Showing papers in "Japanese Journal of Applied Physics in 1976"

Electromechanical Properties in the Composites of Epoxy Resin and PZT Ceramics

Abstract: The complex dielectric, elastic and piezoelectric constants were measured for the composites of epoxy resin and ferroelectric PZT ceramics at 10 Hz as a function of temperature, and the magnitudes and loss tangents of these constants were compared with the theoretical predictions. The piezoelectric constants for a two phase system with piezoelectric spherical inclusions were expressed in terms of the properties of the constituents by use of the known expressions of the dielectric and elastic constants. The observed values of the d-constant (electric displacement/stress) were about 3/4 of the predicted. In the local mode dispersion region of epoxy resin near -30°C, the g-constant (electric field/stress) showed a larger temperature variation than the theoretical prediction.

Piezoelectricity and Pyroelectricity of Polymers

Abstract: This article surveys theoretical and experimental work on piezo- and pyroelectricity of polymers in the 1970's with special emphasis on the origins of these properties. The origins are classified into three types: (A) internal strain (§2), (B) strain- and temperature-dependences of spontaneous polarization (§3), and (C) elastic and/or dielectric heterogeneity of a system with embedded charges (§4). The origin of piezo- and pyroelectricity of poly(vinylidene fluoride) is discussed as a typical example of electret (§5). Piezoelectric relaxations of polymers are discussed in some detail (§6). Methods of measurements of piezo- and pyroelectric constants of polymer films (§7) and applications of polymer films as new transducer materials (§8) are briefly reviewed.

Line Shift Method for Phosphor Temperature Measurements

Abstract: Two possible approaches to spectroscopic measurements of the internal temperature of Y2O2S: Eu are discussed. Methods based on relative Eu3+ fluorescence line intensities are found either to be insufficiently sensitive or to suffer from unavoidable experimental difficulties. The method which is adopted exploits the quadratic shift of the Eu3+5D0→7F0 transition energy with temperature. Controlled-temperature UV- and CR-excited fluorescence measurements establish the temperature calibration, which is then used to obtain the operating temperature of phosphor screens in a demountable CR excitation apparatus and in a tricolor CRT.

Electrical and Optical Properties of GexSe1-x Amorphous Thin Films

Abstract: Measurements of electrical and optical properties have been made on GexSe1-x amorphous thin films of about 1 µm thickness. From the experiment of electrical conductivity at various temperatures, two processes of the d.c. conductivity in GexSe1-x films are observed in plots of ln σ against 1/T. The thermoelectric power exhibits a maximum value of p-type conduction at pure Se and a change of the sign from positive to negative at 0.4

The 1/f Fluctuation of a Traffic Current on an Expressway

Abstract: It is observed that the fluctuation of a traffic current on an expressway obeys the 1/f law for low spectral frequencies. Under proper assumptions the variation of the car concentration is expressed by the Burgers nonlinear differential equation. The observed power spectrum is accounted for as a characteristic feature of the Burgers turbulence.

Structural improvement of carbon fibers prepared from benzene.

Abstract: Carbon fibers have been prepared by thermal decomposition of benzene at temperatures 1050–1080°C. Structural change with stepwise heat treatments up to 3000°C has been studied by X-ray and selected-area electron diffraction. The as-prepared fiber as well as the 1400°C-treated is basically of turbostratic structure, but has a preferred orientation of aromatic carbon planes more or less parallel to the fiber axis. By heat treatment around 2000°C, the preferred orientation is improved enormously; the carbon planes become almost completely parallel to the fiber axis, while the stacking order is still turbostratic. A three dimensional graphite structure is developed by heat treatment above 2400°C, which has qualitatively a similar behavior to that of graphitizing carbon. The fiber heat-treated at 3000°C consists of graphite layers concentrically surrounding the fiber axis.

Electrical and Optical Properties of GaSe-SnO 2 Heterojunctions

Abstract: The capacitance-voltage (C-V) and forward biased current-voltage (I-V) characteristics, electroluminescence (E.L) and photovoltaic effect of GaSe–SnO2 heterojunction diodes are measured. SnO2 layer is deposited on the c-plane of GaSe by using the spray method. The C-V and I-V characteristics of these diodes reveal the existence of a high resistivity layer, probably due to the diffusion of Sn into GaSe. The width of this layer is about 2.6 µm. And the current transport mechanism at low voltage is space-charge-limited. The trap density and the energy level of the trap from the valence band estimated by Lampert theory are about 5×1013~1×1014 cm-3 and 0.4~0.6 eV, respectively. The electroluminescence spectra at 275 K show one emission band due to free exciton recombination.

Preparation of Ultrafine Particles of Refractory Oxides by Gas-Evaporation Method

Abstract: Ultrafine particles of refractory oxides, SiO2, MgO, Al2O3, Fe3O4, Mg2SiO4, CaTiO3 and MgAl2O4, were prepared by the gas-evaporation method. Oxide materials were heated by a CO2 laser beam of output 100 W and their vapors were condensed in the gas environment of He, Ar or Xe of 3.5~670 Torr. Fractional vaporization did not occur except for MgAl2O4. Most of the particles were spherical with the diameter of about 100 A for both of the amorphous and crystalline oxides. They usually stuck to one another and looked like a tangled chain of spheres. The maximum yield of the ultrafine particles was about 10 mg per min. Some applications of the refractory ultrafine particles were discussed especially in connection with earth science.

X-Ray Studies of Polyethylene under High Pressure

Abstract: The phase diagram, growth processes of extended-chain crystal and high pressure phase, and the temperature dependency of lattice parameter in polyethylene have been studied under high pressure up to 6000 kg/cm2 using a new high pressure X-ray diffraction apparatus. The high pressure phase diagram obtained by micro-DTA measurement agrees with that by X-ray measurement. The crystallization process of the high pressure phase seems to be a homogeneous and diffusion controlled two dimensional growth. The growth process of the extended-chain crystal is very rapid, and the direct formation of the extended-chain crystal without passing through the high pressure phase is clarified. The temperature dependency of the lattice parameters of the extended-chain crystal and the high pressure phase at 5000 kg/cm2 were obtained, and the shrinkage of the c-axis in the high pressure phase which shows only a sharp (100) diffraction pattern is discussed with the aid of dilatometric data.

X-Ray Photoelectron Spectroscopic Studies on ZnS: MnF 2 Phosphors

Abstract: ZnS: MnF2 phosphors and their references were investigated with X-ray photoelectron spectroscopy. The atomic ratio of F to Mn in ZnS: MnF2 was found to be remarkably lower than that in MnF2 film. The binding energy of Mn2p3/2 in ZnS: MnF2 is near that in β-MnS and ZnS doped with Mn atoms by heat-treatment. It is concluded that most Mn atoms in ZnS: MnF2 are not in the MnF2 molecules, but replace Zn atoms. This fact is also discussed on the basis of self lattice potential energy.

Epitaxial Growth of Undoped and Mg-Doped GaN

Abstract: Gallium nitride was epitaxially grown on {0001} and {102} sapphire by the vapor phase reaction of Ga-HCl-NH3-Ar system. The growth rate on {102} sapphire is ~12 µm/hr, which is higher than that on {0001} sapphire by a factor of ~1.5. The crystal on {1102} sapphire has a lower carrier concentration than that of the same thickness on {0001} sapphire by a factor of ~0.5. The lowest carrier concentration and the highest electron mobility of undoped GaN obtained in this study were 1.6×1019 cm-3 and 78 cm2/Vs, respectively, at 300 K. When heavily doped with Mg, the crystal grown changes markedly in growth morphology. The orientation relationships developed in an undoped or lightly Mg-doped state are {0001}GaN//{0001}sapphire and {110}GaN//{102}sapphire, and in a heavily doped state {114}GaN//{0001}sapphire and {110}GaN//{102}sapphire.

Semi-Insulating Polycrystalline-Silicon (SIPOS) Passivation Technology

Abstract: Semi-insulating polycrystalline-silicon (SIPOS) films have been used as a replacement of a silicon dioxide passivation layer of planar devices. The SIPOS films are chemically vapordeposited polycrystalline-silicon doped with oxygen or nitrogen atoms. The passivation properties of oxygen-doped SIPOS films have been examined as a function of oxygen concentration. The npn and pnp transistors rated at 800 V and 2500 V have been produced by the SIPOS process in planar-like structures with field-limiting rings. The leakage currents of 800 V pnp transistors did not increase even after the chips were exposed to water vapor at 100°C and to sodium contamination at 200°C. Thus, the SIPOS transistors can be packaged in low-cost molded epoxy as well as metal cans. Furthermore, 10 kV SIPOS transistors with multiple rings have been fabricated and their operation has been found to be stable.

Change with Temperature in Crystal Structures of Nylons 6, 66 and 610

Abstract: It is verified from the results of infrared absorption and X-ray analyses that the hydrogen bonds between the adjacent amide groups in crystalline regions of nylons 6, 66 and 610 are not broken but the motion of amide groups in a molecule is rather restricted in the whole temperature range below respective melting points. All lattice parameters of three polyamides are determined at about 20, 80, 120, 160, 200 and 240°C. It is deduced that the length of a-axis or hydrogen bond varies little, but the large thermal expansion along b-axis causes inversion of (100) and (010) spacings for nylons 66 and 610. The difference in the melting point and in the behavior of the structure change between even polyamide and even-even one is attributed to the degree of ease with which the CH2-segment is rotated.

Solid Solubility of Si in Al under High Pressure

Abstract: By making use of a 15 mm cubic anvil apparatus, Al–Si alloys of Si-concentration up to 15 at% were studied at a pressure of 54 kbar. The liquidus, solidus and solvus of the Al-rich alloys were determined by means of the 4-probe electric resistance measurement. The solubility limit of Si in Al was extended beyond 15 at% at 54 kbar in comparison with 1.59 at% at 0 kbar. The resistivity of the alloy was increased by a solution of Si with a gradient of 0.5 µΩcm/at% up to 15 at%Si. The alloy quenched under high pressure was examined by X-ray diffractometry showing that Si was completely solid-dissolved in Al. The quenched alloy was much more hardened than the ordinary two-phase alloy at 0 kbar.

Stacking Fault Generation Suppression and Grown-In Defect Elimination in Dislocation Free Silicon Wafers by HCl Oxidation

Abstract: Dislocation free silicon wafers were oxidized in dry O2 and dry O2 + HCl (HCl oxidation) to clarify the effects of HCl on the generation and expansion of Frank type stacking faults. These faults were produced from grown-in defects and surface mechanical damage. For day O2 oxidation, stacking faults expanded with increasing oxidation time except for oxidation at extremely high temperatures. For HCl oxidation, they generally expanded during the first stage of oxidation, reached a maximum and finally sharank. A complete suppression of stacking fault generation was observed for higher HCl concentrations. The elimination of grown-in defects occurred during HCl oxidation. The suppression of stacking fault generation and expansion, and the elimination of grown-in defects are considered to occur due to the interaction of these defects with vacancies, which are produced on the silicon surface during HCl oxidation.

Magnetic Domain Structure of an Amorphous Fe-P-C Alloy

Abstract: The domain structure of an amorphous Fe80P13C7 alloy ribbon produced by the centrifugal solidification technique was investigated using the magnetic powder pattern technique. Two different types of domains (a maze domain and a 180°-domain) were observed on the specimen surface. The relationship between the domain structure and the magnetization process was also investigated. The results showed that some of the 180°-walls, which ran nearly parallel to the long axis of the ribbon, caused the hysteresis in the magnetization curve, while the maze domain was responsible for the difficulty in obtaining the saturation in magnetization. The maze domain arises probably from the uniaxial magnetic anisotropy having the direction of easy magnetization perpendicular to the surface. This anisotropy seems to be caused by the magnetoelastic coupling between positive magnetostriction and internal stress in the specimen.

Piezoelectric Effect in Stretched and Polarized Polyvinylidene Fluoride Film

Abstract: The mathematical expressions for the piezoelectric stress-constant, the electrostrictive constant, and the dielectric constant, all as complex quantities, have been derived by means of non-equilibrium thermodynamics on the assumption that the dipole orientation produces a residual polarization. The temperature dependence of these quantities for electretized polyvinylidene fluoride films has been experimentally determined at a frequency of 20 Hz over the temperature range from -100°C to 100°C. The residual polarization calculated from these experimental data is of the order of 103 esu/cm2. This polarization presumably originates from the aligned dipoles associated with the crystalline region. Measurements during poling process show a gradual two-step increase of the residual polarization.

Anomalous Magneto-optical Hysteresis Loops of Sputtered Gd-Co Films

Abstract: Hysteresis loop anomaly in Gd-Co films has been studied by measuring magneto-optical Kerr loops at a temperature range from 20 to 60°C. Anomalous loops were observed at one surface of the films and in a certain temperature range. The other surface always gave normal loops. All the features of the observed anomalous loops can be explained by a magnetization gradient model along the film thickness.

Semi-Insulating Polycrystalline-Silicon (SIPOS) Films Applied to MOS Integrated Circuits

Abstract: A semi-insulating polycrystalline-silicon (SIPOS) film doped with oxygen atoms is deposited on the surface of silicon substrates by a chemical vapor reaction of silane and nitrous oxide in nitrogen ambient, and has been studied for the surface passivation of MOS-IC's, in particular, C/MOS-IC's of channel-stopperless structure. SIPOS films are semi-insulating and intrinsically neutral. A double-layer system consisting of 3000 A SIPOS and 6000 A SiO2 films is employed as a replacement of a thick silicon dioxide layer in C/MOS-IC's of channel-stopperless structure and exhibits excellent field-passivating properties, namely, a small drain-source leakage current, a high drain breakdown voltage, and a high parasitic threshold voltage. Furthermore, the silicon surface passivated by SIPOS films shows high stability under a severe bias-temperature stress. It is concluded that C/MOS-IC's passivated by SIPOS films are not required to have a channelstopper diffusion region and can be operated at high applied voltages, which leads to higher integrating density and higher reliability.

Substrate Current due to Impact Ionization in MOS-FET

Abstract: The substrate leakage current vs. gate voltage characteristics of MOS-FET was examined over a wide range of device parameters and measurement conditions. With the increase in the gate voltage, the substrate current increases until it reaches a maximum value. Then it decreases to the value of the generation-recombination current. The substrate current has a high value at low measurement temperatures, high drain voltages, high impurity concentrations of silicon substrates, thin gate-oxide thicknesses and a large drain current. These experimental results were semi-quantitatively explained on the basis of a model in which the substrate current is caused by the first-order impact ionization of the carriers within the pinched-off region. The observed increase of the substrate current is mainly dominated by an increase of the drain current, and the decrease of the substrate current is mainly dominated by a decrease of the impact ionization coefficient.

A New Chemical Dry Etching

Abstract: A new method for etching by a plasma technique has been developed. Active species with a long lifetime are created by the discharge of CF4-O2 mixture and transported from the discharge region to the reaction region where samples are etched. Consequently, the immersion of the samples in the plasmas can be avoided and the condition of etching process can be easily controlled. An etching characteristics heavily depends on the ratio of flow rate of CF4 and of O2, and the maximum etching rate occurs at the ratio of about 1:1. Activation energies for the etch rate of poly-Si and SiO2 are 1.1 kcal/mol and 4.2 kcal/mol, respectively. Through a mass spectrometric analysis the etching mechanism is hypothesized: (i) COF* creation by CF4-O2 discharge and (ii) F* formation by dissociation of COF* at the surface of samples.

Design and Performance of Holographic Concave Gratings

Abstract: Following a brief introductory remark on the holographic grating, the possibility of designing concave gratings for a specific application is discussed, giving basic ideas of the grating design, actual design procedures, and feasible ways of improving the existing design methods. As a proof of the usefulness of the design method developed by the authors, spot diagrams and experimental results are given for aberration-reduced holographic concave gratings that have been designed and produced specifically for a Seya-Namioka monochromator. The efficiency, stray light, and polarization characteristics of holographic and conventional concave gratings are compared for the purpose of giving some idea about the relative merits of the two kinds of gratings. The design method is also applied to the determination of the ruling parameters needed for the production of mechanically ruled stigmatic concave gratings.

Measurements of the Linear Electrooptic Coefficients and Analysis of the Nonlinear Susceptibilities in Cubic GaAs and Hexagonal CdS

Abstract: The unclamped values of the linear electrooptic coefficients r41T in GaAs and r33T, r13T, rcT and r42T in CdS have been measured at the wavelengths of 1.15, 3.39 and 10.6 µm as well as those of the coefficients rcT and r42T in CdS at 0.633 µm. The measured values are as follows: In GaAs r41T=1.43±0.07, 1.24±0.04, 1.51±0.05×10-12 m/V at 1.15, 3.39 and 10.6 µm respectively. In CdS r33T=3.2±0.2, 2.9±0.1, 2.75±0.08×10-12 m/V, r13T=3.1,±0.2, 3.5±0.1, 2.45±0.08×10-12 m/V, rcT=6.2±0.2, 6.5±0.2, 5.2±0.3×10-12 m/V, r42T=2.0±0.2, 2.0±0.2, 1.7±0.3×10-12 m/V at 1.15, 3.39 and 10.6 µm respectively, and rcT=4.8±0.2×10-12 m/V, r42T=1.6±0.2×10-12 m/V at 0.633 µm. Using the measured data and data on nonlinear optical coefficients obtained by others, the anharmonic potential coefficients are determined and the dispersion of the unclamped linear electrooptic coefficients and nonlinear optical coefficients for SHG are calculated.

Formation of Ultrafine Metal Particles by Gas-Evaporation Technique. III. Al in He, Ar and Xe, and Mg in Mixtures of Inactive Gas and Air

Abstract: Aluminium smokes in He, Ar and Xe at various pressures were studied. Their macroscopic shapes were roughly the same in 200 Torr He, 10 Torr Ar and l Torr Xe. Under these conditions the particle size in the inner zone of a smoke decreased with the molecular weight of the gas. In the course of the experiment, several electron micrographs showing the intermediate stages of particle coalescence in the smoke were obtained. When an inactive gas contained oxygen, the smoke particles were almost perfectly oxidized in the outer zone of the smoke, while the oxidation was slight in the inner zone.