Solid State and Optics Seminar

Wednesday, March 2, 2005

1:00 p.m.

107 Mason Lab

"Ferroelectric Domain Dynamics as a Disorder-controlled Creep Process"

Dr. Patrycja Paruch
University of Geneva

Abstract

Competition between elasticity and disorder governs the behavior of a wide range of physical systems, from vortex lattices to fluid invasion. Ferroelectric domain walls comprise another such system with interesting technological applications. In these materials, microscopic studies are required to discriminate between the contributions of disorder and pinning from the periodic lattice potential. Using atomic force microscopy (AFM), we have investigated the static configuration and subcritical dynamics of ferroelectric domain walls. Measuring individual nanoscale domains, we observe nucleation at the AFM tip, followed by radial domain wall motion. The motion exhibits a non-linear dependence of the velocity on the electric field, which is characteristic of a creep process: v ~exp [-1/E^]. The average value for the dynamical exponent is ~0.6. Independent measurements of domain wall roughness in these films reveal a power law growth of the relative displacement correlation function B(L)~L^(2) at short length scales L, with a wandering exponent ~ 0.26. Combining these results, we obtain an effective domain wall dimensionality of 2.5, in good agreement with theoretical calculations for a two-dimensional elastic interface in the presence of random-bond disorder and long-range dipolar interactions. These results provide a coherent physical picture of ferroelectric domain walls as an elastic disordered system.

Host: Charles Ahn