title: Atomic scale dynamics of a solid state chemical reaction directly determined by annular dark-field electron microscopy.
abstract: Dynamic processes, such as solid-state chemical reactions and phase changes, are ubiquitous in materials science, and developing a capability to observe the mechanisms of such processes on the atomic scale can offer new insights across a wide range of materials systems. Aberration correction in scanning transmission electron microscopy (STEM) has enabled atomic resolution imaging at significantly reduced beam energies and electron doses. It has also made possible the quantitative determination of the composition and occupancy of atomic columns using the atomic number (Z)-contrast annular dark-field (ADF) imaging available in STEM. Here we combine these benefits to record the motions and quantitative changes in the occupancy of individual atomic columns during a solid-state chemical reaction in manganese oxides. These oxides are of great interest for energy-storage applications such as for electrode materials in pseudocapacitors. We employ rapid scanning in STEM to both drive and directly observe the atomic scale dynamics behind the transformation of Mn3O4 into MnO. The results demonstrate we now have the experimental capability to understand the complex atomic mechanisms involved in phase changes and solid state chemical reactions.
authors.affiliation: 1] SuperSTEM Laboratory, STFC Daresbury, Keckwick Lane, Warrington WA4 4AD, United Kingdom [2] Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Pennycook
authors.affiliation: Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom.
authors.forename: Lewys
authors.initials: L
authors.lastname: Jones
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Physics, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Henrik
authors.initials: H
authors.lastname: Pettersson
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: João
authors.initials: J
authors.lastname: Coelho
authors.affiliation: School of Physics, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Megan
authors.initials: M
authors.lastname: Canavan
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Mendoza-Sanchez
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Physics, Trinity College Dublin, Dublin 2, Ireland [3] School of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Valeria
authors.initials: V
authors.lastname: Nicolosi
authors.affiliation: 1] SuperSTEM Laboratory, STFC Daresbury, Keckwick Lane, Warrington WA4 4AD, United Kingdom [2] Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Nellist