A simple and effective method is presented to fabricate surface-roughened InGaN/GaN-based light emitting diodes (LEDs) epistructure using annealing-formed, random-distributed Au particle arrays as dry etching mask. The shapes of GaN nanoislands, with horizontal diameters of 100–500 nm and vertical depths up to 140 nm, are determined by Au mask particles. Importantly, this roughened surface exhibits strong photoluminescence (PL) light-output enhancement by a factor of more than 1.6 orders of magnitude. This method will put forward new promising applications in the electroluminescent devices, especially in solid state lighting.

We investigated the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of identically prepared safranine T/p-Si organic/inorganic Schottky devices (total 26 diodes) formed by evaporation of organic compound solution on p-Si semiconductor substrate. It was seen that the safranine T organic thin film on the p-Si substrate showed a good rectifying behavior. The barrier heights and ideality factors of all devices were extracted from the electrical characteristics. The mean barrier height and mean ideality factor from I-V measurements were calculated as 0.59±0.02 eV and 1.80±0.20, respectively. Also, the mean barrier height and mean acceptor doping concentration from C-V measurements were calculated as 0.67±0.10 eV and (6.96±0.37)×1014 cm-3, respectively. The discrepancy in the barrier height values obtained from I-V and C-V characteristics has been attributed to different nature of the measurements. The discrepancy between these values can also be due to the existence of the interfacial native oxide and the organic safranine T thin layer between the semiconductor substrate and top contact metal.

In order to measure the dielectric permittivity of thin insulting layers, we developed a method based on electrostatic force microscopy (EFM) experiments coupled with numerical simulations. This method allows to characterize the dielectric properties of materials without any restrictions of film thickness, tip radius and tip-sample distance. The EFM experiments consist in the detection of the electric force gradient by means of a double pass method. The numerical simulations, based on the equivalent charge method (ECM), model the electric force gradient between an EFM tip and a sample, and thus, determine from the EFM experiments the relative dielectric permittivity by an inverse approach. This method was validated on a thin SiO2 sample and was used to characterize the dielectric permittivity of ultrathin poly(vinyl acetate) and polystyrene films at two temperatures.

Yttrium iron garnet (YIG) film made as a magneto-optical medium suffers from the problem of crack formation, caused by the heating process. YIG thin film is deposited by radio frequency rf magnetron sputtering; the obtained layer is amorphous and it needs annealing to be crystallized. After heat-treatment at 740 ○C of the sample realized on quartz substrate, we observe cracks on the entire film surface. This is due to the large difference between the thermal expansion coefficient (5.5 ×10-7 K-1 for quartz and 10 ×10-6 K-1 for YIG). In this paper we present a new fabrication method to reduce this problem, we make a multilayer to obtain at the end a uniformly unique layer with excellent crystalline structure. Such films have the possibility to reach a thickness of 500 nm. YIG films have been studied by Rutherford backscattering spectrometry (RBS), optic ellipsometry and the scan electron microscope. The RBS spectra were collected in channelling geometry with incident particles energy 2 MeV and 3.5 MeV. The thickness and the stoichiometric value of the thin films have been evaluated. Simulation of all spectra indicates a constant composition. Ellipsometry method is well adapted to model the thin film structure layers, and to measure the thickness of the film and the complex index of refraction. The theoretical ellipsometric value of the index of refraction is (2.22) while the experimental value is ranging from 2.2 to 2.3 for a wavelength of 1550 nm.

Within the Landauer framework of ballistic transport, we theoretically investigate spin-dependent resonant transmission and magnetoresistance in symmetric cascade junctions of ferromagnetic metal (FM) and semiconductor (SC). It is shown that spin-up and spin-down electrons possess different bandgap structures against the Rashba spin-orbit wave vector. Due to the mirror symmetry, multiple spin-dependent perfect transmissions of electrons can be obtained within the bandgap, thereafter, spin polarization has multiple reversals. Around each resonant wave vector, high spin polarization is achieved and the electrical conductance comes from one kind of spin electrons. The resonant transmissions originate from the spin-dependent quasi-bound states at energies above the potential barriers, which are demonstrated by the electronic charge distributions in the system. Furthermore, if we change the magnetization of FM in the centre of the junctions, inverse magnetoresistance can be observed. The investigations may have potential applications in spin filters and spin switches.

GaN nanowires doped with Dy have been fabricated on Si (111) substrate through ammoniating Ga2O3 films doped with rare earth phosphor. The samples are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM) and photoluminescence (PL). The results demonstrate that the Dy-doped GaN nanowires were single crystalline with hexagonal wurtzite structure. The diameters of the nanowires were about 50 nm and the lengths were up to several tens micrometers. Also, the optical properties of the nanowires were greatly dependent on the doping of Dy. The growth mechanism of crystalline GaN nanowires is discussed briefly.

We study the radiative heat transfer between a spheroidal metallic nanoparticle and a planar metallic sample for near- and far-field distances. In particular, we investigate the shape dependence of the heat transfer in the near-field regime. In comparison with spherical particles, the heat transfer typically varies by factors between 1/2 and 2 when the particle is deformed such that its volume is kept constant. These estimates help to quantify the deviation of the actual heat transfer recorded by a near-field scanning thermal microscope from the value provided by a dipole model which assumes a perfectly spherical sensor.

The main force that detaches a molten droplet from the electrode (wire) during arc welding is the interaction of the arc current with its own magnetic field. The magnitude of this force depends on the current distribution inside the droplet. A method to regulate the current distribution is proposed. The current redistribution is achieved by striking an additional arc with the droplet serving as a cathode of this arc. By the current redistribution it is possible (i) to decrease the threshold current of the globular to spray transition during GMA welding, (ii) to achieve this transition in different plasma gases, and (iii) to control the propelling direction of the detaching droplet. Some preliminary experiments confirm the proposed method.

The initial state development of breakdown is explained on the basis of bubble theory. Application of dc voltage to electrodes immersed in oil results in the creation of small channels. In the next phase an arc channel between the electrodes is formed. Resistance of the plasma channel changes from a few ohms to a few hundreds mΩ due to Joule heating caused by high arc currents which flows through this channel. The dynamics of the arc current depends on the parameters of the outer circuit and is represented by the RLC circuit.

Laser-induced breakdown spectroscopy (LIBS) has been used for brass plasma diagnostic using a Nd:YAG laser at 1064 nm. Optimal experimental conditions were evaluated, including repetition rate, number of laser shots on sample, and laser energy. The plasma temperatures and the electron number densities were determined from the emission spectra of LIBS. Cu and Zn spectral lines were used for excitation temperature calculation using Saha-Boltzmann distribution as well as line pair ratio. It was found that, the excitation temperature calculated by using Saha-Boltzmann distribution and line pair ratio methods are not the same. The electron number density has been evaluated from the Stark broadening of Hα transition at 656.27 nm and the calculated electron number density is agreement with literature.

Classical electromagnetism provides limited means to model electric generators. To extend the classical theory in this respect, additional information on microscopic processes is required. In semiconductor devices and electrochemical generators such information may be obtained by modelling chemical composition. Here we use this approach for the modelling of dye-sensitised solar cells. We simulate the steady-state current-voltage characteristics of such a cell, as well as its transient response. Dynamic simulations show optoelectronic hysteresis in these cells under transient light pulse illumination.

We investigated the electrical properties of polyaniline-coated magnetic nanoparticles as a signal transducer for application in a disposable membrane strip biosensor. The size of these particles (~100 nm) was investigated by a transmission electron microscope. Electrical properties of these nanoparticles were investigated by four-point probe measurements and I-V measurements. Polyaniline-coated magnetic nanoparticles had a resistivity of 0.385 Ω cm and showed ohmic behavior. Resistance decreased with increasing concentration of polyaniline. We also demonstrated that the resistance decreased with increasing concentration of biotinylated IgG conjugated with these nanoparticles.

The phenomenon of arcing is the major cause of electrical contact degradation in electrical switches. Degradation involves contact erosion and/or welding. The use of special contact material and that of specific material processing may permit contact erosion to be reduced, in particular by shortening the arc duration. A short review of these approaches is presented in the first part of this paper. In the second part, the development of a new self-blowing contact material is described. This material has been tested under dc voltages from 14 V to 42 V. A reduction of the arc duration by a factor of 4 approximately was obtained as was a concomitant reduction of the extinction gap to less than 2 mm. This material will contribute to achieving better reliability in high current-high voltages breaking devices, and will aid in their miniaturization, e.g. in relays.

Automotive suppliers use since decades printed circuit boards (PCB) gold plating pads, as direct contact interface for low current sliding contacts. Several gold plating processes are available on the market, providing various wear behaviour. Some specific galvanic hard gold (AuCo or AuNi). plating was developed on PCB's. This specific plating generates extra costs due to the material quantity and also the process complexity. In a cost driven industry, the challenge is to use a standard low cost PCB for systems requesting high reliability performances. After a brief overview of standard PCB manufacturing processes and especially gold plating processes, the global experimental results of wear behaviour of three different gold plating technologies will be exposed and an explanation of the correlation between surface key parameters and wear out will be provided.

It is well-known that arcing phenomena at the break of contacts affect seriously the reliability and lifetime of contacts. Therefore, many papers have reported arc duration, arc extinction current and other characteristics. Recently, in mobile communication application an electro-mechanical switch is said to be superior to a semiconductor switch in insertion loss and isolation, and a RF (radio frequency) MEMS relay has been intensively developed.Based on the above background it is one of important research topics how the frequency of interrupted current affects the characteristics of breaking arc. However, there are few papers on that topic.In this paper the effect of frequency on arc characteristics is investigated in range of the frequency of interrupted current from 50 Hz to 1 MHz. Consequently the followings can be made clear.At the interruption of peak current 2 A arc extinguishes in terms of arc characteristics and circuit conditions up to the frequency of 200 Hz. Above 200 Hz the arc extinguishes at current zero. The current zero extinction takes place up to 500 kHz. Therefore, arc duration decreases with high frequencies and the contact damage caused by arc is reduced with frequency. However, at frequencies higher than 600 kHz an arc is re-ignited after the current zero and failed to extinguish.

Investigations to determine the electrical contact performance under repeated cycles at low force conditions for carbon-nanotube (CNT) coated surfaces were performed. The surfaces under investigation consisted of multi-walled CNT synthesized on a silicon substrate and coated with a gold film. These planar surfaces were mounted on the tip of a PZT actuator and contacted with a plated Au hemispherical probe. The dynamic applied force used was 1 mN. The contact resistance (Rc ) of these surfaces was investigated with the applied force and with repeated loading cycles performed for stability testing. The surfaces were compared with a reference Au–Au contact under the same experimental conditions. This initial study shows the potential for the application of gold coated CNT surfaces as an interface in low force electrical contact applications.