Electrical conductivity was performed on amorphous thin films of Ge1–x Se2Pbx (with x = 0, 0.2, 0.4, 0.6 and 0.8) as a function of temperature in the range 300–450 K. The experimental results indicate that the conduction is through thermally activated process having two conduction mechanisms. In the first region at high-temperatures range, the values of $\sigma _{o}$ suggest that the dominant conduction of charge carriers changes from the extended states to the localized states in the band tails at composition x = 0.8. The experimental results have also been analyzed using Meyer-Neldel Rule. The other one appears in the low temperatures region and the conductivity has been analyzed using Mott's variable range hopping conduction. Mott's parameters were calculated for Ge1–x Se2Pbx films.

We have reported a study of the I–V characteristics of Ni/n-GaAs Schottky barrier diodes (SBDs) in a wide temperature range of 60–320 K by a step of 20 K, which are prepared by magnetron DC sputtering. The experimental I–V data of the device quite well obey the thermionic emission model at 300 and 320 K, respectively. The ideality factor and barrier height values have changed by change of the sample temperature, the case has been attributed to the presence of the lateral inhomogeneities of the barrier height. The barrier inhomogeneity has been explained by the Gaussian distribution models of barrier heights suggested by some authors, Y.-L. Jiang et al. [Chin. Phys. Lett. 19, 553 (2002)]; Y.-L.Jiang et al. [J. Appl. Phys. 93, 866 (2003)], and S. Chand, J. Kumar [Appl. Phys. A 65, 497 (1997)]. It has been seen that the SBH inhomogeneity of our Ni/n-GaAs SBD can be well described by Gaussian distribution model suggested by Y.-L. Jiang et al. [Chin. Phys. Lett. 19, 553 (2002)]; Y.-L. Jiang et al. [J. Appl. Phys.93, 866 (2003)] over whole measurement temperature range. Moreover, the modified ln( $I_{0}/T ^{2}$ ) versus $1/k(T+T_0^\ast)$ plot is obtained using a method developed for T 0 anomaly in the literature. Richardson constant value of 3.37 A cm-2 K-2 for n-type GaAs was obtained from the modified Richardson plot.

In this work, we present experimental evidence and analytical studies of dark current noise spectral density in CdTe detectors for a low and mid frequency range. The measured noise level in CdTe detectors indicates shot noise suppression at 10 KHz; this suppression can occur in CdTe detectors when the diffusion time is greater than the transit time between electrodes. Moreover we show thermal noise is negligible in CdTe resistors, taking into account their high resistance: R # 150 G ${\rm \Omega} $ .

We investigate theoretically a mode of heating layers using a laser beam. In this mode thermal energy, the temperature of the layer, propagates in a steady-state self sustained fashion from the bottom of the layer towards the surface and may exhibit a very steep front. The propagation exhibits a constant speed, related to the intensity of the power flux. To achieve this heating mode the absorption coefficient has to remain low in low temperatures and increase rapidly as a function of temperature in higher temperatures. Additionally, a significant temperature increase must be generated to trigger this propagation mode, for example through the presence of a strongly absorbing layer beneath the transparent layer. The mode is well suited to semiconductors, especially silicon. A few examples of applications are proposed.

The aim of this work is to compare several methods for the determination of very thin films Young's modulus and stress state: the nanoindentation test, the bulge test and the point-deflection method. The tested structures were silicon nitride and silicon nitride/silicon oxide bilayer membranes with different shapes (square or rectangular) and dimensions (from 1 mm to 3 mm). We report new experimental results on submicron thick dielectric membranes with thicknesses down to 100 nm. A Young's modulus of 217 ± 14 GPa have been found for silicon nitride membranes with a residual stress of 411 ± 30 MPa using the bulge test. Using nanoindentation experiments, a Young's modulus higher than 190 GPa has been estimated. The bulge test is still valid for the studied high dimension to thickness ratio membranes and more appropriate to determine the Young's modulus. A mixture law was shown to be possibly applied for Si3N4/SiO2 bilayer membranes for the Young's modulus and stress determination. The point deflection method is limited by the very low stiffness of these structures and only the residual stress can be accurately extracted. As the Young's modulus and membrane geometry have no significant influence on the stress determination by means of the point deflection method for the studied membranes (with a high lateral dimension to thickness ratio), more reliable results have been obtained such as 487 ± 40 MPa using an AFM cantilever for load-deflection experiments, for Si3N4 thin films.

Spectroscopic ellipsometry in the mid infrared spectral range, Raman scattering and TEM measurements on (100) oriented p + and n +-type porous silicon (PS) samples were carried out. Porosities of 68% and 48% for p + and n + wafers, respectively, and thicknesses of 27.6 $\mu $ m and 14 $\mu $ m with the same extinction coefficient k = 0.1 were determined from spectroscopic ellipsometry. Raman scattering measurements show that the resultant surface morphology of the PS layers consists of irregular and randomly distributed nanocrystalline Si structures. Using the phonon confinement model, the diameters of Si nanocrystallites have been estimated as 8 and 3 nm for p + PS type and 12 and 5 nm for n + PS type. Transmission electron microscopy shows clearly defined pores with sizes ranging from 15 to 35 nm, inhomogeneously distributed along the PS surface. We demonstrate that the filling of the PS pores by organic material (Rhodamine 6G) brings about important enhancement on photoluminescence intensity.

A simple chemical route has been deployed to synthesis highly monodispersed and controllable ZnS and CdS nanoparticles (quantum dots) doped with Mn. XRD investigations shows the cubic structure of both ZnS and CdS nanoparticles and doping has no effect on the structure. The size measurement gives an approximate size of 1.5 nm and 2.5 nm for ZnS:Mn and CdS:Mn quantum dots respectively by Deby-Shreer. UV-Visible is used to study the Optical absorption of ZnS and CdS pure as well as doped nanoparticles. Furthermore as the chemical parameters change, the size of quantum dots change systemically. Of course although doping percentage is a significant parameter in photoluminescence properties of quantum dots, but it has no effect on the size. Photoluminescence spectra obtained at 6% molar of the Mn dopant in CdS:Mn (Ex = 315, Em = 495 nm) and ZnS:Mn (Ex = 285, Em = 572 nm). Microscopic images (SEM, TEM) show the 1–3 nm size for ZnS and CdS nanoparticles.

The effect of β-irradiation on silicate and aluminoborosilicate glasses doped with transition metals (TM) and rare earth (RE) elements has been studied using Electron Paramagnetic Resonance (EPR), Raman and luminescence spectroscopy. Irradiation leads to the reduction of both Cr and Mn ions in both types of glass matrix. It is shown that even small amounts of TM dopants completely block defect production, as occurs under irradiation in non-doped glasses. As well, TM doping results in the disappearance of structural changes in the glass (densification, polymerization increase and Na migration) for doses of ~ 109 Gy. Unlike TM-doped matrices, incorporation of RE ions into aluminoborosilicate glass blocks neither defect production nor structural changes in glass matrices during irradiation. Simultaneously, we observe a reduction of RE ions, most clearly demonstrated for Ce4+ ions in aluminoborosilicate glasses. We propose that the relative stability of the different charge states of the RE ions is linked to the efficiency of the reduction process, and therefore to the evolution of the glass structure during irradiation.

A binary Sn-5wt.%Sb solder alloy was chosen as a potential alternative to Sn-Pb solder alloy to be subjected to many studies. It was casted from the liquid state, cold drawn into wires of 1 mm diameters. The study includes the structure, electrical resistivity, tensile strength, hardness and indentation creep behavior using XRD, four probes electrical circuit, conventional tensile testing machine, Vickers microhardness tester, respectively. These properties were carried out for the cold worked alloy and after annealing at 393 and 473 K for 60 min. It was found that annealed samples exhibit more precipitations of the intermetallic compounds SnSb, higher lattice parameters and higher crystallite size, while have lower lattice-strain induced due to the cold working process. These structural changes greatly affect the electrical resistivity and mechanical properties of this alloy.

PET (Poly ethylene terephthalate) fabric was treated using dielectric barrier discharge (DBD) as a type of low temperature plasma under atmospheric pressure for 1 to 15 min and different powers ranging between 0.3 to 5 W. Effects of DBD treatment on the surface of a test PET fabric are examined, reported and discussed. The surface analysis and characterization were performed using X-ray diffraction (XRD), Fourier transition infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) before and following the DBD processing. SEM analysis shows significant surface morphology changes in plasma treated polyester fabric surface, while FTIR analysis indicates that the reactivity of the surface was increased. The discharge parameters used are correlated with the changes in the surface characteristics found after DBD processing of various durations, in atmospheric air environment.

Optical Emission Spectroscopy (OES) is used to investigate the effect of argon gas mixing on the electron temperature, the degree of nitrogen dissociation and the active species concentration in a 13.56 MHz radio frequency (RF) sustained nitrogen plasma. The electron temperature is determined from Ar-I emission line intensities by using the modified Boltzmann's plot method and is found to be increased with argon mixing in nitrogen plasma. The concentration of active species $\rm N_2(C ^3\Pi_{\it u})$ and $\rm N_2^+ (B ^2\Sigma_{\it u}^+)$ is monitored in terms of the emission intensities of nitrogen (0–0) bands of the second positive and the first negative systems respectively. The concentration of $\rm N_2 (C^3\Pi_{\it u})$ active species along with the degree of N2-dissociation is appreciably enhanced by argon mixing signifying the role of argon metastables in the excitation and dissociation processes.

In this paper, several empirical and semiempiricalmodels are used to describe the formative time delay dependence onworking voltages t f   (U) in neon at the pressure of13.3 mbar. Besides our models, the empirical and theoreticalmodels from the literature are successfully applied to theexperimental data, without and with empirical corrections on thebasis of our analysis. Good agreements with experimental data werefound primarily at low overvoltages and with empiricalcorrections even at high overvoltages. The statistically basedmeasurements of the breakdown time delayare shown to be convenient for the study of the formative timedelay under different conditions.

The polyvinylidenefluoride (PVdF) based novel polymer electrolytes have been prepared by solution casting technique for solid state rechargeable magnesium batteries. Tetraglyme and tetrabutyl ammoniumchloride were used respectively as plasticizer and filler. The Mg(ClO $_{4})_{4}$ was used as conducting source. A.c. impedance spectroscopy results reveal that 5 wt% TBACl containing electrolyte show the maximum conductivity of 4.32 × 10-4 S/cm at ambient temperature. This electrolyte was electrochemically stable upto 1.5 V which was observed through linear sweep voltammetry. X-ray diffractograms studies suggest that the electrolytes are completely in amorphous phase. The improved entanglement like surface morphology was well observed for 5 wt% TBACl containing electrolyte by scanning electron microscope. The activation energy and coherence length were calculated.

The objective of this work was to propose and assess, under the light of modern techniques for arc visualization and welding parameter monitoring, a parameter that would quantify properly the effect of the droplets reaching the pool over the bead penetration during MIG/MAG welding (GMAW). High-speed filming shadowgraphy, synchronized with the electrical signals, was used. Dedicated computational programs were employed to measure arc lengths and size, frequency, acceleration and speed of the droplets. Calibration of the system by employing metallic spheres was used to guaranty the performance of the image recording and measurement programs. Statistics were employed for sampling size determination. A non-common approach to correlate Momentum to bead geometry is propose and discussed. The methodology was assessed through MIG/MAG bead-on-plate welds shielded with an Ar+5%O2 blend, at three levels of currents and arc lengths. It was concluded that the proposed parameter denominated in this paper as “Effective Momentum” is the one which better represents the action of the droplets over bead formation.

This paper investigates the influence of static magnetic field exposure on blood flow. We mainly focus on steady flows in a rigid vessel and review the existing theoretical solutions, each based on some simplifying hypothesis. The results are developed, examined and compared, showing how the magnetohydrodynamic interactions reduce the flow rate and generate electric voltages across the vessel walls. These effects are found to be moderate for magnetic fields such as those used in magnetic resonance imaging. In this case, a very simplified solution, formulated by neglecting the walls conductivity as well as the induced magnetic fields, is proven suitable.


In this paper, we are interested in the transition between regimes where either visco-thermal or multiple scattering effects dominate for the propagation of acoustic waves through a 2D regular square array of rigid cylinders embedded in air. An extension of the numerical method using Schlömilch series is performed in order to account for visco-thermal losses. Comparison with experimental data and results from classical homogenization theory allows to study the transition between a low frequency limit (where viscous and thermal effects dominate) and a high frequency regime (where multiple scattering effects become predominant). For this particular geometry, a large frequency domain where visco-thermal and multiple scattering effects coexist is found.