Design of integrated power systems requires prototype-less approaches. Accurate simulations are necessary for analysis and verification purposes. Simulation relies on component models and associated parameters.This paper focuses on an implementation of a physic-based analytical PIN diode model [Power Electron. 8, 342 (1993)] with the very high description language VHDL-AMS [IEEE Computer Society, IEEE Draft Standard VHDL-AMS Language Reference Manual, 1997]. The Lumped Charge (LC) concept of Linvill is employed. The state-of-art of parameter extraction methods is briefly recalled and a step-by-step extraction procedure for the model parameters is described. Due to poor agreement between simulation results and experimental data, an improvement is added to the model. Finally, our improved model is validated with a confrontation of the simulated and the experimental curves for both current and voltage at different range of the operating conditions. All this operation was made under the Free version of the “SIMPLORER©-SV 7.0” environment.

Effect of Pb substitution on the amorphous-crystalline transformationtemperature, optical band gap and crystalline structure of Ge2Sb2Te5 has been studied. In Pb:GeSbTe chalcogenide films prepared by thermal evaporation, an amorphous to crystallization transition is observed at 124, 129, 136 and 138 °C in Pb0Ge20Sb24Te56, Pb1.6Ge19Sb26Te54, Pb3Ge17Sb28Te53 and Pb5Ge12Sb28Te55 respectively. XRD investigations of annealed samples reveal that Pb substitution retains NaCl type crystalline structure of GST but expands the lattice due to large atomic radii. The increase in amorphous-crystalline transformation temperature is followed with the increase in phase segregation. The optical gap shows marginal variations with composition.

Light effect on electrical properties of a pentacene-based transistor was studied. We showed that under optical excitation, the phenomenon of photoconductivity can modify both carrier density and mobility; these changes depend on the wavelength, on the carrier photogeneration rate and on the material absorption coefficient. At first, we examined structural, optical and electrical properties of pentacene films; a thickness of 50 nm is the good compromise to obtain optimal performances. Then we observed the effect of illumination on the drain current in the accumulation regime: at 365 nm, we obtained a maximum ratio of photocurrent to dark current (I dsillumination /I dsdark ) of about 2 × 103 when the gate is turned off, mobility and threshold voltage values around 0.02 cm2 V−1 s−1 and 7.5 V respectively. Moreover the dynamics study (off-state) showed sufficiently fast response times with large current gains to envisage applications in the area of light activated memory components. Finally, we examined the performances of a new component based on the coupling of an organic light emitting diode (with an emission peak at 550 nm) as an input unit with an organic transistor as an output unit. This last study enabled to underscore an increase in mobility without modifying the carrier density for low carrier photogeneration rates.

This study reports highly efficient green multilayer polymer light-emitting diodes (PLEDs). The fluorescent polymer is poly[(9,9-dioctyl-2,7-divinylene-fluorenylene)-alt-co-{2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene}] end capped with dimethylphenyl (ADS108GE). This emissive polymer has been found to behave as an electron transport emitter. A poly(N-vinylcarbazole) (PVK) layer has been introduced as both hole transporting layer/electron blocking layer. Thicknesses of both ADS108GE and PVK layers have been optimized. 3.1 lm/W have been achieved which corresponds to an improvement by a factor 2 comparing to devices without PVK. Luminances as high as 25 000 Cd/m2 at low operating voltage are reported.

Structural and optical properties of thermally evaporated methylene blue trihydrate thin films up to a film thickness of 165 nm have been investigated. The lattice constants and the crystallite size were calculated. The optical parameters were obtained using spectrophotometric measurements of the transmittance and reflectance at normal incidence of light in the wavelengths range 200–2500 nm. Below the absorption edge, subgap absorption in the energy range 0.75–1.4 eV was observed and interpreted in terms of defect states induced absorption phenomena and act as deep traps for charge carriers. The type of optical transition was found to be an indirect allowed transition. The values of the optical gap E opt , the transport gap E t , the exciton binding energy E B , the Urbach's energy E u and the dispersion parameters for as-deposited, annealed and irradiated films with different doses of γ-irradiation were estimated and discussed their influenced by heat treatment and irradiation.

In this paper, the effect of temperature of operation on the turn-on time delay, t d , of semiconductor laser has been re-studied theoretically. We derived a full analytical and exact expression to determine t d in terms of nonradiative, radiative, Auger recombination coefficients, cavity dimensions, threshold carrier density (and in turn threshold current density), injected current and temperature of operation. The temperature dependence (TD) of t d was calculated through the TD of threshold carrier density. The TD of threshold carrier density was calculated according to the TD of cavity parameters and not by the well-known exponential Pankove relation via the use of characteristics temperature and current. A complete agreement between the values of t d calculated by our proposed model and the numerical method, was shown through the simulation results.

The behavior of a coil with ferrite core applied with an ac current and under a magnetic field has been investigated. The field-induced changes of both inductance and impedance have been observed. Based on this, a device for electric current monitoring with the coil has been developed. The result has shown that such a device is very sensitive and high efficiency, and convenient to use in the field of power transmission and management.

This paper presents a set of shape parameters giving an estimation of features for 3D objects, in particular bounded surfaces such as molecular island of self-assembled carbon chains on silicon, in order to classify them. These features are quantified both in 2D and 3D and concern an evaluation of the circularity degree or the fractal degree of the object boundary in 2D and a study of peak dispersion and height variations in 3D. The originality of this approach mainly lies in the way of estimating the isotropic and fractal degrees from the boundary of the surface and in the combination of different data, such as height or distance to the edges, for peak characterization. An application to small molecular islands of carbon, studied in nano-elec-tronics, is also presented, in order to illustrate the purpose and the efficiency of the previous shape parameters. This application also includes a new method of adaptive filtering, processed from distance maps.

Single crystals of semi – organic nonlinear optical (NLO) Tris thiourea zinc cadmium sulphate (TTZCS) have been successfully grown from pH 3.5 solutions by slow cooling method. The thermal behaviour of the TTZCS crystal has been investigated from Thermo gravimetric, differential thermal and differential scanning calorimetric analysis. The micro hardness studies reveal the changes in the mechanical property of the crystals grown at pH 3.5. From Raman spectroscopic analysis, different modes of vibration due to various functional groups present in TTZCS have been observed. The morphologies of the crystals were analysed by Scanning electron microscope (SEM).

PbSe films were chemically deposited with a range of controlled microstructures, from nanocrystalline to monocrystalline films. The crystal size in the nanocrystalline films was controlled in a range 7 to 25 nm with a fairly narrow size distribution, which allowed fine-tuning of the PbSe energy gap. The optical properties of the films were investigated using infrared (IR) transmission and IR photoluminescence measurements. The nanocrystalline PbSe films showed single bandgap values in the technologically important near-IR region. Two bandgap values, corresponding to both bulk and confined nanocrystals, were obtained for films with mixed microstructure. Strong blue shifts in both the absorption and emission peaks of the nanocrystalline layers were obtained. The bandgaps of the PbSe films were found to be in good agreement with theoretical calculations. The results point out the potential of these films for nanoscale optical device applications operating in the near-IR range.

Intermittent operation mode is specific to electrostatic precipitators (ESP) used in workshops where the polluting product is produced in a discontinuous way. The rapping system is necessary in order to ensure a continuous and effective operation of a dry electrostatic precipitator, but causes at the same time, a problem of re-entrainment of dust and thus the degradation of filtration efficiency. The objective of this paper is to propose a procedure based on the methodology of experimental designs (Tagushi's Methodology) aiming at optimizing the rapping process; it consists to determine optimal values of rapping, i.e. the moment, the position and the force of rapping. Several “one-factor-at-a-time" experimental designs followed by a Full Factorial design, made it possible to model the process and to analyze interactions between the factors. The experiments were carried out on a laboratory experimental device which simulates an industrial precipitator with intermittent operation.

We measured in function of helium, argon, and oxygen gas pressure, the evolution of the intensities of the fluorescence spectra of YO molecule issuing from a liquid drop of yttrium oxide melted at the focus of a solar furnace. From this evolution and in a simplified approach assuming the independency of the three molecular systems of YO (A2 Π 1/2-X2 Σ +, A2 Π 3/2-X2 Σ +, B2 Σ +-X2 Σ +) we deduced, through the analysis of Stern-Volmer plots, a mean quenching rate coefficients of this molecule in these states by the above mentioned gases.