Abstract

Elemental analysis on scanning electron microscopes (SEM) by energy dispersive spectrometry (EDS) is a widely used analytical technique across the geosciences. A basic understanding of how energy spectra are generated by the interaction of the electron beam and the samples is key to giving students the skills to produce high-quality data. It is equally important to giving students the skills to be critical consumers of the data, capable of understanding limitations and pitfalls of the technique. Intended as a supplement to 'book-learning', this activity uses the free software DTSA-II from the National Institute of Standards and Technology (NIST) to allow students to produce model energy spectra of elements, compounds, and minerals they specify. A set of spectra recorded from actual samples will also be explored to identify peak overlaps and other common problematic occurrences. By completing the assignment students will have been introduced to concepts in x-ray microanalysis, begun learning the skill of interpreting spectra, and have identified common problems to be aware of when using EDS spectral data.

Context

This activity is newly developed and feedback from attendees is strongly encouraged. The activity can be taught as a topic in a lower-level geoscience course, as part of a lab in an upper-level mineralogy or analytical methods course, or tailored to preparing students who are embarking on independent research.

Why It Works

Energy spectra from compositionally complex minerals can seem bafflingly complex at first glance. By building-up spectra from combinations of elements students can hopefully develop an understanding and comfort which will promote a greater willingness to be engaged in producing—and critically questioning—analytical results.