Tip-Induced In-Plane Ferroelectric Superstructure in Zigzag-Wrinkled BaTiO₃ Thin Films

Abstract

The complex micro-/nanoscale wrinkle morphology primarily fabricated by elastic polymers is usually designed to realize unique functionalities in physiological, biochemical, bioelectric, and optoelectronic systems. In this work, we fabricated inorganic freestanding BaTiO 3 ferroelectric thin films with zigzag wrinkle morphology and successfully modulated the ferroelectric domains to form an in-plane (IP) superstructure with periodic surface charge distribution. Our piezoresponse force microscopy (PFM) measurements and phase-field simulation demonstrate that the self-organized strain/stress field in the zigzag-wrinkled BaTiO 3 film generates a corresponding pristine domain structure. These domains can be switched by tip-induced strain gradient (flexoelectricity) and naturally form a robust and unique "braided" inplane domain pattern, which enables us to offer an effective and convenient way to create a microscopic ferroelectric superstructure. The corresponding periodic surface potential distribution provides an extra degree of freedom in addition to the morphology that could regulate cells or polar molecules in physiological and bioelectric applications.

Polarization Evolution in Morphology-Engineered Freestanding Single-Crystalline BaTiO3 Membranes

“…In addition to the domain switching, more importantly, Dong et al found the continuous rotation of dipoles in the transition region connecting a- and c-domains. The formation of the transition region could buffer the strain mismatch between the a- and c-domains, which prevents brittle fracture in the wrinkled BTO membranes. ,, The emergence of domain variants leads to a decrease in the domain wall energy and overall energy barrier for the domain nucleation during polarization switching, which could potentially contribute to a decrease in the coercive field. − In Figure b, we have summarized the magnitude of the imprint, defined as ( V c+ + V c– )/2, as a function of strain (ε 0 ). With the strain improving, no matter whether the strain state is tensile or compressive, the magnitude of the imprint increases from ∼ −0.04 to ∼0.61 V in the tensile strain state and from ∼ −0.04 to ∼ −0.41 V in the compressive strain state.…”

“…The formation of the transition region could buffer the strain mismatch between the a-and c-domains, which prevents brittle fracture in the wrinkled BTO membranes. 30,31,33 The emergence of domain variants leads to a decrease in the domain wall energy and overall energy barrier for the domain nucleation during polarization switching, which could potentially contribute to a decrease in the coercive field. 34−36 In Figure 4b, we have summarized the magnitude of the imprint, defined as (V c+ + V c− )/2, as a function of strain (ε 0 ).…”

Design of super-elastic freestanding ferroelectric thin films guided by phase-field simulations

“…The formation of various wrinkled structures has been reported in thin film systems such as metals [126] , graphene [132] , organics [130,131,133,134] , gels [147] , biological tissues [148] and more recently in freestanding ferroelectric thin film systems. As shown in Figure 7A, Dong et al successfully fabricated periodic wrinkle-patterned BTO/PDMS membranes based on an as-prepared super-elastic single-crystal freestanding BTO film [63,64] . Moreover, finely controlled wrinkle patterns, such as sinusoidal, zigzag and labyrinthine patterns, were obtained by changing the anisotropy and magnitude of the applied stress or adjusting the interfacial adhesion conditions.…”

“…(H) The electric toroidal moments corresponding to the domain structure in (G) illustrate the presence of in-plane topological domains. Panel A reprinted with permission [63] . Copyright 2020, Wiley-VCH.…”

“…Right: reprinted with permission [62] . Copyright 2020, AIP Publishing), 2D zigzag-wrinkling (Top: reprinted with permission [63] .…”