Measurements are presented of the magnetoelectric (ME) coupling of nontoxic lead-free multiferroic composites 0.4CoFe2O4-0.6[0.948(K0.5Na0.5)NbO3-0.052LiSbO3]. The composites are found to exhibit an interesting dielectric response under a dc magnetic bias field. The positive magnetodielectric behavior and its strong frequency dependence in the composite could be related to magnetoresistance and the Maxwell-Wagner effect. The ME effects are strongly dependent on the driving field frequency and dc magnetic bias field. The frequency and magnetic field dependence of direct and converse ME coefficients are related to the relative dielectric constant and the variation in the piezomagnetic coupling with magnetic field, respectively. In addition, the dependence of direct and converse ME coefficients on frequency and magnetic field is quite similar in this multiferroic particulate composite.

The I-V characteristics of AlGaN/GaN high electron mobility transistors in the temperature range between 100 K and 300 K are studied. It is found that both the maximum drain-source current and transconductance decrease with the increase of temperature. Decrease of the electron mobility with increasing temperature is considered to be the main cause for that condition. The threshold voltage shows a forward shift, which can be explained by the increase of Schottky barrier with increasing temperature. It is found that at VGS = 0 V the drain-source current reduces with the ascending temperature, which should be due to the variation of the electron mobility with the temperature. While at VGS = −5 V the drain-source current is found to increase with the ascending temperature, it is suggested to be caused by the positive temperature coefficient of the electron transport in the depleted region.

The present paper introduces the principles of the Impedance Spectroscopy technique, as an important method in the characterization of the discrete materials working in real conditions in circuits. The method was firstly verified by using an RC series-parallel circuit and then was exemplified in studying two types of (Ni, Zn) ferrite ceramics.

In this article, the experimental results obtained in our laboratory for the last 10 years and related to the reactive Ionized Physical Vapor Deposition (IPVD) processes are reviewed. Titanium oxide and titanium nitride thin films were chosen as case studies. The titanium-based thin films were synthesized from a pure titanium target sputtered in a mixture of argon and reactive gas (oxygen or nitrogen). Two IPVD processes were investigated namely (i) reactive magnetron sputtering amplified by a superimposed secondary inductively coupled plasma and (ii) reactive High-Power Impulse Magnetron Sputtering (HiPIMS). These researches were dedicated to the understanding of the plasma and plasma-surface interaction chemistries by using advanced plasma diagnostic techniques such as energy-resolved mass spectroscopy, time-resolved emission and absorption spectroscopy. The relationships between the plasma chemistry and energetics and the properties of the thin films are emphasized.

p-Type thin films of copper-strontium oxide (Cu-Sr-O) have been deposited by e-beam evaporation technique on microscopic glass substrates. A study of optical, electrical and structural properties was performed on the thin films, varying temperature of annealing. Amorphous Cu-Sr-O films were obtained at low temperature. Partially polycrystalline films were obtained at high temperature of 550 °C with transparency over 72% at wavelength from 600 to 700 nm in the visible region and 83% in the near infrared region (λ = 1800:2500 nm). The optical band gap was estimated to be ~3.5 eV. The Seebeck coefficient measurements showed that the as-deposited films represented n-type conduction and with annealing temperature these films converted to p-type. The electrical conductivity measurements at room temperature of annealed films at temperature of 550 °C represented the best value about 2 S/cm. The other optical parameters such as refractive index, extinction coefficient, dielectric constant and cutoff wavelength were studied as a function of annealing temperature.

We argue the possibility of realization of a polarization-insensitive all-optical switching in a planar metamaterial composed of a 4-fold periodic array of two concentric metal rings placed on a substrate of nonlinear material. It is demonstrated that a switching may be achieved between essentially different values of transmission near the resonant frequency of the high-quality-factor Fano-shape trapped-mode excitation.

We continue the research of low-pressure capillary discharge lamps of 500 μm in radius in Ar/Hg, Kr/Hg and Xe/Hg mixtures. In the previous paper, an experimental approach which combines the optical emission spectroscopy (OES) and tomographic methods was developed to study the capillary discharge. The present work is focused on interpretation of the tomographic reconstruction results for understanding the physical processes occurring in a capillary plasma. Analyzing the results of reconstruction, it was concluded that the radial profiles of Ar, Kr and Xe emission coefficients are in a good agreement with the Schottky theory. According to the Schottky model, ionization processes in plasma are balanced by electrons and ions transfer to the wall due to ambipolar diffusion. Using the Schottky model, the electron temperature in an Ar/Hg capillary lamp was estimated. The value of the temperature was higher in comparison with that in a large-scale Ar/Hg discharge. A simplified model describing the excited atomic states kinetics is analyzed. This model agrees with all radial profiles of emission coefficients, obtained by using a tomography approach, except one for mercury line of 546.07 nm in the Ar/Hg capillary lamp. We suppose that the simplified model did not include the processes which were important for the mercury population balance in Ar/Hg mixture. It was proposed that the transfer of high-excited mercury atoms may play an appreciable role in the Ar/Hg capillary discharge.

The current-voltage characteristics of Cu-nMoSe2 Schottky diodes measured over a wide temperature range 50 < T <300 K have been interpreted on the basis of thermionic emission mechanism assuming Gaussian barrier distribution. A decrease in the experimental barrier height Φb0 and an increase in the ideality factor n with a decrease in temperature have been explained on the basis of barrier height inhomogeneities at the metal-semiconductor interface. It is proven that the presence of a distribution of barrier heights is responsible for the apparent decrease of the zero-bias barrier height. The voltage dependence of the standard deviation causes the increase of ideality factor at low temperatures. The mean barrier height Φb0 = 1.05 eV and the Richardson constant A* = 89.7 A cm−2 k−2 have been calculated by means of the modified Richardson plot. The value of the Richardson constant found is much closer than that obtained without considering the inhomogeneous barrier heights with that of the theoretical value.

A self-consistent kinetic model was developed in order to study the production of active species in Ar-O2 surface-wave microwave plasmas with a relatively small N2 addition. It is shown that the Ar-O2-N2 mixture produces efficiently the same active species as an Ar-O2 discharge, including oxygen atoms, metastable O2(a1∆g) molecules and the VUV emitting Ar(4s) states. Furthermore, active N-containing species are additionally produced, in particular N atoms and NO ground-state and excited molecules, which makes the ternary mixture very interesting for numerous plasma applications.

Use of microorganism as a novel and eco-friendly strategy to production of nanomaterials is an important aspect of modern nanotechnology. Biosynthesis of quasi-spherical silver nanoparticles (Ag-NPs) has been investigated using Pseudomonas aeruginosa. We observe that silver (Ag+) ions when exposed to P. aeruginosa biomass are reduced in solution, thereby leading to the formation of Ag-NPs. Quasi-spherical shape and nearly well distribution and FCC crystal structure of Ag-NPs were confirmed by XRD pattern, STM and TEM micrographs. UV-Vis spectra show a surface plasmon resonance (SPR) band at ~ 435 nm.

The temperature dependence of the pulse length was measured for an 18-fold segmented n-type germanium detector in the temperature range of 77–120 K. The interactions of 122 keV photons originating from a 152Eu source were selected and pulses as observed on the core and segment electrodes were studied. In both cases, the temperature dependence can be well described by a Boltzmann-like ansatz.

In this paper we investigate and optimize the design of an OR gate all optical circuit based on silicon photonic crystals. The OR gate is formed by two ring resonators placed between three waveguides, obtained by removing specific rods from the photonic-crystal structure. To optimize the design parameters, the fill factor (r/a), corresponding to the ratio between the rod radius “r”’ and the inter-rod lattice “a’’, was varied using the plane wave expansion method. The Q-factor has been determined to achieve the optimal performance of the ring resonators. The optical properties and the normalized transmission spectra for the proposed gate based on the photonic-crystal ring resonators have been calculated by the finite difference time domain (FDTD) technique. We have noted that the two rings must be symmetric to the central waveguide to obtain the OR gate function in the output.

The present paper shows for the first time in the literature a complete 2D simulation of the ozone production in a DC positive multi-tip to plane corona discharge reactor crossed by a dry air flow at atmospheric pressure. The simulation is undertaken until 1 ms and involves tens of successive discharge and post-discharge phases. The air flow is stressed by several monofilament corona discharges generated by a maximum of four anodic tips distributed along the reactor. The nonstationary hydrodynamics model for reactive gas mixture is solved using the commercial FLUENT software. During each discharge phase, thermal and vibrational energies as well as densities of radical and metastable excited species are locally injected as source terms in the gas medium surrounding each tip. The chosen chemical model involves 10 neutral species reacting following 24 reactions. The obtained results allow us to follow the cartography of the temperature and the ozone production inside the corona reactor as a function of the number of high voltage anodic tips.

The effect of coupling between levels in quantum wells or quantum dots is described in Green’s function formalism. The structure eigenvalues are shown to have a Brillouin-Wigner continued-fraction expression that allows to give a general and intuitive meaning to levels coupling, described in terms of an off-diagonal self-energy. The concept of coupling is linked to a general potential matrix and can be given the same mathematical form for all kinds of coupling (inter- and intra-quantum dot and quantum well), in which off-diagonal self-energy contributions assume each time a different conceptual meaning. Furthermore, the same scheme, based on off-diagonal self-energies, allows to evaluate renormalization contribution due to each structure energy level in a natural and easy way.

Results of computer simulations describing an interaction between a low-temperature multicomponent plasma and an immersed metal substrate are presented. For this purpose, computer model of volume processes in a DC glow discharge in Ar-O2 mixture and a particle model of plasma-solid interaction were created. The interaction is studied not only in case when a constant value of voltage bias on the immersed substrate is kept, but also when sinusoidal voltage bias is applied. A pressure dependence of the sheath region in electronegative plasma is shown, too.

The DC electrical measurements on Au/ZnTPP/Au planar structure showed two regimes of electrical conductivity depending on temperature, at low temperatures the activation energy is 0.24 eV and variable range hopping in localized states near Fermi level is the operating conduction mechanism, at high temperatures the activation energy is 0.998 eV and phonon-assisted hopping of small polarons is the operating conduction mechanism. The capacitance-voltage measurements on Au/ZnTPP/n-Si/Al showed that the formed junction is linearly graded one. The thickness of depletion region in ZnTPP and n-Si has been determined and the built-in potential is 0.85 V. The concentration gradient of holes and electrons is 2.6 × 1020 holes/m4 and 0.3 × 1020 electrons/m4, respectively. Thermoelectric power measurements showed that ZnTPP films are p-type semiconductor and polaron activation energy is 0.37 eV. A hybrid solar cell of Au/ZnTPP/n-Si/Al had been constructed by growing ZnTPP film via thermal evaporation technique on n-Si wafer. Dark current-voltage measurements of the device at different temperatures showed that there are three conduction mechanisms operating in the device. The dominance of any of them depends on applied potential. The photovoltaic properties of Au/ZnTPP/n-Si/Al hybrid solar had been evaluated.

A novel characterization method using artificial neural networks is presented. This method allows one to determine the intrinsic permeability tensor of ferrite thin-films from S-parameters measurements. Neural networks, efficient to solve inverse problems, are used to compute the permeability tensor components μ and k. This optimization technique is used to find extremely complex functions between inputs and outputs and can be successfully applied on our magnetic thin-film characterization problem. Results of our networks are compared to a theoretical model. A great number of both simulated and measured tests have been performed on many magnetic thin-films. Neural network processing leads to a rapid and robust method for predicting the magnetic characterization of thin-films in microwave range.

Nanocrystalline La0.85Na0.15MnO3 ceramics were prepared via a novel method based on chemical solution combustion. Effects of sintering temperature on electrical transport and magnetic properties were systematically investigated. It was found that the resistivity increases, the magnetization decreases, and the metal-insulator transition temperature shifts toward low temperatures with the decrease of the sintering temperature. In addition, the magnetization of the samples sintered at low temperatures exhibits a broadened paramagnetic-to-ferromagnetic transition temperature. The low field magnetoresistance evidently increases with decreasing the sintering temperature due to the spin-polarized intergranular tunneling.

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.