LaFe1-xMnxO3 (x ≤ 0.5) polycrystals have been prepared using solid-state reaction technique and characterized by X-ray diffraction and electrical transport. XRD data suggest orthorhombic structure for both pure and Mn-doped compositions with space group Pbnma. However, unit cell dimensions are found to decrease with increase in Mn concentration. Resistivity data have been fitted with variable range hopping (VRH) model, from which different parameters like density of state at Fermi level N(Ef), hopping energy (Eh), and hopping distance (Rh) were estimated. It was observed that substitution of Mn in the series leads to the increase in conductivity of the samples with conduction being controlled by the disorder-induced localization of charge carriers.

The high Al content AlGaN epilayers have been obtained by metalorganic chemical vapor deposition (MOCVD), and the optical property has been investigated by photoluminescence (PL) spectroscopy. Longitudinal-optic (LO) phonon mode has been studied by Raman scattering. Further analysis shows that the edge dislocation is an important factor influencing optical quality of AlGaN epilayers, and it also shows that the correlation between the A1 (LO) polar modes and the edge dislocation is intensive, which may be expected to become a characterization method of the related crystal defects.

This work provides a novel approach for enhanced radiative transitions in silicon microelectronics devices. A process based on hot carrier injection is monitored for the creation of a low dimensions defect layer near the emitter-base interface of bipolar transistors. New energy levels are induced together with a potential barrier. Carrier confinement is correlated with the potential barrier height. The increase of light emission is related to high injection effects in the junction. Results present an advance toward Si-based optoelectronic devices.

A nonlinear optical crystal of L-valine was grown from an aqueous solution containing a small amount of phosphoric acid by the slow evaporation method. The grown crystal was characterized by a single crystal X-ray diffraction to determine the unit cell parameters. The powder X-ray diffraction analysis also confirmed the lattice parameters to be a = 9.6687(7) Å, b = 5.2709(4) Å, c = 12.0371(10) Å and β = 90.805(4)°. The results of the Inductively Coupled Plasma Optical Emission Spectrometry (ICPOES) indicate the presence of a small amount of phosphorus in the grown crystal. The Vickers micro hardness test was performed to study the mechanical strength of the crystals. Chemical etching studies were carried out to analyze the dislocation structure. The laser damaged threshold of the grown crystal was measured to be 11.11 GW/cm2 for 10 ns pulse at 1064 nm, which is higher than that of the standard nonlinear optical crystals like KDP. Second harmonic generation of the grown crystals was also 1.44 times that of KDP.

Series of CoxCr1−x thin films have been evaporated under vacuum onto Si(1 0 0) and glass substrates, x ranging from 0.80 to 0.88; these chemical composition values are provided by modeling Rutherford Backscattering (RBS) spectra using SIMNRA program. Thickness ranges from 17 to 220 nm. Microscopic characterizations of the films have been performed with X-ray diffraction (XRD) measurements. The samples have been annealed for 1 h at 700 °C. All the as deposited samples are polycrystalline, with an hcp structure and show a 〈0 0 0 1〉 preferred orientation. The annealed samples, on the contrary, present hcp and fcc phases. The as deposited films are under a compressive stress while the annealed films are under a tensile stress. Grain sizes increase with chromium content decrease and are higher for the annealed films. Excellent orientations of the CoCr crystallites around the normal to the film plane have been observed, the full width at half maximum (FWHM) ranging from 0.49° to 0.79°.

Epitaxial magnesium oxide (MgO) thin films prepared on Si(0 0 1) substrates revealed the contraction of its lattice constants along both out-of-plane and in-plane directions. X-ray Diffraction (XRD) verified the epitaxial growth with the relation of MgO(1 0 0) parallel to Si(1 0 0) [cubic on cubic growth] with large lattice misfit of ~22% instead of the relation of MgO(1 1 0) parallel to Si(1 0 0) [45° rotation growth] with lattice mismatch of ~9%. Although the domain epitaxy explaining the cubic on cubic growth is preferred in terms of crystallography, structural stability is not considered in the concept of the domain epitaxy. In order to explain the contraction of lattice constant from point of view of structural stability, ab initio method was used to evaluate all-electron total energy, and optimal lattice constant was estimated with point defects in the MgO structure.

Bismuth zinc niobate (Bi2Zn2/3Nb4/3O7) thin films were deposited by PLD on fused silica substrates at different oxygen pressures. The structural, microwave dielectric, optical and Raman characteristics of these thin films were systematically studied for both the as-deposited films and films annealed at 600 °C. The microwave dielectric constant at a frequency of 10 GHz of the annealed m-BZN films varied from 56 to 71, whereas the dielectric loss tangent varied from 1.8 × 10−4 to 3.5 × 10−4 as a function of deposition pressure. The as-deposited films exhibit refractive index in the range of 2.06–2.15 with an optical absorption edge value between 3.59 and 3.67 eV. The observed Raman scattering in m-BZN thin films was slightly shifted toward the higher frequency which reveals that the local lattice disorder changes whereas the structure remains the same monoclinic in thin film as well as in bulk.

SnO2 nanoneedles, nanorods and nanowires were synthesized at different temperatures, and their field emission properties were investigated in detail. On comparing the three nanostructures of SnO2, we find that the synthesis temperature has a prominent influence on the morphology, consequently affecting the field emission properties, especially the turn-on field and the emission current density. Among them, the SnO2 nanoneedle possesses the lowest turn-on field of 1.23 V/μm and the highest current density 2.19 mA/cm2 at 3.06 V/μm. The mechanism behind the influence of the synthesis temperature on the morphology and field emission properties of SnO2 nanostructures is discussed in detail. These results can be valuable for the application of SnO2 nanomaterial in the cathodes of field emission based devices.

Field emission (FE) properties of unstructured and patch-structured cathodes with randomly distributed and vertically aligned copper nanocones (Cu-NCs) are reported. The cones of ~28 μm height, 2.4 μm base diameter and 95–220 nm tip radius were fabricated by electrochemical deposition of Cu into conical channels of heavy-ion-irradiated and asymmetrically etched polycarbonate membranes. FE measurements of the unstructured cathodes with slowly-grown Cu-NCs of high number density (107 cm−2) and excellent mechanical stability yield stable currents up to 280 μA from an emission spot of 30 μm. For the structured cathodes with a triangular patch array of less dense Cu-NCs (<106 cm−2), well-aligned FE with ~90% efficiency is reproducibly achieved. A trade-off between low onset field (~22 V/μm) for sparsely grown Cu-NCs with sharp tips and high current limit (~100 μA) for densely grown ones with broader tips is observed. Possibilities for further optimization of such field emitters for cold cathode applications are discussed.

We presented an easy-to-control non-galvanic method for synthesizing CdSe-Ag2Seand CdSe-Ag coaxial hetero-nanotube arrays in anodic aluminum oxide (AAO) template, and investigated their optical properties. Cation exchange method was used to convert the CdSe nanotube arrays into the CdSe-Ag2Se nanotube arrays. Compared with the CdSe nanotubes, the photoluminescence (PL) intensity of CdSe-Ag2Se decreased and the PL lifetime prolonged, which was attributed to the redistribution of the exciton relaxation and recombination processes. In contrast, the CdSe-Ag hetero-nanotube arrays displayed a short PL lifetime, which was mainly due to the interaction and energy transfer between the CdSe and Ag. Our findings may have potential applications in design of the optoelectronic devices.

An experimental study of the delayed threshold phenomenon in a Vertical Extended Cavity Semiconductor Emitting Laser is carried out. Under modulation of the pump power, the laser intensity exhibits a time delay in the vicinity of the threshold. The evolution of this delay is measured as a function of the modulation frequency and is proved to follow the predicted scaling law. A model based on the rate equations is derived and used to analyze the experimental observations. A frequency variation of the laser around the delayed threshold and induced by the phase-amplitude coupling is predicted and estimated.

Using the density functional theory, we perform a full atomic relaxation of the bulk ferrite with 12.5% concentration of monoatomic interstitial Cr periodically located at the edges of the bcc Feα cell. We show that structural relaxation in such artificially engineered alloys leads to significant atomic displacements and results in the formation of novel highly stable configurations with parallel chains of octahedrically arranged Fe. The enhanced magnetic polarization in the low-symmetry metallic state of this type of alloy can be externally controlled by additional inclusion of nonmagnetic impurities like nitrogen. We discuss possible applications of generated interstitial alloys in spintronic devices and propose to consider them as a basis of novel durable types of stainless steels.

Single crystals of L-methionine-doped triglycine sulfate (LMTGS) were grown by the low temperature solution growth method. The influence of the dopant on the morphological changes has been studied and reported. The grown crystals were characterized using Laue X-ray diffraction, microhardness and polaroid absorption studies.

In this paper, based on ring-shaped cathode and cup-shaped axial magnetic field (AMF) anode configuration system, the current density distribution on the cathode surface was measured. Vacuum arc appearance also was observed by a high-speed camera. The experimental results showed that the current density on the cathode was of the order of 106–107 A/m2. For lower current (3 kA), the current density distribution was relatively uniform. For higher current (6 kA), due to the weaker AMF of cathode side, the arc was more seriously constricted and the current density distribution was more nonuniform, the current density of central area was much larger than that of other peripheral regions in the cathode surface. Compared with two cup-shaped AMF electrode systems, the current constriction was more significant for the same current and gap distance.

RF sputtered Zn metal films were processed at O2 plasma at various process conditions. The surface morphology of the processed films was characterized using SEM and AFM techniques. Dense and continuous film surface with good surface morphology were observed in all plasma processed films. The microstructure of processed Zn films was very much dependent on the process parameters especially the plasma power and gas flow rate. The effect of these parameters on particle size and surface roughness was examined carefully. The particle size of all processed films lay in between 23 and 70 nm. Noticeable change on surface morphology, particle size and surface roughness was observed with respect to process parameters. The observed sheet resistance was an evidence of the influence of process parameters especially process time on the electrical properties of processed films. In addition, the influence of surface roughness and particle size on electrical resistance was also discussed.

Documents decontamination using dry methods, less invasive than the wet ones implying toxic nocuous substances for cellulose-based materials, has been the object of numerous studies. In recent years mixed researchers teams have been studying the possibility of one-step document decontamination performed by a dry treatment, the risks of repeated wet manipulation thus being reduced. Among physical methods appropriate to this end, high-frequency cold plasma and corona effect can be mentioned. Our studies were carried out on samples taken from ancient books with no cultural heritage value. The decontamination efficiency and the impact on paper of the two types of treatments were determined by: microbiological analysis, scanning electron microscopy, FTIR, chromatic alterations and gloss determination. The above-mentioned procedures eliminate the use of chemical conservation substances, nocuous for the paper support. At the same time the health risk for conservators, restorers, archivists or archive’s users is removed.

Magnetohydrodynamics (MHD) describes the physical behavior of inductively coupled plasma (ICP). The goal of this paper is to provide a physical understanding of a process ICP torch using a resistive MHD model. This includes a basic description and derivation of the fluid model. Inductive plasma is treated as a continuous, conducting fluid that satisfies the classical laws of motion and thermodynamics. This model combines fluid equations, similar to those used in fluid dynamics, with Maxwell’s equations. Steady fluid flow and temperature equations are simultaneously solved (direct method) using a finite elements method (FEM). The electromagnetic field equations are formulated in terms of potential vector with applied voltage source, so this model is physically more consistent, a more accurate and a faster simulation. The governing resistive MHD equations for an inductive plasma flow under local thermodynamic equilibrium (LTE) and laminar flow are presented, with appropriate boundary conditions. The model enabled to obtain the electromagnetic fields, temperature and flow velocity distributions also allows the determination of the electric parameters such as impedance of the plasma torch, total power, eddy losses, etc.

In many areas of soft and hard matter research science, the amount of material to investigate is rather limited. Partly because the fabrication of larger samples is too expensive or not feasible, yet, partly because the interesting features depend on the size. The aim of this work is to develop a neutron reflectometer optimized for small samples and specular measurements. We present a new concept which is based on state-of-the-art neutron optical elements and which allows studies of samples 100 times smaller than with previous instrumentation. The concept is to use an elliptically focusing guide in the sample plane, and a converging beam geometry in the scattering plane. The latter allows for the simultaneous measurement of a wide angle-of-incidence range simultaneously. Here we report on the prototype setup and first measurements, where we reached a reduction of counting time by one order of magnitude. If a complete instrument is built based on the presented principle, another order of magnitude can be expected.

A 3 kJ plasma focus device was used to study the influence of the soft X-ray on live microorganisms. When Saccharomyces cerevisiae – (yeast) was treated with a dose of 65 mSv of the X-ray radiation (14 shots), no difference in the fertility activity between the control probe and the sample was observed. Also no change in the survival enzyme activity was found after irradiation through a 100 μm Al foil of another type of yeast – Kluyveromyces marxiamus. The irradiation of the Chlamydomonas reinhardtii samples by the PF-X-ray emission through 20 μm Al foil with a dose of 11 mSv produces a considerable change of the photosynthesis parameters. This result is similar to the results of previous studies with plasma focus radiation where strong effects were derived with low doses but with a high dose power.

This paper proposes a generally applicable numerical algorithm for the simulation of two dimensional electrode shape changes during electrochemical machining processes. The computational model consists of two coupled problems: an electrode shape change rate analysis and a moving boundary problem. The innovative aspect is that the workpiece shape is computed over a number of predefined time steps by convection of its surface with a velocity proportional and in the direction of the local electrode shape change rate. An example related to the electrochemical machining of a slot in a stainless steel plate is presented here to demonstrate the strong features of the proposed method.