We are dealing with secondary electron emission phenomena of insulators as they take place at the early stages of irradiation by a narrow electron beam. Charging effects are then negligible. Using a Monte Carlo simulation method, we follow the electronic trajectories by introducing the different interactions (elastic, electron-electron, electron-core and electron-phonon scattering). The secondary electron cascade and the charge trapping effect are taken into account. Quartz-α is considered as the reference material. Then we introduce miscellaneous values for various physical constants (electronic affinity, dielectric constant, trapping parameters, ...) and we study the resulting secondary yield. We can see in particular that the charge trapping parameters are preponderant factors. From the trapping site density values, we can understand why insulators with otherwise similar properties have different secondary emission yields. In fact, secondary electron emission is a revealing of the sample “story”

We are dealing with the problem of the charge distribution within an insulator (present application: SiO2) which is bombarded by a narrow electron beam. The electron trajectories within the sample are simulated via a single diffusion Monte-Carlo method. A mathematical model is proposed for the potential and the charge density. The development of an electric field, a potential and the broadening of the incident beam are taken into account. These two last distributions appear to have a prominent effect. It is shown that the charge distribution tends to a double layer; the shape and thickness of positive and negative distributions are given.

The single scattering technique in the Monte Carlo simulating method is used: the electron trajectory is divided in several straight segments; the length of each segment is a random fraction of the elastic mean free path, an elastic diffusion is considered at the end of each segment. The screened Rutherford cross section accounts for the elastic interaction. Inelastic interaction is introduced: a) either via the inelastic mean free path and the energy loss cross section concepts; b) or by the Bethe-Wittry continuous slowing-down model. The energy loss is assumed to be devoted to secondary electron creation; the secondary electron energy is deduced from the Streitwolf formula. The intensity of the total secondary electron yield is fitted to the experimental results by adjusting the value of two parameters which respectively describe the cascade multiplication rate and the mean absorption coefficient

The problem of the charge distribution within an insulator bombarded by a narrow electron beam is studied using the Monte Carlo technique. In contrast to the conductor or semiconductor case, the electron-insulator interaction is shown to depend closely on the specimen environment; has been taken into account; this assumption is valuable if the specimen is sufficiently large and thick, and if the working distance is not too short. The working distance acts on the spreading of the incident beam via the surface potential.< >

In order to remove the inelastic background from Auger spectra, we took advantage of theoretical work assuming an experimental arrangement corresponding to cylindrical symmetry. The knowledge of the inelastic differential cross-section K(T) is necessary for the background calculation (T is the energy loss), so we calculated K(T) from back-scattering spectra experimentally obtained using either a cylindrical mirror analyser (cylindrical symmetry) or a hemispherical mirror analyser (no cylindrical symmetry). The strict application of theoretical expressions may eventually lead to a K(T) function with some negative part, i.e. without physical meaning. We have interpreted this effect and we consequently succeeded in eliminating any negative part. In settling out the Auger spectra background, we took into account secondary electrons created by Auger electrons by introducing distinct laws for the spectra from the two analysers. 'Intrinsic' Auger spectra, obtained from elemental materials (Si, Ag, Ni, Cu) and registered from either analyser, were compared. Some minor differences remain, according to which analyser is used.

In order to determine the intrinsic (or elastic) energetic shape of Auger peaks two contributions to the experimental spectrum are defined: one elastic and the other inelastic. These contributions are analytically expressed in terms of the elastic and inelastic mean free paths and of the differential inelastic scattering cross-section. Next we show how to directly subtract the inelastic contribution. It is also shown that, under specific and often verified conditions, the deconvolution of the experimental spectrum (by the backscattering spectrum corresponding to an energy of incident electrons which matches Auger energy) makes it possible to determine the desired intrinsic energetic distribution. Both methods were applied to the same experimental spectra and the obtained results were compared. Compared to the "Sickafus law", the method used allows a better account of the secondary electron contribution to the background. To perform the deconvolution, an improved Van-Cittert iterative method has been used.

A review of the main available methods of background removal in Auger electron Spectroscopy and X-ray photoelectron Spectroscopy is given. The major features, assumptions and results of theoretical works, which form the basis of the present method, are presented. This method uses a convolution technique of the experimental spectrum with the single event loss function. It has been applied to Auger electron spectra (Si, Ag, Fe, Ni, Cu, Al). When Auger energy is sufficiently low (Si, Ag), it has been assumed that Auger electrons act as a secondary electrons source within a multiplet energy range. In every case results are satisfactory.

Calcul du facteur de retrodiffusion de Auger dans la gamme d'energie 5,60 KeV. Determination de la dependance de ce facteur envers l'energie primaire et l'angle d'incidence. Distribution spatiale des electrons retrodiffuses et des electrons Auger pour un faisceau incident ponctuel

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