Direct oxygen imaging within a ceramic interface, with some observations upon the dark contrast at the grain boundary

Annular bright field scanning transmission electron microscopy, which has recently been established to produce directly interpretable images with both light and heavier atomic columns visible simultaneously, is shown to allow directly interpretable imaging of the oxygen columns within the Σ13Σ13[12¯10](101¯4) pyramidal twin grain boundary in α-Al2O3α-Al2O3. By using information in the high-angle annular dark field image and annular bright field images simultaneously, we estimate the specimen thickness and finite source size, and use them to explore in simulation the issue of dark contrast in the vicinity of the grain boundary in the annular dark field image.

Research highlights
► Simultaneous HAADF and ABF images of a pristine Σ13Σ13 grain boundary in α-Al2O3.
► Oxygen columns are clearly visible in the grain boundary in the ABF image.
► ABF is more robust than HAADF for imaging defect structures.
► Thickness and source size are estimated from quantitative analysis of the contrast.
► Dark contrast at the grain boundary in HAADF is likely due to strain and vacancies.