Domain switching dynamics for ImClO4 molecular ferroelectric thin films

Molecular ferroelectrics exhibit various advantages as compared to the traditional oxide ferroelectric materials. Despite tremendous experimental and theoretical efforts in the optimization and understanding of molecular ferroelectric systems, their domain -switching dynamics are yet to be discovered. In this study, we use the Imidazolium perchlorate thin films, a representative molecular ferroelectric material as the model system to systematically investigate the domain switching dynamics under a local bias through a Piezoelectric Force Microscopy (PFM) tip. We employed both thermodynamic calculations and the phase -field approach to explore the effects of various factors, including the magnitude of electric bias, distance to the domain wall, domain size, and substrate strain, on the domain switching behavior. Under intermediate bias, local ferroelastic 109 switching dominates. It is shown that the local 180 switching can occur with multiple sluggish and consecutive 71(degrees) switching when the tip is placed far away from the original 180 domain wall; whereas when the tip is placed near the domain wall, the bending of the domain wall towards the tip center can be seen, forming stable curved 180 domain walls. Moreover, the larger the domain size, the smaller the switching area; while the clamping effect from the substrate can inhibit domain switching, leading to a lower switching area with a higher magnitude of compressive strain. We hope to spur further interest in the understanding, designing, and optimization of the molecular ferroelectric thin films.