Chalcogenide glasses with Ge10AsxTe90−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 Ge10AsxTe90−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.

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.

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.

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.

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

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.

FePt:C films were prepared by filtered vacuum arc deposition. A strong dependence of coercivity and ordering of the face-central tetragonal structure on both C concentration and annealing temperature was observed. With C concentration of 21%, the sample with a coercivity of 5.7 kOe was obtained when annealing temperature was only 350 °C. Transmission electron microscope observations revealed that FePt grains with an average size of 4.1 nm were embedded in C and appeared to be well isolated.

In an earlier paper [P.J. Wellmann, A. Albrecht, U. Künecke, B. Birkmann, G. Mueller, M. Jurisch, Eur. Phys. J. Appl. Phys. 27, 357 (2004)] an optical method based on whole wafer absorption measurements was presented to determine the charge carrier concentration and its lateral distribution in n-type (Si/Te) doped GaAs. The submitted results for Si-doped GaAs gave rise to questions concerning the interpretation of absorption mappings in wafers with high dislocation densities. GaAs substrates for optoelectronic devices are strongly affected by dislocations. Therefore further studies were conducted: absorption and Hall measurements were performed on GaAs:Si wafers with high and low dislocation densities. Absorption in Si-doped GaAs is far more complex than in Te-doped GaAs. It shows a co-dependency on charge carrier concentration and dislocation content which causes complications in the quantitative optical determination of the charge carrier concentration. Qualitatively, absorption mappings depict dislocations and variations of charge carrier concentration very well.

This paper deals with positive and negative corona discharge in atmospheric air using a wire-to-plane system. The Poisson's equation is solved numerically using the finite-element method and the current continuity equation. The space charge density is updated using the simplified method of characteristics, where the ion diffusion is neglected. The numerical model takes into account the avalanche length of the corona discharge and the potential corresponding to the minimum ionisation field is directly introduced in the method on the border of the ionisation region. The end geometry of the linear biased probe without wraparound bias plates has been adapted to a wire-to-plane system for use in DC corona discharge. The current density and the electric field are measured; their spatial distributions are given and compared with the computed values. The agreement between the calculated values and those obtained experimentally is satisfactory. The per unit electric field and current density are also represented by a unique function.

A new method for direct evaluation of the electron energy distribution function in plasmas is suggested, which involves the use of audio frequencies distortion factor meters. The amount of distortion suffered by a Langmuir probe AC current produced by superimposing a clean AC voltage on the DC probe voltage is measured. Although such distortions are proportional to the second derivative of the probe characteristic at any point when its neighborhood can be approximated by a second-degree polynomial, the instrument function is always sharper than that of harmonic differentiation. The method is analyzed theoretically, and tested experimentally. It is also shown that distortion additionally provides a direct measure of the electron temperature.

The main goal of this work was the development of methodologies for determining the energetic structure of welding arcs in Gas Metal Arc Welding (GMAW), i.e., with metal transfer. The present article focuses on a methodology applied to short-circuiting transfer. This methodology is based on equations which operate with discrete instantaneous values from measurements of welding current, arc voltage, arc length and electrode + droplet length. Metal transfer images were obtained through the use of laser shadowgraphy aided by high-speed camera. Dedicate computational programs were developed for electrical and geometrical values quantifications. Synchronization between the electrical signals and the metal transfer images made possible to associate total arc voltage measured at any point of oscillograms to the arc and electrode + droplet geometrical parameters. The proposed methodology was validated by using stainless steel GMAW shielded with Ar based blends and N2 contents ranging from 1 to 5%. The results showed that the methodology is sensitive enough for perceiving small variations in the voltage drops that compose the total arc voltage as a consequence of using different shielding blends.

Gate drive circuits for power MOSFET's and IGBT's often require electrical insulation. Different methods of electrical insulation can be used: bootstrap circuits, transformers and optic couplers. It has been proved that Piezoelectric transformer (PT) exhibit suitable characteristics, good integration capability and can be used for both power and signal transfer in low power applications. However, coreless planar electromagnetic transformer (CT) technology is an alternative solution that can also give satisfactory results. This paper compares the performances and the capabilities of integration of these two kinds of transformers (i.e. PT vs. CT). The study and comparisons are carried out in a two-gate driver, functioning in a half-bridge inverter. The two devices have the same structure, similar electric characteristics (operating at resonance frequency in both cases), identical electric values and the dimensions of the two transformers are quite the same. Additionally, some EMI aspects regarding the use of these transformers will be considered.

Two inverses methods are developed to calculate the surface heat flux and temperature of a body during heat treatment. Knowing temperature of an inner point of the solid and taking into account the phase transformation non-linearity, the surface heat flux evolution is estimated by an inverse algorithm. The experimental validation of both methods is performed in XC42 and XC80 steels case.