Materials Science Division
Argonne National Lab
Nanoscale Visualization and Manipulation of Polarization Variants and Screen Charges
Location: EB1 Room 1011
Friday, September 19th 2014 - 11:00 am
Ferroelectric materials possess spontaneous polarization - net electric dipole moment per unit volume, of which magnitude and direction determine the surface charge density, and of which direction can be switched by electric field larger than a threshold called coercive field. As polycrystalline materials have grains with different crystallographic orientations and various grain boundaries dividing those grains, ferroelectric materials usually form domains with different polarizations and various domain boundaries dividing those domains. As such, ferroelectric domain structure and its dynamic behavior determine their macroscopic electric and piezoelectric properties. Furthermore, electric charges in various forms such as charged defects, electrons and ions interact with ferroelectric domains and their boundaries to influence the stability of domains and mobility of each domain boundary. Here I will present our efforts to visualize and manipulate polarization variants and screen charges present in ferroelectric and multi-ferroic materials using piezoresponse force microscopy (PFM), Kelvin Probe Force Microscopy (KPFM), scanning resistive probe microscopy (SRPM) and charge gradient microscopy (CGM), all of which are based on the system of scanning probe microscopy (SPM). Furthermore, I will demonstrate how we could address the origin of domain structure showing polarization variants deviating from ferroelectric easy axes and electrostatically unstable charged domain boundaries in conjunction with the crystal nucleation and growth model. Lastly, the impacts of such domain structures on the local polarization switching behaviors and the ability to manipulate screen charges will be discussed with the future implications for energy harvesting and memory devices.
Dr. Seungbum Hong has graduated summa cum laude with a B.S. from Korea Advanced Institute of Science and Technology (KAIST) in 1994 and received his Ph.D in the field of nanoscale observation of ferroelectric thin films at KAIST in 2000. After a year of post-doc experience in Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland from 2000 to 2001, he joined the probe storage project team as a project leader at Samsung Advanced Institute of Technology from 2002 to 2007. In 2007, he moved to Argonne National Laboratory as a tenured staff scientist, and he has been the principal investigator in local domain and transport studies of oxide heterostructures and polymer ferroelectrics using atomic force microscopy.
He has a broad experience to link the fundamental science with industrial applications (92 peer reviewed journals, 5 book editions, 3 book chapters, 74 patents) with a profound knowledge in the area of nanoscale characterization of ferroelectric and piezoelectric materials. He has been invited in major conferences or universities, has been awarded the Young Investigator Outstanding Achievement Award from International Symposium on Integrated Ferroelectrics in 2008 and has worked as a symposium organizer in MRS Spring 2006 and 2008, MRS Fall 2010, and APS March Meeting 2013.
He holds adjunct professorship at KAIST since 2012, and visited EPFL as an invited professor in 2014. He is currently the chair of CNM user executive committee and member of MSD colloquium committee at Argonne National Laboratory.