Colloquium Series

"Playing with broken symmetries in oxides," by Anand Bhattacharya, Argonne National Laboratory

Abstract: In recent years, we have synthesized and explored heterostructures of complex oxides where we tailor and manipulate broken symmetries. I will present our work on PMN-PT/Fe3O4 heterostructures where we have carried out reversible ferroelastic gating of resistivity and the Verwey metal-insulator transition. I will also present results on how we use synthesis with single atomic layer control to turn a non-polar material into a polar material in a class of layered perovskites. I will discuss the consequences this has for structural and electronic properties.

April 10, 2013

"Enabling and Disrupting Impacts of Interfaces in Energy Systems," by Dawn Bonnell, The University of Pennsylvania, hosted by Chris Fry

Abstract: Recent advances allow us to manipulate, control, and measure local phenomena at nanometer scales. Size dependent behavior of solids has become the hallmark of nanoscale science and nanotechnology. As systems decrease in size, the influence of surfaces and interfaces can dominate the properties. In fact, properties of surfaces and interfaces dictate the behavior of devices ranging from biosensors to solar cells to computer processors. This is particularly true as the size of the constituents decreases.

This talk will present three model examples of behavior at interfaces that have dramatic consequences to energy systems and that also illustrate novel measurements of local properties:

• The first involves size-dependent electronic properties of metal-oxide interfaces, an important issue in device miniaturization.
• The second demonstrates how engineered interfaces in nanoparticle arrays yield new plasmonic interactions useful in energy harvesting.
• The final example illustrates how mechanisms of mass and energy exchange at interfaces in fuel cells can be determined from in situ local probes.