Topological Defects with Distinct Dipole Configurations in PbTiO3/SrTiO3 Multilayer Films

Abstract

Distinct and novel features of nanometric electric topological defects, including dipole waves and dipole disclinations, are presently revealed in the PbTiO_{3} layers of PbTiO_{3}/SrTiO_{3} multilayer films by means of quantitative high-resolution scanning transmission electron microscopy. These original dipole configurations are confirmed and explained by atomistic simulations and have the potential to act as functional elements in future electronics.

Inverse transition of labyrinthine domain patterns in ferroelectric thin films

“…Technically, a first-principles-based effective Hamiltonian 34 is used within Monte-Carlo (MC) simulations to determine the energetics and local electric dipoles in each perovskite five-atom cell of these supercells. The validity of this approach was demonstrated by previous theoretical studies of ultrathin PZT films under compressive strains that (1) yield 180 degrees up and down stripe domains that periodically alternate along [100] (or along [010]) for their ground-state 34,35 , in agreement with experimental observation 36 (note that 'up' (respectively, 'down') domains refer to domains in which the z-component of the dipole is parallel (respectively, antiparallel) to the z-axis, respectively); (2) predict a linear dependency between the width of these periodic stripes and the square root of the film's thickness 37 , as consistent with recent measurements 38 ; and (3) have also led to the prediction of various topological defects such as vortices 39 , dipolar waves 40 , bubbles 41 and merons (or convex disclinations) 42 in ferroelectrics, that have been experimentally confirmed [42][43][44] . Note that the predicted temperature has to be rescaled by a factor of ∼ 1.6 with respect to measurements 45 .…”

“…We find that the coarsening of structures is conveyed by the diffusion and relaxation of topological defects localized at the junction of different tiles and reconciling discrepancies in their prevailing local orientations and/or wavelengths 25 . The examination of elementary point topological defects indeed shows that the densities d | and d ||| of stripe end-points (or convex disclination of + 1/2 Pontryagin charge 27,42 ) and three-fold junctions (or concave disclinations of -1/2 Pontryagin charge 27 ), respectively shown in Figs. 4b and c, feature a gradual lessening upon approaching T inv from low temperatures (Fig.…”

Atomic imaging of mechanically induced topological transition of ferroelectric vortices

“…The single vortex evolution and the stability of vortices are also discussed. Figure 1d shows a polarization map of the PTO layer obtained by calculating the offsets between the 6 Pb and Ti sublattices 22,23 , with the overlaid vectors representing the magnitude and direction of the polar displacements. As a result, the polarization exhibits a continuous rotation, resulting in a vortex structure similar to that reported in a previous study 3 .…”

Optical creation of a supercrystal with three-dimensional nanoscale periodicity

“…In particular, we explore (PbTiO 3 ) n / (SrTiO 3 ) n superlattices (PTO/STO superlattices), where there is a subtle balance between the polarization (Landau), electric, gradient and elastic energies. The energetics of these heterostructures is dictated by interlayer coupling through electrostatic as well as elastic strain gradients, producing confinement and proximity of competing phases [13][14][15][16][17] . When this system is grown on DyScO 3 (DSO) substrates, the SrTiO 3 is under tensile strain, which induces an in-plane polarization, and PbTiO 3 is under compression, which favours out-of-plane polarization.…”