ID-8-P-5749 3D atomic tomography from HRTEM –CeO₂

Nowadays, various advance TEM hardware like Cs corrector and monochromator have been developed with sub-Å resolution. But, we still only get the two-dimensional projections from three-dimensional sample from an aberration corrected TEM. To resolve the lost information along thickness direction, TEM tomography is becoming one critical and powerful technique for analysis of three-dimension structure in materials science. ⁽¹⁾

<span>In this report, we demonstrate to determine the three-dimensional shape at atomic resolution positions of a nanocrystalline specimen CeO₂ from an exit wave via wave back propagation and Big-Bang schemes.⁽²⁾ Exit wave reconstructed from a focal series of HRTEM images of CeO₂ is shown in Fig.1.<span>By back propagating the wave, the position of atomic columns can be decided. The maximum amplitude of the wave reveals the original position of the atomic columns. Next, the true positions of Ce and O atomic columns in the exit surface can be refined with Big-Bang scheme. As we can see in Fig.2,the focal maps show the de-focal values from the exit wave to atomic columns of Ce and O atoms.

<span> After the vertical positions of atoms in 3D Space are retrieved by Wave back-propagation and refined by the Big-bang theory, the thickness of atomic columns in unit of number of atom could be quantified by phase of exit wave. Once the thickness of sample known, then 3D tomography with atomic resolution can then be reconstructed. Based on these methods, three-dimensional reconstructed model with atomic-resolution was proposed.