Enhanced polarization and abnormal flexural deformation in bent freestanding perovskite oxides

Abstract

Recent realizations of ultrathin freestanding perovskite oxides offer a unique platform to probe novel properties in two-dimensional oxides. Here, we observe a giant flexoelectric response in freestanding BiFeO3 and SrTiO3 in their bent state arising from strain gradients up to 3.5 × 107 m−1, suggesting a promising approach for realizing ultra-large polarizations. Additionally, a substantial change in membrane thickness is discovered in bent freestanding BiFeO3, which implies an unusual bending-expansion/shrinkage effect in the ferroelectric membrane that has never been seen before in crystalline materials. Our theoretical model reveals that this unprecedented flexural deformation within the membrane is attributable to a flexoelectricity–piezoelectricity interplay. The finding unveils intriguing nanoscale electromechanical properties and provides guidance for their practical applications in flexible nanoelectromechanical systems.

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

“…Copyright 2020, Wiley-VCH. Panel D reprinted with permission [113] . Copyright 2020, American Chemical Society.…”

“…Flexible freestanding oxides also provide a new direction for exploring outstanding performance, including piezoelectricity and flexoelectricity. By PLD, Elangovan et al fabricated 30-nmthick flexible freestanding piezoelectric BTO thin films with good electromechanical-coupling properties [113] . As shown in Figure 2D, under an external electric field, the thin film could fold gradually and continuously by 180° and the fold-unfold cycles were reversible.…”

On the Role of the Sr3−xCaxAl2O6 Sacrificial Layer Composition in Epitaxial La0.7Sr0.3MnO3 Membranes

“…[13][14][15] In fact, the fabrication of new artificial heterostructures by assembling very dissimilar materials, their integration in conventional materials such as silicon, plastics, and 2D semiconductors, [16][17][18] and the possibility to obtain spontaneous shaped structures [19] is becoming a reality opening the possibility to study novel interface phenomena, nanoengineer their properties, and unlock strain states that might not be available by traditional epitaxial growth. [20][21][22] The use of a sacrificial layer is an appealing approach to fabricate and manipulate freestanding epitaxial complex oxides membranes. [23] This method consists of adding a buffer layer between the substrate and the complex oxide that ensures epitaxial growth and the subsequent detachment upon selective etching.…”

“…[ 13–15 ] In fact, the fabrication of new artificial heterostructures by assembling very dissimilar materials, their integration in conventional materials such as silicon, plastics, and 2D semiconductors, [ 16–18 ] and the possibility to obtain spontaneous shaped structures [ 19 ] is becoming a reality opening the possibility to study novel interface phenomena, nanoengineer their properties, and unlock strain states that might not be available by traditional epitaxial growth. [ 20–22 ]…”

Tuning Piezoelectricity via Thermal Annealing at a Freestanding Ferroelectric Membrane

“…(2) Substrates govern the elastic response of the system, limiting piezoelectric deformations upon application of external electric field. In contrast, freestanding membranes, which are free of substrate constraints, give new platforms for enhanced and tunable functionalities. − Despite these advantages, it is still an open question how to engineer domain structures and thus the related piezoelectric properties in freestanding films after integration on silicon.…”