The nucleation of perfect or partial dislocations from a surface-step of a f.c.c. or diamond-like material is frequently observed. In a recent paper, it is shown how the "stress—stacking-fault energy" plane can be divided into three zones where a partial or a complete dislocation will or will not nucleate. In compound semiconductors, dislocations can dissociate into α or β partial dislocations with mobilities appreciably different. In this paper, this effect is taken into account and yields to large modifications in the partial or perfect dislocations nucleation conditions. The case of GaAs is specially examined.

Admittance spectroscopy has been performed on Al dots deposited on porous Silicon grown on p+ substrates. They exhibit d.c. current-voltage characteristics of a metal-insulator-semiconductor structure containing a large concentration of localized states in the insulator. The admittance is composed of a frequency (ω) independent conductance while the reactance varies as ωs with s = 1. This strongly suggests that conduction through porous Silicon layers is governed by hopping between surface states.

By scratching the (0001)Si surface of 6H-SiC followed by annealing, dislocations were introduced in the crystal that were subsequently characterized by Transmission Electron Microscopy (TEM). Schottky diodes were then manufactured from the dislocated crystal and their electrical properties were studied by capacitance-voltage (C−V), current-voltage (I−V), and thermally-stimulated capacitance (TSCap) measurements. It was found that the deformation introduces deep traps Maynly located in the upper third of the bandgap promoting a significant increase in the series resistance of the diodes. The as-introduced dislocations were predominantly 30° partials and their core nature was determined to be Si(g) by the technique of Large Angle Convergent Beam Electron Diffraction (LACBED). The compensation effects observed after deformation are presumed to be caused not only by Si(g) dislocations but also by the other defects generated during the deformation step.

The thermal behaviour of a sample submitted to a sinusoidal optical irradiation or a sinusoidal electronic irradiation is modelled in axisymmetrical two- dimensional geometry. This modelling mixes an integral transform and a one-dimensional thermal harmonic response. It shows the spherical thermal behaviour of the harmonic heat diffusion. The same solving method is applied to the Navier-Stokes equation using one-dimensional acoustic harmonic responses. The latter solution leads to the calculation of the displacement field. Finally, the two heat sources are compared from thermal and thermoelastic points of view.

Solid state phase equilibria in the ternary Fe-Ga-As diagram were determined at 600 °C using powder X-ray diffraction as experimental techniques. Very limited solid solubilities were measured in the binary constituent Fe-Ga and Fe-As compounds. In the Fe-rich part of the diagram, a ternary phase was evidenced which corresponds in fact to a solid solution into which Ga and As substitute one another on the same sublattice. This phase, which can be expressed by the general formula Fe3Ga2−xAsx (0.20 ≤ x ≤ 1.125), crystallizes in hexagonal symmetry; it is structurally derived from the NiAs type-structure (B81) and can be considered, owing to its c/a ratio (1.23 ≤ c/a ≤ 1.28) close to $\sqrt{3}/\sqrt{2}$, as hexagonal-pseudocubic. The original feature of this experimental diagram is the occurrence of a tie-line between this ternary phase and the semiconductor GaAs which differs significantly from the theoretical diagram, estimated from simplified calculations proposed by Schmid-Fetzer. In particular, it is the first time that such a ternary phase Mx(Ga, As)y (M = transition metal) is found to be in thermodynamic equilibrium with GaAs. This fact suggests that the solid state interdiffusions which occur during the annealing of a Fe/GaAs heterostructure could lead to a ferromagnetic, epitaxial and stable Fe3GaAs/GaAs contact.

Light emission in the Au/Au junction of a scanning tunneling microscope has been detected in air and the property of the control of emission yield has also been evidenced. Experimental results presented in this paper clearly show that this property can still be observed on mineral oil-covered gold surfaces.

We study the limitation possibilities of bulk Bi high Tc materials. For this we test these materials with a.c. or d.c. currents above their critical currents. We study particularly the evolution of the voltage with time or with current. The material, the value of the current and the time duration play important parts. For sintered Bi samples the voltage depends only on the current even for values much larger than the critical current. With textured samples the V(I) curves shows an hysteretic behaviour due to a warming up. The textured materials are more interesting than sintered ones in terms of required volume for the current limitation. In both cases the superconductors are in a dissipative state but not in the normal state. This state is nevertheless reached if the dissipated energy inside the sample is sufficient. We have tried to apply a magnetic field on the samples in order to trigger a more effective limitation. The voltage increases but with a limited effect for currents much higher (3–4 times) than the critical zero field current. We think that the dissipative state is due mainly to the grain boundaries which become resistive above the critical current.

Transport critical current measurements were performed at 77 K on bulk silver-less (Bi, Pb)2Sr2Ca2Cu3O10+x ceramics textured by slow sinter-forging process. The influences of the 85 K superconductive 2212 phase and non-superconductive secondary phases (SrxCa1−x)2PbO4, (Sr,Ca)14Cu24Oy and (SrxCa1−x)2CuO3, are discussed in terms of their amounts, their grain sizes and shapes and their distribution among the 2223 matrix. The importance of the temperature profile and the atmosphere the annealing that follows the sinter-forging process is clearly demonstrated.

For the first time, the influence of an electron beam irradiation on InAs with native oxides was investigated. An irradiation modifies the chemical and physical properties of the surface oxides. The latent image can later be revealed by in situ exposure to Cl2 gas at 190 °C. The etching rate by Cl2 of the irradiated native oxides depends on the experimental conditions; it can be either increased or decreased. In consequence, differently irradiated zones of a sample surface later exposed to Cl2 are more or less etched than the non irradiated areas. The effect depends not only on the dose, but also on the electron energy: an irradiation is more effective at low energy. A stationary beam exposure at 30 keV reveals the contribution of the backscattered electrons, their geometrical and energetic spreading and the effect of a gradual variation of the dose. This experiment is compared to the spatial distribution of the backscattered electrons obtained by means of a Monte-Carlo type calculation.

A $\rm (\bar{1}11)NiSi_2 //(1\bar{1}5)Si$ heterotwin interface has been observed by high resolution electron microscopy (HREM) along the common direction $\rm [\bar{1}\bar{1}0]NiSi_2 //[\bar{1}\bar{1}0]Si$ to identify the long period atomic structural units (ASU's). Coexistence of two different structural doMayns has been found with ASU's corresponding to two different cycles of five-, six-, and seven-atom rings. A dislocation/ledge (DL) has been particularly studied because its separates these two unusual cycles of ASU's. The elastic displacement field u of the atom columns around the DL has been calculated using both crystallographic and anisotropic elasticity properties of the crystals, assuming a two-dimensional u field. From a comparison between the positions of the atom columns as derived from elasticity calculations and as deduced from the HREM image, it is concluded that the DL is a mixed dislocation with the Burgers vector $\rm (-1/4)[111]NiSi_2 + (1/2)[1\bar{1}0]Si= (1/12)[515]Si$, a result also in agreement with the imperceptible ledge height associated with the DL core. Such a Burgers vector underlines the role of the Si matrix dislocations for producing such structural doMayns.

The uniaxial chiral medium, which is a modification of the well-studied reciprocal chiral material, can be created by embedding microscopic metal helices in an isotropic host medium in such a way that the axes of all helices are oriented parallel to a fixed direction but distributed in random locations. In the present investigation, based on the concept of cylindrical vector wave functions in this class of medium, electromagnetic scattering by a uniaxial chiral circular cylinder in the proximity of a PEC plane is rigorously formulated by eigenfunction expansion approach. Formulation of this problem is greatly facilitated by using the image theory of bianisotropic object in the presence of a PEC plane to replace the PEC by an image object with constitutive parameters of image forms. Numerical results indicate the phenomena of backscattering enhancement and polarization transformation phenomenon would occur, simultaneously.

A qualitative description of the plasma jet flow in field reversal configuration confinement scheme has been presented taking into account the conductivity and anisotropic temperature effects which were not included previously following the "free-streaming fluid model".

The structural model discussed in Part I of the present work is applied to "true" behavior – i.e. shear thinning followed by shear thickening (sometimes followed by shear thinning) – very often observed in complex fluids as the applied shear is increased. This model states that the viscosity η of these fluids – described as concentrated dispersions of several classes of Structural Units (SUs) – is a unique function of a flow-dependent effective volume fraction, φeff. The latter is expressed in terms of Si = fraction of "aggregated" particles contained in all the SUis (as SUs of i-class) and Ci = (ϕi−1−1)= "compactness factor", directly related to the mean compactness ϕi of SUis. Shear induced flocculation (SIF) is the more obvious process capable to explain the shear thickening behavior of partially flocculated suspensions (obviously, another process should be required for stabilized dispersions). After progressive reduction of SUs submitted to shear forces (i.e. leading to a decrease of Si), such a behavior should be observed if SIF occurs beyond a critical shear rate ${\dot {\gamma}_{\rm C}}$, then resulting in re-increase of Si, thus of φeff and η. The simplest "SIF-model" will introduce only one class of SUs, with only one variable S governed by a kinetic equation in which the kinetic rate for SU-formation increases with shear, thus giving the expected shear-thickening behavior if ${\dot {\gamma}}>{\dot {\gamma}_{\rm C}}$. However, at high shear rates, SIF is limited by a (Smoluchowski-like) shear decreasing sticking probability. Effects of varying model parameters on predictions of the resulting SIF-model are discussed. Finally, this model is tested by comparison with observed rheological behavior, namely viscosity change vs. pH in aqueous styrene-ethylacrylate dispersions, from Laun's data [2].

This paper is aimed at providing some data on the detonability of methane mixtures at a high initial pressure. The relevant work that has been performed so far was based on a conventional source of ignition, i.e., a blasting cap. Following these initiation experiments at the French German Research Institute (ISL), two sets of experiments were performed in CH4/Air mixtures, at initial pressures in the range of 0.1 to 3.7 MPa, at the University of Washington (UW): (1) using a piston that directly enters the test section in the velocity range of 1100–1800 ms−1 and (2) the piston impacts an intermediate section of CH4/O2. An additional series of experiments was performed using an initiator stage of stoichiometric CH4/O2 ignited by a 150 J conventional fuse cap.

An analysis of inertia effects in controlled stress rheometry is presented. For Newtonian fluids, this study takes exact account of both the instrumental inertia and the discontinuous stress change in this type of rheometer. In fact, supposedly smooth stress ramps are always approximated by a series of stress steps. The significance of this limitation, which is sometimes critical, is pointed out for the first time. The error induced by assuming that the stress ramps are smooth in Krieger's method for inertia correction [1], is quantitatively evaluated. An improved calculation for non-Newtonian, inelastic fluids is described.