Towards quantitative structure determination through electron microscopy

Project members: A.J. den Dekker, S. Van Aert (University of Antwerp), D. Van Dyck (University of Antwerp)

Sponsored by: KNAW

As scientists manage to control the structure of materials on an ever finer scale, more and more materials are being developed with interesting properties which are mainly related to their nanostructure. Parallel to this, one sees an evolution in solid-state theory where materials properties are increasingly better understood from first principle theoretical calculations. The merging of these fields will enable materials science to evolve into materials design. In order to correlate real properties with theoretical simulations, characterization methods in the future need to be able to determine atom positions in aperiodic structures with a precision of the order of 1 pm. Electron microscopy has this potential. From all possible imaging particles, electrons are the best candidates since they interact most strongly with matter to provide local information on atomic scale. However, the goal is not yet reached. Thus far, the technique has mostly been based on a qualitative basis, mainly as a result of the strong and hence complicated interaction of the electrons with the material. However, the directly interpretable resolution is no better than near-atomic (ca. 0.2 nm). For the future, this will be totally insufficient. To meet the future requirements, the electron microscopy images should be interpreted quantitatively instead of qualitatively. It is our goal to show that the interpretation of the images could greatly benefit from a quantitative model-based approach (in which statistical parameter estimation plays a crucial role) accompanied by quantitative statistical experimental design. The final objective is to develop a reliable quantitative electron microscopy method and an accompanying methodology for experimental design, which allow one to determine coordinates of the projected atomic structure with the required precision.