Orientation precision of TEM-based orientation mapping techniques.

Automatic orientation mapping is an important addition to standard capabilities of conventional transmission electron microscopy (TEM) as it facilitates investigation of crystalline materials. A number of different such mapping systems have been implemented. One of their crucial characteristics is the orientation resolution. The precision in determination of orientations and misorientations reached in practice by TEM-based automatic mapping systems is the main subject of the paper. The analysis is focused on two methods: first, using spot diffraction patterns and 'template matching', and second, using Kikuchi patterns and detection of reflections. In simple terms, for typical mapping conditions, their precisions in orientation determination with the confidence of 95% are, respectively, 1.1 ° and 0.3 °. The results are illustrated by example maps of cellular structure in deformed Al, the case for which high orientation sensitivity matters. For more direct comparison, a novel approach to mapping is used: the same patterns are solved by each of the two methods. Proceeding from a classification of the mapping systems, the obtained results may serve as indicators of precisions of other TEM-based orientation mapping methods. The findings are of significance for selection of methods adequate to investigated materials.