Dresden 2011 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 12: Postersitzung I
MM 12.52: Poster
Monday, March 14, 2011, 17:30–19:00, P5
Influence of chemical bonding on HRTEM images of light elements — •Simon Kurasch1, Jannik C. Meyer1,3, Hye Jin Park2, Viera Skakalova2, Siegmar Roth2, and Ute Kaiser1 — 1Central Facility for Electron Microscopy of Materials Science, University of Ulm, 89081 Ulm — 2MPI FKF, 70569 Stuttgart — 3University of Vienna, Department of Physiks, 1090 Vienna, Austria
We improved the HRTEM image simulation by calculating the electrostatic specimen potential via density functional theory (DFT) [1]. This approach takes into account the electron charge redistribution within the specimen due to chemical bonding. Usually this is neglected by calculating the scattering potential as a superposition of isolated atom potentials.
Here we show that chemical bonding is clearly detected in experimental images of nitrogen doped graphene. We found that single atom nitrogen substitutions can be detected in experimental HRTEM images (dZ=1). According to the isolated atom model this should not be possible. However the observation is in excellent agreement with the DFT based simulation. Therefore the observed contrast from the N atom originates from a polarization effect on the neighbouring carbon atoms.
These experiments reveal that bonding has to be included in the TEM image simulation, and that a TEM can be utilized to obtain information about the electronic configuration of the specimen. This opens a way to discern electronic arrangements in point defects or other non-periodic objects that can not be analyzed by diffraction.