title: Dose-rate-dependent damage of cerium dioxide in the scanning transmission electron microscope.
abstract: Beam damage caused by energetic electrons in the transmission electron microscope is a fundamental constraint limiting the collection of artifact-free information. Through understanding the influence of the electron beam, experimental routines may be adjusted to improve the data collection process. Investigations of CeO2indicate that there is not a critical dose required for the accumulation of electron beam damage. Instead, measurements using annular dark field scanning transmission electron microscopy and electron energy loss spectroscopy demonstrate that the onset of measurable damage occurs when a critical dose rate is exceeded. The mechanism behind this phenomenon is that oxygen vacancies created by exposure to a 300keV electron beam are actively annihilated as the sample re-oxidizes in the microscope environment. As a result, only when the rate of vacancy creation exceeds the recovery rate will beam damage begin to accumulate. This observation suggests that dose-intensive experiments can be accomplished without disrupting the native structure of the sample when executed using dose rates below the appropriate threshold. Furthermore, the presence of an encapsulating carbonaceous layer inhibits processes that cause beam damage, markedly increasing the dose rate threshold for the accumulation of damage.
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: 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: 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: Wei David
authors.initials: WD
authors.lastname: Wei
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: Beam damage; Cerium dioxide; Point defects; Scanning transmission electron microscopy