Many theoretical models for HAADF-STEM images were initially developed for crystalline materials. The space travelled by the fast electron beam in STEM can be divided into three processes: from the source to the specimen; inside the specimen; and from the specimen to the detector. In the modeling, only the overall effects on the wave functions entering and exiting the specimen are taken into account.
In STEM analysis, the effect of the beam–specimen interaction in modifying the probe wave function into the sample exit wave function can be modeled using either the Bloch wave approach [1,2] or a multislice approach. [3,4]
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