bluuebunny/crossref_metadata_2025 huggingface dataset:
THERMODYNAMICS OF NUCLEATION AND GROWTH
Authors: TROMP RUUD M. , HANNON JAMES B.
Published: October 2002

Nucleation and growth are often discussed in terms of kinetics, i.e. the adsorption of atoms from the gas phase or a solution onto a surface, the diffusion of these atoms on that surface, and their attachment to a growing nucleus, island or layer. In recent years, scanning tunneling and atomic force microscopy studies have tremendously improved our understanding of such kinetic processes for a wide range of materials. At relatively low temperatures where diffusion is slow, and where typical deposition rates result in adatom concentrations that far exceed the equilibrium concentration of adatoms on the surface, growth is indeed controlled by irreversible atomic scale kinetics. But at higher temperatures this is not necessarily the case. Indeed, the equilibrium concentration of adatoms can be so high that it is only slightly increased by an external flux. Diffusion can be so fast that spatially separated regions on the surface interact on a time scale that is not slow relative to the growth process. In such cases reversible, collective phenomena are more important than individual atomic events, and thermodynamics is more important than kinetics. In this paper we examine a number of cases related to nucleation and growth on surfaces, where a deep and quantitative insight into the growth process can be obtained by detailed consideration of the thermodynamics involved. It is our hope that this paper will help to bring about a balanced understanding of these phenomena, where kinetics and thermodynamics are two poles on a continuum with an importance that depends on the particulars of each experiment.
DOUBLE ATOMIC LAYERS OF GRAPHENE/MONOLAYER h-BN ON Ni(111) STUDIED BY SCANNING TUNNELING MICROSCOPY AND SCANNING TUNNELING SPECTROSCOPY
Authors: KAWASAKI TOYOSEI , ICHIMURA TAKASHI , KISHIMOTO HIROSHI , AKBAR ADE ASNEIL , OGAWA TAKASHI , OSHIMA CHUHEI
Published: October 2002

Using STM, we have directly confirmed the incommensurate stacking of double atomic layers of graphene and monolayer h-BN on Ni(111). The formation of a graphene layer weakens the interfacial interaction between monolayer h-BN and Ni(111), resulting in insulating h-BN layers, while a pristine monolayer h-BN on Ni(111) is metallic. The STS spectra of the double atomic layers showed a tunneling character with a band gap of 0.5 eV.
INTERFACIAL OXIDE LAYERS AT THE METAL–OXIDE PHASE BOUNDARY
Authors: NETZER FALKO P.
Published: October 2002

The nature of oxide phases at metal–oxide interfaces, i.e. of oxide layers in the proximity of a metal surface, is assessed by critically examining the available data in the literature. The data reveal a trend towards the formation of reduced oxide phases with lower oxidation states in the vicinity of the interface with a metal. The physical origin of these interface-stabilized oxide layers is discussed and the possible causes include strong metal–metal bonding, high oxygen affinity of the substrate metal, reduction of the interfacial strain, and the stability of two-dimensional oxide phases.
HUGE MAGNETOVOLUME EFFECT IN AN INVERTED Mn LAYER ON Ag(001) STUDIED BY LEED
Authors: SCHIEFFER P. , KREMBEL C. , HANF M.-C. , GEWINNER G. , GAUTHIER Y.
Published: October 2002

The surface structure obtained by deposition of a Ag monolayer on the ideal c(2 × 2) antiferromagnetic Mn monolayer on Ag(001) at 100 K and subsequent annealing at room temperature is determined by low energy electron diffraction. It is established that this system is actually a good realization of an inverted monolayer, i.e. a pseudomorphic Ag/Mn/Ag(001) structure that corresponds to a reversed composition of the two topmost layers with respect to the Mn overlayer. The Ag–Mn and Mn–Ag interlayer distances, d12 = 1.97 ± 0.015 Å and d23 = 1.97 ± 0.02 Å respectively, indicate only a fairly small contraction of ~ 3.5% (~ 1.5%) with respect to the ideal Ag bulk lattice (Mn monolayer on top) as compared to ~ 10% expected from atomic radii in bulk Mn and Ag. This clearly reveals a spectacular magnetovolume effect related to the high spin state of Mn in this two-dimensional structure.
North Electricity Board: A Case of Restructuring in the Indian Power Industry
Authors: Gurtoo Anjula
Published: October 2002

The State Government of one of the largest states of India restructured its financially unviable electric utility - North Electricity Board (NEB) - into three independent corporations and announced its plans for subsequent privatization of NEB. The State Government argued for initiation of restructuring and privatization as a move to attract capital investments for meeting the growing demand and make the entire operations financially viable. An 11-day strike by the employees, which occurred as a response to the initiation of this radical organizational change, was the largest ever in the last 25 years of Indian labor history. The employees united under one umbrella employees association and negotiated with the government. Despite nation-wide support for the employees and the wholehearted unification of the employees, the strike ended with the acceptance of trifurcation by their union leaders. The dynamics involved in the process of restructuring and the employees' strike highlight the political and economic motivations of the various stakeholders in this organizational change process. In view of this, the issue facing the organization, post-strike, is how to get out of this current unpleasant situation and move forward.
THE EFFECTS OF NICOTINE ON FRACTURE HEALING: AN EXPERIMENTAL STUDY
Authors: Agca Mustafa , Tuncay Ibrahim , Tosun Nihat , Akpinar Fuat
Published: October 2002

This study is aimed to evaluate treatment research the effects of nicotine on fracture healing. Thirty rats were used. Nicotine was injected subcutanously at a dosage of 2 mg/kg/day to group A and 4 mg/kg/day to group B. Control group (group C) received 0.5 ml/kg/day saline solution.

Three weeks later, transverse fractures were performed on to the left ulnar and radial bones for each animal. Animals were designed to one of two follow-up groups which were euthanized either 2 or 3 weeks. On the 14th day of fracture, randomly chosen five rats from each group of A, B and C were sacrificed. At the 21st day of fracture, same procedure performed for all remaining rats. Both had surgical and histopathological evaluation were performed. Transverse fractures performed on the 21st day of study were confirmed by direct radiograms. One rat died spontaneously before completing the study was therefore excluded from the final analysis.

The results indicate that healing process proceeds in each group. There was no significant difference in fracture healing between groups A and B two weeks after the fracture. However, fracture healing was significantly delayed in nicotine treated group comparing to control group. We continue to support the notion that nicotine has a negative effect on fracture healing.
Does Index Futures Dominate Index Spot? Evidence from Taiwan Market
Authors: Lin Ching-Chung , Chen Shen-Yuan , Hwang Dar-Yeh , Lin Chien-Fu
Published: October 2002

By utilizing vector error correction model (VECM) and EGARCH model, this article uses 5-minute intraday data to examine the interaction of return and volatility between Taiwan Stock Exchange Capitalization Weighted Stock Index (TAIEX) and the newly introduced TAIEX futures. VECM model shows that there exists bi-directional Granger causality between index spot and index futures markets, but spot market plays a more important role in price discovery. The results of impulse response function and information share indicate that most of the price discovery happens in index spot market. The evidence of EGRACH shows that the impacts of spot and futures innovations are asymmetrical, and the volatility spillovers between spot and futures markets are bi-directional. However, the information flow from spot to futures is stronger. These results suggest that the TAIEX spot market dominates the TAIEX futures market in terms of return and volatility.
NASH EQUILIBRIA IN LOAD BALANCING IN DISTRIBUTED COMPUTER SYSTEMS
Authors: ALTMAN EITAN , KAMEDA HISAO , HOSOKAWA YOSHIHISA
Published: October 2002

The use of game theoretical techniques has been quite successful in describing routing in networks, both in road traffic applications as well as in telecommunication networks applications. We study in this paper a third area of applications of such games, which is load balancing in distributed computer systems. One of the most important questions that arise in all applications of routing games is the existence and uniqueness of equilibrium. Whereas the existence of Nash equilibrium is known for general models of networks under weak assumptions, uniqueness results are only known for very special applications, i.e., either for very special cost functions or for very special topologies. We establish in this paper the uniqueness of an equilibrium for routing games with topologies that model well distributed computer systems, under quite general assumptions on the costs.
EXISTENCE AND UNIQUENESS OF BLOW-UP SOLUTIONS FOR A CLASS OF LOGISTIC EQUATIONS
Authors: CÎRSTEA FLORICA-CORINA ŞT. , RĂDULESCU VICENŢIU D.
Published: October 2002

Let f be a non-negative C1-function on [0, ∞) such that f(u)/u is increasing and [Formula: see text], where [Formula: see text]. Assume Ω ⊂ RNis a smooth bounded domain, a is a real parameter and b ≥ 0 is a continuous function on [Formula: see text], b≢0. We consider the problem Δu+au =b(x)f(u) in Ω and we prove a necessary and sufficient condition for the existence of positive solutions that blow-up at the boundary. We also deduce several existence and uniqueness results for a related problem, subject to homogeneous Dirichlet, Neumann or Robin boundary condition.
SYMMETRY BREAKING OF EXTREMAL FUNCTIONS FOR THE CAFFARELLI– KOHN–NIRENBERG INEQUALITIES
Authors: BYEON JAEYOUNG , WANG ZHI-QIANG
Published: October 2002

For the Lp(p > 1) version of the Caffarelli–Kohn–Nirenberg inequalities we prove a symmetry breaking result for the extremal functions.
FRANK STARLING MECHANISM ON ALTERNATING PUMP VENTRICULAR MODELS
Authors: ZANNOLI ROMANO , SORBELLO S. , CORAZZA I. , PEPE G. , LEPERA G. , BRANZI A.
Published: October 2002

An alternating pump system simulating the left ventricle in a mechanical cardio-vascular model, has been modified to show Frank Starling regulating mechanism. An inextensible thin plastic wall chamber has been put around the syringe's core and connected to the internal syringe's chamber by two lateral holes. During the filling and the expulsion phases the external chamber changes his volume and the net output depends on the filling pressure.

The regulating mechanism shows a beat to beat response and the dependence of systolic aortic pressure, systolic ventricular work, stroke output with respect ventricular filling pressure show a "physiological" behavior.

This solution will be introduced in the mechanical whole model to study the changes of aorto-ventricular interaction by changing aortic compliance.
A LICENSE MANAGEMENT MODEL FOR PEER-TO-PEER MUSIC SHARING
Authors: KWOK S. H. , LUI S. M.
Published: October 2002

The popularity of peer-to-peer (P2P) file sharing software has created a pressing need for digital music providers to resolve copyright and piracy problems of disseminating digital music through the Internet. Digital Rights Management (DRM) technology ensures protection of rights for distributed music over the Internet. Existing DRM systems emphasize protection based on business-to-consumer (B2C) distribution model, but do not tackle protection on a consumer-to-consumer (C2C) distribution model. This paper proposes a license management model to support not only typical music distribution models from music distributor to consumer (B2C), but also peer consumer to peer consumer (C2C) distribution model. The proposed license management model consists of two types of licenses, namely official licenses and peer licenses. These licenses are to be implemented in XrML. The concepts of these licenses facilitate both B2C and C2C distribution models. Functionality tests of the proposed model with certain common peer-to-peer sharing activities have been conducted.
CALCULATING ACCURATE REDOX POTENTIALS IN ENZYMES WITH A COMBINED QM/MM FREE ENERGY PERTURBATION APPROACH
Authors: FORMANECK MARK S. , LI GUOHUI , ZHANG XIAODONG , CUI QIANG
Published: October 2002

An approach for computing accurate redox potentials in enzymes is developed based on the free energy perturbation technique in a QM/MM framework. With an appropriate choice of the QM level and QM/MM coupling scheme, the intermolecular interaction between the redox center and the protein environment can be adequately described; the speed of QM/MM methods also allows a sufficient configurational sampling for the convergence of free energy derivatives. Following the implementation into the simulation package CHARMM, the method was tested with an application to the first reduction potential of FAD in cholesterol oxidase (Chox). In addition to an accurate QM level and adequate conformational samplings, the effect of long-range electrostatic interactions due to the bulk solvent was also found to be essential. Using a semi-empirical density functional theory (SCC-DFTB) as the QM level, and a multi-stage charge-scaling scheme based on Poisson–Boltzmann calculations for the solvation effect, satisfactory agreements with experimental measurements were obtained. The study of Chox also indicates that large errors in the calculated redox potential might arise if changes in the conformational properties of the protein during the redox process are not taken into account, such as in energy minimization type of studies based on only the X-ray structure of the enzyme in one redox state.
ELECTRONIC DELOCALIZATION: A QUANTITATIVE STUDY FROM MODERN AB INITIO VALENCE BOND THEORY
Authors: MO YIRONG , SONG LINGCHUN , WU WEI , CAO ZEXING , ZHANG QIANER
Published: October 2002

An ab initio spin-free valence bond code called Xiamen-99 has been developed based on an efficient algorithm called paired-permanent-determinant approach, where Hamiltonian and overlap matrix elements are expressed in terms of paired-permanent-determinants. With this tool, we probed the electronic delocalization phenomenon in a few typical examples including benzene, formamide and ethane. Our computations revealed that ab initio valence bond methods are able to estimate the energetic contribution from the delocalization effect to the stabilization of molecules, thus pave the way to illuminate the resonance theory at the quantitative level. In particular, we analyzed the cyclic electronic delocalization in benzene and showed that different understandings on the resonance may originate from the different usage of one-electron orbitals in the valence bond theory. Our investigation into the hyperconjugative interaction in ethane demonstrated that the hyperconjugation effect is not the dominating factor in the preference of the staggered conformer of ethane.
PROTEIN STRUCTURE: INSIGHTS FROM GRAPH THEORY
Authors: VISHVESHWARA SARASWATHI , BRINDA K. V. , KANNAN N.
Published: October 2002

The sequence and structure of a large body of proteins are becoming increasingly available. It is desirable to explore mathematical tools for efficient extraction of information from such sources. The principles of graph theory, which was earlier applied in fields such as electrical engineering and computer networks are now being adopted to investigate protein structure, folding, stability, function and dynamics. This review deals with a brief account of relevant graphs and graph theoretic concepts. The concepts of protein graph construction are discussed. The manner in which graphs are analyzed and parameters relevant to protein structure are extracted, are explained. The structural and biological information derived from protein structures using these methods is presented.
DC Discharge Enhancement of Chemical Activity in Laser-Produced Plasma
Authors: Liu Daming , Jiao Shuliang , Guan Wenjie , Zhiliang Lei Zhiliang Lei , Zaiguang Li Zaiguang Li
Published: October 2002

Using an optical spectroscopy analyzer (OSA), the emission spectra of XeCl-excimer-laser-produced plasma near a YBa2Cu3O7-x(YBCO) target surface were measured. The difference of the emission spectra with and without dc glow discharge was investigated. The results show that dc glow discharge plasma can significantly increase the emission intensity of atomic oxygen and increase emission intensities of atomic ions, but there are no obvious effects for metal atoms and metal oxides. Enhancement of chemical activity of the laser plasma with dc discharge may be due mainly to the increase of concentration of atomic oxygen.
Modulation Dependence and Mechanism of Microwave Absorption in Granular YBa2Cu3Ox
Authors: Tamio Endo Tamio Endo , Haodong Yan Haodong Yan
Published: October 2002

Modulation dependence of microwave absorption (MA) was measured on a ceramic, YBa2Cu3O

x

, at 77 K under a magnetic field to investigate the mechanism of the modulated MA signal in granular superconductors. The three factors of current transition region (CT), number of vortices (VN) and surface slope of the flux (SS) are proposed to interpret the signal. CT is based on the existence of the transition region of the shielding currents in the specimen where MA is smaller. VN is based on the absorption by vortices, and SS on the surface slope of flux distribution. The increasing behaviour of the signal with increasing modulation field (H
m) depends fundamentally on VN. The signal behaviour is dominated by CT in the small H
m regime and by SS in the large H
m regime. CT- and SS-factors are derived from the shielding current mechanism.
Advanced 1.55 µm Quantum-Well GaInAlAs Laser Diodes with Enhanced Performance
Authors: Borchert Bernd , Roland Gessner Roland Gessner , Bernhard Stegmüller Bernhard Stegmüller
Published: October 2002

The fabrication and characteristics of advanced 1.55 µ m quantum-well GaInAlAs laser diodes are presented. The strained layer laser structures were grown by metal organic vapor phase (MOVPE). By employing InP-cladding layers and an etch-stop layer, ridge-waveguide lasers with different longitudinal resonator types were processed by conventional chip technology. The following characteristics have been obtained, which mostly represent best values for 1.55 µ m GaInAlAs laser diodes: for Fabry-Perot (FP) lasers, cw operation at 130°C and a characteristic temperature of 95 K were observed; maximum output power was 46 mW; and the 3 dB bandwidth as high as 17 GHz. Gain-coupled distributed feedback (DFB) lasers with an absorptive grating show a single-mode yield about 75%, their 3 dB bandwidth being 11 GHz. Two-section gain-coupled DFB devices were continuously tunable over 3 nm. For negatively detuned index-coupled DFB devices an ultrahigh 3 dB bandwidth of 18.5 GHz was measured. All these characteristics are comparable to those of 1.55 µ m InGaAsP ridge-waveguide lasers. We report for the first time, the broad-area folded-cavity surface-emitting lasers using GaInAlAs which exhibit a threshold current density of 2 kA/cm2.
Relationship between Molecular Structure of a Doped Dye and the Extent of Laser-Induced Hole Filling in Photochemical Hole-Burning
Authors: Horie Norio Murase
Published: October 2002

This paper reports that the extent of laser-induced hole filling (LIHF) in photochemical hole burning (PHB) is related to the molecular structure of a doped dye. We measured the extent of LIHF for disodium mesoporphyrin (MPS) doped into poly(vinyl alcohol) (PVA) at 20 K, and found it to be smaller than for sulfonated tetraphenylporphine (TPPS) doped into PVA at 20 K. The MPS molecule is flatter, lighter, and more rigid than the TPPS molecule. These features decrease the number of energy levels in the ground state S0 and in the electronically excited state S1 of the dye, resulting in an increase in the site-selectivity in PHB. This causes the smaller extent of LIHF for the MPS system.
Electroluminescent Behaviors in Multilayer Thin-Film Electroluminescent Devices Using 9,10-Bisstyrylanthracene Derivatives
Authors: Aminaka Ei-ichiro , Tetsuo Tsutsui Tetsuo Tsutsui , Shogo Saito Shogo Saito
Published: October 2002

Using nine 9,10-bisstyrylanthracene derivatives (BSA's) with different substituents as emission layer materials, multilayer electroluminescent (EL) devices were fabricated. Among nine BSA's, three BSA's were found to exhibit high EL performance. Four types of devices, a single-layer device with a BSA emission layer, two types of two-layer devices in which BSA emission layers were combined with a triphenylamine dimer as a hole transport layer or an oxadiazole derivative as an electron transport layer, and a three-layer device, were fabricated using the three BSA's. The relationships between the device structures and EL performances of these devices were studied. Ionization potential values in vacuum-deposited films of BSA's were measured. It was found that the introduction of an electron withdrawing group increased electron injection/transport capability, and that of electron donating groups increased hole injection/transport capability. The relative EL efficiencies of various devices were discussed in terms of the electronic nature of BSA's.
High-Resolution Electron Microscopy of Extended Defects in Wurtzite Crystals
Authors: Kunio Suzuki Kunio Suzuki , Masaki Ichihara Masaki Ichihara , Shin Takeuchi Shin Takeuchi
Published: October 2002

Lattice defects in five wurtzite crystals, ZnO, BeO AlN GaN and InN, have been studied by high-resolution electron microscopy for samples pulverized at room temperature. High-density stacking faults were produced in BeO and GaN. With the weak-beam technique, dissociation of basal dislocations was observed in BeO. By high-resolution lattice image observation, both dissociated and undissociated 60°-dislocations were observed in ZnO, AlN and InN. Stacking fault energies were estimated from the separation of partials to be 0.10±0.02 J/m2 in ZnO, 0.041±0.009 J/m2 in BeO, 0.22±0.07 J/m2 in AlN and 0.041±0.008 J/m2 in InN. Stacking fault energies in wurtzite crystals have been correlated with the c/a ratio of the crystals. a+c dislocations climb-dissociated along the basal plane were also observed in ZnO and BeO.
Study of Epitaxial Growth of Rotational-Twin-Free CaF2 Films on Si(111)
Authors: Ohmi Shun-ichiro , Kazuo Tsutsui Kazuo Tsutsui , Seijiro Furukawa Seijiro Furukawa
Published: October 2002

It was shown that the 2-step growth method is very effective for growing rotational-twin-free CaF2 films on Si(111) which is called type-A. Experimental study of the effect of thickness of the first layer in the 2-step growth method revealed the thickness of a first grown layer more than about 8 monolayers (ML) was necessary to obtain uniform type-A CaF2 films, and that mixed or uniform type-B CaF2 if it is less than 4 ML. A growth model in which the 1st layer must be rotated around the normal axis of Si(111) during the substrate temperature elevation just before the 2nd step growth if the 1st layer is less than 4 ML is proposed.
Monte Carlo Simulation of Secondary Electron Emission from Rough Surface
Authors: Ohya Kaoru , Kawata Takayuki Itotani
Published: October 2002

The surface roughness effect on the secondary electron yield, as well as the energy and angular distributions of emitted electrons, is investigated using a direct Monte Carlo simulation of the secondary electron emission from aluminum with a sinusoidal ripple surface. By introducing the roughness into the calculation, the electron yield for normal incidence increases. A low-energy shift of the energy distribution and an angular distribution, being different from the cosine distribution are calculated.
Residual Aberrations and Beam Trajectories of Electron Beam Reducing Image Projection System with Dynamically Compensated Field Aberrations
Authors: Mamoru Nakasuji Mamoru Nakasuji , Hiroyasu Shimizu Hiroyasu Shimizu
Published: October 2002

Calculation formulae for the residual field curvature, astigmatism and distortion aberrations are made. The resolution of a typical symmetrical magnetic doublet with dynamically compensated field aberrations is limited by the diffraction, the residual field curvature and astigmatism aberrations. From the beam trajectories, it has been clarified that distortion is generated because the crossover is shifted from the normal position in the direction of the object for the outer trajectories by the spherical aberration of the first projection lens, and that the distortion is reduced if the crossover position for each trajectory is corrected to the normal position. With this correction, the field curvature and astigmatism are not changed. For a 1.5 m optical path length from the object to the image and for 20 and 0.25 mm of main- and subfield sizes, respectively, the residual beam resolution and distortion are 33 and 1.1 nm, respectively, when the beam energy is 50 keV.
Selective Etching of GaAs for ZnSe Based Surface Emitting Lasers
Authors: Honda Tohru , Yanashima Katsunori , Koyama Fumio , Kukimoto Hiroshi , Kenichi Iga Kenichi Iga
Published: October 2002

We have demonstrated a selective etch process of removing a GaAs substrate for the fabrication of ZnSe-based surface emitting lasers using the PA etchant ( NH3OH:H2O2:H2O=x:33:10) and employing a spray method. The etch rate of a GaAs substrate was 3.7 µm/min with a preferential etch rate ratio of over 20 against ZnSe layers. The surface of the ZnSSe layer after removal of a substrate was smooth enough to fabricate ZnSe-based surface emitting lasers.
Uniformity Improvement of Optical and Electrical Characteristics in Integrated Vertical-to-Surface Transmission Electro-Photonic Device with a Vertical Cavity
Authors: Kurihara Kaori , Numai Takahiro , Yoshikawa Takashi , Kosaka Hideo , Sugimoto Mitsunori , Yoshimasa Sugimoto Yoshimasa Sugimoto , Kenichi Kasahara Kenichi Kasahara
Published: October 2002

We report an improvement in uniformity of both electrical and optical characteristics in an integrated vertical-to-surface transmission electro-photonic device with a vertical cavity. This improvement is due to both highly controlled reactive ion-beam etching and a self-alignment process. Reactive ion-beam etching highly controls etching depth, and leads to uniform electrical and optical characteristics. Self-alignment process makes it possible to fabricate a fine pattern with high accuracy. By using these fabrication processes, the deviations of both the electrical resistance and the optical light-output characteristics are reduced to less than half of those for the wet-etched devices. Furthermore, the remaining deviation in the light-output characteristics is reduced by suppressing light reflection on the surface. As a result, the standard deviation of the threshold current under the CW condition is 0.39 mA. This value is about half of that for the wet-etched devices.
High-Field Electron Transport in SiGe Alloy
Authors: Maxim Ershov Maxim Ershov , Victor Ryzhii Victor Ryzhii
Published: October 2002

Electron transport in unstrained Si1-xGex(0≤x≤0.4) alloy is studied in the present work using the Monte Carlo (MC) simulation technique. Electron transport characteristics (drift velocity, impact ionization (II) coefficient, etc.) are evaluated over a wide range of electric fields. It is found that not only low-field mobility but also saturation velocity and impact ionization coefficients are reduced with increasing Ge fraction due to alloy scattering. More importantly, the high-energy (ε>2 eV) electron population is reduced to a much greater extent than the ionization coefficient. Simple analytical expressions for electron low-field mobility, saturation velocity and II coefficient which can be easily implemented in device simulation programs are proposed.
Fractals on Surface Patterns of KBr Solution Growth
Authors: Fujisaki Naohiro , Aikawa Fumihiro , Kaneko Tsutomu , Futama Hideo
Published: October 2002

The growth patterns on the {100} surface of KBr crystal, growing in aqueous solution at low supersaturation (σ=1.0%), were observed in situ with an optical microscope. Some growth steps appeared at the crystal edges and then advanced toward the center of the {100} surface. The growth steps were bunched and formed lines. They appeared as a complex growth pattern on the growing surface. The complexity of the growth step patterns increased with crystal growth, while the advance rate of the growth steps decreased with it. The complexity was represented as a fractal. The fractal dimension of the growth step patterns was calculated to be 0.87–1.27 during the observation.
Microscopic Approach to Shock Waves in Crystal Solids. I
Authors: Sugiyama Masaru , Hajime Kikkawa Hajime Kikkawa , Kouji Mizuno Kouji Mizuno
Published: October 2002

Shock wave phenomena in one-dimensional crystal lattices at finite temperatures are analyzed theoretically from a microscopic point of view. The basic equations are derived from nonequilibrium statistical mechanics. By using the linearized basic equations, responses of crystal lattices to external impulses are first analyzed by adopting the continuum approximation. Their numerical analysis is also made exactly within the linear theory. Secondly, shock waves in crystal lattices excited by continuous external forces are analyzed in a similar way. Mechanical and thermal effects in shock wave phenomena are discussed in detail.
Roles of Buffer Layers in Epitaxial Growth of SrTiO3 Films on Silicon Substrates
Authors: Bum Ki Moon Bum Ki Moon , Hiroshi Ishiwara Hiroshi Ishiwara
Published: October 2002

Heteroepitaxial growth of SrTiO3 (STO) films with and without buffer layers on Si(100) and (111) substrates has been conducted by a focused electron beam evaporation method. It has been found that thin metallic layers such as Ti and Sr are effective for improving the quality of overgrown STO films, which is probably due to the fact that the metallic layers deoxidize the surface SiO2 layers on Si substrates. It has also been found that a Sr buffer layer is effective for obtaining fairly good epitaxial films on both Si(100) and (111) substrates, while a Ti buffer layer is effective for obtaining good electrical properties of the film and interface.
Multicusp Electron-Cyclotron-Resonance Plasma Source Working with Microwaves Radially Injected through an Annular Slit
Authors: Tuda Mutumi , Ono Kouichi , Masakazu Taki Masakazu Taki , Keisuke Namba Keisuke Namba
Published: October 2002

A new-type electron-cyclotron-resonance (ECR) plasma source has been developed for materials processing. The reactor employed magnetic multicusp fields and microwaves radially injected through an annular slit; this configuration yielded stable, uniform discharges without contamination of the microwave entrance window by sputtered particles. Electrostatic probe and optical emission measurements were made to obtain the plasma properties in Ar. These measurements showed that high-density, uniform plasmas were produced by optimizing the width of the annular slit. Moreover, the electron temperature exhibited its strong peak around the ECR zone near the chamber wall. A simple model indicates the mechanisms responsible for the plasma uniformity obtained: the plasma was dominantly produced around the ECR zone, and then diffused preferentially toward the center of the chamber because of strong magnetic fields generated near the wall surface.
Iodine Absorption-Line-Stabilized Frequency-Tunable Green Light Using Sum-Frequency Generation of Diode Lasers
Authors: Weizhi Wang Weizhi Wang , Motoichi Ohtsu Motoichi Ohtsu
Published: October 2002

A precision frequency-tunable green light source, which involves a frequency reference using a molecular iodine absorption resonance and a tuner, has been demonstrated. The green coherent light was obtained by sum-frequency generation using a 0.82 µm AlGaAs laser and a 1.54 µm distributed-feedback (DFB) laser in a KTP crystal. The reference frequency was locked to an I2 absorption resonance and the residual frequency fluctuation was estimated to be within ±0.5 MHz. A frequency-tunable range of ∼5 THz was obtained. Heterodyne beat signals were obtained to measure the frequency difference between the frequency reference and the tunable output. This system was also proposed for measuring the frequency spacings between different resonances of a molecular absorption spectrum.
Accurate Wavelength Measurement of the Intercombination Line of Calcium
Authors: Ishikawa Jun , Morinaga Nobuhiko Ito
Published: October 2002

We have measured the wavelength of the intercombination line 3P1-1S0 of 40Ca. The wavelength of a dye laser, stabilized to the intercombination line 3P1-1S0 of 40Ca, was compared with the wavelength of an I2-stabilized He–Ne laser by means of a newly developed wavemeter. The estimated uncertainty of the measured wavelength ratio is 7×10-11 (3σ) and the measured wavelength agrees with the previous results within the uncertainty of the I2-stabilized He–Ne laser.
Improvement of the Accuracy of the Atomic Time Scale at Communications Research Laboratory
Authors: Shibuki Masaaki , Sebata Kouichi , Masanori Aida Masanori Aida , Koji Nakagiri Koji Nakagiri
Published: October 2002

We show the results of computer simulations of the time scale generated by the atomic time (TA) algorithm, using data obtained from an ensemble of clocks at Communications Research Laboratory (CRL). Three accuracy evaluations were made using the laboratory type primary frequency standard (CRL Cs1) over the period between February, 1989 and January, 1992. Our results show that the accuracy of the TA(CRL) time scale rate is increased by more than 5–6 times when using the clock data calibrated by the primary frequency standard.
Laser and Microwave Study of Fine and Hyperfine Structures in High Rydbeg States of Indium
Authors: Hong Feng-Lei , Maeda Haruka , Yukari Matsuo Yukari Matsuo , Michio Takami Michio Takami
Published: October 2002

The fine and hyperfine structures in Rydberg states of indium have been studied by optical and microwave double-resonance spectroscopy. The highly excitednf2F5/2,7/2Rydberg series (n=30∼79) are observed by resonant laser spectroscopy with two-step excitation. The quantum defects of the2F5/2and2F7/2series are determined by least-squares fitting of the experimental data to the general Rydberg-Ritz formula. The evaluated term values show that all the studied2Fstates are inverted. The hyperfine-structure splitting of the 39s2S1/2level is determined to be 11.4(10) MHz by the direct measurement of the 39s2S1/2←38p2P3/2microwave transition.
Concentration Profiles of Deep Levels Induced by Gold Diffusion in Silicon
Authors: Takahashi Manabu , Morooka Masami , Hashimoto Fumito Ueda
Published: October 2002

The concentration profiles of the deep levels (E
c-0.54 eV, E
c-0.24 eV, E
c-0.30 eV and E
c-0.16 eV) induced by gold diffusion at 1150° C for 6 h were measured by the deep level transient spectroscopy (DLTS) method. The profile of E
c-0.54 eV agreed well with that of total gold atoms measured by neutron activation analysis. The shape of the profile of E
c-0.24 eV is very similar to that of E
c-0.54 eV, and the concentration ratio of E
c-0.24 eV to E
c-0.54 eV is nearly constant at 0.12 from the surface to the inner part. Whether the level of E
c-0.16 eV is observed or not, depends on the fabrication of the Schottky diode for the DLTS measurement, and the shape of the profile of the observed E
c-0.16 eV is similar to that of E
c-0.54 eV. The profile of E
c-0.30 eV is quite different from those of other levels, and the level concentration is nearly constant from the surface to the inner part.
Evaporation of Oxygen-Bearing Species from Si Melt and Influence of Sb Addition
Authors: Huang Xinming , Terashima Kazutaka , Sasaki Hitoshi , Tokizaki Eiji , Yutaka Anzai Yutaka Anzai , Shigeyuki Kimura Shigeyuki Kimura
Published: October 2002

Evaporation loss from undoped and Sb-doped Si melt in both SiC-coated carbon and a silica crucible was measured in the temperature range of 1440–1560° C. For undoped Si melt in a silica crucible, the evaporation rate changed with temperature in an exponential manner and depended on the area ratio, A
c/A
s, where A
c is the contact area of the Si melt and silica crucible, and A
s the free surface area of the Si melt. There were three trends of the dependence, and the evaporation rate tended to reach a certain saturation value when the area ratio approached infinity, which can be regarded as the intrinsic evaporation rate due to oxygen saturation in Si melt. It was concluded that the oxygen concentration in the Si melt was not saturated under the present experimental conditions. Evaporation from Sb-doped Si melt seemed complex. Under the assumption that the evaporating species from an Sb-containing Si melt in a SiC-coated carbon crucible was antimony vapor only and that the Sb evaporation rate did not change in different crucibles, the total evaporation from the silica crucible was analyzed. From the linear time dependence and nonexponential temperature dependence, the evaporation rate excluding Sb evaporation was concluded to be that of some oxide species but not pure SiO. Such evaporation was greater than the evaporation of SiO from undoped Si melt; more than three times as large at the melting point of Si. Therefore oxygen reduction in highly Sb-doped Cz–Si crystals can be attributed mainly to the enhancement of oxygen evaporation.
Transmission Electron Microscope Observation of Cubic GaN Grown by Metalorganic Vapor Phase Epitaxy with Dimethylhydrazine on (001) GaAs
Authors: Kuwano Noriyuki , Nagatomo Yoshiyuki , Kobayashi Kenki , Oki Kensuke , Miyoshi Seiro , Yaguchi Hiroyuki , Onabe Kentaro , Shiraki Yasuhiro
Published: October 2002

Cross-sectional transmission electron microscope observation has been performed on the microstructure of GaN films grown on a (001) GaAs substrate by metalorgahic vapor phase epitaxy (MOVPE) using 1,1-dimethylhydrazine (DMHy) and trimethylgallium (TMG) as the sources of nitrogen and gallium, respectively. Before the deposition, the surface of the substrate was nitrided with DMHy. High-resolution images and electron diffraction patterns confirmed that the GaN films have a zincblende structure (β-GaN) with the lattice constant of a
GaN=0.454 nm, and contain bands of stacking faults parallel to {111} planes. The interface between GaN and GaAs is made of {111} facets with no interlayer. Misfit dislocations are found to be inserted on the interface approximately every five atomic planes of GaAs. The nitridation treatment with only DMHy for 130 min is found to form a thick layer of β-GaN on the (001) GaAs substrate. Nuclei of β-GaN formed by the pretreatment of surface nitridation play an important role in growing GaN in a zincblende structure during the supply of DMHy and TMG. The formation of facets on the top surface of GaN and on the interface of GaN/GaAs is explained in terms of the diffusion of arsenic in β-GaN. The characteristics of the structure of GaN films grown at 600 and 650° C are also presented.
Optimization of Antireflection Film Structures for Surface-Passivated Crystalline Silicon Solar Cells
Authors: Saitoh Tadashi , Uematsu Osamu Kamataki
Published: October 2002

Spectroscopic ellipsometry has been utilized to measure complex refractive indices of TiO2 and SiN

x

:H antireflection films. The indices of the films are found to vary with measurement wavelength and sample preparation conditions. Using the spectroscopic refractive indices, measured surface reflection spectra are found to coincide with calculated ones. The limit short-circuit current density values for surface-passivated, flat and V-grooved cell structures are calculated and compared as functions of SiO2 and antireflection film thicknesses. The maximum value is calculated to be 44.8 mA/cm2 for MgF2/SiN

x

:H/SiO2-coated, V-grooved surfaces with SiO2 thicknesses less than 10 nm. The realizable conversion efficiency is estimated to be 24.3% at the rear surface recombination velocity of 10 cm/s.
Superconductivity of WC in the NaCl-Type Structure under Pressure
Authors: Rajagopalan Mathrubutham , Saigeetha Pannikar , Gopalakrishnan Kalpana Gopalakrishnan Kalpana , Balan Palanivel Balan Palanivel
Published: October 2002

Here we report the theoretical calculations of band structure and superconductivity of WC in the NaCl-type structure. The effect of pressure on the band structure is obtained using the linear muffin-tin orbital method. The superconducting transition temperature is calculated using McMillan's formula. The value ofTcat ambient conditions is 5.98 K which increases on compression. The increase inTcvalues with pressure may be due to continuous transfer of s electrons from the carbon site to d states of the tungsten site. The calculated value ofTcat ambient pressure and the positive pressure coefficient ofTcare in agreement with other transition metal carbides and nitrides.
Evidence of Hybridization from a Direct Comparison of Semimagnetic and Nonsemimagnetic Ternary Lead Chalcogenides
Authors: Herrmann Klaus H. , Happ Michael , Möllmann Klaus-Peter , Peuker Frank , Tomm Jens W. , Tacke Harald Böttner
Published: October 2002

The results of a study of the optical properties, especially the luminescence behaviour, of PbSe, Pb1-xSrxSe and semimagnetic Pb1-xEuxSe in magnetic fields up to 7 T are presented. The spectra of PbSe and Pb1-xSrxSe consisting of single lines are interpreted as plasma (band-to-band) transitions whereas the double structure in the spectra of Pb1-xEuxSe is explained by additional transitions between conduction band states and states in a valence band which is generated by the unsaturated 4f levels of the Eu ions in the solid solution.
Persistent Enhanced Conductivity Induced by Light Irradiation in Hydrazone-Polycarbonate Dispersions
Authors: Hirao Akiko , Hideyuki Nishizawa Hideyuki Nishizawa , Masahiro Hosoya Masahiro Hosoya
Published: October 2002

Photoinduced spins with extended lifetime have been observed in hydrazone-polycarbonate dispersions. The presence of the spins changed the electrical characteristics of the dispersions. Measurements of electrical current associated with thermal equilibration after photoexcitation in dispersions of diethylamino-benzaldehyde diphenylhydrazone (DEH) in polycarbonate have been carried out. Sandwiched layers of the dispersions were excited with absorbed light. After withdrawal of the light, a voltage was applied and the current was measured. Experimental data provide evidence that photoinduced spins are derived from trapped carriers.
Spontaneous Extinction of Twin Surface in GaAs on Si(100) Grown by One-Step Low-Pressure Metal-Organic Chemical Vapor Deposition
Authors: Sato Kiyotaka , Kenji Togura Kenji Togura , Keiji Sato Keiji Sato
Published: October 2002

In heteroepitaxy of GaAs layers on Si(100) substrates by one-step low-pressure metal-organic chemical vapor deposition (LP-MOCVD), spontaneous extinction of twin crystals was confirmed. From the observation by reflection high-energy electron diffraction (RHEED), the {111} twin surface was found to coexist in the initial stage, and this twin surface was extinguished as deposition proceeded under constant growth temperature. The thickness required to extinguish the twin surface was dependent on both whether or not thermal cleaning was carried out prior to deposition and off-orientation angle toward the Si<011> direction. These suggest that the extinction mechanism of twin crystals is included in the heteroepitaxial growth of GaAs layers. Scanning electron microscopy (SEM) revealed that one-step heteroepitaxy by LP-MOCVD proceeds with embedding of the facet planes with high Miller index.
Physical Properties of Crystalline Films Prepared by Sputtering in Low Impurity Atmosphere
Authors: Ueda Haruhisa , Kitakami Osamu , Shimada Yutaka , Yoshiyuki Igari Yoshiyuki Igari , Isao Kusunoki Isao Kusunoki
Published: October 2002

We report on high-quality crystalline Fe and Cu thin films prepared by sputtering in low impurity atmosphere (SLIA). According to X-ray photoelectron spectroscopy and secondary ion mass spectroscopy analyses, it was found that the SLIA films contain less impurities compared with those prepared by conventional DC and RF sputtering methods. Such a reduction of impurities markedly enhances the crystal growth and reduces the electrical resistivity.
Ferroelectric Domain Structure in a Copolymer of Vinylidene Fluoride with Trifluoroethylene
Authors: Yoshiyuki Takahashi Yoshiyuki Takahashi
Published: October 2002

The domain structure of a poled copolymer of vinylidene fluoride with trifluoroethylene is studied through analysis of X-ray diffraction profiles. The crystal size coherent in diffraction is 20–40 nm, being much smaller than the lateral size of crystals observed by electron microscopy; the crystal is mosaic. The asymmetry of the profiles suggests that (100) domains exist in the poled crystals. Using an electric field of a square pulse to freeze the switching process, the change in the domain structure during the ferroelectric switching is investigated by X-ray diffraction. The line profile is found to broaden in integrated width during the switching by several percent, which is interpreted as the induction of reversed domains in crystals. The change in the integrated intensity during the switching is consistent with the rotation of a chain by 180°.
Application of Artificial Neural Network to Optical Fluid Analyzer
Authors: Makoto Kimura Makoto Kimura , Katsuhiko Nishida Katsuhiko Nishida
Published: October 2002

A three-layer artificial neural network has been applied to the presentation of optical fluid analyzer (OFA) raw data, and the accuracy of oil fraction determination has been significantly improved compared to previous approaches. To apply the artificial neural network approach to solving a problem, the first step is training to determine the appropriate weight set for calculating the target values. This involves using a series of data sets (each comprising a set of input values and an associated set of output values that the artificial neural network is required to determine) to tune artificial neural network weighting parameters so that the output of the neural network to the given set of input values is as close as possible to the required output. The physical model used to generate the series of learning data sets was the effective flow stream model, developed for OFA data presentation. The effectiveness of the training was verified by reprocessing the same input data as were used to determine the weighting parameters and then by comparing the results of the artificial neural network to the expected output values. The standard deviation of the expected and obtained values was approximately 10% (two sigma).
Erythrocyte Sedimentation in Plasma Observed under Microscope
Authors: Idonuma Atsuko , Dobashi Toshiaki , Yoshiharu Toyama Yoshiharu Toyama , Akio Sakanishi Akio Sakanishi
Published: October 2002

In order to elucidate the mechanism of erythrocyte sedimentation in plasma, we have measured the concentration distribution of erythrocytes in a sedimentation vessel using a newly developed image analyzing system. As time passes, erythrocyte-poor domains are formed in the suspension column. The total number of domains as well as the size of each domain, was evaluated by a series of analyses, setting up various volume fraction thresholds H
r for the domain. The total number of domains initially increases, reaches a maximum just when the interface roughness of the suspension column is maximum, and then decreases gradually. These characteristic behaviors are found in a wide range of H
r from 0.03 to 0.46. These results suggest that the sigmoidal erythrocyte sedimentation curve can be explained by an effective upflow of plasma through the erythrocyte-poor domain which is produced by aggregation of erythrocytes. Other previous experimental reports are also discussed on the basis of our results.