High spatial resolution semi‐automatic crystallite orientation and phase mapping of nanocrystals in transmission electron microscopes

Abstract

International audienceA semi-automatic technique for the mapping of nanocrystal phases and orientations in a transmission electron microscope (TEM) is described. It is based primarily on the projected reciprocal lattice geometry, but also utilizes the intensity of reflections that are extracted from precession-enhanced electron diffraction spot patterns of polycrystalline materials and multi-material composites. At the core of the method, experimental (precession-enhanced) electron diffraction spot patterns are cross correlated with pre-calculated templates for a set of model structures. The required hardware facilitates a scanning-precession movement of the primary electron beam on the polycrystalline and/or multi-material sample and can be interfaced to any newer or older mid-voltage TEM. The software that goes with this hardware is so flexible in its intake of experimental data that it can also create crystallite orientation and phase maps of nanocrystals from the amplitude part of Fourier transforms of high resolution TEM images. Experimentally obtained crystallite orientation and phase maps are shown for a clausthalite nanocrystal powder sample, polycrystalline aluminum and copper films, fine-grained palladium films, as well as MnAs crystallites that are partly embedded in a GaAs wafer. Comprehensive open-access and commercial crystallographic databases that may provide reference data in support of the nanocrystal phase identification process of the software are briefly mentioned. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Using Microscopy to Help with the Understanding of Degradation Mechanisms Observed in Materials of Pressurized Water Reactors

“…26), making it almost impossible to study their local structures using electron diffraction in TEM [103]. Nevertheless, the analysis with ASTAR software of HRTEM images acquired on a Cs objective lens corrected TEM allows us to fill this gap [63,104]. Indeed post analysis with ASTAR software replacing electron diffraction pattern by Fourier transformed ones, give access to a precise evaluation of the phases contained in nanometric layers.…”

Features of Transmission EBSD and its Application

“…Combining these automated indexing techniques with the nanobeam diffraction capability of the TEM, the spatial resolution of orientation mapping in the TEM can reach a 2 nm to 3 nm scale. 1 But the accuracy of measured orientations is still limited compared with the results of electron backscatter diffraction (EBSD) in the scanning electron microscope (SEM). The achievable spatial resolution of standard EBSD (s-EBSD) is still at the 20 nm-30 nm level when combined with field emission SEM, although its orientation accuracy is stable and it is generally a range of 0.5°.…”

“…A great advance would be to marry the routine quantitative capability of automated EBSD with the spatial resolution of the TEM-to be able to achieve EBSD spatial resolutions measured in the nm instead of in the tens of nm of s-EBSD. 1 In 2012, Keller and Geiss demonstrated that EBSD patterns could be acquired from a thin film specimen by transmitted electrons in the SEM. 2 They used a s-EBSD detector mounted on their SEM and a thin film specimen (TEM specimen) was tilted in the opposite direction of the standard reflection EBSD configuration to enable a geometry where a transmitted electron can hit the phosphor screen of the EBSD detector in the standard position as shown in Fig.…”

Local Layer Stacking and Structural Disorder in Graphene Oxide Studied via Scanning Electron Diffraction.

“…Real and reciprocal space information is obtained with nanometer spatial resolution and rapid acquisition enables potentially beam sensitive materials, such as GO, to be studied. The 4D-SED dataset contains a wealth of information that can be extracted computationally post-facto [7]. In the case of GO, interpretation of the electron diffraction requires consideration of the effect of disorder, particularly on the diffracted intensities.…”