Domains in Ferroelectric Nanodots

Abstract

Almost free-standing single crystal mesoscale and nanoscale dots of ferroelectric BaTiO(3) have been made by direct focused ion beam patterning of bulk single crystal material. The domain structures which appear in these single crystal dots, after cooling through the Curie temperature, were observed to form into quadrants, with each quadrant consisting of fine 90 degrees stripe domains. The reason that these rather complex domain configurations form is uncertain, but we consider and discuss three possibilities for their genesis: first, that the quadrant features initially form to facilitate field-closure, but then develop 90 degrees shape compensating stripe domains in order to accommodate disclination stresses; second, that they are the result of the impingement of domain packets which nucleate at the sidewalls of the dots forming "Forsbergh" patterns (essentially the result of phase transition kinetics); and third, that 90 degrees domains form to conserve the shape of the nanodot as it is cooled through the Curie temperature but arrange into quadrant packets in order to minimize the energy associated with uncompensated surface charges (thus representing an equilibrium state). While the third model is the preferred one, we note that the second and third models are not mutually exclusive.

Super switching and control of in-plane ferroelectric nanodomains in strained thin films

“…In dots of single crystals, significant in-plane depolarizing fields can be present, because of the reduced objects lateral size, and induce flux closure loops. Such strong effect of lateral depolarizing fields has been reported by McGilly et al in BaTiO 3 single crystals dots 13,15 . A favourable formation of quadrants facilitating fluxclosure at the mesoscale has been observed in vacuum 13 , whereas 180°superdomains have been evidenced in air 15 , showing the effect of surface charges and depolarizing fields on the domains architecture.…”

Superdomain dynamics in ferroelectric-ferroelastic films: Switching, jamming, and relaxation

“…These inplane superdomains are strain-neutral, like those in the right-hand side of our Figure 1. It was found that fourfold vertex closure domains in this material are unstable, unlike those in BaTiO3 [32,101] or PZT, [13] in agreement with the clock-model predictions of Srolovitz and Scott. [51] When treating in the clock model the domain walls, rather than treating the polarization itself, [52] it is clear that bundle-domain switching, which can be described as correlated motion of defects, [86] so that the ferroelastic switching indeed dominates the polarization switching, in analogy to the Kosterlitz-Thouless dominancy in thin superconducting films..…”

Novel high-temperature ferroelectric domain morphology in PbTiO3 ultrathin films

“…A rich variety of new closure domain morphologies, such as Landau-Lifshitz stripe domains [11,12], vortex and triclinic domains [13], have been predicted in PbTiO 3 , and BaTiO 3 thin films under open-circuit boundary conditions using density functional theory, effective Hamiltonian and interatomic potential models [14,15]. Tantalising experimental evidence for these closure domains in platlets and dots of BaTiO 3 has been presented in the form of 90 • stripe superdomains bifurcated by 180 • domain walls [16][17][18] and recent direct observation of vortices in PbTiO 3 /SrTiO 3 superlattices [19].…”