Atomic-resolution electron microscopy-going beyond imagination

David Wang Auditorium, 3rd floor Dalia Maydan Bldg.
Dr. Zaoli Zhang

Dr. Zaoli Zhang

Erich Schmid Institute of Materials Science,
Austrian Academy of Sciences, Leoben

Modern transmission electron microscopy (TEM) offers the extraordinary opportunities for materials research. In the first part of this presentation, I will briefly show my recent studies using various advanced electron microscopy techniques, such as atomic resolution imaging via spherical aberration technique and atomic-resolution scanning TEM (STEM)–electron energy loss spectroscopy (EELS) analysis etc. In the second part, I will demonstrate two examples via a detailed investigation, such as the interface in transition metal nitride films and dislocation cores in oxides.

Important properties of materials, especially in nanostructured materials, are strongly influenced or controlled by the presence of solid interfaces, i.e. from the atomic arrangement in a region which is a few atomic spacing wide. Using simultaneous imaging and spectroscopy, we are able to visualize the defects (N vacancies) at the nitride film interface, and characterize the structure triggered by these vacancies. Some generalized relationships between the vacancy concentration and lattice constants are further deduced. The second example will be about the dislocation core in oxide. Modern TEM allows us not only visualizing detailed atomic configurations of individual dislocation core, but also characterizing the electronic structure and chemistry of the core, and enabling to atomic-scale associate with the properties of materials. Non-stoichiometric chemistry and crystal-field splitting in the core are detected, which are directly linked to the behaviours of dislocation.