskite structure, and that Co atoms occupy the Cu atom sites. Electric resistivity was measured with changing Co atom content and it was shown that T
c did not decrease monotonically with increasing Co atom concentration.
Fabrication of Heavily-Doped Polycrystalline Silicon Film Using a Laser-Doping Technique
Authors: Sameshima Toshiyuki , Usui Setsuo , Tomita Hisashi
Published: November 2005

A structure composed of alternating layers of hydrogenated amorphous silicon (a-Si:H) film and either phosphorus or boron film was used to fabricate low-resistivity polycrystalline silicon (poly-Si) film at low temperature. This structure was formed by a radio-frequency glow discharge process at 230°C and then irradiated by a pulsed XeCl excimer laser at room temperature. Simultaneous crystallization and uniform diffusion of the dopant atoms was achieved. The 240 nm-thick boron-doped poly-Si film had a sheet resistivity of 23 Ω/\Box (ρ=5.5×10-4 Ωcm).
Crystal Structure of Ba2ErCu3O7-x Determined by Neutron Powder Diffraction
Authors: Ishigaki Tōru , Asano Hajime , Takita Kôki , Katoh Hideo , Akinaga Hiroyuki , Izumi Fujio , Watanabe Noboru
Published: November 2005

The crystal structure of the high-T
c superconductor Ba2ErCu3O7-x
has been determined by Rietveld analysis of TOF neutron powder diffraction data. The compound belongs to space group Pmmm and is isomorphic with the orthorhombic form of Ba2YCu3O7-x
. The Ba and Er atoms have an ordered arrangement in a Ba-Er-Ba sequence along the c-axis. Oxygen atoms on the z=1/2 plane are missing, while one of the oxygen sites on the z=0 plane is selectively occupied.
Effect of Composition Change on Superconducting Properties in a Y-Ba-Cu-O Compound System
Authors: Kogachi Mineo , Nakahigashi Kiyotaka , Nakanishi Shigemitsu , Fukuoka Nobuo , Sasakura Hiroyuki , Minamigawa Shinnosuke , Shibuya Ikuo , Demizu Fumihiro , Sawai Hisaharu , Tsuboi Tomokazu , Yanase Akira
Published: November 2005

The superconducting properties in the Y-Ba-Cu-O compound system were investigated by varying the composition ratio Y:Ba:Cu by means of electrical resistivity measurements and X-ray diffractometry. Many compounds exhibited superconductivity and these were located in a comparatively wide composition range, especially in the Cu-rich side, around the ratio of Y:Ba:Cu=1:2:3. The onset temperatures were nearly the same and the measured lattice parameters showed no great differences from those of YBa2Cu3O
y
.
Geometrical Interpretation of the Interfacial Energy between bcc and fcc Lattices and Preferred Orientation Relationship of the Epitaxy
Authors: Gotoh Yoshihiko , Uwaha Makio
Published: November 2005

For the numerical calculation of the interfacial energy between (111)fcc and (110)bcc planes by Gotoh and Arai, a geometrical interpretation based on the atomic structure is presented. The relationships of Nishiyama-Wassermann (N-W) and Kurdjumov-Sachs (K-S) are explained by the configuration of bcc and fcc atoms whose atomic diameter ratio α takes specific values. For combinations of bcc and fcc lattices with α close to those specific values, the N-W or the K-S relationship will also be realized by forming a domain structure. A prediction of the preferred orientation of epitaxy is given for various combinations of fcc-bcc metals.
Ba2YCu3Ox Crystal Formed by Peritectic Reaction
Authors: Takada Jun , Kitaguchi Hitoshi , Osaka Akiyoshi , Miura Yoshinari , Takahashi Katsuaki , Takano Mikio , Ikeda Yasunori , Bando Yoshichika , Yamamoto Naoichi , Oka Yoshio , Tomii Yoichi
Published: November 2005

Melting and crystallization behavior of a high-T
c compound Ba2YCu3O
x
was investigated by microstructural observation, and compositional, thermal and X-ray analyses. Because of an incongruent melting, Ba2YCu3O
x
decomposes into a solid phase, Ba2YCuO5, and a liquid at 1266 K in air. Ba2YCu3O
x
crystals are formed around the primary crystals, BaY2CuO5, by a peritectic reaction on cooling from 1473 K in air.
Refractive Indices of 2-Methyl-4-Nitroaniline (MNA)
Authors: Morita Ryuji , Ogasawara Nagaatsu , Umegaki Shinsuke , Ito Ryoichi
Published: November 2005

We report on the results of ellipsometric measurements of refractive indices and their dispersion over the wavelength range 500 nm-1100 nm on a single-crystal thin film of 2-methyl-4-nitroaniline (MNA). The refractive indices show large anisotropy attributable to the orientation of the molecular dipole moment.
Local Atomic Arrangement in an In0.53Ga0.47As Quasi-Binary Alloy Grown by Liquid-Phase Epitaxy
Authors: Osamura Kozo , Sugahara Mitsuru , Nakajima Kazuo
Published: November 2005

Weak diffuse scattering was observed in the small-angle scattering region from the In0.53Ga0.47As alloy, which is theoretically found to originate from an atomic configuration on the group III sublattice. The experimental results could be explained in terms of the existence of a short-range ordered configuration. Such a deviation from the randomness was limited in terms of the volume of a unit cell, but no long-range order correlation was observed.
Complex Susceptibility of YBa2Cu3O6.86
Authors: Mazaki Hiromasa , Takano Mikio , Ikeda Yasunori , Bando Yoshichika , Kanno Ryoji , Takeda Yasuo , Yamamoto Osamu
Published: November 2005

The superconducting transition of YBa2Cu3O6.86 has been studied in terms of complex susceptibility. It is found that the transition has two phases. One is insensitive to the change in the amplitude, h
0 (5-1000 mOe), of the external ac field. The other is very sensitive to h
0, where the transition width is appreciably broadened as h
0 increases. No frequency dependence is found below 320 Hz. These behaviors are qualitatively common to the other oxide superconductors, La1.9Sr0.1CuO4-x
and ErBa2Cu3O6+x
. Discussion is made in the framework of the phenomenological weak-link loop model.
GaAs MESFET's with a Thermally Stable LaB6 Self-Aligned Gate
Authors: Takatani Shinichiro , Uchida Yoko , Yokotsuka Tatsuo , Nakashima Hisao
Published: November 2005

It was found that lanthanum hexaboride (LaB6) forms a thermally stable Schottky contact with a high barrier height of about 0.9 V on a chemically-etched n-type GaAs(100) substrate. GaAs metal-semiconductor field effect transistors (MESFET's) having excellent DC characteristics were obtained using LaB6 as a self-aligned gate. The high barrier height enabled normally-off MESFFT's to have a large operation margin.
Measurement of the Storage Time of N2 Ions Trapped in an RF Ion Trap
Authors: Yoda Jun , Sugiyama Kazuhiko
Published: November 2005

The storage time of N2 ions trapped in an rf ion trap was determined by resonant absorption of a probing rf field by the trapped ions. It was found that the product between the peak value and the full width at half maximum of the resonant absorption signal was linearly dependent on the total number of trapped ions, and also confirmed that the addition of He gas lengthened the storage time.
Light Scattering Measurement in PMMA Optical Fibers
Authors: Yamashita Tomoyoshi , Shichijyo Shiro , Takemura Tetuo , Matsushige Kazumi
Published: November 2005

A new light scattering measuring system was developed to investigate the heterogeneous structure in plastic optical fibers (POF). Measurements were conducted on commercial PMMA POF of different diameters. The results showed that the correlation length, which characterizes the size of a heterogeneous structure, is substantially larger in POF than in a bulk PMMA specimen, and increases with decreasing fiber diameter. These facts suggest that some structural changes such as molecular orientation and residual stress might be induced during POF formation, resulting in an additional scattering loss.
Characterization of Asymmetrical Molecular Orientation in Langmuir-Blodgett Films by the Stark Effect
Authors: Era Masanao , Fukuda Makoto , Tsutsui Tetsuo , Saito Shogo
Published: November 2005

Three types of Langmuir-Blodgett film of an azobenzene derivative were prepared by hetero Y-type, Y-type and Z-type deposition methods. The molecular orientations in the films were determined from the analysis of the linear Stark effect (electroabsorption) spectra. Molecules in the hetero Y-type film were proved to align asymmetrically. However, molecular orientation in the Z-type films showed very small asymmetry. Investigation of the long spacings determined from X-ray diffraction supported the conclusion from the Stark effect.
Fabrication of P-N Junction Diodes Using Homoepitaxially Grown 6H-SiC at Low Temperature by Chemical Vapor Deposition
Authors: Shibahara Kentaro , Kuroda Naotaka , Nishino Shigehiro , Matsunami Hiroyuki
Published: November 2005

Homoepitaxial growth on a 6H-SiC (0001)Si face was carried out successfully at 1500°C by chemical vapor deposition. This temperature is 300°C lower than typical well-known growth temperatures. The p-n junction diodes were fabricated with the grown layers and showed very good rectification. The breakdown electric field was estimated to be 2.4×106 V/cm using the characteristics of the p-n junction diodes. This value is comparable with high-temperature grown layers. The fabricated p-n junction diodes showed blue light emission in the forward-biased region.
ESR and Constant Photocurrent Studies of Surface and Bulk Defects in a-Si:H
Authors: Xu Xixiang , Morimoto Akiharu , Kumeda Minoru , Shimizu Tatsuo
Published: November 2005

Surface and bulk defect densities in undoped a-Si:H films on a quartz substrate are estimated from the thickness dependence of the defect density by ESR and constant photocurrent method (CPM). For the first time, the thickness of a defective surface layer in a-Si:H is determined by ESR to be about 200 Å. The decrease in surface spin density by HF etching treatment and the difference in photoconductivities measured by illumination from different sides suggest that the free surface layer is more defective than the interface layer on a quartz substrate.
Pulse Width Dependence of Light Intensity and Memory Effect in Ferroelectric Liquid Crystal 8SI
Authors: Kai Shoichi , Nomiyama Miyuki , Takahashi Toshitsugu , Imasaki Masahide
Published: November 2005

The ferroelectric response in the smectic X phase of 8SI is examined for both static and dynamic properties by measuring the light intensity ΔI
0 through the sample. Multistate memory effect is observed and it can be controlled by the pulse width W

p
and height E of the applied field. There are thresholds E
th and W

pth for this memory effect. As W

p
increases for a constant E, ΔI
0 becomes larger. The response time depends on E by the exponential law which can be observed in common ferroelectric materials.
New Evaluation Method of Evaporated Organic Thin Films by Energy Dispersive X-Ray Diffractometer
Authors: Horiuchi Toshihisa , Fukao Koji , Matsushige Kazumi
Published: November 2005

A new method was developed to obtain clear diffraction patterns of organic thin films evaporated on substrates such as Au. In this method, total reflection on substrates was utilized to most efficiently collect the diffracted X-rays from organic thin films. The X-rays were detected with a pure Ge solid-state detector set at a constant scattering angle and analyzed with a multichannel analyzer. Excellent performance of this system was demonstrated for a thin stearic acid film evaporated on Au and Cu-phthalocyanine on glass.
Construction of a Scanning Tunneling Microscope for Electrochemical Studies
Authors: Morita Seizo , Otsuka Ichiro , Okada Takao , Yokoyama Hiraku , Iwasaki Takatoshi , Mikoshiba Nobuo
Published: November 2005

We have constructed a scanning tunneling microscope (STM) for electrochemical studies. Using the STM, we investigated an electrochemically treated surface of a polycrystalline silver electrode in a 0.1 M KCl solution. The STM images of the Ag electrode in the solution exhibited large asymmetric peaks resulting from the large asymmetric current spikes. We found that a plot of the current vs t
-1/2, where t is time, for a single current spike satisfies a linear relation, i.e., the Cottrell equation. Thus, a diffusion-controlled electrochemical reaction was observed at a specific region by the STM.
Electronic Properties of a Photochemical Oxide-GaAs Interface
Authors: Sawada Takayuki , Hasegawa Hideki , Ohno Hideo
Published: November 2005

The properties of a GaAs–oxide interface formed by recently proposed photochemical oxidation in water were studied. Remarkable photoluminescence intensity enhancement was observed after oxidation which previously was interpreted as “unpinning” of the Fermi level. However, the surface current transport and capacitance-voltage measurements consistently indicated a strong Fermi level pinning with an increased surface depletion. These apparently contradictory results can be explained by a new model in which photochemical oxidation does not unpin, but shifts the pinning position of the Fermi level towards the valence band edge.
Effects of Kinetic Inductance on the Performance of a Flux-Flow-Type Josephson Amplifier
Authors: Hashimoto Tatsunori , Enpuku Keiji , Yoshida Keiji , Yamafuji Kaoru
Published: November 2005

The effects of the kinetic inductance of superconducting thin electrodes on the basic parameters of a flux-flow-type Josephson amplifier (FFA) are studied theoretically. It is shown that performance of the FFA can be improved considerably if the kinetic inductance is utilized. A preliminary experiment confirms the theoretical result.
Determination of the Orthorhombic-Tetragonal YBa2Cu3O7-δ Phase Boundary in the δ-T Diagram
Authors: Kubo Yoshimi , Nakabayashi Yukinobu , Tabuchi Junji , Yoshitake Tsutomu , Ochi Atsushi , Utsumi Kazuaki , Igarashi Hitoshi , Yonezawa Masatomo
Published: November 2005

The orthorhombic-tetragonal YBa2Cu3O7-δ phase boundary in the δ-T diagram was determined by a detailed isobar TG measurement under the oxygen partial pressures of 1 to 0.01 atm. The phase boundary was found not to be located at δ = const., but to have a slope of dδ/dT∼-4.7×10-4 K-1. The experimental results are discussed with a simple order-disorder transformation model of oxygen atoms on the Cu plane sandwiched by Ba planes.
Thermopower of High-Tc Materials; Inconsistencies and Anomalies
Authors: Hyland G. J.
Published: November 2005

Attention is drawn to certain discrepancies, in both magnitude and T-dependence, between currently available data on the thermoelectric power, S, of the normal state of new high-temperature superconductive materials, –and, in particular, to the different values reported (in the same investigation) for La2CuO4, according, as it contains equal amounts of Ba or Sr. The importance of taking lattice perturbations into account in interpreting S-data is stressed, and expressions are given for S, assuming the carriers are Cu3+ holes introduced into the lower Hubbard band of the ideal parent material by divalent additives and/or deviations from stoichiometry.
Properties of Alkaline Earth Fluoride Barriers in Nb/Pb Josephson Junctions
Authors: Wang S. Z. , Olsson H. K. , Claeson T.
Published: November 2005

The flourides BaF2, CaF2 and MgF2 have been investigated as barrier materials in Nb/Pb Josephson tunnel junctions. The evaporated films had the same crystal structure as the bulk materials. Fair tunnel junction IV-curves were obtained. The specific capacitance of fluoride based junctions is comparatively small. However, measurements of the dielectric constant using the Josephson plasma resonance and the Fiske resonance gave values smaller and higher, respectively, than the tabulated low frequency values. The junction resistance increased considerably with time when stored in air at room temperature.
Controlled Atomic Layer Doping and ALD MOSFET Fabrication in Si
Authors: Gorkum Aart A. van , Nakagawa Kiyokazu , Shiraki Yasuhiro
Published: November 2005

Controlled atomic layer doping (ALD) in Si is obtained, combining the adsorption and desorption behaviours of Sb in Si molecular beam epitaxy and solid phase epitaxy. SIMS and CV measurements confirm the sharp doping profile. It is shown by Hall measurements that the carrier concentration varies from 9×1011 to 8×1013 cm-2 and the mobility from 250 to 60 cm2V-1s-1 when the Sb concentration is changed from 0.0015 to 1 monolayer. The first ALD-MOSFET, with a gate length of 8 µm and a gate oxide thickness of 100 nm, is made using the ALD layer as the conducting channel, and has a transconductance of 7 mS/mm.
Experiments on Superconducting (Rare Earth)-Ba2Cu3O7-δ down to 30 mK
Authors: Kaneko Tetuyuki , Toyoda Haruhisa , Fujita Hiroshi , Oda Yasukage , Kohara Takao , Ueda Kohichi , Yamada Yoshihiro , Nakada Ichiroh , Asayama Kunisuke
Published: November 2005

The crystal structure of RBa2Cu3O7-δ (R = Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb) was analyzed, and the resistivity, ac and dc susceptibility were measured down to 30 mK. They all showed superconductivity at about 90 K. The complete Meissner effect was found to be unchanged down to 30 mK for all specimens except for the Yb compound, which showed a partial breakdown below 1 K. The effective magnetic moments were found to be nearly the same as those of free ionic states except for the Eu compound.
Resistivity Anomaly Near Room Temperature of Y-Ba-Cu-O and Related Oxides as Created by the Surface Effect of Water
Authors: Kitazawa Koichi , Kishio Kohji , Hasegawa Tetsuya , Nakamura Osamu , Shimoyama Jun-ichi , Sugii Nobuyuki , Ohtomo Akira , Yaegashi Seiji , Fueki Kazuo
Published: November 2005

A number of papers have recently reported the possible presence of superconductivity near room temperature in Y-Ba-Cu-O oxide and related materials, based mainly on resistivity measurements. Close examinations of the electrode contacts during resistivity measurements in the present study showed that similar resistivity anomalies could be reproducibly observed when the specimen surface was wet. The anomaly turned out to be related with artifacts of the electrode contacts which resulted from the reaction of the specimen surface with water, creating electrochemical current paths between the electrodes.
Tetragonal High-Tc Superconductor in the System Ba2Y(Cu1-xGax)3O7-δ
Authors: Hiratani Masahiko , Ito Yukio , Miyauchi Katsuki , Kudo Tetsuichi
Published: November 2005

We synthesized single-phase compounds in the system Ba2Y(Cu1-x
Ga
x
)3O7-δ (x = 0.02, 0.05 and 0.1). They are orthorhombic but the difference between their a- and b-axis dimensions rapidly decreases with increasing x. The compound at x = 0.1 is almost tetragonal (b/a = 1.001), whereas its c-dimension remains nearly the same as that of orthorhombic Ba2YCu3O7-δ. The oxygen content in the compounds increases according to 7-δ=6.92+0.43x. T
c decreases as the Ga content increases, but the effect is not crucial (66 K at x = 0.1). Incorporated Ga is likely to replace Cu on the la(0, 0, 0) site.
Critical Currents of Superconducting Y-Ba-Cu, Dy-Ba-Cu and Gd-Ba-Cu Oxides in Low Magnetic Fields
Authors: Aomine Takafumi , Tsuru Kohji
Published: November 2005

Critical currents I
c of Y-Ba-Cu-O, Dy-Ba-Cu-O and Gd-Ba-Cu-O systems have been measured in a low magnetic field H above 77 K. For increase and decrease of H, I
c(H) shows hysteresis similar to that in superconducting bridges. The hysteresis in oxide samples is explained by taking into account the inclusion of such superconducting, narrow parts as in bridges.
High Resolution Investigation of the Rod-Shaped Scattering from a (111) Si Surface by a Synchrotron Radiation Source
Authors: Kashiwagura Nobuo , Kashihara Yasuharu , Sakata Makoto , Harada Jimpei , Wilkins Stephen W. , Stevenson Andrew W.
Published: November 2005

By using a high resolution X-ray spectrometer in conjunction with a synchrotron radiation source, the rod-shaped scattering due to crystal truncation (RSCT), which is elongated along the normal of a crystal surface through a Bragg point, was investigated for two (111) silicon wafers of which the surfaces were differently processed. It is shown that the characterization of a crystal surface, on the basis of surface roughness on an atomic scale and the misorientation of mosaic blocks, is really possible by the precise measurement of the RSCT.
Y-Ba-Cu-O/AlOx/Nb Josephson Tunnel Junctions
Authors: Nakayama Akiyoshi , Inoue Atsuki , Takeuchi Kiyoshi , Okabe Yoichi
Published: November 2005

We have fabricated Y-Ba-Cu-O/AlO
x
/Nb Josephson tunnel junctions using electron-beam evaporation of Al and Nb films and natural oxidation. Superconducting Josephson current, hysteresis, and rf-induced voltage steps at a voltage greater than 0.4 mV have been clearly observed at 4.2 K. Moreover, rf-induced subharmonic steps have appeared. Magnetic field dependence of the superconducting Josephson current has also been studied.
Superconductivity of YBa2Cu3-xMxOy (M = Co, Fe, Ni, Zn)
Authors: Takayama-Muromachi Eiji , Uchida Yoshishige , Kato Katsuo
Published: November 2005

The superconductivity of YBa2Cu3-x
M
x
O
y
, (M = Co, Fe, Ni, Zn; x = 0.1-0.4) was examined by means of ac susceptibility measurements. The results indicated that Cu in the Cu2 site (between the Y and the BaO layer) plays a more substantial role in superconductivity than that in the Cu1 site (between the BaO layers). Combining this with our earlier results for the La1+x
Ba2-x
Cu3O
y
system, we suggest that holes doped mainly in the O 2p orbitals of the rock-salt-type BaO layers form Cooper pairs through some medium (spin fluctuations or possibly other collective modes) excited in the Cu2 layer.
Electrical, Magnetic and Superconducting Properties of the High-Tc Superconductor Er1-xYbxBa2Cu3O7-δ
Authors: Oota Akio , Sasaki Yoshinobu , Kiyoshima Yoshio , Ohkubo Masataka , Hioki Tatsumi
Published: November 2005

Structure, resistivity, magnetization and susceptibility have been studied on the Er1-x
Yb
x
Ba2Cu3O7-δ system. The results indicate that both Er and Yb atoms order at x = 0.50 on the basal plane with missing oxygen in a unit cell. The results also show that they are present as nearly-free trivalent ions in this system on the basal plane in a unit cell.
The Influence of Oxygen Deficiency on the Electrical Resistivity of High-Tc Superconducting Oxides (La·Ba)2CuO4-y
Authors: Takagi Hidenori , Uchida Shin-ichi , Kitazawa Koichi , Tanaka Shoji
Published: November 2005

Influence of the oxygen deficiency was investigated for high T
c superconducting oxides (La·Ba)2CuO4-y
by measuring electrical resistivity. It is found that the temperature dependence of the normal resistivity changes from metallic to semiconducting as oxygen deficiency increases and that oxygen deficiency degrades the superconductivity.
Composition Dependence of the High Temperature Superconductivity in (Ba, Sr)-La-(Hg, Ag)-Cu-O System with K2NiF4-Type Structure
Authors: Saito Yoshitami , Noji Takashi , Endo Akihiko , Matsuzaki Nozomu , Katsumata Masao
Published: November 2005

High Tc superconductor M-La-Cu-O systems (M=Ba, Sr), with the composition (M
x
La1-x
)2CuO4-y
, have been prepared by a ceramic technique and the compositional change of Tc-value have been examined. Then in each of systems the partial substitution of Ag or Hg for Cu brought the increase of Tc-value.
Stoichiometric Change in Gallium Arsenide after Laser-Induced Thermochemical Etching
Authors: Tokuda Jun , Takai Mikio , Gamo Kenji , Namba Susumu
Published: November 2005

Gallium arsenide surfaces after laser-induced thermochemical etching in a CCl4 atmosphere were investigated by Auger electron spectroscopy. The laser-etched surfaces were deficient in arsenic and the excess gallium was found in a depth down to 20 nm from the etched surface for a laser power from 0.3 to 0.5 W at a scan speed of 6-30 µm/s. The thickness of the arsenic-deficient layers depended on both laser power and scan speed.
Biatomic Layer-High Steps on Si(001)2×1 Surface
Authors: Nakayama Tomonobu , Tanishiro Yasumasa , Takayanagi Kunio
Published: November 2005

Clean Si(001) surfaces with the 2×1 reconstruction are investigated by transmission electron diffraction (TED) and microscopy (TEM). TED patterns from (1̄1l) vicinal surfaces of off-angles of 2-5° indicate the formation of a single oriented 2×1 structure. The 2×1 superlattice reflection spots in the TED patterns indicate first that the surface has bilayer-high steps and dimers are parallel to the steps. Secondly, the 2×1 unit cell displaces across the bilayer-high step by + [110]/2 ( - [110]/2) on the vicinal surface were the mean direction of the steps rotated positively (negatively) from the [110]. Up to about 20 degrees of the rotation, the single 2×1 domain persists.
A Simple Method to Determine the Capture Cross Section of Deep Levels in GaAs by Thermally Stimulated Current
Authors: Tomozane Mamoru , Nannichi Yasuo
Published: November 2005

A new and simple method to determine the capture cross section of deep levels by Thermally Stimulated Current measurement is demonstrated. The cross section is obtained by analysis of the variation in the peak height with the initialization dose. The examplar values of the cross section at 4 K estimated by this method for two levels in semiinsulating GaAs were 2×10-15 cm2 and 1×10-15 cm2.
Investigation on Optical Matching of a Soft X-Ray Undulator with Some Condenser Fresnel Zone Plates
Authors: Maezawa Hideki , Mikuni Akira , Ando Masami , Sasaki Taizo
Published: November 2005

Optical matching characteristics of undulator radiation with some condenser zone plates were investigated in the soft X-ray region using an undulator beamline at the Photon Factory. It was confirmed that the monochromatization of the first harmonic of the undulator radiation was made by meams of a system consisting of a zone plate and a pinhole, but the transmission efficiency and the wavelength resolution of the system were lower than expected. Analyses show that the results can be attributed to the finite source size of the undulator radiation which is determined by the present storage ring operation and also to the longer focal lengths of the zone plates used. It was also found that the virtual source point of the undulator radiation should be assigned at the position of the undulator itself.
Cause of the Higher Breakdown Strength in Ethylene-Styrene Copolymer, a New Insulating Material
Authors: Racz Istvan , Ohki Yoshimichi
Published: November 2005

The breakdown strength of an ethylene-styrene copolymer is reported to be higher than that of a low-density polyethylene. In order to understand the phenomena high energy electrons are injected into polyethylene and copolymer samples. The injected electrons passing through the materials and entering into vacuum are energy analyzed. The electrons are found to be more effectively decelerated in the copolymer. The energy absorption property of the benzene ring might be responsible for the effect.
A Position-Sensitive MOS Device Using Lateral Photovoltaic Effect
Authors: Niu Hirohiko , Aoki Chihiro , Matsuda Tetsuro , Takai Munezo , Maeda Muneo
Published: November 2005

A position-sensitive device (PSD) of MOS is presented which uses for the first time the dependence of the phase of lateral photovoltage on the position of light incident upon the device. The MOS-type PSD presented here has the following advantages over the previously-presented lateral photodiodes: (1) Its sensitivity can be changed electrically by the gate-voltage. (2) No compensation is required for the change in irradiation intensity. A resolution of 1 µm has been demonstrated for an AN-SiO2-Si PSD to measure the position of light incidence, and better than submicrons should be possible by improving the phase-measurement.
Compositional and Structural Analyses for Optimizing the Preparation Conditions of Superconducting (La1-xSrx)yCuO4-δ Films by Sputtering
Authors: Kawasaki Masashi , Funabashi Makoto , Nagata Shunroh , Fueki Kazuo , Koinuma Hideomi
Published: November 2005

Reaction conditions and structural requirements for the preparation of superconducting films of (La1-x
Sr
x
)
y
CuO4-δ(LSCO) by sputtering have been elucidated. There are slight deviations in the film compositions from the target composition, especially when the substrate temperature was high. Optimum conditions for the preparation of superconducting films by 50 Hz ac sputtering include the sputtering in argon without intentional mixing of oxygen, the heating of substrate at moderate temperatures, and the annealing of the as-deposited films in oxygen atmosphere at temperatures between 500°C and 850°C.
Analysis of Crystal Structure of an Y-Ba-Cu Oxide
Authors: Kitano Yasuyuki , Kifune Kouichi , Mukouda Ichiro , Kamimura Hirohiko , Sakurai Junji , Komura Yukitomo , Hoshino Kenichi , Suzuki Morihisa , Minami Asao , Maeno Yoshiteru , Kato Masatune , Fujita Toshizou
Published: November 2005

Results of the analyses on crystal structure and chemical composition of dark-green crystals mainly found in an Y-Ba-Cu oxide specimen which shows high-T
c superconductivity are reported. Crystal structure is investigated by the electron diffraction method and is determined to be orthorhombic with lattice parameters a=1.22 nm, b=0.561 nm and c=0.714nm, and with a space group Pnma (No. 62) or Pna21 (No. 33). Expected d-values are presented and are successfully compared with the X-ray powder diffraction spectrum obtained from this oxide. Chemical composition is analyzed by the EPMA method and is determined to be Y2BaCuO5-y
for the oxide.
High Field Measurement of the Critical Field in (La1-xSrx)2CuO4 up to 40 T
Authors: Nakao Koichi , Miura Noboru , Uchida Shin-ichi , Takagi Hidenori , Tanaka Shoji , Kishio Kohji , Shimoyama Jun-ichi , Kitazawa Koichi , Fueki Kazuo
Published: November 2005

The upper critical field H
c2 was measured for (La1-x
Sr
x
)2CuO4 as a function of temperature in pulsed high magnetic fields up to 40 T. At zero field, the onset of the superconducting transition was observed at 43 K. In the presence of magnetic field, a gradual increase of the magnetoresistance was observed with a positive curvature near the transition temperature. If we define H
c2 by the field where the resistance becomes half of that in the normal state, the linear extrapolation of the H
c2 vs temperature plot gives H
c2(0) = 70 T.
Plasma Spectra of New Superconductors (La1-xAx)2CuO4
Authors: Tajima Setsuko , Uchida Shin-ichi , Tanaka Shoji , Kanbe Shinsaku , Kitazawa Koichi , Fueki Kazuo
Published: November 2005

The optical reflectivity spectra of new superconductors (La1-x
M
x
)2CuO4 (M=Ba, Ca, Sr) were investigated. In the spectra for the metallic samples, a plasma edge was observed at almost the same position for all compositions x and for all substituents. Based on the two-dimensional tight-binding model, the conduction band width was estimated to be about 1 eV from the value of the observed plasma energy.
Superconducting Properties of (La1-xSrx)2CuO4
Authors: Uchida Shin-ichi , Takagi Hidenori , Kishio Kohji , Kitazawa Koichi , Fueki Kazuo , Tanaka Shoji
Published: November 2005

Normal and superconducting state parameters are estimated for high-T
c superconductor (La1-x
Sr
x
)2CuO4. The estimation is based on extensive and systematic experimental results, so that the parameters given here are most reliable at the present stage. It is concluded that this material is a rather clean and extreme type II superconductor.