Secondary Electron Emission from Solids. II. Theoretical Descriptions

A primary beam impinging on a solid target suffers elastic and inelastic collisions with the components of the solid. These collisions can be incorporated into a Monte-Carlo simulation model if all the cross sections associated with the various types of collisions are known. Elastic diffusion effects are mainly related to the interactions of the particles with the real potential V(r) surrounding each ionic core. An essential simplification of the inelastic interactions is to consider that the solid reacts as a whole to an external probe, which is the incident electron beam. The linear response of the solid to an external perturbation is described by its dielectric function. In the present paper, the methods used to evaluate the elastic and inelastic cross-sections and to simulate the secondary electron emission are reviewed and discussed

Secondary Electron Emission from Solids. I. Secondary Electron Spectroscopy

The secondary electron emission spectroscopy can provide useful information about the transitions in the electronic structure from solids and deals with the detection of fine structures superimposed on the true secondary peak, in the kinetic energy range of the true secondary electrons. Several mechanisms have been proposed for the creation of these fine structures: diffraction phenomena, plasmon decay, interband transitions to unoccupied levels, Auger transitions and more recently, autoionization emission. Some features could not be explained as being due to any bulk effect and were considered as indicative of a need to include surface wave-matching arguments in the analysis of secondary electron emission spectra. The authors give a review of the recent literature on the topic, including their own experience on the subject

Modélisation des phénomènes de transport et des effets de charge dans les matériaux isolants

Les propriétés fondamentales des matériaux isolants ainsi que leurs performances technologiques sont fortement influencées par les charges électriques qu'ils ont accumulées en leur sein. Ces charges, qui apparaissent suite aux diverses contraintes subies par le solide engendrent en effet un champ électrique qui favorise le vieillissement et le claquage du matériau. L'éradication de ces effets préjudiciables passe par une bonne compréhension des mécanismes de charge. On propose ici une étude théorique du transport de porteurs de basse énergie (électrons ou trous) dans les isolants. Les interactions avec les phonons jouent dans ce domaine un rôle primordial, conduisant, selon l'intensité du couplage, à la création ou l'annihilation de phonons réels, ou encore à l'auto-localisation des porteurs. Ce travail permet de modéliser les deux expériences de base retenues pour l'étude des effets de charge : les méthodes de miroir électrostatique et de déclin de potentiel. S'agissant tout d'abord des expériences miroir, la simulation Monte-Carlo du bombardement d'une cible isolante avec un faisceau d'électrons de grande énergie conduit à un schéma réaliste pour la répartition des charges implantées. Elle permet ainsi d'avancer une méthode simple d'interprétation des données expérimentales. Une modélisation détaillée du transport des charges occupant le bas de la bande de conduction ou le haut de la bande de valence est ensuite présentée. Des processus de transport par bande et par sauts sont envisagés. Dans les deux cas, l'influence des défauts (pièges) est clairement précisée. Ce travail est mis à profit pour élaborer une description théorique des expériences de déclin de potentiel. Celle-ci permet de mettre en évidence l'influence des différents mécanismes de transport considérés sur les comportements expérimentaux observés.The fundamentals properties of insulating materials as well as their technological performances are strongly influenced by the electric charges they have stored. The charging-up of the insulator can be provoked by various stresses suffered by the sample. It is responsible for the appearance of an electric field which favours the aging and the breakdown of the material. The eradication of such undesirable effects requires a good understanding of the charging mechanisms.NANTES-BU Sciences (441092104) / SudocSudocFranceF

On the Versatility of Urethane/Urea Bonds: Reversibility, Blocked Isocyanate, and Non-isocyanate Polyurethane

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Microscopic description of proton induced electron emission from insulators: Comparison between alumina and aluminum targets

It is well known that the electron emission yield from insulators is larger than from metals. Most of the previous works on electron emission have been on metals, and very few works have been done on insulators, either experimentally or theoretically. We present in this paper a microscopic description of proton induced electron emission from alumina. Elastic and inelastic interactions for the incident protons and excited electrons are considered as well as the charging-up of the target. The characteristics of proton induced electron emission from alumina (especially the yield γ) are calculated by a Monte Carlo simulation method. A comparison with aluminum targets is done, especially with respect to the influence of the electron inelastic mean free path and of the work function.SCOPUS: ar.jinfo:eu-repo/semantics/publishe