title: Influence of spatial and temporal coherences on atomic resolution high angle annular dark field imaging.
abstract: Aberration-corrected (scanning) transmission electron microscopy ((S)TEM) has become a widely used technique when information on the chemical composition is sought on an atomic scale. To extract the desired information, complementary simulations of the scattering process are inevitable. Often the partial spatial and temporal coherences are neglected in the simulations, although they can have a huge influence on the high resolution images. With the example of binary gallium phosphide (GaP) we elucidate the influence of the source size and shape as well as the chromatic aberration on the high angle annular dark field (HAADF) intensity. We achieve a very good quantitative agreement between the frozen phonon simulation and experiment for different sample thicknesses when a Lorentzian source distribution is assumed and the effect of the chromatic aberration is considered. Additionally the influence of amorphous layers introduced by the preparation of the TEM samples is discussed. Taking into account these parameters, the intensity in the whole unit cell of GaP, i.e. at the positions of the different atomic columns and in the region between them, is described correctly. With the knowledge of the decisive parameters, the determination of the chemical composition of more complex, multinary materials becomes feasible.
authors.affiliation: Materials Science Center and Faculty of Physics, Philipps-Universität Marburg, Hans-Meerweinstraße 6, 35032 Marburg, Germany. Electronic address: andreas.beyer@physik.uni-marburg.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Beyer
authors.affiliation: Materials Science Center and Faculty of Physics, Philipps-Universität Marburg, Hans-Meerweinstraße 6, 35032 Marburg, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Belz
authors.affiliation: Materials Science Center and Faculty of Physics, Philipps-Universität Marburg, Hans-Meerweinstraße 6, 35032 Marburg, Germany.
authors.forename: Nikolai
authors.initials: N
authors.lastname: Knaub
authors.affiliation: Materials Science Center and Faculty of Physics, Philipps-Universität Marburg, Hans-Meerweinstraße 6, 35032 Marburg, Germany.
authors.forename: Kakhaber
authors.initials: K
authors.lastname: Jandieri
authors.affiliation: Materials Science Center and Faculty of Physics, Philipps-Universität Marburg, Hans-Meerweinstraße 6, 35032 Marburg, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Volz
keywords: HAADF imaging; III/V semiconductors; Image simulation; Quantitative STEM; Spatial coherence; Temporal coherence