nn7b02188_si_004.avi (1.07 MB)
In Situ Observation of Oxygen Vacancy Dynamics and Ordering in the Epitaxial LaCoO3 System
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posted on 2017-06-11, 00:00 authored by Jae Hyuck Jang, Young-Min Kim, Qian He, Rohan Mishra, Liang Qiao, Michael D. Biegalski, Andrew R. Lupini, Sokrates T. Pantelides, Stephen J. Pennycook, Sergei V. Kalinin, Albina Y. BorisevichVacancy dynamics and ordering underpin
the electrochemical functionality
of complex oxides and strongly couple to their physical properties.
In the field of the epitaxial thin films, where connection between
chemistry and film properties can be most clearly revealed, the effects
related to oxygen vacancies are attracting increasing attention. In
this article, we report a direct, real-time, atomic level observation
of the formation of oxygen vacancies in the epitaxial LaCoO3 thin films and heterostructures under the influence of the electron
beam utilizing scanning transmission electron microscopy (STEM). In
the case of LaCoO3/SrTiO3 superlattice, the
formation of the oxygen vacancies is shown to produce quantifiable
changes in the interatomic distances, as well as qualitative changes
in the symmetry of the Co sites manifested as off-center displacements.
The onset of these changes was observed in both the [100]pc and [110]pc orientations in real time. Additionally,
annular bright field images directly show the formation of oxygen
vacancy channels along [110]pc direction. In the case of 15 u.c. LaCoO3 thin film, we observe the sequence of events during beam-induced
formation of oxygen vacancy ordered phases and find them consistent
with similar processes in the bulk. Moreover, we record the dynamics
of the nucleation, growth, and defect interaction at the atomic scale
as these transformations happen. These results demonstrate that we
can track dynamic oxygen vacancy behavior with STEM, generating atomic-level
quantitative information on phase transformation and oxygen diffusion.