Quantitative EDX Analysis in TEM. Practical Development, Limitations and Standards

Abstract

Principles and methods of EDX microanalysis in transmission electron microscopy are presented. Absorption and fluorescence corrections are not carried out in TEM, as real thickness of the sample in the precise analysis point is unknown, but very small. Therefore it is assumed that the effect of such corrections should be minimum. Small thickness guarantees a lack of spread of electrons to larger areas than the spot size used, which means the possibility of very high spatial resolution chemical analyses. In relation to electron microprobe or scanning electron microscope, microanalysis in TEM presents the advantage of minimum size of analysis spot, but its drawback is its lower analytical quality. As the excited volume is an unknown figure, microanalysis in TEM always produces relative results, that is, only the ratios of concentrations among the various elements can be measured but not their absolute concentrations. This is an intrinsic limitation of the method.