The impact of light and medium mass ions in crystals in the MeV range is of particular interest in high energy implantations. In the present work, extensive continuous wave (cw) and pulsed electron paramagnetic resonance (EPR) studies of a 21R SiC Lely platelet, after irradiation with 8 MeV 7Li2+ ions in the random direction, up to a maximum dose of approximately 1 × 1016 particles/cm2 are presented. The existence of new types of defects induced in the end-of-range region of impinging ions is discussed and analyzed. Due to the complexity of the induced structure, the technique of progressive annealing was utilized, revealing interesting features in the experimental spectra. The results are compared to known literature and an attempt is made to explain the occurring similarities. Furthermore, a new paramagnetic defect was isolated and analyzed, persisting up to 1100 °C during the annealing procedure.

Contactless processing of metallic materials is of great interest and has been used for the fundamental study of melts such as their thermo-physical properties and their solidification behavior. Among the different ways to produce the free suspension of the material, magnetic fields offer a well-adapted mean for metals and alloys. However, due to stability considerations, development of applications has been seriously limited in the past. We present here a new containerless technique combining magnetic suspension with an electromagnetic induction furnace able to produce stable conditions of sustentation even for paramagnetic substances. Suspension experiments on massive metallic samples involving the superimposition of magnetic and electromagnetic forces will be described and analyzed. Conditions to solidify pure Ti and TiAl alloy samples of 45 g without any contact with a container wall are presented.

We have theoretically investigated the subband structure of two coupled Si δ-doped GaAs at T = 0 K. For the uniform distribution we have studied the influence of the separation between the two doping layers. The electronic properties such as the effective potential, the density profile, the subband energies, the subband populations and Fermi energy have been calculated by solving Schrödinger and Poisson equations self-consistently. In this study, we have seen that the subband structure is quite sensitive to the separation between the two doping layers. We conclude that, if the coupling between two δ-doped GaAs layers is significant, the mobility of electrons in this structure is very high compared to single δ-doped structures because of the strong overlap between the electrons and the ionized donors in single δ-doped structures.

Secondary Electron Emission (SEE) yield measurements have been used to investigate the desorption of nitrogen adsorbates from amorphous carbon (a-C) surfaces due to swift heavy ion impact. The fluence dependence of ion induced electron emission obeys an exponential decay law when the coverage rate is in the sub-mono-layer range. This reveals the relative contribution of the both emitting zones, the “clean” one (having the SEE properties of carbon) and the covered one (with a higher SEE coefficient) to the total measured yield. The mechanism for the SEE enhancement effect is connected to the surface termination. Nitrogen adsorbates are believed to provide surface states which generate a downwards energy band bending, which on relative scale pushes up the Fermi level towards the conduction band minimum, reducing the work function and increasing the SEE yield subsequently. A shoulder observed on the rising edge of the peak of the true SE peak is ascribe to the fraction of hydrogenated termination of a-C which exhibits a lower electron affinity.

We analyze the ultimate performance of a superconducting quantum detector in order to meet requirements for applications in near-infrared astronomy and X-ray spectroscopy. The detector exploits a combined detection mechanism, in which avalanche quasiparticle multiplication and the supercurrent jointly produce a voltage response to a single absorbed photon via successive formation of a photon-induced and a current-induced normal hotspot in a narrow superconducting strip. The response time of the detector should increase with the photon energy providing energy resolution. Depending on the superconducting material and operation conditions, the cut-off wavelength for the single-photon detection regime varies from infrared waves to visible light. We simulated the performance of the background-limited infrared direct detector and X-ray photon counter utilizing the above mechanism. Low dark count rate and intrinsic low-frequency cut-off allow for realizing a background limited noise equivalent power of 10−20 W Hz−1/2 for a far-infrared direct detector exposed to 4-K background radiation. At low temperatures, the intrinsic response time of the counter is rather determined by diffusion of nonequilibrium electrons than by the rate of energy transfer to phonons. Therefore, thermal fluctuations do not hamper energy resolution of the X-ray photon counter that should be better than 10−3 for 6-keV photons. Comparison of new data obtained with a Nb based detector and previously reported results on NbN quantum detectors support our estimates of ultimate detector performance.

We have investigated theoretically the electronic structure of Si δ-doped GaAs layers at T = 0 K and at room temperature. For a nonuniform distribution, we have studied their sensitivity to the donor concentration and the donor thickness. In this study, nonuniform distribution is different from Gaussian distribution used by other authors. From the self-consistent calculation, we have seen that at room temperature carriers which appear due to the impurity atoms are more efficient than temperature on the subband structure.

Optimizing process- and layout-design in the development of modern electronic devices is key to achieve required characteristics. Coming along with the growing complexity of device structures, associated effects must be considered in an even more complex manner. The use of three-dimensional process- and device-simulation tools is inevitable. Because of the huge effort concerning computer resources from three-dimensional simulations it is of big interest to enable efficient ways for optimization, as early as possible in process flow. Hence this work shows, how it was possible, to optimize a high-voltage PMOS transistor before starting a complex three-dimensional device simulation.

Dielectric properties of resin/carbon-black nanocomposites were measured and shown to differ from results given by a random sets modeling approach. The origin of the discrepancies was traced back to the presence of sets of carbon planes, detached from the carbon-black particles during the composite preparation. These planes are dispersed in the resin matrix and are nearly invisible, even in HRTEM images. EELS measurements revealed the signature of bonding states typical of graphite-like compounds, in regions of the matrix previously supposed to be free of carbon-black. A new approach to texture characterization of HRTEM images, using Haralick parameters based on pixel intensity co-occurrence matrices, showed strong differences between pure resin and regions of the composite between carbon particles. The nano-scale characterization results explain the values obtained in macroscopic measurements.

Polycrystalline iron thin films on ion-etched monocrystalline In0.5Ga0.5As/InP (001) substrates were prepared using ion-beam sputtering deposition. The interface reaction was characterised by X-ray diffraction and conversion electron Mössbauer spectroscopy experiments, after annealing in vacuum for 1 h at temperatures between 350 and 450 °C. Interdiffusion phenomena mainly result in the formation of five new phases, namely metallic-In, InAs, Fe2As, Fe2InxAs$_{1-x}$ ($0 \leq x \leq 0.2$) and Fe3Ga$_{2-x}$Asx ($x = 0.2 - 0.3$), in agreement with the predictions of the phase diagrams. InAs results from the decomposition of the semiconductor substrate and remains (001)-textured. The iron-arsenide grains grow into the substrate below the Fe/In0.5Ga0.5As interface. The In precipitates reach ~40 nm in size after 1 h annealing at 450 °C, while the Fe3Ga$_{2-x}$Asx phase appears at 400–450 °C with an either textured or disordered structure. Finally, the overall activation energy for the thermal reaction is calculated to be 1.5 eV in the latter temperature range.

The structural and transport properties of thin FePc films of various thickness deposited onto glass substrates have been studied at several temperatures. The structural studies show that the films belong to monoclinic system of β-phase. This structure is confirmed by infrared absorption analysis. The dark electrical resistivity was found to decrease with increasing the film thickness. Graphical representation of $\log \rho$ as a function of reciprocal temperature yields two distinct linear parts indicating in turn the existence of two activation energies $\Delta E_1$ and $\Delta E_2$. Measurement of the thermoelectric power showed that FePc thin films behave as p-type semiconductor over the temperature range $300{-}450$ K. Analysis of thermoelectric power connected with the resistivity results reveals some essential parameters such as: hole mobility $\mu_{\rm h} \approx 2 \times 10^{-6}$ m2 V-1 s-1, hole concentration $p \approx 5\times 10^{18}$ m-3 and the ratio $c = \mu_{\rm e}/\mu_{\rm h} \approx 0.25$. Capacitance-voltage data confirm that the Au/FePc interface does not form a Schottky barrier and measurements of the dependence of capacitance on film thickness indicate that the relative permittivity of the films is approximately 3.7. Room temperature current density-voltage characteristics showed ohmic conduction in the lower voltage range and space-charge-limited – conductivity (SCLC) in the relatively high voltage. The SCLC controlled by an exponential distribution of traps above the valence band edge. The temperature dependence of current density in accordance with the theory for the exponential trap distributions yielded some essential parameters such as: the hole mobility, the relative permittivity, the trap concentration, the characteristic temperature and the trap density.

The accurate simulation of power electronic systems is possible when including accurate models of the semiconductor devices, but practically not affordable. Classical ideal averaged models of the system are not suitable either. Hence, averaged models including the non-linear effects of the power semiconductor devices appear quite efficient. The proposed non-ideal PWM-switch model is a useful method for modeling pulse width modulated converters operating in the continuous conduction mode. The main advantages of the proposed averaged model are the takes into account of the non-linear effects of power devices and the possibility to estimate the dissipated power in the different circuit devices. The proposed electrical model can be applied to bi-directional converters and allows the coupling with thermal model in the power electronic system. A simple technique to evaluate the different static and dynamic parameters of the devices, from manufacturers data sheets or experimentally, is presented.

We present here a new method to calculate, quite instantaneously, the amplitude and phase transverse distribution of the spontaneous emission (SE) produced in a waveguide. The SE is the radiation produced by an electron beam passing through an undulator. It is involved in the operation of Free Electron Lasers (FEL). Some FELs, working in infrared, use a waveguide in place of the vacuum chamber of the undulator. The numerical process which is described here is quasi analytical. It is based on a standard method for wave propagation using the Fast Fourier Transform, and it is compatible with numerical codes for wave propagation. It is limited to planar undulators. Some numerical codes exist to calculate the SE transverse profile, but they are not suitable for waveguide configuration. In addition, a simplified version of the calculation gives the SE radiation without waveguide, i.e. when propagating in free space. In practice, the process can be included in a general code to calculate the cavity losses at the start-up of the FEL operation. These losses are always larger than those for the steady state regime, and they may be large enough to forbid laser operation.

Crystalline particles of palladium are known to form on polycrystalline Pd interacting with low-energy hydrogen ions. These particles disperse on the glassy medium called the “matrix". The particles were recently confirmed by transmission electron microscopy to be classified into two groups: the particles emerging from the projectile-implanted subsurface together with the outflowing matrix and those newly produced on the hydrogen-bombarded matrix. The latter type of particles was nucleated as a crystalline cluster on the disordered substrate, and then underwent three-dimensional growth into a nanocrystal under the bombard- ment of showering hydrogen ions. Some particles presented a bubble-like TEM contrast, independently of their growth history. Such particles were chestnut-like in structure, with a hard shell wrapping the less-dense interior, and their formation may be attributed to a chemical process occurring within the particles.

This paper presents an experimental study using photon emission derived from scanning tunnelling microscopy (STM) of a granular gold surface in Ultra High Vacuum (UHV). The aim is to make a comparison with previous results obtained in air or in UHV. The photon emission spectrum also evidences a significant energy shift as the tip moves on a surface grain. This shift is attributed to the local geometry of the junction and to peculiar crystallographic properties of the surface.

From analytical solutions of the heat conduction equation in an infinite continuous medium with invariable thermal physical properties, the paper regards a laser-irradiated body as a part of the continuous medium, adopts the weighing function of laser power related to the shape of the body, and then gives a semi-analytical approach. The method can approximately estimate the instantaneous temperature field of laser irradiation on an arbitrary shape surface. Comparison of calculation results with accuracy solutions is presented. Finally, examples applied to estimate phase transformation hardening stripes of laser irradiation on cylinder work-pieces are given.

A new iterative scheme coupled with finite element technique is proposed as a numerical tool to solve Poisson's equation in a positive DC wire-to-plane corona using new boundary conditions. We used the model which separates the corona in two distinct regions. The ionisation region radius and the electric field at the ionisation-region/drift-region (IRDR) interface, which corresponds to a zero net ionisation coefficient of the ambient air, are developed by Hartmann in his investigation on the generalisation of the Peek's law. The proposed model allow to take into account the ionisation region thickness and thus avoids the recourse to the first Deutsch assumption, largely used in the literature. The effectiveness of the proposed method has been tested through application to the wire-to-plane geometry where the field has been measured with the linear biased probe. The agreement between the present calculated current density and electric field profiles as compared to the measured values is satisfactory.

In many physical processes, there is uncertainty in the parameters which define the process and this input uncertainty is propagated through the equations of the process to its output. Experimental design is essential to quantify the uncertainty of the input parameters. If the process is simulated by a computer code, propagation of uncertainties is carried out through the Monte Carlo method by sampling in the input parameter distribution and running the code for each sample. It is then important to obtain information about the way in which the parameters are influential on the output of the process. This is useful in order to decide how to sample in the input space when propagating uncertainties and on which parameters experimental effort should be more concentrated. Here, we use dimensional and similarity analyses to reduce the dimension of the input variable space with no loss of information and profit from this reduction when propagating uncertainties by Monte Carlo. Using dimensional analysis, the output is expressed in terms of the inputs through a series of dimensionless numbers, a dimension reduction is achieved since there are less dimensionless numbers than original parameters. In order to minimize the uncertainty of the estimation of the output, propagation of uncertainties should be carried out by sampling on the space of the dimensionless numbers and not on the space of the original parameters. The purpose of this paper is an application of propagation of uncertainties to a code which simulates the interaction of metal drilling with a laser beam, where there exists uncertainty in the absorbed intensity of the beam and the density of the medium. By sampling in the reduced input space, a substantial variance reduction is achieved for the estimators of the mean, variance and distribution function of the output. Moreover, the output is found to depend on the intensity and the density through their quotient.

In a previous study, the porosity of the “Granite des Crêtes” was quantified by 14C-MMA porosimetry. Autoradiographs of the granite close to quarry faces, freshly quarried (A) or weathered for 20 years (B), show an increase in porosity of B in comparison with A, localized in intragranular microcracks and grain joints and in millimetric grain zones [1]. In this study, mineralogical cartography-autoradiograph overlaps led to the identification of the alterated millimetric minerals of B, in which the porosity was higher. Moreover, the SEM analysis led to the quantification of an increase in porosity linked to an enlargement of the intragranular microcracks and the grain joints.

The sputtering rate (Q), in glow discharge, was measured as a function of the discharge power (W). An empirical relation could be obtained having the form $Q = K^{**} W^m$, with the constants $K^{**}$ and m. The equation was compared with theoretical derived equation of Takatsu and Toda, which is based on the mechanism of momentum transfer. Takatsu and Toda theoretical relationship had to be rearranged to obtain the same relationship between the sputtering rate (Q) and the discharge (W). The experimental data obtained in the present work as well as by Boumans and Takatsu and Toda were analysed on the bases of the obtained equation. This analysis revealed that the constants appearing in the Q-W equations are pressure dependent. These dependences are described and discussed.

A method is described that allows the trapping charge kinetics in insulating materials during their electron irradiation in a scanning electron microscope (SEM) to be studied and the total trapped charge to be evaluated. The method consists in analyzing the leakage and the displacement currents measured simultaneously, during and after irradiation, using an arrangement adapted to the SEM. The dynamic trapping properties of glass-ceramic are investigated and the time constants for charging and discharging processes are evaluated. By correlating the leakage and displacement currents, the total electron yield σ during irradiation is also determined.