Highly (111)- and (001)-oriented rhomboedral PZT thin films have been grown at 500 °C onplatinized silicon substrates by in situ RF magnetron sputtering. Crystallization of the perovskitephase was possible provided that a thin TiOx buffer layer was deposited prior to the PZT. Control ofPZT films orientation is demonstrated by changing the $\rm O_2/(Ar+O_2)$ ratio in the plasma gasduring the TiOx sputtering and its consequences on electrical properties of the ferroelectric samplesare presented. The structural properties of the TiOx buffer layer were studied by means oftransmission electronic microscopy in order to understand the relation between the TiOx seeding andthe orientation control of the PZT film.

Following the total yield approach (used to predict the sign of charging of electron irradiated insulators) a positive charging is expected when the primary beam energy Ep is situated in the energy range where the number of outgoing electrons, $(\delta + \eta) I_0$, is larger than the number of incoming electrons, I0. But a negative charging is often experimentally observed when a positive charging is predicted. The present paper is an attempt to elucidate this experimental fact. The arguments being developed are based on the use of a dynamic double layer model (+ for the secondary electron mission, SEE; − for the incident electron implantation) which explains a negative charging via the influence of an evolving S-shape potential function, V(z), which induces a partial freezing of the nominal (uncharged) SEE, δ°, combined to a progressive compression of the negative space charge below the surface. The observed large difference in the measurements of the yield by using pulse excitation methods, or by permanent irradiation methods, δ° or δ is then explained. Furthermore, the influence of an oblique incidence is also deduced.

Magnetic properties of nanocrystalline FeZrB-(Cu)-(Nb) compared to FeSiBCuNb are reported. Observations of domain patterns by magneto-optical Kerr effect (MOKE) method presented herein highlight qualitatively the incidence of stress-annealing on the induced anisotropy in soft magnetic materials. Transverse fine domains found in FeSiBCuNb alloys are consistent to a magneto-elastic interpretation of the stress-induced anisotropy. Nevertheless, it is not the case for FeZrB-(Cu)-(Nb) family where we observe a pronounced longitudinal induced anisotropy. According to the so-called “back stress effect” advanced by Herzer, the negative $\lambda_{\rm s}$ of bcc α-Fe grains, as well of bcc α-FeSi grains, should yield transverse anisotropy. Nowadays, this surprising feature is not still clear. For a technical standpoint, stress-induced anisotropy is interesting for new magnetic components in power electronics.

Light emission excited by scanning tunnelling microscopy (STM) has been observed on multiwall carbon nanotubes. The photon yield depends on the scanned tube but it is constant all along the tube. Simultaneous photon spectroscopy evidences emitted wavelengths in the 600−1000 nm range in good agreement with previous field emission data. Emission characteristics are independent of substrate and of STM tip. We discuss how these new results are consistent with radiative transitions involving localized states in carbon nanotubes.

In this paper, we give nonlinearobservers for the estimation of the rotor flux and the loadtorque in an induction motor. The observers are designed onthe basis of the standard α − β Park's model. Theperformance of these observers are shown via experimentalmeasurements.

The aim of this paper is to explain the intrinsic fail-safe capability of a high-voltage IGBT inverter source. The inverter is an imbricated cells structure which provides redundancy. The major failures can be either a wrong gate voltage (malfunctioning of the driver board, auxiliary power supply failure, dv/dt disturbance) or an intrinsic IGBT failure (over-voltage/avalanche stress, temperature overshoot). The IGBT failures are studied and show that no opening of the bondings can appear and consequently no risk of explosion. Owing to the imbricated cells structure, an IGBT failure can be withstand a few switching periods, with nevertheless non-optimized output waveforms. The design and the lab-test of a sensor able to perform monitoring and failure diagnosis are also presented. This real-time diagnosis allows either a safety stop or a remedial control strategy based on the reconfiguration of the control signals. The real-time reconfiguration allows to decrease internal stresses and to optimize the shape of the output voltage. In this case, a fail-safe operating may be gained for high power applications.

The confinement properties of a low beta argon discharge plasma in a spindle cusp magnetic field was investigated. Plasma was produced by ionisation collisions by the electrons which were produced by thermionic emission of electrons. The central problem involved with plasma confinement by a cusped magnetic field is the loss of particles along the flux lines. Electron and ion leak widths were studied in the ring and point cusps and measured over a range of magnetic field strengths (B), neutral pressures (P) and discharge currents (Id). It was found that the leak width was reduced with increase in Id and B. The ion leak widths were found to be larger than the electron leak widths. The normalised effect of magnetic field and pressure on ion and electron leak widths in cusps are reported, compared and discussed. The dependence of electron and ion leak widths on plasma densities were also studied. At very low pressures, high plasma densities and high magnetic field strengths, a quasineutrality condition was attained.

Investigation of the high voltage vacuum discharge characteristics − current derivative (di/dt), current, voltage, and soft as well as hard X-rays − versus time has been carried out. Recorded traces indicate pinching of the interelectrode discharge column two or three times during which the voltage increases to values as high as the initial voltage or even higher. X-ray radiation of high penetration power is emitted during these events. In addition, sausage instabilities have been observed during the pinch giving rise to extreme penetrating X-rays caused partly by the pinch voltage and partly by the sausage voltage. Visible electrode studies show the fact that the discharge is restricted to a narrow column. Finally, a theoretical treatment of the discharge mechanism that seems to be in good agreement with the experimental result is also presented.

This work describes a glow discharge lamp of the Grimm type. The lamp proved to be stable for periods up to about 2 hours. The intensity to background ratio of the Cu I 237.4 nm line from a brass target was found to be 200. Analysis of the experimental results showed that the discharge potential depends on the discharge current through a power law $(V=Ki^S)$. K and S are also power functions of the pressure P. Intensity was measured as a function of the lamp operating parameters (V, i, and P). Self-absorption was shown to be insignificant. The sputtering rate Q was found to vary with the lamp power W=Vi, Q=C Wm where C and m are constants.

An instrumentation system for measuring wide frequency band complex permittivity of a sample submitted to a microwave irradiation has been optimized in order to allow macroscopic temperature measurements. The reaction of saponification of aromatic esters is studied using this instrumentation. We take interest in the behavior of the ionic conductivity phenomenon occurring in the reactive medium during microwave heating, and we compare it with the results obtained under classical heating. We show that the activation energy associated with ionic conductivity is lower when the reaction is performed under microwaves than when it is performed under classical heating. We thus deduce that microwaves act on the reaction advancement as a catalyst, and thus makes the reaction easier.