bluuebunny/crossref_metadata_2025 huggingface dataset:
High Temperature Photochemical Hole Burning of Tetrasodium 5,10,15,20-tetra(4-sulfonatophenyl)porphin in Polyvinylalcohol
Authors: Sakoda Kazuaki , Kominami Kazuhiko , Iwamoto Masao
Published: February 2005

Persistent spectral holes were burned in a film composed of tetrasodium 5,10,15,20-tetra(4-sulfonatophenyl)porphin and polyvinylalcohol at 20 K–80 K. This is the first observation of a photochemical hole burned above liquid nitrogen temperature. The hole width increased with temperature according to power-law dependence from 20 K to 80 K.
Mapping of EL2-Related Luminescence on Semi-Insulating GaAs Wafers at Room Temperature
Authors: Tajima Michio
Published: February 2005

Deep-level photoluminescence (PL) at room temperature has been used to determine the two-dimensional distribution of the dominant midgap donor EL2 in undoped semi-insulating GaAs crystals grown by the liquid encapsulated Czochralski method. Various fourfold symmetric patterns have been observed in PL maps of the EL2-related band or conventional (100) wafers. The patterns correlate closely with the EL2 distributions reported previously using optical absorption spectroscopy, but not with the patterns for the band-edge PL. A PL mapping under a high spatial resolution reveals a cellular structure in a highly dislocated area in the central part of the wafers.
A Proposal for Measurement of Implanted Ion Dose in Semiconductor Wafers by IR Light Scattering Technique
Authors: Ogawa Tomoya , Sakai Kazufumi , Yamada Yutaka
Published: February 2005

It was confirmed here that the IR light scattering caused by ion-implanted regions of GaAs wafers was inversely proportional to the 4th power of the IR wavelength. The scattering power was increased with an increase in implanted ion dose when the acceleration voltage of the ions was kept constant, and the scattering was also increased with an increase in the voltage.
From this evidence, tracks of the high energy ion particles, where atomic arrangement is locally disordered from the regular positions of atoms by collisions with the ions, act as Rayleigh scatterers, while the deformed volume of ion tracks is dependent upon the energy and species of implanted ions.
Therefore, a new ion dose indicator will be designed using this principle for an in situ dose measurement of an implanter under operation.
Evaluation of Deep States in Amorphous-Silicon/Silicon-Nitride System from Charge-Coupled Device Characteristics
Authors: Sekine Satoshi , Nakamura Satoshi , Oda Shunri , Matsumura Masakiyo
Published: February 2005

Charge transfer characteristics have been investigated experimentally in amorphous-silicon charge-coupled devices under wide operation conditions. Deep states are found to cause the low and frequency-independent transfer efficiency. The deep states in amorphous-silicon/silicon-nitride system have been separated into the bulk states in the amorphous-silicon layer and the interface states, for the first time. Their typical values are 7.0×1015 cm-3eV-1 and 1.2×1011 cm-2eV-1, respectively.
Asymmetric Implantation Self-alignment Technique for GaAs MESFETs
Authors: Kimura Tamotsu , Inokuchi Kazuyuki , Akiyama Masahiro , Sakuta Masaaki
Published: February 2005

A novel self-alignment technique, the asymmetric implantation self-alignment technique (ASIST), has been developed for GaAs MESFETs. This technique is based on the selective self-alignment ion implantation which provides an asymmetric n
+ profile for the source and drain regions. By ASIST, the GaAs MESFET has been fabricated with the heavily doped source and the lightly doped drain and it is demonstrated for the first time that this structure is quite effective in suppressing the short-channel effect without increasing the source resistance. In this letter, the process and device characteristics of the ASIST-FET are described.
Spin-Polarized Scanning Electron Microscope Equipped with a Thumb-Size Spin Detector
Authors: Koike Kazuyuki , Matsuyama Hideo , Hayakawa Kazunobu
Published: February 2005

A 2.5 cm φ×6 cm spin detector which users spin-dependent absorption has been successfully applied to a spin-polarized scanning electron microscope for magnetic domain observation. It typically takes 20 minutes to form a 200×300 pixel image and 5 seconds to form a rough image.
Coagulation of In Atoms in Hydrogenated Amorphous Silicon Islands Deposited on ITO Films
Authors: Hirao Takashi , Kitagawa Masatoshi , Mori Koshiro , Yoshioka Yoshiaki , Wasa Kiyotaka
Published: February 2005

The effects of deposition temperature on the depth profiles of In and Sn atoms in a-Si:H films deposited on ITO and SnO2 films, respectively, were investigated. The concentration profiles of In are highly dependent upon the deposition temperature while those of Sn are nearly independent. The concentration level of In increases as the deposition temperature increases. It was found that the concentration profile of In in the a-Si:H film deposited under such a condition as the best diode characteristics are obtained (200°C) show a high In concentration region (hill). On the other hand, the concentration profiles of Sn in the a-Si:H films do not have such a hill. From the thickness dependence in the range 20–200 Å, it was found that In atoms are incorporated in the interior of amorphous silicon islands in the concentrated form during the initial stage of plasma deposition. The high-concentration regions of In atoms remain even after subsequent deposition.
Coherent Intergrowth Structure of Tetragonal and Orthorhombic Ba2YCu3O7-x Observed by Transmission Electron Microscopy
Authors: Hiroi Zenji , Takano Mikio , Ikeda Yasunori , Takeda Yasuo , Bando Yoshichika
Published: February 2005

High resolution transmission electron micrographs of a superconducting Ba2YCu3O7-x
sample with T
c≃90 K prepared by the standard ceramic method reveal a coherent intergrowth of tetragonal domains in the ordinary orthorhombic (110) twin lamellas. Short-range ordering in the Cu(I)-O plane is observed in some tetragonal domains as lined contrasts running parallel to one of the basal-plane axes.
Electronic Energy Level of Off-Center Substitutional Nitrogen in Silicon: Determination by Electron Spin Resonance Measurements
Authors: Murakami Kouichi , Kuribayashi Hitoshi , Masuda Kohzoh
Published: February 2005

It is demonstrated that a deep level of a paramagnetic off-center substitutional N can be determined by electron spin resonance (ESR) measurements of the peak-to-peak derivative linewidth Δ
H
msl over a wide temperature region from 150 to 550 K. The temperature dependence of Δ
H
msl observed above ∼330 K is interpreted in terms of one type of motional broadening. According to this model, we obtain an energy level of 0.33±0.02 eV below the conduction band and the electron capture cross section σ0 of 1.0×10-15 cm2, which are in agreement with one of the levels obtained by deep-level transient spectroscopy (DLTS).
Effect of Oxygen Content and Sr/Ca Ratio on Superconducting Properties in Bi2Sr2-xCa1+xCu2O8+δ
Authors: Niu Hiromi , Fukushima Noburu , Ando Ken
Published: February 2005

Superconducting properties of the 80 K class superconductor in the Bi-Sr-Ca-Cu-O system were examined from the viewpoints of the oxygen content and the Sr/Ca ratio. The T
c of Bi2Sr2CaCu2O8+δ was reduced with decreasing δ. The solid solution region of Bi2Sr2-x
Ca1+x
Cu2O8+δ was confirmed for x values between -0.25 and 1.0. The T
c changed slightly in the solid solution region. The transition to insulator, however, was not observed by changing the oxygen content or the Sr/Ca ratio.
Superconductivity at 100 K in Bi-Pb-Sr-Ca-Cu-O
Authors: Oota Akio , Sasaki Yoshinobu , Kirihigashi Akihiro
Published: February 2005

The superconductivity with an onset temperature of ∼110 K and a zero resistance at T
c(offset) ≃100 K was observed under measuring current I≤1 mA in the oxide with nominal composition Bi0.7Pb0.3SrCaCu1.8O
x
. The sharp decrease in susceptibility around 110 K due to the Meissner effect and the magnetic levitation on a magnet at 77 K were also observed in the sample. The superconducting and magnetic properties are compared with the ones for the oxides with nominal composition BiSrCaCu1.8O
x
and BiSrCaCu2O
x
.
Effects of Oxygen Stoichiometry for Anisotropic Structural Change in Oriented YBa2Cu3Ox
Authors: Ishibashi Teruo , Nakayama Tsuneyoshi
Published: February 2005

The effects of oxygen content on the structural change of highly oriented YBa2Cu3O
x
have been studied in terms of X-ray diffraction in the temperature range from 77 K to room temperature. It is found that the temperature dependence of the lattice constant c is severely affected by the oxygen content from x=6.83 to 7.00. However, the temperature dependences of the lattice constants a and b are not influenced by the oxygen content in contrast with that of c. Discussions are also given for the anomalous distortion in the Cu-O2 plane through T
c in connection with the formation of anisotropic pairing.
Low-Temperature Growth of High-Tc Bi-Sr-Ca-Cu-O Films by Magnetron Sputtering
Authors: Asano Hidefumi , Asahi Masayoshi , Katoh Yujiro , Michikami Osamu
Published: February 2005

Superconducting thin films of Bi-Sr-Ca-Cu-O have been grown on heated MgO, sapphire, and SrTiO3 substrates by magnetron sputtering. For films grown at substrate temperatures between 560–600°C, T
c onset behavior above 110 K was observed. These films contain a phase having a c-axis lattice parameter, c
0, of 36.83 A in coexistence with a phase having c
0 of 30.67 A. These as-grown films show zero resistence at 56 K. Zero resistence of 90 K was achieved in postannealed films on MgO. A thin-film growth method like sputtering is capable of stabilizing the 110 K phase in the Bi-Sr-Ca-Cu-O system at low growth temperatures below 600°C.
Temperature and Magnetic Field Dependence of the Critical Current in Polycrystalline Ba2YCu3Oy
Authors: Obara Haruhiko , Yamasaki Hirofumi , Kimura Yoichi , Ishihara Takeshi
Published: February 2005

The temperature and magnetic field dependence on the critical current density, J
c, of the polycrystalline Ba2YCu3O
y
have been measured. In the low magnetic field range, 0.6∼7 kOe, the J
c behavior changed at around 70 K. Below 70 K, J
c showed different temperature dependences between field cooling and zero-field cooling, that is, the J
c value measured when the sample was cooled in a fixed magnetic field was different from that measured when the sample was cooled in zero magnetic field and then a magnetic field was applied. Above 70 K, however, such different temperature dependences on J
c were not observed. These experimental results can be attributed to the effects of anisotropy, and a crossover between two- and three-dimensional superconductivity is considered to occur.
Superconductivity in 2- µm Wide Strip Line of Gd-Ba-Cu-O Thin Film Fabricated by Low-Temperature Processes
Authors: Enokihara Akira , Higashino Hidetaka , Setsune Kentaro , Mitsuyu Tsuneo , Wasa Kiyotaka
Published: February 2005

The Gd-Ba-Cu-O film of 500 nm thickness was prepared on a (100) MgO single-crystal substrate at 650°C by an rf magnetron sputtering. This thin film having a smooth surface was patterned to a 2- µm wide and 100- µm long strip line by a conventional Ar ion beam etching (IBE) technique using the negative-type photoresist mask. Without any heat treatments, the patterned strip indicated a zero-resistivity temperature, T
c, of 69 K and critical current density, T
c, of 1.0×106 A/cm2 at 4.2 K.
An Optimum Design of FIB System with a Beam Crossover
Authors: Tsumagari Takashi , Kimata Yoshiaki , Ohiwa Hajime , Noda Tamotsu
Published: February 2005

A study was made to optimize an electrostatic ion optical system with an intermediate beam crossover between two focusing lenses. A description was given of an optimization technique with respect to the relative displacement of the crossover between the two lenses with short working distances. It was shown that a system with the objective lens operated in the bipotential mode had better focusing properties than that in the unipotential mode. Some numerical examples were presented for the high performance lens system designed with this technique.
Glass Transition Behavior of Al-Y-Ni and Al-Ce-Ni Amorphous Alloys
Authors: Inoue Akihisa , Ohtera Katsumasa , Tsai An-Pang , Kimura Hisamichi , Masumoto Tsuyoshi
Published: February 2005

Ductile Al-Y-Ni and Al-Ce-Ni amorphous alloys were found to exhibit a glass transition at temperatures just below crystallization temperature. The glass transition temperature increases from 490 to 582 K with increasing solute concentration. The difference in specific heat between amorphous solid (AS) and supercooled liquid (SL) reaches 9.2 J/mol-K and the temperature coefficient of expansion and viscosity of the supercooled liquid are 100×10-5 K-1 and 3×1013 poise. By the transition of AS to SL, the Young's modulus and tensile strength also decrease steeply by about 63 and 66%, accompanied with an increase of elongation by about 320%.
New Amorphous Al-Ln (Ln=Pr, Nd, Sm or Gd) Alloys Prepared by Melt Spinning
Authors: Inoue Akihisa , Ohtera Katsumasa , Tao Zhang , Masumoto Tsuyoshi
Published: February 2005

New amorphous alloys in Al-Ln (Ln=Pr, Nd, Sm or Gd) binary systems have been formed in the vicinity of 10 at% Pr and in the ranges of 8 to 12%Nd or Gd and 8 to 16%Sm by rapid solidification. Crystallization temperature, hardness, tensile strength and electrical resistivity at 293 K of the binary amorphous alloys increase with an increase of solute content from 453 to 511 K, 150 to 325 DPN, 495 to 960 MPa and 96 to 170 µΩcm, respectively. The compositional dependences are interpreted on the basis of the presumption that the attractive bonding nature between Al and Ln metals is a dominant factor.
ZnSe/GaAs Heterointerface Stabilization by High-Temperature Se Treatment of GaAs Surface
Authors: Kobayashi Naoki
Published: February 2005

An Se treatment of Ga-terminated (001) GaAs substrate surfaces at temperatures as high as 500°C greatly reduces the diffusion of Ga and As atoms into a ZnSe epitaxial layer during growth. High-temperature Se treatment forms several monolayers of GaAsSe on the GaAs surface. The GaAsSe layer are so thermodynamically stable that Ga atoms are bonded tightly with Se atoms at the heterojunction and diffuse very little into the ZnSe layer, Reflection high energy electron diffraction patterns become streaky at the beginning stages of growth, presumably due to the suppression of diffusion. In order to obtain a high-purity ZnSe layer with less vacancy concentration, a combination of high-temperature (∼500°C) Se treatment and low-temperature (∼300°C) growth is proposed.
Rapid Growth of Diamond Films by Arc Discharge Plasma CVD
Authors: Akatsuka Fumio , Hirose Yoichi , Komaki Kunio
Published: February 2005

Diamond films have been synthsized by arc discharge plasma CVD in a hydrogen-argon-ethanol mixture gas. The arc discharge power is about 560 W and the typical gas flow rate is 500–2000 cm3/min, respectively. The growth rate of diamond films has been obtained about 200–250 µm/h which is higher than that of other CVD methods. The obtained diamond films are identified as natural cubic diamond by X-ray diffraction. It is found that graphitic and amorphous carbon are not contained in the diamond films by Raman spectra. Atomic hydrogen (H) plays important roles in the growth of high-quality diamonds.
Observation of Thickness Profiles on Lubricants during Sliding Tests
Authors: Yanagisawa Masahiro
Published: February 2005

Profiles of lubricant thickness on sliding traces are monitored by an ellipsometer during sliding tests. Various thickness profiles for lubricants are observed for two selected lubricant categories, perfluoropolyether as a liquid lubricant and tetracontane as a solid lubricant. The liquid lubricant shows either a swollen portion or a sunken portion in the profile. However, no swollen portion is observed for the solid lubricant, due to its removal from a sliding track as wear debris. Recovery of the lubricant to average thickness is observed for liquid lubricant after an elapsed time. However, solid lubricant does not show thickness recovery.
Cation Ordering in LaBa2Cu2TaO8+y
Authors: Murayama Norimitsu , Sudo Eiichi , Kani Keiko , Tsuzuki Akihiko , Kawakami Shoji , Awano Masanobu , Torii Yasuyoshi
Published: February 2005

LaBa2Cu2TaO8+y
crystallizes in a tetragonal unit cell with the dimensions a=3.9674(2) and c=12.052(1) Å, showing semiconductivity. In this compound, the Ta ions were found to preferentially occupy the Cu1 site between the two Ba layers in the LaBa2Cu3O7-y
-type structure.
Two Unknown Phases and Platinum Solubility in Y-Ba-Cu-O System
Authors: Itoh Masahiro , Saitoh Masatoshi , Oka Kunihiko , Unoki Hiromi
Published: February 2005

Two unknown phases which were found in a process of studying a phase diagram of the Y-Ba-Cu-O system were investigated. Platinum solubility in Y-Ba-Cu-O system was examined in order to see whether those unknown phases were related to platinum, which was used as a vessel plate in quenching experiments. Platinum was found to dissolve easily in the Y-Ba-Cu-O system with a solubility of as much as 14% in the temperature range of 900 to 950°C. It is concluded that at least one of those unknown phases is related to platinum.
Crystal Structure and Superconductivity in Ba2Y1-xPrxCu3O7-y
Authors: Kinoshita Kyoichi , Matsuda Azusa , Shibata Hiroyuki , Ishii Takao , Watanabe Takao , Yamada Tomoaki
Published: February 2005

Crystal structures and superconductive properties of the solid solution Ba2Y1-x
Pr
x
Cu3O7-y
(0≤x≤1) are studied. Although Ba2Y1-x
Pr
x
Cu3O7-y
has an orthorhombic structure which is isomorphic with Ba2YCu3O7-y
, T
c decreases monotonically with increasing Pr concentration, and superconductivity disappears at around x=0.6. The Rietveld analysis of X-ray powder diffraction data shows that both Cu(1)-O(3) bond length and the structural asymmetry of the Cu(2)O2 planes increase by the substitution of Pr for Y. Such structural changes induce the carrier density reduction and localization effects, which may cause the suppression of superconductivity in this system.
Polarized Extended X-Ray Absorption Fine Structure of High-Tc Superconducting Single-Crystal YBa2Cu3Oy
Authors: Maeyama Satoshi , Satow Yoshinori , Oshima Masaharu , Katsui Akinori
Published: February 2005

Polarized EXAFS spectra at the Cu K-edge and the Y K-edge have been measured at room temperature for 90 K superconducting single-crystal YBa2Cu3O
y
. Differences in both the Cu K-edge and Y K-edge EXAFS were observed between the spectra measured with c axis orientation of an orthorhombic single-crystal sample parallel and perpendicular to the X-ray polarization vector. The Fourier transform results of these polarized EXAFS oscillations support qualitatively an oxygen-deficient triperovskite structure model presented by neutron diffraction analysis.
Relation between Superconducting Tc and Hole Concentration: Hall Effect Measurement and Chemical Analysis in Charge-Doped and Oxygen-Doped System Nd1+xBa2-xCu3O7-δ
Authors: Takita Kôki , Akinaga Hiroyuki , Katoh Hideo , Masuda Kohzoh
Published: February 2005

Using single-phase samples of Nd1+x
Ba2-x
Cu3O7-δ sintered under identical conditions, both the Hall effect measurement and the chemical analysis of the average charge of a [Cu-O] unit have been performed. The plot of the superconducting T
c against effective hole concentration p
H (=1/R
H
e) deduced from the Hall coefficient just above T
c, R
H, shows a simple relation between them. A similar plot against hole concentration estimated from the average charge shows a different relation. An estimation of hole concentration in two-dimensional CuO2 sheets, however, based on an assumption proposed by Tokura et al., gives almost the same value to p
H, at least below 80 K. This strongly suggests that the superconductivity of YBa2Cu3O7-δ-like superconductors is determined uniquely by the hole concentration in CuO2 sheets which can be deduced from the Hall coefficient just above T
c.
On the New Substrate Materials for High-Tc Superconducting Ba-Y-Cu-O Thin Films
Authors: Komatsu Takayuki , Tanaka Osamu , Matusita Kazumasa , Yamashita Tsutomu
Published: February 2005

In order to check whether BaAl2O4, BaZrO3, Ba2SiO4 and BaF2 compounds are adequate as new substrate materials for high-T
c superconducting Ba-Y-Cu-O thin films or not, the reactions of these compounds with quenched BaYCuO (nominal composition: Ba2YCu3O7-x
) at 900°C were examined using X-ray diffraction analyses and measurements of superconducting properties. It was found that BaZrO3, Ba2SiO4 and BaF2 did not react strongly with the quenched BaYCuO and were excellent candidates as new substrate materials.
Neutron Diffraction Study on Preferred Orientation of Ag-Sheathed Y-Ba-Cu-O Superconductor Tape with Jc=1000–3000 A/cm2
Authors: Okada Michiya , Okayama Akira , Matsumoto Toshimi , Aihara Katsuzo , Matsuda Shinpei , Ozawa Kunio , Morii Yukio , Funahashi Satoru
Published: February 2005

Ag-sheathed tapes using tetragonal phase of YBa2Cu3O
x
were fabricated by cold rolling. Neutron diffraction study was undertaken to investigate the orientation of YBCO grains in the Ag-sheathed tape. It was clearly observed that the c-plane of crystal was aligned parallel to the cold rolling surface with a standard deviation of 26.7 degree. The preferred orientation was enhanced by using the tetragonal phase.
Magnetic and Magneto-Optical Properties of Laser-Annealed PtMnSb Films
Authors: Shiomi Shigeru , Maegawa Takaaki , Iwakiri Hideyuki , Masuda Morio
Published: February 2005

Sb, Mn and Pt layers have been sequentially deposited and then annealed using Ar+ laser beam to form PtMnSb alloy film. The crystalline, magnetic and magneto-optical properties of films were found to depend on annealing conditions such as laser power P and beam scan rate R. Adequate combinations of P and R resulted in films which were seemingly of the PtMnSb single phase. In these films, M
s ranged between 300 and 450 emu/cm3 and there was neither perpendicular nor in-plane magnetic anisotropy. At the wavelength of 630 nm, the polar Kerr rotation angle took the peak value, which ranged between -0.8 and -1.7° through the glass substrate.
Si-Induced Disordering of In0.53Ga0.47As/In0.52Al0.48As Multiquantum Well Structures
Authors: Miyazawa Takeo , Kawamura Yuichi , Mikami Osamu
Published: February 2005

Disordering of In0.53Ga0.47As/In0.52Al0.48As multiquantum well structures by Si doping and following annealing was demonstrated for the first time. Sputtering Auger electron depth profiling and photoluminescence measurements revealed that a Si-doped In0.53Ga0.47As/In0.52Al0.48As multiquantum well structure is easily disordered during annealing. The mechanism of disordering is discussed based on the fact that disordering takes place when the Si doping level exceeds 1.3×1019 cm-3.
Anomalous Phase Separation Behavior in a Binary Mixture of Poly(Vinyl Methyl Ether) and Water under Deep Quench Conditions
Authors: Tanaka Hajime , Nishi Toshio
Published: February 2005

We have found anomalous phase separation in a binary mixture of poly(vinyl methyl ether) (PVME) and water under deep levels of quenching conditions near the critical composition. After the quick formation of small PVME-rich droplets in motion, a coarse graining effect does not proceed for a very long time. The phase-separated state observed may be stable or metastable. This might be a new type of phase transition which is governed by the competition between the collision dynamics and the dynamics of polymer interdiffusion causing coalescence of droplets. Namely, the phase-separated structure of the droplet is probably stabilized dynamically and not thermodynamically.
Response of Director Field in a Twisted Liquid Crystal Cell to a Poiseuille Flow-Application to Touch Entry Device
Authors: Takaki Ryuji , Kobayashi Shunsuke
Published: February 2005

The director field of the nematic liquid crystal in a twisted cell is obtained theoretically in the case of an electric field perpendicular to the cell and a Poiseuille flow of the liquid crystal. Equations governing the director field are solved numerically, and the electric capacitance of the cell is calculated. The results agree well with previous measurements by one of the authors.
A Simple Modification of the Magnetron Sputtering Method for Deposition of Hydrogenated Amorphous Silicon Films with Improved Optoelectronic Properties
Authors: Batabyal A. K. , Banerjee Ratnabali , Bandyopadhyay A. K. , Barua A. K.
Published: February 2005

A simple modification of the magnetron sputtering system has been proposed to minimise damage of the growing film by ion bombardment, particularly at high rf powers. This is sought to be achieved by placing the substrate in the field of a permanent magnet. Using this modified set up, hydrogenated amorphous silicon thin films have been deposited at different rf powers. It has been found that at higher rf powers, the films deposited with the modified set up exhibit better optoelectrical properties than those deposited with the conventional magnetron sputtering configuration.
Deposition of Tungsten Silicide Films by the Chemical Vapor Reaction of Dichlorosilane and Tungstenhexafluoride
Authors: Hara Tohru , Miyamoto Takaaki , Yokoyama Tadashi
Published: February 2005

High temperature chemical vapor deposition (CVD) of tungsten silicide (WSi
x
) employing SiH2Cl2 (DCS) and WF6 is studied. Deposition rate of 1450–1500 Å/min is held nearly constant at temperatures above 500°C. However, it decreases below 500°C because the surface reaction is dominant. Si/W ratio (Si composition), x, of WSi
x
increases with increasing deposition temperature. Resistivity decreases from 740 to 530 µΩ·cm with decreasing composition, x, from 2.38 to 2.15. Fluorine concentration of DCS WSi
x
is around 1×1017 cm-3 and is about four orders lower than monosilane (MS) WSi
x
.
TEM Observation of Defects Induced by Cu Contamination on Si(100) Surface
Authors: Sadamitsu Shinsuke , Sumita Shigeo , Fujino Nobukatsu , Shiraiwa Toshio
Published: February 2005

The behavior of a Si(100) surface defect induced by intentional Cu contamination was studied with transmission electron microscopy. After annealing at 1150°C for 1 hour in N2 atmosphere, colony precipitates lying along (110) planes were observed only on the surface of the wafer. These precipitates were estimated to be Cu6Si-type silicides by the selected area diffraction pattern. During additional annealing in an oxidation atmosphere, stacking faults were formed from each of colony precipitates. This indicated that colony precipitates were the nucleus of oxidation-induced stacking faults.
Effects of Annealing Conditions on Superconducting Properties of BiCaSrCu2Ox Ceramics Prepared by the Melt Quenching Method
Authors: Komatsu Takayuki , Sato Ryuji , Imai Kouji , Matusita Kazumasa , Yamashita Tsutomu
Published: February 2005

The effects of annealing conditions (annealing temperature, time and atmosphere) on the superconducting properties of BiCaSrCu2O
x
ceramics prepared by the melt quenching method were examined. Although the high-T
c phase (T
c above 100 K) was detected in the samples annealed at temperatures around 1133 K, its amount was very small. It was found that the samples annealed at temperatures above 1073 K in a nitrogen atmosphere were also superconductors with T
c above 80 K.
Superconductivity in the Nd-Sr-Ce-Cu-O System
Authors: Akimitsu Jun , Suzuki Seiichiro , Watanabe Masaru , Sawa Hiroshi
Published: February 2005

A new high-T
c superconductor Nd-Sr-Ce-Cu-O system has been found by the resistivity and magnetization measurements. The highest onset transition temperature is about 28 K. The superconducting phase may be described as (Nd1-x
Sr
x-y
Ce
y
)2CuO4-δ.
Preparation of Single 110 K Phase of the Bi-Pb-Sr-Ca-Cu-O Superconductor
Authors: Koyama Satoshi , Endo Utako , Kawai Tomoji
Published: February 2005

A pure 110 K phase of the Bi-Pb-Sr-Ca-Cu-O superconductor was obtained by co-decomposition of metal nitrates and a solid reaction under low oxygen pressure. The best starting compositions were in the region close to Bi1.84Pb0.34Sr2Ca2Cu3O
y
with a little excess of Ca and Cu. In this region, the samples showed the absence of the 80 K and semiconducting phase, and there was no indication of impurities at all. The 110 K phase without stacking faults is stabilized by the addition of Pb, so that the nominal composition close to the ideal one is required at the start. A little excess of Ca and Cu, however, effectively decreases the 80 K phase.
Modulated Structure of High-Tc Superconductor Bi-Ca-Sr-Cu-O Studied by High-Resolution Electron Microscopy and Electron Diffraction
Authors: Hirotsu Yoshihiko , Tomioka Osamu , Ohkubo Tadakatsu , Yamamoto Naoki , Nakamura Yoshio , Nagakura Sigemaro , Komatsu Takayuki , Matsushita Kazumasa
Published: February 2005

An incommensurate atomic displacive modulation has been clearly observed in high-resolution electron micrographs of the superconductive oxide Bi-Ca-Sr-Cu-O in addition to a concentration modulation in Bi layers. A commensurate form of the orthorhombic modulated structure has cell dimensions a=0.54, b=2.7 and c=3.08 nm. Characteristic features of electron diffraction patterns can be explained when transverse and longitudinal displacement waves for metal atoms along [010] are taken into consideration.
Superconducting Bi-Sr-Ca-Cu-O Thick Films by the Sol-Gel Method
Authors: Kobayashi Toshio , Nomura Kenji , Uchikawa Fusaoki , Masumi Tatsuo , Uehara Yasushi
Published: February 2005

Superconducting thick films of the Bi-Sr-Ca-Cu-O system were prepared on MgO(100) substrates by the sol-gel method. A smooth thick film showing T
co of 117 K and T
ce of 84 K has been synthesized by sintering at 870°C for 2 h. The thick films sintered at above 860°C showed the c-axis perpendicular to the substrate.
Preparation of Superconductive Bi-Sr-Ca-Cu-O Thick Films by Rapid Quenching
Authors: Shimomura Shuichi , Takahashi Koichiro , Ohta Masatsune , Watanabe Akiteru , Seido Masahiro , Hosono Fumikazu
Published: February 2005

Thick films of superconductive BiSrCaCu2O
x
were prepared by rapid quenching without any substrate. The as-quenched film was amorphous-like and not superconductive, but after heat treatment at 850–880°C, it showed superconductivity with a zero-resistance temperature of 60 K and a critical current of 220 A/cm2 at 4.2 K.
Preparation of Superconducting Bi-Sr-Ca-Cu-O Thin Films by dc Magnetron Sputtering
Authors: Hakuraku Yoshinori , Aridome Yoshinari , Ogushi Tetsuya
Published: February 2005

Superconducting thin films of the Bi-Sr-Ca-Cu-O system have been prepared on MgO substrates by dc magnetron sputtering and subsequent heat treatment in order to examine the preparation conditions. The as-sputtered films deposited at substrate temperatures of about 750°C had a slightly crystalline structure and exhibited a superconducting resistive transition from 80 K to 30 K. The annealed films exhibited a superconducting resistive transition between 100 K and 80 K. Large resistivity drops at 110 K were observed when the films were deposited at relatively high substrate temperatures ranging from 650°C to 750°C and heat treated at approximately 885°C in air.
X-Ray Diffraction Study on YBa2Cu3O7-δ Epitaxial Thin Film Grown by an Activated Reactive Evaporation Method
Authors: Kamigaki Kousei , Terauchi Hikaru , Terashima Takahito , Iijima Kenji , Yamamoto Kazunuki , Hirata Kazuto , Bando Yoshichika
Published: February 2005

The as-grown epitaxial thin film of YBa2Cu3O7-δ with T
c∼90 K on a (001) SrTiO3 substrate is investigated by means of X-ray diffraction. It is clearly shown that the c-axis is perpendicular to the SrTiO3 (001) plane and no evidence of a-axis normal appears. Microtwin structures are observed, indicating that the crystal is orthorhombic. The domain size and mosaic spread are also reported.
Superconducting Gap Excitations in Bi-Sr-Ca-Cu-O Superconductor Observed by Raman Scattering
Authors: Yamanaka Akio , Kimura Toshinori , Minami Fujio , Inoue Kuon , Takekawa Shunji
Published: February 2005

Raman scattering is measured in the a
b plane of the Bi2.2Sr1.8CaCu2O
y
superconductor. It is found that the electronic Raman scattering appears as a continuum spectrum in both polarized and depolarized scattering and the electronic continuum interferes with some phonon lines. Below T
c, the electronic continuum redistributes due to a gap formation and a broad peak appears at about 400 cm-1, which is larger than the expected value 2Δ=209 cm-1 of the BCS-theory.
Sintering and Characterization of Er2Ba2Cu1.1Pt0.9O8 Compacts
Authors: Shishido Toetsu , Saito Yoko , Fukuda Tsuguo , Toyota Naoki , Sasaki Takahiko , Iwasaki Hideo , Ukei Kazutoshi
Published: February 2005

Er2Ba2Cu1.1Pt0.9O8 was synthesized successfully by a direct-reaction sintering method with raw materials. Fractured surfaces of sintered compacts are observed. The densities of the specimens sintered at 1400°C are 79.0% of the theoretical density, 8.56 Mg·m-3. Above T≃20 K, the magnetic susceptibility of this compound follows the Curie-Weiss law.
Quality Variation of ZnSe Heteroepitaxial Layers Correlated with Nonuniformity in the GaAs Substrate Wafer
Authors: Matsumoto Takashi , Iijima Takayuki , Ishida Tetsuro
Published: February 2005

ZnSe layers are grown heteroepitaxially on substrates cut from a LEC-grown, undoped semi-insulating GaAs(100) wafer along the diameter parallel to the [001] axis. The intensities of free-exciton photoluminescence and X-ray diffraction from the ZnSe layers show an M-shaped profile along the GaAs wafer diameter, and are inversely correlated with the etch-pit-density distribution of the GaAs wafer. This observation gives, for the first time, experimental evidence that the quality of ZnSe heteroepitaxial layers grown by recent epitaxial techniques can be limited by the quality of GaAs substrates.
p-Channel Amorphous Silicon Thin-Film Transistors with High Hole Mobility
Authors: Oda Shunri , Adachi Naoki , Katoh Sadayuki , Matsumura Masakiyo
Published: February 2005

The problem of low drift mobility of holes in hydrogenated amorphous silicon (a-Si:H) has been solved by controlling the hydrogen content in the film. A-Si:H films with low hydrogen content have been prepared by the radical-controlled method in which the glow discharge of the mixture of SiF4 and H2 is used and the residence time of the reactant species is controlled. A prototype MOSFET demonstrates a hole mobility of 0.12 cm2/Vs and an electron mobility of 0.24 cm2/Vs, suggesting the feasibility of the a-Si CMOS circuit.
Photoassociation of KrF Excimer at 248 nm
Authors: Hakuta Kohzo , Nakayama Kunihiko , Fujino Masashi , Takuma Hiroshi
Published: February 2005

KrF excimers are produced by irradiating the gas mix of Kr and F2 with KrF laser radiation at 248 nm. The excitation process is identified as a photoassociation process between colliding Kr and F atoms via photodissociation of F2 molecules. The present success has made it possible to investigate the collisional processes of KrF excimer quantitatively.
Creation of E' Centers in Silica by Glow-Discharge Plasma and Their Annealing
Authors: Kumeda Minoru , Nagano Hiroki , Kiwaki Minori , Shimizu Tatsuo
Published: February 2005

ESR measurements were performed for silica glasses exposed to rf plasma of various kinds of gases. During a short time of exposure, UV light emitted from the plasma created E' centers in the bulk of glass. After a long time of exposure, the density of E' centers decreased by the influence of plasma particles or high-energy UV light on the surface. The remnant E' centers were easily annealed out, even at room temperature.
MBE Growth and Optical Properties of Novel Corrugated-Interface Quantum Wells
Authors: Tanaka Masaaki , Sakaki Hiroyuki
Published: February 2005

We have systematically studied MBE growth and properties of novel corrugated-interface quantum wells, where the GaAs well thickness is modulated with the average period of 32 Å–324 Å along the interface for possible formation of quantum wire states. The modulation is attempted by the alternate deposition of fractional monolayer of GaAs and AlAs on (001) flat and slightly misoriented substrates. Although the 2-dimensional nucleation is dominant in the growth of AlAs at a lower substrate temperature (T
s<600°C) and prevents the formation of modulation, the growth mode on the most misoriented planes is transformed to step flow at a higher T
s (≧640°C) under the appropriate growth rate and V/III flux ratio, leading to the formation of quasi-periodic GaAs/AlAs or Al
xAGa1-xAAs/Al
xBGa1-xBAs modulated structures. Measured photoluminescence energies are compared with the theory to demonstrate the composition modulation and the laterally confined quasi-one-dimensional electronic states along the interfaces and also to estimate the periodicity fluctuation and the compositional mixing in GaAs-AlAs modulated structures.
Distribution Profiles and Annealing Characteristics of Defects in GaAs Induced by Low-Energy FIB Irradiation
Authors: Miyake Hideto , Yuba Yoshihiko , Gamo Kenji , Namba Susumu , Mimura Ryo , Aihara Ryuso
Published: February 2005

Distribution profiles and annealing characteristics of defects in GaAs induced by various (0.1–150 keV) energy Ga-focused ion-beam (FIB) irradiation were measured by means of deep-level transient spectroscopy and C-V carrier profiling to reveal the importance of low-energy beams for damage-free device processing. Four different electron traps were induced by the irradiation and observed at >2000 A, a depth far deeper than the ion range (about 15 A for 1 keV Ga). The defects were reduced by decreasing the ion energy and easily annealed out, and full recovery in carrier density occurred after annealing at 600°C.
A New Mode of Modulation Observed in the Bi-Pb-Sr-Ca-Cu-O System
Authors: Ikeda Shozo , Aota Katsumi , Hatano Takeshi , Ogawa Keiichi
Published: February 2005

With the aid of transmission electron microscopy, the Bi-Pb-Sr-Ca-Cu-O system has been found to have a new mode of modulation in addition to the conventional one reported earlier in the Pb-free Bi-Sr-Ca-Cu-O system. The new modulation is observed in the perovskite {110} plane, as is the conventional one. The wave vector of the new modulation, however, is parallel to <110 > and the observed wavelength is about 50 Å. Periodicities of the new as well as conventional modes of modulation become less regular in the Pb-added system. The disturbed modulation is argued in light of the strain energy relaxation due to the Pb addition.
Effect of Mg Addition on Superconducting Properties of Ba-Y-Cu-O Ceramics Prepared by the Melt Quenching Method
Authors: Komatsu Takayuki , Meguro Hideki , Sato Ryuji , Tanaka Osamu , Matusita Kazumasa , Yamashita Tsutomu
Published: February 2005

We examined the effect of Mg addition on superconducting properties of Ba2YCu3O
x
ceramics prepared by the melt quenching method in order to clarify why it is very difficult to prepare superconducting Ba-Y-Cu-O thin films with a T
c around 90 K on MgO substrates at processing temperatures around 900°C. We found that a very small amount of the Mg element could be introduced into Ba2YCu3O
x
crystals so that the values of the T
c(zero) would be consequently depressed to 70–75 K.
Effect of 120 MeV 16O Ion Irradiation at Low Temperatures on Superconducting Properties of YBa2Cu3O7-x and La1.8Sr0.2CuO4
Authors: Iwase Akihiro , Masaki Norio , Iwata Tadao , Nihira Takeshi , Sasaki Shigemi
Published: February 2005

YBa2Cu3O7-x
and La1.8Sr0.2CuO4 are irradiated at low temperatures with 120 MeV 16O ions up to fluences of 1.6×1015/cm2 and 2.4×1015/cm2, respectively. With increasing O ion fluence, the transition temperature decreases and the electrical resistance above T
c increases monotonically. The annealing experiments performed after irradiation show that in YBa2Cu3O7-x
the recovery of the electrical resistance occurs above ∼160 K, and this recovery leads to the recovery of T
c. In La1.8Sr0.2CuO4, no recovery of electrical resistance is found up to 300 K.
Y-Ba-Cu Oxide Thin Films Prepared by DC Magnetron Sputtering
Authors: Akune Tadahiro , Sakamoto Nobuyoshi
Published: February 2005

Superconducting Y-Ba-Cu oxide thin films were sputtered on MgO(100) substrates by DC magnetron sputtering from an oxide powder target. The films were deposited at the high rates of 9–29 nm/min and showed, at best, T
ce (R=0) up to 78 K with a transition width Δ
T
c of 5 K, after annealing in oxygen for 1 h at 900°C. The X-ray diffraction pattern showed a highly preferred orientation of the c-axis even in the thick (2.0 µm) film. The film sputtered at a higher deposition rate had a broad transition width Δ
T
c=22 K and its X-ray diffraction pattern showed the coexistence of orthorhombic and tetragonal phases.
Stabilization of Ba2YCu3O7-δ by Surface Coating with Plasma Polymerized Fluorocarbon Film
Authors: Sato Kota , Omae Shinji , Kojima Kuniharu , Hashimoto Takuya , Koinuma Hideomi
Published: February 2005

High-T
c superconducting Ba2YCu3O7-δ pellets were coated with polyfluorocarbon thin films prepared by plasma polymerization of tetrafluoroethene (C2F4). The polymer-coated Ba2YCu3O7-δ preserved its high-T
c superconductivity even after it had been kept standing in water at 60°C, whereas the superconductivity of noncoated pellets was completely destroyed under the same condition. The high hydrophobicity of the film originated from high fluorine content is considered to be primarily responsible for the protection of the superconductor from chemical deterioration by preventing the hydrolysis at the surface.
Properties of Silicon Oxynitride Films Prepared by ECR Plasma CVD Method
Authors: Hirao Takashi , Setsune Kentaro , Kitagawa Masatoshi , Kamada Takeshi , Ohmura Takuichi , Wasa Kiyotaka , Izumi Tomio
Published: February 2005

The compositional and structural properties of silicon oxynitride (SiON) films prepared by an electron cyclotron resonance (ECR) plasma CVD method have been studied using the gas mixture of SiH4-N2-O2.
The concentrations of oxygen and nitrogen incorporated in the films were found to be well controlled by varying the ration of O2/(N2+O2) under a constant microwave power, gas pressure and SiH4 flow rate. Bond configurations in the form of N-Si-O are thought to be incorporated in the films, judging from infrared absorption spectra.
ESR centers relating to both Si dangling bonds and oxygen vacancy were detected in SiON films and silicon oxides (SiO) films, though only the ESR center relating to the Si dangling bonds is detected in SiN films.
Preparation of a Single Crystalline Powder of Superconducting YBa2Cu3O7-x by the Gas Phase Solidification Method
Authors: Setaka Ryoji , Komatsu Wataru , Shibata Toshiaki , Nakajima Minoru
Published: February 2005

The preparation of a single crystalline powder of superconducting YBa2Cu3O7-x
was investigated for the gas phase solidification process by decomposing an evaporated solution of yttrium, barium and copper acetates. A transmission electron microscope observation of particles less than 0.3 µm in diameter showed that the as-produced particles were twinned at transformation to orthorhombic YBa2Cu3O7-x
. The as-produced powder was a single phase YBa2Cu3O7-x
and did not exhibit an isomer from the X-ray diffraction pattern.
Broad Band Emission Behaviors an ZnS Thin Film Electroluminescent Devices
Authors: Nakano Ryotaro , Matsumoto Hironaga , Endo Tadao , Shimada Jun , Sakagami Norio , Miura Noboru
Published: February 2005

Time-resolved emission spectra and transient emission behavior at various wavelength regions were measured for doubly insulated thin-film electroluminescent devices having electron-beam-evaporated undoped ZnS or ZnS:TbF
x
as the active layer under an alternating pulse voltage of 500 ns width. The broad-band emission intrinsic to the ZnS host was observed in the wavelength region from 320 nm to 700 nm, and this emission showed a maximum at 250 ns and then decreased quickly regardless of the wavelength. The emission of Tb3+ ion appeared with the decay of the broad-band emission and was saturated within an applied pulse width.
Evaluation of Laser CVD Tungsten for Gate Electrode
Authors: Matsuhashi Hideaki , Nishikawa Satosi , Ohno Seigo
Published: February 2005

The properties of tungsten (W) film deposited by ArF excimer laser CVD using WF6 and H2 gases, and the characteristics of MOS capacitors with laser CVD-W gates were studied. The intrinsic stress of W film varies from large tensile to small compressive with increasing H2/WF6 gas flow ratio. It has been found that W film is reproducibly deposited on SiO2 when the intrinsic stress of W is less than 4×109 dyne/cm2 (tensile). MOS capacitors with laser CVD-W gates show more excellent properties, particularly lower contamination of SiO2 due to mobile ions, than those with sputtered-W gates.
The Influence of Quantum Size Effects in the Tc of Layered Oxide Superconductors
Authors: Mola E. E. , Vicente J. L.
Published: February 2005

The role played by the quantum size effects of the layered (Cu-O2) perovskite structures in the superconductivity of the La2-x
M
x
CuO4 (M=Ba, Sr,…) compounds is examined. A model based on the Bardeen, Cooper and Schrieffer theory is developed and applied to anisotropic structures (metals and semiconductors like the newly discovered materials). The density of states is estimated and high transition temperatures T
c are obtained.
Composition Dependence and Electrical Properties of Tc>100 K BiSrCaCuO Superconducting Oxide Films Prepared by Sequential Deposition
Authors: Kuroda Kenichi , Mukaida Masashi , Miyazawa Shintaro
Published: February 2005

Preparation of BiSrCaCuO superconducting oxide films with T
c>100 K was investigated by a sequential deposition technique. The nominal composition exhibiting T
c>100 K ranged from 1112 (Bi:Sr:Ca:Cu=1:1:1:2) to 1312, although a volume fraction of the high-T
c phase evaluated by X-ray and magnetic susceptibility measurements was less than 10% at most. A characteristic feature of the films with T
c>100 K was that extrapolations of normal resistance always intersected the temperature axis on the positive side. The temperature dependence of the Hall coefficient for these films is also described briefly.
Electronic Structure of Photochemically Etched Silicon Surfaces
Authors: Ogura Tsuyoshi , Hayashi Tsukasa , Miyazaki Seiichi , Hirose Masataka
Published: February 2005

Photochemical etching of silicon has been carried out in NF3 under ArF excimer laser irradiation. The valence band spectra of a fluorosily layer formed on the etched surface have been systematically investigated for the first time by using in situ X-ray photoelectron spectroscopy. The valence band spectra have indicated that SiF4 and F2 molecular units exist in the surface fluorosilyl layer, and that the top silicon valence band underneath the fluorosilyl layer moves either upward or downward with the progress of etching. It is supposed that these silicon band bendings are caused by the excess photogenerated majority carriers being trapped in the very thin semi-insulating fluorosilyl layer.
Real-Time Observation of GaAs(001) Surfaces During Molecular Beam Epitaxy by Scanning Microprobe Reflection High Energy Electron Diffraction
Authors: Isu Toshiro , Watanabe Akiyoshi , Hata Masayuki , Katayama Yoshifumi
Published: February 2005

GaAs(001) surfaces during MBE growth was observed by scanning microprobe RHEED. A microprobe electron gun for RHEED was installed in an MBE chamber. Using intensity variation of RHEED patterns produced by the scanning of an incident beam, we obtained a microscopic image highly sensitive to the surface structure. Scanning reflection electron images revealed granular features over the whole surface, which came from small undulations on the surface of the MBE grown layer. The undulation became larger along [1̄10] direction as growth proceeded. No contrast was observed in the secondary electron images.