In radiofrequency (RF) helicon discharges the electromagnetic power is transferred from the RF field irradiated by the antenna to the plasma medium by means of plasma-wave coupling of the electromagnetic wave with the electrons. For the common industrial frequencies of tens of MHz, and for typical pressures of few Pascals, the power deposition occurs mostly at the edge of the discharge. In these conditions, ionization and electron heating occur in a layer close to the chamber walls, where a consistent fraction of the plasma is rapidly lost by diffusion toward the surface. The remaining fraction of plasma diffuses inward toward the center of the discharge, setting up a uniform and almost flat density profile, used in applications. A one-dimensional model considering both the plasma-wave coupling of the electrons with the RF wave and the macroscopic transport of ions and neutrals along the radial dimension of a cylindrical processing chamber has been derived and used to evaluate the profiles at equilibrium. The model has been validated through Langmuir probe measurements in helicon processing chambers. The numerical model has then been used to study the power-coupling behavior of the discharge when the pressure of the neutral gas is decreased. When the Knudsen number of the neutral gas approaches unity and in conditions of slightly magnetized discharge, the power deposition shifts from being edge-localized to center-localized, thus reducing the particle fluxes toward the walls and increasing the efficiency of the coupling.

The effect of vacuum heat treatment in the temperature range between 100 and 400 °C on the morphology and optical properties of thermally evaporated thin gold films with mass thickness from 8 to 80 nm was studied by AFM, TEM and optical spectroscopy in the spectral region of localized (surface) plasmons excitation. Our investigations have shown that change of film morphology induced by thermal annealing depends strongly on film thickness. Thus, optical behavior of thin metal films is modified due to being induced by recrystallization film permittivity changes as well as transformation of film morphology. The considered processes might be crucial for thin film optical properties determination and must be taken into account for the choice of adequate thin film optical model. Besides that, post-fabrication thermal annealing enables a wide modification of thin metal films morphology and surface plasmon resonance parameters, offering new possibilities for metal substrates design enhancing surface electromagnetic fields and therefore SERS, SEIRA, luminescence effects.

This work concerns the assessment of the surface temperature of copper anodes submitted to an electric arc in a non-stationary regime in air at atmospheric pressure. An infrared camera is used to measure the decrease of the surface temperature just after a very fast controlled arc extinction. Results are presented for different mean values of the arc current intensity (30, 70 and 130 A) with an electric arc duration in the range of 2–5 ms. The temperature decrease after the arc extinction allows an assessment of the surface temperature just at the moment of the arc switching off. In the present experimental conditions the mean temperatures reached for copper anodes are in the range of 750–1200 °C according to the arc current intensity values. Comparison between experimental results and a numerical modeling of the electrode heating allowed one to assess the surface power balance. The values for the volt equivalent are found about 12 V and the values for the surface power density are found to be near 2 × 109 W/m2.

A hydrodynamic model was developed to simulate the flow and the heat transfer with the gas/plasma system produced by a microwave-driven (500–900 W at 2.45 GHz) axial injection torch, running in atmospheric pressure helium at 3–9 L min−1 input gas flows. The model solves the Navier-Stokes’ equations, including the effect of the plasma upon the momentum and the energy balance, in order to obtain the spatial distributions of the gas velocity and temperature. The model predicts average gas temperatures of 2500–3500 K, in the same range of those obtained by optical measurements. Simulations show that the plasma influences the gas flow path and temperature, promoting an efficient power transfer.

This paper deals with the experimental characterization of discharges propagating over insulators of epoxy and glass, immersed in a gas or a gaseous mixture, under lightning impulse voltages (1.2/50 μs), using a point-plane electrode arrangement. The gases and mixtures we considered are SF6, N2, CO2, SF6-N2 and SF6-CO2. The morphology of creeping discharges and their final lengths are investigated versus the kind of insulator material, the amplitude and polarity of the voltage, the type of the gas (resp. mixture) and its pressure. It is shown that the shape of discharges and their final (stopping) lengths Lf depend significantly on the solid insulator and the type of gas. For given solid and gas, Lf increases quasi-linearly with the voltage and decreases when the gas pressure increases. The discharges do not always present a radial structure as reported in the literature. For given voltage and pressure, Lf is longer when the point electrode is positive than when it is negative while the initiation voltage of discharges is higher with a negative point than with a positive one; and Lf is longer with glass than with epoxy. Lf is shorter in SF6 than in CO2 or N2. On the other hand, the increase of SF6 content in SF6-CO2 mixture leads to a significant decrease of Lf. Therefore, the addition of small concentration of SF6 in a given gas mixture improves the dielectric strength of insulating structure.

The laser-induced fluorescence spectroscopy on a micro-flow discharge with water electrode is carried out in order to investigate OH radicals. The branches P2(6), P1(4) and P2(3) of X2Π, ν′′ = 0−A2Σ, ν′ = 1 transition are used. Laser-induced fluorescence is used in order to estimate the density of OH radicals and density of water vapor in a core of the plasma. Sputtering yield of H2O from the liquid electrode is calculated based on experimental data. It is revealed that plasma core consists of 8–10% of water in both Ar and He discharges. The density of OH radicals in the micro-flow He plasma is higher than in the glow discharge with liquid electrode and in Ar micro-flow discharge due to constriction of the positive column and different mechanism of the OH radical production.

The local structures and the EPR g factors g║ and g┴ are theoretically studied for the tetragonal Ti3+-Vo centers in BaTiO3 bulks and thin films using the perturbation formulas of the g factors for a 3d1 ion in tetragonally elongated octahedra and compressed tetrahedra, respectively, based on the cluster approach. For the Ti3+-Vo center in BaTiO3 bulks, the impurity Ti3+ suffers the displacement away from the oxygen vacancy Vo by about 0.15 Å along the C4 axis due to the electrostatic repulsion of the Vo. Nevertheless, the Ti3+-Vo center in BaTiO3 thin films may exhibit the tetragonally compressed tetrahedron, characterized by the bond angle 55.88° larger than that (≈54.74°) of an ideal tetrahedron. The quite different g factors (especially g anisotropies Δg = g║ − g┴) for the two kinds of samples are discussed, in view of the dissimilar bonding or coordination environments (i.e., incomplete bonding in the thin films may lead to the lower coordination number).

The rate coefficient of the ternary association reaction H++2H2→H3++H2$ {\mathrm{H}}^{+}+2{\mathrm{H}}_2\to {\mathrm{H}}_3^{+}+{\mathrm{H}}_2$ has been measured at a temperature of 11 K using a 22-pole ion trap. The measurements were made over the density range of 0.5–10 × 1013 cm−3 using normal hydrogen (with 1/4 p-H2 and 3/4 o-H2). We measured an apparent binary reaction rate coefficient and from the obtained linear dependence on the hydrogen density we calculated the ternary reaction rate coefficient k3 = (3 ± 1) × 10−29 cm6 s−1. From the measured data we can deduce that there exists very slow radiative association with the rate coefficient of the order of kr ≲ 3 × 10−16 cm3 s−1 at 11 K.

This paper deals with new neural networks based harmonics detection approaches to minimize hardware resources needed for FPGA implementation. A simple type of neural network called Adaline is used to build an intelligent Active Power Filter control unit for harmonics current elimination and reactive power compensation. For this purpose, two different approaches called Improved Three-Monophase (ITM) and Two-Phase Flow (TPF) methods are proposed. The ITM method corresponds to a simplified structure of the three-monophase method whereas the TPF method derives from the Synchronous Reference Frame method. Indeed, for both proposed methods, only 50% of Adalines with regard to the original methods is used. The corresponding designs were implemented on a FPGA Stratix II platform through Altera DSP Builder® development tool. After analyzing those two methods with respect to performance and size criteria, a comparative study with the popular p-q and also the direct method is reported. From there, one can notice that the p-q is still the most powerful method for three-phase compensation but the TPF method is the fastest and the most compact in terms of size. An experimental result is shown to validate the feasibility of FPGA implementation of ANN-based harmonics extraction algorithms.

We have synthesized CdS NCs (NCs) by a thermochemical approach. CdSO4 and Na2S2O3 were used as the precursors and thioglycolic acid (TGA) was used as capping agent molecule. The structure and optical property of the NCs were characterized by means of XRD, TEM, UV-visible optical spectroscopy and photoluminescence (PL). XRD and TEM analyses demonstrated hexagonal phase CdS NCs with an average size of around 2 nm. Synthesized NCs exhibited a band gap of about 3.21 eV and showed a broad band emission from 400 to 750 nm centered at 503 nm. This broad band emission is related to surface states of CdS and our results showed that the emission peak can be attributed to the interstitial sulfur. The best attained photoluminescence quantum yield of the NCs was about 11%. At the same conditions the PL quantum yield of TGA capped NCs was about 20 times higher than that of TG capped NCs.

New flowing afterglow apparatus, Cryo-FALP, was built to study ternary Collisional-Radiative Recombination (CRR) of Ar+ ions with electrons in He/Ar afterglow plasma at temperatures 40–200 K. The obtained ternary recombination rate coefficient at 57 K is KCRR = (3 ± 1) × 10−17 cm6 s−1. It is the first time that the KCRR was measured below 77 K. The measured temperature dependence KCRR ~ T(−4.5 ± 0.4) is in a good agreement with theoretical prediction.

Recent theoretical progress in understanding the nonlinear optical response of noble metal nanocomposite materials with an enhanced third-order nonlinear susceptibility was reviewed. The enhanced third-order nonlinear susceptibility results from the surface plasmon resonance (SPR) of noble metal nanoparticles. And then the enhancement strongly depends on irradiation light wavelength, concentration and surrounding medium of noble metal particles. Furthermore, their applications as optical switchers with ultrashort time response and optical limiters of intense laser radiation were also reviewed. Moreover, the enhancement mechanism of third-order nonlinear susceptibility, and physical process was further discussed in detail, which was very important for further improvement of third-order nonlinear susceptibility and application on optical switchers and optical limiters for noble metal nanoparticles.

Multi-band metamaterial absorber (MA) was proposed at the microwave frequency ranges, which were composed of cave-cross resonator (CCR) with different geometric dimensions, dielectric substrate and continuous metal film. Microwave experiments demonstrated the maximum absorptivity of single CCR structure to be about 99% around 9 GHz. Numerical simulations confirm that the MA could achieve very high absorptivity at wide angles of incidence for both transverse electric (TE) wave and transverse magnetic (TM) wave. Importantly, numerical simulations demonstrate that the MA could achieve perfect multi-band absorption by assembling the multi-CCR structure with different geometric parameters in a coplanar.

The potential of simultaneous to etching deposition for surface roughness control is investigated with a stochastic modeling framework for morphology evolution in (2+1) d. It is predicted that ion-driven etching under simultaneous deposition of etch-inhibitors (e.g., impurities coming from the wafer surroundings, the reactor walls, or the plasma bulk) not only induces roughness formation with a linear dependence on time, but can also induce periodic dots on the surface. The surface roughness can be controlled by regulating the amount of etch-inhibitors.

The atomic and electronic properties of the substitutional phosphorus (P) on the Si(1 1 1)-(2 × 1) surface have been studied by using the ab initio density functional theory (DFT) based on pseudopotential approach. We have considered four different possible binding sites for P adatom in the π-bonded chain labeled sites 1–4 respectively in Figure 1. We have found that the site 1 position in the π-bonded chain was energetically more favorable than the other binding sites, by about 0.1 eV/adatom. We have also calculated the corresponding surface electronic band structure and found one surface state, labeled C, in the fundamental band gap of Si(1 1 1)-(2 × 1) surface. Our calculations show that the P/Si(1 1 1)-(2 × 1) surface has a metallic character in the nature. In order to explain the nature of this surface state in the bonding geometry, we have depicted the total and partial charge density contours plots at the J¯$ \bar{J}$ point of the surface Brillouin zone (SBZ).

In this article, the saturation optical intensity in electroabsorption modulators (EAMs) at 1.55 μm with asymmetric intra-step-barrier coupled double strained quantum well (AICD-SQWs) active region is theoretically investigated and compared with intra-step quantum well (IQW) structure. For this purpose, the two basic escape processes, thermionic emission and tunneling, are considered and the escape times of photogenerated carriers both for the AICD-SQW and the IQW based on the InGaAlAs material system are calculated and compared. From the reduction in escape times, improvement in the saturation optical intensity due to the introduction of the AICD-SQW structure is estimated to be greater than 6 dB at high fields.

The distribution patterns of the second-harmonic generation (SHG) enhancement factor in the incident plane of silver nanoshell at resonance frequencies have been studied by using electrostatic approximation. The mapping feature of SHG corresponding to double frequency local field enhancement is different from that of fundamental case. At longer wavelength (SHG enhancement resulting from local field at double frequency), large SHG enhancements are only observed outside the shell. However, hot spots also take place inside the silver shell at shorter wavelength (SHG enhancement resulting from local field at fundamental frequency). The effect of outer surrounding media on the SHG corresponding to local field at fundamental frequency is also very different from that of double frequency. It has been found that the azimuth angle dependent SHG at shorter wavelength split into two maximums when the surrounding dielectric constant is increased, which is absent for SHG at longer wavelength.

Silicon carbide films were deposited at two deposition temperatures 350 °C and 450 °C by means of ECR plasma reactor with two gas mixtures: (1) gas mixture, SiH4 (5 sccm), CH4 (14 sccm), Ar (6 sccm), NH3 (2 sccm) and (2) gas mixture SiH4 (5 sccm), CH4 (14 sccm), H2 (6 sccm), NH3 (2 sccm). The concentration of species in the SiC films was determined by Rutherford backscattering spectrometry (RBS) and elastic recoil detection (ERD) analytical method simultaneously. Chemical compositions were analyzed by infrared (IR) spectroscopy. Photoluminescence (PL) spectra were measured at 300 K. The RBS and ERD results showed that the concentrations of Si and C in the films are practically the same. The concentration of hydrogen decreased from 30 to 22 at.% with an increasing sample deposition temperature. The films contain a small amount of nitrogen and oxygen. IR results showed the presence of Si-C, Si-N, Si-H, C-H and Si-O bonds. PL results showed the decrease of the PL intensity with an increasing sample deposition temperature.

This paper investigates the performance of hydrogenated amorphous carbon (a-C:H) films as protective coatings for a forming tool made from AISI M2 steel coated with a titanium nitride (TiN) PVD commercial layer. The samples were initially cleaned in ultrasonic baths and subsequently in a plasma ablation procedure. Films were then deposited by plasma immersion ion implantation using 91% of acetylene and 9% of argon at a total pressure of 5.5 Pa. Samples were biased with high voltage negative pulses, P (T = 3.33 ms, pulse on-time: 0.03 ms, pulse off-time: 3.30 ms and application rate: 299 Hz) with amplitudes varying from 1.000 to 4.000 V. The chemical structure and composition of the films were evaluated by infrared spectroscopy. The roughness was determined by profilometry while the surface topography and morphology were investigated by atomic force microscopy and scanning electron microscopy, respectively. The friction coefficient was determined by the ball on disk technique. A decrease in the proportion of C-H and O-H groups was observed while the concentration of dangling bonds enhanced with increasing P. Sharp structures were detected on the film surface affecting roughness in two different ways: it increased with enhancing pulse magnitude in the smoothest substrate (AISI M2) and decreased in the roughest one (AISI M2-TiN). The best tribological result was found for the sample deposited with 3.600 V of bias onto TiN-AISI M2 steel.