Energy‐Dispersive Spectrometry

AbstractEnergy‐dispersive x‐ray spectrometry (EDS) is a technique for measuring the intensity of x‐ray emission as a function of the energy of the x‐ray photons. The excitation source for the x‐rays can be energetic electrons, photons, or ions, and the target can be solid, liquid, or gas, although solid targets are the norm in virtually all materials science applications. The measured x‐ray intensity can be related to the concentration (i.e., mass or atomic fraction) for each element present by performing physical/empirical matrix corrections to account for the interelement modification of the generated x radiation caused by (1) primary radiation stopping power and ionization effects, (2) attenuation of secondary characteristic x‐rays during their passage through matter, and (3) any inefficiencies in detection. In this article, various aspects of the process of obtaining high‐quality x‐ray spectra, the interpretation of spectra, and the accurate extraction of x‐ray intensities from spectra are considered.Materials analysis techniques that employ EDS include the following.Electron excitation: (1) electron probe x‐ray microanalysis (EPMA)/analytical scanning electron microscopy (ASEM), where EDS complements wavelength‐dispersive x‐ray spectroscopy (WDS); (2) analytical electron microscopy (AEM).Photon excitation:X‐ray fluorescence (XRF).Ion excitation:particle‐induced x‐ray emission (PIXE).This article will concentrate on EDS performed in electron‐beam instruments. The general principles of EDS x‐ray detection, processing, display, and spectral manipulation are similar for all analytical techniques regardless of the excitation source. The procedures for quantitative analysis depend in detail on the excitation process. Quantitative x‐ray microanalysis by electron excitation is considered in detail in the section on Electron Probe Microanalysis. Those aspects of quantitative x‐ray microanalysis that are particular to EDS spectral measurement are considered.