Table of contents

The growth and source-depletion characteristics of ZnTe were investigated by the horizontal open-tube method using H₂ carrier gas. The system consists of vapor-etching, supersaturation gas (preferential growth), nucleation and reactor-wall deposition regions from the source-zone downstream. The preferential growth region widens owing to the decrease in the nucleation temperature along with the decrease in the temperature gradient near the source-zone or the flow rate. This region gives smooth, flat epi-layers and can be described by a quasi-equilibrium model. On the other hand, the reactor-wall deposition characteristics can be expressed by a complete equilibrium model if a substrate is set at a position far enough from the critical-nucleation position. Thermodynamic analysis of the laminar and diffusion flows gives good agreement with the experimental results.

Point defect clusters at a twin boundary in pure aluminum are observed by transmission electron microscopy. At the coherent twin boundary, characteristic triangular loops of the vacancy type are formed in quenched specimens, while loops of the interstitial type are formed in electron-irradiated specimens. The direction of the triangles of the vacancy loops is opposite to those of the interstitial loops. These facts can be explained as arising from the difference in the atomic arrangement of the second nearest-neighbor layers around the dislocation loops. It can be concluded that whenever a faulted loop is formed on a stacking fault, the loop is triangular. During electron irradiation of a boundary which contains a vacancy loop, the vacancy loop grows or shrinks depending on the environment around it, while an interstitial loop always grows.

We use a tight-binding (TB) type electronic theory to calculate the core structure and core energy of both screw and 60° dislocations in the covalent semiconductors C, Si and Ge. To represent the repulsive interaction between atomic sites i and j, arising mainly from the core orthogonalization, we introduce a Born-Mayer potential. From the total (attractive and repulsive) energy calculations, we investigate the stability of dissociated partial dislocations. We show that the glide-set dissociated dislocations are more stable than the corresponding shuffle-set perfect dislocation, in agreement with recent experimental observations. The calculated results are also compared with available experimental results on the structure images and the dynamic properties of dislocations. In addition, we investigate the electronic states (sp configuration) of the dangling-bond-like states (DBLS) near the core of the partial dislocations, and discuss the validity of using fixed sp³ hybrid orbitals for calculating the dislocations.

The internal stress in V₃Si film prepared by magnetron sputtering on thermally-oxidized Si substrates was measured as a function of the substrate temperature T_s by the optical interference method. The intrinsic stress in the film has a maximum value at the value of T_s at which the crystalline film starts to be deposited. It then decreases with increase in T_s. The thermal stress also changes markedly at almost the same value of T_s, and increases with T_s. The value of the intrinsic stress in a well-ordered film deposited at T_s=570°C is approximately 1×10⁹ dyn/cm² (tension). The thermal expansion coefficients and Young's moduli for films deposited at various values of T_s have been derived from these data. The effect of stress on the film lattice constants is discussed.

A microcrystalline silicon film is formed on monocrystalline silicon by a staining reaction in a gaseous mixture of HF and NO₂, and the film is then oxidized at 100°C∼500°C. The oxide thickness depends upon the oxidation temperature, although almost all of the oxidation is completed in the first few minutes. It is also found that the unoxidized thickness left between the oxide and the silicon substrate is important in stabilizing the surface. The most suitable oxidation temperature for the device passivation is 200°C∼250°C. The low-temperature oxidation mechanism and the physical properties of the films are discussed.

Secondary ion analysis was performed on a silicon surface during Ar⁺ ion bombardment under simultaneous exposure to chlorine or fluorine flux. The Cl⁺, Cl₂⁺, F⁺ and F₂⁺ secondary ion intensities increased with the amount of reactive gas flux. However, other secondary ion intensities, such as SiCl⁺ and SiF⁺, decreased at large reactive gas flux. In a large reactive gas flux, the Cl⁺ and F₂⁺ secondary ion intensities were related to the Si etching yield. The amounts of reactive atoms adsorbed on one silicon atom are the same in the large reactive gas flux region. The etching rate ratios of silicon, silicon dioxide and silicon nitride had almost the same value, no matter how much the Cl₂ flux increased. No dependence of the etching rate on the crystalline orientation was observed.

Dielectric relaxations associated with the ferroelectric transition have been investigated in a copolymer containing 65 mol% vinylidene fluoride and 35 mol% trifluoroethylene. The transition shows thermal hysteresis, taking place at 100°C upon heating and at 70°C upon cooling. Near the transition point, there is a peak in the dielectric relaxation strength Δε and a shoulder in the relaxation time τ. These anomalies and hysteresis are removed by taking the ratio of τ to Δε, which corresponds to the kinetic coefficient. From its Arrhenius-type temperature dependence, the activation energy is estimated to be 16 kcal/mol both below and above the transition point. The molecular motions responsible for the ferroelectric relaxation in this copolymer are thought to occur intramolecularly by a trans-gauche transformation in the crystalline regions.

In surface discharge, a transition from Polbüschel to Gleitbüschel takes place as the applied voltage is increased. The transition voltage V_g is empirically proportional to C₀^-1/n (n=2∼3), C₀ being the specific capacitance. In this paper, the relation between V_g and C₀ is introduced analytically using an equivalent transmission line model for the surface streamer. The assumption is made that the transition occurs when the total amount of energy dissipated in the whole streamer stem reaches a given critical value. The analytical relation obtained agrees comparatively well with the empirical one, if the circuit parameters are chosen appropriately.

Disaccommodation (DA) and the magnetic annealing effect in amorphous (Fe_1-xNi_x)₇₇Si₁₀B₁₃, 0≦x≦0.8, alloys have been studied as a means of investigating the mechanism of structural relaxation in amorphous solids. The relaxation process is divided into two stages. The first stage, bolow about 200°C, is caused by the movement of metalloid atoms and the second, above 200°C, by diffusion of the constituent atoms. It is shown that the origin of DA is the same as that of induced magnetic anisotropy.

The characteristics of a Johann-type crystal spectrometer with a photodiode array (PDA) are described. The crystal used is LiF(200) with a bending radius of 100 cm, and the sensitivity of the PDA is measured for X-rays of 4 to 17 key. The collection efficiency η of charges created in the PDA is determined as a function of the X-ray energy E(keV): η=-0.026E+0.68. An asymmetrical spectral profile is observed when a monochromatic X-ray beam is incident on the PDA with an angle larger than 40°. The sensitivity of the spectrometer is also calibrated against a conventional X-ray tube. The PDA is used for the observation of X-ray lines from a high-temperature plasma in a vacuum spark. The resultant Fe Kα spectrum shows a spread over several channels due to blooming, when compared with that recorded on Kodak no-screen X-ray film.

Ensemble Monte Carlo simulations are carried out to ascertain the magnitudes of the parallel and perpendicular diffusion constants in n-InP and their dependence on the electric field. The two-dimensional locations of 1000 electrons in real space after many accelerations by the electric field and collisions with phonons are illustrated in order to clarify the anisotropy in electron diffusion behavior. It is also demonstrated how both the parallel and perpendicular diffusion constants are affected by impurity scatterings. It is found that, because of the randomizing nature of impurity scatterings, both the parallel and perpendicular diffusion constants in n-InP with higher impurity density are greater than those in n-InP with lower impurity density.

The annealing behavior (up to 500°C) of semi-insulating GaAs implanted with 2×10¹⁴ Si ions/cm² at 200 keV has been investigated by measuring the sheet resistivity, Hall effect and optical absorption. In the samples annealed at temperatures below 450°C, the sheet resistivity, Hall mobility and optical absorption show the characteristics of amorphous semiconductors. The sample annealed at 500°C recovers to a partially-compensated n-type semiconductor, and the Hall mobility can be explained as scattering due to residual defects.

The measurement of the drift speed of an arc plasma in a self-crowbar air gap is reported, the speed being measured during the growth phase of the current in the device. The drift speed is concluded to be constant with time during this phase, although the force from the magnetic pressure is not constant during current start-up. This makes possible the design of a practical self-crowbar air gap switch. The possibility of designing a self-crowbar rotary air gap switch (SCRAGS), in which the rotary motion of the arc would dramatically lower the heat load on the electrode material, is also pointed out.

A small parallel plate avalanche counter (PPAC) consisting of a 0.2 µm-thick stretched polypropylene film was fabricated. Its characteristics as a time-sensitive detector were examined with α-particles from an ²⁴¹Am source, and a time resolution of 150 psec was obtained. The pulse height distribution of the avalanche electrons was observed and the cause of the distribution was studied. The distribution could be explained as a result of two kinds of fluctuation resulting from energy loss and electron avalanche multiplication.

Using the Rutherford backscattering method, the stopping cross-sections of amorphous silicon doped with rare gases to a concentration of a few percent were measured for helium ions. The effective stopping cross-sections of the rare gases were deduced by assuming Bragg's rule and by using Ziegler's cross-section values for silicon. The results were systematically about 30 percent lower than Ziegler's values for the gaseous state, in the energy range near 1 MeV. The incident energies were 1.0–2.6 MeV for samples containing 8% argon, and 1.0–1.6 MeV for those containing 7% krypton or 4% xenon.

It has been found that Na-PAA molecules in dilute aqueous solution are degraded by shearing stress, oxidation and photolysis during usual viscosity measurements with a capillary viscometer. The results of previous viscosity measurements, mainly about the mechanochemical degradation in air and in air-free conditions, showed that the degradation rate increases with increasing shear stress, and with decreasing polymer concentration. In this work, the effects of the molecular weight and temperature on the degradation rate are measured using a capillary viscometer in air, and the photodegradation of Na-PAA and PAA in aqueous solution irradiated with UV light are studied by viscosity measurements in air, and by UV absorption and ESR methods. The results show that the degradation of molecules is enhanced by an increase in the molecular weight and strongly accelerated by a rise in temperature and by UV irradiation, and is accompanied by free-radical chain reactions.

Acoustoelastic properties of poly (methyl methacrylate) under uniaxial tensile stress were investigated by the ultrasonic measurement at 5 MHz. The softening phenomenon in sound velocity along the stress direction and its anisotropic behavior were confirmed in MHz region, as already observed by Brillouin scattering in GHz region. It was clarified that the origin of this phenomenon was attributed to the formation of embryonic states for submicrocracks, based on the results of small angle X-ray scattering (SAXS) studies on the developments of size and concentration of submicrocracks under various strains. Furthermore, the events of structural conversions from embryos to submicrocracks were detected by the acoustic emission (AE) measurements.

The thermodynamics and the energy distribution function of the neutron gas in a constant power reactor are considered, taking into account the burn-up of fuel. To separate the secular motion of neutrons owing to fuel burn-up and the microscopic fluctuations of neutrons around this motion, a long time of the order of several months is divided into m equal intervals, and the respective states corresponding to m small time intervals are treated as quasi-stationary states. The local energy distribution function of the neutron gas in the quasi-stationary state is given by a generalized Boltzmann distribution specified by the respective generalized activity coefficient for each subsystem. The effects of fuel burn-up on the respective distribution functions for successive small time intervals are taken into account through various quantities relating to reactor physics, depending upon the fuel burn-up, by successive approximation.

A cellulose nitrate track detector, LR-115 (Type II), was studied experimentally to observe its neutron energy response when a radiator, such as fissionable material, is absent. The detector was exposed to monochromatic neutrons from the D (d, n) He reaction produced by a Van de Graaf accelerator. Through-etched and almost through-etched tracks in the detector were counted by two different methods: 1) optical microscope counting with an automatic image analyzing system and 2) spark counting. The detection sensitivity was obtained in the neutron energy region lower than 5 MeV and it was found that only α-particles from (n, α) reactions could be detected in both counting methods. We derived the counting probability of α-tracks induced in the detector and the threshold energies for neutron detection.

The spin polarization in low-energy electron diffraction (LEED) from a clean W(001) surface, as well as from a surface exposed to residual gas, has been measured with a newly-constructed compact Mott detector. At a particular electron energy and incident angle, exposure of a clean surface to 0.5 Langmuir of residual gas causes a significant polarization change, from -45% to +31%. This characteristic is not inconsistent with results reported by other workers under different diffraction conditions.

The energy density profiles deposited in a PMMA resist film by a 0.5 µm square electron beam are calculated by Monte Carlo simulation. The influence of a combination of beam accelerating voltages and beam edge widths on the pattern fidelity is studied by examining some characteristic parameters. Simulation shows that one of these parameters, the energy efficiency, has a tendency to saturate above 50 kV, and that larger beam edge widths are allowable for higher voltages in obtaining the desired values for the characteristic parameters, which are exemplified by a normalized energy edge slope and the roundness of the square pattern. A combination of voltages of 30–50 kV and a beam edge width of <0.2 µm is desirable in 0.5 µm lithography. High-fidelity 0.5 µm patterns are obtained experimentally with an electron beam system employing writing strategies based on this simulation.