Berlin 2015 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 56: Frontiers of electronic structure theory: Optical excitations
HL 56.8: Vortrag
Mittwoch, 18. März 2015, 17:00–17:15, MA 004
Mapping atomic orbitals in the transmission electron microscope: seeing defects in graphene — •Lorenzo Pardini1, Stefan Löffler2,3, Giulio Biddau1, Ralf Hambach4, Ute Kaiser4, Claudia Draxl1,5, and Peter Schattschneider2,3 — 1Physics Department and IRIS Adlershof, Humboldt-Universität zu Berlin, Germany — 2Institute of Solid State Physics, Vienna University of Technology, Austria — 3University Service Centre for Transmission Electron Microscopy, Vienna University of Technology, Austria — 4Central Facility for Electron Microscopy, University of Ulm, Germany — 5European Theoretical Spectroscopy Facility (ETSF)
The possibility of mapping atomic orbitals by using energy-filtered transmission electron microscopy (EFTEM) has been considered for a long time and was recently demonstrated from a theoretical point of view. With the example of graphene, we predict how this approach can be used to map orbitals of a particular character. To this purpose, we have investigated graphene in its pristine structure and with two different kinds of defects, namely an isolated vacancy and a substitutional nitrogen atom. We show that basically three different kinds of images are to be expected, depending on the orbital character as determined from the corresponding projected density of states. To judge the feasibility of mapping such orbitals in a real microscope, we investigate the effect of the optics' aberrations, by simulating the lens system of two microscopes that are commonly used for electron energy loss spectrometry. We find that it should indeed be feasible to see atomic orbitals in a state-of-the-art EFTEM.