Quantitative determination of the chemical composition of an alloy by High Angle Annular Dark Field imaging

Scanning transmission electron microscopy (STEM) high angle annular dark field (HAADF) imaging is now well established as a powerful tool for studying the structural and chemical properties of solid-state matter at atomic resolution. The HAADF image intensity depends sensitively on the atomic numbers of the elements in the atomic column, and important qualitative chemical information at atomic resolution can be achieved by direct inspection of the HAADF image contrast. Nevertheless, if quantitative information on the chemistry of the specimen is sought for, it becomes necessary to compare the experimental results with HAADF image simulations. Alas a satisfactory comparison between experiment and simulation has been so far quite difficult. In particular a recent article [1] raised the problem of discordance between simulations and experiment in the evaluation of the baseline intensity between intensity atomic positions. For this reason this baseline intensity is subtracted in their quantitative evaluation. Quite likely, this baseline additional intensity is due to incoherent effects on the probe.