Elemental mapping of microstructures by scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS): extraordinary advances with the silicon drift detector (SDD)

Elemental mapping at the microstructural level by scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry (EDS), while widely applied in science, engineering, and technology, has been limited in performance by the throughput of the lithium-drifted silicon detector [Si(Li)-EDS] which restricts the number of X-ray counts measured per image pixel. The emergence of the silicon drift detector (SDD-EDS) has greatly extended the X-ray throughput, by a factor of 25 to 70 for the same spectral resolution. This improved performance enables practical X-ray spectrum imaging (XSI), in which a complete X-ray spectrum is recorded at each image pixel. By performing complete quantitative corrections for background, peak overlap, and matrix effects to each pixel spectrum, full compositional mapping can be achieved. Various elemental mapping collection strategies are described, including quantitative mapping at the major (concentration C > 0.1 mass fraction), minor (0.01 <= C <= 0.1), and trace (C < 0.01) constituent levels, extreme pixel density (gigapixel) mapping, rapid mapping (in 10 seconds or less), and high spatial resolution mapping with the thermal field emission gun scanning electron microscope.