Free surface domain nucleation in a ferroelectric under an electrically charged tip

Abstract

This paper examines the process of domain nucleation in ferroelectric perovskites at a free surface due to electrical fields applied through a charged tip above the surface. We use a real-space phase-field model to model the ferroelectric, and apply a boundary element-based numerical method that enables us to accurately account for the stray electric fields outside the ferroelectric and the interactions through electric fields between the external tip and ferroelectric. We calculate the induced domain patterns, the stress and internal electric fields, and the induced surface displacement for various relative orientations of the crystal lattice with respect to the free surface. The effect of the external spatially inhomogeneous electric field leads to the formation of complex domain patterns and nominally incompatible microstructures. Two key findings are: first, in c axis films, a new domain forms beneath the tip through 180 switching and this new domain has the opposite piezo-response as the original domain, leading to a distinct displacement signature on the surface; and second, in a axis films, domain nucleation occurs at lower applied field because polarization rotates to align with the applied field, whereas in c axis films, the polarization magnitude reduces until 180 switching occurs at a higher applied field. We also see that the calculated domain patterns differ significantly from analytical approximations that are often used.

Analyzing piezoresponse force microscopy for reconstruction of probed ferroelectric structures

“…These effects have recently been studied by Yang and Dayal using phase field simulations. 15,16 Clearly, this tip induced that electric field is highly concentrated, as shown in Figs. 1(b) and 1(c) for both out-ofplane and in-plane electric field evaluated on the surface of barium titanate, whose properties are listed in Table I, and the tip radius is assumed to be 25 nm with 10 V applied.…”

Nano-domains and related phenomena in congruent lithium tantalate single crystals studied by scanning nonlinear dielectric microscopy

“…In particular, ε (5) and ε (6), here called super higher order nonlinear dielectric constants, are expected to not only have high spatial resolution but also high sensitivity to nonlinear domain motion under application of a high electric field. although studies of the behavior of local domains using a tip have been carried out both through experimental [9]- [13] and simulation [14] approaches, domain motion at the nanometer scale has not yet been Manuscript clarified. Therefore, in the present work, we also investigated the behavior of microscopic domains under a large concentrated electric field formed by a probe tip by measuring the nonlinear dielectric constants from ε(3) to ε(6) of congruent liTao 3 (clT) [15], which is an important ferroelectric material for nonlinear optical devices [16] and is considered to be a promising medium for high-density ferroelectric data storage [17].…”

Challenges and opportunities for multi-functional oxide thin films for voltage tunable radio frequency/microwave components

“…Dirichlet-to-Neumann maps in combination with the boundary element method provide a method to handle these challenges at reasonable computational expense. 214 Finally, modeling of space charge transport involving diffusion of dopants, role of oxygen vacancies, on the functionality of the thin films is another area of importance as well as of challenge. A recently formulated iterative version of this numerical method 215 has enabled the study of space charges at complex domain patterns near the free surface of thin-film ferroelectrics.…”