Monte Carlo techniques have long been employed to simulate the nature of electron scattering in solid materials. These simulations, in turn, have been used to predict parameters for electron microscopy and x-ray microanalysis such as electron and x-ray ranges and backscattered electron yields. Monte Carlo techniques have also been used to predict analytical behavior in unconventional specimens, such as thin films and particles (e.g., relative intensity as a function of particle size). However, because of limitations in the physical models and lengthy calculations involved, Monte Carlo techniques have only very rarely been applied to actually correct quantitative analysis data.We have explored the practicality of developing a Monte Carlo technique-based correction procedure for microbeam analysis and the current state of accuracy of Monte Carlobased corrections versus "conventional" corrections. By using a simple but accurate numerical approximation for the relative elastic scattering cross section as a function of Z and E, it is possible to develop Monte Carlo procedures to calculate trajectories in multiple-element samples with the same speed as for single element standards. Modern expressions for the ionization cross section and the electron energy loss (particularly at low energies) have significantly improved the agreement between Monte Carlo calculations and experimentally-measured data. Monte Carlo algorithms that produce the same level of accuracy in correcting conventional electron microbeam analyses of thick, polished specimens and thin films are the best of the currently used correction procedures, and are of superior accuracy in the analysis of small particles and samples at multiple accelerating potentials. By combining polynomial a-factors with Monte Carlo-based algorithms in an iterative correction scheme, it is now possible with a fast desktop, PCtype computer to perform practical, online, Monte Carlo data processing. Gauvin et al. (1992) have shown that spherical inclusions embedded in a matrix can be chemically quantified by x-ray IV-1
Proceedings of SCANNING 94/SEEMS 94Charleston, South Carolina, USA microanalysis in the scanning electron microscope using a quantitative procedure similar to that developed by Kyser and Murata (1976) for the quantitative analysis of thin films deposited on a substrate. These quantitative procedures are based on calibration curves obtained from Monte Carlo simulations. A generalized Monte Carlo code allows quantitative analysis of spherical inclusions as well as elliptic inclusions embedded in a metallic matrix, simulations of emitted x-rays and backscattered electrons from these materials, including line scans and images, and a consideration of the effects of inclusion size, shape, composition, matrix composition, and the fractal behavior of electron trajectories in these materials.
ReferencesGauvin R, L'Espérance G, St-Laurent S: Quantitative x-ray microanalysis of spherical inclusions embedded in a matrix using an SEM and Monte Carlo simulations. Scanning 14, ...