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

Area of Science:

• Materials Science
• Electron Microscopy
• Crystallography

Background:

• Directly interpretable imaging is crucial for understanding atomic structures at interfaces.
• Annular bright field scanning transmission electron microscopy (ABF-STEM) offers simultaneous visualization of light and heavy atomic columns.
• Grain boundaries in ceramics like alpha-alumina (α-Al(2)O(3)) significantly influence material properties.

Purpose of the Study:

• To demonstrate the capability of ABF-STEM for directly imaging oxygen columns at a specific grain boundary in α-Al(2)O(3).
• To investigate the contrast mechanisms and potential artifacts in high-angle annular dark field (HAADF) imaging at this grain boundary.
• To correlate experimental observations with simulations for a comprehensive understanding.

Main Methods:

• Utilizing annular bright field scanning transmission electron microscopy (ABF-STEM) for imaging.
• Employing high-angle annular dark field (HAADF) imaging concurrently with ABF-STEM.
• Performing simulations to analyze image contrast and experimental parameters like specimen thickness and source size.

Main Results:

• Successfully achieved directly interpretable imaging of oxygen columns at the Σ13[12¯10](101¯4) pyramidal twin grain boundary in α-Al(2)O(3).
• Demonstrated the complementary information obtained from simultaneous ABF-STEM and HAADF imaging.
• Identified and explored the origin of dark contrast in HAADF images near the grain boundary through simulation.

Conclusions:

• ABF-STEM is a powerful tool for resolving light element columns, such as oxygen, at complex interfaces in advanced ceramics.
• Simultaneous ABF-STEM and HAADF imaging provide a more complete picture of atomic arrangements and potential imaging artifacts.
• Understanding contrast variations at grain boundaries is essential for accurate structural characterization using electron microscopy.