By using solid state ceramic synthesis technique, we have produced high-Tc superconducting ceramics with a fixed nominal composition of Bi1.7Pb0.3Sr2Ca2Cu3Oy (BSCCO). Annealing treatments in air at 800 °C for different time periods from 6 to 30 h were carried out for the BSCCO samples. The influence of annealing time on the superconducting and mechanical properties were examined by measurements of thermoelectric power (TEP), X-ray diffraction, surface morphology, bulk density and Vickers microhardness (V H N). The results reveal that the most appropriate annealing time to obtain the highest peak intensity of high-Tc phase (2223), highest and sharpest transition temperature ($T^0_{\rm c}$), maximum value of density and maximum of V H N is 18 h. Prolongation of the annealing time was associated with a reduction of all these parameters. These observations show that the annealing treatment plays an important role for producing consolidate superconducting compounds with improved mechanical properties.

A model is developed to describe the formation of metallic foams in which liquid drainage acts to collapse the foam before it can freeze. Numerical solution of the foam drainage equation, combined with the equations of heat conduction, provides new insight into the competition between these two processes. It also stimulates and confirms a theoretical analysis which leads to criteria for creating uniform samples of frozen metal foam. The analysis suggests new experiments to clarify the role of the various processes leading to foam formation.

We present simulations of the transmission and reflection of narrow-extent pulses incident upon a chiral sculptured thin film (STF) along its axis of spirality, when the circular Bragg phenomenon is excited. Even though the frequency-domain reflection and transmission spectrums of a sufficiently thick chiral STF slab acquire final shapes within the Bragg regime, the shape and the duration of the transmitted pulse change with slab thickness over the entire range of our simulations. The emergence of a multiple-hump structure in the transmitted pulse is relevant to the use of chiral STFs in digital optics communication.

Multilayers ceramic capacitors (MLCC) presenting non linear behaviours of their C(V) characteristics may have interesting applications in power electronics. Most of them have already been described. Nevertheless, the choice of a particular type instead of another one is all the more so difficult since, on one hand the physical mechanisms able to explain this behaviour is far from being understood. On the other hand, C(V) characteristics are in general obtained for low voltage values different from the ones they are going to be involved in. In this paper, direct in situ characterisations of different BaTiO3 based capacitors commercially available are achieved. The role of the capacitors' type (X7R,Z5U), of the temperature and of the voltage waveform (and more particularly its polarity) is demonstrated. Temperature values up to 200 °C are measured during normal operations in a RCD dissipative snubber without any alterations of the C(V) characteristics. All these results are discussed as regards the main physical properties of the constitutive materials in order to reach an optimisation of their use through an appropriate dimensioning.

Results on the deposition of aluminum nitride thin films on silicon (111) substrates by pulsed laser deposition are reported. A KrF excimer laser was used to ablate in vacuum an AlN target. The intensity and the repetition rate of the laser as well as the substrate temperature were varied and their effects on film properties were determined. The AlN films were characterized by several techniques such as in situ laser interferometry, X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy and transmission electron microscopy. At a deposition temperature of 500 °C and a laser intensity of 1 × 108 W/cm2, highly oriented AlN layers are deposited. Increasing the laser intensity leads to the presence of metallic Al in the films. As temperature is increased from 500 to 920 °C, the growth rate is found to decrease but the crystalline structure as well as the smoothness of the films are both significantly improved. It is also found that a reduction of the growth rate by varying the repetition rate from 30 to 10 Hz leads to a further improvement of the crystalline quality of the AlN layers.

Metal-Insulator-Semiconductor Field-Effect-Transistors based on Dihexyl- quaterthiophene (DH4T), has been realized. Unlike conventional MISFET, these devices work through the modulation of an accumulation layer at the semiconductor-insulator interface. An analytical model that describes the operation of organic thin-film-transistors based on a simple trap distribution, with a single shallow trap level located between the valence-band edge and the Fermi level, has been used to determine some microscopic parameters such as the mobility, the density of traps and the corresponding level of traps.

We use a full quantum model of MOS (metal oxide semiconductor) structure to study the influence of a non-uniform doping profile of the substrate on the capacitance-voltage (C−V) behavior of the structure. For different “realistic” doping profiles, simulations are performed and compared to simulations with an uniform doping and to C−V measurements for samples with oxide thickness in the range [2−5 nm] [1]. In each case, we have extracted the oxide thickness that is found to be independent of the doping and the flat-band voltage which can be shifted up to 200 mV regarding the different profiles tested here. Moreover, below about 3 nm, the shape of the C−V simulation is more affected, which shows that the doping profile of the substrate has a great importance for an accurate C−V modeling of ultra-thin MOS structures.

Low-density plasma is generated in a cylindrical DC magnetron discharge tube. Distribution of the magnetic field strengths in the radial and axial directions is drawn. Langmuir probe data are obtained at the edge of the cathode fall region of Ar gas discharge at pressure range from 0.5 to 4.0 torr. In the presence of the magnetic field, values of the electron temperature Te are smaller than that without magnetic field. While plasma density Ne increases by a factor of two than that without magnetic field. The electron density increases with magnetic field due to electron magnetic confinement. Also, the radial distribution of Te and Ne in the cathode fall region of the glow discharge is discussed. The magnetic field drift velocity plays an important role to make the radial distribution of Te and Ne slightly changed.

Light scattering by liquid helium droplets or gaseous helium bubbles is strongly forward. This has two direct experimental consequences: rare scatterers are very bright in a narrow ($\ll 5^{\circ}$) angular region in the forward direction; and even in the presence of multiple scattering the intensity collected at large angles is linear in the concentration of scatterers. These properties are explained, and the second one is illustrated with a liquid-gas helium spray.

The feasibility of imaging by X-ray fluorescence in a SEM has been tested on a simple laboratory set-up. It has been demonstrated that images generated by the fluorescent X-rays can be directly obtained with the use of simple pinhole relay optics and an incident X-ray beam created in a SEM. These images were acquired with a charge coupled device (CCD) camera coupled to a phosphor screen by a fibre-optic faceplate. This technique provides chemical and topographical images with a spatial resolution in the object plane of a few micrometres. This “global” imaging has the advantage that the acquisition time is only a few minutes for a sample surface of a few mm2.

The aim of this investigation is to study thin-film thermoelectric linear arrays for high spatial temperature measurements and to analyze power laser energy profile. The sensitive area consists of a planar of 16 individual thin-film Au-Pd thermocouple junctions with 8 μm × 8 μm of surface area. This sensor allows 16 temperature measurements per 288 μm. It is processed by means of standard integrated circuit techniques. Thermal simulation of heat conduction in gold and palladium layers has been carried out. The sensor thermoelectric response has been characterized in transient regime and steady state. The time constant of thermocouple response is of the order of 140 μs. A linear relationship between the thermoelectric voltage and the incident power laser has been put in evidence. Using the linear array, a Gaussian profile of the incident laser beam is obtained.