Control of Domain Structures in Multiferroic Thin Films through Defect Engineering

Abstract

Domain walls (DWs) have become an essential component in nanodevices based on ferroic thin films. The domain configuration and DW stability, however, are strongly dependent on the boundary conditions of thin films, which make it difficult to create complex ordered patterns of DWs. Here, it is shown that novel domain structures, that are otherwise unfavorable under the natural boundary conditions, can be realized by utilizing engineered nanosized structural defects as building blocks for reconfiguring DW patterns. It is directly observed that an array of charged defects, which are located within a monolayer thickness, can be intentionally introduced by slightly changing substrate temperature during the growth of multiferroic BiFeO thin films. These defects are strongly coupled to the domain structures in the pretemperature-change portion of the BiFeO film and can effectively change the configuration of newly grown domains due to the interaction between the polarization and the defects. Thus, two types of domain patterns are integrated into a single film without breaking the DW periodicity. The potential use of these defects for building complex patterns of conductive DWs is also demonstrated.

Domain wall-localized phonons in BiFeO3: spectrum and selection rules

“…2b, c. Even though the DW polarization profile is very narrow, the accompanying strain texture, emanating from the areas of DW bending near the surface [33][34][35][36] , extends surprisingly far 37,38 , as seen in Fig. 2b, c.…”

“…It is seen that the DW orients perpendicular to the [P 1 , 0, P 3 ] direction, and a small bending near the surface is observed in Fig. 4a [33][34][35][36] . In very thin films, the wall deviates from the [101] orientation towards the surface normal.…”

Unexpected Giant Microwave Conductivity in a Nominally Silent BiFeO3 Domain Wall

“…Using a simplified Ginzburg–Landau model, one can show that the DW bends toward the normal direction near the surface . We note that the bending of 71° DWs near the surface of BFO thin films has been experimentally observed by TEM and PFM studies . Figure a shows the spatial distribution of P z (out‐of‐plane component of the polarization) in the cross‐section of the film, as simulated by electromechanical finite‐element method .…”

Anisotropic superconductivity induced by periodic multiferroic domain patterns

“…3b, and in Fig. 3d due to the shear strain induced by 71°domain walls 28 . However, this shear strain domain wall is not significant in the 109°c ase, as shown in Fig.…”