Table of contents

The depencence of the signal intensity of the ⁸⁷Rb double resonance on the pumping light which was obtained by a ⁸⁷Rb lamp and a ⁸⁷Rb filter cell was measured. It became clear that the signal intensity depended specifically on the kind and pressure of the foreign gas contained in the ⁸⁷Rb filter cell, and on its temperature. These characteristics correspond to those of the intensity difference of the two hyperfine components of the ⁸⁷Rb D₁ pumping light.

The pressure dependence of the lattice constant of silicon was observed by the X-ray diffraction powder method under pressures up to 65 kbar generated by a cubic anvil press, where kerosene, isopropyl alcohol and a 1 : 1 -volume mixture of pentane and isopentane were used as pressure transmitting liquid media. The observed diffraction lines (111), (220) and (311) indicate that as long as the media maintain the liquid state, the pressure dependence of the lattice constant is in agreement with that obtained by bulk compression. Once the media starts to solidify with pressure, the dependence deviates and the lattice contraction becomes larger to have such values as those obtained when a solid pressure medium is employed. Corresponding to the solidification, the line widths of (220) and (311) become larger remarkably, suggesting the possibility of the lattice deformation in the orthorhombic structure.

Conventional vacuum evaporation of Cu_1.8S produces films with conductivities σ ranging from 10^-3 to 10³ (Ωcm)^-1 which arc an increasing function of the distance from the evaporator. The films with σ less than 10¹ (Ωcm)^-1 contain precipitations of Cu. The films with low conductivities are chalcocite and the highest conductivity of the chalcocite film is probably 10⁰ (Ωcm)^-1. The films with σ of 10²–10³ (Ωcm)^-1 consist of djurleite and digenite. The hole mobilities in films with several 10² (Ωcm)^-1 are 1.1–0.6 cm²/V sec corresponding to the hole densities of 6×10²⁰–9×10²¹ cm^-3. The mobilities in films are only several times smaller than those in bulky Cu_2-xS. The films with σ as low as 10^-3 (Ωcm)^-1 become conductive by sweeping out excess Cu by a field applied during deposition. In the films under the deposition, Cu ions migrate through the activation process with an energy of about 0.2 eV.

This paper has proved, by using Weinreich relation, that a carrier depletion effect is a main cause for power saturation phenomena in the acoustic bulk-wave (BAW) amplifiers formerly reported. By using this proof, a standard of the saturation power in several kinds of acoustic surface-wave (SAW) amplifiers is derived in a general form, and it is indicated that monolithic SAW amplifiers are better suited for obtaining high saturation power than compound-medium ones. The large signal amplification characteristics of the monolithic SAW amplifier are studied theoretically by using a simple analytical nonlinear theory as well as computer calculations and also experimentally by using CdS SAW amplifiers. Finally, it is proposed that the acoustic wave amplifier could have a higher saturation power under constant current drive than under constant field drive.

Electronic switching transitions between on- and off- states in threshold-switching chalco-genide glass films were investigated to explore the electronic processes responsible for the transitions and to obtain information on improving device performances. To this end experimental as well as analytical investigations were carried out on the switching processes. Dynamic behaviors of the recovery processes, as well as threshold-on states, were measured directly by means of the RF reflection technique, which demonstrated a nearly exponential decay of conductivity after elimination of the excitation pulse. Current increase taking place just before switching was measured and shown to be related to switching initiation. Analytical investigations were carried out on the basis of a hot electron model. Applicability of the hot electron model to the electronic processes in chalcogenide films is discussed from various points of view. It is shown that the model can present a consistent picture on switching phenomena, if appropriate energy dependence of electron mobility is taken into account.

The secondary electron emission yield, γ, and the energy distribution of the outer secondary electrons from Al surface by high energy proton or α-particle bombardment are calculated by means of the excitation function for core electrons and the approximate solution of the Boltzmann transport equation. The incident energy dependence of γ and the energy distribution are successfully explained in the incident energy region above 2 MeV/amu. But the value of γ itself is only a third of the value taken from the experimental results obtained by Aarset et al.

The charge storage properties of the Metal-Oxide-Metal particles-Oxide-Semiconductor structure, in which charge storage traps are introduced by interposing metal particles between CVD SiO₂. and thermally grown SiO₂, have been investigated. As metal particles, Pt evaporated by electron beam has been used. The distinct effect of Pt particles on the charge storage properties has been observed, compared to the properties of the Metal-Oxide-Oxide-Semiconductor structure. The amount of the flat-band voltage shift and the retention time are changed with the heat treatment condition in the O₂ atmosphere after the CVD SiO₂ deposition upon metal particles. This is explained by the growth of SiO₂ on Si by the heat treatment in O₂, which is clarified by structural analysis by means of Auger electron spectroscopy.

The electrical resistivities at room temperature have been investigated precisely after partial and complete internal oxidation. The internal oxidation rates obtained through electrical resistivity measurements are always smaller than the real rates which are obtained metallo-graphically. This suggests that the resistivities of subscales after partial internal oxidation are greater than those after complete internal oxidation, and that it is wrong to estimate internal oxidation rates through resistivity measurements. After complete internal oxidation, deviations from Matthiessen's rule (DMR) are observed in the internally oxidized Cu–Al alloys. The DMR's at 20°C have the same magnitudes as those of the residual resistivities and are nearly proportional to the volume fraction of dispersed Al₂O₃ particles. The DMR at 20°C in the Cu–1.0 vol%Al₂O₃, alloy is 0.037 µΩ-cm. The origin of the DMR is attributed to dispersed oxide particles.

The complex piezoelectric constant d=d'-id'' was measured for composite epoxy resin and PZT ceramics at temperatures between 110°C and 160°C in the frequency range from 0.03 to 30 Hz. A remarkable relaxation was observed above 140°C: d' increased with decreasing frequency and d'' showed a peak. This relaxation is ascribed to the d.c. conduction of ionic impurities activated at high temperatures in epoxy phase, because d'' maximum frequency snowed the same temperature dependence as the conductivity. The values of the relaxation time and the relaxation strength were discussed on the basis or a theoretical expression of the piezo-electric constant for a two phase system with spherical piezoelectric inclusions.

MnBi particles were prepared by grinding sintered MnBi in a ball mill. The coercivity of these MnBi particles was measured at 300 K and 85 K. At 300 K, the coercivity increased remarkably by grinding, and showed the highest value of 16000 Oe. At 85 K, the coercivity was very low compared with that at 300 K, and was about 80–400 Oe. For the particles which showed the coercivity of 16000 Oe at 300 K, the temperature dependence of coercivity was measured in the temperature range between 300 K and 85 K. The results were explained by considering the single-domain behavior of these particles.

The photon recycling process, i.e., the excitation of electron-hole pairs by the reabsorption of luminescent light, has large effects on the determination of the minority carrier diffusion length L and the internal quantum efficiency η_in GaAs with a high quantum efficiency. In this report, we show that the separate treatments of L and η_in cause the erroneous results for materials with high quantum efficiency. We developed a consistent method of evaluating the photon recycling effects on both η_in and L, based on the simultaneous measurements of the external quantum efficiency η_ex and the photo-excited current under the short circuit condition I_sc. This method was applied to the specimens with single heterestructure (p-Al_xGa_1-xAs-p-GaAs-n-GaAs) prepared by the liquid phase epitaxial (LPE) process.

The temperature dependence of the small signal alphas α₀₁ and α₀₂, and of the switching gate voltage V_Gs of a silicon p-n-p-n device is analysed theoretically by a method which varies all the device parameters with temperature. The variation of α₀₁ and α₀₂ with gate voltage is shown at various temperatures for different values of lifetime. The effects of the device parameters (lifetime, base width and doping level) are investigated on the variation of switching gate voltage V_Gs, with temperature T. It is shown that the theoretical predictions agree well with the experimental characteristics of V_Gs vs. T in the temperature range -20°∼80°C. This analysis shows that the characteristics of V_Gs vs. T can be tailored to a desired range by properly choosing the device parameters.

The tunability, threshold gain, and mode selectivity of electro-optically tuned distributed Bragg-reflector (DBR) lasers are investigated by using the coupled mode equations. The tuning range is calculated for various values of the pumped length and the coupling coefficient of distributed Bragg-reflectors. It is shown that the electro-optically tuned DBR laser has a tuning range of about 2 Å, if the pumped length and the coupling coefficient are chosen appropriately. Also, the tunable DBR laser considered here is shown to have advantages such as good. mode selectivity and low threshold operation.

The use of a toroidal magnetic field as a lens system is proposed for producing an intense ion beam. The characteristics of the lens system are obtained both analytically and numerically. Some examples of ray-trajectories are presented for different focal lengths. The system is applicable to neutral beam injection heating and micro-pellet implosion for nuclear fusion, and to other fields such as ion beam X-ray lasers.

In order to obtain more information on molecular mechanisms for three relaxations in the γ-loss band in linear polyethylene, the effect of the treatment with HNO₃ at 80°C on the magnitude of the loss tangent associated with these relaxations is investigated. Values of the loss tangent for polyethylene are calculated from those for a composite solid made of polystyrene and polyethylene powder treated variously. For this purpose an extension of the applicability of the empirical formula proposed by Gray and McCrum is examined. It is evident that the γ₁ and the γ₂-relaxations decrease and the γ₃-relaxation increases in magnitude with increase in the treatment time. From these results the γ₃-relaxation is attributed to the motion of cilia which is increased by the treatment, while the other two relaxations are attributed to the motion of folds or other interlamellar amorphous parts.

The ferroelectric phase transition temperature T_c was measured for a ceramic sample of (Pb_0.97Sr_0.03)Zr_0.51Ti_0.49O₃+2 wt% Nb₂O₅+0.45 wt% MnO₂ under pressure in the range from 10 kbar to 55 kbar. The pressure was generated in a pyrophyllite cell inserted in a tetrahedral multianvil apparatus. The transition temperature was determined from the anomaly in the dielectric constant. The initial rate of change with pressure of T_c was 3.1°C/kbar. At 37 kbar and 250°C, there was a break in the curve of T_c versus pressure and the slope suddenly changed to 7.5°C/kbar. It was supposed that this point was a triple point and a new paraelectric phase existed in the high pressure and high temperature region.

Nb–Ge thin films are prepared by co-evaporating Nb and Ge. Dependences of the superconducting critical temperature T_c the lattice parameter a_o and the resistivity on preparation conditions are studied. As the substrate temperature lowers from 1000 to 800°C, a_o remains constant but T_c is lowered. Lowering the deposition rate results in a decrease in a_o and an increase in T_c. T_c stays constant for the film thickness d larger than 2000 Å and is lowered for d smaller than 2000 Å. Especially, T_c is less than 4.2 K when d is smaller than 50 Å. The lattice parameter of the stoichiometric Nb₃Ge is estimated to be 5.12₇ Å by extrapolating the a_o's of single phase Nb–Ge thin films. A morphological study of Nb–Ge thin films is made by transmission electron microscopy. They consist of polycrystalline grains of about 500 Å in diameter.