So far, high-resolution transmission electron microscopy (HRTEM) has largely relied on using the phase of the exit wave function at the exit surface to form a HRTEM image. Recent development of correction of both spherical aberration (Cs) and chromatic aberration (Cc) offers a new imaging mode to achieve amplitude contrast imaging in HRTEM, allowing us to obtain directly interpretable HRTEM images with discrimination between light and heavy atomic columns. Using this imaging approach, we have successfully visualized the atomic structure in a BaTiO₃/CaTiO₃ superlattice with high spatial accuracy and discrimination between Ba and Ca columns, providing direct visualization of the Ca and Ba associated oxygen octahedral tilt that controls ferroelectric behavior in these superlattice structures. DFT calculation based the TEM observation predicts a metastable “interface phase” of CaTiO3 with large ferroelectricity is stabilized by the mechanical and electrical boundary conditions of the BaTiO₃/CaTiO₃ superlattice. Furthermore, we applied this imaging approach to other advanced materials such as SrTiO₃ and CeO₂ nanocubes (as catalyst supports), lithium-ion batteries, and lithium – oxygen batteries.

Argonne Physics Division Colloquium Schedule