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.

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.

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.

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.

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.

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.

The physico-chemical environment around the aluminum impurity atoms in commercial Herasil silica is studied by electron-induced X-ray emission spectroscopy. Despite the low concentration of aluminum and the charging effect occurring upon electron irradiation, we have been able to characterize the environment of the Al atoms. We show that the Al atoms are in an octahedral environment, i.e. surrounded by 6 oxygen atoms. The presence of Al clusters, whose metallic character would make them candidates to be ultraviolet absorption centers, is ruled out.

This paper deals with the causal modeling of a Traveling Wave Ultrasonic Motor; the aim of the study is to build an approach which may take into account the physical contact responsible for the pull-out phenomenon, but straightforward enough to be useful for control. As the parameters available for the modeling can not be obtained following the well known electromechanical equivalent scheme identification, a new identification method is proposed. In this purpose, the model of the motor is expressed in the traveling wave rotating frame.