R. Bindi

A new approach and resolution method of the Boltzmann equation applied to secondary electron emission, by reflection from polycrystalline aluminium

This new Boltzmann equation approach to secondary electron emission does away with most of the simplifying assumptions generally encountered until now in similar studies. The main processes governing the phenomenon, such as elastic and inelastic scattering, the effect of the primary beam diffusion in the excitation function and the fundamental characteristics such as variation of electron density with depth inside the sample and energy dependence of the mean free paths, are simultaneously taken into account. The validity of the present method has been tested by comparing the theoretical results for polycrystalline aluminium with those predicted by previous models and with experimental data. The results obtained satisfactorily describe the energy as well as the angular distribution and the secondary electron yield of emitted electrons.

Theoretical model for thermally stimulated luminescence, conductivity and exoelectronic emission

A theoretical model which takes into account thermally stimulated luminescence (TSL), conductivity (TSC) and exoelectronic emission (TSEE) is proposed in this article. The model is established for the case of a single type of electron trap, a single type of recombination centre and in the presence of thermally disconnected traps. It generalizes the model of Lewandowski and McKeever by taking the TSEE phenomenon into consideration. TSEE is described as resulting from the thermionic effect and so the model applies only to a thin solid film about 10 nm thick. As an application example, the influence of various parameters involved in the model on peak shape and position is investigated.

Theoretical analysis of the simultaneous detection method of thermally stimulated conductivity (TSC) and luminescence (TSL); application to an alpha -Al2O3 monocrystal

A simultaneous detection analysis of thermostimulated luminescence (TSL) and electrical conductivity (TSC) is made using the approximate analytical models of first- and second-order kinetics. Some characteristics are developed and a new approach for evaluating the trapping depth is proposed and tested in the case of an alpha -alumina monocrystal.

Application of the Boltzmann equation to secondary electron emission from copper and gold

The model recently developed for aluminium is applied to secondary electron emission from polycrystalline copper and gold using appropriate noble metals data. The comparison between theoretical and experimental distribution energy curves, normalised for the maximum peak height, may lead to the conclusion that the present approach can be successfully used to describe secondary electron transport. However, the secondary electron yield is underestimated; a more realistic approach to the primary electron diffusion must be made in order to achieve better overall agreement.

Transport equation treatment of transmitted electrons through thin films of aluminium

An approach of the transmission of electrons through thin films of aluminium of various thickness and for primary energy 1.5-3 keV is attempted using the Boltzmann equation treatment proposed by Bethe et al., (1938) and more recently applied to the penetration and backscattering of electron in solids. Semi-empirical expressions for the energy loss on the basis of a continuous slowing down approximation are improved. The results are compared with experimental measurements of the energy distribution and the transmission coefficient. The discrepancy in the energy distribution seems similar to the already pointed out using a Monte Carlo calculation with the continuous slowing-down approximation. The results obtained and a comparison between the theoretical and semi-empirical stopping powers suggest further modifications in order to obtain a satisfactory agreement and justify the validity of this treatment.

Theoretical efficiency of back-scattered electrons in secondary electron emission from aluminium

The secondary electron yield delta 0 due to primary electrons, the yield c eta due to back-scattered electrons, and the efficiency c of these last electrons, are estimated using the recently developed models for secondary electron emission and electron back-scattering, with appropriate assumptions and using the following relation delta = delta 0(1+(c/ delta 0) eta ). The values of c/ delta 0 obtained for aluminium with primary energy of the order of 1 keV seem to agree in the low primary energy range with the more empirical calculations worked out so far. An analysis of the discrepancy which still remains between theoretical and experimental values suggests further modifications in order to achieve better agreement and to extend the models in the region of several keV where scanning electron microscopes are usually operated.

Thermally stimulated exoelectronic emission of CVD diamond films

Exoemissive properties of several CVD diamond films (undoped or doped with nitrogen) are studied by the thermally stimulated exoelectronic emission (TSEE) method. Some experimental results are obtained after UV or X-ray irradiation. After UV irradiation, a single TSEE peak is observed at 605 or 625 K, depending upon the growth parameters. The existence of the exoemission signal is related to the surface morphology: facetted surfaces give rise to exoelectronic emission, more especially in the presence of both 111 and 100 faces, while smooth surfaces do not or only to a limit extent. A possible indication of negative electron affinity is observed at about 273 K.

Theoretical model of the backscattering of electrons by bulk targets of aluminium, silver and copper

Proposes a theoretical model based upon the Boltzmann transport equation written in the continuous slowing down approximation. Elastic scattering is described by means of Rutherford cross-sections with a screening parameter, and inelastic effects are taken into account using experimental range-energy laws. In this context the effects of these two diffusion problems are shown.

Reply to Dr Käämbre's comment

In recent work we described a method which allowed the estimation of the effective electron affinity of α-alumina. The interpretation of these results has given rise to the comment from Dr Kaambre. Here, we develop some arguments in response to this comment.