Investigation of BiFeO3 thin films by aberration-corrected electron microscopy 1 M.D. Rossell1* Electron Microscopy Center, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland *e-mail: marta.rossell@empa.ch BiFeO3 (BFO) is the most widely studied multiferroic material since it is both ferroelectric (TC ~ 1083 K) and antiferromagnetic (TN ~ 625 K) at room temperature, and possesses a very large room-temperature spontaneous polarization (~ 90 µC/cm2). The possibility of coupling between the ferroelectric polarization and antiferromagnetism in BFO has triggered a strong drive to include it in thin film form as micro- and nanostructures. Further, the use of substrate-induced strain provides many opportunities to stabilize phases [1] and defects [2] which are otherwise difficult to obtain in bulk form. In this way, new functional behaviors can be realized. In order to precisely understand the structure-to-property relationship of these BFO thin films, knowledge on their exact microstructure is required. Thus, the ability of aberration-corrected electron beams in scanning transmission electron microscopes (STEMs) to unravel the local atom arrangements, strain fields and chemical bonding states is crucial to significantly enhance our understanding of these complex systems and ultimately tailor their properties. In this talk, different BFO thin film systems will be presented and discussed. Examples will be shown to illustrate the insights that can be gained into the structure-to-property relationship by using high spatial resolution as well as electron energy-loss spectroscopy in the STEM. 1. Atomic structure of highly strained BiFeO3 thin films, Rossell MD, Erni R, Prange MP, Idrobo JC, Luo W, Zeches RJ, Pantelides ST and Ramesh R, Phys. Rev. Lett., 108, 047601 (2012). 2. Evidence of sharp and diffuse domain walls in BiFeO3 by means of unit-cell-wise strain and polarization maps obtained with high resolution scanning transmission electron microscopy, Lubk A, Rossell MD, Seidel J, He Q, Yang SY, Chu YH, Ramesh R, Hÿtch MJ and Snoeck E, Phys. Rev. Lett., 109, 047601(2012). MARTA D. ROSSELL Marta D. Rossell received her doctoral degree from the University of Antwerp (Belgium). Thereafter she carried out postdoctoral studies at the National Center for Electron Microscopy (NCEM), Lawrence Berkeley National Laboratory in the group of Dr. Ulrich Dahmen, and at the University of California at Berkeley in the group of Prof. Ramamoorthy Ramesh. She then moved to Switzerland where she worked at the Swiss Federal Institute of Technology Zurich (ETH Zurich). Marta D. Rossell is now staff scientist of the Electron Microscopy Center of the Swiss Federal Laboratories for Materials Science and Technology (Empa). Her research interests cover various topics in electron microscopy, such as ultra-high resolution, low-voltage electron microscopy and electron tomography. She is particularly interested in the new imaging and analysis techniques that have become feasible through the implementation of aberration correctors and monochromators in (scanning) transmission electron microscopes. In collaboration with various research groups she has published several articles in many different types of materials ranging from perovskite-type materials, modulated structures, metal oxide/sulfide nanoparticles, aluminum alloys, carbon nanotubes and 2D materials.