Effective absorption correction for energy dispersive X ‐ray mapping in a scanning transmission electron microscope: analysing the local indium distribution in rough samples of InGaN alloy layers

Summary We have applied our previous method of self‐consistent k*‐factors for absorption correction in energy‐dispersive X‐ray spectroscopy to quantify the indium content in X‐ray maps of thick compound InGaN layers. The method allows us to quantify the indium concentration without measuring the sample thickness, density or beam current, and works even if there is a drastic local thickness change due to sample roughness or preferential thinning. The method is shown to select, point‐by‐point in a two‐dimensional spectrum image or map, the k*‐factor from the local Ga K/L intensity ratio that is most appropriate for the corresponding sample geometry, demonstrating it is not the sample thickness measured along the electron beam direction but the optical path length the X‐rays have to travel through the sample that is relevant for the absorption correction. Lay description Energy‐dispersive X‐ray spectroscopy and corresponding elemental mapping are routine methods in analytical electron microscopy to measure and visualise the distribution of chemical elements within a sample, with wide applications in materials science, physics, chemistry, life sciences and engineering. In order to measure atomic or weight concentrations reliably and reproducibly in a transmission electron microscope, spectra and maps need to be fully corrected for the effects of backscattering and primary ionisation yield, which depend on atomic number (Z), and absorption (A) and fluoresc...
Source: Journal of Microscopy - Category: Laboratory Medicine Authors: Tags: Themed Issue Paper Source Type: research