title: Detecting structural variances of Co3O4catalysts by controlling beam-induced sample alterations in the vacuum of a transmission electron microscope.
abstract: This article summarizes core aspects of beam-sample interactions in research that aims at exploiting the ability to detect single atoms at atomic resolution by mid-voltage transmission electron microscopy. Investigating the atomic structure of catalytic Co3O4nanocrystals underscores how indispensable it is to rigorously control electron dose rates and total doses to understand native material properties on this scale. We apply in-line holography with variable dose rates to achieve this goal. Genuine object structures can be maintained if dose rates below ~100 e/Å2s are used and the contrast required for detection of single atoms is generated by capturing large image series. Threshold doses for the detection of single atoms are estimated. An increase of electron dose rates and total doses to common values for high resolution imaging of solids stimulates object excitations that restructure surfaces, interfaces, and defects and cause grain reorientation or growth. We observe a variety of previously unknown atom configurations in surface proximity of the Co3O4spinel structure. These are hidden behind broadened diffraction patterns in reciprocal space but become visible in real space by solving the phase problem. An exposure of the Co3O4spinel structure to water vapor or other gases induces drastic structure alterations that can be captured in this manner.
authors.affiliation: Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 USA.
authors.forename: C
authors.identifier: 0000-0001-6425-0779
authors.initials: C
authors.lastname: Kisielowski
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 USA.
authors.forename: H
authors.initials: H
authors.lastname: Frei
authors.affiliation: Department of Material Science and Engineering, University of California-Berkeley, Berkeley, CA 94720 USA.
authors.forename: P
authors.initials: P
authors.lastname: Specht
authors.affiliation: Chemical Sciences Division and Joint Center for Artificial Photosynthesis, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA.
authors.forename: I D
authors.initials: ID
authors.lastname: Sharp
authors.affiliation: Joint Center for Artificial Photosynthesis California Institute of Technology, Pasadena, CA 91125 USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Haber
authors.affiliation: Haldor Topsoe A/S, Haldor Topsøes Allé 1, 2800 Kongens Lyngby, Denmark.
authors.forename: S
authors.initials: S
authors.lastname: Helveg