Atomic-Scale Mechanisms of Defect-Induced Retention Failure in Ferroelectrics

Abstract

The ability to switch the ferroelectric polarization using an electric field makes ferroelectrics attractive for application in nanodevices such as high-density memories. One of the major challenges impeding this application, however, has been known as "retention failure", which is a spontaneous process of polarization back-switching that can lead to data loss. This process is generally thought to be caused by the domain instability arising from interface boundary conditions and countered by defects, which can pin the domain wall and impede the back-switching. Here, using in situ transmission electron microscopy and atomic-scale scanning transmission electron microscopy, we show that the polarization retention failure can be induced by commonly observed nanoscale impurity defects in BiFeO thin films. The interaction between polarization and the defects can also lead to the stabilization of novel functional nanodomains with mixed-phase structures and head-to-head polarization configurations. Thus, defect engineering provides a new route for tuning properties of ferroelectric nanosystems.

Defect-Induced Hedgehog Polarization States in Multiferroics

“…On the other hand, recent observation of a strong interaction between ferroelectric polarization and built-in fields induced by charged impurity defects embedded in the ferroelectric matrix suggests that these defects may be used as nano-building-blocks that can provide a strong electrostatic driven force for stabilization of complex domain structures 13,14 . For example, it has been shown that nanoscale planar charged defects in BiFeO 3 thin films can induce novel head-tohead mixed-phase polarization structures 13 . Nevertheless, these observed impurity defects were accidentally introduced in those films; and the possiblity to precisely control the formation of the defects and thus to generate the desired domain structures, has not been studied.…”

Control of Domain Structures in Multiferroic Thin Films through Defect Engineering

“…It is well known that some common types of defects, such as dislocations and vacancies, can interact with ferroelectric domains and DWs, pinning metastable polarization configurations. Recently, it was also discovered that impurity defects, another major type of defect with a structure different from the host material, can induce dramatic changes in domain structures of ferroelectric thin films . This finding suggests the possibility of using engineered impurity defects in combination with suitable interface boundary conditions to control domain formation and create complex domain structures.…”

“…This finding suggests the possibility of using engineered impurity defects in combination with suitable interface boundary conditions to control domain formation and create complex domain structures. Nevertheless, the observed impurity defects in literature are either accidentally formed in the films or coupled to polarization‐structure changes within a range of only a few nanometers of the defect . The approach of precisely creating ordered patterns of defects that can control the domain structure in the bulk of the film remains unexplored.…”

Design and Manipulation of Ferroic Domains in Complex Oxide Heterostructures

“…Ferroelectric flux-closure domains self-assemble near the interface of the BFO film and an insulating TbScO 3 (TSO) substrate. Another path opening the range of control over the domain state in ferroic thin films consists of introducing defects in stoichiometry during the growth process [45,46]. Recently, Li et al revealed that defects in stoichiometry can influence the domain architecture of thin films [47].…”