Dr. Nina Balke Wisinger
Oak Ridge National Laboratory (ONRL)
Nanoscale Electromechanical Phenomena Studied with Scanning Probe Microscopy
Location: EB1 Room 1011
Friday, March 31st 2017 - 11:00 am
The ability to transform electrical energy into mechanical energy and vice versa is the foundation to many technologies in the area of information and energy, such as sensors, piezotronics, energy harvesting, piezoelectric, electrochemical, and polymer actuators, and artificial muscles. Despite the importance of electromechanical phenomena and numerous applications, fundamental interdisciplinary studies needed to understand and control nanoscale electromechanical phenomena are lacking. This is due to the difficulty in quantitatively determining the relatively small electromechanical coupling coefficients in many systems, the lack of theory describing non-equilibrium responses, and extreme breadth of the areas spanning from condensed matter physics to biology and medicine which can only be addressed in multi-researcher, interdisciplinary research efforts. Here I am going to present research done at the Center for Nanophase Materials Sciences revolving around electromechanical phenomena probed with scanning probe microscopy (SPM). In general, electromechanical phenomena can be described as a change in mechanical properties (such as sample volume or stiffness) as response to an applied electric field. In the special case of AFM, the cantilever and tip are electrically coated to apply electric fields locally and sense the material response at the same time allowing mapping of the electromechanical properties with 10's of nanometer resolution. Despite the technical advances and the development of new SPM-based characterization techniques, the quantification of functional material parameters based on electromechanical phenomena is still elusive. The lack of quantitative and accurate measurement can also lead to the misinterpretation of relevant material physics. Only if quantitative material parameters can be extracted, can a correlation of nanoscale structure-function relationships be derived and SPM can be integrated with techniques probing smaller or larger length and time scales as well as theoretical efforts for a full information integration across different disciplines. I will present examples from different research fields studying ferroelectrics, tunable dielectrics, and ionic conductors, where electromechanical phenomena provide access to functional material parameter such as piezoelectric constant, dielectric tenability, and activation energy for ionic transport. I will talk in depth about the challenges of making SPM-based characterization techniques quantitative, including cantilever dynamics and measurement artifacts, one of the grand challenges for SPM.
Dr. Nina Balke is a research staff member and theme leader for "Electromechanical Phenomena" in the Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory in Oak Ridge, TN. She earned her PhD in Materials Sciences at the Technical University of Darmstadt in Germany working with ferroelectric ceramics. In 2007, she received a Feodor-Lynen fellowship of the Alexander von Humboldt foundation to perform her postdoctoral research at the University of California in Berkeley in the group of R. Ramesh and at Oak Ridge National Laboratory under the leadership of S. V. Kalinin where she focused on scanning probe microscopy (SPM) characterization of electromechanical effects in ferroelectric oxides. Since 2010, she is at CNMS where she focuses on nanoscale characterization of functional oxides including ferroelectrics, low-k dielectrics, Li-ion batteries, and electrochemical capacitors. Since earning her PhD degree, she published over 80 papers in peer-reviewed journals and hold 2 patents for developments of new characterization techniques. She was awarded the Microscopy Today Innovation Award and the Department of Energy Early Career Research Award for her work on Li-ion battery materials in 2011 and received the Robert L. Coble Award for Young Scholars in 2013