The dictum that “New tools lead to new science” [P. S. Weiss, ACS Nano., 2012, 6(3), 1877–1879], is perhaps nowhere more evident than in scanning transmission electron microscopy (STEM). In the last few years, aberration correctors and monochromators have transformed the field of electron microscopy, opening up new possibilities for correlating structure to functionality with atomic-scale resolution. In a STEM, multiple signals can be simultaneously collected, including the transmitted and scattered electrons (bright field and annular dark field imaging modes), along with spectroscopic signals such as inelastically scattered electrons and emitted photons. In this talk, I will briefly review some state-of-the-art applications to materials: from atomic resolution elemental mapping and single atom imaging to applications to real systems, including interfaces and mapping of physical properties such as magnetism. More specifically, I will show how subtle structural variations lead to changes in the physical properties of oxides in interfaces and around defects. I will use the STEM technique for mapping rotational polarization topologies at the nanoscale in ferroelectric thin films. Finally, I will also show how to obtain magnetic circular dichroic signals to study the magnetism of complex oxides with sub-nanometer resolution using electron energy loss spectroscopy.
Dr. Jaume Gazquez obtained his PhD in Materials Science (Universitat Autònoma de Barcelona) in 2007, having performed the research in the Materials Science Institute of Barcelona (ICMAB-CSC). He devoted his time to the microstructural analysis of superconducting thin films by means of Transmission Electronic Microscopy (TEM). After the PhD, he joined the STEM Group at the Oak Ridge National Laboratory (ORNL) with a postdoctoral fellowship of the Spanish Ministry for Science and Education and under the supervision of Dr. Maria Varela and Dr. Steve Pennycook. In September 2010 he joined back the ICMAB as a Ramon y Cajal fellow and subsequently as a permanent staff scientist. His research concentrates on establishing atomic-scale relations between the structure, chemistry and physical properties of transition-metal oxide nanostructures, specifically on elucidating the role of reduced dimensionality, interfaces, and defects on their macroscopic properties. He has published over 100 articles in these areas.
Hosted by: Prof. Rohan Mishra