Retrieving overlapping crystals information from TEM nano ‐beam electron diffraction patterns

Summary The diffraction patterns acquired with a transmission electron microscope (TEM) contain Bragg reflections related to all the crystals superimposed in the thin foil and crossed by the electron beam. Regarding TEM‐based orientation and phase characterisation techniques, the nondissociation of these signals is usually considered as the main limitation for the indexation of diffraction patterns. A new method to identify the information related to the distinct but overlapped grains is presented. It consists in subtracting the signature of the dominant crystal before reindexing the diffraction pattern. The method is coupled to the template matching algorithm used in a standard automated crystal orientation mapping tool (ACOM‐TEM). The capabilities of the approach are illustrated with the characterisation of a NiSi thin film stacked on a monocrystalline Si layer. Then, a subtracting‐indexing cycle applied to a 70 nm thick thin foil containing polycrystalline tungsten electrical contacts shows the capability of the technique to recognise small nondominant grains. Lay description Automated crystal orientation mappings are widely used in numerous fields of activity as it provides a deeper understanding of crystalline materials behaviour. Today, the TKD (or transmission Kikuchi diffraction) and the ACOM‐TEM (or automated crystal orientation and phase mapping for transmission electron microscopes) techniques offers sub‐10 nm spatial resolution. Regarding the ACOM‐TEM...
Source: Journal of Microscopy - Category: Laboratory Medicine Authors: Tags: Original Article Source Type: research