Simulations of local-mechanical-stress-induced ferroelectric polarization switching by a multi-field coupling model of flexoelectric effect

The influence of local stress on the polarization switching of a two-dimensional ferroelectric thin film is investigated by a multi-field coupling model of flexoelectric effect. The evolution law of domain in a ferroelectric film under a local mechanical force is obtained. That is: under increasing mechanical stress, domain evolution in ferroelectric film will experience six stages small angle of rotation? emergence of 90 degrees domain switching -> expansion of 90 degrees domain -> emergence of 180 degrees domain switching -> expansion of 180 degrees domain -> steady state''. f(1111) related flexocoupling type and f(1122) related flexocoupling type both play crucial roles in the whole switching process. 90 degrees switching arises from the combined effect of the gradient of transverse strain in the thickness and horizontal direction as well as the gradient of out-of-plane strain in the horizontal direction, while 180 degrees switching is attributed to the combined effect of the gradient of transverse strain and out-of-plane strain in the thickness direction. (C) 2015 Elsevier B.V. All rights reserved.