Quantitative atomic resolution elemental mapping via absolute-scale energy dispersive X-ray spectroscopy

• Published in: Ultramicroscopy Vol. 168; pp. 7 - 16
• Main Authors: Chen, Z., Weyland, M., Sang, X., Xu, W., Dycus, J.H., LeBeau, J.M., D'Alfonso, A.J., Allen, L.J., Findlay, S.D.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-09-2016
• Subjects: Apertures; Atomic-resolution mapping; Channelling; Electron scattering; Elemental quantification; Energy dispersive X-ray (EDX) spectroscopy; Energy dispersive x-ray spectroscopy; Forming; Mapping; Scanning transmission electron microscopy (STEM); Signal to noise ratio; Simulation; Atomic-resolution mapping; Energy dispersive X-ray (EDX) spectroscopy; Scanning transmission electron microscopy (STEM); Elemental quantification
• ISSN: 0304-3991; 1879-2723
• DOI: 10.1016/j.ultramic.2016.05.008

Quantitative agreement on an absolute scale is demonstrated between experiment and simulation for two-dimensional, atomic-resolution elemental mapping via energy dispersive X-ray spectroscopy. This requires all experimental parameters to be carefully characterized. The agreement is good, but some discrepancies remain. The most likely contributing factors are identified and discussed. Previous predictions that increasing the probe forming aperture helps to suppress the channelling enhancement in the average signal are confirmed experimentally. It is emphasized that simple column-by-column analysis requires a choice of sample thickness that compromises between being thick enough to yield a good signal-to-noise ratio while being thin enough that the overwhelming majority of the EDX signal derives from the column on which the probe is placed, despite strong electron scattering effects.
•Absolute scale quantification of 2D atomic-resolution EDX maps is demonstrated.•Factors contributing to remaining small quantitative discrepancies are identified.•Experiment confirms large probe-forming apertures suppress channelling enhancement.•The thickness range suitable for reliable column-by-column analysis is discussed.