CuAl single crystals of a low stacking fault energy have been deformed along the 〈111〉 direction in an apparatus which consists of a compression machine interfaced with an atomic force microscope. The emergence process of dislocations has been in situ studied during deformation. Plasticity occurs in this material by propagation of Shockley dislocations which generate two possible kinds of stacking faults, extrinsic or intrinsic. The fine structure of slip lines has been investigated by atomic force microscopy. A differentiation between these two possible twin mechanisms in this alloy is attempted. It is concluded that twinning in this material can not only be explained by the intrinsic stacking faults and that the contribution of extrinsic faults has to be considered.

This paper reports on the first realization using high temperature superconducting films of the device proposed in 1965 by Giaever: the DC-DC transformer, which involves flux-flow vortex motion in two superimposed thin films, separated by a thin insulating layer. The device was fabricated using the ramp based multilayer technology from an YBa2Cu3O7 based SIS structure grown by pulsed laser deposition. Transport measurements exhibiting the coupling and decoupling phenomena between the two vortex arrays are obtained. We discuss the possibility of widening the working range of this device, which constitutes an important result in the effort to use high temperature superconductors for electronics.

We show theoretically and experimentally that the wavelength tunability of an Er3+–doped fiber laser is improved by using a twofold filter combining a Mach-Zehnder interferometer and a polarimetric filter. This new filter allows us to tune continuously the wavelength from 1.53 to 1.56 µm without the discontinuity associated to the narrow transmission bands of a Mach-Zehnder tuning filter.

Propagation of electromagnetic waves is considered in a crystalline solid medium with random parameters. We predict the generation of new exciton-type transversal and longitudinal waves caused by fluctuations of concentration and frequency.

For some years, Cunat [1] has developed a formalism based on the thermodynamics of irreversible processes in order to describe the behaviour of continuous media which are not in the equilibrium state. This thermodynamics of relaxation has led to a very general modeling called “Distribution of Non-Linear Relaxations” (DNLR) modeling. This theoretical approach is currently applied in solid mechanics for various ways and sequences of loading. In this paper, the application to primary and secondary unidirectional creep is presented. Only five parameters whose physical meaning is known are necessary. We analyze the role of each of them and indicate a process of identification from experimental data.

In this paper, a simple model classically used to describe electrical behavior in conducting polymers can take into account transport properties in polyaniline doped with two different counter-ions and in polyaniline-polystyrene blends. Conduction is Maynly limited by hopping or tunneling between polaronic conducting clusters. When the structural disorder is less pronounced, a metallic contribution can occur near room temperature in series with the hopping/tunneling one. This heterogeneous picture used for unblended polyaniline can be applied to explain electrical blend properties above the percolation threshold when conduction occurs among completely connected polyaniline paths. Below the percolation threshold, the model has to take into account an additional contribution due to a hopping mechanism between large disconnected segments of polyaniline. It is shown that thermoelectric power reflects essentially the metallic behavior of the conducting clusters.

The effective electrical conductivity of a two-phase material consisting of a lattice of identical spheroidal inclusions in a continuous matrix is determined analytically. The inclusions are located at the node points of a simple-cubic lattice and the axis of rotation of each spheroid coincides with one of the lattice vectors, such that the spheroids are aligned with each other and with the lattice. With an electric field applied in the direction of the rotation axes of the spheroids, the electric potential is found by solving Laplace's equation. The solution is found by analytically continuing the interstitial field into the particle domain and replacing the particles with singular multipole source distributions. This yields an expression for the potential in the interstitial domain as a multipole expansion. Using Green's theorem, it can be shown that only the first coefficient in this expansion is required to determine the effective conductivity of the composite. The coefficients are determined by applying continuity conditions at the particle-matrix boundary and, in a novel approach, this is achieved by transforming the multipole expansion into an expansion in spheroidal harmonics. Results for spheres and prolate and oblate spheroids are compared with experimental data and previous theoretical work, and excellent agreement is observed.

In order to allow non-destructive characterizations by acoustic microscopy, the materials presenting in their properties a gradient perpendicular to the surface are modelled. The method consists in regarding the material as built of a succession of homogeneous layers numerous enough for the acoustic parameters to vary quasi-continuously. The gradient in Young modulus existing in the material is related to a gradient in acoustic properties measurable by acoustic microscopy. The role of the shape of the gradient profile is taken into account in the study of the convergence of the velocity of the surface mode VS. The dispersion of the velocity VSversusd/λ (d is the depth of the gradient area and λ is the wavelength) is studied as a function of the gradient profile. The shape of the curves shows that the best sensitivity to the profile is obtained for d/λ≈1.

In future particle accelerators, silicon detectors will be exposed with large doses of different types of radiation. To understand the corresponding produced damage mechanisms, a systematic study of the influence of the irradiation on the silicon from which the detectors are made has to be carried out. Samples of low n-doped silicon $(n\leq 10^{12}~{\rm cm}^{-3})$ have been irradiated with swift krypton ions $(\langle E\rangle=5.2~{\rm GeV})$, neutrons from a nuclear reactor $(\langle E\rangle \sim 1~{\rm MeV})$ and energetic electrons $(\langle E\rangle=1.5~{\rm MeV})$. Resistivity and Hall effect measurements performed after irradiation show that the silicon is changed to a quasi-intrinsic state, characterized by a very high resistivity. The electrically active defects responsible for that evolution are Maynly acceptor centers, namely divacancy and/or vacancy-doping complexes. Besides, for the highest fluences, only the appearance of a donor center located at about 0.59 eV below the conduction band may explain the observed stabilization of the Fermi level at 0.61 eV. Finally, using a simulation method, the rates of generation of the different defects are estimated.

The dielectric properties of heterogeneous materials for various condensed-matter systems are important for several technologies, e.g. impregnated polymers for high-density capacitors, polymer carbon black mixtures for automotive tires and current limiters in circuit protection. These multiscale systems lead to challenging problems of connecting microstructural features (shape, spatial arrangement and size distribution of inclusions) to macroscopic materials response (permittivity, conductivity). In this paper, we briefly discuss an ab initio computational electrostatics approach, based either on the use of the field calculation package FLUX3D (or FLUX2D) and a conventional finite elements method, or the use of the field calculation package PHI3D and the resolution of boundary integral equations, for calculating the effective permittivity of two-component dielectric heterostructures. Numerical results concerning inclusions of permittivity ε1 with various geometrical shapes periodically arranged in a host matrix of permittivity ε2 are provided. Next we discuss these results in terms of phenomenological mixing laws, analytical theory and connectedness. During the pursuit of these activities, several interesting phenomena were discovered that will stimulate further investigation.

Scanning electron microscopy as well as analytical transmission electron microscopy techniques such as high resolution, electron diffraction, energy dispersive X-ray spectrometry (EDX), parallel electron energy loss spectroscopy (PEELS) and elemental mapping via a Gatan Imaging Filter (GIF) have been used to study complex precipitation in commercial dual phase steels microalloyed with titanium. Titanium nitrides, titanium carbosulfides, titanium carbonitrides and titanium carbides were characterized in this study. Both carbon extraction replicas and thin foils were used as sample preparation techniques. On both the microscopic and nanometric scales, it was found that a large amount of precipitation occurred heterogeneously on already existing inclusions/precipitates. CaS inclusions (1 to 2 μm), already present in liquid steel, acted as nucleation sites for TiN precipitating upon the steel's solidification. In addition, TiC nucleated on existing smaller TiN (around 30 to 50 nm). Despite the complexity of such alloys, the statistical analysis conducted on the non-equilibrium samples were found to be in rather good agreement with the theoretical equilibrium calculations. Heterogeneous precipitation must have played a role in bringing these results closer together.

A reinvestigation of the phase diagram of the Cu–In–Se system along the quasi-binary cut In2Se3–Cu2Se reveals an existence range of the chalcopyrite α-phase that is much narrower than commonly accepted. The presence of 0.1% of Na or replacement of In by Ga at the at.% level widens the existence range of the α-phase, towards In- and Ga-rich compositions. We also investigate the interplay between phase segregation and junction formation in polycrystalline Cu(In, Ga)Se2 films. Here, we attribute the band bending observed at bare surfaces of the films to a positively charged surface acting as a driving force for the formation of a Cu-poor surface defect layer via Cu-electromigration. The electrical properties of this defect layer are different from those found for the bulk β-phase. We suggest that Cu-depletion is self-limited at the observed In/(In+Cu) surface composition of 0.75 because further Cu-depletion would require a structural transformation. Capacitance measurements reveal two types of junction metastabilities: one resulting from local defect relaxation, invoked to explain a light-induced increase of the open-circuit voltage of Cu(In, Ga)Se2 solar cells, and one due to Cu-electromigration.

Thin amorphous CuInS2 films were deposited on the glass substrates by single source thermal evaporation technique. The effect of heat treatments in sulfur atmosphere, in air and under vacuum on the surface layers is discussed in terms of the surface structure of the films. The films were examined by grazing X-ray diffraction and reflectometry (GXRD and GXRR). From a comparison with the GXRD results, the densities of the surface layers are explained by the presence of secondary phases. We established a correlation between stoichiometry and conductivity depending on the annealing conditions.

The strain relaxation in buried strained layers is investigated using an elastic continuum model. The mixture of single dislocations residing at the substrate/strained layer interface (lower interface) and dipolar dislocations in which one is at the lower interface and the other at the strained layer/capping layer interface (upper interface), is proposed. In the mixture, the dislocation distributions are denoted by a parameter which is the ratio of the density of misfit dislocations at the upper interface to that at the lower interface. In a buried strained layer, relaxation of mean strain occurs by introduction of two orthogonal arrays of mixture of single and dipolar dislocations. Considering both the free surface and interactions between dislocations, the total elastic energy per unit area of buried strained layer containing two orthogonal arrays of mixture of single and dipolar dislocations is calculated. The energy is dependent on the misfit dislocation distributions. On energy minimization considerations, the expression of the misfit dislocation distributions in a buried strained layer with arbitrary strain relaxation and capping layer thickness is derived. It is demonstrated that the strain is initially relaxed by the single misfit dislocations and relaxed by the mixture of single and dipolar misfit dislocations in the final stage of strain relaxation in many buried layers of practical interest.

The reflectivity of two-dimensional pyramidal absorbers and the transmittance of photonic crystals made of dielectric fibers is analyzed by means of two approaches. In the first one an integral representation of the scattered field is used and the absorbers are modeled by a stack of gratings of infinite extent. In the second approach, the absorbers and the crystal are replaced by an equivalent multilayered medium obtained by means of two homogenization methods. We assess the efficiency of these methods with respect to parameters such as the density of the gratings, their relative permittivity and the polarization of the incident wave.

A numerical scheme is presented to compute the response of a composite material to an applied field. The scheme is based on an iteration that uses a Fourier transform based projection method to compute the response of a reference material to the applied field, and a contraction mapping to relate the response of the reference material to the response of the composite material. The scheme also utilizes nested uniform grids to improve performance, and to evaluate the refinement of the grid.

The dielectric constant ε and the electrical conductivity σ were measured of crystalline plates cut perpendicular to the a-, b-, and c-axes from K2ZnCl4 (KZC) crystals, pure and doped with Co2+ ions, in the temperature range from 300 to 500 K. A pronounced broad peaks exists at the commensurate-incommensurate phase transition temperature (Tc1). A thermal hysteresis of about 10 K is observed for the transition during heating and cooling processes. The J-E characteristics along the crystallographic axes were measured below and above Tc1. Conductivity anomalies were observed at Tc1. The results of electrical conductivity temperature measurements were analyzed and the activation energies of conduction at different temperature regions have been evaluated. The mechanism of the electrical conduction of the various phases and the anomaly at the transition point was discussed.

Metal structures of diffusion limited aggregation type were obtained by controlled electrodifussion in quartz crystal without macroscopic damages. Conditions of temperature, applied voltage and the form, shape and dimension of electrodes were found, in order to obtain fractal branches. Similarity with fractal DLA structures are described and discussed.

Bulk Y1Ba2Cu3Oy was melt-textured without the use of seed crystals as well as by applying top-seeding with different seeds resulting in different orientations of the c-axis. Samples were examined by elastic neutron scattering and levitation force. The levitation force of the samples strongly depends on the orientation of the c-axis. The local superconducting parameters were found to be reduced with increasing distance from the seed. In order to study this influence, two cubes were prepared by top-seeding, but with seeds of Nd123 that had a parallel and perpendicular orientation of the c-axis of the Nd123-seed with respect to the contact area of the high-Tc superconductor. By this, different distances of the levitating surface, which is the surface that faces directly the magnet, from the seed were obtained. Results are presented and discussed.

It is known that losses of ultra-cold neutrons (UCN) from traps are due to the β-decay, up scattering and absorption on a surface but we have identified for the first time a complementary mechanism. We suppose that this arises from an increase in energy of the neutrons resulting in an upper energy spectral cut-off which is about twice higher than that for initial stored neutrons. The total probability for such a process equals ~10−5 per collision with a trap wall made of stainless steel without or with a Fomblin oil and grease coating.