Dark-field TEM tomography of ordered domain morphology in a Ni4Mo alloy

Abstract

Various TEM imaging modes, such as bright-field imaging, STEM and energyfiltering and so on, have been being utilized in electron tomography [1]. In contrast to the above imaging modes, dark-field (DF) TEM imaging is useful for observing crystalline microstructures such as lattice defects, grain boundaries, ordered domain structures, etc. However, it is not generally considered that dark-field (DF) TEM imaging is applicable to electron tomography, since the image contrast is not a simple function of thickness and density. One has to control the diffraction condition precisely to get well-defined DF images, because the image contrast is quite sensitive also to the direction of the incident electron beam. Contrary to the general understanding, we have shown a technique to obtain a DF TEM tilt series and its applicability to electron tomography for crystalline specimens [2]. In this paper, we discuss our latest results of the tomographic DF TEM observation of variant structures in a Ni4Mo ordering alloy from the view point of 3D morphology of different variants.