bluuebunny/crossref_metadata_2025 huggingface dataset:
Ce-Activated SrS Thin Film Electroluminescent Devices Fabricated by Multi Source Deposition Using Ga2S3 Precursor
Authors: Inoue Yoji , Tanaka Katsu , Okamoto Shinji , Kikuo Kobayashi Kikuo Kobayashi , Kuniharu Takizawa Kuniharu Takizawa
Published: October 2002

For the first time, cerium-doped strontium sulfide (SrS:Ce) thin film electroluminescent (TFEL) devices have been fabricated by multi source deposition using Ga2S3 compound. Ga2S3 is able to provide elemental sulfur without leaving Ga in the phosphor films. This new precursor is excellent for controlling the sulfur supply, due to its low vapor pressure. Highly crystalline SrS thin films have been deposited with preferentially (200)-oriented. Full width at half maximum of the X-ray diffraction peak is 0.22°. The composition of the thin film is close to the stoichiometry, and the element Ga was not detected in the film. The TFEL device shows a luminance level of 160 cd/m2 at 40 V above the threshold voltage, and the CIE color coordinates are x=0.30 and y=0.51.
Treeing Deterioration Characteristics in Cross-linked Polyethylene and Epoxy Resin Composite Materials
Authors: Yuan Changmin , Yoshimura Noboru , Lim Jangseob , Miyata Hiroyuki , Niwa Toshio
Published: October 2002

An experimental investigation for evaluating the treeing deterioration characteristics of composite materials was carried out by preparing an interface between cross-linked polyethylene and epoxy resin. The results of various interface conditions are described in this paper. It was determined that the interface had a significant effect on the treeing breakdown under various specimen arrangements. The time until complete breakdown of the sample is longer than the time required for complete penetration of the sample by one or more tree channels. This erosion process is similar to that of epoxy resin materials. It was also determined that if the gases in tree channels were trapped in the interface, the time until complete breakdown would be much longer.
Modeling, Synthesis and Characterization of a Millimeter-Wave Multilayer Microstrip Liquid Crystal Phase Shifter
Authors: Guérin Fréderic , Chappe Jean-Marc , Pascal Joffre Pascal Joffre , Daniel Dolfi Daniel Dolfi
Published: October 2002

Electromagnetic simulation software is used for modeling the properties of a 2–15 GHz liquid crystal microstrip phase shifter previously designed at Thomson-CSF. After experimental validation of the computed results, the software is applied to the modeling of a new 30–40 GHz multilayer microstrip phase shifter, where the active medium is a liquid crystal inserted between solid dielectric substrates. Measurements carried out at between 10 and 40 GHz on 4.35 cm long lines are in good agreement with theoretical predictions. A maximum experimental phase shift of 219.3° at 37 GHz (about 50°/ cm) was observed for a structure with a commercial liquid crystal (BDH-E44) and silica substrates.
Mixture Alignments on Graphite Substrates in Cyanobiphenyl Liquid Crystals Observed using Scanning Tunneling Microscopy
Authors: Tsutomu Kadotani Tsutomu Kadotani , Seiji Taki Seiji Taki , Shoichi Kai Shoichi Kai
Published: October 2002

New alignments in three types of mixtures (9CB-8CB, 10CB-9CB and 10CB-8CB, where CB means 4'-n-alkyl-4-cyanobiphenyl) are observed. In the mixture of 9CB and 8CB, there is only one specific alignment. For the mixtures 10CB-9CB and 10CB-8CB, there are three and two specific alignments respectively. The feature that is common to all these mixtures is an anti-parallel alignment in a row of neighboring heterogeneous molecules. These characteristic mixture-alignments suggest a variety of molecular interactions in the mixtures.
Optical and Electrical Properties of Lanthanum-Modified Lead Titanate Thin Films with Various Lanthanum Concentrations
Authors: Seong Jun Kang Seong Jun Kang , Yung Sup Yoon Yung Sup Yoon
Published: October 2002

We have studied the effects of La concentration on the optical, dielectric and ferroelectric properties of lead lanthanum titanate (PLT) thin films using the sol-gel method. Most of the properties are greatly affected by the La concentration. The refractive index at λ=632.8 nm increases from 2.39 to 2.44 as the La concentration increases from 15 to 33 mol%, whereas the extinction coefficient is independent of the La concentration. The dielectric constants of the films varied from 340 to 870 with varying La concentration in the range from 15 to 33 mol%. The hysteresis loop becomes narrower with the increase of La concentration from 15 to 28 mol% and slightly wider again with the increase of La concentration from 28 to 33 mol%. Among the films investigated in this research, PLT(28) thin film shows the best dielectric properties for application to the dielectrics of ULSI dynamic random access memories (DRAMs). At the frequency of 100 Hz, the dielectric constant and the loss tangent of PLT(28) thin film are 940 and 0.08, respectively. The leakage current density at 1.5×105 V/cm is 1×10-6 A/cm2. The comparison between the simulated and the experimental curves for the switching transient characteristics shows that PLT(28) thin film behaves like a normal dielectric.
Emission Spectra from Pulsed Discharges in Liquid Helium
Authors: W. DeSilva Wenhong Qin , Fumihiro Tomimoto Fumihiro Tomimoto , Kuninori Sato Kuninori Sato
Published: October 2002

The time-resolved emission spectra from high-voltage pulsed discharges in liquid helium below 4.2 K, 1 atm, and cryogenic helium gas near 4.2 K, 1 atm, have been measured in the visible spectral range. In addition to the well known atomic lines, which exhibit strong and broadened profiles with continua at an early stage, some strong spectral features are observed near 23300 cm-1 ( ∼430 nm) and 25300 cm-1 ( ∼395 nm). The former can be assigned to He 2 transition ( g
3Σ

g

+– a
3Σ

u

+), and the latter is not observed in previously reported works. These features disappear in 77 K and 300 K, 1 atm, He gas under the same experimental conditions.
Production of a Large-Diameter Uniform Plasma by Modified Magnetron-Typed Radio Frequency Discharge
Authors: Yunlong Li Yunlong Li , Satoru Iizuka Satoru Iizuka , Noriyoshi Sato Noriyoshi Sato
Published: October 2002

The properties of a new plasma source, i.e. a large-scale modified-magnetron typed (MMT) radio frequency (RF) plasma source, are investigated for producing a uniform high-density plasma with a large diameter of the order of 1 m. A plasma with uniformity within a few percent is produced over 120 cm in diameter in front of the substrate under an argon pressure of 1 mTorr. The plasma density is 6×1010 cm-3 at the axial center of the RF electrode when the incident RF power is 2.8 kW. The plasma density is almost proportional to the RF power. Since the structure of MMT plasma source is quite simple, it is useful for large area plasma processing.
Compact Electron Cyclotron Resonance Plasma Source Optimization for Ion Beam Applications
Authors: Yamakawa Patrick O'Keeffe , Mutoh Harunobu , Shoji Den Shoji Den , Yuzo Hayashi Yuzo Hayashi
Published: October 2002

A prototype electron cyclotron resonance (ECR) plasma source has been designed and developed to deliver a maintenance-free, stable and controllable current ion beam. The plasma source can accommodate both low and high power microwave applicators for different applications. Selection of the optimum magnetic field arrangement and position with respect to the microwave applicator ensures a high density plasma operational at pressures below 5.0×10-2 Pa. From initial tests a plasma density of 5.0×1010 cm-3, electron temperature of 1.5 eV and a plasma potential of 10 V were measured 10 cm downstream for an input microwave power of 100 W at an Ar pressure of 0.1 Pa. A saturation ion current density of 2 mA/cm2 was measured independently using a biased Langmuir probe and results matched well the calculated values. Ion beams with non-uniformity of ±10% have been used to sputter with control a diamond-like-carbon film with rates of up to 30 nm/h at room temperature.
Development and Characterization of a New Compact Microwave Radical Beam Source
Authors: O'Keeffe Shoji Den , Hayashi Yuzo , Ito Masafumi , Masaru Hori Masaru Hori , Toshio Goto Toshio Goto
Published: October 2002

For plasma-assisted processing of future semiconductor devices, a new compact microwave plasma source has been specifically designed. The source is versatile in that plasma production is possible over a wide pressure range. Measured plasma parameters include electron densities in excess of 1011 cm-3 and low plasma potential (<10 V). Plasma chemistry was investigated by emission spectroscopy and the main excited species found was atomic oxygen radicals. In determining the absolute density of radical species, titration using NO2 gas was employed to correlate the oxygen atom density with the plasma operating conditions. At a microwave power of 300 W and a O2 partial pressure of 16.6 Pa oxygen atom densities in excess of 1.9×1015 cm-3 have been measured, which gives dissociation rates of O2 of approximately 20%. Effects of wall materials on the oxygen atom density were also investigated. Using a Teflon liner at high pressures provides a 37% increase in oxygen atom density due the lower recombination coefficient of Teflon compared to stainless steel.
Relationship between Control of Reactive Plasmas with Magnetic Filter and Formation of Thin Films
Authors: Osamu Fukumasa Osamu Fukumasa , Yasushi Tauchi Yasushi Tauchi , Satoshi Sakiyama Satoshi Sakiyama
Published: October 2002

Plasma parameters (CH4/H2+Ar plasmas) are spatially well controlled using a movable magnetic filter. At any filter position, plasma parameters change dramatically across the magnetic filter. The plasma is divided into two parts, the source plasma region (high density plasmas with energetic electrons) and the diffused plasma region (low electron-temperature plasmas without energetic electrons). Carbon thin films are prepared well in the diffused plasma region. The effects of bias potential of the substrate and control of neutral radicals on formation of thin films are discussed briefly.
Measurements of Ion Energy Distribution Functions in an Radio Frequency Plasma Excited with an m = 0 Mode Helical Antenna and Thin Film Preparation
Authors: Yasunori Ohtsu Yasunori Ohtsu , Gen Tochitani Gen Tochitani , Hiroharu Fujita Hiroharu Fujita , Jinqiu Zhang Jinqiu Zhang , Yuichi Setsuhara Yuichi Setsuhara , Shoji Miyake Shoji Miyake
Published: October 2002

Ion energy distribution functions were measured using an electrostatic analyzer in an Ar radio frequency plasma excited with a helical antenna in a magnetic field, where a plasma density jump occurred. The functions showed a two peak and a single peak profile before and after the density jump had occurred, respectively. The electron temperature and the plasma potential decreased after the density jump. The formation of CN films was also studied by sputtering a cylindrical graphite target in an Ar + N2mixture.
Behavior of Electrons and Negative Ions in a Capacitively-Coupled Radio-Frequency NF 3/Ar Plasma
Authors: Toshiyasu Hayashi Toshiyasu Hayashi , Akihiro Kono Akihiro Kono , Toshio Goto Toshio Goto
Published: October 2002

The behaviors of electrons and negative ions in a low-pressure (100 mTorr) capacitively-coupled radio-frequency (13.56 MHz) NF3/Ar plasma have been studied at a low-power level (2–10 W) using a laser photodetachment technique combined with a microwave cavity resonance method for determining electron density. The wavelength dependent photodetachment measurement indicated that F- is the predominant negative ion species in the plasma. The negative ion density was higher than the electron density by a factor of ∼50 at a NF3 mixing ratio r as low as 1% and the negative-ion/electron density ratio further increased with increasing r mainly because of the decrease in the electron density. The overall change in the negative ion density in the studied range of 1%<r<40% was relatively small (a factor of ∼2). For small r (<∼10%), the negative ion density increased with decreasing r; the change in the electron-attachment and ion-ion recombination rate constants with varying r was investigated to explain the phenomenon.
Spatial Distribution of He Metastable Atoms in Electron Cyclotron Resonance Plasma
Authors: Hiroshi Toyota Hiroshi Toyota , Mahiko Watanabe Mahiko Watanabe , Ken Takiyama Ken Takiyama , Toshiatsu Oda Toshiatsu Oda
Published: October 2002

Axial profile of HeI metastable (21S) atom density was measured along an electron cyclotron resonance (ECR) plasma flow for plasma processing by polarized laser-induced fluorescence (LIF) spectroscopy. A new development in the LIF method was made to avoid laser stray light, which involved observation of fluorescence due to forbidden excitation by electric quadrupole transition. It was found that the metastable (21S) atom density produced was as high as 1011 cm-3 near the outlet of the plasma flow. Doppler profiles of the LIF excitation were measured to determine drift velocity of atoms in the plasma. The production mechanism of metastable atoms was briefly discussed.
Influence of Discharge Geometry on Power Dissipation and Sheath Impedances in Silane Discharges
Authors: Spiliopoulos Nikos , Dimitris Mataras Dimitris Mataras , Dimitris Rapakoulias Dimitris Rapakoulias
Published: October 2002

The influence of the interelectrode distance on the power consumed in rf silane glow discharges, for two different electrode sizes and at two different silane pressures is reported. The effect of the increasing grounded surface area in contact with the discharge is analysed by using a simplified calculation of the rf and grounded sheath impedances. At all cases the power consumed in the discharge increases with interelectrode distance and is higher for higher pressures, for a constant excitation voltage. The sheath impedances are always higher for lower pressures except for the case of the ground sheath when using the large electrode set.
Calculation of Negative Ions and Scattering Using Methods of Electron Atom Collision Theory
Authors: Aleksandar R. Tančić Aleksandar R. Tančić
Published: October 2002

Ab initiocalculation of negative ions is made, and electron affinity energies, phase shifts and momentum transfer cross sections for electron-atom scattering are obtained using the techniques of many-body Green's functions. The basic processes treated here are the slow electron-alkaline earth atom scattering and the electron-noble gas atom scattering. Scattering data are obtained and negative ion calculations are made by solving the Dyson equation.
Dynamic Variation of the Sticking Coefficient of Oxygen Atoms in Helicon-Wave Excited High-Density Oxygen Plasmas
Authors: Jun Matsushita Jun Matsushita , Koichi Sasaki Koichi Sasaki , Kiyoshi Kadota Kiyoshi Kadota
Published: October 2002

The sticking coefficient of O atoms on a chamber wall was determined by lifetime measurements in afterglow oxygen plasmas using two-photon laser-induced fluorescence spectroscopy. The sticking coefficient was strongly dependent on the discharge conditions. When the discharge duration was short or the oxygen gas pressure was low, the sticking coefficient was close to unity and the lifetime of O atoms was equal to the diffusion time determined by the chamber geometry. However, for a long discharge duration and a high oxygen pressure, the sticking coefficient was considerably lower and saturated at ∼0.1. The decrease in the sticking coefficient can be explained by the increase in the surface coverage due to adsorption of O atoms during the discharge. The number of O atoms which was sufficient to decrease the sticking coefficient to ∼0.1 was determined experimentally to be on the order of 1015 cm-2.
Surface Electronic States of Adsorbed Nitrogen Molecules on Oxidized Nickel Surface
Authors: Obara Kozo , Yiji Panli , Chiba Ken-ichi , Fukarek Wolfgang , Möller Wolfhard
Published: October 2002

We present a new technique to investigate the electronic surface structures of metal electrodes and experimental data on oxidized surfaces of nickel electrodes. The experimental system consists of a simple triode structure and an electromagnet to control the momentum of incident electrons. The magnetic field dependence of the transmission electron current to the metal electrodes depends on the electron density at the electrode surface. When the electron density at the surface is high, the incident electrons are scattered by quantized surface states in the surface potential barrier. On the other hand, in the case of low electron density, the incident electrons show resonance characteristics due to the presence of discrete electronic states as a result of the generation of a periodic surface potential. Molecular nitrogen adsorption causes a change in the surface potential, and the bonding states intermediate between covalent bonds and van der Waal's-like bonds are detected.
Nitrogen Plasma Doping during Metalorganic Chemical Vapor Deposition of ZnSe
Authors: Morimoto Keizo , Yuichi Kawamura Yuichi Kawamura , Naohisa Inoue Naohisa Inoue
Published: October 2002

Active nitrogen generated by low-frequency high-voltage plasma discharge was used at pressures on the order of 1 Torr. Using a technique of alternate growth and plasma doping, high-quality N-doped ZnSe layers were grown on GaAs(100) substrates. In the low-temperature photoluminescence (PL) spectra, the narrow and distinct peak for acceptor-bound exciton, together with donor-acceptor pair peaks is predominant, which suggests N-acceptor doping on the order of 1018 cm-3. The strong PL intensity indicated that the layers were free from plasma damage. The successful doping at the relatively high pressures strongly suggests that the metastable state ( A3
Σ

u

+) of a nitrogen molecule is responsible for the N doping. Although as-grown layers are highly resistive, they are converted to p-type layers with a hole concentration of ∼1×1015 cm-3 upon rapid thermal annealing at 700° C.
Effect of Plasma Parameter Control on the Growth of Zincblende Type GaN Films by ECR Plasma Enhanced Metalorganic Chemical Vapor Deposition
Authors: Yasui Kanji , Iizuka Kentarou , Tomoaki Harada Tomoaki Harada , Tadashi Akahane Tadashi Akahane
Published: October 2002

Zincblende type GaN films were grown at low temperatures by mesh-bias-controlled electron-cyclotron-resonance metalorganic chemical vapor deposition (ECRMOCVD) using ammonia and trimethylgallium as source gases. Dependence of plasma parameters such as electron temperature, electron density and plasma space potential in a discharge chamber and a growth chamber, on the mesh bias was investigated using a Langmuir probe and a Faraday cup. Dependence of the properties of GaN films, such as crystal structure, crystal orientation and residual stress, on the mesh bias applied during nitridation and growth was also investigated. The growth of zincblende GaN films was enhanced under conditions of a negative mesh bias at which the space potential was lowest and the impingement of ions was suppressed. The crystallinity of GaN films and their crystal orientation were best under the same bias conditions.
Structure Changes of Coulomb Crystal in a Carbon Fine-Particle Plasma
Authors: Yasuaki Hayashi Yasuaki Hayashi , Kazuo Takahashi Kazuo Takahashi
Published: October 2002

The changes of particle arrangement in a methane/helium plasma during particle growth have been observed and quantitatively analyzed using the Monte-Carlo simulation. It has been suggested that a 3-dimensional Coulomb crystal changes to the liquid phase with the growth due to a change in the direction of force. It has been found that the liquid changes to a 2-dimensional crystal as a result of an increase in particle charge. A force due to polarization of negatively charged particles and the surrounding positive ions in the direction perpendicular to electrodes, as well as an isotropic Coulomb force, plays an important role in the formation of Coulomb crystals.
Modeling of the Evolutions of Negative Ions in Silane Plasma Chemical Vapor Deposition for Various Process Conditions
Authors: Dong-Joo Kim Dong-Joo Kim , Kyo-Seon Kim Kyo-Seon Kim
Published: October 2002

The evolutions of negative ions in the silane plasma chemical vapor deposition (PCVD) reactor for semiconductor processing were analyzed, considering the effects of chemical reactions, fluid convection, diffusion and electrical migration. The 23 plasma chemical reactions and 18 chemical species which might be important for the evolutions of negative ions were considered in this analysis. The governing equations were solved numerically. Most of the negative ions are located in the bulk plasma region and the concentrations of negative ions are almost zero in the sheath regions, as they are expelled from the sheath regions to the bulk plasma by electrostatic repulsion. The concentrations of negative ions at the downstream sheath boundary were higher than those at the upstream sheath boundary due to the effect of convection. As the reactor pressure increases, the concentrations of neutrals and positive ions increase, but the concentrations of negative ions decrease, based on the reaction chemistry proposed in this study. As the electric field strength increases, the negative ion concentrations increase, because more negative ions are contained in the bulk region by the stronger electrostatic repulsive forces.
Future Perspective Magnetic Superresolution
Authors: Takahashi Akira , Murakami Yoshiteru , Hirokane Junji , Nakayama Junichiro , Yukio Kurata Yukio Kurata , Hideyoshi Yamaoka Hideyoshi Yamaoka
Published: October 2002

The magnetic superresolution (MSR) method improves readout resolution of magnetooptical (MO) signals, with a mask that the readout layer creates. The MSR method is advantageous for high-density recording. However, the recording sensitivity and overwrite function of MO media must be improved in order to render it suitable for general use. To meet these requirements, we investigated the MSR method using static coupling force and its future extension.
High Peak-to-Valley Current Ratio GaInAs/GaInP Resonant Tunneling Diodes
Authors: Takashi Oobo Takashi Oobo , Riichiro Takemura Riichiro Takemura , Michihiko Suhara Michihiko Suhara , Yasuyuki Miyamoto Yasuyuki Miyamoto , Kazuhito Furuya Kazuhito Furuya
Published: October 2002

As an Al-free material system, the GaInAs/GaInP heterostructure has a large conduction-band discontinuity. We report the fabrication of GaInAs/GaInP resonant tunneling diodes which exhibit current density-voltage characteristics with a peak-to-valley current ratio of 7.8 at 4.2 K. To our knowledge, this is the highest value obtained for this material system.
Coercivity of Barium Ferrite Particles with Superparamagnetic Coating
Authors: Tung I-Chung , Yang Jyh-Shinn , Tsung-Shune Chin Tsung-Shune Chin
Published: October 2002

The coercivity mechanism of submicron barium ferrite (BF) particles with a superparamagnetic overcoat (i.e. δ- FeOOH or Fe3O4 fine particles) was investigated by experimental observation and micromagnetics based on the two-component Stoner-Wohlfarth model with interfacial coupling. For overcoating microcrystalline δ- FeOOH, BF particles were first coated with an Fe2+ solution at certain concentrations, followed by the addition of NaOH(a
q), and finally oxidized by 35 wt% H2O2(a
q). For Fe3O4 coating, BF particles were coated with a mixed solution of Fe3+ and Fe2+ first at certain concentrations, followed by NaOH(a
q). The results showed that the coercivity of BF particles decreased greatly while their saturation magnetizations were maintained at high levels. When Fe3O4 nanoparticles were used as the coating material, the saturation magnetization of the coated BF stayed at about the same level as that of the pure BF, 70 emu/g. The analytical calculation was successful in explaining quantitatively the effect of the coating, showing that the amount of coercivity decrement was related well to the uniaxial anisotropy constants of δ- FeOOH or Fe3O4 fine particles on the surface of BF. In addition, the superparamagnetic coating was found to behave ferrimagnetically during magnetization reversal. The larger the volume of coating, the lower the coercivity. Moreover, the weaker exchange coupling between the barium ferrite and δ- FeOOH or Fe3O4 further depresses the coercivity for the coated BF with thicker coatings.
Electrooptic Femtosecond Pulse Generation using a Dispersive Optical Fiber
Authors: Dae-Sik Kim Dae-Sik Kim , Yoshiji Matsuda Yoshiji Matsuda , Akihiro Morimoto Akihiro Morimoto , Tetsuro Kobayashi Tetsuro Kobayashi
Published: October 2002

Femtosecond optical pulses are generated electrically from a CW narrow-linewidth laser by the electrooptic chirping-compression method. In the experiments, an electrooptic modulator is fabricated employing quasi-velocity matching by the domain inversion method to yield effectively high optical chirping rates. The sideband spectra of 1.4 THz (FWHM) are produced successfully for single pass operation of the modulator and the phase-modulated light is compressed temporally to an optical pulse train using a 50 m single-mode optical fiber with positive group delay dispersion. As a result, shortest pulses of 660 fs with 16.25 GHz repetition rate are obtained at the modulation index of Δθ=31 rad.
Percolation Threshold of Carbon Black-Polyethylene Composites
Authors: Nakamura Shuhei , Saito Kazuhiko , Kitagawa Goro Sawa
Published: October 2002

In this paper, the percolation threshold of the carbon black-resin composites is discussed based on the experimental results of the changes in resistivity and relative permittivity for loading carbon black, the electric field dependence of current, and the critical exponent of conductivity. It was found that a formation of infinite clusters is interrupted by a tunneling gap in the volume fraction region of carbon black loading where the change in resistivity is extremely large. It was also found that the critical exponent of conductivity for the universal law of conductivity is satisfied if the percolation threshold is estimated at the volume fraction of carbon black where a nonohmic current behavior changes into an ohmic one. It is concluded that the percolation threshold should be defined at this volume fraction of carbon black.
Hydrogenated Carbon Nitride Thin Films Deposited by the Plasma Chemical Vapor Deposition Technique Using Trimethylamine and Ammonia
Authors: Kobayashi Satoshi , Nozaki Shinji , Masaki Hiroshi Morisaki
Published: October 2002

Hydrogenated carbon nitride ( C1-
x

N

x

:H) thin films were successfully deposited on Si and quartz substrates by the rf plasma chemical vapor deposition (PCVD) technique. A gas mixture of trimethylamine ( (CH3)3N) and ammonia ( NH3) introduced to a reaction chamber as material gases was decomposed by glow discharge using an induction-coupled-type PCVD apparatus. The deposited films were characterized by X-ray photoelectron spectroscopy (XPS) and infrared (IR) absorption measurements. They are identified to be C1-
x

N

x

:H without notable contamination during the deposition such as oxygen. The N1s
XPS spectra strongly suggest that the nitrogen atoms are single-bonded covalently with carbon atoms via nitrogen sp2 and carbon sp3 orbitals for all trimethylamine flow rate ratios, and a C–N network grows with decreasing the trimethylamine flow rate ratio. The IR absorption spectra show that both pyridine-like sp2-hybridized carbon and sp-hybridized carbon atoms in cyano-radicals also increase as the trimethylamine flow rate ratio decreases. Since the N–C single bonds in trimethylamine are preserved during the plasma decomposition, a large number of nitrogen atoms are effectively incorporated and form single N–C bonds in the deposited films. The films are pale yellow and have an optical bandgap of 3 eV, estimated from the optical absorption spectra. The film exhibits a photoluminescence spectrum with a broad peak, which can be deconvoluted into two Gaussian curves with peak energies in the ranges of 2.2–2.4 and 2.8–3.1 eV. The higher-energy peak is regarded as band-edge luminescence from the single-bonded carbon nitride network.
Relation between Molecular Orientation and Rubbing Strength Observed by Reflection Ellipsometry
Authors: Ichiro Hirosawa Ichiro Hirosawa
Published: October 2002

The relation between polyimide molecule orientation and rubbing strength (RS) is studied using reflection ellipsometry, and the film structure is considered to be different above and below an RS of 2.2 mm. Above 2.2 mm, the ordering of polyimide increases sharply in the weakly rubbed condition, and then saturates. The tilt angle of the principal dielectric axis of the molecule-oriented layer also increases very sharply to 53° and then monotonically decreases to 39°. However, no marked RS dependence is observed in the thickness of the molecule-oriented layer.
Direct Overwrite Magneto-Optical Disks with Magnetically Induced Super Resolution Readout Function
Authors: Yoshio Fujii Yoshio Fujii , Takashi Tokunaga Takashi Tokunaga
Published: October 2002

Threshold temperature design for a light intensity modulation direct overwrite magneto-optical disk with magnetically induced super resolution readout layers was investigated. It was confirmed that the magnetically induced super resolution read power margin can be enlarged by selecting adequate threshold temperatures for writing and erasing. Also it allowed a sufficient erase power margin for direct overwrite operation and suppressed a cross write. High recording density with a track pitch of 0.7 µm and a mark length of 0.35 µm with a sufficient read and erase power margin was demonstrated.
Parametric Study of Reflection Characteristics at Ahiral-Chiral Interfaces
Authors: Sung Ruyen Ro
Published: October 2002

Materials described by the constitutive relations σ
j
i
=µγ
j
i
+µγ
i
j
+λγ
k
k
δ
i
j
+cκ
j
i
and χ
j
i
=(ξ+ε)κ
j
i
+(ξ-ε)κ
i
j
+ηκ
k
k
δ
i
j
+cγ
j
i
lack inversion symmetry due to chirality in their microstructures. Six wavenumbers are possible solutions for dispersion equations in acoustically active (chiral) medium. Two of these wavenumbers represent longitudinally polarized elastic waves, the remaining four wavenumbers stand for circularly polarized elastic waves. In this paper, reflection characteristics of elastic waves normally impinging upon achiral-chiral interfaces are thoroughly discussed. The effects of the constitutive parameters of chiral medium on reflection coefficients are elucidated. Simulation results illustrate that reflection coefficients may vanish by properly tailoring constitutive parameters of chiral medium. The methods for determining constitutive parameters of chiral medium for zero reflection at achiral-chiral interfaces are developed. Results obtained in this study can be applied for designing state-of-the-art acoustic materials, e.g. acoustic shielding and absorptive materials, using chiral composites.
Nanometer-Scale Erasable Recording Using Atomic Force Microscope on Phase Change Media
Authors: Hiroyuki Kado Hiroyuki Kado , Takao Tohda Takao Tohda
Published: October 2002

We have demonstrated a nanometer-scale recording technique using an atomic force microscope (AFM) with an amorphous GeSb2Te4 film as a phase change medium. Data are recorded by changing the local electric properties of the film using a conductive AFM probe. The conductance of the film can be increased by more than one hundred times by applying a pulse voltage between the probe and the film. The recorded data are read by detecting the change in the conductance using the probe. The smallest possible recording region is 10 nm in diameter, which corresponds to a data storage density of 1 Tbit/cm2. The data can be erased by applying a negative DC voltage to the probe while scanning the probe over the film. The mechanisms of the reversible conductance change in the film are also discussed.
Effects of the Partial Pressure of Copper (I) Hexafluoroacetylacetonate Trimethylvinylsilane on the Chemical Vapor Deposition of Copper
Authors: Lee Seung-Yun , Rha Sa-Kyun , Lee Won-Jun , Kim Dong-Won , Hwang Jeong-Sug , Chong-Ook Park Chong-Ook Park
Published: October 2002

The effects of the partial pressure of precursor on the metalorganic chemical vapor deposition of copper were investigated. Copper was deposited using copper (I) hexafluoroacetylacetonate trimethylvinylsilane as a metalorganic precursor on TiN/Ti/Si substrates in a low-pressure warm-wall chemical vapor deposition reactor. The deposition rate of copper film was a constant value at a partial pressure higher than 0.048 Torr and decreased to below the constant value at a partial pressure lower than 0.048 Torr. The incubation time for copper nucleation decreased with increasing partial pressure of the precursor. The resistivity of copper film decreased to 2.00 µ Ω· cm with increasing partial pressure of the precursor. At a partial pressure lower than 0.048 Torr, copper did not nucleate inside the trench so that the step coverage of copper film became very poor.
Characteristics of Parallel-Plate RF Discharges in C 4F 8 Gas and C 4F 8/O 2 Mixtures
Authors: Kenji Aoyagi Kenji Aoyagi , Itsuo Ishikawa Itsuo Ishikawa , Kazuya Nagaseki Kazuya Nagaseki , Yuuji Hirose Yuuji Hirose , Yukinori Saito Yukinori Saito , Shinji Suganomata Shinji Suganomata
Published: October 2002

The discharge characteristics in a range of driving frequencies from 400 kHz to 1 MHz have been investigated by current-voltage measurements and optical emission spectroscopy. At pressures higher than 0.2 Torr, the discharge impedance is resistive, and the intense emission just in front of the instantaneous anode due to the double layer is observed around the phases of ωt=π/2 and 3π/2. These results are similar to those in strong electronegative SF6 discharges. On the other hand, at 0.1 Torr, the discharge impedance is capacitive, and the discharge is of the so-called wave-riding mode. The discharge structure at 1 MHz is scarcely changed by mixing a large amount O2 with C4F8 at a pressure of 0.5 Torr due to the high electronegativity of C4F8.
Estimation of Reactivity of Isocyanate Groups by Calculation and Magnetochemical Measurement
Authors: Kurihara Ken'ichi , Ata Masafumi , Matsute Masataka , Haruo Watanabe Haruo Watanabe , Jun'etsu Seto Jun'etsu Seto
Published: October 2002

The reactivity of isocyanate groups was examined with molecular orbital calculation and magnetochemical measurement. The linear correlation was confirmed between the atomic charges of the carbon atoms in the isocyanate group so calculated and the logarithmic kinetic constants for the addition reaction of the phenylisocyanates with 2-ethylhexanol. The linear correlation was also confirmed between the 13C chemical shifts of the same carbon and the kinetic constants. This correlation was applied to the estimation of the reactivity of the multifunctional isocyanate hardening agents for industrial use.
Potentiality of the Ag–In–Sb–Te Phase Change Recording Material for High Density Erasable Optical Discs
Authors: Shinotsuka Michiaki , Shibaguchi Takashi , Michiharu Abe Michiharu Abe , Yukio Ide Yukio Ide
Published: October 2002

The feasibility of using Ag–In–Sb–Te phase change material for high density of directly overwritable optical discs has been studied. A linear density of 0.34 µm/bit with a track pitch of 0.74 µm is confirmed to be achievable with a light source wavelength of 680 nm, with an objective lens NA of 0.60 and the criteria of data-to-data jitter of less than 14% of the channel bit length. The recording characteristics are also studied using an optical system with a 635 nm red laser diode in order to investigate the attainment of a linear density of 0.267 µm/bit which is equivalent to the DVD-ROM (read only memory) specification.
Optimization of Surface-Acoustic-Wave Withdrawal-Weighted Filters Using Simulated Annealing
Authors: Makoto Hirabayashi Makoto Hirabayashi
Published: October 2002

A withdrawal-weighted filter is optimized using a positional sequence, which is devised for restricting a bandwidth, instead of the conventional 0-1 sequence. The sequence, which shows the positions of active finger pairs, is used for the variables of simulated annealing. The method yields a maximum sidelobe level of -55.9 dB and a relative 3 dB bandwidth of 0.508 ±0.003%. The calculated results show that the method is effective for nonlinear optimization of withdrawal-weighted filters whose constraints of bandwidths are strict.
Temporal Propagation of Electron Wave in a Periodic Structure with Finite Length
Authors: Jun-ichi Sakai Jun-ichi Sakai , Akira Sugimura Akira Sugimura
Published: October 2002

Performance of quanta having a finite coherence length ℓ c in a periodic structure is studied. Classification between wave and particle properties depends strongly on the magnitude of coupling constant K, determined by the quantum mass, periodic potential depth and wavenumber. It is found that if K increases in a periodic structure with a fixed length, then a transmitted quantum is inclined to show wave properties even if ℓ c is short. As ℓ c becomes short, more quanta transmit through the structure even in the stop band. Coherence and medium lengths play an equivalent role in transmission. Namely, transmittance is nearly identical even if medium and coherence lengths are exchanged. Many oscillations due to the wave properties appearing in the transmission temporal wave can be explained by the effective mode mismatch among many eigenmodes. The oscillation period is controllable by changing the periodic potential depth or the effective mass.
Crystal Growth and Conductivity Control of Group III Nitride Semiconductors and Their Application to Short Wavelength Light Emitters
Authors: Isamu Akasaki Isamu Akasaki , Hiroshi Amano Hiroshi Amano
Published: October 2002

Recent development of technology and understanding of the growth mechanism in heteroepitaxial growth of nitrides on highly-mismatched substrates have enabled us to grow high-quality GaN, AlGaN, GaInN and their quantum well structures. Conductivity control of both n-type and p-type nitrides has also been achieved. These achievements have led to the commercialization of high-brightness blue, green and white light-emitting diodes and to the realization of short wavelength laser diodes and high-speed transistors based on nitrides. The performance of these devices is still progressing, but still requires advances in many areas of materials science and device fabrication.
Rate Determing Step of Anodic Charge-Transfer Process during Porous Silicon Formation in HF Solution
Authors: Takashi Unagami Takashi Unagami
Published: October 2002

Anodic reactions for the formation of porous silicon have been examined with regard to the rate determining step of charge-transfer processes. Porous silicon is formed by local silicon dissolution along with both divalent and tetravalent ions. The divalent anodic reaction based on Lehmann's model is controlled by activation. For the charge-transfer process of the divalent reaction, the second charge transfer step acts as the rate determining step. On increasing the anodic current density, the anode characteristics do not obey Tafel's law. In this region, the influence of the mass transfer process appears. For the case of dilute HF solution, the mass transfer process is entirely the rate determing step of the anodic silicon dissolution reaction.
Photoreflectance Study of Barrier-Width Dependence of Above-Barrier States in GaAs-AlxGa 1-xAs Multiple Quantum Wells
Authors: Fan J. C. , Chen Y. F. , Chen M. C. , Lin H. H. , Lin D. Y. , Huang Y. S.
Published: October 2002

The optical transitions of the quasibound states at the above-barrier region in GaAs/Ga0.77Al0.23As multiple quantum wells have been observed at room temperature by photoreflectance measurement. It is found that the barrier-width dependence of the above-barrier transition energies can be described quite well by the modified Messiah's calculation. However, the simple calculation using the constructive interference condition can only explain the transitions at lower energies, and fails with increasing transition energy.
Block Boundaries Conductivity and Size Effect in (HgCd)Te Mosaic Crystals
Authors: A. Pogrebnyak Victor , M. Rarenko Illariy , D. Khalameida Dmitriy , M. Yakovenko Vladimir
Published: October 2002

A conduction mechanism in mosaic single crystals Hg1-x
Cd
x
Te (MCT) has been ivestigated. It is shown that bulk electron channels appear along block boundaries. By the Shubnikov-de Haas (SdH) oscillation analysis parameters of the channels have been determined: electron concentrations, cyclotron masses and mobilities. In the high magnetic field and at the helium temperature the size effect in magntoresistance has been revealed when the sample's thickness becomes compared with a mean block size.
Effects of PbO Content on the Microstructure and Dielectric Constant of 0.8Pb(Zn1/3Nb2/3)O3–0.1BaTiO3–0.1PbTiO3
Authors: Cho Eu-Seong , Joo-Seon Kim Joo-Seon Kim , Suk-Joong L. Kang Suk-Joong L. Kang
Published: October 2002

The microstructure and the dielectric constant of 0.8Pb(Zn1/3Nb2/3)O3–0.1BaTiO3–0.1PbTiO3 (mol fraction) change considerably with the PbO content. A single perovskite phase was observed to form in specimens with 0.25 or 0.5 wt% PbO deficiency. When the PbO content increased above these values, a liquid phase formed and was present between perovskite grains. As the level of PbO decreased in the specimens, on the other hand, a pyrochlore phase and a ZnO phase formed, as second phases. The pyrochlore grains were sometimes much larger than the perovskite grains. The densification was considerably suppressed with decreasing PbO content. The dielectric constant showed a maximum of 22,000 in the specimen with 0.5 wt% PbO deficiency. The presence of a second phase and the reduction in the sintered density reduced the dielectric constant considerably. The liquid phase, however, was found to be more harmful than the pyrochlore and ZnO phases to the dielectric constant of the material.
Surface Morphology of Ferroelectric Domains in BaTiO3 Single Crystals: An Atomic Force Microscope Study
Authors: Balakumar Subramanian , Xu Jian Bin , Ma Jian Xing , Ganesamoorthy Sarveswaran , Ian Howard Wilson Ian Howard Wilson
Published: October 2002

The surface topography of the ferroelectric domain structure in flux grown BaTiO3 single crystal has been studied by atomic force microscopy (AFM) and optical polarizing microscopy at room temperature. Intersection of 90° wedges and formation of microdomains have been observed. Zig-zag boundaries have also been visualized for the first time by AFM.
Interactions between Servo Loops of an Optical Disk Drive
Authors: K. Bates Tetsuo Semba , A. Fennema Alan
Published: October 2002

In optical disk drives, interactions between the electromechanical actuators and the servo error generation systems can cause instabilities in the operation of individual servo loops. We examine the effects of these interactions on the servo loops of an optical disk drive in which a galvano fine-tracking actuator, a push-pull tracking error detection scheme, and an astigmatic focus error detection method are used. Also, we describe a digital servo controller that effectively cancels the effects of the deleterious interactions, resulting in stable operation.
Ferroelectric Properties in Heteroepitaxial Ba0.6Sr0.4TiO3 Thin Films on SrRuO3/SrTiO3 Substrates
Authors: Abe Kazuhide , Komatsu Shuichi , Yanase Naoko , Kenya Sano Kenya Sano , Takashi Kawakubo Takashi Kawakubo
Published: October 2002

Heteroepitaxial Ba0.6Sr0.4TiO3 thin films with thicknesses from 26 nm to 97 nm were grown on SrRuO3 bottom electrode films on SrTiO3 single crystal substrates. Although the films have a paraelectric composition, ferroelectric hysteresis was observed in displacement versus electric field (D–E) loops. The ferroelectricity is considered to be developed as a result of bi-axial stress, caused by lattice mismatch between the dielectric films and the bottom electrodes. The maximum difference in the displacement was over 0.4 C/m2, even when the thickness of the film was reduced to 26 nm. The hysteresis loops showed an asymmetric characteristic at a polarity of applied voltage. The asymmetry was discussed in terms of an asymmetrical deformation of the crystal structure, which is probably introduced during the heteroepitaxial growth.
Microwave Dielectric Properties of Ba(Mg1/2W1/2)O3–BaTiO3 Ceramics
Authors: Takahashi Hiromi , Kazutoshi Ayusawa Kazutoshi Ayusawa , Nobuyoshi Sakamoto Nobuyoshi Sakamoto
Published: October 2002

Ceramics with the chemical formula x Ba(Mg1/2W1/2)O3–(1-x) BaTiO3 (x=0.40–1.0) are prepared for use as dielectric resonators. The specimens were investigated by X-ray diffraction analysis, scanning electron microscopy and transmission electron microscopy. As x decreased from 1.0 to 0.40, the temperature coefficient of resonant frequency increased gradually from -33 to +303.5 ppm/°C. At x=2/3, the Q×f value increased markedly. The crystal structure with a Mg–W ordered B-site sublattice changed to a crystal structure with a Mg–W–Ti ordered B-site sublattice at x=0.84–0.72. Ba(Mg1/3W1/3Ti1/3)O3 is formed at x∼2/3, and has excellent dielectric properties (ε
r=14.5, Q×f=107000 ( GHz), τ f=-7.6 ppm/°C). The B-site cation of Ti improved the stability of the temperature coefficient of resonant frequency (TCF) for Ba(Mg1/2W1/2)O3 (τ f=-33 ppm/°C).
Dynamic Investigation of the Solid-Solid Phase Transition of Normal-Alkane (Hexatriacontane) by Simultaneous Measurements with Differential Scanning Calorimetry, Small-Angle X-Ray Scattering and X-Ray Television Detector
Authors: Forhad Mina Md. , Tsutomu Asano Tsutomu Asano , Hiroshi Takahashi Hiroshi Takahashi , Ichiro Hatta Ichiro Hatta , Kazuki Ito Kazuki Ito , Yoshiyuki Amemiya Yoshiyuki Amemiya
Published: October 2002

Simultaneous measurements have been performed using differential scanning calorimetry, time-resolved small-angle X-ray scattering and X-ray television (TV) methods to study the solid-solid phase transition of the normal-alkane (hexatriacontane) single crystal. The low-temperature monoclinic form (M L) of hexatriacontane transforms to the high-temperature monoclinic form (M H) by two mechanisms. One mechanism is a direct transition from M L to M H by twin formation without passing any activated state. The other mechanism is a two-step transition through an intermediate orthorhombic state (O), where the molecules stand up from the M L state and then re-incline into the M H state. The subsecond time-resolved investigation by simultaneous measurements reveals dynamic variations during the transition. The former M L→M H transition appears at a lower temperature showing that twin formation requires lower energy, than the two-step process with the activated state. Continuous changing of intensities observed in the X-ray TV indicates that the latter M L→O→M H transition is caused by the coherent motion of the molecules.
Studies of Low Temperature Specific Heats and Thermal Conductivities of the CsCl-type (Pr1-xNdx)Ag ( 0≤x≤1) Intermetallic Compounds: Application to Regenerator Materials
Authors: Yagi Wataru , Iwata Hideki , Mizutani Uichiro
Published: October 2002

The CsCl-type intermetallic compound can be formed over a whole composition range 0≤x≤1 in the chemical formula ( Pr1-
x

Nd

x

)Ag. The low temperature specific heat and thermal conductivity were measured over the temperature range 2–25 K to examine whether a series of intermetallic compounds can be used as regenerator materials in the GM- or Stirling-cycle refrigerator. The volumetric specific heats of samples in which x=0 and 0.1 were found to exceed 1 J/(K cm3) in the vicinity of 10 K whereas that of samples with x=1.0 reached almost 1.5 J/(K cm3) above 20 K, and is claimed to be the largest among those reported so far in the respective temperature ranges. The thermal conductivity of these compounds is found to be 5–10 times higher than that of Er3Ni. The occurrence of a large magnetic specific heat is due to high degeneracies of the ground states. Judging from the present thermal and magnetic studies, we claim that a series of (Pr1-
x

Nd

x

)Ag compounds can be used as good regenerator materials in the temperature range 10–25 K.