Quantitative comparison of bright field and annular bright field imaging modes for characterization of oxygen octahedral tilts

• Published in: Ultramicroscopy 2017-10, Vol.181, p.1-7
• Main Authors: Kim, Young-Min, Pennycook, Stephen J., Borisevich, Albina Y.
• Format: Article
• Language: English
• Subjects: BiFeO3; Bright field; MATERIALS SCIENCE; Octahedral tilt; Oxygen imaging; Perovskite; STEM; Transition metal oxide
• ISSN: 0304-3991; 1879-2723
• DOI: 10.1016/j.ultramic.2017.04.020

•An aberration-corrected BF STEM imaging at an accelerating voltage of 300kV provides a wide range of defocus-thickness imaging parameters and specimen misorientation for precisely locating oxygen positions in a tilted perovskite structure.•BF STEM imaging for the measurements of oxygen octahedral tilts has quantitatively compared with ABF STEM imaging by systematic image simulations.•BF STEM imaging working at 300kV shows superior accuracy for the measurements of the octahedral tilt angles as compared with ABF STEM imaging. Octahedral tilt behavior is increasingly recognized as an important contributing factor to the physical behavior of perovskite oxide materials and especially their interfaces, necessitating the development of high-resolution methods of tilt mapping. There are currently two major approaches for quantitative imaging of tilts in scanning transmission electron microscopy (STEM), bright field (BF) and annular bright field (ABF). In this paper, we show that BF STEM can be reliably used for measurements of oxygen octahedral tilts. While optimal conditions for BF imaging are more restricted with respect to sample thickness and defocus, we find that BF imaging with an aberration-corrected microscope with the accelerating voltage of 300kV gives us the most accurate quantitative measurement of the oxygen column positions. Using the tilted perovskite structure of BiFeO3 (BFO) as our test sample, we simulate BF and ABF images in a wide range of conditions, identifying the optimal imaging conditions for each mode. We show that unlike ABF imaging, BF imaging remains directly quantitatively interpretable for a wide range of the specimen mistilt, suggesting that it should be preferable to the ABF STEM imaging for quantitative structure determination.