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The pressure-volume relationships for EuSe, EuS, YbSe, and YbS have been obtained from high-pressure x-ray-diffraction studies to nearly 300 kbar. Like EuTe, EuSe and EuS exhibit normal compression and undergo the NaCl-to-CsCl-type transition at about 145 and 215 kbar. The compression curves of YbSe and YbS are anomalous in the 150-200-kbar region, which we believe is because of a change in the valence state of Yb from ${2}^{+}$ towards the ${3}^{+}$ state. Among the Eu monochalcogenides EuO is the only substance that shows a valence transformation (\ensuremath{\sim}300 kbar) followed by a NaCl-to-CsCl-type transition (\ensuremath{\sim}400 kbar). However, all the Yb monochalcogenides undergo the valence transformation continuously with pressure. The bulk moduli evaluated from the experimental $P\ensuremath{-}V$ data and the measured pressure coefficients of the energy gap between the $4f$ level and the conduction-band edge from optical-absorption studies of divalent rare-earth monochalcogenides are compared. These data are used to rationalize the occurrence or nonoccurrence of the valence transitions in this series of compounds.

The first utilization of LPE for large scale production is for GaP light emitting diodes (LED's). In this paper we compare various approaches to multislice LPE and techniques of junction formation from the standpoint of LED fabriaction. A new technique involving a combination of thin melt epitaxy and vapor doping is emphasized as a method which is compatible with economic large scale production and state-of-the-art device performance. A detailed account of the growth procedure, surface quality and device performance is presented for a laboratory-prototype mass production system for green LED material.

The repulsive elastic forces between island pairs, due to the overlap of the strain fields induced by the islands in the substrate, are calculated. Allowance is made for the discrete nature of the atoms and the atomic layers in both the substrate and the deposit. A simple model of the Frenkel-Kontorowa type is used. It is proposed that these forces, which are of a short range nature are insufficient to produce island glide, but nevertheless important enough to play a role in crystal growth.

Partial oscillator strengths (β dependent), from threshold to 49 eV, for the ionisation of 1b1, 2a1, 1b2, 1a1 electrons from the valence shell of water vapour have been determined using fast (3.5 keV) electron impact with coincidence detection of the scattered and ejected electrons. The total oscillator strength (photoabsorption) was determined from the forward scattered electron intensity and placed on an absolute basis by normalisation to a total f value of 8 for the valence shell.

Electron microscopic studies of damage to spur gears in an experimental gearbox have shown that rolling contact fatigue plays a major role supplemented by abrasive wear. It is noteworthy that the most voluminous part of the wear debris consisted of extremely fine particles of thicknesses below 0.2 μm.

Granular metal‐semiconductor barriers were investigated on n‐type Si, GaAs, and CdSe single crystals. The barriers were formed by cosputtering metals, Au or Ni, and insulators, SiO2 or Al2O3, onto the semiconductor surface. By varying the relative volume fraction of the insulator over the range 0–90%, the structure of the granular metal changed from that of a continuous metal to that of isolated small ([inverted lazy s]20 A ) metallic particles embedded in the insulator. Even with as little as 10% by volume of the metal, the granular metal contacts were found to behave as metal‐semiconductor Schottky barriers. In the composition range 60–90% insulator in the granular metal, the barrier heights were independent of composition and their values were 0.57, 0.58, and 0.65 eV on Si, GaAs, and CdSe, respectively. In the case of Si and GaAs, the barriers are significantly lower than those observed for the pure metals; in the case of CdSe no such difference is found.

The effect of mutual drag of hot carriers and acoustical phonons on the propagation of strong electromagnetic waves in semimetals (Bi, Sb) with equal electron and hole concentrations is investigated. In the presence of a high magnetic field the frequencies of the plasma—phonon waves are shown to depend on the amplitude of the incident wave E, through the temperatures of the heated carriers and phonons. The frequencies of these waves decrease with increasing E0. It is shown that under the action of the incident wave a semimetal becomes optically non-uniform, i.e. the refractive index is changed from point to point. Expressions for the damping of the field and for the temperature of the carriers have been established under the conditions of a non-linear normal skin-effect. The ohmic and Hall static conductivities depend on E0 both in weak and strong magnetic fields. The basic characteristics of the field and temperature are calculated. [Russian Language Ignored].

By a careful process SiSiO2-interfaces can be made with a low oxide charge Qox and with a low surface states density Nss. For dry oxides on (100) Nss-values as low as a few 109 cm−2 eV−1 are found on samples with an oxide charge density of 3·0 × 1010 cm−2. Only the Nicollian-Goetzberger conductance method is proved to give reasonable results on these structures. The quasi-static low frequency C-V-technique is in good agreement with the conductance technique for samples with Nss-values higher than 1·0 × 1010 cm−2 eV−1. The spatial fluctuation of surface potential, mainly caused by oxide charge fluctuations, is an important parameter when studying the high or low frequency C-V-characteristics. Some irregularities in the experimental Nss-φs-curves are explained.

The etching of α-SiC crystals on various susceptors (tantalum, tantalum coated with tantalum silicide and tantalum carbide, and graphite) was studied in atmospheres of hydrogen and argon at temperatures between 1600–1850 °C. The studies were concerned with reactions occurring at the crystal-susceptor interface. It was found that in the case of tantalum susceptors, the above-mentioned reactions caused the formation of Si-Ta cubic phase based on silicon structure network. The rate of etching and the etch patterns formed on the bottom side of the crystals were related to the type of susceptor used. It was observed that impurities in the susceptor have a catalytic effect on the processes investigated. Photomicrographs of etched crystals are presented.

Cation tracer diffusion coefficients were measured in pure NaF crystals in the intrinsic ionic conductivity range (876–970 °C). The results can be rationalized satisfactorily in terms of contributions to the observed Na tracer diffusivities arising from both free vacancies and neutral vacancy pairs, the latter contribution amounting to about 53 per cent of the total Na diffusion at the highest measuring temperature. The best-fit defect parameters derived in an earlier conductivity study [21] from this laboratory on similar NaF crystals give for the free vacancy contribution Dv*(Na) = 4·25 exp (−2·21 eV/kT) cm2s−1. A combination of these Dv*(Na) values with the present diffusion data yields for the vacancy-pair contribution Dp*(Na) = 1·15 × 108exp (−4·04 eV/kT) cm2s−1. Comparison of the present findings with published values of the anion tracer diffusion coefficient in NaF showed that Dp* (F) is 2·3 to 4·4 times larger than Dp*(Na) over the temperature range of our observations, the difference between the two contributions increasing with decreasing temperature. When approximate account is taken of the temperature-dependence of the two pair correlation factors, this last result indicates that the anion jumps into the vacancy pair occur with a higher frequency, and increasingly so at lower temperatures, than do those involving the cations.

Growth of low energy planes of perfect crystals at low supersaturation requires two-dimensional nucleation. The formation energy of nuclei of i atoms may be written Gi = -ikT1n α+Gs(i), where α is the saturation ratio. An atomistic evaluation of Gi, for a simple model, is in good agreement with the classical form Gs(i)= i1/2β', with a constant edge energy coefficient β', even for very small i. β' includes entropy terms and is significantly lower than the unmodified edge energy coefficient β when β/kT 10, which is typical of growth from the vapour on low energy planes, 2DN is slower than SDG for α⪅10 and is negligible for α⪅2. When β/kT

The response of a symmetrically layered plate subjected to symmetric step normal line face loads is determined. The solution, which is based on the equations of motion from linear elasticity, is obtained in the form of an infinite series of integrals with each term being the contribution from a branch of the underlying frequency equation. Through numerical analysis several of the lower branches of the frequency equation, which depend on layered plate ratios (four material and one thickness) are evaluated and used to write the transient response in the near field. Integrations based on the first five branches show the dominance of the lowest mode in the solution. Applying arguments of stationary phase to the spectrum, yields low frequency-long wave and high frequency-short wave approximations for use in obtaining the far field-long time disturbance. The former governs a front running “head of the pulse” for the layered plate, and the latter, later arriving Rayleigh and Stoneley waves.

The dependence of the effective minority carrier lifetime τeff on a longitudinal magnetic field is investigated up to 140 kG in rod-like germanium samples at temperatures between 5 and 20 K and at 77 K. The effective lifetime increases with increasing magnetic field and reaches a saturation value in the high field region. In accordance with the theoretical model of Lautz and Schulz this value is taken as the average bulk lifetime τv of electrons and holes in the samples. Theory and experimental results are in a good agreement at 77 K; from the comparison an estimation for the surface-recombination velocity s can be obtained. Im Temperaturbereich zwischen 5 und 20 K und bei 77 K wird die Abhangigkeit der effektiven Minoritatstragerlebensdauer τeff von einem longitudinalen Magnetfeld bis zu 140 kG in stabchenformigen Germaniumproben untersucht. Die effektive Minoritats-tragerlebensdauer wachst mit steigendem Magnetfeld an und erreicht einen Sattigungswert. Dieser Wert entspricht, in Ubereinstimmung mit dem theoretischen Modell von Lautz und Schulz, einer mittleren Volumenlebensdauer τv der Elektronen und Locher. Bei 77 K stimmen Theorie und experimentelle Ergebnisse gut uberein aus dem Vergleich kann eine Abschatzung fur die Oberflachenrekombinationsgeschwindigkeit s gefunden werden.

Absorption, photoluminescence, and resonant Raman scattering have been measured in BiI3 at low temperatures with a tunable dye laser. The results do not support the “bielectron” model of Gross et al. Absorption, Photolumineszenz und der resonante Ramaneffekt wurden an BiJ3 bei tiefen Temperaturen mit Hilfe eines durchstimmbaren Farbstofflasers gemessen. Die Ergebnisse konnen nicht im Rahmen des „Zweielektronenmodells” von Gross et al. erklart werden.

By making use of the many band Hamiltonian, the effect of the electron correlation on (1/ T 1 ) orb for ferromagnetic metals is investigated by solving the Green function within RPA. It is found that only the contribution from the interband transition is affected by the electron correlation. For the case of the saturated ferromagnets, it is found that the electron correlation enhances the relaxation rate by a few time, in the tight binding approximation. The numerical calculation of the enhancement factor for nickel is done making use of a simplified two band model. The results shows that the effect of the electron correlation on (1/ T 1 ) orb is important for a comparison with experiments.

The Compton spectrum of graphite is analysed with a high resolution Si(Li) solid state detector. Because of the intensity gain, crystal monochromatization of the incident X-rays became possible so that a spectrum of very good distinction is achieved. The results are in good agreement with earlier measurements by Weiss and Phillips [1]. Das Compton-Spektrum von Graphit wurde mit einem hochauflosenden Si(Li)-Halbleiterdetektor aufgenommen. Auf Grund des Intensitatsgewinns war eine Monochromatisierung der einfallenden Rontgenstrahlung moglich, so das ein sehr sauber definiertes Spektrum gemessen werden konnte. Die Ergebnisse sind in guter Ubereinstimmung mit fruheren Messungen von Weiss und Phillips [1].

The equation of convective diffusion is solved for a channel with a longitudinal variation of velocity and a laminar flow. A formula is derived for the thickness of the diffusion boundary layer.

Observation of the times involved in one switching cycle and the location of the conducting filament formed suggests a mechanism for switching. It is postulated that joule heating in the sample interior predetermines high conducting (avalanche) paths which in turn lead to RC discharge and filament formation.

Le renforcement des elastomeres par des particules dispersees et, en particulier, les noirs de carbone est d’une tres grande importance technologique dans l’industrie du caoutchouc et l’etude des proprietes des composites ainsi obtenus fait l’objet d’un tres grand nombre de travaux. Les revues recentes consacrees a ce sujet (1) (2) font ressortir que les mecanismes des differents phenomenes de renforcement obtenus ne sont pas toujours parfaitement compris, la complexite des resultats etant en general liee a des problemes d’aggregation et de »structure«.

The variational problem of stationary thermal conductivity in an inhomogeneous solid is formulated. It is assumed that the boundary conditions on the boundary of the body are unknown. In order to obtain a unique and stable solution one requires measurement of the temperature at one point and correct selection of the regularization parameter.

Transverse magnetoresistivity data taken for pure nickel and its alloys containing 9.38, 18.77 and 28.32 at.% copper are seen to be governed by Kohler's rule in restricted temperature ranges. The resistivity at zero magnetic induction as a function of temperature, ϱ(B=0, T) has been computed for all the samples from their Kohler plots. It is seen that the spin-disorder scattering constitutes a major part of ϱ(B=0, T) in the temperature range of present investigation.

The electronic wave function of the ion cluster BeH+H2 has been calculated for a series of nuclear arrangements with the aid of the IEPA-PNO method (Independent Electron Pair Approximation using Pair Natural Orbitals) which included valence shell correlation. The equilibrium geometry of BeH3 + has C 2ν symmetry. The four nuclei lie in a plane; the H2 molecule is perpendicular to the BeH+ ion and 1·60 A in front of the Be atom. The stability of the cluster with respect to dissociation into BeH+ and H2 is 24·7 kcal/mole. Perturbation theory has been used in order to get an understanding of the interaction of BeH+ and H2. This attempt however was successful only for larger intermolecular distances (R > 5 A). Additionally, a point on the potential surface has been found, which has all the properties which are desired for a transition state of the isomerization reaction of BeH+D2. The activation energy for this reaction is calculated to be 32·5 kcal/mole (7·8 kcal/mole with respect to separated BeH+ + H2).

Local dislocation densities were measured in glide bands of deformed KCl single crystals revealed by etching. The distributions of local dislocation densities are obtained and their variations along the glide bands, and from one band to another are studied. The degree of agreement of the experimental histograms with two standard distribution functions (Poisson and Gauss), corresponding to random and correlated distributions, respectively, shows that the distribution of screw dislocations agrees with the Poisson-like shape along the total band length. Edge bands show various distribution forms: “Poissonian” as well as “Gaussian” regions are observed. The “Gaussian” behaviour of the distribution in edge bands is related to the elastic interaction between dislocations. The correlation found between the form of the distribution function and the dislocation density is explained on the basis of increasing contribution of this interaction with increasing dislocation density. It is shown that separate portions of the glide band cannot be regarded as representative for the entire glide band, because the parameters of the distribution function and its form change along the glide band. [Russian Text Ignored].

A technique is presented which is applicable to any uniform coupled open transmission lines such as coupled optical integrated circuits. The proposed technique is as follows. The electromagnetic fields of the wave propagating along a coupled line is expressed in terms of a linear combination of the fields associated with the individual lines, as a zero-order approximation. Inserting this trial field description into the variational expression for the propagation constant beta and applying the well-known Rayleigh-Ritz's procedure, accurate solutions for the propagation constants of the coupled lines are obtained. This method can be applied generally to analyze coupled structures in microwave, millimeter wave, and optical wave circuitry. As an illustrative example, the coupling between two optical transmission lines consisting of lens-like dielectric media has been analyzed by means of the proposed technique.

The thickness function of a simply supported rectangular plate is determined such that the fundamental natural frequency of transverse vibrations attains an optimum value. The volume of the solid plate, its size, and data pertaining to its material properties, are assumed to be given. The problem consists of determining the deflection function corresponding to the optimal plate thickness function from a non-linear, fourth order partial differential eigenvalue problem, derived by variational analysis. Second and higher order normal derivatives of the deflection function are singular along the boundary of the domain. This behaviour is investigated analytically, and taken into account in a finite difference formulation of the problem, which is solved numerically by successive iterations.

This paper contains an account of various experiments associated with the propagation of a pressure pulse up a vertical column of liquid. When such a pulse reaches the upper free surface of the liquid it is reflected downwards as a pulse of tension. This method therefore provides a means of subjecting the liquid to tension under dynamic conditions of stressing. If the value of the tension at any depth exceeds a certain critical value the liquid will cavitate. Values of this critical tension T were measured for liquids of varying viscosities η and it was found that the empirical relation T=kη0.1 holds. Secondly, pulse propagation across the interface between two immiscible liquids was studied, and it was found that the maximum tension which could be sustained by an interface separating silicone oil and water is less than the tension which produces cavitation in either of these two liquids. Thirdly, it has been found that the cavitation produced shows several cycles of growth and collapse, a phenomenon which has been observed photographically by previous workers.

We determined the transition line between hcp and fcc helium up to 4.5 kbar using x-ray diffraction. The slopedPtr/dTtr increases rapidly with pressure as predicted recently. Unit cell dimensions are given for both structures at 3.33 kbar and 18.5 K.

A study is made of the oscillatory spectral distribution of the photovoltaic effect of a gold–germanium Schottky barrier in quantizing magnetic fields. The spectra are taken at 4.2 K in the Faraday configuration for fields of up to 70 kG. The results are analyzed in terms of the Pidgeon and Brown coupled bands theory of interband magneto-absorption. Excitonic effects are observed and discussed.

The magnetic after effect due to dislocations is investigated for three types of configurations: i) randomly distributed immobile point defects, ii) Cottrell clouds, iii) strongly bound defects in the dislocation core. It is shown that only the case of the mobile Cottrell cloud leads to a simple Debye process, whereas the other cases must be described by a more general relaxation function. The role of point defects in the core of dislocations is studied in some details. In this case the relaxation time is found to be determined mainly by the binding energy of the impurity atoms to the dislocation core.