Use of Monte Carlo calculations in electron probe microanalysis and scanning electron microscopy

Abstract

Part of the mission of NBS is to disseminate knowledge in the scientific and technical community.To aid in reaching this objective, the Analytical Chemistry Division has sponsored a series of workshops on various topics in analytical chemistry. The workshop topics are chosen to fulfill current needs for detailed discussions on sharply defined subjects in a wide variety of specialist areas.The objective is to bring together specialists from throughout the world to concentrate intensively on a particular subject in order to advance the state-of-the-art.It is often very difficult to achieve this goal at large international meetings where the size and diversity of topics presented often limits detailed discussion of special subjects.Past topics of these workshops and the published proceedings include:Quantitative The workshop format consisted of a keynote talk on each topic followed by extensive discussions. The papers in this volume are based on the keynote talks augmented with some points raised in the discussion.The extensive development of electron beam instrumentation for the microscopy and analysis of samples of diverse scientific interest has resulted in a need for detailed studies of the origin and characteristics of the signals involved. This publication provides a detailed view of one approach to the study of such signals, namely the Monte Carlo technique for electron trajectory calculation.The publication should be of value to the numerous workers who utilize the scanning electron microscope and electron probe microanalyzer. The utility of electron probe microanalysis and scanning electron microscopy is demonstrated by the fact that more than 2500 such instruments costing from $25,000 to $200,000 are now in use worldwide, and more instruments are constantly being added. Moreover, the instruments are at work in fields as diverse as biology, metallurgy, electronics, chemistry, and forensic science.Simultaneously with the development and distribution of the instrumentation, much work has been devoted to the study of electron interactions with solids with the purpose of characterizing the signals which are utilized in microscopy and analysis.One approach which has proven especially useful in both qualitative and quantitative studies of electron interactions is that of Monte Carlo electron trajectory simulation.Monte Carlo calculations have enabled scientists to visualize the electron interaction volume in solids as to size and shape, to predict the parameters characterizing the secondary and back-scattered electrons, the x-rays, and the Auger electrons, and to analyze factors which determine resolution in micrographs.The purpose of the present workshop was to bring together a number of workers in Monte Carlo trajectory techniques to assess the current state of development and to look for areas of future development.The list of participants in the meeting does not include all active workers in the field, but we hope that this document contains a reasonably complete description of the subject.By examining the a...

Accuracy in quantitative electron-probe microanalysis

“…Fortunately, the availability of small computers permitted the on-line execution of more involved data reduction schemes; larger computers could be used in Monte Carlo simulations of the events in the target [3], and the quality of estimates of pertinent parameters, such as the x-ray absorption coefficients, was also improved [4].…”

“…* Systematic study of all sources of analytical errors, particularly of the measurement process, as described by Powell [3]. * Development of problem oriented measurement techniques and analytical strategies, combining SIMS with other analytical techniques yielding confirmatory and supplementary information (example ref.…”

A new fit to secondary emission yield in the low impact voltage regime: An improvement of Vaughan’s expression

“…The number of secondary electrons emitted per incident electron is referred to as secondary emission yield (SEY). [1][2][3][4][5][6][7][8] Modeling of SEY versus impact voltage has been performed for a long time, [1][2][3][4][5][6] using Monte Carlo simulations [9][10][11][12][13][14] and development of semi-empirical models. [15][16][17] Over the years, there have been several proposals for semi-empirical formulae to fit SEY experimental data.…”

Monte Carlo modeling of secondary x‐ray fluorescence across phase boundaries in electron probe microanalysis

“…Monte Carlo electron trajectory simulation provides a powerful tool for the calculation of the three-dimensional distribution of the primary radiation (Heinrich et al 1976). To calculate the spatial distribution of the secondary fluorescence due to the absorption of the primary radiation, a second calculation is needed that describes the propagation and absorption of the x-ray flux in three dimensions.…”