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The electron emission yields from silicon carbide ceramics and silicon surfaces induced by protons in the energy range of 50～250 keV were measured on the 320 kV electron cyclotron resonance ion source(ECRIS) platform of the Institute of Modern Physics, Chinese Academy of Science(IMP, CAS) in Lanzhou. The experimental results show that the variation trend of electron emission yield with proton incident energy of the two kinds of semiconductor targets is similar to the variation trend of electronic energy loss with proton incident energy during the action process. By analyzing the energy source of electron emission, it is found that the electron emission is mainly contributed by the kinetic electron emission, and the potential electron emission can be ignored. The electron emission yield of the two targets is approximately proportional to the electronic energy loss in the process of proton incident on the target, and the proportionality coefficient B varies slightly with the incident energy. The results will provide important reference data for the study of electron emission in the process of ion and semiconductor target interaction and the characteristics of new semiconductor materials. [ABSTRACT FROM AUTHOR]

A Monte Carlo (MC) simulation approach is developed to describe the proton-induced secondary electron emission in solids. First, we calculate the double differential cross-section (DDCS) of excited electrons for different charge fractions of the projectile resulting from electron screening. The DDCS parameter is used in MC calculations to describe electron transport in the medium. This parameter is calculated for electrons excited in the 1 eV − 100 eV energy range. The theoretical electron transport modeling is based on Mott's elastic scattering cross-section and Lindhard's dielectric function for inelastic scattering. The results obtained for aluminum describe the angular and energy distributions of backscattered electrons for incident protons with energy below 25 keV at normal incidence. Additionally, the total electron emission yield is also calculated, showing a good agreement with available measurements. Our predictions for energy and angular distributions could not be compared with experimental results due to a lack of data. [ABSTRACT FROM AUTHOR]

In this work, polypropylene (PP) and its polymer nanocomposites (PNCs) films containing very low contents (2–6 wt %) of Cloisite 20A natural montmorillonite clay platelets were investigated. In a first, they were characterized by means of several analytical techniques such as X-ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and UV-visible spectroscopy. Secondly, the nanocomposites are submitted to an electron beam in a Scanning Electron Microscope (SEM) and the induced currents are measured using a time-resolved current method. These currents are used to determine the trapped charge and the electron emission yield. The aim is to contribute to the understanding of the effect of different concentrations of nanoclay platelets on the studied properties by correlating the results obtained by both techniques. The analytical characterization showed that upon the increase of nanoclays concentration an intercalated structure and an increase of crystallinity are induced. On the other hand, the optical band gap energy is modified because the increasing of the density of localized states in the forbidden energy band. As regards the measurement of the trapped charge, it was found, surprisingly, that not only the leakage current increases as a function of clay loading level but also the trapped charge (or the surface potential). This could be related to the increase of conductivity in one hand and to proliferation of interfaces between nanoparticles and neighboring materials on the other hand. [ABSTRACT FROM PUBLISHER]

We present a model to describe the kinetic internal and external electron emission from an ion bombarded metal target. The model is based upon a molecular dynamics treatment of the nuclear degree of freedom, the electronic system is assumed as a quasi-free electron gas characterized by its Fermi energy, electron temperature and a characteristic attenuation length. In a series of previous works we have employed this model, which includes the local kinetic excitation as well as the rapid spread of the generated excitation energy, in order to calculate internal and external electron emission yields within the framework of a Richardson–Dushman-like thermionic emission model. However, this kind of treatment turned out to fail in the realistic prediction of experimentally measured internal electron yields mainly due to the restriction of the treatment of electronic transport to a diffusive manner. Here, we propose a slightly modified approach additionally incorporating the contribution of hot electrons which are generated in the bulk material and undergo ballistic transport towards the emitting interface. [ABSTRACT FROM AUTHOR]

The electron emission yield γ induced by Ne2+ and O2+ impacting on a clean tungsten surface has been measured. The range of projectile energy is from 3 keV/u to 14 keV/u. The total electron yield gradually increases with the projectile velocity. It is found simultaneously that the total electron yield for O2+ is larger than the total electron yield for Ne2+, which is opposite to the results for higher projectile velocity. After considering the contribution from recoiling atoms to the energy distribution and electron emission yield, we find that recoiling atoms are of crucial importance in electron emission in our energy range. Thus, the unexpected results in our experiment can be explained successfully. [ABSTRACT FROM AUTHOR]

Total electron emission yield for impact of slow Neq+(q = 2, 4, 6, 8) ions with various kinetic energy under normal incidence on n-type Si has been measured. It is shown that for the same charge state, the total electron yield γ increases linearly as the kinetic energy of projectile at impact increases, up to velocities corresponding to the “classical” threshold. Separation of kinetic electron yield γKE and potential electron yield γPE shows that γPE is proportional to the ion charge state and γKE increases linearly with projectile velocity. Finally, based on “single hole without hopping” hypothesis, the expression of the “CRF” F(q) is given, and the relation between γKE and q is obtained successfully for the first time, which is also a basis for judging whether the “trampoline effect” exists. [ABSTRACT FROM PUBLISHER]

Abstract: The electron emission yield due to electron impact on polycrystalline Al2O3 is measured with a technique based on the use of a Kelvin probe (KP method) and a pulsed electron beam. The KP method allows the clear discrimination between the external effects of charging and internal ones. The effect of the incident electron fluence on the yield in the region where the yield is higher than one is investigated. An overall drop of the electron emission yield with increasing the electron fluence is observed. This result is clearly associated to the internal effects of positive charging. Indeed, the recombination of the generated secondary electrons with the accumulated holes beneath the irradiated surface leads to the decrease of their mean free path and to the decay of the secondary electron emission yield. [Copyright &y& Elsevier]

The dependence of ion-induced electron emission yields for graphite, chromium and gold on projectile velocity under 15–34 keV N+ and N2+ ion impacts have been measured. A sublinear molecular effect has been found and discussed in terms of the sweeping-out-electrons process. [Copyright &y& Elsevier]