New Automated Analytical Integration for TEM Operation

Abstract

Current trends seek to make TEM operation more routine and productive. One of these follows the lead made in scanning electron microscopy in which the spatial distribution of crystallographic data over a selected area of a sample surface is determined by automated recognition of Backscatter Kikuchi patterns (EBSD), Adams et al . This method has been extended to the TEM in a novel manner, Wright et al . Dark field images are collected sequentially from the area of interest for all possible incident beam directions over a solid cone of semi-apex angle up to 4 degrees, Figure 1. The images are recorded directly into a computer. Off line automated analysis follows in which all dark field images are searched to determine the beam conditions under which each pixel in the image brightens, i.e. when the corresponding point in the sample came into a diffraction condition. The measurement of three such non-coplanar conditions for a pixel leads to the determination of the corresponding crystallographic orientation. The accuracy of orientation measurement has been improved to 1 degree by the fitting of the determined diffraction vectors to the surface of the Ewald sphere. The analysis allows grain maps to be reconstructed from which grain size distribution can be automatically determined. Figure 2.