title: Atomic electric fields revealed by a quantum mechanical approach to electron picodiffraction.
abstract: By focusing electrons on probes with a diameter of 50 pm, aberration-corrected scanning transmission electron microscopy (STEM) is currently crossing the border to probing subatomic details. A major challenge is the measurement of atomic electric fields using differential phase contrast (DPC) microscopy, traditionally exploiting the concept of a field-induced shift of diffraction patterns. Here we present a simplified quantum theoretical interpretation of DPC. This enables us to calculate the momentum transferred to the STEM probe from diffracted intensities recorded on a pixel array instead of conventional segmented bright-field detectors. The methodical development yielding atomic electric field, charge and electron density is performed using simulations for binary GaN as an ideal model system. We then present a detailed experimental study of SrTiO3 yielding atomic electric fields, validated by comprehensive simulations. With this interpretation and upgraded instrumentation, STEM is capable of quantifying atomic electric fields and high-contrast imaging of light atoms.
authors.affiliation: 1] Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany [2] Center of Excellence for Materials and Processes, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany.
authors.forename: Knut
authors.initials: K
authors.lastname: Müller
authors.affiliation: 1] Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany [2] Center of Excellence for Materials and Processes, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany.
authors.forename: Florian F
authors.initials: FF
authors.lastname: Krause
authors.affiliation: EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
authors.forename: Armand
authors.initials: A
authors.lastname: Béché
authors.affiliation: 1] Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany [2] Center of Excellence for Materials and Processes, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Schowalter
authors.affiliation: Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstraße 31, 93040 Regensburg, Germany.
authors.forename: Vincent
authors.initials: V
authors.lastname: Galioit
authors.affiliation: 1] Institute of Solid State Physics, Vienna University of Technology, Wiedner Hauptstraße 8-10/E138, A-1040 Vienna, Austria [2] University Service Centre for Transmission Electron Microscopy, Wiedner Hauptstraße 8-10/E052, A-1040 Vienna, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Löffler
authors.affiliation: EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
authors.forename: Johan
authors.initials: J
authors.lastname: Verbeeck
authors.affiliation: Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstraße 31, 93040 Regensburg, Germany.
authors.forename: Josef
authors.initials: J
authors.lastname: Zweck
authors.affiliation: 1] Institute of Solid State Physics, Vienna University of Technology, Wiedner Hauptstraße 8-10/E138, A-1040 Vienna, Austria [2] University Service Centre for Transmission Electron Microscopy, Wiedner Hauptstraße 8-10/E052, A-1040 Vienna, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Schattschneider
authors.affiliation: 1] Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany [2] Center of Excellence for Materials and Processes, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Rosenauer