To resolve ambiguities in HAADF image intensities, spectroscopy can be used to provide maps with signals linked to each elemental species present by using the X-rays generated from the sample-electron beam interaction. In previous generations of EDS detectors, low signal collection hampered the achievable signal at atomic resolution, restricting the ability to perform atomic scale mapping. With modern technology, the attainable signal is roughly an order of magnitude higher and these techniques can now be performed at atomic resolution.
Figure 2 shows an EDS map acquired over a repeat unit of the superlattice structure with colors corresponding to each type of element. In contrast to the HAADF image, each distinct layer is now clearly identified including the interfacial monolayers of InSb, removing the ambiguities associated with the black and white Z-contrast image. As demonstrated through the example in Figure 2, EDS clarifies the layer composition as well as the polarity in the sample. Although the signal is clear for the atomically resolved EDS map, the signal rate is still much lower than the typical Z-contrast image. Thus, EDS mapping can have limited application to samples that are sensitive to extensive electron beam radiation.