bluuebunny/crossref_metadata_2025_split huggingface dataset:
GENERALISED PSEUDO-RIEMANNIAN GEOMETRY FOR GENERAL RELATIVITY
Authors: STEINBAUER R. , KUNZINGER M. 
Published: October 2002

The study of singular spacetimes by distributional methods faces the fundamental obstacle of the inherent nonlinearity of the field equations. Staying strictly within the distributional (in particular: linear) regime, as determined by Geroch and Traschen2 excludes a number of physically interesting examples (e.g., cosmic strings). In recent years, several authors have therefore employed nonlinear theories of generalized functions (Colombeau algebras, in particular) to tackle general relativistic problems1,5,8. Under the influence of these applications in general relativity the nonlinear theory of generalized functions itself has undergone a rapid development lately, resulting in a diffeomorphism invariant global theory of nonlinear generalized functions on manifolds3,4,6. In particular, a generalized pseudo-Riemannian geometry allowing for a rigorous treatment of generalized (distributional) spacetime metrics has been developed7. It is the purpose of this talk to present these new mathematical methods themselves as well as a number of applications in mathematical relativity.
A DISCRETE FULLY RECURRENT NETWORK OF SIGMOID UNITS FOR ASSOCIATIVE MEMORY AND PATTERN CLASSIFICATION
Authors: BROUWER ROELOF K. 
Published: October 2002

Fully recurrent networks have proven themselves to be very useful as associative memories and as classifiers. However, they are generally based on units that have binary states. The effect of this is that data to be processed consisting of vectors in [Formula: see text] have to be converted to vectors in {0, 1}mwith m much larger than n since binary encoding based on positional notation is not feasible. This implies a large increase in number of components. This effect can be lessened by allowing more states for each unit in our network.This paper describes two effective learning algorithms for a network whose units take the dot product of the input with a weight vector, followed by a tanh transformation and a discretization transformation in the form of rounding or truncation. The units have states that are in {0, 0.1, 0.2, …, 0.9, 1} rather than in {0, 1} or {-1, 1}. The result is a much larger state space given a particular number of units and size of connection matrix. Two convergent learning algorithms for training such a network to store fixed points or attractors are proposed. The network exhibits those properties that are desirable in an associative memory such as limit cycles of 1, attraction to the closest attractor and few transitions required to reach attractors. Since memories that are stored can be used to represent prototypes of patterns the network is useful for pattern classification. A pattern to be classified would be entered and its class would be the same as the class of the prototype to which it is attracted to which it is.
Two-dimensional Analysis of Resonant Tunneling Using the Time-dependent Schrödinger Equation
Authors: Hideaki Taniyama Hideaki Taniyama , Masaaki Tomizawa Masaaki Tomizawa , Akira Yoshii Akira Yoshii 
Published: October 2002

Numerical solution of the time-dependent two-dimensional Schrödinger equation is used here to analyze resonant tunneling in double-barrier structures. One-dimensional simulation is shown to be insufficient even for a system with a perfect barrier, which is regarded as one-dimensional because it does not include the two-dimensional effect attributed to the effective mass difference between the barrier and well regions. The effect of barrier roughness on tunneling characteristics is also analyzed and the transmitted fraction is calculated for various systems with different structural parameters, including the roughness of the barrier. Decomposition of the fraction into transverse momentum clarifies tunneling characteristics in two dimensions, and two-dimensional calculation is shown to be necessary for accurate analysis.
Effects of Plasma-Substrate Distance on Properties of Hydrogenated Amorphous Silicon Deposited from Hydrogen-Diluted Silane
Authors: Motoaki Kawase Motoaki Kawase , Takao Masuda Takao Masuda , Masayuki Nagashima Masayuki Nagashima , Taisuke Maki Taisuke Maki , Yasushi Miyamoto Yasushi Miyamoto , Kenji Hashimoto Kenji Hashimoto 
Published: October 2002

Hydrogenated amorphous silicon (a-Si:H) was prepared on substrates located away from rf plasma of hydrogen-diluted silane at 3 Torr. Physical and chemical structures of the films were changed by altering the distance between the plasma and the substrates. An optimum separation distance between the plasma and the substrates was found. The effects of substrate temperature and hydrogen dilution on film properties were also examined. The changes in film properties were explained by taking into account three types of film precursors: favorable radicals of lower sticking probability, unfavorable sticky ones and unfavorable polymerized ones.
Large-Diameter Reactive Plasma Produced by a Plane Electron Cyclotron Resonance Antenna
Authors: Takeshige Ishida Takeshige Ishida , Yukito Nakagawa Yukito Nakagawa , Takashi Ono Takashi Ono , Satoru Iizuka Satoru Iizuka , Noriyoshi Sato Noriyoshi Sato 
Published: October 2002

A large-diameter and uniform SF6 (sulfur hexafluoride) plasma is produced by a plane slotted antenna with permanent magnets for electron cyclotron resonance. The plasma is fairly homogeneous similarly to the case of an argon plasma, and the uniformity is within ±3% for a diameter of ∼20 cm at a distance of 20 cm from the antenna. Similar uniformity is obtained in the etching process of polysilicon. The etching rate is enhanced by the assistance of ion acceleration using the RF self-bias technique.
Effect of Isothermal Annealing on Crystallization Mechanism of Amorphous Ni65Cr16P19 Metallic Alloys
Authors: Kouji Maeda Kouji Maeda , Tetsuo Ikari Tetsuo Ikari , Yoshito Akashi Yoshito Akashi , Koji Futagami Koji Futagami 
Published: October 2002

Crystallization behavior of amorphous
Ni65Cr16P19 metallic
alloy during the isothermal annealing process from 617 K to 648 K
was studied using differential scanning thermal analysis and X-ray
diffraction analysis. Two crystallization peaks are observed.
The activation energies E
A for the crystallization
are determined
to be 403 kJ/mol and 306 kJ/mol for the first and the second peak,
respectively. Ni crystals precipitate in the first peak by a
two-dimensional crystallization mechanism with a constant nucleation
rate, and stable Ni3P crystallizes in the second peak. With the
use of the Avrami index, the activation energy for nucleation of
the Ni crystal is determined to be 470 kJ/mol.
Sputtering Behavior of Boron Using Electron Cyclotron Resonance Plasma
Authors: Yoshifumi Ito Yoshifumi Ito , Shunichi Kuriki Shunichi Kuriki , Masahiro Saidoh Masahiro Saidoh , Masahiro Nishikawa Masahiro Nishikawa 
Published: October 2002

Boron sputtering by plasma ions is investigated using electron cyclotron resonance (ECR) discharge of neon gas. The temperature of boron on an electrode during the discharge becomes high enough that the resistance of boron is sufficiently small in comparison with that of the plasma sheath in the application of negative voltage V. Ion current flowing from the plasma and the line emission from the sputtered boron are measured as a function ofVunder conditions of microwave input power 200–500 W and the neon gas pressure 1–10 mTorr. The sputtering yield at ion energyE=3 keV is about one order of magnitude larger than that atE=0.5 keV. Boron thin films are prepared by the sputtering method in the case ofV=-2 kV. The deposition rate normalized by the ion current is about 100 Å/s/A measured at a distance of about 2 cm from the boron surface.
Superparamagnetic Nanocomposite of Silver/Iron-Oxide by Inert Gas Condensation
Authors: Takao Yamamoto Takao Yamamoto , Robert D. Shull Robert D. Shull , Prabhakar R. Bandaru Prabhakar R. Bandaru , Frederic Cosandey Frederic Cosandey , Horst W. Hahn Horst W. Hahn 
Published: October 2002

A superparamagnetic nanocomposite of silver and iron oxide was synthesized by gas condensation. The procedure involved (1) coevaporation of silver and iron, (2) in situ oxidation of iron particles, (3) in situ compaction, and (4) post-annealing in an inert or an oxidizing atmosphere. The magnetization plots against H/T fell on a single curve from room temperature to 160 K, thereby providing evidence of superparamagnetism. Annealing treatment modifies the effective magnetic moment size and saturation value of magnetization. The present process is a potential synthesis route for magnetic nanocomposites useful for applications such as magnetic refrigeration, recording and permanent magnets.
Optical Properties of ZnSe/ZnMgSSe Single Quantum Wells Grown by Metalorganic Molecular Beam Epitaxy
Authors: Jun Suda Jun Suda , Yoichi Kawakami Yoichi Kawakami , Shizuo Fujita Shizuo Fujita , Shigeo Fujita Shigeo Fujita 
Published: October 2002

In this letter we report optical properties of ZnSe/ZnMgSSe single quantum wells (SQWs) grown by metalorganic molecular beam epitaxy (MOMBE). At 4.2 K, a 10.5 monolayer (30 Å) ZnSe SQW confined in Zn0.90Mg0.10S0.18Se0.82 layers exhibited intense purplish blue photoluminescence (PL) peaking at 2.865 eV, whose linewidth was as small as 5 meV. This emission was assigned to the n=1 heavy-hole exciton (E
x1hh). Another peak appeared on the low-energy side of E
x1hh under high excitation and grew nonlinearly with increasing excitation intensity. We tentatively attribute this line to the recombination of biexcitons. The exciton-longitudinal-optical(LO)-phonon coupling constant was also assessed from the temperature dependence of PL measurements.
Simple and Stable Single-Electron Logic Utilizing Tunnel-Junction Load
Authors: Hironobu Fukui Hironobu Fukui , Minoru Fujishima Minoru Fujishima , Koichiro Hoh Koichiro Hoh 
Published: October 2002

Novel tunnel-junction-load single-electron logic (SEL) was proposed, which is simpler than the complementary SEL and its output is more stable than that of the resistance-load SEL. We analyzed the static operation of a tunnel-junction-load inverter by examining the map of stability domains and the dynamic operation using the Monte Carlo simulation. As a result, it was found that the tunnel-junction SEL has sufficient gain when the temperature is under 4 mK, and operates properly even when two inverters having the same parameters are serially connected.
Mechanisms of the Deposition of Hydrogenated Carbon Films
Authors: Möller Wolfhard , Fukarek Wolfgang , Lange Klaus , Keudell Achim von , Jacob Wolfgang 
Published: October 2002

The paper reviews the elementary processes during the plasma-enhanced chemical vapour deposition of hydrogenated carbon films from methane, with special emphasis on the surface processes which determine the growth rate and film structure. Corresponding model calculations are critically discussed in comparison to experimental findings. Whereas a simplified plasma modeling can be performed with some reliability, only very limited information is available on the the surface physical and chemical mechanisms determining the growth rate as well as the stoichiometry and the structure of the deposited films. Proposed surface models involving widely different processes yield similar results and are thus indiscernible in comparison to results from deposition experiments. Nevertheless, reasonable fits to growth data can be obtained using a combined plasma-surface model. For the formation of film structure, recent ellipsometric data indicate that hydrogen chemistry might play a decisive role in addition to or rather than ion collisional effects.
Study of Gas Recycling in the GAMMA 10 Tandem Mirror Based on Numerical Model Calculations
Authors: Katsuhiko Tsuchiya Katsuhiko Tsuchiya , Yousuke Nakashima Yousuke Nakashima , Kiyoshi Yatsu Kiyoshi Yatsu , Mamoru Shoji Mamoru Shoji , Makoto Ichimura Makoto Ichimura , Naohiro Yamaguchi Naohiro Yamaguchi , Masaaki Inutake Masaaki Inutake , Teruo Tamano Teruo Tamano 
Published: October 2002

In this paper, we describe a gas recycling model based on atomic and molecular processes. This model assumes that hydrogen molecules cause various reactions with ions or electrons in a steady-state and uniform plasma. Enhancement of fuelling due to the recycling is evaluated on the basis of the calculated probabilities of neutral and ion production by using the rate coefficients of these reactions. For Ion cycrotron range of frequency (ICRF)-heated plasmas, the results derived from this model are compared with experimental results obtained by using pressure-balance equations and the experimental data. Good agreement is found between both results. This means that this model contributes to our understanding of the recycling mechanism in the GAMMA 10 tandem mirror device as well as in toroidal devices.
Formation and Characterization of GaAs Quantum Wires at Giant Step Edges on Vicinal (110) GaAs Surfaces
Authors: Misaichi Takeuchi Misaichi Takeuchi , Kazuhiro Shiba Kazuhiro Shiba , Kazuki Sato Kazuki Sato , Hu Kun Huang Hu Kun Huang , Koichi Inoue Koichi Inoue , Hisao Nakashima Hisao Nakashima 
Published: October 2002

We report the formation of GaAs quantum wires using giant step structure formed during molecular beam epitaxial growth of AlGaAs on vicinal (110) GaAs surfaces. Atomic force microscope observation indicates that the steps extend to over several µm and are coherently aligned. The growth of an AlGaAs/GaAs quantum well (QWL) on the giant step structure forms quantum wires (QWRs) along the step edges. Carrier confinement into the QWRs is caused by the increase of well width (well-width modulation) and the decrease of Al composition in the AlGaAs barriers (barrier-compositional modulation), which are confirmed by transmission electron microscope observation. Redshift and strong polarization parallel to the wire direction in the photoluminescence spectra support carrier confinement into the GaAs QWRs.
Possibility of High-Temperature Evaluation of Phase Coherent Length of Hot Electrons in Triple-Barrier Resonant Tunneling Diodes
Authors: Michihiko Suhara Michihiko Suhara , Riichiro Takemura Riichiro Takemura , Kazuhito Furuya Kazuhito Furuya 
Published: October 2002

To investigate the possibility of estimating hot electron phase coherence at high temperature, the current-voltage (I-V) characteristic of a triple-barrier resonant tunneling diode (TBRTD) is analyzed taking phase breaking into account. When the central barrier width is larger than 7 nm in GaInAs/InP TBRTD, the width of the peak in the I-V curve is determined predominantly by the phase breaking. Therefore the peak width provides the information of the phase coherent length of the hot electrons. It is shown that the phase coherent length can be estimated up to 100 K using TBRTD.
Phase-Change Optical Recording Films with AgInTe 2–Sb–Te System
Authors: Tatsuhiko Matsushita Tatsuhiko Matsushita , Akio Suzuki Akio Suzuki , Tomoki Nishiguchi Tomoki Nishiguchi , Keiji Shibata Keiji Shibata , Masahiro Okuda Masahiro Okuda 
Published: October 2002

Reversible optical change due to laser irradiation or thermal annealing in amorphous films of the composition triangle AgInTe2-Sb-Te is described. Distinctive features are that there are a composition H (Ag9In14Te37Sb40) representing the best cyclability (≈106) for static repetition tests and a composition L (Ag8In8Te46Sb38) showing the largest reflectivity difference (≈26%) between the as-deposited and the annealed states at λ=830 nm.
Electrical, Optical and Schottky Properties of AgGa(S1-xSex)2 System
Authors: Hiroaki Matsushita Hiroaki Matsushita , Osamu Shiono Osamu Shiono , Saburo Endo Saburo Endo , Taizo Irie Taizo Irie 
Published: October 2002

Crystals of the AgGa(S1-x
Sex)2 system have been prepared by the normal freezing method, and the compositional dependences of the electrical, optical and Schottky properties have been studied. Whereas the compositional dependences of the lattice constants a and c are linear, the optical band gap shows concave decrease. It is found that the electrical resistivity is reduced for all compositions by annealing in vacuum. The Schottky barrier of Al or Au contacts is formed in this system except for AgGaS2. The Schottky properties of annealed samples are much better than those of as-grown samples. The electron affinity of this system is considered to increase linearly with increasing composition x.
In Situ Epitaxial Growth of Superconducting Bi2-Sr2-Can-1-Cun-Oy (n=1, 2) Thin Films by Two-Target Magnetron Sputtering under High Pressure
Authors: Shin-ichi Karimoto Shin-ichi Karimoto , Keiichi Tanabe Keiichi Tanabe , Shugo Kubo Shugo Kubo , Koji Tsuru Koji Tsuru , Minoru Suzuki Minoru Suzuki 
Published: October 2002

In situ superconducting thin films of Bi2-Sr2-Ca

n-1
-Cu

n

-O

y

(n=1,2) are grown epitaxially on S
r-T
i-O
3 (100) and MgO (100) substrates by two-target rf magnetron sputtering under a high pressure of 0.5 Torr. During growth, film deposition materials are supplied alternately from Bi2-Sr2-Cu1.3-O

y

and Ca-Cu-O

y

targets to control the number of C
u
O
2 layers. It is demonstrated that a sputtering gas pressure higher than 0.3 Torr effectively reduces the compositional deviation, which is normally caused by the resputtering effect. It is also demonstrated that alternate deposition from the two targets leads to controlled epitaxial growth with the c-axis perpendicular to the substrate. As grown epitaxial films thus prepared exhibit superconductivity at a T
c as high as 79 K for B
i
2-S
r
2-C
a-C
u
2-O

y

films and 8 to 11 K for B
i
2-S
r
2-C
u-O

y

films.
Observation of In Growth Modes on Si(111)-√3×√3-Ga Using an Ultrahigh-Vacuum Scanning Electron Microscope
Authors: Naoharu Shimomura Naoharu Shimomura , Toshiro Yamanaka Toshiro Yamanaka , Shozo Ino Shozo Ino 
Published: October 2002

Epitaxial growth of In layer on Si(111)-√3×√3-Ga was observed using an ultrahigh-vacuum scanning electron microscope (UHV-SEM). √3×√3-Ga (1/3 ML) and √3×√3-Ga [(1/3+2/3) ML] surfaces were prepared. The latter was formed by deposition of 2/3 ML of Ga on the √3×√3-Ga (1/3 ML) surface at room temperature. After 2 ML of In were deposited on the √3×√3-Ga (1/3 ML) surface, √7×√7 and √3×√3 structures appeared. These structures were clearly observed in the SEM images. Around the steps, ditches were observed. At the In thickness of 6 ML, flat islands with various thicknesses were observed. When 2 ML of In were deposited on the √3×√3-Ga [(1/3+2/3) ML] surface, √3/2×√3/2 structure appeared. All the terraces showed the same number of atomic layers without steps. For further In deposition the terraces had various thicknesses which differed stepwise by one atomic layer.
Effect of Surface Material on Spatiotemporal Structure in O 2 RF Glow Discharge
Authors: Mari Shibata Mari Shibata , Toshiaki Makabe Toshiaki Makabe , Nobuhiko Nakano Nobuhiko Nakano 
Published: October 2002

The influence of the electrode material on O2 radio-frequency discharge structure is investigated using the relaxation continuum (RCT) model. The discharges considered in this study are self-sustained between parallel plates with spacing of 2 cm at 13.56 MHz. The spatiotemporal discharge structure for the pressure of 1.0 Torr and the sustaining voltage of 100–300sin
ωt V is calculated. The results are discussed for two types of material differing in the surface recombination probability of atomic oxygen γ. When γ is changed from 0.015 to 0.001, the number density of atomic oxygen increases and the distribution has less spatial dependence. As a result, the rate of the electron detachment caused by the collision between O- and O increases, and the plasma density and the density ratio of the negative to positive ions decrease. The change of the material surface also affects the fluxes of positive ions and atomic oxygens to the electrode at a fixed sustaining voltage. The influence of the surface on the dissipated power is also discussed.
Fabrication of Lateral Tunnel Junctions and Measurement of Coulomb Blockade Effects
Authors: Wolfram Langheinrich Wolfram Langheinrich , Haroon Ahmed Haroon Ahmed 
Published: October 2002

In order to operate single-electron devices at high temperatures, a fabrication process for laterally arranged double tunnel junctions is presented. The dimensions of the island can be reduced relatively easily down to the resolution limit of lithography, resulting in extremely low capacitances. The basic idea of the fabrication process is a very thin metallic nanowire which is made discontinuous by means of a sharp-edged groove in the substrate. Tunnel junctions are formed at either edge of the groove, and the tunnel barrier gap can be adjusted via the depth of the groove and the deposition parameters of the metal film. Coulomb blockade was observable, which is persistent up to temperatures above 77 K.
Fabrication of 10-Nanometer-scale GaAs Dot Structures by In Situ Selective Gas Etching with Self-Assembled InAs Dots as a Mask
Authors: Go Yusa Go Yusa , Hiroshi Noge Hiroshi Noge , Yutaka Kadoya Yutaka Kadoya , Takao Someya Takao Someya , Tadatomo Suga Tadatomo Suga , Pierre Petroff Pierre Petroff , Hiroyuki Sakaki Hiroyuki Sakaki 
Published: October 2002

We report on a novel method of fabricating 10-nm-scale GaAs dot structures using molecular beam epitaxy and in situ gas etching. Self-assembled nanometer-scale InAs dots are formed first and are used as masks for the subsequent etching of GaAs by Cl2 gas. In this approach, we also make use of HCl gas etching to remove selectively the InAs wetting layer as well as the InAs dots to yield clean and strain-free GaAs dot structures. The height and base diameter of resultant GaAs dots are studied by atomic force microscopy and found to be 10±2 nm and 30±5 nm, respectively.
Ultraviolet Electroluminescent Diode Utilizing Poly(methylphenylsilane)
Authors: Akihiko Fujii Akihiko Fujii , Kenji Yoshimoto Kenji Yoshimoto , Masayoshi Yoshida Masayoshi Yoshida , Yutaka Ohmori Yutaka Ohmori , Katsumi Yoshino Katsumi Yoshino 
Published: October 2002

Electroluminescent (EL) diode utilizing poly(methylphenylsilane) (PMPS) has been fabricated and its optical and electroluminescent characteristics have been investigated. We have succeeded in demonstrating ultraviolet emission at 353 nm from the PMPS EL diode for the first time.
Current vs Voltage Characteristics of Al–Al 2O 3–Pd Tunnel Junction Hydrogen Sensor
Authors: Sumio Okuyama Sumio Okuyama , Katsuro Okuyama Katsuro Okuyama , Nobuyuki Takinami Nobuyuki Takinami , Koichi Matsushita Koichi Matsushita , Yasuji Kumagai Yasuji Kumagai 
Published: October 2002

The conduction mechanism of an Al–Al2O3–Pd MIM (metal-insulator-metal) junction which can operate as a hydrogen gas sensor was investigated using the logarithmic derivative of the current curve, Fowler-Nordheim plot and temperature dependence of the junction current. Al–Al2O3–Pd junctions showed current-voltage characteristics typical of tunneling conduction at voltages above 3 V. The barrier height of the Pd-Al2O3 contact obtained from the position of the logarithmic derivative maximum of the current was 3.4 eV in vacuum, and decreased to 2.7 eV upon introduction of 40 Pa hydrogen. On the other hand, the barrier height of the Al–Al2O3 contact was 1.8 eV in vacuum and was unchanged even when 40 Pa of hydrogen gas was introduced.