bluuebunny/crossref_metadata_2025 huggingface dataset:
Monte Carlo Simulation of Kinetic Electron Emission from a Metal Surface under keV Heavy Ion Bombardment
Authors: Ohya Jun Kawata
Published: October 2002

A Monte Carlo model is developed for charge-state-dependent kinetic emission (KE) of electrons from Au bombarded by keV Arq+(q=0, 1, 2). At low impact energy, the calculated electron yield is smaller than the observed yield due to the absence of potential emission (PE), whereas with increasing impact energy, the calculated and observed yields for Ar+impact approach each other due to dominant KE. For KE, there is a wide spread in the number of emitted electrons, although PE ejects one (one or two) electron for Ar+(Ar2+). The energy distribution of electrons ejected by KE has a peak at 2–3 eV, the position of which is independent of the energy and charge state of the projectile.
Real-Time Observations of Appearance of Crosshatched Pattern during Molecular Beam Epitaxy of Compressive InGaAs on InP
Authors: Morishita Yoshitaka , Goto Shigeo , Nomura Yasuhiko , Tamura Masao , Isu Toshiro , Yoshifumi Katayama Yoshifumi Katayama
Published: October 2002

The microscopic surface features were observed during molecular beam epitaxy of In0.65Ga0.35As on InP (100) substrates by scanning microprobe reflection high-energy electron diffraction in real time. During growth, a narrow line with low contrast appeared along the [01̄1] direction after about 750 Å of growth; the line increased in contrast, density and width as the growth proceeded, and finally formed a clear crosshatched pattern. A cross-sectional transmission electron microscope observation showed that the presence of a surface crosshatched pattern is directly correlated with the presence of interfacial misfit dislocations. The results indicate that the thickness at which the crosshatched line appears represents the critical layer thickness corresponding to misfit dislocation generation.
Higher Frequency Shifts of a Surface Vibration Mode Accompanied by Native Oxide Growth on Silicon in Air
Authors: Hiroshi Shirai Hiroshi Shirai
Published: October 2002

A surface polar vibration mode of native oxide formed on a silicon surface exposed to air has been found to shift continuously to the higher frequency side, after being dipped in diluted hydrogen fluoride solution and rinsed in deionized water, using infrared spectroscopy. The surface mode has a longitudinal character. The shifts strongly indicate an increase in the depolarization electric field accompanied by the spreading growth of “native oxide islands” on the silicon surface.
Carrier Mobility in Vinylidenefluoride-Trifluoroethylene Copolymer
Authors: Hayashi Kotaku , Takemura Masaaki , Tsubakihara Hiroshi , Uichi Kubo Uichi Kubo
Published: October 2002

The carrier mobility of a ferroelectric Vinylidenefluoride-Trifluoroethylene copolymer (VDF: 54 mol%) was measured by the time-of-flight method after irradiation by a KrF excimer laser. The hole and electron mobilities were estimated to be 3×10-6 cm2/V·s and 7×10-6 cm2/V·s, respectively.
Analyses of Plasma Flux and Density Distribution in Plasma Sources Surrounded by Magnetic Multipole Fields
Authors: Nihei Hitoshi , Enomoto Hiroyuki , Nobuyuki Inoue Nobuyuki Inoue
Published: October 2002

Plasma confinement characteristics of plasma sources, the side walls of which are surrounded by magnetic multipole fields, are analyzed using theoretical equations. Experimental data used are those obtained with microwave plasma sources. The plasma flux, the pressure range over which a uniform plasma is produced, the plasma density distribution at a plasma grid and the cusp leak width are discussed. If the leak width is the geometric mean value of the ion and electron Larmor diameters, the results estimated using the theoretical equations are consistent with the experimental ones. It has also been observed from the traces due to the plasma irradiation that the leak width corresponds to the geometric mean value. The validity of the equations has been confirmed. These equations can be used as a basis for the design of a plasma source capable of producing a uniform high-density plasma over a wide area.
X-Ray Photoelectron Spectroscopic Studies on Pyrolysis of Plasma-Polymerized Fluorocarbon Films on Si
Authors: Fujita Ken , Miyakawa Yasuhiro , Norio Hirashita Norio Hirashita
Published: October 2002

Temperature-programmed X-ray photoelectron spectroscopy was used to study pyrolysis of fluorocarbon thin films polymerized on Si substrates in magnetomicrowave plasma with C4F8 gas. Variations of fluorocarbon moieties were obtained at the temperature range between 20 and 700° C. The films, consisting of CF3, CF2, CF and C-CF

x

bonds, were found to be stable up to approximately 200° C and to be pyrolyzed via the dissociation of the terminal bonds above this temperature.
Theoretical Study of Minority Carrier Lifetimes due to Auger Recombination in n-type Silicon
Authors: Kee Jung Hak , Kenji Taniguchi Kenji Taniguchi , Chihiro Hamaguchi Chihiro Hamaguchi
Published: October 2002

The Auger recombination rate and minority carrier lifetime due to electron-electron-hole (eeh) Auger transition are calculated in the range ofn=1×1018/ cm3–1×1020/ cm3. Both matrix elements and overlap integrals used for the calculation of Auger recombination are derived from the first principle theory. We have also analyzed the influence of the degenerate effect and screening effect on the Auger recombination rate. The calculated results reveal that the screening effect is negligible, but the degenerate effect is not. Since the minority carrier lifetimes calculated in the model are in good agreement with experimental lifetimes for theeehAuger process, nonphonon recombination, instead of a phonon-assisted process, is the key process foreehAuger recombination. The derived Auger coefficients are also in good agreement with experimental values and other theoretical calculations.
Evidence of Enhanced Flux Pinning by Dislocations in Deformed Textured Y1Ba2Cu3OxSuperconductor
Authors: Zhang Youhe , Mironova Maria , Lee Dominic F. , Kamel Salama Kamel Salama
Published: October 2002

As-melt and uniaxially deformed melt textured YBCO (123) superconductors have been used to examine the role of dislocations in flux pinning. These superconductors were subjected to a high temperature annealing process. After annealing, the critical current densities (Jc) of both as-melt and deformed superconductors are found to have decreased dramatically both in zero field as well as in an applied field of 1.5 T. Furthermore, the distinct characteristic of deformed superconductors, i.e.,Jc( H||c-axis)≈Jc( H||a-b), has totally disappeared after annealing the samples at 900° C for 48 h in flowing oxygen. Transmission electron microscopy revealed that the high dislocation density normally observed in deformed 123 superconductors has been significantly reduced. In addition, several other microstructural changes were also investigated. These results indicate that the large amount of dislocations generated during the deformation process are effective flux pinning centers in these superconductors. Meanwhile, it is suggested that pinning by stacking faults is magnetically sensitive where the effect is maximum at low fields.
Position Sensing and Communication System Using Fluorescent Doped Plastic Fiber
Authors: Ito Haruhiko , Hattori Hajime , Uchida Takashi Takeo Masayoshi , Moriyama Teruki , Matsui Teruyuki
Published: October 2002

Various telecommunication techniques using supersonic, electromagnetic or light waves have been developed for application to remotely controlled machine operation systems, especially for microsystems. A light wave communication technique using fluorescent light in an optical fiber was considered to be applicable for this purpose. The fundamental communication properties of fluorescent-doped plastic fiber have been examined to realize such a system in a specific narrow space. As a result, the detectable distance of 5m with resolution of 5.6 mm and a communication rate of approximately 500 kbps was obtained.
CH3 Radical Density in Electron Cyclotron Resonance CH3OH and CH3OH/H2 Plasmas
Authors: Ikeda Masanobu , Aiso Kokichi , Hori Masaru , Toshio Goto Toshio Goto
Published: October 2002

CH3 radical densities in electron cyclotron resonance (ECR) discharge methanol ( CH3OH), methanol diluted with hydrogen gas ( CH3OH/H2) and methane ( CH4) plasmas were measured for the first time using infrared diode laser absorption spectroscopy (IRLAS). CH3 radical densities in the CH3OH and CH3OH/H2 plasmas were estimated to be of the order of 1011 cm-3 under the conditions of total pressure of 1.3 Pa and microwave power of 50-800 W.
On the other hand, CH3 radical density in the CH4 plasma was estimated to be less than 1010 cm-3. Moreover, the production and loss processes of CH3 radical in the CH3OH plasma were discussed on the basis of the results of emission intensity of Ar*, the absorption ratio of CH3OH molecule and the decay curve analysis of CH3 radical after termination of the discharge.
Surface Damage in GaInAs/GaInAsP/InP Wire Structures Prepared by Substrate-Potential-Controlled Reactive Ion Beam Etching
Authors: Munehisa Tamura Munehisa Tamura , Yasuaki Nagashima Yasuaki Nagashima , Koji Kudo Koji Kudo , Ki-Chul Shin Ki-Chul Shin , Shigeo Tamura Shigeo Tamura , Akinori Ubukata Akinori Ubukata , Shigehisa Arai Shigehisa Arai
Published: October 2002

We investigated photoluminescence intensity dependence on the width of GaInAs/GaInAsP/InP wire structures prepared by substrate-potential-controlled reactive ion beam etching. As a result, the sidewall recombination velocity was estimated to be 2.5 ×103 cm/s under a low excitation power of approximately 1 W/cm2 (Ar+-ion laser, λ=514.5 nm) at 77 K, and was almost the same as that fabricated by wet chemical etching.
Theory of Scanning Tunneling Spectroscopy Based on the Resonant Tunneling Model II: Relation between Different Approaches
Authors: Kenji Makoshi Kenji Makoshi , Takashi Mii Takashi Mii
Published: October 2002

The expression for scanning tunneling microscopy current given in a previous paper [Jpn. J. Appl. Phys. 33 (1994) 3657] is rewritten into a simpler form in terms of the time-derivative of the occupation number of states connected to the sample electrode. Assumptions made in the previous theory, such as infinitely wide and flat surface, are lifted. It is shown that the resonant width for the cluster orbitals, where the tunneling current flows, is different, in general, from the transition rate to states which carry the current to the electrodes. It is emphasized that the ratio of the sample-cluster tunneling matrix elements to those of cluster-tip tunneling, which increases with decreasing tip-sample distance, affects the scanning tunneling spectrum due to the multiple scattering effect.
The Noise Reduction Effect of the Amplified Metal Oxide Semiconductor Imager
Authors: Andoh Fumihiko , Taniwaki Ryozo , Taketoshi Kazuhisa , Araki Shuichi
Published: October 2002

It is predicted that the amplified metal oxide semiconductor imager (AMI) exhibits carrier movements between adjacent pixels. Consequently, it is considered that a spurious resolution reduction effect or a random noise reduction effect occurs. The authors have clarified these phenomena theoretically and have measured the sensitivity characteristic between pixels and the random noise using devices. As a result, carrier movements below 5% between adjacent pixels were clearly observed, and it was confirmed that 0.89-times random noise reduction already occurred at an intensity of incidence of 1/1000 of saturation, and 0.79-times reduction at intensity of 1/100 of saturation.
Effect of Mode-Mixing on Microwave Reflectometry in the Tokamak and Helical Devices
Authors: Nagatsu Masaaki , Hayashi Takashige , Tsukishima Takashige
Published: October 2002

One-dimensional full wave analysis simulating microwave reflectometry in tokamak and helical plasmas has been carried out in order to investigate the polarization change in an inhomogeneous plasma with magnetic shear. Numerical results show that the mode-mixing process through the nonlinear coupling between the ordinary (O-) mode (or extraordinary (X-) mode) wave and the strong magnetic shear, especially in the helical plasma devices, inevitably occurs near the plasma boundary. Simultaneous reflections from both the O-mode and X-mode cutoff layers in the frequency range where both the cutoffs exist, will significantly affect the accuracy of the phase measurements in microwave reflectometry. The effects of mode-mixing are also numerically examined for microwave reflectometry in tokamak plasmas. It is shown that the reconstructed density profile disagrees with the true profile in the peripheral plasma region, which is due to the simultaneous reflection resulting from the polarization mismatching between the incident wave field and the magnetic field line at the plasma boundary.
\bfiIn situ Monitoring of Product Species in Plasma Etching by Fourier Transform Infrared Absorption Spectroscopy
Authors: Kazuyasu Nishikawa Kazuyasu Nishikawa , Kouichi Ono Kouichi Ono , Mutumi Tuda Mutumi Tuda , Tatsuo Oomori Tatsuo Oomori , Keisuke Namba Keisuke Namba
Published: October 2002

In situFourier transform infrared (FTIR) absorption spectroscopy has been used to detect reaction products resulting from the etching of Si in Cl2plasmas. Silicon tetrachloride SiCl4was the only gas-phase product species detected during etching. Unsaturated silicon chlorides SiClx(x=1–3) were not observed in the plasma within the present level of detection. By comparing the absorbances of SiCl4in Cl2plasma etching of Si and in pure SiCl4gases, it is suggested that the concentrations of SiCl4or product species during etching are comparable to the feedstock Cl2gas densities,e.g., [SiCl4] ∼1 ×1013cm-3at a pressure of 0.5 mTorr. In contrast, on the surface-etched Si, unsaturated silicon chlorides SiClx(x=1–3) as well as SiCl4were found to occur by FTIR reflection absorption spectroscopy (RAS). Moreover, absorption features of silicon oxides were observed both in the gas phase and on the surface, presumably arising from reactions between Si produced from etching and oxygen included in the reactor chamber owing to a small leak.
Stability, Bifurcation, and Chaos of a Structure with a Nonlinear Actuator
Authors: Tseng Chyuan-Yow , Pi-Cheng Tung Pi-Cheng Tung
Published: October 2002

In this work, the steady-state behaviors of a structure with a nonlinear actuator subjected to linear feedback control are investigated analytically. We apply the methods of harmonic balance, Floquet theory, and Melnikov theory with the assistance of numerical computations to plot the global bifurcation diagram in parametric space. Attention is focused on the effects of feedback gains on qualitative behaviors such as the stability of steady-state solutions, chaotic vibrations, fractal basin boundaries, jump phenomena, and the control effectiveness in terms of amplitude modulation.
Nano-Molecular Electronics: Ideas and Experiments
Authors: Wilson Edward Guy
Published: October 2002

Two designs for information processing devices, comprised of organised assemblies of organic molecules, are described. Information is represented by charges in molecular layers. In the inchworm memory bits are shifted between the layers by electric fields; in the optical shift register, bits are shifted by light pulses. The devices are designed to be interfaceable to existing silicon technology.
  Photoconduction experiments are described on molecules assembled by the Langmuir Blodgett technique, which are able to measure electron transport properties, at a molecular level, and on a 35 ps time scale. Interlayer and intralayer intermolecular tunnelling rates are determined, and related to molecular parameters. Control of electron position, at a molecular scale, has been achieved by means of using blocking molecular bilayers.
Ordered Structure Formed by Biologically Related Molecules
Authors: Hatta Ichiro , Nishino Junichiro , Sumi Akinori , Masahiro Hibino Masahiro Hibino
Published: October 2002

The two-dimensional arrangement of biologically related molecules was studied by means of scanning probe microscopy. For monolayers of fatty acid molecules with a saturated hydrocarbon chain adsorbed on a graphite substrate, in the scanning tunneling microscope image, the position associated with the carbon atoms was clearly distinguished. In addition, based on the image for fatty acid molecules with an unsaturated hydrocarbon chain, at the position of a double bond, local electrical conductance was found to increase. Based on the images, it was pointed out that not the position of each carbon but the interaction between a graphite substrate and an alkyl chain plays an important role in imaging. On the other hand, for the surface of Langmuir-Blodgett films composed of phosphatidic acids with cations, the scanning force microscope image shows, for the first time, evidence of the methyl ends in the arrangement of phospholipid molecules.
Light-Induced ESR in Variously Treated Hydrogenated Amorphous Silicon
Authors: Jiang-Huai Zhou Jiang-Huai Zhou , Minoru Kumeda Minoru Kumeda , Tatsuo Shimizu Tatsuo Shimizu
Published: October 2002

Light-induced ESR (LESR) in hydrogenated amorphous silicon at 77 K has been studied using four types of samples: standard, light-soaked, high-temperature-annealed (HTA), and low-temperature-deposited (LTs) samples. It is found that, in general, the density of neutral dangling bonds (D0) increases under illumination. However, for strongly light-soaked samples, a slight decrease of the D0 density occurs at illumination intensities below about 10 mW/cm2. The dependence of the D0 density on illumination is argued to be caused by the conversion between charged and neutral dangling bonds. It is inferred that the densities of both neutral and charged dangling bonds are increased in HTA and in LTs a-Si:H. An asymmetry is observed between the spin densities of the broad (N
b) and narrow (N
n) components of the LESR signal in all the samples. The ratio of N
b to N
n is strongly dependent on the type of sample. However, the illumination intensity dependences of N
b and N
n are found to be identical and follow a power law. This indicates that N
b and N
n are highly interdependent and are probably governed by the same microscopic process.
Identification of Ionizing Radiation with an Imaging Plate Using Two-Wavelength Stimulation Light
Authors: Takebe Masahiro , Abe Ken , Kondo Yasuhiro , Satoh Yoshiyuki , Manabu Souda Manabu Souda
Published: October 2002

Imaging plates are widely used in various fields. However, ordinary reading instruments give no information on the type of radiation. We proposed that radiation type can be identified by stimulation with light of two wavelengths. Recently, we have carried out further investigation and found that the intensity ratio of photostimulated luminescence (PSL) between two wavelengths depends on particle properties. Imaging plates were irradiated with 3.2 MeV protons, 40 kVp X-rays, 200 keV electrons and Co-60, and stimulation spectra were observed for each type of radiation. We compared the PSL intensities at 500 nm with those at 600 nm 18 hrs after irradiation. The PSL intensities at 600 nm normalized by those at 500 nm were observed to decrease in order of irradiation with 3.2 MeV protons, 40 kVp X-rays, 200 keV electrons and Co-60.
Influence of Dopants on Characteristics of X-Ray Detectors Fabricated from Indium-, Gallium-, and Chlorine-Doped Cadmium Telluride Single Crystals
Authors: Sato Toshiyuki , Sato Kenji , Ishida Shinichiro , Ukita Masaaki , Yamada Masayoshi , Kanamori Hitoshi
Published: October 2002

Counting characteristics of X-ray detectors fabricated from indium-doped, gallium-doped, and chlorine-doped CdTe have been investigated. The detectors fabricated from indium-doped and gallium-doped crystals showed radiation-induced polarization, namely, a progressive decrease of count rate with an increase of photon fluence in the high-photon-fluence region, while the detectors fabricated from chlorine-doped crystals did not. Results from current-voltage characteristics of the detectors indicated that the different counting characteristics of these detectors originated from the difference in internal electric fields in each detector.
Adiabatic Charge Transport in Mesoscopic and Nanoscopic Conductors
Authors: Büttiker Markus
Published: October 2002

Transport coefficients are derived which govern the current response of phase coherent conductors in the presence of slowly oscillating external perturbations. We derive the low-frequency admittance if oscillating voltages are applied to the contacts of the sample and discuss the response to an oscillating magnetic flux. Whereas the dc-conductance is determined only by the equilibrium electrostatic potential, the adiabatic transport coefficients discussed here depend on the electrostatic potential that is established in the presence of transport. The symmetry of the transport coefficients under flux reversal is discussed. Novel experiments to find Aharonov-Bohm oscillations in capacitance coeffcients are suggested.
Simulations of Fluctuations in Quantum Wire Mesoscopic Systems
Authors: Gerard Edwards Gerard Edwards , Anna Grincwajg Anna Grincwajg , David Ferry David Ferry
Published: October 2002

We examine the geometry dependence of the conductance fluctuations in a quantum wire, using the recursive Green's function technique, by changing the width of a wire with fixed length. In the experimental situation, the quantum wire is `connected' to `wide' and `long' disordered contact regions which are often ignored in calculations. This more complicated quantum wire geometry lends itself to a numerical approach but would be very difficult to tackle from the viewpoint of the diagrammatic perturbation theory. We can include these disordered contact regions easily in our calculations, and our numerical results suggest that the presence of these contacts tends to reduce the fluctuations. This is a consequence of entering the transport `localization regime', where the sample length is of the order of the localization length, for the longer structure with the disordered contacts.
Novel InGaAs/GaAs Quantum Dot Structures Formed in Tetrahedral-Shaped Recesses on (111)B GaAs Substrate Using Metalorganic Vapor Phase Epitaxy
Authors: Yoshihiro Sugiyama Yoshihiro Sugiyama , Yoshiki Sakuma Yoshiki Sakuma , Shunichi Muto Shunichi Muto , Naoki Yokoyama Naoki Yokoyama
Published: October 2002

We report a novel GaAs/InGaAs/GaAs quantum dot structure formed in a tetrahedral-shaped recess (TSR) pattered on a (111)B GaAs substrate with anisotropic chemical etching. The pseudomorphic heterostructure shows two clear photoluminescence (PL) peaks, which are attributed to an In anisotropic incorporation on (111)B compared to (111)A. Cathodoluminescence at a lower energy peak with InGaAs of 2.5 nm shows bright image at the bottom of TSRs, which indicates the local minimum of potential energy is at the bottom of the TSR.
Transport Properties and Fabrication of Coupled Electron Waveguides
Authors: Hasko Fujio Wakaya , Jones Geraint A. C. , Ahmed Haroon
Published: October 2002

Eigenenergies and eigenfunctions in coupled electron waveguides with Schottky gates are numerically calculated by solving the Schrödinger equation and the Poisson equation self-consistently in order to estimate the strength of coupling between two electron waveguides. It is concluded that very low middle-gate voltage is required for strong coupling. In order to realize strong coupling, a modified structure which has a middle gate with a small gap is proposed and fabricated using electron beam lithography and the lift-off technique.
Self-consistent Determination of the Confinement Potential in Various Etched Quantum Wire Structures
Authors: Wirner Christoph , Hamaguchi Chihiro , Smoliner Jürgen , Reinacher Nils , Gornik Erich
Published: October 2002

The confinement potential in etched quantum wire structures is calculated self-consistently as a function of the etch profile in the shallow as well as the deeply etched regime. The etching effect is taken into account by introducing surface charges at the etched semiconductor interfaces. In single GaAs/AlGaAs heterostructures a remarkable decrease of the confinement in the growth direction is found in the deeply etched regime depending on the wire width. The effect is explained by side depletion of the wire and the ionized donor layer. In GaAs/AlGaAs quantum wells, side depletion results in an asymmetric well potential shifting the electronic wave function towards the top interface of the well.
Quantum Interferometric Spectroscopy: A Novel Technique for Nanometer-Scale Characterization of Heterostructures
Authors: Kiyoshi Kanisawa Kiyoshi Kanisawa , Masafumi Tanimoto Masafumi Tanimoto
Published: October 2002

We propose quantum interferometric spectroscopy (QIS), a novel technique for characterizing heterostructures. Theoretical consideration of tunneling currents of a double-barrier (DB) structure utilizing QIS revealed that individual structural fluctuations of DB structure which cause current differences can be precisely specified. We applied QIS to analyze local current-voltage spectra of DB structures measured by a scanning force microscope using a current-voltage spectra method. We demonstrated that QIS can detect a one-monolayer fluctuation in thickness and fluctuation of less than 0.01 in In mole fraction in the InGaAs well layer on a nanometer-scale.
Strong Photon Localization in Mesoscopic Scaled Optical Waveguide
Authors: Masato Ohtaka Masato Ohtaka , Akihiro Hashimoto Akihiro Hashimoto , Takashi Itoh Takashi Itoh , Takeshi Santo Takeshi Santo , Akio Yamamoto Akio Yamamoto
Published: October 2002

Strong photon localization in mesoscopic-scaled optical waveguide structures has been analyzed through two numerical approaches. The conventional electromagnetic wave analysis and the forced vibrational analysis methods are applied to 2-dimensional mesoscopic-scaled optical waveguide structures. The results indicate that both analysis methods give similar results for the density of states, the photonic band gap and the strong photon localized states according to the introduction of aperiodic structures of the refractive indices in the waveguides. The calculated mode patterns of the midgap states in the photonic band gap indicate that the features of strongly localized states depend on the aperiodicity, and light is localized strongly within a region of several micrometers in the random aperiodic waveguide. We also discuss fabrication techniques for realistic quasi-random aperiodic structures and the smearing out effect by the cladding layer which prevents the strong localization of light.
Self-Oscillations of the Current in Doped Semiconductor Superlattices
Authors: Holger Grahn Holger Grahn , Jörg Kastrup Jörg Kastrup , Klaus Ploog Klaus Ploog , Luis Bonilla Luis Bonilla , Jorge Galán Jorge Galán , Manuel Kindelan Manuel Kindelan , Miguel Moscoso Miguel Moscoso
Published: October 2002

Self-sustained current oscillations have been found in doped GaAs-AlAs superlattices and are investigated experimentally and theoretically. The electric-field distribution in doped superlattices becomes unstable if the carrier density is not sufficiently large to form stable domains. The instability results in self-oscillations of the current, which are due to an oscillatory motion of the domain boundary in the superlattice. A discrete drift model taking into account several regions of negative differential velocity and a large electron density clearly establishes the origin of these oscillations.
Theory of Superconducting Quantum Dot under Magnetic Field
Authors: Yukio Tanaka Yukio Tanaka , Satoshi Kashiwaya Satoshi Kashiwaya , Hideaki Takayanagi Hideaki Takayanagi
Published: October 2002

Basic properties of the quantum dot structure, which is a normal region created inside superconducting matter on a subnanometer scale, are predicted theoretically. The bound states change dramatically as the number of the magnetic flux quanta changes by one. We have clarified the origin of the “nearly midgap states" by intuitive consideration based on the unified picture of interference of the quasiparticle proposed by Kashiwaya.
Growth Temperature Dependence of Boron Surface Segregation and Electrical Properties of Boron Delta-Doped Structures Grown by Si Molecular Beam Epitaxy
Authors: Kumagai Yoshinao , Mori Ryosuke , Ishimoto Kouichi , Park Kyung-ho , Fumio Hasegawa Fumio Hasegawa
Published: October 2002

Reflection high-energy electron diffraction (RHEED) intensity oscillation showed a 4-monolayer (ML) period in the early stage of Si molecular beam epitaxy (MBE) on a 1 ML boron preadsorbed Si(111) surface, as long as the surface-segregated boron coverage was more than 1/3 ML.
Temperature dependence of the boron surface segregation was investigated from the duration of the 4-ML-period oscillation. Effective solubility of boron in Si was one order higher than those reported for 1/3 ML boron preadsorbed cases. Crystallinity of the Si overlayer was satisfactory when the growth temperature was equal to or above 450° C, and 2/3 of the initially adsorbed boron atoms were confined to within about 10 ML (about 16 Å) of the Si overlayer at 450° C. Boron preadsorption was found to saturate at 1 ML, and the temperature dependence of the peak carrier concentration showed the same tendency as that of the effective solubility.
Characterization of GaAs Films Grown on Vicinal Si(110) Substrates by Molecular-Beam Epitaxy
Authors: Yodo Tokuo
Published: October 2002

The optical and structural properties of GaAs films grown at temperatures of between 460 and 690° C on vicinal Si(110) substrates by molecular-beam epitaxy are discussed and compared with the optical properties of (110) GaAs with (100) GaAs. We have discussed the residual strain and stress after annealing. The residual stress in films shifted the PL spectra to lower photon energies as the off-angle increased toward the [001] direction. The orientation dependence of the stress is explainable by the mechanical properties of GaAs films. The thermal stress and strain of (110) GaAs were larger than those of (100) GaAs after annealing. The thermal stress of GaAs on vicinal Si(110) tilted at 6° toward the [001] direction increased from 3×109 to 4.1×109 dyn/cm2 after 1000° C annealing.
Detection of an Oxygen-Excessive Layer in Thermally Grown Silicon Oxide
Authors: Yoshio Watanabe Yoshio Watanabe
Published: October 2002

This paper describes depth profiling of the oxygen (O) content of thermally grown silicon oxide by Auger electron spectroscopy (AES). In this approach, the Auger peak area value obtained by integrating the first-derivative spectrum is used as the signal intensity. After profiling of a number of similar samples, the average values of signal intensities for the same depths are plotted to obtain smooth profiles. The O signal intensities are higher in the oxide/substrate interface region than the bulk oxide region. X-ray photoelectron spectroscopy (XPS) profiling confirms an increase in O signal intensity in the same region. This region approximately corresponds to a structural transition layer of a newly formed oxide.
Subpulse Suppression of Chirped-Pulse Amplification Nd:Glass Laser Pulse with Time-Predelay Second-Harmonic Generation
Authors: Zhang Tiejun , Daido Hiroyuki , Yoshiaki Kato Yoshiaki Kato
Published: October 2002

We present the experimental results on subpulse suppression of a chirped-pulse amplification Nd:glass laser pulse by second-harmonic generation with time predelay. The results show that the intensity contrast ratio of the main pulse to the subpulse is increased by a factor of 10 in comparison with that of the fundamental pulse.
Dry Post-Etch Treatment using SF6 Chemistry for 0.2 µm Contact Hole
Authors: Kim Seung-Joon , Shin Kisoo , Hee-Kook Park Hee-Kook Park
Published: October 2002

SF6 dry post-etch treatment after contact hole etching has been compared with both NF3 and CF4+O2 post-etch treatment (PET) through measurement of electrical characteristics. It is found that SF6 PET produces the smallest contact resistance at 0.2 µ m contact hole. This phenomenon is analyzed by using secondary ion mass spectroscopy (SIMS) and atomic force microscopy (AFM). According to SIMS analysis, the removal effect of the contaminative carbon and fluorine is almost the same for the three types of PETs. AFM results show that the surface roughness of the contact hole bottom after SF6 PET is the greatest among the three different PETs. This indicates that SF6 PET is very effective in reducing the contact resistance by increasing the surface area of contact hole bottom, since resistance decreases with increasing surface area.
Effect of Lens Aberration on Resist Pattern Profiles in Edge-Line Phase-Shift Method
Authors: Nakatani Mitsunori , Kojima Yoshiki , Nakano Hirofumi , Kamon Kazuya , Sato Kazuhiko , Takano Hirozou , Osamu Ishihara Osamu Ishihara
Published: October 2002

In edge-line phase-shift lithography, asymmetrical resist patterns formed by both sides of shifter edges have been observed in the case of a narrow shifter. The effect of phase error, shifter width and shifter edge angle on resist pattern profiles has been investigated by simulations and experiments. It has been confirmed that the asymmetry of resist patterns is mainly due to the coma aberration of the stepper projection lens and is enhanced as the shifter width becomes narrower. The effect of decreasing the shifter edge angle has proved to be equivalent to the effect of narrowing the effective shifter width.
Absolute Measurement of Lattice Spacing d(220) in Floating Zone Silicon Crystal
Authors: Fujimoto Hiroyuki , Nakayama Kan , Tanaka Mitsuru , Guento Misawa Guento Misawa
Published: October 2002

The lattice spacing d
220 of a silicon crystal of National Research Laboratory of Metrology has been measured with a new combined X-ray and optical interferometer, with relative uncertainty of 0.16 ppm. This value is in good agreement with other reported values, whereas the ratio of molar mass M to density ρ measured for this crystal shows discrepancy of around 3 ppm from previously reported ratios. It seems that the conventional route to determining the Avogadro constant from M, ρ and d
220 will require a new characterization technique to estimate the number of silicon atoms in a unit cell volume.
Optical Properties of Ba2NaNb5O15 Film Fabricated by RF Magnetron Sputtering Method
Authors: Masuda Yoichiro , Masumoto Hiroshi , Kidachi Yuuki , Watadzu Akira , Baba Akira , Goto Takashi , Hirai Toshio
Published: October 2002

Tungsten-bronze-type Ba2NaNb5O15 (BNN) thin films were deposited on fused-quartz and Si substrates. The deposition ratio (Ba:Na:Nb) and rate of the films depend on the sputtering conditions. The dielectric constant and dielectric loss factor are 889 and 0.029, respectively, at room temperature. The leakage current density is about 100 mA/cm2 at 1 MV/cm. The remanent polarization and coercive field are 2.39 µ C/cm2 and 8.33 kV/cm, respectively, and the second-harmonic generation coefficient d is about 2.54×10-13 m/V. Moreover, Raman scattering of the BNN films is discussed.
Epitaxial AlN Thin Films Grown on α-Al2O3 Substrates by ECR Dual Ion Beam Sputtering
Authors: Okano Hiroshi , Tanaka Naoki , Kobayashi Masami , Usuki Tatsuro , Kenichi Shibata Kenichi Shibata
Published: October 2002

Aluminum nitride (AlN) thin films have been epitaxially grown on (001), (110) and (11̄2) Al2O3 substrates by ECR dual ion beam sputtering. It was found that (001)AlN could be epitaxially grown on (110)Al2O3 as well as on (001)Al2O3. Not only (110)AlN but also (116)AlN was epitaxially grown on (11̄2)Al2O3. The lattice mismatch in the two types of epitaxial growth was investigated by considering the chemical bonding between the oxygen atoms of α-Al2O3 and the aluminum atoms of hexagonal AlN.
The lattice mismatches of the (116)AlNł(11̄2)Al2O3 and (110)AlNł(11̄2)Al2O3 were +1.7% and -4.4%, respectively. The lattice mismatch suggests that epitaxial growth of (116)AlN as well as (110)AlN on (11̄2)AlO3 is feasible.
Preparation of Pb-Based Ferroelectric Thin Films at Room Temperature Using Excimer-Laser-Assisted Multi-Ion-Beam Sputtering
Authors: Kanno Isaku , Hayashi Shigenori , Takayama Ryoichi , Sakakima Hiroshi , Takashi Hirao Takashi Hirao
Published: October 2002

Pb-based ferroelectric thin films of PbTiO3, (Pb, La)TiO3 and Pb(Zr, Ti)O3 were fabricated on Pt/MgO and Pt/Ti/SiO2/Si substrates using an excimer-laser-assisted multi-ion-beam sputtering technique. During the deposition at room temperature, the surface of the films was irradiated with XeCl excimer laser pulses in order to promote surface reactions. X-ray diffraction and in situ reflection high-energy electron diffraction measurements demonstrated that the films with perovskite structure were epitaxially grown with preferential a-axis orientation. The prepared PZT films exhibited the dielectric constant of 248 and ferroelectric P-E hysteresis loops.
Dielectric Characteristics of a Complex Perovskite Multilayer Ceramic Capacitor with Thin Dielectric Layers
Authors: Takakura Shin-ichi , Katoh Katsumi , Yamada Masayuki , Yasunobu Yoneda Yasunobu Yoneda
Published: October 2002

The demand for multilayer ceramic capacitors (MLC) of smaller size and higher volumetric capacitance is increasing sharply. The electrical properties of multilayer high-dielectric-constant relaxor ceramic capacitors of dielectric thickness from 3 to 32 µ m were measured. MLC (1.0 µ F) conforming to Y5V temperature characteristics were produced in EIA 0402 size (1.0×0.52 mm). The dielectric constant and ac voltage dependence of change in capacitance were found to change with decreasing dielectric thickness.
High-Efficiency Bridge Double Phase-Conjugate Mirrors in Cu-Doped (K0.5Na0.5)0.2(Sr0.61Ba0.39)0.9Nb2O6 Crystals
Authors: Zheng Yujin , Sasaki Akira , Gao Xin , Aoyama Hisayuki , Jisuke Fukaya Jisuke Fukaya
Published: October 2002

In this paper, we report the formation of high-efficiency double phase-conjugate mirrors with the bridge incident geometry in Cu-Doped (K0.5Na0.5)0.2(Sr0.61Ba0.39)0.9Nb2O6 (Cu:KNSBN) crystals. These bridge double phase-conjugate mirrors have high efficiency, even under low incident power. For crystals with different absorption coefficients, the optimum incident geometries of the bridge double phase-conjugate mirrors were observed and discussed.
Effects of Thickness on Ferroelectricity in Vinylidene Fluoride and Trifluoroethylene Copolymers
Authors: Yoshiro Tajitsu Yoshiro Tajitsu
Published: October 2002

The effects of thickness on ferroelectricity in vinylidene fluoride and trifluoroethylene copolymers have been investigated mainly through switching measurements. Switching phenomena as a result of ultimately 180° rotations of individual chain molecules around their axes were observed in the copolymer films with thicknesses in the range of 0.03-1 µ m. With decreasing film thickness, the switching times increase, the switching curve becomes broad and the permittivity at the Curie point decreases. However, the amount of reversed polarization is nearly independent of film thickness. These results are generally reproducible if we assume a surface layer with thickness less than 0.01 µ m, low permittivity, and absence of ferroelectric switching even in the presence of an applied electric field.
Photoluminescence of Erbium Implanted in SiGe
Authors: Chang Shoou-Jinn , Nayak Deepak K. , Shiraki Yasuhiro
Published: October 2002

The optical properties of an Er-implanted SiGe sample have been studied. Sharp and temperature-stable Er-related photoluminescence (PL) peaks were observed at around 1.5 µ m, which correspond to the Er4I13/2to4I15/2transition. It was found that the Er ions form more than three noncubic luminescence centers in the SiGe host. Although the PL intensity quenches at high temperatures, the Er-related PL signal can still be observed at room temperature. For a Si0.87Ge0.13:Er sample annealed at 850° C for 20 min, the activation energy is 130 meV which is slightly smaller than that of the Er-doped Si.
Electronic Conduction Characteristics of Sol-Gel Ferroelectric Pb(Zr0.4Ti0.6)O3 Thin-Film Capacitors: Part I
Authors: Mihara Takashi , Hitoshi Watanabe Hitoshi Watanabe
Published: October 2002

We studied the electronic conduction characteristics of sol-gel ferroelectric Pb(Zr0.4Ti0.6)O3 thin-film capacitors by evaluation of time-dependent leakage current ( I-t ) and current-voltage ( I-V ) characteristics along with the dielectric properties. We found two regions in the I-V characteristics, which were (1) ohmic-like current with strong decay time dependence below about 800 kV/cm, and (2) the current with strong electric field dependence above about 1 MV/cm. The leakage current in the ohmic region strongly depended upon the measurement conditions including decay time and the current obeyed the power law of DC stressing time. The hysteresis loop shifted toward a negative field after DC stressing which implied the trapping of positive charges near the top surface. The conduction mechanism of current at high field was considered to be the mixture of Schottky emission and Frenkel Poole emission, taking the dynamic dielectric constant into account. The barrier height and trapped level were estimated to be 0.58 eV and 0.5 eV, respectively.
Estimation of Initial and Response Times of Laser Dew-Point Hygrometer by Measurement Simulation
Authors: Matsumoto Sigeaki , Toyooka Satoru
Published: October 2002

The initial and the response times of the laser dew-point hygrometer were evaluated by measurement simulation. The simulation was based on loop computations of the surface temperature of a plate with dew deposition, the quantity of dew deposited and the intensity of scattered light from the surface at each short interval of measurement. The initial time was defined as the time necessary for the hygrometer to reach a temperature within ±0.5° C of the measured dew point from the start time of measurement, and the response time was also defined for stepwise dew-point changes of +5° C and -5° C. The simulation results are in approximate agreement with the recorded temperature and intensity of scattered light of the hygrometer. The evaluated initial time ranged from 0.3 min to 5 min in the temperature range from 0° C to 60° C, and the response time was also evaluated to be from 0.2 min to 3 min.
Effect of Oxidation on Localized Heat Generation and Dielectric Breakdown of Low-Density Polyethylene Film
Authors: Takao Tsurimoto Takao Tsurimoto , Masayuki Nagao Masayuki Nagao , Masamitsu Kosaki Masamitsu Kosaki
Published: October 2002

The effect of oxidation on localized heat generation and dielectric breakdown in low-density polyethylene (LDPE) film was studied by thermography. In the non-McKeown-type epoxy-free electrode system, localized heat generation of LDPE film leading to dielectric breakdown increased and breakdown strength decreased upon oxidation. In the McKeown-type specimen, however, the breakdown strength of oxidized LDPE film is higher than that of an unoxidized one. It is considered that enhancement of the thermal process is a major factor of breakdown in the epoxy-free electrode system and that homo-space charge and/or electron scattering effect is dominant in the McKeown type specimen.
Effects of Hydrophile-Lypophile Balance of Emulsifier on Electrooptical Properties and Morphology of Poly(vinylalcohol)/Liquid Crystal Composite
Authors: Ono Hiroshi , Kawatsuki Nobuhiro
Published: October 2002

We clarified the relationship between the morphology of a poly(vinyl alcohol) (PVA)/liquid crystal (LC) composite film fabricated by an emulsification method and a hydrophile-lypophile balance (HLB) of an emulsifier. The LC domain size was affected by the surface tension of the PVA aqueous solution and of the LC.
The surface tension of the PVA aqueous solution and the LC was varied by changing the HLB value. The electrooptical properties, such as threshold voltage and response time, were strongly dependent on the LC droplet size, in good qualitative agreement with results obtained using the equations of Doane et al. [Mol. Cryst. Liq. Cryst. 5 (1989) 1453].
Highly Sensitive Laser Absorptiometric Method Using Triple-Prism Multireflection System
Authors: Iijima Tetsuo , Watanabe Isami , Goto Miki , Arai Toshihiko
Published: October 2002

To obtain high sensitivity in absorptiometry using a standard cell with a 1 cm light path length, two new optical systems have been designed. The sensitive absorptiometric system using the twin or triple prism coupling method provides 10-18 times higher sensitivity than does the ordinary absorptiometer.
Effect of Reticle Erros on Systematic Intrafield Line Width Variations
Authors: Liu Hua-yu , Yu Crid , Bob Gleason Bob Gleason
Published: October 2002

We have studied the contributions of reticle line width ( CD) errors to systematic intrafield CD variations for 0.35 µ m i-line lithography by measuring electrical resistance of lines patterned in polysilicon films. Reticle errors were determined by independent measurements, and their effects on final printed dimensions were analyzed. Both reticles and steppers contribute to the systematic intrafield variation. In some cases, the total variance exceeds the sum of the variances individually associated with steppers and reticles. Because aberrations and reticle errors are not random, analysis of variance must take their correlation into consideration. We have observed cases in which this correlation and nonlinear imaging contribute significantly to total line width variance.
Breakdown Mechanisms in Pseudomorphic InAlAs/InxGa1-xAs High Electron Mobility Transistors on InP. I: Off-State
Authors: Dickmann Jürgen , Schildberg Steffen , Riepe Klaus , Maile Bernd E. , Schurr Anton , Geyer Arthur , Peter Narozny Peter Narozny
Published: October 2002

A systematic experimental study on the mechanisms which are inducing device breakdown in the off-state in L
G=0.28 µ m gate-length pseudomorphic InAlAs/In

x

Ga1-
x

As (0.53< x<0.7) High Electron Mobility Transistors on InP substrate is presented. The study identifies the present limitations of this type of device made with this material system. The investigation encompasses temperature- and mole fractional dependent two-terminal and three-terminal dc-measurements. The results of the investigation clarify that breakdown is a combined process of thermionic field emission and impact ionization. Up to high drain bias, thermionic field emission is the dominant process, only at very high drain bias impact ionization occurs. The experimental results also indicate that off-state breakdown is surface related. The drain-source breakdown voltages were determined to be V
BRDS=8 V, 5.9 V, 5.2 V, 4.3 V, 2.5 V for x=0.53, 0.59, 0.62, 0.65 and x=0.7, respectively. The two-terminal gate-drain breakdown voltages at room-temperature were determined to be V
BRGD=11.9 V, 11.3 V, 7.9 V, 7.2 V, 6.7 V for x=0.53, 0.59, 0.62, 0.65 and x=0.7, respectively.
Analysis of Eddy Current Effects in an Electron Optical Column
Authors: Someda Yasuhiro , Sohda Yasunari , Saitou Norio , Itoh Hiroyuki , Katoh Shin'ichi
Published: October 2002

A new simple method for analyzing eddy currents caused by magnetic deflection in an electron optical column is proposed. This method can be used to calculate the magnetic deflection error caused by eddy currents by changing the magnetic permeability in the optical column between zero and normal permeability. These magnetic permeabilities correspond to the initial and the final states after magnetic deflection. The deflection error is calculated using the deflection sensitivity and rotation seisitivity which is simulated from flux density distribution of the magnetic deflector. Good agreement was obtained between simulation and experiment.