Theoretical Evaluation of Atomic-Resolution X-ray Analysis toward Quantification

The latest aberration-corrected scanning transmission electron microscopes (STEMs) in combination with the large solid-angle silicon-drift X-ray detectors (SDDs) improve limited efficiencies of signal generation and collections. It is no longer dream to acquire atomic resolution X-ray maps and to achieve single atom sensitivity in X-ray analysis by using the latest aberration-corrected instruments. Obvious next challenge is quantification of such atomic-resolution X-ray maps. There are several attempts to perform quantification of the atomic resolution X-ray maps [e.g. 1, 2]. However, quantified results are deviated from expected values from the structures. For example, Ga composition does not reach to 100 % at Ga only columns in a [100]-projected GaAs compound [1]. Clearly, X-ray signals are generated from the specific atomic column where the incident electron is focused but also surrounding columns. For appropriate quantification, it is essential to determine how much X-ray signals are generated from the target and neighboring columns. In this study, X-ray signal generation in an oriented crystalline structure is simulated theoretically toward quantitative analysis. In order to simulate X-ray generation, first, it is required to know how the incident electron probe propagates in an oriented crystalline material. The electron propagation, called the electron wav