bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiple-Reflection Effects in Optical Second-Harmonic Generation
Authors: Morita Ryuji , Kondo Takashi , Kaneda Yushi , Sugihashi Atsushi , Ogasawara Nagaatsu , Umegaki Shinsuke , Ito Ryoichi
Published: February 2005

We report the first observation of multiple-reflection effects in optical second-harmonic generation. The observation has been made possible by the use of a single-mode laser diode as a light source. The experimental results agree excellently with a theoretical analysis which takes account of the multiple reflections of both the fundamental and harmonic waves.
Controlled Formation of Misfit Dislocations for Heteroepitaxial Growth of GaAs on (100) Si by Migration-Enhanced Epitaxy
Authors: Stolz Wolfgang , Horikoshi Yoshiji , Naganuma Mitsuru
Published: February 2005

The strain relaxation by formation of misfit dislocations for GaAs epitaxial layers on (100) Si is investigated by wafer bending measurements and transmission electron microscopy (TEM) studies. The formation of misfit dislocations depends not only on the growth temperature but also on the substrate offorientation. The effective suppression of the dislocation formation at low temperatures leads to a more controlled generation than that under equilibrium conditions. This mechanism is demonstrated by realizing nonbending GaAs/Si wafers. Under appropriate growth conditions, a regular dislocation array at the interface is created, leading to a drastic reduction of dislocations in the GaAs epitaxial layer.
Maskless Ion Implantation of Cerium by Focused Ion Beam
Authors: Kagami Manabu , Shiokawa Takao , Segawa Yuzaburo , Aoyagi Yoshinobu , Namba Susumu , Okada Hiroshi , Ito Toshio
Published: February 2005

Ce liquid metal ion sources using Ce-Cu alloy metal for maskless ion implantation into optical devices have been developed. The emission characteristics, such as voltage vs current characteristics, beam angular current intensity and mass spectra have been measured. Maskless ion implantation into fused quartz using a 200 keV Ce focused ion beam, and the depth profile of implanted Ce are described.
Structure Analysis of the Bi2(Sr, Ca)3Cu2O8.2 Superconducting Crystal Based on the Computer Simulation of HRTEM Images
Authors: Horiuchi Shigeo , Maeda Hiroshi , Tanaka Yoshiaki , Matsui Yoshio
Published: February 2005

The crystal structure of the high-T
c superconducter, Bi2(Sr, Ca)3Cu2O8.2, is analyzed based on HRTEM images with help of the computer simulation. The structural modulation is approximated by the combination of supercells with different sizes. For the major supercell with lattice parameters, a=5.4 Å, b=5b
s=27.0 Å and c=30.8 Å (Amma, orthorhombic), the coordinates and the occupational probability of cations are determined. In the Bi-deficient bands of Bi2O2 sheets, about 40% sites of Bi are statistically substituted by Sr. In the perovskite-like layer, Sr are partly replaced by Bi near the Bi-concentrated bands, while wholly by Ca near the Bi-deficient bands. In the Ca plane about 30% sites of Ca are replaced by Sr.
Observation of Ga0.47In0.53As/InP Multiquantum Well Structure in Air by Scanning Tunneling Microscope
Authors: Osaka Fukunobu , Tanaka Ichiro , Kato Takashi , Katayama Yoshifumi
Published: February 2005

A cross-sectional surface of Ga0.47In0.53As/InP multiquantum wells (MQWs) prepared by cleaving was observed in air by a scanning tunneling microscope (STM), and clear STM images of periodic MQW structures were obtained with nanometer resolution. The apparent height of the STM images on the surface of the GaInAs layers was 50–150 Å larger than that of the images on the surface of the InP layers. This difference between the two kinds of layers was found to be due not to a real corrugation but to some difference in surface electronic properties. It was demonstrated that STM is a useful tool for nanometer scale evaluation of fine structures of MQWs.
The Dynamical Observation of α-Sn (111) This Films Grown on InSb (1̄1̄1̄) by RHEED
Authors: Kasukabe Yoshitaka , Iwai Masaaki , Osaka Toshiaki
Published: February 2005

The α-Sn (111) films of 150 monolayers (ML) will grow at room temperature on thermally cleaned InSb (1̄1̄1̄) substrates having a 2×2 reconstructed surface. The α-Sn (111) surfaces are observed to most clearly exhibit a 3×3 reconstruction at a film thickness of 30 ML by reflection high energy electron diffraction (RHEED). When the 30 ML films are heated at 170°C, the liquid phase begins to appear without the transition to the β-phase. From these result, effects of the InSb (1̄1̄1̄) substrate on the thermal stability of the α-Sn (111) film are discussed.
Novel Three-Dimensional Positioner and Scanner for the STM Using Shear Deformation of Piezoceramic Plates
Authors: Uozumi Kiyohiko , Nakamoto Keiichi , Fujioka Kageaki
Published: February 2005

A new type of coarse and fine positioner of an STM tip has been developed. The x
y-walker has three pairs of composite legs which are made of thickness expansion and thickness shear piezoelectric plates. While one of each pair of legs shrinks, the other leg expands and shear deforms giving rise to one-step displacement. The same type of z-walker is placed on the x
y-walker. The position of the tip is finely controlled by shear deformation of the expanded legs. Two pieces of thickness shear piezo plates and a thickness expansion one are stacked for a rigid scanner. Atomic resolution of the STM unit has been confirmed on an air-cleaved MoS2 surface.
Influence of Preparative Conditions on the Superconducting Characteristics in GdBa2Cu3O7-δ Ceramics
Authors: Kikuchi Akira , Matsuda Motohide , Maeda Takao , Ishii Mamoru , Takata Masasuke , Yamashita Tsutomu
Published: February 2005

The influence of the preparative conditions on superconducting characteristics was investigated for GdBa2Cu3O7-δ ceramics. It was found that the critical temperatures T
c of the specimens sintered in air were strongly dependent on the forming pressure and the sintering temperature. On the other hand, all T
c values of the specimens annealed in oxygen atmosphere indicated above 90 K. However, the critical current densities of the latter specimens were strongly dependent on the sintering and annealing temperatures, and the maximum value of 355 A/cm2 was obtained.
Superconducting Y-Ba-Cu-O Oxide Films by OMCVD
Authors: Nakamori Tomohiro , Abe Hitoshi , Kanamori Takashi , Shibata Susumu
Published: February 2005

Formation of Y-Ba-Cu-O films have been attempted by the organometallic chemical vapor deposition (OMCVD) method using Y(thd)3, Ba(thd)2, and Cu(thd)2 (thd=2,2,6,6,-tetramethyl-3,5-heptanedione), which are organic metal chelates, as gas sources. The results of electron probe microanalysis (EPMA) show that the film formed has a composition similar to that of YBa2Cu3O
x
ceramics. The film has a high resistivity in the as-deposited state. If the film is conditioned at 950°C for 30 minutes, the resistivity reduces extremely, providing a superconductivity. T
c onset is 76 K and T
c final is 60 K.
Electron Irradiation of Y-Ba-Cu Oxides
Authors: Matsui Hisayuki , Ito Susumu , Nakagawa Ippei , Yasuda Kyoichiro , Takeda Michihiko
Published: February 2005

YBaCu2O
y
[1:1:2] was irradiated with 7 MeV electrons (1×1017e/cm2) at liquid nitrogen temperature. The electrical resistivity increased and the diamagnetic susceptibility decreased after the irradiation, in accordance with a slight shift of T
c to a lower temperature. Whereas, Y0.61Ba0.39CuO
y
irradiated (1×1018e/cm2) at room temperature did not show any superconductive characteristics. X-ray examinations at LNT (below T
c) and RT (above T
c) were also carried out for both irradiated specimens.
Raman Scattering in Bi-Sr-Ca-Cu-O Single Crystals
Authors: Sugai Shunji , Takagi Hidenori , Uchida Shin-ichi , Tanaka Shoji
Published: February 2005

Dynamical spin fluctuation and lattice vibration in Bi-Sr-Ca-Cu-O single crystals with T
c=80 K is investigated by Raman scattering. Very broad scattering, ranging from low energy to over 4000 cm-1, is observed together with more than ten phonon peaks. Very broad scattering is assigned to the two-magnon scattering from the overdamped spin fluctuation on the two-dimensional Cu-O layers as in the case of superconducting (La1-x
Sr
x
)2CuO4 and YBa2Cu3O7-y
.
Magnetic Properties of GdBa2Cu2.7M0.3Oy (M=Cu, Fe and Co): Magnetic Ordering of M in Cu(1) site
Authors: Yamaguchi Yuji , Waki Shinya
Published: February 2005

The saturating magnetic moment at low temperatures and the antiferromagnetic transition temperature near 2.2 K of Gd in nonsuperconducting GdBa2Cu2.7M0.3O
y
(M-Fe and Co) were found to be nearly equal to those of GdBa2Cu3O
y
. Difference in paramagnetic moment between superconducting samples and nonsuperconducting ones was observed to be small. It has been suggested that M occupies the Cu(1) site and couples strongly with Cu in the Cu(2) site.
Temperature Dependence of Hydrogen Implant on Passivation of Argon Implant Damage in Silicon
Authors: Chien H.-C. , Ashok S. , Chen M.-C.
Published: February 2005

The influence of substrate temperature during atomic hydrogen treatment of Ar-implant damaged Si surfaces has been studies using the electrical properties of subsequently fabricated Schottky contacts. The recovery of the Schottky electrical characteristics toward the ideal is found to occur only at substrate temperatures above 150°C. However, the Schottky barrier height itself is pinned by a very thin surface layer less than 100 nm thick, and the hydrogen passivation itself appears confined to the subsurface damage.
DSC Studies of Glassy Behavior in P-Doped a-Si:H
Authors: Matsuo Shinji , Nasu Hiroyuki , Akamatsu Chikashi , Hayashi Ryo , Imura Takeshi , Osaka Yukio
Published: February 2005

Differential scanning calorimetry (DSC) studies of P-doped hydrogenated amorphous silicon (a-Si:H) show characteristic behaviors of glass transition phenomena as frequently found in conventional melt-quenched glasses. The glass transition temperature (T
g) detected by DSC agrees well with the equilibration temperature (T
E) determined by the temperature dependence of dc conductivity. Regarding the influence of hydrogen content, T
g decreases as hydrogen content increases.
Conduction-Band Discontinuity of GaInAs/InP Heterojunctions with Graded Donor Concentration
Authors: Ogawa M. , Miyoshi M. , Shimizu S. , Murakami T. , Miyoshi T.
Published: February 2005

We have measured the magnitude of the conduction-band discontinuity and the interface charge density for the heterojunction between VPE grown Ga0.47In0.53As and InP with graded donor concentration. The conduction-band discontinuity was obtained by C-V profiling technique, taking into account the correction for the interface charge density and the graded donor concentration. The simulation is employed to confirm the reliability of the band discontinuity obtained. We have found that the conduction-band discontinuity is 0.16±0.02 eV at R.T., which corresponds to 27% of the band gap difference.
Lateral Distributions of X-ray Intensity and Ablation Pressure on Pellet Shells Irradiated by External X-ray Sources
Authors: Sakabe Shuji
Published: February 2005

The lateral distributions of the X-ray intensity and the ablation pressure on a pellet surface were calculated for the pellet implosion driven by soft X-rays emitted from external X-ray sources. The lateral ablation pressure distribution calculated by ray-tracing with the ablation pressure scaling is in good agreement with that obtained experimentally.
Temperature Dependence of Selective Reflection in Ferroelectric SmC* Liquid Crystal
Authors: Kawaida Masahiro , Nakagawa Masahiro , Akahane Tadashi
Published: February 2005

The temperature dependences of the selective reflection in a ferroelectric SmC* liquid crystal (CS-1017) are measured accurately in homeotropically aligned cells for different cell thicknesses. For over-50 µm cell thickness, those are in good agreement. Especially for 205 µm cell thickness, the wavelength of the selective reflection decreases with temperature near the SmC*-SmA transition point. The results obtained are also compared with the temperature dependences of the helical pitch determined by the laser diffraction method in homogeneously aligned cells.
Induction Time for Nucleation in Amorphous Silicon Films Prepared by Plasma CVD
Authors: Suzuki Masakuni , Hiramoto Masahiro , Oguiura Mitsugu , Kamisaka Wataru , Hasegawa Seiichi
Published: February 2005

The crystallization of plasma CVD amorphous Si films processed by isothermal annealing was studied by X-ray diffraction and Raman spectroscopy. The induction time for nucleation was defined as the period for which crystalline peaks do not appear. The temperature dependence of the induction time for nucleation was expressed by the activation-type relation with the negative activation energy. The results suggest a way to suppress the random nucleation in thermal annealing.
Protection of Organic Materials Against Ultraviolet Rays by Ion-Plated Zinc-Oxide Layer
Authors: Kokai Hideki , Sakamoto Yuichi , Kashiwagi Kunihiro , Morikawa Takitaro , Kuramochi Satoru , Murayama Yoichi
Published: February 2005

When organic insulating material is used in open air, the damage caused by ultraviolet irradiation becomes an essential problem. It is necessary to protect the material by a surface coating film having opacity in the ultraviolet region. In this study, cycloaliphatic epoxy resin and quartz substrates were coated with zinc oxide films by the ion plating method. The samples were irradiated by ultraviolet rays from a high-pressure mercury-vapor lamp with an intensity 14 times stronger than in the natural condition. The toughness and effectiveness of the protective film was proved by the estimation of its electric resistance change.
On the Superconductivity of the Bi/Tl Materials and the Implications for YBa2Cu3O7-δ near δ=0.5
Authors: Hyland G. J.
Published: February 2005

Formal valence considerations strongly suggest that the high-T
c superconductivity in the newly discovered class of materials containing either Bi or Tl involves a metallic d-band based on Cu2+ ions-quite unlike the situation in YBa2Cu3O7-δ where, near δ=0, the carriers are holes in the oxygen band. It is argued that this difference is (a) the principal reason for the greatly enhanced environmental stability of the new materials, and (b) potentially relevant to an understanding of the non-zero T
c (≃45 K) now reported for YBa2Cu3O7-δ, near δ=0.5, and of the associated plateau in T
c (≃60 K) observed for 0.4<δ<0.3; various experimental checks on these ideas are suggested.
Superconducting and Magnetic Properties of the High-Tc and High-Density Superconductor Y1-xLuxBa2Cu3O7-δ
Authors: Oota Akio , Sasaki Yoshinobu , Ohkubo Masataka , Hioki Tatsumi
Published: February 2005

Superconducting and magnetic properties have been studied in high-density samples of Y1-x
Lu
x
Ba2Cu3O7-δ (0≤x≤0.88) with the porosity of 3∼7% through X-ray, resistivity, magnetization and susceptibility measurements. The results suggest that the disorder appearing on the Y plane due to the Lu substitution for Y in YBa2Cu3O7-δ would have an effect on the two-dimentional Cu(2)-O plane, which causes the enhancement of the effective moment of Cu on the plane.
Crystal Phases of BiSrCaCu2Ox Heat Treated in a Vacuum-Sealed System
Authors: Oka Yoshio , Yamamoto Naoichi , Yuba Akiko , Kitaguchi Hitoshi , Takada Jun
Published: February 2005

Heat treatment in a vacuum-sealed system on BiSrCaCu2O
x
was studied in comparison with that in air. The melting temperature was lowered from 880°C in air to 850°C in the vacuum-sealed system. The formation of the phase with 37 Å c spacing was enhanced in the vacuum-sealed system by heating above the melting temperature and the subsequent annealing in air improved the sharpness of the superconducting transition at 110 K. The heat treatment in the reduced pressure also caused the reduction of the Cu ion and it was suggested that the oxidation state of the Cu ion played an important role in the formation of the phase with 37 Å c spacing.
Electrical and Magnetic Properties in Bi2Sr2Ca1-xYxCu2O8+δ
Authors: Fukushima Noburu , Niu Hiromi , Ando Ken
Published: February 2005

Electrical and magnetic properties were examined on Bi2Sr2Ca1-x
Y
x
Cu2O8+δ. A solid solution was confirmed in this system for x between 0 and 1. With increasing Y, the superconducting transition shifted toward lower temperatures, and a transition to an antiferromagnetic insulator was observed. Since the oxygen content was not influenced by Y substitution, the decrease in T
c and the transition to AFI seemed to be attributed to the decrease in the hole concentration in the Cu-O level.
Crystalline Structures and Superconducting Properties of Rapidly Quenched BiSrCaCu2Ox Ceramics
Authors: Kanai Tsuneyuki , Kumagai Teruo , Soeta Atsuko , Suzuki Takaaki , Aihara Katsuzou , Kamo Tomoichi , Matsuda Shinpei
Published: February 2005

Phase changes and superconducting properties of rapidly quenched BiSrCaCu2O
x
ceramics have been studied. The rapidly quenched sample consists of an amorphous state which begins to crystallize around 510°C. The crystal system was found to be tetragonal with a=5.39 Å and c=24.5 Å. By annealing above 700°C, a tetragonal system with a=5.41 Å and c=30.8 Å was produced. The former crystal was a semiconductor and the latter was a superconductor with T
c=75 K. A superconducting phase with T
c=105 K was observed in a sample annealed at 840°C. The superconducting volume ratio in the samples had a maximum at 803–840°C. The decrease of the volume ratio at the higher temperatures is considered to result from a decomposition of the superconducting phase (75 K) into a nonsuperconducting phase.
Processing and Superconducting Properties of GdBa2Cu3O7-δ Ceramics
Authors: Matsuda Motohide , Kikuchi Akira , Ishii Mamoru , Takata Masasuke , Yamashita Tsutomu , Okamoto Shoichi
Published: February 2005

The influences of the processing of the high-T
c superconductor GdBa2Cu3O7-δ prepared under various sintering conditions on the superconducting properties were investigated. The volume fraction of the superconducting phase at 77 K increased monotonically with an increase in the sintering temperature. The critical current density measured by the resistive method showed a maximum value for the sample sintered at 930°C, while the estimated value from the magnetization loop increased with an increase in the sintering temperature, though the critical temperatures of all the samples annealed in oxygen atmosphere were about 90 K. This difference was discussed in terms of the microstructure of the superconducting ceramic.
Crystal Structure, Oxygen Content and Superconductivity of MxLa2-xCuO4-y (M=Ba, Sr and Ca)
Authors: Oh-ishi Katsuyoshi , Kikuchi Masae , Syono Yasuhiko , Kobayashi Norio , Sasaoka Takaaki , Matsuhira Tomokazu , Muto Yoshio , Yamauchi Hiroshi
Published: February 2005

Unit cell dimensions, oxygen vacancy y, and superconducting properties of M
x
La2-x
CuO4-y
(M=Ba, Sr and Ca) with K2NiF4 structure have been determined by means of X-ray powder diffraction, thermogravimetry, and electrical resistivity measurements. The existence percentage of Cu as Cu3+, P=(Cu3+/Cu)%, was estimated from the measured y values on the basis of charge neutrality. The superconducting critical temperature, T
c, is discussed in terms of the P value and Cu-O bond length within the basal plane. Composition dependence of the unit cell dimensions is discussed by taking the P value and the ionic radii into consideration.
Electrical Properties of Eu1+xBa2-xCu3Oy at High Temperatures
Authors: Munakata Fumio , Shinohara Kazuhiko , Yamanaka Mitsugu
Published: February 2005

Oxygen partial pressure, P
O2
, and temperature dependences of the resistances, R, of Eu1+x
Ba2-x
Cu3O
y
compounds were measured to obtain knowledge about the effect of substitution of the trivalent Eu ions for the divalent Ba ions. The resistances of the samples depended on P
O2
according to R∝P
O2

-1/n
. The exponents were caused to vary due to the substitution, which affected the relation between oxygen pressure and oxygen solubility in Eu1+x
Ba2-x
Cu3O
y
compounds.
Magnetic Properties of Pb-Doped Bi-Sr-Ca-Cu-O Superconductors
Authors: Kumakura Hiroaki , Togano Kazumasa , Uehara Mitsuru , Maeda Hiroshi , Takahashi Kazuhiko , Yanagisawa Eiji
Published: February 2005

The D.C. magnetization of Bi-Sr-Ca-Cu-O compound was significantly increased by Pb-doping. However, the hysteresis Δ
M in magnetization curves rapidly decreased with increasing magnetic field, and became almost zero above 0.5 T. This small hysteresis may be related to the thin layers of superconducting phases. Low-temperature tails in superconducting resistive transition curves measured in magnetic fields were drastically decreased by the Pb-doping. H
c2 values at 77 K and 0 K obtained by extrapolation using the transition curves were 60 T and 140 T, respectively, when defined at the midpoint of the transition.
Reduction of Deep Level Concentrations in GaAs Layers Grown by Flow-Rate Modulation Epitaxy
Authors: Makimoto Toshiki , Yamauchi Yoshiharu , Horikoshi Yoshiji
Published: February 2005

In a modified metalorganic chemical vapor deposition, flow-rate modulation epitaxy, the growth rate of GaAs can be higher than one monolayer per cycle (0.28 nm/cycle). Ga-atoms, the number of which is up to 3 times as high as the surface site number, and arsenic are alternately supplied on the (001) GaAs substrates to grow GaAs layers. There is no surface degradation of the epitaxial layers even at a growth rate of three monolayers per cycle. In this method after Ga-atomic layers are formed, As atoms diffuse into the Ga-atomic layers to form a GaAs single crystal. In GaAs layers grown under such conditions, the concentration of the midgap level, “EL2,” is much reduced. Furthermore, photoluminescence measurement indicates that high-quality GaAs layers are grown.
Vapor Phase Epitaxy of GaAs by Direct Reduction of GaCl3 with AsH3/H2
Authors: Hasegawa Fumio , Yamaguchi Hiromu , Katayama Koji
Published: February 2005

GaAs was epitaxially grown at 500–600°C by direct reduction GaCl3 with AsH3/H2. The GaCl3 in a stainless steel evaporator was maintained at about 85°C, and supplied by He carrier gas. The AsH3 diluted with H2 was supplied in a separate line directly to the deposition zone. The growth rate was about 5–10 µm/hr for GaCl3 of 5.5×10-5 mol/min and V/III ratio of 5. The carrier concentrations of the grown layers were 1015 to 1016 cm-3, and the maximum mobility obtained was 10000 cm2/V ·s at 77 K. These results indicate the possibility of a new growth method of III–V compounds.
P-Type Doping Effects on Band-Gap Energy for Ga0.5In0.5P Grown by Metalorganic Vapor Phase Epitaxy
Authors: Suzuki Tohru , Gomyo Akiko , Hino Isao , Kobayashi Kenichi , Kawata Seiji , Iijima Sumio
Published: February 2005

Photoluminescence properties of Mg- or Zn-doped Ga0.5In0.5P grown by metalorganic vapor phase epitaxy were studied as a function of hole concentration (p). The band-gap energy (E
g) value for Mg- or Zn-doped Ga0.5In0.5P, grown under a condition in which undoped Ga0.5In0.5P shows an anomalously low E
g, showed a steep increase for p∼>1×1018 cm-3. This anomalous behavior was attributed to the Mg or Zn diffusion-enhanced randomization of the previously observed naturally formed monolayer {1/2, 1/2, 1/2} superlattices on the column III sublattice.
GaInP/AlInP Quantum Well Structures and Double Heterostructure Lasers Grown by Molecular Beam Epitaxy on (100) GaAs
Authors: Hayakawa Toshiro , Takahashi Kosei , Hosoda Masahiro , Yamamoto Saburo , Hijikata Toshiki
Published: February 2005

GaInP/AlInP single quantum well structures and double heterostructure lasers have been grown by molecular beam epitaxy at 510°C with the dimetric phosphorus beam. The peak energy and linewidth of the photoluminescence spectrum at 10 K from quantum wells as a function of well width have been studied. A 10- µm wide stripe-geometry GaInP/AlInP laser diode has shown a room temperature CW operation with a threshold current of 93 mA and an emission wavelength of 671 nm.
The NMR Spectrum of Poly(3-alkylthiophene)s and Polymer Chain Configuration
Authors: Love Peter , Sugimoto Ryu-ichi , Yoshino Katsumi
Published: February 2005

The α-methylene 400 MHz NMR spectra of poly(3-alkylthiophene)s for n=5, 8 and 10, where n is the number of carbon atoms of the alkyl chain, are used to obtain information on the relative configurations of thiophene rings. The triplet α-CH2 peak of the monomer results in two peaks in the polymer. Highly sterically hindered α-CH2 yields a downfield NMR shift for coplanar rings. This steric hinderance results in markedly torsioned thiophene rings which yield an upfield-shifted α-CH2 peak. The relative peak intensity ratios indicate ∼25% highly torsioned rings for n=5 and 8, and about ∼50% torsioned rings for n=10.
X-Ray Diffraction Profiles for Near 180° Scattering from Mosaic Crystals
Authors: Hashizume Hiroo , Nakahata Takumi
Published: February 2005

Reflectivity curves have been calculated for mosaic crystals in the case of normal-incidence Bragg diffraction with soft X-rays. The enormously broadened angular width of a reflection when the angle of incidence to the reflecting Bragg plane approaches 90° allows a single crystal with a mosaic spread as much as a few degrees to give a reflectivity profile very similar to that of a perfect crystal, when the incident photon energy is scanned. The insensitivity of the diffraction process to crystal mosaicity can be exploited in standing-wave experiments aimed at the determination of substrate-overlayer interface structures.
Epitaxial Growth of AlN Film with an Initial-Nitriding Layer on α-Al2O3 Substrate
Authors: Kawakami Hiroshi , Sakurai Katsuhito , Tsubouchi Kazuo , Mikoshiba Nobuo
Published: February 2005

An epitaxial film of AlN with a flat surface and good crystallinity was grown on an α-Al2O3 substrate by a new MOCVD. An initial-nitriding layer of the α-Al2O3 surface was employed as a buffer layer to reduce a lattice mismatch between the AlN film and the α-Al2O3 substrate. The initial-nitriding layer was formed by chemical conversion of the α-Al2O3 surface in NH3 gas at 1200°C.
Microwave Surface Resistance Studies of YBa2Cu3O7-δSingle Crystal
Authors: Sankawa Izumi , Sato Makoto , Konaka Tsuneo , Kobayashi Mineo , Ishihara Koshi
Published: February 2005

The microwave surface resistance of a superconducting YBa2Cu3O7-δsingle crystal at 24 GHz was measured as a function of temperature and magnetic field. Below the superconducting transition temperature of 91 K, the microwave surface resistance rapidly decreased and was saturated below 75 K at zero magnetic field. Above 60 K, the microwave surface resistance increased linearly with the magnetic field. No hysteresis and no residual resistance were observed in the magnetic field cycling.
Preparation of Highly Oriented Microstructure in the (Bi, Pb)-Sr-Ca-Cu-O Sintered Oxide Superconductor
Authors: Asano Toshihisa , Tanaka Yoshiaki , Fukutomi Masao , Jikihara Kazunori , Machida Junichi , Maeda Hiroshi
Published: February 2005

A highly oriented microstructure in the high-T
c (Bi, Pb)-Sr-Ca-Cu-O bulk samples has been obtained by a modified powder method. Disc-shaped samples consisting of layered grains with the c-axis of the crystal normal to the disc surface were prepared by applying an intermediate pressing between the sintering heat treatments. Enhancement in formation of the high-T
c phase and a significant increase in the critical current density have been reported.
Improvements in the Current Carrying Capacity in High-Tc BiSrCaCuO Superconductors
Authors: Tanaka Yoshiaki , Asano Toshihisa , Jikihara Kazunori , Fukutomi Masao , Machida Junichi , Maeda Hiroshi
Published: February 2005

Remarkable improvements in the critical current density of the BiSrCaCuO sintered specimens have been achieved by a modified combination of heat treatment and pressing. The disk-shaped specimens were pressed uniaxially at room temperature after an initial sintering treatment and heated again at the same sintering temperature. This intermediate pressing method has produced a strongly oriented microstructure with a remarkably large critical current density. Correlation between microstructure and the critical current density, J
c, as well as anisotropy of the J
c with respect to the magnetic field direction has been described.
Appearance of Metallic Reflectance due to Conversion from Precursor Polymer to Poly(2,5-thienylenevinylene)
Authors: Tokito Shizuo , Murata Hideyuki , Tsutsui Tetsuo , Saito Shogo
Published: February 2005

The optical absorption and reflectance of poly(2,5-thienylenevinylene) and its precursor polymer thin films were measured. It was found that the optical properties drastically changed and metallic reflectance appeared during conversion from the precursor polymer to poly(2,5-thienylenevinylene).
Comparative Study of ZnSe Growth Rate by Metal Organic Molecular Beam Epitaxy Using Different Zn Sources
Authors: Kobayashi Naoki , Shinoda Yukinobu , Kobayashi Yoshihiro
Published: February 2005

The substrate temperature dependence of ZnSe growth rate is investigated using dimethyl zinc and diethyl zinc as Zn sources in metalorganic molecular beam epitaxy under the same flux intensity conditions. The growth rate for dimethyl zinc is higher at substrate temperatures above 450°C, and more sensitive to changes in substrate temperature than the growth rate for diethyl zinc. The mechanism resulting in the growth rate difference observed in this study is discussed in relation to the desorption process preceding ZnSe congruent evaporation.
Si Diffusion in Compositional Disordering of Si-Implanted GaAs/AlGaAs Superlattices Induced by Rapid Thermal Annealing
Authors: Uematsu Masashi , Yanagawa Fumihiko
Published: February 2005

The Si diffusion in Si-implanted GaAs/Al0.5Ga0.5As superlattices intermixed in the disordering process induced by rapid thermal annealing (RTA), is investigated by means of secondary ion mass spectroscopy (SIMS). The SIMS profiles indicate that no fast Si diffusion occurs during the disordering, and the disordering occurs when the Si concentration exceeds 1×1019 cm-3, which is about three times larger than the threshold value for the disordering by furnace annealing (FA). The number of Si atoms which are allowed to pass through the heterointerface is considered to be essential for disordering.
Reactive Ion Etching of Transparent Conducting Tin Oxide Films Using Electron Cyclotron Resonance Hydrogen Plasma
Authors: Minami Tadatsugu , Miyata Toshihiro , Iwamoto Atsushi , Takata Shinzo , Nanto Hidehito
Published: February 2005

The dry etching of tin oxide films using electron cyclotron resonance (ECR) hydrogen plasma has been proposed. It is found that the etching rate is drastically increased by the use of reactive gases, such as n-butyl acetone, acetone, alchohols and methane, which are activated by the ECR hydrogen plasma. A high etching rate above 175 nm/min can be achieved by the use of n-butyl acetone as the reactive gas. The mechanism of reactive ion etching using the ECR hydrogen plasma has also been discussed.
The Enhanced and Suppressed Electroless Plating of Copper by UV-Irradiation
Authors: Ishikawa Yutaka , Nakamichi Ichiro
Published: February 2005

The effect of irradiation of ultraviolet (UV) light from a low pressure mercury lamp on the copper electroless plating process has been investigated. Both enhancement of the plating rate and the opposite effect of suppression are obtained. It is possible to make copper film pattern by these effects with resolving power of 50 µm.
Epitaxial Growth of Al on Si by Gas-Temperature-Controlled Chemical Vapor Deposition
Authors: Kobayashi Tsukasa , Sekiguchi Atsushi , Hosokawa Naokichi , Asamaki Tatsuo
Published: February 2005

Epitaxial Al(111) film was deposited on Si(111) by low-pressure chemical vapor deposition with the use of tri-isobutyl aluminum (TIBA) at the substrate temperature of 400°C with the deposition rete of 0.9 µm/min. It was necessary for epitaxy to preheat the TIBA gas just before the deposition on the substrate (gas-temperature controlling). The film surface was very smooth; reflectance was higher than 90%. Streaks were observed in RHEED patterns. The rocking curve measured by X-ray diffraction was very narrow. Analysis by SIMS showed the film contained about 0.1% of Si and 20 ppm of O, C, and H. No hillock appeared on the film after 430°C annealing for 40 min.
Fabrication of Nanostructure by Anisotropic Wet Etching of Silicon
Authors: Shimizu Kazuhiro , Oda Shunri , Matsumura Masakiyo
Published: February 2005

Structural uniformity and processing-related material degradation are two major problems in the fabrication of nanostructure devices. Anisotropic wet etching by using a mixed solution of ethylenediamine/water/pyrocatechol is successfully applied to the fabrication of ultrasmall structure of Si. It has been found that anisotropic wet etching eliminates the structural fluctuations by virtue of the inherent crystallographic nature of Si. A 20 nm-wide structure with specular side walls has been obtained.
Modulation of the Dielectric Constant of the Liquid Crystal System by Means of Photochromism
Authors: Kurihara Seiji , Ikeda Tomiki , Tazuke Shigeo
Published: February 2005

Photochemical, reversible modulation of a dielectric constant of liquid crystals was demonstrated. This novel method of readout of photonic information as electric output is based on the principle of photochemically triggered phase transition in liquid crystals. Thus, the phase transition of a host liquid crystal, 4-cyano-4'-pentylbiphenyl (5CB), was induced by a partial photo-isomerization of a small amount of 4-butyl-4'-methoxyazobenzene (BMAB) doped in as a perturber. This isothermal phase transition brought about a change in the dielectric constants. The change in the dielectric constants is reversible corresponding to the trans-cis photoisomerization.
Anomalous Resistivity of SrTiO3 in the Vicinity of its Structural Phase Transition Temperature
Authors: Sugawara Kazushi
Published: February 2005

Resistivity measurements have been done for SrTiO3 implanted with B ions (acceleration energy=100 KeV, dose=6×1015–1×1017 ions/cm2) at temperatures between about 90 K and 120 K. Anomalous increments in resistivity (excess resistivities) were observed in the vicinity of the structural phase transition temperature, 105 K. The temperature dependence of the excess resistivity is compared with theoretical excess resistivity due to soft-phonon modes. Both theory and experiments reveal similar behavior. From this, the anomaly is conceivably due to the soft-phonon modes, which drive the structural phase transition of SrTiO3.
Densification and Grain-Orientation of Bi-Pb-Sr-Ca-Cu-O Superconductors by Hot-Pressing
Authors: Murayama Norimitsu , Sudo Eiichi , Awano Masanobu , Kani Keiko , Torii Yasuyoshi
Published: February 2005

The bulk density of a normal sintered sample of Bi1.6Pb0.4Sr1.6Ca2Cu2.8O
y
with a T
c of 103 K was 4.81 g/cm3 and shrinkage of the sample was barely observable. By hot-pressing at a pressure of 39 MPa at 800°C in a vacuum of 5×10-5 Torr for 2 h, the bulk density of the hot-pressed sample reached 6.21 g/cm3, which was over 95% of the theoretical density, and the T
c was 72 K. The grains were oriented with the c-axis along the pressing axis. After annealing at 835°C in air for 40 h, the T
c was improved to 108 K and the critical current density at 77 K was found to be 731 A/cm2.
A New Bismuth-Containing Cuprate, Bi2LaCaCuO6.5+y, as an Insulator Phase of Superconductor Bi2Sr2CuO6+y
Authors: Takemura Yasuhiko , Hongo Masashi , Wakaizumi Kazuhiro , Miyanaga Akiharu , Yamazaki Shumpei
Published: February 2005

A new Bi-containing cuprate, Bi2LaCaCuO6.5+y
, was found and its properties were investigated. Its crystal structure was considered to be identical to that of the 7 K-class superconductor, Bi2Sr2CuO6+y
. Semiconductive behavior of electrical resistivity and very weak diamagnetism were observed. Its unique magnetic property is discussed.
Preparation of Compositionally Modulated Bi-Sr-Ca-Cu-O Multilayered Films by Plasma Controlled Sputtering
Authors: Koinuma Hideomi , Nagata Hirotoshi , Takano Akihiro , Kawasaki Masashi , Yoshimoto Mamoru
Published: February 2005

A plasma controlled sputtering method was applied to the continuous deposition of compositionally modulated Bi-Sr-Ca-Cu-O films on MgO substrates. In this method, the target area to be sputtered can be controlled by varying the distribution of magnetic field above the binary target composed of an inner SrCaCu2O
y
plate and an outer Bi metal ring. The designed layer periodicity agreed well with that measured by the low-angle X-ray scattering. The postannealing of a deposited multilayered film at 890°C for 10 h in air made it superconducting with onset and zero-resistivity temperatures at 110 K and 72 K, respectively.
Flux-Pinning Properties of YBa2Cu3O7
Authors: Horie Yuuji , Yasuda Takashi , Youssef Ahmed A. A. , Kondo Ryuji , Shiraki Kazuyuki , Fukami Takeshi , Mase Shoichi
Published: February 2005

The flux-pinning properties of YBa2Cu3O7 semisingle crystalline films are investigated. The flux-pinning force density F
p versus a reduced field b=H/H
c2
* approximately obeys the formula, F
p∝H
c2
*n

b

p
(1-b)
q
(n=2.6 –3.8, p∼0.7, q∼3.0), similarly to the case of the so-called weak-pinning type. Here, H
c2
* is the upper critical field in a limit of zero current. The origin of F
p is briefly discussed.
High-Temperature Electrical Properties of Y1Ba2Cu3O7-x
Authors: Park Jin Seong , Kim Ho Gi
Published: February 2005

The four-probe method for dc electrical properties was used to characterize the functions of temperature and atmosphere on high-T
c superconductor Y1Ba2Cu3O7-x
(0.0<x<1.0). The properties of phase relationship, orthorhombic to tetragonal, and copper valence states were determined by measuring the electrical conductivity. The electrical behavior is not dependent on the phase transition but on the variation of Cu valence states relating to the oxygen content. The electrical conductivity decreases with increasing temperature.
Hysteresis of Critical Currents of a High-Tc Bi-Sr-Ca-Cu-O Superconductor in Magnetic Fields
Authors: Yamamoto Takahiro , Aomine Takafumi
Published: February 2005

Critical current-magnetic field (I
c-H) curves of the Bi-Sr-Ca-Cu-O superconductor have been studied for θ=0° ∼90°. Here, θ is the angle between the sample surface and the direction of the magnetic field. The hysteresis was observed in the Bi-Sr-Ca-Cu-O as well as in Y-Ba-Cu-O system and others. The former hysteresis is smaller than the latter ones. We did not obtain the significant θ dependence of I
c-H curves. The hysteresis is explained by the bridge model.
ESR of Ti3+ Ions in Laser-Quality Chrysoberyl
Authors: Chiba Yoshinori , Yamagishi Kiyoshi , Ohkura Hiroshi
Published: February 2005

We have studied the ESR of Ti3+ ions substituted for Al3+ ions occupying mirror symmetry sites (C
s point-group symmetry) in chrysoberyl of laser quality. From the analysis of the principal values of g-tensor observed, the symmetry of the Ti3+ site is found to be higher than that of point group C
s. The Stark split-energy levels related to the ground state of the Ti3+ ion are estimated to be 1060 cm-1, 1280 cm-1, and 19000 cm-1 with applying Pryce's formula, which was derived by assuming a crystalline field model of D
2h point group symmetry.
A High Resolution Cathodoluminescence Microscopy Utilizing Magnetic Field
Authors: Wada Kazumi , Kozen Atsuro , Fushimi Hiroshi , Inoue Naohisa
Published: February 2005

We propose a new principle to improve spatial resolution of cathodoluminescence microscopy (CL). The resolution of conventional CL is limited by minority carrier lateral diffusion, typically a few microns. The principle, which we named Lorentz force carrier confinement (LC), is to block the lateral diffusion by placing carriers in a circular orbit in terms of the Lorentz force under a vertical magnetic field. Detailed hetero-interface structures of GaAs-AlGaAs quantum wells have been successfully visualized, using the principle. The spatial resolution of LC-CL is improved to be a few thousand Angstrom by applying 0.8 Tesla.
Effects of Applied Magnetic Fields on Silicon Oxide Films Formed by Microwave Plasma CVD
Authors: Fukuda Takuya , Suzuki Kazuo , Takahashi Shigeru , Mochizuki Yasuhiro , Ohue Michio , Momma Naohiro , Sonobe Tadashi
Published: February 2005

By using a microwave plasma deposition system in which distributions of applied magnetic fields can be varied, the effects of the ECR position and plasma species on deposition rate and deposited film quality of silicon oxide are studied. The following results are obtained: deposition rate increases when not only O2 but also SiH4 as a material gas are excited by ECR, and high-quality film equivalent to thermal SiO2 film can be formed when the ECR position is located close to the substrate. It is suggested that the process of forming high-quality film is related to highly excited ions transported to the substrate.
MBE-Related Surface Segregation of Dopant Atoms in Silicon
Authors: Nakagawa Kiyokazu , Miyao Masanobu , Shiraki Yasuhiro
Published: February 2005

The surface segregation process in Ga and Sb doping during Si molecular beam epitaxy was studied as a function of growth temperature. Above critical temperatures, about 200°C for Ga and 400°C for Sb, almost all dopant atoms were found to float on growing Si surfaces. Below these temperatures, dopants were incorporated in the growing layer and a strong temperature dependence was found in incorporation coefficients of which activation energies were almost the same (∼0.5 eV) for the different dopant atoms. It suggests that there is a mechanism in surface segregation phenomena which is universal and does not depend upon the species of dopant atoms during MBE growth.
A Study of Electron-Stimulated Desorption of Adsorbed CO on (001) Plane of Molybdenum Surface by Means of Time-of-Flight Spectroscopy
Authors: Ueda Kazuyuki , Takano Akemi
Published: February 2005

Adsorption and desorption processes of carbon monoxide have been investigated on the (001) plane of molybdenum by using electron-stimulated desorption (ESD) accompanied by time-of-flight (T-O-F) spectroscopy. Thermal desorption spectroscopy has also been performed complementarily on the CO adsorbed surface. A desorption spectrum of excited oxygen ions from CO adsorbed on the Mo(001) surface during heating is very different in shape at higher temperatures from the thermal desorption spectrum. A proposal for a temperature dependence of reneutralization for desorbed ions is given.
Lattice Stability of the Bi4(Sr1-yCay)6Cu4Ox Structure under the Change of Sr-Ca Ratio
Authors: Yoshida Masashi
Published: February 2005

The Ca composition y in the Bi4(Sr1-y
Ca
y
)6Cu4O
x
(B-phase) was found to change from 0.24 to 0.61 as the initial composition of the mixture changed. By the heating of the mixture with y<0.25 or y>0.75, the Bi2(Sr, Ca)2CuO
x
(A-phase) was produced. The lattice parameter of the B-phase along the c-axis changed from 30.9 Å to 30.6 Å (Δ
c/c=1.0%) depending on y, while the change of the lattice parameter along the a-axis was within 0.2%. It was pointed out that the agreement of the lattice parameter of the Cu-O and (Sr, Ca)-O planes was important to stabilize the perovskite structure composed by Cu, Sr, Ca and O.
Preparation and Properties of Bulk Superconductors in the Tl-Pb-Sr-Ca-Cu-O System
Authors: Itoh Takao , Uchida Hiroyuki , Uchikawa Hiroshi
Published: February 2005

The preparation condictions, formation processes and superconducting properties of the materials in a Tl-Pb-Sr-Ca-Cu-O system have been investigated. The superconducting properties are found to depend strongly on the starting composition and heating time as well as the heating temperature. There are at least two superconducting phases with T
c's at 80 and 120 K. The 80 K T
c phase is formed in a short amount of time and then changes to the 120 K T
c phase after prolonged heating periods.
Growth of the 2223 Phase in Leaded Bi-Sr-Ca-Cu-O System
Authors: Hatano Takeshi , Aota Katsumi , Ikeda Shozo , Nakamura Keikichi , Ogawa Keiichi
Published: February 2005

Growth of the 2223 phase has been studied in the leaded Bi-Sr-Ca-Cu-O system. Differential thermal analysis showed that the enhanced formation of the 2223 phase occurs in the temperature range between 835°C and 869°C where partial melting occurs. The density of the pellet was found to increase by 30% at one hour and then to decrease by 40% from the highest density attained. The former is attributed to the growth of the 2223 phase with the aid of the partially melted liquid phase and the latter to the flaky shape of the resultant 2223 crystals. The effect of Pb addition for enhanced 2223 phase formation will be discussed.
Superficial Aggravation of Sputter-deposited Bi-Sr-Ca-Cu-O Films by Annealing
Authors: Tsuchida Kanji , Ishii Mamoru , Takata Masasuke , Yamashita Tsutomu
Published: February 2005

Films of the Bi-Sr-Ca-Cu-O system were prepared on MgO substrates by RF-magnetron sputtering. After annealing, the films showed a superconducting transition at about 80 K. However, the surfaces of the annealed films changed remarkably for the worse. The effects of the annealing process on the superconducting properties and surface condition of the films were investigated.
Structures and Magnetic Properties of Fe/Co Multilayer Films
Authors: Komuro Matahiro , Kozono Yuzoo , Narishige Shinji , Hanazono Masanobu , Sugita Yutaka
Published: February 2005

Fe/Co multilayer films with various Fe layer and Co layer thicknesses ( dFe, dCo) were deposited by an rf magnetron sputtering method. The bcc single phase was obtained for films with smaller thicknesses of Co than 2 nm. A mixture of bcc and hcp phases was obtained for films with larger thicknesses of Fe and Co than 5 nm. Among the bcc single phase films, dFe=dCo=1 nm film showed the highest saturation magnetic flux density ( Bs) value. After annealing at 350°C for 1 h, Bs of this film increased to 2.40 T. This increase was attributed to interdiffusion of Fe and Co.
Second- and Third-Harmonic Generation of Nd:Glass Laser in Fast Red ITR Organic Crystal Fiber
Authors: Muto Shinzo , Yoda Osamu , Sugiyama Akira , Fukasawa Akihiko , Ito Hiroshi
Published: February 2005

As a new nonlinear optical material, Fast Red ITR organic crystal has been grown in the form of crystal fibers from the melt. This crystal has a wide optical transparency range from 340 nm to near infrared and large birefringence. The second- and third-harmonic generations of a Nd: glass laser have been observed in this Fast Red ITR crystal fiber.
Metal-Dependent Schottky Barrier Height with the (NH4)2Sx-Treated GaAs
Authors: Fan Jia-Fa , Oigawa Haruhiro , Nannichi Yasuo
Published: February 2005

Schottky barriers have been prepared on (NH4)2Sx-treated GaAs. The barrier height was observed to change remarkably with the kind of metals, which is predicted in the case of low interface state density. We found that the interface trap density was reduced to 9.8×1012 cm-2·eV-1 by the treatment from 6.5×1013 cm-2·eV-1 for the untreated one.
Overturn of Molecules during the Fully Automatic Horizontal Lifting Deposition using Double Gates
Authors: Kato Teiji
Published: February 2005

Overturn of film molecules during the horizontal lifting deposition of LB films was studied by in-situ polymerization of a photopolymerizable film material, cadmium pentacosa-10,12-diynoate, in order to ascertain the structure. Contact angles of the resultant polymerized LB films with water were measured. It was presumed that film molecules in the outermost layer should overturn once in the upward process of the horizontal lifting deposition in an odd cycle and molecules in the outermost two layers should overturn together at the next upward process in an even cycle of deposition.
Alkali-Developable Silicone-Based Positive Resist for Electron Beam Lithography
Authors: Ban Hiroshi , Tanaka Akinobu , Imamura Saburo
Published: February 2005

Silicone-based positive electron beam resist (SPR) developable with alkaline aqueous solution is first reported. SPR is composed of acetylated polyphenylsilsesquioxane and poly(methylpentene sulfone) as a dissolution inhibitor. Resist sensitivity of SPR reaches up to 5 µC/cm2 for 20 kV electron beam exposure. A two-layer resist system of SPR and a hard baked novolak resin reveals good performance for 0.8 µm pitch line and space pattern fabrication.