Basic literacy in electron-probe x-ray microanalysis with energy-dispersive x-ray spectrometry: Qualitative and quantitative analysis

Abstract

Rigorous electron probe x-ray microanalysis (EPMA) with energy dispersive x-ray spectrometry (EDS) takes place in two sequential steps: qualitative analysis followed by quantitative analysis.Qualitative analysis: Qualitative analysis involves the assignment of the peaks found in the x-ray spectrum to specific elements. One of the most important attributes of energy dispersive x-ray spectrometry (EDS) for qualitative analysis is that we can always view the complete x-ray spectrum. The EDS photon detection process effectively provides parallel detection in energy. Depending on the detector window and spectrometer characteristics, the entire energy range from Be K radiation (0.106 keV) to the incident beam energy can be available for analysis. With an incident beam energy of 15 keV, at least one family of x-ray lines (K, L, or M shell) will be excited for each element in the Periodic Table with atomic number ≥ 4. We ignore at our peril this capability to do a complete qualitative analysis at all specimen locations that we choose to measure. Quantitative analysis is meaningless if qualitative analysis has not been properly perfonned first. The bases for qualitative analysis include the exact energy of the peak(s), which places a premium on spectrometer calibration, the recognition of all members of each x-ray family and the possibility of two (or more) families being excited, the relative intensities ("weights of lines") within a family, and the artifacts associated with each high intensity peak, particularly the escape peak(s) and sum peak(s).