On producing high-spatial-resolution composition profiles via scanning transmission electron microscopy

Abstract

Abstract Measurement of the concentration variation of a grain boundary segregant near a grain boundary has been chosen as a system in which to investigate the spatial resolution attainable by X-ray microanalysis in the scanning transmission electron microscope (STEM). In this paper extensive experimental work on Fe-doped MgO is compared with a theoretical model which examines the effect of incident probe size and electron beam broadening in the sample on concentration profiles measured using standard analysis of X-ray data. It is shown that the spatial extent of segregation can be determined to a resolution dependent on the incident probe size. The magnitude of the peak concentrations determined at the boundary are, however, strongly dependent on beam broadening and hence foil thickness. Comparing experimental and calculated results suggests that the extent of beam broadening may not be as great as current theoretical estimates would predict.