bluuebunny/crossref_metadata_2025 huggingface dataset:
Medium-Range Order of Amorphous Silicon Germanium Alloys: Small-Angle X-Ray Scattering Study
Authors: Muramatsu Shin-ichi , Shimada Toshikazu , Kajiyama Hiroshi , Azuma Kazufumi , Watanabe Takeshi , Kamiyama Tomoaki , Suzuki Kenji
Published: February 2005

A medium-range order of hydrogenated amorphous silicon germanium (a-Si1-x
Ge
x
:H) alloys is investigated using small-angle X-ray scattering. It is found that the scattering intensities I(h) of a-Si:H and a-Ge:H decrease with scattering vector h as represented by I(h)∼h
-3. However, in the case of a-Si1-x
Ge
x
:H alloys, the scattering intensity decreases with h as represented by I(h)∼h
-P
(P<3). This shows that the alloys take on a mass fractal structure. At around x=0.5, the fractal dimension tends to approach the value of 2.
Plasma Metalorganic Chemical Vapor Deposition of Indium Oxide Thin Films
Authors: Maruyama Toshiro , Kitamura Toshio
Published: February 2005

Indium oxide (In2O3) thin films were obtained from trimethylindium and O2 by the plasma metalorganic chemical vapor deposition method (MOCVD). A d.c. glow discharge was used to make the plasma. At a substrate temperature above 200°C, polycrystalline thin films were obtained, while no film was obtained by thermal MOCVD without plasma at the substrate temperature used in this study (<360°C). The transmittance and resistivity of the film depended on the molar ratio of trimethylindium and O2.
Raman Studies of Orthorhombic YBa2-xSrxCu3O7-y
Authors: Matsuda Yasushi , Yoshida Masashi , Hinotani Shigeharu
Published: February 2005

A Raman scattering study was performed in orthorhombic YBa2-x
Sr
x
Cu3O7-y
at room temperature. It is found that the Raman peak associated with Cu-O-Cu stretching mode along the c-axis (502 nm-1, x=0) increases continuously in frequency with increasing Sr content, while the bending mode of the Cu-O (341 cm-1, x=0) decreases in frequency. These results indicate that larger contraction of the Cu-O-Cu bond distance along the c-axis than that of the lattice constant along the c-axis of the orthorhombic unit cell can be attained by replacing Ba sites with Sr ions.
Effects of Pb Content on the Formation of the High-Tc Phase in the (Bi, Pb)-Sr-Ca-Cu-O System
Authors: Rhee C. K. , Kim C. J. , Lee H. G. , Kuk I. H. , Lee J. M. , Chang I. S. , Rim C. S. , Han P. S. , Pyun S. I. , Won D. Y.
Published: February 2005

Formation of the high-T
c phase in the (Bi, Pb)-Sr-Ca-Cu-O system was studied using specimens with various Bi/Pb ratios. The synthesis temperature was suppressed as the Pb/(Pb+Bi) was increased. The lattice constant of the c axis of the low-T
c phase (T
c∼80 K) and high-T
c phase (T
c∼105 K) increased with increasing Pb content. Substitution of 30% Pb for Bi was found to be most preferential for the formation of the high-T
c phase.
Structural Analysis on Tc Variation of Bi2Sr2-xCa1+xCu2O8+y
Authors: Moto Akihiro , Morimoto Akiharu , Shimizu Tatsuo
Published: February 2005

The effects of heat treatment for Bi2Sr2-x
Ca1+x
Cu2O8+y
(x=0.25, 0.5, 0.75, 1.0) were studied by X-ray diffraction and Raman scattering measurements. The curve of T
c vs normal state conductivity ρ-1 is found to attain a maximum through heat treatment and a compositional change, suggesting the presence of an optimum hole concentration, as is observed in the La- and Y-based superconductors. In most cases, T
c decreases with an increase in ρ-1, except for the sample with x=1.0. Furthermore, we found no peak shift of the 466 cm-1 Raman mode induced by the heat treatment and the compositional change, which are expected to vary the Bi-Cu distance.
Preparation of (Nd, Sr, Ce)2CuOx Type Compounds in a Gd-La-Sr-Cu-O System
Authors: Ohashi Naoki , Taniguchi Takashi , Ikawa Hiroyuki , Fukunaga Osamu
Published: February 2005

A synthetic study of the phases in the (Gd, La, Sr)2CuO
z
system was carried out. A (Nd, Sr, Ce)2CuO
x
type compound (T*-phase) was dominant between x=0.55 and x=0.9 of (Gd1-x
, La
x
)2CuO4 coexisting with the Nd2CuO4 type (T'-phase) and La2CuO4 type (T-phase). An almost single T*-phase was prepared in (Gd0.40, La0.55, Sr0.05)2CuO4. On addition of Sr, resistivity of the sample clearly decreased. We discussed the relation between the observed phases and the average ionic radius of the A cation in A2CuO
x
.
Superconductivity of the Tl-Ba-Sr-Ca-Cu-O System
Authors: Kuroda Masanori , Araki Michio
Published: February 2005

The superconductivity of the Tl-Ba-Sr-Ca-Cu-O system was studied. The critical temperature (T
c) of this system was determined as 102 K by magnetic susceptibility measurements. Judging from the XRD measurement, the unit cell of this phase was estimated to be tetragonal with a=3.85 A and c=12.3 A.
Chemical Interaction between High-Tc Superconducting Oxides and Alkaline Earth Fluorides
Authors: Hashimoto Takuya , Asakawa Toshiaki , Shiraishi Tadashi , Yoshida Tsutomu , Yoshimoto Mamoru , Koinuma Hideomi
Published: February 2005

Reactions of high-T
c superconductors and MF2 (M: Ca, Sr, Ba) were investigated by means of ac susceptibility, X-ray diffraction, and TG-DTA measurements. The superconducting transition temperature (T
c
onset) of Ba2YCu3O7-δ powder mixed with MF2 powder decreased as a result of heat treatment at 600°C in air, whereas it did not decrease by the heat treatment under carefully dried conditions. In contrast, neither of the heat-treatment conditions decreased the T
c
onset of Bi2Sr2CaCu2O
x
mixed with MF2 powder. Heating with MF2 at temperatures higher than 700°C reduced volume fractions of these superconductors even in dry atmosphere and the reactivity increased in the order of BaF2<SrF2<CaF2 for Ba2YCu3O7-δ, and SrF2\lesssimCaF2<BaF2 for Bi2Sr2CaCu2O
x
.
Effect of Sb Addition on the Formation of High-Tc Phase in the Bi-Pb-Sr-Ca-Cu-O Ceramics
Authors: Komatsu Takayuki , Sato Ryuji , Matusita Kazumasa , Yamashita Tsutomu
Published: February 2005

We prepared Bi1.6-x
Pb0.4Sb
x
Sr2Ca2Cu3O
y
ceramics (x=0.1 and 0.2) by the melt-quenching method and examined the effect of Sb addition on the superconducting properties. It was found that the formation of the high-T
c phase was remarkably enhanced by the addition of a very small amount (x=0.1) of the Sb element. The critical temperature T
c(zero) of the sample (x=0.1) annealed at 850°C or 860°C for 100h was 102 K.
Properties of Superconducting Whiskers of Bi-Sr-Ca-Cu Oxide
Authors: Jung J. , Franck J. P. , Cheng S. C. , Sheinin S. S.
Published: February 2005

Elastic and crystallographic properties of superconducting whiskers of Bi2Sr2Ca1Cu2O
x
with a transition temperature near 76 K are given. The whiskers can be elastically deformed up to strains between 1 and 3%. Crystallographically the whiskers are identical. The growth direction is along the a-axis. The modulated b-axis lies in their flat side, and the c-axis is perpendicular to this side. Unit cell dimensions are a=5.39 Å, b=5.38 Å, c=30.0 Å, The whiskers show a damped electron energy loss peak near 19 eV, identified as the volume valence electron plasmon.
Relationship between Crystal Structures and Solid Solution of Tl-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O Superconductors
Authors: Soeta Atsuko , Suzuki Takaaki , Takeuchi Seiji , Kamo Tomoichi , Usami Katsuhisa , Matsuda Shin-pei
Published: February 2005

We report on the superconductivity and crystal structures in Tl-(Ba, Sr)-Ca-Cu-O (TBSCC) system. In the case of TBSCC system, the 2223 phase was obtained as a single phase more easily compared with the Tl-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O systems. As a result, we achieved a high superconducting volume fraction, 95% above 100 K. The crystallographic transformation was caused by changing the ratio of Ba to Sr. By the X-ray diffraction and TEM analysis, the crystal structure was determined as a 2223 structure consisting of Tl-O bilayers in the Ba-rich side, and a 1223 structure consisting of Tl-O monolayer in the Sr-rich side.
Superconductivity in the Tl-Bi-Ca-Ba-Cu-O and Tl-Bi-Ca-Sr-Cu-O Systems
Authors: Torii Yasuko , Kotani Toshihiro , Takei Hiromi , Tada Kouji
Published: February 2005

The influence of the substitution of Bi for Tl in forming the superconducting phases in Tl-Bi-Ca-Ba-Cu-O and Tl-Bi-Ca-Sr-Cu-O systems was investigated. In the Tl-Bi-Ca-Ba-Cu-O system, the Tl Ca2Ba2Cu3O9 phase forms from a 10% to 40% substitution of Bi for Tl in the nominal composition. With a further increaseing Bi, the superconducting phase disappears because of the formation of BaBiO3. On the other hand, the superconducting phase of (Tl, Bi)CaSr2Cu2O7 forms from a 10% to 90% substitution of Bi for Tl in the Tl-Bi-Ca-Sr-Cu-O system. It is recognized that the substitution of Bi for Tl stabilizes and accelerates the formation of the (Tl, Bi)CaSr2Cu2O
x
phase.
Electromagnetic Properties and Morphology of Ag-Sheathed Bi-Pb-Sr-Ca-Cu-O Superconducting Wires
Authors: Hikata Takeshi , Nishikawa Takeshi , Mukai Hidehito , Sato Ken-ichi , Hitotsuyanagi Hajime
Published: February 2005

The critical current density (J
c) in Ag-sheathed Bi-Pb-Sr-Ca-Cu-O superconducting wire increased to 17,400 A/cm2 in a zero magnetic field. The magnetic field dependence of J
c was improved according to the increase of J
c in a zero magnetic field. Fine, dispersed, nonsuperconducting phases were observed through SEM and TEM. These phases are expected to act as pinning sites.
Preparation of As-Grown BiPbSrCaCuO Thin Films by Electron-Cyclotron-Resonance Microwave Plasma Sputtering
Authors: Nishimori Yasuhiro , Minomo Shoichiro , Taniguchi Michio , Sugiyo Masato , Fukumoto Yoshito , Fujiwara Yasufumi , Kobayashi Takeshi
Published: February 2005

We have prepared as-grown superconducting thin films of BiPbSrCaCuO by the electron-cyclotron-resonance (ECR) sputtering method. This method is characterized by efficient ECR plasma cooling after the ECR deposition. The ECR plasma suppressed the unfavorable development of growth of the 2212 (low-T
c) phase and enhanced the crystallization of the 2223 (high-T
c) phase during the cooling stage, even under an oxygen gas pressure as low as 10-4 Torr. The highest zero-resistance temperature so far obtained for the as-grown film was 62 K, although XRD observation revealed that the film was dominated by the well-known 2223 high-T
c phase.
Magnetic Properties of Mn-Al Multilayered Films
Authors: Takeuchi Teruaki , Hirayama Yoshiyuki , Futamoto Masaaki , Takagi Kazumasa , Fujiwara Takeo
Published: February 2005

The magnetic properties of Mn-Al multilayered films prepared by alternate deposition of Mn and Al in a vacuum evaporation system are investigated. Such films are found to show ferromagnetic properties when the substrate temperature during deposition is around 300°C. The saturation magnetization is seen to depend on the kind of substrate: the values for MgO(100) substrates are greater than those for MgO(111) and glass substrates. The obtained saturation magnetization of 50 emu/cm3 is expected to increase.
A Split-Disk Geometry Glass Laser Amplifier
Authors: Kim Byung-Tai , Nakatsuka Masahiro , Kanabe Tadashi , Nakai Sadao
Published: February 2005

A split-disk geometry glass laser amplifier, in which a thick glass disk of an ordinary disk laser is replaced by several highly doped thin plates of phosphate glass to improve the cooling efficiency, has been developed. A stored energy of 32 J and a gain coefficient of 0.024 cm-1 were obtained in an active laser volume of 300 cm3 with a pumping efficiency of 0.78%.
A Reflection-Type Surface-Emitting 1.3 µm InGaAsP/InP Laser Array with Microcoated Reflector
Authors: Saito Hideho , Noguchi Yoshio
Published: February 2005

A reflection-type surface-emitting 1.3 µm InGaAsP/InP laser with a microcoated reflector is successfully fabricated by inclined reactive ion-etching (RIF) utilizing a TiO2 mask and Cl2-Ar gas. The typical CW threshold current is 30 mA at room temperature, and the CW surface-emitting light power exceeds 18 mW. A one-dimensional surface emitting laser array is also fabricated.
Nonlinear Quenching in a Monolithically Integrated Semiconductor Laser Logic Device
Authors: Jung Woong , Kwon Young-Se
Published: February 2005

A semiconductor laser logic device with GaAs/Al0.3Ga0.7As double heterostructure is fabricated. A main laser and a control laser are monolithically integrated in the cross-coupled structure in order to bring about optical quenching. This monolithic device is not only capable of conventional linear quenching but also new nonlinear quenching by the in-homogeneous current injection of the control laser. It can be used as a digital optical inverter having small trigger energy. The maximum efficiency of nonlinear quenching is 0.67 times that of the direct modulation of the main laser and 13 times that of linear quenching. Compared to conventional optical inverters based on optical quenching, this nonlinear quenching will improve the efficiency significantly.
Anomalous Defect Processes in Silicon-Implanted SiO2
Authors: Fujita Tetsuo , Fukui Minoru , Okada Shunji , Shimizu Tsutomu , Itoh Noriaki
Published: February 2005

Electron paramagnetic resonance (EPR) spectra of amorphous SiO2 produced by Si implantation have been measured and compared with those produced by Ar implantation. For doses below 1×1015 cm-2, only the E1' centres are generated, similar to that of Ar implantation, while for doses between 1×1016 cm-2 and 1×1017 cm-2, a new spectrum is observed in addition to that of the E1' centre. The density of the E1' centres produced by Si implantation does not become saturated with the dose, unlike that produced by Ar implantation. This is explained in terms of the reduction of the effective cross section for defect annihilation due to the combination of recoiled oxygen with implanted silicon.
Low-Temperature Cleaning of HF-Passivated Si(111) Surface with VUV Light
Authors: Takakuwa Yuji , Nogawa Masafumi , Niwano Michio , Katakura Hitoshi , Matsuyoshi Satoshi , Ishida Hiroyuki , Kato Hiroo , Miyamoto Nobuo
Published: February 2005

Photon-stimulated desorption (PSD) of H+ ions from the HF-passivated Si(111) surface, which is terminated with hydrogen, has been studied using synchrotron radiation. Desorption of H+ ions due to Si-H bond breaking is observed at photon energies above 17 eV. A distinct dependence of the H+-PSD yield on the angle of incidence of a photon beam also is observed. It is found that the H+-PSD yield correlates well with the photoabsorbance. The present results suggest the feasibility of cleaning the HF-passivated Si(111) surface at low-temperature by means of irradiation of vacuum-ultraviolet (VUV) light.
XANES and Raman Spectroscopic Studies of Diamond Films Synthesized by Hot Filament CVD
Authors: Takata Yasutaka , Edamatsu Kunishige , Yokoyama Toshihiko , Seki Kazuhiko , Tohnan Masanao , Okada Tadashi , Ohta Toshiaki
Published: February 2005

Diamond films synthesized by hot filament CVD were studied by SEM, X-ray diffraction, and Raman and XANES spectroscopies. All of these methods have confirmed that the films prepared at low methane concentrations (1.0 vol.% and 4.0 vol.% in H2) consist of diamond crystals. In contrast to these, the deposit at a high methane concentration (7.5 vol.%) does not provide an X-ray diffraction pattern or a Raman signal characteristic of diamond, indicating the absence of diamond crystals with long-range order. Nevertheless, the XANES spectrum revealed that this specimen is composed of small diamond clusters.
High-Beta Plasma Production and Confinement in Screw Pinch TPE-2
Authors: Hayase Kiyoshi , Hirota Isao , Kiyama Hiroko , Kiyama Satoru , Maejima Yoshiki , Sato Yasuhiro , Takeda Shouhei , Yahagi Eiichi
Published: February 2005

A high-beta plasma of βt∼0.1 and εβp>2 is produced and its confinement properties are studied in a screw pinch of moderately elongated cross section. The initially constricted high-beta plasma column is surrounded by a force-free current layer and expands radially. The energy confinement time is much less than that from the empirical scaling of an ohmically heated tokamak, but it gradually improves as βp decreases. The fast plasma-energy decay and the fast boundary diffusion are considered to be caused by the ballooning mode.
Development of Hydrogen Ion Source with a Sheet Plasma
Authors: Hayakawa Satoshi , Kamiya Masaki , Ishii Kazushige , Hosokawa Tatsuzo
Published: February 2005

A large-current hydrogen ion source has been developed by using a sheet plasma. The cathode of the discharge tube developed by the authors was lanthanum hexaboride (so called LaB6), which provided a stable plasma current of up to 30 A. The sheet plasma was formed by applying a pair of flat permanent magnets to a discharge plasma column. The electron density and the electron temperature in the sheet plasma were measured by a probe method. It was observed that the values of the electron temperature and the electron density distributed uniformly along the width direction and those values were about 3.8 eV and 1×1010 cm-3, respectively. On the other hand, the half width of the sheet plasma was about 14 mm in the thickness direction. It was clear that the arc current and the gas evacuation capability were important factors used to obtain the high density sheet plasma.
A Possible Novel Scanning Ultrasonic Tip Microscope
Authors: Uozumi Kiyohiko , Yamamuro Kazuhiro
Published: February 2005

An rf-ultrasonic pulse of about 1.4 MHz has been sent into an STM tip 1 mm in diameter and 8 mm long by a piezoelectric transducer cemented to the end surface of the tip. Well-isolated ultrasonic pulse-echoes have been received by the transducer, and the conventional ultrasonic pulse superposition method has been applied to the pulse-echoes. The phase-sensitive output of the method has been found to change almost reversibly against the tip-to-surface distance in nanometer scale. The possibility of a new scanning ultrasonic tip microscope (SUTM), where the output is fed back to control the tip position instead of the current in STM, is demonstrated.
X-Ray Diffraction Curves from Mosaic Crystals at Near-Normal Incidence Angles
Authors: Nakahata Takumi , Hashizume Hiroo , Oshima Masaharu , Kawamura Tomoaki
Published: February 2005

We obtained data supporting our previous calculations of X-ray diffraction curves from mosaic crystals at near-normal incidence angles. The data were collected from copper crystals with mosaic spreads of 1.2° and 0.4° by scanning the photon energy in the vicinity of 3 keV at a synchrotron-radiation beamline designed for surface science. The 1.2° mosaic crystal showed Bragg-peak widths markedly dependent on the off-normal angle of incidence while the dependence for the 0.4° crystal was much weaker. The observed peak widths agree with calculations if an energy resolution of 2.1 eV is assumed for beamline 1A of the Photon Factory, at which the experiment was conducted.
UV Absorption Spectra of Adlayers of Trimethylgallium and Arsine
Authors: Sasaki Masahiro , Kawakyu Yoshito , Mashita Masao
Published: February 2005

The UV absorption spectra of trimethylgallium (TMG) and arsine adsorbed on silica were investigated. The spectrum of the physisorbed layers of TMG and arsine were similar to the corresponding vapor spectra. On the other hand, the spectrum of the chemisorbed TMG layer was quite different. from that of vapor. Arsine can be chemisorbed on the chemisorbed TMG layer, although it cannot be chemisorbed on silica. The spectrum of the co-chemisorbed layer, consisting of TMG and arsine, was found to extend greatly to longer wavelengths.
Simulation of Intrinsic Bistability in Resonant Tunneling Diodes
Authors: Baba Toshio , Mizuta Masashi
Published: February 2005

Intrinsic bistability occurring in resonant tunneling (RT) diodes is analyzed by the ensemble Monte Carlo simulation, which can handle the wave nature of electrons in RT structures. An unambiguous hysteresis in the current-voltage characteristic is revealed in an asymmetric AlGaAs/GaAs double barrier structure consisting of a thin barrier next to a cathode, a well and a thick barrier. This result strongly supports the existence of bistability as an intrinsic nature. This phenomenon is discussed in relation to dynamical electron accumulation in the well.
Off-Angle SiC(0001) Surface and Cu/SiC Interface Reaction
Authors: Nishimori Katsumi , Tokutaka Heizo , Nakanishi Shuuichi , Kishida Satoru , Ishihara Naganori
Published: February 2005

An off-angle SiC(0001̄)C surface showed an (1×1) LEED pattern. It was very different compared with the just angle surfaces of SiC(0001̄)C and SiC(0001)Si surfaces where they showed (3×3) and (√3× √3)R30° LEED patterns, respectively. A 5° off-angle SiC(0001̄)C surface can be cleaned by thermal annealing at 1000°C. Some silicide formations were observed from the system of Cu/SiC by thermal annealing at 200–300°C, but the Au/SiC system does not show any silicide reactions.
New Reaction Routes for Preparing Single-Phase Tl2CaBa2Cu2O8 and Tl2Ca2Ba2Cu3O10 Powders from Stoichiometric Mixtures
Authors: Wu Nae-Lih , Lee Sern-Nan , Yao Yeong Der
Published: February 2005

Single-phase Tl2CaBa2Cu2O8 and Tl2Ca2Ba2Cu3O10 powders were prepared from stoichiometric mixtures by the following two reactions: (1) CaBa2CuO4+Tl2O3+CuO→Tl2CaBa2Cu2O8 and (2) Tl2CaBa2Cu2O8+CaO+CuO→Tl2Ca2Ba2Cu3O10. Single-phase powders were obtained at 830°C for the first reaction, and at 870°C for the second reaction. At these temperatures, the extent of powder melting and the rate of Tl loss were small. Powders thus prepared showed superconducting temperatures (both the zero-resistivity and diamagnetic onset temperatures) of above 110 K and a saturation Meissner effect of 20% of (-1/4π) at a field of 20 G.
Ba1-xKxBiO3 Thin Film Preparation by ECR Ion-Beam Oxidation, and Film Properties
Authors: Enomoto Youichi , Murakami Toshiaki , Moriwaki Kazuyuki
Published: February 2005

Epitaxial films of Ba1-x
K
x
BiO3 are obtained in wide ranges of K substitution (0<x<0.8) by using an evaporator with an ECR-type oxygen ion source. The lattice constant has a minimum point at x=0.5. As-grown films on MgO and SrTiO3 substrates show superconductivity when the substrate temperature is about 500°C and x values range from 0.2 to 0.5. Optical reflection for the superconducting film has a plasma wavelength of about 700 nm.
Phonon Raman Spectroscopy in Bi2Sr2Ca1-xYxCu2O8+y
Authors: Sugai Shunji , Sato Masatoshi
Published: February 2005

The hole concentration dependence of the lattice vibrations in Bi2Sr2Ca1-x
Y
x
Cu2O8+y
was investigated by Raman spectroscopy. A full assignment of the vibrational modes in CuO5 pyramidal layers was made. The anisotropy between x and y is large for the phonon energies. On decreasing the hole concentration, the energy shifts of the vibrational modes of layered O atoms are larger than those of apical O atoms, which indicates that doped holes enter the layered O sites. The resonant enhancement of the Ag modes at 141 and 187 cm-1 and the B1g mode at 326 cm-1 indicates strong electronphonon interactions.
A New Anode-Electrode Structure for Sputter Deposition of High-Quality Y-Ba-Cu-O Thin Films
Authors: Kisu Takanobu , Ariyoshi Yuji , Enpuku Keiji , Yoshida Keiji , Takeo Masakatsu , Yamafuji Kaoru
Published: February 2005

A new structure of the anode electrode is presented for sputter deposition of Y-Ba-Cu-O thin films. The present anode electrode is expected to reduce the damage due to charged particles incident on the film surface. Using this method, high-quality films with very smooth surfaces and critical current density as large as j
C(4.2 K)=2.1×107 A/cm2 can be obtained reproducibly.
Cross-Sectional Transmission Electron Microscope Studies of Multilayered Bi-Sr-Ca-Cu-O Films
Authors: Ikeda Shozo , Sato Junichi , Nakamura Keikichi
Published: February 2005

Structures of the as-deposited and annealed Bi-O/Sr-Ca-Cu-O multilayered films with a designed period of 2.16 nm have been examined by a cross sectional TEM method. Although the as-deposited film is not superconducting, a clear Bi-O double layer/perovskite sandwich structure with a period of mostly 2.16 nm is observed. For the film annealed at 810°C, which is superconducting, a well defined modulated structure similar to that of the bulk-BSCCO is constructed. It is suggested that the formation of a clear modulation structure is responsible for the development of superconducting transition in the annealed films.
Critical Current Criterion in High-Tc Superconducting Films
Authors: Watanabe Kazuo , Kobayashi Norio , Yamane Hisanori , Kurosawa Hideyuki , Hirai Toshio , Kawabe Hisashi , Muto Yoshio
Published: February 2005

Critical current densities at 77.3 K obtained by a voltage criterion of 2 µV/cm were 5.6×105 A/cm2 at 0 T and 3.1×104 A/cm2 at 27 T for the best Y1Ba2Cu3O7-δ film prepared by chemical vapor deposition. Current-voltage curves were fitted by a power law of the form V∝I

n
with small n-values of 4–14. Since its n-value is 7 at 27 T, the J
c corresponds to 2.8×104 A/cm2 in the 1 µV/cm criterion and also to 2.0×104 A/cm2 in the 0.1 µV/cm one. In the critical current measurement for superconducting oxides, the n-value together with the criterion should always be described.
Preparation and Structure of Sr0.60Ca0.40CuO2 Single Crystals
Authors: Shigematsu Koji , Higashi Iwami , Hoshino Kazutomo , Takahara Hidefusa , Aono Masakazu
Published: February 2005

Single crystals of Sr0.60Ca0.40CuO2 have been grown from the same starting materials as for the crystal growth of high-T
c superconductors of the Bi-Sr-Ca-Cu-O system. The structure (C

m
c
m
; a=3.472(1), b=16.151(5), c=3.879(1) Å) is the same as that of SrCuO2, which can be described as a combination of Cu-O ladderlike chains and Sr-O bilayers. The Ca atoms are present at the Sr sites in a disordered state. The temperature dependence of the electrical resistivity of Sr0.60Ca0.40CuO2 shows that the material possesses semiconductorlike properties. It is confirmed that the proportion of Bi2Sr2CaCu2O8 (T
c=85 K) increases, while that of Bi2Sr2CuO6 (T
c=20 K) decreases upon annealing of the bulk solidified materials containing Sr0.60Ca0.40CuO2. It seems likely that Sr0.60Ca0.40CuO2 is a key material for promoting transitions among the three superconducting phases of Bi2Sr2Ca
n-1Cu
n
O4+2n
(n=1, 2, 3).
A New Method for Atomic-Layer-Controlled Molecular Beam Epitaxy of GaAs Exploiting the Desorption of the Excess Ga Atoms
Authors: Sugiyama Nao-haru , Isu Toshiro , Kamijoh Takeshi , Kajikawa Yasutomo , Katayama Yoshifumi
Published: February 2005

Atomic layer epitaxy of GaAs in a metal-source MBE system has been achieved by exploiting the self-limiting desorption mechanism that occurs in an alternating-source supply method with intervals. The growth rate per cycle is studied as a function of the time interval when Ga atoms of slightly more than one monolayer are deposited without As flux. The results confirm that only the excess Ga atoms are desorbed during the interval at an adequate substrate temperature and, as a result, just one monolayer of Ga atoms remains after a sufficient time interval. The PL spectrum shows that the quality of the ALE-grown GaAs layer is excellent.
Step-Flow Growth on Vicinal GaAs Surfaces by Migration-Enhanced Epitaxy
Authors: Yamaguchi Hiroshi , Horikoshi Yoshiji
Published: February 2005

The mechanism of step-flow growth on vicinal GaAs substrates during migration-enhanced epitaxy are studied using the reflection high-energy electron diffraction technique. Results show that the low As pressure during migration-enhanced epitaxy growth accelerates step-flow growth. In addition, it is also shown that monolayer terraces composed of surface Ga atoms are formed from step edges during the Ga deposition process. A GaAs/AlAs tilted superlattice is established using this growth technique. X-ray diffraction measurement and transmission electron microscopy observations show that the fabricated structure has periodic composition modulation along the axis tilted from the substrate azimuth.
Measurements of Copper Phthalocyanine Ultrathin Films by Scanning Tunneling Microscopy and Spectroscopy
Authors: Mizutani Wataru , Sakakibara Youichi , Ono Masatoshi , Tanishima Satoshi , Ohno Kousuke , Toshima Naoki
Published: February 2005

We have measured very thin films of copper phthalocyanine on graphite by means of scanning tunneling microscopy (STM) and spectroscopy (STS) in air. Microscopic surface structures, such as islands and grains, were found by STM. Among them, a sticklike island, with its edge parallel to the graphite lattice, suggested the epitaxial growth of the deposited film. Although the individual molecular shapes could not be obtained clearly, tunneling spectra taken simultaneously with STM provided information about the local distribution and orientation of the molecules.
Quantum Size Effects in Ge Microcrystals Embedded in SiO2 Thin Films
Authors: Hayashi Shinji , Fujii Minoru , Yamamoto Keiichi
Published: February 2005

By applying an rf co-sputtering technique, we have succeeded in producing Ge microcrystals in SiO2 thin films for which direct characterization by transmission electron microscopy is possible. As the size of the Ge microcrystals decreased from 6.5 to 2.7 nm, the optical extinction (absorption) spectra changed drastically. The structures corresponding to interband transitions in bulk Ge disappeared, and the onset of extinction shifted to higher energies. These spectral changes seem to arise from the three-dimensional confinement of electrons and holes in the microcrystals.
Improvement of Magnetohydrodynamic Stability and Beta Limit by Toroidal Plasma Current in Heliotron DR
Authors: Morimoto Shigeyuki , Yanagi Nagato , Ichiguchi Katsuji , Nakamura Yuji , Wakatani Masahiro , Sato Motoyasu , Obiki Tokuhiro , Iiyoshi Atsuo
Published: February 2005

The effect of toroidal plasma currents on magnetohydrodynamlc stability has been studied for the currentless ECH plasmas (n̄e=(2–3)×1019m-3,Teo=300–400 eV, <β>=0.35–0.5%) in Heliotron DR (R=0.9 m,ap∼0.07 m,B=0.5–0.6 T). It is shown that small plasma currents (\gtrsim500 A) which reduce vacuum rotational transform improve the MHD stability. The experimental result is explained theoretically by the change of the magnetic configuration due to the plasma current (position of =1 surface, shear, well).
Integrated Radiation Detectors with a-Si Photodiodes on Ceramic Scintillators
Authors: Itoh Haruo , Matsubara Sunao , Takahashi Tetsuhiko , Shimada Toshikazu , Takeuchi Hiroshi
Published: February 2005

Solid-state monolithic-type X-ray detectors were fabricated by preparing amorphous silicon photodiodes monolithically on a Gd2O2S ceramic scintillator. The X-ray detection sensitivity of the solid-state detectors was comparable to that of a xenon ionization detector. It could be improved by optimizing the amorphous silicon photodiode and the intermediate materials between the photodiodes and the scintillator. The performance of the X-ray detector did not deteriorate even after 500,000-roentgen irradiation.
A Device Modeling of Amorphous Silicon Based Tandem Solar Cells
Authors: Kida Hirotsugu , Itoh Masao , Fukazawa Shuichi , Ohta Toshitaka , Yamamoto Keiichi
Published: February 2005

A device model for amorphous silicon based tandem solar cells is presented for direct simulation of the characteristics of the tandem structure. The boundary condition for the tandem interface between cells as well as for the electrode-semiconductor interface is discussed. The model is implemented in the developed one-dimensional device simulator called AMO1. The existence of solution under the proposed boundary condition is demonstrated on numerical examples.
Tetragonal-to-Orthorhombic Transition and Disappearance of Superconductivity in the Pb-Doped Bi2Sr2CuOy System
Authors: Maeda Atsutaka , Kato Yusuke , Shibauchi Takasada , Nakajima Yasuyuki , Watanabe Hiroshi , Uchinokura Kunimitsu
Published: February 2005

A series of superconductors Bi2.1-x
Pb
x
Sr1.9CuO
y
with 0.05≤x≤0.5 were synthesized in polycrystalline form. Tetragonal to orthorhombic transition was found at around x=0.1. By the introduction of Pb, it was found that the average valence of Cu increases, whereas the superconducting transition temperature decreases. The system becomes more metallic with increasing x.
Space-Group Determination of a New Superconductor (Nd1-xCex)2(Ba1-yNdy)2Cu3O10-ε using Convergent-Beam Electron Diffraction
Authors: Tsuda Kenji , Tanaka Michiyoshi , Akimitsu Jun
Published: February 2005

The space group of a superconductor (Nd1-x
Ce
x
)2(Ba1-y
Nd
y
)2Cu3O10-ε
was determined to be I4/m
m
m by convergent-beam electron diffraction.
Effect of Neutron Irradiation on Tc of Pb-Doped BiSrCaCuO Superconductor
Authors: Herr Young-Hoi , Lee Kwang-Hee , Kim Chan-Joong , Lee Hee-Gyoun , Kim Chun-Taik , Hong Gye-Won , Won Dong-Yeon
Published: February 2005

A Pb doped BiSrCaCuO superconductor was irradiated in a TRIGA MARK III reactor up to a neutron fluence of 7.6×1017 n/cm2. The measured superconducting transition temperature (T
c) after irradiation was decreased to 92.5 K from nonirradiated data of 102 K. The fractional decrease of the T
c was compared with results fon other superconducting materials. Some recovery of irradiation-induced T
c decrease was observed.
Optical Nonlinearity Caused by Charge-Induced Field Screening in DC-Biased Quantum Well Structures
Authors: Kan Yasuo , Obata Katsuhiro , Yamanishi Masamichi , Funahashi Yoichi , Sakata Yasutaka , Yamaoka Yoshifumi , Suemune Ikuo
Published: February 2005

The optical nonlinear properties caused by charge-induced field screening are observed in dc-biased quantum well structures which are well designed to accumulate photo-excited carriers. The field-induced shift in the peak energy of the exciton absorption is systematically reduced with increasing intensity of the incident light. The rapid change of the absorption coefficient at a low optical power level (∼1 W/cm2) occurs, demonstrating a positive feedback due to the charge polarization. The switching energy and response time are estimated to be 4.6 fJ/µm2 and 460 ns, respectively.
Preparation of Plasma-Polymerized YbPc2 Films and Their Electrochromic Properties
Authors: Yamana Masao , Kanda Kouichi , Kashiwazaki Naoya , Yamamoto Motokazu , Nakano Tomoyasu , Walton C.
Published: February 2005

Ytterbium diphthalocyanine polymeric films for electrochromic displays were prepared by plasma polymerization. Various films were prepared by controlling the RF power and the rate of film deposition. Such films showed electrochromic characteristics comparable with those of a vacuum deposited film.
Effects of InP Surface Treatment on the Electrical Properties and Structures of AlN/n-InP Interface
Authors: Fujieda Shinji , Akimoto Koichi , Hirosawa Ichiro , Mizuki Jun'ichiro , Matsumoto Yoshishige , Matsui Junji
Published: February 2005

We investigated the effects of InP surface pretreatment on the electrical properties and structures of the MOCVD-AlN/n-InP interface. AlN films were deposited at 370°C on n-InP substrates after a thermal pretreatment in PH3 or AsH3 ambient. The frequency dispersion in the C-V (capacitance-voltage) characteristics of AlN/n-InP MIS diodes was suppressed by a thermal pretreatment in AsH3 ambient. The grazing incidence X-ray diffraction measurements revealed a 2×1 superstructure for the AsH3-pretreatment case at the interface between InP and AlN deposited at 220°C. The present results imply that AsH3 pretreatment should result in an As-terminated InP surface.
Growth of Single Crystals of Poly(vinylidene fluoride) under High Pressures
Authors: Ohigashi Hiroji , Hattori Takeshi
Published: February 2005

Lamellar crystals of poly(vinylidene fluoride) about 0.2 µm thick and 10 µm wide are grown in films crystallized at high pressures and high temperatures. Electron diffraction shows that the lamellar crystal is a β-form single crystal composed of all-trans extended chains. DSC and crystallization studies suggest that the β-form crystals are grown in the paraelectric or hexagonal phase which appears above 2.0 kb and 260°C in the heating process and above 2.0 kb and 210°C in the solidification process. The phase diagram of PVDF is proposed. The β-form film has distinctive ferroelectricity and strong piezoelectricity: P
r=100 mC/m2 and E
c=75 MV/m, and k
t=0.2.
Growth of InN on GaAs Substrates by the Reactive Evaporation Method
Authors: Sato Yuichi , Sato Susumu
Published: February 2005

InN films are epitaxially grown on GaAs substrates at 450°C by a rf-excited reactive evaporation method. The epitaxial relationship of (0001)InN//(111)GaAs is confirmed from transmission electron diffraction and X-ray diffraction measurements. The value of a full width at half-maximum of the double-crystal X-ray rocking curve for the (0002) diffraction is 17s. Surface morphologies of the InN films are also investigated by scanning electron microscopy.
Quick Focus Adjustment for Quadrupole Lens System to Form High-Energy Ion Microbeam
Authors: Kinomura Atsushi , Takai Mikio , Namba Susumu
Published: February 2005

A quick adjustment of quadrupole-lens excitation for a high energy ion microbeam was realized by a computerized knife-edge method using a secondary-electron intensity profile for a thin metal pattern on a silicon substrate delineated by lithography and lift-off techniques. Minimum processing time required for measurement of a beam profile with 64 data points was 0.3 s, which was shorter than any other method using a resist exposure or a secondary-electron image.
Gas Polarographic Hydrogen Sensor Using a Zirconia Electrolyte
Authors: Usui Toshio , Asada Akiyoshi , Nakazawa Mitsuhiro , Osanai Hiroshi
Published: February 2005

The hydrogen-sensing capability of a gas polarographic oxygen sensor using a zirconia electrolyte has been investigated at 450°C and 1 atm in H2-N2gas mixtures. The limiting current was realized in H2-N2gas mixtures due to the artificial hydrogen diffusion overpotential behavior at the anode, and is proportional to the hydrogen concentration up to 5% in H2-N2gas mixtures. This result proved that this oxygen sensor can also detect the hydrogen in H2-inert-gas mixtures.
Second-Order Piezoresistance Coefficients of n-Type Silicon
Authors: Matsuda Kazunori , Kanda Yozo , Suzuki Katuhisa
Published: February 2005

The nonlinear piezoresistance effect of n-type silicon was measured under <100 > and <110 > stresses at room temperature, from which the first- and second-order coefficients in stress were determined. Second-order piezoresistance expressions were deduced from a model based on the stress-dependent carrier transfer between the valleys. The experimental results are in fairly good agreement with the theoretical ones.
Si/SiOx/Si Hole-Barrier Fabrication for Bipolar Transistors Using Molecular Beam Deposition
Authors: Tatsumi Toru , Niino Taeko , Sakai Akira , Hirayama Hiroyuki
Published: February 2005

SiO
x
layers were deposited on Si substrates in a Si MBE system by codeposition of Si and O2. The oxygen concentration increased as the deposition temperature decreased and approached the results of SiO2 stoichiometry. O2 pressure was 5×10-5 Torr and the Si deposition rate was 0.2 Å/s. Composition was determined by using X-ray photoelectron spectroscopy and Auger electron spectroscopy, and the electric properties of its MOS capacitor were measured. The growth procedure used here offers high controllability in the thickness of the deposited SiO
x
layer and permits subsequent Si growth in the same Si-MBE chamber. Such Si/SiO
x
/Si structures, which may be applied to the hole-barrier between the base and emitter layers in a bipolar transistor, were also successfully grown using this method. The tunneling currents for electrons and holes in such structures with SiO
x
thickness of 5–60 Å were measured. One-order-larger tunneling currents for electrons than those for holes were measured at the same SiO
x
thickness above 30 Å.
Monte Carlo Simulation of Resonant Tunneling Diode
Authors: Baba Toshio , Al-Mudares Mustafa , Barker John R.
Published: February 2005

A new type of ensemble Monte Carlo simulation for the resonant tunneling diode is proposed. The wave nature of the electrons in the resonant tunneling structure (RTS), i.e., in barriers and well(s), is introduced, for which groups of electrons are regarded as wave packets. Unique features of wave-packet motion are characterized by transmission probability, tunneling and reflection delay time, and average position. Large charge build-up in the RTS in a resonant condition and the transition to the upper valley of the anode in a large bias condition are clearly produced, thus demonstrating usefulness of the present method.
Effect of Light Soaking Temperature on the Metastable Defect Distribution in Magnetron Sputtered Hydrogenated Amorphous Silicon Films
Authors: Bandyopadhyay A. K. , Banerjee Ratnabali , Batabyal A. K. , Barua A. K. , Okushi Hideyo , Tanaka Kazunobu
Published: February 2005

Light induced effects in hydrogenated amorphous silicon for different temperatures of light soaking were measured. The dark conductivity, photoconductivity and photoluminescence of the samples were measured prior to and after light soaking. The aim of this work is two-fold. One is to attempt to get a picture of the relative distributions of defect states for the films for different light soaking temperatures. The other is to check if the metastable effect is essentially a function of the soaking temperature alone or it depends upon the treatment history of the samples. Experimental results are explained by a conventional co-ordinate diagram taking into account the rate equation for the metastable defect formation, which involves both creation and annealing activation energies.
Mercury-Sensitized Hydrogen Radical Photoetching of Undoped Hydrogenated Amorphous Silicon and Crystalline Silicon
Authors: Nozaki Hidetoshi , Sakuma Naoshi , Ito Hiroshi
Published: February 2005

An etching study for undoped a-Si:H films and c-Si has been carried out by using Hg-sensitized H radicals in H2 gas under UV-light irradiation with a low pressure mercury lamp. It has been found that the etch rate of undoped a-Si:H increases with decreasing substrate temperature and H2 flow rate, as well as with increasing UV-light intensity. Concerning H2 gas pressure dependence, a maximum etch rate was observed at around 0.1 Torr. An adsorbed layer, composed of H2 molecules, H radicals, Hg atoms and photoexcited Hg atoms, can be considered to be formed on the surface. The adsorbed layer irradiated with UV light may supply a sufficient number of H radicals near the surface to rapidly cut off the Si network, leading to the formation of volatile SiH
x
.
High Frequency Characteristics of InAlAs/InGaAs HBT's
Authors: Fukano Hideki , Kawamura Yuichi , Asai Hiromitsu , Takanashi Yoshifumi
Published: February 2005

InAlAs/InGaAs heterojunction bipolar transistors (HBT's) grown by molecular beam epitaxy are fabricated. A cutoff frequency (f
T) of 52 GHz is achieved in the HBT's with a base thickness of 1000 Å. A decrease in f
T under a high collector current density condition is observed. This is attributed both to the base widening and base-collector capacitance increase caused by the electron space charge in the collector depletion layer.
Crystalline Phases Precipitated by Heat-Treatment of Rapidly-Quenched Glasses in the Bi-Ca-Sr-Cu-O System
Authors: Tohge Noboru , Tsuboi Shinzo , Tatsumisago Masahiro , Minami Tsutomu
Published: February 2005

The precipitation process of the superconducting phases from the rapidly-quenched glasses has been studied as a function of both heat-treatment temperature and time for the three main compositions in the Bi-Ca-Sr-Cu-O system: Bi2Ca2Sr2Cu3O
x
, BiCaSrCu2O
x
, and Bi2CaSr2Cu2O
x
. The temperature-time-transformation diagram for each composition has been constructed and a difference has been found between those for the former two compositions and that for the last one.
Observation of Microwave Magnetoabsorption in the High-TcPhase of a Bi(Pb)-Sr-Ca-Cu-O Superconductor
Authors: Nishida Akihiko , Horai Kazumi , Fujita Tetsuo , Sasakura Hiroyuki , Minamigawa Shinnosuke , Nakahigashi Kiyotaka
Published: February 2005

Microwave responses at 22.9 GHz of a high-TcBi(Pb)-Sr-Ca-Cu-O superconductor have been studied under magnetic fields up to 12 kG and temperatures of 4–130 K. The microwave magnetoabsorption curve systematically depends on the “magnetic history” after zero-field cooling. We show that the sharp change of microwave absorption in the low field range is not attributed to zero field ESR, but is probably caused by many Josephson junctions in the ceramic sample. By reducing contribution from Josephson junctions, the lower critical fieldHc1bcan be estimated from the magnetoabsorption curve.
Flux Creep in High Jc YBa2Cu3O7 Crystals
Authors: Murakami Masato , Morita Mitsuru , Koyama Noboru
Published: February 2005

Magnetic relaxation measurements have been performed on the YBa2Cu3O7 crystal fabricated by the quench and melt growth (QMG) process using a vibrating sample magnetometer at 77 K. An external magnetic field was applied and subsequently removed, and time decay of remanent magnetization was then monitored. It has been found that the flux creep rate of the QMG-processed samples is much smaller than that of single crystals.
Transport Current Path in Hot-Pressed Bi-Pb-Sr-Ca-Cu-O Superconductor
Authors: Murayama Norimitsu , Torii Yasuyoshi
Published: February 2005

The critical currents (I
c) of hot-pressed Bi0.85Pb0.15Sr0.8CaCu1.4O
y
ceramics with different cross-sectional areas were measured at 77 K in zero magnetic field. I
c was approximately proportional to the cross-sectional area. It seems that transport current flows uniformly across the cross-section of the sample.
Crystal Structure of New Oxide Superconductors, (Sm, Ba, Ce)8Cu6Oz, (Nd, Ba, Sr, Ce)8Cu6Oz, (La, Gd, Ba, Ce)8Cu6Oz and (La, Gd, Ba, Sr, Ce)8Cu6Oz
Authors: Wada Takahiro , Ichinose Ataru , Yaegashi Yuji , Yamauchi Hisao , Takana Shoji
Published: February 2005

The crystal structures of superconducting oxides, (Sm0.500Ba0.334Ce0.166)8Cu6O
z
, (Nd0.500Ba0.167Sr0.167Ce0.166)8Cu6O
z
, (La0.167Gd0.333Ba0.334Ce0.166)8Cu6O
z
, and (La0.167Gd0.333Ba0.167Sr0.167Ce0.166)8Cu6O
z
were analyzed using the Rietveld method for the powder X-ray diffraction patterns. All the crystal structures were of an oxide superconductor, (Eu, Ce)4(Eu, Ba)4Cu6O
z
, type. Gd atoms were found to preferentially occupy the A1 sites for Ce and Ln atoms in (Ln, Ce)4(Ln, Ba)4Cu6O
z
, and La and Sr atoms the A2 sites for Ba and Ln. A relationship between the bond valence sum for the Cu atom and the superconducting transition temperature was obtained.
Comparative Studies between Ag-Sheathed YBa2Cu3Oy Wires and Sintered YBa2Cu3Oy
Authors: Ishii Hideo , Hoshino Haruhiko , Hara Tsukushi , Nakamura Masaaki , Yamamoto Takahiko
Published: February 2005

Comparative studies of certain properties have been performed on Ag-sheathed YBa2Cu3O
y
wire and pressed and sintered YBa2Cu3O
y
. We found for our samples that the critical current density of the Ag-sheathed sample is more than five times larger than that of the sintered sample, whereas the superconducting volume fraction estimated from magnetic moment measurement is larger for the sintered sample. These contrariant results are discussed in relation to the microstructures of the samples observed by means of SEM images, exploring the way to further improvement of critical current density in the Ag-sheathed YBa2Cu3O
y
.
Y-Ba-Cu-O Film Growth by OMCVD Using N2O
Authors: Tsuruoka Taiji , Kawasaki Ryodo , Abe Hitoshi
Published: February 2005

By using N2O gas as an oxygen source, Y-Ba-Cu-O films prepared at the growth temperature of 650°C on the SrTiO3(100) substrate showed zero resistance at 79 K, while by using O2 gas, a growth temperature of 800°C was required to obtain the same film quality. The deposition rate of Y-Ba-Cu-O films on MgO(100) substrates by using N2O gas was nearly one half of that using O2 gas. The deposition rate monotonically increased with increasing of the growth temperature from 600°C to 800°C. The electrical quality of films prepared on the substrate became poorer in the series of SrTiO3(100), MgO(100) and Si(100) substrates. X-ray diffraction patterns of Y-Ba-Cu-O films grown on SrTiO3(100) and MgO(100) substrates indicate c-axis orientation, but those of films on Si(100) substrates did not indicate c-axis orientation.