Monte-Carlo and finite element calculations of X-ray production at interfaces in bulk materials

Analytical electron microscopy of small features, requiring high spatial resolution, is normally considered to be a task for transmission electron microscopy (TEM). However, specimen preparation for TEM can be tedious, difficult and, in some instances, impossible. This paper demonstrates that bulk specimens can be examined in a scanning electron microscope to detect an element with high spatial sensitivity when the element is present in a thin planar interface within the specimen. Detection of less than a monolayer of an element is possible under the right experimental conditions, the most stringent requirement being placement of the electron beam directly on the interface. Monte-Carlo and finite element calculations were performed to model the X-ray intensity from a variety of planar interfaces. The results for a multi-layered metal specimen were assessed by comparison with experimental results. An approximate model was devised and used for quick calculations to gain an understanding of the X-ray production within bulk specimens.