Local quantification of coordination number for perovskite-related oxides using atomic resolution EELS maps

Abstract

The establishment of a method to quantify oxygen in metal oxides with atomic resolution is required in materials science. However, it is, in principle, difficult to experimentally extract such information with atomic resolution using scanning transmission electron microscopy combined with electron energy-loss spectroscopy due to the physically limited spatial resolution caused by the delocalization of inelastic scattering electrons. In this study, an experimental value of the elemental ratio of oxygen/cation obtained from the center of a cation column along a pseudo-cubic [100] observation for perovskite-related materials was correlated with the oxygen coordination number for the cation, although it did not reflect the information with atomic resolution. As a result, there are two types of correlations attributed to the difference in the existence of oxygen in the illuminated atomic column and average oxygen-cation bond length around A and B sites. The application of plural point analysis based on the present approach would be able to overcome the physical spatial limit and identify the position of an oxygen defect with atomic resolution. This result would be readily applicable or practical for studying a local amount of oxygen around interface structures of thin films, dislocation sites, and others.