P-type Sb2−x Bix Te3 crystals with various chemical compositions (x = 0.40, 0.44, 0.47, 0.50, 0.53, 0.56 and 0.60) were fabricated by zone melting method. Transmission electron microscopy and energy dispersive X-ray microanalysis were performed to characterize the evolutions of defects on the sites of Bi, Te and Sb atoms in the lattice. Study of Sb2−x Bix Te3 structure reveals the formation of Bi2Te3 in which native defects are a consequence of overstoichiometry of Bi atoms in Bi2Te3 single crystal. Thermoelectric properties, including Seebeck coefficient (α), electrical conductivity (σ), thermal conductivity (k), and Hall constant were measured at room temperature. In terms of thermoelectric properties, increasing Bi2Te3 content (x) decreased carrier (hole) concentration (and σ, as a result) and increased α. The maximum figure-of-merit (Z = α2σ/k) of 2.7×10−3 K−1 was obtained at about 300 K for 25%Bi2Te3 − 75%Sb2Te3 with 3 wt% excess Te recommended for thermoelectric properties modification. Added Te is considered not only as a dopant, but also to compensate the deficiency of Tellurium understoichiometry. The results compared with reports of several authors to evaluate the dependency of parameters on sites of the atoms. The novelty of this work is to present the sites of the atoms in the lattice of the ternary compounds and the effect of defects occurred due to the atomic sizes of the Bi, Sb and Te.

Recently, research has been concentrated on the study of the magnetic nanoparticules for their use in the design of magneto-optical devices. The magneto-optical waveguides for example exploitthe Faraday effect to obtain a rotation of polarization TE and TM independent of the propagation direction. In this work, we study isolating component whose operating principle is based on the minimization of the phase mismatch between TE and TM fundamental propagation modes.It appeared promising to use as a guiding film the thin layers doped bymagnetic nanoparticules γ-Fe2O3 in order to carry out an adequate phase mismatch. This last can be adjusted by permanent linear birefringence resulting from the application of an external magnetic field during the gelation of the solution which constitutes the guiding film. Many studies were undertaken primarily to minimize the birefringence between TE and TM modes, for that this work represents a new potential means to reach the phase matching by acting on the anisotropy and the thin layer thickness.This condition can be realized in the waveguides with SiO2/TiO2 guiding thin layer doped by nanoparticules of maghemite γ-Fe2O3. The simulations carried out by the FMM method and MATLAB allowed to deduce the conditions to decrease the phase mismatch and increase the conversion ratio of TE/TM modes in order to ameliorate the isolation.

Thermal evaporation technique has been employed to grow silver phthalocyanine nanostructures on glass substrates kept at different substrate temperature in vacuum of 10−5 Torr. These samples have been studied for their structural and optical properties. TEM investigations show the formation of long nanowires in AgPc thin films prepared at substrate temperature of 298 and 303 K, whereas films prepared at 308 K show the formation of nanobelts. XRD observations reveal that silver phthalocyanine nanowires are crystalline in nature. The significant blue shift in the UV-VIS absorption spectra of the silver phthalocyanine nanowires in comparison to bulk sample, indicate of effect of quantum confinement.

In this present communication, we have studied the effect of hot-carrier degradation effects on surface potential, threshold voltage and DIBL of the sub-micron device. We have derived a more accurate model for the threshold voltage in the presence of hot carrier degradation effect. Our model includes a fitting parameter to take care of short channel effects. The validity of our model is verified by the MINIMOS simulator results. Our analysis predicts that the minimum potential position along the channel is not affected by the sign of the hot carrier induced localized interface charge density and always occurs in damage free region. DIBL effect is more pronounced in submicron devices in the presence of the hot carrier degradation effect.

Ba0.65Sr0.35TiO3 (BST) thin films have been deposited by radio frequency magnetron sputtering. The effects of the deposition parameters on the crystallization and microstructure of BST thin films were investigated by X-ray diffraction and field emission scanning electron microscopy, respectively. The crystallization behaviour of the films is clearly affected by the substrate temperature, annealing temperature, and sputtering pressure. The thin films that are deposited at room temperature are amorphous in their as-deposited state. However, an improved crystallization can be observed for BST thin films deposited at higher temperatures. As the annealing temperature is increased, the dominant X-ray diffraction peaks become sharper and more intense. The dominant diffraction peaks increase with sputtering pressure, steadily increasing for films deposited from 0.37 to 1.2 Pa. When the sputtering pressure is increased up to 3.9 Pa, the films have a (110) + (200) preferred orientation. Possible correlations between the crystallization and the changes in the sputtering pressure are discussed. SEM measurements indicate that the films, which consist of small grains, are smooth and that the interface between the film and the substrate is sharp and clear.

In this work, we study the optical interband transitions of InP on silicon (InP/Si) and on porous silicon (InP/PSi) substrates grown by molecular beam epitaxy (MBE). Spectroscopic ellipsometry for photon energies from 2 to 5 eV is used to determine the InP/Si and InP/PSi complex refractive index and thickness. Bruggeman effective medium approximation (EMA) associated to the Cauchy model are used to model the experimental ellipsometric data. We have found that the E 1 and E 1 + $\Delta _{1}$ transition energies of InP/Si and InP/PSi shift to low energies compared to bulk InP. This effect is interpreted as a result of the strain relaxation of the InP layers grown respectively on Si and porous Si substrates.

In this work the surface of (4 0 0) p-type Si wafers is bombarded with 29 keV nitrogen ions at various ion beam fluency varied from 1016 to 1018 ions/cm2 and the results are investigated. Si3N4 film with orthorhombic structure is formed on silicon surface with cubic structure while the lattice parameter of the generated layer is not affected by change of nitrogen ion beam dose. RMS roughness of implanted samples increases by increasing the nitrogen dose, specially when the dose is more than 3×1017 ions/cm2. Surface resistivity of samples is increased by increasing the dose of ion beam. Although changes in the transmission of implanted samples does not differ very much in comparison with row sample but reflection of implanted samples decrease about 60% for the electromagnetic wave in the range of 200 to 1500 nm. Absorption coefficient of samples is obtained and the band gap energy of samples is calculated. It is observed that formation of defect levels changes the magnitude of band gap energy.

We have studied the enhancement of radiative emission rate of CdSe/ZnS core-shell quantum dots on semi-continuous gold films which have been prepared by using sputtering technique. The photoluminescence intensity and the decay rate of CdSe/ZnS quantum dots are affected by the semi-continuous gold films. Both the photoluminescence intensity and the decay rate of the quantum dots are greatly enhanced by the semi-continuous gold films near the conductive percolation threshold and that are caused by the enhanced local electric field due to the surface plasmon resonance on the semi-continuous gold films.

PbS quantum dots (bare and silica coated) have been synthesized in PVA matrix with average size 10 nm and 9 nm. The capacitance-voltage (C − V) and current –voltage (I − V) response of both bare and coated quantum dots have been recorded in different frequency range (Hz–MHz). Both the samples show frequency dependent response except in case of C − V characteristics at MHz range. The I − V responses at low frequency range exhibit step like structures which could be attributed to 'Coulomb blockade'.

We report single transverse and longitudinal mode operation of an all solid-state orange laser pumped at 821 nm. Oscillation at 607 nm by avalanche upconversion in Pr, Yb:BaY2F8 pumped by a Ti-Sapphire laser at 821 nm is obtained with a threshold as low as 570 mW. A maximum output power of 12 mW is obtained for a pump power of 2.5 W.

Magnetic thin films of Co80Cr16Ta4 were sputtered onto identical CrMo seed-layers at –200 V bias and 3 different substrate temperatures (150, 200, and 250 °C). Energy-filtered transmission electron microscopy (EFTEM) was performed to analyze Cr levels at the grain boundaries as well as inside the grains. These quantitative Cr measurements were used to estimate the local values of magnetocrystalline anisotropy (K u ) and, together with grain size distributions, calculate the product of K u and the grain volume (K uV ), a quantity which is a measure of thermal stability. The results show that the coercivity as well as the fraction of stable grains increased with increasing substrate temperature. The increase in the fraction of stable grains is produced by the enhancement in the K u value due to Cr depletion of the grain interiors and the magnetic decoupling between the grains from Cr grain-boundary segregation.

We report on the synthesis of our work on the analysis of active spectro-polarimetric imaging concept of real-world scenes. These synthesis extend from the investigation of depolarization mechanisms up to image analysis and processing. We show in particular that depolarization effects are wavelength dependent and strongly correlated with light absorption of materials. Multi-wavelength images of degree of polarization are recorded and analyzed, evidencing that the polarimetric image must be interpreted in conjunction with its counterpart intensity image in order to extract, the most relevant information from the scene. For real field operation, the noise characteristics of polarimetric images are also investigated under coherent laser illumination. The potential increase of target detection performance brought by properly processing the active polarimetric image is illustrated on a very low contrast scene.

Polypyrrole/ polyaniline (PPy/PAn) composite films have been prepared by direct electrochemical polymerization of pyrrole in an aqueous solution of PAn. Spectroscopic results demonstrated that the polyanion, PAn, was incorporated into the PPy matrix as a dopant. The composite films exhibited a higher thermal stability than that of pure PPy. Scanning electron microscopic images revealed that the composite film had smooth and compact morphology.

Polycrystalline, smooth, and hard thin films of TiN are successfully deposited on AISI-304 substrates using a 1.5 kJ Mather-type dense plasma focus device charged at 18 kV. The purpose of this study is to investigate the structural and mechanical properties of the TiN thin films in terms of ion dose and substrate position to establish the optimum deposition conditions. The films are analyzed using XRD, SEM, electron microprobe and micro-hardness testing. XRD confirms the deposition of a polycrystalline TiN thin film together with the emergence of an iron chromium nickel phase. The surface hardness-in comparison to the unexposed substrate-is found to increase up to 250% when a film is deposited using 30 focus shots at an axial distance of 6 cm. SEM micrographs show that the quality of the film is improved with an increasing number of focus shots. The constituent elements of the film are also confirmed by electron microprobe.

This paper addresses a multiscale strategy for the prediction of anhysteretic magneto-elastic behavior and its application to the definition of a magneto-elastic constitutive law for Terfenol-D. The multiscale modeling is based on an energetic procedure at the single crystal scale. Localization and homogenization procedures are then applied to deduce the constitutive law of polycrystalline media from the behavior of the corresponding single crystal. The method is applied first to define the magneto-elastic behavior of single crystals, and the application to polycrystalline samples is then considered. Modeling results are compared to experimental data.

Direct-illumination CCDs find increasing use in coherent X-ray imaging due to their good spatial resolution and signal-to-noise ratio. These CCDs offer a high quantum efficiency for soft X-rays near the 3d transition metal L edges. We compare front- and back-illuminated CCDs and describe a method to obtain images with a large dynamic range (five orders of magnitude) and high spatial resolution. Back-illuminated CCDs are resistant to radiation damage at the soft X-ray energies and provide a true 13.5 μm pixel resolution. High quality diffraction images are obtained in magnetic studies from metallic multilayer structures in reflection geometry.

This paper deals with the application of schlieren techniques to the optical diagnostics of ultrasonic pulses, passing a grid target. We used bright field schlieren method with the image post-processing by 2-dimensional Fourier transform (2D FT). In case the basic wavelength of the pulse is larger than the grid spatial period, the ultrasonic wave does not resolve the grid and the corresponding modulation is absent in the schlieren images. However the pulse contains also the super-harmonics of its basic frequency, while their wavelengths, which are smaller than the grid period and capable therefore to resolve the target. The resulting modulation is hardly visible in the schlieren images, but could be easily revealed with the 2D FT. The quantitative interpretation of the schlieren images and their FT are presented in the paper as well.