Complex scattering amplitude functions of a small metamaterial spheroid are derived. The Mueller matrix solution for polarimetric bistatic scattering from a layer of random metamaterial small spheroids is then constructed. Bistatic scattering of metamaterial and dielectric spheroids are numerically calculated. Linearly co-polarized backscattering coefficients $\sigma _{hh} $ , $\sigma _{vv} $ and $\sigma _{hh} -\sigma _{vv} $ are presented to show the dependence upon frequency. The co-polarized and cross-polarized backscattering coefficients and polarizability degree of a layer of non-uniformly oriented metamaterial spheroids under illumination of an elliptic polarized plane wave are numerically simulated. Effects of metamaterial parameters on scattering pattern and scattering mechanism are interpreted. Numerical results indicate that the bistatic scattering of metamaterial particles is enhanced largely and demonstrates asymmetric directivity. Meanwhile, polarized difference of $\sigma _{hh} -\sigma _{vv} $ strongly varies with frequency due to constitutive dispersion of $\varepsilon (\omega )$ and $\mu (\omega )$ .

In this work, we simulate and optimize the photocurrent densities in a model of an n-p-n-p type thin film multilayer silicon solar cell for space applications. The incident light penetrates the cell perpendicularly to the junctions. The electrodes tailored inside the structure connect the n-layers together and the p-layers together. The equations giving the photocurrent density produced in each abscissa of the structure was developed. We used Matlab software to simulate and optimize the different parameters of the model. The results of simulation show that the optimized n-p-n-p silicon multilayer solar cell could deliver a photocurrent density of more than 46 mA/cm2 under Air Mass 0 (AM0) solar spectrum (solar constant of 1.36 KW/cm2) and that the photocurrent density produced by the n-p-n-p multilayer silicon solar cell is at least 10% higher than the photocurrent density produced by the simple n-p junction solar cell. We also show that the most important components of the total photocurrent densities (94%) is due to the minority carrier collection which happens on both side of the three space charge regions tailored inside the cell.

W-Cu-W sandwich coatings are prepared by d.c. magnetron sputtering and the film density is evaluated by RBS and scanning electron spectroscopy measurements. In order to improve the film density up to the bulk density and obtain a dense metallic coating, it is necessary and effective to optimize the deposition parameters, such as, increasing target power and decreasing Ar working pressure. The reduction of the film density from its bulk density is induced by microstructure change and incorporated impurity gas, such as oxygen and argon. When film density is increased, oxygen contamination, due to wall desorption or sample storage in air, decreases.

Amorphous thin films of Se $_{80-x}$ Te20Pbx (0 < x < 2) have been prepared by thermal evaporation. The effect of 40 MeV 28Si5+ ion irradiation on the electronic conduction of Se $_{80-x}$ Te20Pbx (0 < x < 2) thin films has been investigated. The DC electrical conductivity of the films increases by two to three order of magnitude with increase in irradiation fluence from 1012 to 5×1013 ions/cm2. The DC activation energy of conduction also increases with increase in irradiation fluence. Results have been explained on the basis of structural disorders and defects formed due to heavy ion irradiation.

The microstructure and morphology evolution in nanocrystalline PbSe films chemically deposited on GaAs(100) and GaAs(111) substrates were compared to PbSe films on Si(100) under the same conditions. On GaAs substrates, dense and continuous PbSe films were obtained. We show that the temperature dependent morphological changes on GaAs substrates occurred as a result of increased sample thickness due to higher reaction rates. Notably, the deposition of PbSe on Si(100) did not lead to continuous films and no preferred orientation was observed. The improved wetting between PbSe and GaAs appears to be a key factor responsible for the differences observed on the two substrates.

The intracavity photon density is assumed to be Gaussian spatial distributions and the nonlinear loss that is due to second-harmonic generation (SHG) to the photon-density equation is given under Gaussian spatial distributions in the rate equations for a diode-pumped passively Q-switched intracavity-frequency-doubling Nd:GdVO4/KTP laser with Cr4+:YAG saturable absorber. These space-dependent rate equations are solved numerically. The dependences of pulse width, pulse repetition rate, single-pulse energy and peak power on incident pump power are obtained for the generated-green-laser pulses. In the experiment, a diode-pumped passively Q-switched intracavity-frequency-doubling Nd:GdVO4/KTP laser with Cr4+:YAG saturable absorber is realized and the experimental results are consistent with the numerical solutions.

Using an Atomic Force Microscope (AFM) operated in contact mode under ambient conditions, we have tried to resolve atomically sharp cracks perpendicular to the basal plane of muscovite mica. However, although tip radius of probes of less than 10 nm allowed a lateral resolution of 0.7 nm and the tip-sample adhesive force has been minimized, our experimental results demonstrate that the molecular structure of crack tips can't still be resolved. Even worse, sometimes the tip-sample friction can disrupt the region around the crack tip. This thus leads to the conclusion that one will fail to resolve atomically sharp cracks under ambient conditions by contact AFM. The inability is due to low lateral resolution of contact AFM and strong tip-sample interaction force under ambient conditions. New techniques of scanning samples in liquids and UHV non-contact AFM both of which have true atomic resolution are strongly recommended for future studies.

In this paper, we present a numerical simulation of three metal cathode (silver, copper and nickel) submitted to a constant flux power flux density ranging between $1\times 10^{11}$ and $5\times 10^{12}~\rm W\,m^{-2}$ . The goal is to compare the interface evolution (vaporization and liquefaction rate, appearance time of liquid and vapour, energetic repartition) to predict the behaviour of the cathodes during an electric arc.

This paper presents a simple and general direct modulation strategy that enables to copy directly modulated waveforms onto output voltages of a multilevel three-phase Diode Clamped Inverter (DCI). A general modelling of this converter is presented. A space vector scheme is developed without using Park transforms. Based on this algorithm, the location of the reference voltage vector is determined and the voltage vectors for the modulation are deduced. Simultaneously, their durations are calculated. The proposed algorithm is general and can be directly applied to a (n+1) levels inverter independently on its topology (Diode Clamped Inverter, Neutral Point Clamped, Flying Capacitor Inverter...). To verify this algorithm, both control algorithms of a 5-level DCI and a 11-level DCI are considered and simulation results are given.

We present a first theoretical evaluation of a new optical technique for diffraction grating metrology. While well-known spectroscopic ellipsometry (SE) is based on classical ellipsometric spectra taken in the usual planar diffraction geometry, we propose to use spectrally resolved full Mueller matrices of the gratings measured in the most general geometry of conical diffraction. We simulate the case of two superimposed one-dimensional (1D) gratings with an overlay defect, i.e. a relative shift of the two gratings with respect to each other. We show that the proposed new technique is sensitive to both the magnitude and sign of the shift, and thus it should be more efficient than usual SE for overlay characterization in real cases.

Characterization of optical gratings by resolution of inverse scattering problem has become a widely used tool. Indeed, it is known as a non-destructive, rapid and non-invasive method in opposition with microscopic characterizations. Use of a neural model is generally implemented and has shown better results by comparison with other regression methods. The neural network learns the relationship between the optical signature and the corresponding profile shape. The performance of such a non-linear regression method is usually estimated by the root mean square error calculated on a data set not involved in the training process. However, this error estimation is not very significant and tends to flatten the error in the different areas of variable space. We introduce, in this paper, the calculation of local error for each geometrical parameter representing the profile shape. For this purpose a second neural network is implemented to learn the variance of results obtained by the first one. A comparison with the root mean square error confirms a gain of local precision. Finally, the method is applied in the optical characterization of a semi-conductor grating with a 1 $\mu $ m period.