The role of laser assisted atom probe tomography (APT) in microelectronics is discussed on the basis of various illustrations related to SiGe epitaxial layers, bipolar transistors or MOS nano-devices including gate all around (GAA) devices that were carried out at the Groupe de Physique des Matériaux of Rouen (France). 3D maps as provided by APT reveal the atomic-scale distribution of dopants and nanostructural features that are vital for nanoelectronics. Because of trajectory aberrations, APT images are subjected to distortions and local composition at the nm scale may either be biased. Procedures accounting for these effects were applied so that to correct images.

The capacitance between arbitrary two sites (vertices) in infinite triangular and honeycomb networks is studied by using Green’s function. Recurrence formulas for capacitance between arbitrary sites of the triangular lattice are obtained. The capacitance for the honeycomb lattice is shown to be expressed in terms of the one for the triangular lattice.

The influence of interfacial charges on the device characteristics of bi-layers structure LEDs with poly[5-methoxy-2-octyloxy-1,4-phenylenevinylene] (MO-PPV) as active polymer layer is investigated. The concept to improve device performance is presented using: a diacetate cellulose (DAC) and a new synthetized 5-{2-(2-chloroethoxy)ethoxy}-2-{(E)-(2-pyridyl)azo}phenol (PDEG) components. The DAC and mixed (DAC+PDEG) layers were inserted between indium tin oxide (ITO) and MO-PPV polymer. The optical properties (UV-Vis) of MO-PPV, PDEG and mixed (DAC+PDEG) in solutions were studied and compared to those on thin films. Detailed current-voltage measurements of the bi-layers devices showed improvements of the threshold voltage (Vth) of the ITO/(DAC+PDEG)/MO-PPV/Al device attributed to the enhancement of carriers injection and transport resulted from the modified electrode structures. Conduction mechanisms of structure LEDs were matched with space-charge-limited current (SCLC) one. The impedance spectra for all devices can be discussed in terms of an equivalent circuit model designed as a parallel resistor Rp and capacitor Cp network in series with resistor Rs. The ITO/(DAC+PDEG)/MO-PPV/Al device showed the lowest impedance attributed to the removal of contaminants and to changes in the work function of ITO. The frequency-dependent electrical properties of the ITO/(DAC+PDEG)/MO-PPV/Al structure is analyzed by impedance spectroscopy as function of bias. We have extracted numerical values of the equivalent circuit model parameters by fitting experimental data. Their evolution with bias voltages has shown that the SCLC mechanism is characterized by an exponential trap distribution.

First principles studies about the influence of electric field and anisotropic oxygen vacancy on the dielectric properties of rutile titanium dioxide (TiO2) are investigated. These results demonstrate that dielectric properties of perfect TiO2 presents dependent on the low electric field that less than 5.2 MV/cm. As a comparison, the dielectric properties of defected TiO2 in (1 1 0) plane and [1 1 0] direction show more sensitive to high electric field. Further more, considering the different positions of oxygen vacancy, the oxygen vacancy locates in (1 1 0) plane of defected TiO2 appears more active to high electric field than it does in [1 1 0] direction. The effect of electric field and oxygen vacancy induce the distorted supercell structure and broken bond between the nearer oxygen atoms and titanium atoms. Moreover, the oxygen vacancy locates in (1 1 0) plane of defected TiO2 can create more potential broken bond. These results account for the difference of dielectric properties in perfect TiO2 and defected TiO2.

We present calculation of critical voltage for AlGaN/GaN high electron mobility transistors (HEMTs) with GaN cap layer. The calculation includes mechanical stress and relaxable energy in the GaN/AlGaN barrier layer. Under high voltage conditions, the high electric field results in an increase in stored relaxable energy. If this exceeds a critical value, crystallographic defects are formed. This degradation mechanism is voltage driven and characterized by a critical voltage beyond which non-reversible degradation takes place. The dependence of the GaN cap layer’s thickness on the critical voltage has been discussed. The calculated results indicate that thicker GaN cap layer results in higher critical voltage.

Based on the finite-differences approach, we study the electronic properties of two-dimensional electron gas under an inhomogeneous magnetic field. Such structure can be realized by deposition of ferromagnetic strips on the surface of a semiconductor heterostructure. It is found that the system exhibits rich band structures. Many bound states are twofold degenerate for θ = π/2, which defines the magnetization direction in the ferromagnetic strips, while few degenerate state exist for θ = 0. Despite of this, there are three kinds of electronic states in our system: the extended, localized and intermediate ones, which is very different from the case of absence of magnetic field.

The magnetic properties of Co thin films obliquely evaporated under silicon and glass substrates are investigated using alternating gradient field magnetometer (AGFM) and magnetic force microscopy (MFM) techniques. The effects of the magnetic layer thickness and the deposition angle are studied. As results, it is found a decrease of the coercive field from 250 Oe, for t = 20 nm, to 95 Oe, for t = 400 nm, and a decrease of the anisotropy field from 1.6 kOe for 20 nm Co thick film, to 0.95 kOe for 200 nm Co thick film. An increase of these fields with the increase of the deposition angle is also found. The easy axis of the saturation magnetization lies in the film plane, whatever is the substrate nature. MFM images reveal well-defined stripe patterns, particularly for the thickest films, where the magnetocrystalline anisotropy is dominant. These results, and others, are presented and discussed.

Recently, there has been a lot of interest on transparent conducting oxide (TCO) materials which have common application in solar cells and some optoelectronic devices. In this work, cadmium oxide (CdO) thin films have been deposited on glass substrates by RF reactive magnetron sputtering technique and subsequently annealed in air from 200 °C to 500 °C. The effect of annealing temperature on the structural, morphological, optical and electrical properties of CdO films is systematically investigated by X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, atomic force microscopy, UV-visible spectrophotometer and Hall effect measurements. X-ray diffraction (XRD) studies showed that the films are polycrystalline in nature with a preferential orientation along (2 0 0) plane. Atomic force microscopy studies showed that these films are very smooth with maximum root mean square roughness of 3.13 nm. The CdO films formed at annealing temperature of 400 °C exhibited optical transmittance of 84%, electrical resistivity of 1.9 × 10−3 Ω cm and figure of merit of 1.8 × 10−3 Ω−1.

ZnO thin films and well-aligned nanowire arrays have been synthesized via electrochemical deposition method, a low temperature and low cost synthesis method. For the ZnO nanowires growth, the electrodeposition consists of two steps: the ZnO buffer layer was firstly deposited on the substrate using galvanostatic method at room temperature following by the ZnO nanowires growth under potentiostatic method at 80 °C. This second step has also used for the ZnO thin films growth directly on substrate. The morphological and microstructural properties of the as-deposited ZnO have been characterized using scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), as well as photoluminescence spectroscopy (PL). The electrical transport of the ZnO thin films and nanowire arrays have been studied at room temperature both in the symmetrical Al/ZnO/Al electrode configuration guarantying a good Ohmic contact and in the asymmetrical Al/ZnO/Au electrode configuration demonstrating a typical Schottky contact at the interface ZnO/Au. The feature parameters such as the series resistance, the Schottky barrier height, and the ideality factor, have been systematically analyzed. Comparing the diode parameters between thin films and nanowire arrays, we deduced that about 1/3 of the ZnO nanowires come into effective contact with the top Al electrode.

In this paper, an Ag ultra thin layer was deposited on the Cu/Co film by thermal evaporation technique in the vacuum. The atomic force microscopy confirms that nanoparticles of Ag were formed on the Co magnetic layer, and subsequently, the longitudinal Kerr signal of Cu/Co/Ag was amplified more than 2 times. This enhancement is resulting from the overlap of the surface plasmon resonance in the silver with the electronic transition in the Co layer. Furthermore, we investigated the effect of transparent semiconductor SnO2 as a cap layer on the magnitude of longitudinal Kerr signal. To obtain the optimal thickness of cap layer, a numerical analysis was carried out using a 4 × 4 characteristic matrix, which takes into account multiple reflections from interfaces within the medium and light transmission through the layers.

This work reports synthesis of PbS quantum dots (QDs) embedded in the poly-vinyl alcohol (PVA) in the presence of graphene quantum dots (GQDs) by the low cost and simple method of chemical bath deposition. The as-synthesized products were characterized by X-ray diffraction, transmission electron microscope and optical studies; absorption and photoluminescence measurements. Results showed that in comparison with GQDs and PbS/PVA, photoluminescence intensity of PbS/PVA/GQDs was improved and this could be attributed to rigidity of the local environment, PVA passivation and energy transformation between GQDs and PbS QDs. These analyses determined good distribution of PbS QDs on GQDs planes which is promising for practical applications in nanotechnology.

We present a plasmonic splitter based on metal-insulator-metal (MIM) structure. This splitter consists of two parallel waveguides and two resonators. One resonator is a ring tangentially connected with the two waveguides, and the other resonator is a semi-ring directly connected to the lower waveguide. The finite-difference time-domain (FDTD) method is used to numerically analyze the transmittance spectra of the splitter. The results show that this splitter is a beam splitter when the wavelength of the incident wave is around 1355 nm or 1553 nm. This splitter can also be regarded as a power splitter. To our knowledge, this is the first designed surface plasmon polaritons (SPPs) splitter which utilize both the communication wavelengths at around 1310 nm and 1550 nm. This characteristics show potential applications in future optical circuits.

Partial discharge (PD) in power transformers is one of the prime reasons resulting in insulation degradation and power faults. Hence, it is of great importance to study the techniques of the detection and localization of PD in theory and practice. The detection and localization of PD employing acoustic emission (AE) techniques, as a kind of non-destructive testing, plus due to the advantages of powerful capability of locating and high precision, have been paid more and more attention. The localization algorithm is the key factor to decide the localization accuracy in AE localization of PD. Many kinds of localization algorithms exist for the PD source localization adopting AE techniques including intelligent and non-intelligent algorithms. However, the existed algorithms possess some defects such as the premature convergence phenomenon, poor local optimization ability and unsuitability for the field applications. To overcome the poor local optimization ability and easily caused premature convergence phenomenon of the fundamental genetic algorithm (GA), a new kind of improved GA is proposed, namely the sequence quadratic programming-genetic algorithm (SQP-GA). For the hybrid optimization algorithm, SQP-GA, the sequence quadratic programming (SQP) algorithm which is used as a basic operator is integrated into the fundamental GA, so the local searching ability of the fundamental GA is improved effectively and the premature convergence phenomenon is overcome. Experimental results of the numerical simulations of benchmark functions show that the hybrid optimization algorithm, SQP-GA, is better than the fundamental GA in the convergence speed and optimization precision, and the proposed algorithm in this paper has outstanding optimization effect. At the same time, the presented SQP-GA in the paper is applied to solve the ultrasonic localization problem of PD in transformers, then the ultrasonic localization method of PD in transformers based on the SQP-GA is proposed. And localization results based on the SQP-GA are compared with some algorithms such as the GA, some other intelligent and non-intelligent algorithms. The results of calculating examples both stimulated and spot experiments demonstrate that the localization method based on the SQP-GA can effectively prevent the results from getting trapped into the local optimum values, and the localization method is of great feasibility and very suitable for the field applications, and the precision of localization is enhanced, and the effectiveness of localization is ideal and satisfactory.

Electromagnetic and thermal characteristics of coaxial monopole antennas of 2.45 GHz and 24.125 GHz for microwave ablation of malignant tumors are investigated. Microwave heating processes in an interaction domain (biological tissue) are described by the coupled electromagnetic and heat transfer problem, which was solved numerically in the present study. Proposed applicators provide reducing of reflected power and localized distribution of temperature in the near-field zone. Different mathematical models are used to optimize the antennas sizes and simulate heating patterns.