PbTe films have been deposited on glass substrates by laser ablation from PbTe pellets pressed from high purity Pb and Te powder. X-ray diffraction experiments and optical characterization of the films have been performed as a function of evaporation conditions (pellet composition and substrate temperature). From transmittance and reflectance measurements the values of the absorption coefficient $\alpha $ , of the refractive index n, and of the extinction coefficient k have been calculated.

Chalcogenide glasses with Ge10Asx Te90−x (x = 20, 25, 30, 35, 40, 45 and 55 at.%) were prepared by melt quenching technique. The glass transition temperature, the crystallization temperature, the melting temperature and the glass-forming tendency were determined from the differential scanning calorimetry measurements. The structural and optical properties of Ge10Asx Te90−x thin films prepared by electron beam evaporation were studied. X-ray diffraction showed that the as-evaporated films are amorphous and crystallize after annealing depending on the As content. The transmittance and reflectance of the films are found to be thickness dependent. The optical-absorption data indicate that the absorption mechanism is direct transition. The optical band gap values are increased with increasing As content while they decrease with increasing the film thickness. Upon annealing the transmittance and the optical band gap decrease whereas the reflectance and the refractive index increase.

ZnO thin films have been deposited on Si(111) substrates at different positions of the focusing lens by pulsed laser deposition (PLD) of a ZnO target in an oxygen atmosphere. The strong influence of the position of the focusing lens on the deposition rate, crystallinity, surface morphology and optical properties of the deposited ZnO thin films are studied. The results show that the ZnO thin films deposited at lens-target distance $(D_{l-t}) =59.5$  cm (the focal length is 70 cm) have the highest deposition rate and crystalline quality. The photoluminescence (PL) spectrum with the strongest ultraviolet (UV) peak and blue peak is observed in this condition. Moreover, the results of scanning electron microscopy (SEM) and selected area electron diffraction (SEAD) indicate that the films deposited at this lens position show the transition from monocrystalline to polycrystalline. Perfect monocrystalline ZnO films are obtained only when D l-t is changed in the range from 63 cm to the focus position.

We produced gallium oxide (Ga2O3) nanomaterials with various widths on chromium (Cr) substrates by the thermal evaporation of GaN powders. We characterized the samples using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and photoluminescence spectroscopy. The results showed that the products consisted of belt-like Ga2O3 nanomaterials, which had monoclinic structures. The photoluminescence spectrum showed a blue light emission.

Surface modification was performed on the indium-tin-oxide (ITO) substrates for organic light-emitting diodes (OLEDs) by oxygen plasma. The effects of oxygen plasma treatment on the surface properties of ITO substrates and its aging were investigated by the measurements of the chemical composition, contact angle and surface energy. We observe that oxygen plasma treatment improves the stoichiometry of the surface and enhances ITO wetting, so as to improve the surface properties of ITO substrates. With the increment of storage time, however, the improved ITO surface properties tend to decay and the surface energy decreases. Furthermore, we studied the effect of aging variation of surface properties of treated ITO substrates on the performance of OLEDs, in terms of driving voltage, luminance, and efficiency. The device performance of the OLEDs was found to become worse with the increasing storage time after oxygen plasma on ITO substrates. The results demonstrate that the device performance of the OLEDs strongly depends on the surface properties of the ITO substrates.

Thin films of Zn $_{1-x}$ Cdx O with x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5 at.% were deposited by electron-beam evaporation technique. It has been found that, for as-deposited films, both the transmittance and electrical resistivity decreased with increasing the Cd content. To improve the optical and electrical properties of these films, the effect of annealing temperature and time were taken into consideration for Zn $_{1-x}$ Cdx O film with x = 0.2. It was found that, the optical transmittance and the electrical conductivity were improved significantly with increasing the time of annealing. At fixed temperature of 300 °C, the transmittance increased with increasing the time of annealing and reached its maximum values of 81% in the visible region and 94% in the NIR region at annealing time of 120 min. The low electrical resistivity of 3.6 × 10−3 Ω cm was achieved at the same conditions. Other parameters named free carrier concentrations, refractive index, extinction coefficient, plasma frequency, and relaxation time were studied as a function of annealing temperature and time for 20% Cd content.

We report on the integration of erbium doped silicon-rich oxide into toroidal microcavities. Coupling of erbium ions to microtorus whispering gallery modes is evidenced at room temperature under excitation of silicon clusters. The fabrication process is controlled so that no luminescence quenching occurs during the silica melting step. The spatial and spectral distributions of outgoing light are investigated thanks to independent excitation and collection optics.

Indium-tin oxide (ITO) thin layers are obtained by an IBS (Ion Beam Sputtering) deposition process. We elaborated ITO films on flexible substrates of polyethylene terephthalate (PET), under soft conditions of low temperatures and fulfilling the requirements of fabrication processes of the organic optoelectronic components. With a non thermally activated (20 °C) ITO deposition assisted by an oxygen flow (1 cm3/min), we got an optical transmittance of 90% in the visible range, a resistivity around 10−3 Ω.cm and a surface roughness lower than 1.5 nm. Thus we realized flexible organic light-emitting diodes (FOLEDs) with good performances: a maximum luminance of 12000 cd/m2 at a voltage of 19 V and a maximum luminous power efficiency around 1 lm/W at a voltage of 10 V (or a maximum current efficiency of 4 cd/A at 14 V) for the (PET(50 μm)/ITO(200 nm)/TPD(40 nm)/Alq3(60 nm)/Ca/Al) structure.

The effect of thermal annealing on the structural properties of electron beam evaporated polycrystalline Si/Ge multilayer structures has been studied using Grazing incidence X-ray diffraction (GIXRD), reflectivity (GIXRR) and Raman spectroscopy techniques. The chemical nature of layers at surface and interfaces has been obtained from X-ray photoelectron spectroscopy (XPS) technique, which revealed the presence of impurities only at the top surface in the form of carbides and oxides in the Si layer and in elemental form in the Ge layer. Reflectivity measurements show that the Si/Ge MLS is stable upto 200 °C and roughness of Si on Ge interface is higher as compared to that of Ge on Si interface. Similarly, GIXRD results show that upto 200 °C, MLS is of microcrystalline nature and further annealing at 300 °C and 400 °C, well-defined crystalline peaks of pure Si and Ge are observed, which is in contrast to earlier reported experimental findings. Observed results are interpreted in terms of diffusion induced crystallization and corresponding increase in grain size.

We describe the design and performance of a slow atomsource based on a 2D magneto-optical trap (MOT) that uses aninnovative simple optical configuration. Metal-coatedretro-reflecting prisms replace mirrors and quarter-wave plates sothe optical power of the cooling laser beam is recycled. Thissource has been characterised for three different configurations:with and without transverse magnetic field gradient, and with apusher beam to obtain a 2D+-MOT. The longitudinal velocity isof the order of 25 m·s−1, with a transverse velocityspread ≤1 m·s−1, while the typical atomic fluxdensity obtained is up to1.3×1014 at ·s−1·m−2 for a cesiumvapour pressure of ~4×10−8 mbar in the source. Weuse this slow atom beam, instead of cesium vapour, to load a 3Dmoving optical molasses that feeds a continuous cold atomfountain. We obtain a gain of a factor ~20 in the atomicflux launched by the fountain.

In this paper, the linear perturbation theory is used to study material instability in a classical elasto-plastic model. In this framework, the well known Rice criterion of bifurcation into localized modes is found to be a limiting case corresponding to unbounded growth of perturbation. In the first part, derived expression of the critical plastic modulus is numerically plotted versus the spherical coordinates of the potential normal to the localization band in order to describe the whole space. In the second part, conditions of occurrence of the other types of instability are established, namely divergence and flutter types of instability, and modelling details influencing them checked. These conditions are also relative to the parameter of growth of perturbations which can be plotted versus the plastic modulus considered as the loading parameter. When several modes of instability are possible, an hierarchy is established.

We report a study of femtosecond laser pulse absorption of wafer grade silicon with an average pulse duration of 150 fs, centred on a wavelength of 775 nm. The electrical response of the laser excited carriers, over a range of fluences up to the ablation threshold for silicon is analysed. The silicon used for the experiments is a uniformly doped P-type wafer with a concentration of 1 × 1012 cm−3 throughout its volume. The purpose of this work is to use the electrical properties of the excited carriers as a method for analysing the interaction between femtosecond pulses and the silicon lattice below the ablation threshold, and to determine the evolution of the excited carriers after the femtosecond pulse is absorbed in silicon. This paper uses simulation software to solve the ambipolar continuity equation for the evolution of the excited carrier group given the initial values and boundary conditions of the experimental system. The paper derives results for the total number of excited carriers created as a function of laser fluence, in addition to the bulk excited carrier dynamics and lifetime after femtosecond laser excitation. Based on the results for the total number of excited carriers as a function of the average laser fluence, a value of 0.09 J cm−2 is measured as the fluence where lattice defects started to reduce the effective quantity of carriers that could be detected and hence indicated incubation lattice damage.

Thin films of thulium and samarium doped AlN are deposited on silicon (111) substrates at 77 K by rf magnetron sputtering method. 200–400 nm thick films are grown at 100–200 watts RF power and 5–8 mtorr nitrogen, using a metal target of Al with Tm and Sm separately. X-rays diffraction results show that films are amorphous. Cathodoluminescence studies are performed at room temperature and two dominant peaks are observed in Tm at 467 nm from $^{1}{\rm D}_{2}$ $\to$ $^{3}{\rm F}_{4}$ transition and 480 nm from 1G4 to the ground state 3H6 transition. Other peaks in the visible region are obtained at 650 nm and 685 nm due to $^{1}{\rm G}_{4}$ $\to$ $^{3}{\rm F}_{4}$ and $^{1}{\rm D}_{2}$ $\to$ $^{3}{\rm H}_{4}$ transitions. Peaks in the ultraviolet and infrared region are also obtained at 371 nm, and 802 nm as a result from $^{1}{\rm D}_{2}$ $\to$ $^{3}{\rm H}_{6}$ and $^{3}{\rm H}_{4}$ $\to$ $^{3}{\rm H}_{6}$ transition respectively. Sm gives four peaks at 564 nm, 600 nm, 648 nm and 707 nm as a result of $^{4}{\rm G}_{5/2}$ $\to$ $^{6}{\rm H}_{5/2}$ , $^{4}{\rm G}_{5/2}$ $\to$ $^{6}{\rm H}_{7/2}$ , $^{4}{\rm G}_{5/2}$ $\to$ $^{6}{\rm H}_{9/2}$ and $^{4}{\rm G}_{5/2}$ $\to$ $^{6}{\rm H}_{11/2}$ transitions. Films are thermally activated at 1200 K for half an hour in a nitrogen atmosphere. Thermal activation enhances the intensity of luminescence.

Data for YBa2Cu3O7 doped with Tb, Pr, and Ceare interpreted in terms of (i) superconductivity in the BaO planes(not in the CuO2 planes), and (ii) the behaviors of YBa2Cu3O7 when doped byTb, Pr, or Ce.

PbO-P2O5-As2O3 glasses containing different concentrations of Al2O3 ranging from 0 to 5 mol% were prepared. Dielectric properties (viz., dielectric constant $\varepsilon{'}$ , loss tan $\delta $ and a.c. conductivity $\sigma_{ac}$ over a moderately wide range of frequency and temperature and dielectric breakdown strength in air medium), optical properties (optical absorption, IR spectra and thermoluminescence) and differential thermal analysis have been studied. The interesting changes observed in these studies have been explained in the light of different structural groups of aluminium ions.

A new approach to calculate the magnetic hysteresis, based on the Brillouin theory associated with the Jiles-Atherton approach, is presented. This study represents a general model compared with the classical Jiles-Atherton one. A Brillouin function, using the kinetic atomic moment $\mathaccent"017E{J}$ , allows to determine accurately the value of the anhysteretic magnetization. The obtained results are compared with experimental ones of the silicon-iron sheets.

The local electric behaviour of IMPATT diodes was studied by scanning transmission electron beam induced current in cross-section method (X-STEBIC). This technique of induced current measurement makes it possible to probe the depletion zone of a junction with the beam of a transmission electron microscope. Two series of experiments were carried out. The X-STEBIC signal was analyzed according to the sample thickness and under different electrical polarizations. Moreover, these measurements were done and compared at room and low temperature (≅110 K). From these data, simulations of X-STEBIC profile allowed us to determine the main physical parameters brought into play in the signal formation. We have shown that, in the vicinity of the junction, the intensity of the induced current partly depends on the avalanche effect. The kinetic energy of the minority carriers generated by the electron beam is sufficient to induce collisions in cascade, even when the junction is not polarized. At low temperature, surface recombination has an essential role on the lateral resolution of the X-STEBIC method. By choosing carefully the range of sample thickness and by positioning the probe in the field of the diode, it is possible to optimize the resolution. Surface recombination annihilates the diffusion of the carriers so that the STEBIC image becomes a true image of the electric field. Consequently, semi-quantitative physical data can be obtained on the junction field.

An electron diode having a ferroelectric plasma cathode (FPS) controlled by optic fibers was operated at a repetition rate of 0.5 Hz during 1 hour, when an accelerating pulse of ~250 kV in amplitude and ~250 ns in duration is applied. The application of the fiber optic decoupling allows easy control and synchronization of the FPS operation with the firing of the HV generator. It was shown that the use of the FPS with fast fall time of the driving pulse allows reproducible generation of an electron beam having a current amplitude of ~1 kA and uniform cross-sectional current density distribution. It was shown also that in the case of the driving pulse ringing, the application of the accelerating pulse during the fall in the negative ringing leads to a plasma pre-filled mode of diode operation due to intense ion emission from the FPS. When the accelerating pulse is applied during the rise in the positive driving pulse ringing, one obtains diode operation with limited plasma emission ability. Only when the accelerating pulse is applied during the fall in the positive ringing of the driving pulse does one obtain diode operation in space-charge limited mode. This dependence of the diode operation on the timing of the accelerating pulse application with respect to the driving pulse is explained by processes related to the screening of ferroelectric bounded surface charges by the plasma charged particles.

A kinetic model and the associated PIC-MCC numerical technique have been used to simulate the plasma generated by a vacuum arc cathode spot fragment and calculate the current densities and net energy fluxes at the cathode surface. The model is based on a comprehensive description of the plasma generation processes, including a detailed representation of metal vapor particle ionization and plasma-cathode interaction. An important feature of this model is its ability to provide details of the spatial variations of plasma parameters within the near cathode region. Calculations are carried out for nickel, titanium and zirconium cathodes as a function of the surface temperature. It is found that below a threshold surface temperature the energy input to the cathode is negative and the spot fragment can not operate in a self-sustained way. The relative importance of the different mechanisms controlling current and energy transfers at the cathode surface are analyzed in detail.

We model the ejection of tungsten atoms from a hot filament by a binomial distribution. A normal approximation is made and the lamp is supposed to fail if the undecayed atomic fraction drops below a critical value. The resulting formula for the lamp survival probability has no free parameter and is shown to be in excellent agreement with the experimental mortality curve.