Kinetic Monte Carlo simulations of ferroelectrics
Abstract
The field of ferroelectrics has long since been dominated by inorganic materials such as BTO and PZT, and more recently the organic polymer PVDF. Recently, a new class of organic ferroelectrics has emerged, that of the small molecules. These organic ferroelectrics have numerous advantages over their inorganic counterparts in that they are cheap, non-toxic, and flexible. Especially this latter quality is of great importance when applying ferroelectrics as piezoelectric sensors or actuators.
Whereas there have been numerous experimental works on the ferroelectric behavior of the small molecular ferroelectrics, a thorough understanding of the underlying processes and kinetics is lacking. Therefore, we have developed a model based purely on electrostatic interactions that, when implemented in a Monte Carlo simulation, can reproduce the experimentally observed ferroelectric behavior.
Specifically, we focus on materials that are columnar liquid crystals, with benzenetricarboxamide (BTA) as the prototype material. Although BTA has for some time been of interest for its self-assembly properties, it has only recently been proven to be ferroelectric. All previous theoretical work on this material has thus been focused on the self-assembly properties and dipole moment of single stacks. More generally, the modelling of (inorganic) ferroelectrics has often been restricted to very simplified systems, such as idealized spherical particles or 2D geometries.
We take the full 3D morphology of the material into account and try to reproduce the experimental ferroelectric properties using kinetic Monte Carlo simulations. We examine polarization, retention, and hysteresis loops and analyze parameter dependencies in the framework of thermally activated nucleation limited switching. The results can provide a detailed insight into the mechanism of polarization switching in organic ferroelectrics. This will help us in designing and perfecting new ferroelectric materials and devices
