We discuss the properties of the nonlinear diffusion equation for the case of diffusion in excited systems. The diffusion coefficient is directly proportional to the concentration of impurities and depends on the time in a special way. For the description of the excited systems, we used a special temperature function, which defined the time dependent diffusion coefficient and the Boltzmann's distribution of the excited vacancies or impurity atoms in solids. This model was used for approximation of very fast diffusion of metastable vacancies irradiated by soft X-rays in an excited Si crystal.

The incorporation of the doping element Na as well as the impact of this element on the structural, morphological and optical properties of evaporated CuInS2 films on Corning 7059 glass substrates is studied. The element Na was evaporated from a thermal evaporation source. The amount of the Na source was determined to be 0–1 at.% compared with CuInS2 source. The substrate temperature was maintained at 200 °C. The effects of Na on films properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical transmittance and reflectance spectra. SEM observation revealed the increase of the surface crystallinity and an enhancement of surface grain size with Na doping. The optical properties of the CuInS2:Na films revealed direct optical transitions which were attributed to the fundamental edge. The optical band gaps of the thin CuInS2:Na films decrease linearly with increasing the Na concentration. An unstable N type conductivity was firstly determined after what the layers are converted to P-type conductivity.

We present an overview of template synthesis as it applies to our nanomaterials research. This bottom-up approach is motivated by our desire to find an alternative to the big, top-down approaches to nanoscience, such as clean-rooms and X-ray lithography. Using universally available templates and materials, and very modest synthesis techniques, we have created a variety of interesting and useful structures. Starting with homogeneous ferromagnetic nanowires, we were able to study and manipulate spin-dependent transport. Next, we branched into multi-layer GMR and spin-valve structures for spintronics. As a side trip, we put carbon-encapsulated fullerene nanoparticles into nanopores for ballistic magnetoresistance studies. Carbon nanotube molecules were grown in templates by CVD self assembly. The carbon nanotubes grown using a cobalt catalyzer show spin-valve, ballistic transport, and Coulomb blockade effects. Very recently, we have started to study templated semiconductor nanorods with the amazing result that their behaviour is very similar to that of the carbon nanotubes and can be reduced to a scaling law. Essentially, the template acts as a skeleton for the nanoscale synthesis and macroscale contact of an infinite variety of materials and structures. It is our hope that by the following examples we demonstrate that high quality nanoscience research is available to everybody.

In this paper, we report the theoretical predictions of a high-index GaAs substrate ((111)A and (311)A) on the subband structure and thereafter on the 2D electron density of Si δ-doped Al0.33Ga0.67As/In0.15Ga0.85As/GaAs pseudomorphic high electron mobility transistor (pHEMT) with an additional InxGa1-xAs (x > 0.15) thin layer embedded in the channel. We have seen that the electronic structures and the electron density are quite sensitive to the additional InxGa1-xAs (x > 0.15) layer thickness, indium composition and to their position in the channel. An optimal position of the additional InxGa1-xAs layer was found to be corresponding to the maximum of the first eigen envelope function for the different growth directions. We report that the optimised electron density is obtained in the structure grown on (111)A GaAs substrate. In this case the electron transfer is significantly higher than those grown on (311)A and (001) GaAs substrates respectively.

A numerical method based on the finite-element methodis developed to study active photonic bandgap materials (PBG) offinite size. After validating our method, we focus on metallicPBGs including diodes. These structures are characterized in thefar-field and the near-field, and the influence of diode statesand material finiteness is examined.

The galvanomagnetic effects in new diluted magnetic semiconductors Pb$_{1-x}$SnxTe:Yb were studied to build the energy level diagram under variation of the alloy composition and establish the connection between the parameters of electronic structure and magnetic properties. It was found that the Hall coefficient increases almost by order of magnitude with increasing the temperature. As tin content decreases, while the ytterbium concentration grows, the hole concentration decreases by several times. The results are explained by assuming a formation of an ytterbium-induced deep defect level in the energy spectrum of the alloys, which moves up to the top of the valence band with increasing the ytterbium concentration and pins the Fermi level within the valence band at sufficiently high impurity content. The hole concentration vs. ytterbium content dependence was used to calculate the energy position of the Fermi level in the frame of two-band dispersion law and to determine the position of Yb level in the alloys. The diagram of the charge carrier energy spectrum under varying the alloy composition was built.

We have calculated the subband structure and confinement potential of modulation-doped Ga$_{1-x}$AlxAs-GaAs symmetric double quantum wells a function of the doping concentration. Electronic properties of this structure are determined by solving the Schrödinger and Poisson equations self-consistently. To understand the exchange correlation potential effects on the band bending and subband populations, this potential has been included in the calculation at 0 K and, at room temperature. We find that at low doping concentrations the effect of the exchange correlation potential is more pronounced on the subband populations.

The contraction of a stressed rectangular plate-like sample has been investigated considering the mechanical stability of its two lateral free surfaces with respect to localized perturbation.The energy variation of the platehas been calculated to determine the condition of development of symmetric and non-symmetric wavelet fluctuations of the two lateral free surfaces when a constant and homogeneous stress is applied to the plate. The contraction has been then studied when a source of non-homogeneous strain is embedded into the plate.

This paper reports an attempt to improve the response of a metalloporphyrin Langmuir-Blodgett films, n-tetraphenyl porphine ruthenium (II) carbonyl, towards several vapor samples by means of surface microstructure modification. Four different surface microstructures were prepared by annealing the thin films samples in air at three different temperatures; 50, 100 and 150 $^{\circ}$C, for one hour. Three types of vapor samples with different physico-chemical properties, namely saturated vapor of methanol, ethanol and 2-propanol in 15 l/min of air flow, were used. The sensing sensitivity was based on the change in the optical absorption of the film upon exposure towards the gas samples that was measured at a particular wavelength, i.e., 514 nm, of the light source. It was observed that the response of the thin films was influenced by its surface microstructure, which the smoother the surface the higher the response is. The correlation between the microstructure of the films surface and its gas sensing property will be discussed.

Bunched and multi-circularly wrapped carbon nanotubes (CNT) are observed to grow on alloy substrates based on iron group metals and copper by a microwave enhanced hot-filament method with a dilute gas of ammonia at a proper RF self-bias. The grown size of CNTs embodied in the grain sizes of conducting bulk alloy catalysts such as Cu-Ni, Cu-Fe, Cu-Co, and Cu-Ni-Fe-Co are controlled by a precursor time of hydrogen plasma etching. Species with different structural features and homogenization of CNTs samples are produced crucially attributed to various reactant gases and self-bias induced by the radio frequency field.

We discuss the fabrication and characterization of undoped hydrogenated and crystallized silicon thin films grown by reactive magnetron sputtering at growth rate of about 2 Å/s and at a temperature as low as 100 °C for various ratios of hydrogen dilution in the gas phase mixture (argon + x% hydrogen). Combined infrared absorption and Raman scattering spectroscopy techniques as well as conventional and high resolution transmission electron microscopy and stress measurements are used to fully characterize the films. In this temperature range, a minimum hydrogen dilution of 30% with respect to the plasma mixture (argon + hydrogen) is necessary to produce nanocrystalline films with crystalline volume fraction of about 65%. Moreover, these films are found to promote much lower stress intensity than those reported in previous works. The nature and strength of the stresses are dependent on the film microstructure.


This paper describe the recent measurements of `Electron efficiency' which has been done with the `CLIO' Free-electron laser (FEL). The `Electron efficiency' is the relative energy loss of the electron beam in the undulator during the FEL interaction. It gives an absolute measurement of the optical power produced by the FEL, which is then compared to the direct measurement using a power meter at the exit of the FEL. A analytical expression of the `Electron efficiency' is given here, and it is compared to the measurements.

The paper presents a reliable model for the susceptibility analysis of a Rectenna (Rectifying Antenna) in the context of microwave energy transfer. The approach allows to take into account both distributed electromagnetic portions of the antenna and the rectifier circuit including lumped elements. From the 3D electromagnetic modelling of the structure the input impedance is obtained as a function of frequency. Then a rational approximation of the Laplace variable is chosen to describe the port behaviour. The technique provides a straightforward way for a time domain simulation using Pspice or Saber. The proposed approach can be efficiently used to provide a non-linear time-domain study in the framework of EMC (Electromagnetic Compatibility) for various electronic equipments involving printed circuit-boards, internal structures of electronic components or Micro-Electro-Mechanical Systems (MEMS).

Thin films of polytetrafluoroethylene (PTFE) were prepared by pulsed-laser deposition (PLD) from bulk PTFE targets using 157 nm F2-laser radiation. The films were analyzed by means of optical polarization microscopy, stylus profilometry, XPS, XRD, FTIR spectroscopy, and by capacitance measurements. The effect of substrate temperature, Ts, on the morphology and crystallinity of the films was studied. Films treated at sufficiently high Ts consist mainly of spherulite-like crystallites. Films with a thickness of more than about 155 nm are continuous, pinhole-free, well adherent to the substrate, and have a composition which is similar to that of the target material. The minimum film thicknesses and deposition rates are much lower than those achieved with pressed PTFE powder targets using 248 nm KrF-laser ablation. This is related to the different deposition mechanisms. Film formation based on KrF-laser ablation of pressed powder targets is mainly related to the condensation of large particulates transferred in a particle jet from the target to the substrate. F2–laser ablation and film formation seems to be based on the ablation and condensation of small fragments. Correspondingly, the morphology, crystallinity, and the optical and dielectrical properties of films significantly differ from each other.

We report a new method of fluorescence lifetime imaging that uses the ultra-fast opticaltemporal gating properties of parametric image amplification. Images with different lifetimes inthe picosecond range are resolved with reliable and reproducible results.

Composites consisting of epoxidized natural rubber (ENR) and organically modified montmorillonite (OMON) in the ratio of 70:30 by weight percent have been synthesized. X-ray diffraction (XRD) measurements were made to estimate the basal plane spacing between the layered structures of the montmorillonite (MON) before and after it was organically modified and also for the composite. The increment in basal spacing of 1.758 nm indicated that intercalation of ENR-50 chains occurred in the silicate layers with the ammonium ion being attached to the layers after the modification. TSC measurements indicated that the intercalation resulted in a suppression of the $\alpha $  peak of the ENR around -25 °C which is also referred to as the T g of the material. Two new and broader peaks around 30 °C and 73 °C appeared in the composite. The suppression of the peak may be interpreted as a result of the increasing rigidity due to the three-dimensional network of physical links formed.

A synthetic route is presented for the preparation of a gold film in the presence of UV-radiation. Methoxypolyethylene glycol, a water-soluble polymer, was used as the reducing agent of gold ions in the presence of an ultra-violet source, and gold nanoparticles resulted. During stirring, a centrifugal force is generated at the center of the solution (at the point where the meniscus is at its lowest level with respect to the vertical orthogonal). At this point, the nanoparticles coalesce and form a self-assembly of smaller subunits that ultimately forms a film like network.

The exchange charge model of the crystal field is applied to calculate the complete energy level scheme of the Cr4+ ions in Y3Al5O12 using $D_{2d}$  symmetry at the Cr4+ position. Mixture of the spin-triplet states arising from the  $^{3}F$ and $^{3}P$ terms of the 3d 2-electron configuration is shown to have a profound effect on the energy levels sequence. Large splittings of the orbital triplets originating from the “parent” Td symmetry are explained by large contribution of the low-symmetry component of the crystal field. Huang-Rhys parameter and effective phonon energy are evaluated from the experimental spectroscopic data available in the literature. Temperature-dependent probability of the nonradiative transition between the ground and first excited states is drawn; the emission band shape is obtained using the single configuration coordinate model.

The phase diagram of nanoparticles is known to be a function of their size. Since this dependence is also a function of the surface to volume ratio and of the surface tensions, it is expected that it varies with the shape of the nanoparticles. The variation of the melting temperature of polyhedral elemental nanosolids is studied theoretically. It turns out that, in most cases, the size variation of the melting temperature of a sphere is less than for the other shapes. However, there is no general rule regarding the order of the shape parameters of the polyhedra.

The aim of this paper is the modeling of a dielectric barrier discharge at atmospheric pressure, in the Townsend regime. This model is based on an equivalent electrical circuit. It takes into account the main physical phenomena of the discharge. This model allows to have a general view of the process and to study the influence of the power supply on the discharge. It is also an interesting tool for the power supply design and the process optimization.