Controllable conductive readout in self-assembled, topologically confined ferroelectric domain walls

Abstract

Charged domain walls in ferroelectrics exhibit a quasi-two-dimensional conduction path coupled to the surrounding polarization. They have been proposed for use as non-volatile memory with non-destructive operation and ultralow energy consumption. Yet the evolution of domain walls during polarization switching makes it challenging to control their location and conductance precisely, a prerequisite for controlled read-write schemes and for integration in scalable memory devices. Here, we explore and reversibly switch the polarization of square BiFeO nanoislands in a self-assembled array. Each island confines cross-shaped, charged domain walls in a centre-type domain. Electrostatic and geometric boundary conditions induce two stable domain configurations: centre-convergent and centre-divergent. We switch the polarization deterministically back and forth between these two states, which alters the domain wall conductance by three orders of magnitude, while the position of the domain wall remains static because of its confinement within the BiFeO islands.

Deterministic Switching of Ferroelectric Bubble Nanodomains

“…These have been demonstrated in magnetic systems, e.g., the use of magnetic skyrmions as well as magnetic domain‐walls for race‐track memory. However, controlled switching at the single defect level in ferroelectrics remains a substantive challenge2c,10,14 even though this has been achieved at the mesoscale . The unambiguous demonstration of deterministic switching between various nontrivial ferroelectric topologies, particularly at the single defect level would lead to a unprecedented handle over the emergent properties and hence entirely new cross‐coupled electro‐mechanical‐optical‐polarization functionalities, as outlined by Martin et al The primary impediment with ferroelectrics is that single topological configurations (i.e., vortex‐like or bubble domain states) have a size only several unit‐cells, which is several orders magnitude smaller than their classical magnetic counterparts.…”

Second harmonic microscopy of poled x-cut thin film lithium niobate: Understanding the contrast mechanism

“…The interest in tailored ferroelectric domain structures ranges from fundamental physics, e.g. for the study of topologically protected properties [12][13][14][15] and to potentially novel type of electronics in conductive domain walls (DWs) [16][17][18][19] , to commercialized applications, such as in nonlinear optical frequency converters [20][21][22] . In the latter one, the engineering and design of ferroelectric domain structures plays a crucial role, as domain grids can be used to obtain phase matching between the interacting beams in nonlinear optical frequency conversion processes by employing the quasi-phase matching (QPM) technique.…”

Geometry confined polar vertex domains in self-assembled BiFeO3 nano-islands

“…Topological structures (e.g. domain walls, vortices) in ferroelectric materials have attracted intensive attention both for fundamental research and technological applications for non-volatile nano-electronic devices [1][2][3][4], since the performance of ferroelectric nano-devices is closely related to the domain structures and their stability to perturbation. Compared to the flux-closure quadrants [1,5] or vortex states [2,4,6] in ferroelectrics, vertex domains-the intersection between two or more domain walls in a ferroic materials-have not yet received much attention to date [7,8].…”

“…Compared to the flux-closure quadrants [1,5] or vortex states [2,4,6] in ferroelectrics, vertex domains-the intersection between two or more domain walls in a ferroic materials-have not yet received much attention to date [7,8]. Actually, ferroelectric vertices exhibit many exotic properties, such as high electric conductivity [3,9], and creep process during vertex interaction [7]. Moreover, previous theory predicted that a pair of separated threefold vertices and a fourfold vertex would exhibit distinct stability, and the transformation between these two types of topological domain pattern may be achieved by the coalescence or separation of the threefold vertex pairs [10].…”