Complex ferroelastic domain patterns in free-standing nanoferroelectrics
Nathaniel Ng (Inst. of High Perf. Computing), Rajeev Ahluwalia (IHPC), David Srolovitz (University of Pennsylvania)
Mechanics of Phase Transforming and Multifunctional Materials
Wed 9:00 - 10:30
CIT 219
Recently, unusual ferroelastic domain patterns have been observed in almost free-standing single crystal ferroelectric nanostructures [1]. Understanding such domain structures is of vital importance for developments ferroelectrics, and in particular, for nanoscale devices such as capacitors for use in ferroelectric random access memories (FeRAM). Using a phase field model in a Ginzburg Landau framework, we investigate the formation of flux-closure domain structures first in 2D, and then extending our study further to the more complex 3D domain structures [2]. Our simulations are carried out using a 3D parallel code where the elastic and electrostatic equations are solved in real space, which is a more natural framework where non-periodic boundary conditions are involved. The energetics of the various polarization domain structures and the role of uncompensated surface charges are explored. The role of electrical boundary conditions, nanoparticle size, and nanoparticle shape lead to a complex interplay between elasticity and electrostatics and thereby a large diversity of domain patterns. Further, our results suggest an explanation for why certain flux-closure domain structures observed in first principles calculations are not easily accessible experimentally. Lastly, it is interesting to observe that this research opens the door to more questions. Why restrict geometries to purely nanocubes and slabs and what new domain patterns could possibly be accessed? How can one exploit the interplay between the elastic and electrostatic effects? 1. A. Schilling et al, Nano Lett. 9(9), 3359-3364 (2009). 2. N. Ng, R. Ahluwalia, and D. J. Srolovitz. Acta Materialia, 60, 3632-3642 (2012).