Regensburg 2013 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 11: Topical Session: TEM-Symposium - STEM
MM 11.3: Talk
Monday, March 11, 2013, 16:30–16:45, H4
Characterisation of ultrathin ferroelectric film using scannning transmission electron microscopy — •Daesung Park1, Anja Herpers2, Tobias Menke2, Regina Dittmann2, and Joachim Mayer1 — 1Central Facility for electron microscopy (GFE), RWTH Aachen, Germany — 2Institute of Solid State Research and JARA-FIT, Jülich Aachen Research Alliance, Fundamentals of Future Information Technology, Research Center Jülich, Germany
Ferroelectric thin films are attractive candidates for capacitors in random access memory (FeRAM), in which a reversible spontaneous polarisation is utilised to store information. However, below a critical thickness, the ferroelectric property usually disappears. Using smaller in-plane lattice parameter of the substrate induces epitaxial strain which tends to enhance ferroelectric distortion. In this study, niobium doped SrTiO3 is used as a substrate due to its 2.2 % smaller lattice parameter in comparison to BaTiO3. To change and balance the possible mixed termination of BaTiO3, 1.5 additional unit cells of BaRuO3 are embedded between a BaTiO3 thin film (7 unit cells) and SrRuO3 top electrode. The critical thickness depends on the termination of the ferroelectric thin film between electrodes. To elucidate the termination at the interface, high angle annular dark filed (HAADF) imaging and StripeSTEM techniques are carried out in STEM mode due to the high sensitivity to the atomic number Z. Fine structure analysis of Ti-L23 edge is performed to account for Crystal field splitting effect which is a result of the distortion of Perovskite structure.