N-doped Cu2O thin films have been deposited on glass substrate by reactive magnetron sputtering method under various N2/O2 flow ratios from 0 to 1.0. The structural and electronic properties of Cu2O:N films were investigated by X-ray diffraction (XRD), four-point probe and Hall effect measurements. XRD pattern showed that crystalline structures of all the samples retained single phase of Cu2O with the increase of N2/O2 flow ratio from 0 to 1.0. However, the crystalline quality of Cu2O:N films reduced with the increase of the N2/O2 flow ratio. The phenomenon of peak shift of Cu2O(1 1 1) implied that N atoms have been doped into Cu2O film. The square resistance of Cu2O:N films linearly decreased from 28.1 to 1.5 (104 Ω/☐) with the increase of N2/O2 flow ratio from 0.2 to 0.6 initially, and then it changed slowly with the increase of N2/O2 flow ratio from 0.8 to 1.0. Hole density of Cu2O:N films with various N2/O2 flow ratios from 0 to 0.6 was measured using the Van der Pauw method. All the samples are p-type, and the hole density of Cu2O:N films was enhanced from 1.2 × 1016 cm−3 to 3.1 × 1019 cm−3 with the increase of N2/O2 flow ratio from 0 to 0.6. The experimental results demonstrated that N doping was an effective method to enhance hole density of p-type Cu2O film.

A novel composite is fabricated through hybridizing graphene with polypyrrole (PPY) nanotube and manganese dioxide (MnO2) nanotube to comprehensively utilize the electrical double layer capacitance and pseudo-capacitance. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy are employed to characterize its structure. The SEM and TEM images illustrate that graphene/PPY nanotube/MnO2 nanotube composite (GPM) presents interconnected structure. The result of Raman analysis demonstrates the intimate interactions among PPY, graphene and MnO2. In addition, cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) techniques are used to measure the electrochemical properties. It is revealed that GPM presents excellent high-rate performance and its capacitance is as high as 469.5 Fg−1 at a current density of 0.3 Ag−1, higher than that of PPY and chemically reduced graphene sheet as well as the materials reported in the literature. Furthermore, long-term charge-discharge cycle test confirms that the fabrication of GPM can effectively merge the merits of graphene, PPY and MnO2. Additionally, EIS analysis illustrates that the presence of conductive graphene as well as the intimate interactions among graphene, PPY and MnO2 lead to the good electrochemical stability.

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.

In this paper, colloidal silver nanoparticles were prepared by chemical reduction of AgNO3 and pure Sn in a new and simple method. The type of crystallite lattice and the size of nanopowders were estimated by X-Ray Diffraction (XRD) analysis. The geometric, heterogeneous and mixing structure of synthesized nanopowders were studied by Scanning Electron Microscopy (SEM). Optical properties such as plasmon absorption and frequency of soluble colloidal nanopowders in two solutions of distilled water and oil were investigated by UV-Visible spectroscopy, which was developed to calculate the absorbance spectra of nanoparticles solution containing a size distribution of particles using the Mie theory. Dipole and quadrupole plasmons related to molecular structure of water and oil were found by absorbance spectra. Also, Differential Scanning Calorimetry (DSC) analysis was used for determining the thermal behavior, endothermic and exothermic peaks of Ag nanopowder.

Effects of admixing argon to air DB discharge, at atmospheric pressure, on the electrical and optical emission characteristics have been studied. Optical emission spectroscopy is used to investigate the effect of argon admixing on the emission intensity of the nitrogen second positive systems (300–450 nm) and its relative population of N2(C3Πu,v′) state. Also the vibrational temperature of the nitrogen second positive systems has been calculated for the sequence Δv = −2, that follows Boltzmann’s distribution. It was found that the vibrational temperature of second positive system can be raised significantly from 0.31 to 0.35 eV in air dielectric barrier discharge (DBD) plasma at discharge current 0.5 mA with admixing of Ar gas at flow rate of 3 L/min. Admixing of argon to air DB discharge also enhances the discharge current, the electron density and the consumed power. Mechanisms of excitation and ionization processes of nitrogen molecules in this mixture have been studied. Processes which are responsible for the enhancement of the population density of N2(C3Πu,v′) and its vibrational temperature have been reported.

Methanol sensing characteristics of conducting polypyrrole-silver nanocomposites are reported here. The nanocomposites are synthesized by wet chemical technique with different amount of silver loadings (5–15 mol%). The sensitivity of the nanocomposites upon exposure to gas molecules is critically dependent on the silver loadings and the concentration of the exposed gas. This is possibly instigated by the modified metal-polymer interface and the polar nature of the constituent metal and the exposed gas. Interaction of the alcohol gas with the polypyrrole chains in the presence of silver effectively determines the change in resistance and hence the sensitivity of the nanocomposites upon exposure to methanol. The adsorption of methanol molecules within the nanocomposites and the subsequent chemical reactions are studied by Fourier transform infrared (FTIR) spectroscopy.

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.

Optical emission spectroscopy and double Langmuir probe measurements are performed on a magnesium plasma from an inductively coupled plasma source. These measurements are performed in order to examine their feasibility to characterize the plasma, its degree of ionization and its deviation from thermal equilibrium.

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.

In this report we present micro/nanostructuring of novel metal isopropoxides-silica containing hybrid sol-gel materials by the femtosecond laser direct writing technique and apply it for the fabrication of various microoptical/nanophotonic components. This approach enables one to photostructure true three-dimensional objects with controlled sub-100 nm spatial definition. Due to self-smoothing effects, surface roughness can be formed below 30 nm making this technique widely applicable for microoptical/nanophotonics devices in visible and near-infra-red wavelengths. After photopolymerization, these materials inherit desired optical properties: high transmittance in the 400–1500 nm spectral range and nearly glass-matching optical refractive index. Doping with organic dyes or quantum dots offers additional functionalities. Fields of applications cover: light guiding, coupling/extraction, trapping, signal processing and transferring, microscopy, biology, etc. In brief, we investigated direct laser writing structurability of these materials and its optimization for manufacturing microoptical/nanophotonic components. We successfully produced microoptical components such as aspheric and Fresnel lenses. We demonstrate the flexibility and reproducibility of this approach to fabricate custom-shaped elements on the tip of the optical fiber, thus producing integrated microoptical devices. The micro/nanostructures were characterized by optical and scanning electron microscopies, and optical profilometry. Their optical functions were measured using a custom-built setup to serve the purpose. The obtained values were in close coincidence to the theoretical values. Further research in the direction of production integrated and multifunctional components to be applied in the fields of photonics, plasmonics and telecommunications as well as optofluidics is currently being carried out.

To investigate the effect of thermal boundary resistance (TBR) on thermoelectric transport, the discontinuity in temperature is considered at the interface through Kapitza’s definition. The effect depends on two factors: the length of thermoelectric element and the value of TBR. More importantly, it is found that TBR has dramatic impact on the reduction in thermoelectric conversion efficiency, which decays exponentially with increasing TBR. The ratio of thermal boundary resistance to the length of thermoelectric element leading to the decrease of effective Seebeck coefficient largely accounts for the degradation of thermoelectric performance at the micro-scale.

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.

A theoretical analysis of a tuneable optical filter is presented by proposing an optical ring resonator (ORR) using photonic crystal fiber (PCF) as the resonance loop. The influences of the characteristic parameters of the PCF on the filter response have been analyzed under steady-state condition of the ORR. It is shown that the tuneability of the filter is mainly achieved by changing the modulation frequency of the light signal applied to the resonator. The analyses have shown that the sharpness and the depth of the filter response are controlled by parameters such as amplitude modulation index of applied field, the coupling coefficient of the ORR, and hole-spacing and air-filling ratio of the PCF, respectively. When transmission coefficient of the loop approaches the coupling coefficient, the filter response enhances sharply with PCF parameters. The depth and the full-width at half-maximum (FWHM) of the response strongly depend on the number of field circulations in the resonator loop. With the proposed tuneability scheme for optical filter, we achieved an FWHM of ~1.55 nm. The obtained results may be utilized in designing optical add/drop filters used in WDM communication systems.

This paper proposes an innovative, generally applicable numerical model for the calculation of the three-dimensional (3D) electromagnetic field generated by high voltage (HV) overhead power transmission lines (OHL) on the buried metallic structures (e.g., pipeline networks). The numerical analysis is based on a coupled finite element-boundary element model (FEM-BEM) designed to calculate the induced potential on buried pipelines for complex geometrical structures of HV OHL networks working on normal or fault conditions. The one-dimensional (1D) FEM technique based on pipe elements is used to discretize the mathematical model that describes the interior of the pipe and is coupled with the mathematical model that describes the exterior of the pipe using 3D-BEM integral equations. The full electromagnetic field model gives the flexibility to calculate the potential distribution in any point of the soil, providing useful information for the step and touching voltages. The computation accuracy of the numerical algorithm implemented is verified through two test problems by comparing the numerical results with those obtained using a software package based on the Transmission Line Method (TLM) and CIGRE formulae. Last part of the paper presents calculations of the induced potential on buried pipeline in the vicinity of a complex HV OHL working on normal and fault condition. The influence of the currents’ direction and magnitude flowing on the HV OHL on the induced pipeline potential distribution is analyzed.

A symmetrical detection configuration was developed to detect inner surface defect in a hollow cylinder by laser-induced ultrasonic. In this method, circumferential waves were detected at two points on the outer surface with ±90° relative to the laser source and their difference was used to obtain the differential circumferential wave. Finite element method was used to analyze the influence of inner surface defect’s position and size on the differential circumferential wave. The results show that the relative energy of differential circumferential wave and the emerging time of the bipolar waveform strongly depend on the defect’s size and the source-defect angle. As a result, the position of defect can be determined by the reach time of the bipolar waveform and the size can be evaluated by the relative energy of differential circumferential wave.

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.

This paper is aimed at the analysis of positive pre-breakdown currents triggered in mineral transformer oil submitted to 50 Hz alternating overvoltages. Different shapes of streamer currents and electrical discharges have been recorded to develop a discrimination technique based on an Artificial Neural Network (ANN) and Wavelet analysis of these currents. This enables us to address a complementary diagnosis tool that can serve as an online transformer monitoring and protection.

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.

This contribution presents an electro-hydrodynamic method for establishing the relationship between the motion of a polyelectrolyte through a solid-state nanopore and the surface-charge density of the nanopore. For a polyelectrolyte driven by an external electric field, our numerical calculations show that the dynamics of polyelectrolyte translocation through a nanopore are mediated by the charge density σ of the nanopore surface. The result implies that the charge density can be an effective way to regulate the polyelectrolyte translocation. Moreover, for the first time results indicate that a threaded polyelectrolyte may be retracted from a nanopore, and that a nanometer-scale channel can act as nanopore tweezers, in the same way as optical or magnetic tweezers allow manipulation of single molecules.

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.