p-type (100) faceted diamond films can be successfully grown by bubbling H2 through liquid B(OCH3)3 during the Microwave Plasma Enhanced Chemical Vapour Deposition (MPCVD). Ramann spectra and scanning electron micrographs (SEM) convincingly illustrate that diamond-film growth on silicon substrates by a three-step process yields good uniformity with preferential orientation. The field emission current density of the boron doped diamond films can be enhanced from 0.7 μA/cm2 for the as grown films to 140 μA/cm2 at an applied field of 20 V/μm by hydrogenation treatment.

A large number of lead-free BaTiO3-based ceramics were prepared. Depending on the composition, some of them exhibit a relaxor behaviour whose characteristics were related to the type of ionic substitution and to the substitution rate. The relaxor effect is all the more favoured as the composition deviates more from BaTiO3 and as the substitution is heterovalent in the 6-coordination number crystallographic site. Some of these materials could prove valuable (dielectrics for capacitors and actuators) because they are environment-friendly.

A comparative nonlinear characterization is carried out between the nonlinear behavior of a composite and the piezoceramic used to obtain it. This study is necessary for using the composite in power transducer applications, as in the Non Destructive Testing (NDT) by ultrasonic waves at high frequencies (300 kHz−800 kHz). Measurements of the losses and the resonator stiffness variations have also been done. Both these effects, as well as the possibility of the frequency hysteresis, show different behavior in the composites, since the increases in the ceramics are different from those in the composites. In this study two measure methods are used; principally the motional impedance increase with the motional current measurements. The results obtained are normalized in order to make them independent of the resonator size, and thus make the comparison between the composite and the ceramic easier. The figure of the mechanical loss tangent tg $\delta_{\rm m}$versus the mean strain $\langle S \rangle $ shows that the losses can be greater in the ceramic than in the composite for soft ceramics. The dependence behavior of the losses versus the mean strain shows that hard composite transducers have lower losses and higher strains than the soft ones. However, these losses in hard composites are higher than those in the bulk ceramic transducers.

This paper proposes a generalised inverse learning structure to control the LCL converter. A feedforward neural network is trained to act as an inverse model of the LCL converter then both are cascaded such that the composed system results in an identity mapping between desired response and the LCL output voltage. Using the large signal model, we analyse the transient output response of the controlled LCL converter in the case of large variation of the load. The simulation results show the efficiency of using neural networks to regulate the LCL converter.

We propose to model the spectral response of p-n junction photodetectors based on gallium nitride and related AlGaN alloys. The model is based on the resolution of the differential equations that govern the excess carrier variation in each layer of the photodiode taking into account all the physical parameters, in particular the presence of deep trap levels in the forbidden gap. We notice that the theoretical results are in good agreement with the experiments. We have also analysed the effect of the recombination velocity at the illuminated surface, as well as the impact of the thickness and the doping density of the p-type layer (illuminated zone) on the spectral response magnitude.

Back-diffusion of electrons to cathode is studied by Monte Carlo simulation for realistic argon cross sections. In particular we study the influence of different aspects of back-diffusion modeling with an aim to simplify the models used in modeling of plasma displays, low pressure gas breakdown and detectors of high energy particles. It was found that the initial electron energy distribution is one of the critical parameters and affects the calculated escape factors very much. The same is true for reflection while angular distribution of initial electrons has a very small influence on the escape factors. The model of cross sections combined with the selection of realistic initial conditions was shown to represent the back-diffusion in argon very well giving good agreement with the available experimental data. Most importantly it was found that the range of electrons returning to the cathode exceeds by far a mean free path and that the number of collisions that they make before returning is quite large. Thus it was found that for a relatively high pressure of around 10 torr the range exceeds d= 1 cm (at E/N=12 Td, 1 Td=$10^{-21} {\rm V}{\rm m}^{2})$ and therefore application of the escape ratios below that value of p d (where p is the pressure) is questionable, i.e. under those conditions calculations should be performed for the actual geometry.

The aim of this work is to study a reactor submitted to a gaseous flow, using gliding discharges along several divergent electrodes supplied by an AC high voltage power supply. This reactor was used for the treatment of gaseous pollutants (such as hydrogen sulfide H2S) generally contained in industrial effluents. A systematic survey of the sulfide hydrogen destruction yield was undertaken according to several variables (H2S initial concentration, hygrometry, gas flow rate, electric power, shape of the electrodes...). We have pointed out also the importance of the residence time of pollutants in the reactor. The best conditions for treatment were defined for the available power supply. A minimum energy density in the 0.1−0.18 kWh/m3 range and a destruction yield > 95% were obtained for a 100 ppmv H2S initial concentration. Finally, we started a discussion about the formulation of the reactional mechanisms leading to the H2S removal and about the energy distribution inside the reactor.

We have measured the basic characteristics of low current diffuse discharges in argon for low pressures. The data for the voltage current characteristics and negative differential resistance were obtained together with the data for the frequency and for the damping coefficient of the induced oscillations. These data were compared with the predictions of a simple analytic model of Phelps, Petrović and Jelenković [A.V. Phelps, Z.Lj. Petrović and B.M. Jelenković, Phys. Rev. E 47, 2825 (1993)] and it was found that, while most observables may be represented correctly, there is a systematic discrepancy between the predictions for frequency of induced oscillations based on the data for transport coefficients from the literature and measurements. The basic idea of the present work is thus to check the fundamental assumptions of the theory and to extend the application of the experiment to study the transition to constrictions in order to initiate modifications of the theory to cover the transition to the constricted regime. Very good agreement was found between the spatial profiles of the electric field calculated from the model and the data obtained from the spatial profiles of emission and these data may be extended to follow the transition to the constricted regime and the development of the cathode sheath.

The formation and the behavior of particulates have been studied in a pure methane rf plasma (13.56 MHz) for pressures in the range 20−150 Pa. The generated particulates are evidenced using laser light scattering. They are mainly observed at the sheath boundaries where they are suspended in well defined traps. Particulate appearance times at the upper sheath boundary have been determined using the 90° scattered light intensity at 514.5 nm. The appearance time of particulates is sensitive to the working pressure: the higher the pressure, the shorter the appearance time. In our experimental conditions, no particulates are observed in the cloud near the biased electrode for pressures lower than 30 Pa. The negatively charged particulates induce changes in the electrical characteristics of the discharge. The generation and the behavior of particulates are correlated with the time evolutions of the laser beam extinction and of the absolute value of the dc self bias voltage during an experiment.