Exploring the Nano World by Electron Crystallography

Louisa Meshi, Department of Materials Engineering, Ben-Gurion University of the Negev, Beer Sheva, Israel (louisa@bgu.ac.il)

Current frontiers in the rational design of nano-scale-ordered functional materials involve progress in both the synthesis of “building blocks” from molecular precursors (i.e., “bottom-up” methods) and the use of these building blocks to create larger, more complex structures. For devising and improving such materials the conventional methods of trial and error are insufficient and a fundamental understanding of materials` structure is required. It is unfortunate that at present determination of atomic structure of nano-materials is still problematic. Because of extremely small size of nano-crystals, the conventional X-ray diffraction technique cannot be used for solving their atomic structure. Only electron crystallography has a potential and the power to do this. Therefore, over the past three decades the technique of electron crystallography has become increasingly important.

Electron crystallography is mainly based on a combination of electron diffraction structural analysis with high-resolution electron microscopy (HRTEM) which allows direct imaging of atomic planes and individual atomic columns. These methods allow full solution of atomic structure of unknown materials and characterization of structural imperfections. Both applications will be covered in current lecture. First, investigation of atomic structure of complex alluminides using electron diffraction tomography will be presented; then, study of antiphase boundaries in high entropy alloys will be shown.