Hierarchical domain structures in buckled ferroelectric free sheets

TL;DR

This study investigates how buckling and delamination in ferroelectric BaTiO3 sheets influence domain structures, revealing hierarchical domain organization and offering new insights for ferroelectric domain engineering in flexible oxide sheets.

Contribution

It uncovers the hierarchical domain organization induced by buckling in ferroelectric sheets, highlighting the role of morphology and orientation in domain stabilization and engineering.

Findings

Buckling leads to self-organized ferroelastic domains along the buckle profile.

Hierarchical distribution of secondary domains caused by misalignment of folding structures.

Distinct domain patterns differ from sinusoidal wrinkle geometries.

Abstract

Flat elastic sheets tend to display wrinkles and folds. From pieces of clothing down to two-dimensional crystals, these corrugations appear in response to strain generated by sheet compression or stretching, thermal or mechanical mismatch with other elastic layers, or surface tension. Extensively studied in metals, polymers and, more recently, in van der Waals exfoliated layers, with the advent of thin single crystal freestanding films of complex oxides, researchers are now paying attention to novel microstructural effects induced by bending ferroelectric-ferroelastics, where polarization is strongly coupled to lattice deformation. Here we show that wrinkle undulations in BaTiO3 sheets bonded to a viscoelastic substrate transform into a buckle delamination geometry when transferred onto a rigid substrate. Using spatially resolved techniques at different scales (Raman, scanning probe and electron microscopy), we show how these delaminations in the free BaTiO3 sheets display a self-organization of ferroelastic domains along the buckle profile that strongly differs from the more studied sinusoidal wrinkle geometry. Moreover, we disclose the hierarchical distribution of a secondary set of domains induced by the misalignment of these folding structures from the preferred in-plane crystallographic orientations. Our results disclose the relevance of the morphology and orientation of buckling instabilities in ferroelectric free sheets, for the stabilization of different domain structures, pointing to new routes for domain engineering of ferroelectrics in flexible oxide sheets.