Showing papers in "Japanese Journal of Applied Physics in 1982"

Dielectric and Piezoelectric Properties of 0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3 Single Crystals

Abstract: The dielectric, piezoelectric and elastic properties of 0.91(PbZn1/3Nb2/3)O3–0.09PbTiO3 single crystals have been investigated as functions of temperature and applied electric field. Two multiple phase transitions at 68°C and 178°C, the crystal changing from the rhombohedral ferroelectric phase to tetragonal ferroelectric and then to cubic paraelectric, have been observed. Both the transitions are of first-order, but both are slightly diffused. Significant increases in the dielectric, piezoelectric and elastic constants are observed at the lower transition point. In particular, the sample poled along the pseudo-cubic [001] axis reveals anomalously large piezoelectric and electro-mechanical coupling constants at room temperature in the rhombohedral phase (d[001]//=1500×10-12 C/N, k[001]//=0.92).

Vapor Deposition of Diamond Particles from Methane

Abstract: Microcrystalline diamond has been formed on silicon or molybdenum substrates by vapor deposition from a geseous mixture of methane and hydrogen. Cubo-octahedral or multiply-twinned crystals were obtained. The structure of the deposits was identified by electron diffraction and Raman scattering.

The Surface Free Energies of Solid Chemical Elements : Calculation from Internal Free Enthalpies of Atomization

Abstract: It is pointed out that the experimentally-measured quantity usually termed "surface free energy" is in fact a part of the free enthalpy which is due to the presence of the surface (referred to unit surface). This quantity, denoted by γio for the polycrystalline solid chemical element i, is connected to the internal free enthalpy of atomization ΔGa,i* by the relation γioio=αioΔGa,i* where io is the molar surface area, and αio is a constant. Its physical meaning is given to a relatively good approximation. Approximate methods of calculation based on experimental data give values of αio at any temperature for metallic, semimetallic and covalently-bonded solid chemical elements. Using these procedures, the values of γio at 298.2 K and at the melting temperature are tabulated.

Ba(Mg 1⁄3 Ta 2⁄3 )O 3 Ceramics with Temperature-Stable High Dielectric Constant and Low Microwave Loss

Abstract: A dense ceramic with an ordered perovskite structure with chemical formula Ba(Mg1/3Ta2/3)O3 is prepared, aiming at materials for a dielectric resonator with temperature-stable high dielectric contsant and low loss at microwave frequency. A small amount of Mn ion is doped to the sample to complete the sintering. The dielectric constant and unloaded Q are 25 and 16800 at 10.5 GHz respectively. The temperature coefficient of resonant frequency is estimated as 2.7 ppm/°C in the vicinity of room temperature. The value of Q we obtained is the highest among those reported so far on ceramics having a similar characteristic.

Growth of Large Single Crystals of Black Phosphorus under High Pressure

Abstract: A large volume high pressure apparatus has made it possible to grow large single crystals of black phosphorus, P. After converting red P powder into black P under a high pressure of 10 kbar at high temperature, a melt of polycrystalline black P has been gradually solidified to bring about the growth of single crystals. Crystal sizes larger than 5×5×10 mm3 are, for the first time, adequate for various measurements of the physical properties expected for this narrow gap semiconductor with a special layered structure. An X-ray analysis has proved the good single crystalline structure.

Thermal Oxidation of SiC and Electrical Properties of Al–SiO2–SiC MOS Structure

Abstract: Silicon dioxide layers have been thermally grown on the (000)C face of 6H–SiC at 850–1100°C in wet O2 and studied by Auger analysis and ellipsometry. These oxide layers are quite homogeneous with a narrow interface width of \lesssim80 A. The oxide thickness vs, the oxidation time follows the general relationship used for the thermal oxidation of Si. Temperature dependencies of the oxidation rate constants were obtained. C-V characteristics of Al–SiO2–SiC MOS structures were measured at 10 Hz–1 MHz. The accumulation, depletion and inversion regions are clearly observed under illumination. In the dark, the inversion does not occur, probably owing to the absence of minority carriers because of the large band gap. Frequency dispersion is not observed. The minimum surface-state density is ~2×1012cm-2eV-1. The oxide resistivity and the breakdown strength are 2×1012 Ωcm and 2×106V/cm, respectively.

Velocity-Modulation Transistor (VMT) : A New Field-Effect Transistor Concept

Abstract: Field-effect transistors of a completely new category are proposed and analysed, in which the conductivity modulation ΔG by the gate voltage Vg is brought forth mainly through the Vg-dependence of electron mobility. Since the sheet concentration of electrons in such FETs need not be modulated, the switching speed of the device is expected to be free from the transit time limitation, reaching the range of subpicosecond. As a specific example, an FET with a dual-channel configuration is discussed.

Ba(Zn 1⁄3 Nb 2⁄3 )O 3 –Sr(Zn 1⁄3 Nb 2⁄3 )O 3 Solid Solution Ceramics with Temperature-Stable High Dielectric Constant and Low Microwave Loss

Abstract: Solid solution ceramics in the Ba(Zn1/3Nb2/3)O3(BZN)–Sr(Zn1/3Nb2/3)O3 (SZN) system have been studied with a view to finding materials for use as dielectric resonators at microwave frequency. The relative dielectric constant and the unloaded Q at 10 GHz are respectively 41 and 5400 for BZN, and 40 and 2000 for SZN. The temperature coefficient of the resonant frequency is estimated as 30 ppm/°C for BZN and -38 ppm/°C for SZN. The dielectric constant of 0.3 BZN–0.7 SZN ceramic is nearly independent of temperature, which gives a very small estimated temperature coefficient of the resonant frequency of -5 ppm/°C.

Optical Fiber Sensor for Measuring Refractive Index

Abstract: An optical fiber sensor for measuring a liquid refractive index is proposed. When an optical fiber is bent and part of its cladding is stripped off, the light energy (E) emerging from the fiber depends on the refractive index of the surrounding medium (nm). The change in nm can be found from E. The light output energy and the measuring sensitivity are calculated numerically as a function of nm for several values of the bending radius R. The fundamental characteristics of the sensor, made of a plastic fiber, are investigated using lamp oil and light oil as specimens, and a measurement accuracy of nm to the third decimal place is easily obtained. As applications of this sensor, measurement of liquid density and detection of oil are described.

Ferroelectric Copolymers of Vinylidenefluoride and Trifluoroethylene with a Large Electromechanical Coupling Factor

Abstract: A large electromechanical coupling factor kt of about 0.3 has been found in vinylidenefluoride and trifluoroethylene copolymers containing 70–80 mol% VDF. These copolymers exhibit clear ferroelectric behavior. The strong piezoelectricity and distinctive ferroelectricity are attributable to high crystallinity, strong preferred orientation, and reduced conformational defects in crystallites, which are induced by annealing and successive or simultaneous poling. The polarization is inferred to grow through rotation of the polar axis by nπ/3 about the molecular axis (c-axis) under an external electric field above the coercive field.

Temperature Dependence of Electron-Irradiation Induced Amorphization of NiTi Alloys

Abstract: Electron-irradiation induced amorphization of NiTi alloys has been investigated in a temperature range from 50 to 393 K by high voltage electron microscopy with the following results: A crystalline-amorphous transition occurs when the total dose of electrons reaches a certain value. The critical value decreases with decreasing irradiation temperature and becomes almost constant with about 2×1025 e/m2 below 100 K. Process of the transition is also revealed.

Electrical Properties of Conducting Polymer, Poly-Thiophene, Prepared by Electrochemical Polymerization

Abstract: Poly-thiophene perchlorate is prepared electrochemically in an electrolyte of 0.5 M AgClO4 and 0.2 M thiophene in acetonitrile. Dark greenish film with the complex of ca. [C4H2S(ClO4)0.26]x is obtained. The electrical conductivity along the film surface is about 0.6 Ω-1cm-1.

XPS and AES studies on the oxidation of layered semiconductor gase

Abstract: We have studied the oxidation of layered compound GaSe with no dangling bonds on the cleaved surface using XPS and AES techniques. At room temperature, the cleaved surface is not oxidized in an oxygen atmosphere. When subjected to Ar ion sputtering, the surface starts to exhibit the behavior of metallic Ga owing to dissipation of the first sublayer of Se in the primitive layer, Se–Ga–Ga–Se. The thin layer of metallic Ga thus exposed is easily oxidized. In the thermal oxidation of cleaved GaSe in air, the oxygen diffuses into the primitive layer and combines with Ga, severing the intralayer bonding between the Se and Ga atoms. At temperature higher than 450°C, the oxygen is also intercalated between the primitive layers from the sides perpendicular to the layers. No Se oxides are observed under any of the oxidation conditions.

Reactive Ion Beam Etching Using a Broad Beam ECR Ion Source

Abstract: A broad beam ion source using a microwave electron cyclotron resonance (ECR) discharge has been newly developed, giving high reliability in operation. The ion source operates at gas pressures higher than about 3×10-5 Torr, and an ion current density of 1 mA/cm2 is obtained at an ion extraction voltage of 1000 V. By introducing C4F8 and SiCl4 into the ion source, SiO2 and Al are etched at rates greater than 1000 A/min, with high selectivities and high-accuracy pattern transfer.

Frequency Stabilization of AlGaAs Semiconductor Laser Based on the 85Rb-D2 Line

Abstract: The frequency of an AlGaAs semiconductor laser was stabilized by using the linear absorption spectrum of the 85Rb-D2 line. By controlling the injection current, the frequency stability of 3.0×10-10σ1.4×10-12 was obtained for 10 msτ500 s. First observation of the saturated absorption spectrum of the 85Rb-D2 line is demonstrated, which can be used as a frequency reference to improve the frequency stability.

Synthesis of Fine Fe4N Powder and Its Magnetic Characteristics

Abstract: A pigment of Fe4N particles for magnetic recording was prepared by nitrogenizing acicular metal iron powder. The chemical treatment needed to obtain stoichiometric Fe4N powder was studied, and it was found that Fe4N powder was obtained when the Fe powder was heated at about 400°C in a mixture of H2–NH3 (65–80 vol.%). The Curie point of the powder coincided well with that of bulk Fe4N. The coercive force of Fe4N was 640 Oe, which is considerably smaller than that of the Fe powder used as the starting material. The dispersion of magnetic anisotropy was measured by a torque meter, and the decrease in the coercivity of nitrogenized iron powder was attributed to the exchange anisotropy of the surface layer.

Thermally Induced Microdefects in Czochralski-Grown Silicon: Nucleation and Growth Behavior

Abstract: The current understanding of thermally induced microdefects in Czochralski-grown silicon crystals is briefly reviewed and our investigations of the defects are described. The microdefects originate in oxygen precipitation occurring during thermal treatments after crystal growth. Both homogeneous and heterogeneous nucleation models have been proposed for the oxygen precipitation. The homogeneous nucleation model is contradicted because a low density of microdefects are induced in recent high-quality crystals even at high oxygen concentrations. A heterogeneous nucleation model is proposed, based on detailed investigations of the thermal behaviors of microdefects. It is demonstrated that the oxygen precipitation is governed by nucleation sites (carbon atoms) and the thermal history of wafers after crystal growth besides the oxygen concentration of the wafer.

Etching of SiO 2 Films by Si in Ultra-High Vacuum

Abstract: SiO2 etching resulting from reaction with impinging Si or substrate Si was clearly observed in an ultra-high vacuum by using step measurement, Auger electron spectroscopy and/or ellipsometry. In etching by impinging Si, the etching rate decreases with the substrate temperature, and increases with the Si impinging rate. These results are explained by a model proposed here that involves Si adsorption on SiO2, and a subsequent chemical reaction. It was found that SiO2 films thinner than 2.5 nm are etched by the same reaction with substrate Si, whereas those thicker than 2.5 nm are not etched at all, since reaction products cannot diffuse through the SiO2 film to the vacuum. These phenomena can be used in Si molecular beam epitaxy.

Selective Silicon Epitaxy Using Reduced Pressure Technique

Abstract: Silicon selective epitaxial growth using the SiH2Cl2–HCl–H2 system was successfully accomplished on a window surrounded by fine patterned insulator films as a mask. Surface planarity was obtained at less than 80 Torr reduced pressure. Good selectivity was realized by suitable HCl injection during epitaxial growth. Moreover, it was found that the induced defect density on the epi-layer was less at lower growth temperature.

Energy Analysis of High-Energy Neutral Atoms in the Sputtering of ZnO and BaTiO3

Abstract: The time-of-flight method has been employed to investigate the type and energy of high-energy neutral atoms bombarding the substrates in films of ZnO and BaTiO3 prepared by both DC planar magnetron sputtering and conventional DC diode sputtering. The high-energy neutral atoms are found to be oxygen atoms. The dependence of the flux of high-energy neutral oxygen atoms and negative oxygen ions on the pressure has also been measured for the planar magnetron sputtering of ZnO. It is shown that the high-energy particles bombarding the substrate are composed of neutral oxygen atoms at higher gas pressures ranging above 0.01 Torr, but negative oxygen ions are comparable with neutral oxygen atoms at pressures of the order of 10-3 Torr. The production mechanism of these energetic oxygen species is discussed.

Unstable Regions in III-V Quaternary Solid Solutions Composition Plane Calculated with Strictly Regular Solution Approximation

Abstract: The behavior of unstable regions in the composition plane for III–V quaternary solid solutions made from among Al, Ga, In, P, As and Sb is analyzed, based on the strictly regular solution approximation for solid solutions. Temperature dependences of spinodal isotherms at 400–1000°C show that unstable regions cover a wide range of compositions. It is suggested that composition ranges exist where the spinodal temperature exceeds the melting point, so that such solid solutions can never be grown by near-equilibrium growth methods. Positions of quaternary critical points in the composition plane are also shown.

Czochralski Silicon Crystal Growth in the Vertical Magnetic Field

Abstract: Czochralski (CZ) silicon crystals with striation free and microscopic homogeneous dopant concentrations are grown under the presence of an axially symmetric vertical magnetic field. The thermal convections of 3.5 kg of molten silicon in a crucible are successfully suppressed by a magnetic field of more than 1000 Oe in strength. Many advantages are found for the method developed in comparison with the conventional transverse magnetic field method in use.

NMR and IR Studies on Hydrogenated Amorphous Si 1− x C x Films

Abstract: NMR and IR studies have been carried out on glow-discharge-deposited a-Si1-xCx:H films. The hydrogen content increases with an increase in x up to 0.4 mainly in gathered form contributing to the broad component of the NMR line. By combining the NMR and IR results, the proportionality between the number of H bonded to C and the intensity of IR absorption due to the C?H stretching mode vibration is ascertained. The proportionality constant is found to be AstrC?H=1.7?1021 cm-2.

A Model of Linear Uranium Accumulation for ESR Age of Heidelberg (Mauer) and Tautavel Bones

Abstract: Electron spin resonance (ESR) dating of anthropologically important Heidelberg and Tautavel bones has been made based on a model of uranium-series disequilibrium and a linear accumulation of uranium. Theoretical equation and graphic solution are presented to obtain the age from the total dose of natural radiation (TD) derived from the result of ESR dating. The model shifts the ESR ages considerably to the old side as the accumulation of uranium into an open-system fossil bone was taken into account.

Photoluminescence of Hydrogenated Amorphous Carbon Films

Abstract: Hydrogenated amorphous carbon films have been prepared by the glow-discharge decomposition of ethylene gas. The film shows wide properties depending on gas temperature during discharge. With increasing gas temperature from 200 to 350°C, hydrogen content in the film decreases, and thereby the optical gap decreases from 2.6 to 1.2 eV and the ESR spin density increases from ~1017 to ~1019 cm-3. The photoluminescence spectrum consists of two emission bands. The peak energy of the main band shifts from 1.93 to 1.64 eV as the gas temperature increases. Emission intensity is very insensitive to measurement temperature.

Temperature Sensitive Helical Pitches and Wall Anchoring Effects in Homogeneous Monodomains of Ferroelectric Sm C^* Liquid Crystals, nOBAMBC (n=6-10)

Abstract: 2-methylbutyl p-(p-n-alkoxybenzylidencamino) cinnamates were synthesized and their helical pitches in the Sm C* phase were measured by optical microscopic and/or diffraction methods. After the phase transition from Sm A to Sm C*, the pitches increase steeply within 0.5°C, attain relatively broad maxima, and then gradually decrease in all the nOBAMBC investigated, except for HpOBAMBC (n=7) whose pitch shows some anomalies at low temperatures. The "odd-even effect" is clearly observed in the dependence of the maximum pitch on the alkoxy chain length. The dependence of the helical pitch on cell thickness has also been studied. During the steep increase, the wall anchoring effect is not observed when the cell is at least thicker than 100 µm; at lower temperatures, however, the pitch depends on the thickness even when the cell is as thick as 200 µm or more. Finally, the observed temperature variation of the pitch is compared with the Landau-type phenomenological theories so far proposed.

Kinetic Model for Self-Sustained Discharge XeCl Lasers

Abstract: A simulation code including the Boltzmann equation which describes the kinetics of the self-sustained discharge XeCl laser is developed. The performances of four different gas mixtures, HCl/Xe/Ne, HCl/Xe/He, F2/Kr/Ne and F2/Kr/He are compared under the same conditions, and the buffer gas effect is discussed in detail. The HCl/Xe/Ne system shows the best performance. With the Ne buffer gas, the elastic collision loss is remarkably small, whereas the electric circuit loss is large owing to the low discharge resistance. The results on the variation of the input energy and total pressure are qualitatively consistent with the experimental results. Useful knowledge on the design of efficient XeCl lasers is obtained.

Observation of p-n Junctions with a Flying-Spot Scanner Using a Chopped Photon Beam

Abstract: A flying-spot scanner that employs a chopped photon beam emitted from a cathode ray tube is reported. The photon beam scanns a planar p-n junction put on a metal electrode through a In2O3-coated transparent electrode and a 15 µm-thick mylar spacer. The ac photovoltage is picked up with electrodes through a condensor formed by the spacer. The photovoltage signal modulates brightness of another cathode ray tube to form a scanning image. Mean wavelength and chopping frequency of the photon beam are 507 nm and 2 kHz. Scanning image analysis is done using photocurrent density equations based on a step-like junction model. Three kinds of junctions, a solar cell, a partly-deep junction and a non-uniformly ion implanted one, have been evaluated to show the validity of the present method.

Inhomogeneous GaAs FET Threshold Voltages Related to Dislocation Distribution

Abstract: Clear correlation between dislocation distribution and FET threshold voltage distribution in undoped LEC GaAs was observed directly for the first time by automatic computer-controlled measurement of drain-source current (Ids) and threshold voltage (Vth). FETs fabricated in the high EPD area, which covers the center and the periphery of (100) wafers, showed high Ids and low Vth, whereas FETs fabricated in the low EPD area showed low Ids and high Vth.