In situ atomic force microscopy observations have been carried out of thin films under external compressive stress. Straight-sided buckling patterns arise perpendicular to the compression axis which tend to attract one another during propagation a few hundred nanometers apart. The mechanisms whereby these debonding patterns interact have been investigated taking into account the elastic energy of both the film and the substrate. The equilibrium distance between two straight-sided wrinkles has been determined; good agreement has been obtained between the experimental results and the mechanics involved.

A few years ago, some authors have observed by X-ray diffraction analysis in metallic multilayers with small period an in plane expansion combined with a large perpendicular expansion. These trends differ from prediction based on simple continuum elasticity theory. This unexpected result has been the starting point of an experimental development in our laboratory for determining the Poisson's ratio in such systems. Applying the $\sin^{2}\psi$ method on film-substrate set which is elastically deformed in an X-ray diffractometer, it is possible to extract the Poisson's ratio of the film. In this paper, we first detail the theoretical principles of the method and, we show its application on 150 nm thick tungsten films elaborated by ion beam assisted deposition on duralumin substrates. The obtained results demonstrate the feasibility of the method and its good precision.

Various properties of spinel iron oxide nanoparticles are reviewed in relation to the control of the particle size and the control of their dispersion in a variety of matrices. The deep knowledge of the different synthesis parameters and the interfacial oxide-solution characteristics allows to prepare a large variety of materials like calibrated nanoparticles and inorganic or hybrid nanocomposites.

The spectral signatures of non-axially excited, absorbing TFHBM slabs are determined, after using a single-resonance Lorentzian model to describe the dispersive properties of the medium. Optical phenomena such as the optical rotation, circular dichroism and ellipticity transformation by absorbing TFHBM slabs are described. The effect of absorption on the functionality of TFHBM-based devices, such as multi-notch filters and ultranarrow-bandpass filters, are noted and engineering guidelines on the fabrication of such devices are provided.

After deposition, by evaporation under vacuum, of Al/Cu/Te. multilayer structures, annealing at 673 K or more for half an hour, under argon flow, allows CuAlTe2 films crystallised in the chalcopyrite structure to be obtained. The optical and electrical properties are interpreted by introducing the influence of impurity foreign phases present in the films. The optical properties are sensitive to the small Al2O3 domains randomly distributed into the CuAlTe2 polycrystalline matrix. The optical band gap is slightly increased (2.35 eV) by the presence of alumina. The conductivity measurements show that a short circuit effect can be induced by a binary Cu $_{2-x}$ Te degenerate phase present at the surface of the films. This effect can be suppressed by KCN etching of the samples that allows the superficial foreign phase to be dissolved.

To determine the mechanical properties of materials in thin layers by the measure of Lamb waves velocities, the acoustic microscopy can be used in two different manners: by the spatial acoustic signature V(z), and, less widespread, by the frequency acoustic signature V(f). However, in this study, we show that for each of these signatures V(z) or V(f), there are complementary domains of use in which the detection and the efficiency of Lamb modes are optimized. A specific formalism permits to foresee each of these domains where the efficiency is optimized.

The nature of the hydrogen bonding and content and their influence on the film microstructure have been investigated in detail, as a function of the H2 dilution and the residual pressure, in hydrogenated amorphous silicon (a-Si:H) films prepared by radiofrequency (rf) magnetron sputtering at a common substrate temperature (~ 250 °C) and pressure (5 × 10−4 torr) and high rates (11−15 Å/s). H2 percentages in the gas phase mixture (Ar + % H2) of 5, 10, 15 and 20% have been introduced during growth. For the 20% of H2, two different pressures of 5 × 10−4 and 50 × 10−4 torr were used. A combination of infrared absorption, optical transmission and elastic recoil detection analysis experiments have been carried out to fully characterize the samples in their as-deposited state. The results clearly indicate that for H2 percentage equal to or lower than 15% , the total bonded H content in the films increases as the H2 percentage increases, and then reaches a saturation value or even decreases for higher H2 percentage. Moreover, the microstructure is also found to be deeply affected by the H2 dilution and pressure. In particular, for high H2 percentage (20%) and high pressure (50 × 10−4 torr), unbounded H as well as polyhydride (Si-H2)n chains, possibly located in structural inhomogeneities such as voids, are also present in the films in addition to the isolated monohydride Si-H and polyhydride Si-H2 complexes. As a result, a reduction of the compactness of the film structure associated with a decrease of the refractive index n is observed. The optical gap is found to be rather controlled by the total bonded hydrogen content. The lowest proportion of isolated polyhydride Si-H2 complexes and the highest density are observed for films deposited with 10% of H2 in the gas phase and a pressure of 5 × 10−4 torr.

HfV2O7 powders were prepared by means of thermal decomposition of a mixture of vanadyl and hafnyl oxalates in air at 973 K. The room temperature structure and its evolution with temperature was investigated using both electron microscopy (TEM and HREM) and powder diffraction (X-ray and neutron) techniques combined with DSC measurements. HfV2O7 exhibits two temperature-induced phase transitions between room temperature and 480 K. Over the highest transition (370 K), HfV2O7 crystallizes in a cubic system with a cell parameter of 8.75 Å and $Pa\bar{3}$ space group. A negative thermal expansion is observed in this high temperature phase and can be correlated to anisotropic oxygen atom displacements. On the other hand, the room temperature structure of HfV2O7 is also described in a cubic symmetry, but the existence of superstructure reflections leads to a cell parameter three times larger than for the high temperature structure (~ 26.25 Å). Moreover, HREM calculations have shown that the atomic positions, usually used to describe the superstructures of the ZrV2O7 compounds, cannot be used in the case of HfV2O7 at room temperature.

We investigated the behaviour in tension and at room temperature of TiNi shape memory alloys in martensitic state. Our first experimental results show that two deformation mechanisms are involved in the behaviour of such materials: martensite platelets reorientation and irreversible plasticity. Moreover when irreversible plasticity appears, we observe an increase in the martensite to austenite transformation temperatures. The present study is especially focused on the deformation mechanisms and intends to identify the nature of the irreversible phenomena. It is shown that the reorientation process and the appearance of interface dislocations are in perfect agreement with a kinematic hardening. Finally a two loading surface model is proposed which allows not only to account for the overall behaviour but also to predict the transformation temperatures under an internal and/or external stress field.

Excited state absorption of laser (≅ 1.3 µm, corresponding to the $^4{\rm F}_{3/2}\to {}^{4}I_{13/2}$ laser channel) and pump (790-860 nm) radiation have been investigated in Nd doped YAl3(BO3)4 non-linear laser crystal. Laser gain slope efficiency measurements as a function of pump wavelength have been used to estimate the excited state absorption of pump radiation. On the other hand, excited state absorption cross-section in the 1300−1400 nm wavelength range has been measured by using two beam spectroscopy. We have obtained that excited state absorption cross-section for pump radiation is negligible whereas around 1.3 µm it is comparable to the stimulated emission cross-section from 4F3/2 state, so that the net gain cross-section becomes negative for certain wavelengths.

Metal nanoparticles (gold, silver, copper) that are embedded in an insulating organic host material exhibit optical plasma resonance absorption in the visible and near-infrared region. The spectral position, the half width and the intensity of the plasma resonance absorption all depend on the particle size, the particle shape, and the optical behavior of the cluster and the host material.The optical extinction of various gold, silver or copper particle assemblies embedded in plasma polymer or gelatin was measured at 4.2 K and 1.2 K as well as at room temperature. The packing density of several samples was high enough to resolve a reversible increase of the plasma resonance absorption intensity towards lower temperatures. Additionally, at larger silver particles $D_{\rm m} >50$ nm a significant blue shift of the plasma resonance absorptionwas measured. Particle size and shape distribution were determined by transmissionelectron microscopy (TEM). For the first time, simultaneous measurements of the electrical and optical properties at one and the same particle assembly were performed at low temperatures. Contrary to the increasing optical extinction, the d.c. conductivity decreased to two orders of magnitude. At silver particles embedded in a plasma polymer made from thiophene a significant photocurrent was measured.

This paper presents a new experimental measurement method of the electrical parameters, shown from the stator, of a squirrel cage induction machine in accordance with its magnetic saturation level. It develops a new two-phase saturated model of the induction machine which uses these measured electrical parameters. This new measurement method has a very big advantage in the industrial domain. It avoids the use of a finite elements calculation program which takes much more time to calculate the electrical parameters. The experimental measurement method is applied on a 4 KW squirrel cage induction machine. A comparison between the real dynamic response of this machine, and the dynamic response of the new two-phase saturated model shows that the obtained results are very encouraging.

In this paper, a new concept called "Floating Islands diode" (FLI-diode) is proposed: the voltage handling capabilityof this new diode is assumed by the association of several PN junctions in series. This concept can be applied to anypower devices (lateral or vertical). An example of vertical power MOSFET based on this concept is presented here: thisnew structure, called "FLIMOSFET", exhibits improved on-state resistance performance when compared to the conventional VDMOSFET. For instance, for a breakdown voltage of 900 volts, the theoretical performance are strongly improved in term of specific on-resistance (reduction of about 70% relative to the conventional structure and 40% relative to thesilicon limit). Moreover the specific on-resistance theoretical limits of FLIMOSFET family are determined and comparedto those of the "Superjunction" MOS Transistor family: this comparison shows the strong interest of the FLIMOSFET inthe 200 volts-1000 volts breakdown voltage range.

A formalism is defined to describe systems composed of several electrical machines with several electrical and/or mechanical converters. So, a first classification of multi-converter multi-machine systems is proposed in order to point out their influences on the global power conversion: cost reduction, conversion quality... Three examples are presented with this specific formalism.

Several novel field emission devices are analyzed in a unitary way. The devices involve the use of field emitter arrays in a special configuration where the emitted electrons are subject to crossed electric and magnetic fields. Due to the acting electric and (magnetic) Lorentz forces, the electrons are either deviated or have a cycloid-like confined motion. The angular deviation of the electron trajectory can be used for measuring magnetic fields. The pulsed electron current produced by a cold cathode can be used to generate electromagnetic radiation. Because the electrons have a confined motion with a long trajectory length, their chance of hitting a residual gas molecule is increased. They can either excite gas molecules, which in turn emit UV-radiation when relaxing back to the stable state, or ionize them, the ionic current being correlated with the gas pressure. Accordingly, devices for generating UV-radiation and vacuum gauges can be devised. Furthermore, if the ion generation takes place in a narrow and well-defined region, then their angular deviation can be correlated with their mass. A mass spectrometer (with miniaturized dimensions and field emission electron source) can be devised on this principle.

The alterations of the resonance frequency of the vibrating tip of an acoustic sensor detect the density and the viscosity of liquids. The employed acoustic near-field sensor has several resonance frequencies which correspond to its different parts. We determined that the resonance of the body of the acoustic sensor is sensitive to the rheological characteristics of viscoelastic media. We carried out experiments with bitumens and we modified the acoustic load on the sensor in two ways: the immersion depth of the tip and the temperature of the bitumen specimens. Theoretical and experimental results are compared.

The Scanning Transmission Electron Beam Induced Current Technique (STEBIC) was adapted to allow the analysis of local electrical activity in semiconductor diodes. This technique enabled us to analyse the in situ properties of IMPATT junctions (IMPact Avalanche Transit Time: which are Si doped $p^+/p/n/n^+$ multijunctions). The samples were thinned down as cross-sections, to be observed and analysed in transmission electron microscopy. The current induced by the electron beam was collected by the depleted zone. By synchronising measurements with each scan of the electron beam, the electrical activity can be viewed at a very local scale. The STEBIC signal was simulated by using a model of drift-diffusion. The prevailing role of the recombination rate on the form of the STEBIC profile was evidenced. We found that the spatial resolution of this method depends on the thickness of the sample and on the zone where the measurement is taken. We show that the spatial resolution of this method is optimal when the electron beam is localised in the p/n depleted zone. In thin areas, the maximum spatial resolution is calculated to be $\le 20$ nm. Outside the electric field the transport phenomena are governed by the diffusion of carriers and the signal width is widened.

The stable corona discharge has found use in a large number of electrostaticapplications and one of their important properties is the inception voltage which can beeasily and accurately measured. The empirical Peek's law which yields the corona inceptionfield is previously made in standard air for wire-to-cylinder geometry and used for manyyears. However, the generalisation of this law, which at present derives from Hartmann'sphysical-mathematical model, requires new measurements with varying air physical parameters.This classical law expresses the inception field at the anode surface in function of theanode diameter, the related air density and the humidity. New measurement method ofthepositive DC corona-current voltage characteristics have been introduced in a wire-to-cylinderand wire-to-plane systems. Remarkable similarities between these basically different systemsare shown in this paper and the steady corona-current voltage characteristics are describedby the Townsend's square law in a large range of related air density. The normalizationfactor at air density equals unity and the humidity function suggested by the model are also determined from the measurements. The model values of the inception field at the wire surfaceagree with measured values in both wire-to-cylinder and wire-to-plane systems.

We study two-phase flow in a tall vertical slot differently heated from the side walls, where one of the phase is fluid and another phase consists of small solid particles. The particles are subjected to downward drag exerted by the gravity and the drag exerted by finite-frequency horizontal vibrations along the layer. In the framework of the generalized Boussinesq approximations we derive non-contradictive set of governing equations describing the dynamics of suspension. The pulsed base flow is obtained and its linear stability is analysed. The comparison of the numerical results with the recent experimental findings is given.

The lifetime of minority carriers in crystalline silicon wafers is determined by means of the contactless microwave phase-shift technique, when the surfaces of the samples are passivated using an iodine aqueous solution of polyvidone. The stability of the passivation is sufficient in order to obtain a lifetime scan map with spatial resolution of 50 µm, using a thin coaxial cable which directs 9.4 GHz microwaves onto the investigated samples and a fiber coupled laser diode which generates carriers in excess. In gold contaminated single crystals an acceptable correlation is found between the lifetime scan maps and the local concentrations of gold determined by deep level transient spectroscopy applied to an array of aluminium silicon diodes. For multicrystalline silicon wafers containing large densities of different extended crystallographic defects, a good correlation is obtained between the lifetime maps and the diffusion length maps obtained by the light beam induced current technique. Both the maps display the same features of extended crystallographic defects and are in agreement with optical micrographs of the scanned samples after they have been chemically etched.