Impact of 3D Curvature on the Polarization Orientation in Non-Ising Domain Walls

Abstract

Ferroelectric domain boundaries are quasi-two-dimensional functional interfaces with high prospects for nanoelectronic applications. Despite their reduced dimensionality, they can exhibit complex non-Ising polarization configurations and unexpected physical properties. Here, the impact of the three-dimensional (3D) curvature on the polarization profile of nominally uncharged 180° domain walls in LiNbO3 is studied using second-harmonic generation microscopy and 3D polarimetry analysis. Correlations between the domain-wall curvature and the variation of its internal polarization unfold in the form of modulations of the Néel-like character, which we attribute to the flexoelectric effect. While the Néel-like character originates mainly from the tilting of the domain wall, the internal polarization adjusts its orientation due to the synergetic upshot of dipolar and monopolar bound charges and their variation with the 3D curvature. Our results show that curved interfaces in solid crystals may offer a rich playground for tailoring nanoscale polar states.

Automatic Ferroelectric Domain Pattern Recognition Based on the Analysis of Localized Nonlinear Optical Responses Assisted by Machine Learning

“…SHG microscopy has proven its efficiency in analyzing polarization states and symmetry aspects in various systems [31][32][33] among which: thermotropic phase boundaries, [34] phase coexistence in thin films [35] and heterostructures, [36] phase transitions, [37,38] non-Ising and chiral ferroelectric domain walls, [39,40] as well as polar domain boundaries in centrosymmetric materials. [41] The variation of the SHG polarization with the light polarization provides a unique way to probe the nonlinear optical susceptibility tensor, and with this, to gain information on the local structure, symmetry, and polarization orientation in ferroelectric materials.…”

Non‐Destructive Tomographic Nanoscale Imaging of Ferroelectric Domain Walls

“…A breakthrough was the advent of nonlinear optical methods that enabled imaging of ferroelectric domain walls in 3D. [16][17][18][19] Their application, however, is restricted to systems with specific optical properties and the spatial resolution is in the order of hundreds of nanometers, whereas domain-wall roughening and bending often occur on much smaller length scales. [20][21][22] Tomographic microscopy approaches offer higher resolution, [23][24][25][26] but data acquisition times are rather long; most crucially, the established tomography methods for domain-wall imaging are destructive.…”