1,721,122 research outputs found
Transport of energetic electrons in solids: computer simulation with applications to materials analysis and characterization
No full textThis book presents the potential of the Monte Carlo (MC) technique to solve mathematical and physical problems of great complexity. This book focusses on the study of the electron-solid interaction (transport MC) and presents some physical problems related to the transport of hot electrons in solid targets using transport MC. The numerical and theoretical results are validated through a comparison with experimental results. The author also addresses methodological aspects. In particular, systematic comparisons among different calculation schemes are presented. Different expressions for the calculation of cross sections and/or stopping power and different simulation methods are described and discussed
Backscattering of electrons from solid targets
No full textA simple equation is derived which describes the electron backscattering coefficient as a function of the target atomic number in the primary enenergy range 2-45 keV. Such an equation, very useful for practical purposes, is in better agreement with the experimental data of Palluell and of Cosslett and Thomas than both the treatments of Everhart and Archard
An analytical approximation of the differential elastic scattering cross-section for electrons in selected oxides
No full textData of electron elastic scattering cross-sections calculated by numerically solving the Dirac equation for a central electrostatic field, and using the relativistic partial wave expansion method (RPWEM), are presented. After that, an analytical expression is proposed to approximate the RPWEM results. It is an approximation that is used to expedite the calculations in applications such as Monte Carlo simulation. It depends on a parameter à which is a function of the target characteristics and on the electron energy E. Typically, during a Monte Carlo simulation, à is calculated by cubic spline interpolation of previously tabulated data. This Letter proposes an analytical approximation that allows to calculate à , for selected oxides (MgO, SiO2, Al2O3) in the primary energy range from 50 eV to 10 keV, avoiding the cubic spline interpolation and, therefore, reducing the computation time. A comparison between the approximated and the RPWEM computations of the differential and the transport elastic scattering cross-section is presented. Then some applications are proposed
Monte Carlo simulation of electron depth distribution and backscattering for carbon films deposited on aluminium as a function of incidence angle and primary energy
No full textCarbon films are deposited on various substrates (polymers, polyester fabrics, polyester yarns, metal alloys) both for experimental and technological motivations (medical devices, biocompatible coatings, food package and so on). Computational studies of the penetration of electron beams in supported thin films of carbon are very useful in order to compare the simulated results with analytical techniques data (obtained by scanning electron microscopy and/or Auger electron spectroscopy) and investigate the film characteristics. In the present paper, the few keV electron depth distribution and backscattering coefficient for the special case of film of carbon deposited on aluminium are investigated, by a Monte Carlo simulation, as a function of the incidence angle and primary electron energy. The simulated results can be used as a way to evaluate the carbon film thickness by a set of measurements of the backscattering coefficient
Monte Carlo simulation of low-medium energy electrons backscattered from C/Al double layer thin films
No full textThe backscattering coefficient of low-medium energy electron beams (from 250 eV to 10,000 eV) impinging on C/Al double layer thin films was investigated by a Monte Carlo simulation. The aim of the research was to study the behaviour of the backscattering coefficient as a function of the beam primary energy and the thicknesses of the two layers. The backscattering coefficient as a function of the primary energy presents features that can be used to evaluate the thicknesses of the two layers
Comparison between Energy Straggling Strategy and Continuous Slowing Down Approximation in Monte Carlo Simulation of Secondary Electron Emission of Insulating Materials
No full textSecondary electrons are commonly used for imaging in scanning electron microscopes, with applications ranging from secondary electron doping contrast in p-n junctions, line-width measurement in critical-dimension scanning electron microscopy and dimensional parameters evaluation in the production of masks and wafers in the semiconductor industry, to the study of biological samples. This paper describes the secondary electron emission yield calculated using two different Monte Carlo approaches. In the first, based on the energy straggling strategy, one takes into account all the single energy losses suffered by each electron in the secondary electron cascade. This method has been demonstrated to be very accurate for the calculation of the secondary electron yield and of the secondary electron energy distribution as well. An alternative way to calculate the secondary electron yield is based on a continuous slowing down approximation and uses as input the electron stopping power of the material being considered. As this work demonstrates that the secondary electron yields calculated using the two approaches are very close and in agreement with the experiment, the much faster continuous slowing down approximation is recommended. On the other hand, if other physical quantities, such as the secondary electron distributions, are required, the energy straggling strategy should be preferred, even if it requires much longer CPU times, due to its stronger physical background
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