title: Oxidation-state sensitive imaging of cerium dioxide by atomic-resolution low-angle annular dark field scanning transmission electron microscopy.
abstract: Low-angle annular dark field (LAADF) scanning transmission electron microscopy (STEM) imaging is presented as a method that is sensitive to the oxidation state of cerium ions in CeO2 nanoparticles. This relationship was validated through electron energy loss spectroscopy (EELS), in situ measurements, as well as multislice image simulations. Static displacements caused by the increased ionic radius of Ce(3+) influence the electron channeling process and increase electron scattering to low angles while reducing scatter to high angles. This process manifests itself by reducing the high-angle annular dark field (HAADF) signal intensity while increasing the LAADF signal intensity in close proximity to Ce(3+) ions. This technique can supplement STEM-EELS and in so doing, relax the experimental challenges associated with acquiring oxidation state information at high spatial resolutions.
authors.affiliation: Materials Measurement Lab, National Institute of Standards Technology, Gaithersburg, MD 20899, USA. Electronic address: aaron.johnston-peck@nist.gov.
authors.forename: Aaron C
authors.initials: AC
authors.lastname: Johnston-Peck
authors.affiliation: Center for Nanoscale Science and Technology, National Institute of Standards Technology, Gaithersburg, MD 20899, USA.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Winterstein
authors.affiliation: Department of Chemistry and Center for Nanostructured Electronic Materials, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Alan D
authors.initials: AD
authors.lastname: Roberts
authors.affiliation: Department of Chemistry and Center for Nanostructured Electronic Materials, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Joseph S
authors.initials: JS
authors.lastname: DuChene
authors.affiliation: Department of Chemistry and Center for Nanostructured Electronic Materials, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Kun
authors.initials: K
authors.lastname: Qian
authors.affiliation: Department of Chemistry and Center for Nanostructured Electronic Materials, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Brendan C
authors.initials: BC
authors.lastname: Sweeny
authors.affiliation: Department of Chemistry and Center for Nanostructured Electronic Materials, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Wei David
authors.initials: WD
authors.lastname: Wei
authors.affiliation: Center for Nanoscale Science and Technology, National Institute of Standards Technology, Gaithersburg, MD 20899, USA.
authors.forename: Renu
authors.initials: R
authors.lastname: Sharma
authors.affiliation: Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11793, USA.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Stach
authors.affiliation: Materials Measurement Lab, National Institute of Standards Technology, Gaithersburg, MD 20899, USA.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Herzing
keywords: Cerium dioxide; Point defects; Scanning transmission electron microscopy