Investigation of BiFeO3 thin films by aberration

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: [email protected]
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.